CAM Bill AN 65 



sucli a manner as to require distinctive names and to admit, so far, of 

 only a teiitative correlation. Our typical and most carefully surveyed 

 section is that in the Rocky mountains i)ro[)er or Laramide raui^e, on 

 the line of the Bow River pass. This has been studied by Mr R. (J. 

 McConnell, and it is the only section for which some direct ])aleonto- 

 logical evidence exists.* The base of the Cambrian is, however, not 

 seen in this section. In the Gold ranges, where "the Cambrian is fre- 

 quently found resting on the Archean, the Nisconlith, its lowest recog- 

 nized niember, varies by several thousand feet in volume, showing that 

 the old surface was a very irregular one and had been greatly modified 

 by denudation previous to the deposition of the Nisconlith. The same 

 circumstance has been noticed by Mr McConnell in the case of the How 

 River series of the Laramide range, where it is found resting on the 

 Archean in the vicinity of the Finlay river, over 400 miles northwest of 

 his typical section, f proving this denudation-interval to be a very im- 

 ])ortant one, although, as already noted, there is often a parallelism in 

 strike between the two series of rocks. 



The Bow River series, in the pass of the same name, consists chiefly 

 of dark-gra}' argillites, with some greenish and purplish bands, associated 

 with quartzites and conglomerates, these coarser materials being most 

 abundant in the upper parts of the formation. Pebbles of quartz and 

 feldspar, evidentl}^ derived from the Archean, are abundant in the con- 

 glomerates, and scales of mica have in some ])laces been developed on 

 the divisional planes of the argillites. The known thickness of the 

 series is 10,000 feet. 



In the eastern part of the pass, resting conformably on the Bow River 

 series, is the Castle Mountain group, with a known thickness of about 

 8,000 feet. This consists chiefly of ordinary gray limestones and dolo- 

 mites, in frequent alternations and interstratified with shales and calc- 

 schists. To the west of the main watershed, however, the character of 

 this series becomes materially changed, and the heavy bedded dolo- 

 mites and limestones are to a great extent replaced by greenish calc- 

 schists and greenish and reddish shales and slates. The change may 

 be traced in its various stages, and is due to the introduction on the 

 west of a greater proportion of earthy matter. 



Fossils of the lower Cambrian (Olenellus) fauna have been found 3,000 

 feet below the summit of the Bow River series. They are also known to 

 characterize the lower part of the Castle Mountain series, which is fos- 



* For details of the Bow River Pass section, see Annual Report, Geol. Siirv. Can., vol. ii (N. S.), 

 part D. 

 t Annual Report, Geol. Surv. Can., vol. vii (N. S.), p. 24 C. 



XI— Bum.. GEor,. Soc. Am.. Vol. 12. 1900 



