钙华分为表生和内生两大类:表生钙华主要起因于水中土壤成因CO2的脱气作用,而内生钙华起因于水中热成因CO2的脱气作用.作为两大类钙华的表生和内生钙华因CO2来源和分压不同,它们的形成机理及其指代的气候环境意义也可能完全不同.本文综述了表生和内生钙华的形成机理及对气候环境指代意义的研究现状和存在的问题,进而提出钙华沉积速率和碳氧稳定同位素组成等气候环境代用指标的水动力控制、表面控制和CO2慢速转换控制的深入揭示,并对这些指标变化与气候(温度、降水)、人类活动(如土地利用)和地震的关系进行定性或定量重建是未来研究的重点.这些突破将为利用钙华记录高分辨率辨析我国季风气候对全球变化的响应规律和可能的机制提供新的科学支撑.
Surface carbonate deposits have been divided into two broad groups, the tufa, which results primarily from the degassing of soil-borne aqueous CO2, and the travertine resulting from the degassing of thermally generated CO2. Because of differing sources and partial pressures of CO2, the formative mechanisms and paleoclimatic interpretation of the two may be completely different. This article summarizes current situations and problems of research on the formative mechanisms and paleoclimatic interpretations of tufa and travertine. It emphasizes that further research should focus on determining the surficial, hydrodynamic and CO2 conversion controls upon climatic proxies such as deposition rates, oxygen and carbon stable isotope ratios, and using them to make quantitative and/or qualitative analyses of the relationships between these proxies and climate (temperature, precipitation), human activity (land use and land cover change) or earthquake activity. This will provide new scientific support for understanding the response of the monsoon climate in China to global change and the true underlying mechanisms when making use of high-resolution records in tufa/travertine.