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 subs idence of the Vestbakken volcanic province, which became filled by sed iments from an uplifted Stappen High. By the Middle Eocene, siliciclas tic shelf sediments were deposited and the infill had reached a balanc e with subsidence. Tectonic movements at this time may have caused loc al uplift, which restricted the ventilation of local basins west of th e 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 it s associated depocentre to the south and west of the study area, and w as less important regionally than the Pliocene-Pleistocene phase. The Pliocene uplift first led to local erosion along the margin. Subsequen t subsidence may initially have had a thermal component. This was foll owed by extensive downwarping under the load of large-scale deposition sourced by regional erosion in the Barents Shelf region. An Eocene vo lcanic phase was probably related to the initiation of seafloor spread ing. Isotopically dated volcaniclastic intervals in one of the cores g ive evidence of a Late Pliocene volcanic phase. This event was associa ted with local tectonic movements, which may be part of a regional upl ift in the western-northwestern part of the Barents Sea. Glaciations c aused by the Neogene climatic deterioration became enhanced by uplift, and this led to extensive regional glacial erosion. The main depocent re was offset to the south by ice flow curving around the uplifted are a.