  The Banda Arc, situated west of Irian Jaya and in the easternmost extension
of the Sunda subduction zone system, reveals a characteristic bowl-shaped
geometry in seismic tomographic images. This indicates that the oceanic
lithosphere still remains attached to the surrounding continental margins of
northern Australia and the Bird's Head microcontinent. Major controversies
exist between authors proposing an allochthonous or autochthonous origin of the
Bird's Head block. Either scenario has important implications for plate
kinematic models aiming to reconstruct the tectonic evolution of the region and
the late Jurassic seaoor spreading geometry of this now subducted
Argo-Tanimbar-Seram (ATS) ocean basin. Wider implications affect the tectonic
conguration of the Tethyan-Pacic realm, the distribution of plate boundaries as
well as the shape and size of continental blocks which have been rifted off the
northeastern Gondwana margin during the Late Jurassic and are now accreted to
the SE Asia margin. We apply structural geology restoration techniques to
unfold the subducted oceanic lithosphere of the Banda Slab. Our slab unfolding
results help to discriminate between the different hypotheses concerning the
origin and kinematic history of the Bird's Head tectonic block. According to
our preferred model, the block is required to rotate 20-35 degrees clockwise
relative to its present-day position and that the initial geometry of the ATS
ocean basin was more or less rectangular shaped. We evaluate currently accepted
plate kinematic scenarios for the Jurassic and younger seaoor spreading history
north of Australia in conjunction with our restored ocean basin geometry and
conclude that the Bird's Head block is autochthonous to western Irian Jaya,
with its western margin being a continental transform margin during the rifting
and opening of the ATS ocean.
