Sea-bed sediments and sediment accumulation rates in the Norwegian part of the Skagerrak
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Grain-size analysis show that the sea-bed sediments over large areas in the Norwegian Trench and along its northern slope consist of homogeneous silty clay with a clay content of 50-75% and generally less than 2% sand. Sediments on the plateau along the Norway-Denmark median line are dominated by fine and very fine sands, which become coarser at shallower water depths towards the southeast, were sand constitutes up to 80% of the sediments, and silt and clay approximately 10% each. These sediments are transported into the Skagerrak mainly by the Atlantic Current, the currents from the North Sea and the Jutland Current, and originate from sea-floor erosion in the North Sea, from rivers on the continent and in Britain and from coastal erosion between Denmark and the English Channel. Sedimentation rates in the Norwegian Trench and on the plateau along the Norway-Denmark median line are generally 10-20 cm\/100 years, increasing to more than 30 cm\/100 years in the southeastern parts of the investigated area. Areas of sedimentation rates >50 cm\/100 years are located on the southeastern and eastern slopes of the Norwegian Trench. Areas of high sedimentation rates generally occur where there is a reduction in hydraulic energy and sediment transporting competency of the ocean currents. It is estimated that 18.6 mill. tons of sediment (dry weight) accumulate in the Norwegian part of the Skagerrak annually.