PHYVSIOGRAPHY OF KLAMATH MOUNTAINS 151 
Trinity River. Between these basins lies that of the Klamath 
and Salmon River drainage, the history of which has been only 
in part parallel to the others. The history of these basins can 
be best known from a study of their later sedimentary deposits. 
THE LATER SEDIMENTARY DEPOSITS. 
The later sedimentary deposits of these basins include only 
those of later Cretaceous and of Neocene ages. 
The Chico deposits —The Cretaceous deposits are largely those 
of the Chico, and consist of shales, sandstones and conglomer- 
ates, the lighter materials generally forming the lower portions 
of the series. As a rule they are fairly fossiliferous, and often 
extremely so. In their distribution the Cretaceous deposits 
occupy both of the basins above described, which appear to have 
been distinct and separate inlets from the sea. Although it has 
been the opinion of Mr. Dillert and others, including the writer, 
that the Cretaceous deposits of southern Oregon and the upper 
Sacramento valley have had a connection through what has been 
called ‘‘the Lassen Peak straits,’ the proof of such a connection 
has not yet been satisfactorily shown, and there is evidence in 
favor of adifferent conclusion. Mr. Diller himself has expressed 
a conviction? that many of the topographic features of the Klamath 
mountains have remained only partially modified since Cretaceous 
time. In this connection it is worth while remembering that the 
granitic and basic crystalline rocks of the Klamath Mountains are 
the counterparts of those in the Sierra Nevadas, but in the latter 
range they are generally conceded to have antedated the later 
Cretaceous. An axis of such rocks certainly extends eastward 
beyond Mount Shasta, and the probability is that the high divide 
between the drainage basins of the Pitt and Klamath rivers is of 
pre-Chico age, éven including some of the older lava flows of 
Mount Shasta and the range to the eastward. This is rendered 
especially probable by the fact that the Chico beds almost on 
the western slope of Mount Shasta contain bowlders and pebbles 
' Highth Ann. Rept. U.S. Geol. Surv., pp. 411-13. 
2 Bull. Geol. Soc. Am., Vol. V. 
