Cosmogenic exposure age constraints on deglaciation and flow behaviour of a marine-based ice stream in western Scotland, 21–16 ka

Deglaciation chronology of the Donegal Ice Centre, north‐west Ireland

“…The TCN ages relating to deglaciation of Aran Island [mean = 21.7 ± 0.8 ka (21.5 ± 1.8 ka)], Bloody Foreland [mean = 21.6 ± 0.7 ka (21.7 ± 1.8 ka)], and Malin Head [a single TCN age of 20.9 ± 0.9 ka (20.7 ± 1.8 ka)], together with the oldest 14 C age from Corvish (20.68 ± 0.16 cal ka BP) indicate progressive eastward retreat of the ice margin along the northern coast of Donegal between ∼21.7 and ∼20.7 ka. The Bloody Foreland and Aran Island ages imply that decoupling of ice sourced in Donegal from the Scottish‐sourced Hebridean Ice Stream commenced within the interval ∼22–21 ka; this is slightly earlier than previous estimates, which have placed initial disengagement of these two ice masses after ∼21 ka (Small et al , ). The single Malin Head TCN age and the oldest 14 C age at Corvish indicate that separation of Scottish‐sourced ice and Donegal‐sourced ice was complete by ∼20.7 ka, implying that by this time a marine embayment extended eastward along the north coast of Donegal, separating ice flowing north and north‐east from the Donegal Ice Centre from the retreating Hebrides/Malin Sea Ice Stream.…”

“…Evidence for marked slowing of ice‐margin retreat as the shrinking BIIS stabilized at or near the present coastline is not limited to northern Donegal. TCN ages reported by Small et al () for the Sea of the Hebrides to the west of Scotland suggest that termination of ice streaming after ∼20.6 ka was succeeded by a ∼3000–4000‐year interval during which the ice margin experienced oscillatory net retreat of only 50–70 km as it became progressively land‐based among the islands of the Inner Hebrides. The slowing of ice margin retreat in this area coincides closely with the period of very gradual ice‐margin recession in northern Donegal.…”

Relative sea-level changes and crustal movements in Britain and Ireland since the Last Glacial Maximum

“…Importantly, many coastal areas close to the centres of ice dispersal in northern Britain and Ireland were ice free relatively early, some perhaps by 20 ka BP (Clark et al, 2012), and more widely by 17 to 16 ka BP (Small et al, 2017). Landforms and sediments from these areas provide critical constraints on RSL reconstructions.…”

Sediment failures within the Peach Slide (Barra Fan, NE Atlantic Ocean) and relation to the history of the British-Irish Ice Sheet

“…This is a large, and relatively unstudied, submarine mass movement complex situated within the Barra-Donegal Fan on the western continental margin of Britain and Ireland. On the basis of seabed and coastal glacial geomorphology it is inferred that during the Devensian the Barra-Donegal Fan was fed by marine terminating ice streams from the Hebrides, North Channel and northwest Ireland (Clark et al, 2012;Dove et al, 2015;Dunlop et al, 2010;Finlayson et al, 2014;Howe et al, 2012;Scourse et al, 2009;Small et al, 2017).…”

“…This paper builds on extensive previous work on the Peach Slide and includes a reanalysis of seismic and other geophysical data (see Owen et al, 2015) as well as new foraminiferal δ 18 O, particle size sedimentology and 14 C dates from a core in the Peach Slide headwall area (using methods presented by Owen et al, 2010;Owen, 2013). These new data are combined with key previous work in the area (Armishaw et al, 1998;Armishaw et al, 2000;Holmes et al, 1998;Knutz et al, 2002;Kroon et al, 2000) and recent studies on the growth, extent and deglaciation of the British-Irish Ice Sheet (BIIS) (Clark et al, 2012;Dove et al, 2015;Hughes et al, 2016;Small et al, 2017) to provide an updated geological model for sedimentation on the Barra Fan. This model is then used to investigate the timing and control of the two most recent slope failures within the Peach Slide complex.…”