The K-T Extinction
Christina Davis
Katie Peth
19 April 2012
K-T Extinction
K-T Extinction
K
•
Abbreviation for Cretaceous
Period, derived from the German
name Kreidezeit
T
• Abbreviation for the Tertiary
Period
• historical term for period of time
covered by the Paleogene and
Neogene periods
http://evolution.berkeley.edu/evolibrary/imag
es/interviews/extinction_graph3.gif
http://en.wikipedia.org/wiki/K–T_boundary
K-T Extinction
• Also referred to as the Cretaceous–Paleogene extinction event
• Approximately 65.5 million years ago
• Associated with geological signature
• K–T boundary: thin band of sedimentation found in various
parts of world
http://en.wikipedia.org/wiki/K–T_boundary
http://en.wikipedia.org/wiki/K–T_boundary
K-T Extinction
• Numerous groups of organisms went extinct, most
notably the non-avian dinosaurs.
• Non-avian dinosaur fossils are only found below K-T
boundary indicating they became extinct during boundary
event
• Very small number of dinosaur fossils have been found
above the K–T boundary (reworked fossils)
• eroded from their original locations then preserved in
later sedimentary
Littlefoot, Cera,
Spike, Ducky, Petri
http://en.wikipedia.org/wiki/K–T_boundary
Fossils
Psittacosaur meileyingensis
Duck-billed Dinosaur
Triceratops
Coelophysis bauri
The T-Rex
• http://www.youtube.com/watch?v=PSI8nP0m24M
http://www.popcrunch.com/wp-content/uploads/2011/05/t-rex-jurassic-park-500x301.jpg
Others That “Moved On”
• Mosasaurs, plesiosaurs, pterosaurs, various plants and
invertebrates became extinct
Prognadothon
Plesiosaur fossil
Juvenile Plesiosaur
Taniwhasaurus
More Casualties
Rudist Bivalve
Belemnites
(cephalopod)
Azhdarchidae (Pterosaur)
Ammonite Fossil
Mammals!
• Mammalian clades passed through boundary with few
extinctions (see Katie’s shirt)
• Mammalian clades then thrived and evolved, along with other
species (more on that later!)
http://images.nationalgeographic.com/wpf/media-live/photos/000/089/cache/mammal-evolution_8984_600x450.jpg
Potential Causes
• One or more catastrophic events?
• Asteroid impacts?
• Increased volcanic activity?
• Several impact craters and massive volcanic activity have been
dated to the approximate time of extinction
• These events would have released massive amounts of dust and
ash released into the atmosphere
• Reduced surface sunlight
• Hindered photosynthesis
• Disruption of Earth’s biosphere
MacLeod, N. J. Geo. Soc. 1997, 154, 265-292.
Controversy
• Many believe the extinction was more gradual from the sea
level and climate changes, and aggravated by impact events or
increased volcanic activity
• Length of time for extinction to occur is controversial
• Signor-Lipps effect: the fossil record is so incomplete that
most extinct species probably died out long after the most
recent fossil that has been found.
• There are very few continuous beds of fossil-bearing rock from
before and after K-T extinction
• Several million years before to few million years after
http://en.wikipedia.org/wiki/K–T_boundary
Controversy
http://blog.beliefnet.com/jesuscreed/files/import/assets_c/2010/02/Extinction-thumb-333x344-11363.jpg
http://scienceblogs.com/gregladen/dinosaur_extinction_theory.jpg
Causes
• Impact
• Alvarez Impact Hypothesis
• Chicxulub Crater
• Deccan traps
• Multiple impact
• Maastrichtian sea level regression
• Supernova hypothesis
• Multiple causes
http://en.wikipedia.org/wiki/K–T_boundary
The
TheImpact
Impact
http://www.dinosaurfact.net/images/dinoextinctpic.jpg
http://www.shivanjaikaran.com/files/ic.c8466846c279a1462f992708570eddfd.xasteroidimpact,j.jpg
Alvarez Hypothesis
• Mass extinction of dinosaurs (etc.) caused by impact of large
asteroid on Earth 65 million years ago
• Named for Nobel-prize winning physicist Luis Alvarez who
first suggested theory in 1980, along with geologist son Walter
Alvarez and chemists Frank Asaro and Helen Michels
http://en.wikipedia.org/wiki/Alvarez_hypothesis
Evidence?
• K-T boundary sedimentary band all over
the world has iridium ranging from 20-160
times normal amount.
• Iridium is rare in Earth’s crust, but
abundant in asteroids/comets
• Also found chromium isotopic anomalies
similar to those found in carbonaceous
chondrites, along with shocked quartz
granules and tektites.
Alvarez, L.W. Science. 1980, 208, 1095-1108.
Alvarez Impact
• Able to calculate size of meteor
• Would have to be 10-15 km in diameter (size
of Mars moon Deimos, or Manhattan)
• Impact of that size would have an incredible
amount of energy
• 1 x 108 megatons, 2 million times greater than
most powerful thermonuclear bomb tested!
Alvarez, L.W. Science. 1980, 208, 1095-1108.
Chicxulub Crater
http://www.lpl.arizona.edu/undergrad/classes/spring2011/Hubbard_206/Lectures4/Apr19.htm
Chicxulub Crater
• Impact site buried underneath Yucatán peninsula in Mexico,
discovered by geophysicist Glen Penfield in the late 1970s.
• Took about 20 years to fully investigate crater, with help from
Alan Hildebrand.
• Evidence for impact:
• Shocked quartz
• Tektites
• Gravity anomaly
http://en.wikipedia.org/wiki/Chicxulub_crater
Alvarez Impact
• Created sunlight blocking dust cloud
• Affects photosynthesis, leading to extinction of plants,
phytoplankton and other organisms dependent on it.
• Sulfur aerosols (12 years to dissipate)
• 10–20% reduction of solar transmission
• Global firestorms exacerbated by high O2 concentration
• Increase in CO2, greenhouse effect once cloud settled
• Reduced global temperature (impact winter)
• Acid rain (relatively minor impact) + megatsunamis!
Kring, D.A. Astrobiology. 2003, 3, 133-152
Alvarez Impact
• 2007- Hypothesis that impact forming Chicxulub crater was
caused by asteroid from Baptistina family of asteroids
• 2011 WISE study begs to differ.
• 2010- 41 scientists reviewed 20 years of literature to rule out
massive volcanism as cause.
• Also endorsed that the asteroidal impact at Chicxulub crater
as being the cause of the extinction
• The collision would have released the same energy as 100
teratonnes of TNT (420 ZJ), over a billion times the energy
of the bombs dropped on Hiroshima and Nagasaki
• Still controversy on whether a single impact was the sole cause.
Deccan Traps
http://johnstodderinexile.files.wordpress.com/2006/10/deccan-flood-basalts.jpg
Deccan Traps
• Large igneous province located on the Deccan Plateau of westcentral India
• One of the largest volcanic features on Earth
• Multiple layers of solidified flood basalt
• more than 2,000 m thick with an area of 500,000 km2 and a
volume of 512,000 km3
http://en.wikipedia.org/wiki/Deccan_Traps
Basalt
• Common extrusive volcanic rock
Deccan Traps
• “Trap” is derived from the Swedish word for stairs and refers to
the step-like hills forming the landscape of the region.
• Release of volcanic gases, particularly sulfur dioxide, during
formation of traps contributed to contemporary climate change
• Average fall in temperature of 2 °C in this period
http://en.wikipedia.org/wiki/Deccan_Traps
Deccan Traps
http://upload.wikimedia.org/wikipedia/commons/3/31/Deccan_Traps_volcano.jpg
Multiple
MULTIPLE
Impact
IMPACT
Theory
• http://images.nationalgeographic.com/wpf/medialive/photos/000/010/cache/massextinction_1077_600x450.jpg
http://images.nationalgeographic.com/wpf/media-live/photos/000/010/cache/mass-extinction_1077_600x450.jpg
Multiple Impact Theory
• Simultaneous impacts around the K-T boundary
• Asteroids/comets
• Boltysh Crater (Ukraine)
• Silver Pit Crater (North Sea)
• Shiva Crater (Indian Ocean, controversial origin)
• Could have had more formed in Tethys Ocean obscured by
tectonic effects.
http://en.wikipedia.org/wiki/Cretaceous%E2%80%93Paleogene_extinction_event
Shiva Crater
• 500 km in diameter, hypothesized by Sankar Chatterjee to be
result of impact with 40 km asteroid.
• Unusually rectangular, with large amounts of alkaline melt
rocks, shocked quartz, and iridium
• Many remain unconvinced; “Shiva Crater” not recognized as
an impact crater by the Earth Impact Database.
http://en.wikipedia.org/wiki/Shiva_crater
Maastrichtian Sea Level
 Maastrichtian was the final part of the Cretaceous period
 Between 72 to 66 million years ago
 Exposed rock layers do not show the kind of erosion, tilting,
distortion and other geologic patterns that are common with
formation of mountains.
 Evidence that sea levels fell dramatically during this time
 Hypothesis: mid-ocean ridges became less active and thus sunk
under their own weight causing marine life form extinction
http://www.helium.com/items/1409742-why-dinosaurs-became-extinct-the-k-pg-extinction-theories
Supernova Hypothesis
 Cosmic radiation from a nearby supernova explosion
 Fallout from a supernova explosion should contain 244Pu, the
longest-lived plutonium isotope (half-life of 81 million years)
 If this hypothesis were correct, detectable traces of 244Pu
should be detected from rocks deposited at the time
 However, there is an absence of
hypothesis
244Pu,
disproving this
http://en.wikipedia.org/wiki/K–T_boundary
Multiple Causes?
• Mixture of previously mentioned
causes
I Will Survive!
• Microbiota
• Radiolaria, Diatoms, benthic
foraminifera
• Marine Invertebrates
• Brachiopods, nautiloids, coleoids
• Fish
• 80% of cartilaginous fish
• 90% of teleost fish
•http://palaeo.gly.bris.ac.uk/communication/Goddard/page1.html
I Will Survive!
• Terrestrial Invertabrates
• Terrestial Plants
• Paleocene recovery of plants began
with recolonizations by fern species
• Saprotrophic organisms
• Polyploidy
• Amphibians
•http://palaeo.gly.bris.ac.uk/communication/Goddard/page1.html
I Will Survive!
• Non-archosaur reptiles
• Testudines (turtles)
• Lepidosaurs (snakes and lizards)
• Choristoderes
• Archosaurs
• Crocodilians
• Dinosaurs (Birds)
• Mammals!
• Diversification stalled.
•http://palaeo.gly.bris.ac.uk/communication/Goddard/page1.html
Conclusions
• Most accepted reason is the Alvarez Impact Theory
• Most likely mixture of this impact and volcanic
activity
• Supernova not supported with scientific evidence
• Ability to survive depended on food source, size,
environment
• Feed on snails or other detritus species
• Tiny is best
• Stable to environmental changes