Absolute dating techniques notes

Archaeologists use many different techniques to determine the age of a particular artifact, site, or part of a site.

Two broad categories of dating or chronometric techniques that archaeologists use are called relative and absolute dating.

absolute dating techniques notes-1

This is different to relative dating, which only puts geological events in time Most absolute dates for rocks are obtained with radiometric methods.

These use radioactive minerals in rocks as geological clocks.

For example, JJA Worsaae used this law to prove the Three Age System.

For more information on stratigraphy and how it is used in archaeology, see the Stratigraphy glossary entry.

In other words, artifacts found in the upper layers of a site will have been deposited more recently than those found in the lower layers.

Cross-dating of sites, comparing geologic strata at one site with another location and extrapolating the relative ages in that manner, is still an important dating strategy used today, primarily when sites are far too old for absolute dates to have much meaning.

So, if you know the radioactive isotope found in a substance and the isotope's half-life, you can calculate the age of the substance. Well, a simple explanation is that it is the time required for a quantity to fall to half of its starting value.

So, you might say that the 'full-life' of a radioactive isotope ends when it has given off all of its radiation and reaches a point of being non-radioactive.

When ‘parent’ uranium-238 decays, for example, it produces subatomic particles, energy and ‘daughter’ lead-206.

Isotopes are important to geologists because each radioactive element decays at a constant rate, which is unique to that element.

Stratigraphy is the oldest of the relative dating methods that archaeologists use to date things.

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