碩士 / 國立彰化師範大學 / 生物學系 / 90 / Abstract
Fossil diatoms can be excellent indicators of the marine paleoenvironments. They have great potential for studies of marine plaeoceanography and provide insight into a variety of environmental conditions. The Core MD972144（19°36’N, 120°53’E） recovered from the South China Sea was examined for the changes in diatom abundance and assemblage composition based on taxonomy and morphology. A total of 245 diatom taxa were identified throughout the core. Among them, Chaetoceros spp., Thalassionema nitzschioides and Thalassiothrix longissima were the common taxa and their relative abundance ranged from 5% to 70%. The diatom assemblage in this core was mainly composed of tropical-subtropocal planktonic species, but it also contained a certain number of neritic and freshwater diatoms, 6-33% and 0-6%, respectively. The abundance failed to explain the variety of productivity due to the dilution of terrigenous materials. But its high value still implied the upwelling occurrence. The variations of relative abundance in the characteristic species of Kuroshio and upwelling indicators showed that productivity was lower during glacial periods, but higher during interglacial periods. There were strong varieties in abundance, species number, diversity index and species composition from stage 6 to stage 5. The trend of the diatom temperature index (Tw) corresponded with the oxygen isotope curves and its values were lower in glacial times, but higher in interglacial times. It meant that the sea surface temperature was lower in glacial times, but higher in interglacial times. Q-mode factor analysis was carried out to analyze the variations of diatom assemblage. It showed that Factor 1, representative of warm-water masses, accounted for 88.5% of the variance. Its loadings dominated over the interglacial periods and were synchronous with the curve of the diatom temperature index. The diatom assemblage of the Core MD972144 during the glacial periods was characterized by lower in the diatom temperature index and the relative abundance of the characteristic species of Kuroshio and upwelling indicators. It corresponded with the marine environments of reducing in the sea surface temperature and high productivity. On the contrary, during the interglacial periods it was characterized by higher in the diatom temperature index and the relative abundance of the characteristic species of Kuroshio and upwelling indicators. It also corresponded with the marine environments of raising in the sea surface temperature and high productivity.
| Identifer | oai:union.ndltd.org:TW/090NCUE0112007 |
| Date | January 2002 |
| Creators | 林靖敏 |
| Contributors | 王瑋龍 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 66 |
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