Middle to Late Pleistocene topography evolution of the North-Eastern Azov region

Abstract

The structure of loess-soil sequences of the North-Eastern Azov region was studied in coastal outcrops and boreholes within four key areas of the terraces of different age. Based on the positions of paleosols in geological sections of interfluve areas, the palaeotopography during interglacial epochs of the last 500 ka was reconstructed. The analysis of the topography evolution showed that the most significant features of the primary fluvial-marine relief remained in subaerial stage of the surface development and were inherited even in modern relief. At the same time, in subaerial stage the surface of interfluves experienced considerable reworking due to loess accumulation, on the one hand, and erosion, on the other hand. It has been established that these processes were controlled by the glacial-interglacial climatic cycles; however, their intensity varied from cycle to cycle. Generally, before the Valdai (Weichselian) glacial epoch, loess accumulation prevailed on the interfluve areas. The intensity of erosion at that time was relatively low. During the Valdai epoch (by indirect evidence, during its final stage, MIS 2, ∼29–12 ka), a phase of exceptionally intensive erosion was detected. Due to it, linear erosion and slope processes developed even within fairly gently slope (2–4°) areas. It has been determined that during this time, the upper parts of gullies were growing rapidly towards watersheds. In the modern topography, a branched pattern of relic hollows inherits their position.