CORRELATION OF ISOGEOTHERMAL SURFACES 39 
the fact that the crystalline rocks are found at a depth of about 2,500 feet at 
Okemah and at about 10,000 feet at Oklahoma City. The observations show 
that the isogeothermal surfaces tend to parallel the granitic bed at the base 
of the sedimentary strata. The irregularities which appear at several points 
along the general trend are apparently due to local uplifts on some of which 
oil fields are located. 
Loca. VARIATIONS OF ISOGEOTHERMAL SURFACES 
The Salt Creek and Long Beach oil domes, Figs. 3 and 4, are excellent ex- 
amples of local uplift in which the isogeothermal surfaces stand in a definite 
R79 W. R.78 W. 

Fig. 3. Salt Creek Dome, Natrona County, Wyoming. 
relation to the strata. In Fig. 3, the closed broken lines represent elevations on 
the “Second Wall Creek oil sand”. Faults are represented by broken lines 
intersecting the contours. The small dots or disks represent well locations 
and the accompanying numbers represent the depths at which a temperature 
of 80°F is reached. The heavy continuous lines represent contours on the 
80°F isogeothermal surface. Fig. 3 shows clearly that the highest point on the 
183 
