广西上泥盆统F—F界线碳同位素的变化特征  

The Pattern of Variations in Carbon Isotope of the Frasnian-Famennian Limestone Sequences in Guangxi, Southern China

作　　者：许冰[1] 顾兆炎[1] 胡滨[1] 李镇梁[2] 

机构地区：[1]中国科学院地质与地球物理研究所,北京100029 [2]广西区域地质调查研究院,广西桂林541003

出　　处：《沉积学报》2004年第4期603-608,共6页Acta Sedimentologica Sinica

基　　金：国家重点基础研究发展规划专项经费资助项目(批准号:G2000077708);国家自然科学基金项目(批准号:40073031)的资助.

摘　　要：发生在晚泥盆世弗拉期(Frasnian)—法门期(Famennian)之交的生物灭绝事件(简称F—F事件)是古生代以来五大生物集群灭绝事件之一,其原因仍含糊不清。碳同位素研究显示,伴随F—F事件全球碳循环发生了显著的变化。但对中国南方F—F事件地层碳同位素变化特征的认识不够,缺乏系统的研究。对广西桂林杨堤上泥盆统灰岩剖面的碳同位素的分析结果表明,在上泥盆统存在两次碳同位素正偏移,分别出现在下rhenana带和F—F的界线,其中,出现在F—F界线的碳同位素正偏移与广西垌村以及欧美和非洲等地的上泥盆统F—F界线附近的碳同位素记录一致,且具有相近的变化幅度。进一步对广西桂林附近的杨堤和垌村剖面F—F界线的碳同位素组成变化模式的分析发现,这次正偏移可能是由多次次级变化组成,与F—F事件中生物的灭绝步骤相似。Carbon isotopic records from Europe, America, African, and Australia show two δ 13 C positive excursions in the upper Devonian, which occur in the late rhenana and F F boundary, respectively. However, the pattern of δ 13 C variations from southern China has not well been constrained. The negative δ 13 C excursion was found in the early studies; however, the detailed study in the Dongcun section shows two δ 13 C positive excursions in the upper Devonian. So further research is needed. The carbonate samples taken from Yandi section in Guilin, southern China have been analyzed for carbon isotopic and elemental compositions. The result shows two δ 13 C positive excursions in the Upper Devonian. The first excursion occurred in the early rehnana zone, and the second around F F boundary, the later is a worldwide pattern. Compared with other records from different paleogeography units in the world, the F F carbon isotope excursion occurred in transition sequences has comparable shapes and amplitudes and ,further support that they must be the result of a global increase in burial organic carbon.

关 键 词：碳同位素组成 界线 变化特征 偏移 剖面 古生代 生物灭绝事件 上泥盆统 晚泥盆世 中国南方 

分 类 号：P618[天文地球—矿床学] Q915[天文地球—地质学]