Stromatolite

Stromatolites (stroʊˈmætəˌlaɪts,_strə-) or stromatoliths () are layered sedimentary formations (microbialite) that are created mainly by photosynthetic microorganisms such as cyanobacteria, sulfate-reducing bacteria, and Pseudomonadota (formerly proteobacteria). These microorganisms produce adhesive compounds that cement sand and other rocky materials to form mineral "microbial mats". In turn, these mats build up layer by layer, growing gradually over time. A stromatolite may grow to a meter or more. Fossilized stromatolites provide important records of some of the most ancient life. Today the living forms are rare. Stromatolites are layered, biochemical, accretionary structures formed in shallow water by the trapping, binding and cementation of sedimentary grains in biofilms (specifically microbial mats), through the action of certain microbial lifeforms, especially cyanobacteria. They exhibit a variety of forms and structures, or morphologies, including conical, stratiform, domal, columnar, and branching types. Stromatolites occur widely in the fossil record of the Precambrian, but are rare today. Very few Archean stromatolites contain fossilized microbes, but fossilized microbes are sometimes abundant in Proterozoic stromatolites. While features of some stromatolites are suggestive of biological activity, others possess features that are more consistent with abiotic (non-biological) precipitation. Finding reliable ways to distinguish between biologically formed and abiotic stromatolites is an active area of research in geology. Be it as it may, multiple morphologies of stromatolites may exist in a single local or geological strata, relating to the specific conditions occurring in different region and water depths. Most stromatolites are spongiostromate in texture, having no recognisable microstructure or cellular remains. A minority are porostromate, having recognisable microstructure; these are mostly unknown from the Precambrian but persist throughout the Palaeozoic and Mesozoic.