西藏岗巴地区古新世-始新世界线地层及底栖大有孔虫的演替  

TURNOVER OF LARGER BENTHIC FORAMINIFERA DURING THE PALEOCENE-EOCENE STRATIGRAPHIC BOUNDARY IN GAMBA,TIBET

作　　者：王曦[1] 万晓樵[1] 李国彪[1] 

机构地区：[1]中国地质大学(北京)地球科学与资源学院,北京100083

出　　处：《微体古生物学报》2010年第2期109-117,共9页Acta Micropalaeontologica Sinica

基　　金：国家自然科学基金(40872016);国家重点基础研究发展计划"973"(G2006CB701403);教育部博士点基金(20070491512)联合资助

摘　　要：古新世与始新世界线(P/E)事件中底栖大有孔虫的绝灭(BEE)以及演替(LFT)在古近纪底栖大有孔虫演化过程中起着非常重要的作用。西藏南部岗巴地区发育有良好的海相界线地层,在宗浦Ⅱ剖面中,对底栖大有孔虫动物群及碳、氧稳定同位素的研究显示全球界线事件对该地区造成明显影响。在界线附近,底栖大有孔虫出现大量灭绝,总灭绝率达71%,界线之上开始出现复苏,底栖大有孔虫的新生率为72%。事件过后,底栖大有孔虫SBZ4动物群被SBZ5-SBZ13动物群代替,以古新统宗浦组的Miscellanea miscella,Lockhartia hai mei,Glomalveolinapri maeva的灭绝和Operculina属的消失及始新统遮普惹组Nummulites willcox,Alveolina ellipsoidalis和Orbi-tolites complanatus出现为特征。在古新世界线顶部,碳稳定同位素值出现明显负偏,峰值为-7.9‰,与全球同一时期碳稳定同位素事件表现一致;氧稳定同位素表现则与全球事件不太相同,这可能是由于成岩作用的影响。The benthic extinction event（BEE）and larger foraminifera turnover（LFT）during the Paleocene-Eocene transition constitutes an important step in Paleogene larger-foraminifera evolution.A marine boundary succession is well preserved in the Gamba region of southern Tibet.Research on larger foraminifera fauna,carbon isotopes and oxy-gen isotopes in the section of ZongpuⅡshows that the signals of global Paleocene-Eocene boundary event are well recorded in the region.At the P/E boundary,the larger benthic foraminifera were extensive extincted with a general extinction rate of 71%.Following the event,larger benthic foraminifera began to recovery with the rate of 72%.SBZ4 fauna was replaced by SBZ5—SBZ13 fauna,as characterized by the gradual extinction of Paleocene taxa such Miscellanea miscella,Lockhartia haimei,Glomalveolina primaeva and disappearance of Operculina in the Zongpu Formation and the rise of Eocene taxa Nummulites willcox,Alveolina ellipsoidalis and Orbitolites complanatus in the Zhepure Formation.A clear negative Carbon isotope shift is recorded at the boundary with the value of-7.9‰ and is well correlated with other standard isotopic event.The change of oxygen isotope is different with global change,probably caused by the diagenesis.

关 键 词：底栖大有孔虫 P/E界线 灭绝 岗巴地区 西藏 

分 类 号：Q915[天文地球—古生物学与地层学]