Figure 24-32. Limestone isolith map. 



It has been necessary here to differentiate areas by contrasting patterns in 

 black. This can be done much more effectively by colors. The best practice is 

 to represent the variations within a given lithologic class by colors restricted to 

 a definite range of hue and tone; for example, the subdivisions of limestones on 

 a limestone isolith map should be shown by various shades of one or two basic 

 colors chosen to represent the carbonate group; on the sandstone isolith, by 

 shades of the basic colors selected to represent coarse clastic rocks. This pro- 

 cedure obviously must be varied when the facies separation is made on the basis 

 of rock color. The only logical map presentation in this instance is to show the 

 rock color facies by a similar color on the map; e.g., red rocks with red colors 

 and gray with gray colors. 



The chart in Figure 24-34 will serve as a guide for coloring lithofacies maps. 

 When colors are used to represent lithologies, it is possible to show gradations 

 from one facies into another by alternate bands of color; for example, where 

 a sandstone facies grades laterally into a limestone facies, the area of gradation 

 would be shown by alternate bands of blue and yellow or brown. If the pro- 

 portions of sandstone to limestone are two to one, respectively, then the yellow 

 bands should be twice as wide as the blue. This plan can be extended to include 

 several color bands. 



490 



