Stromatolites from Wyoming
- Stratifera Form Genus
Time: Archaean (> 2.5 Billion Years Old)
inch): 160 mm by 170 mm (maximum)
Lower Whalen Group, Hartville Uplift, near Guernsey, Wyoming
There are but few Archaean stromatolites sites in North America,
making this an unusual specimen. Clearly much of the ancient reefs
have been ground up into sediment, and perhaps much subsumed back
into the Earth's mantle. These stromatolites come from the Hartville
Uplift that is cut by a granite dike radio-dated at 2.58 billion.
This stromatolite comes from below the granite and is therefore
older. Being dolomite that has been highly metamorphosed, it fits
into the Stratifera form genus.
Some theories hold that stromatolites were widespread
and prolific reef builders in the Archaean and through the Lower
Proterozoic, and steeply declined beginning by the Middle Proterozoic.
The primary microorganism that built stromatolites is believed to
have been a photosynthetic Eubacteria that oxygenated the earth’s
oceans and atmosphere, leading to the “rusting of the seas”
that deposited countless tons of iron.
stromatolites pictures to enlarge