The Dağpazarı carbonate platform (Mut Basin, Southern Turkey): Facies and environmental reconstruction of a coral reef system during the Middle Miocene Climatic Optimum

Abstract

Plate tectonics and climate change have deeply influenced the evolution of coral reef systems of the Mediterranean during the Miocene. Most of this information is based on studies of coral reefs from the western and central sectors of the Mediterranean. This study reports facies analyses, Sr isotope stratigraphy and environmental reconstructions of the Dağpazarı coral reef system, located within the Mut Basin in Southern Turkey. Stratigraphic correlations and Sr isotope ratios on several oyster shells date the Dağpazarı reef to the early Langhian. Ten different facies have been recognized and their arrangement has led to the identification of two main depositional units. Interpretation of the biotic associations indicates that the Dağpazarı depositional system developed constantly within the euphotic zone. The reef framework was mainly built by massive faviid and poritid zooxanthellate corals, whereas loose-grain sediments were essentially produced by Halimeda, coralline red algae, or influenced by the presence of seagrass colonizations. This study highlights for the first time the great importance of Halimeda as sediment producer in the eastern Mediterranean coral reef systems. This role is related to the common occurrence of Halimeda plates within almost all the reef facies, but especially to the presence of large in situ bioherms dominated by the algal segments. Dağpazarı Langhian Halimeda bioherms also represent the oldest of these structures so far recorded in the fossil record. The development of the Dağpazarı platform was mainly controlled by eustatic fluctuations of the sea-level and by the morphology of the antecedent substrate. In particular, the occurrence of a pre-existent topographic high promoted the constant presence of shallow-water environments throughout the depositional history of the reef system, with the production of euphotic carbonates both landward and basinward and the consequent formation of a small, elliptical platform. 87Sr/86Sr ages place the Dağpazarı reef system exactly within the Middle Miocene Climatic Optimum phase, the most recent warm phase of the Earth. This suggests that zooxanthellate corals were able to exert their reef-building capacity in shallow-water settings even during periods of global warming, thus being not exclusively an adaptation to cooling climates as proposed in the recent debates.