THE INTERIOR PLATEAU REGION. 167 



only by mountain climbing, and by the study of a belt of some width on both 

 sides of the line. As, however, we have heretofore been almost without in- 

 formation on the geological structure of the Selkirks, it is believed that the 

 observations made may not be without interest, even though given subject to 

 future correction in detail. This range, where it has been rendered easily 

 accessible by the construction of the railway, has already become noted for 

 its magnificent Alpine scenery, while some of its peaks and glaciers have 

 become the subjects of serious exploration by well-known Alpine climbers 

 from England and Switzerland.* 



Geological Features of the Interior Plateau. — In that part of British Colum- 

 bia which has been called the interior plateau the oldest stratified rocks are 

 gneisses and mica-shists, which from their lithological character are assumed 

 to represent the Archean. The relations of these to the overlying Paleozoic 

 strata are best known on the eastern border of the plateau region, where 

 they are frequently and well shown. With these crystalline schists occur 

 certain old granitoid rocks, which may represent either portions of the schists 

 in which the bedded structure has been obliterated or very ancient intru- 

 sions that, together with the enclosing crystalline schists, have subsequently 

 been affected by heat, pressure and other agencies. Besides these there is in 

 the same region at least one later series of distinctly intrusive granites, which 

 is probably newer in date than most of the Paleozoic rocks. In the Coast 

 range, on the western side of the interior plateau, a similar "complex" of 

 crystalline schists and granites occurs, of which part at least may be of the 

 same age with that just alluded to, though in this case some of the intrusive 

 granites are known to be post-Triassic in date and others are later even than 

 the Cretaceous. 



Stratigraphy. 



The General Section. — The section given in the first column of the annexed 

 table represents the rocks met with near the eastern border of the interior 



*Such geological indications for the Selkirks as have been published may be found in the fol- 

 lowing works: 



Report on the Geology of the Country near the Forty-ninth Parallel of North Latitude, by H. 

 Bauerman. This is the result of observations made in 1859-'(51, in connection with the expedition 

 engaged in fixing the southern boundary of British Columbia in these years, but was first published 

 in the Report of Progress of the Geo!ogi<'al Survey of Canada for 1882-'84. 



Summary Report of the Operations of the Geological Survey for the year 1887, by Dr. A. R. C. 

 Selwyn. This contains a brief note on the character of the rocks near lUecillewaet. 



Explorations in the Glacier Regions of the Selkirk Range, British Columbia, by Rev. W. Spots- 

 wood Green; Proceedings of the Koyal Geographical Society, vol. XI, 1889. Mr. Green here gives 

 a short geological note (p. 167) and refers to the determination by Professor T. G. Bonney of some 

 of the rocks brought back. 



Notes on the Geography and Geology of the Big Bend of the Columbia,-bv Professor A. P. Cole- 

 man ; Trans. Royal Soe. Can., vol. VH, sect. IV, 1889. In this paper the general geological character 

 of districts visited by the author are described and the results of a petrological examination of a 

 number of rocks are given. 



Brief mention has also been made by the writer of the rocks of the Selkirks and neighboring 

 ranges in Descriptive sketch of the Physical Geography and Geology of the Dominion of Canada, 

 1884; Mineral Wealth of British Columbia (Annual Report Geol. Surv. Can., new series, vol. Ill); and 

 elsewhere. A somewhat more detailed account has been given by him of the geology of a part of 

 the western border of the Selkirlis, resulting from a reconnoissance made in 1889 and published 

 in 1890 in his Report on a Portion of the West Kootanie District (Annual Report Geol. Surv. Can., 

 new series, vol. IV). 



