O. V. Shurekova

Correlation potential of the Berriasian dinocysts (Lower Cretaceous) in the Crimean–Caucasian–Caspian Sea region

Abstract. The paper explores the Upper Berriasian dinocysts in the Crimean–Caucasian–Caspian Sea region, the only territory within Russia that belonged to the northern margin of the Tethys paleoocean in the Cretaceous, as opposed to the entire Boreal territory of the country. The emergence of the Caspian Sea paleostrait in the Late Berriasian contributed to the Tethyan and Boreal water masses exchange. This time is considered ideal for correlating the Boreal and Tethyan paleogeographic provinces. The dinocyst assemblages of the Crimean–Caucasian–Caspian Sea region are strikingly similar to one other, while their similarity with the coeval complex of the Boreal Volga region is significantly lower. There are single representatives of the Tethyan and Boreal provinces in the Upper Berriasian assemblage of the Crimean–Caucasian–Caspian Sea region, most of whose species are cosmopolitan. The study aimed to identify the correlation potential of dinocysts found in the Upper Berriasian Crimean–Caucasian–Caspian Sea region, whose first and last appearance correlates to regional ammonite scales of the Boreal and Tethyan regions. The evolutionary changes in dinocysts were analyzed to establish the correlative species Amphorulacysta? expirata, Palaecysta palmula, Egmontodinium torynа, Phoberocysta neocomica. The bioevents for these species are relatively synchronous, which provides additional grounds for comparing the Berriasian deposits in the Boreal and Tethyan regions.

Keywords: Boissieri Zone, index species, Tethys Ocean, paleostraits, bioevents, Boreal-Tethyan correlation