Home – Home – Jornals – Russian Geology and Geophysics 2001 number 1-2

Analyses of clay minerals have been performed on recent and ancient (age 900 years) sediments of the west-east trending Zavorotnyi transect in the North Basin of Lake Baikal (southeastern Siberia). The aim was to study clay minerals to identify the characteristics of the eastern and western sediments and to relate them to catchment areas or to sedimentation mechanisms. Apart from illite, which is the most abundant mineral along the transect, the clay mineralogy changes distinctly between the eastern and western sediments. The western clayey sediments are characterized by high chlorite contents, low smectite and kaolinite contents, and a general good crystallinity of all clay minerals. The eastern clayey sediments have lower chlorite contents, higher smectite and kaolinite contents, and poorer crystallinity of the clay minerals. We suggest that differences in the geological background and morphology of the catchment areas lead to these differences between the eastern and western surface elements as a result of different weathering and transport mechanisms prior to sedimentation. The smectite content and illite-chlorite ratio are possible indicators for differentiating between the western and eastern predominant sediments. From this interpretation it follows that western catchment areas supplied the turbidites accumulated in the center of the Zavorotnyi transect. The great variability in distribution of clay minerals over a few hundred years, most pronounced in the smectite content and illite-chlorite ratio, indicates significant changes in the factors controlling sedimentation in the North Basin. This must be taken into account when using the distribution of clay minerals in Baikal sediments for paleoreconstructions.