Biolaminated deposits

Lecture Notes in Earth Sciences Edited by Somdev Bhattacharji, Gerald M. Friedman, Horst J. Neugebauer and Adolf Seilacher

9 I

III

III

I

I

Gisela Gerdes

Wolfgang E. Krumbein

Biolaminated Deposits I

I

I

Springer-Verlag Berlin Heidelberg NewYork London Paris Tokyo

Authors Dr. Gisela G e r d e s Prof. Dr. W o l f g a n g E. Krumbem GeomlcrobJology Division, University of Oldenburg Carl-von-Ossietzkystr. 9-11 D - 2 9 0 0 OIdenburg, West G e r m a n y

ISBN 3 - 5 4 0 - 1 7 9 3 7 - 2 Springer-Verlag Berlin Heidelberg N e w York ISBN 0 - 3 8 7 - 1 7 9 3 7 - 2 Spdnger-Verlag N e w York Berhn Heidelberg

This work is subject to copynght All rights are reserved, whether the whole or part of the material ts concerned, specifically the rights of translation, reprinting, re-use of tllustrattons, recitation, broadcasting, reproduction on microfilms or in other ways, and storage in data banks Duplication of this pubtlcatlon or parts thereof Is only permitted under the provisions of the German Copynght Law of September 9, 1965, in its version of June 24, 1985, and a copynght fee must always be paid, Vtolations fall under the prosecution act of the German Copyright Law, © Springer-Vedag Berlin Heidetberg 1987 Printed in Germany Pnnttng and bmding Druckhaus Beltz, Hemsbach/E,ergstr 2132/3140-543210

Petrificata parentes libus

montium calcariorum non filii

sed

sunt, cum omnis calx oriatur ab anima-

(Linnaeus,

Systema Naturae,

Ed. XII, T.

III, p. 154, 1760-1761)

PREFACE

The geological only

significance of life has long attracted mankind.

have single groups of organisms been considered,

building animals,

diatoms or "monera"

(radiolarian,

such as

Not

frame-

globigerins,

fo-

rams),

but unitarian pictures were also drawn concerned with the regu-

lation

and

pathways.

feedback The

of geochemical cycles by

enzyme-controlled

back-coupling system of

inanimate matter fascinated Vernadsky crystallographer,

interacting

metabolic living

and

(1863 - 1945), a mineralogist and

and is again stressed in Lovelock's Gaia

and Krumbein's Bioplanet or Bioid approach.

hypothesis

The role of microorganisms

in this respect is well documented in terms of disintegration of rocks, production and mineralization of organic compounds, oxidation

and reduction of metals,

ore formation. of

biomineral

catalyzation of the

formation and

biogenic

Records of stromatolites arising from the vital activity

microorganisms date back to the earliest known sedimentary environ-

ments of the Precambrian era.

The tified

aim of the work presented here is to document the in-situ straaccretion

microbes. duced the

Part

of sediments attributable to the vital I comments on terms

sedimentary structures and products. occurrence of microbial mats

activity

which relate to microbially Part II is concerned

(potential stromatolites)

in

marginal marine environments of arid and temperate coastlines. modes

of

facies

evolution in subenvironments are shown

integration of sedimentological,

microbiological

of prowith

modern Varying

through

the

and faunistic data. In

Part III structures attributed to the activity of Precambrian, and Lower Jurassic microbial communities are analyzed,

Permian

and some comple-

mentary aspects concerned with the geological potential of microbes are summarized.

Acknowledgements

(Gisela Gerdes)

P r e s e n t e d h e r e is a m o d i f i e d v e r s i o n of m y thesis w h i c h encompasses a number of individual publications. I am indebted to m a n y p e o p l e w h o a c c o m p a n i e d my way over the past years. My b e n e f a c t o r in this w o r k was W.E. Krumbein. He first introduced me to the fascinating system of microbial mats. From Gavish Sabkha and Solar Lake we went on to include the "Farbstreifen-Sandwatt" as parts of the expanding biosed i m e n t a r y system. We then turned our a t t e n t i o n to counterparts of all this in fossil records, spanning the gap b e t w e e n b i o l o g y and geology. My first encounter w i t h a c t u o p a l e o n t o l o g y was during my c o o p e r a t i o n w i t h Wo Sch~fer. His b o o k " A k t u o p a l ~ o n t o l o g i e nach Studien in der Nordsee" was the first scientific w o r k w h i c h I was able to follow through from its conception. His "Schule des Sehens", w h i c h was transformed into reality through the r e o r g a n i z a t i o n of exhibits at the Senckenberg Museum, Frankfurt, remains one of the most m e m o r a b l e imp r e s s i o n s of m y stay in that city. H.-E. Reineck p r o v i d e d support and advice in the fields of actuogeology and actuopaleontology. Our c o l l a b o r a t i o n b e g a n in "Senckenberg am Meer", Wilhelmshaven. I w o u l d like to thank h i m for the interest he shared in m y w o r k and for all his h e l p and advice. During our trips to ancient and m o d e r n d e p o s i t i o n a l environments and through our w o r k in the l a b o r a t o r y he taught me to r e c o g n i z e and understand sedimentary structures. My thanks are further extended to my other benefactor, H. K. Schminke. I am grateful also to colleagues from the G e o m i c r o b i o l o g y team and to K. Wonneberger, my former p a r t n e r at O l d e n b u r g U n i v e r s i t y marine b i o l o g y unit, Wilhelmshaven, for their d i s c u s s i o n and advice. Memories o f our w o r k together on Mellum, in the G a v i s h Sabkha, by Solar Lake and in Elat unite me w i t h Eo Holtkamp. Our stay, laboratory w o r k and accommodation on M e l l u m w e r e made p o s s i b l e b y the M e l l u m Council and in Israel by the H. Steinitz Marine B i o l o g y Laboratory, Elat and its staff. I am p a r t i c u l a r l y g r a t e f u l to F. D. Por for his advice during our stay in Israel. I would also like to thank all for a s s i s t a n c e and care in the p r e p a r a t i o n of drawings, reproductions, photographs, thin sections and checking of the manuscripts: R. Fl~gel, G., K. Oetken and H. Gerdes, W. Golletz, A. Gr~nert, E. Johnston, M. and H. M~ller, I. Raether, V. Schostak, L. Tr~nkle. I e s p e c i a l l y want to thank J. Gifford for her p a t i e n t h e l p in t r a n s f o r m i n g this m a n u s c r i p t into readable English. Finally, I am indebted to Dr. Engel and S p r i n g e r V e r l a g for p u b l i c a tion in the Lecture Notes series. I w o u l d like to thank e v e r y b o d y who made this possible.

S U M M A R Y B i o l a m i n a t e d deposits, p r o d u c e d by m i c r o b i a l communities, were studied in m o d e r n p e r i t i d a l e n v i r o n m e n t s and in the rock record. The term microbial, mat refers to modern, the t e r m s t r o m a t o l i t e to ancient analogs. The t e r m b i o l a m i n a t e d d e p o s i t s was used to e n c o m p a s s b o t h microbial m a t s and stromatolites. M i c r o b i a l mat e n v i r o n m e n t s studied are the Gavish Sabkha, the Solar Lake, b o t h h y p e r s a l i n e b a c k - b a r r i e r systems at the Gulf of Aqaba, Sinai Peninsula, and the " F a r b s t r e i f e n - S a n d w a t t " (versicolored sandy tidal flats) on Mellum, an island in the e s t u a r y e m b a y m e n t of the southern N o r t h Sea coast. Three f a c i e s - r e l e v a n t categories were distinguished: (i) the m a t - f o r m i n g microbiota, (2) e n v i r o n m e n t a l conditions controlling mat types and lithology, (3) b i o t u r b a t i o n and grazing. Cyanobacteria a c c o u n t for b i o g e n i c sediment a c c r e t i o n in all cases studied. T h r e e m a j o r groups occur: filamentous cyanobacteria, coccoid unicells w i t h b i n a r y fission and those w i t h m u l t i p l e fission. In the p r e s e n c e of these groups the following mat types evolve: (i) continuously flat (stratiform) L ~ - l a m i n a e (occur i n all environments studied); (2) translucent, v e r t i c a l l y extended L v - l a m i n a e (only Gavish Sabkha and Solar Lake); (3) n o d u l a r granules (only Gavish Sabkha). Basically, the d e v e l o p m e n t of mats is c o n t r o l l e d by moisture. Thus h i g h - l y i n g parts w h e r e the g r o u n d w a t e r table runs m o r e than 40 cm b e l o w surface are b a r e of mats. These are: The circular slope and e l e v a t e d c e n t e r of the G a v i s h Sabkha, the shorelines of the Solar Lake and the e p i s o d i c a l l y flooded upper supratidal zone of M e l l u m Island. The following situations of w a t e r supply w e r e found to stimulate mat growth: (i) Capillary m o v e m e n t of g r o u n d w a t e r to exposed surfaces, (2) shallowest calm water, b o t h r e a l i z e d in the G a v i s h Sabkha and the Solar Lake. On M e l l u m Island, mats form in the lower supratidal zone, w h i c h is flooded in the spring tide cycle and w e t t e d during low tide by capillary groundwater. S a l i n i t y is almost that of normal seawater, w h e r e a s in the Solar Lake, it ranges from 45 °/oo to 180 °/oo and in the G a v i s h Sabkha, it reaches more than 300 °/oo. S a l i n i t y increase is c o r r e l a t e d w i t h rising c o n c e n t r a t i o n s of m a g n e s i u m and sulfate ions. In the Gavish Sabkha, episodic sheetfloods cause h i g h - r a t e sedimentation w h i c h is a c c i d e n t a l to the living mats. Episodic low-rate s e d i m e n t a t i o n stimulates the mats to grow through the freshly d e p o s i t e d sediment layer. This occurs p r e d o m i n a n t l y on M e l l u m Island due to eolian transport. W i t h i n the G a v i s h Sabkha, m i n e r a l o g y of sediments, c o m m u n i t y structures, standing crops, redox p o t e n t i a l s and p H are h i g h l y c o r r e l a t i v e to the i n c r e a s i n g evenness in m o i s t u r e supply w h i c h is r e a l i z e d b y the i n c l i n a t i o n of the s y s t e m b e l o w mean sea level. These conditions bring about a lateral sequence of facies types w h i c h include (I) siliciclastic b i o l a m i n i t e s at the coastal bar base, (2) nodular to b i o l a m i noid c a r b o n a t e s at saline mud flats, (3) r e g u l a r l y stratified stromatolitic c a r b o n a t e s w i t h ooids and oncoids w i t h i n the h y p e r s a l i n e lagoon, (4) b i o l a m i n a t e d sulfate t o w a r d t h e elevated center. High-magnesium calcite in facies type 3 p r e c i p i t a t e s around d e c a y i n g organic matter and forms also the ooids and oncoids. These occur p r e d o m i n a n t l y w i t h i n h y d r o p l a s t i c L v - l a m i n a e w h i c h p r o v i d e n u m e r o u s n u c l e a t i o n centers. W i t h i n the Solar Lake, facies type 3 (stromatolitic carbonates w i t h ooids and oncoids) is m o s t important, and grows to e x t r a o r d i n a r y thickness at the lake's shelf. The regular a l t e r n a t i o n of dark and light

VJ

laminae results from seasonally o s c i l l a t i n g w a t e r depths. These conditions couple b a c k over changing light and salinity intensities t o changing dominance structures of m a t - b u i l d i n g communities. Increasing salinity correlates w i t h d e c r e a s i n g w a t e r depth and a c c o u n t s for the relative a b u n d a n c e of coccoid unicells and diatoms, b o t h active p r o d u cers of e x t r a c e l l u l a r slimes (Lv-laminae). W a t e r depths locally or temporarily i n c r e a s e d favor surface c o l o n i z a t i o n by Mic~ocoleu8 chthonoplastes (Lh-laminae). The b i o l a m i n a t e d deposits of the v e r s i c o l o r e d tidal flats on M e l l u m Island are similar to facies type 1 of the Gavish Sabkha (siliciclastic biolaminites). D i f f e r e n c e s exist in the lithology: Sediments upon or through w h i c h the mats on M e l l u m Island grow are made up of clean sand. The grains originate p r e d o m i n a n t l y from re-worked glacial sediments and are rounded to well rounded. By contrast, the strong a n g u l a r i t y of s i l i c i c l a s t i c grains in the Gavish Sabkha clearly shows their status as p r i m a r y w e a t h e r i n g products. In all environments studied, insects p l a y a s i g n i f i c a n t role. M a i n l y salt b e e t l e s c o n t r i b u t e to the l e b e n s s p u r e n spectrum. There is no indication that b u r r o w i n g and grazing beetles and dipterans are detrimental to the growing mat systems. A c c o r d i n g to the m a r i n e fauna, two distributional barriers exist: (i) p h y s i c a l and (2) b i o g e o c h e m i c a l factors. Physical b a r r i e r s are (a) h y p e r s a l i n i t y and barrier-closing, w h i c h r e s t r i c t the m a r i n e fauna in the G a v i s h Sabkha and the Solar Lake to a few species, m a i n l y m e i o f a u n a l elements such as o s t r a c o d s and copepods. Only in the Gavish Sabkha, one m a r i n e gastropod species occurs w h i c h colonizes mud flats of lower salinity. A salinity barrier of about 70 °/oo separates the g a s t r o p o d h a b i t a t s from the zones of growing mats. Under reduced salinity, the snails are able to destroy the m i c r o b i a l mats completely. (b) D e c r e a s i n g r e g u l a r i t y of flooding in the m i c r o b i a l mat e n v i r o n m e n t of M e l l u m Island excludes intertidal d e f o r m a t i v e b u r r o w e r s such as cockles and lugworms. However, locally the mats are p i e r c e d by numerous d w e l l i n g traces. These stem from small polychaetes and amphipod crustaceans w h i c h are able to spread over the i n t e r t i d a l - s u p r a t i d a l b o u n d a r y and settle up to the MHWS-Ievel. Biogeochemical b a r r i e r s are oxygen d e p l e t i o n w i t h i n the sediments, high ammonia and sulfide contents, which generate through b a c t e r i a l break-down of organic matter. W i t h i n the h i g h l y p r o d u c t i v e mats of Mic~ocoleu8 chthonoplastes on M e l l u m Island, dwelling traces of marine p o l y c h a e t e s and a m p h i p o d crustaceans d i s a p p e a r due to these conditions. Microcoleus chthonoplastes, indiThe name of the m a t - f o r m i n g species, cates its c a p a c i t y to form "soils" (Greek chthonos). While lithology is not altered, the p r e s e n c e of Mic~ocoleu8 mats leads to a h a b i t a t change which excludes t r a c e - m a k i n g "arenophile" i n v e r t e b r a t e species and favors "chthonophile" species w h i c h do not leave traces. S t r o m a t o l i t i c m i c r o s t r u c t u r e s studied in rock specimens were interpreted using m o d e r n analogs: Microcolumnar buildups in P r e c a m b r i a n stromatolites, ooids and oncoids were compared w i t h those of modern microbial mats. The nodular to b i o l a m i n o i d facies type found in the Gavish Sabkha was s u g g e s t e d to be an analog to the P l a t t e n d o l o m i t e facies of Permian Zechstein, North Poland. Studies of the Lower Jurassic ironstone of L o r r a i n e clearly indicate that fungi h a v e b e e n involved in the formation of stromatolites, ooids and oncoids. In conclusion, the comparative study of m i c r o s t r u c t u r e s in m i c r o b i a l mats and stromatolites reveals a b e t t e r u n d e r s t a n d i n g in both fields. In m a n y cases, it was g e o l o g y w h i c h first revealed the s i m i l a r i t y of recent forms to those ancient ones and c o n s e q u e n t l y e n c o u r a g e d r e s e a r c h into them.

CONTENTS

PREFACE ............................................................ ACKNOWLEDGEMENTS ................................................... SUMMARY .% . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I.

LAYERED SEDIMENT ACCRETION BY MICROBES INTRODUCTORY REMARKS .......................................... i.

2. II.

III IV V

TERMS i.i. 1.2. 1.3. THE

IN USE ............................................... Stromatolites and subsequent terms ................... Specific fabrics without direct evidence of microbes Biolaminated particles ~ ..............................

PROBLEM

OF

VERSATILITY

.

.................................

STROMATOLITE ENVIRONMENTS IN T H E P E R I T I D A L ZONE MODERN EXAMPLES ............................................... i.

THE GAVISH SABKHA A HYPERSALINE (GULF OF AQABA, SINAI PENINSULA) -

BACK-BARRIER SYSTEM ............................

.........................................

3 3 5 6 9

13

15

1.1.

Introduction

1.2.

Methods

1.3.

Locality

...........................

18

1.4.

The physical environment ............................. 1.4.1. Geomorphic relief ............................. 1.4.2. Hydrology ..................................... 1.4.3. Temperatures ..................................

18 18 22 24

1.5.

Lithological framework ........................ ....... 1.5.1. Evaporites .................................... 1.5.2. Carbonates .................................... 1.5.3. Detrital clastics ............................. 1.5.4. Internal fabrics of sheetflood deposits .......

25 25 27 27 29

1.6.

Stromatolitic facies types ........................... 1.6.1. The microbiota ................................ 1.6.2. Major mat-s%ructuring organisms ............... 1.6.3. Character and distribution of stromatolitic facies types .................................. 1.6.4. Facies type-related biogeochemistry ........... 1.6.5. Products of early diagenetic processes ........ 1.6.6. In-situ formation of ooids and oncoids ........ 1.6.7. Microbially modified surface structures .......

30 30 31 34 42 45 49 53

1.7.

Faunal 1.7.1. 1.7.2. 1.7.3. 1.7.4. 1.7.5. 1.7.6.

55 56 56 58 65 66 68

1.8.

Modes

1.9.

Summary

.............................................. and

previous

work

influence on the biolaminated deposits ........ Species composition and distribution .......... Trophic relations ............................. Systematic ichnology .......................... Environmental zonation of trace categories .... Skeletal hard parts ........................... Grazing stress (experimental approach) ........ of

stratification and

conclusions

15 16

..............................

70

..............................

72

VIII

2. T H E S O L A R L A K E - I M P O R T A N C E O F S M A L L T E C T O N I C E V E N T S (GULF OF AQABA, SINAI PENINSULA) ..........................

.

75

2.1.

Introduction

.........................................

75

2.2.

Locality

previous

76

2.3.

Bathymetric

2.4.

Sub-environments 2.4.1. The shelf 2.4.2. The slope

and facies types .................... ..................................... and bottom ..........................

78 78 84

2.5.

Lithologic and ichnologic framework .................. 2.5.1. C l a s t i c c o m p o u n d s ............................. 2.5.2. Evaporites .................................... 2.5.3. Ichnologic patterns ...........................

85 85 85 86

2.6.

Summary and conclusions .............................. 2.6.1. Occurrence of facies types compared to the Gavish Sabkha ................................. 2 . 6 . 2 . T i m e i n t e r v a l s r e c o r d e d in s t r o m a t o l i t e s ...... 2.6.3. Importance of small tectonic events ...........

87

and

zones

and

work

...........................

limnologic

cycle

...............

3. V E R S I C O L O R E D TIDAL FLATS (MELLUM ISLAND, S O U T H E R N N O R T H SEA) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .........................................

77

87 89 90

93

3.1.

Introduction

3.2.

Methods

3.3.

Locality and previous work ........................... 3.3.1. Recent sedimentological history ............... 3.3.2. General setting of Mellum Island a n d s t u d y a r e a .............. . . . . . . . . . . . . . . . . . . . 3.3.3. P r e v i o u s w o r k . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

95 97

3.4.

The physical environment of mat formation ............ 3.4.1. C l i m a t e . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.4.2. F l o o d i n g f r e q u e n c y . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.4.3. Salinity ...................................... 3.4.4. Moisture ...................................... 3.4.5. Morphological unconformities ..................

97 97 98 98 98 99

3.5.

Sub-environments and facies .......................... 3.5.1. L o c a l d o m i n a n c e o f m a t - p r o d u c i n g s p e c i e s ...... 3.5.2. S t r a t i f i c a t i o n of living top mats ............. 3.5.3. Internal sedimentary structures ............... 3.5.4. S t a n d i n g c r o p s a n d b i o g e o c h e m i s t r y ............

i01 i01 102 105 106

3.6.

Fauna and ichnofabrics ............................... 3.6.1. Mixed marine-terrestrial composition .......... 3.6.2. Trophic types ................................. 3.6.3. Regional distribution of trophic types ........ 3.6.4. Life habits and ichnofabrics ..................

109 109 iii 114 114

3.7.

D o m i n a n c e c h a n g e a n d its i m p o r t a n c e f o r b i o t u r b a t i o n grades and patterns .................................. 118 3.7.1. Effects of increasing elevation ............... 118 3.7.2. E f f e c t s o f i n c r e a s i n g m i c r o b i a l p r o d u c t i v i t y .. 1 2 4 3.7.3 Promoting and limiting distributlonal factors 125

..............................................

93 94 94 94

IX

3.8.

Intertidal-supratidal sequence ....................... 3.8.1. Change of sedimentary internal structures ..... 3.8.2. Change of sedimentary surface forms ...........

127 128 129

3.9.

Subaerial rise of biolaminated quartz-sand (experimental approach) ..............................

132

Summary

134

3.10.

4.

III.

WHAT

THE

4.

ENVIRONMENTS

HAVE

IN C O M M O N

.......

137

4.3.

Peritidal settings ................................... 4.3.1. The "sabkha cycle" ............................ 4.3.2. Temperate humid coastlines ....................

139 139 140

THE

141

"Purpose"

BETWEEN

organisms

REMARKS

Saltbeetles:

INTRODUCTION

pioneer

- FINAL

4.2.

GAP

as

..............................

Cyanobacteria

2. M E T H O D S 3.

conclusions

4.1.

SPANNING i.

and

of

dwelling

MICROBIOLOGY

AND

...................

137

burrows

138

GEOLOGY

...........

.............

...............................................

143

....................................................

DESCRIPTION

AND

INTERPRETATION

OF

FOSSIL

MICROSTRUCTURES

144 ...

145

3.1.

Precambrian Gunflint iron formation, Ontario ......... 145 3.1.1. Provenance of rock samples and previous work .. 1 4 5 3.1.2. Microstructures ............................... 146

3.2.

Permian Zechstein Plattendolomite of North Poland (PZ3) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.2.1. Provenance of rock samples and previous work 3.2.2. Microstructures ...............................

148 .. 1 4 8 148

3.3.

Lower Jurassic ironstone, Lorraine ................... 151 3.3.1. Provenance of rock samples and previous w o r k .. 1 5 1 3.3.2. Microstructures ............................... 152

3.4.

Summary

and

conclusions

..............................

PATHWAYS INVOLVED IN M I C R O B I A L SEDIMENT ACCRETION: A COMPLEMENTARY SUMMARY ....................................

REFERENCES

.........................................................

154

157

165

PART

LAYERED

-

INTRODUCTORY

SEDIMENT

REMARKS

I

ACCRETION

ON

TERMS

BY

MICROBES

AND

PROBLEMS

-

"The

name

tions

stromatolite

with

a fine,

structure,

in c o n t r a s t

of

...

oolites

transition tion

between

the

laminated

structures

products

comment

attributable

on terms

tic b a c k g r o u n d . also

to

these

generated

The general

sedimentary

I. i. S t r o m a t o l i t e s

KALKOWSKY patterns

(Table

and

i) with

same

gene-

in use led us

of

microbially

terms

the term s t r o m a t o l i t e

only the structure

of their

aggregates

KRUMBEIN,

Subsequently,

namely

thin

structures.

used

by r e f i n e d

paleomicrobiology

the

structures

of terms

on the t e r m i n o l o g y

by o r g a n i s m s

evidenced

stromatoid

of

cover one and the

lack of d e f i n i t i o n s

produced

more

to s e d i m e n t a r y

of m i c r o o r g a n i s m s

in rocks,

1983).

to

IN USE

terms

remarks

and s u b s e q u e n t

(1908)

is also a

The transi-

from a center point."

relating

that these

introductory

formation

1908)

to the a c t i v i t y

the aim of d e m o n s t r a t i n g

ooid-bag

independance

forma-

laminated

sense there

ooid and stromatoid.

polyooid,

I. TERMS

Here we will

flat

to the c o n c e n t r i c

increasing

(E. KALKOWSKY,

to c a r b o n a t e

or less

In a c e r t a i n

from ooid,

denotes

relates

more

refer

..."

1965;

the main

to

that

(translated

suggestion

KNOLL

layered

so small

of m i c r o p a l e o n t o l o g y

& TYLER,

were

to

"have been

is p r e s e r v e d

this v i s i o n a r y

methods

(BARGHOORN

that m i c r o o r g a n i s m s

which

by

was more and merging

& AWRAMIK,

framework builders

of

into 1983),

stroma-

~olites.

The rize

term Spongiostromata

fossil

stromata

crustose

include

origin was

growth

was

structures.

stromatolites

carbonate

introduced

as well

precipitation

by PIA

According

(1927) to PIA,

as oncolites,

by crustose

algae.

to

characte-

the Spongio-

and his

theory of

TABLE 1. Terms relating to m i c r o b i a l l y g e n e r a t e d layered structures and particles

Stromatolites Spongiostromata Algal sediments Cryptalgal fabrics Algal mats B l u e - g r e e n algal bioherms Microbial mats

LAYERED STRUCTURES FOSSIL AND RECENT: SYNONYMOUS TERMS

I.

Growth b e d d i n g FABRICS W I T H O U T DIRECT EVIDENCE OF MICROORGANISMS

II.

III. PARTICLES

Subsequent intertidal

(KALKOWSKY, 1908) (PIA, 1927) (BLACK, 1933) (AITKEN, 1967) (GOLUBIC, 1976) (RICHTER et al., 1979) (BROCK, 1976; KRUMBEIN, 1986) (PETTIJOHN & POTTER, 1964)

Fenestral fabrics Thrombolitic fabrics

(TEBBUTT et al. 1965) (AITKEN, 1967)

Oncoids Ooids

(HEIM, 1916) (KALKOWSKY, 1908)

studies of crustose algae in m o d e r n shallow subtidal environments

of the tropics and subtropics have

PIA's idea that calcareous algae have built stromatolites.

Accordingly,

terms created to designate modern analogs of stromatolites were sediments" or "algal mats".

Further terms used are

and b l u e - ~ r e e n algal b i o h e r m s since

and

supported

"algal

"cryptalgal fabrics"

"blue-green algae" were o b s e r v e d to

be most c o m m o n l y involved in stromatolite formation.

The term "blue-green algae" is the traditional b o t a n i c a l assignment. However,

t a x o n o m i c a l l y they are not algae but g r a m - n e g a t i v e l y reacting,

photosynthetic

bacteria.

Thus

group is now "cyanobacteria" 1979c;

RIPPKA et al.,

the t a x o n o m i c a l l y revised name of

(STANIER & COHEN-BAZIRE,

1977;

the

KRUMBEIN,

1979).

However, we should avoid the term "cyanobacterial mats" to d e s i g n a t e m o d e r n analogs of stromatolites

for two reasons:

i. A l t h o u g h many stromatolites are in fact p r o d u c e d via p h o t o s y n t h e tic a c t i v i t y of cyanobacteria, laminated greens"

rock

structures

are

These

structures

can also originate

organotrophic al.,

it seems important to stress that

1985;

bacteria DANIELLI

1981; KRETZSCHMAR,

not e x c l u s i v e l y

(DAHANAYAKE & KRUMBEIN,

& EDINTON,

1982; KRUMBEIN,

produced

from fungi 1985;

by

"blue-

and

chemo-

DAHANAYAKE

1983; D E X T E R - D Y E R et al., 1983).

wavy

et

1984; GYGI,

2. In

the

light of studies on m o d e r n l a m i n a t e d mats w h i c h

display

very complex b i o c o e n o t i c systems including n u m e r o u s groups of and n u m e r o u s m e t a b o l i c pathways, produced

by

diverse

microbes

it is a s s u m e d that s t r o m a t o l i t e s were

microecosystems

rather than

by

"monocultures".

C y a n o b a c t e r i a l and fungal components are often well p r e s e r v e d in matolites while in

due to their e x t r a c e l l u l a r sheaths,

other a s s o c i a t e d p h o t o t r o p h s and a n a e r o b i c h e t e r o t r o p h s

evidence

however,

(AWRAMIK et al.,

regulate the

1978;

KNOLL &

AWRAMIK,

The

i m p o r t a n t for the trapping and p r e c i p i t a t i o n of

biochemical

c a l c i u m carbonate,

1979a,

which

often

bacteria

magnesium,

copper,

iron,

manganese

1972; FRIED~tAN et al.,

1980; F E R G U S O N & BURNE,

1984; E C C L E S T O N et al.,

occur in a s s o c i a t i o n

with

which

support

the s u c c e s s i o n

salts

1973; KRUMBEIN,

1981; NOVITSKY,

1985; W E S T B R O E K et al., stromatolites.

and

is

minerals

Hence

and fungi are c o n s i d e r e d to be the main p r o d u c e r s of

substrate

are

a c t i v i t y of the a s s o c i a t e d b a c t e r i a

1969; MITTERER,

b; W I L S O N et al.,

LUCAS & PREVOT,

not

These,

"physicochemistry" of a mat system and thus

fundamental.

(KITANO et al.,

are

1983).

particularly e.g.

stro-

envelopes and capsules,

subsequent

1983; 1985), cyano-

organic

biochemical

a c t i v i t y of other bacteria.

A c c o r d i n g l y the term "microbial mat" is p r e f e r e n t i a l l y used today to denote m o d e r n analogs of s t r o m a t o l i t e s 1979;

BAULD,

1984; COHEN et al.,

(BROCK,

1984).

1976;

In their u n c o n s o l i d a t e d state,

m i c r o b i a l mats of varying c o m p o s i t i o n are also termed matolites"

(KRUMBEIN,

1983).

"potential

A s a t i s f a c t o r y d e f i n i t i o n of

mats has been given r e c e n t l y by K R U M B E I N

To

K R U M B E I N et al.,

microbial

(1986a).

finish the list of terms a s s o c i a t e d w i t h s t r o m a t o l i t e s and their

m o d e r n analogs we refer to the atlas of p r i m a r y s e d i m e n t a r y of

stro-

P E T T I J O H N & P O T T E R (1964),

who included stromatolites

structures inasmuch

as

they are "a type of growth bedding".

i. 2. S p e c i f i c fabrics w i t h o u t d i r e c t e v i d e n c e of m i c r o o r g a n i s m s

Upon specific

decay,

sediments can be devoid of m i c r o b i a l cell remains

patterns

but

such as fenestral and t h r o m b o l i t i c fabrics can indi-

cate s e d i m e n t a c c r e t i o n by microbes.

F e n e s t r a l fabrics in laminated m i c r o b i a l mats commonly generate gas bubble formation,

shrinkage and d e s s i c a t i o n

(MONTY,

from

1976). The term

"fenestra"

was

suggested by TEBBUTT et al.

p e n e c o n t e m p o r a n e o u s gap in rock frame work, interstices".

(1965) for a "primary

Fenestrae were found w i t h i n laminae of u n i c e l l u l a r cyano-

b a c t e r i a w h i c h possess usually a great p l a s t i c i t y due to large ties

of gel around cell colonies.

gel-supported

If in stratified mat

quanti-

systems,

the

laminae are sandwiched b e t w e e n laminae b u i l t of filamen-

tous microorganisms,

the voids are elongated,

ding plane and d e s c r i b e a laminoid p a t t e r n & TOSCHEK,

or

larger than g r a i n - s u p p o r t e d

follow the general bed-

(LF-A-type; M U L L E R J U N G B L U T H

1969). On the other hand, more e x t e n s i v e layers d o m i n a t e d by

unicellular irregular

organisms and their e x t r a c e l l u l a r slimes can also show arrangement

sedimentary

of fenestrae

(LF-B-type).

Laminated

an

patterns,

augen structures and lensoids as well as the formation

of

oncoids

and ooids in situ can be derived p h y s i c a l l y a c c o r d i n g

to

law

p a t t e r n formation in laminae of d i f f e r e n t v i s c o s i t i e s

(D'ARCY

of

THOMPSON,

1984).

Thrombolitic ments

the

are

fabrics

due

intergrowing

(AITKEN,

1967)

in m i c r o b i a l l y p r o d u c e d

to irregular d i s t r i b u t i o n of decaying

dead

colonies or internal d i s s o l u t i o n of mineral

around colonies of m i c r o o r g a n i s m s

(MONTY,

sedi-

colonies,

precipitates

1976).

i. 3. B i o l a m i n a t e d p a r t i c l e s

The name oncoid was suggested by HEIM les

(1916) for spheroidal

partic-

w i t h n o n - c o n c e n t r i c succession of more or less concentric

laminae

(FLUGEL,

1982). PIA (1927) regarded them as a subgroup of the Spongio-

stromata, above)

and

is

his

theory

of c a r b o n a t e p r e c i p i t a t i o n by

still in use today,

algae

w h i l e HEIM's suggestion was

(see

that

the

formation of oncoids w o u l d be due to the "aggressive activity of bacterial

colonies"

environments involved; around

we should,

nuclei

empty

spaces

activity"

Whether

Oncoids appear in both the fossil record

together with m i c r o b i a l mats. however,

(bioclasts,

consider whether mineral

m i c r o b i a l clots and lumps,

w o u l d be a b e t t e r i n d i c a t i o n

of

precipitates

lithoclasts)

"aggressive

or not ooids are of b i o g e n i c origin is still a The

name

was

or

bacterial

nucleus.

matter

suggested by K A L K O W S K Y for more

spherical or ellipsoidal grains w i t h uniform, a

modern

(i. e. b a c t e r i a l decay of the organic substrate).

controversy.

ting

and

C y a n o b a c t e r i a are commonly

for

or

less

concentric laminae

coa-

The use of the t e r m ooid is rather c o m p l i c a t e d since

it

is

u n d e r s t o o d to include at least two d i f f e r e n t

(FLUGEL, ooids;

1982).

Generally,

TEICHERT,

ooids

and

oolites

kinds

of

origin

(rocks consisting

of

1970) are studied w i t h the consensus that they origi-

nate in h i g h - e n e r g y environments.

However,

several modern mat environ-

ments show h o w it b e c o m e s p o s s i b l e to o b t a i n laminated p a r t i c l e s by the interaction

of

microbial

communities with a

physical

and

chemical

environment.

LUDWIG

&

THEOBALD

(1852) o b s e r v e d the formation of

concentrically

laminated coated grains in the thermal waters of Bad N a u h e i m w h i c h w e r e called

"Erbsensteine"

and oncoid

(HEIM,

i. e.

pisoids,

the terms ooid

(KALKOWSKY,

1916) being unknown at that time.

1908)

The authors noted

c y a n o b a c t e r i a - and d i a t o m - d o m i n a t e d m i c r o b i a l mats in an o p e n - a i r thermal

w a t e r course and r e c o g n i z e d the formation of coated grains

gas

bubbles,

m e t a b o l i c a l l y derived from the

mats.

authors noted that in fall the mat was degrading, release of the "Erbensteine",

around

Furthermore,

the

which resulted in the

and their d e p o s i t i o n d o w n s t r e a m in sandy

d e p r e s s i o n s as pisolites.

These, intimate

as

well as various other studies,

imply the

existence

genetic r e l a t i o n s h i p s b e t w e e n low energy e n v i r o n m e n t s and the

formation of ooids during p a r t i t i o n of m i c r o b i a l communities 1885,

ROTHPLETZ,

MITTERER,

1892, GIESENHAGEN,

1971). F A B R I C I U S

Bahama

ooids,

slimes

of microorganisms,

the

coatings

grains.

of

noticed

and

1922; SIMONE,

(WALTHER,

1981; FLUGEL,

1982;

(1977), w h e n studying the u l t r a s t r u c t u r e of

epilithic coatings of various

particles

with

immediate p r e c i p i t a t i o n of aragonite within

finally the

genesis

of

concentrically

laminated

He concluded that m i c r o b i a l p a r t i t i o n in the genesis of coated

grains is of p r i m a r y importance, while o v e r s a t u r a t i o n of the water with calcite,

The lites the

a g i t a t i o n and even nuclei supply are of secondary importance.

recent finding of m i c r o b i a l mats b u i l d i n g real domal w i t h i n the Bahama Bank e n v i r o n m e n t strengthens the

initiation

stromato-

argument

of ooid formation w i t h i n m i c r o b i a l mats also

for

of the

Bahama Bank ooid shoals.

In summary, should

we p r o p o s e that the genetic d e f i n i t i o n of the term ooid

imply b i o g e n i c i t y rather than abiogenicity.

We p r o p o s e further

that the term ooid should be p l a c e d into the g e n e t i c a l l y linked sequence

of

laminated s e d i m e n t a r y bodies and strata w h i c h

participation

of m i c r o o r g a n i s m s

(see KALKOWSKY,

form

1908).

under

the

The term ooid

(modi-

TABLE 2. C l a s s i f i c a t i o n of b i o l a m i n a t e d deposits and p a r t i c l e s fied after D A H A N A Y A K E & KRUMBEIN, 1986)

Laminated particles

L a m i n a t e d structures Single structure

Criteria

Assemblage

Single particle

Assemblage

Single Assemp a r t i c l e blage

Stromatolite

Ooid

Oolite

Oncoid

Stromatoloid rock

Ooloid

Ooloid rock

Oncoloid Oncoloid rock

GENESIS Biogenic

Stromatoid

A b i o g e n i c Stromatoloid

Irregular rounded

Concentric discontinous

Concentric continuous

Planar to conical

LAMINAT I ON

(**)

Regular rounded

Tabular, domed or columnar

MORPHOLOGY

(*)

(*)

Oncolite

For o o i d s / o o l o i d s larger than 2 m m in diameter the terms p i s o l o i d (pisolite/pisoloid rock) may be used

(**) For o n c o i d s / o n c o l o i d s oncoid/microoncoloid used

less than 2 mm in d i a m e t e r the terms micro(microoncolite/microoncoloid rock) m a y be

w o u l d then define a regularly concentric, ly

c o n c e n t r i c coated grain.

more

the term oncoid an irregular-

Finally the term stromatoid w o u l d include

or less s t r a t i f o r m lamina types

(Lh- and L v - l a m i n a e as

in this volume), h e m i s p h e r o i d structures

described

(like the d o m a l LLH- and sepa-

rate v e r t i c a l l y stacked SH-types c l a s s i f i e d by LOGAN et al., also BATHURST,

1971).

Logically,

t h o c h t h o n o u s or allochthonous)

rocks composed of ooids

are then oolites,

lites and of stromatoids are s t r o m a t o l i t e s

to

(e. g.

gical o r i g i n is not unequivocal. ted like"

the

suffix

(ooid-like,

"-oloid"

onco-

(1981) and BUICK

geyserites)

(1984) we

deposits

or

or w h e r e the biolo-

In this case the said authors sugges-

(OEHLER,

oncoid-like)

(either au-

of oncoids are

avoid the a b o v e - m e n t i o n e d terms if l a m i n a t e d

p a r t i c l e s are clearly a b i o g e n i c

1964; see

(Table 2).

F o l l o w i n g the suggestions of BUICK et al. propose

pisoid/

1972) w h i c h means a

appearance.

advice w i t h respect to the whole sequence

"stromatolite-

We p r o p o s e to follow

(Table 2).

this

2. THE P R O B L E M OF V E R S A T I L I T Y

Fig. in

1 has b e e n c o n s t r u c t e d to illustrate the p r o b l e m of v e r s a t i l i t y

m i c r o b i a l c o m m u n i t i e s w h i c h may leave a lasting record

sediments.

Laminated

types d o m i n a t e d by d i f f e r e n t major taxa m o o r g a n o t r o p h i c bacteria;

Fig.

(cyanobacteria,

zontally,

che-

There are filamen-

for example, w h i c h arrange themselves either h o r i -

(concordant to b e d d i n g planes)

Furthermore,

so

fungi or

p l a n a r l y or r a d i a l l y and leave b e h i n d lamina o r i e n t e d either

stratiformally

allows

ancient

IA). The w e a l t h of d i f f e r e n t taxa solely

in the group of c y a n o b a c t e r i a has to be considered. tous cyanobacteria,

in

or laminoid structures can derive from c o m m u n i t y

experience

or u p w a r d l y convex.

of p r e s e n t - d a y m i c r o b i a l mat

environments

us to state that life strategies of the m i c r o b e s c o n c e r n e d

varied

that

consistency.

they are able to develop over

substrate

of

are

varying

P r e s u m a b l y w a t e r is a v a i l a b l e p e r m a n e n t l y or periodically.

It

is t h e r e f o r e i n a d v i s a b l e to restrict the formation of stromatolites

to

any one p a r t i c u l a r e n v i r o n m e n t w h i c h w o u l d imply in

f a c i e s - i n d i c a t i v e role

(Fig. IB).

general

their

In the light of the great v a r i a b i l i t y

of l a m i n a - f o r m i n g microbes,

it is e s s e n t i a l to look c a r e f u l l y at other

available

and p a l e o n t o l o g i c a l

sedimentological

facies are concerned. nor

always d e p t h - d e p e n d e n t

5tASSARI,

1980).

environmentally taxa

Dominance induced.

(JANNASCH

&

WIRSEN,

sequence

is

organisms ment

also

1981;

The b i o l o g i c a l growth h a b i t of

is also important.

MONTY,

1977;

each

sediment particles.

made p o s s i b l e w i t h o u t

single

The process of burial

S e d i m e n t a t i o n is often

and m i c r o b i a l mats act as sticky fly papers and bind a l l o c h t h o n o u s

as

structures in m i c r o b i a l mats may be m a i n l y

in turn influences the m o r p h o g e n e s i s .

re-establishment

i n f o r m a t i o n as far

S t r o m a t o l i t e s are n e i t h e r n e c e s s a r i l y intertidal

(SHINN,

and

involved,

1983) w h i c h capture

Growth of the m i c r o b i o g e n i c sedimentation

as

migrating

o v e r r i d e others in order to find the most favorable environ-

(e. g. by phototaxis).

This sort of self-burial is typical and can

be seen in b o t h lacustrine and m a r i n e l o w - e n e r g y environments.

Burial gives rise to various kinds of p e n e c o n t e m p o r a n e o u s within

the

degrees

organic s u b s t r a t e

(Fig. IC):

of b a c t e r i a l d e c a y occur;

tion

and

to

diffusion,

shrinkage,

with

varying

some p o l y s a e c h a r i d e chains and com-

plexes are more r e c a l c i t r a n t than others;

place.

Micromilieus

processes

degassing,

d i s s o l u t i o n and

gas b u b b l e forma-

precipitation

The d i f f e r e n t p l a s t i c i t y of substrates and their b e h a v i o u r

c o m p a c t i o n has to be considered.

Faunal influence c o m p l i c a t e s

take due the

10

overall

situation in so far as feeding and excretion

gration,

and the spreading of microbial

tion of thrombolitic

lead to

disinte-

colonies may support the forma-

fabrics and intraclasts.

MARINE

NON-SEDM I ENTATO IN SUBAERA I LLYEXPOSED LOWSEDM I ENTATO IN

LACUSTRN IE SUBMERSED

PERO I DC I ALLYRAPID SEDM I ENTATO IN

TERRESTRA IL

I•ERIA

FUNGI

/

/

RADA I L,HOR¢ ZONTAL / VERTC I AL / /

~

J

/

OFDF IFERENTMAJORTAXA? ~

C. PENECONT~PORANEOUS

~

~k

~

b ~

C

~

~

EARLY DA I GENESS I (DEGRADATO I N,MN I ERALPRECIPITATION) BIOTURBATIONG , RAZN IG

COMPACTO I NOFSUBSTRATESOFDF IFERENTPLASTICITY Fig. i. Schematic representation relating stromatolitic structures and parameters possibly involved in their formation and early diagenesis. The concern of this scheme is to demonstrate that the appearance of a stromatolitic structure is indicative neither of one single phylum nor of one single environment.

11

The

unifying

principle within the complexity of stromatolitic

brics is that they are products of microbes which by their physiology and

and arrangement in time and space interact with a

chemical

environment

to produce a laminated

fa-

morphology,

pattern

physical (KRUMBEIN,

1983). This basic definition is irrespective of the existence of specific growth patterns (biostromate or biohermal buildups, ticles,

and

laminoid

fenestral

laminated par-

fabrics) which may be

explained

by

biotopic and microbiocoenotic as well as by physical modifications.

A key to the recognition of biotopic and biocoenotic characteristics encoded within sedimentary structures is the study of microbial mats in modern environments. matolites

may

conditions

A limitation of the actualistic approach to stro-

be that many present-day

1980;

KNOLL,

the

strial, mats

ecological

1985a). This consequently

explain why well developed thick stromatolitic sequences are

developed in the present than in the past. to

and

do not function at the same rate and level of efficiency as

in the past (REINECK & SINGH, may

depositional

However,

present-day extension of shelf flats and some lacustrine

and deep sea environments,

less

though restricted special

present-day

witness clearly the constancy of the biolaminite

terre-

microbial

tradition.

The

following chapters deal with stromatolite environments in the peritidal zone

which

apparently include types of potential

always had world-wide distribution.

stromatolites

that

Two of our main study areas are in

the semi-arid tropics and are part of the desert coast adjacent to

the

Gulf

others

are

North

Sea

of

Aqaba

supratidal coastal dies

graben system (Sinai Peninsula) while the

flats

of offshore embankments in the

southern

region which is located in the temperate-humid zone.

describe microfacies types,

stratification microbial structures

bio- and ichnofabrics and

The stumodes

which display depositional dynamics that interfere with

activity.

Comparing

the formative

environments

of

the important role played by climate and geomorphic

becomes evident.

of

these relief

PART

STROMATOLITE

ENVIRONMENTS

-

MODERN

II

IN

THE

EXAMPLES

PERITIDAL

-

ZONE

"Alle jene Gebiete,

w e l c h e ich auf der geolo-

gischen

'Salzthon'

babe,

Karte sind

als

nichts

weiter

ausgeschieden

als

eingedampfte

L a g u n e n und m e e r e n t b l ~ s s t e r Strand." WALTHER,

i. THE G A V I S H S A B K H A

-

(JOHANNES

1888)

A H Y P E R S A L I N E B A C K - B A R R I E R SYSTEM

(GULF OF AQABA,

SINAI PENINSULA)

i. i. I n t r o d u c t i o n

Facies

is the p r o d u c t of specific d e p o s i t i o n a l and b i o t o p i c

tions acting w i t h i n a certain e n v i r o n m e n t biotopic arid

c o n d i t i o n in the Gavish Sabkha,

tropics,

remarkably even are

stable in the annual cycle.

The a v a i l a b i l i t y of

flourish in the Gavish Sabkha

The

Gavish

strong the

in subsurface contact w i t h the

sea.

e v a p o r a t i o n is c o n s t a n t l y r e c h a r g e d by seepage

moistened

is mats

Water

of

sea

by

loss

by

seawater.

Thus

is p r o v i d e d w i t h p e r m a n e n t s h a l l o w - w a t e r environments mud flats.

is

salt swamp).

Sabkha is a t o p o g r a p h i c low separated from the

but

system

water

e n v i r o n m e n t if m i c r o b i a l

(sabkha is a t r a n s l i t e r a t i o n

the arabic term sabkhat or sebkat meaning

bar-closing

1958). A specific

a coastal e n v i r o n m e n t in the

is that the h o r i z o n t a l g r a d i e n t of surface m o i s t u r e

more critical than the h y p e r s a l i n e to

(TEICHERT,

condi-

These p r e v a i l i n g conditions can

be

and

interrupted

a l t h o u g h not always p e r m a n e n t l y changed by w i n t e r flashfloods.

The purpose of this chapter is threefold: of

topographic

sedimentary tolitic

on the d e v e l o p m e n t of

microbially

produced

structures w h i c h r e p r e s e n t analogs of conspicuous

structures

1985a), provide

moisture

(i) to document the effect

(2)

in the g e o l o g i c a l record

(see for

stromaKNOLL,

framework

which

further i n f o r m a t i o n about the e n v i r o n m e n t of deposition,

(3) to

interpret

the

tO d o c u m e n t the lithological and faunal

example

mode

of s t r a t i f i c a t i o n of the sabkha deposits

as

the

16

result

of

changes b e t w e e n long-lasting

conditions

fair-weather

and

short but catastrophic sheetflooding.

i. 2. M e t h o d s

Field

work was carried out from July to October 1981 and

to March 1982. bed

It focussed on the coring and d o c u m e n t a t i o n of undistur-

sediments,

fauna,

on

February

on the sampling of m i c r o b i a l mat m a t e r i a l and

benthic

m e a s u r e m e n t s of p h y s i c o c h e m i c a l p a r a m e t e r s and on the docu-

m e n t a t i o n of surface structures.

The

Gavish

Sabkha m i c r o b i a l mats were first studied by us

early summer of 1978.

in

the

At that time the p e r m a n e n t l y w a t e r - c o v e r e d parts

of the sabkha were floored w i t h e x t r a o r d i n a r i l y m u l t i l a m i n a t e d communities at

(KRUMBEIN et al., the

end

multilaminated loads

of

of

Our next

fully

about one year after the floods.

developed

At that time

(KRUMBEIN et al.,

Data

from

ion

1985).

mineralogy mats

In summary we present in

of

which

sabkha

lished

type 3),

crops

and pH in sediments, Undisturbed long, knife,

surface

permanently water-covered

(2) data from p o s t f l o o d

studies:

sediment distribution,

is

(GAVISH studies: waters,

microbial topographic

c o m p o s i t i o n and

already

reestab-

2 and 4), vertical profiles of redox p o t e n t i a l s

faunal distribution.

sediments

were

taken w i t h plastic

50/70 mm diameter). V e r t i c a l slices

of

of m i c r o b i a l communities w h i c h were

(facies type I,

not

sediments

(I) data from p r e f l o o d

r e l a t i o n to the salinity

m o i s t u r e and salinity gradients, standing

were

we adopt data from p r e f l o o d stu-

analyses and m i n e r a l o g y

of surface sediments,

(facies

with

1979).

seawater

concentrations

the

to interpret

type

p r e s e n t e d here were also obtained during the p r e f l o o d situation et al.,

one

reestablished

Thus,

stage of the m u l t i l a m i n a t e d mat

repeatedly recorded in core segments, dies

and

studies

the benthic systems of the p r e f l o o d p e r i o d were

a l t h o u g h new initial stages had already developed. the

1980

m i c r o b i a l mats of the l a g o o n a r y b a s i n were b u r i e d

terrigenous sediments and died off.

c o n d u c t e d in 1981, all

1979). Then two strong sheetfloods occurred,

of 1979 and the other at the b e g i n n i n g of

tubes

(200/400 mm

sections were made w i t h an electric

(45 x 45 mm) were separated and frozen under

shock

in

liquid oxygen. They were s u b s e q u e n t l y dried in a d r y - f r e e z i n g apparatus

17

and

later h a r d e n e d

REINECK, pared

1970).

and

were

examined

taken

(1962).

The

from

Chips

electron

critical

gold

Sections

tions

a dissecting

Pore

core m a t e r i a l

were

(SEM-Type fixed

Stereoscan

then d e h y d r a t e d

selected

- 6 %)

dilution

the samples

905,

photographs by

HAMBLIN scanning

Instruments).

at

appropriate

series

were

HY

were pre-

for

Cambridge

(2

in e t h a n o l / H 2 0

Subsequently

X-ray

described

180,

in g l u t a r a l d e h y d e

point dried.

sections

microscope.

of the sliced

of

the sliced

distribution.

water

0.63

was

carefully

organic

recovered

geochemistry

carried

sediments) Gulton),

work

measurements

and final-

sputtered

Optical

Microbial This work,

mat

with

samples were

as well

examined

collected

a 0.5 mm sieve and

sorted,

identified

with

fixed

Temperature

and

potential)

(air,

water,

(Tastotherm,

(Ingold)

on a

refractometrically

under

millimeasured

to b u r r o w

(150 mm high,

effect

of grazing

on m i c r o b i a l

graze on mat

measurements,

(HOLTKAMP,

sections

were

1985).

Samples were

and counted.

capra)

seawater

were

To study

lab-cultured

agar

which

was

To study the

(Pi~enella conica) were

w h i c h were b r o u g h t

salinity.

passed

Specimens

25 mm in diameter). gastropods

carried

structures

and s e m i - q u a n t i t a t i v e -

(Bledius

in jelly

mats,

at 50 O / o o

and SEM microscopes.

Her data on c o m m u n i t y

of salt beetles

tubes

seawater

light

the h e l p of specialists

behavior allowed

to

samples

isotope

thermoelement

in 4 % formaldehyde.

into glass

allowed

sediment

pH and redox

i00 mm high).

filled

treated with

was

the frac-

1985).

qualitatively

(190 mm diameter,

were

and

electrodes

are included

through

burrowing

with

w i t h E. HOLTKAMP.

fauna was

corers

specimens

sediments.

of

< 0.063 mm.

mineralogical,

& KRUMBEIN,

as the p h y s i c o c h e m i c a l

concentrations

The b e n t h i c

analysis

for

Salinity

study

into the

Instruments).

out in c o l l a b o r a t i o n and p i g m e n t

mm and

a chrome/nickel

and redox p o t e n t i a l

for the

were w e t - s i e v e d

(temperature,

cored

with

(Knick Portamess).

(American

with

for water

(FRIEDMAN

out in freshly

pH

selected

0.2 - 0.063

and s u b d i v i d e d

was m e a s u r e d

voltmeter

cores w e r e

The sediments

- 0.2 mm,

taken

Physicochemical

the

thin

as

> 0.63 mm,

were

ly

F with hardener

for SEM studies.

grain-size

were

under

(Araldit

specimens,

core m a t e r i a l

was

osmolarities,

resin

the sliced

microscopy

material

ly

in an epoxy

F r o m the h a r d e n e d

to

the

lab

and

18

i. 3. L o c a l i t y and p r e v i o u s w o r k

The

Gavish

Sabkha is located in the southern coastal area

Sinai Peninsula,

o p p o s i t e the Strait of Tiran,

34020 ' east longitude, Gulf of Aqaba widely

(Figs.

the

at 28 ° north latitude,

and is a p p r o x i m a t e l y in 400 m distance 2A and 2B). Shallow h y p e r s a l i n e

surrounded by a i r - e x p o s e d saline flats

setting

of

from the

surface w a t e r is

(Fig. 2C).

The

general

describes the Gavish Sabkha as a d e p r e s s i o n w i t h i n an alluvial

fan w h i c h spreads over the coastal plain b e t w e e n the Sinai Massive

and

the

the

shoreline

sabkha, of

of the Gulf

(Fig. 2B).

Further north and south of

the fan is crossed by m a j o r wadi conducts w h i c h on the o c c a s i o n

flash floods t r a n s p o r t t e r r e s t r i a l m a t e r i a l into the coastal

area,

the Gavish Sabkha and the Gulf.

Sea-marginal by C. G. The

sabkhas of the Sinai Peninsula were already

EHRENBERG

Gavish

(HEMPRICH & EHRENBERG,

Sabkha was first recognized by

g e o l o g i s t and geochemist.

were

followed

GAVISH,

GAVISH,

investigations

1971; G A V I S H et al.,

an

Israelian

(GAriSH,

1974,

1980;

1985). These p i o n e e r i n g studies

by studies of the m i c r o b i a l systems

1979; GERDES et al., E.

E.

(1888).

After the war in 1967, he began sedimentolo-

gical, geochemical and h y d r o l o g i c a l F R I E D M A N & GARISH,

mentioned

1828) and J. W A L T H E R

(KRUMBEIN

et

al.,

1985a; E H R L I C H & DOR 1985). To h o n o r the m e m o r y of

who died in 1981, the c o m p r e h e n s i v e results of interdisci-

p l i n a r y research on sea-marginal sabkha environments using the of the G a v i s h Sabkha were compiled

(FRIEDMAN & KRUMBEIN,

example

1985).

I. 4. The p h y s i c a l e n v i r o n m e n t

I. 4. i. G e o m o r p h i c relief

GAVISH et al. tal

bar

consists

softbottom platform. uplift

its

of an u p l i f t e d reef complex and

sediments

of

the sabkha rest on

Studies conducted by F R I E D M A N

(1965,

an

that

the

underlying

present backreef

1972) indicate that such

of reefs o c c u r r e d about 2,000 - 4,000 years

G A V I S H et al. and

(1985) p r o p o s e d that the b e d r o c k underlying the coas-

ago.

Accordingly,

(1985) suggest that the unique round shape of the sabkha

location w i t h i n the alluvial p l a i n could be the result

preexisting

t o p o g r a p h i c low in the u n d e r l y i n g reef p l a t f o r m w h i c h

s u b s e q u e n t l y uplifted.

of

a was

19

N ~

' ~ LAND

."1

EVAPORITI[

~...~__

'~

/'~ F °'~51-~i'_-~' i-~°~~~Z..~ . :.~. ~.-~.;

/ /

i

BEoou,,

SEA

i

STROP1ATOLITIIZ

i

[LASTI[

I

C

Fig. 2. Map of study areas and g e n e r a l setting of the G a v i s h Sabkha° A) Sinai P e n i n s u l a w i t h l o c a t i o n s of the G a v i s h Sabkha and the Solar Lake along the Gulf of Aqaba. M o d i f i e d after F R I E D M A N & KRUMBEIN, 1985. B) A v i e w t o w a r d W showing the round d e p r e s s i o n of the G a v i s h Sabkha at the shore of the Gulf of Aqaba. F r i n g i n g reefs are v i s i b l e at the bottom, foot hills of the Sinai m o u n t a i n s at the top. After F R I E D M A N & KRUMBEIN, 1985. C) I l l u s t r a t i o n of major g e o m o r p h i c elements of the Gavish Sabkha: coastal b a r slope, rims and b a s i n of the lagoon, elevated center. B a r - d i r e c t e d s i l i c i c l a s t i c s and c e n t e r - d i r e c t e d e v a p o r i t e s interfinger w i t h m i c r o b i a l mats w h i c h form at the lower part.

20

The

p r e s e n t - d a y e n v i r o n m e n t forms a round d e p r e s s i o n about 500 m in

diameter level).

and

is at its deepest part -1.80 m b e l o w

The

m.s.l.

(mean

sea

central part of the d e p r e s s i o n is gently elevated and

is

s u r r o u n d e d by a c o n c e n t r i c channel w h i c h is p a r t i a l l y w a t e r - f i l l e d . The circular slopes rise g r a d u a l l y from the channel upwards to the alluvial p l a i n and coastal bar facing.

Three major g e o m o r p h i c elements of the G a v i s h Sabkha can be guished: The b a r r i e r slope,

The

the lagoon and the center

b a r r i e r b l o c k i n g the d e p r e s s i o n has b e e n u p h e a v e d by

d i r e c t e d currents and waves.

lying bed rock and porous sediment infilling. covered

coastline

Seawater is r e p l e n i s h e d through subsurface

conduits formed by c a r b o n a t e c e m e n t a t i o n plates,

is

distin-

(Fig. 2C).

by dry evaporite crusts.

fissures in the under-

The surface of the slope

Several gullies cut through

slope face and merge at the lower end into sandlobes

(Fig.

2C).

the Sea-

w a t e r springs rise at the sandlobe junctions. The gullies are g e n e r a l l y 0.I0 to 0.40 m deep and tend to meander. result

of

sheet floods

(GAVISH,

Gullies and sandlobes are the

1980).

A wadi conduct runs

at

the

coastal bar plateau.

The lagoon is part of the concentric channel halfmoon-shaped surrounded impondments

by

(Fig.

2C).

b a s i n w i t h w a t e r depths of up to 0.60 m. shallow and p a r t i a l l y a i r - e x p o s e d flats

occur

It forms a The basin is

where

various

(about 50 mm deep and two to three meters in

diame-

ter) w h i c h are fed from seawater springs.

The elevation of the center is about 0.50 m above the w a t e r table of the lagoon.

GAVISH p r o p o s e d that g y p s u m a c c u m u l a t i n g b e l o w the surface

caused the "swelling" of sediments and

gradually

u p h e a v e d the center.

Aerial views show three s e d i m e n t a r y plains sloping g e n t l y to NNE 2B):

(i.) The topmost part,

(2.)

the slope w i t h its e x t r e m e l y gentle incline

(Fig.

which is covered by dry evaporite crusts, towards NNE and

(3)

the rim w h i c h is s u r r o u n d e d by the c o n c e n t r i c channel. Surface m o i s t u r e g r a d u a l l y increases toward the lagoon. several and

holes,

Along the slope and the rim are

e x c a v a t e d b y fisher b e d o u i n s

in order to collect brine

to h a r v e s t the p r e c i p i t a t i n g potash and NaCI.

months

the

higher

w a t e r table of the lagoon.

sediments

of the rim are submersed due

and leaves w h i t e g y p s u m crusts.

During to

the

winter

the

slightly

In summer the w a t e r level

retreats

21

IiH

p0; 12°°

Ii Ii [L

March t982 I I

~

II

0

r-GF--~

LB

~

SMF

~ SL

~ A ? \ G U ELEVATED CENTER SW

A O0 h G N GF

~

SMF ~

GF = Gypsum Fiats LB = Lagoonery Bo.sin SMF= Satine Mud Fiats SL = Sand{obes

A

BAR h

i \ I~

~

~ ~':~~'~:,~'~'~':''! ............... .:~

m r-2

GAVISH SABKHA SURFACE WATER }ULF

SAUNITY INCREASE+

SMF

u

ION CONCENTRATIONS (ppm)

GAVISH SABKHA SURFACE WATER

I LB I

/

£ ~ B r i n e Reflux

ION RATIOS (MOLAR).

~o GF

t

~ e

LNFE[~I

SL

+-- . . . . .

SALINITY INCREASE (

GF- L8 I

S.F

i

IS

~{

3ULF ppm 20 000 10 000

4~ @

4

I

.2

t

;000 "E

I 000

3.4

so#L~

I cE! so4=

-~

.0.2 42.4

300

TOTAL SALINITY (%o]

Fig. 3. Hydrology, salinity and seawater chemistry along a horizontal transect crossing several sub-environments of mat-formation: Sand lobes (SL), saline mud flats (SMF), lagoon (LB) and gypsum flats (GF). A) Generalized horizontal transect showing the connection of the Gavish Sabkha with the Gulf. Hydrodynamic mechanisms are indicated by arrows: Seepage, evaporation and brine reflux. Salinity (upper diagram) increases towards the elevated center. B) Ion concentrations (right) and ratios (left) in surface water including Gulf water (salinity values on abcissa right from GAVISH et. al, 1985; abbreviations refer to sub-environments listed in A). Decrease in Ca and change in ion ratios take place on saline mud flats bordering the lagoon where total salinity is about 85 0/oo.

22

1. 4. 2. H y d r o l o g y

Two

m a j o r effects on the h y d r o l o g i c a l

be distinguished: physical include

(1) physical

system of the Sabkha have

to

factors o p e r a t i n g from the land and

(2)

factors o p e r a t i n g from the sea.

Those o p e r a t i n g from the sea

seawater supply and w a t e r level changes w i t h i n the sabkha

to tidal m o v e m e n t s and w e a t h e r effects re-directed against

w i n d drift,

the

coast,

(e. g.

monsoon)

outside.

w h i c h o c c a s i o n a l l y causes strong w a v e

does not affect the b a r - p r o t e c t e d Gavish

due

Onshoattack Sabkha.

Thus the h y d r o l o g i c a l p r o c e s s e s d e s c r i b e d b e l o w remain b a l a n c e d even if high energy conditions occur in the a d j a c e n t Gulf.

Tidal tidal

influence.

Gulf

range of 0.7 m.

tides are semi-diurnal w i t h a

the Gavish Sabkha at a reduced rate w i t h time delay. of

mean

pools and the b a s i n of the lagoon. is seen in

normal

(up

directly

to

The o p e r a t i o n of these t i d e - i n d u c e d

i0 cm) is common in winter.

This

phenomenon

related to the tidal m o v e m e n t but to seasonal

et al.

1985).

is

variations

communities which colonize these margins.

however,

not in

(monsoon;

Both tidal- and c l i m a t e - i n d u c e d fluctuations of

the w a t e r table do not lead to c o n s i d e r a b l e disturbances of the bial

of

A sudden rise in the w a t e r table greater than

the sea level of the Gulf as a response to climate conditions GAVISH

marginal

the shifting of w a t e r l i n e s at the m a r g i n s

the ponds and the basin.

of

Diurnal m o v e m e n t s

w a t e r levels of about 20 mm h a v e b e e n observed w i t h i n the

fluctuations

annual

This tidal m o v e m e n t affects the w a t e r level

Some faunal

micro-

elements,

w h i c h are restricted to a i r - e x p o s e d w e t l a n d habitats, have to

react by m i g r a t i n g according to the shifting water lines.

Seawater ecological of

the

seepage.

A

significance.

constant supply of seawater This is achieved by

Gavish Sabkha and (ii) the process

(sensu HSU & SIEGENTHALER,

produce

surface seawater

to

respects

salt from seawater.

of

pumping"

formerly used by hill

They c o n s i s t e d of

through gently inclined pipes into

system

greatest

"evaporative

people

a pan w i t h a

volume ratio w h i c h was s u c c e s s i v e l y fed by

running

hydrological

of

1969). The c o m b i n a t i o n of seepage and evapo-

ration is analogous w i t h the b o i l i n g - p a n s to

of

is

(i) the b a s i n m o r p h o l o g y

low the

the Gavish Sabkha differs from

rates basin.

this

in

high of The two

(i) the heat needed to evaporate the water generates from sun

irradiation

and

(ii) the natural pan of the

Gavish

Sabkha

consists

w i d e l y of exposed sediments where the w a t e r table is b e l o w the surface. In these areas "evaporative pumping"

operates

(Fig. 3A).

23

The e v a p o r a t i o n rate is about 4.6 m/year. 30

Relative h u m i d i t y averages

- 50 % w i t h a m e a n annual air t e m p e r a t u r e of 26 °C

h i g h solar irradiation. v e r t i c a l l y and sediments by

P e r c o l a £ i n g seepage seawater sinks into the

and elevates the w a t e r table, evaporation.

w h i c h is lowered s u b s e q u e n t l y

This stimulates upward m o v e m e n t

of

water

the p h r e a t i c zone by e v a p o r a t i v e p u m p i n g and results in a

stant

supply of ions n e c c e s s a r y for mineral

capillary (PURSER,

The

movement

formation.

The

in turn leads to the lateral m i g r a t i o n

vertical of

fluids

lateral m o v e m e n t induced by e v a p o r a t i v e p u m p i n g may not operate

Dhabi

sabkha

(PURSER,

G a v i s h Sabkha, however, water

1985).

as seen,

for example,

The d o w n w a r d i n c l i n a t i o n

in the of

p l a t e s e m b e d d e d in the u p h e a v e d bar

conduits sabkha

the

stimulates the lateral m o v e m e n t of i n t e r s t i t i a l

w i t h i n the s e d i m e n t a r y system as well as the lateral

supply

seepage s e a w a t e r through p e r m e a b l e sediments of the m a r i n e bar. nate

con-

1985).

w h e r e sabkha water tables rise landwards, Abu

constantly

The e v a p o r a t i o n p u m p i n g m e c h a n i s m o p e r a t e s b o t h

laterally.

capillary

within

and

(Fig.

of

Carbo-

2C) p r o b a b l y serve

as

for the seeping seawater. T h e i r gentle i n c l i n a t i o n towards the can

be seen at outcrops t e r r a s s i n g some of the

gullies

which

cross the inward slope of the coastal bar.

Besides the p r e c i p i t a t i o n of evaporite m i n e r a l s at the interfaces by evaporative pumping, posed

to

gypsum)

reflux of brines to the sea is pro-

be an important m e c h a n i s m of mineral

in deeper layers

sediment-air

(GARISH et al.,

accumulation

1985).

(mainly

Local d o l o m i t i z a t i o n

has also been suggested as an outcome of brine reflux,

a l t h o u g h several

other models have b e e n proposed.

S a l i n i t y regimes. A h o r i z o n t a l 340 °/oo,

is

established

s a l i n i t y gradient,

ranging from 50 to

along a t r a n s e c t w h i c h runs from the

slope face of the bar towards the center of the sabkha

The data in Fig.

3A were o b t a i n e d from m e a s u r e m e n t s of interstitial

water

in the gully and sandlobe sediments and of standing surface

ters.

Although

and spring 1982), of

salinity

the data r e p r e s e n t only two annual states they may n o n e t h e l e s s

zones is more or less stable t h r o u g h o u t

1980; G A V I S H et al.,

1985,

wa-

(summer 1981

indicate that the e s t a b l i s h m e n t the

year.

a s s u m p t i o n was r e i n f o r c e d by G A V I S H on several earlier visits 1975,

lower

(Fig. 3A).

see also Fig. 3B).

This

(GAVISH,

24

Short-term

oscillations

the lagoon where wind in the overall conspicuous

can flush-over

stability

change

of salinity

occur

concentrated

of the salinity

in

at the immediate

microbially

regime

produced

brine.

rim

of

This d e v i a t i o n

is r e f l e c t e d

structures

by a

(see

very

section

1.6.3).

Ion c o n c e n t r a t i o n s of

GAVISH's

dissolved SO 4

data

taken

by

(Fig.

CaSO 4

enriched

is

while

depleted

cite highly

in bulk

are enriched

(29 wt.%). reduced

with

concentrations

Mg ++

salinity

similar

a recalculation

to

of

: Ca ++ and Ca ++ measurements our

:

ob-

measurements

to the salinity

in-

lies at 80 to 90 °/oo w i t h i n

the

increase

shows

in p a r a g r a p h

so that b a c t e r i a l

sulfate

takes

a nearly

linear

of the inner

lagoonary

in high m a g n e s i u m

As is shown

is a c c o m p a n i e d

in the surface water,

sediments of the

of salinity

since

on the other hand,

the sediments

concerning

correlates

of C a + + - c o n c e n t r a t i o n s

ratio,

dy

which

Further

Ca++/SO 4 = ratio decreases,

M g + + / C a ++

lagoon,

3B).

3B shows

3A).

of C a + + - c o n c e n t r a t i o n s

flats

by the decrease the

1985)

are quite

up to a solution b a r r i e r

saline mud

ly

(Fig.

Fig.

in surface waters,

These data

later

increase

crease

et al.,

The data are c o r r e l a t e d

GAVISH.

four years

The

(GAVISH

c a l c i u m and sulfate

= ratios.

tained

in surface waters.

calcite

sulfate

of

the

Ca ++ is alrea-

(50 wt.%) these

reduction

The

increase.

shoreline

basin where

1.6.4.,

accordingover.

and

cal-

sediments

interferes

are with

CaSO4-precipitation.

Flashflood passing after

impacts.

the system rainfall

transport

for

Sabkha.

A strong of

evaporation months

in

to

sheetflood

pumping regenerate

Sabkha

in this

area

is i0 nun. Rainfall

is more or less n e g l i g i b l e mountains

freshwater.

the h y d r o l o g i c a l

the Gavish

rainfall

the adjacent

sediment-laden

quences

level

Annual

immediately

and e c o l o g i c a l

in O c t o b e r

completely

(GAVISH et al.,

run-off

sheetfloods

which

tremendous

conse-

conditions

1979 caused

of about 60 cm.

s y s t e m was

causes

Such events have

while

of the

a rise

The steady disturbed.

state It

Gavish

in the water of

took

the five

1985).

i. 4. 3 . ~ T e m p e r a t u r e s

A stable influences

zonal t e m p e r a t u r e - g r a d i e n t of wind,

irradiation

was not o b s e r v e d

and e v a p o r a t i o n

due to changing

operating

in the daily

25

cycle.

In summer,

between

day

nightly

drop

low-water tures

air t e m p e r a t u r e s

and night

temperatures

in air t e m p e r a t u r e

environments

and a n i g h t l y

ring c a p a c i t y

reach

however,

saltcrusts.

ranging

of s h a l l o w - w a t e r

range b e t w e e n

is,

and b e l o w

drop

45 °C and more

between

Data

of

GAVISH

vels. The

The

levels

which

and e v a p o r a t i v e

results

are p r e s e n t e d

g e n t l y dip to NNE

VI

graded

describe

strates

(i) the

relief

above

ration

pumping

(Fig.

different

the buffe-

calculate

4 in the course

level

le-

of a transect: of the center

IV indicates

the b o t t o m of

Sabkha.

(i.

The levels

bar

described

slope.

e. the e l e v a t i o n

of seawater

V

The

b e l o w demon-

(2) the e f f e c t i v e n e s s

recharge

the

niveau

plains

of the coastal

of g e o m o r p h o l o g y

seepage

used to

forming m i n e r a l s

table)

The

in shal-

lower daily tempera-

at d i f f e r e n t

sedimentary

elevations

the g r o u n d w a t e r and

were

part of the G a v i s h

of in-situ

influence

1985)

The

30 °C.

framework

in Fig.

4A).

and

remarkable

crusts.

(0 to -5 cm)

the three

is the deepest

distribution

annual

et al.,

sediments

I to III indicate

the lagoon w h i c h and

(GAVISH

of surface

Here,

20

6 and 8 °C indicate

1. 5. L i t h o l o g i c a l

composition

less

and d i f f e r e n c e s

of the

of

evapo-

prevailing

in

the

cycle.

i. 5. i. E v a p o r i t e s

a) H a l i t e

(Fig.

4B).

High

is over 80 %) a c c u m u l a t e ment

surfaces

other m i n e r a l s water at

(levels

indicates

(level

layer w i t h an

average

frequency

relative

height, levels

at III,

level

the

lutitic

upper

4A)

thickness

(Fig.

4C).

Anhydrite

(levels

The a s s o c i a t i o n

of g y p s u m dehydration,

1 m

It covers

(see p a r a g r a p h gradually

with

of h a l i t e while

layer

a gypsum

c

below).

decreasing the

lower

4B).

occurs

I and VI),

at

to

marine

of the h a l i t e

is 25 - 50 % while (Fig.

sedi-

of h a l i t e

of upward m o v i n g

20 cm.

decreases

frequency

unflooded

abundance

The thickness

of about

of h a l i t e

permanently

averages

B the bulk volume

dry crusts

fraction.

conditions

interface.

(the relative

relative

evaporation

IV and V it is n e g l i g i b l e

b) A n h y d r i t e in

This

the total

I in Fig.

The

of h a l i t e

at the elevated,

I and VI).

at the s e d i m e n t - a i r

the center

amounts

together

with halite

and there m a i n l y and a n h y d r i t e

the f r e q u e n c y

in

only the

may indicate

of a n h y d r i t e

in

26

HALITE

ANHYDRITE

GYPSUM

CARBONATES

DETRITAL CLASTICS

75 - D o %

~

50- 75 %

25-50 %

~

0-25%

Fig. 4. A b u n d a n c e of evaporites, c a r b o n a t e s and detrital clastics in surface sediments at d i f f e r e n t e l e v a t i o n levels of the G a v i s h Sabkha. A) Aerial view from E towards W to show e l e v a t i o n levels: I -III: Upper, m e d i a t e and lower parts of the center (white area = gypsum), IV: Lagoon, V - VI: Lower and upper parts of the coastal b a r slope. B) H a l i t e is in greatest a b u n d a n c e at the most elevated levels I and VI. C) A n h y d r i t e is g e n e r a l l y a s s o c i a t e d w i t h h a l i t e (levels I and VI). D) G y p s u m a c c u m u l a t e s at lower levels (mainly level III, see also A). E) C a r b o n a t e s make up 50 to 70 wt.% of sediments of the lagoon (mgc a l c i t e dominant, a s s o c i a t e d w i t h calcite, aragonite, dolomite). F) S a n d - s i z e d s i l i c i c l a s t s d o m i n a t e at lower parts of the coastal bar. G) F i n e r - g r a i n e d detrital clastics g e n e r a l l y occur at all levels.

27

the

lutitic

fraction indicates that it may be a p r i m a r y

precipitate.

The hot and dry climate makes both p r o c e s s e s possible.

c) Gypsu m (Fig. 4D). to

the

Here,

biological

tary

The only zone w h e r e g y p s u m rarely

b u l k volume of sediments is the lagoon

plain

contributes

(level IV in

Fig. 4D).

sulfate r e d u c t i o n is m o s t active. W i t h i n the sedimen-

III in Fig. 4D,

close to the lagoon,

w h i c h is already part of the

center

the bulk volume of g y p s u m averages nearly

but

i00 %,

thus indicating that the growth must be faster than the a c c u m u l a t i o n of clastic

sediments d e p o s i t e d by wind.

The r e l a t i v e f r e q u e n c y of g y p s u m

decreases w i t h increasing h e i g h t w h i l e in turn h a l i t e becomes more more

dominant

(compare the upward d i r e c t e d d i s t r i b u t i o n

to level I in Fig. 4B). gypsum over

B e l o w the h a l i t e crust of the e l e v a t e d center,

is the most a u t h i g e n i c mineral. 1 m,

the

(GAVISH et al.,

W i t h an average

thickness

layers reach well b e l o w the g r o u n d w a t e r table

surface

(Fig. 4E)

C a r b o n a t e s are m o s t frequent in the surface sediments of the its

(70 %),

margins. while

abundant

of

1985).

i. 5. 2. Carbonates

and

and

from level III

The

m a j o r components are

dolomite

carbonate

averages about 5 %.

c o m p o n e n t of the

clastic

calcite

and

lagoon

Mg-calcite

Aragonite,

w h i c h is

an

sediments

outside,

is

m o s t l y a minor c o m p o n e n t or c o m p l e t e l y absent w i t h i n the sabkha.

We

will

this

return to the q u e s t i o n of in-situ carbonate

highly

h y p e r s a l i n e m i l i e u w h e n referring to the

accretion

in

development

of

b i o l a m i n a t e d sediments and m i c r o b i a l habitats.

i. 5. 3. D e t r i t a l clastics

Terrigenous

clastic sediments in b u l k volumes of 0 - 25 % are mixed

w i t h the in-situ forming minerals. and

are

type).

Coarser grains are w i t h o u t

s u p p o r t e d by m a t r i c e s of g y p s u m or c a r b o n a t e mud

contact

(wackstone-

They r e p r e s e n t fragments t r a n s p o r t e d by n o r t h e r l y and s o u t h e r l y

winds w h i c h b l o w several times in the year. The p r o g r a d a t i o n a l t e n d e n c y of

the

center sloping gently to NNE

(indicated in

Fig.

4A)

m o s t l y due to successive s e d i m e n t i n f i l l i n g by s o u t h e r l y w i n d s 1985; GAVISH et al.,

1985).

may

be

(PURSER,

28

Compacted bottoms

and

sphericity,

surface

layers of terrigenous

sandlobes

4F).

The grains are

which suggests p r i m a r y provenance

from w e a t h e r i n g

cambrian granitic

(level V in Fig.

clastics occur at the gully

rocks of the adjacent Sinai Massif

(Fig.

of of

low Pre-

5A and 5B).

Fig. 5. Sheetflood deposits (thin sections from sediment cores). A) Layer of grain-flow deposits between two microbial mat generations. Scale is 1 cm. B) Texture of g r a i n - f l o w deposits showing badly sorted and rounded particles. Scale is 500 pm. C) Inverse grading of sheetflood sediments with water escape trace (or p o s s i b l y escape trace of insect larva). Scale is 1 mm. D) Sediments resulting from slow sinking deposition from suspension consist of silt, clay, plant debris and some coarser siliciclastic fragments. Scale is 250 pm. E) Sheetfloods also transport seagrasses with epiphytic forams. Scale is 1 mm.

29 Since

we carried out our field work a p p r o x i m a t e l y two years after

last strong sheetflood, exception

of

evaporites, cause and

the

the

we found all other s e d i m e n t a r y plains w i t h the

g u l l y b o t t o m s and sandlobes already

carbonate mud or m i c r o b i a l mats.

debris to flow t h r o u g h a

re-covered

That strong

by

sheetfloods

wadi system on top Of the coastal

bar

to spread over the w h o l e of the l o w e r - l y i n g region is evidenced by

several layers of c o a r s e - g r a i n e d m a t e r i a l w i t h i n the b a s i n sediments of the lagoon.

Silt/clay

fractions

(Fig. 4G)

derive from

suspension

clouds

in

freshwater w h i c h fill the d e p r e s s i o n d u r i n g sheetfloods.

1. 5. 4. I n t e r n a l fabrics of s h e e t f l o o d d e p o s i t s

a) Deposits

resulting

from debris flow:

These are

poorly

sorted

m e d i u m - to c o a r s e - s i z e d quartz sand c o n c e n t r a t i o n s w h i c h imply a gravit y - i n d u c e d lateral m o v e m e n t of debris loads in w a t e r Inverse

grading

(Fig. 5C).

is

Around

r e c o r d e d w i t h i n several the

(Figs. 5A and 5B).

siliciclastic

c i r c u l a r slope of the

sabkha

t h i c k n e s s of the debris flow deposits exceeds several dm° slope direction, central basin,

their thickness decreases. beds of debris

sequences

depression

the

In the down-

In sediment cores from the

flow range in size from a few mm to some

cm.

b) C o n c e n t r a t i o n s of silt, and

some coarser s i l i c i c l a s t i c

tions

clay, p l a n t debris, fragments

some foram skeletons

(Fig. 5D):

result from slow sinking d e p o s i t i o n

These

concentra-

from suspension.

The inter-

spersed coarser s i l i c i c l a s t i c fragments w i t h o u t contact indicate transport

in the c l a y - w a t e r fluid phase.

Haloph~la sp. of

the

forams

The intermixed plant detritus

stems from the m a n g r o v e swamps and lagoons to the

Gavish Sabkha in the order of tens (determined as So,ires

sp.

by L.

of

kilometers.

HOTTINGER)

are

t r a n s p o r t e d with seagrass leaves into the G a v i s h Sabkha

Beds

of

silt and clay are rarely d i s t r i b u t e d around

slope

but

are

c h a r a c t e r i s t i c of the sediments of the

where

the

c l a y - w a t e r fluid phase comes to

s u s p e n s i o n are a few mm to several cm thick.

rest.

The

of

north

Epiphytic

mechanically

(Fig. 5E).

the

circular

central deposits

basin from

30

i. 6. S t r o ~ t o l i t i c

facies types

i. 6. i. The m i c r o b i o t a

Various cipate

species of p r o c a r y o t i c and eucaryotic m i c r o o r g a n i s m s parti-

in forming b i o g e n i c structures in the Garish Sabkha

Since taxonomic d e t e r m i n a t i o n s are still uncertain, to the genera of the organisms found.

3).

we will refer only

Several of these genera are pre-

Oscillato~ia, echococcus, Thioc~ps~, Nitzschia, Navicula). sent w i t h more than one species

(Table

(e. g.

Spirulina,

Syn-

TABLE 3: M i c r o o r g a n i s m s in the microbial mats of the Gavish Sabkha

I.

Procaryotes A. U n i c e l l u l a r c y a n o b a c t e r i a

Gloeothece, Synechococcus, Johannesbaptistia, Gloeocapsa, Synechocystl8, Myxosarcina, Pleunocapsa, Chroococcodiopsis B. F i l a m e n t o u s C y a n o b a c t e r i a

Spirulina, oscillatoria, LPP-formsl: Microcoleus, Hydrocoleum, Phormidium, Lyngbya, Plectonema, Schizothrix C. A n o x y p h o t o b a c t e r i a

Chromatium, Thiocapsa, Ectothiorhodospira,

Chlonoflexus

D. C h e m o l i t h o a u t o t r o p h i c b a c t e r i a

Thiobacillus,

Bsggiatoa, Desulfovibrio) 2

E. C h e m o o r g a n o t r o p h i c b a c t e r i a

Pseudomonas, Spirillum, Spirochaeta, Proteus, Desulfovibrio, s°-reducing and other taxa II. P h o t o s y n t h e t i c eucaryotes Diatoms: Mastogloia, Navicula,

Amphora, Nitzschia 3

1 "LPP"-grouping refers to Rippka et al. (1979). LPP stands for the genera Lyngbya, Phormidium and Plectonema which are r e p r e s e n t a t i v s for structural and p h y s i o l o g i c a l c h a r a c t e r i s t i c s of the LPP-Group. M i c r o c o l e u s should be incorporated in LPP 2 P h y s i o l o g i c a l attributes m e n t i o n e d are only p a r t i a l l y significant 3 Only frequent forms;

for more details see Ehrlich & Dor (1985).

31

I. 6. 2. Major mat-structuring organisms

Types structure capsulated

of primary producers which give the Gavish Sabkha mats are

(i) heavily ensheathed

filamentous

their

cyanobacteria

unicellular cyanobacteria with multiple fission (3)

(2)

slime-

ensheathed cyanobacteria with binary fission.

(i) The main

ensheathed filamentous cyanobacteria present is Micro-

coleus chthonoplaste8

(Fig.

6A). It is a cosmopolitan species found in

Fig. 6. Main mat-structuring microorganisms (modified after EHRLICH & DOR, 1985). Scale is i0 pm for all presentations. A) Ensheathed filament bundles of Microcoleu8 chthonoplastes. B) Pleurocapsalean cells encased in polysaccharid capsules. C) Syneehocysti8 sp. D) Gloeothece sp. The latter both represent coccoid unicells in colloidal matrix. E) Resulting depositional structures: Colonies of M. chthonoplaste8 produce horizontally oriented laminae (Lh) , Pleurocapsalean colonies form cauliflower-shaped nodules, SynecHocystis and Gloeothece contribute to porous, slime-enriched layers containing bubbles and some diagonally to vertically oriented filamentous organisms (Lv).

32 various environments e. g. RING et al.,

1983),

al.,

Solar Lake,

1980),

streifen-Sandwatt, 1942; 3).

Laguna Mormona,

Multiple

Egypt

Australia

Mexico

(KRUMBEIN,

1985b, c; STAL,

(BAULD,

1984; SKY-

(STOLZ, 1983; M A R G U L I S et 1978;

southern North Sea coast

GERDES et al.,

which

Spencer Gulf,

COHEN,

(OERSTEDT,

1984), Farb-

1841; HOFFMANN,

1985; see also this part chapter

e n s h e a t h e d filament bundles are typical of this

are rarely if ever found in a diagonal or v e r t i c a l

species

arrangement.

M i c r o b i a l mats d o m i n a t e d by this species reveal a smooth and u n i f o r m i l y flat

microtopography.

h o r i z o n t a l l y layered, Lh-lamina

vertical sections the mat appears as

a

b e d d i n g plane c o n c o r d a n t lamina w h i c h we call

Within

a

(Fig. 6E; see facies type 1 and 3 in p a r a g r a p h 1.6.3).

(2) The most common capsulated u n i c e l l u l a r c y a n o b a c t e r i a w i t h multiple fission is Pleurocapsa sp. Pleurocapsalean cased

by

(formerly Entophys~lis sp.). Species of

form cell colonies where each individual cell

thick concentric lamellated sheaths

(Fig.

6B).

is

A

en-

crucial

d i f f e r e n c e from Microcoleus chthonoplastes is that the coccoid colonies do not form flat and b e d d i n g - p l a n e c o n c o r d a n t mats but reveal d i s c o n t i nuous,

more

sediment

or

less c o n c e n t r i c structures.

surfaces

The

microtopography

w h i c h are c o l o n i z e d by P l e u r o c a p s a l e a n

of

populations

exhibits a p u s t u l a r structure. C a u l i f l o w e r - l i k e nodules are also common at

sediment surfaces

(Fig.

6E;

see also facies type 2

in

paragraph

1.6.3). (3) The

m o s t common s l i m e - e n s h e a t h e d u n i c e l l u l a r c y a n o b a c t e r i a w i t h

b i n a r y fission are Gloeothece sp.

and Synechocysti8 sp.

(Figs. 6C and

D). These organisms account for the vast p r o d u c t i o n of p o l y s a c c h a r i d e s . Sediments

composed

of or interwoven with

sluggish and y o g h u r t - l i k e if

liquid

(e. g.

these

polysaccharides

seawater)

is

maintained,

due to the dispersal and p a r t i a l d i s s o l u t i o n of the mucilage. of

are

the organisms are i r r e g u l a r l y a r r a n g e d in the slime mass

The cells (MARTIN

&

WYATT,

1974). The species m e n t i o n e d c o n t r i b u t e p r e d o m i n a n t l y to immense

slime

layers

supported from

found in the Gavish Sabkha sediments.

coccoid

Since the

mats form v e r t i c a l l y e x t e n d e d layers

which

the flat and b e d d i n g - p l a n e c o n c o r d a n t L h - l a m i n a e of the

leus mats,

we call them L v - l a m i n a e

slimediffer

Microco-

(Fig. 6E; see also facies type 3 in

p a r a g r a p h 1.6.3). These order

unicellular

organisms

increase their

slime

production

in

to escape p h o t o t o x i c conditions when they form the surface mats.

Slime p r o d u c t i o n is also stimulated by

increase in s a l i n i t y and tempe-

33

rature

(CASTENHOLZ,

Sabkha.

1984).

Photosynthetically

All these

conditions

active populations

occur in the Gavish

of other species

(e.

g.

Mierocoleu8 ehthonoplastes) under the translucent mat benefit from

the

production

for

of large quantities

the channelling

of gel since it is an ideal m e d i u m

of light.

~

,' "~I

ELE

•

'

EVAPORITIC'

1

SEA I~

,~i,,

ULLY

~5~-~-

STROHATOLITIC ~

-

./~

•../

ELASTIE-'--'~

Cat6onates Evoporiles Detritol clastics

Lh- laminae, horizontal orientation [ ~

Lv-laminae,vertlcally extended

['~

Ooids and oncoids Pleurocopsoleon nodules

Fig. 7. Local d i s t r i b u t i o n of stromatolitic facies types. The sequence A) to D) correlates to increasing salinity. The p o s s i b i l i t y of superficial water increases from A) to C) and decreases again in type D). A) Siliciclastic biolaminites (gully bottoms and sandlobes). B) Nodular to b i o l a m i n o i d carbonates (saline mud flats). C) Stromatolitic carbonates with ooids and oncoids (lagoon). D) Biolaminated sulfate (gypsum flats).

34

i. 6. 3. C h a r a c t e r and d i s t r i b u t i o n of s t r o m a t o l i t i c facies types

A of

supply of m o i s t u r e to surface sediments where the initial microbial

Gavish

In

Sabkha m o i s t u r e at or close to the s e d i m e n t a r y surfaces

function of topography.

accumulation

(Fig. 4),

e. g. salinity

patterns

tures.

environments,

va-

An infor-

Their

are d e s c r i b e d in the following sections in

structures,

Community

a

(Fig. 3) and in-situ

o v e r v i e w of the lateral sequence is given in Fig. 7.

community

is

this g r a d i e n t will be used as the

riable to d e s c r i b e the lateral d i s t r i b u t i o n of facies types.

vidual

the

Since the t o p o g r a p h i c m o i s t u r e g r a d i e n t p a r a l -

lels other f a c i e s - r e l e v a n t factors, mineral

mal

growth

mats occurs is essential for their development.

indi-

terms

s e d i m e n t a r y textures and

of

struc-

structure is defined h e r e as the v i s u a l l y o b s e r v a b l e

p r o d u c t of species s e l e c t i o n and d o m i n a n c e at a certain place.

i__t. S i l i c i c l a s t i c b i o l a m i n i t e s

This

facies

is composed of quartz sand and

interlayered

biolami-

The b i o l a m i n i t e s characterize the Lh-type w h i c h is Microcoleus-

nites.

dominated Where

(Fig. 8 )

(Fig.

laminae

6A).

Thickness of laminae differs from 50 to 500 Nm.

are thin

(about 50 pm),

they form a

monolayered

mat.

Thicker laminae comprise several generations of mat development,

aided

by

(Fig.

sufficient surface m o i s t u r e during periods of n o n - d e p o s i t i o n

8A).

Environments slope

are the gully bottoms and sandlobes along the

(Fig. 7).

surface.

Here

Vertical

depend on

the g r o u n d w a t e r table runs -5 to -i0

barrier cm

m o v e m e n t s of the g r o u n d w a t e r table b e t w e e n 2 - 5 cm

the external tidal m o v e m e n t in the Gulf.

Sediment

surfaces

are p e r m a n e n t l y w e t t e d by c a p i l l a r y m o v e m e n t of the g r o u n d w a t e r rative

pumping).

ment-air water

Thin evaporite crusts

interfaces.

table

surfaces.

(mainly gypsum)

During w i n t e r time,

form at

(evaposedi-

o s c i l l a t i o n s of the ground-

lead o c c a s i o n a l l y to the i n u n d a t i o n

Salinity

below

of

the

of interstitial w a t e r is 45 - 60 °/oo.

sedimentary No extreme

shifts occur during the annual cycle.

Sediments are m a i n l y t e r r i g e n o u s and consist of b a d l y sorted to

g r a v e l - s i z e d s i l i c i c l a s t i c sand.

(Fig. 8B). These sediments o r i g i n a t e

The grains are of low from debris-flow.

medium

sphericity

35

Fig. 8. D o c u m e n t a t i o n of facies type i: S i l i c i c l a s t i c b i o l a m i n i t e s . A) X - r a y r a d i o g r a p h of a s e d i m e n t core showing m i c r o b i a l mats in 3 cm d e p t h and at the surface. Scale is 1 cm. B) C l o s e - u p of s i l i c i c l a s t i c sediments showing m i c r o b i a l coatings of sediment p a r t i c l e s (center). Thin section. Scale is 1 mm. C) C l o s e - u p of b i o l a m i n i t e s showing m e m b e r s of the mat community: sheathed bundles of Mic~ocoleus chthonop~as#es, diatoms and filamentous sulfur bacteria. SEM-photography. Scale is 50 pm.

community

structure

(Fig.

8C):

The b u l k of the laminae is made of

e n s h e a t h e d b u n d l e s of M~c~ocoleu8 chthonoplastes. Few u n i c e l l u l a r genera

of

c y a n o b a c t e r i a and diatoms are a s s o c i a t e d w i t h

Mic~ocoleus

the

mat. The mat d e v e l o p s -2 to -5 mm b e l o w the w a t e r surface or u n d e r n e a t h evaporite

crusts.

Both s i l i c i c l a s t i c sediments and

support l i g h t - c h a n n e l l i n g

2. N o d u l a r to b i o l a m i n o i d c a r b o n a t e s

This

term

(nodules)

granular,

cauliflower-shaped

e m b e d d e d in w i d e - s p a c e d b i o l a m i n o i d s

(a

w h i c h defines a less s i g n i f i c a n t l y laminated b u i l d - u p of b i o g e n i c

sediments). and

crusts

(Fig. 9 )

facies type is c h a r a c t e r i z e d by

microbial aggregates

evaporite

for p h o t o s y n t h e t i c activity.

The embedding m a t e r i a l consists of intermixed calcite

mucilaginous

sheaths

of

polysaccharides.

Various tubular relicts

filamentous c y a n o b a c t e r i a are visible around

the

of

mud empty

nodules

(Fig. 9A). T r a n s i t i o n a l stages towards laminoid a r r a n g e m e n t s of smaller

36

granulae exhibit facies

and

filaments can be seen (Fig. 9B)°

a mammillate mierotopography

Surfaces of

(Fig. 9C).

The p a t t e r n

the

mats

of

this

type is stimulated by constant shifts of salinity and depth

of

water.

Environment.

The n o d u l e - b i o l a m i n o i d

facies type dominates

flats just beyond and in b e t w e e n the sandlobes flats

saline mud

(Fig. 7). The saline mud

border the lagoonary basin and are p a r t i a l l y built over

by

the

37

Fig. 9. D o c u m e n t a t i o n of facies type 2: N o d u l a r to b i o l a m i n o i d carbonates (saline mud flats at the lagoon's outer rim). A) I n t r a s e d i m e n t a r y nodules e m b e d d e d in c a r b o n a t e mud. A filigrane m e s h w o r k of d i a g o n a l l y to v e r t i c a l l y o r i e n t e d filaments is visible. Dark sediments at top: reduced. Scale is 500 pm. B) I n t r a s e d i m e n t a r y t w i n - n o d u l e and b i o l a m i n o i d structures (note w a v y d i a g o n a l dark line in the right upper corner). Scale is 2 mm. C) M a m m i l l a t e surface m i c r o t o p o g r a p h y , c h a r a c t e r i s t i c of the noduleb e a r i n g zone. Scale is 1 cm. D) Larger nodules sampled at the surface of small w a t e r - f i l l e d puddles. Scale is 2 cm. E) S E M - p h o t o g r a p h y of a colony of n o d u l e - f o r m i n g c y a n o b a c t e r i a (Pleurocapsalean). Scale is 3 pm. F) S E M - p h o t o g r a p h y of nodule c o m p a r t m e n t s showing capsules of former cells. Note radial a r r a n g e m e n t of compartments. Scale is 3 pm. G) D i s s e c t e d nodule showing radial a r r a n g e m e n t of compartments, the empty center and i r o n - r i c h p i g m e n t s around the cortex. Scale is 2 mm. Figs. A, B and G thin sections from sediment cores.

elevated

sandlobe

"bars"

gullies into the lagoon.

of coarse sediment w h i c h p r o j e c t

tions and feeds the g e n t l y downwards w a t e r film. Lower s a l i n i t y at

sloping mud flats w i t h a trickling

(Ente~omo~pha

sp.). Micro-

bial mats do not d e v e l o p here. The seepage w a t e r a c c u m u l a t e s

into

and

the

drains from these e m b a y m e n t s through

central basin.

the junc-

s e a w a t e r springs b e t w e e n 50 - 70 °/oo is

m a r k e d by a thick scum of b e n t h i c m a c r o a l g a e

embayments

from

Seepage seawater merges at the sandlobe

S a l i n i t y increases w i t h

from 70 to 180 O/oo.

in shallow

narrow

passages

distance

seawater

springs

Some very shallow

(maximum

w a t e r cover i0 cm) are subject to s h o r t - t e r m

from

the

embayments

(commonly

diur-

nal) changes of w a t e r cover and air exposure due to changing conditions of

e v a p o r a t i o n and wind velocities.

observed extreme °/oo.

Short-term salinity

ranging from 70 to 150 °/oo. amplitudes

Other

HOLTKAMP

shifts

were

(1985) r e c o r d e d

ranging w i t h i n a few minutes b e t w e e n 130

more

and

embayments w i t h w a t e r levels b e t w e e n 20 and 40 cm

240

remain

w a t e r - f i l l e d during diurnal and annual cycles. The salinity ranges from 70 to 120 °/oo. Flats around the embayments are usually a i r - e x p o s e d and covered

by

thin e v a p o r a t i o n crusts.

Salinities here can reach up

to

180 °/oo.

S e d i m e n t s are m a i n l y c o m p o s e d of f i n e - g r a i n e d carbonates. G r a i n size analyses

of surface sediments show 38 wt.%

and 30 wt.% 6.3 - 20 pm. saccharides

and

<2 pm,

27 wt.%

2 - 6.3 pm

The s e d i m e n t is mixed w i t h m u c i l a g i n o u s poly-

is of a sluggish,

yoghurt-like

w a t e r - a i r interface of the embayments,

appearance.

thin and fragile

At

the

"calm skinned"

e v a p o r i t e crystals form and are i m m e d i a t e l y d i s i n t e g r a t e d by wind.

The

38

Fig. i0. Documentation of facies type 3: Stromatolitic carbonates with ooids and oncoids (lagoonary basin). A) Sequence of dark (Lh) and light laminae (Lv), growing independently from sediment transport, calcification being a p e n e c o n t e m p o r a n e o u s process (note coatings of diagonally to vertically oriented filaments within the light layer). Scale is 1 mm. B) Close-up of coated filaments w i t h i n a Lv-lamina. SEM-photography. Scale is 5 Nm. C) Ooid embedded in calcified filamentous meshwork. Scale is 500 pm. D) Cluster of coated grains within an extended light lamina. Scale is 500 ~m. E) String of coated grains captured by h o r i z o n t a l l y oriented filaments. Scale is 1 mm. F) Eye-shaped lense, formed by a discontinuous Lh-lamina. Lenses are often the m i c r o - e n v i r o n m e n t of coated grain formation. Note rigid calcification below, within and above the dark lamina. Scale is 500 ~m. G) Ooid surrounded by various intraclasts (dark spots). Scale is 500 ~m. H) View of a biohermal build-up of a mat at the lagoon's margin. The partial destruction is due to slight wind surf. Scale is 5 cm. Figs. A, C, D, E, F and G thin sections from sediment cores. fragments

sink

gypsum mush.

down

to the bottom and form

Some portions become diluted,

mucilaginous

polysaccharides

a

water-saturated

others are embedded

soft

into the

and get colonized by the microbial

commu-

nities. The

community

with multiple cellular

forms

Synechococcu8 The

colonies

(Fig.

colony (Fig.

cyanobacteria

(Fig.

9E).

The compartments

compartment 9F).

The

pigment and

scytonemine

form

cauliflower-shaped

of these

"nodules"

type changes to a more regularly

when

(Fig. 9F). The yellow-

surface m i c r o t o p o g r a p h y

the saline mud flats into the

are also

(Fig. 9A) and at the

cortex

especially the outer surface of

granular

Gloeothece,

cyanobacteria

colors the

following division of the individual of

cyanobacteria

9E, F). Other uni-

producers

and filamentous

show concentric growth around cavities

continuation facies

Figs.

9D) w h i c h occur intrasedimentarily

iron-enriched

maintained

types;

the major slime

Synechocystis)

Pleurocapsalean

sediment surface brown

is dominated by unicellular

(Pleurocapsalean

(predominantly

and

present.

dissected

structure

fission

of

the

of the

each

nodules

nodules

is

cells. With the lateral lagoonary

spaced pattern

basin,

(see next

the sec-

tion). 3. Stromatolitic

carbonates with ooids and oncoids

This facies type is characterized and dark laminae

(Fig.

10A).

(Fi 9. i0)

by regular interlayering

of

light

Both lamina types differ in the vertical

39

40

extension: light

The dark lamina is generally thin (i00 to 200 pm), while the

lamina is up to ten times thicker.

Various vertically to diago-

nally oriented filaments thread through the light layer,

demonstrating

active movements of unsheathed hormogonia and trichomes of cyanobacteria. lOB).

These

Associated

varying

with the light layers are also carbonate

diameters

layers

(Figs. 10C to 10F).

transitions

sections

show

of

light

(Fig. 10D).

(Figs. 10E and F). Some

(ooidal), others are irregularly shaped

from oval to subangular

that

grains

captured by filaments of the dark

laminae which form pockets or eye-shaped lenses grains are regularly concentric

(Fig.

Grains within thickening

show dispersed and sometimes clustered arrangements

Others appear like strings of pearls,

with

filamentous

filaments frequently show calcite coatings

forms

(oncoidal).

concentric lamination of these grains

Vertical is

common

(Fig. 10G). The

environment

seawater

is

the lagoonary basin which is

and probably artesian discharge

by

seepage

(wells) at the basin

fed

bottom.

The 70-cm-deep center of the basin slopes shallowly upwards. facies ject

to

seasonal

changes of water depth

(between i0 and

salinity ranging from 140 (winter) to 280 O/oo (summer; annual changes are performed in a long term, contrast

in

facies.

The surf

build-ups

the

attack the microbial communities tend

with

Recalculation

nodule-biolaminoid

to

of GAVISH's data (GARISH

5

wt.%.

The

form

biohermal

Communities:

al.,

(29 wt.%). consists

of

1985) high

Dolomite is sand-sized

(6 wt.%).

The matrix of this biofacies type is primarily built of

microbial biomass,

mainly of cyanobacteria.

evenness of shallow-water cover, unit

et

the most commom being

remaining portion

(I0 wt.%) and silt-sized quartz

living

in and

(Fig. 10H; see also Fig. IIA).

magnesium calcite averaging 50 wt.% and calcite

the

and

even pattern which is

the shizohaline amphibic zone of

bulk volumes o f carbonate minerals,

found

40 cm)

basin rim is subject to a slight surf caused by the wind.

Sediments: shows

said

Fig. 3). These

to the extreme short term irregularities of water supply

salinity

Under

The

type develops mainly along the shallow shelf area which is sub-

Biomass accumulates under

giving rise to a

which is clearly of stromatolitic

multilaminated

appearance.

The

dark

laminae are created by the predomination of heavily ensheathed filamentous cyanobacteria, light

mainly Mieroco~eu8 chthonoplaste8

(Lh-type).

laminae (Lv-type) are gel-supported and produced by

The

unicellular

41

Fig. ii. D o c u m e n t a t i o n of facies type 4: B i o l a m i n a t e d sulfate. A) R a i s i n - e m b e d d e d microbial mat from the lagoonary rim, laterally d i s t o r t e d b y drying cracks. The d a r k - r e d u c e d zone contains carbonates, the light o x y g e n a t e d t o p m a t i s i n t e r s p e r s e d w i t h elongated gypsum crystals. Note o x i c / a n o x i c b o u n d a r y following the l a t e r a l l y d i s t o r t e d mat surface. Left: S a l t b e e t l e b u r r o w w i t h o x y g e n a t e d halo. Scale is 1 cm. B) G y p s u m crystals growing in a m i c r o b i a l mat expand the space b e t w e e n dark Lh-laminae. Scale is 1 mm. C) F a i n t l y b i o l a m i n a t e d sulfate deposits. Scale is 1 mm. D) G y p s u m deposits, p r o t r u d i n g above the sediment surface. Pupae of the brine fly Ephydra sp. are a t t a c h e d under the crust. Scale is 2 cm. E) I n t r a s e d i m e n t a r y g y p s u m nodule, coated by a m o n o l a y e r e d microbial mat. Scale is 1 mm. Figs. B, C, E from thin sections.

42

Synechocyst~s and

Synechococcus).

Each lamina type is vertically repeated several times.

Up to I0 living

cyanobacteria strata

Gloeothece,

(mainly

thus form which harbor a multitude of oxyphotobacteria

bacteria),

anoxyphotobacteria

flexus), sulfate- and

(e. g. Thiocapsa,

sulfur-reducing

(cyano-

Ch~omatium,

chemoorganotrophic

Chlo~obacteria.

Various products of the metabolic activity of these organisms contemporaneously et al.,

penetrate the vertically structured living system

(KRUMBEIN

1979). Ranging in thickness up to 2 cm, it reflects the multi-

species nature of an organic-rich microbial environment. 4. Biolaminated sulfate Gypsum

(Fi 9. ii)

precipitation

takes place at both the

amphibious

center-oriented rims of the lagoon. As long as bacterial tion (Fig.

predominates

precipitation is restricted to

decreases

due to increasing salinity.

center-oriented rim of the lagoon (Fig. sometimes twin-shaped, above

sulfate reduc-

oxygenated

topmats

IIA). Massive gypsum banks first accumulate where the biological

activity

bial

bar- and

mats

(Fig.

the

This

occurs

at

the

7). Elongated gypsum crystals,

penetrate and fragment the interlaminated micro-

lIB).

Faintly biolaminated sulfate deposits protrude

sediment surface ranging in thickness from

several dm (Figs IIC and lID).

several

cm

to

Microbe-coated gypsum nodules also form

(Fig. lIE). Community structures.

t~8)

dominate

the

mainly Sp~ullnu, face anoxybacteria,

(mainly Synechocys-

Unicellular cyanobacteria

microbial communities.

A few

filamentous

forms,

some halobacteria and at the sulfate-sediment mainly Thiocapsu and Ch?omatium,

inter-

are also present.

This facies is the record of the gradual rise of the terrane towards the

center

and correlates also to the further increase

of

salinity.

Close to the lagoonary rim, salinity ranges between 220 and 300 °/oo in winter and between 280 and 320 °/oo in summer. A maximum of 360 °/oo is maintained

in

bedouin

boreholes which lie just

beyond

the

central

plateau.

I. 6. 4. Facies type-related bio~eochemistry This section deals with local records of standing crops and physicochemical

profiles

(Eh and pH) in sediments.

Measurements

were

made

43

within type

the facies types i),

basin

d e s c r i b e d above:

(2) the saline mud flats

(facies type 3) and

(i) the

sandlobes

(facies type 2),

(4) the sulfate flats

(facies

(3) the l a g o o n a r y

(facies

type

4).

An

informal o v e r v i e w is given in Fig. 12.

St andin ~ crops. carried large

out

by H O L T K A M P

standing

Microcoleus (e. g.

Biomass studies in the Gavish Sabkha mats have b e e n

crops

mats

(1985).

These studies reveal the

(expressed in Ng chl a per

w h i c h form the L h - l a m i n a e in both

w i t h i n the sandlobes;

form

(Fig. 12B

the

2 and 3).

endobenthic

monolayered

mats

Fig. 12B section 3). Gelatinous mats

L v - l a m i n a e are usually lower in

sections

compaction

relatively

in

Fig. 12B section i) and m u l t i l a y e r e d mats

(e. g. w i t h i n the l a g o o n a r y basin; which

cc)

chlorophyll

This can be a t t r i b u t e d to the

content different

of p h o t o s y n t h e t i c a l l y active organisms w i t h i n the

laminae.

The Microco~eu8 mat forms a h e a v i l y c o n d e n s e d network of s h e a t h - e n c a s e d filamentous o r g a n i s m s nisms

(Fig. 8D).

teristic

of

a h i g h slime to cell ratio.

swelling of the biolaminite, decreases

Studies

variations plays

carried

out by BAULD

demonstrate

to

a

cells

(1984) at Shark Bay and Spencer

s i m i l a r i l y that for any one

substantially

affect standing

the most d e c i s i v e role,

ponding

The slime contributes

h e n c e the number of p h o t o s y n t h e t i c

in relation to the total bulk volume of the Lv-lamina.

(Australia)

take

Thus a c t i v e l y p h o t o s y n t h e s i z i n g orga-

are r e l a t i v e l y more a b u n d a n t than in the gelatinous mats charac-

crops.

mat

Water

local

availability

as can be seen in Gavish Sabkha,

where

of seepage waters in the w i n t e r and d e s i c c a t i o n in the

place.

During

Mic~ocoleu8

surface

the w i n t e r p e r i o d the chlorophyll mats

Gulf

type

a

averages ten times that of the

summer

content summer

of mat

where d e s i c c a t i o n takes place.

The data of H O L T K A M P

(1985) reveal h i g h c o n c e n t r a t i o n s of p h e o p h y t i n

(the d e g r a d a t i o n a l p r o d u c t of c h l o r o p h y l l a) in almost all mat types. C o n c e n t r a t i o n s of p h e o p h y t i n a rophyll

a

up to 5 x

were found in L v mats.

p h o t o s y n t h e t i c a l l y active organisms processes. than

A

chlorophyll

g r e a t e r than those of

This indicates that the

chlo-

growth

of

is a c c o m p a n i e d by rigid d e g r a d a t i o n

a / p h e o p h y t i n ~ ratio

(C/P ratio)

1 suggests for several m i c r o b i a l mats of the Gavish

smaller

Sabkha

that

d e g r a d a t i o n of c h l o r o p h y l l a takes over a l r e a d y s i m u l t a n e o u s l y w i t h the p h o t o s y n t h e t i c a c t i v i t y in the same surface layer 3 and 4; values c a l c u l a t e d by HOLTKAMP).

(Fig. 12B sections 2,

44

A ELEVATION AND SALINITY GRADIENTS

B LIVING TOP MATS: PIGMENT CONCENTRATIONS ~ 0

20C/P

o

2o

4o

o

60 ' C/P

Chlorophyll _a

~

Pheophyfin a (pg per co)

8o 1oo/p

o

20 %o 60 %0 i00

zo ~o 6o

[/P

©

NN//,)7/IIo-71q ®

(D

®

C SEDIMENT PROFILES: REBOX POTENTIALS AND pH Eh (mY)

Eh (mV)

'-4~0 '-360 '%o'

-460 '66o '-26o '-~6o' ~' +~6o ' ...... ~,~ 6,8

O

P,,

7,~ 7,6

Eh (mY) I,,,

8

-26o '-16o'6 '+16o',26o' pH

8,~

O

0

-

E

.E

'E

6-

a

1,

'

I\ ; \ t pH

1

®

/×

I

E

14-

®

®

Fig. 12. Effects of terrane inclination and salinity increase on standing crops (data after HOLTKAMP, 1985) and p h y s i c o c h e m i s t r y . A. Schematic p r e s e n t a t i o n to show i n c l i n a t i o n and salinity increase. B: Chlorophyll a, p h e o p h y t i n a (degradational product of c h l o r o p h y l l a) and C/P ratios in surface--mats. The t e n d e n c y of m i c r o b i a l commun~ties to build m u l t i l a y e r e d mats increases w i t h the inclination of the terrane and the salinity increase. Sandlobes (I): Mats are m o n o l a y e r e d and of the Lh-type, Saline mud flats (2), lagoon (3) and gypsum flats (4): Mats consist of two or three laminae. Lowest pigment concentrations w i t h i n the g y p s u m flats (4) and Lv-tO P mats (see 2a, 3a). C/P ratios smaller one indicate that p h e o p h y t i n a takes over. Highest C/P ratios occur in L h mats (see i, 3b). C: Eh- and p H - p r o f i l e s in sediments (M-= surface mat). Reduced h o r i z o n s are dashed or shaded to show their increasing vertical extension.

45

Reduction-oxidation potentials andSterms

of

Eh

Physicochemical properties

and pH are s u m m a r i z e d in Fig. 12C w h i c h relates

to

in the

areas of standing crops d e s c r i b e d above.

Within

the s i l i c i c l a s t i c s of the sandlobes

Eh-values ching

into

sulfate Fig.

the n e g a t i v e sector indicate b u r i e d mats

reduction

prevails

12C section i).

quently

(areas of facies type I)

w e r e found m a i n l y in the p o s i t i v e sector.

reaches

(e. g.

Small peaks where

rea-

bacterial

from -4 to -6 cm b e l o w surface

The pH in p h o t o s y n t h e t i c a l l y active topmats

values a p p r o a c h i n g 9 and falls back in the

in fre-

seawater-

soaked sediments b e l o w to slightly a l k a l i n e m a r i n e conditions.

On

the

mud flats

(areas of facies type 2) only p o s i t i v e

Eh-values

are found in the surface mats. The sediments b e l o w are strongly reduced up to a depth of -12 cm under the surface.

Eh-values of up to

-400 mV

(Fig. 12C section 2) were measured.

The sediments of the lagoon

(localities of facies type 3) are

wise s t r o n g l y reduced right up to the surface Values 6.0

were b e t w e e n 7.4 and 8.2.

to 6.5 were o b s e r v e d by E.

ments

(Holtkamp,

saturated

1985).

e x t r e m e l y low values of pH

H O L T K A M P in the black anaerobic

the h i g h e r the b i o l o g i c a l activity is.

These organisms

rich sediments w h i c h are c o n s e q u e n t l y c o l o n i z e d by

of sulfate as an e l e c t r o n donor.

seepage

seawater

and

chemoorgano-

tration

(see Fig.

with

The sulfate is supplied by

c o r r e l a t e s in its c o n c e n t r a t i o n well

topographic moisture gradient

with

the the the

3). The increase in the concen-

of p h y s i o l o g i c a l l y d e r i v e d reductants within sediments of

strongly

of

form the organi-

trophic b a c t e r i a w h i c h d e c o m p o s e the dying organic material, help

sedi-

The more c o n t i n u o u s l y the sediment surface is

or covered by water,

the p h o t o s y n t h e t i c m i c r o o r g a n i s m s cally

However,

like-

(Fig. 12C section 3). pH-

h y p e r s a l i n e lagoon shows that salinity is a s e c o n d a r y

the

factor

w h i l e m o i s t u r e is of e x t r a o r d i n a r y i m p o r t a n c e for the m i c r o b i a l p r i m a r y producers.

i. 6. 5. Products o_ff early d i a g e n e t i c p r o c e s s e s

The

d e f i n i t i o n of early d i a g e n e s i s

ments after burial

(BERNER,

refers to changes

within

sedi-

1980). Besides burial by sheet flood depo-

sits,

self-burial

by vertical

successions of m i c r o b i a l mats is impor-

tant.

This is achieved by the active p o s i t i o n i n g of m i c r o b i a l

popula-

46

tions relative to their e n v i r o n m e n t a l requirements, to the light field. The rapid gliding m o t i l i t y

latoria sp.

e. g. w i t h respect

(up to 3 cm/h) of 08cil-

a common filamentous species in the Gavish Sabkha,

and its

p e n c h a n t for spreading out under optimal conditions of light and temperature

allows this species in p a r t i c u l a r to override other cyanobacte-

rial topmats

(CASTENHOLZ,

Microcoleu8

chthonoplastes is able to p e r f o r m e n v i r o n m e n t a l

induced

movement

light

conditions

forth

in

complex chomes

its

1969).

Also the filamentous

and accumulates at sediment surfaces (HOLTKAMP 1985).

interactive way

stimulus-

under

reduced

This species usually moves back and

bundled sheath and builds up h o r i z o n t a l

(and hormogonia;

cyanobacterium

(Lh-lamina type).

In crisis

bundles

in

conditions

a

tri-

short filaments of u n d i f f e r e n t i a t e d cells) move

faster and further away from the growth site.

The This

organic is

m a t t e r left b e h i n d exhibits great

evident even in the topmost layers.

The

diagenetic following

variety features

d e s c r i b e d b e l o w can be related to early d i a g e n e t i c processes:

Fig. 13. Patterns of d e h y d r a t i o n and d i s s o l u t i o n in m i c r o b i a l mats. A) S y n a e r e s i s - c r a c k running through an e x t e n d e d h y d r o p l a s t i c Lv-lamina. The dark coating may be caused by subsequent m i c r o b i a l colonization. Thin section from sediment core. Scale is 1 mm. B) Partial d i s s o l u t i o n of g y p s u m o v e r g r o w n by a m i c r o b i a l mat. Filaments of c h e m o t r o p h i c b a c t e r i a and slime threads coat the crystals. Scale is 2 ~m (B to D: SEM-photography). C) Pyrite crystals cover b a c t e r i a l slime. Scale is 3 pm. D) Partial d i s s o l u t i o n of a h a l i t e chip. Scale is 5 pm.

47

(i) Synaeresis cracks

(Fig. 13A)

S y n a e r e s i s cracks are g e n e r a l l y t h o u g h t to like m a t e r i a l

(WHITE,

1961;

BURST,

s p o n t a n e o u s d e h y d r a t i o n even in subaqueous In

the

Gavish

extended (Fig.

13A).

sediments

(PETTIJOHN,

Sabkha sediments synaeresis cracks

hydroplastic

pearance

be c h a r a c t e r i s t i c of gel-

1965) and h a v e b e e n a t t r i b u t e d to

occur

1975).

within

the

layers c o m p o s e d of e x t r a c e l l u l a r p o l y s a c c h a r i d e s

Even the m u c u l o u s clouds r e s p o n s i b l e for the viscous

ap-

of the surface w a t e r c o n t r i b u t e to these layers due to gravi-

tational displacement.

(2) D i s s o l u t i o n p a t t e r n s of evaporite m i n e r a l s

Several d i s s o l u t i o n p a t t e r n s are v i s i b l e evaporites.

on the surface of embedded

D i s s o l u t i o n of g y p s u m in b u r i e d mats

(Fig. 13B) may be m o r e

a b u n d a n t w h e r e b a c t e r i a l sulfate r e d u c t i o n occurs. g y p s u m w i t h b a c t e r i a l slime is evident.

C o m p l e t e coating of

Cobwebs of e x t r a c e l l u l a r mucus

are c o m m o n l y covered w i t h various p y r i t e rosettes as shown in Fig. 13C. In contrast,

the shape of the h a l i t e chip in Fig.

13D indicates p a r t i a l

d i s s o l u t i o n resulting from the d i f f u s i o n of salt into p o r e w a t e r

fluids

of lower concentrations.

(3) Decay centers and formation of a u t h i g e n i c m i n e r a l s

The

term

within situ

a u t h i g e n i c mineral refers to m i n e r a l species

a sediment after burial formation

of minerals,

(BERNER,

1980).

which

grow

By contrast to the in

allochems are formed e l s e w h e r e

and

are

t r a n s p o r t e d to the d e p o s i t s in q u e s t i o n w h e r e they accumulate. A causal factor

in

the formation of a u t h i g e n i c c a r b o n a t e s o c c u r i n g

in

buried

G a v i s h Sabkha mats appears to be the b a c t e r i a l d e c o m p o s i t i o n of organic material

left b e h i n d after death

(BERNER,

1980).

The sheaths of Microcoleu8 chthonoplastes w h i c h form the are

p a r t i c u l a r l y r e c a l c i t r a n t and survive decomposition.

(1985)

have

found

that the sheath m a t e r i a l consists

w h i c h are e v i d e n t l y r e s i s t a n t to m i c r o b i a l attack. after

the c y a n o b a c t e r i a l

composed (COHEN, former

Lh-laminae BOON et

of

biopolymers

The sheath

filaments have disappeared.

al.

Thus

remains

Lh-laminae

of sheaths are often retained even in deeper sediment

layers

1984). E l o n g a t e d a r r a n g e m e n t s of m i c r i t e crystals p o i n t to the p r e s e n c e of f i l a m e n t o u s o r g a n i s m s

(Figs.

14A to

formed by coccoid unicells also p o s s e s s a h i g h degree of

D).

Capsules

recalcitrance

48

while

the enclosed p r o t o p l a s t s are subject to more

resulting

honey-comb

pattern

feature of d e c a y i n g mats

A

coccoid

of h o l l o w spheres is

rapid a

early

The

(Figs. 14E and F).

colony w i t h o u t capsules

(Fig.

15A) may give rise

m i c r i t e - s u r r o u n d e d h o l l o w sphere after decomposition. showing

decay.

characteristic

stages of m i c r i t i z a t i o n are illustrated

to

a

Coccoid unicells in

Fig.

15B.

49

Fig. 14. SEM-photographs showing localized decay and carbonate precipitation in b u r i e d mats at 60 to 80 cm sediment depths (A, B, C, F) and about i cm b e l o w surface (D, E). A) Granular m g - c a l c i t e p r e c i p i t a t e around decaying trichomes of cyanobacteria. At the lower end of the left tube is its empty state visible. Scale is 5 pm. B) Continued precipitation of m i c r o c r y s t a l l i n e mg-calcite replaces g r a d u a l l y the filamentous form. Scale is 25 pm. C) Only the elongated arrangement of micrite crystals points to the former filament. Scale is I0 ~m. D) Polysaccharid capsules are more resistant to b a c t e r i a l attack than protoplasts: Degrading cell encased by the extracellular capsule. Scale is i0 pm. E) Empty capsules of cyanobacteria (probably Pleurocapsalean) surrounded by smaller eoccoids (possibly sulfur bacteria). Empty capsules later give rise to m i c r i t e - s u r r o u n d e d h o l l o w spheres. Scale is I0 pm. F) View of the decaying mat with coated filaments, diatoms and hollow spheres. Note the slightly deformed coated sphere at top. Such spheres also form around gas bubbles abundantly occurring within the decaying mat. Bubbles colonized, coated and fixed are common (see also Fig. 26). Scale is 25 pm.

Single cells appear as completely and oncoids of various records

of

calcified

shapes and sizes

carbonate p r e c i p i t a t i o n

spheres

(Figs.

(Fig.

15D,

15C).

Ooids

E and F) are also

within the buried mats

(see

next

section).

i. 6. 6. In-situ

Self-burial, ly

formation of ooids and oncoids

emphasized

in the previous

w i t h i n the facies type 3 which occurs

lagoon.

It

results

in the vertical

supported Lh- ) and light bial mats.

lations p r e d o m i n a n t l y Lh-laminae evaporites,

(unicellular

The study of thin sections

carbonate which

in the

is recorded main-

constantly

succession of

dark

grains

In sheetflood

horizontally

facies type 3, they are non-existent.

(Fig.

I0).

sediments

and v e r t i c a l l y

with

(compounds

In and the

Their close relationship with the

It is stressed that the ooids are not

in the off-shore waters nor are they found in the layers

with allochems

micro-

shows that ooid and oncoid popu-

are rare.

interfinger

submerged

(filamentous

and gel supported Lv-type)

occur within the light Lv-laminae

L v - l a m i n a e will be examined here. forming

sections,

that have been transported

into the

rich

environ-

ment).

The term ooid is applied to a rounded biogenic and continuous

laminations;

grain with concentric

it is less than 2 mm in diameter

(Table 2).

50

Fig. 15. S E M - p h o t o g r a p h s showing cells and rounded cell clusters in mats w h i c h may give rise to n u c l e a t i o n centers of ooids, compound ooids and oncoids. A) Colony of coccoid unicells p a r t i a l l y a g g l u t i n a t e d showing initial steps of calcite coatings. Scale is 2 ~m. B) M i c r o t e x t u r e of a colony of coccoid unicells during an early stage of lithification. Scale is 2 pm. C) C o m p l e t e l y calcified single cell. Scale is 5 pm. D) Sub-rounded shape of lithifying cell colony. Rod-shaped organisms at right may be c h e m o o r g a n o t r o p h i c bacteria. Scale is 2 pm. E) R e p e t i t i o n of m i c r o b i a l coating of a c o m p l e t e l y round carbonate grain. Scale is i0 pm. F) Sub-rounded grain embedded in a slime m a t r i x and c o l o n i z e d by small unicellular bacteria. Scale is 3 pm.

51

Where

the

laminations are d i s c o n t i n u o u s and irregular and the

are less rounded,

the t e r m oncoid will be applied

D A H A N A Y A K E & KRUMBEIN,

(HEIM,

1916,

grains see also

1986).

In-situ f o r m a t i o n of ooids in p a r t i c u l a r may be striking but can correlated

to

conditions already m e n t i o n e d in the

previous

be

section.

These conditions are summarized as follows:

(1) H y d r o p l a s t i c L v - l a m i n a e provide the space:

In

the vertical sequence m u c h more e x t e n s i v e L v - l a m i n a e

override shaped of

the

(Fig. 8).

gel.

The

partially vugs

thinner L h - l a m i n a e ,

w h i c h may be flat,

repeatedly

w a v y or

"eye"-

The L v - l a m i n a e are c h a r a c t e r i z e d by large q u a n t i t i e s

m u c i l a g e tends to become i r r e g u l a r l y

diluted by interstitial

d e v e l o p due to i r r e g u l a r i t i e s

seawater.

disintegrated

Small-scale

and

pockets

in the slime m a t r i x and the

and

under-

lying Lh-laminae. (2) N u c l e a t i o n centers:

On

a

microscopic

scale,

the w i d e l y spaced L v - l a m i n a e

v a r i e t y of p o s s i b l e nuclei for ooid and oncoid synthesis: bubbles,

intraclasts,

d e g r a d i n g cell clusters.

from Lh-type mats below.

contain trapped

a gas

The bubbles often come

These g e n e r a l l y h a v e a h i g h e r p r i m a r y produc-

tion rate than the L v - l a m i n a e above. The filamentous o r g a n i s m s d o m i n a n t in

Lh-laminae

conditions.

are

able to p h o t o s y n t h e s i s e even under

Metabolic products

(e. g.

reduced

light

02 , CO 2, NH 3, CH 4, H2S), b e c o m e

trapped d u r i n g upward m i g r a t i o n w i t h i n the h y d r o p h i l i c gels w h i c h lower their

diffusion

1979). laminae

The

originate

unicellular duction,

v e l o c i t y by at least the factor ten (KRUMBEIN et

intraclasts

w h i c h can be r e p e a t e d l y o b s e r v e d

from floating and/or

cyanobacteria,

tend

fragmentated

within

mats.

the

Finally,

w h i c h are m a i n l y r e s p o n s i b l e for gel pro-

to form cell clusters rather than regular

arrangements

w i t h i n the s l i m e - s u p p o r t e d layers and p r e s e n t ideal n u c l e a t i o n after death

al.,

centers

(Fig. 15).

(3) N u c l e a t i o n and c o n t i n u e d growth of ooids and oncoids:

Bubbles,

intraclasts,

organic fragments,

filaments,

single cells,

o f t e n on s u b m i c r o s c o p i c scale,

for CaCO 3 p r e c i p i t a t i o n .

cell clusters and may serve as nuclei

Initial CaCO 3 p r e c i p i t a t i o n may be due to the

52

localized

rise in c a r b o n a t e

supersaturation

due to b a c t e r i a l

tions given by B E R N E R

organic

C + CO 2

organic

N ÷ NH 3

2NH 3 + CO 2 + H20

Dissolved

bacteria.

(1980)

+

which

brine

as a result of a m m o n i a

decomposition

of proteins.

and

The

CO 2 reac-

are as follows:

2 NH4 + + CO3=

sulfate

interstitial

alkalinity

is supplied

is c o n s t a n t l y

This a d d i t i o n a l l y

in high

reduced

generates

concentrations

by

the

to sulfide by s u l f a t e - r e d u c i n g

carbonate

alkalinity:

2CH20 + S04= + H2S + 2HC03= Thus, tive is

bacterial

attack on p r o t o p l a s m

zones w i t h i n the host m a t e r i a l more

recalcitrant

commonly

of m i c r o s c o p i c

rough

measurements

6. 4.

do not p e r m i t

ments

is

to

The factors

"hard ground"

living

the c o n t i n u e d

ally

calcified

soft-bodied

ooids

colonization,

which

decomposition, This

process

and oncoids.

brine

to e m p h a s i z e

appears

production

may bring

of excess

protoplasm filled

may be analoand

calculi

to

with

external carbonate

the c o n s p i c u o u s

matrix

the coating

growth of calcareous material

result,

bubbles

layers m a y be due

again a c c e l e r a t e s

of alka-

As a

stones

i.

to disturbances.

in the surrounding

(see for example

8). Thus,

tion.

as a r e a c t i o n

are

measure-

centers

fractalized (e. g.

(kidney)

of the c o n c e n t r a t e d

Fig.

death:

bezoar

but it seems w o r t h w i l e

of m i c r o o r g a n i s m s

any given

ions

itself

centers

in section

The effect of e n c a p s u l a t i o n

of perls,

saturation

ions),

cells,

reac-

so that the rather

shown

of localized

of c o n c e n t r a t e d

growth of c o n c e n t r i c

(overall

gel which

In situ m i c r o e l e c t r o d e

the d e c o m p o s i n g

of m a c r o o r g a n i s m s

continued

scale

parameters

The effect

w i t h CO 2 or CH4).

and sulfate

quent

sediment

highly

reactive

level of CaCO 3 o v e r s a t u r a t i o n .

around

the f o r m a t i o n

found in tissues

These h i g h l y

their recognition.

and other centers

initially

generates

of e x t r a c e l l u l a r

or even s u b m i c r o s c o p i c

of general

a rise in the

CaCO 3 p r e c i p i t a t e s material

habit

decay.

can solve this problem.

linity

gous

against

material

of c o l o n i z i n g

of e x t r a c l a s t s

layers

around

to be achieved the reaction

by

in

initisubse-

chain

after

free energy and p r e c i p i t a -

about the successive

laminations

of

the

53

Finally,

the

nuclei

appears

bubbles

(Fig.

inhabitants), bring

question to be 14F

of the shape

important.

of

pre-existing

Unicellular

soft-bodied

organisms

(Fig. 15C),

shows for example the coating of a b u b b l e

and smaller lithified cell a g g r e g a t e s

(Figs.

a b o u t the c o n c e n t r i c a l l y c o n t i n u o u s ooid type

by

15A, B) may

(Fig. 15E),

the o n c o i d type is b r o u g h t about by less rounded nuclei

mat

while

(Figs. 15D

and

F). All

the

facts m e n t i o n e d above as well as other

biogeochemical COHEN et al.,

studies of m i c r o b i a l mat systems

be

1978,

and 1983;

1984) allow us to infer the p o s s i b l e syngenetic growth of

ooids and oncoids w i t h i n s t r o m a t o l i t i c not

physiological

(KRUMBEIN,

construed

sequences.

that all cases of ooid and

It should,

oncoid

however,

formations

are

c o v e r e d by these models.

i. 6. 7. M i c r o b i a ! l y m o d i f i e d surface structures

Subaerially physical

exposed and s a l t - e n c r u s t e d surfaces bearing a number of

structures such as d e s i c c a t i o n cracks and crinkle

i n c l u d e d here. The aim is to d e m o n s t r a t e h o w p h y s i c a l

marks

are

structures can be

m o d i f i e d by the p r e s e n c e of microbes.

(i) Tepee- and petee structures

The

central e l e v a t e d part of the G a v i s h Sabkha is c h a r a c t e r i z e d

d e s i c c a t i o n cracks w h i c h form polygons. FRENZEL,

1950) are common h e r e

of surface sediments

polygons

(sensu ADAM &

(Fig. 16A). These result from

l i z a t i o n p r e s s u r e in p r e c i p i t a t i n g sion

Tepee structures

(SHINN,

by

crystal-

salts, w h i c h causes a lateral expan1969;

WARREN,

1982).

Tepees

and

in the central part of the sabkha w e r e found w i t h o u t any sign

of m i c r o b i a l life.

On h i g h e r - l y i n g parts of the s e a w a r d - d i r e c t e d crobes

levels rise. For a p e r i o d of several days, les

become glued t o g e t h e r by m i c r o b i a l

During s u b s e q u e n t periods, tallization part.

slope,

however,

mi-

d e v e l o p mats e p i s o d i c a l l y after sheetfloods or w h e n g r o u n d w a t e r

pressure

According

terrigenous

sediment partic-

slime and p r e c i p i t a t i n g

the sediments dry out c o m p l e t e l y and

expands

them as on the surface of

to the m i c r o b i a l influence,

modified

w h i c h show s o m e w h a t c r i n k l e d and c o n v o l u t i o n a l patterns.

the tepees

salts. cryscentral result

In a n a l o g y to

54

Fig. 16. Physically and microbially modified sedimentary surfaces. A) Desiccation polygons and tepee structures, typical for sabkhas, are physical in origin. Elevated center of the Gavish Sabkha. B) Close-up of a tepee structure. C) Crystallization pressure and lateral expansion of surface sediments take also place where microbial slime binds surface sediments. The result is a convolutional pattern (modified tepees or "petees"). D) Sediments glued together by microbial slime form slump structures like a table cloth when moving downslope. Cracking takes place along the crests after drying. Finally "meteor-paper" results (see text). tepees

which originate under merely physical conditions,

microbially modified structures (2) Pseudo-ripples

"petees"

we call

the

(Fig. 16B),

and meteor-paper

On gently sloped,

periodically moistened surfaces,

slump structures

occur

which result from a restricted downslope movement of

glued

together by microbial

slime and precipitating

sediments,

salt (mainly

gyp-

55

sum).

The

structures

formed include small m i c r o f o l d s p e r p e n d i c u l a r to

the d i r e c t i o n of the m o v e m e n t

(Fig. 16C). After drying,

along the crests of the h o l l o w p s e u d o - r i p p l e s ,

c r a c k i n g starts

and finally

paper-like

chips d e v e l o p w h i c h can be b l o w n off by the wind.

The

p r o d u c t was first d e s c r i b e d in 1686 and was initially identified

as m e t e o r - p a p e r sky).

(organic,

p a p e r - l i k e meteorite;

i. e. fallen from the

People saved it so that about 150 years later,

C.

G. E H R E N B E R G

(1839) was able to study it again and found that it was a dried chip of microbially

glued sediments blown off by the wind

(see also

KRUMBEIN,

1986b).

i. 7. Faunal i n f l u e n c e on the b i o l a m i n a t e d d e p o s i t s

The Late P r e c a m b r i a n decline of s t r o m a t o l i t e s coincides in time with the early M e t a z o a n rise cially

of

chiopods

first by

invertebrates

1983;

step in the

increasing (for

d e c l i n e see MONTY,

PRATT,

1982).

"G~tterd~mmerung"

stromatolites

b i o t u r b a t i o n and grazing a c t i v i t y

c o n t r o v e r s a l d i s c u s s i o n of 1973; KNOLL,

the

for space.

P h a n e r o z o i c s t r o m a t o l i t e s and Recent p o t e n t i a l

Late

found in c o e x i s t e n c e w i t h i n the

usually occur in m a r g i n a l to moderate,

ronments. line,

overcome

the fact

known

diversity

or h y p e r t h e r m a l conditions.

by a marine

fauna.

of

f a u n a - p o p u l a t e d envischizoha-

These are d e s i c c a t i o n -

The Gavish Sabkha p r e s e n t s no

even more e f f e c t i v e l y r e s t r i c t e d b y

is are

M i c r o b i a l com-

and thus m a i n t a i n p h y s i o l o g i c a l b a r r i e r s w h i c h are h a r d

p a r t i c u l a r l y as the m i g r a t i o n of faunal elements is

Precambrian

Zones w h e r e they occur are often c h a r a c t e r i z e d by

hypersaline

endangered

was

benthic

stromatolites

s h a l l o w m a r i n e and intertidal b u r r o w i n g faunal habitats. munities

of

W h e t h e r there was a c o r r e l a t i o n or not,

ever

the

1985a, b, c) and the second by competi-

that

if

with

It has b e e n suggested of

tion

rarely

time

rugose and t a b u l a t e corals and articulate bra-

(KNOLL & AWRAMIK,

the

induced

1981). O r d o v i c i a n decline espe-

c a r b o n a t e shelf s t r o m a t o l i t e s coincides in

r a d i a t i o n of bryozoans,

that

(AWRAMIK 1971,

to

exception,

from the adjacent Gulf

b o t h the p h y s i o l o g i c a l

barrier

of h y p e r s a l i n i t y and by the g e o m o r p h i c b a r r i e r of bar-closing.

Nonetheless, Sabkha.

a v a r i e t y of faunal elements is p r e s e n t in the

Gavish

It is the p u r p o s e of this section to elaborate on their facies-

i n d i c a t i v e role.

56

i. 7. 1. Species c o m p o s i t i o n and d i s t r i b u t i o n

Sampling

provided

22

macrobenthic

and

i0

meiobenthic

species

(Table 4). About 80 % of all species are of terrestrial origin,

50 % (17

species) being insects.

Like

the m i c r o b i a l mats,

Sabkha

the b e n t h i c i n v e r t e b r a t e s of

Gavish

are restricted to the zones p e r i o d i c a l l y or c o n s t a n t l y supplied

by water.

While salinity is rarely a restrictive factor in the

ding of microorganisms, fauna.

According

to

strial

arthropods

(insects,

(Unit I);

gastropods,

nematodes,

ostracods,

prefer

margins

copepods,

increase

nohaline

air-exposed

turbellarians

and rotifers the

lagoon's

(3) aquatic insects w h i c h spread all over the aqua-

and w a t e r - s a t u r a t e d areas

salinity

the

(i) terre-

(2) aquatic insects, marine

seawater springs and small impondments at

(Unit II);

gradients

(Fig. 17):

spiders) w h i c h colonize

w e t l a n d s around the aquatic zones

which

sprea-

it plays a d e c i s i v e role in the d i s t r i b u t i o n of the topographic m o i s t u r e and salinity

three m a j o r species assemblages can be r e c o g n i z e d

tic

the

(Unit III).

Unit II is r e s t r i c t e d by

above 130 °/oo and thus has been defined

(GERDES et al.,

a

hyperste-

1985d) while Unit III is defined h y p e r e u r y h a -

line

b e c a u s e its members manage to p o p u l a t e the entire

dient

(Fig. 17). The remarkable evenness in spatial d i s t r i b u t i o n of the

fauna

salinity

b e t w e e n seasons documents well the stability of b i o t o p i c

tions due to the constant seawater influx

(compare Fig.

gra-

condi-

17A and B).

i. 7. 2. Trophic relations

Gut content analyses have shown that the m a j o r i t y of species

living

in the Gavish Sabkha belongs to the c a t e g o r y of p r i m a r y consumers. category

can

diatoms tous

be further split into

(i) types which p r e f e r a

and u n i c e l l u l a r cyanobacteria,

cyanobacteria

and

of

(2) types w h i c h favor filamen-

(3) types w h i c h feed on the

m a t e r i a l of m i c r o b i a l mats.

diet

This

decaying

The largest part of the p r i m a r y

organic consumers

feeds upon diatoms and u n i c e l l u l a r c y a n o b a c t e r i a w h i c h are available in abundance

in

the

Gavish Sabkha.

The h e a v i l y e n s h e a t h e d

bundles

of

Microcoleu8 are seemingly less nutritious. Only one species favors this diet

(Table 5).

the tiger beetles beetles larvae

S e c o n d a r y consumers are p s e u d o s c o r p i o n s (both larvae and imagines)

(Anacaena sp.).

Capturing prey,

and

spiders,

and larvae of h y d r o p h i l i d e

p s e u d o s c o r p i o n s and Anacaena

have been c o m m o n l y o b s e r v e d in d w e l l i n g burrows of

staphilinid

57

TABLE 4. Benthic invertebrates observed in the Gavish Sabkha MAJOR TAXA

I.INSECTA

SPECIES

Cicindelidae Georyssidae Ptiliidae Dytiscidae Hydrophilidae Hydraenidae

Blediu8 capra Bledius angustus Lophyridia aulica Georyssus sp. Actidium sp. Deronecte8 sp. Enochrus sp. Anacaena sp. Ochthebius c.f. au~atu8

L,P,A *) L,P,A L,P,A A A L,P,A L,P,A L,P,A L,P,A

exposed wet exposed wet exposed wet exposed wet exposed wet submersed submersed submersed, exp.wet submersed

Ephydra macellaria Hecamede grisescens Musca c~a88irost~is Orthellia cessation Atylotus ag.estis Bezzia sp.

L,P,A L,P,A

submersed, exp.wet submersed exposed wet exposed wet submersed submersed

DIPTERA

Ephydridae Muscidae Tabanidae Ceratopogonidae 3.INSECTA

HABITAT

COLEOPTERA

Staphilinidae

2.INSECTA

STAGES

L L L,A L,P,A

HETEROPTERA

not determined

exposed wet

4.ARACHNIDA

Pseudoscorpiones Clubionidae

Halominniza aegyptiaca not determined

J,A J,A

exposed wet exposed wet

exposed wet submersed submersed submersed submersed

5.CRUSTACEA

ISOPODA OSTRACODA

Halophiloscia sp. Cypnidei8 torosa

COPEPODA

Robertsonia salsa Nitocra sp.

J,A J,A J,A J,A J,A

Enchytraeidae, n . d . Capitellidae, n.d.

J J

exp.wet exp.wet

J,A

submersed,

exp.wet exp.wet exp.wet exp.wet

Paraeyprideinae

sp.

6.ANNELIDA

CLITELLATA POLYCHAETA 7.MOLLUSCA

GASTROPODA

Potamiidae

Pirenella conica

8.NEMATODES

Enoplus communi~ Oncholaimus fuscus Adoncholaimus oxyris

submersed, submersed, submersed,

9.ROTATORIA

Brachionu~ plicatili8

submersed

10.TURBELLARIA

Mac~ostomum

sp.

submersed

II.PROTOZOA

CILIATA

not determined

*)observed stages: L=Larvae,

P=Pupae, A=Adults,

submersed, J=Juvenile

exp.wet

58

LIIO~AL EASTERN ?AR~

"--L- ::

Fig. 17. D i s t r i b u t i o n and abundance of benthic invertebrates (selected species) along h o r i zontal gradients of w a t e r supply and salinity. A) summer B) winter situation. Unit I: W e t l a n d fauna, restricted to exposed _ flats (e. g. the sandlobes); Unit II: Aquatic fauna, salinity-restricted (hyperstenohaline), members of this group are restricted to mud flats and small impondments of the eastern (coastal bar directed) rim of the lagoon; Unit III: Aquatic fauna, n o n - r e s t r i c t e d by salini~-~ ty (hypereuryhaline). Members of i the latter group (only insects) manage to p o p u l a t e the entire salinity gradient. (Modified B after GERDES et al., 1985).

Sl,d;us

___E.%P~u_'_¢2m_m_u_"ig__

R0b.,~s0~o ,°L,0 Cyp,i~.,, L0,0.~

S,ZZ~0

~&~:=~-

beetles.

NSTRIHUTION

ANO ABUNDANCE 0~ 5£tECTE0

-

-

-

-

SPECIES

Dytiscid beetles which belong to the h y p e r s t e n o h a l i n e unit II

are p r e d a t o r s as well.

i. 7. 3. Systematic ichnology Dwelling,

crawling and feeding traces account for ichnological pat-

terns in the Gavish Sabkha.

59

A. D w e l l i n g traces:

i. Traces of the salt beetle Bledius

Description: face

and

A diagonally oriented

capra

(Staphilinidae)

"bottle neck" starts from the

converts into a v e r t i c a l l y o r i e n t e d b u r r o w

(Fig.

sur-

18A,

B).

L e n g t h of bottle neck 2 to 3 cm, of complete b u r r o w i0 to 12 cm. Diameter: b o t t l e neck about 5 mm, v e r t i c a l b u r r o w about 1 cm. At the conversion

there is a w i d e n i n g w h e r e m i c r o b i a l lumps are stored

The lower end of the v e r t i c a l b u r r o w merges where the

the beetle stores feces.

(Fig. 18C).

into one or more appendices

Female beetles

interrupt the walls

v e r t i c a l l y o r i e n t e d b u r r o w to create b r e e d i n g chambers

During

breeding

each chamber contains one egg

which

of

(Fig. 18B).

is

vertically

o r i e n t e d and stands on a sockle of s e d i m e n t grains.

Habitats:

G u l l y bottoms and sandlobes,

Trophi c relations:

Remarks: surface

The

a i r - e x p o s e d m i c r o b i a l mats.

Grazer.

beetles

rip away at the tough substrates of

mats and carry the food into the store chambers where they use

mandibles

(Fig. 18D)

Positioning

and heads to press the lumps against

wall.

S h e e t f l o o d sediments covering m u l t i l a y e r e d m i c r o b i a l

mats are well d o c u m e n t e d by b u r r o w fillings

(Fig. 18 E).

2. Traces of the salt b e e t l e Blediu8 angustu8

Description: oriented

the

the mat m a t e r i a l close to the surface enhances the chances

of p h o t o s y n t h e s i s .

Traces

consist

endobenthic

"chimneys"

burrows,

(Fig. 19A).

d i a m e t e r up to 5 mm.

(ii)

on

horizontally

wall).

(i)

vertically

oriented

feeding

(iii) v e r t i c a l l y o r i e n t e d epibenthic

of e n d o b e n t h i c burrows:

Length of epibenthic chimneys:

meter up to 1 cm (incl. precipitates

Length

(Staphilinidae)

of a c o m b i n e d system of

traces, p a r a l l e l to b e d d i n g planes

!9A).

air-exposed

up

to

up to 3 cm,

Chimneys are only present when

the surface and glues the sand grains together

5 cm, diagypsum (Fig.

L e n g t h of feeding traces about 5 cm, d i a m e t e r 5 to i0 mm, trans-

verse U-shaped.

Habitats:

Gully

e n c r u s t e d sand.

bottoms

and sandlobes c o n s i s t i n g of loose

or

salt-

60

TABLE

5.

Groups

Trophic relations of benthic i n v e r t e b r a t e s p r e s e n t G a v i s h Sabkha (after studies of gut contents)

Food type

Species Coccoid cyanobact, and diatoms

Terrestrial beetles

Aquatic beetles

Flies and mosquito larvae

X x

H. g r i s e s c e n s E. m a c e l l a r i a Muscidae B e z z i a sp. (larvae)

x x

Isopods

Halophiloscia sp.

Copepods

Detritus

R. s a l s a Nitoc~a

x x

x x x x

X x

X

Ostracods

C. t o r o s a Paracyprideinae

x x

Gastropods

P.

x

Nematodes

E. c o m m u n i 8 Adonchol a i m u s sp.

conica

Prey

x x

sp.

Turbellarians Rotatorians

Filamentous cyanobact.

x

A ~ a d a ~ n a sp. (adult) (larvae) D e r o n e c t e 8 sp. O. a u ~ a t u s Enochrus sp.

Clubionidae H. a e g y p t i a c a

the

(preference)

B. c a p r a B. a n g u e t u s G e o r y s s u 8 sp. A c t i d i u m sp. L. a u l i c a

Spiders, Pseudoscorpions

in

x

x x x

61

T r o p h i c relations:

Grazer.

Remarks:

structures

the

Feeding

endobenthic

evaporation sediment cated

microbial

run -2 to -5 mm b e l o w surface and mats of gully beds

and

sandlobes.

crusts replace tunnel roofings feeding traces

surface.

SCHWARZ

(1936) suggests

Where

furrow

that the use of

b u i l d i n g s econimizes on c o n s t r u c t i o n effort.

furrow

the

prefabri-

E v a p o r a t i o n crusts

also serve as l i g h t - c h a n n e l l i n g systems w h i c h stimulate p h o t o k i n e s i s of cyanobacteria Hence and

a

which

then colonize the furrows made

r e a c t i n g cyanobacteria,

peting

groundwater

table

beetles

three-dimensional

carcrusts

The b e e t l e s manage to survive w h e n epibenthic

cross

the

chimneys,

( r e t r a i t e - b u r r o w sensu BRO LARSEN,

support survival w h e n it falls.

access

beetles.

the latter create a dense b l u e g r e e n

rises by r e t r e a t i n g into the

w h i l e the e n d o b e n t h i c burrows

a

the

w h i c h can easily be grazed under the p r o t e c t i o n of salt

at the s e d i m e n t / a i r interface.

of

by

farming effect evolves from an interplay of b e h a v i n g

1936)

The w h o l e s y s t e m evokes the impression (Fig.

20B) w h i c h allows the

the h o r i z o n t a l l y o r i e n t e d c y a n o b a c t e r i a l

beetle

to

"garden" from both the

s u p e r s u r f i c i a l and subsurficial parts of the burrow.

The

p r e s e n c e of b o t h

piles

Blediu8 species can be recognized by the

of e x c a v a t i o n p e l l e t s they leave b e h i n d on the mat

surface r e s p e c t i v e l y

sediment

(Fig. 18F)o

3. Traces of tiger beetle larvae

Description:

or

typical

(Lophy~idia aulica~ Cicindelidae)

V e r t i c a l l y o r i e n t e d burrows,

length up to 30 cm, d i a m e t e r

up to 1.5 cm.

Habitats:

Gully embankments c o n s i s t i n g of loose,

s a n d - s i z e d sediments

w i t h a low m o i s t u r e level.

T r o p h i c relations:

Predator.

Remarks: Larvae use their h e a v y m a n d i b l e s to close entrances of burrows while

lying

in w a i t for prey.

burrow.

Excavation

burrows

(Fig.

capturing prey

20A).

pellets

M a n d i b l e s w e r e also used to clear

a c c u m u l a t e around the

Adults move freely

(mainly aquatic meiofauna).

entrances

on w a t e r - s a t u r a t e d

of

the the

sediments

62

Fig. 18. Traces of the salt beetle Bledius capra (Staphilinidae). A) The b u r r o w starts w i t h a d i a g o n a l l y o r i e n t e d "bottle neck" and merges into a vertical lower part (burrow of a male). A and B: Resin casts. B) Breeding chambers b r a n c h i n g sidewards off the main shaft characterize the b u r r o w of a female. Note also appendices filled w i t h feces. A and B: Photograph by H.-E. REINECK. C) Thin section showing storage of food (lumps of m i c r o b i a l mats) at the c o n v e r s i o n from the "bottle neck" to the v e r t i c a l shaft. Scale is 1 cm. D) S E M - p h o t o g r a p h y showing head and m o u t h parts of B. capra. Note h e a v y m a n d i b l e s w h i c h allow the beetle to dig and clear its b u r r o w and rip away at tough mat substrates for food. Scale is 250 pm. E) S h e e t f l o o d (grain-flow) sediments filling a b u r r o w of B. capra w h i c h was formed w i t h i n a m u l t i l a y e r e d m i c r o b i a l mat sequence. Thin section from sediment core. Scale is 5 mm. F) Various excavation pellets of salt beetles, i

W B. C r a w l i n g traces: G a s t r o p o d s

Description:

(Pirenell~ conica, Fig. 19C and 20C)

Bilobed crawling trails on the m u d d y w a t e r - s a t u r a t e d

sedi-

m e n t surface.

Habitats:

Seawater springs w i t h benthic m a c r o a l g a l scum

(Enteromorpha

sp., p r o b a b l y also Chaetomorpha sp.). and m e t a h a l i n e mud flats.

Trophic relations: Grazer. Remarks: M i c r o b i a l mats do not form where the snails are abundant.

C. Feeding traces: Water beetles

Description: away

at

(Fig. 19D and 20D)

Irregularly shaped holes on mat surfaces. The beetles rip

surface substrates of submerged m i c r o b i a l mats.

Diameter

of

by the small h y d r a e n i d beetle Ochthebius auratu8 are 1

to

holes

made

2 mm,

holes made by the larger species Enochrus sp.

are 5 to i0 mm in

diameter. Habitats:

Enochru8 sp.

(salinity restricted):

M a r g i n a l impondments with

soft m u c u l o u s and p a r t i a l l y floating m i c r o b i a l mats; Ochthebiu8 auratu8 (non-restricted by salinity): Whole m a t - c o v e r e d aquatic areas.

T r o p h i c relations: Grazers. Remarks: No indication that the o c c u r r e n c e of beetles is d e t r i m e n t a l to the growing mat systems.

63

64

Fig. 19. Further trace records of the Gavish Sabkha fauna. A) Epibenthic g y p s u m - e n c r u s t e d "chimneys" of the salt beetle

Blediu8

angustus. B) Feeding traces of B. angustu8 at the s e d i m e n t - g y p s u m crust interface and entrance to its e n d o b e n t h i c r e t r a i t e - b u r r o w (arrow). C) Bilobed crawling traces of g a s t r o p o d s (P. conica) on m u d d y waters a t u r a t e d flats at the lagoon's margin. D) Feeding traces in subaquous surface mats, made by w a t e r beetles (Enochru8 sp.).

65

[~

DWELLING

-~1 CRAWLING

TRACES

DOMINANT

DOMINANT

INCREASING

[ • - • C h ionmGypsum n e Crust ys ~Detrital

Olastics

FEEDING

TRACES

~

TRACES

DOMINANT

MOISTURE

~

Microbial M a t s

i/~

E-xcuvation Pellets ~ C a r b o n a t e Mud

Fig. 20. The zonation of trace categories (generalized presentation). Dwelling traces are in g r e a t e s t a b u n d a n c e at h i g h e r exposed flats, crawling traces at lower, w a t e r - s a t u r a t e d flats and feeding traces finally at submersed flats. A) B u r r o w and e x c a v a t i o n pellets of tiger b e e t l e larva. B) Burrow, e x c a v a t i o n p e l l e t s and "chimneys" of the salt b e e t l e Blediu8 angustus. C) Burrows and e x c a v a t i o n pellets of the salt beetle Bledius cap~a. D) C r a w l i n g traces of the g a s t r o p o d Pirenella conica. E) Feeding traces of w a t e r beetles on a mat surface.

i. 7. 4. E n v i r o n m e n t a l z o n a t i o n of trace cate~0ries

Dwelling around

b u r r o w s p r e d o m i n a t e on the elevated,

the saline b a s i n of the Gavish Sabkha.

observed

between

margins

t i g e r - b e e t l e larvae and the two salt beetle

B. angustu8 and B. capra, ling

air-exposed

A zonation gradient

due to increasing m o i s t u r e

species

(Fig. 20).

traces are c h a r a c t e r i s t i c of r e s t r i c t e d parts of the

is

Craw-

saline

mud

flats and feeding traces mainly p r e d o m i n a t e on the w a t e r - c o v e r e d microbial

mat surfaces

Blsdiu8

angustu8

w h i c h are,

however,

aquatic beetles.

Blediu8

cap~a

characteristic mats

(Fig. 20).

The g a r d e n i n g effect of the salt

also c o n t r i b u t e s to c h a r a c t e r i s t i c clearly d i s t i n c t i v e

feeding

beetle traces,

from the feeding traces of the

Periods of low-water levels encourage the salt beetle to m i g r a t e into d e e p e r - l y i n g areas and bottle-necked

to

burrows w i t h i n m u l t i l a m i n a t e d

form

their

microbial

(Fig. 20). These burrows clearly indicate periods of air exposure.

66

Fig. 21. Skeletal records of the Gavish Sabkha fauna. A) C o n c e n t r a t i o n of g a s t r o p o d shells w i t h i n sheetflood deposits. X-ray radiograph. Scale is 1 cm. B) G a s t r o p o d shell w i t h infillings of detrital clastics, embedded w i t h i n a m i c r o b i a l mat, indicating t r a n s p o r t by sheetfloods. Scale is 1 mm. C) D e t r i t a l clastics w i t h i n a g a s t r o p o d shell showing g e o p e t a l structures. After e m b e d d i n g w i t h i n a m i c r o b i a l mat, coating by m i c r o b e s took place. Scale is 1 mm. D) Outer and inner c o l o n i z a t i o n of a shell fragment by microbes. Note calcified filaments of c y a n o b a c t e r i a on the internal shell wall. Scale is 1 mm. E) N o d u l e - f o r m i n g P l e u r o c a p s a l e a n w i t h i n and outside a g a s t r o p o d shell. Scale is 2 mm. F) S o f t - b o d y remains of an ostracod, e n c l o s e d by its b i - v a l v e d carapax° Scale is 500 pm. G) The p o s t - m o r t e m c o l o n i z a t i o n of an empty o s t r a c o d carapax by microbes is indicated by the same filigrane network inside and outside the shell. Scale is 250 Nm. H) D i p t e r a n pupa ton in a m i c r o b i a l mat implying in-situ metamorphosis. Scale is 3 mm. (B to H: Thin sections from sediment cores.) i

W

I. 7. 5. Skeletal h a r d parts

Shells ostracod

of

g a s t r o p o d Pirenella eonica,

the

species

and

chitinous fragments of insects

almost all types of strata. most

are

above

two

common

in

zones

(Fig. 17).

The

wide

of their skeletal h a r d parts even w i t h i n places which lie

the salinity b o u n d a r i e s of the faunal p o p u l a t i o n s

lochthonous water

are

the

The animals live in the G a v i s h Sabkha, but

restricted to certain salinity

distribution

carapaxes of

transport

and sediments

which

indicate

is a c h i e v e d by the g r a v i t a t i v e

in the event of sheetfloods.

strationomic analyses are o u t l i n e d below.

The results of

The analyses

al-

flow

of bio-

focussed m a i n l y

on elaborating criteria of transport and in-situ embedding.

a) G a s t r o p o d shells: indicated by sits

showing

shells

(i) c o n c e n t r a t i o n s of shells in debris- and m u d - f l o w depocommonly a low degree

embedded

(Fig. 2 1 B ) ,

A l l o c h t h o n o u s t r a n s p o r t of g a s t r o p o d shells is

of

orientation

in m i c r o b i a l mats and filled w i t h

sometimes

also

showing g e o p e t a l

(Fig. 21A), detrital

structures

(2)

clastics

(Fig. 21C).

Shell fragments embedded in mats are c o m m o n l y c o l o n i z e d after transport by

microbes

from the mats

(Fig. 21C).

Fig.

shell fragment which are already calcified.

21D shows filaments

in

a

67

In-situ

embedding:

Sparse

numbers of juvenile snails

were

found

alive in the shallow water bodies where the nodule-forming Pleurocapsalean cyanobacteria mainly occur. interesting lean

colonies

oncoids reported 1983).

is

typical

(Fig. 21E).

(5 to 8 mm in diameter) from The

After death and in-situ embedding the

nodule formation in the coating of shells by Nuclei of

irregularly

shaped

consisting of gastropod shells are also

the lower Cretaceous of the adriatic

suggestion

Pleurocapsa-

of the author that the

region

(TISLJAR,

gastropods

represent

68

elements of a faunal community which lived under restricted corresponds well to a biotope b) Ostracods:

Fig.

21F

enclosed by its b i - v a l v e d

shows the soft body remains of an carapax.

The animal was p r o b a b l y

with the microbial mat environment the decaying organic matter. relation between bacterial which

acts

trast,

conditions

like the modern Gavish Sabkha. ostracod associated

and after death became embedded

Typical

for the embedding

decay and calcification

substrate

(see chapter

also with the soft body remains of the ostracod.

the ostracod carapax

soft

body.

Cyanobacteria

that

calcification

in Fig.

into

is the 1.6.4),

By

con-

21G does not contain parts of

the

which colonized the empty shell show

again

immediately takes place within the embedding

sedi-

ments. c) Insects: close

Embedded chitinous

fragments

to the microbial mat environments

ments of extremities

and pupae tons

of insects which live in or

include head

i. 7. 6. Grazin 9 stres s (experimental 19C

gives

conica

70 °/oo).

Possibly,

and grazing, the

The

treated

mat formation

coni~a

experiment

with

approach)

Laboratory

hypersaline

seawater

allowed to graze upon the mat section. from the joined appearance

Analyses

of filamentous

mat-forming microorganisms,

are

able

However,

(50

The typical

to survive passage

especially

enriched in unicellular

°/oo).

which Snails

structure,

was were

resulting

cyanobacteria

however,

that many of

cyanobacteria,

intestine

in mat-forming

and grazing proceeds,

colonies

shown

multilaminated

section

unicellular

through the snails'

could also p a r t i c i p a t e

as b i o t u r b a t i o n

of the gastropod

the

and unicellular

of fecal pellet contents have shown,

microorganisms

to

(Fig. 22).

the These

experiments have

was carried out with a mat

was destroyed as a result

snail (up

is hindered here due to b i o t u r b a t i o n

can completely destratify

slightly

the

zone of the Gavish Sabkha

mats can only develop and survive under

of higher salinity.

Pi~enella

mats.

in the metahaline

and m u l t i l a m i n a t e d

protection

that

for reproduction.

an impression of the high abundance of

Pi~enell~

frag-

(Fig. 21H). The pupae in p a r t i c u l a r

indicate that the insects chose the mat substrate

Fig.

capsules,

microbes

unharmed. processes.

in the vicinity

form only diffuse aggregates w h i c h are h i g h l y

types.

Consequently,

bioturbation

and grazing

69

result in a radical transformation, certain others

species,

often unicellular,

even of the c o m m u n i t y type, are favored

(mainly filamentous cyanobacteria)

to

survive,

since while

b e c o m e rarer.

Fig. 22 A). SEM m i c r o p h o t o g r a p h of the u n d i s t u r b e d surface of a m i c r o b i a l mat w h i c h was sampled to study the effect of grazing. Scale is 200 pm.

Fig. 22 B). Grazing activities conica of the snail Pirenella led to the surface d e s t r u c t i o n of the mat. Scale is 1 mm.

Fig. 22 C). As a result of continued grazing, the microbial mat section is d e s t r o y e d and its base consisting of siliciclastic sediments is visible. Scale: 200 pm.

Z0

Fig. 23. Small-scale changes in the s t r a t i f i c a t i o n of Gavish Sabkha sediments, drawn from thin sections from cores. All cores w e r e sampled at the lagoon's margins. M e c h a n i s m s r e s p o n s i b l e for the change are (I) o s c i l l a t i o n s in b i o t o p i c conditions during fair w e a t h e r periods such as p e r i o d i c exposure to w h i c h m i c r o b e s and fauna correspond (2) interruptions of the growing mat sequences by sheetfloods. For details see text.

i. 8. Modes of s t r a t i f i c a t i o n

A

well-defined

sequences

change in facies types c h a r a c t e r i z e s

of the sabkha deposits.

the

vertical

It reflects the influence of

lasting

f a i r - w e a t h e r conditions and short but c a t a s t r o p h i c

events.

A seasonal rhythmic

(varvite-stratification)

is,

long-

sheetflood however,

indicated

for the following reasons:

generally

slower a c c u m u l a t i o n prevail for most of the y e a r or

(i) F a i r - w e a t h e r conditions w i t h longer.

Sheet floods cause rapid s e d i m e n t a t i o n but only for a matter of sometimes (2)

not

after a number of several years of fair-weather

hours,

conditions.

A result of the t o p o g r a p h y is that the d e p r e s s i o n fills w i t h fresh

water

on the o c c a s i o n of stronger sheetfloods.

lishment

of fair-weather conditions,

Even

after

re-estab-

suspended loads of fine m a t e r i a l

settle until the water is e v a p o r a t e d and the conditions of seepage e v a p o r a t i v e pumping again become established, summer.

(3)

and

sometimes first in early

Climatic oscillations over several years result in

sheet

floods of varying energy levels.

The

dynamic

history

is reflected in the d i f f e r e n t

i r r e g u l a r a l t e r n a t i o n of strata types.

thickness

The trend of p o s t - e v e n t coloni-

zation of sheet flood sediments by m i c r o b i a l communities is visible, tation

for instance in core A (Fig. 23A). A further of

the

and

organic m a t e r i a l is visible in the

repeatedly

m o d e of fragmenupper

part.

Such

f r a g m e n t a t i o n is caused by shrinkage of the p r o l i f i c m i c r o b i a l mats and indicates subaerial exposure.

Burrowing of s u b a e r i a l l y exposed mats by

Blelius cap~a can also cause shrinkage cracks. of

The subaerial

exposure

the upper part of the core is also indicated by the burrows of salt

beetles w h i c h are unable to w i t h s t a n d longer periods of flooding.

Core

B

(Fig. 23)

was taken at the saline mud flat

central b a s i n of the lagoon.

from r e g u l a r l y laminated potential (present-day

bordering

The sequence shows the upward

the

transition

s t r o m a t o l i t e s with ooids and oncoids

facies type of the p e r m a n e n t l y w a t e r - c o v e r e d lagoon) to a

strata of the same type w h i c h is i n t e r s p e r s e d w i t h g y p s u m crystals,

and

71

t ~ , ~ _~

Pleurocapsaleau nodules and some

S e d i m e n t s from graln-flow

......

~ ......

o~

f i l a m e n t s in carbonate mud

_~.~:~..~ . ~~'~.~ .

Biolaminoid a r r a n g e m e n t of pleurocapsalean nodules

S e d i m e n t s from mud-flow

Salt beetle burrows. At right: Filled w i t h clastlcs

Gypsum coated

microorganisms

Synaereslscracks and some coarser clastlcs in mats

Faintly laminated sulfate

Skeletal hardparts: Top: Ostracod,

Stromatolitic carbonates with ooids and oncoids. Gypsum crystals at top

Bottom: Gastropod

G

o

oo

o,

io v,, o ~

Fo oo: oo:!

......

m °~1~;

°

°

•

r

•

•

o ,:;: L; i

° ° ° ° ° ° ° ° ° °

• -,

l'~. . . . . . . . o

oooo I

ooo

ooa

oo

o o a o o o o

o a o a

o

o o-1~,.~

o o

ao

oo

o a'-'D o Q D

N::i°~ o l P g t . , l,,e /q*o

E

t

I

i..,.l,rl.,Ol,l

. "o

I

~T

l I'M.[ E] lY: %',~ Y,I S B

shell

.NN

io~ a o o o~ o o. . . r. . . ~.

A

nodule by

C

s

o o.°

ol

72

finally to a thin bed of sheetflood deposits The

(mud with plant detritus).

nodular b i o l a m i n o i d facies of the p r e s e n t - d a y saline mud

flat

is

e s t a b l i s h e d on top of the sheetflood d e p o s i t i o n and, though also interrupted

by a thin clastic flood layer,

surface.

The

is r e - e s t a b l i s h e d again at

the

core shows that ecological conditions allowing the deve-

lopment of the regular s t r o m a t o l i t i c facies w i t h ooids and oncoids w e r e i n v a r i a b l y absent in the growing sequence.

The trend is from p e r m a n e n t

w a t e r cover to subaerial exposure.

Core

C was taken from the c e n t e r - o r i e n t e d saline mud flat which

characterized

at the surface by g y p s u m

precipitation.

The

is

following

h i s t o r y of d e p o s i t i o n can be read from the core:

Section developed

I:

A m u l t i l a m i n a t e d p o s t - e v e n t sequence of m i c r o b i a l

mats

on a thick sheetflood layer and was again b u r i e d by a sheet-

flood. Though this layer is thin it seems to have been c a t a s t r o p h i c for the

m i c r o b i a l community,

the Gavish Sabkha. on

top

p r o b a b l y due to m o v e m e n t of freshwater

During e v a p o r a t i o n a thick g y p s u m layer has

and allowed r e - c o l o n i z a t i o n by m i c r o b e s which

over formed

produced

faint

laminated structures w i t h i n the g y p s u m mush.

Section II: The same upward t r a n s i t i o n from sheetfloods to m i c r o b i a l c o l o n i z a t i o n to g y p s u m is repeated in this section.

Section III: Finally, minated

the evaporite sequence is followed by m u l t i l a -

m i c r o b i a l mats w h i c h d o c u m e n t a longer period free of

bance and with m o d e r a t e water availability. again

On the surface d i s t u r b a n c e s

occur which may be the result of climatic i r r e g u l a r i t i e s

ger e v a p o r a t i o n in summer,

distur-

(stron-

sheetfloods in winter).

i. 9. Summary and c o n c l u s i o n s

Grain sizes and m i n e r a l o g y of sediments, ding

crops,

redox

c o m m u n i t y structures,

p o t e n t i a l s and pH are h i g h l y

correlative

t e c t o n i c a l l y c h a r a c t e r i z e d terrane niveau of the Gavish Sabkha. sing

to

stanthe

Increa-

evenness in m o i s t u r e supply is realized by the inclination of the

system b e l o w mean sea level. effects c o n s e q u e n t l y follow

V a r i e d physical, (Table 6).

chemical and b i o l o g i c a l

73

Summary of interrelated facts which coincide with moisture supply in the Gavish Sabkha

TABLE 6.

increasing

INCREASING MOISTURE SUPPLY COINCIDES WITH CATEGORIES

STUDIED:

A. Seawater chemistry

increasing increasing decreasing

salinity Mg : Ca- ratios Ca : SO4-ratios

B. Microbial communities

increasing increasing increasing increasing

diversity productivity biological self-production of laminated deposits intensity in sulfate reduction

C. Physicochemistry

increasing

anoxic conditions in sediments

D. Lithology

increasing

biogenic carbonate contents (mg-calcite)

E. Stromatolitic structures

increasing

regularity in the lamination of stromatolites abundance of ooids and oncoids

increasing decreasing

F. Faunal influence

To

explain the increasing self-production of sediments by microbial

activity the

grazing and bioturbation intensities

(Table 6B) the convergence of (i) the specific

sediment-forming

undulating

character

of

response

to

microbes and (2) their migrational

environmental

factors has to be

considered.

An

organism

tends generelly to obtain the resource it needs. The individual cell or cell

chain

(sheaths, part

consists capsules,

of a large portion cysts and gels).

of the phenotype of the organism,

diately tion.

of

immobilisated

compounds

Since the immobilised matter is it has to be regenerated imme-

after the motile cell or cell chain has taken up a

new

posi-

This leads to a consequent increase of organic sediments as long

as appropriate environmental conditions are assured.

To

explain

deposits nently

the

(Table 6E), water-covered

increasing structural regularity

of

biolaminated

the evenness of seasonal shifts within the permaenvironments may be emphasized which

allow

organisms to correspond with changing gradients of environmental li,

such as light intensities,

oxidation potentials.

salinity,

moisture,

the

stimu-

pH and reduction-

74

Factors

changing

the light conditions

in the Gavish Sabkha

apart from day-night cycles - light channeling by water-cover, and particles suspended in the water. interface

and

oversedimentation

Salt crusts at the

(by eolian or

are

-

salinity

sediment/air

fluviatile

transport)

also change the light intensity. All these factors can fluctuate seasonally

or aperiodically.

populations

Qualitative change can stimulate subsurficial

to override other topmats.

Thus the variety

of

slightly

shifting environmental factors significantly determines the "depositional

dynamics" of stromatolitic growth-bedding

(sensu PETTIJOHN &

POT-

TER) in the Gavish Sabkha. The

lateral sequence of facies type 1 to 4 is actually the

expres-

sion of arid fair-weather conditions which last at least 9 to i0 months a year.

Interlayered bedding of terrigenous detrital clastics,

evapo-

rites and biogenic sediments provide clues about 1. Gavish

the

climatic

Sabkha:

setting

Long-lasting

of the depositional environment

of

the

stable arid periods without rainfall

are

suddenly interrupted by storm events, 2. sea, wards.

its geomorphic state:

depression,

no surface connection to the

gradually filled by mainland-generated

transport protruding

sea-

"Das s u b f o s s i l e jene n e g a t i v e

Riff am Strand

Bewegung

j~ngste V e r g a n g e n h e i t (JOHANNES

WALTHER,

2. THE SOLAR LAKE - I M P O R T A N C E

(GULF OF AQABA,

lehrt uns,

des Strandes hinein

in die

fortdauert."

1888)

OF SMALL T E C T O N I C

SINAI

bis

wie

EVENTS

PENINSULA)

2. i. I n t r o d u c t i o n

The 2a).

Solar

Lake

According

lies about

to a s t r a t i f i e d

strata

reach up to 65 °C. This

SZKY,

1901)

is c h a r a c t e r i z e d

cation p r e v a i l s August.

The mean

for the w a t e r

forms a basin Microbial

From

these

seepage

& COHEN,

time

Gavish

1974,

COHEN

reaching

The

et al.,

a deeper basin

and c o n s e q u e n t l y

to-depth

ratio c o m p a r e d

to the G a v i s h

of this

resulting

resulting

chapter

a sabkha-type

deposit.

in several

stratigraphic

records

stein is

(PZ3)

based

sequence

of this

1977a,

to the G a v i s h

Part),

ture about this

and

lake.

to

for n e a r l y FRIEDMAN, lagoon

below unusual pro-

2,000 years

1978).

Before to

the

subsidence

of

the

This

a w a t e r b o d y of lower

event

surface~

Sabkha.

Such

facies

a case study of stromatolitic change

(see for example

of core m a t e r i a l

can be i d e n t i f i e d Zech-

The chapter

from the Solar

(for m e t h o d s

of e x i s t i n g

changes

carbonates

in the Permian

III of this volume).

Sabkha m a t e r i a l

(2) on studies

Gulf

similar

from fault movement.

laminated

in Part

(I) on our own studies

sampled p a r a l l e l 1

mentioned

July and

of 5 m

cover the shelf

is to u n d e r t a k e

in r e g u l a r l y

overlying

between

from the a d j a c e n t

change was caused by a sudden

part of the lagoon

facies

Stratifi-

we can read that the s u n - e n e r g y

central

The p u r p o s e

in lower

(KALECSIN-

cycle:

a m a x i m u m depth

the area was a s h a l l o w b a c k - b a r r i e r

Sabkha.

(Fig.

loss by insolation.

produced

in

monomixis

inflow

mat sequences

sequences

energy"

annual

cycle of the Solar Lake has b e e n o p e r a t i n g

(KRUMBEIN that

and June,

Sabkha

temperature

of solar

by a w e l l - d e f i n e d

September

compensate

level.

thickness.

saline w a t e r body, "accumulator

takes place w h e n

Solar Lake sea

moted

between

Overturn

can no longer

200 km north of the G a v i s h

Lake,

see chapter

comprehensive

litera-

76

2. 2. L o c a l i t y and p r e v i o u s w o r k

Coastal

plains typical of the s o u t h e r n part of the Sinai

the Gulf of A q a b a are absent in the n o r t h e r n region. the

coast

Sinai rocky desert flanking the Gulf slope steeply towards

narrow

fringing reefs and frame some s e m i c i r c u l a r sandy b e a c h depressions. Solar Lake, in

w h i c h is about 140 m long and about 65 m wide,

one of these s e m i c i r c u l a r d e p r e s s i o n s

of

M o u n t a i n sides of

(Fig. 24).

The

is located

It is fed by sea-

w a t e r seeping through a c o m p l e t e l y closed gravel bar w h i c h is 60 m w i d e and 3 m above mean sea level.

The s e m i c i r c u l a r terrane, p r o t e c t e d from

wind

by

the m o u n t a i n ridges and from flood recharge and surf

bar,

recalls an a m p h i t h e a t r e on w h o s e

sun,

water

Moreover,

"stage"

by

(the sheltered

and organisms p e r f o r m their s e d i m e n t - a c c u m u l a t i n g the

ritual.

effects of flashfloods w h i c h play an important role

the u n p r o t e c t e d Gavish Sabkha are made milder,

the

center),

in

since the Solar Lake is

separated by its southern m o u n t a i n flank from a larger s h e e t f l o o d b a s i n w h e r e the most part of the s e d i m e n t - l a d e n narrow

freshwater is stored.

Only a

o v e r f l o w p a s s a g e b e t w e e n the coastal bar and the southern moun-

tain flank leads into the Solar Lake.

Fig. 24. The Solar Lake at the shore of the Gulf of Aqaba, Sinai Peninsula. The lake forms a 5-m-deep b a s i n w i t h i n a semicircular depression which is flanked by steep mountains sides. Partial e x p o s u r e of the s h a l l o w shelf of the lake indicating summer situation. Lower part: Coastline with fringing reef. (After GERDES et al., 1985.)

This

lake

may

be among the best i n v e s t i g a t e d in

l i m n o l o g y was studied by POR (1968, (1970) and COHEN et al. nic

carbonates

1978). biogenic

1969),

(1977a). F R I E D M A N et al.

w i t h i n the b i o l a m i n a t e d deposits

K R U M B E I N & COHEN

the

NEUMANN

world.

(1968),

Its

ECKSTEIN

(1973) surveyed bioge(see

(1974) and K R U M B E I N et al.

also

FRIEDMAN,

(1977) studied the

and abiogenic sediment a c c u m u l a t i o n and d e p o s i t i o n a l history.

77

COHEN

et al.

described primary dealt and

the

(1977b,

c),

K R U M B E I N & COHEN

m i c r o b i a l communities

production,

GERDES et al.

(1986).

by BOON GIANI

et

(1985) (1984), al.

studied the fauna. A I Z E N S H T A T et al.

COHEN

A H A R O N et al.

and g y p s u m p r e c i p i t a t i o n

data,

EHRLICH

(1978)

DIMENTMAN & SPIRA

(1982)

B i o g e o c h e m i c a l data were (1984) and C O H E N

(1984) studied the m e t h a n o g e n e s i s

b i o l a m i n a t e d deposits.

(1984)

physiological

mat formation and lithification.

w i t h the d i a t o m flora and POR (1975),

provided

(1977) and

in terms of

et

al.

within

the

(1977) c a l c u l a t e d isotope ratios

from e v a p o r a t i o n experiments.

2. 3. B a t h y m e t r i c zones and l i m n o l o g i c cycle

Three bottom.

bathymetric

surrounded

by

outcropping. of

zones can be

distinguished:

The shelf is a gently inclined, a

Shelf,

slope

and

20 to 25 m wide area w h i c h is with

beach-rock

The slope starts at about 1.50 m w a t e r depth.

sandy shore bare of v e g e t a t i o n and

It consists

an i n i t i a l l y gentle p a r t w h i c h merges in about 2.50 m

water

depth

into a steeper part running down toward the b o t t o m of the basin.

0m

~

0,51,0 1,5

-

2~53,0 3,5 4,0

Fig. 25. V e r t i c a l distribution of temperature, 02 and salinity w i t h i n the lake during w i n t e r s t r a t i f i c a tion (modified after Gerdes et al., 1982).

4,5~ 5~

From

September until May the lake's w a t e r b o d y is s t r a t i f i e d

(Fig.

25). Even snorkling at that time is h a r d since the m e t a l i m n i o n begins a few dm b e l o w the w a t e r surface. -2.50 m

below

w a t e r table,

In b e t w e e n a depth ranging from -i m to

t e m p e r a t u r e increases from 25

to

50 °C,

s a l i n i t y from 70 to 150 °/oo and oxygen d i m i n i s h e s to less than

1 ppm.

In the upper hypolimnion, t e m p e r a t u r e can reach 65 °C and salinity 180 O/oo. The h y p o l i m n i o n is c o m p l e t e l y anaerobic. R e l a t i v e to the

78

meta- and

hypolimnion,

the e p i l i m n i o n is cool at 20 to 25 °C.

It

is

rich in oxygen and the salt c o n c e n t r a t i o n lies b e t w e e n 70 and 80 °/oo.

Since

the

throughout seawater

w a t e r b o d y is four to five m deep and seepage

the

year,

does not lead to drying out in summer,

evaporation unstable.

and w a t e r loss,

but

salinity

In falling b e l o w the s t a b i l i t y point,

of

al.,

1977a).

the entire w a t e r b o d y lies of

with

rate

between

becomes

a sudden m i x i n g up of At this point, 160 - 180 °/oo,

27 °C prevail t h r o u g h o u t the w a t e r column

The period of h o l o m i x i s

of

increasing

the m e s o t h e r m y of the w a t e r b o d y

the p r e v i o u s l y stratified w a t e r bodies takes place.

temperatures

continues

even e v a p o r a t i o n exceeding the inflow

the and

(COHEN

et

lasts from 4 to 13 weeks, m a i n l y

b e t w e e n July and September.

2. 4. S u b - e n v i r o n m e n t s and facies types

2. 4. i. The shelf

a) Biotopic conditions On the r e l a t i v e l y flat shelf the effects of the lake's w a t e r level are considerable. a

change of 1.4 m over the year.

shelf

is exposed

(Fig. 24),

shelf is i0 to 15 cm.

seasonal fluctuations in

COHEN et al.

In late summer,

(1977a) m e a s u r e d of

the

and w a t e r depth in the lower part of

about 50 %

the

During this low-water period springs of seawater

are above the original water level.

With the r e p l e n i s h m e n t of w a t e r in

early fall, seawater springs and finally the whole shelf becomes watercovered and water depth on the lower shelf again reaches 1.50 m.

Light

intensity

oscillating ranges

and

w a t e r table.

salinity values change

b e t w e e n 50 and 80 °/oo,

summer m i x i n g period. anaerobic

with

W i t h i n the s t r a t i f i c a t i o n

the period,

seasonally salinity

w h i l e it is about 180 °/oo w i t h i n

the

Since the shelf is not supplied w i t h the hot and

b r i n e of the deeper basin,

w a t e r temperatures do not

reach

h i g h e r values than 30 °C.

b) Main m a t - b u i l d i n g organisms

The shelf mats are made up p r e d o m i n a n t l y of cyanobacteria. tous species

(oscillato~ia limnetica/Phormidium hendersoni,

Filamen-

O. 8alina,

79

Lyngbya sp.,

Mie~ocoleus chthonoplastes) and unicellular forms (mainly and Synechococcus) are abundant. Unicellu-

of the genera Synechocysti8 lar

cyanobacteria

far

less abundant,

gates

of the Pleurocapsalean

characteristic

(EHRLICH,

of the Gavish Sabkha.

the genera Nitzschia,

1978),

type

Diatoms

diatoms,

however,

With summer,

are well

reCorded

in living surface mats. The

g e n e r a l l y are not preserved

in older sections of the

increasing

light together with less or no water

unicellular

cyanobacteria

reduced

c) Mat construction

in

These organisms

and

form protective colour.

at h i g h e r w a t e r

levels and thus slightly

filamentous

(Microcoleu8 8alina) override the coc-

Osoillatoria limnetica,

c o i d / d i a t o m community.

covering

Synechocystis)

which give the surface a b r o w n - y e l l o w

light conditions,

ohthonoplastes,

(Synechococcus,

in the top layers.

(carotinoides)

In fall, winter and spring, more

are

mats.

diatoms predominate pigments

fission)

Amphora and Navicula predomina-

ting both in species and specimen abundance

microbial

(multiple

hence there is no formation of nodular cell aggre-

O.

cyanobacteria

The surface appears b l u e - g r e e n at this time. and microfacies

As in the Gavish Sabkha,

the b i o l a m i n a t e d

sediments of the shelf of

the Solar Lake consist of sets of dark L h- and light Lv-laminae , the L v usually

4 to 8 times thicker than L h (Fig. 26A).

are characterized

by a high content of extracellular

ty of irregularities bubbles). of

tion of eye-shaped

of Lh-laminae

lenses

microscopy

is common,

(Fig. 26B, D).

the light Lv-laminae.

giving rise to the forma-

voids,

probably derived

electron

from gas

(Fig. 26E).

bub-

Carbonate

takes place mainly in the light layers and the eye-shaped

together

within the

eye-shaped

lenses

particular where oolites and oncolites

devoid of a biostromate

They lie very

(Fig. 26C, D),

w i t h i n the widely spaced Lv-lamina e are more dispersed In

material

Thin section studies and scanning

show that miniscule

and

cyanobae-

The lenses enclose

lenses where ooids and oncoids occur in great abundance. close

voids

of filamentous

are initially colonized by m i c r o o r g a n i s m s

precipitation

slime and a varie-

intraclasts,

form usually condensed horizons built up

oriented ensheathed bundles

teria. The p a r t i t i o n

bles,

(decaying cell clusters,

The dark Lh-laminae

horizontally

from

The light Lv-laminae

others

(Fig. 26F).

in the fossil record

lamination which could imply in-situ

are

formation

80

of

the

indicate similar

grains, the

their close a r r a n g e m e n t w i t h i n e y e - s h a p e d lenses

formational site w h i c h had

to the Solar Lake m i c r o b i a l mats

ooids and oncoids; Fig. 43A, B and C).

formerly

a

may

microtopography

(see for example the

Minette

81

Fig. 26. Microfacies characteristics of the shelf deposits. A) Lamination including dark L h- and light Lv-laminae. Scale is 1 mm. B) Ensheathed filament bundles of the Lh-lamina forming an eye-shaped lense. The lense contains decaying organic matter and p o l y s a c c h a r i d e slimes and initial nucleation of coated grains (see also C and D). Scale is 25 pm. C) "Coated grains": Bedding plane concordant view showing the coating of ooids and oncoids by filamentous microorganisms. Scale is 50 pm. D) Vertical section showing layer with ooids and oncoids. Note arrangement of the grains within the eye-shaped lense. Similar arrangements of coated grains in rocks (compare Fig. 43C) may imply their formation in a similar microbial mat environment. Scale is 250 pm. E) A h o l l o w sphere (bubble?) within a Lv-lamina, coated by diatoms and coccoid unicells. The wall of the sphere is stabilized by polysaccharide slime (internal view). Scale: 25 pm. F) Dispersed arrangement of miniscule spheres within the decaying organic matter and mucus of a Lv-lamina. Scale: i0 pm.

d) S t r a t i f i c a t i o n

Particularly a

vertical

contains nae,

ooids

distance ranging and oncoids

cycle controls

and light laminae

succession

followed

or

tions

from 1.0 to 1.20 m.

carbonate

already described

within

increasing

Synaeresis

numbers

cracks,

the crenulated laminated

and interrupt

the varvite-like

time

time to unconformities

sequence

Sabkha.

The

alternating

the regularly

dark

laminated

sections,

grain-sized

sections

are

sequences.

of small bags,

extraclasts

summary,

form over

whole

for the Gavish

formation of

underlaid by thin strata of mud- or

which also penetrate to

The

is interrupted by more crenulated

Lv-laminae

show

deposits

facies type with L h- and Lv-lami-

a varvite-like

than within the regularly

lenses.

the b i o l a m i n a t e d

(Fig. 27). From time to time,

vertical

sediments.

extension of the shelf mats

on the lower shelf,

the stromatolitic

seasonal

thicker

and vertical

often clastic

commonly

Vertical

pockets

and

sec-

eye-shaped

and gypsum crystals

are common

the thin and fragile Lh-laminae.

formation of the shelf deposits and turns back again

to

changes the

In from

regular

microstratification.

These occurring

patterns

nal change. summers,

indicate

climate deviations

from the norm,

probably

secularly and taking place after a sequence of regular seasoThe climate deviations

are accompanied by h o t t e r and drier

consequently by higher evaporation

and light conditions, sheetfloods.

and higher rainfall

rates, in

increasing

winter,

which

salinity causes

82

Fig. 27. Deposits of the Solar Lake shelf. X-ray radiographs of sections of an o r i g i n a l l y 80 cm long core. F r o m top (section I) to b o t t o m (section IV) the sequence shows the s t r o m a t o l i t i c c a r b o n a t e facies w i t h typical l i g h t - d a r k interlaminations, ooids and oncoids. Individual constituents p r o v i d i n g clues on the e n v i r o n m e n t are listed on the next page. X - r a y radiographs by H.-E. REINECK. Scale is 2 cm for all core sections.

83

IV

g

Legend to Fig. 27 continued: Core section I: a) Intraclasts of varying size and shape, resulting from the liberation of mat fragments from the lake's deeper slope, drifting in the w a t e r and d e p o s i t i n g at the w a t e r rim on top of the s h a l l o w shelf mats. b) S h e e t f l o o d - d e r i v e d mud layers 5 to i0 m m thick. c) Burrows of the salt beetle Bledius capra in 13 to 16 cm depth indicate a former period of subaerial exposure. Section II: d) Deviations from the n o r m a l l y s t r a t i f o r m to a more c r e n u l a t e d p a t t e r n of the dark L laminae, a c c o m p a n i e d by the a g g r e g a t i o n ~f ooids and oncoids w i t h i n the "valleys". The c r e n u l a t i o n comes from m i c r o p i n n a c l e s which form at mat surfaces as a r e a c t i o n of the m a t - c o m m u n i t y to increasing light and salinity (see also Fig. 41F). Section III: e) R e g u l a r l y a l t e r n a t i n g dark and light laminae w h e r e ooids and oncoids show a chainlike a r r a n g e m e n t due to the low e x t e n s i o n of the light-colored Lv-laminae. These sequences indicate growth under a slightly higher w a t e r table and a lower impact of the seasonal change in light intensity. f) W i d e l y spaced l i g h t - c o l o r e d L v - l a m i n a e with clustered and d i s p e r s e d arrangements of ooids and oncoids. These as well as the m i c r o p i n n a c l e s indicate climate deviations from the average, a c c o m p a n i e d by increasing salinity and light conditions. Section IV: g) (sediment depth averages 75 cm at this point). C o m p o u n d ooids and oncoids m e r g i n g into c h a i n - l i k e arrangements, due to increasing c o m p a c t i o n and d e h y d r a t i o n of the l i g h t - c o l o u r e d h y d r o p l a s t i c Lv-laminae.

Light and s a l i n i t y o s c i l l a t i o n s obviously

in seasonal and also secular rhythms

are i m p o r t a n t control mechanisms.

Much more

a c c u m u l a t e under h i g h e r s a l i n i t y and irradiation, ved in the G a v i s h Sabkha and h e r e repeated. directly

polysaccharids

a fact already obser-

A n o t h e r aspect that can be

e n t a n g l e d w i t h the climatic u n c o n f o r m i t i e s

is the

morphology

84

of

the

mat surface itself.

The mats of the lower

r e s t r a t i f y themselves to m i c r o p i n n a c l e nity

and light.

Solar

Lake

formation under increasing sali-

The p i n n a c l e s are conical buildups w h i c h reach

two to three m i l l i m e t e r s upwards from the s t r a t i f o r m mat base.

M~c~o~oZ~us-dominated the pinnacles.

pinnacles.

Ooids

(Fig. 26, see also Fig.

about

Even the

in this case follow the f o r m a t i o n

In v e r t i c a l sections,

c r e n u l a t e d structure, the

Lh-lamina

shelf

of

the p i n n a c l e formation favors the

the formation of bags,

pockets and eyes b e t w e e n

and oncoids here represent

veritable

clusters

27, m a r k e d section d of core section II).

2. 4. 2. The slope and b o t t o m

a) Biotopic conditions

Effects

of

w a t e r level change are no longer

important

where

w a t e r deepens at the slope. Parts of the slope are, however, epilimnion temperature H2S.

Only

and

thus

are g r e a t l y a f f e c t e d by the steady

and salinity,

the

b e y o n d the

increase

of

the d e c r e a s e of oxygen and the increase

of

after the turnover in late summer are

these

environmental

factors m o d e r a t e d for a short period.

Fig. 28. Thin section of the crust at the Solar Lake's b o t t o m showing layered accretion of elongated g y p s u m crystals i n t e r l a m i n a t e d w i t h faint microbial mats (dark laminae). Scale is 2 cm.

85

b) M a t - b u i l d i n g o r g a n i s m s and mat c o n s t r u c t i o n

shelf.

The

mats tend to form soft flocculous fabrics w h i c h p a r t i a l l y drift in

The

initial

slope c o m m u n i t y is similar to that of the

the

w a t e r and are subject to rapid decay. W i t h increasing depth towards the bottom,

sulfur-dependent,

cyanobacteria

which

other a n o x y - p h o t o b a c t e r i a and a n a e r o b i c bac-

08cillatoria

teria increase in number.

remains common,

limnetica is the only species of even at the b o t t o m w h e r e

ratures are h i g h and c o m p l e t e l y anoxic c o n d i t i o n s mats

undergoing

bottom these

of

prevail.

rapid a n a e r o b i c d e c a y cover the lower slope

the lake

(KRUMBEIN et al.,

1977).

and

the

The internal fabric

sediments shows large g y p s u m crystals and

strata of m i c r o b i a l mats

tempe-

Flocculous

faint

of

interlaminated

(Fig. 28).

2. 5. L i t h o l o g i c and i c h n o l o g i c framework

2. 5. i. Clastic compounds

That bances

the p r e s e n t - d a y Solar Lake is nearly devoid of strong b y the wind,

from its d e p o s i t i o n a l record sediments Sabkha. between

enter Mud

(Fig.

i n t e r c a l a t e d in b i o g e n i c deposits

0.5 and 2 mm thick.

read

27). G r a i n f l o w - and m u d f l o w - d e r i v e d

the lake at less i m p o r t a n t rates than in

layers

distur-

the sea and r a i n - d e r i v e d flashfloods can be

the

Gavish

usually

range

Cores from a S - N t r a n s e c t c r o s s i n g

shelf

show that mud layers d i m i n i s h in t h i c k n e s s w i t h increasing

tance

from

the o v e r f l o w passage w h i c h is b e t w e e n the coastal bar

the s o u t h e r n m o u n t a i n flank

(KRUMBEIN & COHEN,

the disand

1974).

2. 5. 2. Evaporites

The layers, tation (1977):

almost

e n t i r e l y b i o g e n i c shelf sediments are

due to b a c t e r i a l sulfate reduction. is

reported

by K R U M B E I N & COHEN

of

gypsum

(1974) and

KRUMBEIN

et

al.

(i) A g y p s u m crust forms b e l o w a surface mat on the slope at a

d e p t h of about 2.5 m.

At this level,

seawater under a r t e s i a n p r e s s u r e

enters the lake and supplies a d d i t i o n a l oxygen. slope

free

Subaqueous gypsum p r e c i p i -

are

(2) Deeper parts of the

covered by a hard crust of g y p s u m and

carbonate,

precipi-

86

tating

from the s u p e r s a t u r a t e d brines

as

to 50 °C and minimal sulfate r e d u c t i o n at

40

concentrations

(Fig. 28).

T e m p e r a t u r e s as h i g h low

organic

matter

favor h i g h g y p s u m a c c u m u l a t i o n rates.

2. 5. 3. !chnologic p a t t e r n s

A

c o m p a r a t i v e study of the fauna of the Solar Lake and

Sabkha that

was carried out by GERDES et al. species composition,

(1985d).

the

Gavish

The study has shown

t o p o g r a p h i c m o i s t u r e - and

salinity-related

zonation in b o t h environments are similar, p a r t i c u l a r l y the p r e d o m i n a n ce of c o l e o p t e r a are

(POR,

1975).

Ichnological p a t t e r n s in the Solar Lake

m a i n l y due to the staphilinid b e e t l e Blediu8 c ~ p ~

w e t l a n d fauna). beetles

live

pockets

of

W h e n the lake's shelf is w a t e r - c o v e r e d on

(member of

the

(winter),

the

the shoreline and b u r r o w in sand-filled

the beachrock.

W h e n the w a t e r l i n e of the lake

retreat in spring or early summer,

cracks

bottle-neck

appearing

shaped

in b u r i e d strata

to

the beetles migrate along the humi-

d i t y g r a d i e n t into the g r a d u a l l y a i r - e x p o s e d shelf area and form dant

and

starts

burrows w i t h i n the

mats

(Fig. 29).

(Fig. 27) indicate that the

deposits

abunTraces have

b e e n subject to exposure.

Fig. 29. Horizontal section of a i r - e x p o s e d shelf mats of the Solar Lake showing a b u n d a n t burrows of the salt beetle Bled~u8 cap~a. Summer situation, w h e r e retreating w a t e r line attracts the beetles to migrate from the sandy shore into the m i c r o b i a l m a t - c o v e r e d shelf area. Scale is 2 cm.

87

Hydrophilid line

beetles b e l o n g i n g to b o t h stenohaline and

aquatic fauna occur in numbers in the Solar Lake and graze on the

mat

surfaces,

Gavish

leaving

Sabkha

cods,

(see Fig.

copepods,

important

feeding 19D).

nematodes,

as in the G a v i s h Sabkha; is

hypereuryha-

traces as a l r e a d y indicated

for

Meio- and m i c r o f a u n a l elements

t u r b e l l a r i a n s and protozoans)

however,

the

(ostra-

are abundant,

the g a s t r o p o d Pirenella

conica w h i c h

in the Gavish Sabkha in terms of grazing and

hard

part

supply is c o m p l e t e l y absent in the Solar Lake.

2. 6. S u m m a r y and c o n c l u s i o n s

2. 6. i. O c c u r r e n c e of facies types c o m p a r e d to the Gavish Sabkha

Grain-flow supported siliciclastic biolaminites nodular the

to b i o l a m i n o i d carbonates

G a v i s h Sabkha,

whereas

(facies type I)

(facies type 2),

both o c c u r r i n g

are absent in the p r e s e n t - d a y Solar Lake

s t r o m a t o l i t i c carbonates w i t h ooids and oncoids

are well developed.

and in

deposits

(facies type 3)

B i o l a m i n a t e d gypsum, w h i c h c h a r a c t e r i z e s the amphi-

bious

rims of the G a v i s h Sabkha lagoon

Solar

Lake

subaquatically

(facies type 4),

at the b o t t o m of the b a s i n

forms in and

the

comprises

another c o m m u n i t y type comparable to the amphibious areas of the Gavish Sabkha.

An

informal o v e r v i e w of the d i f f e r e n c e s m e n t i o n e d here is given

Table 7.

(1)

Reasons

The

Solar Lake a p p a r e n t l y does

not

provide

geomorphological

conditions

suitable to d e v e l o p facies type i.

heaved

o n - s h o r e d i r e c t e d wave energy and does not merge

by

hinterland Sabkha. the

The coastal bar is

is the case with the c i r c u l a r d e p r e s s i o n of the

of the bar and d o w n - s l o p e to form sandlobes and

Thus the h o r i z o n t a l l y

up-

with

the

Gavish

Thus s h e e t f l o o d - d e r i v e d grain flows are not able to run

plateau

mats.

as

in

for these d i f f e r e n c e s are d i s c u s s e d below:

along

to

bury

flat lh-mats s a n d w i c h e d b e t w e e n g r a i n - s i z e d

s i l i c l a s t i c sediments do not occur w i t h i n the Solar Lake area.

(2)

S u b - e n v i r o n m e n t s w h i c h favor the nodular to laminoid

facies

are

also

Gavish

Sabkha,

a p p a r e n t l y not evident in the Solar

these

are the g e n t l y

inclined,

schizohaline mudflats a d j a c e n t to the lagoon.

Lake.

carbonate In

the

water-saturated

and

The same facies type

is

88

TABLE 7. Existence Solar Lake

of

facies types

of the

Gavish

Sabkha

TYPE

i:

Lh-type blo-~-lam---inites sandwiched between siliciclastic sand-sized sediments FACIES

TYPE

TYPE

non-existent

indicating hypersaline shallow water conditions (lagoon)

indicating hypersaline shallow water conditions (shelf)

indicating hypersaline subaerial/ amphibious conditions (rims of lagoon)

indicating hypersaline/ hyperthermal subaquatic conditions (bottom of the lake)

T Y P E 4:

Biolaminated gypsum

found

indicating schizohaline conditions of water-saturated sediments (bar-oriented mudflats)

3:

Stromatolitic carbonates with ooids and oncoids

FACIES

non-existent

indicating grain-flow deposits sheetflood derived (coastal bar slope)

2:

Nodular to biolaminoid carbonates

FACIES

the

SOLAR LAKE

GAVISH SABKHA

FACIES

in

in

mudflats surrounding the Ras Muhamed pool which lies on

southernmost tip of the Sinai Peninsula

(SNEH & FRIEDMAN,

the

1985).

This

environment is very similar to the Gavish Sabkha. (3)

Though vertically more extensive,

the shelf mats of the

Solar

Lake complete the picture already painted of the Gavish Sabkha shallowwater mats. This facies type is also repeated in the permanently watercovered 1985).

shallow depression of the Ras Muhamed pool This environment,

elevation

(SNEH

as well as the Solar Lake,

&

FRIEDMAN,

lacks the central

produced by active evaporative pumping characteristic of the

Gavish Sabkha.

The development of regularly interlaminated carbonates,

ooids and oncoids in areas under the following environmental conditions is

common to all three

environments:

hypersalinity,

shallowness

of

89

water,

lowest

depth,

level energy,

and evenly o s c i l l a t i n g p a t t e r n s of w a t e r

s a l i n i t y and light t h r o u g h o u t the year.

The

d e v e l o p m e n t of s t r o m a t o l i t i c

without

any

layering in all these e n v i r o n m e n t s

o v e r s e d i m e n t a t i o n has led us to avoid the

stromatolites

as being p r o d u c t s of

sediment-fixing,

definition

sediment-binding

and/or s e d i m e n t - p r e c i p i t a t i n g activities of m i c r o o r g a n i s m s al.,

1976;

chemical

BUICK et al.,

1981),

of

(AWRAMIK

et

w h i c h w o u l d imply that p h y s i c a l and

s e d i m e n t a t i o n p r o c e s s e s are n e c c e s s a r i l y needed for stromato-

litic buildups.

2. 6. 2. Time intervals r e c o r d e d in s t r o m a t o l i t e s

Deducing

annual,

characteristic tates

seasonal

or even diurnal

millimetre-scale

periodicity

from

l a m i n a t i o n of s t r o m a t o l i t e s

the

neccessi-

some p r e c a u t i o n s even more if laminae w h i c h at first glance look

massive

are i n t e r n a l l y finely laminated

(PARK,

1976).

The

biogenic

sediments of the Solar Lake may serve as an example.

Core

material

years B.P.

at 1.20 m sediment d e p t h y i e l d e d a 14C age

(KRUMBEIN et al.,

of

2400

1977). The overall g r o w t h c a l c u l a t e d from

this

data is 0.5 m m per year including a p a i r of light and dark

nae.

These

lami-

d e v e l o p w i t h o u t the aid of s e d i m e n t a t i o n as the result

of

two d i f f e r e n t kinds of m i c r o o r g a n i s m s o v e r r i d i n g themselves in order to find

the

They

may thus r e p r e s e n t seasonal rhythmites.

biogenic

m o s t a p p r o p r i t a t e site under seasonal

lamination

changing

However,

conditions.

even the

of the Solar Lake shows some sort of

ties. The m a i n factor r e s p o n s i b l e is the climate oscillation. years

pure

irregulariSeries of

w i t h v e r y r e g u l a r l y u n d u l a t i n g e n v i r o n m e n t a l conditions are

ruptly

or

g r a d u a l l y followed by those

with

weather

ab-

unconformities,

i n c l u d i n g b r e a k s in b i o g e n i c sediment a c c r e t i o n on the one hand, h i g h e r precipitation other

hand.

rates of e v a p o r i t e s and s h e e t f l o o d s e d i m e n t a t i o n on There

remains thus a degree of u n c e r t a i n t y in using

o b v i o u s l y rhythmic lamination as a time scale. Furthermore,

a reduction

of the wet organic m a t t e r by p r o c e s s e s of b a c t e r i a l degradation, formation

to

carbonate minerals,

c o m p a c t i o n and d e h y d r a t i o n

order of about 70 % may be r e a l i s t i c to a s s u m e al., for

the the

transin

the

(PARK, 1976; K R U M B E I N et

1977). The annual a c c r e t i o n rate w o u l d then c o m p r i s e only 0.15 m m one couplet of seasonal rhythmites.

This w o u l d result in a m i c r o -

i n t e r l a y e r e d b e d d i n g r e p r e s e n t i n g 6 to 7 years w i t h i n one single m i l l i metre.

According

to these values,

regularly

biolaminated

sequences

90

developing

during a period of very r e g u l a r l y u n d u l a t i n g

conditions

may

interlayering

at

first glance look like one single

environmental layer

and

its

w i t h u n c o n f o r m i t y layers w o u l d imply p e r i o d i c i t y on

the

millimetre-scale.

2. 6. 3. Importance of small t e c t o n i c events

The chief concern of this chapter has b e e n to d e m o n s t r a t e the record of

change from a s h a l l o w - w a t e r e n v i r o n m e n t into a s u b s e q u e n t l y

basin.

deeper

In c h r o n o l o g i c a l order there have been four stages in the deve-

lopment

of the Solar Lake

(i) a stage open to the sea,

comparable

to

fjord-like embayments w h i c h occur adjacent to the Solar Lake bight,

(2)

a semi-closed stage due to the g r a d u a l l y forming coastal bar,

the

completely basin.

closed

Coring

evidence

stage and finally

and

that

(4) the

(3)

subsidence-derived

r a d i o c a r b o n dating of organic

sediments

the change from the open to the semi-closed stage

pened in the time b e t w e e n 4644 +/- 555 and 3378 +/- 172 B.P. al.,

1977a, K R U M B E I N et al.,

closing Below

may

deep

provided

have

1977; FRIEDMAN,

hap-

(COHEN et

1978). The p r o c e s s of bar-

b r o u g h t about conditions as in the

Gavish

Sabkha.

the 1.20-m-thick b i o l a m i n a t e d deposits on the Solar Lake

shelf,

carbonate mud occurs in w h i c h shells of the g a s t r o p o d Pi~enella

conica

are a b u n d a n t day

Solar

Lake

environments the

(FRIEDMAN,

1978).

This species is absent in the p r e s e n t -

area whereas it is common

along the Gulf coast,

in

various

shallow-water

including the m e t a h a l i n e parts

Gavish Sabkha and also of the Ras M u h a m m a d Pool

(SNEH &

of

FRIEDMAN,

1985). During the semi-closed stage,

the center of the lagoon w h i c h is now

just b e l o w the b o t t o m of the Solar Lake was floored by m i c r o b i a l

mats.

It was surrounded by mud flats w h e r e s l i g h t l y h y p e r s a l i n e conditions or even

normal seawater salinity allowed c o l o n i z a t i o n by

gastropod that

zone was s e p a r a t e d from the m i c r o b i a l mat

zone,

former

on the m i c r o b i a l mats.

This as well as the shallowness

s y s t e m is similar to the p r e s e n t situation of

The

indicating

a salinity b a r r i e r was e s t a b l i s h e d w h i c h h i n d e r e d the grazing

gastropods the

P. conics;

the

of of

Gavish

Sabkha and to the Ras M u h a m m a d Pool. At conlca

about

2490 +/- 155 B.P.

g r a d u a l l y disappeared,

the lagoon closed off and s h a l l o w - w a t e r

established t h r o u g h o u t the lagoon.

completely.

cyanobacterial

These conditions,

P. mats

lasting about 555

9t

SEA PRESENT- DAY WATER TABLE

X•WINTER

SHELF

MARGIN

SUMMER

\

\ \ \

\

/

'\

/

\ 0

.~. 0 ~

:

'\

ii

r-T--~ Carbonate !::i!i: cement ed " ' 'sand ~ Stromatolithic car bonates

~

#

/.

Frcgmentec ::i:i mats

/

\

#",BASIN/./

SUBSIDENCE

o

Sand and Gastropod shells

-A-~Subaqueous gypsum

PRESENT- DAY BASIN SHALLOW BASIN BEFORE SUBSIDENCE

....

Fig. 30. Schematic p r e s e n t a t i o n of facies changes caused by a fault movement which formed the deep Solar Lake b a s i n and its limnologic cycle. Shelf: R e g u l a r l y laminated m i c r o b i a l mats with ooids and oncoids overlying carbonate mud and sand with g a s t r o p o d shells (P. conica). Bottom: Subaqueous, faintly biolaminated gypsum overlying regularly laminated s t r o m a t o l i t i c c a r b o n a t e s which formed b e f o r e the subsidence. Drawings of core successions not to scale, m o d i f i e d after K R U M B E I N et al. (1977).

years, dence

came to the end due to a fault m o v e m e n t of the central

the l i m n o l o g i c a l present while

and

character

changed.

favor the shelf mats

at the b o t t o m

are a l l o w e d

part of the lagoon.

of the

lake

With

These growing

which

conditions to

caused

a deep basin

prevail

extraordinary

only a few s p e c i a l i z e d

to thrive and to i n t e r f e r e

the subsiestablished up to the thickness

microorganisms

with gypsum precipitation.

Thus

92

the change from a peritidal sabkha-type environment into a subsequently deeper

mesothermic,

sequence into

monomictic

lake is recorded within

where carbonate mud containing

regularly

"cerithid"

(i) the

shelf

gastropods

merges

laminated stromatolitic carbonates and (2) the

bottom

sequence where regularly laminated stromatolitic carbonates merge faintly biolaminated gypsum (Fig. 30).

into

That the island

is no firm land,

peak of a m i l e - l o n g the

sand

the

forces

more

3. V E R S I C O L O R E D

(MELLUM

of nature

and more

rience

(M. LUSERKE,

SOUTHERN

that thus

spectacularly

- all

this

to be a basis

SILICICLASTIC

ISLAND,

sand-drift;

here belongs

but the

to

became

of our expe-

1957).

TIDAL FLATS

NORTH

SEA)

3. i. I n t r o d u c t i o n

The the

examples

of the G a v i s h

Sabkha and the Solar Lake

aid of g e n t l y o s c i l l a t i n g

salinity,

temperature)

laminated

sediments

fication

within

internal

stability.

accidental of

borne

purely the

mat

sequences

sedimentation

described

R.

RICHTER

high

environments

studies.

(1926)

sand-drift

tide

flats

environment Early

of M e l l u m latitude

(2) their

here

is to d e s c r i b e

more of

"German

the

to

windSahara"

Island.

Island

represent

(53 ° 43' N)

lithologic

facies

data o b t a i n e d

more

the rise

than

character

(3) they are in open contact w i t h the sea.

and s e d i m e n t o l o g i c a l

the

is

owes m u c h

the i m p o r t a n c e

used the term

calci-

increase

By contrast,

chapter

at M e l l u m

of h i g h e r

Sabkha and the Solar Lake;

paper p r e s e n t e d

in this

potential,

on the other h a n d

To show p i c t o r i a l l y

the c o m m o n

siliclastic;

water

slowly g r o w i n g b i o g e n i c

deposits

"versicolored"

by e c o l o g i c a l tory

quiet

develop.

Physical

sedimentation,

Gavish

an o t h e r w i s e

show that w i t h

(water

origin

sedimentation.

microbial

stimuli

than an aid to g r o w t h of b i o l a m i n i t e s .

w h e n he d e s c r i b e d

The

within

of p u r e l y b i o g e n i c

the

biolaminated

physical

environmental

(i) the is

A i m of

and to i n t e r p r e t

it

from field and labora-

94

3. 2. Methods

Field w o r k was carried out in 1983 and 1984. from

seven

sites w h i c h were chosen to include

elevation above the m e a n h i g h w a t e r rison,

data

Samples were c o l l e c t e d different

(MHW) level.

o b t a i n e d earlier are included

degrees

of

For intertidal compa-

(GERDES & HOLTKAMP,

1980).

E l e v a t i o n of sampling sites was m e a s u r e d w i t h a theodolite.

Methods section

of sampling

preparation

parameters

(Eh,

pH,

(sediments,

temperature)

d e s c r i b e d for the Gavish Sabkha. pared

(REINECK,

sediments cores

m i c r o b i a l mats

and

and m e a s u r e m e n t s of salinity and

fauna),

were identical w i t h methods Additionally,

thin

physicochemical already

relief casts were pre-

1970), and p i g m e n t c o n c e n t r a t i o n s in the upper i0 mm of

were

d e t e r m i n e d using a corer I0 mm in

diameter.

Sediment

for nutrient c o n c e n t r a t i o n m e a s u r e m e n t s were taken w i t h a

corer

2.5 cm in diameter and 12 cm long. Pigments were extracted and m e a s u r e d using the m e t h a n e - h e x a n e e x t r a c t i o n method

(STAL et al.,

1984a). Stan-

dard m e t h o d s w e r e used for extractions of NH4+ and S 2- (PANG & 1976;

H O P N E R et al.,

eveness

(after PILOU)

1979;

DEV,

1984). D i v e r s i t y

NRIAGU,

(after SHANNON)

and

of faunal communities were determined.

3. 3. L o c a l i t y and p r e v i o u s w o r k

3. 3. i. Recen t s e d i m e n t o l o g i c a l h i s t o r y

Climatic

fluctuations in the Q u a r t e r n a r y led r e p e a t e d l y to

tions

(Elsterian,

wide

parts of the North Sea b a s i n on the one h a n d and sea level

within

of the southern coastal area

Holocene and

a c c o m p a n i e d by exposures of

interglacial periods on the other hand.

guration

1978).

Saalian and Weichselian)

glacia-

rise,

The p r e s e n t - d a y confi-

(Fig. 31A) is the result of

w h i c h is by no means c o m p l e t e d today

steps of the b a r r i e r - i s l a n d action

microbial sand

(STREIF & KOSTER,

formation,

and tide currents.

initial

b u i l t up by c o m b i n e d forces

It is h i g h l y p r o b a b l e that

of

initially

films and later mats interfered with stationary approaches of

bodies at MHW-levels.

immobilization bodies

the

L o n g s h o r e bars p a r t l y above and p a r t l y b e l o w the low w a t e r line

the formation of b a r r i e r s at MHW-levels may have been the

wave

rises

immediately

That m i c r o b i a l c o l o n i z a t i o n takes

p l a c e w i t h the

and

emergence

above MHW has been observed at stationary sand banks

sediment of

sand

presently

95

forming

in open tidal

& GERDES,

1984)

along

the

the

some

islands

ronments.

According

range

environments

is somewhat

It

of the

"German Bight",

forms

as

flats

on either

related

levels:

where

of this paper,

Intertidal:

bank

the terms

b e t w e e n mean

low w a t e r

tide

(MHW);

mean h i g h w a t e r

at spring

tide

(MHWS);

the

front

side,

longitudinal centered, tidal

ending

to tidal

slightly

range

extension of

(MLWS)

sand

intertidal

distribution

between

Island

zone

related

embayment

south-north through

and

at spring

the

supratidal

following

tide

supratidal:

and

MHW and

above MHWS.

is the strong

convexity

landwards

with

configuration

marsh

tide

(MLWS)

between

supratidal:

and wide

of

spits

protects

lower

from MLWS to M H W

to the Mean

in the lower part. zone b o u n d a r y

reaches

intertidal or above the

This

supratidal

in

environ-

31B).

recurved

31B).

a

W i t h a spring

cutting

It has a level d i f f e r e n c e

Microbial

MHW and MHWS

between

mats

which parallels

salt m a r s h

is

a

supra-

in

the

-1.80

Sea Level w h i c h

upward to the M H W S - I e v e l

tally w i t h the c e n t e r e d h i g h distance

(Fig.

upper

(MHW),

zone

Upper

have

flats.

i000 to 1200 m.

and +1.30 m

Lower

in two hooks

of the i n t e r t i d a l

intertidal-supratidal Their

of M e l l u m

inlets

cliffed

and intertidal

The

the

feature

(Fig.

envi-

mesotidal

to a m a c r o t i d a l

channels

Eider-

environments

the range of

extend w i d e l y

lie b e t w e e n

at normal

the

occur

and m a c r o t i d a l

island of the estuary

tidal

island

islands

the Jade Bay and

close

flats

mean h i g h w a t e r

A characteristic

Bank

while

flats

M e l l u m and

1975).

2 m and 4 m at springs.

tidal

which

31A),

of b a r r i e r

macrotidal

tide,

side of the islands

to sediments

(Fig.

the tidal

stages

mesotidal

is a l r e a d y

result of larger

For the p u r p o s e are

between

the most w e s t e r l y

a

(GOHREN,

(1980),

between

Island

(REINECK

sections.

fringes

Sea coast younger

represent

to DAVIES

ment.

tidal

North

of over 4 m at spring

tide of 3.40 m, M e l l u m

direction

islands w h i c h

embayment

estuary

in the f o l l o w i n g

represent

and t y p i c a l l y

and Elbe

I s l a n d and study area

"bank islands"

the e s t u a r y

staedt peninsula

tidal

and e a s t e r n

called

in

of M e l l u m

chain of b a r r i e r

smaller

development, mainly

setting

southern

other

the W e s e r

and is also d e s c r i b e d

3. 3. 2. G e n e r a l

Within

flats b e t w e e n

appear

m

crosses at

the w e s t e r n

the hook.

and m e r g e s h o r i z o n -

of the island

(Fig.

(lower and upper b o u n d a r y

31B).

of mat

The

forma-

96

tion)

is 400

points

to t h e

to 700 m. extremely

A maximum gentle

elevation

angle

500

of the

of 40 c m o v e r lower

this

supratidal

distance

zone.

m

L~'-*'.~ 5oR ~lorsh

~

Lower Supratidol Zone

~

Intedidol Zone

m

Subtidol Zone

MHW5

MHW

"

210

t ~

1

27~ Z~

~,®

]m ~o~ ~>~~

J April

Fig. 31. General setting of Mellum Island. A) L o c a t i o n of t h e i s l a n d b e t w e e n t h e Jade Bay and the Weser river. s i t u a t e d a t the b a c k B) S t u d y area, s i d e o f the w e s t e r n h o o k , between t h e m e a n h i g h w a t e r l i n e (MHW) a n d t h e m e a n h i g h w a t e r l i n e at s p r i n g tide (MHWS). Numbers refer to sampling sites. c) R a n g e s o f h i g h t i d e s a b o v e MHW, n = 706 tides from November 1981 t o O c t o b e r 1982. M H W = l o w e r b o u n dary of the versicolored flats, MHWS = upper boundary. In the a n n u a l cycle, areas between these l i n e s a r e f l o o d e d f r o m 70 % (MHW) t o 20 % (MHWS). E x t r e m e h i g h w a t e r at s p r i n g t i d e (EHWS) o c c u r s m a i n ly in w i n t e r a n d spring. During summer, periods of exposure are more extended. (A t o C w i t h p e r m i s s i o n f r o m J. S e d i m e n t . P e t r o l . , 55, 2 6 5 - 2 7 8 , 1985).

97

3. 3. 3. Previous w o r k

The

number

environments literature

of

on

have

in

be c o m p a r a t i v e l y low if one regards

However, already

biolaminations

later r e - n a m e d

a t t r a c t e d a t t e n t i o n in

preceding

Sea

ganisms,

to

microbial

h i d d e n from v i e w

(1942,

1949)

SCHULZ

1841; (1936),

tions i n s p i r e d SCHULZ

of

of

SCHULZ & M E Y E R

a North Frisian island.

the

microor-

see also KRUMBEIN,

studied the m u l t i p l e interactive

visits to Amrum,

1777),

scientists,

1986b).

(1940) and

pathways

c y a n o b a c t e r i a and a s s o c i a t e d m i c r o b e s in their s e d i m e n t a r y during

and

d e d i c a t e d their

mats in lower supratidal settings

(OERSTEDT,

lati-

At the begin-

and e m p h a s i z e d the " i s l a n d - f o r m i n g capacity"

A b o u t a h u n d r e d years later, HOFFMANN

(MULLER,

a group of S c a n d i n a v i a n natural

i n c l u d i n g H O F M A ~ N BANG, LYNGBY, O E R S T E D T and ROSENBERG,

of

tropical

centuries

"blue-green algae" and then cyanobacteria.

ning of the 19th Century,

Baltic

wealth

in tidal flats of h i g h e r

i n s p i r e d t a x o n o m i c and ecologic studies on "conferves",

observations

siliciclastic the

c a r b o n a t e s t r o m a t o l i t e s and m i c r o b i a l mats in

environments. tudes

reports on b i o l a m i n a t e d d e p o s i t s

may

of

environment

The colorful lamina-

(1936) to create the t e r m " F a r b s t r e i f e n - S a n d w a t t "

(versicolored q u a r t z - s a n d y tidal flats).

N i t r o g e n fixing by n o n - h e t e r o c y s t o u s c y a n o b a c t e r i a studied in s i l i c i c l a s t i c tidal flats & VAN GEMERDEN,

1984;

STAL et al.,

of d e p o s i t i o n a l records were given SCHWARZ et al., REINECK

&

emphasized

1975;

GEP~ES,

(STAL & KRUMBEIN,

(EVANS,

1965;

intensively

1981;

1984a, b c, 1985).

CAMERON et al.,

1984).

was

1985; STAL

Several examples

DAVIS,

1966,

1985; GERDES et al.,

1968;

1985b,

The aspect of coastal b i o - e n g i n e e r i n g

by F U H R B O T E R et al.

(1981,

1983) and M A N Z E N R I E D E R

c; was

(1984),

who noted current v e l o c i t i e s of m o r e than 12 times the n o r m needed

for

grain m o v e m e n t w h i c h w e r e made immobile t h r o u g h m i c r o b i a l colonization.

3. 4. The p h y s i c a l e n v i r o n m e n t of mat f o r m a t i o n

3. 4. I. Climate

The s o u t h e r n coast of the N o r t h Sea has a temperate, Low pressures,

w e s t e r l y winds,

p e r c e n t of the time, speeds

of

and h i g h rainfall are typical.

w i n d s come from the southwest,

6 to 15 m/s

(EISMA,

h u m i d climate.

1980).

Seventy

or n o r t h w e s t w i t h

P r e c i p i t a t i o n averages 700

to

98

750 mm

per year.

During winter,

while

in the summer

4 °C

in w i n t e r

3. 4. 2. Flooding

a yearly

MHW level,

flats

average,

but only 20 % reaches spring

only,

while

upper

the

Extreme h i g h water

several

the w a t e r

supratidal

the entire

drift

level.

lower the w a t e r

are

ice accumu-

(EHWS)

level

31C). slope

subaerially

zone

(Fig.

northwesterly level,

31C).

winds

exposed.

winds

November Wind

raise

resulting

On the other hand, dm,

the

(Fig.

Occur m o s t l y b e t w e e n

supratidal

for several

or crosses

the lower s u p r a t i d a l

zone remains

Strong

area. level

reaches

the MHWS

cross

above normal h i g h - w a t e r

tion of the supratidal south

or crosses

tides m a i n l y

at spring tide

and crosses

meters

- 95 %,

1976).

70 % of all h i g h w a t e r

the summer,

influences

During winter, (REINECK,

is 90

air t e m p e r a t u r e s

frequency

During

and April

is common

humidity

Mean annual

and 16 °C in summer.

lation on the tidal

On

the relative

it is 75 - 80 %.

also

it up to

in the inunda-

from the east or

so that even h i g h w a t e r

spring tide does not reach or cross the supratidal

at

zone.

3. 4. 3. S a l i n i t y

Salinity During measured of

in

the h i g h

rainfall

in surface waters

flood waters

time

period

found more

tide

at low tides,

drastic

of insolation, water.

deviation

is a

a minimum

(the general

lies b e t w e e n

in i n t e r s t i t i a l

flats

a maximum SCHULZ

from the normal

46 °/oo

after

described

for

salinity

regime

it may p r o b a b l y

of intense

the G a v i s h

Sabkha

does not control select

After

salinity

& MEYER

9 °/oo after a h e a v y rainfall

fluctuating

factor.

20 °/oo was

range of the o v e r a l l

30 and 32 °/oo).

measured

a period

rather

s a l i n i t y of about

of up to

(1940)

seawater

and the Solar the mat

salinity.

for special m i c r o b i a l

40 °/oo an

Lake,

an

was even

The authors

increase

However,

formation

summer-

observed

and a salinity

insolation.

salinity

a longer

of up to

as

already

oscillating

in general,

though

taxa.

3. 4. 4. M o i s t u r e

The even

sedimentary

surfaces

after a set of several

of the lower supratidal days of subaerial

zone r e m a i n

exposure

which

moist

is common

99

in the summer p e r i o d low

tides

whose

is

(see Fig.

migration

is s u p p o r t e d

1936;

HOFFMANN,

weight

determinations

sediments

31C).

The

due to the c o n t i n u o u s

1942).

by the

fine-grained

Interstitial

show values

surfade-provided

upward movement

water

comparable

(Table 8; see also GERDES

contents

at

groundwater,

sandy texture

(SCHULZ,

obtained

to contents

& HOLTKAMP,

moisture

of

of

by

dry

intertidal

1980).

TABLE 8. W e i g h t p e r c e n t a g e of i n t e r s t i t i a l fluids o b t a i n e d after sectioning of sediment cores into 1 cm thick slices, drying of the sediment p o r t i o n s and c a l c u l a t i o n of the w a t e r loss. S e d i m e n t cores were taken at sites of equate e l e v a t i o n (MHW +30 cm) of the lower supratidal slope.

08cillatoria

S e d i m e n t layers b e l o w surface 0-i 1-2 2-3 3-4 4-5

cm cm cm cm cm

TWO d i f f e r e n t supratidal

nal relief.

amount

dal-supratidal

ments.

drain

JACOBSEN such

internal

crosses

are typical (1980)

the (Fig.

flood

exposed

at low tide.

topography

area at the

relief b e c a u s e

32A).

used the term

the lower

without

the

inter-

junction b e t w e e n This area

of a

flood

has and

a ebb

and m e r g e s w i t h the intertiThe s h a l l o w

elements

"landpriel

shallows"

of sandy coasts. Both channel

and n e a r l y

of b a c k s h o r e

The

types

plains.

The p l a i n s

at MHW w h i l e

surface

This

from ebb d r a i n a g e

results

within

s e a w a r d part of

of the island.

geomorphic

the salt m a r s h h i n t e r l a n d .

subaerially

surface

junction

relief n o n c o n f o r m i t i e s

parallel-sided

even

smooth

salt m a r s h

zone b o u n d a r y

channels

can be d i s t i n g u i s h e d

is a more p r o t e c t e d

of

system which

25.8 wt.% 22.8 " 22.4 " 19.7 " 17.3 "

at the less p r o t e c t e d

has a r e l a t i v e l y

h o o k and the c e n t e r e d

channel

rize

The one,

The other

considerable

(shallows)

unconformities

sub-environments

zone.

w e s t e r n hook,

flood

variation

18.7 wt.% 18.2 " 15.0 " 18.6 " 16.7 "

3. 4. 5. M o r p h o l o g i c a l

the

Microcoleus

variation

are

filled

environ-

to characteebb

channels

bordered

by

are

flooded

at MHWS

and

water

remains

in the

channels

on the one h a n d

are

and

100

mn

0 2

6 8, 10, 12.

from of

C

small front bars on the other h a n d which build up in the v i c i n i t y the M H W - l e v e l from i n w a r d - m o v i n g sand.

characterize the h i g h e r - l y i n g plains

Dense stands of

(Fig. 32A).

halophytes

101

Fig. 32. Area and d e v e l o p m e n t of the v e r s i c o l o r e d tidal flats. Ebb channels b o r d e r A) V i e w of the area of the Mic~ocoleus variation: flood plains w i t h stands of halophytes. M i c r o b i a l mats interacting with low-rate s e d i m e n t a t i o n a~count for the e l e v a t i o n of the flood plains and make sediments rich in n u t r i e n t s thus f a c i l i t a t i n g plant growth. 08cillatoria limosa starts w i t h the mat formation, coloB) Initially, nizing and a g g l u t i n a t i n g sand grains. Scale is 200 pm. C) Mature stage of the v e r s i c o l o r e d tidal flats showing a vertical z o n a t i o n from top to b o t t o m of (i) a c y a n o b a c t e r i a l mat (usually covered w i t h a thin sand layer), (2) a n o x y g e n i c p h o t o b a c t e r i a (purple bacteria), (3) c h e m o o r g a n o t r o p h i c b a c t e r i a (sulfate-reducers). (Modified after GERDES et al., 1982). of D) Mat surface (Microcoleus) showing the densely e n t a n g l e d m e s h w o r k filaments o v e r g r o w i n g the sandy sediment. Scale is 250 pm. (oscillatoria limosa) colonize the much E) F i l a m e n t o u s cyanobacteria thicker filament of a m a c r o a l g a e (Enteromorpha sp.). Scale is 50 pm (after GERDES & KRUMBEIN, 1986). F) Forams (undetermined species) are inhabitants of the mat surfaces. Scale is 200 pm.

3. 5. S u b - e n v i r o n m e n t s and facies

3. 5. i. Local d o m i n a n c e o_~f m a t - p r o d u c i n g species

Frame genera

builders already

of the M e l l u m

mentioned

mats

are

cyanobacteria,

for the Gavish Sabkha and

the

including Solar

Lake

(Mic~ocoleus, O~cillatoria, Spi~ulina, Gloeothece, Synechococcus).

Two

species

the

of

filamentous c y a n o b a c t e r i a

share in the d o m i n a t i o n

of

lower supratidal zone: Oscillato~ia limosa and Microcoleu8 chthonoplas-

tes.

0. limosa,

within

supratidal The

zone

species

organisms

where w i n d - d r i f t e d

is d o m i n a n t

sediments settle at a

high

rate.

is capable of a rapid gliding m o t i l i t y w h i c h

aids

these

to move fast,

sedimentation zone

a very m o t i l e filamentous cyanobacterium,

the less p r o t e c t e d and less v e g e t a t e d seaward part of the lower

events.

away from the growth site in response to The t r a n s i t i o n a l part of the

lower

the

supratidal

(landpriel shallows) m e r g i n g into the c e n t e r e d saltmarsh is domi-

nated by Microcoleu8 chthonoplastes. Specific slow s e d i m e n t a t i o n conditions

c h a r a c t e r i z e e s p e c i a l l y the flood plains w h e r e dense

halophytes

(Salicornia sp.,

Spa~tina anglica,

stands

of

Limonium vulgate) occur

(Fig. 32A). These conditions provide s u f f i c i e n t shelter for the ensheathed

Microcoleu8

bundles to form mats.

d e s c r i p t i o n of the Gavish Sabkha mats,

Mic~ocoleu8

As a l r e a d y m e n t i o n e d in

the

the p e c u l i a r i t y of filaments of

chthonoplastes is to move h o r i z o n t a l l y back and forth

and

102

to

leave their sheaths only in crisis

importance of M. ~hthonoplastes (formation of Lh-laminae,

conditions.

The

geobiological

in the Gavish Sabkha and the Solar Lake

h i g h p r o d u c t i v i t y rates and sheaths which are

r e l a t i v e l y r e c a l c i t r a n t and survive decomposition) was also emphasized. The

dominance

of this species w i t h i n the p r o t e c t e d part of the

lower

supratidal zone of M e l l u m Island results in b i o l a m i n i t e s w h i c h are much more

v e r t i c a l l y e x t e n d e d than those of Oscill~toria

limosa.

seems to represent a typical o p p o r t u n i s t w h i c h colonizes freshly d e p o s i t e d sediments

predominantly

(e. g. on the flats off the shallows and in

the v i c i n i t y of the MHW-level) w h i l e M. chthonoplastes from

O. limosa

seems to b e n e f i t

the sediment stabilizing a c t i v i t y of 0. limosa and low-rate sedi-

mentation.

According species,

to

the

change of dominance and abundance of

we denote the s u b - e n v i r o n m e n t of the outer slope

variation,

these

two

08cillatoria

the t r a n s i t i o n to the centered m a r s h Micnocoleus variation.

3. 5. 2. S t r a t i f i c a t i o n o_~f living t°P mats

Osciallatoria-Variation:

Sections through the living top mat usually

show a v e r t i c a l l y structured set of three to four layers:

i. A y e l l o w - b r o w n top layer, composed of sand. Thickness ranges from 1 to 5 mm. The layer is c o l o n i z e d by diatoms

(the genera Navicula

and Diplonei8 are dominant). 2. A greenish layer underneath, ria. the

Thickness

composed of filamentous cyanobacte-

ranges from 0.5 to I mm.

dominant species

(Fig. 32B).

Oscillatoria limosa is

Also present are

bundles

of

Microcoleu8 chthonoplastes, other filamentous forms of the genera oscillatoria, Spirulina, Lyngbya, Phonmidi~m, and clusters of unicellular cyanobacteria

(Gloeocapsa, Gloeothece, Synechocystis,

Merismopedia). 3. Where

the u n d e r s i d e of layer 2 is aerated,

more than 0,2 mm thick)

a thin (usually

not

red orange h o r i z o n forms w h i c h is rich in

iron hydroxide. 4. A

layer

black w i t h iron sulfide ranging in thickness b e t w e e n

1

and 5 mm follows s u b s e q u e n t l y or in place of the iron hydroxide.

Microcoleu8 variation:

A

well-defined

microbes characterizes this variation.

change in

associations

of

The v e r t i c a l l y s t r u c t u r e d system

103

of the Microcoleus-dominated m i c r o b i a l mat

(Fig. 32C) includes four

to

five layers:

i. The

top

mat is u s u a l l y 50 - i00 pm thick

are

and

monospecifically

of b u n d l e d sheaths of Microcoleus chthonoplastes

composed

horizontal

in orientation.

number of quartz grains

This top mat contains

cyanobacteria.

o r g a n i s m s c o l o n i z e sand grains and interstices organisms

predominantly

vertical

(oscillato~ia,

Lyngbya,

in orientation.

(Fig.

layer

are

The r e p r e s e n t a t i v e s

latoria v a r i a t i o n of the outer sand flats thece, Synechocysti~, Merismopedia). third

32C).

Pho~midium)

u n i c e l l u l a r c y a n o b a c t e r i a are identical w i t h those of the

3. The

minor

c o m p l e t e l y green co-

lored by d o m i n a n c e of filamentous and u n i c e l l u l a r

Filamentous

a

(Fig. 32D);

2. B e l o w is a sandy layer, 600 to 700 pm thick,

The

which

(Gloeocapsa,

is pink from the d o m i n a n c e

of

purple

of

OscilGloeosulfur

Ch~omatium (photosynthetic a n o x y g e n i c bacteria, mainly vinosum and other n o n - i d e n t i f i e d species). Sand grains and grain-

bacteria

supported

interstices

are d e n s e l y c o l o n i z e d by

the

microorga-

nisms. The thickness of this layer ranges b e t w e e n 500 and 600 pm. 4. The

colorful v e r t i c a l z o n a t i o n merges into a fourth layer

which

is b l a c k from iron sulfide and reaches down to several cm.

The top mat is sometimes covered by a thin layer of y e l l o w i s h white, c l e a n l y w a s h e d sand.

Diatoms are not as frequently e n c o u n t e r e d in this

layer as in the Oscillatoria variation.

stage while the The Microcoleus v a r i a t i o n represents the mature 08cillatoria v a r i a t i o n may indicate the p i o n e e r stage of mat development.

The a c c u m u l a t i o n of o r g a n i c a l l y bound carbon,

and

other

the

e n r i c h m e n t of other m e t a b o l i c types.

compounds w i t h i n the n u t r i e n t - p o o r q u a r t z - s a n d

chemoorganotrophic mat.

With

which

gives

bacteria cally the

(e°

bacteria

rise to the d e v e l o p m e n t of g.

Solar Lake, The

w h i c h degrade the

primarily

aerobic

monolayered

02 becomes

anaerobic

sulfur

facilitates

I n i t i a l l y these are

the c o n s t a n t rise of organic matter,

depleted,

chemoorganotrophic

Desulfovibrio Sp.). Finally, the versicolored, verti-

s t r u c t u r e d system,

types.

nitrogen,

a l r e a d y d e s c r i b e d for the G a v i s h Sabkha

d e v e l o p s c o n s i s t i n g of a great v a r i e t y

system b e n e f i t s

of

from a setting w h i c h is p r o t e c t e d

h i g h s e d i m e n t a t i o n rates, wave attack and tidal currents.

and

metabolic against

104

105

Fig. 33. Internal s e d i m e n t a r y structures (thin sections from cores). A - E: Photographs by H.-E. REINECK. Oscillatonia variation. Dark A) Thin laminae c h a r a c t e r i s t i c of the v e r t i c a l lines are tubes of polychaets. A shell fragment is visible b e l o w the mat. Scale is 5 mm. interB) M u l t i l a m i n a t e d sequences w i t h i n the Microcoleus variation, layered w i t h light q u a r t z - s a n d deposits. Scale is 5 ram. C) A thin mat has coated a rippled surface. Scale is 5 mm. buried microbial D) Root shafts of Spa~tina anglica p i e r c i n g through mats. Note filling of root shafts at top and b o t t o m right w i t h sand. Scale is 1 cm. E) T h i n n e r laminae on top of a m u l t i l a m i n a t e d mat sequence consist of heavy mineral grains indicating the former p r e s e n c e of mats. Even w i t h o u t preservation, the captured h e a v y m i n e r a l grains may indicate the former p r e s e n c e of a mat. Scale is 5 mm. F) C l o s e - u p of the placer of h e a v y m i n e r a l s e n r i c h e d on top of a buried mat. Scale is 1 mm. (Figs. B to E with p e r m i s s i o n from J. Sediment. Petrol., 55, 265-278, 1985).

3. 5. 3. Internal s e d i m e n t a r y structures

Thin

sections

wiched

show that the sediments are almost i n v a r i a b l y

b e t w e e n layers of cleanly w a s h e d sand and

microbial

mats

organic

sand-

carbon-rich

w h i c h p r o l i f e r a t e during intervals b e t w e e n

sedimenta-

tion.

The grain-size d i s t r i b u t i o n of the sandy layers is almost w i t h intertidal sediments is

(GERDES & HOLTFu~MP,

identical

1980). The m a i n fraction

made up of f i n e - g r a i n e d sand w i t h a m e d i u m grain size of i00 ~m

(=

3.3 Phi). A fraction of m e d i u m - g r a i n e d sand is g e n e r a l l y admixed averaging

20 to 25 wt.%,

w h i l e silt and clay is not more than 3 wt.%.

lithologic c o n f o r m i t y of sediments shows that the facies are

The

modifications

m a i n l y c o n t r o l l e d by i n u n d a t i o n frequencies to w h i c h m i c r o b i a l and

faunal assemblages

(see chapter 3. 6.) correspond.

The b u r i e d mats appear as compacted, In the 08cillato~ia variation,

bands. 2 mm; mely

Fig.

between

(up to i0 mm;

sedimentation 1

mm

variation).

Light layers b e t w e e n

(Micro~oleu8 variation) and planar,

sand.

however,

It is,

Fig. 33B).

(Fig. 33C).

due

Root

(I

to

v a r i a t i o n they appear extre-

units of q u a r t z - s a n d w h i c h range in

The b i o l a m i n i t e s

predominantly

ripple

laminae are usually thin

33A), w h i l e in the Microcoleu8

thick

indicate

sharply p r o j e c t i n g i n t e r l a y e r e d

several

are m a i n l y h o r i z o n t a l to the p r e d o m i n a n c e of

cm

the

mats

thickness

(08cillatoria

in o r i e n t a t i o n

and

parallel-laminated

p o s s i b l e that a mat covers a s m a l l - s c a l e shafts of h a l o p h y t e s appear w i t h

wave

increasing

106

h e i g h t above MHW. The dense stands of h a l o p h y t e s w i t h i n the Microcoleu8 variation

(Fig. 32A)

piercing

through

are s p e c t a c u l a r l y recorded by the

the b u r i e d m i c r o b i a l mats

root

(Fig. 33D).

systems

Deposits

o r a n g e - r e d Fe(OH) 3 around the roots and filled root shafts occur 33D).

A

of

(Fig.

spectacular a r r a n g e m e n t of h e a v y mineral grains following the

morphology

of a b u r i e d mat is often visible

mineral

is

volumes

ranging b e t w e e n 0.2 to 3.5 wt.%.

mineral

(LITTLE-GADOW,

supratidal

(Fig. 33E

and

F).

c o n c e n t r a t e d in sediments around M e l l u m Island

mats

1978).

Epidot is the most

bulk

abundant

The c o n c e n t r a t i o n of grains on top

may indicate wind a c t i v i t y and

1935; G A D O W & REINECK,

Heavy

with

1969; REINECK & SINGH,

deflation

of

(TRUSHEIM,

1980).

3. 5. 4. s t a n d i n g ' crops and b i o g e o c h e m i s t r y

Standing cro~s. Pigment c o n c e n t r a t i o n s confirm the d i f f e r e n t complexity

of

both

mat types d e s c r i b e d

(Fig. 34A).

In the course

summer the c o n c e n t r a t i o n s increase in b o t h subenvironments. a contents in the 08cillator~a v a r i a t i o n

chlorophyll 50

and

(ranging

flats

(VAN DEN HOEK et al.,

Mic~ocoleus

variations

chlorophyll

a

of

are up to four

times

higher, this

and

of

upper-

1979). The c o n c e n t r a t i o n s

is m a i n t a i n e d only in samples of

the

between

170 mg x m -2) are comparable to those usually found in

intertidal

values

of

Values

in the

bacterio-

variation.

the M i c r o c o l e u s mat are almost comparable to those

The

of

the

(Fig. 34A)

can

G a v i s h Sabkha and the Solar Lake.

The

drastic increase of pigment contents

be

traced b a c k to a b l o o m of m a c r o a l g a e

by

increasing

biomass

m o i s t u r e supply (rain) in

in October

(Enteromo~pha sp.), fall.

Thus,

the

drought-

r e s i s t a n t c y a n o b a c t e r i a and prevents growth of the m a c r o a l g a e

(e. g. in

Fig.

effectively

34A).

Though

favors

microbial

the

August,

can best be estimated w h e n drier weather

initiated

their growth is ephemeral,

the m a c r o a l g a e

contribute to the biomass p r o d u c t i o n and also to the

p l e x i t y of the Microcoleus mat,

com-

since the c y a n o b a c t e r i a tend to inter-

twine w i t h the much thicker filaments of the algae

(Fig. 32E).

(mainly Entermorpha sp.) are p a r t i c u l a r l y abundant in Microcoleu8 v a r i a t i o n while almost absent in the 08cillatoria variation. Ente~omorpha species are able to use a m m o n i u m d i r e c t l y The m a c r o a l g a e

the

without

further b r e a k - d o w n to

nitrate

(RANWELL,

1972).

Hence,

the

107

OSClLLATORIA -VARIATION

l

t

NICROCOLEUS-VARIATtON

PIGMENTS m-2 1000 mg-m-2 800 600

F~

DChlorophyll e • Bacterio chbrophyll

400 200-

_ I._II ,,,I_ 4 6610 4 6810 4 5610 4 6810{month) A 4 6 510 AMMONIA AND SULFIDE S 20 0.2 0.4 0.6 0B 1 2 3 4 0 0.2 0.4 0.6 0.8 1.0 1.2 4 6 510

.

NH~0 0.2 0/. 0.6 Q8 1.0 1.2

.

.

.

.

,/__-,...-

6 d2"o~o'.6 0".8 I 2 3 4

r/

,!/

4.

12

B

REDOX POTENTIAL AND pH 7:0'72, ' 76 8:2 ' 8:6 -400 -200 0 +200 +400

'

ZO

400

' 7:4

200

' 78

0

" 8:2

200

8:6

pH

400 Eh

xq

z, "

"'"S'

T

×---x Eh ~--.o pH

,,,,,

C

Fig. 34. Substrate p a r a m e t e r s in the two v a r i a t i o n s of the v e r s i e o l o r e d 08cillatoria v a r i a t i o n (unprotected sites of the tidal flats. Left: lower supratidal slope), right: MicrocoZeu8 v a r i a t i o n (protected landpriel shallows). A) C h l o r o p h y l l a and b a c t e r i o c h l o r o p h y l l a in surface mats in the course of the summer 1983. The greater c o m p l e x i t y of Microcoleu8 mats (right) can be read from (i) chlorophyll a concentrations a b s o l u t e l y h i g h e r than of the Oscillatoria mats (left), (2) a more drastic summerly increase of c h l o r o p h y l l a and (3) the occurrence of bacteriochlorophyll a indicating the p r e s e n c e of a n o x y g e n i c photosynthetic b a c t e r i a (e~ g. purple bacteria). B) D i s t r i b u t i o n of ammonia and sulfide vs sediment depth. Both rates are increased in n e a r - s u r f a c e sediments, in p a r t i c u l a r in the Microcoleus v a r i a t i o n and less in the Oscillato~ia variation. The p r o f i l e of the Mie~ocoleu8 v a r i a t i o n indicates a site w i t h stands of macroalgae whose growth is favored by the e s p e c i a l l y high ammonia values (compare Fig. 32E). C) Redox p o t e n t i a l s and pH vs sediment depth showing p o s i t i v e Eh-values negative Ehand s l i g h t l y h i g h e r pH in the 08cillatoria variation, values and lower pH in the Microcoleu8 variation.

108

selected

growth of these species may suggest that a m m o n i u m

is high w i t h i n the sediments of the Microcoleus

A m m o n i a and sulfide concentrations. cores

production

variation.

In October 1984 we took sediment

from both s u b e n v i r o n m e n t s to study the vertical d i s t r i b u t i o n

NH4 +

and

S 2-.

variation

and

Both rates were largely increased in

concentrations

were

This

than

is

Microcoleu8

variation.

p a r t i c u l a r l y h i g h in the n e a r - s u r f a c e

d e c r e a s e d more or less rapidly w i t h depth

matter

the

08cillatoria

far less i m p o r t a n t in the

parts

consistent w i t h the p r e s e n c e of freshly

older and more resistant m a t e r i a l

The and

(Fig. 34B).

produced

organic

w h i c h is more easily degradable by c h e m o o r g a n o t r o p h i c

surface

of

(BLACKBURN,

1983).

bacteria The

near-

pool of a m m o n i u m explains why m a c r o a l g a e capable of using

the

reduced intermediate product of N - m i n e r a l i z a t i o n are a t t r a c t e d to colonize the mats. the

On the other hand, the e n r i c h m e n t of sulfide just b e l o w

surface w h i c h is a s s o c i a t e d with the b a c t e r i a l b r e a k - d o w n of

organic

m a t t e r provides a b e n e f i c i a l situation for

trophs w h i c h require light. Thus, the

aerated

purple

lized

32C).

dead photo-

the sandy sediments i m m e d i a t e l y b e l o w

mat m a i n t a i n a large and

active

population

sulfur b a c t e r i a as well as green and colorless sulfur

(compare Fig. soon

surface

anoxygenic

The g r o w t h of the sulfur b a c t e r i a is i n h i b i t e d

as oxygen penetrates b e l o w the surface mat. in the Oscillatoria

v a r i a t i o n where

of

bacteria as

This is m a i n l y

rea-

(i) physical p r o c e s s e s

such

as w a v e energy and (2) the less c o n d e n s e d fabric of the mat support the penetration

of

08cillatoria

oxygen from above into the

mat

is

system.

c h a r a c t e r i z e d by a lower

Furthermore,

productivity

rate

biomass and thus by a lower amount of dead organic m a t t e r to be down

by b a c t e r i a to ammonium.

the of

broken

This may explain why m a c r o a l g a e as well

as larger and more active a n o x y g e n i c p h o t o t r o p h s are lacking there.

Reduction-oxidation

potentials

and ........In the Oscillatorla

tion,

Eh-values were m a i n l y p o s i t i v e

water

b e l o w the mat slightly alkaline typical of b i c a r b o n a t e

seawater.

(Fig. 34C) and pH in interstitial

The above.

Mio~o~oleu8 indicate The

buffered

The values m e a s u r e d in this s u b e n v i r o n m e n t are comparable to

those at the Gavish Sabkha sandlobes and gullies

which

varia-

that

(Fig. 12).

v a r i a t i o n is c h a r a c t e r i z e d by more oxygen is respired than

h i g h amounts of organic matter,

diffusion b a r r i e r s p r o v i d e d by the mats,

anoxic is

conditions,

provided

as well as the

from

effective

allow the e n r i c h m e n t of chemo-

109

organotrophic

bacteria

electron acceptors

Though form

w h i c h are able to use sulfate

(JORGENSEN,

condensed

and

sulfur

as

1977).

layers exist in the Micro~oleu8 v a r i a t i o n in

the

interstitial w a t e r of h i g h e r contents as in

the

of b u r i e d mats,

08cillatoria v a r i a t i o n were usually found (Table 8). This may be due to the

lateral m i g r a t i o n of w a t e r from the creeks and shallows

adjacent

flood plain deposits where mats p r e d o m i n a n t l y

into

form.

densed layers of b u r i e d mats in turn support stagnancy of

the

The con-

interstitial

w a t e r w h i c h allows the e n r i c h m e n t of chemical reductants.

3. 6. Fauna and i c h n o f a b r i c s

3. 6. I. Mixed m a r i n e - t e r r e s t r i a l c o m p o s i t i o n

In

the lower supratidal zone,

meiobenthic

40 species of both m a c r o b e n t h i c

i n v e r t e b r a t e s were i d e n t i f i e d

invertebrates

(Table 9).

and

The m a c r o b e n t h i c

include 12 species of marine and 5 species of t e r r e s t r i a l

provenance.

Marine

macrobenthic

intertidal

invertebrates.

R e p r e s e n t a t i v e s of

fauna including small polychaetes,

oligochaetes,

g a s t r o p o d e s and l a m e l l i b r a n c h s attain h i g h e s t densities highest density

the

amphipodes,

(Table I0). The

(about 56,000 individuals b e y o n d 1 m 2) was found at the

intertidal-supratidal

zone boundary.

Towards MHWS,

the number of spe-

cies and individuals of intertidal i n v e r t e b r a t e s decreases. cies

still

ulvae,

marine

Five

spe-

(Pygospio elegans, Corophium arenarium, Hydrobia divensiaolor and Lumb~ieillus lineatus). The faunal

remain

Nereis

a s s e m b l a g e composed of these five species attains high densities up MHWS

(a

m a x i m u m 30,000 individuals and more b e y o n d 1 m 2

tered).

This

reached

or crossed by only 20 % of h i g h waters in the

(compare Fig.

Terrestrial clude

three

occurrence

yearly

to

encoun-

density is amazing if we consider that the MHWS-Ievel

is

average

31C).

invertebrates.

The five t e r r e s t r i a l species

c o l e o p t e r a n and two d i p t e r a n

species

(Table

found 9).

inTheir

is rather p a t c h y and r e s t r i c t e d to sites close to the MHWS-

level. At some places, however, fauna.

was

Mainly

they occur side-by-side with the marine

beetles c o n t r i b u t e to the

lebensspuren

spectrum.

Two

110

TABLE 9. Benthos fauna of the v e r s i c o l o r e d tidal flats, M e l l u m Island, lower supratidal zone. (*: restricted by increasing h e i g h t above MHW)

MAJOR TAXA

SPECIES

i. M A C R O B E N T H O S MARINE: CRUSTACEA ANNELIDA

AMPHIPODA

Corophium arenanium Bathyporeia Spo* Lumbricillu8 lineatu8 Lumbrificoides benedeni* Pygospio elegan8 Nereis diversicolor Eteone longa* Capitella capitata* Heteromastu8 filifo,mis* Fabnicia 8abella* Macoma baltica * Hydrobia ulvae

CLITELLATA POLYCHAETA

MOLLUSCA

BIVALVIA GASTROPODA

TERRESTRIAL: INSECTA

COLEOPTERA

Bledius speetabilis ssp, fnisius Blediu8 8ubnigen Hetenoeerus flexuosus Scatella subguttata Dolichopodidae sp.

DIPTERA

species of the staphilinide genus Bledius, w h i c h was already emphasized are present, B. subniger and frisius. Even the ecological zonation, the b u r r o w i n g

for the G a v i s h Sabkha and the Solar Lake,

B. 8pectabili8 v. and

feeding

Gavish vish

behavior

of the M e l l u m species resembles

Sabkha species:

of

the

Bledius 8ubnige~ (Mellum) and B. angustus

those

(Ga-

Sabkha) are b o t h of a smaller size W h i c h p r e f e r oxic sandy

sits and feed p r e f e r e n t i a l l y on u n i c e l l u l a r c y a n o b a c t e r i a and w h i l e the B. 8pectabili8

(Mellum) and B. capra

(Gavish Sabkha) are b o t h

larger species w h i c h d o m i n a t e the t h i c k e n e d and m a i n l y anoxic nites.

On Mellum,

depo-

diatoms,

biolami-

these thickened, Microcoleus-dominated b i o l a m i n i t e s

also p r o v i d e an adequate substrate for another b u r r o w i n g beetle,

Hete-

rocerus flexuosus. Meiofauna. diverse

Of

the

23 species i d e n t i f i e d nematodes

systematic group

(17 species).

are

N e m a t o d e s occur in

high

individual numbers in the t h i c k e n e d b i o l a m i n i t e s of the

leu8

variation.

the

most

especially

A vertical d i s t r i b u t i o n occurs also on M e l l u m

MicrocoIsland

111

Table 9 c o n t i n u e d 2. M E I O -

CRUSTACEA

AND

Leptoeythere baltica Leptocythere laeertosa Elofsonia baltica Mesochra lilljeborgi Heterolaophonte minuta Taehidiu8 di~cipe8 Enoplus brevis Enoploides labiatus Viseosia sp. Adoncholaimu8 fuseus Oncholaimus pa~oxyunis Bathylaimu~ australis Tripyloide8 maninus Diplolaimelloides deaoninski Daptonema sp. Theri~tes acer Chromadora nudicaptata Ascolaimus elongatus Sphaerolaimu8 gracili8 Hypodentolaimu8 balticus Praeacanthonchus punctatu8 Halichoanolaimus robustus Desmodora communis

OSTRACODA

COPEPODA

NEMATODES

TURBELLARIA ROTATORIA CILIATA FORAMINIFERA

and

various species not d e t e r m i n e d

thus confirms SCHULZ'

LACH's

observation

(GERLACH, bacterial

MICROZOOBENTHOS

on

observations

(SCHULZ,

1936),

a F a r b s t r e i f e n - S a n d w a t t at

the

a l t h o u g h GERDanish

coast

1977) indicates that the g r e e n o x y g e n a t e d layer of the cyanomats was favored by most nematodes.

Very few were found

in

the u n d e r l y i n g anoxic strata.

Ostracods

(3 species)

and copepods

(3 species) m a i n l y d o m i n a t e

the

aerated mat surface and here o u t n u m b e r all other m e i o b e n t h i c organisms. Forams

(representatives of the microfauna,

Fig.

32F) also

prefer

to

colonize the mat surfaces.

3. 6. 2. Trophic types Calculations

of

dominance

and d i v e r s i t y structures

of

trophic

types p r e s e n t in Recent and fossil faunal a s s e m b l a g e s are often used to

112

interpret trophic ders,

gradients in food resources and physical regimes. categories used are

(3) grazers,

Food

(i) s u s p e n s i o n feeders,

The

main

(2) deposit

fee-

(4) predators.

particles

held

in s u s p e n s i o n for

solely

suspension-feeding

o r g a n i s m s on the one h a n d and s e d i m e n t a t e d detritus for solely tion-feeding above

MHW,

while b a c t e r i a of both filamentous and u n i c e l l u l a r

micro- and m a c r o a l g a e are enriched. be expected. none

deposi-

organisms on the other h a n d are rarely found in the

zone shape,

The d o m i n a n c e of grazers is thus to

This is at least c o n f i r m e d by terrestrial species,

of the trophic categories m e n t i o n e d above is found

in

while

isolation

w i t h the marine macrofauna. We thus introduce here a l t e r n a t i v e terms of (i) m i x e d feeders, terize

more

(2) sandlicker and

expressively

(3) b a c t e r i a

feeder w h i c h charac-

the p e c u l i a r situation

of

coexistence

of

m i c r o b i a l mats and marine benthic fauna in a h i g h tide flat.

M i x e d feeders. The t u b e - b u i l d i n g p o l y c h a e t e Pygospio elegans characterizes during

a

species

ebb- and

w h i c h is able to switch

suspension

flood currents with higher velocities

feeding during slower current velocities observed

from

to

deposition

(GALLAGHER et al.,

the feeding a c t i v i t y of animals of this species

feeding

1983).

We

cultured

in

a q u a r i u m tanks with m i c r o b i a l mats: The animals came out of their tubes with

h a l f of the b o d y length and c o l l e c t e d diatoms,

bacteria

as

well as filaments

of

Oscillatoria

coated w i t h m i c r o o r g a n i s m s were also ingested.

u n i c e l l u a r cyano-

l~mosa.

Sand-grains

Even bundles of Microco-

leu8 chthonoplaste8 enclosed by their very tough e x t r a c e l l u l a r sheathes (Fig. 32D) closed

were

used.

The animals swallowed one end of a

bundle and ripped on the tough sheath material

filaments became liberated. be,

however,

These were ingested.

sheath-en-

until

enclosed

The energy costs may

very e x p e n s i v e for an animal w h i c h does not possess

jaws

Microcoleu8 as the major diet. This may be one of the reasons why Py~ospio ele~ans is sparsely d i s t r i b u t e d in the Microcoleus

to

utilize

variation. The

second mixed feeder occurring in both local variations

b u r r o w i n g p o l y c h a e t e Ne~ei8 diversicolor. grazer,

suspension- and depositional

the

feeder and is also predacious.

contrast

to Pygospio ele~ans,

aid

feeding on tough substrates such as Microcoleu8

the

is

The species is known to be a In

this species possesses h e a v y jaws which mats.

Fecal

p e l l e t contents after a diet of m i c r o b i a l mats show a great v a r i e t y more or less empty c y a n o b a e t e r i a l sheaths

(Fig. 35).

of

113

Fig. 35. Grazing on mats. diver8icolon w i t h i n A) Entrance of a b u r r o w of the p o l y c h a e t Nereis m i c r o b i a l mats surrounded by fecal pellets. Scale is 1 mm. B) L i g h t m i c r o s c o p y of the fecal pellets showing empty sheaths and fragmentated cells of 08c~llato~ia limosa. Scale is i00 ~m.

Thirdly, versatile

also the mud snail Hydrobia ulvae may be c h a r a c t e r i z e d as a feeder w h i c h ingests small sediment particles,

diatoms

and

u n i c e l l u l a r cyanobacteria.

Sandlicker. to

The term was used by REMANE

this s p e c i a l i z e d trophic type:

arenarium tide

flats

single with

and the beetle Blediu8 8ubniger. and

(1940).

the b u r r o w i n g

(Fig. 35C).

Corophium

Both are found in the high

feed on b a c t e r i a and m i c r o a l g a e

quartz grain

Two species belong amphipode

which

colonize

The animals scrape away the

the

coatings

their m a n d i b l e s and deposit the cleaned quartz grains around

the

b u r r o w s on the surface.

B a c t e r i a feeder. Many d e p o s i t i o n a l deposited

feeders are not really feeding on

p a r t i c l e s themselves but ingest the b a c t e r i a coatings around

organic detritus.

This is the case also w i t h Lumbricillu8

d o m i n a n t m a r i n e i n v e r t e b r a t e of the Microcoleu8 variation. of

lineatus, the The b e n e f i t

this species are the numerous b a c t e r i a p o p u l a t i o n s w h i c h are

ciated w i t h the Microcoleus

chthonoplaste8 mats.

asso-

114

Grazer. Both c o l e o p t e r a n species Blediu8 spectabili8 and Hetenocenu8

flexuosu8

browse p r e f e r e n t i a l l y on the Microcoleu8 mats.

Both possess

h e a v y m a n d i b l e s to rip away the tough mat material.

3. 6. 3. Regional , d i s t r i b u t i o n o f trophic types

The mat

following c o r r e l a t i o n of trophic types and local v a r i a t i o n s

d e v e l o p m e n t is recognized

relate

(the terms a r e n o p h i l e

and

in

chthonophile

to p r e f e r e n c e s of the species for either q u a r t z - s a n d or soil- =

Greek chthonos -like substrates; to emphasize the role of M.

the term chthonophile was chosen here

chthonoplaste8 in forming a soil-like sub-

strate in an otherwise q u a r t z - s a n d y depositional environment):

A r e n o p h i l e species

Intermediate p o s i t i o n

C h t h o n o p h i l e species

(Oscillatonia

(Microcoleu8

variation)

variation)

Sandlicker:

Mixed feeder:

a)Bacteria feeder:

Corophium anenarium

Pygospio elegans Nereis diversicolor

Lumb~icillus lineatus

Blediu8 8ubniger

b) Grazer:

HydPobia ulvae, Bledius 8pectabilis Heteroceru8 flexuosu8

3. 6. 4. Life habits and ichnofabrics

The

major trace makers and traces in the b i o l a m i n a t e d sediments

listed below. tures

used

SEILACHER

Their d i f f e r e n t i a t i o n follows

HERTWECK

into internal vs.

(1978).

The

surface

classification

are

struc-

scheme

of

(1953), who classified traces according to e t h o l o g i c - f u n c t i o -

nal categories

(dwelling, grazing etc.),

is also adopted.

I. T r a c e - m a k i n g marine invertebrates

Pygospio elegans (Polychaeta, feeder

and lower supratidal flats Lebensspuren: diameter, i0 cm.

Spionidae).

(suspension-/deposit-feeder,

a) Internal:

vertical

Tube wall:

in

Infaunal semi-sessile mixed

grazer).

Distribution:

Intertidal

(preference for stabilized sand). Dwelling trace.

orientation,

Tube w i t h 5 mm

length ranging b e t w e e n

overall 5

and

M u c u s - c e m e n t e d sand grains. Often r e d - o r a n g e coa-

1t5

tings

of

i r o n - h y d r o x i d e due to i r r i g a t i o n a c t i v i t y of

b) Surface:

Pore-like hole,

the

animal.

not s i g n i f i c a n t in f i n e - g r a i n e d sand.

Corophium arenarium (Crustacea, Amphipoda). Infaunal semi-sessile deposit feeder. Distribution:

Intertidal and lower supratidal

flats

(pre-

ference for s t a b i l i z e d o x y g e n a t e d sand). Lebensspuren:

a)

Internal:

overall diameter, wall:

vertical

Mucus-agglutinated

D w e l l i n g trace. in orientation,

(non-cemented)

B u r r o w w i t h 5 to i0 m m

length about 5 cm. Burrow

sand

grains,

Feeding trace. T o o t h e d - w h e e l - s h a p e d scratch marks, diameter

Newels

( s u s p e n s i o n - / d e p o s i t feeder,

a)

Internal:

overall diameter, i0 cm.

anoxic

vertical

B u r r o w walls:

predator).

m u d d y and sandy substrates. Burrow with 5 to i0 mm

in orientation,

length ranging b e t w e e n 5

Non-solid mucus-coatings

(burrows

Feeding trace. M u c u s - a g g l u t i n a t e d ,

within

oxygenated

surface-furro-

This occurs

w h e n emerging from its b u r r o w to seek food the animal

in contact with the b u r r o w with the tip of its tail. constantly

Hydrobia

be-

remains

In this way

moves sidewards and b a c k and forth w i t h i n the same

to the b u r r o w

Sub-

Dwelling trace.

traces of a c h a r a c t e r i s t i c d e e r - a n t l e r - s h a p e .

cause

feeder

Distribution:

layers show F e ( O H ) 3 - c o a t i n g s due to irrigation of

water), b) Surface: wing

Infaunal semi-sessile m i x e d

grazer,

intertidal and lower supratidal,

Lebensspuren:

and

Surface:

(Fig. 36A).

diversicolo~ (Polychaeta).

tidal,

b)

5 to i0 mm overall

it

trace

(Fig. 36B).

ulvae (Gastropoda).

Distribution:

Epifaunal mobile

grazer/deposit-feeder.

Intertidal and lower supratidal

zone,

m u d d y and sandy

substrates. Lebensspuren: nal

Resting trace. N o n - s i g n i f i c a n t d e f o r m a t i o -

b i o t u r b a t i o n structure,

drought Burrowing (VADER, on

a) Internal:

muddy

periods

few mm b e l o w surface

by b u r y i n g t h e m s e l v e s

does

not

1964).

in the

(the snails survive

sediment

occur at low tide w h e n surface

b) Surface:

water

persists

Browsing trace. N a r r o w furrows, b i l o b a t e

surfaces or w h e n diatoms and c y a n o b a c t e r i a

s a t u r a t e d mush

(Fig. 36C).

at the surface of sand flats

form

a

water-

(Fig. 36D).

II. T r a c e - m a k i n g t e r r e s t r i a l i n v e r t e b r a t e s

Bledius 8ubniger (Coleoptera, Staphilinidae). Endofaunal mobile grazer. Distribution:

Lower

and

upper supratidal,

sandy

oxygenated

sub-

strates. Lebensspuren: vertical

a)

Internal:

in orientation,

D w e l l i n g and b r o w s i n g

3 to 5 man in diameter,

traces.

Burrows

length 2 to 3

cm.

116

Fig. 36. Feeding, resting and dwelling traces. A) Toothed-wheel-shaped scratch marks at the surface are feeding traces of the amphipod Corophium arenarium. Photograph by H.-E. REINECK. is B) Feeding traces of Nerei8 diversicolo~ furrow the surface which viscose by microbial slime. Scale is 1 cm. Photograph by W. HT[NTZSCHEL. C) Low-tide resting snails (Hydrobia ulvae) below the surface. Scale is 2 mm. D) Elongated piles of excavation pellets of the salt beetle Blediu8 8ubni~er, removed from its subsurficial dwelling and browsing tunnels. E) Round piles of excavation pellets of Bledius 8pectabilis. D and E: Photograph by H.-E. REINECK. F) Browsing traces of the beetle Heterocerus flexuosu8 cut through a mat. Scale is 5 mm.

W

Browsing

trace:

Two-sided

few mm below surface,

(similar to B.

to 5 cm long b) Surface: which

furrows

horizontal

an~ustus,

Excavation pellets.

the beetle

removes

leading

from the burrow entrance a

in orientation,

1 to 2 mm wide,

see Gavish Sabkha,

up

Fig. 20B).

Elongated piles of excavation pellets

from its dwelling and browsing

tunnel

(Fig.

36E).

Blediu8 8pectabili8 v. semi-mobile

grazer.

frisiu8 (Coleoptera, Distribution:

Staphilinidae).

Endofaunal

Mainly upper and lower supratidal

salt marshes. Lebensspuren: ved).

a) Internal:

Dwelling

Burrow with a diagonal

trace

top shaft

(browsing traces not obser-

(bottle neck)

and a

vertical

shaft with breeding chambers branching off of the main shaft to B.

capra,

pellets. burrows

see Gavish Sabkha,

Round

piles

Fig.

18).

b) Surface:

of excavation pellets

removed

from

zer. Distribution: Lebensspuren

(only internal):

Burrow horizontal

Carabiidae).

Endofaunal

Mainly upper and lower supratidal

a fenestra-like layer

Dwelling and browsing traces.

in orientation,

elongated

composed

several cm long.

Burrows

cavities

but

in

orientation,

quartz

(GERDES et al.,

sand

which

1985c).

of

thin

allows

Browsing:

Vertical

cutting through the h o r i z o n t a l l y

coleus mat (Fig. 36G).

found on

section shows

similar to the description

commonly deeper below surface.

sometimes

Dwelling:

cavity with a flat floor and a convex

of microbe-bound

coherent roof architecture horizontal

mobile gra-

salt marshes.

M e l l u m ran on top of a buried Mi~roco~eu8 mat: Vertical

trace,

dwelling

(Fig. 36F).

Heteroc~us flexuosu8 (Coleoptera,

roof

(similar

Excavation

a

Burrow

dwelling

section

shows

orientated M~cno-

117

Examples are terns the live

where

numerous.

It has

of species species

lithology

influences

thus to be e m p h a s i z e d

listed b e f o r e

at M e l l u m

in m u d d y tidal

the v i s i b i l i t y

Island

flats.

refer to the live,

filifo~mis is an i m p o r t a n t t r a c e m a k e r

lebensspuren

that the i c h n o l o g i c a l sandy s u b s t r a t e

as most

For example,

of

patwhich

of them are also able

the p o l y c h a e t e

in m u d d y

in

substrates,

to

Hete~omastu8 but in

the

118

sand flats of M e l l u m Island,

traces of this species are not significant

and thus are n e g l e c t e d here.

3. 7. D o m i n a n c e change and its i m p o r t a n c e for b i o t u r b a t i o n grades and p a t t e r n s

Sparse physical

trace

records

conditions

Harshness

of

is often suggested as a reason and is a t t e s t e d

are usual for

stromatolites.

to

be n e c e s s a r y for the e x c l u s i o n of d i s t u r b a n c e s by grazing and b i o t u r b a tion

(AWRAMIK,

the

siliciclastic

unusual

1981;

ment.

1970; GEBELEIN,

However,

responsible Moreover,

We

In this respect to

present

an

abun-

the density of a faunal a s s e m b l a g e is not

for the grade of c h u r n i n g and stirring of a

sedi-

the q u e s t i o n of species d o m i n a n c e and a b u n d a n c e in

given setting should also be a d d r e s s e d

and

1976).

stromatolite e n v i r o n m e n t in that they locally h a r b o r an

dant marine fauna. always

GARRETT,

b i o l a m i n i t e s of M e l l u m Island seem

(CARNEY,

a

1981).

will show by c o m b i n e d studies of faunal compositions b i o t u r b a t i o n structures p r e s e r v e d in relief casts

(Table

(Fig. 37)

10) that

the faunal assemblages in the lower supratidal zone c o m p a r e d w i t h those at

the

intertidal

abundance

base show w e l l - d e f i n e d changes

in

dominance

and

and that these changes account for the type and the grade of

b i o t u r b a t i o n w i t h i n the mats.

A c c o r d i n g to S C H A F E R (1972) the terms are

bioturbation. in

"deformative" and

"figurative"

used to c h a r a c t e r i z e the d i f f e r e n c e s in the type and the grade

The t e r m "deformative" d e s c r i b e s c o m p l e t e l y r e w o r k e d beds

w h i c h no p r e e x i s t i n g sedimentary structures can be

1967). burrows

Figurative and

of

tubes

bioturbation

is

seen

m a i n t a i n e d by the

p i e r c i n g through several sets

of

(REINECK,

occurrence strata

of

without

d e s t r o y i n g t h e m completely.

3. 7. i. Effects of increasing e l e v a t i o n

a) Lower intertidal base The d o m i n a n t type is the cockle Cerastode~ma ciated with several species of h i g h e r density:

thee sp., Arenicola marina.

edule,

and it is asso-

Scolopl08

a~mi~er,

U~o-

119

TABLE i0. Distribution, abundance, S h a n n o n ' s d i v e r s i t y and d o m i n a n c e c a l c u l a t i o n s of m a c r o f a u n a at d i f f e r e n t n i v e a u levels (Abundance x mE). Bioturbation structures corresponding with faunal composition and a b u n d a n c e are shown in Figs. 37A, B, D and F°

Species

Individuals

Lower Upper Intertidal zone

N i v e a u level related to M H W

Reference

MARINE

-130

to Fig.

cm

37A

-i0 cm

37B

m -2

Lower s u p r a t i d a l zone OscillatoriaMicrocoleusvariations

+30 cm

37D

+30 cm

37F

FAUNA:

Pygospio elegan8 66 Corophium arena~ium 4 Nereis diversicolor 43 Lumbricillus lineatu8 1 Hydrobia ulvae 222 Bathyporeia sp. 60 Capitella capitata 132 Macoma baltica 56 Heteromastu8 filiformi8 88 Eteone longa 20 Scoloplo8 a~miger 420 Cerastoderma edule 2.057 Arenicola marina 44 Nephthy8 longo~etosa 9 40 Gattyana cirnosa Urothde sp. 396 Anaitide8 mucosa 28 Nephthy8 hombergi 4 16 Scolelepis bonnieri C~angon crangon 21 TERRESTRIAL

5.506 452 232 603 351 4 866 64 94 18

19.888 1.908 74 1.986 949 35

159 0 1.302 19.462 1.685

FAUNA:

Blediu8 subniger Dolichopodidae

28

larv,

348 227 147 98

Seatella 8ubguttata Heteroceru8 flexuosus Bledius speetabilis Species: 20 Individuals m-2: 3.727 S h a n n o n ' s diversityH': 2.45 P i l o u ' s E v e n n e s s J: 0.57 D o m i n a n c e (l-J): 0.43

i0 8.190 1.75 0.53 0.47

7 24.868 1.06 0.38 0.62

8 23.428 1.01 0.34 0.66

120

121

Q

a Fig. 37. Series of sediment cores showing from A - D the change in bioturbation structures vs i n c r e a s i n g e l e v a t i o n and from D - F vs increasing microbial productivity. The c o r r e s p o n d i n g fauna, studied with the reliefs at same levels and time, is listed in Table i0. P h o t o g r a p h s by H.-E. REINECK. Scale is for all cores 2 cm. A) Lower intertidal zone. P r e e x i s t i n g b e d d i n g is not visible, due to high grade bioturbation. Note life h o r i z o n of the cockle Ce~astoderma edule b e y o n d the surface. B) I n t e r t i d a l - s u p r a t i d a l zone boundary. B i o t u r b a t i o n is still high. Note, however, i n c r e a s i n g v i s i b i l i t y of tubes and burrows. C) Same level as B. One single L - s h a p e d trace, made by a juvenile lugworm, w i t h i n evenly laminated sand. Initial stage of mat formation (see p r o j e c t i n g top layer). The sample has been cored in the landpriel shallows. D) Lower supratidal zone about 30 cm above MHW (08cillatoria variation). High numbers of dwelling traces from intertidal animals p i e r c e through sharply p r o j e c t i n g b u r i e d mats. E) Same level as D (transition towards the Mic~ocoleus variation): Low numbers of d w e l l i n g s t r u c t u r e s reflect the substrate change, caused by i n c r e a s i n g p r o d u c t i v i t y of mats and d e c r e a s i n g sedimentation rates. In b e t w e e n the b u r i e d mats, p h y s i c a l s t r u c t u r e s (laminated sand, cross-bedding) are visible. Dark color indicates reduced sediments. F) Same level as D (Microcoleu8 variation): The sediment is devoid of dwelling traces while roots of h a l o p h y t e s occur in great abundance.

122

The

Ce~astode~ma edule is a s u s p e n s i o n feeder

cockle

b e n e a t h the sediment surface. 1985).

living

just

The m a x i m u m shell length is 5 cm (REISE,

In response to s e d i m e n t a t i o n or erosion,

the m o b i l e p o p u l a t i o n

moves upwards or downwards to find its most a p p r o p r i a t e settling depth, w h i c h is d e t e r m i n e d by the length of siphones h o r i z o n of C. edule in Fig. 37A).

life

(5 to i0 mm; see also the

The h i g h degree of a c t i v i t y of

the p o p u l a t i o n leads to the d e f o r m a t i o n of any newly s e d i m e n t a t e d stratum. The p o l y c h a e t e Scolop108 armiger is a m o b i l e b u r r o w i n g b a c t e r i v o r e (REISE,

1985)

w h i c h migrates through the sediment and

m o t t l e d b i o t u r b a t i o n structures, the

leaves

behind

clearly visible in Fig. 37A. Finally,

b u r r o w i n g p o l y c h a e t e A r e n i c o l a m a r i n a is k n o w n as a very important

b i o t u r b a t o r of sandy sediments. i0)

The number of 44 specimen per m 2 (Table

already represents a m e a n p o p u l a t i o n d e n s i t y because of the

size of the lugworms

(up to 30 cm)°

to a layer of up to 33 cm (CADEE,

As

a consequence,

dominated

by

the

Annual sediment r e w o r k i n g

large amounts

1976).

the p r e s e n c e of this faunal a s s e m b l a g e w h i c h

above-mentioned deformatively

burrowing

is

organisms

leads to s t r o n g l y b i o t u r b a t e d sediments w i t h o u t any visible p r e e x i s t i n g sedimentary structure visible

(Fig. 37A).

b) Upper intertidal belt

This

belt

shows already the a b o v e - m e n t i o n e d

relief

unconformities

m e r g i n g into the s u b - e n v i r o n m e n t s of mat formation w h i c h we have termed

Oscillato~ia v a r i a t i o n and the Mic~ocoleus variation. The core in Increasing Fig. 37B indicates the base of the 08cillatoria variation. Coroabundance of figuratively b u r r o w i n g species (Pygospio elegans, phium a~ena~ium; Table i0) g r a d u a l l y leads to the v i s i b i l i t y of lebens-

the

spuren.

The evenly laminated sand and the L - s h a p e d trace of a juvenile

lugworm

in Fig.

37C indicate one of the landpriel shallows w h i c h cross

Mic~ocoleu8

the i n t e r t i d a l - s u p r a t i d a l zone b o u n d a r y at the base of the variation.

Juvenile

conditions.

lugworms

benefit here from shallowest

Channel filling, however,

m i c r o b i a l mat

(see top of Fig.

37C),

submersal

followed by the d e v e l o p m e n t of a may have had lethal

consequences

for the lugworm. W U N D E R L I C H ' s e x p l a n a t i o n of similar traces is, h o w e v e r that

animals,

event?),

removed

from their natural h a b i t a t by a c c i d e n t

(storm

h a v e tried to escape from the sediment surface by burying and

have p r o d u c e d these lethal escape traces

(WUNDERLICH,

1984).

123

c) Lower

supratidal zone

(08cillatoria variation)

It is notable that f i g u r a t i v e l y b u r r o w i n g dinate

species w h i c h play a subor-

role in the lower intertidal base become more and more a b u n d a n t

w i t h increasing h e i g h t above MHW

(Table i0). The d o m i n a n t type Pygospio

elegans (tube-forming) is a s s o c i a t e d w i t h the b u r r o w i n g amphipode Corophium arenarium, the mud snail Hydrobia ulvae, the b u r r o w i n g p o l y c h a e t e Nerei8 diversicolor and the o l i g o c h a e t e Lumbnicillu8 lineatu8. There

is also a notable q u a n t i t a t i v e change:

the number of species ties

(7 vs. 20),

(25,000 vs. 4,000; mean values).

(3) a r e d u c t i o n of d i v e r s i t y thus

(5)

species,

(i) the reduction

in

(2) the increase in individual densi-

(H'),

Both changes go hand in h a n d with

(4) a r e d u c t i o n of eveness

the increase of p e r c e n t d o m i n a n c e

(i - J).

In

(J)

and

trace-making

the p e r c e n t a g e dominance is:

Pygospio elegan8 Corophium arenarium Hydrobia ulvae Nenei8 diversicolor (mainly juvenile):

about 80

%

about

8

%

about

4

%

about

0.3 %

The remaining 7 to 8 % belong to Lumbricillu8 lineatus, oligochaete. sediments.

a 5-mm-long

Traces of this species are not recognizable w i t h i n This

might

be d i f f e r e n t in silt and clay

deposits

sandy where

d w e l l i n g structures of o l i g o c h a e t e s are often detectable.

Hydrobia ulvae is the only one which p r o d u c e s d e f o r m a t i v e structures during low-tide resting only

4 %

(Fig. 36C).

However,

of the total faunal assemblage,

agglutinated

tubes

this species constitutes

while

animals

which

and burrows reach a p e r c e n t a g e d o m i n a n c e of

form about

90 %.

As a consequence,

the o c c u r r e n c e of this faunal assemblage,

h i g h l y d o m i n a t e d by f i g u r a t i v e l y b u r r o w i n g organisms, bation

patterns

w h i c h is

leads to biotur-

quite d i f f e r e n t from the lower intertidal zone

(Fig.

(Cerastoderma edule) and animals with a large The h i g h - l y i n g area is oxygen demand (Arenicola marina) are excluded. 37D).

S u s p e n s i o n feeders

a p p r o p r i a t e for semi-sessile m a r i n e e n d o b i o n t s living in s l i m e - a g g l u t i nated tubes and burrows. are

visible,

present

P h y s i c a l l y and m i c r o b i a l l y derived laminations

even though the p o p u l a t i o n d e n s i t y of the

is h i g h e r than in the intertidal area

(Table i0).

invertebrates The various

124

buried cyanobacterial

mats visible in Fig.

lags where sedimentation summer span

period where without

flooding occurs

sedimentation,

developing

surface mat which

underlying

sediments

again

(wind

upwards

37D actually represent

did not proceed.

less frequently.

the endobiontic supplies

animals benefit

the the

With sedimentation

microbial

the

going

animals

on

migrate

layer and reinforce their prolon-

slime. Former top mats,

perforated by the upwards movement of the preexisting

time

from

from desiccation.

through each newly deposited

the

During the

them with food and protects

is often the agent of deposition),

gated dwellings by secreting

time-

This is the case during

animals.

now buried,

become

Nevertheless,

laminae remain visible in the

sediments

the (Fig.

37D).

3. 7. 2. Effects o f increasing microbial p r o d u c t i v i t y

The high We

of the 08cillatoria variation are characterized

sediments

population density of figuratively

burrowing

intertidal

calculated a mean distance of 6 mm between the dwelling

(GERDES & KRUMBEIN,

1986).

By contrast,

the sediments

Zeus variation contain lebensspuren of lower density ce

of 24 mm was calculated between burrows,

niles

of

the intertidal

sub-environments

lie at the same elevation

dance of burrowing the

(a m a x i m u m distan-

mainly produced by

juve-

Since

both

level,

there is no reason to

flood recharge.

Control of the abun-

and tube-building

products

Five marine intertidal formation

but

amphipods

and small polychaetes

i0).

tioned

species occur in both sub-environments

before,

changes

This can be correlated

distinguished

in

the Oscillatoria

strongly

sedimentation, grain-size

negative all

sedimentation

and lower pH

other parameters

distribution contributes

are

(open

less

of mat

abundance As mencan

be

protected

(2) higher standing crops;

of reduced metabolic Eh-values

and

(protected shallows)

variation

slope) by (i) lower rates of sedimentation; (3) higher concentrations

dominance

to substrate differences.

the Microcoleu8 variation from

of and

is discussed in the following:

show considerable

(Table

(4)

structures

oscillatoria variation by the Microcoleus chthonoplastes mats

their degradational

a

of the Mic~oce-

polychaete Nereis dive~si~olor).

imply the influence of decreasing

by

species.

compounds

microbially

in both variations

(NH4 +,

values.

Besides induced,

is nearly the

same.

$2-); slow while Slow

on the other hand indirectly to the substrate

change since layers rich in organic carbon are closer together.

125

The substrate change is a c c o m p a n i e d by a change in d o m i n a n c e b e t w e e n trace-making

species and those w h i c h leave no traces behind.

m a k i n g species,

the p e r c e n t a g e a b u n d a n c e is:

Pygospio elegans:

about

Covophium arenarium:

+/-

0

%

Nerei8 diversicolor (mainly juvenile):

about

4

%

B u r r o w i n g beetles

about

3

%

Thus

leu8

0.7 %

Mic~oco-

the mean p e r c e n t a g e a b u n d a n c e of t r a c e - m a k e r s in the

amounts to 8 % while in the 08c~llato~a v a r i a t i o n

variation

The small o l i g o c h a e t e Lumb~ic~llu8 l{neatu8

reaches 90 %.

85 % of the total faunal assemblage.

b~

In trace-

ulvae (Fig. 36C) and diptera.

it

constitutes

The remaining 7 % belong to Hyd~oThe latter also leave

no

internal

traces.

It

is

nearly

notable

domination the

that the total a b u n d a n c e of individuals

the same in both variations

x

m -2

The change in

change d e t e c t a b l e in h o r i z o n t a l d i r e c t i o n

E and F in Fig. 37).

variation

are

Mic~ocoleu8

variation

(see

is c o m p a r a t i v e l y void of faunal

species, traces,

result of about 85 % d o m i n a n c e of the o l i g o c h a e t e Lumb~cil~u8

the as

a

~ineatus

Lumb~icillu8 lineaMicro-

p r e f e r s the i n t e r m e d i a t e p o s i t i o n b e t w e e n the top layer of

coleus mats and the h i g h l y anoxic s u b s u r f i c i a l s i l i c i c l a s t i c where

for

relief

W h i l e the sediments of the 08cillato~i~

m a r k e d by a high d e n s i t y of t r a c e - m a k i n g

w h i c h does not leave any trace in sandy sediments.

tub

is

species

b e t w e e n the s u b - e n v i r o n m e n t s of mat formation accounts

biofacies

casts D,

(Table i0).

sediments

it feeds on b a c t e r i a l and d i a t o m coatings of sand grains

(GIERE,

1975).

The terns

examples p r o v i d e d here show that b i o t u r b a t i o n grades

and

pat-

are e f f e c t i v e l y c o n t r o l l e d by changes in d o m i n a n c e and abundance

of animals w i t h d i f f e r e n t life habits.

3. 7. 3. P r o m o t i n 9 and l i m i t i n g d i s t r i b u t i o n a l

Two

questions

distribution:

(i)

should What

factors

be d i s c u s s e d w i t h respect are

the factors p r o m o t i n g

to

the

marine

i n v e r t e b r a t e s to p e r s i s t w i t h i n an area of irregular flooding?

observed burrowing (2) W h a t

126

are

the

factors

p r e v e n t i n g these organisms

from

burrowing

in

the

t h i c k e n e d b i o l a m i n a t e d deposits?

The first q u e s t i o n may be a d d r e s s e d to the "opportunism" phenomenon. The

Pygospio

most a b u n d a n t t r a c e - m a k i n g taxon is the small p o l y c h a e t e

elegans.

The mode of r e p r o d u c t i o n identifies this species as a typical

opportunist

(GALLAGHER et al.,

1983;

GERDES & KRUMBEIN,

1985).

The

larval d e v e l o p m e n t u s u a l l y includes a p e l a g i c stage w h i c h is c o v e r e d by the tides. benthic.

The life-cycle of this species can, however, In

this case the p r o d u c t s of r e p r o d u c t i o n are laid

into the tube along w i t h n u t r i e n t out

and

entering a pelagic stage reproduction,

observed

(SMIDT,

directly

The d e v e l o p i n g larvae spread parents

without

1951). This species is also capable of

and its increase on d e f a u n a t e d flats

has

been

to be almost e x c l u s i v e l y due to the asexual r e p r o d u c t i o n mode

(RASMUSSEN, This

"eggs"

colonize the area in close p r o x i m i t y to the

asexual

be e x c l u s i v e l y

1953, 1973; H O B S O N & GREEN,

1968; G A L L A G H E R et al.,

1983).

seems to be an ideal tactic to p e r s i s t on the h i g h tide flats

Mellum,

and

in fact,

we o b s e r v e d asexual stages w i t h i n

the

of

samples

o b t a i n e d from Mellum. C h a r a c t e r i s t i c of o p p o r t u n i s t s such as Pygo8pio elegan8 and p o s s i b l y

Co~ophium

also

arenarium (DAUER & SIMON,

1976) is thus a variety

of

methods,

h i g h levels of r e p r o d u c t i o n and short life spans of the indi-

vidual.

It is these groups w h i c h usually r e - e s t a b l i s h t h e m s e l v e s first

after

catastrophic

increased

declines in p o p u l a t i o n

deposition,

caused,

for

erosion or freezing in winter.

example,

A f t e r the

by sub-

strate conditions have been r e - e s t a b l i s h e d they are often s u p e r s e d e d by those p o p u l a t i o n s which were t e m p o r a r l y destroyed. supersession fen-Sandwatt.

are impossible at the supratidal Consequently

Such m e c h a n i s m s

flats of the

of

Farbstrei-

p o p u l a t i o n s of these species first able to

colonize this area remain constant and can - almost w i t h o u t c o m p e t i t i o n - b e c o m e denser than intertidal populations. led

to

Gavish the

The series of events w h i c h

the increase in numbers of the snail Pirenella conica Sabkha and of the o p p o r t u n i s t i c p o l y c h a e t e s and

F a r b s t r e i f e n - S a n d w a t t seems to be related:

facies"

(TEICHERT,

in

amphipodes

"Environment

the in

produces

1958).

The second question should be addressed to chemical conditions vailing in the Mic~ocoleu8 variation.

pre-

The field data e l a b o r a t e d in this

study give some indications that there is a c o u p l i n g effect of low-rate s e d i m e n t a t i o n and h i g h standing crops r e a l i z e d in this variation.

This

127

c o u p l i n g effect results in a pile of reduced organic carbon and reduced intermediate clean,

p r o d u c t s due to b a c t e r i a l b r e a k - d o w n w i t h i n an

otherwise

m a i n l y w i n d - b o r n e d e p o s i t i o n a l e n v i r o n m e n t of quartz-sand.

The

Microleus v a r i a t i o n thus may represent a s u b - e n v i r o n m e n t w h e r e chemical c o n d i t i o n s a s s o c i a t e d w i t h the mat p r o d u c t i v i t y m i n i m i z e the density of trace-makers.

Studies in the l a b o r a t o r y in order to explain and predict

trace-scarcity

with

microbial

(GERDES & KRUMBEIN,

mats

an

increase of d e g r a d a b l e

organic

matter

1986) have revealed the

from

following

results:

i.

Ammonia

Co~ophium

as

a limiting factor:

Both,

the b u r r o w i n g

arena~ium and the t u b e - f o r m i n g p o l y c h a e t e

amphipode

Pygospio

elegans

t o l e r a t e a m m o n i u m contents of r e l a t i v e l y h i g h levels. Values of ammonia m e a s u r e d w i t h i n sediments of the Microcoleu8

concentrations

variation

lie g e n e r a l l y b e l o w the t o l e r a n c e limits of b o t h species. However, (1984) found

suggests tolerance

considered,

a c o n f i d e n c e range of about a tenth of limit,

the

GRAY

actually

if only one single factor such as ammonia

is

since sediments rich in organic matter comprise a m u l t i t u d e

of c o m p l e x l y interacting p r o c e s s e s and m e t a b o l i c substances.

2.

Oxygen

Corophium

d e f i c i e n c y as a limiting factor:

a~enarium

die

Animals of the species

very soon when p l a c e d in

Pygospio elegans,

oxygen

(< 2 mg/l).

oxygen

d e p l e t i o n in pore waters.

on the

sediments

other

hand,

of

low

tolerates

The latter species is also known

to

live in anoxic intertidal sediments.

The sensity to oxygen d e f i c i e n c y explains why Corophium arenarium is to live in sediments of the Mic~ocoleu8

not

able

Fig.

34C).

These sediments restrict,

ele~ans,

however,

polychaete

Pygospio

frequency)

h i g h p o p u l a t i o n d e n s i t i e s occur.

variation

also the

w h i l e at equate level Hence,

(same a

(compare

tube-forming inundation

multifactorial

effect

(enrichment of reduced compounds,

during

periods of subaerial e x p o s u r e and h i g h energy costs of

on

the

stagnant interstitial

tough surface mats) may be r e s p o n s i b l e for the

water feeding

limitation

of

this important t r a c e m a k e r w i t h i n t h i c k e n i n g m i c r o b i a l mats.

3. 8. I n t e r t i d a l - s u p r a t i d a l

sequence

The d e c r e a s i n g influence of tides c o n s i d e r e d mic

and

(I) from the

hydrodyna-

(2) the e c o l o g i c point of v i e w is congruous w i t h the "sum

of

128

modifications" elevation. internal

1838) in internal and surface structures

vs

The following sections summarize the p a t t e r n s of change

(GRESSLY,

in

structures

(Fig. 38) and surface structures

(Fig. 39)

along

the i n t e r t i d a l - s u p r a t i d a l sequence on M e l l u m Island.

Laminated sand Smait.itripp[ebedding Oscillationripplebedding 8io[aminites Bubble sand Highity bioturbated V V-V C~

Plant roots She[its Abundance of traces

.~

high common rare

Fig. 38. Idealized vertical s u c c e s s i o n showing the p r o g r a d i n g intertidal-supratidal sequence and the p o s i t i o n of m i c r o b i a l mats at the i n t e r t i d a l - s u p r a t i d a l zone boundary. Section i: intertidal zone, section 2: lower supratidal zone, section 3: upper supratidal zone.

3. 8. i. Change of sedimentary internal structures

High

grade b i o t u r b a t i o n controls most parts of the lower and

intertidal zone.

upper

W i t h the exception of some current ripple structures,

p r e e x i s t i n g bedding is not visible.

The extensive b u r r o w i n g reflects a

diverse and mobile infauna w h i c h dominates over current and wave

stra-

tification. At

a

boundary,

level a

w h i c h corresponds to

the

intertidal-supratidal

change in a p p e a r a n c e of physical and b i o g e n i c

becomes obvious

(Fig. 38):

zone

structures

129

(i) The physical scale

structures

cross-bedding,

include p a r a l l e l - l a m i n a t e d

sand (secondary p h y s i c a l structure; teristic

of

sand,

r e s u l t i n g m o s t l y from wave ripples, R E I N E C K & SINGH,

l a m i n a t e d sand w h i c h is the d o m i n a n t p h y s i c a l structure though R E I N E C K

bubble

1980), all charac-

sandy tidal flats exposed to wave action.

be p r o d u c e d m a i n l y by wind,

small

and

The

parallel-

may,

however,

(1963) a t t r i b u t e d it also to

swash and b a c k w a s h wave action.

(2)

Buried

mats

appear at a level w h i c h corresponds to

the

MHW-

level. Each mat represents a former surface w h i c h was covered with sand loads

and was s u b s e q u e n t l y b o u n d by m i c r o b i a l activity.

sequence

grades upward into the supratidal environment,

generations

appear.

The spaces b e t w e e n the individual

The more

the

the more

mat

mats

decrease

w i t h i n c r e a s i n g h e i g h t above MHW. At a level w h i c h c o r r e s p o n d s with the b o u n d a r y b e t w e e n the lower and upper supratidal zone and 50 cm above MHW), structures

shafts of salicornia sp.,

root

conditions

(Fig. 38).

(Fig. 38).

(tubes and burrows)

complex change of infaunal assemblages.

are

b e t w e e n 40

the mat h o r i z o n s g r a d u a l l y d i s a p p e a r and p h y s i c a l

(laminated sand and bubble sand) d o m i n a t e

(3) The appearance of individual traces a

(i. e.

reflects

Among the tubes and burrows

which

also

indicate

supratidal

Species w h i c h cause the extensive b u r r o w i n g

in

the intertidal sediments are e x c l u d e d by irregular flooding.

3. 8. 2. Change o f s e d i m e n t a r y surface forms

The

intertidal

indicating

the

supratidal

zone

ripple going

zone

(Fig. 39)

is c h a r a c t e r i z e d by

influence of tidal currents.

diverse

ripple

Around

the

b o u n d a r y smooth patches appear w h i c h

systems.

The

smooth patches indicate

alternate

microbial

h a n d in h a n d with the i m m o b i l i z a t i o n of surface

intertidal-supratidal where

flooding

zone b o u n d a r y is,

frequencies

microbial activity

(REINECK,

however,

are still sufficient 1979).

lower parts of the intertidal zone,

systems

intertidal-

sediments.

a struggling to

with

colonization

interfere

The zone with

L o o k i n g back to the n o n - c o l o n i z e d we see,

however,

clear m o d i f i c a -

tions of the surface relief: The ripple systems are c o n f i n e d to pockets which and

indicate the partial erosion of m i c r o b i a l l y i m m o b i l i z e d surfaces subsequent

ripples

are

rippling of the bare sand

within

d o m i n a n t w i t h i n the e r o s i o n a l pockets.

the

pockets.

W i t h further

Wave in-

130

AREA AROUND MHWS

INTERTIDALSUPRATIDAL ZONE BOUNDARY

INTERTIDAL BASE

131

Fig. 39. Change of surface s t r u c t u r e s vs elevation. Photographs by H.-E. REINECK. A) I n t e r t i d a l base, c h a r a c t e r i z e d by e x t e n d e d ripple systems. B) At the i n t e r t i d a l - s u p r a t i d a l zone boundary: Ripples are c o n f i n e d to flutes w h e r e m i c r o b i a l l y i m m o b i l i z e d surfaces b e c a m e eroded. At the bottom: Freshly deposited sand layer on top of a mat shows more e x t e n d e d ripple systems. (Modified after REINECK, 1979). C) At the level of MHWS: Smooth surfaces predominate. In the vertical section visible are several m i c r o b i a l mat g e n e r a t i o n s w h i c h lie bey o n d a thin a i r - b o r n e layer of sand.

increase number

of

lower

and

supratidal

extension

slope

and g r a d u a l l y

the smooth replace

patches

increase

the e r o s i o n a l

marks

in

(Fig.

39C).

Air-borne action

microbiota placed period

sand

deposited

or currents

before

or from outside.

and ripples

In this

can form

forms

ripples.

on the rippled

When deposition

the

erosional

within

by the size of the pockets, air-borne

sand extend over

Interpretation.

critical

point

Vcrit"

= 0.98

1984).

Biologically

m/s

combination

especially starting

where

point

Example Alameda

of the sediment, the m o r p h o l o g y

is r e s t r i c t e d

surface

then a

retaining

this

expansion

of

to a few decimeters carpets

of

area.

lies b e t w e e n

flow at w h i c h 0.2 and 0.4

secured

sand on

and a m a x i m u m of Vcrit " = 1.56 high

a

the

and newly o v e r g r o w n

in b i o l o g i c a l l y

secured

disby

of

the sideways

speed of water

sand begins

sand is

m/s

transporm/s.

This

average

by

(MANZENRIEDER,

sand is only e r o d e d during bad w e a t h e r w i t h

water

levels

irregularities

and

movement

of

such as b r o k e n

the

sea

and

shells p r o v i d e

a

for erosion.

from

Avenue

(MACKENZIE, closely

of

pockets

the r i p p l e d

wave buried

is followed

is buried,

Although

a larger

increases

following the mat

33C).

The critical

tation of f i n e - g r a i n e d

If this

by

by the

the u n s e c u r e d

further m o v e m e n t

reoccurs,

(see Fig.

can be effected and secured

39B).

surface,

wavy characteristic ripples

mats

case,

(see Fig.

of calm w e a t h e r w i t h o u t

new mat

a

on surface

it is r e c o l o n i z e d

the fossil west

1968,

resembles

record.

In the c r e t a c e o u s

of D e n v e r / C o l o r a d o

1972)

a

Dakota Group

fossilized

bedding

plane

revealed

which

with

eroded

structures

the surface

of the

"Farbstreifen-Sandwatt"

1979).

This

surface

of the flute m a y belong

outcrop

at first evokes

has been

the i m p r e s s i o n

to a l o w e r - l y i n g

that

bedding

at

(REINECK, the

plane

ribbed and have

132

been

r e v e a l e d by weathering.

Sandwatt,

however,

shows

The recent example of the

that

secured by m i c r o o r g a n i s m s may produce these structures both

recent

and

fossil

examples the ripple crests

pockets b l e n d into the smooth surface edges. cates

Farbstreifen-

partial erosion of sandflats

in

the

(REINECK,

In

erosion

This c h a r a c t e r i s t i c indi-

that the flute and the ripples w i t h i n it were formed

flat surfaces

already

(Fig. 39B).

after

the

1979).

3. 9. S u b a e r i a l rise of b i o l a m i n a t e d q u a r t z - s a n d (experimental approach)

The

d e p o s i t i o n a l record shows that sand layers are

tween

layers

of organic c a r b o n - r i c h horizons,

sandwiched

be-

due to m i c r o b i a l

w h i c h p r o l i f e r a t e during intervals of non-deposition.

mats

B e d - b y - b e d recog-

n i t i o n w i t h i n a t e x t u r a l l y and s t r u c t u r a l l y u n i f o r m lithologic sequence thus becomes possible.

In a similar rock record, however,

it may not be

easy to infer c o m p l e t e l y subaerial conditions involved in the raise

of

the

it

biolaminated

quartz-sand.

Thus,

p o s s i b l e w i t h o u t any h e l p of tides, ding

necessary

the question may arise:

Is

or is at least a p e r i o d i c a l

in order to r e - i n o c u l a t e freshly

sedimentated

floolayers

w i t h m i c r o b e s h e l d in suspension?

We studied this q u e s t i o n in the lab (Fig. 40): vated

(i) A core was

the field (M~d~o~oleu8 variation) with a

in

40 cm in d i a m e t e r and 40 cm high.

exca-

plexiglas-cylinder

The filled cylinder was set into

an

a q u a r i u m tank and the space between the cylinder and the tank walls was filled w i t h fine-grained sand. The sand was filled up to about one half of the height of the cylinder. The sediment inside the c y l i n d e r was not flooded, but capillary action was aided by pouring seawater on the sand outside

the

cylinder.

(2) A 5-mm layer of f i n e - g r a i n e d sand

(i00 pm

grain size) was scattered over the mat surface w i t h i n the cylinder with a

sieve.

This simulated low-rate w i n d - l a i d deposition.

s e d i m e n t a t i o n was repeated every four days, development

of

concentrations.

(3)

Low-rate

w h i l e in the m e a n t i m e

new mat was v i s u a l l y o b s e r v e d and m e a s u r e d by

the

pigment

(4) The e x p e r i m e n t was finished after twelve instances

of oversedimentation,

and a relief cast was p r e p a r e d

(Fig. 40).

The test has shown that a m u l t i t u d e of m i c r o b i a l mat g e n e r a t i o n s can develop by

from one and the same p r e e x i s t i n g mat w i t h o u t any

microbes h e l d in s u s p e n s i o n by the tide waters.

inoculation

Apparently,

wind-

133

Plexiglass-Zy[inder

Fig. 40. Subaerial rise of b i o l a m i n a t e d q u a r t z - s a n d (experiment). A) Treatment: U n d i s t u r b e d sediment w i t h a mat on top was cored in the field (section I). Twelve instances of o v e r s e d i m e n t a t i o n (section II), c a r r i e d out in the lab, s i m u l a t e d low-rate w i n d - l a i d d e p o s i t i o n w i t h o u t flooding. B) Relief cast p r e p a r a t i o n showing the twelve generations of m i c r o b i a l mats that o r i g i n a t e d from one and the same p r e e x i s t i n g mat. The test has shown that b i o l a m i n a t e d sequences can g r o w w i t h o u t flooding and inoculation by m i c r o b e s held in s u s p e n s i o n by tide waters. Photograph by H.-Eo REINECK.

134

borne

low-rate

subaerial

sedimentation

flat p r o v i d e d

that m o i s t u r e

The structures zontal

evolving

and r e g u l a r l y

duced

sedimentary

microbial

deposits

in a r a r e l y

is s u f f i c i e n t

interlaminated.

as in the

rich in d i f f e r e n t

shallow-water

of n o n d e p o s i t i o n

environments

aids

action.

hori-

of m i c r o b i a l l y

Gavish

biotypes

the tide

are c o n t i n u o u s l y

No d i v e r s i t y

occurs

which

flooded h i g h

due to c a p i l l a r y

from these p r o c e s s e s

structures

communities

persisting periods

acts as a "stimulant"

rise of b i o l a m i n a t e d

Sabkha,

are

prowhere

facilitated

on the one hand

and

by

long-term

on the other hand.

3. 10. S u m m a r y and c o n c l u s i o n s

Cyanobacteria

account

streifen-Sandwatt" The

biolaminated

Sabkha gy:

up

worked the

strong

Dominant

their

contributing tion

in the h y p e r s a l i n e

stratiform.

unconformities

There

different

with

laminae

grow are re-

By contrast, Gavish

Sabkha

the same

excessive are

transport. crops,

degrees

genera

gel p r o d u c important.

the b i o l a m i n i t e s

sedimentation sediment

Modifications

of p r o t e c t i o n

however,

conditions.

stimulates

layer.

of the

redox p o t e n t i a l s

Wind

is

microbial

and pH are h i g h l y

realized

by

relief

zone.

that b u r r o w i n g

are d e t r i m e n t a l

less

cyanobacteria, low-rate

in the lower supratidal

animals

Gavish

from

unicells,

lack of s h a l l o w - w a t e r

Episodic

standing

is no i n d i c a t i o n

terrestrial

in the

Coccoid

the freshly d e p o s i t e d

the m a j o r agent of sediment

to

the

in the litholo-

products.

representing

extended

of filamentous

to grow through

correlative

grains

environments

vertically

Due to the d o m i n a n c e

structure,

1 of

exist

to well rounded.

cyanobacteria

This may be due to the general

community

type

predominantly

as p r i m a r y w e a t h e r i n g

"FarbIsland.

Mi~rocoleus chthonoplaste8 also the same species as

to translucent,

the mats

originate

Sabkha and the Solar Lake.

are c o n t i n u o u s l y

in the

of M e l l u m

the mats on M e l l u m Island

of s i l i c i c l a s t i c

are filamentous

the Gavish

flat)

to facies

and are rounded

status

accretion

Differences

The grains

sediments

in the case of

in

are similar

upon or t h r o u g h w h i c h

angularity

shows

sediment

sandy tidal

biolaminites).

of clean sand.

glacial

clearly

and

deposits

(siliciclastic

Sediments

made

for b i o g e n i c

(versicolored

and g r a z i n g

by intertidal

to the growing mat

systems.

and

Accor-

135

ding to the marine cal

and

such

fauna,

two d i s t r i b u t i o n a l b a r r i e r s exist:

(2) b i o g e o c h e m i c a l

factors.

(i) physi-

Intertidal d e f o r m a t i v e

burrowers

as cockles and lugworms are c o n t r o l l e d by the p h y s i c a l b a r r i e r of

d e c r e a s i n g r e g u l a r i t y of flooding. pierced

through

In spite of this fact, the mats are

by numerous d w e l l i n g traces.

These stem

from

small

p o l y c h a e t e s and a m p h i p o d e crustaceans w h i c h are able to spread over the i n t e r t i d a l - s u p r a t i d a l b o u n d a r y and settle up to the MHWS-Ievel. chemical

b a r r i e r s are:

ammonia

Oxygen depletion within

and sulfide contents,

down of organic matter.

the

pode

c r u s t a c e a n s d i s a p p e a r due to these conditions.

d w e l l i n g traces of marine p o l y c h a e t e s and amphi-

species, Microcoleus (Greek chthonos).

chthonoplast¢8, While

The name

trace-making

"arenophile"

phile" species.

of

the

indicates its capacity

l i t h o l o g y is not altered,

of Microcoleus mats leads to a h a b i t a t change which

presence

high

Mic~oco-

W i t h i n the h i g h l y p r o d u c t i v e mats of

chthonoplastes,

to form "soils"

sediments,

w h i c h g e n e r a t e through b a c t e r i a l b r e a k -

leus

mat-forming

Biogeo-

i n v e r t e b r a t e species and

favors

the

excludes "chthono-

The latter include high densities of individuals which

do not leave traces behind.

In summary, in

the

the degree of s e l f - o r g a n i z a t i o n of b i o l a m i n a t e d deposits

temperate climate zone is lower than w i t h i n

the

hypersaline,

p r o t e c t e d shallow w a t e r basins of the G a v i s h Sabkha and the Solar Lake. The

b i o l a m i n a t e d d e p o s i t s grow w i t h the aid of q u a r t z - s a n d

tion.

In

correlation

sedimenta-

with the c a p a c i t y of the m i c r o b i a l mats to

e s t a b l i s h themselves on freshly s e d i m e n t a t e d surfaces,

the

re-

sedimenta-

tion rate per time unit is h i g h l y r e s p o n s i b l e for the amount of organic matter

stored

responsible zoans.

within

the sediment column and indirectly it

for the density of traces made by marine

is

burrowing

also meta-

137

4.

This

WHAT

part

considering

THE

ENVIRONMENTS

HAVE

IN COMMON

- FINAL

REMARKS

on m o d e r n s t r o m a t o l i t e e n v i r o n m e n t s may be three

cyanobacteria,

attributes

they h a v e in common:

the

finished

by

presence

of

the trace record relating to salt beetles and the posi-

tion on the m a r g i n of a sea.

4.1.

Cyanobacteria

C y a n o b a c t e r i a as p i o n e e r o r g a n i s m s

are

well adapted to p e r i t i d a l conditions.

capable of surviving e x t r e m e l y high salt concentrations, ture,

strong

drastic

insolation,

short-term

cyanobacteria

They

e x t r e m e l y low w a t e r p o t e n t i a l s as

changes

in these conditions.

For

are

high temperawell

these

as

reasons

have a p p a r e n t l y survived for 3.5 m i l l i a r d s of years

and

c o n t i n u e d to thrive through Earth history.

A

r e m a r k a b l e a t t r i b u t e of c y a n o b a c t e r i a o c c u p y i n g sandy

high

tide

flats such as those of M e l l u m Island is their capacity to fix m o l e c u l a r nitrogen.

Fertilization

of the clean

(mainly wind-borne)

and thus nu-

t r i e n t - p o o r q u a r t z - s a n d g r a d u a l l y takes place through p h y s i o l o g i c pathways of n i t r o g e n reduction,

a c c u m u l a t i o n of o r g a n i c a l l y bound n i t r o g e n

w i t h i n the d e n s e l y p o p u l a t e d mats and its c o n s e q u e n t release by trophic

bacteria.

This

may

signify a mode of f a c i l i t a t i o n

s u b s e q u e n t d e v e l o p m e n t of m a c r o a l g a e and macrophytes. xing enzyme system is, species,

however,

(1984 a, b, c) recognized, however,

the

h i g h tide flats of M e l l u m Island do not possess

are

n e v e r t h e l e s s active in n i t r o g e n fixation.

similarity

rated

that c y a n o b a c t e r i a inoculating heterocysts,

One of the

which

themselves

is striking.

Early in

Proterozoic

mat-

may have b e e n c y a n o b a c t e r i a - l i k e may have

libeelec-

sal H20 as an e l e c t r o n donor, change

represents

earth,

since

it

of

time,

from a n o x y g e n i c p h o t o s y n t h e s i s w i t h H2S as the

tron donor and d e v e l o p e d systems w h i c h enabled t h e m to use the

animals and man.

but

major

to w i d e l y a c c e p t e d theories about the evolution

oxygenic photosynthesis

microorganisms

STAL et

Oscillatonia limosa, is of this type.

forming species,

The

the

for several

called heterocysts.

al.

the

for

The nitrogen-fi-

very sensitive to 02 and,

is p r o t e c t e d in separate cells,

chemo-

univer-

and 02 was formed as a by-product.

p r o b a b l y the m o s t drastic event in the acted as a mode of f a c i l i t a t i o n for The n i t r o g e n - f i x i n g bacteria,

history

fungi,

This of

plants,

however, had to pay for

138

the

e m a n c i p a t i o n from a n o x y g e n i c p h o t o s y n t h e s i s by h a v i n g

the

O 2 - s e n s i t i v e enzyme system under changed conditions

BEIN,

1981; STAL et al.,

4.2.

to

protect

(STAL &

KRUM-

1984 a, b, c).

Saltbeetles:

"Purpose" of d w e l l i n g b u r r o w s

The i n f o r m a t i o n r e v e a l e d by traces a b o u t their b u i l d e r is of p a l e o n tological

interest.

In rock a trace is o f t e n all that remains of

sediments'

inhabitants.

S E I L A C H E R (1951)

the

showed that with a specimen of

t u b e - b u i l d i n g marine p o l y c h a e t e we can learn much from the c o n s t r u c t i o n of

its tube about its "ecological purpose" - the function of the

struction

con-

for its inhabitant in a p a r t i c u l a r e n v i r o n m e n t - and perhaps

t h e r e b y find indicators

for the e n v i r o n m e n t a l conditions p r e v a i l i n g

at

the time of deposition.

Contact w i t h seawater is essential for the survival of marine bearing

organisms.

air-breathing

Such contact can endanger the life of

organisms

which

contribute in all

studied to the l e b e n s s p u r e n spectrum. The

three

gill-

terrestrial environments

"purpose of dwelling burrows"

for t e r r e s t r i a l organisms living in an a p e r i o d i c a l l y flooded depositional e n v i r o n m e n t lies in the fact that ter

is

to

(i) l o n g - t e r m contact with seawa-

be avoided and (2) vital needs can

be

satisfied

without

beetles

(Blediu~

external contact for a certain p e r i o d of time.

The

morphology

angustu8 bill8

of

d w e l l i n g burrows of the salt

and B. oapra in the Gavish Sabkha, B. 8ubniger

on

M e l l u m Island)

protection,

and B. 8peeta

shows that these c o n s t r u c t i o n s serve

sustenance and way of life of their b u i l d e r s in a

w h i c h i r r e g u l a r l y floods and dries out. They are o b v i o u s l y cally

consequences

of living on the interface between land and

they

are

p r e d e s t i n e d to live in a

m i c r o b i a l mats predominate.

directly

comparable fossil traces

still lacking today.

see

through

(3) w i t h these charactedepositional

E x a m i n a t i o n and

their lebensspuren in a p a l e o e c o l o g i c a l as

(i) b i o l o g i -

(2) they could to a large extent avoid the u n f a v o r a b l e

their h i g h l y s p e c i a l i z e d methods of dwelling;

where

the

dependent for their sustenance on the p r e s e n c e of p h o t o s y n t h e t i c

microorganisms;

ristics

in

habitat

environment

interpretation

of

sense is currently theoretical, from stromatolitic deposits

are

139

4.3.

All Within

the environments a hypothetical

the same position, into

Peritidal settings

studied are s i t u a t e d on the m a r g i n of

4. 3. i. The

G a v i s h Sabkha and M e l l u m Island des-

two d i f f e r e n t vertical profile models.

"sabkha cycle"

C o a s t l i n e s of subtropical, the

dynamic

sequence

of the

arid regions p r o g r a d i n g seawards "sabkha cycle".

c h a r a c t e r i s t i c of the P e r s i a n - A r a b i a n Gulf There

stretches

in

zone

with

ooids

lagoons.

m a i n l y dolomite,

KENDALL, be

found

a n h y d r i t e and intertidal

and (3) subtidal half-

M u l t i - l a y e r e d m i c r o b i a l mats in

and oncoids as w e l l as the

the

This is also

(2) t r a n s i t i o n a l zones from supratidal to

of carbonate sediments,

of

1978;

the sequence from the land to the sea can

closed b a c k - b a r r i e r tion

(SHEARMAN,

of (i) w i d e s p r e a d s u p r a t i d a l areas of halite,

g y p s u m deposits,

follow

The SE incline

G a v i s h Sabkha center also shows this p r o g r a d i n g tendency.

1979).

sea. almost

o v e r l y i n g a set of intertidal sediments and merging

upper supratidal sequences.

cribe, however,

a

s t r a t i g r a p h i c s u c c e s s i o n they w o u l d take

nodular

associa-

Pleurocapsalean

a g g r e g a t e s are c o n f i n e d to the c a r b o n a t e sediments of the upper

inter-

tidal zone. On h i g h e r levels they are replaced by sulfate deposits.

The nous

dynamic sequence of the "sabkha cycle" which ends w i t h terrigesediments

can be used as a recent m o d e l to explain

"paleosabkha

cycles". C y c l i c a l l y r e o c c u r r i n g s t r a t i g r a p h i c sequences can be o b s e r v e d in the N a r s s a r s u k

formation in N o r t h w e s t G r e e n l a n d

(Precambrian).

Each

cycle begins with limestone,

w h i c h is s u c c e e d e d v e r t i c a l l y upwards

organically

This facies is i n t e r f i n g e r e d w i t h

higher

up

rich and

dolomite. finally

(STROTHER et al.,

1983;

is

covered

KNOLL,

by

1985a).

fine-grained

red

gypsum

sandstone

The banded dolomite sequence

contains m i c r o f o s s i l s of coccoids and t h r e a d - l i k e organisms as well

Eoentophysali8 of

aggregates

(KNOLL,

G a v i s h Sabkha has already been d i s c u s s e d

formations.

strata

carbonates

In all cases s t r o m a t o l i t e s are found and

are r e p l a c e d by sulfate

(FRIEDMAN & SANDERS,

1978;

PURSER,

the

(Facies type 2).

Similar p a l e o s a b k h a cycles can be found in the m o s t varied cal

as

1985a). The m o r p h o l o g i c a l similarity

this m i c r o f a c i e s w i t h the recent P l e u r o c a p s a l e a n a g g r e g a t e s of

with

by

in

deposits

1980; SHINN,

geologi-

associatioq in

1983).

overlying

140

The r e - e s t a b l i s h m e n t of s t r o m a t o l i t i c carbonates above sabkha sits

can

be

seen in v e r t i c a l p r o f i l e s of the Solar

caused by a tectonic event. responsible

Lake

depo-

sediments,

In other cases t r a n s g r e s s i o n s may h a v e b e e n

(see in Part III the

Permian Z e c h s t e i n sequence).

4. 3. 2. Temperate h u m i d coastlines

In

the

temperate

h u m i d coastal zone,

oxides and iron sulfides, same sediment column, bial

mat-mediated

sedimentation

h o r i z o n s enriched

in

iron

b o t h o c c u r r i n g sometimes w i t h i n one and

may be viewed as the "equivalent"

the

for the micro-

carbonate m i n e r a l o g y in the arid coastal

of siliciclastics is frequent as on M e l l u m

zone.

Island,

If the

vertical set is confined by a regular i n t e r l a y e r i n g of o r g a n i c a l l y rich (and iron sulfide-rich) along

a t e x t u r a l l y u n i f o r m sand is w i d e l y d i s t r i b u t e d

1978;

M E Y E R & MICHAELIS,

LIS,

1980; C O L I J N & KOEMAN,

1975; REINECK & GERDES, 1903).

uniform,

The

(2)

zones

1984; SCHULZ,

growth-bedding

environments,

n u t r i e n t concentrations.

(3) made up

Their occurrence,

of

tidal or

faunal

flat and beach sequences,

r h i z o s p h e r e s of salt marshes,

composition:

mainland

coasts,

merely

teristic

biolaminites

they merge w i t h dune and they bear

a

islands

and

marine on sand banks w i t h o u t c o n n e c t i o n s

to

their charac-

Smooth surfaces alternate w i t h

laminated sand,

sometimes also small-scale

does not show any changes of grain fabrics, matter

cross-

different

b e d d i n g w i t h dark laminae rich in organic matter. The vertical

organic

from

from beaches of

W h e r e v e r these structures develop,

features are repeated:

erosional pockets,

level

ranges

m i x e d m a r i n e - t e r r e s t r i a l on b a r r i e r

t e r r e s t r i a l habitats.

(i)

(4) i n i t i a l l y low

b a r r i e r islands to those of m a i n l a n d coasts. Consequently, overlie

1942; REIN-

fine-grained

however,

b a c k s i d e s of barrier islands to s t a t i o n a r y sand banks,

bedding

al.,

1975; H A U S E R & MICHAE-

w h e r e these structures develop are

low-energy

studies

(POTTS et

1936; HOFFMANN,

quartz sand with very low contents of silt and clay, in

Varied

the North Sea Coast have shown that this kind of

within

KE,

and o r g a n i c a l l y poor horizons.

small ripple

sequence

w h i c h could imply that the

r e s u l t e d from slow sinking d e p o s i t i o n from

suspension

(e. g. tidal bedding). The c h a r a c t e r i s t i c appearance of b i o l a m i n i t e s in the lower dal

zone

of

various geomorphic units led us

deposits as the biogenic laminite subfacies

to

suprati-

characterize

(GERDES et al.,

these

1985c).

PART

SPANNING

THE

GAP

BETWEEN

III

MICROBIOLOGY

AND

GEOLOGY

"Up until n o w I have on

those

places

bodies

which

how

were

my a t t e n t i o n

discovered

give us cause to doubt

w e r e their p l a c e s shown

concentrated

which

unperceptible

that they

of o r i g i n and t h e r e b y

from the p e r c e p t i b l e conclusions."

in

we

I have

can

(N. STENO,

draw

1667)

i. I N T R O D U C T I O N

In

sedimentary

rocks

which

are c o n s i d e r e d

earth.

For many

present-day

fossil

and

systems

1905)

discoveries coastal

on the h i g h recent

are

1985a),

to be the signs

fossil

hypersaline

tion is b a s e d

then

ment

is,

also m e a n i n g f u l .

the gap b e t w e e n

of m i c r o f o s s i l s bial

metabolic out

pathways)

geological

(e. g.

of

since

of p r o c a r y o t e s

time

(CLOUD,

microcolumnar

bring

about these

ching

of mineral

induced

(GEIKIE,

precipitates

mineralization with

with

tary

structures

experience

which

favor the e s t a b l i s h m e n t

forms

to

experience microbial

(i) m a t c h i n g

probably

constancy of

from

through-

processes

ecosystems;

depositional

which

(3) mat-

microbially

of a s s o c i a t e d

communities.

also

microstructures

from m o d e r n

(4) m a t c h i n g

of m i c r o b i a l

an-

from m o d e r n m i c r o -

(and most

(2) m a t c h i n g

from m o d e r n

those

into them.

experience

experience

spans

it was g e o l o g y w h i c h

show a r e m a r k a b l e

with

which

of this state-

and g e o l o g y means

structures

in m o d e r n

mechanisms;

cases

of recent

research

1976);

shape)

structures

The converse

In m a n y

rocks with

cellular

Recent

is the key to the past"

microbiology

in s e d i m e n t a r y

morphotypes

the

(KNOLL,

our eyes to the s i m i l a r i t y encouraged

to

assump-

between

forms.

of

on

similar

facies

and m i c r o b i o l o g y .

cient ones and c o n s e q u e n t l y

Spanning

associated

found

of life

This

similarity

for the genesis

"the p r e s e n t

forms

is assumed.

of m o r p h o g e n e t i c and their

were

environment

in the field of p a l e o m i c r o b i o l o g y

geology

however,

opened

of the earliest

environments

level

stromatolites

is also r e l e v a n t gap b e t w e e n

era m i c r o f o s s i l s

a formational

taken as models

and the s t a t e m e n t

the

first

of the P r o t e r o z o i c

sedimen-

environments

144

The

direct

sitates, matolites

and

outcrops

(e. g. caliche).

often are lithified see DUNLOP et al.,

1980;

BUICK,

and p a r t i c l e s

(for

further SCHOPF

single

are

formational

specific

structures,

fissures discus& WALTER,

we p r e s e n t

processes

studies

than c y a n o b a c t e r i a

examples

have been

given

is

formed

in

with

conditions.

ironstone,

a complementary

summary

iron

may w i d e n the

metabolic

in the formation of

minerals. involved

of

present-day

Gunflint

Lorraine)

of pathways

Zech-

allow the inference

found imply that involved

structures

in the Permian

(Precambrian

and ooids and in the c o n c e n t r a t i o n

accretion.

may

deposits

in i n t e r a c t i o n

similar to the above m e n t i o n e d

and Lower J u r a s s i c

sediment

(b)

on m i c r o b i a l

Poland w h i c h might

as the m i c r o f o s s i l s

chapter

observations mineral

(a) biogenic,

is given of platy dolomite

The other

Canada

inasmuch

matolites

since orga-

1979;

also on p a l e o c l i m a t i c

chapter,

environment

sabkhas.

formation,

problems

the smallest

intrusions

stro-

contamination

w h i c h may shed light on the type of d e p o s i t i o -

(PZ3) of North

depositional

others

specific

One example

stein sequence

scope

causes

& MORRISON,

and oncoids)

and p r o b a b l y

In the following

coastal

CLOUD

that the observed

environment

nal e n v i r o n m e n t

a

1978;

(e. g. ooids

indicate

in rocks.

by s e c o n d a r y

of the a b o v e - l i s t e d

for the reasoning

(c)

Postdepositional

1981)

neces-

resembling

1984).

The c o m b i n a t i o n

situ,

stromatolites

structures

scale are able to p e n e t r a t e

sions

the external

and m o d e r n

Several

(BUICK et al.,

of m i c r o s c o p i c

allow

of ancient

some precautions:

are a b i o g e n i c

of w e a t h e r e d nisms

comparison

however,

types

of stro-

The

in

final

microbial

2. M E T H O D S

Examination insufficient

of thin sections for the r e c o g n i t i o n

the SEM made a decisive BEIN

(1983)

with

different

demonstrate Wenlock multiple kha.

under

of m i c r o f o s s i l s .

breakthrough.

- after an initial levels of a c i d i t y

N. E. Gotland,

division

similar

was

For example,

combination

structures

SEM

are

often

As in other

cases,

KAZMIERCZAK

& KRUM-

of fracturing

and s u b s e q u e n t

that the s t r o m a t o p o r o i d

Stufe,

the light m i c r o s c o p e

and

etching

analysis

- could

of Silurian

rocks

in the

formed by coccoid m i c r o o r g a n i s m s

to the recent

structures

in the G a v i s h

with Sab-

145

The

methods

following comparison weak

other

solution

carbonate minerals

specimens of

the o r i e n t a t i o n

with

and/or

to reduce

in HCI.

chips

of m i c r o s t r u c t u r e s

etched

Pt for SEM studies

of calcite

sectioning

by SEM.

of

Thin

and p o l a r i z i n g

stepwise

and rock

because sections

microscopes,

and s u b s e q u e n t l y

(Steroscan-180,

a a

in inter-

made up of dolomite

thin

obtained

the

We used

for SEM was c h o s e n

under d i s s e c t i n g

fractured,

for

i. e. p r o d u c i n g

species.

reliefs

reliefs

Parallel

of selected

and examined

chips were

carbon

two or more m i n e r a l s

and to m a i n t a i n

insoluble

adopted

etching was preferred,

(1 - 5% HC1)

rocks

and f r a c t u r i n g

were p r e p a r e d selected

by the said authors were

Selective

in relief b e t w e e n

acid

layered

described

studies.

Cambridge

coated Instru-

ment).

The

samples

tion,

studied

come

Ontario/Canada,

Lower J u r a s s i c

from

(i) P r e c a m b r i a n

(2) Permian

Minette

ironstone

Zechstein

of North

of Lorraine.

AND

INTERPRETATION

3. I. P r e c a m b r i a n

3. 1. 1. P r o v e n a n c e

The

Gunflint

Thunder

of

1920;

GOODWIN,

RANDAZZO,

Lake

of rock

formation

Bay about

shore

1956;

including

sins,

probably with 1952;

the

JAMES,

(KNOLL et al.,

1954).

1978)

stromatolitic

comes

and p r e v i o u s

a basal

KNOLL

GARRELS

marine

et al., chert.

were

chert.

Lake

to

towards

the n o r t h e r n

Ontario

(BRODERICK,

et al.,

1973;

MARKUN

&

environmental

set-

within marginal

ba-

to the sea deposited

(TYLER & TWENHO1.9 - 2.0 Ma

chert-taconites, Microfossils

(BARGHOORN 1978).

Ontario

Gunflint

suggested

conditions

shales,

black

buildup

from the basal b l a c k

Schreiber,

authors

Sediments

(3)

work

from the west of

connections

and c o n t a i n

nized

1977;

iron formation,

of

(PZ3),

sedimentary

OF F O S S I L M I C R O S T R U C T U R E S

1966;

shallowest restricted

overlying

in

just west GOVETT,

carbonates

BARGHOORN,

extends

The a b o v e - l i s t e d

tings

FEL,

samples

Poland

forma-

researchers.

180 k m to the east and continues

Superior

1980).

Gunflint

iron

The b a s i c a l l y

o r i g i n of the rocks has b e e n p r o v e d by p r e v i o u s

3. D E S C R I P T I O N

Gunflint

& TYLER,

bedded

have been 1965;

The rock specimen

ago chert

recog-

AWRAMIK

&

studied here

146

Fig. 41. M i c r o s t r u c t u r e s and m i c r o f o s s i l s from the P r e c a m b r i a n G u n f l i n t iron formation, Ontario. A) S t r o m a t o l i t i c m i c r o c o l u m n s form pockets, depressions and cavities containing ooids and oncoids of various shape and size. Scale is 2 mm. B) A b u n d a n t filamentous m i c r o f o s s i l s p r e s e r v e d w i t h i n dark stromatolitic laminae. Scale is 200 pm. C) F i l a m e n t o u s m i c r o f o s s i l s w i t h i n light laminae. Scale is 200 Nm. D) The nucleus of the faint concentric structure shows a m e s h w o r k of filaments (probably intraclast). Left: Oncoid. Scale is 200 pm. E) Outer coating of an ooid showing filaments in c o n c e n t r i c arrangement. Scale is 25 pm. F) Modern microcolumnar build-ups (vertical section) from saltworks (Bretagne) are shown for comparison. Scale is 5 mm.

3. i. 2. M i c r o s t r u c t u r e s

Description: The lower zone of the basal black chert of the G u n f l i n t iron formation shows m i c r o c o l u m n a r stromatolites, ting

dark and l i g h t - c o l o r e d laminae

1979).

(Fig. 41A;

of the microfossils

morphological

compound

maximum pockets, They

similarity

ooids

diameter)

1965;

KNOLL & AWRAMIK,

of various shapes and sizes occur

although a

exists also b e t w e e n the Gunflint (CLOUD,

within

the

(250 Nm

light-colored

close

filaments

to

4 mm

in

and

in

(Fig. 41A).

are associated with intraclasts p r o b a b l y m e d i a t e d by former

of ooids dark

(Fig.

less

1983). Single

laminae

depressions or cavities b e t w e e n the m i c r o c o l u m n s

clusters or fragmentated m i c r o b i a l mats.

the

SEMIKHATOV,

(Figs. 41B, C). The m o r p h o l o -

is similar to cyanobacteria,

and m o d e r n iron b a c t e r i a and

AWRAMIK &

Filamentous m i c r o f o s s i l s are a b u n d a n t w i t h i n the dark and

a b u n d a n t w i t h i n the l i g h t - c o l o r e d laminae gy

built up by alterna-

cell

Intraclasts as well as nuclei

41D) show meshes of filamentous m i c r o f o s s i l s similar to

laminae.

The m a t r i x around the d i f f e r e n t

particle

species

consists of m i c r o c r y s t a l l i n e siliceous and carbonaceous material. Hematitic and pyritic iron m i n e r a l i z a t i o n s also occur. The mineral coatings around the ooids are a l t e r n a t e l y dark (siliceous).

(siliceous/ferruginous)

and light

Filamentous m i c r o f o s s i l s occur also in the outer coatings

and show concentric arrangements

(Fig.

41E).

The ooids are more abun-

dant towards the b o t t o m of the small depressions w h i c h were p r o d u c e d by the m i c r o c o l u m n a r arrangement of the stromatolites.

147

148

Interpretation: present-day

The d e v e l o p m e n t

microbial

most abundant

mats,

in low c o n s t a n t l y

part of the Solar Lake tous

laminated

shelf.

surface mat,

the outer

surface w i t h slime. 5 mm.

where

seawater

hypersalinity surface

of

Mucilage

is r e g u l a t e d

appearance the

pockets for

the

reactive

mat

and their

of masses

specimens

collaboration

of slime

Plattendolomite

A. GASIEWICZ,

(1984)

proposed

underwent

a

slow but p r o g r e s s i v e

a shallow water

rates were h i g h enough to c o m p e n s a t e

model

and

are ideal minerals

for

Gunflint

and even the within the

prerequisites around

highly

and cell aggregates.

of N o r t h P o l a n d

(PZ3)

work

N. Poland were

carbonate

deepening

of

accumu-

observations,

who also c o l l e c t e d

GASIEWICZ

41F).

and intraclasts

and p r e v i o u s

from the Leba Elevation,

outer

(Fig.

settling.

modern

by intraclasts

of rock samples

with

very

oncoids

A mild

the

aggregates

in b e t w e e n

of a u t h i g e n i c

maintained

Zechstein

3. 2. I. P r o v e n a n c e

ooids,

In the light of

localized precipitation decay centers,

3. 2. P e r m i a n

Rock

due to g r a v i t a t i o n a l

and compound

fillings

covers

floating

and pockets

from 1 mm

in salt works

also in the surface water

the cavities

and cavities.

ranges

interspaces

and

filamen-

cover the mats. which

in

are

and coated at

features

may be the most a p p r o p r i a t e

buildup,

of single

pockets

in seawater

occur

the p i n n a c l e s

pinnacle

of slime,

and a c c u m u l a t e s

diluted

cyanobacteria

from the

extension

to c o n s t a n t l y

mats

such as in the lower

emerging

these

in various

Pinnacle

filled with oxygen

Their vertical

the p r o d u c t i o n

late in b e t w e e n

The

The pinnacles,

favors

partially

microcolumnar

basins,

R e c e n t l y we have o b s e r v e d

the p i n n a c l e s

unicellular

submerged

supply

is k n o w n

to as pinnacles.

are often

to

about

of m i c r o c o l u m n s

referred

where

studied

the

in

specimens.

platform

which

sedimentation

for the rate of transgression.

3. 2. 2. M i c r o s t r u c t u r e s

Description: N. Poland It al.,

The P l a t t e n d o l o m i t e

represents

is c h a r a c t e r i z e d 1985).

The

sequence

of the Leba E l e v a t i o n

the p e r i p h e r a l

part of the southern

by dolomites,

limestones

lower and upper parts

and a n h y d r i t e

of the sequence

of

Permian basin.

bear

(PERYT

et

regularly

149

laminated al.,

structures

1981).

uniform tion.

The

character The

record

rock

cooperation

specimens

with

middle

tinuous thick)

(Fig.

noid-fenestral TOSCHEK

also

laminae

and more

to these

open

open

in

lamina-

studied

in

preparation). under

analysis

described

structures anhydrite

nodules

and surrounds

MULLER-JUNGBLUTH

the t u b u l a r

&

is a r r a n g e d

in

ostracodes

are

completely

The nodule

the nodules

the The

show the lami-

bivalved

surface

2 cm

amounts.

and are e m b e d d e d

cauliflower

(up to

filled by a n h y d r i t e

the voids

of a

wavy, discon-

is dolomicrite,

clearly

by

a

commonly

extended

structures

surrounding

displays

varying

structures

in particular.

and resembles

oriented

in

thin,

At some places,

Nodular

filled w i t h

In close p r o x i m i t y trically

patterns.

light

rounded

contain

fabric-type

(Fig. 42B).

al.,

sequence

and calcite

The d o l o m i c r i t e

worm-like

spaced

et

et

relatively

and m i c r o f o s s i l

is c u r r e n t l y

50 to 80 % of the m a t e r i a l

layers

embedded

widely

1 mm thick)

interlaminar

tubular,

are

(about

LF-A

(1969).

shape

sections

of a l t e r n a t i n g

is a n h y d r i t e

These

a

section w h i c h we

(GASIEWICZ

lamination

laminae.

wider-spaced 42A).

gularly

of this m i d d l e

the fabrics

zone of the P l a t t e n d o l o m i t e

fraction

sensu B U I C K

shows

later.

laminae

light

remaining light,

deals w i t h

A. G a s i e w i c z

oriented

dark

12 m thick,

w h i c h bear poor or i n d i s t i n c t

from the lower and upper

horizontally

or s t r o m a t o l o i d

about

description

and will be p r e s e n t e d

The

zone,

w i t h deposits

following

of

Material

(stromatolite-like

middle

different

in

the

surface

structure

more

is irre-

(Fig. 42C).

dolomicrite

is

as a d i s t i n c t

concen-

halo

(Fig.

to b i o l a m i n o i d

facies

42C).

Interpretation: type mite

deposits

that the G a v i s h

topography

sediments

other e x a m p l e s tures

sabkha

1974;

GOLUBIC

1979;

MARGULIS

(LOGAN,

1961;

GOLUBIC

laminae

may

document between

deposits

Sabkha

of

environment

demonstrated

possessing

communities

environments

& PARK,

1973;

et al.,

exist,

& HOFMANN, microbial

KINSMAN

1980) 1976; mats

Plattendoloin Fig.

as a model.

is not meant here but

e. g. at the Persian Gulf

(JAVOR,

sandwiched

sequence

Sabkha may be used here

to a l l o w m i c r o b i a l

of arid coastal

can be found,

AWRAMIK,

of the n o d u l a r

to the m i d d l e

of the Gavish

type of a coastal

saturated

Sabkha

and m o d e r n b i o l a m i n a t e d

is so striking specific the

The s i m i l a r i t y

found in the G a v i s h

water-

thrive.

Several

where

& PARK,

of the

Lh-type

struc-

GOLUBIC

&

1976),

in M e x i c o

Bay,

Australia

The

faint dark

1984).

extended

similar 1973;

and the Shark

the much more v e r t i c a l l y

The

rather

sufficient

to

(PURSER,

BAULD,

42

which

occurred

Lv-laminae

(Figs.

150

MODERN

ANCIENT

42A/42D), structures

and the worm-shaped tubular dolomicrite may represent of vertically or diagonally oriented filamentous

(Figs. 42B/42E).

Evaporative

pumping

may have brought about

ghost

organisms a

pre-

151

Fig. 42. S i m i l a r i t y of ancient and m o d e r n s a b k h a - t y p e microstructures (A - C: Permian Z e c h s t e i n P l a t t e n d o l o m i t e North Poland; D - F: Gavish Sabkha ) . A) I n t e r l a y e r e d faint dark and e x t e n d e d light laminae with open spaces oriented parallel to the dark laminae (laminoid fenestral LF-A fabric-type). Scale is 1 mm. B) Tubular, worm-like p a t t e r n s of d o l o m i c r i t e s u r r o u n d i n g the voids. Some b i v a l v e d o s t r a c o d e shells being visible. Scale is 1 mm. C) A n h y d r i t e nodule s u r r o u n d e d by the w o r m - l i k e dolomicrite. Scale is 1 mm. D) M o d e r n b i o l a m i n o i d structures of the G a v i s h Sabkha (similar to A). Scale is 1 mm. E) Tubular, w o r m - l i k e p a t t e r n s in m o d e r n L v - l a m i n a e consist of filamentous cyanobacteria, coated with m g - c a l c i t e (similar to B). Scale is 1 mm. F) C a u l i f l o w e r - s h a p e d nodule, m a d e - u p by P l e u r o c a p s a l e a n cyanobacteria, s u r r o u n d e d by tubular c a l c i f i e d filaments (Gavish Sabkha; similar to C). Scale is 2 mm.

enrichment of

of Mg over

diagenesis

to the l o c a l i z e d

Aggregate-forming Pleurocapsalean kha,

may

microorganisms which

The

about

anhydrite

or late d i a g e n e t i c

proposed

that

intertidal framed

the

The o o l i t i c (Toarcian of

- Aalenian,

stratigraphy,

THEIN, sitional

1975;

more

regular

ironstone

SIEHL

nodules

& THEIN, beneath

to

early

(after

In conclusion, developed

stromatolites

Sab(Figs.

it is in

an

It may have

of the

strati-

laminations.

and p r e v i o u s

Lorraine)

1978).

cells.

like the m o d e r n

environment.

ironstone,

and

decaying

in the G a r i s h

Lorraine

work

of the n o r t h w e s t e r n

Luxembourg,

stages

of the P l a t t e n d o l o m i t e

coastal

m a r g i n where

sedimentology

environment

of

in early

fission,

part of the PZ3 sequence

of rock samples

Minette

fraction

(replacement).

hypersaline

3. 3. Lower J u r a s s i c

3. 3. i. P r o v e n a n c e

already

filling may be c o r r e l a t e d

platform

form type have d e v e l o p e d

the nodules

processes

middle

to s u p r a t i d a l

an adjacent

organic

with m u l t i p l e

form the c a u l i f l o w e r

have brought

42C/42F). death)

c a l c i u m w h i c h was b o u n d

part

is well

geochemistry

The above authors

the lower w a t e r

of Paris

described

in terms

(BUBENICEK, suggested

line of a wide

Basin

1971; a depo-

shelf area.

152

Fig. 43. Lower J u r a s s i c ironstone, France: Microstructures. A) An extended layer w i t h ooids and oncoids (bottom) grades into a w a v y laminated stromatolitic sequence of light and dark layers (top). Scale is 500 ~m. B) The ooid and o n c o i d - b e a r i n g layer shows some elongated fragments o r i e n t e d parallel to the laminated sequence in A). Scale is 1 man. C) D i s p e r s e d and clustered arrangements of coated grains, the clustered being arranged in a lensoid pattern. Scale is 1 mm. D) S E M - p h o t o g r a p h y of a coated grain surrounded by a m e s h w o r k of filamentous microfossils. Scale is I00 pm. E) Interior of oncoids showing m e s h w o r k s of filamentous microfossils similar to those of the surrounding matrix. Scale is i00 pm. F) C l o s e - u p of the interior showing a branched, fungal-like m o r p h o l o g y of the microfossils. Scale is 3 ~m.

The oolites were thought to be d e t r i t i c p a r t i c l e s derived from tic

soils.

The rock samples studied here were p r o v i d e d by

lateri-

K. DAHANA-

YAKE.

3. 3. 2. M i c r o s t r u c t u r e s

Description: chamosite, calcite

siderite,

and

succession, nating

Ooids and oncoids of the Minette ironstones consist of

limonite

magnetite

and hematite.

The groundmass

w i t h some clay m i n e r a l s

admixed.

In

the ooid and oncoid bearing layers grade into wavy,

black

and light laminae

(Fig. 43A).

parallel

oncoids very

to the laminated sequence above

are i r r e g u l a r l y d i s t r i b u t e d w i t h i n the lower

close together and show a lensoid a r r a n g e m e n t

are d i s p e r s e d w i t h i n the w i d e l y spaced, tous

(Fig. 43B).

grains

and

Some

lie

zone.

(Fig. 43C),

etched,

also

of

(Fig. 43D). shows

The interior of the

oriented

grains,

when

(Fig. 43F)

the

deeply

filaments in abundance which are very similar

the m i c r o f o s s i l s characterizes them as

microorganisms laminae)

others

l i g h t - c o l o r e d matrix. F i l a m e n -

those of the surrounding matrix and the laminae logy

orien-

the elongated fragments and the groundmass w h i c h carries

coated

not

Oooids

m i c r o f o s s i l s occur in abundance w i t h i n the h o r i z o n t a l l y

laminae,

of

alter-

The lower zone does

show these regular laminations but contains e l o n g a t e d fragments ted

is

vertical

to

(Fig. 43E). The morphobranched

w h i c h have formed mycelia

(more

fungal-like condensed

and looser meshes of hyphae.

Interprgtation:

The r e p e t i t i o n of m i c r o f o s s i l s of the same taxonomi-

cal nature w i t h i n d i f f e r e n t fabrics and the c o m b i n a t i o n of h o r i z o n t a l l y

153

oriented coated mat

laminae

grains

or

of b o t h

environment.

laminae oncoid

fragments and

It is r e a s o n a b l e

ooid

and

concentrically

characters

to assume

indicate

that the coated

laminated a

microbial

grains have

154

been

formed

built

the m i c r o b i a l

metals same and

in situ and a c t u a l l y mats.

a n d to e n r i c h

environment

iron

differentiation

may

created

are k n o w n

& SWAIN, depend,

redox

which

selective states

w h i c h have

catalysts

even within

1979). The p r e c i p i t a t i o n however,

by the c o m p l e x e l y

pathways

microorganisms

to be

in d i f f e r e n t

(TRUDINGER

ferrugenous

dissimilative

Fungi

them

by the same

usually

on

of ferric

a microenvironmental

interacting

occur

of the

assimilative

in o r g a n i c a l l y

and

enriched

sediments.

Fungal amounts

mats

of organic

conditions The

may

are

gested with

of

is r a r e

brackish

matter

water

reduced

authigenic

ironstone

by rich vegetation. GYGI

With

(1981)

deep open m a r i n e

and

salinity

iron

and

suggest respect

the

to U p p e r

interpreted

shelf e n v i r o n m e n t

the

large

is reduced.

These

environment

to a

Bubenicek

sug-

associated

was

surrounded

ironstones

depositional

surrounded

points

mudstones

Jurassic

lagoons.

(e. g. s i d e r i t e ) ,

ironstones,

Bituminous

that

if

additionally

Minette

region.

only

black-water

minerals

sediments,

For the

tidal-flat

environments

in estuaries

marine

environment.

a coastal

Jura,

marine

are a v a i l a b l e

in n o r m a l

the o o l i t i c

Swiss

in

found for e x a m p l e

abundance

which

flourish

of t h e

environment

by tropical

as

a

forests.

3. 4. S u m m a r y and c o n c l u s i o n s

This

chapter

microbially stromatolite origin sed

deals

mediated

with

environments

with

special

been

to o o i d s

iron f o r m a t i o n

of

comparative

Results

used

The q u e s t i o n

reference

Gunflint

results

in rocks.

have

of m i c r o s t r u c t u r e s .

Precambrian

some

structures

in p a r t

Lower

studies

studies to

of b i o g e n i c i t y

occurring

and

of

interpret has

in r o c k

Jurassic

on

in m o d e r n

been

the

stres-

specimens

ironstone,

of Lor-

raine.

1. The

following

ooids

-

and oncoids

Microfossils nations

-

close wavy

signatures

(Gunflint

iron

from the s u r r o u n d i n g

biogenicity formation,

and in-situ

Lorraine

mat e n v i r o n m e n t

genesis

of

ironstone):

preserved

in lami-

of ooids,

associations

of o o i d s

and m i c r o c o l u m n a r

as in the l a m i n a t i o n s -

indicate

and light

morphologies

and dark laminae

and bear

the

same

which

show

microfossils

of the ooids,

also close a s s o c i a t i o n s

of ooids,

intraclasts

and l a m i n a

fragments,

155

-

abundant

enrichment

(intralaminar microbial -

the

of o o i d s

within

unconformities

cavities,

typically

pockets

occurring

and lenses

in a b u n d a n c e

in

mats),

same

mineral

species

within

laminae

of o o i d s

and surrounding

matrices.

2. The e x a m p l e s that

of G u n f l i n t

similar

microstructures

of d i f f e r e n t -

-

iron f o r m a t i o n

microbial

In t h e c a s e of L o w e r

and

Jurassic

The f i l a m e n t o u s

microfossils

although

the G u n f l i n t sion, from

filaments

form,

see KNOLL

impact

(with

cyanobacteria

the

the nodular Permian

ghost

the

teria

of

such as m i c r o b i a l

precipitation

filaments

ganotrophic

of

which

bacteria.

photosynthetic

carbon

sterile

experiments

brought

about

ments

degradation also

calcite

and

natural

habitats

indicate BATHURST this

that

in t h e

Mg

(1971)

phenomenon

tain organic ronmental

of

mats.

added

products

microbial

is inferred

tubular

in o r g a n i c 1979a)

of m a r i n e

chemoor-

have

fixation

cyanobacterial

deposits. bacteria

of c a r b o n a t e s

organic

medium.

be

nor have

the i m p o r t a n -

matter.

between

mats

and

to the

significance

biomass.

environment

significance

Gavish

in

experiments

bacterial

malate,

the

experi% in the

observations

of t h e

temperature,

in

mole

in l a b o r a t o r y

bound

seen

These

Mg

Furthermore,

s u c h as f a t t y a c i d s , can

mats

organisms)

indicate

correlation

salinity,

all

that neither

in the p r e c i p i t a t i o n

cyanobacterial

to t h e

shown

to kill

The results

rich

obser-

cyanobac-

experiments

samples

have

sterilized

isolates

of

of t h e

examinations

(1974 a, b,

alongside

con-

dolomicrite,

and the mineralogy

precipitation

to

preferentially

significance

inferences

dioxide

of m i c r o b i a l

(e. g.

discus-

individual

KRUMBEIN

carbonates

applied

refers

(for further

environments,

worm-shaped

carbonate

a positive

is

between

frame-builders)

of

(autoclaved

revealed

also

Control

carbonate

docu-

to be c y a n o b a c t e -

exists

physiological

sabkha

Numerous

were

ce of c h e m o o r g a n o t r o p h i c during

considered

structures

sequence.

fungi have been

1983).

as m a i n

structures

to an u n d e r s t a n d i n g

sediments

show

participation

iron f o r m a t i o n

iron b a c t e r i a

on m o d e r n

and biolaminoid

Zechstein

under

similarity

of d r a w i n g

& AWRAMIK,

of s t u d i e s

sidering

often

and m o d e r n

a l s o of the l i m i t a t i o n s

light

ved

type,

morphological

3. In t h e

led

in the P r e c a m b r i a n

different

a close

form

ironstone/Lorraine,

frame builders.

ria,

minerals

ironstones

phyla.

the p r e d o m i n a n t

ment a completely

and Lorraine

of

in cer-

NH4). T h e e n v i Sabkha,

where

156

positive

correlations

salinity,

productivity trophs

of cyanobacterial

finally

magnesium

between the inclination of the terrane and (i)

(2) M g - e n r i c h m e n t

of the water,

(3) layer t h i c k n e s s

and

mats and (4) activity of chemoorgano-

led to the a c c u m u l a t i o n

calcite within stromatolitic

of large a m o u n t s

growth structures.

of h i g h -

157

4. PATHWAYS

INVOLVED IN M I C R O B I A L SEDIMENT ACCRETION: A COMPLEMENTARY SUMMARY

The

r e c o v e r i n g of w e l l - p r e s e r v e d b i o g e n i c structures

rocks

of

early P r o t e r o z o i c age,

procaryotes, bolic

the r e a s o n i n g that

in s e d i m e n t a r y

the

kingdom

of

solely r e i g n i n g at that time, h a d a l r e a d y d e v e l o p e d meta-

traits including a n o x y g e n i c and o x y g e n i c p h o t o s y n t h e s i s w h i c h we

know

from p r e s e n t - d a y forms,

systems m e d i a t e d lation

the c o n c l u s i o n that the early

microbial

o x i d a t i o n p r o c e s s e s w h i c h finally led to the

of free oxygen into the atmosphere,

accumu-

all this has r e c e i v e d

in-

c r e a s i n g a t t e n t i o n in the a u t e c o l o g y of p r e s e n t - d a y microorganisms.

In the

turn,

a need was r e c o g n i z e d for s e d i m e n t o l o g i s t s to

diversity

sediment

and

accretion

f l e x i b i l i t y of m i c r o b i a l

pathways

and s t r a t a - b o u n d ore formation

in

understand biological

(MARGULIS &

STOLZ,

1983). W i t h a view to c o m p l e t i n g our records some of these aspects will be b r i e f l y summarized.

Basically,

i. an

m i c r o b e s i n t e r a c t i n g w i t h a sedimentary e n v i r o n m e n t use

energy source w h i c h m a i n t a i n s a steady state e q u i l i b r i u m

(ther-

m o d y n a m i c s t a b i l i z a t i o n against entropy), 2. an

e l e c t r o n donor

through

(reducing power) w h i c h regulates the e n e r g y

the cell and p r o v i d e s reduced carbon compounds for

flow

metabo-

lic, m o r p h o l o g i c and m o t i l i t y purposes, 3. nutrients

(carbon,

nitrogen,

p h o s p h o r o u s and other compounds),

cru-

cial to b u i l d the n e c e s s a r y cell compounds, 4. a t e r m i n a l e l e c t r o n a c c e p t o r for energy c o n v e r s i o n s and final of the o x i d a t i o n - r e d u c t i o n reactions

(KRUMBEIN,

The k i n g d o m s of M o n e r a and P r o t o c t i s t a

1983).

(SCHWARTZ &

MARGULIS,

contain various d i f f e r e n t p a t h w a y s to recover these sources. species

which

energy,

some recover e l e c t r o n donors from inorganic sources

ple water,

tion.

bound

(for exam-

H2S) and others from organic sources. The carbon source can (Table

ii).

Some

p e r f o r m aerobic and others a n a e r o b i c r e s p i r a t i o n and fermentaM o r e than that,

several groups including c y a n o b a c t e r i a are able

to c a r r y out a l t e r n a t i v e l y p h o t o s y n t h e s i s and chemosynthesis, from

1982)

There are

use light energy and others w h i c h use c h e m i c a l l y

be CO 2 and in a n o t h e r case it is an organic compound species

steps

inorganic

to organic e l e c t r o n donors and carbon

to switch

sources

(Table

158

ii).

This

metabolic flexibility is an advantage in particular

environment which is sometimes deprived of sufficient light,

in

an

and where

poisoning by hydrogen sulfide or oxygen occurs. According to this great variety and flexibility of microbial metabolic

pathways there is nearly no geochemical medium on

table to microorganisms. or

Consequently,

Earth

unaccep-

mineralization processes induced

controlled by microorganisms are extremely heterogenous

(LOWENSTAM,

1986).

TABLE ii. Microbial metabolic types forming biolaminated deposits (the processes of recovering energy, reducing power and nutrients are given the term "troph") Energy source

Electron donor

Carbon source

Trophic types and examples

Light

Inorganic

Inorganic

Light

Organic

Inorganic

Light

Inorganic

Inorganic

Light

Inorganic

Inorganic

Light

Organic

Organic

Photo-lithoautotroph. Cyanobacteria Photo-organoautotroph . Chloroflexaceae Photo-lithoautotroph. Chromatiaceae Photo-lithoautotroph Chlorobiaceae Photo-organoheterotroph

Bond energy of inorganic compounds such as Fe 2+, S 2-, S o, S2032-

Inorganic

Inorganic

Chemo-lithoautotroph Iron and . sulfur bacteria

Bond energy of organic compounds

Organic

Organic

Chemo-organoheterotroph Sulfate-reducing bacteria + Fungi

Rhodospirilliaceae*

* Switching from one source to another possible

Many

different metabolic types are known to form mats

(Table

ll).

In this volume, we have mentioned already the following types: cyanobacteria Gavish

Sabkha,

(photolithotrophs), the Solar Lake,

frame-builders

of mats

the temperate humid

systems and possibly in the PZ3-sequence,

in

the

siliciclastic

159

-

iron b a c t e r i a iron

(chemolithotrophs),

p o s s i b l y involved in the G u n f l i n t

formation. A l s o m i c r o a e r o p h i l i c

sulfur

bacteria,

niched

for

example into g r a d i e n t s of deep sea hot vents, belong to this group, -

a n a e r o b i c filamentous s u l f u r - b a c t e r i a of the

Chloroflexus-type (pho-

to-organotrophs), -

fungi

(chemo-organotrophs),

s t r o m a t o l i t e frame b u i l d e r s

in the case

of L o r r a i n e ironstone.

C h e m o l i t h o t r o p h s obtain energy via direct o x i d a t i o n of reduced inorganic compounds such as -

S 2-,

S O, S2032-

geochemical product

(e. g.

Thiotrix, Thiobacillus, Beggiatoa). The bio-

p r o d u c t s are sulfate and elemental sulfur.

a b u n d a n c e in lakes,

organisms

streams and bogs of high

It

further oxidized;

Leptothrix, Crenoth~ix). I r o n - o x i d i z i n g b a c t e r i a

Fe 2+ (e. g. in

latter

is a l t e r n a t i v e l y d e p o s i t e d inside or outside the cells.

represents an i n t e r m e d i a t e p r o d u c t w h i c h becomes -

The

latitudes.

create a reducing e n v i r o n m e n t in subsoils and

occur These

subsurface

sediments w h i c h facilitates the m i g r a t i o n of ferrous iron. Electront r a n s f e r reactions,

c a t a l y z e d by these organisms,

lead to changes in

the o x i d a t i o n state of iron in the e x t r a c e l l u l a r environment: Fe 2+ e- ÷ Fe 3+. minerals. and

Biogeochemical A

p r o d u c t s are ferric oxide and

hydroxide

c o n n e c t i o n b e t w e e n the d i s t r i b u t i o n of these

bacteria

the formation of f e r r o m a n g a n e s e nodules w i t h i n d y s t r o p h i c lakes

and bogs is also suggested.

In the early b i o s p h e r e ferrous iron may

have served a b u n d a n t l y as electron donor, hereby

producing

sulfuretum

the catalyzing

organisms

a chemical e n v i r o n m e n t w i t h iron e q u i v a l e n t to

(HARTMAN,

1984).

It

is s u g g e s t e d that the

huge

deposits of the P r e c a m b r i a n era, the b a n d e d iron formations w h i c h contain most of the world's iron ore, nisms DEAN,

a

iron

(BIF's),

g e n e r a t e d by m i c r o o r g a -

t r a n s f o r m i n g ferrous iron into the ferric state

(LUNDGREN

&

1979).

R e q u i r e m e n t s of fungi compounds.

(and c h e m o - o r g a n o t r o p h i c bacteria)

Many fungi excrete substances,

their

external

plexes

for t r a n s p o r t into the cells.

called

e n v i r o n m e n t to t r a n s f o r m Fe3+-ions

are organic

siderophores, into

into

chelate-com-

A l s o a c t i n o m y c e t e s and m y x o b a c t e -

ria possess this instrument.

The

versatility

subsequent

of m e t a b o l i c types involved in the

formation

and

d i v e r s i f i c a t i o n of b i o l a m i n a t e d deposits is well d o c u m e n t e d

in terms of s t r o m a t o l i t i c mineral assemblages w h i c h include

160

H e a v y metal stromatolites

(oxidic)

H e a v y metal stromatolites

(sulfidic)

Iron s t r o m a t o l i t e s C a r b o n a t e stromatolites E v a p o r i t i c stromatolites including Sabkha-type laminites Phosphate stromatolites O r g a n i c stromatolites

(i.e. oil shales,

oil, gas deposits)

S i l i c i c l a s t i c stromatolites

A m i c r o b i a l mat as

a

(the a c t u a l i s t i c model of a stromatolite)

together by trophic chains the

considered

functional a s s o c i a t i o n of d i f f e r e n t p o p u l a t i o n s w h i c h (syntrophism),

are

one species are the b e n e f i t for the others,

raises i m m e n s e l y

g e o c h e m i c a l p o t e n t i a l of a m i c r o b i a l l y colonized substratum. ple,

chemotrophic anaerobic sulfate-reducing bacteria

b~io)

occur

bond

where m e t a b o l i c products

the

For exam-

Desulfoui-

(e. g.

in a b u n d a n c e in the black anaerobic strata

of

of

microbial

mats. T h e y produce quantities of h y d r o g e n sulfide w h i c h are required by c h e m o l i t h o t r o p h i c bacteria. to

H y d r o g e n sulfide on the other hand is known

react w i t h soluble metals to p r o d u c e insoluble metal sulfides

FRO, or

1974). from

I r o n - r e d u c i n g b a c t e r i a use ferric ion from ferric h y d r o x i d e

ferric

oxides and also m a n g a n e s e from MnO 2

a c c e p t o r during a n a e r o b i c respiration.

as

an

(NEALSON,

1983a).

Important k n o w l e d g e of d i f f e r e n t kinds of p h y s i o l o g i c a l of

electron

Thus they form large amounts of

soluble ferrous ions in a n a e r o b i c e n v i r o n m e n t s

mechanisms

(REN-

m i c r o b e s is d e r i v e d from technical

assays.

biotransfer A

growing

interest

is d i r e c t e d to the value of microbes being capable of mineral

transfer

and metal accumulation.

this in

field involve m i c r o o r g a n i s m s mineral concentrate leaching,

heavy

in b i o h y d r o m e t a l l u r g i c a l

efforts

valuable

to

in

processes,

in the clearance of w a s t e water from

metals and other projects of engineering of m i c r o o r g a n i s m s

for example ROSSI & TORMA, is

Important t e c h n o l o g i c a l

(see

1983). The p r o g r e s s in these fields in turn

u n d e r s t a n d the geological potential

of

microbes

in

a d i s t i n c t i o n should

be

nature. In

terms

of b i o m i n e r a l i z a t i o n processes,

made b e t w e e n organisms w h i c h m i n e r a l i z e under controlled conditions and others w h i c h induce m i n e r a l i z a t i o n WEINER,

1984)o

importance

of

Biologically enzymes,

(LOWENSTAM,

1981,

1986; L O W E N S T A M &

c o n t r o l l e d m i n e r a l i z a t i o n indicates

but also proteins,

carbohydrates

and

the other

161

materials that can bind,

concentrate and thus enhance the oxidation of

metal ions such as iron or manganese (NEALSON, 1983a, b).

Mat-forming and mat-colonizing microbes may mainly account for logically

induced

bio-

mineralization processes which are well-defined

by

interactions between metabolite products, cations and anions present in the external environment. Thus the mineral types produced in a "pseudoinorganic manner" (LOWENSTAM, 1986) may reflect much of the environment in which they assembled.

For example,

mg-calcite precipitation in the

Gavish Sabkha is the result of high-rate primary production within multilaminated carbon, metal

mats,

generating

combined

with bacterial break-down

organic

oxidants and reductants and their interaction with

ions supplied by seawater run-off or

example

of

the

evaporation

pumping.

The

shows further that the relationship of carbonate to sulfate is

largely regulated by the microbial activity.

Comparative sterile shown

experiments with isolates of living microbial mats

and

organic matter (incubated to kill all living organisms) that

precipitation occurs especially well in

living microbial communities (KRUMBEIN, GROSOVSKY

(1983),

gold chloride, mechanisms

performing

1974a,

the

of

b, 1979a). DEXTER-DYER

similar experiments with a solution

concluded that many cyanobacterial communities

for

have

presence

the active precipitation or flocculation

of

of

possess metallic

gold. These experiments may shed light on live microbial involvement in the deposition of gold in the 2.4 billion-year-old Witwatersrand system in South Africa.

Weathering of original vulcanic metal deposits surrounding the sedimentary

basins where microbial mats thrive is very important in cation

supply.

Other important sources of cations and anions brought into the

vicinity

of

trapping

and catalyzing microbial mats

are

hot

vents

(sulfides) and oceanographic upwelling systems both in higher and lower latitudes (phosphorites). rites be

Precambrian-Cambrian stromatolitic

have been reported by CHAURASIA (1984),

which are considered to

the characteristic of a palaeoceanographic cold

system.

Seaward

phospho-

glacial

upwelling

winds support very often the penetration of upwelling

waters rich in phosphorous and other compounds (e. g.

opal from diatom

tests) into shallow coastal lagoons. The lagoon's surface water becomes transported in offshore direction and replaced by the rich upwelling waters (REINECK & SINGH, phosphorites

1980).

cold.

nutrient-

Tertiary stromatolitic

formed by fungi have been reported by DAHANAYAKE &

KRUM-

162

BEIN

(1985).

While p h o s p h o r i t e s m e d i a t e d by fungal s t r o m a t o l i t e s

have their base in o r g a n i c - r i c h upwelling water, iron

precipitation

formed

in

such

may

fungal mats catalyzing

as in the L o r r a i n e ironstone may

w a r m shallow coastal systems supplied with

have

been

nutrients

from

tropical rain forests.

Plant communities flores),

animal

(typical xerophytes,

communities

rain forests, peat and swamp

(thickness of shells and other

related to the solubility of carbonates in seawater), (evaporites, opal

p s e u d o m o r p h o s e s of soluble salts,

and other mineral associations)

phenomena

desert p h e n o m e n a

carbonates,

and the often w i d e l y

g y p s u m and distributed

"red beds" are r e p e a t e d l y referred to in literature on p a l e o c l i m a t o l o g y as useful tools. ties

On the subject of stromatolites or m i c r o b i a l communi-

as p a l e o c l i m a t o l o g i c a l

indicators there is,

on the

other

hand,

little discussion.

As a first step,

the following c l i m a t o l o g i c a l

(paleoclimatological)

model is p r o p o s e d basing on individual types of s t r o m a t o l i t e s and their a s s o c i a t e d b i o m i n e r a l assemblages:

A) Ferriferous tropical

(rainforest-mangrove related)

B) Phosphatic sub-tropical C) C a r b o n a t e sub-tropical D) S i l i c i c l a s t i c temperate E) Ferric boreal F) Ferrous boreal

Many bial

(upwelling related) (arid coast related) (with iron s u l f i d e / o x i d e sandwiching)

(lacustrine bog ores w i t h vivianite) (lacustrine c a r b o n a t e / s u l f i d e

questions are still open on the chemical capacities of

communities

m i c r o b i a l mats,

(microbial mats),

and

recycled

questions,

micro-

the sedimentary products of

their d i s t r i b u t i o n in space and time

and through the geological periods) up

sandwiching)

such

(around the globe

and the q u a n t i t y of chemicals piled

during periods of time.

Finding

answers

on

these

we will e v e n t u a l l y be able to piece together the picture of

p a l e o c l i m a t e s and climatic belts

from the occurrence of m a j o r types

s t r o m a t o l i t e s as they are p r o d u c e d by major synergetic,

of

ecological and

climatic c r o s s - r e l a t i o n s and we will be able to set them into an actualistic

and

framework. even

fossil

strata framework as well as

into

a

geographical

Further studies will help to decipher reaction changes

traditions that may be derived from the p r i m o r d i a l Earth or

the evolution of the b i o p l a n e t ' s dynamics.

and from

163

Geochemistry chemical dingly,

is

matter

which

voirs

is c o n c e r n e d

elements

and their

geochemistry

(air,

spread

and i n t e r t w i n e d

lithosphere),

lithosphere.

plinary

work

geological

fields

potential

attention

in concepts is r e g u l a t e d 1982;

of

which

MARGULIS

of microbes

1983;

& MARGULIS,

have

left

to u n d e r s t a n d increase

and the the

of the exoge-

1974;

1986a).

is the

in interdisci-

and may finally

KRUMBEIN,

It and

geomicrobiology

that the g e o c h e m i s t r y

(LOVELOCK

& STOLZ,

hydro-

information

in n a t u r e

assert

by life

- atmosphere,

The progress

biogeochemistry,

about more

organic reser-

the h y d r o s p h e r e

mechanisms

reservoirs.

of m i c r o b e s

nic s y s t e m MARGULIS,

biotransfer

will b r i n g

terms

dead

of

accor-

the other m a i n

is not such a volume.

the atmosphere,

in all these

in the

paleomicrobiology

Unlike

or - in other

with

and d i s t r i b u t i o n

Biogeochemistry,

by the living and

the b i o s p h e r e

Physiological

fingerprints

on Earth.

the biosphere.

ocean and rocks

and

the c o n c e n t r a t i o n

controlled

constitutes

sphere

their

with

isotopes

SCHWARTZ

&

REFERENCES

ADAMS,

J. E. & FRENZEL,

H. N.

N e w M e x i c o . - J. Geol. AHARON,

(1950): Capitan b a r r i e r e reef, Texas and

5_88, 289-312.

P., KOLODNY, Y. & SASS,

tion in the Solar Lake,

E.

(1977): Recent hot brine dolomitiza-

Gulf of Elat,

Isotopic,

chemical and minera-

logical study.- J. Geol. 85, 27-48. AITKEN,

J. D. (1967): C l a s s i f i c a t i o n and e n v i r o n m e n t a l significance of

cryptalgal Cambrian Petrol.

limestones and

and dolomites w i t h

Ordovician

of

illustrations

Southwestern

from

A l b e r t a . - J.

the

Sediment.

3_~7, 1163-1178.

AIZENSHTAT, carbon

Z., and

LIPINER, sulfur

(Sinai).- In: (eds.):

G.

& COHEN,

Y.

(1984): B i o g e o c h e m i s t r y of

cycle in the m i c r o b i a l mats of the

COHEN,

Y.,

M i c r o b i a l Mats:

CASTENHOLZ,

R.

Stromatolites,

W.

Solar

& HALVORSON,

281-312,

498 p.

Lake H.O.

(Alan Liss

Publ., N e w York). AWRAMIK,

S.

M.

(1971):

P r e c a m b r i a n c o l u m n a r stromatolite diversity:

R e f l e c t i o n of m e t a z o a n a p p e a r a n c e . - Science 174, 825-827. AWRAMIK,

S.

M.

(1981): The P r e - P h a n e r o z o i c b i o s p h e r e - three billion

years of crisis and o p p o r t u n i t i e s . -

In: NITECKI,

crisis in ecological and e v o l u t i o n a r y time,

M. H.

83-102

(ed.): Biotic

(Academic Press,

London). AWRAMIK,

S.

M.

& BARGHOORN,

E. S. (1977): The G u n f l i n t m i c r o b i o t a . -

P r e c a m b r i a n R e s e a r c h 5, 121-142. AWRAMIK,

S.

M., GEBELEIN,

C. D. & CLOUD,

P.

(1978): B i o g e o l o g i c rela-

tionships

of ancient s t r o m a t o l i t e s and m o d e r n

BEIN,

W.

E.

logy,

vol.

analogs.-

In:

KRUM-

(ed.): E n v i r o n m e n t a l b i o g e o c h e m i s t r y and g e o m i c r o b i o ~,

165-178

(Ann Arbor Science Publ.

Inc.,

Ann Arbor,

Michigan). AWRAMIK,

S.

M.,

processes (ed.):

MARGULIS,

L. & BARGHOORN,

in the f o r m a t i o n of

Developments

S.

M.

morphology, intergrading

& SEMIKHATOV,

(1976): E v o l u t i o n a r y

s t r o m a t o l i t e s . - In:

in Sedimentology,

S c i e n t i f i c P u b l i s h i n g Company, AWRAMIK,

E. S.

vol.

20,

WALTER, 149-162

M.

R.

(Elsevier

Amsterdam). M. A.

microstructure,

and

stromatolites

from

(1979): The r e l a t i o n s h i p b e t w e e n microbiota the

in

Gunflint

three

vertically

Iron

Formation.-

(1965): M i c r o o r g a n i s m s

from the Gun-

C a n a d i a n Journal of Earth Sciences i_66, 484-495. BARGHOORN,

E.

S.

& TYLER,

S. A.

flint Chert.- Science 147, 563-577.

166

BATHURST,

R.

G.

C.

velopments

in

Sedimentology

(1971): Carbonate sediments and d i a g e n e s i s . - De12

(Elsevier

Scientific

Publishing

Company, Amsterdam). BAULD,

J.

Bay,

(1984): M i c r o b i a l mat in marginal marine environments;

Western

COHEN, Mats: BERNER,

Y.,

Australia CASTENHOLZ,

Stromatolites, R. A.

and Spencer R.W.

39-58,

South H. O.

Shark

Australia.-

In:

(eds.): M i c r o b i a l

(Alan Liss Publ., New York).

(1980): Early diagenesis.

A theoretical approach,

237 p.

Princeton).

(1933): The algal sediments of Andros Island, Bahamas.- Phil.

Trans.

Roy. Soc. London B. 222, 165-192.

BLACKBURN, W. E.

& HALVORSON,

498 p.

(Princeton U n i v e r s i t y Press, BLACK, M.

Gulf,

T.

H.

(1983): The m i c r o b i a l n i t r o g e n cycle.- In: KRUMBEIN,

(ed.): M i c r o b i a l Geochemistry,

tific Publications, BOON, J. J. mats:

63-90,

330 p.

(Blackwell Scien-

Oxford).

(1984): Tracing the origin of chemical fossils in m i c r o b i a l

Biogeochemical

investigations

of Solar Lake

cyanobacterial

mats using analytical p y r o l y s i s m e t h o d s . - In: COHEN, Y., CASTENHOLZ, R. W. & HALVORSON, 342, 498 p. BOON,

H. O.

(eds.): M i c r o b i a l Mats:

(Alan R. Liss,

J. J., LEEUW,

Stromatolites,

313-

Inc., New York).

J. W. DE & KRUMBEIN, W. E. (1985): B i o g e o c h e m i s t r y

of Gavish Sabkha sediments.

II.

Pyrolysis mass s p e c t r o m e t r y of the

laminated m i c r o b i a l mat in the p e r m a n e n t l y w a t e r - c o v e r e d zone before and

after the desert sheetflood of 1979.- In:

KRUMBEIN, vol. BRO

W. E.

5_~3, 368-380,

LARSEN,

E.

FRIEDMAN,

G.

M.

&

(eds.): H y p e r s a l i n e ecosystems - The Gavish Sabkha, 484 p.

(1936):

(Springer, Heidelberg). B i o l o g i s c h e Studien Uber die t u n n e l g r a b e n d e n

K~fer auf Skallingen.- V i d e n s k a b Medd.

Dansk Naturhist.

Foren i00,

1-231. BROCK,

T.

D. (1976): Biological techniques

mats and living s t r o m a t o l i t e s . - In: lites.

Developments in Sedimentology,

vier Publishing Company, BRODERICK,

T.

M.

BUBENICEK,

L.

M. R.

(ed.): Stromato-

vol. 20, 21-30,

790 p.

(Else-

Amsterdam).

(1920):

G u n f l i n t iron district,

for the study of m i c r o b i a l

WALTER,

Economic

g e o l o g y and s t r a t i g r a p h y of

the

M i n n e s o t a . - Economic G e o l o g y 15, 422-452.

(1971): G ~ o l o g i e du g i s e m e n t de fer de L o r r a i n e . - Bull.

Centre Rech. P a u - S N P A 5, 223-320. BUICK,

R.

(1984):

Australia:

Are

Carbonaceous they

filaments from North

fossil b a c t e r i a in

archaean

Pole,

Western

stromatolites?-

P r e c a m b r i a n Research 24, 157-172. BUICK,

R., DUNLOP, J. S. R. & GROVES,

nition

in

ancient rocks:

D. I. (1981): Stromatolite recog-

an appraisal

of

irregularly

laminated

t67

structures

in an Early A r c h a e a n c h e r t - b a r i t e unit from North

Pole,

W e s t e r n A u s t r a l i a . - A l c h e r i n g a ~, 161-181. BURST,

J.F.

(1965): S u b a q u e o u s l y formed shrinkage cracks in clay.- J.

Sediment. CADEE,

G.

Petrol. 35, C.

348-353.

(1976): S e d i m e n t r e w o r k i n g of A ~ e n i c o l a marina on tidal

flats in the Dutch W a d d e n Sea.- N e t h e r l a n d s Journal of Sea

Research

i0, 440-460. CAMERON,

B.,

DAMERON,

D.,

JONES, J. R.

(1985): M o d e r n algal mats in

intertidal and supratidal quartz sands, U.S.A.- In:

CURRAN,

interpreting Tulsa, CARNEY, J.

H.A.

N o r t h e a s t e r n Massachusetts,

(ed.): B i o g e n i c structures:

depositional

environments,

211-223,

Their use in

347

p.

(SEPM,

Oklahoma). R.

S.

(1981): B i o t u r b a t i o n and b i o d e p o s i t i o n . -

(ed.): Principles of marine paleoecology,

357-400,

In: BOUCOT, A. 463 p.

(Acade-

mic Press, London). CASTENHOLZ,

R. W.

(1969): T h e r m o p h i l i c b l u e - g r e e n algae and the thermal

environment.- Bacteriological CASTENHOLZ,

R.

W.

summary.- In: (eds.): Publ.,

COHEN,

Y.,

Microbial mats:

CASTENHOLZ,

R.

Stromatolites,

W.

& HALVORSON,

101-120,

498 p.

H. O.

(Alan Liss

New York).

CHAURASIA,

P.

Cambrian

K.

(1984):

A

report on the glimpses of

stromatolitic phosphogenic

rite deposit,

l_!,

Reviews 3_33, 476-504.

(1984): C o m p o s i t i o n of hot spring m i c r o b i a l mats: A

Kazakhstan,

Precambrian-

Province of Karatan

- phospho-

U . S . S . R . - S t r o m a t o l i t e Newsletter,

vol.

20-26.

CLOUD,

P.E.

(1965): S i g n i f i c a n c e of the G u n f l i n t

(Precambrian) micro-

flora.- Science 148, 27-45. CLOUD,

P.

E.

(1976):

Beginnings

of b i o s p h e r i c e v o l u t i o n and

their

b i o g e o c h e m i c a l c o n s e q u e n c e s . - P a l e o b i o l o g y ~, 351-387. CLOUD,

P.

E. & MORRISON,

K.

(1979): On m i c r o b i a l contaminants,

p s e u d o f o s s i l s and the oldest records of life.- P r e c a m b r i a n

2,

micro-

Research

81-91.

COHEN,

Y.

(1984):

The Solar Lake c y a n o b a c t e r i a l mats:

Strategies of

p h o t o s y n t h e t i c life under sulfide.- In: COHEN, Y., CASTENHOLZ, & HALVORSON, 498 p. COHEN, mats: COHEN,

H.

O.

(eds.): M i c r o b i a l mats:

(Alan Liss Publ.,

Y., CASTENHOLZ, Stromatolites, Y.,

Adaptation

JORGENSEN,

Stromatolites,

R. W.

133-148,

New York).

R. W. & HALVORSON, 498 p.

H. O. Eds.

(1984): M i c r o b i a l

(Alan Liss Publ., New York).

B. B., REVSBECH,

N. P. & POPLAWSKI,

R.

(1986):

to h y d r o g e n sulfide of o x y g e n i c and a n o x y g e n i c p h o t o s y n -

thesis among c y a n o b a c t e r i a . - Appl. Environ. Microbiol.

5]., 398-407.

168

COHEN,

Y.,

Lake

KRUMBEIN,

(Sinai).

W.

i.

E., GOLDBERG,

M. & SHILO, M.

(1977a): Solar

Physical and chemical limnology.- L i m n o l o g y

and

O c e a n o g r a p h y 22, 597-608. COHEN,

Y., KRUMBEIN, W. E. & SHILO, M.

Distribution

of

(1977b): Solar Lake

(Sinai).

p h o t o s y n t h e t i c m i c r o o r g a n i s m s and p r i m a r y

2.

produc-

tion.- L i m n o l o g y and O c e a n o g r a p h y 22, 609-620. COHEN,

Y., KRUMBEIN, W. E. & SHILO, M.

Bacterial

(1977c): Solar Lake

d i s t r i b u t i o n and p r o d u c t i o n . - L i m n o l o g y and

(Sinai).

3.

Oceanography

22, 621-634. COLIJN,

F.

&

KOEMAN,

R.

(1975):

Das M i k r o p h y t o b e n t h o s der Watten,

Str~nde und Riffe um den H o h e n K n e c h t s a n d in der W e s e r m H n d u n g . - Fors c h u n g s s t e l l e fHr Insel- und K H s t e n s c h u t z 2_66, 53-84. DAHANAYAKE,

K.,

GERDES,

G.

& KRUMBEIN, W. E.

(1985): Stromatolites,

o n c o l i t e s and oolites b i o g e n i c a l l y formed in situ.- Die N a t u r w i s s e n s c h a f t e n 72, 513-518. DAHANAYAKE,

K. & KRUMBEIN,

W. E. (1985): U l t r a s t r u c t u r e of a m i c r o b i a l

m a t - g e n e r a t e d p h o s p h o r i t e . - Miner. DAHANAYAKE,

K.

& KRUMBEIN,

W.

E.

oolitic iron formations.- Miner. DANIELLI,

H. M. C. & EDINGTON,

Depos.

M. A.

20, 260-265.

(1986):

Microbial structures

in

Depos. 21, 85-94. (1983): Bacterial c a l c i f i c a t i o n in

limestone caves.- G e o m i c r o b i o l o g y Journal ~, 1-16. D'ARCY THOMPSON,

(1984): On growth and form.- In: BONNER,

Reprint 1917, DAUER, of

345 p.

(Cambridge Univ. Press,

D. M., SIMON, J. L. an

J. T.

(ed.):

Cambridge)

(1976): R e p o p u l a t i o n of the p o l y c h a e t e fauna

intertidal h a b i t a t following

natural

defaunation:

species

e q u i l i b r i u m . - O e c o l o g i a 2_~2, 99-117. DAVIES, In:

J.

L.

(1980): G e o g r a p h i c a l v a r i a t i o n in coastal d e v e l o p m e n t . -

CLAYTON,

K.

M.

(ed.):

G e o m o r p h o l o g y Text 4, 212 p.

(Longman

Group Limited, London). DAVIS,

R.

A.

(1966):

W i l l o w River Dolomite:

O r d o v i c i a n analogue of

m o d e r n a algal stromatolite e n v i r o n m e n t s . - J. Geol. DAVIS,

R. A.

J. Sediment.

Petrol. 38, 953-955.

F A C H G R U P P E W A S S E R C H E M I E IN DER GES.

D E U T S C H E R C H E M I K E R (Hrsg.)

D e u t s c h e E i n h e i t s v e r f a h r e n zur Wasser-, suchung

74, 908-923.

(1968): Algal s t r o m a t o l i t e s composed of quartz sandstone.-

(1984):

A b w a s s e r - und S c h l a m m u n t e r -

(Chemie, Weinheim).

DEXTER-DYER, microbial

B.,

KRETZSCHMAR,

pathways

M.

& KRUMBEIN, W. E.

(1984): Possible

p l a y i n g a role in the formation of

Precambrian

ore deposits.- J. Geol. Soc. 141, 251-262. DEXTER-DYER-GROSOVSKY,

B. (1983): M i c r o b i a l role in W i t w a t e r s r a n d gold

deposition.- In: WESTBROEK,

P. & JONG,

E. W. DE (eds.): Biominerali-

169

zation and b i o l o g i c a l metal accumulation, P u b l i s h i n g Company, DIMENTMAN, tiger

C.

& SPIRA, Y.

larva

J.

533 p.

(D. Reidel

(1982): P r e d a t i o n of Artemia cysts by w a t e r

Anacaena

of the genus

H y d r o b i o l o g i a 97, DUNLOP,

495-498,

Dordrecht).

(Coleoptera,

Hydrophilidae).-

163-165.

S. R., MUIR,

M. D., MILNE, V. A. & GROVES,

new m i c r o f o s s i l a s s e m b l a g e

D. I.

from the A r c h a e a n of W e s t e r n

(1978): A

Australia.-

Nature 274, 676-678. ECCLESTON,

M.,

KELLY,

D. P. & WOOD, A. P.

(1985): A u t o t r o p h i c growth

and iron o x i d a t i o n and i n h i b i t i o n k i n e t i c s of Leptospi~illum

oxidans.- In:

CALDWELL,

D.

(eds.):

P l a n e t a r y Ecology,

Company,

New York).

ECKSTEIN,

Y.

mictic

E.,

BRIERLEY,

263-272,

(1970): P h y s i c o c h e m i c a l

ferno-

J. A. & BRIERLEY,

591 p.

C. L.

(Van N o s t r a n d Reinhold

limnology and geology of a mero-

pond on the Red Sea shore.- L i m n o l o g y and

Oceanography

15,

363-372. EHRENBERG,

C.

G.

(1839): Uber das im Jahre 1686 in Curland vom Himmel

g e f a l l e n e M e t e o r p a p i e r . - A n n a l e n der Physik und Chemie 16, 187-188. EHRLICH,

A.

(1978):

The

diatoms

of the h y p e r s a l i n e Solar Lake

Sinai).- Israel Journal of Botany 27, EHRLICH,

A.,

DOR,

I.

(1985):

Gavish Sabkha.- In: FRIEDMAN, saline

D.

EVANS,

G. M. & KRUMBEIN, vol.

W.

J.

K. S., REINECK,

(1965):

F.

484 p.

Intertidal

H.-E.

&

vol. ~,

Leiden).

flat sediments and their e n v i r o n m e n t s of

d e p o s i t i o n in the W a s h . - Q. J. Geol. Soc. London 121, FABRICIUS,

(eds.): Hyper-

533, 296-321,

(eds.) : G e o m o r p h o l o g y of the w a d d e n sea area,

(Wadden Sea W o r k i n g Group, G.

W. E.

the

Berlin).

(1980): Natural forces.- In: DIJKEMA,

WOLFF, 20-31

P h o t o s y n t h e t i c m i c r o o r g a n i s m s of

Ecosystems - The Gavish Sabkha,

(Springer, EISMA,

(NE

1-13.

209-245.

(1977): O r i g i n of m a r i n e o6ids and g r a p e s t o n e s . - Contri-

butions to S e d i m e n t o l o g y ~, 1-77. FERGUSON,

J. & BURNE,

R. V.

(1981~:

Interactions b e t w e e n saline redbed

g r o u n d w a t e r s and p e r i t i d a l carbonates, lia:

significance

Spencer Gulf,

South Austra-

for models of s t r a t i f o r m copper ore genesis.- BMR

Journal of A u s t r a l i a n G e o l o g y & G e o p h y s i c s 6, 3129-325. FLUGEL,

E.

(Springer, FRIED~L~N,

G.

(1982):

Microfacies

analysis

of

limestones,

633

p.

Berlin). M.

(1965):

A fossil shoreline reef in the Gulf of Elat

(Aqaba).- Israel Journal of E a r t h - S c i e n c e s

I_44, 86-90.

170

FRIEDMAN,

G.

rites

M.

(1972):

and

basinal

Geologists

Bulletin

FRIEDMAN,

G.M.

(Gulf

of

i, 227-235,

Generation example

16,

of

A.

carbonate

Association

beachrocks.-

376 p.

FRIEDMAN,

Science J.,

Petroleum

of P e t r o l e u m E.

(Johns Hopkins

Univ.

Ecological

Environment,

Publ.

Michigan).

Inc.,

M.

& MILLER,

pool,

O. P. Press,

algal

Bulletin

(ed.):

57,

(1973): mats

-

Red Sea.541-557.

and Red Sea

Carbonate

vol.

(Gulf of

cements,

13-

Baltimore).

(1985):

Studies

in

D. S.

Gulf of Aqaba,

Mediterranean

W. E. Ed.

carbonate

Environmental

The A q u a t i c

Geologists

(1971):

generate (ed.):

and laminites

hypersaline

In: BRICKER,

Sabkha.

of

pond of the Red Sea

mats W. E.

BRAUN,

particles

G. M. & KRUMBEIN,

The Garish

algal

KRUMBEIN,

(Ann A r b o r

AMIEL,

G. M. & GAVISH,

Aqaba)

in w h i c h In:

from s e a - m a r g i n a l

American FRIEDMAN,

A sea-marginal

and G e o m i c r o b i o l o g y .

M.,

Association

1072-1086.

or Elat)

394 p.

G.

of Red Sea in p r o b l e m of evapo-

American

Solar Lake:

and laminites.-

Biogeochemistry

FRIEDMAN,

56,

(1978):

Aqaba

particles

Significance

limestones.-

vol.

Hypersaline 53,

ecosystems

484 p.

-

(Springer,

Berlin). FRIEDMAN,

G.

792 p. FUHRBOTER,

A.,

chungen den.

M.

& SANDERS,

(John Wiley

J. E.

& Sons,

DETTE,

(1978):

H. H. & MANZENRIEDER,

der E r o s i o n s s t a b i l i t ~ t

Bericht

Technischen

Principles

Nr.

506

H.

(1981):

In-situ-Untersu-

und der D u r c h l ~ s s i g k e i t

des L e i c h t w e i ~ - I n s t i t u t s

Universit~t

of sedimentology,

New York).

Braunschweig

yon

Wattb6-

fur W a s s e r b a u

(unver~ffentlicht),

70 p.

der (TU,

Braunschweig). FUHRBOTER,

A.,

DETTE,

H. H., MANZENRIEDER,

situ-Untersuchungen von Wattb~den.

- 2.

weiB-Instituts

fur

schweig GADOW,

fluten.-

of

MeSzeitraum Wasserbau

1982.

und der

Bericht Nr.

der T e c h n i s c h e n

S.

(1983):

In-

Durchlissigkeit 552 des Leicht-

Universit~t

Braun-

(unver6ffentlicht).

S. & REINECK,

GALLAGHER,

H. & NIESEL,

der E r o s i o n s s t a b i l i t ~ t

H.-E.

Senckenbergiana E. D., JUMARS,

soft-bottom

(1969): marit.

P. A.

benthic

Ablandiger ~,

Sandtransport

bei Sturm-

63-78.

& TRUEBLOOD,

succession

D. D.

by tube

(1983):

builders.-

Facilitation Ecology

64,

1200-1216. GARRELS,

R.

M.,

Precambrian gen.GARRETT,

Economic P.

PERRY,

iron

Geology

(1970):

restriction

E.

formations 68,

A.

F. T.

(1973):

Genesis

of a t m o s p h e r i c

of

oxy-

1173-1179.

Phanerozoic

by grazing

& MACKENZIE,

and the d e v e l o p m e n t

stromatolites:

and b u r r o w i n g

Noncompetitive

animals.-

Science

169,

ecologic 171-173.

171

GASIEWICZ,

A.

(1984): E c c e n t r i c ooids.- Neues J a h r b u c h fHr G e o l o g i e und

P a l ~ o n t o l o g i e Monatshefte, GASIEWICZ,

A.,

(Permian)

Gerdes,

204-211.

G.,

- A peritidal

Krumbein,

W.

E.

(1986): Platy dolomite

sabkha-type b i o l a m i n o i d

facies.- In p r e p a r a -

tion. GAVISH,

E.

(1974): M i n e r a l o g y and g e o c h e m i s t r y of a coastal sabkha near

Nabek,

Gulf of Elat.- In:

GILL,

D.

(ed.): A b s t r a c t s of papers pre-

sented at the 1972/73 seminar of the Geol. Survey of Israel, GAVISH,

E.

and Elat, 23,

18-19.

(1975): Recent coastal sabkhas m a r g i n a l to the gulfs of Suez Red Sea.- Rapport C o m m i s i o n I n t e r n a t i o n a l Mer M e d i t e r r a n ~ e

129-130.

GAVISH,

E.

Sinai,

(1980):

Recent sabkhas m a r g i n a l to the southern coasts of

Red Sea.- In:

NISSENBAUM,

e v a p o r i t i c environments, shing Company, GAVISH,

233-251,

A.

and

J°

(1985): Geomorphology,

g r o u n d w a t e r g e o c h e m i s t r y as factors of

system of the Gavish Sabkha.- In: (eds.):

(Elsevier Scientific Publi-

Amsterdam).

E., KRUMBEIN, W. E. & HALEVY,

logy

(ed.): H y p e r s a l i n e brines and

270 p.

FRIEDMAN,

217, 484 p.

(Springer,

C.

D.

The effects of the physical,

Developments

in Sedimentology,

S c i e n t i f i c Publishing Company, S.

A.

vol.

5_~3, 186-

Heidelberg).

(1976):

b i o l o g i c a l e v o l u t i o n of the earth.- In: WALTER, tolites.

minera-

hydrodynamic

G. M. & KRUMBEIN, W. E.

H y p e r s a l i n e Ecosystems - The Gavish Sabkha,

GEBELEIN,

GEIKIE,

the

chemical

and

M. R. (ed.): Stroma-

vol. 20, 499-515

(Elsevier

Amsterdam).

(1905): The founders of geology,

486 p.

(McMillan, New

York). GERDES,

G. & HOLTKAMP,

E.

(1980):

S e d i m e n t o l o g i s c h - b i o l o g i s c h e Kartie-

rung der W a t t e n g e b i e t e von M e l l u m s c h u n g s i n s t i t u t S e n c k e n b e r g 39, GERDES,

G. & KRUMBEIN,

Pygospio ele~ans Sandwatt

yon

W. E.

(sHdliche N o r d s e e ) . - Courier

For-

1-185.

(1985): B e o b a c h t u n g e n zur L e b e n s w e i s e von

(Spionidae,

P o l y c h a e t a Sedentaria)

im F a r b s t r e i f e n -

M e l l u m . - V e r h a n d l u n g e n der G e s e l l s c h a f t fHr

Okologie

13, 49-54. GERDES,

G.

& KRUMBEIN,

Stromatolithe grenzende

W.

E.

(1986):

des u n t e r e n S u p r a l i t o r a l s

Potentielle silikoklastische (sHdliche Nordsee)

F a k t o r e n gang- und r ~ h r e n b a u e n d e r mariner

als

be-

Evertebraten.-

Neues J a h r b u c h fHr G e o l o g i e und P a l ~ o n t o l o g i e A b h a n d l u n g e n 172,

163-

191. GERDES, water

G.,

KRUMBEIN,

W.

E. & HOLTKAMP,

E. M.

(1985a): S a l i n i t y and

a c t i v i t y related zonation of m i c r o b i a l communities and poten-

tial s t r o m a t o l i t e s of the Gavish

Sabkha.- In:

FRIEDMAN,

G.

M.

&

172

K R U M B E I N W. vol.

E.

(eds.): H y p e r s a l i n e Ecosystems - The Gavish Sabkha,

5_~3, 238-266,

GERDES,

G.,

Lebens

(Springer, Heidelberg).

W.

- Okologische

von Aqaba GERDES,

484 p.

KRUMBEIN,

& REINECK,

E.

G., KRUMBEIN, W. E. & REINECK,

KRUMBEIN,

aktuogeologische

W.

H.-E.

Petrol. 55,

E.

& REINECK,

Golf

309-323. (1985b): The d e p o s i t i o n a l

v e r s i c o l o r e d tidal flats

North Sea).- J. Sediment. G.,

(1982): G r e n z g ~ n g e r des

Studien an zwei s t r a n d n a h e n S a l z s e e n am

(Sinai).- Natur und M u s e u m 112,

record of sandy,

GERDES,

H.-E.

(Mellum Island,

southern

265-278. H.-E.

(1985c): V e r b r e i t u n g und

Bedeutung mariner m i k r o b i e l l e r Matten im Gezeiten-

b e r e i c h der N o r d s e e . - Facies 12, 75-96. GERDES,

G., SPIRA, Y. & DIMENTMAN,

C.

(1985d): The fauna of the Gavish

Sabkha and the Solar Lake - a comparative study.- In: M.

& KRUMBEIN,

Sabkha, GERLACH,

A.

for

G.

484 p.

(Springer,

Berlin).

d i s t r i b u t i o n of nematodes in a

Bermuda

beach.-

151-165.

D., GIANI,

sis

FRIEDMAN,

(eds.): H y p e r s a l i n e Ecosystems - The Gavish

(1977): A t t r a c t i o n to d e c a y i n g organisms as a p o s s i b l e

patchy

Ophelia 16, GIANI,

E.

vol. 5_~3, 322-345, S.

cause

W.

L., COHEN, Y. & KRUMBEIN,

in the h y p e r s a l i n e Solar Lake

W. E.

(1984): M e t h a n o g e n e -

(Sinai).- FEMS

Microbiol.

Lett.

2_!, 219-224. GIERE,

O.

(1975):

P o p u l a t i o n structure,

role of marine oligochaetes,

food relations and ecologic

w i t h special reference to

meiobenthic

species.- Marine Biology 31, 139-156. GIESENHAGEN,

K.

graphische

(1922): 0ber die s y s t e m a t i s c h e Deutung und die strati-

Stellung der ~itesten V e r s t e i n e r u n g e n Europas und

Nord-

~merikas mit b e s o n d e r e r B e r H c k s i c h t i g u n g der C r y p t o z o e n und Oolithe. III.

Teil: 0ber O o l i t h e . - A b h a n d l u n g e n der B a y e r i s c h e n A k a d e m i e der

W i s s e n s c h a f t e n M a t h e m a t i s c h - p h y s i k a l i s c h e Klasse 24, GOHREN,

H.

im W a t t e n m e e r zwischen Jade und Eider.- Die KHste 27, GOLUBIC, R.

28-49.

S. (1976): O r g a n i s m s that b u i l d s t r o m a t o l i t e s . - In: WALTER,

(ed.):

113-126, GOLUBIC,

1-42.

(1975): Zur Dynamik und M o r p h o l o g i e der h o l o z ~ n e n Sandb~nke

Stromatolites,

790 p. S.

&

Developments in Sedimentology,

M.

vol. 20,

(Elsevier S c i e n t i f i c P u b l i s h i n g Company, Amsterdam). AWRAMIK,

stromatolite environments:

S.

M.

(1974):

Microbial

comparison

of

Shark Bay, Persian Gulf and the Bahamas.-

G e o l o g i c a l Society of A m e r i c a A b s t r a c t s w i t h Programs 6, 759-760. GOLUBIC,

S.

Precambrian

& HOFMANN,

H. J.

(1976): C o m p a r i s o n of Holocene and mid-

Entophysalidaceae

(Cyanophyta)

in

stromatolitic

mats: cell d i v i s i o n and d e g r a d a t i o n . - J. Paleontol. 50,

algal

1074-1082.

173

GOLUBIC,

S. & PARK,

R. K.

(1973): B i o l o g i c a l dynamics of an algal mat -

a sediment a f f e c t i n g m i c r o b i a l c o m m u n i t y sium on E n v i r o n m e n t a l GOODWIN,

A.

M.

Biogeochemistry,

(1956):

(Persian Gulf).- In: Sympo-

1973, p. 5 (Logan, Utah).

Facies relations in the G u n f l i n t Iron Forma-

tion.- Economic G e o l o g y 5_!1, 565-595. GOVETT,

G. J. S. (1966): O r i g i n of b a n d e d iron formations.- G e o l o g i c a l

Society of America B u l l e t i n 77, 1191-1212. GRAY, J. S. 1932 p. GRESSLY,

(1984): O k o l o g i e mariner Sedimente (Springer,

A.

(1838):

O b s e r v a t i o n s g ~ o l o g i q u e s sur le Jura Soleurois.-

Neue Denkschr. allgem, GYGI,

R.

A.

(0bersetzung H. Rumohr),

Berlin).

schweizer. Ges. Naturwiss.

2.

(1981): Oolitic iron formations: m a r i n e or not m a r i n e ? . -

Eclogae G e o l o g i c a e H e l v e t i a e 7_44, 233-254. HAMBLIN,

W. K.

homogeneous HARTMAN, H.

(1962): X - r a y r a d i o g r a p h y in the study of structures in sediments.- J. Sediment.

Petrol. 32,

A s p e c u l a t i o n on the Banded Iron F o r m a t i o n s . HOLZ,

R.

lites,

441-454,

HAUSER,

W.

& HALVORSON,

und

Wracks

Forschungsstelle HEIM,

498 p.

B. & MICHAELIS,

Riffe

201-210.

(1984): The e v o l u t i o n of p h o t o s y n t h e s i s and m i c r o b i a l mats;

M. R.

H. O.

(Alan Liss Publ., H.

In: COHEN, Y., CASTEN-

(eds.): M i c r o b i a l Mats:

Stromato-

New York).

(1975): Die M a k r o f a u n a der Watten,

um den Hohen K n e c h t s a n d

in

der

Str~nde,

WesermHndung.-

fHr Insel- und K H s t e n s c h u t z 2_66, 85-119.

(1916): M o n o g r a p h i e der C h u r f H r s t e n - M a t t s t o c k - G r u p p e .

Teil

3: L i t h o g e n e s e . - Beitr~ge zur g e o l o g i s c h e n Karte der Schweiz 20. HEMPRICH,

W. F. & EHRENBERG,

C. G.

(1828): Reisen in Aegypten,

N u b i e n und Dongala.- In: EHRENBERG,

C. G.

Libyen,

(ed.): N a t u r g e s c h i c h t l i c h e

Reisen durch N o r d - A f r i k a und W e s t - A s i e n in den Jahren 1820 bis 1825, (Mittler, HERTWECK,

G.

Berlin). (1978): Die B e w o h n e r des W a t t e n m e e r e s

gen auf das Sediment.185 p. HOBSON,

(Kramer,

C.

VAN DEN,

REINECK, H.-E.

in ihren A u s w i r k u n -

(ed.): Das Watt,

145-172,

F r a n k f u r t am Main).

K. D. & GREEN,

Pygospio elegan8 HOEK,

In:

R. H.

(1968): Asexual and sexual r e p r o d u c t i o n of

in B a r n s t a b l e Harbor, ADMIRAAL,

Mass.- Biol. Bull. 135, 410.

W., COLIJN,

F. & DE JONGE, N. N.

(1979):

The role of algae and seagrasses in the e c o s y s t e m of the W a d d e n Sea: A review.- In:

WOLFF,

W.

W a d d e n Sea, vol. 3, 9-118 HOPNER,

TH.,

Oldenburg,

ORLICZEK, ein

J.

(ed.):

Flora and V e g e t a t i o n of

(Wadden Sea W o r k i n g Group,

CHR., GAUG, H. & KELLER,

universeller

Analysenautomat

W a s s e r a n a l y s e n . - Vom W a s s e r 5__22, 183-191.

D.

the

Leiden).

(1979): A S A - A n l a g e

fHr

kolorimetrische

174

HOFFMANN,

C.

(1942): Beitr~ge zur V e g e t a t i o n des F a r b s t r e i f e n - S a n d w a t -

tes.- Kieler M e e r e s f o r s c h u n g e n S o n d e r h e f t 4, 85-108. HOFFMANN,

C.

(1949): Uber die D u r c h l ~ s s i g k e i t dHnner S a n d s c h i c h t e n fHr

Licht.- Planta 36, 48-56. HOLTKAMP,

E.

(1985): The m i c r o b i a l mats of the Gavish Sabkha.- Thesis,

151 p., U n i v e r s i t ~ t Oldenburg. HSU,

K.

J.

& SIEGENTHALER,

hydrodynamic

C.

(1969): P r e l i m i n a r y experiments on the

m o v e m e n t s induced by e v a p o r a t i o n and their b e a r i n g

on

the dolomite p r o b l e m . - S e d i m e n t o l o g y 12, 11-25. JACOBSEN,

N.

DIJKEMA, of

K.

(1980):

F o r m elements of the w a d d e n sea

K. S., REINECK,

H. E. & WOLFF, W. J.

the w a d d e n sea area,

Rep.

i,

50-71

area.- In:

(eds.): G e o m o r p h o l o g y

(Wadden Sea W o r k i n g Group,

Leiden). JAMES,

H.

J.

(1954): S e d i m e n t a r y facies of i r o n - f o r m a t i o n s . - Economic

Geology 49, JANNASCH,

235-293.

H. W. & WIRSEN,

C. O.

(1981): M o r p h o l o g i c a l

bial mats near deep-sea thermal

vents.- Appl.

survey of micro-

Environ.

Microbiol.

41, 528-538. JAVOR,

B.

J.

(1979): Ecology,

b l u e - g r e e n algal mats,

physiology,

and carbonate c h e m i s t r y of

Laguna G u e r r e r o Negro, M e x i c o

(Dissertation,

Eugene, Oregon). JORGENSEN,

B. B. (1977): The sulfur cycle of a coastal marine sediment

(Limfjorden, KALECSINSZKY,

Denmark).- L i m n o l o g y and O c e a n o g r a p h y 222, 814-832. A.

VON

(1901):

Uber die U n g a r i s c h e n w a r m e n und h e i s z e n

K o c h s a l z s e e n als natHrliche W ~ r m e a k k u m u l a t o r e n , stellung

von w a r m e n S a l z s e e n und

n a t u r w i s s e n s c h a f t l i c h e B e r i c h t e U n g a r n 19, KALKOWSKY,

E.

(1908):

sowie Hber die Her-

W~rmeakkumulatoren.- Mathematisch 51-54.

Oolith und S t r o m a t o l i t h im n o r d d e u t s c h e n Bunt-

sandstein.- Z e i t s c h r i f t der D e u t s c h e n G e o l o g i s c h e n G e s e l l s c h a f t

60,

68-125. KAZMIERCZAK,

J.

& KRUMBEIN, W. E.

(1983):

I d e n t i f i c a t i o n of calcified

coccoid c y a n o b a c t e r i a forming s t r o m a t o p o r o i d s t r o m a t o l i t e s . - Lethaia 16, 207-213. KENDALL,

A. C.

In: WALKER, KINSMAN,

D.

evolution,

(1979): C o n t i n e n t a l and supratidal R. G. J.

(ed.): Facies Models,

J. & PARK R. K.

Trucial Coast,

Stromatolites,

421-433

(Sabkha) evaporites.-

159-174.

(1976): Algal belt and coastal sabkha

Persian Gulf.- In:

(Elsevier

Scientific

WALTER,

M. R. (ed.):

Publishing

Company,

Amsterdam). KITANO,

Y.,

KANAMORI,

N.

& T O K U Y A M A A.

(1969):

Effects of organic

175

matter

on s o l u b i l i t i e s

and crystal

form of c a r b o n a t e s . -

Amer.

Zool.

2, 681-688. KNOLL,

A.

H.

(1985a): G.

The G a v i s h

Sabkha,

407-425,

484 p.

(1985b):

Patterns

of e v o l u t i o n

A. H.

zoic eons.KNOLL,

A. H.

in the KNOLL,

Paleobiology (1985c):

H.

& AWRAMIK,

KRUMBEIN,

(Blackwell KNOLL,

A.

52,

KRETZSCHMAR,

M.

W.

(1982):

E.

(ed.):

E. S. & AWRAMIK, Gunflint

Fossile

Pilze

(1974a):

E.

(1974b):

of m a r i n e W. E.

(1978):

W.

logy.

The A q u a t i c

KRUMBEIN,

E.

(ed.):

E.

(1979a): A.

vity

W. E. of

(1978):

New microorOntario.-

~,

J.

BIOLOGISCHE (Boysen

l,

HELGO-

& Co, Heide).

209-225,

on

the

6!I, 167-167.

lithification.-

Biogeochemistry

vol.

zur F~llung

ANSTALT

of a r a g o n i t e

Die N a t u r w i s s e n s c h a f t e n and their

von War-

237-260.

Untersuchungen

In:

Calcification

& SWAINE,

Elements,

In: KRUM-

and G e o m i c r o b i o 394 p.

(Ann Arbor

D. J.

by b a c t e r i a

(eds.):

vol. ~, 47-68,

and

algae.-

Biogeochemical

612 p.

(Elsevier

In:

Cycling o f Scientific

Amsterdam).

(1979b):

bacteria

degradation

330 p.

Michigan).

P.

Company,

Facies

104 p.

Environmental

W.

KRUMBEIN,

ecosystems.-

287-315,

Formation,

the p r e c i p i t a t i o n

Environment,

Inc.,

Mineral-forming

50-54, On

Algal mats

TRUDINGER,

Publishing

S. M.

Iron

Mikrobiologische

bacteria.-

BEIN,

Publ.

391-417.

in E i s e n - S t r o m a t o l i t h e n

1973,

Science

Geochemistry,

life

Oxford).

Schiefergebirge).-

Jahresbericht

KRUMBEIN,

39,

Ancient microbial

Microbial

Publications,

LAND:

surface

-

and Protero-

of m i c r o b i a l

Rev. Microbiol.

aus M e e r w a s s e r . -

W.

in the A r c h e a n

and e v o l u t i o n

(1983):

von K a l z i u m k a r b o n a t

KRUMBEIN,

Ecosystems

Berlin).

976-992.

(Rheinisches

KRUMBEIN,

In:

53-64.

S. M.

the A p h e b i a n

on sabkhas.-

(eds.) : H y p e r s a l i n e (Springer,

era.- Ann.

BARGHOORN,

from

Paleontol.

stein

W. E.

Scientific

H.,

ganisms

ii,

W. E.

The d i s t r i b u t i o n

late P r o t e r o z o i c

A.

In:

& KRUMBEIN,

perspective

FRIEDMAN,

KNOLL,

M.

A paleobiological

Photolithotrophic

and algae as related

(Gulf of Aqaba,

Sinai).-

and c h e m o o r g a n o t r o p h i c to b e a c h r o c k

Geomicrobiology

acti-

formation Journal

~,

and 139-

203. KRUMBEIN,

W.

E.

(1979c):

KRUMBEIN,

W.

48,

(Universit~t,

130 p.

KRUMBEIN, space KRUMBEIN,

W.

E.

E.

and time.W.

E.

bial mats.-

(ed.):

(1983):

Uber

Cyanobakterien

der

- Bakterien

Cyanophyten.-

In:

oder Algen?,

33-

Oldenburg). Stromatolites

Precambrian

(1986a):

die Z u o r d n u n g

Research

Biotransfer

In: LEADBEATER,

- The challenge 20,

493-531.

of m i n e r a l s

B. S. C.

of a term in

& RIDING,

by m i c r o b e s R.

(eds.):

and microBiominera-

176

lization

in

Lower Plants and

Animals,

55-72

(Oxford

University

Press, Oxford). KRUMBEIN,

W.

men.- In:

E.

(1986b): Die E n t d e c k u n g i n s e l b i l d e n d e r M i k r o o r g a n i s -

GERDES,

G.,

KRUMBEIN,

M e l l u m - Portrait einer Insel KRUMBEIN,

W.

E.,

WONNEBERGER, model

BUCHHOLZ,

C.

W.

(Kramer,

H.,

E.

& REINECK,

H.-E.

FRANKE,

P., GIANI, D., GIELE,

C. &

(1979): 02 and H2S coexistence in stromatolites.

for the origin of m i n e r a l o g i c a l

lamination

in

W. E. & COHEN, Y.

A

stromatolites

and b a n d e d iron formations.- Die N a t u r w i s s e n s c h a f t e n 66, KRUMBEIN,

(eds.):

F r a n k f u r t am Main).

381-389.

(1974): Biogene, k l a s t i s c h e und evaporiti-

sche S e d i m e n t a t i o n in einem m e s o t h e r m e n m o n o m i k t i s c h e n u f e r n a h e n See (Golf yon A q a b a ) . - G e o l o g i s c h e Rundschau 63, KRUMBEIN,

W.

E. & COHEN, Y.

and lithification:

(1977): Primary production,

p.

(Springer, W.

mat formation

C o n t r i b u t i o n of oxygenic and facultative

genic c y a n o b a c t e r i a . - In: FLUGEL,

KRUMBEIN,

1035-1065.

E.

(ed.): Fossil Algae,

anoxy-

37-56,

375

Berlin).

E.,

Stromatolitic

COHEN, Y. & SHILO, M.

(1977): Solar Lake

(Sinai) 4.

c y a n o b a c t e r i a l mats.- L i m n o l o g y and O c e a n o g r a p h y

22,

635-656. LITTLE-GADOW,

S.

(1978): Sedimente und Chemismus.- In: REINECK,

(ed.): Das Watt, A b l a g e r u n g s - und Lebensraum,

51-62,

185 p.

H.-E.

(Kramer,

F r a n k f u r t am Main). LOGAN,

B.

W.,

REZAK,

R. & GINSBURG,

R. N.

(1964): C l a s s i f i c a t i o n and

e n v i r o n m e n t a l significance of algal s t r o m a t o l i t e s . - J. Geol. 72, 6883. LOGAN,

P.

W.

(1961): C r y p t o z o a n and a s s o c i a t e s t r o m a t o l i t e s from the

Recent of Shark Bay, W e s t e r n A u s t r a l i a . - J. Geol. 69, LOVELOCK,

J.

E. & MARGULIS,

L.

517-533.

(1974): A t m o s p h e r i c h o m e o s t a s i s by and

for the biosphere: the Gaia h y p o t h e s i s . - Telius 26, 2-9. LOWENSTAM,

H.

A.

(1981): Minerals

A.

(1986):

formed by o r g a n i s m s . - Science 211,

1126-1131. LOWENSTAM,

H.

protoctists. lization

H.

p r o c e s s e s in m o n e r a n s

1-17,

401 p.

(Systematics

C l a r e n d o n Press, Oxford). A. & WEINER,

S.

(1983): M i n e r a l i z a t i o n by organisms and

the evolution of b i o m i n e r a l i z a t i o n . -

In: WESTBROEK,

P. & JONG,

DE (eds.): B i o m i n e r a l i z a t i o n and b i o l o g i c a l metal accumulation, 204, 533 p. LUCAS,

and

S. C. & RIDING, R. (Eds.): Biominera-

in lower plants and animals,

Association, LOWENSTAM,

Mineralization

- In: LEADBEATER,

(D. Reidel Publishing Company,

J. & PREVOT, L.

E. W. 191-

Dordrecht).

(1984): Synth~se de l'apatite par voie b a c t ~ r i -

enne & partir de mati~re organique p h o s p h a t ~ e et de divers carbonate

177

de

calcium

dans

G e o l o g y 42, LUDWIG,

des eaux douces

Ablagerung

C h e m i e 87, LUNDGREN,

D.

G.

(1852):

~ber die M i t w i r k u n g

des k o h l e n s a u r e n

G.

&

DEAN,

P.

A.

& SWAINE,

Mineral-Forming

LUSERKE,

naturelles.-

Chemical

Kalkes.-

Annalen

der Pflanzen

bei

der

und

Physik

91-107.

TRUDINGER,

Company,

marines

101-118.

R. & THEOBALD,

der

et

W.

Elements,

(1979): D. J.

Biogeochemistry

(eds.):

211-251,

612

of iron.-

In:

Biogeochemical

Cycling

p.

Publishing

(Elsevier

of

Amsterdam).

M.

(1957):

MACKENZIE,

D. B.

Alemeda

Avenue

Juist

- Verwunschene

(1968): cut,

Studies

Denver,

Insel.- M e r i a n

for students:

Colorado.-

3_XX, 15-20.

Sedimentary

The M o u n t a i n

features

Geologist

~,

of 3-

14. MACKENZIE,

D. B.

(1972):

Group near Denver, MANZENRIEDER,

H.

(1984):

aus der Sicht des den G e s e l l s c h a f t MARGULIS,

Tidal

STOLZ,

J.

F., in

fornia,

Mexico: ii, L.

phyla

does

Verfestigung

S.,

FRANCIS,

E. S. & CHASE, sediment

it have

2,

Dakota

269-277.

von W a t t f l ~ c h e n

der N a t u r f o r s c h e n -

1-60.

BANERJEE,

BARGHOORN,

Geologist

Ver~ffentlichungen

1984,

D.,

the layered

Research MARGULIS,

Die b i o l o g i s c h e

zu Emden

in lower C r e t a c e o u s

The M o u n t a i n

Ingenieurs.-

L., ASHENDORF,

community

sand deposits

Colorado.-

O.

at L a g u n a

Precambrian

S., GIOVANNONI, (1980):

S.,

The m i c r o b i a l

Figueroa,

Baja

analogues?.-

Cali-

Precambrian

93-123. & SCHWARTZ,

K.

of life on Earth,

V.

(1982):

338 p.

(W.

Five kingdoms:

H.

Freeman

Guide

to the

and Company,

San

Francisco). MARGULIS,

L.,

STOLZ,

J.

(1983):

Microbial

of the s e d i m e n t s . -

In: WESTBROEK,

neralization

and

Biological

(Reidel

Comp.,

MARKUN,

Publ.

C.

Research MARTIN,

Iron 12,

T. C.

green

MASSARI,

F.

H.

Formation,

& WYATT,

i0,

Accumulation,

27-53,

Sedimentary

structures

Biomi533

p.

(1980):

Schreiber

Beach,

Ontario.-

in the

Precambrian

J. T.

(1974):

Extracellular

emphasis

investments

on the genus

Nostoc.-

in blueJournal

204-210.

(1980):

Cryptalgal

Alps

& MICHAELIS,

Weges".-

(eds.):

287-310.

ces of V e n e t i a n MEYER,

A. F.

algae with p a r t i c u l a r

of P h y c o l o g y

Metal

and a Gaian view

E. W. DE

Dordrecht).

D. & RANDAZZO,

Gunflint

systematics

P. & JONG,

fabrics

in the Rosso A m m o n i t i c o

sequen-

Roma. H.

(1980):

Forschungsstelle

Das M a k r o b e n t h o s

fur Insel-

des w e s t l i c h e n

und K H s t e n s c h u t z

31,

"Hohe

91-156.

178

MITTERER,

R.

M.

(1971):

p r e c i p i t a t i o n . - In: 258,

376 p.

MITTERER,

(Hopkins,

R.M.

Influence of natural organic matter on CaCO 3

BRICKER,

O.

C.

of

C. L. V.

G ~ o l o g i q u e de Belgique 96, C.

L.

1407-1412.

(1973): P r e c a m b r i a n b a c k g r o u n d and Phanerozoic h i s t o r y

s t r o m a t o l i t i c communities,

MONTY,

V.

fabrics.- In:

(1976): WALTER,

an o v e r v i e w . - Annales de la

C. L. V.

The M.

origin and d e v e l o p m e n t of

R. (ed.): Stromatolites,

15-35,

MULLER-JUNGBLUTH,

cryptalgal

193-249,

790 p.

Amsterdam).

(1977): Evolving concepts on the nature and the ecolo-

gical significance of s t r o m a t o l i t e s . - In: Algae,

Societ~

585,624.

(Elsevier Scientific P u b l i s h i n g Company, MONTY,

252-

(1972): B i o g e o c h e m i s t r y of aragonite mud and oolites.-

G e o c h i m i c a et C o s m o c h i m i c a A c t a 36, MONTY,

(ed.) : C a r b o n a t e Cements,

Baltimore).

375 p.

(Springer,

W. V. & TOSCHEK,

FLUGEL,

E.

(ed.): Fossil

Berlin). P. H.

(1969): K a r b o n a t s e d i m e n t o l o g i -

sche A r b e i t s g r u n d l a g e n . - Science ~, 1-32. MULLER,

O. F.

NEALSON,

K.

(1777): Flora Danica vol. I_~V, Kopenhagen. H.

(1983): The microbial

(ed.): Microbial Geochemistry, Publications, NEALSON, K. H. E.

NOVITSKY,

191-222,

330 p.

W.

(Blackwell Scien L

Oxford).

(1968): Solar Lakes and solar energy.- Nature 219, 851-852. J.

A.

(1983):

c a r b o n a t e in seawater:

A p p a r e n t m i c r o b i a l p r e c i p i t a t i o n of calcium Importance of pH.- In: HALLBERG,

E n v i r o n m e n t a l Biogeochemistry, Bulletins Publishing House, OEHLER,

W. E.

(Blackwell S c i e n t i f i c

Oxford).

tific Publications, J.

330 p.

(1983): The m i c r o b i a l m a n g a n e s e cycle.- In: KRUMBEIN,

(ed.): Microbial Geochemistry,

NEUMANN,

iron cycle.- In: KRUMBEIN,

159-190,

J.H.

(1972):

vol. 35, 259-265,

576 p.

R. O.

(ed.):

(Ecological

Stockholm).

"Stromatoloids"

from Y e l l o w s t o n e Park, W y o m i n g . -

G e o l o g i c a l Society of America A b s t r a c t s w i t h Programs 4, 212-213. OERSTEDT,

O.

S.

(1841):

Alluvialdannelse

Beretning o m e n

E x c u r s i o n til Trindelen,

i Odensefjord.- Naturhistorisk Tidskrift

~,

en

552-

569. PANG,

P.

tion Geol. PARK,

C. & NRIAGU, J. O.

(1976): D i s t r i b u t i o n and isotope composi-

of n i t r o g e n in Bay of Quinte

(Lake Ontario)

sediments.- Chem.

188, 93-105.

R. (1976): A note on the significance of lamination in stromato-

lites.- S e d i m e n t o l o g y 23,379-393. PERYT,

T.

M.,

sedimentation

CZAPOWSKI, of

Przeglad Geol. 33,

G., DEBSKI,

Zechstein 204-211.

J. & PIZON, A.

evaporites

at

the

(1985): Model of Leba

Elevation.-

179

PETTIJOHN,

E.

J.

(1975): S e d i m e n t a r y rocks,

628 p.

(Harper & Row, New

York). PETTIJOHN,

F. J. & POTTER,

s e d i m e n t a r y structures, PIA, J.

F.

vol.

D.

(1964): Atlas and g l o s s a r y of p r i m a r y

370 p.

(1927): T h a l l o p h y t a . -

botanik, POR,

P. E.

(Springer,

In: HIRMER,

M.

Berlin). (ed.): H a n d b u c h der Pal~o-

i, 1-136.

(1968):

Solar Lake on the shores of the Red Sea.- Nature

218, 860-861. POR,

F.

D.

(1969):

coast of Sinai

Limnology

(Gulf of Elat).- V e r h a n d l u n g e n I n t e r n a t i o n a l e

nigung L i m n o l o g i e 17, POR,

F.

D.

Solar

of the h e l i o t h e r m a l Solar Lake on the

(1975): The C o l e o p t e r a - d o m i n a t e d

Lake

Verei-

1031-1034.

(Gulf of Elat,

fauna of the h y p e r s a l i n e

Red Sea).- Tenth E u r o p e a n S y m p o s i u m

on

Marine B i o l o g y 2, 563-573. POTTS,

M.,

rates

KRUMBEIN,

W.

E.

& METZGER,

J.

(1978): N i t r o g e n fixation

in a n a e r o b i c sediments d e t e r m i n e d by acetylene

new 15N field assay, KRUMBEIN,

W.

biology,

E.

vol.

reduction,

and s i m u l t a n e o u s total NI5N d e t e r m i n a t i o n . -

a In:

(ed.): E n v i r o n m e n t a l B i o g e o c h e m i s t r y and Geomicro-

~,

753-769,

711 p.

(Ann Arbor Science Publ. Inc.,

Michigan). PRATT,

B. R.

(1982):

S t r o m a t o l i t e decline - a r e c o n s i d e r a t i o n . - Geology

i0, 512-515. PURSER,

B.

H.

(1980): Les p a l ~ o s a b k h a s du Miocene inf. dans le SE de

l'Iran.- Bull. Centre Rech. P a u - S N P A 4, 235-244. PURSER,

B. H.

(1985): Coastal e v a p o r i t e systems.- In: FRIEDMAN,

KRUMBEIN, 72-102, PURSER,

W.

E.

478 p.

B.

H.

G. M. &

(eds.): H y p e r s a l i n e Ecosystems -The Gavish Sabkha,

(Springer, (Ed.)

Berlin).

(1973): The Persian Gulf, 471 p.

(Springer, Ber-

lin). RANWELL,

D.

S.

(1972): E c o l o g y of salt marshes and sand dunes,

258 p.

(Chapman & Hall, London). RASMUSSEN,

E.

Claparede RASMUSSEN, fauna REINECK,

(1953):

Asexual

reproduction

(Polychaeta S e d e n t a r i a ) . - Nature E.

(1973):

171,

in

Pygospio

elegan8

1161-1162.

S y s t e m a t i c s and ecology of the Isefjord marine

(Denmark).- O p h e l i a i_ii, 1-495. H.-E.

(1963):

see.- A b h a n d l u n g e n

S e d i m e n t g e f H g e im B e r e i c h der s H d l i c h e n Nord-

der S e n c k e n b e r g i s c h e n

Naturforschenden

Gesell-

schaft 505, 1-138. REINECK,

H.-E.

(1967):

Parameter

G e o l o g i s c h e R u n d s c h a u 56, 420-438.

von Schichtung und

Bioturbation.-

180

REINECK,

H.-E.

(1970):

Senckenbergiana REINECK,

H.-E.

Rev.

Geogr.

REINECK, zonte.-

REINKE,

J°

kHste

K.

(1940):

Ostsee0-

In:

und Ostsee, RENFRO,

A.

R.

talliferous

Natur

(1980):

und M u s e u m

Depositional

1903,

114,

305-312.

sedimentary

environ-

der DHnen an der West-

der K ~ n i g l i c h

Preussischen

281-295.

flat ecology,

GRIMPE,

und W u r z e l h o r i -

Auf der Suche nach G r e n z g ~ n g e r n :

Sitzungsberichte

Einf~hrung

Becker

Sea.-

290-296.

(1984):

Die E n t w i c k l u n g s g e s c h i c h t e

Tidal

North

Berlin).

der W i s s e n s c h a f t e n

(1985):

A.

I. B.

Schleswig.-

flats,

und fossile A l g e n m a t t e n

109, G.

(Springer,

(1903):

yon

Akademie

REMANE,

& SINGH,

Dickschliff.-

197-200.

Rezente

& GERDES,

549 p.

projizierbarer

ice action on tidal

nach N e u w e r k - S c h a r h ~ r n . -

H.-E.

ments,

30,

(1979):

und

2, 61-66.

Drift

Natur und M u s e u m

Reise

REINECK,

REISE,

Montreal

H.-E.

Eine

maritima (1976):

H.-E.

REINECK,

ReliefguS

191 p.

(Springer,

in die z o o l o g i s c h e

G. & WAGNER,

E.

(eds.):

Berlin).

Okologie

der Nord-

Die T i e r w e l t

und

der Nord-

und Erler.

(1974): deposits

Genesis

of e v a p o r i t e - a s s o c i a t e d

- A sabkha p r o c e s s . -

Economic

stratiform

Geology

me-

6_~9, 33-

45. RICHTER,

D. K., HERFORTH,

BlaugrHnalgenriffe sel

bei

Korinth

PalMontologie RICHTER,

R.

Natur RIPPKA, Y.

ROSSL,

& OTT,

E.

(1926):

Eine

159,

Neues J a h r b u c h

geologische

289-307.

R.,

J., WATERBURY,

Generic

cultures

A. E.

(Associazione

ROTHPLETZ,

A.

tralblatt SCHAFER,

(1892):

51,

W.

assignments,

of c y a n o b a c t e r i a . -

G. & TORMA,

752 po

(1983): Mineraria

Pleistoz~ne,

brackische

auf der P e r a c h o r a h a l b i n fHr

Geologie

und

14-40.

und M u s e u m 56, DERUELLES,

(1979):

haematites

(Griechenland).-

Abhandlungen

(1979):

pure

A.

mit R i v u l a r i a

Exkursion

in das

J. B., HERDMAN,

strain h i s t o r i e s J. Gen.

Microbiol.

Recent p r o g r e s s Sarda,

Ueber die B i l d u n g

M.

Wattenmeer.-

& STANIER,

R.

and p r o p e r t i e s

of

iii,

1-61.

in b i o h y d r o m e t a l l u r g y ,

Iglesias). der O o l i t h e . -

Botanisches

Zen-

265-268.

(1972):

Ecology

and p a l a e o e c o l o g y

of m a r i n e

environments,

568 p. Edinburgh. SCHOPF,

J. W.

& WALTER,

fossil-like" GROVES, Symp. lation

objects

D.J.

M. R.

- a critical

(eds.):

Pertz,

Aust.,

Pro,

Perth).

(1980):

Archaean microfossils appraisal.-

E x t e n d e d Abstracts,

23-24

(Geol.

Soc. Aust.

In:

Second

and

GLOVER, Internat.

& Internat.

"microJ.

E. &

Archaean

Geol.

Corre-

181

SCHULZ,

E.

(1936):

Das

F a r b s t r e i f e n s a n d w a t t und seine

~kologisch-bioz~notische resforsch. SCHULZ,

E.

Fauna,

eine

U n t e r s u c h u n g an der N o r d s e e . - ~ K i e l e r

Mee-

~, 359-378. & MEYER,

H.

(1940): W e i t e r e U n t e r s u c h u n g e n Hber das Farb-

s t r e i f e n s a n d w a t t . - Kieler M e e r e s f o r s c h u n g e n S o n d e r h e f t 4, 321-336. SCHWARZ, A. lung

(1936): Der L i c h t e i n f l u S auf die Fortbewegung,

und

das

W a c h s t u m bei

einigen

niederen

die Einrege-

(Littorina,

Tieren

Cardium, Mytilus, Balanus, Teredo, Sabella~ia).- S e n c k e n b e r g i a n a i_44, 429-454. SCHWARZ,

H.-U.,

EINSELE,

contoured stromatolites

G. & HERM,

D.

(1975): Quartz-sandy,

grazing-

from coastal embayments of Mauritania,

West

A f r i c a . - S e d i m e n t o l o g y 2_22, 539-561. SEILACHER,

A.

(1951): Der R ~ h r e n b a u von

Lani~e aonchilega (Polychaeta).

Ein B e i t r a g zur Deutung fossiler L e b e n s s p u r e n . - S e n c k e n b e r g i a n a

3_22,

267-280. SEILACHER, der

A.

(1953):

Studien zur P a l i e h n o l o g i e

P a l i c h n o l o g i e . - Neues

I. Uber die M e t h o d e n

J a h r b u c h fur G e o l o g i e und

Pal~ontologie

A b h a n d l u n g e n 9_66, 421-452. SHEARMAN,

D. J.

& SCHREIBER,

(1978): Evaporites of coastal sabkhas.- In: DEAN, W. E. B. C.

(eds.): Marine evaporites,

Soc. Econ. Paleontolo-

gists and M i n e r a l o g i s t s Notes No. 4, 6-42. SHINN,

E.

A.

(1969):

Submarine l i t h i f i c a t i o n of H o l o c e n e

carbonate

sediments in the Persian Gulf.- S e d i m e n t o l o g y 12, 109-144. SHINN,

E.

BEBOUT,

A.

(1983):

Tidal flat e n v i r o n m e n t . -

D. G. & MOORE,

ments, AAPG Mem.,

vol.

SIEHL, A. & THEIN, J.

C. H.

In:

33, 172-210,

L.

SKYRING,

(1978): G e o c h e m i s c h e Trends in der Minette

L. A. & BAULD, J.

c o l o n i z e d by cyanobacteria,

(Jura,

10552-1077.

(1981): Ooids: A R e v i e w . - E a r t h - S c i e n c e Reviews 16,

G. W., CHAMBRS,

sediments

P.A., environ-

708 p. Tulsa.

L u x e m b o u r g / L o t h r i n g e n ) . - G e o l o g i s c h e R u n d s c h a u 67, SIMONE,

SCHOLLE,

(eds.): C a r b o n a t e d e p o s i t i o n a l

319-355.

(1983): Sulfate r e d u c t i o n in Spencer Gulf,

South Austra-

lia.- A u s t r a l i a n Journal of M a r i n e and F r e s h w a t e r R e s e a r c h 3_44, 359374. SMIDT,

E.

(1951):

Animal p r o d u c t i o n in the Danish W a d d e n Sea.- Medd.

Komm. Danmarks Fiskeri og H a v u n d e r s o g e l s e r Ill, 1-151. SNEH,

A.

& FRIEDMAN,

G.M.

(1985): H y p e r s a l i n e sea-marginal flats of

the gulfs of Elat and Suez.- In: (eds.):

mat

L.

G. M. & KRUMBEIN, W. E.

H y p e r s a l i n e E c o s y s t e m s - The G a v i s h Sabkha,

(Springer, STAL,

FRIEDMAN,

103-135,

484 p.

Berlin).

(1985):

N i t r o g e n - f i x i n g c y a n o b a c t e r i a in a m a r i n e m i c r o b i a l

(Dissertation,

R i j k s u n i v e r s i t e i t Groningen).

182

STAL,

L.

J.

Techniek STAL,

L.

& GEMERDEN,

H. VAN

(1984):

Microbielle

Marten.-

Natur en

i_~i, 871-889. J.,

taneous

GEMERDEN,

assay

microbial

of

H. VAN & KRUMBEIN,

chlorophyll

communities.-

W. E.

(1984a):

and b a c t e r i o c h l o r o p h y l l

Journal

of B a c t e r i o l o g i c a l

The simulin

natural

Methods

~,

295-

306. STAL,

L.

J.,

GEMERDEN,

development

of

E c o l o g y 31, STAL,

L.

tion

associated

L. J.

& KRUMBEIN, of

Microbiol. STAL,

L. J.,

Lett.

ii,

(1985):

mat.-

Structure

FEMS

and

Microbiology

W. E.

Biology

(1981):

(1984b):

mat of a

marine

fixa-

laminated

8_22, 217-224.

Aerobic

nitrogen

08cillatoria

marine

Nitrogen

fixation

in pure

(cyanobacteria).-

FEMS

295-298. W. E.

(1985):

Oxygen protection

of n i t r o g e n a s e

nitrogen

fixing,

non-heterocystous

cyanobacterium

sp.- Arch.

KRUMBEIN,

fen-Sandwatt meer.-

Microbiol.

W. E.

- Ein

laminiertes

Ver~ffentlichungen

143,

& GEMERDEN,

72-76.

H. VAN

(1984c):

mikrobielles

Das F a r b s t r e i -

Okosystem

der N a t u r f o r s c h e n d e n

im

Watten-

Gesellschaft

zu Emden

1-60.

STANIER,

R. Y.

& COHEN-BAZIRE,

cyanobacteria.STENSEN,

N.

(Florenz

Ann.

(1967):

Hber Festes,

G.

W. E.

L. J. & KRUMBEIN,

Oscillatoria

~,

Marine

a benthic

in the a e r o b i c a l l y

STAL,

S. & KRUMBEIN,

w i t h the c y a n o b a c t e r i a l

ecosystem.-

cultures

W. E.

marine m i c r o b i a l

111-125.

J., GROSBERGER,

microbial STAL,

H. VAN & KRUMBEIN,

a benthic

Das Feste

In:

F. et. al

s c h a f t e n Neue Folge, Frankfurt STOLZ,

Phototrophic

im Festen. in a n d e r e m

BALKE,

S., GERIKE,

(eds.):

Ostwalds

vol. ~, 8-255

prokaryotes:

the

3!I, 225-274. Vorl~ufer Festen H.,

einer A b h a n d l u n g

eingeschlossen

HARTNER,

Klassiker

(Akademische

W.,

ist

KERSTEIN,

der exakten W i s s e n Verlagsgesellschaft,

am Main).

J.F.

(1983):

Fine

nity at Laguna Figueroa, situ

(1977):

das in der Natur

1669).-

& KLEMM,

G.

Rev. Microbiol.

study

structure

of the s t r a t i f i e d

Baja California,

of the laminated

sediments.-

Mexico.

microbial

commu-

I. Methods

Precambrian

of in

Research

20,

479-492. STREIF,

H.,

kHste.STROTHER,

P.

organisms Western

KOSTER,

Die KUste K.,

R. 32,

(1978):

KNOLL,

from the Late

Greenland.-

Zur G e o l o g i e

der d e u t s c h e n

Nordsee-

30-49. A.

H.

& BARGHOO~N,

Precambrian

Palaeontol.

26,

E.

Narssarssuk 1-32.

S.

(1983):

Formation,

MicroNorth-

183

TEBBUTT,

G.

E., CONLEY,

C. D. & BOYD,

D. W.

(1965): L i t h o g e n e s i s of a

d i s t i n c t i v e carbonate rock fabric.- Wyoming U n i v e r s i t y C o n t r i b u t i o n s G e o l o g y 4, 1-13. TEICHERT,

C.

(1958):

Concepts of facies.- Bull. Amer. Assoc.

Petrol.

Geol. 42, 2718-2744. TEICHERT, Ass. THEIN,

C.

(1970): Oolite,

Petrol. Geol., J,

oolith and ooid: D i s c u s s i o n . - Bull. Amer.

54, 26.

(1975): S e d i m e n t o l o g i s c h - s t r a t i g r a p h i s c h e U n t e r s u c h u n g e n in

der M i n e t t e des D i f f e r d i n g e r Beckens Luxembourg, TISLJAR,

J.

Outer

24, 60 S.

566-575,

TRUDINGER,

(Yugoslavia).655 p.

TRUSHEIM,

P. A. & SWAINE,

D. J.

PERYT,

T.

M.

F.

(Eds.) 612 p.

(1979): B i o g e o c h e m i c a l cycling

(1935): Eine T i t a n e i s e n e r z - S e i f e von W a n g e r o o g e . - Sencken62-72.

S. A. & TWENHOFEL, J.

Neapel

W. H.

(1952): S e d i m e n t a t i o n and s t r a t i g r a p h y

(1885):

und

Die

J.

1-27.

g e s t e i n s b i l d e n d e n K a l k a l g e n des Golfes

die E n t s t e h u n g

strukturloser

D e u t s c h e n G e o l o g i s c h e n G e s e l l s c h a f t 37, WALTHER,

Coated

(Elsevier Scientific Publishing

of the H u r o n i a n of Upper Michigan.- Amer. J. Sci. 250, WALTHER,

(ed.):

Berlin).

Amsterdam).

b e r g i a n a 17, TYLER,

In:

(Springer,

of m i n e r a l - f o r m i n g elements, Company,

Publ. Serv. Geol.

(1983): Coated grain facies in the Lower Cretaceous of the

Dinarides

Grains,

(Luxemburg).

yon

Kalke.- Zeitschrift

der

329-357.

(1888): Die K o r a l l e n r i f f e der Sinaihalbinsel.

Geologische

und b i o l o g i s c h e B e o b a c h t u n g e n . - A b h a n d l u n g e n der m a t h e m a t i s c h - p h y s i schen Classe der K ~ n i g l i c h S ~ c h s i s c h e n G e s e l l s c h a f t der W i s s e n s c h a f ten 14, 439-505. WARREN,

J. K.

(1982): The h y d r o l o g i c a l s i g n i f i c a n c e of H o l o c e n e tepees,

stromatolites,

and

b o x w o r k limestones

A u s t r a l i a . - J. Sediment. WESTBROEK, & VRIND,

Petrol.

P., V R I N D - D E JONG,

in coastal salinas in

E. W. DE, WAL,

P. VAN DER, BORMAN, A. H.

J. P. M. DE (1985): B i o p o l y m e r - m e d i a t e d Ca and Mn accumula-

tion and b i o m i n e r a l i z a t i o n . - G e o l o g i e en M i j n b o u w 64, WHITE, W. A.

M.

5-15.

(1961): Colloid p h e n o m e n a in s e d i m e n t a t i o n of argillaceous

rocks.- J. Sediment. WILSON,

South

52, 1171-1201.

J.,

JONES,

Petrol. D.

31, 560-570.

& RUSSELL,

J.D.

(1980): Glushinskite,

a

n a t u r a l l y o c c u r r i n g m a g n e s i u m o x a l a t e . - Miner. Mag. 4~3, 837-840. WUNDERLICH, 14-18.

F.

(1984): B i o t u r b a t i o n auf Raten.- Natur und M u s e u m 114,