To understand broad contexts, paleontologists need to understand the temporal context of a locality. When material from KRC was originally described by Drs. John Rensberger and Anthony Barnosky in 1982, they used the presence of the Sagebrush Vole to infer how old material from KRC was, suggesting it was between 6,600 years old at the top of the locality and approximately 175,000 years old at the bottom.
The approach for identifying the age of fossil localities, based on the animals contained within them, is called biostratigraphy—an important field of study within paleontology. Unfortunately, since this original description of KRC, fossils of the Sagebrush Vole have been found in additional localities in North America that have been radiometrically dated to be older than the inferred dates for KRC (nearly 1 million years old, in fact).
We know that the material from KRC is at least 6,600 years old, because it is capped by a carbon-dated ashfall from a volcanic eruption. However, we don’t know how old the material underneath that ashfall is, which means we do not have the context needed to use the fossils from KRC to understand the evolution of animals in North America.
Article Source: Burke Museum