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本文对长江口水下三角洲岩芯YD0901(31°11’N,122°30’E)中0～34.22m的沉积物进行高分辨率岩石磁学研究,结果表明:阶段Ⅰ(0～8m)中磁性矿物含量高,含有磁铁矿、赤铁矿及少量的硫化物;阶段Ⅱ(8.0～34.2m)中磁性矿物含量低,磁性矿物包括粗颗粒磁铁矿、赤铁矿和铁的硫化物。磁参数结果指示了沉积物垂向上氧化还原环境的改变,由还原环境(阶段Ⅱ)转为氧化环境(阶段Ⅰ)。受成岩作用影响,阶段Ⅱ中的细颗粒的磁铁矿颗粒被溶解而生成铁的硫化物,但是粗颗粒磁铁矿和赤铁矿受成岩作用影响较小,可以提取原生的古气候信息。根据磁性矿物含量和矫顽力的变化在1300年至7000年之间识别出4个气候突然变冷事件,沉积物磁性矿物矫顽力反映的气候变化周期为800年和220年。
In this paper, high-resolution rock magnetism studies of 0 ~ 34.22m sediments in core YD0901 (31 ° 11’N, 122 ° 30’E) of the Yangtze River Estuary core sediments are carried out. The results show that: in stage Ⅰ (0 ~ 8m) High levels of magnetic minerals, including magnetite, hematite and a small amount of sulfides; low levels of magnetic minerals in Stage II (8.0 ~ 34.2m), magnetic minerals including coarse-grained magnetite, hematite and iron sulfide . The results of the magnetic parameters indicate a change in the vertical redox environment of the sediment from a reducing environment (Stage II) to an oxidizing environment (Stage I). Due to the diagenesis, the fine-grained magnetite particles in Stage II are dissolved to form iron sulphides. However, the coarse-grained magnetite and hematite are less affected by diagenesis and can extract the original paleoclimate information. According to the change of magnetic mineral content and coercivity, four sudden climate change events were identified between 1300 and 7000. The coercivity of sedimentary magnetic minerals reflects the climate change cycles of 800 and 220 years.