The Banda Sea: continental collision at the eastern end of Tethys

Abstract

Continental collision in the Himalayan and Mediterranean segments of the Tethyan domain has produced regions of dramatic local extension within overall compressional environments. In the Mediterranean, deep basins have been created which are partly enclosed by orogenic belts forming arcs with total curvatures approaching 180°. These basins are floored either by attenuated continental crust (Alboran and Aegean seas) or by oceanic crust (parts of the Tyrrhenian Sea), The eastern Indonesia (Banda Arc) segment of the Tethyan collision zone has not usually been considered in terms of continent-continent collision because attention has been focussed on the presentday impact of Australia. Ther e is, however, much evidence for earlier collisions of fragments of the Australasian continent with this margin of Eurasia, and there are striking resemblances to the Mediterranean region. High standing ridges in the centre ofthe Banda Sea include continental material but water depths in excess of 5 km testify to the presence of oceanic crust in the North and South Banda basins. The 180° loop of the Banda Arc can be considered an end member in the spectrum of Tethyan collisional orogens, at the limit a t which oceanic influences (in the form of th e uncollided Indian Ocean west of Australia) remain important.