1. Christina Davis Katie Peth 19 April 2012
The K-T Extinction
Christina Davis
Katie Peth
19 April 2012

2. K-T Extinction

3. 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

4. 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

6. 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

7. Fossils Psittacosaur meileyingensis Triceratops Coelophysis bauri
Duck-billed Dinosaur
Coelophysis bauri

8. The T-Rex http://www.youtube.com/watch?v=PSI8nP0m24M

9. Others That “Moved On”
Mosasaurs, plesiosaurs, pterosaurs, various plants and invertebrates became extinct
Prognadothon
Plesiosaur fossil
---Numerous species of benthic foraminifera became extinct during the K–Pg event, presumably because they depend on organic debris for nutrients, since the biomass in the ocean is thought to have decreased.
----Ostracods, a class of small crustaceans that were prevalent in the upper Maastrichtian, left fossil deposits in a variety of locations. A review of these fossils shows that ostracode diversity was lower in the Paleocene than any other time in the Tertiary. However, current research cannot ascertain whether the extinctions occurred prior to or during the boundary interval itself.2627
----Approximately 60% of late-Cretaceous Scleractinia coral genera failed to cross the K–T boundary into the Paleocene. Further analysis of the coral extinctions shows that approximately 98% of colonial species, ones that inhabit warm, shallow tropical waters, became extinct. Colonial coral species rely upon symbiosis with photosynthetic algae, which collapsed due to the events surrounding the K–T boundary.2829 However, the use of data from coral fossils to support K–Pg extinction and subsequent Paleocene recovery must be weighed against the changes that occurred in coral ecosystems through the K–T boundary.7
----- Except for nautiloids (represented by the modern order Nautilida) and coleoids (which had already diverged into modern octopodes, squids, and cuttlefish) all other species of the molluscan class Cephalopoda became extinct at the K–T boundary. These included the ecologically significant belemnoids, as well as the ammonoids, a group of highly diverse, numerous, and widely distributed shelled cephalopods
---- Approximately 35% of echinoderm genera became extinct at the K–T boundary
-----Approximately 35% of echinoderm genera became extinct at the K–T boundary, although taxa that thrived in low-latitude, shallow-water environments during late Cretaceous had the highest extinction rate. Mid-latitude, deep-water echinoderms were much less affected at the K–T boundary. The pattern of extinction points to habitat loss, specifically the drowning of carbonate platforms, the shallow-water reefs in existence at that time, by the extinction event.32
Other invertebrate groups, including rudists (reef-building clams) and inoceramids (giant relatives of modern scallops), also became extinct at the K–T boundary.3334
---- In North America, approximately 57% of plant species became extinct.
-----Only one family of pterosaurs, Azhdarchidae, was definitely present in the Maastrichtian, and it became extinct at the K–T boundary. These large pterosaurs were the last representatives of a declining group that contained 10 families during the mid-Cretaceous. Smaller pterosaurs became extinct prior to the Maastrichtian during a period that saw a decline in smaller animal species while larger species became more prevalent. While this was occurring, modern birds were undergoing diversification and replacing archaic birds and pterosaur groups, possibly due to direct competition, or they simply filled empty niches
---- However, all non-neornithean birds became extinct, including flourishing groups like enantiornithines and hesperornithiforms.55
Juvenile Plesiosaur
Taniwhasaurus

10. Azhdarchidae (Pterosaur)
More Casualties
Rudist Bivalve
Belemnites
(cephalopod)
Azhdarchidae (Pterosaur)
Ammonite Fossil

11. 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!)

12. 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,

13. 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

14. Controversy

15. Causes Impact Alvarez Impact Hypothesis Chicxulub Crater Deccan traps
Multiple impact
Maastrichtian sea level regression
Supernova hypothesis
Multiple causes

16. The Impact
The Impact

17. 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

18. Evidence?
K-T boundary sedimentary band all over the world has iridium ranging from 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,

19. Alvarez Impact Able to calculate size of meteor
Would have to be 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,

20. Chicxulub Crater

21. 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

22. Kring, D.A. Astrobiology. 2003, 3, 133-152
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 , 3,

23. Alvarez Impact
2007- Hypothesis that impact forming Chicxulub crater was caused by asteroid from Baptistina family of asteroids
2011 WISE study begs to differ.
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.

24. Deccan Traps

25. 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

26. Basalt
Common extrusive volcanic rock

27. 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

28. Deccan Traps

29. Multiple Impact Theory
live/photos/000/010/cache/mass- extinction_1077_600x450.jpg

30. 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.

31. 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.

32. 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

33. 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 244Pu, disproving this hypothesis

34. Multiple Causes?
Mixture of previously mentioned causes

35. I Will Survive! Microbiota Radiolaria, Diatoms, benthic foraminifera
Marine Invertebrates
Brachiopods, nautiloids, coleoids
Fish
80% of cartilaginous fish
90% of teleost fish

36. I Will Survive! Terrestrial Invertabrates Terrestial Plants
Paleocene recovery of plants began with recolonizations by fern species
Saprotrophic organisms
Polyploidy
Amphibians

37. I Will Survive! Non-archosaur reptiles Testudines (turtles)
Lepidosaurs (snakes and lizards)
Choristoderes
Archosaurs
Crocodilians
Dinosaurs (Birds)
Mammals!
Diversification stalled.

38. 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