Soilscape evolution of West Tien Shan during the Late Pleistocene based on humus properties of the Obi-Rakhmat archaeological site

Analysis of the pedogenic humus properties of sediments at the Obi-Rakhmat archaeological site is the basis for reconstructing soil-forming processes as records of climatic fluctuations in the region of West Tien Shan. The stratigraphic section has 10 zones of pedogenesis that are distinguishable by pedogenic humus and other features, and consequently by the character of ancient soil forming processes. We found that most of the sediments accumulated in an environment where serozem soils form, that is, in an arid subtropical landscape (desert-steppe zone). The scheme of the altitudinal landscape sequence and the structure of the soil cover also changed according to climatic changes, and regular displacements of the altitude zones occurred. When analogs of modern dark serozems dominated near the site, the altitude sequence was characterized by the most complexity, with humid as well as arid landscapes occupying areas of the slopes. Climatic change trends both to humidity and to aridity simplified the altitude scheme: when climate was arid, humid landscapes were ousted (mountain brown forest soils occurred only on the slope tops). In contrast, when climate was humid, arid landscapes disappeared from the altitude sequence, and forest and meadow zones were dominant.