A Lateglacial Plateau Icefield in the Monadhliath Mountains, Scotland: reconstruction, dynamics and palaeoclimatic implications

Abstract

The complex record of glaciogenic landforms and sediments in Britain relating to the last British-Irish Ice Sheet provides the opportunity to reconstruct former ice extents, ice dynamics, retreat patterns and examine their links to climate change. Yet in Scotland, as in the rest of Britain, a previously fragmentary approach to palaeoglaciological research has limited our understanding of glacier dynamics and their relationship to climate, particularly during the Last Glacial-Interglacial Transition. The Monadhliath Mountains in the Central Scottish Highlands are dominated by an extensive plateau area that has received little research attention in the past. The few examples of research include work by British Geological Survey officers in the early 1900s and J.R. Young in the 1970s. These studies focussed primarily on the geomorphology and sedimentology of isolated valleys and therefore this PhD research provides the first systematic mapping of the region as a whole. Results of remote and field mapping demonstrate that two coalescent plateau icefields, together covering an area of c. 280 km2, occurred over the southwest and central sector of the Monadhliath Mountains during the Younger Dryas. Equilibrium line altitudes calculated for the icefield are of comparable magnitude to those reconstructed for nearby Younger Dryas ice masses, such as in Drumochter and Creag Meagaidh, but indicate slightly lower precipitation in the Monadhliath Mountains. ELAs of individual outlet glaciers rise steeply from west to east across the plateau, indicating a strong local precipitation gradient. Significant variations in the geomorphology on the plateau and within outlet valleys allowed an examination of former thermal regime and differences in ice dynamics during retreat. In-depth analysis of moraine retreat patterns enabled a detailed insight into palaeoglaciological controls on deglaciation for the first time, concluding that valley morphology and gradient were the most influential factors on the retreat dynamics of the plateau icefield.