Scottish late-glacial moraines: debris supply, genesis and significance

Abstract

A variety of moraine forms were deposited by glaciers during the Loch Lomond Stadial. Study of such moraines and related landforms provides a valuable source of data on patterns of landscape evolution and climatic change. This thesis presents detailed case-studies of moraines in geologically and topographically contrasting areas on the Island of Skye, Scotland. Geomorphological mapping, sedimentological analyses and mathematical modelling techniques were employed to determine the principal controls on moraine morphology, composition and distribution. Particular emphasis was placed on the provenance, transport and deposition of debris, and their spatial variation. The results were used to construct a summary model of glacial landform evolution, which relates different sediment-landform associations to spatial and temporal controls, particularly basin lithology and structure, topography, position of deposition and ice-margin activity. The initial stage of deglaciation in the study area was marked by a series of readvances and/or stillstands. During this stage, the lower-lying glaciers were more sensitive to climatic amelioration than the higher glaciers. The subsequent phase was characterised by more rapid deglaciation. Evidence for one instance of late-stage in situ glacier stagnation is described. The results indicate that landforms hitherto grouped as 'hummocky -moraine' formed by a variety of processes. Such moraines formed by (a) uneven deposition of supraglacially and/or -subglacially-derived debris at active ice margins, (b) deposition at the stagnant margins of otherwise active glaciers, and (c) deposition during uninterrupted glacier retreat or areal stagnation. Differentiation and analysis of so-called 'hummocky moraine' enables glacier behaviour, during the Lateglacial to be interpreted in great detail.