HR: 09:35h
AN: T31G-07    [Abstracts]
TI: Structure and Kinematics of the Indo-Burmese Wedge
AU: * Maurin, T
EM: maurin@cdf.u-3mrs.fr
AF: College de France - Chaire de Geodynamique, Europole de l'Arbois bat Trocadero BP 80, Aix en Provence, 13545, France
AU: Rangin, C
EM: rangin@cdf.u-3mrs.fr
AF: College de France - Chaire de Geodynamique, Europole de l'Arbois bat Trocadero BP 80, Aix en Provence, 13545, France
AB: The Burma subduction trench and the associated Indo Burmese wedge mark the present eastern boundary of the Indian plate in the northern Bengal area. The initiation, duration and history of the Bengal crust subduction beneath Burma is still debated. The aim of this paper is to provide a structural and kinematic analysis of the Indo- Burmese wedge in order to better constraints the Bengal crust subduction history beneath Burma. On the basis of field observations, seismic reflection data interpretation and well logs data we present a structural analysis of the Outer Indo-Burmese Wedge. We also constrain the onset of this Outer Wedge to be younger than 2Ma, implying a recent and fast westward growth (~10cm/yr) since Late Pliocene in close relationship with the onset of the Shillong plateau. Restoration process of a synthetic cross section through the Outer Wedge allowed us to estimate the amount of EW shortening accommodated in the Outer Wedge to be 5.1mm/yr since 2Ma. These results combined with previous available GPS data from central Myanmar suggest strain partitioning at wedge scale. The core of the wedge is affected by shear deformation and acts as a buttress for a frontal wedge that accommodates a more compressive strain component. Finally we propose that the main characteristic of the Indo-Burmese wedge growth mechanism is the progressive incorporation of the most internal part of the wedge, formerly affected by transpressive thin-skinned tectonics, to the buttress where they are subsequently affected by shear deformation. The crustal structure boarding the newly formed buttress seems to be guided by the subducting crust fabrics. We are in favour of a very recent (Late Miocene) onset of the present Indian crust subduction beneath Burma coeval with the global plate kinematics reorganisation related to the Indian/Australian plate spliting. This subduction postdates the Indo Burmese range onset that must have started in early Miocene. This range first began to uplift because of shear deformation at the India/Burma plate boundary in a highly oblique strain context. The subduction may have started when a lower obliquity was reached after the Late Miocene plate kinematics reorganisation.
DE: 8002 Continental neotectonics (8107)
DE: 8170 Subduction zone processes (1031, 3060, 3613, 8413)
SC: Tectonophysics [T]
MN: 2007 Fall Meeting