Ancient Artifacts to Martian Meteorites: Radiocarbon Dating with a Particle Accelerator - PowerPoint PPT Presentation

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Ancient Artifacts to Martian Meteorites: Radiocarbon Dating with a Particle Accelerator

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Title: Ancient Artifacts to Martian Meteorites: Radiocarbon Dating with a Particle Accelerator


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Ancient Artifacts to Martian Meteorites
Radiocarbon Dating with a Particle Accelerator
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Production cartoon
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libby counter
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magnetic mass separation
MASS SEPARATION
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Pioneering studies in AMS
  • Nelson, D.E., Korteling, R.G., and Stott, W.R.
    1977. Science 198, 507-508.
  • Bennett, C.L., Beukins, R.P., Clover, M.R.,
    Elmore, D., Gove, H.E., Kilius, L., Litherland,
    A.E., Purser, K., and Sondheim, W.E. 1977.
    Science 198, 508-510.
  • Muller, R.A. 1977. Science 196, 489-494.

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Accelerator Mass Spectrometer (AMS)
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14C sample processing wood, charcoal, textiles,
carbonates, bone, etc.
  • PRETREATMENT HCl - NaOH - HCl - water
  • COMBUSTION cleaned sample O2 (900oC) ? CO2
  • GRAPHITIZATION CO2 Zn ? CO ZnO
  • CO ? C (graphite) on iron powder
  • graphite ? instrument

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Accelerator Mass Spectrometer (AMS)
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14C age calculation
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Total Error
For a modern sample, ?statistics 0.002 So,
?total 0.0036 (29 years)
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Sample background
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14C age limits
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NSF-Arizona AMS
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14C age calculation
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Tree ring calibration
  • Dendrochronologists have accumulated a continuous
    record of tree rings of known age back to about
    12,500 years before present.
  • These include pine and oak trees from North
    America and Europe, among others.
  • Radiocarbon ages of wood from tree rings of known
    age have been replicated from a number of
    laboratories around the world with high
    precision.
  • ?(Age) ? 0.2 or ?16 years
  • Plots of true age (from tree rings) vs.
    radiocarbon age allow one to calibrate
    radiocarbon ages.

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Calendar Years from Tree Ring Counting
Wiggle-matching band patterns From many trees to
yield a Composite chronology
1 Year
Early Wood
Late Wood
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Tree ring calib
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AMS samples pie chart
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AAR vs AMS
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Clovis/color
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SierraVista
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METEORITES
  • Stony meteorites _at_ 50 oxygen by weight
  • As meteorites travel through space they are
    bombarded by galactic cosmic rays, producing
    radiocarbon 16O p(high energy) ? 14C 3p
  • Travel times of meteorites through space are 106
    to 108 years and equilibrium 14C concentrations
    are achieved.
  • Upon landing on earth, meteorites are shielded
    from cosmic radiation by the earths atmosphere
    and the 14C content of the meteorite decays with
    a half-life of 5730 yrs.
  • By comparing the 14C content of a fallen
    meteorite with the known saturated activity in
    space, the time since it landed can be deduced.

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Martian meteorite
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ALH 84001
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U-Th text
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saturated activity
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Collecting speleothems
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speleothem
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Speleothem calibration
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U/Th dated corals
U/Th dated stalagmites Layer counted sediments
Tree Rings
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Shroud of Turin
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SHROUD OF TURIN
  • First displayed in Lirey, France in the 1350s.
  • Later passed into the hands of the Dukes of Savoy
    and then to the Catholic Church.
  • Brought to Turin in 1578 and placed in the Royal
    Chapel of Turin Cathedral in 1694.
  • In 1988 samples were taken from the Shroud for
    AMS 14C dating.

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Shroud sample
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Shroud results
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Shroud calibration and nature
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scroll
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nefertiti
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Duck decoy
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Vinland Map
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Results of Arizona studies of the Vinland Map
  • Radiocarbon age
  • 46727 radiocarbon yrs BP
  • Calibrated age range
  • 1423-1445 AD (1 sigma, 68.3 confidence)
  • 1411-1468 AD (2 sigma, 95.4 confidence)

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Raphael
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Post bomb curve
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Miami museum
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Cosmogenic isotopes
  • ISOTOPE half-life (yrs)
  • 14C 5730
  • 36Cl 3.0 x 105
  • 26Al 7.2 x 105
  • 10Be 1.6 x 106
  • 129I 1.6 x 107

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Lab in action photo
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Stopping power vs Energy
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dE/dx detector
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Proportional counter for 14C measurement
  • The counter is filled with gas (CO2 or C2H2).
    Wait for 14C nuclei to decay and detect
    electrons. One of the sample will decay in 80
    years.
  • Modern samples give about 15 dpm g-1C. For a 1
    (80 yrs) measurement you need 10,000 counts (11
    hours).

14C ? 14N e-
anode
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Dating studies
  • Skelton et al (1965) linked the map to the
    Council of Basle (1431-1449AD).
  • McCrone (1974) reported this must be a forgery
    due to the presence of anatase (titanium
    dioxide).
  • Cahill et al. (1987) showed the anatase present
    at only trace levels.
  • Donahue et al. (2002) reported that although the
    parchment appears to be coated with a recent
    material, the cleaned parchment gave a medieval
    age.

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Uranium- Thorium dating
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Cutting the samples
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Shroud calibration
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Rubber ball
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cosmogenic radioisotopes
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1948 - 1952
  • F. Ajzenberg-Selove
  • Stanley Bashkin
  • Ray Benenson
  • Corny Browne
  • Don Craig
  • Doug Donahue
  • Ross Douglas
  • Aaron Galonsky
  • Gerson Goldhaber

Truman Hunter Herb Jackson Virgil Johnson Keith
Jones Richard Laubenstein Mollie Jean
Laubenstein Marc McEllistrem Bob Williamson
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