Paper No. 12
Presentation Time: 4:30 PM
EVIDENCE FOR LIMITED EURASIAN ICE-SHEET EXTENT DURING THE LGM VIA LUMINESCENCE DATING OF POSTGLACIAL SEDIMENTS FROM LAKES IN THE AREA OF THE TAYMYR PENINSULA, RUSSIAN HIGH ARCTIC
The last continental area of uncertainty in ice extent during the Last Glacial Maximum (LGM) remains the Russian High Arctic. The limits of the eastward extent of the Eurasian Ice Sheet (EIC) toward the Taymyr Peninsula during the LGM have been controversial, largely because obtaining suitable sediment records and their dating have been problematic. As extant lakes often contain continuous sedimentary records, lakes in formerly glaciated areas can be ideal recorders of the timing of last local and regional glaciations. About 10.1 m of post-glacial sediments overly a diamicton in a 10.5 m core from Changeable Lake (79°N) in the Severnaya Zemlya Archipelago (SZA). Long cores from several lakes in the Taymyr Peninsula just south of SZA contain non-glacigenic sediments which, by pollen evidence, reach into at least MIS 3. AMS 14C dating has yielded dramatically erratic results for Changeable Lake, when datable carbon was available, and limited results from lakes in the peninsula. Photonic dating (infrared stimulated luminescence or IRSL) of 10 samples from the non-glacial sediments in Changeable Lake produce ages increasing monotonically from ca. 4.5 ka in the upper 2 m to 51±5 ka at 9.97 m. The IRSL ages are clear evidence that this lake was last over-ridden by a regional ice sheet (the lake today is 5-10 km from a significant glacier) before ca. 55 ka, probably in cold stage MIS 4 (60-70 ka). Cores from Levinson-Lessing, Lama and Kokora lakes in the Taymyr Peninsula contain non-glacial sediments. The oldest IRSL ages range from 42.7±4.1 ka (L-Lessing) to 48±2.9 ka (Lama) and 48.0±5.3 ka (Kokora), thus supporting the interpretation of the results from Changeable Lake. These luminescence ages provide the first clear evidence that the EIS did not extend eastward this far during the LGM. The northeastern margin of the Barents-Kara-Sea ice sheet is now delimited to somewhere west of the Severnaya Zemlya Archipelago and the Taymyr Peninsula.