| 摘要: |
| 颗石藻生物矿化作用形成的方解石质颗石化石富含地球化学信息，是古海洋研究的理想材料，而典型样品的获取及其矿物学研究是前提与基础。选取南海西部越南岸外夏季上升流区MD05-2901孔柱状样，通过颗石分布特征、生源组分、矿物物相和红外光谱等矿物学特征研究，探讨了颗石化石关联的沉积环境信息，进而探索了古海洋研究的新思路和方法。结果显示：南海西部MD05-2901孔柱状样从顶部到底部（随着深度的增大）颗石化石含量具有表层较高、中部含量最高、底部含量少的分布特征；有机碳含量在1.19%—2.78%，平均含量为1.99%，随深度的增加逐渐减小；以颗石为主的碳酸钙质无机碳含量在0.85%—1.65%波动，平均含量为1.12%，变化呈现较明显的周期性，与颗石的分布特征有强相关性；柱状样C/N分析表明这一时期沉积物主要为海洋自生沉积。富颗石沉积样品矿物物相主要含有方解石、伊利石、蒙脱石、绿泥石、高岭石，以及少量石英等。FTIR分析表明蒙脱石中可能吸附有机质，值得矿物学家深入研究。颗石藻沉积环境的矿物学特征富含沉积信息，为古海洋研究提供了新的研究途径。 |
| 关键词: 颗石藻 颗石化石 矿物特征 晚第四纪 南海 |
| DOI：10.7515/JEE192005 |
| CSTR：32259.14.JEE192005 |
| 分类号: |
| 基金项目:国家自然科学基金项目（41472310，41603041） |
| 英文基金项目:National Nature Science Foundation of China (41472310, 41603041) |
|
| Mineralogical characteristics of coccolith-rich site in western South China Sea |
|
WANG Fudong, ZOU Xiang, SUN Shiyong, MA Biaobiao, CHEN Tingfang, ZHAO Xueqin, DONG Faqin
|
|
Institute of Non-metallic minerals, Key Laboratory of Solid Waste Treatment and Resource Recycle of Ministry of Education, Southwest University of Science and Technology, Mianyang 621010, China
|
| Abstract: |
| Background, aim, and scope Coccolithophores is extremely sensitive to the ocean environment and climate change response because of its main growth in the upper light layer of the seawater, and be controlled by the temperature, acidity, light intensity and nutrient quality of the sea water. Coccolith was formed by Coccolithophores through a procedural process of biomineralization. Calcite fossil contained rich geochemical information, which is an ideal material for paleoceanography study. However, the acquisition of typical samples and the detailed research on minerology are the premise and foundation of obtaining reliable information. In this study, we performed a detailed mineralogical study of marine pore columnar samples from the upwelling area in the South China Sea off eastern Vietnam, in order to extract the sedimentary environment information related to coccoliths, and explore new ideas and methods of paleo-marine research. Materials and methods In the presented study, sediment samples were selected from core MD05-2901 which is in the upwelling area in the South China Sea off eastern Vietnam (14°22′50″N, 110°44′60″E), which belongs to the summer upwelling area off the coast of Vietnam in the west of the South China Sea, with a water depth of 1454 m and a column core length of 36.49 m. The bottom age of the sample was MIS 12, about 450 ka, and the time resolution was about 0.3 ka. The mineralogical characteristics of coccolith fossil species, biogenic components, mineral phases and FTIR spectra were identified for discussing coccoliths-related environmental information. New idea and method for study ancient marine environment were explored through presented study. Results The results show that: (1) columnar samples from the top to the bottom (with the increase of depth) have higher fossil content in the surface, the highest in the middle, and less in the bottom. (2) The organic carbon content ranged from 1.19% to 2.78%, and the average content is 1.99%, which decreased with the increase of depth. (3) The inorganic carbon content of calcium carbonate, which is dominated by pellets, fluctuates between 0.85% and 1.65%, and the average content is 1.12%, which shows obvious periodicity and is strongly related to the distribution characteristics of the pellets. (4) Columnar C/N analysis show that the sediments in this period were mainly marine authigenic deposits. (5) The mineralogical facies of the samples are mainly composed of calcite, illite, montmorillonite, chlorite, kaolinite and a small amount of quartz, etc. (6) FTIR analysis shows that montmorillonite may adsorb organic matter, which is worthy of further study by mineralogists. Discussion The changes of the species of coccoliths in the column reflect the trend of the vegetative cline depth in this area. It is believed that the variation of F. profunda content in the South China Sea is manifested as the characteristics of nutrient cline depth, interglacial deep and shallow deep glaciation, reflecting the change of wind intensity. The C/N in the Late Pleistocene columnar section showed a decreasing trend, indicating that the productivity reflected by coccolithophores decreased with the decrease of land source input. The quartz content increased with the increase of deposition depth, indicating that the columnar deposition environment changed to high-energy environment gradually. It is also found that the clay minerals and their compositions in the samples can reflect the control of terrestrial weathering by the East Asian Monsoon. Conclusions Based on the study of mineralogical characteristics of coccolith fossil species, biogenic components, mineral phases and FTIR spectra, we obtained the vegetative cline changes reflected by the content of coccolithophores in the column samples, as while as productivity reflected by carbonaceous composition and clay mineral was revealed. All this work shows that the detailed research on minerology are the premise and foundation of obtaining reliable information. Recommendations and perspectives The mineralogical characteristics of the sedimentary environment of Phaeophyllum are found to be rich in sedimentary information, which provides a new approach for the study of paleoceanography. |
| Key words: coccolithophores coccolith fossil mineralogical characteristic Late Quaternary South China Sea |
