The Newer Volcanics of Victoria crop out over nearly 25,000 km2. K‐Ar dating, using the whole‐rock technique on 20 samples from 12 widely scattered localities, indicates that activity commenced at least 4.5 m.y. ago and that the main period of eruption was in the Late Pliocene and in the Pleistocene. Some of the basalts contain an appreciable amount of glass or finely crystallized material; from consistency of the data it appears that little or no loss of radiogenic Ar has occurred. The specimens dated were mainly obtained from the same localities that Irving and Green had previously sampled for paleomagnetic measurements. Hence the age data provide additional information on geomagnetic polarity epochs and reversals of the earth's magnetic field. Together with previously published results, the new K‐Ar dates strongly suggest that a change from normal to reversed polarity occurred 0.75±0.07 m.y. ago. This polarity change may be the boundary between the Brunhes normal and the Matuyama reversed epochs; alternatively this change may record a short period of reversed polarity (i.e., an event) about 0.81 m.y. ago in an otherwise normal polarity epoch. The results indicate that the age of the boundary between the Matuyama reversed and Gauss normal epochs is poorly controlled at 2.35±0.15 m.y.
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