Introduction: an Atlas of Submarine Glacial Landforms

Abstract

Glacial landforms and sediments exposed sub-aerially have been the subject of description, analysis and interpretation for more than a century (e.g. De Laski 1864; De Geer 1889). Indeed, such features provided important initial observations informing Louis Agassiz's ideas that ice was a key instrument in sculpting the landscape and that glaciers and ice sheets had extended to mid-latitudes during the past, implying that Earth's climate must have changed considerably through time (Agassiz 1840). It is only in the last few decades that attention has begun to focus on the marine evidence for the past growth and decay of ice sheets that is recorded in submarine landforms and sediments preserved on high-latitude continental margins. This interest has been driven, in part, by the recognition that sediments deposited below wave-base are often well preserved in the Quaternary geological record, and may be less subject to erosion and reworking than their terrestrial counterparts. In addition, new marine-geophysical technologies have enabled increasingly high-resolution imaging and penetration of the high-latitude seafloor, most notably using multibeam swathbathymetric and three-dimensional (3D) seismic-reflection methods, and modern ice-strengthened and ice-breaking research vessels have allowed the effective deployment of these increasingly sophisticated instruments in the often ice-infested waters of the Arctic and Antarctic seas.The geological record from high-latitude continental margins is now recognized to provide key information on former ice-sheet extent, the direction and nature of past ice flow and dynamics, and a well-preserved window on the detailed form and composition of former ice-sheet beds (e.g. Ottesen et al. 2005;Anderson et al. 2014;Jakobsson et al. 2014). The geometry and distribution of submarine glacial landforms on the seafloor, and the underlying glacial-sedimentary stratigraphic record with which they are associated, is the topic of this volume. The aims and purpose of the Atlas are: (1) to provide a comprehensive set of examples of the full range of individual submarine glacial landforms and assemblages of landforms produced beneath and at the marine margins of glaciers and ice sheets; and (2) to integrate this information over entire fjord -shelf -slope systems across the full climatic range of glacier-influenced marine settings, in order to better understand the morphology and architecture of glacimarine environments. This evidence is used to reconstruct the growth, decay and dynamics of past ice sheets, including those of Quaternary and more ancient ice ages.

Sedimentary processes at ice sheet grounding‐zone wedges revealed by outcrops, Washington State (USA)

“…Observations of GZWs on deglaciated continental margins usually rely upon marine geophysical methods, such as multibeam bathymetry and other lower frequency seismic data, which depict the planform geometry and image the interior stratigraphy of these deposits (Shipp et al, 1999;Winsborrow et al, 2010;Bart and Cone, 2012;Dowdeswell and Fugelli, 2012;Batchelor and Dowdeswell., 2015;Anderson and Jakobsson, 2017;Bart et al, 2017). As has been documented in many studies, the deposit morphology is asymmetric, overlying a glacial unconformity formed by previous ice advance over the seafloor.…”

Glacial sedimentation, fluxes and erosion rates associated with ice retreat in Petermann Fjord and Nares Strait, NW Greenland

“…Describing and interpreting the seismic stratigraphy of unlithified sediments in glacier-influenced settings provides the largescale geometries of deposits that can then be related to glacial landforms observed in bathymetry datasets and with sediments directly sampled by seafloor coring (cf. Dowdeswell et al, 2016). In high-latitude fjords and glacial troughs beyond the coastline, the unlithified sediment accumulation may be taken to represent material deposited since these areas were last occupied by grounded ice, during ice retreat following the LGM (e.g., Aarseth, 1997;Gilbert et al, 1998;Hjelstuen et al, 2009;Hogan et al, 2012).…”

The relationship between ice sheets and submarine mass movements in the Nordic Seas during the Quaternary

“…The geological record of high-latitude continental margins contains key information on former ice sheets (Dowdeswell et al, 2016b). Specific landforms and sedimentary sequences have been used to provide information on the extent of palaeo-ice sheets as well as the direction and nature of past ice flow and dynamics (Clark, 1993;Ottesen et al, 2005;Ottesen and Dowdeswell, 2006;Ó Cofaigh et al, 2013a;Jakobsson et al, 2014;Hogan et al, 2016).…”

“…Under full-glacial conditions, the position of each system and thus the dominance of a given mechanism for sediment delivery, shifts its position on the continuum ( Fig. 1b; Dowdeswell et al, 2016b).…”