On the lower boundary of the Quaternary System in the Azov-Black Sea Basin

Abstract

The data on the lowering of the lower boundary of the Quaternary System below the Gelasian Stage at 2.588 million years are presented in the paper. In Azov-Black Sea basin this boundary takes place within the middle of the Kuyalnikian Regionalstage and related to the magnetostratigraphic boundary Gauss-Matuyama and should be drawn under the deposits of the upper Kuyalnikian regionalsubstage, Taman layers of the Akchagylian, alluvium X terrace of the Dnister, Danuba, Prut rivers, the Haprovian layers of the Priazovie and under sediments of the Siverian stage in the loess-soil series of the Ukraine. Below there lie the deposits of the Bogdanivkian stage and the lower Kuyalnikian rocks. The deposits of the Lowerkuyalnikian regionalsubstage, upper and lower Poratian beds and sediments of the Bogdanivkian, Kizlyarkian and Jarkian stage in the loess-soil series related to Piacencian stage and Upper Pliocene. Kuyalnikian deposits in the Odessa (Kryzhanivka) region are the upper part of the Upperkuyalnikian regionalsubstage, above the Tamanian beds and correlations with a Beregovian stage in the loess-soil series. Beginning of the maximum Akchagylian transgression in the Black Sea coincides with a sharp cooling Climate period (2,5-2,6 million years) and compares with the Middle Akchagylian transgression of the Caspian basin. Signs of the late Akchagylian mollusks at the basal beds of the Kuyalnikian of the Priazovie requires additional research, as at that time the formation of the lower Poratian deposits took place in a (with Rugunio lenticularis) Warm climate. The most probable version is the invasion of Akchagylian mollusks during the cocking in Ajdarian time. The author opinion on the reasoning of the lowering of the boundary and the problems of its use in geological mapping are also stated.