“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

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

Phases of Mass Extinction

Biological Causes of Extinction Minimum Viable Population and the Problems of small populations –Demographic Stochastity –Genetic Deterioration –Social Dysfunction –Extrinsic Forces

GAMBLER’S RUIN!

GAMBLER’S RUIN Results $10 Trial ## of flips# pos.# neg $

GAMBLER’S RUIN Results $10 Trial 2$10 Trial 4 $10 Trial 5

GAMBLER’S RUIN Results $5 Trial 3$5 Trial 2 $5 Trial 4

Survivorship Curve

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 13 C where: 13 C= Marine biomass 13 C= -25 ‰ Oceanic carbonates 13 C= -0.5 to 1‰ Increase organic matter burial, 13 C carb goes up Decrease organic matter burial, 13 C carb goes down Ocean anoxic event= + change in 13 C carb

Oxygen isotopes Typically reported as 18 O where: 18 O = Positive 18 O carb values indicate colder climate Negative 18 O carb values indicate warmer climate

Strontium isotopes Ratio of 87 Sr to 86 Sr 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

Ordovician Mass Extinction

Ordovician Invertebrate Fossils Ordovician Mass Extinction

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

Stable Isotope Data Ordovician Mass Extinction

The End-Devonian Mass Extinction Devonian 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

Paleozoic “nemesis” The End-Permian Mass Extinction Permian Mass Extinction

Geochemical Signals

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

Geochemical Signals

Causes of End-Permian Mass Extinction Climate Change Volcanism ? Bolide Impact Sea level Change Anoxia

Cretaceous-Paleogene Mass Extinction

What went extinct? Planktonic foraminifera Benthic foraminifera Calcareous Nanoplankton Organic-walled Nanoplankton Rudist bivalves, ammonites, and belemnites Mosasaurs, ichthosaurs, and plesiosaurs Plants

Geochemical Signals

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?) XX? End-PermianX (Fall)X (cool)XX?X End-TriassicX (Fall)X (cool or warm?) ?X? End- Cretaceous X (Fall)XXX

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.