Pleistocene Palaeoenvironments In The Lower Volga Region (Russia): Insights From A Comprehensive Biostratigraphical Study Of The Seroglazovka Locality

There are many Middle-Upper Pleistocene outcrop sections in the Lower Volga region (Caspian Lowland, Russia) in between cities of Volgograd and Astrakhan. The present study focuses on the Seroglazovka locality, which is among the most famous key sites within the Lower Volga region. The Seroglazovka locality is of great regional interest, because of its clear exposure of genetically variable Middle and Upper Pleistocene deposits containing diverse complexes of fauna and flora. Even though the Seroglazovka locality was studied by many researchers, the diversity and along-strike variability of the depositional facies often makes the stratigraphic interpretation challenging. In this study, we performed an extensive and integrated study of the Seroglazovka locality including detailed outcrop mapping with lithological description, as well as diverse biostratigraphy analysis and OSLdating. In addition to outcrop data, we used recently obtained borehole data near the Seroglazovka locality, which cover almost the entire Quaternary interval. This multidisciplinary approach permitted us to confidently stratify the Quaternary interval of the Seroglazovka locality into a series of regional horizons and subhorizons including the Akchagyl, Apsheron, Tyurkyan, Baku, Khazar and Khvalyn. Furthermore, we correlated the interpreted section to the adjacent parts of the Caspian Lowland and the Regional Stratigraphic Scale. Our results allowed us to determine the main Pleistocene palaeoenvironments and their evolution within the study area. Our findings are important to understand the processes, which led to the modern faunistic composition of the Lower Volga region, and to clarify the role of glacial refugia in the settlement of certain species and further colonization of water basins and land areas with habitable environments. Finally, we suggest the Seroglazovka locality as the key reference Pleistocene section for the Lower Volga region.