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

Abstract

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 (10Be) 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 1 mm ka−1 erosion rate) and 16.15 ± 1.30 ka (using CRONUScalc with SA scaling and 1 mm ka−1 erosion rate). It is inferred that glacier retreat from the moraine occurred in the interval ∼16.5–16.1 ka but that a valley glacier continued to exist, probably until ∼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 ∼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.