二叠纪—三叠纪之交凝块石（微生物岩）的沉积成岩过程——以华南广西百色地区作登剖面为例

二叠纪末大灭绝之后,在我国华南地区广泛发育了一套钙质微生物岩,这套微生物岩以凝块石为主,代表了大灭绝事件后特殊环境下的生物沉积建造。早期对凝块石的分布以及沉积特征有详细研究。通过镜下显微观察,阴极发光照相,背散射成像以及探针元素分析,对凝块石的显微特征进行了详细研究。通过对凝块石中化石的分布,矿物组成以及元素分布规律观察,对比现代凝块石沉积成岩过程总结了二叠纪末凝块石的沉积成岩过程,即早期生长阶段,沉积阶段,早期成岩阶段和后期成岩阶段。清晰的凝块石的沉积成岩过程为解析该时期微生物沉积建造打下基础。

Sedimentary and Diagenetic Processes of Thrombolites near the Permian-Triassic Boundary in the Zuodeng Section,Baise Area,Guangxi Province,South China

Following the mass extinction at the end of the Permian, a set of calcareous microbialites was widely developed in South China. These mainly consist of clotted limestone, which may represent bio-sedimentary formation in a specific environment after the mass extinction. The microstructures of the clotted limestone were studied in detail by microscopic observation, cathodoluminescence photography, backscattered imaging and probe element analysis. The distribution of fossil elements and mineral composition in the clotted limestone were observed and the findings compared with the diagenesis process of modern clotted limestone. The sedimentary and diagenetic process of the end-Permian clotted limestone are summarized, including early growth stage, sedimentary stage, early diagenetic stage and late diagenetic stage. The clear sedimentary and diagenetic processes of clotted limestone lays a foundation for the analysis of microbial sedimentary formation during this critical period.