Subsurface Maps and Illustrations 



951 



generalized broad regional work. Conversely, where control points are 

 numerous, and the data reliable, the percentage maps are better. 



Practical Uses of Lithofacies Maps 



A number of the preceding pages have been devoted to lithofacies 

 maps, how they may be constructed, and what they represent. In most in- 

 stances the lithofacies map, regardless of the type, is only one phase of 



Figure 513. Sandstone isolith contours with shading according to percentage 

 of sands over 25 feet thick. 



regional geologic investigation and analysis. These maps do not depict 

 a complete geologic story, but, rather, present complex stratigraphic data 

 in a simplified form so that broad concepts can be developed. All the 

 various lithofacies maps discussed reveal only the averages of geologic 

 phenomena. None is precisely specific where the stratigraphic section is 



