Juliane Hennig, completed project
This project will examine the ways in which very young intrusive igneous rocks have been brought to the surface to form a high mountain range (2.5 km) in western Sulawesi, eastern Indonesia.
Palu-Koro Fault scarp exposing a high mountain range west of Palu valley
Granodiorite with K-feldspar megacrysts from the western mountain range
Sulawesi is influenced by complex tectonics, resulting in northwest-directed subduction beneath western Sulawesi, south-directed subduction with trench rollback north of the island, formation of small oceanic basins, and the collision of micro-continental fragments (Katili, 1978; Hamilton 1979; Hall, 2002; v. Leeuwen & Muhardjo, 2005). West Sulawesi is dominated by a series of granitoid bodies that have intruded Mesozoic basement rocks and Paleogene volcanic-sedimentary cover units.
Previous models of a collision of the Banggai-Sula terrane with eastern Sulawesi during the Pliocene (Smith & Silver, 1991; Hall, 1996) have now completely changed to an origin from the northern promontory of the northward migrating Australian plate, called the Sula spur, which collided with western Sulawesi in the Early Miocene (Spakman & Hall, 2010). A subsequent slab rollback into the Banda embayment led to extension and caused fragmentation of the spur. Extensional forces are ongoing to present day by subduction retreat at the North Sulawesi Trench, which is connected to the prominent Palu-Koro Fault.
Exhumation histories will be studied from various granitic intrusions in western and central Sulawesi to investigate how and when these granite intrusions were emplaced, using low-temperature thermochronology. This will include Ar-Ar step-heating experiments on biotites, and (U-Th)/He analyses for apatites and zircons. These data will help to define thermal histories for western Sulawesi and to draw conclusions for the tectonic history of eastern Indonesia.
Granite outcrop at the River Lariang, south of Gimpu
