A modern canyon-fed sandy turbidite system of the Norwegian continental margin

The sedimentary processes and evolution of a presumably old but still relatively recent active canyon-fed sandy turbidite system on the Norwegian continental margin, the Andoya Canyon - Lofoten Basin Channel system, were studied using high-resolution seismic, deep-towed side-scan sonar records and cores (gravity and vibro cores). The canyon has a length of about 40 km and represents a continental slope incision of up to 1100 m. From the canyon mouth, a deep-sea channel up to 30 m deep and 3 km wide continues for approximately 200 km into the deepest part of the Lofoten Basin. The most recent activity of this system was deposition of coarse-grained sediments from turbidity currents as indicated by sediment waves on the canyon floor, thin sand layers within the levees and a sandy lobe at the channel mouth. From this modern system we suggest that there are a number of features that could be of relevance for hydrocarbon exploration of deep-water turbidite systems: a) this canyon-fed system probably received sand from piracy of shelf sediments and/or canyon wall erosion, b) the sandy deposits are located in the deepest part of the basin, about 200 km outside the canyon mouth, c) the sandy lobe is connected to the source area by a straight channel with poorly developed mud-rich levees, d) the sandy deposits have a sheet-like or tabular geometry, e) post-depositional deformation of the sand could be widespread suggesting rapid sand deposition. Thus, modern, canyon-fed sandy turbidite systems provide additional data relevant for future hydrocarbon prospecting in deep-water areas

The Andoya Slide and the Andoya Canyon, north-eastern Norwegian-Greenland Sea

Based on GLORIA side-scan sonar imagery, echo sounder records, 3.5 kHz profiles, multichannel seismics and gravity cores the Andøya Slide and Andøya Canyon, north-eastern Norwegian–Greenland Sea were mapped and interpreted. The Andøya Slide covers an area of about 9700 km2 of which the slide scar area comprise ca. 3600 km2. The slide has a total run-out distance of about 190 km. Slope failure is inferred to have occurred during the Holocene because the slide scar has prominent relief on the present sea floor. The area of sediment removal is characterised by an irregular relief were relatively consolidated sediments are exposed at the sea floor. Little or no unconsolidated sediments overlies the slide deposits. Earthquake activity is inferred to have triggered the slide. A Holocene age of the Andøya Slide implies that three giant slides (the Storegga, Trænadjupet and Andøya Slides) have occurred along the continental slope of Norway during the last 10,000 years. A large canyon, the Andøya Canyon, is located immediately south of the Andøya Slide. On the upper slope, the canyon has been incised about 1000 m in the bedrock, and the maximum width at the bottom and between the canyon shoulders is 2 and 12 km, respectively. The Andøya Canyon represents the upper part of the Lofoten Basin Channel. Based on analogy with other deep-sea canyon/channel systems, the Andøya Canyon/Lofoten Basin Channel is possibly of pre-Quaternary age. Holocene sediments recovered from within the canyon, and draping the flanking channel deposits, indicate that the Andøya Canyon is not presently active and has probably not been active during the Holocene. During the Holocene, the canyon acted as a trap for sediments settling from the winnowing Norwegian Current

Late Quaternary palaeoenvironment and chronology in the Traenadjupet 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 Voring Plateau, an area dominated by glacigenic debris flows south-west of the Traenadjupet Slide, the Traenadjupet Slide, and an area of glacimarine sedimentation and a slide scar north-east of the Traenadjupet Slide. The Traenadjupet Slide affected an area of about 14100 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 Voring Plateau and north-east of the Traenadjupet Slide) and another during the mid-Holocene interglacial period immediately prior to 4000 14C kyr BP (the Traenadjupet 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 leve