Observations on a blockstream in the vicinity of Sani Pass, Lesotho highlands, southern Africa

Coarse slope deposits, frequently grading into blockstreams, are common throughout the Lesotho highlands, southern Africa. This paper describes one such blockstream. It is interpreted as a typical lag deposit derived from valley-wide colluvial mantles, which contains superimposed and incorporated Late-Pleistocene blocky material. Blocks are largely derived from local scarps but may contain a component of corestones from mobilized regolith. The widespread mantle argues against landscape-scale glaciation in the Lesotho highlands in the Late Pleistocene. Rather, the environment appears to have been conducive to deep seasonal frost during the period of block production. No unequivocal evidence for permafrost is found. Copyright © 2002 John Wiley and Sons, Ltd.