NEW YOKK HILL. 165 



rial being- redeposited. All indications \Knnt to the tact that tliis material of 

 the interbedded cong'loinerates, was derived from some land mass in close 

 prttxiniity to the present beds, as it seems hardly possil)le from the size and 

 nature of the easily disintegrated limestone that it could have been exposed 

 for any great length of time to subaqueous influences. 



CARBON KIDGE AND SPRING UIl.I. GROUP. 



The area embraced within this block is situated in the center of the 

 Eureka Mountains and stretches in a narrow belt from Diamond Valley to 

 Fish Creek basin. It lies hemmed in between Prospect Kidge and the 

 Countv Peak and Silverado uplift, presenting somewhat th<^ a})pearance of a 

 depressed and broken region bounded by two elevated and well defined 

 mountain masses. This appearance is, in part, due to its relativeh- sliglit 

 elevation, and in part to the struggle for siipremacy between sedimentary 

 strata and the volcanic lavas spread out over them concealing large areas 

 and breaking the continuity of strata. At Pinto Peak the rhyolites have 

 been piled u\) until they have attained an elevation higher than any })oint 

 reached by the upturned limestones. These igneous rocks divide the sedi- 

 mentary beds into two areas, one a northern, of wliich Spring Hill is the 

 center, the other to the south, designated as Carbon Ridge. Both regions, 

 however, present much the same geological conditions and consist wholly 

 of Carboniferous rocks, the only two epochs represented being the Lower 

 Coal-measures and Weber conglomerate. 



New York Hill.- The direct contact between the Silurian and Carlxmifer- 

 ous rocks on opposite sides of the Hoosac fault niay be best seen where tlie 

 Lower Coal-measures of New York Hill rest against the Lone Mountain 

 limestones of McCoy's Ridge, as along the fault between these two ridges 

 no lavas have reached the surface to obscure the sedimentary beds. New 

 York Hill is in some measure isolated from the rest of the Carboniferous 

 rocks, being completely surrounded by lines of faulting. On two sides the 

 Hoosac fault outlines it from the Prospect Ridge uplift while a secondaiy 

 fault of but slight disi)lacemeut breiiks the continuity of strata between the 

 hill and the beds underlying Richmond Mountain on the east and Spring 

 Hill on the south. The limestones of New York Hill strike a]>proxi- 



