摘要:
研究现代及第四纪淡水软体动物一些属种的氧同位素组成,显示如下规律:与海相软体动物相比,淡水软体动物富集轻氧同位素组成,δ16<-5‰;相同水域生活的不同属种的氧同位素组成相差较小（萝卜螺等例外）,不同水域生活的软体动物壳质氧同位素相差较大;全贝壳氧同位素主要继承生活时的水体的氧同位素组成,受气候干湿程度影响;第四纪化石也富集轻氧同位素组成,δ16O分布范围较宽;湿润期,化石富集16O,凉干期,化石富集16O。
Abstract:
Some freshwater Molluscs shells are collected from modern freshwater lake and Quternary stratum in China,in which climate and environment have been known in detail. The oxygen istopic composition of freshwater Molluscs shells are analysed for discussing relationship between the oxygen isotopic composition of shell and terrestrial climate and enviroment,and it used to reconstruct the past climatic chang. In this paper, the whole shell sample are analysed for discussing relationship between shell δ18OPDB and annual mean temperature and δ18OSMOW of lake water. The results show that: Molluscs shell in freshwater Lake are rich in O.δ18 OPDB5‰, in comparision with marine Molluscs. The δ18OPDB value of Molluscs shells which lived in same area are similar; but that which lived in different area are different. During moisture climate, δ18OPDB value of shells range from -5. 1～-10. 2‰. The shell is richer in O, with of gtadually increasing. δ18OPDB of shell is related to δ18OP(SMOW) of annual mean precipitation. The linear equation is δ18Op(SMOW) = 1. 07δ18OS -0. 58. During dry climate. the oxygen isotopic composition of shell is rich in O. All these indicate that the oxygen isotopic composition of whole shell is inherited from that of Lake water. The freshwater Molluscs shell fossils from Quternary stratum is also rich in δ18O, is similar ro modern Molluscs shell, The δ18OPDB of shell range from - 6. 2- 14. 6‰. For example, in Kunming area.the δ18OPDB value of shell fossil from different age is different. The δ18O offset value is up to 7‰. During moisture and warm climate, the Molluses shell fossils is rich in O. in comparision with modern shell in some area. Showing that the global temperature is high,and the precipitation and melt of the snow is on the increase, this water is rich in O6 and flowed to Lake, where the Molluscs Lived in, thus the molluscs is also rich in O1 During dry and cool climate, the Molluscs shell fossils is show that, the global temperature is low, ind the pricipita-tion is decrease, but the evaporation is strong, so that the light isotopic composition are esccped thus, water body is rich in O, and concentrated in lake, where the Molluscs lived in, thus the Molluscs is also rich in O. In all above,the δ18O of fossil shell from lake. Sensetively recorded past wet and terrestrial climate chang.
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