Publications

Cenozoic subduction of the Indo-Australian plate beneath Java began in the Middle Eocene. The East Java forearc preserves a record of Cenozoic sedimentation and tectonic history, and information about the character of the deeper crust. Based on new seismic data, morphology analysis, and correlation with offshore wells and geology on land, the East Java forearc stratigraphy can be divided into six tectono-stratigraphic units with three major unconformities. The lowest unit is a section with continuous strong reflectors that can be seen to depths of 10 sec TWT and is absent beneath the Central and West Java forearc. This unit could be a Paleogene succession which is equivalent to the deep Kendeng Basin on land in East Java. Alternatively, it could be a pre-Cenozoic sequence deposited on continental crust which was rifted from western Australia. We prefer the latter interpretation based on the seismic and morphological characteristics of the deep section. A Middle Eocene to Lower Oligocene sequence was deposited above a Middle Eocene unconformity during an extensional phase. It was followed by Upper Oligocene to Lower Miocene deposition accompanying voluminous volcanism. There was localized contraction of Lower Miocene and older units which records deformation prior to termination of Paleogene–Early Neogene arc activity. This was marked by an explosive supereruption and there is a Lower–Middle Miocene unconformity in a forearc structural high. An extensive carbonate platform was deposited above the Lower–Middle Miocene unconformity during a tectonically quiet period with much reduced volcanism. Significant subsidence to present depths began in the Late Miocene. There was significant deformation at the southern side of the forearc after deposition of the Upper Miocene unit which we interpret to be caused by arrival of a buoyant plateau at the subduction margin. Afterwards, carbonates were buried by Late Pliocene volcanogenic deposits at high rates of sedimentation.