ABSTRACT: Neogene Evolution of the North New Guinea Basin, Papua New Guinea: New Constraints from Seismic and Subsidence Analysis and Implications for Hydrocarbon Exploration
Andrew B. Cullen, John D. Pigott
The present-day North New Guinea basin is a Plio-Pleistocene successor basin that formed subsequent to accretion of the Finisterre volcanic arc to the Australian Plate. Largely detrital marine sediments of the successor basin cover three Miocene infrabasins. The Ramu, Sepik, and Piore infrabasins formed in a forearc setting relative to the continental Maramuni magmatic arc. The evolution of these infrabasins was strongly influenced by accretion of the composite Torricelli-Prince Alexander terrane to the Australian Plate.
Regional reflection seismic data and tectonic subsidence-subsidence rate calculations for seven wells drilled in the North New Guinea basin reveal a complex history. The timing and magnitude of subsidence and changes in subsidence rates differ between each of the Miocene infrabasins. A diachronous middle to late Miocene unconformity generally truncates infrabasin sequences. The Nopan #1 in the Sepik basin, however, has a complete middle Miocene to Pleistocene sedimentary record. This well records late Miocene negative subsidence rates documenting that the Nopan anticline grew as erosion occurred elsewhere in the region. This circumstance suggests that the major, sequence-bounding unconformity results from regional uplift and deformation, rather than changes in global sea level.
The successor basin phase commenced about 5 Ma in association with accretion of the Finisterre arc. Relatively undeformed successor sequences overlie the deformed infrabasins. A major change in the evolution of the successor basin occurred at 3.0 Ma and is characterized by rapid regional subsidence (200 m/ma) and concomitant uplift of adjacent blocks along high angle reverse and normal wrench faults. Uplifted late Pliocene bathyal sediments record local structural inversion of the successor basin. This latest tectonic episode is kinematically related to plate boundary reorganization accompanying the development of the Bismarck Spreading System and suggests that the North New Guinea basin is evolving into a wrench basin.
The Plio-Pleistocene evolution of the North New Guinea basin has two profound implications regarding hydrocarbon exploration. First, the late Pliocene structural inversion of parts of the basin hinders stratigraphic and facies correlation inferred from the present setting. The recognition of basin inversion is particularly important in the Piore basin for predicting the distribution of potential reservoir facies in the Miocene carbonates. Second, the subsidence data suggest that although potential source rocks may be thermally within the oil window, these rocks may not have had sufficient time to mature owing to their recent burial.
AAPG Search and Discovery Article #90097©1990 Fifth Circum-Pacific Energy and Mineral Resources Conference, Honolulu, Hawaii, July 29-August 3, 1990