Records of the Past 40k Years Sedimentation and Climatic Variations in the Northeastern South China Sea

• Main Authors: Ying-Ying Shih, 施迎瑩
• Other Authors: 林曉武
• Format: Others
• Language: zh-TW
• Published: 2011
• Online Access: http://ndltd.ncl.edu.tw/handle/99826713666474924094

碩士 === 國立臺灣大學 === 海洋研究所 === 99 === Northeastern South China Sea receive particles from Taiwan, China, Philippines and other islands. Large amounts of terrigenous suspended sediments from the surrounding rivers control composition of sediments in the South China Sea. Another major source of sediment entering the South China Sea is the biogenic calcium and siliceous biogenetic particles. In addition to terrigenous and biogenic sediments, the type and amount of sediments may vary during glacial and interglacial transitions. Little data are available in addressing variations of particles entering the South China Sea during climatic changes and temporal variations. The objective of this study is to verify if climatic and subsequent sea-level changed were recorded in the study area. Age model was constructed using AMS 14C dating over foraminifera in the sediment to delineate 400,000 years sedimentation and climatic variations in the area. This study also analyzed carbon and nitrogen ratio of organic matter in sediments, organic carbon, calcium carbonate content, major element compositions, and particle size distribution, to understand sources of sediment. The results showed that sediments in the northeastern South China Sea strongly controlled by climate change. Based on their geochemical variations, the following three types of sedimentary environments can be identified : glacial (lower sea level), transition (sea-level rise) and Holocene (higher sea level). Each type of sedimentary environment showed different depositional pattern, with the glacial sediments (lower sea level) showing stronger terrigenous signal with more frequent of coarse particles, low calcium carbonate content, while the transition (sea-level rise) sediment showing a gradual trend from a more terrigenous type sediments to more biogenous sediment, more finer grain particulate matter, in accompany with less terrigenous major ions characters. The Holocene sediments were deposited during higher sea level with a stronger biogenous signal, twice as much of calcium carbonate content than glacial period, more fine-grained substances.