In other words, the age should lie between 197.2 million years and 203.6 million years.However, this error is not the real error on the date.
For example, a geologist may examine a cutting where the rocks appear as shown in Figure 1.
Here he can see that some curved sedimentary rocks have been cut vertically by a sheet of volcanic rock called a dyke.
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?
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.
It is clear that the sedimentary rock was deposited and folded before the dyke was squeezed into place.
By looking at other outcrops in the area, our geologist is able to draw a geological map which records how the rocks are related to each other in the field.
(Creationists do not agree with these ages of millions of years because of the assumptions they are based on.) Because of his interest in the volcanic dyke, he collects a sample, being careful to select rock that looks fresh and unaltered.
On his return, he sends his sample to the laboratory for dating, and after a few weeks receives the lab report.
He would say that the date represents the time when the volcanic lava solidified.