Abstract

Well-preserved submarine landforms from the continental shelf and fjords of northwesternmost Svalbard provide an example of ice-sheet deposition in an inter–ice-stream setting. EM1002 swath-bathymetric imagery covering 1280 km2 was examined. At the shelf edge, a distinctive and continuous belt of hummocky topography represents the grounding zone of a slow-moving Late Weichselian ice sheet. Active ice on the outer shelf is inferred from subtle lineations orientated parallel to flow. Low-amplitude transverse moraines crosscut the lineations, suggesting ice retreat across the outer shelf with brief stillstands. On the middle and inner shelf, large moraine ridges indicate multiple stillstands during deglaciation. There are arcuate moraine ridges at fjord mouths. Streamlined crag-and-tail landforms are preserved from when active full-glacial ice flowed out of the fjords. Clusters of smaller transverse ridges indicate slow retreat of grounded ice through the fjords. Holocene sedimentation is by rainout from sediment-rich meltwater, producing smooth basin fill. Small slides from the fjord walls are common. Little Ice Age glacier readvance produced another set of terminal moraines and smaller retreat moraines in the innermost fjords. A schematic model of this inter–ice-stream glacial landform assemblage summarizes the geomorphic record. It is compared with a model derived from several Svalbard cross-shelf troughs occupied by fast-flowing Late Weichselian ice streams. In general, the seafloor morphology of continental margins affected by ice streams is dominated by streamlined, subglacially produced landforms oriented in the former ice-flow direction, interrupted by major grounding-zone wedges formed during temporary halts in ice retreat. By contrast, between ice streams, shelf and fjord morphology records submarine landforms of various dimensions oriented mainly transverse to ice flow, produced at slowly retreating, grounded ice-sheet margins. There is little evidence for channeled subglacial water flow in the form of eskers and ice-contact fans on the Svalbard margin, implying that basal water is drained or advected mainly within soft subglacial sediments.

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