THE LATE WEICHSELIAN ICE SHEET ALONG WESTERN SVALBARD: ICE FREE AREAS EXISTED
LANDVIK, JON Y.. Agricultural University of Norway, Norway.
Brook, Edward J.. Washington State University, USA.
Gualtieri, Lyn . University of Washington, USA.
Raisbeck, Grant . Centre de SpectromÅtrie NuclÅaire et de SpectromÅtrie de Masse, France.
Salvigsen, Otto . University of Oslo, Norway.
Yiou, FranÉoise . Centre de SpectromÅtrie NuclÅaire et de SpectromÅtrie de Masse, France.
Present reconstructions suggest that glacier ice along the northwest sector of the last Svalbard/Barents ice sheet extended to the shelf edge west of Spitsbergen. This has been shown by the westward distribution of Late Weichselian glacial diamictons mapped by sediment cores and seismic lines. In contrast to the offshore evidence, previous interpretations of the terrestrial stratigraphic and geomorphologic records at several sites have suggested more limited ice extent.
The new field studies reported here have focused on the vertical extent of the Late Weichselian ice sheet along the mountains of western Svalbard. Key areas on NW Svalbard have been revisited in order to map out the boundaries between glaciated and non-glaciated surfaces, and several vertical transects of the mountains along the west coast of Svalbard are now being investigated. In all the study areas, glacial erratics from mainland Spitsbergen are frequent, and suggest at least one former extensive glaciation of the whole area.
Amsterdamøya off NW Spitsbergen is situated only 20 km from the shelf break. The higher parts of the islands (300-500 m a.s.l.) are covered with blockfields previously interpreted to have been associated with nunataks during the Late Weichselian. Our studies show that erratic boulders deriving from Spitsbergen were deposited by glacier ice after the formation of the blockfields. The last ice advance over the higher ground occurred at ca 70 ka or earlier, according to 10Be exposure age dates on these erratics. The lower ground (<100 m a.s.l.) is characterised by glacially sculptured bedrock and fresh looking moraines. Based on late glacial ages obtained from bedrock and erratics in the moraines, we conclude that the fjords and sounds were glaciated during the Late Weichselian. A late Weichselian glaciation of the lower ground is also supported by stratigraphic evidence from sediment sections close to sea level. Mollusc shells found below a till bed with Spitsbergen erratics yielded a radiocarbon age of 43 ka. The young finite age is supported by low aIle/Ile amino acid ratios.
Our studies confirm that nunataks have existed on the west coast of Svalbard during the Late Weichselian, and that the ice sheet was thinner than during preceding Weichselian stadials. We also conclude that the blockfields in NW Spitsbergen have survived extensive glaciation, and that the may be of a preglacial age.
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