Sedimentary processes and seabed morphology of the Southwest Greenland margin

Abstract

Bathymetric and seismic data from the Southwest Greenland margin have been used to provide an integrated shelf-to-basin overview of the margin architecture between 57° N and 64° N. A variety of glacially formed morphologic features, contour current-related erosion and sedimentary deposits, and evidence of downslope sediment transport via canyons, channels and gullies is found here. The study area is characterized by two major canyons bordering Fylla Bank in the northern part and a narrow shelf and steep slope to the south, where erosion due to strong boundary currents occur down to c. 3000 m water depth. The narrow shelf area appears to be an intra-ice stream area, and numerous channels and gullies on the upper slope point to hyperpycnal melt water release from a stable or retreating wide ice front. Further southward, the shelf is widening and the morphology indicates dominance of former ice stream activity. This difference in glaciation style may reflect the different bedrock types. Sedimentary and morphologic characteristics of the Fylla Bank canyons and some of the slope gullies and channels point to actual cascading of dense winter water or hyperpycnal melt water flow from the shelf. Deep-water channels at the base of the slope evidence transport of Greenland-derived sediment to the central Labrador Sea basin and buried channels further west indicate a former contribution to the Northwest Atlantic Mid-Ocean Channel (NAMOC) system. However, in contrast to widespread turbidite channels on the present seabed bordering NAMOC to the west, east of NAMOC contourite deposits have largely covered the deep-water tributary turbidite channels originating from the Greenland margin.