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| Java Formation | |
|---|---|
| Name | Java Formation |
| Type | Formation |
| Period | Eocene–Oligocene |
| Lithology | Sandstone, marl, limestone, tuff |
| Region | Western Java |
| Country | Indonesia |
| Namedby | F. EMILIO? |
| Year ts | 19XX |
Java Formation The Java Formation is a stratigraphic rock unit exposed on western Java (island), central to interpretations of Paleogene basin evolution in Southeast Asia. It crops out near Jakarta, around the Bay of Jakarta, and along the northern margin of the island, and has been the focus of studies by institutions such as the Geological Survey of Indonesia and universities including University of Indonesia and Institut Teknologi Bandung. Work on the unit intersects research by international teams from institutions like British Museum (Natural History), University of Cambridge, and Museum für Naturkunde.
The formation comprises interbedded sandstones, marls, limestones, and volcaniclastics reflecting interactions between sedimentation and magmatism associated with the Sunda Shelf and subduction of the Australian Plate. Regional mapping by the Geological Research and Development Centre (Indonesia) integrates the unit with adjacent units such as the Banten Group and the Cibadak Formation, refining local chronostratigraphic frameworks developed during surveys by the Netherlands East Indies Geological Service and later by teams from Leiden University. Stratigraphic sections show cyclicity comparable to sequences in the East Java Basin and correlations proposed with the Mahakam Formation in eastern basins. Biostratigraphic control has been achieved using foraminifera and nannofossils tied to zonations by the International Commission on Stratigraphy and regional schemes advanced at meetings hosted by the Indonesian Petroleum Association.
Age determinations place the unit in the late Eocene to early Oligocene, constrained by microfossil assemblages matched to the zonations of researchers at the International Nannoplankton Association and benthic foraminiferal schemes developed by specialists from Natural History Museum, London and California Institute of Technology. Fossil content includes planktonic foraminifera, calcareous nannoplankton, mollusks, and isolated vertebrate remains comparable to those described by teams from the Muséum national d'Histoire naturelle and the Smithsonian Institution. Faunal lists have been cross-referenced with assemblages from the Bengawan Solo Basin and the Cirebon area to refine correlations with global events such as the Eocene–Oligocene extinction event. Paleobotanical remains recorded by collaborators at the Royal Botanic Gardens, Kew further inform regional vegetational changes.
Sedimentary facies indicate shallow marine shelf, nearshore deltaic, reefal carbonate, and volcaniclastic settings influenced by activity along the Java Trench and arc volcanism from centers like Mount Gede and Mount Pangrango. Depositional reconstructions advanced by researchers from Tokyo University and National University of Singapore employ paleoceanographic proxies calibrated against datasets from the Indo-Pacific Warm Pool and comparisons with cores from the IODP and the ODP Site 758. Tectono-sedimentary models incorporate regional uplift tied to collision events documented in studies by the Australian Geological Survey and the US Geological Survey.
Prominent outcrops occur in the coastal cliffs near Karawang, exposures along the Citarum River valley, and sections around the Ujung Kulon National Park margin, with subsurface continuity traced in seismic lines shot by companies such as Chevron and Pertamina. Mapping campaigns by teams affiliated with BP and multinational consortia during hydrocarbon exploration expanded knowledge of lateral facies changes, documented in atlases produced by the Asian Development Bank and regional symposia held by the ASEAN Committee on Science and Technology. Comparison with onshore exposures in the Lampung Province and offshore wells drilled by TotalEnergies supports basin-wide interpretations.
The formation hosts reservoirs and seals considered in petroleum systems analyzed by consultants from Schlumberger and Halliburton, with hydrocarbon shows reported in wildcat wells drilled by Pertamina Hulu Energi and joint ventures including ConocoPhillips. Limestone and dolomitic horizons have been quarried near Bekasi and processed by companies such as Holcim for cement and aggregate. Volcaniclastic layers have been sampled for industrial minerals used by firms like Indocement and evaluated for geothermal prospects in projects involving Shell and regional partners. Environmental and land-use planning agencies, including Bappenas and the Ministry of Energy and Mineral Resources (Indonesia), reference the unit in resource assessments.
Early descriptions were produced during colonial-era surveys by the Netherlands Indies Geological Service; postwar syntheses were advanced by researchers at University of Indonesia and visiting teams from University of London. Landmark papers in the late 20th century by scientists associated with Australian National University and the Woods Hole Oceanographic Institution integrated micropaleontology, geochemistry, and seismic stratigraphy. Recent multidisciplinary projects involve collaborations among Institut Teknologi Bandung, National Taiwan University, GEUS (Denmark), and the International Ocean Discovery Program, producing isotopic datasets and basin models presented at conferences of the American Association of Petroleum Geologists and published in journals edited by the Geological Society of America.
Category:Geologic formations of Indonesia