Palaeoenvironmental setting of iron-formations in the depositional basin of the transvaal supergroup, South Africa

This chapter describes the palaeoenvironmental settings of the iron-formations and their relationship with other facies such as ironstones, sedimentary manganese deposits, carbonates, volcanic, and siliciclastic in the depositional basin of the Transvaal Supergroup, South Africa. The Proterophytic Transvaal Supergroup crops out in the Griqualand West and Transvaal structural basins on the Archean Kaapvaal craton. Subtle facies changes between, and physical separation of the two basins are responsible for the different rock-stratigraphic names applied in them. Iron-formations are better developed and more abundant in the Griqualand West area than in the Transvaal area. Seven iron-formation units with formation status and more than ten beds or members are present in the Griqualand West sequence, from near the base of the chemical sedimentary Ghaap Group to near the top of the Postmasburg Group. A recent basinal analysis of the Ghaap Group in Griqualand West by Beukes and one of the Transvaal Supergroup in the eastern Transvaal by Button is the basis of much of the discussion in the chapter. The history of the documentation of the depository and its iron-formations can be divided into a number of periods each with its own outstanding character.