THE PERMIAN-TRIASSIC
EXTINCTION
A.K.A.
P-T Extinction
P-Tr Extinction
Permo-Triassic Extinction
Permian-Triassic Extinction Event
End-Permian Mass Extinction
The “Great Dying”
PART I: The EndEnd-Permian Mass
Extinction
PART II: The Delayed Recovery
By Matt Ajemian
Geological Oceanography
Dr. Doug Haywick
March 26, 2008
Introduction
5 major mass extinctions
• Extinctions are natural, observed
throughout fossil-bearing geological record
White, 2002
• “Background extinctions” occur regularly
• “Massive extinctions” = extinction of a
significant proportion of world’s biota in an
insignificant (cannot be resolved in geo
record) amount of time
Life in Permian Seas,
sweet and dandy!
Permian Seas
Amnh.org
• Attached animals
–
–
–
–
–
Rugose/tabulate corals
Crinoids
Bryozoans
Brachiopods
Trilobites
• Mobile animals
– Infauna
– Echinoids
– Fishes
BIOGEOGRAPHICALLY DISTINCT REGIONS
Benton and Twitchett, 2003
BUT THEN>>>>
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251 my: The Victims
Low Complexity
• 96% of marine
species disappear!
– Attached fauna virtually
gone
– Most mobile taxa lost
– Selective extinction of
forams
(low-O2 taxa survive)
Comsopolitan disaster
taxa thrive…
Benton and Twitchett, 2003
Commotion outside the ocean
2/3 reptiles and
amphibians
lost (large
herbivores),
P-Tr was the
only mass
extinction of
insects!
PAPER 1- How to kill (almost) all
life: the end-Permian extinction
HOW DID THIS HAPPEN?
What happened?
Benton and Twitchett, 2003
Trends in Ecology and Evolution
Vol 18 (7): 358-365
2
Bolide impact?
Bolide Impact?
P-T extinction VERY abrupt (like K-T)
• Other researchers could not reproduce results at
Becker’s site
Traces of “Ar” and “He” (extraterrestrial
noble gases) trapped in fullerenes (Becker
et al., 2001)
• “He” and “Ar” extracted from rocks containing
fullerenes, not fullerenes themselves
• No shocked quartz, tsunami-affected sediment,
sperules, etc. (all found at K-T impact site)
• All in all, not a strong causal link between bolide
impact and P-Tr extinction
Siberian Traps Volcanism
• Now widely accepted that STV was a
significant factor (proposed in 80’s)
• “overnight” event?
Siberian Traps Volcanism
• Larger than any basaltic eruption in history
• Released large quantities of CO2 in
atmosphere (long residence time)
• Not enough CO2 released by STV alone
for a +6C increase in global temp
• Meishan (China)?
Siberian Traps Volcanism
• Precision of STV dates still undergoing
improvements
Global Warming
• Increased levels of CO2 in atmosphere (GHG)
• Shift to lighter oxygen (18O/16O)
• Bolide impact caused the rapid volcanism?
?
X
• Reduced oxygen solubility at surface waters
• Extremely low carbon isotopic signatures – from
STV alone?
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Methane hydrate release?
• From Increased Temp or Decreased P
• Added to positive feedback of warming –
essentially runaway greenhouse
Ian MacDonald
The delayed recovery
PART I: The End-Permian Mass
Extinction
PART II: The Delayed Recovery
• P-Tr exceptionally long compared to other
mass extinctions (e.g. K-T)
• Poor fossilization?
• Large fluctuations in C isotopes
The delayed recovery
“Bottom up” factors
• Toxic deep marine waters: upwelling of
alkaline (bact. SO4-reduction) anoxic
waters
• PROBLEM: Does not explain biotic crisis
in shallow-marine environments
Paper 2: Fraiser & Bottjer, 2007
• Analyzed Triassic epeiric
(shelf-associated)
seaways of eastern
Panthalassa
• Studied skeletonized
marine benthic inverts
• Quantified abundances
(visual estimates)
• Used ecological metrics
for determining dominance
and diversity indices
Disaster taxa
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Paper 2: Fraiser & Bottjer, 2007
Paper 2: Fraiser & Bottjer, 2007
• Aftermath in subtidal East Panthalassa
• Sinbad: Bivalves and microgastropods
- found in 95% of samples
Aftermath in subtidal East Panthalassa
• Thaynes: Bivalve-dominated, ↑diversity?
Bivalves found in 100% of samples
Paper 2: Fraiser & Bottjer, 2007
Paper 2: Fraiser & Bottjer, 2007
Aftermath in subtidal East Panthalassa
DISCUSSION
• Bivalves and microgastropods have highmean rank orders in both areas
• Not evenly distributed (low H’ values)
• Microgastropods are opportunistic
Paper 2: Fraiser & Bottjer, 2007
• Early-Triassic biotic crisis
• “Top-down” mechanism
– Elevated atmospheric CO2
levels
– Increased diffusion of CO2 to
surface waters
– Decrease in pH and CaCO3
saturation state
• Sinbad/Thames refuges from toxic deep?
• Composition of monospecific shell beds
indicates stressful conditions
• Evidence for other mechanism – not all
“bottom up” in the subtidal region
Hypercapnia and Marine
Organisms
• Marine animals are more
sensitive to hypercapnic stress
than land animals
• Animals that secrete carbonate
skeletons very susceptible:
limited buffering capacity
• NO METAZOAN REEFS
• Why did bivalves and small
gastropods make it?
– Rapid metabolisms
– For gastropods, as pH↓ oxygen
affinity↑
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PAPER 2: Conclusions
SUMMARY
• “Bottom-up” mechanisms = kill mechanisms
• Elevated atmospheric CO2 levels, a “topdown” mechanism, sustained ecological
degradation in the shallow-marine
environment
DISCUSSION QUESTIONS
• Should the End-Permian
massive extinction be a lesson
to the modern world?
• Critically evaluate PAPER 2:
Enough evidence for top-down
effects on Triassic subtidal
communities
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