MAGNETOMETER SURVEYS IN CALIFORNIA 1369 
Results of magnetometer survey.—The survey shows a magnetic 
“low’”’ extending from the Lost Hills to the South dome. A very marked 
“high” is east of the “low” and extends parallel with it. On the western 
side of the area, the magnetic “high” is not so great in the south, but 
northwestward the intensity increases and the changes from “‘highs”’ to 
“lows”? become much sharper and more pronounced. This is because 
the sandstone beds in the Upper Etchegoin cause the magnetic “‘highs,”’ 
and in the south the mantle of alluvium is probably thicker, causing a 
greater masking effect on the magnetic beds. At the South dome the 
parallel “highs,” on either side of the area, swing around and close, con- 
forming to the trend of the Mulinea bed. 
At the South dome the magnetometer results are substantially the 
same as those shown by surface and subsurface geology. The trend of 
the magnetic anomalies conforms with the strike of the beds, and the 
manner in which the “high” closes on the north is especially convincing. 
The alternating long, narrow “highs” and “‘lows,’’ in the northwest, 
are undoubtedly caused by interbedded sandstones and sandy shales 
and clays. The magnetic ‘‘highs”’ are on sandstone beds. 
The structural axis at the South dome follows a line of magnetic 
“lows.” The “lows” fall midway between magnetic “highs” caused 
by magnetic sandstone beds near the Etchegoin-San Joaquin clays con- 
tact. Erosion has removed these magnetic beds from along the axis of 
the anticline, leaving their truncated edges on the flanks of the structure, 
with less magnetic beds in the center. This explains the relationship of 
the anomalies to the structure in this area. 
By analogy with conditions existing at the South dome, the axis of 
the structure can be located southward, connecting with the Lost Hills 
field. Immediately north of the Lost Hills oil field, the magnetic ‘‘low”’ 
swings sharply westward and turns northwest to the South dome. As 
the magnetic anomalies are similar to those at the South dome, the axis 
of the anticline probably follows the magnetic “low.” 
From the foregoing evidence the following conclusions can be drawn. 
1. It is possible to show the location of the axis of the Lost Hills- 
South dome anticline. 
2. The structure is continuous from the Lost Hills to the South 
dome. 
3. The position of the axis, according to the magnetometer, corres- 
ponds fairly well with the geologic axis, excepting north of the Lost Hills, 
where it deviates and causes an offset in the trend of the axis. 
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