3-D seismic interpretation of glacigenic sediments from the south-western Barents Sea
Rafaelsen, B.1, Andreassen, K.1, Kuilman, L.W.2, Midtbø, M.1, Lebesbye, E.1 & Hogstad, K3.
1 Department of Geology, University of Tromsø (Norway)
2 Norsk Hydro ASA, Oslo (Norway)
3 Norsk Hydro ASA, Harstad (Norway)
In the south-western Barents Sea several types of sub- and pro-glacial features are inferred from 3D-seismic data within the glacigenic sediments that overly the consolidated bedrock. The close spacing of 3-D lines and the powerful computer work station interpretation techniques have allowed a detailed 3-D mapping of the observed features.
Several generations of glacial grooves observed on four different paleo surfaces are interpreted to reflect flow patterns of paleo glaciers. The grooves are 3 to 9 m deep, 20 to 180 m wide, and 0.78 to 20 km long. All four surfaces show a main lineation pattern of grooves trending N-S, suggesting that the dominant ice flow was moving north across the Barents shelf at least four times during the last 0.8 Ma. Imbricated thrust sheets involving the whole section of up to 120 m of glacigenic sediments are interpreted to be formed by thrusting of sediments in front of a glacier. The most extensive of these features suggest an ice-movement from east to west, and are probably formed during the last glacial maximum. Other less extensive imbrication structures, which seem to suggest an ice-direction towards the east, are probably formed during a later deglaciation phase.
A lobate-shaped ridge complex on the sea floor, interpreted to be an end-/push- moraine, suggests that the last ice movement locally was from west to east. Whereas the morphology of the buried seismic horizons is characterised by different generations of sub-parallel grooves, the sea floor is dominated by more variably oriented iceberg plough marks from the deglaciation phase of the last Barents Sea ice sheet.
Despite relatively low seismic frequencies and hence low vertical resolution of seismic profiles, time slices and sub-horizontal time maps are of high spatial resolution, providing detailed images of different stages of buried Quaternary glacial geomorphology.