FACIES OF SUPRA-GLACIAL SEDIMENTATION ON ICELANDIC AND ALPINE TEMPERATE GLACIERS

Supraglacial debris transported by temperate valley glaciers is classified as supraglacial morainic till, distinct from lodgement till, and melt-out and flow till species on polar glaciers. In Iceland and the Alps, where annual discharges of supraglacial morainic till vary from 200-2000 m3 (compared with a maximum discharge of 26 000 m3 of lodgement till), till is deposited as three facies. Facies 1 occurs where supraglacial morainic till slows the rate of ice melt such that till is slowly superimposed on the subglacial surface in the form of stagnation or disintegration topography. Facies 2 occurs where the till cover is too thin or too coarse and ice melt is unretarded and supraglacial morainic till is deposited as a dispersed bouldery veneer by dumping during which gravity sorting occurs. Facies 3 refers to those stratigraphic sequences where irregular or lensate till horizons alternate repeatedly with ice-contact outwash. -from Author