The Hunter-Bowen Orogeny was a significant arc accretion event in the Permian and Triassic periods affecting approximately 2,500 km of the Australian continental margin.
The Hunter-Bowen Orogeny occurred in two main phases, a Permian accretion of previously formed passive-marginal Devonian and Carboniferous sediments in the Hunter region and mid-west region of what is now New South Wales, separated by rifting, back-arc volcanism and a later Permian to Triassic event resulting in arc accretion and metamorphism during a subduction event.
The Hunter-Bowen Orogeny has resulted in the New England Fold Belt, a tectonic accretion of metamorphic terranes and mid-crustal granitoid intrusions, flanked by Permian to Triassic sedimentary basins which were formed distally to the now-eroded orogenic mountain belt.
While the Great Dividing Range north of Sydney is a prominent landform, this is more the result of Cainozoic volcanism and crustal uplift since the Jurassic than the result of the original orogenic belt which is essentially mimics. Gravity, magnetics and bathymetry indicate that several slivers of crust formerly from the Hunter-Bowen orogen are now spread out across the Indo-Australian plate east of the Australian continental landmass, forming some isolated submerged ocean plateaux and islands, notably Lord Howe Island.
Read more about Hunter-Bowen Orogeny: The Sydney-Gunnedah-Bowen Basin