--> --> Abstract: Basement Controls from Evolution of Inversion Structures, E Java Sea, Indonesia, by Peter A. Emmet, James W. Granath, and Menno G. Dinkelman; #90082 (2008)

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Basement Controls from Evolution of Inversion Structures, E Java Sea, Indonesia

Peter A. Emmet1, James W. Granath1, and Menno G. Dinkelman2
1Consultant-BasinSPAN Programs, ION Solutions-GX Technology, Houston, TX
2BasinSPAM Programs, ION Solutions-GX Technology, Houston, TX

The initiation of thrust-fold belts is often obscure since early structures are eroded or else deeply buried. T-F belts that develop in regions of strong and persistent subsidence, however, may record and preserve a record of their early evolution. An incipient T-F belt is found in a back-arc region in the East Java Sea, Indonesia. The basin is in 200-2000 m deep water, flanked by carbonate platforms to the NW and by ultra-deep water to the SE. Data included a 1982 2D grid supplemented by regional 2D lines from the 2008 ION-GXT long-record JavaSPAN survey. Extension during Middle Eocene to Late Oligocene formed half-grabens which were inverted during the Neogene. Simultaneous regional subsidence prevented, except in a few cases, uplift and erosion of the structures so that most of the record of their growth was preserved. The evolution of some of the underlying Paleogene extensional structures can be demonstrated to be strongly controlled by the structural fabric of the basement, which is a low-grade pelitic schist of the accretionary complex that flanked the Sunda craton during the Cretaceous. The top of that accretionary basement is a profound angular unconformity. Mapping of intra-basement reflections allows recognition of faulted synclines which preserved Cretaceous thrust-fold structures. In the two cases in which basement synclines were mapped, Paleogene half-graben basins appear to have nucleated on existing faults or to have developed new faults parallel to bedding surfaces in basement. The inversion structures of the East Java Sea may provide an early analog to continental T-F belts dominated by deformed platform strata. Continued shortening in the East Java Sea will eventually involve the nearby platforms and may emplace thrust sheets that nucleated on basement synclines in deep water many km landward.

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