Fission track and fault kinematics analyses for new insight into the Late Cenozoic tectonic regime changes in West-Central Sulawesi (Indonesia)

The left-lateral strike-slip Central Sulawesi Fault System (CSFS, composed of the NNW Palu–Koro (PKF) and the ESE Matano faults) is located within the eastern Indonesian triple junction between the Pacific, Indo-Australian and Eurasian plates. Fault kinematic and fission-track analyses show that the Late Cenozoic central Sulawesi deformation results from three successive tectonic regimes: (1) A Late Miocene–early Pliocene (5 Ma) WNW-trending shortening characterized by transpressional deformation along the PKF and compressional in the Poso area. This tectonics resulted from the collision between the Banggai–Sula block with Sulawesi. It produced locally a transpressional regime as a consequence of the northward extrusion of the Central Sulawesi block limited by the PKF. (2) A Pliocene collapse tectonic regime associated with W-trending extension. Coeval with these events regional cooling and exhumation took place. (3) A Quaternary transtensional regime resulting from the combined effects of the Central Sulawesi block northward motion, and extension related to back-arc spreading behind the North Sulawesi subduction (Tomini Gulf).