孟加拉湾晚第四纪浮游有孔虫及其古海洋学意义

对北印度洋孟加拉深海扇远源区水深约３８００ｍ的ＭＤ７７１９０岩心进行了有孔虫定量统计，ＣａＣＯ３质量分数分析和敏纳圆幅虫壳体氧、碳同位素分析，结果表明，该区近１３０ｋａ来的浮游有孔虫组合面貌、表层海水古温度、ＣａＣＯ３质量分数变化的总体趋势与各大洋资料可以对比。ＣａＣＯ３质量分数曲线表现为间冰期升高而冰期降低，反映了研究区陆源碎屑物质对ＣａＣＯ３浓度具有明显的稀释效应。溶解度曲线也表现出相同的变化趋势，同样与陆源物质输入量的变化有关。研究区氧同位素３期各种沉积特征与北印度洋区的季风活动有关，表现出明显的高频气候旋回变化特点。

PLANKTONIC FORAMINIFERA DURING LATE QUATERNARY IN THE BENGAL BAY AND THEIR PALEOCEANOGRAPHIC IMPLICATIONS

Core MD77190(87°49′06″E,07°41′00″N,water depth 3 800 m, core length 8m)is from the lower Bangal deep sea fan. Analyses of foraminifera, CaCO 3 content and oxygen isotope values from tests of Globorotalia menardii show that the changes of the planktonic foraminifera abundance, sea surface temperature, CaCO 3 content in this site over the last 130 ka are consistent with the climatic cycles during that time. The calcium carbonates content was high during the interglacital age but low during the glacial age. The reason of it is that large quantity of terrigenous detrital materals were brought into the abyssal and bethal zones, thus diluting the calcium carbonate deposits. The dissolution was slightly higher during the interglacial age than that during the glacial age. The reason of it is that in the glacial age high productivity increased the CaCO 3 sedimentary flux and large quantity importation of terrigenous detrital materials buried calcium test rapidly, this decreased chemical erosion.