hatden.] GEOLOGY LIGNITIC GROUP SECTION. 31 



eral feet in diameter. Sometimes these concretions are oval or flat, 

 with horizontal layers; but in most cases they fall in pieces, showing 

 concentric coats, the disk like shells falling off from the outside gradu- 

 ally. There is also a species of sea-weed, Halymenites, quite abundant 

 in these sandstones. I call them the transition beds, though they may 

 be Cretaceous, and they correspond with those described as occurring 

 below the coal on the Arkansas. 



Number 7 in the section is the sandstone that usually forms the basis 

 bed of the Lignitic group. This bed is here full of small iron-rust con- 

 cretions, some of them solid, with a gray nucleus, others hollow, the 

 cavity filled with fine dust, a kind of iron-rust. These concretions, vary- 

 in? from an inch to three or four inches in diameter, are so abundant that 

 they cover the ground for some distance from the bluff. About the* mid- 

 dle of the sandstone-bed, there is a band of dark-brown indurated sand, 

 mixed with bits or fragments of vegetable material, about five feet in 

 thickness. This bed or band may, quite possibly, become coal in some 

 localities. At one point in the southern portion of the coal-basin on 

 the Arkansas River, a seam which appears to correspond to this dark 

 band occurs in the lower sandstone, and is quite good coal, two feet in 

 thickness. The quantity and character of the coal at this locality was 

 determined by the sinking of several shafts. In section a, we have 

 two quite thick beds of coal, both of which were penetrated by a shaft, 

 and thus the section may be regarded as correct. 



Section &. 



Feet 



1. Surface-soil 8 



2. Sand 12 



3. Drab-clay 6 



4. Soapstone and clay 9 



5. Slate 5 



6. Sandstone 4 



7. Arenaceous clay 7 



8. Soft slate 6 



9. Coal 1 



10. Sandstone with plants 30 



11. Bituminous shales 11 



12. Sandstone with iron 3 



13. Clay G 



14. Hard black slate 11 



15. Coal 6 



In section &, which is the .record of a shaft sunk at a distant local- 

 ity in the same basin, we have only the upper bed of coal at the 

 base. The two sections give a pretty clear idea of the strata which 

 include the two lower beds of coal. Above the coal-bearing portion, there 

 is an interval which we estimated at about 200 feet, in which the beds 

 were obscure, but thin seams of impure coal cropped out. The mate- 

 rials were clays, arenaceous clays, and thin layers of sandstone, yield- 

 ing so readily to atmospheric forces that no sharp bluffs are formed, so 

 that the character of the strata could not be clearly seen. We theu 

 have a range of high bluffs 200 to 400 feet high, which begin at the base 

 of the mountains, about two miles north of Manitou, and extend across 

 Monument Creek, and reach off to the southeast far beyond the limit of 

 vision, down the entire valley of the Fountain to its entrance into the 

 Arkansas River near Pueblo. The rocks all around Pueblo are Creta- 

 ceous, yet it is quite possible that far to the eastward the Lignitic group 

 overlaps them, haviug originally been connected with the coal-basin to 

 the south near Caiion City. We may thus obtain a dim conception of 



