EXTINCTION: THE GREAT DYING AT PERMO-TRIASSIC BOUNDARY

Question 1

Carboniferous Period

Answer 1

“Age of Carbon” (lots of COAL)

Due to lycopod swamps/burial

Question 2

Photosynthesis – Respiration Cycle

Answer 2

Photosynthesis: CO2 + H2O = CH2O + O2
Respiration: CH2O + O2 = CO2 + H2O (pretty much the opposite)

Question 3

Carbon cycle during the Carboniferous Period (“Age of Coal”)

Answer 3

Ocean surface and atmosphere exchange gases and CO2 a lot
Plants take up atmospheric CO2
Most plants get buried (CO2 gets preserved)

Question 4

Relation between Organic C burial (Coal Swamps) & Atmospheric CO2

Answer 4

Reduces oxidation of organic carbon and return flux CO2 to the atmosphere
Reduces greenhouse gas warming and temperatures drop

Question 5

Stable carbon isotope ratios ( 13C/12C)

Answer 5

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)

Question 6

Carboniferous climate state

Answer 6

large continental ice sheet develops on Gondwanaland

Question 7

Gondwanaland?

What is fossil evidence for the assembly of Gondwanaland?

Answer 7

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

Question 8

geological evidence for large ice sheets on Gondwanaland

Answer 8

Glacial tillites of Carboniferous age rest non-conformably atop crystalline basement rocks in all five stratigraphic sections

Question 9

How do carbon isotopes (13C/12C) in marine carbonates (limestone) change during Carboniferous?

Answer 9

Marine carbonates = inorganic carbon

Carbon isotope ratio goes up

Question 10

Why do carbon isotopes (13C/12C) in marine carbonates (limestone) change during Carboniferous?

Answer 10

Due to the burial of organic material (enriched in 12C and depleted of 13C)

Question 11

What does this tell us about burial of organic C and atmospheric CO2 levels?

Answer 11

More burial of 13C-depleted organic carbon = reduction in atmospheric CO2 levels

Question 12

Background extinction

Answer 12

Background extinction - typical process of turnover and replacement

Question 13

mass extinction

Answer 13

Magnitude: very great (many families going extinct)
Duration: somewhat brief (a few million years or less)
Influence: occurred globally

Question 14

FIVE major mass extinctions during the Phanerozoic

Answer 14

End-Ordovician
Late-Devonian
End-Permian (“Great Dying”)
Late-Triassic
Late-Cretaceous

Question 15

When did the “Great Dying” happen?

Answer 15

end of the Paleozoic Era (Permo-Triassic extinction)

Question 16

Main victims of the “Great Dying” at the end of the Paleozoic Era (i.e. Permo-Triassic Boundary, PTB)

Answer 16

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

Question 17

Most likely cause of the “Great Dying”

Answer 17

Siberian Traps (volcanism, emission of vast amounts of CO2)
Massive release of CO2
More CO2 = global warming
Ocean acidification

Question 18

How do stable carbon isotope ratios (13C/12C) change during the “Great Dying”?

What does this signify?

Answer 18

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

Question 19

How do carbon isotope ratios (13C/12C) during the PTB mass extinction differ from those of the preceding Carboniferous?

Answer 19

Levels of 13C/12C are lower during PTB mass extinction

Question 20

How would a sharp rise in atmospheric CO2 levels affect surface-ocean pH? What is pH?

Answer 20

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