【作者】 王桂芝；

【导师】 高抒；

【作者基本信息】 中国科学院海洋研究所 ， 海洋地质学， 2001， 硕士

【摘要】 本文的研究的主要目的是了解北黄海泥质区的沉积特征和形成的动力过程。基于此目的，在北黄海西部海区进行了两次海洋地质与地球物理调查，并根据对浅钻样品的粒度分析和²¹⁰Pb沉积速率的测定，结合浅地层剖面的解译以及ADCP流速资料的处理，探讨了北黄海西部的沉积层序，讨论了泥质区的物质来源与形成原因，分析了北黄海中部泥质沉积的²¹⁰Pb沉积速率在一定的动水条件下的可信度，并对柱状样粒度参数的相关分析与地层对比之间的关系进行了初步的阐述。 浅地层剖面与岩芯粒度分析表明，北黄海西部的地层划分为三层：上层为粘土沉积，位于北黄海中部、山东半岛沿岸和辽东半岛东南岸；中层为粉砂沉积，分布区域与粘土沉积类似，或者位于粘土沉积之下，或者直接出露海底；下层为粗颗粒砂质沉积，分布于整个海区，在粘土沉积和/或粉砂沉积存在的海域，砂质沉积位于这些沉积的下部，而在其他海域则直接出露海底。粘土沉积与粉砂沉积统称为泥质沉积，内部结构较均一，粒度的垂向变化不大，但两层之间在粒度和地层反射信号等方面的差异还是很明显的，在山东半岛沿岸构成了泥质沉积的两相结构。粗颗粒沉积的粒度垂向变化较大，与上层细颗粒沉积之间的差异显著。 泥质沉积的厚度以山东半岛东端最大，约30m。而沉积速率却很小，在mm/a的量级上，因此在全新世最大海侵后的几千年内形成巨厚的沉积是不可能的，其主要物源可能是古河流。渤海海峡区泥质沉积厚度从南向北、从西向东逐渐变薄，从西向东沉积速率逐渐减小，但沉积速率的绝对值较大，可以在全新世最大海侵后的几千年内形成如此厚的沉积。北黄海中部泥质沉积厚度约在8m左右，位于泥质沉积边缘岩芯中泥炭层的¹⁴C年代约10000aBP，而且²¹⁰Pb沉积速率较小，无法满足几千年内堆积厚层沉积的需要，因此，该处泥质沉积的主体并非全新世最大海侵后形成的，而是早全新世海侵过程中的海岸侵蚀与海底物质的再改造作用提供了沉积物质。整个北黄海西部的泥质沉积总量约有4.41×10¹¹t。 摘 要 对于两个沉积环境可能相似的柱状岩芯，利用粒度参数求取各个层位的最 大相关系数，可以找到具有良好对应关系的层位，其沉积年龄相近。或者说， 在己知一个岩芯的粒度参数和层位年龄的情况下，可以应用柱状样粒度参数的 相关分析，推得另一个粒度参数已知的岩芯的年龄。理论上，这种方法适用于 来自相同动力环境的岩芯。 利用水动力条件与悬沙浓度计算北黄海中部泥质区的沉降通量，与‘’平 测得的结果对比，发现对于粘性颗粒两者的值非常近似，说明在该区的动水条 件下‘’个 测年法对粘性沉积物的测定结果有很好的可信度。更多还原

【Abstract】 For a better understanding of the sedimentary characteristics and related dynamic processes of the northwestern Yellow Sea, two cruises were organized to collect sediment samples and to undertake geophysical survey and hydrodynamic measurements. Using the sediment samples and shallow seismic records obtained about cores and records, analysis of grain size distributions, 210Pb dating and geophysical interpretation as well as ADCP velocity processing have been carried out. By incorporating the processed data, the sedimentary sequence in the northwestern Yellow Sea is delineated and the sediment supply and mechanisms of the mud deposit in the study area are discussed. In addition, the reliability of 210Pb dating under certain hydrodynamic conditions is evaluated, and an approach to sequence correlation on the basis of grain size data is proposed. Shallow seismic records and grain size analysis show that the strata in the northwestern Yellow Sea can be divided into three sections. The uppermost consists of clay, located in the deep water areas, along the coast of Shandong Peninsula and the southeast coast of Liaodong Peninsula. The middle section is mainly silt, distributed in almost the same area as the section of clay. The lowermost consists of coarse-grained sand. Each of the three types of sediments, mentioned above, is exposed in the region. The architecture of the clayey and silty sections which form two-layer structure is characterized by homogeneous features, with apparent differences in grain size and seismic reflection exiting between the two sections. The vertical distribution pattern in the coarse sediments shows grain size fluctuations and differs greatly from the two sections described above. The thickness of the mud deposit reaches the greatest in the east end of Shandong Peninsula, i.e., around 30 m, whilst the accumulation rate is very small, only of the order of mm/a. Thus, it is unlikely for such a deposit to form in several thousand years after the Holocene high sea-level, implying that the supply of sediment is not derived mainly from the modern Yellow River, but perhaps from some old river. In the Bohai Strait the mud deposit becomes progressively thinner from the south to the north and from the west to the east, with a decreasing accumulation rate from the west to the east. Here, the rate is large enough to form the mud deposit since the occurrence of the Holocene high sea-level. In the central northern Yellow Sea the thickness of the mud deposit is around 8m. The 14C age of the turf in the core located at the edge of the mud deposit is around 1 0000aBP. Here, the accumulation rate is relatively small for the formation of the thick mud deposit in several thousand years. Thus, the main body of this mud deposit cannot be not formed since the Holocene high sea-level. It is coastal erosion and seabed reworking that provide the supply of sediment. The whole amount of mud deposit in the study area is of the order of 4.41 X 10. For two cores from a similar sedimentary environment, grain size parameters can be used for sequence correlation analysis. Correlation coefficients for the grain size data can be calculated between the layers of different cores. On such basis, maximum correlation can be identified; the layers with the highest correlation are likely to have the same age. Preliminary analysis has been carried out for two cores from the southern Yellow Sea, and encouraging results were obtained. Theoretically, The mathod applies to cores from the same sedimentary environment.更多还原