Cenozoic geodynamic evolution of the Andaman–Sumatra subduction margin: Current understanding

Abstract

The Andaman-Sumatra margin displays a unique set-up of extensional subduction-accretion complexes, which are the Java Trench, a tectonic (outer arc) prism, a sliver plate, a forearc, oceanic rises, inner-arc volcanoes, and an extensional back-arc with active spreading. Existing knowledge is reviewed in this paper, and some new data on the surface and subsurface signatures for operative geotectonics of this margin is analyzed. Subduction-related deformation along the trench has been operating either continuously or intermittently since the Cretaceous. The oblique subduction has initiated strike-slip motion in the northern Sumatra-Andaman sector, and has formed a sliver plate between the subduction zone and a complex, right-lateral fault system. The sliver fault, initiated in the Eocene, extended through the outer-arc ridge offshore from Sumatra, and continued through the Andaman Sea connecting the Sagaing Fault in the north. Dominance of regional plate dynamics over simple subduction-related accretionary processes led to the development and evolution of sedimentary basins of widely varied tectonic character along this margin. A number of north-south-trending dismembered ophiolite slices of Cretaceous age, occurring at different structural levels with Eocene trench-slope sediments, were uplifted and emplaced by a series of east-dipping thrusts to shape the outer-arc prism. North-south and east-west strike-slip faults controlled the subsidence, resulting in the development of a forearc basins and record Oligocene to Miocene-Pliocene sedimentation within mixed siliciclastic-carbonate systems. The opening of the Andaman Sea back-arc occurred in two phases: an early (~11 Ma) stretching and rifting, followed by spreading since 4-5 Ma. The history of inner-arc volcanic activity in the Andaman region extends to the early Miocene, and since the Miocene arc volcanism has been associated with an evolution from felsic to basaltic composition.

Provenance study on Eocene–Miocene sandstones of the Rakhine Coastal Belt, Indo-Burman Ranges of Myanmar: geodynamic implications

“…Since the Late Cretaceous the Burma micro-plate is assumed to have moved northward, relative to SE Asia, about 1000 km (Mitchell 1993). Chakraborty & Khan (2009) call it a sliver plate forming through rightlateral displacement between the subduction zone and the Sagaing fault, and its southward continuation in the Andaman Sea and offshore Sumatra. The Burma micro-plate constitutes part of the larger …”

Submarine mass wasting and associated tsunami risk offshore western Thailand, Andaman Sea, Indian Ocean

“…They have been described as rift basins (Hall and Morley, 2004;Jha et al, 2010), like numerous other Cenozoic basins across Sundaland (Polachan et al, 1991;Morley et al, 2001;Morley, 2002;Hall and Morley, 2004;Doust and Noble, 2008) and accordingly comprise a sedimentation history that is linked to typical rift stages (Doust and Noble, 2007;Doust and Sumner, 2008;Jha et al, 2010). The formation of the East Andaman Basin and the Mergui Basin results from backarc-related extensional tectonics, active throughout the area (Chakraborty and Khan, 2009;Curray, 2005). For the development of the Andaman Sea basins multi-stage models have been suggested (Kamesh Raju et al, 2004;Curray, 2005;Kamesh Raju, 2005;Chakraborty and Khan, 2009).…”

“…The formation of the East Andaman Basin and the Mergui Basin results from backarc-related extensional tectonics, active throughout the area (Chakraborty and Khan, 2009;Curray, 2005). For the development of the Andaman Sea basins multi-stage models have been suggested (Kamesh Raju et al, 2004;Curray, 2005;Kamesh Raju, 2005;Chakraborty and Khan, 2009). The area of rifting moved from the Mergui Basin over the East Andaman Basin to its current position ( Fig.…”

“…1) during Oligocene to Pliocene, due to increasingly oblique plate motions and changing convergence rates of Indian and Sundaland plates (Curray, 2005). In the Central Andaman Basin active sea floor spreading has occured since 4 Ma (Kamesh Raju et al, 2004;Kamesh Raju, 2005;Khan and Chakraborty, 2009). This modern spreading center links a group of N-S striking dextral strike-slip faults (Sagaing Fault, West Andaman Fault and Sumatra Fault, Fig.…”

“…1a). This system is described to accommodate the oblique convergence of the Indian and Sundaland plates (Michel et al, 2001;Nielsen et al, 2004a;Curray, 2005;Socquet et al, 2006;Chakraborty and Khan, 2009).…”