The Barents Sea Glaciation History and Its Influence from Petroleum Systems

Jochen Knies¹, Jan Sverre Laberg², Eiliv Larsen¹, and Karin Andreassen^2
1Quaternary and Geology, Geological Survey of Norway, Trondheim, Norway.
²Department of Geology, University of Tromsø, Tromsø, Norway.

Glacial erosion during the Late Plio-Pleistocene (~2.7-0.11 Ma) is regarded to be one major cause for partial or complete drainage of hydrocarbons in the southwestern Barents Sea. In addition, repeated ice and sediment loading have had great influence on hydrocarbon migration routes and the temperature history. Detailed control on the glacial erosion, sediment deposition and ice load (i.e., the glacial history) is therefore an important, however insufficiently utilized factor for identification of the remaining hydrocarbon resources in this region.

Here we present conclusive evidence that the first ice domes existed already in the northern Barents Sea during the middle Miocene (~15-14 Ma). Thereafter, mountainous to coastal-style glaciations on the exposed northern Barents Sea have frequently evolved throughout the Neogene. The first glaciations beyond the coastline occurred concomitantly to the intensification of the Northern Hemisphere glaciations at ~2.7 Ma. Short-term pulses of ice rafted debris in boreholes from the circum-Arctic and Atlantic are indicative for this event. The southwestern Barents Sea, however, was not covered by an ice sheet before ~1.5 Ma. Between ~1.5 Ma and the Saalian glaciations (~0.13 Ma), realistic inferences of at least eight shelf edge glaciations are evident from borehole and acoustic data. During the last glacial cycle (<0.13 Ma) the southwestern Barents Sea was at least four times covered with glacial ice.

Accordingly, glacial erosion in the southwestern Barents Sea is much younger than previously thought. Taken the Last Glacial Maximum (LGM, ~20 ka) as an analogue for the middle-late Pleistocene glaciations in the Barents Sea, the erosional source area are mostly the paleo-ice streams located in the Bear Island Trough, Ingøydjupet and along the mainland coast (Fig. 1) covering an area of about 200,000 km². During the LGM, glacial erosion beneath the paleo-ice streams produced a volume of ~1360 km³ consistent with findings of LGM sediment volumes along the southwestern Barents Sea margin. Hence, estimated volumes of erosion in the southwestern Barents Sea can be balanced by glacial erosion predominantly of the trough areas on the nearby shelf. This leads us to suggest that glacial erosion of the shelf throughout the middle and late Pleistocene was selective i.e. erosion affected the troughs mostly.

AAPG Search and Discover Article #90096©2009 AAPG 3-P Arctic Conference and Exhibition, Moscow, Russia