Exploring controls of the early and stepped deglaciation on the western margin of the British Irish Ice Sheet

Sara Benetti, Richard C. Chiverrell, Colm Ó. Cofaigh, Matt Burke, Alicia Medialdea, David Small, Colin Ballantyne, Mark D. Bateman, S. Louise Callard, Peter Wilson, Derek Fabel, Chris D. Clark, Riccardo Arosio, Sarah Bradley, Paul Dunlop, Jeremy C. Ely, Jenny Gales, Stephen J. Livingstone, Steven G. Moreton, Catriona PurcellMargot Saher, Kevin Schiele, Katrien Van Landeghem, Kasper Weilbach

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Abstract

New optically stimulated luminescence dating and Bayesian models integrating all legacy and BRITICE-CHRONO geochronology facilitated exploration of the controls on the deglaciation of two former sectors of the British–Irish Ice Sheet, the Donegal Bay (DBIS) and Malin Sea ice-streams (MSIS). Shelf-edge glaciation occurred ~27 ka, before the global Last Glacial Maximum, and shelf-wide retreat began 26–26.5 ka at a rate of ~18.7–20.7 m a–1. MSIS grounding zone wedges and DBIS recessional moraines show episodic retreat punctuated by prolonged still-stands. By ~23–22 ka the outer shelf (~25 000 km2) was free of grounded ice. After this time, MSIS retreat was faster (~20 m a–1 vs. ~2–6 m a–1 of DBIS). Separation of Irish and Scottish ice sources occurred ~20–19.5 ka, leaving an autonomous Donegal ice dome. Inner Malin shelf deglaciation followed the submarine troughs reaching the Hebridean coast ~19 ka. DBIS retreat formed the extensive complex of moraines in outer Donegal Bay at 20.5–19 ka. DBIS retreated on land by ~17–16 ka. Isolated ice caps in Scotland and Ireland persisted until ~14.5 ka. Early retreat of this marine-terminating margin is best explained by local ice loading increasing water depths and promoting calving ice losses rather than by changes in global temperatures. Topographical controls governed the differences between the ice-stream retreat from mid-shelf to the coast.
Original languageEnglish
Pages (from-to)833-870
Number of pages38
JournalJournal of Quaternary Science
Volume36
Issue number5
Early online date2 Jun 2021
DOIs
Publication statusPublished - 1 Jul 2021

Bibliographical note

Funding Information:
This research was funded by the UK Natural Environment Research Council consortium grant NE/J007196/1 BRITICE‐CHRONO. The work was supported by the NERC Radiocarbon Facility and NERC Cosmogenic Isotope Facility Analysis. Thanks to the staff at the SUERC AMS Laboratory, East Kilbride, for carbon isotope measurements. We thank the officers and crew of the RRS for their assistance with data acquisition, as well as the British Geological Survey and UK National Oceanography Centre for vibro‐ and piston core collection, respectively, during cruise JC106. Also thanks to the entire BRITICE‐CHRONO consortium for fruitful discussions over the duration of the project and the two anonymous reviewers for their constructive comments. James Cook

Funding Information:
This research was funded by the UK Natural Environment Research Council consortium grant NE/J007196/1 BRITICE-CHRONO. The work was supported by the NERC Radiocarbon Facility and NERC Cosmogenic Isotope Facility Analysis. Thanks to the staff at the SUERC AMS Laboratory, East Kilbride, for carbon isotope measurements. We thank the officers and crew of the RRS James Cook for their assistance with data acquisition, as well as the British Geological Survey and UK National Oceanography Centre for vibro- and piston core collection, respectively, during cruise JC106. Also thanks to the entire BRITICE-CHRONO consortium for fruitful discussions over the duration of the project and the two anonymous reviewers for their constructive comments.

Publisher Copyright:
© 2021 The Authors. Journal of Quaternary Science Published by Wiley Periodicals LLC

Keywords

  • Deglaciation
  • Donegal
  • Ice streams
  • Malin Sea
  • Retreat rate
  • ice streams
  • deglaciation
  • retreat rate

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