How to date a fossil using radiometric dating
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.
He may suggest that the rock contained crystals (called xenocrysts) that formed long before the rock solidified and that these crystals gave an older date.
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.
He would say that the date represents the time when the volcanic lava solidified.
Such an interpretation fits nicely into the range of what he already believes the age to be.
He may suggest that some other very old material had contaminated the lava as it passed through the earth.
Or he may suggest that the result was due to a characteristic of the lava—that the dyke had inherited an old ‘age’. 200.4 ± 3.2 million years) implies that the calculated date of 200.4 million years is accurate to plus or minus 3.2 million years.
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.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.It relates only to the accuracy of the measuring equipment in the laboratory.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, there is a whole range of standard explanations that geologists use to ‘interpret’ radiometric dating results.