Thrombolites growing in saline Clifton Lake in Western Australia. These structures, similar to stromatolites, are formed when microscopic cyanobacteria grow and cement together precipitating carbonates and sand grains. The structures here are appoximately 0.5 m in diameter.


Stomatolites and thrombolites are preserved in the geological record, and preserve a record of the oldest know living organisms (3.5 billion years).


Photo, October 2005