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    Foraminifera, Radiolaria and Conodont assemblages from the Early Mississipian (late Tournaisian)/Early Pennsylvanian (early Bashkirian) blocks within the Mersin Melange, southern Turkey: Biochronological and paleogeographical implications
    (ELSEVIER, 2018) Okuyucu, Cengiz; Tekin, U. Kagan; Noble, Paula J.; Bedi, Yavuz; Saydam-Demiray, D. Gulnur; Sayit, Kaan
    The Mersin Melange, a sedimentary complex in southern Turkey, includes blocks of various origins within a Late Cretaceous matrix. Two blocks in the Mersin Melange are herein recognized to be of Carboniferous age. One block (the Kozan Block) is composed of alternating chert and mudstone, and includes radiolarian and conodont assemblages revealing a late Tournaisian (Early Mississippian) age. The other (Keven-West Block) consists of platform carbonate containing abundant foraminifera indicating Bashkirian (Early Pennsylvanian) age. These dates are so far the oldest obtained from the blocks within the Mersin Melange. A correlation of the lithostratigraphies of blocks in the Mersin Melange with the coeval Tauride sequences indicates that they correspond to the successions in the Beysehir-Hoyran Nappes. In these nappes, the late Tournaisian is characterized by radiolarian rich chert and mudstone of an open marine environment, whereas the Bashkirian succession represents a shallow water environment with Foraminifera-bearing limestone. The Tournaisian deepening can be ascribed to the opening of a deep marginal basin to the north of the Tauride Platform and uplifting of the northern Tauride-Anatolide Platform margin during the Late Mississippian and Early Pennsylvanian. A shallowing upward sequence started in the Tournaisian with a pelagic sequence followed by platform carbonates of Bashkirian age in the Beysehir-Hoyran Nappes, and could be related to a major glaciation event during late Visean-Serpukhovian resulting in a sea-level drop and deposition of platform carbonates in the Bashkirian. Given the stratigraphic properties of northerly originated nappe packages (Cataloturan, Hadim and Bolkardag) and parautochthonous/autochthonous sequences in Taurides, sedimentation on the Tauride-Anatolide Platform mainly terminated after the Moscovian, except in the Hadim Nappe with sedimentation in a very shallow sea conditions until the end of the Permian. A depositional break corresponding to the Kasimovian-Wordian time interval in these sequences in the Tauride-Anatolide Platform could be related to the effects of both late Paleozoic Gondwanan glaciation and a possible mantle plume occurrence evidenced by the geochemistry of lavas in the Mersin Melange causing major uplift in the Northern NeoTehys Ocean. However; at the center of the plume, pelagic sequences (e.g., ribbon chert and pelagic limestone) were deposited associated with these lavas due to a progressive developing rift system during the Permian, based on previous studies. (C) 2018 Elsevier Ireland Ltd Elsevier B.V. and Nanjing Institute of Geology and Palaeontology, CAS. All rights reserved.
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    Middle Triassic back-arc basalts from the blocks in the Mersin Melange, southern Turkey: Implications for the geodynamic evolution of the Northern Neotethys
    (ELSEVIER, 2017) Sayit, Kaan; Bedi, Yavuz; Tekin, U. Kagan; Goncuoglu, M. Cemal; Okuyucu, Cengiz
    The Mersin Melange is a tectonostratigraphic unit within the allochthonous Mersin Ophiolitic Complex in the Taurides, southern Turkey. This chaotic structure consists of blocks and tectonic slices of diverse origins and ages set in a clastic matrix of Upper Cretaceous age. In this study, we examine two blocks at two different sections characterized by basaltic lava flows alternating with radiolarian-bearing pelagic sediments. The radiolarian assemblage extracted from the mudstone-chert alternation overlying the lavas yields an upper Anisian age (Middle Triassic). The immobile element geochemistry suggests that the lava flows are predominantly characterized by sub-alkaline basalts. All lavas display pronounced negative Nb anomalies largely coupled with normal mid ocean basalt (N-MORB)-like high field strength element (HFSE) patterns. On the basis of geochemical modelling, the basalts appear to have dominantly derived from spinel-peridotite and pre-depleted spinel-peridotite sources, while some enriched compositions can be explained by contribution of garnet-facies melts from enriched domains. The overall geochemical characteristics suggest generation of these Middle Triassic lavas at an intra-oceanic back-arc basin within the northern branch of Neotethys. This finding is of significant importance, since these rocks may represent the presence of the oldest subduction zone found thus far from the Neotethyan branches. This, in turn, suggests that the rupturing of the Gondwanan lithosphere responsible for the opening of the northern branch of Neotethys should have occurred during the Lower Triassic or earlier. (C) 2016 Elsevier B.V. All rights reserved.
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    Radiolarian biochronology of upper Anisian to upper Ladinian (Middle Triassic) blocks and tectonic slices of volcano-sedimentary successions in the Mersin Melange, southern Turkey: New insights for the evolution of Neotethys
    (PERGAMON-ELSEVIER SCIENCE LTD, 2016) Tekin, U. Kagan; Bedi, Yavuz; Okuyucu, Cengiz; Goncuoglu, M. Cemal; Sayit, Kaan
    The Mersin Ophiolitic Complex located in southern Turkey comprises two main structural units; the Mersin Melange, and a well-developed ophiolite succession with its metamorphic sole. The Mersin Melange is a sedimentary complex including blocks and tectonic slices of oceanic litosphere and continental crust in different sizes. Based on different fossil groups (Radiolaria, Conodonta, Foraminifera and Ammonoidea), the age of these blocks ranges from Early Carboniferous to early Late Cretaceous. Detailed fieldwork in the central part of the Mersin Melange resulted in identification of a number of peculiar blocks of thick basaltic pillow-and massive lava sequences alternating with pelagic-clastic sediments and radiolarian cherts. The oldest ages obtained from the radiolarian assemblages from the pelagic sediments transitional to the volcano-sedimentary succession in some blocks are middle to late Late Anisian. These pelagic sediments are overlain by thick sandstones of latest Anisian to middle Early Ladinian age. In some blocks, sandstones are overlain by clastic and pelagic sediments with lower Upper to middle Upper Ladinian radiolarian fauna. Considering the litho- and biostratigraphical data from Middle Triassic successions in several blocks in the Mersin Melange, it is concluded that they correspond mainly to the blocks/slices of the Beysehir-Hoyran Nappes, which were originated from the southern margin of the Neotethyan Izmir-Ankara Ocean. As the pre-Upper Anisian basic volcanics are geochemically evaluated as back-arc basalts, this new age finding suggest that a segment of the Izmir-Ankara branch of the Neotethys was already open prior to Middle Triassic and was the site of intraoceanic subduction. (C) 2016 Elsevier Ltd. All rights reserved.