Abstract

The Northeast Java Basin is a foreland basin in west Indonesia. It is limited by the Java volcanic belt or geanticline in the south, the Karimunjawa and Bawean ares in the north, the Pati and Cirebon troughs in the west and the Madura ridge and Madura Basin in the east. There are three distinct, east-west trending tectonophysiostratigraphic zones in the basin: the Kendeng zone in south, the Rembang zone in the north and the Randublatung zone in the centre.

The depositional history of the basin encompassed 4 (four) depositional cycles: (1) Ngimbang and Kujung Formations (Eocene-Late Oligocene); (2) Prupuh, Tuban, Tawun and Ngrayong Formations (Late Oligocene-Middle Miocene); (3) Bulu, Wonocolo, Ledok and Mundu Formations (Middle Miocene-Late Pliocene); and (4) Selorejo and Lidah Formations (Late Pliocene-Pleistocene).

Sequence stratigraphic analysis was applied to detailed field observations of the Middle Miocene-Pliocene outcropping sediments of the second and third depositional cycles along the Solo River at Ngawi and the Braholo River at Blora, northeast Java. Along the Braholo River in the Rembang zone, the Tawun, Ngayong, Bulu, Wonocolo and Ledok Formations combine to form four sequences comprised of shallow marine parasequences and parasequence sets. Eight cycles of deep marine, turbiditic genetic units, time equivalent to the Braholo River sections, were observed along the Solo River in the Kendeng zone.

Transgressive marl facies of the Kalibeng and Mundu Formations overlie this stratigraphic succession. This Pliocene sedimentation marked the close of the third depositional cycle. At the end of Pliocene, during a sea level drop, the carbonate facies of the Klitik, Ngepung and Selorejo Formations developed locally in the basin. This carbonate deposition marks the beginning of the fourth and final depositional cycle in the Northeast Java Basin.