Hill–hole pairs on the Norwegian continental shelf

Abstract

Glacitectonic landforms and processes on the Norwegian continental shelf were first described by Saettem (1990). Over the past two decades, multibeam bathymetry has revealed a number of glacitectonic features. Three-dimensional (3D) seismic data have also shown that glacitectonic processes are more widespread than previously thought (Andreassen et al. 2004). Hill–hole pairs have been observed mainly on land (Moran et al. 1980; Aber & Ber 2007) and few examples are known from previously glaciated continental shelves (Fig. 1). Hill–hole pair sedimentology and structural geology have been examined at the terrestrial margin of the former North American Ice Sheet (Moran et al. 1980). The hills comprise thrust-block moraines apparently formed at former ice margins and the holes are source areas. Hill–hole axes are sub-parallel to inferred ice-flow direction. Compressive subglacial stresses, leading to tectonism, are thought to be induced by basal freezing close to thin ice-sheet margins (Moran et al. 1980). Fig. 1. Hill–hole pairs on the continental shelf off Norway. ( a ) Multibeam image of the Steinbitryggen–Sopphola hill–hole pair (S-S) and two less well-defined glacitectonic pairs (B, C) on Tromsoflaket bank. ( b ) Multibeam image of Hesteskoen hill–hole pair on easternmost Traenabanken. Acquisition system for (a) …