ИСТИНА

Chocolate clay is one of the most common facies sediments Lower Khvalinian Northern Caspian, the Lower and Middle Volga region. The Khvalynian transgression started in the second half of Valdai epoch, in conditions of humidifying and heavy waters-flowing from a land. It developed with two stages divided by Enotaevsk regression. The early Khvalinian transgressive stage was maximal one. The valley of Volga River has turned in estuarian basin, which reached almost 600 km upwards on the river at a maximum of transgression. The maximum level of transgression defined in height of the Manych “threshold”, was marked on 46-50 m (abs.). Deposits are represented by chocolate clays, sands, loams and loamy sands. The study of chocolate clay began more than a hundred years ago, but until now there remain a number of unresolved issues related to the conditions: 1 - their bedding, 2 - structure, 3 -, facial structure, 4 - color clays. The thickness of these deposits usually does not exceed several meters.