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

Turner, A.J.; Woodward, J.; Dunning, S.A.; Shine, A.J.; Stokes, C.R.; O'Cofaigh, C.

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 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.

Citation

Turner, A., Woodward, J., Dunning, S., Shine, A., Stokes, C., & O'Cofaigh, C. (2012). 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), 221-232. https://doi.org/10.1002/jqs.1538

• Journal Article Type: Article
• Publication Date: Feb 1, 2012
• Deposit Date: Feb 13, 2012
• Journal: Journal of Quaternary Science
• Print ISSN: 0267-8179
• Electronic ISSN: 1099-1417
• Publisher: Wiley
• Peer Reviewed: Peer Reviewed
• Volume: 27
• Issue: 2
• Pages: 221-232
• DOI: https://doi.org/10.1002/jqs.1538
• Keywords: Loch Ness, Geophysical surveys, Jökulhlaup, Deglaciation, Proglacial.
• Public URL: https://durham-repository.worktribe.com/output/1506051