江西九江红土生物标志化合物的分布特征及其古气候环境意义

Characteristics of Biomarkers in Pleistocene Red Earth of Jiujiang, Jiangxi Province and Its Paleoclimatic and Environmental Significance

为了探求江西九江红土地层中所记录的古气候环境信息,论文在对江西九江红土剖面的野外地貌、岩性和相关沉积环境调查分析基础上,利用气相色谱-质谱联用仪对正构烷烃、一元正脂肪酸等生物标志化合物进行了研究,着重分析了正构烷烃和一元正脂肪酸的来源及其碳数分布特征。结果显示:江西九江红土剖面上部均质红土中正构烷烃的CPI、∑C_(21)~–/∑C_(22)^+及一元正脂肪酸的CPI_L值均大于其下部的网纹红土,且波动较为明显,表明网纹红土的形成气候比其上的均质红土形成时期气候暖湿,反映了中更新世中期(600～300kaBP)的极端暖湿期;正构烷烃的∑C_(21)~–/∑C_(22)^+、(C_(15)+C_(17)+C_(19))/(C_(27)+C_(29)+C_(31))、(C_(16)+C_(17)+C_(18))/(C_(29)+C_(31)+C_(33))、C_(17)/C_(31)在剖面上表现出一致的旋回性变化,反应了江西九江中更新世以来气候的冷暖旋回变化。结果表明红土地层中的生物标志化合物具有很好的古气候环境意义。

In order to get information on paleoclimate and paleo-environment which is recorded in laterite strata of Jiujiang,Jiangxi Province,the authors,on the basis of investigation and analysis of field landform,lithology and related sedimentary environment in laterite profile,studied biomarkers including n-alkanes,n-alkanoic acids and some other factors by means of GC-MS,in which the source and distribution characteristics of their carbon number was emphatically analyzed.The results show that both values of CPI andΣC21^–/ΣC22^+of n-alkanes and value CPIL of n-alkanoic acids in homogeneous red soil located in the upside of the laterite profile in Jiujiang of Jiangxi Province are higher than those of the downside vermicular red soil and exhibit obvious fluctuations,which indicates that vermicular red soil was formed in a warm and wet climate compared with the upper homogeneous red soil,reflecting an extreme warm and wet period in middle Pleistocene;ΣC21^–/ΣC22^+,(C15+C17+C19)/(C27+C29+C31),(C16+C17+C18)/(C29+C31+C33)and C17/C31 of n-alkanes perform consistent cyclical changes in the profile,which reflects cold/warm climate cycles since middle Pleistocene in Jiujiang of Jiangxi Province.The result shows that biomarkers in laterite strata have wonderful paleoclimate and paleo-environment significance.