166 ENVIRONMENT OF VERTEBRATE LIFE, ETC. 



quartzite make it appear that the Park City formation unconformably overlies 

 the Weber quartzite. However, until the beds are studied in greater detail and 

 careful areal mapping is completed it will not be possible to state definitely the 

 extent or magnitude of the unconformity. It seems improbable, however, that 

 the relation between the Weber quartzite and the phosphate beds of the Park City 

 formation can be satisfactorily accounted for in any other manner. Boutwell, 

 who studied the formation in the Park City region of Utah, comes to the con- 

 clusion that the strata lie conformably upon the underlying Weber quartzite 

 and that sedimentation proceeded unbroken from Mississippian time to the end 

 of Park City time. He calls attention, however, to the fact that one geologist 

 reported a marked unconformity at this horizon and that his own studies were 

 not as conclusive or definite as might be wished. Blackwelder,' in his studies of 

 the Wasatch Range, recognized the unconformable relation between the Weber 

 quartzite and the overlying Park City beds and concluded that in the Wasatch 

 Range there is an unconformity between the Weber quartzite and the overlying 

 Park City phosphatic beds of Permian age. In another report Blackwelder^ 

 states that the base of the Park City formation is generally marked by beds of 

 white and pink soft sandstone separated from the Weber quartzite by an obscure 

 unconformity, which appears nevertheless to be one of considerable magnitude. 

 Similarly in the Wind River and Gros Ventre Mountains the Park City is known 

 to rest upon the Tensleep sandstone (horizon of Weber quartzite), in apparent 

 conformity at many localities, but close examination reveals evidence of an 

 uneven erosion surface at the base of the Park City beds. A similar unconformity 

 has also been reported by Richards and Mansfield in eastern Idaho.- The 

 conditions that prevailed during the period of deposition of the Park City forma- 

 tion marks the transition from those under which the great thickness of Weber 

 sandstones was laid down to those under which the sediments formed red shale. 

 The strata indicate deposition in comparatively shallow water and show an 

 unstable or fluctuating shore-line, as it appears that both elevation and depression 

 of the shore occurred. 



"The irregularities and differences in thickness of the Park City formation 

 may best be illustrated by giving some of the measured sections in different parts 

 of the field. Boutwell's type section of the Park City formation is Big Cotton- 

 wood Canyon, Utah, given below (see page i6o of this work), does not state the 

 thickness of the phosphate bed or the phosphatic shale, nor does he show the 

 horizon at which it occurs. However, the work done by Gale in the Park City 

 district in 1 909 proves that the phosphate occurs near the middle of the formation 

 and is included with the 104 feet of beds overlying the 18 feet of siliceous arkose. 

 In discussing the phosphate deposits Boutwell states that the phosphate bed noted 

 at several points is about 3 feet thick and contains 32.6 per cent P2O5, or 71 per 

 cent bone phosphate." 



Schultz gives several sections other than the type section of Boutwell 

 cited above. In commenting on the phosphate rock, he describes its oolitic 

 character and notes the irregularity of the layers: 



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



Geol. Soc. Amer., vol. 21, pp. 531-533, 542, 1910. 

 ^ Blackwelder, Eliot, Phosphate Deposits East of Ogden, Utah. U. S. Geological Survey, 



Bull. 430, pp. 536-551. 1910. 

 ? Richards, R. W., and G. R. Mansfield, loc. cit., pp. 16, 22, 



