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Evolution and Hydrocarbon Occurrences of Rift Basins from the Western Margin of Sunda Platform and Relations with East Andaman Basin

Pritam Jha, Dino Ros, and Andrea Deglialessandrini
Exploration Department, Eni India Limited, New Delhi, India

The western limit of the Sunda Platform of South-East Asia is marked by NNE-SSW trending Mergui Ridge which terminates at the regional strike slip motions of Sagaing Fault System at the north and West Andaman Fault System at the south in the Andaman Sea. The western flank of the Mergui ridge exhibits evidence of intense tectonic activity; first a significant passive margin rifting phase (Eocene-Oligocene) followed by high subsidence phase (Miocene onwards). This new sub-basin is being termed here as the East Andaman Basin and the paper aims to build its relation with the other rift basins (North Sumatra and Mergui) present in the Andaman Sea area.

During Late Eocene-Oligocene, Mergui and North Sumatra rift basins were created as NNE-SSW trending rifts at the western side of the Sunda. At the same time, western flank of Mergui continental ridge also underwent extensive rifting with its thinned continental crust and could be envisaged as a passive margin rift basin (East Andaman Basin) bordering the western Sunda margin. Soon after, the advancement of Indian plate at the west of Sundaland and Miocene-onwards post-collision tectonics of the region resulted in a regional pull-apart system in the Andaman Sea causing considerable subsidence at the western flank of Mergui ridge. The East Andaman Basin therefore witnessed a poly-cyclic history with: 1) Eocene-Oligocene rifting phase at western edge of the Sundaland; and 2) Pull-apart tectonics since Miocene in the Andaman Sea.

The North Sumatra Basin is known as a major petroliferous basin in the world with its typical rift-related petroleum system. Geologically the East Andaman Basin also bears significant resemblance with North Sumatra and shows interesting hydrocarbon potential.