A Paleogeographic Reconstruction A Paleogeographic Reconstruction of Impact Cratersof Impact Craters
April 19, 2008April 19, 2008
Catherine JuranekCatherine Juranek
Dr. David M. BestDr. David M. Best
Earth’s GeologyEarth’s Geology
4.6 billion years old4.6 billion years old
Plate tectonic movementPlate tectonic movement– Arizona has moved through 65° latitude in Arizona has moved through 65° latitude in
past 500 million years [20°S to 45°N] past 500 million years [20°S to 45°N]
174 extraterrestrial impacts174 extraterrestrial impacts
Photo courtesy of: Dr. Ron Blakey, NAU
South America & AfricaSouth America & Africa
19 impactsDensity: 1/614K mi2
8 impactsDensity: 1/861K mi2
Photos courtesy of: The Planetary and Space Science CentreUniversity of New BrunswickFredericton, New Brunswick, Canada
Asia & Australia
Photos courtesy of: The Planetary and Space Science CentreUniversity of New BrunswickFredericton, New Brunswick, Canada
27 impactsDensity: 1/635K mi2
26 impactsDensity: 1/114K mi2
North America & EuropeNorth America & Europe
57 impactsDensity: 1/167K mi2
Photos courtesy of: The Planetary and Space Science CentreUniversity of New BrunswickFredericton, New Brunswick, Canada
37 impactsDensity: 1/108K mi2
Paleomapping SoftwarePaleomapping Software
PointTrackerPointTracker– Plots current impact positions in terms of Plots current impact positions in terms of
paleolocations in past geologic timepaleolocations in past geologic time
PlateTrackerPlateTracker– Moves plates back in geologic time to focus Moves plates back in geologic time to focus
PointTracker locationsPointTracker locations
ARCGISARCGIS– Mapping toolMapping tool
ResultsResults
No correlationNo correlation
Impact Crater Analysisy = 0.0743x + 5.4407
R2 = 0.0094
-90
-60
-30
0
30
60
90
0 50 100 150 200
Diameter (km)
La
titu
de
ResultsResults
Youngest/oldest correlationYoungest/oldest correlation
ResultsResults
26 of 31 youngest are the smallest26 of 31 youngest are the smallest
Impact Crater Analysis of Sizey = 13.542x + 18.796
R2 = 0.2
05
10152025303540
0 0.5 1 1.5 2 2.5 3 3.5 4
Age (Ma)
Dia
met
er (k
m)
ResultsResults
Unprocessed data pointsUnprocessed data points– 33 craters < 10 million years old33 craters < 10 million years old– 13 craters > 600 million years old13 craters > 600 million years old
ResultsResults
Correlation: Younger – northCorrelation: Younger – north
Older - southOlder - south
Impact Crater Analysis
y = -0.0112x + 15.333
R2 = 0.015
-90
-60
-30
0
30
60
90
10 110 210 310 410 510 610
Age (Ma)
La
titu
de
ConclusionsConclusions
26 of 30 youngest craters are the smallest26 of 30 youngest craters are the smallest– Ancient Earth atmospheric effectAncient Earth atmospheric effect– Size of extraterrestrial bodies over timeSize of extraterrestrial bodies over time– Erosion of older smaller cratersErosion of older smaller craters
ConclusionsConclusions
Correlation between latitude and ageCorrelation between latitude and age
Division at 310 million yearsDivision at 310 million years62% older craters in southern latitudes and 62% older craters in southern latitudes and 85% younger craters in northern latitudes85% younger craters in northern latitudes
Possible explanation: shift of land massesPossible explanation: shift of land masses
Does not explain latitudinal differences in Does not explain latitudinal differences in
South America and AfricaSouth America and Africa
ChallengesChallenges
No record of oceanic impactsNo record of oceanic impacts
Software restrictionsSoftware restrictions– Posit processing limited to 10-600 my onlyPosit processing limited to 10-600 my only– Posits 10-100 myo rounded to nearest 10 myPosits 10-100 myo rounded to nearest 10 my– Posits 100-600 myo rounded to nearest 20 myPosits 100-600 myo rounded to nearest 20 my
Graphing and mapping optionsGraphing and mapping options
What’s in the Future?What’s in the Future?
Further AnalysisFurther Analysis
Comparison with terrestrial/marine boundariesComparison with terrestrial/marine boundaries
Spatial analysis of impacts Spatial analysis of impacts
Using nearest neighbor statisticsUsing nearest neighbor statistics
Determine random vs clustered patternsDetermine random vs clustered patterns
Africa and South America – The FITAfrica and South America – The FIT
Photos courtesy of: The Planetary and Space Science CentreUniversity of New BrunswickFredericton, New Brunswick, Canada
What’s in the Future?What’s in the Future?
Possible ConnectionsPossible Connections
Theory of antipodal focusingTheory of antipodal focusing
Astronomical implicationsAstronomical implications
Evidence of asteroid stormsEvidence of asteroid storms
Asteroids impacts as further proof of plate tectonicsAsteroids impacts as further proof of plate tectonics
QuestionsQuestions
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