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ABSTRACT: Tectono-stratigraphic evolution of the North Makassar Basin, Indonesia

Moss, Steve J.1, Wayne Clark2, Peter Baillie3, A. Edy Hermantoro4, and Suryadi Oemar5
(1) IKODA Pty, Perth, Australia 
(2) Ikoda Pty Ltd, Perth, Australia 
(3) TGS-Nopec Geophysical Company, Perth, Australia 
(4) MIGAS, Jakarta, Indonesia 
(5) Pertamina, Jakarta, Indonesia

The formation of the Makassar Straits and nature of crust underlying the straits has long been the subject of debate. Previous interpretations have suggested either purely continental or continental-to-oceanic rifting in the Eocene, Middle Tertiary, Miocene or Pliocene, trapped Cretaceous oceanic crust or an actively forming Neogene-Quaternary foreland basin for the formation of the Makassar Straits. Interpretation of 6600km of newly acquired seismic data over the north Makassar Straits and deepwater Mahakam delta clearly indicate a Middle Eocene extensional origin and that the amount of extension was sufficient to generate seafloor spreading in deeper parts of the northern Makassar Straits. Evidence for the presence of oceanic crust underlying parts of the North Makassar Straits includes the rugose nature of the basement seismic horizon and the presence of volcanic topography (sea mounts). Indications of earlier extension is also clearly evident from lines crossing the southern margin of the Mangkalihat Arch where Paleogene half graben are evident. The North Makassar Basin is a Middle Eocene marginal oceanic basin formed with the extension of the West Philippines Sea and Celebes Sea spreading ridge into east Borneo/West Sulawesi margin of Eurasia during Middle Eocene times. This interpretation is in line with a variety of other geological data including plate tectonic modelling, gravity modelling and palaeogeographic reconstructions. The four most important and prominent seismic stratigraphic markers in the North Makassar represent major phases of the basin development from basin initiation in an extensional setting through to the present-day basin bounded by areas dominated by contractional tectonics. These are described in the context of the tectono-stratigraphic evolution of the basin.

AAPG Search and Discovery Article #90913©2000 AAPG International Conference and Exhibition, Bali, Indonesia