MAGNETIC VECTOR STUDIES 103 
Corunna, Lansing, and Mason all indicate a “high” trend extending 
from Howell toward St. Johns and possibly as far as Ithaca and Stan- 
ton. This magnetic trend should correspond with the known Howell- 
Owosso anticline and suggests a northwestward extension toward 
Stanton. 
The positive vector east of Muskegon plainly suggests the known 
northwesterly anticlinal ridge, which at its intersection with a west- 
easterly ridge, formed the Muskegon anticline. 
A large uplift is indicated by an anomaly of more than 1,500 
gammas in the general neighborhood of Grand Rapids. The United 
States Coast and Geodetic Survey has made observations of the mag- 
netic elements at 7 auxiliary stations near Grand Rapids. The local 
vectors at these auxiliary stations are represented in Figure 3 together 
with a few near-by vectors. The negative vectors at Allegan, Wayland, 
Caledonia, Lowell, and Ionia seem to indicate a regional magnetic 
“thigh” trend west, northwest, and north of these stations as indi- 
cated in the figure. Along this regional trend occurs the large positive 
anomaly of Grand Rapids. The vectors at Grand Rapids and at the 7 
auxiliary stations all point toward a positive area with its center 
slightly east of Grand Rapids. It seems safe to interpret this anomaly 
as a large domal uplift along a regional anticlinal trend. 
Another uplift is suggested by the vectors at Frankfort, Honor, 
and Thompsonville. 
APPLICATION OF MAGNETIC VECTOR MAPS 
In areas like Kentucky, where some of the outcropping beds ap- 
pear to be of a higher magnetic permeability than the deeper strata, 
most of the vectors are necessarily connected with shallow and local 
anomalies. Some of these anomalies may correspond with actual struc- 
tures, others with stratigraphic changes along the surface. Though 
only scant information as to regional and local structures may be 
gained by a study of this vector map, it will, however, be of great 
value for an intelligent planning of detailed investigations by the 
magnetometer. | 
For all these areas, like Michigan, where the deeper strata and 
the basement are of a higher magnetic permeability than the upper- 
most few thousand feet of sediments, the large majority of magnetic 
anomalies may be connected with structural features; some of the 
anomalies may, however, be caused by a variation of the magnetic 
permeability, brought about by changes in the mineral content of the 
magnetically active horizons. Due to the long distances between sta- 
tions the magnetic vector maps at first sight mainly reveal only re- 
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