At Vero Eos Et Accusamus Et Iusto Odio Dignissimos Ducimus Qui Blanditiis

TSK Jena 2018

17th Symposium of Tectonics, Structural Geology and Crystalline Geology

Organising committee

• Kamil Ustaszewski (president elect of the TSK board) • Christoph Grützner

Scientific committee

• Erik Duesterhoeft, Univ. Kiel • Nikolaus Froitzheim, Univ. Bonn • Bernhard Grasemann, Univ. Vienna • Christoph Grützner, Univ. Jena • Andrea Hampel, Univ. Hannover • Renée Heilbronner, Univ. Basel & Tromsø • Petr Jeřábek, Univ. Prague • Jonas Kley, Univ. Göttingen • Piotr Krzywiec, Polish Academy of Sciences, Warsaw • Hannah Pomella, Univ. Innsbruck • Klaus Reicherter, RWTH Aachen University • Magdalena Scheck-Wenderoth, GFZ Potsdam & RWTH Aachen • Stefan M. Schmid, ETH Zürich • Cornelia Spiegel, Univ. Bremen • Michael Stipp, Univ. Kiel • Chin-Ho Tsai, Dong Hwa Univ., Taiwan • Kamil Ustaszewski, Univ. Jena • Bianca Wagner, Univ. Göttingen

TSK board members

• Nikolaus Froitzheim, Univ. Bonn (current president of the TSK board) • Uwe Altenberger, Univ. Potsdam (past president of the TSK board) • Reiner Kleinschrodt, Univ. Köln • Jolien Linckens, Univ. Frankfurt • Michael Stipp, Univ. Innsbruck

Programme TSK 2018, Univ. Jena, 19 – 25 March 2018

Mon, 19 March 2018: Inst. für Geowissenschaften

Pre-conference workshops (09:00 – 16:00) • Workshop 1: Active tectonics and palaeoseismology Dr. Christoph Grützner, Jena. • Workshop 2: 2D- & 3D structural modeling and balancing techniques in geology Kamil Ustaszewski & Philipp Balling, Jena.

Pre-conference field trip (1/2 day, afternoon) • "Tectonic structures around Jena viewed from atop". Guide: Kamil Ustaszewski. Start: 16:00, Markt, Jena

Tue, 20 March 2018: Inst. für Geowissenschaften Pre-conference workshops (09:00 – 16:00) • Workshop 3: 3D photogrammetry / "Structure from Motion" Dr. Bianca Wagner, Göttingen. • Workshop 4: Metamorphic phase equilibrium computations using Theriak- Domino Dr. Erik Duesterhoeft, Kiel. • Workshop 5: Python programming and its applications in structural geology Dr. Ondrej Lexa, Prague.

Guided tour through the mineralogical collection (16:00 – 18:00)

Guide: Dr. Birgit Kreher-Hartmann.

Icebreaker party (from 18:00, Institut für Geowissenschaften, Burgweg)

Wed, 21 March 2018: Rosensäle Morning: S3: Himalayan- and Mediterranean-style collisional orogens Afternoon: S3: Himalayan- and Mediterranean-style collisional orogens

08:30 - 08:50 Welcome and Opening Ceremony

S3: Himalayan- and Mediterranean-style collisional orogens Session chairs: Szilvia Deák-Kövér, Jonas Kley, Jan Pleuger, Hugo Ortner

08:50 - 09:20 Douwe van Hinsbergen: Reconstructing Greater India: paleogeographic, kinematic, and geodynamic perspectives (Keynote)

09:20 - 09:40 Suppe et al.: Subducting of continental rise, slope and shelf basins in Taiwan oblique arc-continent collision: Insight from tomography, surface geology, and seismic reflection data 09:40 - 10:00 Handy et al.: Transfer and rotational normal faulting at the Dinar- ides-Hellenides junction - their relation to tearing and retreat of the Adriatic slab

10:00 - 11:00 Coffee & Posters

11:00 - 11:20 Löwe et al.: Contrasting extension directions along-strike a chain of Miocene metamorphic core complexes at the southern rim of the Pannonian Basin: the quest for a plausible kinematic model 11:20 - 11:40 Schmid: Lithosphere structure of the Western Alps and Alps- Apennines transition 11:40 - 12:00 Groß et al.: The structural and metamorphic record of subduction, exhumation and collision in the Penninic nappes of the central Tau- ern Window, Eastern Alps 12:00 - 12:20 Šumanovac: Slab gap or descending lithosphere slab beneath the Dinarides - comparison of several tomographic models

12:20 - 13:40 Lunch

S3: Himalayan- and Mediterranean-style collisional orogens (continued) Session chairs: Szilvia Deák-Kövér, Jonas Kley, Jan Pleuger, Hugo Ortner

13:40 - 14:10 Ratschbacher et al.: Steady-state plate tectonics, unsteady orogeny: a view from the Pamir (Keynote)

14:10 - 14:30 Basak et al.: Ultrapotassic Granitoid-Diospsidite-Carbonatite in a post-collisional tectonic setting from Chhotanagpur Gnessic Com- plex, Eastern India 14:30 - 14:50 Balling et al.: A kinematic forward model across the Velebit Moun- tains in the External Dinarides, validated by the structural position of various types of carbonate breccia 14:50 - 15:10 Di Rosa et al.: The tectonic half-window of Cima Pedani (Alpine Corsica, France): an example of exhumed continental crust in collisional belt 15:10 - 15:30 Sobel et al.: A rift basin in the External Pamir - paleogeographic implications for reconstructing the Cenozoic deformation history

15:30 - 16:30 Coffee & Posters

16:30 - 16:50 Ghani et al.: Structural evolution of Main frontal Thrust in Pakistan. New evidence from low temperature thermochronology. 16:50 - 17:10 Meier et al.: Tracing trails of fault activity along a major shear zone in Calabria, Southern Italy – Implications for the geodynamic evolution and for methodological aspects of (U-Th-Sm)/He- thermochronology 17:10 - 17:30 Kroner et al.: Oroclines and plate tectonics – Two examples from the Variscides

18:00 - 19:00 Öff. Abendvortrag (deutsch) von Onno Oncken, Aula im UHG:

Der Erdbeben-Zoo und die Bananenschale - was wir schon immer über Subduktionszonen wissen wollten.

Thu, 22 March 2018: Rosensäle Morning: S1: Plate tectonic reconstructions Afternoon: S4-S5: Tectonics of sedimentary basins / Intraplate tectonics S6: Rheology, rates and fluids in tectonometamorphic processes

S1: Plate tectonic reconstructions Session chairs: Douwe van Hinsbergen, Mark R. Handy

08:30 - 09:00 Gerya: Two plate tectonics enigmas: initiation of new subduction zones and ridge-transform spreading patterns (Keynote)

09:00 - 09:20 Advokaat et al.: Dragging and segmentation of the Burma and Sunda slabs caused by increasing curvature of the Sunda Trench 09:20 - 09:40 Abbo et al.: The North Gondwana lower crust: Evidence for sediment subduction and syn-Variscan magmatism from zircons in mafic granulite xenoliths 09:40 - 10:00 Stephan et al.: Early Palaeozoic evolution of the northern Peri- Gondwana shelf – reconsidering the sedimentary, magmatic and the tectono-metamorphic record

10:00 - 11:00 Coffee & Posters

11:00 - 11:30 Suppe: The Second Half of Plate Tectonics: Finding the Last ~200 Ma of Subducted Lithosphere and Incorporating it Into Plate Re- construction (Keynote)

11:30 - 11:50 Gürer et al.: Reconstructing oceans lost: the fate of the eastern Mediterranean Paleo- and Neotethys

Teaser for session S7: Active tectonics and surface processes

11:50 - 12:20 Kopp: From no slip to slow slip: How seafloor geodesy reveals crustal deformation at mm-scales (Keynote)

12:20 - 13:40 Lunch

S4-S5: Tectonics of sedimentary basins / Intraplate tectonics Session chairs: Christoph von Hagke, Piotr Krzywiec

13:40 - 14:00 Kley et al.: Causes of post-Variscan uplift in northern Central Eu- rope

14:00 - 14:20 Franke & Franz: The discontinuous Lower Cretaceous of NE Ger- many: Late Cimmerian Unconformity or Early Cretaceous pre- inversion? 14:20 - 14:40 Nakapelyukh et al.: The geological evolution of the south-west margin of East European platform: from Paleozoic fold-thrust belt to Miocene Foredeep 14:40 - 15:00 Stypa et al.: Paleozoic evolution of the Baltic Basin - preliminary results based on integrated seismic data interpretation and subsidence analysis. 15:00 - 15:20 Jähne-Klingberg et al.: Distribution, tectonic structures and deformation processes of salt-bearing Rotliegend formations in the German North Sea and surrounding areas

15:20 - 16:30 Coffee & Posters

S6: Rheology, rates and fluids in tectonometamorphic processes Petr Jeřábek, Michael Stipp

16:30 - 16:50 Jeřábek: Flow below the continental plateaus? Some answers from the microstructures of felsic granulites in the Bohemian Massif 16:50 - 17:10 Behrmann & Kühn: Textures and physical properties of Naxos white marbles 17:10 - 17:30 Hallas & Kroner: Using quartz microstructures and textures to characterize exhumation channel shear zones in the Erzgebirge, N- Bohemian Massif 17:30 - 17:50 Dietl et al.: A strength profile through the Upper Crust of the Fran- conian Basin

19:00 - 22:00 Conference dinner, Braugasthof Papiermühle

To reach the conference dinner at "Papiermühle", take Bus 16 from the city centre to bus stop "Mühltal", direction Isserstedt or Mühltal.

Fri, 23 March 2018: Rosensäle Morning: S6: Rheology, rates and fluids in tectonometamorphic processes S7: Active tectonics and surface processes Afternoon: S8: Open topics in structural geology and tectonics

S6: Rheology, rates and fluids in tectonometamorphic processes (cont.) Petr Jeřábek, Michael Stipp

08:30 - 09:00 Herwegh: Rheological switches and strain distribution during the exhumation of granitoid continental crust (Keynote)

09:00 - 09:20 Turner et al.: Nanodeformation in nanoseconds: pulsed laser experiments on enstatite simulate micrometeoroid impacts

S7: Active tectonics and surface processes Session chairs: Klaus Reicherter, Kamil Ustaszewski, Christoph Grützner

09:20 - 09:40 Štěpančíková et al.: Holocene tectonic activity on the Mariánské Lázně Fault (Cheb basin, West Bohemia) 09:40 - 10:00 Reicherter et al.: Active faulting in the Upper Rhine Graben: geomorphological and geophysical evidences

10:00 - 11:00 Coffee & Posters

11:00 - 11:20 Ortner et al.: Morphology of normal faults, landscape evolution and ageing of cataclasites at Campo Imperatore, Abruzzi Apennines, It- aly 11:20 - 11:40 Vrabec et al.: Unraveling neotectonic vertical-axis rotations in the Adria-Eurasia collision zone: Paleomagnetic data from Pliocene- Quaternary cave sediments (Slovenia) 11:40 - 12:00 Kázmer and Moro: Archaeoseismology and (in)active tectonics - The case of the Velebit seismic gap along the Adriatic coast, Croa- tia 12:00 - 12:20 Biermanns et al.: Tectonic imprint on landscape evolution at the Dinarides - Hellenides transition (Southern Montenegro and North- ern Albania) 12:20 - 12:40 Zebari et al.: Estimating the Relative Uplift Time of Anticlines based on Landscape Maturity and Evolution Modeling: NW Seg- ment of the Zagros Mountain Front Flexure, Kurdistan Region of Iraq

12:40 - 14:00 Lunch

S7: Active tectonics and surface processes (cont.) Session chairs: Klaus Reicherter, Kamil Ustaszewski, Christoph Grützner

14:00 - 14:20 Dannowski et al.: Ionian Sea: Image of the crustal structure using seismic data

S8: Open topics in structural geology and tectonics Session chairs: Jolien Linckens, Marko Vrabec, Ondrej Lexa

14:20 - 14.40 Gehrmann et al.: Architecture and structural evolution of the Jas- mund Glacitectonic Complex (Rügen, NE Germany) 14:40 - 15:00 Tsai et al.: On the tectonic blocks of the Yuli belt, eastern Taiwan: Petrologic constraints 15:00 - 15:20 Salomon et al.: Viscoplastic finite element modelling of the South American subduction zone before large earthquakes - A parameter study 15:20 - 15:40 Schmidt et al.: Preservation of oscillatory zoning in plagioclase inclusions from the Western Gneiss Region, Norway

15:40 - 16:30 Coffee & Posters

16:30 - 16:50 Novakova & Pavlis: The utilization of digital devices for structural geology field mapping 16:50 - 17:10 Wagner and Leiss: Deployment of digital outcrop models (DOMs) in structural geology - A methodological review 17:10 - 17:30 Cionoiu et al.: Phase transitions under differential stress: Devia- toric stresses or pressure? 17:30 - 17:50 Altenberger et al.: Pseudotachylytes: an approach to estimate the depth of origin 17:50 - 18:10 Peřestý et al.: Pre-Variscan metamorphic structure at the western margin of the Teplá-Barrandian Domain – comparison of the Teplá and Domažlice Crystalline Complex (Bohemian Massif)

18:10 - 18:30 Best student poster award and closing ceremony

Sat 24 – Sun 25 March 2018 Post-conference field trip: "Deformation & metamorphism in the Saxothuringian units of the Variscan orogen". Guide: K. Ustaszewski. Start: 24 March, 08:00, Inselplatz, Jena End: 25 March, ~18:00, Inselplatz, Jena

List of invited speakers at TSK 2018 (alphabetic order)

Speaker, job role Affiliation Talk title Taras Gerya, Prof. Dr. ETH Zürich, Swit- Two plate tectonics enig- zerland mas: initiation of new subduction zones and ridge- transform spreading patterns Marco Herwegh, Prof. Univ. Bern, Switzer- Rheological Switches and Dr. land Strain Distribution during the Exhumation of Granitoid Continental Crust Douwe van Hinsbergen, Univ. Utrecht, The implications of paleoge- Prof. Dr. Netherlands ographic reconstructions of the India-Asia collision zone for the fundamental geodynamics of subduction: how to apply Ockham’s Razor? Heidrun Kopp, Prof. Dr. GEOMAR Helm- From no slip to slow slip: holtz-Zentrum How seafloor geodesy re- für Ozeanforschung veals crustal deformation at & Universität Kiel mm-scales Onno Oncken, Prof. Dr. Helmholtz-Zentrum Der Erdbeben-Zoo und die Potsdam GFZ & Bananenschale - was wir Freie Univ. Berlin schon immer über Subdukti- onszonen wissen wollten. Lothar Ratschbacher, TU Bergakademie Steady-state plate tectonics, Prof. Dr. Freiberg unsteady orogeny: a view from the Pamirs John Suppe, Prof., Dr. University Houston, Finding the last ~200Ma of USA subducted lithosphere in tomography and incorporating it into a new generation of plate reconstructions

List of posters S1: Plate tectonic reconstructions • Friebel et al.: Mapping and structural geological study of a shear zone at South- ern Sweden, Göteborg • Oravecz et al.: Structural mapping, well data and stress field analysis in the surroundings of the Nekézseny Thrust Fault, NE Hungary • Pingel et al.: A new balanced cross section across the southern Dinarides fold and thrust belt in the vicinity of the Montenegro 1979 Mw 7.1 earthquake epicenter

S2: Accretionary systems in nature and experiment • Kohn et al.: Temperature gradient in the Adula nappe and its potential significance for the nappe’s kinematic history • Krýza et al.: Flow of partially molten lower crust and associated regional- scale detachment/diapiric folding driven by indentation in hot orogens - insights from analogue models employing the 2D photogrammetry methods. • Scherman et al.: Preliminary observations on low-temperature shearing and folding of Middle Jurassic siliciclastic formations, SW Bükk, Hungary • Ustaszewski et al.: New views on the crustal-scale geometries of the Taiwan fold-thrust belt

S3: Himalayan- and Mediterranean-style collisional orogens • Di Rosa et al.: How the geo-boundary conditions control the continental crust’s exhumation: three examples from the Lower Units (Alpine Corsica, France) • Frölich: The adventure of applying LA-ICP-MS U-Pb zircon dating to igneous and meta-igneous rocks from Afghanistan • Giese et al.: Footwall exhumation along the Shkoder-Peja Normal Fault vs. regional uplift and erosional denudation (Dinarides-Hellenides junction) • Goris et al.: The Shkoder- Peja Normal Fault system and its relation to the Ko- sovo basin • Grund et al.: Geological map (1 :10 000) of the Shkoder-Peja Normal Fault in its central segment near Bajram Curri (northern Albania) – evidence for distributed normal faulting and extension • Irum et al.: Tourmaline and micas as petrogenetic minerals: Preliminary study from two-mica Mansehra Granite, KPK Pakistan • Kley et al.: Structure of the Main Pamir Thrust and External Pamir thrust belt in Kyrgyzstan and western China • Klug et al.: Deformation and Geochronology of Metamorphic Rocks in the Saltauser Tal, Italy.

• Langner et al.: Peak temperatures in the Seidlwinkl-Rote Wand nappe (Central Tauern Window, Eastern Alps) determined by Raman spectroscopy on carbonaceous matter • Rembe et al.: The influence of Mesozoic structures on the Cenozoic Pamir – The most external occurrence of the Karakul-Mazar nappe, Chinese Pamir • Rezaei et al.: Geochemistry and geotectonic setting of gabbros in the Gasht- Masuleh area, Alborz Mts., north Iran • Sanità et al.: An example of a three-type interference pattern in the Tuscan Nappe, Southeastern sector of Apuan Alps (Northern Apennines, Italy) • Simon et al.: Evolution of the Tropoja basin in NE Albania and possible links to the Shkodër-Peja Normal Fault • Sokol et al.: Assessing viable geodynamic environment for the magmatism within the Sava-Vardar Zone: A case study from the vicinity of Belgrade • Thiede et al.: Uplift and growth of the northwest Pamir

S4/S5: Intraplate tectonics/tectonics of sedimentary basins • Dhansay et al.: Assessing the reactivation potential of pre-existing fractures in the southern Karoo, South Africa: Evaluating the potential for sustainable exploration across its Critical Zone • Djeffal et al.: Tectono-Stratigraphy of The Cretaceous Shelf (Constantinois Plat- form- NE Algeria) • Donhauser et al.: Faults in the Franconian Basin: A Hydraulic Basement-Cover Connection? • Eberts et al.: Tectonic impact on sediment routing systems of evolving rift basins: A case study from the Cenozoic Kerimbas Graben, offshore northern Mozambique • Effendi: The mapping and structural analysis of a shear zone in Ödsmålsmosse, South Sweden • Kufrasa et al.: Late Carboniferous fracture system in NE part of the Lublin Basin (Poland): results of seismic attribute analysis and fracture modeling • Louis et al.: Quantifying the timing and rate of exhumation of the Molasse basin by combining structural and thermochronological data with thermal history and kinematic models • Malz et al.: Styles of Late Cretaceous intraplate shortening in Central Germany - first results from 3D modelling in the Altmark region, Saxony Anhalt • Navabpour et al.: Post-Triassic succession of fault kinematics along the Lichtenau Graben and the implications within the regional tectonic framework • Stypa et al.: Application of backstripping and subsidence analysis in paleothickness reconstruction: case study from the Lublin Basin (Poland) and potential sources of uncertainty • von Hagke et al.: A full appreciation of the uncertainty of thermochronological data in sedimentary basins

• Warsitzka et al.: On the timing of salt structure growth in the Southern Permian Basin

S6: Rheology, rates and fluids in tectonometamorphic processes • Koenemann: Physics and kinematics of S-C-fabric in plastic shear zones • Kryl et al.: Retention versus overprint of deformation microstructures in quartzofeldspathic rocks during polyphase deformation in the Erzgebirge Mountains • Pollok & Langenhorst: Fluid flow through solid rocks: from fracture patterns to retrograde reaction textures • Schaarschmidt et al.: Fluid flow in the Bavarian Pfahl shear zone • Schmidtke & Keppler: Elastic anisotropies of rocks from oceanic and continental crust and the upper mantle

S7: Active tectonics and surface processes • Ourari & Mechane: Neotectonics activity near the South Kabylian thrust fault: Kabylia region – North Eastern Algeria • Bouedja et al.: Travertine occurrences along major neotectonic normal fault zones in the Hammam Debar- Roknia Guelma region ,Nort-East Algeria • Grützner: The geomorphological imprint of active faulting in NW Slovenia and NE Italy – first results from field studies and high-resolution topography data • Grützner et al.: Measuring the slip-rate of the Main Kopeh Dagh Fault, Turkmen- istan • Mechernich et al.: Paleoseismology using bedrock fault planes • Schmitz et al.: Active normal faults within the convergent thrust belt front of the Southern Dinarides (Montenegro & Albania) • Skrgulja & Kazmer: Deformed Roman monuments along active faults in NW Croatia - archaeoseismological studies • van der Wal et al.: Analyzing neotectonic activity through GPR and morphotectonic observations along the Bogd Fault Zone, SW Mongolia • Weismüller et al.: Quantification and identification of fault-geometry and respective features of massively dilatant faults in Iceland using 3D point clouds • Winhausen et al.: Influence of columnar joints on normal fault geometry and evolution – Insight from scaled physical models

S8: Open topics in structural geology and tectonics • Aichholzer et al.: Fault kinematics at the kink of the Periadriatic Line in the SW of the Tauern window • Fodor et al.: Deformation bands in sedimentary basins: their role in depth- temperature-time determinations and regional structural analysis • Gehrmann et al.: The imprint of Weichselian glacitectonism on the recent morphology of Jasmund (Rügen Island, NE Germany) • Gürer et al.: Plate kinematic consequences of double in-line subduction in Ana- tolia

• Hallas et al.: The exhumation channel of the Erzgebirge: constraints from microtectonics and PT estimations • Kemperle et al.: The role of the feldspar solvus for deformation mechanisms and rheology of the lower crust • Klotz et al.: Differential uplift in the northernmost kink area of the Periadriatic fault system – a 4D kinematic model • Kühn et al.: First results on texture and elastic anisotropy of oceanic crust from the slow-spreading ridge at Atlantis Massif, Atlantic Ocean • Kulikov et al.: Geological and tectonical challenges for the construction of a railway line and a cross-border Ore Mountains base tunnel (SN-CZ), INTERREG V project. • Kurzawski et al.: Shallow subduction channel deformation at the Costa Rica erosive convergent continental margin: frictional behavior of subduction input sediments • Linckens et al.: Subgrain development in experimentally deformed rock salt • Liu et al.: Evolution of pull-apart basins with several fault strands based on particle-based modeling • Nabhan & Heubeck: Local and regional controls on the maturation state of carbonaceous matter in the Barberton Greenstone Belt, South Africa. • Nilius et al.: Structural and kinematic constrains on the exhumation of the central Menderes Massif along the Büyük Menderes detachment, western Turkey • Obst et al.: The complex fault pattern in the southern Baltic Sea area reflecting the late Palaeozoic and Mesozoic evolution of the Trans-European Suture Zone (TESZ) • Obst et al.: Fault database of north-eastern Germany: intention, information sources, content • Onuzi: Tectonics and Stratigraphy of the Cukali area • Philipp: Fracture Systems and Fluid Flow in Geothermal Reservoirs • Scharfenberg & de Wall: Radiogenic heat production of Variscan granites - Western Bohemian Massif, Germany • Scheffler et al.: Meta-Selenites and their bearing on a lost Cretaceous Evaporitic Basin of the Eastern Mediterranean • Sieberer et al.: Depositional setting of Cretaceous syntectonic sediments of the external Northern Calcareous Alps, Allgäu, Bavaria • Stephan et al.: Crustal-scale 3D modelling of the Allochthonous Domain of the Erzgebirge-Vogtland-Fichtelgebirge area, Saxo-Thuringian Zone • Youcef et al.: Tectonic analysis of south Setifian domain and its neighboors area (eastern Algeria) • Zebari et al.: Surface Deformation Related to the 12 November 2017 Iran-Iraq Border Earthquake (MW 7.3) and its Aftershocks: Insights from InSAR Data

List of Abstracts

The North Gondwana lower crust: Evidence for sediment subduction and syn- Variscan magmatism from zircons in mafic granulite xenoliths

Avishai Abbo1, Dov Avigad1, Axel Gerdes2

1Institute of Earth Sciences, The Hebrew University of Jerusalem, Israel, [email protected] 2Institut für Geowissenschaften, Goethe-Universität, Frankfurt am Main, Germany

The continental basement of North Gondwana and its transition towards the Peri-Gondwana Cadomian domain to the north is mostly sealed by a thick sedimentary cover and inaccessible. To study geologic and thermal history of the lower crust of the North Gondwana edge we examined the U-Pb-Hf systematics in zircons from mafic granulite xenoliths, brought to the surface by a Pliocene lava cone in North Israel. The xenoliths are composed of plagioclase + orthopyroxene + clinopyroxene ± amphibole ± garnet ± spinel. Zircon age populations vary between xenolith samples, yet display distinct concentrations at 400-1200 Ma, 170-350 Ma, and 3.6-4.2 Ma, demonstrating the lower crust preserves a prolonged thermal and igneous history. Zircons aged 400-550 Ma are shown to be the result of Pb loss, yet the wide scatter of zircon grains aged 550-1200 Ma, alongside their diverse εHf(t) values (-25 - +10), is an extraordinary evidence for the accretion of Neoproterozoic sediments into the North Gondwana lower crust. The U-Pb-Hf signature of these zircons resembles Cadomian sediments of the Tauride block to the north, indicating southward (present coordinates) subduction under North Gondwana and possible accretion of fore-arc sediments to the lower crust through relamination in the latest Neoproterozoic. One of the xenoliths contained only metamorphic-shaped zircons aged 170- 350 Ma with positive εHf values and Hf-TDM of 0.85 Ga interpreted to reflect Paleozoic recycling of the Neoproterozoic juvenile Arabian basement, which we consider to form a major component of the lower crust in the region. An overwhelming cluster of Carboniferous zircons concentrating at 305 Ma with exclusively negative εHf values around -6, was retrieved from three xenoliths. Some of these zircons portrayed igneous textures and shape, indicating the involvement of some amount of late Carboniferous melt in the lower crust. While Carboniferous igneous activity is the hallmark of the Variscan orogeny in Western Europe, the latter did not affect the southern rifted edge of Neo-Tethys where our xenoliths were retrieved from. The Paleozoic age-Hf composition in our xenoliths is therefore interpreted to result from syn- Variscan recycling of Neoproterozoic sediments in the lower crust, and some degree of melting in an un-orogenic environment. Rather than with horizontal plate motions and orogeny, the Carboniferous zircon ages in the xenoliths coincide with significant vertical movements that created continental-scale unconformities and broad (~1000 km) basin-and swell structures known to develop over the entire north Gondwana margin at that time. The Carboniferous-aged zircons in northern Israel lower crustal xenoliths are therefore a unique gauge of the thermal perturbation that accompanied the large-scale mantle dynamics below the then-passive North African margin of Gondwana, while Variscan orogenic accretion occurred on the Eurasian margin. This North Israel granulite xenolith suite tracks the record of a protracted history of the North Gondwana lower crust from the late Neoproterozoic through to the Pliocene.

Dragging and segmentation of the Burma and Sunda slabs caused by increasing curvature of the Sunda Trench

Eldert L. Advokaat1, Douwe J.J. van Hinsbergen1, Wim Spakman1

1Department of Earth Sciences, Utrecht University, The Netherlands; [email protected]

We reconstruct the Cenozoic evolution of the Sunda Trench and segmentation of the Sunda and Burma slabs. Around 45 Ma, the Australian Plate became coupled to the Indian Plate and started moving rapidly northwards causing subduction underneath Eurasia. At the time of this subduction initiation, the Sunda Trench had a linear NW-SE trending geometry along Burma, Sumatra and Java. The eastern section of the Sunda Trench offshore Java experienced subsequent ~45° counterclockwise rotation during the Late Eocene–Early Miocene, thus acquiring a orientation perpendicular to the motion of the Indian-Australian Plate, and became stationary relative to the mantle, which may be an effect of slab anchoring into the mantle. Synchronously collision of India with Eurasia caused at least 15° clockwise rotation of the Burma section of the Sunda Trench, thus acquiring an orientation nearly parallel to the motion of the Indian-Australian Plate, where the Burma slab experienced increasing trench parallel dragging by the motion of the Indian-Australian Plate. This increasingly different orientation along the strike of the Sunda Trench caused increasingly differential motion between different sections of the slab, ultimately leading to tearing and segmentation into the Burma and Sunda slabs respectively during the Oligocene. Another consequence of the curved geometry of the Sunda Trench is that the slab became folded and faulted at depth, which may explain why segmentation of the slab is localized below the Andaman Sea. We propose similar mechanisms may also be responsible for slab dragging and slab segmentation at other strongly curved subduction zones.

Fault kinematics at the kink of the Periadriatic Line in the SW of the Tauern window

Paul Aichholzer1, Hannah Pomella1, Ulrich Burger2

1University of Innsbruck, Institute of Geology, Innsbruck, Austria, [email protected] 2Brenner Basistunnel BBT-SE, Bozen, Italy

The Periadriatic line (PAL) shows a distinctive kink at the location of Sterzing in northern Italy (South Tyrol), 18km to the South of the Brenner Pass. The prominent fault system changes from the SW – NE striking Meran-Mauls fault (MMF) to the approximately W-E striking Pustertal- Gailtal line (PGL). The alteration of direction is linked to a change in the kinematics from Top-to- SE along the MMF in the west to dextral strike-slip along the PGL in the east. For the present study the easternmost part of the MMF has been mapped to obtain the structural data in order to better understand the structural evolution. The results are represented in form of a map and cross sections. The westernmost end of the PGL, on the other hand, was mapped by my fellow student colleague Thomas Klotz, who is going to display his work at this symposium as well. The hanging wall off the Meran-Mauls fault is represented by the paragneiss of the Hirzer unit (Bargossi et al., 2010) which is part of the Meran-Mauls basement (MMB). The latter is part of the Drauzug-Gurktal nappe system which belongs to the Austroalpine nappe stack and is characterised by a only lower greenschist facies alpine metamorphic overprint (Schmid et al., 2004). A thin sliver of Paleogene intrusive rocks, the Tonalitic Lamellae, is cropping out along the MMF and shows a foliation approximately parallel to the general orientation of the MMF and the foliation of the Hirzer unit of the MMB (Pomella et al., 2011).The foot wall of the MMF is build up by the Permian Brixen-Granodiorite which is part of the major tectonic unit of the Southern Alps and shows almost no alpidic overprint (Schmid et al., 2004). The major fault of the MMF as well as the dominant foliations are dipping towards NW-NNW. Proximate to the fault the dip angle is between 55-70° whereas in the distant areas it flattens out to 40-50°. Close to the MMF an approximately horizontal stretching lineation can be observed which is overprinted by a younger dip-slip lineation representing the Top-SE thrusting. Several about N-S oriented strike-slip faults could be observed crosscutting and offsetting the Tonalitic lamellae and the MMF. The offset increases from W-E with a maximum offset of ~900m in the eastern part of the study area, towards the kink of the fault line. Interestingly the orientation of the foliation in the hanging wall as well as the orientation of the MMF fault itself is reasonably consistent over the whole study area and no gradually shifting towards the W-E orientation of the PGL could be observed.

References Bargossi, G. M., Bove, G., Cucato, M., Gregnanin, A., Morelli, C., & Moretti, A. et al. (2010). Erläuterungen zur geologischen Karte von Italien im Massstab 1:50.000 Blatt 13 "Meran". With assistance of C. Ambrosi, P. Cortini, P. Macconi, V. Mair, M. Marocchi, L. Montresor et al. Roma: Servizio Geologico D'Italia. Pomella, H., Klötzli, U., Scholger, R, Stipp, M., Fügenschuh, B. (2011). The Northern Giudicarie and the Meran-Mauls fault (Alps, Northern Italy) in the light of new paleomagnetic and geochronological data from boudinaged Eo-/Oligocene tonalites. In International Journal of Earth Sciences 100 (8), 1827–1850. DOI: 10.1007/s00531-010-0612-4. Schmid, S. M., Fügenschuh, B., Kissling, E., Schuster, R. (2004). Tectonic map and overall architecture of the Alpine orogen. In Eclogae Geologicae Helvetiae 97 (1), 93–117. DOI: 10.1007/s00015-004-1113-x.

Pseudotachylytes: an approach to estimate the depth of origin

Uwe Altenberger1, Christina Günter 1, Giacomo Prosser2, Johannes T. Weidinger3

1University of Potsdam, Potsdam, Germany, [email protected] 2Università della Basilicata, Potenza, Italy, [email protected] 3Erkudok Institut/K-Hof-Museen, Gmunden, Austria, [email protected]

Pseudotachylytes (pst) are the evidence of fossil frictional melts formed by seismic slip, meteoric impacts or large landslides. Fault-related pseudotachylytes record ancient hypocenters, usually located at upper crustal depths. However, evidence derived from both present seismicity and fossil earthquake sources, indicate that also the lower continental crust and subducting slabs may be the site where seismic events can be generated. Giant rockslides and subsequent formation of pst are often triggered by seismic events, too. Pseudotachylyte veins and patches that formed at different depths, i.e. from near surface to deep crust, look often very similar. The present work shows the main distinguishing features of tectonically induced pseudotachylytes in relation to their formation depth. Our results are based on numerous examples showing evidence of generation at different crustal depths, e.g. the Mather Peninsula/Antarctica, the Serrre Massif/Calabria, the Idefjord Terrane/Sweden, the Ivrea Zone/Italy, the Alpine Fault/New Zealand, the Guajira Complex/Colombia, the Bucaramanga Fault/Colombia, Tsergo Ri, Nepal, and others. Independently on their depth of origin and the composition of the protolith, pseudotachylytes are composed of a fine-grained matrix, clasts as relicts of the protolith, newly formed minerals resulting from devitrification or crystallization during rapid cooling. In addition, most pst show chilled margins, flow folds, layering, branching injection veins, cataclastic and ductile grain-size reduction before onset of melting as well as evidence of post-seismic creep. Therefore, the described microstructural features are not diagnostic for the evaluation of the paleo-depth of the seismic failure. One of the best criteria to obtain data on the depth of formation is the stability of newly formed (quenched) minerals, which directly crystallized from the pst melt, as well as post-slip minerals overgrowing the pseudotachylyte matrix. Garnet, biotite and pyroxene play a major role in estimating the depth of frictional melts and, therefore, the depth of the approximately paleo- hypocenters. Frictional melts from normal continental crust and subducted crust behave in most parts similar in respect to fabric evolution. However, high-pressure minerals generated from melts are diagnostic for seismic events in subduction zones. Furthermore, the presence or lack of amygdules, reactivation fabrics and different types of injection veins as well as the composition of the newly formed melts are typical signatures of the paleo-depth. New work on the chemical composition of pst reveals diagnostic heterogeneities. Compositional layering, displayed by chemical segregation, indicates the sequence of previously melted minerals and fluid contents. The new study suggests a pressure-dependant composition and configuration of these layers. The results obtained are intended to serve either as a tool for the depth estimation of paleo-hypocenters of earthquakes generated in different geodynamic environments or the documentation of earthquake-triggered processes, such as large rockslides, occurring near the earth’s surface.

Ultrapotassic Granitoid-Diospsidite-Carbonatite in a post-collisional tectonic setting from Chhotanagpur Gnessic Complex, Eastern India

Ankita Basak1, Bapi Goswami2, Chittaranjan Bhattacharyya3

1Department of Geology, Universty of Calcutta, Kolkata,India, [email protected] 2Department of Geology, Universty of Calcutta, Kolkata,India, [email protected] 3Department of Geology, Universty of Calcutta, Kolkata,India, [email protected]

We report a unique association of ultrapotassic granite-syenite-melasyenite-diopsidite- carbonatite from the Proterozoic Chhotanagpur Gnessic Complex (CGC) of Eastern India. This CGC is considered part of a Grenvillian collision belt between the South and North Indian Blocks. The E-W trending Agarpur granitoid pluton (15km x 2.15km) of the Purulia district, West Bengal, is an elongated sill-like granitoid body intruded along the E-W trending North Purulia Shear Zone (NPSZ). Centimeter to rarely meter-scale clinopyroxenite (diopsidite) and melasyenite veins intruded along E-W trending steeply dipping fracture planes developed within the pluton. Carbonatite (Sövite) also occurs as small meter-scale thick vein intruding the pluton. The Agarpur pluton is composed of alkali-feldspar granite and granite (s.s.) and, quartz-syenite. Their texture varies from homophanous, hypiodiomorphic granular to mylonitic. The minerals are K-feldspar + quartz + albite ± clinopyroxene ± magmatic epidote ± secondary actinolite ± allanite ± sphene ± apatite ± zircon + magnetite. Clinopyroxenite (diopsidite) and melasyenites show cumulate texture and are composed of diopside + K-feldspar + albite + sphene + magnetite. K-feldspars in clinopyroxenites are mostly tabular; however, xenomorphic and resorbed varieties are also present. Megacrystic diopsides may contain calcite grains. Actinolitization of diopside is common. Clinopyroxenite often contain thin veins of coarse crystalline carbonatite. Carbonatite (Sövite) is composed of calcite, phlogopite with minor proportion of tremolite, actinolite, scapolite, zircon, apatite and opaque minerals. Megacrystic calcite grains sporadically occur within medium-grained calcites. Lenticular or triangular grains of dolomite may occur within the megacrystic calcites. The granitoids are ultrapotassic (K2O: 7.58-11.66wt.%), show strong enrichment in LILE relative to HFSE and exhibit negative Ti-Nb- Ta-Zr-Hf anomalies in Primitive Mantle-normalize multi element spider diagram similar to the subduction related magma. By contrast, lack of Eu anomaly and high Sr/Y and (La/Yb)N ratios in many of these samples are similar to adakite-like magma. The associated mafic rocks exhibit relatively restricted SiO2 (43.32-52.72wt.%) and high K2O (0.55-5.14wt.%), Ba, Sr, and Th. These are classified as ‘potassic’ to ‘ultrapotassic’ with a K2O/Na2O ratio reaching up to 4.35. They have moderately high MgO with Mg# values ranging from 62.99-68.86. The mafic rocks show similar and more enriched patterns than the host felsic rocks in multi element spider diagram and also in the Chondrite-normalize REE diagram. The mafic rocks exhibit LREE enrichment with or without Eu anomalies (Eu/Eu*=1.01-0.84). Compared to granitoids (Th: 9- 182ppm, Pb: 28-69ppm), the mafic rocks have higher contents of Th (33-1053ppm) and Pb (18- 103ppm). Carbonatite show very high REE content (∑Re2O3 = 10109.87ppm) and strong fractionation between LREE and HREE (La/Yb = 327.48). They show low Rb (<1ppm), K2O (0.03wt.%), Zr (3.39ppm) and Hf (0.27ppm) contents. Otherwise, they show similar patterns in multi-element spider diagram and REE diagram with those of the granitoids and mafic rocks. Alignment of the granitoid pluton along the NPSZ and its homophanous to mylonitic texture suggest that the magma has been emplaced along the shear zone. Field relations, structural studies and tectonic discrimination diagrams of the granitoids in present study suggest their emplacement in a post-collisional setting. Similar patterns in spider-diagrams and REE- diagrams, and close spatial/temporal association of granitoids, mafic rocks and carbonatite strongly suggest that these have been derived from the same source. Partial melting of a subduction-enriched mantle possibly produced the ultrapotassic silicate melt and immiscible carbonatite. Diopsidite and mela-syenites were formed as cumulates from ultrapotassic silicate magma.

Neotectonics activity near the South Kabylian thrust fault Kabylia region –North Eastern Algeria

Sahra Aourari1, Djamel Machane1

1Algerian Centre of Research Applied for Earthquake Engineering, [email protected]

The structural context of Kabylia region (3.50°- 5.50°E 35.5° - 36.75°N), which is part of the Maghrebides of Algeria, is dominated by regional tectonic fractures parallel to the general trend of its mountains (Djurdjura, Akfadou, Babors). These fractures correspond to the large Miocene E-W overthrusting faults, characterised by conjugate NW-SE, NE-SW faults, and N-S to NNE- SSW faults. The main tectonic limit of Algerian Maghrebides is the abnormal contact separating the internal domain from the external domain. It corresponds to a regional fault system, the Kabylian overthrust fault (FSK). The segment of FSK localized in southern Djurdjura is the Soummam fault. The present study aims to expose neotectonic evidences near the Soummam fault. It is a reverse fault oriented E-W then NE-SW, north-dipping, with a map distance of more than 100 km. Its morphotectonic escarpment overhangs the Soummam valley and is clearly visible from satellite images. Structural indications associated to neotectonic phases, are well marked by folding, reverse faults affecting the Miocene post-nappes, and in some places by fractures affecting the Quaternary deposits. In addition, the uplift of the allochthonous massifs of the North Kabylia domain (Djurdjura, Akfadou) and the seismicity recorded particularly in the South Kabylia domain (Babors), are indications of the recent tectonics.

A kinematic forward model across the Velebit Mountains in the External Dinarides, validated by the structural position of various types of carbonate breccia

Philipp Balling1, Bruno Tomljenović2, Kamil Ustaszewski1

1Institut für Geowissenschaften, FSU Jena, Burgweg 11, 07749 Jena, Germany, [email protected] 2Faculty of Mining, Geology & Petrol. Engineering, University of Zagreb, Pierottijeva 6, Croatia

The Dinarides fold-and-thrust belt on the Balkan Peninsula records the long-lasting history of convergence between the European and the Adriatic plates. The Internal Dinarides are composed of composite ophiolite-bearing nappes, whereas the External Dinarides largely consist of Mesozoic and Paleogene shallow marine Adriatic Carbonate Platform (AdCP) rocks. Due to numerous paleontological studies the chronostratigraphic evolution of the AdCP is well known. However, kinematics, timing, and in some places even the geometry of Cenozoic deformation of the AdCP (i.e. the formation of the External Dinarides) are poorly constrained due to the lack of siliciclastic deposits suitable for dating of deformational events/phases. Consequently, neither exhumation rates nor deformation rates based on low-temperature thermochronology are yet known in this part of the Dinarides. However, the presence of different types of syn-depositional and tectonic breccia, in particular those outcropping over large areas on both sides of the Velebit Mts., could help in constraining the timing of Cenozoic deformational events. For this purpose, besides the definition of age and formation mechanisms of these breccia, their structural position is of crucial importance.

To show the different structural postions we described the different breccia in the field and integrated them into a kinematic forward model of the Velebit Mts, an up to 1800 m high mountain range along the Adriatic coast. The geologically most viable, kinematically forward modelled cross-section is based on geological maps, dip data, four boreholes, an unpublished cross-section and fault kinematic data; the latter revealing that the Velebit structure is controlled by a major NE vergent back thrust. In the northwestern part of the Velebit hinterland, a mostly monomict breccia conformably overlaying Jurassic and Cretaceous carbonates is widely exposed. Based on its structural position that is confined to the footwall of the major NE vergent back thrust and its petrographic characteristics, we interpret this breccia to represent tectonically reworked material mostly derived from lithologies in the footwall of the back-thrust. In contrast, the foreland-facing SW slope of the Velebit Mts. is characterised by the presence of mostly polymict breccia, known as Velebit breccia. Taking its structural position and its petrographic composition into account, this breccia is interpreted as consisting of prevailingly talus and fill-up deposits of a flexural foreland basin that formed during late Paleogene times due to the SW advancing nappe stacking.

Our kinematic forward model suggests that both the cataclastic and the talus breccia must have formed at the same time, because their formation is directly related to shortening and uplift of the Velebit structure. Additionally, we found two types of much older intraformational breccia: Triassic intraformational breccia located in the hanging wall of Triassic normal faults and Cretaceous intraformational breccia, which is not associated to any local structure and hence only reflects pre-contractional emersion phase(s). Our study underlines that a precise distinction of the structural position and the formation mechanisms of seemingly monotonous, but genetically different carbonate breccia with respect to major km-scale faults and fault-related folds, are crucially important to gain an improved understanding of the kinematics and timing of deformation in carbonate-dominated thrust belt portions.

Textures and physical properties of Naxos white marbles

Jan H. Behrmann1, Rebecca Kühn1

1GEOMAR, Marine Geodynamics, Kiel, Germany, [email protected]

In classical times the famous coarse-grained white marbles of Naxos Island (Greece) were extracted in quarries, to serve e.g. as stone for sculptures. At three locations unfinished colossal statues (kouroi) were found. The largest one has 10,5 m height and 80 tons weight (Fig. 1a), found unfinished in a quarry at Apollonas. The five meter long Kouros of Flerio (Fig. 1b) has a more advanced stage of finishing, but is broken at the left knee perpendicular to the long axis. None of the statues show evidence for serious natural defects such as cracks or weathering at the time of working, making it unclear why the workers stopped finishing the statues at the time. This prompted our investigation of texture and elastic properties of marbles from Naxos. Today very similar material with a high reputation for its homogeneity and white colour is quarried in the centre of the island and exported worldwide. For obvious reasons the statues could not be sampled, but a collection of white marbles was used to assess the effects of deformation and metamorphism on microstructure, texture and elastic anisotropy all over Naxos Island.

Fig.1: (a) The Kouros of Apollonas; (b) The Kouros of Flerio. The principal stretching direction of plastic deformation is along the axis of both statues.

The Naxos marbles were syntectionically metamorphosed and recrystallized at peak temperatures between 300°C and well over 700°C. Intense plastic deformation resulted in strong crystallographic preferred orientations (CPO). CPO measurements were performed at the neutron time-of-flight (TOF) texture diffractometer SKAT at the Joint Institute for Nuclear Research, Dubna, Russia. The high penetration capability of neutrons and the large beam cross section allows measurement on large-volume samples (up to 65 cm3) without the need for sample preparation. Rietveld Texture Analysis (RTA) was applied for the CPO calculation using the software MAUD. Finally the CPO was used to model the elastic properties of the samples.Surprisingly CPO does not change much with metamorphic grade and grain size. Strong CPO results in very high elastic anisotropies (Vp anisotropy up to 14.5%). Shear wave anisotropies are about half as high, and there is pronounced shear wave splitting. Vp and Vs anisotropy patterns all show velocity maxima parallel to the mineral/stretching lineation, and minima normal to the foliation. We infer that elastic constants have a high directional variability, inducing elastic stresses in the rocks during processes like tectonic deformation, uplift and removal of overburden by denudation. Because the grain fabric is visually isotropic, such elastic anisotropy may have escaped the attention of the sculptors of the classical Greek period. The Kouros of Flerio was proably broken at the first attempt to move it from the quarry. The Kouros of Apollonas was not evidently moved, but attempts to detach it from its base in the quarry were probably given up after large cracks sub-normal to the long axis (the fast Vp direction) developed in the central part of the statue.

Tectonic imprint on landscape evolution at the Dinarides - Hellenides transition (Southern Montenegro and Northern Albania)

Peter Biermanns1, Benjamin Schmitz2, Kamil Ustaszewski2, Silke Mechernich3, Martin Đaković4, Kristijan Sokol5, Klaus Reicherter1

1Neotectonics and Natural Hazards Group, RWTH Aachen University, Germany, [email protected] 2Institute for Geosciences, Friedrich-Schiller-Universität Jena, Germany 3Institute of Geology and Mineralogy, University of Cologne, Germany 4Geological Survey of Montenegro, Podgorica, Montenegro 5Faculty of Mining and Geology, University of Belgrade, Serbia

The region SW of Shkodër Lake, between Bar (Montenegro) and Lezha (Albania) has proven to be a domain of enhanced seismic activity, hosting frequent moderate as well as occasional strong earthquakes (e.g. Montenegro 1979, Mw = 7.1 or Shkodër 1905, Mw = 6.6). Seismicity generally results from ENE-directed continental subduction of the Adria microplate below Eurasia and is further complicated by the influence of Shkodër-Peja fault zone (SPFZ), marking the transition between Dinarides and Hellenides. The region is characterized by extensive Holocene alluvial plains, only interrupted by NW-SE striking bedrock anticlinal ridges composed of Upper Cretaceous to Tertiary limestones and flysches (Fig. 1). To the N and E, the area is framed by high-relief mountain chains. Landforms within the alluvial plains (e.g. abandoned river channels or beach ridges) as well as observations from shallow drill cores suggest a highly variable landscape history within the past c. 20 kyr, influenced by various factors including sea level fluctuations, alluvial sediment input and tectonic movements. The key role of tectonics is expressed in numerous structures: (i) Large-scale normal fault scarps record movement rates of ~0.5 mm/yr since the LGM and (ii) abandoned river valleys dissect growing anticlinal ridges on top of which they are uplifted to elevations ≤ 325 m above the surrounding plains (Fig. 1). Latter structures therefore represent processes in the 100 kyr scale. Comparison of dry valley elevations on both single and adjacent anticlines enables the recognition of different dry valley formation generations. As valley bottoms of contemporaneously abandoned channels on individual anticlines are now situated at greatly differing elevations, we conclude that (i) timing of nucleation, growth rates and growth modes vary significantly for individual anticlines and (ii) locally constrained simultaneous uplift and subsidence take place in a domain governed by overall contractional tectonics. Enhanced young to recent uplift rates are derived for anticlines in hinterland (NE) as opposed to coastal (SW) positions. While this implies an orogen- perpendicular gradient influenced by mechanisms related to fold-and-thrust belt-propagation, deep erosional levels in combination with young dry valley formation ages in Montenegro (NW) additionally indicate the existence of an orogen-parallel gradient, likely added by SPFZ. Contractional tectonics are proven to act since the onset of Adria-Eurasia collision; local orogen-parallel extensional is by contrast expected to have commenced in relatively recent stages, commonly superimposing young contractionally-controlled structures.

Fig. 1: SRTM-based DEM superposed on shaded-relief map showing the positions of fault scarps and dry valleys on anticlinal ridges. Maximum valley bottom elevation is indicated for individual dry valleys. 26

Travertine occurrences along major neotectonic normal fault zones in the Hammam Debar- Roknia Guelma region ,Nort-East Algeria

Fouad Bouaja1, Ouided laziz2, Chaouki Benabbas3

1Geology and Envirmnment Constantine University Ain Elbey Constantine Algeria; [email protected] [email protected] [email protected]

The tectonic history of Pliocene-Quaternary structures has been documented in the Guelma region from Quaternary travertines and faults relationships. Quaternary travertines deposited from hot springs can reveal much about the neotectonic attributes and histories of structures. The largely developed travertines in the Roknia- Hammam Debar are subdivided into several sequences including the most recent Are observed at the level of the Hammam Debar recent sources. Four facies are observed; the mammal and reed facies in proximal bed, massive and laminated facies in distal bed. In Roknia- Hammam Debar structural studies, field mapping and tectono-stratigraphical considerations on Pliocene and Quaternary units indicate two fault populations: N10° E are associated with Block detachments, collapses and the development of several fibrous calcite generations. These observations prompted us to classify them as probably seismic tectonic structures. N140° E structures already mapped as seismic structures (Maouche et al., 2013) also affect the Roknia travertine.

Key words Roknia- Hammam Debar, Pliocene-Quaternary, travertines, neotectonic

Phase transitions under differential stress: Deviatoric stresses or pressure?

Sebastian Cionoiu1, Lucie Tajcmanova1, Evangelos Moulas2, Holger Stünitz3,4

1ETH Zürich, Department of Earth Sciences, Switzerland, [email protected] 2University of Lausanne, Institut des Sciences de la Terre (ISTE), Switzerland 3University of Tromsø, Department of Geology, Norway 4Université d’Orléans, Institut des Sciences de la Terre d’Orléans (ISTO), France

We performed deformation experiments for the Calcite-Aragonite system in a (Griggs-Type) solid medium deformation apparatus, using different sample geometries. The confining pressure (σ3) was maintained below the Calcite-Aragonite transition while the first principal stress (σ1) exceeded the transition pressure, changing with sample strength. Thus, the bulk sample pressure, P3D = (σ1 + 2*σ3)/3 was closely varying around the transition pressure. Light microscopy, Raman spectroscopy and electron backscatter diffraction (EBSD) show systematic, strongly heterogeneous patterns in the distribution of the phases, grain-sizes and deformation. These result from stress, strain and pressure variations within the sample. To better understand different mechanisms contributing to the phase transition and grain size reduction, the local distribution of first order parameters such as pressure, stress and strain must be known. We performed numerical modelling in order to quantify the stress, pressure and strain distribution within the deforming sample. The numerical results are compared to the stress distribution, as inferred from grain size, and finite strain. These show a good fit with modelling results using a viscous power law rheology. As the distribution of stress and strain in the numerical model matches the experiments, the modelled pressure is expected to depict the experimental conditions as well. Finally, patterns of modelled pressure, stresses and strain are compared to experimentally produced phase-transition patterns. From this comparison the confining stress (σ3) can be excluded as being a driving force for the phase transition. However, the discrimination between local σ1 and local pressure (defined like P3D) still needs better quantification regarding experimental measurements.

Ionian Sea: Image of the crustal structure using seismic data

A. Dannowski1, H. Kopp1, M.-A. Gutscher2, F. Klingelhoefer3, D. Dellong2, A. Krabbenhoeft1, D. Klaeschen1

1GEOMAR Helmholtz Center for Ocean Research Kiel, Wischhofstr. 1-3, 24148 Kiel, Germany, [email protected] 2IUEM, Laboratoire Domaines Océaniques UMR6538, Univ. Brest/ CNRS, Place Nicolas Copernic, 29280 Plouzané, France 3IFREMER, ZI de la Pointe du Diable, CS 10030, 29280 Plouzané, France

The collision between Africa and Eurasia results in a very complex tectonic setting in the Mediterranean. In the area of the Ionian Sea, subduction is still active with a high potential for devastating earthquakes and tsunamis. Knowing the location of faults and the deeper structure of the crust is a prerequisite to estimate the seismogenic hazard. Of special difficulty is the Messinian salt layer, which massively decreases data quality of geophysical imaging methods. Therefore, little is known about the deeper structure and there are ongoing debates among scientists about the nature of the crust. The RV Meteor M111 cruise (10.10.-01.11.2014) targeted the crustal and lithospheric structure of the Calabrian subduction zone and its margins. Along line DY-05, seismic refraction and wide-angle reflection data were acquired using ocean bottom seismometers (OBS) and ocean bottom hydrophones (OBH) in a collaborative project between GEOMAR and IFREMER/Univ. Brest (France). We identified oceanic crust beneath the Ionian abyssal plain that thickens from north to south. Towards the Medina Seamounts, the crustal nature changes from oceanic crust to thinned continental crust.

Assessing the reactivation potential of pre-existing fractures in the southern Karoo, South Africa: Evaluating the potential for sustainable exploration across its Critical Zone

Taufeeq Dhansay1, 2, 3, Payman Navabpour1 , Maarten de Wit2, Kamil Ustaszewski1

1Friedrich Schiller University, Jena, Germany ([email protected]; kamil.u@uni- jena.de) 2Africa Earth Observatory Network-Earth Stewardship Science Research Institute, Nelson Mandela University, Port Elizabeth, South Africa ([email protected]) 3Council for Geoscience, Cape Town, South Africa ([email protected])

Understanding the kinematics of pre-existing fractures under the present-day stress field is an indispensable prerequisite for hydraulically increasing fracture-induced rock permeability, i.e. through hydraulic stimulation, which forms the basis of economically viable exploitation of resources such as natural gas and geothermal energy. Predicting the likelihood of reactivating pre-existing fractures in a target reservoir at particular fluid injection pressures requires detailed knowledge of the orientations and magnitudes of the prevailing stresses as well as pore fluid pressures. In the absence of actual in-situ stress measurements, e.g. derived from boreholes, as is mostly the case in previously underexplored “frontier areas”, such predictions are often difficult. In this study, the potential of reactivating pre-existing fractures in a likely exploration region of the southern Karoo of South Africa is investigated. The orientations of the present-day in-situ stresses were assessed from surrounding earthquake focal mechanisms, implying c. NW-SE oriented maximum horizontal stress and a stress regime changing between strike-slip and normal faulting. A comparison with paleo-stress axes derived from inverted fault-slip data suggests that the stress field very likely did not experience any significant reorientation since Cretaceous times. Maximum possible in-situ stress magnitudes are estimated by assuming that these are limited by frictional strength on pre-existing planes and subsequently, slip and dilation tendency calculations were performed, assuming hydrostatic pore fluid pressures of c. 32 MPa at targeted reservoir depth. The results suggest that prevalent E-W and NW-SE oriented sub-vertical fractures are likely to be reactivated at wellhead pressures exceeding hydrostatic pore fluid pressures by as little as 2–5 MPa, while less prevalent sub-horizontal and moderately inclined fractures require higher wellhead pressures that are still technically feasible. Importantly, actual in-situ stress measurements are essential to test these theoretical considerations and to guide the design of safe and effective exploration linked to fracture manipulation, such as shale gas recovery.

How the geo-boundary conditions control the continental crust’s exhumation: three examples from the Lower Units (Alpine Corsica, France)

Maria Di Rosa1,2, Chiara Frassi2, Francesca Meneghini2, Michele Marroni2,3, Luca Pandolfi2,3

1Dipartimento di Scienze della Terra, Università di Firenze, Firenze (Italia), [email protected] 2Dipartimento di Scienze della Terra, Università di Pisa, Pisa (Italia) 3Istituto di Geoscienze e Georisorse, IGG-CNR, Pisa (Italia)

The Lower Units (Alpine Corsica, France) are a stack of tectonic units that represents the portion of the European plate margin involved in the continental subduction since the Late Eocene time (Molli, 2008). The tectono-metamorphic study of several of these units pointed out a clear linkage between their positions in the tectonic stack and the P-T conditions reached during their subduction/exhumation paths. Although the deformation history shows common features in all the Lower Units, several differences in their metamorphism have been observed, in particular for the P-T values related to the baric and thermic peaks. The comparison between several sectors indicates that these variations are common in all the areas of the Alpine Corsica. These variations seems to be connected with the tectonic position in the stack of the Lower Units, i.e. if the Lower Units are in contact with the Variscan Corsica (i.e. the European plate not involved in the Alpine orogeny), with the Schistes Lustrés Complex (i.e. the oceanic and continental units buried at the deepest level during the Alpine orogeny) or with the Upper Units (i.e. the tectonic units belonging to the Alpine Corsica affected by a weak deformation and metamorphism). The structural analysis on the units surrounding the Lower Units becomes therefore crucial, in order to understand how and how much the Variscan Corsica and the Schistes Lustrés Complex interacted with the Lower Units during their subduction and subsequent exhumation. Following this goal, we have studied three areas in which the Lower Units interplay with the Variscan Corsica, the Schistes Lustrés and the Upper Units, in order to provide the structural and tectono-metamorphic data needed to constrain the behaviour of the continental crust in three different geological settings. The Cima Pedani area, where three units of the Lower Units group occur in a tectonic window under the Schistes Lustrés Complex and the Upper Units, provides the opportunity to study the relationships between the different units of the Alpine Corsica. Also in the Corte area three tectonic units belonging to the Lower Units have been recognized. Among them, the westernmost one directly overthrust the Variscan Corsica whereas the other Lower Units are characterized along their boundaries by thin slices of the Schistes Lustrés Complex (Di Rosa et al., 2017). In the Ghisoni area, the Lower Units are instead represented by a single unit that is interposed between the Variscan Corsica and the Schistes Lustrés Complex.

References Di Rosa, M., De Giorgi, A., Marroni, M., & Pandolfi, L. (2017). Geology of the area between Golo and Tavignano Valleys (Central Corsica): a snapshot of the continental metamorphic units of Alpine Corsica. J. of Maps, 13/2: 644-653. Molli, G. (2008). Northern Apennine-Corsica orogenic system: an updated overview. In: Siegesmund, S.; Fugenshuh, B.; Froitzheim, N. (eds) Tectonic aspects of the Alpine-Dinaride-Carpathian System. Geol. Soc. Spec. Publ., 298: 413-442, London.

The tectonic half-window of Cima Pedani (Alpine Corsica, France): an example of exhumed continental crust in collisional belt

Maria Di Rosa1,2, Francesca Meneghini2, Michele Marroni2,3, Luca Pandolfi2,3

The Cima Pedani half-window (Central Corsica, France) can be regarded as a key-area to reconstruct the tectonic history of the Alpine Corsica. In this area, not wider than 12 km2, the mutual relationships between the oceanic and continental units that characterize the tectonic setting of the Alpine Corsica are well preserved. These units are, from the bottom to the top, the Lower Units, the Schistes Lustrés Complex and the Upper Units. The Lower Units have a continental affinity and represent the portion of the European margin deformed and metamorphosed during the Alpine orogeny (Malasoma et al., 2006). Three units (Canavaggia, Pedani and Scoltola Units), similar in the lithostratigraphy and in the deformation history, have been distinguished on the base of the metamorphic conditions reached during their exhumation paths. The Schistes Lustrés Complex represents the stack of units of both continental and oceanic affinity that were subducted at the deepest levels during the closure of the Ligure-Piemontese basin. In the Cima Pedani area the Schistes Lustrés Complex is represented by the Lento Unit, a fragment of oceanic lithosphere deformed under blueschist facies metamoprhic conditions (Levi et al., 2007). The Upper Units consist of both continental and oceanic units, all characterized by a very weak deformation and metamoprhism. In the area two units of oceanic affinity crop out: the Serra- Debbione and the Pineto Units, both represented by an ophiolite sequence. The Serra- Debbione Unit is located to the north of the Cima Pedani half window and is separated the Lower Units by a normal fault. In turn, the Pineto Unit, located west of Cima Pedani half window, is separated from the Lower Units by the Central Corsica Shear Zone, a sinistral strike-slip fault active during the Late Eocene-Early Oligocene time span (Lacombe and Jolivet, 2005). The meso- and micro-structural analysis coupled with the reconstruction of the P-T-d paths of Canavaggia, Pedani and Scoltola Units allowed to reconstruct the tectono-metamorphic history of the Lower Units in the Late Eocene-Early Miocene, thus providing useful constraints for their coupling with the Schistes Lustrés and the Upper Units.

References Lacombe O., & Jolivet, L. (2005). Structural and kinematic relationships between Corsica and the Pyrenees-Provence domain at the time of the Pyrenean orogeny. Tectonics, 24: TC1003. Levi, N., Malasoma, A., Marroni, M., Pandolfi L., & Paperini M. (2007). Tectono-metamorphic history of the ophiolitic Lento unit (northern Corsica): evidences for the complexity of accretion-exhumation processes in a fossil subduction system. Geod. Acta, 20/1: 99-118. Malasoma, A., Marroni, M., Musumeci, G., & Pandolfi, L. (2006). High-pressure mineral assemblage in granitic rocks from continental units, Alpine Corsica, France. Geological Journal, 41: 49-59.

A strength profile through the Upper Crust of the Franconian Basin

Carlo Dietl1, Hansjörg Baumgartner1, Eberhard Jahns1, Marion Kämmlein2, Michel Bestmann2, Helga de Wall2

1Gesteinslabor Dr. Eberhard Jahns, Heiligenstadt, Germany, [email protected] 2GeoZentrum Nordbayern, FAU Erlangen-Nürnberg, Germany, [email protected]

Our study is aimed to construct a strength profile through the Upper Crust of the Franconian Basin. We assume a slightly simplified crustal model consisting from top to bottom of (1) a clastic sedimentary cover (0 – 1200 m); (2) a metasedimentary pile (1200 – 7000 m) underlain by (3) a granitic basement (Fig. 1). Concerning the depth and thickness of the individual crustal layers we refer to stratigraphic data from several deep wells in the Franconian Basin. Our data base stems from triaxial testing and Mohr-Coulomb analyses of the above described lithologies. The clastic sedimentary cover is represented by an Upper Permian sandstone from the scientific well Obernsees (UPS in Fig. 1), the metamorphic basement is typified by a Saxothuringian metasandstone from the Obernsees well (SMS) and an “average granite” (AG) – calculated from six different granites from the Bavarian forest – stands for the granitic basement. Both peak and residual strength data were retrieved. Based on the obtained strength data we were 0 Sedimentary UPS peak able to calculate both peak and residual UPS residual 1 cover crustal strength for the different crustal SMS peak compartments. Fig 1 shows the increase of SMS residual 2 strength with depth and in particular for the AG peak lower, granitic part a significant strength AG residual 3 PSC reduction when applying residual, post-failure Metamorphic RSC data. 4 basement The observed strength curve is almost logarithmic for these quartzofeldspathic rocks 5 and in addition to mineralogical differences the variation in rock fabrics needs to be 6

depth [km] considered as first order influencing parameter: The UPS is solidified by 7 diagenesis and has the weakest cohesion Granitic between the rounded and relatively small 8 basement quartz and feldspar grains, which constitute its stratified fabric. The SMS has a very fine 9 grained, anisotropic (bedding plus schistosity) crystalline fabric dominated by quartz. The 10 investigated granites (represented by the average granite AG) have a coarse grained, 11 isotropic fabric formed mainly by quartz, 0 500 1000 1500 2000 250 plagioclase and potassium feldspar. strength [MPa] Consequently, we propose to have not only Fig. 1: Crustal strength profile based on the mineralogical composition, but also the rock presented triaxial data (PSC: peak strength fabric in mind, when talking about rock curve; RSC: residual strength curve) strength in general and about strength profiles in particular.

Tectono-stratigraphy of the Cretaceous shelf (Constantinois Platform - NE Algeria)

Rami Djeffal1, Mohammed Chadi2, El Hadj Youcef Brahim3

1Geologic sciences department Constantine 1 University, [email protected] 2Management of urban technics department Constantine 3 University, [email protected] 3Department of Geology, Université of Batna 2, [email protected]

The synthesis of stratigraphic and structural data of Constantinois limestone massifs has allowed the refining of the southern Tellian series at nummilites stratigraphy and proposing a structural model. The most significant sites and less disturbed by tectonics, are the Taxas syncline and southern flank of Guerioun massif, exactly at the Djebel Ras Rihane.

Also, at the level of Taxas syncline, and surmounting the hard ground which ended the Aptian neritic limestone, the marly levels had provided Cenomanian microfauna: Favusella washitensis, Rotalipora appenninica, R. cushmani, R. brotzeni, Hedbergella sp., and Praeglobotruncana stephani. On the southern reverse of Djebel Ras Rihane, at the level of Chaabet Ras Chiboub notch, we can observe, on the hard ground that terminates the Aptian nerititic limestones, a clayey Cenomonian over one hundred meters of thickness. The samples from these clays have provided many Hedbergella, Rotalipora brotzeni, R. cushmani, R. globotruncanoides and Praeglobotruncana gr. Stephani. The top of these clays has provided Coniacian foraminifera and revamped Cenomanian rotalipora. The study of the stratigraphic series of s neritic massifs allowed the refining of our predecessor’s results. Also the yellow marls stratigraphically surmounting the terminal Aptian- basal Albian through a hard ground, represents the Cenomanian-Turonian. Microscopic analysis of samples from this hard ground highlights sedimentological phenomena that attest the emersion of Constantinois platform during the terminal Aptian- basal Albian. In the Constantinois limestone massifs, ‘’the southern Tellian units at Nummilites ‘’ represent the normal marly cover of neritic limestones.

Keywords: Constantinois limestone massifs, Albo-Aptian, Southern Tellian units, Eastern Algeria.

Faults in the Franconian Basin: A Hydraulic Basement-Cover Connection?

1 1,2 1 1 1 Ines Donhauser *, Carlo Dietl , Alfons Baier , Johannes A.C. Barth , Helga de Wall

1GeoZentrum Nordbayern, Friedrich-Alexander-Universität Erlangen – Nürnberg, Schlossgarten 5, D-91054 Erlangen. 2Gesteinslabor Dr. Eberhard Jahns, Hospitalstraße 13, D-37308 Heiligenstadt. *[email protected]

A complex lineament pattern in the Franconian Basin, NE Bavaria, is revealed by DEM-based analysis (1 m resolution). Main trends are compatible with (i) Variscan (NE-SW) and (ii) Late Variscan (NW-SE) structures. The compilation also includes N-S and E-W trending lineaments. Major fault systems are investigated in terms of their extent, significance and a possible hydraulic basement-cover connection with structural and hydrogeochemical methods. A field record of structural elements in selected quarries (Fig. 1A) underlines the polyphase tectonic history of the Franconian Basin and highlights the importance of a N-S fault system in addition to Variscan (NE-SW) and Late Variscan (NW-SE) trends. At many places normal faults also obvious as boundary faults of the NW-SE trending Staffelstein Graben (Upper Triassic to Upper Jurassic; von Freyberg, 1969) are reactivated as dextral strike slip faults (σ1 directed NW-SE). Subvertical N-S faults show mainly sinistral displacement. Considering the direction of maximum horizontal stress in the Franconian Basin (126-138°, Heidbach et al., 2016), N-S faults with sinistral displacement along with dextral reactivation of NW-SE directed fault structures may form a conjugate fault system. Previous hydrogeochemical studies reveal a very divers composition of groundwaters in the Franconian Basin (Udluft, 1979, Bauer, 2000). Water samples of both basement and basin 13 areas (this study) indicate recharge by precipitation. δ C and pCO2 data (Fig. 1B) point to local hydraulic connection from basement to sedimentary aquifers at intersection of conjugated faults.

Fig. 1: A) Sets of normal and strike slip faults in subhorizontal Jurassic strata. B) Results of δ13C analysis compared to the partial pressure of CO2 (pCO2). Measurement error lies within the size of symbols.

References Bauer, W. (2000). Geothermische Verhältnisse im Fränkischen Becken, Hydrogeologie und Umwelt, 22, 1–186. Heidbach, O., Rajabi, M., Reiter, K., & Ziegler, M. (2016). World Stress Map Database Release 2016, GFZ German Research Center for Geosciences, Potsdam. Udluft, P. (1979). Das Grundwasser Frankens und angrenzender Gebiete, Steir. Beitr. Hydrogeol., 31, 5– 128. von Freyberg, B. (1969). Tektonische Karte der Fränkischen Alb und ihrer Umgebung, Erlanger geol. Abh., 77, 1–81.

Tectonic impact on sediment routing systems of evolving rift basins: A case study from the Cenozoic Kerimbas Graben, offshore northern Mozambique

1 1 1 2 Andreas Eberts , Dirk Kaufmann , Harald Stollhofen , Dieter Franke

1GeoZentrum Nordbayern, Friedrich-Alexander-Universität (FAU) Erlangen-Nürnberg, Erlangen, Germany, [email protected] 2Bundesanstalt für Geowissenschaften und Rohstoffe (BGR), Hannover, Germany

Knowledge of the submarine channel architecture and of related tectonosedimentary processes is crucial to assess sediment influx and to locate potential hydrocarbon reservoirs. Such systems are highly sensitive to changes of seabed topography, often strongly linked to tectonic uplift, faulting and seismicity. To reveal the impact of tectonic activity on channel pathways, we carried out a morphotectonic analysis of the Kerimbas Graben, an active rift basin situated in the Mozambique Channel. This area is highly influenced by the Cenozoic to recent tectonic evolution of the East African Rift System. Three high-quality geophysical datasets including high-resolution bathymetric, multichannel reflection seismic and Parasound data were acquired during two cruises of the research vessel SONNE in early 2014. By combining these datasets, we were able to map the lateral and vertical extent of topographic features such as fault scarps and channel incisions, and to interpret them in terms of their relation to tectonic activity. Our results show that the study area is divided into two distinct parts, comprising differences in both morphotectonic characteristics and in the evolution of channel pathways. The northern part, occupied by the Kerimbas Graben, shows N-S trending fault scarps the most pronounced of which are associated with the eastern and western border faults of the rift basin. Farther south, an area of “diffuse extension” is accompanied by horst-and-graben structures, acting as right- stepping transfer zones for the southward impinging eastern border fault. The observed spatial variations are also represented by differences in fault throw, revealing that fault scarps in the southern part of the study area show significantly lower vertical offsets. By assuming a roughly coherent age of the corresponding faults this suggests higher uplift rates in the Kerimbas Graben area, which in turn would imply differences in the impact of tectonics on sediment routing systems along strike of the rift. Concerning this, two basic types of interactions in the downstream parts of submarine channel systems can be inferred: (1) a complete blocking of the channel pathway (Fig. 1a) occurred in areas where the rate of rift shoulder uplift exceeded the rate of channel incision. Uplifted channel remnants on the eastern rift flank of the Kerimbas Graben are indicative for this process. Since they were formed at least during the Late Miocene, they confirm Cenozoic tectonics to be responsible for the formation of the rift basin; (2) In contrast, active incision into the rift shoulder occurred in areas where the uplift rate of the shoulder is substantially lower than the downward erosion of the channel system (Fig. 1b). This is most likely the case for the southern part of the study area where a channel has incised deeply into the eastern rift shoulder. Based on these results, we established an evolutionary model for the interaction of tectonic activity and sediment routing systems of the Kerimbas Graben and adjacent southern areas, ranging from the Late Miocene to recent times.

Fig. 1: Linked depositional and tectonic evolution of the study area. a. In the Kerimbas Graben, channels were blocked during uplift along the eastern border fault, resulting in channel remnants on the graben shoulder. b. In the southern part, downward erosion of channel systems was sufficiently large to compensate uplift, leading to deeply incised valleys. 36

The mapping and structural analysis of a shear zone in Ödsmålsmosse, South Sweden

Sumaya Effendi1

1Martin-Luther-Universität Halle-Wittenberg, FG: Petrologie und Lagerstättenforschung, Halle (Saale), Deutschland, [email protected]

The following thesis is about a shear zone located near the village Ödsmålsmosse north of the city Göteborg in S Sweden. With an extent of 0,5 km² the area is situated on the Idefjorden terrain which is principally made up of volcanic, plutonic and metasedimentary units approximately 1660 – 1520 Ma ago. These sequences are in some locations interrupted by amphibolites and ultramafites. All these rocks were metamorphized during the Sveconorwegian orogenesis ranging from granulite-facies to amphibolite-facies (Bingen et al., 2008). Occuring rocks in the mapped area are metagranodiorite, metasediment, pegmatite and amphibolite. A feature of the shear zone are the mylonites which could be found in some places. The mylonite horizon shows individual characteristics such as a very dark colour and a fine-grained fabric, that in some cases also displays an almost glazed complexion. The horizon could be found between a metagranodiorite and pegmatite above and a metasediment underneath. During the field work it could be noticed that shearing and rate of migmatisation increased in direction of the shear zone. This thesis contains a detailed mapping of the shear zone with orientated sampling following the microscopical analysis of the rocks as thin sections. By collecting the outcomes of the mapping and the microscopical analysis, these results should help create a 3-D model of the subsurface. Therefore, an orthogonal grid of cross sections will be laid upon the area of the shear zone and will be correlated afterwards.

References Bingen, B., Øystein, N., & Viola, G. (2008). A four-phase model for the Sveconorwegian orogeny, SW Scandinavia. Norwegian Journal of Geology 88, 43-72. Trondheim.

Deformation bands in sedimentary basins: their role in depth-temperature-time determinations and regional structural analysis

László Fodor1,2, Barbara Beke1, Szőcs Emese1, Attila Petrik2, Kinga Hips1

1MTA-ELTE Geological, Geophysical and Space Science Research Group, Eötvös Univ., Budapest, Hungary, [email protected] 2MTA-ELTE Volcanological Research Group, Eötvös Univ., Budapest, Hungary, [email protected]

Deformation bands (DB) are strain localization structures which play an important role in sedimentary basins dominated by clastic sediment infill. They are widespread in such rocks and should be present in all basins. They are similar but distinct with respect of faults, particularly in their deformation mechanism. Instead of frictional sliding characteristic for faults, deformation bands are formed by grain rotation, grain boundary sliding, and, during later steps of their evolution, by cataclasis. The DBs could form only in relatively unconsolidated material, thus they provide information on early structural evolution, prior to formation of “true” faults. In this presentation we would like to take attention to these structures, which may be used in analysis of the upper part of sedimentary basins. Within the northern Pannonian basin where we studied formations having been formed just before, during and after the main rifting phase. With a combined methodology, one can determine depth (pressure) – temperature – time conditions of these structural elements; the result is similar to traditional pT path used for metmarophic rocks. The frame of the ‘time factor’ is coming from regional structural analysis, mostly from fault-slip analysis. Then we used subsidence analysis, based on available thickness and stratigraphic data. In next step, we can calibrate the burial depth of the sample during a given deformation phase by crossing the subsidence curve of the host rock with the age interval of the fracturing phase; this gives us the depth (z, pressure) axis. We combined subsidence analysis with thermal modelling using knowledge on heat flow history. Thermal modelling can thus predict temperature for a given deformation phase and for a given time span. We moved even more: this temperature estimates were cross-checked with information coming from structural diagenesis. We checked autigenic diagenetic minerals in the host rock and also in the DBs. Autigenic albite during DB formation could constraint formation temperature of 60-65°C, while autigenic quartz post-dating DB formation formed near the temperature of ~ 80°C. Crossing these temperature data with subsidence and thermal modelling we could establish of time and depth when DBs terminate to form, ca 650-1200m, at the late stage of syn-rift phase. One side of the application of DBs is the refining the brittle structural evolution of the host sediments. The basic concept is that deformation bands show clear variation in type (mechanism) depending on the burial of the host rock; the deformation is pressure-dependent in a semi-quantitative way. In this manner, formation mechanism of DBs gives us relative chronology of brittle structures. In this was we were able to give much more detail in structural evolution of the study area with respect to evolution deduced only from fault-slip analysis (Petrik et al., 2014, 2016). As an example, for pre-rift deformation phase, we could demonstrate 3 events instead of one, deduced earlier only from faults. Finally, DBs play role in fluid flow analysis. DBs can promote fluid flow along the structure in their early evolutionary step, play barrier against flow during later steps, and, finally, when changed to faults, can again guide fluid motions along the evolved late brittle structure. This research is supported by OTKA grant No. 113 013.

References Petrik, A., Beke, B., & Fodor, L. (2014). Combined analysis of faults and deformation bands reveals the Cenozoic structural evolution of the southern Bükk foreland (Hungary). Tectonophysics 633, 43–62. Petrik, A., Beke, B., Fodor, L., & Lukács, R. (2016). Cenozoic structural evolution of the southwestern Bükk Mts. and the southern part of the Darnó Deformation Belt (NE Hungary). Geologica Carpathica, 67/1, 83–104.

The discontinuous Lower Cretaceous of NE Germany: Late Cimmerian Unconformity or Early Cretaceous pre-inversion?

Sandra Franke1, Matthias Franz1

1Geowissenschaftliches Zentrum der Universität Göttingen, Abteilung Angewandte Geologie, Göttingen, Germany

The Late Cimmerian Unconformity (LCU) and Late Cretaceous inversion are key elements in the late Mesozoic evolution of the North German Basin (NGB, Ziegler 1990). In the eastern NGB, erosional unconformities within the Lower Cretaceous succession witness noticeable synsedimentary tectonics between the two major phases of intraplate tectonics. As a result of Early Cretaceous tectonics, narrow isolated grabens formed at the Darß and the islands of Rügen and Usedom. The grabens comprise up to 450 m thick Lower Cretaceous successions contrasting with the only few metres thick Lower Cretaceous successions next to the grabens. A detailed study of seismic and well data gives insights into repeated phases of subsidence and graben formation alternating with phases of uplift and erosion of Lower Cretaceous strata in NE Germany. (1) Successions of Berriasian (Wealden-type), Hauterivian, Barremian and Aptian strata are only present in the grabens. (2) The analysis of depositional environments points to former wide-spread covers of Lower Cretaceous strata in NE Germany. (3) Biostratigraphic data and variable sedimentary thicknesses within the Lower Cretaceous succession suggest Berriasian- early Valanginian, late Hauterivian, late Aptian and late Albian phases of subsidence and graben formation. (4) Disconformities within the Lower Cretaceous succession suggest late Valanginian-early Hauterivian, early Aptian and early Albian phases of uplift and erosion. (5) Outside grabens more than 400 m of Berriasian to Aptian strata were eroded. (6) The widespread occurrence and balanced thickness of Cenomanian strata mark the cessation of Early Cretaceous tectonics in NE Germany. (7) The Early Cretaceous tectonics represent either descendant phases of the LCU or ascendant phases of the Late Cretaceous inversion and therefore are considered Early Cretaceous pre-inversion.

Figure 1: Two-Way-Traveltime-interpreted seismic profile of the western Darß-graben. BUC: Base Upper Cretaceous; BLJ: Base Lower Jurassic; TM: Top Muschelkalk; BLT: Base Lower Triassic.

References Ziegler, P. (1990). Geological Atlas of Western and Central Europe, Band 1, Shell Internationale Petroleum, p 239.

Mapping and structural geological study of a shear zone at southern Sweden, Göteborg

Anna Friebel1, Denny Droesler1, Nicolas Meyer1

1Martin-Luther-Universität Halle-Wittenberg, Institut für Geowissenschaften und Geographie, Germany, [email protected]

The geological setting in SW Sweden is strongly influenced by the Sveconorwegian orogeny (1.1- 0.9 Ga). During this deformational event the Idefjorden Terrain was aggregated onto the Baltic Shield and large crustal units have been sheared on Baltica and stacked on each other. These crustal units consists mainly of meta-sediments (ca. 1.67 Ga), which have been intruded by several magmatic suites (ca. 1.5-0.9 Ga) of felsic to ultramafic composition (Ahäll & Conelly 2008). The investigation area is situated on the island Tjörn (SW Sweden), where a complex shear zone was mapped. The shear zone is well visible at the road between Aröd and Stockevik, where the zone is several hundred meters exposed and consists of several slices of sediments, ultramafic to felsic igneous rocks. These rocks are highly overprinted by metamorphism and affected by boudinage and displacement as a result of the orogeny. Finally this process these units are staked on each other. The shape of the slices north of the outcrop suggests that the main shearing was followed by another compressional event or oblique shearing. Tectonic data show that there are different directions of foliation in the surrounding metasediments, which could cause by several deformation events. However, another focal point of our field works to distinguish between different lithologies, which are present in the shear zone. It occur gneiss units of two generations with nearly equal ages, mineralogy and mainly the same rock fabric. Microscopical observations show that they are cogenetic. This study aims to model the deformation history of this area by tectonic data collected during field work and cross sections. Furthermore the different lithologies are analysed microscopically with special focus on shear sense indicators as well as mineral and stretching lineation. Moreover the grade of the metamorphism was determined to reconstruct the p-T-conditions during this deformation.

References Ahäll, K.-I. & Conelly, J. N. (2008). Long-term convergence along SW Fennoscandia: 330 m.y. of Proterozoic crustal growth, Precambrian Research 163: 402-421.

The adventure of applying LA-ICP-MS U-Pb zircon dating to igneous and meta- igneous rocks from Afghanistan

Sonja Frölich1

1TU Bergakademie Freiberg, Institut für Geologie, Germany, [email protected]

The western flank of the Pamir with its Paleozoic-Mesozoic sutures and Cenozoic tectonic reactivation crops out in the geologically nearly unexplored northern Afghanistan. I present the first modern geochronological study on igneous and meta-igneous rocks from an E-W traverse through the province of Badakhshan, using a combination of LA-ICP-MS U-Pb zircon and 40Ar/39Ar mica dating. The new ages were also used to evaluate Rb-Sr ages (Desio, 1975) out of the 1970s, and stratigraphically determined ages. Foremost, I aimed to understand the geological subdivision of northern Afghanistan in terms of subduction-accretion and arc formation processes and the Cenozoic tectonic overprint. On a stony path – with lead loss and common lead problems – I dated very interesting rocks. A pegmatitic orthogneiss from the westernmost Shakhdara gneiss dome, one of the largest Cenozoic metamorphic core complexes on Earth, yielded a protholith crystallization at 1809 Ma and a lead loss event, interpreted as migmatization, at 12.2 Ma. I double-dated two 66.6 Ma and 69.5 Ma orthogneisses (U-Pb ages) from the Shiwa lake that gave cooling ages at 16.6 Ma and 13.4 Ma (40Ar/39Ar), respectively. A 323 Ma tonalite, a 220 Ma pegmatitic orthogneiss, a 32.5 Ma granite, and a 22.2 Ma pegmatite crop out arround Fayzabad city. The pegmatite shows – typical for many pegmatoids in the Tajik Pamir – a high common lead disturbance. My results allow a first correlation with the more extensively dated rocks in the Tajik Pamir; they also show that the former Rb-Sr dating provide, on the first order, meaningful data. Given the complexity of the rocks, I applied heating at 850°C for 72 h on half of each sample’s zircons to anneal partly metamict zones of the crystals. I did not detect any difference in the ages and uncertainties between heated and unheated aliquots, as it was expected (Allen & Campbell, 2012). However, I observed a decrease in the isotope 204Pb through the heating procedure in six out of seven samples (e.g., Fig. 1) – probably caused by lead evaporation. I show that the isobaric isotope 204Hg has a minor influence for the comparison between heated and unheated zircons.

Fig. 1: Density distribution functions of the mass spectrometer’s 204Pb isotope channel [CPS] for the heated and unheated aliquot of zircons from granite 13912D1, showing a decrease of common lead by heating.

References Allen, C. M., & Campbell, I. H. (2012). Identification and elimination of a matrix-induced systematic error in LA–ICP–MS 206Pb/238U dating of zircon. Chemical Geology 332-333, pp. 157–165. Desio, A. (1975). Geology of Central Badakhshan (North-East Afghanistan) and Surrounding Countries. Italian expeditions to the Karakorum (K2) and Hindu Kush. 3rd Volume: Istituto di Geologia, Università di Milano (Italy) (III. Geology - Petrology).

Architecture and structural evolution of the Jasmund Glacitectonic Complex (Rügen, NE Germany)

Anna Gehrmann1, Martin Meschede1, Heiko Hüneke1, Karsten Obst2, Stig A. Schack Pedersen3

1Ernst-Moritz-Arndt-Universität Greifswald, Institut für Geographie und Geologie, Friedrich- Ludwig-Jahn-Straße 17a, D-17487 Greifswald ([email protected]) 2Geologischer Dienst, LUNG M-V, Goldberger Str. 12, D-18273 Güstrow 3Geological Survey of Denmark and Greenland (GEUS), Øster Voldgade 10, DK-1350 Copenhagen

Glacitectonic deformation in the Upper Weichselian caused the tectonic framework of large- scale folds and displaced thrust sheets of Maastrichtian (Late Cretaceous) chalk and Pleistocene glacial deposits in the southwestern Baltic Sea area. A wide spectrum of methods has been compiled integrating digital elevation models (DEM), cross sections and field observations to unravel the structural evolution of the Jasmund Glacitectonic Complex (divided in a northern and southern structural sub-complex). Geological cross sections from the eastern coast (southern sub-complex) are constructed and restored using the software Move™ and the complementary module 2D Kinematic Modelling™. The final constructions show a small-scale fold and thrust belt. It includes three different orders of architectural surfaces (cf. Pedersen, 2014): erosional surfaces and detachment faults (1st order), thrust faults (2nd order), and hanging-wall anticlines as well as footwall synclines (3rd order). Thrust faults inclined towards the south indicate a local glacier push from the S/SE. A comparison of these structures with sandbox models from e.g. Dixon & Liu (1992) allows for the conclusion that the pressure induced a spatial and temporal transition from detachment folds in the south (proximal) over fault propagation folds to fault bend folds in the middle and north (distal). Furthermore, the tectonic framework of the southern sub-complex can point to certain environmental conditions like pore-water pressure, stress development or influence of permafrost. Supplementary landform analyses indicate the influence of the structures on the morphology of Jasmund. They provide an insight into the relationship between the northern and southern structural sub-complex and the chronology of their formation. A combination of all these information is our opportunity to come up with a more self-consistent genetic model for the entire Jasmund Glacitectonic Complex.

References Dixon, J. M., & Liu, S. (1992). Centrifuge modelling of the propagation of thrust faults. In: McClay, K. R. (Ed.): Thrust Tectonics. Chapman & Hall, London: 53-70. Pedersen, S.A.S. (2014). Architecture of Glaciotectonic Complexes. Geosciences, 4: 269-296.

The imprint of Weichselian glacitectonism on the recent morphology of Jasmund (Rügen Island, NE Germany)

Anna Gehrmann1, Martin Meschede1, Heiko Hüneke1, Karsten Obst2, Chris Harding3

1Ernst-Moritz-Arndt-Universität Greifswald, Institut für Geographie und Geologie, Friedrich- Ludwig-Jahn-Straße 17a, D-17487 Greifswald ([email protected]) 2Geologischer Dienst, LUNG M-V, Goldberger Str. 12, D-18273 Güstrow 3Iowa State University, Department of Geological and Atmospheric Sciences, Ames, IA 50011, USA

Glacitectonic deformation in the Upper Weichselian led to the tectonic framework of large-scale folds and displaced thrust sheets of Maastrichtian (Late Cretaceous) chalk and Pleistocene glacial deposits in the southwestern Baltic Sea region. The involved processes formed the characteristic morphology of today’s Jasmund Peninsula, which can be detected in digital elevation models (DEM). The Jasmund Glacitectonic Complex represents a small-scale fold and thrust belt including transitions from detachment folds over fault propagation folds to fault bend folds with hangingwall anticlines and footwall synclines. Those structures have a surface expression in form of sub-parallel ridges and elongated valleys in between. DEM analyses suggest a division into two structural sub-complexes – a northern part with morphological ridges striking NW–SE and a southern part with SW–NE trending ridges. Geomorphological mapping and detailed landform analyses provide an insight into the chronology of sub-complex formation and help to find a consistent terminology for the tectonic setting of Jasmund. The northern part of the glacitectonic complex is suggested to have been generated before the southern one, considering the partly truncated northerly ridges and their superimposition by the southern sub-complex. Furthermore, the term push moraine used for Jasmund in many papers, is no longer recommended. Based on our results and taking into consideration modern classifications of glacitectonic complexes (cf. Aber & Ber, 2007) the morphological ridges are better described as composite ridges. Although there is a high number of scientific publications on the glacitectonic evolution of Jasmund, the presented models often lack a consistent theory for the development integrating all parts of the 100 km2 large complex. Therefore, the landform investigations together with structural analyses provide an opportunity to come up with a more self-consistent genetic model for the entire Jasmund Glacitectonic Complex.

References Aber, J. S. & Ber, A. (2007): Chapter 5 Composite ridges – In: Aber, J. S. & Ber, A. (Eds.): Glacitectonism. Developments in Quaternary Science 6: 59-82; Amsterdam (Elsevier).

Two plate tectonics enigmas: initiation of new subduction zones and ridge- transform spreading patterns

T. Gerya1

1Institute of Geophysics, ETH-Zurich, Sonneggstraße 12, 8092 Zurich, Switzerland [email protected]

Global networks of subduction zones and ridge-transform spreading patterns represent inherent features of terrestrial plate tectonics. A fundamental unresolved problem is how these networks formed and why they are maintained. Although most of the presently active intra-oceanic subduction zones are relatively young and initiated during the Cenozoic, subduction initiation process remains enigmatic and controversial. One significant problem is that quantitative models of subduction initiation often had to assume excessive weakening of tectonic plate boundaries that does not reconcile with laboratory rock strength measurements. In order to resolve this long-standing problem, we investigated incipient spontaneously initiating intra-oceanic subduction by exploring new numerical hydro- thermo-mechanical (HTM) approach, in which solid rock deformation and fluid percolation are fully coupled (Dymkova & Gerya, 2013). Based on 2-D numerical experiments, we demonstrate that subduction can naturally start in the presence of porous fluid inside oceanic crust and pre- existing fracture zones. During subduction initiation, fluid percolation is localized along a system of multiple listric propagating thrusts with coalescing nearly horizontal roots located near the oceanic Moho of the forming subducting slab. These coalescing roots form future subduction interface, which decouples upper and lower plates. High pressure of aqueous fluid flow, which spontaneously focuses along this interface, compensates lithostatic pressure, thus dramatically decreasing friction between the plates. Similar fluid- and melt-induced weakening mechanisms could be responsible for the onset of plate tectonics on the Archean Earth with predominantly mafic, oceanic-like crust, which was disrupted by plume-induced subduction initiation (Gerya et al., 2015). Similarly, initiation of orthogonal ridge-transform spreading patterns remains poorly understood and contentious. Our work employs high-resolution 3D thermomechanical numerical models of the incipient oceanic spreading to investigate nucleation and long-term evolution of ridge-transform spreading patterns (Gerya, 2010, 2013). This model allows for large strains and accounts for plate cooling by both heat conduction and hydrothermal circulation as well as for partial melting of the asthenosphere and oceanic crust growth by magmatic accretion. According to the numerical experiments, ridge-transform spreading patterns form spontaneously by a dynamical instability caused by an asymmetric plate accretion (Gerya, 2010). In case of oceanic or continental plate breakup, orthogonal ridge-transform oceanic spreading patterns forms gradually and become fully established several million years after the plate breakup. Moreover, it is demonstrated on the basis of simple analyses that the ridge-transform system is a long-term plate growth pattern that is generally different from an initial plate rifting pattern. Geometry of the ridge-transform system is governed by geometrical requirements (180° rotational symmetry for open space occupation) for simultaneous accretion and displacement of new plate material within two offset spreading canters connected by a sustaining rheologically weak transform fault. According to these requirements, the characteristic spreading-parallel orientation of oceanic transform faults is the only thermo-mechanically consistent steady state orientation.

References Dymkova, D., & Gerya, T. (2013). Porous fluid flow enables oceanic subduction initiation on Earth. Geophysical Research Letters, 40(21), 5671-5676. Gerya, T. (2010). Dynamical instability produces transform faults at mid-ocean ridges. Science, 329(5995), 1047-1050. Gerya, T. V. (2013). Three-dimensional thermomechanical modeling of oceanic spreading initiation and evolution. Physics of the Earth and Planetary Interiors, 214, 35-52. Gerya, T. V., Stern, R. J., Baes, M., Sobolev, S. V., & Whattam, S. A. (2015). Plate tectonics on the Earth triggered by plume-induced subduction initiation. Nature, 527(7577), 221.

Footwall exhumation along the Shkoder-Peja Normal Fault vs. regional uplift and erosional denudation (Dinarides-Hellenides junction)

Jörg Giese*1,Marc Grund1, Sascha Zertani1, Mark R. Handy1, Stefan M. Schmid2, Jan Pleuger1, Kujtim Onuzi3

1Freie Universität Berlin, Department of Earth Sciences, Berlin, Germany; joerg.giese@fu- berlin.de 2ETH-Zürich, Institute of Geophysics, Zürich, Switzerland 3Polytechnic University of Tirana, Institute of GeoSciences, Tiranë, Albania

The orogen-perpendicular Shkoder-Peja Transverse Zone defines the structural boundary between the Dinarides and Hellenides and an associated normal fault called Shkoder-Peja Normal Fault (SPNF) is believed to accomodate clockwise rotation of its hanging wall around a nearly vertical rotation axis close to the city of Shkoder in northern Albania (Handy et al., this volume). The exact timing of faulting remain poorly constrained; until now, Mid-Miocene clastic sediments in the fault-bounded western Kosovo basin (Elezaj, 2009) provide the best constraint on the onset of extension (Handy et al., 2017 and this volume). Here, we present apatite fission- track (AFT) data from 8 samples along two profiles across the SPNF close to Shkoder (northern Albania) and Peja (Kosovo), and another sample from within the distant footwall of the SPNF in order to better constrain the timing and differential throw along the SPNF. All samples from both foot- and hanging walls of the SPNF were (partially) annealed and yield apparent AFT ages between 57 ± 17 Ma and 21 ± 6 Ma, thus predating the assumed Mid-Miocene onset of normal faulting. The apparent AFT ages of eight samples close to the fault overlap within 1s uncertainty and feature comparable single-grain age distributions that show (1) large spreads in single grain ages, and (2) a significant number of single grain ages in the range between 25 and 10 Ma. We interpret the Early- to Mid-Miocene single-grain age range to date cooling below the lower limit of the partial annealing zone (PAZ) of 60° for apatite and the apparent AFT ages to represent mixed ages containing an inherited component of earlier cooling. This is puzzling in light of microstructures from calc-mylonites from the central part of the SPNF indicating syn- deformational temperatures in excess of 200°C. Such temperatures would completely erase any inherited signal in the AFT data from the footwall. A way out of this dilemma is to recall that the AFT data from the footwall of the Peja section are from the East Bosnian Durmitor unit, which is structurally higher than the calc-mylonite from the High Karst unit. Samples from the footwall of the Shkoder section come from the Krasta-Cukali nappe, an even lower structural unit. Another issue arises from similar AFT data in the hanging- and footwalls of the SPNF, which suggest contemporaneous cooling (within the precision of the method) on both sides of the normal fault rather than enhanced cooling only in the footwall due to its exhumation. However, normal faulting in the Peja profile is distributed within a system of several smaller branches striking parallel to the SPNF (Goris et al., this volume). In any case, these similar ages indicate that regional uplift and erosional denudation – possibly starting prior to extensional tectonics along the SPNF – played a major role in the low-temperature crustal evolution of this region, possibly masking the thermal effect of normal faulting along the SPNF.

References: Elezaj, Z. (2009). Cenozoic molasses basins in Kosovo and their geodynamic evolution. Muzeul Olteniei Craiova. Oltenia. Studii şi Comunicări. Ştiinţele Naturii. Craiova, v. 25, p. 343-350. Goris, D., Grund, M., Giese, J., Handy, M.R., & Onuz, K. (2018). The Shkoder-Peja Normal Fault system and its relation to the Kosovo basin. This volume. Handy, M.R., Giese, J., & Schmid, S.M. (2017). Slab rollback and Neogene deformation at the Dinarides- Hellenides junction. 13th Workshop on Alpine Geological Studies, Sept. 2017. Zlatibor Mts., Serbia. Handy, M.R., Giese, J., Onuzi, K., Pleuger, J., Schmid, S.M., Spakman, W., & Ustaszewski, K. (2018). Transfer and rotational normal faulting at the Dinarides-Hellenides junction – their relation to tearing and retreat of the Adriatic slab. This volume.

The Shkoder- Peja Normal Fault system and its relation to the Kosovo basin

Daniel Goris1, Marc Grund*1, Jörg Giese1, Mark Handy1 and Kujtim Onuzi2

1 Freie Universität Berlin, Department of Earth Sciences, Berlin, Germany 2 Polytechnic University of Tirana, Institute of GeoSciences, Tiranë, Albania

The Peja basin forms the northwestern part of the western Kosovo basin (also named Dukagjini depression or Metohia basin). The Peja basin measures ~50 km in N-S and ~25 km in E-W directions and its surface lies at an average altitude of ~600 to 300 m asl. To the East, it is limited by units of the West Vardar Ophiolite (WVO) exposed at the surface as isolated inselbergs in the Drenica area. To the West and to the North, the Peja basin is delimited by the imbricated East Bosnian Durmitor (EBD) and the WVO units (Elezaj & Kodra, 2012). The Middle Miocene to Upper Pliocene basin fill overlies the WVO and has a thickness of up to 1000 m (Elezaj & Kodra, 2012). The basal clastic sediments of Middle Miocene age are deposited above an erosional surface (Elezaj & Kodra, 2012) and are considered to mark the onset of normal faulting along the Shkoder-Peja Normal Fault (SPNF; Handy et al. 2017) flanking the basin to the West and to the North. Detailed geological mapping near the Kosovar city of Peja at the western limit of the Peja basin reveals that Middle Miocene clastics unconformably overlie both the mélange of the WVO, the EBD and the SPNF in between. The SPNF, however, displaces this unconformity north of Peja, also indicating post-Mid-Miocene extensional tectonics. Furthermore, the surface of the Middle Miocene succession exposed along the northwesternmost edge of the basin is lies at an altitude up to 200 m higher than the average basin surface. We tentatively attribute this to drag in the hanging wall of the SPNF. All basin units show terraces and river incision, suggesting that the Peja basin was uplifted and/ or the base level of erosion lowered during post-Middle Miocene time. Unfortunately, the Miocene deposits are only locally exposed and in most areas are covered by younger sediments, thus obscuring the relationship between normal faulting and Miocene sedimentation. The part of the SPNF defining the contact between the EBD and WVO cannot account for the entire extension related to the formation of the western Kosovo basin; extension is also accommodated within the ophiolitic mélange where we observe triangular, flat-iron like facets marking a prominent fault scarp directly at the western boundary of the basin. This raises the possibility that the normal faulting associated with the SPNF is accommodated by a system of normal faults that propagated from the footwall into the hanging wall.

References Elezaj, Z., & Kodra, A. (2012). Geology of Kosova. Prishtine: Shtypshkronja "Printing Press"- Prishtine. Handy, M.R., Giese, J., & Schmid, S.M. (2017). Slab rollback and Neogene deformation at the Dinarides- Hellenides junction. 13th Workshop on Alpine Geological Studies, Sept. 2017. Zlatibor Mts., Serbia.

The structural and metamorphic record of subduction, exhumation and collision in the Penninic nappes of the central Tauern Window, Eastern Alps

Philip Groß1, Jan Pleuger1, Mark Handy1, Timm John1

1Freie Universität Berlin, Germany, [email protected]

We investigate an internally ordered subduction channel and its evolution with the aim of improving the interpretation of geophysical images of subduction channels. Subduction channels are usually believed to lack internal structure, with blocks of oceanic crust tectonically mixed in a low viscosity matrix of metasediments, altered mafics and serpentinized ultramafics (e.g. Franciscan mélange). However, other channels display an internal structure comprising a large-scale layering. These are particularly interesting, because their continuous layering can be potentially imaged with geophysical methods (e.g. receiver functions), thus enhancing our view of subduction processes in active channels. The central Tauern Window in the Eastern Alps provides a well-exposed example of such a structured subduction channel, with relics of the Alpine Tethyan ocean isoclinally folded and sandwiched between the Adriatic upper and European lower plates. Cross-sections across this fossil subduction channel based on newly compiled maps, as well as own structural analysis and thermobarometry reveal that a km-scale sheath fold formed during subduction and exhumation in the Tauern subduction channel. The sheath fold affects oceanic units from the Alpine Tethys as well as a very thin, distal unit of the European continental margin. The front of the sheath fold is deformed by 100m amplitude, tight upright folds that trend perpendicularly to the sheath fold axial plane and that coincide in both location and orientation with structures affecting exhumed continental basement units. We interpret these later folds to have formed during Alpine collision, possibly at the front of a duplex roof thrust that separates subduction structures, including the sheath fold, in its hangingwall from collisional structures in its footwall. The formation of the sheath fold in the central Tauern Window coincided with consistent top- foreland thrust kinematics and syn-deformational decompression from peak metamorphic conditions (ca. 20 kbar at 500°C; for T-estimates see Langner et al., this volume), rendering it a typical example of a sheath fold formed by amplification of initially slightly curved fold axes in homogeneous simple shear (e.g. Cobbold & Quinquis, 1980). Models of fold nappe (Escher & Beaumont, 1997) and sheath fold (Alsop & Holdsworth, 2012) formation show that these structures can exhume a rock body relative to its surroundings in an overall convergent setting, if exhumation is accommodated by concurrent thrusting and normal faulting at the base and top of the body, respectively. However, a suitable top-hinterland normal fault that could be invoked to exhume the sheath fold and its HP assemblages has not been found in the field so far. Regardless of the exhumation dilemma, we argue that sheath and nappe folding could be a widespread process in subduction channels that generates crustal-scale layering and therefore could be imaged by high-resolution geophysical methods in active subduction zones. Synthetic seismograms of such geometries may provide new insights in the interpretation of seismically imaged anomalous structures at the top of downgoing slabs. We propose that similar structures may be found at the top of the down-going slab beneath the Eastern Alps as currently targeted by the dense seismological station array (Swath D) of AlpArray.

References Alsop, G., & Holdsworth, R. (2012). The three dimensional shape and localisation of deformation within multilayer sheath folds. J. of Struct. Geol., 44: 110-128 Cobbold, P., & Quinquis, H. (1980). Development of sheath folds in shear regimes. J. of Struct. Geol., 2: 119-126 Escher, A., & Beaumont, C. (1997). Formation, burial and exhumation of basement nappes at crustal scale: a geometric model based on the Western Swiss-Italian Alps. J. of Struct. Geol., 19: 955-974

Measuring the slip-rate of the Main Kopeh Dagh Fault, Turkmenistan

Christoph Grützner1, Yevgeney Bezmenov2, Geldy Begenjev2, Stacy Carolin3, James Jackson4, Robert Mirzin2, Edward Rhodes5,Maksim Sadykov2, Richard Walker3

1Friedrich Schiller University Jena, Institute for Geological Sciences, Burgweg 11, 07749 Jena, Germany, [email protected] 2Institute of Seismology, Academy of Sciences, Turkmenistan 3Dept. of Earth Sciences, Oxford University, UK 4Dept. of Earth Sciences, Cambridge University, UK 5Dept. of Geography, Sheffield University, UK

The relative motion between the South Caspian Basin (SCB) and its surroundings is accommodated by left-lateral fault systems in Iran, and the right-lateral Main Kopeh Dagh Fault (MKDF, aka Ashgabat Fault) in Turkmenistan. Determining the rates of slip on these faults is key for understanding the motion of the SCB. However, several different tectonic models exist due to the uncertainties in the existing data. Here, we present the findings from fieldwork in Turkmenistan with the aims of (i) Providing estimates of the long-term slip-rate on the Main Kopeh Dagh Fault, (ii) Providing estimates of its past earthquake activity, and (iii) Better understanding the seismic hazard to the city of Ashgabat which is home to ~1 million people. We show surface evidence for a large magnitude earthquake that is not known in the historical record and we report offset geomorphic markers that will allow estimation of slip rates. We concentrated on five sites to the NW of Sünce, about 150 km away from Ashgabat. Judging from the geomorphology, this region is characterised by slip partitioning: (i) A NW-SE trending strike-slip fault offsets linear and planar markers such as terraces and streams, and (ii) A thrust fault with the same strike shows vertical offsets in the youngest alluvial deposits a few kilometres further to the NE. We analysed satellite imagery of the strike-slip fault to identify suitable targets for long-term slip rate estimates. Streams incised into alluvial fans of various ages record right-lateral offsets of up to 750 m. In order to date the abandonment of the surfaces, we excavated pits up to 2 m deep into the alluvial fans and sampled fine-grained material for OSL/IRSL burial dating. All samples are currently being processed, but first results from the lab indicate a terrace abandonment around 100 kyrs ago. This would give a slip rate of ~7.5 mm/yr, which fits with estimates based on GPS and InSAR. Along the thrust fault that parallels the strike-slip fault we found river terraces with up to 10 m vertical offset. We measured the vertical separation of the surfaces with differential GPS (DGPS). The terrace units include mainly coarse fluvial gravels, but also show fine-grained bands near the surface. These silty-sandy layers were sampled for OSL/IRSL dating, which is underway, and shall allow us to determine a vertical slip rate for this part of the fault. In order to better understand the seismic hazard of the MKDF, as characterised by earthquake recurrence intervals, magnitudes, mechanisms, and slip per event, it is necessary to extend the earthquake catalogue by means of paleoseismic trenching. We identified a paleo-surface rupture along the strike-slip fault with more than 5 m horizontal offset that probably occurred in a single, large event. In most places we also observed a dip-slip component of the rupture that formed an uphill-facing scarp. The surface rupture can be traced for several tens of kilometres and may correspond to an earthquake of M~7.5 based on scaling relationships between offset/length and earthquake magnitude. Hand-dug trenches were excavated across the fault where sediment had ponded against uphill-facing scarps. The 1-1.5 m deep trenches revealed fine-grained sediment (fine sands and silt) juxtaposed with coarser material that was surrounded by a sandy-silty matrix. Our interpretation is that a surface-rupturing earthquake offset the coarse alluvial fan material vertically and horizontally. Fine-grained sediment then ponded against the scarp and filled the accommodation space. We sampled the fine-grained material for OSL/IRSL dating, which is currently underway.

The geomorphological imprint of active faulting in NW Slovenia and NE Italy – first results from field studies and high-resolution topography data

Christoph Grützner1

1Friedrich Schiller University Jena, Institute for Geological Sciences, Burgweg 11, 07749 Jena, Germany, [email protected]

The eastern Southern Alps-Dinarides region is subjected to the strongest crustal motion in the entire Alps. It marks the transition from head-on thrusting on E-W thrust faults in Italy to right- lateral strike-slip faulting on NW-SE striking structures mainly in Slovenia (Fig. 1). In the framework of SPP 2017 ‘Mountain building processes in 4D’ we started the project ‘Earth surface response to Quaternary faulting and shallow crustal structure in the eastern Adria- Alpine collision zone and the Friulian plain. A consortium of geologists, geophysicists, and geochemists will investigate the geometry of major active faults, their sense of motion, and how they drive erosion using a set of interdisciplinary tools: a) high-resolution digital elevation models from airborne LiDAR surveys, stereo satellite data, and drones; b) near-surface geophysical surveys to image surface traces and the sub-surface structure of active faults; c) palaeoseismological trenching to determine long-term slip rates, earthquake recurrence intervals, and palaeo-magnitudes; d) the erosional response to active faulting using catchment- wide erosion rates from in situ cosmogenic 10Be in river sediment. Here I report results from the first field work campaign and remote sensing studies. I document landscape features that indicate Holocene tectonic activity along some of the main faults, such as offset slopes, displaced alluvial fans, and deformed river terraces. These sites will be subject to geophysical investigations in spring 2018 to check their suitability for later trenching studies.

Fig. 1: Our working area in the Alps-Dinarides transition zone. Here the style of faulting changes from head on thrusting on E-W striking faults in Italy to right-lateral strike slip and transpression on NW-SE striking faults in Slovenia. Main faults of interest (black lines) are labelled.

Geological map (1:10 000) of the Shkoder-Peja Normal Fault in its central segment near Bajram Curri (northern Albania) – evidence for distributed normal faulting and extension

1 1 1 2 Marc Grund* , Jörg Giese , Mark Handy , Kujtim Onuzi

1Freie Universität Berlin, Department of Earth Sciences, Berlin, Germany, [email protected] 2Polytechnic University of Tirana, Institute of GeoSciences, Tiranë, Albania

The Shkoder-Peja Normal Fault (SPNF) is a NE-SW striking, orogen-perpendicular structure along the boundary between the Dinarides and the Hellenides. Geological cross sections across the SPNF in the vicinity of the Neogene Bajram Curri basin in northern Albania constrain the vertical offset to be 2-7 km. The fault segments locally change strike from NE-SW to N-S and E- W. Along all segments, the Western Vardar Ophiolitic unit in the hanging wall, the highest nappe of the Dinaric nappe-stack, is downthrown relative to the structurally lower Dinaric units (High-Karst unit in the northeast, Krasta-Cukali unit to the northwest). From SW to NE, the SPNF excises progressively higher stratigraphic units in its footwall; however, most displacement is accommodated within a broad zone of Cretaceous flyschoid argillaceous shale in the footwall and variegated rocks (shales, phyllite, quartzite, amphibole gneiss, serpentinite) of the Jurassic ophiolitic mélange forming the base of the Western Vardar unit in the hanging wall. Normal faulting in the footwall is best documented, where limestones of the High-Karst unit show ~35-45° SE-dipping fault planes that truncate the bedding at high angles. Slickensides, striations and tension joints indicate slightly oblique normal motion. At the northeastern limit of the mapped area, subhorizontal bedding of Triassic limestone in the footwall is progressively dragged towards the SPNF; the fault plane itself is marked by calc-mylonite derived from the footwall indicating syn-tectonic temperatures of at least 200°C and is transitional to an ophiolitic fault breccia in the hanging wall (Giese et al., this volume). Further south along strike, this mylonitic fabrics has not been found so far, and normal faulting in the limestone is purely cataclastic. Large-scale upright Dinaric folds in the Krasta-Cukali unit (footwall) are truncated discordantly by normal faulting of the SPNF. Pleistocene deposits of the Plio-Pleistocene Tropoja basin south of the SPNF seal the fault contact between foot- and hanging walls; river terraces at the entrance of the Valbona valley are undisturbed and thus appear to post-date displacement on the SPNF. Furthermore, the SPNF itself appears to be openly folded in one place by NW-SE trending folds at the contact between High Karst and ophiolitic mélange; an observation that, however, needs to be verified by further investigation. Unambiguously, another set of similarly oriented NW-SE trending minor normal and/or strike-slip faults offset the SPNF in several places, thus clearly indicating a post-SPNF phase of deformation. The significance of these younger faults is ambiguous at this writing, but may be related to ongoing orogen-parallel extension in the area as indicated by available GPS data (Jouanne et al., 2012).

References Giese, J., Grund, M., Zertani, S., Handy, M., Schmid, S.M., Pleuger, J., & Onuzi, K. (2018). Footwall exhumation along the Shkoder-Peja Normal Fault vs. regional uplift and erosional denudation at the Dinarides-Hellenides junction. This volume. Jouanne, F., Mugnier, J.L., Koci, R., Bushati, S., Matev, K., Kuka, N., Shinko, I,, Kociu, S., & Duni, L. (2012). GPS constraints on current tectonics of Albania. Tectonophysics, v. 554–557, p. 50-62, doi: 10.1016/j.tecto.2012.06.008.

Plate kinematic consequences of double in-line subduction in Anatolia

Derya Gürer1, Douwe J.J. van Hinsbergen1, Claudio Faccenna2

1Department of Earth Sciences, University of Utrecht, Utrecht, The Netherlands, [email protected] 2Laboratory of Experimental Tectonics, Department of Sciences, Università degli Studi Roma Tre, Rome, Italy

The onset and arrest of double subduction in which two plates are subducting synchronously along two subduction zones with similar polarity have been attributed to major accelerations and decelerations in plate convergence. Such a setting characterizes the modern Philippine Sea Plate surrounded by the Izu-Bonin-Mariana and Ryukyu trenches. Such geometry has also been invoked to explain major India-Asia convergence rate fluctuations in the past. Neotethyan ophiolites found throughout the Anatolian orogen, on Cyprus, and on northern Arabia are relicts of the oceanic ‘Anadolu’ plate that intervened a double subduction setting. Geological data were previously interpreted to show that the northern trench was stationary and active from Early Jurassic to Paleogene time, whereas the southern trench was mobile (retreating/advancing) and active from the Late Cretaceous to at least Neogene time. Here, we reconstruct the kinematic evolution of the double subduction zone to assess the influence of the onset, evolution and demise of the simultaneous activity of two in-line subduction zones on plate motions. We find that the arrest of double subduction around 70 Ma along the eastern 50% of the plate boundary correlates with a sharp decrease in convergence rate of 1.5-4 cm/yr, whereas arrest of double subduction in the remaining 10-20% of the plate boundary in Anatolia, in two steps at ~60 and ~25 Ma, does not correlate with major plate convergence fluctuations. Effects of initiation of double subduction around 100 Ma cannot be correlated to convergence rate fluctuations in absence of magnetic anomalies between ~125 and 83 Ma. We conclude that double subduction evolution in Anatolia may have influenced Africa-Europe convergence rates by several cm/yr, and may have contributed to the counterclockwise rotation of Africa/Arabia relative to Eurasia. Furthermore, the variation in the style of subduction (stationary vs. mobile) had a first-order effect on the geometry and rates of subduction in the upper mantle, as well as on magmatism and the first-order geological architecture of the Anatolian orogen.

Reconstructing oceans lost: the fate of the eastern Mediterranean Paleo- and Neotethys

Derya Gürer1, Douwe J.J. van Hinsbergen1, Wim Spakman1,2

1Department of Earth Sciences, University of Utrecht, Utrecht, The Netherlands, [email protected] 2Centre of Earth Evolution and Dynamics (CEED), University of Oslo, Norway

The geological record of the eastern Mediterranean region holds record of the subsequent closure of the Paleotethyan and Neotethyan oceanic realm and microcontinents therein due to subduction since the Triassic. Kinematic restorations suggest that at least four subduction zones were responsible for this consumption, two consuming the Paleotethys, and two consuming the Neotethys. The latter co-existed in Cretaceous to Paleogene time bounding and consuming an oceanic plate – termed Anadolu, of which remnants are found thrust into the Anatolian orogen. Reconstructing subduction evolution in Anatolia using a variety of field-based tools (structural geology, sedimentology, stratigraphy, isotope geochemistry, paleomagnetism) and integrating these observations in a kinematic model, reveals that the subduction zones bounding the Anadolu Plate evolved into segments each with their own dynamic history. We present a kinematic reconstruction of Anatolian subduction zones back to the Early Triassic, which is integrated into the global plate circuit using GPlates reconstruction software. We use the resulting kinematic plate model to interpret the upper and lower mantle structure underlying the Eastern Mediterranean, and unravel the remnants of Paleotethys and Neotethys ocean lithospheres lost to subduction since the Triassic. We show that the net sinking rate of these remnants results from the geodynamic history of their upper mantle subduction, whereby slabs subducted at stationary trenches (Pontide slab) sank much faster than those that rolled back (Herodotus, Egypt slab) or advanced (Cyprus slab).

Using quartz microstructures and textures to characterize exhumation channel shear zones in the Erzgebirge, N-Bohemian Massif

Peter Hallas1, Uwe Kroner1

1TU Bergakademie Freiberg, Institut für Geologie, B. v. Cotta Straße 2, 09596 Freiberg, Germany, [email protected]

Mid-crustal exhumation channels of former intracontinental subduction zones can be observed in collisional orogens as exemplified by a well exposed shear zone sequence in the Erzgebirge (N-Bohemian Massif). Here, the extrusion of deeply subducted continental material into a pre- existing medium to high grade metamorphic nappe pile can be observed (Willner et al., 2002, this study). Isothermal decompression of the channel rocks caused advective heat transfer into the wall rocks characterized by heating-decompression. The retrograde paths of the (ultra) high and medium-pressure units coincide at PT conditions at 12-14 kbar and 600-700 °C. Kinematic indicators reveal a top to WNW overthrusting of the channel rocks onto the medium pressure gneiss complex in the foot wall and a top to ESE underthrusting in the roof shear zone indicating a general WNW exhumation direction. Progressive grain size reduction towards the shear zones indicates strain concentration towards the channel boundaries. Despite the well constrained general features of the exhumation channel the development of the quartz fabric in the particular zones is under discussion. Here we present results from detailed studies of quartz texture analyses by time-of-flight neutron diffraction (ToF) and electron backscatter diffraction (EBSD) measurements. The combination of both methods allows the characterization of the global quartz textures as well as the investigation texture forming processes at micro-scale. Quartz crystallographic preferred orientation (CPO) can be distinguished into two characteristic endmembers. In central parts of the upper and lower shear zone suite [0001] pole figures exhibit small girdle distributions around z or x (strain coordinates of the shear zone) and point to a {10-11}, i.e. the positive rhombs maxima in z (group 1). In contrast, the channel center as well as the foot and hanging wall of the channel, i.e. the peripheral parts of the shear zone suites are characterized by a pronounced point [0001] maxima in y (group 2) and a higher texture strength. Moreover, microstructural observations and EBSD analyses point to a higher SGR than GBM recrystallization with the dominant misorientation axes <0-110> and <11-21> in group 1. Additionally, a low intergranular misorientation density, calculated over the grain kernel average misorientation (gKAM, Kilian and Heilbronner, 2017) is recognized in this group. Whereas, group 2 is dominated by GBM recrystallization, a high gKAM and the misorientation axes <0001>. In conclusion, the textural differences of group I and II can be explained by the interplay of GBM and SGR recrystallization and the involved crystallographic misorientation axes.

References Kilian, R., and Heilbronner, R., 2017, Analysis of crystallographic preferred orientations of experimentally deformed Black Hills Quartzite: Solid Earth, v. 8, no. 5, p. 1095. Willner, A., Sebazungu, E., Gerya, T., Maresch, W., and Krohe, A., 2002, Numerical modelling of PT- paths related to rapid exhumation of high-pressure rocks from the crustal root in the Variscan Erzgebirge Dome (Saxony/Germany): Journal of Geodynamics, v. 33, no. 3, p. 281-314.

The exhumation channel of the Erzgebirge: constraints from microtectonics and PT estimations

Peter Hallas1, Uwe Kroner1

1TU Bergakademie Freiberg, Institut für Geologie, B. v. Cotta Straße 2, 09596 Freiberg, Germany, [email protected]

The rapid extrusion of ultra-high pressure metamorphic rocks into a pre-existing nappe stack, i.e. the over- and underthrusting of medium to high pressure units is a striking feature of the western Erzgebirge. Because of complex deformation, the tectonic accretion, the subduction and the exhumation mechanism as well as their directions are a matter of discussion. Here we present results from detailed studies along two profiles crossing the boundary and shear zones of the ultra-high pressure units. Field work and microscopic observation reveal that the entire zone is characterized by a subhorizontal main foliation partly overprinting pre-existing steeper inclined fabrics. The complex particle path in the shear zone is indicated by a large scatter of the x axis of the finite strain ellipsoid. In the medium to high pressure units an initially NE-SW oriented stretching lineation is obliterated by a second elongation with WNW-ESE azimuth. In contrast, the ultra-high pressure units preserve a WSW-ENE oriented stretching lineation. The results show opposite shear directions, i.e. the top-to-W directed shear sense at the footwall and the top-to-E shearing at the hanging wall shear zone. PT conditions were estimated using electron microprobe analyses on the mineral assemblage of garnet, plagioclase, muscovite and biotite. Medium to high pressure paragneisses show a temperature increase during decompression. In contrast, the ultra-high pressure units were affected by isothermal to slightly cooling and decompression. The retrograde paths of the ultra- high and medium to high pressure units coincide at the PT conditions at 12-14 kbar and 600- 700 °C. We postulate a two-step model for the tectonic accumulation of continental crust and the emplacement of deeply subducted ultra-high pressure rocks. First, NE-SW directed plate convergence (D1) resulted in nappe stacking during continent-continent collision. The final emplacement (D2) of the deeply buried continental crust occurred in a transpressional regime with horizontal σ1 (NNW-SSE) and σ3 stress axes. West directed lateral escape of isothermally exhumed high pressure units lead to the formation of an exhumation channel, while the coincide of the PT conditions at 12-14 kbars and 600-700°C is interpreted as the juxtaposition of the UHP and MP-HP units and therefore as the starting point of shear zone formation. Additionally, retrograde heating of the medium to high pressure units and the opposite shear directions along the boundary shear zones, imply an uplift of the ultra-high pressure units within an exhumation channel.

Transfer and rotational normal faulting at the Dinarides-Hellenides junction - their relation to tearing and retreat of the Adriatic slab

Mark R. Handy1, Joerg Giese1, Kujtim Onuzi2, Jan Pleuger1, Stefan M. Schmid3, Wim Spakman4, 5, Kamil Ustaszewski6

1Inst. f. Geol. Wissenschaften, FU-Berlin, Germany, [email protected] 2Inst. Gjeoshkencave, Energjise,Ujit dhe Mjedisit, Tirana, Albania, [email protected] 3Inst. f. Geophysik, ETH-Zürich, Switzerland, [email protected] 4Inst. of Earth Sciences, Utrecht Univ., the Netherlands, [email protected] 5Center of Earth Evolution and Dynamics (CEED), University of Oslo 6Inst. f. Geol. Wissenschaften, Univ. Jena, Germany, [email protected]

The Dinarides-Hellenides junction along the Adria-Europe plate boundary in northern Albania, Montenegro and Kosovo is marked by the Skhoder-Peja Transverse Zone (SPTZ) that coincides with an orogen-parallel change in the structure and Mesozoic stratigraphy of nappes derived from the down-going Adriatic plate. Across the SPTZ, the depth of the tip of the Adriatic lithospheric slab abruptly increases along strike, from <150 km N of the SPTZ, to > 150 km just to the S, and finally, to several hundreds of km S of the Kefalonia fault. The SPTZ accommodated initially pre-Miocene motion associated with dextral offset of the West Vardar (Mirdite) ophiolite nappe front by ~80 km in map view. In Miocene time, shortening N of the SPTZ was <10 km as indicated by offshore thrusts offsetting Miocene strata, whereas S of the SPTZ shortening is ~100 km which is based on the orogen-normal distance between Ionian nappe units along the orogenic front and in the Peshkopie Window of NE Albania. Miocene-to-Recent thrusting along this part of the orogenic front reactivated Paleogene thrusts and folds formed during the main phase of Adria-Europe convergence, and affected Mio- Pliocene clastic sediments of the Periadriatic foredeep in central and northern Albania.

Orogen-parallel normal faulting along a SE-dipping normal fault, the Skhoder-Peja Normal Fault (SPNF) within the SPTZ, began no later than mid-Miocene time (15 Ma) as dated by basal clastics of the Kosovo-Metohia Basin (discussions in Giese et al., Grund et al., Goris et al., this volume). A throw of ~7 km of the SPNF along the basin margin is estimated from vertical offset of the base of the West Vardar nappe projected in a cross section of the SPNF at the Albanian- Kosovo border. From there, the throw decreases to the SW along strike of the SPNF to zero near the city of Shkoder. Thus, we interpret the SPNF as a rotational extensional fault that accommodated SE-downthrow and ~10° clockwise motion of its hanging wall about a vertical rotation axis at Shkoder. Extension and block rotation of the hangingwall of the SPNF are linked kinematically to Mio-Pliocene out-of-sequence thrusting and folding along the orogenic front S of the SPNF. This thrusting is in turn connected with the offshore orogenic front in central and southern Albania via dextral transfer zones. Faulting along this mid-Miocene system continues today, as documented by offset Holocene strata, earthquake focal mechanisms and GPS motion vectors. Miocene and younger extension is focused S and E of the SPNF, where there is widespread evidence of episodic uplift and river incision during Plio-Pleistocene time (Simon et al., this volume).

We propose that the geodynamic driver of tectonics since the mid-Miocene is the enhanced rollback of the Hellenic slab in the aftermath of slab breakoff beneath the Dinarides, which focused slab pull toward the south. Downward pull and retreat of the Hellenic slab segment induced clockwise bending of the Dinarides-Hellenides orogen, which localized along the SPNF and related faults in mid-Miocene time. Accelerated SW-directed rollback and arcuation of the Hellenic slab segment in Mio-Pliocene time was associated with greater upper-plate extension and uplift S and E of the SPNF. The SPNF is therefore part of a system of Neogene-Recent faults that accommodate expansion of the Hellenic arc above and behind the SW-retreating Adriatic slab.

Rheological switches and strain distribution during the exhumation of granitoid continental crust

Marco Herwegh1, Alfons Berger1, Philip Wehrens1,2, Roland Baumberger1,2, Nibourel Lukas1, Daniel Egli1

1Institut für Geologie, Universität Bern, Switzerland, [email protected] 2Federal Office of Topography, Swiss Geological Survey, Switzerland

Volumetrically, quartzofeldspatic rocks dominate the continental crust. Given the high abundance of quartz, it is this mineral which is often considered to be rheology controlling. For that reason, many geodynamic models rely on quartz rheology to express the general deformation behavior of the granitoid crust. Based on new findings from the exhumed crystalline Aar massif (Central Alps, Switzerland; Herwegh et al., 2017), we are able to document strain localization and associated deformation processes in the granitoid crust ranging from depths of ~20 kilometers up to the surface (Wehrens et al., 2016; 2017). Already at depth (650 MPa, 450°C), strain is localized in high strain shear zones, which enclose lenses of moderately deformed host rocks (= background strain). The importance of ductile deformation processes is supported by the occurrence of ductilely elongated quartz lumps with dynamic recrystallization structures and, more importantly, by the dominating polymineralic mylonites and ultramylonites, which deform by viscous granular flow. Despite this evidence for ductile deformation, the same shear zones display concurrent brittle features such as fracturing during the onset of deformation under high grade conditions as well as fluidized non-cohesive gouges. The latter are injected into the wall rock during fluidization, before being again overprinted by ductile deformation. In this sense, deformation processes are highly variable in time, where seismic brittle events cyclically interplay with interseismic ductile creep at conditions of ~400°C. During exhumation and related cooling, strain localizes further within the already existig fault zones, involving mineral reactions from qtz-(2)fsp-bt-(ep) dominated mylonites to qtz-(2)fsp-wm- chl-ep dominated ones. The latter are able to accommodate ductile deformation to temperatures as low as 200°C, i.e. far below the ductile behavior of quartz. With further cooling, a change from viscous granular flow to frictional granular flow occurs. Again, pre-existing shear zones are reactivated and the former ultramylonites transform into ultracataclasites and non-cohesive fault gouges. An increase in volumetric strain and permeability at this stage allow enhanced fluid circulation in these fault zones down to depth of up to 8-10 kilometers (T <250°C). Seismic fracturing alternating with interseismic frictional granular creep manifest rheological switches also in the upper crustal domains. We relate this behaviour to fast changes in fluid pressure and loci of instantaneous stress release, which is recorded in microstructures of different breccia types. To summarize, general observed structural and compositional heterogeneities of the granitoid continental crust control the deformation style in space and time. In this light, a classical quartz- dominated crustal rheology may overestimate the crustal strength, which is primarily controlled by the existing heterogenities and granular flow processes in polymineralic weak zones.

References Herwegh, M., Berger, A., & Kissling, E. (2017). Large-Scale Crustal-Block-Extrusion During Late Alpine Collision. Nature Scientific Reports. doi: 10.1038/s41598-017-00440-0. Wehrens, P., Baumberger, R., Berger, A., & Herwegh, M. (2017). How is strain localized in a mid-crustal basement section? Spatial distribution of deformation in the Aar massif (Switzerland). Journal of Structural Geology 94, 47-67. Wehrens, P., Berger, A., Peters, M., Spillmann, T., & Herwegh, M., (2016). Deformation at the frictional- viscous transition: Evidence for cycles of fluid-assisted embrittlement and ductile interseismic deformation. Tectonophysics, 693A, 66-84. doi: org/10.1016/j.tecto.2016.10.022.

Structural evolution of Main frontal Thrust in Pakistan. New evidence from low temperature thermochronology.

Humaad Ghani1,2, Edward R. Sobel1, Gerold Zeilinger1, Johannes Glodny3

1Institute of Earth and Environmental Science, University of Potsdam, Potsdam, Germany, [email protected], [email protected], [email protected] 2Department of Earth and Environmental Science, Bahria University, 44000, Islamabad Pakistan 3GeoForschungsZentrum (GFZ) Potsdam, Potsdam, Germany, [email protected]

The Main Frontal Thrust (MFT) marks the southern boundary of the Himalayan fold and thrust system. In Pakistan, two prominent portions of this fault system are the Salt Range Thrust and the Surghar Range Thrust, bounding the Salt and Surghar ranges, respectively. These ranges represent the topographic front formed above the ramp and upper flat of the MFT. In order to better understand the kinematic history and structural style of the MFT, we have constructed balanced cross-sections and conducted low-temperature thermochronology analysis; Apatite (U-Th-Sm/He) (AHe) and Apatite fission track (AFT) dating. We have systematically sampled Cambrian to Pliocene sandstones along strike from different stratigraphic sections in the Salt and Surghar Ranges. The initial data suggest totally reset AHe and AFT ages from the Mesozoic sandstones in the Surghar range. Similarly, preliminary data from the Salt Range suggest totally reset AHe ages from Cambrian to Permian sandstones. The broad range of AFT ages in the Salt Range suggests partial resetting, with the exception of a single sample at the western-most part, which is totally reset. Interestingly, the AFT partially reset ages directly correspond to the sample position and distance from the range front. The AFT ages of the Lower Permian sandstone samples from different sections yield partially reset ages: samples located farther north, beneath a relatively thick stratigraphic section, are younger than samples located farther south, near range front, beneath a thinner section. This pattern of partially reset ages is helpful for projecting the thickness of the eroded section above the MFT in balanced cross-sections. Structural reconstructions based on industry seismic reflection data combined with outcrop measurements and completed using the program MOVE show 20 to 30 Km of slip on the MFT in the Salt Range and 15 km of slip in the Surghar Range. The spatial distribution of AHe and AFT ages and balanced sections suggest movement on the MFT beneath the Surghar range commenced prior to slip beneath the Salt Range. We anticipate that the complete data set will better constrain the deformational history of the MFT in Pakistan.

Tourmaline and micas as petrogenetic minerals: preliminary study from two- mica Mansehra Granite, KPK Pakistan

Irum1, 2, Uwe Altenberger1, Gerold Zeilinger1, Christina Guenter1, Ghani Humaad1, 2

1Institute of Earth and Environmental Sciences, Uni Potsdam, Germany, [email protected] 2Institute of Earth and Environmental Sciences, Bahria University, Pakistan

The Mansehra Granite Complex (MGC) is exposed over a large area in the Lesser Himalayas of Pakistan. It is intruded into the Precambrian Tanawal Formation and is bounded to the east by the Himalayan western syntaxsis and to the west by the Swat Metamorphic Complex. The focus of the study presented here is the chemistry of tourmaline and biotite and their association and significance as a petrogenetic indicator for the evolution of Mansehra Granitic Complex. Combined with observations of field relations and the analysis of the whole rock petrography, the Mansehra Granitic Complex is subject of a detailed structural and petrological investigation. The MGC has a mega-porphyritic texture on a large scale and is comprising micas and tourmalines with sufficient chemical variation for differentiating the magmatic phases. The phenocrysts size in some sections range from 0.5 to 9 mm. Both fine grained magmatic and high-temperature deformation textures, such as strong foliation, types are locally present. The granites are strongly peraluminious and tourmaline is associated with two types of mineral assemblages: 1) Quartz + K-feldspar + Plagioclase + Muscovite +Chlorite ± Biotite ± Garnet ± Andulasite, and 2) Quartz + Plagioclase + Muscovite ± Garnet ± Biotite. Biotite granite is the abundant variety in comparison to the tourmaline-rich granites. Those granites having the major amount of tourmaline have less or no biotite, and vice versa. The tourmaline in the Mansehra granites is typically of varying color and composition, showing brownish, zoned and coarse grains or brown to bluish colored and zoned grains. The tourmaline is of schorlitic composition and present in association with muscovite. Several factors control the stability of tourmaline in felsic magmas, like boron content of the melt, the amount of Al2O3, FeO, MnO MgO, whole rock composition, temperature, oxygen fugacity, aH2O and fluctuating environmental conditions. Biotite constitutes the important mafic mineral in Mansehra granites and ranges in size from fine to coarse grained. It shows prominent pleochroic halos in several sections and is altered to chlorite across and along the grain. These halos have subhedral to euhedral crystals of zircon and prismatic crystals of apatite in several sections. The saturation of biotite is dependent on the FeO, MgO, K2O, and Al2O3 in granitic melt while its stability is related to the oxygen fugacity, temperature, and pressure conditions. The generation of compositional phase diagrams is ongoing work in order to determine the relationship between tourmaline and micas in the granitic rocks. So far the petrography and mineral chemistry suggests distinct stability fields for tourmaline rich and biotite rich granites.

Keywords: Mansehra granitic complex, lesser Himalayas, tourmaline, biotite, petrogenetic indicator

Distribution, tectonic structures and deformation processes of salt-bearing Rotliegend formations in the German North Sea and surrounding areas

1 2 1 Fabian Jähne-Klingberg , Michael Warsitzka , Rüdiger Lutz

1Bundesanstalt für Geowissenschaften und Rohstoffe (BGR), Hannover, Germany, [email protected] 2Institute of Geosciences, Friedrich Schiller University Jena, Burgweg 11, 07749 Jena, Germany

In the central parts of the Southern Permian Basin (Northern German Basin and southeastern parts of the North Sea) salt structures are built up of Upper Permian (Upper Rotliegend to Zechstein) evaporitic rocks. The speciality of the Upper Rotliegend (Elbe Sub-group) evaporitic succession is that it contains 10 to 100 meters thick fine siliciclastic layers, whereas the salt layers generally reach thicknesses of only a few decameters. In the regions of the southern Horn Graben and the Glückstadt Graben, the initial salt thickness of Upper Rotliegend salt layers was probably much larger. The Upper Rotliegend is characterised by a finer cyclicity compared to the Zechstein succession and rock salt is the subordinate formation lithology in most parts of the study area. Despite the small thicknesses of individual salt layers, the Upper Rotliegend clastic-evaporitic succession is often strongly involved in halotectonic movements. The distribution of the evaporitic Rotliegend facies (e.g. Plein 1995) and salt structures incorporating Upper Rotliegend evaporites have been mapped by e.g. Reinhold et al. 2008, Jähne et al. 2012 but they do not provide explanations for the deformation style and the kinematics behind. Based on results from basin and petroleum systems modeling (www.gpdn.de) and seismic interpretation, we present the structural characteristics of the mobilised Upper Rotliegend succession and possible explanations for the dynamics of its mobilisation. The distribution of deformed Upper Rotliegend formations mostly coincides with the occurrence of large-offset basement faults and intense mobilisation of the Zechstein salt formations. The Upper Rotliegend often forms salt pillows in the root zones of diapirs mainly consisting of Zechstein evaporites. However, in areas without intense deformation of the Zechstein salt, mobilised Upper Rotliegend also forms low amplitude pillows and anticlines at the base of the Zechstein. The interpretation of 2D seismic data reveals that major faults in the basement of the Zechstein show partly flats in the Upper Rotliegend interbedded strata (detachment layer). In seismic data of the Horn Graben it is observed that above an undisturbed Lower Upper Rotliegend to Permo-Carboniferous basement parts of Lower Upper Rotliegend formations (Havel Sub-group), which do not contain major rock salt layers, are also involved in folding. Thus, halokinesis cannot be the main driving mechanism for halotectonic-like features of the Upper Rotliegend successions. We suggest that increased fluid pressure below the sealing Zechstein and Upper Rotliegend salt layers caused undercompaction of the clastic layers of the Upper Rotliegend. Increased fluid pressure was probably caused by fluid influx from underlying Carboniferous source rocks during the Triassic or by reduced fluid escape in the buried clastic layers already from Upper Rotliegend time onward. This undercompaction then resulted in a decrease of the shear strength of the entire Upper Rotliegend succession so that it became easily mobilised during Triassic extensional faulting. Because of this rheological behavior of Upper Rotliegend strata, it is supposed that the main driving mechanism for the mobilisation were internal pressure gradients and viscous shearing due to the flowing Zechstein salts during the onset of diapirsm. At the end of the Triassic most of the study area was influenced by major basement faulting, which probably caused bypasses in the Upper Rotliegend and Zechstein barriers. Hence, the redistribution of salt reduced the barrier function so that most of fluids from Permo-Carboniferous source rocks and fluids captured in the Upper Rotliegend escaped. References Jähne, F., Bebiolka, A., Arfai, J., & Lutz, R. (2012). Deformation of Rotliegend "salt formations" and their influence on the structural pattern in the German North Sea. Schriftenreihe der DGG 80, 521. Plein, E. (1995). Norddeutsches Rotliegendbecken; Rotliegend-Monographie Teil II. Stratigraphie von Deutschland I. Courier Forschungsinstitut Senckenberg 183, Frankfurt am Main, p. 193. Reinhold, K., Krull, P., & Kockel, F. (2008). Salzstrukturen Norddeutschlands 1:500 000, Hannover (Bundesanst. Geowiss. Rohstoffe). 59

Flow below the continental plateaus? Some answers from the microstructures of felsic granulites in the Bohemian Massif

Petr Jeřábek1, Petra Maierová2,3, Ondrej Lexa1, Karel Schulmann2,3, Jan Franěk2

1IPSG, Charles University, Prague, Czech Republic, [email protected] 2CLR, Czech Geological Survey, Prague, Czech Republic 3UMR7516, Université de Strasbourg, Strasbourg, France

Domains of continental collision are typically associated with crustal thickening, which may progress into the development of continental plateaus. Lateral redistribution of lower crustal material away from the thickened domain is the necessary prerequisite to form continental plateaus. It is expected that the redistribution of crustal material occurs through horizontal channels where weak crustal material flows along a lateral pressure gradient. Such channels are marked by a drop in viscosity allowing the crustal material to flow even at relatively small pressure gradients. The viscosities of down to 1018 Pas were inferred for the chanels below the plateaus on the basis of their spreading rate and dynamic topography (e.g. Clark et al., 2005). However, bearing in mind the existing flow laws for lower crustal materials, such viscosities are rather unrealistic (Copley and McKenzie, 2007) and so the microphysical mechanism behind the channel flow is not well understood. In this contribution, we focus on an example of the lower crustal flow operating in felsic granulites in the orogenic root of the Bohemian Massif (Maierová et al., 2017). Detailed microstructural study of these rocks revealed various stages of microstructural evolution associated with 1) the lower crustal flow and 2) followed by exhumation. During the lower crustal flow, the most prominent microstructural change is the transition from coarse grained ternary feldspar dominated banding into extremely fine-grained mixture of two binary feldspars, i.e. plagioclase and k-feldspar. This chemically induced change is associated with the transposition of original orthogneiss banding and development of discrete cleavage croscutting quartz bands and resulting into formation of platten quartz. Our numerical simulations of the granulite microstructure evolution is based on the numerical solution of Bercovici and Ricard (2012). The modeling results show that the extremely low viscosities of felsic lower crust in the order of 1018 Pas can not only be achieved but also maintained over milions of years. Such extreme rheology is only possible because of the inhibited grain growth of the two feldspar mixture due to pinning.

References Bercovici, D., & Ricard, Y. (2012). Mechanisms for the generation of plate tectonics by two-phase grain- damage and pinning. Earth and Planetary Science Letters 202–203, 27–55. Clark, M.K., House, M. a., Royden, L.H., Whipple, K.., Burchfiel, B.C., Zhang, X., & Tang, W. (2005). Late Cenozoic uplift of southeastern Tibet. Geology 33, 525. Copley, A., & McKenzie, D. (2007). Models of crustal flow in the India-Asia collision zone. Geophysical Journal International 169, 683–698. Maierová, P., Lexa, O., Jeřábek, P., Schulmann, K., & Franěk, J. (2017). How to keep the lower crust weak - a computational study of deformation mechanisms and grain size evolution in granulites. Earth and Planetary Science Letters 466, 91–102.

Archaeoseismology and (in)active tectonics - The case of the Velebit seismic gap along the Adriatic coast, Croatia

Miklós Kázmér1, Ernest Moro2

1Eötvös University, Department of Palaeontology, Budapest, Hungary, [email protected] 2Università degli Studi di Padova, Italy, [email protected]

The northeastern shore of the Adriatic Sea is bordered by a seismically active zone, ranging from Greece in the south through Albania, Montenegro and Croatia as far as Italy in the north. There is a conspicuous gap in this zone, between the latitude of Zadar and latitude of Rab island, where only a minimal amount of historical and instrumental seismicity has been recorded. This sector is probably a locked fault (M. Herak, pers. comm., 2017). A reconnaissance field trip to assess the archaeoseismological potential of the Kvarner and Velebit area was conducted in July 2017 to test the working hypothesis that the Velebit gap - while seismically inactive today -, was seismically active in the past. Evidence for past earthquakes have been recognized by damage preserved on ancient buildings and by post- seismic repair features. During the trip we visited the islands of Cres, Losinj, Pag, Rab and Krk, and travelled along the Velebit coast from Starigrad to Senj. Main churches and medieval palaces of port towns and additional ancient churches - dating back to the 9th century - were visited and surveyed. We suggest that inactivity of the Velebit seismic gap is a short-time feature only; archeoseismology allows the recognition of additional major earthquakes, missing from the documentary record. Further research needed to assess the duration of fault locking in the Velebit gap.

Fig. 1: Minimum earthquake intensity values nearby the Velebit seismic gap, proven by damaged ancient buildings. Seismicity map from Markušić et al. (2016). Data on Porec and Pula intensity are from Kázmér (2013).

References Kázmér, M. (2013): The rocking columns of Poreč – archaeoseismology in the Istria Peninsula, Croatia. In: Grützner, C., Rudersdorf, A., Pérez-López, R., Reicherter, K. (eds): Seismic Hazard, Critical facilities and Slow Active Faults. PATA Days. Proceedings of the 4th International INQUA Meeting on Paleoseismology, Active Tectonics and Archaeoseismology (PATA), 9-14 October 2013, Aachen, Germany, pp. 117-120. Markušić, S., Gülerce, Z., Kuka, N., Duni, Ll., Ivančić, I., Radovanović, S., Glavatović, B., Milutinović, Z., Akkar, S., Kovačević, S., Mihaljević, J., Salić, R. (2016): An updated and unified earthquake catalogue for the Western Balkan Region. - Bulletin of Earthquake Engineering 14, 321-343.

The role of the feldspar solvus for deformation mechanisms and rheology of the lower crust.

Marina Kemperle1, Reiner Kleinschrodt1

1Universität zu Köln, Inst für Geologie und Mineralogie, 50674 Köln Zülpicher Str. 49b, [email protected]

The study of granulite fabrics is thought to reveal information on the rheological behaviour of the lower crust (Brown et al., 2011). However, many granulites show partial or even complete overprint according to different stages of retrogression. In line with this, observed microfabrics correspond to post-peak metamorphic amphibolite facies conditions and even lower grades. As a result, rocks altered in this way represent rather upper crustal material and, thus, rheological principles of lower crustal granulites do not fit. In this study, we use the deformation fabrics of feldspar (and quartz) to reveal changes in the rheology of the transition from lower to upper crust. The deformation of feldspar in the transition from upper to lower crust is subject to exsolution processes due to the miscibility gap of plagioclase and alkali feldspar below 650° C (Benisek et al., 2010). The subsolvus deformation leads to recrystallization of feldspar solid solution porphyroclasts to fine-grained aggregates of chemically altered 2-phase pl–kfs layers or, with quartz mobility on grain boundaries, to 3-phase pl-kfs-qtz layers. The hypersolvus case is characterized by deformation and recrystallization of feldspars without a compositional change of the recrystallized grains producing coarse-grained aggregates or, in case of just few crystals, “ribbon” shaped feldspars. Unlike many other granulite terrains, the Highland Complex of Sri Lanka underwent a nearly stress-free exhumation from the lower crust (Kleinschrodt & Duyster, 2002). Consequently, lower crustal structures are well preserved and only altered by grain coarsening and exsolution of feldspars developed undisturbed during very slow cooling (2-3° C/ Ma) from T ~850° C (Hölzl et al., 2001). This led to a coarse-grained recrystallization of quartz and feldspar with isolated feldspar ribbons within quartz. The latter show high aspect ratios and well developed CPOs indicating typical high-T slip systems. According to this, dislocation creep flow laws can be considered valid for quartz and feldspar in the lower crust. We compare these features to other granulite terrains (Indian and Variscan Granulite Terrains), where stresses drastically change the granulite facies textures towards decreasing temperatures while granulite facies parageneses still persist. Grainsize and grainsize evolution seem to be key factors for the rheological behaviour of granulites, i.e. the switch between grainsize-sensitive and insensitive mechanisms (e.g. Maierova et al., 2017). A combination of quartz and feldspar fabric parameters (grainsize, SPO and LPO) can be used as proxies for the rheology of middle to lower crust.

References Benisek, A., Dachs, E., & Kroll, H., (2010). A ternary feldspar mixing-model based on calorimetric data: development and application. Contrib. to Mineral. and Petrol., 160(3): 327-337. Brown, M., Schulmann, K., & White R. W., (2011). Granulites, partial melting and the rheology of the lower crust. Jour. Metamorph. Geol., 29: 1-6. Hölzl, S., Köhler, H., Kröner, A., Jaeckel, P, & Liew, T. C. (2001). Geochronology of the Sri Lankan basement. Geol. Surv. Dept. Sri Lanka Prof. Pap., 5: 237-257. Kleinschrodt, R., & Duyster, J., (2002). HT-deformation of garnet: An EBSD study on granulites from Sri Lanka, India and the Ivrea Zone. Jour. Struct. Geology, 24: 1829-1844. Maierova, P., Lexa, O., Jerabek, P., Schulmann, K., & Franek, J. (2017). Computational study of deformation mechanisms and grainsize evolution in granulites – Implications for rheology of the lower crust. EPSL, 466: 91 -102.

Structure of the Main Pamir Thrust and External Pamir thrust belt in Kyrgyzstan and western China

Jonas Kley1, Edward R. Sobel2, Thomas Voigt3, Johannes Rembe2, Chen Jie4, Langtao Liu5

1Universität Göttingen, Geowiss. Zentrum, Göttingen, Germany, [email protected] 2Universität Potsdam, Inst. Erd- und Umweltwissenschaften, Potsdam, Germany, [email protected], [email protected] 3Universität Jena, Inst. f. Geowissenschaften, Jena, Germany, [email protected] 4China Earthquake Administration, Institute of Geology, State Key Laboratory of Earthquake Dynamics, Beijing, China, [email protected] 5Hebei University of Engineering, Hebei, China, [email protected]

The northern front of the Cenozoic Pamir mountains is formed by the Main Pamir Thrust (MPT) and the north-verging fold-thrust-belt of the External Pamir (EP) in its footwall. The thin-skinned EP borders the Alai valley, which is also overthrust from the north by the mostly thick-skinned front of the Tien Shan mountains. We describe the MPT/EP system and its variations from the Altyn Dara valley in the west (Kyrgyzstan) to the Yimaik valley in the east (western China) over an along-strike distance of some 270 km. The MPT everywhere emplaces rocks of Carboniferous age, including thick successions of pillow lavas, over younger strata. The metamorphic grade in the MPT hanging-wall decreases from greenschist facies in the west to anchimetamorphic in the east. A large, probably pre-Cenozoic thrust sheet of greenschist to amphibolite-grade metamorphic rocks and with possible affinities to the more southerly Karakul- Mazar domain of the Northern Pamir overlies the anchimetamorphic metasediments and forms the leading edge of the MPT in the east. The EP generally comprises a northward younging succession of Permian/Triassic through Neogene strata. In the west, these strata form a northward imbricated stack of thin, often refolded thrust sheets. In the east, the EP widens to occupy the entire Alai valley up to the Tien Shan front. It consists of four large thrust sheets comprising Cretaceous to Upper Neogene strata. Permian and Triassic are only exposed along its southern border in half-windows beneath the gently dipping MPT. The MPT/EP system is the best candidate for accommodating the 300 km of northward indentation and southward intracontinental subduction that have been invoked to explain the northward convex Pamir arc and south-dipping slab. Semi-balanced cross-sections suggest about 60 km of shortening for the EP regardless of the strong variation in structure that may reflect higher Cenozoic thicknesses in the east and/or stronger erosion in the west. Restoration of the shortened cover also indicates that the low-angle MPT cuts into basement too far south to simply link up with the top of the steeply dipping Pamir slab imaged by geophysical methods. The displacement on the MPT is not well constrained but would have to exceed 200 km to match the postulated 300 km of convergence together with shortening in the EP. On the other hand, more recently proposed delamination models where Indian lithosphere forcefully peels off Asian lower crust and mantle to form the Pamir slab predict predominantly south-directed thrusting. The exclusive northward vergence of the MPT/EP therefore still calls for some scenario involving large-scale southward underthrusting or subduction.

Causes of post-Variscan uplift in northern Central Europe

Jonas Kley1, Fabian Jähne2, Hilmar von Eynatten1, István Dunkl1

1Universität Göttingen, Geowissenschaftliches Zentrum, Göttingen, Germany, [email protected]; [email protected]; [email protected] 2Bundesanstalt für Geowissenschaften und Rohstoffe, Hannover, Germany, Fabian.Jaehne- [email protected]

After the Variscan orogeny large parts of Central Europe began to subside again in Latest Permian to Triassic time and were covered by extensive sedimentary successions of an intracontinental basin. However, the history of deposition was repeatedly punctuated by uplift events of varying magnitude, location and spatial extent. Some areas actually remained elevated such as the Bohemian massif inside the Variscan orogen, or the London-Brabant massif and Ringkøbing-Fyn High in its foreland. In the intervening basins an overall transgressive trend culminated in Early mid-Jurassic time. A slightly later, transient uplift of the Central North Sea was followed by the establishment in Early Cretaceous time (timing uncertain: see below) of a broad emergent area largely coinciding with Germany´s recent upland regions. Although diminished in size by Late Cretaceous sea-level rise, this elevated area widened again in the early Cenozoic and essentially persists to the Present. It is not always easy to relate this history to tectonic or other causes. The long-standing highs have thicker crust that apparently escaped to some degree the pervasive destruction of the Variscan orogen´s crustal root or was inherited from still earlier tectonic events in the foreland. The long-term subsidence of the basin is interpreted to reflect protracted cooling slowed by the blanketing sediments and periodically enhanced by extension. Short-lived mid-Jurassic uplift in the North Sea is thought to reflect the rise and decay of a mantle plume. The persistent rise of the German uplands is somewhat enigmatic. Thermochronologic and organic maturity data increasingly suggest that larger areas than previously thought must have had a substantial post- Triassic sedimentary cover that was only removed in Late Cretaceous time. This denudation event coincides with thrust-related uplift of the Thuringian Forest, Harz and Flechtingen High basement ranges but is too widespread to have been caused by it. Basement thrusting and inversion of grabens was superimposed on regional uplift of much larger wavelength. This conclusion is supported by the lack of syntectonic Late Cretaceous sediments around the uplifting Thuringian Forest and southern Harz. If sediments shed from the rising basement uplifts were not continuously channelled out but stored in their vicinity, they must have been eroded again before Eocene time. The most likely process to induce relative rapid, long- wavelength uplift of a crust of unchanged thickness is mantle upwelling (dynamic topography), whereas the persistence of elevation over almost 100 million years probably requires long-term thinning of the lithospheric mantle. Increasing mantle temperature over the Cenozoic is compatible with sparse occurrences of latest Cretaceous basalt and three rifts (Upper Rhine graben, Lower Rhine graben and Eger rift) arranged in a kind of triple junction geometry around a central area where more frequent and voluminous Miocene basalt eruptions are focussed.

Differential uplift in the northernmost kink area of the Periadriatic fault system – a 4D kinematic model

Thomas Klotz1, Hannah Pomella1, Ulrich Burger1, Bernhard Fügenschuh1, Martin Reiser1, Massimiliano Zattin2, Matteo Massironi2

1Institute of Geology, University of Innsbruck, Innrain 52, 6020 Innsbruck, Austria, [email protected] 2Department of Geosciences, University of Padova, Via G. Gradenigo 6, 35131, Padova, Italy

N-S sections illustrating the upper crustal structure of the western Tauern Window have been published (e.g. Brandner et al., 2008; Schmid et al., 2013) according to geological reconnaissance of the Brenner Basistunnel (BBT). Crossed nappes are allocated to the Silvretta-Seckau System, to Ophiolite-bearing Penninic units, as well as to Subpenninic nappes of the Venediger Duplex and its hanging wall. The southernmost part cuts across Southern Alpine rocks. A narrow corridor near Mauls (Italy) between the Adriatic indenter and the Tauern Window accommodates a set of major fault zones. This study attempts to specify regionally distinguishable relative uplift rates and should contribute to understanding the regional tectonic history of the Sterzing/Mauls area. Therefore, cooling ages of subsurface samples (collected in the course of Brenner Base Tunnel excavation) of adjacent fault separated blocks were identified. Hence, derived cooling path modelling assembles three age-temperature pairs per sample: zircon (ZFT) and apatite (AFT) fission track as well as apatite U-Th/He analysis cover an adequate temperature range between approximately 260°C and 60°C. Dominant foliation, nappe boundaries and fault structures in the Maulsertal area show steep to overtilted orientation. Main striking directions of planar elements vary between NW-SE, E-W and NE-SW, whereas the stretching lineation trends E-W. ZFT results along the sampled transect (almost perpendicular to dominant foliation) exhibit (starting south) • Lower Cretaceous ages in permian granite, • Late Oligocene to Early Miocene ages in periadriatic tonalite, • Late Oligocene to Early Miocene ages along an imbricated zone composed of tonalite and austroalpine slices, • a section dominated by Late Jurassic to Lower Cretaceous ages of presumably austroalpine origin, very likely representing the northernmost hanging wall of Defereggen Antholz Vals line (DAV) during normal faulting, • Oligocene to Middle Miocene ages in an austroalpine domain heading towards younger, • Middle to Late Miocene ages near the southern border of the Tauern Window. AFT ages show earliest cooling in southern alpine units (Late Oligocene). Middle to Late Miocene ages characterizing the tonalitic block appear to increase with distance from the Pustertal fault. Whether this effect should be ascribed to exhumation rate or fault derived temperature effects cannot be answered by our data. A decrease in age of both AFT (Middle to Late Miocene) and ZFT ages towards north in the northernmost, partly intensely fractured austroalpine sampling zone can most likely be attributed to Tauern Window exhumation and temperature anomaly. Cooling path modelling for thermochronological distinguishable blocks reveals three dominant cooling events. The first one, valid for the southern alpine block, indicates highest rates between Upper Cretaceous and Early Oligocene. Although ZFT ages are quite similar, no constraints regarding cooling rates could be set for the austroalpine block south of DAV due to bad apatite conditions. The tonalitic block in between seems to be affected by highest cooling rates between Late Oligocene to Middle Miocene. Rapid cooling of the austroalpine block north of DAV occurred between Middle and Late Miocene. Investigations in the Maus-Sterzing area appear to be essential for the periadriatic deformation history. Therefore, a western succession of this study is carried out contemporaneously (see poster/abstract by Paul Aichholzer). A 4D evolution model for the Mauls area is scheduled.

Deformation and Geochronology of Metamorphic Rocks in the Saltauser Tal, Italy

Linus Klug1, Michael J. Schmidtke1, Frank Tomaschek1, Markus Lagos1, Nikolaus Froitzheim1

1Rheinische Friedrich-Wilhelms-Universität Bonn, Germany, [email protected]

The metamorphic rocks of the Saltauser Tal (Italy) have been studied to constrain the architecture and evolution of the Texel Complex and neighbouring units. Structural investigations established a sequence of Alpine deformation phases, covering Eoalpine compressional, Eoalpine extensional and Tertiary compressional tectonics. Tertiary northward compression led to the S-vergent overturned folding of the Texel Complex (Pomella et al., 2016), where the Saltauser Tal is in the overturned limb. By retrodeforming N-S trending late Eoalpine folds and E-W trending Tertiary folds, prograde top-to-ESE shear senses (Sölva et al., 2005) and retrograde top-to-W shear senses can be reconstructed to top-to-WNW and top-to-E, respectively, in accordance with regional tectonics of the Austroalpine. The late Tertiary brittle Forst Fault (Bargossi et al., 2010) crops out in the Saltauser Tal separating the Marlengo Slice from the Texel Complex. PT-modelling using Theriak-Domino was applied to calculate a pseudosection of a garnet- bearing Two-Mica-Gneiss sample. Mineral parageneses, garnet composition and silica content in white mica constrain the growth of garnet to pressure of 10-12 kbar and temperature of 640- 660°C. Furthermore, laser ablation U-Pb dating of zircon from orthogneisses of the Texel Complex and the Merlengo Slice give time constraints on the pre-Variscan evolution. An amphibole-bearing orthogneiss of the Texel Complex yields 470±11 Ma as protolith age. The leukocratic orthogneiss of the Marlengo Slice yields 449+7/-8 Ma. A Proterozoic magmatic evolution is preserved in inherited zircons.

References Bargossi, G. M., Bove, G., Cucato, M., Gregnanini, A., Morelli, C., Moretti, A., Poli, S., Zanchetta, S., & Zanchi, A., (2010). Note illustrative della Carta Geologica d‘Italia 1:50.000 foglio 013 Merano. CARG. ISPRA, Istituto Superiore per la Protezione e la Ricerca Ambientale, Roma. Pomella, H., Stipp, M., & Fügenschuh, B., (2012). Thermochronological record of thrusting and strike-slip faulting along the Giudicarie fault system (Alps, Northern Italy). Tectonophysics, 579: 118–130. Sölva, H., Grasemann, B., Thöni, M., Thiede, R., & Habler, G., (2005). The Schneeberg Normal Fault Zone: normal faulting associated with Cretaceous SE-directed extrusion in the Eastern Alps (Ita- ly/Austria). Tectonophysics, 401: 143–166.

Physics and kinematics of S-C-fabric in plastic shear zones

Falk H. Koenemann1

1Im Johannistal 19, 52064 Aachen, [email protected]

The terms and concepts by which deformation is described to this day were coined in the 18th C (stress: Euler 1776, strain: Lagrange 1784). The theory was worked out by Cauchy 1827, by adapting Newton’s mechanics which is energetically conservative. The Euler-Cauchy theory was written before the discovery of physical work (1829), the modern understanding of geometric space (1840-60), bonds in solids (1849), and the First Law of thermodynamics (1847) and thus the body of non-conservative physics. It is therefore unable to describe deformation work; it is not in line with standard geometry; it cannot consider bonds, and it follows the wrong energy conservation law (Koenemann, 2008, 2014). The entire energetic thinking which developed from 1840 on, which is so fundamental for modern physics, has been ignored completely in continuum mechanics. It is a straightforward proof to show that the Cauchy stress theory is not valid. It is also well known that strain contains insufficient information to describe a deformation: from a given strain it is not possible to tell how the deformation came about. Instead, the full information is given by the displacement field. By nature, elastic deformation (the loaded state, “stress”) is a reversible change of state in the sense of the First Law: work is done upon a system during loading which is reversed during unloading. A correct approach to elastic deformation and proper understanding of stress must therefore be based on thermodynamics, and it must deliver the displacement field as result. These requirements are satisfied by a new deformation theory (Koenemann, 2008b). For the boundary conditions of simple shear, the stress (a force vector field) has non-orthogonal eigendirections forming the angles 101 and 79°. The contracting eigendirection is at 112° to the bulk shear direction, the extending eigendirection is at 11°. The S-plane in S-C fabrics is the 11° direction into which elongated porphyroclasts (σ-clasts) are rotated. The C-plane at -28° follows the bisector of the 79° angle enclosed by the eigendirections, it is the maximum shear direction and rotates against the sense of bulk shear during progressive deformation into the S-plane. δ- clasts are restricted to this sector only. Joints and cracks in shear zones follow accurately the contracting eigendirection at 112°, which is also the regional maximum stress direction along the San Andreas fault in California (observed at 111 ± 14°), and the divider line between δ- and σ-clasts in porphyroclast studies in mylonites. The entire set of fabric elements and kinematic indicators in shear zones is therefore completely predicted. Energetic model calculations for pure and simple shear indicate that plastic simple shear costs 27% less energy than pure shear for identical strain. The prediction is in accord with experimental results. It follows from the principle of least work that shear zones are massively favored in plastic flow.

References Koenemann, F.H. (2008a). On the systematics of energetic terms in continuum mechanics, and a note on Gibbs (1877). Int J Modern Physics B 22, 4863-4876 Koenemann, F.H. (2008b). An approach to deformation theory based on thermodynamic principles. Int J Modern Physics B 22, 2617-2673 Koenemann, F.H. (2014). Cauchy's stress theory in a modern light. Eur J Physics 35, 015010

Temperature gradient in the Adula nappe and its potential significance for the nappe’s kinematic history

Victoria Kohn1, Jan Pleuger1, Martina Menneken1, Timm John1

1Freie Universität Berlin, Institut für Geologische Wissenschaften, Berlin, Germany, [email protected]

The Adula nappe in the Central Alps is one of the Penninic units derived from the former Euro- pean margin that experienced high-temperature (HT) and high- (HP) and even ultrahigh- pressure metamorphism during the Eocene. Petrological studies firmly established peak- pressure and -temperature gradients with increasing PT records in southward direction, i.e. the direction of underthrusting. A major problem, especially concerning the pressure gradient, is that peak pressures, if converted into depth assuming realistic lithostatic gradients, give a greater former vertical extent of the nappe than its present horizontal length, although the nappe was even stretched horizontally upon exhumation by top-N shearing. Two end-member scenarios were proposed that potentially resolve this problem. Nagel (2008) proposed that the Adula nappe had a very steep subvertical orientation in the subduction zone and was exhumed from mantle depth into a top-N shear zone where several subnappes were sheared off to the north one after another. Such alternating ortho- and paragneiss-dominated subnappes can indeed be mapped out and substantiate a nappe-internal geometry of a foreland-dipping duplex. Pleuger and Podladchikov (2014) argued that peak pressures reported from the Adula nappe may have been reached at the base of thickened orogenic crust and have a significant proportion of tectonic overpressure. We present new data concerning the temperature gradient constrained by the very robust Zr-in-rutile method (Ferry and Watson, 2007) based on electron microprobe measurements on HP-HT eclogites. Samples collected from a north-south cross section along the nappe yielded a temperature gradient that is lower, but comparable to earlier studies (c. 2°C/km; c. 620 °C in the north to c. 690 °C in the south). We will combine these robust temperatures with the Raman-based SiO2-inclusion in garnet barometry (Ashley et al., 2014) on the same sample set, to archive pressure estimates that are basically purely based on physics rather than interpretation of domains of thermodynamical equilibrium. If the northernmost sample, that is likely to preserve a Variscan metamorphic peak, is excluded, our data can be interpreted in terms of a steady north-south T gradient. On closer inspection, however, they may also give rather homogeneous peak-temperatures for each individual subnappe from which the eclogites were collected; c. 620 °C for the highest eclogite-bearing (Fanella) subnappe, c. 640 °C for the middle (Trescolmen) subnappe, and c. 690 °C for the lower subnappe. Thus, they may reveal the burial of these subnappes to different depths. In this case, the T gradient would only be an apparent one resulting from the particular nappe-internal geometry where structurally lower subnappes occur more to the south. This interpretation is compatible with the model of Nagel (2008) but needs to be supported by further temperature and pressure determinations, including Raman barometry of SiO2 inclusions in garnet.

References Ashley, K.T., Steele-MacInnis, M., & Caddick, M.J. (2014). QuIB Calc: A MATLAB® script for geobarome- try based on Raman spectroscopy and elastic modeling of quartz inclusions in garnet. Comp. Geosci., 66, 155-157. Ferry, J.M., & Watson, E.B. (2007). New thermodynamic models and revised calibrations for the Ti-in- zircon and Zr-in-rutile thermometers. Contrib. Mineral. Petrol., 154, 429-437. Nagel, T.J. (2008). Tertiary subduction, collision and exumation recorded in the Adula nappe, central Alps, in Tectonic aspects of the Alpine-Dinaride-Carpathian system, edited by S. Siegesmund, B. Fügenschuh, and N. Froitzheim, Geol. Soc., London, Spec. Publ., 298, 365-392. Pleuger, J., & Podladchikov, Y.Y. (2014). A purely structural restoration of the NFP20-East cross section and potential tectonic overpressure in the Adula nappe (Central Alps). Tectonics, 33, 656-685.

From no slip to slow slip: How seafloor geodesy reveals crustal deformation at mm-scales

Heidrun Kopp1, Dietrich Lange1, Florian Petersen1, Katrin Hannemann1, Morelia Urlaub1

1GEOMAR Helmholtz Centre for Ocean Research Kiel, Kiel, Germany, [email protected]

The seafloor stores crucial information on sub-seafloor processes, including stress, elastic strain, and earthquakes. This information may be extracted through the nascent scientific field of seafloor geodesy. The GeoSEA (Geodetic Earthquake Observatory on the SEAfloor) array uses acoustic signals for direct-path ranging and relative positioning at mm-scale resolution. The transponders also include high-precision pressure sensors to monitor vertical movements and dual-axis inclinometers in order to measure their altitude as well as any change in submarine fault zones and characterizing their behavior (locked or aseismically creeping). A further component of the network is GeoSURF, a self-steering autonomous surface vehicle (Wave Glider), which monitors system health and is able to upload the seafloor data to the sea surface and to transfer it via satellite. Seafloor transponders are currently installed in three different tectonic settings: across a dextral strike-slip fault to measure the instability of the eastern flank of Mt Etna in Sicily, and along the North Anatolian Fault offshore Istanbul to measure the strain build-up along the fault in a seismic gap (Sakic et al., 2016) and on the marine forearc and outer rise of the South American subduction system around 21°S (Kopp et al., 2016). The first 12 months of all geodetic installations were analyzed and we discuss baselines with precision less than 5 mm for ranges up to 2000 m of distance and compare them with synthetic baselines.

Fig. 1: Seafloor geodetic array composed of ten seafloor stations measuring baselines (green lines) within the network. The array is located on the Chilean lower continental slope at water depth of ~5800 m.

References Sakic, P., Piété, H., Ballu, V., Royer, J. Y., Kopp, H., Lange, D., Petersen, F., Özeren, M. S., Ergintav, S., Geli, L., Henry, P., & Deschamps, A., (2016). No significant steady state surface creep along the North Anatolian Fault offshore Istanbul: Results of 6 months of seafloor acoustic ranging. Geophysical Re- search Letters, 43(13). S. 6817-6825. DOI 10.1002/2016GL069600. Kopp, H., Lange, D., Hannemann, K., Krabbenhoeft, A., Petersen, F., Timmermann, A., eds. & Scientific Crew SO244-II, (2016). RV SONNE Fahrtbericht / Cruise Report SO244/2, GeoSEA: Geodetic Earth- quake Observatory on the Seafloor, Antofagasta (Chile) – Antofagasta (Chile), 27.11.-13.12.2015. . GE- OMAR Report, 034: 86 pp. DOI 10.3289/GEOMAR_REP_NS_34_2016.

Oroclines and plate tectonics – Two examples from the Variscides

U. Kroner1, T. Stephan1, R. L. Romer2

1Institut für Geologie, TU Bergakademie Freiberg, Germany, [email protected] 2Deutsches GeoForschungsZentrum GFZ, Potsdam, Germany

The arcuate-shaped Variscides resulted from the recycling of continental crust of the plates of Laurussia and Gondwana north and south of the Rheic Ocean, respectively. The Rheno- Hercynian–Moravo-Silesian Arc and the Ibero–Armorican Arc constitute first order oroclines. There exist contradicting models for the formation process of oroclines. For the Ibero-Armorican Arc, syn- or postcollisional bending has been explained by the interference of different shortening directions (Weil et al., 2000) or by a special geodynamic scenario, i.e., self-subduction at the Pangea plate (Gutiérrez-Alonso et al., 2008), respectively. Based on the orogen-wide provenance pattern of pre-Variscan Peri-Gondwana shelf sediments (Stephan et al., 2018) and the Late Paleozoic plate kinematics between Gondwana and Laurus- sia (Kroner et al., 2016), we present a plate tectonic model explaining the formation of Variscan oroclines. The collisional tectonics includes two principal steps: (i) Early Variscan shortening after the subduction of the Rheic Ocean predominantly occurred in the Avalonian part of Laurussia and the western shelf of Gondwana, i.e., the Armorican Spur as the leading edge of Gondwana. The Moravo-Silesian Arc resulted from the collision of W-Gondwana blocks, i.e. Saxo-Thuringia and Tepla-Barrandia (upper plate), with an early Variscan back-arc basin of Laurussia (lower plate). (ii) The eastern shelf of Peri-Gondwana remained a passive continental margin until the Late Devonian, when the Paleotethys Ocean began to open. Plate-wide reorganization processes led to the detachment of eastern Peri-Gondwana from mainland Gondwana. The subsequent westward extrusion of the detached segment resulted in the collision with already accreted W- Gondwana / Laurussia crust and caused prolonged and orogen-wide transpressional tectonics that culminated in the formation of the Ibero-Armorican Arc. Different shortening directions during the Variscan orogeny, responsible for the oroclines, reflect the interplay of rigid plates of Gondwana and Laurussia and lateral extrusion of the vast eastern Peri-Gondwana shelf.

References Gutiérrez-Alonso, G., Fernández-Suárez, J., Weil, A. B., Brendan Murphy, J., Damian Nance, R., Corfú, F., & Johnston, S. T., (2008). Self-subduction of the Pangaean global plate: Nature Geoscience, 1(8): 549-553. Kroner, U., Roscher, M., & Romer, R. L., (2016). Ancient plate kinematics derived from the deformation pattern of continental crust: Paleo- and Neo-Tethys opening coeval with prolonged Gondwana–Laurussia convergence: Tectonophysics, 681: 220–233. Stephan, T., Kroner, U., & Romer, R. L., (2018). The pre-orogenic detrital zircon record of the Peri- Gondwana crust: Geological Magazine, doi:10.1017/S0016756818000031. Weil, A. B., Van der Voo, R., van der Pluijm, B. A., & Parés, J. M., (2000). The formation of an orocline by multiphase deformation: a paleomagnetic investigation of the Cantabria–Asturias Arc (northern Spain): Journal of Structural Geology, 22(6): 735-756.

Retention versus overprint of deformation microstructures in quartzo-feldspathic rocks during polyphase deformation in the Erzgebirge Mountains

Jakub Kryl1, Petr Jeřábek1, Ondrej Lexa1

1Institute of Petrology and Structural Geology, Faculty of Science, Charles University, Albertov 6, Prague 2, Czech Republic, [email protected]

The aim of this study is to characterize deformation microstructures related to distinct deformation fabrics in orthogneiss of the central part of the Erzgebirge Mountains. Primary focus is given to the possible retention of microstructures during the polyphase deformation. The studied area was previously interpreted as a large-scale nappe stack, however our recent investigation revealed a sequence of deformation overprints which comply with the observed microstructural differences and their spatial distribution. Erzgebirge is composed of mainly Proterozoic and early Paleozoic rocks including various types of orthogneiss, garnetiferous micaschist, quartzite and phyllite. Based on our structural investigation of the studied area, we identified three main deformation fabrics. i) S1 is defined by shape preferred orientation of quartz aggregates intercalating with feldspar porphyroclasts and it is well preserved in the eastern part of the studied area and in relics elsewhere. This deformation fabric of originally steep orientation is isoclinally folded and overprinted by, ii) gently NNW- or SSE -dipping S2, defined by well-developed monomineralic bands. S2 bears subhorizontal east-west trending stretching and/or intersection lineation associated with relics of cm-scale quartz isoclinal folds. Due to the intense overprint of S1 by S2, both fabrics are subparallel and generally subhorizontal. iii) S3 is represented by ENE-WSW trending discrete/crenulation cleavage with subhorizontal crenulation lineation. Four different microstructural types I-IV associated with subhorizontal S1/S2 fabrics were identified in the orthogneiss of the studied area. Type I is defined as relatively coarse-grained microstructure containing porphyroclasts of K-feldspar with mostly idiomorphic shape. Type II is characterized by recrystallized plagioclase forming aggregates with polygonal grains, elongated recrystallized quartz aggregates with amoeboidal grain shapes and relics of K-feldspar porphyroclasts. Type III shows recrystallized monomineralic bands of quartz and K-feldspar intercalating with bands of mixed plagioclase, quartz and K-feldspar matrix. Type IV microstructure is characterized by elongated recrystallized quartz aggregates, thin bands of recrystallized K-feldspar with locally preserved small relics of K-feldspar porphyroclasts. The matrix consists of mixed K-feldspar and plagioclase. Quantitative microstructural and texture analysis revealed further differences among the microstructural types I-IV, documented namely by differences in grain size of dynamically recrystallized quartz and in activity of quartz slip systems. Type I and II reveal coarse grained quartz microstructure with median grain size of 129-208 microns and dominance of prism slip system. In contrast, Type III and IV show fine grained quartz microstructure with median grain size of 77-98 microns. The analysis of crystallographic preferred orientation in Type III and IV quartz microstructures shows combination of prism/rhomb/basal slip systems. Single girdle distribution of quartz c-axes locally shows the cleft girdle distribution suggesting constrictional symmetry of strain. The spatial distribution of described microstructural types I-IV does not comply with the spatial occurrence of the previously recognized nappes. The quantitative microstructural and texture analyses of dynamically recrystallized quartz allowed us to separate two microstructural groups covering types I-II and types III-IV. These two groups are interpreted to correspond to the two main deformation fabrics S1 and S2, respectively. The constrictional symmetry of deformation observed in Type III microstructures can thus be related to the overprint of S1 by S2. At the same time, the difference between Types I and II, and between Types III and IV is interpreted as a difference in strain intensity during formation of S1 and S2, respectively.

Flow of partially molten lower crust and associated regional-scale detachment/diapiric folding driven by indentation in hot orogens - insights from analogue models employing the 2D photogrammetry methods

Ondřej Krýza1,2, Prokop Závada2, Ondrej Lexa1,3, Karel Schulmann3,4

1Institute of Petrology and Structural Geology, Charles University, Albertov 6, 128 43, Czech Republic, [email protected] 2Institute of Geophysics of the CAS, Boční II/1401, 141 31 Prague 4, Czech Republic 3Czech Geological Survey, Centre for Lithosphere Research, Klárov 3, 118 21 Prague 1, Czech Republic 4Université de Strasbourg, IPG-EOST, UMR 7516, 1 Rue Blessig, Strasbourg 67084, France

Dynamics of orogenic systems is controlled primarily by few key parameters such as the indentation velocity (deformation), heat transfer and rheology of the lithospheric layers. During indentation, significant heat redistribution in these accretionary systems takes place within the partially molten weak domains by the Couette flow, Poiseuille flow or Rayleigh-Taylor instability evolution. The most advanced techniques for prediction of the material transfer pathways in the accretionary systems are methods of numerical and analogue modeling. In our study, we employ the PIV (Particle Image Velocimetry) to trace the material transfer within complex analogue models of crustal scale detachment/diapiric folding above a weak anatec- tic layer. We developed models that represent the late Paleozoic detachment folding associated with building of the Eastern Pyrenees, Chandman dome (Mongolia) or the Chinese Altai mountain ranges. We applied the PIV method and derived dynamical parameters based on the velocity field, such as divergence, velocity components, flow azimuth, strain-rate or vorticity. Re- sults reveal dynamic feedbacks between the ductile flow and topography evolution as well as the deformation of ductile lithospheric layers. In crustal scale detachment/diapiric folding experiments, we used divergence as quantification for redistribution rate of the molten material alongside the mantle-crust interface as well as for redistribution of melt into the core zones of amplifying folds. Negative anomalies of divergence field represent zones of melt inflow parallel with the fold limbs and accumulation zones beneath the hinges of detachment folds. These anomalies are balanced with positive values of divergence field that are situated below the folds in the source layer of partially molten material. The time evolution of divergence is related to the amount of melt as measured from the side-view photographs of progressively evolving models. Both parameters, the divergence and melt volume, are compared with strain-rate fields and show polyphase dynamics of fold development. This is marked by three following major stages: 1) initial slow amplification of the multilayer and coalescence of melt below the hinge zones, 2) rapid amplification and vertical redistribution of melt along the axial zones of the folds, 3) vertical extrusion of the weak hinge domain along steep limbs during further horizontal compression of the locked-up folds. Our results show distinct advantages and the potential of the photogrammetric methods for post-processing of geodynamic and tectonic analogue models.

Late Carboniferous fracture system in NE part of the Lublin Basin (Poland): results of seismic attribute analysis and fracture modeling

Mateusz Kufrasa1, Łukasz Słonka1, Piotr Krzywiec1

1Institute of Geological Sciences, Polish Academy of Sciences (ING PAN), Twarda 51/55, 00- 818, Warsaw, [email protected], [email protected], [email protected]

The aim of this study was to construct a viable fracture model for Carboniferous strata based on the interpretation of an enhanced seismic cube and attribute analysis, and to derive the orientation of the late Paleozoic stress field operating during basin inversion. The research area is located in the NE part of the Lublin Basin – a Paleozoic tectonic unit, formed at the southwestern slope of the East European Craton and defined by the present-day extent of Carboniferous rocks in sub-Mesozoic view. A sedimentary wedge thickening to the SW is composed of Neoproterozoic-Carboniferous strata, which were faulted and shortened in late Devonian/early Carboniferous and late Carboniferous times due to a NW-SE- and NNE-SSW- oriented compressional stress field, respectively. The analyzed area was only mildly deformed at the end of the Carboniferous, and therefore, it is preferable to investigate the regional strress field operating at that time. 3D time- and depth-migrated seismic cubes were used in this study. Postprocessing of seismic data including dip-steering techniques and structurally-oriented filtering was carried out in order to improve the visibility of faults on seismic images. Seismic attribute analyses were based on fault likelihood volumes. An analysis of rose diagrams for seismic-derived fractures compared to results obtained from fracture modeling allowed for the interpretation of fracture sets that developed in a compressive stress field with a NNE-SSW-oriented axis of maximum compression. Shear fractures appear to be the most frequent discontinuities. This interpretation corresponds well to fault orientation measurements collected in excavations of a hard coal mine near the research area (Fig. 1).

Fig. 1: Rose diagrams showing fracture sets derived from seismic attribute analysis and modelled sets based on structural restoration. Results fit well with the faults measured in hard coal mine nearby the investigated area.

Acknowledgements 3D seismic data were kindly provided by the Orlen Upstream. This research was supported by the BlueGas GASŁUPSEJSM research project funded by NCBiR.

References Majewska, E., (2013). The tectonics of 382 seam in the northern part of Bogdanka hard coal deposit at different stages of recognition. MSc thesis, AGH University of Science and Technology, Kraków.

First results on texture and elastic anisotropy of oceanic crust from the slow- spreading ridge at Atlantis Massif, Atlantic Ocean

Rebecca Kühn1, Michael Stipp2, Bernd Leiss3, Jacek Kossak-Glowczewski4, Jan H. Behrmann1

1Geomar Helmholtz-Zentrum für Ozeanforschung Kiel, Marine Geodynamik, Kiel, Germany, [email protected], [email protected] 2Universität Innsbruck, Institut für Geologie, Innsbruck, Austria, [email protected] 3Universität Göttingen, Strukturgeologie und Geodynamik, Göttingen, Germany, [email protected] 4Universität Bonn, Steinmann Institut, Bonn, Germany, [email protected]

At slow-spreading mid-oceanic ridges discontinuous melt flow is counterbalanced by large faults which can lead to the obduction of upper mantle rocks. At the sea floor and and along these faults, rocks are highly alterated resulting in new mineralogies, e.g. talc-amphibole-chlorite schists and serpentinites. Some minerals within the rocks yield high single crystal anisotropies like antigorite and talc. Further deformation of the rocks leads to a pronounced crystallographic preferred orientation (=texture), which furthermore increases the bulk rock elastic anisotropy. IODP Expedition 357 to the Atlantis Massif sampled exactly these rocks on an east-west transect across the southern wall of the Massif. Texture analysis will quantify the crystallographic preferred orientation and thus elastic anisotropy in these rocks. Due to the large difference in grain size of fresh and alterated rocks, we used two different methods. Neutron texture analysis was utilized for coarse grained fresh rock samples like gabbros. Experiments were conducted at the SKAT texture goniometer at the Frank Laboratory for Neutron Physics (FLNP) in Dubna, Russia. This instrument is especially suited for large sample volumes necessary for coarse-grained rocks. Finer grained samples were measured using synchrotron radiation at beamline ID11 at the European Synchrotron Research Facility (ESRF) in Grenoble, France. To compensate for the small beam size of ~1 mm, several slices of the samples were measured in transmission, i.e. measuring the full sample diameter of 15 – 20 mm. Data of both methods are analyzed using Rietveld Texture Analysis leading to the calculation of an orientation distribution function (ODF) of the certain mineral phases. The ODF is then combined with single crystal elastic constants to model the elastic anisotropy of the rocks. First results show no or weak texture for gabbro, with probably magmatically aligned plagioclase crystals causing the weak texture. This results in a weak elastic anisotropy. Serpentinites so far analyzed show only a weak texture and resulting elastic anisotropy, which might be due to the unconventional lattice disorder of some serpentine minerals. Talc-amphibole-chlorite schists however, show a strong texture of the included phyllosilicates, probably a result of distinct shear zones. This generates a strong elastic anisotropy of these rocks. The results show that seismic anisotropy of rocks formed at slow-spreading ridges is very heterogeneous, with high elastic anisotropy in rocks which might be significant for localized deformation and low elastic anisotropy in fresh or non-deformational alterated rocks. This has to be discussed with regard to seismic tomography data from slow-spreading ridges, which shows generally lower elastic anisotropy than for oceanic crust created at fast-spreading ridges.

Geological and tectonical challenges for the construction of a railway line and a cross-border Ore Mountains base tunnel (SN-CZ), INTERREG V project

1 1 1 Sabine Kulikov , Ottomar Krentz , Elisabeth Seidel

1Saxon State Office of Environment, Agriculture and Geology, Dep. Geology, Freiberg, Germany, [email protected]

The actual railway line between Dresden (Germany) and Praha (Czech Republic) runs through the Elbe Valley which acts like a bottleneck. To handle the growing volume of freight traffic and reduce the travel time also for passenger traffic, a new railway line is planned outside the valley and therefore through the eastern part of the Erzgebirge (Ore Mountains), dominantly as an about 27 km long base tunnel. Besides, this route has further advantages like reduce of the thread by floods or noise pollution for residents and visitors. The Project INTERREG V is a corporation between the Czech Railways, the Czech Geological Survey, the Saxon State Ministry for Economic Affairs, Labour and Transport (SMWA), the Uni- versity of Jana Evangelisty Ústí nad Labem, and the Geological Survey of Saxony (part of the Saxon State Office of Environment, Agriculture and Geology). After a comprehensive data research, geophysical and geotechnical investigations were run since 2011 and included geoelectric and seismic measurements, a 3D modelling of smaller subsections of the working area, and finally the compilation of a cross-border geological map. Besides the geotechnical challenging areas of the Elbtalschiefergebirge in NW or the Erzge- birgsabbruch in SE, the area near the Czech/German border needs further investigations. This area is dominated by gneisses of the eastern Erzgebirge and crosscut by faults of different ages (Paleozoic – Cenozoic). Since 2017 further seismic sections were measured to detect complex fault zones, like the SE striking Petrovice-Döbra Zone (PDZ). According to geoelectrical investigations the PDZ is a NE dipping fault zone of several hundred meters thickness with brecciated Quartz and Fluorite/ Bar- ite mineralization. The planned railway tunnel crosses directly the intersection of the PDZ and the NNE striking Gottleuba Valley, south of the Gottleuba water reservoir. Due to the new results of seismic measurements the Gottleuba Valley is also considered as fault zone. Therefore, the complicated fault inventory, especially along the intersection has to be regarded during the railway line construction. The contribution will present how the complex geological situation within the eastern Erzgebirge forces the planning preparation.

Fig. 1: Map of the working area (black dotted – railway; black lines – faults; orange shaded area – Petro- vice-Döbra Zone; yellow shaded area - Gottleuba Zone; blue – seismic profiles; red circle – area under investigation).

Shallow subduction channel deformation at the Costa Rica erosive convergent continental margin: frictional behavior of subduction input sediments

R. M. Kurzawski1,2, A. R. Niemeijer3, M. Stipp4, D. Charpentier5, J. H. Behrmann1, C. J. Spiers3

1GEOMAR Helmholtz Centre for Ozean Research Kiel, Kiel, Germany, [email protected] 2Institute of Geosciences, University of Kiel (CAU), Kiel, Germany 3HPT-Laboratory, Utrecht University, Utrecht, The Netherlands 4Institute of Geology, University of Innsbruck, Innsbruck, Austria 5Université de Franche-Comté, Besancon Cedex, France

The Costa Rica Seismogenesis Project (CRISP; IODP Expeditions 334 and 344) was designed to study fault zone behavior during earthquake nucleation and rupture propagation at a convergent continental margin characterized by tectonic erosion. In particular, lithological controls on the onset of seismicity at the updip limit of the seismogenic zone were in the focus of attention. The CRISP study area is located offshore Osa Peninsula (Costa Rica), where active and long-lived subduction erosion occurs along the Middle America Trench. This area is characterized by low sediment supply, fast convergence rate, abundant plate interface seismicity, and a change in subducting plate relief along strike. The spectrum of slip modes occurring along shallow portions of the plate boundary décollement in subduction zones includes aseismic slip, slow slip, and seismogenic slip. The factors that control slip modes directly influence the hazard potential of subduction zones for generating large magnitude earthquakes and tsunamis. Here, we report on results from hydrothermal rotary shear experiments conducted on simulated fault gouges prepared from CRISP samples. The velocity dependence of friction was explored using all major lithologies, and covering a wide range of conditions representative for the initial stages of subduction. Temperature, effective normal stress, and pore fluid pressure were varied systematically up to 140 °C, 110 MPa and 120 MPa respectively. Sliding velocities up to 100 µm/s, relevant for earthquake rupture nucleation and slow slip, were investigated. The only sediment type that produced frictional instabilities (i.e. laboratory earthquakes) was the calcareous ooze carried by the incoming Cocos Plate, which by virtue of its slip weakening behaviour is also a likely candidate for triggering slow slip events. We evaluate this mechanism of producing unstable slow slip and consider alternatives. Locking and unlocking of plate boundary megathrusts are not only related to variations in pore fluid pressure, but may also depend on the presence of pelagic carbonate- rich lithologies. Subduction systems containing such input are likely low-latitude, with buoyant (i.e. young and/or thick) lower plates.

Peak temperatures in the Seidlwinkl-Rote Wand nappe (Central Tauern Window, Eastern Alps) determined by Raman spectroscopy on carbonaceous matter

Tim Langner1, Philip Groß1, Jan Pleuger1, Martina Menneken1, Timm John1, Mark R. Handy1

1Freie Universität Berlin, Institut für Geologische Wissenschaften, Berlin, Germany, [email protected]

The central Tauern Window exposes a section across nappes assembled from the former Pen- ninic ocean and adjacent European margin. From bottom to top, these are the Sonnblick- Romate nappe (European basement and post-Variscan cover), the Trogereck and Seidlwinkl- Rote Wand nappes (mostly Mesozoic sediments from the distal European margin), and the Glockner nappe (mostly Cretaceous sediments, greenschist, and serpentinite from the Penninic ocean). The Seidlwinkl-Rote Wand nappe forms a north-closing sheath fold (Seidlwinkl fold) and locally overlies rocks of the Glockner nappe that were infolded from above. The Seidlwinkl-Rote Wand nappe reached peak metamorphic conditions of c. 1.7 GPa/570 °C (Dachs & Proyer, 2001) at c. 39 Ma (Kurz et al., 2008). According to the same authors, metamorphism in the Glockner nappe peaked a bit earlier (c. 42 Ma) and under somewhat higher conditions of 2.0 GPa/600 °C. In both nappes, high-pressure (HP) metamorphism was documented only from a few outcrops. The absence of HP relicts in large parts of the nappe may be attributed to the lack of bulk compositions that are suitable for producing mineral assemblages characteristic of HP metamorphism. Since published PT paths show that the temperature peak in the Seidlwinkl-Rote Wand and Glockner nappes was reached shortly after the pressure peak (Kurz et al., 2008), the pattern of peak temperatures is expected to largely reflect the post-HP deformation of the nappes. Therefore, we investigated samples collected along two profiles through the Seidlwinkl-Rote Wand nappe and neighbouring units by Raman spectroscopy of carbonaceous material (RSCM). Together with some additional samples, these provide a first step to establishing this pattern. Peak temperature estimates were calculated using the calibration of Aoya et al. (2010). Along the southern profile, peak temperatures decrease from the Sonnblick-Romate nappe (c. 480°) to the Seidlwinkl-Rote Wand nappe (c. 460 °C). A similar and even more pronounced trend (from 490 °C to 430 °C) was observed along the eastern part of the northern profile in the Trogereck nappe. In the western part of this profile, temperatures increase to c. 500°C within the Seid- lwinkl-Rote Wand nappe and decrease again somewhat in the overlying Glockner nappe (c. 460 °C). Additional samples taken in the north of the study area yielded significantly lower temperatures both for the Seidlwinkl-Rote Wand nappe and the cover of the Seidlwinkl-Romate nappe (c. 400 °C). This distribution of peak temperatures is compatible with the emplacement of the Seidlwinkl- Rote Wand nappe along a thrust in the inverted limb of the Seidlwinkl sheath fold, while displacement between the Seidlwinkl-Rote Wand nappe and the Sonnblick-Romate nappe in the front of the Seidlwinkl fold was minor or non-existant at the time of the peak temperature. We speculate that the kinematics of the Seidlwinkl-Rote Wand nappe was similar to that of fold nappe formation described by Escher and Beaumont (1997). References Aoya, M., Kouketsu, Y., Endo, S., Shimizu, H., Mizukami, T., Nakamura, D., & Wallsi, S., (2010). Extend- ing the applicability of the Raman carbonaceous-material geothermometer using data from contact metamorphic rocks. J. metamorphic. Geol., 28: 895-914. Dachs, E., & Proyer, A., (2001). Relics of high-pressure metamorphism from the Grossglockner region, Hohe Tauern, Austria: Paragenetic evolution and PT-paths of retrogressed eclogites. Eur. J. Mineral., 13: 67-86. Kurz, W., Handler, R., & Bertoldi, C., (2008). Tracing the exhumation of the Eclogite Zone (Tauern Win- dow, Eastern Alps) by 40Ar/39Ar dating of white mica in eclogites. Swiss J. Geosci., 101: 191-S206. Escher, A., & Beaumont, C., (1997). Formation, burial and exhumation of basement nappes at crustal scale: a geometric model based on the Western Swiss-Italian Alps. J. Struct. Geol., 19: 955-974.

Subgrain development in experimentally deformed rock salt

1 1,2 1 3 Jolien Linckens , Johanna Heeb , Gernold zulauf , Michael Mertineit

1Institut für Geowissenschaften, Goethe Universität Frankfurt am Main, Frankfurt am Main, Germany, [email protected]; [email protected]; [email protected] 2Now at: Department of Applied Geology, Curtin University, Perth, Australia 3Bundesanstalt für Geowissenschaften und Rohstoffen (BGR), Hannover, Germany, [email protected]

Subgrain boundaries, with a low-angle misorientation of up to ~10°, form in metals and minerals during deformation dominated by dislocation creep when recovery takes place. The size of the subgrains in rock salt is related to the differential stress (Carter et al., 1993) and an increase in misorientation angle of the subgrain boundaries can be correlated with an increase in strain (Pennock et al., 2004). These experimentally derived characteristics of subgrains are important in their use as paleopiezometer and, possibly, to estimate the finite strain of naturally deformed rock salt. However, during deformation, different types of low angle misorientation boundaries develop that evolve differently with strain (e.g. Drury and Pennock, 2007). In rock salt, deformation band boundaries (also called orientation splitting boundaries) can form during deformation (e.g. Drury and Pennock, 2007; Linckens et al., 2016). A detailed study relating the active slip systems and initial grain orientation to the formation and characteristics of deformation bands and their boundaries is lacking. To close this gap, we performed experimental deformation experiments on natural coarse grained (average grain size of 2.0-2.8 mm) rock salt from the z2HS unit (Hauptsalz of the second Zechstein cycle) of the Asse mine, Germany. Cuboid samples (6.0*6.0*3.5 cm, 6.0*6.0*4.5 and 4.5*4.5*4.5 cm) were deformed under bulk plane and constrictional strain at a temperature of 345°C and a strain rate of ~10-7s-1, until the desired strain was attained (maximum shortening strain (εZ) of -36%). Before and after deformation microstructural analysis with the optical microscope and SEM in combination with EBSD was conducted on selected thick sections.

Some grains in the initial samples show subgrains, with an average size of around 200 µm and a misorientation mainly between 1-5°. After deformation most grains contain equiaxed subgrains with an average size varying from 33 to 97 µm with a large standard deviation ranging from 23 to 55 µm. These equiaxed subgrains have relatively small misorientations mainly between 1-5°, with some segments between 5-10° and some >10°. In all experiments some grains contain an alignment of subgrain boundaries throughout the grain, forming bands. The subgrains within the bands are bigger than those outside the bands. The EBSD misorientation data indicates that in most grains, these aligned boundaries have large (>10°) misorientations, in some cases >30°. Some subgrain sized new grains are formed within the deformation bands. The pole figures show a continuous change in orientation from outside to inside the band. The analyses demonstrate that within one grain and one sample, a large variation occurs in subgrain size, misorientation angles, variations in orientations, and formation of high angle grain boundaries. The variations have consequences for the use of the subgrain paleopiezometer in natural samples and for our understanding of dynamic recrystallization in rock salt.

References Carter, N. L., Horseman, S. T. Russell, J. E., & Handin, J., (1993). Rheology of rocksalt. J. of Struc. Geol., 15(9): 1257–1271. Drury, M. R., & Pennock, G. M., (2007). Subgrain Rotation Recrystallization in Minerals, Mater. Sci. Forum, 550: 95–104. Linckens, J., Zulauf, G., & Hammer, J., (2016). Experimental deformation of coarse-grained rock salt to high strain. J. of Geophys. Res. Solid Earth, 2010: 6150–6171. Pennock, G. M., Drury, M. R., & Spiers, C. J., (2004). Investigation of subgrain rotation recrystallization in dry polycrystalline NaCl. Mater. Sci. Forum, 470: 597–602.

Evolution of pull-apart basins with several fault strands based on particle-based modeling

Yuan Liu1, Heinz Konietzky1

1Geotechnical Institute, TU Bergakademie Freiberg, Freiberg, Germany, [email protected]

Pull-apart basins are surficial depressions that form in releasing sidesteps or bends where the strike-slip faults have the same sense of slip and stepping (Fossen, 2016). A pull-apart basin can develop from releasing sidesteps with two master faults (Mann et al., 1983) as well as with several fault strands. In this study, a scale-independent modeling approach based on the Discrete Element Method is established to simulate crack propagation and pull-apart basin evolution in releasing sidesteps with several fault strands. The numerical models with four predefined strike-slip faults in 30° underlapping, 90° non-overlapping, 150° overlapping releasing sidestep systems show the same trends of crack propagation and pull-apart basin evolution. At the initial stage, Riedel-shears begin to occur at a low angle clockwise to the trace of the master faults. As slip increases, the Riedel-shears propagate. Later on, basin sidewalls form, and three extensional depressions appear. With more offsets, the depressions coalesce into composite basins, forming a large basin. The basin length is comparable to the strike-slip displacement which corresponds to the evolution stage. The basin width is the sum of the separations between the master strike-slip faults. Modeling results are compared with basins in nature. The Secretary-Nancy basin at the southern segments of the Alpine Fault in New Zealand (Barnes et al., 2005) and the Koehn Lake basin on the Garlock Fault in southern California (Aydin & Nur, 1982) show the formation of a wide composite basin with increasing strike-slip offset which is similar to the predictions of the numerical models with several fault strands. For releasing sidesteps with two master faults, basin width does not change significantly and remains fixed by the separation of the master strike-slip faults. However, basin width could become larger when there are more than two strands of master faults. The natural examples of the Secretary-Nancy basin and the Koehn Lake basin show how this takes place. Our numerical modeling reproduced the processes. Moreover, the 30° underlapping model with several pure strike-slip fault strands shows the tendency of the en-echelon strike-slip faults to straighten themselves because of the formation of the diagonal faults in each small pull-apart.

References Aydin, A., & Nur, A., (1982). Evolution of pull-apart basins and their scale independence, Tectonics, 1(1): 91-105. Barnes, P. M., Sutherland, R., & Delteil, J., (2005). Strike-slip structure and sedimentary basins of the southern Alpine Fault, Fiordland, New Zealand. Geological Society of America Bulletin, 117: 411-435. Fossen, H., (2016): Structural geology. Cambridge University Press, New York. Mann, P., Hempton, M. R., Bradley, D. C., & Burke, K., (1983). Development of Pull-Apart Basins. The Journal of Geology, 91: 529-554.

Quantifying the timing and rate of exhumation of the Molasse basin by combining structural and thermochronological data with thermal history and kinematic models

Sarah Louis1, Christoph von Hagke1, Elco Luijendijk2

1RWTH Aachen University, Endogene Dynamik, [email protected], chris- [email protected] 2Georg-August University Göttingen, Structural Geology and Geodynamics, [email protected]

Since the Neogene, the alpine foreland basin has experienced 2-3 km of exhumation. The exhumation of the Subalpine Molasse as well as the Plateau Molasse can neither be explained by deformation and tectonic uplift and erosion nor by tectonic transport up the basement ramp alone. Existing thermochronology and vitrinite reflectance data from the western Molasse basin in combination with a new thermal history model (PyBasin) shows that the timing of exhumation cannot be constrained. Both proximal and distal parts of the Molasse basin were extensively uplifted and eroded. This points to a long-wave exhumation signal that cannot be explained by tectonic processes and is likely related to mantle dynamics. While the western part of the Molasse Basin is well studied and sampled, there is little information on the thermal history of the central and eastern parts of the Molasse Basin. Timing and rate of exhumation in the central and eastern Molasse Basin will be quantified by collecting samples along several profiles and generating low-temperature thermochronology (apatite- (U- Th)/He and fission-track) and vitrinite reflectance data. This dataset will be used for calibrating the thermal history model and for quantifying the timing and rate of exhumation in the Molasse Basin. To quantify the contribution of tectonic exhumation, we will compile structural information along our selected profiles and use this for kinematic modelling. We compare our results to new geophysical data and geodynamic models of slab-dynamics during the late stage of the Alpine orogeny that will be generated in the SPP program Mountain building in 4D. By studying the poorly sampled central and eastern Molasse basin we aim to generate a data set and a numerical model that can explain the long-wave exhumation signal observed in the western Molasse basin.

Contrasting extension directions along-strike a chain of Miocene metamorphic core complexes at the southern rim of the Pannonian Basin: the quest for a plausible kinematic model

Georg Löwe1, Sami Nabhan1, Kamil Ustaszewski1

1Friedrich-Schiller-University Jena, Institute for Geosciences, Jena, Germany, [email protected]

The Sava Zone represents a suturing accretionary prism separating the northernmost Adria- derived thrust sheets of the Dinarides in a lower plate position from Europe-derived units in the hanging wall. It hosts a Late Cretaceous succession consisting of predominant trench fill sediments and subordinate bimodal igneous rocks. Both Sava Zone and northernmost Dinarides thrusts sheets feature numerous metamorphic core complexes (MCC’s) that were exhumed in Late Oligocene to Middle Miocene times, concomitant with the opening of the northerly adjacent Pannonian Basin. We studied four MCC’s in Bosnia and Hercegovina and Serbia that are aligned ± along-strike (Fig. 1) and which expose different structural levels of metamorphosed Sava Zone (Prosara and Motajica MCC’s) and distalmost Adriatic margin series (Cer and Bukulja MCC’s). Exhumation occurred along one or more low-angle detachments that likely reactivated suturing Maastrichtian thrusts. Prosara MCC exposes a structural level deformed at mid- to lower greenschist-facies conditions. Stretching lineations and shear-sense criteria indicate dominant N-S extension. Motajica MCC exposes structurally deeper parts, containing amphibolite-facies rocks intruded by a Late Oligocene granitoid. Kinematic indicators suggest dominantly E-W-directed extension. Cer MMC in western Serbia forms part of the Jadar-Kopaonik thrust sheet (i. e. distal Adriatic passive margin; Schmid et al., 2008) and is located in a more external position with respect to the Sava Zone. Exhumation of an Oligocene multi-stage intrusion together with an upper greenschist- to lower amphibolite-facies succession of Late Paleozoic metapelites took place along a N-dipping low-angle detachment associated with dominantly Top-N sense of shear. Deformed andalusite-blasts in metapelites in contact with igneous rocks suggest a contact- metamorphic overprint during shear. RSCM-thermometry data on garnet- and staurolite-bearing mica schists reveal metamorphic temperatures of approx. 550 °C. Bukulja MCC, located still further east, also consists of a central intrusion, which was exhumed along with its envelope of amphibolite-grade metasediments, but under dominantly E-directed senses of shear. Our observations of strongly differing, but very likely age-equivalent extension directions (i.e. N-S vs. E- W) in the four MCC’s (Fig. 1) call for a plausible kinematic model. At the crustal scale, the multidirectional extension observed likely reflects oblate strain during Oligo-Miocene crustal thinning along the southern margin of the Pannonian Basin. Fig. 1: Tectonic map showing the locations of the four studied MMC’s and dominant extension directions (After Schmid et al., 2008, modif.).

References Schmid, et al. (2008). The Alpine‐Carpathian‐Dinaridic orogenic system: Correlation and evolution of tectonic units, Swiss J. Geosci.

Styles of Late Cretaceous intraplate shortening in Central Germany - first results from 3D modelling in the Altmark region, Saxony Anhalt

Alexander Malz1, Christoph Nachtweide1, Sophie Emmerlich2

1Landesamt für Geologie und Bergwesen Sachsen-Anhalt, Halle (Saale), Germany [email protected] 2TU Clausthal, Institut für Geologie und Paläontologie, Clausthal-Zellerfeld, Germany

The Late Cretaceous “hercynian” intraplate contraction affected large areas of Central Europe and created a variety of structures of different style. Many of these are due to inversion of basins and (half-)grabens, which originated in several events of distributed extension during Late Triassic and Late Jurassic/Early Cretaceous times. Notably they coexist with large basement-cored uplifts and detached thrust systems resembling structures typically known from fold-thrust-belts in the foreland of orogens. The Altmark region in northern Saxony-Anhalt is a comparatively small (~8000 km2) region that serves as an excellent case study area comprising a full spectrum of structures occuring in a plate’s interior. In our contribution we present various fault zones in the Mesozoic cover of the Altmark area resembling the above mentioned structural spectrum of intraplate contraction. The results are based on a large-scale 3D modelling campaign carried out by the Geological Surveys of northern Germany. In the Altmark area we consulted approximately 6.500 km of interpreted 2D reflection seismic sections and ~700 deep boreholes to construct the existing fault network in 3D. Single fault strands in seismic sections were correlated to complex fault zones. Fault zone kinematics were derived from thickness distributions of selected stratigraphic units derived from regional depth maps. Our results show that the Altmark area can be subdivided in areas of different tectonic style: (1) thick-skinned basement uplifts in the south, (2) an approximately 20 km wide dominantly thin-skinned fold-thrust-belt in their northern foreland and (3) a large area of basin and graben inversion in the northeast and northwest. This subdivision in combination with our “catalogue of fault zones” will help to better understand the structural configuration and the kinematics of intraplate contraction in Central Germany

Fig. 1: Overview of northern Saxony-Anhalt with interpreted regions of different tectonic style. 82

Paleoseismology using bedrock fault planes

Silke Mechernich1, Sascha Schneiderwind2, Jack Mason2, Peter Biermanns2, Benjamin Schmitz3, Ioannis Papanikolaou4, Kamil Ustaszewski3, Klaus Reicherter2

1Institute of Geology and Mineralogy, University of Cologne, Zülpicher Strasse 49b, 50674 Köln, Germany ([email protected]). 2Institute of Neotectonics and Natural Hazards, RWTH Aachen University, Lochnerstr. 4-20, 52064 Aachen, Germany. 3Institut für Geowissenschaften, Friedrich Schiller Universität Jena, Burgweg 11, 07749 Jena, Germany. 4Laboratory of Mineralogy and Geology, Department of Natural Resources Development and Agricultural Engineering, Agricultural University of Athens, 75 Iera Odos Str., 11855 Athens, Greece.

Coseismic slip on bedrock fault planes was recently observed on several faults, for instance during the 2016 Apennine earthquake sequence (24.08.2016 Mw 6.0, 26.10.2016 Mw 5.9, 30.10.2016 Mw 6.5) and the 1981 Alkyonides earthquake sequence (24.02.1981 Mw 6.7, 24.02.1981 Mw 6.4, 04.03.1981 Mw 6.3). These earthquakes resulted in the exhumation of the fault planes by several decimeters, which can be easily identified by differences in color and roughness properties. This study uses different weathering indicators to reveal distinct stripes that are related to past exhumation events on limestone fault planes in Greece and Montenegro. For instance, the central part of the 25-km-long Pisia fault (eastern Gulf of Corinth) shows a clear stripe of contrasting color whose height is in accordance with the reported exhumation of ~0.6-1.5 m during the 1981 Alkyonides earthquake sequence. Above this stripe, we observed five to seven additional stripes of 25-100 cm height. They were detected by color changes, lichen colonization, karst features (pitting and solution flute termination), and by terrestrial laser scanning data analyses of both, near-infrared backscatter signal intensity and high precision surface roughness. These criteria revealed similar horizontal stripes on the fault planes of the ~11-km-long Lastros fault (Crete), the ~18-km-long Spili fault (Crete), and the ~10-km-long Bar fault (Montenegro). For all three faults, up to three stripes were identified that indicate fault plane exhumations in the range of 10-40 cm. The stripes are interpreted as indicators of coseismic slip events that stepwise exhumed the respective fault planes. A continuous mapping of distinct coseismic exhumation steps along the strike of the fault, allows an estimate of the paleoearthquake magnitudes using empiric correlations. The timing of earthquake exhumation can be constrained using cosmogenic 36Cl concentration modeling. In the case of the Pisia fault, paleoearthquake ages of ~2.0 kyr (EQ2), ~3.1 kyr (EQ3), ~4.4 kyr (EQ4/4a,b), ~6.0 kyr (EQ5), and ~7.3 kyr (EQ6,6a,b) are obtained. These ages correspond to a slip rate of 0.5-0.6 mm/yr. The age uncertainties are ~±0.7 kyr, which is in the same range as age uncertainties in traditional paleoseismic trenches. Hence, we suggest considering bedrock fault plane observations as a valuable option to reconstruct the Holocene seismic history.

Tracing trails of fault activity along a major shear zone in Calabria, Southern Italy – Implications for the geodynamic evolution and for methodological aspects of (U-Th-Sm)/He-thermochronology

Katrin Meier1, Cornelia Spiegel1, Patrick Monien1, Andreas Klügel1, Vera Kolb1

1Universität Bremen, Fachbereich Geowissenschaften, Bremen, Germany

The Calabria-Peloritani Terrane represents a peri-Mediterranean orogenic Alpine nappe system and consists of the Sila massif and Catena Costiera, the Serre and Aspromonte massif with the Peloritani Mountains in Siciliy. In the northern Serre, Calabria, a major shear zone is exposed, adding an alpine overprint to the Variscan basement. This zone is called the Curinga-Girifalco Line and separates granulite-facies metapelitic rocks from underlying amphibolite facies orthogneisses. The contact comprises c. 200 m thick mylonitic rocks, which have locally experienced a later cataclasitic overprint. To further constrain the thermal history of the area and to derive the geodynamic history, we directly sampled the fault zones, as well as their ± undeformed protoliths from the overlying and underlying units. Apatites from these samples were separated, analysed for their chemical compositions, and dated by (U-Th-Sm)/He thermochronology. In agreement with the expected thermal signature of a normal fault, the hanging wall revealed older cooling ages (15.6±3.6 Ma) than the footwall of the shear zone (14.1±3.0 Ma). Thermal history modeling of our apatite (U-Th-Sm)/He dates in combination with previously published fission track data by Thomson (1994, 1998) indicates rapid uplift of the footwall in early Miocene and slightly slower uplift of the hanging wall from late Oligocene to early Miocene. A common evolution and thus cessation of fault activity from mid to late Miocene time (13 Ma – 11 Ma) onwards is derived. We propose an assignment of normal fault activity with the opening of the Algerian-Provençal basin coupled with the rotation of the Calabria- Peloritani Terrane in late Oligocene to early Miocene times. While the ensuing collision with the African plate and the Sicilian margin from early Miocene onwards suggests a participation in the uplift. Coinciding with the separation of Corsica-Sardinia from the Calabria-Peloritani Terrane due to incipient opening of the Tyrrhenian basin from mid-Miocene times on the fault activity terminates (Bonardi et al., 2001). Our data revealed furthermore that the rocks taken directly from the shear zone are consistently younger than those from the undeformed protoliths (mean apatite (U-Th-Sm)/He age of 9.5±5.9 Ma (hanging wall) and 11.9±4.0 Ma (footwall)). Chemical compositions of apatites from the deformed rocks of the shear zone also differ strongly from the apatite compositions of their undeformed protoliths. We therefore suggest that the apatite crystals from the shear zones underwent dissolution and precipitation processes, and that these processes controlled the resetting of the apatite (U-Th-Sm)/He system rather than thermal processes. If our interpretation is correct, this would have significant impact on future understanding of (U-Th-Sm)/He thermochronological data.

References Bonardi, G, Cavazza, W, Perrone, V, & Rossi, S. (2001). Calabria-Peloritani terrane and the northern Ionian Sea. In: Vai GB, Martini IP (eds) Anatomy of an Orogen: the Apennines and Adjacent Mediterra- nean Basins. Kluwer Academic Publishers, Dordrecht:287-206 Thomson, S. N. (1994). Fission track analysis of the crystalline basement rocks of the Calabrian Arc, southern Italy: evidence for Oligo-Miocene late-orogenic extension and erosion. Tectonophysics 238:331- 352 Thomson, S. N. (1998). Assessing the nature of tectonic contacts using fission-track thermochronology: an example from the Calabrian Arc, southern Italy. Terra Nova 10:32-36.

Local and regional controls on the maturation state of carbonaceous matter in the Barberton Greenstone Belt, South Africa.

Sami Nabhan1, Christoph Heubeck1

1FSU Jena, Institut für Geowissenschaften, Jena, Germany, [email protected]

The volcanic-sedimentary fill of the 3.57 - 3.21 Ga Barberton Greenstone Belt (BGB) of southern Africa is affected by hydrothermal, metasomatic, metamorphic and magmatic events. While the BGB’s center shows a regional lower-greenschist facies metamorphism, contact metamorphism reaching amphibolite-facies equivalent temperatures dominates its margins. Geothermometers, determined by Raman spectroscopy of carbonaceous matter (CM) from metasediments, contribute important information to identify different processes of thermal alteration. The uppermost unit of the BGB, the up to 3.5 km thick, 3.2 Ga old Moodies Group is dominated by siliciclastic metasediments of shallow to non-marin facies. These conglomerates, sandstones and shales are mostly preserved as quarzites still showing their original sedimentary structures such as dessication cracks, ripples, cross-bedding and imbrication. Furthermore, CM-rich strucktures like fossilized biomats and paleosols are widely preserved and can be used to estimate metamorphic peak temperature variations with a high spatial resolution. Calculated peak temperatures range from 330°C to 470±50°C and are independent of stratigraphic position since the Greenstone belt is dominated by SW-NE trending folds and faults. However, the temperature range can be seperated into three domains. The lowest reaching from 330°C to 360°C clearly mirrors the regional metamorphic overprint wheras the second T-window of 400°C to 420°C can be linked to contact metamorphism. The highest temperatures of 450°C to 470°C can only be observed in silicified domains within samples that otherwise show temperatures consistent with the contact metamorpic overprint. This implies that the position of the CM in the samples is of utmost importance, especially if two or more populations of CM-maturity are present within one sample (Fig.1).

Fig. 1: Maturity dependance of CM. A Thin section image of silica cement within a coarse grained sandstone, the frame outlines the area shown in B where the silicified area is coated (dark bands) by, and contains inclusions of, CM. The mappings C and D illustrate the intensity of the two most prominent CM peaks as shown in the two spectra in E. The ratio of the areas covered by the peaks depends on the maturity of the CM and shows mostly a linear correlation to its thermal alteration. The lower spectra is representative for the CM-lamination below the silicified area and indicates a maximum thermal alteration of ~400°C, wheras the upper spectrum of an CM inclusion whithin the silicified area indicates a maximum thermal alteration of ~460°C. 85

The geological evolution of the south-west margin of the East European Platform: from Paleozoic fold-thrust belt to Miocene Foredeep

Mykhaylo Nakapelyukh1, Yuriy Yakibyuk1, Ivan Kuts1, Anna Murovska2

1Zakhidnadraservice, Lviv, Ukraine, [email protected] 2Institute of Geophysics, Kyiv, Ukraine

The SW margin of East European Platform (EEP) comprises an ancient fold-thrust belt that has finally evolved into a Foredeep with the history of shortenings and extensions that were perpendicular to the orogenic strike. Herein, we constrain the evolution of the Ukrainian part of the Carpathians Foredeep by cross-section balancing and decompaction of reinterpreted and recently acquired seismic reflection data. Four main stages are distinguished including: (1) Upper Carboniferous shortening, (2) Jurassic passive continental margin extension, (3) Paleocene compression and (4) Middle–Upper Miocene extension. Variscan (Upper Carboniferous) deformation structures of the pre-Permian sedimentary rocks are interpreted as a thin-skinned fold-thrust belt above the basal detachment (Krzywiec et al., 2017); it represents a crystalline surface of EEP which descents gradually southwestwards under the Carpathians orogen. Northwest trending, large thrust faults within the Paleozoic fold- thrust belt were mapped by drilling and seismic data. Most of these faults dip ~25–40° SW and have a vertical offset of hundreds to thousands of meters, which caused ~20 km of thin-skinned shortening. Paleozoic shortening was followed by intensive erosion and tectonic quiescence. The Pangea collapse triggered extensional processes within the SW margin of EEP. A Lower–Middle Jurassic terrigenous sedimentary pile up to 3 km thick indicates reactivation of Paleozoic thrusts into low-angle normal faults. During Upper Jurassic–Cretaceous, marine transgression spread further north and covered a vast area with prevailing shallow-water carbonate facies. Paleocene shortening caused significant uplift of the studied region. Jurassic normal faults were transformed into reverse ones; as a result, Cretaceous and Jurassic deposits within the most exhumed blocks were completely eroded. Two distinct canyons up to 1.7 km deep incised Mesozoic and Paleozoic rocks and transported sediment material into the Carpathians basin. The terrestrial condition remained until the end of Middle Miocene. Propagation of the Carpathians fold-thrust belt promoted subsidence and marine transgression to the adjacent margin of EEP. The upper Badenian evaporites (~13.6 Ma)—mainly gypsum and anhydrite up to 60 m thick—covered Paleozoic and Mesozoic rocks by an almost continuous sedimentary cover (de Leeuw et al., 2010). At ~ 13 Ma, an extension event reactivated the Paleozoic–Mesozoic fault array and led to deposition of 3.5−5.5 km of sediments due to tectonic loading. The youngest deposits in the Foredeep assessed as ~10 Ma indicate the orogeny termination. The extremely rapid sediment deposition on average rate of 1.5 km/Ma, caused significant syn-subsidence compaction, which had strong influence on sediment deformation.

References Krzywiec, P., Gągała, Ł., Mazur, S., Słonka, Ł., Kufrasa, M., Malinowski, M., Pietsch, K., & Golonka, J. (2017). Variscan deformation along the Teisseyre-Tornquist Zone in SE Poland: Thick-skinned structural inheritance or thin-skinned thrusting?, Tectonophysics, doi: 10.1016/j.tecto.2017.06.008 de Leeuw, A., Bukowski, K., Krijgsman, W., & Kuiper, K.F. (2010). Age of the Badenian salinity crisis; impact of Miocene climate variability on the circum-Mediterranean region. Geology 38, 715–718

Post-Triassic succession of fault kinematics along the Lichtenau Graben and the implications within the regional tectonic framework

Payman Navabpour1, Madeline Richter1, Jonas Kley2, Christoph Heubeck1, Thomas Voigt1

1University of Jena, Institute of Geoscience, Jena, Germany 2University of Göttingen, Geoscience Center, Göttingen, Germany

The study area is located in the central German platform a prominent structure of which is the Lichtenau Graben. The graben has a strike of c. N030 and continues towards the north into the similarly oriented Leinetal Graben. At their junction, both grabens interfere with the NW-SE- striking Eichenberg-Gotha-Saalfeld fault zone of the Thuringian Basin. Here, we address the kinematic evolution of the Lichtenau Graben for the first time based on fracture pattern analysis through stereographic projections and stress tensor inversion of fault- slip data collected mostly from the mid-Triassic Muschelkalk limestone. Field based observations of kinematic change indicators on fault slickensides and relative tilt geometries between the fractures and strata suggest a succession of fault reactivation. (1) An early dextral strike slip motion could be recognized along the graben indicating a N065 σ1. (2) A normal faulting regime is dominant along the graben and indicates a N115 σ3. (3) A younger sinistral strike-slip motion occurred along the graben indicating a N140 σ1. A thrust faulting regime also indicates a NW- SE-trending σ1 suggesting reactivation of preferably oriented pre-existing fractures, i.e. tilted strata and normal faults, under the youngest stress field. The age of affected rocks indicates that the succession of fault reactivation belongs to post mid- Triassic events. The early dextral motion along the graben suggests that this structure should have existed within the underlying rocks prior to the normal reactivation. This is consistent with the NNE-SSW-trending Eichsfeld Swell that controlled Lower Triassic Buntsandstein thickness. The NW-SE-striking normal faults of Thuringia could not be found in the study area, which may indicate that those fracture kinematics have not existed or been obliterated by successive reactivation. A synthesis of data within the structural framework of the central German platform suggests that the normal and sinistral fault reactivation along the graben could be consistent with a change in stress regime from the European Cenozoic Rift System to the present day NW-SE- trending maximum horizontal shortening (SHmax).

Structural and kinematic constrains on the exhumation of the central Menderes Massif along the Büyük Menderes detachment, western Turkey

Nils-Peter Nilius1*, Christoph Glotzbach2, Andreas Wölfler1, István Dunkl5, Cüneyt Akal4, Caroline Heineke3, Ralf Hetzel3, Andrea Hampel1

1Institute of Geology, Leibniz University of Hannover, Callinstraße 30, 30167 Hannover, Germany 2Department for Geology und Geodynamics, University of Tübingen, Wilhelmstraße 56, 72074 Tübingen, Germany 3Institute of Geology and Palaeontology, University of Münster, Corrensstraße 24, 48149 Münster, Germany 4Dokuz Eylül University, Engineering Faculty, Department of Geological Engineering, Tınaztepe Campus, Buca, 35160 Izmir, Turkey 5University of Göttingen, Geoscience Center, Sedimentology and Environment Geology, Goldschmidstraße 3, 37077 Göttingen, Germany

Commencing in the late Oligocene to early Miocene, the Alpine contractional regime, which formed the Anatolide nappe stack in western Turkey, changed into a sustained regime of continental extension, leading to the exhumation of the Menderes Massif. The extension was accommodated by low-angle detachment faults and led to the formation of two E-W striking graben systems which separate the central Menderes Massif from the northern and southern submassifs. The late Cenozoic exhumation of the central Menderes Massif was accommodated by the north-dipping Gediz detachment and the south-dipping Büyük Menderes detachment and led to the exhumation of the Bozdaǧ and Aydın mountain ranges, respectively. Many of the previous structural and thermochronological studies focused on the evolution of the well exposed Gediz detachment and inferred a similar development for the Büyük Menderes detachment. The concurrent activity of both detachments since the middle Miocene is indicated by thermochronological data (Buscher et al., 2013; Wölfler et al., 2017), which revealed two phases of increased footwall cooling in the middle Miocene and latest Miocene/Pliocene. However, a comprehensive tectonic model on the exhumation of the Aydın range is impeded by the scarcity of field data from structures related to late Cenozoic extension and thermochronological data, which further provide more detailed constraints on the timing and along-strike changes of the Büyük Menderes detachment. Here we present new results from structural and geological mapping, which imply that the Büyük Menderes detachment consists of two overlapping fault segments, and not a single continuous detachment fault. New zircon and apatite (U-Th)/He and fission track ages in the western part of the Aydın range corroborate the middle and latest Miocene/Pliocene cooling events. Thermo-kinematic modeling revealed exhumation rates of ca. 0.5 km/Myr and a fault slip rate of about 2-3 km/Myr on the eastern segment of the Büyük Menderes detachment during the latest Miocene/Pliocene. High-angle normal faulting on the northern boundary fault of the Büyük Menderes graben is documented by late Pliocene and Quaternary apatite (U-Th)/He-ages.

References Buscher, J.T., Hampel, A., Hetzel, R., Dunkl, I., Glotzbach, C., Struffert, A., Akal, C., & Rätz, M. (2013). Quantifying rates of detachment faulting and erosion in the central Menderes Massif (western Turkey) by thermochronology and cosmogenic 10Be. Journal of the Geological Society, London 170, 669–683.

Wölfler, A., Glotzbach, C., Heineke, C., Nilius, N.P., Hetzel, R., Hampel, A., Akal, C., Dunkl, I., & Christl, M. (2017). Late Cenozoic cooling history of the central Menderes Massif: timing and slip rate of the Büyük Menderes detachment and the relative contribution of normal faulting and erosion to rock exhumation. Tectonophysics 717, 585–598.

The utilization of digital devices for structural geology field mapping

Lucie Novakova1, Terry L. Pavlis2

1IRSM CAS, Prague, Czech Republic, [email protected] 2UTEP, El Paso, Texas, USA, [email protected]

During the last several years, the utilization of smartphones, tablets, and iPhones increased rapidly. These devices are parts of our lives and many people can not imagine their lives without them. On the other hand, they might be very useful tools for geologists in the field. When measuring the big set of data, the usage of classic geological compass might be time- consuming. In contrast, digital devices are very fast and friendly to use. But are they also as precise as the classic compasses? In our study, we did several tests with three devices – a tablet, a smartphone, and an iPhone. We evaluated potential electronic noise effects of the devices in both standard and airplane modes. We tested various applications for smartphones (FieldMove Clino, Rocklogger, Geo Lab Tool, Structural Compass, Mining Compass, eGEO Compass GS, Geo clino for Android) against the classic Freiberg geologic compass. During the experiment, 25 fractures varying in azimuth and dip were measured using both devices (Fig. 1). We also tested 18 smartphones and 5 iPhones with the application FieldMove Clino (Midland Valley 2014) and measured strikes and dips of the planes at least 30 times to obtain relevant statical data sets. A high level of disagreement was observed with discrepancies as high as 80° with azimuthal errors dominant. Analysis of the time series in the data suggests the source of the problem was instability in the magnetic sensor for the smartphone, despite the fact the device passed the initial stability test (Novakova & Pavlis 2017). Generally, measurements with iPhones were more precise than with the smartphones. Some smartphones however provided as good data as iPhones. Presence of a gyroscope seems to correlate with good results.

Fig. 1: Azimuths of the measured planes as measured by different applications installed on the same smartphone, A : Geoclino for Android, B : еGEO Compass GS, C : Russian Mining compass, D : Structural Compass, E : Geo Lab Tool, F : Rocklogger, G : FieldMove Clino ; H : Freiberg compass

References Midland Valley (2014). FieldMove Clino Android User Guide. Novakova, L. & Pavlis, T.-L. (2017). Assessment of the precision of smart phones and tablets for measurement of planar orientations: A case study. J. Str. Geol., 97 : 93-103.

The complex fault pattern in the southern Baltic Sea area reflecting the late Palaeozoic and Mesozoic evolution of the Trans-European Suture Zone (TESZ)

Karsten Obst1, Elisabeth Seidel2, André Deutschmann1, Martin Meschede2

1Geologischer Dienst, LUNG M-V, Goldberger Str. 12, D-18273 Güstrow, Germany, [email protected] 2Ernst-Moritz-Arndt-Universität Greifswald, Institut für Geographie und Geologie, F.-L.-Jahn-Str. 17a, D-17489 Greifswald, Germany

Numerous faults or fault zones, which are mainly NW to NNW oriented, cross the Baltic Sea area between Scania (Sweden) and Bornholm (Denmark) in the north and Rügen (Germany) and Wolin (Poland) in the south. They either belong to the Tornquist Zone and the Tornquist Fan, a north-westward widening zone of dominantly Palaeozoic faults in the transition between the East European Craton and the Western European Platform, or to the complex Western Pomeranian Fault System generated during Mesozoic extensional movements. Reinvestigations of offshore seismic lines acquired during oil and gas exploration in the vicinity of Rügen in the 1980s, enabled a detailed reconstruction of the formation and reactivation of these faults in the northern part of the Trans-European Suture Zone (TESZ). Besides known major faults, new minor faults could be detected. Furthermore, the geological development of different crustal blocks from the Caledonian Avalonia-Baltica collision until the Late Cretaceous- Palaeogene inversion tectonics was studied. Several stages were recognized indicating a polyphase evolution of the area (Deutschmann et al. 2018, Seidel et al. 2018). Post-Caledonian extension led to the formation of the Rügen Basin, filled with shallow marine sediments in the Middle Devonian to lower Carboniferous. This tectonic phase is mainly documented by downfaulting of the Middle Rügen Block along the NW–SE oriented faults of the Tornquist Fan. A compressional tectonic phase in the late Carboniferous, induced by the Variscan orogeny, caused reverse faulting along these NW trending faults, especially at the Wiek Fault System that demarcates the uplifted blocks of the Møn and the Arkona High from the Falster, the Middle Rügen and Wolin blocks. Permian thermal subsidence, which led to the formation of the North German Basin as part of the Central European Basin System, was accompanied by extension and formation of graben systems, e.g. the Gryfice Graben. Transtension during the Mesozoic, mainly initiated by the rifting in the Arctic-North Atlantic region, resulted in the formation of the Western Pomeranian Fault System. This fault system is considered to represent en-echelon faults that developed above the northern part of the TESZ. Compressional movements since the Late Cretaceous led to reverse faulting, which is best documented along the Adler-Kamień Fault Zone by overthrusted Mesozoic strata on the Arkona High and Wolin Block (inversion of the Gryfice Graben), but also visible along the faults of the Wiek Fault System as suggested by a slight flexure in the overlying lowermost part of the Cretaceous. These movements, which were frist triggered by the Pyrenean Orogeny, also led to the uplift of structures, such as the Grimmen High.

References Deutschmann, A., Meschede, M., & Obst, K. (2018). Fault system evolution in the Baltic Sea area west of Rügen, NE Germany. – In Kilhams, B., Kukla, P.A., Mazur, S., McKie, T., Mijnlieff, H. & van Ojik, K. (eds): Mesozoic Resource Potential in the Southern Permian Basin. Geological Society, London, Special Publi- cations (in press). Seidel, E., Meschede, M., & Obst, K. (2018). The Wiek Fault System east of Rügen Island: Origin, tectonic phases and its relation to the Trans-European Suture Zone. – In Kilhams, B., Kukla, P.A., Mazur, S., McKie, T., Mijnlieff, H. & van Ojik, K. (eds) Mesozoic Resource Potential in the Southern Permian Basin. Geological Society, London, Special Publications (published on-line).

Fault database of north-eastern Germany: intention, information sources, content

Karsten Obst1, Sabine Matting1, André Deutschmann1, Jasmaria Wojatschke1

1Geologischer Dienst, LUNG M-V, Goldberger Str. 12, D-18273 Güstrow, Germany, [email protected]

Numerous major and minor faults occur in Mecklenburg-Western Pomerania and the adjacent Baltic Sea area that were formed during different tectonic phases since the late Palaeozoic. These faults may represent single structural elements, but more often, they are aligned (sub)- parallel to each other forming fault zones, or they belong to a complex fault system (e.g. the Western Pomeranian Fault System; Krauss & Mayer, 2004). The knowledge of these occurrences is mainly based on 2D seismic measurements and deep boreholes measured and drilled during oil and gas exploration between 1950s and 1990s. Their postulated length varies between a few houndreds of metres and more than 30 km; in a few cases fault segmentation is assumed. Whereas the fault strike and lateral extent is rather well documented, uncertainties exist in respect to the fault dip and amount of lateral and/or vertical displacement. However, information about main fault orientation, the mode and amount of displacement as well as the number of intersected lithostratigraphic horizons are necessary to determine the formation mechanism and to estimate the age of fault formation and reactivation, and the genetical relationship to large- scale tectonic events. Thus, a fault database will be established at the Geological Survey of Mecklenburg-Western Pomerania to get a profound overview of all known or indicated faults. This is needed for a detailed description of the development of different crustal blocks, basins or grabens. Furthermore, it will be the base for 3D modelling of the subsurface geology of the Federal State of Mecklenburg-Western Pomerania, the North German Basin (TUNB project) or small-scale structures as anticlines above salt pillows etc. Besides, the permeability of faults or fracture zones is in focus of research projects (e.g. „StörTief“; Gorling et al., 2016). Finally, the activities of faults will be one important criteria in the evaluation process of finding suitable sites for permanent nuclear waste storage in Germany. Various sources of information about faults exist. Major faults, often named after distinct locations (e.g. town, river, block or other structural element) in their vicinity, are more or less well described in published articles about the regional geology of north-eastern Germany and the adjacent Baltic Sea area. They are also shown on maps of different scale. Minor faults, often unnamed, are only mentioned in special geophysical reports or are visualized on interpreted seismic sections as well as on maps of local structures. A profound search of faults and their characteristics in literature and unpublished reports, which are stored in various archives of geological and mining authorities, exploration companies, universities and other research institutions, is time-consuming but necessary. The fault database of Mecklenburg-Western Pomerania and adjacent areas contains the fault ID, the correct name of the fault and synonyms. Further information include, where it was published first, the relationship to a fault zone or fault system, the location and a link to a shape file or gocad object. It is also indicated, if the fault is a fault segment or part of a set of faults, especially in the case of complex graben structures. Besides, the main strike direction(s), the lateral extent, the mode of movement, the lateral and/or vertical offset – so far as known or with given uncertainties. The age of fault generation or reactivation is also noted but can often only be estimated from intersected lithostratigraphic units. Up to now, there are about 50 records in the database.

References Krauss, M., & Mayer, P. (2004). Das Vorpommern-Störungssystem und seine regionale Einordnung zur Transeuropäischen Störung. Zeitschrift für Geologische Wissenschaften, 32 (2-4), 227-246. Gorling, L., Agemar, T., Alten, J.A., Gramenz, J., Kuder, J., Suchi, E., Moeck, I., Weber, J., von Hart- mann, H., Stober, I., Hese, F., Thomsen, C. (2016): Verbundvorhaben „StörTief“. Die Rolle von tiefrei- chenden Störungszonen bei der geothermischen Energienutzung. Endbericht, LIAG Hannover.

Der Erdbeben-Zoo und die Bananenschale - was wir schon immer über Subduktionszonen wissen wollten

Onno Oncken1 1GFZ Potsdam, [email protected]

Die Gebirgsbildung an konvergenten Plattengrenze ist stets von Erdbeben begleitet. Am Bei- spiel des südamerikanischen Plattenrandes wissen wir heute, dass die Bildung der Anden wäh- rend der letzten 50 Millionen Jahre durch eine Reihe von Eigenschaften der oberen, südameri- kanischen Platte gesteuert wurde und wird. Hierzu zählen die Plattenkonvergenz selbst, aber vor allem die Prozesse, die zeitlichen Veränderungen unterworfen sind, wie die Klimaentwick- lung, die Entfestigung der Platte infolge der Verformung, und die Wechselwirkung mit dem tie- fen Erdmantel. Im Allgemeinen wird dabei erwartet, dass diese Entwicklung über den Erdbe- benzyklus am Plattenrand moduliert wird. Die Deformation auf der seismischen Zeitskala (weni- ge Jahrzehnte) ist jedoch sehr heterogen und hat eine enge Korrelation mit den mechanischen Eigenschaften und den Bewegungen an der Plattengrenzfläche. Die Topographie Chiles scheint dabei ein Langzeitgedächtnis an die heute instrumentell messbare seismische Kopplung zu haben – ein Hinweis auf die Langzeitstabilität der beobachteten Heterogenität der Kopplung an der Plattengrenzfläche? Dies hat einerseits grundlegende Implikationen für die räumliche und zeitliche Verteilung der seismischen Gefährdung - Erdbebenmuster der Vergangenheit könnten sich wiederholen, wie es etwa die vergangenen zehn Jahre zeigten. Schließlich scheint die Art der Kopplung an der Plattengrenzfläche, die dieses Verhalten steuert, stark durch das hydrauli- sche System an der Grenzfläche bestimmt zu sein. Neben den Implikationen für die seismische Gefährdung ergibt sich aber insbesondere die Frage, wie die mögliche Verbindung zwischen dem Erdbebenzyklus und dem allmählichen Prozess der Gebirgsbildung beschaffen ist.

Tectonics and stratigraphy of the Cukali area

Kujtim Onuzi1

1Institute of Geosciences, Energy,Water and Environment (IGEWE),Tirana, Albania, [email protected]

The Krasta-Cukali Zone is located in the north of Albania and is divided in two sub- zones: Cukali Subzone and Krasta Subzone. It is characterized by rifted volcanoes during the Late Anisian, and carbonatic and siliceous pelagic sediments from Ladian until Late Creta- ceous overlain by flysch deposits until Middle Eocene. The Cukali Subzone is manifested as a tectonic half-window outcrop, which is covered by the Albanian Alp Zone in the north and the Mirdita Zone in the south. The structure of the Cukali Subzone from a regional point of view is represented by a mega-anticline with a host-shaped rise with NE-SW extension direction. In the core of the folds are the limestones and radiolarites of the Mesozoic epoch, whereas in the flanks of it, flysch and glass-schists of Cretaceous-Paleogene age are present (Figure 1). The Cukali subzone includes the following formations: Triassic deposits, Jurassic deposits, Cretaceous deposits and Maastriktian-Eocene (Fig.2). Triassic deposits in the Cukali subzone have a considerable spreading in particular in its south-western sectors. Geological surveys and studies have distinguished the middle and upper Triassic deposits. Jurassic deposits in general lie over limestoness with siliceous lenses of upper Triassic called ‘Prekali Limestones’. In the lower part, they are represented by Prekali schist, siliceous lenses of marly limestones, and siliceous marly schists. Then the section continues with thinlayered to platey, biomicritic limestones with radiolarites, fine cri- onoids and rare pelagic bivalvia. The Maastrichtian-Eocene Xhani schist formation which en- circles the Cukali carbonatic structure spreads from Drishti in the southwest to Kolshi Pass in the northeast. This formation is overthrusted by Albanian Alps Zone in the west and north west, and by Mirdita Zone in the southeast. In general, the Xhani schist formation lies over Cukali limestones with Globotrucana through a transitional pack. This transitional pack consists of alternating biomicritic limestones with clay and marl layers. Above the transitional pack, the section comprises argilous and marly argilous schist, with sandstone layers generally turbiditic as well as pieces, pebble and blocks (oliistolites) within schist.

Fig. 1: Geological map of the Cukali subzone. Fig. 2: Stratigraphy of the Cukali subzone.

Structural mapping, well data and stress field analysis in the surroundings of the Nekézseny Thrust Fault, NE Hungary

Éva Oravecz1, László Fodor2,3, Szilvia Kövér2

1Eötvös Lorand University of Budapest, Hungary, [email protected] 2MTA-ELTE Geological, Geophysical and Space Sciences Research Group, Hungarian Acade- my of Sciences at the Eötvös Loránd University 3MTA-ELTE Volcanological Research Group, Hungarian Academy of Sciences at the Eötvös Loránd University

The Bükk and Uppony Mts. located in NE Hungary are two adjacent structural units with different origins: while the nappes of the Bükk Mts. once formed part of the Inner Dinaric nappe system, the Uppony Mts. are correlated with the Western Carpathians (Schmid et al., 2008). The mainly S-SW-vergent Bükk and N-NW-vergent Uppony Units are separated by the Nekézseny Thrust Fault along which the Bükk-type Permomesozoic formations are thrust upon the Uppony- type Paleozoic and Senonian formations (Schréter, 1945). Despite of its obvious structural importance, the structural evolution of the Nekézseny Thrust Fault hasn’t been studied in details. The possible timing of its movements is between the Seno- nian and the Early Miocene. In their preliminary structural study Fodor et al. (2005) interpreted the results in the lights of the Paleogene deformation of the Darnó Deformation Zone. In contrast, based on paleogeographic considerations Schmid et al. (2008) consider the Nekézseny Thrust Fault as the suture zone of the Meliata Ocean thus assume that the age of this structural contact is Early Cretaceous. Consequently, the aim of our study was to understand the deformation geometry and the timing of activity along the Nekézseny Thrust Fault. As part of the study core samples from boreholes that drilled through the supposed structural contact were reviewed, sampled and interpreted. Detailed structural mapping in the surroundings of the Nekézseny Thrust Fault was followed by stress field analysis and preparation of cross-sections. According to our preliminary results, at least five tectonic phases could be separated. Field work in the gently folded Senonian Nekézseny Conglomerate revealed both pre- and post-tilt low-angle thrust faults. While the pre- tilt thrust faults are clearly the results of NW-SE compression (D1), the post-tilt thrust faults can be separated into three groups that show slightly different N-S, NW-SE and E-W compression (D2). These deviations from the general NW-SE post-tilt compression only appear immediately at the Nekézseny Thrust Fault. The tilting itself is connected to NW-SE compression as well. The subsequent three deformation phases are connected to the later rotational events and extensional deformation history of the Pannonian Basin (D3: Early Miocene NNE-SSW extension, D4: Middle Miocene E-W extension, D5: Late Miocene—Pliocene NW-SE extension; Budai & Fodor 2008; Fodor et al. 2005). All this may contribute to understanding not only the deformation history of the Nekézseny Thrust Fault, but the role of the Darnó Deformation Zone during the Mesozoic structural evolution of the area. The research was supported by the research found NKFIH OTKA 113013 and the ÚNKP-17-2 New National Excellence Program of the Ministry of Human Capacities. References Buda, T., & Fodor, L. (2008). Geology of Vértes Hills: Explanatory Book to the Geological Map of the Vér- tes Hills (1:50 000). Geological Institute of Hungary, Budapest, pp. 368. Fodor, L., Radócz, Gy., Sztanó, O., Koroknai, B., Csontos, L., & Harangi, Sz. (2005). Post-Conference Excursion: Tectonics, Sedimentation and Magmatism along the Darnó Zone. GeoLines, 19: 141-161. Schmid, S.M., Bernoulli, D., Fügenschuh, B., Matenco, L., Schefer, S., Schuster, R., Tischler, M., & Ustaszewski, K. (2008). The Alpine-Carpathian-Dinaridic orogenic system: correlation and evolution of tectonic units. Swiss Journal of Geosciences, 101: 139-183. Schréter, Z. (1945). Geologische Aufnahmen im Gebiete von Uppony, Dédes und Nekézseny, Ferner im Gebiete von Putnok. Annual Report of the Geological Institute of Hungary, 1941-42: 197-237.

Morphology of normal faults, landscape evolution and ageing of cataclasites at Campo Imperatore, Abruzzi Apennines, Italy

Hugo Ortner1, Diethard Sanders1, Hannah Pomella1

1Institut für Geologie, Universität Innsbruck, Österreich, [email protected]

The development of the Apennine range of Italy is characterized by nappe stacking followed by extension combined with vertical uplift, which is still active, as indicated by numerous historical earthquakes. We study the morphology and geology of the Assergi and Campo Imperatore fault systems, respectively, to demonstrate that the appearance of cataclasites changes with age.

The morphology of the fault systems is controlled by: (1) interaction of landscape-forming processes (e.g., slope denudation, stream incision, fanhead trenching) and normal faulting, (2) shifting activity of initially isolated fault segments that progressively overlap with time and finally merge, and (3) structural inheritance (not dicussed here).

All studied faults are located at the toes of south-dipping slopes, and are therefore comparable. The mountain flank crossed by the Assergi fault system is characterized by gently convex slopes with a long, rectilinear planar upper slope segment (~35-40° dip) intercalated with regularly-spaced snow avalanche chutes. Erosional excavation of the scarp of the dormant fault proceeded at a higher pace than denudational lowering of the slope by periglacial processes.

In contrast, the Campo Imperatore fault (CIF) rejuvenates the morphology of the inherited periglacial slopes by vertical offset of talus deposits. Geomorphological indices (elevation, catchment area, outlet spacing, height of triangular factes) indicate that the older parts of the CIF are located in its eastern third, and the CIF grew toward the West.

The field appearance of cataclasites reflects these differences: in the eastern part of the CIF and at the Assergi fault, cataclasites are strongly overprinted by meteoric-diagenetic processes as recorded by dissolution vugs lined or filled by cement, internal breccias, and karstic voids with geopetally-laminated internal sediments; these diagenetic features can also be found reworked into younger cataclasites. In contrast, the cataclasites in the westernmost (youngest) segment of the CIF are very poor in to typically devoid of, both, meteoric-diagenetic phenomena as well as cataclasite intraclasts.

The field appearance of cataclasites is therefore a first-order criterion for relative age estimation of fault activity on the time scale of intramontane basin-scale landscape evolution, which is probably in the range of a few tens of ka to more than 100 ka.

Pre-Variscan metamorphic structure at the western margin of the Teplá- Barrandian Domain – comparison of the Teplá and Domažlice Crystalline Complex (Bohemian Massif)

Vít Peřestý1, Ondrej Lexa1, Pavla Štípská2, Petr Jeřábek1, Martin Racek1

1Institute of Petrology and Structural Geology, Charles University in Prague, Czech Republic, [email protected] 2Czech Geological Survey, Prague, Czech Republic

Two metasedimentary complexes at the western margin of the Teplá-Barrandian Domain preserve pre-Variscan regional metamorphism. We will discuss similarities and differences in the tectonic evolution of the Teplá Crystalline Complex (TCC) and the Domažlice Crystalline Com- plex (DCC), based on ongoing research covering in-situ U-Pb LASS ICP-MS monazite and xe- notime dating, petrography, P–T modelling and structural analysis. The first important difference is the age of major metamorphic event. In the TCC, 95% of analysed monazites yielded Variscan age (c. 375 Ma), while in the DCC, no Variscan monazite has been identified. The remaining 5% of the pre-Variscan monazites in the TCC belong to a single Cambro-Ordovician age group (c. 486 Ma). Similar ages ranging between 489 – 510 Ma have been obtained from the monazites and xenotimes in the DCC. Cambro-Ordovician monazites in the TCC are restricted to the samples containing two-stage garnet and since some of these monazites occur as inclusions in the first garnet generation, the pre-Variscan age can be attributed to the growth of garnet I. The garnet I in cores of two-stage garnets is the only remnant of pre-Variscan mineral assemblage in the TCC. The remaining index minerals, represented by staurolite, kyanite and sillimanite, clearly belong to the Barrovian MP-MT Variscan overprint. In contrast, mineral assemblages in the DCC show well-preserved LP-HT associations containing garnet, staurolite, andalusite and sillimanite. P–T conditions calculated for mineral assemblages in the DCC range from 530 – 560 °C and 2.8 – 3.7 kbar to 620 – 670°C, 4 – 6 kbar. These conditions overlap with P-T conditions previously modelled from relict garnet cores in the TCC (550°C and 3 kbar to 600 – 650 °C at 5 – 6 kbar, Peřestý et al., 2017). Strong Variscan deformation overprint in the TCC limits the reconstruction of the primary pre- Variscan structures. However, our structural analysis combined with systematic spatial variations in the pressure difference between the estimates for pre-Varican and Variscan events suggest that the pre-Variscan event is characterized by normal metamorphic zoning and shal- lowly dipping fabric that is later responsible for exhumation of the metamorphic isograds (Peřestý et al., 2017). The structural record in the DCC suggests much lower overprint by Var- iscan deformation represented by open to closed large-scale folds with moderately to steeply NW-dipping axial planes. Thus the pre-Variscan structures can be reconstructed more precise- ly. The primary orientation of dominant Cambro-Ordovician metamorphic foliation S2 prior to Variscan folding was probably gently to moderately SE-dipping and had been formed by near isoclinal transposition of older fabric S1. S2 is characterised by normal metamorphic zoning with rapid increase in metamorphic grade from phyllites to garnet-sillimanite bearing migmatitic gneisses in c. 3 km wide N-S trending zone of transitional garnet-staurolite- sillimanite±andalusite paragneiss. In conclusion, both complexes record similar LP-HT regional metamorphism with geothermal gradient 30 – 60°C/km, which is nearly obliterated in the TCC but uniquely preserved in the DCC. The two domains jointly show structures that can be interpreted in terms of rift-related exhumation of metamorphic isograds during the development of Cambro-Ordovician passive margin.

References Peřestý, V., Lexa, O., Holder, R., Jeřábek, P., Racek, M., Štípská, P., Schulmann, K., & Hacker, B., (2017). Metamorphic inheritance of Rheic passive margin evolution and its early-Variscan overprint in the Teplá-Barrandian Unit, Bohemian Massif. Journal of Metamorphic Geology, 35: 327–355.

Fracture Systems and Fluid Flow in Geothermal Reservoirs

Sonja L. Philipp1,2

1geophil – Geologie Prof. Dr. Sonja Philipp, Oberursel, Germany, [email protected] 2Geoscience Centre, University of Göttingen, Göttingen, Germany

In most geothermal reservoirs, fluid flow is largely controlled by the permeability of its fracture system. To act as geothermal reservoirs with economically appropriate fluid flow, significant permeability is necessary. In some reservoirs – particularly in fault zones with favourable orientations in relation to the current stress field – the existing fracture system, together with the host rock matrix, provides sufficient fluid flow. In other reservoirs, however, interconnected fracture systems need to be formed either by creating hydraulic fractures or by massive hydraulic stimulation of the existing fracture system in the host rock. Both for the direct use of reservoirs, as well as for effective stimulation, the geometry of the existing fracture system and its likely future development need to be known as accurately as possible. Here I present relevant parameters and multidisciplinary approaches, indicated in the diagram (Fig. 1), altogether aiming for reliable estimations of the existing fracture system and potential fluid flow in geothermal reservoirs. Emphasis is on two topics: 1) Field studies in paleogeothermal reservoirs in fault zones in Great Britain and in outcrop analogues of potential reservoir rocks in Germany; 2) Numerical models of local stress fields that provide the basis for models of fracture propagation and fluid flow in geothermal reservoirs. Focus is on the effects of rock heterogeneities on the host-rock mechanical properties, the infrastructures of fault zones, and fracture-system parameters. These studies increase our understanding of fluid flow in geothermal reservoirs and thus maximise the likelihood of success of geothermal wells and help improve planning of well paths.

Fig. 1: Parameters (white) and methods (grey) for fluid-flow estimations in geothermal reservoirs. Black arrows indicate interdependencies of parameters, mechanical facies and fracture propagation. White arrows, in contrast, indicate parameters to be obtained with the respective methods. For example, field studies in outcrop analogues provide data on the mechanical facies and fracture systems in similar rocks. General understanding of interdependencies of these parameters also comes from field studies in paleogeothermal reservoirs. Geomechanical models, needed for well-path planning, are based on information on the stress field, reservoir pressures and mechanical rock properties. Numerical models, in turn, use data from mechanical facies to the current stress field, to estimate fracture system and stimulation parameters as well as potential fluid flow in the geothermal reservoir. 97

A new balanced cross section across the southern Dinarides fold and thrust belt in the vicinity of the Montenegro 1979 Mw 7.1 earthquake epicenter

Janis Pingel1, Benjamin Schmitz1, Philipp Balling1, Kamil Ustaszewski1

1Friedrich-Schiller Universität Jena, Institute of Geoscience, Burgweg 11, 07743 Jena

The fold and thrust belt of the Dinarides on the Balkan Peninsula results from a long-lasting convergence between the Eurasian and the Adriatic plates since the closure of the Neotethys Ocean in the Late Cretaceous. Shortening continued throughout much of the Palaeogene and involved the passive margin of the Adriatic microplate into the SW-verging nappe stack of the Dinarides. Prior to convergence, the now consumed passive margin underwent extension and subsidence to variable amounts, creating a series of basins and highs characterized by various neritic and pelagic successions of mostly Mesozoic age. The southern part of the Dinarides fold and thrust belt between Montenegro and Albania also hosts some of the strongest earthquakes in Europe (Mw 7.1 earthquake, 1979). The motivation of this study was to provide an improved structural model for the onshore segments of the frontalmost thrust belt in the vicinity of the 1979 epicenter. A new balanced cross section was construced between the Adriatic coast near the city of Ulcinj and the Lake Shkodër in southern Montenegro (Fig. 1). The cross section comprises three major tectonic units, characterized by rheologically contrasting neritic and pelagic successions of Mesozoic age. From bottom to top (or, from W to E), these are the Dalmatian, the Budva-Cukali and the High Karst units. While Dalmatian and High Karst units are characterized by platform carbonates, the Budva-Cukali unit represents a pelagic basin. All Mesozoic series are overlain by largely Eocene synorogenic clastics. Following the construction of a deformed-state cross section, we iteratively forward-modelled the cross section using the fault-parallel flow and trishear algorithms implemented in Midland Valley’s MOVE 2017.2 structural modeling software to match the deformed-state geometry. Our final forward-modelled cross section has a length of c. 38 km. It shows a series of five overthrust faults with flat-ramp-flat geometries that developed in sequence from E to W (Fig. 1). Within the tectonically highest High Karst nappe, the basal detachment follows Late Permian to Early Triassic strata. Towards the foreland, this detachment gradually ramps through the stratigraphic succession to reach the Jurassic – Cretaceous interface in the tectonically lowest Dalmatian unit. There, it ramps through the Cretaceous and Palaeogene succession. Most shortening is likely of Late Eocene to Oligocene age. The total shortening amounts to 39 %, corresponding to an absolute shortening in the order of 24 km.

Fig. 1: Balanced cross section between the Adriatic coast at Ulcinj (left) and Lake Shkodër, southern Montenegro. View towards NW.

Fluid flow through solid rocks: from fracture patterns to retrograde reaction textures

Kilian Pollok1, Falko Langenhorst1

1Friedrich-Schiller-Universität Jena, Institut für Geowissenschaften, Jena, Germany, [email protected]

Fracturing of metamorphic rocks is an important prerequisite for fluid-driven retrograde mineral reactions. Such fractering can be induced by tectonic stresses, but can also be the result of the volume increase during hydration or volatisation reactions. While the infiltration of fluids is often restricted to shear zones providing only local conversion of high-grade to lower-grade metamorphic rocks, pervasive retrograde metamorphism is often associated with a reaction- driven fracturing (Jamtveit & Austrheim, 2010). However, complete conversion of high- to low- grade rocks is further depending on fluid availibility within the crust and rarely complete on regional scale. While metamorphic petrology is mostly focusing on rocks that survived the retrograde path (e.g. for maximum p-T estimates), the perished rocks and their textures received much less attention. In the present work, the common regression from eclogite to amphibolite is examined on thin section scale as a case study on sample from Drangovo (Eastern Rhodopes, Bulgaria). It focuses on the distribution and length of fractures, the mode of replacement, the mass/volume balance of the reactions, and the conditions of retrograde overprinting. Fractures crosscutting neighbouring garnets and omphacites can be traced over a thin section scale. While fractures in garnet are filled with epidote, the fractures in omphacite are enlarged by forming an fine grained amphibole(amph)-plagioclase(plag) reaction texture. Inclusions of primary rutile are acting as a fluid barrier that accelerate the breakdown of the host as the reaction zones spread around these obstacles. The coexisting amph and plag suggest a temperature of 520 ± 30 °C for the retrograde reactions. This is further substantiated by nanometric exsolutions in plag (peristerite gap) which also point to an equilibration at 500 °C. In samples that experienced higher fluid flow, the omphacite is completely replaced by amph+plag±qz leaving a streaky replacement texture with rhythmic quartz trails that still indicate the fluid flow direction. Mass balance calculation point to an overall isochemical reaction which is consuming about 1 wt% H2O. Surprisingly, the pervasive fluid flow at grain scale seems not impose any stress gradients due to volume changes of mineral reactions. This would point to a large scale stress field (e.g. by extension) that produces brittle fracturing followed by fluid flow at the greenschist to amphibolite facies boundary.

References Jamtveit, B., & Austrheim, H., (2010). Metamorphism: the role of fluids. Elements, 6: 153–158.

Steady-state plate tectonics, unsteady orogeny: a view from the Pamir

Lothar Ratschbacher1 and the TIPAGE and TIPTIMON teams

1TU Bergakademie Freiberg, Geologie, Freiberg, Germany, [email protected]

Plate motions are constant over large periods. This is indicated as well by the motion path of India with respect to Eurasia. Although this is an extreme case, as it includes a massive continent-collision, convergence rates have been interpreted to either have decelerated continuously or remained constant over 10−30 Myr periods, changing abruptly in between (c.f. Molnar and Stock, 2009, Ingalls et al., 2016). Studies of orogeny in collisional mountain belts show that orogeny is unsteady, with―for example―periods of large-scale extension during apparently steady-state plate convergence or the punctuated rise of entire mountain belts over ~10 Myr. Here, I address two ‘catastrophic’ orogenic events in the evolution of at least the western India- Asia collision zone in the Pamir, Hindu Kush, Karakorum, and western Tian Shan. First, I illustrate the change from crustal shortening to crustal extension at ~20 Ma across the Pamir, Hindu Kush, and the Northern Himalayan gneiss domes that occurred during ongoing India-Asia convergence, and produced extensional metamorphic core complexes as large as the Swiss Alps (e.g. Shakhdara-Alichur dome of the South Pamir). I present the pressure-temperature- deformation-time changes of this event, its rates, and the impact they had on the orogen and its forelands. I conclude that it was triggered by a lithospheric event, i.e., the break-off of Greater India from Cratonic India. Second, I show the crustal effects of the geophysically-traced deep lithospheric indentation of Cratonic India into Cratonic Asia (Tajik-Tarim craton). These effects are renewed shortening and deep crustal foundering in the orogen, lateral (westward) extrusion of the collapsing Pamir-plateau crust into the Tajik depression, producing one of the largest foreland fold-thrust belts of the India-Asia collision zone with shortening normal to the convergence direction, and the sudden growth of the Cenozoic Tian Shan. I conclude that orogeny is by nature unsteady, dominated by catastrophic events. These events govern the thermal and rheological states and the gravitational equilibrium of the orogen, drive foreland−hinterland interactions, and rule surface responses. These events are mantle−crust−surface and foreland−hinterland reactions to deep lithospheric processes. The latter govern orogeny on its biggest scale.

References Ingalls, M., Rowley, D. B., Currie, B., & Colman, A. S., (2016). Large-scale subduction of continental crust implied by India–Asia mass-balance calculation. Nature Geoscience, 9, DOI: 10.1038/NGEO2806.

Molnar, P., & Stock, J. M., (2009). Slowing of India’s convergence with Eurasia since 20 Ma and its implications for Tibetan mantle dynamics. Tectonics, 28, TC3001, DOI:10.1029/2008TC002271.

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Active faulting in the Upper Rhine Graben: geomorphological and geophysical evidence

Klaus Reicherter1, Stephane Baize2, Jessica Thomas1, Jochen Hürtgen1, Joachim Ritter3

1Neotectonics & Natural Hazards, RWTH Aachen University, Lochnerstr. 4-20, 52056 Aachen, Germany, [email protected] 2Institut de Radioprotection et de Sûreté Nucléaire, BP 6, 92262 Fontenay-aux-Roses, France, [email protected] 3KIT, Geophysikalisches Institut, Hertzstr. 16, 76187 Karlsruhe, [email protected]

The Upper Rhine Graben (URG) is the central part of the Central European Cenozoic Rift System (ECRIS) and one of the tectonically active regions in Europe. The URG extends from the Jura thrust and fold belt in the South near Basle city (Switzerland) to the Rhenish Massif in the North near Frankfurt and is limited by sinistral strike-slip faults on either sides. Several studies suggested particularly the fault system at the eastern margin to be active, as the Basle earthquake 1356 AD was situated there. Ongoing earthquake activity testifies to active faulting, however, there are many faults and fault strands, many of them are regarded as normal faults, others as reactivated normal faults with a sinistral sense of movement. This is due to a major change in stress direction from SW-NE towards a SE-NW direction in Miocene times. The URG is a low-strain setting with long recurrence intervals of large earthquakes. Moreover, the fault morphological signal is perturbed by anthropogenic land-use, the climate of the area, which is located in the temperate zone, and the erosion and sedimentation of the Rhine River. The eastern margin faults lack any neotectonic and paleoseismological investigations, in contrast to the western border faults that have been examined during the last decades, while the area encompasses critical facilities in a vulnerable region such as, dense population, agriculture, mining, geothermal facilities. Our projects in the frame of an IRSN study and the DFG-SPP AlpArray aim to fill this gap of knowledge in large and infrequent earthquakes, through a paleoseismological investigation of eastern side faults. We used a multidisciplinary approach to improve the input data of seismotectonic models, which include faults and their activity potential in the calculation of seismic hazard assessment and are based on a weak data set at the moment. First results of different locations around Freiburg in the southern URG and around Karlsruhe are presented: the Rhine River fault system about 20 km SW of Freiburg, NE of Freiburg at the eastern border fault system about 10 km. At both sites we used a digital elevation model (DEM) derived from LiDAR-data (5x5m) and together with geophysical measurements performed with ground-penetrating radar (GPR) and electrical resistivity tomography in order to track and identify possible fault scarps. A detailed geomorphological study of the DEM was performed to identify and map superficial expressions of the neotectonic activity of the faults and deformed and offset alluvial terraces and fans. We apply ERT and GPR for imaging the geophysical contrasts at depth, such as faults and stratigraphy in detail. Nevertheless, for the unambiguous verification of these structures and the determination of key fault parameters, such as magnitude, age of last events, slip rate and return periods, additional paleoseismological trenches are needed, which will be the next step of the project.

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The influence of Mesozoic structures on the Cenozoic Pamir – The most external occurrence of the Karakul-Mazar nappe, Chinese Pamir

Johannes Rembe1, Edward R. Sobel1, Jonas Kley2, Renjie Zhou3, Klaus Wemmer2, Chen Jie4, Langtao Liu5

1Universität Potsdam, Inst. Erd- und Umweltwissenschaften, Potsdam, Germany, jrembe@uni- potsdam.de, [email protected] 2Georg-August-Universität Göttingen, Abt. Strukturgeologie/Geodynamik, Göttingen, Germany, [email protected] 3The University of Queensland, School of Earth and Environmental Sciences, Brisbane, Austral- ia, [email protected] 4China Earthquake Administration, Institute of Geology, State Key Laboratory of Earthquake Dynamics, Beijing, China, [email protected] 5Hebei University of Engineering, Hebei, China, [email protected]

A long-lasting history of terrane accretion characterizes the Pamir orogen as a part of the Hima- layan-Tibetan mountain belt. Those terranes shaped the Asian continental margin, prior to its collision with India and therefore have an influence on the present day geometry of the mountain chain. In the North Pamir Terrane two paleogeographic domains can be distinguished: (1) the North Pamir-Kunlun domaine, built up by Palaeozoic (meta-)sediments and (ultra-)mafic volcanics and (2) the Karakul-Mazar domain south of (1), representing a Permo-Triassic accretionary prism that formed during the northward subduction of the Palaeo-Tethys Ocean and the subsequent collision of the North Pamir Terrane with the Central Pamir Terrane (Robinson et al., 2012; Robinson, 2015). The North Pamir Terrane lies north of the Tanymas Suture Zone (i.e. the Paleo-Tethys suture) and thus belongs to the Palaeozoic to Triassic margin of Asia. The adjacent Central Pamir has a Gondwanan affinity. The Karakul-Mazar domain underwent regional metamorphism during its collision with the overriding Central Pamir in the Early Juras- sic. During the Middle Cretaceous, crustal thickening caused maximum amphibolite facies conditions and the formation of the Shala Tala thrust (Robinson et al., 2004), which placed parts of the Karakul-Mazar domain onto the North Pamir-Kunlun domain. A flat-lying metamorphic nappe now exposes greenshist to amphibolite facies rocks on top of anchizonal sediments of the Kunlun domain. Robinson et al. (2012) report local evidence of Miocene underthrusting of the Karakul-Mazar domain beneath the North Pamir-Kunlun domain along the Ghez Fault. We mapped and sampled at several localities of previously undescribed metamorphic rocks along the potentially northeasternmost outcropping portion of the Karakul-Mazar nappe in the Chinese Pamir. Field mapping was supported by multispectral image analysis of ASTER data. Micro- and macrostructural kinematic markers indicate ductile N to NW directed transport of the nappe. Lithologies are various and comprise greenschist, mylonitic marble and amphibolite. South of the village of Bostantielieke we mapped a several 10s of meters thick thrust that places greenschist onto anchizonal greywacke. This fault is interpreted to represent a portion of the Shala Tala fault. We are currently analyzing the temporal and thermal history of the fault using K/Ar dating, and illite crystallinity. U/Pb dating on mylonitic marbles is also underway. Our goal is to constrain the deformation history of the Karakul-Mazar Nappe. If this nappe has moved during the Cenozoic the offset must be considered when calculating the total amount of Ceno- zoic shortening within the Pamir. References Robinson, A. C.; Yin, A.; Manning, C. E.; Harrison, T. M.; Zhang, S.-H. & Wang, X.-F. (2004): Tectonic evolution of the northeastern Pamir: Constraints from the northern portion of the Cenozoic Kongur Shan extensional system. Geol. Soc. Am. Bull., 116, 953-974 Robinson, A. C.; Ducea, M. & Lapen, T. J. (2012): Detrital zircon an isotopic constraints on the crustal architecture and tectonic evolution of the northeastern Pamir. Tectonics, 31, TC2016 Robinson, A. C. (2015): Mesozoic tectonics of the Gondwanan terranes of the Pamir plateau. Journal of Asian Earth Sciences, 102, 170-179.

102

Geochemistry and geotectonic setting of gabbros in the Gasht-Masuleh area, Alborz Mts., north Iran

Leila Rezeaei1,2, Martin Jan Timmeman2, Mohssen Moazzen1

1University of Tabriz, Department of Earth science, Tabriz, Iran, [email protected], mo- [email protected] 2University of Potsdam, Institute of Earth and Environmental Sciences, Potsdam, Germany, [email protected]

The E-W trending Alborz Mts in north Iran link Azerbaijan and the Lesser Caucasus to northern Afghanistan and were formed during several geological events, from Late Triassic collision to recent ongoing contraction and volcanism. To the south they border the Central Iran microplate and its northern boundary is the Palaeo-Tethys suture zone. Palaeo-Tethys subduction and later extension events produced a variety of volcanic and plutonic rocks of varying age in the Alborz range. The Gasht-Masuleh area in the west-central part of the Alborz Mts, south of the Caspian Sea, is dominated by Paleozoic metasediments and Mesozoic sediments, with smaller volumes of (pre- Cambrian?) metamorphosed rocks. Near Zudel, Gilvanderud and Chapoul these are intruded by small, kilometer-sized gabbro bodies which in turn are cut by later dolerite and diorite dikes. The gabbros often show magmatic layered on a cm-scale but are not deformed, apart from tilting and local brittle deformation. Petrographically they can be divided into isotropic gabbros and cumulates; the latter are orthocumulates mainly composed of cumulate clinopyroxene and olivine, with plagioclase as intercumulus phase. Some samples contain orthopyroxene, opaque minerals, phlogopite and apatite. Spinel appears to be absent. The crystallization order is Ol ± Opx + Cpx, followed by Pl, opaque minerals and Phl ± Ap. Cpx is mainly diopside (En41.0-49.8, Fs0.9-12.7, Wo41.2–51.7), Opx is enstatite and Ol has moderate Mg contents (Fo65.7-75.3). Pl shows a wide range in composition from andesine to bytownite (An29.7-89.2), which may be primary magmatic (crystallization An-rich early Pl followed by An-poor interstitial Pl) or may be due to later alteration. Opaque minerals are mostly (titano-) magnetite and dark mica is phlogopite.

Whole rock compositions show a large variation in MgO (3.9-20.7 Wt%), Al2O3 (2.5 - 20.8 Wt%),Ni (13 - 299 ppm) and Cr (11 – 1630 ppm), and MgO vs. Al2O3, Na2O + K2O, TiO2, CaO, Sc, Cr, Ni and Sr plots show simple, linear positive and negative mixing trends reflecting accumulation of Cpx, Ol and Pl. Primitive mantle normalized multi-element patterns show enrichment in large ion lithophile elements, Nb and Ti negative anomalies and relatively low high field- strength element abundances. Chondrite normalized rare earth element plots show light REE enrichment ((La/Yb)N = 3.5 - 9.3), low heavy REE abundances ((Dy/Yb)N= 1.4 - 1.8) and no obvious Eu negative or positive anomalies. LREE enrichment and HREE depletion may point to relatively low degrees of mantle melting in the presence of residual garnet. Whole rock trace element and Cpx compositions preliminary suggest generation of subalkaline parent melts in a subduction related (arc) setting, but a rift setting cannot completely ruled out. The LREE enrichment and Nb and Ti negative anomalies may also be due to contamination of the mafic parent melt with continental, hence eventually arc-related, crustal material.

103

Viscoplastic finite element modelling of the South American subduction zone before large earthquakes – A parameter study

Chris Salomon1, Kamil Ustaszewski1, Thomas Jahr1

1Friedrich-Schiller-University, Institute of Geosciences, Jena, Germany, chris.salomon@uni- jena.de

The subduction zone between the South American and Nazca plates is known for some of the strongest earthquakes since the beginning of the earthquake recording. Additionally, the corresponding Wadati-Benioff zones show earthquake hypocentres down to depths of 600 km. Such deep earthquakes are supposedly caused by fluid movements as well as thermal melting processes. In this work we are interested in the computation of the current three-dimensional temperature and stress distribution in the subduction zone of the central Andes down to a depth of 400 km using the finite element method. For this purpose a coupled thermo-mechanical simulation running over 150k years will be realized based on an elastic-viscoplastic Drucker-Prager rheology. Our current reference model serves to examine the influences of the most important parameters on the model and is therefore kept ideally simple. For the geometry we use a simplified cross section of the northern Chile subduction zone extended to the third dimension. The gravitational force acts as the only external force on the system. The movements of the Nazca and South American plates are generated using velocities of 10 cm/yr in total. Furthermore, the boundaries of the asthenosphere are fixed to account for surrounding rocks. The model as a whole has a size of 1350 km x 400 km x 400 km and consists out of c. 23000 elements. During the parameter study we are investigating the influences due to a change in the movement direction of the plates as given by GPS observations and the kind of rheology (i.e. elastic, plastic or viscoplastic). Moreover, changes of the viscosity, the inner and outer friction coefficient and the thermal expansion coefficient are studied according to a common range of these parameters as given by other studies. The basic parameters density, Young’s modulus and Poisson ratio are well determined by preliminary geophysical observations and are thus not varied.

104

An example of a three-type interference pattern in the Tuscan Nappe, Southeastern sector of Apuan Alps (Northern Apennines, Italy)

Edoardo Sanità1, Chiara Frassi1, Maria Di Rosa1,2, Luca Pandolfi1

1Dipartimento di Scienze della Terra, Università di Pisa, Via Santa Maria 53, 56126 Pisa, Italy, [email protected] 2Dipartimento di Scienze della Terra, Università di Firenze, Firenze (Italia).

The study area is located in the Northern Apennines, which is composed of oceanic and continental-derived tectonic units, stacked toward NE during Apennine subduction (Oligocene to present). The continental-derived units, representative of the Adria paleomargin involved into the collisional phases of the Alpine orogeny, are, from the lower to the upper structural levels: the Apuan Alps Unit, the Massa Unit and the Tuscan Nappe. The Apuan Alps Unit consists of pre-Mesozoic metamorphic basement and metasedimentary cover rocks, ranging from Triassic to Oligocene, deformed and metamorphosed under green- schists facies conditions. The Massa Unit, is also characterized by pre-Mesozoic metamorphic basement unconformably covered by Middle to Upper Triassic metasedimentary rocks. It recorded higher metamorphic conditions respect to underlying Unit. The Tuscan Nappe, instead, is detached from its basement and it is composed by Late Triassic to Early Miocene non- metamorphic sedimentary rocks. This Unit was deformed at shallow structural levels. In the southeastern sector of the Apuan Alps, sedimentary rocks of the Tuscan nappe crop out. Particularly, in the study area, this unit includes only LateTriassic - Early Cretaceous rocks (Ca- rosi et al., 2005). Field observations and structural data allowed us to elaborate a 1:5.000 scale structural map. Structural analyses highlighted a comlplex deformation history, composed by five deformation events (from D1 to D5), documented a different scale. The D1 event is testified by S1 foliation classifiable as slaty cleavage. In thin section, S1 is emphasised by preferential orientation of phyllosilicates and lenticular domains composed of quartz, calcite, detrital micas, albite and oxides. Open to isoclinal similar folds (F2) with NW-SE trending axes are associated to the D2 event. F2 folds are associated to a well developed S2 axial plane classifiable as crenulation cleavage without significant re-crystallisation. The D3 event is not well developed in this area and it is locally recorded in the fine-grained rocks where it produced isoclinal folds with scattered axes and axial planes oriented N-S. The previous architecture is reworked by folds with chévron geometry and sub-horizontal axial plane associated to the D4 event. Finally, D5 event is characterized by open folds with sub-vertical axial plane and three systems of normal to transtensive faults. These brittle structures, could be interpreted as conjugate faults of the Mon- te Croce-Pescaglia faults system. In conclusion, field observations and structural analysis conducted both at the micro and at the mesoscopic scale, indicate that Tuscan Nappe exposed in the study area was affected by a km- scale three-type interference pattern (Ramsay, 1967). Furthermore, our studies suggest that the faults played a role of great importance in the present architecture of this sector of the belt.

References Carosi, R., Frassi, C., Montomoli, C., & Pertusati, P. C. (2005). Structural evolution of the Tuscan Nappe in the southeastern sector of the Apuan Alps metamorphic dome (Northern Apennines, Italy) Geol. J., 40, 103–119. Ramsay, J.G. (1967). Folding and fracturing of rocks. McGraw Hill: London.

105

Fluid flow in the Bavarian Pfahl shear zone

Anna Schaarschmidt1, Michel Bestmann1, Stefan Krumm1, Helga de Wall1

1Friedrich-Alexander-Universität Erlangen-Nürnberg, GeoZentrum Nordbayern, Germany, an- [email protected]

The >150 km-long Pfahl zone, which trends NW-SE from E Bavaria (Oberpfalz) to Upper Aus- tria, is an impressive example for long-term activity of a localized fault zone in the continental crust. The terminal major ductile imprint by dextral shear movements formed nearly vertical dipping mylonites and ultramylonites of former gneisses and granitoids which predominately shape the shear zone. Independently of the host rock this last ductile deformation is characterized by development of a strong foliation (Pfahlschiefer) under greenschist facies conditions (ca. 400-450°C). Especially the quartz recrystallization fabric indicates a final static heat pulse. CL analyses reveal a strong influence of fluids during deformation which cause dissolution precipitation recrystallization of the otherwise brittle behavior of feldspar. There is also indication (CL) of fluid flow along grain boundaries in the quartz fabric. This structural predesign is used as pathway for localized fluid flow during subsequent reactivation of the Pfahl zone in the Upper Permian to Lower Triassic documented in multi-stage quartz mineralization (Peucker-Ehrenbrink & Behr, 1993; Yilmaz et al., 2014). Three main fluid pulses (phase I to III) are constrained by crosscutting relationship in the here studied sector of the Ba- varian Pfahl. δ18O isotope data show a remarkable trend in isotope ratios from SE to NW. This 18 regional variation points to (i) variation in fluid composition (increasing δ Ofluid from SE to NW) and homogenous mineralization temperature; or (ii) variation in mineralization temperature (decreasing temperature from SE to NW) and homogenous fluid composition. The options will be discussed in our poster presentation.

Fig. 1: (A) Sample sites of mylonites and hydrothermal quartz along the Bavarian Pfahl structure. (B) Trend in oxygen isotope pattern of quartz.

References Peucker-Ehrenbrink, B., & Behr, H. J., (1993). Chemistry of hydrothermal quartz in the post-Variscan ‛Bavarian Pfahl‛ system, FR. Germany. Chemical Geology, 103: 85-102. Yilmaz, T. I., Prosser, G., Liotta, D., Kruhl, J. H., & Gilg, H. A., (2014). Repeated hydrothermal quartz crystallization and cataclasis in the Bavarian shear zone (Germany). J. Structural Geology, 68: 158-174.

106

Radiogenic heat production of Variscan granites- Western Bohemian Massif, Germany

L. Scharfenberg1, H. de Wall1

1Geozentrum Nordbayern, Friedrich-Alexander-Universität Erlangen-Nürnberg, Im Schlossgar- ten 5, 91054 Erlangen, [email protected]

From global geochemical models an average heat production < 1 µW/m3 is estimated for the continental crust (Jaupart et al., 2016). In granites, heat production rates are well above this value (world average: 3.54 µW/m3; Hasterok & Webb, 2017) and will produce distinct anomalies in the total crustal heat budget. However, the radiogenic heat generation of granites intrusions is strongly variable, e.g. controlled by the petrogenetic/tectonic setting during melt generation. Heat production data are an essential input for thermal models of the continental crust and granite magmatism is seen as main cause for accumulation of heat producing elements in the upper crust. Impressive examples for the extensive volumetric contribution of granitic bodies in middle to upper continental crust are seen in exposed Variscan basement in Europe. We studied granitoids in the Western Bohemian Massif comprising I-type to S-type granites emplaced between 330 to 298 Ma in Saxothuringian and Moldanubian crust. Radiogenic heat production rates (A) are calculated from heat producing element concentrations measured by a portable spectrometer (for method, refer to Scharfenberg et al., 2016). Heat production values range from of 2.36 µW/m³ to 7.64 µW/m3. Th/U ratios are variable and range from 0.2 (Steinwald Granite, Ober- pfalz) to 7.7 (Saldenburg Granite, Bavarian Forest). We will present heat production maps for the studied areas which can serve as a database for further geothermal modeling.

Fig. 1: Radiogenic heat production A (µW/m³) versus Th/U ratios for the study areas.

References Hasterok, D., & Webb, J., (2017). On the radiogenic heat production of igneous rocks. Geoscience Frontiers, 8: 919- 940. Jaupart, C., Mareschal, J.-C., & Iarotsky, L., (2016). Radiogenic heat production in the continental crust. Lithos, 262: 398-427. Scharfenberg, L., de Wall, H., & Bauer, W., (2016). In situ gamma radiation measurements on Variscan granites and inferred radiogenic heat production, Fichtelgebirge, Germany. Z. Dt. Ges. Geowiss. (German J. Geol.), 167(1): 19-32.

107

Meta-Selenites and their bearing on a lost Cretaceous Evaporitic Basin of the Eastern Mediterranean

Franziska Scheffler1, Adrian Immenhauser2, Amaury Pourteau1,3, Osman Candan4, Roland Oberhänsli1

1Universität Potsdam, Institut für Erd- und Umweltwissenschaften, Potsdam, Germany, [email protected] 2Ruhr-Universität Bochum, Institut für Geologie, Mineralogie und Geophysik, Bochum, Germany 3Curtin University, Department of Applied Geology, Bentley, Perth, Australia 4Dokuz Eylül Universitesi, Department of Geological Engineering, Izmir, Turkey

Earth’s geological archive is largely represented by proxy data from sedimentary successions. Most of the pre-Triassic sedimentary archives in oceanic settings have been lost in subduction zones and orogens. Variable degrees of diagenetic to metamorphic overprint, deep burial, subsequent uplift, folding and thrusting, and erosion affect sedimentary archives in the form of petrographic, mineralogical, and geochemical alteration. Evaporites are peculiar amongst sediment types as they represent a unique depositional environment. Evaporitic minerals have the potential to preserve the trace element distribution, fluid inclusion composition, and isotope ratios of their ambient fluids. The partition coefficients and the fractionation processes of fluid and evaporite minerals are well known and can be used to extract environmental information. Moreover, their morphologies are governed by environmental parameters such as salinity, temperature, and availability of organic matter. Nevertheless, evaporites are prone to dissolution, a fact that results in a preservation bias in the geological record. The oldest evaporites are solely maintained as pseudomorphs. This raises important questions regarding the potential of meta-evaporites and their pseudomorphs as archives in the geological record. Rosetta Marble refers to radiating fan structures made of dm- to m-scale calcitic rods in a HP-LT metamorphosed carbonate platform succession in SW Anatolia. The calcite rods resemble modern selenite textures and represent pseudomorphs (Fig. 1). Geochemical analysis of 18O, 13C, 78Sr/86Sr, and trace element distribution (electron microprobe, cathodoluminescence) show mid-Cretaceous sea water characteristics and a crystal zoning following former selenite crystal habits. This implies that primary information are preserved, despite the metamorphic and pseudomorphic overprint. The Rosetta Marble meta-selenite – meta-radiolarite succession is unique in the Earth’s record. Our interpretation favors a crystallization in deep-water evaporitic pools caused by dense shelf brines that were cascading downwards to the basin lows. Although cascading brines are observed in modern settings (Roveri et al., 2014), the growth of m-scale selenite crystals in deep-water setting has no modern analouge. During Aptian times massive evaporites deposited at the margins of the opening Atlantic ocean. The Rosetta Marbles are remains of a subducted evaporitic basin that has to be taken into account for global ocean element mass balance calculation of Aptian times. Addionally, this lost evaporitic basin has an impact on the paleo-geography reconstruction of the Tethyan realm.

Fig. 1: Rock forming selenite pseudomorphs (stacked swallowtail twins). Rosetta Marble, Turkey. Hammer shaft width is 3 cm.

References Roveri, M., Manzi, V., Bergamasco, A., Falcieri, F. M., Gennari, R., Lugli, S., & Schreiber, B. C., (2014): Dense shelf water cascading and Messinian canyons: a new scenario for the Mediterranean salinity crisis. American Journal of Science, 314(3): 751-784. 108

Preliminary observations on low-temperature shearing and folding of Middle Jurassic siliciclastic formations, SW Bükk, Hungary

Benjamin Scherman1, Melinda Fialowski1, László Fodor1,2, Szilvia Kövér1, Martin Reiser3

1MTA-ELTE Geological, Geophysical and Space Science Research Group of the Hungarian Academy of Sciences at Eötvös University 2MTA-ELTE Volcanology Research Group of the Hungarian Academy of Sciences 3Geological Survey of Austria, Wien

The Bükk Mountains in NE Hungary are part of the ALCAPA unit, It was part of the Neotethys passive margin, during the Triassic-Jurassic. The Bükk Mts are built up by four units: 1 Paraau- tochthonous Unit; 2 Mónosbél; 3 Szarvaskő accretional units and 4 Darnó subophiolitic melange unit. The structure of the Bükk Mts. is controversial. One side states that it is a complex nappe system whereas the other believes that it is a continuous sedimentary sequence. Our aim is to understand the structural differences between the units/nappes and to create a deformation history. We have done geological mapping, gathered meso and micro scale structural data on field, investigated relevant boring cores and collected samples for Fission Track measurements. Balla (1983) and Csontos (1999) believed that the area faced similar folding with axial plane schistosity (Fig 1.a), whereas our field observations show spatial variation of episodical shearing (Fig 1.b). On fault-slip analysis we were able to define four different deformational phases. D1 pre-tilt E-W compression caused thrusting, which often form duplexes with E vergence. These thrusts were tilted and often seem like normal faults in present setting. We also recognized overturned sandstone lences in shale, and fault bend folds. D2 NW-SE compression is responsible for the main folding and tilting, varying from NNW-SSE to WNW-ESE. D3 and D4 are post-tilt phases. D3 post-tilt is a NNW-SSE compression when the tilted layers got sheared by brittle thrusting, back thrusting and also some brittle to non-brittle folds belong to this phase. D4 post-tilt normal faults sheared the tilted layers, these are related to Miocene extension. Our study helps understanding the Alp-Carpathian-Dinaridic systems orogenic evolution. Also it gives a direction for further researches to be done in the area.

References Balla, Z. (1983). Stratigraphy and tectonics of the Szarvaskő synform (Hung.). Ann. Rep. Hung. Geophys. Inst. for 1982, 42- 65. Csontos, L. (1999). Structural outline of the Bükk Mts. (N Hungary). Földtani Kölöny 129/4, 611–651. Haas, J. Kovács S., Krystyn L., & Lein, R. (1995). Significance of Late Permian-Triassic facies zones in terrane reconstructions in the Alpine-North Pannonian domain. Tectonophysics 242, 19–40.

109

Lithosphere structure of the Western Alps and Alps-Apennines transition

Stefan M. Schmid1

1Institut für Geophysik, ETH Zürich, Switzerland, [email protected]

The interpretation of available p-wave mantle tomography models based on teleseismic events either suggest recent break-off of the European mantle lithosphere along an E-W transect across the Western Alps (Lippitsch et al., 2003), or alternatively, a continuous E-dipping Euro- pean lithosphere reaching a depth of some 400km, extending laterally as far as east of Milano (Zhao et al., 2016). Unfortunately the interpretation of Zhao et al. (2016) does not properly correct for the effects of the Ivrea mantle slice at shallow depth, nor does it take into account the 90° bend of the descending Europe Moho around the arc of the Western Alps (Waldhauser et al. 1998). It is shown that this, together with other shortcomings, leads to an unrealistic lithosphere scale structure of the Western Alps by Zhao et al. (2016). The mantle tomography model of Lippitsch et al. (2003) is in perfect agreement with more recent results of a high resolution 3-D p-wave tomography study of the Alpine crust, based on local earthquake tomography (Diehl et al., 2009). The latter data have been combined with a series of crustal transects across the Western Alps (Schmid et al., 2017) allowing for more ac- curate 3-D outlines of the Ivrea mantle slice that largely controls the present-day crustal geometry of the Western Alps, which formed as a result of WNW-directed indentation linked to out-of- sequence thrusting along the Pennine Frontal Thrust at 25-25 Ma ago, combined with oroclinal bending after 25 Ma ago, linked to the formation of the Apennines (Schmid et al., 2017). For understanding the Alps-Apennines transition it is essential to realize that the upper plate of the Western Alps lacks Adria-derived allochthons such as the Austroalpine nappes; the upper plate of the Western Alps is made up of elements of the former Piemont Liguria Ocean, including ocean-continent transition elements that were part of the Adria plate (i.e. Canavese, Che- naillet ophiolite, nappe supérieure of the Préalpes). The internal parts of the Northern Apennine are made up of retro-thrusted upper plate units of the former Alps that extended south to Corsi- ca and beyond. They also comprise upper plate remnants of the Alpine Piemont-Liguria ocean that did not close during Alpine orogeny (Antola nappe; internal Ligurides); later, during Apenni- nic orogeny, they were thrusted onto the continental part of the Adriatic plate. In southern Italy Apenninic orogeny is linked to some 1000km of ESE-directed slab retreat of the west-dipping Calabrian slab (the oceanic part of the Adria plate) underneath the continental parts of the Adria plate commencing at around 35 Ma and leading to the opening of the Western Mediterranean oceanic basins. This slab retreat induced a reversal of subduction polarity in the Northern Ap- ennines that was also instrumental for oroclinal bending in the southernmost Western Alps after some 25 Ma ago. This reversal in subduction polarity affecting the northern Apennines including the Ligurian Alps is linked to SW-directed subduction of the Adriatic plate beneath the northern Apennines and, for purely geometrical reasons, necessitates slab break-off of the E-dipping European slab as postulated by Lippitsch et al. (2003). References Diehl, T., Husen, S., Kissling, E., & Deichmann, N. (2009). High-resolution 3-D P-wave model of the Al- pine crust. Geophys. J. Int., 179: 1133–1147. Lippitsch, R., Kissling, E., & Ansorge, J. (2003). Upper mantle structure beneath the Alpine orogen from high-resolution teleseismic tomography. J. Geophys. Res., 108, doi: 10.1029/2002JB002016. Schmid, S.M., Kissling, E., Diehl, T., van Hinsbergen D.J.J., & Molli, G. (2017). Ivrea mantle wedge, arc of the Western Alps, and kinematic evolution of the Alps–Apennines orogenic system. Swiss Journal of Geosciences, 110: 581-612. Waldhauser, F., Kissling, E., Ansorge, J., & Mueller, St. (1998). Three-dimensional interface modelling with two-dimensional seismic data: The Alpine crust-mantle boundary. Geophys. J. Int., 135: 264-278. Zhao, L., Paul, A., Malusa, M.G., Xu, X., Zheng, T., Solarino, S., Guillot, S., Schwartz, S., Dumont, T., Salimbeni, S., Aubert, C., Pondrelli, S., Wang, Q., & Zhu, R. (2016). Continuity of the Alpine slab unrav- elled by high-resolution P wave tomography, J. Geophys. Res. Solid Earth, 121: 8720–8737, doi:10.1002/2016JB013310.

110

Preservation of oscillatory zoning in plagioclase inclusions from the Western Gneiss Region, Norway

Katharina Schmidt1, Xin Zhong2, Johannes Vrijmoed3, Lucie Tajcmanova1, Oliver Plümper4

1Institute of Geochemistry and Petrology, ETH Zürich, Switzerland, kathari- [email protected] 2Physics of Geological Processes (PGP), University of Oslo, Norway, 3Institute of Geological Sciences, Freie Universität Berlin, Germany, 4Department of Earth Science, Utrecht University, Netherlands

For many minerals, chemical diffusion is sufficiently fast on the geological time scale to homogenize chemical heterogeneities at temperatures exceeding 700°C. Therefore, the observation of preserved chemical zoning at high temperatures is difficult to explain. This is particular problematic for oscillatory zoned minerals with sharp compositional steps experiencing high-temperature metamorphic conditions for several million years. Here we investigate a rock specimen from the Western Gneiss Region (WGR) that experienced Caledonian ultra-high pressure (UHP) metamorphism with peak metamorphic conditions of 800°C and 3.2 GPa, and a post UHP overprint (with T >750°C and 1.2 GPa) during exhumation. ∼ Polymineralic inclusions in garnets encompass amphibole, biotite and oscillatory zoned plagioclase of 150 x 200 μm size with thin compositional lamellae of 1-10 μm alternating from core towards the rim. The zoning of the plagioclase grain is reverse with increasing anorthite content from the inclusion core to the rim. We conducted a detailed microstructural characterisation utilizing a combination of electron microprobe analysis (EPMA), electron backscatter diffraction (EBSD) measurements and analytical transmission electron microscopy (A-TEM). The high-resolution analyses show that the compositional profile has sharp contacts between each lamella. Such sharp contacts exclude the possibility of pervasive diffusional modification. In order to understand how such a high-temperature microstructure with sharp chemical zoning can be preserved on the million years’ time scale, we apply conventional and unconventional diffusion quantification methods. It is shown that conventional (Fickian) diffusion would have equilibrated this microstructure within thousands of years. In contrast, we apply the newly developed approach where chemical diffusion is coupled to mechanical deformation (Zhong et al., 2017). We show that the preservation of such a compositional zoning in minerals can be strongly influenced by this coupling. A significant pressure gradient is developed inside the grain due to the chemical diffusion at the very early stage of the chemical re-equilibration. Due to slow viscous relaxation, this pressure gradient is then able to inhibit further concentration homogenization, explaining the preservation of the oscillatory zoning.

References Zhong, X., Vrijmoed, J., Moulas, E., & Tajcmanova, L., (2017). A coupled model for intragranular deformation and chemical diffusion. Earth and Planetary Science Letters, 474: 387-396.

111

Elastic anisotropies of rocks from oceanic and continental crust and the upper mantle

Michael J. Schmidtke1, Ruth Keppler1

1Rheinische Friedrich-Wilhelms Universität, Bonn, Germany, [email protected]

Current seismic studies allow increasingly better resolutions and imaging at higher depth, however the interpretation of these images is only possible with precise data on petrophysical properties (i.e. elastic anisotropies) of the rocks involved. In the olivine dominated mantle these anisotropies result from strain induced crystallographic preferred orientation (CPO) of olivine. However, in the polyminearlic crust, CPO of all constituent mineral phases contribute to the overall seismic anisotropy. In order to obtain representative elastic anisotropies from oceanic crust, continental lower crust and upper mantle, samples were collected from two different locations. In the Italian Western Alps in the Lago di Cignana area (Kirst & Leiss, 2016, Zermatt-Saas-Zone), eclogites and blueschists of oceanic origin are exposed whereas near Finero (Northwestern Italy) parts of the Ivrea body are accessable. Here lower crustal rocks and mantle peridotites are exposed. The CPO of the constituent mineral phases of these samples were measured using time-of- flight neutron diffraction, allowing to gain representative bulk textures. Using these CPOs and single crystal elastic anisotropies the petrophysical properties of the samples were modelled. We present the preliminary results of our investigation.

References Kirst, F., & Leiss, B., (2016). Kinematics of syn- and post-exhumational shear zones at Lago di Cignana (Western Alps, Italy): constraints on the exhumation of Zermatt–Saas (ultra)high-pressure rocks and deformation along the Combin Fault and Dent Blanche Basal Thrust. Int J Earth Sci (Geol Rundsch). Sprin- ger-Verlag; Berlin Heidelberg.

112

Active normal faults within the convergent thrust belt front of the Southern Dinarides (Montenegro & Albania)

Benjamin Schmitz1, Peter Biermanns2, Kamil Ustaszewski1, Silke Mechernich3, Martin Đaković4, Kristijan Sokol5, Klaus Reicherter2

1FSU Jena, Institute of Geosciences, Jena, Germany, [email protected] 2RWTH Aachen University, Neotectonics and Natural Hazards Group, Germany 3University of Cologne, Institute of Geology and Mineralogy, Germany 4Geological Survey of Montenegro, Podgorica, Montenegro 5Faculty of Mining and Geology, University of Belgrade, Serbia

The Southern Dinarides comprise one of the seismically active regions in Europe. The compressional focal mechanism of the desastrous Mw = 7.1 earthquake in 1979 offshore Montenegro is in line with recent GPS studies, that show ongoing SW-NE convergence between the Adriatic plate and Eurasia. In contrast to this, we report on evidence for active extension in the coastal areas of southernmost Montenegro and northern Albania. Within the timespan of instrumentally recorded seismicity (c. the last 100 years), none of the available focal mechanisms show an extensional fault plane solution. This area was hitherto believed to be exclusively characterised by ongoing horizontal contraction.

One prominent example of active extension is a c. 16 km long, intermittently traceable normal fault scarp along the Rumija chain in southern Montenegro between Donja Poda and Bojke (Fig. 1). It juxtaposes Mesozoic bedrock against colluvial slope scree of Quaternary age, with an average topographic offset of 4-7 m in sections that are unaffected by gullies.The fault plane gradually is changing its orientation and dip from 270/55 (in the W) to 193/70 (in the E). Fault striae are uniformly plunging (251/52) for the major part of the scarp, unaffected by along-strike undulation of the fault-plane. The only exception appears to be a smaller section of c. 750 m NW of Bojke which is sub-vertical and shows a considerable left-lateral strike-slip movement (132/37) linking two larger dip-slip segments of the scarp. Alongstrike the scarp, distinct horizons of various weathering indicators like differences in color, lichen growth or karstification imply periodic motion along the fault plane, possibly during earthquakes. Commonly, these fault scarps are interpreted to represent cummulative earthquake features that due to glacial surface flattening only evolved in the Holocene or after the Last Glacial Maximum (c. 18,000 BP). As a preliminary slip rate of the normal fault we calculated 0.2-0.38 mm/a for 18 ka, and, respectively higher rates for 15 ka and 12 ka. Magnitude estimates based on the empirical correlations of Wells & Coppersmith (1994) imply magnitudes between Mw = 6.2 (based on the mapped average displacement of 0.13 m for the last events) and Mw = 6.5 (based on surface rupture length) which are in the range of extensional earthquakes in the Southern Appenines. Further information is expected to be obtained from 36Cl cosmogenic dating, as we already Fig. 1: Location of extensional fault scarp traces with sampled the free face. dip-slip (solid) and strike-slip (dashed) components.

References Wells, D. L., & Coppersmith, K. J., (1994). New Empirical Relationships among Magnitude, Rupture Length, Rupture Width, Rupture Area, and Surface Displacement. – Bulletin of the Seismological Society of America, 84: 974-1002.

113

Depositional setting of Cretaceous syntectonic sediments of the external Northern Calcareous Alps, Allgäu, Bavaria

Anna-Katharina Sieberer1, Hugo Ortner1

1Institute of Geology, University of Innsbruck, Austria, [email protected]

Within the thin-skinned fold-and-thrust belt of the Northern Calcareous Alps (NCA), syntectonic sediments got deposited during Cretaceous Alpine orogeny from the Aptian onwards. In the external NCA, tectonic elements like Cenoman-Randschuppe, Allgäu nappe and northern Lechtal nappe show deposition of three syntectonic Fms.: Tannheim (Aptian-Albian), Losenstein (Albian) and Branderfleck (Cenomanian-Santonian) Fms. (Gaupp, 1982). The sediments of the Branderfleck Fm. were deposited unconformably as thrust-sheet-top deposits on the deeply eroded northern Lechtal nappe, and conformably as upper-footwall deposits on the Cenoman-Randschuppe (Ortner and Gaupp, 2007). (Mega)breccias, deep water tur- bidites, and marls consist mainly of material derived from the underlying units. The exotic clastic material (i.e. phyllites, quartz porphyry and serpentinite grains in the sand fraction) was most probably derived from the internal Alpine orogen, whereas Upper Jurassic to Lower Cretaceous may be sourced from a hypothetic realm in the north (Gaupp, 1983). Fold growth during sedimentation of the Branderfleck Fm. created growth strata with progressive unconformities between sedimentary layers. This documents ongoing contraction after nappe emplacement. Local scarp breccias with red marls on top, fine grained sandstones, and brown marls form one of the investigated growth strata located southwest of Branderschrofen, Allgäu (Lechtal nappe). All Cretaceous syntectonic deposits are affected by major subsidence. Intermittent uplift and related exhumation prior to deposition of syntectonic sediments can be related to stacking of thrust sheets, followed by subsidence from subaerial to shallow marine to pelagic conditions. We suggest that the depositional environment of the Cretaceous syntectonic deposits is a foreland basin. Foreland subsidence is a mechanism that could affect also thrust sheets (carrying piggy-back basins) emplaced within the foreland. The Branderfleck Fm. shows small thickness (a few tens of meters), compared to the syntectonic sediments of the Gosau Group in the more internal part of the nappe stack (several hundreds of meters). Located in an external part of the suggested foreland basin (Branderfleck Fm.), close to the forebulge, less accommodation space could cause less deposition. The forebulge could therefore be the source of Lower Cretaceous shallow water carbonates, providing the hypothetic depositional realm in the north. The available data are consistent with a foreland basin setting for syntectonic deposition in the external NCA, as suggested by e.g. Ortner et al. (2016) for the NCA.

References: Gaupp, R., (1982). Sedimentationsgeschichte und Paläotektonik der kalkalpinen Mittelkreide (Allgäu, Tirol, Vorarlberg). Zitteliana, 8: 33-72. Gaupp, R., (1983). Die paläogeographische Bedeutung der Konglomerate in den Losensteiner Schichten (Alb, Nördliche Kalkalpen). Zitteliana, 10: 155-171. Ortner, H., Gaupp, R., (2007). Synorogenic sediments of the western Northern Calcareous Alps. Geo.Alp, 4: 133-148. Ortner et al. (2016). Geometry of growth strata in a transpressive fold belt in field and analogue model: Gosau Group at Muttekopf, Northern Calcareous Alps, Austria. Basin Research, 28(6): 731-751.

114

Evolution of the Tropoja basin in NE Albania and possible links to the Shkodër- Peja Normal Fault

Daniel Simon1, Jörg Giese1, Mark R. Handy1, Marc Grund1, Kujtim Onuzi²

1Freie Universität Berlin, Department of Earth Sciences, Berlin, Germany, si- [email protected] 2Polytechnic University of Tirana, Institute of GeoSciences, Tirana, Albania

The Plio-Pleistocene Tropoja basin in NE Albania is one of several sedimentary basins in the hanging wall of the Shkodër-Peja Normal Fault (SPNF). The initiation and evolution of these basins are directly linked to the SPNF and hence provide insight into the development of this fault system. The central Tropoja basin features at least three main and several subordinate river terraces created by the successive incision of the Valbona, Gashit and Bushtrices rivers. While the Bushtrices river in the southeast remained in its streambed since incision began, the Valbona and Gashit rivers successively abandoned parts of their previously separate riverbeds and presently join near the northwestern limit of the Tropoja basin. Abandoned terraces, - channels and -riverbeds are preserved east and southeast of the currently active streambed, indicating either that the basin was uplifted and/or that the base level of erosion has dropped. Using topographic level of these terraces as a proxy for their age, we discern at least a three- step shift of the riverbeds progressively from east to west within the basin. Karstification and degradation of terraces in the central northern Tropoja basin preclude a correlation of some of the terraces.

It is unlikely that varied erodibility of the basin substratum is responsible for the westward shift in the channels of the Valbona and Gashit rivers because Pleistocene deposits forming this substratum are lithologically homogeneous throughout the study area as indicated by stratigraphic profiles in several locations. More likely, although not proven to date, is that the channels migrated to the W due to NW tilting of the Tropoja basin in the hanging wall block of the SPNF. Thus, the flow of the Valbona/Gashit river sub-parallel to the strike of the SPNF in the northwestern part of the basin marks the latest drainage axis in response to NW-SE directed extension. More geomorphological and structural investigation is needed to unravel the evolution of the Tropoja basin.

115

Deformed Roman monuments along active faults in NW Croatia - archaeoseismological studies

Rosana Skrgulja1, Miklós Kázmér2

1Sisak City Museum, Sisak, Croatia, [email protected] 2Eötvös University, Department of Palaeontology, Budapest, Hungary, [email protected]

Proximity of the active faults of Croatia is being studied for evidence of past earthquakes by archaeoseismology. Due to (literally) low-level preservation of Roman monuments in Pannonian Croatia, we had to reserve ourselves to the study of deformation structures near or below ground. Andautonia (Scitarjevo) displays shifted and tilted column bases adjacent to a Roman road. The basin of Aquae Iasae (Varazdinske Toplice) displays a curious, 'unfinished' collapse structure, best explained as caused by liquefaction. Excavations of the Roman city of Siscia (Sisak, Croatia) yielded large chunks of thick brick walls (considered to be the city wall), collapsed in the adjacent ditch in their entirety. The wall is made of brick masonry on both sides and a thick concrete infill between them. Much of the collapsed portion is entire, there are not even joints between adjacent bricks. Wall chunks are found in various orientation: the original layering of masonry is now mostly vertical, even overturned. The remaining foundation displays features of twisting and shearing. There is considerable distance between the foundation and the collapsed portion: foundation and wall are about 2 m apart. The construction level is underlain by sandy clay. Significant recycling of construction material occurred in later centuries, so original dimensions are estimates only. We suggest that a major earthquake damaged the city wall of Siscia. Excitated by site effects of loose soil, high peak ground acceleration caused the wall to be removed from its foundation, landing it ultimately in the ditch nearby. Presumed intensity of the earthquake was IX. Fault activity within a couple of kilometres was responsible for this collapse. Rebuilding of the city wall in the late antique period suggests that the first wall collapsed between the beginning of the 3rd and the middle of the 4th century. This earthquake between ~200 AD and ~350 AD are missing from historical catalogues. We suggest that fault activity in Croatia is more widespread than previously considered. Archeoseismical features - even if lacking proper dates - must be added to the catalogues of historical earthquakes of the region.

Fig. 1: Six metre long portion of stone-and-concrete Roman city wall of Siscia (Sisak) collapsed in the adjacent ditch. Overturned wall on the left, twisted and sheared top of wall foundation on the right.

116

A rift basin in the External Pamir - paleogeographic implications for reconstructing the Cenozoic deformation history

Edward R. Sobel1, Jonas Kley2, Johannes Rembe1, Baiansuluu Terbishalieva1, Chen Jie3, Ren- jie Zhou4

1Universität Potsdam, Inst. Erd- und Umweltwissenschaften, Potsdam, Germany, edso- [email protected], [email protected], [email protected] 2Georg-August-Universität Göttingen, Abt. Strukturgeologie/Geodynamik, Göttingen, Germany, [email protected] China Earthquake Administration, Institute of Geology, State Key Laboratory of Earthquake Dy- namics, Beijing, China, [email protected] 4The University of Queensland, School of Earth and Environmental Sciences, Brisbane, Austral- ia, [email protected]

The Cenozoic Pamir consists of earlier accreted, east-west trending Mesozoic-Paleozoic terranes and intervening sutures broadly correlative with units exposed to the east, in Tibet, and to the west. The lateral offsets of sutures and the West Kunlun - North Pamir belt are thought to constrain the magnitude of Cenozoic Pamir indentation, which is typically assumed to be 300 km. South of the narrow Alai foreland basin, the External Pamir (Trans-Alai range) comprises a thrust stack of Carboniferous to Neogene sedimentary rocks detached from the underthrusting Tien Shan-Alai crust, forming the Pamir Frontal Thrust system (PFT). The Northern Pamir is emplaced northwards over the External Pamir along the Main Pamir Thrust (MPT). The Northern Pamir comprises two major tectonic units separated by the Kunlun suture: (1) Paleo- zoic metasedimentary and (ultra)mafic igneous rocks equivalent to the Kunlun terrane (in the north) and (2) the Karakul-Mazar paleogeographic domain of Paleozoic metamorphic rocks intruded by Permian-Triassic plutons (in the south). The Karakul-Mazar terrane is bounded on the south by the Tanymas (Jinsha) suture, which represents the Triassic closure of the Paleo- Tethys ocean following north-dipping subduction. We have studied Paleozoic - Mesozoic sections of the External Pamir in the Qimgen valley, in NW China, and the Altyn Darya valley, in the Kyrgyz republic. Both localities expose a clastic sequence with red sandstones that are offset by normal faults, pyroxene-bearing basalt dikes and flows, and rhyolites. Similar basalts can be found along-strike in Tajikistan. Both the structures and the bimodal volcanism suggests a rift setting; the size of the basin is not yet clear. The age of the deposits is poorly constrained. In China, the strata are mapped as upper Permi- an in age, while the basalts and rhyolites are mapped as Triassic. To date, we have obtained a 222.1±1.1 Ma whole rock Ar/Ar age from a Chinese basalt; similar Kyrgyz units were too strongly metamorphosed to be dated. The minimum ages of detrital U/Pb zircons from the Chinese red sandstones also suggest a Triassic depositional age. In turn, the Triassic ages suggest that the basin formed in the back-arc of the Tanymas suture. We suggest that this extensional basin stretched along the rim of the entire Pamir; however, there is no evidence that this belt continued eastward into the Kunlun. It is not yet clear whether this basin closed during the Mesozoic or the Cenozoic. The existence of this basin has important implications for the paleogeographic evolution of the Pamir region. When the basin opened, it would have offset the North Pamir southward with respect to Tarim, north of the Kunlun. In turn, this suggests that the North Pamir and the Kunlun may not have formed a linear belt in Mesozoic time or at the beginning of the Cenozoic. Since this alignment forms the basis for calculating the amount of northward indentation of the Pamir with respect to the Kunlun, existing geodynamic models may need to be reconsidered. Further- more, if the rift basin only represents the margin of a broad oceanic basin which closed in the Cenozoic, the seismically-imaged south dipping slab beneath the Pamir could represent oceanic material being subducted. Therefore, understanding the geodynamic evolution of this rift basin will help to constrain how the Pamir has deformed during the Cenozoic.

117

Assessing viable geodynamic environment for the magmatism within the Sava- Vardar Zone: A case study from the vicinity of Belgrade

Sokol Kristijan1, Dejan Prelević1,2, Marinko Toljić1, Nenad Čokulov1

1Faculty of Mining and Geology, University of Belgrade, [email protected] 2Institute of Geological Science, University of Mainz

The Sava-Vardar Zone in the Balkans represents a remnant of the most recent suture between European and Adriatic plates generated after the closure of the Neotethyan Ocean (Gallhofer et al., 2015). Slightly metamorphosed or just terrigenous sediments with carbonates and rare but widespread magmatic bodies of the Cretaceous age are the most important lithologies that occur along this zone. Our new results of the P-T conditions from the mantle-derived lamprophyres from Tešića Maj- dan vary between 1100-1200 °C and around 15 kbar (~50 km depth) based on Cpx thermoba- rometer (Putirka, 2008) and biotite thermometer (Righter and Carmichael, 1996). When the magmatism in the Sava-Vardar Zone occurred, a change in kinematics was also registered (Toljić et al., 2018). The conditions changed from contraction to extension deformation settings where large numbers of NNW-SSW oriented syndepositional normal faults were created, which indicate an overall WSW-ENE direction of extension. Lamprophyres can be considered as tectonomagmatic time marker of changes in geodynamic conditions (Scarrow et al., 2011). Rocks from Tešića Majdan represent such change, and mark the initiation phase of the extensional episode at 85 Ma, while most of the magmatic bodies from the other locations within the Sava-Vardar zone are slightly younger between 82 and 80 Ma. There are two models that are trying to explain the magmatism in the Sava-Vardar zone. In the first model, magmatism is generated in the forearc region of the subduction environment (Toljić et al., 2018). In the second model, volcanism is generated in the intracontinental environment as a result of transtensional tectonics along the suture between already collided Adria and Eu- ropean plate (Prelević et al., 2017). Based on the results of this investigation, our goal is to re- fine the two already existing tectonic models.

References Gallhofer, D., Quadt, A. v., Peytcheva, I., Schmid, S. M., & Heinrich, C. A., (2015). Tectonic, magmatic, and metallogenic evolution of the Late Cretaceous arc in the Carpathian-Balkan orogen. Tectonics, 34: 1813-1836. Prelević, D., Wehrheim, S., Reutter, M., Romer, R. L., Boev, B., Božović, M., van den Bogaard, P., Cvetković, V., & Schmid, S. M., (2017). The Late Cretaceous Klepa basalts in Macedonia (FYROM)— Constraints on the final stage of Tethys closure in the Balkans. Terra Nova. 29: 145-153. Putirka, K. D., (2008). Thermometers and Barometers for Volcanic Systems. Minerals, Inclusions and Volcanic Processes, 69: 61-120. Righter, K., & Carmichael, I. S. E., (1996). Phase equilibria of phlogopite lamprophyres from western Mexico: biotite-liquid equilibria and P-T estimates for biotite-bearing igneous rocks. Contributions to Mineralogy and Petrology, 123: 1-21. Toljić, M., Matenco, L., Stojadinović, U., Willingshofer, E., &Ljubović-Obradović, D., (2018). Understanding fossil fore-arc basins: Inferences from the Cretaceous Adria-Europe convergence in the NE Dinarides. Global and Planetary Change. In Press, https://doi.org/10.1016/j.gloplacha.2018.01.018.

118

Holocene tectonic activity on the Mariánské Lázně fault (Cheb basin, West Bohemia)

Petra Štěpančíková1, Tomáš Fischer2, Filip Hartvich1, Petr Tábořík1, Thomas Rockwell3, Jakub Stemberk1, 3, Jakub Široký3, Hamid Sana1

1Institute of Rock Structure and Mechanics, Czech Academy of Sciences, Czech Republic, ste- [email protected] 2Faculty of Science, Charles University, Prague, Czech Republic, [email protected] 3Dpt. of Geological Sciences, San Diego State University, California, [email protected]

Paleoseismic trenching, geophysical survey, and numerical dating (OSL and radiocarbon methods) were used to study tectonic activity of the NNW-SSE trending Mariánské Lázně Fault (MLF), which is situated in the western part of the Bohemian Massif in the West Bohemia. The northern segment of the MLF controls the morphologically pronounced mountain front of the Krušné hory Mts and the eastern limit of Cenozoic Cheb basin, which is famous for earthquake swarms (max. ML=4.6) and CO2 emanation. We performed 2D and 3D geophysical survey (electric resistivity tomography, ground penetration radar) and 3D trenching (fault-parallel and fault-crossing trenches) at the study site Kopanina to look for large surface-rupturing prehistoric earthquake responsible for the pronounced mountain range front. Seven excavated and six hand-dug trenches revealed a complex geology and deformation probably as a result of right- lateral transpression during Late Quaternary. Repeated movements along several fault strands of various ages within the MLF zone migrated towards the basin. The youngest fault displaced and deformed Holocene deposits of the age interval 5.3 - 1 ka BP, which is the youngest proved surface faulting in central Europe, reported so far. The youngest observed faulting occurred during two earthquakes of suggested minimum magnitude Mw=6.3 – 6.5.

Fig. 1: (a) Aerial photo of trenching area with MLF fault trace, trench position and ERT Profile A position, (b) photo of the convex-shaped part of the slope (upper arrow) controlled by the fault F1, which was also exposed in the trench.

119

Early Palaeozoic evolution of the northern Peri-Gondwana shelf – reconsidering the sedimentary, magmatic and the tectono-metamorphic record

Tobias Stephan1, Uwe Kroner1, Rolf L. Romer2, Delia Rösel1

1Institut für Geologie, TU Bergakademie Freiberg, B. v. Cotta Str. 2, 09599 Freiberg, Germany, [email protected] 2Deutsches GeoForschungsZentrum GFZ, Telegrafenberg, D-14473 Potsdam, Germany

Plate-tectonic reconstructions require precise and reliable knowledge of the pre-orogenic architecture of the involved plate margins. The Variscan-Appalachian orogeny reworked the entire shelf of northern Gondwana, which dominantly comprises Early Palaeozoic passive margin sequences. Due to complex Variscan orogenic processes and the Alpine overprint, there exist a large number of palaeogeographic reconstructions that are in mutual conflict. In order to test the various models, we analysed statistically a large data base of detrital zircon from 770 sedimentary and the geochemistry / geochronology of 479 magmatic rocks. The analysed Palaeozoic units are distributed over the entire orogen. We show that the Western and the Eastern Peri- Gondwana shelf, although part of the same contiguous shelf differ significantly in sediment provenance, the timing and chemistry of magmatic activity, and the tectono-metamorphic and litho-stratigraphic record: (1) Statistical analysis of 58601 detrital zircon U-Pb ages of the Palaeozoic sedimentary units yields a contiguous Peri-Gondwana shelf but with three areas of contrasting provenance, namely an Avalonian, West African, and East African-Arabian zircon province (Stephan et al., 2018). (2) The magmatic record reveals a trend from Cambrian bimodal, peralkaline magmatism in the western shelf to Ordovician calc-alkaline, peraluminous magmatism in the eastern shelf. (3) The litho-stratigraphic record reflects the differentiation into two contrasting shelf areas. The magmatic sequences are reflected in volcano-sedimentary series and massive oolithic Fe- formations in the sedimentary record. The correlation of stratigraphic discontinuities allows for the differentiation of the evolution of the western, i.e. the Rheic shelf and the eastern, Proto- Tethys shelf. (4) The Middle Ordovician sedimentary discontinuity correlates with the tectono-metamorphic “Sardic event” (or “Cenerian Orogeny”). The high-grade metamorphic and compressional event is a characteristic feature of the eastern shelf and is not recorded in the western shelf.

Our palaeogeographic reconstruction takes these constraints into account. We explain the provenance pattern of the Gondwana shelf as a result of two independent and contrasting Gondwana super-fan systems that were separated by the remains of the Trans-Saharan Oro- gen. This continental watershed divides the shelf into a western and eastern part. Both shelf areas were affected by different tectono-metamorphic and magmatic events. The temporal and chemical variation of magmatic rocks reflects Early Palaeozoic extension that propagated from the (d)rifting of Avalonia away from Gondwana (opening of Rheic Ocean) and within-plate magmatism within the western shelf (i.e. the formation of the Armorican Spur, Kroner & Romer, 2013) to subduction-related magmatism at the eastern shelf. Different rates of extension and plate-tectonic reorganization due to the Avalonia-Laurussia docking lead to the decoupling of both shelf areas in the Middle Ordovician epoch. This event is reflected by the “Sardic” compressional and high-grade metamorphic event at the passive margin of the Proto-Tethys. A resulting temporary uplift of this shelf area lead to erosional gaps in the geological record. The resulting shelf architecture is the underlying cause for the first order geometry of the Variscan- Appalachian belt, e.g. the Bohemian and the Ibero-Armorican orocline. References Kroner, U., & Romer, R. L. (2013). Two plates—many subduction zones: the Variscan orogeny reconsidered. Gondwana Research, 24(1), 298-329. Stephan, T., Kroner, U., & Romer, R. L. (2018). The pre-orogenic detrital zircon record of the Peri- Gondwanan crust. Geological Magazine, 1-27.

120

Crustal-scale 3D modelling of the Allochthonous Domain of the Erzgebirge- Vogtland-Fichtelgebirge area, Saxo-Thuringian Zone

Tobias Stephan1, Peter Hallas1, Uwe Kroner1, Stefan Buske2

1Institut für Geologie, TU Bergakademie Freiberg, B. v. Cotta Str. 2, 09599 Freiberg, Germany 2Institut für Geophysik und Geoinformatik, TU Bergakademie Freiberg, B. v. Cotta Str. 2, 09599 Freiberg, Germany

Geophysics combined with 3D modelling may significantly contribute to address and visualize geological problems. Nevertheless, in orogenic complexes, such as the Saxo-Thuringian Zone, existing geophysical and geological methods (reflection and refraction seismics, drillings etc.) were not able to shed light into the lower parts of the crust. Modern high-resolution geophysical methods allow to unravel the entire crustal architecture of orogenic complexes. Here, we present a crustal-scale 3D model of the allochthonous part of the Saxo-Thuringian Zone based on high-resolution deep seismic profiles combined with an extensive geological datasets including 2658 drillings. The seismic DEKORP profiles (MVE90, FB01-EV0 and GRANU95, 9HR) were re-processed by Kirchhoff prestack depth migration. The model is further constrained by gravi- metric and magnetic anomalies and the recent earthquake distribution.

Results of the 3D modelling reveal shallow dipping metamorphic units in the upper crust that are ruptured by a fault network of upper-crustal, listric NE-dipping faults (e.g. Gera-Jáchymov Zone, Flöha Zone, Elbe Zone, Lausitz Thrust) and steep, crustal-scale faults (e.g. the Franconian Line, Mariánské Lázně Fault). The transition to the mantle is represented by a laminated mafic lower crust at 27–30 km depth. A NE striking, steep zone of weak reflectivity until the upper mantle constitutes the early Variscan strike-slip fault and boundary between the high-grade Al- lochthonous Domain and the low-grade Wrench-and-Thrust Zone. The geochemically distinct granites of the Erzgebirge form isolated granitic bodies and were emplaced along major tectonic structures. According to our seismic imaging results, most of the granites terminate at a depth of 5–10 km suggesting a laccolithic structure.

Fig. 1: From seismic interpretation to three-dimensional geological modelling: a snapshot of the crustal- scale architecture of the Erzgebirge-Vogtland-Fichtelgebirge complex (the 3D model can be visualized with common internet browsers using https://efc.giga-infosystems.com/webgui/).

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Paleozoic evolution of the Baltic Basin - preliminary results based on integrated seismic data interpretation and subsidence analysis

Agata Stypa1, Aleksandra Stachowska1, Wojciech Kozłowski2, Piotr Krzywiec1, Mateusz Kufrasa1

1Institute of Geological Sciences, Polish Academy of Sciences (ING PAN), Twarda 51/55, 00- 818, Warsaw, Poland, [email protected], [email protected], [email protected], [email protected] 2Faculty of Geology, University of Warsaw, Żwirki I Wigury 93, 02-089 Warsaw, Poland wlko- [email protected]

The aim of the study was to estimate a reliable amount of post-Silurian erosion in the Baltic Basin (N Poland), which underwent substantial flexural subsidence during the Caledonian orogeny and post-orogenic uplift. The presented results are based on the interpretation of a regional seismic profile of the PolandSPAN® survey and subsidence analyses of key calibration wells. The study area is located in northern Poland and is a part of the Baltic Basin, a Paleozoic, pericratonic sedimentary basin which developed above the SW edge of the East European Craton. Its tectonic evolution includes Neoproterozoic rifting, Cambrian-Ordovician post-rift thermal subsidence, and Silurian flexure due to Caledonian collision. The Silurian sedimentary cover of the Baltic Basin is capped by a regional, erosional unconformity above which the Perm- Mesozoic cover of the Polish Basin developed. However, the Caledonian foreland basin may have also comprised a Lower Devonian succession, still present in the Lithuanian part of the basin (Poprawa et al., 1999). The Middle-Upper Devonian and Carboniferous deposits might have been also deposited in this area (Narkiewicz, 2007; Środoń, 2001, 2009); however, the amount of uppermost Silurian-Carboniferous deposits that have been eroded remains a subject of dispute. In order to constrain the geometry of the basin, a NE-SW oriented 2D regional seismic profile, calibrated by three deep research wells: Słupsk IG-1, Lębork IG-1 and Darżluie IG-1, has been interpreted. Then, a subsidence analysis was carried out for calibration wells, in order to estimate the thickness of eroded uppermost Silurian – Carboniferous? strata. Two scenarios of subsidence modeling were proposed: one assuming a variable heat-flow and moderate erosion rates, and a second assuming a constant heat flow and higher erosion rates. The models were calibrated with the use of vitrinite reflectance data (%Ro) and bottom hole temperatures (BHT). A subsidence model assuming constant and similar to the present-day heat flow was selected due to its better fit to well data. Seismic data interpretation and subsidence modelling revealed that a large-scale, wide spread post-orogenic erosion occurred and might have led to a removal of up 4.5 km of the uppermost Silurian – Carboniferous? deposits. ION Geophysical is thanked for providing PolandSPAND® seismic data used in this study. The authors are indebited to Platte River Associates, Inc. for providing the BasinMod® software for subsidence analysis. This study was funded by NCN grant No 2015/17/B/ST10/03411.

References Narkiewicz, M., (2007): Development and inversion of Devonian and Carboniferous basins in the eastern part of the Variscan foreland (Poland). Geological Quarterly, 51: 231-256. Poprawa, P., Sliaupa, S., Stephenson, R., & Lazauskiene, J., (1999). Late Vendian–Early Palæozoic tectonic evolution of the Baltic Basin: regional tectonic implications from subsidence analysis. Tectono- physics, 314: 219–239. Środoń, J., & Clauer, N., (2001.: Diagenetic history of Lower Palaeozoic sediments in Pomerania (northern Poland), traced across the Teisseyre – Tornquist tectonic zone using mixed-layer illite-smectite. Clay Mineralogy, 36:15-27. Środoń, J., Clauer, N., Huff, W., Dudek, T., & Banaś, M., (2009). K-Ar dating of the Lower Palaeozoic K- bentonites from the Baltic Basin and the Baltic Shield: implications for the role of temperature and time in the illitization of smectite. Clay Minerals, 44: 361-387.

122

Application of backstripping and subsidence analysis in paleothickness reconstruction: case study from the Lublin Basin (Poland) and potential sources of uncertainty

Agata Stypa1, Mateusz Kufrasa1, Łukasz Słonka1, Piotr Krzywiec1

1Institute of Geological Sciences, Polish Academy of Sciences (ING PAN), Twarda 51/55, 00- 818, Warsaw, [email protected], [email protected], [email protected], [email protected]

The aim of the study was to estimate a reliable amount of late Devonian and late Carboniferous erosion in the southeastern part of the Lublin Basin. Cross-section balancing and subsidence modeling methods were used as independent and complimentary methods in order to unravel the structural evolution of the Małochwiej anticline. The Lublin Basin is a Paleozoic structural unit defined by the present-day sub-Permian- Mesozoic extent of Carboniferous strata. Its tectonic evolution includes Neoproterozoic rifting, Cambrian-Ordovician post-rift thermal subsidence, Silurian flexure due to Caledonian collision, late Devonian thick-skinned faulting, and late Carboniferous thin-skinned folding and thrusting. A representative 2D seismic depth-converted line striking acros the Małochwiej Anticline was used in the cross-section restoration. In order to analyze the compaction effect on present-day thickness an averaged lithology was used in the backstripping workflow and in subsidence modeling. Two scenarios of subsidence modeling were developed: one assuming a variable and another one assuming a constant heat flow. Both models were calibrated by vitrinite reflectance data and bottom hole temperatures. 2D seismic data were depth converted using a polynomial model of the velocity field, as it fits best to the measured data (Fig. 1). The subsidence model assuming a constant, similar to present-day heat flow, was selected due to its better fit with well data. Integrated analysis revealed that the research area underwent two major tectonic events at the end of the Devonian and the Carboniferous, respectively, during which a total amount of ~3.5 km of Paleozoic strata was eroded.

Fig. 1: Plot showing difference in calculated depth of chronostratigraphic boundaries for particular velocity models.

Acknowledgements Chevron Polska is kindly acknowledged for providing 2D seismic profiles used in this study. The authors are indebited to the Midland Valley Exploration Ltd. and Platte River Associates, Inc. for providing the Move and BasinMod software for cross-section balancing and subsidence analysis, respectively.

123

Slab gap or descending lithosphere slab beneath the Dinarides - comparison of several tomographic models

Franjo Šumanovac1 1University of Zagreb, Faculty of Mining, Geol. and Petr. Eng., Crotia, [email protected]

Since the theory of plate tectonics initiated, some considerations about a subduction of the Adriatic microplate beneath the Dinarides have been introduced, although there have been no evidences on the existence of a sinking lithosphere slab in the area. First evidence of the Adriat- ic subduction in the geological history was presented by Pamić (1998), which took part from the Jurassic to the Paleogene. However, recent geological models were constructed considering the absence of a lithospheric slab or “slab gap” at least beneath the northern Dinarides (Handy et al., 2015). These models were mainly based on some regional and global tomographic models (Piromallo and Morelli, 2003; Koulakov et al., 2009) that pointed to a lack of the fast anomaly beneath the north Dinarides and presence of the shallow fast anomaly in the south Dinarides. Teleseismic tomography can efficiently discover lithospheric slabs sinking in the asthenosphere on the basis of fast velocity anomalies. The method is characterized by very good horizontal resolution and poor vertical resolution. Teleseismic events are used and incident rays at the receivers are sub-vertical and steeply inclined, and horizontal velocity changes can be easily detected, while vertical velocity changes can’t. However, a good horizontal resolution depends on the space sampling, which means the study area should be uniformly covered by the receivers. Seismic arrays applied in the Piromallo-Morelli and Koulakov models do not satisfy this re- quirement, so the space sampling is poor. In the both arrays several stations were used in the north Dinarides and several in the south Dinarides, while the central Dinarides were not covered. The study area was much better sampled by the array applied by Šumanovac et al. (2017), and the seismic stations in the central Dinarides were also used. This model has better resolution due to 39 seismic stations used, contrary to 18 and 12 stations in the previous arrays. Šumanovac et al. (2017) interpreted shallow lithospheric slab beneath the north Dinarides and deep lithospheric slab beneath the south Dinarides on the basis of the Dinaridic fast velocity anomaly. Shallow fast velocity anomaly in the north Dinarides was for the first time discovered by Šumanovac and Dudjak (2016). In the model of Šumanovac et al. (2017) the fast anomaly is attenuated in the area of the north Dinarides and gives an impression about the break in the lithospheric slab between the north and south Dinarides. Synthetic model was constructed with the shallow vertical slab (down to 250 km) in the north Dinarides and the deep vertical slab in the south Dinarides (down to 450 km). Inverse velocity model for the initial synthetic model shows an attenuation and taper of the fast anomaly in the north Dinarides, so apparent discontinuity could be noticed, such as in the inverse model for the observed data. Besides, a close correlation between the inverse models for the synthetic and the observed data can be noticed. Accordingly, this seismic modelling verifies previous interpretation that the shallow Adriatic slab exists beneath the north Dinarides and the deep Adriatic slab beneath the south Dinarides, which is in general uniformly thick, and there is no breakage in the slab. References Handy, M.R., Ustaszewski, K., & Kissling, E. (2015). Reconstructing the Alps-Carpathians-Dinarides as a key to understanding switches in subduction polarity, slab gaps and surface motion. Int. J. Earth Sci., 404/1, 1-26. Koulakov, I., Kaban, M.K., & Tesauro, M. (2009). P- and S-velocity anomalies in the upper mantle beneath Europe from tomographic inversion of ISC data. Geophys. J. Int., 179, 345-366. Pamić, J. (1998). North Dinaridic late Cretaceous-Paleogene subduction-related tectonostratigraphic units of southern Tisia, Croatia. Geologica Carpathica, 49/5, 341-350. Piromallo, C., & Morelli, A. (2003). P wave tomography of the mantle under the Alpine-Mediterranean area. J. of Geophys. Res., 108/B2, 2065, doi: 10.1029/2002JB001757. Šumanovac, F., & Dudjak, D. (2016). Descending lithosphere slab beneath the Northwest Dinarides from teleseismic tomography. J. Geod., 102, 171-184, doi: 10.1016/j.jog.2016.09.007. Šumanovac, F., Markušić, S., Engelsfeld, T., Jurković, K., & Orešković, J. (2017). Shallow and deep lithosphere slabs beneath the Dinarides from teleseismic tomography as the result of the Adriatic lithosphere downwelling. Tectonophysics, 712-713, 523-541, doi: 10.1016/j.tecto.2017.06.018.

124

The second half of plate tectonics: finding the last ~200 Ma of subducted lithosphere and incorporating it into plate reconstruction

John Suppe1, Jonny Wu1

1Department of Earth and Atmospheric Sciences, University of Houston, Houston TX USA, [email protected], [email protected]

Precise plate-tectonic reconstruction of the Earth has been constrained largely by the seafloor magnetic-anomaly record of the present oceans formed during the dispersal of the last super- continent since ~200Ma. The corresponding world that was lost to subduction, which accounts for ~100% of the surface area of the Earth, has been only sketchily known. We have developed methodologies to map in 3D these subducted slabs of lithosphere in seismic tomography and to unfold them to the Earth surface, using them to constrain plate tectonic reconstructions. Slab edges are commonly formed at times of plate reorganization (for example bottom edges typically record initiation of subduction) such that unfolded slabs fit together in picture-puzzle fashion at times of reorganization, analogous to the fitting together of Africa and South America. Map- ping to date suggests that a relatively complete and decipherable record of lithosphere subducted over the last ~200Ma exists in the mantle today, providing a storehouse for new discov- eries.

References Wu, J., Suppe, J., Lu, R., et al., (2016). Philippine Sea and East Asian plate tectonics since 52 Ma constrained by new subducted slab reconstruction methods. Journal of Geophysical Research: Solid Earth, 121(6): 4670-4741. Wu, J., Suppe, J., (2017). Proto-South China Sea plate tectonics using subducted slab constrains from tomography. Journal of Eath Science, https://doi.org/10.1007/s12583-017-0813-x.

125

Subducting of continental rise, slope and shelf basins in Taiwan oblique arc- continent collision: Insight from tomography, surface geology, and seismic reflection data

John Suppe1,2, Yu-Huan Hsieh3, Char-Shine Liu3, Hsin-Hua Huang4, Maryline LeBéon5

1Earth and Atmospheric Sciences, Univ. Houston, Houston TX USA, [email protected] 2Geosciences, National Taiwan University, Taipei, Taiwan 3Ocean Center, National Taiwan University, Taipei, Taiwan, [email protected], [email protected] 4Institute of Earth Sciences, Academia Sinica, Taiwan, [email protected] 5Earth Sciences, National Central University, Taoyuan City, Taiwan, [email protected]

The active Taiwan arc-continent collision is oblique, showing a south-to-north transition from oceanic to continental subduction, resulting from the impingement of the N-S trending Luzon Arc of the Philippine Sea plate with the NE-SW trending Asian passive margin on the Eurasian plate. Here we focus on the role of major sedimentary basins of the continental shelf and slope that are below the Eurasian subduction interface and are undergoing initial stages of subduction, currently imaged to depths of 35-50 km in seismic tomography. In this study, we integrate deep multi-scale geophysical/geologic transects across the plate boundary in southern and central Taiwan with maps of the Eurasian subduction interface, base of the sedimentary and metasedimentary upper crust and the Eurasian Moho, based on local Vp and Vs tomography. These maps and transects reveal deep sedimentary basins below the Eurasian subduction interface.

126

Uplift and growth of the northwest Pamir

Rasmus Thiede1, Edward R. Sobel1, Paolo Ballato2, Konstanze Stübner1,4, Mustafo Gadoev3, Ilhomjon Oimahmadov3, and Manfred Strecker1

1Potsdam University, Erd- und Umweltwissenschaften, Potsdam-Golm, Germany 2Università Roma Tre, Dipartimento di Scienze, Sezione di Scienze Geologiche, Roma, Italy. 3University of Tübingen, Institut für Geowissenschaften, Tübingen, Germany 4Acad of Science of Republic of Tajikistan, Inst. Geology, Seismology, Dushanbe, Tajikistan

The Pamir forms the northwestern tail of the Tibetan plateau and is acting as a first-order feature indenting northward into Asia due to the Cenozoic Indo-Eurasian collision. Although new geophysical datasets image the large-scale geodynamic setting, the deformation and topographic uplift of the NW-Pamir is not well constrained and understood. Here we focus on northwestern unglaciated plateau margin of the Pamir, Darvaz and Peter-the- 1st Range. We analyzed it geomorphic characteristics using longitudinal river profiles. To compare these with the regional crustal cooling history related this to rock uplift and exhumation history. We present a new dataset of low-temperature-chronology, with 46 new Zircon U-Th- Sm/He (ZHe) ages, which range between >250 and 4 Ma, 5 Apatite fission track (AFT) ages ranging between 14 and 4 Ma and 11 Apatite U-Th-Sm/He (AHe) ages between 17 and 3 Ma. The NW-Pamir-margin consists of three main geologic units: the Central Pamir, the North Pamir and deformed Tadjik foreland basin. All three units are characterized by unique cooling paths, suggesting that they developed independently. In the central Pamir, all low-temperature thermochronologic data clusters between 14-10 Ma. The Darvaz Range, bounded by the Darvaz fault zone (DFZ) in the northwest and Badakhshan fault zone (BFZ) in the southeast, is characterized by rapid late Oligocene-Early Miocene cooling between 26 and 17 Ma, with a NW to SE younging trend. In contrast, ZHe ages obtained from Jurassic sandstones exposed within the DFZ yielded 11 unreset Triassic-Jurassic ages (~250-170 Ma) and 3 reset ages of ~5 Ma and one AHe 2.5 Ma age. Within the Peter-the-1st-Range, we obtain spatially-variable unrest and reset ages for ZHe but reset AFT ages of 4 to 5 Ma in the western and central western regions. Drainage pattern and DEM analysis indicate that the Panj River forms the base level that controls the river network draining the entire central and western margin of the Pamir. The Punj longitudinal riverprofil indicate that it has been established in the geologic past, has facilitated deep valley incision during uplift when crossing the Darvaz Range, but itself has not been uplifted significantly. Within the Darvaz Range we discovered extensive low-relief landscapes uplifted to 2 km in elevation above present day regional base level. Fluvial tributaries in these landscapes are characterized by gentle, concave-upward longitudinal upstream river profiles at high elevation. These are interrupted by major knick points and steep downstream segments, draining towards the deeply incised Panj River. Prior to uplift, this landscape had km-scale relief that was subsequently partly filled and covered by upper Neogene sediments, indicating pre- existing topography prior Neogene sediment filling and late-stage uplift. Exposed high-elevation uplifted paleo-landscapes and Neogene sediments (>3000 m asl.) cut by deeply incised river gorges (<1 km) document recent uplift along the plateau margin of the northwestern Pamir. The ZHe, AFT, and AHe ages from Central Pamir gneiss dome rocks indicate that rapid cooling during early to late Miocene dome extrusion ended at ~12-10 Ma. The scatter of ZHe, AFT, AHe ages indicate that the samples stayed in helium partial retention zone. The ZHe-ages of the rocks of Darvaz Range reflect major cooling during early Miocene exhumation in the hanging wall of the Main Pamir Thrust and DFZ, which we relate to thrusting during that time. Rapid cooling since ~5 Ma suggests that the Mesozoic together with the Paleogene and Neogene sections of the Tajik foreland depression have subsequently accommodated crustal shortening, causing enhanced uplift and erosion of the hanging wall of the Pamir Frontal Thrust to the north. In summery our results indicate that crustal shorting along the northwest Pamir indenter was dominated by two main deformation events. Distributed north-south contraction took place during the late Oligocene-early Miocene and was resumed during late Miocene and continuous today and caused synchronous uplift of Tien Shan and northern Pamir since then.

127

On the tectonic blocks of the Yuli belt, eastern Taiwan: Petrologic constraints

Chin-Ho Tsai1, Chiao Liu1, Wen-Han Lo1, Chih-Ying Yeh1

1Dept. Natural Resources & Environmental Studies, National Dong Hwa University, Hualien, Taiwan, [email protected]

Small, discontinuous metamafic and serpentinitic composite bodies in the metasediment- dominated Yuli belt had been described as “tectonic blocks” in literature (Liou et al., 1975). Origin(s) and evolution of these blocks are still largely unclear. The Yuli belt is recently interpreted as a middle-late Miocene accretionary prism on the basis of detrital zircon ages of the host metasediments (Chen et al., 2017). The tectonic blocks differ greatly from the host metasediments (pelitic and psammitic, with minor chloritic) in geochemical and textural characteristics. However, whether they were metamorphosed under the same or different conditions is a critical question yet to be answered. High-pressure (HP) metamorphic minerals, such as glaucophane and omphacite, have been identified in the tectonic blocks but not in the matrix metasediments yet. Nevertheless, new observations on field relations confirm that the former are embedded within the latter. Therefore, it seems less likely that both were metamorphosed at different physical conditions as previously thought. We have constrained representative litho-types from two of the major blocks and adjacent metasediments by applying petrogenetic grids, geothermobarometry, and computed equilibrium assemblage diagrams. Peak metamorphic temperatures for HP rocks in the tectonic blocks and their country rocks (metasediments) are fairly consistent at around 500-580°C, whereas peak metamorphic pressures, albeit less well constrained, are in the range of 10-17 kbar (cf. Beyssac et al., 2008; Tsai et al., 2013; Keyser et al., 2016; Baziotis et al., 2017). These P-T estimates indicate that both tectonic blocks and surrounding metasedimentary rocks are isofacial in petrologic evolution and represent a type of “warm” subduction zone metamorphism. The field occurrences of host metasediments and blocks of metabasite, serpentinite, chlorite schist, metagabbro, and/or metaplagiogranite can be interpreted as metamorphosed melanges. The apparent difference in mineral assemblage, metamorphic grade, and texture for some similar or different rock types probably reflects complex nature and superimposition controlled by bulk-rock chemistry, fluid activity, metasomatism, oxidation state, deformation, and retrogression.

References Baziotis, I., Tsai, C. H., Ernst, W. G., Jahn, B. M., & Iizuka, Y., (2017). New P-T constraints on the Tama- yen glaucophane-bearing rocks, eastern Taiwan: PERPLE_X modeling results and geodynamic implications. Journal of Metamorphic Geology, 35: 35–54. Beyssac, O., Negro, F., Simoes, M., Chan, Y. C., & Chen, Y. G., (2008). High-pressure metamorphism in Taiwan: from oceanic subduction to arc-continent collision? Terra Nova, 20: 118–125. Chen, W. S., Chung, S. L., Chou, H. Y., Zugeerbai, Z., Shao, W. Y., & Lee, Y. H., (2017). A reinterpretation of the metamorphic Yuli belt: Evidence for a middle-late Miocene accretionary prism in eastern Tai- wan. Tectonics, 36: 188-206. Keyser, W., Tsai, C. H., Iizuka, Y., Oberhaensli, R., & Ernst, W. G., (2016). High-pressure metamorphism in the Chinshuichi area, Yuli belt, eastern Taiwan. Tectonophysics, 692: 191-202. Liou, J. G., Ho, C. O., & Yen, T. P., (1975). Petrology of some glaucophane schist and related rocks from Taiwan. Journal of Petrology, 16: 80-109. Tsai, C. H., Iizuka, Y., & Ernst, W.G., (2013). Diverse mineral compositions, textures, and metamorphic P-T conditions of the glaucophane-bearing rocks in the Tamayen mélange, Yuli belt, eastern Taiwan. Journal of Asian Earth Sciences, 63: 218–233.

128

Nanodeformation in nanoseconds: pulsed laser experiments on enstatite simulate micrometeoroid impacts

Doreen Turner1, Kilian Pollok1, Falko Langenhorst1 1FSU Jena, Institute of Geosciences, Analytical Mineralogy of Micro- and Nanostructures, Carl- Zeiss-Promenade 10, 07745 Jena, Germany, [email protected]

Asteroids are largely made of mafic minerals such as pyroxene. To simulate micrometeroid bombardments on these airless bodies, we performed femtosecond laser irradiation experiments on single-crystal enstatite. Together with solar wind irradiation these micrometeoroid impacts alter the target surface and produce so-called space weathering effects (Bennett et al., 2013). To study possible anisotropy in the deformation behaviour, Kilosa enstatite (En93) was cut parallel to specific crystallographic planes. Laser irradiation was performed on the polished surfaces under vacuum (10-3 mbar) using a Ti:sapphire laser at 800 nm wavelength, creating a mechanical shock wave. Pulsed laser beams were focused to 38 µm spots and had a duration of 100 fs. This reproduces well the spatial and temporal conditions of natural micrometeoroid impacts (Fazio et al., 2017). The recovered material was investigated with SEM and TEM. The laser single shots produced spherical to semi-spherical microcraters with a distinct glass layer in splash-like radial shape around the crater rim. TEM investigations reveal a layered depth structure of the craters with a glass layer on top, a highly deformed layer containing shock effects like planar microstructures and dislocations and the undeformed substrate at the bottom (Fig. 1A). There are open fractures partly extending up to the surface. Fractures and other planar microstructures appear to be parallel to crystallographic planes, but the orientations are variable depending on the crystallographic orientation of the sample with respect to the shock wave. They show an inclination to the surface normal of 30° to 50°. The dominant planar microstructures in each sample are mainly subparallel, show en échelon displacement and partly fan out (Fig. 1B). This indicates that simple shear is probably the dominant deformation mechanism. In the upper part of the deformed layer the planar microstructures are amorphous with up to tens of nm width (Fig. 1C). The glass is generated along the shear planes due to frictional heating. Deeper in the sample adjacent to the undeformed crystal the microstructures are however not amorphized. High-resolution (HR) TEM indicates that some of these microstructures are stacking faults, while others are simply microfractures. Similar observations were also made on natural samples like the Martian Meteorite Allan Hills 84001 showing shock- induced deformation features (slip, microfracturing, intragranular glass lamellae), as well Barber & Scott, 2006).

A B C

Fig. 2: STEM (A, B) and HR-TEM (C) images of the microstructures of a crater irradiated on the (210) cleavage plane. (A) Layered depth structure. Glass layer and open fractures appear black, undeformed areas are dark grey. Strained crystallites, microfractures and dislocations appear bright. (B) Planar microstructures that are displaced en échelon. (100) is the dominant shear plane, the upper part shows a potential shear band. (C) Amorphous lamellae that are slightly displaced and a stacking fault. References Barber, D. J. & Scott, E. R. D., (2006). Meteoritics & Planetary Science, 41: 643-662. Bennett, C. J., et al. (2013). Chemical reviews, 113(12). Fazio, A., et al. (2017). Icarus, 299. 129

New views on the crustal-scale geometries of the Taiwan fold-thrust belt

1 2 1 Kamil Ustaszewski , John Suppe , Yiqiong Zhang

1Institut für Geowissenschaften, Friedrich-Schiller-Universität Jena, 07743 Jena, kamil.u@uni- jena.de 2Dept. Earth & Atmospheric Sciences, University of Houston

Taiwan is located along an active plate boundary between the Eurasian and Philippine Sea Plates, with convergence rates amounting to c. 8 cm/yr. The island has since long served as a cradle for many tectonic concepts (e.g., fault-related folding, critically tapered thrust wedges, or climatic forcing on orogen growth). Yet, the internal parts of the Taiwan fold-thrust belt (FTB) are still improperly understood in terms of fault kinematics, internal geometries and the amount of shortening they underwent since the onset of arc-continent collision in the Mio- to Pliocene. As a consequence, geometrical restorations of the Eurasian passive margin prior to continental subduction are often guesses rather than quantitative estimates. We constructed three new crustal-scale geological cross-sections at various latitudes of the Taiwan FTB, with crust-mantle interfaces constrained from a recent 3D-model employing seismological data. We consider the Tananao Schist Complex in the Central Range to contain imbricates of Eurasian basement, exposed in the Tailuko Belt. The Tailuko Belt overthrusts Cenozoic passive margin series and is in turn tectonically overlain by the easterly adjacent Yuli Belt. The latter consists of a dominantly greenschist-facies metasedimentary succession, containing detrital zircons as young as Miocene (Chen et al., 2017), and volumetrically subordinate mafics and ultramafics with relics of blueschist-facies metamorphism. The Yuli Belt is tectonically overlain by the Coastal Range series, derived from the Philippine Sea Plate. A tentative restoration of one of our sections yields a minimum shortening of 120 km in the Eurasian passive margin series, with about 50% of the basement, on top of which the accreted material was initially sitting, already subducted below the Philippine Sea Plate (Fig. 1).

Fig. 1: (a) deformed and (b) restored cross section of the fold-thrust belt across central Taiwan.

References Chen, W.-S., S.-L. Chung, H.-Y. Chou, Z. Zugeerbai, W.-Y. Shao, & Y.-H. Lee (2017). A reinterpretation of the metamorphic Yuli belt: Evidence for a middle-late Miocene accretionary prism in eastern Taiwan, Tectonics, 36, 188–206, doi:10.1002/2016TC004383. 130

Analyzing neotectonic activity through GPR and morphotectonic observations along the Bogd Fault Zone, SW Mongolia

Jorien L.N. van der Wal1, Christopher Weismüller1, Klaus Reicherter1

1Neotectonics and Natural Hazards, RWTH Aachen University, Germany, [email protected]

The Bogd Fault Zone (BFZ) in southwestern Mongolia has been the subject of paleoseismological studies since the 1957 8.3 M earthquake which ruptured over a length of 260 km (Kurushin et al., 1997). The BFZ is characterized by sinistral transpression and it is part of the E-W to NW-SE striking Gobi-Altay ranges which formed as a result of far-field intracontinental stresses related to the India-Eurasia collision. Morphotectonic observations, enabled by arid climate conditions in the area, show that sediments deposited along the fault zone have been affected by a multitude of earthquakes. However, previous studies have shown that deformation rates along both thrust- and strike-slip dominated fault segments are low: 0.1 mm/yr and 0.5-1 mm/yr, respectively (Rizza et al., 2011; Vasallo et al., 2007). In this study, we focus on the neotectonic activity of the faults on the northern margin of the Ikh Bogd mountain (44°59N; 100°13E). With the aim of characterizing these faults in terms of magnitude, slip rates, and return intervals, we combine results from ground-penetrating radar (GPR), digital elevation models (DEMs) extracted from drone imaging, remote sensing and field observations, as well as OSL and cosmogenic nuclide dating. First results include observations of offset and blocked drainages, as well as surface ruptures which show little degradation, ruptured pebbles and liquefied lake sediments. At depth, reflectors in GPR profiles are observed to be folded and terminated, indicating deformed sediments which are probably related to recent fault activity. Detailed mapping of local hydrological systems based on drone DEMs will create more insight into surface (rupture) morphologies. The results from these two methodologies combine to create a unique and promising 3D data set for neotectonic analysis up to 22 m depth.

References Kurushin, R.A., A. Bayasgalan, M. Olziybat, B. Enhtuvshin, P. Molnar, C. Bayarsayhan, K.W. Hudnut, J. Lin, 1997. The Surface Rupture of the 1957 Gobi-Altay, Mongolia, Earthquake R.Geol. Soc. Am. Special Papers, 320, 144pp Rizza, M., Ritz, J. F., Braucher, R., Vassallo, R., Prentice, C., Mahan, S., Bourlès, D. (2011). Slip rate and slip magnitudes of past earthquakes along the Bogd left-lateral strike-slip fault (Mongolia). Geophysical Journal International, 186(3), 897–927 Vassallo, R., J.-F. Ritz, R. Braucher, M. Jolivet, S. Carretier, C. Larroque, A. Chauvet, C. Sue, M. Tod- bileg, D. Bourlès, et al. (2007). Transpressional tectonics and stream terraces of the Gobi-Altay, Mongo- lia, Tectonics 26, TC5013

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Reconstructing Greater India: paleogeographic, kinematic, and geodynamic perspectives

Douwe J.J. van Hinsbergen1, Shihu Li2, Peter C. Lippert3, Wentao Huang3,4,5, Eldert L. Advokaat1, and Wim Spakman1,6

1Department of Earth Sciences, Utrecht University, Budapestlaan 4, 3584 CD Utrecht, the Netherlands, [email protected] 2State Key Laboratory of Lithospheric Evolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China 3Department of Geology and Geophysics, University of Utah, Salt Lake City, Utah, USA 4Department of Geosciences, University of Arizona, Tucson, Arizona, USA 5Key Laboratory of Orogenic Belts and Crustal Evolution, Ministry of Education, School of Earth and Space Sciences, Peking University, Beijing, China 6Center for Earth Evolution and Dynamics (CEED), University of Oslo, Sem Saelandsvei 24, NO-0316 Oslo, Norway

Key in understanding the geodynamics governing subduction and orogeny is reconstructing the paleogeography of ‘Greater India’, the Indian plate lithosphere that subducted since Tibetan Himalayan continental collision with Asia. Here, we discuss this reconstruction from paleogeographic, kinematic, and geodynamic perspectives and isolate the evolution scenario that is consistent with all three. We follow recent constraints suggesting a ~58 Ma initial collision and update a previous kinematic restoration of intra-Asian shortening with a recently proposed Indochina extrusion model that reconciles long-debated large and small estimates of Indochina extrusion. The reconstruction is tested against Tibetan paleomagnetic rotation data, and against seismic tomographic constraints on paleo-subduction zone locations. The resulting restoration shows ~1000-1200 km of post-collisional intra-Asian shortening, leaving a 2600-3400 km wide Greater India. From a paleogeographic, sediment provenance perspective Eocene sediments in the Lesser Himalaya and on undeformed India may suggest that all Greater Indian lithosphere may have been continental, but may also source from the Paleocene-Eocene western Indian orogen unrelated to the India-Asia collision. A quantitative kinematic, paleomagnetic perspective prefers major Cretaceous extension and ‘Greater India Basin’ opening within Greater India, but data uncertainty may speculatively allow for minimal extension. Finally, from a geodynamic perspective, assuming a fully continental Greater India would require that the highest subduction rates recorded in the Phanerozoic would have been driven by a subduction of a lithosphere-crust assemblage more buoyant than the mantle, which seems physically improbable. We conclude that the Greater India Basin hypothesis is the only scenario sustainable from all perspectives. We infer that old pre-collisional lithosphere rapidly entered the lower mantle sustaining high subduction rates, whilst post-collisional continental and young Greater India basin lithosphere did not, inciting the rapid India-Asia convergence deceleration ~8 Myr after collision. Subsequent absolute northward trench migration and slab overturning terminated Gangdese arc activity despite ongoing oceanic subduction.

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A full appreciation of the uncertainty of thermochronological data in sedimentary basins

Christoph von Hagke1, Elco Luijendijk2, Leonard Kaiser1, Alexander Malz3

1RWTH Aachen University, Germany, [email protected] 2Georg-August University Göttingen, Germany 3Landesamt für Geologie und Bergwesen Sachsen-Anhalt, Germany

Thermokinematic models are a key tool in Earth sciences to quantify the metamorphic and tectonic history of orogens and sedimentary basins. To estimate exhumation rates using thermochronological data, some studies assume steady state temperature, for instance by using age-elevation profiles. Other approaches include more complex solutions of the heat equation, ranging from 1D to 3D models that may be coupled with landscape evolution models. State-of-the-art models take into account that heat transfer by diffusion and advection, as well as changes in geothermal gradient over time caused by changes in structure or thermal properties of the crust. Thus, thermokinematic models quantify perturbation of the isotherms due to tectonic movements, external factors, and changes in topography. However, thermokinematic models of fold-and-thrust belts are uncertain because they commonly do not account for structural uncertainty at depth as well as the thermal history of the source areas of the sediments. In this contribution we explore the uncertainty of quantifying the thermal and geological history of sedimentary rocks by combining a thermal history model with a high-resolution thermochronological data set from the folded and thrusted part of the northern foreland basin of the European Alps. As kinematic model we constructed a new balanced cross section and carried out a structural uncertainty analysis. We show that taking the uncertainty of the provenance history and geometries at depth into account renders straightforward tectonic interpretation of the data more difficult. Differences in ages that would commonly be interpreted as significant differences in exhumation may not be statistically meaningful. Our data shows lack of correlation between cooling rates and elevation, relief and glacial erosion, which may mean that exhumation is locally structurally controlled but may predominantly be the result of a separate long-wavelength process.

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Unraveling neotectonic vertical-axis rotations in the Adria-Eurasia collision zone: Paleomagnetic data from Pliocene-Quaternary cave sediments (Slovenia)

Vrabec Marko1, Pruner Petr2,3, Zupan Hajna Nadja3, Mihevc Andrej3, Bosák Pavel2,3

1Department of Geology, FNSE, University of Ljubljana, Slovenia, [email protected] lj.si 2Institute of Geology of the Czech Academy of Sciences, Praha, Czech Republic 3Karst Research Institute ZRC SAZU, Postojna, Slovenia

Vertical-axis rotations in the upper crust, inferred from paleomagnetic declinations recorded in rocks and unconsolidated sediments, are produced by various tectonic mechanisms such as large-scale plate motion, propagation and rotation of thrust sheets, or by rotation of rigid blocks in strike-slip fault zones. Paleomagnetic records can therefore provide important information about the timing and magnitude of tectonic episodes, but the consolidated rocks suitable for paleomagnetic analysis are often significantly older than the deformations which produced the rotations. We used paleomagnetic data obtained from cave sediments to document neotectonic (0 - 5 Ma) vertical-axis rotations in the northeastern corner of the Adria-Eurasia collision zone. Magnetostratigraphy, radiometric dating, biostratigraphy, and geomorphologic constraints were combined to establish a robust chronology in the spatially and temporally highly discontinuous sediment record preserved in karst areas. Derived rotation rates range from 2 to 10°/Ma with peak activity from 3.0 to 1.5 Ma. Post-1.5 Ma slowdown of rotations correlates with a decrease in fault-slip rates and the onset of inversion in Quaternary strike-slip basins, which was so far not well-constrained in time. We distinguish two tectonic domains from the rotation patterns: the Adriatic coastal thrustbelt which exhibits early clockwise, probably syn-emplacement rotations, followed by post-1.5 Ma counterclockwise rotations, whereas the continental interior displays persistent counterclockwise rotations suggesting domino-like rotation of rigid blocks bound by NW-SE-trending faults. These data provide new constraints on the Pliocene to Recent tectonics in the Adria collision zone and suggest that the northeastern peri-Adriatic belt is fully detached from the Adria microplate, which rotates <0.5°/Ma in a counterclockwise sense. Our study demonstrates the potential of using cave sediments to provide robust and consistent paleomagnetic declination datasets, which bridge the gap between short-term deformation-rate determinations from geodetic and tectonic geomorphology studies, and long-term geological- time scale observations, therefore they can provide important new data for quantitative neotectonic studies.

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Deployment of digital outcrop models (DOMs) in structural geology - A methodological review

Bianca Wagner1, Bernd Leiss1

1Geoscience Centre of the University of Göttingen, Göttingen, Germany, [email protected]

Digital outcrop models (DOMs) - also called virtual outcrop models (VOMs) - represent geometry, orientation and selected spectral information of natural outcrops and can be utilized as close-to-reality displays. Such models are created by the application of different technologies (LiDAR, Structure-from- Motion) and devices strongly varying in costs and handling level. In the last years, the number of users and the spectra of applications have increased rapidly. Low costs of some devices and easy-access software as well as the digitalization hype might be the major reasons. Further- more, these close-range technologies fill the gap between large-scale remote sensing techniques and small-scale lab methods (Wagner, 2017). Beside other digital mapping trends, DOMs are strongly influencing, transforming and supple- menting structural field work. Actually, five main fields of application can be outlined: visualiza- tion & representation, documentation, manual analysis & interpretation, automatic extraction of geometrical data, and automatic extraction of spectral information. The utilization of DOMs for illustrating issues aims mainly at the provision of visually appealing models of instructive, remarkable or inaccessible outcrops for teaching, public relations activities, and exhibition purposes. Beside the pure representation on the screen, the digital models are combined with Augmented Reality (AR) and Virtual Reality (VR) tools as well as 3D printing solutions. Furthermore, DOMs are applied to keep complex field data available over a long period for subsequent interpretation and conservation of temporary or threatened outcrops. Frequently, the DOMs are supplemented by lithological, structural or age data. In many cases, the geometric and spectral information of DOMs is utilized for manual extraction (digitalization) of traces or planes that represent bedding, foliation, cleavage or faults. The ensuing structural analysis of the outcrop inventory is often extended by the construction and restoration of a geometric 3D-model. The automatic extraction of geometric objects like planes and/ or edges from DOMs targets mainly at the recreation of fracture networks and their investigations in terms of stress regimes, fracture behaviour and permeability. Increasingly, DOMs are used to determine and describe plane roughness at various scales as parameters for fracture or fault characterization/classification. Beside geometry and orientation data, DOMs usually comprise spectral information like reflected blue, green and red light or reflected near-infrared radiation (laser intensity) which are applied for automatic extractions of significant lithological differences. Sporadically, multi- or hy- perspectral acquisitions of reflected near- to short-wave infrared radiation as well as thermal images are superimposed to discriminate various rock types, alteration zones or mineralized veins. This methodological review is pointing out gains and obstacles of the deployment of DOMs in the outlined scopes of application, focusing on the usability and transferability of workflows.

References Wagner, B. (2017): Close-range sensing in the geosciences – expressed in sketches. – The Photogram- metric Record 32(160): 350-353. DOI:10.1111/PHOR.12226.

135

On the timing of salt structure growth in the Southern Permian Basin

Michael Warsitzka1, Fabian Jähne-Klingberg2, Jonas Kley3, Nina Kukowski1

1Institute of Geosciences, Friedrich Schiller University Jena, Burgweg 11, 07749 Jena, Germany 2Federal Institute for Geosciences and Natural Resources, Stilleweg 2, 30655 Hannover, Germany 3Geoscience Centre, Structural Geology and Geodynamics, Georg-August-University Göttingen, Goldschmidtstr. 3, 37077 Göttingen, Germany The tectono-stratigraphic evolution of the Mesozoic to Cenozoic cover of the Southern Permian Basin (SPB) is strongly affected by the redistribution of Upper Permian salt and resulting formation of salt structures, such as diapirs and pillows, as well as rim synclines filled with syn- kinematic sediments. The timing of salt structure growth provides insights into the temporal and spatial distribution of tectonic deformation in different parts of the SPB. We reviewed published literature about the SPB to identify evolutionary stages of each salt structure and assumed that these stages can be classified by three specific ages of the growth history, which are (1) the age of initiation defined by the first indication for deformation in the vicinity of the salt structure, (2) the age of main activity representing the interval of fastest growth of a salt structure, and (3) the age of burial of diapiric structures representing the deceleration of growth. Furthermore, we attributed a potential mechanism that triggered the initiation of salt structures in distinct regions (sub-basins, platforms) in order to characterize the tectonic grain of the SPB. The outcomes of our study, illustrated in a series of maps, revealed that the earliest salt movement was initiated in deeply subsided graben structures and fault zones during the Early Triassic. In these areas, salt structures reached their phase of main activity already during the Late Triassic or the Jurassic and were mostly buried during the Early Cretaceous. Salt structures at the flanks of these grabens, in less subsided sub-basins and platform regions mostly started to grow during the Late Triassic, whereas the phase of main activity and burial of these salt structures took place from the Late Cretaceous to Cenozoic. Analyzing trigger mechanisms revealed that most salt structures were initiated by sub-salt extensional and transtensional faults, in particular in the large graben structures. On the graben flanks and in less subsided sub-basins minor normal faulting associated with thin-skinned extension detached from major basement faults prevailed as a trigger mechanism. Furthermore, regional gravity gliding of the supra-salt cover led to thin-skinned extension coeval with thin- skinned shortening in some parts of the SPB. Shortening and basin inversion during the Late Cretaceous led to reactivation of the growth of many salt structures and provoked the formation of new salt anticlines especially in the western and southern parts of the SPB. Compared to previous overview studies, our compilation provides a more detailed pattern of salt tectonic activity over the study areas, especially in the early post-Permian history. The synthesis of the timing of salt structure growth and tectonic phases implies that most of the structural grain of the SPB was already activated in the Early Triassic and later reactivated multiple times depending on the direction of tectonic stresses.

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Quantification and identification of fault-geometry and respective features of massively dilatant faults in Iceland using 3D point clouds

Christopher Weismüller1, Michael Kettermann2, Christoph von Hagke2, Janos Lajos Urai2, Klaus Reicherter1

1RWTH Aachen University, Neotectonics and Natural Hazards, Aachen, Germany, [email protected] 2RWTH Aachen University, Structural Geology, Tectonics and Geomechanics, Aachen, Germany, [email protected]

Extensional faults in cohesive rocks can develop massive dilatancy close to the Earth’s surface and potentially to greath depths. These massively dilatant faults (MDF) form pathways for water, magma or hydrocarbons and are therefore of interest for geohazard assessment, hydrocarbon exploration or the supply of geothermal energy. However, the deep structures and evolution of MDF are poorly known. Within the scope of a larger multidisciplinary project investigating the structure and evolution of dilatant faults, this work aims to identify and characterize surface geometries along MDFs in Iceland. Iceland is located on the Mid-Atlantic Ridge, with the Reykjanes Ridge in the SW and the Kolbeinsey Ridge in the N. Our study sites in Iceland offer exquisite outcrop conditions and access to MDF formed in a variety of rocks and kinematics. We distinguish between oblique rifting on the Reykjanes Peninsula and rift-perpendicular extension in the North, e.g. the well known fissure swarm of the Krafla vulcanic complex. Especially the fissure swarms in the SW on the Reykjanes Peninsula expose MDF with unfilled cavities accessible to depths of more than 20 m. Apparent opening widths of more than 30 m and vertical discplacement of more than 35 m peak in Thingvellir, NE of the Reykjanes Peninsula. As base for our datasets, we created high-resolution (~5 – 10 cm per pixel) 3D point clouds, digital elevation models (DEM) (Fig.1) and orthophotos using drone imagery of more than 20 km of faults. After georeferencing the models, we are able to take quantitative measurements such as length, opening width, strike, dip, heave and throw. A first review of the results shows strong variability of geometries along the fault strike, e.g. relay ramps and breached relays, antithetic fractures or tilted blocks, which we can compare with analogue models of MDF. The opening width is heavily influcenced by those geometries and may increase strongly at relays or nodes, where two fault segments have grown together.

Fig. 1: Left: 3D point cloud displaying a section of the Thingvellir MDF, calculated from drone imagery. The black frame indicates the area of the DEM on the right, which has been derived from the 3D point cloud.

137

Influence of columnar joints on normal fault geometry and evolution – Insight from scaled physical models

Lisa Winhausen1, Michael Kettermann1, Christoph von Hagke1, Janos L. Urai1

1Institute for Structural Geology, Tectonics and Geomechanics, RWTH Aachen University, Lochnerstraße 4-20, D-52056 Aachen, Germany www.ged.rwth-aachen.de

Normal faults at mid ocean ridges develop enormous opening mode fractures close to the surface that remain open up to a certain depth. These massively dilatant faults (MDF) are ubiquitous structures in brittle rocks such as the basalts of Iceland. MDF geometry and mechanics depends on the mechanical properties of the basalt, which in turn are governed by columnar jointing: whereas the intact rock and the rock body at depth has a high cohesion (up to ~50 GPa),in horizontal direction it has almost no tensile strength due to the columnar joints: the material is orthotropic. To understand evolution of MDF we first need to understand how this anisotropy influences fault mechanics. We present a new set of scaled physical model experiments. To model columnar jointing in basalt we use desiccated cornstarch, which develops a columnar joint pattern similar to cooled basalts (fig.1A). Length and diameter of the columns can be controlled by drying speed. To scale the models (50 cm in size) to natural prototypes, we measure the mechanical parameters of our materials using uniaxial compressive strength experiments and direct measurements of tensile strength between columns. Results show the starch columns have a rather high compressive strength; to fail in hybrid or shear mode several meters of overburden would be required. Consequently, our models represent the upper 500 - 1000 m of natural basalt. For the first time we are able to show a mechanically correct model of this part of the faults, that is strongly controlled by the orthotropic anisotropy. We build our models from multiple layers of cornstarch columns – analog to different generations of lava flows – in a 30 x 50 cm wide sandbox with a rigid basement fault (63° dip) and glass sidewalls. Sequential high-resolution photographs from both sides and the top (stereo set-up in map view) allow us to understand the fault evolution with increasing displacement and the reconstruction of 3D models of the surface at any given time (fig.1B). Results show a vertically complex fault zone with multiple stockworks of open cavities. Due to the horizontal weakness of the rock, columns and blocks break off from the walls and are wedged and jammed in the dilatant fault, effectively forming floors. Open cavities are formed up to great depths. Laterally, the columns influence the shape of the fault at the surface. On a large scale, the fault shows less curvature than in isotropic rocks, whereas on a small scale, the fault follows a path along the fractures with lowest cohesion. Structures like relay ramps and tilted blocks form and compare well with natural features mapped on Iceland.

Fig. 1: (A) Columnar joints in desiccated cornstarch. (B) 3D model of sandbox experiment: Normal fault in two layers of cornstarch columns comprise open fractures and tilted blocks at the surface. 138

Tectonic analysis of the South Setifian domain and its neighbouring area (Eastern Algeria)

El Hadj Youcef Brahim1, Mohammed Chadi2, Abdelkader Khiari3 and Rami Djeffal4

1 Department of Geology, Batna 2 University, Algeria, [email protected] 2 Constantine 3 University, Nouvelle ville, Ali mandjli, Algeria, [email protected] 3 Department of Geology, Oum El Baouaghi University, Algeria, [email protected] 4 Constantine 1 University, Zouaghi sliman, Algeria

The present study focuses on area located at the southern fringe of the external zones of the Eastern Algeria alpine belt, situated on the Aures meridian (Batna). In this area, fracturing is well developed, although vegetal cover masks often structural and geological information. This study aims to enhance the identification of major events and their associated geological structure in order to facilitate mapping by using Landsat satellite images and SRTM DEMs. Structural analyses undertaken in this work have permitted to get new results specifying or modifying the results obtained by our prodecessors. We can distinguish two types of folds: faulted-folds, in the northern part of the study area and propagation folds in the southern area, all anticlines associated to overlaps are verging south and we cannot extend them to tangential tectogenesis. The validation of these results was made on the basis of existing geological maps, photogeolo- gy, and field knowledge.

KEYWORDS: Algeria, Landsat, satellite images, SRTM DEMs, structural analysis, folds

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Estimating the Relative Uplift Time of Anticlines based on Landscape Maturity and Evolution Modeling: NW Segment of the Zagros Mountain Front Flexure, Kurdistan Region of Iraq

Mjahid Zebari1, Payman Navabpour1, Christoph Grützner1, and Kamil Ustaszewski1

1Institute for Geological Sciences, Friedrich-Schiller-University Jena, Jena, Germany, [email protected]

In tectonically active regions, the geomorphic indices and hence the landscape maturity can be used as proxies to disclose the related tectonic activity. As an active orogenic belt, the Zagros Mountains can serve best to employ such approaches. One of the dominant morphotectonic boundaries within the Zagros is the Mountain Front Flexure (MFF), which separates the Simply Folded Belt from the Zagros Foredeep. It has been allocated to an inherited basement fault that has been reactivated c. 5 Ma ago due to the Eurasia-Arabia plate convergence. The MFF marks a dominant topographic step and is characterized by numerous active anticlines atop of fault strands emerging from the basement fault. In this study, geomorphic indices such as hypsometric integral, surface roughness, surface index, and stream-length gradient index were used to evaluate landscape maturity of three anticlines (from SE to NW, the Harir, Perat and Akre anticlines), to identify the most active structures and to estimate the slip rates of the underlying faults. The Akre anticline shows deeply incised valleys and advanced erosion, but Harir and Perat anticlines have a relatively smooth surface and are supposedly younger than the Akre. Hence, the present-day topography of the less mature Harir and Perat anticlines served as an input in a landscape evolution model built with Landlab toolkit (Hobley et al., 2017) to estimate the relative time difference between the maturity stages of the three anticlines. The stream power equation was used to introduce erosion from a fluvial system, and the hillslope diffusion equation was applied to account for sediment transport. For different time steps of model evolution, we calculated the hypsometric curves together with other indices of the landscape generated from the Harir model. A comparison of the values to those of the present- day Akre topography reveals that it will take the Harir and Perat anticlines 140±20 kyr to reach the maturity level of today’s Akre anticline. Since the factors that control geomorphology (lithology, structural setting and climate) are similar for all three anticlines, and under the assumption of constant growth and erosion rates, we infer that uplift in Akre started 140±20 kyr before Harir and Perat started to grow. This method can be applied to many other anticlines in the MFF region reconstructing a model of temporal evolution of this fold and thrust belt. This will shed light on lateral fold evolution over time in a setting where deformation of detached stratigraphic succession is controlled by a major basement fault.

References Hobley, D.E., Adams, J.M., Nudurupati, S.S., Hutton, E.W., Gasparini, N.M., Istanbulluoglu, E., and Tucker, G.E.: 2017, Creative computing with Landlab: An open-source toolkit for building, coupling, and exploring two-dimensional numerical models of Earth-surface dynamics, Earth Surf. Dynam., 5, 21–46, doi:10.5194/esurf-5-21-2017.

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Surface Deformation Related to the 12 November 2017 Iran-Iraq Border Earthquake (MW 7.3) and its Aftershocks: Insights from InSAR Data

Mjahid Zebari1, Payman Navabpour1, Christoph Grützner1, and Kamil Ustaszewski1

1Institute for Geological Sciences, Friedrich-Schiller-University Jena, Jena, Germany, [email protected]

On 12 November 2017, an earthquake of MW 7.3 occurred in the Zagros Mountain Belt, Iran- Iraq border area, at a depth of 19 km with an oblique thrust faulting focal mechanism. We used Interferometric Synthetic Aperture Radar (InSAR) data to determine the ground deformation of the main shock and two largest aftershocks on 11 Dec. 2017 (M 5.4) and 11 Jan. 2018 (M 5.5) using Sentinel-1 Toolbox. For the main shock, ascending (11 and 23 Nov.) and descending (07 and 19 Nov.) Sentinel-1A data were used. The obtained deformation field was then compared to location of different focal mechanisms taken from various data sources to find the best fitting source. We then used Sentinel-1A and Sentinel-1B data to investigate the first and the second aftershock, respectively. We also used Sentinel-1A data covering 52 days after the main shock, beginning on 19 November 2017, to investigate the afterslip. The results indicate a maximum uplift of c. 100 cm south of the epicenter, and a subsidence of c. 30 cm around the epicenter of the main shock. We found no noteworthy ground deformation related to the first aftershock. This earthquake had a pure strike-slip mechanism. For the second aftershock we found subsidence of c. 7 cm around the epicenter. This earthquake had a pure thrust mechanism. We can further show that significant afterslip of c. 10 cm uplift occurred post-seismically in the first 7 weeks after the main event and that the locus of the uplift moved southwestward, in-line with epicenters of the aftershocks. The computed ground deformation matches best with the hypocenters provided by GCMT and EMSC. The variation in the earthquake mechanisms enables us to relate the shocks to oblique, lateral and frontal ramps underlying the Zagros frontal thrust. We speculate that static stress transfer led to the loading of neighboring fault segments, which consequently triggered a series of M > 5.0 earthquakes that occurred weeks after the main event.

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List of participants Abbo Avishai The Hebrew University of Jerusalem Advokaat Eldert Lieven Utrecht University Aichholzer Paul Universität Innsbruck Altenberger Uwe University Potsdam Balling Philipp Friedrich-Schiller-Universität Jena Basak Ankita University of Calcutta Behrmann Jan H. GEOMAR Bestmann Michel Friedrich-Alexander Universität Erlangen-Nürnberg Biermanns Peter RWTH Aachen University Brugger Matthias Technical University of Munich Cionoiu Sebastian ETH Zürich Dannowski Anke GEOMAR Helmholtz Centre for Ocean Research Kiel Degen Thomas Johannes Martin-Luther-University Dhansay Taufeeq Friedrich-Schiller-Universität Jena Di Rosa Maria Università di Pisa Dietl Carlo Gesteinslabor Dr. Eberhard Jahns Donhauser Ines Friedrich-Alexander-Universität Erlangen - Nürnberg Droesler Denny Martin-Luther-Universität Halle Wittenberg Duesterhoeft Erik CAU Kiel Eberts Andreas Friedrich-Alexander-Universität Erlangen-Nürnberg Effendi Sumaya Martin-Luther-Universität Halle-Wittenberg Fialowski Melinda Eötvös Loránd University Fiedler Julia Freie Univerität Berlin MTA-ELTE Hungarian Academy of Sciences -Eötvös Uni- Fodor László versity Franke Sandra University of Göttingen Friebel Anna Institute for applied geoscience Frölich Sonja Andrea TU Bergakademie Freiberg Gehrmann Anna University of Greifswald Gerya Taras ETH Zürich Ghani Humaad University of Potsdam Ghanizadeh Khob Ladan Friedrich-Schiller-Universität Jena Giese Joerg Freie Universität Berlin Groß Philip Freie Universität Berlin Grund Marc Freie Universität Berlin Grützner Christoph Friedrich-Schiller-Universität Jena Gürer Derya Utrecht University Hallas Peter TU Bergakademie Freiberg Handy Mark R. Freie Universität Berlin Herrmann Marie-Luise Friedrich-Schiller-Universität Jena Herwegh Marco University of Bern Irum Irum University of Potsdam Bundesanstalt für Geowissenschaften und Rohstoffe Jähne-Klingberg Fabian (BGR) Jerabek Petr Charles University, Faculty of science Jouvent Marine University of Prague, Charles University Kazmer Miklos Eötvös University 142

Kemperle Marina University of Cologne, Institute for Geology and Mineralogy Kleinschrodt Reiner Universität zu Köln Kley Jonas Uni Göttingen Klotz Thomas University of Innsbruck Klug Linus Universität Bonn Koenemann Falk H. retired MTA-ELTE Hungarian Academy of Sciences Eötvös Lo- Kövér Szilvia ránd University Budapest Krämer Alexander RWTH Aachen Kroner Uwe TU Bergakademie Freiberg Kryl Jakub Charles University Krýza Ondřej Charles University Institute of Geological Sciences, Polish Academy of Sci- Krzywiec Piotr ences Kufrasa Mateusz Polish Academy of Sciences Kurzawski Robert Marek GEOMAR Helmholtz Center for Ocean Research Langner Tim Freie Universität Berlin Laziz Ouided Constantine University Leiss Bernd University of Göttingen Lexa Ondrej Charles University Linckens Jolien Goethe Universität Frankfurt am Main Liu Yuan TU Bergakademie Freiberg Lohmann Christian Michael Martin-Luther-Universität Halle-Wittenberg Louis Sarah RWTH Aachen University Löwe Georg Friedrich-Schiller-Universität Jena Malz Alexander Landesamt für Geologie und Bergwesen Sachsen-Anhalt Mechernich Silke University of Cologne Meier Katrin Universität Bremen Meyer Nicolas MLU Halle-Wittenberg Nabhan Sami Friedrich-Schiller-Universität Jena Nakapelyukh Mykhaylo Zakhidnadraservis Navabpour Payman Friedrich-Schiller-Universität Jena Niemann Karin RWTH Aachen University Nilius Nils-Peter Leibniz Universität Hannover Institute of Rock Structure and Mechanics Czech Academy Novakova Lucie of Sciences Obst Karsten Geologischer Dienst Oncken Onno GFZ Potsdam Institute of Geosciences, Energy, Water and Environment Onuzi Kujtim (IGEWE) Oravecz Éva Eötvös Lorand University Ortner Hugo Universität Innsbruck Peitsidis Achilleas Aristotle University of Thessaloniki Peřestý Vít Charles University, Prague Philipp Sonja Leonie geophil - Geologie Prof. Dr. Sonja Philipp Pingel Janis Friedrich-Schiller-Universität Jena Pleuger Jan Freie Universität Berlin Pollok Kilian Friedrich-Schiller-Universität Jena Ratschbacher Lothar TU Bergakademie Freiberg Reicherter Klaus RWTH Aachen 143

Rembe Johannes University of Potsdam Rezaei Leila Universität Potsdam Richter Madeline Friedrich-Schiller-Universität Jena Rosenau Matthias GFZ Potsdam Salomon Chris Friedrich-Schiller-Universität Jena Sanità Edoadro Università di Pisa Schaarschmidt Anna FAU Erlangen-Nürnberg Scharfenberg Lars Friedrich-Alexander Universität Erlangen-Nürnberg Scheffler Franziska Universität Potsdam Scherman Benjamin Eötvös Loránd University Schmid Stefan ETH Zürich Schmidt Katharina ETH Zürich Schmidtke Michael Jared Rheinische Friedrich Wilhelms Universität Bonn Schmitz Benjamin Friedrich-Schiller Universität Jena Sächsisches Landesamt für Umwelt, Landwirtschaft und Seidel Elisabeth Geologie Sieberer Anna-Katharina University of Innsbruck Simon Daniel Freie Universität Berlin Sobel Edward R. Universität Potsdam Sokol Kristijan University of Belgrade, Faculty of Mining and Geology Institute of Rock Structure and Mechanics, Czech Academy Štěpančíková Petra of Sciences Stephan Tobias TU Bergakademie Freiberg Stipp Michael Universität Innsbruck Stypa Agata Polish Academy of Sciences Šumanovac Franjo University of Zagreb Suppe John Edward University of Houston Thiede Rasmus C. Univ. Kiel Thiele Lisa TU Bergakademie Freiberg Tsai Chin-Ho National Dong Hwa University Turner Doreen Friedrich-Schiller-Universität Jena Unger Anne TU Bergakademie Freiberg Ustaszewski Kamil Marek Friedrich-Schiller-Universität Jena Jorien Leonorah Van der Wal RWTH Aachen Ninon van Hinsbergen Douwe J.J. Utrecht University Viscolani Andrea RWTH Aachen von Hagke Christoph RWTH Aachen University Vrabec Marko University of Ljubljana Wagner Bianca University of Göttingen, Geoscience Centre Warsitzka Michael Friedrich Schiller University Jena Weismüller Christopher RWTH Aachen University Winhausen Lisa RWTH Aachen University Youcef Brahim El Hadj University of Batna 2 Zebari Mjahid Friedrich-Schiller-Universität Jena Zhang Yiqiong Friedrich-Schiller-Universität Jena Zorc Laszlo Friedrich-Schiller-Universität Jena

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Geology of Jena

Geological map of Jena without Quaternary units (TLUG, dl-de/by-2-0). 145

Geological map of Jena with Quaternary units (TLUG, dl-de/by-2-0). 146

Pre-conference field trip 1: 19 March, 2018 Tectonic structures around Jena viewed from atop

Excursion leader: Kamil Ustaszewski

Itinerary: Walk from downtown Jena (143 m) up to the Hausberg (392 m)

Stop 1: Saale river at Camsdorfer Brücke

Stop 2: Gypsum-bearing veins within Röt (Oberer Buntsandstein), Schillstraße The outcrops displays numerous bedding-parallel, cm-thick extension veins with subvertically oriented fibres of anhydrite and gypsum, testifying to pore pressures exceeding overburden stresses.

Stop 3: Karst fissures in gypsum-bearing layers within Röt (Oberer Buntsandstein) This stop shows several m-sized karst fissures within coarse-crystalline gypsum layers (“Gipsschlotten”), possibly enhanced by fluvial erosion. Notably, he site has been officially acknowledged by the municipality of Jena as a protected geotope.

Stop 4: Boundary between Buntsandstein and Muschelkalk with Gelbe Grenzbank (“Yellow boundary layer”) at Ulmers Ruh’

Stop 5: Fuchsturm, Panorama around Jena

Stop 6: Sigmoidal vein structures (“Querplattung” or “Wellenstreifung”) within marly limestones of the Lower Muschelkalk This stop is located along the hiking trail along the crest of the Hausberg. Marly limestones in the Lower Muschelkalk of central and southern Germany frequently exhibit synsedimentary, mm- to cm-spaced fractures at high angles to the bedding. At times, these fractures have a sigmoidal shape in cross view. Such structures have been first described in Germany in the early 20th century (see Wagner [1967] for a review). They are termed “Querplattung” or “Sigmoidalklüftung” when viewed in cross section and

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“Wellenstreifung” when looking onto bedding planes (Figs. 1 and 2). The most frequent English term in use is “Vein structures” (Cowan, 1982; Brothers et al., 1996; Ohsumi and Ogawa, 2008). Next to fossil settings in the limestone-dominated Lower to Middle Triassic of Germany (e.g., Föhlisch, 2002) and the Western Carpathians (Rychlinski & Jaglarz, 2017), vein structures were mostly described from (hemi)-pelagic argillaceous and siliceous sediments in numerous Neogene to recent accretionary trench-fill series of the circum-Pacific region (see Ohsumi and Ogawa, 2008 for a review). Wagner (1967) interpreted such structures as principal stress indicators (Fig. 1). Broth- ers et al. (1996) performed analogue experiments with diatomite powder subjected to vibrations and could reproduce a range of vein structures very similar to those found in natural settings. They interpreted vein structures as a kind of “seismites” that form due to the passage of seismic p-waves through unconsolidated sediments (Fig. 2). This interpretation was questioned by Ohsumi and Ogawa (2008) based on the notion that earthquake surface waves have too large wavelength (in the order of km) to produce mm- to cm-spaced fractures. They performed shear box experiments with dry clay powder subjected to oscillating vibrations. During each experiment, the dry powder separated into an upper layer behaving as if liquefied, and a lower, stiffer layer, which gradually developed systematically aligned vein structures with increasing shear along the interface separating liquefied and stiffer layer. Ohsumi and Ogawa (2008) hence con- cluded that rather than p-waves of earthquakes, high-frequency periodic shear waves can provide the external forces to create vein structures. Such high-frequency shear waves can be triggered by density flows (e.g., submarine landslides, debris flows, or faulting), without the need of invoking earthquake activity.

Fig. 1: Interpretation of vein structures as principal stress indicators comparable to stylolite peaks (from Wagner, 1967).

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Fig. 2: Interpretation of vein structures as “seismites” due to the passage of seismic p- waves through unconsolidated sediment (from Föhlisch, 2002; based on Brothers et al., 1996).

Fig. 3: Interpretation of vein structures as resulting from oscillating vibration induced by high-frequency shear waves. The sche- matic diagrams show the development of a vein structure in a shear box experiment with dry clay-sized powder. The darker top zone is the liquefied part, below which shearing occurs. Vein structures formed first as systematic fractures, then they were developed by resonance into several orders with closer spacing. Finally, veins developed in a Riedel shear zone causing the array to tilt to the right and the veins to become sigmoidal in shape. From Ohsumi and Ogawa (2008).

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Stop 7: Non-tectonic “Lasagne”-folds within gypsum-bearing marls of the Röt (Oberer Buntsandstein) The outcrop is located along a roadcut right underneath the main building of the Institute of Geosciences. The strata exhibit cm- to dm-scale folds of variable wavelength and amplitude, apparently linked to the presence of fibrous gypsum-bearing veins. Possibly, the folds are related to the precipitation of veins, concomitant with phase transitions from anhydrite to gypsum that are linked to a volume increase, triggering contraction of the sediments (Fig. 4, left). They would hence be of rather non-tectonic origin and should be termed “Lasagne”-folds (in analogy to folds forming in Lasagne due to volume increase of pasta; Fig. 4, right).

Fig. 4: left: natural “Lasagne”-folds in strata of the Röt member associated with vein precipitation (Teufelslöcher, Jena). Right: Lasagne folds formed at laboratory conditions in Italian pasta. The folds formed due to volume increase of the pasta layers of a few percent during heating at 180°C for 50 min, while the bounding box, made of low-thermal expansion borosilicate glass, remained undeformed. Vertical scale approx. 5 cm.

References Brothers, R. J., Kemp, A. E. S., & Maltman, A. J. (1996). Mechanical development of vein structures due to the passage of earthquake waves through poorly-consolidated sediments, Tectonophysics, 260(4), 227-244, doi:http://dx.doi.org/10.1016/0040-1951(96)00088-1. Cowan, D. S. (1982). Origin of ‘vein structure’ in slope sediments on the inner slope of the Middle Ameri- ca Trench off Guatemala. In: Von Huene, R., Aubouin, J., et al. (Eds.), Initial Report of DSDP, vol. 57, pp. 645-650. Föhlisch, K. (2002). Synsedimentäre Deformationen im Unteren Muschelkalk des Germanischen Be- ckens. PhD thesis, Institut für Geowissenschaften, Friedrich-Schiller Universität Jena, 171 pp. Ohsumi, T., & Ogawa, Y. (2008). Vein structures, like ripple marks, are formed by short-wavelength shear waves, J. Struct. Geol., 30(6), 719-724, doi:https://doi.org/10.1016/j.jsg.2008.02.002. Rychliński, T., & Jaglarz, P. (2017). An evidence of tectonic activity in the Triassic of the Western Tethys: a case study from the carbonate succession in the Tatra Mountains (S Poland), Carbonates and Evapo- rites, 32(1), 103-116, doi:10.1007/s13146-016-0327-0. Thieme, M., Malz, A., Fügenschuh, B., Linnemann, U., Jähne-Klingberg, F., & Ustaszewski, K. New constraints on the timing and kinematics of Late Cretaceous intraplate contraction in the Thuringian Forest Uplands (Central Germany) from combined fission-track and U-Pb LA-ICP-MS dating, International Jour- nal of Earth Sciences, in revision. Wagner, G. H. (1967). Druckspannungsindizien in den Sedimenttafeln des Rheinischen Schildes, Interna- tional Journal of Earth Sciences, 56(1), 906-913, doi:http://dx.doi.org/910.1007/BF01848770. 150

Fig. 5: Geological overview of central Germany (from Thieme et al., in revision)

Fig. 6: Crustal-scale cross section across the Thuringian syncline (modified from Thieme et al., in revision).

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Fig. 7: Geological map 1:50.000 around Jena (TLUG, dl-de/by-2-0).

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Fig. 8: Cross section across the Saale valley at Jena and sketch of the Jenzig Plateau (modified after sketches by T. Voigt, Jena).

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Fig. 9: Topo map of the excursion route with stops (TLVerm, dl-de/by-2-0). 154

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