ИСТИНА

On the watersheds of the eastern Azov region, there are dozens of large depressions. Their sizes can reach tens of square kilometers. The outlines of these depressions are like a drop or an egg. The vast majority of large depressions are oriented approximately north. To date, the problem of the origin of large depressions in the eastern Azov region does not have an unambiguous solution. The following hypotheses were put forward: paleothermocarst, erosion-suffusion, subsidence-loess, estuary-lake. Yet, none of them is not finally confirmed and not refuted. This is due to the lack of correct data on their geological and geomorphological structure. Also, the problem of these large depressions evolution in the future remains unclear. Is their extensive growth possible or will they remain stable? The goal is to find at and identify the mechanisms for the formation of large depressions. As a result of the morphometric analysis of large depressions, a unity of their origin was revealed. For geological and geomorphological research, we chose a key object. It is a typical large depression - "Chervonaya pad'". The material for the study was obtained by hand drilling and outcrop investigation on the coast of the Taganrog Bay. As a result of the research, we obtained a new data on the geological structure and morphology of large depressions. Two types of sediments were distinguished in the structure of large depressions and interfluves. At the top lays the loess cover with paleosols developed in it. Sub-aqueous deposits lie beneath the loess cover. The thickness of the loess inside the depressions is less then on watersheds and the number of paleosols is also less. The roof of the underlying sub-aqueous deposits lies sub-horizontally. Traces of lake sediments, cryogenesis, and tectonic faults were not found in the structure of large depressions. The new data allow us to make some important conclusions on the origin and mechanisms of formation of large depressions in the eastern Azov region: 1) Large depressions of eastern Azov region were formed by a directional flow. 2) These depressions were formed with not water-related processes. 3) They were formed by denudation in the loess. 4) The position of the buried soil complexes allowed us to estimate the age of the studied depressions. According to the obtained data, depressions were already formed by the beginning of the Eemian inter-glacial. 5) As a result of the study, we proposed an eolian denudation mechanism for the formation of large depressions. This research was supported by RFBR project 16-35-60069 and State Task №0148-2019-0005, Registration Number 01201352491.