The Ross Orogen and Lachlan Fold Belt in Marie Byrd Land, Northern Victoria Land and New Zealand: implication for the tectonic setting of the Lachlan Fold Belt in Antarctica

Correlation of the Cambrian Delamerian Orogen of Australia and Ross Orogen of the Transantarctic
Mountains widely accepted but the extension of the adjacent Lachlan Orogen into Antarctica is controversial. Outside
the main Ross-Delamerian belt, evidence of this orogeny is preserved at Mt Murphy in Marie Byrd Land and the in
Takaka Terrane of New Zealand. In all pre-break- configurations of the SW Pacific, these two areas are far removed
from the Ross-Delamerian belt. Evidence from conglomerates in the Takaka Terrane, however, shows that in Late
Cambrian times it was adjacent to the Ross Orogen. This indicates major tectonic displacements within Gondwana after
the Cambrian and before break-up. The Lachlan Orogen formed in an extensional belt in a supra-subduction zone
setting and the Cambrian rocks of Marie Byrd Land and New Zealand are interpreted as parts of a rifted continental
ribbon on the outboard side of the Lachlan belt.