448 N. H. DARTOIS" PALEOZOIC AND MESOZOIC OF WYOMING 



ing thin beds of sandstone. In some places there is at the top a bed of 

 gray or brown sandstone, which is 4 to 8 feet thick. In the Mud Creek 

 region the basal sandstone is 30 feet thick, the overlying purple shales 

 carry eherty concretions and thin layers of brown and bufE sandstone, and 

 at the top are several layers of brown sandstone. In tlie ridge north of 

 Eed creek, southwest of Thermopolis, the formation is about 150 feet 

 thick and presents three bodies of sandstone separated by purplish and 

 gray shales and thin-bedded sandstones. Along Bighorn river north of 

 Thermopolis the basal member is 35 feet of hard, massive, light gray 

 sandstone, conglomeratic at the bottom. Above are 20 feet of softer buff 

 sandstone, 30 feet of purplish shale, and 6 feet of slabby dark buff sand- 

 stone whicli weathers brown. Southeast of Embar the formation is more 

 than 200 feet thick and consists of two prominent sandstone members, 

 the lower one the thicker, separated by purplish clays and shales, with 

 thin-bedded sandstone. Southeast of Black mountain there are at the 

 l:)ase 30 feet of hard white to gray sandstone, massive and in part cross- 

 bedded, then 100 feet of clay, and at the top about 10 feet of hard slabby 

 to massive sandstones which weather to a dark color. The clays between 

 the two sandstones are of strong purple color for 30 feet or more near the 

 top, paler below, and in the middle pale greenish gray. They contain a 

 few layers of fine sandstone of white, buff, and greenish tints and several 

 bands of calcareous and eherty nodules, a common feature in the Owl 

 Creek region. On ISTorth fork of Muddy creek the basal sandstone is of 

 very light color, and it contains in its lower portion a thick mass of white 

 conglomerate. 



^Yind River-Rattlesnal-e mountains. — Tlie Cloverly sandstone is much 

 less thick in the "Wind Eiver and Eattlesnake u])lifts than in the region 

 north and east. In the ridges about Lander it is represented by buff sand- 

 stone, often cross-bedded, which is only 25 feet thick in places, but forms 

 a characteristic hogback ridge. In Eattlesnake mountain the amount is 

 60 to 80 feet and the rock is a hard, massive sandstone, mostly conglom- 

 eratic, capping a hogback ridge. 



Casper-DougIas-j\h'dicinc Bow region. — The Cloverly sandstone is 

 prominent in the ridges south of Casper, especially in the two deep gorges 

 Avhich it causes in Platte river above and below the mouth of Poison 

 Spider creek, tlie wide, high plateau of Haystack range, and .the ridges 

 near Freeland and Alcova. Much of the rock is a brown, massive, coarse 

 conglomerate 40 to 60 feet thick. Near Freeland it is 40 feet thick (see 

 plate 29). In Muddy Creek valley, at tlie east end of Casper mountain, 

 the formation caps tlie usual hogback, and where vertical rises as a steep 

 wall. The basal conglomerate is 25 feet thick, with many pebbles a half 



