Field Guide to Samos and the Menderes Massif: Along-Strike Variations in the Mediterranean Tethyan Orogen (GSA Field Guide 23)

Field Guide 23

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THl GLOLOGICAL SOCIETY OF AMERICA

Along-Strike Variations in the Mediterranean Tethyan Orogen

By Klaus Gessner, Uwe Ring, and Tali p GUngo r

Field Guide to Samos and the Menderes Massif: Along-Strike Variations in the Mediterranean Tethyan Orogen

by Klaus Gessner Western Australian Geothermal Centre of Excellence and Centre for Exploration Targeting School of Earth and Environment The University of Western Australia M006 35 Stirling Highway Crawley WA 6008 Australia Uwe Ring Department of Geological Sciences University of Canterbury Private Bag 4800 Christchurch, New Zealand Talip Güngör Department of Geological Engineering Dokuz Eylül University Tinaztepe Campus Buca 35160 Izmir, Turkey

Field Guide 23 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. GSA Books Science Editors: Marion E. Bickford and Donald I. Siegel Library of Congress Cataloging-in-Publication Data Glessner, Klaus, 1967–. Field guide to Samos and the Menderes massif : along-strike variations in the Mediterranean Tethyan orogen / by Klaus Gessner, Uwe Ring, Talip Güngör. p. cm. — (Field guide ; 23) Includes bibliographical references. ISBN 978-0-8137-0023-6 (pbk.) 1. Orogeny—Greece—Samos Island. 2. Orogeny—Turkey. 3. Geology, Stratigraphic—Miocene. 4. Tethys (Paleogeography) 5. Geology—Fieldwork. I. Ring, Uwe. II. Güngör, Talip. III. Title. QE621.5.G8f54 2011 555.62′6—dc23 2011026962 Cover: Panoramic view of the Kerketas Massif in the southwest part of Samos Island, Greece (Locality 1.1 of this field guide). Outcrops of monotonous dolomite of Kerketas Nappe form the Mount Kerkis ridge in the background and variegated sequence of schists, quartzite, marble, and amphibolite make up the lower ground of the Ampelos Nappe in the foreground. The mylonitic foliation in the quartzite of the Ampelos Nappe is dipping to the SE and contains an ESE-trending stretching lineation associated with top-ESE shear sense indicators. View is toward the southwest. Photo courtesy of Klaus Gessner, 17 May 2010.

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Contents

Abstract . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 Geology of the Eastern Mediterranean . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 Paleogeography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 Regional Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Important Tectonic Contacts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Metamorphic History . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Basal Unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Cycladic Blueschist Unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Menderes Nappes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 Eocene–Oligocene Crustal Thickening . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 Miocene to Holocene Extension . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 Part A. Samos Island, Greece . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 Geology of Samos . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 General Architecture of Samos Island and Important Tectonic Contacts . . . . . . . . . . . . . . . . . . . . . . 11 Structural History and Deformation-Metamorphism Relationships . . . . . . . . . . . . . . . . . . . . . . . . . . 14 Day 1—Localities 1.1 to 1.6 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 Locality 1.1. Ridge East of Mount Kerkis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 Locality 1.2. Glaucophane Schist at Road Intersection North of Neochori . . . . . . . . . . . . . . . . . . 16 Locality 1.3. Breccia of Basal Conglomerate Formation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 Locality 1.4. Limestone of Pythagorion Formation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 Locality 1.5. Hora Formation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 Locality 1.6. Conglomerate of Mytilini Formation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 Day 2—High-Pressure Assemblages along the Northern Coast (Localities 2.1 to 2.3) . . . . . . . . . . . 18 Locality 2.1. Around Agios Konstandinos . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 Locality 2.2. West of Avlakia and East of Turnoff to Vourliotes . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 Locality 2.3. Gankou Beach . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 Part B. The Menderes Massif . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 Some Remarks about Controversies on Menderes Massif Tectonics. . . . . . . . . . . . . . . . . . . . . . . . . . 21 Architecture of the Menderes Massif . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 Miocene to Holocene Extension in the Central Menderes Region . . . . . . . . . . . . . . . . . . . . . . . . . 21 Alpine Nappe Tectonics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 The Menderes Nappes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 The Cycladic Blueschist Unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 The Cyclades-Menderes Thrust . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31 Interpretation of Deformation-Metamorphism-Timing Relationships . . . . . . . . . . . . . . . . . . . . . . 31 Menderes Massif Field Trips . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

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Contents Day 3—Around Selçuk (Localities 3.1 to 3.5) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34 Locality 3.1. Selçuk-Aydın Road Cut . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34 Locality 3.2. Ephesus Fault . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34 Locality 3.3. Metaconglomerates and Metapelites of the Dilek Nappe . . . . . . . . . . . . . . . . . . . . . 34 Locality 3.4. Yavansu Fault near Kuşadası . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35 Locality 3.5. Dilek Nappe Outcrops along the Coast Road . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35 Day 4—Section across the Bozdağ and Aydın Mountains . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35 Bozdağ Mountains (Localities 4.1 to 4.6) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36 Locality 4.1. Kuzey Detachment at Çakaldoğan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36 Locality 4.2. Kuzey Detachment Surface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36 Locality 4.3. Bayındır Nappe . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36 Locality 4.4. Bozdağ Nappe . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38 Locality 4.5. Küçük Menderes Graben . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38 Locality 4.6. Çine Nappe Garnet-Bearing Augen Gneiss . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38 Ödemiş Area and Aydın Mountains (Localities 4.7–4.11) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38 Locality 4.7. Çine Nappe Granitic Augen Gneiss . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38 Locality 4.8. Çine Nappe Augen Gneiss near Halıköy, Mercury Mine . . . . . . . . . . . . . . . . . . . . . . 38 Locality 4.9. Migmatite Gneiss at Adaküre (Adagide) Village . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38 Locality 4.10. Çine Nappe Granites and Gneisses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39 Locality 4.11. Metabasic Lenses in Çine Nappe . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39 Day 5—Western Aydın Mountains: Cyclades-Menderes Thrust and Güney Detachment (Localities 5.1 to 5.4) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40 Locality 5.1. Bozdağ Nappe North of Ortaköy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40 Locality 5.2. Bozdağ Nappe North of Yemişler . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40 Locality 5.3. Crossing the Cyclades Menderes Thrust . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40 Locality 5.4. Kuzey Detachment North of Meşeli . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40 Day 6—Southern Menderes Massif: The Selimiye Shear Zone and the Lake Bafa Area (Localities 6.1 to 6.7) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43 Locality 6.1. Foliation Boudinage in Çine Nappe Orthogneiss . . . . . . . . . . . . . . . . . . . . . . . . . . . 44 Locality 6.2. Çine Nappe Orthogneiss on the Edge of Selimiye Shear Zone . . . . . . . . . . . . . . . . . 44 Locality 6.3. Selimiye Shear Zone . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44 Locality 6.4. Intrusive Contacts within the Çine Nappe . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44 Locality 6.5. Platform Carbonates of the Dilek Nappe . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45 Locality 6.6. Folding in Lycian Nappes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47 Locality 6.7. Carpholite in Lycian Nappes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47 Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48 References Cited . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48

The Geological Society of America Field Guide 23 2011

Field Guide to Samos and the Menderes Massif: Along-Strike Variations in the Mediterranean Tethyan Orogen Klaus Gessner* Western Australian Geothermal Centre of Excellence and Centre for Exploration Targeting, School of Earth and Environment, The University of Western Australia M006, 35 Stirling Highway, Crawley WA 6008, Australia Uwe Ring* Department of Geological Sciences, University of Canterbury, Private Bag 4800, Christchurch, New Zealand Talip Güngör* Department of Geological Engineering, Dokuz Eylül University, Tinaztepe Campus, Buca 35160, Izmir, Turkey

ABSTRACT In this field-trip guide we explore the tectonics of Samos and the Menderes Massif, two fascinating areas within the eastern Mediterranean section of the Tethyan orogen. We include detailed outcrop descriptions, maps, and diagrams to explore along-strike variations in the Hellenide-Anatolide orogen, including the architecture of the Early Tertiary Alpine nappe stack and its strong Miocene extensional overprint. The suggested itinerary is based on the 2010 Geological Society of America Field Forum “Significance of Along-Strike Variations for the 3-D Architecture of Orogens: The Hellenides and Anatolides in the Eastern Mediterranean.” We start the outcrop descriptions with Day 1 in Samos, where, untypically for the N-S–stretched Aegean region, Miocene extension is E–W. We describe a section in western Samos, where the Cycladic Blueschist Unit is in contact with the underlying External Hellenides along a large-scale thrust, reactivated as a Miocene top-east extensional shear zone. The focus of Day 2 is on high-pressure assemblages in northern Samos. The following three days explore the Anatolide Belt in western Turkey where the Menderes nappes—also known as the Menderes Massif—form the tectonic footwall below the Cycladic Blueschist Unit. The outcrops in western Anatolia include the Cycladic Blueschist Unit in the area around Selçuk (Day 3) and sections across the Bozdağ and Aydın Mountains including the Kuzey and Güney detachment faults and the Cycladic Menderes Thrust (Days 4 and 5). Outcrops on Day 6 showcase structures along the southern margin of the Menderes Massif in the Milas–Selimiye area.

*[email protected]; [email protected]; [email protected]. Gessner, K., Ring, U., and Güngör, T., 2011, Field Guide to Samos and the Menderes Massif: Along-Strike Variations in the Mediterranean Tethyan Orogen: Geological Society of America Field Guide 23, 52 p., doi:10.1130/2011.0023. For permission to copy, contact [email protected]. ©2011 The Geological Society of America. All rights reserved.

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INTRODUCTION

ern Turkey to evolve in sharply different ways. We believe that better identification and understanding of those differences will potentially clarify how eastern Mediterranean subduction zones evolved, how pre-orogenic architecture controls crustal thickening and the subsequent exhumation of high-pressure rocks, and how large-scale continental extension evolves. These studies also bear on a number of new and innovative methods for interpretation of geochronologic data for direct dating of deformation and metamorphism (Glodny et al., 2002, 2008). Deciphering temporal aspects of orogenic processes is an important objective in tectonics. The key to successful dating of orogenic processes directly depends on appropriate sampling in the field; therefore, it is crucial that this aspect be discussed thoroughly in the field. The spatial and temporal evolution of the HellenideAnatolide orogen is also significant economically because of its key importance to understanding spatial controls on faults and basins for hydrocarbon generation, metallogeny, and geothermal resources.

Much of the conceptual understanding of the development of orogens is still largely based on assuming “cylindricity,” i.e., the premise of structural continuity along strike. However, lithospheric architecture and strain in orogens usually vary substantially, both across and along strike. Consequently, along-strike variations have been described from a number of orogens, including the European Alps, the North American Cordillera, the Andes, and the Hellenide-Anatolide orogen of southeastern Europe. The causes for along-strike variations might be different, but pre-orogenic paleogeography, continental architecture, lateral changes in the nature of the downgoing (subducting) lithosphere, and kinematic-geometric variations at the lithospheric scale potentially play an important role. Along-strike changes in orogens have a profound impact on how major orogenic processes proceed in time and space. Here we present an example of along-strike variations in the Hellenide-Anatolide orogen in the eastern Mediterranean. This field guide has evolved from an informal document handed out to the participants of the Geological Society of America Field Forum, “Significance of Along-Strike Variations for the 3-D Architecture of Orogens: The Hellenides and Anatolides in the Eastern Mediterranean,” which the authors organized together with Nikos Skarpelis, Dov Avigad, and Olivier Vanderhaeghe from 16 to 22 May 2010. The field forum itself was borne of trans-disciplinary field-based studies pointing out major along-strike variations in the Hellenide-Anatolide orogen (Gessner et al., 1998, 2001c; Ring et al., 1999a) that bear strongly on future research directions. These studies have shown that differences in pre-orogenic paleogeography caused the Hellenide orogen of eastern Greece and the Anatolide Belt of west-

GEOLOGY OF THE EASTERN MEDITERRANEAN Paleogeography The relative motion of the Adriatic plate (here referred to as Adria) controls the late Mesozoic to Holocene orogenic development of the Mediterranean region to a large degree. Adria is a small tectonic plate (microplate) that broke away from the African plate in the Cretaceous and is thought to still move independently of the Eurasian plate. In the eastern Mediterranean, Adria pinches out. Figure 1 shows a schematic paleogeographic reconstruction of the area. In the eastern Mediterranean, little is known

Eurasia

N o rt h e

‘Pin

Sakarya

rn N e o te th y s

Tavşanli

V ardar-Izmi r-A nkara ocean

Pelagonia

dos

Rift

Adria

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’

Lycian platform

Afyon / Ören k oce an’ Cycladic - Dilek platform

‘S e lç u

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Anatolia

rm Tripolitza platfo

ift’ ‘Ionian R Southern Neotethys

Africa

?

Figure 1. Simplified and speculative reconstruction of the Cretaceous (ca. 70 Ma) paleogeography in the eastern Mediterranean, based on Şengör and Yilmaz (1981), Gessner et al. (2001c), and van Hinsbergen et al. (2010). Dashed lines refer to contentious interpretations, such as the link between Adria and Anatolia (Dürr et al., 1978; Şengör and Yilmaz, 1981) versus the existence of a small backarc “Selçuk ocean” (Ring et al., 1999a, 2007a; Gessner et al., 2001c). The Cyclades-Dilek platform provided the protolith for metasediments in the Dilek Nappe, which constitutes the lower part of the Cycladic Blueschist Unit.

Field Guide to Samos and the Menderes Massif about the Mesozoic to early Tertiary paleogeography of the Adriatic plate. In the Greek transect, Adria is characterized by ribbons of normal-thickness continental crust and intervening parts of highly stretched and thinned crust that may or may not have been partly oceanic (Jacobshagen, 1986; Robertson et al., 1991). Stretching and possible generation of oceanic crust resulted from Mesozoic rifting during and prior to the Cretaceous, when Adria was the northern part of the African plate. These rifting processes ultimately separated Adria from Africa. Farther east, Neotethys broadened (Robertson et al., 1991; Stampfli et al., 2001), and a number of continental blocks that rifted off Gondwana in the Jurassic and Cretaceous drifted northward toward subduction zones at the northern margin of Neotethys. In the eastern Mediterranean the continent directly east of Adria was Anatolia (Gessner et al., 2001c). Regional Structure The Hellenide orogen of Greece and the Anatolide Belt of western Turkey form an arcuate orogen to the north of the present-day active Hellenic margin, which marks the site of northeastward underthrusting of the African plate underneath Europe (Fig. 2). Both regions consist of stacked nappes that are limited to the north by the Late Cretaceous to Paleogene Vardar-IzmirAnkara Suture Zone. The Hellenides can be subdivided from top (north) to bottom (south) into (1) an “internal zone,” consisting of the Rhodope-Sakarya-Strandja Block, (2) the Vardar-IzmirAnkara Oceanic Unit, (3) the Pelagonian-Lycian Unit, (4) the Pindos Unit (including the Cycladic Blueschist Unit), (5) the External Hellenides, comprising the Gavrovo-Tripolitza Block and the underlying Ionian Block, and (6) the Mediterranean Ridge Accretionary Complex (Fig. 2). The main aspect of this field guide concerns the lowest tectonic units of the Anatolide and Hellenide nappe stacks. In the Anatolides the Pindos Unit overlies the Menderes nappes, which are part of Anatolia, whereas in the Aegean region the Pindos Unit overlies the Basal Unit, which is part of the Gavrovo-Tripolitza Block (External Hellenides) (Dürr et al., 1978; Robertson et al., 1991; van Hinsbergen et al., 2005). The major differences between the Menderes nappes and the Basal Unit are that the nappe piles have distinct architectures (Gessner et al., 1998; Ring et al., 1999a). What we summarize as the Vardar-Izmir-Ankara Oceanic Unit represents the remnants of a Triassic to early Paleocene ocean that were subducted below Eurasia or Sakarya since the Cretaceous. In western Turkey we include Cretaceous to Paleogene subduction-accretion complexes in the footwall of the actual Izmir-Ankara-Erzincan suture, including the Tavşanlı zone, and the Bornova Flysch zone (sensu Okay and Tüysüz, 1999; Okay, 2011). In southern Bulgaria a volcanic arc related to the subduction of the Vardar-Izmir-Ankara Oceanic Unit was initiated at ca. 90 Ma (von Quadt et al., 2005). The Pelagonian-Lycian Unit, in which we include the ÖrenAfyon zone rocks (Okay and Tüysüz, 1999; Pourteau et al.,

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2010), occurs structurally below the Vardar-Izmir-Ankara Oceanic Unit. Parts of the Vardar-Izmir-Ankara Oceanic Unit and of the Pelagonian-Lycian Unit were metamorphosed under blueschist-facies conditions between ca. 125 and 85 Ma (Lips et al., 1999; Sherlock et al., 1999; Ring and Layer, 2003; Ring et al., 2003a; Pourteau et al., 2010). Above the southern edge of the Pelagonian-Lycian Unit, the Meso-Hellenic and Thrace Basins formed in a forearc position at the beginning of the Eocene (Vamvaka et al., 2006; Huvaz et al., 2007). The units to the south, i.e., in the footwall of the PelagonianLycian Unit, do not have a Cretaceous orogenic history. They became involved in subduction-accretion and associated highpressure metamorphism at least 20 m.y. later than the Pelagonian-Lycian Unit and the Vardar-Izmir-Ankara Oceanic Unit (Ring et al., 2010). The Pindos Unit (Fig. 2) is a heterogeneous paleogeographic domain that mainly includes normal-thickness, continental basement–cover sequences. Also, the Pindos Unit contains thick radiolarite sequences, indicating that it was either underlain by oceanic crust or by thinned continental crust (Pe-Piper and Piper, 1984; Robertson et al., 1991). In the Cyclades the uppermost unit of the Pindos Unit is the highly attenuated ophiolitic Selçuk Mélange (Okrusch and Bröcker, 1990; Ring et al., 1999a; Katzir et al., 2000), which now traces the suture between the Pindos Unit and the overlying Pelagonian-Lycian Unit (Ring and Layer, 2003). Slivers of oceanic crust (gabbro, plagiogranite, basalt) that formed at ca. 80–65 Ma (Keay, 1998) formed blocks with a serpentinitic matrix of the Selçuk Mélange. Below the Selçuk Mélange the continental rocks of the Cycladic Blueschist Unit constitute the most deeply exhumed parts of the Hellenides. This unit comprises a Carboniferous basement of schist and orthogneiss, and a late- to post-Carboniferous passive-margin sequence of marble, metapelite, and volcanics (Dürr et al., 1978). The passive-margin sequence is unconformably overlain in southwestern Turkey by middle to upper Paleocene flysch (Özer et al., 2001). Initial flysch deposition slightly predates the beginning of sedimentation in the Meso-Hellenic and Thrace forearc basins. The flysch and forearc basin sediments were deposited in response to the inception of subduction of the Pindos Unit (Ring et al., 2010). The different elements of the Pindos Unit are part of an accretionary complex that formed between ca. 55 and 30 Ma (Ring et al., 2003a, 2010; Jolivet and Brun, 2010). The Gavrovo-Tripolitza Block represents a continental platform unit of Triassic to Eocene age and is partly overlain by late Eocene to early Oligocene flysch (Jacobshagen, 1986). Underthrusting of the Gavrovo-Tripolitza Block commenced at ca. 35–30 Ma (Thomson et al., 1998; Sotiropoulos et al., 2003). In the Cyclades, high-pressure rocks of the Gavrovo-Tripolitza Block are usually referred to as the Basal Unit, which is locally exposed in tectonic windows through the overlying Cycladic Blueschist Unit (Godfriaux, 1968; Shaked et al., 2000), including in Samos (Ring et al., 2001b). Farther south in the Peloponnese and in Crete the rocks of the Gavrovo-Tripolitza Block and the Pindos Unit are only weakly metamorphosed. The Ionian block

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Quaternary

Unit Pindos Unit (including Cycladic Blueschist Unit)

Rhodope-SakaryaStrandja Block Vardar-Izmir-Ankara Oceanic Unit

Menderes Nappes Gavrovo-Tripolitza Block

ca.

ca.

ca.

Figure 2. Simplified tectonic map of the Aegean region, showing the main tectonic zones above the Hellenic subduction zone (modified from Jolivet and Brun, 2010). The Mediterranean Ridge represents the modern accretionary wedge that is bounded to the north by a major backthrust system. Red line-patterns indicate the positions of subduction-related magmatic-arc rocks from ca. 38 Ma to the Holocene (Fytikas et al., 1984; Barr et al., 1999; Pe-Piper and Piper, 2002). The migration of this magmatic arc in the overriding plate mimics the retreat of the Hellenic slab. Also shown in the north is a volcanic arc related to the subduction of the Vardar-Izmir-Ankara Oceanic Unit at ca. 90 Ma.

Field Guide to Samos and the Menderes Massif comprises Late Carboniferous to possibly Triassic rocks overlain by limestone and late Eocene to Miocene flysch (Jacobshagen, 1986). Rocks of both the Gavrovo-Tripolitza and Ionian Blocks do not crop out in western Turkey (Fig. 2). The southernmost and most outboard tectonic domain of the Hellenides is the Mediterranean Ridge Accretionary Complex (Fig. 2) (Kopf et al., 2003). The onset of accretion occurred at ca. 19 Ma during ongoing subduction of Triassic oceanic crust of the eastern Mediterranean Ocean (van Hinsbergen et al., 2005). Along the central Mediterranean Ridge this oceanic crust of the eastern Mediterranean Ocean has been completely consumed, and the leading edge of the African passive continental margin is currently entering the subduction zone. The overall structure of the Anatolide Belt consists of the Lycian nappes as part of the Lycian-Pelagonian Unit. Recently the Lycian nappes have been subdivided into the high-pressure Ören-Afyon Zone and the unmetamorphosed Lycian nappes sensu stricto (Pourteau et al., 2010). The Lycian nappes rest on the Cycladic Blueschist Unit, the latter of which have been thrust along the Cyclades-Menderes Thrust onto the Menderes nappes (Gessner et al., 2001c). The Menderes nappes comprise four main tectonic units that we interpret as nappes (Ring et al., 1999a; Gessner et al., 2001c; Régnier et al., 2003). From top to bottom these are (1) the Selimiye Nappe, (2) the Çine Nappe, (3) the Bozdağ Nappe, and (4) the Bayındır Nappe. The Çine and Bozdağ Nappes have a polyorogenic history, which extends back into the Neoproterozoic–Cambrian (Candan et al., 2001; Gessner et al., 2001a, 2004; Ring et al., 2001b). The Selimiye Nappe at the top of the nappe pile contains Paleozoic metapelite, metabasite, and marble (Schuiling, 1962; Çağlayan et al., 1980; Loos and Reischmann, 1999b; Régnier et al., 2003; Gessner et al., 2004). The Eocene Selimiye Shear Zone separates the Selimiye Nappe from the underlying Çine Nappe (Régnier et al., 2003). Most of the Çine Nappe consists of deformed orthogneiss, largely undeformed metagranite, and minor pelitic gneiss, eclogite, and amphibolite. Protoliths of much of the orthogneiss-metagranite intruded at ca. 560–530 Ma (Loos and Reischmann, 1999b; Gessner et al., 2001a, 2004). The underlying Bozdağ Nappe is made up of metapelite with intercalated amphibolite, eclogite, and marble lenses. Protolith ages of all rock types of the Bozdağ Nappe are unknown, but geologic constraints (Candan et al., 2001; Gessner et al., 2001a) suggest a Precambrian age for at least parts of these rocks. The Bozdağ Nappe was intruded by granitoids at 240–230 Ma (Dannat and Reischmann, 1999; Koralay et al., 2001). The Bayındır Nappe contains phyllite, quartzite, marble, and greenschist of inferred Permo-Carboniferous to Mesozoic age (Özer and Sozbilir, 2003). The rocks were affected by a single Eocene greenschist-facies metamorphism (Catlos and Çemen, 2005; Çemen et al., 2006). The analysis of regional structures and metamorphism shows that the tectonic units below the Cycladic Blueschist Unit are different in Greece from those in western Turkey. The oldest known basement rocks in the Phyllite-Quartzite Unit are

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ca. 510 Ma (Romano et al., 2004), whereas there is evidence for a Pan-African orogenic cycle in parts of the Menderes nappes (Oberhänsli et al., 1997; Gessner et al., 2001c, 2004; Ring et al., 2004). The Late Triassic to Eocene platform sequence of the Gavrovo-Tripolitza Block has no equivalent in the Menderes nappes of western Turkey. The orogenic history of both tectonic units was also different: The Gavrovo-Tripolitza Block did not enter the subduction zone until ca. 35–30 Ma, whereas the Menderes nappes were already underthrust by that time. Important Tectonic Contacts Critical for understanding the local geological architecture are the nappes of the Gavrovo-Tripolitza Block (the Basal Unit on Samos), the Cycladic Blueschist Unit (Selçuk, Ampelos and its mainland equivalent Dilek, and Agios Nikolaos Nappes both on Samos and in western Turkey), and the Menderes nappes of western Turkey (Fig. 3). In the following we describe the tectonic contacts between these units from top to bottom. On top of the succession in both Samos and western Turkey is the Selçuk Ophiolitic Mélange, which is separated from the underlying Ampelos-Dilek and Agios Nikolaos Nappes by the Selçuk Normal Shear Zone (Gessner et al., 2001c; Ring et al., 2007b). This shear zone must have been a thrust during early Eocene subduction and accretion. However, the present kinematics in the Selçuk Normal Shear Zone are top-to-the NE, and it resulted from normal faulting between 42 and 32 Ma (Ring et al., 2007b). As mentioned above, the Ampelos-Dilek and Agios Nikolaos Nappes rest on different units. In Samos, both nappes have been placed atop the Basal Unit along the Pythagoras Thrust (Ring et al., 1999b), whereas in western Turkey both nappes have been put on top of several of the Menderes nappes along the CycladesMenderes Thrust (Gessner et al., 2001c), including the Selimiye Nappe. The Pythagoras Thrust is supposed to have been reactivated as a top-to-the-E extensional fault associated with midTertiary basin development in Samos (Ring et al., 1999b). The Cyclades-Menderes Thrust has top-to-the-S kinematics (Gessner et al., 2001a) and operated coevally with the Selçuk Normal Shear Zone (Ring et al., 2007b). The Menderes nappes beneath the Cyclades-Menderes Thrust were imbricated by top-to-the-S movement on the thrusts between the various nappes. The thrust zone relevant for this field-trip guide is the Eocene Selimiye Shear Zone, which separates the Selimiye and the Çine Nappes. Metamorphic History In this section critical rock types of the Basal Unit (on Samos), the Cycladic Blueschist Unit (Selçuk, Ampelos, and Agios Nikolaos Nappes both on Samos and in western Turkey), and the Menderes nappes of western Turkey will be described, followed by estimates of pressure-temperature (P-T) conditions of metamorphic events. Details of the metamorphic history have

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S

N

Cyclades and western Anatolia Vard ar-Iz Oce mir-Ank anic a Unit ra

B Uni

t

Pela goni an Lyci an U nit

Crete Gavr

ovo-

Ionia

n Zo

Tripo li

tza

Pind os Dilek (Cyclade s platf orm) Base men t Gavr ovoT (Bas ripolitza al Un it)

?

ne

Lycia n Amp

elos

Ana tolia

Napp

Lycia n

es

k Na

ppe Agio Niko s Kerk laos etas Napp e

Napp

es

M

M

/ Dile

Cyclades

Selç u Ocea k nic Unit

Dilek Men

Menderes

Napp

dere

e

s Na

ppes

Figure 3. Schematic architecture of tectonic units in the Aegean Sea region and western Anatolia (cf. Figs. 1 and 2). Modified from Ring and Layer (2003).

been extensively discussed elsewhere (Mposkos, 1978; Will et al., 1998; Ring et al., 2001b, 2007b; Whitney and Bozkurt, 2002; Régnier et al., 2003). Basal Unit There are hardly any diagnostic metamorphic minerals in the various marbles of the Kerketas Nappe on Samos. Most of the marbles contain phengitic white mica, talc, and chlorite. The metabauxite deposits on the western flank of the Kerketas Massif show early diaspore that has been transformed to corundum, and corundum then reacted back to diaspore (Mposkos, 1978). The correlative Almyropotamos Nappe on Evia in the western Aegean shows similar parageneses as the Kerketas Nappe on Samos (Shaked et al., 2000). However, sporadic glaucophane has been found in the Almyropotamos Nappe. P-T conditions of 8–10 kbar and ~400 °C have consistently been reported for the Basal Unit in the central Aegean (Ring et al., 1999b; Shaked et al., 2000). This weak high-pressure overprint occurred at 24–21 Ma (Ring et al., 2001a, 2003b; Ring and Reischmann, 2002). At a later stage, probably during regional extension, the Kerketas Nappe heated slightly to >420 °C as indicated by the transformation of diaspore to corundum (Mposkos, 1978).

Cycladic Blueschist Unit The P-T conditions inferred for high-pressure metamorphism in the Agios Nikolaos Nappe of the Cycladic Blueschist Unit have shown to be ~18–19 kbar and ~510–530 °C (Will et al., 1998). Age data for the Cycladic Blueschist Unit for a number of islands (e.g., Sifnos, Naxos, Ios, Syros, Tinos, Ikaria) across the entire Aegean are interpreted to date the peak of high-pressure metamorphism from 55 to 30 Ma (Wijbrans et al., 1990; Tomaschek et al., 2003; Ring et al., 2010). 40Ar/ 39Ar dating of phengite showed that ages of >45 Ma have to be envisaged for the peak of high-pressure metamorphism in the Cycladic Blueschist Unit on Samos (Ring et al., 2003b). The temperatures inferred for the strongly foliated chloritoid–kyanite–white mica schists from the Ampelos-Dilek Nappe are 500–540 °C, but with pressures ranging from ~5 to 15 kbar. A possible interpretation of these data is that the rocks underwent a near isothermal decompression from eclogite to epidote-amphibolite and greenschist-facies conditions related to tectonic extrusion of the Ampelos Nappe between 42 and 32 Ma (Ring et al., 2007a). In metagabbro from the basal Selçuk Nappe in western Turkey, calculations were carried out on mineral assemblages containing

Field Guide to Samos and the Menderes Massif barroisitic hornblende, epidote-zoisite, plagioclase, chlorite and ± quartz. Clearly, this is an assemblage transitional between the middle to upper greenschist and lower blueschist facies. Furthermore, the jadeite barometer was used for the omphacite-bearing massive metagabbros. A garnet-amphibolite from the Selçuk Nappe in western Turkey yielded well-constrained P-T conditions of 550 ± 18 °C and 12.4 ± 1.2 kbar, which is considered to reflect maximum P-T in the Selçuk nappe. The conditions inferred correspond with estimates on undeformed metagabbros from Samos: 8–12 kbar and 400–500 °C and are transitional between epidote-amphibolite and eclogite facies conditions. In contrast, strongly foliated, mylonitized Selçuk Nappe metagabbros in the Selçuk Normal Shear Zone consistently yielded P-T values of 4 ± 1.5 kbar and 450 ± 40 °C. Similar greenschist-facies P-T estimates of ~3–4 kbar and 420–440 °C were also obtained for Selçuk Nappe metagabbros that occur as lenses in the underlying Ampelos Nappe (Ring et al., 2007a). Evidence for high-pressure metamorphism in the Selçuk Nappe is preserved only in the unfoliated samples but is no longer present in the mylonitized metagabbros from the Selçuk Normal Shear Zone. Presumably, this is the case, because fluid ingress hydrated the mylonitic metagabbros in the Selçuk Shear Zone and caused retrogression of the rocks under greenschist-facies conditions of 3–5 kbar. This deformation-related greenschistfacies overprint in the Selçuk Nappe apparently occurred before 32 Ma (Ring et al., 2007a). The Eocene eclogite-facies metamorphism (10–12 kbar) of the Selçuk Nappe was followed by a shearing-related greenschist facies overprint at 3–4 kbar. These data imply that the Selçuk Nappe must have been exhumed by ~20–30 km between the high-pressure metamorphism and the end of the mylonitization event. This decompression was accompanied by only slight to moderate cooling from 500 °C to 420–440 °C and is ascribed to Eocene normal shearing in the Selçuk Normal Shear Zone (Ring et al., 2007b). The P-T data reveal a pronounced metamorphic break (up to 10 kbar) toward higher pressures and temperatures between the Kerketas and Agios Nikolaos Nappes. An inverse break in metamorphic pressure of ~3–5 kbar occurs above the Agios Nikolaos Nappe. Menderes Nappes High-grade metamorphism in the Çine and Bozdağ Nappes occurred before the intrusion of granites at ca. 550 Ma (Gessner et al., 2001a, 2004); this topic will be addressed in a later section. Reliable P-T estimates for the Tertiary tectonometamorphic evolution exist only for the uppermost nappe of the Menderes nappe pile, the Selimiye Nappe (Whitney and Bozkurt, 2002; Régnier et al., 2003). Metasediments from the Selimiye Nappe have maximum P-T conditions of ~130 °C until 5 Ma; the footwall of the Güney Detachment (BMD) started to cool below ~130 °C at 14 Ma, but final cooling occurred only after 2 Ma (Ring et al., 2003a).

Field Guide to Samos and the Menderes Massif ■

PART A. SAMOS ISLAND, GREECE

Samos is not one of the typical Aegean “turtle-back–shaped core-complex type” islands like Ios or Mykonos, for example. The general structure of Samos is dominated by steep faults, and the overall architecture of the islands is best described as a horst. The topography of Samos is rugged and dominated by the sheer cliffs of 1433-m-high Mount Kerkis in the western part of the island (Fig. 7). The geology of Samos consists of a number of metamorphosed nappes, one non-metamorphosed nappe, and a Miocene graben. The island offers a look at an exceptionally complete nappe stack of the Central Hellenides, ranging from the highpressure–metamorphosed Basal Unit (as part of the External Hellenides), all the way up to the ophiolitic Selçuk Nappe and the non-metamorphosed Cycladic Ophiolite Nappe. This field guide is concerned with the two structurally lowest units, the Basal Unit and the overlying Cycladic Blueschist Unit, as well as the Tertiary sediments. Geology of Samos A simplified geological map of Samos Island is shown on a map (Fig. 8) and two cross sections (Fig. 9). The nappe pile and the Neogene basins are summarized schematically in Figure 10. The nappe stack consists of six major tectonic units, which are described in descending order: 1. The Kallithea Nappe is part of the Cycladic Ophiolite Nappe, which probably belongs to the Vardar-Izmir-Ankara Oceanic Unit. The Kallithea Nappe consists of peridotite, basalt, Triassic-Jurassic limestone, radiolarite, and sandstone (Theodoropoulos, 1979). The Katavasis Complex, consisting of amphibolite-facies schist, marble, and amphibolite, forms a tectonic block in the Kallithea Nappe (Ring et al., 1999b).

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2. The Selçuk Nappe is the uppermost nappe of the Cycladic Blueschist Unit and is exposed only in a few patches. It is far more extensively exposed on the westernmost Turkish mainland some 10–20 km east of Samos (Gessner et al., 2001c; Ring et al., 2007b). The Selçuk Nappe is essentially an ophiolitic mélange and contains metagabbro, in part in primary contact with serpentinized peridotite and mica schist. 3. The Ampelos Nappe is composed of the shelf sequence of the Cycladic Blueschist Unit and contains marble (with metabauxite lenses), metapelite (including conspicuous chloritoidkyanite schist), quartzite, glaucophane-epidote schist, and greenschist. Detailed work showed that the Ampelos Nappe is correlative with the Dilek Nappe of adjacent western Turkey (Candan et al., 1997; Ring et al., 1999a, 1999b; Gessner et al., 2001c). 4. The Agios Nikolaos Nappe at the base of the Cycladic Blueschist Unit is, like the Selçuk Nappe, exposed only in a few outcrops at the northern coast between the church of Agios Nikolaos and Konstandinos. It forms part of the Carboniferous basement of the Cycladic Blueschist Unit and consists of metagranitic gneiss, garnet-mica schist, and dolomitic marble. 5. The Kerketas Nappe of the Basal Unit is made up of a succession of monotonous dolomitic marble at least 1000 m thick, the base of which is not exposed. The Basal Unit is generally correlated with the Gavrovo-Tripolitza Block of the External Hellenides (Godfriaux, 1968). 6. Molasse-type sediments were deposited in the Miocene and Pliocene in N-, NE-, and WNW-oriented Karlovasi, Pyrgos, and Mytilini Grabens, which are filled with fluviatile and lacustrine sediments (Figs. 9 and 10). Above the Basal Conglomerate Formation are the Pythagorion and Hora Formations, which laterally interfinger. The sediments of the Hora Formation are thought to have formed in a deeper basin than the limestone of the Pythagorion Formation (Weidmann et al., 1984). A major angular unconformity is present at the top of the Hora Formation. Lacustrine sedimentation is succeeded by fluviatile conglomerate of the basal Mytilini Formation. Weidmann et al. (1984) showed that in some places the unconformity occurs on top of the Old Mill beds, whereas in other places it occurs below these beds. This difference might indicate that the unconformity did not occur at the same time in all parts of the basin, or it might indicate that the Old Mill beds are time-transgressive. General Architecture of Samos Island and Important Tectonic Contacts

Figure 7. View of Samos from the NE, showing the Kerketas Massif, which is part of the lowest tectonic unit in Samos, the Basal Unit.

The island of Samos in the Aegean Sea exposes highpressure metamorphic rocks of the Cycladic Blueschist Unit, which are sandwiched between the mildly blueschist-facies Kerketas Nappe below and the overlying non-metamorphic Kallithea Nappe. The general architecture of the island is depicted in two generalized cross sections in Figure 9. Overall the nappe pile dips to the east.

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Figure 8. Simplified geological map, showing major rock units, thrusts, and and representative measurments of Samos (modified from Theodoropoulos, 1979). Lower series of graben fill comprise Basal Conglomerate and Pythagorion and Hora Formations. Upper series of graben fill include Mytilini and Kokkarion Formations (see also Figs. 9 and 10). The D1 Ampelos and Selçuk Thrusts are the basal thrusts of the Ampelos and Selçuk Nappes, respectively. The D2 Pythagoras thrust put the Cycladic Blueschist Unit on top of the Kerketas Nappe. The Kallithea Detachment is a late-D3 low-angle normal fault. Middle to late Miocene volcanic and volcanoclastic rocks occur at the eastern and northeastern margins of the Karlovasi and Pyrgos Grabens and at the western side of the Mytilini Basin. Numerous reverse (D4) and normal (D5) faults overprinted all earlier ductile contacts. We interpret the curved D5 high-angle normal faults to have a listric geometry.

Figure 9. Serial cross sections A–A′ and B–B′ through Samos Island, showing general architecture of the island (refer to Fig. 6 for transect positions). The trace of the main foliation illustrates the generally E-dipping structure.

Field Guide to Samos and the Menderes Massif

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Figure 10. Idealized comparative tectono-stratigraphic column of the nappe pile on Samos Island. Notice that the dashed line between the Hora and Mytilini Formations is an unconformity.

The base of the Kerketas Nappe is not exposed. At the northern end of the island the dolomite of this nappe can be followed from the top of Kerkis Mountain down to the sea. The contact of the Kerketas Nappe with the Agios Nikolaos Nappe has been excised, either by Eocene out-of-sequence thrusting and/or subsequent Eocene normal shearing, or by Miocene extensional shearing (see “Structural History and Deformation-Metamorphism Relationships” section). What is well exposed is the Pythagoras Thrust, separating the Kerketas Nappe from the overlying Ampelos Nappe (see Locality 1.1 descriptions). 40Ar/ 39Ar phengite ages of ca. 30–35 Ma have been interpreted to date shear-related phengite recrystallization during thrusting of the Cycladic Blueschist Unit onto the Kerketas Nappe (Ring and Layer, 2003). The Pythagoras Thrust was then reactivated as a top-E extensional fault in the middle Miocene, probably associated with the formation of the middle Miocene basins. The base of the Agios Nikolaos Nappe is nowhere exposed. The upper contact of this nappe is poorly exposed in the northern Ampelos Massif at the central north coast of the island. Whereas there is no unambiguous evidence as to whether this contact is a thrust-type or normal shear zone, it has been speculated that the latest penetrative ductile deformation might have normal-sense kinematics relating to the Eocene motion of the Selçuk Normal Shear Zone (Ring et al., 2007b).

The Selçuk Normal Shear Zone separates the Ampelos Nappe from the overlying Selçuk Nappe. Using detailed 40Ar/39Ar and Rb–Sr dating of mylonitic rocks, Ring et al. (2007a) showed that the Selçuk Normal Shear Zone represents the roof of a late Eocene extrusion wedge. Normal shearing caused extensive retrogression of the high-pressure parageneses in the Selçuk Nappe (see further discussion in the following section). Normal shearing is a geometric effect that facilitated the extrusion of the Ampelos Nappe (together with its western Turkish equivalent, the Dilek Nappe); it is not related to wholesale crustal extension of the region. The next major contact in the tectonic sequence is the Kallithea Detachment in western Samos, which was active between 10 and 8.5 Ma (Ring et al., 1999a). Zircon fission-track dating (Brichau, 2004; Kumerics et al., 2005) revealed that the Kallithea Detachment, or a splay of it, continued moving until, or was reactivated at, ca. 7 Ma. The Miocene basins on Samos have a complex architecture and tectonic history. It seems that formation of the basins was related to extensional reactivation of the Pythagoras Thrust in the middle Miocene in a transtensional setting. Based on the facies distribution and basin geometry, Ring et al. (1999a) argued that a transtensional scenario might best explain the abrupt lateral facies changes of the Hora and Pythagorion Formations. There is plenty of evidence for folding in the Hora and Pythagorion

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Formations, which was caused by a short-lived shortening event at >ca. 8.6 to 9 Ma. Structural History and Deformation-Metamorphism Relationships Structural and metamorphic analysis (Ring et al., 1999b, 2001a, 2007b; Ring and Layer, 2003) shows that deformation can generally be divided into four main stages: 1. Eocene and earliest Oligocene approximately ESEWNW–oriented nappe stacking (D1 and D2) was associated with blueschist- and transitional blueschist-greenschist-facies metamorphism (M1 and M2). Maximum high-pressure assemblages in the Cycladic Blueschist Unit developed during the first deformational event, D1, and are therefore referred to as M1. The associated S1 foliation was porphyroblastically overgrown by glaucophane, chloritoid, and kyanite during a static growth event. Internal imbrication of the nappes of the Cycladic Blueschist Unit under M1 peak high-pressure metamorphism occurred at ca. 44–37 Ma and followed, and also was followed by, high-pressure mineral growth (Ring et al., 1999b; Ring and Layer, 2003). D2 deformation caused emplacement of the Cycladic Blueschist Unit onto the Kerketas Nappe, which started at ca. 35–30 Ma and eventually caused high-pressure metamorphism in the latter at 24–21 Ma (Ring et al., 2001a). Maximum pressure in the Kerketas Nappe occurred during the D2 deformation, and therefore the mildly blueschist-facies event in the Kerketas Nappe is regarded as M2. D2 thrusting was out of sequence and occurred during decompression, bringing 18–19 kbar rocks of the Cycladic Blueschist Unit on top of 8–10 kbar rocks of the Kerketas Nappe. During D2 deformation the M1 high-pressure assemblages in the Cycladic Blueschist Unit were replaced by M2 transitional blueschist-greenschist facies assemblages. The deformation-related greenschist facies overprint in the Selçuk Normal Shear Zone at the top of the Selçuk Nappe occurred at the same time as the basal nappes of the Cycladic Blueschist Unit were thrust onto the foreland (Ring et al., 2007b). As mentioned above, these data that constrain greenschist facies metamorphism in the uppermost Selçuk Nappe can generally be grouped into the M2 event, having occurred before 32 Ma. 2. Subsequent Miocene horizontal crustal extension occurred during D3 deformation. In the Ampelos Nappe there is evidence that D3 took place before, during, and after a greenschist facies metamorphism (M3). This greenschist-facies metamorphic overprint was characterized by the prograde formation of garnet and more rarely by biotite in metapelite of the Agios Nikolaos and Ampelos Nappes, constraining metamorphic conditions to ca. 6–7 kbar and 450–490 °C (Chen, 1995) for M3, with slightly higher temperatures in the western than in the eastern part of the island. The data show that M3 occurred during further decompression but with increasing temperature. This M3 greenschist-facies event cannot be related to the above mentioned >ca. 32 Ma greenschist facies metamorphic event in the uppermost Selçuk Nappe and must be a second greenschist

facies event that can also be seen as a post-high-pressure metamorphic event in the Kerketas Nappe (characterized by the reaction of diaspore to corundum during increasing temperature and decreasing pressure) and should therefore be younger than the high-pressure emplacement of the Cycladic Blueschist Unit onto the Kerketas Nappe at ca. 21 Ma (Ring et al., 2001a). Ductile flow during D3 was characterized by a high degree of coaxial deformation, but in general caused displacement of upper units toward the ENE. Fission-track dating shows that ductile top-ENE extensional reactivation at the base of the Selçuk Nappe occurred in the early Miocene, as indicated by zircon fission-track ages of 20–18 Ma (Brichau, 2004). The zircon fission-track ages consistently young ENE in the direction of hanging-wall slip (Kumerics et al., 2005). One zircon fission-track age of 14.1 ± 0.8 Ma from a conglomerate at the southern slopes of Kerkis Mountain suggests that the Kerketas extensional system is slightly younger than the extensional fault at the base of the Selçuk Nappe. The pattern of fission-track ages suggests that both extensional fault systems are unrelated. Late-stage D3 emplacement of the Kallithea Nappe had a top-NW to NNW sense of shear (Ring et al., 1999b). Inception of the Kallithea detachment is fairly well dated at ca. 10 Ma. 3. A short period of brittle E-W crustal shortening (D4) occurred between >ca. 8.6 and 9 Ma. D4 shortening caused numerous W-vergent folds and reverse faults and affected only the lower sequence of the Neogene sediments below the unconformity. 4. A phase of N-S–directed normal faulting ensued (D5, 8.6 Ma to Holocene). A granodiorite dike truncated by the Kallithea Detachment yielded a zircon fission-track age of 7.3 ± 0.6 Ma (Brichau, 2004), indicating that the Kallithea Detachment continued to operate or was reactivated during D5 extension. The cause for the short-lived D4 shortening event between 9 and 8.6 Ma remains enigmatic. It is also not fully clear whether E-W shortening during D4 was coeval with N-S extension as suggested for the central Cyclades (Avigad et al., 2001); however, the general absence of NW-striking sinistral and NE-striking dextral strike-slip faults suggests that E-W shortening was not coeval with N-S extension. However, it might be that the extensional emplacement of the Kallithea Nappe continued during the short-lived shortening event. Day 1—Localities 1.1 to 1.61 Locality 1.1. Ridge East of Mount Kerkis Summary. Traverse from Ampelos into Kerketas Nappe. Excellent exposure of variegated sequence of the Cycladic Blueschist Unit that rests above dolomite of the Kerketas Nappe (see Figs. 11 and 12).

1

A Google Earth file containing the Samos and other localities is available in the GSA Data Repository. GSA Data Repository Item 2011292 is available at www .geosociety.org/pubs/ft2011.htm, or on request from [email protected] or Documents Secretary, GSA, P.O. Box 9140, Boulder, CO 80301-9140, USA.

Field Guide to Samos and the Menderes Massif

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Day 2

Day 1

Samos Dilek Peninsula

Figure 11. Above: areas of Samos covered on Days 1 and 2 (Fig. 17). Below: location map for stops on Day 1. Modified from Google Maps (© 2011 Google—Map data © 2011 Basarsoft, Tele Atlas). Location maps such as these are intended for basic reference and to show the relations of the localities to one another.

Locality 1.1 Locality 1.6

Locality 1.5 Locality 1.2

Locality 1.4

Locality 1.3

Location. About 2 km NW of Marathokambos (37°44′35.98″ N, 26°39′14.50″ E). Access. Take the road from Marathokambos to Kastania, and after ~100 m turn left and take a dirt road to the windmills; there are some modern windmills and ruins of old windmills. Carry on for ~5–6 km up the hill until you reach the top of a saddle from where the road drops down to the N. Park your car here (37°44′35.98″ N, 26°39′14.50″ E) and follow a goat track toward the southwest to the end of the section (~37°43′54.29″ N, 26°38′30.91″ E). Geology. You will walk through a generally moderately E-dipping variegated sequence of phyllite (in part carbon bearing and thus dark gray to black), marble, greenschist, chlorite-rich schist, and quartzite of the Ampelos Nappe (Fig. 12). Most rocks are strongly foliated and have a WNW-trending stretching lineation. After ~1 km you will reach the grayish-white dolomites of the Kerketas Nappe. Directly at the contact a dolomite slice is present in the phyllite. The contact zone is well exposed, but no distinct mylonitic shear zone has been mapped. Instead, it appears that the relatively strong deformation recorded in the Ampelos Nappe rocks on the ridge took up the deformation heterogeneously. The metadolomite of the Kerketas Nappe, in contrast, has only a weak to moderately developed foliation, and no increase in foliation intensity is observed as the contact is approached.

Figure 12. Panoramic view of contact between Ampelos Nappe (right) and light-gray, dolomitic marble of Kerketas Nappe (left). Schists of Ampelos Nappe are usually covered by greenish-brown vegetation, whereas dolomite commonly has no vegetation. The sequence dips E (right).

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Quartz-c-axis fabrics from quartzites along the contact zone yielded asymmetric fabrics indicative of top-ESE shear (Ring et al., 1999b) (Fig. 13). One single zircon fission-track age of 14.1 ± 1.2 Ma from a metamorphosed conglomerate at the southern slope of the Kerketas Nappe is about the same age as the supposed age of the breccia at the base of the Neogene sequence of the Karlovasi Basin. Because the closure temperature for fission tracking in zircon is about the same as the lower limit of quartz ductility (~280 °C), the top-ESE shear sense might be middle Miocene in age and related to extensional reactivation of the Kerketas-Ampelos nappe contact and formation of the Neogene basins on Samos Island. Note that the reasoning is somewhat circumstantial. If you enjoy hiking, you may find your way up to the top of Kerkis Mountain. Toward the top you will walk through a variegated sequence of Ampelos Nappe rocks again, containing some large and beautiful glaucophane crystals (this, however, depends on which route you choose in this rugged terrain). Locality 1.2. Glaucophane Schist at Road Intersection North of Neochori Summary. Good exposure of glaucophane schist of the Cycladic Blueschist Unit.

Location. About 1 km N of Neochori (37°42′53.10″ N, 26°46′6.67″ E) (Fig. 11). Access. At turnoff from main Pyrgos-Karlovasi road to Neochori. Owing to extensive improvement of the road, the outcrops have changed considerably in past years. Geology. Epidote-glaucophane schist is exposed on the northern side of the road. The well-foliated rocks are characterized by large prismatic, dark-blue to black glaucophane, reaching 1 cm in length. The glaucophane sits in a yellowish-green matrix made up primarily of epidote with subordinate chlorite. Locality 1.3. Breccia of Basal Conglomerate Formation Summary. Road cut of the base of the Tertiary sediments in Karlovasi Basin. Location. Near Skoureika (37°41′42.36″ N, 26°46′8.89″ E) (Fig. 11). Access. From Neochori head S, then W to Koumeika. In Koumeika, turn E to Skoureika. You will drive through gently rolling hills of thick-bedded limestone of the Pythagorion Formation. About 500 m W of Skoureika you should begin seeing coarse, reddish-brown breccias. Geology. At the base the cobbles are poorly sorted and angular; some boulders may reach 1 m3 in diameter. The pebbles

Figure 13. (A, B) Detailed map and cross section of Pythagoras Thrust at the eastern side of the Kerketas Massif. The ductile D2/ D3 shear zone in the cross section is shown schematically. Attenuation of section above the Kerketas Nappe is documented by omission of the Agios Nikolaos Nappe and direct contact of marble of the Ampelos Nappe with dolomitic marble of the Kerketas Nappe. (C, D) Stereographic projection of pre-D3 foliations and stretching lineations from (C) Kerketas Nappe and (D) Ampelos Nappe. (E) Fault-slip data and principal strain axes of D4 faults.

Field Guide to Samos and the Menderes Massif consist entirely of metamorphic rocks (quartzite, marble, and phyllite) (Fig. 14). Cross-bedded sands occur above the cobbles; these may have filled channels in the rounded gravels. At the top, brown to yellow siltstone with thick paleosoils, many cut by gravels, are present. The depositional environment has been interpreted as a proximal to distal floodplain; the breccia has a minimum age of 11.2 Ma, and the pebbles are derived from the local basement (Weidmann et al., 1984) (Cycladic Blueschist Unit). This view is in line with zircon fission yielding ages between 20 and 18 Ma for the local metamorphic basement (Brichau, 2004). Locality 1.4. Limestone of Pythagorion Formation Summary. Thick-bedded, travertine-like limestone. Location. N of Koumeika (37°42′54.15″ N, 26°44′38.35″ E) (Fig. 14). Access. Follow the road to Koumeika. In road cuts just south of the turnoff, thick-bedded, grayish-yellowish-white limestone of the Pythagorion Formation crops out. Geology. The limestone was deposited in a shallow lacustrine environment. Freshwater gastropods, stromatolites, and oncolites are present, and desiccation cracks and wave ripples are common. Near the volcanic rocks the limestone is locally strongly silicified. Tuffaceous layers also occur. The thick-bedded limestone laterally interfingers with the thin-bedded marl of the Hora Formation, indicating abrupt lateral variations in the depositional environment of shallow to relatively deep lacustrine conditions. A view toward the E shows the limestone in the hills below the main road to Pyrgos and marble of the Ampelos Nappe along the road. Both lithologies are separated by a S-dipping D5 normal fault.

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Access. Take the main road to Marathokambos, which climbs smoothly up through marl of the Hora Formation. Geology. The thinly bedded marl is exposed in many road cuts. This marl commonly shows slumps and other features of soft-sediment deformation and was deposited in a relatively deep lacustrine environment. In a large road cut on the NE side of the road the slump folds are folded by upright D4 folds (Fig. 15). The harder carbonate layers are commonly boudinaged in the limbs of the folds. Locality 1.6. Conglomerate of Mytilini Formation Summary. Well-exposed fluvial conglomerates of Mytilini Formation. Location. Platanos turnoff (37°44′1.63″ N, 26°44′13.72″ E) (Fig. 11). Access. On main Pyrgos-Karlovasi road, just northwest of turnoff to Platanos. Geology. Reddish conglomerate is exposed on the northern side of the road (Fig. 16). The conglomerate rests above the unconformity in the basin succession. The unconformity and the fluviatile depositional environment of the conglomerate is the consequence of the short-lived D4 shortening event that caused uplift of the region. The uppermost beds of the Mytilini Formation are

A

Locality 1.5. Hora Formation Summary. Slump folds in marls. Location. On main Pyrgos-Karlovasi road, just west of turnoff to Koumeika (Fig. 11).

B

Figure 14. Breccia of Basal Conglomerate Formation. The clasts are mainly derived from the nearby metamorphosed nappes (Weidmann et al., 1984).

Figure 15. (A) Slump folds in thinly bedded marl of the Hora Formation; zones characterized by slumping are restricted to a few layers in marl. (B) Upright D4 fold in marl slump folds; a good example can be seen in right limb of fold.

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Gessner et al. tuffaceous sands and marls, signifying a change from fluviatile to lacustrine deposition owing to subsidence related to D5 normal faulting (for timing of tectonic events, see Figs. 9 and 10). Abundant rhyolite clasts in the conglomerate indicate that the rhyolite is older than ca. 9 Ma. Furthermore, abundant metamorphic rocks can be found in the conglomerate.

A

Day 2—High-Pressure Assemblages along the Northern Coast (Localities 2.1 to 2.3)

B

Figure 16. (A) Conglomerates of the Mytilini Formation near turnoff to Platanos; clast size becomes larger toward top of outcrop. (B) Section below that shown in A, depicting more marl zones.

Locality 2.1

Locality 2.1. Around Agios Konstandinos Summary. Excellent exposure of garnet glaucophanite; garnet-mica schist is also exposed. Location. East of Agios Konstandinos (37°48′15.72″ N, 26°49′41.95″ E) (Figs. 11 and 17). Access. On main road from Karlovasi to Samos town, just east of Agios Konstandinos; outcrops are in road cuts and on beach section. Geology. Garnet-mica schist and garnet glaucophanite of the Agios Nikolaos nappe are exposed. Both rock types preserve excellent high-pressure parageneses (Fig. 18). The main foliation in the outcrop is considered to be S2, which started to develop during high-pressure metamorphism and was then retrogressed during ongoing deformation as evidenced by chlorite growth in garnet rims. The internal foliation within the garnets is a highpressure foliation defined by aligned glaucophane (Fig. 18). Farther west on the northern (beach) side of the road is a house-sized dark-green block of well-foliated garnet glaucophanite. The foliation is defined by aligned glaucophane and formed during high-pressure conditions. There is abundant evidence for quartzcalcite–filled veins. A sample from this outcrop yielded the highest pressure recorded on Samos, and Will et al. (1998) reported P-T conditions of ~18–19 kbar and ~530 °C.

Locality 2.2

Figure 17. Localities covered on Day 2. Maps © 2011 Google—Map data © 2011 Basarsoft, Tele Atlas. Locality 2.3

Field Guide to Samos and the Menderes Massif

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Locality 2.3. Gankou Beach Summary. Great exposure of chloritoid. Location. 37°45′59″ N, 26°57′35″ E (Figs. 11 and 17). Access. At the northern end of the small Gankou bay, quartzite and quartzitic schist of the upper Ampelos Nappe, containing several millimeters-long chloritoid crystals, are exposed. Geology. The rocks in the outcrop are characterized by a penetrative S1/2 foliation. An E-W–trending stretching lineation, STR1/2, occurs on the foliation planes, and this lineation is expressed by stretch quartz-albite aggregates and aligned phengite. Some small-scale intra-folial folds with axes parallel to STR1/2 can be observed. Thin sections are dominated by the assemblage chloritoid + phengite + quartz (Fig. 19). Chloritoid

is commonly rotated. This assemblage has also been described for western Turkey (Gessner et al., 2001c). The deformation age for a mylonitic quartzite from this outcrop has been constrained (Ring et al., 2007b), which structurally belongs to the upper contact of the Ampelos Nappe and thus is considered part of the Selçuk Normal Shear Zone. Rb-Sr analysis of the minerals that constitute the mylonitic foliation has been hampered by the lack of apatite and also problems in producing a clean feldspar fraction. Magnetic separation of the white mica populations revealed two chemically distinct white micas. Rock texture suggests that some of these phengite-paragonite intergrowths form textural relics within an otherwise penetratively deformed matrix (see figure 5c in Ring et al., 2007a). Rb-Sr data show no age–grain size correlation, which is in line with complete synkinematic recrystallization as inferred from textural observations. Despite evidence for incipient weathering, the whole rock was analyzed as well. Integration of the whole-rock data with the different white mica results leads to an apparent deformation age of 37 ± 5 Ma, which we interpret as an accurate estimate for late stages of mylonitic deformation. 40Ar-39Ar spot-fusion ages show a large variation in ages of ca. 10 Ma. Two pre-mylonitic, non-recrystallized, high-Si phengite-paragonite intergrowths in sample Sa01-1 yielded ages of ca. 50 Ma. The mylonitic phengite yielded no spot-fusion ages >ca. 42 Ma. Analyzed spots from relatively coarse-grained (ca. 60–80 mm), early recrystallized phengites in mylonitically sheared layers give systematically older ages than spots from late-stage recrystallized phengites (>~50 mm). The age scatter has been interpreted to be due to progressive recrystallization of phengite, which might reflect different increments of shear-zone deformation (Ring et al., 2007b).

Figure 18. Photomicrograph showing the high-pressure assemblage garnet + glaucophane + epidote + chlorite + phengite + quartz in blueschist of the Agios Nikolaos Nappe; notice that garnet is rotated. Sample Sa80-154 (plane-polarized light; photo width, 3 mm).

Figure 19. Photomicrograph of the assemblage chloritoid (light olive green) + phengite + quartz in metapelitic schist of the upper Ampelos Nappe; chloritoid is rotated. Gankou Beach, eastern Samos (planepolarized light; photo width, 3.7 mm).

Locality 2.2. West of Avlakia and East of Turnoff to Vourliotes Summary. Spectacular exposure of E-directed D4 reverse fault. Location. West of Avlakia (37°48′11.23″ N, 26°51′3.82″ E) (Figs. 11 and 17). Access. Directly at main road from Karlovasi to Samos town just west of Avlakia. Geology. The view from the road toward the south shows a huge marble sequence of the Ampelos Nappe in the west. The relief between the top of the marble and the Neogene sediments of the Mytilini Basin to the east is >500 m, and the structural relief is >1000 m. In the road cut a D4 reverse fault puts marble of the Ampelos Nappe above the Tortonian marl of the Hora Formation. The fault dips WSW, and the shortening direction is WSWENE. The sediment is partly silicified; drusy quartz fillings and red iron staining are common in places.

Field Guide to Samos and the Menderes Massif ■

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PART B. THE MENDERES MASSIF Figure 21

Some Remarks about Controversies on Menderes Massif Tectonics The Menderes Massif is a complex geological terrane. Despite much research progress in the past ten years, there are still substantial unresolved issues regarding its tectonic and metamorphic history. Although we would like to outline some key controversies here, we recommend the review section in Bozkurt and Oberhänsli’s 2001 editorial article (Bozkurt and Oberhänsli, 2001) and van Hinsbergen et al. (2010) for an attempt to reconcile local structure with geodynamics. The pre-Miocene tectonics of the Menderes Massif have been interpreted in terms of a large-scale recumbent fold (Okay, 2001; Gessner et al., 2002), a series of nappes stacked during south-directed thrusting (Ring et al., 1999a; Gessner et al., 2001c), and a series of north-directed thrusts that subsequently collapsed either in a bivergent fashion (Hetzel et al., 1998) or through top-to-south extension (Bozkurt and Park, 1994; Bozkurt, 2007). The key controversies are focused on which structures are related to the kinematics of early Tertiary Alpine crustal shortening, which ones are related to late Tertiary crustal extension, and how this fits with the observed large-scale architecture of the massif. Whereas the role of Miocene to Pliocene normal fault systems bounding the Gediz and Büyük Menderes Grabens (see the section on “Miocene to Holocene Extension in the Central Menderes Region” below) is more or less agreed on, the ages of kinematic indicators in the metamorphic rocks of the Massif, and in some cases the ages of the protoliths, are still contested. Top-N-NNE shear-sense indicators are common in association with deformation fabrics in amphibolite facies metamorphic rocks in the Menderes Massif. Such structures, which clearly predate Miocene extension in the Menderes Massif, were originally interpreted as early Tertiary nappe stacking (e.g., Bozkurt, 1995, 2007; Bozkurt and Park, 1994; Hetzel et al., 1998). This interpretation is at odds with regional tectonic models (Şengör and Yilmaz, 1981; Şengör et al., 1984; Collins and Robertson, 1998; van Hinsbergen, 2010), which imply that major tectonic events during Tertiary convergence should be characterized by top-S shearing. In the following sections we favor the late Eocene assembly of the Menderes nappe stack as proposed by Ring et al. (1999a, 2003, 2004, 2007a, 2007b), Gessner et al. (2001a, 2001b, 2001c, 2004), and Régnier et al. (2003). Architecture of the Menderes Massif Topographically, the central west coast of the Anatolian Peninsula is characterized by the transition from the Anatolian Plateau to the Aegean Sea. The landforms of the area are mainly controlled by a series of E-W and ESE-WNW–oriented horsts and grabens that delimit mountain ranges and highlands (Fig. 20). This basin and range-type topography is a consequence of Neogene to recent normal and strike-slip faulting.

km

Figure 20. Topography of the central western Anatolia coastal region. Notice the E-W and SE-NW trend of the Aegean Graben. White outline gives location of Figure 21.

Miocene to Holocene Extension in the Central Menderes Region Since the early Miocene the Anatolide Belt underwent extensional deformation (Dewey and Şengör, 1979). Defined by structural architecture and cooling history, the Central Menderes Metamorphic Core Complex extends ca. 100 km eastwest and 50 km north-south in the central part of the Anatolide Belt (Fig. 21). This complex is bounded by two approximately east-striking, opposite-facing detachment systems, the Kuzey Detachment in the north and the Güney Detachment in the south (Emre and Sözbilir, 1997; Hetzel et al., 1995b; Gessner et al., 2001b). These normal fault systems cut the upper levels of the Alpine nappe pile for a lateral distance of ~80 km, displacing the hanging-wall regions to the north above the Kuzey Detachment, and to the south in the Güney Detachment. The Kuzey Detachment dips 15°–20° N, and its hanging wall consists of southdipping Miocene alluvial sediments locally underlain by small volumes of amphibolite-grade orthogneiss. The footwall exposes a greenschist facies, mylonitic shear zone of early Miocene age (Hetzel et al., 1995a, 1995b). The Güney Detachment is exposed along the northern shoulder of the Büyük Menderes Graben as a

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Figure 21. Tectonic map of Anatolide Belt in western Turkey. Cyclades-Menderes Thrust (CMT) separates Alpine highpressure units in its hanging wall from Menderes nappes in its footwall. Circled letters refer to cross sections A–A′ to D–D′ in Figure 22. Asterisks refer to high-grade orthogneiss lithology, used as markers to estimate displacement along Kuzey Detachment; earthquake data related to March 1969 Demirci and Alasehir earthquakes (Eyidogan and Jackson, 1985). GG—Gediz Graben; KMG—Küçük Menderes Graben; BMG—Büyük Menderes Graben; CMCC—Central Menderes Metamorphic Core Complex. Inset: Area of upper plate of Kuzey and Güney Detachments. Modified from Gessner et al. (2001b).

Field Guide to Samos and the Menderes Massif 0°–15° S-dipping cataclastic shear zone that constitutes the basal cutoff to Neogene supra-detachment basins. Downdip displacement along the detachments is largest in the central part of the core complex; laterally the faults either die out or terminate against small-offset, high-angle normal faults. A distinct garnet-bearing orthogneiss that occurs in the internal part of the Central Menderes Metamorphic Core Complex, as well as in the hanging wall of the Kuzey Detachment, suggests a minimum downdip displacement of ~12 km (Gessner et al., 2001b); this displacement magnitude has been supported by numerical models (Wijns et al., 2005). Displacement-to-length relationships of the fault suggest a similar displacement at the Güney Detachment. The Kuzey and the Güney Detachments root in the PliocenePleistocene to Holocene Gediz Graben and the Büyük Menderes Graben, both of which have been seismically active in historic time (Schaffer, 1900; Eyidogan and Jackson, 1985) (Fig. 21). The Gediz and Büyük Menderes Grabens are associated with a number of geothermal fields (Faulds et al., 2009), and Miocene to recent volcanic activity north of the Gediz Graben is related to ongoing lithospheric extension (Seyitoglu et al., 1997). The Gediz Graben and the Büyük Menderes Graben separate the central Menderes Metamorphic Core Complex from adjacent plateau-like areas: the Gördes Massif to the north and the Çine Massif to the south (Fig. 21). In both the Gördes and Çine Massifs, flat-lying Miocene sediments overlie the sub-horizontally foliated basement. Eocene foliation, bedding of the Miocene sediments, and remnants of a late Miocene erosion surface are parallel to each other and also parallel the fission-track cooling age pattern (Fig. 22). Across the Central Menderes Metamorphic Core Complex, however, Eocene foliation and the boundaries of the tectonic units define an east-trending syncline with a wavelength of ~45 km and an amplitude of ~10 km (Fig. 22). Across this syncline, fission-track cooling ages become younger in the hanging-wall displacement direction. Miocene sediments occur only in fault-bounded blocks in the hanging wall of the detachment faults. As the earlier contractional history of the Central Menderes Metamorphic Core Complex is similar to that of the Gördes and Çine Massifs, syncline formation postdates earlier crustal shortening. Alpine Nappe Tectonics The Menderes Massif has traditionally been interpreted as the eastern lateral continuation of the Cycladic zone or Cycladic Massif (Dürr et al., 1978), where an old crystalline core is overlain by Paleozoic and Mesozoic cover series with metamorphic grade decreasing up section. This longstanding view was challenged by geochronological studies, which show marked differences in the age of the basement of the Anatolide Belt and the Cycladic zone, respectively, indicating that the basement of the Cycladic zone and the Anatolide cannot be correlated, and that two different units, the Cycladic Blueschist Unit and the underlying Menderes nappes, make up the Anatolide Belt (Ring et al., 1999a; Gessner et al., 2001a, 2001b, 2001c; Régnier et al., 2003).

23

In the Menderes nappes, pronounced magmatic activity occurred at the Proterozoic-Cambrian boundary (Hetzel and Reischmann, 1996; Dannat and Reischmann, 1999; Gessner et al., 2001a; Reischmann and Loos, 2001), in the mid-Triassic (Dannat, 1997; Koralay et al., 2001), and in the Miocene (Hetzel et al., 1995a; Collins et al., 2002). In the Cycladic zone, the granitic basement is of Carboniferous age (Reischmann, 1997; Engel and Reischmann, 1998). In addition, there were Triassic intrusions (Reischmann, 1997; Ring et al., 1999b) and other prominent Miocene to Holocene magmatic activity in the Cycladic zone (Altherr et al., 1982). The major difference between the Anatolide Belt and the Cycladic zone is that only the upper parts of the Anatolide Belt can be correlated with the Cycladic zone (Candan et al., 1997; Ring et al., 1999a; Gessner et al., 2001c). The Anatolide Belt can be subdivided into three major tectonic units where the IzmirAnkara Zone and the Lycian nappes form the upper unit, and the Dilek Nappe and the Selçuk Mélange form the middle unit (Figs. 23 and 24). These upper and middle units can be correlated with tectonic units in the Cycladic zone. The lower unit, the Menderes nappes, consists, in ascending order, of a lower metasedimentary succession, the Bayındır Nappe, a metapelitic succession with abundant amphibolite and a few marble lenses named the Bozdağ Nappe, a Proterozoic-Cambrian basement succession named the Çine Nappe, and an upper metasedimentary succession of intercalated marble and calcschist, the Selimiye Nappe. The Menderes nappes have no counterpart in the adjacent Cycladic zone. According to this subdivision the structurally lowest unit exposed in the Menderes nappes, the Bayındır Nappe, is affected only by one major Alpine tectonometamorphic event, whereas in the overlying Bozdağ, Çine, and Selimiye Nappes, pre-Alpine and Alpine events are documented. The Menderes Nappes Deformation history. Three Alpine deformation events, abbreviated DA3–DA5 (the A in the subscript indicates an Alpine age), have been recognized in the Menderes nappes (Figs. 24 and 25); the Alpine deformation events DA1 and DA2 are found only in the Cycladic Blueschist Unit, see below). Some of the Menderes nappes were affected by a pre-Alpine event (DPA). The Menderes nappes consist, from top to bottom, of the (1) Selimiye Nappe, (2) Çine Nappe, (3) Bozdağ Nappe, and (4) Bayındır Nappe (Ring et al., 1999b; Gessner et al., 2001a, 2001c) (Figs. 23, 24, 26, 27). Selimiye Nappe. The Selimiye Nappe (Figs. 24 and 26) contains a metasedimentary sequence the basal part of which is of Precambrian age (Hetzel and Reischmann, 1996; Loos and Reischmann, 1999b). An amphibolite-facies fabric of as yet unresolved kinematics and age was overprinted by the Alpine DA3 top-to-the-S Selimiye Shear Zone, which separates the Selimiye Nappe from the underlying Çine Nappe. The tectonometamorphic history of the Selimiye Nappe remains controversial. Interpretations of the greenschist-facies Selimiye Shear Zone include (1) Alpine shortening (Gessner et al., 2001a, 2004);

24

Gessner et al.

Southern Çine Massif

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Section lines D′

D C′

Gördes Massif

C B′

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A

Figure 22. (A, B) Cross sections (for position and legend, refer to Fig. 21) and cooling ages within the Central Menderes Metamorphic Core Complex (CMCC). FTT—fission-track thermochronology. Notice that the cooling rate in the footwall of the Kuzey Detachment shows a pronounced increase at ca. 5 Ma. Modified from Gessner et al. (2001b).

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T > ~ 450°C; cooling below 400° C at ca. 43-37 Ma (Hetzel and Reischmann, 1996)

T ≤ 400°C

4

Cycladic basement as exposed on Samos (Figure 8) Inferred ophiolite unit (Figure 8)

Late DA3 out-of sequence emplacement of CBU

Figure 23. Interpretive thrust sequence during formation of the Anatolide Belt (Gessner et al., 2001c). CBU—Cycladic Blueschist Unit; CMT— Cyclades-Menderes Thrust.

Field Guide to Samos and the Menderes Massif D PA top-N shear

Cycladic Blueschist Unit

Tectonic units

D A1 ?

D A3 D A4 D A5 top-S top-N bivergent thrusting extension extension

Selçuk Mélange ≤ ~450°C ~500°C

Dilek Nappe C Y C L A D E S - M E N D E R E S

Selimiye Nappe Menderes nappes

D A2 top-NE shear

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670-730°C

Bozdag Nappe

480-660°C

Figure 24. Table of pre-Alpine and Alpine events DPA and DA1 to DA5 in the tectonic units of the Anatolide Belt in western Turkey. Temperature estimates after Gessner et al. (2001c), except for Çine and Bozdağ Nappes (Ring et al., 2001b) and Dilek Nappe (Will et al., 1998). Diagram indicates that the Anatolide Belt was assembled during DA3; subscripts PA and A denote pre-Alpine and Alpine deformation ages, respectively. After Gessner et al. (2001c).

≤ ~450°C

Bayındır Nappe ≤ ~400°C

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Structural position of sample TAB: orthogneiss intruded into metapelite 541±14 SHRIMP age

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Structural position of sample Tu23: metagranite intruded into orthogneiss 566±6 SHRIMP age

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Figure 25. Schematic diagram of Alpine-age structures (Lineation LA3, Foliation SA3) associated with deformation event DA3 and their kinematics (arrows depict hanging-wall transport direction), which overprint pre-Alpine structures of DPA in the Selimiye, Çine, and Bozdağ Nappes and are the only fabric in the Bayındır Nappe. Geochron sample TAB is from the Lake Bafa area, and sample Tu23 from the central Çine Massif (Gessner et al., 2004).

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Gessner et al.

Figure 26. Tectonic map of western Turkey and Samos Island (Gessner et al., 2001c). Lines for cross sections A–A′ to G–G′ (Fig. 27) and location of Figure 47 (small rectangle near center) are indicated. CMT—Cyclades-Menderes Thrust; CBU—Cycladic Blueschist Unit.

(2) Precambrian and Alpine polymetamorphic deformation (Régnier et al., 2003); (3) post-Precambrian, pre-Alpine monometamorphic deformation (Régnier et al., 2006); (4) folding during Alpine shortening (Erdogan and Güngör, 2004); and (5) late Alpine extension (Bozkurt and Park, 1994). Bozkurt and Park (1994) have interpreted this shear zone as an extensional feature, but there is inconsistent evidence for a telescoped metamorphic field gradient or for a change in cooling history across it. Another contentious issue is that a number of authors claim that the granitic rocks intrude lithologies that can be correlated with Mesozoic sediments and are therefore “Alpine” in age (Şengör et al., 1984; Erdogan and Güngör, 1992, 2004; Bozkurt et al., 1993, 2001), whereas radiometric ages of the intrusions give late Proterozoic to Cambrian ages (Reischmann et al., 1991; Hetzel and Reischmann, 1996; Gessner et al., 2001a, 2004); thus lithological correlations in highly deformed metapelites can be problematic. In the Central Menderes Massif, top-NE shear-sense indicators dominate. At the northwestern margin of the Çine submassif, symmetric fabric elements such as strain shadows around feldspar and foliation boudinage occur (cf. Fig. 55) together with minor top-NE kinematic indicators. In the central Çine submassif, both

top-NE and top-SW kinematic indicators have been mapped. We would argue that there is no evidence that the top-NE and top-SW kinematic indicators are of different generations, and no evidence that they developed during different metamorphic conditions. However, locally we observed that the top-SW indicators are inverted top-NE kinematic indicators owing to later recumbent tight to isoclinal folding about axes parallel to the NE-trending DPA stretching lineation. Reconnaissance mapping of the Çine Massif (unpublished) has revealed five generations of granitic intrusions, two of which are not affected by amphibolite-grade shearing. U-Pb dating has produced Proterozoic to Cambrian ages for these rocks (Gessner et al., 2004), similar to the Birgi metagranite east of Ödemiş (Hetzel et al., 1998). A further problem is that the Selimiye Shear Zone appears to be wrapped around the granites and orthogneisses toward the western outcrop limit of these lithologies, which has led to contradicting interpretations (Gessner et al., 2001b; Régnier et al., 2003, 2006; Gemici, 2004). There is little doubt, however, that the schists and marbles overlying the Selimiye Nappe can be correlated with Cycladic blueschists, and that these and the Lycian nappes preserve high-pressure metamorphic relicts for which

A3

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Figure 27. Cross sections A–A′ to G–G′ (positions of sections given in Fig. 26). Section A–A′ shows that the Cyclades-Menderes Thrust cuts up-section toward the south in the direction of the tectonic transport parallel to the orientation of LA3. Traces of foliation are projected into the section plane and used to infer geometry of subsurface structures. CMT— Cyclades-Menderes Thrust; IAZ—Izmir-Ankara Zone.

Menderes nappes

Selimiye nappe

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Selçuk mélange

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Miocene granodiorite

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Gessner et al.

there is no evidence in the Menderes nappes (Oberhänsli et al., 1998a, 1998b, 2001; Ring et al., 1999a; Rimmelé et al., 2001). Çine and Bozdağ Nappes. The Çine and Bozdağ Nappes are characterized by a distinct overprinting sequence of ductile fabrics. The structurally higher Çine Nappe consists of amphibolite to granulite-facies ortho- and paragneiss with intercalated metabasite (Dora et al., 1995), whereas the Bozdağ Nappe is composed of amphibolite-facies garnet-mica schist and metabasite. The DPA event in the Bozdağ and Çine Nappes occurred during amphibolite-facies metamorphism at ca. 550 Ma and caused top-to-the-NE shear (Gessner et al., 2001a) over wide areas of the Menderes Massif. DPA was overprinted by a DA3 greenschistfacies tectono-metamorphic event. The corresponding SA3 foliation crosscuts SPA and produced a variably spaced shear-band foliation and a well-defined stretching lineation associated with top-to-the-S kinematic indicators in both nappes and also in Triassic metagranite (Figs. 26–28) (Gessner et al., 2001a). Bayındır Nappe. The Bayındır Nappe at the base contains shelf sediments of inferred Permo-Carboniferous (Osman Candan, 1998, personal commun.) to Mesozoic (Özer and Sözbilir, 2003) age, which were metamorphosed under lower greenschist-facies conditions at ca. 37 Ma (Lips et al., 2001). The absence of biotite in rocks of suitable bulk composition suggests temperatures below ca. 400 °C. The Bayındır Nappe was deformed by the syn-metamorphic DA3 event, which is the first deformation event recorded in this tectonic unit. The corresponding SA3 foliation is penetrative and associated with a finegrained, N-trending stretching lineation, LA3 (Figs. 29 and 32). LA3 is expressed by stretched quartz, albite, and chlorite aggregates and aligned tourmaline. In the structurally highest parts of the Bayındır Nappe north of Aydın (see Fig. 26 for location), DA3 ductile shear bands and sigma-type objects indicate a topto-the-S shear sense. Miocene extension in the Menderes nappes. North of Bozdağ Mountain, mylonite formed during the intrusion of the middle Miocene Turgutlu and Salihli granodiorites. Miocene extension (DA5) is expressed by normal-fault systems of Miocene to Holocene age (Cohen et al., 1995; Hetzel et al., 1995b; Emre and Sözbilir, 1997; Gessner et al., 2001b; Isik and Tekeli, 2001; Collins et al., 2002). Since the Pliocene, two oppositefacing normal-fault systems, the Kuzey Detachment in the north and the Güney Detachment in the south, have produced the synclinal structure of the Central Menderes Metamorphic Core Complex by gradients in footwall uplift (Gessner et al., 2001b) (Fig. 27). Summary. The structural data constrain two important aspects: (1) There is no evidence for Alpine high-pressure metamorphism in the Menderes nappes, and (2) the available data are consistent with the assumption that grade and age of metamorphism associated with DA3 decrease structurally downward. Temperatures in the Selimiye Nappe were >450 °C and occurred before 43–37 Ma (Hetzel and Reischmann, 1996), whereas in the Bayındır Nappe temperatures barely reached 400 °C and occurred later at ca. 37 Ma (Lips et al., 2001).

The Cycladic Blueschist Unit Lithology and metamorphism. In western Turkey the Cycladic Blueschist Unit is made up of the Selçuk Mélange and the underlying Dilek Nappe (Figs. 24 and 26) (Erdogan and Güngör, 1992; Candan et al., 1997; Güngör, 1998; Ring et al., 1999a; Gessner et al., 2001c). The Selçuk Mélange consists of blocks of metagabbro and metabauxite-bearing marble, which are surrounded by a matrix of serpentinite and garnet-mica schist. The Dilek Nappe is a metamorphosed Permo-Mesozoic shelf sequence, which includes a quartzite conglomerate with interlayered kyanite-chloritoid schist, metabasite, phyllite, and marble containing metabauxite. The depositional age of the marble ranges from Late Triassic through middle Paleocene, and the passive-margin sequence is overlain by an early to middle Paleocene flysch (Dürr et al., 1978; Özer et al., 2001). The Selçuk Mélange correlates with the Selçuk Nappe, and the Dilek Nappe with the Ampelos Nappe on Samos (Candan et al., 1997; Ring et al., 1999a). In contrast to exposures on Samos, no Carboniferous basement and no Basal Unit rocks are exposed below the Dilek Nappe in western Turkey (Fig. 30). P-T conditions of >10 kbar and