--> Abstract: The Structure and Sequence Stratigraphy of Extensional Basins: A Case Study Offshore Sarawak and Sabah, by Kenneth J. Thies, Daniel J. Tearpock, Richard E. Bischke, Jeffrey Boyer, Ahmad Mansor, and Mohamad Hamdan; #90039 (2005)
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The Structure and Sequence Stratigraphy of Extensional Basins: A Case Study Offshore Sarawak and Sabah

Kenneth J. Thies1, Daniel J. Tearpock1, Richard E. Bischke1, Jeffrey Boyer1, Ahmad Mansor2, and Mohamad Hamdan2
1 Subsurface Consultants & Associates, LLC, Houston, TX
2 Petronas, Kuala Lumpur, Malaysia

A structural and sequence stratigraphy study based on a reprocessed regional grid of 10,000 line kilometers of seismic covering the deepwater portion of offshore Sarawak and northwest Sabah Basin was undertaken with the objective of improving the present understanding of the tectonics, paleo-depositional environments, and overall hydrocarbon potential of the offshore deepwater Sarawak and northwest Sabah Basins. This paper confines itself to a portion of the regional study which consists of the Oligocene to Early Miocene syn-rift section contained within extensional Previous HithalfNext Hit-graben sub-basins situated beneath a regional Mid-Miocene Unconformity. Several of these Previous HithalfNext Hit-grabens exhibit ramp-flat-ramp geometries analogous to the productive Corsair Fault trend/ Brazos Ridge Trend, offshore Texas, USA.

The deepwater offshore Sarawak and northwest Sabah region has evolved in response to the complex tectonics related to the opening of the South China Sea starting between 37 and 32 Ma and lasting until ca. 15 Ma. Intense rifting during the rift-drift transition created a series of characteristic wedge-shaped Previous HithalfNext Hit-grabens. These Previous HithalfNext Hit-grabens are bounded by large scale listric faults that expand the stratigraphic section and often appear to sole-out at depth. Further extensional synthetic faulting has sub-divided the Previous HithalfNext Hit grabens into multiple compartments. Later compression appears to have uplifted and folded some of the Previous HithalfNext Hit-grabens.

The oldest rift-fill stratigraphy penetrated to date is Oligocene in age and was deposited in an inner to middle neritic depositional environment. Based on regional analogues, it is possible that the earliest rift-fill was deposited in fluvial and/or lacustrine environments. Post-rift infill of the Previous HithalfTop-grabens culminated in lower coastal plain to shallow marine sedimentation. The rift-fill section can be sub-divided by several sequence boundaries.

AAPG Search and Discovery Article #90039©2005 AAPG Calgary, Alberta, June 16-19, 2005