Regional variation in the composition of Neoglacial end moraines, Jotunheimen, Norway: an altitudinal gradient in clast roundness and its possible palaeoclimatic significance

Matthews, John A. 1987 06 01: Regional variation in the composition of Neoglacial end moraines. Jotunheimen, Norway: an altitudinal gradient in clast roundness and its possible palaeoclimatic significance Boreas , Vol. 16, pp. 173–188. Oslo. ISSN 0300–9483. Quantitative indices of clast roundness from Neoglacial end moraines in front of 81 Jotunheimen glaciers were compared and analysed. Statistical techniques, including non‐metric multidimensional scaling, multiple regression and partial correlation, were used to relate clast roundness to selected environmental variables. Three independent variables – site altitude, glacier length (interchangeable with height of headwall relative to glacier length) and aspect – cumulatively accounted for about 58% of the variability in clast roundness. A climatic factor complex (represented by altitude and aspect) was found more important than morphological factors (such as glacier size and headwall size) in accounting for clast roundness variations between glaciers. The scale of the independent effects of altitude, morphology, aspect and geology was found in the approximate proportions 4:1.5:1:1. Several theoretical mechanisms are proposed which could explain a causal relationship between climate and clast roundness by influencing the relative importance of supraglacial and subglacial debris supply. The palaeoclimatic implications of the results are discussed with particular reference to the prediction of mean annual temperatures from clast roundness; one unit increase in clast roundness corresponding to an increase in mean annual temperature of about 1.4°C within the study area.