GEOLOGICAL SUEVEY OF THE TEEEITOEIES. 149 



the various formations are shown in a nearly horizontal position, or 

 inclining southwest at a small angle. Indeed, Oil Creek flows through 

 a sort of synclinal valley in part, and near the source of it the red or 

 triassic beds rest upon the granites. All along this creek, where the 

 unchanged rocks are well shown, the lower cretaceous beds seem to 

 pass down into a narrow belt of ashen gray sands and sandstones, which 

 continue down into a variegated series of beds, a part of which I regard 

 as Jurassic. 



Near the oil springs there are, above the reddish beds, sis layers of 

 massive sandstones, varying from ten to twenty feet thick, with seams 

 of arenaceous clays, from a few inches to ten feet in thickness. These 

 rocks exhibit all the indications of shallow water deposition in places, 

 but not a fossil of any kind could be found, and, therefore, it is dif- 

 ficult to determine whether they are lower cretaceous or Jurassic. 



As to the sources of this oil, I could gain no reliable information. The 

 borings have gone down into the pudding-stones of the lower triassic, 

 and yet no reservoir has been found. It is not known but that the oil 

 may come up from the granites. Great quantities of salt water issue 

 from the springs with the oil, and the oil is taken from the surface of 

 the salt water. 



At Caiion City, where the Arkansas comeS out of the mountains, 

 on the south side of the river, the principal ridge or '' hog-back," which is 

 composed of No. 1, dips 34°, and has a trend about southwest; while on 

 the north side the Img ridge, of which there is a very high one, like a 

 lofty wall, composed^of the sandstones of No. 1, w^hile a lower outer ridge 

 is made up of the fine calcareous sandstones of No. 2, filled up with 

 Inoceramus. It is from this low ridge that the stone for building pur- 

 poses is obtained. It is not very durable, but works easily and makes 

 handsome structures. This regular wall extends northward, bordering 

 the plain in a straight line for five or six miles, and is very conspicuous. 



Issuing from the ground, between the ridges of cretaceous No. 1 and No. 

 2, in the valley, about a mile above Caiion City, is one of the finest mineral 

 springs we have seen in the West. It is quite small, but the water is de- 

 licious. It is doubtless the same, essentially, as the springs at Colorado 

 City. 



Just back or inside of this sandstone wall No. l,is an ashen-gray bed 

 of arenaceous layers, with a bed of fine silicious limestone, containing 

 what seems to me to be indistinct fragments of fresh water shells. This 

 belt passes down into the red pudding-stones below. Passiug up the 

 Arkansas a few hundred yards further, we come to the metamorphic rocks. 



About four miles below Caiion City, on the Arkansas Eiver, are some 

 isolated hills, looking in the distance like fortifications, composed of Nos. 

 4 and 5 cretaceous, capped with a rusty yellow sandstone, which I regard 

 as the lowest bed of the coal formations. 



Both the cretaceous and tertiary beds seem to dip southwest five to ten 

 degrees, while on the south side of the Arkansas the tertiary beds incline 

 rather northeast, so that there is an obscure synclinal which shows the 

 influence of the ranges of mountains on each side of the valley. The coal 

 strata have all the characteristics of the older tertiary sandstones, as 

 shown in the Laramie Plains. 



Between Canon City and Hardscrabble Creek, the tertiary beds jut 

 up against the Wet Mountain range, concealing all the older rocks. 

 About half a mile east of Caiiou City, the high cretaceous ridges are seen, 

 and then they disappear beneath the tertiary beds, and reappear at the 

 head of Hardscrabble Creek, about thirty miles to the eastward. 



High up the foot of the granite hills of Wet Mountain, an obscure syn- 



