The Ventersdorp supergroup: an overview

The Kaapvaal Craton, South Africa: no evidence for a supercontinental affinity prior to 2.0 Ga?

“…The c. 100 My lacuna (Maphalala and Kröner 1993;Beukes and Nelson 1995) separating these two supergroups was characterized by tectonic shortening and erosion resulting in the loss of ≤1.5 km of stratigraphy of the earlier unit (Hall 1996). Applying a plume model to the largely volcanic Ventersdorp succession (cf., Hatton 1995) is compatible with the lower, c. 2 km thick Klipriviersberg Group (2714±8 Ma; Armstrong et al 1991) (Figure 2b) flood basalts of the Ventersdorp Supergroup, which also include basal komatiites (van der Westhuizen et al 1991); ponding of mafic magma beneath thinned lithosphere underlying the earlier Witwatersrand foredeep basin, related to a plume head which was possibly marginal to the Kaapvaal craton, has been suggested . Subsequent crustal extension concomitant with this envisaged geodynamic setting formed a set of graben/half-graben basins within this volcanic floor, within which immature clastic sedimentary and bimodal volcanic rocks accumulated to form the medial unconformity-based Platberg Group (c. 2709±4 Ma; Armstrong et al 1991) of the Ventersdorp succession (van der Westhuizen et al 1991, and references therein).…”

“…Applying a plume model to the largely volcanic Ventersdorp succession (cf., Hatton 1995) is compatible with the lower, c. 2 km thick Klipriviersberg Group (2714±8 Ma; Armstrong et al 1991) (Figure 2b) flood basalts of the Ventersdorp Supergroup, which also include basal komatiites (van der Westhuizen et al 1991); ponding of mafic magma beneath thinned lithosphere underlying the earlier Witwatersrand foredeep basin, related to a plume head which was possibly marginal to the Kaapvaal craton, has been suggested . Subsequent crustal extension concomitant with this envisaged geodynamic setting formed a set of graben/half-graben basins within this volcanic floor, within which immature clastic sedimentary and bimodal volcanic rocks accumulated to form the medial unconformity-based Platberg Group (c. 2709±4 Ma; Armstrong et al 1991) of the Ventersdorp succession (van der Westhuizen et al 1991, and references therein). The uppermost two units of the supergroup which succeed the Platberg Group, the widespread and sheet-like Bothaville and Allanridge Formations, point to an overall regime of thermal subsidence, with continued plume (minor komatiites in the latter formation) and graben influences (e.g., van der Westhuizen et al 1991;Eriksson et al 2002).…”

“…In a widely accepted scenario, post-Witwatersrand deformation has been related by many to incipient collision along the LMB on the northern margin of Kaapvaal (e.g., Stanistreet and McCarthy 1991); however, recent dating does not support this, with only a collision of the exotic Central zone of the Limpopo with Kaapvaal at about 2691-2610 Ma Kreissig et al 2001;Zeh et al 2009), well after formation of the Ventersdorp Supergroup. The latter was unconstrained by the existing tectonic architecture and grain of the Kaapvaal craton and can be interpreted within a fully mantle-thermally dominated plume model, resulting in 2714±8 Ma locally komatiitic mafic volcanics at the base, 2709±4 Ma medial graben-related bimodal volcanic and sedimentary deposits, with undated uppermost thermal subsidence related widespread sedimentary and volcanic lithologies (e.g., Armstrong et al 1991;van der Westhuizen et al 1991;Eriksson et al 2002).…”

“…Subsequent crustal extension concomitant with this envisaged geodynamic setting formed a set of graben/half-graben basins within this volcanic floor, within which immature clastic sedimentary and bimodal volcanic rocks accumulated to form the medial unconformity-based Platberg Group (c. 2709±4 Ma; Armstrong et al 1991) of the Ventersdorp succession (van der Westhuizen et al 1991, and references therein). The uppermost two units of the supergroup which succeed the Platberg Group, the widespread and sheet-like Bothaville and Allanridge Formations, point to an overall regime of thermal subsidence, with continued plume (minor komatiites in the latter formation) and graben influences (e.g., van der Westhuizen et al 1991;Eriksson et al 2002).…”

A case study of microbial mat-related features in coastal epeiric sandstones from the Paleoproterozoic Pretoria Group (Transvaal Supergroup, Kaapvaal craton, South Africa); The effect of preservation (reflecting sequence stratigraphic models) on the relationship between mat features and inferred paleoenvironment

“…The most complete Transvaal succession is that in the Transvaal basin (TB; Fig. 2), which begins with a set of "protobasinal" (a purely descriptive appellation) rift 7 depositories filled with immature sedimentary as well as volcanic rocks which mature stratigraphically upwards as thermal subsidence replaced mechanical subsidence (Eriksson et al, 2006 and references therein). A recent 2.66-2.68 Ga age on a dyke swarm to the east of the preserved basin-fills suggests that these protobasinal rifts may have been related to late Ventersdorp Supergroup volcanism (Olsson et al, 2010), as the c. 2.7 Ga Ventersdorp mantle plume event came to an end (van der Westhuizen et al, 1991;Eriksson et al, 2002a). Thin, undated fluvial sheet sandstones of the Black Reef unconformably succeed the protobasinal rifts (e.g., Els et al, 1995) and grade up into a thick chemical sedimentary, epeiric seaway platform succession (dated at ca.…”