Implications of a revised fit between Australia and Antarctica for the evolution of the Eastern Indian Ocean

Abstract

GRIFFITHS¹ suggested that the computer fits of Australia and Antarctica^2–4 are not supported by geology and that a better fit can be obtained by moving Australia 250 km westwards along the coast of Antarctica in the computer fitted reconstructions. Griffiths's revised fit eliminates the overlap of the South Tasman Rise, now known to be of continental origin⁵, and the Iselin plateau. Laird et al.⁶ showed that new geological evidence from Tasmania and East Antarctica favour such a revised reconstruction over the older computer fits. We present a slight modification to the fits given by Griffiths and by Laird et al. that, in addition, allows a good fit of magnetic anomaly lineations and fracture zone trends on the India⁷ and Antarctic⁸ plates (Fig. 1). This revised reconstruction thus implies that India and Australia have been parts of the same plate since the time of anomaly 22 (about 50 Myr ago). It also substantially reduces the size of the postulated Greater India^9–11 (Fig. 2).