EXTINCTION: THE GREAT DYING AT PERMO-TRIASSIC BOUNDARY Flashcards
Carboniferous Period
“Age of Carbon” (lots of COAL)
Due to lycopod swamps/burial
Photosynthesis – Respiration Cycle
Photosynthesis: CO2 + H2O = CH2O + O2
Respiration: CH2O + O2 = CO2 + H2O (pretty much the opposite)
Carbon cycle during the Carboniferous Period (“Age of Coal”)
Ocean surface and atmosphere exchange gases and CO2 a lot
Plants take up atmospheric CO2
Most plants get buried (CO2 gets preserved)
Relation between Organic C burial (Coal Swamps) & Atmospheric CO2
Reduces oxidation of organic carbon and return flux CO2 to the atmosphere
Reduces greenhouse gas warming and temperatures drop
Stable carbon isotope ratios ( 13C/12C)
13C has an extra neutron
13C/12C ratio: if this ratio is positive (or over 0), then that means it is enriched in 13C (like in the oceans). If the ratio is negative, then it is 13C depleted (like in photosynthesis)
Carboniferous climate state
large continental ice sheet develops on Gondwanaland
Gondwanaland?
What is fossil evidence for the assembly of Gondwanaland?
Glossopteris fossils (tongue-like leaves) and other fossils found on all continents suggest that they were once connected in a huge land mass (Gondwanaland) Gondwana rocks also suggest this
geological evidence for large ice sheets on Gondwanaland
Glacial tillites of Carboniferous age rest non-conformably atop crystalline basement rocks in all five stratigraphic sections
How do carbon isotopes (13C/12C) in marine carbonates (limestone) change during Carboniferous?
Marine carbonates = inorganic carbon
Carbon isotope ratio goes up
Why do carbon isotopes (13C/12C) in marine carbonates (limestone) change during Carboniferous?
Due to the burial of organic material (enriched in 12C and depleted of 13C)
What does this tell us about burial of organic C and atmospheric CO2 levels?
More burial of 13C-depleted organic carbon = reduction in atmospheric CO2 levels
Background extinction
Background extinction - typical process of turnover and replacement
mass extinction
Magnitude: very great (many families going extinct)
Duration: somewhat brief (a few million years or less)
Influence: occurred globally
FIVE major mass extinctions during the Phanerozoic
End-Ordovician Late-Devonian End-Permian (“Great Dying”) Late-Triassic Late-Cretaceous
When did the “Great Dying” happen?
end of the Paleozoic Era (Permo-Triassic extinction)
Main victims of the “Great Dying” at the end of the Paleozoic Era (i.e. Permo-Triassic Boundary, PTB)
Lots of marine invertebrates
Trilobites
Articulate brachiopods
Tabulate and Rugose Corals (two major coral groups)
Sea scorpions
Therapsids were hit very hard, but still managed to hang on
Most likely cause of the “Great Dying”
Siberian Traps (volcanism, emission of vast amounts of CO2)
Massive release of CO2
More CO2 = global warming
Ocean acidification
How do stable carbon isotope ratios (13C/12C) change during the “Great Dying”?
What does this signify?
Drop in 13C/12C ratio, due to the excessive release of 12C
Plants took in a lot of 12C with burial as they turned into coal, until the volcanoes burned them and released all the 12C back into the atmosphere
Carbon contains the sun’s radiation that is reflected off the surface of a planet (think of a greenhouse)
Ice sheets in Permian have melted because of this
How do carbon isotope ratios (13C/12C) during the PTB mass extinction differ from those of the preceding Carboniferous?
Levels of 13C/12C are lower during PTB mass extinction
How would a sharp rise in atmospheric CO2 levels affect surface-ocean pH? What is pH?
pH is a measurement of the concentration of hydrogen ions in a solution
Oceanic uptake of CO2 lowers the pH of water: CO2 +H2O+CO3 -> 2HCO3
