Publications

Quartz-rich sandstones in the Banda Arc Islands are thought to be the equivalent of Mesozoic sandstones on the Australian NW Shelf, where they are important proven and potential reservoirs. Previous studies suggested that rivers draining Australia provided most of the sediment input, and there have been suggestions of a northern provenance for some Timor sediments. We summarise results from a provenance study of Triassic and Jurassic sandstones of the Banda Arc between Timor and Tanimbar, which used several methodologies including conventional light and heavy mineral point-counting, textural classification, and laser ablation (LA-ICP-MS) U-Pb dating of detrital zircons. Some of the new results challenge traditional ideas, some new sources are suggested with implications for palaeogeographic reconstructions and sediment pathways. Most sandstones are quartz-rich and detrital modes suggest a recycled origin and/or continental affinity, consistent with an Australian source. However, many of the sandstones are texturally immature and commonly contain volcanic quartz and volcanic lithic fragments. Heavy mineral assemblages are dominated by rounded ultra-stable minerals, but mixed with angular grains, and indicate an ultimate origin from acid igneous and metamorphic sources. Detrital zircon ages range from Archean to Mesozoic, but variations in age populations indicate differences in source areas along the Banda Arc both spatially and temporally. They suggest that sediment was derived mainly from the Bird’s Head, Western and Central Australia in the Triassic. In the Jurassic new local sources close to Timor need to be considered, combined with recycling of NW Shelf material. In the Tanimbar Islands and Babar, sediment came from both the Australian continent and from the Bird’s Head. Sandstones in Timor show a greater acid igneous signature in the east, whereas the west is more dominated by metamorphic sources. A new palaeogeographic model is proposed to explain the history of some of these islands in relation to the autochthonous Bird’s Head.