Dona Mihut and R. Dietmar Müller
Journal of Geophysical Research, 103, 27135-27150, 1998.
Abstract. The western margin of Australiais characterized by synrift and postrift magmatism which is not well understood. A joint interpretation of magnetic anomaly, satellite gravity anomaly andseismic data from the Cuvier Abyssal Plain and margin shows that the breakupbetween India and Australia started circa 136 Ma (M14) and was followedby two rift propagation events which transferred portions of the IndianPlate to the Australian Plate. Post breakup magmatism continued withthe emplacement of the Wallaby and Zenith plateaus (~17-18 km thick attheir centers) along a transform margin. Two narrow magmatic edificesadjacent to the Wallaby Plateau (Sonne and Sonja ridges) represent an extinctridge and a pseudofault, respectively. They formed by excess volcanism,probably by lateral migration of buoyant melt along upside-down crustaldrainage channels from the melt source underneath the Wallaby Plateau. In a mantle plume scenario a small plume (~400 km diameter) located underneaththe rift could have locally uplifted the Bernier Platform and Exmouth Sub-basinin the Early Cretaceous and left a track consistent with the azimuth ofthe Wallaby and Zenith plateaus. In this case, ridge-plume interactionwould have caused two consecutive ridge propagation events towards theplume while the ridge moved away from the hotspot. The abrupt endof the hotspot track west of the Zenith Plateau would be a consequenceof the accelerating south-eastward motion of the spreading ridge relativeto the mantle after 120 Ma, leaving the mantle plume underneath the IndianPlate. An alternative nonmantle-plume scenario is based on the observationthat between breakup and chron M0 (~120 Ma) the ocean crust in the southernCuvier Abyssal Plain was formed while the spreading ridge abutted Indiancontinental crust. Small-scale convection may have been initiatedduring rifting in the Early Cretaceous and maintained until the Wallaby-Zenithridge-transform intersection passed by the eastern edge of Indian continentalcrust at chron M0.
a) hotspot model for formation of Wallaby and Zenith Plateauvolcanics (see JGR paper for alternative model)
b) Gravity anomalies and magnetic anomaly identificationsin the Cuvier abyssal plain
Breakup volcanics along the western margin of Australia(from Planke and Symonds)
Sills and dikes in Triassic sediments in the Exmouth-subbasin, NW shelf, Australia