Why is radiocarbon dating only rarely applied in geological work
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.A fossil that is significantly contaminated with younger material will produce a calibration that is too young even if a lag time might partly offset the error.In the example below, the calibration is too young because a C age reflects not only the age of ancient plant remains but also more recent contaminants.The most reliable ages are from fossils that got their carbon directly from the atmosphere.If you want accurate results, the bottom line is that the C ages are obtained and the bad apples reveal themselves.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.
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.
Storage on land, prior to transport and later deposition, may not cause an error in the age of the fossil, but there will be a potential mismatch or lag between the age of the fossil and the younger varve in which the fossil was eventually deposited.
Lag times in glacial or periglacial environments may be significant because of the ability of cold environments to protect plant fossils on land from decay for long periods of time.
The calibration of a glacial varve record, series, or chronology is accomplished by applying numerical or calendar ages to existing varve numbers.
The true calendar age of a varve sequence can be obtained in areas where varves can be counted back from the present in modern lakes with varve deposition.
These ages will result in a calibration that is too old and often well outside the uncertainties associated with the precision of C measurement.