The Style and Extent of Younger Dryas Glaciation in the English Lake District

Abstract

Reconstructions of the maximal extent of Younger Dryas (~12.9-11.7 Ka BP) glaciers in the English Lake District have changed considerably over the past 60 years. Early interpretations assumed an alpine-style glaciation, however, more recent studies have identified large areas of plateau-style glaciation across the region. In response to this, a reassessment of Younger Dryas glaciation of the Helvellyn Range in the central Lake District was undertaken, with the aim of considering both glacial style and extent, as the region has not received attention since the early work that assumed alpine-style glaciation. Detailed remote mapping, using topographic data and aerial imagery, was therefore carried out to identify glacial landforms and determine the maximal and lateral glacial extent of Younger Dryas glaciers. This was used in conjunction with 3D glaciological modelling and the reconstruction of palaeo sediment transport pathways (through clast form analysis) to determine glaciation style. Soil development on moraine crests was assessed through B-horizon thickness and colour to distinguish Younger Dryas glacial features from landforms of older glaciations. Through which the northernmost site of Wolfs Crag is suggested to predate the Younger Dryas period. In this study, glacial landforms have been identified beyond the bounds of previously mapped glacial extent within five of the Helvellyn valleys, indicating a more extensive maximal extent. A sequence of recessional moraines has been identified in the previously unmapped valley of Rydal Beck, indicating an almost 4 km long Younger Dryas glacier. Evidence is presented for a combination of alpine- and plateau-style glaciation over the Helvellyn range. The reconstructed extent of three cirque glaciers in the Glenridding valley remains unchanged from previous studies. However, evidence for a small, satellite icefield has been identified in the north of the range, surrounding the summit of Stybarrow Dodd and drained by three outlet glaciers. A large cover of glacier ice was identified over the southern summits, draining into the five major valleys and connecting to plateau ice over the Eastern Fells. However, the western extent of these icefields remains unclear due to the lack of identifiable glacial landforms in these areas. Together, this evidence indicates a greater cover of glacier ice during the Younger Dryas than previously envisaged, both through more extensive valley floor extent, and the glaciation of multiple summit regions across the Helvellyn Range.