A Plio-Pleistocene sediment wedge on the continental shelf west of central Ireland: The Connemara Fan

• Published in: Marine Geology
• Main Authors: Mccarron, Stephen, Praeg, Daniel, Ó Cofaigh, Colm, Monteys, Xavier, Thébaudeau, Benjamin, Craven, Kieran, Saqab, Muhammad Mudasar, Cova, Andrea
• Other Authors: Department of Geography Maynooth, National University of Ireland Maynooth (Maynooth University), Istituto Nazionale di Geofisica e di Oceanografia Sperimentale (OGS), 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 ), Department of Geography, Durham University, Geological Survey of Ireland (GSI), Joyce Country and Western Lakes Geopark
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2018
• Subjects: [SDU.STU]Sciences of the Universe [physics]/Earth Sciences; [SDU]Sciences of the Universe [physics]; Porcupine Seabight; Svalbard
• Online Access: https://hal.science/hal-03573127; https://doi.org/10.1016/j.margeo.2018.02.009

International audience Glacigenic sediment fans recording shelf edge deposition from marine-terminating ice sheets have previously been recognised along the NW European continental margin from Svalbard to as far south as Donegal, off north-west Ireland. Here we present evidence of a previously unrecognised partially glacially-fed Plio-Pleistocene sediment wedge on the continental shelf west of central Ireland using 2D and 3D seismic reflection data correlated to a commercial borehole. The ‘Connemara Fan’ covers a shelf area of approximately 9000 km2 in water depths of 125–310 m, extending westwards into the Porcupine Seabight from the Irish Mainland Shelf. The wedge comprises up to 160 m of sediment that culminates in a prominent moraininc ridge at seabed and contains two discordant reflection surfaces (R1 and 2) that subdivide it into three seismic units (SU1–3). Stratigraphic boreholes 27/24-2 and 2A located on the inner shelf show that the lower unit (SU1) is composed of Pliocene marine sediments, while SU2 and 3 comprise glacially influenced facies of Quaternary age. Extracts from a 3D seismic data volume within the central part of the fan show channels within the Pliocene succession, while iceberg scours are observed on the R1 and R2 reflectors. The Connemara Fan is inferred to record sediment supply from central western Ireland, with Quaternary units probably recording at least two glacial advance-retreat cycles with ice sheets repeatedly grounding across the inner (Irish Mainland) shelf. Our findings extend the range of glacially-influenced grounding line depocentres southwards along the NW European continental margin.