Advance and retreat of the marine-terminating Irish Sea Ice Stream into the Celtic Sea during the Last Glacial: timing and maximum extent

Scourse, J. et al. (2019) Advance and retreat of the marine-terminating Irish Sea Ice Stream into the Celtic Sea during the Last Glacial: timing and maximum extent. Marine Geology, 412, pp. 53-68. (doi: 10.1016/j.margeo.2019.03.003)

Abstract

The dynamics of the British-Irish Ice Sheet (BIIS) during the Last Glacial were conditioned by marine-based ice streams, the largest of which by far was the Irish Sea Ice Stream (ISIS) which drained southwest across the Celtic shelf. The maximum extent and timing of the ISIS have been constrained by onshore evidence from the UK and Ireland, and by glacigenic sediments encountered in a small suite of vibrocores from the UK-Irish continental shelf, from which a single radiocarbon date is available. These data have long supported ice advance to at least the mid-shelf, while recent results suggest the ISIS may have extended 150 km farther seaward to the shelf edge. The glacigenic sequences have not been placed within a secure seismic-stratigraphic context and the relationship between glaciation and the linear sediment megaridges observed on the outer shelf of the Celtic Sea has remained uncertain. Here we report results of sedimentological, geochemical, geochronological and micropalaeontological analyses combined with a seismic-stratigraphic investigation of the glacigenic sequences of the Celtic Sea with the aims of establishing maximum extent, depositional context, timing and retreat chronology of ISIS. Eight lithofacies packages are identified, six of which correlate with seismic facies. Lithofacies LF1 and LF2 correlate to a seafloor seismic facies (SF1) that we interpret to record the postglacial and Holocene transgressive flooding of the shelf. Lithofacies LF10 (till), LF3, LF4 and LF8 (glacimarine) correlate to different seismic facies that we interpret to be of glacigenic origin based on sedimentological, geotechnical and micropalaeontological evidence, and their distribution, supported by geochemical evidence from lithofacies LF8 and LF10 indicate extension of ISIS as far as the Celtic Sea shelf break. New radiocarbon ages on calcareous micro- and macrofauna constrain this advance to be between 24 and 27 cal ka BP, consistent with pre-existing geochronological constraints. Glacimarine lithofacies LF8 is in places glacitectonically contorted and deformed, indicating ice readvance, but the nature and timing of this readvance is unclear. Retreat out of the Celtic Sea was initially rapid and may have been triggered by high relative sea-levels driven by significant glacio-isostatic depression, consistent with greater ice loads over Britain and Ireland than previously considered.

• Item Type: Articles
• Additional 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 (allocations 1530.0311, 1577.0911 and 1606.0312). We thank the staff at the SUERC AMS Laboratory, East Kilbride for carbon isotope measurements, and the crews of the RRS James Cook, the BGS vibrocorer and the NOC piston corer. Daniel Praeg's participation has been in part supported by the Italian PNRA project IPY GLAMAR (grant number 2009/A2.15).
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Fabel, Dr Derek and Moreton, Dr Steven
• Authors: Scourse, J., Saher, M., Van Landeghem, K. J.J., Lockhart, E., Purcell, C., Callard, L., Roseby, Z., Allinson, B., Pieńkowski, A. J., O'Cofaigh, C., Praeg, D., Ward, S., Chiverrell, R., Moreton, S., Fabel, D., and Clark, C. D.
• College/School: College of Science and Engineering > Scottish Universities Environmental Research Centre
• Journal Name: Marine Geology
• Publisher: Elsevier
• ISSN: 0025-3227
• ISSN (Online): 1872-6151
• Published Online: 16 March 2019
• Copyright Holders: Copyright © 2019 The Authors
• First Published: First published in Marine Geology 412:53-63
• Publisher Policy: Reproduced under a Creative Commons license