Interrelations of the Bryansk paleosol (end of MIS 3) with the Holocene surface soils in micro-depressions of the central forest-steppe within the Russian Upland

Abstract

A catena of the Holocene soils and interstadial Bryansk paleosol has been studied within a small closed depression in the Kazatskaya Steppe site on the Central Russian Upland. This depression is located on the territory of the Central Chernozem Biospheric Reserve, Kursk region and presumably originated from suffosion processes. Our research is aimed at understanding of interrelations between the macro- and micromorphological characteristics, certain physical and chemical properties of the Bryansk paleosols, on one hand, and those of the superimposed Holocene soil on another, taking into consideration various conditions of the present-day microrelief. The studied catena is a typical component of the landscape and soil cover structure for watersheds of the Central Russian Upland. On the micro-elevation rising 80 cm above the micro-depression bottom, the Typical Chernozems (Haplic Chernozems) are developed, on the slope – the Leached Chernozems (Luvic Chernozems), and at the bottom – the Meadow Chernozems (Stagnic Chernozems). The upper humus horizons of the Holocene soil present in all sectors of the catena. The thickness of the Ah horizon increases slightly, whereas the AB horizon decreases toward the bottom of the depression. On the slopes and at the bottom of the depression, the Ah2 sub-horizon is replaced with the AE horizon, and the Bk horizon becomes carbonates-free and turns into the Bt horizon.The change of the “normal” profile of paleosol of warm interstadial in final phase of MIS 3 started already in the last stages of its formation. The Bryansk soil is heavily deformed by cryogenic processes during the Valdai glaciation maximum (the Vladimir cryogenic horizon, MIS 2). The secondary diagenesis of the Bryansk paleosol is related to the Holocene soil-forming processes. The Holocene soils are superimposed on the Middle Valdai Bryansk paleosol, transforming it in different ways in different sectors of catena. On micro-elevation the Holocene diagenesis is minimal and consists in fragmentation by mesofauna, additional penetration of carbonates in the upper horizon of the paleosol. At the bottom of the micro-depression the Bryansk paleosol is the most transformed, and the entire profile of the Bryansk soil turned into illuvial horizon of the Holocene meadow-chernozem soil.