ABSTRACT

Examination of sediments at the terminus of the Mendenhall Glacier, Juneau, Alaska, indicates that the relative volumetric abundance of various pebble types can be used to determine direction of transport from source terrane and differences in energy flux between contrasted depositional environments. Both an increase in transport distance and an increase in energy flux independent of transport distance result in a relative enrichment of mechanically, strong detrital rock species. Extremely strong and extremely weak detrital species produce smooth compositional gradients with respect to source terrane and are relatively unaffected by differences in depositional environment. Rock species of intermediate resistance to disintegration reflect both down-valley degradation and an environment l effect. The general nature of functional relationships between the relative abundance of a detrital species and distance is greatly influenced by the spectrum of resistances associated with the assemblage and the variations in degradational energy affecting the detritus.