On the fit of Broken Ridge and Kerguelen plateau

We present revised finite rotation parameters for Australia and East Antarc tica in the Early Tertiary incorporating new magnetic data off of Wilkes La nd, Antarctica. Reconstructions based on these and recently published rotat ion parameters document a relatively stationary position of Broken Ridge ab utted 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 ar e the first which are consistent with geological and geophysical constraint s 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 s trike-slip motion within Kerguelen Plateau. We also find that the finite ro tations for chrons 20 to 34 outline the area of rough topography inferred f rom the satellite-derived free-air gravity for the Diamantina Zone and Labu an Basin. A consequence of these rotations is that there is considerable ov erlap 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 (less than or equal to 79 Ma) extension or tran sform motion in the Bass Strait, or late Cretaceous or Cenozoic extension i n Wilkes Land. The reconstructions also agree with prior estimates of rough ly 150 km of motion between East and West Antarctica since chron 20. (C) 20 00 Elsevier Science B.V. All rights reserved.