150 GEOLOGICAL SURVEY OF THE TEERITOEIES. 



clinal valley can be seen, through which 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 croi^s out in 

 many places. In the sandstones are the X3eculiar concretionary forms 

 which are common in these beds everywhere. Their general appearance 

 points out their age to the eye at once. 



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

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



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. 



4. 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 oi 

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

 are abundant. 



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

 of gypsum. Much selenite is scattered through the beds of clay and 

 coal. The jilants, so far as I have seen, are found in the clays just above 

 the coal. 



The yellow arenaceous clays of No. 5, in the Arkansas Valley, pass up 

 into a somewhat extensive series of what I call mud beds, composed oi 

 alternate thin layers of clay and mud sandstones, with aU 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 Inoceramm. 

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

 upon them is a thick 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 Eiver, and the Eaton Mountains. 

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

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

 shells, with Baculites ovatiis — ^plainly 'So. 5. 



It is now clear that the Canon 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 explained, and that it was 

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

 Denver, southward m 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 CaQon City, between Wet Moun- 

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

 before reaching Hardscrabble Creek. It is about twenty miles from 

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

 small portion of it will furnish coal. The coal itself is quite good for 

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

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

 these beds. 



The Arkansas Eiver flows through the synclinal depression, below 

 the mouth of Hardscrabble Creek. 



