Absolute dating

Absolute dating in archaeology

  • Created by: Emma
  • Created on: 26-05-10 21:17


  • Most acurate form of chronometric dating
  • early cells- early in annual growth
  • late wood- late in annual growth
  • produces visible rings until the bark
  • the rings are wider in good conditions e.g heavy rainfall
  • rings a narrower where there are bad conditions e.g. little rainfall.


  • Sapwood discarded by carpenters can hold up to 16 rings, making the date an estimate.

site example

  • central slump in sea henge (april/june 2050 BC)
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Radio Carbon Dating ( C-14)

  • All living things absorb several types of carbon from the atmosphere
  • 1% of this is unstable and decays at a known rate.
  • by comparing the amount of carbon remaining with the the carbon isotopes(don't decay) when in organic sample we can work out how much C14 has decayed.
  • this indicates how long it has been since decaying began.


  • amount of carbon in the atmosphere has varied over time,leading to many dates being underestimated by up to 1000 years
  • due to this results have to also be calibrated
  • carbon in sea is 400 years older than that on land.


  • bone, shell, plant remains, charred bone, wood samples, twigs, nuts from trees

200-10000 years most reliable

40,000 less reliable.

80,000 pushing it

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thermoluminescence (TL)

  • radiocarbon decay in quartz crystals found in clay builds up an electric charge at a known rate which is then released as light when crystals are heated .
  • when crystals are heated the 'clock' is re-set.


  • flash of light energy released by a given weight of a ceramic sample can be measured in a lab to calculate the number of years since pottery was fired.


  • less acurate than C14 and can give faluse readings die to radiation from soil or if firing was at a low temperature


  • glass and burn flint or stone

400,000 years to present day

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Optically Stimulated Luminescence (OSL)

  • electrons from decaying radio active elemnts are trapped in crystals/ quartz.
  • when stimulated with light the electrons free themselves giving off luminescence(light energy) in the process.
  • amount released is used to date the last 'clock setting event'
  • measures the time since sediment was last exposed to sunlight/ heated.
  • calculated with more accuracy than TL

50- 1 million years

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Potassium Argon dating

  • as potasium in rock crystals decay it produces argon gas at a known rate
  • measuring amount in a lab provides the date that crystals are formed
  • used in volcanic regions to date layers of rock which sandwich human remains.
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Amino acid racemization

  • chemical structures of amino acids found in all living things change slowly over time at a known rate


  • can vary with climate


  • bones
  • teeth
  • shells


  • ostrich eggs on Paleolithic sites in Africa

1000-1 million years

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Fluorine dating

  • buried bones take up fluorine from surrounding soils.
  • the amount of fluorine that it absorbs is proportional to ammount in the sorrounding deposit and the length of time that the bone has been burried


  • pitdown man
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  • earths magnetic field changes over time. when iron oxide is heated to 600c and then cools it record the magnetic field at that time.
  • variations in earth field have been calculated which enables the data to be established.


site mustn't be disturbed.


  • ceramics
  • lava
  • hearth
  • kiln- containing iron oxide

up to 50,000 years

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Electron Spin resonance (ESR)

  • electric charge build up at a known rate in some crystal structures. time since process begin can be calculated by measuring the charge.


  • works best in dry environments


  • teeth enamel
  • shells
  • calcite depostis in caves

50,000- 1 million years

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Fission track dating

  • uranium decays regularly though fission (SPLITTING) which releases energy and damages crystalline structures leaving a TRACK.
  • tracks and holes then counted to estimate the time the process of decay has taken


  • 10% error margin


  • glass
  • obsidian (burnt)
  • heated stones(containing uranium)
  • sites sandwiched between volcanic layers

10,000 - several million years

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Varve Analysis

  • stems flowing into still bodies commonly deposit layers (varves) or summer silt and winter clay through the year.
  • autumn/winter- dark colour due to dead vegetation
  • reast of year- light colour
  • this creates annual layers -like tree rings
  • changing climate will lead to changing deposits, which can be cross referenced over large areas

up to 12,000 years

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