156 GEOLOGY OF THE EUREKA DISTRICT. 



dropped about 1,000 feet, causing a picturesque escarpment. It is a fine 

 example of a limestone wall formed by a displacement. The easterly 

 inclined beds, begining at the base of the cliff with a dip from 15 to 25, 

 gradually fall away with a less and less angle, stretching in low broken hills 

 and knolls far out toward the plain. Along the face of the cliff on the west 

 side of the anticline the strata incline into the mountain, arching over from 

 an angle of 25 on the crest of the ridge to 55 along the western base in 

 Hayes Canyon. At the southern end of the ridge the beds rise steeply 

 out of the Quaternary plain along the line of an east and west fault. 

 They strike a few degrees east of north, gradually curving more and more 

 to the east, coinciding approximately with the trend of the i-idge until at the 

 northern end they fall away toward Newark Valley and pass beneath the 

 east base of Diamond Peak. The limestones of Newark Mountain belong 

 to the upper portion of the Nevada Devonian. They are usually dark blue 

 and gray in color and distinctly bedded. It is estimated that there are 

 exposed on the mountain about 3,500 feetof these upper Nevadalimestones, 

 which would carry the beds down nearly to the middle of the formation 

 They may be correlated readily with the limestones of Silverado Hills by 

 the sequence of strata and by their physical habit. Their stratigraphical 

 position is determined without doubt by the overlying White Pine shale in 

 Hayes Canyon, the contact between the two formations being easily trace- 

 able for miles, all the way from the entrance to the canyon around to the 

 northern base of Diamond Peak. Paleontological evidence confirms other 

 evidences by the finding of upper Devonian species in several localities in 

 two distinct horizons, one, near the summit of the limestones along the west 

 base of the mountain, the other, several hundred feet lower down in light 

 gray, somewhat shaly beds on the south side of Milk Canyon. Fossils 

 may also be obtained near the summit of the mountain. A list of the 

 species obtained from both horizons will be found in the chapter devoted to 

 the discussion of the Devonian rocks, and, while they both contain specific 

 forms having a wide vertical range, they are characterized by types found 

 only in the upper Devonian. The species Beyrichia occidentalis, obtained just 

 below the White Pine shale in Hayes Canyon, occurs on the east side of 

 the mountain 1,000 feet or more below the summit; it has also been identi- 



