INDUSTRIAL PROGRESS DURING THE YEAR 187G. xciii 



Quebec group. Trenton forms have been found in New Mexico 

 and parts of Arizona and Nevada, associated in the latter region 

 with the characteristic graptolites of the Utica. It would thus ap- 

 pear that the faunas characteristic of all the principal paleozoic di- 

 visions of the East arc already recognized in different parts of this 

 great Western basin. Large deposits of gypsum, with strong brines, 

 are found in Colorado near the base of the Carboniferous series 

 a fact which recalls similar deposits at the same horizon in various 

 parts of Eastern North America. 



MESOZOIC OF THE WEST. 

 Powell has, moreover, given us a section of the Mesozoic and Ceno- 

 zoic rocks. Instead of the conformable succession observed by King, 

 as well as by Hayden, Comstock, Bradley, and more recently by Jen- 

 ney, for the whole series of Paleozoic and Mesozoic rocks, it has been 

 seen that in the Colorado section we have a stratigraphical break at 

 the base of the Tonto group. Another occurs at the summit of the 

 Carboniferous, upon the eroded edges of which is a conglomerate 

 forminc: the base of the Mesozoic. The lower Mesozoic here consists 

 of 5200 feet of sandstones and limestones, often chcxty, with gypsum 

 at many horizons; the whole series, divided by Powell into four 

 parts, is regarded as the equivalent of the Jurassic, perhaps including 

 at its base a representative of the Triassic. 



COAL -BEARING SERIES. 



Overlying conformably these gypsiferous and calcareous sandstones 

 are the Cretaceous and Tertiary coal-bearing strata, consisting chiefly 

 of sandstones, carbonaceous shales, and beds of coal or lignite. Of 

 these he refers 6100 feet, including, in ascending order, the Henry's 

 Fork, Sulphur Creek, Salt Wells, and Point of Rocks divisions, to the 

 Cretaceous. Upon the plicated and eroded surface of the latter rests 

 the Bitter Creek group of 3000 feet of sandstones, with some lime- 

 stone, much gypsum, carbonaceous shales, and numerous lignite beds, 

 followed by 800 feet of the similar strata of the Lower Green River 

 division, upon the eroded surface of which rests a mass of sandstone 

 overlaid by the calcareous beds and lignites of the Upper Green 

 River division, 300 feet in all. This forms the summit of the great 

 lignitic coal-bearing series, of which, as we have seen, 6100 feet are 

 by Powell referred to the Cretaceous, and 4100 to the Tertiary, mak- 

 ing a total thickness of 10,200 feet. 



Conformably above this comes the Bridger group of 3000 feet of 

 sandstones, chiefly glauconitic, with limestones, marls, and flints, sep- 

 arated by a stratigraphical break from 1800 feet of somewhat sim- 

 ilar rocks, called the Brown's Park group ; while over the disturl^cd 

 and eroded surface of this spreads, the highest of all, the Bishop's 

 Mountain conglomerate of 300 feet, making a thickness of Mesozoic 



