6o 



E. HUNTINGTON-J. TV. GOLDTHWAIT 



however, the displacement continued as a true fault to Fort 

 Pierce, beyond which it split. One part, which followed the 

 old fault line, seems to have greatly diminished, but, as indi- 

 cated by the broken lavas that Button describes, was of con- 

 siderable importance where it crossed the Grand Canyon. The 

 other passed into a long gentle monocline, and, leaving the old 



Fu;. S. — Mukuntuweap canyon, looking north. I'he skj'-line on the right shows 

 a portion of the mature topography of the Colob pleateau. On the left the Temples 

 of the Virgin, of red Kanab sandstone capped by the white cross-bedded Colob 

 formation, rise 2,500 feet. They have been carved by the erosion consequent upon 

 the uplift which introduced the canyon cycle. The level foreground is a lake plain, 

 formed when the stream was obstructed by landslides similar to those seen in Fig i. 



Hurricane fault line, bent to the southwestward until at Black 

 Rock it joined the Grand Wash fault. This, like the Hurricane, 

 is a young displacement following the line of an old one, as is 

 shown by the relation of lava flows to the strata preserved 

 under them. The line of dislocation, then, which separated the 

 uplifted Plateau province from the Basin Range province 



