Tuesday, 28 August 2007
2.PS-68
Crustal architecture of the oblique-slip conjugate margins of George V Land and southeastern Australia
Howard M.J. Stagg, Geoscience Australia, GPO Box 378, Canberra, ACT, 2601, Australia and Anya M. Reading, School of Earth Sciences, University of Tasmania, Private Bag 79, Hobart, Tasmania, 7001, Australia.
A structural interpretation of the conjugate, oblique-slip margins of George V Land, East Antarctica, and southeast Australia, has been constructed based on seismic and sample data. This interpretation is characterised by pronounced asymmetry in width and thickness and depth-dependent crustal extension at breakup in the latest Maastrichtian. The Antarctic margin is broad (>300 km) and developed on thick crust (~42 km) of the Antarctic craton, whereas the Otway margin of southeast Australia is narrower (<200 km) and developed on the thin crust (~31 km) of the Ross–Delamerian orogen or Lachlan Fold Belt. The seismic data indicate that the upper basement (velocities ~5.5 km.s-1) and the deep continental crustal layers (velocities >6.4 km.s-1) appear to be largely removed across most of the rift between the rift bounding faults, whereas the mid-crustal, probably granitic layer (velocities ~6 km.s-1) is largely still present.