ELKO AND RIVER RANGES. 595 



Elko and River Eanges. — From Osino Canon to Moleen Canon, the 

 Humboldt River runs.througli a wide bottom-land, which, to the southeast, 

 extends close up to the foot-hills of the Elko Range, but on the northwest 

 is bounded by low, bench-like spurs of the River Range. The beds which 

 compose these spurs are almost entirely of volcanic ash, generally of white 

 color, and containing enclosed fragments of rhyolite. They slope off gently 

 toward the centre of the valley. Along the foot-hills of the River Range, 

 under these volcanic beds, which belong to the Humboldt Pliocene, are 

 found occasional outcrops of upturned beds of the Green River Eocene. 

 These are best seen near Penn Canon, at the northern end of the valley, 

 where attempts have been made to develop their included coal-seams. At 

 the coal-mines, the strata dip 45° to the south, with a strike a little north 

 of east. They consist of beds of white, earthj^ limestone from six inches 

 to a foot in thickness, with white, finely-laminated, calcareous and arena- 

 ceous shales, and seams of clay from two inches to a foot and a half in 

 thickness. There have been found here three beds of coal : one of two • 

 feet in thickness, one of from five to six, and another of three. The coal 

 is a very light lignite, black and lustrous, still retaining somewhat of a 

 woody structure, and abounds in grains of yellow mellite. It is tolerably 

 pure, and free from ash, but breaks up readily, on exposure to the air, into 

 fine dust, and has thus far proved of little economical value. Adjoining 

 the coal are beds of fine bituminous shales, which very closely resemble 

 the brown paper-shales of the Green River series at Green River City in 

 Wyoming. In them are found the same plentiful remains of fishes, and 

 also occasional insects. Some of the shale beds have also abundant casts 

 of deciduous leaves remarkably well preserved.. It was impossible to make 

 an estimate of the aggregate thickness of these beds, as they are concealed 

 beneath the white Pliocene beds, which often so closely aj)proach them in 

 lithological character that they cannot be easily distinguished. A roughly- 

 measured thickness of 300 feet was obtained near the coal-mines, but, judg- 

 ing from the position of the outcrops and the dip of the beds, it would seem ' 

 that as many thousand are probably represented. It is evident that these 

 beds have suffered much more disturbance than those of the Green River 

 Basin, since their angle of dip, which at the mines is 45°, shallows a little 



