Cenozoic sedimentation along the southwestern Barents Sea margin in relation to uplift and erosion of the shelf

The distribution of Cenozoic sediments along the southwestern Barents Sea margin reflects the progressive opening of the Norwegian-Greenland Sea towards the north. The Lofoten Basin fill consists of Early to Middle Tertiary mostly undeformed sequences of great lateral extent, overlain by a huge sedimentary wedge which extends over both continental and oceanic crust. This wedge, the Bjørnøya Fan, comprises 3–4 km of Late Cenozoic deposits. Regional seismic lines enable tracing of sequence boundaries westward until they terminate onto oceanic basement of known age, thus providing maximum ages of the sediments above. Additional age constraints come from exploration wells and shallow boreholes in the southwestern Barents Sea as well as paleoenvironmental indicators from deep sea drilling. The pre-glacial units (sequences Te1–Te4) are controlled by the plate tectonic setting and basin geometry at the time of deposition. The seismic stratigraphy of the Bjørnøya Fan (reflectors R1–R7) indicates three main phases of glacial erosion and sedimentation: (1) 2.3 Ma (R7) dates the onset of extensive continental shelf glaciations, (2) 1.0 Ma (R5) marks an increase in the intensity of glaciations, giving rise to increased accumulation rates and the onset of large-scale mass movements and (3) 0.44 Ma (R1) marks the end of ne erosion in the outer parts of the Bjørnøya Trough. The wedge represents about 70% of the sediments in the Lofoten Basin and its young age indicates that a large thickness of sedimentary strata has been eroded and deposited over a short geological time period. Using volumetric calculations, Cenozoic erosion and sedimentation rates have been quantified. Furthermore, the sediment yield and denudation rates for the main glacial sequences in the Bjørnøya Fan are calculated.