LOWER CRETACEOUS DEPOSITS CALIFORNIA AND OREGON

CRETACEOUS SEDIMENTARY DIVISIONS 81
Lower Cretaceous deposits of western Europe and the American West
Coast belong to different faunal provinces, direct correlations between
them are not often easy to make, but indirect correlations between parts
of their general columns are sometimes possible, and to some extent the
faunal order in the Lower Cretaceous in England and California is somewhat
parallel throughout. Some of the faunal assemblages described
from the section at Speeton, England, and from western Europe seem to
have counterparts in the Lower Cretaceous of California, but there is
not always a close agreement in the order of their occurrence in the two
provinces.
For the present, therefore, the correlations made here with the standard
chronological divisions in the Lower Cretaceous of Europe are offered
with some reserve and are subject to alterations as the faunas become
better known and their faunal zoning becomes more complete.
Southwestern Asia,—From the study of the collections so far made, it
appears that, in part at least, relations between the faunal assemblages
in the Lower Cretaceous of California and southwestern Asia and Australia
are closer than between those of California and western Europe.
Although geographically remote, the agreements in faunas and faunal
succession (Hauterivian to Aptian) in the Caucasus region and in the
the Sacramento embayment seem surprising but are none the less understandable.
The Lower Cretaceous faunas of New Caledonia are not yet sufficiently
well known to be compared with those of the American West Coast, and
the some may also be said concerning those of Japan.
FAUNAL RELATIONS
General Statement.—When one considers the varied character of the
Lower Cretaceous faunas and the faunal succession herein described, it
seems evident that the areas and environmental conditions of the known
troughs and embaymenta of the West Coast are too limited to have been
the cradles of their origin and development and that one must look elsewhere
for centers of dispersal from which migrations could have reached
these regions.
It is not yet clear to what other regions one should look for the sources
of their several elements, nor do the conditions of sea and land about the
Pacific basin seem capable of providing sources or the necessary routes
of travel for all of them. Their biotic relations and possible sources are
suggested by the charactcr of some of the elements themselves, although
they point to remote regions and require speculative hypotheses to meet
the demands of migration thither. However, in the absence of better
guiding facts, these suggestions may be considered as acceptable until
better ones have been found. If the history of the Pacific and its environs