【作者】 孙海龙；

【导师】 刘再华；

【作者基本信息】 中国地质科学院 ， 地质工程， 2008， 博士

【摘要】 近2000年气候与环境变化研究在全球变化研究中具有特殊的重要性。过去2000年的气候和环境变化研究,要求尽可能高的时间分辨率,在此基础上取得的气候指标统计基础,才有可能在其中寻找气候和环境变化的信息,以寻求气候演变的规律,预测未来发展趋势。分布于地表的钙华沉积物,以其具有的比石笋气候记录更高的分辨率和灵敏度的气候记录,成为近年来古气候研究的重要载体。然而,要想利用钙华进行高分辨率的古气候重建工作,必须从地球系统科学思想出发,全面了解钙华沉积过程中地球化学指标的变化及其控制机理。只有如此,才能更好地建立钙华沉积物环境替代指标与气候因子之间的定性和定量关系,才能为利用钙华记录重建古气候环境奠定坚实可靠的基础。由于气候环境因子对钙华环境替代指标的控制机理非常复杂,地域性很强,这也使得国外已有研究成果的适用范围有限,并不一定适合中国的情况,而且很多研究主要是针对大气成因类钙华的,而对于如本文要研究的深部岩溶动力系统中形成的钙华,即所谓的地热成因类钙华的环境替代指标与气候因子之间的关系则缺乏研究。本文采用水化学仪器自动记录、现场测定、取样进行实验室测试相结合的方法,通过水化学和碳氧稳定同位素组成时空动态的综合分析,对云南白水台地区现代钙华沉积的环境替代指标与气候因子关系进行了全面系统的研究,得出以下主要结论:（1）白水台地区冬、夏季风期间降雨云团可能存在不同的源区,即,夏季降水的源区主要是印度洋和孟加拉湾,而冬季降水的气团则主要受大陆内部气团影响。雨水氧同位素与降雨量有很好的线性负相关关系,反映了大气降水的降水量效应。（2）通过对白水台引水渠道及钙华池内钙华氧同位值(δ¹⁸O)季节变化的分析发现,大气降水的降水量效应（P）以及降水云团不同源区的转换,是控制白水台热成因类钙华中δ¹⁸O季节变化的原因。白水台地区的钙华δ¹⁸O的季节变化是春夏季（雨季）偏负,而秋冬季（早季）偏止。δ¹⁸O与P的定量关系是P每增加100mm,钙华δ¹⁸O偏负0.70‰;温度（T）对白水台钙华δ¹⁸O的影响系数较O’neil方程小1倍左右,即T每增加1℃,钙华δ¹⁸O偏负0.1‰。（3）通过对白水台引水渠道和钙华池中钙华δ¹³C值的季节变化分析发现,雨水及雨后形成的坡面流是控制白水台地区钙华δ¹³C值季节变化的主要原因。在雨季雨后形成的坡面流(δ¹³C受土壤CO₂的影响,因而偏低)进入引水渠道,对引水渠道水进行了稀释,因而造成雨季形成的钙华δ¹³C值偏负。从而使钙华δ¹³C值呈现出春夏季（雨季）偏负,而秋冬（旱季）偏正的季节变化。（4）通过对白水台引水渠道和钙华池内钙华沉积速率的季节变化研究发现,降雨量是控制白水台地区钙华沉积速率快慢的主要因素。在雨季,稀释效应造成的钙华沉积速率的降低超过了温度升高导致的钙华沉积速率的增加,从而使白水台地区钙华沉积速率呈现出在雨季（春夏季）降低、秋冬季（旱季）升高的反常现象,这与在日本大气成因类钙华中发现的规律正好相反。（5）建立了白水台钙华年层的肉眼识别标准,即白水台地区一个钙华年层包括薄的疏松褐色层和厚的致密浅色层。（6）钙华池内水生植物在春夏季（雨季）较强的光合作用使钙华δ¹³C值偏正的影响小于雨季雨后形成的坡面流进入钙华池对池水的稀释使钙华δ¹³C值偏负的影响,因此受水生植物影响的钙华池内的钙华δ¹³C值的季节变化也主要是受降雨量控制,从而呈现出春夏季（雨季）偏负,而秋冬（旱季）偏正的季节变化。夏季较强的光合作用虽然能够加快钙华的沉积速率,但是由于雨季时雨水及坡面流对池水更强的稀释作用,使得受水生生物影响的各钙华池内的钙华沉积速率的季节变化同不受水生生物影响的钙华池内的钙华沉积速率的季节变化类似,反映的都主要是降雨量对钙华沉积速率的控制,均表现为春夏季（雨季）沉积速率低于秋冬季（旱季）。更多还原

【Abstract】 The information on climatic and environmental change in the past 2000a is very important to the investigation of the global change.The latter program requires information with higher time resolution so as to find out how climate and environment change,to reveal the regulation of the climate evolution,and to forecast the future climate change.Travertine and tufa in karst areas are one of the most important geological archives for the study of past climate changes because of their high resolution and sensitive record of climate and environment.However,before one uses the travertine or tufa to reconstruct the paleo-climate changes,one must understand the climatic implication of proxies in travertine or tufa and their controlling mechanisms.The climatic implication of proxies in travertine or tufa and their controlling mechanisms are generally complicated and of site-specific.Therfore,the direct application of previous studies at one site to another site may be problematic.Moreover,the previous studies focused mainly on the meteogene tufa records and paid little attention to thermogene travertine records.To understand the climatic implication of proxies in travertine and their controlling mechanisms,a case study at Baishuitai of Yunnan was conducted.The methods of one hydrologic year hydrochemical data logging,in-situ titrating and experiment and laboratory sample analysis were used to understand the spatial-temporal variations in geochemistry and stable isotopes of water and modern travertine at Baishuitai.The following conclusions were obtained through the study:（1） Two vapour sources of precipitation during summer and winter monsoon have been recognized at Baishuitai.One is from the Indian Ocean and Bengal Bay during summer,and the other from the inner continent during winter.The precipitation amount effect on rainwaterδ¹⁸O is significant at Baishuitai.（2） Theδ¹⁸O of travertine was lower in summer rainy season and higher in winter dry season.The remarkable seasonal variations inδ¹⁸O of travertine were due to the precipitation amount effect and the change of vapour sources of precipitation.The quantitative relationship between the travertineδ¹⁸O and the precipitation amount was that the travertineδ¹⁸O decreased by 0.7‰when the precipitation amount increased by 100mm.The temperature effect coefficient on the travertineδ¹⁸O,being -0.1‰/℃was smaller than that in O’neil Equation. （3） The lower travertineδ¹³C values in travertine-depositing canal and travertine-depositing pools during the warm and rainy seasons were related to the dilution of overland flows after rainfall,which was mainly influenced by soil water,and so had lowerδ¹³C values.（4） The deposition rate of travertine decreased in warm and rainy seasons because of the dilution of the rainfall and the overland flows after rainfall,which had lower concentration of [Ca²⁺]and[HCO₃^-].Obviously,the dilution effect to decrease the deposition rate of travertine is stronger than the temperature effect to increase the deposition rate of travertine.（5） The seasonal travertine laminas were distinguished with the color change.The thin brown porous lamina was formed in the warm and rainy season,while the thick dense white lamina was formed in the dry season.（6） The effect of aquatic plants to increase theδ¹³C values and the deposition rate of travertine was weaker than the dilution effect.Therefore,theδ¹³C values of travertine and the deposition rate of travertine were lower in warm and rainy season than in dry season.更多还原