STROMATOLITES

Fossils are amazing. Some children dream that if they dig deep enough in their backyards, they will find fossils from dinosaurs, ferns, sea shells or any other imaginable ancient living thing. Many people don’t know, however, that some of our oldest records of life on earth have modern relatives that are living and growing today. Stromatolites are essentially layers of microorganisms which have trapped and cemented sediments, and even though some stromatolites are found alive and growing today, the oldest stromatolite fossil samples are estimated to be close to 3.5 billion years old!

Ancient stromatolites formed in an oxygen-poor environment compared to today, prior to what biologists call the oxygen revolution or the “great oxygenation event”. Cyanobacteria, or “blue-green algae”, began to take advantage of available water and photosynthesized, eventually inundating the atmosphere with oxygen. Mats of microorganisms, particularly cyanobacteria, bound and cemented layers of sedimentary grains, building the layered stromatolites that we continue to study today. 

The featured picture is one of living stromatolites in Shark Bay, Australia, which is home to a great amount of today’s living stromatolite samples, although they are found in many areas of the world, particularly in hypersaline lakes.

-BN 

Photo Credit: http://www.flickr.com/photos/77516097@N00/514063316

Further reading and resources:
http://hoopermuseum.earthsci.carleton.ca/stromatolites/OXYGEN.htm
http://www.pbs.org/lifebeyondearth/alone/highway/highway.swf
http://www.dmp.wa.gov.au/5243.aspx
http://www.sharkbay.org/Stromatolitesfactsheet.aspx