NEOCENE DEPOSITS OF CALIFORNIA 391 
the Hay Fork and Hyampour valleys also favors this correlation, 
for lignite is very characteristic of the Ione formation, another 
supposed equivalent of the San Pablo formation. 
However, it seems to the present writer more probable that 
the rhyolite tuff was derived from the Lake county volcanoes. 
Where isea-creat mass, of tut in’ the upper endof the great 
valley, extending west of the Sacramento River, and clearly 
referable to the Lassen Peak volcanic range as a source, but it is 
andesitic in character. None of this reached the Trinity county 
basins so far as I am aware. The occurrence of the rhyolite 
tuff in the southern part of Trinity county alone seems to imply 
that it was showered from the south and not from the east. 
Strong winds come oftener from the direction of Lake county 
than from that of the Lassen Peak range. 
I am informed that the volcanic series of Lake county is 
essentially Middle Pliocene in age, being apparently the equiva- 
lent of the Berkeleyan series. About the close of deposition of 
the San Pablo sandstone, rhyolitic ashes seem to have been 
widely showered over the northern Coast Range region, and it is 
probable that at this time similar material reached the Trinity 
county basins. 
Whether we refer the source of the tuff to the Sierra Nevada 
Lassen Peak or to the Lake county volcanoes, we arrive at 
virtually the same result in the matter of the probable age of 
the tuff-bearing portion of the Neocene gravels of the Klamath 
region, namely, about the time of transition from the Lower to 
the Middle Pliocene. 
The lignite and tuff are found near the rock-floor of the old 
Neocene valleys, and simply tentatively fix the age of the lower 
portion of the gravel series. The accumulation of the gravel 
continued until the inception of the profound orographic dis- 
turbance to which the Pleistocene valleys are due. Ina separate 
paper it is hoped to show that the latter are equivalent to the 
Sierran valleys of the Sierra Nevada province, and that the 
orographic disturbance referred to in this paragraph was that 
which terminated the Pliocene and inaugurated typical Quater- 
