ABSTRACT: Sedimentary Basin Evolution in Western Southeast Asia: A Consequence of Oblique Subduction Following Eocene Plate Reorganization in the Indian Ocean

PACKHAM, GORDON H., Ocean Science Institute, University of Sydney and Affiliate of Petroconsultants, Australasia Pty Ltd., Sydney, New South Wales, Australia

A model is presented for the stages of the Cenozoic basin evolution in western Southeast Asia based on present day plate interactions and the Indian Ocean sea-floor spreading history.

The Australia-India plate is currently being obliquely subducted under the Burma plate. Partial coupling applied a dextral stress on the hanging wall plate northwest of Sunda Strait.

It is proposed that prior to the middle Eocene plate reorganization in the Indian Ocean, the India and Australia Plates were separate and a leaky transform boundary lay between them. The reconstructed position of this boundary is west of Sumatra. The boundary of the Australia Plate against Southeast Asia, southeast at least from northernmost Sumatra, was relatively inactive until the middle Eocene when Australia started to move rapidly north and subduction into the Sunda Trench commenced.

This initiated the present regime of oblique subduction and partial coupling of the combined Australia-India plate to the Southeast Asia part of the Eurasia plate. The resulting dextral shear and the inertia of the largely continental plate have been the driving forces in basin genesis and development in the region. The evolution of the subduction zone and associated magmatic arc, set in train a sequence of tectonic events which show spatial variation, diminishing in intensity away from the active plate boundary. The major tectonostratigraphic units are identified in the basins from the Sumatran margin, east to the Malay basin and central Thailand.

AAPG Search and Discovery Article #91015©1992 AAPG International Conference, Sydney, N.S.W., Australia, August 2-5, 1992 (2009)