Fingerprinting sand from Asian rivers to the deep central South China Sea since the Late Miocene

Abstract

Abstract The complex sedimentary processes from source to sink lead to a substantial fractionation of sediment size and composition. Relatively coarse-grained, continent-derived detritus is rarely transported and deposited in the deep ocean, and the terminus of this sediment routing system is poorly understood. Sandy turbidite deposits within the Upper Miocene–Pleistocene strata drilled in the deep central South China Sea during the International Ocean Discovery Program (IODP) Expedition 349 provide valuable samples for evaluating the evolution of sediment contributions from different Asian landmasses. This study reconstructs this ancient source-to-sink system based on an integration of heavy mineral and detrital zircon analyses (including U-Pb age, trace element, grain size and shape), obtained from IODP sites U1431 and U1432, as well as a zircon age-based mixture modeling of well-defined provenance end-members. The results show several provenance shifts that correspond to more complex and dynamic source-to-sink scenarios than previously envisaged. Certain source areas, like East Vietnam, present a different provenance signature than that of today. Multiple provenances have been mixed and diluted during sediment transport, exhibiting a large regional variability. We interpret that siliciclastic turbidite deposits in the central South China Sea were mainly derived from East Vietnam during the early Late Miocene and Pliocene, and the Pearl River Basin during the late Late Miocene and Pleistocene. Additional, but less significant, contributions from the Red and Mekong river basins and coastal Southeast China are also observed.