Middle and Late Pleistocene climate and continentality inferred from ice wedges at Batagay megaslump in the Northern Hemisphere’s most continental region, Yana Highlands, interior Yakutia

Abstract. Ice wedges in the Yana Highlands of interior Yakutia – the most continental region of the Northern Hemisphere – were investigated to elucidate the winter climate and continentality during the Middle to Late Pleistocene. The Batagay megaslump exposes ice wedges and composite wedges that were sampled from three cryostratigraphic units: the lower sand unit of Marine Isotope Stage (MIS) 6 age, the upper Ice Complex (Yedoma) and the upper sand unit (both MIS3 to MIS2). A terrace of the nearby Adycha River provides a Late Holocene (MIS1) ice wedge that serves as a modern endmember for analysis. Stable-isotope values of ice wedges in the MIS3 upper Yedoma Ice Complex at Batagay are more depleted (mean δ 18 O about −35 ‰) than those from 17 other ice-wedge sites across coastal and central Yakutia. This observation points to lower winter temperatures and, therefore, higher continentality in the Yana Highlands during MIS3. Likewise, more depleted isotope values compared to other sites in Yakutia are found in Holocene wedge ice (mean δ 18 O about −29 ‰). Ice-wedge isotopic signatures of the MIS6 lower sand unit (mean δ 18 O about −33 ‰) and of the MIS3-2 upper sand unit (mean δ 18 O from about −33 to −30 ‰) are less distinctive regionally and preserve traces of fast formation in rapidly accumulating sand sheets and of post-depositional fractionation.