四川盆地早古生代灰泥丘中的微生物及其造岩和成丘作用

Microbial Fossils and Their Biosedimentation & Buildup in Paleozoic Mud Mounds, Sichuan Basin

作为生物礁的特殊类型 ,灰泥丘在古生代十分发育 ,许多学者都认为它们是通过微生物造岩作用而形成的 ,而且 ,也在现代湖泊中发现了由兰菌藻的生命活动所形成的灰泥沉积物及灰泥丘。但是国际上一直没有在古生代灰泥丘中发现过细菌等微生物的实体化石 ,微生物促使碳酸钙沉淀、聚集的能力和机理也不明确。四川盆地北缘寒武纪和志留纪灰泥丘发育 ,笔者通过扫描电镜及能谱分析 ,在国际上首次发现了 (川西北志留纪 )灰泥丘中菌藻类微生物的实体化石及其特征的造岩成丘现象 ,发现的菌藻类微生物实体化石有三种类型 :1.表面光滑的卵形球体型 ;2 .表面粗糙的椭球体型 ;3.网状结构型。而且 ,对寒武纪和志留纪灰泥丘凝块石作生物标志化合物分析也证明了其有机质生源为菌藻类微生物。这些凝块石灰泥丘中的菌藻类实体化石都显示了不同的沉积、造岩和成丘功能 ,因而证实了微生物在形成古生代灰泥丘中具重要作用。

As one of the special bioherms, mud mounds (micrite mounds) developed during the Paleozoic. According to recent researches, many experts in the world have believed that many mud mounds be built by different microbes in the Paleozoic, the lime mud sediments and the mud mounds built by cynobacteria have also been found in modern lakes. But the body fossils of microbes such as bacteria have not been seen in the Paleozoic mud mounds, and the function of the microbial biosedimentation & buildup, and how the bacteria made carbonate deposition are not clear. During Early Paleozoic, there were many mud mounds developed in the north Sichuan. According to the SEM studies, the authors found three kinds of microbial body fossils from the Silurian mud mounds and the microbial biosedimentation:1.Smooth ball-like body fossil with egg shape,5μm × 3μm in size; 2. Rough ellipsoid fossil, 60μm×50μm in size; 3. Foamed network-like fossil formed by foamed network biofilm material covered the micrite. The biomarks analyses also proved that the microbial materials are in mud mounds. The microbial body fossils of mud mounds shower different functiosn of biosedimentation & buildupmentation. The studies confirmed the microbes were very important in the mud mound formation in Paleozoic.