Why is radiocarbon dating only rarely applied in geological work
Unfortunately, there is no way to directly determine the span of a lag time for a single fossil.
However, there are some general guidelines in choosing material for dating that may help remove or diminish some uncertainties regarding the lag time problem.
By far the most common numerical ages applied to varve sequences are from radiocarbon (C ages it is still the most accurate calibration data available in most lacustrine environments where glacial varves occur.
As a result there can be a lag between the time the organism was alive and when it was finally transported to the lake and deposited with lake sediment.
One must also remember that all plant fossils are in some state of decay, which can introduce contaminants.
Most often contamination is the result of younger material added to a sample in a particular field setting.
Shown below is what happens when a fossil that has acquired old carbon during its lifetime is used to calibrate a varve chronology.
C age of a fossil, as a result of the living organism incorporating old carbon, are not appropriate for varve calibration.
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This gives us the impression that all but a small percentage of the dates computed by radiometric methods agree with the assumed ages of the rocks in which they are found, and that all of these various methods almost always give ages that agree with each other to within a few percentage points.