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| 本文报道了笔者对四十六枚现生和化石四组介形类标本(现生海 洋、现生淡水湖泊、化石海相、化石陆相介形类)壳体的内表皮层(即钙质层)进行能谱无机成份定量分析的结果。初步研究表明:介形类钙质壳体中各微量元素的出现频度、平均含量、钙镁比值等有关指数与它们的生活环境有密切关系。 |
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| ANALYTICAL RESULT OF TRACE ELEMENTS IN OSTRACOD SHELLAS INDICATORTO RECONSTRUCT PALAEOENVIRONMENT |
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| Abstract: |
| Trace chemical elements of forty-six ostracod shells have been accurately measured by using SEM with electron probe. According to their living environments and geological age, the specimens Leguminocythereis sp., Neomonoceratina sp., Abrotocythere quadricornis, A. ovata, A. plegadis, Cyprinotus sp., Jlyocypris sp., I. caohaiensis, I, weiningensis, I. bradyi, I. subbiplicata, Leucocythere plena, Limnocythere (Xinanolimnocythere)tribulosa, Hungarocypris sp., and Notodromas sp., can be divided into four groups: living marine ostracod group, living nonmarine ostracod group, fossil marine ostracod group and fossil nonmarine ostracod group. The living ostracods were collected from the South China Sea, Bohai Sea, East Lake in Wuhan Cith, Caohai Lake in Guizhou Province and a pool near the Daqing City, Heilongjiang Province, while the fossil ostracods were from the Tertiary and Quaternary strata in Jiangsu and Guizhou Provinces. The result reveals that the ostracod shells contain 9 kinds of chemical elements, calcium(Ca), aluminium (Al), iron (Fe), magnesium (Mg), potassium (K), chlorine (Cl), sulpher (S), sodium (Nay and barium (Ba) in the order of their value of content from high to low, in which the calcium is the most abundant (32-34%) and the total amount of all other trace elements is less than 10%. It is found that there is an obvious difference between the ostracods living in the sea and those in the fresh-water in their chemical content of shells. This paper deals with the difference to deduce the palaeoenvironment of fossil ostracods where they once lived in. Based on the available data, it is considered that the value of Ca/Mg, the frequency and average value of trace elements in ostracod shells are very significant in the recons-tructionof palaeoenvironment. In general, Ca/Mg of the marine ostracod shells is below 60, while that of nonmarine ones is above 80. The value of Ca/Mg between 50-90 indicates that the ostracods probably lived in the oligohaline environment. Ca, Mg, Si and Al of the marine ostracod shells occurred in the frequency of 100%. On the contrary, all element of nonmarine ones but Ca occurred less than 50%. In addition, the average value of magnesium and potassium in marine ostracod shells is six or seven times higher than that in nonmarine ones, while the average value of calcium and chlorine is rather different, the former being much lower than the latter. The analytical result of chemical content of ostracod shells helps throw light on the cause of different colors on ostracod shells and the process of their formation. Therefore, as indicator, the analysis of chemical elements on ostracod shells is very important not only for palaeontologists but also for sedimentologists to reconstruct palaeoenvironment. |
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