70 



GUIDEBOOK OF THE WESTERIs^ U:N^ITED STATES. 



miles 



making sandstone and comes 



stone and shale of the Rock Springs coal group/ wliich contains tlie 



prmcm 



sandstone 



s 



railroad crosses the massive 

 the Mesaverde formation and 



emerges mto an open space occupied by the marine sh 

 farther east is called the Steele shale, Tliis is separated 

 younger massive sandstones of the Mesaverde formation by a thick 



from 



''badland^' sIoidcs. 



forms prominent 



^ino^s g^rouD is mn 



miles north of Thayer Junction. About 2 miles northeast of Superior 



HiU 



form 



intruded into the stratified rocks, and dikes cuttino^ 



Thayer Junction. 



Elevation 6,434 feet. 



Omaha 791 miles. , , - 



across the sedimentary strata. Associated with these 

 intrusive rocks are volcanic cones and lava flows. These rocks have 

 long been objects of scientific interest because of their unusual char- 

 acter. Lately they have attracted additional interest by reason of 

 the potash-rich mineral, leucite, they contain^ which may some day 

 be utilized if a process can be found for extracting the potash cheaply. 



Hills 



ms more than 197,000,000 t« 

 Baxter sidmg is near the 



center of the Rock 



£rs dome 



The several eastward -dipping formations crossed between Bitter 



Creek station and Thayer Junction once arched over 

 ^^ ^' ' the top of this dome and now dip in the opposite 



Sa^'ir* direction on its western slope, as is indicated in the 



profile on the accompanying map (sheet 12). A mile 



west of Baxter siding a branch line runs northward 3 miles to Gunn, 



where mines have been opened on the lower beds of tlie Rock 



Tings 



Two miles west of the siding the route enters a 



1 The Rock Springs group of coal beds is 

 of lower Mesaverde (middle ITpper Creta- 

 ceous) ^e and is the most important group 

 of coals in "Wyoming, for it contains many 

 beds of bituminous coal of higher grade 

 than that of the other groups of this region. 

 The basal portion of the group of rocks 

 consists of hea\'y ridge-making coal-bear- 

 ing sandstones (PI. XV, ^, p. 67), and the 



vn, yellow, and white 



um 



thicknei^ 



ma 



thick. 



hat r^n- 



lariy distributed through the group and 

 are fairly persistent along the strike. 



ha 



rings 



around the end of the dome to Superior. 



rng 



shale 



coal 



400 



K 



least 



south of Superior, as in this locality the 

 coal beds are somewhat thinner and are 

 fewer in number than between Superior 

 and Rock Springs. 



