320 B. WILLIS — LEWIS AND LIVINGSTON RANGES, MONTANA 



Probably Triassic or Permo-Triassic Divisions F, G, and H. 



Carboniferous and Devonian Division D. 



Cambrian Divisions A, B, and C. 



The correlation appears to have been made on lithologic resemblances 

 and the existence of the supposed unconformity between the red argil- 

 lite C and the limestone D. A, B, and C are now known to be Algonkian, 

 on fossil evidence. Mention is made by Dawson of the absence of fossils 

 from C, but nothing is said about their occurrence or non-occurrence in 

 D. Weller's careful search in the Siyeh limestone (D) showed the pres- 

 ence of indistinct remains, as already noted, but it also proved that fos- 

 sils are rare and obscure in the formation. If the rock is of Carbonif- 

 erous age, it is remarkable that it should not contain some of the larger 

 characteristic forms, as the Carboniferous limestone on Yakinikak creek, 

 but 26 miles distant, carries an abundant fauna. There is no metamor- 

 phic or structural condition affecting the one rather than the other in a 

 degree sufficient to explain the difference, in faunal content. Moreover, 

 the Carboniferous limestone on Yakinikak creek rests unconformably 

 on beds of the series of which the Siyeh limestone (D) is apparently a 

 conformable formation. 



The writer concludes that the Siyeh limestone is not of Carboniferous 

 age, and that there is no evidence to justify its being separated from the 

 underlying Algonkian, to which it is conformable and with which it is 

 related in the obscure character of its fossils. This conclusion applies 

 also to the Sheppard and Kintla formations, which Dawson placed in 

 the Permo-Triassic. He could not otherwise refer them, conceiving 

 them to overlie the Carboniferous, as the}^ have strong Triassic charac- 

 ters ; but with the assignment of the Siyeh limestone to the Algonkian, 

 they also take a related place in that system. Nevertheless, to give full 

 expression to Dawson's views, the following paragraphs are quoted from 

 his report : * 



" South of the line of the Crow Nest pass, the limestone series (Carboniferous) 

 is conformably overlain by rocks which are referred to the Triassic or Permo- 

 Triassic. In the vicinity of the South Kootanie pass, an interbedded, amygda- 

 loidal diabase everywhere occurs at the base of the Triassic rocks. This, though 

 classified under a separate letter (E) in the general section of that region. (p. 39 B), 

 is now known from the occurrence of a similar bed (if not the extension of the 

 same one) among the distinctively Triassic rocks of the summit of the North 

 Kootanie pass (p. 60 B) to be more properly ranked as a member of that series. 

 The trap flow has a thickness of fifty to one hundred feet, and is overlain near the 

 South Kootanie pass by red beds and fawn-colored magnesian sandstones 600 feet 

 in thickness. Near the North Kootanie summit it forms part of a similar series 



* Canada Geological Survey, Report 1885, p. 161. 



