Publication Name: The Sedimentary Basins of WA
Authors: Dona Mihut and R. Dietmar M?ller
Publication Volumne: 2
Date Published: December 1998
Number of Pages: 19
Reference Type: Book Section
Abstract:Lineated, northeast-southwest trending short-wavelength gravity anomalies in the Argo Abyssal Plain visible in satellite derived gravity anomalies agree with the basement fabric mapped from seismic data (Gopala Rao et al., 1994) and disagree with all published plate models for its formation, which suggests a west-northwest oriented direction of opening. We have reinterpreted all available magnetic data jointly with gridded gravity and bathymetry data to construct a new plate kinematic model. A complete set of anomalies from M26 (155.0 Ma) to M21 (150.4 Ma) was interpreted, resulting in an average halfspreading rate of 5.0 cm/y and a northwest-southeast oriented spreading direction. The direction of opening is sub-parallel to the northern Exmouth Plateau
margin, indicating that it represents a transform margin rather than a Jurassic rifted margin. The margin's step-like appearance is most likely due to several ridge propagation events. These events might be responsible for the development of a series of horsts, grabens and half grabens (the Wombat Plateau, Echidna and Emu spurs and Montebello and Swan canyons) north-northeast of the Exmouth Plateau. This model is in good accordance with the results from Ocean Drilling Project (ODP) Leg 123, which set out to drill the northern Exmouth margin as a typical Jurassic rifted margin, but, as would be expected for a transform margin, found no Jurassic sediments.
Flowlines for our plate kinematic model follow small circles about the same stage pole that describes the early opening of the Perth Abyssal Plain. This similarity may indicate that the formation of the Argo Abyssal Plain is due to the gradual breakup between Australia and Greater India by means of a southward-propagating rift.