PERMIAX-TRIASSIC ? 435 



Feet 



Sandy shales aud sandstones, mostly red ; gray sandy beds 



near base; much gypsum; chert nodules in middle 100 



Red shale 60 



Limestone, gray, moderately massive 8 



Red sandy shales and sandstones Con Tensleep sandstone) . SO 



Total 908 



In the slopes 3 miles north of ]\Iediciue Bow tlie thickness is alxjiii 

 1,300 feet. At the top are about 10 feet of red shales, followed in de- 

 scending order b}- 20 feet of gray, slal^l^y sandstone, 100 feet of red, sandy 

 shales, 8 feet of gray, slal)by sandstone, 30 feet of red shale, 2 feet of gray 

 sandstone, slabby and ripple-marked, 3 feet of red sliales, 8 feet of soft 

 gray sandstone, and then a thick succession of red sandy shales and soft 

 red sandstones. Toward the base are several members of thin-bedded 

 sandstone 5 feet and less in thickness. 



At Boswell spring, 23 miles east of Medicine Bow, the red beds inciiuh! 

 a 3-foot bed of impure pink limestone wliich may belong either in the 

 lower part of the Chugwater formation or represent the Pontile limestone. 

 It lies on red, slabby sandstone merging doM'n into red shale, which under- 

 lies the valley extending to the slopes of sandstone (Tensleep). A sim- 

 ilar limestone 4 feet thick appears near the head of Sybille creek, where 

 it is separated from the Tensleep sandstone by 125 feet of red shale. 



Laramie basin. — ISTear Laramie and to the south and southwest the 

 Chugwater formation consists mostly of red shales and fine-grained, red 

 sandstones, with a subordinate amount of lighter colored sandstones, 

 thin beds of limestone, and deposits of gypsum. The latter are notahly 

 thick and prominent in the Red Mountain neighborhood. The fine- 

 grained, massive sandstones weather with rounded outlines, especially 

 wliere the beds are horizontal, and in places they rise in "monuments," 

 one of which is shown in plate 27. The following complete section of 

 tlie formation was measured by Mr Siebenthal in the north face of Red 

 mountain : 



Section of ChiKjtrutcr Fortnutiaii in Red Mountain, Wyoming 



Feet 

 Morrison shales and limestone. 



Light sandstone 12 



Terra cotta to blue shale 20 



Soft sandstone or sandy shale 10 



Terra cotta shale 1 " 



Light buff, soft, massive sandstone 30 



Terra cotta, blue, and green sliales 05 



Light shales 22 



Heavy, flaggy, light to buff sandstone ;ind liirlit shales oO 



XLI — Bull. Geol. Soc. Am., Vol, 19, 1907 



