Publications

The anticlockwise rotation of the Bird’s Head microplate relative to Australia is the primary control on the tectonics of eastern Indonesia. The rotation, about a pole located in the southern Arafura Sea, is accommodated by extension behind the Bird’s Head block, and compression in front of it. The extension is expressed as an active triangular pull-apart basin (a sphenochasm), the Aru Trough, and a now-inactive sphenochasm, Cenderawasih Bay, which underwent extension during the Pliocene. Extension in Cenderawasih Bay was accommodated by massive subsidence in the Waipoga Basin on the southeastern margin of the bay, and by the development of a core complex on the southwestern margin. To the north of Cenderawasih Bay the northern limit of extension was accommodated on the Yapen Fault Zone, which for a short interval changed its sense of motion from left-lateral at the present and during the Late Miocene, to right-lateral during the Pliocene. Continued east-west widening of Cenderawasih Bay at the present day (without active crustal extension) is accommodated by left-lateral offset on the southeastern margin of the bay, and by right-lateral offset on the western margin. Crustal shortening in front of the rotating Bird’s Head block is accommodated across the Banda Arc, with the anticlockwise rotation of the Bird’s Head primarily responsible for the tightness of the Banda Arc curvature.