| Primary Study on Quantitative Reconstruction of Middle-Late Eocene Climate in Jianghan Basin |
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| 作者单位： | Tong Guobang,Liu Zhiming(Institute of Hydrogeology and Environmental Geology, Chinese Academy of Geological Sciences, Zhengding 050803; Open Laboratory of Saline Lake Resources and Environment, Chinese Academy of Geological Sciences, Beijing 100037);Zheng Mianping(Institute of Mineral Resources, Chinese Academy of Geological Sciences, Beijing 100037; Research & Development Center of Saline Lake and Epithermal Deposit, Chinese Academy of Geological Sciences, Beijing 100037);Wang Weiming(Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, Nanjing 210008)
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| 基金项目： | ThepaperissupportedbytheNationalNaturalScienceFoundationofChina
(No .498330 1 0 ) |
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| 摘 要： | ＩＮＴＲＯＤＵＣＴＩＯＮＴｈｅｑｕａｎｔｉｔａｔｉｖｅｒｅｃｏｎｓｔｒｕｃｔｉｏｎｏｆｐａｌｅｏｃｌｉｍａｔｅｆａｃｔｏｒｓｉｓｔｈｅｆｏｃｕｓｏｆｓｔｕｄｙｏｎｅｎｖｉｒｏｎｍｅｎｔｉｎｔｈｅｐａｓｔ ,ａｎｄａｎｅｆ ｆｅｃｔｉｖｅｔｏｏｌｆｏｒｔｈｅｑｕａｎｔｉｔａｔｉｖｅｒｅｓｅａｒｃｈｉｎｔｏｔｈｅｐａｌｅｏｃｌｉ ｍａｔｅｉｓｔｈｅｔｒａｎｓｆｏｒｍａｔｉｏｎｏｆｓｐｏｒｅ ｐｏｌｌｅｎｄａｔａ .ＴｈｅｍａｉｎｐｅｒｉｏｄｔｈｕｓｉｎｖｏｌｖｅｄｗａｓｔｈｅＱｕａｔｅｒｎａｒｙｉｎｓｔｅ…
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Primary Study on Quantitative Reconstruction of Middle-Late Eocene Climate in Jianghan Basin |
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| Authors: | Tong Guobang Liu Zhiming Zheng Mianping Wang Weiming |
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| Abstract: | This paper reports our primary effort in the quantitative reconstruction of paleoclimate based on the thrine in phytoecology of the affinity parent plants in the stratigraphic pollen records. The Eocene pollen data come from our former study on the Mingjia borehole 1 in the Jianghan basin. The fluctuating trend in the parameter curve of climate shows that the climate in the Middle Eocene in the Jianghan basin was more or less comparable with that of the present 22°-26°N, characteristic of a humid, semi-humid central-southern subtropical climate. The annual temperature at that time dropped by 1 ℃-4 ℃ in the Late Eocene, approximately equal to that of the present 23°-28°N of northern-central subtropical climate. However, the climate composite at that time, characterized by higher temperature, small annual range and big fluctuation in precipitation, was quite different from the present one. The average temperature in January in the Middle Eocene, higher than that of today, ranged between 5 ℃ and 9 ℃, indicating that no effect of winter monsoon occurred in the Middle Eocene, though such an effect may have occurred occasionally in the Late Eocene. Major temperature decline is recognized at the depth of 2 100 m in the borehole, as was indicated by the decline in average January temperature, the increase in annual range, and the increase in the deciduous broad-leaved types of trees in the spore-pollen assemblage. The sharp fluctuation in the annual precipitation, usually raging from 300 to 1 700 mm, was favorable for the migration and accumulation of salty deposit. When the precipitation was lower than 1 000 mm, ephemera shrub increased at the same depth as that of the salty deposit. It is, therefore, deduced that the formation of the salty deposit was attributed mainly to the dry and hot environment in the high mountains and deep basins. The small annual precipitation and the intense fluctuation are favorable for the sustainable accumulation of the salts, which is different from the present salty accumulation in the Northwest China. |
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| Keywords: | quantitative reconstruction of paleoclimate annual range function of thrine in phytoecology fuzzy mathematics Eocene Jianghan basin |
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