Review of Recent Geological Literature. 
333 
section of Pescadero, he concludes that “ the uplift and exposure ” 
preceding the deposition of the former “ may have been local.” It is 
scarcely necessary to point out that an apparent conformity in a single 
cliff section is but weak evidence for the general conformity of the two 
series when confronted by facts that point in the other direction. The 
legitimate conclusion would seem to be that we have here a basal 
Miocene conglomerate resting un conform ably upon older sandstones. 
The main erosion interval would then mark the lower limit of the Mio¬ 
cene as we should naturally expect, and not be within the latter. 
Although field work in other portions of the Coast ranges does not 
apparently preclude the possibility of the existence of one or more un¬ 
conformities within the Miocene, yet in this particular case, the uncon¬ 
formity described between the Miocene shales of the Monterey series 
and the Miocene conglomerate just mentioned, would seem to require a 
little further demonstration, more particularly as the writer makes it 
depend mainly upon an alleged conformity between the Monterey series 
and the Merced series which there is very good reason to believe does 
not exist.* 
The strongest evidence adduced in favor of a conformable relation 
between the Merced and Monterey series is the presence of so-called 
“transition beds” near the base of the former in the section along 
Seven Mile beach. The distinction between these beds and the un¬ 
doubted Pliocene is made purely upon the evidence of the fossil remains, 
and, as the writer says, the drawing of the line of demarcation “would be 
largely governed by individual inclinations.” Under the circumstances 
one may well express some doubt of the validity of drawing any line at 
all. He elsewhere refers to the present impossibility of correlating with 
absolute exactness, the Pacific Coast faunas with their nearest eastern 
equivalents, but nevertheless, employs just such rigid methods in this 
particular case. The paleontological discussion does not leave it at all 
clear that the fauna of the so-called “transition beds ” is any less typi¬ 
cally Pliocene than the series taken as a whole. 
Successful correlation of deposits requires that there be taken into 
account not merely their faunal contents, but also the physical revolu¬ 
tions recorded by unconformities and sudden alterations in the character 
of the sediments. The general tendency of the paper before us is to 
under-rate the last two factors and to exalt the first. There is one 
rather startling reversal of this tendency, however, when a bed of white 
volcanic ash, averaging about a foot in thickness, which was noted by 
Prof. Lawson in the Merced series, is unhesitatingly correlated with the 
Miocene shale of the Monterey series, and used as evidence of a contin¬ 
uous sedimentation from Miocene times up into the Pliocene, and even 
into the Pleistocene. 
“Transition beds” are also described near Santa Cruz as passing 
gradually and conformably into the Miocene. The author says, “As 
the bottom of the Transition beds is approached, the beds take on more 
and more the character of the white Miocene shale until before the 
*Lawson, loc. cit ., p. 354. 
