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ABSTRACT: Cretaceous Stratigraphy of Eastern Irian Jaya, Indonesia

GRANATH, J. W., Conoco, Ponca City, OK, T. O. SIMANJUNTAK, GRDC, Bandung, Indonesia, and M. S. GAGE, Conoco, London, United Kingdom

Basic lithostratigraphic divisions within the Kembelangan Group were defined by the GRDC/BMR mapping program in western Irian Jaya in the early 1980s. New data from along the thrust front enhance correlation to sections in Papua New Guinea (PNG) and permit tentative sequence breakdown within the Cretaceous. The Woniwogi Sandstone (upper Valanginian to lower Hauterivian; equivalent to the Alene Member of the Ieru in PNG) and Barremian shales transgressively overlie middle Jurassic clastics in central Irian Jaya, Late Jurassic and earliest Cretaceous rocks are preserved under the unconformity in eastern Irian Jaya, and correlate to the Imburu and Toro formations in PNG. Overlying the Woniwogi, the shale-dominated Piniya Formation (Aptian through Turonian) is composed of at least two pro radational wedges built out to the north. The Piniya overlaps the Woniwogi to the south, and thus records the prolonged rise in Cretaceous relative sea level. The Ekmai Sandstone (Coniacian through Campanian) marks an abrupt downward shift in relative sea level, followed by transgression and the early stages of construction of a shelf margin wedge. The lower Waripi Formation, Maastrichtian in age, is composed of interstratified shallow water carbonate and clastic rocks. It completes the shelf margin wedge. The upper (Paleocene) Waripi oversteps the lower toward the south, placing a transgressive sequence boundary near the top of the Cretaceous within the Waripi Formation Debris flows and angular unconformities within the Waripi suggest an overprint of late Cretaceous tectonics on passive margin subsidence.

 

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