Sediments and sedimentation at the NE Faeroe continental margin; contourites and large-scale sliding

Abstract

High-resolution seismic profiles of the NE Faeroe continental margin show a wedge-shaped sedimentary sequence of up to 2 km thickness on top of lower Tertiary basaltic basement. The sedimentary section can be divided into four major seismic sequences separated by unconformities. The uppermost upper slope deposit is interpreted as a contourite which formed later than the Mid-Miocene by the southerly flow of bottom water along the margin of the SW Norwegian Sea, which is subsequently deflected to the east by the NE Faeroe continental margin and Fugloy Ridge. A scoured channel about 85–90 m deep at about 1000 m water depth associated with the contourite partially follows and modifies a preexisting slump scar. Large-scale slumping and sliding of the middle and lower continental slope below 1500 m water depth have affected sediments of presumably Miocene, Pliocene and Quaternary age. A TOBI deep-tow side-scan sonar mosaic composed of ten lines recorded in 1995 semi-parallel to the slope, shows that mass flow deposits are partially covered by recent contourite sediments on the middle slope. The slump complex at the middle/lower continental slope is younger and has a steep, 250–300 m, irregular, deep main scarp and very large, sometimes rotated blocks near the main scarp. At the base of the slide, numerous 10–15 km long, narrow tracks with individual blocks at the end are found. Several types of debris flows have been mapped, some with a longitudinal flow fabric.