Holocene Seismically and Climatically Driven Mass Wasting Processes in Boguty Valley, Russian Alta

Study of post Last Glacial relief evolution in the southeastern part of Russian Altai (SE Altai) revealed that debris flows were widely presented in the region. After degradation of the last Pleistocene glaciation and drying giant ice-dammed lakes seismic excitation was one of the main factors that controlled intensification of slope activity. Geological and geomorphological researches of 2011–2015 in the Boguty river valley, SE Altai, were focused on studying geomorphic processes and reconstructing landscape evolution within the eastern periphery of the Chuya intermountain depression and Chikhachev range during the late Pleistocene-Holocene. Multidisciplinary approach, including determination of bio-composition of plant remnants from deposits of different genesis, tree species composition from charcoal fragments, micromorphological studies of surface and buried soils as well as litho-stratigraphic and pedogenetic analysis were applied for paleoclimatic and paleoenvironmental reconstructions. Geochronological investigations included radiocarbon dating of fossil soils, buried peats, lacustrine gyttjas and charcoal fragments. Within area of investigations seven sections were studied and 18 radiocarbon age estimations, covered time interval of the last 14 ka, were obtained. Obtained results indicate the tectonic origin of tributary valley of the Boguty river, which was settled along one of the faults in the late Pleistocene. Periods of tectonic quiescence and slope stability were repeatedly interrupted by periods of intensification of slope processes. Debris flows took place here about 7000, between 2800 and 1000, 650, 250 cal. years BP and could be triggered by both climatic and seismic events.