生物壳体Sr/Ca、Mg/Ca、~(87)Sr/~(86)Sr比值在恢复古气候、古环境中的应用——以小渡口剖面为例

生物壳体的Sr/Ca、Mg/Ca比值能反映其沉积水体的Sr/Ca、Mg/Ca比值 ,在一定条件下反映水体的盐度、温度 ,并分别与宿生水体的盐度、温度呈正比关系。生物壳体的87Sr/ 86Sr比值是恢复盆地古水文条件的一种重要手段。本文以著名的泥河湾盆地小渡口剖面的第 2 8层为实例 ,力图通过对有孔虫、介形虫、腹足类生物壳体Sr/Ca、Mg/Ca比值与87Sr/ 86Sr比值的对比研究 ,并结合前人所作的中更新世古地理特征研究 ,来恢复生物壳体沉积时泥河湾古湖水的温度、盐度 ,进而进行古气候、古环境的恢复。研究结果表明 :在 0 .97～ 0 .94Ma间 ,古泥河湾湖为一陆相湖泊 ,湖水的温度、盐度变化趋势相吻合 ,均呈低—高—低的演化特征 ,可能对应着盆地水体的扩展—退缩—扩展变化。其中 ,在 0 .96～ 0 .95Ma间 ,古泥河湾湖具有较高的温度、盐度特征。

THE APPLICATION OF Mg/Ca, Sr/Ca AND 87Sr/86Sr RATIOS OF BIOGENIC SHELLS IN RECONSTRUCTION OF PALAEOCLIMATE AND PALAEOENVIRONMENT AS EXAMPLIFIED BY XIAODUKOU SECTION

The Ma/Ca,Sr/Ca ratios of biogenic shells can indicate the equivalent ratios of their lived water body, and also can mirror the salinity and temperature of their lived water body, depending directly on the salinity and temperature of their lived water body, respectively. The HT10.5,0.25] 87 Sr/ 86 Sr ratio of biogenic shells is an important approach to palaeohydrological reconstruction. As exemplified by the 28th bed of the Xiaodukou section, Nihewan Basin, in combination with the previous study on the character of mid pleepoch, we will reconstruct the palaeotemperature and palaeosalinity of previous Nihewan lake through research and contrast of Ma/Ca, Sr/Ca and HT10.5,0.25] 87 Sr/ 86 Sr ratios of foraminifera, ostracods and gasteropods. The results revealed that within 0.97 0.94 Ma, Nihewan was a continental lake, the variation tendency of temperature and salinity is consistent from low high low. Maybe, they are corresponding to a tendency of expansion retreat expansion of the water body. Therein, within 0.96 0.95 Ma, Nihewan Lake had considerably high temperature and salinity.