Microbially Induced Sedimentary Structures(miss)from The Mesoproterozoic Yunmengshan Formation Of Western Henan Province

Yunmengshan Formation, belonging to Ruyang Group, lies in the south margin of the North China platform and exposed predominantly siliciclastic sedimentary successions. In the first, second and fourth of this unit, abundant microbially induced sedimentary structures (MISS)are present, with eighteen distinctive types that can be grouped in to four genetic categories including mat growth, mat metabolism, mat destruction and mat decay structures. These structures are closely associated with herringbone, swaley, and high-angle planar cross stratification, ripple cross lamination, ripple marks, and mud cracks, suggesting microbial mat colonization and growth in peritidal siliciclastic environments from the intertidal to supratidal zones. Thin sections exhibit ancient microbial mat remains: black carbonaceous layers, small grains, oriented grains and aggregates of hematite/limonite after pyrite. The abundance and diversity of MISS indicate thriving microbial mats colonized in this area and played an important role in sedimentary process once. The biogenic mechanisms of microbial mats have been the basis for speculations about higher sedimentation rates and accordingly thicker siliciclastic accumulations in mat covered areas. As the structure of the widespread Precambrian and Phanerozoic of the limitations of distribution, on the one hand, it help us in the past global changes and environmental evolution of understanding in order to better predict future climate and environmental changes trends, survival and development of mankind, has an extremely important scientific and realistic significance; On the other hand, the study on the MISS for understanding micro-organisms in the geological history of the role and evolution of life on Earth played an important role issues will be further evidence of sedimentology.