Late Permian to Cainozoic tectonics of the New England Orogen

Abstract

Abstract The development of the New England Orogen, until the middle Permian, was divided into three tectonic periods by Harrington and Korsch (Aust. J. Earth Sci. 32, 163–179,1985). These tectonic periods were dominated firstly by W‐facing volcanic arc systems which in tectonic period (TP) 3 were replaced by the E‐facing Gympie arc system. In TP4 the upper marine beds and coal measures of the Sydney, Gunnedah and Bowen basins were deposited and were covered by Early Triassic strata. In the W there was little structural disturbance in TP4 except in the Gunnedah Basin near the Mooki Fault where the Lower Triassic is unconformable on the Permian coal measures, but in the E there was a fundamental change with the formation of the major Late Permian and Early Triassic TP4 magmatic arc in Zone B and in the Yarrol Orogen. During TP5, in the Middle and Late Triassic, the Stanthorpe Plutonic Suite was intruded and the Ipswich Basin was formed and filled with volcanics and coal measures. A deformation in the Late Triassic at the beginning of TP6 was significant throughout the orogen, causing the deformation of the Gunnedah, Bowen and Ipswich basins which are overlain unconformably by the Surat and Moreton basins. In TP7 in the Late Jurassic and Early Cretaceous, there was volcanism and deformation in the Maryborough Basin and granitoids were intruded. It is inferred that there was major deformation and plutonism in Zone C because the major Rangitata Orogeny occurred in New Zealand. In TP8 the Whitsunday belt of mid‐Cretaceous silicic volcanics and high‐level plutons was probably a major feature because volcanic debris is abundant in sediments of the same age in the Surat and Eromanga basins. In TP9, in the Late Cretaceous and Cainozoic, Zone C was removed from Australia when the Tasman and Coral seas opened, the eastern part of Australia developed into a cymatogen by vertical movements, and there were extensive eruptions of basaltic volcanoes and lava fields in a set of arcs. Seven sets of granitoid rocks occur in Zone B and the Yarrol Orogen and it is thought that they formed by the subduction of continental crust (C‐subduction).