湖相沉积物有机地球化学在古环境研究中的应用

Application of lacustrine sedimentary organic geochemistry to reconstruction of paleoenvironment

湖相沉积物中的有机质蕴含着丰富的地球化学信息,是古环境研究中必要的基础资料之一。文章综述了近年来湖相沉积物有机地球化学在古环境研究中的应用,结果表明:1在应用有机地球化学信息探讨古环境时,首先要根据有机质组成特征区分其来源,不同来源的有机质,其地球化学特征存在差异;2有机质碳同位素(δ13Corg)是研究古气候变化的常用指标,在区分暖湿、暖干、冷湿、冷干气候类型时需结合沉积物中总有机质丰度(TOC)、总有机氮丰度(TN)、自生碳酸盐氧同位素(δ18O)等资料;3脂肪酸不饱和度可作为恢复古环境温度的定性指标,UK37和UK37'在定量恢复古湖水表层温度中有较好的应用效果,TEX86有望应用在古湖水表层温度的重建;4生物标志化合物可较好地区分沉积物中有机质的来源、沉积水体的盐度及氧化还原性。可见,有机地球化学是研究古环境常用且有效的技术手段,多项有机地球化学参数相互验证能够更精确地重建古环境并预测其演化趋势。

Lacustrine sedimentary organic matter contains plenty of geochemical information, which is useful in the study of paleoenvironment. The research on reconstruction of paleoenvironment by lacustrine organic geochemistry analysis in recent years was summarized in this paper, with some conclusions reached： （1） Organic matter source should be identified by organic composition data before the performance of paleoenvironmental reconstruction which is based on geochemical information, because the characteristics of organic matters from different sources are different. （2） δ13Corg is a common index for the study of paleoclimate, which should be combined with TOC, TN, 8180 of authigenic carbonate data to determine paleoclimate characteristics （e. g., warm, humid, dry and cold）. （3） The polyunsaturated fatty acids of lacustrine sediments are qualitative indexes of paleoenvironment temperature. The application of U K37 and U K 37＇ to the quantitative reconstruction of past lake surface temperatures has been proved quite effective. TEX86 may be a new index for determination of past lake surface temperatures. （4） The sources of organic matter, salinity and redox property of sedimentary environment can be identified by biomarkers. Therefore, organic geochemistry is a common and effective method to elucidate paleoenvironment. The paleoenvironment can be more accurately reconstructed and predicted by integration of data from multiple parameters of organic geochemistry.