Zircon Pb-evaporation age determinations of the Oak Tree Formation, Chuniespoort Group, Transvaal Sequence: implications for Transvaal-Griqualand West basin correlations

摘要

Single zircon Pb-evaporation age determinations have resulted in an age of 2550 ± 3 Ma for a tuff layer in the Oak Tree Formation of the Malmani Subgroup, Chuniespoort Group, Transvaal Sequence. This result represents one of the first precise chronostratigraphic markers in the lower part of the Transvaal Sequence. The 2550 ± 3 Ma age is in good agreement with the known ages of correlated units in the Griqualand West Sequence and demonstrates that the lower part of the successions of the Transvaal and Griqualand West Sequences, which can be correlated in broad lithostratigraphic terms, are also coeval. In addition, the new date contributes to an improved understanding of rock accumulation rates and periods of non-deposition or erosion in the two successions.