REPORT OF THE CHIEF ASTRONOMER 7 



SESSIONAL PAPER No. 25a 



The Eastern Geosynclinal Belt is characterized by open folds, fault-blocks, 

 and overthrusts, with but moderate regional metamorphism and quite sub- 

 ordinate igneous action. The Western Belt is characterized by close folding, 

 mashing, strong regional metamorphism, and by both batholithic intrusion and 

 volcanic action on a grand scale. From the western crossing of the Kootenay 

 river to the Kettle river at Grand Forks the section crosses the West Kootenay 

 Batholithic province, which is partly overlapped by the Rossland Volcanic 

 province. West of Grand Forks is the Midway Volcanic province. The Okana- 

 gan (eastern) division of the Cascade mountain system is composed of the 

 Okanagan Composite Batholith, and the heart of the Skagit range is made up 

 of the Skagit Composite Batholith. 



These various geological provinces are treated in the order of succession 

 as they are encountered in passing from east to west. Numberless problems 

 have arisen during the progress of the work. Special studies have been made 

 on the relations and origin of the igneous rocks, which occur in the section on 

 a scale not often surpassed in other mountain chains. 



A chapter on the nomenclature of the Cordilleran ranges at the Interna- 

 tional Boundary illustrates the need of a systematic attack on the difficult 

 problem of names. The long discussed but ever new question as to the origin 

 of limestone and dolomite, coupled with that as to the cause of the rarity of 

 fossils in pre-Silurian sediments, has prompted a theoretical chapter which, 

 like the chapter on nomenclature, has already in largest part been published. 

 Other subjects, including glaciation and physiography, were more inevitably to 

 be considered and need no special introduction at this place. 



