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ABSTRACT: Petroleum prospects in the Ramu-Markham foreland basin, northeastern Papua New Guinea

Milsom, John1 and Robert H. Findlay2
(1) University College London, London, United Kingdom 
(2) Geological Survey of Papua New Guinea, Port Moresby, Papua New Guinea

The Adelbert and Finisterre ranges (AFR) of northern Papua New Guinea are separated from central New Guinea by the broad valleys of the Ramu and Markham rivers, which are underlain by sediments which may be more than 6 km thick. Gravity data indicate still greater sediment thicknesses beneath the southward-thrusting Finisterre Range. The nature, provenance and thermal history of these sediments are poorly known, and prospectivity assessments must be based on reconstructions of geological history.

Stratigraphic studies indicate derivation of the majority of Ramu-Markham and AFR sediments from the south, and place severe constraints on the possible past separation of the AFR from central New Guinea. Seismic zones dipping both north, beneath the AFR, and south beneath the New Guinea Highlands testify to the former presence of oceanic crust between the two but do not require a basin more than a few hundred kilometres wide. The Solomon Sea, believed to be of Miocene age, is an eastern extension of this basin. A hypothesis compatible with all the presently available data invokes Miocene back-arc spreading, to create the oceanic crust, followed by arc reversal and basin destruction. Source, seal and reservoir rocks, derived more from Central New Guinea than the recently emergent AFR, are all likely to be present beneath the depression. Lack of thermal maturity presents the highest potential risk, and the most favourable conditions for hydrocarbon generation are likely to occur beneath the overthrust mountain belts.

AAPG Search and Discovery Article #90913©2000 AAPG International Conference and Exhibition, Bali, Indonesia