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

• Published in: Journal of Quaternary Science
• Main Authors: Turner, Andrew, Woodward, John, Dunning, Stuart, Shine, Adrian, Stokes, Chris, Ó Cofaigh, Colm
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: Wiley-Blackwell 2011
• Subjects: F600 Geology; F800 Physical and Terrestrial Geographical and Environmental Sciences; Dammed Lake; Ice Sheet
• Online Access: https://nrl.northumbria.ac.uk/id/eprint/6316/; https://doi.org/10.1002/jqs.1538

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.