JURASSIC SYSTKM 439 



shales with conspicuous hard layers. On the north slo2:)e the outcrop ex- 

 tends from a point rt miles west of Embar nearly to Deranch and also 

 around the Thermopolis anticline. On the south side it extends westward 

 from ISTorth Pork of Muddy creek to the base of Black moiintain, and it 

 also appears in small exposures near longitude 108° 30', at the upper end 

 of Bighorn canyofl and in the two uplifts between Dry and Muddy creeks, 

 near longitude 109°. The local stratigraphy varies somewhat. At the 

 base are sandstones; the middle and upper beds are mainly shales, and 

 there is more or less sandstone for about 40 feet at the top. The shale.s 

 are greenish or dark gray and contain limestone in concretions and thin 

 layers, often highly fossiliferous. In the western portion of the uplift 

 one of the upper sandstone beds is so hard that it causes high, narrow 

 ridges, which are especially prominent in the divide west of Dry creek. 

 iSTear Embar and eastward a hard, dark gray sandstone, 12 feet thick, 

 which makes a prominent ridge, is underlain by the basal member, 80 feet 

 thick, of shale and soft greenish gray sandstones containing many Gnj- 

 [ilicea calceola. 



Section of Sundance Funnation on Owl Creek, 7 Miles 'Northwest of Thermop- 

 olis, Wyoming 



Feet 

 Green, soft.' sandy shales and hard greenish fossiliferous 



sandstone in alternating layers 70 



Gray sandstone -4 



Green sandy clay 20 



Gray limy sandstone 2 



Dark greenish gray, sandy clay, with many belemnites 40 



Greenish gray sandstone, with occasional hard layers 30 



Green sandy shale 20 



Greenish gray sandstone, thin-bedded 4 



Hard, buff, impure limestone, breaking into small rectangu- 

 lar blocks ; . . . 2 



Green sandy shale lying on "Red beds" 2 



Total 194 



Tlie exposure at south end of Bighorn canyon is in the east bank of the 

 river. Here there are about 250 feet of alternating layers of greenish 

 gray sandy shale and dark gray, fossiliferous sandstone. 



TfmcZ Eiver-Eattle snake mountains. — Along the slope of Wind Eiver 

 mountains and in the uplifts passing east of Port Washakie and Lander 

 the Sundance formation is about 300 feet thick and consists of greenish 

 gray shales and sandstones, with thin but prominent ledges of impure, 

 liighly fossiliferous limestone in their iipper part. In the northern foot- 



