126 C. W. TOM LIN SON 



Basal Division of the Jefferson Dolomite 

 (M.T. for Wyoming, 101 feet, Crandall Creek) 



3. Fetid, dark-brown, saccharoidal dolomite, mostly thin-bedded. M.T., 

 95 feet, Labarge Mountain. 



2. White, light-drab, or very pale lavender, dense or finely crystalline dolomite, 

 breaking up into small, sharply angular talus. Locally carries ostracods.. 

 M.T., 202 feet, Blacksmith Fork. (Probably included with the Silurian 

 by Kindle and Richardson in Utah because of its light color. Possibly of 

 Silurian age.) Lies directly on the Ordovician in many sections, locally 

 with marked disconformity. 



1. (Typically developed in the Crandall Creek section only.) Thin-bedded, 

 greatly variegated dolomite, with thin bands of red shale and black chert. 

 Dolomites saccharoidal to very dense and closely laminated. Thin lime- 

 stone conglomerate at the base. Lies directly upon the Ordovician at 

 Crandall Creek. M.T., 47 feet, Crandall Creek. 



Break in Sedimentation 



(In Wyoming and Montana ; not in Utah ?) 



SILURIAN 



(Not known in Wyoming, Montana, or Colorado; typically developed at 

 Blacksmith Fork, Utah, where it includes the following members:) 



8. Massive, brown-gray dolomite, medium finely crystalline, with rough 

 weathered surface. 190 feet. 



7. Thin-bedded, slabby limestone. 5 feet. 



6. Massive, pearl-gray or whitish limestone, medium finely crystalline, with 



hackly talus; lower 45 feet contains abundant nodules of snow-white chert 



like Member 5. 140 feet. 

 5. Massive white chert, with many quartz geodes. 10 feet. 



4. Extremely massive, cream-colored, coarsely crystalline dolomite. Upper 

 20 feet contains much chert like Member 5. Basal 5 feet full of internal casts 

 of a Pentamerid shell. 145 feet. 



3. Massive, cream-colored or brownish dolomite, medium fine-grained, 

 weathering to smooth surfaces. 15 feet. 



2. Like Member 8. 138 feet. 



1. Like Member 4. Basal 20 feet crowded with casts of Pentamerids and 



corals. 112 feet. 

 Marked Disconformity . 



MIDDLE AND UPPER ORDOVICIAN 



Richmond (Upper Bighorn, Upper Fish Haven) 



9. White to light-gray or buffish, dense to coarsely crystalline dolomite, mostly 

 thin-bedded. Less resistant than Member 8. Cherty and very fossilifer- 

 ous at Goose Creek Ridge. M.T., 68 feet, Goose Creek Ridge. 



