DOCSLIB.ORG

Science Articles to Further Science and Education

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Science Articles to Further Science and Education Vol. 6, No. 4 April 1996 1996 Annual GSA TODAY Meeting Call for A Publication of the Geological Society of America Papers Page 17 Electronic Dipping Reflectors Beneath Abstracts Submission Old Orogens: A Perspective from page 18 the British Caledonides Registration Issue June GSA Today John H. McBride,* David B. Snyder, Richard W. England, Richard W. Hobbs British Institutions Reflection Profiling Syndicate, Bullard Laboratories, Department of Earth Sciences, University of Cambridge, Madingley Road, Cambridge CB3 0EZ, United Kingdom A B Figure 1. A: Generalized location map of the British Isles showing principal structural elements (red and black) and location of selected deep seismic reflection profiles discussed here. Major normal faults are shown between mainland Scotland and Shetland. Structural contours (green) are in kilome- ters below sea level for all known mantle reflectors north of Ireland, north of mainland Scotland, and west of Shetland (e.g., Figs. 2A and 5); contours (black) are in seconds (two-way traveltime) on the reflector I-I’ (Fig. 2B) pro- jecting up to the Iapetus suture (from Soper et al., 1992). The contour inter- val is variable. B: A Silurian-Devonian (410 Ma) reconstruction of the Caledo- nian-Appalachian orogen shows the three-way closure of Laurentia and Baltica with the leading edge of Eastern Avalonia thrust under the Laurentian margin (from Soper, 1988). Long-dash line indicates approximate outer limit of Caledonian-Appalachian orogen and/or accreted terranes. GGF is Great Glen fault; NFLD. is Newfoundland. reflectors in the upper-to-middle crust, suggesting a “thick- skinned” structural style. These reflectors project downward into a pervasive zone of diffuse reflectivity in the lower crust. This zone of diffuse reflectivity corresponds to a theoretical depth interval of low strength that represents distributed shearing separating upper crustal and uppermost mantle lay- ABSTRACT ers of greater strength. Prominent dipping reflectors also occur After two decades of deep seismic reflection profiling, our within the high-strength uppermost mantle beneath the Cale- understanding of dipping reflectors in the crust and upper donian orogen. Reflectors within the stronger upper-to-middle mantle beneath old orogenic belts, and especially their rela- crust and upper mantle are not connected across the Moho tion across the crust-mantle boundary, remains incomplete. discontinuity and thus seem kinematically distinct, although The Caledonian orogenic front (Moine thrust) and the Iapetus mantle reflectors in places appear to continue upward into the suture in Great Britain, two of the world’s most studied com- lowermost crust. Dipping crust and mantle reflectors probably pressional belts, show a consistent pattern of discrete dipping originated from different geologic events: dipping reflectors in the crust first took form as thrusts during the early Paleozoic Caledonian orogeny, whereas those in the upper mantle *Present address: Illinois State Geological Survey, Natural Resources Building, 615 East Peabody Drive, Champaign, IL 61820. Dipping Reflectors continued on p. 2 IN THIS ISSUE GSA TODAY April Vol. 6, No. 4 1996 Dipping Reflectors Beneath Old 1996 GSA Annual Meeting Orogens: A Perspective from the Call for Papers ......................... 17 GSA TODAY (ISSN 1052-5173) is published British Caledonides .................. 1 monthly by The Geological Society of America, Inc., Penrose Conference Report ............. 33 with offices at 3300 Penrose Place, Boulder, Colorado. Geology and Geologists in the Former Mailing address: P.O. Box 9140, Boulder, CO 80301- Soviet Union: Opportunities for Interaction GSA on the Web ....................... 35 9140, U.S.A. Second-class postage paid at Boulder, Colorado, and at additional mailing offices. Postmas- Life of Geologists ...................... 6 Environment Matters ................... 36 ter: Send address changes to GSA Today, Membership Volcanoes in Kamchatka ................ 8 Letter to the Editor: USGS RIF ........... 39 Services, P.O. Box 9140, Boulder, CO 80301-9140. Kazakhstan: Environmental Restoration ... 9 Copyright © 1996, The Geological Society of America, Calendar .............................. 40 Inc. (GSA). All rights reserved. Copyright not claimed PEPTALK ............................... 10 on content prepared wholly by U.S. Government SAGE Remarks ......................... 11 GSAF Update .......................... 42 employees within the scope of their employment. Per- mission is granted to individuals to photocopy freely all Correction: Dinofest .................... 11 1996 Committees and Representatives . 44 items other than the science articles to further science and education. Individual scientists are hereby granted Forum ................................. 12 GSA Meetings ......................... 45 permission, without royalties or further requests, to About People .......................... 13 Classifieds ............................. 46 make unlimited photocopies of the science articles for use in classrooms to further education and science, and to make up to five copies for distribution to associates in the furtherance of science; permission is granted to Dipping Reflectors continued from p. 1 (1) Can dipping crustal reflectors beneath make more than five photocopies for other noncom- mercial, nonprofit purposes furthering science and edu- the Caledonides be unequivocally linked cation upon payment of the appropriate fee ($0.25 per have an even older history associated with compressional structures at the sur- page) directly to the Copyright Clearance Center, 27 with an as yet unrecognized episode face, and how are compressional struc- Congress Street, Salem, Massachusetts 01970, phone (508) 744-3350 (include title and ISSN when paying). of subduction or Late Proterozoic rifting tures distributed deeper within the crust? Written permission is required from GSA for all other of the Laurentian supercontinent. Crust (2) Does dipping reflector structure in the forms of capture, reproduction, and/or distribution of and mantle reflectors were likely reacti- upper mantle beneath the Caledonides any item in this journal by any means. GSA provides this and other forums for the presentation of diverse vated by Mesozoic and younger North have any relation to Paleozoic or younger opinions and positions by scientists worldwide, regard- Sea rifting, which may also have pro- features in the crust above it—what really less of their race, citizenship, gender, religion, or politi- duced, or at least enhanced, the diffuse are the admissible interpretations for upper cal viewpoint. Opinions presented in this publication do not reflect official positions of the Society. reflectivity in the low-strength lower mantle reflectors? (3) Finally, we argue that crust. the crust and upper mantle were mechani- SUBSCRIPTIONS for 1996 calendar year: cally decoupled during Caledonian com- Society Members: GSA Today is provided as part of INTRODUCTION pression, and that crust and mantle defor- membership dues. Contact Membership Services at mation structures beneath the Caledonides (800) 472-1988 or (303) 447-2020 for membership Since its inception in 1981, the British have separate origins. information. Nonmembers & Institutions: Free with Institutions Reflection Profiling Syndicate paid subscription to both GSA Bulletin and Geology, (BIRPS) has been accumulating deep seis- otherwise $45 for U.S., Canada, and Mexico; $55 else- DIPPING CRUSTAL REFLECTORS where. Contact Subscription Services. Single copies mic reflection data over the offshore parts may be ordered from Publication Sales. Claims: For of the Caledonian orogen. To date, about Moine Thrust nonreceipt or for damaged copies, members contact Membership Services; all others contact Subscription 17,000 km of profiles have been recorded The Moine thrust (Fig. 1A) is Services. Claims are honored for one year; please allow around the British Isles. The major crustal the classic structure of the Caledonide- sufficient delivery time for overseas copies. framework structures of the Caledonian Appalachian system, and is probably anal- orogen, namely the Caledonian orogenic ogous to the Taconian suture in the North STAFF: Prepared from contributions from the GSA staff and membership. front (locally Moine thrust) and the Iape- American Appalachians. Where it crops Executive Director: Donald M. Davidson, Jr. tus suture, are arguably the best studied out in mainland Scotland, the thrust Science Editor: Suzanne M. Kay Paleozoic orogenic features in the world, floors a thick east-dipping mylonite Department of Geological Sciences, Cornell University, Ithaca, NY 14853 particularly from the standpoint of deep zone that separates metamorphic rocks Forum Editor: Bruce F. Molnia reflection data. These two structures of the thrust belt to the east from the less U.S. Geological Survey, MS 917, National Center, together effectively delimit compressional deformed Precambrian foreland and cover Reston, VA 22092 Managing Editor: Faith Rogers deformation resulting from the Caledo- sequence to the west (Barr et al., 1986). Production & Marketing Manager: James R. Clark nian orogeny (Silurian–Early Devonian) Deep seismic data over the offshore pro- Production Editor and Coordinator: Joan E. Manly in Britain (Fig. 1A). The goal of this report jection of the thrust reveal a thick wedge Graphics Production: Joan E. Manly, Adam S. McNally is to summarize results of our recent work of east-dipping reflections in the middle- on the British
Load more

Recommended publications
  • Frontiers in Earth Sciences
    Frontiers in Earth Sciences Series Editors: J.P. Brun, O. Oncken, H. Weissert, W.-C. Dullo . Dennis Brown • Paul D. Ryan Editors Arc-Continent Collision Editors Dr. Dennis Brown Dr. Paul D. Ryan Instituto de Ciencias de la Tierra National University of Ireland, Galway “Jaume Almera”, CSIC Dept. Earth & Ocean Sciences (EOS) C/ Lluis Sole i Sabaris s/n University Road 08028 Barcelona Galway Spain Ireland [email protected] [email protected] This publication was grant-aided by the National University of Ireland, Galway ISBN 978-3-540-88557-3 e-ISBN 978-3-540-88558-0 DOI 10.1007/978-3-540-88558-0 Springer Heidelberg Dordrecht London New York Library of Congress Control Number: 2011931205 # Springer-Verlag Berlin Heidelberg 2011 This work is subject to copyright. All rights are reserved, whether the whole or part of the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations, recitation, broadcasting, reproduction on microfilm or in any other way, and storage in data banks. Duplication of this publication or parts thereof is permitted only under the provisions of the German Copyright Law of September 9, 1965, in its current version, and permission for use must always be obtained from Springer. Violations are liable to prosecution under the German Copyright Law. The use of general descriptive names, registered names, trademarks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use. Cover design: deblik, Berlin Printed on acid-free paper Springer is part of Springer Science+Business Media (www.springer.com) Preface One of the key areas of research in the Earth Sciences are processes that occur along the boundaries of the tectonic plates that make up Earth’s lithosphere.
    [Show full text]
  • Kinematic Reconstruction of the Caribbean Region Since the Early Jurassic
    Earth-Science Reviews 138 (2014) 102–136 Contents lists available at ScienceDirect Earth-Science Reviews journal homepage: www.elsevier.com/locate/earscirev Kinematic reconstruction of the Caribbean region since the Early Jurassic Lydian M. Boschman a,⁎, Douwe J.J. van Hinsbergen a, Trond H. Torsvik b,c,d, Wim Spakman a,b, James L. Pindell e,f a Department of Earth Sciences, Utrecht University, Budapestlaan 4, 3584 CD Utrecht, The Netherlands b Center for Earth Evolution and Dynamics (CEED), University of Oslo, Sem Sælands vei 24, NO-0316 Oslo, Norway c Center for Geodynamics, Geological Survey of Norway (NGU), Leiv Eirikssons vei 39, 7491 Trondheim, Norway d School of Geosciences, University of the Witwatersrand, WITS 2050 Johannesburg, South Africa e Tectonic Analysis Ltd., Chestnut House, Duncton, West Sussex, GU28 OLH, England, UK f School of Earth and Ocean Sciences, Cardiff University, Park Place, Cardiff CF10 3YE, UK article info abstract Article history: The Caribbean oceanic crust was formed west of the North and South American continents, probably from Late Received 4 December 2013 Jurassic through Early Cretaceous time. Its subsequent evolution has resulted from a complex tectonic history Accepted 9 August 2014 governed by the interplay of the North American, South American and (Paleo-)Pacific plates. During its entire Available online 23 August 2014 tectonic evolution, the Caribbean plate was largely surrounded by subduction and transform boundaries, and the oceanic crust has been overlain by the Caribbean Large Igneous Province (CLIP) since ~90 Ma. The consequent Keywords: absence of passive margins and measurable marine magnetic anomalies hampers a quantitative integration into GPlates Apparent Polar Wander Path the global circuit of plate motions.
    [Show full text]
  • Evidence for Terrane Boundaries and Suture Zones Across Southern Mongolia Detected with a 2‑Dimensional Magnetotelluric Transect Matthew J
    Comeau et al. Earth, Planets and Space (2020) 72:5 https://doi.org/10.1186/s40623-020-1131-6 FULL PAPER Open Access Evidence for terrane boundaries and suture zones across Southern Mongolia detected with a 2-dimensional magnetotelluric transect Matthew J. Comeau1* , Michael Becken1, Johannes S. Käuf2, Alexander V. Grayver2, Alexey V. Kuvshinov2, Shoovdor Tserendug3, Erdenechimeg Batmagnai2 and Sodnomsambuu Demberel3 Abstract Southern Mongolia is part of the Central Asian Orogenic Belt, the origin and evolution of which is not fully known and is often debated. It is composed of several east–west trending lithostratigraphic domains that are attributed to an assemblage of accreted terranes or tectonic zones. This is in contrast to Central Mongolia, which is dominated by a cratonic block in the Hangai region. Terranes are typically bounded by suture zones that are expected to be deep- reaching, but may be difcult to identify based on observable surface fault traces alone. Thus, attempts to match lithostratigraphic domains to surface faulting have revealed some disagreements in the positions of suspected terranes. Furthermore, the subsurface structure of this region remains relatively unknown. Therefore, high-resolution geophysical data are required to determine the locations of terrane boundaries. Magnetotelluric data and telluric-only data were acquired across Southern Mongolia on a profle along a longitude of approximately 100.5° E. The profle extends ~ 350 km from the Hangai Mountains, across the Gobi–Altai Mountains, to the China–Mongolia border. The data were used to generate an electrical resistivity model of the crust and upper mantle, presented here, that can contribute to the understanding of the structure of this region, and of the evolution of the Central Asian Orogenic Belt.
    [Show full text]
  • Thermochronology of the Miocene Arabia-Eurasia Collision Zone of Southeastern Turkey GEOSPHERE; V
    Research Paper GEOSPHERE Thermochronology of the Miocene Arabia-Eurasia collision zone of southeastern Turkey GEOSPHERE; v. 14, no. 5 William Cavazza1, Silvia Cattò1, Massimiliano Zattin2, Aral I. Okay3, and Peter Reiners4 1Department of Biological, Geological and Environmental Sciences, University of Bologna, 40126 Bologna, Italy https://doi.org/10.1130/GES01637.1 2Department of Geosciences, University of Padua, 35131 Padua, Italy 3Eurasia Institute of Earth Sciences, Istanbul Technical University, Maslak 34469, Istanbul, Turkey 4Department of Geosciences, University of Arizona, Tucson, Arizona 85721, USA 9 figures; 3 tables CORRESPONDENCE: william .cavazza@ unibo.it ABSTRACT ocean, and has been linked to mid-Cenozoic global cooling, Red Sea rifting, extension in the Aegean region, inception of the North and East Anatolian CITATION: Cavazza, W., Cattò, S., Zattin, M., Okay, The Bitlis-Pütürge collision zone of SE Turkey is the area of maximum in- strike-slip fault systems, and development of the Anatolian-Iranian continental A.I., and Reiners, P., 2018, Thermochronology of the Miocene Arabia-Eurasia collision zone of southeast- dentation along the >2400-km-long Assyrian-Zagros suture between Arabia and plateau (e.g., Şengör and Kidd, 1979; Dewey et al., 1986; Jolivet and Faccenna, ern Turkey: Geosphere, v. 14, no. 5, p. 2277–2293, Eurasia. The integration of (i) fission-track analyses on apatites, ii( ) (U-Th)/He 2000; Barazangi et al., 2006; Robertson et al., 2007; Allen and Armstrong, 2008; https:// doi .org /10 .1130 /GES01637.1. analyses on zircons, (iii ) field observations on stratigraphic and structural rela- Yılmaz et al., 2010). The age of the continental collision has been the topic of tionships, and (iv) preexisting U-Pb and Ar-Ar age determinations on zircons, much debate, with proposed ages ranging widely from the Late Cretaceous to Science Editor: Raymond M.
    [Show full text]
  • Download Preprint
    EarthArXiv Coversheet 29/04/2021 Caribbean plate boundaries control on the tectonic duality in the back-arc of the Lesser Antilles subduction zone during the Eocene N. G. Cerpa*, R. Hassani, D. Arcay, S. Lallemand, C. Garrocq, M. Philippon, J.-J. Cornée, P. Münch, F. Garel, B. Marcaillou, B. Mercier de Lépinay, and J.-F. Lebrun * corresponding author : [email protected] This manuscript is a non-peer reviewed preprint submitted to Tectonics and thus may be periodically revised. The final version will be available via the ‘Peer-review Publication DOI’ link on the right-hand side of this webpage. Please feel free to contact the corresponding author; we welcome feedback. Caribbean plate boundaries control on the tectonic duality in the back-arc of the Lesser Antilles subduction zone during the Eocene N. G. Cerpa1,2,*, R. Hassani2, D. Arcay1, S. Lallemand1, C. Garrocq1, M. Philippon3, J.-J. Cornée3, P. Münch1, F. Garel1, B. Marcaillou2, B. Mercier de Lépinay2, and J.-F. Lebrun3 1 Geosciences Montpellier, University de Montpellier, CNRS, Université des Antilles, Montpellier, France. 2 Geoazur, Université Côte d’Azur, CNRS, Observatoire de la Côte d’Azur, IRD, Valbonne, France. 3 Geosciences Montpellier, Université des Antilles, Université de Montpellier, CNRS, Guadeloupe, France. *Corresponding author: Nestor G. Cerpa ([email protected]) Abstract The Eocene tectonic evolution of the easternmost Caribbean Plate (CP) boundary, i.e. the Lesser Antilles subduction zone (LASZ), is debated. Recents works shed light on a peculiar period of tectonic duality in the arc/back-arc regions. A compressive-to-transpressive regime occurred in the north, while rifting and seafloor spreading occurred in Grenada basin to the south.
    [Show full text]
  • Pan-African Orogeny 1
    Encyclopedia 0f Geology (2004), vol. 1, Elsevier, Amsterdam AFRICA/Pan-African Orogeny 1 Contents Pan-African Orogeny North African Phanerozoic Rift Valley Within the Pan-African domains, two broad types of Pan-African Orogeny orogenic or mobile belts can be distinguished. One type consists predominantly of Neoproterozoic supracrustal and magmatic assemblages, many of juvenile (mantle- A Kröner, Universität Mainz, Mainz, Germany R J Stern, University of Texas-Dallas, Richardson derived) origin, with structural and metamorphic his- TX, USA tories that are similar to those in Phanerozoic collision and accretion belts. These belts expose upper to middle O 2005, Elsevier Ltd. All Rights Reserved. crustal levels and contain diagnostic features such as ophiolites, subduction- or collision-related granitoids, lntroduction island-arc or passive continental margin assemblages as well as exotic terranes that permit reconstruction of The term 'Pan-African' was coined by WQ Kennedy in their evolution in Phanerozoic-style plate tectonic scen- 1964 on the basis of an assessment of available Rb-Sr arios. Such belts include the Arabian-Nubian shield of and K-Ar ages in Africa. The Pan-African was inter- Arabia and north-east Africa (Figure 2), the Damara- preted as a tectono-thermal event, some 500 Ma ago, Kaoko-Gariep Belt and Lufilian Arc of south-central during which a number of mobile belts formed, sur- and south-western Africa, the West Congo Belt of rounding older cratons. The concept was then extended Angola and Congo Republic, the Trans-Sahara Belt of to the Gondwana continents (Figure 1) although West Africa, and the Rokelide and Mauretanian belts regional names were proposed such as Brasiliano along the western Part of the West African Craton for South America, Adelaidean for Australia, and (Figure 1).
    [Show full text]
  • Stylolites: Characteristics and Origin
    • STYLOLITES: CHARACTERISTICS AND ORIGIN Joseph M. Montello A senior thesis submitted to fulfill the requirements for the degree of B.S. in Geology and Mineralogy • Winter Quarter, 1984 The Ohio State University ~2.~r·Thesis Advisor Department of Geology and Mineralogy Abstract • Stylolites are alternating interpenetrating columns of stone that form irregular interlocking partings or sutures in rock strata. They are most common along bedding planes of limestone but some are oblique or even perpendicular to bedding . Although the vast majority of stylolites occur in calcareous rocks, stylolites have been found in sandstone, quartzite and gypsum. The word "stylolite" refers to each individual column of stone. A cross section of a group of stylolites parallel to their length presents a rough, jagged line called a "stylolite seam" that resembles the sutures of a human skull. Stylolites always have a dark colored "clay" cap at the ends of the columns. The sides of the columns are typically discolored with a thin film of clay and show parallel flutings or striations that parallel their length. The shapes of individual stylolites vary greatly from broad flat­ • topped columns to pointed, jagged and tapering forms. After much controversy concerning the origin of stylolites, it is generally believed that they form by a process of chemical solution under pressure in lithified rock along some crack or seam. The interteething is produced because of differential solubilities and pressures within the rock unit. The clay cap on the stylolites is the non-soluble residue of the dissolved rock. Stylolites are only one of the possible end products in the spectrum of limestone responses to stress.
    [Show full text]
  • Collision Orogeny
    Downloaded from http://sp.lyellcollection.org/ by guest on October 6, 2021 PROCESSES OF COLLISION OROGENY Downloaded from http://sp.lyellcollection.org/ by guest on October 6, 2021 Downloaded from http://sp.lyellcollection.org/ by guest on October 6, 2021 Shortening of continental lithosphere: the neotectonics of Eastern Anatolia a young collision zone J.F. Dewey, M.R. Hempton, W.S.F. Kidd, F. Saroglu & A.M.C. ~eng6r SUMMARY: We use the tectonics of Eastern Anatolia to exemplify many of the different aspects of collision tectonics, namely the formation of plateaux, thrust belts, foreland flexures, widespread foreland/hinterland deformation zones and orogenic collapse/distension zones. Eastern Anatolia is a 2 km high plateau bounded to the S by the southward-verging Bitlis Thrust Zone and to the N by the Pontide/Minor Caucasus Zone. It has developed as the surface expression of a zone of progressively thickening crust beginning about 12 Ma in the medial Miocene and has resulted from the squeezing and shortening of Eastern Anatolia between the Arabian and European Plates following the Serravallian demise of the last oceanic or quasi- oceanic tract between Arabia and Eurasia. Thickening of the crust to about 52 km has been accompanied by major strike-slip faulting on the rightqateral N Anatolian Transform Fault (NATF) and the left-lateral E Anatolian Transform Fault (EATF) which approximately bound an Anatolian Wedge that is being driven westwards to override the oceanic lithosphere of the Mediterranean along subduction zones from Cephalonia to Crete, and Rhodes to Cyprus. This neotectonic regime began about 12 Ma in Late Serravallian times with uplift from wide- spread littoral/neritic marine conditions to open seasonal wooded savanna with coiluvial, fluvial and limnic environments, and the deposition of the thick Tortonian Kythrean Flysch in the Eastern Mediterranean.
    [Show full text]
  • Structural Evolution and Sequence of Thrusting in the High Himalayan, Tibetan-Tethys and Indus Suture Zones of Zanskar and Ladakh, Western Himalaya: Discussion
    Journal of Structural Geology, Vol. 10, No. 1, pp. 129 to 132, 1988 0191-8141/88 $03.00 + 0.00 Printed in Great Britain Pergamon Press pie Structural evolution and sequence of thrusting in the High Himalayan, Tibetan-Tethys and Indus Suture zones of Zanskar and Ladakh, Western Himalaya: Discussion P. B. KELEMEN Department of Geological Sciences A J-20, University of Washington, Seattle, WA 98195, U.S.A. I. REUBER Laboratoire de G~ologie Stratigraphique et Structurale, Universit~ de Poitiers, 40, Avenue du Recteur Pineau, 86022 Poitiers C6dex, France and G. FUCHS Geologische Bundesanstalt, Rasumofskygasse 23, A-1031 Wien, Austria (Received 19 May 1987; accepted 29 July 1987) M. P. Searle's recent paper in the Journal of Structural Reuber 1986). In addition, Eocene strata have been Geology (Searle 1986) included a major departure from identified in the melange at the base of the klippe published structural interpretations of the Ladakh (Colchen et al. in press). Thus the final emplacement of Himalaya. The geologic history of Ladakh is a vital key the klippe must post-date Lower Eocene sedimentation to understanding the timing and sequence of events (at least as young as 55 Ma). during the Himalayan orogeny. Ophiolitic rocks and Thrusting of the klippe may have begun substantially island arc volcanics along the Indus Suture zone (Frank earlier than its final emplacement, especially if the possi- et al. 1977, and many others) constitute remnants of a bility of intra-oceanic faulting (Reuber 1986) is con- broad oceanic basin, formerly north of the Indian craton. sidered as part of the emplacement 'event'.
    [Show full text]
  • Provenance of Sandstone Blocks and 1 Transition
    The Yarlung suture mélange, Lopu Range, southern Tibet: Provenance of sandstone blocks and transition from oceanic subduction to continental collision Item Type Article Authors Metcalf, Kathryn; Kapp, Paul Citation The Yarlung suture mélange, Lopu Range, southern Tibet: Provenance of sandstone blocks and transition from oceanic subduction to continental collision 2017, 48:15 Gondwana Research DOI 10.1016/j.gr.2017.03.002 Publisher ELSEVIER SCIENCE BV Journal Gondwana Research Rights © 2017 International Association for Gondwana Research. Published by Elsevier B.V. All rights reserved. Download date 26/09/2021 15:58:40 Item License http://rightsstatements.org/vocab/InC/1.0/ Version Final accepted manuscript Link to Item http://hdl.handle.net/10150/626129 1 The Yarlung Suture Mélange, Lopu Range, Southern Tibet: Provenance of Sandstone Blocks and 2 Transition from Oceanic Subduction to Continental Collision 3 Kathryn Metcalf1* and Paul Kapp1 4 1Department of Geosciences, University of Arizona, Tucson, AZ, USA 5 *Corresponding author. Email: [email protected] 6 Abstract 7 With the aim of better understanding the history of ocean closure and suturing between 8 India and Asia, we conducted a geologic investigation of a siliciclastic matrix tectonic mélange 9 within the western Yarlung suture zone of southern Tibet (Lopu Range region, ~50 km northwest 10 of Saga). The siliciclastic matrix mélange includes abundant blocks of ocean plate stratigraphy 11 and sparse blocks of sandstone. Metapelite and metabasite blocks in the mélange exhibit lower 12 greenschist facies mineral assemblages, indicating that they were not deeply subducted. We 13 obtained detrital zircon U-Pb geochronologic and sandstone petrographic data from sandstone 14 blocks in the mélange and sandstone beds from Tethyan Himalaya strata exposed to the south of 15 the suture.
    [Show full text]
  • The Structure of a Major Suture Zone in the SW Iberian Massif: the Ossa-Morena/Central Iberian Contact
    Tectonophysics 332 12001) 295±308 www.elsevier.com/locate/tecto The structure of a major suture zone in the SW Iberian Massif: the Ossa-Morena/Central Iberian contact J.F. Simancas*,D. MartõÂnez Poyatos,I. ExpoÂsito,A. Azor,F. Gonza Âlez Lodeiro Departamento de GeodinaÂmica, Universidad de Granada, Campus de Fuentenueva, Granada E-18002, Spain Abstract We have investigated the stratigraphy,structure and metamorphism of the boundary between the Ossa Morena Zone 1OMZ) and the Central Iberian Zone 1CIZ),two signi®cant continental portions of the Variscan Iberian Massif. The OMZ/CIZ contact is marked by a strongly deformed and metamorphosed NW±SE trending narrow band,namely,the Central Unit,in which partially retrogressed eclogites are included. During the Middle-Late Devonian the CIZ overthrust the OMZ,and in the footwall km-scale recumbent folds and thrusts developed with decoupling and underplating of the lower crust. At the same time,in the hanging wall there took place intense though localized back-folding and back-shearing. In the Early Carboniferous a transten- sional tectonic regime sank the overthrust block resulting in the exhumation of eclogites. These eclogites probably came from the underthrust OMZ lower crust,and they are at present included in the suture zone 1Central Unit) of this continental collision. The extension is responsible for the origin of a basin and bimodal magmatism on the southern border of the CIZ. A late episode of folding and fracturing signi®cantly contributed to the ®nal complex picture of this suture boundary. q 2001 Elsevier Science B.V. All rights reserved. Keywords: collision tectonics; eclogite exhumation; oblique extensional collapse; Variscan suture; SW Iberian Massif 1.
    [Show full text]
  • The Relationship Between Tectonic Stylolites and Fold Morphology in Limestones of the “Croatica Deposits” (Croatia)
    Geologia Croatica 55/1 79 - 81 4 Figs. ZAGREB 2002 The Relationship Between Tectonic Stylolites and Fold Morphology in Limestones of the “Croatica Deposits” (Croatia) Domagoj JAMIÈIÆ Key words: Stylolites, Tectonics, Compression, lolites appears in the plane perpendicular to the main Limestone, Croatica Deposits, Lower Pannonian, stress (s 1) whereas the second generation is connected Croatia. to extension of left transcurrent fault. This paper describes the tectonic deformational sequence which led to formational processes of tectonic stylolites in Pannonian clayey limestones (“Croatica Abstract Deposits”). The genetic link between faults and fracture Stylolites associated with axial plane fractures occur in Lower Pan- creation and the process of stylolitization under the nonian clayey limestones (the “Croatica Deposits”) from the “Ham- povica 6” deep exploration well. A genetic link has been observed influence of local stress with the same orientation has between the origin of fractures and the process of stylolitization. been noticed. Strong tectonic deformations are present which have been formed Stylolites often occur in limestones and marls, either under the influence of reverse bed faulting. Deformation is pro- nounced in the shape of folded marl layers along with the creation of a) parallel to, or b) at an angle relative to the bedding thick cleavage (0.3-0.5 cm). Along the fractures of axial plane cleav- plane. The first stylolite type, parallel to beds has been age, microlithons are separated and moved apart for similar values (2- formed as a result of gravity and sediment compaction. 5 mm) forming a moderate synform. Stylolites are formed in the last The initial thickness of sediments can be reduced by phase of structure shaping when the effects of the local compressional stress have weakened under the influence of which the breaking off gravitational processes up to 20-30% (TI©LJAR, 1978).
    [Show full text]