Unique Green Eocene Stromatolites from Green River Formation

Chlorellopsis sp. Stromatolites

Geological Time: Middle Eocene

Size: 6.3 x 4.5 x by 4 inches

Fossil Site : Green River Formation, Tipton Shale Member, Green River Basin, Wyoming

Eocene Stromatolites from Green River FormationThis 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, a time when stromatolitic formations on earth were on the defensive and ubiquitously replaced by modern reef systems.

By the Eocene, stromatolites had markedly declined on earth, and their formation was no longer predominately of prokaryotic 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 to be at least in part of algal biological origin. But, it is reasonable to conjecture that multiple and competing microorganisms, both prokarytic and eukaryotic could probably contributed to the formation of these unique and very pretty stromatolites.

Cyanobacteria that were responsible for Precambrian stromatolites were once grouped with photosynthetic Algae, and such grouping is still very prevalent in printed and Internet literature (e.g., such terminology as algal mats). They are excluded in modern molecular biology owing to large differences such as the lack of organelles bound by a membrane, the bacterial, single circular chromosome, and ribosomes having different size and content from those of Eukaryotes. Algae are Eukaryotes and conduct photosynthesis within membrane-bound organelles called chloroplasts. Chloroplasts contain circular DNA and are similar in structure to Cyanobacteria, presumably representing reduced cyanobacterial endosymbionts. The exact nature of the chloroplasts is different among the different lines of Algae possibly due to different endosymbiotic events in deep time on Earth.

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