Print-ISSN 3079-2886; E-ISSN 3079-2894

Pleistocene Manych straits and their role in the history of Pontian-Caspian basins

Svitoch A.A. 

The occurrence of four straits periodically connecting the Pontian – Caspian basins has been recorded in the Pleistocene history of the Manych Valley: Bakinian – Late Chauda, Early Khazarian – Early Euxinian, Late Khazarian- Karangatian, and Early Khvalynian – New Euxinian.

It is typical for their morphology the heredity of the basic features of the straits’ relief from the structure of the older strait’s beds. In today’s relief of the Manych Depression only traces of the Early Khvalynian Strait and preceding Burtas Lake are displayed. Small gradients of the Strait’s primary bed and relatively fine grained sediments infilling the Strait testify to a quiet hydrological regime. The active hydraulics with a deep erosional incision periodically occurred in the eastern and western mouths of the Strait and is associated with the existence of a “plug” (high threshold) near Zunda – Tolga and variability of the water level regime of the Azov – Black Sea basin.

The role of the Manych in the history of Pontian – Caspian basins was different due to the occurrence of strait or land neck in its depression. Occurrence of the Manych Straits had always been connected with the rise of the Caspian Sea level and elevation of the threshold near Zunda – Tolga. The Caspian waters entered the Pontian basins consequently caused changes in their level, salt composition and migration of the fauna. The Caspian Sea level after opening of the Strait was lowering, but the Black Sea level was rising. The infilling of the Black Sea with the water of Caspian type salinity and one -way migration of the brackish Caspian fauna were recorded. There is no proper evidence of the Black Sea water inflow into the Caspian Sea, and Pontian fauna appeared only in Manych and adjacent areas of the Northern PreCaspian. The maximal impact of Caspian waters on the Black Sea was recorded during Bakinian and Early Khazarian transgressions, a small impact – during Early Khvalynian transgression, and a minimal influence – in the Late Khazarian time.