RADIOCARBON CHRONOLOGY OF HOLOCENE DEBRIS FLOWS IN THE BOGUTY RIVER VALLEY (RUSSIAN ALTAI)
Comprehensive geological-geomorphological and geochronological investigations were made into the post-glacial dynamics of landscapes in the Boguty depression which is the eastern branch of Russian Altai’s largest Chuya depression. The main stages of landscape evolution and climate changes in the Late Pleistocene and Holocene are outlined. It is established that in spite of the arid climate dominating this part of Altai, debris flows occurred among the processes transforming the slopes of the deglaciated valleys, within the western macroslope of Chikhachev Range surrounding the Boguty depression. We studied seven profiles of Lower Quaternary deposits of a different genesis with chronomarkers (paleosoils, peats, gyttjas and charcoals) and obtained 18 radiocaron dates. Data obtained indicate that there was no land ice-sheet within the Boguty depression 14 ka already. It is established that the climate of the first half of the Holocene was warmer and more humid when compared with today’s climate, and forest vegetation grew in the now treeless valley for a long period of time. The latter half of the Holocene is, in general, characterized by a colder climate and by a progressive aridization. New radiocarbon dates allowed us to reconstruct the Holocene chronology of large debris flows occurring within the study area about 8000-7000, 2900-1000, 650 and 300 cal BP. The last large debris flow occurred in 2017. In addition to climatic factors, such as permafrost degradation and snowmelt, one of the triggers of debris flows in the region can be earthquakes.