Using Geochemistry of Rare Earth Elements to Indicate Sediment Provenance of Sand Ridges in Southwestern Yellow Sea

The Jianggang Harbour-centered radial sand ridge(RSR) is the largest sand body in the Yellow Sea. Its formation and evolution are of interest for scientists of various fields; however, the sediment provenance is uncertain. In this study, rare earth element(REE) geochemical compositions of the RSR sediments together with their potential sources are investigated to identify the provenance of the RSR sediments. The typical parameters((La/Yb)_N,(La/Sm)_N and(Gd/Yb)_N) as well as the upper continental crust-normalized patterns of REEs can only be associated with source rocks, and thus can be used as effective tracers for the origin and sources of sediments. However, the REE contents of sediments are affected by many factors, such as particle sorting and chemical weathering. Onshore RSR sediments are different in REE geochemical composition from offshore RSR sediments to some extent, suggesting that not all of the offshore RSR sediments have the same sources as the onshore RSR sediments. Meanwhile, the sediments adjacent to the northeast of Cheju Island and at Lian Island near the Lianyun Harbour were not the source of the RSR sediments due to their distinctive REE patterns, dEu,(La/Yb)_N,(Gd/Yb)_N and(La/Sm)_N. The Korean river sediments could be dispersed to the Jiangsu Coast slightly impacting the fine fractions of the RSR sediments, particularly the offshore RSR sediments. Additionally, geochemical comparisons show that the modern Yellow River was responsible for the onshore RSR sediments, whereas the sediment loads from the Yangtze River could serve as a major contributor to the RSR, particularly the offshore RSR. In addition, the offshore RSR could also be partly fed by an unknown source due to some high values of(La/Yb)_N,(La/Sm)_N and La contents differing from those of the Chinese and Korean river sediments.

Evolution of the Pearl River and its Implication for East Asian Continental Landscape Reversion

As the link connecting the South China Continent and the northern South China Sea(SCS),the Pearl River is the focus of sedimentology and petroleum geology research.Its evolutionary process and controlling factors are of great significance in revealing the East Asian continental landscape reorganization during the Late Cenozoic.Based on published data,’source-to-sink’provenance analyses allow systematic deliberation on the birth and evolutionary history of the Pearl River.Close to the Oligocene/Miocene boundary,an abrupt shift in the sedimentary composition indicates significant westward and northward expansion of the river’s watershed area,followed by the establishment of a near-modern fluvial network.This sedimentary change generally concurred with a series of regional geological events,including the onset of the Yangtze throughflow,large-scale development of the loess plateau,and formation of the northwestern arid zone and Asian Monsoon system.These major changes in the geology-climate-ecoenvironment system are in close response to the process of the Cenozoic Xizang(Tibetan)Plateau uplift.Consequently,the East Asian continental landscape and most of midCenozoic drainage systems underwent critical reversion into east-tilting,or east-flowing networks.