Seismic Contours 

 on 



Trenton 



Contour Interval = 50 fleet 



32 



T Structural Contours 

 on 

 Devonian 



Contour Intervol = 50 feet 



Figure 588. Trenton structure by seismograph work prior to drilling compared with 

 subsurface contours on Devonian from well data, London field, Illinois. (After 

 Lyons. Reproduced permission Geophysics.) 



