Structure and kinematics of the Indo-Burmese Wedge - Recent and fast growth of the outer wedge

Aug 21, 2026

This paper analyzes the structure and kinematics of the Indo-Burmese Wedge using seismic reflection, geodetic, and geological field data. The wedge is identified as a zone of diffuse strain partitioning, combining right-lateral shearing internally with E-W shortening externally. Outer-wedge thick-skinned deformation overprints thin-skinned deformation and is linked to rapid westward propagation above an efficient clayey décollement layer. Seismic evidence indicates outer-wedge deformation younger than 2 Ma and enhanced by sediment loading in the Sylhet flexural basin.

LanguageEnglish

CategoryResearch & Report

FormatPDF

Pages21

Reading Time53 min

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Introduction

Tectonic Setting

Seismic and Geodynamic Framework

TECTONICS, VOL. 28, TC2010, doi:10 . 1029/2008TC002276, 2009 Structure and kinematics of the Indo-Burmese Wedge: Recent and fast growth of the outer wedge Thomas Maurin 1 and Claude Rangin 1 Received 14 February 2008; revised 19 December 2008; accepted 15 January 2009; published 28 April 2009 . [1] The northern Sunda subduction zone, offshore Burma, and the associated Indo-Burmese Wedge mark the active eastern boundary of the Burma Platelet jammed between the India Plate and the Sunda Plate. The aim of this paper is to provide a structural and kinematics analysis of the Indo-Burmese Wedge based on seismic reflection, geodetic, and geological field data. We found out that the Indo-Burmese Wedge is the place of diffuse strain partitioning: right-lateral shearing in the innermost part and E-W shortening in the outermost part. In the outer wedge, thick-skinned deformation overprints thin-skinned deformation. It can be explained by the required preservation of the critical taper after the fast westward propagation of the outer wedge above a very efficient clayey dcollement layer. The thick-skinned deformation is here characterized by major right-lateral strike-slip faults (the Kaladan Fault and the Chittagong Coastal Fault) and yet a typical internal deformation of the IndoBurmese Wedge. We suggest that the westward migration of internal right-lateral shear deformation allows preservation of the strain-partitioning ratios between internal N-S trending right-lateral shearing and external E-W shortening. Some seismic lines show that the outer wedge deformation is not older than 2 Ma. Its propagation could have been enhanced by the large amount of sediments filling up the Sylhet flexural basin formed after the Pliocene tectonic uplift of the Shillong Plateau. Citation: Maurin, T. , and C. Rangin (2009), Structure and kinematics of the Indo-Burmese Wedge: Recent and fast growth of the outer wedge, Tectonics, 28, TC2010, doi:10.1029/ 2008TC002276 . 1. Introduction [2] The Indo-Burmese Wedge results from the India/ Sunda plate’s oblique convergence (Figure 1) . Within this geodynamic framework, strain partitioning is responsible for the individualization of a sliver plate [Jarrard, 1986; McCaffrey, 1992], the Burma Plate. The Indo-Burmese Wedge marks the western margin of this sliver plate. The Sagaing right-lateral strike-slip fault marks its eastern 1CEREGE, UMR 6535 and Collge de France, Chaire de Godynamique, CNRS, Aix en Provence, France. Copyright 2009 by the American Geophysical Union. 0278-7407/09/2008TC002276 boundary and accommodates two thirds of the parallelto-the-trench strain component [Vigny et al., 2003] . The deformation within the Indo-Burmese Wedge accommodates the remnant amount of oblique stress [Nielsen et al., 2004] . Consequently, the main process responsible for the Indo-Burmese Wedge growth is N-S dextral shearing as it is confirmed by various geological observations and seismotectonic analysis [Le Dain et al., 1984; Ni et al., 1989; Guzman-Speziale and Ni, 1996; Rao and Kumar, 1999] . This wedge has grown and migrated rapidly westward along the southern edge of the Shillong Plateau [Lohmann, 1995](Figure 1) . [3] Curray et al. [1979] and Curray [2005] have proposed that the subduction of the Bengal crust beneath the Burma Plate is active since the closure of the Neo-Tethys in Late Mesozoic [Curray et al., 1979; Curray, 2005] . According to Curray et al., the major changes in tectonic deformation within this microplate are related to the indentation of the Eurasia by the India Plate and to the inferred clockwise rotation of Indochina. Acharya [2006], on the basis of a detailed analysis of the structural emplacement setting of the ophiolite belts in Burma and in Andaman Islands (Figure 1), proposes that the microplate has been constructed by the amalgamation of various microcontinents with the progressive westward jump of the subduction zone. According to Acharya, the present configuration i

FAQs

What data sources are used to study the Indo-Burmese Wedge’s structure and kinematics?

The analysis combines seismic reflection data, geodetic measurements, and geological field observations to derive structural and kinematic interpretations.

How does strain partitioning manifest within the Indo-Burmese Wedge?

The wedge shows diffuse strain partitioning: right-lateral shearing in the innermost part and E-W shortening in the outermost part.

What controls the transition from thin- to thick-skinned deformation in the outer wedge?

Outer-wedge deformation is explained as thick-skinned processes overprinting thin-skinned deformation, consistent with the need to preserve the critical taper after fast westward propagation above an efficient clayey décollement layer.

Aug 21, 2026

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