Paleogeography of South China in the Early Paleozoic: evidence from U–Pb geochronology of detrital monazite

Abstract

The tectonic affinity of South China in paleogeographic reconstructions of the Gondwana supercontinent during the Early Paleozoic remains controversial. Here, we present new detrital monazite U–Pb age data from Lower Devonian Posongchong Formation clastic sedimentary rocks in the Youjiang Basin in southwestern South China to explore the link between South China and Gondwana. U–Pb detrital monazite geochronology yields dominant Pan-African (657–460 Ma) and minor early Neoproterozoic (998–798 Ma) contents. Taking into account the direction of marine transgression, Northern India, Himalaya, Lhasa, Qiangtang terrane, Hainan Island, and Western Australia, located on the northern edge of East Gondwana, are the main provenances of the Youjiang Basin, with the Jiangnan orogen also providing some clastic materials. The source of the clastic material is also closely related to the Pan-African movement and the Neoproterozoic collision between the Yangtze Block and the Cathaysia Block. It is thus suggested that South China constituted part of East Gondwana in the Early Paleozoic. The unconformity between the Late Cambrian and Early Ordovician in South China, named the Yunan event, was a product of the final assembly of East Gondwana. Detrital monazite is an effective near-source indicator in tracing the provenance of the basin.