Calcretes, Silcretes and Intergrade Duricrusts

Abstract

Calcretes and silcretes are the most widely encountered ‘rocks’ in the Kalahari sandveld that covers much of Botswana. This chapter presents the first holistic overview of current knowledge about these duricrusts at a national scale. It does so by considering the distribution, classification, macromorphology, geochemistry and mineralogy of each duricrust type in turn, alongside various models used to explain their formation. The chapter then reviews our understanding of a variant of duricrust encountered more in the Botswana Kalahari than anywhere else in the world—the silcrete–calcrete intergrade duricrust. The chapter concludes with a summary of knowledge about the age of duricrusts in Botswana before pointing to potential directions for future research.