ABSTRACT: Tectono-Stratigraphy of a Late Eocene Rift System within the Kangean PSC Block-East Java Sea, Indonesia

HENK, BO, Arco Bali North, Inc., Jakarta, Indonesia

Late Eocene extension led to the formation of an east-west trending rift system within the Kangean Block: the East Java Sea, Indonesia. Late Miocene structural inversion has overprinted the earlier extensional fabric thus making detailed basin reconstructions necessary for interpreting the Late Eocene system. Seismic sequence analysis,

structural and isopachous mapping, and subsequent flattening exercises has resulted in identification of a series of sediment filled, facing and non-facing half-grabens.

Lithostratigraphic and biostratigraphic studies indicate tectonic control of the stratigraphy. Asymetric half-graben axes became the depositional sites for Ngimbang Clastics source and reservoir facies and subsequent deepwater Ngimbang Carbonate facies. Structurally high basement blocks on the ramp margins behaved as sites for thin clastic deposits and thick shallow water carbonate buildups. Ngimbang Shale blanketed the entire carbonate system thinning over the highs and thickening into the half-graben axes.

Ngimbang Clastics source rocks consists of oil and gas prone carbonaceous shale and coal deposited within shallow lacustrine and estuarine environments. Reservoir rocks are comprised of alluvial fan and axial transported fluvial deltaic sands of the Ngimbang Clastics, high energy platform margin grainstone buildups and fractured lagoonal wackestones and packstones of the Ngimbang Carbonate.

AAPG Search and Discovery Article #91015©1992 AAPG International Conference, Sydney, N.S.W., Australia, August 2-5, 1992 (2009)