Late Quaternary glacigenic contourite, debris flow and turbidite process interaction in the Faroe-Shetland Channel, NW European continental margin

Abstract

Abstract The Faroe-Shetland Channel is an important conduit or gateway for the southward flow of cold bottom waters formed in the Norwegian Sea. This Norwegian Sea Overflow Water (NSOW) finds several spillover channels across the Wyville-Thomson Ridge, eventually descending into the northern Rockall Trough and Iceland Basin. The Neogene channel floor succession predominantly displays a broad sheeted drift geometry. Bottom current scours and channels were apparently inherited from an episode of enhanced bottom current activity in late Oligocene/early Miocene. The late Quaternary channel-floor succession is dominated by distal glaciomarine sediments, derived from the shelf and slope during glacial stages and mostly transported by ice-rafting. Glacigenic debris flows and minor turbidity currents were also active across the slope region. Consequently, the principal channel-floor facies are glacigenic contourites that show extensive bioturbation, rare primary structures, mixed composition and marked grain size variation. These features indicate the important influence of cyclical fluctuations in bottom current velocity throughout both stadial and interstadial or interglacial periods. However, the concentration of sandy contourites, erosive surfaces and top-only contourites during interstadials/interglacials and during phases of marked cooling or warming testify to the significance of climate-control on contourite deposition.