ABSTRACT: Mesozoic tectono-sedimentary evolution of the Banda Arc area
Thurow, Juergen, John Milsom, and Delphine Roques , University College London, London, United Kingdom
The Banda Arc lies at the centre of the East Indonesian triple junction, the region of interaction between the Eurasian and Australian plates and Pacific-related microplates. Comparative studies of Mesozoic sediments on Buru, Buton, Seram, eastern Sulawesi and plateaus off the NW Australian Shelf (Ocean Drilling Program, Legs 122, 123) are gradually defining the development of hydrocarbon systems in this frontier exploration area.
Pre-collision sediments record a complicated rift-drift-history from considerable higher latitudes at the NW Australian continental margin during the Mesozoic and include source and reservoir rocks (e.g. Triassic sandstone and platform carbonates/black shales), some of which show oil, oil seeps, asphalt (E. Sulawesi & Buton, Buru, Seram). These sediments represent the rifting phase off NW Australia. Widespread, but condensed juvenile oceanic sediments with abundant macrofossils of Late Jurassic age overlie them. In some areas this sequence is preceded by a volcanic phase with basaltic lava and abundant ash layers. From the Early Cretaceous onward sediments are uniformly pelagic throughout the area with abundant radiolaria. The Late Cretaceous is characterised by 'couches rouges' facies rich in calcareous plankton. The first Eurasian microfaunal elements occur as early as Maastrichtian, indicating the beginning of collision. Faunal correlations are of special importance. Microfaunas in the Mesozoic pelagic sediments of NW-Australia are of typical Austral affinities (high latitude) and clearly distinctive from Tethyan faunas; those from the Banda Arc show a mixture of Austral and Tethyan faunal elements. Sediments have been deposited in a more subtropical environment within the transitional zone between Tethyan and Austral waters.
AAPG Search and Discovery Article #90913©2000 AAPG International Conference and Exhibition, Bali, Indonesia