Buried Late-Holocene Luvisols of the Oka and Moskva river floodplains and their anthropogenic evolution according to soil and pollen data

According to radiocarbon dating, the ages of the four major soils developed on the floodplains are as follows: (1) modern, (2) 2500-800 cal BP, (3) 4700-3000 cal BP, and (4) 7000-5300 cal BP. The Late-Holocene soil 2 is usually defined as Albeluvisol or Luvisol. It has a developed profile with clearly expressed argic horizons (Bt). It is markedly different from the underdeveloped soil 1 (Fluvisol) and soil 4 (Phaeozem or Chernozem) that have a dark humus (mollic, chernic) horizon. Soil 2 has a typical light gray color of the humus horizon and is characterized by the accumulation of clay fraction in the Bt horizon as compared with the overlying E horizon. Micromorphological data indicate that the Bt horizon has well-developed clay films on pore walls and on the surface of aggregates. Cultural layers belonging to the Iron Age or early Middle Ages are sometimes located in Soil 2. Pollen analysis of this soil attests to its development under forest vegetation, which corresponds to the genesis of Luvisols and Albeluvisols. However, in some places near ancient settlements, characteristic features of the E and Bt horizons become weakly pronounced, and a well-developed dark humus (umbric) horizon is diagnosed in the soil profiles. These soils are marked by the abundance of pollen of herbs, including cultivated cereals and weeds. This is evidently related to the anthropogenic activity and the propagation of secondary grassy and ruderal vegetation that replaced forests on the floodplains. Floodplain environments are considered unsuitable for the development of Luvisols and Albeluvisols within a larger part of the Holocene. These soils appeared on the floodplains in the Late Holocene in relation to the propagation of forest vegetation and extremely low floods within a relatively long time.