Past climate and continentality inferred from ice wedges at Batagay megaslump in the Northern Hemisphere's most continental region, Yana Highlands, interior Yakutia
2019
Abstract. Ice wedges in the Yana Highlands of interior Yakutia – the most continental
region of the Northern Hemisphere – were investigated to elucidate changes
in winter climate and continentality that have taken place since the Middle Pleistocene. The
Batagay megaslump exposes ice wedges and composite wedges that were sampled
from three cryostratigraphic units: the lower ice complex of likely
pre-Marine Isotope Stage (MIS) 6 age, the upper ice complex (Yedoma) and the
upper sand unit (both MIS 3 to 2). A terrace of the nearby Adycha River
provides a Late Holocene (MIS 1) ice wedge that serves as a modern reference
for interpretation. The stable-isotope composition of ice wedges in the MIS 3 upper ice complex at Batagay is more depleted (mean δ18O
about −35 ‰) than those from 17 other ice-wedge study
sites across coastal and central Yakutia. This observation points to lower
winter temperatures and therefore higher continentality in the Yana
Highlands during MIS 3. Likewise, more depleted isotope values are found in
Holocene wedge ice (mean δ18O about −29 ‰)
compared to other sites in Yakutia. Ice-wedge isotopic signatures of the
lower ice complex (mean δ18O about −33 ‰)
and of the MIS 3–2 upper sand unit (mean δ18O from about −33 ‰ to
−30 ‰) are less distinctive regionally. The latter unit
preserves traces of fast formation in rapidly accumulating sand sheets and
of post-depositional isotopic fractionation.
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