Late Cenozoic geohistory of Seram, Indonesia

Abstract

Two sections in Plio - Pleistocene basin deposits were measured and systematically sampled in the southwestern part of Seram, the largest island in the northern Banda Arc, Indonesia. A geohistory analysis of field and laboratory data allows for a reconstruction of the vertical movements of the area and demonstrates that the basement of southwestern Seram was subsiding at an average rate of 50 cm/ka during the Late Pliocene - Early Pleistocene, an episode of relative tectonic quiescence, following Late Miocene compressional deformation and uplift. In the Late Pleistocene, compressional deformation and uplift was renewed but differed in style and orientation from the Late Miocene events. This history of the basins in southwestern Seram is very similar to that of the oil producing basins in the northeastern part of the island. The Late Cenozoic tectonic history of Seram can be interpreted in the frame of regional plate motions. Due to an anticlockwise rotation of the island and a relatively north to northwestward motion of Irian Jaya, the overall tectonic regime in the area gradually changed from compressional in the Late Miocene to strike-slip in the Late Pliocene. Finally, collision of Seram with the continental crust of Irian Jaya resulted in renewed compressional deformation from the Late Pleistocene onwards.