FIGURE 4. Modern microbialite microstructure compared to fabric of ancient carbonate deposit.

a, b, Modern microbialite microstructure; c, ancient carbonate deposit. a, SEM shows individual bushes of calcified filamentous microfossils and trapped sediment. Authigenically calcified picoplankton comprise calcareous sediment matrix. SEM specimens were impregnated in expoxy resin, etched in 2M HCl, and Ir coated. b, Branches of dendrite consist of radiating splays of larger calcified filaments, supported by a framework of thinner calcified filaments, calcified extracellular matrix, and trapped and bound sediment particles. c, Optical thin section shows dendritic fabric of potential ancient analogue Epiphyton. In the early Cambrian Shady dolomite of southwest Virginia⁵, Epiphyton forms mound-like structures similar to the large mounds found in Pavilion Lake.