Abstract
ABSTRACTThis paper systematically reviews the glacial geomorphological evidence of the Loch Lomond Stadial (LLS; Younger Dryas) glaciation in Britain (12.9–11.7 ka). The geomorphology of sub‐regions within Scotland, England and Wales is assessed, providing the most comprehensive synthesis of this evidence to date. The contrasting nature of the evidence at the local scale is reviewed and conceptual themes common to multiple sub‐regions are examined. Advancements in glaciological theory, mapping technologies, numerical modelling and dating have been applied unevenly to localities across Britain, inhibiting a holistic understanding of the extent and dynamics of the LLS glaciation at a regional scale. The quantity and quality of evidence is highly uneven, leading to uncertainties regarding the extent of glaciation and inhibiting detailed analysis of ice dynamics and chronology. Robust dates are relatively scarce, making it difficult to confidently identify the limits of LLS glaciers and assess their synchroneity. Numerical models have allowed the glacier–climate relationships of the LLS to be assessed but have, thus far, been unable to incorporate local conditions which influenced glaciation. Recommendations for future research are made that will allow refined reconstructions of the LLS in Britain and contribute to a more comprehensive understanding of glacier–climate interactions during the Younger Dryas.
Highlights
Following the Last Glacial Maximum (LGM) between 26.5 and 19 ka (Clark et al, 2009) the Northern Hemisphere experienced abrupt cooling during a period known as the Younger Dryas (YD)
These effects were not experienced synchronously across all regions, the abrupt nature of the transition into cold conditions during a period of increasing insolation supports the long-held assumption that the YD was caused by disruption of the Atlantic meridional overturning circulation (AMOC), which moderates the region’s climate (Carlson, 2010; Golledge, 2010)
Cosmogenic dating of a boulder on a ridge identified as an end moraine (Sissons, 1980b; Ballantyne and Harris, 1994) of the Keskdale glacier (Chronological Site 2, Fig. 22) gave an age of 14.0 Æ 0.9 (0.7) ka, while the bedrock lip higher up in the cirque was not exposed until 13.2 Æ 0.8 (0.5) ka (Hughes et al, 2012). Both dates fell within the Loch Lomond Stadial (LLS), suggesting that there were two phases of glacier retreat, but recalibration for this paper indicates that the outer ridge potentially predates the LLS
Summary
Following the Last Glacial Maximum (LGM) between 26.5 and 19 ka (Clark et al, 2009) the Northern Hemisphere experienced abrupt cooling during a period known as the Younger Dryas (YD). Ballantyne (2007a) argued that the moraines in the lower reaches of Glen Rosa, Glen Sannox, North Glen Sannox, Coire nam Meann, Gleann Easan Biorach, Glen Catacol and Glen Iorsa pre-date the LLS and that the extents of LLS glaciers were marked by the (usually) fresher and less fragmented, boulder-strewn moraine ridges found in the upper cirques (Fig. 8c) This glacial reconstruction contrasted with Gemmell’s (1971, 1973) interpretation, most significantly for Glen Iorsa. This age is younger than would be expected, the absence of Lateglacial sediments within the core supports a LLS age
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