Structure and Debris Characteristics of Medial Moraines in Jotunheimen, Norway: Implications for Moraine Classification

Abstract Four medial moraines on three glaciers in Jotunheimen, Norway, are described. The structure and debris characteristics of the moraines allow three debris-transport routes to be identified: (1) discrete concentrated longitudinal septa containing subglacially comminuted debris; (2) diffuse longitudinal septa containing passively englacially transported debris; and (3) supraglacially transported spreads containing rock-fall debris entrained below the firn line. Two of the moraines, occurring down-glacier of nunataks, are nourished by a combination of (1) and (3). The remaining two moraines are nourished solely by englacially transported rock-fall debris (2). Transport routes (1) and (2) represent two distinct types of longitudinal englacial debris septum. The contribution of debris from more than one glacial transport path to single medial moraines indicates the value of a flexible, process-based approach towards moraine classification, with emphasis on the dynamic links between basin morphology, glacial debris entrainment, and moraine characteristics.