Revised tectonic evolution of the Eastern Indian Ocean

Published plate tectonic models for the Australian-Antarctic plate pair imply geologically improbable scenarios at either, or both, ends of the Cretaceous rift and spreading system. Controversy also exists around the location of and motion at the plate boundary extending west of Australia-Antarctica, through the Kerguelen Plateau region. We present a plate tectonic model of relative motions among India, Australia and Antarctica from the onset of continental rifting to the establishment of rapid seafloor spreading, at ~43 Ma. The model conforms to a wide range of geological/geophysical evidence and reconstructs the formation of both the western Kerguelen region and the eastern Tasman region. The incorporation of spatio-temporally continuous plate boundaries reveals the presence of a plate boundary beneath the contiguous Central Kerguelen Plateau and Broken Ridge for ~65 million years. To investigate the relationship between the plate boundary system and the Kerguelen plume we test three alternative absolute reference frames. Using a fixed hotspot reference frame, the Indian Ocean mid-ocean ridge system remains within 500 km of the Kerguelen plume, while the proximity of the plate boundaries and the plume is more variable with a moving hotspot reference frame. Proximity between the plume, plate boundaries, and the Central Kerguelen Plateau/Broken Ridge for ~65Myrs, suggests that these specific features were not formed by a single, short-lived (5–10 Myr) pulse of magmatic activity, but rather by a ~25 Myr period of relatively high magma flux followed by ~40 Myr period of lower volume magmatic activity, an interpretation not excluded by the relatively sparse dredge and drill ages.