氧同位素第6期北印度洋的一次重大古海洋学事件

方念乔; 丁旋; 胡超涌; 宋成兵; 张振芳

氧同位素第6期北印度洋的一次重大古海洋学事件

1.
中国地质大学海洋地学研究中心，北京 100083
2.
中国地质调查局发展研究中心，北京 100037

基金项目:

国家重点基础研究发展规划项目 G1998040800

国家自然科学基金自由申请项目 40272074

详细信息

作者简介:
方念乔(1950-)，男，教授，博士生导师，主要从事沉积学、地层学和海洋地质学的研究工作

中图分类号: P736
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出版历程
- 收稿日期: 2003-12-03
- 刊出日期: 2004-03-25

A Significant Paleoceanographic Event Taking Place in Northeastern Indian Ocean during Oxygen Isotope Stage 6

1.
Institute of Marine Geology and Geophysics, China University of Geosciences, Beijing 100083, China
2.
Development and Research Center, China Geological Survey, BeOing 100037, China

摘要

摘要: 北印度洋赤道海岭的远洋沉积记录在氧同位素第6期的早期, 即167~ 160ka期间, 揭示出一次重大的古海洋学事件.在多项代用指标中, 浮游有孔虫组合和通量的变化对该事件的反映最为强烈, 因此将其命名为“第6期海洋生态环境严重恶化事件”.该事件以广适性种Globigerinita glutinata的高度发育、凉水种Neogloboquadrina pachyderma和Globigerina bulloides的异常增多、其他有孔虫常见种的普遍减少及有孔虫总量的大幅度降低为特征.结合其他代用指标和邻区资料, 认为导致事件发生的主控因素在于超强的南亚冬季风及其所引发的表层水温降低和贫瘠的深层水团上涌.一般情况下, 南亚冬季风对研究区环境的影响力远较夏季风弱, 它的阶段性超常强化似乎总与青藏高原的强烈隆升有关.可推测, 发生在第6期的生境恶化事件很可能是最近一次高原大规模构造抬升的产物.
- 氧同位素第6期 /
- 古海洋学事件 /
- 生态环境恶化 /
- 南亚冬季风 /
- 青藏高原隆升
Abstract: The pelagic sedimentary records conserved on the equatorial Ninetyeast Ridge have mirrored a significant event dating from the early oxygen isotope stage 6(167-160 ka). We call it the"great event of worsened ecologic environment" because the strongest indications of the event among all proxies are from an exceptional change of assemblage and flux of planktonic foraminifera. The event is characterized by a high development of the eurytropic species Globigerinita glutinata, an unusual promotion of the cool-water species Neogloboquadrina pachyderma and Globigerina bulloides, an evident reduction of the major common species and a large downfall of the foraminifera sedimentary quantity. Referring to the otherindications and the materials from the neighboring areas, we believe that the essential factor resulting in the eventis "ultraintense" south Asian winter monsoon that leads to the lower temperature of superficialwater and upwelling of infertile deeperwater. In general, the wintermonsoon ismuchweaker than summermonsoon for affecting the environmentof the study area in the system of the south Asian monsoon. Its periodic extraordinary intensification seems to relate constantly with the violent uplift of the Tibetan plateau. We guess thatthe"great event of worsened ecologic environment" revealed in this paperis very probably the resultof the last extensive tectonic elevation of the plateau.
- oxygen isotope stage 6 /
- paleoceanographic event /
- deterioration of ecologic environment /
- south Asian winter monsoon /
- uplift of the Tibetan plateau

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图 1 MD81349取心位置及若干岩心反映的研究区CaCO₃分布

●.MD81349位置; .赤道海岭钻心位置; ○.深海扇活塞岩心位置.括号内的数字表示岩心位置的水深(m) 和末次冰盛期以来沉积物的平均CaCO₃含量(%)

Fig. 1. Situation of core MD81349 and CaCO₃ distribution in study region reflected by some cores

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图 2 MD81349心的δ¹⁸O曲线、光谱反射曲线和氧同位素分期

A.Toba火山灰层; B.玫瑰色抱球虫末现面; 反射光谱λ=450 nm

Fig. 2. δ¹⁸O and color reflectance curves and oxygen isotope stages in core MD81349

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图 3 氧同位素第6期赤道海岭δ¹⁸O曲线的振荡型式与SPECMAP的比较

1.Martinson标准化氧同位素曲线; 2.MD81349氧同位素曲线; 3.ODP758氧同位素曲线

Fig. 3. Comparison of oscillation pattern of δ¹⁸O curves from equatorial ridge with that of SPECMAP (Martinson et al., 1987) in stage 6

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图 4 MD81349心浮游有孔虫组合的变化与事件层(框内的放大部分反映了事件层内的变化细节, 阴影区指示事件发生前的有孔虫特殊发育期)

Fig. 4. Variation of planktonic foraminifera assemblage and event layer in core MD81349 (the details reflecting the event can be seen in the lower part of the figure)

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表 1 氧同位素第6期依据平均速率推知的年代数据与SPECMAP的比较(Martinson et al., 1987)

Table 1. Comparison of ages based on average sedimentation rate in stage 6 with those of SPECMAP ka

表 2 MD81349心暗色钙质沉积物所在位置与CaCO₃含量

Table 2. Levels of dark calcareous sediments and their ranges of CaCO₃ content in core MD81349

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