THE BASIN PROVINCE 131 



has named them the Embar formation. These beds increase in thickness and 

 change considerably in character in passing westward to the Hoback and Salt 

 River ranges, and there they may be divided into several formations, corre- 

 sponding probably to those recognized by Gale in southeastern Idaho and 

 Utah, namely, the phosphatic Park City formation below, the Woodside shale 

 in the middle, and the Thaynes limestone at the top. As not all parts of these 

 strata are fossiliferous, the exact equivalence of the divisions in the eastern and 

 western sections has not been established, but it seems to be approximately as 

 stated. The phosphate beds lie near the base of the Embar formation to the 

 east and the Park City formation to the west and are associated with dark shale 

 and fossiliferous limestone. In the Gros Ventre Range the limestone above the 

 phosphate beds is largely replaced by chert and fossils are very scarce. 



"The individual beds of phosphate rock are subject to much variation in 

 character and richness. In the western sections they are generally considerably 

 thicker than in the east and northeast. The richest variety of phosphate rock 

 is commonly a black oolithic material — firm but not particularly hard. When 

 broken it emits a disagreeable odor of petroleum. From this richer variety there 

 are all gradations, through hard phosphatic limestone and soft phosphatic shale 

 and sandstone down to beds that contain but little phosphoric acid. 



"In the canyon of Snake River in western Wyoming the total thickness of 

 phosphatic beds, both rich and lean, exceeds 40 feet. * * * 



"On the north side of the Wind River Range the phosphate beds have dwindled 

 to 3 or 4 feet in thickness and consist largely of gray phosphatic sandstone, which 

 contains only 35 to 45 per cent of tricalcium phosphate. Across the Wind River 

 Valley, in the Shoshone and Owl Creek mountains, the deterioration of the phos- 

 phate deposits is still more marked, for there the beds are but 2 to 4 feet thick 

 and generally contain less than 20 per cent of tricalcium phosphate. * * * 



"From the work of other geologists in Wyoming it is believed that phosphate 

 deposits exceeding a few inches in thickness do not occur much north of the Owl 

 Creek Mountains, northeast of the southern part of the Bighorn Range, nor east 

 of the low ranges between Casper and Lander. There is no information as to 

 the southward extension of the material, but it has never been recognized south 

 of the Wind River Range in Wyoming. It is highly probable, however, that lean 

 phosphate beds of some importance stretch north by west across Yellowstone 

 Park into southern Montana. * * *" 



From the Gros Ventre Mountains northward and eastward it is scarcely 

 practicable to discriminate the formations known as Park City, Thaynes, 

 and Woodside in southeastern Idaho and northern Utah. The corresponding 

 interval is occupied by a gray or buff alternation of shale, limestone, and 

 chert, with black layers of shale and phosphate rock, which is believed to 

 represent the Embar formation. 



To the west of the areas described by Dale, Richards, and Mansfield 

 there is evidence of the continuation of the Weber quartzite horizon. 

 Lindgren^ in 1899 described the Wood River series. The rocks are all 

 badly disturbed and in places metamorphosed by contact with the great 



^ Lindgren, W., The Gold and Silver Veins of Silver City, De Lamar, and Other Mining 

 Districts in Idaho, 20th Annual Report, U. S. Geological Survey, 'part ni, pp. 89-90 

 and 194, 1899. 



