Keele Research Repository

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Carboniferous–Triassic siliciclastic sediments of the Karaburun Peninsula in western Turkey were studied to unravel their provenance and the tectonic setting of depositional basins within the Palaeotethyan realm. A set of complementary techniques including petrography, bulk-rock geochemistry and single-grain analysis of rutile, garnet and chrome spinel were applied to provide a diverse dataset for testing existing palaeotectonic models using both, established and recently published diagrams. We show that tectonic discrimination diagrams of siliciclastic sediments based on major and trace element whole-rock geochemical data do yield ambiguous results and are only partly in accordance with regional geological events. Chondrite-normalised REE patterns of Upper Palaeozoic samples are characterised by enrichment of LREE and a flat trend towards HREE. The degree of fractionation allows for discrimination between sandstones of Karaburun (LaN/YbN = 8.00–14.79) and adjacent Greek islands of Chios (5.82–9.23) and Inousses (7.40–9.95). Petrographic observations and compositional data from single-grain analysis indicate significant supply from low- to medium-grade metamorphic rocks of generally felsic character and minor input of (ultra)mafic detritus. Detrital chrome spinels in the Lower Triassic Gerence Formation are different in composition and shape compared to chrome spinels in Carboniferous–Permian sandstones. They were derived from a very proximal source and exhibit variable, but generally high Cr- and Mg-numbers, consistent with chrome spinels from podiform chromitites that have been formed in an intra-oceanic back-arc setting above a supra-subduction zone. We conclude that most of the Carboniferous–Triassic successions were deposited along the southern active margin of Eurasia in a continental-arc environment during the time period when Palaeotethys diminished in size and finally vanished. Large volumes of detritus were probably derived from rock units located in the present-day Balkan region and the Sakarya Zone, or equivalent successions that are not present anymore.