Glacially eroded cross-shelf troughs surrounding Iceland from Olex data

Abstract

Iceland is surrounded by a continental shelf of around 100 km in width, sloping gently towards a shelf break at 250–400 m below sea level. Incised into the shelf are numerous cross-shelf troughs positioned radially and mostly reaching the shelf-edge. The troughs are typically about 100 km long and 20 km wide. They vary in depth between 15 and 350 m and are interpreted to have formed by glacial erosion beneath fast-flowing ice streams or outlet glaciers of former Icelandic ice sheets that extended to the shelf-break (Ingolfsson & Norddahl 1994). Bathymetric images combining interpolated depth-soundings from Olex (multiple single-beam echo-sounder lines; http://www.olex.no/index_e.html) and IBCAO v. 3.0 (Jakobsson et al. 2012) databases show that the Icelandic continental shelf is incised by numerous linear to curvilinear depressions, positioned radially (Fig. 1a). These troughs are generally relatively short, narrow and straight in the eastern and southern areas of the continental shelf, large and long on the western shelf, and deep, long, sinuous and distributive on the northern shelf (Fig. 1). Their locations and geometries are shown in Figure 1a and their dimensions recorded in the table. Cross-profiles of the troughs vary from symmetrical and flat-bottomed to asymmetrical and U- or V-shaped (Fig. 1e). Prominent breaks …