The Precambrian Fossil Record

A Precambrian Time Line

3800 Ma: Isua Banded Iron (unusually old for Banded Iron Formations)

3550 Ma: Warrawoona Series of northwestern Australia: bacteria, cyanobacteria, stromatolites

• Microfossils preserved in Dark Chert
• very small roundish things. consistent with abiotic synthesis.
• see Archean Fossil Record at UC Berkely Museum of Paleontology
• for pictures of stromatolites, see Fossil Record of Cyanobacteria at UC Berkely Museum of Paleontology

3400 Ma: Fig Tree Formation of Southern Africa: stromatolites, cyanobacteria, bacteria

2800 Ma: Stromatolites invade salty lake environments

2500 Ma: Peak development of Banded Iron formations world wide: The banded iron formations make up much of the iron found in the world. They are thought to be the direct results of photosynthetic release of oxygen, which bound with the reduced iron that was at that time dissolved in the oceans. The background image of this page is a magnified view of banded iron from Australia.

2300 Ma: Youngest Uraninite deposits in paleosols. Uraninite can only exist in the absence of oxygen

see about the Buildup of Oxygen at UC Berkely Museum of Paleontology
see a site that has some info about Banded Iron in Minnesota

2100 Ma: Grypania spiralis reported from Michigan

2220 Ma to 2060 Ma: Carbon isotope evidence of a rapid rise in global oxygen levels

2000 Ma: Gunflint Chert, Lake Superior, Stromatolites with chert and excellent preservation of a large variety of prokaryotes--cyanobacteria Note that this is found within the banded iron formations

1850 Ma: First of the Acritarch fossils

1800 Ma: Last of the banded Iron Formations

1400 Ma: Grypania spiralis, a eukaryotic algae, found abundantly in China and Montana

0.9 Billion Years: Bitter Springs Chert, Central Australia prokaryotes, some Eukaryotes

• These may represent the first Eukaryotes. They were not metazoans, but consisted of loose agregations of cells.
• the theory of the symbiotic incorporation of different prokaryotic cells into the early eukaryotes
• see Bitter Springs Chert at UC Berkely Museum of Paleontology

800 Ma: Development of a diverse Acritarch Fauna

600 Ma: End of the Precambrian Glaciations

• unknown affinities "jellyfish" and "worms" thought to be coelenterates, but recent work has come up with slightly different stories.
• Associated with sandstone--probably shallow water.
• Other late precambrian fossils are chitinozoans.
• see Vendian Animals at UC Berkely Museum of Paleontology

• Tommotian Faunas
• Dissolved from limestones and dolomites Made of phosphate
• see Tommotian at UC Berkely Museum of Paleontology