Fossil microorganisms and formation of Early Precambrian weathering crusts

摘要

Weathering crusts are the only reliable evidence of the existence of continental conditions,.Often they are the only source of information about exogenous processes and subsequently about conditions under which the development of biosphere occurred. A diverse complex of fossil microorganisms was discovered by Scanning Electron Microscope investigations. The chemical composition of the discovered fossils is identical to that of the host rocks and is represented by Si, Al, Fe, Ca and Mg. Probably, the microorganisms embedded in the rocks played the role of a catalyst. Decomposition of minerals, comprising rocks, and their transformation into clayey (argillaceous) minerals, occurred most likely under the influence of microorganisms. Perhaps the unique weathering crusts of Early Precambrian were formed due to interaction between specific composition of microorganism assemblage and conditions of hypergene transformations. So it is possible to speak about the colonization of land by microbes already at that time and about existence of single series from weathering crusts (primitive soils) to real soils.