Dating post-LGM aeolian sedimentation and the Late Palaeolithic in Central Yakutia (northeastern Siberia)

Abstract

Central Yakutia is a large region in northeastern Siberia characterized by extensive permafrost, large river valleys, mountain glaciers, and large massifs of aeolian sands; the geological history of the region is complex and, at present, poorly constrained. In recent years, it has been shown that aeolian sands cover up to 60% of large parts of Central Yakutia. This paper presents the results of luminescence dating of aeolian sedimentation at the Diring Yuriakh Palaeolithic site located in the middle reaches of the Lena River. Field studies identified several thick units of aeolian sand, which cover an old deflation surface with Late (Duktai culture) and Early Palaeolithic (Diring culture) artefacts. The reliability of the OSL chronology was assessed by comparison of ages based on the optically stimulated luminescence from quartz and the infra-red stimulated luminescence from potassium-rich feldspars; these age pairs are in good agreement, implying that at least the quartz grains were sufficiently bleached before sedimentation. We obtained OSL ages that reflect three periods of accumulation between the LGM and the Holocene: ∼21 ka, 15-14 ka, and 12.5-10 ka. These periods of accumulation broadly coincide with global cooling episodes during the Last Glacial Maximum, the Older Dryas, and the Younger Dryas, with some extension into subsequent warmer intervals, whereas the intervening intervals without preserved sediments are taken to reflect dune stability during warmer periods. The sand on the terraces, sourced from alluvial bars in the river channel, was blown up the valley slope during cold and dry periods when the vegetation cover was sparse. When the climate warmed, the vegetation took some time to spread, and so the accumulation of aeolian sand on the high terraces continued into the warm periods. We also infer periods of deflation (wind erosion) that occurred before 21 ka and between 20-15 ka, presumably due to increased aeolian activity and localized remobilization of sediment. The new OSL chronology shows that the younger artefacts located at the cape of Diring Yuriakh, belonging to the Late Palaeolithic Duktai culture, are older than 15 ka. The new ages also show that the post-LGM aeolian sand sequences at Diring Yuriakh are correlated with the regionally developed subaerial Dolkuma Formation.