洞穴石笋δ^18O与δ^13C气候意义研究

The Paleoclimatic Significance of Carbon and Oxygen Stable Isotopes in Speleothems

利用洞穴次生化学沉积物进行古环境重建是第四纪全球变化研究的一个热点,而碳氧稳定同位素是最重要的气候替代性指标。不少研究者利用洞穴次生沉积物如石笋中碳氧稳定同位素的记录已恢复了部分地区不同时间尺度古气候。同时,研究人员也面临着合理解释一系列机理性问题的挑战,如氧稳定同位素气候意义的多解性、碳氧稳定同位素在定量重建古气候方面存在一定程度失真现象等诸多问题。文中全面论述碳氧稳定同位素在古气候重建中定性与定量研究上存在的局限性,并在此基础上指出:要分别探究石笋中δ18O与δ13C各种来源进入洞穴石笋的地球物理化学全过程及其控制机制;研究现代大气降水同位素组成的各种效应在不同时空的组合规律;尽快建立更为科学的大陆矿物-水地质温标。

The significance of speleothems in reconstructing the paleoenvironment has been a hot spot in the research of the global changes in Quaternary. The carbon and oxygen stable isotopes have been considered to be the most effectual proxy indexes in reconstructing the paleoclimate of Quaternary. Although great achievements about the reconstruction of paleoenvironment have been acquired by scientists based on the extensive applications of carbon and oxygen stable isotopes recorded in speleothems, such as stalagmites, there are still some confusion with reasonable explanation of a series of mechanism questions, such as different explanation of climatic significance of the oxygen stable isotopes, the precise significations about the two stable isotopes when the paleoclimate is reconstructed quantitatively with them. By discussing the limitations of the qualitative and quantitative studies of the two isotopes in the reconstruction of paleoenvironment, it is pointed out that it is necessary to respectively explore the geophysical and chemical process of the various sources of δ^13 C and δ^18O in the stalagmites and the entire controlling mechanism during the process, and to study the combination laws of the various effects of the isotopes at different time and space in modern precipitation, and to establish a more scientific mineral - water geological temperature scale for the mainland as soon as possible.