Keywords: 
• microbes /
• mud mound /
• biosedimentation /
• buildup /
• Early Paleozoic

Abstract: 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.