Geology of Indonesia

The Indonesian Archipelago is located in the Equatorial area between longitude 94º and 141º N and latitude 8º N and 13º S, comprised more than 17000 islands with a total land area of > 1.9 million sq km and a sea area of > 5.8 million sq km or 25% and 75% of the total territory respectively. The Archipelago is situated on a crossroad between two eceans, the Indian and Pacific, and bridges two continents, the Asia and Australian. The stable platforms, the Sundaland in the northwest and the Sahul Shelf in the southeast are interwined with a complex zone comprising island arcs, volcanic arcs, continental terrains, oceanic terrains and submarine trenchs. Within the complex zone there are regular features shown by the intimate relationship between volcanicity, belts of earthquake foci and the belts of gravity negative anomalies.

The regional geology of Indonesia is a reflection of its complicated nature which has been brought about by the collision of three megaplates, i.e. the Eurasian, Indiaaustralian and Pacific. As a result, the regional stratigraphy shows rock assemblages which differ from place to place, depending upon their tectonic environment, such as continetal margin, oceanic basin, island arc, accretional subduction, collision complex, allochtonous continental fragments and allochtonous oceanic fragments.

Most geological elements and tectonic regimes of various ages and style from Paleozoic to Cenozoic are well preserved in the region. Some assemblage of mineral and energy resources shows close relationship with the tectonic style of each crustal plate. Magmatic and sedimentary processes since the earliest period have made Indonesia rich in mineral and energy resources. However, the activity of volcanism and seismicity, and also instability of land combined with heavy rainfall make the region one of the most potentially geological hazardous.

Oldest rocks expose at Merangin, Sumatera region are dated as Paleozoic sediments that age range from Carboniferous to Triassic while in eastern Kalimantan region Devonian limestone is found as block in Telen River. In Papua, the oldest rock is represented by Silurian limestones that cropped out at Sara river and including into Modio Dolomite.

Topographic of the western Indonesia region shows a strongly peneplainization stage which is reflected by low land hills and “U” shape river. In contrast to the eastern Indonesia as the more active region is exhibited by high undulation and “V” shape river.

The current geological knowledge of Indonesia could be summarized by the Lexicon Stratigraphy of Indonesia presented on this database. Some synopsis are also included in this database concerning significant geological features, tectonic, and mineral and energy resources.