Marion Bay Australia Stromatolite Colony

Description: Stromatolites are remnants of the most ancient of colonial organisms. Stromatolites are fossils that are the result of the work of simple blue-green “algae” or Cyanophytes, which lived in chains or mats covered in a jellylike substance. By taking in carbon dioxide as a food source, the precipitate limy deposits on the jelly that builds up in layers. Thus these organisms build up stony supports for their colonies. These mound like structures can be anywhere from several centimeters to several meters in height. The production of oxygen is thought to have led to the “rusting of the seas” which brought about deposition of extensive iron deposits such as the Mesabi Range. Hematite is an iron mineral, and is one of the components of this banded structure (dark bands). Stromatolites have persisted to the modern day in such places as Shark Bay, Australia where they continue their billions of years old lifestyle. The oval to circular structure in these images is an entire stromatolite colony that dates from the Pleistocene to the Holocene, a time when stromatolites were no longer prevalent and abundant. By the Cambrian, photosynthetic bacteria responsible for the biogenic formation of stromatolite structures no longer had the earth to themselves. The oxygenated atmosphere had become toxic to some bacteria, and they had to compete with other organisms, some of which would have been predaceous to this most ancient of life forms. No wonder that this stromatolite shows the Girvanella-like shape that was a group of small independent colonies, never reaching the large domes of the Proterozoic. The location is now a park with no access to collectors, making this example from an old collection impossible to replace.