长江口外CX21柱样的磁性特征及其影响因素

马鸿磊; 张卫国; 胡忠行; 贾铁飞; 董辰寅; 刘莹

长江口外CX21柱样的磁性特征及其影响因素

1.
华东师范大学河口海岸学国家重点实验室,上海 200062;
2.
浙江师范大学地理与环境科学学院,浙江金华 321004;
3.
上海师范大学城市与旅游学院,上海 200234

详细信息

中图分类号: P9
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出版历程
- 收稿日期: 2011-02-01
- 修回日期: 2011-05-01
- 刊出日期: 2012-05-25

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

1.
State Key Laboratory of Estuarine and Coastal Research, East China Normal University, Shanghai 200062, China;
2.
College of Geography and Environmental Science, Zhejiang Normal University, Jinhua Zhejiang 321004, China;
3.
School of Urban and Tourism, Shanghai Normal University, Shanghai 200234, China

摘要

摘要: 以长江口外、长340 cm的CX21柱样为对象，在磁性特征、地球化学和粒度分析的基础上，结合前期对Y7柱样的研究，探讨粒度、早期成岩作用和物源变化对沉积物磁性特征的影响.研究结果表明，该柱样磁性特征和粒度垂向变化显著.磁性参数、SIRM、fd和fd%与 2~4 m、4~8 m粒级含量呈相对较弱的正相关, 而ARM、ARM/SIRM和ARM/与16 m以下的各细颗粒组分有较强的正相关，表明CX21柱样沉积物磁性特征受到粒度变化的影响.利用BCR方法进行的铁的形态分析结果表明，CX21柱样170 cm深度以下具有较强的还原环境，磁性矿物受到较强的早期成岩作用影响.氧化还原不敏感元素Ti的垂向变化指示了物源变化，Ti向表层的增加与和SIRM向表层的增强具有同步性，说明物源变化也是CX21沉积物磁性特征影响的重要因素.尽管粒度组成和沉积速率不同，CX21与Y7柱样的磁性特征在垂向上具有相似性，表明磁性特征可作为长江口外沉积物地层对比的工具之一.
- 长江口 /
- 磁性特征 /
- 地球化学 /
- 粒度 /
- 物源
Abstract: Core CX21(12230 E，3000 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 ARM, ARM/SIRM and ARM/ and the fractions finer than 16 m. , SIRM, fd and fd% display relatively weak, but positive correlations with the finer fractions (24 m and 48 m). 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 ( 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.
- Yangtze Estuary /
- magnetic properties /
- geochemistry /
- particle size /
- sediment source

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