Late Cretaceous-Early Eocene tectonic development of the Tethyan suture zone in the Erzincan area, Eastern Pontides, Turkey

Six individual tectonostratigraphic units are identified within the Izmir-Ankara-Erzincan Suture Zone in the critical Erzincan area of the Eastern Pontides. The Ayikayasi Formation of Campanian-Maastrichtian age is composed of bedded pelagic limestones intercalated with polymict, massive conglomerates. The Ayikayasi Formation conformably overlies the Tauride passive margin sequence in the Munzur Mountains to the south and is interpreted as an underfilled foredeep basin. The Refahiye Complex, of possible Late Cretaceous age, is a partial ophiolite composed of similar to 75 % (by volume) serpentinized peridotite (mainly harzburgite), similar to 20 % diabase and minor amounts of gabbro and plagiogranite. The complex is interpreted as oceanic lithosphere that formed by spreading above a subduction zone. Unusual screens of metamorphic rocks (e.g. marble and schist) locally Occur between sheeted diabase dykes. The Upper Cretaceous Karayaprak Melange exhibits two lithological associations: (1) the basalt + radiolarite + serpentinite association, including depleted arc-type basalts; (2) the massive neritic limestone + lava + volcaniclastic association that includes fractionated, intermediate-composition lavas, and is interpreted as accreted Neotethyan seamount(s). The several-kilometre-thick Karadag Formation, of Campanian-Maastrichtian age, is composed of greenschist-facies volcanogenic rocks of mainly basaltic to andesitic composition, and is interpreted as an emplaced Upper Cretaceous volcanic arc. The Campanian-Early Eocene Sutpinar Formation (similar to 1500 m thick) is a coarsening-Upward succession of turbiditic calcarenite, sandstone, laminated mudrock, volcaniclastic sedimentary rocks that includes rare andesitic lava, and is interpreted as a regressive forearc basin. The Late Paleocene-Eocene Sipikor Formation is a laterally varied succession of shallow-marine carbonate and siliciclastic lithofacies that overlies deformed Upper Cretaceous units with an angular unconformity. Structural study indicates that the assembled accretionary prism, supra-subduction zone-type oceanic lithosphere and volcanic are units were emplaced northwards onto the Eurasian margin and also southwards onto the Tauride (Gondwana-related) margin during Campanian-Maastrichtian time. Further, mainly southward thrusting took place during the Eocene in this area, related to final closure of Tethys. Our preferred tectonic model involves northward subduction, supra-subduction zone ophiolite genesis and arc magmatism near the northerly, Eurasian margin of the Mesozoic Tethys

Cadomian (Ediacaran-Cambrian) arc magmatism in the Bitlis Massif, SE Turkey: Magmatism along the developing northern margin of Gondwana

Copyright © 2008 Elsevier B.V. All rights reserved.Small granitic plutons and associated granitic dykes that intrude the pre-Devonian basement of the Bitlis Massif were previously inferred to have a broadly Late Palaeozoic crystallisation age related to the Hercynian orogeny; this was tested during this work. The brittle-ductile-deformed Mutki granite pluton and nearby granitic dykes comprise mainly quartz, alkali feldspar, plagioclase, subordinate biotite, muscovite and rare amphibole. Based on the results of whole-rock major-element and trace-element analysis, the Mutki pluton and associated dykes are inferred to have crystallised from metaluminous, to peraluminous subduction influenced I-type melts. Sm-Nd isotope systematics indicate melting of a mantle source (of notional 1.3 Ga age), with increasing amounts of crustal contamination through time. U/Pb zircon dating of the Mutki granite and a nearby granitic dyke by laser inductively coupled plasma mass spectrometry (LA-ICP-MS) yielded 238U/206Pb crystallisation ages of 545.5 ± 6.1 Ma and 531.4 ± 3.6 Ma, respectively (Ediacaran-Early Cambrian). This shows for the first time that the regionally extensive Bitlis Massif was affected by Cadomian arc-type magmatism. The Ediacaran-Early Cambrian granitic rocks of the Bitlis Massif can be compared with similar-aged metagranitic and metavolcanic rocks within basement units exposed in the Tauride-Anatolide Platform (Menderes-Taurus Block) in western Anatolia and also in NW Turkey. Similar-aged rocks are also exposed in the basement of Iran. All of these magmatic units and their host rocks are interpreted as fragments of a Cadomian active margin bordering the northern margin of Gondwana after its final amalgamation. Formation of the Bitlis Massif granites and contemporaneous granitic units elsewhere in Turkey as fragments of an Andean-type margin adjacent to the Arabian-Nubian Shield is favoured over an alternative explanation as exotic terranes transported > 2000 km eastwards from a Cadomian active margin near West Africa-Amazonia (now NW Africa). © 2008 Elsevier B.V. All rights reserved.P. Ayda Ustaömer, Timur Ustaömer, Alan S. Collins and Alastair H.F. Robertsonhttp://www.elsevier.com/wps/find/journaldescription.cws_home/503362/description#descriptio

Eocene continental arc magmatism along the southern Eurasian margin: New U-Pb LA-ICPMS Sm-Nd and whole-rock geochemical data from Marmara Island NW Turkey

Copyright © 2007 European Geosciences Unionhttp://www.cosis.net/abstracts/EGU2007/00670/EGU2007-J-00670.pd

Evidence of Precambrian sedimentation/magmatism and Cambrian metamorphism in the Bitlis Massif, SE Turkey utilising whole-rock geochemistry and U-Pb LA-ICP-MS zircon dating

The Bitlis Massif is a regional-scale, south-vergent allochthon that was finally emplaced by collision of the Eurasian and Afro-Arabian plates during Miocene time. The Bitlis Massif includes a large outcrop of Precambrian continental crust, the closest counterpart to which is the Arabian-Nubian Shield ~1000km to the south. The Massif is sub-divided into two rock associations: a pre-Middle Devonian high-grade basement and a Middle Devonian-Triassic low-grade cover. The pre-Devonian basement comprises meta-granitic plutons emplaced into high-grade metamorphic rocks, including schist, paragneiss, amphibolite and eclogite. New laser-ablation zircon ages obtained for zircons separated from a meta-granite body and its host paragneiss provide constraints on magmatism, sedimentation and metamorphism. Whole-rock geochemical data indicate that the pluton crystallised from peraluminous I-type melts from an arc-type subduction influenced source. Sm-Nd isotope systematics suggest crustal contamination. Zircon dating yielded a 206Pb/ 238U age of 572±4.8Ma, interpreted as the time of crystallisation. Igneous zircons exhibit metamict metamorphic domains dated at 529Ma (Early Cambrian), interpreted as the time of latest Pan-African metamorphism. Nine detrital zircon grains from host paragneiss yielded Neoproterozoic ages (992-627Ma). Combined with the crystallisation age data, this suggests that the sedimentary protolith of the paragneiss was deposited from ~627 to ~572Ma (Ediacaran). The late Neoproterozoic ages suggest the Bitlis Massif is a peri-Gondwanan terrane with a likely origin in northeast Africa where similar early Neoproterozoic (0.9-1.0Ga) ages have been reported. © 2011 International Association for Gondwana Research.P. Ayda Ustaömer, Timur Ustaömer, Axel Gerdes, Alastair H.F. Robertson and Alan S. Collin

Testing models of late Palaeozoic-Early Mesozoic orogeny in Western Turkey: support for an evolving open-Tethys model

Copyright © 2004 Geological Society of LondonField evidence from north–south transects tests three tectonic models for Tethys in Western Turkey for when a Late Palaeozoic ocean was closing and an Early Mesozoic ocean opening. In Model 1, a Palaeozoic ocean subducted southwards, rifting continental fragments from Gondwana and opening a Triassic Neo-Tethys to the south. Closure and collision occurred by latest Triassic time. In Model 2, a wide Palaeozoic Tethys subducted northwards with an active Eurasian margin and a passive Gondwana margin. The northern Gondwana margin rifted in the Triassic; fragments either remained nearby (Taurides) or drifted northwards (e.g. Karakaya) attached to a north-subducting plate. New oceanic crust replaced Palaeo-Tethys with Neotethys and back-arc marginal basins opened along the south Eurasian margin (e.g. Küre). In Model 3, a Palaeozoic ocean also subducted northwards opening wide marginal basins. A wide Southern Neotethys opened along the Gondwana margin. Rifted Eurasian (Anatolides) and Gondwana (Taurides) fragments collided in mid-Tethys by latest Triassic time. Field evidence from the Pontides supports north-dipping subduction models (Model 2 or 3 above). Key features are a south-vergent, HP–LT accretionary prism, magmatic arc and back-arc basin system bordering the Eurasian margin. Also, evidence from the Tauride Mountains favours Model 2 over Model 3. Critically, the Anatolides and Taurides appear to have a common history and were unlikely to have been located on opposite sides of Tethys, as in Model 3.Alastair H. F. Robertson, Timur Ustaömer, Elizabeth A. Pickett, Alan S. Collins, Theo Andrew & John E. Dixo

Late quaternary evolution of the Canakkale Strait region, Dardanelles, NW Turkey : implications of a major erosional event for the postglacial Mediterranean - Marmara sea connection.

Seismic and bathymetric data from the Canakkale Strait and its extensions onto the shelves of the Marmara and Aegean seas indicate that the strait was formed mainly by an erosional event. Four seismic units are observed on seismic profiles. The lower two of these (units 4 and 3) constitute the basement of a regionally widespread erosional unconformity (ravinement), which developed during marine isotope stage 2 (MIS 2). The two upper units (units 2 and 1), which overlie the ravinement surface, form a higher-order sequence. Sequence stratigraphic analysis indicates that units 2 and 1 deposited as lowstand and highstand systems tracts respectively, since the end of MIS 2. The transgressive systems tract is represented by a major erosional event which occurred throughout the Canakkale sill area when the Mediterranean-Marmara Sea connection and, hence, the Canakkale Strait was formed. The existence of the erosive Aarkoy Canyon along the shelf edge of the southern Marmara Sea demonstrates that the flow direction causing the erosion was from south to north, thus proving that it was produced by Mediterranean water flowing over the sill into the Marmara Sea basin

Morpho-tectonic evolution of the Marmara Sea inferred from multi-beam bathymetric and seismic data

In an initial stage, the Sea of Marmara developed as a graben and, in due course, considerable volumes of sediments were deposited in this basin. Before 200 ka, a new fault (New Marmara Fault) cutting through the whole basin developed, which postdated large sub-marine land sliding in the western part of the basin. This mass movement created the Western Ridge. The initiation of this strike-slip fault indicates that the extensional stress regime was replaced by a new, shearing stress field. In the eastern part of the Marmara Basin, the New Marmara Fault consists of two branches. The northern one replaces the normal faulting at the bottom of the northeastern slope of the basin. As a result, this slope has been rejuvenated. The southern branch is located along the central axis of the basin, forming the major extension of the North Anatolian Fault Zone within the region. Two restraining bends were formed because of the counterclockwise rotation of that part of the Anatolian Block. This resulted the uplifting of the Eastern Ridge and the formation of the positive flower structure within the Tekirdag Basin. The establishment of the compressional regime around the Sea of Marmara also resulted in the northwest-southeast shortening of the initial Marmara Basin