长江口北支潮流沉积物磁性特征与沉积环境分析  

Magnetic Properties and Sedimentary Environment of the Xinglong Sand in the North Branch,the Yangtze Estuary

作　　者：周开胜[1] 孟翊[2] 刘苍字[2] 洪雪晴[3] 

机构地区：[1]蚌埠学院食品与生物工程系,安徽蚌埠233030 [2]华东师范大学河口海岸国家重点实验室,上海200062 [3]华东师范大学地理系,上海200062

出　　处：《海洋通报》2008年第5期47-55,共9页Marine Science Bulletin

基　　金：国家重大基础研究发展规划项目(2002CB4124);国家自然科学基金项目(40676028);国家自然科学青年基金(40206013)

摘　　要：通过对兴隆沙XL1孔沉积物磁性特征的研究,为揭示潮汐河口潮流沉积物的磁性特征和建立长江口沉积相序提供新的手段,并在拓展环境磁学的应用领域方面进行有益的探索。研究表明:该地区沉积物的磁性矿物以低矫顽力亚铁磁性矿物为主;当χ、SIRM和χfd%、χARM同处于低值时,反映细晶粒磁铁矿优先溶解,晶粒粗化,可作为还原环境的判据,而在近地表环境下SIRM/χ、Bcr和HIRM的高值,以及S-100mT的低值,一般显示赤铁矿、针铁矿的含量相对较高,可以作为氧化环境的标志。可用χfd%、χARM等参数值的大小来判别长江口北支水动力强弱。按磁化率等磁参数曲线的变化特征将XL1孔自下而上划分出3个磁性层。同时,参照沉积物的粒度特征和有孔虫分析结果,探讨了兴隆沙沉积环境自下而上的演变序列为:潮流沙脊→潮汐水道→潮滩。In order to disclose the magnetic properties of tidal estuary sediment and set up the order of lithofacies, the study on the magnetic properties of the XL1 in Xinglong Sand offers a new instrumentality and the useful exploration in environmental magnetic application. Magnetic measurements were conducted on Core XL1 from the Xinglong Sand, the North Branch of the Yangtze Estuary. The result indicates that ferrimagnetic mineral of multi-domain （MD） / pseudo-single domain （PSD） in size dominates the magnetic properties of the samples. When the numerical value of χ, SIRM and χfd%,χARM are simultaneously lower, we can infer that the less magnetic granule of mineral has been dissolved, and the magnetic granule becomes thick, which can be looked upon as the foundation of reductive environment; while the numerical value of SIRM/χ, Bcr and HIRM are higher and the numerical value of S-100 mT is lower near the earth＇s surface environment, it can be indicated that the content of hematite and needle iron ore is higher, which can be regarded as the sign of oxidation environment. We also think that we can use the magnitude of parameters of χfd%, χARM et al to differentiate the strength of the hydrodynamic in the North Branch of the Yangtze Estuary. The core of XL1 can be divided into three layers according to the variations of magnetic susceptibility and other magnetic parameters. On the basis of magnetic properties, lithofacies and foraminifer and assembled character, it can be found that the mode of environmental evolvement of Xinglong sand bar： tidal current ridge→tidal channel→tidalflat（intertidal zone and supertidal zone）, forming the sedimentary facies sequence of the filled estuary. In addition, the significance of some magnetic parameters on determining sedimentary hydrodynamics and geochemical environment is discussed.

关 键 词：兴隆沙 磁性特征:沉积环境 

分 类 号：P736.2[天文地球—海洋地质] P512.2[天文地球—海洋科学]