Detrital zircons and heavy minerals from the Palu Formation, Sulawesi, Indonesia: constraints on exhumation of the Palu Metamorphic Complex and drainage evolution

Abstract

The Palu Formation, previously known as the Celebes Molasse in the Palu area, is understudied and was previously considered to be associated with the Pliocene collision between an Australian-derived micro-continent – Banggai Sula– and the eastern margin of Sundaland (West Sulawesi). Here, we present sedimentological, heavy mineral, and zircon geochronological data to provide insights into sediment provenance and to elucidate Neogene tectonic activity in Sulawesi. These analyses suggest that the Pleistocene Palu Formation comprises syn-orogenic alluvial fan to braided river deposits that record the rapid uplift of metamorphic and granitoid rocks in the Neck and west Central Sulawesi. The Palu Formation is characterised by predominant granitoid and metamorphic clasts and heavy mineral assemblages dominated by pyroxene, amphibole, and garnet. Detrital zircons record youngest grain ages of ca. 2.5 and 3.0 Ma with a significant Pliocene age population and subsidiary Eocene, Cretaceous, Jurassic, and Late Triassic age peaks. Rapid uplift and erosion associated with mountain building shaped the topography and influenced the evolution of Palu River networks. Thematic collection: This article is part of the Mesozoic and Cenozoic tectonics, landscape and climate change collection available at: https://www.lyellcollection.org/topic/collections/mesozoic-and-cenozoic-tectonics-landscape-and-climate-change Supplementary material: https://doi.org/10.6084/m9.figshare.c.7033388