would require an intensity of magnetic polarization that is well within reason. 
However, this magnetization would have to be in a reverse direction from that of 
the earth's present magnetic field. 
Several possible explanations of this inverse relationship between the magnetic 
and the bathymetric relief may be suggested. 
1. The rock comprising the bathymetric relief is in actual fact reversely mag- 
netized. This would indicate that there probably has been a reversal of the earth's 
magnetic field since the time of original solidification of the rock. 
2. The top of the body causing the magnetic anomalies may be buried at some 
depth. Consequently, it is possible that the magnetic source has a surface relief re- 
lated inversely to the bathymetric relief, perhaps owing to tectonic processes related 
to the formation of the ridge. 
3. A pattern of correlating intrusions exists. This pattern may be either of 
granitic intrusions correlating with the bathymetric highs or of ultramafic intrusions 
correlating with the bathymetric lows. 
The dashed line in the lower part of Figure 32 shows calculated estimates of depths 
to top of magnetic surface, using two-dimensional approximations. Over most of the 
profile, there is excellent agreement between these calculated depths and the recorded 
bathymetric depths. This agreement was found to be true also for data gathered over 
other parts of the ridge. This indicates that the top surface of the magnetic body is 
probably not buried at any considerable depth. 
This phenomenon of inverse relationships between magnetic total intensity profiles 
and bathymetric relief has been observed at widely separated points. Bromery, Emory, 
and Balsley (1960) describe such an area off the west coast of the United States; Keller, 
Meuschke, and Alldredge (1954) mention briefly a similar occurrence found in the Gulf 
of Alaska. 
Further investigations may determine that in at least some instances these inverse 
relationships are indicative of changes in the direction of the paleomagnetic field. 
In such cases, the direction of remanent magnetism derived from magnetic data in the 
ocean areas then can be compared with paleomagnetic data from land areas. The 
combined data then might make it possible to draw inferences concerning the age of 
oceanic crustal rocks. 
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