The Late Cenozoic Erosion of the High-Latitude South-Western Barents Sea Shelf Revisited
Jan S. Laberg, Karin Andreassen, and Tore O. Vorren
Dept. of Geology, University of Tromso, Tromso, Norway.
High-latitude continental shelves owe their present morphology from severe erosion by large ice sheets. This “late” period of erosion may have influenced on the maturation history and distribution of hydrocarbons. Therefore, reconstructions of the spatial and temporal variations in glacial erosion provide important parameters for evaluating the prospectivity of Arctic shelves. Here we present a case-study from the south-western Barents Sea, an area that has experienced profound erosion during the last ~2.7 Ma. This resulted in the development of a characteristic glacial morphology of the continental shelf and deposition of a several-km-thick sediment fan, the Bear Island Trough Mouth Fan along the western margin prograding into the deep sea. In the period from ~2.7 to 1.5 Ma, proglacial processes including fluvial/glacifluvial erosion dominated. The total average erosion of the shelf was found to be 170 - 230 m, the average erosion rate 0.15 - 0.2 mm/yr, and the average sedimentation rates on the fan 16 - 22 cm/kyr. Subglacial erosion affected an area of ~575,000 km2 during the ~1.5 - 0.7 Ma period. Total average erosion was estimated to 330 - 420 m and the average erosion rate was 0.4 - 0.5 mm/yr. Average sedimentation rates were 50 - 64 cm/kyr. During the last ~0.7 Ma, glacial erosion mainly occurred beneath fast-flowing paleo-ice streams topographically confined to troughs (~200,000 km2). The total average erosion is estimated at 440 - 530 m, average erosion rate at 0.6 - 0.8 mm/yr and average sedimentation rate on the continental slope at 18 - 22 cm/kyr. The amount of erosion was mainly determined by the duration of the glaciations and the location, velocity and basal properties of the ice streams. In total, glacial erosion of the troughs has been relatively high throughout the last ~2.7 Ma, about 1000 - 1100 m. For the banks, erosion is inferred to have increased from ~2.7 Ma, to a peak between 1.5 and 0.7 Ma. Later there has been little erosion in these areas, which implies a total of 500 - 650 m of erosion. Compared with other high-latitude areas our rates are among the highest so far reported. This comparison also demonstrates that there have been large variations in the rate of sediment delivery to the glaciated continental margins.
AAPG Search and Discovery Article #90130©2011 3P Arctic, The Polar Petroleum Potential Conference & Exhibition, Halifax, Nova Scotia, Canada, 30 August-2 September, 2011.�������������������������������