Valley glaciers persisted in the Lake District, north-west England, until approximate to 16-15 ka as revealed by terrestrial cosmogenic nuclide (Be-10) dating: a response to Heinrich event 1?

The Lake District of north-west England acted as an independent centre of ice dispersal within the more extensive British-Irish Ice Sheet (BIIS) during the Last Glacial Maximum, but relatively little is known about the pattern and timing of glacier retreat. Four new terrestrial cosmogenic nuclide (Be-10) surface exposure ages from boulders from a lateral moraine in the Duddon valley, south-west Lake District, have yielded internally consistent ages with uncertainty-weighted means of 16.51 +/- 0.78 ka (using the Loch Lomond production rate with Lm scaling and 1mm ka(-1) erosion rate) and 16.15 +/- 1.30 ka (using CRONUScalc with SA scaling and 1mm ka(-1) erosion rate). It is inferred that glacier retreat from the moraine occurred in the interval approximate to 16.5-16.1 ka but that a valley glacier continued to exist, probably until approximate to 15 ka. The Duddon valley ages agree with other surface exposure ages from Wasdale, Watendlath and the Shap fells, together demonstrating that glacier ice was still widespread in the Lake District at approximate to 17-15 ka. There is also consistency with ages from other sectors of the BIIS that are considered to have responded to North Atlantic Heinrich event 1.