恒河深海扇东北区域晚第四纪气候和海平面变化对沉积作用的控制

CLIMATIC AND GLACIO-EUSTATIC CONTROL OVER THE RECENT QUATERNARY SEDIMENTATION IN THE NORTHEAST GANGES DEEP SEA FAN

通过对恒河深海扇沟道间均质细粒沉积物的氧同位素地层划分,本文讨论了晚更新世以来冰川—气候旋回和海平面变化对印度洋北部大陆坡地带各种活跃的沉积因素(陆源和碳酸盐物质的沉积通量、浊流活动的强度和频度、粘土矿物分布、碳酸盐浓度和钙质生物壳的溶解度)的控制作用和因素间的相互关联。

This work is based on a detailed stratigraphic and sedimentologic study of Ganges deep sea fan cores. The main methods used are the mineralogic, calcimetric, granulometric, oxygen isotopic, spectral analysis and also the paleomagnetism data. In our study area, the uniform hemipelagites predominate in the major cores. The record of the oxygen isotopic stratigraphic log can be correlated to that of the world's abyssal plains. According to this result, we set up a detailed chronology of the cored sediments since the Upper Pleistocene. We also could recognize the glacial episodes and calculate the sedimentary flux. After eliminating the partial perturbation of a certain event such as turbidity pulse and bottom current, we find a signifigative normal background fluctuation presented by the studied cores. Though the causes are different, both the terrigenous and carbonate flux variations of the best preserved core(MD 77181) show periodicities which correspond to the earth orbital parameters periodicities (precession, obliquity, eccentricity). These relations support the hypothesis of an astronomie, climatic and glacio-eustatic control in the sedimentary process of the studied area. Moreover, a close and complex relation between the terrigenous input, the clay mineral composition, the CaCO3 concentration, the calcareous shell dissolution and the climatic period alternation has been demonstrated in this paper.