Geological Field Trips in Central Western Europe: Fragile Earth International Conference, Munich, September 2011

@®©U©~TI~cmn fTI®UcQl tnrilfP)~ TI!fl) (C®Ifl)ttlicmU W®~tt®lilfl) [E(WJ[J@[p)®~ Fragile Earth International Conference, Munich, September 2011 edited by Sara Carena, Anke M. Friedrich, and Bernd Lammerer

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Field Guide 22

THE GEOLOGICAL SOCIETY OF AMERICA®

Geological Field Trips in Central Western Europe: Fragile Earth International Conference, Munich, September 2011

edited by Sara Carena Ludwig-Maximilians Universität München Department of Earth and Environmental Sciences Luisenstr. 37 80333 Munich Germany Anke M. Friedrich Ludwig-Maximilians Universität München Department of Earth and Environmental Sciences Luisenstr. 37 80333 Munich Germany Bernd Lammerer Ludwig-Maximilians Universität München Department of Earth and Environmental Sciences Luisenstr. 37 80333 Munich Germany

Field Guide 22 3300 Penrose Place, P.O. Box 9140

Boulder, Colorado 80301-9140, USA

2011

Copyright © 2011, The Geological Society of America (GSA), Inc. All rights reserved. GSA grants permission to individual scientists to make unlimited photocopies of one or more items from this volume for noncommercial purposes advancing science or education, including classroom use. In addition, an author has the right to use his or her article or a portion of the article in a thesis or dissertation without requesting permission from GSA, provided the bibliographic citation and the GSA copyright credit line are given on the appropriate pages. For permission to make photocopies of any item in this volume for other noncommercial, nonprofit purposes, contact The Geological Society of America. Written permission is required from GSA for all other forms of capture or reproduction of any item in the volume including, but not limited to, all types of electronic or digital scanning or other digital or manual transformation of articles or any portion thereof, such as abstracts, into computer-readable and/ or transmittable form for personal or corporate use, either noncommercial or commercial, for-profit or otherwise. Send permission requests to GSA Copyright Permissions, 3300 Penrose Place, P.O. Box 9140, Boulder, Colorado 80301-9140, USA. GSA provides this and other forums for the presentation of diverse opinions and positions by scientists worldwide, regardless of their race, citizenship, gender, religion, sexual orientation, or political viewpoint. Opinions presented in this publication do not reflect official positions of the Society. Copyright is not claimed on any material prepared wholly by government employees within the scope of their employment. Published by The Geological Society of America, Inc. 3300 Penrose Place, P.O. Box 9140, Boulder, Colorado 80301-9140, USA www.geosociety.org Printed in U.S.A. Cataloging-in-Publication Data for this volume is available from the Library of Congress. Cover: Digital elevation model, from Shuttle Radar Topography Mission (SRTM) data, of the region covered by the field trips described in this volume. Color indicates elevation, with a low of 50 m a.s.l. in the Rhine Graben, and a high of 4000 m in the western Alps.

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Contents

Preface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . v 1. The Geodetic Observatory Wettzell—A fundamental reference point . . . . . . . . . . . . . . . . . . . . . . . 1 Urs Hugentobler, Alexander Neidhardt, Pierre Lauber, Martin Ettl, K. Ulrich Schreiber, Reiner Dassing, Thomas Klügel, Stefan Riepl, Günther Herold, Gerhard Kronschnabl, Christian Plötz, and Uwe Hessels 2. KTB Deep Drilling Site and Czech-Bavarian Geopark—Two best practice examples of geoscience outreach . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 Frank Holzförster and Andreas Peterek, with a contribution from Joachim M. Rabold 3. Geo-education and geopark implementation in the Vulkaneifel European Geopark . . . . . . . . . . 29 Peter Bitschene and Andreas Schüller 4. Sedimentary facies and paleontology of the Ottnangian Upper Marine Molasse and Upper Brackish Water Molasse of eastern Bavaria: A field trip guide . . . . . . . . . . . . . . . . . . . . . . 35 Simon Schneider, Martina Pippèrr, Dorothea Frieling, and Bettina Reichenbacher 5. Rhenodanubian Flyschzone, Bavarian Alps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51 Reinhard Hesse 6. Field trip to the Northern Alps between Munich and the Inn Valley . . . . . . . . . . . . . . . . . . . . . . . 75 Bernd Lammerer, Hugo Ortner, and Alexander Heyng 7. Field trip to the Tauern Window region along the TRANSALP seismic profile, Eastern Alps, Austria . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101 Bernd Lammerer, Jane Selverstone, and Gerhard Franz 8. Glaciological and hydrometeorological long-term observation of glacier mass balance at Vernagtferner (Vernagt Glacier, Oetztal Alps, Austria) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121 E. Mayr, H. Escher-Vetter, C. Mayer, M. Siebers, and M. Weber

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Preface

The field trips described in this volume were organized in conjunction with the “Fragile Earth” international conference of 4–7 September 2011, in Munich, Germany. The conference was jointly organized by the Geological Society of America and the German Geological Societies (Geologische Vereinigung and Deutsche Gesellschaft für Geowissenschaften), and it was hosted by the Department of Earth and Environmental Sciences at Ludwig-Maximilians Universität (University of Munich). The topics of the field guides represent the focus of the conference, which was defined as “Geological processes from global to local scales and associated hazards and resources.” Chapter 4 is included in this volume, even though this trip was not offered at the time of the conference, because its theme matched the scope of the meeting. “Fragile Earth” is one of the scientific themes at the Department of Earth and Environmental Sciences at the University of Munich. This theme emphasizes that the Earth’s surface is highly sensitive to the exogenic and endogenic geological processes that generate both natural resources and events such as earthquakes, volcanic eruptions, landslides, storms, or tsunamis. The vulnerability of a region to geological processes and the possible global implications were demonstrated in March 2011, when a magnitude 9.0 earthquake occurred offshore northeastern Japan. The fault rupture that produced this earthquake displaced the seafloor by several meters, causing both a large tsunami and subsidence of the coastal area between Sendai and Fukushima in northeastern Japan. Tsunami waves flooded the populated coastal area and seriously damaged the cooling system of the nuclear reactor of Fukushima, with the end result of a significant radiation release into the environment. Thousands of Japanese lost their lives, and hundreds of thousands were still homeless two months after the earthquake-tsunami-nuclear reactor event series. MunichRe, the world’s largest reinsurer, recently reported an economic loss for the first quarter of 2011 of more than 1 billion euros. In addition, the nuclear disaster of Fukushima triggered protests against nuclear power plants and led to a significant revision of nuclear energy policies of several other countries. Thus a regional geological event had important social repercussions worldwide as well. The occurrence of great earthquakes, tsunamis, and other natural events at the regional scale is ultimately controlled by global dynamic processes in the Earth’s interior. These processes build and modify the lithosphere and its surface, which is also affected by climatically driven processes. Therefore, the lithosphere and its surface are unique recorders of geological processes at all scales. The understanding of geological structures, deposits, and landforms at the regional scale and the quantification of surface deformation is of particular importance in linking the global driving forces to resultant local hazards and resources. This series of field trips examines the records and recording tools of geological processes, from plate motions (Chapter 1), to deep crustal structure and deformation (Chapters 2, 5, 6, 7), to near-surface processes and interactions between the Earth’s surface and climate (Chapters 3, 4, 8). Chapters 1–3 focus on observatories and communicating geosciences to the public through geoparks, while Chapters 4–8 loosely define a north-south geological cross-section through the eastern Alps of Germany and Austria and its foreland basin (Fig. 1).

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Figure 1. Top: Digital elevation model, from SRTM data, of the region covered by the field trips described in this volume. Each trip area is shown by a rectangle; numbering corresponds to the chapters in this volume. Color indicates elevation, with a low of 50 m a.s.l. in the Rhine Graben, and a high of 4000 m in the western Alps. Bottom: the same region as above is shown together with the main drainages; several significant physiographic and geological features are also marked on this image.

The Geological Society of America Field Guide 22 2011

The Geodetic Observatory Wettzell—A fundamental reference point Urs Hugentobler* Alexander Neidhardt Pierre Lauber Martin Ettl Forschungseinrichtung Satellitengeodäsie, Technische Universität München, Arcisstr. 21, 80333 München, Germany K. Ulrich Schreiber Reiner Dassing Thomas Klügel Stefan Riepl Günther Herold Gerhard Kronschnabl Christian Plötz Uwe Hessels Bundesamt für Kartographie und Geodäsie, Geodätisches Observatorium Wettzell, Sackenrieder Str. 25, 93444 Bad Kötzting, Germany

ABSTRACT This field trip provides the opportunity to visit a prominent fundamental observatory where a variety of space geodetic instruments are routinely operated for precise location of a stable reference point in space, serving the geodetic community and society. The co-location of three large radio telescopes and two laser ranging facilities at the same observatory is exceptional; the large “G” ring laser is a unique instrument. Staff members are available to explain technical and operational details and to answer questions. Last but not least, the observatory is located in the picturesque landscape of the Bavarian Forest.

OVERVIEW OF THE FIELD TRIP

formance, and will answer questions. The Geodetic Observatory Wettzell (Fig. 2) is a fundamental observatory, where several space geodetic techniques are employed to realize a well-defined reference point in space. It hosts radio telescopes, satellite laser ranging telescopes, equipment to track satellites of the Global Navigation Satellite Systems (GNSS), the world’s most stable active laser gyroscope, a superconducting gravimeter, a frequency and time

This one-day field trip explores the Geodetic Observatory Wettzell in the Bavarian Forest, ~200 km east of Munich, close to the Czech border (Fig. 1). After a short introduction to the observatory, the different space geodetic instruments are open for visiting. Staff members will explain operation principles as well as per-

*[email protected] Hugentobler, U., Neidhardt, A., Lauber, P., Ettl, M., Schreiber, K.U., Dassing, R., Klügel, T., Riepl, S., Herold, G., Kronschnabl, G., Plötz, C., and Hessels, U., 2011, The Geodetic Observatory Wettzell—A fundamental reference point, in Carena, S., Friedrich, A.M., and Lammerer, B., eds., Geological Field Trips in Central Western Europe: Fragile Earth International Conference, Munich, September 2011: Geological Society of America Field Guide 22, p. 1–6, doi:10.1130/2011.0022(01). For permission to copy, contact [email protected]. ©2011 The Geological Society of America. All rights reserved.

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standard consisting of hydrogen masers and cesium atomic clocks, a seismometer, and additional sensors for monitoring the environment (Fig. 3). The main objective of the observatory—in conjunction with similar observatories distributed over the globe—is the realization of highly accurate and long-term stable global reference frames as a metrological basis for the measurement of variations and interpretation of processes in the Earth system.

FUNDAMENTAL OBSERVATORIES The geophysical interpretation of changes and mass variations in the Earth system, such as tectonic plate motions, global and local deformation, glacial isostatic adjustment, hydrological and atmospheric loading, or sea-level rise requires a highly precise and long-term stable global reference frame as

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Figure 2. Geodetic Observatory Wettzell with the 20 m and the two 13 m radio telescope dishes as well as the two satellite laser telescope domes.

the metrological basis for referencing the measurements. The International Terrestrial Reference Frame (ITRF; Altamimi et al., 2011) is established and regularly updated by the International Earth Rotation and Reference Systems Service as one of the primary products of the Global Geodetic Observing System (GGOS; Plag and Pearlman, 2009). The realization and maintenance of the reference frame relies on global networks of different space geodetic sensors such as GNSS permanent receivers,

Very Long Baseline Interferometry (VLBI) radio telescopes, Satellite and Lunar Laser Ranging (SLR/LLR) telescopes, and Doppler Orbitography Radiopositioning Integrated by Satellite (DORIS) beacons. At fundamental geodetic observatories, several of these techniques are co-located at a single site, allowing the tying together of technique-specific networks. As cornerstones, they enable joint analysis of the observation data sets from different

Figure 3. Location of the instruments at the Geodetic Observatory Wettzell (photo composition: Amberg, BKG).

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techniques. This in turn allows for exploitation of the strengths of the individual techniques for a combined reference frame. As an example, satellite techniques—in particular SLR—allow the precise location of the frame origin defined as the mean center of mass of the Earth, while VLBI is the only technique that is able to provide the orientation of the Earth in space. Last but not least, a fundamental observatory represents a primary reference point of high importance for national reference frame maintenance, and it is an important component of the geodata infrastructure of the country operating the station. HISTORY OF THE GEODETIC OBSERVATORY The Geodetic Observatory Wettzell is operated by the German Federal Agency for Cartography and Geodesy (BKG, Bundesamt für Kartographie und Geodäsie) and by the Research Facility for Satellite Geodesy (FESG, Forschungseinrichtung Satellitengeodäsie) of the Technische Universität München. Its origins go back to the year 1971, when the former Institute for Applied Geodesy (now the BKG) selected the area in the former Air Defense Identification Zone for the installation of satellite laser ranging equipment. In September 1972, a first-generation satellite laser ranging system was installed (measurement accuracy of 1 m) that was replaced in 1977 by a third-generation measurement system (measurement accuracy of 1 dm). From 1980 to 1983, the 20 m radio telescope was built in the framework of a Collaborative Research Centre, funded by the German Science Foundation. Since 1986, the development of the observatory and related research has been coordinated by the Research Group Satellite Geodesy (Forschungsgruppe Satellitengeodäsie), a joint venture of BKG, FESG and the Institute of Astronomical and Physical Geodesy of the Technische Universität München, the German Geodetic Research Institute (DGFI, Deutsches Geodätisches Forschungsinstitut), and the Institute of Geodesy and Geoinformation of the University of Bonn, Germany. RADIOINTERFEROMETRY The most prominent instrument located at the Geodetic Observatory is the dish of the 20 m radio telescope. It is used for VLBI observations of very distant compact radio sources (quasars). The observations are carried out by large radio telescopes on all continents and are pursued in the framework of international programs coordinated by the International VLBI Service for Geodesy and Astrometry (Schlüter and Behrend, 2007). The Wettzell radio telescope was specially designed for geodetic measurements and participates in all corresponding international observation campaigns. The measured quantity is arrival time differences of microwave signals from quasars at distances of up to 10 billion light years at two or more large radio telescopes on different continents. The signals are recorded—together with signals from ultrastable hydrogen maser frequency generators—on fast hard

discs (data rates of up to 2 Gbit per second). The data is transferred by surface mail or fast Internet connections to correlation centers, where interferometric fringes are identified and converted to light traveltime differences between the participating telescopes with typical precision of ~10 ps. These observations are the basis for measuring and monitoring the Earth’s rotation in space and its variation with an accuracy of fractions of milliarcseconds. The effort of the international network of geodetic radio telescopes leads to the realization of an ultra-stable inertial reference frame, the International Celestial Reference Frame, whose second version was published in 2010 (Fey et al., 2009). Furthermore, the VLBI observations contribute to the realization of the International Terrestrial Reference Frame as well as to the monitoring of Earth orientation parameters that are, for example, important for the navigation of interplanetary space probes. In fall 2010, two new 13 m radio telescopes were built at the Geodetic Observatory. Currently, the high-frequency electronics is being installed. These new Twin Telescopes Wettzell conform to the vision developed under the acronym VLBI2010 (Niell et al., 2006), a concept resulting in more accurate and short latency interferometric measurements using telescopes with fast slew rates (12 deg/s in azimuth, 6 deg/s in elevation) and employing broadband microwave receiving electronics (2–14 GHz). The telescopes will go into service in 2012 and will support the 20 m radio telescope, which has already been operating for nearly 30 years. Hand in hand with these new installations, development of concepts are ongoing that allow for a high degree of automation of telescope control and execution of observation sessions. SATELLITE AND LUNAR LASER RANGING The first space geodetic instrument installed at the Geodetic Observatory was an SLR telescope. Today, the Wettzell Laser Ranging System is in routine operation. It consists of a 75 cm monostatic telescope that is used to send ultra-short (120 ps) pulses of Nd:YAG lasers (wavelengths of 1064 nm—infrared, and 532 nm—green) at a rate of 10 Hz to satellites equipped with Laser Retro Reflectors, and to receive the reflected photons. The traveltimes of the light pulses are measured by event timers with an accuracy of 2 ps, allowing us to measure the distance between the telescope and the satellite at the sub-centimeter level. The laser system is operated 24 hours per day and 365 days per year. Main targets are geodetic satellites such as LAGEOS 1 and 2 (orbit height: ~6000 km), Starlette and Stella (~1000 km), ETALON 1 and 2 (~20,000 km), altimetry satellites such as Jason 1 and 2 (~1000 km) and ENVISAT (~1000 km), as well as satellites of the Global Positioning System (GPS) and Global Navigation Satellite System (GLONASS) constellation. The measurements—together with the observations of other observatories worldwide—are used to determine precise orbits for the observed satellites. This in turn helps us measure the gravity field of the Earth, obtain precise orbit height for the altimetry satellites measuring the sea surface height and its variations

The Geodetic Observatory Wettzell using short radar pulses, and validate orbits determined with alternative measurements. The Wettzell Laser Ranging System was and will again be used to measure ranges to reflectors located on the surface of the Moon placed there by the Apollo and Lunokhod missions. Lunar ranging measurements help us in understanding the internal structure of the moon and to test the strong equivalence principle of general relativity. The laser system was used to perform one-way range measurements to the NASA Lunar Reconnaissance Orbiter and it will be used for laser time transfer to the ultra-stable ACES (Atomic Clock Ensemble in Space) clocks that will be flown onboard the International Space Station between 2013 and 2015. The current number of satellites equipped with retroreflectors required the installation of a new ranging facility, the Satellite Observing System Wettzell that will become operational in 2011. The new system uses a bistatic telescope with a receiving aperture of 50 cm. The Titanium Saphir laser operates at two frequencies (425 and 850 nm) at a pulse repetition rate of 1 kHz. PERMANENT GNSS STATIONS Permanent GPS equipment has been operating in Wettzell since 1986. Today a number of different permanent GPS and GLONASS equipment is in operation. One of them is the official International GNSS Service (IGS, Dow et al., 2009) station, while the others are used for comparison, monitoring of local deformation, time transfer, or specific experiments. Two receivers, connected to the same antenna, are capable of tracking the new signals broadcast by the Galileo test satellites GIOVE-A and -B. This station is part of the Cooperative Network for GIOVE Observation (CONGO), a global tracking network installed by the German Aerospace Agency (DLR), BKG, the Deutsches GeoForschungsZentrum, and the Centre National d’Etudes Spatiales, and currently consisting of 16 receivers (Montenbruck et al., 2010). Additional GNSS equipment is operated by staff from Wettzell in different countries worldwide. RING LASER GYROSCOPE A unique instrument operated at the Geodetic Observatory is the large active ring laser gyroscope called “G” built in 2001. It is installed in a large and thermally stable underground laboratory and consists of a square cavity filled with laser gas through which two laser beams propagate clockwise and counterclockwise, reflected at the corners by perfectly reflecting mirrors. The laser revolves around an area of 4 m by 4 m and is mounted on a thermally inert Zerodur dish. Due to Earth rotation, the two counter-rotating beams cause an interference pattern at detectors mounted at the corners. The corresponding Sagnac frequency of this interference allows us to measure the variations of the Earth rotation with high precision. The ring laser thus acts as a giant and ultra-stable inertial sensor.

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In addition to the Earth’s rotation, variations of the orientation of the ring laser plane due to local deformations and seismic signals are also recorded by the ultra-sensitive device. It allows measurement of rotational components of teleseismic waves from earthquakes occurring anywhere on the globe (Schreiber et al., 2009) as well as microseismicity caused by storm-induced waves in the Northern Atlantic. Pressure loading signals from passing atmospheric high and low pressure areas can also be identified in the recorded time series. The ring laser operations in Wettzell and the associated research are performed in close cooperation with the Department of Physics and Astronomy of the University of Canterbury, Christchurch, New Zealand. TIME AND FREQUENCY, GRAVIMETRY, AND OTHER SENSORS Space geodetic observations are based mostly on light traveltime measurements and thus rely on precise realization of time and frequency at the station. Consequently, several ultra-stable hydrogen masers and cesium atomic clocks are operated at the Geodetic Observatory that distribute time and frequency to the various instruments and contribute to the International Atomic Time realized by the Bureau International des Poids et Mesures in Paris. Complementary to geometric measurements, gravimetric observations are also routinely performed at the Geodetic Observatory Wettzell. A superconducting gravimeter is in permanent operation, and campaigns using absolute gravimeters are periodically pursued. In addition, the observatory acts as a platform for comparison campaigns of absolute gravimeters operated throughout Europe. A number of additional sensors are installed at the observatory that log environmental parameters such as seismicity, groundwater flow and hydrology, and meteorological conditions. TIGO AND O’HIGGINS BKG operates not only the Geodetic Observatory Wettzell (together with TUM) but also similar, although smaller, observatories. The Transportable Integrated Geodetic Observatory (TIGO) equipped with VLBI, SLR, and GNSS instruments is located in Concepción, Chile, and is operated jointly with the Universidad de Concepción. VLBI and GNSS observations are also performed at the German Antarctic Receiving Station in O’Higgins that is operated by DLR. With these two fundamental observatories in the Southern Hemisphere, German institutions significantly invest into global monitoring of the Earth, because a homogeneous distribution of observatories around the globe is essential for the realization of a stable global reference frame. ACKNOWLEDGMENTS We would like to acknowledge the many comments and suggestions contributed by the two reviewers, Roland Pail and Ralf

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Schmid, as well as Florian Hofmann for the careful preparation of the site map. REFERENCES CITED Altamimi, Z., Collilieux, X., and Métivier, L., 2011, ITRF2008: an improved solution of the international terrestrial reference frame: Journal of Geodesy, doi:10.1007/s00190-011-0444-4. Dow, J.M., Neilan, R.E., and Rizos, C., 2009, The International GNSS Service in a changing landscape of Global Navigation Satellite Systems: Journal of Geodesy, v. 83, no. 3–4, p. 191–198, doi:10.1007/s00190-008-0300-3. Fey, A.L., Gordon, D., and Jacobs, C.S., eds., 2009, The second realization of the International Celestial Reference Frame by Very Long Baseline Interferometry: Frankfurt am Main, Earth Rotation and Reference Systems Service Technical Note, no. 35, ISBN 3-89888-918-6. Montenbruck, O., Hauschild, A., and Hessels, U., 2010, Characterization of GPS/GIOVE sensor stations in the CONGO network: GPS Solutions, doi:10.1007/s10291-010-0182-8.

Niell, A.E., Whitney, A., Petrachenko, B., Schlüter, W., Vandenberg, N., Hase, H., Koyama, Y., Ma, C., Schuh, H., and Tuccari, G., 2006, VLBI2010: Current and future requirements for geodetic VLBI systems: 2005 International VLBI Service for Geodesy and Astrometry (IVS) Annual Report, p. 13–40, NASA/TP-2006-214136. Plag, H.-P., and Pearlman, M., eds., 2009, Global Geodetic Observing System: Meeting the Requirements of a Global Society on a Changing Planet in 2020: Berlin, Springer, 332 p., doi:10.1007/978-3-642-02687-4. Schlüter, W., and Behrend, D., 2007, The International VLBI Service for Geodesy and Astrometry (IVS): current capabilities and future prospects: Journal of Geodesy, v. 81, no. 6-8, p. 379–387, doi:10.1007/s00190-006 -0131-z. Schreiber, K.U., Hautmann, J.N., Velikoseltsev, A., Wassermann, J., Igel, H., Otero, J., Vernon, F., and Wells, J.-P., 2009, Ring laser measurements of ground rotations for seismology: Bulletin of the Seismological Society of America, Special Issue on Rotational Seismology, v. 99, no. 2B, p. 1190– 1198, doi:10.1785/0120080171. MANUSCRIPT ACCEPTED BY THE SOCIETY 19 APRIL 2011

Printed in the USA

The Geological Society of America Field Guide 22 2011

KTB Deep Drilling Site and Czech-Bavarian Geopark— Two best practice examples of geoscience outreach Frank Holzförster* GEO-Zentrum an der KTB, Am Bohrturm 2, D-92670 Windischeschenbach, Germany Andreas Peterek* Geopark Bayern-Böhmen, Marktplatz 1, D-92711 Parkstein, Germany with a contribution from Joachim M. Rabold Urwelt-Museum Bayreuth, Kanzleistraße 1, D-95444 Bayreuth, Germany

ABSTRACT This excursion gives an introduction to the geoscience education region of northeastern Bavaria. Thanks to its rich mining history, the geological variability and the long record of geological research in the area itself and its eastward continuation into Bohemia, northeastern Bavaria is a prime destination for geoscience education of non-geologists. Ordinary people experience to what extent their living environment is related to geology. Geoscientific knowledge is a major requirement for future sustainable development, but it is currently underrepresented in society. The geological outreach center at the continental deep drilling site is based on the famous Continental Deep Drilling Program (KTB) that probed the deeper crust of the Earth between 1987 and 1994. The outreach center communicates modern geoscience research results from the perspective of a dynamic Earth, which directly affects everybody’s life. Centrally positioned in a geologically unique area, it highlights the geological significance of the entire region. It is an almost natural development that such a region qualified to become the Czech-Bavarian Geopark. Its key topics are geodynamic and morphodynamic processes, human activity as a factor of landform development, geology as a fundamental base of economic and cultural development, the geological center of Europe, and the development from neptunism to the System Planet Earth. Geological outreach of the geopark obviously combines with social and cultural aspects. The geopark aims to emphasize the specific regional features in order to improve the public understanding of geological objects and their meaning in nature, and it provides an opportunity for the identification of the population with their regional living environment. Last but not least, geoscience outreach in the area is widely recognized as providing a significant benefit to the tourism industry.

*[email protected]; [email protected]. Holzförster, F., and Peterek, A., 2011, KTB Deep Drilling Site and Czech-Bavarian Geopark—Two best practice examples of geoscience outreach, in Carena, S., Friedrich, A.M., and Lammerer, B., eds., Geological Field Trips in Central Western Europe: Fragile Earth International Conference, Munich, September 2011: Geological Society of America Field Guide 22, p. 7–27, doi:10.1130/2011.0022(02). For permission to copy, contact [email protected]. ©2011 The Geological Society of America. All rights reserved.

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INTRODUCTION The region of northeastern Bavaria and the eastward neighboring Bohemian part of the Czech Republic are characterized by an extreme geological variability. Variscan basement rocks, Mesozoic to Cenozoic marine to terrestrial sediments, Cenozoic volcanics, an excellent fossil record, a complex structural development, and a long and vibrant mining history make the region unique in Bavaria. Geoscience research in this area goes back to a long line of famous people and projects, including Johann Wolfgang von Goethe (1749–1832), Mathias von Flurl (1756–1823), Alexander von Humboldt (1769–1859), Carl Wilhelm von Gümbel (1823–1898) and eventually the German Continental Deep Drilling Program (1987–1994). The unique geology, the geoscientific history, and the geoscientific infrastructure in the region naturally translate into the development of a geoscience outreach program. This program development is largely carried out on two fronts: (1) the restructuring of the former KTB Deep Drilling Site from a pure research institution to a geoscience education center that is open to the public, and (2) the development of the Czech-Bavarian Geopark, which coordinates the already existing multifold geoactivities for everybody (e.g., guided tours, exhibitions, museums, show mines, talks, etc.). Together, both institutions create a regional identification with the geological specifics in northeastern Bavaria. Both units have become relevant factors for the recognition of the region and thus for the regional tourism sector, too. Also significant is the financial aspect for the population, because geoscience outreach contributes to personal income. In addition, geoscience education programs carry geological knowledge to the public all over Bavaria and elsewhere. Through experiencing geoscience in hands-on workshops, during specific field trips, thematic guided tours, and visits to numerous museums and exhibitions, expert knowledge spreads to ordinary people who start realizing that they actually face climate change, soil degradation, water shortage, limited resources, etc. Current decision-makers in politics, industry, and administration have to deal with geoscience-related problems, usually without sufficient understanding, because geoscience topics were largely neglected in general education. However, in order to handle those challenges by means of sustainable development, both the adult and the growing generation need a solid understanding of the “System Earth” we depend upon. Together the Czech-Bavarian Geopark and the “GEOZentrum an der KTB” aim for this goal and provide a qualified geoscience education to the entire public. GEOLOGICAL FRAMEWORK OF THE CZECHBAVARIAN GEOPARK The area of the Czech-Bavarian Geopark (CBG) is composed of three geological units (Fig. 1): the Mesozoic cover sediments of the Franconian platform (Jurassic to Upper Cretaceous), the block-faulted sedimentary cover along the border zone of

the Bohemian Massif (Triassic and Upper Cretaceous), and the Variscan basement of the Bohemian Massif (Precambrian to Lower Permian). The excursion will touch both the block-faulted border zone and the Variscan basement. The CBG is situated in the western Cenozoic Eger Rift. For the geological evolution of the area, three phases are crucial. First phase: In the course of the Variscan orogeny in the Devonian and Carboniferous (ca. 410–290 Ma), the large continental blocks of Laurentia and Baltica collided with periGondwana–derived crustal fragments such as “Avalonia” and “Armorica.” During the orogeny, the Paleozoic rock units (sediments and volcanics) were subducted, folded, and metamorphosed. Toward the end of this orogeny, granites intruded into the metamorphosed framework. Second phase: During post-Variscan times, the Bohemian Massif was subjected to polyphase regional uplift and denudation for a long time. In particular, this is well documented by the nearly complete late Paleozoic to Cenozoic stratigraphic record in the western foreland (Schröder et al., 1997). Paleogeographic and tectonic reconstructions from the stratigraphic record are in a good accordance with thermo-geochronological data from the basement area (e.g., apatite fission track ages; Wagner et al., 1997). Third phase: Since the late Eocene, the continental Eger Rift evolved in the area of the Paleozoic suture that originated from the Variscan collision of Laurasia and Gondwana. Basement Area Saxothuringian Region The basement units in the geopark area are assigned to various geological units. The so-called “Saxothuringian region” comprises Paleozoic units in the Frankenwald area, the Fichtelgebirge, the western Erzgebirge (Krušné Hory), and the northernmost part of the Oberpfälzer Wald (Upper Palatinate Forest). These units are deformed by several NE-SW–trending anticlinal and synclinal structures offset by prominent NW-SE–trending fault zones, which experienced polyphase post-Variscan tectonics (e.g., the Franconian Lineament = Fränkische Linie in German, and the Mariánské Lázně Fault). Whereas the units of the Frankenwald are non-metamorphosed or only weakly metamorphosed, the rocks in the other areas underwent polyphase metamorphism. Late Variscan metamorphism reached low to medium

Figure 1. Geology of the field trip area. Base: Geol. Karte von Bayern 1:500,000 (4th ed., Bayerisches Geologisches Landesamt, 1996). Inset: Subdivision of the Variscan orogen in central Europe according to Suess (1903, 1912) and Kossmat (1927). A—Franconian platform; B—Block-faulted border zone; C—Variscan basement. FG—Fichtel Mountains (Fichtelgebirge); H.—Hunsrück Mountains; MM— Münchberg Mass; Mo—Moldanubian s.str.; O.—Odenwald; R.— Ruhlaer Kristallin; S.—Spessart Mountains; SG—Sächsisches Granulitgebirge; SW—Black Forest (Schwarzwald); T.—Taunus Mountains; TB—Tepla Barrandium; ZEV—Zone of Erbendorf-Vohenstrauss.

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pressure conditions and temperatures of up to 650 °C. In the Saxothuringian region of the CBG two lithological sequences are distinguished: (i) the Thuringian facies sequence, consisting of Cambrian to early Carboniferous marine sediments with intercalated intra-plate volcanics, and of an Upper Devonian sequence with intercalated, widespread submarine basaltic volcanics; and (ii) the Central Fichtelgebirge sequence, which comprises gneisses, mica schists, phyllites, quartzites, marbles, and calcsilicates. Their protoliths were deposited during Cambrian and Ordovician times. Furthermore, there are metamagmatites such as leucocratic, feldspar-rich orthogneisses. Protoliths for these orthogneisses might be Ordovician acid volcanics and/or intrusives (e.g., granites). Late Variscan granites intruded into the Central Fichtelgebirge sequence. Moldanubian Region The complex “Moldanubian region” comprises large areas that are composed of paragneisses, metabasites, leucocratic orthogneisses, and metacarbonates. During late Variscan times, many granitic plutons intruded into these metamorphic rocks. In the CBG, the Moldanubian region comprises the nappe unit of the Zone of Erbendorf-Vohenstrauß, including the Erbendorf Greenschist Zone, and the Moldanubian sensu stricto. These units can be distinguished by differences in the lithology, stratigraphy, and structural-metamorphic evolution. In the northern Oberpfalz, the Moldanubian s.s. is dominated by a monotonous paragneiss series which consists of metapelites, metagreywackes, and interbedded metapsammites. Calc-silicates derived from former marls, amphibolites, and marbles are intercalated. Basic and acid magmatic protoliths are rare. Geochronological data of the youngest detritic zircons point to a Neoproterozoic to lower Paleozoic sedimentation age of the Moldanubian s.s. unit. The unit is dominated by a low-pressure– high-temperature (LP-HT) metamorphism. Locally, migmatites and diatexites occur. The Zone of Erbendorf-Vohenstrauss and the western part of the Teplá-Barrandian (Fig. 2), the so-called Zone of TepláDomažlice, show a similar lithological and tectono-metamorphic evolution. The Zone of Erbendorf-Vohenstrauss and the underlying Erbendorf Greenschist Zone are in tectonic contact to the adjacent Saxothuringian and to the Moldanubian s.s. units. The Zone of Erbendorf-Vohenstrauss is characterized by interbedded paragneisses and amphibolite units, and subordinate meta-ultrabasites, granitoid orthogneisses, metapegmatites, calc-silicates, marbles, and graphite-bearing gneisses. Typical features of the gneiss-amphibolite sequences are a medium pressure (MP) metamorphism between 380 and 400 Ma (Lower to Middle Devonian), high pressure (HP) relics in metabasites, and Cambrian to middle Ordovician intrusion ages of metagabbro protoliths (Teipel et al., 2004). The sedimentation age of the paragneiss protoliths is still unclear. Neoproterozoic to Cambro-Ordovician sedimentation with volcanic intercalations appears most likely. The lithology and the tectono-metamorphic evolution of the Zone of Erbendorf-Vohenstrauss and the Erbendorf Greenschist

Zone are similar to that of the Münchberg Mass, which is situated north of the Fichtelgebirge (Fig. 2). Since the Münchberg Mass is in tectonic contact to the underlying non-metamorphic Saxothuringian units, it is interpreted as a tectonic nappe complex. Emplacement of the Münchberg Mass nappe occurred under brittle crustal conditions during the late Lower Carboniferous (Franke, 1984), whereas emplacement of the different nappes that formed the Münchberg Mass occurred synchronously to a medium pressure metamorphism during the Lower to Middle Devonian, which is significant in the Zone of ErbendorfVohenstrauss, too. Based on the similarity of the lithology and tectonometamorphic evolution the Münchberg Mass, the Zone of Erbendorf-Vohenstrauss, and the Teplá-Barrandian together are interpreted as an autonomous unit that is in tectonic contact with both the Saxothurinigian and the Moldanubian s.s. units. These three subunits form the “Bohemikum.” Late Variscan Intrusives Toward the end of the Variscan orogeny, melts intruded into the metamorphosed units. Today, the basement area of the CBG shows large areas with Variscan intrusives dominated by granites, some granodiorites and diorites, and subordinate gabbroid intrusions (Hecht, 1998, and references therein). With only few exceptions, these intrusives have not been affected by ductile deformation. Intrusion ages range from 325 to ca. 286 Ma (Hecht, 1998; Siebel et al., 2003, 2010, for the Fichtelgebirge; data for the Oberpfalz in Siebel et al., 1997). According to their isotopic composition, the granites are mostly classified as S-type granites, meaning they were formed by melting processes from former para-rocks in lower to mid-crustal levels. The granites of the CBG form two main age groups. The older group intruded between approximately 325 and 310 Ma

Figure 2. Geotectonic building units of the Bohemian Massif in the Czech-Bavarian Geopark and its surroundings (based on Stettner, 1992). MM—Münchberg Mass; ZEV—Zone of Erbendorf-Vohenstrauss.

KTB Deep Drilling Site and Czech-Bavarian Geopark and can be subdivided into an early and a late phase. These usually coarse-grained, porphyric granites with large K-feldspar phenocrysts are widely distributed all over the area of the CBG. The younger granite group with intrusion ages of up to 286 Ma only exists in the Fichtelgebirge (e.g., the geochemically very distinct tin granites).

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and—in contrast to that—relative subsidence of the basement area east of the Hessenreuth Forest (HF in Fig. 3) along its southern branch. The latter is clearly indicated by the recent altitude of the synvolcanic peneplain in the area of the “Rauher Kulm” at ~750–800 m and—contrary to that—relicts of Paleogene saprolites and overlying basaltic lava flows at altitude of ~520 m close to the KTB site (Figs. 3 and 4).

Post-Variscan Evolution of the Western Foreland of the Bohemian Massif and of the Franconian Lineament

Cenozoic Evolution of the Western Eger Rift Area

The block-faulted sedimentary cover along the Bohemian Massif is superimposed on a Permo-Carboniferous graben (Naab Basin, Schröder et al., 1998; Paul and Schröder, 2010), which consists of a number of differentially subsided fault blocks delimited by the complex Franconian fault zone (Franconian Lineament), the Eisfeld-Kulmbach-Freihung fault, and the Pfahl fault. This fault system was repeatedly reactivated during the Permo-Triassic, the late Lower Cretaceous, the latest Cretaceous to Paleocene, and again during the Neogene (Fig. 3). The available data show that the Permo-Carboniferous basin underwent transpressional deformation prior to the late Permian Zechstein transgression. The development of individual subbasins during a late stage of the Carbono-Permian indicates a progressive crustal deformation that was most likely controlled by dextral wrenching (Peterek et al., 1996, and references therein). Synsedimentary tectonic activity along the Franconian Lineament persisted into the Early Triassic, as documented by “Bunter” clastics representing alluvial fan deposits in front of the fault. Later on, isopachs and facies patterns of the post-Early Triassic to Late Jurassic sediments indicate that the Franconian Lineament was overstepped by platform sediments, reflecting tectonic stability (Schröder et al., 1997). During the Lower Cretaceous, the Franconian Lineament has been strongly reactivated by a first phase of basin inversion (Schröder, 1987; Peterek et al., 1996). It is estimated that the basement east of the Franconian Lineament became uplifted by some 1500 m, resulting in the total erosion of its former sedimentary cover. A second phase of inversion tectonics occurred during Late Cretaceous to Paleogene time. During this stage, reactivation of the Franconian Lineament and of other preexisting fault systems played an important role and substantially contributed to the present configuration of the western border zone of the Bohemian Massif. Based on thermo-geochronological data (apatite fission-track ages, Wagner et al., 1997), uplift of the KTB surroundings reached up to 3000 m during this phase of inversion tectonics. This is in accordance with some 100-m-thick Upper Cretaceous to Paleogene alluvial fan deposits immediately west of the Franconian Lineament. Along the western border zone of the Bohemian Massif, late Paleogene and post-middle Miocene fault reactivation and a complex pattern of differentially uplifted and downthrown blocks strongly influenced the late Cenozoic landscape evolution. Reactivation of the Franconian Lineament occurred non-uniformly, as indicated by the uplift of the western Fichtelgebirge in the north

During late Eocene times the approximately 50-km-wide and 300-km-long, ENE-WSW–striking, continental Eger Rift (Fig. 5) started to evolve as part of the European Cenozoic Rift System (Kämpf et al., 2005; Peterek et al., 2011). Since the oldest intraplate alkaline volcanism occurred already during Late Cretaceous to lower Paleogene time in the Ceské stredohori Mountains/Böhmisches Mittelgebirge (Ulrych et al., 2003), the initial processes of the Eger rifting most likely started somewhat earlier in this region. According to Ulrych et al. (2003), Geissler et al. (2004), and Kämpf et al. (2005), three periods of Cenozoic alkaline volcanic activity were recognized in the western Eger Rift area: (1) early Oligocene to early Miocene (31–20 Ma) volcanics of the Eger Rift and its westernmost continuation, reaching as far as to the northern Oberpfalz area; (2) middle to late Miocene (16.5–8.3 Ma) volcanics synchronous with the graben formation dated by its pre-mid Miocene (>11.7 Ma) to late Pliocene sedimentary fill; and (3) middle to late Pleistocene (0.7– 0.3 Ma) volcanics of the Cheb Basin area. The areal distribution of clastic deposits and the reconstruction of related source areas on the basis of heavy mineral assemblages (Schröder and Peterek, 2001; Suhr, 2003 and references therein) indicate that the region south of the recent Eger (Ohře-) Graben was originally drained by rivers running toward the north across the formerly non-existing graben depression. Incipient formation of the ENE-WSW–striking depression occurred during the late Eocene and accelerated during late Oligocene to early/middle Miocene time (27–15 Ma, Elznic et al. 1998). Uplift and northerly tilting of the Krušné Hory (Erzgebirge) might have also initiated during the late Eocene (Elznic et al., 1998; Schröder and Peterek, 2001). However, a morphologically well-expressed escarpment bounding the Krušné Hory against the Eger (Ohře-) Graben evolved since the early Miocene at the earliest (27–15 Ma; Elznic et al. 1998). Synchronously to the onset of accelerated uplift of the Krušné Hory, the drainage system was reorganized, and the Ohře River started to drain the Eger (Ohře-) Graben toward the NE. Since the stratigraphic record is rather incomplete, it is difficult to reconstruct the evolution of the Eger (Ohře-) Graben during lower mid-Miocene to late Pliocene time. Therefore, it remains uncertain when intra-basinal differential block faulting and separation into individual subbasins occurred. Strong activity along the NNW-SSE–trending Mariánské Lázne fault is well documented by the asymmetric subsidence of the Cheb Basin and synchronous deposition of the coarse-grained Vildštejn Formation during late Pliocene to at least middle

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Figure 3. Structural evolution of the Franconian Lineament (FL) since the uppermost Jurassic, depicted along a crosssection from Nuremberg across the northern part of the Franconian Platform and the Upper Cretaceous of Hessenreuth into the Oberpfälzer Wald area (modified from Peterek et al., 1994; after Schröder, 1990).

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Figure 4. Geological cross section across the volcanic vent of the “Rauher Kulm” near Kemnath, showing also (semi-transparent gray) the original topography and the now-eroded rocks (modified from Peterek et al., 2007).

Pleistocene times. Pleistocene to Recent intra-basinal blockfaulting is indicated by a morphologically well-expressed fault scarp (Bankwitz et al., 2003; Schunk et al., 2003), by the displacement of fluvial terraces of the Ohře River (Peterek et al., 2011), and by the subsidence of Holocene basins. Late Oligocene to early/middle Miocene sediments (27–15 Ma) and volcanics related to the formation of the Eger (Ohře-) Rift are also preserved in the Fichtelgebirge and the northern Oberpfalz. In a very similar manner to the area further east, the shaping of today’s landscape largely took place during Pliocene and Pleistocene times as a consequence of young crustal movements.

Recently Active Geodynamic Processes in the Western Eger (Ohře-) Rift Area Active rifting processes in the Eger (Ohře-) Rift area can be observed especially in the area of the Cheb Basin and its surroundings (Fig. 5; Kämpf et al., 2005). They are accompanied by CO2 emanations at the surface in northwestern Bohemia, southern Vogtland, eastern Fichtelgebirge, and the northern Oberpfalz area, alkaline volcanic activity, neotectonic uplift, and earthquake swarm activity in the surroundings of the Cheb basin and close to the town of Marktredwitz.

Figure 5. Geological setting of the study area and the Eger Rift. Subregions of the Eger (Ohře-) Rift: CB—Cheb Basin; DB—Domažlice Basin (CD + DB—Cheb-Domažlice Graben CDG); DV—Doupov volcanic complex; MB—Most Basin; NUPB—Northern Upper Palatinate Basin; SB—Sokolov Basin. MLF—Mariánské Lázne Fault. Source: Geological map 1:1 Mio., Federal Republic of Germany, Bundesanstalt für Geowissenschaften und Rohstoffe BGR (1993). From Peterek et al. (2011).

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The Vogtland/NW-Bohemia region is known as one of the most interesting European regions for earthquake swarms, with thousands of small and intermediate magnitude earthquakes (local magnitude <5). The term “earthquake swarm” (“Erdbebenschwarm”) was first introduced for this region by Credner (1900). It is used for sequences of earthquakes that cluster in time and space (for further information see Geissler et al., 2004; Kämpf et al., 2005). The studies of Geissler et al. (2005) indicate that the recently active geodynamic processes in the western Eger (Ohře-) Rift are related to an active zone of mantle melting and magmatic underplating (Fig. 5). According to Geissler et al. (2005), the following sub-processes are distinguished: • release of CO2-dominated fluid/magma from isolated meltreservoirs at 30–60 km depth; • active MOHO updoming from ~31 to 27 km; • separation of CO2 from the melt and channel-like CO2transport through the crust; • triggering of seismicity by fluids in the depth range of 6– 15 km, which is caused by high pore fluid pressure in fault zones; and • significant CO2-transport through the upper crust due to its permeability. Geissler et al. (2005) supposed that the recent active processes in the upper crust (earthquake swarm activity and magmatic CO2 emanations at the surface) are related to ongoing magmatic processes within the uppermost mantle beneath the western part of the Eger (Ohře-) Rift. THE CZECH-BAVARIAN GEOPARK—BREAKING FORTH INTO THE EARTH’S INTERIOR Introduction The border-crossing Czech-Bavarian Geopark (CBG; in German called Geopark Bayern-Böhmen; see Fig. 2) puts into practice the idea of a large area unit in the heart of Europe. The geopark is situated in one of the most geologically unique areas worldwide. Based on the complex geological structure and evolution along the northwestern margin of the Bohemian Massif, the geopark area is characterized by narrow contrasts of geology, landscape, hydrology, soils, vegetation, and even climate conditions. In the CBG, the close interconnection of these conditions with the economic development (mining, industry) can be demonstrated as a key factor influencing settlement and culture of the people from the far history to the present. With its combination of active geological processes (young volcanism, intense CO2 emanation, occurrence of earthquakes) and an enormous density of geologic objects (“geotopes”), the CBG offers an ideal tool to reach the general public in order to promote the understanding of the effects of the System Earth society and to help people understand fundamental geoscientific topics. The overall territory area of the CBG takes 7771 km2, ~55% of it lying on the German territory (Bavaria) and 45%

belonging to the territory of the Czech Republic (precisely, in the western part called “Bohemia”). All the area is remarkably varied from a geographical point of view. The densely populated agricultural and industrial lowland zones are in contrast to less populated mountain landscapes. The rarest and less populated natural territories are protected as nature parks and other protected areas. The density of the settlement on the Czech side was strongly influenced by the demographical changes after World War II (resettlement of the German inhabitants, wide protected boundary zone between two political world systems, military zones). Most of the CBG is in protected nature areas. The protection conditions on both sides of the state boundary are given by existing national legislative regulations. In the Czech Republic, the main nature areas are natural areas (e.g., the Slavkovský les), national natural reserves and natural reserves (e.g., Soos, Božídarská rašeliniště, Kladské rašeliny, Diana, Přimda, etc.), national natural monuments and natural monuments (e.g., Svatošské skály, Komorní hůrka, Železná hůrka), natural parks (e.g., Český les, Smrčiny, Přebuz, Zlatý kopec), and protected areas of natural water accumulation. In Bavaria, the following categories exist: natural monuments (“Naturdenkmale”), nature reserves (“Naturschutzgebiete,” e.g., Eger valley, Waldnaab valley, Naturwaldreservat Fichtelseemoor, Luisenburg), conservation areas (“Landschaftsschutzgebiete”), and natural parks (“Naturparks,” i.e., Naturpark Fichtelgebirge, Naturpark Steinwald, Naturpark Nördlicher Oberpfälzer Wald, and, in parts, Naturpark Fränkische Schweiz–Veldensteiner Forst). The declaration of a cross-boundary cooperation with the aim of forming a joint CBG was signed in 2003 by the regional presidents of the Czech administrative units Karlovy Vary Region and Plzeň Region, and by the heads of the Bavarian districts of Neustadt a.d. Waldnaab, Tirschenreuth, Wunsiedel im Fichtelgebirge and Bayreuth. At present time, the CBG is organized in three different parts: the Bavarian part (consisting of the four Bavarian districts, the city of Weiden, and more than 60 communities), the Karlovy Vary part (administered by the Karlovy Vary regional government), and the Plzeň part (administered by the geopark association Geoloci). These parts are financed in different ways. The Bavarian part is funded by the European Union, the Bavarian ministry of environmental affairs, and the districts (“Landkreise” and communities); the Karlovy Vary part is financed by the Karlovy Vary regional government (Kraj); and the Plzeň part is funded by an alliance of villages and the European Union. The Bavarian part of the geopark is coordinated by the geopark association GEOPARK Bayern-Böhmen e. V., where a management office has been established (responsible: Dr. Andreas Peterek). The Karlovy Vary part is coordinated by the Sokolov museum, which belongs to the regional government of the Karlovy Vary district (responsible: Michael Rund, Jiri Loskot; www.omks.cz). The coordination of the Plzeň part has been taken by a private company (RECEPTT; www.receptt.net). All

KTB Deep Drilling Site and Czech-Bavarian Geopark parts of the geopark are in permanent contact to coordinate the establishment of a joint geopark. An application of all three parts of the CBG for joining in the European Geopark Network is planned for 2011/2012. The main aims of the CBG are (1) to publicize the regional specific features, which are not generally known by the public, (2) to improve public awareness of geological subjects and to nature, (3) to support a cross-borders cooperation in tourism, and (4) to support the regional identity of the population. The Main Topics of the CBG The CBG presents the following six topics to the public. The Dynamic Earth—Geodynamic Processes In the CBG, a broad range of geodynamic processes can be shown in a relatively small area. The study of young and active geological processes in the Eger (Ohře-) Rift system (with CO2 flux from the upper mantle to the atmosphere) is key to understanding the geodynamic processes of the geological past and of the structure of the geopark area. Landscape Changes—Morphodynamic Processes Tectonics and exogenic processes (such as weathering and erosion) continuously change the earth surface and the landscape. Particularly, the great variety of landforms in the geopark area provides an excellent access to this topic. Remnants of former landscapes and related weathering relics (e.g., kaolinite) demonstrate the change of landscape evolution and climate through the earth history. The position of the CBG in the hydrogeographical center of Europe predestines it to take up the topic of river basins, the natural behavior of streams, and the consequences of human impact on the stream dynamics. Across the CBG, the main European water divide separates different drainage systems: the Danube River drainage basin, which drains to the south, and the Rhine River and the Elbe River drainage basins, both draining the northern part of the geopark toward the north. Different landforms on both sides of the watershed and the “battle for the watershed” greatly demonstrate landscape forming processes. Landscape is not only the consequence of river activity. In the westernmost part of the geopark, subsurface solution of the Jurassic limestones has created a unique karst topography, most particularly the underground caves in the “Fränkische Schweiz” natural park. Human Activity as a Factor of Landform Development In addition to natural processes, human activity has a strong impact on the landforming processes. Land utilization over hundreds of years for agriculture and exploitation of mineral resources has created landforms developed and cultivated by man. This can be shown in the geopark area by many examples. But there are also many examples for successful recultivation of formerly intensely used areas, e.g., the former open-pit browncoal mining districts.

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Geology as a Fundamental Base for Economic and Cultural Development Due to its mineral wealth (gold, silver, tin, iron), this region has been subjected to mining activity since the Late Middle Ages. In the southwestern part of the geopark, iron mining and iron craft were especially important until the middle of the seventeenth century, resulting in the characterization of the region as the “Ruhr district of the Middle Ages.” In the first half of the sixteenth century, tin mining in the Bohemian part of the geopark was as important as that of the Cornwall district of the UK. In the nineteenth century, the discovery of rich china clay deposits promoted the development of the porcelain industry, which was the most important one in Europe until the end of the last century. The geology and the environmental conditions strongly influence humans and their economic and cultural development. On the other hand, human activity has many and varied impacts on the development of the surrounding environment and landscape. The CBG—The Geological Center of Europe The CBG is not only situated in the geographical center of central Europe but also at the Variscan suture zone of large crustal fragments (terranes). Moreover, the main European watershed runs across the geopark, marking its particular position in Europe as well. The great variety of rocks, geological structures, landforms, and active geological processes predestines the area of northeastern Bavaria and western Bohemia for a cross-border geopark in the heart of Europe. From Neptunism to the System Planet Earth In the last decade of the twentieth century, the Continental Deep Drilling Program of Germany (KTB) attracted attention worldwide and marked the beginning of direct sampling of the Earth’s interior. Therefore, it is one of the substantial topics in the CBG. Roughly 200 years ago, the earth sciences took their first wary steps. The famous poet Johann Wolfgang von Goethe and the universal genius Alexander von Humboldt, among others, studied the geological phenomena of the region and introduced important contributions to the young scientific discipline. The Motto of the CBG The motto of the CBG, “Breaking forth into the Earth’s interior,” is derived from its main topics and alludes to: • the broad Eger (Ohře-) Rift uprise with the central graben system (“breaking up of the earth’s crust”); • the numerous faults, e.g., the Franconian Lineament and the seismically active Mariánská Lázně Fault (“the broken crust”); • ancient mining of ore minerals (“breaking the rocks for mining”); • the superdeep borehole of the KTB;

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EXCURSION STOPS Day 1 Depart by train from Munich Central Station to Weiden Train Station (Weiden in der Oberpfalz), continuation by coach. Overnight stay in Windischeschenbach. The excursion stops are indicated in Figure 6.

Stop 1-1: Parkstein Volcano—One of the Prettiest Geotopes of Bavaria The Parkstein is a morphologically prominent feature in front of the rise of the Oberpfälzer Wald to the Northeast. Within the generally flat foreland to the southwest of the Franconian Lineament it rises ~200 m above the surrounding landscape consisting of Late Triassic and Cretaceous stratigraphy. Even from this distance, the cone-shaped Parkstein hill suggests a volcanic origin. Indeed, impressive columnar jointed basaltic rock is exposed in a former quarry near the top of the hill making this site one of the “100 prettiest geotopes of Bavaria” (Glaser et al., 2007).

Figure 6. Geological overview map of the field trip area with stops indicated as numbers within circles (base map modified after Rohrmüller and Mielke, 1998). KTB—Continental Deep Drilling Program; ZEV—Zone of Erbendorf-Vohenstrauss; ZTM—Zone of Tirschenreuth-Mähring.

KTB Deep Drilling Site and Czech-Bavarian Geopark Petrographically, the columnar basalt represents a magnetite-bearing nepheline-basanite (Huckenholz and Schröder, 1985) that yields much fewer olivine xenoliths than most other tertiary basaltic rocks of the region. It reveals K/Ar ages of 24.9 ± 1 Ma and 22.3 ± 0.9 (Rohrmüller et al., 2005). The basanite is almost completely surrounded by a very poorly sorted vent breccia consisting of basalt and country rock fragments of arkose, kaoline-bearing sandstone, pebbly sandstone, mudstone, basement rock (Schröder, 1963, 1965), and sand-sized quartz and feldspar grains. The vent breccia is nicely exposed in numerous caves dug into the hill for food storage purposes during medieval times. At the western margin of the former quarry, the vent breccia is seen in immediate contact with the columnar jointed basanite. The axes of the basanite columns generally point radially away from the Parkstein hill and, at the road level, appear to dip at an angle of 5–10°. This suggests a downward-pointing, funnel-shaped mold that was flooded by the basanite. Higher up in the quarry face, the basanite columns appear to bend upward. This structure suggests the existence of a lava lake where, during cooling, crystallization, and contraction of the lava body, the columnar jointing develops simultaneously from both the lava/ atmosphere and the lava/country rock contact. Taking into account the high fragmentation grade of the volcanic material, the picture of a maar-diatreme volcano becomes apparent. Groundwater/magma contact, together with volcanic earthquake tremors, presumably initiated the explosive fragmentation of the magma at a depth of a few hundred meters below the paleo-land surface. The eruption then blasted away the overlying country rock and caused the formation of an initial funnel-shaped crater. Ongoing rise of magma and influx of groundwater triggered further eruptions that deepened and widened the maar crater to a diatreme. With the end of magma/water contacts, the eruption ceased and the eruption column finally collapsed, largely into the crater. Further rising magma could now intrude the diatreme fill from below and apparently reached the surface and flooded the crater floor. Because the columnar jointed basanite forms the highest elevation of the Parkstein, it suggests a pre-eruptive land surface tens to perhaps even hundreds of meters above the Parkstein. This agrees with Schröder’s (1965) work that, on the basis of the spectrum of country rock xenoliths in the volcanic breccia, expects the land surface considerably above the top of the Parkstein hill. The instructive outcrops of the Parkstein “volcano” are used by the CBG and by the “GEO-Zentrum an der KTB” for geoscience outreach as a field example of geological observation and field relationships in order to identify and integrate complex developments in nature on the basis of rock types and structures. Stop 1-2: “GEO-Zentrum an der KTB”—From the KTB Deep Drilling Site (1987–1994) to a Modern Geoscience Outreach Center Aims of the KTB drilling program (1987–1994) The Continental Deep Drilling Program (Kontinentales Tiefbohrprogramm der Bundesrepublik Deutschland, KTB) follows

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an idea to investigate the continental crust with an ultradeep borehole, which was initially discussed by the Senate Commission on Geoscientific Research of the Deutsche Forschungsgemeinschaft (Emmermann and Lauterjung, 1997). Before the 1980s, the rapid progress in geophysics and geochemistry enormously broadened the knowledge of the composition and evolution of the continental crust. Numerous scientists interpreted large data sets and presented “geophysical pictures” of the subsurface. They realistically felt that those interpretations lacked verification by nature itself. Still missing was the direct investigation of the geophysical and geochemical conditions of the continental crust and of the processes therein. Effectively the rocks themselves were to be examined. Almost all geological disciplines contributed to a discussion that resulted in the application for an ultradeep research borehole. Their overall aim was the in situ investigation of the physical and chemical conditions and processes in the deeper crust to understand the dynamics and evolution of the intracontinental crust (Behr and Emmermann, 1987). It was never meant to reach a new depth record. Instead, the temperature range of 250– 300 °C marked the geological target. At those temperature conditions, the brittle/ductile transition—a significant change of the rock rheology—and an acceleration of the reaction kinetics were expected. Thus a depth range of 12,000–14,000 m became the calculated drilling depth (Behr, 1987), on which basis the scientific and technical concept was to be developed. Under that general focus, the KTB program concentrated on five major research topics (Projektleitung KTB, 1987): • the nature of geophysical structures and phenomena, i.e., seismic reflectors, geo-electrical, magnetic, and gravimetric anomalies; • the stress regime and the brittle-ductile transition, i.e., the orientation of stresses and the shear strength of rocks as a function of depth; • the thermal structure of the crust, i.e., heat production, heat flow and temperature distribution; • the fluid flow processes, i.e., sources of fluids, fluid equilibria, fluid paths; and • the structure and evolution of the variscan crust in central Europe, i.e., characteristics, deformational mechanisms, dynamics of superimposed deformation phases in the crust. With the identification of the major research topics, four localities were envisaged: the Hohenzollerngraben, the Hohes Venn, the northern Oberpfalz, and the northern Black Forest (Schneider et al., 1983). Intensive surveys found that all regions would contribute important aspects to the research program. Furthermore, numerous geoscientific problems, then under discussion, could be addressed in those regions. Eventually, a unanimous resolution was made for the northern Oberpfalz area. The deciding factor was a reduced geothermal gradient expected in this area. Of additional importance was the clear and coherent crustal model based on the structural, petrological, and geophysical data that had been obtained in a broad preliminary survey

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(Weber and Vollbrecht, 1986). According to that survey, a series of tectonic nappes make up the variscan orogen, which evolved due to collision of the Saxothuringian and the Moldanubian terranes in a southerly directed subduction zone. Behr and Emmermann (1987) highlighted the most compelling reasons for drilling an ultradeep borehole in the northern Oberpfalz area. • It is the suture zone of the two large crustal fragments “Saxothuringia” and “Moldanubia” of the variscan orogen. • Crustal complexes of different evolutional and metamorphic history had been explained with an interesting but strongly discussed model, which could be tested with the ultradeep drilling. • Drilling would occur in a zone of marked Bouguer and magnetic anomalies, which is also characterized by a prominent electric anomaly. • Seismic reflectors occur at reachable depths. • A prominent electrical conductor of unknown origin was situated between 9 and 11 km depth. • The proximity of the young Eger (Ohře-) Rift might be documented by thermal and geochemical anomalies. A variety of technical prerequisites had to be taken into account in order to perform the ultradeep drilling into the crystalline rocks that form the geological Zone of Erbendorf-Vohenstrauss (Fig. 1). The major challenges were the expected rock temperatures, the large drilling depth, and the rock types. Although standard oil and gas exploration and production activities resulted in significant experience that could be applied to this project, the specific drilling technique had to meet largely different requirements for the crystalline rocks of the Zone of Erbendorf-Vohenstrauss. Thus the concept of two-hole drilling was developed. The profile (Fig. 7) of metagabbros, amphibolites, paragneisses, hornblende gneisses, and alternations of these rock types and the subordinate calc-silicate rocks, ultramafitites, lamprophyres, and aplites expected in both holes were considered largely very hard and steady, but highly abrasive in terms of drilling. Their uniaxial pressure resistances are very high. Furthermore, they show largely discontinuous rock characteristics: foliation dips 60°SW, the rocks are intensively folded, and fault zones are characterized by cataclasites. Drilling of such zones usually causes strong instabilities of the drill hole, with large breakouts from the wall. For the planned drilling depth of 10–15 km, a maximum temperature of 300 °C was expected. Thus, in order to meet the planned budget and timeframe, a special drilling strategy was developed (Engeser et al., 1996): • two-hole concept with the KTB-VB (“Vorbohrung”) as pilot drilling and the KTB-HB (“Hauptbohrung”) as ultradeep main drilling, each one targeting special purposes; • construction of a “fit-for-purpose” drilling rig; • development of a heavy-duty drill string; • development and application of a vertical drilling strategy aiming for a preferably vertical drill hole;

• realization of a cost-effective drilling and casing program; • development of downhole motors for effective drilling at great depth; • improvement of the coring methods and development of a mud system for hP/hT conditions for the KTB-HB; and • perfection of the logging systems and sampling methods. Results of the KTB Drilling Program (1987–1994) Based on the main research topics, a wide variety of scientific results from the KTB program has been published (ICDP, 2009). A summary by Emmermann et al. (1995) is taken as the reference for the results described below. Most of the results concern the structure and crustal evolution, the stress regime, and the thermal evolution of the crust.

Figure 7. Geological sections of the KTB-VB (Continental Deep Drilling Program pilot hole) and KTB-HB (Continental Deep Drilling Program main hole) with fault zones indicated (from Rohrmüller and Mielke, 1998, according to Hirschmann, 1996).

KTB Deep Drilling Site and Czech-Bavarian Geopark Structure and Evolution of the Continental Crust The KTB-HB drilled the boundary zone between the Saxothuringia and Moldanubia terranes, both of which form a major part of the central European crust. The drilling penetrated steeply inclined units of the Zone of Erbendorf-Vohenstrauss, which showed an unexpected grade of brittle deformation (Fig. 8). The most prominent fault zone by far is situated between 6860 and 7260 m depth. It comprises several cataclastic shear-zones characterized by graphite impregnation and sulphide mineralization. This fault zone is the continuation at depth of the Franconian Lineament, which separates the outcrops of the variscan basement rocks to the NE from the Permian to late Mesozoic stratigraphy of the Germanic Basin to the SW (Freudenberger et al., 1996). In fact, it is a deep reaching fault zone separating the Bohemian Massif (which lacks the Mesozoic cover) from the Southern German Block with its Mesozoic cover. It can be traced for ~200 km from the Thüringer Wald in the NW to the Bayerischer Wald in the SE and passes the KTB-site just 5.5 km to the south of the drill hole. The Zone of Erbendorf-Vohenstrauss is characterized by marine protoliths originally deposited from turbidity currents in the proximal parts of a small-scale marine basin. Those are represented by the orthogneisses of the Zone of ErbendorfVohenstrauss. The amphibolites and metagabbros of the Zone of Erbendorf-Vohenstrauss fit into such a premetamorphic depo-

Figure 8. This NE-SW cross section shows the geology and structure at the Continental Deep Drilling Program (KTB) site (from Harms et al., 1997). At a depth of 7100 m, the borehole penetrates the fault zone of the Franconian Lineament. That cataclastic zone is correlated with the seismic reflector SE1 and surface outcrops (e.g., Schröder et al., 1992).

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sitional environment, as they show geochemical characteristics of ocean floor basalts of small oceanic basins like the modernday Red Sea. Furthermore, the alternations of paragneisses and hornblende gneisses with intercalated marbles and calc-silicate rocks indicate a shallow marine, tectonically active environment suggesting an accretionary wedge. All those marine sediments and submarine volcanics experienced a medium pressure (MP) metamorphism at temperatures of 650–700 °C and pressures of 6–8 kbar. However, their metamorphic history is much more complicated in detail. Although the numerous individual blocks underwent variably quick subsidence to much different depths, they all show a similar history of uplift and exhumation. This MP-metamorphism has been dated at 410–380 Ma. In addition, a high pressure (HP) metamorphism can be dated at ca. 480 Ma. Surprisingly, many deformation phases during the uplift history of the Zone of Erbendorf-Vohenstrauss are characterized by physical conditions representing the brittle-ductile transition. Structural analyses unravel a very complex development during the final phases of the orogeny—and until today. Rather surprising was also the observation that temperature substantially influences the rock characteristics at depths of less than 7500 m only. This led to the interpretation of a compressional thickening of the Zone of Erbendorf-Vohenstrauss after the variscan orogeny. In such a scenario, the Franconian Lineament is thought to represent the frontal ramp of a wedge of crustal segments that got uplifted from a ductile detachment zone at 9–10 km depth. Paleo-Fluid Activity and Recent Fluids The paleo-fluid and recent fluid activity was the second main point of the KTB project. Some very interesting observations have been made concerning this topic. Despite the metamorphism, the rocks preserved their oxygen and sulfur isotope signature. This was a surprising result, being important for the understanding of metamorphism as a result of independent systems of local fluid flow and fluid penetration instead of regional fluid activity. Within the Zone of Erbendorf-Vohenstrauss, the rock deformation was accompanied by intense fluid activity, which was concentrated in fault zones where it caused a large variety of mineralizations. Graphite, together with iron-sulfide minerals and chlorite, occurs as a widespread, mm-thick secondary mineralization on faults. Locally this graphite is extremely enriched and causes abnormal electrical conductivity. The hydrothermal sulfide mineralization of the Zone of Erbendorf-Vohenstrauss coincides with that found in the Russian Kola-SG3 ultradeep drill hole. Such mineralizations indicate pressure conditions of 2–3 kbar and temperatures between 250 and 300 °C. They are apparently typical for continental basement. The drilled rocks contain surprisingly high volumes of free fluids. Particularly dry gases such as methane and helium accompany the graphite-coated faults. Hydrous fluids occur throughout the entire depth of the hole: above 1500 m depth normally mineralized groundwater is present, but below 3100 m, highly saline calcium-sodium-chloride waters

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occur in horizons up to several tens of meters thick. They are characterized by high contents of dissolved nitrogene, methane, helium, argon, and radon. Fluid influx rates to the drill hole were analyzed in order to understand the permeabilities of crystalline rocks at depth. Despite the enormous overburden, the rocks at the final depth of 9101 m still have remarkable permeabilities that are orders of magnitude higher than those expected on the basis of laboratory experiments. Geophysical Structures and Phenomena The geophysical understanding of structures and phenomena grew tremendously due to the KTB-project, as a huge geophysical data set could be referenced and calibrated with real rock and in situ data. For the first time, the strong seismic reflectors in crystalline rocks were identified as fault zones. During the early

surveys, a strong reflector (SE-1) was found to cross the planned course of the drilling at a depth between 6600 and 7100 m. It was correlated with a branch of the Franconian Lineament. Indeed, the hole cut through a prominent cataclastic fault zone extending from 6860 m to 7260 m depth (Fig. 9). Strong electrical anomalies in the Zone of ErbendorfVohenstrauss clearly correlate with graphite mineralization of steeply inclined, cataclastic fault zones. The graphite enrichment on the faults forms a layer of N-type conductivity that connects zones of different redox potential. Thus, in principle, this tectonic block forms a geo-battery. The mineral causing the magnetization of the gneisses and meta-basalts is pyrrothine rather than the expected magnetite. Geomagnetics also show a strong magnetic anomaly in the uppermost part of the crust. This is characterized by a massive

Figure 9. Schematic block diagram delineating the geological layout in the vicinity of the Continental Deep Drilling Program (KTB) drilling locality (modified from Hirschmann, 1996). ZEV— Zone of Erbendorf-Vohenstrauss.

KTB Deep Drilling Site and Czech-Bavarian Geopark reduction of the magnetic field intensity. Below 1200 m, the magnetic field intensity increases rapidly with depth, being three to five times higher than expected. Stress measurements showed that the rigid upper crust acts as a stress transmitter that causes an increase of the stress applied to the brittle upper crust. In the zone of the brittle/ductile transition, at temperatures of ~300 °C, maximum stress values close to the fracture strength of the rocks are reached. The geothermal conditions were surprising as well. Down to almost 1000 m depth, the measured temperature increase coincided with the initially predicted geothermal gradient of 21 °C/km. Between 1000 m and 1500 m, however, a strong temperature increase occurs, and from 1500 m downward, a near-constant geothermal gradient of 29–30 °C/km was found. Scientific Perspective and Future Development of the Drilling Site After the active phase of drilling was completed, some long-term measuring programs were started in the KTB boreholes. To date, the two ultradeep boreholes are in use as the Deep Crustal Laboratory of the “Helmholtz Centre Potsdam GFZ German Research Centre for Geosciences” and form part of the International Continental Scientific Drilling Program (ICDP). This unique laboratory facilitates measurements and experiments at a site where extremely high temperatures and pressures in the boreholes require high engineering demands on measuring devices. Thus it offers an ideal test environment for high-tech development in geophysical logging and allows the calibration of measuring devices for further drilling projects within the ICDP, which was much encouraged by the successful national KTB-project. While the KTB-project was still ongoing, the international geoscientific community strongly encouraged a more formal multilateral continental drilling program. Because of the highly successful KTB-project, Germany was asked to take a lead role and to organize an international meeting to examine the scientific justification and management needs for such a multilateral international program. In 1993 the meeting was held in Potsdam, Germany. The scientific themes were intended to be as comprehensive as possible attempting to cover a broad spectrum of contemporary Earth sciences in order to discuss how scientific drilling could complement ongoing geoscientific studies and make it possible to address fundamental, unresolved questions critically relevant to both societal needs and to an improved understanding of the Earth and its lithosphere (Zoback and Emmermann, 1994). Following the Potsdam meeting, science managers from 15 participating countries met at the KTB site to formally consider the establishment of an Integrated Continental Scientific Drilling Program (ICDP). The ICDP then started officially on 26 February 1996 when a memorandum of understanding was ratified by representatives of the U.S. National Science Foundation, the Chinese Ministry of Geology and Mineral Resources, and the German Federal Ministry of Education, Science, Research and Technology/GeoForschungsZentrum Potsdam at the German Embassy in

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Tokyo. ICDP-funded workshops were held since 1996 and ICDP drilling projects commenced in 1998 with co-funding of the Baikal Drilling Project (excerpts from ICDP, 2009). For the drilling locality itself, dismantling of all facilities and recultivation of the site had been already envisaged during the planning phase of the project. During the active phase of drilling, the public interest in the project grew much more than expected. Interested visitors began asking for guided tours to the drilling site, and eventually the scientific staff of the field laboratory was asked to do this part of public relation activities. The relevance of transparency and the necessity of good public relations were soon understood. As a consequence, an information center with its own staff was installed in 1996 at the drilling site with governmental financial aid. After completion of the drilling project, the public interest did not decline, but the funding of the information center was not settled. Foundation of a registered society (“GEO-Zentrum an der KTB e.V.”) on 27 July 1998 secured the further operation of the information center, which was then named “GEO-Zentrum an der KTB.” The task and purpose of the society is to establish the “GEO-Zentrum an der KTB” as a Geoscience Outreach Center and to strengthen the geosciences in the German educational system (Holzförster and de Wall, 2010). Six years later, the financial basis of the institution required reorganization. This was achieved by the communal, commercial, and industrial founders (district Neustadt a.d. Waldnaab, district Tirschenreuth, Vereinigte Sparkassen Eschenbach Neustadt Vohenstrauß, KCA DEUTAG Drilling GmbH, town of Windischeschenbach) of the foundation GEO-Zentrum an der KTB, with the sole purpose of supporting the GEO-Zentrum an der KTB. It owns the real estate with the KTB-drilling rig and all buildings. From 2006 to 2008, the foundation built several new facilities (Fig. 10) in order to secure the permanent operation of the GEO-Zentrum an der KTB. Acknowledgment and support was signaled to the institution by several awards: “Selected Landmark in the Land of Ideas 2006” (national innovations), “E.ON Bayern Umweltpreis 2007” (environmental education), “Netzwerk Umweltbildung.Bayern 2008, 2010” (environmental education), “United Nations Decade of Education and Sustainable Development Decade Project 2010/11” (education), “Umweltstation 2010” (environmental education). GEO-Zentrum an der KTB—Information and Education Several modifications and upgrading of buildings as well as additional construction activities completed the modern GEOZentrum an der KTB and established this institution as a Geosciene Outreach Center. The former information center is now the home of a gift shop, a cafeteria, four spacious laboratories and seminar rooms (GEO-Labor), and the administration offices. A newly constructed exhibition building accommodates the standing exhibition “System Earth,” a lecture hall and space for temporary exhibitions. Thus those rooms are on offer as a venue for workshops, meetings, and small conferences. Usually they are in use for public evening lectures on geoscience topics.

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Figure 10. (A) The Continental Deep Drilling Program (KTB) location during the active phase of drilling consists of the drilling rig, service containers and the station for downhole measuring (1), the field-laboratory (2), and the information building (3). (B) The current layout of the geoscience outreach center with the information building (3) and the recently constructed exhibition hall (4), the core-shed for the KTB drill cores (5) and the wooden hall containing large drilling equipment (6).

After dismantling the temporary service buildings of the drilling project, the area around the KTB drilling rig was modified by the foundation. The first step was the development of a modern core shed that now houses the entire collection of samples of the KTBproject. Thereafter, a large semi-closed wooden hall was erected to accommodate the components of the drill string and a collection of drill bits. Moreover, exhibition modules show the application of drilling for industrial and scientific purposes. An overview of the major international scientific research projects ICDP (International Continental Scientific Drilling Program) and IODP (Integrated Ocean Drilling Program) and an insight in drilling technologies for hydrocarbon exploration and for drinking water supply is given. New technologies such as photovoltaics and ground source heatpumps are in use for the energy supply of the institution. Displays show the functioning of those technologies. The GEO-Zentrum an der KTB offers a variety of learning opportunities (Fig. 11). Guided tours to the exhibitions, the drilling site and the working platform of the drilling rig attract ~25,000 visitors per year. People from all age groups and all education levels can gain, refresh, and deepen knowledge on the interrelation of the various aspects of the System Earth. The movie Expedition Earth introduces to the exhibition, which comprises interactive modules on volcanism, earthquakes, climate, cycles on Earth, the System Earth, Earth history, mineralogy, geothermal energy, the KTB ultradeep drilling, scientific drilling and the application of drilling. Temporary exhibitions, lectures, special programs for children, meetings, conferences, seminars and special tours, e.g., to the core shed, can be booked. Visitors can climb the tallest landbound drilling rig in the world (83 m) up to the working platform (Fig. 11), where a video shows the drilling technique and the daily working process during the drilling phase of KTB-HB. The student laboratory offers learning modules on geoscientific topics, including plate tectonics, earthquakes, volcanism, tectonics, rocks, mineral resources, soils, and climate. Those topics have been didactically adapted to the requirements of the various levels and age groups of the German school system, from kindergarten to the 12th year in secondary school (Fig. 11). Student groups can combine individual learning modules in halfday to multi-day programs and may add field trips guided by the experts of the institution. In order to guarantee high-level scientific and didactic quality, a geologist experienced in teaching and research is responsible for the GEO-Zentrum an der KTB (Dr. Frank Holzförster). Pedagogically and didactically educated scientists and teachers instruct the groups of learners. The personnel who guides tours in the various parts of the exhibition is regularly trained. Close relationships to geological research institutions like the GeoZentrum Nordbayern of the University of Erlangen-Nürnberg or the Bayerische Geoinstitut of the University of Bayreuth and the cooperation with the Bavarian Geological Survey ensure that actual geo-relevant topics and information on running geoscience projects are integrated into the curriculum of the Geoscience Outreach Center in Windischeschenbach.

KTB Deep Drilling Site and Czech-Bavarian Geopark

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Day 2 Regional transport by coach. Return from Weiden to Munich Central Station by train. Stop 2-1: “Urweltmuseum Oberfranken,” Bayreuth (A contribution by J. Rabold.) The “Urwelt-Museum Oberfranken,” located in the city center of Bayreuth, displays both the living (animal and plant fossils) and the non-living (rocks and minerals) Earth history of the Oberfranken region. In the past, fossils were interpreted very differently from today: in the vault of the museum, such “proofs” for various myths and legends are shown. The garden of the museum is home to life-size dinosaur replicas. Visitors can stroll among the legs of these impressive creatures to feel their size. Two halls usually host special exhibitions on Earth history worldwide.

Figure 11. (A) Working with teaching materials developed by the scientists and teachers of the “GEOZentrum an der KTB” allows students to get hands-on experience in understanding geoscientific topics like the rock cycle. (B) Visiting the working platform of the Continental Deep Drilling Program (KTB) drilling rig is an important aspect of connecting technical understanding, geoscientific methods and the System Earth. (C) A view into the exhibition hall with the standing exhibition “System Earth” that outlines the modern geoscientific understanding of the dynamic planet Earth.

Aims and Concepts of the Museum The museum aims to present Earth history as such, and the Earth history of the Oberfranken region in particular, to a nonexpert public. Children and teenagers are encouraged to come in contact with natural sciences. A focus lies on an aesthetic element in the presentation of exhibits and learning objectives. Written texts are reduced as much as possible. Hands-on learning, adventure, and research are emphasized. The museum follows three principles. (1) Learning objectives are presented in an enticing way particularly to children and teenagers. They, and also their parents, should understand the scientific contents and develop a curiosity for the topics of Earth history. (2) Regularly changing special exhibitions on geoscientific topics aim to give insight into all facets of Earth history. This concept is also the fundament of the standing exhibition, where the samples are replaced regularly. Thus, the museum remains interesting and ensures that the visitors will come back. (3) The regional aspect of the exhibitions is a vital aspect of the Urwelt-Museum. Many samples collected within the region itself are on display. Those are findings from former mines, which are not accessible anymore, or collections of plant fossils, which are extraordinarily comprehensive and complete. The presentation of the largest Ichthyosaurus burial site near Mistelgau (south of Bayreuth) accentuates the strong regional aspect of the museum. Architecture and Layout of the Exhibition Halls and Presentation of Samples In the city center, the museum comprises (1) part of the pedestrian zone where a dinosaur model is placed, (2) the entrance, with several exhibits, (3) the three-floor main exhibition building, (4) the dinosaur garden, and (5) a function room.

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Storage rooms, workshops, and laboratories are situated outside the city center, in an industrial area. In order to display fossils and minerals in an aesthetically pleasing way, and to provide some measure of a “thrilling” atmosphere, all rooms have a deep dark-blue color. Lights are reduced to the exhibits only. Thus an adventurous atmosphere develops and even less spectacular samples are enhanced by proper lighting. Many displays encourage touching of samples (Fig. 12): a skull of Temnodontosaurus sp., a 7-m-long skeleton of Nothosaurus sp., and the historic study (Biedermeier-style) of the famous paleontologist Graf Münster are both available for tactile exploration. An ice-age cave of a cave bear is kept dark, and must be explored using a flashlight. Visitors can enter a billiontimes-enlarged gold crystal of 3 × 3 × 3 m size, completely equipped with mirrors on the interior walls. Inside, the gold atoms can be touched and the infinity of the crystal structure becomes very apparent. Stop 2-2: Gold Mining Museum Goldkronach The village of Kronach (“dorf Kranach”) was first mentioned in 1317. Owing to nearby gold deposits, it rapidly developed into a larger settlement, which was granted a town charter and mining privileges in 1365. The town itself has been known by the name of “Goldtkranach” since 1398. Mining thrived as long as gold deposits were close to the surface and thus easily accessible. Starting in the fifteenth century, however, mining in the Goldkronach area often suffered setbacks due to the rising costs resulting from the necessity of mining further below ground, from numerous wars, from plague epidemics, from the tapping of gold deposits in the New World, and from problems of ore processing. Attempts undertaken in 1793 (by the Prussian mining supervisor Alexander von Humboldt) and 1920 (by the private company “Fichtelgold AG”) to make local mining profitable failed again. After a period of 600 years, mining was discontinued in 1925. The Gold Mining Museum Goldkronach was opened in March 2004. Planned on the principles of modern museum didactics, the museum presents itself with an attractive design, offering a great number of exhibits and several displays. The following exhibition rooms exist. • From village to town—Town history. • Searching for gold—“Venetians” washing-out/panning for gold in brooks. • Gold in Goldkronach—how come? Variscan orogeny, formation of gold quartz veins, Franconian Lineament, diversity of minerals. • How to get the gold—History of the mines, ore mining and extracting the gold, visitor mines. • Toil rewarded—World of underground mining, hazards and religiousness, yield. • Miners and mining statutes—Privileged mining and other privileges, mining authorities and ordinances, mining supervisor Alexander von Humboldt.

• Alchemy—Searching for the philosopher’s stone, fraud or innovation. • Working gold—Gold from Goldkronach, hammering gold, gold-plating. Stop 2-3: Geotourism in Goldkronach— The Goldkronach Geosites The town of Goldkronach is located in a complex geological structure. Lateral movement along two en-echelon segments of the Franconian Lineament has produced a steeply dipping sequence of the sedimentary cover and the pre-Mesozoic basement. During the past years, several geotouristic projects have been realized to give the public an understanding of the geological layout. These projects include the restoration of rock cellars originally built for the storage of food (beer, potatoes, turnips), installation of a system of information boards, and the building of the visitors’ gold mine. The steeply dipping units in the area of Goldkronach enable to walk across the strata from the Upper Triassic (Keuper) to the Variscan basement on a short walk through the town. The rock cellars give the opportunity to study the different strata

Figure 12. Display layout of Temnodontosaurus sp. (Lower Jurassic) from the Mistelgau clay pit near Bayreuth.

KTB Deep Drilling Site and Czech-Bavarian Geopark underground and give insights into the geological structure. They make geology come alive by allowing visitors entrance into the third dimension and by giving them the emotional experience of the underground and of the Earth’s interior. At the geosite “Franconian Lineament,” a mechanically driven model visualizes the nature and the evolution of one of the most prominent faults of central Europe. The model is located very close to a temporary trench across the fault that was dug some years ago to better localize and to investigate the fault zone. The results of this study, as well as the regional relevance of the Franconian Lineament, are documented on the information boards.

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Merck from Hamburg, who was a partner of Florentin Theodor Schmidt from Wunsiedel. In this way, Schmidt got around Napoleon’s regulations, although the town of Wunsiedel had just been integrated into the new kingdom of Bavaria, which had been created by Napoleon in 1806. During this time, Florentin Theodor Schmidt financed the extension of the garden surrounding the boulder “Helgoland.” Therefore, the arrangement of the “Island of Helgoland,” the “Hat/Ship of Napoleon” (“Napoleonshut”), and the “Sugar loaf” (“Zuckerhut”) are an ironic allusion to the historical facts. In German, the term “Hut” means both “Hat” and “to look out for.” Thus, the name of the boulder clearly plays with the double meaning of the term.

Stop 2-4: The Luisenburg Labyrinth near Wunsiedel The Luisenburg labyrinth is one of the most well-known and visited geological sites in the Bavarian part of the CBG (more than 80,000 visitors per year). The Luisenburg is an extensive granite boulder labyrinth at the northeastern slope of the Kösseine massif (939 m). The first to describe the rock formations in a scientific manner was the famous German poet and naturalist Johann Wolfgang von Goethe. He visited the Luisenburg in 1785 and 1820, and came to the conclusion that it was not created by earthquakes or heavy rainstorms, which had been the popular belief by then. He explained the Luisenburg labyrinth as the result of weathering processes lasting over long time periods (Fig. 13). Originally, the area of the Luisenburg was called “Luxburg” (“Licht’burg,” which means “castle of brightness”). In 1790, citizens from Wunsiedel began to open up the tangle of granite boulders at the slope above the town. Their aim was to design a natural park in the style of an English garden. For that purpose they arranged a promenade through the rock formation, also by blasting the rocks. These activities have been strongly influenced by the ideals of the Age of Enlightenment. Since everyone who was walking through the garden had to make the same effort, it was enlightenment in the sense that nature does not know any social classes. For funding the garden, sponsors had been granted the opportunity to engrave inscriptions into the granitic boulders. The Luxburg was enlarged in 1805 on the occasion of the visit of the Prussian royal couple Friedrich Wilhelm II and Luise in the nearby spa town of Alexandersbad. In honor to Queen Luise, the garden was renamed as “Luisenburg.” The third stage of the garden’s history started in 1811. The rearrangement of boulders (if really rearranged) and renaming of the blocks around the isolated huge boulder “Insel Helgoland” was motivated by the economic and political situation during that time. In 1810, the industrialist Florentin Theodor Schmidt established a factory in Wunsiedel to process sugar from overseas. During this time, Napoleon imposed a freeze for trade in goods with England. The English tried to evade this freeze by smuggling the goods (like the sugar) from the island of Helgoland in the German Bight of the North Sea to the continent. One of their conspiratorial helpers was the industrialist Heinrich Johann

Figure 13. Rock formations at the Luisenburg (drawn by the researcher J.W. v. Goethe in 1785). (A) Goethe noted the development of the rock formation from an originally upright, slightly dipping attitude: following the weathering of slab a, the upper rock slab b will slide down in a position bb. Weathering of the lowermost slab c will cause the obelisk d to turn upright in position dd. Only the rock slab e in front had not changed. The drawings B, C, and D illustrate the same principle with the original geometry reconstructed in the left column (shading delineate the slabs that have weathered away) and the modern-day post-weathering situation in the right column (from Wilhelmy, 1981).

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Holzförster and Peterek

Since 1820, the Luisenburg has been among the most attractive touristic destinations of the region. However, the original character of the natural garden of the “Luxburg” and the later “Luisenburg” garden has been lost in the mind of the visitors while the aspect of the natural monument came to the fore. In 2005, the anniversary of the visit of Queen Luise 200 years ago, the Luisenburg labyrinth was restored, and the old character of the English garden has strongly dominated the touristic marketing during the past years. However, in cooperation with the CBG, a guided tour has been worked out to appreciate also the wonderful geological background. The Luisenburg labyrinth is well-suited to exemplify the belief of the scientists 200 years ago about the origin of the granite and of its weathering forms. For that purpose, excerpts from the scientific and literary writings of Goethe are used. ACKNOWLEDGMENTS We thank J. Rohrmüller and J. Kraus for critical reviews that further improved the manuscript. J. Rabold is thanked for his contribution on the Urwelt-Museum Bayreuth. REFERENCES CITED Bankwitz, P., Schneider, G., Kämpf, H., and Bankwitz, E., 2003, Structural characteristics of epicentral areas in Central Europe: study case Cheb Basin (Czech Republic): Journal of Geodynamics, v. 35, p. 5–32, doi:10.1016/S0264-3707(02)00051-0. Behr, H.J., 1987, KTB und kontinentale Krustenforschung—warum ein wissenschaftliches Tiefbohrprogramm: KTB-Report, v. 87-1, p. 1–35. Behr, H.J., and Emmermann, R., 1987, Scientific objectives and site-selection studies of the Continental Deep Drilling Program of the Federal Republic of Germany (KTB), in Behr, H.J., and Vidal, H., eds., Observation of the deep continental crust II. Exploration of the deep continental crust: Springer, 325 p. Credner, H., 1900, Die vogtländischen Erdbebenschwärme während der Zeit des Juli und August 1900: Berichte über Verhandlungen der Königlich Sächsischen Gesellschaft der Wissenschaften, v. 52, p. 153–177. Elznic, A., Cadková, Z., and Dušek, P., 1998, Palaeogeography of the Tertiary sediments of the North Bohemian Basin: Sbornik Geologickych Ved Geologie, v. 48, p. 19–46. Emmermann, R., and Lauterjung, J., 1997, The German Continental Deep Drilling Program KTB: Overview and major results: Journal of Geophysical Research, v. 102, p. 18,179–18,201, doi:10.1029/96JB03945. Emmermann, R., Althaus, E., Giese, P., and Stöckhert, G., editors, 1995, KTB Hauptbohrung, Results of geoscientific investigation in the KTB field laboratory, final report: 0-9101 m: KTB-Report 95-2, p. 1–198. Engeser, B., Hoffers, B., Kücker, R., Tran Viet, T., and Wohlgemuth, L., 1996, Das Kontinentale Tiefbohrprogramm der Bundesrepublik Deutschland KTB, Bohrtechnische Dokumentation: KTB-Report, v. 95-3, p. 1–800. Franke, W., 1984, Varizischer Deckenbau im Raum der Münchberger Gneismasse—abgeleitet aus Fazies, Deformation und Metamorphose im umgebenden Paläozoikum: Geotektonische Forschung, v. 6, p. 1–253. Freudenberger, W., Schwerd, K., Bader, K., Doben, K., Doppler, G., Frank, H., Gebauer, D., Jerz, H., Meyer, R.K.F., Mielke, H., Ott, W.D., Risch, H., Rohrmüller, J., Schmidt-Kaler, H., and Unger, H.J., 1996, Erläuterungen zur Geologischen Karte von Bayern 1:500.000: Bayerisches Geologisches Landesamt, 329 p. Geissler, W.H., Kämpf, H., Bankwitz, P., and Bankwitz, E., 2004, Das quartäre Tephra-Tuff-Vorkommen von Mýtina (Südrand des westlichen Eger-Grabens/ Tschechische Republik): Indikationen für Ausbruchs- und Deformationsprozesse: Zeitschrift der geologischen Wissenschaft, v. 32, p. 31–54. Geissler, W.H., Kämpf, H., Kind, R., Bräuer, K., Klinge, K., Plenefisch, T., Horálek, J., Zednik, J., and Nehybka, V., 2005, Seismic struc-

ture and location of a CO2 source in the upper mantle of the western Eger (Ohre) Rift, central Europe: Tectonics, v. 24, TC5001, 23 p., doi:10.1029/2004TC001672. Glaser, S., Keim, G., Loth, G., Veit, A., Bassler-Veit, B., and Lagally, U., 2007, Geotope in der Oberpfalz: Erdwissenschaftliche Beiträge zum Naturschutz, v. 5, p. 1–136. Harms, U., Cameron, K.L., Simon, K., and Brätz, H., 1997, Geochemistry and petrogenesis of metabasites from the KTB ultradeep borehole, Germany: Geologische Rundschau, v. 86, p. 155–166. Hecht, L., 1998, Granitoide des Fichtelgebirges (NE-Bayern): Magmengenese und hydrothermale Alteration (Exkursion J am 18 April 1998): Jahresbericht und Mitteilungen des Oberrheinischen geologischen Vereins: Neue Folge, v. 80, p. 223–250. Hirschmann, G., 1996, Ergebnisse und Probleme des strukturellen Baues im Bereich der KTB-Lokation: Geologica Bavarica, v. 101, p. 37–52. Holzförster, F., and de Wall, H., 2010, Das GEO-Zentrum an der KTB: Informations- und Bildungseinrichtung in der Nachfolge eines nationalen geowissenschaftlichen Großprojektes: Geologische Blätter für NordostBayern, v. 60, p. 199–208. Huckenholz, H.G., and Schröder, B., 1985, Tertiärer Vulkanismus im bayerischen Teil des Eger Grabens und des mesozoischen Vorlandes (Exkursion G am 13 April 1985): Jahresbericht und Mitteilungen des Oberrheinischen geologischen Vereins: Neue Folge, v. 67, p. 107–124. ICDP (International Continental Drilling Program), 2009, www.icdp-online.org. Kämpf, H., Peterek, A., Rohrmüller, J., Kümpel, H.J., and Geissler, W., editors, 2005, The KTB Deep Crustal Laboratory and the western Eger Graben: Schriftenreihe der Deutschen Gesellschaft für Geowissenschaften, v. 40, p. 37–107. Kossmat, F., 1927, Gliederung des variszischen Gebirgsbaues: Abhandlungen des Sächsischen Geologischen Landes-Amtes, v. 1, p. 1–39. Paul, J., and Schröder, B., 2011, Rotliegend im Ostteil der Süddeutschen Scholle, in Deutsche Stratigraphische Kommission, ed., Stratigraphie von Deutschland, Rotliegend Teil I: Schriftenreihe der Deutschen Gesellschaft für Geowissenschaften, v. 61 (in press). Peterek, A., Hüser, K., and Schröder, B., 2007, Reliefentwicklung und Tektonik in der oberfränkisch-oberpfälzischen Bruchschollenzone zwischen Frankenalb und Fränkischer Linie, in Maier, J., ed., Das geographische Seminar—spezial: Exkursionsführer Oberfranken, p. 153–163. Peterek, A., Hirschmann, G., Schröder, B., and Wagner, G.A., 1994, Spät- und postvariskische tektonische Entwicklung im Umfeld der Kontinentalen Tiefbohrung Oberpfalz (KTB): KTB-Report, v. 94-3, p. 123–148. Peterek, A., Rauche, H., and Schröder, B., 1996, Die strukturelle Entwicklung des E-Randes der Süddeutschen Scholle in der Kreide: Zeitschrift für Geologische Wissenschaften, v. 24, p. 65–78. Peterek, A., Reuther, C.D.,and Schunk, R., 2011, Neotectonic evolution of the Cheb Basin (Northwestern Bohemia, Czech Republic) and its implications for the late Pliocene to Recent crustal deformation in the western part of the Eger Rift: Zeitschrift für Geologische Wissenschaften, v. 39 (in press). Projektleitung KTB, 1987, Arbeitsprogramm KTB Oberpfalz VB: Niedersächsisches Landesamt für Bodenforschung, 223 p. Rohrmüller, J., and Mielke, H., 1998, Die Geologie des Fichtelgebirges und der nördlichen Oberpfalz—Nordostbayern: Jahresbericht und Mitteilungen des Oberrheinischen geologischen Vereins Neue Folge, v. 80, p. 25–47. Rohrmüller, J., Horn, P., Peterek, A., and Teipel, U., 2005, Specification of the Excursion Stops—First day: Geology and structure of the lithosphere, A contribution to Kämpf, H., Peterek, A., Rohrmüller, J., Kümpel, H.J., and Geissler, W.H., eds., The KTB Deep Crustal Laboratory and the western Eger Graben, in Freiwald, A., Röhling, H.G., and Löffler, S.B., eds., GeoErlangen 2005 System Earth—Biosphere Coupling, Regional Geology of Central Europe, 24–29 September 2005, Exkursionsführer, Excursion guide: Schriftenreihe der Deutschen Gesellschaft für Geowissenschaften, v. 40, p. 46–63. Schneider, H.J., Borrmann, H., Bustani, K., Crotogino, F., Gomm, H., Kosinowski, M., Münch, H.G., Panzer, D., Ritzmann, U., Schneider, H.J., Schnürpel, W., Stöver, W., Behr, H.J., Dietrich, H.G., Vidal, H., Walter, R., and Wittke, W., 1983, Vorplanung und Untersuchung über die Realisierbarkeit kontinentaler Tiefbohrungen für wissenschaftliche Zwecke einschließlich einer Kosten- und Risikoabschätzung sowie über eine Organisation für die Planung und Durchführung einer Tiefbohrung: Bundesministerium für Forschung und Technologie Forschungsbericht (RG 83-03), Band II. p. 1–288.

KTB Deep Drilling Site and Czech-Bavarian Geopark Schröder, B., 1963, Gliederung und Lagerungsverhältnisse in der Randfazies der Trias bei Weiden-Parkstein (Opf.): Geologische Blätter für NordostBayern, v. 13, p. 98–141. Schröder, B., 1965, Tektonik und Vulkanismus im oberpfälzer Bruchschollenland und fränkischen Grabfeld: Erlanger geologische Abhandlungen, v. 60, p. 1–122. Schröder, B., 1987, Inversion tectonics along the western margin of the Bohemian Massif: Tectonophysics, v. 137, p. 93–100, doi:10.1016/0040 -1951(87)90316-7. Schröder, B., 1990, Spät- und postvariszische Schollentektonik des KTBUmfeldes: KTB-Report, v. 90-4, p. 293–299. Schröder, B., and Peterek, A., 2001, Känozoische Hebungs- und Abtragungsgeschichte im Umfeld des westlichen Egergrabens: Zeitschrift der Deutschen Geologischen Gesellschaft, v. 151, p. 387–403. Schröder, B., Bankwitz, P., Franzke, H.J., and Bankwitz, E., 1992, Die Fränksiche Linie und ihr geologischer Rahmen, in Bankwitz, P., Kämpf, H., and Bielefeld, E., eds., Münchberger Gneismasse und ihr geologischer Rahmen: Exkursionsführer der Gesellschaft für Geowissenschaften, p. 99–126. Schröder, B., Ahrendt, H., Peterek, A., and Wemmer, K., 1997, Post-Variscan sedimentary record of the SW margin of the Bohemian massif: a review: Geologische Rundschau, v. 86, p. 178–184, doi:10.1007/s005310050129. Schröder, B., Klare, B., Menzel, D., and Peterek, A., 1998, Das Permomesozoikum des Vorlandes der Böhmischen Masse (Exkursion K am 18 April 1998): Jahresbericht und Mitteilungen des Oberrheinischen geologischen Vereins Neue Folge, v. 80, p. 251–270. Schunk, R., Peterek, A., and Reuther, C.D., 2003, Untersuchungen zur quartären und rezenten Tektonik im Umfeld der Marienbader Störung und des Egerer Beckens (Tschechien)—erste Ergebnisse: Mitteilungen des Geologisch-Paläontologischen Instituts der Universität Hamburg, v. 87, p. 19–46. Siebel, W., Chen, F., and Satir, M., 2003, Late-Variscan magmatism revisited: New implications from Pb-evaporation zircon ages on the emplacement of redwitzites and granites in NE Bavaria: International Journal of Earth Sciences, v. 92, p. 36–53. Siebel, W., Trzebski, R., Stettner, G., Hecht, L., Casten, U., Höhndorf, A., and Müller, P., 1997, Granitoid magmatism of the NW Bohemian massif revealed: gravity data, composition, age relations and phase concept: Geologische Rundschau, v. 86, supplement, p. S45–S63, doi:10.1007/ PL00014665.

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Siebel, W., Shang, C.K., and Presser, V., 2010, Permo-Carboniferous magmatism in the Fichtelgebirge: dating the final intrusive pulse by U-Pb, 207 Pb/206Pb and 40Ar/39Ar geochronology: Zeitschrift für Geologische Wissenschaften, v. 38, p. 85–98. Stettner, G., 1992, Geologie im Umfeld der Kontinentalen Tiefbohrung, Oberpfalz: Bayerisches Geologisches Landesamt, 240 p. Suess, F.E., 1903, Bau und Bild der Böhmischen Masse, in Diener, C., Hoernes, R., Suess, F.E., and Uhlig, V., eds., Bau und Bild Österreichs: TemskyFreytag, 1110 p. Suess, F.E., 1912, Mitteilungen über die Münchberger Deckscholle: Sitzungsberichte der Akademie der Wissenschaften Wien Mathematischnaturwissenschaftliche Klasse, v. 121, p. H10. Suhr, P., 2003, The Bohemian Massif as a Catchment Area for the NW European Tertiary Basin: Geolines (Praha), v. 15, p. 147–159. Teipel, U., Eichhorn, R., Loth, G., Rohrmüller, J., Höll, R., and Kennedy, A., 2004, U-Pb SHRIMP and Nd isotopic data from the western Bohemian Massif (BayerischerWald, Germany): Implications for Upper Vendian and Lower Ordovician Magmatism: International Journal of Earth Sciences, v. 93, p. 782–801, doi:10.1007/s00531-004-0419-2. Ulrych, J., Lloyd, F.E., and Balogh, K., 2003, Age relations and geochemical constraints of Cenozoic alkaline volcanic series in W Bohemia: a review: Geolines (Praha), v. 15, p. 168–180. Wagner, G.A., Coyle, D.A., Duyster, J., Henjes-Kunst, F., Peterek, A., Schröder, B., Stöckhert, B., Wemmer, K., Zulauf, G., Ahrendt, H., Bischoff, R., Hejl, E., Jacobs, J., Menzel, D., Nand Lal, P., Ven den Haute, P., Vercoutere, C., and Welzel, B., 1997, Post-Variscan thermal and tectonic evolution of the KTB site and its surroundings: Journal of Geophysical Research, v. 102, p. 18,221–18,232, doi:10.1029/96JB02565. Weber, K., and Vollbrecht, A., 1986, Kontinentales Tiefbohrprogramm der Bundesrepublik Deutschland. Ergebnisse der Vorerkundungsarbeiten Lokation Oberpfalz. 2. KTB-Kolloquium Seeheim/Odenwald 19–21 September 1986: Universität Göttingen, 168 p. Wilhelmy, H., 1981, Klimamorphologie der Massengesteine: Akademische Verlagsgesellschaft, 254 p. Zoback, M., and Emmermann, R., 1994, Scientific rationale for establishment of an international program of continental scientific drilling: GeoForschungsZentrum Potsdam, 194 p. MANUSCRIPT ACCEPTED BY THE SOCIETY 4 MAY 2011

Printed in the USA

The Geological Society of America Field Guide 22 2011

Geo-education and geopark implementation in the Vulkaneifel European Geopark Peter Bitschene* TW Gerolsteiner Land GmbH, Brunnenstraße 10, 54568 Gerolstein, Germany Andreas Schüller* Vulkaneifel Natur- und Geopark GmbH, Mainzer Str. 25, 54550 Daun, Germany

ABSTRACT In the middle of western Germany, there is a moderately high mountain range that is composed mostly of Paleozoic folded sediments partly and unconformably overlain by younger Mesozoic to Cenozoic sediments. The mountain range is named “Rheinisches Schiefergebirge” (“Rhenish Slate Mountains”), its western part bearing the name “Eifel.” Geologically, the Eifel is famous for its rich Mid-Devonian marine fauna, especially the trilobites, and for its intraplate, mostly monogenetic volcanic field comprising alkali basaltic scoria and cinder cones, tuff rings, lava flows, and maars; the term “maar” was coined in the Eifel. The geological wealth of the Eifel was already known by the beginning of the nineteenth century, when famous naturalists like Goethe, Humboldt, Steininger, and others visited the Eifel. The positive side of the visits of these naturalists and lovers of nature was the first scientific descriptions of maars, xenoliths, and Devonian trilobites and eco-systems. The latter were especially important when Murchison came here to compare similar limestones and fossils between Great Britain and Germany. This work finally led him to set up the “Devonian” system. The negative side of these visits by numerous naturalists and lovers of nature was that quarries, fields, and other private and public property were destroyed by fossil hunters. Fossil and rock selling was a common business, which led to the exhaustion and destruction of geosites with unparalleled Devonian faunas or upper mantle and lower crustal xenoliths, and to general landscape degradation. A black market for fossils and rocks without monetary, scientific, or official control developed. Annoyed local farmers, angry public bodies, speechless scientists, and an increasing number of disappointed visitors looking for a pristine Eifel landscape were also direct consequences of this “evil side” of geotourism. As a consequence of the uncontrolled exploitation of rock and fossil occurrences and of the destructive consequences for the landscape and outcrops, the authorities of the small towns of

*[email protected]; [email protected]. Bitschene, P., and Schüller, A., 2011, Geo-education and geopark implementation in the Vulkaneifel European Geopark, in Carena, S., Friedrich, A.M., and Lammerer, B., eds., Geological Field Trips in Central Western Europe: Fragile Earth International Conference, Munich, September 2011: Geological Society of America Field Guide 22, p. 29–34, doi:10.1130/2011.0022(03). For permission to copy, contact [email protected]. ©2011 The Geological Society of America. All rights reserved.

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Bitschene and Schüller Hillesheim and Gerolstein in the Westeifel decided to enact protective legal measures in 1984. Additional geo-educational and geo-touristic measures were implemented in the mid-1980s with the first geopaths around Hillesheim, and in 1988 with the planning and establishment of the “Geopark Gerolsteiner Land” that in 2000 evolved into the “Vulkaneifel European Geopark,” Germany’s first geopark and co-founder of the European and Global Geoparks Network.

INTRODUCTION Today’s “Vulkaneifel Nature- and Geo-Park”—this is the official full name of our European and Global Vulkaneifel Geopark—comprises not only the “Vulkaneifel County” but also adjacent areas containing volcanic features and rocks. Covering a surface of 1220 km2, there are more than 400 km of geotrails with signage and nearly 300 geopanels within the Vulkaneifel Geopark. The geology, palaeontology, and volcanology of our geopark (comprehensive reviews are found in the following books and articles: Steininger, 1820; Büchel, 1994; Meyer, 1988; Landesamt Geologie und Bergbau RLP, 2005; Ritter and Christensen, 2007; Schmincke, 2009; Lutz and Lorenz, 2009) is outstandingly rich and was crucial for setting up the geopark. This field trip will lead you to famous geosites in the Vulkaneifel (Fig. 1), in order to explain the special geologic value of the sites, how to protect the sites, and how to both educate and entertain the visitor with geology. The daily work within the geopark and its attached geo-museums consists of the reconciliation of geosite and landscape protection and investigation with open access and public viewing of the geosites. In this regard, the most notable steps in the Vulkaneifel European Geopark are (Frey et al., 2006; Bitschene and Schüller, 2006; Bitschene, 2010): Protection of landscape and geosites: Legal protection where necessary and possible; fencing of geosites that are under pressure; design of a visitor guidance system with well-marked geotrails; bringing geotourists into museums to watch, feel, and understand, without selling rocks, fossils, or minerals. Geo-education and entertainment: Circular geotrails with parking lots and gastronomy where possible; open access to geosites with well-designed panels; brochures and leaflets with explicit geological content; and guided public geo-excursions and open lectures. Scientific investigation and public education: Facilitate and strengthen investigation and science in the region; give lay paleontologists and volcanologists a home and a voice in the museum; bring latest scientific research results into the region; and familiarize the public with the ideas and the concept of geoparks. No doubt, there are significant issues that accompany this concept: How to exercise law enforcement when clandestine fossil hunters dig in the region; how to control the sale of rocks and fossils via the Internet, bourses, and private dealers; and—a great challenge, but which is nonetheless a fundamental idea of the

European and Global Geopark Networks—how we can encourage children and students of all ages to understand the Earth and its rocks and fossils without removing specimens from the locality at which they were found. FIELD TRIP STOPS Stop 1: Gerolstein Recreational Park Geology, hydrology, volcanology, and archaeology are combined here at their best. In the early nineties of the last century, it was here that geotourism became a fully accepted segment within the regional tourism strategy. This was followed by the availability of trained geopark guides and well-designed explanatory notes throughout the region (Frey, 1993). The “Helenenquelle” is the place where the unique Gerolsteiner mineral water can be tasted. The water is pumped from a nearby borehole sunk 117 m deep into Mid-Devonian marl, limestone, and dolomite, where the water is collected at ~50–80 m depth. The mineral water has a pH value of 6.17 and a temperature of 11 °C, and it is rich in hydrogen carbonate (2101 mg/l), magnesium (121 mg/l) and calcium (388 mg/l), with low chlorine (55 mg/l) and sodium (155 mg/l) values. In general, the origin of the dissolved Ca and Mg in this mineral water is the Devonian limestones and dolomites, whereas up to 70% of the gas phase, including CO2, is attributed to upper mantle degassing (Griesshaber et al., 1992). Water is an excellent carrier for geo-education. No wonder that several educational programs have been designed in order to explain the origin and value of the mineral water, and how to protect it. Programs with children (“Water Detectives”) and with adults (“Wonder World of Water”) have been designed, as well as flyers in different languages. A few meters along the Kyll River, there is the site where bubbling mineral water was already gathered in Celtic and Roman times. This site is perfect for explaining that 2,000 years ago, people came here to drink the mineral water, and that just across the river Kyll a villa rustica with central heating served the visitors. Some 100 m downstream, the wide front of a lava flow can be recognized. The front of the lava flow exhibits columnar jointing, and a closer view also shows vesicle pipes in the middle part of the flow. With Ar-Ar stepwise heating techniques the nephelinitic lava flow was dated at 30,000 ± 11,000 years (Mertz, 2010, personal commun.), thus being the youngest lava flow in Germany. This site serves to explain the velocity at which geologic events happen: lava flows advance with a few km/h, and it takes

Vulkaneifel European Geopark 30,000 years for the Kyll River to cut 4 m through basaltic lava and incise 3 m deep into the bed rock.

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that tapped distinct magma chambers at different depths. Several quarries today exhibit all evolutionary stages of a typical Eifel volcano. An Eifel volcano eruption cycle starts here with tephra rich in lithics from Devonian country rock indicating a maar-type eruption. The maar-eruption then is followed by subsidence and listric faulting, where blocks of the maar-tephra slump toward the nearby crater. After this hydro-volcanic episode, a more pyro-volcanic episode evolves, indicated by dark, basaltic tephra

Stop 2: Rockeskyller Kopf Volcanic Complex The Rockeskyller Kopf Volcanic Complex is the most complete volcano in Germany. The 474–360 ka (Shaw et. al., 2010) old volcanic complex is the result of coalescing eruption centers

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layers stemming from Strombolian-type eruptions. The final episode of a typical alkali basaltic Eifel volcano is then displayed by exposed feeder dikes and lava flows that cover the top of the volcano. The Rockeskyller Kopf also provides a unique suite of xenoliths from the upper mantle through the lower and upper crust, with glazed sandstones being just another spectacular feature of this volcanic complex (e.g., Haart, 1914; Shaw, 2009). It is here where the dimensions and activities of Eifel volcanoes can be demonstrated. Another special feature is that the open quarry is still exploited for volcanic ash and lava, and partially used as a site for solid waste disposal. Stop 3: Mühlenberg Quarries and Caves The Mühlenberg is a conical-shaped volcano that had a strong final lava outpouring. The final lava flow is still exploited and has the tallest (up to 12 m) and thickest (up to 2.80 m) basalt columns in the Vulkaneifel. On top of the Mühlenberg volcano, several m of basaltic agglutinates and welded scoria developed. This material is extremely porous, though hard and resistant, and has been used for millstone production for centuries. Even today, people can enter the places where in past times workers hammered the millstones out of tough basaltic lava. The sites with millstones can be seen in open pits and in the caves. The hardship of carving out the millstones by hand can be explained here, as well as the need to understand the difference between true lava flows, loose scoria and rubble, and welded basaltic scoria and agglutinates. A secondary but important issue is that bats use the man-made caves for hibernating. Therefore, visiting the caves is not allowed between November and April, which is obeyed to by the local geopark guides and the tourist offices.

The Mühlenberg is an excellent place to combine geology and biology and to give the visitor a more holistic view of what happens in extinct volcanoes. Stop 4: Gerolstein Geo-Field The “Gerolstein Geo-Field” is the latest educational installation set up in the Vulkaneifel Geopark. It is located in an old lava extraction site that was later back-filled with soil and rock from construction sites. On top of the fill, a plateau was formed where today several heaps of rocks (basaltic ash and lapilli, dolomite, limestone) allow the visitors—especially families with children—to touch, smell, scratch, and understand the rocks. Also, at the eastern side of the geo-field is a wall of black basaltic pyroclastic fall deposits from the nearby Kasselburger Hahn volcano. These alternating proximal pyroclastic strata bear some white and red xenoliths from the Mid-Devonian country rock. A second wall reveals brown to gray pyroclastic ejecta from the also nearby Gerolstein maar, which discordantly overlie the ashes and lapilli strata of the Kasselburger Hahn volcano. The geo-field was installed to provide educational programs with an alternative for families with kids to learn about rocks, minerals, and fossils without having to enter quarries or other private properties. Thus, original sites are protected, and everybody who wants to can still investigate the natural rocks brought here. Stop 5: Daun Maars The Daun maars comprise three perfect maar lakes: Gemünden maar, Weinfeld maar, and Schalkenmehren maar (Fig. 2). The most easily accessible site to observe two water-filled maars

Figure 2. Geological sketch of the famous “Three Maars of Daun,” selected as one of Germany’s great geotopes (Eschghi, 2002). Map projection UTM 32U.

Vulkaneifel European Geopark out of the three is the road from Daun to Brockscheid and Eckfeld. When Steininger (1820) first described the Eifel maars as volcanic edifices, he most probably had the place right here on top of the saddle between the Weinfeld and the Schalkenmehren maars in mind. These two maars are set into Lower Devonian sandstones and siltstones, and although only 200 m distant from each other, their water tables have a height difference of more than 70 m, indicating that the country rock does not permit a hydraulic shortcut. The Weinfeld maar lake is 52 m deep and has a diameter of 525 m. With its circular shape, the ring of maar tephra and the blue water it is the perfect example of an Eifel maar. The Schalkenmehren maar can easily be recognized as the result of two coalescing maar craters. The “two maars view” is exceptional and attracts several hundred thousand visitors a year. The easy accessibility, the panoramic views, the perfect shape and color of the maar lakes (“eyes of the Eifel”), the well-kept circular trails, and the picturesque little village of Schalkenmehren make this site probably the most visited geo-site in the Vulkaneifel. The site is enhanced by a visitors’ platform at the Weinfeld Maar, abundant information panels, and an extensive visitor guidance system. On the other hand, a plethora of different panels and signs, and sometimes littering, are among the problems that occur at “most visited” sites! Stop 6: Holzmaar One of the most prominent maars for research is the Holzmaar. It has a diameter of 325 m and is 21 m deep. Because of its easy accessibility, it was here that research into maar lake sediments began and has continued, the latest outcome being a very detailed study of the Eifel climate during the past 11,000 years (Litt et al., 2009). Altogether, the Holzmaar sediments reveal environmental information for the 23,000 years since the last glaciation (Zolitschka et al., 2000). Maar lakes, with their laminated year-by-year varves, are extraordinary sites to investigate climate and environment, biology and human impact on a local and regional scale. Around the Holzmaar, there are also history and saga trails that tell the stories of local heroes and events, thus delivering old stories and wisdom to the mostly young visitors. Therefore, the Holzmaar has been developed toward an outstanding geo-educational site where geology and volcanology, climate and flora and fauna, and local history are explained. Stop 7: Strohn Lava Bomb and “Vulkanhaus Museum” The small village of Strohn is among the best known places in the Eifel because it is home of a 120 t lava bomb. This lava bomb was found during the exploitation of the nearby Wartgesberg volcano. The 120 t volcanic “monster” bomb was saved by the local authorities and now is a prime attraction in the Vulkaneifel Geopark. Of course, the bomb never flew through the air but gained its volume and weight by rolling uphill and downhill in the then-active crater. Another interesting finding

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was a lava wall coated with lava tears and tips. This lava wall developed in an open eruption fissure which held enough heat and hydrothermal activity after its last lava expulsion so that droplets of lava could slowly creep down the fissure’s walls and coat them with lava tears and tips. This lava wall is displayed in the “Strohn Volcano House,” together with a lively exhibition of volcanic rocks and stories, which is partially interactive. The Volcano House is one of five geo-museums that dot the Vulkaneifel Geopark. These museums are visited by ~80,000 visitors per year. Some say there are too many geo-museums, while others are happy to be able to visit a different geo-museum each day of the week. Stop 8: Pulvermaar Pulvermaar is nearly perfectly round, with a diameter of ~980 m and a maximum depth of 72 m. It is the deepest Eifel maar, and it has a high touristic value because it can easily be reached directly by car, and swimming is allowed in a portion of the maar lake. There are camping sites adjacent to the water, and circular paths follow along the shore. But let us focus now on the open quarry west of the maar lake. The quarry is set into the tephra ring of the maar eruption. Alternating layers of tephra rich in lithic clasts can be seen that clearly reveal the pulsating mode of eruption during maar formation. Another feature to be observed is dune and anti-dune bedding, typical for surge deposits resulting from collapsing ash plumes and clouds. Also, syneruptive displacements resulting from near-crater sliding of tephra stacks are visible here. The maar tephra itself is composed of up to 80% Devonian siltstone and sandstone, some slates, and occasional lava bombs. The dynamics of maar eruptions can be read from this sequence of tephra layers. Stop 9: Wallenborn Cold-Water Geyser The Vulkaneifel Geopark has dozens of mineral springs that are quite different in composition, but have one feature in common: a very high amount of dissolved and free CO2. Here, a 40-m-deep borehole has captured artesian ground water and a high flux of CO2 from depth. In contrast to hot water geysers elsewhere, which are driven by boiling water, the Wallenborn cold-water geyser is driven entirely by cold water supersaturated in CO2. Once the underground water is saturated in CO2, the free CO2 gas rises through the water column in the steel tube that draws water from below. This degassing process starts currently every 50 minutes with a rising water table and an outburst of cold water that reaches up to 5 m in height. Once the CO2 has escaped, the water column collapses, and the borehole returns to bubbling quiescence until the next outburst. Here the authorities have installed visitor information panels that explain the peculiar cold-water geyser. The village of Wallenborn maintains the site and charges an entrance fee for visiting the geyser and information panels. More than 30,000 visitors per year come here to see, hear, and smell (sulfur odor!) the geyser, and of course to learn

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about the dormant Eifel volcanoes, the breath of which are the CO2 emanations. ACKNOWLEDGMENTS The authors wish to thank Prof. Alan B. Woodland of Goethe University Frankfurt, and Wofgang Reh of Eifel-Tourismus GmbH Prüm for reviewing this paper. REFERENCES CITED Bitschene, P., 2010, Geotourism and geosite protection in the Vulkaneifel European Geopark Gerolsteiner Land—a tale of two stories: Hannover, Schriftenreihe Deutsche Gesellschaft für Geowissenschaften, v. 66, p. 20. Bitschene, P., and Schüller, A., 2006, Towards an attractive and efficient geopark—the Vulkaneifel European Geopark Gerolsteiner Land: 2nd UNESCO International Conference on Geoparks, Belfast, Abstracts, p. 92. Büchel, G., 1994, Volcanological map of West- and Hocheifel: Institut für Geowissenschaften Universität Mainz, scale 1:50 000, 1 sheet. Eschghi, I., 2002, Geo-Infoband Vulkaneifel: Geo-ZentrumVulkaneifel und Landkreis Daun, Daun, 218 p. Frey, M.-L., 1993, Der Geo-Park in der Verbandsgemeinde Gerolstein: Planung und Realisierung, in Eifelverein, ed., Die schöne Eifel Gerolstein: Düren, p. 106–113. Frey, M.-L., Schäfer, K., Büchel, G., and Patzak, M., 2006, Geoparks—a regional, European and global policy, in Dowling, R.K., and Newsome, D., eds., Geotourism: Amsterdam, London, New York, Elsevier, p. 95–118. Griesshaber, E., O’Nions, R.K., and Oxburgh, E.R., 1992, Helium and carbon isotope systematics in crustal fluids from the Eifel, the Rhine Graben and the Black Forest: Chemical Geology, v. 99, p. 213–235.

Haart, W., 1914, Die vulkanischen Auswürflinge und Basalte am Kyller Kopf bei Rockeskyll in der Eifel: Berlin, Jahrbuch Preussische Geologische Landesanstalt, v. 35, p. 177–253. Landesamt Geologie und Bergbau, 2005, Geologie von Rheinland-Pfalz: Stuttgart, Schweizerbart’sche Verlagsbuchhandlung, 400 p. Litt, T., Scholzel, C., Kuhl, N., and Brauer, A., 2009, Vegetation and climate history in the Westeifel volcanic field (Germany) during the past 11,000 years based on annually laminated lacustrine maar sediments: Boreas, v. 88, p. 695–707. Lutz, H., and Lorenz, V., 2009, Die Vulkaneifel und die Anfänge der modernen Vulkanologie: Mainz, Mainzer naturwissenschaftliches Archiv, v. 47, p. 193–261. Meyer, W., 1988, Geologie der Eifel: Stuttgart, Schweizerbart’sche Verlagsbuchhandlung, 2nd edition, 615 p. Ritter, J.R.R., and Christensen, K.R., 2007, Mantle Plumes—A multidisciplinary approach: Heidelberg, Springer Verlag, 501 p. Schmincke, H.-U., 2009, Vulkane der Eifel: Heidelberg, Spektrum Verlag, 160 p. Shaw, C.S.J., 2009, Caught in the act—the first few hours of xenolith assimilation preserved in lavas of the Rockeskyller Kopf volcano, West Eifel, Germany: Lithos, v. 112, p. 511–523. Shaw, C.S.J., Woodland, A.B., Hopp, J., and Trenholm, N.D., 2010, Structure and evolution of the Rockeskyller Kopf Volcanic Complex, West Eifel Volcanic Field, Germany: Bulletin Volcanologique, v. 72, no. 8, p. 971–990. Steininger, J., 1820, Die erloschenen Vulkane in der Eifel und am Niederrheine: Mainz, Kupferberg, 182 p. Zolitschka, B., Brauer, A., Negendank, J.F.W., Stockhausen, H., and Lang, A., 2000, Annually dated late Weichselian continental paleoclimate record from the Eifel, Germany: Geology, v. 28, no. 9, p. 783–786, doi:10.1130/0091-7613(2000)28<783:ADLWCP>2.0.CO;2.

MANUSCRIPT ACCEPTED BY THE SOCIETY 27 APRIL 2011

Printed in the USA

The Geological Society of America Field Guide 22 2011

Sedimentary facies and paleontology of the Ottnangian Upper Marine Molasse and Upper Brackish Water Molasse of eastern Bavaria: A field trip guide Simon Schneider Bayerische Staatssammlung für Paläontologie und Geologie, Richard-Wagner-Strasse 10, D-80333 München, Germany Martina Pippèrr Dorothea Frieling Bettina Reichenbacher Department of Earth and Environmental Sciences, Palaeontology & Geobiology, Ludwig-Maximilians-Universität München, Richard-Wagner-Strasse 10, D-80333 München, Germany

ABSTRACT As a chronostratigraphic stage of the Paratethys realm, the Ottnangian comprises a single third order sequence and is correlated with the middle Burdigalian (Bur3). In the North Alpine Molasse Basin, the Ottnangian encompasses the most extensive transgression of the Paratethys Sea as well as its final retreat and replacement by brackish water ecosystems. The respective sediments of the Upper Marine Molasse and Upper Brackish Water Molasse are generally widely distributed in the eastern part of Bavaria (SE Germany). This field guide focuses on the development of the sedimentary facies and fossil biota of the Ottnangian strata in the OrtenburgPassau and Simbach am Inn regions. The entire marine succession, which comprises the Untersimbach Beds, Neuhofen Beds, and “Glaukonitsande und Blättermergel,” as well as the nearshore equivalents of these facies can be observed in the presented outcrops. Two of the outcrops exemplify the lower Ottnangian transgression on a granitic basement. Moreover, the lower portion of the Upper Brackish Water Molasse is featured with two outcrops, which show the typical sedimentary succession of these strata. Both sections include the so-called “Schillhorizont,” a famous coquina and marker bed, which is almost exclusively composed of millions of shells of a single brackish water bivalve species.

Schneider, S., Pippèrr, M., Frieling, D., and Reichenbacher, B., 2011, Sedimentary facies and paleontology of the Ottnangian Upper Marine Molasse and Upper Brackish Water Molasse of eastern Bavaria: A field trip guide, in Carena, S., Friedrich, A.M., and Lammerer, B., eds., Geological Field Trips in Central Western Europe: Fragile Earth International Conference, Munich, September 2011: Geological Society of America Field Guide 22, p. 35–50, doi:10.1130/2011.0022(04). For permission to copy, contact [email protected]. ©2011 The Geological Society of America. All rights reserved.

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INTRODUCTION The North Alpine Foreland Basin, or North Alpine Molasse Basin by definition, stretches from eastern France across Switzerland, southern Germany, and Austria where it merges into the Carpathian Molasse toward the east. In southern Germany, the basin reaches its largest extension, with a narrow, tectonically disturbed southern portion, situated along the northern rim of the Alpine orogen, i.e., the Subalpine Molasse ( = Allochthonous Molasse), and a much broader, more or less evenly bedded Foreland Molasse ( = Autochthonous Molasse) that follows up toward the north. To the NW and NE, the South German Foreland Molasse is bordered by the Swabian and Franconian Alb, and the Bohemian Massif. In Germany, the sediments of the North Alpine Foreland Molasse are usually underlain by Mesozoic strata, whereas they often rest on the crystalline basement of the Bohemian Massif in Austria. As a whole, the sedimentary succession of the molasse deposits comprises two transgressive-regressive megacycles, each of which is characterized by marine sediments at the base and terrestrial sediments or an erosional gap at its top (e.g., Lemcke, 1988; Schwerd et al., 1996; Fig. 1). The first megacycle, which started in the Late Eocene and ended in the Early Miocene, comprises the Lower Marine Molasse, Lower Brackish Water Molasse, and Lower Freshwater Molasse (Fig. 1). During the second megacycle, the Upper Marine Molasse (Eggenburgian– middle Ottnangian), the Upper Brackish Water Molasse (upper Ottnangian), and the Upper Freshwater Molasse (Karpatian to Badenian) were deposited (e.g., Doppler et al., 2005). In the eastern part of the German Molasse Basin, however, the rock record preserves exclusively marine strata up to the middle Ottnangian, but with a hiatus between the two megacycles. In eastern Bavaria, the oldest strata of the Foreland Molasse that are exposed at the surface are the middle Eggenburgian (upper Aquitanian to lower Burdigalian) “Ortenburger Meeressande” ( = Ortenburg Marine Sands). The Ortenburg Marine Sands also form the base of the Upper Marine Molasse in this area, and were deposited on granitic basement, Upper Jurassic limestone, or Upper Cretaceous silt- and claystones. Today, the Ortenburg Marine Sands are no longer accessible, as all former outcrops are now restored. The Ottnangian portion of the Upper Marine Molasse in eastern Bavaria was deposited above a hiatus, which obviously comprises the upper Eggenburgian. The lithostratigraphic units of the marine Ottnangian include, from bottom to top, the “Untersimbacher Schichten” ( = Untersimbach Beds), “Neuhofener Schichten” ( = Neuhofen Beds), and “Glaukonitsande und Blättermergel” ( = glauconitic sands and laminated marls) (Fig. 2). Up to

Figure 1. Schematic lithostratigraphic overview of the German part of the North Alpine Foreland Molasse (modified from Heckeberg et al., 2010). BWM—Upper Brackish Water Molasse. The segment that is relevant for this field trip is shaded in gray (see Fig. 2 for details).

Ottnangian Upper Marine Molasse and Upper Brackish Water Molasse of eastern Bavaria now, these units have not been formalized, and there are diverging opinions whether to treat them as formations or members. The Untersimbach Beds sensu Wenger (1987) include the series of “Grobsande” ( = coarse sands) and “Sandmergel” ( = sandy marls) of Hagn (1953) and the “Robulus-Schlier s. str.” of Knipscheer (1952). The type locality of the Untersimbach Beds, a hillslope near the village of Untersimbach, is included as Stop 3 in this guide. The subsequent Neuhofen Beds are composed of clayey to fine sandy marls. In Eastern Bavaria, they reach a maximum thickness of some 220 m, which decreases toward the north. At the type locality, i.e., an abandoned clay pit near the village of Neuhofen, only a few meters of sediment are still exposed. Thus, we will visit another exposure at Höhenmühle, which is still intensively mined, and exposes the top portion of this unit. The typical facies of the Neuhofen Beds indicates considerably deep water. Further toward the coast, shallow water equivalents of the Neuhofen Beds were deposited, termed “Strandfazies von Holzbach und Höch” ( = littoral facies of Holzbach and Höch) by Unger (1984) and usually interpreted as middle Ottnangian by Wenger (1987). These facies, now partially re-dated as lower Ottnangian (Pippèrr, 2011), have been deposited during the transgression of the early Ottnangian Molasse Sea. Partially, this transgression occurred on a granitic basement, and we will visit two localities, i.e., Neustift and Gurlarn, that document this process (Stops 1 and 2). As can be observed at Höhenmühle, the marls of the Neuhofen Beds successively grade into the “Glaukonitsande und Blättermergel.” As already indicated by the informal lithostratigraphic term, the latter sediments comprise two facies, i.e., glauconitic sands and finely layered to laminated marls that intercalate or interfinger laterally and reach a maximum thickness of ~70 m (Doppler et al., 2005). We will see these facies in rather different appearance at four of the sites. At Neustift (Stop 1), the “Glaukonitsande und Blättermergel” are well exposed, but decalcified. At Gurlarn (Stop 2), we will also see a relatively untypical facies

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largely lacking the finely laminated marls. The Höhenmühle pit (Stop 4) and the base of the Prienbach section (Stop 5) both show the typical sedimentology of this unit. The transition from the marine “Glaukonitsande und Blättermergel” to the Upper Brackish Water Molasse ( = Oncophora Beds) is marked by a change in sedimentation, but the decrease of salinity seems to occur gradually. At least the basal parts of the “Mehlsande” yield an impoverished Foraminifera fauna (Cicha et al., 1973; Hagn, 1953; Reichenbacher, 1993). A lithostratigraphic classification scheme of the Upper Brackish Water Molasse in Eastern Bavaria was established by Schlickum and Strauch (1968). According to these authors, the lower Oncophora Beds comprise the “Mehlsande” ( = flour sands), “Schillhorizont” ( = shell bed horizon), and “Glimmersande” ( = mica sands), while the upper Oncophora beds are divided into “Aussüssungshorizont” ( = desalinization horizon), “Schillsande” ( = shelly sands), “Uniosande” ( = Unio sands), and “Lakustrische Schichten” ( = lacustrine beds). Altogether the Oncophora Beds document a continuous decrease in salinity, the establishment of lacustrine habitats, and finally the infill and/or exhumation of the former marine basin. The “Ortenburger Schotter” ( = Ortenburg Gravel), which is regarded as more or less time-equivalent to the Upper Brackish Water Molasse, is probably the most controversially discussed stratum of the area. Consisting almost exclusively of gravels of different sizes, the Ortenburg Gravel is interpreted either as a submarine channel fill or as a fluvial deposit. Its timing, provenance, and relation to the other strata are not yet resolved (Unger, 1984; Haas, 1987). The Ortenburg Gravel is mined in several impressively large pits north of the village of Ortenburg and is also exposed at our first stop in the Neustift granite quarry. Naturally, the arrangement of the localities to be visited is mainly controlled by the availability of outcrops. Sand and clay mining have largely ceased in the area of our field trip, and there are only few alternatives where to look at Ottnangian sediments.

Figure 2. Stratigraphic overview of the Ottnangian deposits in eastern Bavaria (part of Fig. 1 shaded in gray). Chronostratigraphic correlation of the Ottnangian stage adapted from Piller et al. (2007). Miocene geochronology and polarity chrons according to Lourens et al. (2004). Sequence stratigraphy follows Hardenbol et al. (1998). Lithostratigraphic units merged from Wenger (1987) and Doppler et al. (2005). OMM—Upper Marine Molasse. OBM—Upper Brackish Water Molasse.

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Nevertheless, the outcrops described in this guide provide a more or less complete suite of the marine strata of Ottnangian age deposited in Lower Bavaria. Moreover, two impressive localities in eastern Upper Bavaria show the lower part of the upper Ottnangian Upper Brackish Water Molasse ( = Oncophora Beds) (Fig. 3). The program presented here is compiled for a one-day field trip. Due to limited outcrops and restriction in time, localities showing the Upper Oncophora Beds are not included. HISTORICAL BACKGROUND AND STATE OF THE ART Research on the Ottnangian molasse deposits in eastern Bavaria started in the middle of the nineteenth century, when Josef Waltl (1847) and Ludwig Wineberger (1851) provided first

descriptions of the geology of the region, including the Molasse strata. These were followed by several general geologic treatments of the area that involved the molasse strata (Kraus, 1915; Stadler, 1925; Unger, 1984; Unger and Bauberger, 1985). The earliest studies that focused exclusively on molasse sediments were executed by Gümbel (1887), Ammon (1888), and Suess (1891). In the twentieth century, Ferdinand Neumaier and his students forced the sedimentological exploration and description of the Ottnangian strata in eastern Bavaria. Several comprehensive publications, the more recent ones supervised by Wolf-Dietrich Grimm, treat both the Upper Marine and Upper Brackish Water Molasse (e.g., Neumaier and Wieseneder, 1939; Zöbelein, 1940; Neumaier, 1957; Buchner, 1967; Salvermoser, 1999). During the past 60 years, the microfossil content of the Ottnangian Upper Marine Molasse deposits in eastern Bavaria was quite intensely studied, with a strong focus on the stratigraphically relevant Foraminifera (Knipscheer, 1952; Hagn, 1953; Hagn et al., 1981; Wenger, 1987; Frieling et al., 2009; Pippèrr and Reichenbacher, 2010; Pippèrr, 2011). As already noted, Foraminifera have also been recorded from the basal parts of the Upper Brackish Water Molasse (Cicha et al., 1973; Hagn, 1953; Reichenbacher, 1993). The Ottnangian Ostracoda were comprehensively treated by Witt (1967, 2009). In contrast, the rich Ottnangian marine macrofauna, mainly collected from the marginal marine facies of the early Ottnangian Sea, received only minor attention. Among several lists of the macrofauna, the earliest ones, which were compiled by Gümbel (1887), were the most comprehensive ones. Until recently, only the Scleractinia and Bryozoa (Kühn, 1965) and some fish remains (Brzobohatý and Schultz, 1973) had been thoroughly studied. A few years ago, however, paleontological research on the Upper Marine Molasse was revived and resulted in studies on echinoderms (Kroh, 2005, 2007), cirripedes (Carriol and Schneider, 2008), brachiopods (Bitner and Schneider, 2009), serpulids (Jäger and Schneider, 2009), mollusks, and general paleoecology (Schneider et al., 2009). Compared to the marine macrofauna, the mollusks of the Upper Brackish Water Molasse received significantly more attention. After a first description of several species by Ammon (1888), the mollusks were subject of several publications by Richard Schlickum, finally leading to a comprehensive monographic treatment of the fauna (Schlickum, 1964). A major part of these mollusks was restudied by Kowalke and Reichenbacher (2005). FIELD TRIP STOPS Geographic coordinates are given in the Gauß-Krüger coordinate system. Stop 1: Neustift Granite Quarry

Figure 3. Geographic overview of the excursion area in eastern Bavaria. Numbers refer to field trip stops: 1. Neustift. 2. Gurlarn. 3. Untersimbach. 4. Höhenmühle. 5. Prienbach. 6. Edbach.

Locality Granite quarry of “Niederbayerische Schotterwerke Rieger & Seil GmbH & Co. KG” (R 45 88 260, H 53 83 670) (Fig. 4).

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Figure 4. Neustift granite quarry. Overview from the eastern edge of the outcrop. The granitic basement is overlain by sediments of the Upper Marine Molasse (“beach facies,” “Glaukonitsande und Blättermergel”). The succession is topped by gravel of the “Ortenburger Schotter.” OMM—Upper Marine Molasse.

Chronostratigraphy Lower and ? middle Ottnangian; upper Ottnangian. Lithostratigraphy Upper Marine Molasse: nearshore equivalents of Neuhofen Beds; “Glaukonitsande und Blättermergel”; “Ortenburger Schotter.” Lithology and Facies Marine carbonatic fissure fills; transgression conglomerate; beach boulder facies; nearshore sands; shallow marine sands and marls; gravel (facies under discussion). Description and Interpretation At Neustift, the early Ottnangian Molasse Sea transgressed on a relatively low granitic relief. Fissures and local depressions were filled with a dark-gray micritic limestone (Fig. 5) that con-

Figure 5. Neustift granite quarry. Basal transgressive deposits of the Lower Ottnangian Upper Marine Molasse. Angular granitic rock fragments (A) are embedded in grayish marine limestone (B). Wellrounded granitic boulders, up to several decimeters in size (C) characterize the beach deposits directly above.

tains macrofossils (shark teeth, internal molds of gastropods and bivalves, pectinid shells) and granite clasts and hardly reaches a thickness of 0.5 m. These patchily occurring carbonates are overlain by a ~0.5-m-thick transgression conglomerate, consisting of granite boulders up to several decimeters wide embedded in a matrix of grayish marls that were dated as early Ottnangian based on benthic Foraminifera (Pippèrr, 2011). Usually, the boulders are well rounded, suggesting long-term exposure to high water energy at or directly below the littoral zone. Fossils accumulated in the interstices between these boulders and display various states of mechanical wear. The following layer (~0.5–1.2 m in thickness; currently covered by debris and thus not visible at outcrop) is composed of medium- to coarse-grained sands, which are interpreted as shallow marine and may represent the maximum of the early Ottnangian transgression. These sands contain an abundant macrofauna that is predominantly composed of shark teeth and calcitic shells of Pectinidae and Ostreidae. The following five to seven meters of the succession comprise decalcified sediments attributed to the “Glaukonitsande und Blättermergel” (Fig. 6), which are likely middle Ottnangian in age. They consist of finegrained occasionally bioturbated sands that are intercalated with sandy or silty laminated marls at decimeter to centimeter scale (Fig. 7). The succession is discordantly topped by several meters of medium- to coarse-grained gravel beds that are assigned to the upper Ottnangian “Ortenburger Schotter” (Fig. 8). Macrofauna. The macrofauna, found exclusively in the basal layers of the succession, is dominated by several taxa of shallow-water mollusks. These include the bivalves Aequipecten macrotis (Sowerby), Ostrea digitalina Dubois de Montperreux, Gastrana fragilis Linnaeus, Glycymeris deshayesi Mayer, and Tapes sp., and several trochid, turritellid, and conid gastropods. Additionally, the stratigraphically significant bivalves Pecten herrmannseni Dunker (all Paratethys records of P. dunkeri Mayer are synonymous to this species), Flexopecten palmatus (Fontannes), and F. davidi (Fontannes) are present, but relatively rare. Moreover, numerous other mollusks, brachiopods (Bitner and Schneider, 2009), corals, bryozoans, shark and ray teeth, and

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Figure 6. Neustift granite quarry. Oblique erosional discordance (arrows) between well-layered “Glaukonitsande und Blättermergel” (left side) and Ortenburg Gravel (right side).

others may be found. While calcitic skeletons are well preserved, aragonitic shells are usually dissolved, and the respective taxa occur as solid internal or composite molds. Microfauna. Only a single sample from the base of the molasse succession (marly matrix of boulder horizon) contains a rich and relatively well-preserved Foraminifera fauna, while all samples from higher up in the section are decalcified. In the micro-samples, echinoid spines and fragmented bryozoans, balanids, and mollusks are abundant; ostracods and fish teeth also occur. The comparably diverse benthic Foraminifera assemblage is characterized by a high abundance of typical shallow water taxa, i.e., Ammonia beccarii s.l. and Elphidium spp. Planktonic Foraminifera are rather common (plankton/benthos ratio = 14.3%). The planktonic assemblage is dominated by Globigerina ottnangiensis. Globigerina praebulloides, G. dubia, G. lentiana, Globoturborotalia woodi, Globigerinoides trilobus, and ?Paragloborotalia acrostoma occur in lower numbers.

Figure 7. Neustift granite quarry. Close-up of “Glaukonitsande und Blättermergel” of Figure 5. The typical intercalation of marl and sand layers is well discernable. Bioturbation (arrow) is evident, but it does not significantly affect the fabric.

Stop 2: Gurlarn Clay Pit Locality Clay pit of the “Tonwarenfabrik und Granitwerke Fürstenzell Ferdinand Erbersdobler” (R 45 98 740, H 53 76 940). Chronostratigraphy Lower to middle Ottnangian. Lithostratigraphy Upper Marine Molasse: near-shore equivalents of Neuhofen Beds; “Glaukonitsande und Blättermergel.” Lithology and Facies Transgression conglomerate with carbonate patches; marginal marine clay facies; shallow marine marls and sands. Description and Interpretation The base of the outcrop is formed by a highly structured granitic relief including granite boulders up to several meters in size (Fig. 9), which are often still overgrown with oyster shells or balanid discs (Fig. 10; Carriol and Schneider, 2008). A comprehensive description of the entire succession, including data on sedimentology and biostratigraphy, has been provided by Frieling et al. (2009). During the fieldwork for this study, the thin, only locally preserved transgression conglomerate at the base of the marine sediments was not exposed and is thus not included in the descriptions. This conglomerate interfingers with or passes over into a highly fossiliferous basal layer containing numerous bryozoans, bivalves, brachiopods, and others, embedded in a matrix of clay or marl. Locally, the siliciclastic matrix is replaced by patches of light bluish-gray micrite. The basal horizon is followed by a succession of marls and sands, which locally includes lenses of coarse-grained sand in its central part (Figs. 11–13). While the lower part of the section is dated as lower Ottnangian based on benthic Foraminifera and may be interpreted as a marginal marine equivalent of the Neuhofen Beds, the upper portion is middle Ottnangian in age and corresponds to the “Glaukonitsande und Blättermergel” (Frieling et al., 2009).

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Figure 8. Schematic section of the molasse deposits at Neustift. The basal part of the succession was not exposed during fieldwork in 2007.

Macrofauna. Apparently 80 different macrofossil taxa were recorded from the basal fossiliferous layer at Gurlarn. Some 50% of these taxa are bryozoans, followed by bivalves (16 taxa), cirripedes (7 taxa), echinoderms, corals (5 taxa each), brachiopods, fishes (4 taxa each), serpulids, and gastropods (3 taxa each) (Schneider et al., 2009; Bitner and Schneider, 2009; Jäger and Schneider, 2009). Additional organisms were recorded by the presence of typical ichnotaxa, including predatory drill holes and bite marks. Analysis of aut- and synecological indicators suggests that the fauna thrived in a near-shore shallow marine setting at a

water depth of 5–20 m. The environment obviously was characterized by three distinct but interfingering habitats, i.e., (1) rocky slopes and boulders, (2) seagrass meadows, and (3) bryozoan meadows (Schneider et al., 2009). Typical Ottnangian taxa include the pectinids Flexopecten palmatus and F. davidi, and the shark Scyliorhinus fossilis. Moreover, one genus and two species of brachiopods and one species of cirripedes have been described as new from Gurlarn (Fig. 14). The coarse-grained sand lenses in the middle part of the section contain an allochthonous fauna of usually strongly worn and

Figure 9. Gurlarn clay pit. Overview showing part of the former submarine relief (B = basement) and the overlying Ottnangian marine sediments.

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Schneider et al. fragmented shallow-water oysters and pectinids, balanids, fish teeth, and bryozoans, along with some other taxa. Microfauna. The benthic Foraminifera assemblages from Gurlarn can be confidently assigned to the lower to middle Ottnangian, based on the occurrence of the stratigraphically characteristic species Sigmoilopsis ottnangensis, Bolivina scitula, Amphicoryna ottnangensis, and Pappina breviformis (Frieling et al., 2009). In both samples from the basal fossiliferous layer, benthic Foraminifera are common and diverse (39 species from almost 300 individuals per sample). Planktonic Foraminifera are fairly abundant (13%–20%). Both benthic and planktonic Foraminifera are large- to medium-sized and usually well preserved. Most individuals lack signs of erosion and re-deposition and only a few specimens are fragmented. The benthic assemblage is dominated by Cibicides/Cibicidoides, Lenticulina, Elphidium (mainly keeled) and Ammonia beccarii s.l. and shares conspicuous features with the fauna from the lower Ottnangian Neuhofen Beds. In particular, the characteristic and most abundant species of the Neuhofen Beds, i.e., Spiroplectammina pectinata, Sigmoilopsis ottnangensis and Lenticulina inornata/L. melvilli (see Wenger, 1987, for details) occur at Gurlarn, although S. pectinata

Figure 10. Gurlarn clay pit. Basal discs of the large cirriped Chesaconcavus gurlarnensis Carriol and Schneider, 2008, on a granitic boulder.

Figure 11. Gurlarn clay pit. Schematic sections of the Gurlarn clay pit (modified from Frieling et al., 2009). OMM—Upper Marine Molasse.

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Figure 12. Gurlarn clay pit. The topmost exposures of the granite basement (B) and boulders at Gurlarn.

and S. ottnangensis are less numerous because of the shallower water depth. Up-section, the abundance and diversity of benthic Foraminifera decrease significantly (Frieling et al., 2009). The rich and diverse ostracod fauna from the basal fossiliferous layers has not yet been analyzed. Stop 3: Untersimbach Locality Natural exposure at forested hillslope (R 46 00 920, H 53 73 580). Chronostratigraphy Lowermost Ottnangian. Lithostratigraphy Upper Marine Molasse: Untersimbach Beds (type locality). Lithology and Facies Laminated marls with intercalated thin veils of sand; outer littoral to inner shelf deposits.

Figure 13. Gurlarn clay pit. Lower part of the Gurlarn Molasse succession, showing spring horizon (white arrows) and transition of colors from bluish-gray to brownish (black arrows).

Description and Interpretation The outcrop exposes a more than 5-m-thick, homogenous succession of beige to brownish, laminated marls that are intercalated with millimeter-thin layers of fine sands. The sediments are dated as lowermost Ottnangian based on benthic Foraminifera, and assigned to a distinct lithostratigraphic unit, i.e., the Untersimbach Beds by Wenger (1987). The Untersimbach Beds represent the lowermost part of the lower Ottnangian and include, from base to the top, the “Grobsande” (coarse sands) and “Sandmergel” (sandy marls) of Hagn (1953), the latter named “Robulus-Schlier s. str.” by Knipscheer (1952) (Wenger, 1987). Today, the outcrop of Untersimbach exposes only a part of the originally accessible 10–12-m-thick sediment

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Figure 14. Fossils from Gurlarn clay pit. Gurlarn is the type locality of the following taxa. (A) Gurlarnella waltli Bitner and Schneider, 2009. (B) Aphelesia winebergeri Bitner and Schneider, 2009. (C) Chesaconcavus gurlarnensis Carriol and Schneider, 2008. Scale bars: 5 mm.

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package exclusively comprised of the “Sandmergel” facies (Figs. 15 and 16). The uppermost 3–4 m of the marls, which were assigned to the basal Neuhofen Beds by Wenger (1987), are no longer accessible. Macrofauna. With regard to size, the macrofossils recorded from Untersimbach may rather be denoted as microfossils. They include minute spines of spatangid echinids, small fragments of pectinid bivalves, branching bryozoans, and balanid plates. Microfossils. In the five samples that were analyzed from the Untersimbach section, Foraminifera are rare to abundant (Pippèrr, 2011). Additionally, ostracods, radiolarians, and diatoms (Coscinodiscus) occur. The plankton/benthos ratio of the Foraminifera is fairly variable, from 18.6 to 36.4%. The most abundant species of the low diversity plankton assemblages is Globigerina praebulloides. Abundance and diversity of benthic Foraminifera increase upwards. The benthic assemblages are dominated by Lenticulina inornata/L. melvilli (up to 66.3%); Nonion commune and Cibicidoides lopjanicus/C. tenellus are abundant to common. Both the benthic Foraminifera assemblages and the P/B ratios are indicative of a middle neritic environment. In the uppermost part of the section, char-

acteristic taxa of the Neuhofen Beds, i.e., Sigmoilopsis ottnangensis, Spiroplectammina pectinata, and Amphicoryna ottnangensis appear, indicating a gradual deepening and transition to this facies.

Figure 15. Untersimbach section. Outcrop at hillslope exposing wellbedded marls of the upper portion of the Untersimbach Beds.

Figure 16. Untersimbach section. Laminated marls of Untersimbach Beds with Scolicia isp. dwelling structure of a spatangoid sea urchin (arrow).

Stop 4: Höhenmühle Locality Clay pit of the “Tonwarenfabrik und Granitwerke Fürstenzell Ferdinand Erbersdobler” (R 45 93 981, H 53 71 718). Chronostratigraphy Lower to middle Ottnangian. Lithostratigraphy Upper Marine Molasse: Neuhofen Beds; “Glaukonitsande und Blättermergel.” Lithology and Facies Open marine marls; shallow marine laminated marls interbedded with fine-grained sand.

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Figure 17. Höhenmühle clay pit. Overview from western end of the pit

Description and Interpretation The clay pit at Höhenmühle, which is still actively mined, exposes the upper portion of the Neuhofen Beds and shows the gradual transition of this unit to the “Glaukonitsande und Blättermergel” facies (Fig. 17). The lower, ~3-m-thick part of the section, which is assigned to the Neuhofen Beds, is composed of marls that are intercalated with minute lenses or layers of finegrained sand. Up-section, this facies shifts to an 8–10-m-thick coarsening-upward succession of laminated marls and thinly interbedded marl and sand layers (Fig. 18), which is attributed to the lower part of the “Glaukonitsande und Blättermergel.” In the uppermost part of the section, up to several centimeters thick, lens-shaped bodies of middle- to coarse-grained sand occur (Fig. 19). Based on biostratigraphy (benthic Foraminifera), the basal part (Neuhofen Beds) is assigned to the lower Ottnangian and

grades into the middle Ottnangian toward the upper part without any visible discontinuity. Macrofauna. The sparse macrofauna of Höhenmühle comprises typical taxa of the Neuhofen Beds, i.e., bivalves of the genera Nucula, Nuculana, and Abra, and the scaphopod Laevidentalium, all of them adapted to soupy soft substrates, as provided by the fine-grained siliciclastics seen at Höhenmühle. Additionally, minute fragments of pectinids and oysters, gastropods, balanids, bryozoans, echinoid spines, shark teeth, and teleost otoliths occur, which have obviously been swept in from shallower habitats, and are particularly enriched in the minute sand intercalations. In the upper part of the section, macrofossils are absent. Microfossils. Besides a relatively diverse benthic Foraminifera assemblage, the Neuhofen Beds at Höhenmühle contain planktonic Foraminifera and ostracods. The benthic Foraminifera tests are largely well preserved, and include both small- and large-sized individuals (Pippèrr, 2011). Most abundant are hyaline taxa, while only two agglutinated species, i.e., Spiroplectammina pectinata and Textularia gramen, and a single miliolid, i.e., Sigmoilopsis ottnangensis, occur. The fauna is dominated by representatives of the Lenticulina inornata/L. melvilli species flock. Additionally, Nonion commune and Cibicidoides lopjanicus/C. tenellus are common. In the “Glaukonitsande und Blättermergel,” both Foraminifera and ostracods are comparably rare. Most abundant are Ammonia beccarii s.l., Bolivina dilatata, and Nonion commune, while miliolid or agglutinated species are absent. Across the whole section, the plankton/benthos ratio is relatively high (19.7%–22.6%), although the diversity of planktonic taxa is generally low; most abundant are Globigerina ottnangiensis and G. praebulloides. Stop 5: Prienbach-Dötling

Figure 18. Höhenmühle clay pit. Detail of the “Blättermergel” facies at Höhenmühle, showing the intercalation of marls and minute sand layers.

Locality Hollow way at the left (northern) flank of the Inn Valley (R 45 79 195, H 53 50 660).

Ottnangian Upper Marine Molasse and Upper Brackish Water Molasse of eastern Bavaria Chronostratigraphy Middle to upper Ottnangian. Lithostratigraphy Upper Marine Molasse: “Glaukonitsande und Blättermergel”; Upper Brackish Water Molasse: “Mehlsande,” “Schillhorizont,” and “Glimmersande.” Lithology and Facies Shallow marine laminated marls intercalated with finegrained sand; silts and fine-grained sand with or without a significant content of mica deposited in shallow brachyhaline waters; shell bed of brackish water bivalves. Description and Interpretation Close to the lower end of this 200-m-long hollow way, a small outcrop exposes a 2-m-thick portion of the top of the “Glaukonitsande und Blättermergel,” showing typical “Blät-

Figure 19. Schematic section of Höhenmühle.

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termergel” facies, i.e., finely laminated marls with intercalations of mm-thick layers of fine-grained sand. Following a gap of several meters, where sediments are overgrown by vegetation, the flanks of the hollow way expose the classical succession of the lower part of the Upper Brackish Water Molasse (“Oncophora-Schichten”; Buchner, 1967; Schlickum and Strauch, 1968; Fig. 20) forming steep, more than 4-m-high walls at both sides of the trail. The succession starts with the “Mehlsande” ( = flour sands), a silty to fine-sandy sediment largely lacking any clay content. The term “flour sands” accurately describes the haptic features of this sediment: grinding a small amount of it between the fingers, the “Mehlsande” feels like whole-grain flour. The “Schillhorizont” overlies the “Mehlsande” by a sharp, irregular, erosive boundary. At Prienbach, this coquina, which is interpreted as a marker bed within the Upper Brackish Water Molasse succession, reaches some 12 cm in thickness (for more detailed information, see next stop). As already suggested by the denomination, the overlying, 12-m-thick “Glimmersande” ( = mica sands; Fig. 21), which are composed of evenly bedded, light-gray, finegrained sands, are characterized by a high content of light mica. The shiny appearance of the sediment caused by these minerals, and the totally different haptic features readily help to distinguish the “Glimmersande” from the “Mehlsande” even in small outcrops. Whether the different composition of these two sediments points to different sources of the siliciclastics, or whether it is an expression of changing environment (Schlickum and Strauch, 1968, assume largely diachronous facies), is still a matter of discussion. Macrofauna. No macrofossils have been recorded from the “Blättermergel” at Prienbach. In all three strata of the Upper Brackish Water Molasse, its index fossil, i.e., the bivalve Rzehakia guembeli (Gümbel), which was formerly assigned to the genus Oncophora, is the most abundant faunal constituent. In the basal “Mehlsande,” it occurs scattered or enriched in thin horizons, but usually with contiguous valves, indicating their autochthonous position, and is partially accompanied by the lymnocardiid bivalve Limnopagetia bavarica. In the “Schillhorizont,” R. guembeli accounts for more than 90% of the specimens—and surely almost 100% of the total biomass. Additional taxa recorded are Limnopagetia bavarica, Mytilopsis rottensis, and Ctyrokia spp. Finally, the Glimmersande also yield scattered, double-valved R. guembeli in life position, Limnopagetia sp., and several gastropods. Microfauna. In the “Blättermergel” at Prienbach, both benthic and planktonic Foraminifera as well as ostracods are extremely rare and the assemblage is of low diversity. Most abundant are Ammonia beccarii s.l. and Nonion commune. The lowermost part of the “Mehlsande” still contains a sparse microfauna of extremely small, partially stunted, benthic and planktonic Foraminifera, documenting a gradual reduction of salinity. The benthic Foraminifera assemblage includes ?Nodogenerina adolphina, ?N. scabra, Bolivina spp., Nonion commune, and Ammonia sp.

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Figure 20. Schematic section of the Prienbach hollow way.

Stop 6: Edbach Locality Exposures along the undercut banks of the Edbach stream, east of Simbach am Inn (R 45 75 857, H 53 49 567). Chronostratigraphy Upper Ottnangian. Lithostratigraphy Upper Brackish Water Molasse: “Mehlsande”; “Schillhorizont”; “Glimmersande.”

Lithology and Facies Silt and fine-grained sand with or without a significant content of mica; thick shell bed of brackish water bivalves; all sediments deposited in shallow brachyhaline waters. Description and Interpretation At this last stop of the excursion, we focus at the “Schillhorizont,” which reaches its maximum thickness of ~60 cm here, and currently has its best exposures on the banks of the Edbach. Similar to Prienbach, the “Schillhorizont” is deposited discordantly on the “Mehlsande” (Fig. 22). The shell bed itself consists mainly of well-preserved to moderately eroded shells of the

Figure 21. Prienbach hollow way. Upper portion of section exposing the “Glimmersande” ( = mica sands), which form the top of the lower portion of the Upper Brackish Water Molasse.

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Figure 22. Overview of “Schillhorizont” at Edbach section (photographed by D. Jung).

Figure 23. “Schillhorizont” at Edbach section. Close up of main shell bed, showing dense stacking of shells of Rzehakia guembeli.

bivalve Rzehakia guembeli, which are at places still preserved as attached valves, indicating minor or no transport. Additionally, Limnopagetia spp. and several hydrobiid gastropods are important constituents of the fauna. However, the taphonomic signatures of the shell bed are laterally variable. In parts of the Edbach section, imbricated, frequently fragmented single valves dominate the coquina (Fig. 23). The shells are closely packed, locally almost without sandy matrix, often aligned to a certain current direction, and sometimes showing rosette or vertical stacking (Hartauer, 2009). The total thickness of the horizon varies strongly. In places, the shell bed diverges into several layers, enclosing sandy layers or lenses with the same texture as the overlying “Glimmersande” (Fig. 22). Locally, the contact to the “Glimmersande” is sharp and distinct, and the shell content abruptly ceases. However, no substantial sedimentological change of the matrix occurs, and in other places, the coquina gradually fans out into the “Glimmersande,” which may also contain several less prominent shell beds up-section. A peculiarity of the “Schillhorizont” in eastern Bavaria is its former economic status. Up to the middle of the twentieth century, the shells were systematically mined in tunnels below ground, to be used as an aggregate for chicken feed. The bivalve shell carbonate ensured the production of eggs with a stable eggshell.

Hans Georg Krenmayr (Geologische Bundesanstalt, Wien) and Martin Zuschin (Institut für Paläontologie, Wien) significantly improved the manuscript.

ACKNOWLEDGMENTS We owe special thanks to Peter Gusek (Niederbayerische Schotterwerke, Neustift) who gave useful advice on local geology, and to Ferdinand Erbersdobler (Tonwarenfabrik und Granitwerke Fürstenzell, Gurlarn), who kindly granted access to the clay pits at Gurlarn und Höhenmühle. Dietmar Jung (Landesamt für Umwelt, Hof) and Gunther Pippèrr (Munich) provided photographs. Moreover, Dietmar Jung and Albert Ulbig (Schlagmann Baustoffe, Zeilarn) kindly provided information on outcrops of the Upper Brackish Water Molasse. Careful reviews by

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ronments of the Central Paratethys: Palaeogeography, Palaeoclimatology, Palaeoecology, v. 289, p. 62–80, doi:10.1016/j.palaeo.2010.02.009. Reichenbacher, B., 1993, Mikrofaunen, Paläogeographie und Biostratigraphie der miozänen Brack- und Süßwassermolasse in der westlichen Paratethys unter besonderer Berücksichtigung der Fisch-Otolithen: Senckenbergiana Lethaea, v. 73, p. 277–374. Salvermoser, S., 1999, Zur Sedimentologie gezeitenbeeinflußter Sande in der Oberen Meeresmolasse und Süßbrackwassermolasse (Ottnangium) von Niederbayern und Oberösterreich: Münchner Geologische Hefte, v. A26, p. 1–179. Schlickum, W.R., 1964, Die Molluskenfauna der Süßbrackwassermolasse Niederbayerns: Archiv fuer Molluskenkunde, v. 39, p. 1–69. Schlickum, W.R., and Strauch, F., 1968, Der Aussüßungs- und Verlandungsprozeß im Bereich der Brackwassermolasse Niederbayerns: Mitteilungen der Bayerischen Staatssammlung für Paläontologie und Historische, v. 8, p. 327–391. Schneider, S., Berning, B., Bitner, M.A., Carriol, R.-P., Jäger, M., Kriwet, J., Kroh, A., and Werner, W., 2009, A parautochthonous shallow marine fauna from the Late Burdigalian (early Ottnangian) of Gurlarn (Lower Bavaria, SE Germany): Macrofaunal inventory and paleoecology: Neues Jahrbuch für Geologie und Palaontologie—Abhandlungen, v. 254, p. 63–103, doi:10.1127/0077-7749/2009/0004. Schwerd, K., Doppler, G., and Unger, H.J., 1996, Gesteinsfolge des Molassebeckens und der inneralpinen Tertiärbecken, in Freudenberger, W. and Schwerd, K., eds., Erläuterungen zur Geologischen Karte von Bayern 1:500,000, Munich, Bayerisches Geologisches Landesamt, p. 141–149. Stadler, J., 1925, Geologie der Umgebung von Passau: Geognostische Jahreshefte, v. 38, p. 39–118. Suess, F.E., 1891, Beobachtungen über den Schlier in Oberösterreich und Bayern: Annalen des kaiserlich-königlichen naturhistorischen Hofmuseums, v. 6, p. 407–429. Unger, H.J., 1984, Geologische Karte von Bayern 1:50,000, Erläuterungen zum Blatt Nr. L7544 Griesbach i. Rottal: München, Bayerisches Geologisches Landesamt, 245 p. Unger, H.J., and Bauberger, W., 1985, Geologische Karte von Bayern 1:50,000, Erläuterungen zum Blatt Nr. L7546 Neuhaus a. Inn: Munich, Bayerisches Geologisches Landesamt, 103 p. Waltl, J., 1847, Briefliche Mittheilungen über die geognostischen Verhältnisse der Umgebungen von Passau und des Bayerischen Waldes oder des Böhmergebirges: Correspondenzblatt des zoologisch-mineralogischen Vereins in Regensburg, v. 1, p. 29–32, 44–48. Wenger, W.F., 1987, Die Foraminiferen des Miozäns der bayerischen Molasse und ihre stratigraphische sowie paläogeographische Auswertung: Zitteliana, v. 16, p. 173–340. Wineberger, L., 1851, Geognostische Beschreibung des Bayerischen und Neuburger Waldes: Passau, Dietenberger & Breßl, 141 p. Witt, W., 1967, Ostracoden der bayerischen Molasse (unter besonderer Berücksichtigung der Cytherinae, Leptocytherinae, Trachyleberidinae, Hemicytherinae und Cytherettinae): Geologica Bavarica, v. 57, p. 1–120. Witt, W., 2009, Zur Ostracodenfauna des Ottnangs (Unteres Miozän) der Oberen Meeresmolasse Bayerns: Zitteliana, v. A48-49, p. 49–67. Zöbelein, H.K., 1940, Geologische und sedimentpetrographische Untersuchungen im niederbayerischen Tertiär (Blatt Pfarrkirchen): Neues Jahrbuch für Mineralogie, Geognosie, Geologie und Petrefakten-Kunde: BeilagenBand, v. B84, p. 233–302.

MANUSCRIPT ACCEPTED BY THE SOCIETY 5 MAY 2011

Printed in the USA

The Geological Society of America Field Guide 22 2011

Rhenodanubian Flyschzone, Bavarian Alps Reinhard Hesse* Earth and Planetary Sciences, McGill University, Quebec, H3A 2A7, Canada, and Ludwig-Maximilians Universität München, Department of Earth and Environmental Sciences, Luisenstr. 37, 80333 Munich, Germany

ABSTRACT The Rhenodanubian Flyschzone stretches for 500 km from the Rhine River at Lake Constance to the Danube at Vienna. In Bavaria, it comprises a 1500-m-thick turbidite succession that was deposited from the Hauterivian/Barrêmian to the Maastrichtian, which is the subject of this field trip. The two stratigraphic columns for the northern Sigiswang and the southern Oberstdorf Facies reflect a pronounced facies variation across strike. The Hauterivian/Barrêmian Tristel Formation is a carbonate turbidite succession with abundant shallow-water bioclastic components that require a carbonate shelf source. The siliciclastic Aptian-Albian Rehbreingraben Formation (Flysch Gault) indicates a switch from a tropical shelf environment to intense subtropical-humid weathering conditions affecting the shelf platform that had at least been partially stripped of its carbonate cover. Both formations occur in the Oberstdorf Facies. Paleocurrent directions were uniformly from W to E but switched to E to W during deposition of the Cenomanian-Turonian Reiselsberg Sandstone, which occurs both in the Sigiswang and Oberstdorf facies but is considerably thicker in the former (up to 600 m) than in the latter (50 m and less). Its mica-rich sandstones probably had a southern source and are texturally and mineralogically relatively immature, different from the mature glauconitic quartzarenites of the Flysch Gault, which may be first-cycle quartzarenites. The middle Coniacian to lowermost Campanian Piesenkopf Formation is a thin-bedded, fine-grained carbonate turbidite unit of distal character, both in the Sigiswang and Oberstdorf facies belts. It is followed by the lower to middle Campanian Kalkgraben Formation, the middle to upper Campanian Hällritz Formation and the upper Campanian to Maastrichtian Bleicherhorn Formation. These three carbonate turbidite formations with a western source occur in the Sigiswang Facies. Differentiation among them is by the thickness ratio of calcarenitic turbidites to their pelitic marlstone caps. The stratigraphic equivalent of the three Late Cretaceous carbonate turbidite formations in the Oberstdorf Facies is the Zementmergel Formation, in which the thickness of the pelitic marlstone caps

*[email protected] Hesse, R., 2011, Rhenodanubian Flyschzone, Bavarian Alps, in Carena, S., Friedrich, A.M., and Lammerer, B., eds., Geological Field Trips in Central Western Europe: Fragile Earth International Conference, Munich, September 2011: Geological Society of America Field Guide 22, p. 51–73, doi:10.1130/2011.0022(05). For permission to copy, contact [email protected]. ©2011 The Geological Society of America. All rights reserved.

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Hesse outweighs that of their calcarenitic turbidite hosts. The Rhenodanubian Flysch is an allochthonous tectonic unit whose original paleogeographic position can be traced back via the Falknis and Tasna nappes to the middle Penninic Briançonnais Platform at least 100 km south of the Ultrahelvetic paleographic unit it may have originally been in contact with. Its internal tectonic structure and geodynamic evolution will be discussed during the field trip.

INTRODUCTION The Cretaceous–Early Tertiary Rhenodanubian Flyschzone at the northern foothills of the East Alps is a 500-km-long, forested paleogeographic-tectonic unit that stretches from the Rhine River at Lake Constance in the west to the Danube at Vienna in the east. It is one of the five major tectonic units of the Eastern Alps, which from north to south include (1) the Alpine Molasse basin, the prototype of a retroarc- or foreland basin; (2) the Helvetic and Ultrahelvetic zones, which represent the southern continental shelf and slope of Europe in Jurassic-Cretaceous and Early Tertiary time; (3) the oceanic Penninic zone including the Rhenodanubian Flyschzone which, apart from the latter, was mostly eliminated in the subduction process involved in the Alpine orogeny; (4) the Northern Calcareous Alps or Austroalpine Zone and the Southern Alps, which together represent the northern continental shelf of the Adriatic plate as part of Africa; and (5) the South Alpine foreland (or Molasse) basin. This field trip will visit Lower and Upper Cretaceous flysch exposures at three localities south of Munich—the Lainbach Valley near Benediktbeuern and the Lahne and Kappel Creeks near Grafenaschau—and study the stratigraphy, facies and tectonic structure of the Rhenodanubian Flyschzone in Bavaria and discuss its significance for the paleogeography and geodynamic evolution of the East Alpine sector of the Paleotethys during Cretaceous-Tertiary time. STRATIGRAPHY AND FACIES The ~1500-m-thick succession of turbidite formations of the Rhenodanubian Group in Bavaria shows a remarkable facies constancy along strike of the flysch belt and considerable facies variations across strike, which has given rise to the establishment of two separate stratigraphic columns, one called Sigiswang Facies for the northern part of the flysch zone and the other called Oberstdorf Facies for the southern part (Fig. 1). The Oberstdorf Facies starts with the Hauterivian–Barrêmian Tristel Formation, a carbonate turbidite formation that consists of up to 2-m-thick turbiditic calcarenites interbedded with alternating layers of green and black claystones. The calcarenites contain the full suite of turbidite structure divisions, including gray marlstone at the top (Te structure division). Light-colored lutitic limestone up to 30 cm thick forms either separate beds or caps the calcarenite. Dark spots in the calcilutites are due to bioturbation. Whereas the carbonate-free claystones indicate deposition below the calcite compensation level (CCL), the calcarenites contain a high percentage of biogenic detritus. This consists of a rich

shallow-water fauna of foraminifera (“miliolid” limestone) and bryozoan, bivalve, gastropod and echinoderm fragments as well as subordinate algae (Diplopora) that is clearly allochthonous and requires a carbonate shelf source. The fauna is reminiscent of the coeval “Urgon Facies” of the Helvetic shelf to the north, but may also have been derived from a more southern source in the middle Penninic Briançonnais Platform. The upper age limit of the formation is given by the top of magnetochron M3 (Mesozoic magnetic anomaly), which was identified by Hauck (1998) to coincide with the lithostratigraphic boundary between the Tristel Formation and the overlying Rehbreingraben Formation. The M2/M3 boundary falls into the Barrêmian. The lower boundary could not be determined because the formation is bound by a thrust fault at the base and the substrate is unknown. The Rehbreingraben Formation (new stratigraphic term, Wortmann, 1996), conventionally known as Flysch Gault, shows a striking lithologic contrast to the carbonate turbidites of the Tristel Formation (Fig. 2). It is a siliciclastic succession of glauconitic carbonate-bearing quartzarenites alternating with black and green hemipelagic claystones that indicates a drastic change in paleoclimatic/paleogeographic conditions from a tropical shelf to subtropical humid weathering of the basement of this carbonate platform from which the carbonate cover had at least partially been removed by erosion (Wortmann et al., 2004). The quartzarenitic turbidites average 1 m in thickness, reaching a maximum of almost 4 m and contain mostly turbidite structure divisions Tb (lower division of parallel lamination), Tc (ripple-cross lamination and convolute lamination) and Td (upper division of parallel and convolute lamination). Thin caps of gray marlstone generally not exceeding 20 cm in thickness represent the pelitic division Te (Fig. 3). A coarse, feldspar-rich bed in the lower third of the formation that consists of the massive and graded Ta division serves as a marker bed. The green and black carbonate-free/carbonatepoor claystones formed under suboxic and anoxic diagenetic conditions, respectively. Organic carbon concentrations in the black claystones reach up to 6% by weight but remain below 1% in the green claystones. Based on detailed geochemical analyses (Figs. 4, 5) Wortmann (1996) and Wortmann et al. (1999) interpreted the black-green rhythms as paleoclimatically controlled productivity cycles that may reflect Milankovic periodicities. The formation has been stratigraphically subdivided at the bed level, as it has been possible to correlate detailed measured sections of the Flysch Gault bed-by-bed over a distance of 115 km between Oberstdorf in Allgäu in the west and Lake Tegernsee in the east (Fig. 6; Hesse, 1973a, 1973b, 1974). It is the stratigraphically best-subdivided unit of the Rhenodanubian Flysch. The

Rhenodanubian Flyschzone, Bavarian Alps Ma

STAGE

65

Danian

OBERSTDORF FACIES SOUTH

SIGISWANG FACIES NORTH

CCZone

53

26

Maastrichtian

25

?

?

?

?

?

?

24

70

23

Bleicherhorn Formation (Altlengbach Formation)

>200 m

75 22

Campa- 21 nian

Hällritzer Formation

230-250 m

Zementmergel Formation 350-650(?) m

20

19

80

Kalkgraben Formation

170 m

Piesenkopf Formation

200-250(?) m

18

85

Santonian

16 15

Coniacian

14

90

Upper Variegated Claystone (Seisenburg Fm.) 0-10 m

13 12

Turonian

600-200 m

Reiselsberg Sandstone

50 m

11 10

95

Cenomanian 9 100

105

20-30 m

Offerschwang Formation 200 m

Lower Variegated Claystone 20 m

Albian 8

110

Rehbreingraben Formation (Flysch-Gault) 225 m

115

Aptian

7

Barrêmian

6

Hauterivian

5

120

125

130

Tristel Formation >150 m substrate unknown

135

Figure 1. Stratigraphic columns for the Sigiswang (north) and Oberstdorf (south) facies of the Rhenodanubian Group in Bavaria. Nannostratigraphic classification after Egger and Schwerd (2008) and Egger (2008 personal commun.; 2010). Ages in m.y. from the geologic time scale of Gradstein et al. (2004).

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Figure 2. Average mineralogical composition of siliciclastic (terrigenous) and carbonate turbidite formations of the Rhenodanubian Flysch in Bavaria. ft—Tristel Formation, fg— Flysch Gault, fs—Reiselsberg Sandstone, fp—Piesenkopf Formation, fz—Zementmergel Formation, fh—Hällritz Formation, fb—Bleicherhorn Formation. Circle in center: no. of thin sections analyzed. All samples from basal portion of beds. (Data from Hesse, 1973b; Von Rad, 1973).

correlation is supported by detailed mineralogical investigations of the composition of the quartzarenite beds of the formation (Fig. 7). The bed-by-bed stratigraphic subdivision of the formation is a purely lithostratigraphic subdivision. Down-current bed thickness variations of individual beds (Fig. 8) show that beds decreasing distally in thickness alternate with beds that increase in thickness, thus compensating in part for the loss of thickness. The gradients are very low, in the mm/km range. The thickness of the formation totals 225 m in the completely exposed section of the Rear Rehbrein Creek near Unterammergau. Paleocurrent directions in this unit and the underlying Tristel Formation are uniformly from W to E (Fig. 9). The top portion of the formation includes the Lower Variegated Claystones (Fig. 1), an up to 20-m-thick, mostly clayey succession that contains red claystones. Whereas the Tristel Formation and Flysch Gault have no equivalents in the northern Sigiswang Facies, the top part of the Flysch Gault may in part be correlative with the Upper Albian to Lower Cenomanian Ofterschwang Formation of the Sigiswang Facies. This is a carbonate turbidite unit with usually less than 50-cm-thick calcarenites capped by up to meter-thick marlstones and followed by thin carbonate-free green claystones. The formation anticipates the kind of carbonate turbidite sedimentation that becomes predominant in the Late Cretaceous starting in the Campanian (see below). The Cenomanian-Turonian Reiselsberg Sandstone occurs both in the Sigiswang and Ofterschwang facies, although its thickness is significantly reduced in the latter (50 m and less) compared to values of up to 600 m in the former (Mattern, 1988, 1998). Deposition of the Reiselsberg Sandstone signals a distinct change in the character of turbidite sedimentation in the Rhenodanubian flysch trough. Paleocurrent directions in the

Figure 3 (continued on following page). (A) Turbidite structure divisions. Modified from Hesse (1991a).

Rhenodanubian Flyschzone, Bavarian Alps

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Figure 3 (continued). (B) Hypothetical proximal to distal variations in turbidite-structure division sequences in an elongate basin plain. a— schematic structural sequences in turbidites; b—Hypothetical proximal-distal variations of structure sequences in elongate turbidite basin; c—schematic lithologic columns showing expected appearance of proximal (I) vs. distal (V) sections. Modified from Einsele, 1963.

Reiselsberg Sandstone point predominantly from E to W (Fig. 9). The formation contains the highest proportion of sandstone of all stratigraphic units of the Rhenodanubian Flysch; grain size of the sediment shed into the basin at this time is significantly coarser than before; individual beds reach considerably greater thickness of up to 10 m, and bed amalgamations are abundant, partly explaining the greater bed thicknesses. The continuity of individual beds is limited to 15 km (Mattern, 1999). Petrographically the sandstones are mica-rich quartzarenites that, depending on the degree of carbonate cementation, are hard calcareous sandstones or easily disintegratable “soft” sandstones with a rela-

tively low degree of textural and mineralogic maturity. The latter predominate. These features impart a proximal character to the Reiselsberg Sandstone. The prominent petrographic-mineralogic differences between the two siliciclastic formations, the Flysch Gault and the Reiselsberg Sandstone, reflect different composition and proximality of the source areas. Mattern (1998) explains the fact that the proximal character of the formation persists in the western Rhenodanubian Flyschzone over more than 200 km parallel to strike by postulating laterally juxtaposed and in part overlapping deep-sea fans that were supplied with sediment via submarine canyons from a southern crystalline basement that

Figure 4. Detailed geochemical sections across a black claystone that overlies a turbiditic marlstone (Te) showing the gradual establishment of hemipelagic signatures in the claystone due to delayed settling of finest-grained turbiditic material (carbonate). Note absence of turbitic influence above 40 cm. Breitenbach near Tegernsee. HI—hydrogen index, TOC—total organic carbon (modified from Wortmann et al., 1999, fig. 8).

Figure 5 (continued on following pages). Geochemical analyses (~100 samples) of a 3-m-thick section of the Flysch Gault in Breitenbach Valley near Tegernsee. Concentrations of carbonate, S, Al (%) and Si/Al, P/Al, Ba/Al, Fe/Al, Ti/Al, Zr/Al, Na/Al, K/Al, Mg/Al, Ca/Al, Sr/Al, Mn/Al plotted against organic carbon (Corg) in wt%. Errors are less than the diameter of the circle used for the data points. Black and gray—black and gray claystone; squared pattern— green claystone (from Wortmann et al. 1999, figs 3–5).

56 Hesse

57

Figure 5 (continued).

Rhenodanubian Flyschzone, Bavarian Alps

Hesse

Figure 5 (continued).

58

was unroofed for the first time in the Cenomanian. Since the Late Cenomanian and Turonian were times of sea-level rise, which tends to hold back the delivery of clastic sediments across the shelf, tectonic activity and uplift of the source areas had to be intense in order to produce terrigenous clastic sediments in sufficient quantity, which could then overcome the effects of sea-level rise and find their way into the deep basin. Hesse (1982), on the other hand, postulated left-lateral strike-slip faulting between the southern margin of the European plate and the oceanic Penninic domain. This would have affected the southern tectonic boundary of the flysch trough across which a diachronous sequence of deep-sea fans was deposited in a conveyor-belt fashion from one (or a few) source(s) located to the S and E, while the flysch trough moved paleogeographically west with respect to the source area to the south. In addition to different source areas and proximality, climate likely was a significant factor contributing to the prominent petrographic-mineralogic differences between the two siliciclastic formations producing the high-maturity glauconitic quartz sands of the Flysch Gault, which may be first-cycle quartzarenites. Climate in the Aptian, particularly the Late Aptian was subtropical humid causing intense weathering of the source

areas that provided the terrigenous detritus for the Gault turbidites (Wortmann et al., 2004). During the Coniacian to middle Campanian, the influence of the southern source had become extinct and sedimentation was dominated by calcareous sediment with a low siliciclastic component delivered from the west. The switch to a western source is documented by a renewed change in the paleocurrent directions (Fig. 9) that now are again from W to E (e.g., Hesse, 1974, 1982). The middle Coniacian to Campanian Piesenkopf Formation is an up to 250-m-thick succession of distal turbidites consisting of alternations of thin-bedded calcisiltites to calcilutites with green and, in the basal part of the formation, red carbonate-free claystones. The beige to light-gray calcisiltite-calcilutite beds are generally less than 15 cm thick and may bear a cap of gray marlstone. This is the only unit of the Rhenodanubian Flysch, which displays a considerable thickness of thin-bedded distal turbidites alternating with individual hemipelagic layers of about equal thickness. The red claystones at the base of the formation represent the Upper Variegated Claystones (Fig. 1), which correspond to the Cretaceous Oceanic Red Beds (CORBs) of Hu et al. (2005) in the Atlantic.

Figure 6. Bed-by-bed correlation of 48 sections of the Aptian-Albian Flysch Gault between Oberstdorf (W) and Lake Tegernsee (E) covering a total distance of 115 km.

Rhenodanubian Flyschzone, Bavarian Alps 59

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Figure 7. Mineral plots for quartz and feldspar to support the bedby-bed correlation of the Flysch-Gault based on thin-section studies of samples from the base of three sections (25, 32, 41; section numbers in ascending order indicate decreasing proximality; for location, see Fig. 2). Beds that deviate significantly from the overall correlation are denoted by black dots.

In the Upper Cretaceous above the Piesenkopf Formation the distinct facies differentiation between the northern Sigiswang Facies and the southern Oberstdorf Facies (Figs. 1, 10) takes shape. The lower to middle Campanian Kalkgraben Formation of the Sigiswang Facies is a calcarenitic turbidite succession with beds 0.5–1.5 m thick capped by gray marlstones and calcareous marlstones (Te division) of about equal thickness and alternating with green carbonate free claystones (Hesse, 1991a). Calcilutites up to 40 cm thick rarely occur as caps of the calcarenites or as individual Te beds. The carbonate turbidites have a western source. Bed-by-bed correlations of detailed measured sections of the Kalkgraben Formation proved the continuity of individual turbidites for a distance of 40 km parallel to strike of the flysch zone showing that the same constraints (see below) controlled turbidite sedimentation in the Campanian as during the AptianAlbian (Hesse, 1995). The Kalkgraben Formation is overlain by the middle to upper Campanian Hällritz Formation, which is lithologically distinctly different from the former by lacking the thick marlstone caps of the calcarenites, particularly in the lower third of the formation. The lithostratigraphic boundary between the two formations is drawn where the last more than 50-cm-thick marlstone caps occur in the Kalkgraben Formation. The calcarenites or calcarenitic quartzarenites reach up to 3 m thickness. The thickest beds contain the coarsest material at the base with grain sizes up to 3–4 mm. Bed amalgamations are common involving erosion of the green, carbonate-free hemipelagic interlayers between the turbidites. The top of the beds is predominantly capped by a calcilutite Te division rather than a marlstone. The medium to finergrained calcarenite varieties typically contain up to 10% glauconite. The middle part of the stratigraphic section of the Hällritz Formation contains a thin-bedded facies similar to the Piesen-

Figure 8. Proximal to distal bed thickness variations of individual beds of the Flysch Gault showing that down-current decreasing bed thickness is in part compensated by beds with down-current increasing thickness thus maintaining a more or less flat basin floor. Average gradient of beds with down-current decreasing thickness: –4.2 mm/km, average for beds with down-current increasing thickness: 2.7 mm/km. Gradients obtained by linear regression analysis. Note general upward thickening trend (beds with higher numbers are generally thicker). On the basin plain such a trend may reflect a systematic increase in the availability of fine-grained sand-sized material inherited from a prograding deep-sea fan in the source region. Columns to the right: average bed thickness and standard deviation r.

kopf Formation, which includes red claystones (Hesse, 1991a), that are an equivalent of the Perneck Formation in Austria (Egger, 1995). The lithologic-petrographic observations (grain size, bed thickness, paucity of fines) suggest that the Hällritz Formation represents deposition in the deepest part of the flysch trough where current velocities were highest and the fine-grained sediment constituents were deflected toward the south (see below) or bypassed the location. The youngest stratigraphic unit of the Rhenodanubian Flysch in Bavaria is the Upper Campanian-Maastrichtian Bleicherhorn Formation, which is part of the Sigiswang Facies like the previous stratigraphic units. In this formation, calcarenites of the type observed in the Hällritz or Kalkgraben formations occur together with carbonate-poor, mica- and clay-matrix–rich quartzarenites (“soft sandstones”) of the kind typical of the Reiselsberg Sandstone (Fig. 2). Obviously two sources were active simultaneously, a western source supplying the calcareous sediments and an eastern/southern source supplying the immature sandstones. This suggests a reactivation of the southern source that supplied the sandstones of the Reiselsberg Formation. Measured paleocurrent directions are consistent with this interpretation (Fig. 9). Egger and Schwerd (2008), however, assume a northern source. The Bleicherhorn Formation contains the thickest marlstone caps of the turbidites of any formation reaching up to 5 m. For the first time in the evolution of the Rhenodanubian Flysch, the green hemipelagic claystones of the Bleicherhorn Formation pick up

Figure 9. Paleocurrent directions in the Rhenodanubian Flysch trough for three time slices: Early Cretaceous, “Middle” Cretaceous, and Late Cretaceous. Modified from Hesse (1973b) and Von Rad (1973, table 1).

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Figure 10. Palinspastic cross section for the central portion of the Rhenodanubian Flyschzone in Bavaria (between rivers Lech and Inn). ft— Tristel Formation, fg—Flysch Gault (Rehbreingraben Formation), fo—Ofterschwang Formation, fs—Reiselsberg Sandstone, fp—Piesenkopf Formation, fk—Kalkgraben Formation, fz—Zementmergel Formation, fh—Hällritz Formation, fb—Bleicherhorn Formation. Circled dots— formations with paleocurrent directions from the west; circled crosses—formations with predominant paleocurrent directions from the east. For explanations, see text.

some calcium carbonate (Fig. 11), which could be due to filling of the flysch trough by sedimentation raising its floor above the CCL, but also due to lowering of the CCL to 5000 m depth in Maastrichtian time (Thierstein, 1979). The Zementmergel Formation is the southern equivalent in the Oberstdorf Facies of the three formations of the Sigiswang Facies described above, i.e., the Kalkgraben Formation, the Hällritz Formation, and the Bleicherhorn Formation. At present it is not clear whether the Zementmergel Formation covers the entire time span of these three formations (Fig. 1), because age determinations for the Zementmergel Formation (Turonian to Maastrichtian) are based on rare findings of Globotruncana sp. (Pflaumann, 1968, p. 132) and spores (Wolf, 1963, p. 350; 1964) but not yet confirmed by modern nannostratigraphy, which so far yielded only Campanian species (Egger, 2008, personal commun.; 2010). The Zementmergel Formation consists of a monotonous succession of calcarenites capped by thick gray (Te) marlstone layers that were used for concrete (cement) production in the past, giving the formation its name. The large thickness of the Te marlstone division may be explained by a Coriolis Effect. Turbidity currents flowing eastwards in the flysch trough will be deflected toward the south as a consequence of the Coriolis force with the result that the upper surface of these currents will be raised southward. Since the fine grain sizes are concentrated

in the upper levels of the flows, the fines will preferentially be deposited in the south, that is, in the Oberstdorf Facies. TECTONIC STRUCTURE The Rhenodanubian Flysch is an allochthonous unit that has been transported northward as a nappe between the Late Eocene and Early Miocene (Decker et al., 1993; Trautwein et al., 2001). The “northward” transport direction denotes a relative sense of motion, because in a plate-tectonic context, the southern European margin with the Helvetic shelf and Ultrahelvetic slope was involved in southward subduction. Retaining the conventional notion of northward transport, the tectonic transport distance has been estimated to be at least 100 km (Hesse, 1973a, 1991b) based on the correlation of the Lower Cretaceous Tristel Formation and the Flysch Gault with their stratigraphic equivalents in the Falknis and Tasna nappes in Liechtenstein and the Engadin Window of eastern Switzerland (Hesse, 1973a). The thrust fault separating the Rhenodanubian Flysch Nappe and the HelveticUltrahelvetic zones is dipping 60°S near the surface, where it has been encountered in deep drill holes (Hesse and Schmidt-Thomé, 1975). Based on reflection seismics and refraction seismic studies, the dip becomes shallower at greater subsurface depth toward the south (Reich, 1960).

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3

75

50

25

0 245

711

715

704

Flysch Zone

811

911

Kössen

Reichenhall

Gosau

Osterbach

Ultrahelvetic.

Figure 11. Calcium carbonate content of turbidites, hemipelagic green claystones and pelagic limestones of the Rhenodanubian Flysch, the Ultrahelvetic Zone and the Kössen and Reichenhall Gosau Basins. 245—Aptian-Albian Flysch Gault; 704–715—Lower to mid-Campanian Kalkgraben Formation; 811—Mid- to upper Campanian Hällritz Formation; 911—Upper Campanian to Maastrichtian Bleicherhorn Formation. As the carbonate distribution shows, the Rhenodanubian Flysch remains below the calcite compensation level until the Maastrichtian, when some calcium carbonate (<20%) appears in the hemipelagic sediments indicating deposition in the lysocline zone. The carbonate-bearing sample in section 711 is in all likelihood due to sampling error (sample containing turbiditic carbonate admixed by bioturbation). The Kössen Gosau Basin remained below the calcite compensation level (CCL), whereas the Reichenhall Basin was clearly above the CCL. Modified from Hesse and Butt (1976).

Figure 12. Comparison of the paleogeographic models of Hesse (1973a) and Egger (1992) for the middle Penninic Briançonnais Platform as source for the Lower Cretaceous turbidite formations of the Rhenodanubian Flysch.

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The Rhenodanubian Flyschzone is tectonically further subdivided into internal thrust sheets and tectonic slivers. The main internal thrust separates the Sigiswang and Oberstdorf facies belts. In tectonic context, these two facies belts have been called Sigiswang Nappe and Oberstdorf Nappe dating back to Kraus (1927, and later). The thrust is folded and has been estimated to involve 3 km of northward transport in the Allgäu (Mattern, 2004). PALEOGEOGRAPHY AND GEODYNAMIC EVOLUTION The middle Penninic Briançonnais Platform is generally assumed to be the source for the Lower Cretaceous turbidite formations of the Falknis and Tasna Nappes and the Rhenodanubian Flyschzone (Hesse, 1973a; Egger 1992). Different paleogeographic reconstructions for the position of the source

with respect to the receiver basins have been proposed by these authors (Fig. 12). A third alternative reconstruction has been offered by Springhorn (2007), who derived the Falknis-Sulzfluh and Tasna zones from an original Lower Austroalpine position on the Apulian plate margin by transferring it along a transform fault to the Briançonnais platform, which is considered to have formed an eastern promontory of the Iberian-Ligurian plate (Fig. 13). A schematic hypothetical paleobathymetric cross-section is shown in Figure 14. For the various tectonic units of the East Alps (and Carpathians) see Figure 15. The turbidite successions of the Rhenodanubian Flysch are pristine deep-water sediments that have been deposited, depending on the depth of the CCL in Cretaceous time, in water depths between 4 and 5 km. The hemipelagic claystones at all stratigraphic levels are carbonate-free except in some samples from the Bleicherhorn Formation (Fig. 11). The carbonate of the black claystones of the Flysch-Gault (Fig. 5) is

Figure 13. Late Jurassic (ca. 145 Ma) evolution of the Alpine Tethys by sea-floor spreading showing the development of the South Penninic oceanic domain (Piemont Ocean) and the transfer of the Falknis-Sulzfluh and Tasna zones from the Lower Austroalpine realm of the Apulian plate to the mid-Penninic Briançonnais Platform along a transform fault (from Springhorn, 2007, fig. 4; reproduced with permission of the author).

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Autochthonous Allochthonous Helveticum Helveticum

Helvetic Zone Littoral-Shelf Shale Sandstone Limestone Hemipelagic Marl not to scale

Ultrahelv. Marginal Zone Flysch Zone UpperMiddle Bathyal

Middle-Lower Bathyal

Silty Marl Foraminiferal Nanno Marl

Flysch Zone

Calcite-free Hemipelagite

Lower Bathyal-Abyssal (Hadal)

Carbonate Turbidite Coarse Turbidite Pelagic Marl Wildflysch (Melange) Calcite Free Hemipelagite Carbonate Turbidite Northern Penninikum

Turbidites Planktonic Foraminifera Benthonic Foraminifera

Southern Penninikum

Penninic Realm

(Jurassic - Turon)

Calcareous Benthonic F Agglutinant Benthonic F

Figure 14. Schematic hypothetical paleobathymetric cross-section across the northern Alpine Tethyan Sea. Foraminiferal associations and geochemical data (carbonate content) are used to reconstruct the paleobathymetry (from Butt and Herm, 1978).

Figure 15. Major sedimentary/tectonic units of the Alps and Carpathians. RDF—Rhenodanubian Flysch, F.N.—Falknis Nappe, T.N.—Tasna Nappe. (Modified from Hesse, 1982.)

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of diagenetic origin, most likely consisting of complex manganese carbonates as suggested by the correlation between the Ca/Al and Mn/Al ratios. Flysch as a tectono-sedimentary facies is characterized by the synorogenic deposition of thick marine turbidite facies in elongate depositional basins in a subduction-related tectonic setting. The repeated paleocurrent reversals in the Rhenodanubian Flysch (Fig. 9) suggest that the basin floor was relatively flat so that the turbidity currents with opposing flow directions did not have to flow against a gradient, which energetically would prevent long flow distances. The narrow elongate basin may have been bound by relatively steep basin walls that guided the turbidity currents to form sheet floods that covered the entire basin

floor (but see below). This is the prerequisite for the continuity of individual layers for more than 100 km. On a deep-sea fan, current directions would radiate with time over the fan in a windshield-wiper fashion preventing the long-distance continuity of thick successions of beds. Taken together, these observations suggest a deep-sea trench as depositional/tectonic environment for the Rhenodanubian Flysch. However, it was a tectonically largely inactive trench, because the stack of turbidite formations of the Rhenodanubian Flysch is not affected by syndepositional deformation. The prominent northward increase in the thickness of the Reiselsberg Sandstone (Fig. 10) might signify a short subduction pulse in Mid-Cretaceous time in an otherwise “dormant” trench. A modern analogue for a dormant trench could be the

Figure 16. (A) Bathymetry of the Puerto Rico Trench showing the main tributary channel (Mona Canyon) on the south wall and escarpments on the south and north walls that do extend down to great water depth but not to the hadal turbidite plain. (B) Detailed bathymetric map of the central part of the hadal plain with core locations. Isobath in fathoms. From Hesse (1982), modified from Conolly and Ewing (1967).

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Figure 17. Inferred schematic arrangement of paleogeographic zones of the Alpine Tethys in Albian time (after Gwinner, 1971; Hesse, 1973a; Tollmann, 1969; modified from Hesse, 1982).

Puerto Rico Trench, which has not seen subduction activity since the Miocene. The fact that it is still in existence despite its strong negative gravity anomaly and has not been affected by inversion tectonics is due to the overall compressive stress regime. The Puerto Rico Trench borders the North American–Caribbean plate boundary, which is a left lateral strike-slip zone. The Puerto Rico Trench contains a trench hadal plain that is not bound by steep basin walls (Fig. 16). Turbidites have been recovered in piston cores from this trench plain that can be correlated for 200 km (Conolly and Ewing, 1967). Hesse (1982) speculated that the Greater Antilles/Lesser Antilles loop arc of the Caribbean Sea and the loop arc of the South Scotia Sea in the Atlantic might be suitable tectonic analogues for the geodynamic evolution of the Alpine Carpathian Arc. An inferred schematic arrangement of paleogeographic domains of the Alpine Tethys in Albian time is shown in Figure 17.

ROAD LOG Rhenodanubian Flyschzone in Upper Bavaria: Lainbach Valley near Benediktbeuern and Lahnegraben and Kappel Laine Creeks near Murnau Geologic maps 1:25.000: Blüher (1935), Doben (1985) From Weilheim, we drive east, via Benediktbeuern, to the Lainbach Valley parking lot. From here, the group will walk on a comfortable road up the low-gradient valley for a 5 km roundtrip and visit a series of outcrops in the folded Cretaceous (Fig. 18) exposing the Tristel Formation, Flysch Gault, Reiselsberg Sandstone, and Zementmergel Formation. Upon reaching the Schmiedlaine tributary, we shall leave the road and turn south into the creek for continuously exposed Zementmergel Formation turbidites. For outcrop locations, see Figure 19.

Figure 18. NW-SE cross section, Rhenodanubian Flysch, Lainbach Valley near Benediktbeuern. 1—Tristel Formation; 2—Flysch Gault (Rehbreingraben Formation) with Lower Variegated Claystones, numbers indicate bed-by-bed correlated sections; 3—Reiselsberg Sandstone; 4—Piesenkopf Formation; 5—Zementmergel Formation; 6—Cenomanian of the Limestone-Alpine marginal tectonic sliver (“Randcenoman”); 7—Liassic (Spot Marlstones). Section numbers in Flysch Gault indicate location of detailed measured sections that have been correlated bed-by-bed.

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Figure 19 (continued on following page). (A, B) Geologic sketch map for the Rhenodanubian Flyschzone between rivers Isar and Ammer showing location of the stops. 1—Tristel Formation; 2—Rehbreingraben Formation (Flysch Gault); 3—Ofterschwang Formation; 4—Reiselsberg Sandstone; 5—Kalkgraben Formation/Zementmergel Formation; 6—Hällritzer Formation; 7—Bleicherhorn Formation; 8—Lower Cretaceous.

Hesse

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Figure 19 (continued).

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Stop 2-1. Flysch Gault, Lainbach Valley The first stop in the Lainbach Valley is to see sections 44 and 45 on opposite sides of the road, which expose bed successions from the Upper Quartzarenite-Rich Member of the AptianAlbian Gault Formation (Fig. 20). Stop 2-2. Flysch Gault, Lainbach Valley Sections 46–52 (Fig. 20) descend stratigraphically to lower members of the formation, including the Middle Claystone–Rich Member (section 48) and the Lower Quartzarenite–Rich Member (sections 48–52). Only selected, easily accessible sections will be visited. Stop 2-3. Tristel Formation, Lainbach Valley The (Hauterivian) Barrêmian Tristel Formation is best exposed near the water level of the creek where the various lithologies (see Stratigraphy and Facies above) and primary sedimentary structures can be seen. Along the road (SW side) spectacular fold structures are observed. Stop 2-4. Flysch Gault, Lainbach Valley Sections 53–60 include a portion of the Lower Claystone– Rich Member (section 56), which contains a pebbly mudstone ~2 m thick that is also present in section 32 in Ammergau ~30 km to the west and attests to considerable flow distances of mud-rich debris flows. In this section, the marker bed F2 (feldspar bed) is amalgamated with underlying bed F1. Stop 2-5. Reiselsberg Sandstone, Lainbach Valley Vegetation permitting, the Cenomanian-Turonian Reiselsberg Sandstone is visited here to show its lithologic character which is strikingly different from the underlying siliciclastic formation of the Flysch Gault with its mature glauconitic quartzarenites. The Reiselsberg Sandstone is a petrographically relatively immature mica-rich sandstone that, depending on the degree of carbonate cementation, forms either hard calcareous sandstones or easily disintegratable “soft” sandstones (Mürbsandsteine). Although the outcrop is fault-bounded, so that the true thickness cannot be assessed, the Reiselsberg Sandstone of the Oberstdorf Facies is generally less than 50 m thick. Stop 2-6. Zementmergel Formation, Schmiedlaine Creek Entering the Schmiedlaine Creek a continuous S-dipping succession of carbonate turbidites is exposed. The main characteristic is the thick pelitic Te division of gray marlstone, which caps calcisititic-calcarenitic lower structural divisions. In general, the carbonate turbidites are separated by green, carbonatefree hemipelagic claystone. Beyond ~760 m above sea level folding sets in.

10 m

5

0

Figure 20. Bed-by-bed correlated sections 44–60 of the Flysch Gault in Lainbach Valley near Benediktbeuern (from Hesse, 1973b).

Figure 21. Detailed measured Reiselsberg Sandstone section, Lahnegraben Creek near village of Grafenaschau (Stop 2-7). Structural and fabric features described in text.

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The next stop is W of the town of Murnau, ~30 km to the west of the Lainbach valley, in the flysch of the Hörnle-Aufacker Mountain group. Stop 2-7. Reiselsberg Sandstone, Lahnegraben Creek near Village of Grafenaschau Between 830 and ~950 m elevation this creek exposes a thick succession of the Reiselsberg Sandstone (Reiselsberg Formation). Beds reach more than 10 m thickness with abundant amalgamations explaining the unusual bed thickness (Fig. 21). Besides bed amalgamation, normal and reverse bedding, clast imbrications, and dish structure are the predominant structural and fabric features. Parallel lamination, cross-lamination and even cross-bedding occur in some beds. Thinner calcarenitic beds may show extreme convolute lamination. Stop 2-8. Kappel Laine Creek near Unterammergau The Kappel Laine Creek on the western slope of the HörnleAufacker Group exposes Upper Cretaceous formations of the Sigiswang Facies, from the Coniacian to lower Campanian Piesenkopf Formation through the lower to middle Campanian Kalkgraben Formation, the middle to upper Campanian Hällritz Formation to the upper Campanian-Maastrichtian Bleicherhorn Formation. Time may not permit to see more than the lower two formations, the Piesenkopf Formation and the Kalkgraben Formation between 920 and ~1050 m elevation. The objectives are to study the distal characteristics of the Piesenkopf turbidites and to compare the sand-rich turbidite facies of the Kalkgraben Formation of the Sigiswang Facies with the pelite-rich Zementmergel Formation of the Oberstsdorf Facies (Stop 2-6). REFERENCES CITED Blüher, H.-J., 1935, Molasse und Flysch am bayerischen Alpenrand zwischen Ammer und Murnauer Moos (mit einer geologischen Karte 1:2500): Abhandlungen der Geologischen Landesuntersuchung am Bayerischen Oberbergamt München, v. 16, p. 7–55. Butt, A. and Herm, D., 1978, Palaeo-oceanographic aspects of the Upper Cretaceous geosynclinal sediments of the Eastern Alps, in Closs, H., Roeder, D., and Schmidt, K., eds., Alps, Apennines, Hellenides: Stuttgart, ICG Scientific Report 38, p. 87–95. Conolly, J.R., and Ewing, M., 1967, Sedimentation in the Puerto Rico Trench: Journal of Sedimentary Petrology, v. 17, no. 1, p. 44–59. Decker, K., Meschede, M., and Ring, U., 1993, Fault slip analysis along the northern margin of the Eastern Alps (Molasse, Helvetic nappes, North and South Penninic flysch, and the Northern Calcareous Alps): Tectonophysics, v. 223, p. 291–312, doi:10.1016/0040-1951(93)90142-7. Doben, K., 1985, Geologische Karte von Bayern, 1:25,000 Blatt 8334 Kochel am See, mit Erläuterungen (Geologic Map of Bavaria 1:25000, Map Sheet 8334 Kochel on the Lake): Bayerisches Geologisches Landesamt München (Bavarian Geological Survey Munich), 134 p. Egger, H., 1992, Zur Geodynamik und Paläogeographie des Rhenodanubischen Flysches (Neokom-Eozän) der Ostalpen: Zeitschrift der Deutschen Geologischen Gesellschaft, v. 143, p. 51–65. Egger, H., 1995, Die Lithostratigraphie der Altlengbach-Formation und der Anthering-Formation im Rhenodanubischen Flysch (Ostalpen, Penninikum): Neues Jahrbuch für Geologie und Paläontologie, Abhandlungen, v. 196, p. 69–91. Egger, H., and Schwerd, K., 2008, Stratigraphy and sedimentation rates of Upper Cretaceous deep-water systems of the Rhenodanubian Group

(Eastern Alps, Germany): Cretaceous Research, v. 29, p. 405–416, doi:10.1016/j.cretres.2007.03.002. Einsele, G., 1963, Convolute bedding und aehliche Sedimentstrukturen im rheinischen Oberdevon und anderen Ablagerungen: Neues Jahrbuch für Geologie und Paläontologie Abhandlungen, v. 116, no. 2, p. 162–198. Gradstein, F., Ogg, J., and Smith, A., 2004, A Geologic Time scale: Cambridge, Cambridge University Press, 589 p. Gwinner, M.P., 1971, Geologie der Alpen: Stuttgart, Schweizerbart, 477 p. Hauck, J., 1998, Paläomagnetische Untersuchungen an ausgewählten Profilen der Kreide in der Rhenodanubischen Flysch-Zone. (Paleomagnetic studies of selected Cretaceous sections of the Rhenodanubian Flysch Zone) [unpubl. Ph.D. thesis]: Ludwig Maximilians University, Munich. Hesse, R., 1973a, Flysch-Gault und Falknis-Tasna Gault (Unterkreide): Kontinuierlicher Übergang von der distalen zur proximalen Flyschfazies auf einer penninischen Trogebene der Alpen: Geologica et Palaeontologica, Special Issue 2, 90 p. Hesse, R., 1973b, Lithostratigraphie, Petrographie und Entstehungsbedingungen des bayerischen Flysches: Unterkreide: Geologica Bavarica, v. 66, p. 148–222. Hesse, R., 1974, Long-distance continuity of turbidites: Possible evidence for an Early Cretaceous trench-abyssal plain in the East Alps: Geological Society of America Bulletin, v. 85, p. 859–870, doi:10.1130/0016 -7606(1974)85<859:LCOTPE>2.0.CO;2. Hesse, R., 1982, Cretaceous-Palaeogene Flysch Zone of the East Alps and Carpathians: identification and plate-tectonic significance of “dormant” and “active” deep-sea trenches in the Alpine-Carpathian Arc, in Legget, J.K., ed., Trench-Forearc Geology: Geological Society (London) Special Publication 10, p. 471–494. Hesse, R., 1991a, Schichtenfolge (Stratigraphie) Flysch-Zone, in Hesse, R., and Stephan, W., Geologische Karte von Bayern (Geological Map of Bavaria): Bayerisches Geologisches Landes-Amt (Bavarian Geological Survey), München, 1:25 000, Erläuterungen zum Blatt Nr. (Explanations for Map Sheet no.) 8234 Penzberg, p. 20–74, Hesse, R., 1991b, Lagerungsverhältnisse (Tektonik): Alpiner Bereich, in Hesse, R., and Stephan, W., Geologische Karte von Bayern (Geological Map of Bavaria): Bayerisches Geologisches Landes-Amt (Bavarian Geological Survey), München, 1:25 000, Erläuterungen zum Blatt Nr. (Explanations for Map Sheet no.) 8234 Penzberg, p. 198–208. Hesse, R., 1995, Bed-by-bed correlation of trench-plain turbidite sections, Campanian Zementmergel Formation, Rhenodanubian Flysch Zone of the Eastern Alps, in Pickering, K.T., Hiscott, R.N., Kenyon, N.H., Ricci-Lucchi, F.S., and Smith, R.D.A., eds., Atlas of Deep Water Environments: Architectural Style in Turbidite Systems: London, Chapman and Hall, p. 307–309. Hesse, R., and Butt, A.A., 1976, Paleobathymetry of Cretaceous turbidite basins of the East Alps relative to the calcite compensation level: The Journal of Geology, v. 84, no. 5, p. 505–533, doi:10.1086/628229. Hesse, R., and Schmidt-Thomé, P., 1975, Neue Jodwasser-Vorkommen im Bereich der bayerischen Alpenrand-Strukturen bei Bad Tölz (aufgrund von Tiefbohrungen 1957–1967): Geologisches Jahrbuch, v. C11, p. 31–66. Hu, X.M., Jansa, L., Wang, C.S., Sarti, M., Bak, K., Wagreich, M., Michalik, J., and Sotak, J., 2005, Upper Cretaceous Oceanic Red Beds (CORBs) in the Tethys: Occurrences, lithofacies, age, and environments: Cretaceous Research, v. 26, p. 3–20, doi:10.1016/j.cretres.2004.11.011. Kraus, E., 1927, Neue Spezialforschungen im Allgäu (Molasse und Flysch): Geologische Rundschau, v. 18, p. 189–221, 263–298. Mattern, F., 1988, Die interne Überschiebungstektonik im Flysch (Kreide) der westlichen Bayerischen Alpen: Berliner Geowissenschaftliche Abhandlungen, Reihe A1, v. 101, 94 p. Mattern, F., 1998, Lithostratigraphie und Fazies des Reiselsberger Sandsteins: Sandreiche, submarine Fächer (Cenomanium-Turonium, westlicher Rhenodanubischer Flysch, Ostalpen): Berliner Geowissenschaftliche Abhandlungen, v. A198, 139 p. Mattern, F., 1999, Mid-Cretaceous basin development, paleogeography and paleogeodynamics of the western Rhenodanubian Flysch (Alps): Zeitschrift der Deutschen Geologischen Gesellschaft, v. 150, no. 1, p. 89–132. Mattern, F., 2004, The main internal flysch thrust, thrust tectonic subdivision, and structure of the western Rhenodanubian Flysch belt (eastern Alps): Zeitschrift der Deutschen Geologischen Gesellschaft, v. 155, p. 11–34. Pflaumann, U., 1968, Flysch-Zone, in Pflaumann, U., and Stephan, W., Erläuterungen zur Geologischen Karte von Bayern 1:25 000 Blatt Nr. 8237 Miesbach, p. 111–142, München (Bayerisches Geologisches Landes-Amt).

Rhenodanubian Flyschzone, Bavarian Alps Reich, H., 1960, Seismische Untersuchungen des Flyschtroges bei Lenggries westlich und östlich der Isar: Nachrichten der Akademie der Wissenschaften Göttingen, II: Mathematisch-physikalische Klasse, v. 11, p. 205–255. Springhorn, R., 2007, Geology of the Engadin Window, especially the upper Val Fenga (East Switzerland): Zeitschrift der deutschen Gesellschaft für Geowissenschaften, v. 158, no. 1, p. 67–87. Thierstein, H.R., 1979, Paleogeographic implications of organic carbon and carbonate distribution in Mesozoic deep sea sediments, in Talwani, M., Hay, W., and Ryan, W.B.F., eds., Deep Drilling Results in the Atlantic Ocean: Continental margins and paleoenvironments: Washington, D.C., American Geophysical Union, Maurice Ewing Series, v. 3, p. 249–274. Tollmann, A., 1969, Die tektonische Gliederung des Alpen-Karpathen-Bogens: Geologie, v. 18, p. 1131–1155. Trautwein, B., Dunkl, I., and Frisch, W., 2001, Accretionary history of the Rhenodanubian Flysch zone in the Eastern Alps—evidence from apatite fission-track geochronology: International Journal of Earth Sciences, v. 90, p. 703–713, doi:10.1007/s005310000184. Von Rad, U., 1973, Zur Sedimentologie und Fazies des Allgäuer Flysches: Geologica Bavarica, v. 66, p. 92–147.

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Wolf, M., 1963, Sporenstratigraphische Untersuchungen im “Randcenoman” Oberbayerns: Neues Jahrbuch für Geologie und Paläontologie, Monatshefte, no. 7, p. 337–354. Wolf, M., 1964, Sporomorphen aus dem bayerischen Flysch: Fortschritte der Geologie von Rheinland und Westfalen, v. 12, p. 113–116. Wortmann, U., 1996, Zur Ursache der hemipelagischen schwarz/grün Zyklen im Apt/Alb der bayerischen Flyschzone (Factors causing the black/green cycles in the Aptian/Albian of the Bavarian Flysch Zone) [unpubl. Ph.D. thesis]: Technical University Munich, 212 p. Wortmann, U.G., Hesse, R., and Zacher, W., 1999, Major-element analysis of cyclic black shales: Paleoceanographic implications for the Early Cretaceous deep western Tethys: Paleoceanography, v. 14, no. 4, p. 525–541, doi:10.1029/1999PA900015. Wortmann, U.G., Herrle, J.O., and Weissert, H., 2004, Altered carbon cycling and coupled changes in Early Cretaceous weathering patterns: Evidence from integrated carbon isotope and sandstone records of the western Tethys: Earth and Planetary Science Letters, v. 220, p. 69–82, doi:10.1016/S0012-821X(04)00031-7. MANUSCRIPT ACCEPTED BY THE SOCIETY 26 MAY 2011

Printed in the USA

The Geological Society of America Field Guide 22 2011

Field trip to the Northern Alps between Munich and the Inn Valley Bernd Lammerer Ludwig-Maximilians-Universität, Department für Geo- und Umweltwissenschaften, Luisenstr. 37, 80333 München, Germany Hugo Ortner Universität Innsbruck, Institut für Geologie und Paläontologie, Innrain 52, A 6020 Innsbruck, Austria Alexander Heyng Ludwig-Maximilians-Universität, Department für Geo- und Umweltwissenschaften, Luisenstr. 37, 80333 München, Germany

ABSTRACT This field trip leads from Munich through the nappe stack of the Northern Alps. The folded Molasse zone, which clearly reacted to the tectonic events in the alpine collision zone. The Flysch zone covers the underfilled deep sea basin along the Cretaceous pre-collisional active margin. The Helvetic nappes carry Cretaceous to Paleogene sediments that show strong facies differentiation due to an increasingly unstable European platform. These will be visited in two isolated windows. A cross section through a good part of the Northern Calcareous Alps along the Valepp Valley will give insight into the structure of the fold-and-thrust belt and the preand post-Gosau phase deformation. Sedimentological response to Late Cretaceous geodynamic processes will, finally, be studied in the famous Muttekopf area and its spectacular outcrops

trips series covers the northern front of the alpine orogenic wedge in the area between Munich and the Inn Valley. The trip follows in part the TRANSALP seismic line (Lüschen et al., 2004, 2006). It includes from north to south, or from bottom to top: (1) The wedge-shaped peripheral foreland Molasse sediments, which are folded close to the Alpine front (Bachmann and Müller, 1992; Lemcke, 1988; Roeder, 2009; Schmidt-Thomé, 1955; Schwerd et al., 2011). (2) The small zone of Cretaceous to Eocene cover rocks of the Helvetic zone, a nappe complex, which is detached from the stable European plate and thrust over the Molasse basin (Schwerd, 1996). (3) The Rhenodanubian Flysch nappes, which comprise Early Cretaceous to Upper Eocene turbiditic sequences

INTRODUCTION The Eastern Alps represent a double-vergent orogen, which formed during the collision of the European plate in a lower tectonic position with the Adriatic microplate in an upper tectonic position. The Eastern Alps are widely covered by the Austroalpine nappes that include the Northern Calcareous Alps and their basement, e.g., the Greywacke- and Quartzphyllite zones and the Ötztal-Stubai-Silvretta crystalline complexes, which derive from the Adriatic microplate and camouflage deeper units. Only the Tauern window (TRANSALP field trip, part 1, Lammerer et al., this volume, Chapter 7) allows a deeper look down to the Penninic ocean units and to the cover and basement of the European plate (Schmid et al. 2004). This part 2 of the TRANSALP field

Lammerer, B., Ortner, H., and Heyng, A., 2011, Field trip to the Northern Alps between Munich and the Inn Valley, in Carena, S., Friedrich, A.M., and Lammerer, B., eds., Geological Field Trips in Central Western Europe: Fragile Earth International Conference, Munich, September 2011: Geological Society of America Field Guide 22, p. 75–100, doi:10.1130/2011.0022(06). For permission to copy, contact [email protected]. ©2011 The Geological Society of America. All rights reserved.

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that developed along the front of the approaching Austroalpine nappes within the Alpine Tethys basin (Hesse, 1974; 1982; this volume, Chapter 5). (4) The Austroalpine nappes of the Northern Calcareous Alps, which are part of the Adriatic Plate (Schmid et al., 2004). They are detached from their basement south of the Inn valley. The stratigraphic succession starts with Late Permian clays and evaporites and reaches the Late Cretaceous and Paleogene cover successions. During the Eo-Alpine orogeny in Mid Cretaceous to Early Paleogene times, its nappes were deformed and metamorphosed in their southern parts (Gawlick and Königshof, 1993; Handy and Oberhänsli, 2004). During this phase, the tectonic transport was mainly directed west in the Central Alps and northwest in the Northern Calcareous Alps (Ratschbacher, et al. 1989; Eisbacher and Brandner, 1996). Three main nappes compose the Northern Calcareous Alps in the vicinity of the TRANSALP line. The Allgäu nappe is only visible in a small and poorly exposed strip on the northern rim. It is heavily dissected and thicknesses of the units are generally small. The Lechtal nappe covers most of the area and the entire Valepp section, which will be visited in the course of this field trip. The Inntal nappe crops out south of the Inn Valley and to the west of the Achensee (Auer and Eisbacher, 2003; Tollmann, 1973, 1976). During a Miocene phase of lateral escape, the sinistral Inn Valley Fault formed (Frisch et al., 1998; Ratschbacher et al., 1989, Neubauer et al., 2000). (5) The Late Cretaceous–Paleocene Gosau basins and the Inner Alpine Tertiary (Wagreich and Faupl, 1994; Ortner, 2001). This field trip has a duration of six days, beginning and ending in Munich. The detailed description of the second day is provided by Hesse (this volume, Chapter 5). The trip consists of both roadside stops, and of long hikes between mountain huts.

attributed to the bending of the European plate under the load of the Alpine nappes and the weight of Molasse sediments Fig. 2). The Molasse sediments alone have been shortened by more than 24 km in the sector of the TRANSALP line (Fig. 3). The change from the underfilled flysch stage to a filled or overfilled Molasse stage in mid Oligocene times seems to be connected with the breakoff of the subducting European slab under the Alps, causing accelerated exhumation, rapid isostatic surface uplift and erosion in the Alps (von Blanckenburg and Davies, 1995; Sinclair, 1997a, 1997b; Kissling et al., 2007; Lippitsch et al., 2003). About 20 million years ago, during the Miocene, a large part of the Molasse area was again inundated by a shallow sea (Upper Marine Molasse). Its northern limit is marked by a cliff line and by boreholes carved by lithophagous mollusks into the Jurassic limestones. This phase of accelerated subsidence in the Eggenburgian, at ca. 20 Ma, coincides with the onset of rapid exhumation of the Tauern window, which was thrust northward along a deep reaching reverse fault, the Sub-Tauern ramp. This additional load might have caused an episode of enhanced subsidence in the foreland of the Eastern Alps and a marine transgression. Since late Eocene times, ~56,000 km3 of sediments have been deposited, their provenance being mainly from the rising Alps in the foreland basin. Smaller amounts were also added from northern areas, e.g., from the Bohemian Massif (Kuhlemann, 2000; Kuhlemann et al., 2001a, 2001b). Close to the Alpine front, the Molasse reaches 4000–5000 m in thickness, and locally even higher (Müller 1970). Main deposition phases started in early Oligocene with the deep marine (“Flyschmolasse”) of the Deutenhausen beds or the Fish-shales in the Swiss Molasse, and it lasted until late Miocene times (Fuchs, 1976; Lemcke, 1983, 1988). Porous rocks contain small hydrocarbon deposits all over the Molasse basin (Roeder and Bachmann, 1997). In Großaitingen, near Augsburg, the largest oil field was opened in Bavaria in 1979. Some 40,000 tons of crude oil of excellent quality were produced here annually; over a million tons have so far been

DAY 1. THE MOLASSE BASIN SOUTH OF MUNICH (Total driving distance: 130 km, total walking distance: 5 km.) Introduction to the Molasse Basin The Molasse basin spans ~1000 km from France through Switzerland and Germany to Austria. At Lake Geneva, it measures ~20 km in width and it widens in Bavaria, up to ~130 km. Further east, it passes into the Vienna Basin and the foredeep of the Carpathians. Beneath the Molasse sediments, Mesozoic strata or crystalline basement occur (Fig. 1). The Molasse Basin was formed when the European continental lithosphere was elastically bent under the weight of the Helvetic and Austroalpine nappes, and by its own sediments. This effect extends until the area of Nürnberg (Doppler et al., 2002). Thus, the 2°–4° southward dip of the Swabian and Franconian Jura is also

Figure 1. The Mesozoic rocks under the Molasse sediments. 1—Hercynian metamorphics and granites; 2—Early Triassic Buntsandstein; 3—Middle Triassic Muschelkalk; 4—Late Triassic Keuper sand and clay; 5—Liassic shale; 6—Dogger sand and marl; 7— Malm limestone. After Lemcke (1988).

Figure 2. Vibrosiesmic reflectors (TRANSALP) and drillholes in the foreland Molasse, depth-migrated. Legend: LMM—Lower Marine Molasse; LFM—Lower Freshwater Molasse; UMM—Upper Marine Molasse; UFM—Upper Freshwater Molasse. Deep wells from left to right: Erding 1, Anzing 1, Anzing 2, Moosach 1, Höhenrain (after Lüschen et al., 2006). Length of section: 86 km, vertical scale in kilometers.

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recovered from this small deposit. More important for many years have been the coal deposits. The brackish and freshwater sediments of the Cyrenen strata contain up to 26 seams of pitchcoal, which was mined at Peiting, Peißenberg, and several other places until 1971 (Gillitzer, 1914, 1955; Geissler, 1975; Lemcke, 1988). Recently, prospecting activities have successfully concentrated on thermal water for electric power plants and heating. In the area close to the Alps, the pore fluid pressure is still enhanced due to tectonic processes, which caused problems for deep drillings (Lemcke, 1988; Müller and Nieberding, 1996). Two large synclines developed over triangle structures—the Murnau syncline and the Rottenbuch syncline. The anticlines are missing (see Fig. 7), only in the section of the Ammer River at the Echelsbacher Bridge an anticline is developed (see Fig. 8). Due to the prevailing depositional environment—marine or terrestrial—the formations of the Molasse zone are divided into four groups: • Lower Marine Molasse (Untere Meeresmolasse; UMM), Rupelian, from ca. 34 to 28 Ma.

• Lower Freshwater Molasse (Untere Süßwassermolasse; USM), Chattian and Aquitanian, ca. 28 to 22 Ma. • Upper Marine Molasse (Obere Meeresmolasse; OMM), Burdigalian and Langhian, ca. 22 to 16 Ma. • Upper Freshwater Molasse (Obere Süßwassermolasse; OSM), Serravallian, Tortonian and Pontian, ca. 16 to 5 Ma. Itinerary From Munich, Luisenstrasse 37 (Institute of Geology), we take the highway 952 to Starnberg, and from there the interstate highway B2 to Pähl (46 km). (Fig. 4). Stop 1-1. Parking lot at Hirschbergalm East of Pähl; Pähl Gorge (47°54′36″N; 11°11′12″E; coordinates refer to WGS 84 datum) From the parking lot we ascend to the viewpoint of a small circular hill (687 m) on top of a ground moraine. This is one of several glacier mill kames in the area, which are formed by

Figure 3. Restoration of the subalpine Molasse (by using 2DMove software)

Northern Alps between Munich and the Inn Valley sediments fallen into glacier mills of the last glacial period. The glaciers retreated from around 20,000–14,000 years ago (Würm glaciation; Jerz, 1993). To the west, the flat silt plain of the Ammersee extends far to the south, indicating the much larger expansion of the lake in early post-glacial times. Behind, the western lateral moraine forms an elongated ridge, incised by late glacial dewatering channels. The small village of Raisting is built on an alluvial fan at the mouth of a glacial meltwater creek, which was running along the lateral moraine of a recession stage. To the southwest, the Hohenpeißenberg, our next stop, can be seen in front of the Northern Calcareous Alps. From the top of the hill, we head northward for 300 m, cross the main road (use caution because of fast cars!) and climb 10 m down to the Pähl creek. At the cut bank, a whitish fine-grained till from the Würm ground moraine is exposed. It contains unsorted scratched gneiss or amphibolite cobbles from the Central Alps. This marks the transfluent glacier stream, which crossed the Northern Calcareous Alps at the Fernpass and at Seefeld and was flowing along the Loisach valley. We walk for 200 m along the course of the Pähl Golf Club and descend along a steep trail (caution: may be slippery after rainfalls!) 40 m down to the creek. The Pähl creek comes down in a scenic waterfall over a conglomerates layer from an outwash plain of the Mindel glacial period (380,000–400,000 yr. B.P.), . Within these cross-bedded conglomerates, pebbles from the Central Alps are completely missing due to a different stream pattern

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of the Mindel glaciers in comparison to the later Würm glaciation (100,000–15,000 yr. B.P.; Jerz, 1993). We follow the creek downstream for another 300 m and encounter, on the southern cut bank, yellowish marls and fine sandstone with mica of the Upper Freshwater Molasse (Miocene, 15–5 Ma). These are deposits from a lazy river running from the area of Salzburg westward and parallel to the Alpine chain into the Rhone River—a pattern completely different from the subsequent, recent river system (Lemcke, 1984, 1988; Herbst, 1985) (Fig. 5). Stop 1-2. Hohenpeißenberg 988 m (47°48′05″N; 11°00′57″E) We continue by car from Pähl via Weilheim, along road 472 to Hohenpeißenberg, for 26 km. The Hohenpeißenberg is situated at the contact between the undeformed Foreland Molasse and the folded Subalpine Molasse (Figs. 6 and 7). The strata here are bent in a large monocline to a vertical position and are even overturned at the tip of the “unfolded” Molasse (Fig. 8). From the viewpoint at the top, we have a great view over the Northern Calcareous Alps and the ridges of the Molasse folds to the south and of the flat Molasse foreland and the Ammersee glacier basin to the north. Like in the Pähl Gorge, the summit area consists of Upper Freshwater Molasse deposits, but here they are in a different facies. We find coarse unsorted conglomerates with pressure

Figure 4. Digital elevation model (Shuttle Radar Topography Mission [SRTM]; courtesy: Deutsche Gesellschaft für Luft- und Raumfahrt, Oberpfaffenhofen).

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solution dents in some pebbles. Like other promontory hills— for example, the Rigi in Switzerland, the Pfänder in Austria, the Auerberg near Kempten, and the Irschenberg south of Munich— the Hohenpeißenberg represents an alluvial fan at the mouth of Neogene rivers leaving the Alps. Between 500,000 and 1,000,000 tons of a pitch-coal was mined annually at the Hohenpeißenberg and at nearby Peiting from 1930 to 1971, but smaller activities reach back to the sixteenth century. The 26 mined coal seams reach only between 0.3 and 1.2 m in thickness. The coal seams were relatively highly contaminated by marly or sandy host rock and contained only 50–90% of usable coal (Geissler, 1975; Gillitzer, 1955). We descend a small trail down to the village of Hohenpeißenberg at the guesthouse Hanslbauer and to an abandoned small quarry, where overturned glauconitic sandstones of the Upper Marine Molasse are exposed. The 70° south-dipping finegrained strata represent the base of the “unfolded” Molasse at the overturned limb of a fold-propagation-fold, or a triangle zone beneath, or a combination of both (Fig. 8). Stop 1-3. Schnalshöhlen (47°46′14″N; 10°57′07″E) From Hohenpeißenberg, we continue along road 472 by car to Peiting, where we turn south and take road 23, a section of the “romantic road” through Bavaria (“Romantische Strasse”), for one kilometer to Ramsau (total distance 8.5 km). After passing the few houses of Ramsau we turn left and enter a small gravel road, pass an open gravel pit and park at the forest edge. We follow the path down to the Ammer river (90 m elevation difference). From post Holocene gravel, a spring of calcite-oversaturated water flows out on the slope and along its way, travertine precipitates and builds small levees and sinter terraces. We cross the Ammer River on a wooden bridge and climb up 60 m on the eastern side of the steep slope, where we reach the Schnals caves. Sandstone, fine conglomerate, and marl of the Lower Freshwater Molasse occur in an overhanging cliff. Horizons of impure coal seams extend for several meters. The sandstones were mined in former times for glass production and are therefore called Glassande (glass sands). We find still traces of the mining activities in the caves.

The high quartz content and the heavy mineral spectrum of rutile, zircon, tourmaline, and andalusite are typical for a provenance from the Bohemian Massif (Füchtbauer, 1964, 1967). This is confirmed by cross-bedding indicating transport from north to south. The glass sands represent sediments from rivers flowing from north to south along the inclined Molasse surface. They formed a delta into the small relic sea close to the alpine front. Terrestrial plant fossils (Daphnogene, a laurel genus plant) and brackish water fossils (e.g., cyrena, a brackish-water mussel) indicate a marginal marine environment. Stop 1-4. Echelsbach Bridge (9 km from Ramsau; 47°42′38″N; 10°58′34″E) The Echelsbach bridge was built in 1929 across the Ammer gorge in Melan-Spangenberg construction. It measures 183 m in length, and it is 76 m high. At that time, it was the highest steel-arch bridge in the world. Joseph Melan, a Bohemian engineering professor in Vienna, had first described a reinforced concrete construction, in which he replaced the expensive and particularly complex support structure over deep ravines with a steel skeleton-arm, which was then covered with concrete. According to this proposal, two steel arches were built from both sides freely into the air, which met accurately in the middle. Munich Professor Heinrich Spangenberg extended the application of this design. He placed gravel ballast to preload the steel arch structure and replaced it later step by step with an equally heavy concrete coating. This prevented uneven deformation of the structure during concreting. On the opposite cliff of the gorge, the 40° north-dipping basal strata of the Upper Freshwater Molasse, the Bausteinschichten (building rock strata) crop out. They are exposed in a small old quarry at the eastern slope 50 m south of the bridge. Cross-bedded gray to yellowish sandstones and fine conglomerates contain plant fossils. Stop 1-5. Meyersäge (47°39′01″N; 10°59′58″E; Echelsbacher bridge–Saulgrub– Altenau–Meyersäge; 11 km from Stop 4) We follow the Ammer River for 600 m northward, where we encounter the early Oligocene Deutenhausen beds, the oldest

Figure 5. Cross section along the Pähl Gorge: 1—lake sediments of the silted Ammersee; 2—Upper Freshwater Molasse fine sands and sandy marls; 3—regression moraine of the Pähl stage; 4—Mindel ice stadial conglomerates; 5—glacier mill deposit; 6—ground moraine of the latest glaciation (Würm glaciation).

Figure 6. Tectonic map of the Peissenberg segment of the Subalpine Molasse (compiled from Gillitzer, 1914, 1955; Geissler, 1975; Scholz, 2003; and the geologic maps 1:25.000 of the Bavarian Geological Survey). The trace of the seismic section (see Fig. 7) is schematic. White circles: exploration wells. Coordinates: Deutsches Hauptdreiecksnetz, GK-Zone 4. Figure drafted by H. Ortner, 2011.

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Figure 8. Cross section from Schongau to the frontal thrust of the Northern Calcareous Alps (right end). Legend: Helv.—Helvetic nappes, D—Deutenhausener beds; T—Tonmergel beds of the Lower Marine Molasse; B—Baustein beds; LFMl—Lower Freshwater Molasse, lower part; C—Cyrenen transitional delta sediments, contains coal seams; LFMu—Lower Freshwater Molasse, upper part; UMM—Upper Marine Molasse; UFM—Upper Freshwater Molasse. Modified after Grottenthaler and Müller (2011) and Schmidt-Thomé (1955).

Figure 7. Seismic section across the Subalpine Molasse (adapted from Schuller et al., 2009). OSM—Upper Freshwater Molasse (Obere Süßwassermolasse); OMM—Upper Marine Molasse (Obere Meeresmolasse); USM—Lower Freshwater Molasse (Untere Süßwassermolasse); SBM Freshwater-Brackish-Molasse (Süß-Brackwassermolasse, Cyrenenschichten). Figure drafted by H. Ortner, 2011.

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Northern Alps between Munich and the Inn Valley strata of the Molasse zone here and the southern end of the Molasse. Within the vertical or overturned claystones and marls, up to several meters thick banks of sandy turbidites are intercalated. Gravel, sand, and clay were deposited in different depositional centers, such as deltas, coastal and shelf areas, but also as deeper marine formations of the continental slope, from submarine canyons to deep basins, like the fish shales of Switzerland. We recognize complete and incomplete Bouma cycles and a great variety of sole marks (e.g., groove casts, flute casts, load casts), convolute bedding, and slump structures. Some bedding planes are coated with plant remnants or even thin lenses of asphalt from oil migration. The Deutenhausen beds are considered as deep water sediments by Lemcke (1988). In contrast, Maurer et al. (2002) claim a “less deep” environment. Stop 1-6. Scheibum (47°39′55″N; 10°59′14″E) We wade through the shallow water and cross the tributary Halbammer river over a water–channel bridge, which feeds the electrical power plant of the German Railway Company (DB). We follow the channel for one kilometer and encounter the Scheibum at the narrowing of the valley. The clays and marls of the marine Molasse show channels filled with fine-grained sandstones and occasional distal turbiditic beds (Fig. 9). When crossing the Lower Marine Molasse boundary, the sandy material increases in the transition zone, and layers of fine conglomerates and several thin coal seams up to 30 cm in thickness indicate the growing terrestrial influence. Along a network of fissures within the conglomerate, asphalt occurs as a sign of oil migration. A thick vertical layer of red coarse conglomerate with broken and sheared pebbles shows clear inclined bedding, indicating transport from south (after back rotation). This is the base of the Weißach beds, which reach a thickness of 1400 m. From here we walk back to the cars and drive 38 km to the Weilheim Naturfreundehaus (overnight lodging; 47°49′43″N; 11°07′32E″).

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chain, respectively. Thus, a northern (Adelholzen facies; present in the locality Rohrdorf) and a southern (Kressenberg facies; locality Hinterhör) facies are distinguished by lithological and sedimentological characteristics in the foreland of the Alps in Upper Bavaria. Both Helvetic units record mirror tectonic processes taking place in the course of the alpine orogenesis. Stop 3-1: Abandoned Quarry of the Hartsteinwerk Werdenfels, South of Murnau (47°37′48″N; 11°09′00″E; from Weilheim to Murnau and Grafenaschau—29 km drive from Weilheim—then 1 km walking; Fig. 10) The large quarry (1.1 km diameter) was abandoned in 2000 due to environmental problems in the protected high moor area. Its strata dip steeply to the south and were deeply excavated, and the bottom of the quarry is now filled with groundwater. Visible at the northern wall of the quarry are the marly brownish basinal sediments of the Drusberg beds and the platform limestone of the Schrattenkalk member, both Early Cretaceous in age (Barrêmian–Aptian). The overlying Garschella formation

DAY 2. FLYSCH ZONE For a description, see Hesse (this volume, Chapter 5). DAY 3. HELVETIC NAPPES OF UPPER BAVARIA Helvetic units form large mountain ranges in the Swiss Alps and in the Allgäu Alps of southwestern Bavaria, but they occur only in isolated small windows along a narrow strip south of the Molasse zone in the sector of the TRANSALP line. The Helvetic units formed in a shallow shelf sea at the southern margin of the European continent, comprising sediments of Early Cretaceous (Barrêmian) to Paleogene (Lower Oligocene, Latdorfian) age. In the Paleogene, the Helvetic sedimentary environment was geographically separated in two basins by the Intrahelvetic High, present regionally as submarine high or island

Figure 9. Columnar section of the transition zone of the Lower Marine Molasse to the Lower Freshwater Molasse at the Scheibum. 1—Rupelian marine clays and marls (Tonmergelschichten); 2–8—Bausteinschichten, marine; 2—Late Rupelian marine clays and marls; 3—marls with thin coal seams; 4—marls and fine-grained sandstone; 5—sandstone and some marl; 7—alternating marl and sandstone; 8—gray conglomerate, topped by the Echelsbach-Scheibum coal seam of 25–35 cm; 9—alternating conglomerates and marls containing small coal seams; 10—reddish conglomerate of the Lower Freshwater Molasse; foreset beds indicate sediment transport to the north.

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(Aptian–Cenomanian) contained up to 60 m of a weatheringresistant glauconitic quartzite, that was mainly quarried. It served as a base for railroad tracks. The glauconitic quartzite is a condensed sandstone with quartz matrix and rich in fossils (belmnites, cephalopods, gastropods; Schwerd, 1996). Within this formation a piece of amber was found by a worker, and it is now preserved in the Museum of Murnau (Schlossmuseum). The formation is relatively rich in phosphorite along several horizons, which may indicate rising deepwater. Along the southern rim of the quarry, the Seewer limestone crops out. The deepwater limestone contains also centimeter-sized phosphorite nodules. Stop 3-2. Quarry Hinterhör (“Mühlsteinbruch”) (47°46′40″N; 12°09′18″E) From Stop 3-1 we drive to Altenbeuern, District of Rosenheim, Upper Bavaria (105 km). The abandoned quarry east of the village is hidden in the woods, and it belongs to one of Bavaria’s most beautiful geotopes. In the abandoned Quarry Hinterhör the equivalents of the “Roterz,” the “Schwarzerz,” and the “Nebengestein” (local name: “Mühlsandstein”) of the early Eocene southern Helvetic Kressenberg facies (Cuisian–Lutetian) are present. The latter is a graycolored, middle- to coarse-grained calcareous quartz-sandstone of fluvial origin, which was used to manufacture millstones from the year 1489 until 1860. Impressive traces of this ancient industry are still preserved. Stop 3-3. Quarry of the Südbayerische Portland-Zementwerk Gebrüder Wiesböck and Co. Gmbh, Southeast of Rohrdorf, District of Rosenheim, Upper Bavaria (7°47′20″N; 12°10′55″E; 4 km from Stop 3-2)

Three lithostratigraphic formations of the Helvetic group are present in the concrete quarry of Rohrdorf (Fig. 11): the northern Helvetic Adelholzen Formation and the Stockletten Formation, with intercalated slumps and turbiditic beds of the “Lithothamnium Limestone” (Buchholz, 1989). Based on differences in lithology, sedimentology and fossil contents (in particular large foraminifera of the genera Nummulites, Assilina, and Discocyclina) the Adelholzen Formation (lower Lutetian–lower Bartonian) is further divided into seven subunits (Fig. 12), from the bottom to the top these are: Nummulitenköpfl, Ramberg, Höllgraben, Schneckengraben, Fadengraben, Rohrdorf, and Spirka Members (Heyng, 2003). The lithological succession, with marly sands at its bottom and limestones and pelagic marls at the top, reflects a general trend of subsidence of the northern Helvetic sedimentary basin in the period of sedimentation of the Adelholzen Formation. This trend started in the lower Lutetian and it is continuing with sedimentation of the overlying Stockletten Formation (Hagn, 1981). Sharp lithological boundaries between the different members indicate a gradual deepening of the Helvetic sedimentary environment, probably reflecting a more step-by-step flow of tectonic processes in the course of the alpine orogenesis. The overlying Stockletten Formation of Priabonian age is dominated by pelagic sedimentation, and thus it mainly comprises marls and marly limestones rich in pelagic foraminifera (Globigerina). Several intensely bioturbated beds of blue-gray sandy marls with high contents of fine-grained glauconite and quartz are visible predominantly in the lower parts. In the upper parts (late Priabonian) of the Stockletten Formation several beds with varying thickness of the Lithothamnium Limestone are present (Figs. 13A, 13B), which reveal different facies types (slump facies, breccia facies, coarse- and fine-grained turbiditic facies; Buchholz, 1989) according to genesis. These beds were formed by event-sedimentation (slumps, turbidity currents), probably triggered by increasing tectonic disturbances in the course of the alpine orogenesis in the late Priabonian (Figs. 13C, 13D). The major part of highly diverse components, such as algal detritus, echinoderms, mollusks, solitary corals, and clasts of various lagoonal sediments, originate from an algal reef-complex with an associated lagoon to the north, situated at the northern margin of the Helvetic basin. From Rohrdorf we drive 78 km to the Kaiserhaus, Valepp Valley, for overnight lodging. The Kaiserhaus got its name because the Austro-Hungaric Emperor Franz Joseph and his famous wife Elisabeth (“Sissi”) stayed there many times, and visitors can still sleep in their beds. DAY 4. SECTION THROUGH THE NORTHERN CALCAREOUS ALPS

Figure 10. Position of the Helvetic Kögel in the Murnau Moor area. The Murnau syncline plunges to the west here and marks the southern margin of the Molasse zone north of the yellow line. Stop 3-1 is situated in a small Helvetic window marked by the two small parallel ridges in the moor.

Hint: The geological maps 1:50.000 of this area—sheet 89 (Angath) and sheet 120 (Wörgl)—can be downloaded for free from the Geologische Bundesanstalt Wien: http://www.geologie.ac.at/. The strata of the Northern Calcareous Alps were deposited, together with those of the Southern Alps, on the southeastern

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Figure 12. Geologic section of sediments outcropping in the Rohrdorf quarry (Adelholzen Formation; Stockletten Formation; Lithothamnium Limestone).

Northern Alps between Munich and the Inn Valley margin of the disintegrating Pangea in a hot and dry environment. Its post-Variscan sedimentary history starts with Late Permian to Early Triassic red fanglomerates (Verrucano) and sandstones or playa sediments with clay and evaporites, locally containing thick salt layers (Haselgebirge) that were mined since Neolithic times. Those salt layers acted as main detachment horizon during nappe transport. From Mid Triassic times on, a carbonate platform developed over a large area in a tropical tidal sea, which has no actual comparison. (Haas et al., 1995; Mandl, 1984). In general, deepwater facies occurs in the southeast, along the outer shelf to the Hallstatt-Meliata Ocean (Hallstatt facies). Water depth was shallow in the central parts, the depositional realm of the Inntal-, Lechtal- and Allgäu nappes. To the north, the terrestrial Germanian Keuper has some influence to the facies which becomes impure and sandy.

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In the Ladinian, a broad belt of isolated carbonate platforms formed. Shallow lagoons were surrounded by a reef belt and a fore-reef zone (Wetterstein limestone), where the reef interfingers with basinal sediments (Partnach beds). Algae (dasycladacea) are frequently found in the lagoonal, bedded Wetterstein limestone or dolomite. A short phase of sea-level drop correlates with the Raibl beds, mostly represented by dolomites, limestones, evaporites, cargneuls, sandstones and, occasionally, coal seams. The Raibl beds pile up under the Wamberg anticline where they were drilled at Vorderriss 1 for nearly 3000 m—mostly anhydrite and shales (Bachmann and Müller, 1981). They form another detachment horizon. The relief of the floor of the shelf platform was smoothed at the end of the Karnian stage and a broad tidal sea extended for the entire area. Up to 2000 m of Hauptdolomit were deposited in just 10 million years.

Figure 13. (A, B) Faulted beds of Lithothamnium limestone (fine-grained turbiditic facies) in the southern part of the quarry Rohrdorf. (C, D) slump facies of Lithothamnium limestone, northern area (grid square I 13 in Fig. 9). Photos: A. Heyng, August 2007.

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From now on the carbonate platform starts to break apart. Local basins form, e.g., the Seefeld basin north of Innsbruck. In its stagnant waters, countless fish are well preserved in the blackshales. Even tar has been distilled until recently for medical purposes. The basin was filled partly by turbidites and slump masses (Brandner and Poleschinski, 1986; Donofrio et al., 2003). Facies changes with basins (Kössen beds) and patch coral reefs (Rhaetian reef limestone) characterize the latest Triassic stage. After a short regressive phase, the Jurassic strata indicate rapid deepening due to tectonic extension of the whole area. Fissures in late Triassic rocks, slump masses, and deep basins below the calcite compensation depth (CCD) and submarine highs with condensed strata characterize this time span. Cherts and Late Jurassic aptychus limestones and Early Cretaceous aptychus marls were deposited in the Valepp area. Starting in Mid Cretaceous times, the Northern Calcareous Alps experienced a first compressive phase (Eoalpine phase) and even a low-grade metamorphism in its southeastern parts (Frey et al., 1999; Gawlick et al., 1994). In the Valepp area, the late Cretaceous Gosau transgresses over deeply eroded and folded Triassic rocks. The Valepp valley offers the most accessible and nearly straight section through most of the Northern Calcareous Alps. Its orientation is normal to the fold axes trend (Fig. 14). The Valepp River and the Brandenberger Ache deeply incised into Triassic dolomites and limestones that form two large anticlines of 10 km in wavelength and several kilometers in amplitude (Figs. 15A, 15B). The folding of the Guffert Anticline must have partly taken place earlier than Late Cretaceous during the Eoalpine phase. After restoring the post-Gosau thrusts along the Alpine front, the Gosau horizon becomes flat and attains a position close to sea level (Fig. 16). Stop 4-1. Gosau Transgression South of Pinegg (47°30′45″N, 11°53′53″E) From Kaiserhaus we drive to Pinegg and then continue for 2 km along the road to Brandenberg. At a roadcut, a transgressive surface of Gosau sandy limestones is exposed. It is marked by colonies of thick-shelled mussels (Rudists), which once settled along the rocky shore of the Gosau sea. The well-bedded Hauptdolomit below dips steeply (65°) to the south. Two hundred meters southward, a gently dipping thick-bedded, coarsegrained hybrid Gosau arenites contains plant remnants and phosphorite nodules. We then drive back to the Kaiserhaus and park. From here and for the rest of the day, we hike northward along the Valepp valley to the Erzherzog Johann Klause (overnight lodging) and beyond (total hiking distance ~12 km). Stop 4-2. Kaiserklamm (47°32′25″N; 11°55′00″E; Wetterstein anticline, Gosau unconformity) From the Kaiserhaus we hike 2 km on a small secured trail through the Kaiserklamm gorge. We cross through the

Wettersteinkalk, the oldest exposed Triassic member here, which forms a large anticline (Guffert anticline) with the Kaiserhaus in its center (Fig. 15A). At the entrance of the gorge, the limestone is massive and the gorge is extremely narrow, but it widens when the limestone becomes bedded. At the northern end of the gorge, red Gosau breccias lie in angular unconformity over 60° north-dipping Middle Triassic limestone. The breccia is monomict, with clasts derived from the Wetterstein limestone, and beds gently dipping to the west. More than 2000 m of Jurassic and Triassic sediments were eroded in Early Cretaceous times over the anticline in the Triassic rocks (Fig. 16). Stop 4-3. Trauersteg Bridge (47°33′03″N; 11°54′14″E; northern limb of the Gosau syncline) We already crossed the small Gosau basin, and to the west of the bridge, purple-red sandstones and fine conglomerates dip 50° southward. Some 50 m behind the outcrop, a subvertical wall of gray Hauptdolomit marks the faulted contact to the Gosau sediments here. The sedimentary succession records deepening, from alluvial fan deposition (cross bedding, sand lenses, and channel fillings) of a continental environment, to beach-derived conglomerates and shallow-marine hummocky cross-bedded sandstones (Sanders, 1998) (compare introduction to Day 6 and Stop 6-1). Stop 4-4. Bridge over the Brandenberger Ache (47°33′17″N, 11°53′38″E; 1 km NNW of Stop 2) We cross the faulted contact of Gosau beds and Hauptdolomit and discover an anticline only after careful observation. The Gosau beds are cut along a northeast-striking, steep fault. Red, angular, poorly sorted clasts mark the base of the contact. Striations gently plunging to the west indicate strike-slip movements. From here we move for about 2 km farther to the north in gently northward-dipping Hauptdolomit until, after passing a gentle syncline, the thick brittle rocks are heavily fractured and crushed into a tight overturned anticline. We cross through the overturned limb for another 500 m and find the still overturned Plattenkalk, Kössen beds (covered by vegetation along the road) and encounter the massive Rhetian reef limestone. Liassic red limestones and cherts can be found in the scree, but are not exposed along the road. The aptychus limestones that follow are intensely sheared due to the Achental thrust, which crops out in this position. From here northward we pass the Neokom Aptychenschichten, Cretaceous marls and marly limestones in upright position. Stop 4-5. North of Erzherzog Johann Klause (47°34′53″N, 11°53′18″) We follow the forest road northward and cross the Marchbach on a high bridge, built over the contact between Cretaceous and Jurassic aptychus beds. The Jurassic beds show tight overturned asymmetric folds of small wavelength, indicating top to north movement along the Achental thrust.

Northern Alps between Munich and the Inn Valley Stop 4-6. Reichsteinalm (47°35′28″N, 11°54′05″E) We continue upward through folded Malm aptychus beds and reach the base of the Jurassic strata 200 m beyond the Reichsteinalm. At this locality, the Jurassic succession is extremely incomplete. Within a few meters, the following succession is observed: Rhaetian reef limestone; red Hierlatz limestone; nodular Adnet limestone; white, thin-bedded limestones with radiolarians; red nodular limestone (?Klaus limestone, Doggerian); and red and gray slumped limestones of the Ammergau-Formation.

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The cherts and cherty limestones show nice slump folds and disrupted strata at the edge of a slump horizon, which extends for more than 10 km to the east. In red Liassic limestones, a set of strike-slip faults is indicated by fiber crystals of calcite. A massive light-gray Rhaetian reef limestone follows to the north and forms a steep cliff. It is cut by fissures, which are filled with red Jurassic crinoidal limestones and red marls, indicating Early Jurassic extension. Within the reef limestones, corals may be seen both in life position and reworked. Around the corner, brownish Kössen marls and limestones are remarkably well

Figure 14. Geological sketch map of the Valepp Valley (2 km grid). Legend: 1—Wettersteinkalk, massive to thick bedded limestone and dolomite, (Ladinian); 2—Raibler Schichten, evaporates, cargneuls, and sandstones (Carnian); 3—Hauptdolomit, thick or medium bedded dolomite, up to >2000 m in thickness (Norian); 4—Plattenkalk, well-bedded limestone on top of the Hauptdolomit (Rhaetian); 5—Kössen beds, marls, and thin lumachelle limestone beds alternating; 6—Late Rhaetian reefal limestones with corals (thecosmilia clathrata) and reef detritus limestone; 7—nodular limestone or crinoid limestone, red or gray with chert, locally cherts (Liassic); 8—Aptychenschichten, light-gray aptychus limestones and marls, well bedded (Malm); 9—Neokom Aptychenschichten, marls, limy marls, spotted marls (Early Cretaceous); 10—Gosau formation, red or gray breccia, conglomerate, sandstone and clay; south of the Kaiserhaus: glauconitic sandy limestones with rudists and glauconite limestones and horizons full of thick-shelled gastropods (actaeonella).

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Figure 16. Restoration of the Northern calcareous Alps to pre Gosau tectonic configuration. The Guffert anticline is clearly a Pre-Gosau structure. Reconstruction by means of 2DMove software (Midland Valley Inc., Glasgow).

Figure 15. (A) Cross section through the northern part of the Valepp gorge. (B) Cross section through the southern part of the Valepp gorge. For legend of formation numbers, see Figure 14.

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Northern Alps between Munich and the Inn Valley exposed. Continuing into the Plattenkalk, again signs of slumped material are visible, showing the general tectonic activity at the end of Triassic and beginning of the Jurassic era (Schlager and Schöllnberger, 1973). From here, we walk back to the Erzherzog Johann Klause for overnight lodging. DAY 5 We leave the Valepp, study the Inneralpine Molasse, and proceed to the Muttekopf area. In the eastern Inn Valley the remains of the wedge-top of the peripheral Alpine foreland basin (Molasse basin) are preserved (Fig. 17). The Oligocene rocks of the Inn were also termed “Inneralpine Molasse” (e.g., Fuchs, 1976). The Oligocene sediments are preserved in a syncline-anticline system over 50 km of lateral extent along the Inntal shear zone, which is a major fault system in the Eastern Alps with approximately 40 km of sinistral offset (Ortner et al., 2006). The sedimentary succession of the “Inneralpine Molasse” is closely related to the Subalpine Molasse (Ortner and Stingl, 2001): Eocene–Lower Oligocene carbonates and marls record deepening from shallow-marine to pelagic conditions. Increased deposition of siliciclastic material in pro-delta turbidites in the late early Oligocene shows progradation of a delta system, until late Oligocene fluviatile conglomerates indicate a continental environment. The Inntal shear zone is a major sinistral ENE-striking fault that was active during post-collisional shortening from the early Oligocene to the late Miocene, and it is probably still active (Ortner, 2003; Ortner et al., 2006; Reiter et al., 2007). The Oligocene and Miocene activity was tied to the exhumation of the Tauern Window in the internal Eastern Alps. Ductile thickening, stacking and folding in the Tauern Window was accompanied by E-directed stretching. The Inntal shear zone was the northern limit of east-directed flow of material (Figs. 17, 18). The analysis of brittle structures along the Inntal shear zone shows sinistral transpression (Ortner, 2003; Ortner et al., 2006). The TRANSALP deep seismic line crosses the Inn Valley near the western end of the Oligocene deposits. A key feature, recognized already in the earliest interpretations of the TRANSALP seismic data, is the south-dipping reflections in the depth range between 4000 and 10,000 m at CDP 5000–5200 (number 6 in Fig. 18), which continue to great depth (e.g., TRANSALP Working Group, 2002). These are believed to be related to Miocene crustal stacking in the Tauern Window, which is kinematically connected to the Inntal shear zone (see above). The apparent continuation to the surface is a south-dipping zone across which seismic reflectivity decreases upward (Brixlegg thrust, number 8 in Fig. 18). At the surface, the seismic contrast coincides with the contact between the Northern Calcareous Alps and the Greywacke zone, which originally was the low-grade metamorphic basement of the Northern Calcareous Alps. The Greywacke zone was emplaced onto the Northern Calcareous Alps by the Brixlegg thrust. Oligocene sediments

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preserved on the hanging wall of the Brixlegg thrust (Fig. 18) preclude major post-Oligocene vertical offset; therefore the Brixlegg thrust is interpreted as a Paleogene out-of-sequence thrust (Ortner et al., 2006). Stop 5-1. Oberangerberg and Volldöpp (47°27′10″N/11°53′33″E) The section Voldöpp lies along a small road from the northeastern part of Kramsach to the Oberangerberg. In the morning, we walk back to the Kaiserhaus (10 km hiking) and proceed by car 15 km down to the Inn Valley to study the Inneralpine Molasse at Volldöpp. The section Voldöpp is designated as type section for the Oberangerberg Formation, one of the sedimentary units of the Inneralpine Molasse. A succession of typical continental Molasse-type conglomerates crops out in the Oberangerberg area (Fig. 17). The dominating lithofacies types present are component-supported coarse conglomerates with or without normal grading, with imbricated components. Occasionally planar cross-bedding is observed in the topmost portion of conglomerate beds. Horizontally laminated sandstones to siltstones, and occasionally ripple cross-bedding, interrupt the conglomerate sedimentation. The coarse conglomerates of a slightly sinuous, braided river system (Krois and Stingl, 1991) indicate perennial high-energy runoff. The main facies elements are channel fills with longitudinal bars and large-scale ripples. The scarcity of overbank fines (levees, crevasse splays and floodplain deposits, mud-filled abandoned channels) supports the model of a highly mobile channel system. Transport directions derived from imbricate clasts and cross-bedding are oriented from NW-W to SE-E. Biostratigraphic dating of the Oberangerberg Formation is debatable. Plant fossils (Cinnamomum cf. scheuchzeri and C. cf. spectabila Heer) not indicate an Oligocene to Miocene age (Hamdi, 1969). Only an interpretation of the succession based on sequence stratigraphy provides some evidence for the lower boundary of the Oberangerberg Formation to be near the base of the Chattian. As the first pebbles from rocks of the Bernina, Err, and Julier nappes in the Upper Engadine Valley appear in the Aquitanian of the Molasse zone, and are lacking in the Oberangerberg Formation, the erosional upper boundary of the Inneralpine Molasse must still be within the Oligocene. Modeling of the thermal history based on vitrinite reflectance data in the Häring-Oberangerberg area resulted in the prediction of a total thickness of 1300 m of eroded sediment (Ortner and Sachsenhofer, 1996). More than 1000 m thickness of the Oberangerberg Formation is preserved north of the Kaisergebirge (Ortner and Stingl, 2001). Stop 5-2 From Volldöpp we drive via Innsbruck to Hoch-Imst (106 km), and ascend by cable lift to the Alpjoch (2100 m); from here we hike along a narrow mountain trail, which cuts well exposed Gosau sediments. We reach the Muttekopf Hütte (1934 m) after 1 hour of hiking.

Figure 17. Geological sketch map of the Inneralpine Molasse of the Inn valley (adapted from Ortner et al., 2006). Diagrams: Miocene brittle deformation of the Inntal shear zone from data measured in 14 stations in Oligocene rocks. Two examples from stations at the Oberangerberg are given in diagrams 1 and 2. PDZ—principal displacement zone, R—Riedel shear; a—typical fault pattern observed in data sets associated with sinistral shearing across the Inntal shear zone with oblique reverse slip on Riedel and Anti-Riedel shears; b—contour plot of poles to all fault planes measured associated to sinistral shearing across the Inntal shear zone, indicating that the majority of fault planes is subvertical to steeply south-dipping; c—contour plot of all slip lineations measured associated to sinistral shearing across the Inntal shear zone, indicating that slip across the Inntal shear zone was essentially horizontal; d—contour plot of all compression and tension axes, which were calculated using an angle between fault plane and P-axis of 30°. The maximum densities give approximate mean orientations of NNE and ESE for σ1 and σ3, respectively, irrespective of complexities regarding the boundary conditions of shearing.

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Figure 18. The TRANSALP seismic section from CDP 3600 to CDP 5300 (adapted from Ortner et al., 2006). Bottom: Migrated seismogram (Lüschen, 2002, personal commun.). Numbers refer to explanations in text. Top: Interpretation of the seismogram. Interpretation of Northern Calcareous Alps north of the Inn valley taken from Auer and Eisbacher (2003). Black circles—apatite fission-track ages by Most et al. (2003); gray circles—apatite/zircon fission-track ages by Angelmaier et al. (2001); white circles—apatite fission-track ages by Grundmann and Morteani (1985).

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DAY 6. MUTTEKOPF GOSAU: CONIACIAN TO ?PALEOCENE SEDIMENTATION IN A THRUSTSHEET–TOP BASIN—THE GOSAU GROUP OF THE MUTTEKOPF AREA Due to the high Alpine character of the excursion area, the sequence and selection of stops during this part of the field trip might change according to weather conditions. The Gosau Group is an Upper Cretaceous, synorogenic carbonatic-siliciclastic sedimentary succession, which unconformably overlies deformed Triassic to Jurassic rocks (Wagreich and Faupl, 1994; Sanders et al., 1997). Generally, deposition started in a terrestrial environment, which subsided to neritic conditions (Lower Gosau Subgroup). After a pronounced subsidence event, deep marine conditions prevailed (Wagreich, 1993), and the Upper Gosau Subgroup was deposited. The relationship between the contracting orogenic wedge and the coeval major subsidence is not well understood at present, and different models have been put forward (e.g., Wagreich, 1993; Froitzheim et al., 1997). The younger, deep marine part of the sedimentary succession (Upper Gosau Subgroup; Wagreich and Faupl, 1994) was deposited during transport of the thin-skinned nappes of the Northern Calcareous Alps over tectonically deeper units (Fig. 19). In the Muttekopf area, internal deformation of the moving nappe led to the formation of fault-propagation folds in the subsurface of the Gosau sediments and hence to the formation of several (progressive) angular unconformities within the sedimentary succession (Ortner, 2001; Figs. 19, 20). Sedimentation of the Lower Gosau Subgroup in the Muttekopf area began near the Coniacian-Santonian boundary with deposition of a few meters of braided-river deposits followed by an alluvial fan succession up to 300 m thick that is restricted to the easternmost part of the Gosau outcrops (Plattein). Upsection, conglomerates with perfectly rounded clasts representing a transgressive lag are intercalated below thick neritic deposits (“Inoceramus” marl unit). The siltstones to sandstones of the “Inoceramus” marl unit contain a variety of marine fossils that were used to date the rocks to the Coniacian–Santonian boundary (Ampferer, 1912; Leiss, 1990). The deep marine Upper Gosau Subgroup mass transport complex is divided into three sequences (Ortner, 1994a, 1994b, 2001; Fig. 20): All three sequences are dominated by vertically stacked, upward-fining, laterally continuous, unchannelized conglomerates and sandstones that display little to no lateral variation in facies. The boundary between Sequence 2 and 3 is the Rotkopf unconformity (Fig. 20). The boundary between Sequence 1 and Sequence 2 is the base of the 2nd fining-upward sequence, which is significantly below the most prominent unconformity in the area (Schlenkerkar unconformity, outside the field trip area). The three sequences can also be distinguished by clast- and heavy-mineral compositions (Ortner, 1994a, 1994b). The age of the deposits of the Upper Gosau Subgroup is poorly constrained. The turbiditic marls occasionally contain

corroded nannoplankton and rare foraminifera. According to these data, the upper part of Sequence 1 has an age of Late Santonian to Early Campanian or younger, Sequence 2 is Early Campanian to Early Maastrichtian or younger, and Sequence 3 is Late Maastrichtian to ?Danian (Oberhauser, 1963; Dietrich and Franz, 1976; Lahodinsky, 1988; Wagreich, 1993–1995, personal commun.). The deposits are organized in facies associations, which are related to proximal or distal sedimentation in relation to a sediment source. Each sequence has a proximal facies association at the base and a distal facies association at the top. The associations are: (1) megabreccia association, made of fluidized mud-rich conglomerates, slabs of other facies associations of the Upper Gosau Subgroup, and house-sized clasts of Triassic rocks; (2) thick-bedded turbidite association, with m-thick mudrich conglomerates, grading into sandstones that often display complete or amalgamated Bouma-sequences, which in turn grade into m-thick yellowish to light gray turbiditic marls; and (3) thin-bedded turbidite association, with cm-thick sandstones (Bouma Tb or Tc intervals) alternating with dark-gray to black calcite-free marls, which are sometimes laminated; thick conglomerate beds are irregularly intercalated. The occurrence of calcite-free marls in the most distal facies association and a bathyal trace fossil association (Gröger et al., 1997) led to the conclusion of sedimentation below (a local) CCD. The Upper Gosau Subgroup of Muttekopf was deposited during transpressive fold growth (Ortner et al., 2010). Kilometric folds are segmented by and kinematically linked to dextral tear faults. In the segments between the tear faults, depositional units overlap the folds, but clear wedging toward the anticlines can be observed. Growth strata above tear faults show combined rotational offlap-onlap-overlap, caused by changes in strike instead of changes in dip (l.c.). The principal unconformity connects to the tear fault. Post-depositional surface to subsurface sediment remobilization is an important aspect of the Gosau Group of Muttekopf, which contributed substantially to the observed sediment geometries (Ortner, 2007). Active shortening and fold growth of km-scale folds stimulated continuous surficial sediment remobilization (slumping), but also tectonic deformation of soft sediment. Changing rheologies of conglomerates, sandstones, and marls during increasing lithification caused a vast array of structures related to tectonic deformation, whereas slump-related structures are restricted to the earliest stages of lithification. Intrastratal fluidization of conglomerates is an important process accompanying downslope creeping of sediment packages. Fluidization is commonly associated with downward and upward injection of conglomerate into neighboring deposits.

Figure 19. Geologic sketch of the Gosau outcrop at Muttekopf and location of Stops 1–8 (modified from Ortner and Gaupp, 2007). Growth unconformities: a—Schlenkerkar unconformity; b—Fundais unconformity; c—Rotkopf unconformity; d—Alpjoch unconformity. Inset A: Location of the Muttkopf outcrop in Austria. Inset B: Tectonic position of the Gosau Group at Muttekopf on the thrust sheets of the western Northern Calcareous Alps.

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Figure 20. Panoramic view of the excursion area at Muttekopf from the east, showing the three sequences and the tectonic structure within the Upper Gosau Subgroup (modified from Ortner and Gaupp, 2007). Stops 2–8 are indicated.

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Northern Alps between Munich and the Inn Valley Stop 6-1. ?Coniacian to Santonian Succession of the Lower Gosau Subgroup and Transition to the Upper Gosau Subgroup (50 m in elevation above and along the path from Muttekopfhütte to Platteinwiesen, 600 m ENE of Muttekopfhütte) Stop a. Clast supported, partly matrix-free conglomerates with crude trough stratification, sieve deposits with red, sometimes laminated mud and pebbles exclusively composed of Hauptdolomit Formation Conglomerates with perfectly rounded dolomite clasts and chert found as blocks on the way to Stop b. Stop b. Fossiliferous foliated siltstones (“Inoceramus” marl unit) in contact with sandstones and conglomerates of the Upper Gosau Subgroup. View to the west of refolding of fluidized layer by N-vergent folds. Points of discussion will be the facies and environment of conglomerates, which are interpreted to be deposited on the upper- to mid-fan of a semiarid alluvial fan (Haas, 1991), and the mechanism of subsidence from subaerial to deep marine conditions in a contracting thin-skinned foldand-thrust belt. Stop 6-2. Succession at the Transition from Sequence 1 to Sequence 2 of the Upper Gosau Subgroup (Locality: along the Malchbach, 300 m SE and S of Muttekopfhütte.) Stop a. Thin-bedded turbidite association, cm-thick silt- to sandstones alternating with black dolomitic marls, overlain by a nonlayered conglomerate bed with flame structures and minor normal faults at the base; diffuse internal shear planes within the conglomerate. Stop b. Thick-bedded turbidite association, dm- to m-thick sandstones alternate with m-thick yellowish marls overly a matrix rich coarse-grained conglomerate. Stop c. Giant block of Upper Rhaetian limestone within a conglomerate bed of Sequence 2. Karstic dikes on the surface of the block. We discuss the bathymetry of the Upper Gosau Subgroup and the mechanism of deposition of coarse-grained beds (highdensity turbidites versus debris flows). Stop 6-3. Fluidized Layers and N-Vergent Folds in ThickBedded Turbidites of Sequence 2 (150 m WSW of Muttekopfhütte) Sediment transport directions are indicated by flute casts and tool marks at the base of sandstone beds. Isoclinally folded sandstone beds in a conglomerate matrix show plastic deformation within the sandstone beds. Shingle-like stacking of sandstone slabs and semi-brittle deformation within N-vergent folds with stacking of horses in the forelimb of the fold and local plastic deformation arise questions about tectonic deformation versus gravity-induced deformation. Surface or subsurface fluidization and significance of fold axes within fluidized layer will be discussed.

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Stop 6-4. Giant Blocks (“Blaue Köpfe”) in Megabreccia Layer of Sequence 2 (2300 m, at junction of trails 600 m S of the Muttekopf summit) Giant blocks of Upper Rhaetian limestone projecting out of a chaotic breccia layer of the Megabreccia association. The mode of sediment transport of giant blocks will be discussed. Stop 6-5. Sequence 3 Succession in the Core of the Muttekopf Syncline (Locality: 2460 m, along the path to Pleisjoch, and [optional] on the way scrambling up to the Rotkopf [2692 m].) We observe conglomerates containing abundant brick-red marl intraclasts, injection of marl clasts by conglomerate dykes, and systematic sandstone-filled joints in coarse sandstone. White calcite-rich marls alternating with m-thick sandstones occur in the hinge of the syncline. Panoramic view of the Muttekopf syncline toward the west from the Rotkopf summit, submarine topography around the Große Schlenkerspitze, anticlinal crest within Gosau deposits east of Schlenkerspitze. We discuss the origin of overpressure in breccia beds and the geometry of syntectonic sediments in the vicinity of the Schlenkerspitze. Stop 6-6. Rotkopf Unconformity at Pleisjoch (2560 m) and Pleiskopf (2580 m) Erosional steps at the Rotkopf unconformity leave two possibilities: Is the Rotkopf unconformity a growth unconformity or an erosional unconformity? In the sediments a fluidization of conglomerate produces flame structures and injection of conglomerate into sandstone. A channel-like geometry of Sequence 3 may be seen from the Pleiskopf. Stop 6-7. Hydroplastic Deformation of Conglomerates (Locality: 50 m S of the saddle located 340 m west of the Hinteres Alpjoch.) Meter-scale asymmetric linear flames of marl into conglomerate are found here, together with a conglomerate sill with clasts up to 20 cm in diameter intruded downward into sandstone. Here are some questions that can be addressed at this locality: Are the linear flames an expression of dewatering, or are these structures actually mullions formed during beddingparallel shortening at a rheologic interface in wet sediment? Why does the conglomerate intrude downward, when lithostatic pressure decreases upward? Stop 6-8. Panoramic View of the Hinteres Alpjoch from the Vorderes Alpjoch, Mountain Station of the Chairlift (2121 m) A change of the geometry of the Alpjoch syncline in Sequence 2 can be observed from here. The tight chevron fold in the outer layers grades into an open fold in the inner layers (Fig. 20, left). In addition, there is a rotative onlap across the Alpjoch unconformity. To the left, the tectonic contact of the Larsenn klippe to the Gosau sediments can be seen (Fig. 20). The

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relevance of geometric and mechanic fold models for the geometry of syntectonic sediments and unconformities related to fold growth will be discussed here. DAY 7 From Muttekopf descend to Imst, then drive back to Munich via the Fernpass and Garmisch-Partenkirchen (150 km). ACKNOWLEDGMENTS Particular thanks are due to Sara Carena for many helpful suggestions and critical remarks. We wish to thank Midland Valley Exploration Ltd. (Glasgow) for providing the balancing software 2DMove for free. REFERENCES CITED Ampferer, O., 1912, Über die Gosau des Muttekopfs: Jahrbuch der Geologischen Reichsanstalt, Wien, v. 62, p. 289–310. Angelmaier, P., Dunkl, I., and Frisch, W., 2001, Vertical movements of different tectonic blocks along the central part of the TRANSALP traverse: Constraints from thermochronologic data, in Brandner, R., Konzett, J., Mirwald, P., Ortner, H., Sanders, D., Spötl, C., and Tropper, P., eds., 5th Workshop of Alpine Geological Studies, Obergurgl, Abstracts: Geologisch-Paläontologische Mitteilungen der Universität Innsbruck, v. 25, p. 17–18. Auer, M., and Eisbacher, G.H., 2003, Deep structure and kinematics of the Northern Calcareous Alps (TRANSALP profile): International Journal of Earth Sciences, v. 92, p. 210–227. Bachmann, G.H., and Müller, M., 1981, Geologie der Tiefbohrung Vorderriß 1, (Kalkalpen, Bayern): Geologica Bavarica, v. 81, p. 17–53. Bachmann, G.H., and Müller, M., 1992, Sedimentary and structural evolution of the German Molasse Basin: Eclogae Geologicae Helvetiae, v. 85, p. 519–530. von Blanckenburg, F., and Davies, J.H., 1995, Slab breakoff—A model for syncollisional magmatism and tectonics in the Alps: Tectonics, v. 14, no. 1, p. 120–131, doi:10.1029/94TC02051. Brandner, R., and Poleschinski, W., 1986, Stratigraphie und Tektonik am Kalkalpensüdrand zwischen Zirl und Seefeld, Tirol: Jahresbericht Mitteilungen Oberrheinischer geologischer Verein: Neue Folge, v. 68, p. 67–92. Buchholz, P., 1989, Der Lithothamnienkalk Südostbayerns. Sedimentologie und Diagenese eines Erdgasträgers: Geologica Bavarica, v. 93, p. 97. Dietrich, V.J., and Franz, U., 1976, Ophiolithdetritus in den santonen Gosauschichten (Nördliche Kalkalpen): Geotektonische Forschungen, v. 50, p. 85–109. Donofrio, D.A., Brandner, R., and Poleschinski, W., 2003, Conodonten der Seefeld-Formation: ein Beitrag zur Bio- und Lithostratigraphie der Hauptdolomit-Plattform (Obertrias, westliche Nördliche Kalkalpen, Tirol): Geologisch-Paläontologische Mitteilungen der Universität Innsbruck, v. 26, p. 91–107. Doppler, G., Fiebig, M., and Meyer, R., 2002, Erläuterungen zur Geologische Karte 1:100,000 der Planungsregion Ingolstadt, Bayerisches Geologisches Landesamt, 172 p. Eisbacher, G., and Brandner, R., 1996, Superposed fold-thrust structures and high-angle faults, northwestern Calcareous Alps, Austria: Eclogae Geologicae Helvetiae, v. 89, no. 1, p. 553–571. Frey, M., Desmons, J., and Neubauer, F., 1999, Metamorphic maps of the Alps: Map of Alpine metamorphism: Schweizerische Mineralogische und Petrographische Mitteilungen, v. 79, no. 1. Frisch, W., Kuhlemann, J., Dunkl, I., and Brügel, A., 1998, Palinspastic reconstruction and topographic evolution of the Eastern Alps during late Tertiary tectonic extrusion: Tectonophysics, v. 297, p. 1–15, doi:10.1016/ S0040-1951(98)00160-7. Froitzheim, N., Conti, P., and Van Daalen, M., 1997, Late Cretaceous synorogenic low-angle normal faulting along the Schlinig fault (Switzerland,

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The Geological Society of America Field Guide 22 2011

Field trip to the Tauern Window region along the TRANSALP seismic profile, Eastern Alps, Austria Bernd Lammerer* Ludwig-Maximilians-Universität, Department für Geo- und Umweltwissenschaften, Luisenstr. 37, 80333 München, Germany Jane Selverstone Department of Earth & Planetary Sciences, University of New Mexico, Albuquerque, New Mexico 87131-0001, USA Gerhard Franz Department of Applied Geosciences, Technical University of Berlin; 13355 Berlin, Germany

ABSTRACT During the TRANSALP project, deep seismic surveys and accompanying geophysical and geological projects were carried out to better understand the deep structure of the Eastern Alps south of Munich. The TRANSALP field trip series roughly follows the route in three parts: the Tauern Window, the Northern Calcareous Alps and its foreland, and the Southern Alps including the Dolomites. In this Tauern Window field trip, we will visit most of the geologically important sites along the middle part of the traverse or in its vicinity. The main topics covered in the Tauern Window will be the early Alpine paleogeographic situation on an extending European continental margin, Alpine nappe stacking and ductile rock deformation, metamorphism, uplift modes and exhumation, lateral escape, and the Brenner normal fault.

INTRODUCTION The Alps are the best-studied mountain range on Earth, following more than two hundred years of detailed geological and mineralogical exploration. The role of nappe tectonics in the Alps was described more than a century ago (Bertrand, 1884; Termier, 1904, discussed by Tollmann, 1981, and Trümpy, 1991). During the past decades, much progress has come from geophysical surveys, large tunnel projects and deep wells. New insights have also come from modeling the evolution of orogenic wedges,

cosmogenic surface dating, and measuring the velocity field by Global Positioning System and Very Long Baseline Interferometry techniques. In recent decades, several research programs were carried out to better understand the deep structure of the Alps that, finally, led to a new tectonic map (Schmid et al., 2004). The FrenchItalian ECORS-CROP Profile (Etudes Continentale et Océanique par Reflection et Refraction Sismique, and Crosta Profonda) and the Swiss NFP20 (Nationales Forschungs—Programm No. 20) provided three seismic sections through the Western Alps (Roure

*[email protected] Lammerer, B., Selverstone, J., and Franz, G., 2011, Field trip to the Tauern Window region along the TRANSALP seismic profile, Eastern Alps, Austria, in Carena, S., Friedrich, A.M., and Lammerer, B., eds., Geological Field Trips in Central Western Europe: Fragile Earth International Conference, Munich, September 2011: Geological Society of America Field Guide 22, p. 101–120, doi:10.1130/2011.0022(07). For permission to copy, contact [email protected]. ©2011 The Geological Society of America. All rights reserved.

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et al., 1996; Pfiffner et al., 1997; Schmid et al., 1996). The most recent effort was undertaken by the German, Austrian, and Italian TRANSALP program, which resulted in a 300-km-long continuous geophysical section through the Alps between 1998 and 2001 (Fig. 1). Vibration and explosion seismics were carried out along the main traverse and the cross lines, accompanied by gravimetric and teleseismic tomographic studies (Lippitsch et al., 2003; Kummerow et al., 2004; Lüschen et al., 2004; Ebbing et al., 2006; Lüschen et al., 2006; Zanolla et al., 2006). The Eastern Alps differ from the Western Alps in several respects: (1) They are covered almost completely by the thick Austroalpine nappes (Fig. 1), whose basement was affected by the Pan-African orogeny. Due to long exposures at or near the surface of Pangaea, the basement rocks are strongly oxidized. Starting in the Permian, progressive marine flooding proceeded from east to west until the entire Austroalpine realm was covered. This transgression resulted in carbonate platform deposits up to 5 km in thickness in the time span of middle and late Triassic (Southern Alps, Dolomites, Northern Calcareous Alps, Brenner Mesozoic area, etc.). In contrast, only a relatively thin veneer of sediment was deposited on the European plate during the entire Triassic (Helvetic nappes of Switzerland and the Eastern Alps, Tauern Window). In the Austroalpine nappes, there are two major gaps through which lower tectonic units emerge. In the Engadine window, calc-mica-schists and ophiolites of oceanic origin occur. In the Tauern Window, basement and cover rocks of the margin of the European plate are also exposed beneath the oceanic nappes. The Tauern Window is therefore a unique tectonic structure in the Alps. (2) The Pusteria Fault—a suspected eastern continuation of the Insubric line—is displaced by ~60 km to the north along the northeasterly trending Judicarie Fault (see Fig. 3). This displacement reflects deep penetration of the Adriatic plate into the eastern Alps (Adriatic indenter). Lateral extrusion of the Tauern Window and the Austroalpine nappes and backthrusting along the Val Sugana Fault are related to this indentation. (3) Within the Eastern Alps, two orogenic wedges are developed: one to the north, as in the Western Alps, and a second, later one to the south (Dolomites, Southern Alps, Belluno basin) that is actively growing today, as indicated by seismic activity along the southern rim of the Alps (e.g., Friuli earthquake of 1976, with ~1,000 victims; Carulli and Slejko, 2005). In the western Alps, an active retrowedge is missing to the south or is only developed in a narrow strip, as in the Orobic Alps and the Maritime Alps (Castellarin and Cantelli, 2000). (4) Geophysical studies of mantle tomography show another major difference: In the Western Alps, the presumed subduction is directed to the east (southwestern Alps) or to the south (Swiss Alps). The subducting mantle is con-

nected to the European plate. In the Alps east of the Judicarie Fault, however, the high-velocity zone that reflects recently subducted mantle is displaced to the northeast and appears to be connected to the Adriatic plate. The direction of subduction must have reversed (Lippitsch et al., 2003; Kissling et al., 2007). Key paleogeographic and tectonic processes responsible for the evolution of the Eastern Alps include the following: (1) Long-lasting subsidence from the Mid Permian on led to a marine transgression that started in the east and proceeded westwards until Middle Triassic times. In Middle Jurassic times, the Penninic-Ligurian Ocean formed as a small side branch of the North Atlantic, during the disintegration of Pangaea, between Africa (including the Adriatic plate) and Europe. There was no connection with the great Tethys Ocean and the small Hallstadt and Meliata Oceans in the far east (Channell and Kozur, 1997; Stampfli and Borel 2002; Handy et al., 2010). Extensional tectonics and acidic volcanism (Permian quartz porphyries) preceded the opening. During the opening, subsidence accelerated and submarine basins and swells evolved (Ortner and Gaupp, 2007; Ortner et al., 2008). The consequences of this subsidence will be seen on the TRANSALP 3 field trip to the Dolomites, Southern Alps. (2) The spreading of the Alpine Tethys (“Penninic-Ligurian and Valais Ocean”) was extremely slow, allowing substantial cooling of the exposed mantle, and only a small amount of new oceanic crust was formed along an “ultraslow spreading ridge” or magma-poor rifted margin (Schaltegger et al., 2002). Sub-continental mantle was hydrated and metasomatically altered to serpentinites or ophicalcites. It was exposed at the seafloor over vast areas, covered by disintegrated remains of continental crust in tectonic contact (“extensional allochthons”) and newly formed sediments. (3) Contemporaneous with the opening of the North Atlantic and the Penninic-Ligurian Ocean, a subduction zone was active along the complex and poorly understood eastern margin of Pangaea. In Late Cretaceous times, the Adriatic plate experienced the Eoalpine orogeny during the closure of the small Hallstatt-Meliata Ocean in the east (Neubauer et al., 2000; Schmid et al., 2008). Cretaceous eclogite-facies metamorphism and deformation, deep erosion, and deposition of flysch and wildflysch sediments (“Gosau sediments”) witness this early stage, which is detectable only in the Austroalpine nappes (Ortner and Gaupp, 2007). We will trace this history on the TRANSALP 2 field trip to the Northern Calcareous Alps. (4) During the main Paleogene phase of the Alpine orogeny, the Alpine Tethys Ocean was consumed and the Adriatic plate collided with the European plate. The subduction direction was to the south during this phase. Because the European plate was welded to the oceanic lithosphere, it was drawn under the Adriatic plate until buoyancy and

Figure 1. Tectonic map of the Alps. a—Austroalpine basement nappes (AA) and South Alpine basement; b—Austroalpine cover nappes and South Alpine cover; c—European basement; d—European cover nappes; e—oceanic nappes and ophiolites of the Piemontese–Valais Oceans (P); f—Briaçonnais terrane (Br); g—Tertiary intrusives and volcanics; h—molasse sediments, in yellow: folded; i—faults: strike slip (solid line), thrusts (dotted line); EW—Engadine Window; TW—Tauern Window; TAL—TRANSALP Line; B—Brenner normal fault; K—Katschberg normal fault; Ins—Insubric dextral fault; J—Judicarie sinistral fault; P—Pusteria dextral fault; SEMP—Salzach-Ennstal-Mariazell-Puchberg sinistral fault.

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Figure 2. Cross section along the TRANSALP line. The Eastern Alps are characterized here by a thin-skinned wedge in the north (left) and a thick-skinned wedge to the south and the imbricate and upthrust Tauern Window in the center. Lower crustal wedges led to thickening of the South Alpine crust. The actual dip of the Adriatic mantle is to the northeast.

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friction brought this process to a halt. Abraded sediments of the Alpine Tethys (Bündnerschiefer, Rhenodanubian flysch) and remnants of oceanic lithosphere (e.g., Glockner Nappe in the Tauern Window) overthrust the continental margin of the European plate. The crystalline basement of the Adriatic plate and its overlying sediments (Austroalpine nappes) were in turn thrust over the oceanic nappes, which were completely buried. An orogenic wedge developed to the north and northwest by stacking of Austroalpine, Penninic, and Helvetic nappes. The edge of this nappe pile crops out in the Eastern Swiss Alps and along the northern edge of the Eastern Alps, though only as fragments of the sedimentary cover. The nappe stack will be crossed during this field trip. (5) Before about 30–40 Ma ago, the subducting oceanic lithosphere broke off and sank into the mantle (von Blanckenburg and Davies, 1995). In response to the sudden lack of negative buoyancy, the central part of the Eastern Alps rose quickly by ~2 km. The associated inflow of hot asthenosphere caused localized melting in the deeper crust. Granites, tonalites and mafic dikes intruded ca. 40–30 Ma ago near the Defereggen-Antholz-Vals Fault (Rieserferner), the Pusteria Fault (Rensen) and the Judicarie Fault (Adamello). (6) Thereafter, the direction of subduction changed in the Eastern Alps and the lithospheric mantle detached from the Adriatic plate and sank in a northeasterly direction (Lippitsch et al., 2003; Kissling et al., 2007). This reversal of subduction caused a second orogenic wedge to develop in the south (TRANSALP 3 field trip). To the east of the Judicarie Fault, the Adriatic plate pushed ~60 km northward, deep into the nappe stack (Figs. 1 and 3). This indentation led to further imbrication and ductile deformation within the Tauern Window and, finally, to its exhumation (Fig. 2; Fügenschuh et al., 1997; Neubauer et al., 2000; Lammerer et al., 2008). (7) Part of the orogen escaped to the east, in response to the indentation of the Adriatic plate and to the eastward rollback of the Carpathian subduction zone. This escape was facilitated by conjugate faults such as the sinistral Salzach-Ennstal Fault and the dextral Pusteria and Mölltal Fault (Genser and Neubauer, 1989; Ratschbacher et al., 1989; Frisch et al., 1998; Mancktelow et al., 2001). The large-displacement, north-south–trending Brenner and Katschberg normal faults also record the Neogene east-west extension contemporaneous with north-south

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Tauern Window region along the TRANSALP seismic profile compression in the Eastern Alps (Fügenschuh et al., 1997; Rosenberg et al., 2007). THE TAUERN WINDOW The Tauern Window is the largest tectonic window in the Alps. It extends from the Brenner Pass in the west for over 160 km to the Katschberg Pass in the east and covers a total area of ~5600 km 2 (see Fig. 1). It is the only place in the Eastern Alps where the European basement is exposed in an area over 100 km wide. The European plate margin was affected by the Variscan Orogeny and the early stages of the breakup of Pangaea. This led to horst and graben structures and small-scale sedimentary patterns at the end the Carboniferous (Veselá et al., 2008). Complex inversion structures developed during subsequent Alpine compression. Because the entire Eastern Alps were re-deformed by the uplift of the Tauern Window, understanding the structural controls exerted by the European basement is crucial for understanding the architecture of the Eastern Alps (Lammerer et al., 2008). Figures 3 and 4 show the main units of the western Tauern Window in map and cross-section view. The present tectonic structure of the inner Tauern Window results from: - an early detachment and folding of Post-Variscan cover rocks; - stacking of basement nappes, e.g., the Ahorn-, Tux-, Zillertal- and Eisbrugg gneisses, which represent former granitoid sills or laccoliths and its host rocks; - folding of the entire nappe stack with large amplitudes and wavelengths to the Ahorn-Tux dome and the Zillertal dome; and - a triangle zone at the tip of the sub Tauern ramp led to backfolding at the northern margin, which was first described by Rossner and Schwan (1982). From north to south—or from the deeper to the shallower nappes—these tectonic units are the Ahorn-, Tux-, Zillertal- and Eisbrugg units. All these units show a common characteristic: they are directly covered by the Late Jurassic Hochstegen marble in the northern sector, but by Late Carboniferous or Early Permian clastic sedimentary rocks in the southern part (Thiele, 1974, 1976). Basement gneisses and granites were exposed and eroded and the debris filled the depressions or tectonic grabens. During the Jurassic, accelerated subsidence related to the breakup of Pangaea resulted in deposition of the Hochstegen marble on top of all the units (Veselá et al., 2008). The sedimentary cover was locally detached and folded in tight, north-vergent folds. The entire nappe stack was subsequently overprinted by open folds with wavelengths in the range of kilometers. This led, locally, to synformal anticlines and antiformal synclines in the metasedimentary cover, which is evident especially along the northern rim of the window (Frisch, 1968). A final phase of south-vergent backfolding during the uplift of the Tauern Window and the development of a triangle structure on its northern tip, beneath the Austroalpine cover nappes, led to further complications.

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METAMORPHIC HISTORY All units within the Tauern Window underwent metamorphism in response to crustal thickening during the Alpine orogeny. Maximum temperatures were attained at ca. 25–30 Ma (e.g., von Blanckenburg et al., 1989; Christensen et al., 1994), during nearly isothermal decompression following deep burial. In general, metamorphic grade increases from greenschist facies at the margins of the window to mid-amphibolite facies in the central portions (e.g., Morteani, 1974). In detail, however, imbrication and differential movement between units resulted in a more complex picture. Oceanic rocks exposed at the surface today reached a pressure maximum of only 7–8 kbar in the southwestern corner of the window (Selverstone and Spear, 1985), but of 12–17 kbar in the Glockner nappe of the south-central region (e.g., Dachs and Proyer, 2001), where the prograde breakdown of lawsonite into mica-epidote-albite occurred at 30 Ma (Gleißner et al., 2007). In the latter area, they are separated from underlying units of European affinity by a tectonic slice of eclogite-facies oceanic rocks (600 ± 50 °C, 20–25 kbar; e.g., Spear and Franz, 1986; Hoschek, 2007). Maximum pressures calculated from the European units are in the range of 10–12 kbar (e.g., Selverstone et al., 1984; Brunsmann et al., 2000). These data indicate that the basement-cover contact within the Tauern Window was buried to depths of at least 35–40 km during the Alpine orogeny. All major structures in the Tauern Window, resulting from strong N-S lithospheric shortening and simultaneous minor E-W extension, began developing coevally with high-pressure metamorphism in the Eclogite Zone (ca. 32 Ma). Large-scale strikeslip shear zones such as the Olperer Shear Zone started to form at ca. 32–30 Ma and facilitated the spatial accommodation of simultaneous shortening and extension. The Greiner Shear Zone at Pfitscher Joch shows ages indicating continuous activity from 27 Ma to 17 Ma (Fig. 4). The Tauern Window nucleated in the south-central part of the Eclogite Zone, and most of the regional deformation at ca. 32–30 Ma is today found at the periphery of the window and in the adjacent Austroalpine units. Afterwards, transpression continued, the window grew to the E, W, and N, and deformation progressed to those parts of the window. Ductile deformation in the present-day surface level ceased at ca. 15 Ma (Glodny et al., 2008). ITINERARY The field trip begins in Munich and ends at the Pfitscher Joch, 28 km ENE of Sterzing (Vipiteno) in South Tyrol (Fig. 3). We will drive into three valleys—Zillertal, Tuxertal, and Pfitschtal— and take several long hikes to mountain huts. Latitude and longitude coordinates below are given in WGS84 datum. Day 1. Cross Section from Munich to the Center of the Tauern Window (170 km drive and three hours walking; driving distances are given from the Munich entrance of the E 52 freeway.)

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Figure 3. The western Tauern Window and adjacent areas and the excursion route (dotted line, red indicates hiking parts), with the day number indicated by red numbers. TRANSALP line with Common Depth Point numbers (CDP 4000–7000) is shown. Legend: 1—Early Paleozoic metamorphic Greiner series; 2—Late Paleozoic clastic metasediments; 3—Late Jurassic Hochstegen Marble; 4—Glockner nappe system (Bündner schists with ophiolites and Permo-Triassic remnants; 5—Basal clastic red bed sediments of the Northern Calcareous Alps; 6—Tertiary granites; dashed-dotted line—Austrian-Italian border. JF—Judicarie Fault, TJ—Tuxer Joch Haus, PFJ—Pfitscher Joch Haus, SH—Spannagel Haus, BH—Berliner Hütte

Figure 4. Composite section through the Tauern Window with seismic reflectors from the TRANSALP line. The internal structure is characterized by an early detachment of cover rocks followed by stacking of basement nappes, refolding with large amplitudes and wavelengths. A triangle zone at the tip of the sub Tauern ramp led to backfolding at the northern margin. The south vergent backfolding was first described by Rossner and Schwan (1982). The trace of the Salzach-Ennstal-Mariazell-Puchberg Fault (SEMP) is drawn after Rosenberg and Schneider (2008). Legend: Qph—Quartzphyllite zone; W—Wustkogel series (Early? or Late? Triassic clastic metasediments); B—Bündner schists; Tr—Middle Triassic carbonates; K—Kaserer series (Devonian–Carboniferous colored mélange); RS—Riffler-Schönach clastic basin; PM—Pfitsch-Mörchner clastic basin; EB—Eisbrugg clastic basin, E—Eisbrugg gneiss nappe; AF—Ahrntal fault; MK—Maurerkees basin; AA—Australpine south of the Tauern Window; TNBF—Tauern North Boundary Fault; SEMP—Salzach-Ennstal-MariazellPuchberg Fault; Sub-TR—Sub Tauern Ramp; DAV—Defereggen-Antholz-Vals Fault.

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We follow the freeway (E 52) from Munich southward, cross the flat, late glacial plain of Munich (Münchner Schotterebene), and near Holzkirchen reach the moraines of the Riss Ice Age. We leave the freeway at the Holzkirchen exit and drive through gently rolling moraine landscape to the Tegernsee (km 47). Here, we enter the Alps and its closely imbricated and folded Flysch and Helvetic zone. At the bottom of the Tegernsee, small quantities of crude oil seep out from Helvetic units. At St. Quirin, monks of the monastery sold this oil during the Middle Ages as a health remedy and as oil for lamps. Modern oil exploration started in 1912 in Bad Wiessee. They found no oil, but warm iodine water, which gave the locality a big boost as a medicinal bath. From Tegernsee to the lake of Achensee and further down into the Inn Valley near Jenbach we pass through the entire Northern Calcareous Alps, but no stops are planned, as this area is covered in detail on the TRANSALP 2 field trip. Stop 1-1. Entrance of the Ziller Valley, Quarry near St. Gertraudi (47° 24′19″N, 11° 50′35″E) In a large abandoned quarry, we see the base of the Northern Calcareous Alps and we can touch here the Late Paleozoic surface of Pangaea, dipping 70° to the north: Red sandstones of the Alpine Buntsandstein (Scythian) with detrital muscovite grade downward into a few meters thick, reddish-purple, poorly sorted breccia with dolomite as a main component. The breccia unconformably covers a steeply inclined, massive, whitish-gray crystalline dolomite of Early Devonian age (Schwazer Dolomit). The dolomite reaches up to 600 m in thickness and represents the youngest member of the weakly metamorphic Greywacke Zone, which is part of the metamorphic basement of the Adria plate. It ranges in age from Early Ordovician to Early Devonian (Schönlaub 1980). Within the dolomite, traces of copper ores may be seen in veins. Tetrahedrite is the main mineral, a copper-antimony sulfosalt. By oxidation and hydration, green malachite or blue azurite has formed. Nearby, in Schwaz and Brixlegg, copper, silver, and mercury sulfosalts were mined in the period between the fifteenth and nineteenth century and contributed much to the wealth of Tirol. South of the Schwaz dolomite, the fine-grained Ordovician and Silurian Wildschönau schists occur. Locally, they show nice kink folds with steeply plunging axes, but generally they are poorly exposed and form rounded mountains with smooth surfaces. The schists contain layers or lenses of fine-grained gabbro and of rhyolites. The border to the next deeper tectonic unit, the Quartzphyllite zone, is marked by the Kellerjoch orthogneiss, an Ordovician (Wenlock) sill that intruded ~425 million years ago (Satir and Morteani, 1979). Stop 1-2. Hofer Supermarket on the Southern Outskirts of Zell am Ziller (47° 13′22″N, 11° 52′50″E) From the parking lot of the Hofer Supermarket, we follow the Schweiberweg road for about one hundred meters to the

southeast, where a steeply south-dipping quartz phyllite is visible in a roadcut. The age of the phyllite is Ordovician here, but in other places (e.g., in the Southern Alps near Agordo, along the Val Sugana Fault) Late Cambrian acritarchs can be found in related rocks. Nearby, at Hainzenberg, gold occurs in quartz veins within the quartz phyllite and was mined in the seventeenth and nineteenth century. Our outcrop is situated only ~50 m north of the limit of the Tauern Window (Fig. 5). It is influenced by two independent fault systems: the sinistral Salzach-Ennstal-Mariazell-Puchberg Fault which was active since Oligocene (Rosenberg and Schneider, 2008) and the Neogene reverse Tauern North Boundary Fault (Lammerer et al., 2008). The dark gray and fine-grained quartz phyllite occurs here in an overturned position and displays quartz fiber crystals on small fault planes, indicating sinistral aseismic movement, as is typical for the Salzach-Ennstal-MariazellPuchberg Fault. This Miocene fault runs partly along the northern contact of the Tauern Window and enters eastwards the Northern Calcareous Alps. It is still active (Plan et al., 2010). A set of south-dipping microfaults produced sigmoidal micro wrinkles that indicate reverse movement and relative uplift of the southern side. This movement is attributed to the Tauern North Boundary Fault. Stop 1-3. Mayrhofen: Visitor Center of the Verbund Austria Hydro Power plant The Verbund controls four large reservoir lakes in the Zillertal catchment area. These mainly serve as pumped storage for power plants with a total capacity of ~1.1 GW and an annual production of 1.5 GWh. Benefit is taken from the high relief of that area and a constant water supply by several glaciers. Water is pumped into the reservoirs when excess electricity is available and can be released within seconds when needed. Stop 1-4. Old Bridge at Hochsteg over the Zemmbach, South of Mayrhofen (47° 09′17″N; 11° 50′09″E) This is the type locality of the Late Jurassic Hochstegen marble (Oxfordian, Kimmeridgian, Portland; Kiessling 1992): From the wooden nineteenth century covered bridge, one has a spectacular view down the steep north-dipping contact between Hochstegen marble and Ahorn granite. We descend to the river and encounter the Hochstegen marble (Kiessling, 1992). Up to 500 m in thickness, the bluishgray Hochstegen marble is more variable in its lower and older part. Sometimes it is dolomitic or contains mica and quartz, indicating shallow marine conditions. In this portion, an ammonite from the Perisphinctes genus was found by v. Klebelsberg (1940) that is now recognized as a Late Oxfordian orthospinctes semiradskii n. nom. (Kiessling and Zeiss, 1992). The upper portion of the Hochstegen marble is more homogeneous and limy with occasional chert nodules. Sponge spicules and several species of radiolaria document a deepening of the water and an age from Kimmeridgian to Early Tithonian (Kiessling

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Figure 5. The northern margin of the Tauern Window with Stop locations 1-2 to 1-4 and projected positions of the Spannagel Haus (Day 3) and Tuxer Joch (Day 4). Legend: 1—Austroalpine Innsbruck quartzphyllite, overturned in its southern part; 2—clastic metasediments of unclear age (Late Triassic?); 3—Mid Triassic limestones and dolomites, weakly metamorphic; 4—clastic metasediments (“Wustkogel series,” Late Permian–Early Triassic?); 5—dolomite-cargneul horizon; 6—clastic metasediments similar to 4; 7—Kaser series, mainly clastic metasediments, with lenses of marbles and serpentinites; 8—Hochstegen marble (Late Jurassic); 9—Meta rhyolite (“Porphyrmaterialschiefer”); 10—Tux gneiss nappe; 11—Ahorn alkaligranite; 12—clastic metasediments of the Riffler Schönach basin; TNBF—Tauern North Boundary Fault; SEMP—Salzach-Ennstal-Mariazell-Puchberg Fault.

and Zeiss, 1992). The massive Hochstegen marble dips steeply to the north and exhibits horizontal striation due to sinistral fault movement along the contact. A few meters of a blackish quartzite (Liassic?) and brownish limestone (Dogger?) are locally present along the contact with the Ahorn granite but are not well exposed here. The Ahorn granite is rich in biotite and K-feldspars. The Alpine foliation dips 70°–80° to the north. The Ahorn granite gneiss is the oldest and most deeply exposed intrusive body in the Tauern Window. Potassium-rich porphyritic biotite granites (in Europe called Durbachit or Redwitzit) intruded into migmatic host rocks 335.4 ± 1.5 Ma ago (Veselá et al., 2011). Here, in its northern part, the granite is covered by the Hochstegen marble. Stop 1-5. Breitlahner (Parking lot; 47° 03′40″N; 11° 45′00″ E, 1240 m, Grawandhütte [1½ hours walking] 47° 01′55″N; 11° 46′35″E, 1640 m) Immediately south of the Breitlahner guesthouse some mafic varieties (tonalite, diorite) of the intrusive suite of the Tux gneiss may be observed along the creek (Fig. 6). On the hike along the gravel road, mostly granodioritic scree of the Tux gneiss is crossed. The uniform gray and medium grained granodiorite of the Tux unit has an age of 292.1 ± 11.9 Ma (Veselá et al., 2011), which is significantly younger than the Ahorn granite. Muscovite dominates over biotite in this two-mica granite. The valley sides were smoothed by glacial grinding and show surface-parallel exfoliation by post-glacial pressure relief. About 50 m north of the Grawandhütte the tectonic contact between Tux gneiss and a serpentinite from the Greiner series will be crossed.

Stop 1-6. Grawand-Alpenrose (1873 m, 1½ h walking; 47° 01′31″N; 11° 48′05″E) We enter the Grawandtrett, gentle grazing land that developed over an old sagging mass, and enter the gorge of the Zemmbach (Fig. 6). Here, the rocks of the Greiner Series are best exposed. The Greiner Series belongs to the basement complex. The main rock types are hornblende garbenschists, amphibolites, and graphitic schist (locally called Furtschaglschiefer). The garbenschist texture (characterized by radiating bundles of hornblende; garben = “sheaves”) is developed in rocks with a range of bulk compositions. The garbenschist protoliths were likely marls with variable amounts of volcaniclastic input. After crossing the gorge, poorly exposed graphitic schists and paragneisses follow until the Alpenrose guesthouse (see Fig. 10). From north to south, we pass in the Zemmbach gorge the following rock types: - Amphibolite with some biotite and chlorite. - Amphibole-bearing graphitic schist, banded with hornblende garben. - Calc-silicate amphibole gneiss with garnet and epidote; hornblende sheaves grow along preexisting joints or foliations. - Graphite-garnet-hornblende schist with graphite-free reduction spots around clear almandine garnets; some of the amphiboles are postkinematic. - Alternation of calc-silicate–amphibole–gneiss and graphitic schist with large quartz veins. - Dark amphibolites with aplitic veins. - Lighter quartz- and garnet-rich hornblende garbenschists with graphite- and calcite-rich layers.

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Figure 6. Geological map of the Berliner Hütte area (Zillertal Alps).

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Tauern Window region along the TRANSALP seismic profile - Garnet-rich amphibolite and carbonate-garnet-amphibolite with rotated garnets (southern part upwards), found after crossing a side stream. - Garnet amphibolites with Fe-carbonates, injected by aplitic dikes or apophyses. Along three horizons, ~20 larger and smaller bodies of serpentinite are embedded, the largest of them, the Ochsner-Rotkopf Massif measures more than 1 km3. Because the serpentinites contain particularly abundant Mg-carbonates and calc-silicate minerals, they probably derive from ophicalcite rocks of an Early Variscan colored mélange zone. The stratigraphic age of the Greiner Schists is indirectly estimated by zircon dating of comparable rocks from the central Tauern Window. An upper limit is given by Early Devonian detrital zircons (Kebede et al., 2005). A lower age limit of 293 Ma results from the dating of a rhyolite that cuts the Ochsner serpentinite and the Greiner schists and by the intrusive contacts against the Zillertal gneiss (Veselá et al., 2008, 2011). Stop 1-7. Alpenrose Guesthouse—Berliner Hütte (½ h walking; 47° 01′28″N; 11° 48′47″E; 2042 m) The Waxeggkees with its distinctive lateral moraines of the Little Ice Age (1600–1890) and some recessional moraines come into focus. From here to the Berliner Hütte we will walk over paragneisses that are injected by granites, giving them a migmatitic appearance. The Berliner Hütte itself stands on beautiful injected amphibolites, which are well exposed in a glacierpolished outcrop in front of the hut. Stop 1-8. Glacially Polished Bedrock below the Berliner Hütte (47° 01′23″N; 11° 48′87″E; 2022 m) After crossing two moraine walls (from 1850 and 1890) we reach after 5 minutes the glacially polished outcrops of Zillertal gneiss. On the bedrock surface grooves in two different directions are developed and superimposed: the older and deeper scratches are relics of the mighty glacier of the last glaciation (Würm glaciation, corresponding to the Wisconsinian stage). The younger and smoother striations developed during the cold period of the seventeenth to nineteenth century, the “Little Ice Age.” The same applies to linear groups of crescent cracks. The cracks of the great glacial period are larger and deeper and east-west oriented, those of the Little Ice Age are smaller and document an ice flow from south to north. The bedrock consists of younger, fine-grained homogeneous granite and older porphyric granite with schlieren or nebulitic migmatitic features. In the fine-grained granite, rounded clusters of biotite and quartz in the core and potassium feldspar in the rim are present (proto-orbicules). The contact of the two granites is well exposed. The migmatitic streaks are cut by the fine-grained granite, clearly showing the age relationships. Amphibolitic xenoliths are found in all stages of assimilation. The amphibolites were already metamorphosed and foliated before intrusion. This outcrop marks the base of the Zillertal gneiss, a variable series of ultramafic to acidic intrusives, with a large proportion of

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tonalite and with ages of 309 Ma for the mafic rocks and 295 Ma for the youngest granites (Cesare et al., 2002). Numerous aplitic, pegmatitic or lamprophyric dikes cut the Zillertal gneiss. Like the Ahorn and Tux granites, the Zillertal gneiss is directly covered by Hochstegen marble in its main portion— except the southern segment at Eisbruggjoch, which is covered by clastic rocks. At the Maurerkees to the southeast of the Berliner Hütte, in a similar tectonic position, late Carboniferous remnants of fossil plants can be found (Franz et al., 1991; Pestal et al., 1999). Day 2. The Paleozoic Suture Zone in the Tauern and the Alpidic Metamorphic History of the Garbenschists All-day walk on mountain trails to Schwarzsee (2470 m) and Eissee (2680 m) to cross through the Greiner schists. Stop 2-1. Berliner Hütte—Schwarzsee (47° 02′23″N; 11° 49′46″E; 2470 m) Leaving the Berliner Hütte, we follow the well-marked mountain path to the Schwarzsee (Fig. 6). We first cross schlieren gneisses with xenoliths or disrupted layers of amphibolite that were injected by granitic melts. Locally, garnet or potassium feldspar megacrysts occur. From the trail, the Schwarzenstein glacier and its Little Ice Age moraines will be visible. The heavily vegetated outermost wall is attributed to the year 1610, the oldest moraine of the postglacial cold period. Nevertheless, it is very well preserved. The younger moraines are much less vegetated and contain coarser blocks. The marked difference in vegetation is due to soil formation during the long warm periods before the earliest Little Ice Age glaciation. The first glacier advance scratched off this soil and deposited it along its front. We continue through graphitic schists and amphibolites, which have an andesitic composition and show a nice boudinage. Immediately before the Schwarzsee, we reach a postVariscan metaconglomerate, which rests unconformably on the Greiner schists. It can be traced from here to the Pfitschtal (see Day 5). Coarse blocks of serpentinite are fallen from the Rotkopf Mountain. At the Schwarzsee, the typical hornblende garbenschists show a large range of textures. In many cases, hornblende appears to be post-kinematic. Steffen et al. (2001), however, argued that development of the garbenschist texture records grain-boundary diffusion creep during shearing. Rapid growth of large hornblende crystals subsequently strengthened the rocks and shifted deformation to weaker horizons. The fabulous Schwarzsee is a typical tarn and a relic of the Great Ice Age. It is dominated in the northwest by the mighty dark serpentinites of the Ochsner and Rotkopf peaks. The main serpentine mineral here is antigorite, with chrysotile found only in crevices. Abundant carbonates (ankerite, breunnerite) and calc-silicate minerals such as diopside, grossular, vesuvianite, tremolite, and others (Koark, 1950) record a pre-metamorphic

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phase of calcium metasomatism. The abundance of calcic minerals supports the interpretation that the serpentinite is a former ophicalcite. West of the summit of the Ochsner, the serpentinite is cut by early Permian quartz porphyry confirming the pre-Alpine emplacement age of the serpentinite. Along the contact, the serpentinite is sometimes chloritized and often bears idiomorphic magnetite octahedra. Famous two-colored diopside crystals— green at the base and colorless at the tips—also occur here. Stop 2-2. From Schwarzsee to the Mörchnerscharte (47° 02′33″N; 11° 50′29″E) We take the steep trail in direction to the Mörchnerscharte. We follow roughly the contact to the deformed metaconglomerates to an elevation of 2630 m. Here, the syncline of the conglomerate ends in a narrow upright fold with an axis plunging 40° to the west. The fold limbs dip generally 65°–70° northward and southward in the Greiner schists. We move into the northern of two main synclines in the Greiner series. The southern syncline is only visible at the Schönbichler Horn to the west of the Berliner Hütte. Graphitic schists and amphibolites are here deformed together with an underlying granitic sill. The presence of the younger conglomerate in the center of the fold indicates a true syncline and not just a synform. This does not rule out more complex folding of parts of the crystalline basement during an earlier phase of deformation. Stop 2-3. Mörchnerscharte-Eissee (47° 02′40″N; 11° 50′03″E) Without a trail, we cross a mélange of different garbenschists, metarhyolites, quartzites, graphite schists, and several serpentinite bodies of a few cubic meters in size. Around the Eissee, several smaller ultramafic bodies are exposed: serpentinites of varying sizes (m3 to km3), metaophicalcites, and rock bodies that are completely transformed into chlorite or actinolite blackwall zones are embedded in a metapelitic or conglomeratic matrix (Barnes et al., 2004). The rock association resembles an olistostrome or a mélange-type complex (100–500 m). Thin bands of quartzites containing bright chromium-bearing white mica (“fuchsite”) and marble are present, but cannot be traced for long distances. Stop 3-4. From the Eissee to the Rotkopf Serpentinite The dominant serpentinite mineral is antigorite, with chrysotile only present along the contacts or in shear planes and fissures. In some places, idiomorphic octahedra of magnetite may be found in a chlorite matrix. Colorless and green transparent diopside, uvarovite and grossular garnet, titanite, actinolite, fuchsite, platy hematite, amethyst, and many other minerals were also found in this area. The Greiner schists bend around the body of the OchsnerRotkopf serpentinite, but the post-Variscan metaconglomerate that forms the core of the Greiner basin is unaffected by the underlying structures. These observations indicate that the conglomerate was deposited in angular unconformity over already

deformed Greiner schists. From the Eissee we head back to the Berliner Hütte. Day 3 We cross the margin of the inner Tauern Window and enter the folded Ahorn gneiss and the Paleozoic postvariscan clastic metasediments of the Riffler-Schönach basin, and we visit the highest karst cave of Austria. Stop 3-1. Gasthof Schöne Aussicht near Finkenberg (47° 09′03″N; 11° 49′27″E) We hike down to the parking lot at the Breitlahner guesthouse (2 h) and continue by car to Finkenberg. Along the small road and at the parking lot of the guesthouse, an imbricated contact of Zentralgneis and its sedimentary cover dips steeply to the northwest. Granite-orthogneiss, graphitic schists, brownish limestone, and gray Hochstegen marble are well exposed here. The sequence is doubled by a small low-angle thrust. The detachment runs beneath a thin slice of granite—probably an exfoliation sheet from unloading at the postvariscan surface. Stop 3-2. Hintertux Parking Lot (47° 06′30″N; 11° 40′ 33″E; 1500 m) Between Finkenberg and Hintertux we cross the oceanic Bündnerschist series without stopping. Hintertux, like Mayrhofen, is situated 1500 m a.s.l. on the northern slope of the inner Tauern Window. It is known for excellent year-round skiing possibilities and for its thermal water, which comes from several springs along the rim of the Tux gneiss with temperatures up to 22 °C. The thermal waters have been used for wellness and medical purposes since 1850, but were known in earlier times. The water of this highest thermal spring of Europe is relatively poor in minerals, but it is slightly radioactive due to small amounts of radon and uranium. Stop 3-3. Tuxerferner House (47° 04′38″N; 11° 40′16″E; 2660 m) From Hintertux, we take the cable lift up to the Sommerbergalm and further to the Tuxerferner House. The house is built on a migmatitic Tux gneiss thrust sheet of only ~100 m in thickness. From here, we have a nice panoramic view: To the north, we recognize the grassy Bündnerschiefer Mountains with the northern Calcareous Alps in the background. To the east, the synformal anticline of the Höllenstein (Höllenstein Tauchfalte; Frisch, 1968) bends around the Ahorn granite core. Metaconglomerates and Hochstegen marble of the Riffler-Schönach basin were detached, squeezed out and folded by the advance of the Tux granite-gneiss nappe and later refolded together with the Ahorn gneiss. The conglomerate horizon ends on the northern ridge of the Hohe Riffler (3231 m) at the thrust plane of the Tux gneiss. The southern sector is mostly glaciated and the bedrock is made from Tuxer granodioritic orthogneiss. Its sedimentary cover of Hochstegen marble can be seen in the western

Tauern Window region along the TRANSALP seismic profile sector. Here, the clastic basal rocks are missing. The strata dip around 40° to the northwest and are visible along the steep wall of the Kleiner Kaserer (3095 m), the type locality of the Kaserer series, which we will visit the next day. The outcrop runs subparallel to the fold axis, which gives the fold a somewhat strange appearance. Stop 3-4. Spannagelhaus (47° 04′48″N; 11° 40′16″E; 2529 m) The refuge was built on Hochstegen marble, which shows nice folds immediately in front of the hut. Three meters of brownish marble and another meter of black quartzite may represent earlier Jurassic beds (Fig. 7A). Stop 3-5. Outcrops of Metaconglomerates (~500 m along the trail to the Friesenbergscharte) From the refuge, we follow the trail to the east in direction to the Friesenbergscharte. On the way down, we cross metaconglomerates of the Riffler Schönach basin, which can be traced for over 40 km into the central Tauern Window. The pebbles are strongly flattened here and kinked or folded. Finer-grained metaarkoses are found in deeper sections, and their color changes from gray to greenish, indicating climatic or depositional changes. Stop 3-6. Spannagel Cave (Spannagelhöhle) The entrance to the highest cave in Austria is directly under the hut. It reaches at least 800 m horizontally to the west and at least 500 m downward. The cave is cut into banded Hochstegen marble, which is topped by the thrust plane of the Tux gneiss. This contact is visible in the cave. We find a strongly black- and white-banded variety of the marble and initial travertine and stalagmite formation. Karst waters have obviously enlarged preexisting fractures in the marble. The cave formed during glacial periods, beginning at least 550 ka ago. U-Pb and U-Th dates on flowstones in the cave reveal several episodes of growth around 550 ka, 350 ka, 295 ka, and 267 ka (Cliff et al., 2010). Day 4. All-Day Walk from Spannagel Haus to Tuxer Joch Haus We cross from the Riffler Schönach basin through the Tux gneiss nappe and proceed into the base of the Glockner nappe. We touch the enigmatic Kaserer Series and a Cambrian gabbro and walk through backfolded area. Stop 4-1. Outcrop in Glacially Polished Rocks to the South of the Sommerbergalm We take the gravel road down to the Sommerbergalm for about one kilometer to an elevation of 2100 m. We follow roughly the contact between the Hochstegen marble and its substratum of Permo-Triassic clastic metasediments and the thrust plane on top, and we cross in the lower part the Tux gneiss nappe. After crossing the lateral moraine of the year 1850, we

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can study the contact between the Tux gneiss and the Hochstegen marble above it in detail on the glacially eroded surface. The migmatitic gneiss is strongly sheared in its uppermost part and covered by two meters of brown, sandy limestone that grades into the bluish-gray banded Hochstegen marble. The marble is generally limy but contains boudinaged dolomitic layers. Graphitic bands alternate with graphite-free bands in a cm to dm scale. They are cut by a synsedimentary normal fault, which is smoothed out by sedimentation. The marble appears less deformed than the granite gneiss, which suggests an extensional detachment fault developed on the seafloor (possibly a metamorphic core complex). Stop 4-2. Kaserer Scharte (47° 04′52″N; 11° 38′41″E; 2446 m) We ascend for ~250 m, in the lower part over grassy slopes and sheep pastures and reach, after 40 minutes, the Kaserer Scharte to the north of the Kleiner Kaserer, the type locality of the Kaserer series. From here, we have a spectacular view of the tightly folded Triassic marbles on the Schöberspitzen in the west (Fig. 8). Stop 4-3. Frauenwand We follow the small trail to the Frauenwand, crossing chlorite schists, graphitic schists, thin marble bands, and arkosic gneiss layers of the Kaserer series. A shallow-water or turbiditic facies is discussed; sometimes weak graded bedding may be visible. The small peak of the Frauenwand is made of Hochstegen marble, which comes up here in an isoclinal anticline. It is disrupted by slope tectonics and shows karstification. Stop 4-4. Trail to the Tuxer Joch On the way down to the Tuxer Joch, we again cross the Kaserer series with green and black schists and meta-arkoses, and reach the Weisse Wand (white wall). The white color results from Triassic dolomitic and limy marbles. We cross (from south to north): 25 m of white dolomite; 5–7 m of dark gray dolomite; 15–20 m of light gray dolomite, 5 m of yellowish cargneuls and a few meters of greenish chlorite and schists. Stop 4-5. Ski Lift Building South of the Tuxer Joch At a small ski lift building, a fine-grained metagabbro or metadolerite is exposed for 20 m. The grain size is at mm scale, between a dolerite and microgabbro, and the rock is sheared at its basal contact. This rock was thought to be Cretaceous in age by Frisch (1974), but its zircons show a Cambrian age (Veselá et al., 2008). Two contrasting interpretations can be made: the rock contains inherited zircons from older crust, or this is a tectonic sliver of a basement gabbro at the base of the Glockner nappe. Stop 4-6. Trail Approaching the Tuxer Joch (47° 05′56″N; 11° 38′58″E) We continue northwards and encounter graphitic schists with one black horizon rich in carbonaceous matter (possibly

Figure 7. (A) Cross section through the Western Tauern Window, northern part. This is the area around the Spannagel Haus (SH) and Tuxer Joch Haus (TJH). (B) Cross section through the Western Tauern Window, southern part. This is the area around the Pfitscher Joch. Legend to A and B: Austroalpine nappes (AA) and Tarntal Mesozoic nappe (TM): 1—Jurassic shale, marl, limestone, breccia and chert; 2—Serpentinite; 3—Triassic carbonate and cargneul; 4—Quartzphyllite (mainly Ordovician); 5— gneiss south of the Tauern Window; 6—Rensen granite and dykes. Glockner nappes: 7—phyllite and calcphyllite of the higher Bündnerschiefer nappe; 8—Amphibolite and Prasinite; 9—thrust horizon with lenses of serpentinite and Triassic quartzite, Dolomite, gypsum and breccia; 10—Phyllite of the lower Bündnerschiefer nappe; 11—?Permo–Triassic clastic metasediment and cargneul; 12—dolomite marble (Middle Triassic); 13—tectonic horizon with lenses of Cambrian microgabbro. Inner Tauern Window duplex system has the following three parts. (1) Post Variscan metasediments: 14—Hochstegen marble (Upper Jurassic); 17—clastic sediments, metaconglomerates, meta-arkoses (Pre Upper Jurassic); 18—dazitic porphyry. (2) Late Variscan Plutonites: 19—Ahorn porphyric biotitegranite; 20—Tux granodiorite; 21— migmatic rocks and injection gneisses; 22—Zillertal granites, granodiorites tonalites and gabbros. (3) Pre-Variscan and early Variscan rocks: 23—black graphiteschists; 24—amphibolites and garbenschiefer; 25—serpentinites and meta-ophicalcites; 26—injected gneisses and amphibolites.

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Figure 8. View to the west from the Kaserer Scharte to the Schöberspitzen 2600 m. The isoclinal south-vergent folding of the Triassic dolomites is due to late backfolding.

equivalent to the Late Triassic Lettenkohle horizon of the German basin) and sandy layers; greenish quartzites or quartz-rich schists with some carbonate horizons of centimeters in thickness, and white quartzites up to 20 m thick. Brownish calcschists resemble the Bündnerschiefer series. The Tuxer Joch Haus is built on greenish quartzites of the so-called Wustkogel formation—although it is not entirely clear whether it is the same horizon as at the type locality in the central Tauern Window. Day 5 We discuss the Brenner normal fault, cross the Bündnerschiefer and enter the Pfitsch valley with its vanished lake; we have a look to the famous Wolfendorn section and reach the Pfitscher Joch. We descend down to Hintertux and continue by car to Innsbruck and the Brenner Pass, the lowest pass of the central Alps (1360 m). The Brenner Pass marks a major normal fault, the Brenner Line, where the hanging wall of the Ötztal-Stubai crystalline basement (a part of the Austroalpine nappe stack) has been displaced westward relative to the Tauern Window (Behrmann, 1988; Selverstone, 1988). The horizontal component of slip on this structure is estimated to be several tens of kilometers since Miocene times (Selverstone, 1988; Axen et al., 1995; Frisch et al., 2000). Top-to-the-west ductile shearing was dated at ca. 22–18 Ma (Glodny et al., 2008). There is still some minor earthquake activity here. A similar, top-east extensional fault (Katschberg fault) bounds the eastern edge of the Tauern Window.

Stop 5-1. Brennerbad (46° 58′46″N; 11° 29′05″E) South of the Brenner Pass, at Brennerbad, a small gravel road leads us to outcrops of mylonitic calc-mica schist of the Bündnerschiefer series. Well-developed S-C-C′ fabrics and late semi-ductile and brittle shear zones indicate top-to-thewest extensional movement associated with the N-S–trending Brenner fault zone. The youngest, brittle incarnation of the Brenner Fault excised ~2 km of the Bündnerschiefer, indicating that the fault dips more steeply than the westward plunge of the Tauern Window. However, top-west extensional mylonites within the Bündnerschiefer and lower Austroalpine units point to an early history as a low-angle, ductile shear zone (Behrmann, 1988; Selverstone, 1988; Axen et al., 2001). Footwall uplift was accomplished by subvertical simple shear along numerous, closely spaced, high-angle normal faults. West-down structures were active at depths of 10–20 km and ~450 °C and were overprinted by east-down faults active at 2–10 km depths and 300 ± 50 °C (Selverstone et al., 1995). Stop 5-2. View to the Landslide of Afens We continue into the Pfitsch valley until the bridge west of Afens. A postglacial landslide within the calc-mica schist unit filled the valley at least 300 m deep and caused a natural reservoir lake to form in the upper part of the Pfitsch valley. Around the year 1100, the barrier failed and the lake flooded the lower Pfitsch and Sill Valleys and destroyed the Roman Garrison station of Vipitenum (Sterzing/Vipiteno today).

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Stop 5-3. Standing on an Ancient Lake Ground South of Kematen and Discussing the Wolfendorn Section Near Kematen, an old fisherman’s village with houses older than one thousand years, we stop at the former lake floor. Nice terraces and deltas mark the former water level of the barrier lake, which vanished in the beginning of the twelfth century. From here, we have a perfect look to the Wolfendorn (Spina Del Lupo, 2771 m) to the north. The west-plunging Zentralgneis is covered by ~10 m of brownish Triassic marble and by 20 m of black kyanite-mica schist. Kyanite is black because of inclusions of graphite (Rhätizit, rheticite). Two meters of brown, sandy limestone mark the beginning of the Hochstegen marble, which is upright in the lower part and inverted in the middle part and again upright in the top at the peak of the Wolfendorn (Fig. 9). Several workers tried to understand the section exposed on the Wolfendorn (Tollmann, 19663; Frisch, 1974; Fenti and Friz, 1973; Lammerer, 1986). As the crest runs subparallel to the axial plunge direction, the isoclinal fold within the Hochstegen marble of the Wolfendorn was not recognized for a long time. To the west, the Kaserer series follows. It was here that a stratigraphic contact was proposed by Frisch (1974), but this is doubted by other workers (Tollmann, 1963; Baggio et al., 1969). The Kaserer Series is topped by Mid Triassic dolomites of the Kalkwandstange and the Bündnerschiefer (Frisch, 1974). The Weißspitze is topped by a whitish dolomite klippe which may either mark the base of the Austroalpine nappes, or the upper part of the Brenner Mesozoic sequence, juxtaposed against the Bündnerschiefer by the Brenner normal fault (Selverstone, 1988). In the latter interpretation, ~10 km of the Austroalpine nappe stack has been excised by the fault.

Stop 5-4. The Quarry of Stein (46° 58′46″N; 11° 38′25″E) Vertically oriented l quartzites and phengite-chloritoidquartz schists of the Middle or Late Triassic from the base of the Glockner nappe are mined here for flagstones and façade panels. A local increase in thickness of the weathering-resistant quartzite forms this economically important outcrop. Stop 5-5. 200 m along the Trail to the Hochfeiler At the third bend of the road, we park and walk 200 m upwards along the creek. We encounter calcschists of the Bündnerschiefer and we may find in the talus boulders of amphibolite with pseudomorphs of albite, white mica and clinozoisite after the high-pressure mineral lawsonite. Stop 5-6. Acid Waters and Metaconglomerates at the Fourth Bend of the Road We continue by car up the gravel road. After the third bend, we cross a small creek with red ferrous precipitation from acidic iron-rich water escaping from a pyrite-rich layer. At the fourth bend we reach conglomerate gneisses with flattened pebbles that form the southern limb of the tight Pfitsch syncline. After the curve we enter graphitic schists (“Furtschagelschiefer,” Early Carboniferous?) that are tightly to sub-isoclinally folded. Further up we cross arkosic gneisses and marble bands of the Kaserer series. Stop 5-7. Scenic View to the Griesscharte and the Glockner Nappe At the sixth bend of the road to Pfitscher Joch we have a good view of the rocks of the Glockner nappe: In the south,

Figure 9. The Wolfendorn seen from the Pfitsch valley near Kematen. 1—Tux granite gneiss; 2—dolomitic marble with some hematite bearing quartzite at the base (Triassic); 3—graphitic quartzitic schist with black kyanite and some black marble (Liassic?); 4—brownish sandy limestone, 5—lower Hochstegen marble, banded and locally dolomitic; 6—homogeneous Hochstegen marble with occasional chert nodules. The lower part of the section is in normal position, the middle part inverted due to isoclinal folding with an axis subparallel to the outcrop, and the upper part is again in an upright position.

Tauern Window region along the TRANSALP seismic profile tightly folded calcschists and greenschists form impressive walls in the Bündnerschiefer. Two hanging glaciers come down the steep mountain flank of the Hochferner Massif. To the east, at the Griesscharte, strata from the base of the Glockner nappe dip vertically: white marbles and quartzites (the continuation of the series from Stop 5-4), graphitic schists and arkosic gneisses from the Kaserer series and two thin bands of Zentralgneis and Hochstegen marble crop out. They are in contact with graphitic schists from the Greiner series to the north. Stop 5-8. Pfitscher Joch Haus (46° 59′32″N; 11° 39′28″E; 2276 m) From here, we have a good panoramic view over the western Tauern Window. The Zillertal anticline in the south and its nappe cover of the Glockner nappe plunges 25° to 30° to the west. Down in the Pfitsch valley and beyond the silted lake floor, the late Alpine syncline between the Tux and Zillertal anticlines is clearly visible. The rock mass of the Weißspitze is topped by a white Austroalpine klippe of marble, and in the far background the Austroalpine nappes of the Stubai Mountains protrude. The southern flank of the Tux anticline with the Hochstegen marble cover bends down from the Wolfendorn into the valley. Day 6 In the Pfitscher Joch area, we discuss the kinematics of the tight syncline, the sedimentary facies of the post-Variscan rocks and the strain history of the Greiner shear zone and surrounding area. We visit the post-Variscan unconformity surface and its soil horizon.

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Stop 6-1. Pfitscher Joch Area (Fig. 10) We start in the Tux gneiss, which is in tectonic contact with a Paleozoic amphibolite that shows a prominent mineral stretching lineation gently plunging to the west. Stretching continued until the brittle stage, documented by fissures filled with biotite, chlorite, feldspar, quartz, laumontite, and other low-grade minerals. A porphyritic granite dike showing nice shear sense indicators (delta clasts, S-C fabrics) and late feeder veins cut the amphibolite. The Pfitsch metaconglomerate or metabreccia is only moderately deformed along the northern limb of the Pfitsch syncline. Original bedding and sedimentary features can still be recognized. Poor sorting, angular components up to 30 cm in size, and poorly selected pebbles from granite to limestone and shale are typical for this coarse-grained clastic sediment (Veselá and Lammerer, 2008). The unit fines upward and is overlain by an Early Permian metarhyolite that is dated at 280 Ma (Veselá et al., 2011). Epidote-ankerite-biotite schists, which are considered to be former playa sediments, and hematite-bearing quartzites overlie the metarhyolite. The white to light gray appearance of the quartzites comes from finely disseminated, platy hematite, indicating that the protolith was a red sandstone (possibly equivalent to the Early Triassic Buntsandstein of the German basin). In a special horizon, which can be followed eastwards for ~1 km, kyanite, staurolite, and lazulite are found together with several rare aluminum phosphates (Morteani and Ackermand, 1996). This quartzite is crosscut by isoclinally folded tourmalinite veins, indicating a post-Triassic hydrothermal activity. The axis of the syncline plunges 40° or more to the west in this sector. The younger Mid Triassic dolomites and cargneuls and the Hochstegen marble are therefore only exposed farther to the west.

Figure 10. The Greiner schists seen from northwest. To the left: the Greiner (3199 m), to the right of the Center the glacier covered Möseler (3478 m) in the background and in front of it, the ridge of dark graphite schists (Furtschagelschiefer) of the Hochsteller (3097 m) and, closer to the right, the Rotbachlspitze (2895 m) with the characteristic brownish altered rocks of the Greiner shear zone. At the right margin in the middle ground: Bündnerschiefer and whitish marbles at the Griesscharte (2901 m) in vertical position. The lighter gray Tux granodioritic gneisses to the left contrast clearly with the darker Greiner Schists and the Tux conglomerates.

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The southern limb of the syncline exhibits the sequence in mirror symmetry, except that the thickness of the units is greater, even where the flattening strain is much higher. It is suspected that this reflects a deepening of the basin to the south. Stop 6-2. Rotbachlspitze (2895 m) Hiking east toward the Rotbachlspitze (Fig. 9), we traverse both the Permo-Mesozoic metasedimentary units and the older hornblende garbenschist of the Greiner series. Locally, lenses of magnetite-rich, staurolite-chloritoid schist decorate the contact between the Pfitsch metaconglomerate and the garbenschist. These lenses are extremely enriched in aluminum and iron and depleted in silicon, calcium, and potassium. In general, Al+Fe contents are highest immediately adjacent to the metaconglomerate, and decrease over a distance of a few meters toward the garbenschists. These unusual rocks are interpreted to represent a paleosol developed along the unconformity between Paleozoic rocks of the Greiner Series and the Pfitsch conglomerate (Barrientos and Selverstone, 1987). The extreme enrichment in Al+Fe and the scale of the chemical zoning are consistent with deep weathering and formation of a lateritic soil. Metamorphism of this unusual bulk composition resulted in growth of Fe ± Al-rich minerals such as chloritoid, staurolite, and magnetite. Chloritoid within these rocks occurs in radiating sprays that are intergrown with quartz. These chloritoid-quartz intergrowths are likely pseudomorphs after Fe-Mg carpholite. If this interpretation is correct, it indicates that the rocks passed through blueschist-facies conditions prior to equilibration in the amphibolite facies. Below the cliff to the south of the soil horizon, intense shearing has transformed rocks of the Greiner Series into quartz-pyrite schists. These rocks give the Rotbachlspitze (red stream peak) its name. Continuing to the southeast, we encounter highly graphitic schists (Furtschaglschiefer) that locally contain hornblende garben, and then to garnet-biotite ± hornblende schists that locally contain garnets up to 5 cm in diameter. These latter schists were dated by Christensen et al. (1994) to constrain the duration of garnet growth (<5 m.y.) and the timing of the thermal peak of metamorphism (30 ± 1 Ma) in this part of the Tauern Window. Day 7 We discuss the large scale and small-scale deformation of the large intrusions, which are folded and sheared, then we drive back to Munich. Stop 7-1. Polished Area with Shear Zones and Dikes of the Stampflkees Depending on the weather conditions and the actual schedule, a morning hike toward the Stampfl Kees can be made. The tour goes along the eastern moraine of the glacier and we can see firstly the strongly deformed varieties of the Zentralgneiss, which gradually transition into less deformed metagranites. Intrusion relations of different types of Zentralgneiss are still well

preserved. A leucocratic metagranite variety is associated with molybdenite-quartz veins, which were mined at the Alpeiner Scharte further northeast. This former molybdenite porphyry is also enriched in Be and may contain blue beryll (aquamarine). Aplitic dikes are abundant and show Alpine deformation, concentrated in shear zones. The protoliths of the gneisses were crosscut by Triassic-Jurassic (?) mafic dykes, probably associated with the early stages of extension. During the Alpine metamorphism they were transformed into biotite-schist. The hike continues crossing the outcrops below the glacier and we can hike back on the western moraine. From the Pfitscher Joch we drive back to Munich via Innsbruck and Garmisch. REFERENCES CITED Axen, G.J., Bartley, J.M., and Selverstone, J., 1995, Structural expression of a rolling hinge in the footwall of the Brenner Line normal fault, Eastern Alps: Tectonics, v. 14, p. 1380–1392. Axen, G.J., Selverstone, J., and Wawrzyniec, T., 2001, High-temperature embrittlement of extensional Alpine mylonite zones in the midcrustal ductile-brittle transition: Journal of Geophysical Research, Solid Earth, v. 106, B3, p. 4337–4348, doi:10.1029/2000JB900372. Baggio, P., et al., 1969, Note illustrative delia carta geologica d’ltalia 1: 100.000, foglio 1, Passo del Brennero; Foglio 4a, Bressanone: Servizio geologico d´Italia, p. 120, Roma. Barnes, J.D., Selverstone, J., and Sharp, Z.D., 2004, Interactions between serpentinite devolatilization, metasomatism, and strike-slip strain localization during deep-crustal shearing in the Eastern Alps: Journal of Metamorphic Geology, v. 22, p. 283–300, doi:10.1111/j.1525-1314.2004.00514.x. Barrientos, X., and Selverstone, J., 1987, Metamorphosed soils as stratigraphic indicators in deformed terranes: an example from the Eastern Alps: Geology, v. 15, no. 9, p. 841–844, doi:10.1130/0091-7613(1987)15<841: MSASII>2.0.CO;2. Behrmann, J.H., 1988, Crustal-scale extension in a convergent orogen—the Sterzing-Steinach mylonite zone in the Eastern Alps: Geodinamica Acta, v. 2, p. 63–73. Bertrand, M., 1884, Rapports de structure des Alpes de Glaris et du bassin houiller du Nord: Bulletin de la Société Géologique de France, v. 3, p. 318–330. von Blanckenburg, F., and Davies, J.H., 1995, Slab breakoff—A model for syncollisional magmatism and tectonics in the Alps: Tectonics, v. 14, no. 1, p. 120–131, doi:10.1029/94TC02051. von Blanckenburg, F., Villa, I., Baur, H., Morteani, G., and Steiger, R.H., 1989, Time calibration of a PT-path in the Western Tauern Window, Eastern Alps: The problem of closure temperatures: Contributions to Mineralogy and Petrology, v. 101, p. 1–11, doi:10.1007/BF00387196. Brunsmann, A., Franz, G., Erzinger, J., and Landwehr, D., 2000, Zoisite- and clinozoisite-segregations in metabasites (Tauern Window, Austria) as evidence for high-pressure fluid-rock interaction: Journal of Metamorphic Geology, v. 18, no. 1, p. 1–21, doi:10.1046/j.1525-1314.2000.00233.x. Carulli, G.B., and Slejko, D., 2005, The 1976 Friuli (NE Italy) earthquake: Giornale di Geologia Applicata, v. 1, p. 147–156, doi:10.1474/GGA.2005 -01.0-15.0015. Castellarin, A., and Cantelli, L., 2000, Neo-Alpine evolution of the Southern Eastern Alps: Journal of Geodynamics, v. 30, p. 251–274, doi:10.1016/ S0264-3707(99)00036-8. Cesare, B., Rubatto, D., Hermann, J., and Barzi, L., 2002, Evidence for Late Carboniferous subduction type magmatism in mafic-ultramafic cumulates of the Tauern Window (Eastern Alps): Contributions to Mineralogy and Petrology, v. 142, p. 449–464, doi:10.1007/s004100100302. Channell, J.E.T., and Kozur, H.W., 1997, How many oceans? Meliata, Varda and Pindos oceans in Mesozoic Alpine paleogeopgraphy: Geology, v. 25, p. 183– 186, doi:10.1130/0091-7613(1997)025<0183:HMOMVA>2.3.CO;2. Christensen, J.N., Selverstone, J., Rosenfeld, J.L., and DePaolo, D.J., 1994, Correlation by Rb-Sr geochronology of garnet growth histories from different structural levels within the Tauern Window, Eastern Alps:

Tauern Window region along the TRANSALP seismic profile Contributions to Mineralogy and Petrology, v. 118, p. 1–12, doi:10.1007/ BF00310607. Cliff, R.A., Spötl, Ch., and Mangini, A., 2010, U-Pb dating of speleothems from Spannagel cave, Austrian Alps: A high resolution comparison with U-series ages: Quaternary Geochronology, v. 5, p. 452–458, doi:10.1016/j .quageo.2009.12.002. Dachs, E., and Proyer, A., 2001, Relics of high-pressure metamorphism from the Grossglockner region, Hohe Tauern, Austria: Paragenetic evolution and PT-paths of retrogressed eclogites: European Journal of Mineralogy, v. 13, no. 1, p. 67–86, doi:10.1127/0935-1221/01/0013-0067. Ebbing, J., Braitenberg, C., and Goetze, H.-J., 2006, The lithospheric density structure of the Eastern Alps: Tectonophysics, v. 414, p. 145–155, doi:10.1016/j.tecto.2005.10.015. Fenti, V., and Friz, C., 1973, Il progetto della galleria ferroviaria VipitenoInnsbruck (versante italiano): I—Ricerche geostrutturali sulla regione del Brennero: Mem: Museo Tridentino di Scienze Naturali, v. 20, no. 1, p. 1–59. Franz, G., Mosbrugger, V., and Menge, R., 1991, Carbo-Permian pteridophyll leaf fragments from an amphibolite facies basement, Tauern Window, Austria: Terra Nova, v. 3, p. 137–141, doi:10.1111/j.1365-3121.1991 .tb00865.x. Frisch, W., 1968, Geologie des Gebietes zwischen Tuxbach und Tuxer Hauptkamm bei Lanersbach (Zillertal, Tirol): Mitteilungen der Geologie- und Bergbaustudenten, v.18, p. 287–336. Frisch, W., 1974, Ein Typ-Profil durch die Schieferhülle des Tauernfensters: Das Profil am Wolfendorn (westlicher Tuxer Hauptkamm, Tirol): Verhandlungen der Geologischen Bundesanstalt, Wien, p. 201–221. Frisch, W., Kuhlemann, J., Dunkl, I., and Brügel, A., 1998, Palinspastic reconstruction and topographic evolution of the Eastern Alps during late Tertiary tectonic extrusion: Tectonophysics, v. 297, p. 1–15, doi:10.1016/ S0040-1951(98)00160-7. Frisch, W., Dunkl, I., and Kuhlemann, J., 2000, Post-collisional orogenparallel large-scale extension in the Eastern Alps: Tectonophysics, v. 327, p. 239–265. Fügenschuh, B., Seward, D., and Mancktelow, N., 1997, Exhumation in a convergent orogen: the western Tauern Window: Terra Nova, v. 9, p. 213– 217, doi:10.1046/j.1365-3121.1997.d01-33.x. Genser, J., and Neubauer, F., 1989, Low angle normal faults at the eastern margin of the Tauern window (Eastern Alps): Mitteilungen der Österreichische Geologische Geselleschaft, v. 81, p. 233–243. Gleißner, P., Glodny, J., and Franz, G., 2007, Age of pseudomorphs after lawsonite in metabasalts from the Glockner nappe, Tauern Window, Eastern Alps: European Journal of Mineralogy, v. 19, p. 723–734, doi:10.1127/0935-1221/2007/0019-1755. Glodny, J., Ring, U., and Kühn, A., 2008, Coeval high-pressure metamorphism, thrusting, strike-slip, and extensional shearing in the Tauern Window, Eastern Alps: Tectonics, v. 27, p. TC4004, doi:10.1029/2007TC002193. Handy, M.R., Schmid, S.M., Bousquet, R., Kissling, E., and Bernoulli, D., 2010, Reconciling plate-tectonic reconstructions of Alpine Tethys with the geological-geophysical record of spreading and subduction in the Alps: Earth-Science Reviews, v. 102, p. 121–158, doi:10.1016/j .earscirev.2010.06.002. Hoschek, G., 2007, Metamorphic peak conditions of eclogites in the Tauern Window, Eastern Alps, Austria: Thermobarometry of the assemblage garnet plus omphacite plus phengite plus kyanite plus quartz: Lithos, v. 93, no. 1-2, p. 1–16, doi:10.1016/j.lithos.2006.03.042. Kebede, T., Klötzli, U., Kosler, J., and Skiöld, T., 2005, Understanding the Pre Variscan and Variscan basement components of the central Tauern Window, Eastern Alps (Austria): constraints single zircon U-Pb geochronology: International Journal of Earth Sciences, v. 94, p. 336–353, doi:10.1007/s00531-005-0487-y. Kiessling, W., 1992, Palaeontological and facial features of the Upper Jurassic Hochstegen Marble (Tauern Window, Eastern Alps): Terra Nova, v. 4, p. 184–197, doi:10.1111/j.1365-3121.1992.tb00471.x. Kiessling, W., and Zeiss, A., 1992, New palaeontological data from the Hochstegen Marble (Tauern Window, Eastern Alps): Geologisch-Paäontologische Mitteilungen Innsbruck, v. 18, p. 187–202. Kissling, E., Schmid, S.M., Lippitsch, R., Ansorge, J., and Fügenschuh, B., 2007, Lithosphere structure and tectonic evolution of the Alpine arc: new evidence from high-resolution teleseismic tomography, in Gee, D.G., and Stephenson, R.A., eds., European Lithosphere Dynamics: Geological Society of London Memoirs 32, p. 129–145.

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The Geological Society of America Field Guide 22 2011

Glaciological and hydrometeorological long-term observation of glacier mass balance at Vernagtferner (Vernagt Glacier, Oetztal Alps, Austria) E. Mayr Department of Geography, Ludwig-Maximilians-Universität München, Luisenstr. 37, 80333 München, Germany H. Escher-Vetter C. Mayer M. Siebers M. Weber Commission for Geodesy and Glaciology of the Bavarian Academy of Sciences and Humanities, Alfons-Goppel-Str. 11, 80539 München, Germany

ABSTRACT Long-term glacier monitoring by the Commission for Geodesy and Glaciology of the Bavarian Academy of Sciences and Humanities has been taking place at Vernagtferner (Vernagt Glacier) since the early 1960s. Starting from 1974, the hydrometeorological station “Pegelstation Vernagtbach” provides runoff information. Additional, meteorological parameters, i.e., solar radiation, air temperature, humidity, pressure, precipitation, wind speed, and wind direction are recorded. This information is used to determine the glacier mass balance based on the geodetic, glaciological, and hydrological methods. Since 1981, the glacier mass and area have been shrinking significantly. If this trend continues, the major part of Vernagtferner will disappear within the next 60 years. During the field trip, participants will visit the different measurement sites on and around the glacier and will learn about the glacier’s past and future evolution. For more information about the Commission for Geodesy and Glaciology and its research at Vernagtferner, visit www.glaziologie.de.

INTRODUCTION Vernagtferner (Vernagt Glacier) (46°52′ N/10°49′ E) is located in the Vernagt Valley in Tirol, Austria, which is a tributary valley to Rofen Valley (Fig. 1). The catchment has an area of 11.4 km2 and extends from 2640 m a.s.l. to a maximum elevation

of 3630 m a.s.l. (Braun et al., 2006). The glacier has a total area of 7.92 km2 with a maximum ice thickness of 90 m and covers 69% of the basin area (data from 2010, www.glaziologie.de). The main part of the glacier is exposed to the south. Due to its plateau character, ~80% of its area is situated in elevations between 3100 and 3300 m a.s.l. (Hagg, 2003).

Mayr, E., Escher-Vetter, H., Mayer, C., Siebers, M., and Weber, M., 2011, Glaciological and hydrometeorological long-term observation of glacier mass balance at Vernagtferner (Vernagt Glacier, Oetztal Alps, Austria), in Carena, S., Friedrich, A.M., and Lammerer, B., eds., Geological Field Trips in Central Western Europe: Fragile Earth International Conference, Munich, September 2011: Geological Society of America Field Guide 22, p. 121–125, doi:10.1130/2011.0022(08). For permission to copy, contact [email protected]. ©2011 The Geological Society of America. All rights reserved.

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The Vernagtferner is among the best observed glaciers in the Alps. First observations date from the year 1600, when the glacier began to flow rapidly into the Rofen valley and caused the formation of an ice-dammed lake, which then drained rapidly after failure of the dam, with disastrous results for the villages downstream. These so-called “surge-type” glacier advances occurred again in intervals of ~80 years, with the last observed in 1845–1848. Between June 1844 and June 1845, the terminus advanced 882 m (2.5 m/day). The ice velocity increased from June to October 1845 to 1.0 m/day, from October 1845 to January 1846 to 2.1 m/day, from January to May 1846 to 3.3 m/day, and finally from May to June 1846 to 12.5 m/day. The lake, formed by the ice dam in the Rofen Valley, contained a water volume of ~10 × 106 m3 that emptied slowly in summer 1846 and suddenly in June 1845, May 1847, and June 1848. The floods caused great damage in the villages downstream and even in Innsbruck they caused a rise of the level of the river Inn of ~0.6 m. The transported ice blocks could be found all the way into the Danube River (Hoinkes, 1969). These surges were probably caused by increasing ice thickness in the upper glacier part, whose pressure led to a change of the drainage system of the glacier and thus to increasing speed. The ice from the upper glacier part was transported downward and allowed the rapid advance of the glacier. Surges are followed by a period of quiescence with ice speeds less than balance velocity, so the glacier thickens in the reservoir area again (Hooke 2005).

In 1889, S. Finsterwalder surveyed the glacier by terrestrial photogrammetry and produced the first detailed topographic map of an entire glacier (Finsterwalder, 1897). The accuracy was comparable to modern maps and, since then, the glacier surface was surveyed repeatedly by different geodetic methods (Braun et al., 2006). The Commission of Geodesy and Glaciology of the Bavarian Academy of Sciences and Humanities has been studying this glacier in detail since the beginning of the1960s within the framework of a long-term glacier-monitoring program. In 1973, the hydrometeorological station “Pegelstation Vernagtbach” was built, financed by the German Research Foundation (DFG) (Fig. 2). Because of constantly increasing runoff, the station had to be remodeled in 1995 and again in June 2000, when a second renovation was necessary due to flood damages. The station is situated at 2640 m a.s.l., ~1.5 km downstream from the glacier terminus. At this station, accurate long-term records of the total discharge of the Vernagtferner are collected. In addition to the runoff information, a climate station provides meteorological parameters, i.e., radiation, air temperature, humidity, air pressure, precipitation, and wind speed and direction (Braun et al., 2006). During the field trip, the dynamics of the glacier and its influence on the geomorphology of the area will be explained at several stops in the proglacial area and on the glacier itself. We will visit the hydrometeorological station and other monitoring locations where the different monitoring methods and their actual results will be shown.

Figure 1. Location of the Vernagtferner basin in the Alps.

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Figure 2. Gauging station “Pegelstation Vernagtbach.”

MASS BALANCE MONITORING AT VERNAGTFERNER One of the primary goals of the long-term glacier-monitoring program at Vernagtferner is to determine the mass balance of the glacier. The monitoring at the gauging station and at the glacier provides the necessary data. Three methods of mass balance determination are applied: the geodetic, the glaciological, and the hydrological method. The calculation of volume changes using the geodetic method started with the first large-scale glacier map of 1889 (Finsterwalder, 1897), followed by measurements in 1912, 1938, 1954, and 1969 and, since then, approximately every ten years. These and the subsequent maps were produced using photogrammetry. The recent maps have been replaced by orthophoto maps, and the volume changes have been calculated based on the differences in digital elevation models (Reinhardt and Rentsch, 1986). Direct measurements of glacier surface changes (glaciological method) were initiated in 1964. At Vernagtferner, winter and summer mass balances are determined separately in accordance with the “fixed date” system (Reinwarth and Escher-Vetter, 1999). Accumulation during the winter season is measured by numerous snow depth soundings and a smaller number of snow pits to determine the water equivalent of the snow pack, both distributed over the whole glacier. These spring surveys have been carried out since1964, too. Since 2004, the positions of the depth measurements have additionally been determined by Global Positioning System (Escher-Vetter et al., 2009). The annual mass balance is based on up to 50 ablation stakes (Fig. 3). At these stakes, melt is determined several times per year by measuring the stake length above the ice. Based on this data, the mass gain

or loss of the glacier over one glaciological year (1 October–30 September) is determined. The summer balance is calculated by the difference between annual and winter balance. The hydrological method was originally designed to determine glacier mass balance as a residual of the water balance. For this purpose, all other terms of the hydrological cycle need to be quantified. This means that precipitation, runoff, and evaporation data are required. Basin precipitation is determined separately for the winter and summer seasons. In winter, practically all precipitation falls as snow. Therefore, a direct measurement of the water equivalent of the snow pack on the glacier at the end of April is a good way to estimate cumulative winter precipitation (Braun et al., 2006). The main challenge in calculating basin precipitation is the transfer of point observations at the gauging station to the whole basin area. This is achieved by applying hydrological models; basin precipitation is determined as a residual. Runoff is measured at the gauging station in a defined measurement channel (Fig. 2). The amount of water, ice, and snow that is lost by evaporation is difficult to determine, but generally small compared to precipitation and runoff. Evaporation is estimated at Vernagtferner by models and by investigations at Vernagtferner and other glaciers (Braun et al., 2006). Using all these factors of the water balance, the annual mass balance of Vernagtferner can be calculated. RESULTS OF OBSERVATIONS The diurnal variation in discharge has increased over the thirty-seven years of observation due to strong glacier mass losses since 1980 and to the thinning of the firn areas, which act as hydrological buffers. The previously mentioned renovations

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Figure 3. The Vernagtferner basin with position of recording sites and location of ablation stakes and snow pits. Drainage basin area is 11.4 km2.

of the gauge in 1995 and 2000 were necessary in order to capture the total runoff and to protect the station against flood damage when strong melt is combined with intense rainfall (Reinwarth and Braun, 1998), which was the case, for example, in 1994. Meltwater alone produces maximum discharge values of up to 15 m3/s in summer but, in combination with rainfall, discharge can rise up to 20 m3/s. These values are contrasted by winter discharge of only ~10 l/s, which is typical for the glacial runoff regime. In general, the annual cumulative discharge has nearly doubled since the start of measurements in 1974 (Braun et al., 2006). The mass balance results are shown in Figure 4. After a period of positive glacier mass balance years in the 1960s and 1970s, the glacier is shrinking significantly. While the ice mass was 372 · 109 kg in 1969, it has decreased to 217 · 109 kg in 2010. The glacier area has decreased during the same time from 9.65 km2 to 7.92 km2. This recession is basically caused by the sum-

mer mass balance, which shows a clear trend from −1000 mm w.e. in the 1960s and 1970s to about −2000 mm w.e. in the 1980s and 1990s and up to −3000 in 2002 and 2003 (Braun et al., 2006). In this year, a very strong mass loss was driven by the extremely hot summer of 2003. Because of these mass losses and therefore the missing thickening in the upper glacier part, the glacier is no longer able to surge. The annual mass balance correlates strongly with the summer mass balance, but not at all with the winter mass balance. These results show the importance of separate determination of summer and winter mass balance which is very important for the climatological interpretation of glacier fluctuations. Current maximum ice thickness of Vernagtferner is ~90 m. In the central area of large ice thicknesses, the mean ice loss during the last decade was ~1.5 m/yr, ice transport is negligible. Even for similar climatic conditions, without taking into account additional warming, the major part of Vernagtferner would disappear within the next 60 years. Modeling results using the

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Figure 4. Winter, summer, and annual mass balance of the Vernagtferner for the period 1964/1965–2009/2010.

SURGES model in the framework of Glowa-Danube considered many feedback effects and shows the complex melting of the glacier until 2038 (Weber and Prasch, 2009). ACKNOWLEDGMENTS The staff of the Commission for Geodesy and Glaciology of the Bavarian Academy of Sciences and Humanities is acknowledged for their support collecting the information about the glacier and the gauging station. We also wish to thank the reviewers W. Hagg and L. Braun for their helpful comments on the manuscript. REFERENCES CITED Braun, L.N., Escher-Vetter, H., Siebers, M., and Weber, M., 2006, Water balance of the highly glaciated Vernagt basin, Ötztal Alps, in Proceedings, The water balance of the Alps—What do we need to protect the water resources of the Alps?, Innsbruck University, 28–29 September 2006: Innsbruck University Press. Escher-Vetter, H., Kuhn, M., and Weber, M., 2009, Four decades of winter mass balance of Vernagtferner and Hintereisferner: Methodology and results: Annals of Glaciology, v. 50, p. 87–95, doi:10.3189/172756409787769672.

Finsterwalder, S., 1897, Der Vernagtferner: Wissenschaftliche Ergänzungshefte zur Zeitschrift des Deutschen und Oesterreichischen Alpenvereins, v. 1, p. 5–96. Hagg, W., 2003, Auswirkungen von Gletscherschwund auf die Wasserspende hochalpiner Gebiete, Vergleich Alpen—Zentralasien, Münchner Geographische Abhandlungen, A 53. Hoinkes, H., 1969, Surges of the Vernagtferner in the Ötztal Alps since 1599: Canadian Journal of Earth Sciences, v. 6, p. 853, doi:10.1139/e69-086. Hooke, R., 2005, Principles of Glacier Mechanics: Cambridge University Press, 429 p. Reinhardt, W., and Rentsch, H., 1986, Determination of changes in volume and elevation of glaciers using digital elevation models for the Vernagtferner, Ötztal Alps, Austria: Annals of Glaciology, v. 8, p. 151–155. Reinwarth, O., and Braun, L.N., 1998, Structural adaptation of a high-alpine gauging station (Vernagtbach, Oetztal Alps/Austria) to greatly enhanced glacial discharge, in Chalise, S.R., et al., eds., Proceedings of the International Conference on Ecohydrology of High Mountain Areas, Kathmandu, Nepal, 24–28 March 1996: Kathmandu, ICIMOD (International Centre for Integrated Mountain Development), p. 199–205. Reinwarth, O., and Escher-Vetter, H., 1999, Mass balance of Vernagtferner, Austria, from 1964/65 to 1996/97: results for three sections and the entire glacier: Geografiska Annaler, v. 81A, no. 4, p. 743–751. Weber, M., and Prasch, M., 2009, Einfluss der Gletscher auf das Abflussregime (des Einzugsgebiets der Oberen Donau) in der Vergangenheit und der Zukunft: GLOWA-Danube-Projekt, LMU München, Global Change Atlas, Einzugsgebiet Obere Donau, München. MANUSCRIPT ACCEPTED BY THE SOCIETY 27 APRIL 2011 Printed in the USA