Formations containing consistent populations can also be correlated across a basin.
Our primary geochronological service is detrital zircon U-Pb geochronology.
In principle, sedimentary rocks may be divided into two groups according to the nature of the Rb-bearing phase present.
However, they are highly susceptible to recrystallisation after burial and do not necessarily remain closed systems.
In practice, the two distinct dating approaches associated with these sediment types have tended to converge.
Analysis of detrital sediments has moved towards the analysis of fine-grained, almost authigenic, minerals such as illite, in order to escape the effects of the detrital component.
Absolute dating of the time of deposition of sedimentary rocks is an important problem, but one that is very difficult to solve.
Accurate dates depend on thorough re-setting of isotopic clocks.