Publications

Palaeogeographic maps for intervals between the Cretaceous and Late Miocene illustrate the complex evolution of West Java. Basement is of Mesozoic age and in West and Central Java there are ophiolitic and arc rocks accreted to the margin of Sundaland in the Late Cretaceous. The oldest Cenozoic rocks in West Java are Middle Eocene formations in the Ciletuh Bay area that formed in quite different settings. There are volcanogenic turbidites and breccias containing abundant basaltic material that we suggest are deep water deposits, associated with the onset of subduction, formed close to a new arc or in its forearc. Nearby are quartz-rich sandstones deposited predominantly in a shallow marine shelf edge environment interpreted to be derived from basement highs. We assign these rocks to different formations and their present juxtaposition is suggested to be due to thrusting.We interpret there to have been a large southerly prograding delta system in SW Java during the Late Eocene. There is a considerable thickness of quartzrich sandstones, forming an overall shallowing-up sequence, sourced from the north and probably derived from Sundaland. The Oligocene of West Java includes terrestrial quartz-rich sandstones, reefal and foraminiferal limestones and volcanogenic sediments deposited in fluvial to deeper water marine environments. The Early Miocene saw an important phase of explosive arc volcanism in south Java. By the Middle Miocene volcanism had diminished or ceased, allowing carbonates to be deposited on the arc rocks. In the Late Miocene volcanism resumed further to the north resulting in a new phase of volcanogenicturbidite deposition.It is not certain when subduction began beneath West Java and where the arc was situated. Except at Ciletuh the volcanic component of Paleogene sequences is relatively minor. This has suggested that subduction-related volcanism did not commence until the Late Oligocene. However, we suggest that subduction-related volcanism began in the Eocene, but the arc did not become emergent until the end of the Oligocene. Loading by the volcanic arc formed a broadly E-W trending flexural basin to the north of the arc which filled with volcanogenic material from the south and continental clastic debris from the north. The distance between the Paleogene quartz-rich shelf sequences and the volcanic arc has been reduced by Neogene thrusting.