360 GEOLOGY OF THE DENVEE BASIN. 



over the Denver field depends upon recognition of the associated beds of 

 sandstone and shale and the horizon bearing- the fossil Ostrea. Identifica- 

 tion of the horizontal beds is easiest, and in the area of the Coal Creek 

 syncline this lias been definitely accomplished. 



The seams present in the Coal Creek syncline may be conveniently 

 numbered as follows: That which separates sandstones A and B, the lowest, 

 as No. 1; that immediately overlying B, No. 2; the next, which occurs 

 with regularity at the distance of 16 feet above the last, No. 3; and finally, 

 as No. 4, the one, of constant presence and at the same time workable, 25 

 feet above No. 3. Above the No. -t occur at various intervals several 

 non persistent seams, from 1 to 3 feet in thickness, the lower being those 

 more commonly present and also the better developed; but identification 

 of these, except, perhaps, of No. 5, is impossible. 



The shaft sections on PL XYII are chiefly from the records of super- 

 intendents, but they have been supplemented and verified by personal obser- 

 vation wherever possible, both in mines and at the surface. 



The basis of identification of the beds of the Coal ('reek syncline is 

 the heavy sandstone B and the band of shales which separates seams Nos. 

 2 and 3, these seams being everywhere present and their relative distance 

 from each other quite uniformly preserved. 



seam No. i. — (Figs. CI, H, J, PI. NIX.) This has been exploited only in 

 tlie Erie district. Its presence has been determined in the Stewart and 

 Mitchell mines, and in the latter it has been worked. Near Louisville it 

 is also reported, in a boring from the bottom of the shaft of the Old 

 Welch mine (abandoned), but the data concerning its thickness and depth 

 are unreliable. The presence or absence of this seam is an important 

 consideration in estimating the value of coal lands, and should be one of 

 the first points determined by mine owners. The coal, where opened, is 

 usually free from partings and of excellent quality. 



seam No. 2. — This lies immediately above sandstone B. It preserves its 

 identity throughout the entire Coal Creek syncline and is readily recognized 

 I iv its position in the series of associated strata It has been proved of 

 workable thickness inmost of the mines in the Erie field and in the greater 

 portion of the Lafayette district thus far explored, but in the Louisville 



