Abstract

Many researchers concur to the opinion that the age of chocolate clays (CC) themselves is universally recognized to be Early Khvalynian. Caspian Sea level stood at 50 m abs. and at that time CC accumulated at depths about 80 m, i.e. CC are the deepwater facies of sediments. In our opinion CC accumulated in shallow lagoons under the protection of barrier. A geomorphologic analysis of CC, wherefrom mollusk shells were sampled for absolute dating, made it possible to assert that on the whole the radiocarbon data from the Northern Caspian Sea, theVolga delta and adjacent regions gave more or less reliable results, according to which the age of the Khvalynian transgression is approximately 11 to 20 ka. Yet, this is not the age of the transgression maximum but only the age of its final transgressive-regressive stage, i.e. the Late Khvalynian transgression. The conclusion is made that the age of the high Early Khvalyn terraces formed during the maximum of the Early Khvalynian transgression should undoubtedly be older, within the interval 40 to 70 ka. Chokolate clays in many cases form the base of Baer Knolls which are widely spread in Volga delta and adjacent areas. The author considers these forms to be the analogues of river bedforms. Their formation can be attributed to very wide streams moving from NE to SW and further to Manych passage, which existed for the last time not during the Early Khvalynian, but in the Late Khvalynian time.

Keywords: Volga delta, chocolate clays, lithology, sea level oscillations, lagoon-transgressive terraces, Khvalynian transgressions, Baer Knolls.