Clast-fabric strength in tills and debris flows compared for different environments

Abstract

Elongated-clast fabrics of Alpine till from western Allgäu (southern West Germany) and of lowland ice-sheet till from The Netherlands are compared with published results from other areas. A quantitative comparison is made through the use of an eigenvalue method which produces measures of fabric shape and strength for three-dimensional orientation data. Clast fabrics of subglacial till in Western Allgäu tend to have lower strength than those from The Netherlands. Similar differences have been noted by comparing melt-out till fabrics of the Matanuska Glacier (Alaska) with Cordilleran ice-sheet and Alpine tills in North America. The possible reasons for these differences are discussed. Clast fabrics of ice-marginal debris-flow deposits in western Allgäu are similar to fabrics from sediment-flow deposits reported from other areas. Eigenvalue plots of clast fabrics do not distinguish clearly between subglacial till and debris flows from western Allgäu.