Archaeological Dating Methods

Types of dating methods

Relative Dating and Absolute dating

Relative Dating

Dating method based on ordering or sequencing archaeological data

Absolute Dating

Dating method based on absolute time-scale

Types of relative dating 

stratigraphy, seriation, typologies, environment sequence 

Stratigraphy

observed layering of strata, or the layers of matrices, and features

• Strata based on soil properties or cultural material in specific stratum 

• Studies the temporal and functional meaning of the observed strata

• Strata create sequences of deposition, not age of materials 

  • Artifacts in layer could be associated with layer but could be intrusive 

Strata

based on soil properties or cultural material in specific stratum 

Laws of superposition (stratigraphy)

The sequence from the bottom to top reflects the order of deposition from earliest to latest

Laws of association

Artifacts found in a strata are associated with the time period of that strata 

Laws are ____ unless there has been disturbance

universal

Types of Disturbances

• Disturbances can make it challenging to understand site stratigraphy and impact archaeological dating 

  • Natural 

  • Cultural

  • Bioturbation

Seriation

• Relative dating method

• Seeks to order artifacts based on cultural regularities in a series 

  • Adjacent members in the series are more similar than members farther apart in the series

Seriation is also

• Based on patterns of style through time 

  • Need to control spatial variation

• Traits can be placed in chronological order based on frequency

  • Based on the assumption that stylistic frequency increases and decrease over time

Typology

• Group of archaeological data defined by particular artifact traits 

• Typology determined by the observer 

• Uses principles of seriation to determine a spatial and temporal framework 

Relative Dating: environmental sequences

• Climatic fluctuation related to glacial (Cold) and interglacial (Warm) periods

  • Ice Cores 

    • Counting ice sheets 

  • Deep-Sea Cores 

    • Foraminifora, microscopic shells,  help to identify sea temperature  

Absolute Dating Methods

Used to establish a calendrical age range

• Non-radiometric and Radiometric

Does not measure the radioactive decay

non-radiometric

Non-radiometric

dendrochronology

Measures the radioactive decay

radiometric

Radiometric

• Radiocarbon dating 

• Potassium argon/Argon-Argon dating

• Uranium series 

Dendrochronology

• Counting tree rings as method to identify age 

• Best method of directly dating wood

• Effective in areas where there is consistent rainfall and growth patterns

• Highly effective to calibrate radiocarbon dates

Radiometric dating methods

• Based on measuring radioactive decay of different elements: the transformation of unstable radioactive isotopes into stable elements

To establish dates we calculate the _____ of isotopes: the period required for one half life of the unstable atoms to decay and form a stable daugther isotope 

half-life

can you predict the full amount of radioactive decay?

no you cant 

• you can measure decay within a given time with high statistical probability 

Radiocarbon dating 

• First dating method to link relative sequences to absolute dates on worldwide basis

• Dating the half-life of carbon 

  • Based on principle of radiocarbon cycle

  • proportion of C14(Living) and C12  

• Date carbon based materials up to 50 000 ya

Radiocarbon cycle 

• All living things made of Carbon (C 12)

• Carbon (C 12) enters in atmosphere, zapped by sun rays, becomes  (C 14) 

• Carbon (C 14) enters back in atmosphere, becomes CO2 and consumed by plants 

• Animals eat plants 

• Once animal or plant is dead, C14 begins to decay 

• Archaeologists measure decay! 

Potassium Argon - argon argon

• Half-life of type of potassium that forms into Argon 

• 50 KYA - 5 MYA

  • Can date more recent samples

• Dates samples from geological formations that have potassium 

  • Obsidian created through volcanic activity

• Method improved by Argon-Argon dating

  • Does not require large sample

Argon-Argon dating allowed archaeologists to date what?

Pompeii eruption

Uranium seires

• Half-life of a Uranium isotopes 

• 10-75 KYA

• Deposits in caves, springs, lakes,