THE CENTRAL LABRADOR SEA - FACIES AND DISPERSAL PATTERNS OF CLASTIC SEDIMENTS IN A SMALL OCEAN-BASIN

The upper 500 m of the 2 km thick sedimentary section in the central Labrador Sea consists of Upper Pliocene-Pleistocene clastic sediments associated with the globally unique submarine trunk channel of the Northwest Atlantic Mid-Ocean Channel (NAMOC) and its system of tributaries. Turbidity currents in the NAMOC fractionate their sediment load into fine-grained, mostly silty-clayey spill-over sediments on the natural levees, and coarse-grained channel-fill sediments. The natural levees of the NAMOC are composite features containing shallow second-order channels (tributaries and satellite channels) which have their own, subdued levees. These shallow channels are much less efficient in fractionating the sediment into coarse and fine fractions compared to the NAMOC. The second-order levees are sandy. Based on high-resolution seismic profiles and sediment cores, eight different facies have been differentiated in the surface sediments of the central Labrador Basin: (1) deep channel-fill facies on the NAMOC floor; (2) slide- and slump facies on the NAMOC walls; (3) spill-over facies on the NAMOC levees; (4) channel-fill facies of shallow, second-order channels; (5) sandy spill-over facies of shallow, second-order channels; (6) debris-flow deposits on the NAMOC levees; (7) pelagic sediments with ice-rafted debris; and (8) contourites. © 1990.