ОПОРНЫЙ РАЗРЕЗ ТОЛОГОЙ (ВЕРХНИЙ КАЙНОЗОЙ, ЗАБАЙКАЛЬЕ): РЕКОНСТРУКЦИЯ УСЛОВИЙ И ОСОБЕННОСТЕЙ ОСАДКОНАКОПЛЕНИЯ

This paper presents new data on the structure and the lithological, geochemical and granulometric features of the Quaternary sediments of the multi-layered key section Tologoi (Late Cenozoic, Transbaikalia). On this basis, the location of paleosols horizons across of the section and their thickness have been established. Four main sedimentation cycles have been identified, each of which was completed with the formation of soil horizons. It is shown that the climate during the formation of the deposits had cyclical nature: the moist periods were replaced by arid epochs of different intensity and duration. During warming and formation of soil horizons, distant and medium-range provenance areas prevailed. Biochemical postsedimentation transformations of deposits in situ dominated during of the most intensive pedogenic processes as reflected in the sediments chemical composition changes. It is shown that the most warm conditions and activation of weathering and leaching processes during the Pleistocene occured in the paleosol horizons at 16.4-15 m. In the studied geochemical profile the stages with prevailed cryogenic conditions are clearly recorded. For these periods the low values of salinization indices and high – calcification indices, as well as low values of leaching (hydrolysis) and redox conditions indices, positive Eu*, high ΣCe/ΣY and low La/Sm are characteristic.