ii6 



ELIOT BLACKW ELDER 



rather generally and without notable interruption from the early 

 Eocene to about the middle of the Miocene as those epochs are now 

 generally correlated, but that near the middle of the Miocene the 

 Tertiary beds were folded strongly so that the late Miocene sedi- 

 ments now rest with marked discordance upon the early Miocene 

 and older strata. In central Washington, Willis, Smith, and 



Fig. II 



Calkins have likewise shown that rocks containing early Miocene 

 plants are highly folded and intruded by granites, and that upon 

 their trunkated edges late Miocene lavas and sedimentary beds lie 

 with but little change in their original attitude. In the Grand 

 Canyon region of Arizona the studies of Huntington, Goldthwait, 

 and others lead them to the conclusion that the conspicuous faults 

 of the plateau region were begun long before the late volcanic 

 eruptions, but also long after the gentle folding of the Cretaceous 

 beds. There have also been subsequent movements along the same 

 fractures. A broad study of the Middle Tertiary disturbance has 



