Accuracy of fossil dating methods

15 Jan

The field relationships are generally broad, and a wide range of ‘dates’ can be interpreted as the time when the lava solidified.

What would our geologist have thought if the date from the lab had been greater than 200 million years, say 350.5 ± 4.3 million years?

From his research, our evolutionary geologist may have discovered that other geologists believe that Sedimentary Rocks A are 200 million years old and Sedimentary Rocks B are 30 million years old.

Thus, he already ‘knows’ that the igneous dyke must be younger than 200 million years and older than 30 million years.

Let us imagine that the date reported by the lab was 150.7 ± 2.8 million years.

Our geologist would be very happy with this result.

Would he have concluded that the fossil date for the sediments was wrong? Would he have thought that the radiometric dating method was flawed? Instead of questioning the method, he would say that the radiometric date was not recording the time that the rock solidified.

Even different samples of rock collected from the same outcrop would give a larger scatter of results. He would again say that the calculated age did not represent the time when the rock solidified.

In fact, he would have been equally happy with any date a bit less than 200 million years or a bit more than 30 million years.

They would all have fitted nicely into the field relationships that he had observed and his interpretation of them.

by Tas Walker A geologist works out the relative age of a rock by carefully studying where the rock is found in the field.

The field relationships, as they are called, are of primary importance and all radiometric dates are evaluated against them.