Cenozoic Inversion Structures, East Java Sea, Indonesia: Can Tectonic and Eustatic Influences on Stratal Architecture be Distinguished?

Peter A. Emmet and Peter R. Vail

A detailed structural and stratigraphic study of a deep water (>200 m) sub-basin in the East Java Sea utilized 2-D seismic and well data in the vicinity of Amoco wildcats drilled in the early 1980s. Extensional half-graben basins in the Sunda back-arc were filled by middle Eocene non- marine siliciclastics, including lacustrine coals, and were transgressed by late Eocene shallow-water carbonates on the margins of the rift basins with shale dominating in the basin axes. Regional subsidence characterized by sag basin geometries followed during the late Oligocene to early Miocene, with continued aggradation of shallow-water carbonates on the basin margins and deep-water carbonate mudstone and shale deposition in the basin axes.

The onset of compression during the early Miocene was reflected by an increase in subsidence and sedimentation rates. The Paleogene extensional basins progressively inverted as thick wedges of Miocene and younger calcareous mudstone accumulated on their flanks. During the Miocene the northern margin of the basin was strongly progradational reflecting relative tectonic stability and a dominantly eustatic stratal influence, while the southern margin back-stepped due to higher tectonic subsidence related to the inversion process. In the deep basin, horizons defining growth phases of inversion structures correlate with eustatically-controlled unconformities on the basin margins. The geometry (wedge, drape) of the growth packages and the internal stacking pattern of eustatic sequences with n the growth packages is controlled by local tectonics.

AAPG Search and Discover Article #91019©1996 AAPG Convention and Exhibition 19-22 May 1996, San Diego, California