Stromatolites: a 3.5-billion-year ichnologic record

Stromatolites are trace fossils that record the interaction between microbial communities and sediments. Macroscopically, the shape of the stromatolite may represent stronger environmental controls. Study of the scalar attributes can yield insight into microbialethology, and foster biostratigraphic and facies analysis over the past 3500 million years. Stromatolites have largely been treated as structures analogous to colonial organisms or eukaryotic algae, even though only a fraction of fossil occurrences contains an organic component and none are made by a singular colonial animal orindividual plant. Stromatolites and other microbialites are primarily composed of mechanical sediments and cements produced through the activities of a microscopic consortium. The internal fabric and macroscale attributes of stromatolites have been used for biostratigraphic correlation and facies analysis, even though the taxonomic affinities of the microbial community are usually unknown. Indeed, it is quite probable that a particular microbial ecosystem may be responsible for more than one type of microbialite, and several different microbial consortia may construct a unique microbialite.