RESUME UPPER CARBONIFEROUS AND RED BEDS 439 



are apparently Upper Carboniferous, although no fossils were observed 

 in the lower 100 feet. It has been suggested that the non-fossiliferous 

 basal beds may represent the Lower Paleozoic series, but the overlap 

 relations north and south do not sustain this, except that if the lime- 

 stones represent all of the Hartville formation of the Hartville region 

 the lower beds may possibly include rocks of later Mississippian age. 

 The limestone series contains several red sandstone members, but at the 

 top gives place rapidly to the thick body of Chugwater red shales. The 

 Tensleep sandstone appears to be represented, containing thin layers of 

 limestone in its middle and on Chugwater creek another one near its 

 top. Then succeed typical soft red sandy shales, which, on Horse creek, 

 include a 20-foot bed of limestone, apparently representing the Minne- 

 kahta horizon, a bed not found on Chugwater creek. 



Near the Colorado-Wyoming state line the Upper Carboniferous lime- 

 stones were found to merge into red sandstones, apparently by the ex- 

 pansion of included reddish sandy layers observed northwest of Chey- 

 enne and a corresponding thinning of the limestone.* A mass of red 

 sandstones and conglomerates, which lies at the base of the limestone 

 for some distance, is seen also to thicken gradually to the southward. 

 The product of this change is a great lower series of coarse Red beds, 

 containing three thin limestone layers which persist for several miles. 

 All through this region the supposed Tensleep sandstone horizon is well 

 marked, and it was traced without difficulty southward to beyond the 

 Garden of the Gods. It is the " Creamy sandstone " at the summit of 

 the lower Wyoming of Eldridge, as described in the Denver monograph, 

 and I feel certain that the conspicuous white sandstone ledge lying im- 

 mediately in front of the gateway to the Garden of the Gods is undoubt T 

 edly the upper part of the southern extension of the same bed, so that 

 it is an important horizon marker. Throughout its course in Colorado 

 it marks the transition from the coarse deposits of the lower coarse Red 

 beds (lower Wyoming) to the bright red gypsiferous shales of the Chug- 

 water formation (upper Wyoming), although it is sharply demarked 

 from both. It is possible that in the Denver region it comprises more 

 of the Upper Carboniferous column than the topmost sandstone north- 

 west of Laporte, for the two thin beds of limestone which it contains 

 west of Denver suggest that it includes the extension of the thin lime- 

 stones underlying the supposed Tensleep sandstone northwest of Laporte. 



The thick mass of red sandstone sediments of the lower Wyoming is 

 believed to represent Upper Carboniferous only, but, as suggested above, 



*A similar relation on the west side of the range has been described by Wilbur C. Knight in the 

 Journal of Geology, vol. 10, pp. 412-422. The limestones were found to contain Upper Carbonif- 

 erous fossils. 



