Nicole J. Baeten

Late Weichselian and Holocene sedimentary environments and glacial activity in Billefjorden, Svalbard

Abstract Swath bathymetry data and one sediment core were used to improve the understanding of the Late Weichselian and Holocene glacier activity in Billefjorden, Svalbard. Grounded ice existed in Billefjorden prior to 11.23 cal ka BP (calendar years before present), depositing a basal till and producing glacial lineations. The glacier front retreated from the central parts to the inner parts of the fjord between c. 11.23 and 11.2 cal ka BP. Annual recessional moraines suggest that this retreat occurred at a rate of up to 170 m a−1. During the early Holocene, the glacier Nordenskiöldbreen was comparatively small and sediment supply to central Billefjorden occurred mainly from the fjord sides. An increase in ice rafting around 7930 cal a BP is ascribed to enhanced sea-ice formation. The activity of Nordenskiöldbreen increased around 5470 cal a BP. Ice rafting was generally low during the past c. 3230 a. This was most likely related to the formation of a more permanent sea-ice cover. Nordenskiöldbreen reached its maximum Holocene extent around AD 1900, generating glacial lineations and depositing a terminal moraine in the inner fjord. Annual recessional moraines were formed during its subsequent retreat. Icebergs from Nordenskiöldbreen generated iceberg ploughmarks during the late Holocene.

Origin of shallow submarine mass movements and their glide planes—Sedimentological and geotechnical analyses from the continental slope off northern Norway

Submarine landslides are often characterized by a basal surface of rupture parallel to the stratigraphy, in which downslope movement is initiated. However, little is known about the sedimentology and physical properties of the sediments within these surfaces. In this study, we present a multiproxy analysis of the sediments collected from a giant piston core penetrating a shallow submarine mass transport deposit, in combination with high-resolution seismoacoustic data to identify and characterize the basal glide plane and the weaker sediments in which movement was initiated. The initial phase of instability consists of a single fracture that formed due to the downslope movement of a mostly intact slab of sediments. The 16 m long core, comprising mostly undisturbed massive and laminated ice-rafted debris-rich clay penetrated this slab. The base of the slab is characterized by a high-amplitude semicontinuous reflection visible on the subbottom profiler data at about 12.5 m depth, interpreted to originate from the glide plane on top of a plumite deposit. This plumite has dilative behavior with pore pressure decrease with increasing shear strain and high undrained shear strength. Movement probably started within contouritic sediments immediately above the glide plane, characterized by higher sensitivities and higher water contents. The occurrence of the mass movements documented in this study are likely affected by the presence of a submarine landslide complex directly downslope. The slide scar of this landslide complex promoted retrogressive movement farther upslope and progressive spreading of strain softening along the slide base and in the slide mass. Numerical models (infinite slope, BING, and retrogressive slope models) illustrate that the present-day continental slope is essentially stable and allow reconstruction of the failure processes when initiated by an external trigger.

Shallow Landslides and Their Dynamics in Coastal and Deepwater Environments, Norway

In this manuscript, we present the first results of integrated slope stability studies to investigate smaller-scale mass movement processes in different physiographic settings of Norway. These include coastal areas (Sorfjord, Finneidfjord), and pristine open ocean settings in intermediate (Vesteralen) and deep waters (Lofoten) on the Norwegian margin. Triggers, pre-conditioning factors and sedimentary processes associated with these landslides are currently not well constrained.

Sediment Failure Affecting Muddy Contourites on the Continental Slope Offshore Northern Norway: Lessons Learned and Some Outstanding Issues

The formerly glaciated continental margin off Norway has experienced a relatively large number of submarine landslides of varying sizes, volumes, and ages originating from contourites deposited on the continental slope. We review: (i) the origin and occurrence of weak layers involved, (ii) sediment disintegration and initial flow, and (iii) sediment run-out and resulting deposits. The following major knowledge gaps, critical for further progress in this field are identified: information on lithology and sediment properties of material recovered from below the depth of conventional coring, and in situ measurements of sediment physical properties at the depth of weak layers.

Submarine mass movements affecting contourites on the continental slope offshore of the Lofoten Islands, North Norway

The Norwegian continental margin has been shaped largely by glacial processes during the last c. 2.7 Ma, including high inputs of glacigenic sediments particularly beyond the mouths of ice streams (e.g. Dahlgren et al. 2005). The Lofoten Islands are located between 68° N and 69° N, west of the former Fennoscandian Ice Sheet that covered most of Scandinavia during glacial times (Fig. 1). The supply of glacigenic sediments to the continental slope west of the Lofoten Islands was relatively low because the alpine relief of the islands acted as a barrier guiding the large westward-flowing palaeo-ice streams draining the ice sheet to the shelf edge both south and north of the Lofoten Islands (e.g. Laberg et al. 2002; Fig. 1b). Sediment input to the continental margin west of the Lofoten Islands has been dominated by contour currents. This led to the development of the Lofoten Drift (Laberg et al. 1999). The drift sediments were deposited mainly during glacial maxima, and have been affected by several submarine mass movements occurring on the middle to lower slope in water depths of 1100–2500 m (Baeten et al. 2013). These failures have volumes of 0.06–8.7 …

First Results of the Geotechnical In Situ Investigation for Soil Characterisation Along the Upper Slope Off Vesterålen: Northern Norway

High-resolution geophysical data reveal the presence of several spatially-isolated, small-scale landslides along the gently dipping (~3–4°) upper slope off Vesteralen, Northern Norway. Dynamic slope stability analysis suggests that seismicity may be largely responsible for the occurrence of these slope failures. The landslides are clustered in two groups, with one group of parallel features with their headwalls in ~500 m water depths. The second group is found in ~800 m water depths.

Ocean-current controlled sedimentation: the Lofoten Contourite Drift, Norwegian Sea

Sediment deposition from ocean-bottom or contour currents leads to the development of contourite drifts. On the continental slope offshore of Norway, contourite drifts have developed from sediment deposition from the alongslope-flowing Norwegian Current which brings warm and saline water masses into the Norwegian Sea. The present pattern of circulation of the Norwegian–Greenland Sea water masses developed as a result of the opening of the Fram Strait separating Greenland and Svalbard to the north from the general subsidence of the Greenland–Scotland Ridge to the south (e.g. Laberg et al. 2005). The Lofoten Contourite Drift is located on the continental slope offshore of northern Norway (Fig. 1). It is a mounded, elongate, separated giant drift ( sensu Faugeres et al. 1999) up to 360 m thick, about 150 km long (along drift axis) and is characterized by a layered, continuous, parallel to slightly divergent seismic signature of medium-amplitude reflections (Fig. 1d). The uppermost part of the drift includes mainly homogeneous or bioturbated mud and sandy mud that is …