A seismo-stratigraphic analysis of glaciomarine deposits in the eastern Riiser-Larsen Sea (Antarctica) |
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Authors: | K Solli B Kuvaas Y Kristoffersen G Leitchenkov J Guseva V Gandjukhin |
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Institution: | (1) Department of Earth Science, University of Bergen, 5007 Bergen, Norway;(2) VNIIOkeangeologia, 1, Angliysky Ave., 190 121 St. Petersburg, Russia;(3) PMGRE, 24, Pobedy Street, 189510 Lomonosov, Russia |
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Abstract: | Multichannel seismic data from the eastern parts of the Riiser-Larsen Sea have been analyzed with a sequence stratigraphic
approach. The data set covers a wide bathymetric range from the lower continental slope to the abyssal plain. Four different
sequences (termed RLS-A to RLS-D, from deepest to shallowest) are recognized within the sedimentary section. The RLS-A sequence
encompasses the inferred pre-glacial part of the deposits. Initial phases of ice sheet arrival at the eastern Riiser-Larsen
Sea margin resulted in the deposition of multiple debris flow units and/or slumps on the upper part of the continental rise
(RLS-B). The nature and distribution of these deposits indicate sediment supply from a line or a multi-point source. The subsequent
stage of downslope sediment transport activity was dominated by turbidity currents, depositing mainly as distal turbidite
sheets on the lower rise/abyssal plain (RLS-C). We attribute this to margin progradation and/or a more focussed sediment delivery
to the continental shelf edge. As the accommodation space on the lower rise/abyssal plain declined and the base level was
raised, the turbidite channels started to backstep and develop large channel–levee complexes on the upper parts of the continental
rise (RLS-D). The deposition of various drift deposits on the lower rise/abyssal plain and along the western margin of the
Gunnerus Ridge indicates that the RLS-D sequence is also associated with increased activity of contour currents. The drift
deposits overlie a distinct regional unconformity which is considered to reflect a major paleoceanographic event, probably
related to a Middle Miocene intensification of the Antarctic Circumpolar Current. |
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Keywords: | Antarctica Debris flows Deep-sea deposits Riiser-Larsen Sea Seismics Turbidites |
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