Abstract
Neogene syn-and post-orogenic sedimentary rocks in Sulawesi are important to understand the history of collision of Australian continental crust with SE Asia. However, they have received relatively little attention, and have generally been considered to be molasse-type deposits of similar characteristics across Sulawesi—the Celebes Molasse. New field sedimentological observations, results from heavy mineral studies and detrital zircon U–Pb geochronology, together with conventional sandstone petrography identify three important provenance shifts, that can be correlated with significant tectonic events and enable the reconstruction of the Neogene palaeogeography of SE Sulawesi. The first provenance shift was related to the Early Miocene collision of Australian crust and the North Sulawesi volcanic arc, accompanied by ophiolite emplacement in East Sulawesi, marked by a change from pre-collision carbonates to ultramafic-rich clastics of the Bungku Formation. A second change in the Late Miocene was marked by input of abundant metamorphic detritus including blueschists into the Pandua Formation indicating exhumation of Oligo-Miocene subduction zone material. The third provenance change, of Mio-Pliocene age, was from the ophiolite- and blueschist-rich Pandua Formation to the quartz-rich Langkowala Formation, and records blocking of the ophiolite debris pathways by the rise and progressive unroofing of low- to high-grade metamorphic rocks. The Neogene sedimentary rocks of SE Sulawesi record Early Miocene collision and ophiolite emplacement, followed by extension which led to exhumation of Mesozoic and metamorphic rocks, driven by Banda subduction rollback.
Keywords
geochronology, light and heavy minerals, palaeogeography, provenance, SE Sulawesi, Sediments, zircon