Stromatolite

Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. Stromatolites (from Greek ¿¿¿¿¿¿, str¿ma, mattress, bed, stratum, and ¿¿¿¿¿, lithos, rock) are layered accretionary structures formed in shallow water by the trapping, binding and cementation of sedimentary grains by biofilms of microorganisms, especially cyanobacteria (commonly known as blue-green algae). They include some of the most ancient records of life on Earth.A variety of stromatolite morphologies exist including conical, stratiform, branching, domal,[1] and columnar types. Stromatolites occur widely in the fossil record of the Precambrian, but are rare today. Very few ancient stromatolites contain fossilized microbes. While features of some stromatolites are suggestive of biological activity, others possess features that are more consistent with abiotic (non-organic) precipitation. Finding reliable ways to distinguish between biologically-formed and abiotic (non-biological) stromatolites is an active area of research in geology.