40Ar/39Ar Thermochronology of Pulsed Deformation in Eastern Australia

The Tasmanides of eastern Australia were affected by a number of seemingly discrete periods of Phanerozoic deformation related to convergent-margin processes. To evaluate potential regional-scale continuity in the effects of these deformational periods, we obtained new 40Ar/39Ar cooling ages from the northern part of the Tasmanides, and we combined these results with previous 40Ar/39Ar data from the southern part. The compiled dataset thus consists of 40Ar/39Ar cooling ages from across eastern Australia, covering an along-strike distance >3000 km. The compilation points toward six important periods of Tasmanides deformation, with 40Ar/39Ar age peaks centred at approximately 490, 450, 400, 330, 300, and 250 Ma. These cooling age peaks correspond with east Australian periods of tectonism (the Delamerian, Benambran, Tabberabberan, Kanimblan, and Hunter-Bowen Orogenies, as well as a period of widespread late Carboniferous to early Permian rifting) that were originally defined based on regional-scale unconformities and cross-cutting relationships. Our results also reveal close temporal correspondence between periods of mid-Palaeozoic deformation in eastern and central Australia.