EXTINCTION: THE GREAT DYING AT PERMO-TRIASSIC BOUNDARY (4/20)

Question 1

Carboniferous Period => “Age of Carbon” (lots of COAL)

Answer 1

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

What is fossil evidence for the assembly of Gondwanaland?

Answer 6

○ 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 7

What is geological evidence for large ice sheets on Gondwanaland?

Answer 7

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

Question 8

Photosynthesis “fractionates” carbon isotopes =>

Answer 8

preferential uptake of lighter isotope (12C) Thus, both organic matter and coal are depleted in the heavy isotope (13C)

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 vs. Mass extinction

Answer 12

○ Considers number of families extinct per million years

Background extinction - typical process of turnover and replacement

Question 13

How is a mass extinction defined?

Answer 13

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

Question 14

When were the FIVE major mass extinctions during the Phanerozoic?

Answer 14

• When were the FIVE major mass extinctions during the Phanerozoic?
		○ End-Ordovician
		○ Late-Devonian
		○ End-Permian (“Great Dying”)
		○ Late-Triassic
		○ Late-Cretaceous

Question 15

When did the “Great Dying” happen?

Answer 15

○ The 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

• 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

Question 17

Most likely cause of the “Great Dying”: Siberian Traps (volcanism, emission of vast amounts of CO2)

Answer 17

• 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

Question 18

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

Answer 18

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

Question 19

What does this signify?

Answer 19

• What does this signify?
○ 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 20

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

Answer 20

• 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

Question 21

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

Answer 21

• 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