Ciletuh Subduction, West Java - New Findings, New Problems: Regional Implications to Cretaceous-Paleogene Convergence of Sundaland Margin and Its Petroleum Geology

Abstract

Ciletuh, southwest Java has been well known as one of the places in Java where pre-Tertiary basement rocks are exposed (Verbeek and Fennema, 1896; Duyfjes, 1940; van Bemmelen, 1949; Sukamto, 1975). In plate tectonic point of view, Ciletuh has been known as place outcropping melange complex related to pre-Tertiary oceanic plate subduction (Thayyib et al., 1977). Ciletuh subduction regionally has been linked to the Cretaceous subduction zones of Luk Ulo/Karang Sambung (Central Java) and Meratus Mountains (South Kalimantan) (Hutchison, 1973; Asikin 1974; Hamilton, 1979). Ciletuh subduction however, has not been dated using metamorphic rocks formed in its subduction zone. Its link to Luk Ulo and Meratus subduction zone only based on the presence of melange, which also lacks of data Meanwhile, subduction zones of Luk Ulo and Meratus have been dated and analysed. We herewith present the results of new field studies and various analyses carried out in the last five years of the Ciletuh subduction complex. The indication of Cretaceous subduction has not found from the date measurement, Ciletuh shows Eocene related subduction. Most of the ophiolites were island-arc tholeiitic or island-arc basalt formed in supra-subduction zone. The overlying olistostrome deposits were younger than previously considered and lasted until early/middle Miocene. Some of the basaltic pillowed lava is considered as part of the ophiolite, while the ones at Gunung Badak is more likely a part of the early Miocene Jampang volcanism. Link of Ciletuh to Early Cretaceous subduction of Luk Ulo is not supported by geochronological data. The new knowledge of Ciletuh subduction implies the pre-Tertiary and Paleogene geology of Java, and petroleum prospectivities of the Paleogene objectives of southern West Java. New problems arise and need more field data and analyses to find out the answers.