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.
While the Great Dividing Range north of Sydney is a prominent landform, it is more the result of Cenozoic volcanism and crustal uplift since the Jurassic, which broadly affects the same area as the Hunter–Bowen orogeny did.
[1] The Hunter–Bowen orogeny produced a ~3,000 km long structural foredeep above a Late Carboniferous and Palaeozoic margin, adjacent to the weakly consolidated Australian continental crust which at this time was part of Gondwana.
These encounters interrupted subduction at those locations and resulted in the formation of triple junctions, which began moving apart north and south along the trench, eventually being replaced by a dextral transform fault.
The coastal terrane which stretches from Coffs Harbour in the south to Broad Sound near St Lawrence, Queensland in the north, underwent 500 km of southerly displacement.
This brought it into its current position relative to the rest of Australia, and formed a major structural fold inland from Coffs Harbour.
[2] This structural foredeep filled with marine deepwater sediments and later fluviatile sandstones, which during the Permian and Triassic formed vast accumulations of coal from entrapped organic matter.
Thrusting of the Permian sequences westward in a Rocky Mountains-style foreland basin system continued as metamorphism began affecting the lower parts of the offshore island arcs, composed primarily of Devonian marine sediments of continental origin, and Carboniferous flysch.
To the north, significant thin-skinned deformation affected the Carboniferous Marlborough and Yarrol Terranes, resulting in magmatism and restricted granite emplacement.