The Makassar Strait located between Kalimantan and Sulawesi Islands in Central Indonesia is a north-south orientated seaway, around 700 km long, 125-400 km wide with maximum water depths almost 2500 m. Bathymetrically, the Makassar Strait is divided into the northern and southern depressions and are hence sometimes referred to as the North and South Makassar Basins.
While the Paleogene history for the opening of the Makassar Straits is commonly agreed by many authors, the mechanism of the opening of the Straits and nature of the basement underlying the straits have been the subjects of considerable scientific debates. The debates in history are mainly because of lack of data representing direct data on the geology of the Makassar Straits. Most debates were based on modeling of subsidence history, gravity, magnetic and plate tectonics.
Satyana (2015) presents new data of the North Makassar Strait basement penetrated by two exploration wells: Rangkong-1 and Kaluku-1. The basement analyses include: Petrography, XRD, biostratigraphy, petrochemistry,
magnetic susceptibility, multi-isotope geochronology, and organic geochemistry. Oils discovered by Kaluku-1 well in Eocene section provides further information based on analyses of bulk properties, carbon isotope, and various
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Last week, my colleague from TGS, Ian presented a talk in the 38th Indonesian petroleum Association annual meeting. He talked about the structures and hydrocarbon prospectivity of Nias forearc basin, which is situated in the central part of the offshore Sumatra forearc area. 1868 km of newly acquired long offset 2D seismic, covers the area in between Nias and Sumatra mainland. Compare to the other offshore Sumatra forearc basins, the water depth in Nias basin is much shallower (~500m), than the other basins (up to ~1500m), reflecting much more carbonate platform growth and forearc sediment fill. The new data set show thick sediments with half-graben/syn-rift character beneath the Neogene sequences that interpreted as Paleogene. By using using the low geothermal gradients observed in wells in the area, the temperature in the bottom half of the Paleogene section is calculated to be sufficient to expel hydrocarbons from lacustrine or coaly sediments.
This is a title of an article that has been presented at the IPA Annual Convention and Exhibition 2007. This article reviews the tectonics of Central Java Indonesia. This area shows a conspicuous re-entrant or indentation of its coastline compared to those of the western and eastern parts of Java Island. This indentation is considered to express wrench segmentation of two major Paleogene strike-slip faults with opposing trends and slips are responsible for the indentation. The two faults are considered to cause significant geologic changes in Central Java.