The Cenozoic western Svalbard margin: sediment geometry and sedimentary processes in an area of ultraslow oceanic spreading
2011
Amundsen, Ingrid Marie Hasle | Blinova, Maria | Hjelstuen, Berit Oline | Mjelde, Rolf | Haflidason, Haflidi
The northeastern high-latitude North Atlantic ischaracterised by the Bellsund and Isfjorden fans on thecontinental slope off west Svalbard, the asymmetricalultraslow Knipovich spreading ridge and a 1,000 m deeprift valley. Recently collected multichannel seismic profilesand bathymetric records now provide a more completepicture of sedimentary processes and depositional environmentswithin this region. Both downslope and alongslopesedimentary processes are identified in the study area.Turbidity currents and deposition of glacigenic debris flowsare the dominating downslope processes, whereas massfailures, which are a common process on glaciated margins,appear to have been less significant. The slide debriteobserved on the Bellsund Fan is most likely related to a2.5–1.7 Ma old failure on the northwestern Barents Seamargin. The seismic records further reveal that alongslopecurrent processes played a major role in shaping the sedimentpackages in the study area. Within the Knipovich riftvalley and at the western rift flank accumulations as thickas 950–1,000 m are deposited. We note that oceanicbasement is locally exposed within the rift valley, and thatseismostratigraphic relationships indicate that fault activityalong the eastern rift flank lasted until at least as recently as1.5 Ma. A purely hemipelagic origin of the sediments inthe rift valley and on the western rift flank is unlikely. Wesuggest that these sediments, partly, have been sourcedfrom the western Svalbard—northwestern Barents Seamargin and into the Knipovich Ridge rift valley beforecontinuous spreading and tectonic activity caused thesediments to be transported out of the valley and westward.
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