LIKHVIN (HOLSTEINIAN) INTERGLACIAL SOIL COVER RECONSTRUCTION BY PALEOPEDOLOGICAL DATA FOR THE EAST EUROPEAN PLAIN, RUSSIA

The aim of this study is to elucidate long-term climatic change over the East European Plain during the Middle Pleistocene. For this purpose, we investigated about 40 loess/paleosol sections. We reconstruct the genesis and secondary transformations of the oldest Middle Pleistocene interglacial paleosol (the Inzhavino paleosol) in the Oka, Don and Dnieper River basins (48-56° N, 32-44° E). The Inzhavino paleosol corresponds locally to the Likhvin interglacial and regionally to the Holsteinian interglacial of Western Europe.

Micromorphology indicates that the Inzhavino paleosol is polygenetic and implies that boreal to sub-boreal conditions prevailed during the stage of most pronounced soil formation, corresponding to the thermal optimum of the Likhvin Interglacial. There are clear indications of distinct pre-optimal and post-optimal stages of soil formation. The soil of the optimal stage has a zonal structure. In the northern part of the region, it is distinguished by a conspicuous textural differentiation through the profile (Ah-Ae-Btf-Bg). South of 52° N, the eluvial horizon is usually not pronounced morphologically, instead in situ weathering signs are more evident (Ah-(Aej)-Btgj). South of 51° N in the Don River basin and south of 50° N in the Dnieper River basin, the Inzhavino paleosol has a chernozem-like profile with a thick Ah horizon, carbonate accumulations and numerous krotovinas. The boundaries of the soil zones are aligned from WSW to ENE, probably because of the influence of the Atlantic Ocean. In some sections, for the pre-optimal stage of soil formation, there is micromorphological evidence of an earlier generation of lessivage and humus illuviation. These features are more pronounced in the NE part of the region where they are accompanied by iron illuviation. There, we identify two Bt sub-horizons. South of 52° N, especially in the middle Dnieper River basin, we observe a Btj horizon at the bottom of the optimal stage chernozem-like solum.

Humus accumulation is the most pronounced process for the post-optimal stage. It is also distinguished by two Ah sub-horizons and a very low position of the Ae horizon. Finally, there are two generations of small-polygon cryogenic deformations at the top of the Inzhavino paleosol.