The Kirsa paleovalley and the drainage network transformation in the upper reaches of the Vyatka and Kama rivers

Abstract

A latitudinal hollow between the Vyatka and Kama upper reaches (where the rivers take opposite direction, near the city of Kirsa) is proved to be paleovalley, presumable of the Pliocene age. During the Early and Middle Pleistocene the water flow was directed southwestward, from Kama to Vyatka. No flow existed during the Late Pleistocene and the Holocene. The drainage network transformation took place at the Middle/Late Pleistocene boundary, probably due to the valley division into two parts by a lobe of the Dnieper ice sheet, though neotectonic factors could contribute to the process.