ИСТИНА

Calcareous- and humus-containing pendants are highly perspective, and only initially studied as an intrasoil paleoenvironmental archive. Especial value of these pedofeatures as a proxy of environmental change is a principal possibility to be dated. There were some examples to apply similar pedofeatures as the environmental archive, and certain experience of 14C dating calcareous pendants, but no attempts are known to date organic carbon of humus-containing pendants. This study is aimed to reconstruct and date evolutionary phases of pedogenesis basing on the analysis of calcareous and humus-containing pendants, and to compare these data with sedimentary proxies of environmental change in the basin, and in the region. Study site is located in the South-East Altay, 50° N 89° E, 2200 a.s.l., in ultracontinental, cryo-arid steppe. Parent materials are derivates of granite and gneiss; ones may contain carbonates as an accessory. Calcareous and humus-containing pendants were described at four motphological levels, sampled and AMS 14C-dated in Haplic Cambisols Humic Turbic Pisocalcic Skeletic. Multilayered, rich in humus and/or carbonates pendants on clasts are the key characteristic of these soils. Part of calcareous coatings also contains amorphous SiO2 (opal). These pedofeatures are contradictory within a single soil profile because Al-Fe-humus compounds, calcium and silica needs different pH conditions for their migration and intra-soil accumulation. Combination of calcareous, opal-containing and Al-Fe-humus containing calcareous coatings or layers of compound coatings within a single profile can be explained as a result of different evolutionary stages: carbonate and opal 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 was supported by mezo- and submicromorphological observations. To date the stages of pedogenesis pendants were grinded off as average samples. In the upper Bkh horizon two samples were dated: one whitish, highly calcareous layers; another one of moderately calcareous layer, brownish, enriched with humus. Both C of carbonates and C of humus were dated in the last sample. In the lower Bk horizon highly calcareous pendants were dated. An additional date was obtained from pendant on a clast from a robbed burial mound in a neighborhood. Dates obtained from carbonates of whitish layers are similar in Bkh and lower Bk horizons and vary around 7000 cal BP. The date on carbonates of the brownish layers is approximately 1 thousand year older. Organic carbon in the same sample is dated as 3687 – 3877 cal BP. Carbonate pendant from the burial mound is dated as 517-591 cal BP. Thus, as based on soil studies, pedogenic accumulation of carbonates corresponding to arid-semiarid conditions started in the basin not later than 8000 cal BP, most possibly this process was active throughout the Holocene with interruption during a humid phase of Al-Fe-humus migration around 3000-4000 years BP. The youngest date is a clear evidence for revival accumulation of carbonates after the interruption. Intra-basin sedimentary archives – pollen, diatoms, chironomids in lake sediments – haven’t recorded the humidization in the second half of Holocene, whereas a data on glacier fluctuations in the region testifies on the most humid stage of the Holocene between 4900-4200 BP which is evidently correlative with humidization stage recorded in soils.