434 X. H. DARTON PALEOZOIC AXD MESOZOIC OF WYOMIKG 



La Bonte creeks, wliere the formation contains considerable gj'psum near 

 its base. Extensive exposures occur in jSTorth Platte river, in the big 

 bend 7 miles due south of Douglas. In the axis of the anticline in this 

 bend the Minnekahta is bared, lying on red shale of which 50 feet are 

 exposed. Here the limestone outcrops in massive ledges, but it is thin- 

 Ijedded. Its upper part is mottled dark gray, but at the top are 5 feet of 

 more massive light colored limestone. The basal red shales, 80 feet thick, 

 are exposed in the gorge of "Wagonhoimd creek 9 miles soiith-southwest 

 of Douglas, lying on dark Tensleep sandstone at top of Casper formation. 



Southwest of Casper the Chugivater formation consists of the following 

 beds : 



Section of Chugicater Formation, l^t Miles Southwest of Casper, Wyoming 



Feet 



Massive, pale red, fine sandstone ; some red shale 60 



Hard, slabby, purplish limestone 15-25 



Red sandstone and red sandy shale 500 



Thin-bedded buff limestone 2 



Red sandy shale 40 



Limestone, slabby below, massive and hard at top 15 



Red shale (on Tensleep sandstone) 30 



The hard limestone member near the top of the formation is a con- 

 spicuous feature at the west end and south side of Casper mountain, about 

 Alcova, and in the Shirley and Freezeout hills. It usually caps a red 

 wall where dips are low or causes a ridge, as shown in plate 27, where 

 dips are steeper. Near Freeland it is 20 feet thick and separated from 

 basal gray sandstone of Sundance formation b}' 60 feet of red, massive 

 sandstone. ISTorth of Difficulty it is 8 feet thick, but in northeast por- 

 tion of Freezeout hills it is only 4 feet thick and lies on 10 feet of gray 

 sandstone. ISTorth of the mouth of IMedicine Bow creek there are three 

 limestones in the upper part of the formation. A short distance farther 

 west there is only one upper limestone, which is 8 feet thick and lies be- 

 tween 250 feet of red shale above and 900 feet of red beds below. The 

 latter include 3 thin limestone beds near their base. In the Freezeout 

 hills these basal limestones give place to a 30-foot bed of gypsum. In 

 the vicinity of Alcova the following section is typical : 



Section of Chufficater Formation Southeast of Alcova, Wyoming 



Feet 



Red sandstone 40 



Red shale and slabby sandstone ; some buff 125 



Limestone, hard, gray ; caps "Red wall" 20 



Red shale 15 



Red sandstone 10 



Red sandy shales and sandstones 450 



