Abstract: Tectonic Development of the Indonesian Archipelago and its Bearing on the Occurrence of Hydrocarbons

T. O. Simanjuntak

The present geological and tectonic configuration of the Indonesian archipelago may represent a typical triple junction plate convergence, which has developed since Neogene times due to the northward-moving Indo-Australian plate, the westward-moving Pacific plate, and the south-southeastward-moving Eurasian Craton. The occurrence of a number of microcontinents in eastern Indonesia makes the geology and tectonics of the region more complex. The archipelago is one of the most complicated regions from the plate tectonics point of view.

The geological evolution of the Indonesian archipelago is recorded by the occurrence of both tectonic convergence and tectonic divergence. Various types of plate convergences include a Cordilleran type subduction, which has been reoccurring since Paleozoic until present times in western Indonesia; a Neogene Tethyan type collision in the Banda region; and a double-arc collision in northern Maluku, central Indonesia.

Tectonic divergence, which was preceded by rifting due to thermal doming and magma rise in the northern margins of the Australian Craton and followed by the detachment and west-northwestward displacement of continental fragments in Mesozoic, gave rise to the development of the microcontinents in eastern Indonesia.

Hydrocarbons have mostly been generated from Paleogene back-arc sequences in Indonesia in western Indonesia. Oil and gas generation and accumulation seem to be related closely to the rifted sequences in the back-arc and foreland regimes and the subsequent back-arc thrusting episode.

By contrast, the hydrocarbons in eastern Indonesia may have been sourced from the Mesozoic continental margin sediments, which are mostly of Tethyan passive margin affinities. Remigration and accumulation of such hydrocarbons seem to be related with the tectonic diapirism due to thrusting and folding during the Neogene Melanesian Orogeny in Irian Jaya and Papua New Guinea, and Banda Orogeny in central Indonesia.

AAPG Search and Discovery Article #90982©1994 AAPG International Conference and Exhibition, Kuala Lumpur, Malaysia, August 21-24, 1994