Stratigraphy and facies analisys of the Langhian Dağpazarı reef complex (Mut Basin, Southern Turkey)

During the Early/Middle Miocene, the eastern part of the Mediterranean region registered the narrowing, and the ultimate interruption of the connections with the Indian Ocean. This event represented one of the most important episodes in the Cenozoic evolution of the Mediterranean marine biota. For this reason, the study of Middle Miocene reefal communities from this area can offer an important contribution for the reconstruction of the palaeogeography and palaeoecological settings of the Mediterranean shallow-water, carbonate-producers. The primary aim of the present study is to provide a small-scale, detailed reconstruction of the stratigraphy and facies associations of a Langhian reef complex from the Mut Formation (Mut Basin, Southern Turkey). This study has been based on field observation and microfacies analysis, with a particular emphasis on the characterization of calcareous algae associations (both corallines and green codiacean) and coral fauna. The Dağpazarı reef represents a portion of a small, isolated carbonate platform located 12 Km north from the town of Mut. Its early Langhian age has been determined by 87Sr/86Sr isotope analyses performed on several well preserved oyster samples. Dağpazarı reef is represented by two main stratigraphic sequences separated by a major erosion surface. Only a few meters of lowermost sequences are exposed, while the upper one measures about 72 meters in thickness and is characterized by the superimposition of four different cycles. During the first cycle, the amplitude of the sea transgression allowed the growth of a massive coral framestone on the shelf-edge, associated to well developed slope deposits toward the basin. In particular, concentrations of small rhodoliths with large nuclei and laminar/columnar structure characterize the shallower part of the slope, while in the middle slope the presence of Halimeda bioherms indicates a palaeodepth of about 30/50 meters. The two subsequent cycles show the superimposition, on the shelf-edge, of two similar shallowing-upward sequences, each of them related to a small-scale, transgressive phase. In particular, each sequence exhibits at the base a coralline red algae bindstone, typical of low hydrodynamic conditions, made of thin, laminar/foliose crusts associated to discoidal/irregular rhodoliths. This facies is followed by Halimeda bioherms and biocalcarenite deposits, the latters characterized by the presence of abundant “hooked” and foliose coralline algae crusts associated to gastropods concentrations. The coexistence of the latter features within biocalcarenite deposits is considered a reliable marker of the presence of seagrass beds. Both sequences terminate with the occurrence of shallow-water, massive coral framestone on the top. The fourth Dağpazarı reef cycle developed on the shelf-edge and started with a coralline red algae bindstone, but in this case, corallines colonizations were followed by a fine-grained, mud-supported biocalcarenite whose stratification dips landward. The top of the succession is characterized by coarser biocalcarenite deposits containing small, coral patches. Due to its stratigraphic setting and composition, this last sequence has been interpreted as a back-reef facies association, related to the progradation of a reef framework (now eroded) as a consequence of a final highstand phase of the sea-level. This work provides new information on some important shallow-water carbonate producers, for example Dağpazarı Halimeda bioherms represent so far the oldest recorded examples of this kind of structures; at the same time it offers a detailed frame for further, specific studies on Middle Miocene reef-building associations.