The U.S. Geological Survey has recently measured and sampled the Phosphoria formation at many localities in Montana and other western states. These data will not be fully synthesized and analyzed for several years, but segments of the data, accompanied by little or no interpretation, are published as preliminary reports as they are assembled. This report, which contains abstracts of the sections measured in southwestern Montana (fig. 1), during 1951, is the fifth Montana report of this series. The field and laboratory procedures adopted in these investigations are described in a previous report (McKelvey and others, 1953).
Many people have taken part in this investigation. Crushing and splitting of the samples in the field were done by T. K. Rigby. The laboratory preparation of samples for chemical analysis was done in Denver, Colo., under the direction of W. P. Huleatt.
The P205 and acid insoluble analyses were made for the Survey by the U.S. Bureau of Mines at the Northwest Electrodevelopment Laboratory, Albany, Oreg., under the direction of S. M. Sheldon and M. L. Wright.