Jaume Llopart

Slope Instability of Glaciated Continental Margins: Constraints from Permeability-Compressibility Tests and Hydrogeological Modeling Off Storfjorden, NW Barents Sea

Climate variations control sediment supply to the continental slope as well as glacial advances and retreats, which (a) cause significant stress changes in the sedimentary column and redistribution of interstitial fluids, (b) induce a particular margin stratigraphic pattern and permeability architecture and (c) are at the origin of isostatic adjustments that may reactivate faults. We test this hypothesis using a combination of geophysical and geotechnical data from the Storfjorden Trough Mouth Fan, off southern Svalbard. The results of compressibility and permeability testing are used together with margin stratigraphic models obtained from seismic reflection data, as input for numerical finite elements models to understand focusing of interstitial fluids in glaciated continental margins and influence on timing and location of submarine slope failure. Available results indicate values of overpressure of 0.23–0.5 (slope-shelf) that persist to present-day. This overpressure started to develop in response to onset of Pleistocene glaciations and reduced by half the factor of safety of the continental slope.

Glacigenic debris-flow deposits, Storfjorden Fan

Glacigenic debris-flow deposits (Laberg & Vorren 1995; Laberg et al. 2012) are the most prominent component of high-latitude trough-mouth fans (TMFs), which develop off fast-flowing ice streams which occupy cross-shelf troughs during full-glacial periods. Glacial erosion and sediment transport to the shelf edge are most effective during glacial maxima; debris-flow deposits therefore represent short periods of a very high input of glacigenic sediments to the continental slope when the ice front reaches the shelf break. Conversely, relatively limited amounts of mostly hemipelagic sediments accumulate on the continental slope during interglacial periods (Dowdeswell et al. 2002). Storfjorden TMF consists of three coalescent lobes (I–III) produced by three ice streams (Fig. 1a, b). It is dominated by an extensive network of gullies on the upper continental slope (Pedrosa et al. 2011; Lucchi et al. 2013) that do not cut back deeply into the continental shelf and are typically 5–20 km long (Fig. 1c, d). The gullies are nearly straight or have a low sinuosity, and are generally less than …