Extensive glaciation of the Verkhoyansk Range, northeastern Siberia, during the Last Glacial Maximum

The Pleistocene ice-cover history of northeastern Siberia represents an important gap in our understanding of Northern Hemisphere glaciations. Significant uncertainties remain for large segments of this vast, cold, and remote region, including the ice extent associated with the Last Glacial Maximum (LGM, 26.5-19 ka). Here, we focus on the glacial history of the Verkhoyansk Range, the westernmost mountain chain in northeastern Siberia and the first major topographic barrier met by moisture sources from the west. We have mapped glacial landforms in the Verkhoyansk Range using ArcticDEM, a high-resolution digital elevation model. We also present 28 new cosmogenic 10Be exposure ages from glacial boulders and bedrock in the Undyulyung and Sakkyryr valleys—two major glacial troughs dissecting the western and eastern flanks of the central Verkhoyansk Range, respectively. Our new exposure ages show that large mountain glaciers were present in the Verkhoyansk Range during the LGM; ice filled the valleys and extended up to 100 km westward and eastward from the central range axis. Exposure ages from the Undyulyung valley indicate that the ice last retreated from the western range front around 19-16 ka, whereas exposure ages from the Sakkyryr valley suggest that glaciers last retreated from the eastern range front around 18–14 ka. These findings challenge previous assumptions that the Verkhoyansk Range has been largely ice-free since >50 ka. Rather, our results demonstrate the presence of an icefield in the Verkhoyansk Range during the LGM, consistent with broader trends showing significant mountain glaciations across large parts of northeastern Siberia during this period. Our detailed mapping of glacial landforms indicates a distinct east-west asymmetry with respect to the extent of pre-LGM glaciations in the Verkhoyansk Range; at the western range front, there is evidence for larger pre-LGM glaciations, whereas pre-LGM glaciations at the eastern range front seem to have been similar in size to the LGM glaciation. This suggests that, while ice-mass volumes progressively decreased in the Verkhoyansk Range during the Late Pleistocene, the decline was primarily driven by shrinking ice volumes along the western portion of the range.