Geology of Sulawesi Island, Indonesia

Geologically, Sulawesi Island and its surrounding area is a complex region. The complexity was caused by con­vergence between three lithospheric plates: the northward-moving Australian plate, the west­ward-moving Pacific plate, and the south-southeast-moving Eurasia plate. The Makassar Strait, which sepa­rates the Sunda Platform (part of the Eurasia Plate) from the South Arm and Central Su­lawesi, formed by sea-floor spreading originat­ing in the Miocene. North of the island is the North Sulawesi Trench formed by the subduc­tion of oceanic crust from the Sulawesi Sea. To the southeast convergence has occurred between the Southeast Arm and the northern part of the Banda Sea along the Tolo Thrust. Both major structures (the North Su­lawesi Trench and Tolo Thrust) are linked by the Palu-Koro-Matano Fault system.

Based on lithologic association and tectonic development, Sulawesi and its surrounding is­lands are divided into 5 tectonic provinces:

• The Tertiary Western Sulawesi Vol­canic Arc
• Quarternary Minahasa-Sangihe Volcanic Arc
• Cretaceous-Paleogene Cen­tral Sulawesi Metamorphic belt
• Cretaceous Eastern Sulawesi Ophiolite Belt and its associ­ated pelagic sedimentary covers
• Paleo­zoic Banda Micro-continental fragments derived from the Australian continent

The contacts between those provinces are faults.