The End-Permian Mass Extinction

• The Permian period was between 290-252 Ma. (One Ma, or Mega Annum is one million years) Five major mass extinctions
• At that time the land was in one mass called a supercontinent: PANGEA.
• 95% of all marine species were killed.
• 70% of all land life (families) became extinct.

This has been in part due to a dearth of sedimentary sections dating from this time, as the result of a widespread marine regression which reduced sediment deposition rates, thus reducing the diagenesis of new rocks entering the geological record.

The recent discovery of sections from the Permo-Triassic boundary in localities in places such as Italy, Pakistan and South China has allowed more detailed analysis to take place. This has permitted new hypotheses of possible extinction mechanisms to be drawn up, and older hypotheses of what caused the mass extinction to be either discredited or backed up.

The majority of the extinction occurred in the low latitude equatorial regions, with marine species being particularily affected. These marine species were mostly benthonic, living in the warm, shallow tropical seas of the continental shelf surrounding the continents.

These were mostly filter feeders, often utilising a calcium carbonate shell for a means of protection and to support the soft bodied parts allowing feeding and respiration. It is these hard parts which are usually found in the fossil record, soft parts only ever being seen in circumstances of exceptional preservation.

The discovery of the more complete sections of strata from this time has allowed the extent and rate of the extinction to be better assessed, through study of the contained fossil remains and isotope ratio studies.

It is seen that many species were in decline throughout the Permian, before the final apocalyptic extinction event. This suggests that there may have been a prolonged climatic extinction mechanism, or a combination of many factors, rather than one catastrophic event.

The Permian-Triassic times that are being studied in this project are part of a much larger, longer set of time scales used by Earth Scientists. To see where the Permian-Triassic fits into Geological times visit the Wikipedia page on Geological time scales.

This will also give names to some of the sub periods referred to on this site.