Reconstruction of Antarctica and Australia at breakup (95 ± 5 Ma) and before rifting (160 Ma)

Abstract

Previous reconstructions of Antarctica and Australia were made by fitting the bathymetric outlines of the conjugate margins and aligning pre‐existing structures; the precise position of the continent‐ocean boundary (COB) and the amount and azimuth of pre‐breakup extension were unknown. Seismic and magnetic data collected off Wilkes Land by the S.P. Lee provide: (1) the basis for a unique fit of the COBs by confirming the fit of the oldest magnetic anomalies; and (2) together with information about the deep crustal structure of the Australian margin, an estimate of the azimuth and amount of pre‐breakup continental extension. By these means, Antarctica and Australia are reconstructed at the mid‐Cretaceous breakup and onset of drift (95 ± 5 Ma) by fitting the conjugate COBs, as determined from seismic and magnetic profiles; and before the mid‐Jurassic (160 Ma) onset of rifting by removing the 360 km of continental extension estimated from the crustal structure of the 700 km wide junction zone.

Key words:

• Antarctica
• Australia
• continental extension
• continental reconstruction
• seafloor spreading