Publications

Bone Bay separates the South and SE Arms of Sulawesi. It is one of several enigmatic basins around this unusual K-shaped island and has been interpreted as rift-, collision- or arc-related and underlain by either oceanic or continental crust. Evaluating different interpretations has been hindered by lack of data. New insights into Bone Bay are based on a seismic stratigraphic study of regional 2D grid and seabed bathymetry data, both acquired in 2007. Bone Bay has multiple depocentres and structural highs. A major basin trend, orientated approximately N-S, is divided into three depocentres by the Kolaka Fault zone in the north and by a W-E Basa basement high in the south. The two northern depocentres contain a thick sedimentary succession in a narrow basin. In places the acoustic basement can be traced below the 8 second TWT cut-off. Accommodation was produced by extensional displacement on major basin-bounding faults. The southern depocentre is characterised by basement-involved domino fault blocks with extensional growth-strata visible in some half graben. There is onlap and burial of post-extension topography with development of a large N-S submarine canyon system visible from 4 seconds TWT to the seabed. Two other depocentres formed later than the central basin: a small depocentre between the island of Kabaena and the SE Arm, and a narrow N-S orientated extensional basin located adjacent to the island of Salayar. Early growth strata are interpreted to have been deformed by strike-slip movement along the western margin of the central basin. Deformation was followed by development of a widespread carbonate shelf on the eastern margin of Bone Bay displaying at least one phase of progradation. Stratigraphically higher, a regional unconformity is interpreted to correspond to a latest Miocene event seen in two wells: Kampung Baru-1 and BBA-1X. This marks a brief tectonically-induced regional shallowing, followed by a phase of basin-wide subsidence causing drowning of local shallow water carbonates producing pinnacle morphologies that are interpreted to step back to topographic highs. Subsidence was accompanied by an increase in sediment supply.