360 R. A. DALY THE OKANAGAN COMPOSITE BATHOLITH 



parts of the Canadian Cordillera were affected by severe orogenic stresses 

 at the close of the Laramie period.* It is probable that the stresses were 

 even greater along the Pacific coast than they were in the eastern zone, 

 where the Eocky Mountain system was built.. To this post-Laramie, pre- 

 Eocene epoch the shearing of the granodiorites may be best referred. 



We have seen that there are good reasons for considering the composite 

 Kruger Alkaline body as younger than the granodiorites. It is clearly 

 older than the Similkameen granite, as proved by the discovery of fine 

 apophyses of the granite cutting the nepheline rocks. The Kruger body 

 once extended some distance farther west over an area now occupied by 

 the granite. The former, when first intruded, was an irregularly shaped 

 mass without simple relation to its country rocks, the Paleozoic complex. 

 The mode of intrusion was that of either a stock or a chonolith. In the 

 first case the body was subjacent and enlarged downwardly; in the second 

 case it was injected and its downward cross-section may have diminished. 

 As with so many other instances, the contacts are too meagerly exposed to 

 fix the true alternative. The nepheline syenite was in part injected into 

 the nearly contemporaneous malignite. The common fluidal structure of 

 these rocks also points to a mode of wedge intrusion more like that of 

 dike or laccolith than like that of a stock. The Kruger body may thus 

 represent a composite chonolith, but the problem of its style of intrusion 

 must remain open. The date of the intrusion was post-Laramie. The 

 alkaline magma may have been squeezed into the schists while mountain 

 building progressed or after it had ceased. The crushing and incipient 

 metamorphism of this body is on a scale more appropriate to the thrust 

 resulting from the irruption of the younger Similkameen granite than to 

 the more powerful squeezing effect of the post-Laramie mountain building. 



True batholithic irruption was resumed in the replacement of schists, 

 nepheline rocks, and possibly much of the granodiorite by the Simil- 

 kameen batholith. This great mass is uncrushed, never shows gneissic 

 structure, and has never been significantly deformed through orogenic 

 movements. 



The composite batholith received its last structural component when 

 the Cathedral granite finally cut its way through Eemmel granodiorite, 

 Similkameen granite, remnant Paleozoic schists, and possibly through 

 Cretaceous strata, to take its place as one of the most imposing geological 

 units in the Cascade system. The field proofs are very clear that the 

 Similkameen granite was solid and virtually cold before this last granite 

 ate its way through the roots of the mountain range. See the large in- 



♦Bull. Geol. Soc. Am., vol. 12, 1901, p. 87. 



