STABLE ISOTOPE COMPOSITION OF CARBON IN SOILS AND BOTTOM SEDIMENTS OF RIVER VALLEYS IN PREBAIKALIA ( Southeastern Siberia )

Using total organic carbon and stable carbon isotopic analyses, an attempt is made to characterize the geochemical nature of soils and stream sediments of various landscapes in Prebaikalia, southeastern Siberia. Changes of isotope ratios do not show any noticeable dependence on total organic carbon content but do show a relationship to the age of soil sections. This trend may be related to variations in landscape vegetation and climate conditions in the Late Pleistocene. The increase in δ13C values in the superflood terrace, slope and summits of valley profiles evidently marks a paleoclimatic boundary due to the replacement of predominantly grassy vegetation by the recent taiga landscapes. The age of this boundary needs to be determined by age dating methods but is evidently not older than the onset of formation of recent flood plain terraces.