Triassic Reservoir Characteristics of the Bird's Head, New Guinea, Indonesia: New Insight from Provenance Study
Authors: Gunawan Indra , Hall Robert , Sapiie Benyamin 
Published: May 2016

Abstract
The Bird's Head area of New Guinea is underlain by Australian continental crust and has relatively complete Palaeozoic to Recent stratigraphic record. One of the siliciclastic formations of the Bird's Head is the Tipuma Formation. Its age has been estimated as Triassic to Jurassic and is a potentially important hydrocarbon reservoir. New fieldwork was carried out, complemented by analysis of light and heavy minerals, U-Pb zircon geochronology, and quartz CL luminescence study.
The Tipuma Formation was previously dated only by its stratigraphic position and was suggested to have been deposited in a continental passive margin. This study shows sandstones and conglomerates were sourced from acid volcanic, metamorphic, and recycled sedimentary rocks to the north, and from the North Australian Craton. Cathodoluminescence study on detrital quartz supports the importance of the important of volcanic quartz. The quartz provenance of sandstones from the Lower, Middle and Upper Members of the Tipuma Formation are dominated by low-T metamorphic and volcanic with little plutonic origin and there is some variation with stratigraphic position and in the Middle Member the abundance of volcanic quartz declines. The youngest zircon ages indicate it was deposited in the Triassic. Permo-Triassic (205–275 Ma), Neoproterozoic (c. 975 Ma), Early Mesoproterozoic (1.4–1.6 Ga), and Paleoproterozoic (1.8–2.0 Ga) populations, with a few grains of Archaean age (2.8–3.2 Ga) characterized most Tipuma Formation sandstones.
The Tipuma Formation was probably not deposited in a simple continental block setting and was influenced by volcanic activity in the Bird's Head during its deposition. The long-lived Palaeozoic volcanic activity interpreted to indicate subduction of the palaeo-Pacific oceanic plate under the Australian continent associated with an Andean-type active margin. The decline of the abundance of volcanic quartz, Permo-Triassic zircons, and increase in Carboniferous and Proterozoic zircons within the Middle Member indicate a reduced contribution of sediment from the arc and an increased contribution of sediment from northern Australia.

Introduction
The Bird's Head of West Papua (Figure 1) is located in the western part of New Guinea and is surrounded by active or recently active tectonic zones, where three of the Earth's major tectonic plates, the Eurasian, Indian-Australian and Pacific Plates (with Philippine Sea and Caroline sub-plates) converge. Relative to the Eurasian plate the Indo-Australian plate is currently moving NNE, and the Pacific plate is moving WNW. The Tipuma Formation of the Bird's Head of New Guinea, Indonesia is a potentially important reservoir. This siliciclastic sequence has therefore been one of the main objectives for oil and gas drilling since the early 70's. However, its unfossiliferous character makes it difficult to determine its true age. There is not much information about the composition of the formation or variations in lithologies and no research has been carried out concerning its provenance prior to this study.