Cretaceous microfossils as indicators of cooling episodes (Boreal and Peri-Tethyan Russia

The main palaeogeographic features of the Late Cretaceous Eastern European Platform and its southern framework are based mainly on micropalaeontological data. An integrated foraminiferal-radiolarian zonation for the Upper Albian-Maastrichtian is presented for all this area and serves as a basis for palaeogeographic reconstructions. The study is focused on time slices of Late Albian–Cenomanian, Turonian–Coniacian, and Santonian–Campanian intervals. The Late Albian was characterized by the gradual disappearance of a meridional seaway and the opening of connections into the Tethys Ocean and parts of the Peri-Tethys seas during the Cenomanian. As a result, mainly carbonate sedimentation prevailed during the Middle Turonian–Santonian time of high global sea level. A cold Boreal water influence can be recognized not only along the northern margin of the East European Platform, but as far south as the Northern Caucasus during certain time intervals, particularly during the Campanian. The Western Siberia Boreal basin also influenced the study area, giving evidence on climatic fluctuations through the Palaeo-Ural territory and the Turgai strait.