Evidence for high energy landforming events on the central African plateau: eastern province, Zambia

Late Quaternary climate and vegetation changes are thought to have induced important changes to landscape dynamics throughout the tropics, including t he savanna areas of central Africa. Evidence is presented of high energy la ndforms in the Chipata District of eastern Zambia, comprising landslides, d ebris slides and coarse fan deposits. Local geology includes steep quartzit e beds alternating with granulites which are deeply weathered to a ferralli tic saprolite. Landslides have occurred within the weathered granulite, on the slopes of residual hills. The debris forms ramparts and lobes of coarse quartzite rubble, and masses of weathered schist incorporating quartzite b oulders. These deposits overlie alluvial fan facies containing boulders up to 1 m diameter. Numerous fans have formed from small catchments and are as sociated with wide areas of more amorphous, sandy colluvium. Post depositio nal weathering and the occurrence of thin ferricrete in the colluvium, alon gside the absence of any evidence for comparable activity within the presen t-day climate regime, is taken to indicate a late Quaternary origin for the se features. The landscape of the Chipata District. has clearly gone throug h one or more periods of intense, high energy landforming activity which ha s strongly modified the relief. The dominant landscape style, however, demo nstrates close adjustment of form to petrography and structure, suggesting that mass movement leading to slope retreat is interspersed with much longe r periods of incremental lowering of the landscape. The presence of the sed iments in the present-day landscape also points to the potential for rapid redistribution by erosion, if the balance of the morphogenetic system is di sturbed by climate change or intensification of land use.