Wide shelves as discriminators between hinterland tectonic and intra-basin rifting signals

Abstract

Decoding interwoven tectonic and climatic drivers in global source-to-sink systems remains a major challenge in Earth science. This study demonstrates that the very wide shelf in the northern South China Sea acted as a critical discriminator of signals related to hinterland tectonism and basin rifting. The rifting process is the main driver of variations of detrital zircon (DZ) signals in the succession of the wide shelf. DZ data show an increasing proportion of intrabasinal sediment source that is in phase with seafloor spreading and crustal extension (ca. 32–16 Ma), and then a gradual increase of extrabasinal source until the Pleistocene, in step with post-rifting thermal subsidence. These DZ variations are free of the strongest Cenozoic tectonism, the uplift of the eastern Tibet-Himalayan orogen since ca. 23 Ma, although this regional uplift dominated the DZ-signal variations in the entire deep-water basinal areas of the northern South China Sea basins fed by the Central Canyon of the Qiongdongnan Basin. Moreover, rising of global sea-level driven by the Miocene Climatic Optimum had little impact on sediment delivery in the shelf-to-basin system. The strong decoupling of DZ-variation trends between the shelf and the deep basin in this study underscores the importance of wide shelves in distinguishing different allogenic drivers in global source-to-sink systems.