Post-glacial sand drifts burying De Geer moraines on the continental shelf off North Norway

Abstract

Glacial landforms are continuously modified by sedimentary processes after deglaciation. Examples of post-depositional modification occur on the continental shelf off Vesteralen, North Norway, an area that is thought to have been covered by a relatively slow-flowing or stagnant ice dome during the Last Glacial Maximum (LGM) (Ottesen et al. 2005). In this period, the Lofoten-Vesteralen archipelago would have been largely sheltered from fast-flowing ice streams of the Fennoscandian Ice Sheet draining NE and SE of the area. Multibeam bathymetry nevertheless reveals evidence of local glacial activity on the continental shelf offshore Vesteralen, including glacial lineations indicative of faster ice-flow in cross-shelf troughs (Elvenes 2009). After the ice retreated from the shelf, glacial and glacimarine deposits on the surrounding shallow banks were eroded and reworked by waves and currents. Later winnowing of shell material has led to deposition of bioclastic sand in sand fields (Boe et al. 2009). On the present-day seafloor, sandy sediment drifts are migrating over moraines and other glacial deposits, burying and obscuring the surficial signatures of glaciation. The narrow continental shelf extending about 20–40 km off the Vesteralen archipelago is characterized by many shallow banks (40–120 m deep) intersected by 100–500 m deep, steep-sided troughs. These troughs may be cross-shelf or coast-parallel, and several contain series of transverse, evenly spaced ridges …