ИСТИНА

We have studied the calcareous- and humus-containing pendants or cutans in the South East Altay 50° N 89° E, 2200 a.s.l., in ultra continental, arid, and permafrost affected steppe. This study is aimed to reconstruct and date evolutionary phases of pedogenesis in permafrost-affected steppe soils of the South Siberia basing on the analysis of calcareous and humus-containing cutans, and to compare these data with sedimentary proxies of environmental change in the basin, and in the region. Parent materials are composed of derivates of granite and gneiss; ones may contain carbonates as an accessory. Calcareous and humus-containing pendants were described, sampled and 14C-dated in two horizons of soil characterized by extremely ultracontinental cryo-arid environment. Multilayered, rich in humus and/or carbonates pendants on clasts are the key characteristic of these soils. Features related to accumulation of carbonates along with Al-Fe-humus cutans are contradictory within a single soil profile; those can be explained as attributed to different evolutionary stages: carbonate accumulation in semiarid-arid phases, and Al-Fe-humus migration along with destabilization, degradation and re-crystallizing of carbonates during relatively humid phases. This hypothesis is supported by meso- and submicromorphological observations. There were collected the cutan samples in two horizons: in the upper illuvial Bkh were collected separately brown Al-Fe-humus cutans which impregnate the carbonate layer and pure light in color carbonate cutans. We have dated the carbonated cutans impregnated with humus and non-impregnated carbonate cutans in the same BC horizon. The carbonates of humus impregnated cutans (7350±30) were about 1000 years older than non-impregnated ones (6260±30). It was also dated humus impregnation of carbonate cutans. The age of humic subcutan over carbonate cutan was significantly younger- 3500±30 14C years BP. The different ages show the times of the climatic changes. We can suggest that the climate in this region was very dry in Preboreal and Atlantic periods of Holocene and became significantly more wet, with more precipitation in the end of Atlantic, beginning of Subatlantic period. There was also dated the carbonate cutan from the lower part of BC horizon at 6060±30 14C years BP, which is closed to the results for the non-impregnated cutan age in the upper part of the horizon. The 14C age of the rock from the robbed burial mound founded in the A horizon near the studied soil was dated close to modern at 540±25 14C years which shows that in the modern arid environment the this process of carbonate cutan formation is renewed