The Geology of Indonesia/Preface
Indonesia is the largest archipelagic state in the world comprising five major islands and about 300 smaller island groups. Altogether there are 13,667 islands and islets of which about 6,000 inhabited. The archipelago is situated on a crossroad between two oceans, the Pacific and Indian oceans, and bridges two continents, the Asian and Australian. Indonesia has a total area of 9,8 million sq km, of which more than 7,9 million sq km are under water. Physiographically, the islands of Sumatra, Java and Kalimantan are attached to the Sunda Shelf of the Asian continent. On this landmass the water depth does not exceed 200 meters. To the east, Irian Jaya and the Aru islands lie on the Sahul Shelf, which are parts of the Australian continent. Located between these two shelves is the island group of Nusa Tenggara, Sulawesi, Maluku and Halmahera. These islands are encircled by deep seas which in many places reach 5,000 meters.
About 60 Tertiary sedimentary basins, spread out from Sumatra in the west to Irian Jaya in the east, are identified in Indonesia. So far only 38 basins have been explored and drilled for petroleum and 14 of the are now producing oil and gas. Seventy three percent of these basins are located offshore, about one third of them in the deeper sea, with water depth exceeding 200 m.
In 1949, R. W van Bemmelen published a compilation of reports and data on the Geology of Indonesia. The book was reprinted in 1970 with no additional data. This book has documented a lot of data and geological understanding before the second world war and only covered onshore geology of Indonesia. W. Hamilton published a book titled Tectonics of the Indonesian Region in 1979 which include offshore seismic data and remote sensing. The Indonesian geologist celebrated the 50th anniversary of R. W. van Bemmelen's book in a conference titled "Tectonics and Sedimentation of Indonesian" in 1999 and published "An Outline of the Geology of Indonesia" the following year (2000). The data and the knowledge on the geology of Indonesia are so much and make it so difficult to compile them in a single book. In 2007 the Wikibook of the Geology of Indonesia was started by converting Än Outline of the Geoloyg of Indonesia"to a digital version. The idea is to include as many geoscientists as possible to keep the information on the geology of Indonesia as good as possible. This online version of the Geology of Indonesia will also give a chance to renew or update the information stored at anytime.