Contextual Inference: Time

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Topic 8 Contextual Inference Time Text Chapter 7
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Dimensions of Inference
Contextual Dimensions
1. formal
2. spatial
3. temporal
Cultural Dimensions
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3 TEMPORAL
inference based on chronology
Assumption variation through time will be even,
unless other factors intervene
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Temporal Context what are we dating?

• Direct dates the artifact itself

• Indirect dates the context

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Relative
one artifact or level is older than another
Chronometric
age in calendar terms
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RELATIVE DATING
1. Stratigraphy
2. Geochronology
3. Seriation
4. Sequence Comparison
5. Obsidian Hydration
6. Bone Chemistry
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1. Stratigraphy
assumption Law of Superposition
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2. Geochronology
geological strata
e.g., Olduvai Gorge
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3. Seriation
dating based on changes in style

• stylistic (similarity)

• frequency (pattern)

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Stylistic (similarity) Seriation

• based on similarity in style

• measured by variables or by types

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Frequency (pattern) Seriation

• based on assumed pattern of stylistic variation
  through time

increase - peak - decrease
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4. Sequence Comparison
cross-dating
comparing unknown sequence to known
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5. Obsidian Hydration
absorption of water by volcanic rock
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6. Bone Chemistry
e.g., fluorine nitrogen
Piltdown hoax
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CHRONOMETRIC DATING
statistical approximation

• Radiometric

• Trapped Energy

• Non-Radiometric

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Radiometric
decay of radioactive materials
1. radiocarbon
2. potassium / argon
3. fission-track
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1. Radiocarbon 14C
organic material only
75,000 - 200 ya
(yayears ago)
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2. Potassium / Argon (K/A)
volcanic rock only
2 billion - 100,000 ya
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3. Fission-track
rock with 238U
2 billion - 150,000 ya
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Trapped Energy
1. electron spin resonance
2. thermoluminescence
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1. Electron Spin Resonance
teeth shell
1 million ya - 10,000 ya
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2. Thermoluminescence
fired clay fired chert
100,000 ya - present
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Non-Radiometric
1. dendrochronology
2. archaeomagnetism
3. aspartic / amino acid racemization
4. varve dating
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1. dendrochronology
preserved wood
10,000 ya - present
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2. Archaeomagnetism
stable fired clay
5,000 ya - present
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3. Varve Dating
meromictic lakes
10,000 ya - present