冲绳海槽晚第四纪沉积特征及其物源和环境意义

IOCAS-IR > 海洋环流与波动重点实验室

	冲绳海槽晚第四纪沉积特征及其物源和环境意义
	蒋富清
学位类型	博士
	2001
学位授予单位	中国科学院海洋研究所
学位授予地点	中国科学院海洋研究所
学位专业	海洋地质学
关键词	沉积特征物源和环境意义冲绳海槽
摘要	本文通过对冲绳海槽北端和南部两个海区沉积物样品的粒度、矿物和元素组成与分布特征的研究，探讨了冲绳海槽沉积物的来源，给出了一定元素组合的物源意义。通过对冲绳海槽两个柱状沉积物的粒度、矿物、元素在地层中的分布特征的研究，结合浮游有孔虫氧同位素地层划分，探讨了冲绳海槽晚第四纪沉积记录的古环境意义。冲绳海槽陆架和陆坡沉积物明显具有陆架残留沉积的特征，沉积物主要由陆源碎屑矿物、生物碎屑、粘土矿物和少量自生矿物组成。在冲绳海槽北端，陆架和陆坡砂质区沉积物的主要来源是冰期低海面时古黄河的残留沉积，在现代沉积环境下受到海洋生物和自生沉积作用的改造；济州岛南部的细粒沉积区的物源主要是周围陆架残留沉积，在黄海暖流和黄海沿岸流的综合作用下，残留沉积中的细粒组分再沉积形成的。冲绳海槽北端海槽区沉积物主要是火山活动的产物，火山玻璃和火山型的辉石、紫苏辉石和磁铁矿明显富集。冲绳海槽南部沉积物的主要物源是长江沉积物，此外还有大量的海相生物沉积和自生沉积。对元素分布特征的研究表明，冲绳海槽陆架区富含陆源粗碎屑组分SiO_2和生源碎屑组分CaO和Sr，生物沉积对陆源沉积明显具有稀释作用。陆坡区由于受黑潮暖流的影响，往往富集Fe_2O_3和P_2O_5。在海槽区，陆源细粒组分以及与细粒组分相关的元素A1_2O_3、K_2O、Cu、Zn、Co、Ni和Cr等明显富集。利用R型因子分析的方法确定了两个研究区元素组合，结合沉积物的矿物组成给出不同元素组合的物源意义。对冲绳海槽北部(Y127孔)和南部(E017孔)两个柱状沉积物的浮游由孔虫的δ~(18)O进行了分析，将其与本区具有高分辨率的柱状样氧同位素曲线对比进行，结果表明，δ~(18)O值较敏感地记录了冲绳海槽晚第四纪以来的古环境变化。δ~(18)O的高值往往与冷期相对应，δ~(18)O的低值与暖期相对应。冲绳海槽在12ka BP左右开始了逐渐转暖的过程，在10ka BP左右(YD事件)发生了短暂的降温过程，但降温幅度很小。根据沉积物化学组成在地层中的变化规律，大部分元素较敏感地记录了全新世气候转暖事件，但是对于千年尺度的YD事件，多数元素对此没有明显的响应。冲绳海槽火山活动对沉积物的组成和沉积环境的塑造起到了至关重要的作用。根据氧同位素地层划分，在冲绳海槽北部12ka BP曾有火山活动的纪录，距今约8ka BP以来，冲绳海槽有两次较大规模火山活动的记录。火山活动往往会在短期引起气候的变冷，从而造成海区生态环境的破坏，生物沉积作用减弱。但从长期变化来看，可能是气候变暖的因素之一。火山层的主要特征为沉积物主要由粉砂组成，平均粒径明显高于周围层位，在矿物组成上表现为蒙皂石、火山玻璃和火山型的辉石、紫苏辉石和磁铁矿的含量较高，在化学组成上表现为Na_2O与Zr的同高于周围层位，而陆源性较强的元素TFe_2O_3和K_2O，以及生源组分CaCO_3和Sr的含量普遍低于周围非火山层。
其他摘要	The composition and distribution of the grain size, minerals and elements for surface sediments from the north and south Okinawa Trough are investigated. Based on the result, the sources of the sediments are analysed, and the soure indications of some groups of element are given. Based on the distribution of grain size, minerals and elements for two core sediments, combined with the distribution of the oxygen isotopic ratios, the relationship between the sedimentary records and their paleo-environmental indications are investigated. The sediments from the shelf and slope of the north and south Okinawa Trough are similar to the residual sediments. The sediments are mainly composed of terrestrial debris, biogenicial debris, clay minerals and autogenous deposits. In the north Okinawa Trough, the sandy sediments from the shelf and slope mainly derived from the residual sediments of the Yellow River during the ice age, in present envieronment, the sediments are rebuilded by the biogenic and autogenous deposits. The fine-grained sediments froln the area to the south of the Chejudo islands mainly derived from the shelf residual deposits. Some of the fine-grained sediments in the residual sediments redeposit in the role of the Huanghai Sea warm current and the Huanghai Sea coastal current. The sediments from the trough of the north Okinawa Trough mainly derived from the volcanic activity. There are a lot of volcanic glass, augite, hypersthene and magnetite in the area. The sediments of the south Okinawa Trough mainly derived from the Yangtz River. In addition, there are some marine biogenic and autogenous deposits. According to the distribution of elements, the sediments of the continental shelf in the Okinawa Trough are mainly composed of terrigenous composition, such as SiO_2, and biogenic compositions, such as CaO and Sr. The biogenic deposits dilute the terrigenous deposits. The elements, such as Fe_2O_3 and P_2O_5, rich in the slope, where is influenced by the Kuroshio. Some elements, such as A_2O_3、 K_2O、 Cu、 Zn、 Co、 Ni and Cr, mainly hosted in the fine-grained sediment, rich in the trough. Based on the result of the R-model factors analyses, the elements are devided into different groups, combined with the minerals distributions, every elements group are given a different source indication.The δ~(18)O ratio of planktonic foraminifera for two core sediments from the north (core Y127) and the south(core EO17) Okinawa Trough are analysed. Stratigraphic correlation of oxygen isotopic ratios show that the ~(18)O ratio record the change of the paleo-environment of the Okinawa Trough. The higher the δ~(18)O ratio, the colder the weather is, and vice versa. The weather becomes warm at about 12ka BP, and then there is a short cold stage at about 10ka BP. According to the change of elements in the stratigraphy, most of the elements recorded the event of Holocene warming, and only several elements recorded the YD event. The volcanic activity plays a very important role on the composition of the sediments and the sedimentatry environment in the Okinawa Trough. According to the oxygen isotopic stratigraphy, There exit two large-scale volcanic activity records from 8.0ka BP to now. Only in the north Okinawa Trough recorded the volcanic activity occoured at about 12 ka BP. Volcanic acitivity makes the weather colder, results the ecological environment destorys and the biogenic deposit reduced in a short period. From a long period, volcanic activity makes the weaher warmer. The characteristics of the volcanic layer are that the grain size of the sediment become coarser, the content of smectite, volcanic glass, augite, hypersthene, magnetite, Na_2O and Zr become higher, and the content of terrigenous compositions, such as TFe_2O_3 and K_2O, and the biogenic compositions,such CaCO_3 and Sr, become lower than the adjacent layers.
页数	139
语种	中文
文献类型	学位论文
条目标识符	http://ir.qdio.ac.cn/handle/337002/1009
专题	海洋环流与波动重点实验室
推荐引用方式 GB/T 7714	蒋富清. 冲绳海槽晚第四纪沉积特征及其物源和环境意义[D]. 中国科学院海洋研究所. 中国科学院海洋研究所,2001.

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