Siderian Period

What happened during this time?

Geological

• Abundance of banded iron formations (BIFs), which form from oxygen bonding with iron in the oceans

  • Iron was dissolved in oceans and oxidized by photosynthetic bacteria into insoluble magnetite (Fe3O4) and hematite (Fe2O3), which precipitated and formed deposits on the ocean floor

  • These deposits are layered in cycles

  • ~20x more oxygen than today's atmosphere is trapped in BIFs

• Oxygen increases in the atmosphere creating the Oxygen Catastrophe or Great Oxidation Event

  • Many anaerobic bacteria go extinct 

  • Evidence of microbial mats on the land during this time (Lenton & Daines, 2016)

  • Oxygen in the atmosphere reacted with organic material in sediments, "creating a regulatory mechanism whereby the oxygen was consumed by the sediments at the same rate at which it was produced." (Daines et al., 2017)

• Huronian glaciation begins during this period (2.4 Ga)

  • Lasts until Rhyacian (2.1 Ga)

Biological

• Stromatolites with cyanobacteria continue to belch oxygen into the atmosphere

  • Proposed "multicellularity" in cyanobacteria around 2.3 Ga (Schirrmeister et al., 2013)

  • Cyanobacteria may have evolved multicellular forms between 3.5–3.0 bya (Grosberg & Strathmann, 2007; Knoll, 2003; Schopf, 1993). 

Above: Banded iron ore