Subsurface Maps and Illustrations 



941 



Isolith Maps 



The ratio and percentage maps show lines of constant relationship 

 of the thickness of one lithologic group to the total thickness of the 

 remaining groups or to the total thickness of the formation, respectively. 

 The isolith map differs from these in that actual thicknesses of each class 

 are contoured. In a sandstone isolith map the total aggregate thickness of 

 all the sandstones in the formation is the numerical value contoured on the 

 map. For the case cited above this number is 163. As in the series of 

 ratio or percentage maps, one isolith map should be made for each of 

 the lithologic classes in order to provide a means for a thorough sedimenta- 

 tion analysis. 



•^"^^ •»* 



Arhose, Siltstone,3s. 



Lime., (jyp., Silt. 



I/ime., DoiO; Silt. 



Ark., (Syp., Silt. LLm£.,3ilt. Lime.,Dolo. 



Figure 503. Combination isopach and lithofacies map. 



