Karol Petreshock

1
The Eltanin Impact Event

• Karol Petreshock
• 3/4/03
• Research Mentor Dallas Abbott, LDEO
• Seminar Advisor Martin Stute , Environmental
  Science, Barnard College

2
WHY STUDY IMPACTS?

• Evolution of atmosphere and life
• Atmospheric CO2 as killing mechanism (Morgan
  2003)
• Particulate clouds and albedo (Stothers 2003)
• At least two glaciations in late Pliocene
  (Messina 2003)
• Relation to global climate data problems of today
• 165 Impact craters on Earth (Gersonde 2002)
• Its estimated that there should be 35 or more
  deep ocean impact craters present on Earth
  (Reynolds 2001)

3
THE ELTANIN LAYER AN OCEANIC IMPACT EVENT

• Location Bellinghausen sea , Centered at 537S,
  901W
• Diameter 130 Km (Glatz et all 2002)
• First discovered as iridium anomaly 1981(Kyte et
  al 1981)
• Unmelted meteoritic fragments and vesicular
  impact melt (Kyte 2002)
• Ni-Rich spherules like that of K/T Boundary
  ejecta(Gersonde 1995)
• Late Pliocene 2.15 mya to 2.6mya

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REMODELING THE EVENT

• Eltanin Asteroid hits earth in the late
  Pliocene-tsunami theory
• Possibly 200-300m high hitting southern tip of
  South America (Asphaug 2002)
• Disturbed sediments over several Km
• Ejecta blanket
• Vapor explosion meteoritic/ sedimentary debris
  into high atmosphere (Gersonde 2001)

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THESIS

• Provide a date for the Eltanin impact event
• Magnetostratigraphy
• Biostratigraphy
• K/Ar dating
• Related to late Pliocene climate change?
• Other late Pliocene impact layers, continental
  debris in cores?

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APPROACH

• 6 Eltanin Cores RC12-228, RC12-230, RC17-211, RC
  18-33 and ELT 13-4, ELT 13-3
• Barrington Magnetic Susceptibility Meter
• Sieves 150, 63, 38 microns, magnetic separation
• SEM Analysis photos and chemical composition
  provided by Dee Breger, LDEO
• Microprobe analysis-mineralogy

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PROVIDING GEOLOCAL DATES

• Magnetostratigraphy
• Magnetic polarity reversals on Earth well dated.
• Ocean sedimentation rate .2-100cm /1000 yr
• Rapid sedimentation rate due to impact
• Biostratigraphy-microfossils
• Potassium-Argon Dating-radioactive isotope K-40
  and Ar-40

• -US geological Survey
• http//wrgis.wr.usgs.gov/docs/chron/paleomag/TIME.
  HTML

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PRELIMINARY RESULTS

• Currently waiting for
• Magnetostratigraphic date
• Possible biostratigraphic and or/ K/Ar date
• Microprobe analyses
• Results obtained
• Magnetic susceptibility anomalies
• Possible meteoritic debris
• Continental impact debris

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MAGNETIC ANOMALIES

• High magnetic susceptibility in impact layer
  correlated with meteoritic debris
• Possibly correlated with iridium anomalies

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A PLUTONIC ROCK

• Figure
• SEM backscatter image of a plutonic rock
• Found in core RC 18-33
• Plagioclase feldspars and pyroxene grains
• Part of the oceanic crust

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OCEANIC IMPACT EVENTS

• Figure
• SEM Backscatter of an oceanic impact spherule
• Found in ELT 13-4
• High in Fe
• Diameter 154 µm

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CONTINENTAL DEBRIS?

• Figure
• SEM backscatter image of a microkrystite spherule
• Also found in core Elt 13-4
• Na, and K-feldspar rich
• Continental origin
• K/AR dating may be possible

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DISCUSSION

• Discovery of impact structures on the ocean
  floor a rare discovery
• Are we finding other late Pliocene impacts?
• Are continental debris result of the same event?
• Did the different types of debris form at the
  same time?
• Are there any climate changes associated with the
  date of the the Eltanin impact event?

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REFERENCES
Asphaug, E., and Ward, S.N., , (2002) Impact
Tsunami-Eltanin Deep Sea research II 49
1073-1089 Gersonde, R, Kyte, F.T.,B. Diekmann,
J Flores . Bliel, U. G. Kuhn, A. Abelmann, D.
Volker F.J. Sierro and J.A. Bostswick .(1997)
Geological record and reconstuction of th eLAte
Pliocene Impact On The Eltanin Asteroid in the
Southern Ocean Nature 357-365 Gersonde, R,.
Duetch, Alexnader Duetch, Boris Ivanoc, Kyte,
Frank (2002) Oceanic Impacts- A growing Field on
Fundamental Geoscience Deep Sea REesearch II
(49) 951-957 Gersonde, R, Kyte, F.T., Abelmann,
A. Bliel, U. G. Kuhn and F.J. Sierro.(2001)A
Late Pleistocene Asteroid Impact into the Deep
Ocean- it Documentation and Paleoenvironmantal
Application Glatz, C.A. Dallas, A. (2002)
Senior Thesis A possible Abyssal Ocean Impact
Crater University of Maine Kyte, . Frank (2002)
Composition of melt Debris From the Eltanin
impact Strewn field, Bellinghausen Sea Deep Sea
research II 49 p1029-1047 Morgan, J Phipps
(2003). Contempotaneous Mass Extinctions Are
Mantle Plume-Induced Lithosphere Gas Explosions
the Causal Link? Earth and Planetary Science
Letters 1-3 Stothers, Richard B. (2003) Volcanic
Eruptions and Climate Change Institute for Space
Studies, Goddard Space Flight Center, NASA
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ACKNOWLEDGEMENTS

• Dallas Abbott
• Martin Stute
• Dee Breger
• Lloyd Burkle
• Dennis Kent
• Charles Mandeville
• Sydney Hemming