Abstract

Upper Permian and Triassic sediments of the Caspian (Prikaspiyskaya) depression are represented by a thick sequence of red beds and in the Upper Triassic, by grey continental deposits. Marine and lagoonal sediments are developed in the lower part of the Kazanian Stage of the Upper Permian and in the Lower and Middle Triassic. The depression is characterized by the presence of salt domes, with the result that some of the beds are disturbed by salt tectonics.

In the Upper Permian the Ufimian (assumed), Kazanian and Tatarian Stages can be distinguished. Near salt domes and in areas between them, the Triassic lies on different horizons of the Upper Permian. However, there may be cases of conformable succession.

All divisions of the Triassic are represented. In the Lower Triassic are the Vetluga and Baskunchak series which may be subdivided into formations. In the Lower and Middle Triassic 7 to 9 biostratigraphic zones have been recognized, according to ostracod and charophyte assemblages. The boundaries and ages of some formations and zones are still in dispute, however.