Rifted continental margins are strongly influenced by the location of zones of preexisting crustal weakness. Apatite fission track thermochronological data indicate that the Paleozoic lithospheric boundary between the Kanmantoo and Lachlan fold belts in western Victoria, Australia, was reactivated during Mesozoic rifting as a transfer fault. To the east of this boundary, 1-2 km of material was denuded during extension, while essentially no denudation took place during rifting to the west. The correlated tectonic boundary within the Bowers terrane of northern Victoria Land, Antarctica, was also reactivated upon rifting. During fragmentation of Gondwana, movement on this zone perpendicular to the direction of rifting probably determined the location of the Tasman Fracture Zone. When Australia and Antarctica are reconstructed along the trace of the Tasman Fracture Zone, the tectonic boundary in Victoria falls into precise alignment with the Bowers terrane.