The Nemaha Mountains1 in eastern Kansas and southeastern Nebraska were the first major structural features of the buried pre-Cambrian surface in the United States to be outlined by drilling. As the prolific Eldorado oil pool was above this “granite ridge,” much interest was created, especially after several other pools were discovered with the same geologic relationships. The height of this structural feature on the pre-Cambrian surface is about 2500 feet; the reflected surface structures have a closure of less than 200 feet. Naturally, the presence of so large a subsurface structure was unsuspected from the attitude of the surface rocks, and this discovery threw new light on the interpretation of other surface structural features in the mid-continent region. The buried Amarillo Mountains of the Texas panhandle furnish another typical example of the many buried structural features that have been discovered by drilling.
Borings for oil, . . .