GEOLOGICAL FRAMEWORK OF THE SOUTH TASMAN RISE, SOUTH OF TASMANIA, ANDITS SEDIMENTARY BASINS

The South Tasman Rise is a continental fragment of 200 000 km(2) lying south of Tasmania and surrounded on three sides by Late Cretaceous an d Palaeogene oceanic crust, which assumed its present configuration in the Palaeogene. The western side of the rise is dominated by the Tasm an Escarpment, the northernmost part of the Tasman Fracture Zone. The South Tasman Rise consists of three structural blocks, linked to Tasma nia by thinned continental crust, that moved southward with Antarctica from Tasmania in the Late Cretaceous. All have been affected by north west-southeast strike-slip motion in the Late Cretaceous and north-sou th extension in the Tertiary. The western block moved from west of Tas mania, had the longest and most intense tectonism, and consists of lar ge basement highs and the complex Ninene Basin. Basins on all three bl ocks are generally fault-controlled and are believed to contain Late C retaceous to Early Oligocene detrital non-marine and shallow-marine se dimentary rocks, and Late Oligocene and younger bathyal to pelagic cha lk and ooze. The Ninene Basin is more extensive and generally somewhat thicker (up to 5 km) than basins on the other two blocks. Basins on a ll three blocks have longterm petroleum potential but only the central block is in presently drillable water depths.