BULLETIN OF THE AMERICAN ASSOCIATION OF PETROLEUM GEOLOGISTS 
VOL. 18, NO. 1 (JANUARY, 1934), PP. 39-62, 17 GRAPHS 
EARTH RESISTIVITIES AT DEPTHS LESS THAN 
ONE HUNDRED FEET! 
W. D. KELLER? 
Columbia, Missouri 
ABSTRACT 
Empirical data on the resistivities of different kinds of rocks to depths of 100 feet 
were obtained under known field conditions. The resistivity-depth relations are plot- 
ted in the conventional manner. 
A series of graphs shows the resistivity of the rocks along three geologically known 
sections across the Cap-au-Gres fault in northeast Missouri, the adjacent rocks across 
the fault surface being different in each case. 
INTRODUCTION 
‘While prospecting for near-surface deposits of clay and hematite 
in central Missouri during 1930 and 1931, the writer’s attention was 
turned to the use of the earth-resistivity method of geophysical 
prospecting. Being wholly unfamiliar with the technique, the writer 
found it necessary to read as much of the literature available on the 
subject at that time as was possible. It was disappointing, however, 
to find hardly a single systematic study of the elementary principles 
published which would be applicable to work at shallow depths. 
Consequently, several weeks of field work was done simply to ob- 
tain, empirically, typical resistivity values over shale, sandstone, 
limestone, alluvium, a known thickness of one type of rock over 
another, and other relationships, at depths less than 100 feet. It was 
believed that a determination of these resistivity values in the field 
under known conditions would be of more practical value than ob- 
servations on miniature “‘synthetic’”’ laboratory structures. After ob- 
taining data on known conditions, it was proposed to apply them to 
the unknown. Since similar data have not appeared in the literature 
to date, the writer offers his results in the hope that they may be of 
aid to others. 
The work was carried on in 1930 and 1931, as previously stated, 
and was done wholly within Missouri. The specific location of each 
observation is indicated in its write-up. 
Through the courtesy of the A. P. Green Fire Brick Company, 
1 Manuscript received, May 15, 1932. 
2 Assistant professor, department of geology and geography, University of Mis- 
souri. Introduced by W. A. Tarr. 
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