82 



ANNALS NEW YORK ACADEMY OF SCIENCES 



Section of the Morrison Formation in the N. E. Yi Sec. 3, T. 16 N., R. 10 E., 

 near Shannon Creek, Montana 



Feet Inches 

 Kooteuie formation. 



Beds concealed 20 , . . 



Shales, red and green, containing ironstone layers at base 46 



Limestone, light colored, fossilif erous 5 



Shale, green, sandy, fossiliferous 25 



Limestone, white, fine-grained, thin-bedded 6 



Shale, green, sandy 13 



109 6 





I I L i=j: 



Fig. 36. — Section of the Morrison forma- 

 tion on Belt Creek, Montana. 



Scale, 125 feet to 1 inch. (Fisher.) 



Fig. 37. — Section of the Morrison forma- 

 tion near Shannon Greek, Montana. 



Scale, 125 feet to 1 inch. (Fisher.) 



BIGPIOElSr MOUNTAINS 



The Morrison formation is exposed along the eastern, northern and 

 western sides of the Bighorn Mountains. The following description is 

 taken largely from Darton (1906, 2). 



The band of outcrops is almost a continuous one, except in a few local- 

 ities where it is overlain by Tertiary deposits. Owing to the softness of 

 the material of the formation, most of the outcrops are poor and are often 

 covered with talus. 



The thickness of the formation varies from 100 to 250 feet. West of 

 Greub it is 160 feet, southwest of Buffalo 250 feet, northwest of Buffalo 

 150 feet, on Little Eapid Creek it is 200 feet, on Wolf Creek less than 

 100 feet, on Little Tongue Eiver 120 feet, on Amsden Creek 150 feet, 

 and about 150 feet or a little less on the northeastern side of the moun- 

 tains in Montana. There is a considerable variation on the southeast 

 side of the mountains. East of Barnum it is about 150 feet, east of 

 Houck's 100 feet, near Griggs 200 feet, on the uplift south of Tisdel's 

 ranch it is 250 feet. In the vicinity of Tensleep it is about 250 feet. 

 On Alkali Creek, north of Cloverty, it is 282 feet, and in the region of 

 Thermopolis, 120 to 130 feet. 



Near Cloverly, where the dip is low, the outcrops cover large areas. 

 In most localities the Morrison occupies a low saddle between the slopes 



