Unique Eocene Stromatolites from Green River

This stromatolite in natural un-cut form is unique from several perspectives, color, age and its naturally polished state. The distinctive green coloration is most unusual that may represent a high copper content. Interesting, due to exposure of the outcrop, the specimen has been polished by wind and sand - in essence, sandblasted by nature to have a smoothened surface. Finally, it is indeed, very young for stromatolites, coming from the Middle Eocene of the Green River Formation in Wyoming.

Cyanobacteria remained principal primary producers of stromatolites beginning in the Archaean and continuing throughout the Proterozoic. By the Eocene, stromatolites had markedly declined on earth, and their formation was no longer entirely mediated prokaryotic cyanobacteria origin, as eukaryotic life such as plant-like algae was abundant and diverse in marine and aquatic environments. This particular formation, as indicated by the name Chlorellopsis, is presumed by be of algal origin. But, it is reasonable to conjecture that multiple and competing microorganisms, both prokarytic and eukaryotic could have contributed to the formation of these unique and very pretty stromatolites.