East Java: Cenozoic basins, volcanoes and ancient basement

Abstract

East Java on land is divided here into four broadly E-W zones: (1) the Southern Mountains Zone, an Eocene to Miocene volcanic arc, separated by (2) the present-day volcanic arc from (3) the Kendeng Zone which was the main Cenozoic depocentre in onshore East Java; and to the north (4) the Rembang Zone which represents the edge of the Sunda Shelf. Several synthems separated by unconformities can be identified and correlated between the different zones. There is a regional angular unconformity above Upper Cretaceous and older basement. The oldest rocks above the unconformity range from Mid Eocene to Lower Oligocene and record a gradual transgression and, in SE Java, an increase in volcanic material up-section.