Abstract
In order to interpret the marine clastic record preserved in the sedimentary basins of the East Asian marginal seas, it is important to understand how sediment transport and chemical weathering affect the composition of sediment enroute to its sink. Here we present a new data set for fine-grained sediment (<63 μm) from the Yangtze River and its major tributaries, which represents a baseline for interpreting sediment in the East China Sea. We demonstrate that there is no significant coherent downstream variation in the major element contents, which are generally more enriched than the average upper continental crust, except for water-soluble elements including Sr, Rb, Na, and K. Nd isotopes show that most of the sediment comes from the eastern and middle Yangtze Craton, as well as the Songpan-Garze Terrane. Chemical weathering varies significantly across the basin with upstream tributary sediments being relatively unweathered compared to those in the lower reaches. However, sediments in the main Yangtze stream show no trend in chemical weathering along its course, with some of the least weathered materials being found closest to the delta. Grain size and the abundance of hydrodynamically sorted heavy minerals affect the bulk geochemistry, especially the rare earth elements (REEs).
Highlights
The Yangtze River is the largest river in eastern Asia and supplies sediments to the marginal seas of the Western Pacific, as well as filling sedimentary basins onshore between Tibet and the modern delta (e.g., Clark et al 2004; Zheng et al 2013)
We use
In this study, we analyzed a series of samples from the mainstream of the Yangtze River, as well as its major tributaries, to see if there were any patterns in the major and trace element chemistry that could be used to constrain provenance and chemical weathering processes within this major river system
Summary
The Yangtze River is the largest river in eastern Asia and supplies sediments to the marginal seas of the Western Pacific, as well as filling sedimentary basins onshore between Tibet and the modern delta (e.g., Clark et al 2004; Zheng et al 2013). Understanding what controls the intensity of chemical weathering and the strength of bedrock erosion are important goals if we are to quantify how climate and tectonic activity influence the development of the Earth’s surface and the composition of sediments deposited on the surrounding continental margins. Understanding where sediment is being derived from, what its composition is and how that changes during transport due to abrasion and chemical weathering is essential if the marine sediment archive is to be exploited (e.g., He et al 2013b). The geochemistry of bedload and suspended sediments has been used by many workers to determine the provenance, weathering, and tectonics of several river basins
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