Pre-breakup continental extension in East Gondwanaland and the early opening of the eastern Indian Ocean

摘要: Abstract Extension of continental crust by up to 360 km on a north-northeast azimuth in the Great Australian Bight occurred prior Middle Cretaceous (96 Ma) onset seafloor spreading between Australia and Antarctica. This large amount extension is constrained Late Jurassic (≈ 160 Ma)-Middle interval, about pole estimated lie 40° southeastward southeastern Australia. Using bathymetric data combined with seismic magnetic determinations continent-ocean boundaries off Australia, India Antarctica, we determine revised fit East Gondwanaland extension, at various stages thereafter. In first stage from 132.5 Ma M11), India-Australia rotated Antarctica crustal largely transform motion Coromandel Coast margin Kron Prins Olav Kyst second stage, 96 Ma, northwestward away Australia-Antarctica, producing M10 younger anomalies along western Continental was greatest during this stage. The newly determined 132.5-96 rotation provides an improved orientation observed M10-M0 southward decrease rate margin. Together bathymetry, new parameters lead identification abandoned ridge Lost Dutchmen Dirck Hartog ridges. Naturaliste Fracture Zone found nearly parallel Early direction suggesting that slow spreading, required accommodate further east, M4-M0 adjacent Plateau. reduces eastward extent Greater 95° E but does not change its as far north Cape Range Zone. for Australia-Antarctica lies within 15° southern tip India, significantly closer than previous determinations, thereby reducing generated Africa India-Antarctica rotation, thus offering possible solution perceived spreading-rate problems M11 M0 Somali, Mozambique Antarctic basins.