ELECTRICAL METHODS 



571 



Of especial interest in connection with this work are: (1) the sub- 

 stantiation of the indicated structurally low ground to the northeast of the 

 Phillips No. 6-Santa Fe Location and (2) substantiation of the low and 

 relatively flat structure between the Conoco No. l-G-12 and the Shell 

 No. 1-A wells in the southeastern part of the area. 



The indication of low structure in the latter case is particularly sig- 

 nificant inasmuch as it disproved the theory of a possible connection 

 between the Monument Structure to the southeast and the East Vacuum 

 pool. The Shell No. 1-A well is reputed to have been drilled as a result of 

 recommendations based upon a seismic survey in this vicinity. This 

 area is particularly difficult for seismic operations due to two factors : 

 (a) irregular velocities in the near-surface beds, and (b) large variations 

 in thickness of the anhydrite zone overlying the limestone. 



Fig. 353. — Aerial photograph of Meteor Crater, Arizona. {A.I.M.E. Geophysical Pros- 

 pecting, Technical Paper, 1932.) 



Structural Investigation of Meteor Crater 



Meteor Crater (Figure 353) lies in the high plateau of northern 

 Arizona, t It is a natural wonder whose origin and age have been dis- 

 cussed for many years. Data from geologic and topographic surveys 

 have shown that in both geologic and topographic effects the crater is 

 unusually symmetrical for so large a structural feature. 



t J. J. Jakosky, C. H. Wilson, T. V/. Daly, "Geophysical Examination of Meteor Crater, 

 Arizona," A.I.M.E. Geophysical Prospecting, 1933, pp. 63-97. 



