The late Archean to Mesoproterozoic major unconformity-bounded units of the Kaapvaal Province of southern Africa—reply

Abstract

Abstract The late Archean to Mesoproterozoic (⩽3.1−1.4 Ga) sedimentary and volcanic successions in the Kaapvaal Province of southern Africa previously have been subdivided into numerous lithostratigraphic units that generally were believed to have been deposited in local or regional basins. However, these lithostratigraphic units are remnants of thirteen unconformity-bounded sequences or units 103 m thick, with composite strike lengths of 250–1100 km, and with durations of 107 to 108 yr. All of these units rest somewhere on the crystalline basement. The stratotypes (but not the full geographic extents) of these sequences, from the base upward, are the Dominion Group, West Rand Group of the Witwatersrand Supergroup, Central Rand Group of the Witwatersrand Supergroup, Klipriviersberg Group of the Ventersdorp Supergroup, Platberg Group of the Ventersdorp Supergroup, Pniel Group of the Ventersdorp Supergroup, Black Reef Quartzite Formation and Chuniespoort Group of the Transvaal Supergroup, Pretoria Group of the Transvaal Supergroup, and the interval represented by the Dullstroom Formation, Rooiberg Group, and the Loskop Formation. Three or more major unconformity-bounded units occur in younger Proterozoic rocks in the Kaapvaal Province but are not definitive of it; two occur in the Soutpansberg Group, and one is most of the Waterberg Group. Some of these unconformity-bounded units are remarkably similar to Phanerozoic cratonic and miogeoclinal sequences. They are the natural building blocks for reconstructing Archean and Proterozoic depositional basins, plate tectonic events, continents and a provincial time scale.