152 C. A. HEILAND 
such in the figure occur. As the Pliocene.strata are cut off in the west 
by the fault, a conductive triangle, so to speak, occurs between the 
points A, B, and C. Below the line BC, the strata are less conductive, 
and the same is true of the strata above the water table. Due to the 
absence of water west of the, fault in the Cretaceous section, these 
strata also are poor conductors. 
The resistivity profiles 7J, [J and IV are similar to each other, but 
differ greatly from the profile I. They indicate a high resistance peak, 
corresponding with the Quaternary top layer and the Fernando strata 
above the water table. Then the resistivities drop to very low value, 
corresponding with the depth of the conductive triangle which is in- 
volved in every case. Thus, the horizontal part of the resistivity curve 
indicating the part of this triangle traversed by each traverse, is very 
short in traverse JV, longer in J/J, and still longer in traverse JZ. As 
soon as the impervious strata are reached, the resistivity curves go up 
again, this rise occurring at the shallowest depth in traverse JV, being 
deeper at III, and the deepest in traverse IJ. In other words, the point 
where, on each curve, this rise begins, gives approximately the depth, 
and thus the dip of the impervious formations. The agreement with 
the geologic section goes still further. After the impervious layer has 
been traversed in each section, the recorded resistivities are in pro- 
portion with the resistivities of the section below this impervious 
series. Thus, if we take a certain point on each curve, for example, 
those corresponding with a deflection of 20 millivolts, and connect 
these points, the resulting line gives directly the dip of the strata be- 
low the impervious layers. 
The resistivity curve obtained at the traverse J indicates forma- 
tions of much higher resistivity than the curves obtained on the other 
traverses. The peak corresponding with the dry layer above the 
water table which was obtained on the other traverses is also missing. 
A distinct break occurs in this curve which is explained by the fact 
that the apparent resistivity drops when a depth is reached which is 
equal to the horizontal distance (at that depth) of a better conducting 
medium from the traverse line. We, therefore, interpret this break 
in the traverse J as the effect of the strata east of the fault plane. 
In Figure 35, the results of two potential-drop-ratio traverses 
across an area in the Spring Coulee district in Alberta are shown. 
The geologic section is Cretaceous below glacial drift, the Cretaceous 
being alternating shales and sandstones of the St. Mary and the Fox 
Hills formations. The measurements are made with a Racom equip- 
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