Seismic geomorphology and high-resolution seismic stratigraphy of inner-shelf fluvial, estuarine, deltaic, and marine sequences, Gulf of Thailand

Pleistocene fluvial, estuarine, marine, and deltaic depositional systems were identified in the uppermost 80 m (262 ft) of the central Gulf of Thailand modern continental shelf, situated approximately 70 m (∼230 ft) below sea level. Integration of offshore three-dimensional (3-D) seismic reflection...

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Bibliographic Details
Published in:	AAPG bulletin Vol. 95; no. 11; pp. 1959 - 1990
Main Authors:	Reijenstein, Hernán M, Posamentier, Henry W, Bhattacharya, Janok P
Format:	Journal Article
Language:	English
Published:	Tulsa, OK American Association of Petroleum Geologists 01-11-2011
Subjects:	aggradation bars Cenozoic deltaic environment Earth sciences Earth, ocean, space Economic geology energy sources estuarine environment Exact sciences and technology fluvial environment fluvial features geophysical methods geophysical profiles geophysical surveys Gulf of Thailand high-resolution methods Hydrocarbons incised valleys marine environment North Pacific Northwest Pacific Pacific Ocean paleogeography petroleum petroleum exploration Pleistocene point bars Quaternary Quaternary geology regression sea-level changes Sedimentary rocks seismic methods seismic migration seismic profiles seismic stratigraphy sequence stratigraphy South China Sea stacking Stratigraphy surveys thickness three-dimensional models transgression two-dimensional models valleys West Pacific South China Sea West Pacific Asia Pacific Ocean Far East Thailand Gulf of Siam continental shelf thickness oxbow lakes boreholes modern seismic reflection Cenozoic high resolution inner shelf estuarine environment Quaternary high frequency point bars seismic stratigraphy offshore aggradation fluvial environment hemipelagic sedimentation channels marine environment discontinuities Phanerozoic petroleum exploration sea level deltaic environment meanders Pleistocene
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Summary:	Pleistocene fluvial, estuarine, marine, and deltaic depositional systems were identified in the uppermost 80 m (262 ft) of the central Gulf of Thailand modern continental shelf, situated approximately 70 m (∼230 ft) below sea level. Integration of offshore three-dimensional (3-D) seismic reflection data, high-resolution shallow-penetration two-dimensional (2-D) seismic reflection sparker and boomer profiles, and shallow geotechnical borehole measurements enabled the identification of seven depositional sequences. The 3-D plan-view images at successive time slices exhibit single meandering channels (as much as 600 m [1969 ft] wide) and channel belts (as much as 10 km [6.2 mi] wide) deposited in the shelf during times of subaerial exposure. Additional geomorphic features imaged include incised valleys, interfluves, oxbow lakes, neck and chute cutoffs, and point-bar meander scrolls showing evidence of expansion and translation. The high-resolution 2-D profiles, with a tuning thickness of approximately 25 cm (∼9.8 in.), enabled the discrimination of high-frequency stratigraphic discontinuities (sequence boundaries) and allowed a detailed bed-scale seismic facies characterization of fluvial (point bars), deltaic (clinoforms), estuarine, and marine deposits within a sequence-stratigraphic context. The complete succession shows that most fluvial systems lie within incised valleys in the lower parts of each depositional sequence, fluvial channels show a degradational stacking pattern, and no evidence of fluvial aggradation is observed; aggradation is limited to hemipelagic sedimentation during marine incursions. A shallow (<35 m [<115 ft]) single-story incised valley was described in detail, placing particular emphasis on the recognition criteria and the controls on valley formation and preservation potential of different systems tracts in an inner-shelf location. The 3-D characterization of this system allowed differentiation of sand-prone point-bar deposits and mud-prone abandonment channel facies. The sinuous but continuous mud-filled channel may act as a lateral muddy barrier or baffle that can potentially subdivide a reservoir system into discrete compartments.
ISSN:	0149-1423 1558-9153
DOI:	10.1306/03151110134