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  • James Scourse
    University of Exeter
  • Margot Saher
  • Katrien Van Landeghem
  • Edward Lockhart
  • Catriona Purcell
  • Sarah Louise Callard
    Durham University
  • Zoe Roseby
    School of Ocean Sciences, Bangor UniversityNational Oceanography Centre, SouthamptonUniversity of Southampton
  • Ben Allison
    School of Ocean Sciences, Bangor University
  • Anna Pieńkowski
    The University Centre in Svalbard (UNIS)
  • Colm Ó Cofaigh
    Durham University
  • Daniel Praeg
    OGS (Istituto Nazionale di Oceanografia e di Geofisica Sperimentale), TriesteUniversidade Federal Fluminense
  • Sophie Ward
  • R.C. Chiverrell
    University of Liverpool
  • Steven Moreton
    Natural Environment Research Council, Radiocarbon Facility, East Kilbride, Scotland, G75 OQF, UK
  • Derek Fabel
    Scottish Universities Environmental Research Centre
  • Chris Clark
    Sheffield University
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.

Keywords

  • Shelf (morphology and stratigraphy), Glacial sediments, Geophysics (seismic), Quaternary stratigraphy, Micropaleontology (forams), Europe
Original languageEnglish
Pages (from-to)53-68
JournalMarine Geology
Volume412
Early online date16 Mar 2019
DOIs
Publication statusPublished - 1 Jun 2019

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