深海碳酸盐岩心天然热释光变化特征

东北印度洋赤道90°E海岭和孟加拉扇MD81349,MD77181岩心记录了30万a来气候变化的历史.分析发现浮游有孔虫壳体(方解石晶体)的天然热释光变化与δ18O反映的冰川旋回存在着良好的一致性:天然热释光强度的增大与间冰期对应,降低与冰期对应.对MD81349岩心天然热释光时间序列的频谱分析结果显示热释光的显著周期为99,46,23,20和11ka,其中99,46,23,20ka分别与天文学周期中的地球轨道偏心率周期100ka,地轴倾斜度(黄赤交角)周期54,41ka,太阳辐射年度差异的岁差周期23,19ka接近,这表明地球冷暖交替与太阳辐射强度周期性变化密切相关,在不同海水温度条件下结晶形成的方解石晶体的热释光强度差异显著,因而有孔虫壳体积存的热释光能够反映地球气候的变化.

Natural thermoluminescence characteristics of carbonate in deep sea cores

The natural thermoluminescence (NTL) of foraminiferal shells from piston cores MD81349 and MD77181 from the Ninetyeast Ridge and the Bengal Fan of the Indian Ocean were studied for the climate changes during the past 300 ka. It has been found that the TL fluctuations are closely correlated to the oxygen isotope curves. The high and low TL intensities correspond to the interglacial and glacial stages respectively. The spectrum analysis of TL profile reveals several significant periodicities at 99, 46, 23, 20 and 11 ka. Apparently, the periodicities of 99, 46, 23 and 20 ka coincide with the orbital eccentricity, obliquity and processional cycles respectively. The results of spectrum analysis and TL fluctuations indicate that glacial-interglacial climatic cycles are controlled by the change in the solar insolation. The TL intensities of planktonic foraminiferal shells can be used to indicate the paleoclimate changes and the solar insolation.