LOWER CRETACEOUS DEPOSITS CALIFORNIA AND OREGON

CRETACEOUS SEDIMENTARY DIVISIONS 41
includes all of tbe Lower Cretaceous sequence ("Neocomian to Gault
inclusive") found in the Great Valley, but it should terminate at the basal
beds of the Chico series, the earliest of the California Upper Cretaceous.
As far as detailed exploration has extended in California and in Oregon,
these relations have been found at both the bottom and top of the Shasta
series, They have been found at its base near Mount Diablo by Taff,
and in the Berkeley Bills by L- W, Henry and the writer, and in the
Santa Clara Valley and farther south. In southern Oregon (Douglas and
Curry counties), Lower Cretaceous deposits contemporaneous with the
Shasta series axe well known in which similar basal conglomerates have
been described by Diller (1898, 1924) and have been observed by the
writer. In some localities they rest upon beds that may belong to the
Knoxville series, and in other places upon older formations. The basal
relations here are similar to those in California; namely, those of unconformity.
In this region the stratigraphic relations at the top of the Shasta
series are not fully known, although they are perhaps the same as in
California* About the Rogue River Valley, and near Riddle, Oregon,
lower beds of tbe Chico series rest directly upon pre-Cretaceous formations
and thus show conditions of a wide overlap in late Albian and Cenomanian
times.
Stratigraphic Groups.—The Shasta series in the Great Valley sections in
California has been divided into two major groups, primarily upon
paleontologies! grounds, but tbe division is supported by other important
criteria, found in their distribution and lack of coincidence, and in the
thick beds of conglomerate usually lying between them, and in some
places by direct evidence of disconf oiraity and transgression.
The later, and somewhat thicker, portion of the series constitutes the
Horsetown group. As originally defined by White (1885), this term seems
to'have covered the whole of the Lower Cretaceous, and thus became
synonymous with the Shasta "group" of Whitney. It is in accord with
stratigraphical facts to restrict the name Horsetown, as was done by
Stanton and Diller (18&4) and to include the lower portion of the series in a
unit, for which the name Paskenta group is appropriate. These terms arc
applicable not only in the district about Paskenta, Tehama County, but
in the Cottonwood district, Shasta County, and throughout California and
southwestern Oregon. As interpreted by Stanton, the base of the Horsetown
group occurs immediately at Ono, Shasta, County, and is recognizable
in Tehama County. This division is supported by both stratigraphic and
faunal criteria.
PASKENTA GEOCP
General Statements—The name Paskenta was suggested by the writer
long ago (Anderson, 1902a, p. 43-45) for the lower part of the Shasta
series, as since defined, in the belief then prevalent that it formed a repre-