Quick Search:    advanced search

GSW Home   GeoRef Home   My GSW Alerts   Contact GSW   About GSW   Journals List   Help

This Article Figures Only Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Laberg, J.S. Articles by Vorren, T.O. Search for Related Content GeoRef GeoRef Citation

The paleo–ice stream in Vestfjorden, north Norway, over the last 35 k.y.: Glacial erosion and sediment yield

J.S. Laberg^1,, R.S. Eilertsen² and T.O. Vorren³

¹ Department of Geology, University of Tromsø, N-9037 Tromsø, Norway
² Geological Survey of Norway, Polarmiljøsenteret, N-9296 Tromsø, Norway
³ Department of Geology, University of Tromsø, N-9037 Tromsø, Norway

Correspondence: E-mail: jan.laberg{at}ig.uit.no.

The basal erosion rate and sediment yield of the Vestfjorden paleo–ice stream, a marine-based part of the northwestern Fennoscandian Ice Sheet, were elucidated during a complete advance-retreat cycle using high-resolution seismic data and multi-beam bathymetry. In most of the area, there is a semitransparent, continuous upper seismic unit showing a southwestward (down-fjord) progradational pattern with megascale glacial lineations on top, interpreted to represent a subglacial deformable till. The till formed a continuous bed beneath most of the Vestfjorden paleo–ice stream, except for the upstream parts, where ice streaming is inferred to have occurred above bedrock. The till thickness is up to an order of magnitude larger than those reported from modern ice streams due to a more efficient transfer of material from the source area to the ice streambed. The till is draped by glaciomarine and marine sediments. The average sedimentation rate in the paleo–ice stream drainage route during the period from ca. 35 to 11 ka was ~2.6 m/k.y. This equals an average sediment discharge of 35 x 10⁶ t/yr and an average sediment yield of 6.4 x 10³ t km^–2 yr^–1. From this, we estimate an average erosion depth of ~40 m or rate of ~1.7 mm/yr in the sediment source area, the encircling fjord, and valley landscape. These values are in agreement with the results reported from similar settings in southern Norway, but they are nearly twice the figures reported for arctic ice-stream erosion. They are also significantly higher than the rates estimated from the British Ice Sheet. In conclusion, glacial erosion beneath paleo–ice streams seems to have been more efficient in subarctic regions.

Key Words: paleo–ice stream • Late Weichselian • Fennoscandian Ice Sheet • glacial erosion • sediment yield