Publications

Java has an apparently simple structure in which the east-west physiographic zones broadly correspond to structural zones. In the north there is the margin of the Sunda Shelf, and to the south of the shelf are Cenozoic volcanic arc rocks produced by episodes of subduction-related magmatism. This simplicity is complicated by structures inherited from Cretaceous subduction beneath Java, by extension and subsidence related to development of the volcanic arcs, by late Cenozoic contraction, and by cross-arc extensional faults which are active today. During the Paleogene arc volcanoes acted as a load which caused a flexural basin to develop between the Sunda Shelf and the Southern Mountains Arc which can be traced from West to East Java. The basins contain quartzose clastic and volcanic debris derived from north and south. Based on field observations in different parts of Java we suggest that major thrusting in southern Java has displaced the Paleogene volcanic arc rocks northwards by more than 50 km and eliminated the flexural basin in West Java. The amount of thrusting diminishes from West to East Java. We suggest Java can be separated into three distinct structural sectors which broadly correspond to the regions of West, Central and East Java. Central Java displays the deepest structural levels of a series of north-directed thrusts, and Cretaceous basement is exposed, the overthrust volcanic arc has been largely removed by erosion. In West and East Java the overthrust volcanic arc is still preserved. In West Java the arc is now thrust onto shelf sequences that formed on the Sundaland continental margin. In East Java the volcanic arc is thrust onto a thick volcanic/sedimentary sequence formed north of the arc in a flexural basin due largely to volcanic arc loading. Structural and stratigraphic traps beneath the overthrust arc offer new hydrocarbon exploration possibilities, particularly in West Java.