DiLLEiU SUBSIDENCE. 59 
The amount of erosion which has taken place in the glaciated region, 
not only in the Klamath Mountains, but also at many other points in 
Oregon and California, since the ice disappeared, is very small, so that 
the glaciation of that region has been relegated generally to a late 
portion of the Glacial epoch. 
The bearing of this glaciation upon the age of the younger valleys 
is direct, and indicates that the river valleys were cut out almost to 
their present extent at least as early as the later portion of the Glacial 
epoch. 
There is another bit of evidence bearing upon the age of these later 
valleys which should be mentioned. On the North Fork of Coquille 
River, 8 miles northeast of Myrtle Point, Coos County, Oreg., a frag- 
ment of a mastodon's tusk was found buried in alluvium close to bed 
rock within 5 feet of the river. According to Mr. Lucas, the piece of 
tusk is of a form having a peculiar enamel band, and is probably of 
Pliocene age. Other bones have been found in the same locality, and 
it is the opinion of the writer, who examined the deposit, that the 
bones have not been transported far from their original deposit. The 
tusk gives rise to a suggestion that even the later valleys were prac- 
tically completed in Pliocene time. 
SUBSIDENCE ALONG OREGON COAST. 
Concerning the oscillations and subsidence after the continental 
border stage and the reelevation during the marine terrace stage 
enough has been said in the brief summary at the beginning of the 
paper, but concerning the subsidence along the coast of Oregon more 
facts should be given. 
Tide water runs up Rogue River about 4 miles from its mouth, and 
to about the same extent in all the important rivers south of it at 
least as far as Cape Mendocino, but in the opposite direction the rela- 
tion of river to tide level is very different. In Coquille River the tide 
puns up to the mouth of the North Fork, a distance of over 30 miles. 
Formerly it ran up farther, but by aggradation the stream has short- 
ened the tide run by nearty 4 miles. In Coos River the tide ascends 
pearly 1 he same distance. In the Umpqua it goes up at least 25 miles, 
to Scottsburg, penetrating much farther into the Coast Range at that 
point than anywhere else south of Columbia River, where it goes up 
to Cascade Locks, a distance of 150 miles from its mouth. In the 
smaller streams between the Umpqua and Columbia the ascent, 
which is less extensive chiefly on account of the smaller size of the 
streams, being in all cases roughly proportional to the erosive power 
of the stream, is as follows: Nehalem, 13 miles; Tillamook, 7 miles; 
Nestugga, 7 miles; Little Nestugga, 8 miles; Siletz, 21 miles; Yaquina, 
28 miles; Alsea, 14 miles; Siuslaw, north fork, 11 miles; Siuslaw, main 
Bream, 28 miles. 
