History of an ice stream (Storfjorden, NW Barents Sea): Impacts on sedimentation, margin hydrogeology and slope failure

IPY2012 Conference Montréal. From Knowledge to Action, 22-27 April 2012, Montréal, CanadaThe mechanisms of sediment transfer from the base of ice sheets to the continental margins determine the stratigraphic architecture and sedimentation style of glaciated continental margins and control the pathways of fluid migration and massive slope failure. The Spanish projects SVAIS and DEGLABAR and the Italian projects EGLACOM and MELTSTORM, all within the frame of International Polar Year (IPY) Activity 367 (NICE -STREAMS; Neogene ice streams and sedimentary processes on high-latitude continental margins) are using a series of geophysical (multibeam mapping, seismic reflection profiling) and geological/geotechnical techniques (sediment coring, dating and physical properties analysis), to unravel the Quaternary glacial and sedimentary history of a polar continental margin in response to ice sheet dynamics: the Storfjorden Trough and Trough Mouth Fan, off southern Svalbard. The build-up of the sedimentary structure of this margin appears to be controlled by short-lived episodes of extreme sedimentation. Deglaciations, when the ice stream is grounded at or near the continental shelf edge, produce terrigenous sediment focusing on the upper continental slope in the form of interlaminated plumite sequences, consequence of the initial subglacial meltwater outbursts. The dating of top and bottom of post-LGM plumites suggests that deposition might have occurred in a few hundred years with an extremely high sedimentation rate of 3.2 cm a-1. Glacial maxima that may last a few thousand years produce tens of m of massive diamictons (Glacigenic Debris Flows; GDF), so that 45 m of deposit would also result in high sediment accumulation rates of 1.1 cm a-1. The Quaternary style of sediment accretion in this margin and its architecture appear to depend on alternation of these two sediment types and their rates of accumulation. We observe that lateral distribution of GDFs and plumites depends on position of ice streams and the history of their retreat from the shelf edge. Physical properties and modeling h ave shown that the distribution of different sediment types and rapid loading from sediments delivered by ice-streams induces important stress changes in polar continental margins that help explaining the distribution through space and time of observed massive slope failures. Current work is aimed at elucidating how ice loading and unloading of continental margins acts to modify interstitial fluid flow patterns. We also aim at establishing past ice thickness along the path of a retreating ice stream using the preconsolidation pressure of tills measured in consolidation cellsPeer Reviewe