Australia: The Land Where Time Began

A biography of the Australian continent 

The Delamerian Supercycle

This supercycle is comprised of 2 cycles. The first records a prolonged rifting event from 750 Ma to about 580 Ma, a time when Rodinia was broken up. The Adelaide Rift Complex (Adelaide Geosyncline) represents the inboard part that is largely amagmatic. From 600-580 Ma development of smaller rift basins and a major alkaline magmatic rift system characterises the outboard part of the Delamerian Supercycle.

The second cycle involves a switch to convergent margin magmatism that began in the outboard part of the Delamerian Orogen at about 525 Ma, approximately synchronous with a new rifting event that led to the formation of the Kanmantoo Trough in the inboard part of the orogen. The formation of mafic to ultramafic boninitic forearc crust in western Tasmania, and on the mainland, probable arc rocks as well as forearc crust, reflects cycle 2. Both east and west-dipping subduction  has been proposed, and the author¹ suggests there may have been more than 1 arc that developed subsequently About 510-505 Ma there was accretion of arc and forearc rocks, followed by extension, post-collisional volcanism, and at the end of the Cambrian, deformation.

Dick Glen

Geological Survey of New South Wales, Department of Primary Industries PO Box 344 Hunter
Region Mail Centre NSW 2310

Sources & Further reading

  1. Glen, Dick, The Lachlan Orogeny: New Boundaries, new data, new ideas, new deposits.
Author: M. H. Monroe
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