CENOZOIC MARGIN DEVELOPMENT AND EROSION OF THE BARENTS SEA - CORE EVIDENCE FROM SOUTHWEST OF BJORNOYA

Five stratigraphic boreholes at the western Barents Sea margin reveal an evolution from a Palaeocene normal shelf setting to a complex Late Cenozoic offshore-marginal marine system influenced by mass flows, and finally a glacially-influenced shelf environment. Palaeocene epeiric sea sedimentation was sourced by erosion at the Stappen High. Earliest Eocene extension associated with volcanism was followed by rapid subsidence of the Vestbakken volcanic province, which became filled by sediments from an uplifted Stappen High. By the Middle Eocene, siliciclastic shelf sediments were deposited and the infill had reached a balance with subsidence. Tectonic movements at this time may have caused local uplift, which restricted the ventilation of local basins west of the Stappen High, but marine conditions existed in the area until Early Oligocene times, when subaerial exposure was caused by tectonic uplift and probably also a fall in eustatic sea-level. Pronounced Oligocene and Pliocene unconformities reflect major events of uplift and erosion at the margin, and abundant fossil reworking indicates erosion of the uplifted Cretaceous and Tertiary strata. The Oligocene erosion had its associated depocentre to the south and west of the study area, and was less important regionally than the Pliocene-Pleistocene phase. The Pliocene uplift first led to local erosion along the margin. Subsequent subsidence may initially have had a thermal component. This was followed by extensive downwarping under the load of large-scale deposition sourced by regional erosion in the Barents Shelf region. An Eocene volcanic phase was probably related to the initiation of seafloor spreading. Isotopically dated volcaniclastic intervals in one of the cores give evidence of a Late Pliocene volcanic phase. This event was associated with local tectonic movements, which may be part of a regional uplift in the western-northwestern part of the Barents Sea. Glaciations caused by the Neogene climatic deterioration became enhanced by uplift, and this led to extensive regional glacial erosion. The main depocentre was offset to the south by ice flow curving around the uplifted area.