The Cambrian Ross Orogeny in northern Victoria Land (Antarctica) and New Zealand: A synthesis

In the Cambrian, the paleo-Pacific margin of the East Gondwana continent, including East Antarctica, Australia, Tasmania and New Zealand, was affected by the Ross-Delamerian Orogery. The evidence from geochemistry of volcanic rocks and petrography of clastic sediments in northern Victoria Land (Antarctica) reveals that orogenesis occurred during a phase of oblique subduction accompanied by the opening and subsequent closure of a back-arc basin. A similar sequence of events is recognized in New Zealand. In both regions Middle Cambrian volcanic rocks are interpreted as arc/back-arc assemblages produced by west-directed subduction; sediments interbedded with the volcanic rocks show provenance both from the arc and from the Gondwana margin and therefore place the basin close to the continent. Rapid back-arc closure in the Late Cambrian was likely accomplished through changes to the subduction system. (C) 2008 International Association for Gondwana Research. Published by Elsevier B.V. All rights reserved.