Sedimentary and foraminiferal records of Late Quaternary environmental change west of Ireland and implications for the last British–Irish Ice Sheet

Abstract

Palaeoenvironmental change following deglaciation of the last British–Irish Ice Sheet on the continental shelf west of Ireland was investigated using multiproxy analyses of sediment and foraminifera data from nine sediment cores. Lithofacies associations record various depositional regimes across the shelf, which evolve from subglacial to postglacial conditions. Census data provide the first characterisation of benthic foraminifera populations across the continental shelf and multivariate analyses reveal three distinct biotopes. Biomineralization within these biotopes is restricted to ≤21 200 cal a bp by four radiocarbon ages. The transition from glacial to postglacial benthic foraminifera populations near the shelf break marks the establishment of productive, nutrient‐rich, ice‐distal conditions at ~20 900 cal a bp; these conditions may also mark the start of favourable conditions for postglacial cold‐water coral growth. Postglacial conditions on the inner shelf were not established until <14 500 cal a bp, suggesting glacial conditions west of Ireland may have persisted into the Bølling–Allerød Interstadial.

Timing and pace of ice‐sheet withdrawal across the marine–terrestrial transition west of Ireland during the last glaciation

“…A recent study of deglacial benthic foraminiferal populations from the Porcupine Bank and western Irish shelf indicates the persistence of glacimarine conditions until c. 20.9 cal ka bp on the outer shelf, and at least c. 18.5 cal ka bp on the mid‐shelf (Peters et al ., 2020). Several deep‐water cores from along the Irish margin, notably core OMEX‐2K from the Goban Spur (Scourse et al ., 2009; Haapaniemi et al ., 2010) and core MD01‐2461 from the Porcupine Saddle (Peck et al ., 2007), contain high percentages of N. pachyderma sinistral during this period, implying low sea‐surface temperatures (Fig.…”

“…The inference of high RSL and low water temperatures is supported by the presence of benthic glacimarine foraminifera and associated lithofacies in sediment cores from the Slyne Trough (see ‘Sedimentology and radiocarbon measurements’ above; cf. Peters et al ., 2020).…”

“…On the Atlantic shelf bordering west and northwest Ireland, previous work has documented glacial geomorphological and sedimentological evidence recording the advance and retreat of the BIIS across the continental shelf, typically to the shelf edge, during the Last Glacial Maximum (LGM) (Benetti et al ., 2010; Dunlop et al ., 2010; Ó Cofaigh et al ., 2012a, 2019; Callard et al ., 2018, 2020; Peters et al ., 2015, 2016, 2020; Roberts et al ., 2020; Craven et al ., 2021). These studies have shown that the ice sheet retreated in a glacimarine environment and radiocarbon dates on marine fauna in deglacial glacimarine sediments constrain the timing of this retreat.…”