stromatolite

1. (geology) 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.Examples: "Most modern and ancient stromatolites occur in carbonate sediments and sedimentary rocks, but they can form by trapping and binding of any sediment particles."; "2003, David M. Paterson, Rebecca J. Aspden, R. Pamela Reid, Biodynamics of Modern Marine Stromatolites, Andrew H. Knoll, Life on a Young Planet: The First Three Billion Years of Evolution on Earth, page 44, Stromatolites are the predominant features of carbonate rocks formed in Precambrian oceans."; "The formation of modern stromatolites is highly dependent on sediment accretion rates and their associated microbial assemblages that trap and bind sediment particles that fall on the surface of the structures."