Abstract of Swirydczuk, K., G.P. Larson, and G.R. Smith. 1982. Volcanic ash beds as stratigraphic markers in the Glenns Ferry and Chalk Hills Formations from Adrian, Oregon, to Bruneau, Idaho. Ibid.:543-558.

Multivariate ordination of ash beds based on chemical composition of each ash allows stratigraphy of Miocene and Pliocene strata of the Chalk Hills and Glenns Ferry formations. The ash stratigraphy confirms the biostratigraphy based on fish.