456 K. H. DAETON PALEOZOIC AND MESOZOIC OF WYOMING 



beds are concealed. Five miles east of Jelm moimtain the Mowry mem- 

 ber is underlain by 20 feet of drab, brittle, sandy shale, 6 feet of black 

 sandstone, 4 feet of -^vhite sandstone, and 145 feet of black shale lying 

 on Cloverly. On Laramie river, 3 miles north-northeast of Jelm moun- 

 tain, the upper Benton beds are 5 feet of black shale, 27 feet of soft, gray, 

 heavy, flaggy sandstone, 8 feet of interbedded sandstone and shale, and 

 30 feet of black shale. In the syncline northeast of Eed mountain, the 

 lower 110 feet of the formation are black shales overlain by 30 feet of 

 yellowish to gray shales, and then 10 feet of flaggy, buff sandstone con- 

 taining impressions of long, narrow, willow-like leaves. On the soiitli- 

 east side of Hutton lake, 10 miles southwest of Laramie, the steep-dipping 

 lower Benton l)eds have 100 feet of dark shale at the base, with a few thin, 

 sandstone layers, 25 feet of gray sandstone, 30 feet of dark shale, and 

 Mowry beds 100 feet or more thick. The lower shale also contains a bed 

 of bentonite in this vicinity. On the east bank of Sand creek, 11 miles 

 northeast of Eed mountain, the formation contains a bed of bentonite 

 4 feet thick underlain by 7 inches of soft, gray sandstone. 



In Laramie basin the JSTiobrara formation outcrops at intervals from 

 the foot of Jelm mountain northeastward past Laramie. It also outcrops 

 on both sides of the syncline in Centennial valley; it appears in the 

 faulted block near Jelm, and there is another small area 3 miles west of 

 the summit of Eed mountain. For much of its course, however, it is 

 buried beneath later deposits. The most extensive exposures are in the 

 large hollows west of Laramie and in bluffs along Laramie river south- 

 west of Laramie. It consists largely of impure chalk rock of light gray 

 color which weathers bright yellow and contains large numbers of Ostrea 

 congesta. The thickness is 425 feet in the sharp upturn 2 miles north- 

 west of the Union Pacific Soda lakes, west of Laramie. The middle 

 member is dark gray shale. The chalk rock is in beds varying from thin 

 layers to slabs an inch or two inches in thickness, and sometimes it is 

 sufficiently hard to give rise to buttes which are of conspicuous bright 

 yellow color. 



East side of Laramie mountains. — On the east side of Laramie moun- 

 tains the Benton consists mainly of shale, but several members are recog- 

 nizable. The Greenhorn limestone of other regions is represented by a 

 tliin layer of impure slabby limestone containing the characteristic 

 Inoceramus lahiatus. The ]\Iowry member is distinct, and near the base 

 of the Benton there are 15 to 20 feet of hard sandstone, in most places 

 rising in a small, sharp ridge often more conspiqiious than the Cloverly 

 sandstone. A representative section in vertical beds near Horse creek is 

 as follows : 



