1080 



Subsurface Geologic Methods 



Figure 571. Residual-gravity map of Ramsey field, Payne County, Oklahoma, 

 showing position of producing weUs. (After Evans.) 



to the south and then steepens to indicate the location of Kettleman 

 south dome. A pronounced gravity minimum is indicated farther to the 

 southeast, which corresponds to the location of the Lost Hills anticline. 

 According to Boyd,^^ 



There must be some geological reason for this rather remarkable phe- 

 nomenon of such a sudden change from gravity maximum representing a 

 structural high at South Dome to a gravity minimum representing a structural 

 high at Lost Hills. An examination of the stratigraphy of Lost Hills shows a 

 considerable thickness of the Reef Ridge (Miocene) shales. These shales 

 are described as being punky and diatomaceous. Specific gravities run on 

 several dry samples show an average of about 0.9. At the northern end of the 

 structure these shales have a thickness of about 900 feet, which increases some- 

 what to the south. ... It is probable, then, that this extremely light material 

 being present over the structure is sufficient to produce the Lost Hills gravity 

 minimum. 



Wellington Field, Colorado — The strong gradient of gravity shown 



*■ Boyd, L. R., Gravity-Meter Survey of the Kettleman-Hill-Lost Hills Trend, Cailfornia: Geophysics, 

 vol. 11, no. 2, pp. 121-127, Apr. 1946. 



