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Diatom Flora Assemblage Study of Deep Sea Core from South China Sea (II)
Past global changes (PAGES);Deep sea core;South China Sea;Diatom;Fossil assemblage
|Issue Date: ||2013-03-12T01:50:02Z
|Abstract: ||本研究分析南海岩心MD972144，結果顯示矽藻化石群共計66 屬245 種，其保存度良好，較常見的種類有Chaetoceros spp. 、Thalassionema nitzschioides 和Thalassiothrix longissima，前者相對豐度在5－30％間變化，後兩者相對豐度在5－70％間變化，並相互交替消長成為優勢種。群集的組成以熱帶、亞熱帶大洋浮游種類為主，仍有一定比例的淺海種和淡水種。豐度受到陸源物質的稀釋無法反應出生產力的變化，但其高值仍可指示湧升流的存在。黑潮特徵種和湧升流指標種的相對豐度變化，呈現冰期低、間冰期高的現象。顯示本區湧升流的強度在冰期因黑潮的影響變小而減弱，反應出低生產力的海洋環境；在間冰期則是呈現增加的趨勢，反應出高生產力的海洋環境。矽藻化石群的豐度、種數、多樣性指數和種類組成等在氧同位素第6 階進入第5 階的區段皆有劇烈的變化。暖水指標的趨勢和氧同位素曲線大致相符，呈現冰期低、間冰期高的變化，即冰期時海水表面溫度較低、間冰期時較高，可視為東北季風的指標。Q 型因子分析結果顯示，第一因子可解釋88.5%的變方，主要反應暖水團的訊息，並呈現冰期低、間冰期高的趨勢和暖水指標的變化一致。|
A total of 245 diatom taxa were identified throughout the Core MD972144. 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 varie+G4ty 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.
|Relation: ||國科會計畫, 計畫編號: NSC90-2611-M018-001-IM; 研究期間: 9008-9107|
|Appears in Collections:||[生物學系] 國科會計畫|
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