64 THE PERMO-CARBONIFEROUS RED BEDS OF 



assic. In the lower portion of the Chugwater formation, lo miles southwest of 

 Casper, a cast of Schizodus wheeleri was found. The form is usually regarded as 

 Pennsy 1 vanian . " 



In the Black Hills the Minnekahta and Opeche are regarded as probably 

 Permian. The Minnekahta is a light pinkish or purplish limestone grading 

 downward into purple, pink, and red shales, which weather with a nodvtlar 

 surface and finally pass rapidly into the deep red, sandy shale of the Opeche 

 formation. The Opeche is assigned to the Permian because red beds occur in 

 the Permian of Kansas and Nebraska as intercalated layers between lime- 

 stones. The material is a soft red sandstone and a red shale (plates 14 

 and 15). 



In Professional Paper 32, United States Geological Survey, Darton dis- 

 cusses the character of the Red Beds of the Front Range of the Rocky Moun- 

 tains. The vipper Carboniferous limestone is found in the northern part of 

 the Front Range near the Wyoming line, and in the Culebra Range it appears 

 to merge into the Fountain Red Beds, which he believes to be the exact 

 equivalent of the lower Wyoming of Eldridge and the Badito of Hills, and 

 to represent the Amsden formation and overlying Tensleep sandstone of the 

 Bighorn Mountains and the Minnelusa formation of the Black Hills (p. 80). 

 The lower Red Beds of the Rocky Mountain Front Range have yielded no 

 fossils and undoubtedly merge into limestones both on the north and the 

 south and can be correlated with formations in the Black Hills and the Big- 

 horn Mountains. Darton says fvirther: 



"Throughout the Black Hills, the Bighorns and much of the region to the south 

 the upper Carboniferous and Red Bed series presents a general succession as follows, 

 beginning at the top: A thick mass of gypsiferous, red, sandy shales; a thin mass 

 of thin-bedded limestone; a thin mass of red, sandy shales; a thick, hard, light- 

 colored, fine-grained sandstone; and, at the base, limestones and sandstones giving 

 place to sandstones and conglomerates, the basal series lying unconformably upon 

 the Mississippian limestones, on Cambrian, or on old granites and schist" (p. 159). 



"Near the Colorado-Wyoming State line the upper Carboniferous limestone 

 may be seen to merge into red sandstones, apparently by the expansion of included 

 reddish sandy layers observed northwest of Cheyenne and a corresponding thinning 

 of the limestones. A mass of red sandstones and conglomerates, which lies at the 

 base of the limestones for some distance, is seen also to thicken gradually to the 

 south" (p. 161). 



"The name 'Fountain formation' has been used to comprise all of the red beds 

 in the region northeast of Canyon and southwest of Puelalo, and if, as I believe, the 

 Chugwater (upper Wyoming) formation thins out a short distance south of the 

 Garden of the Gods, the Fountain formation corresponds in the main to the lower 

 Wyoming, and is the product of similar conditions at the same geological epoch. 

 I do not see the slightest reason for supposing that the two formations are not 

 equivalent. 



"The character of the beds northwest of Pueblo and in the Garden of the Gods 

 region is precisely the same as in the district west and north of Denver, arid although 

 I made special search I could find no evidence of overlaps or unconformities of any 

 kind within the great uniform mass of red grit deposits. 



