160 ENVIRONMENT OF VERTEBRATE LIFE, ETC. 



containing thin stony seams intercalated at intervals in the soft, easily eroded 

 matter. This is immediately followed by 75 feet of a yellowish-gray, brittle, 

 easily decomposed limestone. Next above are 100 feet of light-colored, very 

 thinly bedded limestones, that give way to 100 feet more of dark, siliceous, tough 

 limestone, which breaks under the hammer with great difficulty, yielding an 

 exceedingly rough, ragged fracture." 



Blackwelder^ regards the alternating series of dark limestone and shale 

 with local sandstone beds, which rest upon the Weber quartzite as corre- 

 sponding to Boutwell's Park City formation. '-'There is considerable al- 

 though not conclusive evidence of an important unconformity between 

 the Weber and the Park City formations." ^ 



In the Uintah Mountains, as described by Weeks,^ there are 600 feet of 

 Permo-Carboniferous red and purple shales and blue limestone on the east 

 side of the Duchesne River below the mouth of the West Fork, followed by 

 "1,000 feet of light gray and white sandstones, with some interbedded 

 limestones in the lower part. In the upper part these sandstones occur in 

 alternating layers of soft and compact beds full of peculiar black points and 

 specks. These are succeeded by 800 to 900 feet of red shales, with a promi- 

 nent band of light-colored shale at the top." 



In northeastern Utah, southeastern Idaho, and southwestern Wyoming 

 the various limestones and shales of the Wasatch and Uintah Mountains 

 give place to the phosphate-bearing Park City formation of Boutwell, 

 originally described and named in 1907.^ It was more fully discussed in 

 1912.' The later description is quoted in part below: 



"This formation is made up largely of calcareous members, but it also embraces 

 several sandstones and quartzites. * * * in general the formation comprises a 

 thick limestone in its lower part, several minor limestones in its upper part, and 

 a number of thin calcareous beds near the base, with intercalated quartzites and 

 sandstones." 



The type section of the formation is exposed in the Big Cottonwood 

 Canyon : 



Grayish-white limestone, with fine gray and white cherts increasing toward bottom 19 



Shale and fine buff sandstone 19 



Dark-gray limestone; thin chert, red shale, and porous loose members at base 7 



Sandy shale 11 



Yellowish-gray quartzitic sandstone changing into cherty white lime below 21 



Gray and white banded chert with few white sandstone intercalations 52 



Fine calcareous sandstone, with lentils of chert and brecciated fragments of sandstone 8 



' Blackwelder, Eliot, New Light on the Geology of the Wasatch Mountains, Utah, Bull. 

 Geol. Soc. Amer., vol. 21, p. 517, 1910. 



^Willis, Bailey, Index to the Stratigraphy of North America, U. S. Geological Survey, 

 Professional Paper No. 71, p. 379, 1912 (citing Blackwelder). 



' Weeks, F. B., Stratigraphy and Structure of the Uintah Range, Bull. Geol. Soc. Amer., 

 vol. 18, p. 439, 1907. 



^ Boutwell, J. M., Stratigraphy and Structure of the Park City Mining District, Utah, 

 Jour. Geol., vol. 15, p. 439, 1907. 



5 Boutwell, J. M., Geology and Ore Deposits of the Park City District, Utah, U. S. Geo- 

 logical Survey, Professional Paper No. 77, p. 49, 1912. 



