Late Ordovician

What happened during this time?

• End of Ordovician ice age

  • At least two glaciation events over 447-444 Ma

    • End of Katian event, and end of Hirantian event

    • Each glaciation thought to last between 0.5-1.5 Ma

    • Sea levels frequently rise and fall during these glaciations

  • 2nd largest extinction in Earth's history; First extinction of the "big five extinctions"

• 50-60% of marine life goes extinct; maybe as high as 85%

  •  Reducing conditions, with low to no oxygen and little to no hydrogen sulfide levels, are probably playing a much more important role in this extinction (Kozik et al. 2022)

• Volcanic activity created silicates that absorbed CO2 from the atmosphere

  • Carbon dioxide levels dropped from 7,000 ppm to 4,400 ppm

• Appearance of early land plants (bryophytes) may have triggered the 2nd largest glaciation event (Lenton et al. 2012, Retallack 2015)

  • Increased weathering of rocks that absorb carbon dioxide levels

  • Carbon is buried in deep sea sediments dropping global CO2 levels

• The earliest, putative evidence of stomata comes from this time from Zbrza, Poland (Salamon et al. 2018; Clark et al. 2022)

• Putative branched sporophytes have been described from 445 Ma (Salamon et al. 2018)

  • The preservation of these fossils makes it difficult to know if they had vascular tissue