Observations on the distribution of paraglacial reworking of glacigenic drift in western Norway

Abstract

This paper presents new data on the extent of and controls on paraglacial reworking of glacigenic drift by debris flows and snow avalanches at eight localities in western Norway. At sites around Jostedalsbreen, gully density is in the order of c. 10-100 gullies per km. Drift slopes at the sites in the Jotunheim massif are generally much less extensively modified by paraglacial processes (gully density nowhere exceeds 8 km^-1 in either site). Factors controlling paraglacial drift modification include gradient, sediment availability and water supply. Gully density generally exceeds 20 gullies per km where drift is steeper than c. 30° and thicker than c. 10 m, and where the void ratio of unreworked sediment exceeds c. 0.35. Widespread gullying is also favoured at sites of high and focused water input, in particular where melting snow and ice are involved. A significant implication of these findings concerns the preservation of glacigenic sediments and landforms in different paraglaciated landscapes. Understanding the detailed constraints on paraglacial processes is essential for realistically assessing the geomorphological significance of paraglaciation in a range of environments.