THE BASIN PROVINCE 165 



and gray limestones, some beds of which are from 5 to 25 feet thick. The upper 

 member of shaly Hmestones has thus far not furnished any identifiable fossils, 

 but nevertheless has lithological characteristics so distinctive that it is easily 

 recognized wherever it is exposed. On Brush and Little Brush Creeks and in the 

 vicinity of Green River on both sides of the range this member is considerably 

 thicker than at the west end of the field and consists of grayish-drab limestone 

 and shaly limestone with a few streaks of pink or red clay near the top, all 

 weathering to a dull slate gray, so that the entire series, seen from a distance, 

 looks like a gray clay bank. In some respects these beds resemble the Dinwoody 

 formation along the east side of the Wind River Mountains, in western Wyoming. 

 Future detailed work may result in differentiating them into a formation, but 

 for the present they are retained as a part of the Park City formation. 



"The upper cherty limestone member is variable in detail, but is prominent 

 and easily recognized throughout the range. It consists of massive gray to 

 cream-colored limestone 20 to 25 feet thick (underlain by gray and greenish 

 dark chert in a matrix of shale). It is a controlling factor in the topograph}' and 

 produces long faceted dipslopes along the south side and a part of the north side 

 of the mountain front. Certain parts of this member are highly fossiliferous and 

 contain abundant specimens of Leioclenia, Derbya, Spiriferina pulchra, and 

 Lingtdidiscina utahensis, other parts resemble somewhat the Rex chert member 

 of the Phosphoria formation of eastern Idaho. 



"The phosphatic shale is probably the most distinctive member of the Park 

 City formation. It is made up largely of black and green, decidedly fissile shale 

 40 to 50 feet thick and beds of limestone, sandstone, chert, and phosphate ranging 

 in thickness from a few inches to several feet. Some of the beds of limestone and 

 phosphate contain an abundance of fossils, a few of which have been collected for 

 identification. In addition to the Bryozoa there are numerous comminuted 

 fossil fragments, glauconite, and scattered foraminiferal shells. This member is 

 probably equivalent to the lower part of the Phosphoria formation in eastern 

 Idaho, as described by Richards and Mansfield.' 



"The lowest member consists chiefly of massive limestone with some beds of 

 shale and sandstone. It is more variable than the overlying members and in 

 some localities appears to be entirely missing, as the phosphate shale or phosphate 

 bed rests directly upon the Weber quartzite. It is probably owing to variations 

 in this member and the upper member of the formation that the Park City 

 shows so great differences in thickness throughout the field. The total thickness 

 ranges from 250 feet or less to 850 feet or more in parts of the field where the beds 

 have been measured. In certain portions of eastern Idaho where the phosphate 

 deposits have been studied in great detail the lowest member of the Park City 

 formation as here described was considered a separate member of the Park City 

 formation and later was included with the Weber quartzite and underlying beds 

 as a part of the Wells formation. It appears, however, from the facts thus far 

 gathered in the Uinta range, that it must be considered as a part of the Park City 

 formation as defined by Boutwell in his Park City reports. 



"The contact between the Weber quartzite and the overlying Park City 

 formation has been a subject of considerable study without definite results. 

 The beds in many localities appear to be conformable, but the relations from 

 place to place and the position of the phosphate series with regard to the Weber 



' Richards, R. W., and G. R. Mansfield, Geology of the Phosphate Deposits Northeast of 

 Georgetown, Idaho, U. S. Geological Survey Bull. 577, I9r4. 



