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Liv Plassen, Geological Survey of Norway (Norway)
Dag Ottesen, Geological Survey of Norway (Norway)
Chris D. Clark, University of Sheffield (United Kingdom)
Kjell T. Svindland, University of Tromsų (Norway)
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On the basis of the sea floor morphology from detailed bathymetric data and seismic lines a palaeo-ice stream that followed Andfjorden during the Last Glacial Maximum (LGM) has been reconstructed. The palaeo-ice stream was 50-60 km long, up to 25 km wide and filled the whole sedimentary basin of Andfjorden.
The Fennoscandian Late Weichselian Ice Sheet extended to the shelf edge of Andfjorden during the LGM. Three well-defined U-shaped pathways or tributaries excavated in the sedimentary bedrock indicate the existence of three partitioned ice-flow systems into Andfjorden during glacial periods. Two subglacial medial ridges separate these paths. Parallel to the axis of these pathways, extensive (mega-scale) glacial lineations have been mapped.
Based on different character of mega-scale glacial lineations (MSGL) the Andfjorden trough can be classified into the following zones:
- Convergent streamlined pattern eroded in (sedimentary) bedrocks at the onset zone.
- Large-scale parallel streamlined pattern carved directly into sedimentary bedrocks along the central trough.
- Classical MSGL in glacial diamicton.
- MSGL of high spatial frequency in glacial diamicton at the outer shelf.
The increase in frequency of MSGL at the outer shelf indicates a two step glacial advance to the shelf edge during LGM, where the second advance erased older lineations only leaving lineations from the later advance at the inner shelf, while making a second set at the outer shelf. From surrounding topography and adjacent ice stream pathways, we will discuss whether the Andfjorden ice stream operated continuously for a long time, or as short-lived pulses during glacial draw-down phases.
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