The Sklinnadjupet slide and its relation to the Elsterian glaciation on the mid-Norwegian margin

The Sklinnadjupet Slide Scar is a large buried feature on the continental slope southeast of the Vøring Plateau. The mass-flow occurred ca. 250,000 years ago on a slope angle of ca. 0.5°, and removed glacial debris from the up to 350-m-thick Naust S sequence on the upper slope. This part of the mid-Norwegian margin appears to have been fairly stable throughout the last 2.8 million years. Naust S represents the third last glacial unit in the Skjoldryggen region, and was deposited during the Elsterian (ca. 400-200 ka BP). During this glaciation, a wide depression was formed on the continental shelf between Haltenbanken and Trænabanken, with the strongest glacial erosion in the west-trending Sklinnadjupet palaeo-trough. This trough leads directly towards the deep, 90-km-wide slide scar, indicating that a local depocentre was formed here before the mass-flow occurred. The shallowest crest of the Helland-Hansen Arch is located below the southern part of the slide scar, and two large craters were formed on the surface of this anticlinal structure. Our model suggests that the deposition of glacial sediments above the Helland-Hansen Arch caused high excess pore pressures along the shallowest crest of this structure and formed a high pore-pressure gradient towards the sea floor on its western flank. An earthquake possibly triggered the initial slide where the slope was steepest west of the crest. Most of the slide scar was already formed when the slide finally eroded into the anticline. High excess fluid pressure subsequently mobilised the diatomaceous oozes in the Helland-Hansen Arch and formed the craters. Much of this material flowed down-slope without being totally disintegrated, and was deposited as levee ridges and mounds above slide deposits from the first phase of the mass-flow. They have previously been wrongly interpreted as diapirs.