Publications

The South Halmahera Basin is situated at the southern edge of the Philippine Sea Plate in a complex region of modern and ancient island arc and continental fragments. The basin was influenced by a long arc history, a collision with the Australian continental margin in the Early Miocene, and Neogene strike-slip faulting. A synthesis of the basin’s tectono-stratigraphic evolution and potential petroleum systems was obtained from an integrated analysis of regional 2D seismic surveys and geological mapping of Halmahera Island and adjacent islands. The basin was initiated by rifting in the Late Eocene to form a west-east elongated Paleogene backarc basin in which terrestrial to marginal marine clastic sediments, including coals, were deposited, followed by thick deep marine turbidites. Early Miocene arc-continent collision is interpreted to have caused uplift, erosion and of a major unconformity above which widespread Miocene limestones were deposited. After deposition of the limestones two sub-basins formed in the late Neogene, separated by a topographic high of older rocks. The northern and southern sub-basins were a response to the formation of the Halmahera volcanic arc to the west and strike-slip movements along the Sorong Fault Zone (SFZ) to the south. Pliocene-Pleistocene events related to movements on the SFZ resulted in NW-SE fault propagation folding in the southern sub-basin, deformed the high area separating the sub-basins, making geometry and style of older structures unclear, and initiated magmatic activity along the deformation zone. An oil seep from Halmahera, and similarities to the productive Salawati Basin south of the SFZ suggest that this frontier area has potential to contain effective petroleum systems. Two carbonate successions, Eocene and Miocene reefal limestones, are potential reservoirs. Eocene coals are one potential source, and Miocene deep water limestones in the centre of the South Halmahera Basin could resemble source rocks in the Salawati Basin.