Glacial landform assemblages in Spitsbergen fjords from the last full-glacial, deglaciation and the late Holocene

Abstract

Fjords are characteristic features of the western and northern coasts of Spitsbergen. They formed during repeated glacial cycles when grounded glaciers drained large ice sheets occupying the Svalbard–Barents Sea region. Since grounded glaciers often erode and remove pre-existing deposits from fjord basins, depositional sequences in fjords are typically limited to the last glacial–interglacial cycle (e.g. Forwick & Vorren 2010). Holocene sediment drapes in Spitsbergen fjords are not usually thick enough to obscure glacial landforms and deposits from the last full-glacial and deglacial period. Glacier advances related to climatic cooling during the late Holocene, together with glacier surges, have led to the formation of complex landform assemblages close to many fjord heads (e.g. Ottesen & Dowdeswell 2006; Ottesen et al. 2008; Streuff et al. 2015). The floors in the central and outer parts of several Spitsbergen fjords, including Kongsfjorden, Isfjorden, Billefjorden, Sassenfjorden and Tempelfjorden, reveal multiple streamlined sedimentary lineations orientated sub-parallel to fjord axes (Figs 1a, b, c, 2a; e.g. Ottesen et al. 2005; Baeten et al. 2010; Forwick et al. 2010). The ridges are≤5 km long, 15 m high and<500 m wide, with a spacing of up to 800 m; length-to-width ratios exceed 10:1. Elongate landforms with length-to-width ratios smaller than 10:1 are also found in Kongsfjorden and Raudfjorden (e.g. Ottesen & Dowdeswell 2009; MacLachlan et al. 2010). Fig. 1. Examples of glacial landforms and sediments in Spitsbergen fjords. ( a ) Location of study areas (red boxes; map from IBCAO v. 3.0). Red boxes show locations of (b)–(d) and Figure 2. ( b ) Sun-illuminated multibeam-bathymetric image from Billefjorden (after Baeten et al. 2010). Acquisition system Kongsberg EM300. Frequency 30–34 kHz. Grid-cell size 5 m. ( c ) Sun-illuminated multibeam-bathymetric image from Kongsfjorden and southern Krossfjorden (courtesy of Boele Kuipers, Norwegian Hydrographic Service; for details see MacLachlan …