Abstract

The recent compilation of a new tectonic map of Indonesia as part of the Geotectonic Map Project of East Asia has prompted a reassessment of the contrasted tectonic styles represented by currently developing orogenic belts. These orogenic styles provide a range of models illustrating the diversity and complexity of tectonic processes which may provide the key to the interpretation of other orogenic belts elsewhere in the world. The following distinctive types of orogenies have been recognized within Indonesia. 1. Sunda Orogeny in Java and Nusa Tenggara: involving subduction of oceanic crust with normal convergence, producing an orogenic belt of Andean type with trench, accretionary complex, forearc basin and Quaternary magmatic arc with active volcanoes built on the margin of the Sundaland continent. 2. Barisan Orogeny in Sumatra: with strongly oblique convergence and major strike slip transcurrent fault movement within the magmatic arc, along which a segment of continental crust is being displaced northwards along the western margin of Sundaland. 3. Talaud Orogeny in the northern Molucca Sea: convergence of the Sangihe and Halmahera oceanic magmatic arcs as the Molucca Sea Plate subsides beneath them. 4. Sulawesi Orogeny in eastern Sulawesi: collision of microcontinental blocks with subduction systems along the eastern margin of Sundaland. 5. Banda Orogeny in the southern Banda Arc between Sumba and Tanimbar: collision of the northern margin of the Australian continent with the subduction system along the southern segment of the Banda Arc. 6. Melanesian Orogeny in Irian Jaya and Papua New Guinea: a more advanced stage in the collision of the northern margin of the Australian continent with a magmatic arc on the Philippine Sea plate, commencing in the early Miocene with a partial reversal of polarity and the subduction of the Caroline plate beneath the collision zone.

The present phase of orogenic activity in most of these occurrences commenced in mid-Miocene times and orogenic processes are still in progress.