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  • Edward Lockhart
  • James Scourse
    College of Life and Environmental Sciences, University of Exeter, Penryn Campus, Penryn, 9 TR10 9EZ, UK.
  • Daniel Praeg
    Istituto Nazionale di Oceanografia e di Geofisica Sperimentale (OGS)Géoazur (UMR 7329 CNRS), Rue Albert Einstein, 06560 Valbonne, France
  • Katrien Van Landeghem
  • Claire Mellett
    Wessex Archaeology, Portway House, Old Sarum Park, Salisbury, Wiltshire SP4 6EB, UK
  • Margot Saher
  • Sarah Louise Callard
    Durham University
  • Richard C. Chiverrell
    Department of Geography and Planning, University of Liverpool, Liverpool, L69 3BX, UK
  • Sara Benetti
    School of Geography and Environmental Sciences, Ulster University, Coleraine, Londonderry, BT52 1SA, UK
  • Colm Ó Cofaigh
    Department of Geography, Durham University, Lower Mountjoy, South Road, Durham, DH1 3LE, UK
  • Chris D. Clark
    Department of Geography, Sheffield University, Sheffield, S10 2TN, UK
The Celtic Sea contains the world's largest continental shelf sediment ridges. These megaridges were initially interpreted as tidal features formed during post-glacial marine transgression, but glacigenic sediments have been recovered from their flanks. We examine the stratigraphy of the megaridges using new decimetric-resolution geophysical data correlated to sediment cores to test hypothetical tidal vs glacial modes of formation. The megaridges comprise three main units, 1) a superficial fining-upward drape that extends across the shelf above an unconformity. Underlying this drape is 2), the Melville Formation (MFm) which comprises the upper bulk of the megaridges, sometimes displaying dipping internal acoustic reflections and consisting of medium to coarse sand and shell fragments; characteristics consistent with either a tidal or glacifluvial origin. The MFm unconformably overlies 3), the Upper Little Sole Formation (ULSFm), previously interpreted to be of late Pliocene to early Pleistocene age, but here shown to correlate to Late Pleistocene glacigenic sediments forming a precursor topography. The superficial drape is interpreted as a product of prolonged wave energy as tidal currents diminished during the final stages of post-glacial marine transgression. We argue that the stratigraphy constrains the age of the MFm to between 24.3 and 14 ka BP, based on published dates, coeval with deglaciation and a modelled period of megatidal conditions during post-glacial marine transgression. Stratigraphically and sedimentologically, the megaridges could represent preserved glacifluvial features, but we suggest that they comprise post-glacial tidal deposits (MFm) mantling a partially-eroded glacial topography (ULSFm). The observed stratigraphy suggests that ice extended to the continental shelf-edge.

Keywords

  • Holocene, Late Pleistocene, Western Europe, Celtic sea, Stratigraphy, Glaciation, Tidal sand ridges, Irish sea ice stream
Original languageEnglish
Pages (from-to)156-170
JournalQuaternary Science Reviews
Volume198
Early online date10 Sep 2018
DOIs
Publication statusPublished - 15 Oct 2018
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