1/27 notes

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• 1/27 notes
• Group 1 Meet at Tree-Ring Lab 930
• (west stadium 104)
• Group 2 Meet at RadioCarbon Lab 930
• (Physics Atmo Main Lobby)
• Start tree-ring crossdating activity today
• Due next Thurs Feb 3
• Reading for dating lecture
• E Haury HH-39 Recollections of a Dramatic
  Moment in Southwestern Archaeology
• Focus on bridging the gap

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• "Everything which has come down to us from
  heathendom is wrapped in a thick fog it belongs
  to a space of time we cannot measure. We know
  that it is older than Christendom, but whether by
  a couple of years or a couple of centuries, or
  even by more than a millenium, we can do no more
  than guess.Rasmus Nyerup, 1802
• Emil Haury Recollections (Reading)
• descriptions of ruins, study of pots and pans,
  and efforts to recreate ancient history were
  sterile without a valid sense of time.

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Dating Terms

• Precision
• Accuracy
• Labels--
• 500BC
• 2500b.p.
• but AD 2008

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Know what is being Dated !

• Dated Event
• Tree-ring growth
• Decay of element/death of organism
• Movement of magnetic pole
• Target Event
• Building construction
• Site occupation
• Last use of fireplace (hearth)

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Dating Techiques

• Relative (before, after, earlier, later)
• Stratigraphy (think layer cake Grand Canyon)
• Seriation Changes in style (think changes in car
  bodies video games, etc)
• Both used extensively in Southwestbut must be
  calibrated against some known date

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• Dating Techniques (Pertinent to SW)
• Absolute
• Radiometric
• Archaeomagneticburned things 500B.C.
• 14C for recent organic material 35,000 bp
• both calibrated with Dendrochronology
• Dendrochronology
• Trees, about the last 2000 years
• Crossdating outside activity 1
• Due Tuesday

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Archaeomagnetic Dating
Hearths, Burned clay walls, etc. (not movable
objects)
Southwest
From Michaels, J. 1973
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14C (Radiocarbon dating) Dates Organic
Stuff (not rocks)

• Wood, charcoal
• Cloth (Shroud of Turin, etc.)
• Bone and antler
• Peat, organic-bearing sediments
• Marine and fresh-water shell
• Carbonate deposits
• Caliche (CaCO3)
• UA has a GREAT Radiocarbon lab

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Radiocarbon Dating

• 14C is formed in the upper atmosphere through
  the effect of cosmic ray neutrons upon 14N. The
  reaction is
• 14N n 14C p
• (Where n is a neutron and p is a proton)
• The radiocarbon method is based on the rate of
  decay of the radioactive or unstable carbon
  isotope 14

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Carbon

• 12C stable, 98.9 of all Carbon
• 13C stable, 1.1 of all Carbon
• 14C radioactive, 1 x 10-10 of all Carbon

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Think ratios--- ½, ¼, etc.
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14C Dating Errors

• Variations atmospheric 14C production
• Natural over time due to solar
• Post bomb
• Postdepositional contamination
• percolating groundwater
• incorporation of older or younger carbon
• contamination in field or laboratory
• Determination of half-life
• Now 5730 40 years

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• Andrew Ellicott
• Douglass
• 1867 - 1962
• Astronomy
• 1894 Flagstaff to build Lowell Observatory
• Sunspots a lifelong interest impact on Earth
  climate?

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• 1906 Tucson as UA Professor of astronomy,
  physics, geography, dean, acting president
• Founder of LTRR - 1938
• 1929 Natl. Geog. Magazine
• Secrets of the SW Solved by Talkative Tree Rings

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Douglass

• 1904 observed a ring pattern in Flagstaff
  sawmill logs
• 1904, 1902, 1899, 1896, 1894, and 1891 were
  narrow
• Compared, confirmed other Flagstaff trees oral
  history
• Flagstaff chronology
• 1911 Prescott trees confirmed the pattern
• Climate caused? Solar variation?

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Long Chronologies

• SW 2000-3000 years
• Bristlecone pine of West
• Oldest tree known was 4900 years old
• Chronology now at 8700 years
• Europe
• Oak chronologies at 10,000 years
• Composed of short segments

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The 2nd Radiocarbon Revolution (1960s)
Another GREAT discovery at the UA
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• Outside Activity Skeleton Plotting
• Access through our course web page
• http//www.ltrr.arizona.edu/skeletonplot/
• introcrossdate.htm
• Read explanatory pages
• Try skeleton plotting for yourself
• When you succeed
• alt-print screen
• Edit-Paste (or Paste Special) into a word
  document
• Fill in page with text
• Insightful observations on crossdating
• MUST HAVE Your plot, Master plot, Answer box
  (begin/end year), comments
• Due next Tuesday 2/2

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Some Tips
Answer box
core
Master Plot
Your plot

• Your homework should look like this paragraph
  here , blah, blah

WARNING Easy to cheat, Easier to See if you
cheated!!!
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Steps Plotting
Mark ONLY small rings on graph paper From bottom
up
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Steps Looking at the Master
Align Your graph paper with the Master so Every
Ring Matches