386 OSCAR EL EUET:S LILGN4 
into the gravel, but was forced on to the metamorphic rocks to 
the eastward, and so came to trench its new valley. 
If we will project the reconstructed surface of the gravel 
deposit toward the east, we will find that it about intersects the 
general summit level of the ridge of metamorphic rocks between 
the old and the new courses of Trinity River. Beyond the new 
valley we will find no elevation prominently reaching above this 
plane until we get well up toward the summit of Trinity Moun- 
tain. As there is no evidence of faulting since the accumulation 
of the Neocene gravels, it is evident that at the completion of 
the river deposit, when its surface had reached that now repre- 
sented by Buckeye Mountain and the Greenhorn Flats, the allu- 
vial plain was bordered on the east by a low, flat belt of country, 
five and perhaps in places ten miles wide, a local baselevel of 
erosion. It is not certain that this was a perfect flat all over; 
indeed, it is probable that it was a series of broad valleys in 
which flowed the tributary streams, separated by low, smooth, 
in places indistinct, divides. 
Certainly, the country for some miles east of the old channel 
was low enough to enable Trinity River to rapidly migrate across 
it until it had reached a distance of three to seven miles from 
the old course, when the vertical component of the uplift became 
the controlling factor, and the river simply stopped migrating 
and cut down into the underlying metamorphic rocks. 
It is presumed that the uplift of the Klamath region was 
general throughout the province, but the amplitude varied. The 
country was bowed up into one or more great arches without 
faulting, except possibly on the northeastern and southwestern 
borders of the mountain system. From the group of high 
mountains west of the old Trinity valley to the present Sacra- 
mento valley near Redding, I regard as the eastward slope of 
one of these great arches. Between Redding and Shasta there 
are traces of an old peneplain*earlier in age than that on 
which the Red Bluff gravels lie, and this I would correlate with 
the late Neocene baselevel developed on the east border of 
tJourR. GEOL., Vol. II, pp. 34, 35. 
