Figure 14. Biotic composition and silicification of green algal-dominated mats on Microfacies 2 sinter. (1) Overview of an unsilicified green mat showing a predominance of spherical cells that are 2-4 µm in diameter. Minor amounts of bacilli are also present. (2) Silicified portion of a green mat on the top (young) sinter surface. Note the incorporation of equivalent sized spherical cells into the (older) sinter body (red arrows) (cf. Figure 11.6). (3) Alternating laminae of sinter composed of silicified biomats (red arrows) and layers of featureless, massive, vitreous silica (yellow arrows). (4) Sharp boundary (red arrow) between a biotic and an abiotic layer. (5) Close-up of silicified cells incorporated into sinter beneath living green mat. Some silicified cells include endospores. (6) Preservation of cellular impressions (red arrows).