Sedimentology and chronology of the advance and retreat of the last British-Irish Ice Sheet on the continental shelf west of Ireland

Abstract

Citation for published item:etersD tFvF nd fenettiD F nd hunlopD F nd ¡ y gofighD gF nd woretonD FqF nd heelerD eFtF nd glrkD gFhF @PHITA 9edimentology nd hronology of the dvne nd retret of the lst fritishEsrish se heet on the ontinentl shelf west of srelndF9D uternry siene reviewsFD IRH F ppF IHIEIPRF Further information on publisher's website: Use policyThe full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. Abstract 12The last British-Irish Ice Sheet (BIIS) had extensive marine-terminating margins and was 13 drained by multiple large ice streams and is thus a useful analogue for marine-based areas of modern 14 ice sheets. However, despite recent advances from investigating the offshore record of the BIIS, the 15 dynamic history of its marine margins, which would have been sensitive to external forcing(s), remain 16 inadequately understood. This study is the first reconstruction of the retreat dynamics and chronology 17 of the western, marine-terminating, margin of the last (Late Midlandian) BIIS. Analyses of shelf 18 geomorphology and core sedimentology and chronology enable a reconstruction of the Late 19Midlandian history of the BIIS west of Ireland, from initial advance to final retreat onshore. Five 20 AMS radiocarbon dates from marine cores constrain the timing of retreat and associated readvances 21 during deglaciation. The BIIS advanced without streaming or surging, depositing a bed of highly 22 consolidated subglacial traction till, and reached to within ~20 km of the shelf break by ~24,000 Cal 23 BP. Ice margin retreat was likely preceded by thinning, grounding zone retreat and ice shelf 24 does not allow us to determine conclusively whether these readvances were a glaciodynamic 38 (internally-driven) response of the ice sheet during deglaciation or were climatically-driven. 39Following the <18,500 Cal BP readvance, the Galway Lobe experienced accelerated eastward retreat 40 at an estimated rate of ~113 m/yr. 41

On the timing and nature of the multiple phases of slope instability on eastern Rockall Bank, Northeast Atlantic

“…Facies TB can be found only in CE11_03, CE1 _04 and CE14_14, which are the cores closest to the axis of the Rockall Trough and nearest the Irish margin (Figure 1b). We interpret this facies as fine grained-turbidites originating from meltwater plumes from the BIIS that was covering the Irish shelf to the east of the study area at the time (Peters et al, 2016). They correspond to the turbidites that are found as thicker and slightly coarser sequences in cores more proximal to the Irish slope , but they are not found in cores closer to Rockall Bank.…”

“…The affected area on Rockall Bank lies a few kilometers inboard of this radius ( Figure 10). During that time (22 ka), the ice sheet was still very close to its maximum extent, still occupying the Irish Shelf (Peters et al, 2016), that is, most of the ice load was still in place. Models based on relative sea level data from around Ireland and Scotland show that deglaciation was very rapid after 21 ka (Brooks et al, 2008).…”

“…The Irish continental margin lies at the boundary between the glaciated and the glacially influenced sectors of the European Atlantic margin (Weaver et al, 2000). During the last glaciation the British Irish Ice Sheet (BIIS) was covering the entire island of Ireland and, at the Last Glacial Maximum, 24 ka, it extended and was grounded close to the shelf edge (Peters et al, 2016). Retreat of the ice margin began at 22 ka, but the ice shelf persisted for the next 2,500 years (Peters et al, 2016).…”

Clast abrasion of a rock shore platform on the Atlantic coast of Ireland

“…Normal tidal range reaches within 30-50 m of the cliff toe, depending on platform slope. During the Last Glacial Maximum~24,000 cal BP the study area was covered by the British Irish Ice Sheet (BIIS) (Peters et al, 2016). The study site is composed of two Upper Carboniferous sedimentary sequences, the Tullig (exposed on the platform) and Kilkee (exposed in the cliff) cyclothems, which form part of the larger Central Clare Group (Hodson and Lewarne, 1961;Rider, 1974;Pulham, 1989;Collinson et al, 1991).…”

“…The study site is composed of two Upper Carboniferous sedimentary sequences, the Tullig (exposed on the platform) and Kilkee (exposed in the cliff) cyclothems, which form part of the larger Central Clare Group (Hodson and Lewarne, 1961;Rider, 1974;Pulham, 1989;Collinson et al, 1991). During the Last Glacial Maximum~24,000 cal BP the study area was covered by the British Irish Ice Sheet (BIIS) (Peters et al, 2016). The western margins of the BIIS retreated from the areã 15.5 ± 1.0 ka BP (Bowen et al, 2002).…”