The 2.80 Ga age for the top of the Koodoovale unit in the western Filabusi and Gweru NW belts confirms (with greater stratigraphic control) earlier precise geochronology and provides an age for the start of sedimentation in the overlying Manjeri basinal deep-water sub-facies. The 2.79 Ga felsic sample from within the Reliance unit in the Shangani N belt is likely from a Koodoovale-derived, post-eruptive mass flow deposit. In the Midlands SE belt, the new felsic rock ages support the conformable relationship between the uppermost Koodoovale unit and overlying Manjeri unit but place the transition at c. 2.87 Ga, significantly earlier than in belts further west.
The new ages for the Koodoovale unit and the revised age for the Reliance unit introduce new perspectives on the development of the Bulawayan Supergroup: (1) The Koodoovale-Manjeri transition is diachronous across the Zimbabwe craton, (2) the duration of Manjeri sedimentation varied from 50 Ma to 120 Ma in the basinal deep-water and shallow-water sub-facies, respectively, to 80 Ma in the platformal facies in the east where sedimentation is estimated to have begun at 2.83 Ga; such prolonged sedimentation is controversial but can be explained by extended periods of non-deposition in the basinal deep-water sub-facies, (3) using all published precise ages, Reliance-Zeederbergs volcanism may have lasted 70 Ma (2.75-2.68 Ga), much longer than Phanerozoic plume systems, and (4) the previously proposed correlation and late Archean ¡®nearest neighbour¡¯ relationship between the Zimbabwe and Slave cratons are provided further support.