LAUSR

Abstract The pre-collisional sedimentary provenance of southern Taiwan not only can offer important information about the paleogeography of the region prior to the Taiwan orogeny, but may also provide significant constraint for understanding the origin of the Central Range of Taiwan and the history of the orogen. Although there have been previous studies on sedimentary provenance of the Hengchun Peninsula, the southernmost part of the Taiwan mountain belt, these studies appear to have limited sample coverage. Therefore, we performed detrital zircon U-Pb geochronology and hafnium isotopic analysis of samples covering all three Mid-Late Miocene stratigraphic units of the peninsula. Our results suggest that, whereas the Minjiang (Min River) and the Jiulongjiang (Jiulong River) in SE China are the primary sediment sources for the Shihmen and Lilungshan Formations, the Loshui Formation was likely deposited in a deep sea fan originated from a rifted continental fragment in the south. The developing accretionary prism and proto-Taiwan may have also provided sediments to the area. The proposed presence of a continental fragment that provided sediments in the Loshui Formation supports the hypothesis that the Taiwan orogen may have formed as a double collision that incorporated not only the Luzon Arc and the Eurasian continental margin, but also rifted continental blocks in between.