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Short Communication |
1 1British Antarctic Survey, High Cross, Madingley Road, Cambridge, CB3 0ET, UK (e-mail: t.riley@bas.ac.uk)
2 2British Antarctic Survey c/o NERC Isotope Geosciences Laboratory, Keyworth, Nottingham, NG12 5GG, UK
3 3School of Geological and Computer Sciences, University of Natal, Durban 4041, South Africa
4 4PRISE, Research School of Earth Sciences, The Australian National University, Mills Road, Canberra, A.C.T. 0200, Australia
UPb SHRIMP ages are reported for three rhyolite flows from the Lebombo rift region of the Karoo volcanic province. Two flows are interbedded with the Sabie River Basalt Formation and a third sample is from the overlying rhyolitic Jozini Formation. The interbedded rhyolites yield ages of 182.0 ± 2.1 and 179.9 ± 1.8 Ma, whilst the overlying Jozini Formation rhyolite yields an age of 182.1 ± 2.9 Ma. Combined with existing 40Ar/39Ar geochronology, the new SHRIMP data fine-tunes the chronology of the Karoo volcanic province and indicates the 12 km succession of volcanic rocks in the Lebombo rift were erupted in 12 million years and lends considerable support to the links between the PleinsbachianToarcian extinction event and the global environmental impact of Karoo volcanism.
Keywords: Lemombo rhyolites, UPb, flood basalts, rhyolites, Karoo.
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