stromatolite noun1 •A laminated, columnar, rock-like structure constituting a large share of all fossils from 3.5 to 0.5 billion years ago, with some still being formed at present, some or all of which result from the deposit of minerals by microorganisms such as cyanobacteria.Most modern and ancient stromatolites occur in carbonate sediments and sedimentary rocks, but they can form by trapping and binding of any sediment particles. — 1979 formsstromatolites
