LOWER CRETACEOUS DEPOSITS CALIFORNIA AND OREGON

58 3WJWEH CRETACEOUS DEPOSITS IN CALIFORNIA AND OREGON
although little information has been given as to its thickness or stratigraphical
limitations. According to Diller the "Myrtle formation" in
this district contains beds of conglomerate, sandstone, limestone, and
shale, Small limestone areas have been mapped and described as the
"Whitsett limestone lentils," in which are found a few imperfect fossils,
among which Stanton (Diller, 1898) recognised Opis califcmica and a
species of "HopUtea" closely related to, or identical with, "if." dilleri
Stanton. In the sandstone, within 300 feet of the "Whitsett limestone"
in its type area, well-preserved specimens of AuceUa crassicoUis were
reported. Concerning this limestone, Diller says, in part:
"The Meurrcnea of limestone in the tipper part of the Knoxville of the Dillard
area is not exceptional, for it occurs at that horizon in several places along the west
aide of the Sacramento Valloy in California."
in this text the "upper part of the Knoxville" refers to the Paskenta
group in which limestone of the same kind occurs in lentils on the west
border of the Sacramento Valley. All the fossils clearly identified in
Diller's notes have been found in the Paskenta group in California, and
no clear evidence of older beds associated with the "Whitsett limestone
lentils" has been recorded.
Probably most of the conglomerates found in the Dillard district occur
in the lower part of the Paskenta group, and they might be taken as indicating
its unconformity upon older formations. In the Dillard area the
same uncertainty regarding the occurrence of Knoxville strata exists as
about Riddle. Further investigation is needed to determine what stratigraphic
groups are included in the "Myrtle formation," as it has been
mapped. The same also appears to be true in other areas in western
Oregon where Knoxville beds have been reported. In the Riddle area
tbe oldest clearly determined Cretaceous strata contain Dichoiomiies,
Lyiicoceras, Neocomites, AuceUa crasflicollia, and other forms of V&langinian
age, and therefore belong to the Paskenta group.
If any Knoxville beds oeeur in this district tbey may include the lowest,
plant-bearing beds in the "Myrtle formation" about Buck Peak, described
by Diller, though they contain only a scanty suggestion of the rich Tithonian
faunas found on tbe west border of the Sacramento Valley. Their
determination as Knoxville can hardly be regarded as conclusive, although
future collections of molluscan and plant remains from these beds may fix
their age as definitely Jurassic (Tithonian).
There is little known evidence that Horsetown beds (Hauterivian to
Albian) occur in any of the Cretaceous basin areas of southwestern Oregon.
No published record has been found of the occurrence of rich cephalopod
faunas here such as are known in the Great Valley of California and in
Canadian and Alaskan areas farther north.