242 The American Geologist. October, 1897 
gon cofist according to Mr. Diller. He says:* "The last 
movement of the land by which the Oregon coast came to its 
present position was one of subsidence. This movement had 
a. marked effect upon the rivers. They are drowned on the 
lower portions of their courses, and the tide comes far in- 
land." The last subsidence is thus seen to have been a gen- 
eral one. There is no doubt that in certain places on the 
California coast, as at the Golden Gate, it is more pronounced 
and noticeable. 
It might be argued from the character of the large valleys 
opening out through tlie Coast Ranges to the ocean that we 
have no definite means of discriminating the Pleistocene from 
the Pliocene, that the latter may be encountered onh'^ a slight 
distance below the surface, and that no reliable evidence can 
be gained from the study of this aspect of the supposed post- 
Pliocene elevation. Does the Pleistocene occupy a depression 
eroded out of the Pliocene which it is believed filled or partly 
filled the most of the older valleys of tlie Coast Ranges? It 
is admitted that much of the needed information is at present 
lacking, but there is nevertheless some of great value at hand. 
In the first place the Pliocene is found to be more or less 
tilted and faulted wherever it occurs, the Pleistocene on the 
contrary has simply been elevated in the epeirogenic move- 
ment of the coast without any other noticeable disturbance. 
From the Santa Ana plain on the south, to the region about 
San Francisco bay, wells possessing more or less of an artesian 
character have been found in the most of the larger valley^s. 
The record of the material passed through in drilling these 
wells has been kept in many cases and it appears that it is gen- 
erally quite uniform. It consists of unconsolidated gravels, 
sands and clays. Where fossils have been found, as in the San- 
ta Clara valley and the Great valley, the strata are distinctly 
shown to be of Pleistocene age. Their position is somewhat 
basin-like and so entirely undisturbed that with some experi- 
ence it can often be told quite definitely how deep certain stra- 
ta lie in different parts of any particular valley. If the beds 
were of Pliocene age we know that this regularity would not 
be found to exist. I believe then that we have a right to ex- 
tend our generalization from these valleys where fossils have 
*17th Annual Report of the U. S. Geo!. Sur., p. 50. 
