Abstract

The Eastern part of the INDONESIAN ARC presents special characters in relation with peripheric collision with the AUSTRALIAN and PAPUAN craton. The BANDA Sea has a complex submarine morphology which has received several different explanations.

The external arc is made of fragments of continental terranes and of accretionnary wedges. It is separated from the internal volcanic arc by an inter-arc trench which may be very deep in the eastern part (WEBER TROUGH).

Geological reconnaissances in KAI and TANIMBAR Archipelagoes show special features at the apex of the arc. There is an East-West succession of geologic unit :

– folded paleogene and miocene series belonging of Australian borderland and accreditionnary wedges

– neogene basins with overpressured shales which are the origin of numerous mud volcanoes

– melange olistolites or nappes overthrusting a part of the neogenic basins

– Pre-Tertiary basement terranes in the Western part

All these units overthrust a downwarped Australian borderland with the subduction plunging NW in the Southern part of the Arc (TIMOR) and SSW in the Northern part (CERAM). So the BANDA Arc which is growing eastwards would be an "inducted" arc as described by BRUNN. The BANDA Sea would represent a stretched internal sea.