The K-T Extinction

Christina DavisKatie 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://en.wikipedia.org/wiki/K–T_boundary

http://evolution.berkeley.edu/evolibrary/images/interviews/extinction_graph3.gif

• 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

K-T Extinction

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

http://en.wikipedia.org/wiki/K–T_boundary Littlefoot, Cera, Spike, Ducky, Petri

Fossils

Psittacosaur meileyingensis

Coelophysis bauri

Triceratops

Duck-billed Dinosaur

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

Juvenile Plesiosaur

Plesiosaur fossil

Taniwhasaurus

Prognadothon

More Casualties

Azhdarchidae (Pterosaur)

Rudist Bivalve

Belemnites(cephalopod)

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://scienceblogs.com/gregladen/dinosaur_extinction_theory.jpghttp://blog.beliefnet.com/jesuscreed/files/import/assets_c/2010/02/Extinction-thumb-333x344-

11363.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

http://www.dinosaurfact.net/images/dinoextinctpic.jpg

The ImpactThe Impact

http://www.shivanjaikaran.com/files/ic.c8466846c279a1462f992708570eddfd.xasteroidimpact,j.jpg

• 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

Alvarez Hypothesis

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

• 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!

Alvarez Impact

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.

http://johnstodderinexile.files.wordpress.com/2006/10/deccan-flood-basalts.jpg

Deccan Traps

Deccan Traps

• Large igneous province located on the Deccan Plateau of west-central 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

• Common extrusive volcanic rock

Basalt

• “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

Deccan Traps

http://en.wikipedia.org/wiki/Deccan_Traps

Deccan Traps

http://upload.wikimedia.org/wikipedia/commons/3/31/Deccan_Traps_volcano.jpg

MULTIPLE IMPACT

• http://images.nationalgeographic.com/wpf/media-live/photos/000/010/cache/mass-extinction_1077_600x450.jpg

http://images.nationalgeographic.com/wpf/media-live/photos/000/010/cache/mass-extinction_1077_600x450.jpg

Multiple Impact Theory

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 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

Maastrichtian Sea Level

http://www.helium.com/items/1409742-why-dinosaurs-became-extinct-the-k-pg-extinction-theories

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 244Pu, disproving this hypothesis

Supernova Hypothesis

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