西菲律宾海15万年以来的浊流沉积及其成因

TURBIDITE DEPOSITION RECORD AND ITS MECHANISM SINCE 150 KABP IN WESTERN PHILIPPINE SEA

MD06-3052孔取自西菲律宾海吕宋岛岸外上陆坡,通过AMS14 C测年、沉积物粒度和浮游有孔虫氧同位素记录,揭示了15万年以来5个浊流沉积层的特征和浊积事件的发生时间。浊流沉积物粒度明显较上下层的粗,主要组分为砂质和粉砂质沉积。通过AMS14 C测年和氧同位素年代标尺,计算了5个浊流沉积层发生的时间分别为13.3、20.4、34.3、41.7和121.8kaBP,其中上部4次浊积事件发生于末次冰期,特别是MIS 3晚期和MIS 2期的低海平面时期,仅底部一次出现于末次间冰期MIS 5e中期相对低海平面时期,因而推测研究区浊流沉积事件的主要诱因是低海平面时期的海平面波动造成临近陆架上的沉积物不稳定,同时较陡的陆坡为浊流沉积提供了有利地形,因而造成了向陆坡方向的浊流搬运。

Core MD06-3052 was taken from the continental slope off the Luzon Island in the western Philip- pine Sea. Multiple proxies such as AMS14C dating, sediment grain size and foraminiferal oxygen isotope were used to reveal the 5 turbidite events since 150 kaBP. The turbidites have coarser grain size than the normal layers, mostly composing of sand and silt. The occurrence time of the 5 turbidite events was calcu- lated by AMS14C dating and oxygen isotope as 13.3, 20.4, 34. 3, 41.7 and 121.8 kaBP, separately, of which the latter 4 ones occurred in the low sealevel stages of the last glacial, especially in MIS 2-3, and the earliest one at the relatively low sealevel stage in MIS 5e, indicating that rapid sealevel oscillation during low sealevel stages was probably the main cause of the turbidite events. However, the steep slope may be a favorable topography for the sediment instabilities in Core MD06-3052.