The advance and retreat of the Irish Sea Ice Stream in the Celtic Sea and its influence on shelf evolution

• Main Authors: Lockhart, Edward, Scourse, James, Praeg, D, van Landeghem, Katrien J.J., Mellett, Claire, Saher, Margot, Callard, Louise, Chiverrell, Richard C., Benetti, Sara, Cofaigh, Colm Ó, Clark, Chris
• Other Authors: School of Ocean Sciences Menai Bridge, Bangor University, University of Exeter, Géoazur (GEOAZUR 7329), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de la Côte d'Azur, COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD France-Sud ), Istituto Nazionale di Geofisica e di Oceanografia Sperimentale (OGS), Wessex Archaeology Salisbury, Department of Geography (UNIVERSITé DE DURHAM), Durham University, University of Liverpool, School of Geography and Environmental Sciences, University of Ulster, Department of Geography Sheffield, University of Sheffield Sheffield, European Project: 656821,H2020,H2020-MSCA-IF-2014,SEAGAS(2016)
• Format: Conference Object
• Language: English
• Published: HAL CCSD 2019
• Subjects: [SDU.STU]Sciences of the Universe [physics]/Earth Sciences; [SDU.STU.GL]Sciences of the Universe [physics]/Earth Sciences/Glaciology; [SDU.STU.GM]Sciences of the Universe [physics]/Earth Sciences/Geomorphology; [SDU.STU.OC]Sciences of the Universe [physics]/Earth Sciences/Oceanography; [SDU.STU.ST]Sciences of the Universe [physics]/Earth Sciences/Stratigraphy; Ice Sheet; Sea ice
• Online Access: https://hal.science/hal-02363197

International audience The reconstruction of the largest ice stream to drain the British-Irish Ice Sheet at the Last Glacial Maximum (LGM) can provide essential palaeoglacial observations required for constraining numerical ice sheet models. The Irish Sea Ice Stream (ISIS) was long considered to have terminated on the mid-shelf of the Celtic Sea, based on sediment cores and seismic data collected in the 1970s. Here we summarise findings from sediment cores and geophysical data acquired since 2009, and multi-beam bathymetric data acquired since 2001, which permit an updated evolution and palaeoglacial reconstruction of the Irish and UK sectors of the Celtic Sea shelf. In near-shore areas, multi-beam data reveal over 2000 glacial features, including moraine ridges, streamlined bedrock and meltwater channels, recording the southwest advance of the ISIS towards the shelf-edge and its subsequent retreat. The mid- to outer-shelf is characterised by the largest known linear shelf sediment ridges. These vary from long and linear features, the megaridges, in the northwest to sinuous and shorter ridges in the southeast. This ridge field was initially interpreted as tidal in origin, but glacigenic sediments have been recovered from the flanks of the megaridges. Correlating decimetric-resolution geophysical data to sediment cores, the megaridges comprise three main units. 1) A superficial fining-upward drape above an unconformity, inferred to record decreasing ocean energy during marine transgression. Underlying this drape is 2), the Melville Formation (MFm), which comprises the upper bulk of the megaridges, displaying dipping internal acoustic reflections and consisting of medium to coarse sand and gravel, characteristics that could be consistent with either a tidal or glacifluvial origin. The MFm unconformably overlies 3), the Upper Little Sole Formation (ULSFm), previously proposed to be of late Pliocene to early Pleistocene age, but is here shown to contain glacigenic sediments dated to the LGM. This stratigraphy ...