Late Quaternary seismic stratigraphy and geological development of the south Vøring margin, Norwegian Sea

Abstract

High-resolution seismic data and sediment cores show that an up to 280 m thick sedimentary sequence has been deposited on the south Vøring margin, off mid-Norway, the last ca 250 ka. The sedimentary succession has been divided into six seismic units, dominated by hemipelagic sediments. Five wedge-shaped massive sequences, of marine isotope stages 8, 6 and 2, interfinger the hemipelagic deposits on the upper slope. The wedge-shaped sequences represent glacigenic debris flows that have been fed by till transported to the shelf edge by grounded ice sheets during maximum glaciations. The hemipelagic units show well-defined depocentres, of various thicknesses, on the upper continental slope. Seismic facies interpretation indicates that the sediment distribution locally has been controlled by currents. Commonly, the hemipelagic units are characterised by parallel and continuous reflectors. However, the second youngest unit identified, deposited between 15.7 and 15.0 14C ka BP, is acoustic transparent. We suggest that this unit has been sourced by along-slope transported meltwater plume deposits, released during the initial stage of the last deglaciation of the Norwegian Channel. The hemipelagic sedimentation rates have varied considerably throughout the studied time period. Until ca 21 14C ka BP the rates did not exceed 1.4 m/kyr, whereas during the Last Glacial Maximum the rates increased and reached values of about 36 m/kyr before decreasing again at ca 15 14C ka BP. Observation of iceberg scourings, of MIS 8 age, about 800 m below the present day sea level, suggest that the south Vøring margin has subsided by a rate of 1.2 m/kyr in the Late Quaternary.