Australia: The Land Where Time Began

A biography of the Australian continent 

The Hunter-Bowen Supercycle¹

This Hunter-Bowen Supercycle is in the New England Orogen, and represents a convergent margin, that is east-facing, and is characterised by a continental margin arc, a forearc basin and subduction complexes to the east. In the north a backarc basin has been identified, though at the time of writing none had been identified in the south. Following convergence that occurred in the Late Devonian to Carboniferous deformation and exhumation of the subduction complex, imbricate thrusting in the forearc basin and exhumation of the arc, that the author¹ suggests may have been triggered by an intraoceanic arc being accreted that had been identified in the northern part of the New England Orogen.

The author¹ suggests rollback of the subduction zone may be reflected in the extension, basin formation and granite formation that took place in the Early Permian. Rifting that occurred to the west of the New England Orogen resulted in the initial stages of the Bowen-Gunnedah-Sydney Basin System as a series of rift to transtensional basins that were converted to foreland basins in the Early Permian to Triassic as a result of crustal loading in the New England Orogen as a response to renewed exhumation and convergence. According to the author¹ the roots of a continental margin arc that formed oceanward of the older arc from the Devonian to the Carboniferous, are represented by granites of Permian - Triassic age intruding into older subduction complexes. The collision of an intraoceanic arc that occurred in the Middle to Late Triassic terminated the Hunter-Bowen Supercycle. The Bowen-Gunnedah-Sydney Basin System was converted from a foreland basin to an external part of a foreland fold thrust belt by a migrating wave of thin-skinned deformation that propagated cratonward reaching the western part of the basin system in the Late Triassic.

Sources & Further reading

1. Glen, Dick, The Lachlan Orogeny: New Boundaries, new data, new ideas, new deposits.
2. Glen, R.A., 2005, The Tasmanides of Eastern Australia. In: Vaughn, A. P. M., Leat, P. T. & Pankurst, R. J. Terrane Processes at the Margins of Gondwana. Special publication of the Geological Society, London, 246, 23-96.