What is the purpose of employing biostratigraphic zones?

Employing biostratigraphic zones primarily serves to establish age equivalence within sedimentary sequences. Biostratigraphy is the branch of stratigraphy that uses fossil organisms to date and correlate rock layers. By examining the distribution of different fossils within sedimentary layers, geologists can identify specific biostratigraphic zones, which are defined by the presence of particular fossil assemblages. These zones allow scientists to interpret the relative ages of the sedimentary sequences they study, creating a framework to understand the temporal relationships among different geological formations. This correlation across different geographic areas enables geologists to establish a timeline of the geological history and assists in identifying periods of time during which specific organisms thrived or went extinct.

While other options involve relevant geological concepts, they do not capture the core function of biostratigraphy, which is rooted in dating and correlating rock layers based on their fossil content.