Seabed sedimentary environments and sediments (genesis) in the Nordland VI area off northern Norway

Abstract

This report presents maps of sedimentary environments and seabed sediments (genesis) in the Nordland VI management area off northern Norway. The maps, which cover about 25 000 km\u00B2 and water depths from 60 m to 2700 m, are based on multibeam echosounder data (bathymetry and backscatter), 215 video lines each 700 m long, seabed sediment samples from 40 stations (grab, boxcore and multicore) and 5500 km of sub-bottom profiler data. The sedimentary environment map has 6 classes, focussing on present depositional environments (erosion and deposition). Large parts of the Nordland VI continental shelf are dominated by erosion processes, but some deposition occurs in topographic depressions and glacial troughs like Trænadjupet and Vesterdjupet. Hemipelagic sediments are deposited in deep water areas on the continental slope and abyssal plain. The seabed sediments (genesis) map comprises a geological interpretation of the uppermost few metres of the seabed, and has 10 classes. On the continental shelf, we find marine suspension deposits, bedload (traction) deposits, bioclastic sediments, till and bedrock with thin or discontinuous sediment cover. The continental slope is dominated by mass movement deposits and a major contourite deposit with the following classes: contourite, debris flow deposit, mass movement deposits and hemipelagic sediments, mass movement deposit (locally covered by younger sediments), debris flow deposits and laminated sediments (>1m) underlain by debris flow deposits.