Abstract A new long-offset, long-record crustal-scale seismic survey of 9600 km called JavaSPAN was acquired in the Java Sea and Makassar Strait. The East Java Sea is underlain by continental basement with a prolonged multiphase history of deposition punctuated by extensional and compressional events. This East Java Terrane is a major component of SE Sundaland lying between the Meratus suture, the contemporary Java arc, and the west Sulawesi orogenic belt, but is poorly constrained on the north under the North Makassar Basin and in Kalimantan. A Precambrian to Permo-Triassic sedimentary section up to some 8.5 km in thickness overlies crystalline basement in a number of fault blocks and synformal structures below a strong angular unconformity. A thin overlap assemblage of Cretaceous to early Cenozoic sediments overlies that unconformity. Middle Eocene to Neogene clastic and carbonate rocks overlie another angular unconformity that marks the initiation of a well known history of Palaeogene extension, sag, and Neogene inversion. The East Java Terrane rifted from the Bonaparte-Arafura sector of northern Australia in the Jurassic and accreted onto a magmatic arc on the SW flank of what is now Kalimantan in the Cretaceous.

Abstract Rich palynomorph assemblages have been obtained through a marine Oligocene succession from the East Java Sea (Indonesia) and provide the first instance of an independently dated Oligocene succession from SE Asia that has yielded a good quality palynological record. The succession has been independently dated by nannofossils and foraminifera. The palynomorph succession suggests climatic control on Oligocene vegetation, on which basis a regionally applicable zonation is proposed. The Early Oligocene is characterized by common rain forest elements, suggesting an everwet, rain forest climate. The early part of the Late Oligocene contains much reduced rain forest elements with grass pollen, indicating a more seasonal climate, whereas for the latest Late Oligocene, rain forest elements return in abundance, suggesting a superwet rain forest climate. This palynological succession is similar to that from the Sunda Basin in the West Java Sea, allowing the Sunda Basin succession to be dated by correlation. The study also extends the stratigraphic range of Dacrydium and Casuarina , two plant taxa previously thought to have dispersed from the Australian Plate into SE Asia at the time of the collision with Sunda, to well before the time of collision. A different means of dispersal for these taxa is proposed.

The stratigraphic record of volcanic arcs provides insights into their eruptive history, the formation of associated basins, and the character of the deep crust beneath them. Indian Ocean lithosphere was subducted continuously beneath Java from ca. 45 Ma, resulting in formation of a volcanic arc, although volcanic activity was not continuous for all of this period. The lower Cenozoic stratigraphic record on land in East Java provides an excellent opportunity to examine the complete eruptive history of a young, well-preserved volcanic arc from initiation to termination. The Southern Mountains Arc in Java was active from the middle Eocene (ca. 45 Ma) to the early Miocene (ca. 20 Ma), and its activity included significant acidic volcanism that was overlooked in previous studies of the area. In particular, quartz sandstones, previously considered to be terrigenous clastic sedimentary rocks derived from continental crust, are now known to be of volcanic origin. These deposits form part of the fill of the Kendeng Basin, a deep flexural basin that formed in the backarc area, north of the arc. Dating of zircons in the arc rocks indicates that the acidic character of the volcanism can be related to contamination of magmas by a fragment of Archean to Cambrian continental crust that lay beneath the arc. Activity in the Southern Mountains Arc ended in the early Miocene (ca. 20 Ma) with a phase of intense eruptions, including the Semilir event, which distributed ash over a wide area. Following the cessation of the early Cenozoic arc volcanism, there followed a period of volcanic quiescence. Subsequently arc volcanism resumed in the late Miocene (ca. 12–10 Ma) in the modern Sunda Arc, the axis of which lies 50 km north of the older arc.

Abstract In the east-west-trending Tertiary basin of East Java (Indonesia) 132 million barrels of oil have been produced since 1888 from some 20 fields grouped around the centers of Tjepu and Surabaja. The upper 6 kilometers of the infilling of the basin have been penetrated by the drill. Of this sequence of known Tertiary, the lowermost 4 kilometers consist almost entirely of Miocene bathyal shales and marls which may have acted as oil-mother formations. In the north of the basin the upper 2 kilometers of sediments are neritic and littoral and contain in the Tjepu and Surabaja districts the sands from which the oil of East Java is produced. During Plio-Pleistocene the basin was folded into 3 east-west-trending zones of different tectonical character. The northern one, the Rembang zone, is formed by anticlinoria on which many minor anticlines with steep southern flanks are superimposed. Several of them are productive. In the Tjepu area oil was trapped in the porous sands covering directly the Miocene shale series but toward west and east their reservoir properties are poor. Locally some younger sands are also productive. In Surabaja the producing horizons lie still higher (upper Pliocene, lower Pleistocene). In East Java 3 types of oil are produced—shallow asphaltic oil from the Surabaja area, and a light, and a heavy paraffinic oil from the Tjepu area.