LATE QUATERNARY ENVIRONMENTS IN SOUTHERN SIBERIA: LANDSCAPE RESPONSE TO CLIMATE CHANGE AND HUMAN ACTIVITIES IN THE BAIKALO-PATOM UPLAND

The evolution of landscapes in southern Siberia have been influenced by climate and neotectonic processes while the relative role of modification due to human activities has increased since the late Pleistocene. There is geomorphic and stratigraphic evidence of Late Pleistocene glaciation in the Baikalo-Patom region. Chronologic control is primarily based on radiocarbon dates of vertebrates associated with glacio-fluvial deposits, and stratified Paleolithic occurrences within fluvial terrace deposits adjacent to the Mamakan and Vitim Rivers. Post-glacial environmental changes are recorded in terrace deposits along the Zhuia River, a tributary of the Chara River. Within the Chara basin glacial outwash deposits dating to around 11,000-10,000 radiocarbon years before present (RCYBP) are overlain by Holocene sediments. The 5 m terrace along the Zhuia at Tolondo Lake consists of ~3.5 m of gravels overlain by ~1.4-1.2 m of post-glacial sediments, reflecting Late Pleistoce-Holocene aggradation. The early Holocene deposits, dated to before 8,655 ± 115 RCYBP (COAH-6578) and after 5,900 ± 125 RCYBP (COAH-7013), consist of micaceous alluvial silty sands interbedded with thin lens of clays and organics. Middle Holocene silty clays dated to around 2,890 ± 85 RCYBP (COAH-7012) signify low energy deposition and exhibit post-depositional convolutions. The late Holocene sediments are modified by pedogenesis and contain Rangifer (caribou) bones. The sequence shows a substantial increase in tree pollen (Abies siberica, Picea obovata, Pinus siberica, P. sylvestris) during the late Holocene as well the presence of taxa associated with disturbed landscapes. Human modification of the landscape seems to have intensified during the late Holocene with the introduction of semi-sedentary pastoralism (such as reindeer herding), mining, and logging, as well as continued hunting. Environmental change during the late Quaternary appears to have been the consequence of both natural climate variability and intensified land-use by humans.