Extinction 2 Flashcards
What are the characteristics of the permian/triassic extinction?
Big Mother of Extinctions Defines end of Paleozoic. 57% families, 98% species extinct. Very rapid, <1Ma. Majority of sea creatures
What is the evidence for this extinction?
Southern hemisphere coal content South african rivers Rock boundaries of fungal spores Carbon isotopes Mud colours
What is the evidence in the coal? p/t
in Southern Hemisphere, there is an abrupt change to NO coal. Prolific swamps that produce the coal were killed.
Found in australia.
In our hemisphere, coal fades away slowly.
What is the river evidence? p/t
In south african karoo, sudden change from meandering river to braided stream facies.
No plants to stabilize the river banks.
Continental interiors become dry and arid.
What is the evidence in rock layers? p/t
In ora Italy, they collected samples between boundary of permian and triassic, and found only fungal spores!!
Fungal spores indicate fungi decomposing a dead forest only.
What is the carbon evidence? p/t
Decrease in Carbon 13 anomolie.
Indication of a mass extinction. A decrease in C13 indicates a relative increase in C12 (a dilution of C13). C12 is enriched in oceans indicating photosynthetic/organic matter isn’t using it anymore = DEATH of those organisms.
What is the black mud evidence?
Green/red muds replaced by anoxic black muds in China, South america, australia greenland and russia.
Represents period of lack of oxygen, lack of circulation!
once well ventilated systems now have no oxygen and world’s oceans just..die.
What are the possible causes of the perm-triassic extinction?
- Continental configuration - formation of pangea (wouldn’t explain the whole thing)
- Release of H2S/co2 from the oceans. When it ‘overturns’ it would release C02 buildup. i.e. Lakey nyos, cameroon in 1986 lake outgassing.
If saturated water rose it would produce a dense cloud of co2, and this is possible at higher temperatures because ocean circulation slows down, and anaerobic decay generates c02 and h2S (but why would oceans die in the first place?) - ET impact. possible.
i. large structure in australia but its not actually linked anymore to it. more possibly to continental rifting. “Bedout High” also no evidence of ejecta.
ii. Buckminster fullerenes (buckyballs C60) which have a special extraterrestrial signature (house He 3 when most earth stuff has He4) These buckyballs were found around places at boundary, but no ejecta! and there would have to be a significant impacting body. -
Siberian Traps. Plume activity, which send a head of basalt super thick the size of russia. The last plume we had was in 17MA in yellowstone causing columbia river basalts. THis one was much larger. 1.5 million km2 area, 3 million km3 basalt. Super intense for like 1 million years.
Whats this cause?
- sulfate aerosis: signficantly cool atmosphere in short term
- destruction of ozone layer
- greenhouse gas effect (real evidence for this)
Siberian traps release enough C02 to cause 5 rise in temp.
What did scientists find in greenland to support the idea of an extinciton in per=tri?
Paul wignall found a section in greenland (jameson land) that spanned P-Tr boundary and found lots of fossils tracing extinction event.
Found that it wasn’t a sudden inpact and occured over many years.
3 distinct phases
1. Starts on land, 40,000 yars
2. Goes to ocean, after 40,000 years
3. Goes BACK to land and is 80,000 years in total.
Wignall also noticed a 2nd dip in carbon 13 anomolie.
What caused the 2nd carbon 13 dip?
Methane trapped in clathrates!
Lots more c12 would enter the system due to this methane.
Methane is trapped in water ice at the bottom of the ocean where its cold and high pressure.
Normally they are unstable, but as oceans warm, the clathrates becomes unstable and release their methane which is rich in c12, which makes temp rise even MORE.
What is eutrophcation?
sharp definition of warm and cold water. (lid on warm water).
What was the new information found about the p=tr extinction from MIT?
- Archaea- anareobic methanogens had a genome change around this time, and allowed them to produce more CH4. THis would help add to the bad effects from the siberian traps (which are still the trigger). The traps release nickel which is what these new super methanogens need to fertilize themselevs.
- C02 hypercapnia and ocean acidity.
-extra c02 from traps dissolves in oceans and causes to omuch c02, acidic poison really. c02 is more soluble than o2.
The oceans are hit more by this because they are less adapted to high c02 levels, whereas terrestrial beings are adapted to increasing c02 better.
Aquatic species reduce protein production and decrease fertility rates.
the acidification of the oceans explains why calcite creatures were hit harder and why corals were wiped out. - The sulfate reducing h2S byproduct producing bactera are back. IN oxygen depleted oceans, these would thrive again and hydrogen sulfide remember is toxic to metabolism of organisms. things die. this is seen in chinese shallow water sections indicating mixing up into shallow water, not just deep stuff, extending into photic zone.
What are the charictaristics of the Crestaceous Paleogene extinction? K/PG
Dinosaur killer.
Killed 50% of species.
ON land, nothing over 25kg survives.
IN water, ammonites die, marine reptiles die, 85% species lost.
Who were walter and luis alverez and what was their theory? what was their EVIDENCE?
Found latest cretaceous clay layer in Italy, enriched in iridum, which is found in ET objects. iridum is usually found continually coming down from our atmsophere, so concentration of it means not as much sedimentation in a particular area, but they found a LOT of iridum. It was also GLOBAL. So two possibilities
1) slow, no sediment accumulation for 10,000 years
2) sudden delivery, impact event.
What is further evidence for the impact event scenario?
- Fern spores: are found in abundance in beginning of paleogene, which is the species that follows forest fires. they are found isolated and globally. (the spores - proxy for forest fires)
- Soot layers associated with the iridum layer (more global fires, suggesting world catches on fire at the same time??? how?)
- Tektites: natural glass droplets made from melting rocks from impact. Tiny things that look like hersheys kisses
- Shocked quartz: made when high pressure waves pass through, cross hatched pattern called shock lamellae. Impact feature of shattering rock.
- Tsunami deposits. Evidence of global tsunami in sedimentary deposits.
- The CRATER!! Found in Yucatan peninsula. (more on this in anther card)
