THE TERTIARY PERIOD 



283 



Distribution and Character of the Rocks 



General Distribution. — Lower Tertiary (Eocene and Oligo- 

 cene) strata appear at the surface in North America over the areas 

 indicated on map Fig. 175. Disregarding the countries south of 



Fig. 175 

 Map showing the surface distribution (areas of outcrops) of Lower Tertiary 

 (Eocene and Oligocene) strata in North America. Tertiary lavas are 

 separately shown on map figure 184. (Modified by W. J. M. after Willis, 

 U. S. Geological Survey.) 



