There are three consecutive magmatic arcs found in Java, namely the granitic pluton of Cretaceous-Eocene age in the norti (Java Sea); the andesitic, basaltic arc of Middle Oligocene-Lower Miocene age in the south ;Indian Ocean) and the third arc is represented by the present row of active volcanoes along the axis of Java. Each magmatic arc is accompanied by its corresponding subduction zone. Shifting of the magmatic arc from the north to the south left an area the whole width of Java as a basin, the Bogor Basin, possibly underlain by a Cretaceous-Eocene accretionary prism. During the rest of the Tertiary period, the Bogor Basin remained and developed as a back-arc basin. The turbidite fans in the Bogor Basin, progressively young toward the north. Deep sea fan distributions are in coincident with the thrust fault patterns. Unconformities were formed in the south, while further north continuing sedimentary processes were prevalent. The periodic loading of successive thrust sheets, must have been the cause of episodic basin subsidence and fan development throughout the history of the Bogor back-arc basin in Java.
Author : Soejono Matodjojo