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The sediment provenance identification and paleoenvironmental characteristics in the western shelf area of the South Yellow Sea, are of great significance to study the environmental evolution of the Chinese Shelf Sea since the Last Glacial period and to solve the environmental geological problems in the exploitation of the shelf. In this paper, the UCC-normalized rare earth element (REE) distribution patterns, the provenance index of sediments (PI) and the correlation between 5Eu and ∑REE are used to analyze the sediment provenance since MIS5 in the western shelf area of the South Yellow Sea. Based on the analysis of mineral assemblages, sediment grain size, foraminifera and sporopollen of core NT1 and NT2, and combined with the distribution characteristics of paleochannel, the paleoenvironmental characteristics in the western shelf area in the South Yellow Sea during the marine isotope stage MIS4 and MIS2 are further studied. The results show that, in the core NT1, sediment provenances of MIS2 and MIS4 in Core NT1 mainly sourced from the Yellow River and the main sediment provenances of MIS1, MIS3 and MIS5 from the Yangtze River. In core NT2, the main sediment provenance of MIS3 period was from the Yellow River, and the main sediment provenances of MIS1, MIS2, MIS4 and MIS5 sourced from the Yangtze River. All the results incdicicated that the western shelf area of the South Yellow Sea was in a cold and low-sea-level sedimentary environment during MIS4 and MIS2, and the main vegetation types were grassland, coniferous forest and conifer-broadleaf forest. [ABSTRACT FROM AUTHOR]

Abstract  The internal structure and composition of a 37-mm-thick Co-rich Mn crust from the Lamont Guyot in the Marcus-Wake Seamount cluster have been studied in detail by means of electron-probe microanalysis (EPMA). 184 point analyses for 16 elements were carried out at an average spacing of 0.20 mm and each point was dated using the Co-geochronometer method. Two types of variation in composition were observed in the crust: long-term trends and short-term erratic variations. The long-term trends were identified using the fifth order polynomial. Mn and Ni were shown to increase in concentration from 23.3 Ma to a maximum at about 20 Ma and then decline steadily to the Present, whereas Fe, P and Si showed the opposite trend. By contrast, Co displayed a double humped pattern with maxima at about 19 Ma and 3.5 Ma and minima at 23.3 Ma, about 11 Ma and at Present. The long-term trends in element concentrations in the crust lead us to suggest that much of the Fe in western Pacific Ocean ferromanganese crusts is aeolian in origin and derived from the deserts of central Asia. Cooling of the Asian mainland at about 20 Ma led to an increase in the flux of Fe to the oceans. This was supplemented by an additional input of Fe into the crusts as a consequence of the dissolution of biogenic CaCO3 tests at 4.5−10.5 Ma. For the short-term erratic variations, three periods of 0.61, 0.96 and 1.65 m.y. were identified by spectral analysis. The second harmonics of these periods are 1.22, 1.92 and 3.30 m.y., which may correspond to the highest-order periods for eccentricity of 1.31, 2.04 and 3.47 m.y. This suggests the possibility that the high-frequency oscillations of the time series data are linked to climatic changes controlled by the highest-order periods of the Milankovitch cycles. [ABSTRACT FROM AUTHOR]