Why do archaeologists use relative dating
These artifacts are referred to as "residual" or "residual finds".
It is crucial that dating a context is based on the latest dating evidence drawn from the context.
Cuts represent actions that remove other solid contexts such as fills, deposits, and walls.
An example would be a ditch "cut" through earlier deposits.
Relative dating methods are unable to determine the absolute age of an object or event, but can determine the impossibility of a particular event happening before or after another event of which the absolute date is well known.
When archaeological finds are below the surface of the ground (as is most commonly the case), the identification of the context of each find is vital in enabling the archaeologist to draw conclusions about the site and about the nature and date of its occupation.
One issue in using stratigraphic relationships is that the date of artifacts in a context does not represent the date of the context, but just the earliest date the context could be.
If one looks at the sequence in fig A, one may find that the cut for the construction of wall 2, context 5, has cut through layers 9 and 10, and in doing so has introduced the possibility that artifacts from layers 9 and 10 may be redeposited higher up the sequence in the context representing the backfill of the construction cut, context 3.
In this instance we can now use the date we have for finds in context 7 to date other sites and sequences.
In practice a huge amount of cross referencing with other recorded sequences is required to produce dating series from stratigraphic relationships such as the work in seriation.