Publications

The island of Timor, together with the nearby smaller islands of Roti and Savu, forms part of the non-volcanic Outer Banda Arc. The Banda Arcs (Outer and Inner) are located between the Timor and Arafura seas off northwestern Australia .and the Flores and Banda seas of southeast Asia. The Inner and Outer Arcs are separated by the Savu Sea which is up to 100 kilometres wide and 3,000 metres deep, and by the eastern part of the Banda Sea, which attains a depth of 7,000 metres. Between the Outer Arc and the Australian Sahul Shelf lies another deep marine trough - the Timor Trough. Onshore, a maximum elevation of more than 3,000 metres above sea level is reached in the central range of Timor. To date the very complex structural setting of the Timor area has hindered the reconstruction of a definitive stratigraphic history, especially of the older sequence. It appears almost impossible at this stage to define normal lithostratigraphic units in the conventional sense, i.e. with respect to time distribution, thickness and so on. Field work has shown that many of the so-called stratigraphic contacts referred to by some authors, are in fact tectonic contacts. Considerable reworking of the microfauna and flora has also complicated palaeontological and palynological dating of the sequence. However, a preliminary stratigraphic summary has been attempted. As a working procedure it has been found convenient to consider the rocks under two main categories: 'pre-orogenic' and 'post-orogenic'. The 'pre-orogenic' category incorporates all the highly tectonised sediments of Permian to Middle Miocene age that were caught up in the mid-Miocene orogenic climax. The 'post-orogenic' sediments are a locally thick sequence of Upper Miocene to Recent age which were deposited in a series of distinct basins. Renewed tectonic stresses, gravity sliding or diapiric movements of the frequently incompetent substrata, have in turn disturbed this younger sequence. Numerous surface oil and gas shows in Timor attest to the fact that hydrocarbons have been generated in the area. Potential reservoir and seal rocks are evident in the stratigraphic sequence. The presence of active seepages, together with mud volcanoes and geopressured intervals, suggest that migration is still proceeding. Several types of hydrocarbon exploratory play have been established and are outlined in this study.