Formation of ribbed bedforms below shear margins and lobes of palaeo-ice streams

Abstract. Conceptual ice stream land systems derived from geomorphological and sedimentological observations provide constraints on ice–meltwater–till–bedrock interactions palaeo-ice beds. Within these systems, the spatial distribution formation processes of ribbed bedforms remain unclear. We explore conditions under which may develop their organization with (i) an experimental model that reproduces dynamics streams subglacial (ii) analysis selected examples beds Laurentide Ice Sheet. find a specific kind bedform can subglacially through soft-bed deformation, where flow undergoes lateral or longitudinal velocity gradients ice–bed interface is unlubricated; oblique beneath shear margins, whereas transverse below frontal lobes. infer strike orthogonally to compressing axis horizontal strain ellipse surface development reveals distinctive types drainage patterns: linked cavities margins efficient meltwater channels These act as convenient geomorphic markers reconstruct constrain dynamics, characteristics streams.