Hunter-Bowen orogeny

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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 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 Rise which includes Lord Howe Island.^[1] Lord Howe Rise has a total area of about 1,500,000 square km.^[1]