LAUSR

The Eocene and Oligocene transition sections (Priabonian–Rupelian) of the Aral–Turgai, West Siberian, Volga–Don, and Crimea–Caucasus regions have been studied in detail [1], and the global biospheric crisis events have been estimated at the turn of the Eocene and Oligocene. In spite of the idea of the gradual regression in the Priabonian with drainage of the inner sea basins, it has been established that shallowing of the sea was preceded by repeated transgression that continued for 1 Ma with warming up and humidification of the climate. The final regressive phase (130–200 ka) was accompanied by frequent eustatic and climatic fluctuations, reconstruction of the isotopic and geochemical background, and also the recurrence at the boundary between layers in certain continuous sections.