Abstract

Recent radiometric dating of carbonates and banded iron-formations on the Kaapvaal Craton, southern Africa, has suggested that late Archaean and Palaeoproterozoic carbonate sedimentation was diachronous across the craton. We present new SHRIMP U–Pb zircon ages of 2583±5 Ma and 2588±7 Ma for two samples of a tuff bed, 320 km apart in the upper Oak Tree Formation, Transvaal Supergroup. These ages, in conjunction with published data, support previously established sequence stratigraphic correlations that show the temporal equivalence of late Archaean carbonates in the region. A review of the sequence stratigraphy and geochronology of the Mount Bruce Megasequence Set on the Pilbara Craton, Western Australia, and the newly named Highveld Megasequence Set on the Kaapvaal Craton, indicates a remarkably similar geohistory. Both cratons are characterized by a divergent megacycle (Hamersley Range and Vaal Megasequences) followed by a convergent megacycle (Chichester Range and Drakensberg Megasequences). Our data show that the megasequence boundary is marked by drowning of both cratons at approximately the same time (c. 2590 Ma), which permits more meaningful geotectonic correlations between them.

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