摘要
This paper reports our primary effort in the quantitative reconstruction ofpaleoclimate based on the thrine in phytoecology of the affinity parent plants in the stratigraphicpollen records. The Eocene pollen data come from our former study on the Mingjia borehole 1 in theJianghan basin. The fluctuating trend in the parameter curve of climate shows that the climate inthe Middle Eocene in the Jianghan basin was more or less comparable with that of the present22°―26°N, characteristic of a humid, semi-humid central-southern subtropical climate. The annualtemperature at that time dropped by 1 ℃― 4 ℃ in the Late Eocene, approximately equal to that ofthe present 23°―28°N of northern-central subtropical climate. However, the climate composite atthat time, characterized by higher temperature, small annual range and big fluctuation inprecipitation, was quite different from the present one. The average temperature in January in theMiddle Eocene, higher than that of today, ranged between 5 ℃ and 9 ℃, indicating that no effect ofwinter monsoon occurred in the Middle Eocene, though such an effect may have occurred occasionallyin 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, andthe increase in the deciduous broad-leaved types of trees in the spore-pollen assemblage. The sharpfluctuation in the annual precipitation, usually raging from 300 to 1 700 mm, was favorable for themigration 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, deducedthat the formation of the salty deposit was attributed mainly to the dry and hot environment in thehigh mountains and deep basins. The small annual precipitation and the intense fluctuation arefavorable for the sustainable accumulation of the salts, which is different from the present saltyaccumulation in the Northwest China.
This paper reports our primary effort in the quantitative reconstruction ofpaleoclimate based on the thrine in phytoecology of the affinity parent plants in the stratigraphicpollen records. The Eocene pollen data come from our former study on the Mingjia borehole 1 in theJianghan basin. The fluctuating trend in the parameter curve of climate shows that the climate inthe Middle Eocene in the Jianghan basin was more or less comparable with that of the present22°―26°N, characteristic of a humid, semi-humid central-southern subtropical climate. The annualtemperature at that time dropped by 1 ℃― 4 ℃ in the Late Eocene, approximately equal to that ofthe present 23°―28°N of northern-central subtropical climate. However, the climate composite atthat time, characterized by higher temperature, small annual range and big fluctuation inprecipitation, was quite different from the present one. The average temperature in January in theMiddle Eocene, higher than that of today, ranged between 5 ℃ and 9 ℃, indicating that no effect ofwinter monsoon occurred in the Middle Eocene, though such an effect may have occurred occasionallyin 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, andthe increase in the deciduous broad-leaved types of trees in the spore-pollen assemblage. The sharpfluctuation in the annual precipitation, usually raging from 300 to 1 700 mm, was favorable for themigration 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, deducedthat the formation of the salty deposit was attributed mainly to the dry and hot environment in thehigh mountains and deep basins. The small annual precipitation and the intense fluctuation arefavorable for the sustainable accumulation of the salts, which is different from the present saltyaccumulation in the Northwest China.
作者
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
基金
ThepaperissupportedbytheNationalNaturalScienceFoundationofChina(No .498330 1 0 )
