The Bird's Head terrane of West Papua, Indonesia has a poorly understood geologic origin and tectonic evolution. As recently as a decade ago, few data were available to constrain tectonic models for the evolution of east Indonesia. Delineation drilling and extensive coring of the Permian to Paleocene section of the super giant Tangguh gas field in the late 1990's provides important geological data that must be considered in any tectonic reconstruction of the greater Bird's Head. The most critical observation is that the Tangguh field stratigraphic section, including age, thickness, facies, hiatuses, and key markers, contrast strongly to the previously well-known Kembelangan Group stratigraphy of the Bird's Head derived from outcrops and regional wells. The Mesozoic section of the Bintuni platform is thin, with most of Mesozoic time represented by a hiatus. At Tangguh, clean quartzose sandstone of Middle Jurassic age unconformably overlies Permian elastics, coals and carbonates. In adjacent areas, the Triassic section is generally present. Our interpretation is that the Tangguh Middle Jurassic reservoir sandstones were deposited in an incised valley that had cut out the entire Early Jurassic and Triassic interval. The clean quartzose Middle Jurassic sandstones of the incised valley fill are clearly cratonally derived and the strata are observed to stack or transgress eastward (present geography) toward their cratonal source. Currently, the area east of the Bintuni platform is Cenderawasih Bay and not a valid candidate for a cratonal source for the Middle Jurassic Tangguh reservoir sandstones. We speculate that Tangguh and the Bintuni platform incised valley have been detached from the NW Shelf of Western Australia, translated northward at least 500 km. and rotatedcounterclockwise by 50°-90° along a dextral strike-slip fault system during the Late Neogene to its current position.
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