Abstract:
This study presents a detailed facies analysis of shallow-water platform and ramp deposits of an extensive Tertiary carbonate platform. Temporal and spatial variations have been used to construct a palaeogeographic reconstruction of the platform and to evaluate controls on carbonate sedimentation The late Eocene to mid-Miocene shallow-water and outer ramp/basinal deposits of the Tonasa Carbonate Platform, from the Pangkajene and Jeneponto areas of South Sulawesi respectively, formed initially as a transgressive sequence in a probable backarc setting. The platform was dominated by foraminifera and had a ramp-type southern margin. Facies belts on the platform trend east-west and their position remained remarkably stable through time indicating aggradation of the platform-top. In comparison outer ramp deposits prograded southwards at intervals into basinal marls. Tectonics, in the form of subsidence, was the dominant control on accommodation space on the Tonasa Carbonate Platform. The location of barriers' and the resultant deflection of cross-platform currents, together with the nature of carbonate producing organisms also affected sedimentation, whilst eustatic or autocyclic effects are difficult to differentiate from the affects of tectonic tilting. Moderate- to high-energy platform top or redeposited carbonate facies may form effective hydrocarbon reservoirs in otherwise tight foraminifera dominated carbonates, which occur widely in SE Asia, and have not been affected by extensive porosity occlusion