Archean* microbial communities created complex structures that reflect both the behavior of bacteria in the community as well as environmental conditions. Results suggest that two distinct microbial communities coexisted in close proximity and affected local calcite* precipitation differently. Current work focuses on geochemically characterizing the remnant organic matter and encasing calcite cements*. Preliminary results suggest a metabolic influence on carbonate precipitation from one of the communities but not the other. (See also these paper abstracts: Calcite-Microbe Interactions, Archean Carbonate Precipitation and Oxygen, Fenestrate Microbialites, and a GSA abstract.)
The polished slab on the left shows the complex geometry of the microbial communities (black) and the abundance of void-filling calcite cements (grey and white). Some of the microbial communities grew up vertically whereas others formed more common, horizontal and draping mats. The grey calcite cements consist of herringbone calcite. The scale bar at the bottom right is 1 cm long.