Abstract: Tertiary Wrench Tectonics and Sedimentation in the Central Basin of Myanmar

Anthony J. Tankard, H. R. Balkwill, A. Mehra, Aung Din

The Central basin of Myanmar (Burma) contains a Cenozoic fill of sedimentary and volcanic rocks, which are locally thicker than 10 km. The Sagaing wrench fault separates the basin from the Shan plateau. In the west, the Arakan Yoma forms a southward-plunging anticlinorium of Mesozoic and lower Tertiary rocks. Internally, the basin is dissected into a series of depocenters by cross-basin faults. Seismic evidence indicates that the Central basin originated in the early Eocene as an array of pull-apart rift segments along the oceanic/cratonic transform zone between the Indian and southeast Asia lithospheric plates. From late Eocene to the present, the basin has been influenced by oblique subduction of the Indian plate, and by dextral slip along the intracratonic Sagaing transform fault.< P>

A line of Cenozoic volcanics in the axis of the Central basin marks the approximate suture between the cratonic (eastern) substrate and subducting (western) substrate. The volcanic line separates parts of the basin with different dynamic processes. Western basin segments form a trough that is underlain by Mesozoic melange, which is regionally detached above subducting Indian plate oceanic crust. Eastern basin segments are underlain by thick Phanerozoic (or upper Proterozoic) cover rocks that lie on thinned sialic basement; the architecture of these segments is controlled mainly by the effects of dextral slip on the Sagaing transform fault that bounds the eastern flank of the basin. Reflection seismic data show that the western and eastern basin segments maintained structural and strat graphic independence throughout the Tertiary.

AAPG Search and Discovery Article #90982©1994 AAPG International Conference and Exhibition, Kuala Lumpur, Malaysia, August 21-24, 1994