tlie Muddy Mountains, Nevada, etc. 57 



of Callville Mountain lias been removed by erosion, 

 whereas to the west and south the strata involved in 

 the movement have been carried downward by normal 

 faulting, leaving Callville Mountain as the only remnant 

 now exposed. 



Subsequent to the overthrusting, pronounced doming 

 has occurred north of Muddy Peaks, permitting the strip- 

 ping which has exposed the thrust plane. Normal fault- 

 ing, accompanied by tilting of blocks, has also affected 

 Callville Mountain, and many of the scarps have a re- 

 markably fresh appearance. The Arrowhead fault is 

 marked by a fault-line scarp, the thro^vn block now occupy- 

 ing the higher position. Exposed portions of the actual 

 plane have striations which dip westward 40° from the 

 horizontal, thus indicating that the shove was greater 

 than the throw. The Eogers Spring and White Basin 

 faults, each with displacement of at least 2,500 feet, 

 bound a high, narrow horst. The dropping of fault 

 blocks is chiefly responsible for the depression known as 

 White Basin. Faults with large displacement affect the 

 western part of Callville Mountain, and a number of these 

 bound narrow tongues of Horse Spring limestone which 

 have been dropped into the mountain mass. 



Southern division. — The axes of Bitter Wash and Sand- 

 stone Spring anticlines are parallel, and both are essen- 

 tially parallel to the long axis of Muddy Peaks dome. 

 Moreover, the three structures are almost equally spaced, 

 and the intensity of folding is practically the same in all. 

 The Sandstone Spring anticline plunges sharply at both 

 ends, and therefore it is actually a dome with elliptical 

 plan. Without doubt the three folds belong to the same 

 series, and thus the central and southern divisions of the 

 Muddy Mountains and the northern part of the Black 

 Mountains are to some degree a unit in structure. Both 

 the Bitter Wash and Sandstone Spring anticlines are 

 greatly modified by faulting. 



Deformation of intermontane deposits. — On the south 

 side of Muddy Valley the intermontane clays show little 

 disturbance, but have a perceptible general inclination 

 toward the valley ranging from 100 to 200 feet per mile. 

 In the Virgin Valley, however, the clays have been con- 

 siderably folded. Northeast of Bluepoint a zone of dis- 

 turbed strata follows the direction of the Rogers Spring 



