Гривный рельеф юга Западно-Сибирской равнины: морфология и возраст (на примере Черноозерской гривы, Саргатское Прииртышье)

Abstract

The article is devoted to the study of the crest relief, which is widespread in large areas of the south of Western Siberia: morphology, the genesis of the relief, the stages of its formation, the amount of accumulation of material, the rate of its accumulation. Geomor-phological studies of the relief of the southern part of the West Siberian Plain are carried out on the example of the Chernoozerskaya crest (Sargatsky Priirtyshye). The territory is a wide left-bank part of the valley of the river Irtysh. The absolute height of the surface varies from 62,5 m (the water level Irtysh river) to 71 m (southern edge of the village of Chernoozerye). The increase in heights occurs from the southeast to the northwest, from the riverbed Irtysh to the slope of the inter-river Nizhneyrtysh plain. The district is in the lower reaches of the valley complex (Sargatskoe Priirtyshie). In the structure of the valley stands a floodplain and a series of above-floodplain terraces stretching a wide strip of tens of kilometers. The Chernoozerskaya crest is located on the first terrace above the floodplain, which has a late Pleistocene age. The terrace does not have a continuous distribution and is expressed in relief in the form of remnants in the rear part of the high floodplain. The remains of the terrace existed during the late Pleistocene in the form of an island in the flood-plain, which was occasionally flooded with water, as evidenced by the nature of the sediments: thin low-layered sandy, sandy-loamy, gravel deposits are interbedded with subaerial sediments in the form of loose unbroken, uncertified partially humus sandy loams, loams and sands. In the Holocene, the remains passed into the terrace mode, preserving the morphological appearance characteristic of the high floodplain island. In the upper thickness of the sediments, alluvial deposits are not observed. During the Holocene, the surface of the mane was not flooded with water. The crest deposits are of eolian origin. They are loose, uncemented sands and sandy loams, which accumulated under the conditions of activation of deflation. Aeolian deposits alternate with buried soil horizons, which accumulated during the humid periods of the late Pleistocene-Holocene. Eolian sands are underlain by alluvial deposits of the first terrace above the floodplain Irtysh. Data were obtained on the average intensity of eolian sedimentation in the late Plestocene-Holocene. Formation of aeolian deposits occurred unevenly both in space and in time. The average rate of accumulation of the deposits of the Chernoozerskaya crest in the Holocene was 0,05-0,075 mm/year. In some periods of the Holocene the eolian accumulation rate could reach several millimeters per year. In the last half century, there has been a sharp activation of the formation of subaerial deposits, which are loose loamy, slightly horizontally layered sandy loam and loam. The average speed of modern eolian accumulation is 8,7 mm per year. The age of the mane deposits is late Pleysto-cene-Holocene. Archaeological finds found in the crest deposits date from 10,5 to 14,5 thousand years. Based on the average rates of eolian accumulation and the power of the eolian crest, it can be assumed that it began to form around 27-30 thousand years ago.