Fossils index

Stromatolites

Stromatolites are layered structures formed in shallow water by biofilms of microorganisms, especially cyanobacteria (commonly known as blue-green algae).

Live blue-green algae

Stromatolites were much more abundant in Precambrian times, but blue-green algae are still alive today (see left).

Domain: Bacteria
Phylum: Cyanobacteria
Stromatolites
Size: 30mm

Timescale: Stromatolites have been around since Precambrian times, more than 542 million years ago.


Stromatolites 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).

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.