On the fit of Broken Ridge and Kerguelen plateau

We present revised finite rotation parameters for Australia and East Antarctica in the Early Tertiary incorporating new magnetic data off of Wilkes Land, Antarctica. Reconstructions based on these and recently published rotation parameters document a relatively stationary position of Broken Ridge abutted against Central Kerguelen Plateau between chron 34 (83 Ma) and chron 20 (43 Ma), prior to the commencement of seafloor spreading between the two Late Cretaceous features. These reconstructions are significant as they are the first which are consistent with geological and geophysical constraints in not producing an overlap of Broken Ridge and Kerguelen Plateau between chron 34 and chron 24 (53 Ma) and not requiring significant extension or strike-slip motion within Kerguelen Plateau. We also find that the finite rotations for chrons 20 to 34 outline the area of rough topography inferred from the satellite-derived free-air gravity for the Diamantina Zone and Labuan Basin. A consequence of these rotations is that there is considerable overlap of continental crust in the region of Tasmania, the South Tasman Rise and East Antarctica in the Late Cretaceous. Solutions to this problem may imply either post-Santonian (≤79 Ma) extension or transform motion in the Bass Strait, or late Cretaceous or Cenozoic extension in Wilkes Land. The reconstructions also agree with prior estimates of roughly 150 km of motion between East and West Antarctica since chron 20.