x84 KNOWLTON 



and must be considered as the lower member of the Fort Union. 

 So far as known to the writer the Laramie is not present in this 

 general region. 



Areal Distribution and Paleontologic Contents of Lower 

 Member of Fort Union Formation. 



i. hell creek, montana. 



In 1907 Mr. Barnum Brown" published a valuable contribution 

 on the geology of the Hell Creek region of northeastern Montana. 

 To the beds in this area which contain a rich dinosaur fauna he gave 

 the name Hell Creek beds, and alFO stated that: 



These beds are exposed on the Yellowstone River at Sentinel [Cas- 

 tle?] Butte near Forsyth; at Glendive; near Eklaka; and at Hockett 

 P. O., south of the Yellowstone. They are probably continuous 

 with the dinosaur-bearing beds of the Little Missouri, and of the 

 Grand and Moreau Rivers. 



The "Hell Creek beds," which are between 300 and 400 feet in 

 thickness, are stated by Brown to rest unconformably on the Fox 

 Hills, and are composed of two members, a basal massive sandstone, 

 and an upper member of alternating dark arenaceous clays, carbon- 

 aceous shales and sandstones. Overlying the dinosaur clays, and 

 forming an "uninterrupted continuation" of them, are the so-called 

 lignite beds 100 feet in thickness which are characterized by the 

 presence of numerous beds of coal; they are referred by Brown with 

 question to the Fort Union. Above the lignite beds without appar- 

 ent break are the light-yellow sandstones and clays of the "identi- 

 fied Fort Union." At several points in the "Hell Creek beds," but 

 particularly in the massive basal sandstone. Brown records the pres- 

 ence of numerous concretions which are sometimes of very irregular 

 shape, but often resemble huge tree-trunks. It is perhaps noteworthy 

 that similar concretions occur in approximately the same stratigraphic 

 position at widely scattered localities within this lower member of 

 the Fort Union, as at Forsyth, Miles City, near Glendive, Montana, 



• Bull. Am. Mus. Nat. Hist., vol. 23, 1907, pp. 823-845. 



