NEOCENE DEPOSITS OF CALIFORNIA 387 
Trinity valley. The former rises from six hundred to about one 
thousand feet above the sea in less than three miles. Projecting 
this plain westward and the tilted baselevel of Trinity valley east- 
ward until they intersect, we would find that nearly all of the 
gulches lie below this level, while the mountain tops which reach 
above it have a more subdued and older-appearing topography. 
Completed baseleveling was only effected on narrow strips 
on the border of the Sacramento valley and on the east border 
of the Trinity valley. The country between was quite undulat- 
ing, 
1,000 and even 2,000 feet above the neighboring baselevel. 
These residuals were of the same category as those in the 
and contained rounded mountains reaching elevations of 
McCloud-Pit projection of the Klamath mountains, which may 
be shown to rise as monadnocks above an uplifted baselevel, 
represented by Bagley Flat. . 
At the Big Bend of Pit River and along Kosk Creek, a 
northern tributary, the Ione sandstone, as identified by Diller * 
is strongly developed, having a probable thickness of about six 
hundred feet. It dips easterly at a low angle, and passes under 
the lavas of the Lassen volcanic range. On the west, the surface 
of the metamorphic rocks of the Klamath region, here chiefly 
Jurassic in age, come out from under it and rise to the westward 
at about the same angle as the eastward dip of the sandstone. 
The Ione pebbles are scattered over this slope to a distance of 
several miles from the present Ione escarpment. This slope 
represents the pre-lone surface of the Klamath region, and con- 
sequently is not the equivalent of the latest stage of the Sierra 
Nevada peneplain. 
On the north side of Pit River, west of Cafion Creek, there is 
a high terrace known as Bagley Flat. It is a shelf cut into the 
slope of the Klamath mountains. Its present altitude is about 
2 ViSOuleet, Of 1,200" feetrabove writ Kiver.) ltcornresponds in 
height with the lava plain on the south of the river, but instead 
of being a constructional plain of sandstone overlaid by andesite, 
it is a baselevel of erosion. The Neocene lava occurs as rem- 
tLassen Peak Folio of the Geologic Adlas of the United States. 
