Dynamics of the Late Weichselian ice sheet on Svalbard inferred from high‐resolution sea‐floor morphology

Boreas - Tập 36 Số 3 - Trang 286-306 - 2007
Dag Ottesen1, Julian A. Dowdeswell2, Jon Y. Landvik3, J. Mienert4
1(e‐mail: [email protected]), Geological Survey of Norway, NO‐7491 Trondheim, Norway
2Scott Polar Research Institute, University of Cambridge, Cambridge CB2 1ER, UK
3Norwegian University of Life Sciences, IPM, P. O. Box 5003, NO‐1432 Ås, Norway
4Department of Geology, University of Tromsø, Dramsveien 201, NO‐9037 Tromsø, Norway.

Tóm tắt

High‐resolution bathymetric mapping of the fjords and continental shelf around the Svalbard archipelago shows an extensive pattern of large‐ and medium‐scale submarine landforms formed by differences in ice‐flow regimes. Mega‐scale glacial lineations, lateral moraines, transverse ridges and glaciotectonic features are superimposed on the large‐scale fjord, shelf and cross‐shelf trough morphology of the margin. From these landforms we have inferred the flow and dynamics of the last ice sheet on Svalbard. Major fjords and their adjacent cross‐shelf troughs have been identified as the main routes for ice streams draining the ice sheet. On the west coast of Svalbard major pathways existed along Bellsund, Isfjorden and Kongsfjorden. Along the northern Svalbard margin most of the ice drained through the Woodfjorden cross‐shelf trough and Wijdefjorden‐Hinlopen strait. Extensive areas with trough‐parallel glacial lineations in the cross‐shelf troughs suggest fast ice flow by palaeo‐ice streams. Lateral ice‐stream moraines, several tens of kilometres in length, have been mapped along the margins of some of the cross‐shelf troughs, identifying the border zone between fast ice flow and stagnant or slow‐flowing ice on intervening banks. Several general implications can be drawn from the interpretation of the glacier‐derived submarine landforms around Svalbard. Firstly, the Late Weichselian ice sheet was partitioned into fast‐flowing ice streams separated by slower moving ice. Secondly, our submarine morphological evidence supports earlier sedimentological, stratigraphical and chronological studies in implying that a large ice sheet reached the shelf edge around almost all of western and northern Svalbard in the Late Weichselian. The idea of a relatively restricted ice sheet over Svalbard, with ice‐free conditions in some areas of the west coast at the Last Glacial Maximum, is therefore unlikely to be correct. Thirdly, the ice sheet appears to have retreated more rapidly from the cross‐shelf troughs and outer fjords, although sometimes this occurred in a punctuated pattern indicated by grounding‐zone wedges, and more slowly from the intervening shallower banks. In addition, a grounding zone for the ice sheet has been mapped at the shelf edge 10–20 km off the northwest coast of Svalbard, suggesting that ice did not reach the adjacent Yermak Plateau during the Late Weichselian.

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Boreas

Tập 36 Số 3

286-306

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