The Seram Thrust System in Eastern Indonesia in Relation to Banda Back-Arc Spreading
For many years the eastern end of the Banda Arc has been portrayed on standard tectonic maps to bend to the north and form an acute syntaxis between the island of Seram and the western portions of New Guinea, despite the difficulties that configuration poses to crustal mechanics at depth. New syntheses of the regional geology based on potential methods datasets, earthquake seismology, and both new and reinterpreted reflection seismology, suggest that the crustal scale shortening previously interpreted as a Benioff or subduction zone north of Seram is actually a crustal-scale thrust fault driven by back-arc spreading in the South Banda Basin. Originally, the eastern end of the Arc curled more strongly around the eastern side of the continental fragments composited to form Sulawesi, and was related to the opening of the North Banda Basin. Rollback of older continental crust north of Australia as it subducted under the Banda Arc in late Neogene accentuated back-arc spreading and induced a sweeping of the Arc toward Australia and the opening of the South Banda Basin. The northern tip of the Arc swept past Buru and Seram on a transform south of the islands. The western tip was fixed south of Sulawesi near the southern end of the Bone Basin, where a pivot point of sorts confined the back-arc extension to the east and south of the more intact eastern Sulawesi. Opening of the South Banda Basin immediately south of Seram confined the shortening deformation to Seram itself—Buru to the west is unaffected despite a similar geology and on-strike location. The earliest portions of the thrust belt are thin-skinned, as displayed on the island of Seram itself, which was later undercut by and carried in the hanging wall of the deeper, thick-skinned thrust system. Several hydrocarbon accumulations discovered in the thin-skinned belt may be duplicated along strike, but may also indicate that the foreland in the Seram Trough is also prospective with a similar petroleum system.
AAPG Search and Discovery Article #90090©2009 AAPG Annual Convention and Exhibition, Denver, Colorado, June 7-10, 2009