258 



(Erosion surface. 



[ Conglomerate, 2,000 ft. (609 m.). 

 Lower Cretaceous I Black shale, with marine shells, 500 ft. 

 — Jackass Mt. ] (152 m.). 



series. Green and grey arkoses, with plant 



remains; 300 ft. (91 m.). 

 Base not exposed. 



Unconformable relation. 



Lower Mesozoic — 



Boston Bar group — Thin-bedded grey argillites. 

 Palaeozoic — 



Cache Creek group — Cherty argillites, limestone, quart- 

 zite, serpentine; thickness and order of succession 

 indeterminate. 



Western part (Hope to Vancouver). 



Quaternary — Till, stream gravels, etc. 

 Unconformable relation. 



[Basaltic and andestic lavas. 



Eocene I Conglomerates, grits, shales with plant 



(remains; 3,000 ft. (914 m.). 

 Unconformable relation. 



Lower Cretaceous? — Quartz porphyry flows. 

 Unconformable relation. 



[Limestone, 1,000 ft. (304 m.). 

 Palaeozoic — ] Black shale, 3,000 to 4,000 ft. (914 to 



Agassiz series — I 1,219m.). 



I Conglomerate, 3,000 to 4,000 ft. (914 to 

 (1,219 m-)- 

 The above sections do not include the granitic rocks, 

 which are apparently of two ages, Jurassic and post- 

 Lower Cretaceous. The older rocks are usually gneissic 

 and sometimes sheared, and include both granodiorites 

 and granites. The younger rocks are always fresher and 

 never gneissic, and usually more acid than the older type. 

 They are dominantly hornblende-rich, in contrast to the 

 older type in which the hornblende is subordinate to a 

 greenish biotite. 



