Glacial sediment and landform record offshore NW Scotland: a fjord-shelf-slope transect through a Late Quaternary mid-latitude ice-stream system
Current estimates of ice-mass loss from ice sheets vary, but there is consensus that the rate of loss has increased over the last two decades from c. 100 to c. 400 Gt a−1 with the great majority occurring within ice-stream systems (e.g. Shepherd et al. 2012; Hanna et al. 2013). Where ice streams ter...
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| Format: | Book Part |
| Language: | unknown |
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Geological Society of London
2016
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| Online Access: | http://nora.nerc.ac.uk/id/eprint/515812/ http://mem.lyellcollection.org/content/46/1/421 |
| Summary: | Current estimates of ice-mass loss from ice sheets vary, but there is consensus that the rate of loss has increased over the last two decades from c. 100 to c. 400 Gt a−1 with the great majority occurring within ice-stream systems (e.g. Shepherd et al. 2012; Hanna et al. 2013). Where ice streams terminate in open-marine settings large volumes of ice are discharged into the oceans via calving, as currently seen in Pine Island Bay, West Antarctica or at Jakobshavn Isbrae, West Greenland. At the Last Glacial Maximum (LGM), an ice sheet covered more than two-thirds of the British Isles (50–61° N) and reached onto the continental shelf, in places extending to the shelf edge in the west (Gibbard & Clark 2011; Clark et al. 2012). In this contribution we summarize the Pleistocene sediment and landform record of a large mid-latitude ice stream that once drained the NW sector of the British–Irish Ice Sheet (BIIS). Drawing on marine geophysical and geological data from the NW UK continental shelf collected over four decades, we describe the main elements of the system along a transect stretching for >300 km from the heads of the fjords to beyond the shelf slope. The work draws largely on previously published research (Stoker et al. 1993, 2006, 2009, 2010; Stoker & Bradwell 2005; Bradwell et al. 2007, 2008a, b; Bradwell & Stoker 2015a, b), but includes some new insights and interpretations. The bedrock geology of NW Scotland and the Hebrides Shelf is structurally complex and lithologically diverse. Unsurprisingly, the geological structure imposes a general first-order control on the topography of the region with resistant upstanding Precambrian rocks typically forming the extant landmasses and bathymetric highs, and the weaker Mesozoic cover rocks flooring |
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