Test-pit excavations from 1989 in Room 2 of Cathedral Cave yielded a diverse faunal assemblage, but age estimates derived from radioisotopic dates and bio chronological assessment were widely disparate. New excavations were undertaken in 2003 to increase faunal samples and clarify chronological resolution. Arvicoline rodents recovered from the 2003 excavation include Allophaiomys pliocaenicus, Microtus meadensis, M. paroperarius, Microtus sp., Mictomys meltoni or M. kansasensis, 4- and 5-triangle morphotypes of Lemmiscus curtatus, Ondatra zibethicus, and representatives of both ancient and recent lineages of Phenacomys. A maximum age for the fauna falls between 146.02 ± 2.584 and 153.7 ± 6.4 ka, as determined through uranium-series analyses of flowstones collected near the base of the excavation. Paleomagnetic analyses, and morphological data from recovered Ondatra, are consistent with that age interpretation. Cathedral Cave contains the youngest known Irvingtonian fauna, including the youngest records of Allophaiomys pliocaenicus, Microtus meadensis, and Microtus paroperarius. These records diminish the utility of those taxa for biochronologic refinement of fossil localities in western North America. Differences in biogeographic patterns of vertebrates in the Great Basin throughout the latest Pleistocene and Holocene are tied to topographic gradients and independent faunal histories. The Cathedral Cave biota provides a greater temporal depth for that dynamic, and provides important data demonstrating that higher-elevation fossil deposits yield diachronous biochronologic boundaries relative to lowland sites, and may require independent biochronologies. Recognition of the provincial nature of biochronologic boundaries is not new, but documented local-scale provincialism highlights conceptual challenges for broad-scale application of arvicoline biochronology in North America.