MEGA-SCALE GLACIAL LINEATIONS AND CROSS-CUTTING ICE-FLOW LANDFORMS

Landsat images reveal a previously unsuspected large-scale pattern of streamlining within drift that is assumed to reflect former phases of ice flow. Such a glacial grain can be regarded as a landform assemblage comprised of a number of components. Drumlins and megaflutes form part of the pattern, but in addition there are two previously undocumented ice-moulded landform elements: streamlined lineations of much greater proportions, referred to as mega-scale glacial lineations, and a distinctive cross-cutting topology within the grain. The ice-moulded landform assemblage is described and illustrated with reference to examples from Canada. Possible modes of genesis of such landforms are discussed and their glaciological implications outlined. The discovery of this pattern indicates the pervasive nature of subglacial deformation of sediment, and demands a radical re-interpretation of ice sheet dynamics.