Modal and Sandstone Composition of the Representative Turbidite from the Majalengka Sub-Basin, West Java Indonesia

摘要

The Majalengka sub-basin is composed of an approximately 4 km thick turbidite-sequence subdivided into three formations as follows Cisaar, Cinambo and Cantayan Formations. The last formation is composed by two members, i.e . Halang and Bantarujeg Formations, which is distinguished by the volcanic content. All sedimentary rocks were deposited during the middle to late Miocene, where the magmatic and tectonic influences are particularly dominant. Petrography and geochemical analyses suggested that the sandstone composition was derived from multi-source sediment, which is incorporated in same strata sediment. This indicates that the tectonic event occurred actively. Most sediment-sources were derived largely from two main provinces (geological terrain) such as recycled orogen and the magmatic arc. The recycled orogen is represented by the development of thrust-fault belts, which the sediment was eroded from uplifting the paleohigh. On the other side, the magmatic arc corresponded to the Southern Mountains, as a product of the early subduction in Java during the Oligocene. According to geochemical data, this indicates that there is no evidence supporting from the sediment source derived directly from the continental terrain. The quartz content is interpreted as occurring from resedimentation processes of previous sediment. Meanwhile, lithic fragment are dominantly composed by andesitic grains, which indicates that the magmatic terrain as a sediment source relates to subduction processes.