Potassium‐argon ages on the Cainozoic Volcanic rocks of Eastern Victoria, Australia

Abstract

The Cainozoic volcanic rocks of eastern Victoria comprise most of the Older Volcanic Series. K‐Ar ages of volcanic rocks in South Gippsland range from middle Palaeocene to middle Eocene; the older ages are to the east. In the Eastern Highlands the majority of lavas are of late Eocene to middle Oligocene age, with some lavas of late Oligocene to Pliocene age. The Cainozoic volcanic activity in Victoria is thought to have been almost continuous since it started in the early Palaeocene, with peaks of activity from Palaeocene to Eocene and from Pliocene to Pleistocene. The uplift of the Eastern Highlands is thought to have taken place in three sub‐equal stages, starting in the middle Mesozoic. The last uplift is inferred to have begun some time after the Oligocene, and to have resulted in less than 300 m of uplift in the central and southern parts of the highlands, and negligible uplift in the northern. In the Oligocene the highlands had a relief of over 1000 m, and a drainage system similar to that of today.