Sedimentation and environmental dynamics of the Tunka rift valley (Baikal region) in the Late Pleistocene-Holocene based on the analysis of lithological and rock magnetic properties of the deposits from Upper Paleolithic sites

The Tunka depression is a valley in the Baikal rift system. It contains several Paleolithic archaeological sites, however, the number of finds varies sharply across the different sections of the valley. The purpose of this study is to reconstruct the natural environment and sedimentation conditions of Upper Paleolithic deposits in the Tunka valley and to explore the effects of these conditions on the prehistoric humans that peopled the landscape. A total of 923 samples from 6 section sites (with different geological structure, thickness of layers, and geomorphological position) were evaluated for grain size and rock magnetic properties. The age of all sections is supported by C-14 and TL dates. Sedimentation at Belyi Yar 1 and Belyi Yar 2 is characterized by high deposition rates and a large influx of loose sedimentary material due to catastrophic floods that prevented soil formation and resulted in unsuitable conditions for the habitation of prehistoric humans. Sedimentation rates at the Shimki site (which has not yet yielded archaeological finds) were also high but the presence of paleosol horizons indicates milder environmental conditions. The numerous archaeological finds at the Tuyana site, located at the highest geographical altitude, are explained by the features of the sedimentary environment: low sedimentary input, well-developed buried soils and a lack of signs indicating catastrophic flood. The Zaktui site, with its lower altitude, is characterized by less suitable conditions for human habitation which also explains the restricted number of archaeological finds in the section. An intermediate position is occupied by the Slavin Yar section, where sedimentation rates were higher than at Zaktui or Tuyana and paleosol horizons are quite well developed, but poor archaeological finds are explained by the influence of catastrophic floods. The integration of the studied parameters helps to reconstruct different sedimentary conditions in the explored sites of the Tunka depression and to estimate their suitability for prehistoric human habitation.