Fig. 9

a A FESEM image of a freshly broken chip from a darker layer of stromatolite showing many suspected microbes in dark color above the surface of calcite crystals. EDS analysis shows that the light-colored host consists of calcite crystals (b) whereas the dark-colored matter is suspected microbes (organic matter) (c); d A FESEM image of a polished chip showing that there is much organic matter (in dark color) remaining in intercrystalline spaces of calcite; e A FESEM image of a polished chip showing calcite crystal (C), clay mineral (CM) and suspected microbes; f A FESEM image of a polished chip showing residual organic matter in intercrystalline spaces which looks like the cells of microbes (in dark color)