Evidence for Heinrich event 1 in the British Isles

Abstract

In the north Irish Sea basin (ISB), sedimentary successions constrained by AMS 14 C dates obtained from marine microfaunas record three major palaeoenvironmental shifts during the last deglacial cycle. (i) Marine muds (Cooley Point Interstadial) dated to between 16.7 and 14.7 14 C kyr BP record a major deglaciation of the ISB following the Late Glacial Maximum (LGM). (ii) Terminal outwash and ice-contact landforms (Killard Point Stadial) were deposited during an extensive ice readvance, which occurred after 14.7 14 C kyr BP and reached a maximum extent at ca.14 14 C kyr BP. At this time the lowlands surrounding the north ISB were drumlinised. Coeval flowlines reconstructed from these bedforms end at prominent moraines (Killard Point, Bride, St Bees) and indicate contemporaneity of drumlinisation from separate ice dispersal centres, substrate erosion by fast ice flow, and subglacial sediment transfer to ice-sheet margins. In north central Ireland bed reorganisation associated with this fast ice-flow phase involved overprinting and drumlinisation of earlier transverse ridges (Rogen-type moraines) by headward erosion along ice streams that exited through tidewater ice margins. This is the first direct terrestrial evidence that the British Ice Sheet (BIS) participated in Heinrich event 1 (H1). (iii) Regional mud drapes, directly overlying drumlins, record high relative sea-level (RSL) with stagnation zone retreat after 13.7 14 C kyr BP (Rough Island Interstadial). Elsewhere in lowland areas of northern Britain ice-marginal sediments and morainic belts record millennial-scale oscillations of the BIS, which postdate the LGM advance on to the continental shelf, and pre-date the Loch Lomond Stadial (Younger Dryas) advance in the highlands of western Scotland (ca. 11-10 14 C kyr BP). In western, northwestern and northern Ireland, Killard Point Stadial (H1) ice limits are reconstructed from ice-flow lines that are coeval with those in the north ISB and end at prominent moraines. On the Scottish continental shelf possible H1-age ice limits are reconstructed from dated marine muds and associated ice marginal moraines. It is argued that the last major offshore ice expansion from the Scottish mountains postdated ca. 15 14 C kyr BP and is therefore part of the H1 event. In eastern England the stratigraphic significance of the Dimlington silts is re-evaluated because evidence shows that there was only one major ice oscillation postdating ca.18 14 C kyr BP in these lowlands. In a wider context the sequence of deglacial events in the ISB (widespread deglaciation of southern part of the BIS → major readvance during H1 → ice sheet collapse) is similar to records of ice sheet variability from the southern margins of the Laurentide Ice Sheet (LIS). Welldated ice-marginal records, however, show that during the Killard Point readvance the BIS was at its maximum position when retreat of the LIS was well underway. This phasing relationship supports the idea that the BIS readvance was a response to North Atlantic cooling induced by collaps...

Ice sheet advance, dynamics, and decay configurations: evidence from west central Scotland

“…17D), is consistent with aspects of the reconstruction by Salt and Evans (2004) (their stages F and G). Renewed, climatically-driven ice sheet growth over northeast Ireland during the Killard Point Stadial has been suggested by McCabe et al (1998), and is supported by recent cosmogenic exposure ages of 15.6 10 Be ka BP from moraine sequences in north-western Ireland .…”

“…17B,C,D) (Knight, 2002) and a variety of inverse ice sheet models reconstruct an ice ridge over the North Channel linking the Southern Uplands and Lough Neagh dispersal centres during, and following, the LGM (e.g Boulton et al, 1991Boulton et al, , 2002. (McCabe et al, 1998;McCabe and Clark 2003;McCabe et al, 2007a). We speculate that the strong westward ice flow during stage C (Fig.…”

“…2,5,14) shows location of study area in west central Scotland. Proposed former glacier ice limits and ages from Sissons (1967b), Dawson (1982, Rose et al (1988), Peacock and Merritt (1997), McCabe et al (1998McCabe et al ( , 2003, Thomas et al (2004), Ballantyne (2007), and McCabe (2008). Key place names are shown.…”

“…Knight and McCabe, 1997;McCabe et al, 1998McCabe et al, , 2005McCabe et al, , 2007a). Bedform patterns demonstrate that an ice sheet dome existed in the vicinity of Lough Neagh for much of the glacial cycle (Fig.…”

Pre-Late Devensian high-arctic marine deposits in SW Scotland

“…At glacial maximum it has been argued that the peninsula was overridden by the main Scottish Ice Sheet, and during deglaciation a series of ice streams crossed the area, until final disappearance of the ice sheet toward the end of the Lateglacial Period (Charlesworth, 1926, Kerr, 1982, McCabe et al, 1998, Salt & Evans, 2004, Bradwell et al, 2008. Three decades ago, it was suggested that high-arctic marine deposits formerly seen in two claypits in SW Scotland were possible representatives of the high-arctic Errol Clay Formation of eastern Scotland, and were thus of Devensian lateglacial age (Peacock, 1975).…”