广西来宾铁桥剖面二叠系生物地球化学信号的解读  

Biogeochemical interpretation of the Permian of Tieqiao section in Laibin,Guangxi

作　　者：沈尔卜[1] 胡超涌[1] 马仲武[1] 李牛[1] 颜佳新[1] 

机构地区：[1]中国地质大学(武汉)生物地质与环境地质教育部重点实验室,湖北武汉430074

出　　处：《古地理学报》2010年第2期194-201,共8页Journal of Palaeogeography：Chinese Edition

基　　金：中国石油化工股份有限公司海相油气勘探前瞻性项目"海相优质烃源岩形成的地球生物学过程"(编号:G0800-06-ZS-319)资助

摘　　要：二叠纪被认为是全球生物繁盛的重要时期,其大气含氧量、温度等条件和现代地球极为相似,因此,二叠纪古海洋生物和环境的研究对当代环境和气候变化研究具有重要的启示作用。通过分析广西来宾铁桥剖面二叠系的275个海相碳酸盐岩样品的地球化学组成,考察Ca、Mg、Al、Ti及其比值的变化特征,研究它们的生物和环境意义。结果发现,从栖霞组沉积时期到吴家坪组沉积时期,海水中Mg/Ca值总体上呈单调下降趋势,表明海底洋中脊扩张,洋中脊热液循环加快,全球海平面上升;Al/Ti值在栖霞组沉积时期到吴家坪组沉积时期呈现一种起伏式的变化,其中栖霞组沉积中期和茅口组沉积后期表现出与其他时段有显著差异的高值,表明这两个阶段海洋生产力繁盛;在瓜德卢普统—乐平统界线,Al/Ti值低,与玄武岩(Al/Ti值约为6)相近,指示火山活动强烈,为火山活动导致生物灭绝说提供了地球化学新证据。Permian, when oxygen content in the air and temperature as well as other parameters were much comparable with those of modern days, is believed to be a very important episode of prolific biology, so researches in paleo-ocean biology and circumstance of the Permian may provide an ideal example for the understanding of modern environment and climate change. In the study, by analyzing 275 marine carbonate samples from Tieqiao section, we first investigate the geochemical composition of Ca, Mg, A1 and Ti, and then interpret Mg/Ca and Al/Ti as the proxies of marine chemistry and paleo-productivity respective- ly. We found, Mg/Ca value presented a monotone decline trend from the depositional period of the Qixia Formation to the Wujiapin Formation, and it indicated that ridges expanded, hydrothermal circulation speeded, and global sea level rose ; Al/Ti fluctuated from the depositional period of the Qixia Formation to the Wujiapin Formation, with two peaks in the middle depositional period of the Qixia Formation and the late depositional period of the Maokou Formation, and it indicated that two high productivity phases; An intense volcanic event was identified at Guadalupian-Lopingian boundary by a low Al/Ti value, analog to basalt （ Al/Ti=6 ）

关 键 词：二叠纪 AL/TI 生产力 火山活动 生物地球化学 广西 

分 类 号：P593[天文地球—地球化学]