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长江口外CX21柱样的磁性特征及其影响因素

ISSN号：1000-5641
期刊名称：《华东师范大学学报：自然科学版》
时间：0
分类：P9[天文地球—自然地理学]
作者机构：[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
相关基金：国家自然科学基金（40771201）;国家自然科学基金创新群体项目（40721004）

作者：马鸿磊[1], 张卫国[1], 胡忠行[2], 贾铁飞[3], 董辰寅[1], 刘莹[1]

关键词：长江口, 磁性特征, 地球化学, 粒度, 物源, Yangtze Estuary, magnetic properties, geochemistry, particle size, sedi- ment source

中文摘要：

以长江口外、长340cm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x、SIRM、xfd和xfd％与2～4μm、4～8μm粒级含量呈相对较弱的正相关，而XARM、XARM／SIRM和XARM／X与16μm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170cm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X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．

英文摘要：

Core CX21（122°30＇ E,30°00＇ N） is 340 cm in length, obtained off the Yangtze Estu- ary, 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. Resuits indicate that there are strong positive relationships between （ARM, ARM/SIRM and ARM/ and the fractions finer than 16μm. g, SIRM, xfd and xfd % 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 concentra- tion related magnetic parameters （X 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.

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