INDUSTRIAL PROGRESS DURING THE YEAR 1876. xci 



With the exception of some red sandstones at the base, it is chiefly 

 a quartzite ; though in parts becoming a coarse sandstone, occasion- 

 ally conglomerate. Though as yet without discovered fossils, it is 

 shown to belono; to the Carboniferous from the fact that it is con- 

 formably overlaid by 2000 or 2500 feet of shales, sandstones, and 

 chert-beds, with arenaceous limestones, holding throughout Coal- 

 measure forms, and represented in some parts of the distribution by 

 a continuous body of limestone. In the marine limestones of the 

 Wahsatch division there are found, in Middle Nevada, some plant- 

 bearing earthy coal-beds. We have thus a series of at least 16,000 

 feet of sediments belonging to the true Coal-measures ; following 

 which are a few hundred feet of argillaceous, sandy, and calcareous 

 rocks, the fauna of which appears to offer a transition to the Permian. 

 The Permian strata themselves are wanting to the west of the Wah- 

 satch. It is, according to King, a question Avhether the Eozoic bar- 

 rier which, in Western Nevada, was the limit to the Paleozoic basin, 

 was continental in its character ; if so, it would appear, from the 

 Carboniferous strata in the Blue Mountains of Oregon and the Bass 

 range in California, that it included deep westward bays in which 

 Paleozoic sediments were deposited. 



THE BLACK HILLS. 



The late observations of Jenney have given us further illustrations 

 of the geological succession in the Black Hills of Dakota. The 

 Eozoic strata of this region, which doubtless once formed an island 

 in the Paleozoic sea, are described as consisting of gneisses, and 

 micaceous, hornblendic, and chloritic schists, with interbedded and 

 intrusive granites, overlaid in apparent unconformity by a series of 

 argiliites and quartzitcs. Both of these series are much disturbed 

 and folded, and include auriferous quartz veins. Resting uncon- 

 formably upon these are 250 feet of sandstones, which at the base 

 are conglomerate, including fragments of the older rocks and of their 

 auriferous veins ; and higher up soft sandstones and shales, with 

 fucoids. Above this are 300 or 400 feet of massive Carboniferous 

 limestone, sei^arated from the underlying fucoidal beds by a few feet 

 of calcareous sandstone, holding the same fauna as the limestone. 

 To this succeeds over 400 feet of red sandstones, limestones, and 

 marls, with gypsum, regarded as Triassic, overlaid by Jurassic strata 

 with an abundant fliuna, and not exceeding 500 feet in thickness ; to 

 which succeed the Cretaceous and Tertiary strata of the region. 

 The whole section, up to the summit of the Cretaceous, presents no 

 evidence of want of conformity, and offers not more than 700 feet as 

 the representative of the Paleozoic period. The strata below the 

 Carboniferous are l)y him regarded as Cambrian, and called Pots- 

 dam. 



