NOTE ON BAKED CLAYS AND NATURAL SLAGS IN 

 EASTERN WYOMING 



E. S. BASTIN 

 Chicago 



A striking feature of the country just to the east of the Big Horn 

 Mountains, and one which adds greatly to its picturesqueness, is the 

 widespread development of red beds and slaglike materials in conse- 

 quence of the burning-out of lignite beds in the Laramie division of 

 the Cretaceous. The baking and accompanying reddening of the 

 sandstones and clays have in some districts been so extensive that the 

 landscape somewhat resembles that of the typical "Red Beds" of 

 Jura-Trias age. 



Explorers and geologists who have visited this region, from the 

 times of Lewis and Clarke down to the present day, have noted the 

 occurrence and characteristics of these beds, and have in most cases 

 properly interpreted their origin. Mr. J. A. Allen, who accom- 

 panied the Northern Pacific Railroad Expedition, has given us an 

 excellent account 1 of these beds, and has summarized the previous 

 literature. It is the intention here merely to add a few notes on the 

 field occurrences and something as to the microscopic characters. 



At the suggestion of Professor R. D. Salisbury, Mr. A. E. Taylor 

 and the writer spent a few days in the study of these beds during the 

 summer of 1903. These studies were confined to the district between 

 Gillette and Buffalo, Wyo., but beds of a similar nature give color 

 to the landscape and exert a notable influence upon the topography 

 over a much more extensive region. Their occurrence has been 

 reported over practically the whole northeastern quarter of the state 

 of Wyoming, and over an area of about equal size in southeastern 

 Montana and adjacent parts of the Dakotas — a total extent of at least 

 100,000 miles. This vast region is characterized by horizontal or 

 gently inclined strata, made up largely of clays and fine sands, with 

 occasional seams of lignitic coal, the latter usually only a foot or two 



1 Proceedings of the Boston Society of Natural History, Vol. XVI (1874), pp. 246 ff. 



