the mesozoic era came to an end 65 million years ago,€¦ · k/t or k/p (paleogene) boundary one...
TRANSCRIPT
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The Mesozoic Era came to an end 65 million years ago,
when the Earth had a very bad day
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From the top to the bottom of the food chain, land and sea species became extinct during this massive event. Dinosaurs, who had ruled the land for 160 million years disappeared forever.
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Cretaceous: “The Chalk”
White Cliffs Dover
K = Cretaceous
K/T or K/P (Paleogene) boundary
One of the big 5 mass extinctions
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K/T Cretaceous/Tertiary boundary
One of the largest mass extinctions in history Sepkowki (1994)
extinction
25% of families,
50 % species
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Large flying reptiles, including the pterodons and pterodactyls, also suffered complete extinction.
QuickTime™ and aCinepak decompressor
are needed to see this picture.
Ammonites, mososaurs, pterodactyls
http://www.ucmp.berkeley.edu/diapsids/pterosauria.html
http://www2.gasou.edu/musenews/mosasaur50.gifa
Marine reptiles, including ichthyosaurs, plesiosaurs, and mosasaurs, disappeared
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severely affectedplanktonic foraminifers: three species survived out of >23
Guembelitria cretacea, Hedbergella monmouthensis, H. holmdelensisnannofossils
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Cretaceous/Tertiary (K/T) boundary
extinction of 25% of families, 50% speciesDinosaurs
marine reptilesflying reptiles
ammonites and belmnitesrudists
75% marsupials
planktonic foraminifers: three species survived out of >23 Nannofossils 90+% extinction
coral, bivalves, gastropods, bryozoans severely affectednot affected: most land plants??
mammals (1/9 extinction's)crocodiles, lizards, snakes, turtles survived
?most benthic organisms
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65
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% Judithian dinosaur suriving (m-l Campanian)
Were dinosaurs on the decline? Sloan’s (1986) data indicate they may have been. Yet, they became extinct at a knife’s edge (vs. Archibald’s arguments for Paleocene dinosaurs!)
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What caused the K/T extinction? causes speculated on over the years:
1) cosmic radiation due to supernova
2) sea-level change
3) change in fertility/productivity of ocean
4) magnetic field collapse
5) climate changes: CO2 Greenhouse warming (McLean, 1978)
6) Arctic spillover (Theirstein & Berger; Gartner & Keany, ‘78)
untestable
our work: no change
an effect, not a cause
no, boundary in a reversed polarity
surprisingly small climate change; our data confirms this
bad data
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Two theories have dominated thought since 1978:
Impact (Alvarez et al., 1980)
Volcanic outpouring (McLean, 1978; Officer and Drake, 1981)
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Boundary stratotype at El Kef, Tunisia
Bottom: time scale showing K/T boundary in C29r at 65.0 Ma
Kent (1972): mass extinction occurred in <0.5 m.y. (Chron C29r)
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http://www.planetary.org/html/news/Italy/whyitaly.html
Iridium is found enriched in extraterrestrial material(comets, asteroids) and deep within the Earth
Iridium Element 77
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http://palaeo.gly.bris.ac.uk/Communication/Lee/irspike.html
Iridium Anomaly at Gubbio
Extraterrestrial impact
Asteroid or comet
10 km in diameter
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Alvarez measured Ir
Expected slight enrichment due to hiatus (time gap)
Found huge Ir increase (Ir-anomaly)
Hiatus cannot explain Ir
Postulated impact of ~6-10 km asteroid
Dust blocks out sun, disrupts food chain
Meteor crater, Arizona1 km diameterImpact ~50 ka
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Global distribution of dust shuts down photosynthesis:
~3 months.
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TTAPS study (Turco, Toon, Ackerman, Pollack, and Sagan) that suggested the possibility of drastic dust-induced climatic cooling ("Nuclear Winter") as a consequence of large scale nuclear war.
Science Vol. 222, 1983, Global Atmospheric Consequences of Nuclear War, pg. 1283.
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http://www.phy.mtu.edu/apod/ap970701.html
Asteroid 253 Mathilde:'s Large Craters
Image of the subglacial eruption in Vatnajökull, Icelandhttp://www.norvol.hi.is/eruptimg.html
Impact or Volcanism?
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counter hypothesis: great outpouring of basalt lava (Deccan Traps)
caused outpouring of CO2 and warming that killed dinosaurs?cause outpouring of dust
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The Asteroid vs. Volcano Debate Dewey McLean vs. Luis Alvarezhttp://filebox.vt.edu/artsci/geology/mclean/Dinosaur_Volcano_Extinction/index.html
So Dewey is now a forgotten person in the field, or when he is remembered, it is only for a few good laughs, at the cocktail party at the end of the Deweyless meeting . . . . I’m sorry to say I see you going down the Dewey McLean lane.—Luis Alvarez, letter of intimidation, 1984
If [asked what] I thought about Dewey McLean, I’d say he’s a weak sister. I thought he’d been knocked out of the ball game … nobody invites him to conferences anymore. —Luis Alvarez, The New York Times, 19 January 1988
Operating in a science you do not comprehend, you publicly insult paleontologists. In the New York Times you abased paleontologists as "not very good scientists...more like stamp collectors," and attacked opponents by name as "weak sister," "incompetent," and "publishing scientific nonsense." —Excerpt from McLean’s Open Letter to Luis Alvarez, 1988
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Bohr (1984) first identification of shocked quartz
Bass River, New Jersey photos and identifications from Izett
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The discovery of the cause of this mass extinction event is one the of the great scientific detective stories of the 20th
century.
Walter Alvarez tells his part of the story in “T. rex and the Crater of Doom.”
Where was the impact crater?
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The cenote at Chizchén Itzá Mayan site in Yucatán http://www.athenapub.com/crater1.htm
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Transient crater 85 km diameter,caused by a 10-14 km meteor.
Overall crater three rings: peak ring 80 km130 km inner ring, and 195 km outer
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most scientist now discredit volcanic cause, favor impact
but the plot took a twist
Although foraminiferal micropaleontologists had for years shown that the extinction of planktonic foraminifera was at a knife edge (Olsson, 1960 in NJ; Premoli-Silva and Luterbacher at Gubbio; Smitat Caracava & Gubbio others at Stevns Klint), Keller and coworkers muddied the waters by claiming that the foraminiferal extinctions were stepped and somewhat gradual.
Keller has and continues to work on the Mexican sections that contained mega-tsunami deposits.
Keller argued that the highest occurrence of Cretaceous planktonic foraminifera were above the Ir anomaly in the Mexican/Texan sections especially those at El Mimbral
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Tsunamite overlying spherule bed at El Mimbral, Mexico
The direct effects of the impact of an asteroid at Chixulub resulted in intense stratigraphic mixing in the Caribbean/Gulf of Mexico region and made the record in this region debateable
The good guys from New Jersey to the rescue!
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K/T Mass Extinction, Bass River, NJ
R.K. Olsson, K.G. Miller, J.V. Browning, P.J. Sugarman, 1997Spherule layer (~6 cm thick) fallout of impact ejecta from Chicxulub Crater in Yucatan, Mexico. (incineration of terrestrial organisms and settling though the water column of 100 m beginning at ~10 minutes after impact Furthest north that a distinct layer has been identified (some 2500 km from the crater)
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Confirmation of "continuous" deposition across the K/T boundary on the Atlantic seaboard.Uppermost Cretaceous strata are overlain by lowermost Tertiary Zone P0, indicating that deposition was continuous on a scale of 10's of thousands of years.
Continuous deposition was interrupted by the abrupt fallout of the ejecta layer. Because the NJ boundary is far enough from "ground zero," it provides clear identification of the K/T boundary and its relationship to the effects of the impact, versus the Gulf of Mexico, where proximity to the impact obscures these relationships.
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Ocean Drilling Program Leg 171A, Site 1049
Similar storyPrettier coreBetter PR agent than RU
“the most significant scientific discovery of the last 20 years” NSF Geoscience Director
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Still bucking theory of how dinosaurs diedPrinceton geoscientist calls Mexican meteor idea flat-out wrong.
By Tom AvrilInquirer Staff Writer Oct. 25, 2006
Brazos, TX corehole. Keller et al. (2006) yields a surprising history:
a series of 3 spherule beds,
an overlying “event bed” of reworked spherules (sea-level fall),
an overlying 80-cm thick clay interpreted as in situ, and the K/T boundary/extinction event.
Keller et al. (2006) interpret this as one or more impacts at Chicxulubtime with no effect on life, a sea-level lowering, a sea level rise, and another “killer” impact.
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20-cm thick bed diverse, well-preserved, ammonite (including Discoscaphites iris, a marker for the top of the Maastrichtian , mollusk, and shark fauna and the mollusk genus Pinna), interpreted as autochthonous facies.
The life position of the Pinna shells argues against any transport.
The bed contains dinocyst markers indicative of the latest Maastrichtian (including Palynodinum grallator)
Overlying is a bed of clay clasts of reworked Cretaceous material including fragments and spectacular, nearly whole specimens of reworked D. ir s. We suggest these reworked clasts are the equivalent of the clay clasts found in Leg 174AX coreholes.
No spherules were reported from the outcrop section, but a modest Iranomaly (~0.5 ppb) was measured at the base of the Pinna bed
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Little climate change across the K/T boundary, k.y. and m.y. scales. Long-term climates may have warmed (note oxygen isotopic decrease), but the dramatic warming/cooling predicted were too short (< <10 k.y.) to be recorded.
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RugoglobigerinaAnomalinoides
0.70786 0.707880 0.707900 0.707920
87Sr/86Sr
Dep
th (f
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δ18O δ13C
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ies
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3
2
1, 2, 3
1
1260
1265
1270
-3-2-1 0 1 2
spherule bed
Ma
befo
re K
0
C30n
C29r
Dec
can
Trap
vol
cani
sm
Strangelove ocean
global warmingmore basaltic
weathering?
C30
nC
29r
Paleodepth Mag
neto
stra
50100
P%=80
P%=30
C30
n
65.58 Ma
Bass River, New Jersey
Miller et al Leg 174AX s mmar Fig 8
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what happened to ocean productivity?evidence for a dramatic shutdown in ocean productivity:Strangelove Ocean
benthic and planktonic δ13C difference maintained by the biologicalpump of productivity.
planktonics have high δ13C valuesdue to photosynthesis, benthics low due to organic Cregeneration in deep water
This surface to deep δ13C difference(i.e., the biological pump) disappeared in the earliest Paleocene:shutdown of primary export productivity
confirmed at Bass River
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Was the impact oblique as suggested by Schultz and D’Hondt (1996)? Simulation of impact of bullet in dolomite shown.. Distribution of the thickness of the spherule layer is consistent with this interpretation.
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Who survived and why?
Opportunistic taxa such as Guembelitria cretacea
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What other impacts and mass extinctions?
251 Ma Permian/Triassic
Great Dying
Little firm evidence
for impact
201 Ma Triassic/Jurassic
Some evidence for impact
Manicouagan slightly older
35.7 Ma Chesapeake Bay impact (80 km) &
Popagai (Siberia): Shoemaker/Levy style?
No evidence for extinctions!!!
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A spherule layer (~6 cm thick) resulted from fallout of impact ejecta from ChicxulubCrater in Yucatan, Mexico. This layer represents extremely rapid deposition (incineration of terrestrial organisms and settling though the water column of 100 m beginning at ~10 minutes after impact, smothering the bottom within 30-60 minutes). This is the furthest north that a distinct layer has been identified (some 2500 km from the crater)
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Surviorship (Emiliani, Kraus, Shoemaker 1981)PlanktonicCoccolithophoridae 13 Foraminifera 13Diatoms 31Dinoflagellates 78Radiolaria 93
NektonicAmmonoids 0Belemnoids 0Nautiloids 50Elasmobranchii 67Osteichthyes 4Ichthyosauria 0Plesiosauria 0
http://www.chez.com/extinctions/fourthemassextinctionatthektlimit.htm
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As the World Warms:
65 Million Years of Hot and Cold
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The Geologic RecorEllesmere Island`
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Ellesmere Island 50 MaMary Dawson of the Carnegie Museum with ~50 million year
old fossil of an alligator
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Is this Possible?
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Eocene Forests in the Arctic Metasequoia stumps at Axel Heiberg Is.
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Metasequoia stumps Axel Heiberg Is.
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Eocene Fossils from WyomingCrocodile Sycamore
Borealosuchus Platanus wyomingensis
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The ArcticThen
Now
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The Geologic Evidence
• Paleontological and Paleobotanical Remains
• Marine Records– Large Geographic Coverage - 70% of Earth– Net Repository of Sediments
• Continuous recorder climate change
– Heat Transport and Carbon Storage
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The Oxygen Isotope Recorder
• Stable Isotopes of Oxygen
• 16O = 99.76%
• 17O = 0.04%
• 18O = 0.20%
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Stable Oxygen Isotopes
18O/16Osam - 18O/16Ostd
δ18O ‰ = ____________________________ * 100018O/16Ostd
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Stable Oxygen Isotopes
• Paleo-temperature Equation
Τ°C =
16.9-4.2*(δ18OCaCO3- δ18Owater )+0.1*(δ18OCaCO3
- δ18Owater )2
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Stable Oxygen Isotopes
Changes in δ18Ocalcite
∆δ18Ocalcite = -0.23 * ∆T°Cfor every 1°C warming, δ18Ocalcite will decrease by 0.23‰
∆δ18Ocalcite = ∆δ18Owaterfor every 1‰ increase in δ18Owater, δ18Ocalcite will increase by 1‰
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Temperature EffectGalapagos SSTs and Coral δ18O
14
16
18
20
22
24
-4.25
-4
-3.75
-3.5
-3.25
-3
1960
1965
1970
1975
1980
1985
Year
Sea Surface Temperature °Cδ1
8 O
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The δ18Owater Effect
Ice Volume = ~ 1‰ for 100 m of sea level equivalent
Local Salinity Effect Variable, but is most pronounced near rivers/estuaries
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Sea Water δ18O = 0.0‰
Present
Glacial Ice δ18O = -40‰
Sea Water δ18O = 1.2‰
20,000 yrs. B.P.
∆Sea Level = 120 m 120m/4000m = 0.03 ∆δ18Owater = 1.2 ‰ 0.0‰ - (-40‰ x 0.03)
Mean Depth of Oceans = 4000 m δ18O = 0.0‰
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ice sheets
1070 60 50 40 30 20 0
Age Ma
Plio-Pleistocene
MioceneOligoceneEocenePaleo.
Cretaceous
possibly ice free
"ice free"
2
4
6
8
10
12
14
modern0
4
6
8
2
Modified after Miller et al.,�Paleoceanography, 2, 1-19, 1987.
Antarctic Ice Sheets
N. Hemisphere Ice Sheets
4
3
2
1
0
-1
δ18 O
äT°C
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The Hot House to Ice House Transition
• Greenhouse gases
• Thermohaline circulation
• Continental Configurations
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Greenhouse gases
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What caused the pCO2 to change?
• High pCO2 during early Eocene could have resulted from:
– Seafloor spreading changes
– Large-scale volcanism
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High pCO2 during early Eocene
• Large-scale volcanism
• Giant’s Causeway in N. Ireland
• Early Tertiary age
• Columnar Basalts
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Decreasing pCO2 after ~50 MaMt. Everest
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Decreasing pCO2 after ~50 Ma
• Collision began ~50 Ma
• Accelerated in Miocene
• Increased weathering = Atm. CO2 decrease
• CaSiO3 + CO2 = CaCO3 + SiO2
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Atmospheric pCO2
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Many myths about dinosaurs and their disappearance….
Did dinosaurs become extinct 65 million years ago or did they live on with humans,
as maintained by “creation scientists”?
H. sapiens appearred ca.100,000 years ago
Recent evidence that humans and dinosaures lived together from CN (Cartoon
Network)!
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