QUATERNARY DEPOSITS 503 



of the height of the bank. Above it is brown sand. The banks impress 

 one traveling in a boat as being 15 to 20 feet high, but may be 25 or 

 even 30 feet high in places. Of course, most of the year the river is 5 to 

 10 feet higher. 



At Swabin the north bluff, at the edge of the pine country, is a reddish 

 bank of fine gravel and silt, suggesting the variegated silt formation. 

 Its surface is even, but some of the pine country in sight may be a little 

 higher. At the upper end of the bluff dull greenish and dark carbona- 

 ceous layers are present. Thence to the mouth of the Waspuc River the 

 banks, 30 feet high, are of Modern alluvium, with an occasional ex- 

 posure of black rock, presumably andesite. That on the south side of 

 the Wanks River, half a mile below the Waspuc, is a dark brown vesicular 

 lava of rather coarse crystalline texture. Some of it is decidedly basic in 

 appearance and some abounds in feldspar phenocrysts. It impressed me 

 as being about on the border line between a basalt and an andesite, but 

 the microscope would probably prove it to be the latter. The rock ex- 

 posed opposite the mouth of the Waspuc is a very coarse volcanic ag- 

 glomerate, made up of quite a variety of andesites. Near the water level 

 it is hard and black on the surface, but higher in the bank it is very 

 much decomposed. The bank is nearly 50 feet high, flat on top, and said 

 to become stony at a short distance from the river and in a mile to pass 

 into the pine country. 



The trading post of Waspuc Mouth is situated on the floodplain, which 

 rises 30 feet above the low-water stage of the river, but has been covered 

 during an abnormal flood by 6 or 8 feet depth of water. No higher 

 ground is in sight on the south on account of the tall trees. The distance 

 to the mouth of the Wanks River is said to be 194 miles, but was esti- 

 mated by us at 145 miles. 



In ascending the Waspuc and Pis-Pis rivers to the Big Falls, an esti- 

 mated distance of 80 miles, bedrock was frequently seen and will be 

 treated more fully in a later section. The Quaternary deposits consist 

 exclusively of the Modern alluvium and the soil. The Waspuc River at 

 first flows in a channel 100 to 200 feet wide, with 30-foot banks of dark 

 reddish brown sandy silt, with only a few small gravel bars at low levels. 

 Above the Yahook Falls the banks are only 10 feet high and for a long 

 distance the river is relatively wide and sluggish. Then narrow rocky 

 gorges alternate with wide, alluvium-floored sections of the valley. In 

 one bar the gravel consisted chiefly of andesite of finer grain than most 

 of that seen down the river. With it were various kinds of fine-grained 

 igneous rocks, including a hard greenish rock that may be an altered 

 andesite. The silica pebbles are generally chalcedonic. Much of the 

 ZXXVI — Bull. Geol. Soc. Am., Vol. 23, 1911 



