Stromatolites with Small Girvanella Form from Nevada Area 51

This is stromatolite has a most unusual form genera. It is essentially filled with concentric spheroids called Girvanella that are commonly called algal balls. Coming from a Lower Cambrian formation, these stromatolites date to a time when stromatolites were no longer prevalent and abundant on earth. The massive cyanobacterial stromatolite reefs of the Proterozoic had yielded to new reef systems with abundant and diverse life forms. For more than two billion years the cyanobacteria had oxygenated earth’s atmosphere through their photosynthetic, autotrophic metabolism. Earth was now hostile to them in many ways, with other heterotrophic, eukaryotic microbes to compete with or be eaten by, and the atmosphere that they had created was essentially poison to them.

We cannot say for sure that the microbes that produced these Girvanella were cyanobacteria. Perhaps they were plant-like eukaryotic algae. What seems probable is that each little spheroid was once an independent colony that was never able to grow into the large domal structures like those of Proterozoic-time.

The locality is another interesting aspect of these stromatolites. It comes from a small pod between two Ollenelus trilobite zones immediately adjacent to Area 51 near Racheal, Nevada. As we know the secrets of Area 51 are as prominent as the uncertainty of the stromatolites’ makers.