| 淡水软体动物壳化石碳氧同位素组成及其在恢复古气候环境中的应用 |
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| 引用本文： | 李玉成,徐永昌.淡水软体动物壳化石碳氧同位素组成及其在恢复古气候环境中的应用[J].沉积学报,1990,8(2):105-112. |
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| 作者姓名： | 李玉成 徐永昌 |
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| 作者单位： | 中国科学院兰州地质研究所生物、气体地球化学开放实验室 |
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| 摘 要： | 本文研究了昆明滇池和太湖无锡湾软体动物壳化石的碳氧同位素组成,利用化石同位素组成,恢复了昆明盆地百万年以来和太湖无锡湾近四万年以来的古气候环境。研究表明:淡水软体动物壳化石氧同位素组成,在不同的环境条件下,最大差值可达7‰;钻孔中的不同层位的贝壳化石碳氧同位素组成与现代贝壳同位素相比,既有富集重碳氧同位素的层段,也有富集轻碳氧同位素组成的层段,氧同位素变化周期为十万年;富集轻碳氧同位素组成层段与湿润期对应,而富集重碳氧同位素组成层段与干燥期对应。化石氧同位素记录了昆明盆地古气候干湿变化有十万年的周期,随时代变新,气候逐渐干燥;以化石碳氧同位素为主,综合沉积物特征,推断太湖无锡湾近20m地层形成于近四万分年至今,气候温和潮湿,环境可能为河口相。
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| 关 键 词： | 淡水软体动物壳化石 氧碳同位素组成 古气候环境变迁 昆明盆地 太湖无锡湾地区 |
| 收稿时间： | 1989-09-01 |
LACUSTRINE ENVIRONMENTAL AND CLIMATIC EVOLUTION RECORDED BY ISOTOPE OF INORCANIC CARBON AND OXYGEN |
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| Institution: | Lanzhou Institute of Geology, Academia Sinica |
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| Abstract: | Based on the analogical method on studying Paleotemperature and Palecoclimate with foraminiferal isotope in marine sediments, the features of carbon and oxygen isotopic compositon in lacustrine shell fossils from (he wells of Kunming Basin, Taihu lake and Chaidamu Basin with their climatic and enrironmental signiticance have been reported for the first time in this paper.By arialysising isotopic compositions of about one hundred shell fossils in different terrestrial environments, some regularities are found by comparing them with as follows:(1) Change of oxygen isotopic light and heavy composition in marine and terrestrial shell fossils is similar and show a period over 100, 000years.This that global climatic change is synchronows.(2) Change of oxygen isotopic composition of marine shell, utmost of which is 3‰ , if not considering evolution of sea water and seasonal temperature change, is cheifly controlled by annually average temperature. As temperature has a change of 4.2℃ , isotope has a change of 1‰, However oxygen isotopic composition of terrestrial shell, is not only influenced by temperature, but mainly by oxygen isotopic composition of pricipitation and evaportion. That is, temperature, change of 1℃ causes isotopic change of 1‰.(3) In the same section, isotopic compositions of terrestral shells with different age change quite. δ18O difference of total shell is more than 7‰, and δ13C is about 5‰.For Kunming Basin, authors set up a climatic curve of oxygen isotope, chiefly based on data of this experiment and referencing paleomagntic dating, uranrum dating and ，14C dating measuredl by others. This curve coincides with oxygen isotopic curve of deep sea foraminifera and paleoclimatic curve of loess paleosoil sesimentary system. Late Wurm glacial epoch (200, 000-100, 000 YBP) is period to accumulate most violently heavy isotopic composition (δ18O = -3.5‰-7.5‰, δ13C = -3.5‰) which implies that this period was the coldest and driest in Kunming basin. This result has been suppoted by data of sedimentary rock and palaeontology. The Period of the most violent accumulation of light isotopic composition was 500, 000- 600, 000 YBP (δ18O=-14.6‰, δ13C=-8.3‰) and it is deduced that preicipiation of this period was 150mm-200mm / Y more than that of moder time. Isotope of shell fossils distributed in 10 meters thickness of lacustrine silt clay under the base of Taihu lake is abundant with lighter compositim (δ18O = 7. 1‰-8.4‰) .and it is suggested that sediment was deposited during Wurm subinterglacial epoch (400, 000-200, 000 YBP) and was in estuary environment of restricted marine.Isotopic composition of Holcence shell show that the transgression did not reach Taihu lake. |
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