ИСТИНА

Rostov lowland is a middle size depression (550 km2, 60-80 m deep) which situated about 170 km to the NE from Moscow. The lowland is surrounded by moraine hills of Saalian glaciation. About 10% of area of the lowland is occupied by Lake Nero. On the west bank of Lake Nero the city of Rostov is located - one of the oldest cities in Russia, founded in 862. The modern lake level is 93 m asl. From the Lake Nero flows out the Kotorosol River. The Kotorosol River flows into the Volga River near the city of Yaroslavl. On the slopes of the Rostov lowlands are situated 5-6 lake terraces. There is a discussion about the age of the terraces and the reasons of lake level fluctuations. According to Kvasov (1975) at the end of the Late Pleistocene the level of lake rose to 145 m asl and the lake had a connection with the huge system of proglacial lakes. According to Aleshinskaya and Gunova (1997), the level of Lake Nero in the late Weichselian epoch did not exceed 110 m asl and highest terraces was formed in late Saalian epoch. In many ways, this discussion is due to the weak use of dating methods in older works. We investigated the topography of the terrace complex of the Rostov lowlands. On the basis of SRTM we identified areas with well-defined terraces. Using DGPS the height of the terraces on the eastern side of the basin was fixed: T1 - 94-95 m asl, T2 - 102-104 m asl, T3 - 108-109 m asl, T4 - 123-125 m asl, T5 - 130-134 m asl, T6 - 145 m asl. 11 boreholes were drilled on the terraces of the eastern side of the basin. A series of radiocarbon dates from terraces has been obtained. The dating results indicate that the level of Lake Nero in the Late Weichselian did not exceed 110 m abs, which refutes the model of Kvasov (1975). The terrace of 110 m is also well marked on the sides of other adjacent basins - Yaroslavl, Kostroma, Galich. This suggests the existence of a single interconnected system of glacial lakes in the Late Valdai on the territory of the Yaroslavl Volga region. This research was supported by the project of the Russian Science Foundation 18-77-00083.