Abstract

K-Ar and Rb-Sr ages were measured on rapidly cooled igneous rocks from Kinnekulle, Sweden (Ordovician bentonite), the Cerberean Cauldron, Australia (late Devonian felsic volcanics), Mount Dromedary, Australia (Cretaceous monzonite) and Cooma, Australia (Jurassic syenite). No systematic bias was detected between the ages determined by the two techniques, calculated using the constants recommended by the I.U.G.S. Subcommission on Geochronology. The K-Ar and Rb-Sr ages of the Jurassic syenite also were indistinguishable from its zircon U-Pb age. The Kinnekulle A1 bentonite gives a minimum age of 446 ± 3 Ma for the early Caradocian Diplograptus molestus Zone. The Cerberean Cauldron volcanics give a minimum age of 367 ± 2 Ma for the early Frasnian. These data are consistent with a small upwards revision of the ages in Gale et al.'s 1979 time scale as proposed by Gale et al. (1980).

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