Hunter–Bowen orogeny

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: The first being Permian accretion of passive-marginal Devonian- and Carboniferous-age sediments, occurring in the Hunter region, as well as the mid-west region of what is now New South Wales, followed by rifting, back-arc volcanism. The later Permian to Triassic event consisted of arc accretion and metamorphism related to ongoing subduction.

The Hunter–Bowen orogeny is today represented by a geological structure known as 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, 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. Gravity, magnetics and bathymetry indicate that several slivers of crust formerly from the Hunter–Bowen orogeny 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 Rise which includes Lord Howe Island. Lord Howe Rise has a total area of about 1,500,000 square km.

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