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Techniques of recovery include: Data collection and analysis is oriented to answer questions of subsistence, mobility or settlement patterns, and economy.
The age of the pottery, in principle, may then be determined by the relation Age = Accumulated dose / Dose per year Although conceptually straightforward, TL has proven to to be far from simple in practice.
The most commonly used chronometic method is radiocarbon analysis.
It measures the decay of radioactive carbon (14C) that has been absorbed from the atmosphere by a plant or animal prior to its death.
In areas in which scientists have tree rings sequences that reach back thousands of years, they can examine the patterns of rings in the wood and determine when the wood was cut down.
This works better in temperate areas that have more distinct growing seasons (and this rings) and relatively long-lived tree species to provide a baseline.
These strata are often most visible in canyons or gorges which are good sites to find and identify fossils.
Stratigraphic dating is based on the principle of depositional superposition of layers of sediments called strata.
They do not, however, give "absolute" dates because they merely provide a statistical probability that a given date falls within a certain range of age expressed in years.
Chronometric methods include radiocarbon, potassium-argon, fission-track, and thermoluminescence.
This number is usually written as a range, with plus or minus 40 years (1 standard deviation of error) and the theoretical absolute limit of this method is 80,000 years ago, although the practical limit is close to 50,000 years ago.
Because the pool of radioactive carbon in the atmosphere (a result of bombardment of nitrogen by neutrons from cosmic radiation) has not been constant through time, calibration curves based on dendrochronology (tree ring dating) and glacial ice cores, are now used to adjust radiocarbon years to calendrical years.