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New Guinea lies on the northern Australian plate boundary and has been a sensitive tectonic recorder of Cenozoic plate interactions between the Australian and Pacific plates. The specific plate interactions are documented by the evolution of the Northern New Guinea fault system and
the basin it overprints, the Northern New Guinea basin. Consideration of plate kinematics suggests convergence became increasingly oblique during the Cenozoic. We have calculated an average convergence of N6°E at 11.9 cm/year (4.7 in./year) during the Paleocene to Eocene, N60°E at 6.8 cm/year (2.7 in./year) during the Eocene to Miocene, and N60°E at 9.3 cm/year (3.7 in./year) during the Miocene to Holocene. Present-day Australian and Pacific plate vectors indicate predominantly left-lateral strike-slip motion in northern New Guinea.
The sinistral Northern New Guinea fault system defines this zone of plate interaction and represents a suture between continental crust to the south and intermediate crust to the north. The fault system extends more than 3,000 km (1,900 mi) from the Huon Gulf of Papua westward into eastern Indonesia, and is comprised of the Ramu-Markham (Papua) and Sorong (Indonesia) faults. This system is particularly well defined along the Ramu-Markham valley by recent earthquakes of focal depths between 41 and 300 km (25 and 186 mi). First motion studies of these earthquakes indicate both compressional and strike-slip events. Maximum compressive stresses delineated from conjugate shear fractures studied in the field closely agree with the first motion solutions. When combined with the trend analyse of surface fold axes and reflective seismic structural information, these data are consistent with the regional left-lateral deformation of this Tertiary basin.
Hydrocarbon exploration strategies within the Northern New Guinea basin must address not only sedimentation, but also must deal with the basin's complex structural and tectonic evolution. A static tectonic classification will not adequately define the Northern New Guinea basin. It is better described as an evolving basin being overprinted by wrenching.
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