126 BRUCE CLARK 
FAUNA OF THE MEGANOS OF CALIFORNIA 
CORRELATION 
Correlation of Different Meganos Sections in Coast Ranges 
Evidence for Correlation of Meganos of Coast Ranges with Beds of 
Siphonalia Sutterensis Zone Which Form a Part of the Ione Formation 
of the Foothills of the Sierra Nevada as Mapped by the United States 
Geological Survey 
General Correlation 
SUMMARY OF CONCLUSIONS 
INTRODUCTION 
The problems connected with the divisions of the marine 
Tertiary of the West Coast are complicated and their solutions 
difficult. This is due to the original conditions of deposition 
and to the magnitude of the crustal movements which have affected 
all the formations of this province, including the Pleistocene. 
The sediments were, for the most part, deposited in geosynclinal 
troughs, some of which appear to have been rather local. The 
deposits are of enormous thicknesses as compared with those 
of the same period in the Gulf and Atlantic Coast provinces. 
The aggregate thickness of the Tertiary of the West Coast exceeds 
40,000 feet. Clastic materials predominate, and, over wide 
areas, the beds are either unfossiliferous or the preservation of 
the fossils poor, due to the leaching out of the original material 
of the shells. The destructive leaching is more general in the 
marine Tertiary of California than in that of Oregon and Washing- 
ton. Crustal movements occurred along the West Coast more 
or less interruptedly throughout the Tertiary, and the groups 
of strata representing the major epochs of this time are, as a rule, 
separated by angular unconformities. The intense folding and 
faulting which accompanied these movements, together with the 
paucity and poor preservation of the faunas, have made the 
problems of correlation difficult, and it is only by detailed mapping, 
combined with careful paleontological work, that we can hope 
ultimately to arrive at the final solution. Due in part to these 
conditions and also to the fact that workers have been few, little 
has been accomplished toward distinguishing minor faunal divisions 
in the Tertiary of the West Coast, i.e., such faunal divisions as 
