Example: wood found in a grave of known age by historically reliable documents is the standard for that time for the C14 content.
This standard content of C14 can then be used for wood not associated with a historically documented date.
And this big sequence is then used to 'correct' C14 dates. (3.) Even if the rate of decay is constant, without a knowledge of the exact ratio of C12 to C14 in the initial sample, the dating technique is still subject to question.
(4.) Traditional 14C testing assumes equilibrium in the rate of formation and the rate of decay.
So they tested some of the ring sequences by C14 to put the sequences in the 'right' order.
Once they did that they developed the overall sequence.
Despite this she continually uses the c14 dates to create 'absolute' chronologies.
She says this is ok so long as you take into account the correction factors from dendrochronology.
For object over 4,000 years old the method becomes very unreliable for the following reason: Objects older then 4,000 years run into a problem in that there are few if any known artifacts to be used as the standard.However, as with any dating technique there are limits to the kinds of things that can be satisfactorily dated, levels of precision and accuracy, age range constraints, and different levels of susceptibility to contamination.Radiocarbon dating is especially good for determining the age of sites occupied within the last 26,000 years or so (but has the potential for sites over 50,000), can be used on carbon-based materials (organic or inorganic), and can be accurate to within ±30-50 years.Regardless of the particular 14C technique used, the value of this tool for archaeology has clearly been appreciated.Desmond Clark (1979:7) observed that without radiocarbon dating "we would still be foundering in a sea of imprecisions sometime bred of inspired guesswork but more often of imaginative speculation." And as Colin Renfrew (1973) aptly noted over 30 years ago, the "Radiocarbon Revolution" transformed how archaeologists could interpret the past and track cultural changes through a period in human history where we see among other things the massive migration of peoples settling virtually every major region of the world, the transition from hunting and gathering to more intensive forms of food production, and the rise of city-states.