Implications of a 24,000-yr palynological record for a Younger Dryas cooling and for boreal forest development in northeastern Siberia

A sediment core from Smorodinovoye Lake (SML), northeastern Siberia (area to the east of the Verkhoyansk Range) spanning the last 24,000 C-14 yr indicates that vegetational and climatic changes in the upper Indigirka basin resemble those in eastern Siberia (Lena basin and westward). For example, maximum postglacial summer temperatures at SML probably occurred 6000-4000 C-14 yr B.P., an age more in accordance with eastern than northeastern records. Larix arrived near the lake by 9600 C-14 yr B.P., approximately when forests expanded in the east but ca. 1500 C-14 yr later than forests were established in the neighboring upper Kolyma basin. Paleobotanical data further suggest that Larix possibly migrated southward from populations in the arctic lowlands of eastern Siberia and did not originate from interior refugia of the upper Kolyma basin. Although a Younger Dryas cooling has been noted in eastern Siberia, SML provides the first evidence from the northeast for a similar climatic reversal. Climatic variations seemingly have persisted between the Indigirka and Kolyma basins over at least the last 11,000 IT yr, despite the proximity of the two drainages and the occurrence of major changes in boundary conditions (e.g., seasonal insolation, sea levels) that have influenced other regional climatic patterns. (C) 2002 University of Washington.