GLACIATION OF THE TAYMYR PENINSULA, ARCTIC SIBERIA
ALEXANDERSON, HELENA . Dept of Geology, Lund University, Sweden.
Hjort, Christian . Dept of Geology, Lund University, Sweden.
MÑller, Per . Dept of Geology, Lund University, Sweden.
The maximum glaciation of the Taymyr Peninsula in north-central Siberia (Fig. 1A) probably took place during the Saalian (Illinoian) ice age, when the entire peninsula was ice covered. The resulting deep isostatic downpressing led to widespread postglacial marine inundation, the so-called Boreal Transgression during the Eemian (Sangamonian) interglacial. During the Weichselian (Wisconsinan), three glacial stages of successively decreasing amplitude took place (Fig. 1B). We have mapped and dated these stages by doing fieldwork, interpreting satellite images and using dating methods such as optically stimulated luminescence (OSL), radiocarbon (14C) and electron spin resonance (ESR).
The glacial geomorphology and drainage systems, the direction of glaciotectonic deformations and the provenance of crystalline erratics indicate that the glaciations affecting the northwestern and central Taymyr Peninsula during the Weichselian were mainly caused by ice sheets coming from the Kara Sea shelf. No sign of any local Weichselian glaciation has been encountered, although the higher easternmost part of the Byrranga Mountains, not studied by us, may at times have acted as a local centre of glaciation.
The most widespread glaciation dates from the Early Weichselian and culminated at c. 100 ka BP. At most the ice-front reached some 400 km inland from the present coast, leaving a series of more or less distinct zones of ice-marginal features south of the Taymyr Lake basin (Fig. 1B). Due to the large glacio-isostatic downpressing, the ice-sheet front retreated in a marine basin, resulting in a series of marine deltas formed at c. 100 m a.s.l. on the southern side of the Byrrangas (Möller et al. 1999). There are no signs of any glaciation reaching south of the Byrrangas after the Early Weichselian and continuous lacustrine/aeolian sedimentation took place in the Taymyr Lake basin (e.g. Pavlidis et al. 1997, Möller et al. 1999). The Middle Weichselian ice-sheet advance, which occurred around 65 ka BP, was of intermediate extent and reached only some 100 km inland from the present coast (Fig. 1B).
During both these events, the ice sheets dammed large proglacial lakes, filling the lake- and river basins both north and south of the Byrranga Mountains and, during the final stages of the different deglaciations, also lowland areas along the present coast. The water from north of the mountains drained southwards along the Taymyr River valley (where today the water flows northwards) into the Taymyr Lake basin and thereafter in most cases probably westwards to the Kara Sea shelf.
The last and least extensive glaciation – contemporaneous with the Last Global Glacial Maximum (LGM) – was short (<8000 years), culminated between 18 and 16 ka BP and was largely gone from present land by 12 ka BP. The thin ice (<500 m) seems to have been topographically controlled and limited to low-lying coastal areas and large river valleys. Nonetheless, it reached up to 100 km inland (Fig. 1B). No proglacial lake was formed at this time, but the subaerial proglacial drainage was reversed to the south, which caused a change in the sedimentation rate in the Taymyr Lake basin.
We have studied the North Taymyr ice-marginal zone (NTZ; Fig. 1B), the northernmost of the major ice-marginal features on the Taymyr Peninsula, in some more detail since it seems to contain traces of all three Weichselian glacial events. It comprises ice-marginal and supraglacial landsystems dominated by 2-3 km wide block-thrust moraines and large-scale deformation of sediments and ice. Large areas are still underlain by remnant glacier ice and a supraglacial landscape with numerous ice-walled lakes and kames is forming even today. The proglacial landsystem is either subaqueous (e.g. deltas) or terrestrial (e.g. sandur plains), depending on location/altitude and time of formation. The nature of the NTZ in association with subglacial sediments found there and near Cape Chelyuskin suggest that the ice sheets, which covered the area, had a margin frozen to the bed and an interior moving over a deforming bed.
Results of dating (OSL, 14C) indicate that the NTZ was first initiated c. 80 ka BP during the retreat of the Early Weichselian ice sheet and that it also records the maximum limit of a Middle Weichselian glaciation (c. 65 ka BP). Part of the NTZ was also reached by the Late Weichselian (LGM) ice sheet.
This study has been done within the European Science Foundation’s QUEEN (Quaternary Environment of the Eurasian North) programme and its European Union-financed, mainly terrestrial sub-programme, ‘Eurasian Ice Sheets’. The combined results of the different groups working along the Eurasian arctic coast and in the adjacent seas suggest a Weichselian glacial maximum in northern Eurasia during the Early Weichselian and a considerably smaller ice sheet during the Late Weichselian (the last global glacial maximum), cf. the QUEEN volume of Global and Planetary Change (2001; vol. 31). These results falsify the concept of Grosswald and co-workers, who propose a large pan-Eurasian ice sheet during the Late Weichselian (e.g. Grosswald & Hughes 2002).
Grosswald, M.G., Hughes, T.J., 2002, The Russian component of an Arctic Ice Sheet during the Last Glacial Maximum: Quaternary Science Reviews, v. 21, p. 121-146.
MÑller, P., Bolshiyanov, D.Yu., Bergsten, H., 1999, Weichselian geology and palaeoenvironmental history of the central Taymyr Peninsula, Siberia, indicating no glaciation during the last global glacial maximum: Boreas, v. 28, p. 92-114.
Pavlidis, Yu.A., Dunayev, N.N., Shcherbakov, F.A., 1997, The Late Pleistocene of the arctic Eurasian shelves: Quaternary International, v. 41/42, p. 3-9.
Figure 1. A. Map of northern Eurasia showing the location of the Taymyr Peninsula. B. The Taymyr Peninsula with mentioned geographical names and major ice-marginal zones (hatched = uncertain). EW - Early Weichselian, MW - Middle Weichselian, LW - Late Weichselian, NTZ - North Taymyr ice-marginal zone.
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