Several attributes of the last British-Irish Ice Sheet (BIIS) make it a potentially important analogue to marine-based sectors of modern ice sheets, which are sensitive to oceanic and climatic changes and unstable during the current global climate warming. However, limitations on knowledge of the last BIIS's marine termini hinder the use of this ice mass in comparative assessments or modelling. This research addresses this critical knowledge gap through multiproxy examinations of BIIS marine landforms, sedimentation and ice-proximal palaeoenvironments. A multifaceted examination of the outer shelf (Porcupine Bank and Slyne Trough) using geomorphology, sedimentology and geochronology provides the first confirmation of BIIS shelf-wide extension during the last glaciation (Late Midlandian/Late Devensian) west of Ireland. Multivariate biofacies examinations from the outer shelf suggest the introduction of relatively warm and saline Atlantic water following BIIS decoupling and ice shelf formation. Shelfwide analyses of glacigenic deposits (till and glaciomarine) and landforms (moraines and grounding-zone wedges) provide the first estimates of BIIS marine-margin retreat rates and detailed reconstructions of BIIS marine-margin behaviour west of Ireland. These analyses reveal a major stillstand (<3,300 years) that punctuated overall retreat and deposited a large (~IS0-km long) grounding-zone wedge. Prior to this stillstand, the BIIS was stabilised by a buttressing ice shelf and its grounding line retreated at ~ 74 km/yr; following the stillstand and the loss of the buttressing ice shelf, the BIIS marine-margin retreated to the modern western Irish shoreline at an accelerated rate of ~ 113 m/yr. Radiocarbon analyses of glacitectonised glaciomarine sediment record the first evidence of an Irish ice mass readvancing offshore during the Nahanagan (Younger Dryas) Stadia. Shelf-wide palaeoenvironmental assessments using both novel and well-established multivariate and statistical techniques elucidate a previously unknown, likely climate-driven readvance (the Galway Lobe readvance) and suggest that initial BIIS marine-margin retreat was forced by climate or ocean warming.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:697540 |
| Date | January 2016 |
| Creators | Peters, Jared Lee |
| Publisher | Ulster University |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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