The evolution of the East Java Basin, Indonesia.

Shields, Martin L.

The East Java Basin has a geological life span of more than 50 Ma, with a diverse structural and stratigraphic development history. The basin originated during the Eocene on continental crust and developed northeast to southwest trending linear paleo-highs at its inception. These antiformal uplifts are cored by contractional structures, but also exhibit minor crestal extension. The parallel and convex paleo-highs are separated at a spatial wavelength of 80-100 km. The well and sediment information is recorded and evaluated herein as subsidence histories. By coupling the convex profiles from geohistory information with low heat flows recorded in well bottomhole temperatures, the evidence points to an origin of lithospheric flexure and buckling of the continental crust. The stratigraphy documented in well and outcrop samples indicates a preponderance of shelfal carbonate deposits with an influx of quartz sandstone during the Miocene. The quartzite source is north of the basin in Borneo associated with an exposed granite massif.

Only Pliocene-Recent sediments (<5 Ma) are sourced from adjacent volcanic eruptions to the south. In contrast to previous studies where rifting is proposed as the mechanism for basin initiation, the evidence uncovered in this research points to crustal buckling of continental crust as the correct mechanism. Well subsidence histories indicate folding or flexure of the continental crust caused by contraction of the lithosphere which appears to be responsible for Eocene-Miocene basin subsidence. The research evidence suggests the basin developed in four stages identified in the structure and stratigraphy captured in the geohistory profiles. The first stage of East Java Basin development, crustal buckling, originated with Middle Eocene with sediments deposited in geographic lows on folded continental crust. Stage two, the flexural deepening phase, started in the Late Oligocene with gradual subsidence until the Lower Miocene. The third phase, foreland inversion, started in the Middle Miocene and persisted until the Middle Pliocene. The last stage of basin development, arc convergence, began in the Upper Pliocene with the northward vergence of the Sunda magmatic arc. During the Pleistocene the north verging thrusts on the south side of the basin initiated a reversal of the basin symmetry. (Winzeler database)

Ph.D. thesis (Geology, Geophysics), University of Wisconsin-Madison.