BULLETIN OF THE AMERICAN ASSOCIATION OF PETROLEUM GEOLOGISTS 
VOL. 18, NO. 1 (JANUARY, 1934), PP. 97-105, 4 FIGS. 
MAGNETIC VECTOR STUDY OF KENTUCKY AND 
SOUTHERN MICHIGAN! 
W. P. JENNY? 
Houston, Texas 
ABSTRACT 
The principle of the magnetic vector method is briefly explained. 
The salient geological features of Kentucky are investigated as to their regional 
magnetic effects. It is found that the Western and Eastern geosynclines show up mag- 
netically as negative anomalies, but that also the Cumberland River arch and the 
Lexington dome show up as negative anomalies. From this follows that some of the 
outcropping bedsin Kentucky are of a higher magnetic permeability than the underlying 
bets and Basement complex. 
‘The study of the magnetic vector map in Michigan reveals a number of magnetic 
high trends, which are shown to correspond to known structural trends, such as the 
Howell-Owosso anticline and the Muskegon anticline. The deepest area of the Michigan 
basin is indicated by a negative magnetic anomaly. 
Practical value and application of the magnetic vector maps to field problems is 
explained by the example of the newly discovered Hart field. Apart from the valuable 
information obtained by magnetic investigations alone, such investigations are of great 
help in the interpretation of data gained by other geophysical methods. 
INTRODUCTION 
The principle of the magnetic-vector method, which has been 
fully explained elsewhere,? may be briefly summarized as follows. 
In order to obtain the direction in space and the intensity of the 
magnetic lines of force as due to local structures, the ‘‘normal”’ values 
of the earth’s magnetic field have been deducted from the absolute 
measurements at the United States Coast and Geodetic Survey’s sta- 
tions of the declination, and of the vertical and horizontal magnetic 
intensities. 
The differences between the absolute and “‘normal”’ vertical and 
horizontal intensities have been combined into a vector triangle, in- 
dicating the direction and intensity of the local magnetic force. The 
vector triangles have been plotted on the maps at their respective 
stations, by turning the triangles through go° around the horizontal 
component (which is the dashed line starting at the station point) 
1 Manuscript received, October 26, 1933. 
? Geologist and geophysicist, 2102 Bissonnet Avenue. 
3 W. P. Jenny, “Magnetic Vector Study of Regional and Local Geologic Structure 
in Principal Oil States,” Bull. Amer. Assoc. Petrol. Geol., Vol., 16, No. 12 (December, 
1932). “Structural Trends in Florida,”’ The Oil Weekly (October 2, 1933). 
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