South African StromatolitesThese circular structures are stromatolites; some of the dominant fossils
South African StromatolitesThese circular structures are stromatolites; some of the dominant fossils from the first half of Earth’s history. These are found in rocks from the Ghaap Plateau of South Africa; an area that today is high-ground but about 2.5 billion years ago was a shallow sea with an area comparable to the island of Great Britain today.Although it is possible some stromatolites formed without the influence of life, these stromatolites are the fossil remnants of colonies of single-celled organisms.Stromatolites like these leave rock records because of how they grow; carbonate sediments and muds in the waters would stick to the outer layers of a growing stromatolite, building the mass outwards. The cells would then grow outwards, bypassing the sediment that had collected on the surface and trapping the carbonate mud as a layer inside the growing colony. Repeating that cycle over and over would then create layered objects like these which would build up carbonate-reefs as time goes on.The lens cap is there for scale.-JBBImage credit:http://www.flickr.com/photos/mmj71/327293712/Read more:http://books.google.com/books?id=adcEIp7ODpIC&lpg=PA21&ots=OcNeEmZ3gH&dq=ghaap+plateau+stromatolite&pg=PA21#v=onepage&q=ghaap%20plateau%20stromatolite&f=falsehttp://www.ncbi.nlm.nih.gov/pubmed/11542814http://www.fossilmall.com/Science/About_Stromatolite.htm -- source link
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