Structural Style and Evolution of the Songkhla Basin, western Gulf of Thailand

Chanida Kaewkor, Ian Watkinson, Peter Burgess

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The Gulf of Thailand is part of a suite of Cenozoic basins within Sundaland, the continental core of SE Asia. The Songkhla Basin, in the southwestern gulf, demonstrates several properties that have previously been considered to be characteristic of these basins, such as: multiple distinct phases of extension and inversion, rapid post-rift subsidence, association with low-angle normal faults; and a Basin and Range-style. A large asymmetric half-graben, bounded by NNW-SSE-trending faults along its western edge, the Songkhla Basin is approximately 75 km long, 30 km wide, and is separated from other subbasins in the gulf by a N-S trending basement horst block, the Ko Kra ridge.

Two oil fields in the Songkhla Basin produce approximately 12,000 bbls/d, but the structural evolution of the basin remains relatively poorly known. This paper utilises 3 wells and 2,250 km2 of 3D seismic from the Songkhla Basin to understand basin structure and evolution.

Structural elements in the Songkhla Basin include a major border fault, inversion-related compressional structures and inter-basinal faults. Sediments thicken to the west along growth fault surfaces. Most of the faults are east-dipping but some are antithetic. Three dominant sets of normal faults, trending NNW-SSE, N-S and rarely NE-SW are developed in this basin. The NNW-SSE faults bounds the basin and are sub-parallel to the rift axis of the Songkhla basin. Pre-Cenozoic basement fabrics are oriented broadly N-S, slightly oblique to the dominant Cenozoic fault orientation.

There are three major tectonostratigraphic packages in the Songkhla Basin:1) syn-rift, which can be divided into three sub-extensional packages and expressed as Eocene initial rifting I; Oligocene II; and the final rift stage Lower Miocene III;2) a period of positive inversion and deposition of post-rift package I; the inversion started from early Middle Miocene and was followed by post-rift thermal subsidence terminated by the Mid-Miocene Unconformity (MMU); 3)the last tectonostratigraphic package is post-rift II, that was deposited from the start of the Late Miocene to Recent.
Original languageEnglish
Title of host publicationProceedings of the International Conference on Geology, Geotechnology, and Mineral Resources of INDOCHINA
Place of PublicationKhon Kaen, Thailand
Number of pages12
Publication statusPublished - 23 Nov 2015

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