COAL FIELDS OF SOUTHERN UINTA COUNTY 543 



and Green rivers. Prior to the deposition of the Tertiary rocks that cover the 

 greater portion of this region there was a long period of erosion, and these folds 

 were greatly reduced, and in many places all of the Laramie, as well as other 

 lower groups, were removed. In more recent times the present water-courses have 

 uncovered small areas of the Cretaceous rocks, and in many places these are found 

 to be very rich in coal seams. The greatest amount of coal has been found in the 

 Laramie, which has a maximum thickness of about 5,000 feet. The coal veins that 

 are workable are usually inclined from 15 to 40 degrees, and have been mined at 

 the head of Twin creek and Almy. There are twelve known workable veins in 

 this formation that vary in thickness from 5 to 86 feet. There are several that vary 

 from 15 to 30 feet, The 86-foot vein is located at Adaville, about 4 miles west of 

 Kemmerer, and was opened up by a foreign company, but did not furnish fuel for 

 the trade. This vein is most remarkable for its immensity and unusual purity. 

 While I have examined a cross-cut made through the vein, I did not measure it, 

 but believe that the engineer that gave me the figures was reliable. The coal is a 

 medium grade lignite, and in examining it in the cross-cut tunnel I found it solid 

 coal with the exception of a very thin band of sandstone which was less than an 

 inch in thickness. 



All of the Laramie coals are lignites ; but they vary greatly in composition. 

 The mines at Almy have produced a very desirable locomotive fuel for a period of 

 thirty years. Typical outcrops of the Laramie can be seen at Almy, Twin creek, 

 and at the head of Muddy creek. 



Below the Laramie there is a very thick bed of shale containing a few bands of 

 sandstone. The shales vary from a drab to a gray color, and west of Kemmerer 

 have a thickness of about 5,000 feet. This formation can be traced south to Hil- 

 liard, where it has about the same lithological characteristics and thickness. In 

 the Survey of the Fortieth Parallel this formation was given a questionable place, 

 but mentioned as being above the supposed Fox hills. Since there is no formation 

 corresponding to this shale bed that I am familiar with in the state, I propose the 

 name Hilliard for this horizon, the name being derived from the town of Mil- 

 liard, which is located on these beds of shale, and cite the shale beds west of 

 Kemmerer and extending as far as the east portal of the Oregon Short Line tunnel 

 as a typical section. There are some associated fossils with these shales, but 

 typical ones cannot be given at this time. 



Below the Hilliard formation there is a second and very important coal-bearing 

 formation, but one that has but recently been discovered. This extends from 

 Kemmerer southward passing through Diamondville, Cumberland, Spring Valley, 

 and just east of Hilliard, and is composed of very thick beds of compact sand- 

 stone, with shales and coals having an approximate thickness of 2,000 feet. This 

 has been called Fox hills, but upon making a careful examination I could not find a 

 Fox Hill fauna such as is common to the Fox hills of the eastern part of Wyoming. 

 On this account I have found it advisable to call these beds the Frontier forma- 

 tion, the name being derived from the town of Frontier, just north of Kemmerer. 

 This formation is characterized by the presence of Ostrea soletiiscvs, which has a 

 maximum length of about 12 inches, and so far as I am aware occurs only in this 

 formation. In the Frontier there are several seams of coal varying in thickness 

 from 4 to 20 feet, and mines are being operated at Frontier, Diamondville, Cum- 

 berland, and Spring Valley town. The coal is a superior bituminous fuel, being 

 quite hard, with little water and ash, and from tests made withabom calorimeter 



