有孔蟲殼體微量元素比與穩定同位素組成：南海之校正與古海洋應用
None Long-term climatic and environmental reconstruction from marine sediments relies heavily on the reliable geochemical proxies from foraminiferal shells. Therefore, the aim of this dissertation is to improve our understanding and confidence in planktonic foraminiferal proxies as indicators of sea...
| Main Authors: | , |
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| Other Authors: | , , |
| Format: | Thesis |
| Language: | English |
| Published: |
2007
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| Subjects: | |
| Online Access: | http://ir.lib.ncku.edu.tw/handle/987654321/213301 http://ir.lib.ncku.edu.tw/bitstream/987654321/213301/1/index.html |
| Summary: | None Long-term climatic and environmental reconstruction from marine sediments relies heavily on the reliable geochemical proxies from foraminiferal shells. Therefore, the aim of this dissertation is to improve our understanding and confidence in planktonic foraminiferal proxies as indicators of seawater physical (e.g., sea surface temperature, SST) and chemical (e.g., composition and pH value) properties. Toward this goal, natural laboratory calibration works of foraminiferal shell chemistry have been carried out by using specimens collected from sediment traps and core-top sediments in the South China Sea (SCS). First of all, high-precision and high-accurate measurements on trace element ratios, boron and strontium isotopic compositions in planktonic foraminifera were investigated, and have been successfully developed for carbonate samples (CHAPTER 2). This technique would allow us to obtain more reliable trace elements and isotopic compositions in foraminiferal shell calcites, and provides a powerful tool to study the paleoceanographic reconstructions in the SCS. Applying this analytical technique, in situ Mg/Ca-SST calibration equation for the three abundant planktonic species in the SCS can be described as Mg/Ca = 0.32 exp (0.090*T) using time-series sediment trap, and intense dissolution artifact has also been taken into account for obtaining more accurate SST records (CHAPTER 3). In addition, a dissolution-corrected equation was developed using trap data from different depths. These temperature equations are Mg/Ca= (0.38-0.02* water depth (km)) exp (0.090*T) and Mg/Ca= 0.30 exp (0.090*T) for fall-winter and spring-summer season, respectively. These equations can be applied for accurate reconstruction of mixed layer and thermocline temperatures in sediment cores. Changes in the local SST and freshwater budget over the last 22 kyrs have been reconstructed from the tropical SCS (CHAPTER 4). Through the comparison of the east-west (zonal) SST gradient between western and eastern Pacific, a persistent ... |
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