72 CHESTER R. LONGWELL 



the vicinity of Muddy Peaks Basin suggest that the overthrust plate 

 moved from southwest to northeast. Further evidence favoring 

 this conclusion is furnished by the strike of the minor overthrust 

 north of the Arrowhead fault. Very probably this thrust was asso- 

 ciated with the major movement, and had the same general direc- 

 tion. Some caution must be used, however, in drawing conclu- 

 sions from the present strike of the smaller thrust plane, for it may 

 have been changed considerably by the normal faults that cut the 

 block. 



GENERAL DEDUCTIONS 



The east side of Callville Mountain is less than 40 miles from the 

 Grand Wash Chff s ; and the original eastern edge of the overthrust 

 plate was probably much nearer the western edge of the plateau. 

 Thus there is evidence of intense compressive deformation near the 

 border of the Basin Range region, closely adjacent to a wide area in 

 which the effects of crustal compression are practically absent. 

 Further evidence of the intensity of the post- Jurassic revolution 

 in this part of Nevada is seen in the closely compressed and over- 

 turned fold extending north from Callville Mountain. This close 

 folding and the over thrusting involve the same Mesozoic strata, 

 and therefore may be different expressions of the same general crus- 

 tal movement. 



Rowe has reported an overthrust in the Spring Mountain Range, 

 40 miles west of the Muddy Mountains, stating that "the Carbon- 

 iferous limestone is thrust over the red Mesozoic sandstone. "^ This 

 description suggests the possibility that the feature is contempora- 

 neous with the Muddy Mountain overthrust. It is a noteworthy 

 fact that in a large part of the Spring Mountains and in neighboring 

 ranges folding is gentle or practically absent. The writer ventures 

 the suggestion that detailed mapping may show some of these 

 ranges to be faulted portions of a great overthrust plate. Evidently 

 the post- Jurassic revolution had a profound effect in at least a part 

 of southern Nevada, and further field work may be expected to 

 reveal additional evidence of the movement. 



' Quoted by J. E. Spurr, U.S. Geol. Survey Bulletin No. 20S, p. 177. 



