Contour Currents in Deep-Water Records from Bay of Bengal and Its Environmental Implication
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摘要: 实地观测和对沉积记录的研究表明, 孟加拉湾存在强大的等深流活动.通过采自孟加拉深海扇东部和中部的3支活塞岩心的沉积学研究表明, 那些氧化色彩强烈、钙质生物壳体溶蚀严重、不存在粒序层理的粉砂质薄层实际上是等深积作用的产物.源自两极的等深流是全球温盐循环系统的关键组分, 它们在过去15 0ka的历史中曾经多次得到强化, 不仅对研究区的环境变化产生重要影响, 而且可能作为纽带, 加强了低纬地区与极区在气候意义上的遥相关.等深流的强化与冰川旋回之间似乎不存在密切关联, 氧同位素第3, 4, 5期内均可发现明显的强化记录.关于强化的控制机制有待深入探讨.Abstract: The analysis of measured data and sedimentary records shows that strong contour currents-occur in the Bay of Bengal. The sedimentary research into 3 piston cores from the middle and eastern Bengal deep-water fan indicates those thin-bedded muddy silts, with heavy oxidation colors and a few calcareous gravely-corroded shells but free of any graded bedding, are products of deposition of reworked materials by geostrophic bottom currents. The contour currents derived from the Arctic and Antarctic, essential constituents of the global thermohaline circulation, were repeatedly enhanced in the past 150 ka. This intensification of the currents, presenting a great impact on the environment changes in the province under study, may serve as a link to make a climatic enhancement of the tele-connection between the low-latitude and the pole regions. It is very unlikely that there is a close relation between the intensifications of the contour currents and the glacial cycles. The records of intensified contour currents can be observed in oxygen isotope stages 3, 4 and 5. The enhanced controlling mechanism remains to be further investigated.
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图 1 孟加拉深海扇细粒沉积物的粒度分布
a.半远洋沉积物; b.浊积物; c.等深积物; d.等深积物
Fig. 1. Granulometric distribution of fine-grained sediments from the Bengal deep-sea fan
图 2 细粒浊积物和等深积物在研究岩心中的分布
1~7.氧同位素分期
Fig. 2. Distribution of the fine-grained turbidite and contourite in the studied cores
图 3 等深流在孟加拉湾的影响范围
a.当代(据Kolla等[9]资料编绘); b.等深流强化期(据沉积记录推断)
Fig. 3. Area influenced by the contour currents in the Bay of Bengal
图 4 MD81349 (孟加拉扇区) 等深流记录与东经90°海岭记录的对比
Fig. 4. Correlation of the contour current records of MD81349 from the Bengal fan to ones of the Ninety east Ridge
表 1 研究岩心的位置和长度
Table 1. Location and length of the studied piston cores
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