ИСТИНА

The Arctic and Caspian Sea basins divide in the north of the East European Plain is crossed by a palaeovalley of River Kama (now flows to the Caspian Sea) formed in the Pliocene - Early Pleistocene when Kama flowed to the Arctic basin. In a 45 m deep core in the middle part of the palaeovalley, the alluvial-lacustrine succession was found at depth of 24-45 m and OSL-dated to 160-140 ka (late MIS 6). A set of lithological analyses revealed a change up the section from alluvial sands to lake silts and loams formed first in a low-flow and then in a closed lake. Pollen and macrofossil data show replacement of taiga forests by forest-tundra and then tundra, but even in the most unfavorable climatic conditions (upper part of the section) some woody species were preserved in the lake vicinity, which was facilitated by high enough summer temperatures. The lake was dammed by the MIS 6 ice sheet, which boundary is assumed to lie some 50 km to the north, and drained around 140 ka due to the ice sheet decay. The alluvium in the lower parts of the section could belong to the Kama River as well as the local rivers. Therefore, it is still uncertain whether the turn of the Kama into the Caspian Sea occurred exactly in MIS 6 or earlier. However, it can be considered proven that this event did not happen in MIS 2, as assumed by many authors earlier.