![]() |
ИСТИНА |
Войти в систему Регистрация |
Интеллектуальная Система Тематического Исследования НАукометрических данных |
||
Soils record information on their local environment in situ, unlike sedimentary systems that preserve generalized environmental information on the areas of their sedimentation basins. Soils can serve as environmental archives of a high spatial resolution, whereas sedimentary records can have a very good temporal resolution, but nearly always a low spatial resolution. The use of paleosol records has certain advantages for paleoenvironmental reconstructions, especially, in areas with a high spatial variability of environments. Surface polygenetic soils (underwent at least one environmental change that resulted in detectable changing of a set of soil features and genetic horizons) and soil-sedimentary sequences were both studied as markers of landscape stability and sources of paleoenvironmental information in the South-East Altai. Pedolithostratigraphy and soil morphology were studied in the field. Further micromorphological diagnostics of pedogenic processes were conducted using thin sections under a Nikon E200 Pol polarizing microscope. Morphological results were supported by analytical data (humus content and composition, content of carbonates, particle size distribution, etc.) obtained by standard soil methodology. The 14C dates were obtained for the buried soils. It was found that all studied surface soils of the former sedimentary basins had recently developed under conditions of water deficiency , while all buried soils were formed in permafrost-affected steppe, meadow-steppe and forest-steppe landscapes. The buried soils had features related to ‘wet’ cryogenesis (turbations, glossic boundaries of A hor., frost sorting, etc.); dark, humus-rich mollic horizons (topsoil), abundant secondary carbonates below topsoil, sometimes accumulated from ground-waters; redoximorphic features indicative of short over-moistening periods. Thus, all studied buried soils were formed under milder environmental conditions (i.e., with less water deficiency as compared to the contemporary surface soils), in a more favourable environment for intra-soil biological activity, mostly within steppe or forest-steppe landscapes. Two humid stages can be distinguished on the basis of the soil data obtained: 1. A humid and relatively warm period at around 8-11 ky ca BP corresponding to pedogenic textural differentiation, which was clearly imprinted only in one soil-sedimentary sequence located at the highest position (2400 a.s.l.); 2. a period consisting of two humid and cold sub-stages between 2.5 and 3.8 ky cal BP (one at around 3.6-3.8 ky BP and the other earlier than 2.5-2.9 ky BP) with processes of Al-Fe-humus migration and accumulation of humus (Fe) layers in multilayered pendants, whichalso were most clearly recorded at the highest topographic positions of 2200-2400 a.s.l. The results showed that the last 1-2 kyr corresponded to the most extreme conditions of soil formation within the Holocene. It was concluded that the paleosol record, as compared to the sedimentary record, was a much better representation of locally-specific environmental change and differences in chronology between localities.