Magnetic properties of the core CX21 off the Yangtze Estuary and its influencing factors

Abstract

Abstract: Core CX21(122°30′ E，30°00′ N) is 340 cm in length, obtained off the Yangtze Estuary, China. In this study, magnetic, geochemical and particle size analyses were conducted on sediments from the core CX21 to determine the major factors (including early diagenesis, particle size and sediment provenance) that control the down-core variations of magnetic properties. Results indicate that there are strong positive relationships between χ_ARM, χ_ARM/SIRM and χ_ARM/χ and the fractions finer than 16 μm. χ, SIRM, χ_fd and χ_fd% display relatively weak, but positive correlations with the finer fractions (2—4 μm and 4—8 μm). This suggests that particle size plays an important role in the variation of magnetic properties. Iron species analysis using the BCR method indicates that sediments below 170 cm experienced more reducing environment than that above, which is consistent with the phenomena of stronger reductive diagenesis of magnetic minerals. Ti, an element insensitive to redox conditions, reveals sediment provenance changes in the core CX21. The increase of Ti toward the surface is accompanied by an increase of concentration related magnetic parameters (χ and SIRM), suggesting that sediment source is also a main factor influencing magnetic properties. In spite of the difference in sedimentation rate and particle size composition, CX21 and the previously studied core Y7 show similar down core variations of magnetic properties, implying that magnetic properties can be used as a tool for core correlation in area off the Yangtze Estuary.

Key words: Yangtze Estuary, magnetic properties, geochemistry, particle size, sediment source

CLC Number:

MA Hong-lei, ZHANG Wei-guo, HU Zhong-xing, JIA Tie-fei, DONG Chen-yin, LIU Ying. Magnetic properties of the core CX21 off the Yangtze Estuary and its influencing factors[J]. Journal of East China Normal University(Natural Sc, 2012, 2012(3): 120-129,153.

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