evidence for impact generated mass extinctions
TRANSCRIPT
Evidence for Impact Generated Mass Extinctions
The Cratering Record
The Moon
Impact Craters on the Earth
From Grieve 1993
Barringer “Meteor” Crater, Arizona
Impact History of the Earth and Moon
Sleep et al., Nature 342 139 (1989)
Impact Event at the 65 myr old Cretaceous/Tertiary Boundary
Some Consequences of the KT Impact
• Severe ground shaking, Tsunami
• Injection of dust into stratosphere, global darkness global fires
• Atmospheric injection of CO2 from carbonate target, global warming
65 myr old Cretaceous-Tertiary Boundary
Iceland
Some Consequences of Volcanism
• Release of toxic pollutants, sulfur, CO2, fluorine, chlorine
• Environmental degradation of ecosystems and habitats (e.g. acid rain, ocean anoxia)
• Atmospheric injection of volcanic CO2 from eruptions, global warming
Shocked Quartz, Microspherules, Tektites
Soot from the 65 myr old K/T Boundary Clay
Stevns Klint, Denmark
Buckminsterfullerene
Kroto et al., Nature 318, p. 162 (1985)
Kratschmer et al., Nature 347, p. 354 (1990)
Fullerene ‘Bucky’ Generator
Extraction Protocol for Fullerene Carbon
Noble Gas Incorporation in Graphitic Smokes
E. K. Olsen, T. D. Swindle, J. A. Nuth, F. Ferguson, LPSC XXXI, 2000
Sublimation of Fullerenes
Toluene extractedfullerene from Swindleresidue. Fullerene canalso be sublimed directlyfrom the soot
‘Window Mechanism’ for the encapsulation of atoms inside thefullerene cage.
A. B.
(A) C60 or buckminsterfullerene. (B) C60 with an atom inside.
(C) C60 with an atom inside and with a bond broken (open window).(D) Same molecule as (C) but with the atom moving out through thewindow.
C. D.
Don Davis
Fullerenes at the 65 myr old KT Boundary
Soot from the 65 myr old K/T Boundary Clay
Heymann et al., Science 256, 545 (1994)
The Origin if Fullerenes at the KT Boundary
Possible scenarios for fullerenes in the KT impactdeposits are:
(1) the fullerenes were formed on impact
(2) the fullerenes were already present and survived theimpact or
(3) Fullerenes in the KT sediments were formed as a result of global wildfires triggered by the impact event(Heymann et al., Science 1994)
KT Fullerene Results
Fullerenes isolated from several KTB sites worldwidecontained trapped helium that was similar tosome meteorites and interplanetary dust particles
The Great Dying
Fullerene Results from the PTB
The helium concentrations for both the Meishan, China and Sasayama, Japan PTB sediments are similar to the “planetary” component in meteorites (~1.4 x 10-4)
Measured 3He/36Ar also resembles the “planetary” ratio(as opposed to a solar gas reservoir)
The 40Ar/36Ar ratios are a mixture of air and “planetary”(75% to 25%) with an atmospheric 38Ar/36Ar ratio, alsoconsistent with a carbonaceous chondrite (e.g. Murchison)
Noble Gas Results for PTB
Impact TracersCarbon Isotopes
Carbon ‘Soot’
Iridium
Chixculub Crater
Shattercones
Fullerenes
Microspherules
Shocked Quartz
The Permian-Triassic Boundary in Antarctica
Coal Sac Bluff, Queen Alexandra Range
Fullerenes w/trapped Noble Gases at Graphite Peak, Antarctica
Impact Site for the PTB?