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Glacial geology of outer Bjørnøyrenna, southwestern Barents Sea

Marine Geology
Publication Date
DOI: 10.1016/0025-3227(92)90007-5
  • Archaeology
  • Earth Science


Abstract The Upper Cenozoic glacigenic succession in outer Bjørnøyrenna (Bear Island Trough), southwestern Barents Sea is investigated utilizing data from six shallow boreholes (< 143 m below sea bed) and seismic profiling. Overdeepened troughs in the lowermost part of a large Plio-Pleistocene wedge at the shelf margin are interpreted as glacial erosion forms. This suggests that the overlying succession, which basinward attains a thickness of several km, was deposited during a period with glaciations. Large scale possible sand ridges in the stratigraphic lower part of this succession are confined to two north-south trending zones parallel to the present shelf break. They probably formed in a continental shelf/coastal environment with exceptionally high sediment supply and fluctuating relative sea level related to glaciations. A core from a channel fill in the lower part of the succession consists of possibly glaciofluvial gravelly sand intercalated with till. Most of the other cores are dominated by Middle and Upper Pleistocene muddy, massive, partly fissile diamictons interpreted to be mainly tills. Undrained shear strength of these cores ranges from about 20 kN m −2 to more than 300 kN m −2, and both underconsolidated intervals compared to the present burial depth are found. An underconsolidated interval comprising Eemian interglacial, biourbated marine sediments overlain by laminated Weichselian glaciomarine sediments on the outher shelf, is covered by 50–100 m of muddy diamicton. This diamicton is suggested to be mainly till deposited by a late Weichselian ice sheet which was grounded to more than 500 m below present sea level. Earlier Weichselian ice expansions did not reach the outer shelf. Based on the stratigraphy in the shallow cores and seismic interpretation we suggest that there have been five major expansions of grounded ice to the shelf break since ca. 440 ka. The present study suggests that glacial erosion was a major process in the Late Cenozoic denudation of the Barents Sea, and in large areas perhaps as much as 200–250 m of preexisting strata could have been eroded by glaciers since about 440 ka.

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