Late Quaternary palaeoenvironment and chronology in the Trænadjupet Slide area offshore Norway

The northern mid-Norwegian continental slope was studied based on high-resolution side-scan sonar data, multibeam bathymetry, high-resolution and multichannel seismics together with gravity cores. Sedimentary provinces identified include a partly buried slide on the eastern, inner Vøring Plateau, an area dominated by glacigenic debris flows south-west of the Trænadjupet Slide, the Trænadjupet Slide, and an area of glacimarine sedimentation and a slide scar north-east of the Trænadjupet Slide. The Trænadjupet Slide affected an area of about 14 100 km2 and mobilised about 900 km3 of sediments. Little is known about the areal extent and volume of the older events. The glacigenic debris flows and glacimarine sediments were deposited while the Fennoscandian ice sheet was at the shelf break during the late Weichselian glacial maximum (prior to 13.2 14C kyr BP). Hemipelagic and/or contouritic sedimentation prevailed during the Holocene period. Two large slide scars were probably formed sometime prior to or during the late Weichselian glacial maximum (inner Vøring Plateau and north-east of the Trænadjupet Slide) and another during the mid-Holocene interglacial period immediately prior to 4000 14C kyr BP (the Trænadjupet Slide). The two older scars may represent one event or two separate events. Deposition of poorly permeable glacigenic sediments over high-water-content fine-grained hemipelagic and/or contourites may have prevented water escape and increased failure potential. Thus continental slope areas of episodically high sediment input of glacigenic sediments are prone to failure as illustrated by this study, which has identified at least two large slope failures. Failures have occurred both during glacial maxima, periods of climate deterioration and low global eustatic sea level, and during interglacials as today with improved climatic conditions and a high global eustatic sea level.