STRUCTURE 



295 



The means by which these several structural features are determined 

 may be here pointed out. Such a statement will also serve to explain 

 why only the major structural relations are determinable. 



CALCAREOUS 

 Kp^ SLATE SERIES 



LEGEND 



Cono/omer<9te 



Figure 1. — Sketch Map showing P re-Cambrian Structure in northern Blaok Hills 



Within this series of schists there are only a few stratigraphic mem- 

 bers which are sufficiently persistent and distinctive to permit tracing 

 along the strike with complete assurance that a definite horizon is being 



