AGE, CHARACTER AND PROVENANCE OF THE TIPUMA FORMATION, WEST PAPUA: NEW INSIGHTS FROM DETRITAL ZIRCON DATING

摘要

The Bird's Head of West Papua is underlain by Australian continental crust and has a relatively complete Silurian to Recent stratigraphy. It is surrounded by active or recently active tectonic zones. The Tipuma Formation of the Bird's Head is a potentially important hydrocarbon reservoir and it also records part of the region's Mesozoic tectonic history. However, little is known about variations in lithologies and their composition, and nothing is known about its provenance. New field and laboratory studies are providing new information, which suggests a more complex history than the continental block setting widely accepted previously. The age of the Tipuma Formation is uncertain due to the absence of fossils, and its suggested Triassic age has been based solely on stratigraphic position. The formation rests unconformably on the Silurian-Devonian Kemum Formation and conformably on the Permian Aifam Formation and is overlain by the Cretaceous Jass Formation. It is dominated by red to cream well-bedded mudstones, sandstones and conglomerates deposited in a fluviatile setting. Sandstones are generally compositionally and texturally immature. They are quartz-rich and most samples contain volcanic quartz.