黄河三角洲潮滩沉积物磁性特征与沉积环境分析

Magnetic Properties of Sediment and Sedimentary Environment in Tidal Flat of the Yellow River Delta

环境磁学方法作为沉积记录研究的重要手段，已在黄土、湖泊和陆架沉积物中得到广泛应用，但将此方法应用于潮滩沉积环境的研究并不多。因此，通过测量黄河三角洲潮滩YDZ1柱样沉积物磁学和粒度参数，结合AMS^14C测年数据，对末次冰盛期后黄河三角洲潮滩沉积物磁性特征与沉积环境进行分析。结果表明：以假单畴（PSD）～多畴（MD）晶粒为主的亚铁磁性矿物主导了潮滩沉积物的磁性特征，磁学参数中的χARM,χARM／SIRM和χARM／χ可视为粘土（〈4gm）或细粒级组分（〈32μm）含量的代用指标。潮滩沉积相序自上而下为泛滥平原相、河流相、三角洲前缘相、浅海相、潮坪相和河流相，沉积环境表现为强（陆相）、弱（海相）、强（陆相）的演变过程。

Environmental magnetism is a newly rising frontier science among earth science, environmental sci- ence and magnetism. It reveals environmental actions, environmental processes and environmental problems of different temporal and spatial scales through the magnetic measurement and analysis of the magnetic miner- al assemblage and characteristics. Due to the type, the content and the grain size of magnetic mineral related to the sediment sources, sediment transport capacity and early digenesis, and changes of these factors are heavily influenced by environmental changes, the information of sedimentary environment change can be extracted through the analysis of the magnetic characteristics of sediment. At present, environmental magnetic method has been widely used in loess, lake and shelf deposits as an normal mean for studying sedimentary record, but using this method on sedimentary environment in tidal flat is seldom. Hence, by measuring the magnetic pa- rameters and the grain size parameters of the core YDZ1 in tidal flat of the Yellow River Delta, and combined with data of AMS^14 C dating, this paper analyzes the sediment magnetic properties and its sedimentary environ- ment after the Last Glacial Maximum in tidal flat of the Yellow River Delta. The results show that the ferro- magnetic mineral of pseudo-single domain （PSD） and multi-domain （MD） dominates the sediment magnetic properties of the core YDZ1. Among the magnetic properties of sediment, the parameters of χARM, χARM/SIRM and χARM/χ can be regarded as the substituted indexes for the clay （〈4 μm） content or the fine-grained compo- nent （〈32 μm） content. The sedimentary facies from surface to bottom in tidal flat of the Yellow River Delta has experienced the floodplain facies, the river facies, the delta-front facies, the neritic facies, the tidal flat fa- cies and the river facies, and the sedimentary dynamical environment had a variation process from strong to weak, and then strong again.