Annually resolved events of Younger Dryas glaciation in Lochaber (Glen Roy and Glen Spean), western Scottish Highlands

Abstract

This paper presents the results of micromorphological analysis of laminated sediments that accumulated in ice-dammed lakes in Lochaber (Glen Roy and vicinity) during the Younger Dryas (Loch Lomond) Stadial. These lakes were responsible for the formation of the famous 'Parallel Roads of Glen Roy' (Agassiz, 1840), prominent shorelines cut into the valley sides of Glen Roy and adjacent valleys. Annually deposited (varved) layers, which can be distinguished from other rhythmites by micromorphological examination, have enabled the construction of a varve chronology which underpins the glacial history of the region, the duration of the lake stands and rates of ice margin advance and retreat. The lake system existed for a total of 515 a. During a rise in lake levels, the lowermost (260 m), middle (325 m) and highest (350 m) lakes existed for minimal periods of 191, 112 and 116 a, respectively, and the fall of lake levels from 350 m to 260 m took 95 years. Ice advance rates of between 13.4 and 41.9 m a À1 are inferred, while ice retreat is estimated to have been $38.5 m a À1 . A provisional correlation between the Lochaber varve and GRIP ice core records suggests that the lakes started to form at ca. 12 165 a BP, in turn implying that the Loch Lomond Readvance limits in this area were not achieved until late in the Younger Dryas interval, a conclusion which does not accord with that based on numerical model simulations.

Timing of glacier response to Younger Dryas climatic cooling in Scotland

“…Here we report new evidence that provides more precise chronological constraints for growth of YD ice in the Loch Lomond Global and Planetary Change 79 (2011) (Palmer et al, 2010) and with some evidence for growth of the Main Inland Ice Sheet in Norway during the YD (Mangerud et al, 2010).…”

A glacial geomorphological map of the Monadhliath Mountains, Central Scottish Highlands

“…The only extensive body of research is found in the southwest corner of the region in the area around Glen Roy (e.g. Fabel, Small, Miguens-Rodriguez, & Freeman, 2010;Lowe & Cairns, 1991;Palmer, Rose, Lowe, & MacLeod, 2010, Palmer, Rose, & Rasmussen 2012Peacock, 1986;Sissons, 1978Sissons, , 1979Sissons & Cornish, 1983). As a result, the lack of systematic glacial geomorphological mapping across the Monadhliath Mountains as a whole has led to a restricted and inconsistent understanding of ice mass fluctuations and dynamics, with the majority of current knowledge constrained to the major valley systems.…”

The Parallel Roads of Glen Roy, Scotland: geoconservation history and challenges

“…Several landslides in Glen Roy and Glen Gloy have also been linked to slope instability associated with the sudden draining of the lakes and the rapid unloading of the ground, while detailed levelling of the shorelines has demonstrated differential glacio-isostatic uplift and dislocation of crustal blocks Cornish, 1982a, 1982b). More recent studies have added to the scientific understanding and value of the area (Fabel et al, 2010;Macleod et al, 2011;Palmer et al, 2010Palmer et al, , 2012Ballantyne, 2012;Bendle et al, 2015;Boston and Lukas, 2016;Devine and Palmer, 2016;Sissons, 2016aSissons, , 2016b, with key issues also discussed during and following Quaternary Research Association (QRA) Field Meetings in 1989 and 2008 (Peacock and Cornish, 1989;Palmer et al, 2008;Peacock, 2009 …”