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, A.J., Woodward, J., Dunning, S.A., Shine, A.J., Stokes, C.R., O'Cofaigh, C.
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: John Wiley 2012
• Subjects: Loch Ness; Geophysical surveys; Jökulhlaup; Deglaciation; Proglacial; Dammed Lake; Ice Sheet
• Online Access: http://dro.dur.ac.uk/11092/; 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 jökulhlaup 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 jökulhlaups are important for sediment supply into proglacial fjord/lake environments and may compose >20% of proglacial sedimentary sequences.