LATE PLEISTOCENE CYCLE OF EROSION DISSECTION AND INFILLING OF THE DRAINAGE NETWORK IN THE NORTH-EASTERN STAVROPOL'E (PAPER 2. RECENT BALKAS. HISTORY OF THE DRAINAGE NETWORK)

Abstract

In the northeastern Stavropol Highland erosion network depth and density were much higher at the Middle/Late Pleistocene (MP/LP) boundary than at present. During the Valdai (Vistulian) cold epoch of the LP, erosion network was filled with slope and alluvial deposits. Probable incision in the Late Glacial interrupted the infilling tendency, but the erosion network rejuvenation had much smaller scales compared to the preceding erosion dissection. Therefore, the upper reaches of the erosion network at the MP/LP boundary were almost buried and transformed into hollow systems by the beginning of the Holocene, while in lower reaches thick LP deposits make wide valley bottoms. In the Holocene, sedimentation processes proceeded both in hollows and in small valleys, but their rates decreased considerably. Land cultivation started in the region in the middle XIXth century. During the last 150 years, sedimentation in valley and hollow bottoms continued to prevail over erosion. This shows that artificial lowering of landscape sustainability by land cultivation has not led to incision along the modern and ancient erosion network. The probable explanation is that modern climate is not so favorable for erosion as it was at the MP/ LP boundary and in the Late Glacial.