Abstract

Recent fieldwork in western Irian Jaya has led to recognition of a Late Phanerozoic rift-drift sequence in the Birds Head – Misool region. The presence of this sequence in Eastern Indonesia has many implications for the interpretation of the tectonic development of the region.

The timing of events in this rift-drift sequence is closely related to similar events described from Northwest Australia and suggests that the sequence was formed during the opening of the Indian Ocean in Mesozoic times.

It is suggested that the Banda Sea formed during the opening of the Indian Ocean and was subsequently trapped between the Arafura Platform and Sundaland craton by cenozoic plate adjustments caused by a continent-island arc collision in northern New Guinea; a Mesozoic age for the floor of the Banda Sea is supported by heat-flow data reported by Bowin and others (1980). It is further suggested that the 180° bend in the Banda Arc is largely inherited from the pre-existing configuration of continental and oceanic crust.

Graben formed by the Mesozoic rifting may have controlled the location of Tertiary basins in the Birds Head of Irian Jaya, and western Irian Jaya may have potential for hydrocarbon generation and entrapment beneath the Tertiary limestone cover.