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Submarine deglacial sediment and geomorphological record of southwestern Scotland after the Last Glacial Maximum

Arosio, Riccardo; Dove, Dayton; Ó Cofaigh, Colm; Howe, John A.

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Authors

Riccardo Arosio

Dayton Dove

John A. Howe



Abstract

Understanding the style and pattern of retreat of the offshore sectors of the last British-Irish Ice Sheet (BIIS) is critical to any attempt to reconstruct its history following the Last Glacial Maximum (LGM). This paper presents a new seismo-stratigraphic analysis of Quaternary deposits on the inner continental shelf offshore of southwestern Scotland. It correlates these data with new high resolution seafloor bathymetry and sediment cores to reconstruct the post-LGM retreat dynamics of the Hebrides Ice Stream, a major outlet of the last BIIS which drained across the continental shelf offshore of northwest Britain. Two primary glacigenic units (Units III and IV) are observed in seismic sequences from the region. Unit III partly corresponds to the previously defined Barra Formation, but is re-interpreted here as a time-transgressive subglacial to ice-proximal deposit. On the mid-shelf, this unit comprises grounding-zone wedges (GZWs). Within inshore waters and sea lochs Unit III can be found at or near seabed, where it is associated with retreat moraines, as well as with proglacial outwash sediments near the Kintyre coast (RSL ~10 m OD). The younger Unit IV (equivalent to the Jura Formation) represents ice-proximal to hemipelagic conditions. Bathymetric data imaged streamlined subglacial landforms recording ice sheet flow onto the inner shelf and a variety of transverse landforms collectively interpreted as moraines recording episodic retreat. These new data indicate that during the last deglaciation of the shelf offshore of southwestern Scotland the retreat dynamics of the Hebrides Ice Stream followed three main stages: i) tidewater margin retreat punctuated by stillstands on the inner shelf, ii) topography-controlled fjordic retreat, with evolution from a coherent ice-sheet to separate tidewater glaciers, and iii) stabilisation at the transition from a tidewater to land-based ice margin.

Citation

Arosio, R., Dove, D., Ó Cofaigh, C., & Howe, J. A. (2018). Submarine deglacial sediment and geomorphological record of southwestern Scotland after the Last Glacial Maximum. Marine Geology, 403, 62-79. https://doi.org/10.1016/j.margeo.2018.04.012

Journal Article Type Article
Acceptance Date Apr 19, 2018
Online Publication Date Apr 26, 2018
Publication Date Aug 1, 2018
Deposit Date May 1, 2018
Publicly Available Date Mar 29, 2024
Journal Marine Geology
Print ISSN 0025-3227
Publisher Elsevier
Peer Reviewed Peer Reviewed
Volume 403
Pages 62-79
DOI https://doi.org/10.1016/j.margeo.2018.04.012

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