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

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

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.

Europe, Geophysics (seismic), Glacial sediments, Micropaleontology (forams), Quaternary stratigraphy, Shelf (morphology and stratigraphy)
0025-3227
53-68
Scourse, James
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Saher, Margot
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Van Landeghem, Katrien J.J.
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Lockhart, Edward
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Purcell, Catriona
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Callard, Louise
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Roseby, Zoe
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Allinson, Ben
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Pieńkowski, Anna J.
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O'Cofaigh, Colm
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Praeg, Daniel
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Ward, Sophie
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Chiverrell, Richard
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Moreton, Steve
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Fabel, Derek
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Clark, Chris D.
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Scourse, James
ba90dfd0-a440-4e94-8dcc-ad81080123a2
Saher, Margot
429b77fb-84ff-4e50-8966-09525d3cf6be
Van Landeghem, Katrien J.J.
03327df2-1ada-4d53-852f-6a4f4f63508e
Lockhart, Edward
13f41eb9-a9f7-4e39-915e-79851547e1b3
Purcell, Catriona
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Callard, Louise
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Roseby, Zoe
c40d5935-51f6-48ea-9b42-57963ebc5e1a
Allinson, Ben
d3d8a890-579d-49b8-8d2b-40a9e0bb477d
Pieńkowski, Anna J.
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O'Cofaigh, Colm
435f4670-76d8-43e0-8377-a11b37960446
Praeg, Daniel
8b717e97-9bcf-4da6-82ab-5690b0e79ef2
Ward, Sophie
325d0882-147a-4b0c-bc5d-41120cd1e3bc
Chiverrell, Richard
193e87d2-aae0-499c-b92b-af07eb2a494d
Moreton, Steve
73ae4597-dc75-497c-9d59-531f2fbe6d3f
Fabel, Derek
8690b593-84c3-4f0e-8f83-d6373dae20ce
Clark, Chris D.
d0ab3280-f6b2-4dff-b4b7-efbf23d3cdd7

Scourse, James, Saher, Margot, Van Landeghem, Katrien J.J., Lockhart, Edward, Purcell, Catriona, Callard, Louise, Roseby, Zoe, Allinson, Ben, Pieńkowski, Anna J., O'Cofaigh, Colm, Praeg, Daniel, Ward, Sophie, Chiverrell, Richard, Moreton, Steve, Fabel, Derek and Clark, Chris D. (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, 53-68. (doi:10.1016/j.margeo.2019.03.003).

Record type: Article

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.

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Accepted/In Press date: 13 March 2019
e-pub ahead of print date: 16 March 2019
Published date: 1 June 2019
Keywords: Europe, Geophysics (seismic), Glacial sediments, Micropaleontology (forams), Quaternary stratigraphy, Shelf (morphology and stratigraphy)

Identifiers

Local EPrints ID: 429656
URI: https://eprints.soton.ac.uk/id/eprint/429656
ISSN: 0025-3227
PURE UUID: ae32ba0e-c9e3-471a-810b-45a0a960550d

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Date deposited: 03 Apr 2019 16:30
Last modified: 09 Dec 2019 17:39

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Contributors

Author: James Scourse
Author: Margot Saher
Author: Katrien J.J. Van Landeghem
Author: Edward Lockhart
Author: Catriona Purcell
Author: Louise Callard
Author: Zoe Roseby
Author: Ben Allinson
Author: Anna J. Pieńkowski
Author: Colm O'Cofaigh
Author: Daniel Praeg
Author: Sophie Ward
Author: Richard Chiverrell
Author: Steve Moreton
Author: Derek Fabel
Author: Chris D. Clark

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