The Paleogene Dinoflagellate Сyst and Nannoplankton Biostratigraphy of the Caspian Depression

The Pricaspian Depression in the southeast of the East European Platform is one of the deepest depressions formed over the Baikal folded basement. The sedimentary cover consists of four structural levels corresponding to the major stages of its formation. The Riphean and the Vendian beds constitute the first structural level. The second one comprises deposits from the Devonian to the Upper Triassic. This includes the Lower Permian plastic salt-bearing beds. The post-salt deposits of the second structural level are up to 4-5 km thick. The third structural level of the sedimentary cover is composed of the Triassic-Oligocene beds, with the total thickness as high as 2.5 km; in some sections, the Paleogene sediments are over 1000 m thick. The principal accumulations of oil, gas and potassium salts are confined to the second and the third structural levels of the Pricaspian Depression.