Sedimentation Rates in the Western Philippine Sea

西菲律賓海之沉積速率

陳榮盛(Ron-Sheng Chen) ； 鍾玉嘉(Yu-Chia Chung)

《Terrestrial, Atmospheric and Oceanic Sciences》 1卷1期 (1990/03) Pp. 111-125

摘要

西菲律賓海之沉積速率由三活塞岩心，以超量釷二三○定年法側定之，在探海盆地區，由兩岩心所得之沉積速率，在過去七萬年問，分別為每千年5.3與6.8毫米。在此之前有一岩心顯示有一擾亂帶與最後一次冰河期之起始時間約略相同。在此擾亂帶之前，依同法所得之沉積速率為每千年17.4毫米，但並非毫無問題。另一解釋則認為更早期亦有類似之擾亂帶，而界於此二擾亂帶間之沉積速率為每千年10.6毫米。
在琉球海溝西南端所得之岩心，其超量钍二三○之活性太低，此法不太適用。就地質環境言，其沉積速率甚為快速，於試用此法時，得每千年13毫米，但其誤差極大。本文所得之沉積速率與前人在菲律賓海所得者大致相符。

並列摘要

Sedimentation rates in the western Philippine Sea have been determined on three piston cores using the excess (superscript 230)Th method. In the deep basin, the sedimentation rates as determined from two cores are 5.3 and 6.8 mm ka^(-1) at least for the past 70,000 years. Immediately before that time, a disturbed zone which is recognized at one station appears to have coincided with the onset of the last glaciation. Dating back further, the data suggest a higher sedimentation rate of 17.4mm ka^(-1). However, the data are by no means unambiguous; another interpretation suggests a slower rate (10.6mm ka(-1)) between yet another disturbed zone at greater depth and the one just mentioned.
In the southwestern end of the Ryukyu Trench, the excess (superscript 230)Th activities are too low to allow a meaningful treatment with this method. The sedimentation rate is expected to be high due to the geologic environment of the trench. A value of about 13mm ka(-1) with a large uncertainty is obtained when the method is attempted. These sedimentation rates are quite consistent with those obtained in the Philippine Sea by earlier workers.