149 



and referred by him to the Miocene, as then defined for 

 western stratigraphy [5, p. 80]. Dr. Drysdale is still inclined 

 to regard the lavas as of lower Miocene age (see page 243), 

 though recent paleontological and stratigraphical work 

 by Lambe and Penhallow seems to show that these rocks — 

 hereafter called the Kamloops Volcanic group — should be 

 assigned to the Oligocene. The fossils in question, fish 

 remains and plants, have been found in the Tranquille 

 beds, a series of local, tuffaceous, partly fresh-water sedi- 

 ments intercalated near the base of the Kamloops volcanics. 



The Tranquille beds are estimated to have a thickness 

 of 1,000 feet (305 m.) ; the Kamloops lavas, a maximum 

 thickness of at least 3,000 feet (914 m.), with an original 

 average thickness probably greater than 2,000 feet (610 m.) 



The Kamloops volcanics are the youngest bed-rocks 

 known in the railway section. Up to the present time no 

 Miocene or Pliocene sediments have been found there. 

 Within sight of the railway, at Mission Junction, is the 

 Pleistocene-Recent volcano, Mt. Baker. 



PLEISTOCENE SYSTEM. 



The Quaternary formations are briefly noted at various 

 appropriate places in this guide-book. 



GENERAL STRUCTURE. 



The sedimentary rocks of our trans-montane section 

 belong to three geological provinces. 



The Beltian and Lower Cambrian strata of the 

 Selkirk mountains and their equivalents in the 

 Rocky mountains, with the conformable formations 

 of Middle Cambrian to Permian age, together form 

 a single mass of rocks. In the Selkirks there is 

 perfect conformity between the Lower Cambrian and 

 Beltian systems ; in the Rockies their relation is 

 reported to be that of conformity at some contacts, and 

 that of moderate unconformity at others. (See page 172). 

 There is no thorough-going unconformity in this gigantic 

 series. It is, in fact, best regarded as a single geosyn- 

 clinal prism of the first order. The maximum thickness 

 of strata here represented is, perhaps, greater than that of 

 any other measured group of sediments. With varying 



