Suspension sedimentation of coarse silt and sand in northern Skagerrak: textural and mineralogical trends

Abstract

The minor coarse-silt and sand fraction of muddy bottom sediments at 74 sites in northern Skagerrak is interpreted to have been mostly transported in suspension, aided by frequent reworking and the buoyancy of large aggregates. The overall sediment fining trend towards the Norwegian Trench is consistent with changes of bathymetry. Sediments in shallow shelf settings are mainly transported by a combination of traction and near-bottom suspension processes predominate on the trench slopes, whereas in the bottom of the trench there is a more balanched combination of near-bottom suspension and hemipelagic suspension deposition. Heavy-mineral distributions have weak geographic trends. due to the natural variability, and relatively non-selective and random character of the processes transporting coarse-silt and sand in suspension. Only biotite has a well developed distribution pattern and a relatively good correlation with grain size, probably related to single-particle transport together with fine silt. With consideration for the interpretative limitations of the individual heavy-mineral distributions, it is valuable to evaluate several mineral trends simultaneously, as well as the grain-size trends, in order to interpret patterns. Transport from southern areas and from the north is indicated.