18 UNITED STATES GEOLOGICAL SURVEY— TERTIAEY FLORA. 



3. Drab fire-clay, 4 feet. 



2. Coal (No. 1), 11 to 14 feet. 



1. Sandstone. 



This section shows eleven beds of coal, some of which are worked, on a 

 thickness of six to fourteen feet ; this in about four hundred and fifty feet 

 of measures. An analogous distribution is recorded by other sections in the 

 Boulder Valley and northward to ten miles south of Cheyenne. 



Passing westward from Cheyenne, along the Union Pacific Railroad, the 

 Lignitic measures over the Laramie Plains are covered with more recent 

 deposits. The Cretaceous reappear in the valley of Rock Creek, and from 

 Medicine Bow to Carbon the Lignitic is exposed again. At this last locality 

 we have a section of the mines through one hundred feet of measures, 

 exposing three beds of good coal, which have been actively worked since the 

 construction of the railroad. The section at the shaft is, in descending, — 



Feet. 



Shale, clay, and sandstone at top 35 



Ferruginous clay, with a profusion of dicotyledonous leaves 3 



Clay shales and sandstone, with plants at top 18 



Coal (main) 9 



Fire-clay and shale, with dicotyledonous plants 20 



Coal 4 



Fire-clay and shale 8 



Coal 4 



From Carbon to Black Buttes, geological disturbances bring to the sur- 

 face older formations in the Rawlins's Basin, but the Tertiary soon reappears 

 ten miles farther west, in entering the so-called Bitter Creek series, near 

 Separation, where a bed of coal, reported eleven feet, has been exposed ; far- 

 ther, at Creston, where another coal-seam, four feet, has been passed by a bor- 

 ing eighty-three feet from the surface; then at Black Buttes Station, where 

 two beds of coal, one four and the other eight feet, are exposed and worked. 

 In following the railroad passing along the anticlinal ridge whose axis is near 

 Salt Wells, to Rock Springs, coal strata are still exposed at Hallville and Point 

 of Rocks. At Rock Springs, two beds of coal are worked, as at Black Buttes, 

 one four and one eight feet; and besides, as seen by the records of the borings 

 for water made at this locality, and copied in Annual Report, 1872, p. 335, 

 fourteen beds of coal were passed to the depth of seven hundred and twenty- 



