ANT100Y1 Lecture Notes - Lecture 7: Simple Features, Carbon-12, Upper Paleolithic
05/11/2015
Lecture 2
Geomagnetism
• looks at large-scale reversals of north-south polarity
• used only occasionally, to confirm other dating methods
• good for archaeology
Radiocarbon Dating
• not useful for anything over 50,000-40,000 years-old
• Willard Libby 1949
• A radiometric dating method, based on radioactive decay of isotopes
• Isotopes are differet fors of a eleet with differet atoi weights (differet
numbers of protons and neutrons in the nucleus)
• Some isotopes are stable, others unstable—they gradually decay, changing into stable
elements (for example, after death—used to tell how long its been since someone died)
• Can be used to sate objects, if you know
Original amount of isotope
Amount retaining at present
Rate of radioactive decay
Rate of decay is measured by a half-life
• Most common form of carbon is CARBON 12 (stable)
• Cosmic radiation produces unstable CARBON 14
• Plants absorb C14 in carbon dioxide during photosynthesis; eaten by herbivores and
carnivores
• Continually replaced during life until death
• C14 is unstable, decays gradually
• Half-life = 5730 years
• As C14 decays (converting to N14), it releases radioactive beta particles
• Geiger counter used to measure beta emissions
• Allows estimate of amount of C14 left in sample
Accelerator Mass Spectrometry (AMS), Improved Radiocarbon dating
• Conventional dating—measuring beta emissions—requires about 5gm pure carbon =
10gm charcoal,
• Limitations of all C14 dating
Contamination before sampling; carbon in groundwater, modern plant roots,
etc.
Contamination during sampling—cardboard labels, glue, mould, etc.
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05/11/2015
Sample is older than context (such as old wood used to build a house could have
been reused for centuries—the date would be of the tree when it died)
Some materials contain ancient carbon (such as sea mammal bone, seals,
mammals, marine fish eat other fish that also eat carbon, and so can come up
over 300 years old)
Maximum date about 50,000 years
Potassium-Argon Dating (K40-Ar40)
• Another form of radiometric dating
• Used to date volcanic rock, not artifacts or other human products
• Minimum age 5000 years, no maximum age (half-life = 1,330,000,000 years)
• Used to date first hominins in Africa
• Useful in regions with lots of volcanism
***with all dating methods, demonstration of association is key
• Generally, try to use at least two methods to confirm date
Ex. stratigraphy + C14 method
• Every dating method has problems and limitations
***AMS dating has freed archaeologists to date things more directly
Analysis and Interpretation
5 MAIN CLASSES OF DATA:
1. Artifacts
Any object made or modified by people
Archaeologists specialize in particular types (such as stone tools,
ceramics/pottery)
FORM (size and shape)
TECHNOLOGY (how it was made)
2. Ecofacts
Natural object used or affected by people
Zooarchaeology/Archaeozoology is the study of animal remains in the
archaeological record; domestication, hunting patterns, etc.
Palaeoethnobotony is the study of plant remains in the archaeological record
Ex. seeds, pollen, phytoliths (silicon dioxide nodules from plant cells)
3. Features
Non-portable material remains
Midden = a concentrated area of refuse
Simple features
Ex. hearths, burials, storage pits, post holes
Complex features
Ex. buildings (houses, temples, granaries, etc.)
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find more resources at oneclass.com
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ANT100Y1 Full Course Notes
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Document Summary
Geomagnetism looks at large-scale reversals of north-south polarity: used only occasionally, to confirm other dating methods, good for archaeology. Radiocarbon dating : not useful for anything over 50,000-40,000 years-old, willard libby 1949, a radiometric dating method, based on radioactive decay of isotopes. Accelerator mass spectrometry (ams), improved radiocarbon dating : conventional dating measuring beta emissions requires about 5gm pure carbon = 10gm charcoal: limitations of all c14 dating . Contamination before sampling; carbon in groundwater, modern plant roots, etc. Contamination during sampling cardboard labels, glue, mould, etc. Sample is older than context (such as old wood used to build a house could have been reused for centuries the date would be of the tree when it died) Some materials contain ancient carbon (such as sea mammal bone, seals, mammals, marine fish eat other fish that also eat carbon, and so can come up over 300 years old)
