142 GEOLOGY OF THE EUEEKA DISTRICT. 



fault line. The Diamond Peak beds may be represented in their full 

 development near The Gate, but they gradually die out to the southward 

 in a wedge-shaped body and finally disappear altogether, beyond which the 

 fault may be followed for a considerable distance, with Nevada limestone 

 walls upon both sides. This long body of Diamond Peak quartzite rests 

 conformably upon the Nevada limestone to the westward, both series of 

 strata dipping uniformly to the east, We have here, then, a duplication of 

 strata made up of the Upper Nevada limestone, overlain by the Diamond 

 Peak quartzite. Small drainage channels, branches of Reilley Creek traverse 

 the quartzite, affording fair cross sections. Numerous minor dislocations, 

 at right angles to the Modoc fault, trend easterly across the ridge, dying 

 out in the plain beyond, but, while they tend to break up the uniformity 

 of structure, do not cause any very decided dislocation in the Nevada lime- 

 stones. 



Perhaps the best' section, the one showing the greatest vertical thick- 

 ness across the Nevada limestone, may be found on the ridge north of 

 Modoc Peak. This section is given on page 66. Starting in at the Modoc 

 fault in Reilley Canyon, nearly due west of Modoc Peak, it crosses the 

 strata nearly at right angles and terminates at the base of the hills in Dia- 

 mond Valley. The beds strike N. 50 to 55 W., measuring about 5,400 

 feet in thickness. Just north of Modoc Peak a fossiliferous shaly limestone, 

 200 feet in thickness, crosses the ridge. It is the belt designated No. 3 of 

 the section, and is the equivalent of the rich fossiliferous shale which has 

 yielded such an abundant Devonian fauna at several localities in the Dis- 

 trict, notably, at Brush Peak, about 2 miles southward. Higher up in the 

 strata, corals of the middle and upper horizons were obtained, but nowhere 

 immediately along the line of the section was any special fossiliferous zone 

 recognized. 



Both north and south of the line of the section the strata are easily 

 traceable, striking obliquely across the ridge, the upper horizons being 

 developed on Signal Peak and the lower on Modoc and Brush Peaks. Just 

 below the summit of Brush Peak the fossiliferous shale belt, which is here 

 about 150 feet in width, determines the position of the beds without ques- 

 tion. It is at this locality that the shales have furnished such an excellent 



