TERTIARY FAUNAS OF THE PACIFIC COAST 521 
geology has heretofore been considered as a unit, is believed to be 
related to the positive or upward-tending forces accompanying or 
immediately preceding the important volcanic activity which took 
place during early Miocene‘ time adjacent to the Sacramento Valley, 
and northward into Washington, but 
which are absent or insignificant in 
the region contiguous to the San 
Joaquin. In this connection it is 
also worthy of note that the greater 
part of the Willamette Valley was 
also out of water during the lower 
Miocene.’ 
DISTRIBUTION AND CHARACTER OF 
SEDIMENTS 
The Vaqueros or lower Miocene 
proper, and the Monterey or lower 
middle Miocene epochs have been 
included in mapping and discussing 
the lower Miocene, for together they 
mark by subsidence the beginning 
of a new geologic cycle following 
the Oligocene elevation. Locally 
the Vaqueros and Monterey have 
totally unlike histories. ‘The Vaque- 
ros in the Coast Ranges of central 
California is characteristically con- 
glomeratic at the base, and sandy, 
with minor quantities of shale, in 
its upper portion. In the northern 
part of southern California it is 
largely dark arenaceous shale as- 
sociated with minor quantities of 
a as* ne van “er 
429° 
47 ar 
Lecenn rebt 
MARine 4 
/ me) 
I % 
FRESHWATER a Std 
=I Gi 
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Fe LAND = oon 
K 
jer " 
[pee 5 Jt mae 
43") 
fe) 
R 
g / 
¢ \ 
» 
N fF 
Are j 
=} ~ j J ‘i 
—* Ory § / 
2 a a / 
/ SH 
= / | 
4 > i 
i j 
iV 
= ! 
/ 
S ™ E— 
\ Y A 
Fa = \ aA 
ol ; 
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Ni 
NS 
Si 
: Sales 
== \ 
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=s - a 
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| Lower Miocene =i en 
a Uy = ae 
Rarph Amnola, 1404 Sons: 
Fic. 3.—Map showing hypothetical 
distribution of land and water on the 
Pacific Coast during lower Miocene 
time. 
sandstone. The Monterey, on the other hand, is composed 
largely of diatomaceous material with minor quantities of sand- 
stone, fine volcanic ejectamenta, and limestone, the last three 
1 J. C. Merriam, Bull. Dept. Geol. Univ. Cal., Vol. V, p. 173. 
2 Oral communication from Mr. Chester W. Washburne. 
