Previous studies in south-central Idaho have shown the presence of great thicknesses of pre-Cambrian and Paleozoic stratified rocks, conspicuous differences in the rocks of neighboring areas, and the apparent lack of accord between the stratigraphy of this and of better-known regions to the southeast and east.
In the course of studies carried on since 1923 the writer has discovered that although some localities exhibit rapid lateral variation and details of stratigraphy differ between this region and those heretofore better known, nevertheless, the relationship between the larger stratigraphic units of Paleozoic age in south-central Idaho and neighboring regions can now be established. The outstanding fact about the stratigraphy of this region is that the Paleozoic beds accumulated to relatively great thickness east of a shore line approximately coincident with the present southeastern border of the Idaho batholith. There is good reason to believe that Belt (pre-Cambrian) shallow-water marine sediments (not . . .