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This paper presents several types of new information including U–Pb radiometric dating of ophiolitic rocks and an intrusive granite, micropalaeontological dating of siliceous and calcareous sedimentary rocks, together with sedime...
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This paper presents several types of new information including U–Pb radiometric dating of ophiolitic rocks and an intrusive granite, micropalaeontological dating of siliceous and calcareous sedimentary rocks, together with sedimentological, petrographic and structural data. The new information is synthesised with existing results from the study area and adjacent regions (Central Pontides and Lesser Caucasus) to produce a new tectonic model for the Mesozoic–Cenozoic tectonic development of this key Tethyan suture zone.The Tethyan suture zone in NE Turkey (Ankara–Erzincan–Kars suture zone) exemplifies stages in the subduction, suturing and post-collisional deformation of a Mesozoic ocean basin that existed between the Eurasian (Pontide) and Gondwanan (Tauride) continents. Ophiolitic rocks, both as intact and as dismembered sequences, together with an intrusive granite (tonalite), formed during the Early Jurassic in a supra-subduction zone (SSZ) setting within the ?zmir–Ankara–Erzincan ocean. Basalts also occur as blocks and dismembered thrust sheets within Cretaceous accretionary melange. During the Early Jurassic, these basalts erupted in both a SSZ-type setting and in an intra-plate (seamount-type) setting. The volcanic-sedimentary melange accreted in an open-ocean setting in response to Cretaceous northward subduction beneath a backstop made up of Early Jurassic forearc ophiolitic crust. The Early Jurassic SSZ basalts in the melange were later detached from the overriding Early Jurassic ophiolitic crust.Sedimentary melange (debris-flow deposits) locally includes ophiolitic extrusive rocks of boninitic composition that were metamorphosed under high-pressure low-temperature conditions. Slices of mainly Cretaceous clastic sedimentary rocks within the suture zone are interpreted as a deformed forearc basin that bordered the Eurasian active margin. The basin received a copious supply of sediments derived from Late Cretaceous arc volcanism together with input of ophiolitic detritus from accreted oceanic crust.Accretionary melange was emplaced southwards onto the leading edge of the Tauride continent (Munzur Massif) during latest Cretaceous time. Accretionary melange was also emplaced northwards over the collapsed southern edge of the Eurasian continental margin (continental backstop) during the latest Cretaceous. Sedimentation persisted into the Early Eocene in more northerly areas of the Eurasian margin.Collision of the Tauride and Eurasian continents took place progressively during latest Late Palaeocene–Early Eocene. The Jurassic SSZ ophiolites and the Cretaceous accretionary melange finally docked with the Eurasian margin. Coarse clastic sediments were shed from the uplifted Eurasian margin and infilled a narrow peripheral basin. Gravity flows accumulated in thrust-top piggyback basins above accretionary melange and dismembered ophiolites and also in a post-collisional peripheral basin above Eurasian crust. Thickening of the accretionary wedge triggered large-scale out-of-sequence thrusting and re-thrusting of continental margin and ophiolitic units. Collision culminated in detachment and northward thrusting on a regional scale.Collisional deformation of the suture zone ended prior to the Mid-Eocene (~45?Ma) when the Eurasian margin was transgressed by non-marine and/or shallow-marine sediments. The foreland became volcanically active and subsided strongly during Mid-Eocene, possibly related to post-collisional slab rollback and/or delamination. The present structure and morphology of the suture zone was strongly influenced by several phases of mostly S-directed suture zone tightening (Late Eocene; pre-Pliocene), possible slab break-off and right-lateral strike-slip along the North Anatolian Transform Fault.In the wider regional context, a double subduction zone model is preferred, in which northward subduction was active during the Jurassic and Cretaceous, both within the Tethyan ocean and bordering the Eurasian continental margin.
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摘要 :
This paper presents several types of new information including U–Pb radiometric dating of ophiolitic rocks and an intrusive granite, micropalaeontological dating of siliceous and calcareous sedimentary rocks, together with sedime...
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This paper presents several types of new information including U–Pb radiometric dating of ophiolitic rocks and an intrusive granite, micropalaeontological dating of siliceous and calcareous sedimentary rocks, together with sedimentological, petrographic and structural data. The new information is synthesised with existing results from the study area and adjacent regions (Central Pontides and Lesser Caucasus) to produce a new tectonic model for the Mesozoic–Cenozoic tectonic development of this key Tethyan suture zone.The Tethyan suture zone in NE Turkey (Ankara–Erzincan–Kars suture zone) exemplifies stages in the subduction, suturing and post-collisional deformation of a Mesozoic ocean basin that existed between the Eurasian (Pontide) and Gondwanan (Tauride) continents. Ophiolitic rocks, both as intact and as dismembered sequences, together with an intrusive granite (tonalite), formed during the Early Jurassic in a supra-subduction zone (SSZ) setting within the ?zmir–Ankara–Erzincan ocean. Basalts also occur as blocks and dismembered thrust sheets within Cretaceous accretionary melange. During the Early Jurassic, these basalts erupted in both a SSZ-type setting and in an intra-plate (seamount-type) setting. The volcanic-sedimentary melange accreted in an open-ocean setting in response to Cretaceous northward subduction beneath a backstop made up of Early Jurassic forearc ophiolitic crust. The Early Jurassic SSZ basalts in the melange were later detached from the overriding Early Jurassic ophiolitic crust.Sedimentary melange (debris-flow deposits) locally includes ophiolitic extrusive rocks of boninitic composition that were metamorphosed under high-pressure low-temperature conditions. Slices of mainly Cretaceous clastic sedimentary rocks within the suture zone are interpreted as a deformed forearc basin that bordered the Eurasian active margin. The basin received a copious supply of sediments derived from Late Cretaceous arc volcanism together with input of ophiolitic detritus from accreted oceanic crust.Accretionary melange was emplaced southwards onto the leading edge of the Tauride continent (Munzur Massif) during latest Cretaceous time. Accretionary melange was also emplaced northwards over the collapsed southern edge of the Eurasian continental margin (continental backstop) during the latest Cretaceous. Sedimentation persisted into the Early Eocene in more northerly areas of the Eurasian margin.Collision of the Tauride and Eurasian continents took place progressively during latest Late Palaeocene–Early Eocene. The Jurassic SSZ ophiolites and the Cretaceous accretionary melange finally docked with the Eurasian margin. Coarse clastic sediments were shed from the uplifted Eurasian margin and infilled a narrow peripheral basin. Gravity flows accumulated in thrust-top piggyback basins above accretionary melange and dismembered ophiolites and also in a post-collisional peripheral basin above Eurasian crust. Thickening of the accretionary wedge triggered large-scale out-of-sequence thrusting and re-thrusting of continental margin and ophiolitic units. Collision culminated in detachment and northward thrusting on a regional scale.Collisional deformation of the suture zone ended prior to the Mid-Eocene (~45?Ma) when the Eurasian margin was transgressed by non-marine and/or shallow-marine sediments. The foreland became volcanically active and subsided strongly during Mid-Eocene, possibly related to post-collisional slab rollback and/or delamination. The present structure and morphology of the suture zone was strongly influenced by several phases of mostly S-directed suture zone tightening (Late Eocene;pre-Pliocene), possible slab break-off and right-lateral strike-slip along the North Anatolian Transform Fault.In the wider regional context, a double subduction zone model is preferred, in which northward subduction was active during the Jurassic and Cretaceous, both within the Tethyan ocean and bordering the Eurasian continental margin.
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The Mid-Tertiary (Mid-Eocene to earliest Miocene) Misis-Andirin Complex documents tectonic-sedimentary processes affecting the northerly, active margin of the South Tethys (Neotethys) in the easternmost Mediterranean region. Each ...
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The Mid-Tertiary (Mid-Eocene to earliest Miocene) Misis-Andirin Complex documents tectonic-sedimentary processes affecting the northerly, active margin of the South Tethys (Neotethys) in the easternmost Mediterranean region. Each of three orogenic segments, Misis (in the SW), Andirin (central) and Engizek (in the NE) represent parts of an originally continuous active continental margin. A structurally lower Volcanic-Sedimentary Unit includes Late Cretaceous arc-related extrusives and their Lower Tertiary pelagic cover. This unit is interpreted as an Early Tertiary remnant of the Mesozoic South Tethys. The overlying melange unit is dominated by tectonically brecciated blocks (> 100 m across) of Mesozoic neritic limestone that were derived from the Tauride carbonate platform to the north, together with accreted ophiolitic material. The melange matrix comprises polymict debris flows, high- to low-density turbidites and minor hemipelagic sediments. The Misis-Andirin Complex is interpreted as an accretionary prism related to the latest stages of northward subduction of the South Tethys and diachronous continental collision of the Tauride (Eurasian) and Arabian (African) plates during Mid-Eocene to earliest Miocene time. Slivers of Upper Cretaceous oceanic crust and its Early Tertiary pelagic cover were accreted, while blocks of Mesozoic platform carbonates slid from the overriding plate. Tectonic mixing and sedimentary recycling took place within a trench. Subduction culminated in large-scale collapse of the overriding (northern) margin and foundering of vast blocks of neritic carbonate into the trench. A possible cause was rapid roll back of dense downgoing Mesozoic oceanic crust, such that the accretionary wedge taper was extended leading to gravity collapse. Melange formation was terminated by underthrusting of the Arabian plate from the south during earliest Miocene time. Collision was diachronous. In the east (Engizek Range and SE Anatolia) collision generated a Lower Miocene flexural basin infilled with turbidites and a flexural bulge to the south. Miocene turbiditic sediments also covered the former accretionary prism. Further west (Misis Range) the easternmost Mediterranean remained in a pre-collisional setting with northward underthrusting (incipient subduction) along the Cyprus arc. The Lower Miocene basins to the north (Misis and Adana) indicate an extensional (to transtensional) setting. The NE-SW linking segment (Andirin) probably originated as a Mesozoic palaeogeographic offset of the Tauride margin. This was reactivated by strike-slip (and transtension) during Later Tertiary diachronous collision. Related to on-going plate convergence the former accretionary wedge (upper plate) was thrust over the Lower Miocene turbiditic basins in Mid-Late Miocene time. The Plio-Quaternary was dominated by left-lateral strike-slip along the East Anatolian transform fault and also along fault strands cutting the Misis-Andmn Complex.
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The Ulukisla Basin, the southerly and best exposed of the Lower Tertiary Central Anatolian Basins, sheds light on one of the outstanding problems of the tectonic assembly of suture zones: how large deep-water basins can form withi...
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The Ulukisla Basin, the southerly and best exposed of the Lower Tertiary Central Anatolian Basins, sheds light on one of the outstanding problems of the tectonic assembly of suture zones: how large deep-water basins can form within a zone of regional plate convergence. The oldest Ulukisla Basin sediments, of Maastrichtian age, transgressively overlie melange and ophiolitic rocks that were emplaced southwards onto the Tauride microcontinent during the latest Cretaceous time. The Nigde-Kirsehir Massif forming the northern basin margin probably represents another rifted continental fragment that was surrounded by oceanic crust during Mesozoic time. The stratigraphic succession of the Ulukisla Basin begins with the deposition of shallow-marine carbonates of Maastrichtian-Early Palaeocene age, then passes upwards into slope-facies carbonates, with localised sedimentary breccias and channelised units, followed by deep-water clastic turbidites of Middle Palaeocene-Early Eocene age. This was followed by the extrusion of c. 2000 m of basic volcanic rocks during Early to Mid Eocene time. After volcanism ended, coral-bearing neritic carbonates and nummulitic shelf sediments accumulated along the northern and southern margins of the basin, respectively. Deposition of the Ulukisla Basin ended with gypsum deposits including turbidites, debris flows, and sabkhas, followed by a regional Oligocene unconformity. The Ulukisla Basin is interpreted as the result of extension (or transtension) coupled with subsidence and basic volcanism. After post-volcanic subsidence, the basin was terminated by regional convergence, culminating in thrusting and folding in Late Eocene time. Comparisons of the Ulukisla Basin with the adjacent central Anatolian basins (e.g. Tuzgoelue, Sivas and Sarkisla) support the view that these basins formed parts of a regional transtensional (to extensional) basin system. In our preferred hypothesis, the Ulukisla Basin developed during an intermediate stage of continental collision, after steady-state subduction of oceanic crust had more or less ended ("soft collision"), but before the opposing Tauride and Eurasian continental units forcefully collided ("hard collision"). Late Eocene forceful collision terminated the basinal evolution and initiated uplift of the Taurus Mountains.
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The northern Balkan Peninsula, including Serbia, Montenegro, Bosnia, Croatia and the Former Yugoslavian Republic of Macedonia, represents an excellent region for the study of tectonic processes related to Mesozoic Tethyan ophiolit...
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The northern Balkan Peninsula, including Serbia, Montenegro, Bosnia, Croatia and the Former Yugoslavian Republic of Macedonia, represents an excellent region for the study of tectonic processes related to Mesozoic Tethyan ophiolite genesis and emplacement. We first summarise the main tectonic units of the northern Balkan Peninsula and then use this information to discuss tectonic processes, including rifting, sea-floor spreading, ophiolite genesis and emplacement, melange accretion, ocean-basin closure and collision. We then discuss alternative models of ophiolite genesis and emplacement for the region and suggest that multi-ocean-basin interpretations fit the data better than single-ocean-basin interpretations. Rifting of Adria (Gondwana) during the Triassic created a rift in the south (Budva zone) and opened a Triassic oceanic basin further north (Dinaride ocean). Occurrences of inferred sub-continental mantle lithosphere in the Dinaride ophiolite belt (e.g. Zlatibor) may record extensional exhumation within an ocean-continent transition zone bordering the Adria/Dinaride continent. This was followed by emplacement together with ophiolites and melange during Upper Jurassic-Early Cretaceous time. Upper Triassic radiolarites and mid-ocean ridge-type basalts formed at a spreading ridge after continental break-up. The oceanic lithosphere of the Dinaride ophiolite belt was partly generated above a subduction zone. The metamorphic soles of the Dinaride ophiolites formed during Mid-Late Jurassic mainly based on K/Ar dating. Widespread melange that is associated with the ophiolites represents a subduction complex, controlled by tectonic accretion and sedimentary reworking in trench and fore-arc basin settings. A possible cause of Jurassic Dinaride ophiolite emplacement was collision of a subduction trench with a continental margin. Further north, Mesozoic oceanic lithosphere subducted northeastwards (present coordinates) opening a Late Jurassic marginal basin in the Main Vardar zone. The Dinaride ocean in the south closed during Late Jurassic-Early Cretaceous time (Tithonian-Berriasian). Deformed oceanic crust, melange and magmatic arc rocks further north (Main Vardar zone) were transgressed by mainly clastic sediments during the Early Cretaceous. However, part of the Vardar ocean (Vardar zone western belt, or Sava zone) remained partially open until latest Cretaceous time. Generally northward subduction within this remnant ocean triggered further supra-subduction zone ophiolite genesis during the Late Cretaceous. The ocean closed by the Maastrichtian, followed by Early Cenozoic regional-scale southward thrusting that locally intercalated older and younger Mesozoic ophiolites and melanges. Future progress particularly depends on determining the crystallisation ages of the ophiolites, obtaining better structural data on the direction of initial ophiolite emplacement and unravelling the Palaeozoic tectonic development of the Eurasian continental margin.
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The Alasehir (Gediz) Graben exemplifies clastic sedimentation in a long-lived continental half-graben in a semi-arid setting, developed within relatively incompetent metamorphic rocks. Early Miocene to Recent rift-related sediment...
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The Alasehir (Gediz) Graben exemplifies clastic sedimentation in a long-lived continental half-graben in a semi-arid setting, developed within relatively incompetent metamorphic rocks. Early Miocene to Recent rift-related sediments are exhumed on both flanks of the graben, allowing detailed three-dimensional study. During the Early Miocene, small fan-delta lobes were shed northwards from the rugged Menderes Metamorphic Massif into a bordering lacustrine basin. During Early to Mid-Miocene time, large alluvial fans prograded northwards into this basin. Through-drainage to the Aegean Sea was established as the basin widened and filled. Discrete lobes of coarse alluvial fan sediments of latest Miocene(?)-Pliocene age, also shedding northwards, are likely to have been climatically influenced. Quaternary alluvium party infills the modern Alasehir rift basin. The sedimentary information can be used to test two alternative tectonic models for the Alasehir Graben. In the first model, an E-W graben bounded by high-angle faults was active during latest Miocene(?)-Recent time, whereas earlier Miocene sedimentation was controlled by N-S faulting related to a N-S compressional stress regime. In the second hypothesis, the Alasehir Graben was initiated much earlier, in the Early Miocene and was then either continuously or episodically active until Recent. Our results, especially facies and palaeocurrent data from alluvial sediments, indicate that clastic sedimentation was controlled by mainly E-W faulting in a N-S stress regime. Assuming the Early Miocene clastic sediments are correctly dated, this supports the second (long-lived extension) model. However, rather than steady-state extension for ca. 15 Ma, the sedimentary evidence and regional context are consistent with a pulsed extension model, whereby initial Early to Mid-Miocene extension and related clastic sedimentation was followed by a second phase of extension in latest Miocene(?)-Pliocene time. The driving force of initial, Early Miocene extension was probably gravity spreading towards a south-Aegean subduction zone, whereas the inferred second extension pulse is seen as being triggered by westward "tectonic escape" of Anatolia towards the extending Aegean back-arc region.
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The Baer-Bassit ophiolite, of inferred Late Cretaceous age, was emplaced from the south Tethys ocean onto the leading edge of the Arabian continental margin in latest Cretaceous (Maastrichtian) time. Dismembered sequences in diffe...
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The Baer-Bassit ophiolite, of inferred Late Cretaceous age, was emplaced from the south Tethys ocean onto the leading edge of the Arabian continental margin in latest Cretaceous (Maastrichtian) time. Dismembered sequences in different thrust sheets can be correlated to produce a complete ophiolite sequence, with a metamorphic sole at the base, overlain, in turn, by upper mantle tectonite, rate cumulates, massive and layered gabbros, localized high-level plagiogranites, sheeted dykes, basic extrusives and minor Fe-Mn sediments (umbers). The restored ophiolite sequence is similar to that of the more inttact Troodos and Hatay ophiolites, but dissimilar to Oman. The Baer-Bassit extrusives are magnesian and strongly depleted, comparable to primitive island arc tholeiites and some boninitic lavas, which favours a subduction-related origin. A well-developed metamorphic sole is divisible into high-grade (amphibolite facies) assemblages in the north and lower-grade (greenschist facies)assemblages in the centre of the region, but no complete inverted metamorphic gradient is preserved in any one local area. The protoliths of both the high-grade (amphibolites) and lower-grade rocks (greenschists) are interpreted as alkali basalts and pelagic sediments, including chert, similar to the volcanic rocks in an underlying unmetamorphosed melange. The metamorphic fabrics progressively evolved from ductile to brittle during tectonic transport towards the southeast. Most of the metamorphic fbrics evolved during intense shearing, but some of the alkaline metabasites apparently were metamorphosed under relatively staitic strain conditions. The apparent absence of preserved inverted metamorphic gradients in Baer-Bassit may reflect a complex deformation history during emplacement. Alternatively, differing P-T conditions may be recorded at different depths at the base of theover-riding mantle wedge. During emplacement, the front of the ophiolite was tectonically imbricated and overthrust by the main ultramafic slab (Bassit massif). The thickest massif the ophiolite was tectonically imbricated and overthrust by the main ultramafic slab (Bassit massif). The thickest massif (Baer) is underlain by a high-grade metamorphic sole and was internally shortened but without thrust duplication of the entire ophiolite sequence. Following covering by Late Maastrichtian-Palaeogene marine calcareous sediments, the area was subjected to mid-Tertiary regional folding. This was followed by Neogene dominantly left-lateral, strike-slip deformation deformation along the African-Eurasian plate boundary, extending from south of Cyprus to the Dead Sea transform fault. As a result, the along the African-Eurasian plate boundary, extending from south of Cyprus to the Dead Sea transform fault. As a result, the originally emplaced thrust sheets were dissected into three main compostie units (Baer, Bassit and the Southeastern units), separated by strongly faulted and sheared ophiolitic blocks and unmetamorphosed volcanic-sedimentary melange.
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Western Turkey is one of the classic regions for the study of extensional processes. In a recent interpretation, the regional metamorphic basement, the Menderes Massif, was exhumed related to large-scale extensional processes, pos...
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Western Turkey is one of the classic regions for the study of extensional processes. In a recent interpretation, the regional metamorphic basement, the Menderes Massif, was exhumed related to large-scale extensional processes, possibly during latest Oligocene time. Regional-scale NE- SW-trending basins, including the Goerdes and Selendi basins, were created, associated with this exhumation. The NE SW-trending basins are seen as regional-scale "corrugations" (10-15 km across) in the surface of an extensional detachment orientated parallel to the direction of extension. The detached upper plate is represented by erosional remnants of unmetamorphosed Tethyan ophiolitic melange. We describe and interpret the Goerdes and Selendi basins separately and then show that their sedimentary facies and evolution are very similar. Basal coarse alluvial fan deposits accumulated after extensional removal of the upper plate. These basal sediments, rarely exposed, were rotated by up to 50°, probably as a result of local extension or transtension. Later during the early Miocene, the Goerdes and Selendi basins were infilled by a generally fining-upward succession derived from the south, based on palaeocurrent evidence. Coarse alluvial fan deposition was followed by the deposition of finer-grained alluvial deposits from braided streams flowing northwards over a topographically subdued flood plain. Later, deposition was within shallow ephemeral lakes after a possible change to a moister climate. Calc-alkaline magmatism was initiated with the fall-out of fine-grained silicic ash, followed by coarser-grained tuff derived from local magmatic centres. During early Pliocene time, the basins were dissected by E-W extensional faults, associated with the establishment of the modem pattern of westward drainage to the Aegean Sea. We use the assembled sedimentary evidence to test alternative tectonic models for Miocene basin formation in western Turkey. Our preferred tectonic model emphasises the importance of deposition in regional basins created by exhumation of metamorphic basement that was previously assembled during early Tertiary closure of the Tethys ocean.
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The Mersin Melange underlies the intact Mersin Ophiolite and its metamorphic sole to the south of the Mesozoic Tauride Carbonate Platform in southern Turkey. The Melange varies from chaotic melange to broken formation, in which so...
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The Mersin Melange underlies the intact Mersin Ophiolite and its metamorphic sole to the south of the Mesozoic Tauride Carbonate Platform in southern Turkey. The Melange varies from chaotic melange to broken formation, in which some stratigraphic continuity can be recognized. Based on study of the broken formation, four lithological associations are recognized: (1) shallow-water platform association, dominated by Upper Palaeozoic-Lower Cretaceous neritic carbonates; (2) rift-related volcanogenic-terrigenous-pelagic association, mainly Upper Triassic andesitic-acidic volcanogenic rocks, siliciclastic gravity flows, basinal carbonates and radiolarites; (3) within-plate-type basalt-radiolarite-pelagic limestone association, interpreted as Upper Jurassic-Lower Cretaceous seamounts with associated radiolarian sediments and Upper Cretaceous pelagic carbonates; (4) ophiolite-derived association, including fragments of the Upper Cretaceous Mersin Ophiolite and its metamorphic sole. Locally, the ophiolitic melange includes granite that yielded a K/Ar radiometric age of 375.7 ± 10.5 Ma (Late Devonian). This granite appears to be subduction influenced based on 'immobile' element composition. The Mersin Melange documents the following history: (1) Triassic rifting of the Tauride continent; (2) Jurassic-Cretaceous passive margin subsidence; (3) oceanic seamount genesis; (4) Cretaceous supra-subduction zone ophiolite genesis; (5) Late Cretaceous intra-oceanic convergence-metamorphic sole formation, and (6) latest Cretaceous emplacement onto the Tauride microcontinent and related backthrusting. Regional comparisons show that the restored Mersin Melange is similar to the Beyşehir-Hoyran Nappes further northwest and a northerly origin best fits the regional geological picture. These remnants of a North-Neotethys (Inner Tauride Ocean) were formed and emplaced to the north of the Tauride Carbonate Platform. They are dissimilar to melanges and related units in northern Syria, western Cyprus and southwestern Turkey, which are interpreted as remnants of a South-Neotethys. Early high-temperature ductile transport lineations within amphibolites of the metamorphic sole of the Mersin ophiolite are generally orientated E-W, possibly resulting from vertical-axis rotation of the ophiolite while still in an oceanic setting. By contrast, the commonly northward-facing later stage brittle structures are explained by backthrusting of the ophiolite and melange related to exhumation of the partially subducted northern leading edge of the Tauride continent.
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One of the few detailed records of Mesozoic deep-water sedimentation and volcanism preserved along the tectonically emplaced Arabian continental margin is from the Baer-Bassit region of northern Syria. South-Tethyan units there oc...
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One of the few detailed records of Mesozoic deep-water sedimentation and volcanism preserved along the tectonically emplaced Arabian continental margin is from the Baer-Bassit region of northern Syria. South-Tethyan units there occur as blocks, broken formation and disrupted thrust sheets within the Bear-Bassit Melange. Two overall composite successions are identified. The first comprises mainly sedimentary successions ranging from Late Triassic to Late Cretaceous (Cenomanian) in age. The second is dominated by Middle Jurassic-Lower Cretaceous alkaline/per-alkaline volcanic and minor intrusive igneous rocks. The extrusives are intercalated with radiolarian sediments and capped by Cenomanian ferromanganese-rich pelagic limestone. Facies comparisons and the regional setting suggest that the Triassic to Cenomanian, mainly sedimentary units, formed in deep water near the base of the slope of the Arabian continental margin. The contrasting volcanogenic successions developed in a more distal off-margin setting. Regional comparisons (e.g. with southwestern Cyprus and southwestern Turkey) suggest that continental break-up to form a South-Tethyan oceanic basin took place in Late Triassic time, associated with alkaline volcanism. Similar alkaline volcanism of Middle Jurassic to Early Cretaceous age could reflect the activity of a mantle plume beneath the Arabian plate. Overall, sedimentation was mainly controlled by an interplay of post-rift thermal subsidence, plume-related uplift, siliceous oceanic productivity, climatic change and eustatic sea-level change. The South-Tethyan marginal to oceanic units in northern Syria were detached from an inferred oceanic basement in latest Cretaceous time, emplaced onto the Arabian continental margin, then transgressed by Maastrichian and younger autochthonous successions.
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