Reconstruction of glacial history of the area north of Svalbard/Spitsbergen

Catalina.Gebhardt [ at ]


Vast areas of the Yermak Plateau have been affected by major glaciations during the Quaternary. Our understanding of the timing and dimensions of the marine-based ice sheets in the Svalbard-Barents Sea region during the Quaternary today is still limited. The main objective of this thesis is to improve the knowledge in the glacial history on the aspect of when and how the Arctic Ocean with the Svalbard-Barents Sea Ice Sheets has been reconnected. Multibeam swath bathymetry, high-resolution subbottom acoustic profiling and sediment coring can be combined to identify ice-grounding events in the past. A case study is presented here for the Yermak Plateau and northern Svalbard margin located between 79° and 83°N and 2° and 16°E. The geophysical datasets were acquired from research vessels, Polarstern (PS) and Maria S. Merian (MSM), during the expeditions PS92 and MSM31. Three types of subglacial features were detected from bathymetric mapping, in the form of ice- produced mega-scale glacial lineations, iceberg plowmarks of various dimensions and a grounding-zone wedge. The acoustic stratigraphy showed four acoustic facies: the first with undulating laminated upper surface and very little acoustic penetration below, indicative of highly disturbed sediments by ice action; a second with a thick laminated strata over acoustically transparent lenses, resulting from debris flow; a third with well-developed stratification produced by sedimentation under calm condition, often laminated with parallel to sub-parallel internal reflectors; and the last with well-stratified strata also produced by sedimentation under calm environment but present over a strong and undulating reflector at the base. Mega-scale lineations are attributed to be formed during the Saalian with the grounding of large ice shelf fragments exiting towards the Fram Strait. Quasi-linear huge plowmarks are likely to be formed either by multiple keels of a single megaberg or by keels of several icebergs that are trapped together within multi-year sea ice whereas, fresh-looking and irregular smaller plowmarks might have been formed by single keels of icebergs. The grounding-zone wedge, at its maximum position at the shelf edge, represents the maximum extent of the Late Weichselian ice sheet extended from Svalbard-Barents Sea. The geotechnical properties of the sediments from gravity cores recovered, did not possess any qualities of overconsolidation but showed a hint of slightly higher consolidation at certain core depths, implying the sediment erosion by grounded ice shelves or icebergs. Undisturbed lineations but rather faint ones due to younger sediments on top at the southernmost Yermak Plateau and an acoustic reflector at the sediment depth of 15-20 m below sea floor at the plateau crest suggest that there might not be any connection between the Arctic Ocean and Svalbard-Barents Sea Ice Sheet through Yermak Plateau after MIS19/20 boundary.

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Thesis (Master)
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Adhikari, D. (2016): Reconstruction of glacial history of the area north of Svalbard/Spitsbergen , Master thesis, Department of Geomatics.

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