The geochemistry and development of lateritized footslope benches: The Kasewe Hills, Sierra Leone

A series of lateritized footslope benches are observed on the isolated hill masses which rise to 500 m above the interior plain of Sierra Leone. Field observations and chemical analyses of samples indicate that each bench has a characteristic geochemistry controlled by its own topography, hydrological environment and leaching history. The benches are related, each inheriting material from above and providing material for the bench below. The material is transported both mechanically and in solution. As a result, the parent material of each bench is not only the bedrock (metamorphosed volcanic and sedimentary rocks of Proterozoic age in the case of the Kasewe Hills), but also material which has undergone various degrees of lateritization. This cratonic region has been subjected to denudational processes since Mesozoic times at least. Denudational processes, especially etchplanation, are long continued, yet weathering, the development of breakaway slopes and subterranean flushing are patently continuing processes: these palaeosurfaces and palaeosoils may, therefore, be ancient in origin but they cannot be considered as being fossilized.