50 SURVEY OF COLORADO AND NP:W MEXICO. 



clinal valley can be seen, throngli wliich flows a small branch called Oak 

 Creek. The dip of the tertiary beds on either side is nowhere more 

 than ten degrees, seldom more than five degrees. The coal crops out in 

 many places. In the sandstones are the peculiar concretionary forms 

 which are common in these beds everywhere. Their general appearance 

 points out their age to the eye at once. i 



About ten miles below Canon City a coal bed has been opened and 

 wrought to some extent. 1 obtained here the following section of the 

 strata : 



9. Sandstone and clay to the summit of the hill - 30 to 40 feet. 



8. Carbonaceous and arenaceous clay - 10 feet. 



7. Yellowish, gray, soft, fine-grained sandstones - 10 feet. 



6. Carbonaceous clay, passing up into laminated clay - 20 feet. 



5. Coal ______ 1 foot. 



1. Drab carbonaceous clay _ - - - 10 feet. 

 3. Coal _____ _ 5 feet. 



2. Drab clay - - - - -4 to 8 feet. 

 1. Yellow ash-colored arenaceous clay, passing down into a yellowish 



gray sandstone. 



In the clay are nodules of iron ore, which are full of impressions of 

 deciduous leaves, like Salix, FlatanuSj Thuya, and a broad flag-like plant 

 are abundant. 



All through the clay there is a yellow powder, oxide of iron, and seam; 

 of gypsum. Much selenits is scattered through the beds of clay anu 

 coal. The plants, so far as I have seen, are found in the clays just abo\( 

 the coal. ' 



The yellow arenaceous clays of No. 5, in the Arkansas Yalley, pass u]> 

 into a "somewhat extensive series of what I call mud beds, composed o j 

 alternate thin layers of clay and mud sandstones, with all kinds of mud' 

 markings, sort of transition beds or beds of passage. In the upper 

 portion of these layers I found an imperfect specimen of InoceramuH. 

 This group of beds is from fifty to one hundred feet in thickness. Besting 

 upon them is a tliick bed of rusty yellow sandstone, which I regard as 

 the lower bed of the tertiary deposits, and marks their commencement in 

 the Laramie Plains, on the Arkansas River, and the Eaton Mountains. 

 Below these beds of passage there is a yellow, arenaceous, marly clay, full 

 of iron-rust concietions, with an abundance of small bivalves and other] 

 shells, with Bacidiies ovatus — plainly Ko. 5. 



It is now clear that the Caiion City coal formation occupies a very 

 restricted area; that the entire thickness of the beds cannot be more 

 than six hundred to eight hundred feet; and that it is an isolated portion, 

 protected from erosion in a manner not easily exiflained, and that it was 

 once connected with the same formations in the Laramie Plains, about! 

 Denver; southward in the Eaton Mountains, and most probably also 

 with those containing coal in the valley of the Eio Grande. The area 

 occupied by the coal beds lies east of Caiion City, between Wet MounJl 

 tain and the Arkansas Eiver, with the eastern limit three or four milef \ 

 before reaching Hardscrabble Creek. It is about twenty miles fron ' 

 east to west, and five to eight miles wide from north to south ; and only 

 small portion of it will furnish coal. The coal itself is quite good 1 • ; 

 the purposes of fuel, but the beds are not thick, and the quantity is n«. 

 great. There is the usual quantity of brown iron ore connected witi 

 these beds. 



The Arkansas Eiver flows through the synclinal depression, below 

 the mouth of Hardscrabble Creek. 



