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