Tectonic Evolution of Onshore Southwestern – Central Java Basins – A New Perspective on Active Margin (2009)



Considerable contrast in basin – fill stratigraphy that existed since older geological record reflects a fundamental geological divide between onshore Southwestern – Central Java basinal areas, covering Bogor and Cimandiri Trough, Tanjung, Pemalang, Kendal, Citanduy, Banyumas, and Bobotsari Sub – basins, with offshore Northwestern Java Sea basinal areas. Indicate active tectonism that influenced onshore Java areas ruled out the simple rift – sag- inversion model commonly used to describe the Northwestern Java Sea basins. The hydrocarbon potential of onshore Southwestern and Central Java basins was influence by subsequence changes in deviatoric stress pattern resulted from the interplay and timing of tectonic event, rather than simple lithostatic stress. The importance of pre-existing structural assemblage in controlling tectonic development is often neglected. Standard model for the plate tectonic evolution of onshore West and Central Java areas is being refined by integrating regional-scale observation and smaller-scale observation. Re-examination and correlation of combined dataset based on; regional gravity anomaly data, existing and newly acquired seismic surveys, and surface geological data emphasizing on specialized studies on sedimentology and provenance analysis, in conjunction with published biostratigraphic data, reveals a new perspective of tectonic evolution and structural assemblage that developed in onshore West and Central Java areas. The Southwestern – Central Java Basin formed in active margin setting, forming elongate arcuate NE-SW to NW-SE orientation controlled by major strike-slip pair faulting during the process of northward subduction of the Australian plate under the Sundaland southern margin. The active tectonism periods are marked by widespread unconformities notably; Early Cretaceous, Late Oligocene, and Mid– Late Miocene events that can be traced on West Java to Central Java areas, characterized by unique structural style assemblage of prograding series of high-angle thrusts forming linear fold-thrust belts and downwarped synclinal depression that controls the sedimentation pattern since Early Cretaceous. Uplifted structures formed the site of carbonate build-ups such as; Rajamandala and Bodas Limestone. Newly formed depression are subjected to rapid infilling by turbidite sedimentation of eroded materials such as; Saguling and Cinambo Formation in West Java and Merawu and Penyatan Series in Central Java stratigraphic nomenclature. Additional dataset and re-interpretation upon tectonic evolution of onshore Southern – Central Java basinal areas could refine our understanding on plate tectonic model along the collisional zone between Sundaland and Australian plate as well as improving new play-concept for hydrocarbon exploration in these areas.


Author : Danny Nursasono, Setyo Rini, M. Alfatih S, Bobby Yusuf, Lovya Niranda, Krishna Pratama Laya