26 



low alluvial flats and islands. The few terraces present 

 have been mostly built up by detritus brought down by 

 tributary streams. Above the Kitsumgallum, the river 

 is engaged in scouring out its old channel partially filled 

 up by over sedimentation during the closing stages of the 

 Glacial period. 



Mile 95-2 to 104. — East of the Kitsumgallum river 

 the Kitsalas volcanics are replaced for some miles by 

 granodiorites, often porphyritic in texture. These rocks 

 are precisely similar in mineral composition to those in the 

 main Coast Range batholith, and may be a spur from it. 

 They are not schistose, but are strongly jointed and, in 

 places, have a columnar appearance due to the intersection 

 of two sets of jointage planes. They include numerous 

 fragments of the neighboring dark rocks, and are cut by 

 acid dykes and by a later group of coarse basaltic dykes. 



Mile 104. Kitsalas Canyon. — The Skeena river 

 here forces its way through the narrow rock-walled Kit- 

 salas canyon, one of the most picturesque points in its 

 course. 



The canyon is about a mile in length, and in places, 

 scarcely ioo feet (30.4 m.) in width, and is sunk through 

 the greenish and greenish-grey volcanics of the Kitsalas 

 formation, the junction of these with the granites occurring 

 near its foot. 



The origin of the canyon is plain. The valley here at 

 the close of the Glacial period, when the Coast region was 

 depressed, was filled with estuarine clays, sands and 

 gravels to a height of 170 feet (51 .8 m.) above the present 

 water level. On the retreat of the sea the river commenced 

 cutting down through these, and the canyon marks a reach 

 where the new channel deviated from the old one, and 

 crossed a buried spur from the bordering mountains. 



In passing Kitsalas canyon the roughness of the ground 

 necessitated the construction of four tunnels on the railway, 

 one through a clay ridge. 



Mile 105 to 112. — Occasional cuts along the railway 

 expose the rocks of the Kitsalas formation. They are 

 more schistose than farther west and in places resemble 

 the Prince Rupert altered sedimentaries. 



Mile 113. — A long cut across a low terrace at this 

 point exposes estuarine clays and sands overlaid by river 

 wash. 



