156 : F. M. ANDERSON 
probable that the Cascade range is an accumulation of volcanic 
materials of as many different epochs. In many places, as near 
the Klamath River, this succession of periods, as well as the suc- 
cession of minor flows, is well illustrated. At the head of the 
Little Shasta River, no less than four epochs are represented by 
as many different effusions. Dutton recognized the same long 
duration of volcanic activity in the Cascades of southern Oregon 
stating that it probably prevailed throughout nearly the whole 
of the Tertiary.” 
The Tuscan tuffi—One of the later periods of volcanic activ- 
ity is represented by what has been called the Zuscan tuff. This 
consists of a series of volcanic fragmental material, sometimes 
stratified and sometimes without stratification. It has a wide 
distribution in the upper Sacramento valley, where it has been 
described and mapped by Mr. Diller.2, The volcanic tuffs of 
the Cascades north of Mt. Shasta, as well as the Jone and the 
Chico, demonstrate the secular accumulation of the lavas form- 
ing the range. As a rule the tuffs are interstratified with lava 
flows of somewhat different characters, some of which are older 
and some younger than the tuffs. Rhyolitic and andesitic tuffs 
have a wide distribution to the east of the Cascade Mountains, 
occurring abundantly in the basin of the Klamath Lakes, where 
they overlie, for the most part, the diatomaceous deposits as 
already stated. They also form thick deposits in the region of 
Silver and Summer lakes. 
Faulting of the region.—A large amount of faulting has taken 
place subsequent to the distribution of these tuffs, often leaving 
them exposed in conspicuous cliffs. These fault lines, in so far 
as they occur in the region of the Klamath Mountains, are only 
outlying members of the great system of faulting traversing 
northern Nevada and southeastern Oregon, and which have been 
described by King,? Russell,* and others.5 
t Seventh Ann. Rept. Geol. Surv., pp. 100-1. 
2 Fighth Ann. Rept. U. S. Geol. Surv., Pt. 1, pp. 422-24. 
3 Fortieth Parallel Repts., Vol. I, 1878, p. 735 et seg. 
4 Monograph XT, U.S. Geol. Surv., 1885, p. 26 ef seg. 
5 Proc. Cal. Acad. Sci., 3d ser., Vol. I, p. 262 e¢ seg. 
