Abstract

Bituminous Upper Triassic and Lower Jurassic sediments of the continental margin of northern Australasia are now widely dispersed on islands scattered around the Banda Sea. Data from Buton, Buru and Seram indicate that these islands were parts of a single block which included eastern Sulawesi. This separated from Australia as a microcontinent in the Jurassic and collided with the Eurasian margin to form the Sulawesi orogen in the Oligocene or Early Miocene. Collision was followed by extension and dispersion, creating the Banda Sea and involving parts of the former microcontinent in the new collision zone in the Outer Banda Arc. The known oil fields of Seram are often ascribed to sources in the currently underthrusting New Guinea margin, but the oil seeps and asphalt deposits of Buton, which remained attached to Sulawesi, indicate that hydrocarbons could have been sourced from Triassic sediments within the Outer Banda Arc.

Comparative studies of Mesozoic sediments on Buru, Buton, Seram, eastern Sulawesi and plateaus off the NW Shelf are gradually defining the development of hydrocarbon systems in this frontier exploration area. Faunal correlations are of especial importance. Mesozoic pelagic microfaunas from NW Australia are of typical Austral affinities and clearly distinct from Tethyan faunas for most of the Mesozoic, while those from the Banda Arc show a mixture of Austral and Tethyan faunal elements. North Tethyan elements have also been identified. The widespread but often ignored Mesozoic sediments of eastern Sulawesi, and their relationships with similar sediments on Buru, on the far side of the oceanic North Banda Basin, are of crucial importance.