2002 ARCSS All-Hands Workshop

Limiting Extent of Ice Sheets in the Russian High-Arctic During Isotope Stages 2–3 from IRSL Dating of Lake Sediments, Taymyr Peninsula

Glenn W. Berger¹, Martin Melles², Alexandra Raab^3
1Desert Research Institute, 2215 Raggio Parkway, Reno, NV, 89512-1095, USA, Phone 775-673-7354, Fax 775-674-7557, gwberger@dri.edu
²Institute of Geophysics and Geology, University of Leipzig, Talstrasse 35, Leipzig, D-04103, Germany, melles@rz.uni-leipzig.de
³Institute for Geography, University of Regensburg, Regensburg, D-93040, Germany

The reconstruction of MIS 2-3 ice-sheet dimensions and ice-flow directions for the Eurasian Arctic remains controversial, with the maximalist view (Denton and Hughes, 1981; Grosswald, 1998) perhaps now (2001) being out-balanced by the minimalists' view (Brigham-Grette et al., 2001; Möller et al., 1999; Svendsen et al., 1999; Velichko et al., 1997). For accurate reconstruction of global ice volumes during at least the LGM, it is essential to resolve this controversy. Changeable Lake, in the Severnaya Zemlya Archipelago (79° N, 96° E) at the northern end of the Taymyr Peninsula, contains consolidated till at the base of a 10.5 m core. This represents the last time glacier ice over-ran this area. Younger core deposits represent non-glacial conditions. A minimum date for this till would place a clear temporal limit on the last presence of an ice sheet here.

Application of 14C AMS dating to humic acids, pollen grains, insects, and undetermined organics give some age reversals and scatter, with the youngest ages near 10 ka (upper 4 m) and the oldest at 22-28 ka in the 8.5-9.8 m zone. AMS ages for two samples of benthic foraminifera in the marine facies directly overly the bottom till are "infinite" ( >48 ka). Fine-silt infrared-stimulated luminescence (IRSL) dating yields (with one exception, at 5 m) a clearer age-depth trend, from 4.0±0.4 ka in the upper 2 m to 33±2 ka at 9.6 m. A sample from the marine facies (9.95 m) immediately overlying the till gives an age of 53±3 ka. Thus, an ice sheet was last present in this area before 50 ka, probably in MIS 4 or even before MIS 5. This improved chronology supports the minimalists' view of the Eurasian Arctic ice sheets, and the "precipitation-shadow" view of Möller et al. (1999) for the LGM at the Taymyr Peninsula.

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