148 GEOLOGICAL SUEVEY OF THE TEEEITOEIES. 



exhibit au irre^lar but distinct "en eclielon" arrangement; and at a 

 number of localities, the ranges will i^ass off in the prairies, south or 

 southeast, in groups, thus causing an abrupt notch or bend in the range. 

 There is also in the caiion of the Arkansas an extensive bow or notch, 

 where the upheaved ridges are very conspicuous and numerous, where 

 the complete series of formations, in their regular order of sequence, are 

 thrown up to the vision. 



After entering among the upheaved ridges we find the lower creta- 

 ceous sandstones forming a consx^icuous ricjge, inclining thirty degrees 

 to forty degrees about northeast. Then come the variegated sandstones 

 and the brick-red beds inclining at various angles as heretofore described. 

 Before reaching the Arkansas some of the ridges become very large and 

 high, from five hundred to six hundred feet. In very many localities, 

 for a long distance, the red sandstones lie distinctly against th© granite 

 hills. Not unfrequently for fifty miles or more along the eastern base 

 of the mountains, all the unchanged beds have been worn away from the 

 metamori)hic, and a smooth, grassy valley intervenes, so that it is some- 

 times difficult to find the two classes of rocks in contact. 



About ten miles north of the Arkansas we have an immense ridge, at 

 least eight hundred feet high, capped with lower cretaceous sandstones, 

 , and below them fine arenaceous sands, clays, thin beds of limestone pass- 

 ing down into variegated layers, with a heavy bed of gyi)sum, from 

 fifteen to thirty feet thick, at its base. This bed of gypsum seems to 

 form a sort of dividing line between the brick-red beds and the varie- 

 gated sandstones above. Passing Beaver Creek we come into a fine oval 

 park, with the large ridge on the east side, and the low red sandstones, 

 which lie on the granite, on the west side. This park is about foiu- miles 

 long and half a mile wide. The bed of gypsum is very conspicuous. 



In the vicinity of the Arkansas Valley the cretaceous formations be- 

 come quite appareiit, and while there seems to be no marked line of sep- 

 aration between the divisions, yet portions of IS'os. 1, 2, 3, 4 and 5 can 

 be distinctly seen. On Oil Creek, near Caiion City, there are high iso- 

 lated hills which show the black shales of No. 4, gradually passing up 

 into the rusty arenaceous clays of No. 5. High on the iianks of the 

 mountains can be seen the carboniferous beds, inclining at large angles. 

 The hills are covered with small pines, mostly the piiion, fFinus edulis,J 

 but all the lumber has to be brought from a distance of thirty or forty 

 miles. 



High up in the foot-hills of the mountains, in the valley of Oil Creek, 

 a branch of the Arkansas, are the celebrated Oil Springs. There are 

 four of them from which oil is taken, but they are near together, and 

 probably all come from the same source. The oil seeps out through 

 sandstone seventy or eighty feet beneath the surface. A hole has been 

 bored down three hundred feet, but no regular reservoir has been found. 



About four thousand gallons of refined oil have been made here -pev 

 year, for the ijast three years. There are many impurities in the crude 

 oil: twelve per cent, benzine; fifty per cent, heavy oil ; the remainder is 

 tar and nitrogenous matter ; much of it is paraffine, and paraffine oil. There 

 is also about fifteen per cent, of useless matter. I saw more than twenty 

 barrels of refuse oil at the spring, which had been rejected from the 

 refinery. This is used for gTeasing wagons, &c. Specific gravity 38. 



The lower cretaceous rocks rise in vertical cut bluffs, four hundred 

 to six hundred feet above the oil springs, and the creek cuts through 

 the upjDcr i^art of the variegated beds. The course of Oil Creek is nearly 

 south. A range of mountains extencls down along the east side of th e 

 creek, and runs out before reaching the Arkansas, and on the west side 



