M. R. Thorpe— The Abajo Mountains, Utah. 383 



Faults. 



In the Abajo area faulting is rarely . found, whereas 

 none was noted by Emery in the Carrizo Mountains of 

 Arizona and but few faults were described by Gilbert as 

 a result of his studies in the Henry Mountains. The most 

 noticeable fault of the Abajo area is south of South Peak. 

 It trends nearly north and south and hence lies at right 

 angles to the main intrusion. The eastern wall of Recap- 

 ture Canyon at this place is the steep western escarpment 



Fig. 4. 



Fig. 4. Upturned La Plata sandstone; south side of Abajo Mountains. 



of the fault. This block is broken from similar strata 

 on its southern boundary by another fault, trending at 

 right angles to the major one and running parallel with 

 the uplift. These faults form a block whose surface dips 

 12° to the east until it merges with the regional dip of 3° 

 east. The maximum amount of throw was about 500 feet. 

 Marginal faults may be seen in many places where blocks 

 have been broken off and carried either up to the moun- 

 tain summits or high up their flanks. Slickensided 

 surfaces are common in the roof rock indicating a consid- 

 erable amount of movement during the adjustment of the 

 cover. 



