贵州紫云猫场剖面二叠纪-三叠纪之交有孔虫的灭绝过程

THE EXTINCTION PATTERN OF FORAMINIFERS DURING THE PERMIAN-TRIASSIC CRISIS AT THE MAOCHANG SECTION,ZIYUN,GUIZHOU PROVINCE,SOUTH CHINA

本研究通过对贵州紫云地区猫场剖面长兴组上部及二叠系-三叠系界线附近地层进行高密度采样和系统切片,获得有孔虫化石标本1 178枚,共鉴定出有孔虫37属65种,包括类有孔虫4属7种。其中35属63种有孔虫消失在生物碎屑灰岩与微生物岩界线之下,包括所有的类有孔虫,其种级和属级灭绝率分别为96.9%和94.6%。这与华南其它微生物岩剖面类似,进一步表明浅水相有孔虫的灭绝发生在长兴期末期。猫场剖面长兴组生物碎屑灰岩中Dagmarita和Cribrogenerina两属非常丰富,其个体数量分别为209枚和126枚,占总数量的28.4%,是该动物群的优势分子,称为Dagmarita-Cribrogenerina组合。猫场组微生物岩中仅发现有孔虫Earlandia和Postcladella两个属,称为Earlandia-Postcladella组合。

65 species in 37 genus of foraminifers, including seven species in four genus of fusulinids, were identified within 1178 specimens that collected from the upper part of the Changxing Formation and the Permian-Triassic boundary strata at the Maochang section, Ziyun area, Guizhou Province, South China. Similar with those from the sections characterized by microhialites in South China, a total of 6a species（96.4G） in 35 genus （94.6 G）of foramini- fers disappeared below the boundary between the bioclastic limestone and the overlying microbialites, which demon strated that the mass extinction of the foraminifer occurred at the end of the Changhsingian in shallow marine facies. This foraminifera biota in Changxing Formation was assigned to Dagrnarita-Cribrogenerina assemblage considering that it was dominated by the genus Dagmarita （209 specimens） and Cribrogenerina （126 specimens） which occupy 28.4% of all specimens. In contrast, only two genus, Earlandia and Postcladella, were found from the overlying microbialites of the Maochang Formation in the studied section, and was assigned to Earlandia-Postcladella assem- blage.