Aeolian sediments: ancient and modern

Copyrlgttto 11...1.

Aeolian Sediments

ANCIENT AND MODERN

Aeolian Sediments: Ancient and Modern Edited by K. Pye and N. Lancaster © 1993 The International Association of Sedimentologists ISBN: 978-0-632-03544-1

Aeolian Sediments ANCIENT AND MODERN

Edited by K. Pye and N. Lancaster

SPECIAL PUBLICATION NUMBER

16 OF THE

INTERNATIONAL ASSOCIATION OF SEDIMENTOLOGISTS PUBLISHED BY BLACKWELL SCIENTIFIC PUBLICATIONS OXFORD LONDON EDINBURGH BOSTON MELBOURNE PARIS BERLIN

VIENNA


of Scdimentologists aoo published for them by Blackwell Scientific Publications Editorial Ofliccs: Osney Mead. Odord OX2 OEL 25 John Street. London WC1N 2BL 23 Ainslie Place. Edinburgh E H 3 6AJ 238 Main Street. Cambridge Massachusctts 02142. USA 54 University Street. Carhon Victoria 3053. AUSlralia Olher Editorial Offices: Librairie Amene SA 2. rue Casimir-Dclavignc 7S006 Paris France Blackwell Wissenschafl5-Verlag Gmbll Meinekcstrassc 4 0-1000 Berlin 15 Germany Blackwell MZV Feklgassc 13 A-123!! Wicn Austria All rights reserved. No part of this publication may be reproduced. stored in a retrieval system. or transmil1ed. in any form or by any means. electronic. mechanical. photooopying. recording or oillerwise without the

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Contents

vii

Preface

Modern AeoliaJl Envi"onments 3

Particle dislodgement from a flat sand bed by wind: a re-analysis of Willetts & Rice's data B. B. Willells and I. K. McEwan

13

Aeolian dynamics on the windward slope of a reversing transverse dune, Alexandria coastal dunefield, South Africa J.R. BurkillshalV alld I.

23

. Rusl

Late Quaternary development of coastal parabolic megadune complexes in northeastern Australia K. Pye

45

The modern and ancient pattern of sandHow through the southern Namib del1ation basin I. COrbell

61

Internal structure of an aeolian lune using ground-penetrating radar

c.J. Schellk, D.L. Gowier, G.R. Olhoejt alld I E Lucills .

71

.

.

Origins and sedimentary features of supersurfaces in the northwestern Gran Desierto Sand Sea

N. Lallcasler Ancient Aeolian Environments

87

Aeolian genetic stratigraphy: an example from the Middle Jurassic Page Sandstone, Colorado Plateau K. G. Navholm, R. C. Blakey, M. Capps, L.S. JOlles, D. D. Killg alld G. Kocurek

109

Downwind changes within an ancient dune sea. Permian Ced,,,· Mesa Sandstone. southeast Utah R. P. Langford (Jlld M. A.

Itall

v

oll/ents

vi 127

Low-stand aeolian influence on stratigraphic completeness: upper member of the Hermosa Formation (latest Carboniferous). southeast Utah, USA S. C. Atchley lind D. B. Loope

151

Draa reconstruction, the Permian Yellow Sands, northeast England

1'. 163

hrintl "lid L. B.

Index

lemmellsen

Preface

sedimcnts. both an cien t and a number of im porta nt c onc eptual advances ill reccnt years, In partic ular , Ihere has becn a move away from descriptions of Studics

develo pmen t of most thick acolian sediment se­

of tleoli(1O

quenc es . bOl'h rel a ti vely reccnt alld ancient. has

modern. Imve exhibited

sediments.

bedforms

and

sedimcntary

been e pisodic . in response to cxrcrnnl c hange s that affect sediment supply ancl bedform mo bili ty , 'rhe

key to u n de rstanding the episodic nature of aeolian accumulation h as been provided by the recognit ion that nHljor boullliing su rfaces (supc rsu rfa(.'Cs) sep nratc genetic units in the depos its of ma ny ancient nnd modern sand seas, Supersurfaces tl'uncme aeoi i
environ·

Illcnt s towards a new cmphasis on the dynamics of

acolinn dcposition al syslems :at different tempo ra l


r ep l aced by dcfhllioll or n uvia l cl'Osion ave I' larg e

pa pers which were prescnte d at the s ymposiu m

Africa, The cOll trols on aeolian processes and their effects I:lt the dUllcfield and re gional sc,-lles
areas of a sand sea. Recogni tion nnd tracing of super bound i n g surfaces formed by d i ffe ren t processes provide the basis for constructi ng aeolian event slrat igra p hics and for the reconstruction of the de positio n a l histo ry of both modern and nn c i ent sHnd seas. as the papers by La n caster and Havholm and co-workers d rnonstrate, respectivel y , An u nders tanding of the sp ntitl l chn nges in the geo mor­ pholo gica l and sed im e n tological character f aeolian genetic units (e,g, variations in dune type, grain size tre nds and changes in the propo l'l ions of non­ aeolian facies p re se nt) also provides an im po rtan t 1001 for Lho un ravellin g of the evolution of sand seas , Lnngford & han p rov ide criteria for evaluating the pos it i o n of g en e t ic u nits wi thi n (I sun el sea , usi ng exa mp les from rhe Permian Ccdar Mesa Sandstone, Determination of the causes of episod ic behaviour in aeolian sedi ment ary sequenc cs pres en ts pe rha ps the gre a test ch H llen g e in acoliall sediment ology,

illustrated in the papers by Pye and Corbell. which

and requires careful evaluation of the effects of

entitled 'Acolinn Sediments, Ancient and ModeI'll' held during the Thirteenth International Sedimcn· ongrcss in Nottingham (Augu st 1990), We have also added a n umber of papers from those

tolog ic al

who were not able to attend the mee tin g. but whose

work represe nts im portant aspects of contemporary I'eseareh in aeolian sed i mentology , A

full

understanding

of ocolian

scd ime ll t nry

systcms requires k nowledge of the nnturc of the

opcrat ive proccsscs rangi ng from the scale of the

ind iv idual grain to that of the regional s an d SCI.l, ol1 ti n uing work 011 thc mcchanics of sand entrain· ment by wind is c](cmpli fi ed in the paper by Willc tts & M cE wa n, while intcnlctions bctween wind, sund t ran spo rt an d bed mor phology at the dune scale nrc il lustrated by B urk i nshnw & I liSt'S field studies in thc modern A le xandria coastal dunefield of Sout'h

changes in cli mat e and se a level On sand sup ply ,

present data from active systems on the Queensland

W;:lter I"ble levels, vegetation cover nnd wind reg im e .

coast and in the Namib Desert. respectively. Both

of these pupers dem onstrate Ihm sand nccumul:ation

Atchley & Loo pe show how cyclic ma rine sccli­

in these areas has a long h isto ry , and evolution of

mentation affected

aeolian sedimentation in the

while Chrintz and

Icmmcnscn demonst rat e how

the dllllcfieids has been grcatly influcnced by changes

Carboniferous Paradox Basin of southeast Utah,

New t echn iqu es c a n contribute sign i fica ntl y ro

careful i nve stigation and m o del li ng of sedi mcnt a ry

in cl i mate and se a le ve l .

the I'ccognition of gen etic units in modern a eo lia n

Structures can be u sed to reconstruct aeolian proccss

accumulations. Particul a rly exciting in this context

environmcnts and to document thei r chn nges ovcr

is the re ce nt app l ic ati on of ground-penetrating radar

time, thereby allowing c orrelation with other geo*

to stu d ies of sediment a ry structures at Grem S�llId

I lines.

logic(ll evi denc e of e nvironmental ch angc,

There can be litt l e doubt that stuelics of active

ol o rado , by Schenk and his co-workers,

and l ate Q uat e rnary aeolian scdimcnmry systems

It is now bccomi ll g increas in g l y clear that th e

vii

Prelace

viii

provide import;lI11 inform
Equally,

careful studies of thick aeolian sedi m cnt sequcnccs

in the t'Ock rccol'd. which allow a dcwilcd thl'cc­

dimcnsional picture of sand sea SlI'UCtUl'C to be

built up and IOI,s-rel'll' evolutionary trcl,ds to be identificd, provide

a

context within which the recent

;mel likcly fu tU1'c development of modern sand sens

eil!) be framed. Without doubt. this cross-fertilization of i"c�ls between 'modern' �lI1d ' �lIl cient ' in aeolinn sedimenlOlogy will continue to grc;1I effect.

We would l ike 1O thank all those who a�sistcd with the task of revicwing rhe mcliluscripts in accordal,ce

with the standards of Sedimentology. Speciallhanks

arc due to G. BlOUIn. S.O. F"ybcrgcl', .I.E. Mftl·zolf. M.L.

POrlcr. V,P. TchakCl'i�ln,

Butlcl'ficld, K, P't'l.!

Reading,

K. Glennie, G.

H. Tsoar lind D.S.G. "!'"homfts.

UK

N. LAN ASTI!H

Heno. Nevada.

USA

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Modern Aeolian Environments

Aeolian Sediments: Ancient and Modern Edited by K. Pye and N. Lancaster © 1993 The International Association of Sedimentologists ISBN: 978-0-632-03544-1

SPI.:C. Pllb/�' 111(. Ass. SedimCllt. ( 1 �93) 16,3-11

Particle dislodgement from a flat sand bed by wind: a re-analysis of' Willetts & Rice's data B.I.

WILL

TTS (/1/(/ I.K.

M

WAN

Deparrmellf of Ellgi/leering, Ulliversiry of Aberdeell, Killg's College, Aberdeell 11 /39 2UE, UK

AIlSTRACT A number of lIumerical simulmiolls of aeolian Sflhation have been (,."Onstructed in the last few years. each rC(luiring illdepelldent checks

10

ensure its validity. The object of this paper is to dell10llSll'llie

comp.uibililY between data cll!culntcd by onc of Illesc saltation models (McEwan & Willetts, 1991) rind cxperimcntully derived data frolll lracer gl'ain c..-. :perimcllls. The cxpCriml!IlLS arc disclissed wilh rcfci'lmcc to two n�lIncrical simulatiolls. Finnl}'. thc depiction or dyed gJ'ains from ,) coloul'cd strip is modellcd, cllilbling di);lodgemcnl ratcs

10

be calculated. This simulation j)j

�l

rcworking of dislodgemellt

dalt) previously publishcd by Willclls & Ric..:c (1988); till impor1tlnt C01ll1)Qllcnt ill this �c\"or'king is an exponential reptation length distribution derivcd from the !;altlltion Illodel of McEwan & WiIlCl!S

(19�1). Iinportill'ltly. thc rcvised values uf dislodgc..:I1lClll rute co1culilLCd show closer agrccmclil wiLh other published work (Anderson. 1986; Jensen & Sorensen, 1986: Williams el al., 1990). Secondly. the progrcss of the coloured grains IOwaI'd

!l crccp trap placed downwind of the coloured strip is modelled,

again using an c)(cursion length clistr'ibulion <':IJh;uhllcc1 by the saltation modcl. A l'caSOl1flb1c matc..:h is found between the calculated and cxpcrimctlwlly measured grain arriv'll CUI'VCS.

INTROOUCTION

grain si.w experil1lentally, so the 'spl
Recent advances in the lInden,tnnding of aeolian

used to portray the erfects of collision in numcrical

transport have clarified the role of intcrMgrain colM lision and. in gcnel'al terms. of the change induced

models cont tl in nO inform9tiOll about grain size,

1991). The conspicuous consequence of this change

lent considerable confidence ro physicnl irltct'p"ct­

by SflitatiOll in the ncm-bed wind (Anderson er iff . .

It can be argued that nUlllerical modell ing , having

5

years , is On the POilll of

is lhat trnllspoJ'lecl grains of compact shape at wind

(\lions during the last

speeds above Ihreshold are mobilized predominantly

outst'rippillg the observational base on which

by saltating grains colliding wilh the bed (impact

depends. There is nn ur'gcnt nced for confirmation

iI

dislodgemcnt), while direct dislodgement by the

by obscrvntion thut the equilibrium rates of disM

wind plays a minor role. Numerical modcls incor­

lodgement. the excursion Icngth distribution of

porating calculated trajectories,

trealM

dislodged grains
mCnn; of collisioll and elementary nuid meclUlllics

arrived at by the models arC renlistic. Moreover,

statistical

of the interaction between saltHlillg grains and

the library of data availa bl e is inadequate for the

the wind have demonstrated the attainment of a

purpose of elucidclling the intlucncc on the mmsport

transpol't' ['ate in equilibrium with rhe driving wind

process of thc distribution of grain sizes presenr in

because of the modification of the b oundary layer

the parcTll (bed) miltcrial. Since surface resorling is

induccd by the load of transported grains (Werner.

associated with rippling. ilild since both arc universill

1 99 1).

quantify the role of size distribution anc! perhaps

1990; A,)derson & Haff, 1991 � McEwan

& Willetts .

features of aeolian activity, it is clearly impOl'lant

The cnlcul;Hion has bccn made only for

\0 \0

material or uniform gr(lin si�e. because the ejecta

dcvelop a generation of models which incorporatc a

produced by c oll isio n have not been idclltillcd by

hypothesis about its role. The existing datu have

Aeolian Sediments: Ancient and Modern Edited by K. Pye and N. Lancaster © 1993 The International Association of Sedimentologists ISBN: 978-0-632-03544-1

3

8.8. Willew' alld I. K. McEw11ll

4

been acq uire d with grem difficulty. and acquiring

bUlion arc k nown. It i

reasona b le to suppose t h a t

both o f t'hcse will be di fferent for di fferc ill size

the necessaril y more detailed observations which arc now requi re d will be even Illore difficuh. Therefore

fractions in the populntion, sO equrllion

it seems likely that e vidence will be accumuhllcd of

be evaluated fraction by frac t ion, If

those details which can be observed and have a n

disti nguished ,

implicit bearing o n the maLlcr, ral her than of those fI, =

i n resolvin g u ncerta i n lY. The p resent study reworks grain dislodgement data first shown in Willetts & Rice

,,-41

IVdx

ciA

(2)

,1'-0

where i re present s the fracl i on CQuntCI'.

(1988). Moreove r,

Not only the ll'anSpOI'l rate. but' also the !mns­

it introduces previo usly u np ubl i shed daHl (obtained

poned load and i ts distribution, depend on dis­

f!'Olll lhe same sludy) 011 the mean progl'css velocity

of grains. A reconciliation is sought between the

lodgcmclll rate and excursion length distribution.

two data sets. using an estimate of path l ength

A nderson (1987) has demonstrated the influencc

distribution derived from a numerical model of the saltation cloud (McEwan & Wi l le tts .

i_I

( I) should

fract ions al'c

�.-),,,,,,, ,1'.),

2: f f II

which. were they attainable. would be most e ffecti ve

/I

of excursion length dis tr i but i on on rippl c gmwth,

It is <1 straightforward i nfc ren ce from his argument

1991). The

differences

data eame from wi nd- tunnel experiments lIsing a

that

qUilnz dune sand with a n a t ural size distribu tion

(Fig,

t); the sa lliHioll model employs uniform grai n s

d i ffere nt size fractions will rcsult in differential surfacc sorting a l o ng the ripple wavclength. Because

If r is the dislodgement rate pCI' unit area and

justified va lues can be assi gned to the two vari n bl cs

time, and p)" the probabil i ty thaL a dislodged grai n

in d iscussion and simulation of the transport p roccss .

of the modal size of this distribution.

of this

will have excursion l e ngt h A.. then the tra nspor l rate.

((Iii of grains i n thus:

n

unifo rm

flow field

=

ff

),,-0.,'-11

disu'ibutions

for

pcrvm:.;ivc i nnucnce, it is impOl'I;,HH Ihm well

mation about the two parameters. Jcnsen & Sorense n

(1986) used estimated values of dislodgcmcnt ra te .

1',

PAl' dx cI)'

such

There Me a sm
can be e x pressed

).."",.t'-)" If,

betwcen

and IHunch vclocity in a detai l ed simulation of

the wind-tunnel expe ri m ents of W i ll iams

(I)

(L964).

Thc estimates were m odi fi ed by tl'i:.ll until reason­ able

where x is dis(;)nce mc..lsured downwind,

agrcement

was

achieved

with

Williams's

observations or nux pl'Ofile. Ande rson

(1986) al so

Thus the transport ratc can bc determined if the

explorcd dislodgement rate by estimating the valuc

dislodgement rate and the e xcursion l e ngth distri -

I'equired to render saltHtion layer calculalions com-

35

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20

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...

� �

'"

0 0

'"

0 � N

2

N

-

N

0

'" -

0

�

Grain size (,um)

3

(¢I

Fig. I. Size dislribution of the sand and idclllificlllioll of the coarse. mcdium (inc! fine fractions,

PaNicle distodgemelll from

p.uible wilh observed tnlnspOrt rates, Willetts & Rice ( \ 988) mndc dil'ect obscrvations of t he de­ piction rate of dyed grains rrom a pre-laid strip and estimated the dislodgement rale from the observed depletion rate. The estimation procedure involved an assumption about the distribution of cxcursion length: the distribution was assumed to be linear, very short excursions being thc mode. For values of shear velocity, U"" between threshold and SO cm s I , the Jensen & Sorenscn and thc Witlclts & Rice cstimatcs arc of thc same order of m(1gnitude: the Anderson values of dislodgemenL rate are an order smaller. Williams el al. ( 1 990) investigatcd rates of aerodynamic elltft.linment from n{lrrow transverse strips of loose grains placed ;Il three positions up to 130 cl11 from the leading edge of a Rat plate which had been roughened by the attachment of idclllic.iI grains. They fOUllet that aerOdynamic dislodgement r:He decreased with distance from the leading edge of the nut plnte and concluded thaI this was due to Un incrci.\sing skewness in the instantaneous shear stress distribution. resulting in a lower frequency of events in which the instantaneous shear stress was grel:H er than the threshold shear stress for the secli­ ment. Moreover Williams el lIl. found aerodynamic dislodgement rates an order of magnitude higher lhnn thc impact dislodgemenr rales found by Willetts & Rice ( 1 988). They suggested that t h is apparently paradoxic"l result was caused by two ractors: firstly, thm replenishment in the experiments or Willcns & Rice ( 1 988) caused the impact dislodgement nile to be underestimated; and secondly, that the hetero­ geneous size distribution in the bed used by Willelts & Rice suppressed dislodgement. This paper will rework Ihe original data or Willetts & Rice ( I Y88) using a revised excursion length distributi n calcu­ lated by the saltation model of Me wHn & Willetts ( 1 991) to recalculate the i nfluence of replenishment. '110 present generation of sHilation models provide further estimates of dislodgement rate, Anderson & Harr (199 1 ) calculme a dislOdgement rate or 1 000 gmins cm -2 s- 1 for 250 �lin grains a t U" SOcm S - I . Sorensen ( 199 1) calculates the dislodgement rate to be 1540 grHins CI11 -2 S- 1 for 300�lm grains 1.1 I the same wind speed while the saltation model o f McEwan & Willetts (199 1 ) calculates the dislodge­ ment raLC lo bc 560 grains clll-l s l at U. = 50 CIll S I for 300 fAlll grail'S. These calculated values of impact dislodgement nUc nrc broadly consistent and arc tlpproximt.ltely an order of magnitude larger than those cstimated by Willetts & Rice ( 1 988). This paper will rework the dam of Willetts & =

(I flat

sOlld hed

5

Rice ( \ 988) usillg a distribution of excursion length revised by reference to a numerical model of' t'he tr
E X P E R I M E N T A L I'R O C E D U R E A N D R E S U LTS

Experiments were performed in a wincl-tunnel of cross-section 500 x 500 111111 <'Incl lcnglh 1 0 m, Air was blown along the lUnnel 'Inel, ncar the upwind end, was seeded with sane! released into it tit u few cen­ timetres above the bed. Also at the upwind end of the tunnel a variable porosity grid was used to prematurely thicken the boundary layer on lhe tunnel floor. The urrangcment is reported in more detail in an earlier paper (Phillips & Willetts, 1Y79). The experiments discussed here arc t hose in Willetts & Rice (1988). In t hese experiments the whole of the wind-tunncl floor was covered to a depth of 1 0 111111 with a predominantly quartz sand obtained from local sand dunes. Thc size distri­ bution, obtained by sieving, is shown in Fig. I . which also indicates three fractions, nominated 'coarse', 'medium' (lnd 'finc'. Sand taken from this population was dyed, " s a means of idcntification in observations of gmin movement. A thin cold waleI' dye was uscd which, it W(lS considered, would not measurably alrer the grain properties. The sand was separated illto the thI'ce indicated fractions, each of which wus then dyed u different colour. The coloured fractions were then remixed in the proportions found in the parent s;uld (22.2(Yo cmlrse, 49.8% medium and 28.0% fine by weight), This coloured sand was then spread over the IOcm of uncoloured sand to a thickness of approximately one grain in a straight transverse strip situated 6 III from the upwind end of the tunnel) spanning the tunnel width, anti 100 mill in extent i n the flow dircctioll (Fig, 2). The intention WilS thm, in this strip, each small bed area should contain coloured gmins. and no uncoloured ones should be visible in ..I plan view of the strip, A camern mouilleci :,bove the tunnel roof W(lS focused on all �'I'C,I of Ihe strip Ilem ilS upwind edge

6

0.8. Willetts and I. K. McEwan

(ount ar ea tunnel cen tre -

l i ne

�

w i n d d i re c t i o n

I 100mm

11Zcm

coloured str i p

bed load trap

Fi�. 2 . The designoted uren for counting I'clati ...c to the p l nccd st ri p o r coloured grai ns
and on the centre line of the tunnel noo r . I r was lI sed to "Ike colollred slide pholOgrHphs before the S!ilrI of each experiment and
The rcsults 1'01' the coal'se fr�lclion are sUlllmarized in Figs 4 and 5 . ( De pict io n rates for medium and fine fl'actions for the same experiments lIrc givcn in Willetts & Rice ( 1 988).) Figure 5 shows that the largest number of gnlins Cilier the trap at U.. = 39 cm s- l . Moreover, by coincidence, there were fcwer grains prcsent On the t racer strip at V. ;: 39 cm s i rhan at thc other shear velocities (sec 'able I , Willelts & Rice, 1988). The prescnt authors ae! VrtI1CC the following reasoning for lhis result. The depiction curves for the coloured strip show that ::lI low shear velocities somc coloured gn1ins rcmnined on thc strip after 90s. This suggests a relatively long residence time 011 the strip and, by inference, ;, slow progression IOwards the bed­ loud trap located downwind, Thus the sl11all cmch I of grHins made til U. 24 em S- (see Fig. 5) was expected. As the shear velocity is increased rhe rcsidence time (all the strip) is decreased and more grains reach the trap during the pcrioe! of the cxper­ iment. However, it is plausible that at the highest shcar velocity many Inore coarse grains �Ire entering successive saltation, participating ill longer hops. and thus pass over the tmp. Note thaI although there are fewer grHins caught in the bcd-load IraI' m V... 48 em S- I th a n at U"" = 39 cI11 5- 1 , those grains tlHl1' nrc caught 1l
=

=

Particle disiodgelllem from a jllll sand bed

3mm

A

7

��.IO�)e of sand langle of repose remains same after r u n l

L - ---, !...------- ---r .- Sand Sand

10mm

Tunnel base

18mm

bed level

i I

50mm

I FI------------------ --- � 3mm

�

8

��,

Fig. J. (A) Sketch o f the bcd-load tl'llp without the colleetol' box. (13) A sect i o n showillg the II':JP in relation 10 bed level

.

Dislodgement rate

I t can readily be shown ( Wi l le t ts & Rice, 1988) that t he net rate of removal of coloured grains from a

small area at a distance x from the upwind edge of
dt

-

Ill' ,I'

J

f"�,,,

kNX.I

of coloured grains from Ihe population between the upwind edge of the coloured strip and .\', The effect of t his tenn . as its form im pl ies is influenced by Ihe excursion length distribution.

.\'

NUMERICAL S I M ULATIONS

=

300mm

U

.

-dN" ,

3mm

)..0

dN

p , - (.,'

dl

- ).)1 d),

(3 )

Here N,� ., is the surviving number of grains at position x al1(1 ti m e I, k is Ihe dislodgement rate time constant. A is cxcursioll le n g t h having maximum value Anl 1lx. and /h is defincd as above. The lasl terlll i n equation (3) represcnts replenishment .11 posi t i o n ,

There is no secure evidcllce as to the form of this distribution. W i l letts & Ricc ( 1 988) considered following Anderson ( 1 987) and lIsing a gamma dis· lribution to represent the distribution of excursion lengths. HOWCVCI', t hey believed that vcry shon excursions werc much morc commOn than the gammn distribution would indicate und used in­ stend a trinngular distribution in which very short excursions were the mode. There remains considerable doubt about both the £omin dislodgement nHC. and the excursion length distribution for a given grain population and wind condit ion. I lowevcl'. nUlllerical Illodels

8.8. Willett.\' and I. K. McEwatl

8 a.

'.5'" 100 90

Coarse grains

c: 0

Cl c: c:

'n; E i!! '"

c:

'§

Cl

"0 �

-

� 0

(; u

0

1l. .,

�

c:

� u -

� Il.

( 1 99 1 ) is s h ow n in Fig. 6. The number of very short excUI's i o n s is so much larger than was assuIl1cd in earlier i nvestigations that doubt is cast on the significancc o f the replenishment tcrms in equalion (3) in thc determinations of dislodgCIllCllt made in WiliellS & Rice ( 1988), We have recalculated dis-

. U* )C U* Q U* II U*

80

70 60 50 40

24 em S-1 32 em S-1 39 em $-1 = 48 em S- 1

=

=

=

, •

30

20 10

•

, .

,

-" '" -"

,

'b"-:: ' ��-9--<>-L� '=-' ''=--:90:c ' 0 L-� 1 0-"-,20 30 40 , ..,;,, 50-"-,60 7 0 '-::' 80

o

Q.

Time elapsed (sl

Fig.

4. The depiction of the coloured strip for the coarse fraction at four V. values. rrom Wi l le ns & Rice ( 1988).

of the equilibrium saltation layer which have n ow become available (Werner, 1990; A nde rson & I-Inrr. 1 99 1 : McEwan & W i l letts. 199 1 ) providc values. albeit su rrog,ltc ones, for these variables. A distri­ bution of excursion length (or dislodged gnlins genermcd by the model of McEwnn & Willcll�

80 X(cml

o

Fig. 6. Excursion length distribution for ejectcd grains gCl1crmcd by the sa l UlI io ll model ;1I U. - 30 c m s - ' .

80 64

/

/'

o w

-" 32 e

/'

�

z

16 ./

/'

/

/'

U.

U. - U. ---

=

48 cm s - '

=

32 cm s - '

=

24 cm s - '

O +-���----��=-������� o

20

40 60 Time (sl

80

100

Fig. 5. The urrivul of the coan;c fractions nt lhe bcd-load trap :It four U. volues. Note that lhe cumuli'l i ve number of collected graills is shown.

160

Punicle dislodgement from a JIM sand bed l odge me n t nHCS using a discrctizcd fOfm of eq u a t ion

(3),

nne! emI'l y in g t h is mode l led e xcurs ion l en gth

9

At this point, we have an excu rs ion length distri­

bution nnd

B

revised eSlimate of dislodgement

distribution, arriving at values which are pl ottcd in

rate which , toge t her , make it poss i b le to trac k ,

by the sa l "' ti on

wind-tunnel. Thus�

7 together with d is lodge m e n t rates calculated model or M c Ewan & Willetts ( 199 1 ) . The exponent i n the rchll io nshi p between dislodge­ Fig.

men t fate and s he a f velocity is 2.6. This is s ubject to

n good deal of uncertainlY because of the l i m i ted

data: t he corresponding exponent' for the dis loclgc­

mcnt ra tc intcl'Ilal to t he saltation model is also 2.6.

probabilistically, the progress of grains a l on g the ,I

s i mulation of the observations

of coloured grains co ll ected in the trap can

iltte m ptcd .

Grain

be

progress towurds the trap

Thc vnlucs of di s lodgcme nt ratc arc mllch highcr

The simulnt ioll of grain progrcss from t h e coloured

( 1988)

strip to t he trap is re port ed for the coarse fract ion

because the excursion Icngth distribution assumed

only. The calculation ndvanccs in I s sleps. rem apping

in that study caused rcplenishment to be under­

grain position at

t h a n t hose estimated by Willetts & Rice

estimated, as has been suggcst ed by W il l iams

( 1990) and Sorensen ( 1 99 1 ) .

el lli.

Howeve r , the ex per­

eac h step. At

e ach step, each grain

is a ssigned a random number which dete rmi nes

whether it is to move or not; if it does move, then it

imcllial values of dislodgemellt ilre still lower than

is a l locfltcd nil excursion length in accordance with

those calculatcd by the sa l tati o n model. The calcu­

the

liHCd v
Fig. 8. This excursion length distribution is based 011 the full distribution of sa11mion path

300 �ll11 un iform

Sllnd whe reas

the cxperimelltal v<'l l ucs arc for a well graded n
1).

This Illay well sli pport t h e observfltion

of Williams (:1 "I. ( 1 990) that d isl odgemen t fiHes arc likcly to be less in beds

or heterogeneous grai n

size

because or i ncre�,scd shellering. shape varimion,

calculated distribution

s hown

of

excursion

lengths

ill

Icngths genera ted by a saltation model

W i l letts, 1 99 1

)

( M c Ewa n &

,md hence it illcorpol'a te s Ihe distri.

bution shown i n Fig. 6. Grnins ma k i ng a n excursion

of 27 cm or 1110re were assum ed to cntel' a seq ue nce

th res h old ranges and more complcx SUPI 0 rt geo­

of repeated sa hat io ns and to be 10S1 1O the calculatio n .

mcny. Th u s the need to dcve l op models or saitHtion

The figure or 27cm is nrbitri.lry, but thc assumption

incorporming Ill ulliple grain size is emphasized.

accor ds with the ge ne ra l observations of Ts u chiy n &

'",1.00

"

20

30

1.0

Shetlf veloclw (em .- ' )

60

"

Fig. 7. Dislodgement ratc showll llgainst shcnr vc locity: ( + ) dcl'i\'cd from IracX:r cxpcrimclll; (0) clJ1cutatcci from Sall
o

1

4

6 �I(ml

a

10

11

Fig. 8. The excursion lensth distribution for the full grain popu la t ion at U. - 48cm s I .

13. O. Willetts al/(1 I. K. MCClIIllll

10

et al. ( 1 986) and the & Haff ( 1 99 1 ) . Results of the simulalion arc s how n i n Fig. 9 for t he experiment co n ducted at U. 48 em S- I ,

Kawat" ( 1 972)

and Mitha

impact simulations of Anderson

�

saltation

models

incoq)orating ll1ult i ple grain size

is emph asized . Now m e,lnS

th m transport rates nrc be i ng calculated by of models which simulate the physics of the

tra nsport process. it is necessary to establish control by checks on the rate at which subprocesses proceed. SUMMARY

There i s a dearth of competent dnHl for such checks.

A N D CONCLUSIONS

This study has sought to check the mutual con· !listeney of a cal c u lat e d distribution of excursioll

The reclliculation o f dislodgement rates from rhe data of W i l letts & Rice ( 1 988) using a revised esti­ mate of the excursion length distribution cc:a1culmed by t he saitation 1110del of McEwan & Willetts ( 1991)

lengths with observed shifts of location of a popu·

results in

i m proved

agreement with

previously

published dislodgement data (Anderson, 1986; Jen sen & So re nse n, 1 986: Williams el al. . \990). Moreover. t h ere is sOl11e Hgrccment between the experimental results and the snltalion model of McEwan & Willetts ( 199 1 ) and t h e forl11 of the rel;:uiol1ship be t wee n dislodgement ra te and shear velocity.

However,

d i fferences

remain

between

magni tudes of d i slodgcm e n t rale fou n d experimen­

lation of colour�Wggcd gn.l ins. The overall success of th e progress is i mpressi ve (Fig.

simulation of grain 9). However. there is

more than one combination of the assumed excursion length distribution and intcl'prctation of the loss rate frem the coloured s tr ip ( Figs 4 nnd 5) which wo u ld give good results. There fo re internal checks

tlrc important to supplement the check on the finished

prediction

of progress

to t h e t rap .

One such check is !hat the delay before grains start mrivillg a t the trap is fOl'eC�lSI reasonably cor· recl ly by the calculation based 011

d i slodgemc nt rates found i n the hHtcr !ll u cl y may

rhe distribution 8). This. togcthe r with a co rrec tl y timed build-up to the full catch of coloured grnins, and the dependency of thc calculated dis­ lodgeme n t rate on the excursion length dist ri bution , provide quite st l'On£, evidence fo r the validity of

part

the simulmioll.

a uniform sizc sand. Thus the need to develop

the

tally by Will i am s el !II. models of Anderson &

( 1990) and Huff ( 1 99 1 )

by th e ,aitation

and

McEwan &

and those calculated frolll the exper­ imental results of Willetts & I ice ( 1988). The lower Willetts

( 1 99 1 )

in resu l t from the heterogeneous grain size bed used i n their experiments: the other results arc for

of excursion le ng t hs (Fig.

Thcl'e is. howeve r , n il

degree

instructive q ua li fi cat i on of 10 illustrtltcs

of success Hchieved. Figu re

40

30 � c

.�'" 0 �

"

!

20

/

/

I

,/

- -

.....

-

/

.0 E :> z

10

! 0

/

/

/

/

.....

20

40

Time lsecl

60

80

100

Fig. 9. The l.I rri va t or coa rsc grains al the bl.;d-Ioad trap III V• • 48cm s I . Thc so li d li nc indicutes Ihe simulalion rcsuhs unci lhe

dashed linc dcnotes the

cxperil11entally mcasured I.;ur"c.

II

Parficle dislodgemellt from a jim ,\'{Iml bed

20 16 '"

.: ..

�12 o -'

Fig. 10. TIle arrival of <.'Oarsc grains nl the bcd-load lrap :11 U. 32 ern 5- 1 . The clashed line i ndic:ncs the cxpcrilllcillally measured curve and the solid curves represcnt three scpnrntc simulnlions. the only di fference being in the sequence of I'anclom numbc� chosen in the cillculalion (sec Summary and conclusions).

Timelsec ) . 10Z

I h e outCome of repeated simulations of the sume experiment. The p rocedu re is identical; �III that is changed is thai the random number sequence from which the dislodgement is determined is entered at a di ffel'ent point. The ' n u merical e x pe riment ' hns .l different outcome for diffcrcill

/

/

r
numher

sequences. Since we believe thm Ihe number of coloured gntin movements in the simulations can­ rorms reasonably lO Il m u re , it seems evident th..\1 a

!l umber of physicul expcl'irncnts at the sallle wind

speed would also show di rferent results.

Considerable caution is still required. therefore.

in interpreting these results. However. we believe

thal the evidence is strong e no ugh to justiry rllrthcr

tracer experiments of rhe same general type, under­ IHkcn with the specit1c objective of providing datH

with which to check the soundness or Illll11eriC<.ll simulations of grain transport.

R E F E R E N e Il S ANI)I!KSON, R.S. ( 1 986) Erosion profiles due: to part icles entrained by wind: nppliellkSON, R.S. ( 1 987) A theorctieul model ror aeolian i m pact ripples. Sedilllellw/ogy 34, 943-956.

A1'I1)P.RS01'l. R,S. & HMP. P.K. ( 199 1 ) Wind rnoC\ificillion rind bed rcspollSC during sahation or SUlld i n air, Acla Mec:/ulII;C{1 SIJPP/, 1 , 2 1 -52.

ANlJllkSON. R.S .. SOI(ENSEN, M. & WILLHTI'S. 13.13. ( 199 1 ) A rcvic.:w O r reccnt progress in o u r under!;landing or

acolian scdill1clH l ransport. AcU/ Mec:/ulIIi<:t1 SlIp!,l, I . 1 -20. JI!NSeN. J.L. & SoItI:NSHN, M, ( 1 986) ESlilllatlon of some aeolian saltation trunsport parnmclcrs: a rc-nnnlysis or Williams' daHl. SellillwlI/ology 33, 547-558. McEwA1'I. 1 . K. & W I L I .I:TrS. 13.13. ( 199 1 ) Numerical model of the stlltmioll cloud. ACIlI Mec/umic(/ SII/lpl, I . 53-(>6, MITIIA, S . . TItAN, M.O . . WEItNI;J{, 13,1', & '·L\FfI. P.K, ( 1 986) The gnlil) l>cd impact process in aeolian s,lllalion, At·1tt /I1ec://{l/Iic(l 63. 263-278. PIII I.I_II'S. c.J . & WII.I.I!ITS. 13.13. ( 1 979) Predicting sand ()I/JI, deposition at POI'OUS rcnt.:cs. J. Waterways I)or/, O(,(!lI1I Div., Alii. Soc. ill, £II8S IOS(WW I ) . 1 5 -3 \ . SOItI!NSIJN. M . ( 199 1 ) All analytic model o r wind-blown SHod transport. ACflI Meclwllica Suppl. 1 , 67- 82. TSUCIIIYA. Y. & KAWATA. Y. ( 1 972) Chunlclcrislics of saltlltion of gnlills by wind. Proc. 13/ft lilt, o(lswl £118. COllf · 1 6 1 7 - 1 625. WekN�R, B.T. ( 1 990) A stcady·state model of wind blown sand tnlllsport, J, Oeol, 98. 1 - 17.

B.D. & RICE. M.A. ( 1988) Purtidc dislodge· ment fl'om .1 nUl sl1llcl bed by wind, Earth SUI!. Proc. Um"}: 1 3. 7 1 7-728. WIt.I.IAMS, G. ( 1 964) SOllie ilspects or the eolian slilimion

WII.Llrns.

loads. Seliill1ell1ology 3. 257-287.

WILUM.IS. J.J . . BU'I'l'IlimEl.D. G , R . & CL\kK. D.O.

( 1 990)

Riltes of acroclynumie cllU'<"l illment in n developing boundary layer, SedimelltOlogy 37, 1039- 1048,

S{JCC

Pllbl.... Jill.

A....s. Sedimelll. ( 1993) 16. 13-21

Aeolian dyna mics on the windward slope of a reversing transverse dune, Alexandria coastal dunefield, South Africa J. R.

B U R K I N S H A W allli I . C .

R U ·1'

/lI,wiJIIJI' /01' COlls/al /(esellrc:". Depfll"ll1lelll of Geology. UlliI'ersilY of POri Elizaberh.

PO lJo", 1600,

POI"(

EIiZflbeth 6000. SO/III, IIfricfI

A B S T Il A CT

Few empirical rnca�urernents describing the intcr·relationship between wind shear. scdimCIlI /lux and dune shape havc becn reIXH"lcd. We compare the results from two of several dctniled field experiments conducted as pan of (l study of airflow on the windwl:\I'(t �:i1<,pe of a 7 m high reversing tn:lIlsvcrse eomanl clUIlC. Thc scnsonul reversal of the dune in responsc to oPl)Osing summcr nnd winter wind regimes provides an idenl opport unity 10 siudy the relationship between dUlle shupe ancl airflow dmructeristi(,.'S. The wind speed profile. erosion .lnd deposition nl tcs (HId values of surracc gmdielH were recorded along ,l scction line normul to the crest lille of the dune. Qur pnper deilh; �pccifically with wind :o:pccd measured al 6 c Ill above the surface. The two experimcnts were conclUl.:tcd 3 weeks apart Ilt the SHIrt ot' the summer wIlld season on the cast Onllk t>f the dUlle, Wind conditions were sirnilar but the differcnce in the erestul gcolllciry of the dune resulted in (,.'Olltrastillg cro�ional responses. Varintion ill sediment Oux c.ln be rchltco not only to th!,! absolute gradicnt of the dune surface but also to changes in gradient. We recognize three phases in the crosional response of the dune which nrc determined by cllange III the rate 01" cllIlIlgC of gradient. and which give 1111 ill�ight into the self�rcgllhltory rcitUionship between form and now. Erosion pins net liS a sensitive mcasure of variation in sheHr strcss on the dune surface. and could possibly be used in future shear :o:trcss determinatiOn once II data base of vmiubles rein ted to shenr :o:tress hus been lIcquircd.

I N T R O D U C TI O N made an allempt to rc h.l te sund t ransport LO wind speed andlor d i re ct io n (Tsoar. 1 983; Lancaster.

The intrusion of an aeolian bedform into the
1 985: Livingslone,

now 011 t he upstream sidc of t h e dune fOI'I11. The

extenl of

the i n ll ue nce of t he fmlll

t n.ll1sve rse dune dy· e xpe ri men t cxn m i ning aerodYl1 l.1l11ics and sand t ra n s po n on tl 1 III high lnms ve rsc coastal dUlle ( Hcsp e/ til 1 989)� variation namics

the sclf·regultllO l'Y response of aeolian bedforms to the

compressiOll

of '-' i rtlow streamlines have yel

chan ges

so far is an

i n sand tra nsport' rates w..tS related to varhHioll in

Variation in sed i me n t flux on the w i ndward sl o pe

and

puh lis h cd

..

to be cvallwted. occurs bccause

1 986).

Thc most detailed study of

on the now a nd

of ch a nges

wind ve l oci t y .

in surface shear st ress ,

b u t the shape of the dune was not takcn into accoul\I. Bagno ld ( 1 94 1 ) rclmcd t he rate of snll d removal.

in tile gradicnt and o rienta t i o n

s l ope rc1:l Iive to the ollCOm i llg wind

of rhe (H ow;lrd eJ al.,

1 978 : Lai & Wu,

1 978: Walson, 1987). Fewcmpirical

measurements

descri bing

(he

(lQ/d,\', to the langent of the angle of inclination of

t he d\lJ1c slope <\) : ,

inler·rclationship

betwee n wind shear st ress. sediment flux and d U lle shape have been reported. H own rd e/ til. ( 1978) successfu ll y related sand IranSpOri 10 wind measure­ men t s on a bell'chan dunc in a study supplclllcllied by wind-tunnel obsCl'v
clQ

- oc y t a n cp elr

w h ere y i s the s pe ci fic wei gh t of Si.lIH.I in bu l k . This

13

is

.I.I?

14

Burkillshaw alld I.

a ge o metrica l relationship bu sed on dune shape, and indicates that there is neither erosion nor deposition al the dune crest, a n d that the ra te of re mov al is greatest where the local slope is steepest, As Bagnold himself recognized (p. 20 I ) . the C(l lI Hti oll is ap­ propriate for preserving the curva t u re o f the sloss sl o pe, but neglects the variation of the wind fo rce along the dune sU I'face . Sand transport rates arc determined by surface shear stress, as measured by shear velocity. I/*! which for wind blowing over
.

Rust

Walson ( 1 �87. p. 516) advocated ,ha, 'since variations in shear stress are rclfHcd to chnngcs in now velocity and pressure gradient, future work should
---'( "- ", " '} � , 5.751og(llk'}

where .z is the height at which v is measured. Bagllold ( 1 94 1 ) found thal for a n;.\lurally graded sand, \II ( threshold velocity) is 4 m S- I , and suggested I hm OJ va l ue of I cm be assigned to k ' , which C
'-./"""""" ,, Alvor

- lJird 1$

ALGOA BAY

.\lInm.,

WIND

lor

20 k m � _ _ O'- _

Ihe

ROSE tlunellotd

•• ,1 ",I"d.

I'i/.!. I. Loc:llity

lllap of the Alexandria cll;lswl duncficld i ncl ud i ng n stylized wind rose for Ihc dUllclicid. (Moclilled from IIIcllbcrgcr & RUM. 1988.)

A eolian dy"amic:.\· of a reversing Irtlllsl'erse (Julie

IS

Fig. 2 , Vertical
km strc tch o f thc smull reversing IrtlllSVerSC dunes i H the Westcrn edge o f the dUIlCficld, January 1989. '11c dunes arc ISO-300m in length and dUlle SI)(ici ng varies from 80 to 130m. (Photograph: \,·lcrncr K. I lIcnbcrgcr.)

response which correspond to chnnges in the rate of change of gradicnt of the windward slope.

M ET H ODS

We measured airflow pl'Ofiles 011 the windward slope along a number of t r�lI1svcrse scction lines nonnal to the dune crest; in this paper we refer exclusively 10 t he data for aile specific section linc, known as SL60. Two anemometer arrays, each consisrillg of fOllr micro·uncll1()ll1etcrs mounted at avenlge heights of 6 cl11. 20cm. 60crn and 140 cIll above the dune surface. were deployed; one array was stationed permanently tit the crest. while the othcr wns de­ ployed at different locations
I n this paper. we provide data for the full measurcd wind speed profile but Ollr discussion focliscs 011 the dOI;l recorded at 6 em above the surface. We plall to denl with the e n t i re measured wind speed profile in another paper. For a variety of technical reasons, the ilnem· ometers were not rigged at consistent heights
16

j . R . Burkinslw).V {mel /. C. Rust hIIlg"'1 In motrell

R E S U LTS

14

Wind SI)ccd dahl

"

cOlllpilnllive purposes wind spee d data at the various measuring stations arc normalized wi1h respect ro the wincl speed measured at 140cm h e ig h t nbovc the du ne crest ( I he lOp anemometer of the
For

17 Novelliber 1 988

'0 8

wind

crest

.....

22m

'2m

8

2

waSI

eaSt

\J

6m

\l.

ba5e

,a.5m .. 9__--...

SLeo

'ii'

o� � -�--�--�--� -� � --" o 5 m 10 20 � 30 30 40 horlzontSI distance In metres

The windward slope geometry of SL60 on 1 7 November 1988 (the beginning o f the mon i to ri n g session) shows rhe rounded nature of the crcst on rhm date (Fig. 3), Crcswl wind speed as measured

by the reference anemOnleter HI 22/SL60 a veraged a m S- I between 12:00 alld 1 4: 00 . and th en dropped off gradually to a value of I O.O m s- 1

speed of 1 3 . 1

by 16:00.

The SCI of wind specd dara (Table L), based On a l l

20 �l I1cmOmelcr sl�llions, i nd ic'ltcs thaI the wind speed measured (or interpolated) at 6 cm <.lbovc

the dune surface was fastest at m i d·slo pe (auemo· meIer 61 1 2/SL60). The ai rstream accelerated from 1 1 2 , O m s- LO 8 , l m s - as it moved from the base rowards Illid·slopc; this l'cpl'eselHs all il1crc("lsc of 40% of the wind speed n o r mn l ized rehll.ive to the crest a] wind :-;pced. A i rtlow decelerated by 1 3% between mid·s]opc and the cre st ( a i r speed decreased from 8. 1 m s I to 6. 1 III s I ). Assuming i.l con st a n t threshold value of 4 III S - I Table I . Wind speed data as mCIll:'urcd o n 1 7 Novcmber 1 9�8! figures lire velocity (m s- I)

"ig, . 3.

Wind ward slope geomctry of SL60, 17 Novembcr 1988. Opcn arrows ind iClltc the Stillion locmiollS or the

movable anemometer

at I em

height�

w i th i n 6 cIll of

mray.

calculated va l u es of the surface show a

shear velocity

p

cOI'J'cs onding

i ncren se on the lower slope from 0,37 111 s- al 6/61 SL60 to 0.91 m s-I ,)1 6!12/SL60, nnd a cOl'l'cspondillg clecrease 10 0 .47 01 S I ," the erCsl (Table I ) . 7 DecemlJcl'

1988

ReconSlrUClion of lhe windward slope geometry 3 wceks latcr Oil 7 December 1 988 shows I'hat thc cresl IHH.I ..Hhlincd �I triangular p ro f i le ns :l result of a re ln t i vc l y straight windwurcl slope flnel a sh a rp l y penkcd crest (Fig, 4). On lhis day the crcstnl wind speed averaged 1 3 .0 - 1 3 . 7 In s 1 Ht 1 47 cm he igh l over a 2 h l im e period (Table 2 ) .

figlll'CS in

pnrcm hcscs

rare sheor velocity

(In s ' ) ; olher

Anemomeler height (cm) Swtioll 22/SI..6(l I I :58- 14:(l4

6

20

60

1 40

vr..,r

13. 1 ( 0. 1 2 )

13.1

"

(0.47)

( 1 .47)

1O.5h

12.� (0.83)

16.5/SL6O 1 2 : 1 2 - 1 2:47

(0.67)

7.n

12. 1 ( I .7 1 )

12.3 (0.07)

1 4. 1 (0. 7 1 )

12.7

12/51.60 13:27- 14:W

8. l h (0.9 1 )

1 1 .2 ( 1 .(7)

1 1 .9 (0.25)

12.2 (0. 1 2 )

13.5

5.7h (0.37)

(0.9)

7,6 (0.2 1 )

7.9 (0. 1 2 )

11.1

2.6 (0.2)

3.7 (0.48)

4.6 (0.36)

10.0

('ISIB) 1 4 : 5 6 - 1 5:37 O/SI.60

1 6:07- 1 6: 2 1

(). l "

2.0'

7

Reference velocity me:isul'cd ,il 140cm ::JOOvc the crest. h I ruerpolmcd value.

It

17

Aeo/ial1 t/YlIlllllics of (I l'el '('I',\'iIiS (1"fI1l,\'lIerSe dl/J/e

2. Wind :o;pecd dut:1 us rncaSlII'cd on ligures nre \,elocity ( m s I )

T:tblc

7 Oc,-'Cmbcr

1988; ligurc� in parcnthcsc�

,'Ire sheur veloci ty ( m s I ) ; uthcl'

Anemometer height (em) 60

140

llrel

12h

3 40 1 . 1 (0.5 1 )

13.7

13.7

10.7 ( 1 .4)

1 2 , 1 1• (f). 5 1 )

13.1

(IUS)

11I. 1 ( 1 .43)

( 0. 47 )

I I AII

1>.7

�/SI..6() 15: 1 7- 15:45

().5h (0.56)

(0.77)

(0.33)

9.7

13.7

0/SI.60 16:04- 1 6 : 1 5

2.6

(11.26)

4.7" (0.47)

13.0

Still io n

6

20

2 1 /SI..60 14:3(,- 14:54

9.lh ( 1 . 13)

(0.97)

1 7/SL.60 1 4 :04- 1 4:24

6.5 (0.56)

13/SLc,o 14:3(,- 14:54

6.6"

�.8

3.4b

"

Reference velocity mc..,�;urcd ill 140 el11 above the crcs l .

I.

h I nterpolated \'u l ue.

helOh\ In mItre!! 14

" '0

wind

--+

17m

8m

13m '9 \l

2'm ..

IZ

bue , \l SL60 o �--�--�--��� 3' '0 o � � e ro � � horizontal distance In metre s

fig.

2 ) . A maximum shear ve l oci t y of I . 13 m s 1 was calculo.llcd within Clcm 01: the sUI'face in lhe crcs ta l area.

cresl

• •

wesl

east

4. Windward slope geometry of SL60 , 7 December

Erosion

pin and g,rudicnt dutu

For comparative purposes, the I'
1 988. Open arrows indicatc the station locmions of the mo\'oblc anemometer array.

17 /Vol'ember 1 988

The winclno\\' plHtcrn differed significttntly from the flow recorde d on 1 7 November. The wind speed nt a uniform height of 6cT1l above Ihc dune surface I showed a IlHiximUIll vn l u c of 9. 1 III S- at Ihe crest ( 2 1 /SL60): however, Ihe rate of acceleratioll fl'Olll ('he base of the slope lowards the eres! was not uniform. After Ihe initial Hcccleration of tht.: nir speed 011 the lower slope of t he dune from n va l u c of 2 . 6 111 ,- I a' O/SL60 (base of 'he dune) '0 a value of 6.5 m S - I at 8/SL60, �lir speed reillained Illore or less COllstalH in the middle 10 upper regions of the slope until 17/. L60. Rapid acceleration occurred between this stat ion and the crest. Shear velocity c
The erosion pi n daHl set is subdivided into two timc periods corresponding to the initial period of strong wind ( 1 1 :30- 1 4 :(KI) and 'he period of declining wind 'peed ( 14:00- 1 6:05) (Table 3, Fig. 5). The avcr<.lgc rmc of crosion (calculntcd over the initial pcriod of 1 50 min of steady wind) illcf'cased eightfold from O. l l11l11 l11in I a t thc dune base to I 0.8 111111 m i n- l11id�wny up the slope, beyond which the erosion rate decrctlscd to zcro, l:hanging to deposition of s• .Ind ill the flattencd ereslnl area. The I ra te of deposition at the brink was 1 .241ll1ll l11in a 10Iai th i ck ne ss of 25 c m of sand accumulating at the brink during the entire period of obsCrVtllion (270 min) (Fig. 5 ) . The split o f t h e data sct into two timc periods shows lhtll during t he second hnlf of the measuring session ( 1 4:00- 1 6:05) . when the wind speed was

j, I? IJllrkillshfllV amI I. .

18

200� m� '"� 'mt � "' � c ' __ - __ __ __ __ __ __ __ __ __ __ __ __ __ � , SL60 PI'lIlB$

decreasing. the n a t u re of t he i n tcnlClion between wi ndstream and dune surface did not cJHl nge, but the rate of erosion was less: by estimation. ilbout

half the pre v i o us rate. Deposi tion conlillucd i n

1

the c rcsl a l Phese

-'00 # 2oo

wind speed.

3

decrease in gradient from a value of 240 ctose to the

18 wlnclward stope dlstanCB In metres !all 11130-'4100

clUllC basc to (l v a l ue of 20.50 1 2 m upslope

( Fi g . 7,

Tab lc 3), Higher up the sl o pe . lhe g radient decreased morc rapidly by 3-40 pe r 2 III slope distance between 1 4/SL60 and 201 L60 as the dune rounded towards

_ '4,00-18:011

Fig. 5. Erosion pin dow as measured along SL60 on the wi ndward slope. 17 November 1988.

100

during t h e pcriod o f decreasing

At lhc Sl;.lrt of lhe measurcment session, the

,4

10

"lrca

smoothly cu rved windward slope showed a gl'f.1dual

4-�-t-�-t--'--t-�-t--;,,:--� e

Hils/

the c re st . The gradient decreased abr u p tly from

8,80 to 1 ,5° al (he crcst. The rounded shape of the

mlillmo,tOS

SL60

o

Phase

1

reduced gradient

sharp crest

'0

-loa

SL60

Phf;'lO$ 1

••

-200

Ph6se

2

.0

-,oo L-����� '" e a m 12 ,4 '0 18 ,g ro 21 22 23 o windward Slope distance In mot res

•

1:8 12100-17100

Phesa

:3

__ � � � � S 10 12 1" 10 18 20 22 24 slope distance In metres

o L� � � __ � � �-L � 0

"�ig. 6. Erosion pin dnla a� mcosurcd along SL60 on the windwurd slope, 12:00. 7 December 19 8.

:2:

e

Fig. 7. Gradient I1lC[lsurCmCnls made at thc cl'osioll pi ns. 1 1 :30, 17 November 1988. Arrows indicate inncction points. Tuble 3. Erosion pin nnd gl'l.Idicnt dulu monitored on the wi ndward slope or SL60. 17 November 1988: lIegl.ltivc vulues indicate crosion; pOsitive vnlucs indic;'rtc deposi t ion

Slope

d is tilllCe (m)/SL60

2 4

6 8 10 12 14 16 18 20

22 24

Sed. nux (mill)

1 1 :30- 14:00 - 17 -58 - 97 - 98 - 122 - 1 10 - 107 - 88 -2 1 -7 60 186

Slope (degrees)

1 1 :30

24 2 1 .5 20.5 18 15.4 12 8.8 1 .5 0.5

Sed. nux (m111)

Slope (degrees)

14:00-16:05

16:05

-13 -27 -27 -54 -45 - 52 - 40 - 17 18 32 60

23.5 22 20.5 19 15 13.5 10.5

7 5

19

Aeolian dYllamics of a reversillg trans\lerse dune upper slope was the product of st-rong unidirectional easterly winds d u ri n g t he pre v ious 2 days, By thc cnd of thc Il1c'lsuremcnl session, the gn\di­ cn! of the upper slope had steepened from less thHn 2° to 7° as a result of the accretion of sand in the

The average rate of erosion

(calculated over a pe rio d

6

I

- 19t - 1 35

8

10 l2

d une) to 0.6 m m m in- ' at 8/SL60 (lower mid-slope). E rosi on dropped off ra p id l y at 12/SL60 to 0.03 mm m in -

- 1 05 - 1 05

4

of 300 min or fairly steHdy wind speed) increased I rrom a rate of 0,03 mm min - at O/SL60 (base of the

16

-10 -30 -75

19

- 92

14

and then increased again towards t h e crest

or sU ll d was eroded during the entire 5 h period of observation; lhis I'cpresenls an a v erage ' rate of 0.83 m Ol Ill in- (Fig. 6). where 25 em

18

- 65

20

- 160 -250 -250 - 135

21

22

Whereas the windward slope appeared superfici;'lily

5.5 2 1 .5 22 22

9

- 40

2

23

Slope (degrees) 1 7 :00

12:00

l2:00-17:oo

0

December 1 988

S lope (degrees)

flux (mm)

Sed.

Slope

distoncc ( m )ISL60

c rest a l region (Table 3).

7

Tublc 4, Erosiol1 pin lind gl'adicilt dala monitored 011 the willdwnrd slope of SL60, 7 Decembe r 1988: negative vailies il1diclItc erosion: positive values indicate depOSition

19 22 22

22 22

19

19.5

15 13

17

19

16

22

l5.5 16.5

17

18

13

l4

t5

22 16

15

to be a regul a r inclined surf<'lce sloping up a t about

a si g nifica nt I'cduction in gradient was prese n t i n the u pper mid-slope (Fig. 8). The crestal zone also showed a reduction in gra d i e n t , but not nea rl y as marked as w;.\s the case 3 wec ks before, The general

22°, terminating in a Sharply triangular crest,

I N T E R I ' ll ETATION The data set reported here provides insight into the i nter-relationship between airflow response, 10c.ll

nature o f the windward

gradient measuremcnts, change in local gradient

southwesterlies which

l'i lo pc rcsulted from thc blew for 4 days Hbou t a

fll1d salld flux.

By the end of the measurement session the steep­

in ('he rapid acce leration of the wind speed rrom

wcek previously, ened

gradie n t in the crcstal regi on had decreased by

seve ral degrees, cOfl'csponding to thc erosion in t h i s region Crable 4).

A i rflow comprcssion

()11 17

Novem bc r rcsulted

the base of 'he dune to 12/SLGO at 6 cI11 above the su rface, with (I

corresponding increase

in shear

velocity, This is the region of maximum acceleration of the airflow (wind speed increased by 400/0 relative to thc

in

crcstal wind speed). The progressive increase

e rosion OVCI' this distance reflects a syste ma t ic

and rapid illcrease i n wind shcar strcss close to thc g rsl1lenl

20

surface. "rhe decreasc in the gradient of

I n 110grOO5

S L6':-

W
"

_ _ _ _

to those of

slo pe

conventional stoss sl pc,

Higher up the slope ucce lcration of the ai rflow

reCluce(:l gradient

closer to the surface diminishcd in sharp cresl

o L-����� o 6 8 10 12 14 16 18 20 22 2. slope distance In metres

mC
7 Decembe,' 1988.

respo n se

to 1:1

morc mpi d ch a n gc of gradient as the clulle roulided

thc cre s l . Rcduction of cOIl'tprcssion re­ lower shear stre:o:s cl ose to rhe surfuce, which is confirmed by lhe lecrease in erosion be­

towards

s ulted in tween

,

Fig. 8, Gradient


t he

high co m pa re d

14/SL60

and 1 8/SL60.

The notable decrease in upslope gradient from 8.8' at 20/S L60

to l .so at 22/SL60 resulted in a

marked reduction in wind speed between these two stations, The d i vergence of airflow

and red uced

shear Stress caused the OnSCt of deposition of sand at

the creSI'. Thus depOSition at lhe creSt can be rel�HC(1

.I. U. BlIl'kills/l(lw (lIId I, C.

20

to chn n gc of grn d i en l rather llwil absolute grad ie n t ns su ggested by Bagnold's formula, which p redicts the minimum sand removal in regions of low g ra d i ent . 011 7 Decembe r the acceleration of t he tlirflow against the lowe I' s lo pe of section line SL60 ( wh i ch had <.1 constant gra d ie n t of 22°) was reflected in the erosion lrctld� this i mplies a sufficient increase in shear strcss to pl'Ogrcss i vcl y illcrcilSC I he ra te of C I'OS i Oll On t he lower slope. As On 1 7 N ovembe r . the gr ad ien t of !'he l owe r slope was steepe r than Ihm of a stoss sl o pe produced under unidi rectional co n di l ion s. The ab r u p t decrease in the crosion !'ale a t 1 2 / SL60 corresponds t o a lack of acce le ra t ion of the flow mid-slope. This c ou l d be attributed to diver­ gence of the now and i nc i p i e n t separat ion ovcr the ch a n ge i n g rad ien t at 12/S L60, The low ra te of erosion be lween 14/SL60 and I S/SL60 could also be a t tr i b u te d to thc cont i nued reciucliol1 in grn d ie n t . The normalized wind speed i ncreased by 1 6% from 1 7/SL60 10 2 1 ISL61J al I h e crest clue 10 renewed comp ression of airnnw "ga i ns t the steeper crest, which resulted in i n cre ased crosion lOwards t h e crcst. The low rate o f e rosi o n at 1 8/SL60 could bc ascribed to i.l she lte ri ng effect induced by the ubrupt stee pe n i ng of the slope downwind at I YlSL60. Comparison of t he gr;.l dicn t values with the erosion pill data of 7 Deccmber shows that the maximull1 rate of erosion is associated wirh
SUMMARY AND

CONCLUSIONS

O n bo t h occasions the windward f"lce was under­ go i n g revcrsal, so t h a t the airnow response was const an t l y
change

the slope on 1 7 November wns such that

Rust

grad i e nt. and can be iden t i fi ed as illtlecrion po i nts in Fig. 7, Phase I is a region of !low acceleration co rrespo n di ng to the area of maximum co mpressio n on t h e lower sl ope , The rate of el'Os io ll increases over t h i s dista nce (Fig, 5)
by Ihc wind a l ters w i t h the nppl'Ooch

of the wi n d . Maximum compression will occur when the wind i:1 1:J I)rOtlchcs t h e w i n dW(l rd face of t he dune ,It 90° to I'he contour l i ne s, Bagnold' s ta nge nt re la t ionsh ip is val i d for a slo pe with an aerodynamic gra d i e n t . such that the cur· vmu l'c of the s lope is preserved with t he flclvnllcc of th� dUlle, but it does n ot hike into aceOUlH surface il'l'cgularilies even whcn the slo pt: is i n i.lpproximatc equilibri u lll wil h the prevai l i ng wind, Our resu l ts confirm that maximul1l s hear stress docs occur 011

Aeoliall

dynamics oj (j reversillg II'fIllSvef'se

Ihe steepest slope where maximum compression occurs, However, airflow response appea rs to be very sensitive to changes in gradient, and surface shear stress is affected by su rf�lce i rregularities. Our study dcmonstrates how erosion pins act as a rapid and sensitive measure of the response of the dune surface to changes i n sheHl' stress distriburi n ,

oastal M r A.T.

dUJle

21

Research , University Sayers. Depnrlmenl.

gincering, Univcrsity of

of Port

Elizabeth.

of M ec ha n ical En­

ape Town, enabled the

calibration of the anemometers, Werner I l lenbergcr

I'e..ldily supplied the technical cxpenise to get the

anemometer sys te ms arc

up

and running. for which we

1110st gratefu l .

I n contrast, wind speed measured a t 1 40cI11 above

the

surface does not reflect subtle changes of s h ea r

a wus evoked u n d er very similaJ' WiIH.1 co nd it i ons for what appeared

stress (li the surface, The two data sets rcve::11 t'h�lI tot a l ly

di ffe rent

erosional

response

supe rficially to be the S(lmc dune surfncc on two se pa rate The

occHsions. height of 6cm

above the

surface

for the

lowest anemometers was an arbitrary height. chosen as

�I

resul t of the limitations of OUI' equipment, How�

ever, wind speed measured at 6 c m above the SUI'� fa ce at five loca t i oll s

011 the windward s lope seems su cce ss fu l ly gene ra l ch a nges in shear wh i c h corres pond to those recorded by the

to reg iste r

S tress

erosion pins, Accurate and reliablc ll1eilsuremelll of

airHow

is

particularly difficult' in the field when attempting to

work close to the dune surface. A mOI'C acc u rate dctcrminntion of sh ea r SLress could be achieved w i t h a n array of p i tot tubes within 20cm o f t h e d u n e su rfnco; we h�l\,c �tnrted t o b u i l d suihlblc devices t o pursue this work, I t is, however. t he erosion pin data which yicld the finer resolution of shear stress

changes

on

the

dune

surface.

a nd in future it is

possible thai such simply obtained data could

used

be

to i n terpolate shear stress where grcldienr.

g ra i n size :In(i ot h e r st ress
fnctors re l : H i ng

10

crit i ca l shear

A C K N O W LlW C E M E N T S

of EnvirOllmelll Affairs. SQuth the project t h rough the I nst i t u te for

T h e Department Africa. fu n ded

R E F E R Il N C E S

U,\ON()I.J), R , A , ( 194 1 ) Tlte Pltysics of /)/OWII Sill1(1 and DeJert Dillies, Methuen. London, 265 PI'. H I:St', P,A.. I r.I.IlNIIIJROIIU, W , K RUST. I . . . McI..,\cHI.M
Aeo/itlll GeolllOl'/JllOlogy (Ed. Nickling. W , G , ) pp, 97- 1 1 2, Allen & Unwin. Boston, M U Ll.IOM ... . K , R , ( 1 988) Ve locity prolilcs measurcd on the w i ndward slope of ,; t['illlSVcrsc dune, £(lI'/h SIO): PrOC.

l.{///(I/. 13. 573-582.

TSOAI(, H, ( 1983) Dynamic processes. tiCl ing On II lon�i­ IUdinal sMd dUllC, ScdilllclilOiog)' 30, 567-57!o!, WATSON, A , ( 1 9ft?) Variations in wind velocity and sand transport 011 the windward nallk of desert S�llld dUlles, Discussion, SedillJelliology 34. S 1 1 - 520,

Spec. Pubis /111. A ...·s. S(!(limelll. ( 1 993) 16. 23-44

Late Quaternary development of coastal parabolic megadune complexes in northeastern Australia K . I' V E Pasigradllllie Research Imj/;If.lfe Jor Sedimelllology. UI/;vcrs;/y oJ Readillg. WhileklligiIl.I'. Readillg RG6

2AB.

UK

ABSTRACT Large coastal dUlleficlds o n the CQ�lst of northc<Jstern AuStralin displuy smuigraphic and morphological

evidence of 1.1 lOl lS period of s4ll1d acculnul"Hion during the Quaternary. Mony of the older dune ullilS nrc

highl)' weathcred .md dceply podzolized. although the p
i� presently avnilClble to be certnin about the number. liming. extent and causes of
different arens, However. the limited mdiocmbon. thennolumi nesccncc (TL) and urani um-series ugc daHl oVElilnblc suggest thilt SOllle neolirlil activit)' oecurl'ed during both high ancl lower stl.HlclS of sea level. There is good evidence thaI significant tram;grcssivc clune bu ildi ng activity was associaled with the carly

Holocene marine t rol1sgrcss ion . whel' coastol sediments were partinlly rewor'ked hUldwJI ·ds. Artel' sen level a l l < 1 ined approximately its pl'cscnt position around 6000 8 1>. s hore l i r l e erosion ceased ill1d \Vas replnccd by progradution in muny l\re�rS. leading to

n

reduction in sUlld supply rrolll the bench lInd

widespread dune siabilizalion. I n northern Qllcenslllnd stabili�1tion Illily ulsQ hrrve been encouraged b)' wetter conditions i n the mid-Holoccne. I n some areas inlund dunes have been rctlcliv;;Hed ilnd others

inil imed during thc lllter H ol oce ne following natural and IIlltlll'opogcnic dist urbance to Ihe vegetation.

I N T R O I) U

T I ON

Despite morc lhan a century of research. the factors

5 the nature of the su rround i n g and underlying

which determine the morphology or aeolian sand

lopogr!l phy:

accu lllu lat ions re ma i n poor ly understood. In part

6 cl i m a t ic and sea level changes; and 7 long-term patterns of tectonic u pl ift :and subsidence.

this is bee.luse there have been few field studies of wi ndt10w and sediment

M a n y of these factors are inter-dependent and

t rHnsport. and pnrtl y it

changes i n one lIl ay bring a bo ll t a complcx. fre­

reflects the diffic u l ty i n extrapo l at i ng from sl11(llI­ scale Hnd short-term studies to the scale of

whole dUlles and duncficlds which may lake dccades or

q ue ntl y non-lincar, morphological response. Despite

centuries to develop.

now avai h tb l c indic(lICS that I nl'ge bnrchuns. trans­

the possib l e complexities. however . the evidence ve rse dunes and dome dUlles arC th e p redom i nan t

In broad terms. the rorm and scale of aeolian

sand acc u m u la t i o ns arc likely to be dcterm i nc d by

forms which develop in arid

ve locity

va r i a bili t y :

distribution

with a h i gh ly

CHnl cross- wi nd . these forms may displa y asymmctry.

sand availability:

rcversi ng behaviour. superimposed bedforms with a

2 grai n size distribution:

3 willd

areas

u n idi rectional wind regime. Where there is a signifl­

seve n main factors:

and

different oricntalion or somc degree of sideways movement (see Pye & Tsoar, 1 990, for a more de�

directional

tailed d iscussio n ) .

4 vcgct;lIioll cover ;Ind g row t h characteristics: Aeolian Sediments: Ancient and Modern Edited by K. Pye and N. Lancaster © 1993 The International Association of Sedimentologists ISBN: 978-0-632-03544-1

23

In

m a rked l y acute b id i rectiona l

K. Pye

24

wind regi mes . l ineal' dunes of the seif type arc most like l y to develop, while in obtuse bimodal and 1l1ultimodal wind regimes , reve rsi ng, t ransverse and star dUlles nrc t he most common f0n11S. III h um id areas with rel a t ivel y dense vcgc tH t i on cover, formation of e lon ga te parubolic dUlles is fnvoured by a unidirectional effective wind regi m e , while i n llrcas of bimodal or com ple x wind regimes parabolic dUlles arc likely to have a low ICllglh:widlh ratio and may be asymmetrical or d igitate i n fo r m . Contrary 1'0 Wi lson's ( 1 972) s u ggest io n. grain size docs not appeal' to exe rc ise :1 IllHjor con t rol 011 the m o rphology (tllcl size of dunes, with the exception of zibal' for� n1tllioll. Sand fl va i l ub i l ity exercises some control on clune morphology. but does not tllways show a direct relmionship la the morphology. size and spaci n g of individual dunes within an area, For example. although barchHns tend to form i n un vegetated areas when sand supply is re l ati ve ly restricted. a n d t ransversc ridges dominatc when sand i s relatively abundant, individual barchans can attain mc gad u nc proportions even when sand is scarce, as indicated by the equivnlent sand thickness ( EST) in an area, In many sand sens the I nrges t , most w ide ly spnccd dunes OCClII' <1l t he gre.Hcst distance from the source due to growth of the bedforms as rhey move dOWlla wincl. 01' to long-term accumulation of sand as suc­ cessive generations of dunes beco me s u pe ri m posed within a topographically or c l i mmically cOlltl'OlIcd si:lnd sin k . This paper examines some of the factors w hich ha ve i n A uc nced th e dcve lop m e nt . form, oricllWlion and st ru ctu re of pHrabolic d u nefields Hlong the const of north east Austral i a . Large coastal sand masses have fonned in sOllthern Ouecnsland as "I res u l t of lo ng-te rm ,lccu mulatiOIl of !)Hlld transpo r ted north­ wards
i cl i rccti o ll n l wincl regimc. Many of the OuccnslHncl dunes nrc 1110re than 200m high and several kilometres in length . The excepti ona l size of these nH�g�l dunes reReels the combined effe cts of high wind encrgy, abundant stlnd supply provided by landwa rd l'ew01'king of elongate,

ref-le c ti ng

a

1110re

un

salld dUl'ing periods of changing sea level, and t he resistance c reat ed by the re g io IHl1 vegetation LO downwind dunc migration, leading to stucking and supel'imposition of several gcnermions of dunes during Ihe la te r Qw.ltel'1lary.

STUDY

AREA

Large coastal dUllerields occur a t several locat io ns in northeast AustJ'ulia. mos t nOHlbly On the east coast of Cnpe York Peninsuh_1 and in southern Quecnsland, Smaller dunefields occur on the const and offshol'e islands of central Qu ee nsla n d (Pye. IY831:1 ) . No large pari of the coast is entircly with­ out clUllC5, although they are pOOrly deve l o ped o r IOCHlizcd on sections o f coaSL w hich nre sheltcred from. or are al igned parallel to. the prevailing south­ easterly tracle winds. These include the western shores of Broad Sound. the P roscrpi nc 10 Townsville sector, Princess Chal'lottc B a y and the wcstern coast of "pe York Pe n i nsu la (Fig. I ) . The accumulation of coastal sediments during the QU(llcrnary hns beel) st l'O il g l y influenced by tectonic factors which have determined the coastal orientation. physiography and l i thological outcrop pattern. The entire eastcrn continental shelf has experienced slow subsidence since the hac Tert i ary . associated w i t h block r.wlting ;,llong a predominant north-Ilorthwcst - soul h-southenst axis. wh i le the e(lstern pan of rhe mainlalld has experienced varying clegrees of uplifl (Maxwell, 1 968). The shelf shows marked contrasts 10 the Ilorth Hnd sOllth of Sandy Hpe on Frase r lslond. To the south of Ihis point the shelf has il maximum w i d t h of 40 km lJlld i s re l a t i vely sreep with few offshore islands. The wflve climate is dominated by 10ng­ period oCCall swell . To t he nOl'lh , the shelf widens to (I l11aximulll of 250 kill betwcen Rockhomp tO ll and Mackay. is characteriz.ed by a genller grndien t , and i s broken b y n umerous high islands o f cona tincillal rock and cO I'a l rce fs (Bird. 1 97 1 <-1 ) . Avcnlge W�lIel' depth exceeds 60111 around Mackay, falling to 30 In Ilol'lh of Townsville. l'efJect i n g greater sub­ sidence of the shelf lowan.ls the south. Wave energy on the semi-protected shelf of central and northern Queensland is dominated by short-pc]'iod wind waves generatcd over moderate fetches. As in sou the rn Queensland. the predom i nant wave ap­ proach dircction is sou t h eastc rl y. res ul t ing in a net nonherly drift along much of the coast, but both longs hore anll cJ'Ossashorc sediment tra ns p0J' t arc

Ltlle Quaternary developmeNt oj /IIegarlw/(,: f:.olllple).·es

25

'0·

Gu l f

Of

I

C a r p e n f a r l a

I��-----+-----i 1$0

o >-

,

"

EOwI.II R,ve,

t

o o Ru,lInll "j.I�.

•

Major dunefield Minor dunefield

•

" " � . V " Caral Sea

o

MOun,

, ..

o ...........

".

Darling

OOWfiS

ISO'"

Fig. I .

Localion of major coastal

duncfields in nonhCaSICl'lt AuSlralili.

.�...

26

K. Pye

morc res t r icte d within the Great B a r rie I' Reef Province (Maxwell, 1968). Pye ( 1 983a) divided the Queensland coast into fou r sect i o ns 011 t h e bHSis of Ihe degree of dune development:

1 t h e west coast of Ca pe York Peninsula

and the

lowlands, characterized by extensive beach r i d ges and ch e n i e r pl ai lls wi t h vcry small·scalc clune d eve lo p m e nt (e.g. Rhodes, 1982): <1pC York Pcninsul
__ fHU�SDAY

:-- { WEIP,,--=

6:!-,

0

G u l f of Ca rpen ta ri a

sa n d

dUlle is l an ds of Fraser Island. Moreton Island and North Stnldbrokc Is l an d . toge the r with the Ifl rge mainlancl clulle complex at Coo l oola (Coflldrflke. 1 962: Ward. 1977: Thompson, 1 983), Mincralogic.ll evidcnce suggests that m uc h of the Sl:\nd comprising the southcrn QucenslHncl sand IlMSSeS is derived frolll l'ivCl' cn tch mc n t s i n n o n hc l'll New South WHles. nnd the ;)rell HppcHni t o have acted as a long-tcrm sink for scdi1l1cnl which d r i fte d northwards along the c;o nlinCIll
Basins of southern Queensland. VirlUally fi l l of rhe conSlnl clune sand within the G re,l! Barrier Reef Province is !-iil iccolJ!-i. n nd i!-i �\Iso d eriv ed from tcr­ ri ge no lls sourcl,;S ill Qu ee ns l o n d . The l a tte r include catchments with major o lltc:: rops of g ra n it ic , mcta­ morphic imd arenaceolls secl i me n l:.l ry rocks. Ex­ tensivc areas of a pe York Pe nin su l a arc covel'ed by blankcts of resid u a l .md alluvial siliccous sand, in places several mctres t h i c k . which is t r;J nspor1e d to the coast by rivcrs 01" rewor ke d ill sitll by (l'flllS­ grcssivc d U lles (Smarl (It a/_. 1974: Wr i gh t , 1 976: W i l l l110ll (� Powe l l . 1 1) 7 7 ) . n rbo n a te dUlles arc ex t re mc ly limited in cxtent, occurri n g only in slllall

isolated bays and on islands which receive little terrigenous sediment (Bird & Hoplcy. 1 969: B i rd . 1 97 I b) . The clil11Hlc o f t h e Qucensland coast ranges from season a l l y h u m i d tropic�ll in lhe north to humid s u btro p i ca l i n t h e south, The preva i l i n g w i nds arc the southeastcrly Cornl Sen Tmdes which blow par-

IS�AND

...

V r "­ \

\

,

I ! l

Q U E E N SLAND

COOICTOWN

lA ,

0

.../.CL f V EL A ND

/� � I� CAPE

,

_ _ _ _ _

Fig. 2. Rcsulwlll wind vectors for effective sand-movillS winds at four Qucensland eoaslnl stations. calculaled using data supplied by lhe B u reau of Meteorology . The index of wind energy ( I WE) is calculated urte r Pye ( 1985).

ticlll;.nly strOll :-tly in nOl'lhcrn nnd ee nl rn l Queensland du r in g ( he dry season (Apri l - Ocrober) (Fig, 2 ) . During the w e t season they are pe riod ica l l y re p l 'l ccd in nonhel"ll Oueensland by a weak l10rlhwesterly airflow from the G u l f of Ca rpe l1l
this

sect io n of coast arc al so shei t'cl'cli by offshorc is la nd s .

and the p rcsen ce of high coastal ra nges forces the winds to rise, crea ti n g relnlively sheltered co n d i t io ns at t he ir foot (Pye, 1983c). DUlles On this section of

I... (lte QlIlltel'1ltlry developmelll oJ meglldlllie complexes

CO�'st arc generally rcstricted to bays on the south side of mnjol' headlands tlnd estuarine barrier sp i ts wit h a

southeasterly

orientation (Figs 3 and 4 ) .

27

winds blow from the southcma. where the vector

resulwnl is N 134'E (Fig, 2), Al Thursclay Island, where there is a la rger easterly wind component

There are also illlpol'I'ant latitudinal variations ill the seasonal distribution of wind energy. At

(Swan, 1979, 1 98 1 ) , Ihe vector resulHlnl is N I I O'E,

Thursday Islalld in TOl'res Strait. >74% of the total

more i m porHHlI than fun her north. and there is

annual wind energy occurs during the dry season

gre•.I1cr overall directional v ari ab i l i ty

( M a y- Nove m be r) ,

The signific:'lIlcc of local v�H'ialions in wind regime en u sed by coastal OriCnll.Hioll and lhe nature of sUI'I'ounclillg rop()graphy is clc
but

this perccntage dcclines

southwards to 68% 1.11 Low Isles (l1e..,r Port Douglns ) , 6 1 % H t Cape Icvclnncl. 50% a t Pine I s lc t (nenr

M ..\ckay)

and 38%

at

aloundra. north of Brisbane

(Pyc, 1985), The I110St unidirectional w i n ds are found 011 t he cast coast of Cape York. north of Port Douglas, At ooktown, >99% of the effective snnd·t f
In southern Queensland. winds from the south are

increase i n size and complexity towards the more

exposed

dune · capped-, \ barrier

�

\ Low IJI.$

,

,

\ \ \

Fig. 3. The coast between ape Grafton and Cape Tribulation. northern Queensland, showing the location of small d u neficlcls and the Low Isles wind resultant.

,

northern end

of

the c lll bn y mcnt (Pye,

K. Pye

28

m a ngroves ,md chenier ridgcs [lrc the Iypicnl depo­ sitional fo rm s ( B i rd & Hopi y, 1 969; Frankel, 1 974; Be l peri o , 1983; happell o r III. . 1 983; happell & G ri nd rod , 1984). ,

of sedi me n t supply to the near­ arc high near the mouths of major ri ve rs such as lhe B urde k in , Pioneer and Norma ll by ( Bcl peri o , 1983; Pye , 1 983a). Al t hou gh dunes Present-day rmes

/

, I I ,

Ql

\

shore zone

.. .. .1F,t",�IIJ"d

represent an iTnpOl'tallt componellt of rhese active

IolllnUI

.' , , "

(

r�1

\

'I

0 �'" 10 '_ L _ _ J'

I !

jI

N

depositiolll:1I systcms, t h cy

�lre less well d ev el oped a ppea r to receive

Ihull i n other areaS which todny

UI)Y. sa n d

lilli e, i f

1'1'0 1)1 ICl'rigcllous o r contincnwl

sys­ l a rge ly relict features which are presently u nde rgoi ng va ry i ng deg rees of ill sifll reworking.

shelf sOurces. The majority of the major dune te m s appear to be

D U N E F I £1_0 M O R I' H O L O G Y

1.1,."---.,,

Point

Dune formations on the Queensland coast occur in
The

l a rgest

transgressive

res po nd to types case

(Fig.

of lype E,

6)

E

dune

represen ted

COl'·

complexes

::Inc! F shown i n Fig. 5.

by t he

In

the

Hpe Manifold

anei Cape Flallcry duncFiekls (Fig.

7),

trallsgressive dUlles have climbed over cOHstal hills.

alluvial pln i n s find older generations o f dunes to p rodu ce a stac ked sequence of aeolian sediments, The Il'uncared t rai l i n g arms of somc of t hese dunes suggest that t h ey origi n3ted some distance seaward

of rhe pl'cscn ! shorcline. possib ly at il l i m e of lower

sea level. I n sev e rn I plnccs. i n c l u d i n g

ooloohl Queensland. coastal erosion has ex posed
Fig,

4. Tile perennially weI lfopjetll sector of the northern Queensland COOSl bClwCCI\ Dunk islund and ape Gmflon. Pilrobolic dunes iX:cur only On the exposed bellches ;'I1 Wide Bay and Oornbullghi Beach; low forcdullcs and lIcol;')1l cnppings superimposed on beach ridges arc present ill owlcy Beach. The Fitzroy Island wind rCSlIll:IIlL is also shown.

podzolizcd dunes exten di ng b
(Coa ld ra ke , 1962: Tho m pso n H ub b le , IY77: Wa rd el al.. 197Y: Thompson,

last i nt c r · glJcia l peJ'iod

&

1 98 1 , 1 983).

Type F s h o w n i n Pig, S i l luStnllCS the stru c tu re Iypicnl

of

the southern

t l'i.ltlsgressive

Most of the ve ry large dUlle sys te m s 011 the coast occur where the no rtherl y drift o f nea l'shore SJlld has been i m ped ed by a prominent bedrock hc adl n nd . crc;;l ti ng <.I c l osed ; scd il1i c n l co m pa rt m c lll' (cf. Dn v i es , 1 974) 01' ' rece pt i ve shore' (or. Cooper , 1958). n t h e leeward side of such hcadlHnds, the sed i me n t s arc freq uently poo rl y sorted; IllU(lnats, IYS2b).

Q ueens l a nd

semel islHnd s .

which consist of a s Hlckcd series of pal'li ally drow n ed (Laycock, clearly

du nes

1978).

beg.. !)

anchored

I n i tiation

by

fit a ti m c when sen

t h a n at preSCnt

be(l rock

highs

snnd is l a nd s Ic ve l was lower

or t he

(Ward. 1977). (Ihhough sOme IrOnS· grcssivc (Ju n es were a l so active during periods of marinc lrHllsgrcssion and h igh sl
LllIe QIIlIfel'lllll'Y developllfcw of mcgacilllu! complext!.'i

A

c

B

Peol

MSL

F

MSL

(Fig. 9) and Moreton Island. were trimmed by marine erosion

wh ich

(Ward,

1982),

but

tra nsgre ss i ve

d unes

orig i nated at or n eil r the e rodi ng shoreline

cominued to m ove inland .mel

climb ovcr oldcr,

stabi lized dunes. Sand eroded from exposed pa rts of th e stlild isl a n ds

has, i n

D

-

E

,,'jg. 5. Six contrasting styles of aeolian accumulmion foulld 011 lho Queensland coast. Type B represents the typic.ll l11orphc)logy found on prograding shores al t he pl'C�CIH da)'. Types C. D. E unci F me Iypically associated wilh consUlI erosion. (After Pye. 1983a,)

29

some instances, been

deposi ted in more shel tered areas as progm d m io n n l beach ridge pl ai ns (e . g . Fig. 9).

P A ll A IIO L I C

D U N E M O Il I) H O L O G Y

described ns ' p arabo l i c' forms i n detail . A distinction can

arc described (IS lobate , and t hose with a

lengt h:width of >3,0 nl'e referred to as elongate. A sche­ ma t i c model for the formation of elongmc purabolit.: dunes from an isol
Queensland cO llsi sts o f
D u nes which arc loosc ly

in

show a v ari e t y of

sh�lpcd sand tamp or sand sheet

be

made between simple . cOlnpolllld and complex pa ra bo li c fOrlns. fo l l ow i ng the distinction made by McKee ( 1 979). Si m p le parabolic dUlles cons i st of a s i ng le dune form which co n ta ins tlll'ee basic elements, a 'nosc' 01' apienl sand m o u lld HI the dow n wi nd end. two trai l i llg 'nrms' or ridges . ulld a deflation corridor or t ro u gh which is open at the upwind end, S i m pl e p:1 rabol i cs may be further subclassified On the basi s of thcir Jc ngt h : w id t h ratio (Fig. IDA). Dunes with iI 1cnglh:wichh ratio of <0.4 arc described here ::as II/illite. thosc with ..I length:width r at i o o f O A- I .O are described ns IWl1Iic:y(;/ic . t hose wirh n Icngth:width rat io of 1 ,0-3.0

pnrabolic­

upon which

arc

superimposed tra nsverse ri dge s or small barchan forms , The m a rgin s o f the t ra nsgress i ve sand sheet arc o flen c1 efincd hy n pMlially ve getated ridge. They arc si m i l a r to lhe ' l o n g-wa l led transgressive l' i d!;;c' dUlles dcscribed i n

New South

el uf., 1 978) a nd OJ few rcsemble the

r i dges '

described i n O regon by

Wa l cs (Tho lll

'precipitation ( 1 958).

(lopeI'

Somc of t h e vegctatcd complcx para bo lic d U lles found On t h e southern Q ueen sl a n d sand

islands arc

cxceptionally large. Il1cnsuring morc w i d t h
than 6 kill i n lind 9), These

l eng t h ( I::'jgs 8 h ave c l ea r ly experienced a co m plex e vol u ti on ary history, in vo l vin g several phases of m cga cl u llcs

K. Pye

30

Fig. 6. Vcnical

air photognlph or Ycgc1[Itcd ncstcd and supcrimpo);cd elongate parabolic duncs south of C.lpC MlJllifold. central Queensland. (Reproduced by permi ssion of the Depll rl lllcnt of National Mapping, QlLcllllbcyun.) aeolian sl
similnr nncl is l i kely 10 influence the dune morphology

v�ltion or reworking by younger 1 t'allsgl'cSSivc dunes.

i n sil11i1nr ways.

The variation i n parabolic dUI1C morphology ob­

D u n e size is clearly related 10 sand availability.

sCI'vee! in d i fferent dUllcficids along the Queens l a nd

The Illegadu nes which occur i n both n ort he rn and

directional variability at t h e rc gi o n ni scale and to Ihe

aeolian reworking of older dune u n i ts. Complex

cOnst appcius to be clue both 10 variations in w i n d

sou t hern Queensland have formcd as i.l rcsult of

i n l1ucllcc o f local \opogr;)phy which i s responsible

and compound fOl'llls have rcsultcd where severnl

for local deviations in the wind regime (e.g. Fi g . 9).

ge nerations of uuncs hnve becn i n i l i a rcd in rela­

The typical elongate pnrabolic dune fOfms i n the

t i vely quick succession, often as n resu lt of bl owo u t

Cape York Pcnillsula d u n cficl ds reflect the h i g h l y

dcvelopmcnt w i t h i n otherwise stabil ized dunes and

1I1l i d i l'CctiollU1 nature of t h e regional wind regime.

sanei sheets (e.g. Figs i 2 anci i 3) .

The morc irregu l a r pli111 fOI'm o f t h e dunes on the

southerll Queensland sand islnnds ;.'ppoa l's to reflect

a more Vilri
locnl topogra phic i n O ucnccs. A l lhough there arc some d i fferences in the nature of tile dune vcg­

cl
J;lckes,

1 98 1 ) , the sequence of plant

broadly

Pyc & co m m u n i t i es i s

S T R A TI G R A P H Y AND

AGE STRUCTURE

OF THE

D U N E FI E L DS

Cope Bcdf'ord-CllpC FI�ltli.!ry duncficld Drilling investigations at a

numbcr of locations

LUft! Qlltllel'lltlry del'eloplllt!lIi oj megadt/I/e cOlllplexes

31

30 km

'� .

.", -

\J •

9

Fig. 7. Satellite p hotogrn ph of the

of Cnpc York the npe Bedford-Cupe F1nltery dUlle complex (black) on lllc lower l'ighl. southeastern part

rcninsulll, showing

in

Queensland

(Thompson.

1 98 1 .

Bowmall, 1 9R4: Pye & Rhodes.

1 983;

Pye &

1 985) have con­

overlying an old salldpl::tin surface. The older of [he two dune genel'lltions became stabilized and

firmed the stratigraphic complexity of many of the

su ffered podzo l izH t i o n

ciuncficlds. The oldcr dune gcncI'Cltions tire typicully

pnl' t i a l l y reworked during mignltioll of lhc younger

highly

clune. During the period of stabilization a significnnt

weathered

nnd show vluying degrees of

before being buried and

( W a rd

thickness of the older dunc sand body became

el lll., 1979; Pye. 1 98 1 . 1 982c. 1 983<1; Thompso n .

swined by fel'ric oxyhyclroxidcs ilnd some layers

reddening

and

podzol

soil

development

1 983 : Thompson & Bowmnn.

t nlsl:ing

stratigraphic

examples

1 9 � ) _ Three con­ from

the

Cnpe

were cemented to f01'1ll 'pet rofcrric ironstone layers'. Subsequent

deflation during the

passage of the

in

younger dune ex posed the weathered s
Fig. 14. Case A i l l ustrates a relatively simple case

su rface of t he deflation corridor, lind the incor­

Bcdford-

ape

Flanery dunefield

arc

shown

of an active elongate parabolic dune composed of

poration of fcrrugin ized grains has given the active

pure quartz sand which

dune sands H pale orange colouration. R:tdioc
has transgressed over a

1 98 1 ; Pye & $wilsur. 1 98 1 )

vegctnted aeolian Sfll1c1plain slIrfflce. This slIrf,lce is

dating studies (Pye,

underlain by deeply podzolize d sands characterized

have shown Ihm t h e podzolic "eddening process a1

by

I.l

3-4 111 deep bleached A2 horizon and a 3 - 4 III

ape Flattery is rclfltivcly nlpid, taking only a few

thick h u mate stained Bh horizon. The bleached A2

thousand

horizon snnds have been eroded by the wind i n the

langei' time periods leads to gradual removal of iron

water table. and have been incorporatcd into Ihe

black humic colloids within the zone or groundwater

mobile dune.

Ouetu"tion ( Pye, 1 9K2c. 1983d; Thompson. 1 983).

deflmiol1 trough down LO the level of the c.lry�scason

�Ise B represents a more complex situation with two Slacked

generations

of l m nsgressive

dUlles

years.

Progressive

podzolization

over

frolll the profile and accumulation of dal'k brown (0

Over vcry long time periods, the humic mailer may itself be destroyed, leaving a residual sand cemented

K. Pye

32

Fig. g, VCl'lical

�il' phologrnph showing purl of the Coolooln snnd mass. southern QlIccllslund, NOle Ihe vfll'iublc oriciltutioll of thc tlctive stllld blows. which rc llecls lopogr:lphic int1ucllccs on local willd paltcrlls. (Reproduced by perm i ss ion of the Deptll'tmcnl of Nation;11 Mllpping. Qucnnbcyan,)

only by kaolinite nnd gibbsite ( Wnre! et ai" 1979: Pye. 19�3c). During Ihe process of weathering the sh;.trpncss of the forms becomes subdued by sub� aerial processes (Ward, 1977: Pye, 1 983d: Thompson & Bowman, 1984). Cnse in Fig. 14 represents a situation involving three dUllc generations transgressing over �I deeply podzolizcd sandplain SUI'f:lcc. In this case. however, the mignllioll or successive dUlles has not involved signil1canl reworking of the underlying malerial, l cadillg to preservation of the former depositional surfaces within a st:.lckecl sedimentary sequence. The age structure or the dUlles on the Quccnsl'lIld Collst has received considerable attention in the laSI few years (Ward. 1977: rimes. 1979: ook, 1 986: Ward & Grirncs, 1987: Cov cn lry 1988; Lecs el ai" IY90). I'yc & SIVilSur ( 1 9M I ) iclentified three gen­ ermiol1s of d U llcs �tt ape Bedford and CHPC Flanery based 011 rHdiocilrbon d at i n g of include d wood and .

charcoal. The oldest dune unit. which is exposed in low coas",1 cliffs northwest of "pc Flnncry (Fig, 13), is deeply podzolized tlnd is partly cemented by humate. An ;'1 sitll tree roOl from this fOl'llHllion gnve H 'background' age of >48 000 1,1 yrs BP (0-2085). Three samples o f charcoal from t h e second dUlle gencrntion identified (section locntcd nenr the Ca pe F lalte ry M i lli n g Camp), which is also podzolizcd and extensively reddened, gave agcs of 7480 : 75 (O-20M I ). 7560 : 90 (13-2494) Hnd 8200 ", 85 " 'e yrs I3P (Q-2082). The youngest gencrotion of dUlles. including those still active, pal'lly overlies the two older generations (Fig. 12). Using measure­ ments of the modern rale of dUlle movement nnd air photograph evidence, Pye ( 1982[1) concluded Ihm activation of many of these dunes hns occurred within thc last few hundred ye;Hs. Lees el (//. ( 199()) cX;.lmincd a 40111 section with numcrous pnlf.lcosols ,Inel six intcr-bedded sand

Late Quatemary del'elopmelll of me8adull(� cOlllplexes

33

Fig. 9. VCl'1iclll llir pholOgrarh of thc Ilo�thcl'll prm of North Stritdbrokc Isl;:Wd. showing slIIbilizcd p:m.oolie mcgnclullcs which havc been trullClltcd by murinc erosion. fol lowc(1 by n pcriod of beneh ridge pluin construction, ( R pr d uced by permission of Ihc DCplIrtlllellt of National Muppillg. Qucanbc)'illI.)

eo

®

®

long·wolled tronsgresslve dune

Parabolic (Plan lenglh/widlh rolio <3)

lunole (L/W <0·4)

WIND i

�

�

,,' "

t� b..::�o-'oA

':

brlnll

;: �:.o ."" ' ... """ + ... .,..!'i , ' , ' , " '. ' : /::... , ', ': " '. b�r�'�o�d,s�e�t ::

ro .,:,,,

hemlcyc1ic ..... (L/W 0' 4.1'0) �

portiolly veQetoled slip loce

' W : : � ··c oller�d : :

<��:' . . bo rchonold or I roniverse rido e

vegetoled compound r-._,�J terminal ridoe

t

WIND

© nested

iV

en-echeton (rolle·llk.)

d(ffffi

rr

superimposed remnant

of digitate

porobollc (vegetoted)

Fig. 10. Morphologicul vnrillllts of pari.bolic dUIlCS, (A) Simple dunes . ( 13 )

oCllvely Ironsgressive terminot rldQe

omplex dunes, (C)

f}ry .L

olllpound dunes,

K. Pye

34

'Windrift'dune low sand 'tongue'at Converging arms

apaK breakthrough

decreasing height

KEY

D D

Bare sand Vegetation

-�

�

.,

@

.... . ...

Dune crest Undercut 'knife -edge' Diverging arms

Slip face

increasing height

Lake Swamp Gegenwalle ridge

Mature elongate Parabolic dune with vegetated Parabolic

slip face and

dune with

undercut

unvegetated

windward

slip face

'knife-edge'

1.

1b

parabolic

Incipient

dune

elongate parabolic dune with apex breakthrough and active slip face

(j �

2

5

4

3

6

Fig. 1 1 . Schematic model showillg the evolutiollilry dcvcloP111C I I l of elongate parabolic dunes from 11 spot blowout lit Cape FII1I1er), . (After Pye. 1982a . )

layers exposed i n a blowout ncar Red Hil l , approxi­ mately 12 kill so u t hwes t of the

apc Flattery settle­

no signilic(Ult di ffcren ce i n thc age o f de pos i t io n can be inferred, Below this deposit,

men t . The sand layers were designated A - F' (from

inciuralCd,

top to bottom) and snmples collected for radiocarbon

"

lind thermoluminescencc

(TL)

d a ting .

IHl rcmli

col l ected from a depth of 0.6 m at the basc of Unit A. composed of pale yellowish sand, gave an age , , B P ( A N U 6 1 7 1) . A TL sample col­ of 220 ± 70 , leeled frol11 U n i t 13 a1 i:I depth of approximately 2 m save a" age of 2000 ± 1 000 B P ( Xi a " Au-03). A sample laken from U n i t

TL age of

at 10 m d ep th gave a

1 9 200 ± 34(X) BP ( X i " " All- I S ) , a sample

from Unit D at u dep t h of 20 m gave an age of

k ao l i n i tic

however, is a h ighly F') wh ic h gave

sand u n i t ( U n it

TL age of 1 7 1 000 ± 1 3 000 BP ( X i ,, " AlI'OSO)

( Lees el 01., 1 990). III places U n i l F h as also beell

eroded, exposing

311

eve n morc firmly i ndurated

u n i t which could not be sa m p le d for TL. A sampl e

collected from an adjacent site nt

an elcvation

i n ferrcd to be sl raligraphicn lly lower t ha n Unit F

gave a minimum

TL

age of >66 000 yrs (,,·2589 ) .

The sequence investigated b y Lees el 0/, (1990) is

similar 10 Ihal described bl'iefly by Pye ( 1 983d) at Elim liffs. norlhwest of ape Bedford (Fig. lS).

22700 ± 2S00 B P (Xiall Au· 1 9) . a"d a sample fro m

The sequence here consists of n n upperl110st unit

Unit E (sepal'alcd from D by an crosional brenk)

of w h i te to very pflle yellow sHllds. ilssociated with

gave " " age of 1 9 800 ± 2300 B P (Xi,," Au·(4). Since these ages overlap al I sw nda rd devi(ltion ,

of pa rti ally rcddcned sands which contain

presc ntly active d u n es , overlying more than 60 m four

35

L(I(e QI/(ffemary delleloplllelll of lIIegadune complexes

Fig. 12. Vcrticni llir photognl ph of the southern pan of the l\pC. Flattcry duncfield. sllowing currcntly ncti\'c compound parabol ic mcgadulics which UfC t ra nsgressi ng over 1111 oldef sandplnin surfucc composed of i ndu rn tc d dUllC sands. (Reproduced by permission of the Depllr1nlCnt of National Mapping. Qucnnbcyun.)

major erosional discoll tinuities (Fig. 1 6).

M id�way between the Elim ! i ffs scclion �) I,d the Mci vor River. two distinct. h igh l y inch mnccl and cross­ bedded sand rock horizons nrc exposed just nbovc the high-w:uer mark. Th e uppermost unit . 2-3 111 t h ic k , is dark brown to yc l lowi sh brown. while the lower unit, at l east 2m thick, is palcr in colour. These units arc clearly of consid e ra b l e age. A lth o ugh they were grou p ed toge t her within the Flattery San d U n i t by Pye & Swi tsu r ( 1 98 1 L it is by no means cerlain thnt t hey arc of the same age as the deeply podzo l ized and hum�lIe cemen te d sands exposed a l o n g the sh o res of Flattery Bay. If the TL ages reported by Lees el al. ( 1 990) are rcliable, t h e evidence would suggest that tmlls­ gl'essivc d u nes werc aClive in the ape Flatte ry a rCH d u ring the last glacial maximum when the sea level stood more than 1 00 rn l owe r a nd t h e sho re l i ne l a y along the shelf edge on the outer side of the ribbon reefs. However, as pointed out by Pye ( 1 9�4), the region.1I winds would have needed to hnve been much stronger t o maintain dune move mc n t fit a distil1lce of more than 40 kill from the shore. sincc wind vclocities today show a Illilrkcd reduction only a few kilometres inland. D u ring low se�l level stnnds the continental shelf would IHlve been characterized by hi gh l y irregulnr topography. emergellt reefs illld

deeply

i n cised Iluvial

ch " n ne ls (Maxwell,

Th ese would have further served to

19(8).

reduce wind velocities before I hey reached the prescn t npc Bcd fo rd - npe FI4lItcry arca. For t h ese rcasons. Pye ( 1 984) proposed t ha t the older pre- Ho l ocene dune units ill the ,lrCft rlre more likcly to h ave been associated with carlier inter-glacial or i n t er-stad i a l high sca levels. Further d nt i n g information. including co n firm at ion of the re l i u b i l i ty o f the TL ages, is requircd before this issue can be :.uJcq u
K, r')le

36

N

�

o D

Fig. 13. Sketch !>how i ng. the major lIlorphostraligraphic in lcrprcuuion find Held survey.

o

manyrove,

2

,

3

I

bare sand

ope Fluttery

features of the

I

rock outcrops

duncticld, l>osed on air phologrnph

the ave rage annual dose nile to which grains have

b i l i l y o f ovcrc�liJllatioll of the average arlTlual dose

been subjected. whilst i n the case of some podzolic

rate within the

B horizon sands Ihe y Illay ovcrcstil11C1lC it due to

long-term accu mulation of U and Th. Reported '"L age estimates which Itlkc illsufllcicnt accoullt of the

possible effects of we a the r i n g . translocation and

waler content changes may be i n sign i fi c:l ll t error.

podzo l ic

B

h orizo n i.lntl mechanical

Iransloc;uiol1 of fines through the sand p ro fi l e ,

as discussed above. A si m i la r age of 1 5 000 ::1: 1 1 1 0 B P «(\'-2594). also interpreted as a minimum estimate.

was obl<.lineci from the fine f!'action of fc rru gi n ize d

sunds with similar appearflncc ncar Conical H i l l . northwest of Cape Grenville. A t the second Red Cl iffs sile, located 1 00 m away

Shelburne B�l)' UU llcficld

from the first. a TL age of 28400 ±

Lees el al. ( 1 990) also reported TL results for samples co l lceled from three secti ns i n

hclburnc Bay and

one sec t iOIl a L t he northern margin of I he Temple BelY

dUllefield.

A TL date of

1 7 60 0 ± 1400 BP (,,-2597)

W(IS obHlincd (!'Om the fine fraction (4 - 1 1

podzolic 13 horizon ill a

in the fi rst Red

�lIn) o f a depth of a pproxi ma tely 8 In

mrs section. This was interpreted

by the authors to be n m i n i m u m age due to the possi-

1300 BI' (Xian

Au-07) \Vas obtained from pale brown sand. overlain by wh i le snnd. a t a depth of approxinwtcly 6 111 .

The brown sands arc underlain by grey sand with

brown pipes which yielded " TL age of 29 900 ± 2400

8 1'

(Xi an Au-OY). A t the base of this section is a

humicrctc co n ta i n i ng dctriwl logs, the cellulose

frnclion of o ne of which gave a radiocarbon age o f

29740

14

yrs

BP ( A N U 4980).

37

Ltue Qflatemal'Y del'eloplllt!1I1 of megadlllle complexes

CASE A direeHon 01 movement

level

01

lOp

" ""\m�

_

-

humaTe

stained

(si" of seasonal lalle)

�

"

_

bleached AZ horl zon

_ _

sandi elpaud

mSO"� WATER

)

_

sonds beinQ

while

deflated

'" l

' ' ' p loce

At

oroon l c r l r h horizon \ oreyl

/

sand.

I

,a,z bleoche
�B, ,,,,,,, ��'�"."�,':,. �� "\.� . "''\.� ��'"'\.��'\.� of O'OundwaTer

TABLE (BASE L[VEl FOR OEFl.ATlON)

CASE

podzal (brown/block)

8 Zone 01

r-

net depo.ition

� A � __ __ __ �

__ __

" lOp Of I rai li noa rm. ,

,,,or

Zone 01 neT

:

: -�

CASE C

deftollon

r_----'A'-__--; Buried AI

rOOll

-

,J'"

.Up

soli

hO"lon Wllh

.. Iree Ill,ImOI (dorlo,oreyl

" ee

i

(Olluyially reworked lands wilt'! mulliplC Al ",,,n.

Fig. 14.

Schematic diagram showing three contrasting dune stnttigraphics in the 'lpC Flattery urea. based on the results or field drilling.

K. Pye

38

0

�:J § •• , • • •

Dr.1I hoLu Mengl'O""

Con'jlIGR1.'.'U WBt�'

OUI�fOP

••••••

0,

01 IIrruQtll0uS UMllOIlll

Pell oulCfOP

: '::;:='�--"_--"5m"u ::::;::!'::;::¢ 5k.lomllfU

I ... £

P.,.'

. i i 6L -

O n the southern side of Shelburne Bay at Double Point, a thin co m posi te layer of aeolian sUlld (2-5 In thick) overlies bcdl'Ock. Lees e/ {II. ( 1 990) recognized an upper u n it of while sancl, interpreted as modern, and a lower u n i t of brown, humic·rich sand. The lalter gave " coarse-fraction (90-125 1I1n) TL age of 23 800 ± 2400 BP (Xian Au-06). The southeastern part of the Temple Bay dUlle­ field comprises a series of beach ridge and back· bnrricr lagoon deposits which have been parliHlly buried .tnd reworked by a transgressive dune sheet (Pye, 1983b). Shell hash from the youngest beach ridge underlying this t ransgressive dune sheet gave a reservoir-corrected 14 age of 930 ± 135 yrs B P (B-5045). This da te provides il maximum age for the overlying d u nes, and is consistent with Pye's ( 1 983d) conclusion, based on air pholograph measurements

Fig. IS. Map showing coastal

sandrock lind pent outcrops in the CrIPC Bed ford dUllcfic1d.

and assumed rmes of dUllc m()vement, thnt ncolian rework ing of these deposits Illuy have bcgun 300-500 yrs ago. Cobourg Pcninsuhl dUllcficld

Samples collected for dating fl'Om stabilized d u n es to the south of De Courcy Hend on the Cobourg Peninsula, Arnhem Land, Northern Territory, indiciHed the presence of four Ho\ocene dune units (designated A - D) which ovcrlie more indurntcd sands presumed to be of Pleistocene age (Unit ) (Lees el ,i1., 1990). TIle currently active dunes (Unit A) were not snmpled for dating. The oldcst nOI1indurated dUllc unit (Unit D) yielded a TL ugc of 8600 ± 14()() B I' (Au-13)_ The partially superimposed yielded TL ages of 2600 ± 300 B P (Au- 17) Unit

39

Late Ql/lIfer/lillY development of megadlllle cOll 1ple.res

Fig. l(j. An 80m high eOllswl cliff section fit Elim. nOrLhwest of Cl\pC Bedford. The dune sllml sequence contains nt least four m ajor

crmiional disconformilies (boUllding surfaces) whieh correspond LO lhe pnss(lgc of Lnll1sgrcssive dUlles. The colour of the sands is hi ghl y v::u·iablc. ra ngi ng from while 10 brown and dnrk rcd. .

2800 :!: 51iO BP (A u . 1 6) while U n i t B gave a n 1 900 :!: 400 B P (Au.15). A '[ol11ple of 'and co llected immediatcly benea th a residual pi sol i tic and

age of

lag dcposi l on the surface of a degraded olcler dune

( in tcrpreted as U n i t E), l oca ted 10 the south of the d a ted U n i t D d u n e . gave a TL age estimate of 9300 ± 1 1 00 SP, but this is a l most ccrtainly a gross underestimate due 10 pedogenic concentrarion of U and Th i n and adjaccl1l to the p iso l i t ic laycr (Lees

el llJ., 1990). A sccond sample from grcHlcr dcpth below a s i m i l a r

p i so l i t i c

layer i n co m p a ra b lc

sa n dy

deposits south of Bl"Ogdcll Poillt. 011 fhe southern

Cobourg Peninsula. gave a TL age estimate

of

8 1 4QO :!: 8500 Br ( A u · 1 2 ) . This may a lso be a n underest imate o f ("he Inle age.

Other Quccnsl:Jnd duncficlds At RamsilY Bay, on

H i nchinbrook Island, dating

of backbarrier man grove PC,HS associ ated with the dUlles indicatccl thill the dUlle bn r ri e r was i n existence

:H Icast by 9000 Ille yrs S P . Two maj o r plwses of pnrabolic clune activity were i de n t i fi ed One associ

IHCcJ

,

wirh

the

H o l oce ne

marine

·

Inlnsgrcssion

K. Pye

40

1�lg. 17. A recent parabolic dune fOl'lllCd by blowout deve lopment in (l vegetated s
(9500- 6000

"

y r s B P ) a nd

apparenl i n p u t of

n ew sand

d U lle system after about 900

"

one re l a ti n g

to an

to t h e nearshore a n d

yrs B P (Pye, 1 982 b; Pye & Rhodes, 1985). Rad i o m et ri c evidence from a number of cmba y m cnts in northerll New South Wales also suggests Ihal o n s ho re migrmion of cJimb� il1g dunes was associated with the ea r ly Holoccne

& B ow m an . 1 984). In southern Queensland. eighl dune l1lorpho� strutigraphic u n i ts and eight beach sand units have

marine transgression ( Py e

been identified based on a i l' photograph ilHcl'prc­ t al io n

a n d a uger

d ri l l i n g to determine the depth o f

Li tt le , Ins; Ward, 1977). were made based On a corrcl{ltion with marine shore l i nes in Victoria. b\lt nO di rect age determinations we re presell ted, Gri mes ( 1 979) reported a "c dme of >39 300 yrs BP (SU A-860) 1'01' a tree trunk embedded in Ward's Poyungan beach sand at Triangle l i ff, l oen t cd in the northwcstern p(u't of Fnl sc l' Isl(llld. Two da lcs podzo lization (Ward &

Tcn tat i ve flgc cstilllHtes

of 5690 ± 120 t4 yrs Bf' (SUA-S59) and 4480 ± 1 1 5 yrs B P (SUA-S58) were obtained respectively from a wood slUmp and peoH in a peal bed w i t h i n Ward ' s 'Woorim' beach sand at the S<'I J11C l ocali ty . i\ sample o f charcoal from a sample of soil developed on the Poyungan beach sand, and lying beneath Ward's 'Tl'ianglc C l i ff' clUI1C sand, which g.wc a dme of 3880 ± 105 '4 yrs BP (SU A-433), was i nte r p reted by Grimes as giving a ma x i m u m nge for the time when ' fri ang le Clirr dunc sand transgl'csscd ovcr the Poyungan beach sand in I'his [!rca. Subsequent rcintcrprctHtion of the field evidence by Ward & G rimes ( 1 987) led to the conclusiol1 llwl the peat bed cI�Hecl by Grimes, which was designated 'Bcd T', is 1101' pari of the Woorim beach sand unit b u t is more l i kcly t o bc a lime e quiv ale n t o f the Wnlhumba be
41

Lllfe QlIlIfel'lwry del'elop",ellf of lIIegadw/e cOlllplexes

unit. Ward & Grimes also reported a new date of

model'll sea leve l benetlth a ln rge stahil ized para­

for carbonaceous

bolic dune on the western side of NOl'lh Stl'!ldbroke

yrs

6740 ± 80 "

BP (B-330 I )

pltHlI matcrial contained within stabil ized Triangle

Isl a nd , The corals occlir within

liff slip face sallds at Trianglc Cliff. The dme of 38S0 ± 105 1 4C yrs 81' previousl y obtained by Grimes

sedimcnts which were buried as the large dune

frol11 the pnla cosol

bencath the Triangle

Cliff dune

aclva llccd towa rds B P I suggest ing

1'00ts of plants which grcw on the eroded face of the

dose

ization.

time aftcr its sw bi l ·

I t was t herefore cOllcluclcd by

Ward &

illlcl·-tidi:ll

northwest . Three species of

conll yielded �I mean 2Jf'Thtl:"'I U age of !O5000 yrs

sand was reinterpreted as represe nting int rusive Triangle Cliff dune sand some

thc

tllin

the

occurrence of

a

sea level stand

to the present level during isotope SlHge 5c.

Pickell Itt lIl. proposed thut the overlying dune sands
n

the dune sands and the co ra l- be a ri ng sedilll c llls WHS

wards during the e ar ly to mid-Holocene marine

the two cannot be ruled Oul. The corals therefore

transgression . Thc unit is therefore considered by

provide only a lll,-i ximul11 age for the overlying dune.

these authors to be timc tr�l Ilsgressive, u ndcrlyi ng and older tlHIII the W;.t th um b a beach sand u n i t o n

but i t is uncertain whether t hese represent bu ried .

Grimes ( 1 987) that

this dune u n i t was

il1itiated

al

lime of lower Holocene seH level and m igrmcd lan d·

t he

cast side of Frase r Island b u t ovcrlying find

younger than it On t he western side of I he island.

not observed. and t he

possibi l ity of a hiatus between

Thc corals overlie at least 40 III of while sands.

ifl situ aeol ian sands or sands which have becl) rcdcposi wd subti d ally.

The entire basis of the scheme prescntcd by Ward & by

Grimes has been

seriously questioned

ovcntry ( 1 988). who argued thm insuffkient

SUMMARY AND CONCLUSION

evidence is availablc (0 support the recognition of the d i fferent morphostratigraphic u n i t s , The two in his initial

Stratigraphic evidence cl early i nd i catcs \1 long history

mHpping work, dune morphology and depth to rhe

of coaswl dune b u ildi ng i n northeastern Austral ia ,

base of the podzolic A2 horizon, are i n themselves

bur considerable unccrtainty still surrounds t h e ages

principal criteria uscd by Ward

( 1 977)

un i nsu fficie nt- basis on which to recognize d iscrcre

of the dunes nnd the extent to wh ich

phases of aeolian sedimentation. Thompson's

( 1 98 1 ,

episodes in d i fferent a reas wcrc COIncident. Drilling

work at Cooloola i n southern Q uee nsla nd

has shown that i n sevenll area� dune sa nds extend

1 983)

h
more t ha n

40 III

major l.1 col i n n

below presen t sea level, indicating

thai aeolian activity occurred i n m least some places

horizon , is st rongly dependent on t he height of ..I

during cold stage

clune and the position of the water tablc. The latter

level was lip to I LO

is often controlled by the natul'c of the surrounding

the Holocene marine tra nsgressi on. and probably

topogrHphy and the composition of the underlying

also during cnrlier t ra nsgrcssions , the margins of

of the late Qua le rnary when sca III

lowe r than at presen t . During

Dune size and morphology nrc also

the sand masses were t ri m med by marine erosion .

dependent partly on the underlying topogra phy,

I n several areas there is strong radiocarbon evidence

sediments.

i n particular whether the advancing dunes move

that new tra nsgressive dunes werc i n i t iated along,

ovcr and partially I'cwork olclcr dune sand u n its.

or close to the eroding shorelines. These dunes

The nature ,lncl nlte of podzolizflIion may also be strongly affected by thc s a nd composition, with important

d i fferences

occurring

between

dunes

l11igr'Hcd l a ndwa rds during the period

BP.

10000-6000

climbing over bedrock hills. alluvial plains an I

older generations of stabilized dunes. During this

composed of 'new' material supplied from the bench

process the underlying sediments wcre p<-irliully

and dunes composed of sand rewo r k ed from dunes

reworked and incorpormcd into the active dunes.

an d

in places exposing the more i n du rated podzolic B

which have already been

highly weathered

deeply podzolizcd. To date. no grain size, minera­ logicnl or geochemical evidence has been presented to support the l11orphOSlratigraphic subdivisions an d c ross-regional

cOlll pnrisons

made by Ward and his

horizons which acted as local dcOnt ion bases, Dune formation has continued throughout the

latcr I-Iolocene, although generally on a smal ler

sc<;l Ic t h a n

during the early H oloce ne . The presellt

evidence suggests that the timing of thesc latc

"Issoci�lles. recovered thirty-nine species

H olocene cvcntS has vnried bctween dUllcnelcls,

of ill situ scle rac tinia n corHls from <1pprox ill1i1tCly

ind icat i ng
Pickell et lI/.

( 1 985)

K. Pye

42

globa l 01' reg i o na l c h a n ge i n clilTHlIC 01' sea level. AI the p,'cserH da y , some d u ne fie lcls arc crull'e l y stabi l i zed w h i te othe rs sho w vflr'y illg degrees of aeolian activity. I n some dUllcfickls active d u nes have been i n i liHtcd in the past fe w hundred years well irllancl of t h e shor'c l i n e (Fig. 1 7 ) : I le arsh ore scdimcllI b udge t ch a l tgc s, sea [evel rise a n d shore­ line erosion due to changing storm freq ue ncy call t h e refo re be ru led out as co n trol l i n g facrors in these i nstances. However, the possi b l e signi fica nce of i ncre ase s in windi ness Or l oss of vege tat ion cover due to d rough t , waterlogging. dise ase 01' bu rn ing remains to be established. I n vi r t uCl l l y all of the m aj o r dUIlCficlcls, i nsuf­ ficient dcwilcd stratigraphic evidence is �lVa i l a b l e to be cer tai n about the n u m be r ..lIlcl co rre l a t io n of i:l colian scd i m c ll tary u n i ts p resen t . O n ly t he yo u n ge st de posi ts hnvc so fnr been darccl by rnclioca r bon nnd TL methods, and too few dates arc av ai l a b l e 10 e srab l is h the extent 10 which aeolian events i n d i f­ fercnt areas wcre sy nc h ro n o u s . The pattern of weathering and ped oge nesi s o n t h e stabilized dunes i s complex, wi th

si g nificant

d i ffe re n ces even on d iffe re n t parts of the same

dune

due to va ria ti o n s in

local

d rai nage co ndi tions.

St ra t ig ra p h ic corrcl ation bascd solcly o n ped ogc n ic fcnlures, s uch (IS sand colour Hnd depth of b l each i n g ,

is thereforc

po ten ti a lly

unsound.

The u n u s u a l l y l arge size of the PMHbolic d u nes

and d u nefields in no r th east e rn Austnllia rell ects

the long history of sand accumulation, i n volv i ng p;.I!'l ial re wo rk i n g by su ccessi vel y younger generations of

dunes. There is no firm evidence to SUppOI't t h e

suggeslion that stronger wi n ds were respo nsi bl e for

the construction of the la rge r Pleistocene �Ind eHrly H ol oce ne dunes, although evidence of i ncre ases in trade wind i n t e ns i ty d ur i ng gl aci al cold stages has been provi ded elsewhere. The genera l l y smaller scale of the Ime H ol ocen e features may be related morc closc ly to a reduction in sed illlcnt supp l y a fte r SCH l eve l rcached n pproxi m nrely its present posi ti o n nround 6000 yeurs �lgO, leading to cessn t i o n of shorc� lille erosion a nd , in som e areas, pl'ogntda t i o n of beach r idge/ fo red u n e plains. In northem QueensInnd

,It l e'lsl, i.l seco nd factor contributing to sta b i l i zation of dUlles i n the mid- Holocene

may h a ve been i n ­ creased ra i n fn ll ( cf. Kershaw, 1986), The size of dunes which have deve l o ped from i n l an d blowouts in the late Holocen e is d i rectly related (Q the size of the area in which v egeta t i o n cover has bCCll d isru p tcd by burning 01' some other faclo r, and to t h e degree of local wi n d exposure (e.g, Bird. 1974).

ACKNOWLEDGEM ENTS The research upon which this paper i s bnsed was funded by t he N E R t he Royal acicly, the Lever� h u l m c Tr ust ;lI1d t he N u ff1 e l d Founda t i o n . U n i versity of Reading P R I S COll l rib u t i o n No. 2 1 2. •

B �LI'Eluo. I A.P. ( 1 983) Tel'rigenous sedimentation in t he crHral Great Barrier Reef: :1 mode l for the Burdekin regio n . [)MR J, AIlS'. Oeol. Geoplrys. 8 , 1 79- 1 90. 1�1Iu). E,C,r, ( 1 965) The formfl t ion of cons wI d unes in the

humid tropi,s: some evidencc from Nonh QlIccnslillld. AilS'. J. Sci. 27, 25::;'-2 59 , B I IH). E . . F. ( 1 97 1 ,1) TIn: COlltirlCIlll.l1 shclf of caSICI'1l Au:mnli.l �lId ils i " n ucllcc on ooaswl geomorphology. QUlIIe/'l1{/ri(l 14 . 275-284 . OIItD. E.C.r:. ( 1 97 I b) The mi gin of be(lch sediments on the North Quecll!llnnd canst. Earth Sci. J. 5, 95-104. O I ItD. E.C,P. ( 1974) DUllc swbility on Frase r Island. Q/d Nmllra/isf 2 1 . 1 5 - 2 1 . I3IItD, E.C.F, & 1-lol'l.I!'!'. D, ( 1 969) Geomorphological fc(\tlll'cs On lhe North Quec nsl a nd coma . AU,I·I. Geog.

Sf"d. 7 . 89- 1 08.

IIIV/\S. A . . W/\l.Lt:NSKY. . , l'Ol.ACIl, H . A . AI-lMION . P . ( 1 983) H olocene p(llococnvir'onmenwl changes, Ccntral to North Great Om'rier Red i nne r zOlle. IJMR .I. AIISf. Octol. Geophys. 8. 223-235. CI EMI'!!Ll.. J . & t H I N OltoD. J. ( 1 9g.:j) henier p l ai n fonn
O-tMI'I!.l.I.. J . .

&

t io n i n northcrn Austrnliu. In: (;o(lsw/ Geoll/olplw/ogy ;/1 Allstratio (E.d. Thom. B.G.) PI'. 1 97-23 1 . Acodo mic I'ross. S)'dney. COAWII.M Oi. J . E . ( 1961) The e<.:osystCIll of t he co,lswl lowlands ('W.d l l l m ' ) of southern Quec r ls k llld . csmo

283. 1 1 9 P I'. . ( 1 962) The I.:ollstal dUIlCs of soul hc l' l1 Quecnsland. Proc. Noy. Soc. QItI 72. 1 0 1 - 1 1 6 . COOK. P . G , ( 1 9g6) A rc vi ew of coaslnl duncbuilding i n eastcl'll Ausmt l i u . AIISI, Geog. 1 7 , 133- 1 43. OO('I!It. \V.S. ( 1 95�) oastal sand duncs of Oregon ane! WaSh i ngton . Geol. Soc. Am. Mem. 72, OVI!Nr�Y. R . J , ( 1 98� ) I iscussion : hisIOI'), or coastell duncs <11 Tl'illnglc l i ff, Fraser Isl,l n d , QlIccllslillld. Arw. 1. £(11'111 Sci. 35, 579-583.

/3,,1/.

COtd.I)RMW. J.

O"vu:s, J . L . ( 1 974) The (.:oastal sediment comp:U'tlllelll.

A ( lst. OeoS. Stud. 1 2 . 139- 1 5 1 . FMN K l!I•• E . ( 1 974) I'�eccnt sedimentation i l l the Princcss Chnrlolle Oay nrell, Great I3nrricr Reef Provi nce, Proc.

2nd III(, Coral Reef Symp. 2, Brisballe. 355-369.

G ENTI I.l.I • .I. ( 1 97 J ) The main c1imirlologicul elemcnts. In: WorM Sltnl(IY of Climatology 1.1 (Ed. G e n t i l l i . .I .)

p p . 1 1 9- 1 88.

Iscvier. Amstcrdam.

GRIMl!S, K.G. ( 1979) nrbon- 1 4 elalCS and thC evolution of Fniscr Island. Qld GOII' r\tlill . .I. 80. 79-82. K �HSII,"V, I P. ( 1 9�6) li mm ie change and Aboriginal burning in no l't h-east Australia during the last two glaeial/intcrglaci
I'm . !loy. Soc. Qld M8. 39-48.

Lare Qllutemllry

L/WCOCK,

J.W,

development of megad/me compleJ.:es

( 1 97::;) North Strnclbrokc Islul1d,

Ulli\!.

Qld /)epi Geol. Pap. 15. 89-96. Y. & H !1I\ D . J . ( 1 990) RceonttflisSllncc Lm:s, B .G

.. Lu.

thermolumincscencc dflting of llonlicl'n Auslniliilll coa�tal dune �y!\tcms. QlUll. Res. 34, 169- 1 �5. Lrrn,I:, J . P .. AII.MtTMlI:. T.M. & GtI.KES. R.J . ( 1978) WcHthering

of qUUt'lZ clunc �flnds under subtropicul

conditions, Ceo(/el'lllll 20, 225-237.

LOUlI.tiNSZ, R . S . ( 1 977) Tropical (,'yc!olles ill file AIf�·I,.fIli(/1/ Regiol/ . july 1909-JIIIIC 1975. Mct col'Ologicnl SUlIllllary

for the Bureau of MctCOI·ology. Austl'alhHl GOVC1'111HCllt Publishing Servicc. Melbournc. I I I pp. MAXWELl.. W. I. H . ( 1 968) All(ls of fhe Grt!(// IJorriel' Rf1cJ.

Elscvicr. Amstcrdam, 258 pp.

fI study o f global sand scas. I n : A Global Sflldy of S(lild Seas ( �d. McKee, E . D . ) pp. 1 - 19. US Geol. Surv. Prof. r.p. 1052. PICK!!'IT. .I.W .. TltOMI'SoN. C.H., Km.Lt!Y. R . A . & ROMJ\ N , D. ( 1985) Evidencc of high sea level during isotope sInge 5e in Queem;l�tlld. Australia. QII(I/. Res, 24. \03- 124, P'o'l!, K. ( 1 98 1 ) R�l te of dulle redde ning in ,I humid II'opiea l climate. N{f/III'I!. 290, 582-584. r)....:, K. ( 1982a) Morphologic:11 dcvelopment of 'O
McKliE. E,D. ( 1979) Introduction to

2 1 3-227. hE, K. ( 1 982b) Morphology and sediments of the Ramsay Gay s[lIld dunes, Hillchinbrook 1�lallcl, North Ql1CCnslnllC1. ProC'. !
humatc-ccmented sands (Ilumicretcs) at Capc Flattery. Queelll;:lund, Austmlill, Ceo{, Mag. 1 1 9, 229-236. PVll. K. ( 1 983[1 ) FOrllllllioll und history (If Quecnslllnci coustal dUIlCS, Z. Geolllol1Jh. SIIPI). Bd. 45. 175-204. PVll, K, ( 1983b) The coaSHlI dune for1l1ations of northern upt.: York Peninsula. Quc,m;lnnd. Pl'()c. Ro)'. Soc. QId 94. 33-39. IlYEI K. ( 1983e) Dunc formation 011 thc humid tropical sector of the North Quccllsl:lnd coast. EIII'III 051111. Pmc. Lmlf//, 8, 37 1 -38 1 . PVE, K . ( 1983d) Post-dcpo�itiotl:ll reddcning of latc OlllltCrtlar), coastal clune sands, northcastcrn Austmlia. In: Rcsidual Depo,\'//s (Ed, Wilson . R.C.L.) pp. 1 1 7 - 129. Geo!. Soc, Lo nd . Spcc. 1)1Ibl. 3.5. Blackwell Scientific Public1llicns. Osforcl, Pvu, K. ( 1983c) Formation of quartz silt during humid tropical wcathcring of dunc s:I11Cls. Sed. Ceo!. 34, 267-282. Pvt!. K. ( 1984) Models of transgrc!;sivc dunc building, episodes and their relationship to Quntcl'1lary SCli level changes: n d iscuss io l l with rcfcrcllcc to evidcnce from northcastern Australia. In: o(/!iwl 1?(!.\·(!ol'('II: UK IJe/,sJlcctivc:i (Ed, Clark. M . ) pp, l-l 1 - I04. Geo Books. Norwich. P"H. K. ( 1 98.5) Controls on l1uid thrcsholcl vclocity. rates of l1colilln sand transport and dune grain � ilc pal'amclers along the Quccnsl:lI1d coa.st. I n : JJ1'{Jc'eedillgs oj' III(' flllel'lUlf;OIwl WOI'Juhop 011 fhe Physic,\' of lJIo wn 5(/1/(1. Aal'ltm. 28-31 May 1985. VOllIIlI1! 3 ( -d. 13u mdol'ff­ N iclsc n . O , K . Moll er . J.T .• Romcr Rasmussen, K. & Willctts. B . B . ) PI'. 483-50lJ. Dcpartl1lcnt of ThcOI'ctical SWListics. I nstitute of Mathclllntics. Univcn;ity of Aarhus. Memoirs R ,

43

& BOW M AN . \I'Ilm:grcssioll ilS it

G . M . ( 1 984) The Hol occnc m'H'inc f rcing function in cpiso(lic dU llC ("lctivity on thc C'ISlcrn Australia coast. In: Coaswl Ceo/llol'pholoSY ill A IISfl'tilio (Ed. Thom. B.G.) pp. 179- 1 96. Acadclnic Prcss. Sydney, [tYll, K. & JACKI\S, B_ ( 198 1 ) Vegctation of the coastlll duncs at ape Bedford ancl Cupe A!1Itcry. North Qucenslund, Proc. Roy. Soc:. Qld 92. 37-42. PVti. K. & RtIODtlS. E.G. ( 1 985) Holoecne clevelopment of <'Ill episodic t l'ilnsgressivc dune barricr. Ra1ll�ay 13.1)" Nonh Qucc nsl ;l nc 1 . Australia. M(II'. Ceol. (.4, I g9-202. PV �, I K, & SWITS U II. . V . R . ( 1 98 1 ) Radiocarbon dates frOIn the npc Bcdford and ape Fl:lttcry dUl1cticlds, North Qucensland. Si!{ll'cll 12. 225 - 226. PVli. K. & TsOAII. . H. ( 1 990) Aeoliall Smu/ (Iml Smu/ Dillies, U n wi n I-lyman, London. 396 pp, R I lODtl_�. E . G . ( 1 982) Depositional model for i1 chenier plain. Gulf of CmpcnlHria. Am;tralia. Sedimelltology 29. 20 1 -22 1 . ROY, P,S. &. TI IOM . B.G. ( 198 1 ) Latc QUUlernal'Y marinc deposition in New South Wa les nnd southern Quecns­ land - an cvolutionary model. 1. Oeol. Sot.:, Ausi. 28. 471 -489. S M Atn·. I IlOWELL. B .S . & POWt:.Li., D,L, ( 1974) Auger drilling. northern Cape York Pcninsula. Quccnslanti, 11M!? J. A'IXf. Geol. Geopliy.\· . I . 2 1 1 -2 18. S\\,.\N. B. ( 1 979) The presence of sand dunes in a trop­ ic.ll low cnergy zonc. Torres Strait (Austnllia), RCII. GCOIlt011)/r. DYII. 28. 6 1 -72. SWI\N. 13. ( 198 1 ) Duncs of FI'iday Island. Torres Strait. NOt'th Qucellsl
. . .

Holorell!,! Age S'I'tlC'fUl'e of CO(ISIIII S(llId /)(Il'l'iel's il l New SOlllh W(tle�·. AuslJ'(llio. Dcpt of Gcogr:Jphy. F:lculty

of Military Studies. U n h'c rsi t y of New South Wales. DUlllroon, 86 PI' . THOMIISON, C , H . ( 1 98 1 ) Podzol chronosequenccs 011 coaslal dunes of C
45. 205-225.

.H. & 130Wf.t/\ N , G.M. ( 1984) S ubac rial dCllucimioll and we:lthcrillg of vegetatcd cotlstal d Ul lCS in cllstern Australia. I n : Coosm! Geolllorphology il/ Aus,/,alia (Eel. TI10111. (j.G,) PI' . 263-290. Academic Ilrcss. Sydney, . H , & H U UBt.l!, G , D , ( 1 977) Sub-l ropiclIl TIIOMPSON. podzols (spodosol:- and rcl�ltcd soils) or CO-2 13. WAkl), W , T , ( 1 �77) SUllcl movcmClll 011 Fmscl' Is101ld: ;, rcspollsC to ch angi ng clilll"lI�s. Univ, QId Alllhropology Mllselllll OlX. Pap. 8. 1 1 3- 1 26. WAIt\), W.T. ( 1982 ) Formation HlIti devdopmcnt of t ile shoreline al T�lIlgllloomll Point. Moreton Island. PI'OC', lioy. Soc. Qld 93. 1 1 -20. W,\lm, W,T, & GIl.tMI!S. K , G . ( 19R7) History of coastal duncs lH Tril1nglc Clifr. Fr
TltOM I'SON.

A IISI. J, £(I/" h Sci, 34.

WAt(D, W,T, &

325-33�,

Lu-n_l1. J . P , ( 1975) Timcs of constal sand ,�ccl1lllulation in southeasl Queensland, PI'O(" Eml. Soc.

44 QI" 9, :1 1 3- 3 1 7 . WAIU>. W.T . . Ll'l"l'I.l3. I . P. & TIIOMI'SON.

K. Pye

. 1-1 . ( 1 979)

SLrtlligl'nphy of two sllndrocks at Rniubow Belich. Queensland, and some notes on their composition.

PlI/acogcQg. • Pa/tI(!oC/inlt/tQ/. . 1'(I/lII!Oec:o/, 26. 305 - 3 1 6 . WILUIOTI', W . F . & IJowm.L, B.S. ( 1977) ExplmUllol'Y NOIe,\': 1:250 0(1) Geologiclil SlIee(, CC/pt! WeyIllQ/II/t.

Qlleem'/(lful. l3urcllu of Mineral Resources, Hllbcrra. WILSON, 1 .0 . ( 1 972) Univcrsnl di:':cQlllilluilics in bedforms produced by the wind. ), Sed. f'(!/I'ol. 42, 667-679. WRIGlfr, A . I I . ( I !.I76) Genesis of low iron bauxite. north. eastern ape York. QlIccnslund. Australia. Ecoll. Geol. 7 1 , 1 526- 1532 .

Spec.:. PI/bls flit. Ass. Sr:{lillrelll. ( 1 993) 1 6. 45-60

The modern and ancient pattern of sandflow through the southern Namib deflation basin I.

O R B ETT

Deparlmew oj Gcology, Univer,\·iry of Cope To 11111,

f?ondebo,w:1I 7700.

SOlllh Africa

A II S T R A C T The neolian system within the 0-20 k m wide coastal tmet of the southern Namib deOutiOn btlsin iii governed by unimodal southweste rl)' Lo solltlHoUlhcaslcrly surface \Vitldllo\V, A strollS scnsonulity choractcrizcs the wind energy of thC systcm, with the pc�l k occurring from Scptcmber to Murch. when I gusling al SO- I OOkm h- is commOn. Despitc the high enel'gy of the ileoliill) s)'steill. beach denali n supplying sediment to the aeolian systcm is restricted to log-spi nll fmd sou t h-fnd ng rc-entrant cmbaymeills. along the othc" wise e:<posed Atlllntic eotlstline. S,Jlld trap dilta from

(I

tnlvcrsC pcrpcncliclIlol· to s(ll1dnow somc 30km downwind of

olle such point source provc thm rathcr th
tl

1 - 2 klll wide

linear, wi lld�panLl lcl zOne, This LOne antl other similnr lincar ZOIlCS fife dclincotcd by bOfch
10

120 k m from the eOilst to the Nnmib SlInd Sell. The high-s�lndnow zones thus

ilct as aeoli;1I1 transport corridors. in which optimal conditions for aeoliun crecp transport occur. The possible cxistence of longilUdi lltll voniecs within the planetary boundary layer abo"e the (leOation basin provides one meeh:lIlisl11 by which the eOl'l'idors might bc maintained. The distribution of YCirdnngs formcd frol1l PrcclImbril)1l dolomite on t he noor of the pl'cscnt-day deflation basin supports the conclusion thllt the position of acoliall tramip 1'1 ('"OITiclors lws \!aricd with limc, PalaeOYlirdang surfaces, lying outside the prcscnt tlcolilln transport corridors, arc undergoing modifiemion by solution wealhcring. These features must. howe"er, hllvc previously lain within the plllh of an aeolian tra nsport corridor gencnlled from II regressive coastline. Thus the diStributiOn of :Ieoli<.lli Irnnsport corridors has been. and still is. governed by coaswl morphology. which is 11 function of SCII level nuclU�ltion and denatioll b:lsin morphology. IWllges of lhis son provide a key to ulH.lerstundillg the periodic expansion
I NT R O O The

N,1ll1ib is n coastal descl"

C T i ON tuclics of factol's controlling dUlle morphology and

locl.l t'ccI o n t h e wcstern

Ni:lmib

Illnrgin of t he southern A frican subco n t i ne n t. . I I is

lhe development and maintenance of the

bounded to the west by Ihe A l l a n t i c Occ n n l1ncl

S a n d S e a h a v e t h erefore not f u l l y appreciated the

to the cast

by the GretH

Escarpment (Fig.

rolc of the denatioll basin , which is an inlegnll part

I ),

of the aeolian system us �\ whole.

Ahhough the dynamics of the clune systems com­ have becn the

Prior to (his study, the sediment budget has been

Dean,

examined using estimates from wind d'lla of the

1979; Ward, 1984� Lancaster, 1985). the deflation

potential sandHow through the denation basin (e,g.

prising the main Namib

Sand Se..l

su bjec t o f many studies (e.g. Fryberger

&

basi n , which lies w i t h i n a restl'iclc I diamond area,

FI'ybel'gcr

has 1)01 received the snll1e nmount o f HttClllion.

&

Dean, 1979: Lancaster, 1985). Such on a deal' understan ding of

approach f�l ils to provide

the l i n k between defla tion basin dynamics and the Prescnt ilddrcss: Dc l3ecrs Marine (PlY) LId. PO Box 2605. Cnpc Town SOOO . Soulh A(rica.

Aeolian Sediments: Ancient and Modern Edited by K. Pye and N. Lancaster © 1993 The International Association of Sedimentologists ISBN: 978-0-632-03544-1

aeolian

system

of factors such

45

as a whole bcenuse cognizance as sediment supply which impose

I.

46

orbell

const raints 011 1111 aeolian trnnSport system no maHer

world's most

how high-energy it may be, cannot be accounted for.

operates ( Rogers. 1977).

This paper is based On 4 yc.trs of sandflow duta

dynnmic aeolinn systems currently

Geomorphological evidence shows that changes

collected along a n c�lsl- wCSI traverse perpendicular

have occurred i n

to the dominant sttlldflow direction through tlH':

the deflation basin in the past. which can be inter­

southern Namib deflmion basin. Foul' sand traps

preted on the basis of the model explaining the

were

dC I loyed

together

with

one

anemometer

the s3ndflow panel'll

through

present-day sundAow distribution. This approach

station (Fig. Ie). The sand traps were aligned to

has ident ified a relationship between sand sea ac­

cntch t he northbound sandnow only.

cumulation n n d cUSHttic sea level movement. which


design was based on thm of I l Icnbcrger

&

their Rust

has implications for studies secking to relate the

( 1 986) n"d Horikawn & Shen ( 1 960). A modified

version of the Horikaw:J

&

dynamics of lil rge aeolian sand bodies to the concepts

Shen design was COIl1-

of seismic sequence stratigraphy.

pal'tl11cntalizcd to examine the verticill v
M O R I' H O L O G Y OF T H E S O U T H E R N N A M I B D E F L A T I O N B AS I N

111<11 all s
of IlHltcrial transported up to

1 .83 m above the

bcd. The results ill ustrate the spatial and tempontl variations i n the distribut ioll of sandnow through

The deflmion bnsin is wedge-shaped in plan, with

the prcSCll[-dHY dcnation basin. where one of the

its apex i n the south situated on the south side of

e

..·s

••

U·

_

".

! ..

'1:>

IOGf;....ELS

ZS·

C • C'

"-':QtAN�

""" . T"..... b'

I �'"

1;3

lfig. I .

(A)-( ) Mops sh wing the

locntion of the southern Namib dellatioll basi" and the position or the C1llc1ll0mCtcr und ( l' ) sand tmps used in t his study.

Salldflow through the sO/ahem Chameis Bay. I t is about 20kn'l wide to tltc cast of Uidcl'itz, about 1 25 km to thc n o rt h , where i t meets rhe Namib Sand Scn. I n contrast to the Namib Sand Sea, m i n i m il i l oose sand covers the deflat i on bm:ii" noor. Hnd the regional north-sout h structural trend which has greatly innuenced the development of Ihe rugged delimion basin to pogra p hy is clea rl y seCn (Fig. 2). Many of the south - north oriented sub-basins within the main dcllation basin arc cildoreic, with no direct cOllnection with [he sen (Fig. 3). The largest c nd ol'c ic basins can be traced ovcr 35 km from south to north, and salt pans commonly occupy base- le vel loca t io ns

''Ig. ' 2. Oblique flcri.)1 view loo k i ng sOUlh over llle dcflalioll basin. The strollg stl'llctllrfll trcnd of t he Lnte PrecmubriDIl Bogcnfcls FOl'lll
Fig. 3, Oblique ncri::!1 view to the Ilorth showing the leI,lInl, an clldoreic busin n l iSllcc1 approximAtely p
Nalllib

47

within th em (sec Fig, 2) , M a n y of the s ub- b a s i ns (\ro Hoared by, and developed within, clastic litho logies of the Bogenfels Formation which arc susceptible to m ech an i cal breakdown by SHit weathering; the prod u c ts arc rapidly removed by aeol i a n abrasion and denation. Consequently! some base-levels have becn lowered below the present sea level. The orientation of the endoreic basins thus follows the regional structul'al trend, which is coincidentally n ligllcd with thal of the preva.iling southerly surface winds, and the features do not represent y;;lI'C;langs attributable to aeol i an processes alone,

I. COrfJell

4R

l'ATTE ll N O F S U R F A C E W 1 N 1H' L O W

the ciiffcrentinl heating and cooling of the seH ancl land surfnccs. The peak energy of this componelH,

The pattern o f sllrfHcc windnow over the soutilern

which is primHri ly respons ible for driving the aeoli�Ln

Namib can be subdivided spati
system. occurs seaso na l ly between

parallel zones on the bnsis of cha nges in the distri­

March each year. The d i u l'Ilal pea k , when gusting Ilt

bution and orientiltion or acoliHIl bedforms.

SO- I OO k m h

I

ctober and

is most common. OcCurS between

1 3 :00 and 1 6 : 00 hOllrs. There is also some evidence

rol'

COllstill high-cncT/.:y regirne

regional sou t h - nort h ve loc ity grmlicnt i n

1.1

addition t o rhe bettci' defined west-east onc ovel'

The nal'l'Qw unimodal regim e of the 20 kill wide coastal tract containing the dcnation basin is domi­ U ll fed by high-cllcq�.Y sout h-sourhwcslcrly ro sOlllh· southeasterly su rface winds t h roughout most of the ye" r (Fig. 4). Occ asi onal revcrsn ls. which cha r;lc­ tcristically result in h igh-energy Ilort herly winds

the deflation basin ( Rogers, 1 977: L�l Ilcast er, 1985).

Although the formcl' is prescntly ill defined, the cxpCriC[lCe of living i n t h e re gio n supports the concept o f t i wind energy i ncrease towards PO[11011a before it declines grm l un l l y LOwnn.Js the start of the sand sea, whe l'e depositional processes dominate.

for brief periods between April and August. arc, however, an important seasonal component. The soul'hc l' ly component is govcmcd by the SO�ll h Atlanlic (lilt icyclo" ic system. which displays

Hlld di u rn a l vHrinlions ill response 10 changes i n the p ressure grn c iicil l which rcsult rrol11

s t rong scnsonfll

Wind speed 11

1m s

1 .8- 4.4

4.5- 6.9 7.0- 9.7

9.8-12.5

12.6-15.3 15.4

Apr.-Jun. Jan.-Mar.

o

20

F/eCluenCy (% )

lolund regimes

Two rUfther coast�parHllel belts characterized by in c re asi n gly complex surface wind re gi mes OCClII' to the east or t he coastal hig h-e ne rg y tracl. I n bmh cases, the increasing complexity, resul t i ng in first bim oda l ancl t llcn lri mod,ll regimes, can be attributed to the diminishing i n llucnce of the South A[lantic
over the Namib Sa ncl Sea within t h e central Namib,

wherc the coastal u n i modal rcgimc "Iso gives way to b i mod a l and t['imodal regimcs to the cast, away rrom the coast ( Frybe rge r & De�1 I1 , 1 97Y; Lanc(lSlel',

)

1 983, 1985: Ward. 1 984 .

I'R IlS E N T - D A Y PATT E R N OF SAN DFLOW

Jul.-$ept.

• •

Coastal scdilllt;II' entry puillts mut burchfLn dune tnlins

The high-energy Atlantic coast line bord eri ng the southern Namib dcl'hltioll hasin is ch at'lIctcrizcd by sleep beaches. which arC pre dom i n a n tly com posed of granulcs and small pe bb l es .

and rocky shores.

Sandy beaches conta ining abundallt mat'erial suitable Fig. 4. Wind roses summarizing [he scaSO lll H variation in surfllCC wind direct io n at Bogenfels during I V87. when detlliled sand trap results were obtained.

for deflation ancl subsequent incorporation into the acolian system hy the Iligh�cne l'gy southel'ly SUI'� face

\v i nds

tHe ['csu"icted to rour widely se parate d

Slllld/fOIV

throllgh the .\'0111/1(11"11 Nalllib

cmbnymcnts. Two of th e embnymcnts arc o f n JogMspiraJ form, and t he othcrs tire sQ u l hMfaci ng rCMemrant b"ys.

Trains of b.uc h an dunes, which are up (0 30 III high tlnd m igrate iH 30- 50 m y r- 1 ( Ka ise r , 1926: Corben, 1989), develop di re ct ly to the north o f the coastal sedimcnt entJ'y points (Fig. 5 ) , i.llld aJ'C a major feat u re of rhe southcm N a m i b deflation basin (Kuiser, 1 926 ; 1977). In

all

Halla""

1964; O'Brien, 1972; Rogers,

cases, the

of

path

lhe dune trains is

rema r k ab ly slr
maint,dned at

the coast . the longest

can be traced from its inception poi n t at Chameis B<.' Y. t h l'O u gh the cmirc basin, to the point

Sand

cn.

at wh i c h

125 kill o f

thc d cna tion

it en te rs the mHill Namib

pHssing Bogcnfels is clcHrly demo nstratcd by the sand nap results for site C, which represcn t a con­ tinuous pel' iod of "l bo u t 2 ye a rs from 2 Dcccmbcl' 1 986 (Fig. 6A). The sa",e pntlern

a

is

shown by lhe

de ta i l ed monitoring period be twecn

2

December 1986 tlnd 28 May 1987 , wh i ch confirmed

that the salld no\\' d i m i nish e s rapidly from Feb ruary o n wa rds . Shorter-term nuct u"lIiOI1S wcrc also sec n

within thesc dara, and it was observed that I

cuks in

sa nd ll ow d o not always correspond w i t h those i n surracc w i n d vclocilY

high

t he wind energy o f t h e aeolian system is greatest: and/or

2 the storage o f san d within thc :lColial' system

ilSelf. Although ben!.:h progra 1<.Il'ion

sll rfa cc

(Fig.

6 B ) . This cycl i ca l pall.crn

10 l ow sand now is i n terp rc ted as evidence for

the strong i n O u ence which sed im en t
Fig. 5. Oblique "crilll view to the

wlJlh a lo llS the barch a n clulle lI'ain that mignl lcs 10 I h e Ilorlh past

B()gcnfcls. S<."lnd trap sitc C wns close 10 Ihe wcstCI'll ar1ll of the 30m high b,lI'chnll ill the foreground.

creates

;]

1<11'ge1'

arCH over which deflation can operatc ,

t h e re by i nt rod uci ng more material to the aeolian

system, the i ncid e n ce of infrcquent, h ig lHl1 agn i tu de

'sand storm' e vc n ts i ndicates that sand storage is the more i lllpOrl
stOlle pavemcnts

alld wi th i l l

ncolian currCnt Shildows of vtifious scalcs, i n c l udi n g

The seaso na l fluctuation in rhe quantity of sHndtlow

of

on the dyna m ic s of the acolian systcm . W i t h i n the sOlllhcrn N,lmib, sedimcnt ava i l ab i l i ty i s most l i ke ly 10 fl uc t uate in response to: I se aso n a l bcach progradation, which rcaches its m ax i m u lll between December and Fe b ru a ry , when

between

Tcmpornl Sfllldflow vllrhlfion

res ul t s of

49

has

shadow dunes.

The silnd stor m event which occurred between 1 0 and 12 FebruHry 1987, when the southerly to soulhMsoutheasterly surface winds accelerated from 1

to 70 km h - 1 ovcr �l few minutes, grl;lp h icB l ly i l l uSLralcd the ability or pulses in surface wi nd energy to entrain material frolll these slOr<.lge sites. This si n gl c evCnt accounted for 14°/" of the sandflow measured at s i re between 2 Deccmbcr 1986 and 5 Janu<1t·y 1988. This con tl'ad i cts the statement made by Lancaste r ( 1 985), who, cmp l oyi ng estimates of potential sHndtlow, COIlM eluded Ih:l I i n freq u e n t , hig h- magnitude sa nd storm' events do n o t play a sigilificilill role ill the Namib. a n average velociry of about 7 k m h-

'

T h i s d i ffere nce ill

results cll.lci d 'l t cs t h e d i frlcu ltics

I. Corbell

50 A g

§

!O

25 20

� 15

"

E

:? � � �

'0

5

o*-��----.---.--� 200 o 400 600 800 Julian d6VS

B

�.

- .. - • .

88 8. 85-104

O�lra7 22101"7

: :��

1----,1---, ,- I ,-

I

involved in

calculating meaningful sediment budgets wi nd dnw alone, n n d i nd i ca tes a n e ed for mO re empirically based studies of defl at ion bilSill d y n am ics if aeolian sy stems arc to be more fully using

understood.

Simtiul sundtlow vm'iution

i n the northbound bns i n to the cast of Bogc nfcls is clearly den ned by the sand (rap resulls (Fig. 7 ) .

SHndnow passing I h raugll the deflation

14.5 �'B 4

02102 1111 12102'87

----I--"

____ _ ;�:l:: ___ ' _______ Variation of sand flow (tim widlh/24 h)

The markc(i spHtial va ri at i on

-,

1 0 5 -12,4 12 5 ...�

22101/81 OVCMl7

1$.8_1 1." IIJ,�-20.

wind ,peed 1m '- 'I

o

10

20%

�

Fr&qulllntv

Fig. 6. (A) Gn,ph showing tlie seasonul vnritHioll in the qmlntity of nOrthbOund Mlndtlow (cumulative) transported tOWtlrds the muin Namib Silild Seil, December 1986Fcbrunry 1989. ( 8 ) Oetuiled Slilidfluw rcsults over short time pcriods t\l site C. Cyclical \'nrialion in sand flow pCHks is secn 1101 to correspond with periods of ptlrtieulurly high wind energ)'.

Approximately 7 . 1 ton n es per metre wi d t h (tmw) of sand now passed site from 22 January 1987 t0 28 May 1 987, wh ilst 0.63 t m w and 0.57 tlllW passed si tes 1\
Salle/flow

Fig.

7. Graph sunullllrizing �paliat

vnri:l I io n ill s:lmlnow along all ea�l­ west t raverse IJCroSS the prevailing

tlirollgh the sOf{fflel'll

� • ANEMOMETER

.. SAhO TRAP

southerl)' surfuc:c wind now IlCllr llogcnfc1s.

where numcrous workers (e.g. Ka ise r, 1 926: J- Ia l l�'Ill. 1964: O'Brien, 1972: R ogers, 1977) have previously shown tlHlt the material e nte rs t he aeolia n syste lll .

A E O L I A N T R A N S I' O R T C O R R I DO R S Ccncnltion

The length of beach within Bakers Bay a long which denation can act. coupled with the distribution of vegetarion, which is restr ic tcd to <.IrOnS of lesser sa n cl llow, show thaL the widt h of the h igh�sHnclnow zonc cielincHted at Bogcn fcl s is only about I kl11 at the coast (Fig. 8). I-Ience matcrial e nt e r ing the aeolian systcm via the denation of il coaSl<\1 point source docs not fan o u t downwind to produce an ev...: n distribution of stinclAow across the c n ti rc basin . bu t remains within a narrow zone, termed un ' aeolian transpol't corl'idor', which rllns approximatcly parnllcl to t he southerly surface winds. Mninlcmmcc

Although lopogr n p h ic interaction with the surface win d flow u n do u blCd l y inlluenccs thc p3th taken by s
0

Namib

BOG£NFELS BEACH C'f!' .q'1-

51

OO_AN� AEOLI AN SANDFLOW M£C T ION

'<;oJ

in dc pc n lent of loc'll to pogra phy, and the ge n e rat ion of secon d ary now pnl le rns is one process by w h ich this might he ilt;hieycd. The arri val of southerly surfat;c wi nds at the warm land surface of the denatio" basin fl fter fl owin g over the cold su rface water of the Atlanlic Ocea n pl'Ovidcs ideal circulllstances for the prod u ct io n of cOllsider­ ahle thermnl contrast. Such conditions arc con du ci ve to the developme n t of lhermal inst a b i li ty wi t hi n t h e plnncHl ry houndary 1�lyer and. provided t l1:lt su fficient shear occurs, this c�ln result in the gene rati on of l o ngi t u d i nal spin" vo rt i ces (c.g. Jeffreys, 1928; Wi l a n der . 19(4). Tnmsvcrsc i nsta bi lit y of this type i n rl ucn ci ng su rface w ind llow is widely a c k no wl ed ged 10 he important in Ihe lllu i n tcn l1 n cC of lin e a l' dune systems (1-l tlTlila . 1 1)69: Mabbul1 et (II" 1969; Glennie, 1970: Folk, 1 97 1 ) , in addition to gove rn i ng thc dis­ t ri b u t i o n of dust alld po l l u t a n ts i n the atmosp h e re (Brown, 1983). Thc occul'I"cnce of IineHr dune systcms throughout the so u th e m Namib (Fig. 9) thus supports the co n ce pt thnt seco n cl n ry flow wilhin the pl:.lnc t:lry bounda ry layer is wide l y de ve l o ped over Lhe regi o n, with add it io n a l evidcnce being pl'Ovidl;!d hy the occasional presence of cloud stre ets �Ibovc the dcnatioll btlsi n . The creswl si lic i n g of the linear dUlles to the southeast of the dcllnt ion basin varics from 250 to 500 Ill. whilst in thc SOllthern pari of the main Namib and Sca it is about 2 kill, which r o u gh l y corres pon ds to the estima te d width of the Bakers Bay acoli'ln t ran s po rt corridor. Theoret ic
I. COl'lJeff

52

CCl1trutiOIl of s�lIldAow t ravel l i ng ovel' the bed within the n co l in ll transport corridor

is

p redi ct ed t o occur

along th e separation line of adjaccllI longitudinal vss

vortex cells, which is proba bl y delincatcd by thc

b<.lrc hn n s comprising the dune t rn in . Whc l'c sufficient

....

III eOA$'I'Al. SA8l
sed i m e n t is

avai l a b le

a number of pn rn ll c l barchan

dunc t r a i n s can develo p and be mainwined w it h i n adj ace n t pt:li rs o f lon gi t ud ina l

vortex cells. a s seen at

Gl'i l l elllal di rectly to the so uth of t h e main N a m i b Sa n d Sea (Fig. 1 1 ) . Thrcc major acolian transport corridors currcntly opcratc w i t h i n t he southcm Namib denatiotl basin, as e vi de nced by the de v elop me n t of barchan dune tr", i lls . A l l o r these occur dowllwind of l og-s p i ra l cmbaymenls

HI

Ch
Prillze llbucht (Fig.

AEOLIAN TRANSPORT CORRIOOR G£N£AATION

12).

Bay.

Bakers Bay a n d

A fou rt h , smaller corridor

is generatcd at the small south-rHcing re-e ntrant embayment called Van Rc c llcn Bny. In addition,

sandflow is also generated by beach elenation �dong [hc coast in the vicinity of El i za be t h BHY, which

nlso provides an important scdimcnt sou rce fOt' t h e neoliflll syste m .

-1

oastal mo rp hology t h e refore pla ys

an i mport a nt role i n cictcrm i n i llg the frequency and

DOMINANT WAVE DIRECTION

s pac i n g of aeolian t n.IIlSpo r t corridors, which ;1I'e

thus s uscepti ble LO c ha nges brought nbout by SOH

Icvel movcment.

! ...

D u ri n g p rol o ngcd pcriods of so u t h e rly s u r frlce

� 2,Km

_ _ _

wincl, the
Fig. S. Sketch showing the Bukers Bay log-spiral embaYlllent. which :.Jels tiS a point source for sediment e lt teri ng the Bakers Bny barchan dune train as II result beach dCnlllion.

of

the crcstnl spaci ng of t he d i fferent l i near clulle systems

could he due 10 the co m press io n

with the prevailing wind conditions.

Provided thaI abrupt peaks i n w i n d velocity d() no t occur. there is a p rogre ss i ve bu i ld -u p in the q lw nt i ty

of th e i:l ll licyc i o n ic

of sal ta ti o n load stored within t h e aeolian syste m .

Brief. high-e nel'gy pulses of so u therl y surface wind I'api lIy entmin this materi a l , p l'od uci n g infrcquent, h igh -magn i t u de s<'lIld stol'01 eve!HS which play an i m portan l role in the Namib aeoli.) n systcm. Sandllow

is main t.lined ..It much higher levels within aco l i a n

w i nd syst e m
I'n:lll sport cor r id ors d u r i n g such

forms an orograph i c ba rr i e r . The aeol i a n tl'anspol't

i n flucncc of ne o li H Il tnmspor\' corridol'5 on lhe dis­

corrido r may thus correspond to the corlcCplual

Ill ode l of Allen ( 1 982) for secondary now i n n sys te m

tl'ibution o f si.lndflow

d i m inishcs

evenl::;, but the greatly

during

i n frcq ue n t , h ig h -e n ergy , n o rthe rl y wind reversals.

in which there is i nsu ffici e n L sediment to cover the

U n d e r these circumsl
bed (Fig. l O A ) . The margi ns of the UCOIiHIl Ir
entrained from storage sitcs which arc only sta b lc

corrielor on the dcnation bHsin 11001' wou l d Ihen

under southerly wind conditions, with the res u l t tlHlt

represent the position along which the longitudillal

high sanclnow occli rs basi n -w id e .

re a tl
would d i rect the Ilwtcrial i n towi.1rds the barchan

dUlle t rai n (Fig. lOB). The maximum arenl COI1-

DisphlcCJ11Cnl Yardangs

of .--,colian 1I,.lltsport corridors

are w idely distributed t h roughout the

defl at i o n basin, but they are best developcd whcrc

Late Preca mbrian Bogcnfels Formation dolomitc p l'Ovi d cs u pst a n d i ll g relief due to i ts resistallce to

Sl/l/{ljlOlIi through tIle ,\'olllhem

o

Nallli/)

53

20t<m

LEGEND

B

T

COMPOUND BARCHANOID

DUNES

L

COMPOUND TRANSVERse DUNES COMPOUND LINEM DUNES

S

STAR DUNES

',', '\,

ls SIMPLE LINEAR DUNES

P

NAMIB SA,ND SEA

PLINTH

DUNE CRESTS BAACHAN DUNE TRAIN SAND SHEET

Fig. 9. Map showing the rcgional di�tributiol1 of aeolian lincar dUlle systems within the southern Namib.

HIGH GROUND

s<.Ilr weathering, The y,udangs arc unusual because they arc formed from crysta l l i n c mck. ,mel lhe lectonic st ru ctu re has had sOme i n n ucllce, with thc best forms occurring where the dolomite strikes

cast-west and dips to lhe north ( Fi g . 13). Evidellce of the extremely abrasive nature of the aeolian system is provided by the devclop1l1cIll of beautiful ve ll t i ­ facts, with sOlll e of the most complex and polished forms being produced fro m dol0111 ite (Fig. 14). Areas i n w h i ch yardang forll1alion is ,I clivcly occulTing todi.lY arc restricted to lhe paths of the currenrly active aeo l i a n tnillsport cor rid ors (Fig. 1 5 ) . U nd cr these conditions. ymdallg sllrf�lccs ilre Sill Othly polished llnd fl u t i n g is vCI'y evident. A

nu mber of yn rd a ng

the i nll u c n ce

of the

fields do, however. lie beyond present-day aeo l i a n tnlllsporl

corridors nnd I hey ill'C IlO longer cleveloping actively.

In t h cse cases, the once smoothly pol ished surfaces :Ire now rou g h and colon ized by l i chell, w i t h fluling

btu'ely ident ifiable due to slirface mod ific.lIioll by solution weathering of Ihe dolomite. The Bogenfcls yMdung field is prese ntly sH unted on the coasl. where dcflation or t h e st ra i gh t . steep. high-energy

bCHeh

provides

inpul to lhe aeolian syst e lll .

minimal

sediment

This yardung fi e l d Illust therefore !lave de ve l o ped d U l' i ng a regressio n , when bnys providi ng cOHS1�d po i n t sources for neolian transport corridor gcncrntioll wo u l d hnvc Inin further

I. Corbett

54

·?Y·:; ; ·, ;.'

··.·'AEOLIAN . . ''..,' .··:·:� ..:·:·>r;: : -.

I

: TRANSPORT CORRIDOR

�

@>.. � APPROX. I

I

I - 2 Krn

LEGEND

�

BARCHAN DUNE

POINT SOURCE OF SEDIMENT TO AEOLIAN ENVIRONMENT

\. PATTERN OF " SECONDARY FLOW ON THE BED

1

EXPOSED COAST

�

LOG-SPIRAL EMBAYMENT

'.'t.,.."

AEOLIAN TRANSPORT

�

. • •

" '/.:.: CORRIDOR

Fig. 10. (A) Conccptualized pnltern of helical secondary vortices which nre proposed as n mecimn il!1ll for Illilintaining aeolian transport corridors, (8) Proposcd rOle of helicill secondary now in cOllstmining S
Ss��_ �/

NAMIB

_)

o

,.

wesl. COllversely, lloll-
Fig. I I . Adjuccllt bilrcllllil dune tl'ains c rossi ng the Gril lClltid Vi'dle)' to the south or Koll1l.inskop. Note the regular spneing which might rencet the pn:scllce of hcl ic�11 sCI.:omlary vortices contrOlling the spacing of the dunes which define the pnth of aeolian trililSpOrl corridors.

t h e cast, e i t h e r t h e width or the c:oastnl

In.lel

must be

incrcHscd or thc pos i t io n of the high-cnergy Ir(let

imply a rc la t i ve shift of Ihe aeol ian system to t h e

itself llluSl a l tcr. The lallcr case m ig h t be expected

governed by the width of lhe coaswl high�cncrgy

e ast ward s h i ft in t h e rclative position of the zones

cast. The locmi on of Ihe denntioll bnsin m a rgi n is tract domi ne-Hc(1 by sou[hc1'ly surf;'lcc windflow. I II o r Ie!' 1O HCCOUllt for I h e IlHHgin being di�plac:cd [0

ro occur dUl'ing a tl'fl llsgressivc pc ri od . when an

L:omprising t he regional pattern o f surf. . cc windi10w ove!' t h e Namib mig h t be alHicipalcd,

SllIIdllo11' ,,,,.o//gh 'he sowl,ern

Nalllib

55 -

I

N

PRlNl£N8UCHT

o o <" • ..

Fig. 12. The present-cllIY distribut iOIl of aeolian transport cOI'ridors within the southern Numib denation bllsi n , which nrc responsll>le for the maintenance o f the main Namib S
FI�, 13, Oblique {reriol view to lhe cnst showing 10-15 III high y:ml:lngs fOl'llled from !.:rYMulliuc dolomitc immediatcly west of l3ogenfels,

Fig, 14, Magnilicel1t exal1lple of all aeolinn vCluifncl consisting of blndes and spikes of crystalline dolomite. Note the extrelm: dl.!\'dupmclIl of the ero�ional fcuturcs 011 the south face of tile blol.!k, Seale is I D e m .

I. CorfJetf

56

......

o

10 km

? \ \

\ PALAEO·MARGIN \OF DEFLATION \BASIN \ \

\

?

• illii!l!!l rutl!!W

[:::;::1 1)\;, /',1

LEGEND ACTIVE YARDANG FIELD NDN·ACTIVE YARDANG FIELD HIGH·SANDFLOW ZONE NAMIB SAND SEA

Fig. 15. M:,p showing the:: di:itribution of currently tletivc yurclHllg liclcl:i wilh respect to the present-day pHltcrn of slIlIdOow. together with non-active ticlds which urc no longer maintaincd by ilcolian ubrasioll.

INFLUENCE OF SEA M O V E MENT ON DVNAM ICS

LEVEL

DEFLATION AND

Il A S I N

SAND SEA

M A I NT E N A N C E

windllow pattern rH<.Iy hnvc shi fted westw3n.ls ill response to

n

ch.1I1ge i n the position of the shoreline.

The highest-cnergy tract of the prescnt-day system is delineated by the dcnation basin and the coastal

Extensive regional mapping has shown that at Icnst

belt of compOllnd t ransversc dunes along the westcrn hOl'dcr of the main Namib Sand Sea, which Ward

four pnlacodl,lllc systems deposited by southerly

( 1 984) htls shown to be considcrably marc dynamic

quadrant palaeowind regimes arc represented w i t h i n

th�l11 the IineH!" dune systcms to the easl. Thus.

t h e southern a n d cCIlIn.il Nnmib ( P i g . 1 6 ) (Ward.

conceptually , a cOllsidc rnbly less dynamic eastern

1984, 1 987:

ZOne of sand SC�I (core) is bordered to the west by

orbc t t , 1989: Ward

&

orbett, 1 99()),

I n all cases the palucodunc systems were larger t h a n

increasingly dYllnmic coast-parallcl belts, charac­

the present-tlay m a i n N
terized

Formation), and thus provide evidence for sand

of sandHow_ These dynamic belrs arc the most

paiacodullc syslcn1S it is believed thm s
about by cha nges in denation basin dynamics related

exp;'lIlsion(s) occurred during Ilwrillc rcgression(s).

to sen levcl mOvemC n t .

sea expansion. Although i t is d i fficult to elmc the

when the zones comprising the I'Cgi O l1
by

a

progressively

greater

thl'Oughput

responsive to changes in lhe aeoli a n system brought

57

S(llulj1ol1' ,hrollgh the sOli/hem N(IIlIil)

SUMMARISED SEA LEvEL cuRvE

§ ?

HOLOCENE

� � z >

� w >� � 0

N o Z w U

� >� w >-

Fig,

16, Lithostratigraphy or

palucodutlc systcms preserved within the sOuthern Namib denalion basin.

>w � u

,'-

��

"<� 1-- --

MlOCENE

OLiGOCEN�

�OC[H( P "' l ", EOC£M:

KI$lU' ,.14tI '(O'HoU. 'OOH �I"' $�'T(IMC

� <:

PLEISTOCENE

, > �

SANDSTONes R£:PR£:S£:NTING P4LAEO-OVN[ 5V5lEM5

�

�

u

6

• M,

l S

--

S c

2

,

""� ..�,,- .".

<>

"

'"

Itoc...("(� UNOS'Ot«

" ....,,'" ..�.....

F-

'""

BMSL

j �

��

!

t

"".."t

<>.

SCH i s reworked 110t only by nearshore marine pro­

Response to regression

During a regression i t is believed that thc zones of

d i ffc)'Cll l su rface wi ndflow s h i ft 10 thc wes t , as thc continciltal shclf a l o ng the maJ'gin

of the f01'lner

ccsses but by acolian proccsscs tiS well. This is prob
S
Regiona l bounding surface fornmtioll

thc (\ellmioll basin hi then envisaged to accrctc as

�ca cxp
arriving at the southcrn cnd of the s
wedges along the

fo rm er

plinth, with the resu l t

t h a t the sand body cxpands westwards, A l t h o ugh

deflation of the newly exposcd shclf initially also

su ppli es sed i mc n t , i t is p robably finite due to t he devcl o p mcnt ofsmble stolle pavemcnts and deflation lags. The weste rn bclt of high sandflow
be maintained by the continued int roduction of sandt10w via aeolian

transport corridors. which

may increase 01' de c rcase in

numbcr depc nd i ng

on changes in co astal morp hology. It is p red i cted that, in timc, fonner bclts of co m pou n d tranSVCrse dunes would I c rcph1ced by lille�lr dune fo rm s u n d , WCI'C sections t h ro ug h t h e pa l aeod u ne sequences avn i l a b le , it. is suspected that changes of t h is type would be refl ected i n the p ri m a ry scdimentary structure preserved within the sanel body. Response to trollsgrcssion

Ol1ccptllally, th e coastal

belt of high sftllclflow mi gratcs converscly to the cast elul'ing a tr<111sgrcssion, with

the result that rhe weslern margin of the sand

Based On p resen t knowledge, lwO pe riods of sand

'-hc oldest, represented by th e Fiskus SalldslOl1e

Bcds, was the precursor of t h e prese n t sand sea, and probably devcloped from around I() M a , w h i l st the OI'hcr snnd bod y for which we have some evidcncc

is l'cprcscllLcd by t h e Anl1cntal sandstonc. nnd was

pl'Ob(lbly depos i ted d u ring the la�t glacial maximum, about 1 8 000-20000 BI'. As a resuit of t h e denation

basin environment mi grat i ng 10 the east in response

to transgression subsequcnt to the deposi t i o n of

these two sand bodics, the prcsent'4dny aeoli:11l system is actively rcwOI'king thcln al the southcm extrcmity of the m ai n Nami b . and

ca. The AnnClltal

sandstol1e has IlOW been Inrgely eroded, l eaving rnrC i so lated reill nants in slcep sided coastal glll1cys

nnd within

the deeper ephemeral SLre�11l1

beds,

but due to thc partial cementation of t hc Fiskus

Sandstone Bcds t h c lallcr arc be i ng crodcd morc

s low ly to form an exte ns i ve crosional planc. This crosional p l a ne val'ies from be i ng slIbhol'izolllnl to

fo rese ts of fo nn er dune forms arC clearly seen on its surface

fo rm i ng a ge n tl e incline, and thc crescentic

(Fig. 1 7) , It is interpreted as a regional bounding s u rface, or supcrsurfacc. w h i ch is i n the process of

I. Corbell

58

F ig ' . 17. �ro�ional. regional bou n dins slII'fllcC being CUI in the Fiskus Sandstone Beds as a resull of n shifl in lhe locm i on of the soulhCl'n Namib dcllntiol1 basin.

.

·

devel oping The coarsc g rn inccl IHltUTC of the Fiskus Sandstone Beds is n clistirlguishing fc,l I u rc of this sand body. which contains SubSHlntial qmllltitics of granules w i t h i n Ihe grn i n tlow strata of cros:,-bcdclcli sels. The dcllulion of the sCl n cis tonc ollce it has weathered p rovides material for incorporntion into large gmllulc ripples which occu r extensively on the regionul bou n ding surface. and the weat heri n g products arc a lso frequently illcOI'por:l lctl into ephemeral stream systems which cross th e surface. I f the regional houn di n g surfncc described above was subsequelltly covered by sand SCH ex pa ns io n during set! level rcgrcsf\ion. the nbscncc of datable alluvial or murine deposits separating successive pnlaeo(\u[)c SC411CllCCS would obscure the trllc naturc of thc bounding slIrf:u;;,c. At l ea st onc perlod of sand sen expansion represcnted by the !\nncntal sHnd­ stolle would therefore go lInt'ccognizcd, and evidence for othcrs mighl "Iso have bcen removed hy aeolian erosiun. Under these circulllstances Ihe correct incorpora ti o n ofswckcd p a lacodu nc sC4 uences. s uch as t hose prcservcd in the southern Nomib Desert. i n t o a sequ e nce stratigraphic frnmcwork appears to be difficult to accomplish.

SUMMARY AND CONCLUSIONS

sediment availability and su bstrn tc lypC, I II the case of h i g h e ne rgy systcms such riS that of the so u thcrn Namib den a tion basin , calculmiolls of potcnti�1I s{l.nclnow from wind dtltn (ilonc arc unable to ac­ count for t hese factors, masking thc significance of i n frcq u c nt high-magnitude sand storm events for the I.I colian s),slcm. Sediment supply to the aeolian system within thc southern Namib is restricted to l og sp i ra l and south-faci ng rc-cntnlll1 cmbayments. Material dctlated fl'Ol1l the beach cllvironmclll cnters thc aeolian system via aeolian transport corridors which vary from I to 2 km in width, run p;mlliel to the preva i lin g southerly surf'lcc windnow. and a re cha ...tctcrizcd by conditions of very high sandftow, The pnssagc of aeolian transport corridors thi'Ough the dclhl1ion basin is defined by Il'I.lil1s of barchilll dunes, which migrate along strikingly s tra i ght pa ths It is suggested that longitudinal sccon dnry vortices within the plunctary boundary layer arc rcsponsible for thc I11ninlcnancc of aeolian t ranspol'l corridors. which appcal' to opcrate independ cntly of deRmion basin fopography. Four acolian transport corridors currcntly operate whhin the dcflation basin. with
.

-

,

corridor. On arrival at the Namib Sand Sea. sandflow

i s concluded thai empirical sandllow data arc rcquired i n orde r to determine fully the sedimcnt dy n a mics of dena ti on basin environments. which are complicated by variations i n sediment supply, 11

derived from aeolinn t ransport corridors is believed

to rcmain wilhin it narrow, high-energy coastal t ract charnctcrizcd by co mpoun d transverse dunes. Much of the material which CIHers therefore prob(lbly

Silll elf/olV

IhrollSil file sOlllilem

bypasses the less dyn Ol m ic eastern 'core' which forms the majority of the ,and body. Thc fre quency and spm i a l distribution of aeoliOln transport corridors arc not co ns w n t in either time 01' s pace . Such changes are b ro ught about by sea level movcment, which lllodHies coasta l morph o logy unci thus alters the si tes ;:It which log-s pira l and sou t h� facing re-e ntrant bays form t h ro ugh t he d row n i ng of POl'liOllS of cndoreic basins which arc the main geomorphological c lc m c n ts of the deflmion basin. Lateral shifts in thc zona l surface wind patte1'll arc prediCted LO accom pa ny f'cgrcssio ll alld tnlllsgrcssioll. Palueodullc systems p reserved within the N a m i b provide e vi dence for a t l east t h ree pc ri od s of sand sea expan si o n d u r in g regressi ve events, which is e n vi saged to occur by the a ccreti on of wedges of m ateri a l along the former sand seH pl i nth as the cOIHincntal s he l f is progressively exposed. Th e western margin o f the ex pa n ded sand sea i s reworkcd by both ne a rshorc marine and aeolian processes d u ri n g t ra nsgress io n . which results in sand sea co n t ract io n such as can bc sec n toda y . Palacodunc sys te ms are inAucnccd by len�tion basin dY l1 n m i cs as the zo n a l componcnts of the surface wind pattern m ig rate easrwards, which resu l ts ill extensive erosion Oil a rcgio nn l scale to p rod u ce nn u nd u l ;.l ti n g re g io n a l bOU ll d i llg slirface. V i rtu a l ly all evid e nce of sand sea cxpnnsi ol1 during rhe last gl ac ial maximum. abollt 1 8 000-20 000 8 1' . has now been removed . The full significllnce of the rcgion a l bounding surface, i f i t were subsequently t o b e covered d u r i n g sand sca cxp:lIlsion. would be vi rt u al ly i m possible to aSCCI'l
ACKNO W L E D G E M ENTS I l i s a pl cusu rc to thank M r J . B . Hawthorne, Dr

. R . C l e me n t ancl M r K . R . Hazell of the A n g l o American orpor:Hion of Sout'h Africa ;md DM ( Pty ) Lld for t he i r sllpporl u nci pe r m i ss io n r o lI n de r� take this st ud y . I wo u ld particularly like to t h a n k the Secu rit y Departmen t of CDM ( Pty) Uti for provi di ng t h e hel i cop t er n igh ts from w h i ch this proj ect has benefitcd gl'ctll ly. I would also like 10 t han k the co rp ora t ion for en abl i ng mc to a t te nd the co n fe rence and to present this paper, and acknowledge the draughtsmanship of M r B. Griffin's tea m at De Bccrs Mnrine.

Namib

5�

The rcscmch recounled in this paper forms pan of my Ph . D . thesis. which was u nde rta ke n
R EFERENCES AI.I.eN, J.R.L.

( 1 982) St!dimellltll'y Structures: Their C/Il/ml'ter lIlIll PIly!)'ictl/ Blisis. Elscvicr. Amstcrdam.

21>1>3 PI'. GAGNOU). R.A. ( 11)54) Till! Physics of 810WII SlInd Wit/ De�'el'l DIllies. 2ml cdn. Methuen. London, 265 pp. BKOWN, R.I\. ( 1983) Thc now in the planctary boundary layer. In: Eo/hili SCl/i,,,cllls muI IJ}'()Cesses (Ed. Brookfield, Ahlbntl1dt. T.S.) pp. 291-310. Developmcnts in Sedimentology 38. Elsevier, Aillsterdam.

M.E. & Oklurl1',

o/ Ille diamond· deposils within the Sperrgeblel. Nmllibill.

1 . 0 . ( 1 989) The .\'edimellt% gy

l/eI'OII.\· de/ftlfio/l

Unpublished P h . D . thesis, University of Cape Town,

430 PI'.

FOL.K. R.L. ( 197 1 ) Longitudinal dUlles of the northwest­

ern edg.e of the Simpson Descrt. Northern Territory, AlISll·l1liil. 1 . Gcotllorphology nnd Bruin size reliH iolish ips.

SedimelllOlQgy 16, 5-54. FKYUI!MoeM. S.G. & DEAN, G . ( 1 979) Dunc forms and wind regime. In: A Swdy of Global Suml SellS (Ed. McKee.

. D . ) 1'1'. 136- 1 69. US Geo1. Surv. l)t'O(. Pnp. 1052. K. W. ( 1 970) Deserl Sedimeutaly £lIvi/'OII' melllS. Dcvelopments in Sedimcntology 14. Elsevier. Amstcrdam, 222 pp. 1·IAI.tAM, .D. ( 1964) The geOlogy of the coastnl diumond dC l>osits of Southern Africil ( 1959). In: TIl{' Geology of Some Orc Deposit!>· ill SOllthem A/rictl (Ed. Haughton, S . H . ) PI' . 67 t - 728. Spec. Pub!. Geo!. Soc. S. Mr. .

G l.. ll NNIE,

JolHlnncsburg. H"""NA, S.R. ( 1969) The formntion of longitudinal sand dunes by hlrgc helical eddies ill the atmosphcrc. J. AppJ. Meteorol. !oJ. 874- 3 . HOMIKAWA, K . & S I H : N . H . W . ( 1960) Sand movement by wind nctioll - 011 Ihe charactcristics of silnd tmps. JJe(lcli erOSiQI I BOf/l'd Teclt. Mem. IIV. 5 1 Pl'. t LI.llNIII!KGIW, W . K . & RUST, 1. . ( 1 986) Venturi-com· pensnlcd eolian sand Imp for field usc. J. Sed. Pel/'o/.

56. 54 1 -542. JIWllKllYS, H. ( I92S) Some cascs of inswbility ill nuid Pl'Oc. Hoy. Sac. LOlldoll SCI'. A 1 18, 195-208.

mOlion.

KAISl!K, E. ( 1 926) Dic jungell scdimcntllren neubildung

0111 extrelll-aridenklima der Namibwliste. In:

Die

/)j(,­

(Ed. Kaiser. E . ) pp. 317-380. Dietrich Reimer (Ernst Vohscn), Berlin. LI\NCASl'llM. N. ( 1983) Linear dunes of the Namib Sand $c,1. Z. Geo/llo,ph. SII{Jp/, 45. 27-49. IIUllllellwti.\·w SiidelVe�'/{/fl'ikas 2

I. COrbCfI

611

LANCASTlllt. N . ( 1 �85) Winds anti sl.lnd 1TI0W.:IllCnts in the N,imib Sand Set\' EWlh Sill}: PrOt', Lwul}: 1 O. 607 -6 I Y. MI\lUW'IT. J . A . . WOODING, R.A. & JeNNINGS. J . N . ( 1 969) The asymmetry of AU:ill':lliflll dcscn salle! ridges. AIlS/l'lIfiall 1. Sci. 32. 159- 1 60. O'13IU1lN. R. F, ( 1972) The b!l l'clHlIIS of the SOllthern NlHllib: grain size analysis. Prot'. 4(h S. Alr, Ulliv. Ceo};,.. COllf ,

22-3 1 . ROGllI<s. J , ( 1977) Scdirncnl,)lion 0 1 1 tllc conlinent..1 1 ll1i:Ll'gill of the Orongc River and the Namib Desert. Joill/ Ceol.

SIII'I1, S. AJi-, & V'lill, of Cr'l)e TOIIII/ /11(11', CCQSci. Ullil Rep. 7.

Wi\ItD.

J ,I), ( 1 9H4) Aspects of ,Ire Cellozoic J;c!O/08Y ill rite

Klliseb River \lolley, CC/llm! Namib De,w:,-I , Unpublished

Ph . D . thesis. U niversity of Nnw!. Piclcl'rnorilzb�II'g. ;\ 1 0 P I'. W,\lw. J . D . ( 1 9M7) The 'cllQ'loic succession ill Ihc Kuiscl> V:lllcy. central Nmnib I)escrt. Melli. Ceol. Srl/·v. N(lII r iui(1 9, 1 - 1 24. \\I,\Il!:), J . I & OIWI!'I'I'. L B . ( 1 91)0) Towards an age fOI' amib. In: N(//llib Ecology: 25 YC(ll '�' oj' Nlllllib the ReSl1l1l'dr (Ed . Seely. M . K . ) P I'. 17-26. Tl':lllsvaal Mus. Monogr'. 7. WU..ANOI;i(, P. ( 1 %4) onvectivc instability i n a two layer Ouid heated uniformly from above. Te/lll$ 16. 349-359.

Spec.

I�IIIJI� 1111. Ass.

Se(/imelll.

( 1 91)3) 16. 6 1 - 69

Intemal structure of an aeolian dune using ground-penetrating radar _ J. S

I-I E N K ,

D _ L _ G A U T I E R , G , R , O L H O E FT (llId J , E , L U

US Geological Slirvey, MS

97/,

IU

Box 25046, Deliver, CO 80225, USA

A BS T R A CT A grou nd-pcnctrfll i ng rudar survey was made on u large complex lIcolian dune along the 111�lI'gill of Grcnt Salld DUlles Ntltion�lI Monumcnt.

llol'nclo, to dclillCfltc the intcrnal structures formed by dune

migration in tI complex wind rcgime. Radar waves were partially reflected from !)cdimcnl interfaccs that had di frcring densities or moisture (,'()IIICnts. In this wny bounding surfaces between sels could be intcrpreted frolll chrlllgcs in the uttitudc of sets of rencctors. The radur reflectors wcre rccorded to depths of 1 5 m . but thc best resolution of bounding surfaccs was obtained ill the upper 5 111 of the dune s/lml. Bounding surfilces i ntcl'pl'cted from rdlcclors clcfillc a lIIain dUIiC sct 5-8 111 thick, with foresets

up 10 23 m long, Thicknesses of othcr wcdge-shaped and tubular plnnnr sets wngc from U,75

10

1 .5 m.

avcraging 1 m : sct lengths mngc from 6 to 12 m. averaging 8 . 5 m . Trough-shnpcd SCtS range ill Ihiekncss from 0.5 10 3 m , averaging l . l m . and I'ange ill wi(lIh frolll S to 22 m, Ilvcraging 10 m. 'nlesc trough smlc­ lures Illay hove been caused by the lIIigrlllion of seoul' pits associated Wilh smull supcrimposed dUlles, or Illil}' be thc result of seoul' fHl� rormed during rcvc(sing winds. Reversing winds also fOflllcd numcrous subtle boulldingsul'faccs (renetivntioll surfaces) .1I01lg the leudi IIg edge of the dum: as it mignllcd. defining

sets mnging in t hickness frolll 0.5 10 2 m . avcragillg I m. and wilh forescl lengths ranging frolll 15 to 23 Ill. avcr:lging 20 m. This study dClIlonstnHes the usefulness of gl'ound-pel letT
multiple directions of sand-carrying 0,' sand-scou ring winds. In a teclOnically active b,lsin such ns the San Luis V
I N T RODUCTION The inlel'llal structures of la l'ge modern aeolian

a la rge cross-scclIQn (tens to h U lldreds o r metres

dunes are known from only ,} rew studies because of

long. sevenll met res deep) can be made thm allows

the obvious difficulties i n excavming or trenching

i n terpreHllion

unconsolidated sand. Trenching, is generally l i m i ted

geometry of some model'll sediments without re­

or

the

t h ree-dimensional

internal

by the depth to the local watcr table, but most hand­

sOl'l ing to excava t io n . The purpose of this srudy is to

du g trenches seldol11 extend beyond about I III deep,

demonstrate the application of ground-penetrating

L:u'ge trenches were bul ldozed through scvcral

radar ill determining the intermll structu res and

dunes al While Saoels, New Mexico (McKee, 1966),

geometry or

but the excavations were Illnde possible 10 a large

appl ic�ltiol1s

degree by slight cemcntation of the gypsum s�II'cI.

involved tt senrch for buried objects (pipes, cables,

Excavations on this scale huvc not been carried

drums of chcmic
QuI

Siruclion

ror quartzose dune sand, These kinds of studies �Ire

necessary if we are to further our understanding

( I mai el flf

archaeological

1987; D an ie ls et af

(Moorman el ai"

sand-currying winds.

As

with

.•

radar

have

investigations

1988), but I'"dar is

1 990)_

high - reso l ution

studies. ground-penetrating

technique whereby

Aeolian Sediments: Ancient and Modern Edited by K. Pye and N. Lancaster © 1993 The International Association of Sedimentologists ISBN: 978-0-632-03544-1

gl'ound-pcllCtrating

bcgi ll l1 i llg to be applied to sedimentological problems

of the relationships between aeolian dUllc type.

11

of

sites and

. •

dunc intern:.1 structure and complexity of effective Ground-penetrating rtldar is

a large aeolian dune. Most prcvious

61

seismic

geophysical

radar is a form of rcmote

C.l.

62

Schellk ot nl.

sensing; i n l ern:)\ structures a n d bounding s urfaces a rc i n te rpreted fro ln processed (law rather than being viewed d i rectly. The main thrust of this study

to interpret bo u nd i n g su rfaces between from the radar record. as bounding su rfaces outline the 3t'chitcctural e l em en ts of aeolian de pos its. Generally, bo u n din g surfoces can be recognized o n the radar t ransect. depending on the wavelength of the radar antenna. The bounding s u rfaces werc of second t\lld third o rder ( B rookfie ld . 1977; Kocurek, 1 988, 1 99 1 ) , o r what have been called growt h surfaces" (Fryberger, 199 1 ) . Loss o f resol­ ution with lower-frequency antennas meant Lhat bounding su rfaces could not be int erp rc rcd with cerw i n ty below a depth of 5 m.

waS to try

sediment packages

'

Il A D A R

Ground-penetrating

OPERATION

radar

electromagnetic energy to electrical

pl'Ope rt i es

in

uses

rnelio-frequency

me asure CQntnJsts i n

sediment

(Duke,

1990;

Olhoefl, 1990a). The energy radiated into the ground

by all antenna is refl ected tit interfaces where electri­

cal properties change. When recorded and processed , the two-way travel times p roduce

a cross-sectional i mage of vari n t io ns in electrical prope rt i es Radar antennas are built to radiate certain frequencies. The higher the antenna frcq uel'cy the shallower t h e .

.

W

120

I

depth of penetration, but the grealer the reso l u t i on

of internal structure. As lower frequencies arc used, fcwcr reflectors are identified. and bOUilding surfaces and sediment packages arc less dcfil)cd. However. Ihe depth of penetration increases ( F i g I). I n this st udy frequencies o f 30n. son a n d 900 MHz we re used, and the reco rds were stacked to produce a final cross-section. The ground-penetrating radar hardware used i n this s t u dy is cOlll lllerci'llIy a va i l a b le in the U S A , but Ihe software is nOI commercially available for processillg dalfl to rhe extent illustrated in Fig. I . I n operation. e ach .IIHe nna is pulled at a constant ve locity across the sand surface. Location marks ( eve ry 1 0 m) are used to correct the rceor I fo r variations in the speed of the antenna movement. The line of transect WtlS surveyed with a laser the do li t e to correct the radar l'ecol'<.1 for t opogra phic vari­ ations. Results of a walk-awl-lY test for ve l oc i ty and dielectric permittivity were used to transform the radar time seel i o l) 10 a deplh section. G I'QUlld-poI1ctratillg rad ar appears to work best in homogeneous. damp to wet, clay-free sedimcn t (Olhocft , IY90b). Several types of signal loss and attenuation C�lIl occur with radar waves. 'nlC most importllnt losses for sand-sized sedimellt appc{tr to be relatcd to thc pt'cscnce of saline pore wfHers, and surfHce-l'cacLivc clay such ns smec t i te in t he intcrstices of the sand and in layers or drapes. Wave.

,

E 100 I

m

Fi�. I. Portion of the 'OITCCICd (" rudar dcpth section rrom 120m 10 100m along Ihe cast-west transect (sec Fig. 5 ) . illustrating thc radar record priur to t he pl,lccmcnt of intcrp ret i ve lines. The banding (boundaries greater th[\n about 5 m. VCl'ticnl and hol'i7.ollwl !)Culcs arc in metrcs with IlO vertit:ul e;(lIggcf
DIllie

spreading losses can also be i mporlant i f the sedi· ment package in lhe sa n d

the

sallle

scale as the

body

63

sll'llcf/ll'e /lsil/g grol/l/(/·pellell'ating I'lldal'

is predominantly

011

w�1Vclcngth of the c m i ucc\

radar energy.

RADAR SURVEY OF A LARCE DUNE Dcscri l)Hon of sludy �lrC'1 A l a rge , co m p l ex aeolian dUlle s i tuated along the ea stern margi n of G reat Sand Dunes National MOl1ument, ol o rado , was chose n for the rndnr

Stu dy (Fig. 2). GrctH Sand Dunes formed in �I rc­ entrnnt a l o ng Ihe margin o f the Sn n gre de risco M o un tai ns ,

al ong the eastern edge of the San Luis (Wi egand , 1977). S a n d- m ov i ng winds are predominantly from t h e southwest throughout most of th e year, but st ron g easterly storm winds and minor winds from the north also resulL in sand transport. The upper parts of the l a rgc duncs arc ncal'iy rcvcrsed from the normal clirectioll of mi­ gra t io!} during thc s t ['OllS cast w i nds . The result of t h ese multidirectional winds has been the ac­ cumulation of more than 250 III of t\colian dunc sa lld along the ca ste rn ma rgi n of t h e an Luis bas i n . A compa ri son o f sand-carrying w i n d cl i rect io ns with the orientation of t h e larger d U lles (Fig. 2) suggests that the l
to low·relief features. form i n g low-nngle eros i o n a l bounding su rfaces. Strong c as t w i nd s com mOll l y forl11 'vortex scours' (Fry berger el a l . , 1 984) on th e upper pa rts of the dunes during ti mes o f w i n d reversal . Vortex scours are wide. t ro ug h-sh a ped e J'Os i on al de p ressi on s (o u tli ned by wide, trough-shoped bO U ll c1 i ll g s u rfaces) that can fill in during sand movemcnt by the preva ilin g win ds . The geneml shape a n d 10cHt'ion of these l a rge dunes (It Grem S a nd D u nes has rcmnined re l a t i ve ly stable over a pe riod of sevcra l yea rs ( W i eg(\ n d , 1977: A n drews , 198 1 ) . bu t the morphology and location of smal l-scale superimposed dunes ch a nge eo n s i dcra b l y 1'1'0111 se aso n to scaso n .

scour these small dunes down

Valley

to the dominant southwest winds, and nearly trans­

vcrse, but in a revc rsc cl sense, ro t h e strong, blll shO['I-lived eas t winds. Thc st fO llgcst control Oil IlHlintenance of the l a rge d u n e a l ign m e n t may be ,1 fu nc t i on of the cast winds, but the mnjor sl i p fHCCS t h l'O ughou t l he year arc controlled by the so u t hwest winds. The obl i q ui ty of thc southwest winds to the l a rge dunes Illay be pa rt i a l ly responsible for the forlllHtion .Ind migrmion o f smaller duncs on the windward and Icc slopes of the la rge r dunes. The smaller dunes arc more mobilc than the larger dUllcs.

The dunes along the eastern mflrgin of t hc dune­ field exhibit co m p l cx mOI·phologics. The l a ['se d U lles havc slip faces w hose orientation is pa rti a l l y ll1{lin­ tained by the p re va i l i n g southwCSl wind. The u ppe r parts of t hese slip faces are perioclicnlly blown back by strong eaSL winds. I n winter, strong winds associ­ ated with fronts commonly scour down to the level of clamp sand (Fryberger, 1 990<1), in some �' re a s r e m oving tens of centimetres o f sund. These winds serve to sm ooth or round o ff the upper pa rts of the d u nes (Fig. 3). Many of the larger dUlles have s m a l l c r dunes « 2 III high) superimposed on the witldwal'd and Icc slopes. S tro n g winl'er winds commonly

Dcscl"iptiol1 of rodur transect

The rada r t ransect run during t h i s

study pi:lri:llielcd

t h e predom inuill storm wind direction, .md esscntinlly

followcd (In east-west orientation. The trnnscct,

approximately 300 m

long. began in

the bed of

Medano Creck, proceeded west across flat. alluvium,

climbed the lee slope of the d u n e com ple x , and con t i n uc d �,cross the dune for the remainder of the tnillsect. Stmians we re nagged c vc ry 10 III for l oca tio n marks 0[1 the record. nnd wcrc flagged as stations for t h e topogmphic pro1i l in g. ach antenna was pulled slowly along the t ra nsect (Fig. 4). a n d lhc clata were recorded On tape for lat e r processing. The po rt io n of the 300 III Ir;,lnSccl illuslnltcd i n Fig. 5 ( facing p. (4) of this study is t he western I SO III that cOlHained the acolian dune sediments,

Results of th e rndur trunsect The �tackcd radH r

cross-section illustrates the ge nera l attitude of refl ecto rs 10 a d e pth of a pp rox i m a te ly 15 m nlong the cas t - west trallsect (scc Fig. 5). Resol u tio n o f subsu rface st ructure i s best wi t h the h igh e r-freq u cn cy wavelengths, (lJ1d resol ution de­ c rease s with d ept h . The reflectors arc th e result of reco rd e d differences in dielectric p ropc rl i cs of lhe sediment, including ch a nges in moisture
These sol i d l i llcs oLltlinc erosional bo u n di ng s u rfaces

b et wee n aeoliHn sediment packages. The lo ss o f rcso l uti on with de p t h allows r wcr inlcrprel,Htions of

b ou nd i ng su rfaces

in the deeper

(>5 111) part or

thc

c.J. Schenk ct al.

64

t N

RO�

Colorado Denver

45 km to Alamosa �

o

' 50 km

Fi�. 2. Low-altitude nCl'i�11 pholOlllosaic of Greal Sand Duncs National Monument, olorado. The m;tll1 dune mass is bordered ()II the cast by Mcdano reck ( M ). 1111(1 011 the west by Sand reck (S ). Strong cast winds (black
Dillie strllc/Ure IIsil/g groflllti-pellell'ttfillg 1'(f(lur

65

Fil; . .). SU'ong enst winds lIrc ohll'l llC to the predomina nt soulhwcl)t winds. and modify the forcse! slopes of the dUlles. The upper part of the forese! (F) or thi:-o lurge dune has been blown back (large arrow) ontO the windward slope of Ihe dunc by the ensl wind:-o. Thc!\e winds have �llso scoured Ihe foresel slope down to dump sand. producing a subtle ero:.ional bounding surface (rel1clivUliol1 surfuce) on the forese! . These bounding surfm::es . arc common in Ihe rndnr record (!\cc Fig. 5. 70-20 111). Scouring hfls also exhumed clamp s:.lnLl straw on uther pllrll'> of the d unc (small arrow). Southwest winds will cventually remove !his sand and deposit it on Ihe forcsct. The forescl on Ihe bOltom lefl-llllne! side of the figure is about 1 6 m high.

record. The dashed ( i n terpretive) lines on the CI'OSS­

seclion indicate reneclOrs that may represent eithcr a sclected set of cross-strata or the gcnend nuitude

of a sedimem package. GreaLer resolution i n the uppcr 5 III or rhc cross-scction meant that

morc

bounding surfaces were inte rpretcd in that port ion.

Analysis of bounding surfnccs and attitudes of

reflectors i n the cross-section indicatcs thnt

I h is

recorded reflectors that arc i n tcrpretcd as subtle

erosional bounding su rfaces

formcd on

the Icc slope

or the dune. This portion or th e trn nscct is

charac­

terizcd by numerOliS bounding su rr"ccs that par­

t ia lly bevel pre-cxisting foresel cross-strata. Such bounding slIrfnces may be common in the section from 1 1 5 m to 50 111 , but thc lack of rcsolUlioll with

the lower-frcqucncy antCllll:l (300 MHz) precl udes

large clune, which is probubly typical or dunes along

their interpretation.

histol'y of deposi tion and erosion. From 176 m to

section

derine a large dune with forescts up to 23 III in length.

The t roughs arc gcncr�llIy wide

ness. The sweeping, tangential natlll'c of the t'cftectOl's

from 0.5 to 3 III in thickncss, averaging I m .

w i t h aeolian ripple Strata were preserved. This largc

strong reflectors t h a t begin <-II thc surracc of Medano

the e
5), the rencctors

The set of cross-stratn runges !'mlll 5 to Sm i n thick­

il1dic.ttcs that a Inrgc d U lle rorcset and (IUIlC apron

sct grades to the

c

a st at

150

III

into n zone of complcx,

irrcgular rcflectors that extend to (lpprox imtltcly 1 1 5 m . The loss of resolution with the 300 M H z

antcnnH makes it difi1cult t o interpret SII'uctures or

bounding su rfaces bcyond thc prcscnce of i l'l'cgul;.II' rencctors. These rencctors may reprcsent sediment

packages that werc deposited by ::-rnallcr dUlles migrming with a north -sout h c-omponcl1l. 1 1 5 m to 20 m along the

From

transect, thc rcncctors

suggest Ihal a la rge dune migratcd to the eHst.

possibly coeval with the forese! at 176- 150 Ill. The

rellcctors outline sloping. possibly rorcset . bedding

From 160 III to 80 Ill, the uppcr 3 - 5 m of thc cross­ is

characterized

i n tcrprctcd as

by

t rough-shaped

n u merous

renectors

bounding slIl·fuccs.

and shallow.

ranging

from 5 to 22 In in width. �Ivcraging 1 0 111. and ranging From 40 m to O m

011

t h c t ranscet,

H

series or

Creek gently dips beneath the dune sed imcnts. This set of rellcctors is i n tcrpreted as the cxpression of the local watcr table (outli ned by the he;lVY black

l i n e ) . The rnd.lI' transecl was rUIl in Dccembcr;

the creek was rrOZell, as was thc LIpper 25cm of the s.md.

Evolution of dune struClures The weSlern end of the transcct begins w i t h IMgC clune foresets more thall 20m

long Illignating to

the eusl-nonheasl, probably under the innucncc

Ihm developed as the Icc slope of l h e clunc migrated

of Ihc sOlllhwcSI winds. This clune foresct WilS pro­

From 50 111 t o 20 m the higher-resolution a n tennas

50-20 m . T h e zone o f irrcgu l a r rcncclors between

to the east-northeast.

b;lbly �,ctive at the samc time :-IS thc large foreset a t

C.l. Schenk Cl

66

31.

BI

A

1;'lg. 4. Rador operation. (1\) Vicw of the line of the radar transect from the bed of Meduno reck westward up Ihe Icc slope and ilcross the lu rge dune. The transect w;)s measured by tnpc. ilnd erich 10 m segment wns nagged us 1\ station during each rudor run (arrow). The trunseel wus 300 m long, U�Om or which WlIS across the large dum::. The Clible shown ICCfUIOf 10 puil ihe ill1lCl1na at II conSlillll speed wilhoul cubic drag. The view is to the north. (C) The surface of the Inrge dune in the slIIdy :trell is covered with scour femures of low I'clief (u few tells of CC.lIilllctrcs of felid) that were fonnerly fictive superimposed dunes. TIle dark arca� arc exposed darnp snncl; Ille remainder of tile su rfoee is covered Willi 0 Illin « 2 elll) veneer of dry sa.,el. The scour of Ihe surcrimposcd d U l les produced n low-.-lIlg1c, subtle bounding surfncc. (D) The Icc: slope of the large dune in the eastern pari of Ihe study Jlrcn Wi.IS Ch<'lraeLerizcci by low-relief, scoured, superimposed dUlles. A t Ihe lime or the lrunsccl thc dunes were scoured down 10 dnmp s,lI1d, producin II low-angle. subtle bounding surface on the Icc slope (see Figs 3 and 5).

150m Hnd 1 1 5 m probably represents u common geomorphic situation along lhc eastern tmugin of G reat Sand Dunes. in which smallcr superimposed dllnes migrale al some obliquc angle to the migration direction of the l a rger clunes (Fig. 4D). For som e reason the largc d U llC al 176- 1 50 m ceased to mi· grate, and probn bl y devolved to the cas t inlo a low n n gl e slope covered by smaller superimposed d u ncs, the SU rfHce being affected by blowouts formed during wind n:vcnmls. Thus. the western dune gradually mcrged with the eastern dUlle, producing a larger complex dune that was pa r l i a l l y covercd with sllwller dunes. -

The multiple, subtle bou n d i n g su rfllces on the lending c Igc or lhe dune arc pro ba b l y due to scouring by winds during reversals, and ilre of the Iype com­ monly ca l l ed 'reactivalion surfnccs'. Reversing winds are typically I'clated to Slorms, and strong winds associated w i t h lhe s tor ms scour down to Ihe level of damp sand. i n some cases several lens of centimctres dcep 'nlesc scours arc recorded by Ihe bounding SlJI'filces. D u r i n g wincl revcrsnl, winds co m mo n l y travel a t SOme oblique angle to the Icc slope of the dune. scouring and deposiling the sand on Ihc windward slope of t h e dune (Fig. 3). The 7.OnO of troughs between 1 60 m tlncl 80 m may .

67

DUlle Slmct/lre /lsillg grollful-pcllelrmillg radar

have been formed by .my of several mechanisms, Trough-shaped scour surfaces C�1I1 form as pits in from of adv::lncing bedfol'll1S, possibly by the migration of smaller dunes, Scours can also form in .II'cas like G reat Sand Dunes where wind reversals al'CCOlllmon, The re versing winds impact the foresets on the dunes at an oblique tingle; the wincl commo n ly scours pits (vortex seoUl'S) into the upper p;.arts of the dune forescl and t h e windward slope as strong winds reverse the 110rmal direction of sand tnillsporr. The deep t rough strllcture between 125 m Hnd 1 10 m exhibits cross-stralH facing aw.IY from the direction of the nor m a l wi n d s. proba bl y rilled with sand carried by reversing winds from the east. Other troughs in this ZOlle may h.we Iwd a similar origin. I n some arCaS of Grcat Salld DUlles, winds scour broad troughs that arc unrelated to either scours in front of dunes or vortex scours. This could be the origin for some of the troughS. Wide, trough-like struc­ t u res have been described from other Beoli'lIl sands (McKee. 1 966. 1979; Big(lfella. 1979; Rubin & I l unLcr. 1983; Rubin. 1987). •

Qunntilicntion or Icngth-sculcs from the radnr c

ross-secti on

Lengtll-sCHlcs of scdimclH packages in two dimen­ siolls were measured from the radar cross-section. The troughs in the zolle between 160m and ROm range frolll 5 to 22 m in width, ave rag ing 10 m . The thickness of the t roughs ranges from 0.5 to 3 m , and ave rages I . l m . The direction from which I h e tro ughS filled is vari..tble. SOl11e troughS appear to be (illed with sand carried by caSl winds, SOme by southwest winds. and some by winds with it north-sQuth component. The subtle bounding surfaces at the leilding cdge of t he dune bracket sets that range i n length from 1 5 10 28 m, averaging 20111, and range in thickness from 0.5 to 2 m . a veragi ng 1 m . This scale of sct geometry may be typ ical of a large part of the dune sand body from 90 rn 10 0 111 ;llong the eross-scetioll, Th e one l a rge set al the western cnd of the t ranscct is 23 m long. Hnd ranges from 5 to 8 III thick. Other miscellaneous sets in the cross-section with reliable bounding s u rfaces range from 6 to 1 2 m in lengt h averagin g 8.5 m , and runge in thickness from 0.75 to 1 . 5 m , [lvcfIIgil1g 1 m. The dn l ll on set le n gt h an I t h i kncss demonstrate the variabili ty in sct dimensions within one large dune at Gre.lI Sa nd Dunes. The effect of the reversing e"lst wind is important in producing conditions of ,

erosion thtH l enel t o the formll t iOll of Ihe tl'Ough­ sh aped sets nnd 10 the ll u merOus reactivation sur­ faces a lo ng t he lead i ng edge of t he dune. These erosional bounding surfaces ilre prcse rved allcl resul t in the sand body being comprised of Il U lllero us sels with differing geometries. This large clune 1 11 Greal Sand Duncs is likely to be partially prescrved. as it is being covel'cd by the next large. clim bi ng d un e . ,

D ISCUSS I O N The nt(lnr-clcrived cross-scclion illustrates the relationship between the complexity of dune inte rna l structure "nel the complexity of sand-trnnsporting winds. Winds from several directions can scour as well as deposit sand during different times of the yeaI" crcm ing bou ndi ng surfaces and deposits that would nOt bc predicted to occur from the external morphology of the dune alone. Dunes with simple external morpho l ogies C�1Il exhibit complex internal structures. McKee ( 1 966) denlOnst ratcd t he presence of numerous bOllnding surfaces in externally simple dUlles
,

.

c.J. Schenk et " I .

68

n u merous examples from aeolia n san d s tones t h e compl e xities

of

internal

structure

produced

by

migrating aeol ian bedforms. He i nte r prets palacodunc morp ho logy and general palaeowind regim e from a ca re fu l analysis of bo u nd ing slJl'faccs

and Fred BUllch o f ("he Na t iOlHl l Park Service were invHllI�lblc to t he study. {IS was Edg
the USGS.

and aeolion

coset architectu re. Radar�dcrivcd :m.:h i tccturn l daw

REFERENCES

regim es may hdp refi ne input datil for complex

ANDIU.l\\'S , S. ( 1 98 1 ) Sedimento logy o f Grcilt S("1I1d DUlles, olol'
from model'll aeolian dUlles formed in known wind

bedform migration m ode ls slich as those he h a s CrCnlc..! . The complexity o f dune internal struclUl'C i s also im porta n t in u n d erstandi ng and pred i ct i n g Iypes of fl u id· flow reservoirs.

h e teroge nei ty

in

h yd roc a r bon produce oi l 311c1 reservoirs (Ire in pa rt acoli:l11

A eo l ia n sandstones

gas in IlHlny a reas, Clnel the heterogeneous

because

of

intcTmll

a rch i tectu re

( We ber, 1987: Li ndq u i s t , 1 988; Luthi & Ba n avtl r , 1988). Dma such as characteristic cross-strata set dimensions arc needed by engin eers as t he y a ltem pt LO i llcrease tluid recoveries frolll a eo l i a rl I·esel'voir's.

fIIlll wi<:II/(l/i()1I 0/ (If/elllU//ioll lIml dielcctric perlllillivify I'ctrsr/.\" depth, U np ubl is h ecl M,lSICr'S thcsis, Color,ldo

SUMMARY A N D CONCLUSIONS

The gro�lnd-penClrating radar reco rd ed reflectors thut define bounding surfaces and i n l c l'Ilai sedimctll packages in the upper 5 111 of il complex acol f a n clune along the margin of G reat Sand Dunes. The ra da r resolution at depths gremcr than S ill was genera lly n o t e no u gh to resolve bounding SurfHCCS of any variety with certa i n ty . The rndar dClllonstr
in sediment with 11 high pcrce ntage

of surfocc- re,activc clays slich as smect i tc ,

01'

whcre

pore wa ters are sa l i n\.! , These conditions may l i m i t

its usefulness i n c1ciincming sedimentary s t ructures i n Olhe!' sedimentary environments.

School of Mines. Goldcr\. , ( 1 97�) I une form ane! wi lid I'cgi mc . I l l : A Stlldy oj' lob(11 Salld S(!(lS (Ed. McKce, E.I).) PI'. 1 37- 1 69. US Geo!. Surv. Pr'or. Pilp. 1052. FII.YllI!ItGBIt, S.G, ( 1 \)<)0(1) ,,'ell ! Sil nd DUliCS dcposi tion a l systcm - nn ovc rview . Ill: Model'll (tlld Alldelll Eolirlll

FRYBBKGIIII., S.

Deposils: Petrolelllll E.l'plOl"lIIiOIl (/JIll Pro(llIelioll: Rock.y Mowlf (Fryberger. S . G . . Krysl i ni k , L.F, & Sc he n k , C.J.) pp, 1 - 1 - 1 -9 , Rocky Mtll Sec. SOl.:. Econ, PuIC(lnIOI. Mineral . . Dc nve r ,

( 1 990b) ConSilii de pos it s or Orego n , USA. Guerrero Negro, Mexico, !l1ll1 .I afuru h sand sea,

FII.'I'IIl;II.CHIL S.G.

S�ludi Ambiil, In: Modem

Petroleum

(/1/(/ Ancicl/t Eoliall Del}(}:;iIS; �xplol"(lfiol/ (lnd Prodllction: Rock.y Morfllt

(Frybergcr, S,G., Kryst i l l i k , L.F. & Schenk, C..J.) pp. 1 1 . 1 - 1 1 . 1 5. Rocky Mtn Sec. Soc. ECOll. PalconLol. Minera l . . Denver. FIt'l'IlEItGIIK. S,G. ( 1 991) Pcrson H I communication. FII.'I'Ili!KGEk. S , G . . AIILBItAN r)T, T.S. & ANi)ltl!WS. S. ( 1 979) Origin, sedimentary features. and significance of low­ Ittlglc colill n 'sand sheet' deposits. Grcat Sa nd Dunes National Monument ami vi ci n i ty. Colonldo . .1. Se(l. Petrol. 49. 733-746. I,1SI I1\II1 , T.J . , Rtz,vt, FItYItEII.GllK, S , G . . AI.·SAlH, A . M . , S . A . R . & /\L· HI NAI . K.G, ( 1 9S4) Wincl scdimcllwtioll in Ihe .Iufurah �and sea, Saudi Ambia. Sc(lillll!lItology

3 1 . 4 1 3-43 1 .

A C K N O W L E D G E M E N TS

We thank William Wellman. Superintendent G rea l Sand Dunes Nmional Monument,

of

olol'ndo,

for his u nfni l in g support of OUl' radar work , and for his support of sci ence in gC llcnd

Dunes

for the

pns t

several years.

:lI Gre,lt Sand Wi l l i a m Havilland

HUNTI:It, R . E . . Rl('lIMOND, I3.M. & AI.I'Ilt\, T. R . ( 1 98J) Siorm-cotltrolled oblique dUlles of the regon coast. 1)1111. Gt!ol. Soc. Alii. 94, 1450-1 465. l�iAl. T. . SAK,\YAMA, T. & KI\NI!MQH1, T. ( I YS7) Usc of ground- probi ng rada r .and resistivity survcys for archaco­ logical investigations. Oeollhysil.'s 52. 1 37- 1 50. KOCUII.IiK, G. ( 1 9S8) First-order IIml s u per boullding sur­ races ill eoli<1I1 sequcnces - bo u nd i n g surfaccs revisited, Sed. Greol. 56, 1 93-206.

Dllne SIl'tIc/Ul'e /lsillg grOf/lld-pcllelmt;'lg rallm'

KOCUWUK, G , ( 1 99 1 ) InlerprcUition of ancient eoliHn sand dUlles, AIIII, Uev. £al'lh PllIl/et. Sci. 19, 43-7.'5. Lt\NCAs'l'IHl. 1'1 . . GWlll!LBY. R, & C I I IUS'I'L!NSL!N. P . R . ( 1 9K7)

Dunes of the Gron Dc:-;icrlo sand-sell, SOllora. Mexico. £(",h SlIIf. Pro('. Lal/d}: 1 2. 277-288. LIN I)QUIS'I', S.J. ( 1988) I) raet ietll clml':letcriu l lion of colian l'cscl'voirs ror dcvelopmc llt : Nugget SrllldstQIlC. Utah­ Wyoming thrust bell. SCII. Gcol. 56. 3 1 5-339. LUTHI. S.M. & BANA'it\K. J . R . ( 1 988) Application of borehole im!JBcs 10 three-dimcnsional modeling of eolillll s."'ndstollc reservoirs. Permiun Rotlicgcnc!e. NOl'th Sea. /)/1/1, Alii. A,)$(X-'. 11e//'OI, Oeol, 72. 1074- I t IHI). McKim. E.!), ( 1 966) Structures of (Iulles fit White Sands National M on u me n t , Ncw Mexico (ol\d a compari:-;on wilh struChll'cS of dunes rrom otllcr selected areas). Scdilllel/fOlogy 7. 1 -69. McKI!E. E,n. ( 1 979) ScciimentM)' �tl'lIctures in clUIIC::'. I n : A Study 0/ Glob(ll Saud SellS (Ed. McKee. E.n.) 1'1' . 83- 1 13. US Geol. Surv. rrof. rap. 1052. MOOKMt\N. 0 . .1 . . S�IITII. 0,1) . . JUDGI!. A.S. & JOL. H . M . ( I WO) As:-;cssirlg lhc o b il i l y of grollnd penetrating mdar to dcli nc llIc cliffc l'cllt nuvhll systcms lubslf!lctl. I n : 'n/;I'(/ /1I(enrfllioll(l/ COI1!cI'em;e 011 Cl'olllld IJenetrmillg I?a(/(II',' A b�'lrat'ls o!file Te<:/rll/c(ll Meetillg: Ltlkell'ood. Colol'(ldo (Ed. Lucius. J . E . , Olhocrt. G . R . & Duke. S . K . ) p. 44. US Geol. Surv, Open-file Rep. ��..j 14. OLliOefl'. G . R. ( 1 990<1) Ground pellctr::l t ing radar data processing und modeling labslr::lctJ. In: Third 1I1/('I'lI(lIioIl(II

69

COllferellce 011 Gm/llld IJcllemllillg Radrl/',' A IJ.wra('t.� oj' Ihe Tedlllic(I/ ."'1eelillg,' Lakewo(}(l, CQ/orado (Ell. Lucius. J . E . . Olhoefl. G . R . & Duke. S . K . ) p. 49. US Gcol. Surv. OpclI�fi1e Rep. 00-4 1 4 . OLlIOI:;t--r. G . R . ( l lJI)Ob) PerMlnal cOllll11unicntion. RUUlN. D.M. ( 1 987) Cross-bedding. bedforms . and palco­ currcnts. Soc. ceol/. PlI/eollfol, Millel'tl'. . Concepts i/l Ser/imelllO/ogy (lnd Paleontology I . SEI'M. Tulsa. 187 pp. RUlIlN. n . M . & I- I UNt£k. R.E. ( 1 98�) Reconstructing bedfol'lll ilsscmbluges from compound cro�s-bcdding. Ill: £Olillll SediIllC!ltI.\· {llId IJroceS.W!S (Ed. Brooklield. M . E . & Ahlbnllldt, T.S.) pp. 407-427. Developments in Sedimcntology 3X. Elscvier. Amsterdam. W�Ut!K. K.J. ( J9M6) I-low heterogcneity affccts oil recovery. I n : Ueservoir C!wl'l/('/t!I'izmioli (Ed. L:lkc. L.W. & Carroll. I-I . B . ) pp. 487-544. Acadcmic Pre�. New York. WI!Ili!k, K.J. ( 1987) Computntioll or iniliul well pro­ ductivitics in ueol i �1 I I sandstone on the bUl'Iis of u gco­ logical mode l . Leman Gus Field. U K . I n : Re:,'el'l'oir Sedimentology (Ed . Tillrnull. R.W. & Wc be r. K . J . ) pp. 333-354. S pcc. Publ. Soc. Ecoll. PI:llcOlltol. Millcr!!!. 40. SEPM. Tulsa. WII:Gt\ND. J . I), ( 1 977) Dillie /IIorphology (/1/(/ Se{/illlellt% J,:), (If Grem Smlll Dill/c.) NlIfiollol MOII/wiel/I. Colortldo. Unpublished Mnstcr's thesis. Colorado State Ul1ivcrsit)'. FI Collins.

Spec, Pllbls 1111, As�', Sediment. ( l993)

16, 7 1 -83

Origins and sedimentary features of supersurfaces i n the llorthweste.-n Gran Desierto Sand Sea N . LANCASTER Quat(!I'J/(O'Y Sciences Cellfer! Deserl /?(!s(!arc:il JJ/wi'uu�, University of Nevada System, PO Box 60220, 11""0. N V 89506. USA

ABSTRACT SlLIdics o f s(1nd sheets find d U lles i n the northwestern margins o f the Gran Desierto S.md Sca provide

criteria for the recogn ition of rcgiolHiI-sc
sond supply to the area rrom the Colomdo River val ley resulted i n dcflntion or sand sheet deposits

a p rotcctive

lag 11IIel ro rmed

until

on s u persu rfnce A. Renewed sand sheet and dune accumulation was ended

by climatic ciul I1gcs resul ting in un increase in the vegetation cover. slabiliz.mion of the SUI'facc fllle!

pedogcnic altcration of u nderlying deposits to form supcrsu rfacc B, III this urell. it appears that super· surfaces resulting from tel'mination of sanel supply )JI'C chnraclcrizcd by dcll;o lion ilnd dcvclopmc nt or surface lags. whcrcas thoS(: resulting frol11 regional climatic ch llngcs arc marked by pedogenic .,lteration,

I N TlW D U C T l O N

different

sets of processes can be recogn ized at the outcrop sca le. St u d i es of supersurfaces fo rme d ill mode rn sand seas can help to provide critcria

The processes b y which 1 ,l rgc acoli<1Il sand bodies

(s,;lI1c! seas , ergs)
el al., this volume) havc rccogni zed

to i de n t i fy the processes that created ancient super·

rcgional-scale

bo un d i ng SU rfi:1CCS

su r faces , This paper documents ( i ) the e x i s ten ce of

(supcrsu l'faces)

Onm I 08ic['to Sa I,d Soa in northcrn Mexico, a nd (ii) thc sed i m c nHl r y fCHturc:) flssocialed with these surfaces, Possible mechnnisJ1ls for the fonmllion of the surfaces arC then discussed . s u pe l'su r faces in the norr hwestcl'll part of the

some ancient acolian sandstones allel s ho w n

in

that they scpnnHc gcneticnlly distinci soncl bodies, The 5urfnccs represent h ia tu ses of erosion or

accumulation in aeolian

non�

sequences w h i ch resulted

from changes in seH level, dimate, regiollal tectonics

or sand sea m igr a t i o n . In modern sand seas, there is

an i net'c asi ng

body of ev i dcnce

Ihat suggests

t h � lI

they 100 have accu m u lated ep isod ica l l y (c.g, Talbot, 1985: Kocu re k el (II. , 1 99 1 : Lancaster, 1 990), wirh

T H E G RA N

The Gran Dcsierto Sand Sea (Fig. 1 )

QU(ltcl'IHlry cli m a t ic nnd eustatic changes providing i.l

Recogn iti on �lI1d tracing of super bounding sutfaces make up a potentially important tool foJ' regional

as

correlation

of

aeolian

sandstones,

well as for t h e I'cconstruction of the d c posi t i o n a l

history of a nci en t a nd moclcl'Il salHI scas. I n order to be able

to

reCO nstru ct depositiomil

h i s tori es effect·

ivcly, i t is i m porta n t 11wI supersu rfaces formed by

Aeolian Sediments: Ancient and Modern Edited by K. Pye and N. Lancaster © 1993 The International Association of Sedimentologists ISBN: 978-0-632-03544-1

covers

an

a rca

of 5700 km'2 On the ['Or'thcastc['[l shOt'cS of the Gulf of California. e a st o f the Co lora d o River delta. There arc two m a i t) areas of d u nes in Ihe sand sea ( La ncaste r el al., 1987): a n eastern group of compound a nd compl e x crescentic dunes .10-80 m high, and a western a rca of ch a i n s and cl uste rs of Slar dunes 80- 1 50 n1 h igh that arc surrounded by re vers i ng and crescentic d un es LO-20 III high

major con t ro l On n eo l i n n scdimcntntioll patterns,

strntigra phic

D E S I E R TO S A N D S E A

7l

N. UIIICIl$rer

72

GULF

OF

CAl.IFORNIA

.. �

\:!,

Fig. I .

The Grall

, . . .

. . , . . . .

.

,

.

.

Desierto Snnd Sen: location Ilmp. Box indicalcs

In add i t ion , t here arc areas of stabilized dUlles 5- 1 0 tl1 high 01) the mal'girls of [he SI."II' clune area <111c1 in some inler-dune '1n;:aS bel ween tile chains of star dunes. S;)nd sheets ,1ncl stre:.tks (Fig. 2).

crescentic

. .

area covered

by

LnndStit imtlgc in Fig. 2.

and s1111:111 areas of act i ve crescentic dunes OCClIl' in I'he wes t nnd northwest parts of the sand sea. The western stnr uUlles
Fig. 2. LHmlsm image of northwestern pH1'1 of Gran I)csicl'lo Sand Serl. Note areas at' slnr dune

dl
SlIperSlllface.\' ill rile G/'all Desie/'to and small areas of active cresce ntic dunes, �rhe

D es i e rto is an exce l l e n t area in which LO s l lIdy the effects of cl i m a tic, tcctonic and eusLHlic

Gnll1

cha nges on sond supply and sand sca development.

on thc margins of a ra pid l y subsiding basi n . the Salton Trou gh . The de ha region Oflhc Col orado River hns been deformed extensively over the past 5.5111 yrs in associHtion with t he open­ ing of the G u l f of a l i fornia (Winkler & Kidwell, 1 986) , r'csu l t ing in a westward migration of I h e olo!'ado River during t h e Pliocene and Pleistocene The

BrCi!

is s i t u
73

River noodplain and delta. Later i np u ts of sand

w11l1e from the modern

olorado River Hoodplnin

and coastal areas south of the sand sea i n the region of the Bahia del Adair. Relatively brief periods of aeolian deposition have been separated by l o ng

intervals of .scomor'phic stability during which

ex isti n g stlnci pop u h u ions were reworked, soils were formed and dcllntion of existing d u n e ,Heas and

sund sheets

aecuned in many pans af rhe sand sea.

The extensive silnd sheets of the Gran Desierto that me juxtnposcd with duncs of apparently d i fferent

a n d uplift of the Mesa A rcnosa along the western

ages and sou rce sedimcnts provide an excel le n t

margin of the snnd sea (Colletta & O rt l i eb, 1984),

opport unity to examine supersu rfaces in

Evidence frol11 lake levels and pack rat middens

aeolian envil'onmeilt.

(Van Devendcr Of III"

1987;

Van

a modern

Dcvcndcr, 1 990)

that the region that i n cl u des the Gran Des i erto Sand Sea has experienced H number of

indicates

periods of i ncreased rainfall during the IHte Pleisto­ cene und Holocene. although the area of the sand

sen has pt'Obably al ways been arid during this time (

ole, 1986),

Eu s tn ti c changes in sea level i n the

a 111{ljor i n n ucncc on the pMtcrn of deltaic sedi ll1cl1Huion (van Andel, 19(4), As the Colorado delta is H nlHj or source of sediment for (he sand sea, these events probably had a s ign i fica n t inlluence on !.Ieo l i a n sedimentation patterns. region have hnd

S A N D S H E ETS IN T H E N O R T H W ES T E R N G R A N D E S I E R T O SAND S E A Topography und gener,,1 description

and the texture and mineralogy of aeolian sediments

Sand sheets cover all area of I OO()- 1500km2 in t h e Ilonhwcslcrn PiHts o f the Grarl Desierto (Fig. 2). They form a nu t LO ge n t l y u ndu la t ing surfllcc Wilh a m a x i m u m local re l ief of 1 - 5 III (Fig. 3), wh ich includes scvcrnl small a reHs of very degrndcd, slilbi l� izcd crescentic d U lles 3-5 III h igh (A on Fig . 2). Vege t at i on consists mostly of sparse grass clumps and creosote bushes. To [he tlOl'th and west. the

indicates Ihnt

sand sheets thin out on the highest a l l uvial te rraces

The O rrin Desierto Sand SC.1 has accu mulated

episodic
IY90).

(Blount &

Evidence from cl u ne morp hology

there arc three major sarld popu lations.

representing three pulses of sediment i n pu t . The

oldest sands were derived from I he
Fi�. 3.

Ground view of snne! sheets, View norrheast towards Ti nnjali Altas Moulltains (on horizon). Vcgct:llion is mostly dead white bursagc (Altlbl'O�'i(l r!1II110:i a),

olora 10

of the

alor'ado River and the distal areas of a l l uv i al

fans that head in

the Tinajas

Altas Moulltnins, To

N.

74

LWIClIster

the soulhcnsl, Ihe snnd sheets are intercalated with

Description of' sand sht!et units

crescentic and reversing dUlles Ihilt form the weSlel'1l margin of the m"lin dune <-Il'ca. I n many respects, the

Unit I

nrcn nppenr; 10 be a Iypical ' back erg' ( Porter, 1 986) or 'trailing erg margin' (Swect el al. . 1988).

Unit I forms rhe surface sands ovcr la rge arC�lS of

2). l oge t he r

the sand sheets. It ranges i n thickness from as little

consist of a series of coalescing streaks o r s t ri n gers

undulations, with an average thickness of 20-40 cm .

L"lnds;u images of the region ( Fig.

as 5 ern i n hollows to 1 .5 III on thc crests of the h ighe r

with field i nvestigations , show that the sand sheels aligned <.It 1500 i n central al)d western parts of the

Below the act i ve wind ripples o f t h e surface. Unit

area, and 1 650 i n the cas t (Fig. 2). The streaks afC

I consists of well developed horizonwi to gently

imaged as areas of highe r albedo lhal contrast w i t h

dipping (2-3° app�lrent di p ) plUIlH r scts of wind­

a darker unde rlyi n g unit, t h e surface o f wh i c h is

ripple l am i nae ( Fig . 5). Very similar sedimentary

composed or n coa rse sand and granule lag.

structures have been desc ribed from sparse ly vege­

that they ;.arc composite featu l'cs co nsisting of suc­

D unes ( Frybe rge r el

m a i n genetic units can be rccognized, termed Units

sheet, distinct sets of very fine (3.5- 4.0 cp) and

Trenc h ing nne! sampling of t he sand sheels show

tated sand sheeLS in Saudi Arabia and af Great Sand al., 1 979, 1 984; Koc u rek &

Nielson, 1986). I n the eastern parts of t he sand

cessive generations of ,-,col i a n accumulations. Three

(2 <1» l a m inae 1 - 5 cm thick equi vn le n t to the

I - I I I i n order of increasing age. They are sepunltcd

coarse

by two pl'Omirlcnt and lateral ly extensive su rfaces

'Type n' of Fryberge r el (II. ( 1 979) are COIll IllOn.

(Surf�\ccs A und B ) . Figurc 4 shows the topographic

There is very little evidence of bioturbation Of r enC l ivHtion surfaces within this unit.

and stratigraphic relmionships bctween the units

Unit I is composed of lighL brown LO reddish

and su rfaces i n rcprcscllli:1tive areas of the sand shcets.

yellow ( M ullsell 7.5 YR 6/4-6/6) slInd, The sand is

A

NW

SE

�I 5J!?ln

Urllt

_ _ _1

_

_

_

SURFACE 8 COARSE SAND. ORANULE

B NW

..3-

I.AO

SE

1,,1 . ,,1

000

O O -_ _ __::h. __ ��__

__

· 'L o

100 m

__

-° 1-=-"_ SURFACE 8 ORANULE LAG

_

__

m Jiig. 4. Topogra phic

and $traligraphic relationships between $cdimclltal'Y units ;n Ihe sand shcets. (A) In central areas of the s::tnd sheets. (ll) In non hCl'll areas.

Supersurfaces

in the Grall

75

De,\'ierlO

1;·jg. 5. Scdi lllcntnrY :;;!ruclurcs in Units I nnd I I . Note pal'Lll l c l \Vin(l�rtpplc lalllinnc or Unit I nnd SLl'ucturclcss sands of Unit I I .

predom inantly (>90% ) subroundecl t o subnngular q u a rtz. The finc and vcry fine sa n d fract ions arC

clear or Frosted. MecliuIl1 and coarse sands commonly

have a reel b!'Own (2.5 YR 5/6) p�Hin(l. Thc COiJrsc

and very coarse sand fruct io ns arc dominatcd by

dark l i t hic fragments and feldspars. The texturc

1 is v,lriable, but commonly consists of mediulll sand and 23-45% fine sund (Fig. 6 ) , Most deposil's of U n i t I [I I C ul�imod�il, w i t h a moda l size of 2.0 cp (0.25 111 m ) . M c a n gra i n size varies betwcen 1 ,95 rtncl 2,25 (/> . B u l k samples c x h i b i t moderMe t o 1'001' sOI'ling (01 = 0.70- 1 . 1 0). a l l hough illdividual I n m ilHlc Hppear well soned. Sa m ples

of U n i t

40-50%

'

from the eastern p;ut of the sand sheet .\I'CH
somcwhm

I I nc r, with a mean grain size of 2,32 and

dUlles.

The 1 (lt e ra lly extensive n a t u re of this feature

suggcsts that il i s H supc l'sUI'i'nce i n the termino logy of THIDOl ( 1 985) anci Kocurek ( 1 988) and is lermed S u rfa ce A. Unil II is composed of redd ish yellOW (7.5 Y R 616). very wcakly lamill
is moderately to wenkly

i n d u l'uted. The thickness of U n i t II

ranges from

20cm 01' the flanks of' the s al, d st l'cl:lks 10 1 ,5 m in the highest �l I"C(lS of tlte s,1IId sheets. U n i t I I is

lexturHlly very si."i1<.lI' to U n i t I , and

is composed

of

approximutely equal propo rtions of medium a n d fine sand (Fig. 6 1 3 ) . The Ill ode is al 2.0 <1>. Mea n

gl'<.tin size ranges from 2. 10 to 2.50 ¢ and bu l k samples arc moderalely 10 poody sOI'led

(0, = 0.70- 1 . 10).

moderme sorting (01 = 0. 8 1 ) . I n rhis arcn, which is

located close m a reas of active crescentic dlll)cs,

Unit I s.l1ld is bimodal, with and a fine mode at 3,5-4.0 cp.

Ullil III U n i t 1 1 1 direct.l y IIIl1.JcrJics U n i t I I in mOSt parts of the arca. However. ill the c�\stel'l1 arca of the sand sheets. U n i t 1 1 1 underlies U n i t I (Fig.

Ulli, II U n i t 11 u nderl ies Unit J i n the high a l bedo sneaks, but not in the darker areas 01' in l'he northeast p.Ht of the area (Fig, 4 A ) . I n the coalescing strcaks. U n i t I is separatcd from U n i t I I by a horiz-on 5 - IOcm thick

48). A

Sharp

boundary with a well devcloped surface crw;! (ves­

icu i tl l A soil horizo n ) and a coarse !KInd 10 granule '

lag

one

01' two grnin diamctcl'S thick sepanllcs

by u weakly developed su rface crust ( vesicular A

8). This bOlllldnry ( S u r face B) appears 10 he planar in nature nnd cnn be t raccd to the dark streak areas where it is ex posed at the surftlce (Fig, 9). U n i t I I I is a t least 1 In thick and overlies indurated silty sands and gravels of the

hol'i w n ) . The palacosol follows t h e


in which the windel'ipple laminae become indistinct

(Fig. 7), This zone forms a palacosol that is c
locHI topography

in a subdued manner, and can be t raced throughout

the h ighc r al'CHS 01" t ile semd sheets and i n to aclj[lcCllt

U n i t I I I rrom overlying units ( r:ig.

U n i t I I I (Fig, 9) is composed of s t r u c l lIrclcss, reddish

yellow (7.5 YR

616). moderalely

consolidaled

N,

76 30

Umcllster

mode ra te l y sOl'tell

(oJ = 0.75-0.90). Calcium car­ bona te occurs ill (I d iffuse fOJ'1ll t h ro ugh ou t the 2-5% L wi t h small unit ( tot a l c,lrbOllalC CO_Hem ( 1 -3 cm) cn l iche nodules a t a depth of 50-70 clll in so m e localities. I n the classification of G i le el lli. ( 1 %6), Unil I I I exhibils wea k Sia ge I I ca l iche development,

Unn I

=

25 20

'"

15 10

Dunes in

6 0 0.0 0.6 1.0 1 .6 2.0 2.6 3.0 3.5 4.0 Pan

..

30

Unn II

26 20

'" 1 6 10 5 0 0.0 0..5 1 .0 1.6 2.0..2.6 3.0 3.6 4.0 Pan

Unn

III

the

northwestern Gran Oesierto

There arc several sets of degraded and vegctalcd cresce n t ic duncs with a hcight of2-4 III and a spac i n g of lOO-200 T11 within the 'He�l of the sa nd sheets (area A on Fig. 2 ) . These dunes h ave stoss slo p e a n gl es between 3 a nd l L alld m oderate l y to pom ly sorted (o[ ;;:: 0.70- 1 . 1 0) . 'fhey arc u n l i k e the surface sands o f t ile active dunes of the mn i n s�ltld SC(i to t h e southea�t . which arC com lll only fincr (mcan grain size 2.05-2.45 ¢ ) , and we l l 1 0 ve ry well sorted .

-

0.0 0.5 1.0 1.5 2'04>2.5 3,0 3.6 4,0 Pan

-

Fi�. 6. unilS.

Typicul I>"rlicle size distl'ibul iolls

from S("111(1 ShCC l

very fine sand, with ra re gravel clnsts. COIll­ parcd to U n i ts I a n d I ! . t h e re is an i n c rease ill very fine sand to 1 5-20% , and H significant (3-5% ) s i l l and clay co n te nt i l l this u n i t . The mode remains at 2.0 $. U n i t I I I is gertCl'Ully finc)' thnn OI'hcr lIllits, w it h a mean grain size of 2. 1 0-2.45 (p. and is a l wilYs fine to

'

,

'

SuperslIr!lIl:es i" the

Grall

77

Desierto

.

;: n'" II -.......- :. . . , If

''-ig. 7. Surface A (arrowed) fQrming division betwccn Units Rne! I I .

1

I'·ig. g. Surfacc B (arrowed) between Units I and I I I .

(0, 0.33-0.57) . bUl arc very silllilar t o tho,e or Unit I of the �\djaccnt �H'nd sheets. U n i t 2 o f the dune sediments consists of structurc­ less 01' vcry weakly Imninntcd rcd di sh brown (7.5 Y R 6/6) mcdium to tinc sands. There i s extcnsive roo( mottling ,md biot u r bat i o n of this u n i t . espc c ial ly 011 the Icc face (Fig. 1 1 ) . Unit 2 is much finer than Unit 1 . wi t h a mean gmin size betwecn 2.0 unci 2.5
=

D I SC U S S I O N Origin of the tmnd shecls

Sand sheets tire an import;'lllt component or many snnd seas and Illny form i n condit ions thnt include a high water table. periodic l1ooding. significant amOllnts of COtll'SC st\llds. surrnce ceme n tat i o n Hnd the prescncc of a vegetarian cover ( Kocurek & N i e l son . 1986). or lhcse factors. coarse semel and/or vegetation seem to be the most common ractors Ilssociatcd with sand sheets world-wide. losely associnl.ed wi t h arcas of sa n d shcets in ll1ilny sand

N. L{UI(;usu:r

78 .'

:

I" .

,, �

'

·.......:. 1

'.

--

-

Fig. 9. Unit I I I . Note siruclurc:]css character of unit. surface crust und lag of granules and vcry coarse sand. NW

SE SANO SHE E T S

C R e S CE N T I C DUNES

G,l,i "" '<:" (

SURFACE

"

.

'

_ _

n _

_ _

A

�_�

:� . ;: &;::; 2 ' 1

_

_

,

'''

�."!'i . ���""" .•'i .• t'i .'';

_

_

_

SURFACE e NOT

TO

SCALE

fig. 10. Schl!mutie view of dUlle �tl'iuigt'tlJ'hy and compnrisol1 with that of s.lne! shCet tlreas.

seas arc low-relief bedforms without slip faces called

prominent

zibars (Nielsoll & Kocure k . l�m6).

U llvcgctared sand sheets and zibars. which tend to

Although high w ill er tnblcs may have occurred '

loc�dly ill the nort h weste rn G I'(l1l Desi erLO l:I l Ou n d

Laguna Pri cw. there is no ev iden ce (e.g. i n the

of

f01'1ll

secondary preci pitation of eVHporitc m i nerals) 10

suggest t h a t high waler tables h a ve beeH signillcanl in the formation

or the

sancl sh ee ts in rhis area.

Comp
mode

at

2
in

cont[,�ISI

be bimodal ( Kocurek & Nielson.

to

many

1986). Thc active

'cap' of many cresce ntic dunes, as well

as the

active

I'cvcrsing :LI�d SlHr duncs in the wCstern pol!'t of the Grnn Desierto SHod has

n

C;'I. arc composed of silnd thut

mode of 2.0 or 2,5 . which is typical of many

dune sands. The s1.\nd sheets i n the northwestern puns of lhc Gran Desierto are therefore composed

in the northwestern Gnu, Desierto with those ill

of sands thm arc c!e:1t'ly in lhe range commonly

some other sand SC;'IS (Fig. 1 2 ) rcvc
found i n dUlles, and lheir formation is 1101. the result of a significmlt proponion of CO;;lrsc or very COilfSC

th a i is chilracleristic of Illany unvcgc\iltcd or sparsely

salld. which aClS to suppress the formation of dunes

vegetated sand sheets. Thc modal size fraction ill

with sl i p faces.

2.0 or 2.5 (0 . • 80 . 5 - 1 .5 'P (0.35-0.71 m m )

the Gran Desierto sand sheels is

0 . 25 m m ) , comp" red 10

i n Namibian n n d Algodones sand sheets (lnt.! ziburs.

With the cxceptioll of SOmC U n i t I sHnds, the Gran Desierto snnd sheets are also u n imod a l

wi t h

a

Today. the vegetation cover in the area is sparse. w i t h a maximum percentage cover of 1 0 - 1 5 % , This is insufficient to prevent sand transport l<'king place, but surncicllt to C�l USC di vergence alld convergence

of

nirfiow
79

Supersurfaces ill fhe Gmll Dcsierto Unl l

20 %

15 10 5 o

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 P.n • Algodones Dune "tid

0,0 0.5 1.0 1.5 2.0 2.5 3.0 3.6 4.0 Pa.n •

Fig. I I . Extensive bioturbation in Unil 2 of the dunes. overlain by weakly larni n:Hcd Unit I .

s uggested by Ash & Wasso n ( 1 983) and Frybcrger ef 01. ( 1 979), and gi ving dsc to localized de pos i tio n . Well sorrcd fine s"'ld is d epos ited i n ' sa n d tails' i n t h e Icc of grass clumps du r i n g periods o f strong winds and covcrs p re-c x i sti ng wind ripples (Fig. 1 3 ) . Wind ri pp l es can migrate i n t o are�lS p ro t e c ted b y vegclalioll, where l ocal incrcascs i n aerodynamic roughness and clecl'cascs i n Ileal'-su l"face wind spec Is " cs u l t in deposition (e.g. Hesp. 1%3). I f sa nd supply is ve ry high then i l is possi b l e that th ese efFects CHI1 Ici:ld to dune initiation (e.g. Kocurek ef al 1992). However, d u nes arc not b e i ng initiated by these proccsses in this part of the Gran Desierto. I t appears t herefore tha t sand supply is a l i m i ting fa clo l' , a n d t h e spi.lrse vegct:ltioll cover leads to deposition of a poorly so rted m i xllIl'c of rine nnd coarse snnd. Sand shect U ni t I n nd dune U n i t I were (illlel probably still al'c) bei ng depositcd u nde r these conditions. In the t crm inology or Kocurek & H nvh o l m (in . •

Namib Sand Sa.

10 5 o

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.15 4.0 Pa.n •

riA. t2. ompllI'isoll between pnl·ticlc size dislI'ibutiol1:-: or Grun Dcsiel'lo sand sllcct Unit I and deposits of s(ll1(1 sheets ill thc Algodones dUllcficld :lIId the Namib Sond Sell.

prcss ) , the area today is probHb l y

a bypass supcl'Sur­ sediment budget. Any accumu­ lation suc h as U n i t I therefore prob,lbly represents ,\ tcmporary s to ragc of medium and fine sa nd that i s fOH.:e. wi t h (I ne u t r al

80

rig, 13, Deposition on sand sheols on the margins of lhc Gran Des ierto star dune area, Notc 'l;n nd will;' 0" !ihadow dunes bellind cpllcmeml herbs and isolated creosote bushes. and migrating wind ripples i n intervening flrCHS,

ell route to its final the sand sea.

dcposit'ional si le ii' the dunes of

Units II and I I I i n the sand sheels IHCk \Vind�ripplc

laminations. hu t have n text u r e that is similar to U n i t I. They were probably de posi ted in s i m i l a r

co ndi t ions ;.lilt! o rigina lly had a similar sel o f sedi­ mentary structures. These h a ve

been

deslmycd by

post-depositional

and

pe d ogen es is .

bioturbation

The ma i n effects of pedogenesis have been Ull i ncreasc in the pe rce m age

of very

fine sand and s i l t ;'lnc! c1Hy

by infilt,'atio1\ of rilles alld possibly by weathering, but no 8 t horizons or chly Imnellae were no ted , Some redde ning has occurred. evidenced by a n illcranse ill M u nse l l chroma frolll /4 to 16. U n i l ] 1 1 is wC
1989), New Mexico (Welt, el al., 1990) and west

TCXHS (Gilc, 1979), This may i ndicate a relatively

young �lg� or fI lack

for the accu mulations Bnd su rface s,

of pedogenic activity as a result of

ai' a r i d

climate,

Devclopmcnl of supersurfaces

Surface A separates

the w i nd-ri pple deposits

gra p h i c pos i t i on s Hl w ide l y sepHnncd lOcations ind ic• .It cs thm it is of reg i o na l extent. In nddition, t he vesicular A horizon and pa l ae osol that unde rl ie i t indicate that thc sand surface w as stable for some pc r iod of time, S u rface A ex h i bi ts topographic rel i ef of I -2 m and follo\1/5 t h e prcse n t su rfacc. Thcre

arc no lag d e posi ts ;'lssoei uwd wi t h Surfnce A , Hncl

primary scd imcl1wry st ru ctu res i n U n i t II hnvc been

de stroyed

by pe do ge n esi s . Surface

rcp ,'cselll 11

forlllcr land s u rface

A appears

to

dcv el ope d on ('

gc n t ly u lldu l a t i l'g silnd sheet that was stablc a nd nOl subject to signiric
fo u n d in c�\stcrn pans ofrhc sand sea LOday (Fig. 1 4 ) , T h i s i m pl ies an increase i n vegetation cover, which pro tect'cd the surface and nlso cut off sa n d supply, A cl i m at ic change to co nd i t i ons of i n creased ra i n fa l l is i m pl i ed . Smface A is thus similar 10 the regional­ sca l e bounding s u rfaces descri bed by Talbot ( 1 985) and V/jkcl (1 989) thOlt resu lted from stflbilization of larc P lc is t oce ne duncs b y vcgctfltiol1 a n d ped ogcI1csis i n the cHrly H o l oce ne pe r iod of i n crea sed raillfnll i n the S ah e l . I t c;,m b e c l ass i fl ed a s a stabilized surface in the term in ology of Kocurek & H av h ol m (in press) . Thc age of S u r face A and t he c limat i c cha nges thm led to its dev e lopm en t
of

Mounwins 50 kill

no rt h of the nrcn

(Vnll Dcvcnder,

U n i t I fl'Ol11 the slructureless sands of Unit I I . Similar

1990) indicatcs i ncreased wintcr rai n fa l l and coolcr

t ex t u ra l

lClllpc ratures coeval with the l
charncleristics and remnant wi n d -ripp le

I n .n i nntioll$ in U n i t I I i n d i l;(I tc that both units

ac­

1 4 000 BP.

H oweve r , data from the Y u m a arca

cumulated ill a similar IllHnnCl', In ind iv id ua l t rel1ches

11 o,'t h wcsl o f the Gran Desi c l'to

S u rface A m i gh t be take n for a l'cacLivHtion surface ,

city con d it ion s ii'

but its occu r re nce in s i m i l a r topogra p h i c an d s t rat i -

l i llle (Cole, 1 986). I u r in g the mid-Holocene. there

indicatc continued

t h e lowe" Colorado Dcsc l't a t this

·

IIpersllIfac:es ill the Grall Desierto

81

FiJ,\. 14. Vegelation-stubilizcd �"Ild sheet ill eastern Grall Desierto. $Ucil salld sheets arc currently fonning II stabilized supcr.;urfacc , si m i l llr to thai represe n te d by Surfncc A,

is evidence from a vu r iety of

sources for increased

summer rainfall
grasses throughout the l owe r Sonoran Desen (Van Dcvende r,

1990).

and i t is possible Ihnt $ u r fnec

dates to this pel'iod.

Surface B

A

is a very extensive plmwr surfncc that

underlics sand shect Units I and I I as well as the cquiv<1lent dune units northwest of the main star d u n e .a rCH, It is cha ractcrized by a t h i n (one to two grain diameters), very coarse sand The undcrlying U n i t

III

01'

granule lag,

is! howcvct', composcd

hll'gely of fine and medium sand with a low percent·

« 5% ) of coa rse and very conrse sand. The rinc· grai ll ed n a t u l'c of this u n i t suggests that it hi not l:l

age

' t ra i l i ng margin' deposit len behind by the migration

of the dUlles of the sand sea towards tile southeast. The amou n t of detlation implied by the concentration of coarse grains to form

(1

l ag suggests that the

su rface W.1S cxposed for a cOllsidcrnble pcriod of

1990), Tcrm inmion of

sand sup pl y from this source

may have been rhe result of eustatic changes in

sen

level rhm changed the pallel'll o f nuvial seclimen·

Hltion in the de l HI system, For eXfllllplc, durillS the

last GI�lcial Max i m u m the dellH fron t W�IS locflted as much as

100 kill southC.lSt of its modern posi tion 1964). resu lting in the formation of n

( va n A n d e l .

d eeply incised v'llIcy i n t h e vicin ity of the present

clella regi on . I n the absence of a sand input frol11 the

Colorado River, 'c'Hl nibalization'

of cxis ti n g acoliarl

deposi ts then took plnce with dc/1:Hioll con t i n u i n g

ulltil a su rface l a g

formecl.

Once t h e surf'lcc had

stnbi lizcd. pedoge n i c p rocesses were tlbl e to alter

prc-exisling deposirs.

Il is proba ble thm s i m i l a r

processes o r e operating today in the northwcstel'll

Gran Des ie r to Sand Sea, now that sand supply fmlll the

lower Colorado

River valley has been ter m in a ted

by agricultural development.

timc i n thc absence of sigl)i fici:"IIH vcgcUltioll cover.

This is supported by the degree of pedogenic alter� .uion. inCluding the development of caliche. i n Unit I I I . Likewise. t he l:lbsence of significant to pog raphy

S U M M A RY A N D CONCLUSIONS

on this su rFace suggests minimal vegel�ltion COVCI'.

Sand sh ee ts i n the northwestern part o f the Gnm

veloped as

I'CSU I t of the termination of SHllci i n p u t

depos i ti o n by wind r i pples in areas of sparse desert

dcllalionary or cl'Osional supcl'surface deve l oped i n

regime (wind enel'gy > sand supply), Changes i n

The major sou rce for the sands of the wcstCt'll

opment of regional-�c;llc or super bounding su rfaces.

Su pcrs u rf
to t h e sand sea due t o non-climatic causes, ,lilt! is a

conditions o f n negative sediment budget for lhc BrCa.

Desicrto in Mexico havc developed as a I'CSUIt of vegetation and an

undcrsatumted sand tflillsport

climate r lll d /or sand supply

Gran Desierto Sand SeH was probably point bms

Term ination of sa nd

find ri ver terrace deposits of the lower

changes but w i t h

olorado

River downstream from Yuma (Blollnt & Lancaste r ,

110

gave

supply

rise 1 0 t h e devel­

because of eustmic

cocv.ul c1im1Hc cha nge led to

the development of a supel'surfacc dominated by a

N. LOIu':(lslcr

82

granule lag. Climatic changes leading to all Increase in the vcgclation cover tCl'lninmcd dcposilioll ..lilt! gave risc to pedogenic l1itc1'
A C K N Q W Ll W G E M E N T S The study was supported h y National Sciellc!'; FOllll­ dation Grant EAR 89-0 1457. 1 thank Gary Kocurek and Steve Fryberger for lheir conslructive reviews and comments.

R EFERENCES ANI)Ii[" T. I I. VAN ( 1 964) RCccllt mnrilic sclliments of the Gulf of alirol'lli,!. In: MlIfill(! Geology of the Gulf of (Ilifomio (Eel. Allelel. T.I-I. van & Shor. G.c.) pp. 2 1 6-310. Amel'icOIl1 A:.::.:uciutioJ1 of Petroleum Gcologist!i, Tulsa. ASII. J . & WI\SSON. R.J. ( 1983) Vcgctfllion :inc! sand mobility in thc Ausll'lllian descrt dum:fidd. Z. O(�O/JlOI1}11. SlIfJfJl. 45, 7-25. I3l.OuNr. G. & LI\NCAsTEM. N. ( 1 99()) Dl.!velopmclll of the Grtlll Desicrto Sa lid Seu. Geology 18. 724-728. Clt UI!CIIWAlm. I I.M . ( 1963) Suil studies at Swan !-till. Victol'i... Auslraliil. I l l . Sumc aSpC(;LS of soil development on acolint1 Ill'Jlerials. A llsf. J. Soil Res. I . I [ 7 - [ 28. COLI!. K.L. ( 1 986) The Lower Colcm)do River Valley: tl 1)lcis1OCCIlC descrt. Qua/em. R(!.\·. 25. 392-400. COI.I.lnTI\. B. & OtttLII!ll. L. ( 1 984) Ocfm'llllltions of the middle and latc ]>lcislOecnc dclwic dcpositt"

G1t.�. L . H . ( 1979) Holocene soils i n eoliun sedimellts of B'litey Count)" Te)(:1s. Soil Sci. Soc. Alii. J. 4.1. �94 - I On3. GII. I�. L.l t . . PI£THR�ON. F.r. & GU.OSSM,\N . R.Il. ( 19M) Morphologica[ and genetic sequences 01' carbonate acclIlllllbitiOI1 in desert solis. Soil Sci. 1 01 . 347-360. HI!.�l'. P. ( 19t!3) MorphodYIl:lI11icsofthc incipicllt forcdulles in New S�lt1th Wales. Austntlia. I n : co/ilill Sedilllt!llIs (/lui Pl'oft.wses (E
Posamcnticr. I-I . & Wcimcr, P.). Am. Ass�)e. Pel. Gco[ . . Tulsa. KocuRllK, G H,WII()I.M. K.G .. OEYNOUX. M . & BLAKEY. R.C. ( I � I ) Amalgamatcd acculllulations rcsulting from c:timatic lind eustutic changes. Akclmr Erg. Mauritania. Sedimellfology 38. 75 1 -772. KOCURI!K. G. & NIEUi()N , .I . ( 1986) COllditions favourable for the formlltion of wllrm·climate neolian sandshctts. Scdimclltology 33. 795-8 1 6. KOCURBK, G . . TowNsu:Y. M . . Yl:lI. E . . HAVIl0LM. K . & SWIll·T. M . L . ( 19(2) DUlle ;In(\ dUllcfield dcvclopment on Padre Island. Texas. with implications for interdune deposition ami w:ltcr·t:lble·t.'OIurolled nccutllulation. J. Sed. Pell·ol. 62. 622-635. L\N(·MiTER. N . ( 1 990) Palaeoclimatic evidence from sand !'>eH�. I'(I/{{eog('og. . l)alo('odilfl(lIOI. . Pal(l(!O(:('ol. 76, 279-290. LANC,\STI!R. N .. GlumUlY. R. & ClIRtS I'I:NSI!N, P,R. ( 1 91:\7) Dunes of the Gnlll Dcsicl'Lo Sand Sea. SOllora. Mexico. Etll'fh 1111. PI'Ot'. Lmulj'. 12, 277-2SH. NmLSON. J. & KO('URI!K, ( ]t )86) Climbing r.jbar� of the Algodones. SuI. Ct:ol. 4R, 1 - 1 5. PORTUI<' M . L. ( 19/:O\()} Sedimctll:lI'Y I'ccol'd o f crg migration. G(!Qlogy 14. 4n-500. RUBIN. D . M . & h�I'r),\. 1-1. ( 1 990) Flulllc cxpcl'irncllls on the JlignmCl1l of 1,·anSVCI·SC. oblique and longiludillill duncs in dircctionally varying nows. Sedimelllology J7. (173-(�4. SWllIll. M . L .. Nmt.soN . .I .. I Ilwllor M. K. & r."RIV\LI.�Y. J . ( 1 9�S) Algodones clunc ficld o f SOlil hcastCl'I1 nlifornin: cusc history of H migruting modern dUllc field. Sed/lllellf{)· lo�y 35. 9:W-952. TI\l.lI01·. M . R . ( 19$5) Miljor bounding surfuccs in ucoliol1 S�ll1c1slOncs: 11 climatic modcl . Sedilliellfo(o,;'y 32. 257-266. V,\N DI!VENI)ER. T.R. ( 191)0) LHC OWHcmnf), vcgct<-l lion lind r,: linult(; of the SOllor/IIl Desert. United StaleS [1111.1 Mexico. I n : PII('k l'(/I Middell.�: flie L(,.\·t 40000 Ye(tr.\· (If moyie ClltIlige (Ed. Detancourt, J.L. . Devcnder. T.R. Vlltl & Martin. P . S . ) pp. 134- 166. University of Arizona PrCll-s. Tucson. VAN DHVI!NDHM. T.R . . THOMPSON, R.S. & B£TANC:OUII.1', J.L. ( 1 987) Vegetation history of the deserls of south· western North America; tile Illltlire 1I1ld timing or the .•

I.

Supersllljaces ill tile Grall Desiel'fo Laic Wis(;onsi l l - I loloccnc 11'allsilion. I n : Non" A lllel'ic.·(1 Ocenm' Owing (he Uw Deglaciatioll (Ed. Rucldimnll. W.P. & Wright. I· I . E .. Jr) pp. 323-352. Geological Society of Amcrka. Boulder. Vti K l iI• . J . ( 1 989) Form,Hion of dunes and pcdogcnc);;is as palacoclimatic ind icators in Ihe eaSlern 1':11'1 of the Republic of Niger (Sahara and Sahel). Pal. Ali'. 20. 37-54. a/ld A djacc/lt

WELI.S. S.O .. McFAI)[)ItN. L.D. & SCHUI.TZ. J . D . ( 1990) Eolian landsc,lpC evolution lind soil fonmllioll in the

83

Chaco dune ficlcl. sOUlhcl'll olorllClo Pllllell u. New Mexico. In: SOill' ({1U1 1.(lIIr/scope Evo/lllio". Proceedillgs

0/ tlte 21ST IJillg/I(IIIIIOII SYlllposilll1l ill Geoll/orphology

.•d. Knucpfcr. P.L.K. & McFadden. L.D.) PI). 5 17-546. .I�cvicl·. Amstcl'd�llll. WIN Ktl:lI.. . 0 . & Kmw m. J .• S . M . ( 1986) Paleocurrent evidcncc for l:lIcml displaccl11clll of thc Plioccne Colorado River della by the San Andreas fault system. southeast· crn California. Geology 14. 788-79 \ .

(

Ancient Aeolian Environments

Aeolian Sediments: Ancient and Modern Edited by K. Pye and N. Lancaster © 1993 The International Association of Sedimentologists ISBN: 978-0-632-03544-1

Spe(', Pubis {fll, Ass, Se{limem,

( 11)93) 16, 87-107

Aeolian genetic stratigraphy: an example from the Middle Jurassic Page Sandstone, Colorado Plateau H A V H O L M " , R . C . B L A K E Y' . M . A P I' S ' , ' L . S . .I N E S , D . O . K I N G ' """ G . K O U R K '

K.G.

"'f)�partmC!1/I of Geological SciellC:es, UI/i versity of Texas tit AilS/iII, Allstill, TX 78713, USI\; allli t Def}rlrllllellt oJ Geology, Norrhel'l/ /\1'1'(.011(1 Universily. Flagstaff, A Z 8601 1 , USI\

A BSTRACT Regional trueing und corl'cllllion o f super bounding sl1rfaees :lnd the llcoliun nccumul they cap show that the Middle Jurassic Pflge Sandstone consists of a thrce-dimcm:ional 1110saic of tlH!sc basic aeolian building blocks, These bosic supcrsurfaee bounded units can be grouped illto six lIl'chilCClLlral asscmblngcs tCl'mccl lhe Basal, Lower, Isolated. Middlc, Upper and T1'nllsitioll Units. TIle I3tlsul Ullit is a complex. dis(,.'o ntinuous asscmblagc for111cd on the il'l'egular J·2 regional unconformity and Illay not reprcscnt gCllcticaHy rehlled stmla; seOLLl'illg aSSQCiuted with emplaccmcnt of the overlying unit i ndicates thut it W,IS initially more widespread, The main bod)' of the Page consists of thrce asscl\\blnges. The Lower Unit pinches Out ugninst the I'ising J-2 sUI'race along thc Monument OCl\l..'h . and i� bounded in II stcpwise fashiun by Sllpel'SlIrraCC� thai show the progressive Cl.lSllYard transgression of Ihe Illllr'inc Judd I- Iollow Member of the Cilflllcl FOl'l1ltilioll Wilh Sllpcn�urfaccs cxtclillinl:, inlillid. The Isolntcd Unit, occurring tiS outliers, is Icnt,H ively corrctlltcd with the B(lsul alld Lowcr Units. The Middle Unit inter­ tongues throughout Wilh the Oirmcl Formntion, lind consisls or the :lmalgUl\1Ulioll of layers ancl lcnses of aeolian units scpanHcd by Illultiple trullcational supersurf,lccs. some of which can be traced into tongues of the 'Hmcl. The Upper Unit of thc Page is 10c
I N T RODUCTION Scp;\I'alcd by surfaces h
ThaI the accumulation or a n ([colian successiO'1 can be an episodic process was lirsl recognized w i l h Pleisl ocene- l=Iolocene acoli n n successions I hal clearly I'cprcscnl more than onc pcriod or acculllU­ laliol1 (e. g . Glenl1ie. 1970: McClure, 1 978: Anlol1, 1 983), Surraces re p rese nt i n g h i n w l events i n acolian accumulation were first int erprcted in a n anciclH u n i t . the Permian edal' Mesa Silndstonc. by Loope ( 1 985), Since then examples or acolian accumulations Prct'cn l addl'css of first author: Geoiogiclil Sciences, AJ·20. University or WaShington, Seattle. WA 9�IY5, USA.

III

Aeolian Sediments: Ancient and Modern Edited by K. Pye and N. Lancaster © 1993 The International Association of Sedimentologists ISBN: 978-0-632-03544-1

87

K, G, !-Ifill/101m is

caused

by

a

el HI.

•

change in t h e sediment b ud get �onenvironment and t h ere fo re a

ditions ill t h e aeo l i a n

single 'lccul1lulalion and its cnpping SlIPCI'SlI l'f'ICC

re presen t the basic unit Or b u i ld i ng block fro m ..Ill a eoli a n succession is b u i l t , This basic Hcolian unit has c l e m ents of sim ila r i ty to olher types of s t ratigrap h i c unit. Like the 'genelic st rat igra p h i c sequcncc' or Gnlloway ( 1 989). each b'1Sic aeolian u n i t rcprese n ts <.I distinct. coherc n t e p i sod e of sedi­ me n tati o n , a genetic u ll i t , and it i s with this sense tlHlt the Icrm 'gcnctic' is used throughout lhis study. L i ke the 'sequencc' of scquence st rat igra phc l'S (Van Wagoncr (:1 al., 1985). each basic aeolian u n i t is defincd by bounding su rfaccs formcd during sub­ aerial cxposure, However. i n sCi.l lc the basic gc nc t ic aeolian unit may be morc comparable to pnra­ sequcilces or parasequcnce scts I h a n to the larger sequences. I n addition, I h e faclors I hal co n t ro l coast,l l/marine sequence or panlscquencc forllltition ilrC not exact ly the SelmC tiS those that control acoliun stnlligmphic patlerns ( H av ho l m , 1 99 1 : Kocu rek & which

I-I"vholm, 1993).

ll1C pu rpose or this stud y is Lo demonstrate thm

supersurfaces can bc used On n regional scnle to hclp sepal'ate an aeo l i an (orl11 (1liol1 into its gC llc ti cu l l y distinct parts. t h a t is. pack age s of I'Ock that re p rcse n t pcriods of accul11ulation and thc su pcrsu r faces t h at sc pu ra t e l he m a n d re p rcse n t pe riods of h i a t lls i n acculllulation. Th is pu ts ac ol iall strat igr a p hy 011 a n event -stratigl'aphic footing. ( I l low ing rccognitio ll or the events associtlted with the developlllent or an aeolian succession
iH.ldressed hel'c, I-Icnce. whm follows is a casc-study

genetic-str:lligmphk architccture or the Middlc J u rassic ( Baj ocia ll I3nt ho n i a n ) Page San ds to ne is dcfincd on the bas is of supcrsurfncc geometry. thc stl"H ificmioll sty le of the accu m ula t io n s bounded by the s upC rSU l' fHCeS and Lhe I'c lH t i onsh i ps of t hese units to one a not h e r and adjacc ll l non-a eol ian u n i ts . in

which

thc thrce·dimcnsiol1�11

­

Fig. l . Gene ral palaeogeographic sclling of the Middle Jurnssic Page Erg nnd urea of this study. modified (rom

Blake),

j'/

(II. ( t VS3)

lind

Suleeby & Busby·Spera ( 1992).

craton, l ap pi n g onto the Mo n ulllen t U pwlIrp (Fig,

I ).

fin area that was a st r'ucllIrnl bench d u r i ng early

1986). The Page Sa ndslOn e was chosen for t h is st ud y for several reasons. I t has large expanses of exce l l e n t . gene ra l ly accessihlc exposu res . It COVCI'S �t relatively small gcognl J> h ica l area by Co lora do Plateau standards :.md is nowhe re thicker than 100 I'll (Pig. 2). It COn­ tains Ill ultiple lat e ra l l y cxtellsivc su rfaces that have features t h a t gc n c rnl l y d i st i n gu i sh them from o thc r relatively feal lIl'cless. less exte llsive surfaces in the Page Sandstone. These s u rfa ces have been inter­ preted :IS su pe rsu rfaces based on their lateral co n ­ t i n u i ty nnd t hei r distinctive features and bec;lusc they gene ra l ly separate aeolian stl'ata represen ti n g M i d d l e .lu rassic lime (PelerSo n .

dunes of di fferent sizes and typcs (Hovholm. 1 9 9 1 �

Kocu rek el al, . 1 99 1 b) . The surface features i Ilcludc

pronounced Incal relief associtltctl with denation of a damp

or

cemented s u rface. the presence of OVCI'�

ly i n g wavy-In minatcd. finc-grained sabkha deposits

nbundant fnlctures thai in plan view arc poly­ pol ygonal fractures have bee n in te r­ preted ;'lS the result of expHlision und contr�lction of an c\lapori tc-cemcntcd substrate (Kocurek & H u n t e r, 1996). M o r e ove r . the Page S a n ds to n e i n le r- fin gers wilh nnd is overlain by the marinc and

and

gonal. These

llon-acoli�\Il coastal pla i n sediments of th e

aeo l i a n

ncclllllulations a nd their capping surfaces

with their eq u i va lcnt expression in I' A G E S A N D S T O N E

The Page Sandstone has been i n t erpre te d a s a coaswl erg thm lay a lo ng Ihe Carmel inland sCHway Ilear the west e rn cclge of the Middle J u rassic North Al1lcricHn

ol'mel

�orm
non-acolian unit.

Ihe lit hofacies de­ scri p t i o n , environmental interprctation an d tectonic alld stratigraphic framework of the Pagc [lild lIl'mel Fo rm a t io ns can be found in Voorhees ( 1 978), Gees'IIlH1I1 ( 1 �79), Pe te rso n & Pi p i ri ngos ( 1 979), Considerablc work providing

89

Page stratigraphy

Ca plil O ( I �80). 13 I"key el lli. ( 1 9�3), Peterson ( 1�86). Blakey el lli. ( 1 988) and Kocure k ,,, III. ( 1 99 I b). The dctailed wOI'k from which much of this paper i s summarized is presented i n Ca pps ( I YYO) J o lles ( 1 990), l -I avholl11 ( 1 99 1 ) and King ( 1 992). In the course of th is project, 321 sections were measllred (Fig. 2: ppendi x Table A I ) . Fi gu re 3A (fueing p, 88) i l l ust rates the three-dimensional archi­ tecture of the Page Sandstone by way of a fence d i ag ru l11 whose location is shown on Fig. 2A, Some Illore detailed Irnverses al'e shown on Fig, 41\ - E ( Fig. 4D & E face p. 1 12 ) : t he i ,' locations. which diHcr slightly from the travcrses shown i n thc fence In diugralll in Fig. :lA, arc indicated on Fig. 2 some cases, surfaces and units had to be correlatcd bc[wecn scctions, but in other cases they wcrc (rnccd cithcr by physically walking thc surfaces or by following them on photographic p�Hlor;.'mas. The stratigraphic fru mc wo r k defined by t h e gell­ etic a rchitcclll rc of the Page Sandstone is at odds with t h e formal slral igl'aphic divisions of the Page Sandstone. A co m pa rati ve chan (Fig. 3B) shows how the major supcrsurfilce bounded units, describcd below. relate to the forlllni stratigraphic divisions. FOl' ll 1a l l y . in (he west and south the Page Sandstone is subdividcd inlo two members by the Judd Hollow Tongue of [he ,H'l11cl Forll1ation� the part of the PilgC Snndstonc underlying the Judd Hollow is the H a rr is W
.

•

Upwilrp (Fig. I ) , n structural bench duri ng the J urassic ( Peterson. 1986). The I)age Sa ndstollc is hcrc subdivided into six major units. some of which arc �omposcd of sll1 u l l e r gcnetic units. Figure 5Ashows an example of cach of thcse units. T h e oldcst Page strata above the .1-2 su rface com pri se a distinctive. discontinuous unit I'cferrcd to here �IS the B asa l Unit. The younger main body of the Page Sandstone consists of thrcc primal'y architect lJral uilits; Lower, Middle and U ppe l' Units. A uilit found o i l l y in ou t li e rs of the P:Jgc SnndslOlic ( Isolmed U n i t ) is tClltatively corrc· latcd with thc lower purt of the Page Sandstone. in cludi ng part or all of the Basal. Lowcr und lower Middle Units. The Upper Unit has filled scours cut into its upper surface. The P:lge SundslOlic is capped in many areas by n Transition U n i t associmcd with t h e onset of Carmel accumulation across mu c h or the region. Thc names of the six major units of the Paga.: Sandstone lire capilHl izcd he re for cw�e of COI11Illunicating our ideas and wc do not mcan to imply t ha t thcse should bc t"ken as fO l'ln a l stratigraphic subdivisions. BaSHI Unit ( I)Ud, PHs), bnslll sUI"face (S··b) The lowermost genetic

accumulation of as II t h in

Sandstone (PBd, PBs) occurs

t he Pngc

lInit (5 111

thick o r less excep t in the Page, Arizona arCa whe re it is up to 1 5 m t h ick). with two distinct lithofacies (PBd. I'Bs). In the south, the Sa sa l U n i t (PBd) is a ty pi c'l lly bimod,,\. fine- to medium-grained �lndS1onc showing wavy lallli n�lc. low-angle wind-ripple strat:;l

and

l ess

common

intervals with ad hesiOn-ripple

structures tw d scts of high-anglc dUllc cross-straW.

fCHtures ahcm'lIe vertically dnd grade latemlly patchwork accul11u­ lalion of a eo l ian �i
into one unother, rep rese nti ng a

the Harris Wash.

G ENETIC STR A T I G R A P H I C U N I T S A N D S U P E I� S U R F A C "S

The Pnge S�lIldslOnc cverywhere rests on the .1 ·2 unconformity. one of six regioll
representcd by il claycy - sandy siltstone with sand­

stonc layers and lenses (PBs). The siltstonc local ly contains siltstone rip-up c\ .lSts ; and hal ite cl'ystal moulds: the sa n oston e shows wl.lvy l ami n nc �lIld brcccius of win cl - ri pplc strata. This l i t hofncics is believed to havc becn deposi tcd in U Illuddy s{l b kha to a possi blc fluvial and cVClponl livc lacustrine ellVirOllnlenl. The Ba sa l Unit is complex and not necessarily a s in gle genetic u n i t . It is typically cHpped by a

90

K.C. !-fflv/lOfm ct 31.

��.a_

A

•• _

..

_.

-

··- '·-··

I

o-MA!"l.lfl

•. _ _ _ _ _,

!.jAN

, :

, .

I

: I

'"

I

,' - ' .. . ..! I

o BJandlng

,

"',..

0

•..

'

.

_ JI . _ .. _ . . I

,-' - --- " -.. - - .�f,�I"' I i i I i i I

supcl'surface (S··b) with well developed polygonal fracLUfcs. As seen on Fig. 48, D & E, in some cases the B�ls,,1 U n i t is confined to lo pog ra ph i c depressions 011 the J-2 su rface (unit A ill Kocurek el al. , 1 99 1 b) , und this m a y ,'cprcscnl the or g i n a l depositional extent of t he lIllit. E h ;cw h c l'c , however, the uilit i s clc<.II' l y truncated by erosion associated with troughs scoured during accumulation of the overlying Lower Ullil. and here i t may hnve ori gina l ly been more i

.. _

..

_.

_.

.- -

o.

FiJ.:. 2. (A) Isopach map or 1)lIgc Sandston ; contours l;how 10lal thickness or the Page Sand�lonc in metres (including the thickness of tongues of the em'mel Fonnalioll thfll tIre within the Page Sllllcistoru.:), OOIS ore loc:uions of measured sections: three-Jetler labels arc nbbrcvialiotls for 1H1tllCS of measured sections (�C Appendix for section nnrnes ancl loCfltiolls), Traverse lines flet as the bUlie of the fencc diagram ill Figs 3A & 13. The orea within the dashed rcculIlglc is enlarged i n Fig. 28. (B) Enlargement of salt t hcl'll cud of Page Sandstonc Olllero!, area showing section :lbbre\'i�ltiolls (sec Appendix) :lI1d isopach l.'UlllOurs (in metres), ( ) Mnp of the southern end of the Page S;1IldStonc oUlcrop arca showing the IOC(rtions of the traverSC:-l illu�trnled in Figs 4A- E.

extensive (Fig. 411. 0 & E). The silty racies (PBs) is more continuous than the unit in the south. but i t (00 pinches out against palacolopognlphic high areas on the J-2 surface (e.g. northwest or sect i o n SI-I D. Fig. 3A). As discussed in Bla key el al. ( 1988) and Kocurek ('/ III. ( 1 99 I b) . rocies grouped here "s the Basal U n i t developed as (he initial deposits 011 t h e regio n a l J-2 unconformity. alld these Ihin accum u lations Illay have forllled at various limes

91

Page stratigraphy

B

,,,,'

o

. ""

N

1

£"''''0'

�..

.�,

• _1 IIN"'t• I,a

•

rr'�

_0 101'\.0 ' �

TW.....

olOP1 . .� ..."

",WI M2· IWIJ,4,'

. ..,:""

';-

• lWI1,I,

--

- -

,:'t�It".

_". olllW.II

."" .

,,,,,'

...

""'0'

coi,,1

1111'1,10

•

FI,IW · .",'

cu ·

.... .

... . wo

... '

.� I!ICH

•• • �MI

IJol'T"j icc �I)\I - -�

FiA. 2. (col1l inued)

K.G. I-/lIvhoflll et n l .

92 c

0 1•.,,,, ,

C"

.'

00-

"

• . - .- . - . - .

.\

_ .. _ . . _ .. _ .

.�r - - - -

' -

•

10 2(J "'"

Fig. 2. (continued)

•

and

d raas

Kocurek el rd. ,

1�� l b ) . In the Ca nn on v i l le are" the Lower U n i t i s th i n overall a n d consists o f th i n , si m p l e aeolian sets and contorted to st rucr ll rc l css sand­ s to lle (PU 011 Fi gs 3 A & 4 ), In Ihe T ioa boo a,eH fll1d in the al'ell 11 0 rt l1 of Duchcsnc. the Lower U n i t is rephlced hnc l'ally by t h e Erg M a rgi n U n i t ( P E , i g . 3 A ) I h n ! consists o f a S lack of d u n e cross­ straHl an d sabkha beds, It'UllCiltcd by up to ninc supersurfiloos ; the Erg Ma rgi n Unit (P£) is probnbly a l so partly cC(\JivalenL lO rhe lower M idd le U n i t' . The Lower U n i t hus a d i lfcrcllt cupp i n g supcr­ sU I"f
d u r i n g exposure of the J-2 surface and may re presen t

morc than one accumulation eve n t .

Lower Unit (PL, PLf). c81>ping supcrsurf�lccs (including S--.Ih), Erg Margin Unit (PE)

with ncolian scouring in the Middle U n i t north and

O verl y i n g Ihe Basal U n i l (I'Bti. PBs). o r Ihe J·2 unconformity where t he Basal Unit is absent , is lhe Lowel' U n i t (PL, PU). w h ich fOfms the ge ogra p h i ­ cally most cXlcllsivc unit of the Page Sandstone

(Figs 3A, 4A -

cross-stram th a t

very

-

o

I1Hlinly of

( H uvholll1, 1 99 1 ; u n i ts B and

"

"0

consists

represent large s i n uou s crescentic dunes

Eacahml9

o Canonville � -:

' -

D & E) a n d

E •

& 6). This unit is thickest in the

Harris Welsh to Brimhall Arch

ilrCaS ( se ct io n s J-IWS, BI-I A , west of Ticaboo, Fi g . 3A) alld t h i n s and p i nch e s out agn i nsl the J-2 unco nformity a lo ng the palacotopographic h i g h of the Monumcnt B e n ch a lo n g i ts i n ln n d . so uth ea stern m a r gin (Hlollg Lakc Pow e ll i n Figs I & 3A , to t h e sOll t hcl\rlly re p l a ced hHcrally by the lowcr Middle Unit (PMI) and the Judd Hollow To n gue of thc Ci.lrmcl FOl'mation ( J ) in a stepw ise manner best illustrated in Fi g , 4 E : i n other areaS the tnlns­ g ressi n g marine and sa b kha u n i t s of the J u dd Hollow simply ovel'lie the LowcL' U n i t (c.g. t hc westernmost part. Fig. 40). To the lIorth nlong the axis of the Page S.\I1(\slO lle. the Lower Unit thins 10 lhe north or H a n k sv i l l e . but th e n thickcns again in the San Rafael Swell (se eli o l1 BKW. Fig, 3A), Whe,e il is next seen. north of D u c h esne . it i s thinner l\gni n (section LFK. Fig, 3A) ilnd pi nch es o u t northward, The ma i n part of the Lower U n i t is a finc- to mediu m-grained sa n ds to ne (PL. Figs 3A & 4A. B ,

southCHSl o f Esca l a n te . nile!

'

cast of Wct.herill

allyon (sccliol1 WLC, Fig, 3A). Elsewhere the Lower U n i t is copped hy OllC of a seri es of surfaces extending inland from the ndv(lnc­ i ng transgression that form the base of th e Middle U n i t (c.g. new' Judd Hollow. sections BPT-CME. Fig. 40: frolll Escalante to so u t heast of Ea r l y Weed BCllCh, sccriol1s TBX - DFC, Fig, 4E) or by a latcr s\lpcrs �lrfn ce

(S--�L]») that truncates clOWll to the

Lower Unit cast alollg Lak e

Powel l (e.g. sou th ca st H u rricane Wash. s ectio n s H W A - FM R. Fi g , 4 ) . Loc a ll y there is a :) u pcrsu rfa ce or group l'>f Sur­ faces ( l ower s u rface zone. S--I) wi t h i n this unit (Figs 3A & 4A . D & E) suggeSl ing Ihal it ,'epresents IWO accurn ulHtion cvents. Thi!; s u rfa ce . or an equivalent s urface zone. is clisCO I L l i l1l1olls. tr unca ted by t ro ug hs in the overlyi n g unit (Fig. 40 & E ) , The occurrence of t h i s surf�lcc. or the cqu ivn lc nt ZOne of seve ra l su rl'Hccs. in widely spHced arcas suggests that it may h a ve becil a much more widespread s u rface 01' sur­ face zo ne before t ru n ca tio n . The exprcssion of t h is su pcrsurface varies fro m are<.l 10 a re a . SOlllhcasl of Escalante from Enrly Weed Bench to Fi fty n1 i l c Ridge (scclio n s E W B - FM R . Figs 3 A & 4E) su ,faces in th i s group typica l l y hnve large pol ygo n a l fractures and. more rarcly, Hrc overlain by th i n sabklHI bcds, Norlhwcst of Page. Arizona in the .lucid Hollow of

Page

stratigraphy

13- M E , Fig. 3 A : B H - M E , Fig. 40J it consists o f H di sc n t i n lioliS zo n e of thin sets of ,aeo l i a n cross-str;l\i.l separated by sabkha beds anel area ( W

corrugated to polygonally fractured su rfa ces,

Isoillt.cd Unit (PI) Around Moab arc pods of Page Sandstone that nrc isol a te d ill topographic lows on th e .1-2 surf'lcc ( P I . Fig. �A ) . These have n pa rt i c ul arl y low proportion of dry acolinn strata, and i n cl ude subaqueous r i ppl e strata as well as sabkha sediments (see also wezey. 1 99 1 ). Bec au se of rheir i so la t io n . these localized lenses of Page Sandstolle can n ot be correlated with confidence 1'0 u ni ts in thc main body of the Pngc Sandstone. However. based on their sedimcntation stylet which bears similarity to both the Basal Unit (PBd) and the Erg Mal'gin U n i t ( P E ) . and their locatioll far to t he nonh o f H rc as thnt contnin t he U ppe r U n i t ) the Isolated Unit is probably co r rc la ble to part or a l l of the Basal. Lower and lower Middlc Unils. Middle Unit (PMI, PMmt PMu). middle surfl1cc zone

(S--jh, S--rm, S ·- ue)

The M id d le Unit of the Page Sa nds ton e ( PM I . PMIll. PMu) i nteJ'�fingcl's with or grades laterally westward into two members of the Carmel Formation to the west, the Judd Hollow Tonguc (.Icj, CJ) and t h c Crysw i Creek Member (Jcc), Also incl u d ed i n this parl of the Page Sandstone is il marille to s;lbkhu R . Ihis unit (' red marker' of B la k ey "I III" 1983; study) that was previously considered LO be "l tongue of th e stratigraphically higher Crystal Cree k Member o f the al'mel. before Jones (1990) demonstrated that it is an upper tongu e of the .Judd I iollow Member of the Carme l (F igs 3A & 4C). The Middle U n i t or the Page , un dstol1C consists of dllne strnta lrllllCH ted by up to ninc supersu rfaccs. The resu lting package is an amalg
Koc u re k el III . . 1 99 1 b: lig. 20a. Havholl11 , 1 99 1 ) . This unit is thickest to the south­ west in rhe West 'Iltrk Belich area (e.g. scctions W B - CS Fi�. 3 A , sect i on PWA. Fig. 40). where it beg i ns to i n te r-fi nge r with lhe flrmel Formation. It thins westward (bnsinw(\rd) as it is re pl aced by the Judd Hollow Tongue (0. C R. Jci) and the ry"al reck Member (Jcc) of lhe Cmll1cl Formation ( Figs 3A & 4 & E). To the cast and southeast thc Middle Unit thins as i t is c ['osion a l ly t r u ncated from above

4 A - E ; rig. 3 ,

•

93

by t he S--ue su rfflce (Figs 3A & 413 & 0) and by the

S--up su rface (e as t end of Fig. 40 & E ) . The dune slI'ma i n t h e Middle U n i t (PM I , P M m , P M u ) rcpl'csent accumulation b y a variety of clune lypes and sizes, but the dunes were genera l l y smaller ('han those that produced the underlying Lower Unit (J-Iavholm. 1 99 1 : K ocu re k et ( Ii. . 1 99 1 b) . I n v ari o us nreas of this lone, pa rt ic ularly along the IlU\l'giJ1S of t h e PHge S,lIldslone, nco l i D n Strain are contorted or slumped. and the proportion of sabkha to <1colian strOta also in c rei.lses townrds the m
LOIVer Middll! Ullil (PM/J. H I

sllIftlee (S·-}iI)

The lower part of the Middle U ni t (PMI) und e rl i es the J udd lIollow Tongue of the Carlllci (CJ) or the equivalent supel'Su rface (S--j h , r-igs 3A & 4D & E). FJ'ol11 the sculnntc .1I·Cft to the southcclst (sccl i o l1 S P K- R W L . Fi gs 3A & 4 ) this �Init conl;lins n series or sllpcrsurfnces that extend from t h e i.\(\Vi.\nc· ing Judd Hollow Tongue inla nd into the erg with stratigraphically h i gh er s u rfaces extending progres­ sively fU l'l h e r inland. Fu nhc r south in t h e Judd I iollow area (se ct i on s BPT-CME. Fig, 4 D), this archileclUral clemellt is al so presenl but is much less

extensive.

The lower Middle Unit (I MI) i s probably tillle­

cq u i va lclll to tile lowermost part of the J udd Hollow

Tongue basinwi1rd and to the uppermost part of the Lower U n i t i nla n d . As th c lI'unsgressioll progressed inland. Hcoli:m accumulation of the Lower U n i l continucd cicc I' i l l Ihe el'g, w h i l c ill t h e erg 11HIJ'gillS

K.G. Nallholm

94

ct ill.

B

Jpl

, '- '

- , _

Joj

-------

-

- - -:;:..-

Jp, --------�'_

�

::-��

-O ------------ ---__

_

i �

Jp

J··2

Jo

Formal Stratigraphic Terminology

PTp

� .. ..

. - - -

_ _ _ ..P!:l!! _ _ _ _ _ _ _

-

.. .. ..

- T p' , S··rm-------= .:.!:.

Joj

PBd

Jo

PBd

PTb

Genetic Stratigraphic Terminology

e xplon allon of Symbols In Flguras 3,4,6

Ped PBs

PL

Sob S_I

Basal Unit, Mndy 1acles

Basal Unit, silty lacles LOWQi Unit, moln part Lowor Unit, mtlrgrf\{ll llDI beets Middle Unit Middle Unit, Iowar part

S-jh

PLf PM PMI PMm Middle Unit, rro'ddle P
��

Transitional

S-rm

S-uo S-CII

S-up J··2

lOp 01

Basal Unit 'NIlhln tho Lowor Unh lOp 01 lowor Unit lOp 01 middle Middle Unit

CJ CR CC

Upper Unit within tho Uppg( Unll lOp 01 Upper Unit

Jph JpI

Unll, main pm!

transitional Unit, build-ups

Jpu

this slud)', Below is the csphlllutioll for

nil

IOwor IOnguo 01 the Judd HoUow uppor tongue of the Judd Hollow channol lBclo, cul lnlo Jml,l

base 01 111101

Carmal FOrmal Units

unconrormity, base Page

..IeJ

PS!)O Formal Units

Fig. 3B. Diugrtlill i l l u�trOlillg the �c l (l t io nsh i p

ill

Carmal U nllS (this rsport)

Page Super Surfaces

Page Genetic Units

Jcc

Jcf,l

Hartis Wash Mambo,

Thovsand Poc:kot!!. Mombor Pago, undivld9d

In

Judd Hollow TongUG

Crystal Crook Memoor Uppor

Momoor

Navajo Sal'ldstone

of the fOI'llHlI slr'lltigr;:'phic �11\ilS to most of the stt"lIill.l'aphic lInits ullit abbreviatiotls used i l l this study.


defined

Figs 3A & 4

aeolian (lccu mulat ioll was pun ctuated by pe r i ods

Hollow.

supersurfacc formation

& E) is the middle Middle U n i t ( P M m ) . an a eol ia n

(IS

the

of marine �1I1d sabkha

elwirollmcnts approached,

•

unci red 11l;.\I'kcr. C R :

unit t ha t i s bO['dcrcd

on

1

D

r h e no l'th ;.l n d west by sandy

and m u d dy S!Jbk h a st ra t a , II is res l r ic ted to the

Middle Middle VI/if

(PNII1l).

BCIWCCll Lhe two

longues of the

N. M

slIIj'{/ce (5'--1'111) (lrmcl (Judd

southcrn pan of thc Pagc , UlldstOllC, i n contrast ('Q t he

Lower U n i t (PL) (Fig. 6 ) . The extent of the middle M idd le U n i t does not represent its original

95

Page stratigraphy

d eposi t i oll a l extent because i t is erosi on al l y truncated On i ts s o u t h clls tc rn m a rgi n (Fi gs 3A & 4E), and perhaps A l so its no rt h easte rn IllHrgin (Fig. 6), by the upper erosional su rface of [ h e Page Sandstone

(S--up). I n the Lake Powell area, from the Sand

Hills cast (from secti o n SHL, Fig. 40), thcre are tro u ghs scoured through surfaces within this u n i t . They are u p t o L 2 m dee p a n d frolll 1 0 m to morc than 100 III across

,

and many are clongare i n a

M iddle Unir thickens (sect ion s WLT- SC, Fig. 3 A ; sections S D V - C KS, Fig. 4 0 ) . I t i s not clear w heth e r this eastw.ud t h i n n i n g is because of t ru ncati o n ( by the S-- ue su rface) or whether i t is replaced latcmlly by th e Upper U n i t (sections SDV- KS, Fig. 4D). Near rhe erg m a rgi n , this upper Middle Unit grades over sevcral kilometres into the Crystal 8rmel Formation (Jee) Member of the northwest i n the

Creek

to the

:.tnnonville area (Figs 3A & 4 ) .

northeast-so u thwest d i rection. Th ey occur sep­

Th e Crys ta l Creck Member in this a rea h as bee n

n ra te ly or in cl u sters with younger

rei n ter preted a s a ri d fluvial/alluvial strata (JOI1CS, 1990). In ad d i ti on , ch(\l1ncls (hat cut into the upper Middle Unit in the Pari" area ( , Figs 3A & 40) hnve been reinterpreted to be wad i channels with pa l aeocu rre n t indicators showing flow to the north­ eas t (Jones, 1990) . The u ppe r Middle Unit (PMlI) is very s i m il a r to the middle Middle U n i t ( P M m ) in that it consists of erg la yers and lenses u'ullcated by supersurfaces, h:.ts supcrscoops w i th i n it. and i ts

ones tr u nca ti n g olcler ones on the southeast side, These nrc i n ter­ p re ted as superseoops ( B l a key e! III. . 1 988; B lakey & Pa rnel l , in pre ss) . These scours (Fig. 4D) a re Oiled with complex irregu lar to t rough cross-stratified aeol i a n sandstone, and many conta i n pods of benton­ ite. n the western m argi n of th e PclgC Sal)clstOIH � . n ea r Cannonville, rhe m i dd l e Middle Unit i s only loca l l y p rese rved as isolated mounds of brecciHled to disLOrted to i n ci i st i nct' l y lnminated sandstone, encased i n J udd Ho l low s tr ata ( n ca r section HBC, F ig . 3A, section RSP. Fig. 4C).

The RM su rface ( S-- rl11 ) extends across the Page andstonc (Figs JA & 4A - E) e xcept where it is

westernmosr cxpressiol) is ill isolnted. rotated blocks

of aeol i an and stlbkhfl StHlhl partly encased by J u d d Ho l lo w strata (sectio n B O S . Fig. 3 A ; secl i on W N , Fig. 4 ).

Truncating the upper portion o f t h e Middle U n i t

t r uncated by scou rs or by I'he upper cl'Osional surface

( P M Il1 , P M u ) . a t least

of t he Page

Pngc Sandstollc

onclstone

(S--u p ,

lit G rego ry B"y,

secti o n GBS, Fig. 40) ;.)nu where ir laps out onlO th e J-2 slIrf"ce (Fig. 4B). The RM s u rface underlies the red m a rker (CR), wh i ch represents the l ast

ll1ajor

t ra n sgressio n of the Carmel sea i nto thc Pagc

in t h c southern part o f the Oli l crop area, i s the UE surfa ce (S--lIe), overlying which is the Upper U nit of the

Page Sandstone (Figs 3 A & 4A - 0 ) . A l tho ugh this

su rface d oes no t ge n era l l y

h ave pO l ygon a l fractures,

sand

it is in many areas coincident for sOme d i st a n ce wilh

sea, This sUI'face continues i nl < lIl d , where i t repl'c­

v:.tl'ious polygonally fractured surfaces of the M iddl e

sen ts a h ia tu s in aeo l i a l\

accumu!
t hu t corrc l u tcs to the trnnsgrcssion. "rhe RM sl.l rfnce is

planar

lO po lygo lla ll y frHctured and com m o n l y

ovcrlilin by silbkha sed i ll1en t .

Unit. The U E sUI'facc (e.g. ;,l l on g Lake Powell

(S--ue) has i rregu l a r relief from the Sa n d H i lls to Fa ce

Canyon, sections SH I.A - FBS , Fig. 4 D ) , and to the east and sou t h the U E sU l'fa ce is t ru n ca ted by thc UP s u r face (S-- u p , c . g .

Vpper Middle VIIi! (PMII). VE slIIface (S--lIe)

The m a rgi ns of the

ililyon. secti on

B M S I - BMS2, Fig. 4 B ) .

upper Middle U n i t ( P M u ) . which

lies above the upper tongue of the J udd Hollow an d

the

at Fiu::e

FBN2! Fig, 4 D . Hnci near Tse Esgizzi, sect io ns

RM s u pe rsu rfa ce (S--rrn, Figs 3A & 4A - E ) , arc

s h i fted evcn furthcr south th a n the middle Middle

Upper Unit (PUI, PUu), scours (I'S) und lIl)pcr

s"pcrsurf�lccs (S�·cs. S--up)

Upper U n i t

of

the Page Sandstone

( P U I , rU u )

The t'he south. where it is rep l aced by the Upper Unit (sect ion R DT­ E C H , Fig. 3A, M NW - LCK , Fig. 4 B ) . I t l a ps up o n to the J-2 u nco n form i ty to th e sou t he ast ( Fig.

The

4 8 ) . but is t r u n cate d by thc uppcr cl'Osional sU l'face

northeast of Page, A rizona ( Fi gs 3A & 4B & D ) . To the wes t of Page. A rizona i t is locn l ly thinned by erosion fro m the top and by g rad u a l replacement of its b�lse

Unit ( P M rn ) . a n d

also to t h e

west (Fig. 6).

upper Middle U n i t ( P M u ) t h ins to

of the Pagc Sa nds t onc (S--up)

to thc

norrhc�)st of

P(lgC , Ariz.ona �\Iong Lake Powell (sect ion

13 N ,

Fig. 4 D ) and southeast o f Esca l a n te (sec t io n SFL,

F i g. 4 E ) . To

the west

of Page. Arizona the u pp e r

is o n l y present to the sO ll th (Fig. 6), <:lIld is t h ick es t al'Ollnd West Cl a rk Bench (W

B, CKS),

Page,

Arizona ( R DT , M N W ) a n d to the south of Page,

Arizona (ECI- I , F igs 3A & 4A & D ) . It t h in s by erosional trunciJlion to the soul'heas! a n d

by the upper Middle Unit ( Fi gs 3A & 4 D ) .

K. G. I/llvllO/l1I cl al.

96 A

Ii. S

A

N

Monson Mesa MMW ,

BGP GYP I I

MMS ,

ECH4 I

FWM ECH\ ECH2 ECH3 I I I I

c C W Bull Volley

BGN ,

aGS ,

�

W S W N ,

c' E Butler Valley SPC ,

PRN ,

R�P

RVO ,

avo ,

In

Om

C

HBC ,

v, e, '" 100 X

2000 m

FI�. 4. (A)-(E) Cross-sections of Page Sandstone; location Intlp is Fig. 2 . Fig. 4D & E fnce p. 1 12. Solid l i lles represent supc.'surfaces: dashed lines arc other surfaces. Bold solid l i lies nrc the sUI'frll;cs separating the major Page Sandstone units n:> described in the text. In the C'lrmc! Formution units. carbOIHllCS arc :-.howl1 with a brick paltern. siltstones tlnd silty slLndstC)ncs iJrc !'ohowll wilh a dOlled pattern. 1111 I conglolllcfIIlcs with 11 grllvcl pallel'll. Page unit.. consist Illuinly of aeolian slInd..wnc. btl! locally ;llso include contorted to structurclc:.s sandstones.

B

B'

B NW

SE

Moo,"" Meso MNW ,

Tse Esgizzi

MMN ,

PAP ,

ANC ANC2 ,

,

LeI<5 ,

LeKS I

LCK4 I

LCK2 LCKIO LCK9 LCK1 •

I

I

I

CS

BMS1 SMS2

TSL2

LCKII ,

,

��� :: =

-'"

,

�� .

N O<> ", ,,, "' ''' 0- 0"

-=:::--;:-:�:--f

�-==---= =-

-..L � �____ ___-==-�

,

'" '" 0,

cs

_ / :....

;,c

." "

�

�.

-S".

In

Fig. 4. (conlinued)

:s

K.G. Navhollll ct a\.

98

c

A

Fig. s. (A) The lower t hree · q uarte rs of the Page Sandstone at Ferry SWlIlc (WC�t from section FSV. Fig. 41) . Arrows point to, from bottom 10 top. t he J·2 ullconf(H'mit)'. the S-b �urfilcc. t he S·-jh �u rface l1nd the S--rm su rface . Sec Fig. 3B for cxplan:Hion of rock unit symbols. Th ic k ness of the Bas�11 (PBd) unci Lowe r (PL) Units together he re is approxi ma tely 1 0 m . (B) Upper three-quarters of the Page Sllndstone lit Ferry Swalc (cast from section WPP. Fig. 4D). Lower Mrow poiillS to the S--jh sllrface; upper arrow points 10 the S·- rm su rface. See Fig. 3B for expl:1I1atiOIl of rock unit symbols. Note pefSQl1 in I wcr left for scale. (C) lsolatcd Unit (PI) of the P a ge Sandstone :11 Do u bl e Arch (section DBA) in Archc� National Park, Lowcr arrow points to the J-2 unconfo rmity : the upper arrow poi nts to the Page- Carmol contact.

B This Upper Unit has two main l i thofacies. The lower one

CP U l )

compl'ises n i l of t h e U pper U n i t

except from west o f the Judd Hollow a rea (J H L) to the

annonvillc mea. wh ere il is overlain by the

u ppel' Upper U n i t (PUll. west of section .I 1-I L, Figs

with planar bounding surfaces. IOC;llly interspersed w i t h sa b k hn stt'mil and/or lJ'uncatcd by corrugated

sul'faccs. From just west of Pngc. Arizonn. enst to Antclope Island (seclions W I' I'- A I N . Fig. 40) and to the

B ) , t rough-shaped scours (PS) cut

3A & 40). The lower Upper U n i t (PUI) is replaccd

south ( Fig. 4A

from the base by the upper Middle U n i t (PMu)

into the Upper U n i t . Thesc scours are up to 30 111

110flhwcstwnrd until oilly the upper Upper U n i t

dcep and 3

(PUu) rcmuins in the nrC:;l (I rO tllld

,il nllOllvillc (Figs

3A & 4C & 0 ) . The lowe r Upper U n i t (PUI) consis ts o f thick sets (up to 25 m) of si m pl e and compound cross-strata representing very I:u'gc d!,;Jas ( 1=I
kill

&

wide and may occur i n bundles en�

echelon w i t h youngel' scours to the soulhcnst. They ,II'C rnm;tly filled with !Icolian sInHa

but locally co n­

t a i n sabkha straHl and bCIl1011ite laye rs . These scours

ilrC interpreled ils superseoops ( B lakey, 1 1)88: B la ke y

& Parnel l , i n press).

A n erosional sl1pCrsurhlce ( S-- u p ) caps the Upper

U n i t ( P U I . P U u ) and the filled scours (PS) in the

a su rface has beell recogn ized within the lower Upper

sOllth and southwest part of the Page Sandstone

Unit ( P U I ) thm a t least locally di vides i t i n to two

outcrop area, This UP su rface t runcates the U pper

( se c t i on

FBS,

Fig. 4D)

parIS (S--cs. Fig. 4A, B & 0 ) . This surface has 9-

U n i t clllh'ely nOI'theast

15 m of relief on it from Antelope Isl8nd ( A I N )

and southeast (section B MS I . 2. Fig. 4B) of Page.

eastwa rd (Fig. 40). The upper U pper Unit ( P U u )

Arizona (.nd clilS down into rhe upper Middle U n i t ,

consists of thinner sets o f simple d u n e croSS·Slral'a

also t ru ncating it e nti re ly at G regory B a y (section

Page ,wf'lIligmplty

99

. .... . - ­

.

..., .. l .

N

o

... . _. ... .

,

/!

.. ,-

., J

1 ' - '_ _ -

_

PL

I

o Hanksville • -

_.---

'.

'-

o

Fig, 6, Map showing thc currcnt geogrophic cxtent of major units in the Page Sfll1(h.tOIlC, with younger units covering u progressivcl)' sTmllicr ;lI'C;I, Units highcr in the secTion (PMrn, f'Mu, PUu) were originlllly lllOI'C extcnsive .mel IHlve been lrtlllC;llccl by the uppennosl (S-up) supcrsurfuec of the Page Sandstone.

I=ig. 41)). This sUl'face has irrcguln r topography ( Figs 3A & 4A, B. D & E). In some areas il is overlain direcl l y by Illudstones 10 sil!slOlles of the Carmel Formation (e.g. cast of Judd Hollow at section ME, Fig. 40), but in mosl areas il is ovcrlain by '-' unit lhal is transitional between the main aeolian body of the Page Sandstone and the mostly non-aeolian C
•

---'-

- •. - - .

- - - - "-

1

Blanding

- . . _ - - - .. -;;;,.. ... ..� .

Transilion Unil ( Ill'". PTh)

I n much of the southern part of lhc outcrop
100

K. G. Hm'/lOlm

sandstone to si lty sa ndsl'O nc faci es cons i st i ng vf.lfi­ ably of wnvy laminations, ad hes io n - rippl e stnH a , suba q u eou s- ri pple strntil. contoned straW n nd t h i n s i l ty 10 m u d d y d ra pes deformed locally into flume S t ructu res . In so m e areas this u n i t has all its upper sUl'face raised r i dges lip to 1 m i n height H rrangcd in polygonal patterns with polygon diameters u p

to 15 III that a ppe a l' to be la rge tcepee SU'uClurcs ( J-Iav hol m , 1991). The o the r l i thofacies, which has been recogni zed in t h e Lake Powe l l arCH enst of A n tel ope Island, consists of build-ups at' t h e lOp of the Page SailcisiOI1C a n cl associated detached sand bodies that overlie t h e transition zone (PTb, Figs 3 A & 4B, D & E). The bu i l d-u ps consist o f l i nea r to curvilincnr ridges of san dstone ranging up to 1 2 m h i gh , 0.5 k m wide and 5 kill long. a rc ori e nted gen­ emi l y southwest - northeast and Q(.'cur bo th in iso­ lation and in groups with reg u la r s paci ng of the order of 0. 1 -0.2 km. The cores of the builcJ-ups consist m a i nl y of h igh -a n gl e aeolian straw and arc typic ally scpnralcd frolll t h e main body of the Page Sandstone by up to scven.lI metres of noo-aeolian struta of the oth er facies of t h e Tra ns iti o n U n i t (PTp ) . Strata in t h e build-ups comlllonly show evid­ ence of sl u m pi ng Hnd Iluidizalion and may have n
ct

0.1 1. SUMM AR Y

AND CONCLUSIONS

areful t raci ng o f su persu rfa ces . combined with re­ cogni t ion of the va r io us aeolian and relatcd strati­ fication types, has allowed the distinction of six majo r sandstone packages wi th i n the Page SanclslOllc . These com p l' ise a basa l sabkha/sand sheet' to fluv;o­ lacustrine unit (1'13). ll lowcr erg u n i t (PL). a middle amalgamated erg u n i t ( P M ) , <)n upper erg uni! (PUL a n uppermost unit transi t i o n a l from t he aeolinn P<1ge Sandstone to the n o n-a eo li a n ,Hmel Formation (PT) unci a u n i t found in outliers enst of the m a i n body of the Pase Snll(lstollo (PI). SOl11e of th ese major packages arc themselves made up of two o r more supcrsurfilce bo u n d ed aeolian units. This i l l us­ trates that s upcrsu rfn ccs , which represent hiatal peri ods in erg accu m u la t ion , can be used to define a genetic strat i graph ic framewol'k within an aeolian sandstone on i.l regi ona l basis, Because s u pe rs u rfaces represent pauses in aeolian acculll ulation. which in tUI'll rcpl'esent changes in the aeolian sediment b u dge t in the a rea , oneh sllpers u rfacc bounded sandstone puckage represents
pods and d rapes on dune forcsets have been fo u nd in a l l u n i ts of th e Page Silndstonc except t h e Basal U nit. Such ben to n i t.es jue also ubiquitous i n the nrmel Fo rm a t i o n . within which t h ey have b een ra d io m clric.a l l y duted, and con'eluted on the bnsis of zil'con morphologies ( Eve ret t el al., 1 990). This suggests thaI a n absolute time frame may be ndded to the genetic s l nil igra p h i c framework of the Puge Snndstone. Gencral theOI'etical d i scussi olls of the cont rols on sequence a rch i tect u re have not included aeolian sandstones (c.g. Posamcltticr el al 1 988; G a l lowa y . 1989). part l y bccnuse we have nOt understood the basi n-scttle process and response of �Ieolian systems very w e l l . H owever. some progress has been made in u nd ers t a n di n g controls on aeolian stra t igra p h ic architecture and how Lhey di ffer from those of marine and tl u v i n l units (e.g, K ocu re k & H av h o l rn . 1993). S eve ra l wOl'kcrs h.we h eg u n to n()lC t h e position of aeolian uni!.s rel n ti v c to b a s i n a l sequcnce archi­ tect"re (e.g. K a illol a , 1989: Marzolf. 1990: Atch ley & Loopc , lhis vol u m e) . This study shows th.11 aeo l i a n events can now be recogni ze d with greal d cta i l in the s tra t igra ph ic recc l·d . I n tegration of these seve ra l a pproa ches should allow us 10 move lowards i n te­ g ra t i o n of aeolian systems with systems of other scd i men ttlry environments in b'lsi n seq u e n ce st ru t ; ­ gra phi c an a l ysis . .•

IfII

Page Jtl'{lligl'llplty

A C K N O W t E D G E M E NT S The staff o f the National Park Service III len C"lnyon National Recrc
mils �llIowing <:ICCCSS to Navajo lallel and this co­ operation is grcally ('pprccioHCd. Funding wns provided by NSF grailis EAR·8719972 and Ihe Organized Research Commillce. N rthcrn Arizona University. N . Lancaster and J . Marzolr kindly reviewed the manuscripl.

A P PE N D I X Table A I . List or sccLions (section localioilli

ill italics

Section IIflll1C AET AlE AIN AIW AN APT

ARC ARM ARN ARS AT

AV BCH BOC BGN BGP BG5 B I- I A

01-111' ilKII'

BM5

81'0 HI'T BRC BRT IlTD BTR BT5 BVD BYF I-IR KB

Ante lope Tank

Antelope Island Northeast A n te lo pe Ishmd North Antelope Island West Antelope Canyon ( I ) (ACN) Antelope Cnnyon (2) A;rporl ( I ) A;,'po'" (2) A; rpol'l (3)

Answer Clnyon

Arrowhead Mesa Arches Nonh Arches South Antelope Creek ( I ) Antelope reek (2) Antelope Creek (3) Antelope reck (4) Antelope reck (5) Ant elope Creck (6) Anlclope reck (7) A nte lope Creek (8) Antelope reck (9) Averell Creek

Bridger

Huyon !-Ieud Boulder emc t e r) '

Bull Valley Gorge North Il;g P Bull Valley Gorge Soulh Brimhall Arch Big Hollow Wllsh ( I ll ) Big Hollow Wush (2) Big I-I ol low Wnsh (3) l3uckhorn Wash

Oilman Spring ( I ) Gitmnn Spring (2) Gut'r Po i n t Overlook IlI'idger I'oint l3alu nccd Rock :111)'011

Ollfr Trnil IlUl:k Tank Draw (L. U) Ilc h i nd the Rocks I3ctltonitc Section

arc

ill Arizonfl.

the ot hers arc

By

DK KH DK DK

M M MC

DK OK

KH KH OK OK OK DK DK

DK I K DK DK U

KH, U M , KH U KI-I, DK U

KH KH K I' I K I' I KH

DK OK KH KH. U KH

KH KI-I KH

Butler Valley Draw

U

Buoy Fiftcen Courthouse Rock Creek Ocd

KH KH DK

Locmion SEI/�, S16, T39N. Ili0E SWI 14, S3�. T42N, 119E SWI 14, S3�, T�2N, II9E SWIN. S7. nlN. 119E SWIN. S23. T�IN, rl9E NEIN. S26. T�IN. 119E S E 1 14, 52 1 . 1"355. 1{3 5E114, S22, 1"355. R3 S E 1 14, 5 1 6 . 1"355. R.1E SEIN, 527, T�ON, 1112E NWIN, 56, T36N, 1112E SW 114. 53, 1'255, IU I R S W I I 4 . S I S . 1'255, R2 1 E SWI/4. S�, T39N. Il i0E NEI/4. 517, T39N, IlIOIJ.­ NWI/4, S5, TJ9N, RJlIE NEII4_ 526, T40N, 1191S SEIN, 59, 7:l9N, 11101' . NWI/4, 518. T39N. IliOE SEIN, S5, T39N. Ili0E NEI/4. 531, RIOE. T40N NISI14. 5311. T40N. IIIOE

RB RB

MC,

ill Utah)

KH

112, S22_ ·I"3IlS. R2W 5 1 12, 532. T�3S, R I E 5 E 1 14, 20_ 1"335, R4E N 112. 528_ 1"38S, R3W SWI/�. 512. T�ON. 1181S N W 1 14, 527. 1"385. R3W 5 W 1 14 . 532, T35S, R9E S E 1 14. 56, T395, R7E N W I I�. 55, T39$, R7E S E I I�, S32. 1"38S_ R7E N W 1 14 , 5 1 'J , 1"195, RI I E SWIN, S2�. r�ON. RI2E SWIN, 512, T39N, R i l lS 5 E 1 14 . S26. nos, R I 3E 5W 114. 54, '1"445 , R i ll 5 W 1 14 . 52�. T425 . R8E W 1 12. S 1 5 , T345, RSE S E 1 14, 58 + N W I I�. 5 1 7 + S 114_ 5 1 8 . T43S, R2E 5 E 1 14, 52 1 , " 1'275, R22E SIYIN. S13. T�IN, 118E 1/4 m i les N of Jen B ut le r Valley Dmw anti ollollwood reck, 1"39S, R I ll' SWII2, S�. T-I-JS. lISE N W 1 14. S28, T24S. R20E N W 1 14, 56, 1"3SN. R I OE

K.G. Ntiliholm ct al.

\02 Table A I . (continued) Section nrllnc ockscornb haol C:U1YOIl ( 1 )

Chool Conyon (2) Chaol anyOIl (3) Ccdnr Mountain <.lSI

CRW CS

erc

CWC

DBA DFC

DOC DMR DR DRN DRS DW

E H

E

P

ERIJ ESD

E1'P EWIl

FBN FilS FCC

FCL FCW FMR FMW

Ilt f'aslurc Cu\'c Point ( 1 ) ClI\le Point (2) Capi lol Reef Watet'fall alstairs C;tnyon Cottonwood Canyon Circular White Hffs ( I ) Circular White liffs (2) Circular White l i ffs (3) Circular While Jiffs (4)

C ircular

White

Hffs (5)

Dou b l e Areh (E. C. w. WE ) Dry Fork 0yole ( I ) Dry Fork Coyole ( I a) Dry Fork 0yole (2) DlJllgcoll Canyon Deud Monkey Ridge Dangling Rope Canyon Dr)' Rock rec k North 01'), Rock reck South Driftwood Canyon cho Cliffs ( I ) 'ho Cliff, (2) Echo CHffs (3)

Echo Cliffs (4) ho Cliffs (5) gypl ( I ) Egypl (2 ) gYPI (3) ighty-ninc Rood Bend Escalante DUlllp Edge of Thousimd Pockets Early Weed BCltch ( 1 ) Early Weed Belich (2) Enrly Weed Bench (3) Enrly Weed Bench (5) Early Weed Belich (6) Elirly Weed Bench (M) Face Bay North ( I , 2) FitCe Bay South Fuce (\1I)'on (A) Fuce CUIl)'on (8) Facc DIo1)'00 (C) Face Cnn)'on ( D ) Face Cun yon (8) Fuce Canyon (F) Face Cnn),on (G) FitCC (111)'011 (I-I) filet Cnn)'ol1 ( I ) face CUIl),on (J) Fuce hffs ( N . w . SW. E) Face al1)'on West ( 1 -3)

Fiftymilc Ridge Fiftymilc Wash

By

U

DK

DK DK KH. U

M

KH KH

M C . KI-I

U U

DK DK DK

DK DK

KH KH KH KH R B . KH KH. DK KH RB KH KH

DK

DK DK DK DK

M MC

MC KH M RB. KH KH

KH KH

KH KH M RB RB KH KH KH

KH KH KH KH KI-I KI-I KH RB

RB

K I' I K I' I

Location

S E I I4. S I I . 1'43S. R2W 5E1/4. 531. TJ9N. RI2E 5E1/4. 55. TJ8N. RI2E NWI/4. 522. T38N. RI2E 5 E 1 I4. 54. 1'44S. R2E 5E 1 I4. 523. 1'38S. R6E NW1/4. S35. '1'405. R8E N W I I4. 535. 1'405. R8E N E I I4. S I S. 1'295. R7E S E I I4. 525. R2 W , 1'42S W1/2. 53 + E1I2. S4. T4IS. R I W SWI/4. 525. T38N. R9E NEI/4. 520. T38N. R9E NEI/4. 530. T38N. RIOE NEI/4. 520. T38N. RIDE NWI/4. 517. T38N, RIOE NW 114. 530. 1'245. R22E E 112. 526, 1'385. R6E

, 525. 1'38S. R6E 5 1 12. S25. TIllS . R6E N W I I4. 58. 1'43S, R7E SWI/4. 59. T38N. R9E SWII4. 530. 1'425. R8E S 1 I2. 514. 1'42S. R7E S E II4. 522. 1'42S. R7E 5 1 12 . S27. 1'425. RSE .I'EI/4, 531, T40N. R8E

W 1 12

N E II4. 512. 1'39N. R8E N E II4. S 1 4. 1'39N. R8E N E I I4. S16. 1'39N. RSE NW 114. S26. TI9N. RSE

S E I I4. S35. TI65, R6E 5E1I4. 5 1 0 . 1'375. R6E N E I I4. 5 1 5 + NW1/4. 5 1 4. 1'3 75 . R6E NEI/4, 516. T39N. R8E NW II4. S16. TI5S. R3E 5W1/4. 524. T41N. IUE N E 1 /4. I . 'l"38S. R6E N W I /4. 5 1 . 1'38S . R6E S E I /4. S35. 1'37S. R6E S E I /4 . S34. 1'37S. R6E S1; 1 I4 . S33. 'l'37S . R6E N W I I4. S I . 1'385 . R6E N 112. S35. 1'43S . R6E

S 1 12. S36. '1'435. R6E NWI/4. 531. T42N. IIIIE NWI/4. 531. ·1'.I2N. R i l E SEI/4. 55. T4IN. RilE SWII4. 533, T42N. IlI l E S 1 12. 53. 1'445. R6E E1I2. 532. T42N, RII E N E I I4. I I . 'I'44S. R6E N W I I4. S I I . 1'445. R6E S E I I4. 53. 1'445. R6E 5 E 1 I4 . 53. 1'44S . R6E N W I I4. 53. 1'445 . R6E

E 1I2. 55. T44S. R6E

S E I /4. 5 1 1 . 'I'4 I S. R 8 I /2E N E II4. 5 1 2 . 1'4 15. R8E

103

Page Sll'tlligrtlphy Tuble /\ t. (colllil1uccI) By

Section Ilamc FSV FTH FTC FWD FWM GBN GBS GBV GCN GCS GOE GHO GLI' GWE GWW HAN HBC HBT HCB HCM HCN HCS HHS I- I I R HSC I-ITM HWA HWH HWL HWS HYO I-IZO J T JI-IB Ji- I E JHL JKN IN KBT KSP LBE LBW LCA L B LCE LeM LCR

FCfI'Y SW;,lIC View Fourth Valley Fault Mesa Four Wheel Drive Aal Wide Mesa E. G regory Bay North E. G regory BtlY Soulh Goblin Vnllc), Grotto any n North Grotlo unYOIl Soulh Garden of Edcn Good Hope Mesa Overlook Gravel Pit Grollo-Wetherill Enst Grotto-Wetherill Wcst '·Ianna Hackberry anyon Hackberry T
KH K I-I OK OK OK RB RB KH Rll RB KH KH OK KH KH KH

W

KI-I KN KN Rll KH KN KH KH KH. KI'I M Kii M M OK DK KH KH. KH, KN.

OK

W W W

JK KI-I KI-I KI-I Rll Rll KH KH KH RB, K H K H . OK OK OK OK OK OK OK OK OK OK OK DK

Locntion NE:IN. S20. T·IIN. RHE: SW1/2. S2. T445. R I E SWIN. SUo T39N. R i l E: SE:I I-1. SO. n8N. RIOE: SIVI I-I. S2-1. T-ION. 118E: N W 1 /4. 5 1 3 . T435. R6112E N W 1 /4. 52'. T43S. R 6 1 12E 5 E I /•. 5 1 1 , 1'255, R i l E N E i l., 55. T435. R7E S E 1 /4 . 55, T43S. R7E 5W I /•. 524. 1'24S. R21E SE1/4. S36. T351125. RI2E NEII-I. S13. T-ION. !l8E SW1/4. 533. T421/25. R7E SW I /•• S33, T421/25. R7E If. S 1 /2. 53 1 . T I N . R7W E I /2, S3 1 . T38S. R I W NEI I-I, S21. T4IN. 118E Ir. S32. T38S. R I I c N E 1 /4. 532, T38 112S, R i l E S W 1 /4. S23. T385. R I OE S E I I4. S25. T385. R IOE NW I I4, S27, 1'28S. R I2E N E 1 /4. S33, T40 112S, R9E SE1/4. S7, 1'27 . R I 6E NWII4. 52, T37N, R i l E: SW1/4. S26. T39S, R7E N W 1/4. S35. T36S. R4E S W 1 /4. 526. T39S, R7E S E I I4. S33. T36S. R5E N E i l•. S5. T36S. R5E NEII-I. S18. T-ION. 119E: NE:1I4. S9. T-ION, R9E: 5 E 1 /4. 5 1 5 . T435, R2E SW 114. S3 1 . T435, R2E 131/2, 536, T435. R I E S E 1 /4. 535. T435. R I E NE:1I4, S24, T4iN. liSE N W 1 /4. 5 1 4 . T32S. RI2E NE:II-1, S29. T37N, IU2E: S W I /4. S 12. 1'28S. R22E N E i l•• 57. "1'445. R6E 5 1 /2 , S I . T445, R5E N E I /4, 52, T4 1 N , R IOE NEII-I. 52, T-IIN. RIOE N W I /4 , 530, T38 , RI2E E 112. 56. T445, R6E NWII4. S13, T-ION. II IOE NWII4. S3, T-ION, RIOE: 5WII-I, S33, T-II N, IIIOE SEII4. S33. T-IIN, 11101] NWI I-I, S19. T-IIN. 1I10E SWII4, S18. T-IIN, RIOE: NEII4. 518. T-IIN, RIOE: SE:I I-1, S29. T-IIN. RIOE 5E:1I4, S2. T-ION. RIOE NEII4. SII, T40N. RIOE: SE:l14, 530. T-ION, R i l E SWII-I, S31, T-ION. R i l E

K. G. Hal/holm et H I .

1 04 Tnbl\: A I . (COJilirlucd)

By

Section name LCW

L1)R

LFK LKW LNM

LP LPO LSF MAN MEF MOS MHN MKF MMN

MMS MMW MNE MNR MNW M RN

MRS MS

L.'1kc ..nyon West Lo n g D[',IW 1';1 kc F01'k Lick Wash

Lion MOLintain Lower Pocl un k Creek I.....akc Powell Overl oo k lillie S pencer Fillt ( I ) Little Spencer Flat (2) Mu n i la

Mile Eighly.tivC Middle Section

Moulit I-Iolmc$ North Ma rke r Fifteen Mtll1son Mcsn N MUlison Mesa SOll i h Munson Mesa NW (MNW) Mani:ion Mesa N E Mormon Ridge ( 1 )

Mormon Ridge (2) Manson Mesa N W ( M M W ) Middle Rock reck Nor'th Middle Rock reck So u t h

M�llcshoc anyon MOLJntain S hee p

MTS MW N N NHIl NM o

Muidcl1wfllcr Creek N avaj o Canyon New Home Bench Nightmare orner Oak reck Ci.lIlyon

PHO

PhOlogmph Gap

PAP P K

P,lgC Airport Pine Creek

PLR PRN IlRV I"TK I"TM

Power Line Road Pal'iil River North PUI'in River View

PWA ON IlBK

Poulas Tanks

Pcunul Mcsn ( 1 ) Peanut Mes., (2) Peanut Mc:m (3) ('canul Mcsi1 (4)

I\u'ia Wilderness Area

Question Cnn),on

Red Greak, ( I ) Re(1 Break' (2)

RBM RBO RCW RO ROR

ROT ROV RrC RH RPN RPS

Red Break' (3) Road Ilend Mesa Road Bend 160

Ro(;k Creek Wesl

Red an)'on Red Ridge ( I ) Red Ridge (2) Red Ridge (3)

Rticlio To\vcrs Red Vnllcy Radio Faci l i ty Rawhide Clive RAinbow Pl:lIcnu Nonh Rainbow Plnteuu Soulh

KH

N E 1 /4 , S3.1, T3H 1 /2S. R i l E

U

KI-I

U M

U

. KH

KH M M '

K I -I M

KH

KI'I KH OK OK K H . OK K H , DK OK DK K I-I , DK Ril K I-I K I-I Ril

KH KI-I M KH M • KI-I OK M KH

I) K 1 .1 •

KI-I K I- I OK

OK

DK DK KH. LJ DK MC M MC KH. OK OK RB KI-I . MC OK

DK OK

KI-I KI-I MC KI-I

KI-I RB

Loc;uioll

SW1/4. S8, T43S, R I W N E 1 /4 , S3. T I N , R5W N E 1/4, S I . T40S , R4W N W 1 /4. 526 + N E 1 /4 , S27. '1'305. R5E 5 W 1 /4. 530, T395, R.1W N 13 1 /4. 53. 1'''' 15, R2E N 1 12 , 529 , '1'355. R4E N W 1 /4. 535, T35S. R4E

5W 1 /4, 56. T2N . R20E

SE1 /4, 535. D3S, R4E

NWII4. 522, ToliN. liSE

N W 1 /4. 528, '1'345. R I2E S 1 I2, 54. T44S. R5E SEI I4, S19. T4 IN. R9E NWI I4. 531 , T4IN. 1195

NWII4, 519. T-IIN. 119E E1I2, S20. T-II N, [191:: NI,1I4, .18, T36N, fllI£ o5WIN. 5 1 1 . T3oN, 11 1 1 5 NWI I4, 519. T-II N. R9E N E 1 /4. 5 16. 1'42 5 . R7E N E 1 /4. S2 1 . T425. R7E

S 1 /2 _ 5 1 8 , 1'28$, R2.1E N W 1 /4. S8, T435_ R8E S W 1 /4, 526 + N W 1 /4. 53S. 1'33$, R I 2 E NI::1I4. 516. T4IN. 11105

S W 1 /4. 535_ T33S. R4E 5WI I4. o523. ToliN. 118£ N E 1 /4. 530 + N W 1 /4, S29. 1'3 1 5 . R7E 551 1-1. 520, T-IIN, 1/9E S W 1 /4. S29, T345. R3E N E 1 /4. S29. D I S . R23E Nc·IN. 519. 'I:19N. II I I E N W 1 /4. 529. D85, R2W N E 1 /4. S23 , T43S, R I W SE 1 /4. 52, D6S. R i l E NEII-i. S33. nON. 11115 SEII4, 521. T39N, II I I E NEII4, S21, t39N, IWE NWII-I. S34. T39N, lUi 12'

N W 1 /4,

14. 1'435, R I W

N£1I4, S35, T40N. 1112£

5WI'/4. 5L4 + N W 1 /4 . 523, T36S. RSE

E 1 /2. S 1 5 . 1'365, R5E N 1 /2, S 1 6 , '1'365. RSE

s e,f 519. N e,f 530, TJ8N, 11 1 1 Ii S W I I-I. S8. T3SN. 1195 Middle, S6, 1'425. R7E 5 1 /2. S23, D2S. R7E N511-1, 529, T37N, RI25 SEI I4. 532, TJSN. RI2E NWI I-I. S8, T37N, 11 125 SEII4, 523, T,I I N, R8E NW 1 /4. 54, T44S , R2E S W I M. S24. D55. R4E SEII./. 520, T4 IN, RBE S1I2. 535, T-I2N, 119E S1I2. 535. T-I2N. R95

105

Page Slrlllig rtlphy Table A I , (continued)

SCl.:tion name RPT RRT RSB RSP RVD RWL

SOP SDV SEC SFL SFT SI-ID SHL SRD SRK SLM SNG SNIV SP SPM SIlP SSP STR SWW TIlX TDll 1'FM

TMF TND TPS TSO TSG TSL 1'W 1'MW UNM VWP weB W E IV N wes W W WI-IC WHT

Red Point Railroad Tra\:k ( 1 ) Railrotld Track (2) Railroad Track (3) Rw;h Beds Rock Spring.') Round Valley Draw Red Well ( I ) Red Well (2) Red Well (2d) Red Well (3) Sewage Disposal Pond Sand Valley Second Valley Seep Aat South Fork Ticaboo Sahantn DUlles $m1(1 I-Hils (2. 4) Semd I-Hils (3) Sh ting Range Shooting Range Suit L.,kc Meridian Sooner Gulch ( I ) Sooncr Gulch (2) SOOller Gulch (4) Sooner Wash ( I . I n ) Sooner Wnsh (2) 'heep rcck Stcep Mes.
Soda 5pl'iug (2) Sicinakcr SIMling Walel' Wash The Box Tidwell Bottoms TwcllIynvc Mile Wash ( I ) Twelllynvc Mile Wash (2) Tenmile 1=1111 ( 1 -3) The Needles Thc Post Tensd'llc Tse Esgizzi ( I ) Tsc E..'igizzi (2) Tsc Esgizzi (3) Tse Lichii (2) Twilight Canyon Twcntymile Wash Unnamed Mesa ( I ) Unnamed Mesn (2) View Point ( 1) View Point (2) West Clark Bench West Clnrk Bench E.ast Willis rec k North Willis Creek South West C"irk Bench West Water Holes unYOIl Wild Horse Tnlp Mesa

Ily

KI-I DK DK OK U U U

KH KH KH KH DK KH KI-I MC KH KI- I Ril Ril DK KH KI-1 . LJ KI-I KI� KH KI-I KI-I U

DK DK KI-I KH OK DK MC KI-I

MC MC

MC KH MC, KH MC. KI-I DK DK DK OK K I- I MC M M

DK DK KH U U U U

KI-I KI-I

Loc;)\ion S£114, S22, T41 N, R8£ N£lf.I, 53-1, T39N, 1lI0£ S£1I4, S3, T38N, RIO£ S£1I4, S23. T38N, 1110£

N W I I4, S I . T40S, R I W S E I I4. S22, 1'385, R2W SW114, 533, 1'38S, R I W 5W112, SICI + N W 1 12 . S 1 5 , ' I':19S, R7E 5 E 1 14, 510, 1'39S, R7E SWII.I, 5 1 1 , 1'39S. R7E N W I I4, S 14, T39S, R7E NWl f.I, SIS, T40N, R9£ SWII-I, S34, T-I2N, R7£

N E I I4, S2. T44S, R I E Middle. S6. 1'37S. R5E S W I I4, S27. 1'35112S, R I 2E N W 1 14. S24, 1'3 15, R I2E S E 1 14, 534, 1'435, RSE SW114, 535, T435, RSE N£1I4, 55, T-ION, 119" 5112. 5-1, T-ION, 1i9£

5W114, 530. T43S. R I E N 112. S26. T405. R8E N E I I4. S26. T405, R8E N W I I4, 526, T405, R8E N W 1 14, S16, 1'405, R8E N E I I4, S 16, 1'40S. R8E SE114, 524, 1'385, R3W S E I I4, S \.5, T40N . R9E S E 1 14, S28. T40N , R9E N E I I4, S2, T41S, RSE NW 1 14. 5 1 , T4 15_ R8E 536, TIN. R2 1 E 5 E I I4, 530, 1'39N, R I2E NW1 14, 512, 1'345. R2 5W114, 56. T225, R 1 4 5W114, 529. 1'375, R6E S W I I4, 532, 1'375, R6 N W I I4. 516. '1'365, R4E W 1 I2, 527, "1'24 '. R I813 W I I2 , 52.5, T345. R8E 5 E 1 I4, 5 1 7 , T295. R4E N"II-1, S20, T39N, 1l12" 5£114, SIJ, T39N, R I I " SWI I4, 512, T39N, I II II! 5Wl f.I, 530, T40N, RI2£

N E I I4. 523. T425, R8112E N W I I4. S28. 1'375. R.5E SW II4, S3. 1'36S, R5E N W 1 14. 59, T36S, R5E SWII4, 55, T39N, R i l l'. SWII4, 58, T39N, R i l l'.

N E 1 14, 522, T43S, R I W S1V 1 14, 528 + N E 1 14, 529, 1'435, R I W NW 114, 523, T38S. R3W SEII4, 523, 1'385, R3W 5W 1 I4, 536, T435, R I W 5WI I-I, 525, T40N. 1181'. S1'.1I4, 516, T38N, 1110£

K.C. Hovho{lI/ ct (II.

106

Tllblc A I. (contillued) ily

Section nilllle

WHV

WLT WPP WRK WL WST wsw

Water Holc Valle)' ( I ) Water I-Iole Valley (2) W:l1cr I-Iote Valley (3 ) Willow Tank Wooden Power POle)) Whiterocks Wetherill Canyon We:)1 Canyon ( I ) West Canyon (2) West Canyon W

I)K

DK I)K KH KH Kl- l RO KH Kl-l RO

Locntion

NEII-I, S9, T,18N, IlI / E NWII-I, 516, T38N, 1I 1 1 E: SWI I-I, 58, '/'J8N, IlI I E' 5£/14, 5 1 9, T4IN, liSE: NBII4, .\'21 , T4 IN, IISB

SW1/4, S� + N W I H. S 1 7. T2N, R I E SW1/4, S 1 3 . '1'43 • R7E N E 1 /4. S23. '1'435, R 6 1 /2E S E 1 /4, S24, '1'435 , R(' 1 /2 N E 1 /4. S3(" T43S, R6E

DK, Duve King; r K . Gllry Kocurek; JK. Julia Knight: KI-I, Karen H:1 Vh Q l m : 1...1 . larry Jones: Me. Mark Ca pps: R I3. Ron Il i like ),.

[( E F E It E N

ES

ANTON, O . ( 1 983 ) Modem coliun (ICposilS of the eastern pl'ovince of Saudi Arabhl. I n : £o/ioll Sediments (/11(/ l)ro(.'C!sses ( � d . Ilrookficlcl. M . E . & Ahtbnln(l l . 1'.S.) PI'. 379 -406. !)cvclopmcIlIS i n Sedimell tology 38. Elsevier. AmSICt'dam. Bl.AKEY, R. , ( 1 938) Supc rscoops: their significallce as clements of eoliAn archi tccture. Geology 16, 483-487. I3i..AKl!Y, R, , & PAKN1!l.l" R . A " .IK (ill press) Middlc Ju rassic mI:TllKSON, P., /\I'UTO . M.V., GIHiSAMAN. R . . & VOOKIIl!I!S . B.J. ( 1 98.1) I>alcogeograph)' of Middle J urassic continclllnl, shoreline. un{1 sllallow marine sedi­ mentation, southern Utah. I n : Mcsozoic P(lleogeosmpfly 0/ rhe W(!s/-cc/II1'fI1 US ( d. Reynolds. M , W , & Dolly. E.I . ) PI'. 77- \ 00. Rocky MOlJllt,lin IJaleogcog,.uphy Symposi Ll 1l 1 2 . Ro!,!ky MIn Section. Soc. Eeoll, PalcolHol. Miner'a!.. Dc nver. 131.,\Kt�Y. R.C" PIiTUKSON, F. & KocuK�K, G . ( 1 988) Syn­ thesis of latc I)aleo�oic and Mesowic eolian dcposits of t hc Wcstcl'n I merior of Ihe United States. I n : Late Palem.oil ' fllld Mesoz.oi(' Colian O(!po.I'its oJ !lw WCSlel'lJ lllferiOl' of ,lie Ulli/cd Simes (Ed. Kocurek . G . ) PI'. 3- 125,

Sed. Gcol. 56. i\I'I'$, M. ( 1 990) Presellce (Illd sigllijic(Ul(:e 0/ regiol/al bOllndillg slII/(lces tlnd gem:!i, sequences ill (III eoliall �'(//ul.wolI(!: Page S(lIIdsiOIlC (Jw'(lssie), sottt!t·cCIIII'(11 U1(l!t .

Unpublished MS lhcsi�, Northern ArizQnu Uni\'cl'�ity, Flagstaff. CAI'U'ro, M. V. ( 1 9HO) O(!pO.l'iliolUll lJi.l'IOIY of Middle JlIl'lISSit; claslic shO/'elillc .1'CfllleIlCf!S ill SOw/llveSlem Uwll . Unpub­ lishcd MS thcsis, Nonhcrn Arizona Univcrsity. DI!YNOUX. M" KO(:UKI!K, G, & P�OU�T, J,·N, ( \ 989) Latc Protcrozoic pcriglaci,11 aeolian deposits 011 the West African Platform. TaQucicni Basin. western Mali. Sedimf!lIIofogy 36, 53 1 -)49,

EVIlKHTI'. B , I-I , . KOWALLIS. B .,J . . CUKISTli\NStiN , E , I-! . &

DHiNO. A. ( 1 990 )

Correlillion of J u rassic sedimcnts of reck Form,uions of southern the C.lnn e l and Twill Uwh using bClllonitc cha ractc1'istil."S. Utah Gcologicol (111(/ Millel'(ll SlIrvey Opell Pilt! Rf!pol'/ 169. FltvlmIl.G �K. S . O . & KOIll,MI�I .. M . I -I . ( 1 986) Rangely Ficld: eoli:ill syste m-boundal'y trap i n lhc Perrno·Pcnnsylvnnilln Weber Snndlltonc of northwest ColoradQ, I?ocky MOllfl­

I(lill Assof'i(l/ioll of Gcologisl.\' Symposilllll, 1 29- 1 49 . G M.I.OW/\Y. W,E. ( 1 989) lenctic stratigraphic sequencell

in basin :1I1.l I),sis I: architecture and genesis or nooding­ surface bounded depositional units, Am, A�'s, PClrol, Geol. IJulI, 73. 1 25- 1 42 .

GIHISAM/\ N, R . . ( 1 979) Seditm!III(lI'y J{/f:ies of the Cal'llwl POl'Il/olioll, .�f)l/Iltellst Ulaft. Unpublishcd MS thesis, Northern A l'izonn Ullivc r�ity. Gl.t!NN I L I K . W . ( 1 970) Oeser/ Sedill/ell/tII')' E'l1IirOlIIlU!IIIS. Elsevier. AmSlcrdnm. 222 pp. 1-!i\VIIOt.M. K.G. ( 1 9\) 1 ) Eolioll eVl!/II .\'trmigmp/ty: IftcO/'y. (Illd flpplit'(l/irm

/Q Ifte Middle JIIJ'(/.'i.�ic Ptlgl! Stllldstollc. Cofomdo PIII/eall, USA . Unpublished PhD thesis. Uni·

versity or Texas. Austill, JONES, L.S. ( 1 9�) S/I'(ltigrtlplly (III(/ depositiOllal hi.I'IO/,)' of tire j)age S(I/It/Sf()lIe (/lid cOI're/mille IIflits oj file Corlllcl FOl'lluuioll, Middle Jtl/,{/.�.\'I'c. S(JIII/t'C(!flll'(t/ Utn!1 . Unpub­

li�hcd MS thesis. Northcrn Arizona Univcrsity, Flagstaff.

KAMOI.,\, D.L. ( 1 989) Pc nninn - Trinssic boulldary in sout ll·

celllntl Utah: palc()fclicf ancl sequence stratigraphy labsI I'Act ] . Ceol. Soc. Am. AIIII. Mlllg, AIJ.I'tl'(lCIS willi

Pl'OgmJ/J.I' 2 1 , ABO. KINC:, 0 . 0 , ( 1 992) Srmligr(lplric (tI1lI/y,�i,\' of rllf! /(llId1ll(1I'(/ margin of tIle Mit/c//e Jtlrtlssic Page S{lI/clSIOlle, Coconillo COIlIfIY. lIon!t-('clltl'(t! Arizol/{I. Unpublished MS thesis,

Northcrn A ri;wna U ni\'cr::;it)', Flagstaff.

KOCUREK. G, ( 1984) Origin of firsl�orclcr bounding surfaces

in �lcQlian sandsloncs - reply. Sedimentology 3 1 , 1251 27 , Koculo,K, G. ( 1 988) First order und super bounding sur­ faces in eolian seq ucnccs - bounding surfacc.!j revisitcd.

111: Ltlle Pa/cozoic and MC�iowic Eo/itll/ Df!po�'its of tire Wcsrcr" III/erial' of Ihc Ulliled Sillies (Ed, Kocurek, G , ) pp, 1 93-206 . Sed. Gco!. 56. KOCUKI!K, G .. DliYNOUX. M . . BI.AKI:!Y. R.C. & \-I,\VILOLM, K . G , ( \99 1 a ) Amalgamated deposits rcsulling from

107

Page sll'aligmp"y

climatic and eustatic changes. Akchar Erg. Mauritania. Sedimentology 38. 751 - 772. KOCUKEK. G . & H"VII01.M. K . G . ( 1993) Eolian cvcnt stl':ltigraphy - a conceptual framework. In: Recellf AdvlIIlces ill IlIId Applic:aliolts of Silicic/listie Selfllem:e Smlligl'llplty (Ed. Weimer. P. & Posmncnlier. H . ) . Am.

Ass. Petrol. Gco!. Mcmoir. Am. Ass. PetrOl. Ceol .. Tulsu (in prcss). KOCUKI.iK. G. & HUNTEk. R . E . ( 1 9t-16) Origin of polygonal fractures in snml. uppermost NUV(ljO and Page S!ulcl­ stOnes. Pagc. ArizolHl. J. Sed. IJetl'ol. 56. �95-904. KOCUltHK. G . . Kl"IIGt-ll' . J . & l lAVtIOt.M, K. ( 1 9�lb) Outcrop nnd scmi-regional tl irce-climciisionni nl'CllilecLurc lind rCI.:onstruction of 1I ponioll of the eoliull l)l1gc Snndslonc (J urussie). In: Three-llimells;ollal Facies Ard,itec:lllre (Ed. Minll. A. & 1')'ler. N . ). Soc. Ecan. Pnlconl. Minera l . Atlas pp. 25--13. Soc. COIl. P�lconlOl. Mincra l . . Tulsn. LOOl'Il. 0.1l. ( 198.1) pisodie deposition one! prcserv[llion of colifll1 sands: n lute I)a leozoie cxample from sou1h­ eastern Uwh. Geology 13. 73-76. M,\RZOl.l'. J . . ( 1 990) Spcculation on the sequcllce strati­ grnphic signifi(.:n,,(.:e of colion sandstones: exomples from the westcrn iuterior. Absl. IJtlt Jll/el'll(l(ioll(l/ Sedimelll­ ologi(,(11 COl/gress. Noitillg//{/Ill. 334. Me I.Ukll. !- I . A , ( 1978) AI' Rub'al Khali. I n : QU(ffc!I'II(uy Petio(1 il/ Saudi Ambitl (Ed. AI-Soy:u·i. .S. & FilUf'c. J . G . ) PI'. 2.12-263. Spri nger-Vcrl.li;. Wicil. PETEKSON, r. ( l 98() J U nlssie paleoteetoni/,."S i n thc WCi't­ central plll't of the Colorado Plutcau. Utah and Arizona. I n : J"altJOleCIO/lit's (I/ld SC!dimC!II((lIioll. f?oc::k )1 MOII/I/aill J?egioll. US (Eel. Pelcrson. J . A . ) pp. 563'-596. Am, Ass. Petl'Dl. Geo!. Spcc. Mem. 4 1 . Am, Ass, ('etrol. Gcol .. Tulsll. Pl!TIlKSON. r. & l'Il'lltll"lGos. G . N . ( 1 979) Smlligl',q)hic

relution" of the Nuvujo Sundstonc 10 Middle Jurassic formations. southern Utuh Clncl northern Arizonn. US Ceol. Sill'll. IJmf, Pup, IOJ51J. B I - B43. POS"M�l"InI:k. I I .W . . J llRVIlY. M.T. & V,\II.. P.R. ( 1 988) Eustlltic controls 011 clastic dcpositlon l -l.'ollccptuul frul1lewOl'k . In: SC(" /I'I'eJ Chal/ge.,·: lIlI IlItegl'lI/c{1 APf"'O(lch (E(1. Wilgu�. .K . . Hastings. B.S . . Kcnda l l . CG.St C . . POS;)IllClllier. H.W . . Ross. C.A. & Van Wagol1l!r, J . ) pp. t o<J- 124. Soc. Eeon. Palcontol. Mincral. Spec. Pub. 42. So<.:. Econ. PalcolHol. M i neral . . Tulsil. SAI.riEllY. J. & BUSlly·$I'likA. C. ( 1992) Enrly Mesozoic lectonic cvolution of the western US Cordi llera. I n : Ti,e COI'f/iI/CI'IIll O,'egoll: COnle/'llli/llI.� US (Ed. B U I'l!llfield. B. . el (1/.). Geological Socicty of Amcrica. The Decadc of North Amcric!ll1 Geology. G-3. pp. 1 07 - 168. Gcel. Soc. Am .. Boulder. SWH>tIH'. C. ( 1 99 1 ) De.\'(·r;J'/;oll ((1/(/ illlel'pt'eilltioll of tlte JlIl'lIs.�ic )·2 II//co/lj()l'fnily of tlte Wc.'t'/em Itllel';ol' (USA). Unpublished MA thesis. University of Tcx[ls. Austin. TAtUO,/,. M . R . ( 1 �85) Major bounding sutfoccs. in ;lcoli:lll San(J:.,loncs-il cli mfllic mOdel. Sel/ill/elltolog), 32. 257265. Vi\I'
.

CUl'tlw/ FOl'lIImio/l ( Middle JlI l'lIs.\·ic). sQwltIVesle1'll Uf(lIt ,

Unpubllshcd MS thesis. Northcl'1\ Arizolla University. Flagstuff.

S,)(!(,. rub's 1111. Ass. SCllimclII,

(1993)

16. 1 09- 126

Downwind changes within an ancient dune sea, Permian Cedar Mesa Sandstone, southeast Utah R.P.

L A N G F O R D ' lIlId M . A .

C I I AN·

*8/1reflll of ec:onomic: Geology, Ulliversity of Texas 1lI A llst;lI, A /will. TX 78712, USA : lIlId tUll iI'er.'iity oj Uta". Salt Lake City. ur 841 /2. USA

A fl S T R A C T

Strtltigrtlphic sections along 1I wind-p�lrallel transect within thc upper pan f the Permiull Cedur MC:);l Sandstone iliustnHe changes I'dative to the downwind erg l1'IMgin, Si1' phcnomena may help to dennc the erg margin: biolUrblilion. wide inter-dune nl'CIlS, abundant sand sheets or zibars. abundflll(,.'C of non­ aeolian facies, �l11ullcr Hnd different types of (leolil1l1 dunes. und un incrcuscd abundance of erosion surfaces, Each phcnomenon responds di fferently to stratigraphic and p:llacogcornorphologicol changes, Bioturbation varies stnttigraphicnlly nuher thull laterally. und lIluy reSIX.U1d to climatic or water table controls rmher thun to chrlllgc:; in position within the dune sea. Dune spncing and the sizcs of each type of dune do not show much straligraphic or Intend downwind change. Thc proportions of different dune types clwlIgc rcgulurly as the abundance of Imgc-trough C(Oss-slf'atit1cd sct� decreases downwind. 'n'e proportion ofsllnd sheet deposits increases regularly downwind. Gruin size decreases regularly downwind but docs not in licatc posit ion rellilive to the erg mlll'gil1, Non·aeolillll rucies increase towards the erg margins, but cun ;1lso forn} a significant pl'oporlion well into the dUlle sen. Erosion SUf'fnccs incl'case i n frcquency a t the dowllwilld Cl'g Inn l Bi n {!'O1ll one per 1 7 III o f section in the live upwind sections t o one pCI' 9 111 of section and offer the IllOst dramutic indicntor of murginality, The consistent average grllin size tIl eilch sectioll indicates thaI the sources of !leolian sand dicl nol significmllly cluUlge either in position or in sand compositioll throughout the periods of deposition, Individunl denation slIrfuce bounded stnltigraphic units do not change in gruin size upward, implying that (i) periods of erosion were not long-lived. or (ii) the sand supply wos shut orf during periods or denillion. either due to removal of the supply or through ,I change in the transporting wind direction. '

I NTRODUCTION

To whot extcnt d o changes i n depositional features

spatial changcs in features of ancicnt aeolianites

within aeolian sandstoncs indicatc expansion. COil·

have also been relatcd to erg margins, The Pcrmian

traction or migration of the erg?

Cedar MeSH Snndstone provides a uniquc oppor­ t u n i t y to measure the spatial changcs within sand

Some studies have emphasized the sensitivity of aeolian deposition to clwngcs in climare And othcr lnnuc nces (for discllssion

sec

K ocu re k ,

dUlle seas because the

m n rgi n s

of the dunc sea were

rel ativel y sHlble through timc. Thus di ffercnces within

1988).

cd"II' Mesa may relmo to spmial I'ather than

Reccnt papcrs have documented di fferences be­

the

tween the i n teriors of modcl'Il sand dune scas and

temporal changes in Hcolian sccl il11cntation,

their Jl1argins, These pa l ers suggcst that erg margins

One Objective of this paper is to sllmll1�l'izc some

may be mOrC vegetaLCd nnd more biolllrbated�

of the current ideas 011 the recognition of spatial

contain wider. 111 0rc i ntegrated i n tcr·dunes; have

changes within modcrn and
abundant sand sheets or zibol'S; have extra·crg.

margins, The second objective is to determine the

nOIHlcolian environmentS such as s:lbkhas. pl�lyas

applicability of these critcria 10 n well exposed

and/Ol' Iluvial channels; ..lIlel contain smnller and

ancicill example from the Pcrmian

di fferc ntly shaped aeolian bedforms. Tcmpon.1I iJnd

Sandstonc. I n panicular. the paper describes the

Aeolian Sediments: Ancient and Modern Edited by K. Pye and N. Lancaster © 1993 The International Association of Sedimentologists ISBN: 978-0-632-03544-1

109

edar Mesn

I? P. Lallgford alld M. A . ClulII

1 10

ch a nges thnl occur in st ratigraphic sections al on g a

have f"i ner-g ra i ne d i nter�dunes, and also exhibit a n

wi!1(l·parallel Irn nsect within the upper' pHI'l of the

increase in s Ofl i n g with no decre ase i n grain size

features to position rel a t i ve to the erg nla l'gin s.

upward on ind i v i lual dUlles and 1986).

edar Mesa Sandstone, and relates depos i t i o na l

dnlas

( La ncaste r' .

DillIe size allli dllne /orl1l.\'

BACKGROUND

Numerolls authors have noted that d U lles decrcase Spatial changes described from mo lern and ancient sand dune seas will be discussed in the fol l owi ng s i x

ca tego ries :

in sizc and com plex ilY :H erg ma rg ins . Maps of the Whire

nnds cluncficld showed complex barchalloici

dunes between clornal dUlles at thc upwind Illargin

I gr a i n size nnd sor t in g:

Hnd

pnrHbol ic

d u nes

ut

the

downwind

mu rgi n

(McKee. 1966). Fry be rger el al. ( 1 979) and Andrews

2 d u ne size and d u n e forms; 3 dune spacing;

4 ab u ndance of sand s hee ts , zibars and

5 ab u nda nce of bioturbation:

( 198 1 ) found smnll. simple co ppice, pa ra bo l ic and

inter-dulles:

tr a n sverse dunes within t he margi na l sand sheet of

th e Great Sand Dunes of

6 abu nd an ce of non-aeolian deposits.

o lo rad o , compa red t o t he

co m plex transverse a nd star dunes within the dune

For each of the ca t ego ri cs numbered above, both

mass. Lancaster ( 1 983) m apped dune height' in th e

modern and ancicill exam ples al'c b r i efl y cited to

N a m i b Sand Sea . Large and complex dunes were

summarize the literature and La clem o nst r..llc the

amount of di versi ty that has been observed in e rgs

nnd their Ill n rgi ns .

found at po rtio ns of the margi ns of Ihc dunc scn.

However. duncs On the ma rgins werc gcnc nd ly smaller and simpler in form. pa rticul arl y on the

upwin I margin. Barch a noi d and t ra n sve rse

were

Modern studies

dunes

concentrated on the upwi n d ma rgi n s while

complex lincar and star dunes formed the bulk of the duneficld i n cl uding lhe downwind JI1 H rgin .

Graill size (llId sOl'rillS

However, clune type nHly also chnngc w i t h i n Ihe

Grain size a n d SOI't ir1g ch n rlgcs w i t h i n ergs (lrc dc­

intcrior of du nc seas. Lancaster ( 1 983) i l l u st r a tes the

sc ribed by n u me ro u s authors (Folk, 1 97 1 : Lanc(lstcr.

spatial chan ge s rrom s i m ple to complex lineM d u nes

1 9 2, 1 986; Ash & Wasson, 1983; Wasson, 1983).

10 stur dunes w i t h i n the Namib desert.

Grain size has been clescribed as a function of source sediment (Folk.

1 97 1 ; Wilson,

1973;

Lancaster,

1 982, 1983; Wasson. 1983) and d ist a nce of transport

Dillie .\'{Jac:ill8

Dunes become

Dune spaci n g varies i n its relationships to crg mar­

filler-grained and bet te r sorted downwind, �lpproach­

gi n s . However, rlUIllCrOlIS o t he r controls also a frect

i n g a well sorted pOpuhHion of grains between 2 and

dune sptlci n g . Large, complex linear nnd stnr dUllcs

( Wi lso n ,

3



1973; L'"1c"ster,

(Folk.

1 986).

1 97 1 ; Wilson, 1 973; Lancaster, 1983,

1986; Wasson, 1983). Two distinct

Iypes of e rgs arc differenliated

accordi ng to whelher sand sources (Ire coa rse r , o r n l lcrnat ivel y finer, than li ne-grai ned St1nd ( Lan caste r,

wi th in the samc dune sen may respond to di fferent

processes than e!

smallcr l i n ear , lrill1Sverse and

ba rcha noi cl dunes (Lancaster, 19158).

om mon l y ,

linear nnd oblique d u n es are more widely spaced at erg m a rgi n s . Mai ngll ct & Chem in ( 1 983) showed

1 986). Wilson ( 1 973) and La n ca ster ( 1 982, 1983)

inter-dune corridors widening at t h e margi n s of

dcscribed grain size trends i n co arse -sou rced ergs,

S a hnra n dUllcfields.

while Wasson (1983), La n caste r ( 1 986) a nd Folk

( 1 97 1 ) desc ribed fine-sourced ergs. The p ri m a ry

Breed el

al.

( 1 979) showed

several cl ea rly photographed ex am p le s of i n creases in i n te r-d u ne nreas on the m a rgi ns of ergs,

d i fferences between the two types arc that coa rse­

However, in bMchanoid, tr:tnsverse or sror d une ­

coarser­

Helds, dune spaci ng decreases towards the ma rgi ns .

sourced ergs ha ve ill ler-dunes that arc

grained than lhe durleS. aile! also ex hibi l trends

Lancaster ( 1 983) mapped sJll:lller dune spacing a t

of decre asi ng g ra in sizc and i ncreasing sor ti n g

most o f t h e margins of t h e Namib Sand S e a . Dune

u pwa rd on i ndi vid u a l dunes and drnas (W i l son .

spacin g correla ted w i t h gnlin size and with dune

1973; Lancasler, 1982, 1983) . G rai n size also de­

height� and maximum du n e spaci ngs correlated w i t h

creases downwind (Wilson, 1973). Fine-sourced ergs

the l a rgest dunes i n th e cen tre o f t h e erg. B re ed

Downwind c!ulIlge.\· with ill

et ai, ( 1 979)

furnished several examples where d u ne

spacing and size dccrc:lse m erg m a rgi n s, Wilson

( 1 973) mapped dune heig h t an d s pacing , alld notcd that these corrclated with the percentage of areil

(11/

(lIlc:ielll dUlle sea

III

of vegetmion a nd coa rse gra i ns fOl'lned, Fla t , siliciclastic sabkhas were concentrated On t he sea­ ward margin of the Saudi d u ne sen ( rybcrgcr "I "I" 1983),

cove red by sa n d and average S;:l nd thick ness. He nOlcd Ihm thick erg deposits were associated with large, complex dunes and draas, whereas thin erg depos its were associa te d with smaller, simple dune fO l'm s . Thcl'e was

tl

drastic decrea se

i n dune size Hnd

spaci ng m the erg margins, I n ter-dunes arc more variable than their aceolll­ pa llyin g aeo l ia n d e posits and record environmental conditions of deposition ( K oc u rek. 198 1 ) . Some aut hors have described incre ases in the inter-dune area at the ma rgin s of clunefielcls. A lt h o ugh indivi­ dual inter-dunes arc smaller, they cover a larger proportional area. McKee ( 1966) notcd that inter­ dune areas covered a !tll'ger percen tage of totnl
AiJllIId(lIlce of bioturbation

A l though vegetation in duncficlds w i th in a given regi n is
Abundallce of 11011-lIeoli{Ul deposits

Ablflulfllu:e of sand ,�heets,

zib{fl'.�' lIIld iflter-dlllles

Wi de , low-relief d eposit io na l areas also cha racterize erg m a rgi n s, T h ree low-relief aeolian features thm ha ve been d escri bed are 2ibal'5,

sand sheets and

inter-dunes, Nielson & Kocurek ( 1 986) docu m ente d zibars.

coarse-grained. low- re l ie f aeolian bedforms

m a rgi n a l to the Algod one s duncfield in southern

C"llifornia, Kocurek & Nielson ( 1986) docu m e n ted extensive sand sheets on the m a rgins of t he G reat Sand Dunes. A l god on es and mn Desierto dune­ fields, Pe riodi c flOOding, vegeta tio n and a coa rse­ gr n i ned sa n d su pp ly were inferred to favour sand

Glennie ( 1 970) described in te r- bedded Ouvial nnd aeo li n l1 deposi ls frolll the margins of dune seas in Sa udi Arabia and noted Ihe im po rta n ce of 110n­ aeolian de posits , Ahlbrandt & Fry berge r (198l) created � I m odel in which dune fields were surrounded by (In extra-dune environment whcrc acoli(ln and non-aeolian deposits were intcr-Illixe I. Frybc rge r ei ll/, ( 1 979) and Andrews (1981) documented Huvial channels und pl aya s inter-bedded with aeolian de­ posits at the Great Sand Dunes, Fryb erger ( 1 979) and La ngford ( 1989) described mud-draped aeoli.n dunes formed through Hoodi ng of inter-clune and sand sheet a reas , La ngford ( 1 989) described nuvial

sheet development.

reshaping of aeolian landscapes that resulted in

Breed el III, ( 1 979 ) illustrated the global distri­ bution and common occu rrence of sand sheets on the margins of ergs. Frybe rger et ai, ( 1 979) desc ribed extensive sand sheet deposi ts adjacent to the G rea t Sancl Dunes, The low-angle, cross-stratified sand sheet sands were interpreted as i m po rta n t erg 11"Inrgin deposits, G e n t l y dipping fine- and co arse-gra ine d laminae were common wi thi n these deposits . Fryberger el til, ( 1 983) o bse rve d sand sheets tran­ sition a l between aeolian and non-aeolian facies i n n cl u ne sea in easte rn Saudi Arabia. Sand sheets were i n te rpreted �IS a resid ua l facies, formed after the pass..lgc of ma n y dunes when a protective mantic

dist i ncti ve /looded i nter-d u n e de posi ts, Breed et ai, ( 1 979) described num erous examples of sabkhas, st l'eam s , play as a n d sa nd sheets at the Illlu'gins of lllany of t he great ergs of the world. Swnllwry

These descriptio n s of modcl'll ergs suggest that ancie n t erg m
1 12

R. P. Lallsford and M./l.

sort - d. Downwind margins should be (i nc r-gnl i ncd and bellcr soned. 2 Dune sct heights should be thinner d u e LO smaller, closer spaced and some t i m es morc rap i dl y m i gnHi n g d U lle s . 3 Ae ol i a n dune deposits should re flect de posi t io n frOIll s i m pl e r a nd cl ose r spaced dune fOl"ms. 4 MOI'c abu n d a nt , low-angle aeolian deposits should forl11 f!'OIll deposilion in ex tensi ve sand sheets, zibars, silicicbstic sabkhas and i nte r-d U lles . Di s t i nc ti ve z i ba r . su b k ha a n d sand sh eet de posi ts should be recognizable. liller-dune deposi ts should be more

due to the propor t i onn l ly g/cillcr inter­ dune �\re<.l, but perh aps t h i n n e r d ue 10 more rapi d d une m i grati on . 5 Biolu rbm io n (by roots a nd burrows) should be pre­ sent in eithcr aeolian dunc or inter-dune sand�tonc. 6 1 1l lc rc<.l l mc d llon-aeoli
abundalH

Ancient siudies

Studies of ancient

sl rala hav� interpreted erg m
and erg interior environl11enls based

critcri
on the SHme six

as those discussed for modern studies.

Graill size {lIU/ sorting o8 rse-granule h o ri zo n s

nne! ventifacts

we re as­

with Triassic erg m argi n de po s i ts i n Nova Scotia (Hubert & Merlz, 1980). Cl c lll ll1 c nsc n &

socia ted

A b ra h am se n

( 1 983) and Brookfield ( 1 989) noted

�lbul1dant

gra n u le hOl'izons within inferred illler­ dunes in Pe rm ia n erg m a rgi n de pos i ts in Scotland, han ( 1 989) a n d Steele ( 1 987) noted a bu n d a nt coa rse-grained 1�l milHlC ill sheet sft l1ds t one facies i n the White Rim Sandstone i n U w h . Kocu re k ( 1 98 I b) de scri bed coarse-grained deposits at the nuvial m a rgi n of the Entrada erg, Dillie size al/d dww forms (as illjerred /1'011/

preserved Cfoss-slraw)

An upw i n d erg m
fum

Thesc s
of

rc cent l y

I'c inrcrpl'cted as

o b l iq u e dunes (Sneh,

Rotl iegendes,

Brooktielcl

1988).

I n the

( 1 989) nOled t h e

cont ra s t

be twee n the si mp l e d U llcs dcscl'ibcd fl'Om Permian erg m�l rgi n de posi ts by CICI11111CI1SCI1 & AbrH h H Ill sc I1 ( 1 983) unci e rg i n terior. complex dunes in t lte

D u m fries basi n . The rnnrgins of a Perm i a n erg ill the S l:h n eb l y I-lill l::o rm <1 ti o l1 in northern A rizol1 a wCre formed by small biowoul dunes, i n contrast to the l a rgc com­ plex d raas in the erg interior (Blakey & M idd lelO n . 1983). Rapidly mov ing transverse dUlles were in fe rred to form the u pw i n d margin of the Proterozoic Bigbc<.l I' erg i n Clnada. whereas complex bal'chans formed within the intol'ior (Ross, 1983). Th i nn er foreset coset lhicknesses were used to i n fe r Hil erg

se t t i n g in which dunes m igrHtcd more nl pid l y 1983). S m il i l e r p�l rflbolic d u nes formed the down wind m argi n of the Q U fltc rn fl ry Nebrm:ika sn n d hills (A h l b ra n d t el til., 1 983). I'orter (1 987) described m a rgi n

(Ross.

isol a t e d pods of small , simple aeolian d U llcs from dow n wi nd

crg

Sandstone

in

margin deposits of the J ur assic Aztec Nevada

and

southern

Aeoli�ln dUl1cs were interpl'cted t o

Californ i a ,

beco m c I
lhe Navajo erg i n te do r Wilhin t h c Jurassic Entrada Sandstone

nne! marc complex low::ards (Poner, 1 987),

( h e re were d nll11alic di fferences between marine or i"luvial m argi n and erg interior cross-scI thick nesses ( Kocurek, 1 <J8 I b ) , Foreset dip d i recti on s were "Iso di fferen t at the marine margin, Coastal dunes wcrc i n terpreted as simple crescc n tic dunes. Erg interior du ncs wcre n1l1ch larger, co m po u n cl crescentic dra
DOWI/IV;IIc/ change'li "/)lIl1dlllu;e oj saml .\'1!eels, zibars olld inrer·dulles "

I n the J urassic Moenave Formation. Icmmcllscn ( ( 1 98Y) indici.lIcd clwnges from acolinli dlillC 1 0 sand sheet f�lcies within 1-5 k m d bta llces nt the erg m a rg i n The sand sheets extended ovCr 30-60 kill distances before grading inlo inlilnd sabkha facies. Widespread sand sheet dcposi!'s were described from I cl'lnian erg margin deposits in Sc o t l;l I1 d ( IcIl1J11CIlSCn & Ab ra hamse n , 1983). PoneI' ( 1 987) described small isolated dunes within iI matrix of zi ba rs and s�ulcl sheets from onc m a rgin of the J u rassic Navajo erg. Thc clo w n wind margin of longi· tudinal dunes in the Permian Yellow Sands of Eng l and was inferred to be n series of sand patches and sheets ( Steel e . 1983), An extensivc sand sheet with isolated small dunes formed on thc upwind ma l gin of t he Proterozoic Bigbcl.lr erg (Ross. 1983). An extensive sund sheet containing siliciclastic sabkha depos i ts and i sol a ted smClI! si m p le barchan dunes formed the downwind m argi n of the Permian White R i m crg ( han, 1989), An crg ma rgi n o rigi n is inferrcd for a sand sheet fa ci cs within the T ria ss ic Dolores Formation in southwestern Color�ldo (Blodgell. 1984, Kocu rek & Nielson, 1 986). The facies is characterized by a h or i zonta l l y bedded sandstonc with nbundant mud drapes and fea tu res associated w i t h wind ripples. Isolated sand sheets h�vc been described frolll the En trflcl'l Sa nd ston e (Kocurek. 1 98 I b) . Thicker illlcr�dunal deposits have been used to identify crg margins in Pcrminn sandstones in Scotl;lllc1. as contrasted to thc t h i ck er and more �Ibllndallt i nter·clune cleposits in ferred to bc erg margin deposits (Cl c lll lllensen & Abrahamscn. 1983). Brookfield ( 1 989) noted the importance of both tecto nica l l y derivcd geomorphology and w i nd d i rection in de te r m i n in g the abundclnce and extcnt o f il1ter·beddillg o f non-acol hll1 f(lcies. Alternatively, Kocurek ( 1 98 I a) found that intcr-dune depos i ts wcre l a rge l y a bsent fmlll e rg mHrgin d eposi ts and we re most cOlll mo n within thc erg i nte r i or as�ociatcd with regularly spaced dUlles, Within the crg margin de­ posits, marine d e pos its repla ce d ill1cr'�dunes.

til.

1 13

wi,hin fill fIIu:ielll dune Jell

.

'

"/Julldallce oj /JiolflriJmioll

Ribbon-like trace fossils in l he Pcrminll Caspar Sandstone in Wyoming were ;.,scribed to i"lll erg margin env i ro n m ent ( Ha n l ey el "I. . 1 97 1 ) , Well prcserved horizontal Hnd vertic-H I trace fossil s a rC fou nd i n e rg m a rgi n facies of the J u rassic Navajo

Sandstone (Middlcton & Blakey. 1983). Sand sheel deposits in the Triussic Dolores Formation. Ill a rgin a l to t he Wing.. l1c erg. conwin calcretes and abundant root Sl ructurcs and burrows (B l odgcn. 1984: Kocu re k & Nielson. 1986 ) , Trace fossils ind u din g m a rine t races we re i nte rp rete d to indicate an erg m a rgi n position with i n the Penlli�1I1 Wh i te Rinl Sa nd st o ne (Ka1l1()la & Chan. 1988). A /mlldallce oj 1101I -aeoUwl deposils

D U lles fklllk e d

with nuvinlly de ri ved mudstone, and aeolian sandslollcs and rapid lateral t r
.

,

,

.

. .

1 14

R . P. Langford

J1(1I/

alld M . A .

t h rough sea le ve l chnngcs and I'cpeated ueflation of tile ergs.

Other features

U1-:icd

C E D A R M ESA S A N D T O N E

to infer erg margin origins in­

The Permian

clude a bu nd a n t deflationary erosion surfaces (Hubert

& Mem. 1980;

La n gford &

l emme nsen & Abrahamsen. 1983).

anyoiliallds of

southeastern Utah. I t is a cli ff-forming (Ieolian sand­

stone, I OO- 300 m thick (B l a key el III . , 1 989). The

han ( 1988) mapped an increase from

foul' erosion surf;'lces to seve n tee n HI the erg mar­

gi n within the Perminn

edar Mesn Snnd Slon e i s well exposed

along the Colorad o River in Ihe

Cedar MesH Sandstone out'crop is almost continuous along the crest of the M on u ment Upwarp (Fig.

eclar Mesa Sandstone i n

A t t he

southern U t a h . Numerous t h i n , erOSionally bounded

I).

nonhern end o f the upwilrp i n Canyonl�l1lds

upwnrd drying cycles within t he J urassic Moenave

N a tion a l P�lrk . the Cedar Mesa SandsLOllc inter­

Formiltion on the Colo J'tldo Plateau ind icated in­

to ngu es

stabi l i ty within the erg that resulte d in fluvial influx

Form{ltion and mal'ine sandstones and limestones

with

fluvial

sandstones

and org expansion and cOntract ion ( Icmmenscil al., 1 989). Kocurek ( 1 98 I b) and Kamo l a & Chan ( 1 988) suggested that large deformation and brec­ ci ation features were indicative of a marine erg

of th e lower Cu t ler beds

m a rgi n setting.

tongues with

el

margi n , the

(Fi g . 2).

of

t he

Cutler

Along its southeast

eclar Mes.. inler-tongues with fluvial

ancl lacustrine deposits of the Culler Formation. To the west, i n the subsurface, the

eclar Mesa i n ter­

marine li mestones and

sandstones

� L.UapArea I I�

50 k m

o

t

:z: I O � ::o \ 5 u

N

j

� • Alono-wincI ItO margin Erolmtrior

_

_

_

Monument Upwarp --'_ _ _ _ --L.

ARIZONA

_

UTAH _

_

I I I I I I I I I

..J

Ing. I . Map of utler I':orm:llion and Cedar Mesa Sandstone outcrops lind palacogcogl'llphic map of the utler- edilr Mesa depositional system, with outline of Ihc Palncozoic Uncompahgre Uplift. The ,Irrow indiculcs wind dispcrsal dil'cclions of aeolian sediment.

Do wIJwind challges lVithin

(111

1 15

(il/c:ient dUl/e sea

EAST

WEST MONUMENT UPWARP

SAN RAFAEL SWELL

UNCOMPAHGRE UPLIFr

Fig. 2. Schematic cnst - west cross-section i l l ustrating Ilcrmion stratigrnphic re lat ions of the

(Blakey et al. ,

1989).

The clune-forming wi lids orig­

i n a te d in the n or t h west as i n fer red from (oresel d i p

directions (Fig. I ) (Mack, 1979; Loopc, 1984).

A u n i que characteristic of t h e Cedar Mesa Sand­

stone is that port i o ns of the upwind, downwind and along-wind erg m a rgi n s arc we l l exposed, The

m a rgi n s of I' he dune sen were fa i rl y s t a b le du ri ng

cdor Meso dune sea.

t i ngu i shed by d i ffe re n t aeolian cross·stratifie3tion

and i n t erpreted as d i ffe re n t dune forms or m orph o­ l ogi es , and

H fou r t h sand �hect fucics.

Large Iro/lgh �'e(s

This facies is co m posed of cross-stratified sandsto n es

much of the Cedar Mesa depOSition and. as n res u lt ,

with forescts 1 - 7 m thick. Fo resets are concave i n

w i th i n rc l lllive ly narrow zones (Fig.

a ver ag i ng 2-2.4 m thi ck and

th ick CI'S m argi n aeolian sandstones were de pos i ted I ) . E x posed

zones of i n tcr·tonguing aeol i a n and norH:lcoJian

deposits occu py w e l l defined bands,

In u p rt:vi ou � study of the northeastern ( a l o n g· wind) margin of t he cl u ne sea we obse rv e d l i ttle change i n ileolian deposition from th e erg m a rgi n i nto th e i n te rio r

(La ngfo rd &

Chan. 1988.

1989),

bedding plane exposu res wi th

p rese rved

sco u rs

6 III acrosS (Fig. 3A).

B as al scours e i rh e r are co n cave scoops or hnve flat b ases with concave router mclrgins. Large tro ughS

may be isol ated , but ty p ica l l y occur in clusters of

laterally adjacent arld supcl'imposed sets, The forescts

commonly have low·angle toes « lowest 0.5 - 1 m.

I n tern a l l y

15°) wit h i n the

the t oes contain thin

We did not quantify changes in gra i n size or bio­

wi nd ·ri p p l e l a m i n ae p rod u ced from m i g rati ng win I

d u ne types or abundance. The major changes were

la m i n ae

t u rbati on . but ther'e were no obse rva b l e changes in

i n the a b u ndallce of n u via l ly dep os i t ed inte r-beds,

il n d in th e abundance of erosion sUI'faces wh ic h

decreased from sevelllcen to four over

I S klll .

We have also observed, but not studied, mo rc

obv ious ch a nges in two areas

of t h e Cedar Mesa

outcrop, In the northern part of the Maze Distt'iet of t he

t

anyonlands. sand shee de posi ts re p lace dunes

within a n a rr-ow band al the oilly exposure of the

u pw i n d erg ma rg i n . I n Lower G r
r ipp l es

(H u n te r ,

1977).

i n ter·tongue

These

w i th

ripplc-stnUi fic(1

lenticular.

ge n era l l y

massive tongues of sa n d deposited from ava l an ch es

on the d un e foresets (Hunter, 1977). Along the for c se ts , th i n l a m i na t ed reg io ns arc i r regu l a rl y inter­

beddcd w i t h t h icker I'cgions of ava l a nche deposits, e Me COHrsest a t the base ane!

The nvah l l1chc to n gu s

becoll1e finer-grained and less well defined nem the

to ps of the forese t s . The medium-grained av a l a nch e tongues are among the c oarsest·gra i ned d eposits of

rh e

eclar M esa S a ndsto ne ,

I n most be d d i ng pl..lne ex pos u res . the fot'escts are

of sand sheets w i t h rare irl(cl'speJ'sed d u nes,

symme t rica l l y distributed above the basal scours and

Fncics

Over Mcas of scvcm l squarc kilomct res the scour­

Four aeol ian facies are prevalent within the Cedar Mesa Sandstone. These include three facies dis-

m i gra t io n was pa ral le l 10 the lon g axes of t h e scours,

t rough a xes a n d fo reset di ps nre well a l i g n e d , with

low d ispersion, Trough axes i n the same area and

stratigraphic u ni t arc usually aligned w i t h i n 10°.

1 16

N. /�,

L.ul/8!ord al l d

M.A. Chan

B

A

l·jg. 3. Pliotogruphs of aeolian morphologic!; in the Ccd"r Mesa S:mdstOllc. (A) l..mgc- trough cross-strati fied selS. ( B ) Small cross-slnlli ficd sets. (C) Planar cross-stratified SCI:-I. Note the wedge of 10w':Ingle CI'OS$-strata formed :11 the \OC of �1 reactivatiOI1 su rface within the pl:lII:tr cross-set. The relationship results f['om reshaping (lowering the slope
However, in the Silille un i t iH different loctllions t rough axis orientation I1lHy vary by as much
.mls

The smull-trough cross-slral ified sets (lrc significantly

s ma l le r than the l a rge-trough sets. form ing a statis­ tica l l y significantly smallcr il11c1 H'1cr-gl'n incd popu­ lation. ;.lVcrnging 0. 6 - 0.8 111 in hcight (Figs 3B & 4). Like the large-trough se ts . t he slllHII-t rough sets have concave e ros io na l bases and concave forescts. Typical small troughs avcrage n.S- l m thick. with prescrvcd scours <3 III across. The i n ternal stl'UC­ tures of the 8111<111 troughS nrc difrerent from t hose

Fig. 4. "vcrag!; SCI heights or d i ffcl'clU clune

l11orphol()g.ic�: (0) lilrgc troughs: ( .l ) Sl11tdl lroughs: (.) planar scts: (Do) sand nat. Error bat's tIrc 95% conidcncc l inlcrvnb.

D01V1lwi1ll1 dUlIIges withill

{III

{II/cient dl/lw

1 17

.\'ell

of the large troughs, consistillg prcdominantly of

nat-bedded wind-ripple laminae a n d smal l-trough

migrating wind-ripplc lamillac. FOI'cset dips arc

sers. Rcactivtllioll surfaces arc vcry common and

typic�)lly lower «

stratal relationships indicate that this was due to

15°) than in large troughs. Small

troughs comlllonly occur i n stacked sets separated

rcshHping (lowering the slope angle) of the foresets

by subparallel erosional bounding surfaces. These

(Fig. 3

su rfaces dip in various orientMions but moSt cOm­

bedform u�yl11mctry are u n ique ( Rubill,

monly dip paralicl 1O the axes of the troughs, This

) , The Sll'lIctll,'es produced by changing

(e.g. Fig. 3

1987) lllH.1 ) probably resliited from large-scale

implies that the small-tl'Ough sets were created by

reshaping or the dLlllC by wind directions d i ffering

small. three-dimensional dUllcs migrating down the

from those or the foreset-producing winds.

slope of a large r . low-rclief bedform (sec Rubin,

1987,

rig .

The planar sets nre nlso notably coarse-gra ined and arc as coarse as oj' coarser thun Hssociated la rge

65, ror all example). The dips of sct

troughs (Fig, 5 ) . Planar eosel's almost i nvf.l l'i"lbly

boundaries rnnge from 2 to 5°.

occur as i�olated sets, surrounded by other facies.

ScouHrough axes and forese ls dip in the same direction as

those of associated large-trough sets. As

Set heights arc thicker than t hose of Olher associated

in the large-trough sets, the foresets are symmetrically

sets and do not (!ccreasc downwind (Fig, 4),

pcrsioll of wcll exposed sma ll-trough axes was only

PlaruH' sets are interpreted as deposits of mignrting. two-d imcnsional dune forms that migrated lrans­

distributed within the scours i n plan view. The dis­

versely [0 the pr'cdom inant w i n d dircction. The

slightly higher than of associated large-trough axes,

reaclivntion su rfaces indicate that the duncs were commonly

Planar sets

rcshapcd by winds at high a ngles to the

predom inant dcposiliollOI winds,

Planar sers arc the fhickest cJ'()ss-stnHificd sets, averaging 6-8 111 , The forese ls
S(/lul sheet deposits

section 10 those of la rge troughS but arc straight [Ill I nor concave i n plan view (Fig. 3C), Extensive

Sand sheet facies are thi n-bedded deposits consisting of low-flllgie «

bedding planc ex posUl'cs r'cvc:1 l thm the foresets are l i ne,lr ,lIld extend in somc hlsmnccs 1'01' at least

4") laminae enclosing n u mero u s

thin cross-sets of the SIlli-l l l -tl'Ough typc, Sand shects

400 m , The foresets di p perpendicularly to the axes

arc lhe finest-grained

of associated small nncl I�rrge troughs. Avalanche deposits form the. g rea test proportion

of the Heolian facies (Fig. 5 ) .

Beds nre lenticular, separated b y low-angle erosion surfaces. Bioturbation by planls and animals COn1� monly obscures sedi mentary structures, Sc c.li rn cil lilry

of the planar sets, becom i n g finer-grained upwHrd within

Ihe fOI'esels. Steeply inclined avalanche tongues m a y reach lhe basc of t h c forescl, or the fmcsct rnny

SI J'uctur'CS ;lI'C poody defincd. and grain size is rela­

terminate i n a basal wind-ripple domin ated 'toe',

tively homogeneous vcrtica l l y t h rough sand shcet unils. Typical small-trough sets average 0 . 5 - 1 m

similar to I'hose of the troughs. Some foresets i n ler­

thick, with preserved scours <3 111 ncross: excepting

tongue u pward into low-angle beds composed o f

their discontinuolls occurrence, they ilrC s i m i l a r fO

0 .3 ,...-:----cttro ugh:""" B -largo :=;:; = 'iT "' --,... =--:-:; •-.-.. Small trougr,s

�..-...

E ..§.

I

� �

0.2

:? 0.1

� Fi/.:. S, Avc l'ltge grain size of [lcolinn facies plolled ngninsl distance downwind.

: ><"

a....

"

'--

:::::: �::::�:::�:;\

/ -"

--.-.--�

••••

"

- :_ "

__

"

Q •••

Pllln!1f

Sand rIlIl _,_..... .. , AIIII. extrll-erg

<>�=,:::::::::�::::::;:;:::�;;:,;�;,:,�.

\'-

\,'lI.

, _ , _ , .,_,_,

..... . . ,. ,e,.,_._' .. -,- •• , . ,.

o,o-l-�--.-�-.--�-.----.---..---_--,--+ o 10 20 30 40 50 60 70 BO Distance (km)

1 18

It P.

Langford {md M . A .

Chan

t he sm a l l t ro ugh s described above. Troughs may be

on a selll i�quanliHHive scale, created by

abundant and sand sheets rnay grade l;nera l l y into

and converted to a percentage. The 2 percentage of a 0.25 m area that was bioturbated or

D roser &

BOlljer ( 1986),

�

the sm a l l l l'O ugh facies .

i n which sedimentary sU'uctu l'CS were obscured was measured. The

thickncss

of biotlll'ba tcd

was recorded . Thicknesses of

T R A N S EC T

low�anglc

iIHcl'vals

aeolian de­

posits and non-aeolian deposits were measured as

For this st udy , erosion su rfaces i n the uppermost

edar Mesa Sandstone were t ra ced a l o ng an 80 kill t ransect (Figs I & 6). Although t he Cedar Mesa i s not incised deeply enough to expose

the erosion surfaces along approximately 1 5 km of the t ra n sec t the relative co n t i nu i ty and extent of the exposed port i on s of the s urfaces s uggest that th ey are con­ t i n u ous bencnlh the covered interv.l1s. orrelation .

of d efl a ti o n su rfaces a llows identification of rela­ tive l y synchronous deposits wi th i n the Cedar

S a n dsto ne

.

Me sa

of measured

st ratig raph ic sections.

Additional measurements included dune se l heights

�lIld the thic kness of i n ferred i n tcr�dulle beds.

The distribution of sedimentary structures WaS mapped for a 1 m wide zone along the measured

sections. Cross-bed and bounding surface oriell� tations were measured and used to o bta i n the dune mo rpho logy by the methods p ropose d by Rubin & H u nter ( 1983). G rai n size was measured by visu al ly estimating t he average grain size a t I T1l illlc rva is within each stra t i gra p hi c section. Where a coarser pOpu l
s ize and t h e percenl'uge o f totnl grains were csti�

Melhods

mated. Samples

Six stratigraphic

sect i o ns

were measured �ilong [he

transect (Figs I & 6- 1 1 ) . B ioturbation was measured

o

a proportion

KilOr"r'ltltrfll

10

20

30

wken

fr0111 fifty o f

these mensure­

ment sites wcm t h i n�secl ioned. Two hundred gr a i n

diameters in cach sam p le wcrc

40

so

00

mCHsured

70

10�

Fig. 6.

III�

ross-sect ion

Subsudaee

<.llong transect

- - .. - - _ ..

Inferred correilltions

showing the loca ti on

of measured sect io ns and

exposure along the transect .

under

AD

1 19

Down willd changes wilhil1 lU/ llllciellf dlllle sea BIOTURBATION %

GRAIN SIZE (PHI)

Grain Size (Phi)

Bioturbation

o

%

o •

o •

E

�

o M

r

o �

•

MAXIMUM GRAIN SIZE

o •

�

MAXIMUM GRAIN SIZE

R SURFACES

Large Planar Sets

Facies

� �

Large Trough Sels Sand Flat Small Trough Sels

•

�

SURFACES

large Planar Sets

Facies

�

�ER � I§

Large Trough Sets

Small Trough Sets

Sand Flat

•

Extradunal

Fig. 8. White Canyon seclion.

Extradunal

with ileolian depositional fcaturcs ( Loope, 1 984,

Fig. 7. Andy Millcr section.

1985). polarizing microscope measurements.

n

10

calibrate the visual

I N T E R N A L STRA T I G R A P H Y Supersurfaces

Extensive cr05iOI' surfaces strfHigl'aphicHlly subdivide the edar Mesa dune sea (Loopc. 1985: Langford & han, 1 988). These 'supersurfaces' arc commonly underlain by patches of biOlut'balcd ilcolhlll sandstone and arc irregular. with up to 15 m of relief over a 3 kill distance. Locally, sevcml lllcll'cs of relief arc evident. These have been inlerpreted as surff.\ccs of aeolian erosion because of associated s u bHc ri ui fossils and lrace fossils and association

The morc cx(cnsive surfaces repreScllt w idesprcnd deAationary events that can be traced over 1 00I OOO km 2 (ucas within the Cedar Mesa outcrop belt ( Loope. 1985). Some of Ihese eXlend across Ihe elllirc transect und arc used here to define the internal stratigraphy of the formation (Fig. 6). These are labelled as supersurfaces sepnnHing slnttigraphic unilS A-G (Figs 7- 1 1 ). The iticnlifica l i o n of Ihe supersurfaces that extend frolll Moqui Dugway to Kaehina Bridge sections is uncertain. Throughout the rest of the transect, surfaces were w�llked OUl for correlation purposes. The lower surfaces arc not exposed in upper White allyon between the White Canyon and Kachina Bridge anel thus correlation here is inferred. These extensive supersurfaces are probJbly dcft"lIiol1 surfaces 011 which net erosion oCCUl'rCcl llCI'OSS t he clunerleld. Loope ( 1985) inferred

120

R , P.

Grtlln ,I�e (pili ) 2 3 •

o

Lllllgford alld M . A .

Chan

BIQlurbllllon (%)

5

20

�O

60

80

100

'" 20

'"

G

g

� .!> •

90

�

10

"

O L _ -'-

_ _

•

M<Jxlmum

grain

�

slzo

Faciol>

� �

Fig.

� �

Large trough sets

$m811

trough S619

9. Chcescbox

_

70

uper8urfaces

llHgO planar sols

"

Sand flat

"

Extra-dunal

"

.lnYOIl sect ion .

"

(hut aeol i n n deposition in the Cedar Mesa was cpi�

s od ie and the dcAmioll surfaces were fOfmed during

regional erosional evelllS, In this st udy !

tI�is type of

su rfa ce wilt be rercl'I'cd to as a dej!{I(ioll .nil/ace

fo l lowing the usc by Loopc

Less

( 1 985).

"

, L--h���nf+H�

exte nsi ve erosion surfaces arc associ mcd

with l h e m�\I'gins or t h e dune sea and Occur be tw een the dcAnli()llilry su rfaces (Lnngforcl &

h an , 1988).

These SlIrfnccs rep rese n t more localized aeol i a n CI'O� s i on nnel me associated with non-a eo l in n (ftuvial)

d eposi ts . Coexistence of non-aeolian und neol ia n

� � Small

�

Fecles

Lerge trough sets

�

trough sets

dcpositiotl lllay be demonstrated. illdict H i n£, that t h e

l ess extensive su rfaces formed duril1g pc ri ods of

CI'05iol1 Wilhil) an aCli ve l y uggr.\d i ng erg (L
&

__ � �__

__

�Io n

fig. 10, K lich ina Bridge section,

_

8vrfocos

L.llrge plOMr sets

Sond /llI! EICtrll·dunlll

h a n , 1 1)88, \989). These supersu rfaces w i l l be

refer red

to

also Illurk

nation.

<.\s loclIl ,\·upe,.sl/Ijaces, although t hey

at least

Langford

'nood surfaces',

localized find sho rt-terlll de­

&

Chan

named

these

aeolian sanclstones of t h e Western Imerior, This happy c i rculllstance results in easily measurable grain

size changes al' a l l scalcs. Grain size vHficd along the tra nsect due 10 a num be]' of factors. Therc was

DOWNW I N D IN

( 1 988)

grained lhan most of the Palaeozoic und Mesozoic

CHANGES

DEPOSITION

a

well defined dow n-wi n d decrease in ave l'age gmin

diurnctcrs of approximately O. l o m m km - r (Fig.

12).

The ave rage of t h e di a me ters of the coarsest fraction

Gruin size

decreased approximately

The Cedar Mesa SnudSI'OilC i s noticeably coarser-

mpidly to Kachina

0.27 111III k ill r

(Fig.

1 2).

Thc average o f the coa rse r fractions decreased

B ri dge , 44 kill

downwind, and

DOWllwilld cli(mges lVithili

(11/

alldew dlllle sell

121

.

BiOlurbollon (%1

thereafler decrcased morc slo wl y The h iSlogran)S of nvcrnge grH i n sizes indic'lte a bimodal pOpul�ition i n t h e u pw i n d sections. Therefore. a chi-square test' was run for a l l of the section s and f r pail's of

sections. The chi-squurc variable i ncrc nsc d w i t h

distance between

sec t ions (Fig. 12).

I t w a s significant

at a 95% level of confidence fOl' sect io ns more [han 20 kill apart. Grain size also varies between facies (Fig. 5). The the upw ind sect i ons

coarsesr facies in

arc

l a rge

troughS alld plallar types. The � wcr'agc gra i n size of

these fncies was significantly coarser (at a 95% level

of confidencc) t h a l1 that of s m a i l troughs a n d bio­ turbatcd horizons at Rock .anyon

(Fig. I ) .

Al White

anyon and Andy M i l ler anyon, the mean gr(lin

sizes for large troughs, sll1 a l l lroughs and planar sets wCI'e sigllinccliltly conrscr th a n the

mcan for sand Brid ge and Moqui D u gway . sand sh ee ts arc ft n e r- gnl i ncd than

sheets. At Kachina small troughs and

large tf'Oughs 311d planal' dcposits but arc much coarscr-gnlined 11Hill 1l1lVh.ll deposits

.

l he aeolian facies

A l t hough ;,111 of

decrease i n

grai n size downwind. a proporti on o f the dow nwi n d decrease in grain size is Hccount'cd for b y a dow nw i nd Moxlmum grllin ,ilC Facies

�

1m Fig.

II.

Moqui

decrease i n tile abundance of large rroughs, from

""""SuPllraurfoce8 ""'-

LU\le lrOUlltl lcll

Smali llough IEUt

� = •

Lorge planllr

75% ill the illlel'ioJ" of the clune sea to 30% neal' the

dow n wi nd margin.

I(lIS

I n dividual cross-sets were (jner�gl'ai ned h ighe r up

th e foresels. GrHin �ize was fou n d

\'0 decrease slightly,

Sand lIet

correspo nding with forcset height on thick p la na r

Exlra·dunsl

predominantly gra i n n o w deposits, with about 70%

)

and trough sets (Fig. 1 3 . The lower foresets were

grl:l i n now and 30% grainfall deposits

DugW!i)' �cctiol1.

The lowest

nca rc r

the top.

1 m of these dunes was commo n l y a

0 . 4 ,-------�--,

E g,
� c �

•

�0

0.3 • 0.2

"

o

I"ig. 12. Avernge mean a nd average ploltcd aguinsl maximum grain disl flllCC downwind.

size

.... '" 0>

•

•

•

• •

0 '"

�

O. I

•

u

en

c: OJ

•

..

0

0 <0

Dlslance (km)

01

<0

•

Average Grain Size Ave rage Coa rsest Gr. S i ze

-Jb=�T=�r=====r==;=L�-r_��__l o

20

40

D i st a n c e

60

(km)

80

"

0 :c '" .!! :;; 0 > '" � '" 0

..

0(/)

0

u

�

'"

122

R , P, Lansford fwd M. A . 0.26

E

� •

� � ,

�

�

•

e

• •

�

However. the uppermost unit is less biot u rbated, and bec;.)usc bioturbated in te rva l s lend to be com­ posed of nne- (md very fine-grained sandstone. 1'he d i fference in grain size Illay result from d i fferellli
0.24

0.22 0.20 0.18 0.16 0.14

Chall

preservation of vcgetatcd arCi.1S , Bioturbated horizons

I ,-,

Biot urbmed

horizons

are

i n tervals within which

sedimentary structures a rc largely indisti nguislH.lble due to

biolog ical acti v i ty , Bioturbated horizons 00111supersur­

monly underlie both deflation and local ,

3

,

,

Helghl above Dune au. 1m)

7

Fig. 13. Mean gt'(t i n size itS ,\ fllnclion of height above the bilSC or ,hickel' cross-stratiflcd SCIS. � 1't'OI' b,lrs �lrc 9.5'Yu conlidcl1cc i tl lcrvtl ls.

faces. Some sand sheets and fluvial dcposits me also extensively biotul'bated. I n the upwind sections

( Rock

l ' nyon, A n dy Mil i c I' Canyo n and White


gnli llcd i n tervals. I n the rema ining downwind sec· lions the grain size i s nCar the avernge for n i l facies.

The Moqui Dugway section. within LO kin of the

wi nd- r i pp le lamin uted 'foresel loe' and \Vas also

downwind margin of the Cedar Mcsi.1 Sandstone.

� ncr·grH incd. A

contains a

1'101 o f grain s izes against height abOVE: the b.\sc of the dunes reveals thm a m o re restricted gr<1in size is found at the lOpS of the

forcser, the range dCCt'c
The u ppe I' mos t unit (0) within the cdar Mesa was consislcrllly coarser-gra ined \h;)n the i mlllediately " n dcrlyi ng "nit

(E)

(Fig.

1 4) . The d i lle rence i n

s ign i fi cantly

higher

turbated sandstone (Fig,

percentage of

bio­

I I) . I=!owever, the pcr­

cCl1Iagc of h i oturbated intervals within the othel' nvc

sectiOllS offers 110 obvious [I'eltel, varying widcly
The percentage o f

bioturbmcd sandstones is ob­ abundances of non­

viously parti.ally relat.ed to the

(lcOl i, lIl and sand sheet f'lcies within the measured

average a n d average m a x i m u m gl'a i n size would

sections, Although the pcrcentage of bioturb,l1cd

correspond

dune sandstone decreases downwind, the percent­

il shift of 10 km in thc aeolian sand (I�ig. 14),

approximately to

position o f the source o f

age

of bioturbatcd sand sheet nnd nOIHleolian de­

posits increases (Fig. 1 5 ) . Bioturbation a lso varies

stratigraphicnlly. Twelve pCI' cen l' of the upperlllost

MAX o

MAX

UNtT G UNIT E

�I rn ti gnl ph i C int crv.tl is biolurbated. where as 29% of

the underlying u n i t is bioturbated (Figs 7, 8 & 10). This vClri
is i ndepcnd em o f distance from

the edge of the erg and abundance of no n -aeo l i H n

deposits,

I n dependcnce of stratigraphic o r

nOIl­

,l co l i al1 illn ucnccs suggests chnngcs in climate or

groundwntcr table tluctuntions

.5 � "

of

as

possi ble cuuses

bioturbation,

DUIIC set height

Dislonee

(km)

I"ig, 14, Gruin size plotted � lgai ns t distance for units E nnd G. the uppermost (;olltilluOLIS units ill the Ce(!
The i.lvc[·agc pJ'cserved SCt heights for the d i fferent dune types do not change significantly downwind ;llong the t ra n sect (Fig,

4).

Th e heights of p reserve d

cross·st rolificd sel� nrc cOni rolled by Il1clny facrors. ross-strata are preserved through the climb ()f migrating bedforms relative to the depositio n'J I SUt'·

fa ce and thl'Ough the l11 igrH tion o f sco u rs ( R ubin &

I l ul1.el', 1 982. 1983). The tllick l1ess o f cl'oss-stratified

DowNwind cil(lIlges willi ill 0.5

(Ill

tilltiellt dUlle sell

123

Planur CJ'oss�strati fied ,..:.ls occur as isolated set s .

On so m e of the dunes, Il a t l y i ng top-sct beds com­ posed of small-trough c rOS�H)e ts and sand sheet de� posits are p reserved . Prese rvation of top sets [1I�d o f pl(\Jwr sets of co nsist e n t thickness indicates that these selS represent a fundamental be dform h eigh t . Because t he average bed for m h e i gh ts remain COn� w

t:

.2 ti

" en

'0 c:

" u �

"

D-

OA o

0.3

sistent downwind, tile size of bedforms probably did

0.2

not c h a nge downw i n d ,

0.1 0.0

o

p rox i m i ty of the m argi ns of the dune sea a rc the s u pers u rfaces within the aeolian sandstones (Figs 7- 1 1 ). N u mc ro us n dd i t i o n a l loca l s u pers u rfa ces appear w i t h i n 20 km of the erg nUl!'­ gins (Fig. J 1 ) . i n creasi n g in freq u en cy at the erg margin from One p e r 1 7 111 of sect i on in t h e five u pw i n d sections to one per 9 111 of sect ion at Moqui Dugway. The addi ti ona l local supersurfaces a re com­ Anothcr ind icatol' of the

o 0

toc..! supcr.surfnccs

20

40

Dlstanca

60

80

(km)

•

Percent Bioturbation

•

Sand flat, Shalf3s and Bioturbated

o

Sand Flat

•

Siltstones and Shales

)(

Blotu rbated Sandstone

Fig. IS. Plot of biotllrb
monly

overlain by �I q ueo usly dep os itcd sil tstones undcrl
and shales H nd

sa l�dsron c.

Both local and deRa t ion su pers u rfn ces arc inte\,­ prclcd as ma rk i n g pe riods of ueoli�111 dcn at io n as­ sociated wi t h dccrea:scs in the aeolian sa n d su pp l y . Wilson ( 1 973) s u ggested that ergs nre loctdizcd by saturat ion of the aeolian t ra ns po rt i ng winds wilh sand. Aggradation o f ergs OCClI l'S when w inds arc sand-s;'l1uralCd. Deflation occurs when win ds mc lITl lel'sallll'(1teci

sets cl'eated by bedform climb is I'e l a ted to t h e

spaci n g , speed o f migration a n d a n g l e of c l i m b of the dunes. The depositional surfa ce mny be a fo resct itself all I i n c li n ed to rhe u nderly ing and o verl y i ng su pcrsu rfaces. The h ei gh ts of foresets fi l li ng mig­ rati n g scours are controlled by the same considcr� ation in
wi th sancl, Wilson ( 1 973) ma pped

sand coverage in Sahunlll e rgs and i n fel'l'cd rhat ergs arc c ha racte rized by ccnlrnl region s in which winds arc supersaturated and aggradmiol1 occurs, E rg m a rgi ns arc characterized by sa tura ti o n of trans� porting winds where sand is transported as m i gra ti n g aeolian dunes bur aggradat io n does not occur, Loope ( 1 990) suggests that erg mal'gins are chal'
ill dune s i zc, t>p tl c i n g, n.He of m ignlt i On or nile of cl i m b will res u l t in v
of t h e cOlltributil�g fncrors, challges

&. HUl11er. 1982: Kerr, 1989). sm a l l-t ro ugh cross-stratified scts arc crcated by down w ind m igration of sco u r pi t s or t lucewdimcnsional dunes. The consi stc n t set t l lick� ness req u i re s thaI the de p t h of scour pi ts 01' dUI�cs

(Kocurek, 1 98 1 : Ru b i n

SUMMARY A N D C O N C L U S I ON S

remained f{l i r l y CQnSt[lnt and lhat the amount of

t ransect a l lo ws several i n fere n ces to the Cedar Mcs,,1 dune seas thnt deposited its u ppe r most stratigrnphic ullits. I The well defined downwind decrease i n g rai n size and the consistent average gra i n size at each sect ion

mai ncd fairly constant along the tl'anSCct .

change

Large- and

climb between sllccessive scour pi ts or d u nes reo

A na l ys is o f the

be made oboul

indicate rlHll thc sources of aeolian sand did not

e it h e r in pos i tio n 0 1' in sand com pos i ti o n

124

R.P, Langford lIlId

throughout the periods of deposition. H
units do not change ill grain size upward, This has implications for the nature of the el'Osionnl periods th;1I cre;.l1ed the extensive deflntion surfnccs. I f signifkam acoliun tranl:iport;ltion occurred during long periods of erosion. then the coarse-grained

M . A . Chall

ll1�lIcrial composing the upwind s�lIldslones should have been reworked downwind as a conrse-grained

lag. Since this reworking has not occurred, thcn either (i) t h e pe ri ods of erosion wcre not long­ lasting, or (ii) the sand supply was shut off during deflationary pe ri ods either due to remov;'11 of the supply or th rough a change in the transporting wind direction. 3 Within the edar Mcsa Sandstone: (a) bioturbotion a ppe a l's 10 vary stratigraphically more lhan spatintly perhaps due to cl i m ati c nuctu
(b) dune spacing and mOl'phologies of individual dune types do not vnry downwind� (c) gr�lin size decreases gradually downwind: (d) propm'lions of different dune types changc rcgularly as the abundance of large-trough sets clccre:lses downwind: (c) the proportion of sand sheet deposits increases regullHly downwind: (f) non-aeolian f
DownlVind c/wuge.'i witllill

A I'IUmAND'r. T,S . . ANDIU1WS, S, & G WYNN I: , D.T, ( 1 97M) Bimu rbtHioll in colillil dcpositli, J, S('d. Pe/rol. 48,

83Y-848.

AIILlHtANDT. T.S, & F�YIlI\k(aBt. S . G . ( 1 98 1 ) Scdimc lU ary rCH t u rcli Hnd Sigllilkttllcc of illtcrciunc dcposits. I n : Recellt liliti Allciell/ NOIlI1U1/'ille DeptJ.l'itiollal Modcl,\' jor ExplO/"(l/iolf (Ed. Ethe ridge. F.G. & FIQres. R . M . ) PI' . 293-3 14, Spec. Pub!. Soc. Ecol1. Palcoill . Minet'a l . , Tulsa, 3 1 , AIILlJk,\NO'i'. T. S . . SW1N HIART, .1.13. & MAItONEY, I).G.

( 1 983) Ti r e d)'llamic Holocene dune fields or lhe Greut Plains nnd RocKY MOUlltflin 13(lsins. USA, [ n : £oli(1II Sedimelll:'· lIlId PI"()('e.I·,H�,," (Ed. Brookfield. M . E . & Ahlbrnndt. T.S.) PI'. 379-406. Dey. Scd i me nt . 38. Elseyier, Amsterdam. ANDRI!WS, S , ( 1 98 1 ) Sedimentology of Great Sand D U llcs. Colonu.lo. I n : Recent (llId A m.:iem NOIlII/(lrine! I)f!po.�i1ioll(i1 ""Iodel�' [o/, Explormion (Ed. Etheridgc. F. G . & Flol'cs. R , M . ) pp, 293-3 14. S pec . Publ. Soc. Econ. Pa1c01l1. Mineral . . TlIlsll, 3 1 . ASII, J . E , & WASSON. R.J. ( 1 983) Vcgctation and sand mobilit}' in the Australilln dc:>Crt dUllcficid. Z. GCOIIIOl'plr. NF SIIf}pl·b(1 45. 7-25. B,\GNOL[). R. ( 194 1 ) The Physics nf 81nwlI Samls ({lid De.I'c/·t Olllle�·. Chapman & I-Ia l l . Lond n . 265 P I' . I3LA Kl\Y , R.C_ & M IDI)U':T()N. L.T. ( 1 983) rermil.lll ShOt'C­ line eolian t.:omplcx i n eCI1\1',11 Arizona: dunc Ch:lllgCS itl rcspollse 10 cyclic SCtl Icycl cha n gcs . I n : colhlll SedillH1ltl� (/lid PI'oce�·.I·es (Ed. Brookficld. M . E . & Ahlbnltldl. T.S.) pp. 55\ -582. Dey. Scdimc n 1 . 38. Elsevier. Amsterdam , 1h./lKLiY, R . C . , PI:TIH(SON. F. & KOCUI<:I:K. G. ( 1 98�) Syn­ thesis of 1'l Ie Paleozoic: lind Mesozoic eolian deposits of thc western interior of the United Stale:>. Sed. CeDI. 56. 3- 125. Bt.ODGIH'I', R.J-I. ( 1 984) Nonmarine depositional cl1\'iro n­ menls and paleosol deyelopment in the Uppe r Triassic

Dolorcs Formation. southwe�tern Colorado. GllitleiJook, 37,h /1111/11(11 MeelillS, Rm'ky MOII/oaill Sectinll oj' fhe Geologicfll Society o[ Americ(I. Olmlllgo, 46-92. I3l<:mm. .S FI<:YII !R(iI:K. I S.G ANIJKFws. S Me AUtI!Y, C., LI!NNi\KTZ. F,. GEIlEL, D. & HORSn"\N, K. ( 1 979) IkgiOllill studies of liflnd SCliS using Landsat ( E RTS) imagery. Ill: A S",dy o/ Global Smul Seas ( d. McKec. . D . ) pp. 305-398. US Gco]. Surv. P"of. P'p. 1052. IlKllEO, C.S. & G�ow. T. ( 1 979) M o rpho logy tITld disu·j­ but ion of dunes in salld !\cas obscl'yed by remote sensing. I n : A Sludy o[ Glob,,' S(lIId Sefls (1;;(1. McKee. E . D . ) pp. 253- 304. US Gco!. S�II'V. PI'Of. plJp. 1052. B�OOKFIt'.LD. M.E. ( 1 989) Rotliegendes desert scdirnellUltion in S,otlatld. Z. Oeol. Wis�·. 17, 205-24 1 . CAKItUTI II!KS. R.A. ( 1 987) Aeoliall sed imc nt a t io n froil l thc Gultymore Forlllfllioll (Dcyoniull), Ircluncl. Ill: Desert SedilllclII:"; AII(.'ielll (//1l1 Modem (Ed, Froslick. L.E. & Reid. I . ) P I'. 251 -26M. Spec. Pu b1. Geol. Soc. London .•

.•

35.

HAN. M , A , ( 1989 ) Erg m(lrgin of thc Pcrlllii\1l White Rim SOl1dstone.

SE Uwh, Se(/imclltolog,l' 36. 235 -25 1 .

CUlMMl!NSl!N. L.B, & AijllAIIM.1SIlN. K. ( 1 983) Aeol itlll

stnuificmioll alld facies association in dcsct'l scdi mc rl ls . Arran basin (Permian) Scotland. Sedimentology 25. 587-6(14 .

(lliciellt tilllle sea

125

I,UMMI!NSI.lN. L . G .. Ot...5t\/"I. I-I, & BI,/IICEY, R.C. ( 198\.1)

R E F E ll E N C ES

.•

fli/.

E rs- m:II'gi n deposils in the lowcr Jurasliic Moena vc Formation and the Wi ngatc Sandstonc. southern Utah,

Ijllll. Geol. Soc. Alii. 1 0 1 . 759-773. DnosHK. M . & BOI'I'JL!IC D.J , ( 19M) A licmi-quantitlltivc field clll)):>ification of ichnorabric., Ceol. So(.'. Alii . . Cordilleroll Sec/ion 82nd /IlIIlIwl Meefing. AIJ.\·tmcl with

Programme 18, 102. FOLK. R.L. ( 197 1 ) Longiludinal dunes of the l1orth­ welitern edgc of the Simpson desc.rt. Northern Terri­ lory, Australia. I . Geomorphology and grain-size relutionships. Set/illll!lIfology 16 , 5- 54. FRYIiEIt .11K. S.G. ( 1 979) Eolian- fluyiuti lc (cQntincntlll ) origin of nncient !Strat igraphic tnlp ror petroleull1 in Weber San dstone . R'·1Ilgcl), oil field. COIOl'lldo. MOW/I, Cwl. 16. 1 - 36.

Strmigraphic traps for petroleul11 Blfff. Am. A.\':". Petrol. Geol. 70.

FltYBI:It(;HK. S.G. ( 1 986)

in wind�l<"lid rocks.

17(,5- 1776.

FItYllliK(i liK. S.G . • A I I LlJRANI>T, T.S. & ANI)RI'WS. S. ( 1 979) Origin. sedimcntary fClH ul"es, and liignificulicc of low­ angle 'sund shcct' depositli, Grent Sand Dlincs NatiOnal Monumcnt al1(l vicinity. Colomdo. 1. Sed. Petrol, 49.

733-746.

FRYlmKCEK, S.G., A I. S ,\ RI , A . M . Eolian dune, interdunc, sand

·

& CUSItI\M, T,J. ( 1 983) sheet. and silicidUlitic sabkha sediments of .In offshore pl'ogrnding s::ulCl seu, Dhtdlf<1t1 area, Saudi Arabia. /JIIII. Am. A�s. Pell·nl.

Ceol. 67. 280-3 12. GI.I!NN II!. K.W. ( 1 970) Descl"l sedimcntary environmcnts. Dell.

Sed. 14, 222 pp.

GLI!NN lI �. K.W .. MuoD.

O . . & Ni\Cj·IH ji\i\ L. 11.J.C. ( 1 \.I7t{) Depositional environment and diagenesis or Permiun Rotliegcndes sandstones in lhe Lchrnllll Bank lind Sale Pit llrcas of the UK southern North Sea. J. Ceol. So(.'. Lond. 135. 25-34.

I li\NLI:lY • .1.1'1 .• S'1'llIt),I'MI\N N • .J .I�. & TOOTS. I-I . ( \ 97 1 )

Tracc fossils ft'orn thc C(1�pCI' SiHldstOilC (Permian) southern L;:lr:lmic Basill. Wyoming :uld oIOI·ado . .I. Sed, Petrol. 4 1 . 1065 - 1 06�. l-IuUl!kT. J,F, & Mmuz. K.A. ( 1 9�O) Eolian dune field or Latc Triassic age. Fundy Basill. Noya Scot ia . GeoloKY 8, 5 16- 5 19.

HUN 1'I!K. R.E. ( 1 977) Basic types 01" stnltif'ication in stlHlII eoliull dUllcs.

Sedilll(!IIfOlogy 24. J6 1 -3�7. IIAN. M . A . ( 1 9&;) oastal dUlle facies. Pcnnil:Hl Cutler Fonmltion (White Rim Snrlclstonc) . Capitol Reef NatiOnal Park uren. sOuthenl U W h . Sed.

KAMOLA, D.L. &.

G,!ol, 56. 3·1 1 - 356. D . It, ( 1 9�9) Set/illu:lltrJ/ogy (Illd .\'tmlisr{/jJlty of Pelllrsylwlllimr (Iud IOIVer Perllliall Strata (Up/ler Alllsdell

KI:KR.

FOI'IIl(lfioll (/lui Tellsleep SlIItds/(Jlle) ill Nor/It Ct!II//'(/1 Wyomillg. Unpublished PhD thesis. Ulliycrsity of Wisconsin. KI:!KIt, D . R. & Do 1"1 , It. H . ( 1 9�6) Eolian dUlie types preserved in the Tcnslcep SanclstollC (Pe: III1SyIYiln i�l ll ­ Pe rm ian ) , north-cclltnll Wyoming. KOc.:VKI1K. G. ( 198In) Significance of interdune deposits and bounding surfuecs in eolian dune: sllnds. Sedill/ellt· ology 28. 753- 780. KOC:tJItEK. G . ( 1 !l81b) Erg reconstruction: the EntradH Sands\()llc (J ura!\....ic) (If northwestern Utah :Hld Colorado. PCI/rl(I(J!;t!Og Pf//(If:odilll . . Polaeol!col. 36, 125 - 153. KOCUIU:K. G, ( 1 9�8) First-ordcl' <1l1d SUpCI' bOllnding ••

1 26

R. P. Lallgford (lilt! M . A .

surfaces in eolian sequences- bounding surfaces I'c\'isiICd. Sed. eol. 56. 1 93-206. KO(,UIH !K, G, & N I I!LSON. J, ( 1 9g6) Conditions favorable for the forma tion or wi.lnn-dinUlIC IIcolitill s:md sheets. Sedimelliology 33. 795 - 8 1 6 . LANCASTI;R, N. ( [ 982) Dunes or the skeleton COnSt. Nt'uni bill (SOLIth Wc:-;t A frien): gcornol'phology and grain silc rcl!ltiollships. /J(1I'I1! Sf/If Prof, Lm,d/. 7, 575-587. LANtASTI!K, N. ( 1 983) ol1ll'ols of clune morphology in the Namib silnd sea. I n : Eolio/l Sedimellf,\' ((11(/ Pl'oce,\'ses (Ed. 131'00l dicld. M.E. & Ahlbrandl. T,S.) PI'. 26 1 -290. Dev. Sedimenl. 38. [sevier. Amsl�rdnm. LANCAS'rI!It, N. ( 1 986) G rai n-size chi.lI'<.lclcl'islics or lincnr dunes in the sOLJlhwc.�ICt'n Knlih
395-40 1 . LANCASrllH.. N , ( 1 988) The dcvelopmelll or Illr£e ,lcolillll bedforms. Sed. Geol. 55. 69-89. LANGIiOIH> . R.P. ( \ 989) Modcrn and (Incient Iluvhl l -eolin n i n teractions. Pan I . Modern systems. Sedilllemology 36. 1023- 1U35. LANG..-ORI>. R . P . & ClI/\N. M . A , ( 1 988) Flood surfaces lind

dcA;:llioll sul'facc:-; within the CUller l:'urm'l lion tlnd Cedllr Mesa S::lI1d:stollc (Permi
GeQI.

SO(·. Alii. 100. 1 54 1 - 1549. LANGFORD, R.I'. & CHMIoI, M , A, ( 1 989) Modem and Hncient Auvial-colian i nlCr<'lctions. PMt 2. Ancient systems.

SedillllJufoloSY 36, 1 037- 105 1 . LIXH'E. 1).13. ( 1 984) Eoli{lIl origil) of upper Paleozoic snndslonc�. sOlltheastern Utilh. j, Sed. Pe/m/. 54. 563-580. LooI'!!. D . O . ( 1 985) Episodic depositiun of uppcr Paloo'Wk: S.lIldstoncs, solltheastcl'll Utllh. Geology 13. 73-76. LOOI'H. 0 . 8 . ( 1 990) Pcn-onal communication. M,\CK. G.H. ( I 971:i) The survivability of lighHnineraJ grains i n tluvi:ll. eolian (lnd illll1'iIlC cllvirOlllllents, The Permian Cutler and edar Mesa F'orliiilt ions . Sedimelll% gy 25.

587-604.

MACK. O . H , ( 1 979) Lilton)] marine depositional model for

the Ccd!lr Mesil Sandstone (Permian), Clinyonlllnds NmiollilJ Park. I n : Permialll(lmi (Ed. BiWI'S, 1 . L . ) pp. 53-68 . Four Corners Gcol. Soc, Ninth Ficld onfercilce, Durango. M "INGU!fI·. M . & CI I�r.tlN. M .e. ( J 98�) Sand seas on the Sahur:J tlnd the Sahel: an explanation of theil' thick­ neSS tlml suml dune type by the sand budget pl'inciplc. In: Eolia/l Sctlimems (I"d Processes (Eel. I3rooklicld. M,E. & A h l bnllldl. T.S.) pp. 353-364. Dev. Sedimc n t . 38. Elsevier. Alll�lCrdalll. MAk%.OI.F. J.E. ( 1 �83) Changing wind and hydrologic regimes during dcp{)sition of the N avajo and Aztec Sandstone, J urassic (1), southwestern U n i ted SWtcs. I n : EOIi(UI Sl1dilJlellls (Illd PI'O('('sses (I�d. Ol'Ookficld. M . . & Ahlbnlmll. T.S.) PI'. 635-660. Dc\,. Sediment. 38. Elsevier. Amstt!rdlJln.

hall

McKHt:. E.D . ( 1 966) Structures of d U lles Itt White Sun(b National MonumclH. New Mexico (unci a comparison with structures of dUlles from other selectcd .. reils). Se(limefllology 7. 1-69, MIDOl.liTON, L.T. & BLAKEV. R,C. ( 1 983) Proccsses (11)(1 controls On the i n tcrtonguing or the KflyelH,1 olld Navajo Ponnotions, nortllcl'1l AI'izona: eolia n- nuvia J illlCfnCtiolis. III: Eolia" Se(limelfls (fIul Processes ( Ed. I3rookllcld. M . E . & Ahlbrunclt. T.S.) pp. 613-634, DC\I. Sedimcnt. 38. E.lsevicr. Amsterdam. NIBLSON, J. & KOCUR!!K, O . ( J 9t16) Climbing zibars of thc eol. 48. 1 - 1 5 , Algo(loncs, Sed. PORTEK, M . L . ( 1 987) Sedimcntology o f
661 -61lO.

Ross. G . M . ( 1 983) Bigbcnl' el'g: a ProterOi:oic intermontanc eolian sanel seu in the Hornby Blly Grollp, NOl'lhwest Territories. nnad,!' I n: Golioll Sedilllelll.\' (llid PI'OC(!sse.\· (Eel. Broo kfield, M . E. & Ahlbl'tll1eli, T . S . ) PI'. 483-520. Dev. Sedimell t . 38. Elsc\'icr. Amsterdam, RUltIN. D . M . ( 1 987) Cl'oss-bedding, bedforms. <.m
oll(.'ept:,· ill currents. So(.'. £eoll. Pa/(:ollfol. Millertd. . Sed. (/1/(/ Po/colI/f)l. /. SEPM. Tulsa. 187 pp.

RuniN. D . M . & HU NT!!K. R. �. ( 1 982) Bedform climbing in t heory and nnHlrc. Sedilllc!lIology 29. 1 2 \ - 1 38. RUIUN. D . M . & l I U NTt�N. R.E. ( 1 983) Recollstructing bed� rorlll asscmblages rrom compOllllcl cl'Oss�bcdding. I n : Eoliflll Set/iII/elliS {/lid IJI'O('t!sses (Ed. Brookflcld, M . E . & A h lbl'illlclt. "I'.S.) P I'. 407-428. 1 ev. Sediment. 38.

Elsevier. Amsterdalll. SNt:lt. A, ( I �8S) I)CI'Illii.lfi dune pHucrns in nonhwestcrn E U I'opc Ch'lllcll£C(1. J. Sed. Petrol. 58. 44-5 1 . STlllH.l!. R.P. ( 1 9S3) Longi wdin'll (Irtl,1 i n the PCI'mian Yellow SlLnds of north�e('st Ellglond. In: Eolion Sedimellts (llId PrO('(!s.H!S (Ed. Brookficld. M.E. & A h lbrtlnclt. "['.S.) 543- 550. Dev. Sc(limclll. 38. Elsevicr. Amsterdam.

PI'.

ST�El.I!. 13 . R . ( 1 987) Depositionsl ellvironmcllts of the White Rim SillldstOllC member or the lItler FOl'l1llllioll. ilnyolilunds National Pilrk Utah, BIII/. US Ceol. Sill'll. 1592· /3 . 20 PI '. T,\LUO·I'. M , R , ( 1 91:i5) MujoJ' bounding SlI J'f,h::CS in ueolian s.tllldstOIlCS, n climatic model. Sedimellt% gy 32, 257-265. THOMI'SON. D . O , ( 1 969) Dome-shlipcd colion dunes in thc Fl'odshitlll Mcmbc� or thc so-called 'Kcu per' Stindstonc FOI'Ill�llion (Sc)'t hian -Fr�lslli;lll : Tri;1ssie) at Frodsham, tlcshire ( Engll1lld). Sed. Ceol. J , 263-289. W/\SSON. R . J . ( 1 9�3) Dune sediment type. sand colour. sediment prOVel1tL llCC :111<1 hydrOlogy ill the Strzelecki· Simpsol1 dUllerield, Austrulill. I n : Eoliall SedilJlellls (//,,1 IJro('e�'st!,\' (Ed, Broukfield. M.E, & Ahlbnllldt. T,S.) pp, 165- 196, Dc\', Sediment. )8. Elsevier. Amsterduill. WILSON. I .G , ( 1 973) Ergs, Set l, CeQI, 10 , 77 - 1 1 0.

S{)C(.'. . Pllbl.\' Jill. Ass, Scdill/Cllt, ( I !)<')J) 16.

127- 149

Low-stand aeolian influence on stratigraphic completeness: upper membel' of the Hermosa Formation ( latest Carboniferous), southeast Utah, USA S.

. AT

li L E Y ' alld

O . B . LOOPE

t)epartmellf of Geology. Ullj l'ersifY of Ne/JI'ft.l'ka, Uncoll/, N E 68588. USIl

A BSTRACT

'1l(: L::lle PClllbylvllnian (Iatcst Cll'bonifcrous) record of the Par:tdox Basin of southc:lst Utah includes a thick SC(IUenccof cyclically inle r-l>edded murine. nuvi:tl and aeolian deposits. We 11:\ve rCCOllstructcd tile tlre,'ll distribu t ion ond rClntivc water depths of murine depositional ellvironmen ts on the basis of l ithology find facies slfIeking order within fourth-order cycles (cswblished through Mtl,'kov eh.lin mlulysis). stimates of water depths for facies make it possible to subdivide fOlll'Jh-order cycles into t ransgressive and regres�ivc fifth-order cycle sels. Fourth-order cycles nrc most often diseonfol'n1l1bly overltlin b)' no n­ marine low-stand deposits. The facies associations within fou rt h-order cycles suggest superimposition on a third-order cycle, Thil'd-ol'osiliorl. gl'ain supported ma rine carbonates remained ulilithilicd after exposure, I)uring fourth-order low �tands. some of these sediments were reworked into aeolian (Iune�. TIle marine record wns paniully or JOlally stripped ilway, making correlation of fourth- alld fiflh-order cycles diHicul1. '111e fundnmental nature of lhe basin fill was thus strongl), illt1uclleed by dcn.lIion. I NT R O D U C T I O N

1 936; I-Ieckel . 1980). Unique t o t h e west -ce n tral is th�1I cy cl ic Ime Pal a cozo ic rocks ,'cco,'c! the sys te m at ic s u peri m p os ition of shelf cOIrbonmcs by aeolian sands (Dricse & DOl t . 1 984; Loope, 1 985; Loope & Ha ve rl a n d. 1 988; R ice & Loopc, 1 99 1 ). 1�hc ncolinn dcposits frcquclllly i n clude �I high percentage of tn:t l' i nc carbonate bioc1asts :.tne! lit hoclasls. Wh�l t was thc mcchanism for cycl ici ty? It is difficull to imagine all aU lOcyclic proccss thm co u ld (i) j u x w · pose s h e l f and acolian filCics. or (ii) IC�ld 10 t h e d eve l o pm e n l of deep desiccation fiss u res (Loope & H a ve rla nd . 1 988) and o x i da ti on of pyrit izcd fossils and lraces within the mnrir)c units (Loope & Watkins. 1989). Quaternary ..colian cnrbonntes have been considered a low-Ialitudc signature of glaciation

Purpose

U A . h owever .

I n the Parado x Basin of southeast Utnh, imcr· bcdded ca r bo nule ;mel siliciclnstic Slrata of the Late Pcnnsylvanian ( i a te sl nrbonifcrous) upper member of the I l c rm osa Form a t ion ( Fig, I) record cyclic trallsitions from tnarine 1O te rrest r ia l depositional processes. I· l i t e ( 1 960) and Go l d h u m m e r el al. ( 1 989) nOled cyc lic it y of II si m i l a r sc�\lc ill the e va por i t e domin:.ltcd M iddlc PCllnsylv:tnian Pamdox MCll'lbcr of the Hermosa Form a t io n and other workers have rcported cycl ic Pennsylvanian strata from other rcgion s und continents (e.g. Wanlcss & She p a rd , •

Prese nt address: Exxon P roduction Rescilrch Company.

1'0

Box 2 1 R9. I-Iouston. TX 77252·2 189. USA.

Aeolian Sediments: Ancient and Modern Edited by K. Pye and N. Lancaster © 1993 The International Association of Sedimentologists ISBN: 978-0-632-03544-1

127

128

A rcilley lIJ/d D./3. Loope

S.c.

'} . 'D ,

'

.

&

M al i n ky ( 1 985), ( 1 988) have argued Ime

Cedar Mesa Ss,

,).'" '�

North

American

M id-cont inent

Rocky Mountain cyclothe11l�. I::"u rthernlol'e, B oa rd m n n & I leckel ( 1 989) ha ve correlated Texas

cyclothems

one-for-one

with

the

Mid-co n t i n e n t ,

extending the evidence for an inter-regional al locycl ic

Rico Fm. and eouivalents

,:,

( 1 986) and Goldstein

for glacio-custatic control of

and

, ,'

Palaeozoic

Heckel

mcchnn islll for cyclicity. Clearly. however. subsidence dUl'ing Middle to

LaIc Pcnnsylvi:1nian time p rov i dcd accommodation space for t hese strata. Could 'jerky' subsidence

be

the C;,lUSC of sOllle (or all) of the cyclicity? As pointed Out

ThIa

Study

upper member

H a rdie

( 1 986)

and

Koerschncr &

Read

jerky subsidence alone C
eme rgencc

o( mn l' i nc

facies - ' t rampoline tectonics'

must be i n voked (or the

fourth- and fifth-order

cycles.

rJ) �

an

e �

individual

upper Hermosa cycles be corre­

lated acl'Oss the Paradox

is

c o .0 .... co

Hermosa Fm.

Basill?

Lateral continuity

cOnllllonly put fOTWf.lrd as the best test of iluto­

cyclic vs allocyclic hypotheses C/ lit. •

1990).

(Heckel, 1 977; Kozar of facies

Since rhe vertical sequence

and the d i s t ribution of diagenetic features in our

U

sections are

....

incompatible

with ..In aUlOcyclic

origin,

these cycles - whe the r due to eustasy 01' to jerky

Q) a. a. ::J

subsidence -should, like other allocycles (e.g. 1988; Postl mcn l i c r & V a i l , 1988: Posamcnticl' et al SMg, 1988� Vnn Wagoner CI al 1 988), correlate bnsin-w idc . If. as suggested by Lewis & 11 m pbcII ( 1 965). these cycles cannol be corrclated b Isi .. n-widc, pe rhaps the LHle Pennsylvanian marine record of the Paradox Basin is. relative to published examples fl'Om other basins. incomplete. Although Ihe low­ stand sedi m cn Hl ry record includes both acolian nnd nuvial deposits, ollr observations i n d icf.l tc Ihal �Ieolian de fl a ti on caused Ihis incompleteness. We cla im . as 'lid I alrymple el 11/. ( 1986) and Rice & Loope ( 1 99 1 ), that the fUl1chullemal nature of the stratigrH p h i c reco rd of () ric.l (and pre-vegetation) intervals was strongly influenced by dcnation. We have attempted 10 de tcr m i ne the preferred su ccessi on of facies betwecn unconformities, a nd have used the relative watcr depths of m u rin e f:.tcies to consll'uct
. •

lower �

member

::f;

.:-

:

) Molas

Fm.

Leadville Ls.

Generalized slruligraphic t:Qlullln show i ng relationship of upper member of 1-lcrmos:1 rormalion (this study) to the cVlIpori tcwbcaring Paradox Member of the Herl11usa Fonntllion (Goldhammer ef of., 1989). (Stratigraphic terminology IIfler Hile & U uck ne r 19tH.) Fig. 1 .

,

(Johnson.

by

( 1 9 9),

1968:

Fa i rb r idge & Johnson,

palilcolllagilctic and sedimentologic.ll

1978). From dala, it has

the southern morgin or

(average 25 m thick) and t h i rd-order (average 2 1 3 m thick), bilsed

on

their

Gondwana passed over the southern pole and was

by old ha m mer el al. underlying Pa ra dox

glaciated during

Formation.

been demonstrated

thaI

the late

rowe l l . 1 985 : Vccvers &

Palf.tcozoic (Caputo &

Powell. 1987).

Boardlll�1Il

si mila ri ty

fi ft h - , fourth- and t h i rd-order

i n thickness to the

cycles documcntcd ( 1 989) from the i mm cd i mc l y Member of the Hermosa

129

Murine l:lll'bolUlfe L'Yl:/es

Five scc t i o ns were measured within t he soulhern ;.II1d centrul po rtio ns of t h e Paradox Basin along canyon walls or the Colo l'lulo and San Juan Rivers and their tributaries (Fig. 2). SU rfi.1CC sections were augmented by two su bs ur face scetiollS (Fig. 2). We will lISC t h e st ra t i grn p h i c 110111ellc1aturc of I l i t e & Buckner ( 1 9H I ) , and w i l l foclis exclusively on Ille upper m e mber of the Hermosa Formntion (J-foIl Hker T rai l Formation of Wengerd. 1973). which for sim­ plicity w i l l be referred to as the u ppe r Hermosa. The rock s described in t h is paper represent lhe penultimate fi l li n g of th e Paradox Basin. and there­ fore have distributions limited by the st ruct u m l elements which surrounded the basin during th e l at est Pe nnsy l van i a n .

by the nco m pahgre Uplift. to t he west and northwest by the E mc ry (Piutc) Positive Arcu. to t h e southwest by the Kaibuh Arch and to the south by the Dc fiunce - Zu ni Positive

bordered on the nort he as t

Gcogl'UI>hic and strutigraphic setting

At t h a t

time, the Pa rad ox Basin was an elo n ga te northwcst - southeast t l'ough

A rca (Blakey. 1%0) (Fig. 2). The Paradox Basin was actively subsiding during Pe n nsy l van i a n t i me. cnus i ng i ncre ased deposition lOwards the basin ax i s . The up pe r Hel'lnosCi increases in th i ck ness from 250m Hlollg the sou t hwesl basin margin (Lewis & arnpbcll. 1965), to more Ih H Il 1 600 III alon g t he basin axis ( Fl'tlhmc & Va ugh n , 1 983).

F A C I ES A N A L Y S I S I nt e r prctat i o n of the preferred facies succession, and therefol'e cycles w i th i n the uppel' i-Iel'lllOStt , req u i res the estnb l ishm en t of critcrin th a t first allow facies di fferentiation. O u tcro p .111(1 su bsu r fa ce sections were constructed wi t h
ffi: ' ---

,,,......

..

componen t bioclnstic and siliciclaslic

grains .

and

structures. Facies bouncinrics were catego r ized as sh a rp. g rada tiona l . cove red o r m iss i n g (in co re ) . Thin seClions were pl'cpared from t h e 259 sa m p l es that we re collecteci lInci .a visua l estimate of percentage and maximum size of bioclastic and s i l icic lasti c g rains was recorded, along wit h a visu a l estilnatc of percentage or c;:lrbonntc/clay m atri x sedimentary

--

-- --

---

--

--

andlor c;llcite ccment.

E lev e n

marine

and non­

identified. Averaged com­ posi t io n al toltlls for sa m pl es from eHch facies, a lo ng with ca rbon "llc texture. grnin type and characteristic sed i mc ntary structures. al lowed t h e gC llcrm i o n of a faci es co m pos i te (Ta b le I ) . Figu res 3 & 4 prov i de ph ot om icrog raph s rcpresentHt i ve of each facies, I n mak i n g an environmcntal i nterprC t;lI ion for a given facies. Enos ( 1 983) suggests th a t no single sedimentological or b i o l ogi cn l clement be considered marine lithofacies were

diagnostic. Rather. he recommends consideration of t h e ve nica l rock sequence. wi t h e m p h asi s on

Study arcn in the Paradox Basin. southeast Utuh. Five surface sections Wl!I'C mcasured along the eu nyons of the olom
Loopc . 1984.)

faci es transitions. Wi,lthcr's Law stares that (he

vefticHI succession o r facies results

from the Interal of juxta l)Oseci depositional environments. I n tu i t ivel y , the l'ecQnstl'ltction of i alen1 i fildes re l a�

m i grat i o n

lions is a straighlforwnrd Lask, since t h ese

lire recorde d successively

relations

in the vertical sequence. A

complication. as pointed out by Middlctoll ( 1 973).

is that Wnlther's Law app l i es 10 stratigraphic suc­ w i t hou t major breaks, Facies separated by unconformities do not nec cssilr i l y reprcsent the j ux ta posed de posi ts of con ti gu o u s depositional cessions

environments.

'5 Table I. Ocs("Tiplions and imcrprcI31ions of facies and locir ocposilioliat CIWlronmcnLS: Icltcring scheme non-marine (K)

renecLS speclrum of cn\'ironmt:nIS

from deepest mari ne (A) 10

Facie!> dcsignal ion

Ope"

Facies inlcrprclation

Euxinic basin

marine

10 sho .. 11

Tcxlurc andlor

Organic-rich

Wu4:'kcslonc

Boundstone

dassiftcalion

slope

mudstone

0

C

B

A

Algal mound

Shool

E

Hypersaline '''goon

Packslone 10

grain!:llOnc

Mudstone

"

F

G

Shoreface (a foreshore

Shoreface to foreshore

Coastal plain nuvial andlor

Ooid grainstone

Siliciclastic packstone

C1k.lrcOUS argilhu.:cous

10

siltstone

Iii hie

arkose

sandstone 10 bioclaslic grainslooc

Planar t.TOSS·bcds. occ;-cJSional

Massive to thinly

laminatcd .

low-angle tabular and small·scalc

burrows

rhizoliths. mudcracks

trough cross-beds

Largc-SC'.t!c. high·angle trooghs.

10=

grainstone Bedding and sedimentary

Grain-Row (turbiditc)

structures

laminac

Massive to inclincd laminac

Massi\-c

Planar

cross-beds. abu ndant

Massive to laminatcd

Planar

cross-bc(b

burrows Dominant carbonatc grains

Crinoid. brachiopod. bryozoan

BrJozoan.

crinoid.

Phrlloid

alg:lc

rorum.

rugose coral.

BrJozo:lO. crinoid. (oram,

Brachiopod.

ostr.lt:odc

Ooid

brachiopod

Pcrcentage

carbonatc grains and

Trace

(-0.50 "') N=6

• ,%

(- 1 ..10
N = 39

N=3

(-0.6< "')

3% (0..13 "' )

N = 21

N = 19

26% (2.60 <\»

20% (3.30 ""

.5'" N = 22

n% N = 19

13%

( -2·50 lP)

29%

53%

(0.50 "') N= 15

Coaswl plain flu\1<11

Lacustrine

Micaceous arkose 10

SilK:iclaslic

Mudstone

Bryozoan.

Lithoclasts

LilOOclasls

Lithoclasts

and di,'cf'SC bioclasts

and diverse

and di\'crsc

bioclasts

bioclasts

( 1 .60
19%

3% (0.50 <1»

( 1 .20 <1»

11% ( 1 .87 "')

N = 19

N = 31

N= II

N=91

.7% (3.10 "')

.>1%

45%

I....

Massi\-clo horiZOfltal

laminae

rhizoliths

crinoid. fornm. brachiopod

brachiopod

K

A(.'Oli:ln

Ostracode

16%

8%

Pc,rr;:cntagc siliciclastics and a\'cragc maximum sizc

(J.3O ",)

N=J

N=6

(2.80 "') N = 39

Intcr·gr.mular

s.t% N=6

51% N = J9

87% N=3

"olumc as percentage malrix. cement and/or cia}'

N=n

N = 19

3% (2.50 "') N = 16

.......

N = IS

<0%

(2.50",) N = 19 .,% N= 19

J% ( 1 .50 <1» N=3

1%

N=JI

(3.50 ..)

50%

36%

....%

N = II

N=91

96% N=3

,\' = ] 1

§

"'

(2.50 <\» N = 91

g.

� t>

(1.10 91 N = 1I

::,.

"-

a\'crase

maximum sizc

;"

"

N=J

r-

� <> ."

"

Murine ClIrbOl/life (:ycle,\'

131

Fig. J . Photomicrographs representative o f facics, Bnr scnlc - I lllrH. (n) Fncies A; Gibson Dome core a t 759 tn . Note the

lamina along which relmively coarse siliciclastic grflil1s nrc concentrated. (b) Elk Ridge core at 661 m. DiagllOl:itic of this f,ICics is the IIbuncluncc of diverse fossil fragmcnts sUPPol'tcd by lIliCl'itc matrix, Cllld the relatively low pcrcclltllgc of siliciclClstic grains. (c) Facies C: Elk Ridge core at 638111. Diagnostic of this "!Ides tll'C phylloid algal grains obscrved trending fr0111 thc upper Icft to lower right llcross the photograph. (d) Fncies 0: � I k Ridge core at 482 m . Note high concentratiOIl or relatively coarsc siliciclustic lind biol:iastic gruins which have fitted ond/or suturcd COI1I<1C{:-,. (e) Facies E; Gibson Dome core 1\t 541 m. Fossil fmgmcnts lin: uncommon. Note lurgc brl.lchiopod fmgrucilt (u l>PCI' left), and disarticulated ostracod valve (middle right), Very fine silicicJustic gruins nrc common. but arc sLispended within micrite matrix. (f) Facies F: Gibson Dome core tit 397 m, The internol slructurc of ooids is rarely Pl'cscrvcd. but whcn present, shows concentric laminae. Note open fubric,

1 32

S. C.

A/ch'ey

"IU' D. B.

Loope

Fig. 4. Photornicrographs representative of depositional fades. Bar scale = I 111111 . ( Ol ) Faci es G; i1ppro;'l; i m alcl y 165 III above base of Dark Canyon section. (b) Facies 1-1 ; approximately 38 m ..bove b,ISC of Dilrk Canyon sccliolL Note bimoda lity of the siliciclastic and highly abraded ca rbo nate grains. Ma ny of the abl'adcd c,II'bona\c li thoclilSIS Me reworked fragments from facies B and E. (c) Facies I ; Gibson Dome L,,()rc al 423 m. (d) Facies .l: a ppt'ox i mmcl y 46 III IIbo\'e base of Cane Creek A n ticli ne section. This facies is ty pic nl ly composed of medium- ("0 coarse-grnined. I'clalivcly imlllat ul'C sil iciclastics. Also diagnostic is the presence of conrsc mica grains (rlrrow). (c) F
133

Marille <:ar/JUIU/le c;y(.;/{!s MoSI rece n l ly . Busch &

I

Roll ins (1 9R4). G ood w i n

& A nde rso n ( 1985) nne! Van WCl go ner el af. ( 1988)

L-. C -.J

s u ggeSl th a t t he marine s t rtl l igra phic record

is lurgely (geo logi cn l ly ) instantaneous Hoodi n g surfaces (d i astclll s) overlain by progradmionnl sedi lllentary deposit s. The resu l t i n g cycl es arc th i n (3-30 Ill) , and reco rd
Using the method of Walker ( 1 979), we applied

Markov elwin anal ysi s to the griJdutionol

marine f"cies

�

Deep A -+ O - D � E � F � G Shallow

Since ff.lcies

was

rHrc l y

observed on outcrop or

i n corc, ils assigned rclative water depth is ba:-;ed less on slmistic.lI infol'llWlioll, "Ild more on the was only ob­

qunlitative observa tion thut fncies served graci;.Hionalty preceded

by

fucies

grada tio n ally succeeded by facies E.

faci es

O. ;md

onsequcntly,

is te n t a t i ve l y considered to

be n l a tera l

equiv..llent of fnc ic s D. This preferred succession suggests that although ;\brupl

marinc lil hof;lcies

contacts c..\used by storm events Illay be prese n t , they are superi m posed o n t O a fifth-order cyclic record.

Non-marine facies wcre not sta t i sticall y

analysed because

( i ) their occurrence is l i m i ted

to l11ajol' Ullconfonnities sepH rating fourth-order cycles. il1lcJ ( i i ) !1uctuating bOIse-level seems u n l i k e l y to be c1carly expressed in a succession of no n- m a rine facies,

Based on both the ph ysi cal feat u res of cuch facics and

their

preferred

progradational

succession.

deposi tiollnl cnvironments MC i n terpreted to have

A B ) through a shoal-bar complex ( , D and E) to lagoonal ( E ) , to shoreftlcc and foreshore ( r and

successions within fift h-ol'der cycles (Tuble 2). I n the

gnld n tionn l l y ranged from open marine ( facies

gencration of the trullsition count ll1<.l Irix, a total

and

of S6 row/col u m n 1l1ism:Hchc� were recorded; we

intcrprct these to re Aect t hc analysis of only unidi rec­

G ) and thence to n mosaic of aeolian. nuvial und

tional progradational facies tl'allsitions (Table 2 ) . To

lacustrine environments (Tablc I ) .

determine the significunce of ench gradational facies transition. binomial probabilities were cHlculated

accord i n g to

C Y C LI C IT Y

the procedure of Harper ( 1 984) (Table

3). The smaller the binomial probability. the more s i gni f ica n t the transition. b i nom i al fifth-order

p robab i l it ies . cycles

have

onsider�Hion of lhcse

therefore, the

suggcsts

followi n g

that

pl'efelTed

p l'ogm dalion al marine facies succession:

Thus far. o u r discllssion o f upper J-Ierlllosu cyc l i ci ty

has been limited to 11 de m on st rat ion of the preferred Walthcrian facies sliccession within fifth-order cycles .

The presence of these cycl es suggests potent i a l for

a

Tuhle 2. Culculatcd binomial probabililics (applying the procedure of Harpe r. 1984) of observed grad:uiona t facies transitions for positive valucs within the probability dirference Imllri»;

Facic� transition

N

A- IJ Il- C 1l - 0 -E O-E O-G E-F E-G F- G G-O

21 21 I 17 17 6 6 2 I

�

/I

/1

"

Binomifll probabilit y

9 3 8 I 7 9 3 2 2 I

O.I�7 0.083 0.278 0.732 0.375 0.350 O. I IS 0.275 0.255 0. 1 79

0.8 1 3 0.917 0.722 0.268 0.625 0.650 0.882 0.725 0.745 0.82 1

2.796 X 1 0 7 0.251 0.206 0.732 5.735 X 10-' 0.1)<)<) 0.025 0.524 0.065 0.179

S. C. Atchley fllld D. B. Loope

134

Tublc 3. (a) Trunsition COUIll IlHllrix. (b) observed trilllSilion probabilities. (e) transition prob,ibilitics f r a runclolll scqucll(.'C and (d) probability dirrcrcn<:c matrices gCncrulcd through Mmkov chain analysis: the high number of row/column rnism:llchcs is because oilly gr'ldntiollnl r'lcics trnnsitions within fifth-order cycles nrc considered: analysis wos limited 10 such sucl.-cssions. because marine facies conW,(s lit abrupt lifth·ordcr boullClarics may represent non-contiguous depositional environments juxl:lposcd due to nlpid base-Ie"el rise

(a) Trunsitioll count matrix A

B

D

F

G

9

A B

7

3

I

7

D E F G

o

3

9

10

15

Rowlcolumn m i smatch

9

9 2 2

17 I> 2 I

9 12 2 7 9 13 4

14

57

56

21

2

I I

3

Column sum

Row sum

(,

(b) Observed transition probubilities A

B

A Il

C

0. 1 4

G

D

E

F

0.38

0.33

0. 10

0.05

0.06 0.50

0.53 0 .33

I

0.41

D E F

0. 1 7

I

G

(c) Tra nsi t io n probabilities ror (I !'(IIHlom scquclH.:C A A B

0. 1 9

0 0

D E

F G

IJ

0 0 0 0

0.16 0.22 0. 1 8 0. 1 6 0.16

0.06 0. 08

D

E

0.2 1 0.28

0.31 0.42 0.27 0.37

0.18 0.G7 0.06 0.05 0.05

0.20 0. 1 8 0. 1 8

0.27 0.27

D

E

-0.06

-0.21

+0 .06

+0. 1 0 -O. I �

F

0.12 0. 1 7

0. 1 1 0. 1 5 0. 1 2

0 . 29 0.39 0.25 0.3 5 0.27 0.25

0. 1 1

(d) I'robnbility difference matrix A

A

B

+0.81

IJ

D E F

-0. 1 6 - 0.22 - 0. 1 8 - 0. 1 6 - 0. 1 6

-0.07 -0.06 -0.05 -0. 05

-0.D3 -0. 1 8 +0.82

F

G

-0.31

-0.12

-0.09 +0.73 +0.04

-0.07

-0.29 - 0 .34 -0.25 +0. 1 8 +0.06 +0.75

- 0.27 -0.27

cyclic hierarchy in which fifth-order cycles SLack into transgressive and regressive sets within fOUrlh-orcicr cycles (Vail el (II. . 1 977a: Posamcnticr el (1/. . 1 988: Posnmenlier & Vail, 1988; Van Wagoner el al.,

-0. 1 1 -0.09 +0.38

-0. 1 1

1 988). This stratigraphic framework was applied to the upper Hermosa to deLect the hierarchy and mechanism(s) of cyclicity. It is impOl'l
Marine Clfl'/}olltlle cycles

promoted by the previously cited sequence str·nti· gruphcrs is a qualitative hierarchy, while placing an

'order' 10 the cycles is time·implicil ( M i a l l , 1990). HowcvcJ'. thc nrnount o f time rcprcsented by t he

135

Loop e ( 1 9H5) considered

the marine beds a product

of sen level rise, i.H'ld lhe nOll-marine beds a product

of low stnnd.

Rccognition

of decpening (rc [ l'Ogl ad m i o na l ) and '

The orderi ng o f upper Hermosa cycles

shallowing ( p rogr"ldational) fifth-order cycle sets requires assignment of relative watcr depths to each

( non-li me-specific) ordering. The similarities betweerl

(i.e. rising 01' falling) betwecn fourth-order cycles

the quantitative h ierarchy described by olclhalllmcr el lIl. ( 1 989) from the underlying Paradox Member.

Hl::iS igncd to express rhe relt1tivc wHfer depths of each

upper member of the H crrl'losa is very poorly can·

strained.

p resented i n this study is, therefore, a qualitative

our hierarchical ordering of the upper Hermosa (lnd

facies (Tab le I ) . The d i rection of sca level cha nge

wa� dCLCfmined semi-quillltitativcly: numbers were

facies in the previously described ideal Walther's

howcver, suggcst thal the two units Illay record

succession:

SCCIUCIH.:e stratigraphy

J, I Deep A --7 B --+ D --+ E --+ F --+ G - H - K Sha l low L. --.J'

cycles of similar duration.

2

Application oj cOllc:ep'

3

4

5

6

7

From this, trunsgrcssive ( w i t h each successive fifth·

I n outct'Op and the subsurface. cyclicity within the upper Hermosa is Pl'Olloullced, consisting of fourth­

order cycle having a progrcssively deepcr�water

thickness fro m

shnl lowcr-watcr facies asscmblagc) fifth-order cycle

order

ma rine-non-mari ne

couplcts

8 to 46 III (Pig. 5 ) .

Fig. 5. Acolian cross-strata resting directly on subtid,1I marine limestonc (uppcr member. Hermosa Formalion, appro:..: il11<1lcly 24 km upstream from rhe mOluh of D,ltk C'IIlYOIl ) . M:ln is slanding orl knife-sharp tlooding surface between oolitic grainstonc (facies F) and shelr wnckcstone (facies 0). At shouldcr he ight , IOW-SIUIle! acolinn sandstonc (racies H) abruptly overlics tllc t ronsgrcssivc lirth-ordcr cycle sel. Regr'cssiollal firlh-order cycles succeeding rJcies 13 ,Irc not present. ,II1d ,O'C thought IQ h(lvc bcon removed by de(l;)tion.

In

ranging

in

a gcncral sensc,

facies assembl age ) and regressive (with each suc­

cessive

fifth-ordcr

cycle

having a

progress ively

1 36

s. C.

A/chley lIlld D. /1.

selS were identified. and toget he r define founh­ order cycles. Fi ft h·o rdc r t ral lsgressive and regressi ve cycl e sets w ithi n cneh fourlh-order sC �l lIe ncc were determined for (III s u rfa ce and subsurface sec ti ons ( Figs 6 & 7 ) , Uninterrupted successions of nOIl-marille facies (aeo l i a n , coasl H I pl ain (f"luvial andlor loess) (Ind lacuStrine) i.lbruptly overlying marine transgressive or regressive deposits were i nterpreted as low stand. As will be discussed Imel', this designation is tentative for cycles capped by coas w l plain facies, inasmuch as V
A recurring theme of sequence stratigraphy is that

Loope

cycl i ci ty

resu l ts from Hccolllmoc.l'lIion ch a nges which may record eustatic sea level change (Kendall & Le rch e , 1988). For the cause of cyclic c h ollges i ll g lob a l se
record simil�ll' high-frequency, ghlcio-eustatically driven cycles. U pl i ft o f Ihe A nces tral Rockies and subsidence o r the Parndox Basin were greatest during D CSn'loincsinn time, bUI conlinued through lhe end of the Pe nn sy l va n ia n ( Ma l lo ry . 1975� Stone, 1977, Fra h m e & Ya ugh n , 1983, Klulh, 1986). There were, thus. at least two sQ u rces of sed imenta ry accolllnlodat ion. Evidence

within

the upper Hermosa suggests

CUSli:Isy. I'ather than jerky subsidence, induced IIfrh- and fourth-order cyclicity. Because t he Paradox Basin was tectonically active d u ring the Late Pcnnsylvanil.l ll, it m igh t seem thHt instantilneous subsidence, as su ggested by i,ne ( 1986). co u l d havc caused episodic base-level ri s c and, therefore, deposi[ion of fifth-ot'dc]' cycl cs. This is cons istc n t with the variable thicknesses of fifth-order cycles; they do not show a predictable increase i n th i ckn ess upsect ion wi1hin transgressive deposi ts ill res pon se to .� p rogre ssive incrcHse in Hccomnlod.ltioll, Or a similar decrease in thickness upsection within the re gre ssi v e cieposits i n rcsponse 10 a decrease in acco lll m oda t i on . The subsi d e n ce h ypoth es is , however , fa i l s to e xpla i n the repctitive, orclcl'ly succession of rctrogrHd,Hional ,lnd HggrclciotioMI to progradational fifth-order cycles, Jerky subsidence would induce o n l y a bHsc-level rise, As n resu lt , ca rbo mHe sed im e nts wo u l d aggrad e to the raised base-level , and wo uld be grada tion al ly succeeded by progradational lidal flat facies . Shelf faci e s would nOt become desiccated 01' exposed to oxidizing meteoric water. Ex pos u re surfaces (I'ourth·orcler se­ q ue n ce boundaries) nbruprly sepnl'at'e deeper-water that glacial

8' Ridge No.

Gibson Dome NO. 1 T30S R21 E Sec. 21

T37S Rl9E sec. 23 ""

'"

Honaker Trail

T41 S Rl8E � 29

,

(I)

'" tHe

.,---. .

G

F

(3)

(')

.".

A

:;;:

"

�. � " " � ""

S!

§

.,.,.,

....

-

'"

� Q.

o �� � 1 1 1 1I 1

�

--

d__

fu\'l

Regressive

b:J

Aeoion LCl'NStand Deposits

f7l22

Tronsgressive

�

Coastol PIoin Lowstand Deposits

Fig. 6. Stratigraphic columns fo. Gibson Dome No. I . Honake. Trail and Elk Ridge No. I . Recorded in column ( I ) for each section is thc vertical distribution of transgressive. regressive and low·stand deposits, along with the fourth-order cycles in which they occur (the numbers used to idc. m ify each founh-ordcr cycle are unique to each measured section). Note that the Honaker Trail section and Elk Ridgc corc have the most complete marine record (i.c. founh·order cycles with both mlnsgrcssi\'c and regressive deposits preserved). These more 'complcte' fourth-ordcr cycles arc ahnosl always capped by tcrrestrial coastal plain to nu\..Jal low-stand deposits. Col umn (2) is a graph of relative sea Icvel generated by assigning relativc water depth values to facies H/IIJ/K (shallow) through to A (decp). and then shOlding in the corresponding \'alue for each facics documented, such that the further 10 the right the shading occurs. the deeper the relative waler depth that is recorded. From this scmi-qu3mil3rivc graph of relative sea level. if appears that the fifth- and fou nh order c)'clcs shown in columns (2) and (1) are in (Urn superimposed on the third- and sccond-ordcr eycles shown in columns (3) and (.t) respectively.

-

w ....

S. C. Atchley (/ltd D. 8. Loope

138

Spanish Bottom

Oark Canyon

T3:lS AISE Me. Z4

� IIoVIlKIe 31 S3'30' W longitude

1 1 0 12'00'

�)

�) (I) H.K w;;;-r,

G

F

E

C.O

B

(I) H.I( -m=-r-r-

'"

Cane Creek Anticline

G

F

E

C.O B

A

Big Spring Canyon

T26S R21E MIC. 36

N 1a�lude 38 13'00'

W IOngll'ud, 109 49'30'

I2l

t:illi

Regrosslva

rn

Aeolian Lowstand Deposit.

!?l23

Transgressive

�

Coostal Plain lowstand Deposin

marine facies from ove r lyin g terrestrial low-stand

deposits ( Fi gs 5 - 7 ) . Enos & Perkins ( 1 977), Be
( 1 982) llnd H a rd i e ( 1 986) incliclltc that exposure sur­

faces capping QualCrnnry c�lrbonale shelf sequences result from higlHlnlplitucic glacio-eustatic sea level

f1uclu<.lIions, This is because (he nlte of sc,) l e ve l

lowe ri ng exceeds t h e rate of Lidal flat pl'ograd:H ion

(Hnrdie el lll. , 1986: Read er "I. , 1986). As a result,

all e x posu re surface is fOl'nlCd with s h e l f marine

units abruptly overlain

by

terrestrial

low-stand

deposit'S. The giant desiccation fissures descri bed by Loope

& H averland

( L 988) and the evidence for

oxidntioll of pyrit ized fossils ( Loope

& Watkins,

rig. 7. Slraligrophic

COIUIllIlS for DMk ::1I1yon, Sp:'l1lish Bottom. anc I'cck Anlicline alld BiS Spring ,u nyon. ohunn ( I ) shows the d istl'i but io n of transgressive, regressive nncl low-swncl deposits 1.II0lig wi t ll the rourth-onler cycles in which they occur (the !lumbers lIsed to identify cueh fourth-oreler cycle IIrc unique to each measured section), Unlike the sections at HOllaker Trilil rll�d Ik Ridge (Fig. 6). marine lII)its at these sections (Ire vcr)' thill find rorely hnve tr:lllsgl'cssivc mHI'inc deposits succeeded b)' marine regressive deposits. Transgressive deposi ts nrc IIcarl), always abruptly overlai n by thick
1 989) fr0111 the upper

Hcrmosa marine units are

clCtll' evidence nOt only of subacrial cxposure, but (\Iso o f Sea level fall.

BeC(lUse i t h.ly beyon d the trough axis from the

Uncompahgre

front,

the

Cane Creek Anticline

section (Fig. 2) sho u l d have been ins u l a tcd from

thc innux of clastics, yct be in a posit ion where the effects o f subsidence would be maximize 1. Low­

(l111plitucic sea level osci llations

produ<.:cd

by jcrky

subsidencc would have n l lowed the acculllulation of relatively com p le te marine cycles. H igh-ampl itude sca level oscillations, on thc other hand, would

have brought about total wit hdrawal of the sen

MatiJle ca""Olltlle cycles Deeper

a

_._-

139

Deeper .......

b

..

H-KI GI F I E Ic.t( 81 A

H·KI G I F I E I� B I A

H

Lowstand deposits Cyc� 6

H

F

�

.91

�

� OJ

"E 0 i: u;

Q; "E 9 J:

..

5

B

Bas<> Top

6

In OJ

Lowstand deposits

for Cycle 1 2

Cycle

11

Regress;"'a deposits

In .,

OJ

�

F

D

"*

- -8 - -

Q;

Q; �

'0

i: u;

0

i:

..

H

�

Transgressive

deposits

0

G Lowstand deposits (a) Example of an incomplete fourth-order cycle (cycl e 5; Dark Canyon). In t l l is illSWIlCC, the aeo l ia n dominated low-stu nd deposits arC abrupt ly o\'c r'iain by two tr
Fig. 8.

(even

though tectonic Hccomlllodmioll was at a

I t i s poss i bl e t h a t thi rd-order cycliciry is a busin­

maximum), thereby exposing marine units to tc r­

wn rd mallifcstalioll of episodic tectonic pu lse s which

l'estrinl erosional and deposi tional processes, The

Maek

sect 1011 is dominated by tC 1'1'est rial low-smnd deposits ( Fi g .

7, Table 4), attesting to the dominance of hi gh ­

amp l i t u dc . glndo-eustatic se a level l1uctuations.

From thcl:ic obscrv'J l ions, it appcars t lHl1 t ecto n ic

accommodation space

W(IS

ad de d

so

l:il owl y Ihn!

the influe nce on fifth- '.IIld fo u rth-order cycles was negligible. If so, thell it seems that tectonic cyclicity

should be man ifested at a lower order. Goldhmnmcr

el (fl.

( 1 989) suggest tiull sequences within the sub­

& Rasm ussen ( 1 984) suggest led to depo· sition of a l l uvial megacycles within the Pcrmo­ Pennsylvanian

utler Formation on

the

eastern

margin of t h e Pa radox Basin. Th i rd-orde r cyclicity may

be I-l t ll'i b u ted to eithcr a tectonic 01' a long-term

glacia l mechanism (Miall, 1 990), The only cOllvincing c v id c n ce of a tcc to n i c i n tl ucncc is the observation thal the

th i r d-o rd e r

deepening event at the LOp

fhe G i bson Dome and Elk Ri Ige cores consists

of of

fifth- and fourth-oreler cycles dominate I by shal lower­

sh a l lowi ng a n d deepening set w h i c h defines ;:1 200111

water rc.,des t ha n the t h i rd-order deepening event at the base of these sections (Fig, 6), Furthermore.

the graph of relmive water depth for the Gibson

G o ld h a m m e r el al. ( 1 989) in the underlying Paradox

jacent Para.dox Member o f the I-IcI'n10sa occur in

;\

t h ick . t h i rd-order cycle. Based on obscrvation of

the third- and fourth-ordcr cyclcs dcscribed by

DOIne. Elk Ridge tlnd Honaker Trail sections. wc

Member arc domi mued by

ident ified

upper H e nn os;) becomes progressively do m i na ted

a

2 1 3 m t h i rd -orele r cycle which is similar

i n I hickncss 1'0 the th ird-order cycles of GoldlHlml11CI' el

al.

( 1 989) i n Ihe

underlying Pnrn,lox Member of

the Hermosa Formation (Fig,

6).

I'IHII';110 facies, while t he

by terrestrial low-stand deposits upscclion (I�ig.

6).

From this, it appcHI'S that t h i rd-order cycles w i t h in lhe Paradox Mcmbcr and uppcr Hermosa may be

140

S. C.

Atchl"y {/lid D. B.

Loop"

Tuble 4. Tota l number of mClfCS (pcrcenlllg.cs in pnrcnlhcscs) occu pi ed by c!lch facies for each section: lowls marked with ustcrisk do 1101 include covered inlel'vllls or zones of missi ng core; sections include Spanish Botlom (SB), Elk Ridge ( R). une Creek A n t icline (C ) . Big Spring "11)'011 (BS ) . Honaker Twit (HT), Durk Ca nyon (0 ) find Gibson Dome (GO) Fncics

9. 1 (6)

A

29.2 (8)

15.1 (7)

13.7 (9)

36.6 ( 1 0)

1 .5 (I )

76.9 (21 )

I) 14.6

L02.5 (28)

( 16)

19.9 (24)

GD

3.1 (2)

3.0

«

50.2 (33)

B

D

HT

BSC

SIJ

22.0

(6)

22.0 (6 )

16.4 ( 18)

39.0 ( 18)

47.6 ( 13)

10.0 (I I)

17.3 (8)

1 .5

2.7 (3)

7.6 (5)

D E

6.1 (4)

F

«

G

I) 73.2 (20)

H

32.9 (9)

4.2 (5)

26.0 ( 1 2)

3.0 (2)

1 1 .0

12.5 ( 15)

32.5 ( 15)

7.6 (5)

7.3 (2 )

73.0 (48)

25.6 (7 )

36.4 (40)

39.8 (48)

8.7 (4)

107.9

4.6 (3)

65.9 (18)

4.5 (5)

6.6 (8)

77.8 (36)

12.2 (8)

2.7

6.4 (7)

1 .5

I)

«

«

I)

(3 )

69.6

( 19)

(71 )

69.5 ( 19) 29.3

(8) 3.7

3.U (2)

K 91

366'

152

Tow1

83

(I)

152

2 1 6.4·

366·

s upe ri m pose d o n a longer-term. tcctOlliCHlly induced

been controlled by gla ci a l eustasy. not by a more

second-order cyc l e

local

( Fig . 6 ) . This i nte rp re t a ti on fol­ lows Ihose of Ma l l ory ( 1 975), F ra h m c & Vaughn ( 1 983) a nd Kluth ( 1 986). who suggest muximull1

mechanism

like deIUl-swirching. Bused on

similurities i n the

relative sea level cu rvc ge llcra t cd

uplifl

correlate both the seco n d-o rder episode of basi n

a n d subsidence of the A n ces t ra l

Rockies

for Ihe upper Hermosa (Fig.

6),

il is possibl e 10

d u ri ng de posi t io n of the Paradox Member (Middle

n i l and the thil'd�order cycl es beLween the

Pe n nsylvan i a n time).

co nt i n uous secti o ns

decrcilse

in

followed by

,-\

prog ressi ve

tectonism during depos ition of lhe

upper H e r m osa and Rico ( LlItc PennsylvHnian to

and Honaker Trail).

(

most ,ibson Dome, Elk R id ge

The fourth· and fifth-order cycles arc a no ma l o us for two rCHsOnS. Fi rst ly , t hey arc extremely hard to

E..l rl y Pe rm i a n ) .

corrclatc. even on a local sca le. Lewis

( 1 965) Il E H E A D E D S E Q U Il N H Y P O T H ES I S

Il

&

n m pbc l l

noted t h e lenticulm nature of upper Hermosa

l i mestones. Within our HonakcrTrnil and Elk R idge sections, which

nre

only 44 km nport, only one-third

to ollc-quarter of the fourth-order sequences from

The lateral cO ll t i n u i ty o f dcpOSitionll1 cycles o r indi· vidual components of de pos itio na l cycles can be an i m porta n t clue to the control of cyclicity. B ecllllse he co u ld t race i n d ividual thin black shales fo r h u ndreds

of k i l omel res .

Heckel ( 1 977)

a rgued I hat Ihe de­

positional cyc l es conta ining the shales must have

Ik R i dge

can

be correhHcd (Wilh marginal con­

fl Icncc)

to sequences in the Honaker Troil section

9).

orrclmion of foul'lh- and fiflh-ordcr cycles

(Fig.

was accom pli sh ed by looking for simil ari t i es

in t h e

shape of the !-iemi-qun n t i W l ivc gr n ph of relative sea

level a l o ng cnrrcspondillg port inns of the thi rd-order

141

Marine carbollate cycles

sea level curve generated ror the most continuous sections (Figs 6 & 9). Secondly. fourth-order mnrinc deposits arc absent rrom many sequences ( Figs 5. 6 & 7 ) . Only the Elk Ridge and Honaker Trail sections have a significant number of fo u rth-o rde r cycles with ,'egressive marine deposits preservcd, FOlll'th-order cycles a t G ibson Domc, Big Spring Cnnyoll, a ne reck, Sp(lt l is h Bollom n nd Dark allyon h a ve virtually 110 rcgt'es­ sive deposits. Furt hermore, nOI only do the Dark anyon and Spanis h BO Hom sec t i on s ge n e ra lly lack regressive marine deposits. they also have thill. deeper-Willer tran sg ressi ve deposits ( Fig. 7). This is interesting considering that the Elk Ridge and HOllakcr Trail sections have coastal pl'lin (facies I ) dominatcd low-stand dcposits, while the Big Spring anyon. a ile reck A nti cl i n e Spanish Bottom and Dark anyon sections havc aeolian dominated ,

low-sli.lnd clcposilS, Sections dominiHcd by coas!;'ll plain 10W-Sland deposits (nuvial transport processes during sub(lcrial exposure) have the mosl complete m;.lrine record. while sections dominmed by aeolian IOW-Sland deposits (acoliall transpol'l processes during subaerinl exposure) have the most incomplete m u r i ne record ( F i gs 5, 6 & 7 ; Table 4), Ex p l a n a tions must' be p rovided for the distribution of regressive marine and low-stand non-ll1arine de posi ts . and for our inability to correlate many of the fourth-oJ'der cycles within the busin. Shallow marine racies C-G, which werC for th e 111051 pari deposited above wave basc . arc less abundant in sections with aeolian dominated low­ stand deposits (Ta ble 4). Goldhammer el al. ( 1 987) d escr i bed a Ihick sequence o( Tri assic cmbonates i n which cycles were capped by subtidal fncics thal had been strongly altcred by meteoric diagenesis. The Elk R id ge No. 1

Honaker Trail

H4< G

Fig.

F

E CIO B

A

9. Detailcd slnlligruphic

columns for portions of Elk Ridge tlnd Honaker Trail sections. showing correlalions of fi fl h- and fout'th�ordcr cycles rro m (I basin margin (Holluker Trail) 10
Gradalional boundary Knife-sharp conlact

m

CJ

Coaslal plain (facies I) Lowsland Deposits Aeolian (facies H) Lowsland Deposils

S.c. A lchle), {Illd

142

fnci es wns . Hl ri b u led to Lh c h i gh eust at ic sca l evel c ha n ge : sh o rel i n es m i gra ted fas ler t ha n co as ta l sed i me n ts co u l d pro­ grad e , The l ack o f fou rt h-order regressive d epos i ts in o u r basin-ward sections might be due to a si m i l a r Irick of peritidal

am p l it ude o f

mcchnn islll. U n l ike t h e Triassic example, however, palaeosols i nd ictl t ive

of long epi sodes of su bae ri a l no t present at t h e tops of Our fourth­ order cycles. The lack of s u ch palaeosols in our sections tllle! the a bru pt con tacts betw een su b tida l m a ri ne rock s a nd overl y i ng aeolian strata suggest lhat erosion may have re moved p a rt o f t h e m a ri ne reco rd p ri o r to de pos i tion of th e aeolian strata. Patterson & K i nsm an ( 1 981) st ress t h e i m porta nce of the coa sta l h yd rologi ca l regi m e in the preserva t io n of H olocen c tidal flat mudstoncs nnd ev apo r i tes margin a l to the Persi a n G ulf. They indicnlc t ha i prograd a t ional sedi m en ts d epos i ted d uri ng Ihe last 4000 - 5000 y rs w h ich are a bove the regiona l water table are being st ri pped by wind erosiol1, We argue that thc im pol't3ncc of den ati on would be much grcater duri ng pe riod s of custatic sea levcl fall. I t see illS l i k cly t h a t i f high�amplitudc sea level osci l1clliolls outpaced coast ..ll plain (f�lcies I and .I) progrndn t i o n . and i f the continued fnll or sea leve l n l lowe d I he g roll nd wa te r Inble LO drop be low the sed i mc nt su r fa ce . mnrinc carbonates would have been v u l n e ra b l c to deflation. Sand-sized murinc ca rbon ates would have been stripped from the cCll lral and wes t e l' n pOl'lion of th e basin and would have evcn t ua l l y acclIlll u lmed do wn wi n d as low-stand aco l i nn i tcs , A rca s n l o ng the southcrn basin ma rgi n h ad ma rine h i gh -s ta ll d deposi t s that wc rc covered by a n arl110uring m:) n tl e o( coast;)1 p!;,lin sediments soon aftcr e x posu re (Fig, 9 ) . Aside from ex p l ai n i ng the lack of palacoso ls . the scoured nspect of the cycle tops (Ind the distribution of preserved marine 1111d a eo l i a n sands. this would a lso he l p to exp l a i n th e h i gh percentage of m a l'inc a l l och c ms il1 Ihe exposure �'rc

D . B . Loop"

facics, the more u nderlyi ng facics i t (orms n n crosional contact w i t h . Aeo l i a n facies H has the most ncgm ive column sum (Table 5) und t hc refore may h;wc been deposi ted on nn erosi on a l 10 nOIl­ deposi t i ona l surface. Facies I and B also h ave h igh negat i ve values. The negative column s u m for facies B is a rcsponsc to d isco nform ab l y juxttlposcd facics a l on g fifth-order flooding surfaces ( Figs 5 & Sa & b), while the nega t i ve column sum for fncies I is B re s u l t of de pos i ti o n onto an erosional to non ­ given

dc posit io ll a l

su rface.

As

will

be

demonstrated,

however. we consider fluvial erosion of mal'illc st rat a

1.0

ha ve been less s ign i fi ca n t Ihan wind deflatioll,

and. i n f(lct . l11ay lHtve en h:lncec1 t h e prese rv a t i on of

u nde rl y ing marinc units, Mud·rich. cohesive sediments can be dcflat ed

K i nsm a n , 1981), b.1I p robabl y n ot as read i ly a s non·coh esiv e (sa nd -r i ch , gnln u l a r) sedimenls, Facies A , B a n d E h a ve a hi gh per­ centage of interstitial Ill ud ( m icri te) , while facies C. D , F :: lIld are m u cl�poo r to ITI ud· free (Table I .

( Pa t te rson &

I::"i gs 3 & 4). Wind reworkillg i mpl i es t hat ex pose d

IlHirinc

sh el f scdimcnts wcre

u n l i t h ified,

Pu rser

( 1 978) and H i rel & Tucker ( 1 988) su ggest thnt a

cl osed fabric. which is recognizcd by fillCd. s u t u red and crushed grnins, indicates thai early ccmcnts were nbscnt. Facies D , F and G were an a l yse d In de t e r m i ne if they have an open or cl osed fabric. 1\11 sh a ll ow marine facies. cxcc p t facics F «()o i d gn_I inslOl1c), h,we n cl osed fabric and arc thus i n ter­ pretcd to have bce n u n co nso l idmcd u po n ex pos u re , •

A cco rd ing to Ward ( 1 973)

a nd

Wright ( 1 988) the

dational nature of a gi ve n facies to u ndc r ly i n g facies.

of e:uly cements that d ev e lops i n marine c<-I rbona t cs du r in g ep i sod es of subaerial exposure is climate de pendent : thc morc wmer that moves t h ro u gh the pores. the morc ceme n t is empl aced . Prev io usly reported obse rva t ions or th e upper Hermosa (L o pe , 1985. 1 988; Loope & Haverla"d. 1 988; Loope & Wa tk i n s, 1989), as wel l as those made during th i s study, are consistent with ;'1 Lnte Pennsylvanian ari d pa laeocl imu tc for the Pa ra dox Basin, 111C open fabric of facies F cou l d be a res u l t of marine ccmellullion, The u p pe l' surface of one ookl gl'n i nst on e within t he u l pCI' H er mosa at D�lI'k anyoll is c l e a rl y a h a rdgrou nd ; it is encru stcd by Ulbulate corals a nd is pCllc t f'll tcd by abundmll borings ( Loope & Boyd . 1 99 1 ) . I n t h e u ppe r H e rm osa, th e most com p l et e m a ri ne reco rd (wh cl'e fourth-ordel' cycles with bot h trans­ gressi ve a nd regrcssive depos i t s me p rese rved ) i s fo u nd a l o ng the southern ma rgi n of t h e Pnradox

such Ihal the mol'C nega t i ve Ihe column sum for

Basin at t he Elk Ri dge and HOIHlker Tra i l sections.

aeolian d eposi t s . I n an attc m pt to test this hypot h esi s . we a na lysed the vertical slIccession of facics. MiaJl & G i bl i ng ( \ 978) suggest t hm crosionnl contacts within n sll'Hti­ gnlp h ic succession may be iden tified I hro ugh t h e

ge nerat io n of
facies association wi th scou ri n g. i nd i ca t i ng

nOll-erosional

Column sums represcnt

:and

positive Scores

boundary

conditions,

Ihe IOHtl e rosio na l

01' gra­

a

vo l u m e

Mlll'ine CarbOlWfe cycfe.�

143

Tiible S. Tl'Ollsition counts of (o) the gradm iona l (Gij ) iHld (b) the r.;rOsiOllill (Eij) m a t ri ces used in constructioll of (c) the con tact matrix (elj): l.Icolinll facies H hns the most Ilcgmivc (elj ) column sum, indicating it is the facies which most l u m n sums. the fol lowin g e rosion al frequcntly forms sharp (erosional) cont
(a) GraciuliolHll tra nsi t ion matrix A

B

0 0 0 0 0 0 0 0

9

A B C D E

F

G

H

0 3 0 0 0 0 0 0 0 0 0

0 0

0 0 0 0 0 2 0

0 0 0

I

J K

(Gij)

0

D

E

0

0 7 I 7 0 0

8 0 0 I 0 I 0

I

G

I-I

0

0 I 0

0 0 0 0 2 0 0

2

0 0

0 I

9

3 0 0

2 2 0

0 0 0

0 0 0 0

0 0

0 0

F

0

0 5 0 0

0

K 0 0 0 0 0 0

I 2 0

2

0

0 0 0 0 0 0 0 0 0 0

0

0 0 0 0 0 0 0 0 0 0 0

ToWI = 72 (b) ErosiOIl tra nsition matrix (EIJ) B

A

I

0

A B

5

0

I 0

4

[)

D E

r

I J

K

F

G

I-I

0

0

0 I 0

0 0 0

10

2 0

0 0

15

9

I

0

I

I

0 0 0 5

0 I 3 2 4 0 0

5

9

0 0

0

I

0 3 3 5

0 0 0 0 0

5 3 3

2 I 0 0

H

E

0 0

2

0 0

G

D

I

()

2 I 0

2 2 0 0 0 4 0 0

2

2 4 3 4 0 0 12 4 2

K 0

10

0 S I I 6 15

() 3 I

0 2

0 0 I I 0 5 5 0 0

0 0 0 0 0 0 0 2 0 I 0

1 ' otlll = 215 (1;) Contact llulU'ix (elj ) A

A B C D

E

-I -I

-I

I

-I

COIUIllIl SUIll

+1

-I -I

-4

E

F

+0.6

+0.7 +1 +0.7

+0.3

-I -0.7 -I

-I

-O.�

-0 6 -I

-6.8

D

-0.5

-I -I

H

J K

+0.8 -I

F

G

B

-I

+1

-4.4

-I -I -I

-I

+1

G

+1 +0.6

+1

-I -I -I -I -0.2

-I

-I

-I

-I

- 1 .7

+ 1 .6

-I - 1 .6

1-1

-0.4 -I -I -7.6

K

-I

-I

-I -I -I -0.7 - O_S

-I

-0_2 -I -6.7

-I

-I -I

-5.0

-I -I -2

.\',C, A lcldey alld D,8, Loop"

144

Herr.;, re gressive deposi t s succeeded by l ow-stan d inv(Hiably cBppcd wi t h nuvial facies t . Eros io n a t limes preceded fodes I deposi tion as can be seen al the l-IorHlkcr Trail, G i bsOll Dome and Elk Ridge seclions where Irnnsgrcssivc de pos i t s arc abruptly overlain by nuvial facies I low�stalld de pos i t s wit hollt any ev i de n ce of 1.111 i l1lcrvcning regressive episoue (Fig. 6). Furthermore. facies 1 and .l most often form discon formnbtc COlHnels with underlying mal'inc units (Ti:l blc 5 ) , and occa sionally have carbonate biod�ISls nnd lilhoclasts as H d e t rita l sedimentary co m po n en t (Fig. l Oa & b ) . North o f t h e E l k R i Ige nnc! Honaker Trail sections, the lack or aggradational coastal plain deposits <'lpparciltly left shclf carbonate. scdiments exposed

ex posure nrc

1 1 proccsscs. I n these sectio ns. there is to subacri�

lack of bOlh coastal plain and shallow marine deposits. suggesting Ihat low·st:lnd processes pre · ceding constal pl a i n deposition along t h e sOllthern mnrgill of the P�lr�lclox Basin werc not as erosive as the low-stand processes preced ing aeolian deposition within the bHsin centre Crable 4, Fig. 7). A t rou b li n g point is derermining h o w it is possible to de pos i t and p rese l've thick sllccessions of fi ne-grn i n cd fluvial to acolian (loessite) sediments during low stand of bOlh sea level and rhe t e rrestri a l water table. II seems these sediments would be rewor k ed by the wind during. episodes or ba sc·l cvc l (alld water tHblc) lowering. An altcl'Ilativc explanation would be 10 consider the COOlS{(11 plain facies at Honaker a

Fig, 10, PholOlllicrogrnplis. Bal' scillc I min, (0) Fac.;ies I (coast,1I pl,lin); Elk Ridge core ,II 4 1 5 111 below gl'ounel level. The large cnrbomllC lithoclflst ill thi� sample \Vus incorporated into !'"dcs I til rough e l'osio ll or Illilrillc facies E, (b) Facies J (c.;omilnl plaill): Gibson Dome core Ht 451) '" below groulld level. NOIe ilbu1\(b1\1 carbonate biQclaSI� ami lilhoclmas that were croclcd rr01l1 marine Simla, (e) rtlcics r (marine): Gibson I)olllc COfe :'11 527m below gl'ound level. This gl'ilinS1otlc fBcics cornpri:)cs [I rcl.Hivcly thin :)l1CCCSSiOIi of I'cgl'cssivc rllfll'ine deposils (cycle I I ) . Note Ihill lhi� ooid grainstone is abruptl), oVCr'itiill by II luw-stnnd tlcolitlllitc (Fig, 6), (
145

Marillt C:ilrbollate cyc:les Ik R id ge as part of thc aggrada t i OIHl l to

Trail and

p rognJ d a t i o n n l

se di 1l1c n m ry wedge de pos i ted du ri n g

middle to laic h i g h st a nd . Th i s i n lc rpre ta t i on makes it eas i er

ro

e xp l n i l1 necretiol1 of t he f l nc-grail1cd

COl.lShti phl i n sed i me n t

sediments through

binding. high

allows a ggra d at io n al

h i gh -s t a n d

the presence of a

w,ller luble, nnd fu rt h e r

ve ne e ri ng o f u nderl y i n g

m n ri n e

de pOSi ts, t he reby p ro tect i ng them from

low-st'Hnd e ros io n . Although this cxplanntion is p l a us ibl e , it is contradicted by seve ra l lines of evid­ ence. Fi rst l y , if the coastal p l a i n sediments alo ng the so ut h e rll margin of the basin we re de pos i t ed d u ri n g

sea

level

high

sta n d , t h e n t h e y should b e succeeded

sen l e vel . I m pl i cit' i n this

h ypo th esi s is that the

com po ne n ts of ' m i ss i ng' ca r bon � He faci es shou l d

occllr as clasts wi t h i n low-stand aeolianites. To test this idcH, marine facies were gro u ped ilHO t hose of

relatively deep-water (fudes A a n d B), or sh al l ow

­

water (facies

- G ) or i gi n . Facies percentages fo r these ca tego ries were calculated i n each sccti on nnd compared to the percentage of a eol i a n and fluvirti facies (Fig. I I ) . Sect i on s dominated by low-stand a eol i a n d epos it s gen era ll y lack shal low-water facies.

determine if shallow m a ri n e sed i m e nts occu r a s d et r i tus i n low-st and aeo l i a n ites , n i ne ty-o ne aeo l ia n i tc sa m p l es wcrc point-counted to d ete r m i ne

To

st nll i graph icn lly by d e posi ts (o r SUl'faces) towal'cls

the mCHn percentage of r ecog n i z a bl c carbollate

nly the

bioclasts ,lIld lithoclasls. The observed perccntagcs

the

bm;in centre which

G i bson Dome

arc low-swnc. 1 .

si te appe�\rs transitional between

coastill pla i n
6).

I-Iere,

regressive m ari ne de pos it s do n ot gi ve way u pse ct i on to coast a l

plain and then aeolian deposits. Rather.

coastal p l a i n and ae o lia n de posits are randomly s u ggest i ng

inccr-beddcd,

d u r i ng ICl'fcstl'ial

aU locycl ic

cxposurc.

de pos i t i on

W i th rega rd to t hi s

is i n te re st i ng to consider the work of .Ioh IlSOIl ( 1 989). which suggests t hat M idd le observntion, it

Pe n nsy l va n i a n to Eilrly Permian M a roon Formation loessires along rhe so u t h ern mil rgi n of t he Engle

ra nge d frolll 33% to less than 1 % , h av i ng n mea n vHlue of I I % . These arc minimum values, because o n l y recognizable Cfubollale grains we re counled (mal1Y grains werc squashed beyo nd recognition). arbon:Hc gra i lu. within ac()lianites a rc domi nated by b i ocl a sts from fac ies D a n d G , but a l so i ncl ud e lithoclasts auributcd fO facie s B . E a nd F (Figs 4b & I I) . T h i s suggests that altho ugh B , E and F wcre lithined, the subaerial processes �I cling On thcsc

units could none l h el ess and donation.

promote

disintegration

Second ly . if coastal p l a in facies were part of a rc&

p resen te d . it appems end-membcrs of st rat i grap h ic completeness are m a n i fes tcd in the uppcr mcmbel' of thc Hermosa For m a t i on of the Parndox Basin (I:"ig. 12). Alon g the southern m a rgi n of I he basin in t h e vi ci n i ty of the Elk Rid ge and Honaker Trail sections, t he

g ress i ve s u ccession , t h e n i nd i v i d u a l f i ft h-orde r cyc les

tI'ansgressive

wou l d gnl d at io na l ly beco m e mo re dom ina ted by

I1fIIH)rcicr components of fourth-order cycl es fi'cq u clHly preserved . This pl'cscrvation may

Basin (Ccntral Colorado Trough) we re derived from co n fcm p ora nco us dUllcs found to the n01'l11 w i t h i n

t h e basin cenlre. I t se ems t he succcss io ns of facies I a lon g the southern m; l rgi n of t he Pnradox Basin could

be a low-stand an alogue to Johnson's observations.

coustnl plflin facies as these cycles stacked towards

succccd i ng fourth-order cycle boundary. In the s r u d ied , howcvel', re gressi ve fi ft h-o rd er cyc l es co ns i st sole ly of marinc fnci cs H b r u ptly tCr& minated by coasta l p la i n faci es nu h e r t h a n bccom i n g p rog ressi ve ly dominated by coasta l plain facies (Fig. 6). ru rt h c l'm orc . t ra nsgrcss i ve Illa r i ne de pos i t s were m t i mes ahru pt ly ovcrlain by coastal pla i n racies without an i ll tc rv c n i ng shoaling n1(II'ine facies succession (Fig. 6). Fi n H lly , I1H11'illC b iocJ asts aile! l i t hoclasls arc a fairly cOmmon dctrihd component i n coastal p l a i n sediments, th e reby s ugges t i ng base l e ve l lowc ri ng and erosion of an e x posed marine shelf (Fig. 10). t he

sections

­

The bc hcil dc d sequence hYPolhesis s ugges ts t h a t' our

i nn b i l i ty

t o corre latc

be the res u l t of pa rti n l o r

fourth-order cycles may total denation of Ill a ri ne

ca rbo nat e un i ts du ri n g foul'tll-ol'der low stands of

Based o n the observations

that two

�l Il

d

regressive

marine

carbonate

were have becn enhn nccd by an ;;lrmouring mantle of al l uv i u m or loess du ri ng foul't h-ordcr low sltlnds. W i th i n lhe m o re centrnl part of rh e b'lsin to thc no rt h , d en a ti on s t ri pped a po rti on or all or the trnnsgrcssivc find I'egressive m a ri n e c"lrbonme rccord. Subsequently, co rre latio n of fourth-order cyc le s across the b
SU M M A RY A N D CONCLUSI ONS D e ta i l ed fa ci es a n alys is

o f se ve n

s u rrace and sub­

sUI'face sect i ons of Upper Pe n n sy lva n i an rocks

member of the

(upper

H C l'l11osa FOl'lna tiOl1) within Ihe

Pnradox Basin revea ls t l Ul 1 c l eve n ma r i ne a nd no n ­ ma ri ne de posi t ion al environmcnts arc

re prcse n tc d .

S. C. Atchley lIlId D. B. Loope

� §

1 00

�

50

'5

Spanish Bottom

Dar1< Canyon

Big Spring Canyon

Cane Creek Sections With

Aeolian Dominated

Lowstand Deposits

o

� §

1!l ,E '5 ..

� �

1 00

Elk Ridge no. ,

Honaker

Trail

Coastal Plain

50

Dominated lowstand DeposllS

o

1 00

Weighted Facies % From Sections Whose Lowstand Deposits Are

�

Weighted Facies % From Sections Whosa Deposits

�

Aeolian Dominated

rn

'0

Dome no.

Sections With

(fJ

,§

Gibson

Are Coastal Plain Dominated

rn

,§

50

'5 50

o

Marine faci es A

+

B (deeper water)

Marine facies C to G (shallow water) Aeolian facies H Coastal plain facies I + J

2 Ma r kov chain analysis

of g rad n t ioll n l facies con­

tacts w i t h i n fift h -orde r cyc l cs a l lows reconstruction

of t he prognidat ionnl succession of marine facies.

T hro ugh cOllsiciermion of both the p h y� i ca l

of the

featurcs

Fig. I I . Facies percentages for ench section studied. The totnl percentage of section occupied by relatively deep·wliter marine fllcics, ,ind rClutivcly shal low-wutcr facics, were ploltcd with Ihe percentage of section occupied by aeolian facies, and coastal plain facies. Sections were separated into those with acoliun dominated low·stfl nd deposits. and thosc with coaslul plnin dominuted low-stand deposits. For these two cHtcgorics, the weighted perccntages of deep and shallow m'lrinc, and coastal plain ami aeolian, facies were determincd. Observation of the facies percentages indic:lles tilat, wilh :111 increase in aeolian domin:lnc.:c. there is .111 :lssocialcd deere.1se in shallow tnnrinc facies. onverscly, w i l h an increase in coastal plAin dominance, there is an incrense i n the percentage of shallow marine deposits.

each fifth-order cycle,

H

hierarchy of slratigraphic

cycl icity can be ,'ccognizcd within the upper mcmber

'of rhc I-icl'lnosn FOl'm atioll. Wi th in this fn.1I1lcwo r k , fifth-order

les occur i n deepe n i ng (trnnsgrcssive)

cyc

facies anti their idc�ll Wa lt he ri a n succCSSiOll

n n d shallowing (regress ive) se ts to form fourthMordcr

[he

cycles. w h ich in t u rn nrc grouped into a third-order

s he l f

dee pcn i ng and shallowing cvent. Finnlly) this third­

w i t h i n H f i ft h-o rde r cycle. il was determined t h a t marine facies were de posi ted on Itlildward f!'Om which was

tl

a bnrred

tcrr cs t ri n l mosaic of

aeol i a n , laclIsll'ine �lnd nuvial e n v i ro n me nts .

3 Using the rel a t i ve water depth assemblage

rol'

order cycle -

is i n te rp re te d to be superimposed on

1.1

seco n d or der episode of basin fill. High·amplitude glacio-eustatic sea level oscillations �lre proba b ly

147

Mal'ille car/JOllllfe cycle.'!

Spanish Bottom

North

Elk

Dark Canyon

Coastal Pltdn

Honaker Ridge Trail

South

Mud·rlCh CarbonatltS (ReiatNelv Coop Waler)

•

Mud·loan Carbonates (Re/e.live\y Shallow W",tor)

Aeolian

Fig. 12. D iugru numuic cross-section showi ng configuration of fncics and deflation sur faces for five hYPOlhcticnl fourth­ order cycles. To the north, much of the marine portion of fourth-order cycles was reworked by the wind into low-stand

aeolianites. orrcltltion of northern tru ncaled eycles with the relativcty more complete cycles difficull. NOle extrcme vct·tical cxaggeration ( X lOOO).

to

tlte south would hc

I

responsible for creating the fifth - a nd fou rt h-ord e r cycles . Val'iations in subsi d e nce rate generated the secondo. a n d pe rh a ps the third-order cycles. 4 A l th o ugh fou rt h -o rd e r cycl i ci ty is attributed to an "Ilacyclic mechanism (glacio-eustasy) , few indiviuunl cycles call be cOITclated across the bl.lsi n . Fourth-ordcr cycles nppear t o be t runcmcd in that tra ns g ressi ve deposits are r ..trely succeeded by aggradational to prograd a t io nal deposits. Those cycles with an abbrev i ated marine history are usually overlain by
and K. I lavholl11 and R.P. Langford ( Uni versi ty of 'rcxas) reviewed thc manuscript and offered vcry cOnstructive cr it i c i s m .

R E t" E R E N C E S ( I Y82) Deposiriolllll (fIuf dillgellelic !Ii.\·lory of f)/io(,(!IIe- PldsltX'e/1e carbOlUlle.\· of IIQI'tIJ WC.\·I(!1'II Gn:M H(IllfIllW /J(lIIk; (!l'O/Ulioli of (t Cor/lO/IfIIC "Imfol'm. Unpublh:hcd PhD t hcsis. Univcrsity of Millmi. G I.,"':: !!". R.C. ( 1 980) PClIllsylvuni
257. Soc. Econ. Palcont. Mi rleral . . Roc ky Mounlain

Sect ion. Rocky Mountain Pu tcogcogt'aphy Sy m posi um I . P. H. ( 1 9�9) G lllci tl l ­ CIISllllic SC:I level curve for' cmty LaiC Pellnsylvanian scqucnce ill llon h-ccll Irnl Texas and bioslrlHigr:.tphic con·ctrHion with cllrve 1'01' midcontincnl North Amcrica.

Bn,\ImMAN 1 1 , D . R . & H I ! C K EI •.

Geology

A

K N O W L E O G E M ENTS

Funded b y NSF Granl E A R·881 6222. M a t e ri a l s a n d by Exxon ompany. U S A . South­ westcrn Division, and D . H . B li ck n e r of Denver. oto",do. R.F. Diffc nda l , J . B . Swinehart and W . J . Wayne ( U n i versi t y of Nebraska) , R . K . Goldhamlllcr and S. R. Schullcr ( xxon Production Research)

data were provided

17. 802-805.

BOAIO){lII\N I I . D . R . & MALIN K Y . J , M .

( I YS5) G luda l­

C lLSl
148

S.c. Atchley III/d D.n. Loope

CI· t U MAKOV. N . M . ( 1985) Glat:iul cvcnls o f l hc PUSI nnd their gcologictll significance. Pa/(Ieogeog. . P(I/(t(JoC/imalOl. , Plifa(Joeco/. 5 1 . 3 1 9- 346.

CISNE. J . L . ( 1 986) E'II'l hquakcs r'CCOf'dcd slf'(Lligl'aphicully 011 ciHbollnlC pirnfol'llls. NlIIlIl'C 323. 320-322 . CHOW�I.L. J . . ( 1 982) Continental glaciation through geologic limes. Jill/me ill Eftrlh Ni!>'tol'Y pr. 77-82.

Nalionnl Academy Press. DALItVMI'Lll. R . W . . NAItIJONNI!. G , M , & S�tlTI I , L. ( 1 986) Eolian aClion and the distribuliorl of fimbrial1 shales i n Nonh Amer'ic,. . Geology 1.3, 607-6 1 0 . DItIES!!. 5 . G . .& DOTl', R . H . , J II . ( 1 984) Model fOI' $nnd� slone-carbonate 'Cyclothems' based 011 upper' member' of MOI'gnll Formation (Middle I" cn nsylvilninn) of Ilot'lilcrn Utah and Colorado. /)HII. Am. Ass. Pel/·ol. Geol. 6H,

574-597.

ENOS. P. ( 1 983) Shelf. In: Carbol/me Deposi/ion(ll £11L'ironlllellt.l· (Ed. Scholle. P . A . Bebout. D . G . & Moorc.

e . I' I . ) Pl'. 267-295. Mem. A m . Ass, retl'Dl . leol. 33. ENOS. I'. & PeRKINS, R , D , ( 1 977) QUfLtcrn[lI'Y sed i ment­ tllion in soutll Flo,·ida. Melli. Ceol. Soc:. Am. 147, 198 PI'· FI\ IIHlIll DGE. R . W . & JOHNSON, D . L . ( 1 978) Eolianite. I I I ! TIll: £m;ydoptuli(i of Sedimt:II(ology ( E d . Foi ,·bl·idgc.

R.W. & Boul'geois, J . ) PI'. 279-283 . l owden . H \ltchill­ SOil & Ross, Stroudsburg. FRAI-IMU, C.W. & V,\UCillN. E . B . ( 1983) Paleoz.oic gcology llnd seismic s l fi.Higrnphy of the northcrn Uneompahgrc fro i l l . Gnlnd ounty. Ulah. I n : Rorky MOIlllftlin Fore­ lalld iJflsiw' and Uplijis ( d. Lowell. J . D . ) PI'. 201-21 1 . Rocky Mcuntl.lin A�sociilljOIl of Geologists. Fk,\ KBS. L.A. ( 1 979) Clima(es tlll'ollgholll Ceologh' Time. Eisevicr, New YOl'k. 3 1 0 pp. GOI.DIIAMM !I( I , R . K .. DUNN. P, A. & HAkDII.!. L.A, ( 1 987) Higll-frequcl1c)' glo..:io-eu!'tillic sea level oscill�ltiolls with Mihll1koviteh chfll·actel·istic.:s rccol'Cled ill Middle Triassic platform cfll'bolHHCS in Ilorthern I tilly. Alii. J. Sci. 287.

853- 892. GOLDHA MMER. R.K .. OSW,\LI), E.J, & DUNN. P . A . ( 1%9)

Tile hicrnn.:hy of strutigraph i..: forci n g - a n cX<:I lllplc from middle Pcnnsylvulliilll (DCSIllOillSCl:' l l ) shelf car­ bonates of the southwcst Pn1'l,dox Basi n . l -lol1ukcr Tr
8 1 . 59-74.

HAIU)LH. L.A .• BOSHLLINI. A. & GOWHi\MMHK. R . K . ( 1 986)

Repealed �ubaerial exposul'e of subtidal e�lrboll:llc platfonm:. Trias�ic. northern I taly: evidence for high frequency sca levcl oscillalions on n 10-' ycar sealc. Puleoceullog. 1 . 447 -457 .

1" 1/\� I'mL C.W . . JI( ( 1 984) Improved methods of facies sequence !'Il11lysis. I n : Ftldt:�· AiJode/�·. 21lcl edition (Ed, W;1lkcr. R . G . ) pp. 1 1 - 1 3 . Rcprint Series I . Geosr.:iellcc unada.

I·IECKEL. P. H. ( 1977) Origin of phosphulic black shale fades in Pennsylvuniall cyclothems of Midcontinent North AlIlcric<.l. 13//11. Alii. Ass. Petrol. Ceol. 6 1 , 1 045- 1068. HECKEL. P . H . ( 1 980) Pidcogeogl'llphy of eus-tillie model for deposition of mid":olltincill upper Pennsylvaniun Cyclothems. In: Palt!ot.oic Plileogeog/'llplly of Ille Wesl"

L'en/ral Ullile(1 SWles (E.d. Fouch, T,D. & Mngalhllll, E. R . ) pp. 197-215. Soc. �eoll. Pllleon l . Mineral . . Rocky MOlLllloin Seclion. Rocky Mountain PaleogeQ&wph)' Symposiulll J . I-II!CKIlL. P. I" I . ( 1 986) cJ�levcl CUI've fOI' Pennsylvanian eustatic Illarinc Irnllsgrcssive- rcgrcs�ivc depositional cycles along midcontinel1t OUlcrop belt, North Americu, Geology 14. 330-334. HIRD. K. & TUCKI�". M . E . ( 1 988) Contrasting diagenesis of two CarbonifcrOlls oolites from south Wnles: a tulc of climutie influcnce. Sedilllentology 35. 587-602.

Hrm.

R..I. ( 1 960) Stratigraphy of the s<.illne r'lcies or thc l)nnHlox Membcr of the Hernlosa Fo rma t iOI1 of south­ eastern Utuh ..nel southwcstcrn Colorado, in geology of the ri:lr[ldo:< Oasin fold ,Ind f;1U1t belL FOIII' COl'I/er.l· Geological Sodt:ty Gllidebook. 3"d Field Conference .

86-89. HlTIl. R .J .

\;' BUCKN I:Iol. D . H . ( 1 981 ) Siratigraphie eor­ rclfllions. fucies COllccptS, and cyclici ty ill Pellllsylvuniull rocks of the Paradox Hasin. /?m'ky MOIIII/aill Asso<:iatioll a/ Geologisfs. 1981 Field ol/ference, 147- 1 59. .I011N50N. D. L. ( 1 96M) Quaternary eoli
1 2 1 . 15U- 1 5 1 .

JOI-tNSON. S . Y . ( 1989) SigllificllllCC o f locssite ill lhc Maroon FOr11l1l11(m (Middle Pennsylv;1llinll 10 Lowel' Permian). E..'gle Bnsill. 110l'IhweSI Colol'tuio. J. Sed. Petrol. 59.

782-79 1 .

. & LIlIolCI iE. I . ( 1 9a8) The risc and fall t}f l!lIstHSY. I n: Sea·level CIt(lI/ge.I·: (III Imegrmed A{ J fJI'o(IC:1r (Ed. Wilgus. C.K. el (II. ) pp. 3- 1 8. Spec. Pub!. Soc, Ec..'o n. Pnlco n l . M i nen-Ll, 42. Tulsil. KLUTI I . C.F. ( \ 986) Plate tCt.:loll i!..'S or the Ancestral Rocky MOuntl.lins. I n : 1),r/colec/()lIics alld Sedilllell/tII;o/l (Ed. Peterson, .I . A , ) pp. 353-369. Mem. Am. Ass. ])el l·o! . Geol. 4 1 . K(H!RSCI·INlm 1 1 1 . W . F . & RH/\I). J.r. ( 198!J) Field ,"ld modeling stlLdies or Cillnbriull cnrbomHC cyclcs. Vil'ginin App�II" chinl1s . .I. Sell. Petrol. 59. 654-6.,l{7. KOZAR, M.G .• WI!II Hk , L.J. & \VAI.Klm. K. R. ( 1 990) Field :md mode lling studies of Cambriall caroomlle cycles. Virginia Appa lachi u ns - lIisclLSsioll . .f. Sed. I)e(rol. 60.

KENDALL. C . G . Sl'

790-794. LHwIS, R.O. & C,\MI'UllLL, R . I'!. ( 1 965) Geology ancl

uraniulll deposits of Elk Ridge tll1d vicinit)'. Son JUt\I1 oUllty. U l:uh. US Ceol, SIII'I'. Prof. Pap. ·./7.J-fl. 6!J pp. LOOI'!!, D . B . ( 1 984-) Eolitlll origin of UppCI' PH. D. \3. ( 1 985) EpiSOdic deposition �1I1d pl'cservtl tion of eol1;111 :-lands: a laIC P,lle()wic example frolll soutilcl.lSI Utah. Geology 13. 73- 76.

LOOI'E, D . B . ( 1 9�) RhiZOliths in ancicnt eolianites. I n :

I_till.! p(jleozoic (/1/(1 Mesozoic Eoliall Deposil.\· uf (lte Wesl
1'1' . 30 1 - 3 1 4. Sed. Ocol. 56. LOOl'�, I 0 . 13. & Boy!>. D.W. Cemellted sca·nOOrs of Pellllsylvnnilill age, s(mtile!lstcrn Utah. Ceol. SOL". Alii . .

Mal'i/le c((r!Jo/wle cycles A/)str. Progl'tllllS 23. A66. LOOI'I!. D.S. & H"VllIU.AND, Z.E. ( 19S8) Giant dcsiccatioll fissuJ'cs filled with clilcureous colian sand, Hermos;, l�orl'r'l (ltiorl (Pcllnsylvllniii n ) . sOuthcastcrn Uwh. I n : LMe Paleozoic (llId Mesozoic £0/;(111 Deposits oj' tlte Wesrenr hrrerior of rlre Unired Sillies (Ed. Kocurek, G . ) pp. 403-413. Sed. Geol. 56. Lool'l!, 0 . 1 3 . & WATKINS. O . K . ( 1 989) Pcnnsylv'lIlian rossils replaced by rcd chert: early oxidalion of p}'1'itic precursors, j, Sed. Petrol. 59, 375- 386. MACK. 1 , 1 = 1 , & RASMU SSEN . K . A . ( 1984) Alluvhll ran scdimcntmion or thc Cutler Formation ( Pcrmo� PCllllsylvnleogcognlphic implicl1tiolls. Sed. GeQI.

2 1 . 279-286.

M IODLlfI'ON . G , V , ( 1 973) JOlliltltlCS W(llther's Inw of cor­ relation of facies. 13/111. Geol. Soc. Alii. 84. V79-9SS. . .I.1. ( 1 9M I ) l-Iyd1'l..1 logie PI\TI'I!KSON, R.1. & KINSM,\N, frumcwork of a sabklm along Arabian lulr. BIlII. Am. Ass, Petrol, ·eol. 65. 1457- 1475. POSM1 �NTIIlK. H , W , . JllKVHY, M,T. & VAi l •• P.R, ( 19H8) Eustutic controls On clnstic t.\cposition I - conccptual frllmcwork. I n : Sea·level Cllllllgel'; {III Illtegraled Ap­ pW(I(:1I (Ed. Wilgus, C,K, er af,) pp. 1 0 9 - 1 24, Spec, Publ. Soc, Econ, P"llcOIlt, Mincral. 42, POSMII:NTII:R. H.W. & VAIL. P , R . ( 1 988) EUSHltic cOntrols On clllstic dcposili()11 I I - sequence ilnd systcms lnlCI models. I n : Sca-Iel'el Challges: WI JIII(!gJ"tIl(!(f Approllch (Ed. Wilgus. C . K . ef (t/.) pp. 125- 1 54 . Spec. Pub!. Soc. EL'OIl. Palcont. Mineral. 42. PUKsm�, \3 , 1-1. ( 1 978) Early diagenesis and the preservation porosity in Jurassic limestones. 1. Petrof. CeDI, I . 83- 94. REAl), J . F .. GI(OI-L.INGlJk. J . P .. BovA. J , A , & KOI�KSCIINI!K. W . F. ( 1 986) Model I'or genenltion of curbollutc cyclcs. Geology 14. 107- 1 1 0. RI(.:1i. J , A . & UxH'll, D, B , ( 1 99 1 ) Willd-reworked marinc C.lI·bollalcs. IfllC Paleozoic of nOrlhwcSl ArizOlla and SOlllhcl"Il Ncv�lda. /Jul!. Ceol. Soc. Alii. 1 03. 254- 2(,7 . S,\KCi. J.P. ( 1 98R) Carbollale sequellcc strtltigraphy. III:

D

149

S(!{/'/Clle! C/I(III,(;l1s: (/11 IlIfcgl'ttlcd AppJ'()(tt'll (Ed. Wilgus. C , K . el (II, ) PI', 1 5 5- I H I . Spec. Publ, Soc, Ecol1, Polconl. MiliCi'll!. 42. STONIl. 0.5. ( 1 977) Tectonic history of the Uncompahgrc Uplift. Ill: c.l·plora/ioll FrOllri(!I".\' of lite Cel/fr{// alld SOllfh(!1"1/ f?ockies (Ed. Venl. H . K . ) PI'. 23-30. Rocky MoulllUin Association of Geologists Guidebook, VAIL. P . l t . MITCI IUM, R . M . . JK & TtIOM I'SON I I I , s, ( 1977b) Seismic strcltigrnphy ,I lid global cllallgcs or sell level, pal'[ 3: relative chllnges of sen level from causwl onl(lp. I n : SdSlllir Slrmigraphy - ApplicClliolls 10 I-Iydroc(lrholl £.I·plomtiol/ (Ed. Cla)'ton, .E,) PI'. 63-81. Mcm. Am . Ass. Petrol. Gco!. 211. V,\lL, I).R .. Mn'clluM, R.M .. J I! , TOI)I}. R . O .. WII)MWI{. J .• TII01" ill E.U J'ulcokarSls [lild puleosols as iltliicli­ tor1' of paleoclimate and porosity evolution: 11 C.\SC stud), from the Carbolliferc>us of Soulh Waks. In: Illl/eokol"l"1 (Ed. JtltnCS. N . P , & Choquettc. P.W , ) pp. 329- 34 1 . Springer-Verlag. Nr.:w YOrk.

Spec. P"vls fm, Ass, Sedimellt,

( 1 993) 16, 1 5 1 - 161

Draa reconstruction, the Permian Yellow Sands, northeast England T.

H R I N T Z ' alld L . B .

LEM M E N S E N

Illstiulfe of General Geology. University of Copel/hagel/. (J)stel' Voldgade DK· /J50 Copel/hagen K, Denmark.

A Il S T R A

10.

T

The lower Pcnllian Ye l low Snnds of northeast Ensland havc

bccn p rcserved tIS fI number of 1 , 5-3.5 km ridges. The three-dimensional scdi­ rnelilary build-up or [leoliull architecture of t he se dnHl ridges i s bCllutifull)' exposed in a numbcr of 1n rsc q utll'rics. Studies of thesc outcrops nllow a rct:onstl"uction of draa morphodynamics. The sediments i n the d raa ridges arc composed o f tWO superimposed inter-clraa- draa clement sets. The draa clements. which Me the focus of this p:lper. ("Irc composed o f abund
sinuosities that migrated ,dong-crest. The dnlils lind superi mposed dunes werc in equilibrium and appnret1lly formed in a bimodal wind regime wilh altcnHlting northwest

or nonll winler winds ond southeasl or c ast summer winds. The resllilalU sl.Iml transport direction was pantllcl lo the draa ridges. suggesting tliat these also were longitudinlll bedforms during the final phase of draa sedimentation,

I NT R O D U C T I O N The recons tructi o n o f a eo l i a n

bedfol'n' Iype and has lo n g intcresLCcI sed i men to logists, and rhe coneet i n tcrp rctn tion of a nc ien t aeolian bedforms has impOrl3nl i mpl icat i I1S not only fo r pal aeogeographic and pa l aeocl i m m i c reconstructions, but a lso for practical cha racterization o f aeolian rescrvoil·s. The cl assic approach is to make compa nlli ve a n al yses of t he sedimentary structures of a specific ancient deposi t nnd of modern I.lco l in n bedForms (e.g. McKee, 1.979a, b ; Tso,,,, 1982). Add i t i o n a l

and studies o f the amount a n d dist-ribution o f acoliun slnuif"ication lypeS (e.g. H u n te r , 1 98 1 ). The inter­ prcHi t i on of a nc i e n l acol i a n bedfo r ms h a s be e n t reale d rece n t l y i n much detail by Rubin ( 1 9 7), who used com pute r programs to reCl'eate the morphology Hnd beh a viou r of t h e bed fo rm s thai produced a specific deposit. This latter appronch is em p l oye d

methods i n volve studies of foreset bedding attitudes

or aco li ml architcclUre, of a

(e.g. G l e n n i e .

struction of .leolian morphodynam ies,

bch�lViour from OUlcrop

chu:.l

1 970; A h l b ra ndl &

(llso in this study. Such compuLCr-aided reconstr uctions of (lcolinn 111 0 rphodynamics arc dependelll on de t a i l ed field studies of t h e t h ree-dimensional structural bu i ld- u p ,

Fryberger, 1980).

is •

Prescnt

:Idd r

ess :

NSR

DK-3450, Aller0d, Denmnrk.

ousult.

Sortemoscvcj

Aeolian Sediments: Ancient and Modern Edited by K. Pye and N. Lancaster © 1993 The International Association of Sedimentologists ISBN: 978-0-632-03544-1

best

done

exposu I'es, The Pe rm i an

2.

151

spedf"ie depos i t .

Recon­

therefore,

on h i gh -q u a l i ty Ihrce-dimcllsiolHll Yellow Sands of nOrlheast England

152

T.

hrillll. alld L . /l ClellllllenW:1I

I

Fig. I . Map showing the location of

the quarries studied ill the Yellow Sands. (After Clcmmcnscn, 1989,)

�lrC well exposed in three d i mensions i n a

n umbcI' ncar Durham ( Fi g. I ) . Repented visits to these qu n rri cs sillee 1 984 have given us a good knowledge of facies and facies architecture i n the Yellow Sands (e.g. Chrintz & Clcllll11cnscn, 1989, 1 990: C lcmmcll sen , 1 989).

of large, act ively worked

q u a rri es

I n this study, we intend to describe the aeolian architecture of the Yellow Sands in some derail, with emphasis on the dominant trough-shaped (d u n e) clemenr. and to reconstl'lIct aeo l ia n mo rphodyn
seem to constitute one of the very few examples of l i n ear aeolian bedforms preserved in rhe ancient record (e.g. R ubi n & H unrer, 1 985).

G E OLOG I C A L S E TT I N G The Yellow Sands arc a n aeolian fOl'llliHion of Permian age which QU[C['ops extensively in northeast England (Fig. I ) . The fOl'matio[l ['ests u nco n fo rm ­ ably on arboniferous st rata tlncl i s overlain by Latc Permian marine rocks (e.g. Smith & FranciS, L967). The Yellow Sands have been ascribed lo the Wcisslicge n d . which corresponds to thc uppcrmost

Draa recolls/rucfiol/ ill /lorr!H:asl Ellg/fWd nOll-reddened

Rotl iegencl sandstone

part of the

seq uen ce (Glennie & Buller,

1 9:0) 1 . The aeolian

deposits arc be l i eved 10 re prese n t pMt of i.l l arge

erg ut the northwestern margin of the So u the rn Pcrmillil Bas i n (e.g. G len n i e , 1983).

The Yellow Sands have beel' preserved as seve ra l

sand ridges

lip to

high and

57 111

1 .5-3.5 km

sepnrntcd by O.S-2 kill widc corridors with

sand

cover

( S l ecl e ,

l emmc n se n ,

1 983;

wide, �l

th i n

p reserved �\coliHIl morphology,

The pl'csellt i n vestigation is based p ri ma ri l y on

st ud ies of four large q ua rries i n Durham: Quarrington

of

ridges,

I. Aeolian

but the relative posi t i o n of the q uarries

Basic components

Micro-sc;.Lle

Texture clements Sinttificmioll types Architectural clements Sedimentary storeys

Meso-scale Macro-scale Mega-scale

Erg clemcnt

The ori gi n of the Ye l l ow San Is has been the

s u bjcct of much i lllcrcs t . Al t ho u gh a n (tcolhlll origin

has been accepted by all btll I' ryo r ( 1 97 1 ) . there has

been no ge neral agreement on the exact mo rph o­ Sm i t h

&

Aeolian processes I3cdfol'lll dynamIC!; Desert evolution

Francis.

Low-order

I n termedia te-oretel'

Draa clement Ili ter-drutl clement DUlle clemcnt IlIler-dulie clement

Strilti ficl.l tiOIi clemen I

Simd shcel c l emen l Sabkha elclllc llI

dy n a m ics of the aeol i a n bedforms that p roduced the

(cf.

Sorting proccs�es

TulJlc 2. Acolil'n nrchitcctunll clements (lIfter C1Cmmc.I\Scll. 1990, 1991)

varies frol11 the ridge ce nt re to t h e ridge margin,

1983; G l e n n i e &

Application

Seale

High-ol'clef

the quarries arC situated w i th i n the sa nd

Yellow Sands

architecture (Mtcr CICmIllCtlSCll, 1 990,

Ph. !-Iettons Down

Quarry and McCall's Qual'l'Y (Fig, I ) . All

199t)

1989).

These sand ri d ges (Ire thought to represent pa rti a l ly

H i l l Quarl'Y. Sherburn H i l l Sand

'ruhle

1 53

1967� G l e n nie,

Buller, 1983; Yardley, 1984; Mader

& Ya rd l ey . 1985), The most recent view, ex\ ressed

which a rc : erg clement. dnw c l eme n t ,

inter-draa

Clem mc nsen ( 1 989) �lI1d hrintz & Icmmensen ( 1 990). cons ide rs the bedforms to be large com pou n d l i n eal' d U ll es 01' dnuls, In this paper we shall further

element, clullc

dOClllllent lind cxtcild this i ntcrprctation of the

or bedform tllod irication elemcnt ( Tab l e 2). The

by

c le me n t , inter·dllllc clcment, sand s hee t clement, sabk ha element and stratification Yellow

Yellow SandS.

Si:ln ds

contain <'111 but the sabkha element

(Fig, 3). Aeolian mega-scale architecture re fers to

th e number and geometry of wel l defined erg u ni ts or aeolian storeys wirhin the st ud i e d fo rmation, I n

A E O L I A N A R C H I T EC T U R E The three-dimcnsional

a col i a n

scclill1cntat'y s tt'u ct u re o r

n rchitcclul'C of the Yellow Sands i s wcll

exposed i n t h e q ua rries studied (Fig, 2). A prel i m i n a ry

t h e Ye l l ow S{l1Ids on ly one mfl i . , erg UI)it seems to

be prese nted) a nd the mcga�sca l c archi tecture is

therefore relatively s i m ple _ I n the following only lhe macl"C)-scalc aeolian architecture will be described.

account of the aeo l i a n ilfchitcCIlIl'C was givcn by

Chrintz & C lc mm enscn ( 1 989). A morc compl'chcn­ sive


el e m e nt

an a l ysis

here b ased on the nomenclature in ( 1 99 1 a ,

b).

is presented lcmmcilsen

I n general, aeo l i an architecture can be described on four levels: mic ro-scale, meso-scale, ll1acro-sc�l le a nd mega-scnle sedilllenwry �lrchi tectu l'e (Table I ) . Meso-sca le

aeol ian

a rch i tect u re

refers

Lo

the


and

wi l l

be brie fly cOlll mented

upon dUI'ing the description of macro-scale acolian

architccture. The latter rc fe rs to the amount and dis­ t r i b u t ion of the basic a co lin n architcctural clements.

M�,cro-scnlc llcoliml nrchitccturc £rg efemcm Because the Yellow Sands �,re considered to represcnt.

only one erg u n i t , the erg element co rrespo n d s to n i l sediments ill the formation, As all'c�ldy mentioned,

Ihis erg clement constitutes several l a rge sa n d ri dges

rcp l'cscn ti n g part ly preserved lincar draas,

I t is evident frolll field studies I'h a t the cl'g elemellt

in ea ch sanel ri d ge is com posed of twO superimposed

intcr-draa-draa clement se ls overlain by a th i n sand

sheec cle m e n l (Figs 2,

3&

4:

Icmmcnscn, 1�89).

Fig. 2. Three-dimensional exposure of lhe Ycllow Sands (YS) in McCall's Quarry. TIlc far wall is orientated northwCSI-southcasL or nearly perpendicular 10 the sand ridge. while Ihe nearest walls are both orientated nc..1rly parallel to the sand ridge. The Yellow S..nds arc here re presented by the upper draa clement (exposed lhickncss c.25 m) overlain by a thin nnd sporadically preserved s.1nd sheer clement (SS). TIIC draa clement is composed of relatively large dune clements (up 10 IO m lhick) thai arc (rough-shaped in the trans\'ersc section and of labular geometry in the longitudinal scclions. Discontinuous lines indicate lower bounding surfaces in sclccled clCmenL'i. The Yellow Sands arc overlain by marine Zt.-chslein deposits (Z).

Draa recollstruction ill IlOft/liwsr Ellgland

155

--=-=-=-: M�l�LA� (.!!: P�M.!!N J:---=-:-=--


;;;

o ....J ....J W >lOR Fig. 3. Idcalizc.:d cross-section or u s<1IId ridge in the YellOW Suncls il lustrating lhe scdilllcllillry archilCctul'c of the aeolian deposits. D R . Draa clement; l O R , inteNtr"" CIClllCllt: D U , dune clemen!; I O U . inter-dul1c clement: ST, stnHifictltiOn clement; SS. sand sheet elemcnt: M. sand reworked during Zechstein transgression.

....

•••

, Sandtlow slrala

CARBONIFEROUS STRATA

... .. - Wind- ripple sIrota

'--

rSm Um

Aeolion strata. undifferentiated

Fig, 4, Part or erg clement ill the Sherburn Hill Sand Pit. The w,111 trends ncarly perpendicular to lhe salld ridge and is composed o r a I wermost nat-bedded to [ow-angle stl'mified illlcr·draa - draa plinth clement ( l O R ) . II middle and rclutively thick draa clement ( D R ) nnd lin upper t h i n sund sheet clement (SS), The upper eOIl\'ex-u p surface of the Yellow Sands is thought to rcprcscnt the original, somewhat subdued morphology of the dl"las.

The uppermost pa rt of the sand sheet el eme n t shows ev ide nce of marine rewol'k ing (Fig. 3). The cl'Osiomil surface between

the uppermost

dran c leme n t and the sand sheet element docs n o t

contain any fCi.HlIrcs such us soil Or bio turba t ion

Draa elen/ellis Each sand ridge ill the Ye l low Stlnl.ls is composed of

two intel'-draa-dnHl element sets s· pnrfltcd by an inler-dt'aa-order

or

nrsl-order

bounding

surface

indic
(cf. Clemmensenj

starvation poss ibly coupled to the early phase of

served t h i ck ness and geometry of the two draa

sand supply.

" sheet-like geometry nnd a thick ness of <.:.3 m. It

sand sheet elcmelll therefore seems to i ndicate dr:.I<.l

marine l ra nsgressio n a n d a res u l li ng decrease i n

( 989), Bot h draa elements arc

underlain by an inter-draa element. but the pre­

clements differ greatly. The lowe r dl'lUl c leme nt has

156

T.

hrilllZ fllld 1... . 11. Clenllllem'ell

formed d ur ing a n episod e of slow l ate r a l migrat io n

of the draas. The upper draa clement forms convex

ridges lip to 3000 m wide and I O -40 m high (Figs 3

& 4). This u ppe r draa clement formed pl'il1larily

d u ri ng an

e p i sode

of vertical t,lr�Ul ,lccrclion, but

draa sediments were eroded to some extent by wind priol' to s{ iIld sheet fOfmalion, Both drrli.! clements arC

com posed mainly

of trough-�h�lpcd

bo u ndin g su lfacc in transverse sectiolls (Figs 2, 3 & 6 ) . 1l cont�lins s l ightl y oblique cross-bedding, with sal1cHlow �ilrata in the morc steeply dipping

'prox i m a l ' part, and wind-ripplc strata i n the less

steeply 01' cOlll1rcr-d ipping ' d ist a l ' part. The clemcnt

a ppears ill

b ot h

right�hand unci l eft- h a n d versions,

wh ich often resu lts i n I'he fOl'nl:llion of i nte r�digital.ion

zOneS. In longitudinal sections the clement has a

d U lle clements. The descri ption of dnHl a rchitecture

alld l11orphoclynal11ics refers mainly 10 the upper draa cleillent

( Figs

2. 4 . 5 & 6).

The snnd I'i dgcs contain two i nl cr-dnHl - drnn l linth clements, but o n l y the upper one is well exposed,

This upper i n ter-draa el e m en t rests on all i n lCf­

draH-ordcr su r!'
has a typ ica l thick ness of 5 - 9 01 , The sedimentary

featul'cs and

genes is of

this elcment hnve

a l read y

bcen described in detail by Clcl11l11enscn ( 1 989),

Dillie elelllellf.\'

This element ma kes u p c.90% of the uppel' draa

clcment and is the most co n sp ic lious elcment i n

the Yellow Sands: a corrcct inte rpl'clation o f i t is

crucial to the understanding of the acolifll1 rl'orpho�

c.ly namics, This

c lemen t

more detail here.

is t h e refo re described i n

The element is 2-40 m wide <.wd 0.5- 1 1 m t h ick

and possesses an asym metr ic trough-shaped lower

Fig. 6.

Dunc clemcnts exposed in transverse section,

Hcttons Down Quarry.

Fig. S.

DUllc clements exposed ill longitudinal 10 oblique section, Heltons Down Quarry. Discolllinllolls lines define one clement.

a

Draa

l'eCOIIS(I'{ICfioll

ill Iior/hellsi Ellglllild

1 57

a bimodal d i p distribution (Fig. 7 ) . I t s hould bc

nO[cd, however. that the majority of the bou nd ing

+

surfaccs only d i p 2- 10° and display a ncarly pc rfect

C ross - beds

+ t +.

+ + + +++ .., + .. ,,'+ + '1: +.. .t + ++ ++ + +

bipolar

+

,70

p:IltCt'll

w i t h modcs towards thc northwest

alld southeast (scc also Yat·ellcy. 1984). The r h i c knc ss of

thc e1cmcnt

is rela t ive ly constant

<.It <.Illy one l ocal i t y (qUHI'ry). but clement rhickncss varies systematically between the localities. Quart'ics situuted nenr the edge of a sttnd ridge possess the

00

t h i n ncst elclllcms (mean situated

neal'

r i dge

a

e1emcnts (mcan

=

=

2 m ) . whcrc 4un r ries

centrc

havc

the

t h ickest

maximum = 1 1 m ) .

5 111:

The cl eme nts often displtly scallopcd cross-bedding

".

(d. R u bi n . 1987)

as secn i n borh transvcrsc and

l o ngitudi n a l sections. Each sca llop. wh ich is here

lcrmcd a st ra ti fica tio n clcmell! o r bed form lllodil1ca ti o n clement, is bounded above ancl below by

'"

d i pp i ng bounding s.u rfaces (Fig. 3).

The size of the Irollgh·sh�lpcc.l cl e me n t suggests

that it represents aeolian bedforms (dunes) super·

B o u nd i ng

s u rfaces

imposed on the la rge lineal' draas. The geometry

and internal di stri b ut ion of aeolian str�lta suggest

thaI. the cl emcn t I'ecords deposition on ba sa l slip

faces and i n ndjaccnt potholes or seoul' pits, The +

'"

bimodal oricntntioll of cross·becls and

bo u nd ing

su rfaces i lldic. ltcs de pos i t io n 011 the opposed A n n ks

+ .. + + .. � + •+ • + .

of reversing. linear a n d lon gi t ud i n a l bed fo rm s , and

alon g-crest component of

rhe occu r ren ce or a n

90

dip 10 the cross'Deds i s ex p lai ned by along-crest

mignHion of sinuosities 011 the li nca!' dUllc. Th is

general intcrpretat io n of the clement w i l l be tested and furt her rcflned by c o m pu te r-g raph i cs modc l li n g .

IlIfer·dulle eJelllellt.�·

This elcment makes u p c . IO% o f t h e d raa clement.

"" 1"ig. 7. Data on cross· bed and bounding surface oriellllltiQIl. dune clements, Yellow Sands. D:na were collected in all the qunrrics examined.

all hough i t is scarce ly prescnt i n so mc of t he quarri es s i t uatcd

nCnr the ri dge centrc. The i n tc l··dune­

dune pl i n t h clement

is of wea k l y we dge -shaped

flppearance i n transve rse sections. It is up to

3m

th i ck Hnd up to 20 m wide, and composed of low­ rathcr planar lowcl' bou ndi ng surface. and i n thesc

scctions the elemen t actually appears to be of t a b u l a r geometry ( F i g .

5).

MCnSurCIllClllS of foresct be dd i ng attitudes yicld

a well ordered pattern. which CHIl be cI,lssifled tlS a squeezed bimodal compa" rose (Fig,

7).

The

angle to horizontal win d-ripple strata. The elemont

mosr comlllorlly occu rs

[IS a n

isolated rcalUrc inler·

bedded between thicker dune elemen1s (Fig. 3).

The e l e me n t is t h o ught to rep rese n1 depos i t ion i n

inter·dune corridors a n d on low·nnglc dUlle plinths

associutecl with the s u pe r imposcd l i neal' dUlles. Its

forcsets dip up to 25-3()0, wi t h one mode towards

rare prcsencc is ascribed primarily to comlllon wind

the northwest (meiln = 3 1 3° ) and one mode towards

ct'Osion (scour fOI'mariorl) in rhe intcr-dunc fIl·cas.

thc south·southcast (mean

=

1 7 1 °) . Th c two l1lodcs

mc of ne a rl y equal ilnportancc. Readi ngs of the

associated dune·order bounding surfaccs Hlso yi eld

T.

158

hrilllZ alld L. 11. Cleml1ulIIsell

8EDFORM RECONSTRUCTION The

ae olia n bedforms t h a t produced the Yellow Sands huvc previously been inte rpreted as simple linear dunes (seifs) (Smith & Francis , 1 967, Glennie, 1970, G l e n n i e & B ulle r , 1 983), linear (and longi­ tudinal) dnms ( Ste ele . 1983) a nd transverse draas (Ya rd le y, 1984). The large size of the sand ridges, their elongated fOI'nl alld consisre n t nOl'lheast-soUlhwcst orie n tation

indicate that the Yellow S a n ds do represent linear bed fo rm s of draa size (cf. Sleele,

1983, Cl e m m ensen ,

1 989), The Imcicnt linear bedforms had On average

widt'h of 2150 111 and (Ill average s pa cin g of 3100111, and are the re by somewhat larger t h a n Ihe largest

modern linear draas (see Lancnstcl', 1983. 1988 ) , linear draas seem to have been obliq u e bedfoJ'llls during an cady phase of sedimentation, bu t truc lo" siludinal bcdfol'lns d u r i n g the linal plHlse of draa sedimentation ( Clc m m cn sc ll , 1989).

These an cie n t

The sedimenl
indicmcs lhe exist cllce

forms.

S tee le ( 1 983)

of s u pe r im posed aeolian bed­ i n te rpre ted these s u peri m posed

aeolian bedforms as crescentic transverse dunes,

but computer simulation of bedrorms comparable to those en v i sa ged by Steele y i e lds sedirnellwry sl t'uclures and a cross-bed dip pattern d ifferent from t hose characterizing t h e Yellow Sands (scc Rubin, 1987, fig. 56).

i nte l-prcr the superimposed ncolian bedforms li near dunes, and from t h e architecture o f rhe dune clcment we infer l ha t these lincHr d unes werc I'cversing (reversals in bedform a sy m m et ry ) . We

as s i n u ou s

longitudinal bcdfonns with sinuosities that migrated

:lIang-crest. The reconstruction of the

forms

is based on

lrial-ancl-errol'

ncolian bed­

simuitHion of the

field (d. Rubin, 1 987), one of these com p u te r cxperiments arc illustrated in Fig, 8, The sinuous longitudinal dunes in the m od e l are characterized by vertical climbing (cf. Rubin, 1987, fig. 77). AI rhe same time t he draas were slowly migrating s idew t l ds find cvclltually accl'cling vCl'lical1y (cf. Clemillenscn, 1 989). The structures formcd by the longi tudinal dunes are lrough-sh�lpcd i n tntnsvcrse sections, but of nearly tabular geomclry in lon g it u dina l sections, In tra nsve rse sections structures (or clcn,ents) fOI'll) regu l a rly spaced zones of intcr-digitmion in which structures obse rved in the The results o f

r

Fig, 8, Computcr-graphics rcconstruction of sedimentary structures produced by longiwdilwl rc::vcrsing sinuous dunes (cr. Rubin. 1 987, fig, 77), In the Yellow Sands these longitudinal d unes (A) were superimposed 011 lhe eelllral part of the clrilLl ridges (D), The structures produced C
Draa

reCOllSfrlfctiOIl ill northeast EI/.g/(md

structures. One

C ross - beds

159

is the re l a t i ve ly large amount of

a l o n g-crest dipping cross-beds in t he Yellow Sa n ds

.

Evidently the cl'Oss-beds re present Ihe lopognl p h i ­ cally lowest porri Oll of the superi mposed du ne

­

inter-dune system, and to j u dge fJ'OIll the geometry of thesc structurcs,

frcquently

!I9_�""'�II!\If""",---- "

27'

the a nc ie n t'

i n ter-dune areas may

have con t il i ned Sll<.lllow

scour pits

formed

by secondary airflow. The occurrence of wi nd scour i s to be expected in imer·dunc areas if they arc not prote cte d from del1ation ( Kocu re k ef al. , 1 992).

In

[he pre fe r red

reconstruclion the i nter-dune areas occurred befween

'" '" Bounding surfaces

l i near dunes supcrimposed Oil rhe maill draa. l t is likely therefore tha t the inter-dune areas were well above grou n dwa te r level, faci litating wind scour. Another d i fference is the slight angular d evi a t i o n betwecil m o ny cross-beds in t h e Yellow Sands a nd the related bo u n d i ng surfnces, which is most apparent ror data in the southeastern qu a d ran t . This devimion may Once aga i n suggest the impo rtance of wind scouring and success ive filling of the d e­ pressions formed in combination wi th the ove ral l along-crest Illigl'll tion o f dune Silluosities.

Thus, based on Olilcrop datn n nd com p u ter­ gra p h i cs modclling, i t is concluded that rhe Yellow Sa lld s rep resen t lil rgo l i ncar (oblique to l o ngi tu dinal) drH
other geological formalions (Beli, 1 99 1 ) , bUI Ih ey are cOl11mon ill se ve ral (he N ami b Sand SCtl

,eo

li·ig. 9. ompulcr imtlgc of cross-bed� nnd bounding s�lrf{lccs produced by the bedforms in the theoretic!ll model (Fig. 8).

left-hand and right-hand versions of the clements

'

are a lmost syJll m ctric�llly d i s tri b u ted on dt he l si Ie o f

.

mirror p l ane The cl em en rs me also ch a ra cte ri zed by scallo pe d c ross-bedcli ng . -innlly th e cross-bed plol of the bedforms exa min ed is of a sq u eezed bimodal appearance (Fig. 9), with iI marked down­ wind asymmetry. Th us i n n ea rly a l l aspects the observed st ru ctures and the structures p rodu ced by the sinuous longitudinal dUlles i n th e computer m ode l l i n g a re i den tical. There arc also so me i mportan t di ffe rences, howe ver

, between

(e . g .

LUllcaster,

'

1983), the

and rhe R u b a l Khali of Sfludi An�bia (Brced el ClI. , 1979). I t i s considered likely th ere fore lhat conti n ued studies of aeolian for m a t ion s will result in new finds of fossil com po u nd Saham ( Breed

a

modern sand sens, including

I'he observed ((nd the modelled

el

al., 1 979)

linear or longitudinal dunes.

W I N O IlEG I M E The large sand ridges ( d ra as) tre nd
ill the same di rectio n (55 -235°) as the rcsu ltant sa n d drift direction (238Q). I l i s cOllcluded th erefore t sc thnl the large linear bedforms d u ri ng the final ph .. of draa sedimentation were l o n gi tudinal draas that were in equ i l i bri u m w it h t h e wi n d regime. The gene s is of longitudinal aeolian bedforllls has becn much d i scussed (e.g. Lancaster, 1 982; Tsoar, 1982: Rubin & H u n ter, 1985; Glennie, 1 987; Rubin, 1990). A cco rd i n g 10 R u bi n & H u n ler ( 1 987), Ihe trend of aeolian

bedforms is determined by rhe

maximum gross bedform-normal rule. Longitudi n a l

1 60

T. Ch,.illfl. lIlUl L. IJ. CIl!IIII11(!II.\'en

bedforms can form in bidirectional wind regimes if the divergence angle between dominant
SUMMARY AND

CONCLUSIONS

I The Early Permian Yellow Sands form sevcral largc paral le l -t ren d ing sand ridges representing pa rtly p rcse rved lineal' draas. The draas expe rienced till early p h a se of lateral migration ( o bliqu e bed­ forms) und {l sccond ph ase of vertical 1.Iccret ion ( l on gi t u d in a l bedforms) befOl'e thcy were covered by aeolian stilld sheet deposits, alld ultimately wcre preservcd bencHlh low-energy murinc dcposits. 2 St u d i es of aeolian architecture and computcr­ graphics mod el l i ng indicme I ha l the dl'aas wcre superi m posed by sinuolls longilUdinal d u n es. The superimposed d u nes were reversing, non-l1ligrnting and had sinuosities Ihal migrated along-cres t . The longitudinal dunes were separated by inter-dune arcns in which shal low wind scours formed frequently. 3 I n thc final ph ase of dma sedimentation, compound l o ngitlldi n(l l bedforms formed ill a bimodal wind regime with (llternaling northwest or north winter winds and southeast or east summer 'monsoon' winds.

A C K N O W L E D G E M E NTS

This st lldy was supported by thc Gcologicnl illstitutc, University of ope n h age n , and by the Dunish M i nis t ry of Energy. We wish to thank M. Tucker and G. ulI'Woocl (Durham) for support during the initial phnsc of the investi gat io n, and the quuny owners for permission 10 work i n the quarries. Journal referees are thanked for cOI1structive reviews.

c . I O°

reasonable therefore to interpret the northwcst or north winds us winter season trade winds and thc southeast or cast winds as summer 'monsoon' winds. These '1110nS00l1' winds seem 10 have been re la ti ve ly d ry . In co n tras t to t h i s view, Glennie ( 1 9R2. 1 983) has considered Ihe Yellow Sa n ds 10 have fonne cl during the innucnce of strong unidirectional winds fl'ol11 the northeast, and S n eh ( 1 988) has postulated unidirectional winds t'1'01ll the north during the fOl'mHtion of t he I ol li egen (1 .

REFERENCES

AIIL.IIKANDT, T,S. & FKYIIEKGt:k. S.G. ( llJHO) Geologica l

unci paleoccologic studies of Ncbrnskn Stine! Hills. US Ceol. S,II·I' . p,.of. p(/P, 1 120·A. 24 PI', Om.L. C,M, ( 199 1 ) The relationships betwecn scdi lllc ll t­ llry structul'CS, Iram:porl direclions and dune types ill Mesozoic aeolian S:lIldSloncs. Amenmu Region, hilc. Sedimel/fology 38, 289- 300.

IlRlmo. C.S . . FKYlUlItGlllI.. J . G . . ANI)IH�WS, S . . MCCAULl!Y. .. LllNNMU'Z. P . , G I! II I!I .• D. & HOKSTMAN, K. ( 1 979) Regionul studies of sand scas, using Landsnt ( E RTS) i magc r), . I n : A Study of C/obal Saml Set/:; (Ed, McKee. E , D . ) pp. 305-391. US Geol. Surv, Prof, Pap. t052. CtIRIN'1'Z, T. & LHMMllNSIiN, L.B. ( 1 989) ompound lincar dUllcs ill lhc Lower Pcrmian Yellow Samls, NE Englllnd: !\c l iM Hfchilccture '1I1d dyn�mjcs. A/)s/raC'ls, 28111 fill. Geo/. CO/lgress. WMI!;'I!;IOII, J)C. 290-291. IiKINrz. T. & I.EMMENSIiN. L.Il. ( 1 990) Draa reCOil'

Draa recOlI.'ilrtlttioll ill lIortheast Ellg/alltl

Slr'u(;lion . l hc Permi�ln Ycllow S'll1ds. 1l01'lhCiist Eugltlrld, Absfl'(lCIS, 13111 1111. Sed. COIIl;I'C:ss. NOllillghmll, �.1- 95.

I.I!MMI!NSHN, L . B . ( 1 9H9) PrcSel''';lliOIl or iuterclrau aile! draa plinth deposits by the Imcrnl misratioll of la rge linear clraas (Lower Permian Yellow Sands. north cast nghllld) , Se(l. Ceol. 65, 13�- 1 5 1 . CLEMMHNSliN. LI3. ( 1 9�1 a ) Icolisk (u"Kiwktllr og ajlejrilfSs·

(/YIl(IHlik. Ell I/Ird(!,..H�gel:,'e (1/ Iii (coliske ((flejri/l!-:'\'�'ysli!l1Ier (Pm:kolllbrilllll- Recellt) /m dell 1I0rd(ttl(lllliske regiull.

Unpublished Dr Scient. thcsis. UI�ivcl'silY or Copcnll<'lgcll. LI!MM !NSIlN I . L . G . ( 1 99 1 b) Aeoliall ,Il'chitcci lirc and rescr· voir ehnractcristics. Absll,(ltU, Chal'(I(:terismioll oj" Ph'lliM alld Alwlia!! Re!u:rvoil's. Aberdeell, 2-l-27 MardI . GI.HNNIE. K.W. ( 1 �7()) Desert sedilllcllIary environnlcllIs. In: J)ev(!/oplllt:llfS ill Sc(/imelltology 2-l. Elsevier, Am· Sterdmll . 222 pp. GI.I-:NNlr.. K . W . ( 1 982) 12.11'1), I'crllliun ( Rotliegcll(lcs) pal<Jcowinds of the North SCiI, Sed, Ceol, 34, 245-265. GI.ENNIH. K.W. ( 1 983) Lowcr Penni,1I1 ROllicgcm.l dcsl;rt scdimentl.llioll ill Ihe North Sell [u'Cn. hi: Aeolitlll SedilllelliS (lnd Processes . (Ed. 13rooklicicl. M.E, & Ahlbrandt, T.S.) pp. 52 1 -54 1 . Developments il1 Scdimclltology 3H. Elscvier. AIIlSICl'dl.1rH. Gl.I�NNI,",. K.W. ( 1 987) Dcscr! scdimclltury ellvironments. present and Pflst -
6. 475-504.

LI\NCI\ST�R. N. ( 1 9M3) Lineal' dunes or Iitc Namib sand scn, Z. Geomorph. Nf' 45, 27-41).

161

LANC,\$TIiK. N . ( 1 93t{) The de"elopment of largc acolinn hcdfol"ms. Sed. Cleol. 55 . 69-8<) , M,\IJER. D. & YAKDI.llY. M . J . ( 1985) Migration, rnoditic'Hioll and mcrging in aeolian �ySlC11lS and the significance (If the depositional ITlCciUlilislllS ill Permian :Jnd Triassic dllne sands Of E u ropc and North Amcricl.l. Sed. Geol. 43. 85-2 1 8. Mc:KIH�. B.D, ( 1 �79a) Sedimcntary structun.:s in duncs, In: A Study Of Global S(IIul Seal' (Ed, Mf.:Kcc. E , D , ) pp. 83- 134, U S Gcol. Surv. Pror. Pup. 1052. Mc:Kllli. E , D . ( 1 t)79h) Ancient slIndstoncl' considered to be acolian, I l l : A Srlldy oj' Olo"fll 5alld Se(j.� (Ed. McKee, E . D , ) pp. IS7- 238. U S Geo!. Surv. Prof. Pap. 1052. PKYOII.. \v.A. ( 1 97 1 ) !'clrolog)' of the Permian Yellow Sands of lloniteustel"l1 England nnd their North Sea cquivalents, Sed, Ceol. 6. 22 1 - 254, RUOIN, D . M , ( 1 9M7) ro�·beddillg. bedforms UII
Index I)agc nu mbers in iltllic refer to ligures :tnd tobles. adhesion-ripple strata 89. 100. 1 13 aeolian accumulation us an episodic process 87 punctuated by supcrsurfacc formation 93-4 of sand, determining faclors 23 aeolian an:hilcclUfC architectural clements /53 mucro-scn lc 153. 155-7 mega. and meso-scale 153 acolian- Auyial lransilion 1 13 aeolian strata, contorted/slumped 93 aeolian stratigraphy 87- 8 aeolian trnnsport corridors 5 1 -4, 55, 57, 58-9 displacement of 52-4 gcncnltion and mainlcmlncC of 5 1 -2 acoliull units 88 ;:\Crod)'ll11mic dislodgement 5 airflow, on windward dune slope 14, 1 5 , 2 1 airflow compression 19, 20- 1 wind speed data 16- 17 , 20 Alexandria coastal duncflcld 14, 14- 2 1 Algodones dUllcficld 1 1 1 lllluvilll mcgacycles 139 Anncnllli sandstone 57. 5H uutocyclic deposition 145 av;lIanchc slip face 14 ;tVil!;lIlchc tongue� 1 15 Aztec Stil1dS10nc

clilcrctc caliche

39-40

23. 24. 1 12

23

beltcadcd sequence hYPQlhesis 140-5 belllon i te 95, 100 Bighc<11' erg 1 12, 1 1 3 bioturbation 80, 1 12 abundnncc within ergs I I J . 1 13 Cdi.lr Mesa SilndslOne 1 1 7. 1 18. 122. 124 blowout dunes 40. 1 12 blowouts 66

65 . 92 , 1 12 , 122-3 89 and snbkhn beds. stnckcd 92 simple and compound 98

cross-straIn

Il igh-angle

Oogcnfcls Fonmnioll 47. 47. 52 Oogen fcls yordnng field 53-4 bou n di ng. surfaces 1 1 8 pianoI'

cross-stratification Cedar Mcsu Sandstone sand sheet sands 1 1 1

98

on mdar transcets

62. 63. 65

Aeolian Sediments: Ancient and Modern Edited by K. Pye and N. Lancaster © 1993 The International Association of Sedimentologists ISBN: 978-0-632-03544-1

28, 30-6, 40

active compound parabolic rncgaduncs 35 contrasting dune stratigraphic!) 37 morphostratigraphic feat u res 36 sandrock nnd pcat outcrops 38 Cape Manifold dunetlelds 28.30 Cape York f'cninsula dUllctlelds 24 carbonates aeoli�ul. QuoHcnwry 127-8 carbonate dunes 26 marine 127-47 Casp�lr Sandstone 1 13 Cedar Mesa dune seas, inferences concerning 123-4 Cedar Mesa Sandstone 87. 1 1 3 , 1 1 4- 18 downwind chnnges in deposition 120-3 internal stratigrnphy 1 19-20 cements. early, in mnrine earbonat.es 142 chenier plains 26 clasts, within low-stand acoli;:mitcs 145 dirnutic change, and bounding surfaces 80 climbing dunc� 28, 67. 158 migration of 40 s(!e (/I,�o bedrorm climb cloud strcets 5 1 coaswl ph)in deposits. I.\eking 144 coastal plain facies 136. 141 coasls morphology of, and aeolian transporl corridors 52 .\'/!(! also bcuchcs: Queensland coast Cobourg Peninsula duncflcld 3S-9 contael lll<1triX 142 ooloola dune complex 26, 32 podzolized dunes 28, 4 1 coppice dunes 1 1 0 corals, scleractinhm 4 1 cross-bedding 34 , 1 56 orientation of 1 1 8 scalloped 157. 1. 58

Basal Unit, bas., I surfncc. Page S
I13 76, 81

Cape Bedford- Cape Fla ne ry dunefield

1 12

back erg 74 back burrier mangrove peats, t"c dating of bnrchnn dune tmins 49. 49, 52. 58 lind high sandllow 50 parallel 52, 54 bnrchanoicl dunes 1 1 0, 1 1 6 bilrcllans

rcgionnl. formation of 57-8 trough·shaped 65 Yellow Sunds (Permian) 155, 157, 159 S(!t! (//�'o supersu rfaces build-ups. Pnge Snnclstonc 100 bypas. ' 5 supcrsurfacc 79

163

1 15 - 1 7

Index

1 64 ryswl

reck Mcmbcl'

1 14,

utlcr FOl'llliliiOIl cyclicity

133-40

Illlirginal sabkha deposits 1 1 3 equilibrium silit.uion layer 7-�

93. 95

J lS. \:\9

mechanisms and hierarchy of 136-40 cyclothems, glacio·eustatic control or. North Arnet'iell

12M

dcnation 3 1 . 58. X I . J 14, 145 of Il1tlrinc c<.roomHcs 142

und stratigraphic incomph.!LcllCSS 128 dcll:Hion basin I1Hlrgin 54 dcnation surfaces 1 1 9- 20, 123, 124 deposition crcslnl 19-20 regressive. lacking 1 4 1 . 142 Lransgrcs:o;ivc lind rcgn:ssivc 135, 136. dcsicciilion fissures 138 detrital logs 36 di,lgCl1csis, meteoric 1 4 1 diasWIl1S 1 3 3 direct di!:\iod!lcI11Cnl 3 dislodgement rale 4-5. 7-9, 10- 1 1 Dolores Form
dUllcs 23. 1 10. 1 12 dran c l eme nts 155-6 sedimentary builclMup of

tlggnld[llion 1\nd degradat io n bllCk erg 74 110 cOMsC- unci fine-soUl'ced COMIUI

145

I) u m fries b(lsin

erosion

142

;) col i a n iJCCUlllulatioll 28-9, 29. reversillg tf4111SVCI'SC clunc 1 7 - 1 9 ,�ee al,w) dcOiltion cl'O:;ioIHII plallCs 57 erosiomd truncation 95. 136 cxcursion length distribution 4, 5. 7. ij, 9, 10 lind ripplc growtl1 4 exposure surfnccs 136. 138

cotlslol. Mel

158

1 12 1 5 1 -60

41

facies, verticlil successioll or 142 fllcies lind depositiolllil e l l virolllllcnts. descriptions :1nd

1 15 156-7

130

interpretlltions


6 1 -8 159. 160

1 8- 1 9. 19- 20

foresc t:; 65, ()5 . 1 2 1 -2 bedding altit udes 156-7 migration o(

III

1 15

fou1'lh-ordcl' cycles

128. 134. 140- 1 . 146

dctliled 135-6
Gilltymol'c rOl'ln ation Bibbsilc 32

14- 1 5 llorthwestcl"II Grall Dcsierlo 76-7 reversing 1 3-2 1 , 24. 74, 1St{ small. migration of 1 1 7 spacing within ergs I l a- I I . 124 s uperimposed 66. 1 60

147 1 13

glaciation 136 IJnd :.1eoli'.I11 carbO lla tes glncio-euslflsy

.\'ee (i/so m a i n dune types

1 12. 1 1 3

nuvinl reshaping. o f aeOliun IlIndscape�

rOfln i.lI1d flow. self-regula tory relationship bctween

i\CliSOnill revCrsul o f

ape Oc d fo l'd

129 fifth-order cyclcs 1 28. 1 33, 140- 1 , 1 45. 146 transgressivc :m<1 regrcssive sets 1 34- 5. 136 Fiskus Sandstonc Beds 57- 8 n:rmc slructures 100 nat sand bcd. panicle dis\{)dgemcilt from 3- 1 1 cXPCI'illlcntal procedure lind results 5-6 numericl.II si11lulntiOlls 7- 1 0 facies boundaries

("'Ol11plcx I I I crcsccntic 7 1 . 72. 73. 92, 1 1 6 active Clip 78 degradell n lid vegetated 76 migration of 32. 40. 4 1 . 65. 66 morphology 24. 4 1

Elim coast:ll cliff section, endorcic basins 47. 5l) Entnlch i Sundstolle (erg)

124

migr
1 12

cttrbOllillc 26 change ill slop!.;

H8

011 II

draa reconstruct ion. nort heasl England dnw swrvut iol l 153. 155 venical ,lcel'ction 155-6, 158. 160 dune ,11>1'0n 65 d l J lle JVJlallChcs
1 12

123

comrols on sand acclimulation

92, 98, 1 1 1 . 1 12

compound cresce ntic

153-4

ergs

damal

cinms

erg clemcnt

erg interiors, di rrerillg dUllc types erg Illlll'gins 109, 1 12 '-IIICicIII. Cl'itCI'iil for 1 1 1 - 12 decreasc in dune size 1 10- 1 1 l11arine seuing 1 14 and sand sheets I I I tr!:l iling crg Illargin 74

34-5, 39

127-8 131:-:, 14U. 147

inducing l'iftl,- und rourth-ordcr cycJc:-o GOII(\wmHI gluciiHioll 128, 136 gradational cllv iromncllls 1.10, 133 gwin dislodgM�Cl1t d
1 3()

20

165

ludex nllel

dunc l11orph ol ogy

reversing

158 136 aeolian deposits 1 4 1 , 142 cOlistal pla i n deposits 1 4 1

24

low sta n ds

vUl'ying bctwecn f:1Cics

1 1 7, 1 2 1 g rn i n size lind sorting. within c rg:) 1 10. 1 1 2 grninfull deposits 1 2 1

processes, Pamelox Bnsin 1 38, /40. /4/. 142-5 lower Cutlcr beds 1 1 4. //5 Lower Unit. c;'lppin g supersurfnces. Erg Mllrgin Uni t . Page Sand sto nc 92-3

grainllow deposits 1 2 1 Gran Desicrto Sund Seu 7 1 -3 northwestern. s;lnd sheets in 73-81 developn�c nt of supcrsurfaccs SO- I origin of t he S31ld sheets 77-80 sand sheet units clescribed 74-6 pu lses of sedime nt input 73 granule horizons

marine earbonale cyeles 127-47 murine-non-marillc couplets 135 murine regression, response to 57 marino st rutigraph ic record . composi t ion of marine transgression, response 10 57

1 12

gnullLle ripples 58 Great Sand Dunes, Colorado 1 10. I I I radar slIl'vey or II large clune 6.1-8 grOllnd-pcrlet r.. tillg ruclilr

rad,'II' operation

Murko\' elmin analysis

62-3, 66

used to delincate internal growth surfaces 62

dune st ruelUres

6 1 -8

133. 146

Muroon Formntion loessitcs 145 mnximum gros.� bedform- no rmal rule 159 megadu llo complexes, A ust ral ia 23-42 dUllcficid 1ll01'phology 28-9 parabolic dune morphology

Moenavc Formation sand sheets 1 1 3

cyclicity

1 33-40 f;]cies analysis 129-33

:\9 - 4 1

24

156

157

Ol'cgo l l . cOlls",1 dUlles

in tcr-cluncs

1 10 . I l l . 1 1 2, 1 1 3, 159 marino !nIH'gin 1 1 3 mud-filled 1 13 inter-sruin collision 3 l so l:.ucd U n i t . rugc Sandstonc 93

Page Sa ndstone

lack.ing

St), 92. 93, 95

142

1 12

39 Inst glaeiul maximum 35

2!.1 . 33

en-echelon

29, 33

29 . .10 , .13 superimposed 29 . 30. .1.1 clongate 24. 29 . .10. 30. 33, 3.J nested

74. M I , 82

morphology or simple 29 . 33

pisolitic. rcsitluul

lcngth:width ratio, Qucenslnnd lineur dune systems 5 1 . 53

dunes

24, 29

lineor dUllcs

23-4. 1 10 along-crest sinuosity migrmiorl crcstal spacing of 5 1 -2

157. 160

56. 59

pur;:lbolie dunes 39- 40 . .J(J. 42. 1 1 0. 1 12 compOund 29-30. J3 digitnle

kaOlinite

l,.'OIJI'se sand �nd gran u le

R8-9

paklcodune systems. Namib Sand Sefl p n lncosols 32. 34. 75, 80

128. 136. 138

hiS de posits

67

ge net ic stratigraphic u n i ts and supcrsurfacc� 89- 1 00 major sandstonc packages 100

Judd ! Iallow Tongue. Cannel Formation

32 KClq)Cr S(l llds to nc

124

or within ergs I I I . 1 1 3- 1 4 see (llso marine corbomlle cycles Nortll Stfi:ldbroke I sla nd , stabilitcd po ra bol ic Incglldlln� abund
33

inter-dune corri do rs 1 10 intcr-tl lI ne -dune pl in t h clemo11t imcl'-ClUlle el crnelH s 157

j erky subsidence

Namib coast. sandy beaches 48-9 Namib desert 45 Namib Sand Sea 45. 56. 159 Navajo Sa nds tonc /erg 1 1 2. 1 13 margilHll Iluvi
5

intcr-draa-draa element sets 153. /54. /55. 155 inter- dma -dr.", plinth clements 156

intcr-drna clements

1 14

Monument B c nch 92 Monumcnt Upwarp � , 89 . 1 1 4. 1 15 mud drapes 100. I I I . 1 1 3

significancc o f local winds 27 horizon differentiation 35 h u micre tc 36 humid areas, developmen t of pOfubol ic dunes hydrocarbon reservoir's, aeol ia n 68 im p: lct d islodge mc n t 3 im pact dislodgemcnt rotC

29-30

stratigraphy and age Slructllrc of the d U llclic itls 30-41 Middle Unit. middle sur'(nce ZOnC, Pflge StiIldSlOlle 93-9 M inne lusa Formation 1 13

hardgrounds 142 Harris Wnsh Member 89 Hermosa Formn tio n (uppcr) 127-47 beheaded sequcnce hypot hc sis 140-5 Hinehi nbrook Island Ramsay l3ily duncficld

133

hcmicyclic

lobate

29 - 30

29 . 33

29 . .13

l un:l IC 29. 33 vegeta ted 29. I I I Pnradox

Ba.sil1

127-47

166

Index

Parndox Basin (col/r'd) gcographical llnd stflHigruphicnl selling Paradox Member 139

Qucensland mcgt1dunc complcxes 129

port icle site distribution. role of 3-4 pedogenesis 42, 80 pedogenic alteration 8 1 . 82 pedogenic translocmion 35 Permian sandstones. Scoliand 1 12, 1 13 pClrofcrric ironstone layers 3 1 planar sets. Cedor MesA Sandstone 1 1 7 , 123 playa muds 1 13 podzol izli tion 31 -2. 35. 4 1 und sand composition 4 1 polygonal fractures 88. 89, 92, 93 progradalionlll dcposils 133. 135 Queensland cO�ISI 24. 26 climate 26-H dune development 26

79, 124

snnd traps 46 siindOow, through southern Namib basin sputial voriation 50- \ s:uldflow strow 156

45-59

sandstone

adhesion· rippled 1 1 3 ncoli(II\. complex intcrlllli architecture

second-order cyclcs 146. 147 tcctollica ll y induced /37, 140 secoudury Oow, plnnctary boundary sediment compartments 28 sediment flux 13, 1 7 - 1 9 , 20 see a/so sundOow

67- 8

nnd sand sea

la ycl'

S l . 52. 54. 58

sedimcnt supply

sabkha deposits 88. 89, 98, 100 inerc.ise in 93 stlbkhas 1 1 3 siliciclastic I l l . 1 12 :wlt P:111S 47 Sllll(ltioll, th reshold for 6 salwt iotl models 10 and dislodgement niles 5, 9 Sulton Trough 73 snnd availability 24, 30 see (I/so sand supply; sediment supply sand dune islands 26 28-9

sand (dullc) seas 24

oucien!. downwind chul1£es i n 109-24 ephemeral nature of 1 13- 14 expansion during marine regression 56. 57 modern 159

spatinl chnnges in 1 10 - 1 8 sond ridges 153. J 55 sand sea plinth 57, 59 sand sheets I I I . 1 12, 1 1 3. I IS edar Mcso Sandstonc 1 1 7- 18, 124 llorlhwcSICI'Il ru n Desiel'lo Sand Scn sond sources

sand storm evcms 49. S2 sand supply. limiting dune formation sand wi Is 79. 80 sand t ransport rates 1 3 - 1 4 o n Il sloping surCtlce 1 4 and surface sheur stress 1 4

cross-strutificd 95 Schnebly Hill Formation 1 12, 1 1 3 Scour pits 6 7 , 157 migration o( 123 see (I/so vOrtex SCQur!) scours 89.90. 92, l i S , 159 migration of 122 and revcl'sing wind!) 66-7 see nhQ supcrscoops; vortex scours sea levcl change 1 1 4 eustutic 73. 8 1 , 136. 142 glacio-eustatic 138-9. 146- 7 influence on deOntion basin dynamiCS maintenance 56-8

rndiocarbon daling 32 Ramsay Btl)' duncficld 39-41 reactivalion surfaces 65. 66. 67 ,'cccptivc shores 28 red marker unit 93. �4, 95 reddening. of dunes 3 1 . 32 . 34 replenishment 8. 9 reworking in siw 28 marine 153, 155 Page Sandstone 100 p. lrt ia l 3 1 of sund sea margins 57 by wind 142 ripple Slr3ta 65 rippling, and surCace rcsorling 3, 4 Rotliegendes. erg interior deposit$ 1 1 3

initiation of

26

in 122 sand storage 49 shift

73-81

Oueensland near·shol'c zone 26, 28 southcrn Nnl1lib dcnatioll basin 48-55. S8 western Gran Desicrto and Sea 8 1 sedimcntary wedgc 145 sequcnce strntigl'aphy 135-6 shal l ow I11m'inc (aci cs 1 4 1 -2 shenr stress 5, 2 1 surface 1 4 shear velocity 6 , 10. 1 4 , 1 7 . 1 9 Shelburne Bay dunelicld 36, 38 shonling upwards cycles 133 SQSSUS Sand Formation 56 South Atlantic onticyc1onie system 48 sout hern Namib deOatioll basin aeolian transport corridors S I -5 influence of SCI] level movemcnt on deflation basin dynam ics and sand sen Illuinlcnancc 56-8 morpholog)' of 46-7 pallel'll of !Surface windnow 48 present-day snndOow PUIICTII 48-SI stlndf10w through 45-59 Southern Pcrmiun Basin, palocolntitude 160 spiral vortices, longitudinal 5 1 sHlbilized surfaces 80 star dUlle clm ins 72 star dunes 24, 7 1 . 1 10

Illdex

133 storm events SlOSs slope 1 4 subaqueous.ripplc StraIn 100 subsidence 136 insttlnltil1cous jerky 128. 136. 138 Queenslund coast 24 varying rules of 147 supcrscoops 95. 98 sllpersurfoees 89- 100 Cedar Mesn Sandstone 1 19-20. defined 87-8 Gran Desierto Sand Sen 7 1 -82 120. 123 local

affccting ail'flow 7t:J-9 Oil dUlle area margins I I I and megadune complexes vCl1tifacts 53, 55

124

�

Tcmple Bay dUlleltcld 38 Tcnslcep erg 1 12 tlterm:ll ins tability. planctnry boulldary layer 51 _ thermolu llullesccnce dOling 34 . 36 reliabilit), suspect 35-6 third-order cycles 128. 146. 147 und tectonic pu lses 137. 1 39-40 Thousand Pockets Member 89 threshold velocity 1 4 topognlphy. ufrccting dune size �lIld Illorpholog)' tmee fossils 1 13 trampoline tectonics 128 tmnsgrcssive dunes 41 CalX! Flattery Itre�1 35 Transition Unit. Poge Snndstone 99-100 t rnnsporl nlles 4. 10 transverse dUlles 23. 24. 1 10 . 1 12 reversing, aeolian d)'mHllics of 13-21 1 7- 19 erosion pin ;mel gradient data 1 6- 1 7 wind �peed duta

um:onroTlllitics 129 regional 89 upwurd drying cycles vegetation

76

1 14

24 ' 29

vortex cells 52, 53 vortex scours 63. 67

tangent rclationship ( Bagllold) 1 3- 1 4. 20 leeton c cycl icity. and third-order cycles 137. 139-40 lCC10lllcs affecting sand supply 73 lind coustal sediment accumulation. Queensland 24. teepee structures 100

Triungle Cliff dUlle sand 40- 1 trough sets, Cedar Mesa Sandstone

1 67

1 15- 1 7. 123

41

26

wadi channels 94, 95 Wnhher's Law 129 wntcr toblcs 4 1 . 78 locHI 65 WlIlhumbn bench slind 40 wnvy lumill
yardung surraces 53 yardangs 52-4. 55. 56 1 13 Yellow Sands (Permian) northeast England. drau reconstruction ncolian architecturc 1 53-7 bedrorm rcconsu-uetion 157-9 geological setting 1 52-3 wind regimc 159-60 ,ibn",

77-8. 1 1 1 . 1 1 2. 1 13

1 59-60

alional

15 1 -60