摘要
主要介绍了氧同位素的地球化学特征 ,并利用这些特征在沉积环境方面的指示意义 ,分析了东濮凹陷下第三系盐湖沉积的氧同位素。分析结果表明 :尽管保存在碳酸盐中的氧同位素的值不能定量地反映原始氧同位素的值 ,不能够作为区分海陆相的标志 ,但它可以定性地探讨碳酸盐沉积时的沉积环境。通过对东濮凹陷下第三系盐湖沉积的氧同位素分析发现 ,从沙四上到沙一时期 ,除了沙三上的δ1 8O有些突变外 ,基本上呈递增趋势。这反映出 ,从沙四上到沙一时期该区的气候逐渐向干旱过渡 ;沙四上到沙三上一段δ1 8O明显比沙一和沙二上偏低 ,说明在沙四上到沙三上时期 ,该沉积区的蒸发作用还不是很显著 ,而另一方面也说明在由沙三上向沙二上过渡时 ,该区可能存在一次气候突变 ,使得沙二上和沙一时期的蒸发量远大于降雨量 ,δ1 8O的值也因此迅速增大。同时 ,也做了碳酸盐同位素系数Z值的研究 。
Geochemistry of oxygen isotope is introduced in the paper, and also oxygen isotope of the lower Tertiary saline lake sediments in the Dongpu depression is analyzed by making use of the environmental significance of the geochemical characters. The analysis indicates that though the oxygen isotope values in the carbonate are not equal to the original ones and thus cannot be used to distinguish from marine and continental carbonate, it can be used to quantitatively analyze the sedimentary environment when the carbonate was deposited. The oxygen isotope analysis indicated that the δ 18 O values gradually increased from the upper Es4 to Es1 except the break at the upper Es3, which shows that the climate got drier and drier. And the δ 18 O values were smaller from the upper Es4 to the upper Es3 than the ones from the upper Es2 to Es1, indicating the evaporation was not strong from the upper Es4 to the upper Es3, and there may have been a break of such climate from the upper Es3 to the upper Es2, which made the evaporation stronger than rainfall and thus the δ 18O values also increased rapidly. At the same time, Z values are studied, and the sedimentary environment revealed by the Z values are mostly the same as revealed by the oxygen isotope.
出处
《海洋地质动态》
2003年第5期29-33,共5页
Marine Geology Letters
