BULL. GEOL. SOC AM. 



VOL. 15, 1903, PL. 27 



Figuuk I.— Gkeenhorn Limestone east of Pueblo, Colorado (Photographed by G. K. Gilbert) 



Figure 2. — Greenhorn Limestone south of Edgemont, South Dakota 



TYPICAL ALTERATION OF THIN LIMESTONE BEDS AND SHALE 



