340 GEOLOGICAL SUEVEY OF THE TERRITORIES. 



proceed farther north. Before reaching the granitic jyoint, a stratum of 

 hornbleudic trachyte is found to cover the sedimentary rocks, the dip of 

 which has increased at that point to about 30°. Standing on station 38, 

 the highest point of the vicinity, at an elevation of 12,795 feet, the sedi- 

 mentary rocks are seen to form a craterlike figure all around this cone, 

 showing on all sides a strong radiating dip from it. On the sides 

 nearest to the cone, the strata are exposed, presenting a face of about 

 1,200 feet in thickness, and falling off nearly vertically. The trachyte 

 that partially covers the top shows itself in a distinctly-marked pre- 

 cipitous ridge capping the limestones, a large portion of which are 

 changed to marble. On the south side, at station 38', it was impossible 

 to find that the strata there had any connection with those farther down 

 the valley, while on the eastern and northern sides they slope off for 

 some distance; on the southern decreasing their dip as they proceed. 

 This point is so very characteristic and unique in its details that it is to 

 be regretted that not more time could be given to a careful study of 

 the changes that have occurred in stratigraphical and lithological condi- 

 tions. 



A section running through this wall of strata, with the thickness of 

 beds estimated, shows the following arrangement : 



The lowest members that can well be distinguished are about 320 

 feet of light gray to bluish to almost white limestones, (a,) with quartz- 

 itic segregations characteristic to the strata of that horizon, and sparse 

 remains of crinoids. Although the identification is necessarily not a 

 very thorough one, these beds have been referred to the Silurian. 

 Above that follow 80 feet (b) of yellow and gray shales, regarded as 

 Devonian ; then 175 feet of variegated shales (d) partly sandy, with 

 isolated banks of limestone, weathering smoothly, with a steep face; 

 260 feet of light-gray and yellowish limestones follow, interstratifled 

 with narrow bands of shale, and partly altered so as to appear like 

 marble ; the whole is covered by 40 feet of light shales, separated from 

 45 feet of the same material by a 20-foot stratum of dark-blue Carbon- 

 iferous limestone (e) full of fossils ; a short synopsis of which will be 

 given at the end of the description of Carboniferous. This stratum is 

 a well-marked horizon, and can be traced along for considerable dis- 

 tance, forming a narrow, dark line between the lighter rocks that over- 

 and underlie it. Upon this follow 150 feet of light-blue and yellow 

 limestones, (/,) dolomitic in part; a large portion of them altered into 

 marble. Single bands of quartzite appear also, and almost all the 

 strata contain a few fossils. Overlying there are 50 feet of yellow, red- 

 dish, and whitish shales without any fossils ; 70 feet of a horublendic 

 trachyte (Ji) cover the whole. 



About seventy square miles are covered by the Carboniferous at that 

 point, but no connection is made with that on the north side of the 

 canon of the Gunnison. Ascending the heights north of the canon, 

 the same conditions are found to occur as on the south side ; the sedi- 

 mentary beds sloping down toward the river. At the point where the 

 canon opens into Taylor Eiver Valley, the Carboniferous strata make a 

 sweep down the hill, for a short distance form the bed of the river, 

 and extend across it to the south, but only for a short distance. Station 

 42 is located on the north side of the canon on a trachyte that covers the 

 Carboniferous, which extends northward beyond the limits of our sec- 

 tion. In thickness and stratigraphical relations, there exists an almost 

 perfect identity between the formations on the two sides of the caiion. 



Although the quantity of fossil remains occurring in that stratum of 

 dark-bine limestone is very considerable, there are but few species, and 



