BLACKWELDER: new formations in WYOMING 423 



Dorwin sandstone member is given, from Dorwin Peak in the 

 Gros Ventre Range, which is capped by this sandstone. It is 

 separated from the underlying jNIadison by a distinct discon- 

 formity, but graduates into the overlying part of the Amsden. 

 In spite of the absence of fossils, the stratigraphic position of the 

 sandstone indicates that its age is early Pennsylvanian or late 

 Mississippian — probably the former. 



The Dorwin sandstone averages about 60 feet thick in the 

 Gros Ventre Range, but dwindles slowly southeastward to the 

 vicinity of Lander, where it is about 15 feet thick. Westward 

 it has been traced in typical condition as far as Teton Pass, but 

 has not been clearly distinguished farther southwest in Idaho. 

 It ranges northward into Yellowstone Park, and northeastward 

 as far as the southern part of the Bighorn Mountains. Else- 

 where it is generally represented by reddish sandy shales. 



PARK CITY FORMATION 



BoutwelP gave this name to certain Carboniferous beds in 

 Utah. Having traced them thence, range by range, from near 

 Park City, into central western Wyoming, the writer now de- 

 sires to indicate their relation to other formations in that region 

 and to show the lithologic variations involved. The rocks are 

 dolomites, shales, limestones, cherts, and phosphatic beds, con- 

 stituting the lower part of Darton's Embar formation, which is 

 typically developed in the Owl Creek Range. It includes the 

 equivalent of the Phosphoria formation, as defined by Richards 

 and Mansfield^ in eastern Idaho, but in addition also the upper 

 part of their Wells formation. From the underlying Tensleep 

 sandstone it is separated by a disconformity, but it is concordant 

 with the overlying Dinwoody beds. Its abundant fossils belong 

 to a somewhat unfamiliar fauna which Dr. G. H. Girty assigns 

 to the Pennsylvanian and Pennian. Although large collections 

 have been made from the formation in the Wind River Range, 

 they have yet received only preliminary notice in printed form,' 

 and many of the species are undescribed. 



5 BouTWELL, J. M., Journ. Geol. 15: 437-458. 1907. 



^ Richards, R. W., and Mansfield, G. R., U. S. Geol. Survey Bull. 577. 1914. 



7 Amer. Journ. Sci. 36: 177-179. 1913. 



