Showing papers by "Jan Sverre Laberg published in 2015"

Chronology and extent of the Lofoten–Vesterålen sector of the Scandinavian Ice Sheet from 26 to 16 cal. ka BP

Abstract: The interplay between the onshore and offshore areas during the Last Glacial Maximum and the deglaciation of the Scandinavian Ice Sheet is poorly known. In this paper we present new results on the glacial morphology, stratigraphy and chronology of Andoya, and the glacial morphology of the nearby continental shelf off Lofoten–Vesteralen. The results were used to develop a new model for the timing and extent of the Scandinavian Ice Sheet in the study area during the local last glacial maximum (LLGM) (26 to 16 cal. ka BP). We subdivided the LLGM in this area into five glacial events: before 24, c. 23 to 22.2, 22.2 to c. 18.6, 18 to 17.5, and 16.9–16.3 cal. ka BP. The extent of the Scandinavian Ice Sheet during these various events was reconstructed for the shelf areas off Lofoten, Vesteralen and Troms. Icecaps survived in coastal areas of Vesteralen–Lofoten after the shelf was deglaciated and off Andoya ice flowed landwards from the shelf. During the LLGM the relative sea level was stable until 18.5 cal. ka BP, and thereafter there was a sea-level drop on Andoya. Thus, relative sea level (i.e. a sea level rise) does not seem to be a driving mechanism for ice-margin retreat in this area but the fall in sea level may have had some importance for the grounding episodes on the banks during deglaciation. The positions of the grounding zone wedges (GZWs) in the troughs are related to the morphology as they are often located where the troughs narrow.

The Kongsfjorden Channel System offshore NW Svalbard: downslope sedimentary processes in a contour-current-dominated setting

Abstract: Submarine channel systems on and off glaciated continental margins can be up to hundreds of kilometres long, tens of kilometres wide and hundreds of metres deep. They result from repeated erosion and various downslope processes predominantly during glacial periods and can, therefore, provide valuable tools for the reconstruction of past ice-sheet dynamics. The Kongsfjorden Channel System (KCS) on the continental slope off northwest Svalbard provides evidence that downslope sedimentary processes are locally more dominant than regional along-slope sedimentation. It is a relatively short channel system (~120 km) that occurs at a large range of water depths (~250–4000 m) with slope gradients varying between 0° and 20°. Multiple gullies on the Kongsfjorden Trough Mouth Fan merge to small channels that further merge to a main channel. The overall location of the channel system is controlled by variations in slope gradients and the ambient regional bathymetry. The widest and deepest incisions occur in areas of the steepest slope gradients. The KCS has probably been active since ~1 Ma when glacial activity on Svalbard increased and grounded ice expanded to the shelf break off Kongsfjorden repeatedly. Activity within the system was probably highest during glacials. However, reduced activity presumably took place also during interglacials.