SEETOYA MOUNTAINS. 605 



forming in places an impure anthracite coal. The section exposed is as 



follows : 



Feet. 

 Conglomerate. 



Blue limestone, with shales 100 



Bluish-black, finely- divided, argillaceous shales 150 



Coal-seam 15 



Bituminous shales 50 



Gap 100 



Black shales 10 



Argillaceous limestone. 50 



Yellowish calcareous shales 200 



Drab siliceous limestone, with shales 200 



Blue limestone, with seams of white calcite 50 



Rusty quartzite 50 



Compact blue fossiliferous limestone 100 



Blue limestones and shales 200 



Granite (unconformable). 



From the lower fossiliferous beds were obtained the following Coal- 

 Measure fossils : 



Produdus semireticulatus. 



Syringopora multattenuata. 

 Cyatliophylloid fragments. 



In these easterly-striking limestones, the same curious bed of rhyolite 

 was observed as on the western slope. On the spur to the south of the 

 mouth of Coal Creek is a body of gray trachyte, stained with streaks 

 of iron oxide, which overlies a porphyritic decomposed rock resembling 

 a rhyolite, but whose position would suggest that it may be an inter- 

 calated porphyry of Carboniferous age. If this be so, the interbedded rhyo- 

 lites which encircle Nannie's Peak should have the same origin. 



The trachyte is made up of sanidin and plagioclase-feldspar, with some 

 little biotite, in a gray, somewhat porous, felsitic groundmass. Under the 

 microscope, the groundmass is seen to be nearly colorless, and to contain 

 feldspathic microlites, with very little ferrite, and also some little titanite. 

 The porphyry or rhyolite has the same constituents as the trachyte, with 

 addition of free quartz ; but its groundmass has a peculiar half-glassy sphse- 

 rulitic texture, as distinguished from the granular semi-crystalline texture 

 of that of the trachyte. 



