The field relationships, as they are called, are of primary importance and all radiometric dates are evaluated against them.
For example, a geologist may examine a cutting where the rocks appear as shown in Figure 1.
His geological cross-section may look something like Figure 2.
(They conveniently forget to mention that the tree ring chronology was arranged by C14 dating.
The scientists who were trying to build the chronology found the tree rings so ambiguous that they could not decide which rings matched which (using the bristlecone pine).
In fact, 14C is forming FASTER than the observed decay rate.
This skews the 'real' answer to a much younger age.
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.