Subsurface Maps and Illustrations 



955 



adjudged to be of adequate thickness are considered in tabulating values 

 from the logs. In this case the isolith map itself is the eifective reservoir 

 map. It should be pointed out, though, that this artificial classification 

 might yield values which would be difficult to contour or which would give 

 erroneous trends. By following the procedure set forth all significant 

 sands are dealt with in the isolith map so that more reliable thickness 

 trends are established. The overlay map is then contoured according to 

 the general grain of the sandstone-isolith map. It is assumed that the thick 



Figure 517. Generalized lithofacies map showing granitic uplifts of different ages. 



