--> Abstract: Cenozoic Basin Formation in Southeast Asia, by L. A. Lawver, L. M. Beckley, and T-Y. Lee; #90958 (1995).
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Abstract: Cenozoic Basin Formation in Southeast Asia

Lawrence A. Lawver, Lila M. Beckley, Tung-Previous HitYiTop Lee

Several interesting trends can be identified in the pattern of sedimentary basin formation across Southeast Asia. Prior to the middle Eocene, basin formation appears to be restricted to the Indochina and South China margins. At 50 Ma, basin development starts southeast of Kalimantan. It is not until the middle Eocene to Oligocene, though, that basin formation occurs on a regional scale. During this time period, a number of basins form near the major Southeast Asian Plate boundaries. Between 44 Ma and 20 Ma, the Mergui Bask the Gulf of Thailand basins, and basins in central Thailand resulted from the hard collision of Greater India with Eurasia. Regionally, no major changes in basin history occurred from Oligocene until the middle to late Miocene, when the main phase of ex ension and sediment accumulation ended in the basins in eastern Sumatra, the Gulf of Thailand and near the margin of Indochina. The last major episode of basin formation occurred near Timor, between 4 Ma and Present.

A sub-regional pattern of basin opening can be identified in the outer-arc basins associated with the Java Trench. The opening of these basins appears to progress from the north (Sibolga and Nias Basins, 30 Ma) to the southeast (Timor Basin, 0 Ma). The progression of basin opening in the eastern Sumatra and Java areas is not as simple. During the middle Eocene, the Sunda Basin to the southeast formed first, and then the Mergui, North Sumatra, Central Sumatra and South Sumatra basins formed later during the Oligocene.

It is thought that the last episode of basin formation is caused by the collision of the Australia-New Guinea plate with the Banda Arc but it is not readily apparent why extensional basins should form during collisions unless the collision is off-axis and results in extrusion as when India collided with Eurasia. The inclusion of sedimentary basins on paleoreconstructions of Southeast Asia highlights the complexity of the tectonic history of the region.

AAPG Search and Discovery Article #90958©1995 AAPG Pacific Section Meeting, San Francisco, California