Geophysical surveys of the sediments of Loch Ness, Scotland: implications for the deglaciation of the Moray Firth Ice Stream, British-Irish Ice Sheet

Turner, Andrew, Woodward, John, Dunning, Stuart, Shine, Adrian, Stokes, Chris and Ó Cofaigh, Colm (2011) Geophysical surveys of the sediments of Loch Ness, Scotland: implications for the deglaciation of the Moray Firth Ice Stream, British-Irish Ice Sheet. Journal of Quaternary Science, 27 (2). pp. 221-232. ISSN 0267-8179

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Abstract

We present results from three geophysical campaigns using high-resolution sub-bottom profiling to image sediments deposited in Loch Ness, Scotland. Sonar profiles show distinct packages of sediment, providing insight into the loch’s deglacial history. A recessional moraine complex in the north of the loch indicates initial punctuated retreat. Subsequent retreat was rapid before stabilisation at Foyers Rise formed a large stillstand moraine. Here, the calving margin produced significant volumes of laminated sediments in a proglacial fjord-like environment. Subsequent to this, ice retreated rapidly to the southern end of the loch, where it again deposited a sequence of proglacial laminated sediments. Sediment sequences were then disturbed by the deposition of a thick gravel layer and a large turbidite deposit as a result of a jo¨kulhlaup from the Spean/Roy ice dammed lake. These sediments are overlain by a Holocene sheet drape. Data indicate: (i) a former tributary of the Moray Firth Ice Stream migrated back into Loch Ness as a major outlet glacier with a calving margin in a fjord-like setting; (ii) there was significant sediment supply to the terminus of this outlet glacier in Loch Ness; and (iii) that jo¨kulhlaups are important for sediment supply into proglacial fjord/lake environments and may compose >20% of proglacial sedimentary sequences.

Item Type:	Article
Subjects:	F600 Geology F800 Physical and Terrestrial Geographical and Environmental Sciences
Department:	Faculties > Engineering and Environment > Geography and Environmental Sciences
Depositing User:	Helen Pattison
Date Deposited:	19 Apr 2012 14:03
Last Modified:	13 Oct 2019 00:31
URI:	http://nrl.northumbria.ac.uk/id/eprint/6316

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