CRETACEOUS PLAINS OF COLORADO. 61 



have been run, and shafts sunk in several locaHties Avithout success ; all 

 the important deposits of workable coal lie to the southward. 



Near what has been taken as the base of the Laramie formation occurs 

 a bed of friable red sandstone, which may be followed for a long distance 

 by a low bank or ridge. In this red sandstone, numerous beds of coal and 

 carbonaceous clays outcrop, many of them having been more or less ex- 

 plored. At the extreme northern limit of the Laramie formation, about 18 

 miles southwest from Cheyenne, and 5 or 6 miles west from Carr Station, 

 on the Denver Pacific Railroad, in this same red sandstone, occurs one of 

 the earliest discoveries of coal in Colorado. 



It derives some interest from its being the most northern occurrence 

 of coal, before the beds pass under the Tertiary deposits. At this locality, 

 the sandstones dip between 10° and 12° to the eastward. A tunnel has 

 been run in on the coal for 100 feet.*' The seam of coal between the im- 

 pure clays measures 3 feet. 



The following section was made along the bank, beginning at the top: 



1. Reddish-yellow sandstone. 



2. Arenaceous clay 3 feet. 



3. Blue clay 1 foot. 



4. Coal 3 feet. 



5. Black clay and impure coal 1 foot. 



6. Red sandstone. 



In the sandstone overlying the coal may be collected large numbers 

 of shells belonging to the genus Ostrea. 



The coal appears to be of poor quality, and the mine was soon aban- 

 doned. It possesses a jet-black color, a somewhat resinous lustre, but 

 crumbles readily on exposure to the air. 



Following this red sandstone southward, the coal outcroppings may be 

 traced for a distance of several miles along a shallow longitudinal valley, 

 which trends a few degrees west of south. Along the eastern ridge, usu- 

 ally above the outcropping clay beds, the same shell of the genus Ostrea 

 was found as already mentioned, but very poorly preserved. Still farther 

 southward, the same sandstone rocks would appear to gradually assume a 

 less dip until they are seen, nearly west of Park's Station, lying horizont- 

 ally, terminating to the eastward in abrupt escarpments, overlooking a 



