1058 



Subsurface Geologic Methods 



part of Clarke County, Alabama. (See fig. 556.) The anomaly extends 

 over an area of some 325 square miles with a magnitude of about 700 

 gammas. Rough estimates based on the depth rules for a sphere indicate 

 that the center of the disturbing mass must lie at a depth of about thir- 

 teen miles. If 50,000 feet is allowed for the radius of this sphere, the depth 

 to the top surface of the disturbance would be in the order of 15,000 

 feet. The sediments in this area are thought to be about 13,000 feet 

 thick, which would place the source of the magnetic anomaly within the 



Figure 557. Magnetic anomaly over Jackson uplift in Rankin and Hinds Counties, 

 Mississippi. (After Peters. Reproduced permission Mines Mag.) 



basement complex. A well drilled by the Magnolia Petroleum Company 

 in 1934 to a total depth of 6,010 feet gave evidence that a structural 

 low existed over the anomaly, although regional well control was limited. ^^ 



Jackson Uplift, Mississippi — The Jackson gas field in Rankin and 

 Hinds Counties, Mississippi, is expressed by a magnetic anomaly of some 

 1,200 gammas extending over an area of about 400 square miles. (See 

 fig. 557.) The anomaly is roughly symmetrical, and depth rules for the 

 sphere would place the center of the disturbance at about 8,500 feet. 



■^ Eby and Nicar, Magnetic Investigations in Southwest Alabama; Alabama Geol. Survey Bull. 43, 

 41 pp., 1936. 



