The Pliocene Rattlesnake Formation and Fauna of Eastern Oregon, with Notes on the Geology of the Rattlesnake and Mascall Deposits

During the summer of 1916 a field party from the Department of Palaeontology, University of California, visited the type localities of Rattlesnake and Mascall formations on the John Day River in eastern Oregon. Five weeks were devoted to an examination of these later Tertiary deposits, primarily for the purpose of securing larger vertebrate collections from the two horizons. The lack of topographic maps and the necessity of spending much of the time in fossil collecting curtailed the geological observations that were made. The facts concerning the geology of the Rattlesnake and Mascall formations should be regarded, therefore, as constituting only a reconnaissance report. While the Mascall deposits yielded also mammalian remains, it seems desirable to reserve the consideration of the Mascall fauna for a later paper.