PALHO/OK" SKCTION. 1 1 



accoiiipaiiicil I)y ])r(it'()Uii(l lon^itiidiiial faults, several of wliicli cxteiid thy 

 cutiri' length ot" the inountains, and ha\e j)la>'ed a most iinnortant part in 

 'oringiuo- about the present orooraphic cDuditions. 



Although these mountain masses stand so intimateh- i-elati'd to each 

 other that it is frefiuently ditHcult to draw sharp topographieal lines between 

 them, the Eureka Mountains may be divided into six blocks with well 

 marked sti-uctural and geological ditfereuces. These blocks may be desi"'- 

 uated us follows: 



Prosijcct Ki(lg(\ 



Fish Creek Monntaius. 



Silverado and County Pealv group. 



Mahogany Hills. 



Diamond ^Mountain. 



Carlton IMdge and Spring Hill group. 

 Paleozoic Section.— As alread\" numtioned, the Eureka Mountains lie just 

 eastward of the old shore line. In this and tln^ following chajjters the 

 evidence is presented, derived from the history of the rocks themselves, to 

 show the close proximity of a land area when the beds were laid down. 

 The nature of the.se olf-shore deposits near the western border of an okl 

 Paleozoic sea form one of the principal olijects of this investigation. .Much 

 of the material, such as the coarser conglomerates, nnist necessarily have been 

 oiT-shore deposits The sedimentary rocks which make up the mountains 

 present a great developnumt of linu'stones, (piartzites, sandstones, and shales, 

 comprising many thousands of feet of Camlman, Silurian, Devonian, and 

 Carboniferous bed.s. From the lowest exjxised nn'mbers of Cambrian strata 

 to the to]) of the Coal-measures there are represented a series of sedinu-ntarv 

 dej)osits 30,000 feet in thickness. Nowhere within the limits of the Eureka 

 district can there be found any one ex])osure which shows the beds with- 

 out a l)reak in their contiiniity, the longest unbroken section representing 

 about one-third of the entire sequence of strata, yet the region offers in so 

 many instances such continuous exposures of beds and so many in which 

 the series of sti-ata overlap each otluM- with siu'h a constant repetition of 

 beds, that the reconstruction of the entire section is easily made out when 

 the individual parts are carefully compared and studied. The reason Avhy 

 there is no oni' unbroken section may be readily undcn-stood by a glance 



