Oncoidal Facies Across the Carboniferous‐Permian Transition (Hadim Nappe, Southern Türkiye): Paleoenvironmental Implications and Correlations

ABSTRACT The cortoid and/or oncoid‐bearing carbonates of the Girvanella Limestone Facies of the Hadim Nappe that were deposited during the early–middle Gzhelian–middle Asselian time interval are represented by a succession that laterally extends over dozens of kilometres and is up to 60 m thick. This facies is easily distinguishable from the facies above and below and is considered a significant sedimentological marker unit by its lithological properties (e.g., brownish‐red colour and large oncoids). Eight microfacies types are recognised from the Girvanella Limestone Facies: cortoid grainstone/floatstone, cortoid‐bioclastic grainstone/rudstone, cortoid‐aggregate grainstone, bioclastic grainstone to packstone, oncolite packstone/rudstone, oncoid grainstone/floatstone, mudstone/wackestone, and algal fenestral bindstone that are indicative of moderate to high‐energy shallow marine carbonate platform settings (e.g., sand shoals and bank zone and lagoon–peritidal zone). Oncoid‐bearing facies across the Carboniferous–Permian transition in the Hadim Nappe show a well correlation with similar deposits from South China, Iran, Mexico, Carnic Alps (Austria), and Japan. This widespread and synchronised deposition of the oncoid‐bearing facies corresponds to the major phase (Glacial period III) of the Late Palaeozoic Gondwana glaciation and global sea‐level drop associated with this glaciation.