Stevenson.] ^1^ [Oct. 7, 



Beyond the axis of the synclinal, the rocks rise rapidly westward and at 

 the head of the canon one is brought very near to the horizon of Goal bed 

 H. An opening has been made in a bed at a little way beyond the head 

 of the canon, but in the absence of all exposures near at hand, the place 

 of the bed could not be determined. The lowest sandstone of the group 

 is reached at a short distance beyond and shows the same features as those 

 to be described on Oak creek. The middle Cretaceous rocks lie immediately 

 behind the great sandstone and continue thence to the foot of the mountain, 

 where the Dakota rests on the metamorphic rocks. The transition from 

 the Coal group to the Fort Pierre is very gradual and no line of separation 

 can be tound. 



Oak creek. The canon of this stream follows a north-easterly direction 

 across the field and affords by far the best series of exposures. It is fol- 

 lowed by the Coal branch of the Atchison, Topeka and Santa Fe railroad 

 to Rockvale, where the Caiion Coal Company has sunk the shaft, No. 1, 

 with the view of working Coal bed A. The outcrop of that bed is poorly 

 shown in this canon along the eastern side of the field, but that of Coal 

 bed C is frequently exposed. Shaft No. 2 of the Canon Coal Company 

 opened this bed and a slope is under way to reach the same bed for the 

 Colorado Coal and Iron Company. The section at shaft No. 3, including 

 the measurements in the shaft, is as follows : 



1. Sandstone, seen on the bluflf 15' 



2. Shales 10' 



3. Concealed to curb of shaft as estimated from the 



dip 120' 



4. Clay and gravel in shaft 30' 



5. Shale and thin sandstone , 31' 



6. Coalbed'E 1' 6" 



7. Shale and thin sandstones 47' 6" 



8. Goal bed C 4' 6" 



9. Fireclay 0' 5" 



A coal blossom, indicating a thickness of about 8 inches, was seen at a 

 few rods east from the shaft. Allowing for the dip, this bed belongs near 

 the middle of the gravel at the top of the shaft, and is therefore Goal bed 

 G. Coal bed E contains very good coal, but as it is not of workable 

 thickness, no tests have been made to determine its value. Coal bed C is 

 mined in the shaft where its structure is 



Coal, 2' 2" ; clay, 2" ; coal, V 9" to 2' 2". 



An outcrop on the opposite side of the valley shows the bed 3 feet 10 inches 

 thick, as reported by the local superintendent of the company, and there 

 the parting is present also. But lower down the stream the bed becomes 

 very thin and at several exposures it is insignificant. In the sliaft it 

 yields an excellent coal, which is hard, must be blasted but comes out in 

 large blocks. Tlie underlying fireclay aids much in mining, but it is soft 

 and is likely to be a source of annoyance in the immediate vicinity of the 

 shaft. The dip is a little south of west at 5 degrees. 



