Meteorite Impact Cratering on Earth: Geological and ...a0008654/mace2006/Koeberl.pdf · Meteorite...
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Meteorite Impact Meteorite Impact CrateringCratering on on Earth: Geological and Earth: Geological and
Biological ConsequencesBiological Consequences
Christian Koeberl
Dept. of GeologicalSciences, University
of Vienna, Austria
Mercury Mariner 10
Venus – 32 km crater Aurelia
Venus – 30 km crater
Mars – crater in stream
Mars – 2.3 km crater with sediments?
Mathilde and Eros
Ida and Dactyl
Eros
Callisto
Ganymede crater chain
Dione
Mimas
Comet Borelly
Comet Tempel 1
Meteor Crater, Arizona
Tenoumer, Mauritania
Ries-crater(Germany)
24 km diameter, 14.6 Ma
Impact Craters on Earth (2005)
CRITERIA FOR IDENTIFICATION OF IMPACT STRUCTURES
A. MorphologyCircular OutlineRim StructureCentral Structure
B. GeophysicsGravity MagneticsSeismics
C. Mineralogy and GeochemistryBrecciationShock MetamorphismTraces of Meteoritic Material
Meteoritic Components in Impactites: Second possibility (apart from shock metamorphism) to confirm impact origin of a geological structure or of an ejectadeposit
P TR J K T
P/TR
TR/J
P/TJ/K
A/AC/T
K/T
LEMM
L G T S A L C N H S P T A B B B BO K TC HV A A C T S C M D T Y L B P C M1 PM3RC
% e
xtin
ctio
nm
arin
e ge
nera
40302010
0
6050
70
Ma 250 200 150 100 50 0
Raup, D.M. & Sepkoski, J.J., 1982. Mass extinctions in theMarine fossil record: Science, v. 215; p. 1501-1503.Sepkoski, J.J., 1996. Patterns of Phanerozoic extinctions:a perspective from global data bases: Walliser O.H. (Editor),Global Events and Event Stratigraphy, Springer, p. 35-52.
(A. Montanari 2004)
P TR J K T
P/TR
TR/J
P/TJ/K
A/AC/T
K/T
LEMM
L G T S A L C N H S P T A B B B BO K TC HV A A C T S C M D T Y L B P C M1 PM3RC
% e
xtin
ctio
nm
arin
e ge
nera
40302010
0
6050
70
Ma 250 200 150 100 50 0
80-180 km
Giant impact structures in 250 Ma
ChesapeakePopigaiChicxulubMorokweng
Puchezh-KatunkiManicoaugan
(A. Montanari 2004)
P TR J K T
P/TR
TR/J
P/TJ/K
A/AC/T
K/T
LEMM
L G T S A L C N H S P T A B B B BO K TC HV A A C T S C M D T Y L B P C M1 PM3RC
% e
xtin
ctio
nm
arin
e ge
nera
40302010
0
6050
70
Ma 250 200 150 100 50 0
80-180 km
20-80 km
More smaller impacts
(A. Montanari 2004)
K-T boundary at Frontale di Apiro, Italy
Chicxulub impact structure - KT boundary age
Chicxulub – a 200 km diameter 65 Ma impact crater
Chicxulub Impact Structure, Mexicoca. 200 km diameter
65 Ma; K-T boundary
YAX-1 Drill Site
Yax-01 Stratigraphy(Dressler et al. 2003)
Tertiary 0.00 - 794.63 Massive, (cross-) laminated, soft sedimentary deformation
Impactites 794.63 - 894.94 Suevites, melt breccias
Cretaceous 894.94 - 1510.97 Megablocks: Limestone, dolomite anhydrite (27.4%). Impact brecciaand melt dykes + petroleum
•• Evidence of a hydrothermal system at Evidence of a hydrothermal system at ChicxulubChicxulub–– extensive evidence of hydrothermal alteration in extensive evidence of hydrothermal alteration in impactitesimpactites
•• ZurcherZurcher et al. (LPSC 34), et al. (LPSC 34), ZurcherZurcher and and KringKring (LPSC 34), Hecht (LPSC 34), Hecht et al. (LPSC 34)et al. (LPSC 34)
–– evidence of post impact fluid and organic matter mobilization inevidence of post impact fluid and organic matter mobilization inmegablocksmegablocks
•• WittmanWittman et al. (LPSC 34), et al. (LPSC 34), LüdersLüders et al. (LPSC 34)et al. (LPSC 34)–– hydrocarbonhydrocarbon--rich material in rich material in megablocksmegablocks
•• prepre--, post, post-- or or synsyn--impact?impact?•• source?source?
A. Jones 2004
Yax-1 Lithostratigraphy
K-T
Boundary
Section
Alleged crater “Bedout” near Australia
From Koeberl et al. (2004) Geology
Permo-Triassic boundary:
• No shocked quartz
• Small Ir anomaly
• PGE ratios non-chondritic
• Os isotopes terrestrial
• No He-3
• No impact – evidence for extensive volcanic influence
What Happens When an Impact Takes Place?Bolides (up to 5 MT)• Great fireworks display, no damageTunguska-class (15 MT) impact• Damage similar to large nuclear bomb (city-killer)• Average interval for whole Earth: 100 yr.• Minor risk relative to other natural disasters(earthquakes, etc.)Larger local or regional catastrophes (e.g. 10,000 MT)• Destroys area equivalent to small country• Average interval for whole Earth: 100,000 yr.• Moderate risk relative to other natural disastersGlobal catastrophe (> 1 million MT)• Global environmental damage, threatening civilization• Average interval for whole Earth: 1 million years• Major risk relative to other natural disasters