He may suggest that some other very old material had contaminated the lava as it passed through the earth.
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.
The geologist may have found some fossils in Sedimentary Rocks A and discovered that they are similar to fossils found in some other rocks in the region.
He assumes therefore that Sedimentary Rocks A are the same age as the other rocks in the region, which have already been dated by other geologists.
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.
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.
He would say that the date represents the time when the volcanic lava solidified.