Mesozoic-Cenozoic reconstructions of Western Australia Breakup and SE Asian Growth

Hall, Robert
Earth Sciences, Royal Holloway University of London, Egham, United Kingdom.

The Sundaland region was assembled by closure of Tethyan oceans and addition of continental fragments. Its Mesozoic and Cenozoic history is illustrated by a new plate tectonic reconstruction. The Luconia-Dangerous Grounds continental block, rifted from Asia, was added to eastern Sundaland in the Cretaceous. Continental blocks rifted from Australia from the Late Jurassic are now in Borneo, Java and Sulawesi. West Burma was not rifted from western Australia. The Banda (SW Borneo) and Argo (East Java-West Sulawesi) blocks collided with the SE Asian margin between 110 and 90 Ma, and at 90 Ma the Woyla intra-oceanic arc collided with the Sumatra margin. Subduction beneath Sundaland terminated at this time. A marked change in deep mantle structure reflects different subduction histories north of India and Australia since 90 Ma. India and Australia were separated by a transform boundary from 90 to 75 Ma that was slightly convergent from 75 to 55 Ma. From 80 Ma, India moved rapidly north with north-directed subduction within Tethys and at the Asian margin. It collided with an intra-oceanic arc at about 55 Ma, west of Sumatra, and continued north to collide with Asia in the Eocene. Between 90 and 45 Ma Australia remained close to Antarctica and there was no significant subduction beneath Sumatra and Java. During this interval Sundaland was largely surrounded by inactive margins with some strike-slip deformation and extension, except for subduction beneath West Sulawesi between 63 and 50 Ma. At 45 Ma Australia began to move north; subduction resumed beneath Indonesia and continued to the present. No active or recently active ridge was subducted in the Cretaceous or Cenozoic beneath Sumatra and Java. The slab subducted was Cretaceous or older, except at the very western end of the Sunda Arc where Cenozoic lithosphere has been subducted in the last 20 Ma. Subduction rollback was probably the most important process driving basin formation, offshore fold and thrust deformation, and mountain building, particularly in eastern Indonesia where Neogene activity is implicated in the development of several frontier basins of hydrocarbon interest.

AAPG Search and Discovery Article #90155©2012 AAPG International Conference & Exhibition, Singapore, 16-19 September 2012