上次間冰期以來南中國海北部沉積物之古環境紀錄

Paleoenvironmental Records on Northern Slope in the South China Sea Since Last Interglacial

謝英宗(Ying-Tzung Shieh) ； 陳思宏(Szu-Hung Chen) ； 陳民本(Min-Pen Chen)

《國立臺灣博物館學刊》 61卷2期 (2008/06) Pp. 13-39

摘要

南中國海位於太平洋、印度洋以及亞洲大陸之間，因邊緣海的特性使全球古氣候紀錄在此出現放大的效應，成為研究古環境變遷極佳的區域。由於南海北坡快速的堆積速率可提供高分辨率的沉積物紀錄，因此本研究挑取位在南海北坡。ODP 1144 站位(20°03.18'N，117°25.14'E；水深2047 公尺) 岩芯中的浮游性有孔蟲Globigerinoides sacculifer 進行碳氧同位素分析，配合浮游性有孔蟲族群豐度及碳十四定年，進行高解析度古環境變遷的研究。結果顯示南海的氣候變遷主要是受到全球冰川體積消長的控制，在氧同位素地層第3階時可能受到夏季季風增強的影響，造成南海表層水的溫度比臨近的太平洋高，但鹽度則較低。本研究結果亦顯示，新仙女木事件期間南海北坡冬季季風較強。南海的季風系統在冰期時，可能因日照與降雨減少，陸地氣候乾冷，使冬季季風強度增強；相對的，在全新世與間冰期，南海的氣候型態則受夏季季風系統影響較大。

關鍵字

古海洋 ； 有孔蟲 ； 氧同位素 ； 南中國海

並列摘要

The South China Sea (SCS) is surrounded by the Pacific Ocean, the Indian Ocean, and the Asian continent in southern Asia. The climatic records are strongly magnified in the SCS because of its distinctive marginal sea feature. This unique geographic setting makes the SCS an excellent area for examining environmental changes in the past, especially the history of the East Asian monsoon. An extremely high sedimentation rate environment in the northern slope of the SCS offers a good opportunity for reconstructing high-resolution paleoclimatic records. ODP Site 1144 (20°03.18'N, 117°25.14'E, water depth 2047m) is selected for establishing paleoclimatic records since last interglacial using oxygen and carbon stable isotope compositions in combining with Cl4 dates and planktonic foraminifera assemblages. These results indicate that the paleoclimate pattern at the northern SCS was mainly affected by the changes of global icc volume. During the stable isotope oxygen stage 3, stronger summer monsoon caused in an increase in sea surface temperature and a decrease in salinity. The winter monsoon was stronger in northern SCS during the Younger Dryas Event. The study results also indicate that the Asian monsoon system ...hews a different pattern during the glacial-interglacial periods. During the glacial period, the winter monsoon system was stronger due to decrease in solar insulation and precipitation, and a cold and dry Asian continent. As a consequence, the land-sea atmospheric pressure gradient was increased and caused the northeast monsoon became stronger. In the interglacial period such as the Holocene and last interglacial, the climate condition was in reverse, and the East Asian monsoon was dominated by the southwest wind.

並列關鍵字

paleoceanography ； foraminifera ； oxygen isotope ； South China Sea