REPORT OF THE CHIEF ASTRONOMER 373 



SESSIONAL PAPER No. 25a 



land-plants. Those found at the creek have been tentatively referred by Pen- 

 hallow to the Lower Cretaceous. For present purposes it seems safer to refer 

 these beds, more broadly, to the Mesozoic. Those occurring in the conglomerate 

 are too poorly preserved to be of stratigraphic service. The relatively 

 unmetamorphosed Beaver Mountain sediments carry abundant, carbonaceous 

 plant-stems but no useful fossil has been discovered. 



3. The volcanic breccias of Malde and Sophie mountains overlie the 

 Carboniferous ( ?) sediments unconf ormably. 



4. The Trail granodiorite batholith cuts schists which are almost certainly 

 the equivalent of the Pend D'Oreille schists. It cuts the older lavas (andesites 

 and basalts) of the Rossland volcanic group and the ultra-basic monzonite and 

 hornblendite at the Columbia river. 



5. The Sheppard granite cuts the Trail granodiorite, the Pend D'Oreille 

 schists and the conglomerate on Lake mountain. 



6. The Coryell syenite batholith cuts the youngest recognized members of 

 the Rossland volcanic group as well as the Sutherland schistose complex. 



7. Numerous dikes of biotite-augite syenite porphyry cut the Rossland 

 volcanics, the Sophie mountain conglomerate and the conglomerate at Monu- 

 ment 169. A few dikes of this porphyry cut the Coryell syenite. 



8. Dikes of biotite-granite porphyry cut the syenite porphyry just 

 mentioned. 



9. The Coryell syenite is cut by at least one dike of missourite and by 

 narrow dikes of syenite-aplite. 



10. The Sutherland schists are cut by at least one dike of unsheared 

 camptonite, which may be a lamprophyric derivative of the Coryell syenite. 



11. The Sophie mountain conglomerate is cut by dikes of monzonite 

 porphyry; others of the same kind of dikes cut the Beaver Mountain lavas. 



12. The small stock of crushed biotite granite east of Cascade cuts the 

 greatly metamorphosed andesitic rocks or greenstones mapped as part of the 

 Rossland volcanic group but probably of Paleozoic or, at least, pre-Cretaceous 

 date. 



13. This biotite-granite stock is cut by dikes of dunite. Masses of dunite 

 cut the older andesitic lavas of the Rossland group. 



14. The Life and Baker gabbros and peridotites cut the old greenstones 

 -just mentioned. 



15. A small mass of biotite-olivine-diallage peridotite cuts the Baker 

 gabbro. 



16. Dikes of the syenite porphyry mentioned under "7" cut the small body 

 of " harzburgite " northwest of Monument 172. 



17. Large dikes of biotite-granite porphyry (probably apophysal from the 

 Trail batholith) cut the Pend D'Oreille schists near the crossing of the Colum- 

 bia river and Boundary line; dikes of augite minette cut both schists and 

 granite porphyry. A dike of hornblende-augite minette cuts the dikes of augite 

 minette. 



18. Many dikes of minette and some of kersantite cut the Pend D'Oreille 

 schists east of the Columbia river. According to Brock and Young, dikes of 



