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ABSTRACT: Late Cenozoic reconstructions in SE Asia: new GPS and tomographic constraints

Rangin, Claude1, Manuel Pubellier2, Nicolas Chamot-Rooke3, Harmen Bijwaard4, and Wim Spakman4
(1) Ecole Normale Superieure, 75005 Paris, France 
(2) CNRS-Ecole Normale Superieure, Paris, France 
(3) CNRS-ENS, Paris 
(4) Utrecht University, Utrecht, Netherlands

Most of the Cenozoic marginal basins floored with oceanic crust and fringing Sundaland to the east are presently subducting, and sedimentary basins are inverted. Subduction and basin contraction are associated with collision of the Australian (AU) and Philippine Sea (PH) plates with Sundaland (SU) since the Miocene. The finite motion of these large plates is relatively well constrained but the amount of deformation within the colliding plates is still not quantified.

GPS data show most of the PH/SU convergence is absorbed along the opposed Manila/Philippine trenches in the north, whereas 20% of this convergence is absorbed within Sundaland west of the Sangihe/Halmahera trenches. This could explain active shortening along both continental margins of Borneo. In eastern Indonesia active deformation is distributed within a wide area. The present kinematics of the rigid Banda block enable us to compute the subduction rate along the Flores trench, and eastwards convergence across the Makassar Strait. The GPS velocities obtained for the distinct crustal blocks are tentatively extrapolated back to 15 Ma using the timing of island arc volcanism related to each subduction zone, and the length of subducted slabs imaged by tomography.

We can reasonably extrapolate our GPS data back to 5 Ma, and good constraints were obtained for the Philippine trench and various subduction zones around the Sulu, Celebes and Banda Seas. Farther back in time a 9cm/yr subduction rate along the Manila trench since 11 Ma appears reasonable, and a minimum 10 cm/yr subduction rate of the Molucca Sea since 15 Ma.

AAPG Search and Discovery Article #90913©2000 AAPG International Conference and Exhibition, Bali, Indonesia