REPORT OF THE CHIEF ASTRONOMER 13 



SESSIONAL PAPER No. 25a 



Chapter XII. — The Priest River terrane, the formations of the Summit 

 series, and the Pend D'Oreille group are cut by batholiths, stocks, and dikes of 

 igneous rocks of varied nature. Chapter XII is largely devoted to the petro- 

 graphy of these eruptive bodies as exposed in the Selkirk range. In addition, 

 certain minette dikes of the Eossland mountains, being closely related to others 

 occurring in the Selkirks, are described in this chapter. A thoroughly abnormal 

 ' granite,' probably a hybrid rock, cuts the Kitchener quartzite at the edge of 

 the Kootenay river alluvium. A tentative correlation of all the formations 

 composing the Selkirk mountains within the Boundary belt is given in tabular 

 form. 



Chapter XIII. — Though the Eossland mountain group is a small sub- 

 division, the ten-mile belt crossing it shows an extensive variety of formations, 

 chiefly igneous. Possiliferous Carboniferous limestones, and Cretaceous ( ?) 

 shales occur near Eossland; and conglomerate bearing fossil leaves (Cretaceous 

 or Tertiary in age) was found on Sophie mountain. The areally important 

 formations include the Eossland and Beaver Mountain groups, (latites, ande- 

 sites, and basalts), the Trail batholith (granodiorite), the Coryell batholith 

 (syenite), the Eossland monzonite, and the stocks of Sheppard granite. A 

 peculiar : olivine syenite,' occurring also in the Bonnington range, and a dike 

 of the rare petrographic type, missourite, are described. The structural and 

 time relations of the formations are discussed. 



Chapter XIV. — Between Christina lake and Midway the bed-rocks form a 

 complex, which is very similar to that in the Eossland mountains. The Chris- 

 tina range is chiefly composed of plutonic rocks, which include the gneissic 

 granite (sheared granodiorite) of the Cascade batholith and the aplitic granite 

 of the Smelter stock. The origin of the banding in the batholith is briefly dis- 

 cussed and a lateral-secretion hypothesis favoured. 



Across the north fork of the Kettle river the formations have been studied 

 in detail by Mr. E. W. Brock, from whose report liberal quotations are made. 

 For purposes of convenience in later correlations the present writer gives special 

 names to two of the formations described by Mr. Brock. These new names are : 

 Attwood series, and Phoenix Volcanic group. The usual tentative correlation 

 tdble is appended. 



Chapter XV.— Just east of Midway the section enters the Midway volcanic 

 province, representing thick Tertiary lavas and pyroclastic deposits. "West of 

 the volcanic mass is a broad band of metamorphosed Paleozoic sediments extend- 

 ing to the Osoyoos batholith. This chapter describes the two provinces, the 

 Midway province demanding the greater detail of statement. The Paleozoic 

 sediments, with included greenstone and basic schists of igneous origin, are 

 named the Anarchist series. This series is unfossiliferous, but on lithological 

 grounds, is correlated with the Cache Creek series and other upper Paleozoic 

 groups described north and south of the Boundary. Unconformable upon it is 

 the fossiliferous (Oligocene) Kettle Eiver formation, composed of conglomerates, 

 sandstones, and shales. These sediments are conformably overlain by thick 



