The Cenozoic western Svalbard margin: sediment geometry and sedimentary processes in an area of ultraslow oceanic spreading

Abstract

The northeastern high-latitude North Atlantic is characterised by the Bellsund and Isfjorden fans on the continental slope off west Svalbard, the asymmetrical ultraslow Knipovich spreading ridge and a 1,000 m deep rift valley. Recently collected multichannel seismic profiles and bathymetric records now provide a more complete picture of sedimentary processes and depositional environments within this region. Both downslope and alongslope sedimentary processes are identified in the study area. Turbidity currents and deposition of glacigenic debris flows are the dominating downslope processes, whereas mass failures, which are a common process on glaciated margins, appear to have been less significant. The slide debrite observed on the Bellsund Fan is most likely related to a 2.5-1.7 Ma old failure on the northwestern Barents Sea margin. The seismic records further reveal that alongslope current processes played a major role in shaping the sediment packages in the study area. Within the Knipovich rift valley and at the western rift flank accumulations as thick as 950-1,000 m are deposited. We note that oceanic basement is locally exposed within the rift valley, and that seismostratigraphic relationships indicate that fault activity along the eastern rift flank lasted until at least as recently as 1.5 Ma. A purely hemipelagic origin of the sediments in the rift valley and on the western rift flank is unlikely. We suggest that these sediments, partly, have been sourced from the western Svalbard-northwestern Barents Sea margin and into the Knipovich Ridge rift valley before continuous spreading and tectonic activity caused the sediments to be transported out of the valley and westward.

Late Pliocene–early Pleistocene deep‐sea basin sedimentation at high‐latitudes: mega‐scale submarine slides of the north‐western Barents Sea margin prior to the shelf‐edge glaciations

“…c). The presence of contouritic sediments have also been suggested within the Pliocene–Pleistocene succession north of the study area (Eiken & Hinz, ) and, in particular, within the same stratigraphic interval along the SW of Svalbard–Bellsund TMF (Amundsen et al ., ) (Fig. a).…”

“…c). Pressure ridges have usually been reported to be associated with debris flow deposits (Eiken & Hinz, ), and they usually occur where mass‐transport complexes are free to spread out across the seafloor in an unconfined manner (Prior et al ., ; Mosar et al ., ; Dahlgren et al ., ; Amundsen et al ., ). For comparison, frontally confined mass‐transport complexes are usually characterized by the development of large‐scale fold and thrust systems (e.g.…”

“…c). This interpretation can be supported by previous studies, which suggested the presence of contouritic sediments within the preglaciogenic late Miocene–Pliocene and late Pliocene–Pleistocene predominantly glaciogenic sediments in the west of Svalbard (Eiken & Hinz, ; Amundsen et al ., ). The onset of contouritic current in the western Svalbard margin has been suggested to be related to opening of the gateway between Svalbard and Greenland, Late Cenozoic climate cooling, or to palaeographic changes (Laberg et al., ).…”

Geological Controls on Fluid Flow and Gas Hydrate Pingo Development on the Barents Sea Margin

“…At our study site located within the Sørkapp‐Hornsund High, only a thin (~35–150 m) drape of Pleistocene low‐permeability glacial sediments exists. The trough mouth fan, which has accumulated products of glacial erosion from the shelf, drastically thickens outside the Sørkapp‐Hornsund High westward and southward along the fault zone (Amundsen et al, ; Eldholm et al, ; Rebesco et al, ; Figure ), causing a thicker seal, which may hinder gas release over a large area (Figure ). Furthermore, it is a depocenter of postglacial sedimentation of cohesive, soft muds (Rasmussen et al, ) favorable for deformation, gas hydrate growth, and carbonate precipitation.…”

Ice-sheet-driven methane storage and release in the Arctic

“…1 ). The region is characterized by a sediment blanket that diminishes from several hundred metres over the continental slope to a minimum of a few tens of metres on the shelf 10 11 . The tectonically induced Forlandsundet graben ( Fig.…”