LOWER CRETACEOUS DEPOSITS CALIFORNIA AND OREGON

CRETACEOUS SEDIMENTARY DIVISIONS 51
That the sea advanced into this basin from tbe Sacramento embayment
can hardly be doubted, since both faunas and floras were compared with,
and correspond to, those of the Paskenta group in its type district in the
Sacramento Valley.
Wilbur Springs*—South of its type district the Paskenta group is *
continuous along the west border of the Great Valley, and its lower beds
at least are highly f ossiferous in many places (Newville, Winslow, Government
dam, near Elk Creek, and near Wilbur Springs). Most of the fossils
found in these beds are species of Aucella, of tbe robust, heavy-shelled
types {A, infiata, A. crassa, and A. uncitoides), and a species of Aeroteuihis.
The unconformable relation of these beds to the underlying
Knoxville shales is well shown at Newville, at the Winslow bridge, at the
Government dam, and also at Wilbur Springs.
The district about Wilbur Springs is typical and of more than ordinary
interest, partly for having had frequent mention by earlier writers. One
and a half miles northeast of the Hotel, near Bear Creek, tbe lower thinbedded
sandstones of the Paskenta group contain Auceila crassa, A. inflata,
A, unciioides, and Acroteuikis ep. At this point these beds rest in part
upon Knoxville strata and in part upon older rocks. Two miles southwest
of the Hotel tbe same beds rest upon Franciscan cherts or upon associated
serpentine, but they contain these same fossils. Between these localities
are the "white limestones," often mentioned as containing RhynchoneUa
whilneyi, Pecien comphxicosta, and ModioUt major, resting directly upon
serpentine and Franciscan rocks. Along Bear Creek the Knoxville beds
are exposed beneath those of the Paskenta. From the former Stanton
(1895, p. 19, 20) has reported Aucella piochi Gabb, PhyUoceras knoxvil-
Icnsel, and Belemniies sp. All these species h ave since been obtained hare,
although the belemnite appears to be a form of Belernmrpsis, not uncommon
in the Knoxville beds.
The conglomerates mentioned by Stanton (1895, p. 19) fife at the base
of the Paskenta group, south of the Hotel, and of tbe Gibson mine, and
also east of Bear Creek.
It is important to note here tbe overlap of the Paskenta beds across
the narrow zone of the Knoxville and their contact with various types of
older rocks.
Morgan Valley, Lake County.—This district was visited by Whitney,
Stanton, and later by the writer. The beds exposed here are chiefly sandy
shales, but they also include clay shales, limestones, sandstones, and
pebbly conglomerates. The pebbly conglomerates constitute the basal
beds of the Paskenta group that appear to rest directly upon formations
referable to the Franciscan series, including cherts, and other types, all
much disturbed by serpentine intrusions. There are also exposures of
Knoxville beds in parts of the district, but they cannot be described here.