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Abstract: The formation of a broad tidal flat along the coast of the northern Jiangsu Province of China depends largely on the sediment supply from the Yellow and Yangtze Rivers although the relative contributions from each of these two large rivers remain uncertain. Knowledge of sediment sources to the tidal flat is critical for understanding the evolution of this muddy coast impacted by the large rivers. The present study focuses on tracking the sediment source of the tidal flat deposits based on sediment magnetic properties and geochemical analyses as well as statistical analysis. The study shows that sediments to the north of Yangkougang (site 9) have lower values of saturation isothermal remanence magnetization (SIRM), magnetic susceptibility (χ), demagnetization parameter S−100 ratios, lower Fe/Al values and higher Ca concentrations, while the opposite is true for samples south to Haozhigang (site 18). In addition, SIRM values of the <16μm and >63μm fractions generally display increasing trend from north to south. These results suggest that sediment sources rather than particle size variation are the dominant factors influencing the bulk magnetic properties. In light of the sediment composition comparison between the Yellow River and Yangtze River, factor analysis is used to identify sediment source of the tidal flat sediments. It is indicated that the Yellow River in its former course is the dominant supplier for sites to the north of Yangkougang (site 9), while the Yangtze River is the dominant supplier for sites to the south of Haozhigang (site 18). The coast between Yangkougang (site 9) and Haozhigang (site 18) is a transition zone influenced by both rivers. The inferred provenance contrasts are consistent with the pattern of coastal geomorphological evolution. Our data also suggest that sediments eroded from the former Yellow River delta have contributed to the evolution of the Yangtze Estuary in historical time. This study demonstrates that a combined magnetic and geochemical fingerprinting techniques in couple with statistical analysis is valuable for identifying sediment sources of tidal flats and deltas influenced by large rivers in the world. [Copyright &y& Elsevier]

Abstract: Loess deposits are widely distributed over the islands in the Bohai Gulf and neighboring regions of northern China. The coastal loess, located to the east of the Chinese Loess Plateau (CLP), is believed to have a local source from exposed marine sediments and a distant source from inner arid regions in Asia. In this study, magnetic, geochemical and diffuse reflectance spectroscopic analyses were conducted on the loess to explore its relationship with the loess on the CLP and its paleoclimatic implications. We find that the coastal loess shows similar geochemical composition, background susceptibility and magnetic enhancement to loess on the CLP. Magnetic minerals characteristic of pedogenesis are more important in the paleosol layer, with fine ferrimagnetic minerals abundant in paleosol layer SB1 and hematite in paleosol layer SB2. Geochemical evidence suggests that weathering intensity in paleosol SB2 is similar to or even stronger than in paleosol SB1. Pedogenic enhancement of magnetic susceptibility in the study area is not so strong, which may be due to enhanced hematite formation as opposed to ferrimagnetic mineral production and preservation. [Copyright &y& Elsevier]