484 EEPOET UNITED STATES GEOLOGICAL SUEVEY. 



tlie region, and indeed the apparent omission in certain localities of any 

 cessation in the conditions Ikvorable to the acicumulation and deposition 

 of calcareous matter, by which the Upper Quebec limestones were made 

 to form part of an uninterrux)ted series of limestones reaching up into 

 the (Jarboniierous. 



In the southwest the horizon is occupied by a heavy ledge of light- 

 colored, rough- weathered fragmentary quartzite or quartzitic sandstone, 

 of which a thickness of at least 50 feet is exposed in the Mount Putnam 

 Eidge. Low in the southwest flank of the Blackfoot Eange occurs a 

 conglomeritic quartzite, which may be the equivalent of the above-men- 

 tioned ledge. It is also possible that the similar quartzite, remnants of 

 which outcrop in the edge of the lower valley of the Snake, along the 

 northeastern foot of the Caribou Eange, may belong to the same hori- 

 zon. But in the T6ton Mountains the siliceous, or, at least, the quartz- 

 itic materials are replaced by argillaceous matter, and which occui)ies a 

 vertical space of, perhai)S, 100 feet. The exposures were at no place 

 sufficiently free from debris as to admit of satisfactory examination of 

 the horizon. But in the sides of West T^ton Valley slide exposures are 

 met with at this horizon, revealing drab clay shales, and throughout this 

 quarter the space between the Upper Quebec and Niagara limestones 

 shows a steep talus, or sometunes a bench of greater or less width, in- 

 dicating the presence of subjacent soft deposits. Such is the character 

 of the horizon in the western portion of the Gros Ventre Mountains, 

 with, however, indications of the presence of interlaminated indurated 

 calcareous material. But to the northeast, in the vicinity of Buffalo Fork 

 Peak, these deposits are absent, the Upper Quebec limestones being fol- 

 lowed by apparently conformable limestones, which pass up into weU- 

 determined Carboniferous deposits. 



NIAGARA. 



In 1871, Dr. Hayden discovered in the Wasatch Eange, vicinity of 

 Ogden, Utah, rocks of the age of the Magara of the East, a determina- 

 tion made on the occurrence in the limestones of the coral Halysites cafe- 

 nulata. In the northern extension of the same general mountain range, 

 where it sinks to the level of the Snake plain, at the northern terminus 

 of the Mount Putnam ridge. Professor Bradley, during the following sea- 

 son, recognized, on stratigraphical position and lithological characters, 

 the same formation. But in this latter ridge, at Station II, it is evident 

 that the Niagara is wanting, the more or less maguesian limestones, con- 

 taining crinoidal and other Carboniferous fossils immediately succeeding 

 and resting upon the quartzitic sandstone which here constitutes the 

 passage bed interj^osed between the Upper Quebec and Lower Carbon- 

 iferous limestones. It is not improbable the same state of things exists 

 in the Blackfoot Eange ; at all events, no rocks of Niagara age were 

 identified in this quarter during the present season. Professor Bradley 

 mentions the occurrence of light maguesian limestones at the north end 

 of the Caribou Eange, which, lithologically, bear close resemblance to 

 Niagara beds in the Teton Mountains, a determination which, although 

 the exposures in this vicinity are not so satisfactory as could be wished, 

 is probably well founded. 



In the same manner was the lower magnesian limestone horizon in the 

 Teton Eange identified with the Niagara beds occurring to the south- 

 west. During the present season the above determination of the age of 

 the latter deposit was fully confirmed by the discovery of the presence 

 in these beds, at the northern end of the range, of Halysites and other 



