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Transcript of “There are millions of different species of animals and plants on earth— possibly as many as...
“There are millions of different species of animals and plants on earth—possibly as many as forty million. But somewhere between five and fifty billion species have existed at one time or another. Thus, only about one in a thousand species is still alive—a truly lousy survival record: 99.9% failure!”~David Raup
Mass Extinction!
Presented by: Livia Montone ([email protected])
How do you define “Mass Extinction”?• Any substantial increase in the amount of
extinction (ie. lineage termination) suffered by more than one geographically widespread higher taxon during a relatively short interval of geologic time, resulting in at least temporary decline of standing diversity. (from Sepkoski, 1986)
How do you define “Mass Extinction”?• Any substantial increase in the amount of
extinction (ie. lineage termination) suffered by more than one geographically widespread higher taxon during a relatively short interval of geologic time, resulting in at least temporary decline of standing diversity. (from Sepkoski, 1986)
• An extinction of a significant portion of the world’s biota in a geologically insignificant period of time. (from Hallam and Wignall, 2000)
Outline
• Geologic Time Scale
• Background and mass extinctions
• Phases of extinction
• Biological causes of extinction
• Physical causes of extinction
• Geochemical Toolbox
• The Big Five
A side note about time units vs. rock units…
Time Units (ie. periods of time)
• Eon• Era• Period• Epoch • Age
• Rock Units (ie. sequence of rocks)
• Eonothem• Erathem• System• Series• Stage
Biological Causes of Extinction
• Minimum Viable Population and the Problems of small populations– Demographic Stochastity– Genetic Deterioration– Social Dysfunction– Extrinsic Forces
GAMBLER’S RUIN Results$10
Trial # # of flips # pos. # neg.
1 158 74 84
2 14 2 12
3 192 91 101
4 24 7 12
5 432 211 221
$5
1 147 71 76
2 23 9 14
3 15 5 10
4 241 118 123
5 45 20 25
Proposed Physical Causes of Extinction
Mass Extinctions• Global climate change• Global sea level change• Change is salinity of
ocean• Anoxia• Volcanism• Extraterrestrial Impact
Background extinction• Regional climate change• Regional sea level
change
Geochemical Toolbox
• Carbon isotopes• Oxygen isotopes• Strontium isotopes• Iridium and platinum
group elements
Carbon isotopes
• Typically reported as 𝜹13C where: 𝜹13C=• Marine biomass 𝜹13C= -25 ‰• Oceanic carbonates 𝜹13C= -0.5 to 1‰
• Increase organic matter burial, 𝜹13Ccarb goes up• Decrease organic matter burial, 𝜹13Ccarb goes down• Ocean anoxic event= + change in 𝜹13Ccarb
Oxygen isotopes
• Typically reported as 𝜹18O where: 𝜹18O =
• Positive 𝜹18Ocarb values indicate colder climate
• Negative 𝜹18Ocarb values indicate warmer climate
Strontium isotopes
• Ratio of 87Sr to 86Sr is the result of:– Continental weathering processes– Interaction of seawater with basalt at mid-
ocean ridges• Marine carbonates correspond to seawater
values
Iridium and Platinum Group Elements
• Increased Iridium (several ppb) as an indicator of bolide impact
• Increased Ir with appropriate ratios to Platinum, Gold, and Asmium
The Big Five
• Paleogeography
• Pre-extinction Taxa
• Big Losers
• Geologic and Fossil Record
• Possible Causes
• Geochemical Reconstructions
What went extinct in the Ordovician?• 57% of genera; >25% of families
• Graptolites, conodonts, nautiloids, plankton, brachiopods, trilobites, ostracods, bryozoans, echinoderms, bivalves, rugose and tabulate corals, stromatoporoids…
Ordovician Mass Extinction
O-S GSSP Location- Dob’s Linn, Scotland
• Other well-studied locations on Anticosti Island, Quebec
Ordovician Mass Extinction
Causes of Ordovician Mass Extinction
• Glacial episode beginning in Mid-O
• Sea level regression
• Global cooling
Ordovician Mass Extinction
Selectivity of End-Devonian Mass Extinction
• Kellwasser (Frasnian-Famennian)– Preferential loss of warm-water taxa– Loss of shallow-water taxa– Loses among some pelagic groups
• Hangenberg (Devonian-Carboniferous)– Most severe extinction in water column – Less in benthos
Devonian Mass Extinction
Geochemical Signals
• Carbon-isotopes– Ambiguous records
• Oxygen-isotopes– Equally as confusing
• Ir and trace metals – Enriched in Ni and V
Devonian Mass Extinction
Causes of End-Devonian Mass Extinction
• Bolide impact
• Anoxia
• Cooling?
• Warming?
• Brackish oceans
Devonian Mass Extinction
Causes of End-Permian Mass Extinction
• Cosmic Radiation
• Brackish Oceans
• Regression
• Bolide Impact
• Cooling? Warming?
• Hypercania
• Volcanic Winter
• Global Marine Anoxia
End-Triassic Mass Extinction
• Not well-studied• In marine realm- 48% extinction of invertebrate
genera– Cephalopods– Bivalves– Gastropods– Brachiopods
• Continental realm– Plants less affected than marine– Tetrapod turnover
Causes of End-Permian Mass Extinction
• Climate Change
• Volcanism ?
• Bolide Impact
• Sea level Change
• Anoxia
What went extinct?
• Planktonic foraminifera
• Benthic foraminifera
• Calcareous Nanoplankton
• Organic-walled Nanoplankton
• Rudist bivalves, ammonites, and belemnites
• Mosasaurs, ichthosaurs, and plesiosaurs
• Plants
Causes of K-P Mass Extinction
• Bolide Impact
• Volcanism
• Climate Change
• Marine Regression
• Anoxia
Summary of Possible Causes of the Mass Extinctions
Mass Extinction/
Cause
Sea Level Rise/Fall
Climate Change
Global Ocean Anoxia
Brackish Ocean
Bolide Impact
Volcanism
End-Ordovician
X (Fall) X (Cool)
End-Devonian
X (cool or warm?)
X X ?
End-Permian X (Fall) X (cool) X X ? X
End-Triassic X (Fall) X (cool or warm?)
? X?
End-Cretaceous
X (Fall) X X X
References(in order of importance)
• Hallam, A. and P.B. Wignall (2000), Mass extinctions and their aftermath. Oxford University Press. (Chapters 1,3,4,6, and 9).
• Raup, D. M. (1991), Extinction: bad genes or bad luck? W.W. Norton and Company, New York.
• Stanley, S.M. (2005), Earth System History. W.H. Freeman and Company, New York.
• Prothero, D.R. (2004)., Bringing Fossils to Life. McGraw Hill, New York.