Transformation of the Bryansk Paleosol in Microdepressions in the Center of the East European Forest-Steppe during the Maximum of Valdai Glaciation and in the Holocene

Abstract

Recent and Late Pleistocene soils of the central forest-steppe in the East European Plain have been studied. The main objective of the work is to reveal changes in the properties of the Bryansk paleosol (final phase of MIS 3), one of the most important geosols of the Late Pleistocene. These changes could be induced by cryogenesis during the Valdai glaciation maximum (MIS 2) and by the Holocene pedogenesis (MIS 1) under different conditions of the modern microtopography. We have studied the catena of Holocene soils underlain by the Bryansk paleosol within a small closed depression in the Kazatskaya Steppe of the V.V. Alekhin Central Chernozemic Biospheric Reserve in Kursk oblast. The depression is supposedly the result of loess subsidence. Haplic Chernozems develop on the microelevation; Luvic Chernozems, on the microslope; and Luvic Chernozems (Stagnic), in the bottom of the depression. The upper humus horizons of the Holocene soils are similar in all parts of the microcatena. On the slopes and in the lower part of the microdepression, the Ah2 subhorizon is replaced by the AE horizon, and the Bk horizon becomes carbonate-free and turns into the Bt horizon. The change in the “normal” profile of the paleosol of the Bryansk Interstadial began already at the latest stages of its formation. The Bryansk soil was strongly deformed by cryogenic processes during the maximum of the Valdai glaciation (Vladimir cryogenic horizon). The secondary diagenesis of the Bryansk paleosol is associated with soil formation in the Holocene. Holocene soils are superimposed on the profile of the Bryansk paleosol, transforming it differently in various parts of the catena. On the microelevation, the diagenesis in the Holocene is regarded as minimal. The Bryansk paleosol is most transformed in the bottom of the microdepression.