It is the purpose in this paper to discuss the stratigraphic distribution of altered volcanic materials and related clays, and the correlation of the formations that include them. The correlations are based on the comparison of collected and listed faunules from the strata, and an analysis of the published correlations of other geologists. More precise correlation of the formations may develop as detailed stratigraphic work on the clay beds progresses.
The mineralogic study of the specimens by P. F. Kerr has not been completed. Thin sections reveal volcanic structures in some of the specimens. X-ray diffraction studies and chemical analyses show the clays to differ from bentonite, with which they have frequently been identified, but to be closely similar to one another if not identical. The clays are composed of a clay mineral constituent not identified as a described mineral, and differing from montmorillonite and beidellite, the constituents of . . .