Abstract

Recent offshore sedimentary basins in Indonesia, located in water depths below 200 m, are discussed on the basis of their tectonic origin and evolution. They are described in terms of their shape, their sedimentary fill and petroleum potential.

Some of the basins discussed have sedimentary thickness up to 5 seconds two way seismic time. In cases where basins are underlain by continental crust the sedimentary column can be considerably thicker if the sedimentary rocks of the underlying continent are added. Basins are delineated by the 1.0 second thickness for hydrocarbon prospecting.

Forty-one basins fulfill the definition of having a sedimentary fill of more than 1 second of seismic data (TWT). These basins cover an area 1,252,250 km2 and occupy 55% of the total area of all basins in Indonesia.

The basins can be situated either marginal to emerged land of isolated from it. In the first type, basins are narrow, parallel to the emerged land, often bounded by faults and are filled with clastic erosional products. Shales are dominant but fill also includes coarser clastics. Deltaic and littoral clastics are subordinate while turbidites predominate. Carbonates are devoloped occasionally on basement highs or near shore. The socond type of basin is often located in deep water. Recent sediments are only deposited as veneer.

Structural deformations, which are visible on many seismic sections show a larger amplitude at depth as compared to those in the Recent deposits. A large variety of possible traps including compressional folds, dragfolds, block faulting and also shale diapirism, draping-over-highs and reef-buildups are exhibited in recent sedimentary basins throughout Indonesia.