Attenuated and highly elongate glacial lineations, known as mega-scale glacial lineations (MSGLs), are produced on the deforming bed of fast-flowing modern and palaeo-ice streams (Canals et al. 2000; Stokes & Clark 2001; King et al. 2009). Large cross-shelf troughs, often containing glacial lineations, are also diagnostic of past glacial activity. MSGLs are widespread on the exposures of the western Murzuq Basin in Libya (Moreau et al. 2005); examples of these and other streamlined landforms, together with converging patterns of past ice flow and evidence of deformable-bed conditions, have been found in the 440 Ma old Late Ordovician rocks here and elsewhere in North Africa (Deynoux & Ghienne 2004; Moreau et al. 2005; Denis et al. 2009; Moreau 2011). This demonstrates the presence of an ancient ice sheet over North Africa when the region was in a polar position.