LOWER CRETACEOUS DEPOSITS CALIFORNIA AND OREGON

56 3WJWEH CRETACEOUS DEPOSITS IN CALIFORNIA AND OREGON
Douglas County, Oregon, It was thought to be in large part equivalent
to the "upper Knoxville" beds in California on account of its fauna. The
term was later applied to similar deposits in the Coos Bay and Port Orford
areas (Diller 1903b). The formation was later reviewed by Diller (1908)
and somewhat modified so as to include also the "lower Knoxville." In
the text of the Port Orford folio, as well as in his later contribution, Diller
seems to have recognized two or more distinct stratigraphic units within
its span, although he did not go so far as to separate them. One of these
units was said to be characterised by abundant plant remains and by the
occurrence in it of ^uceila -piochi Gabb; the other was composed of conglomerates
and sandstones, as on Elk River, Curry County, and carried
the following molluscan fauna:
Aucella crasicoUia Keyaerling Inoceramm ovatua Stanton
Turbo morgtmenstt Stanton "Qlceulephanuti mulabilis" Stanton
"Hoplitet" hyatti Stanton Behmmtn tehamaemie Stanton ?
BeltrmnUtt imprests Gabb
Of the seven species in this list, six are typical of the Paskenta group in
the Shasta series of California. As no species referable to the Knoxville
series (s. s.) was positively identified, we may accept the formation as
properly representing the Paskenta. Thus it appears that the "Myrtle
formation" in Oregon is in large part equivalent to the Paskenta group of
the Shasta series in California.
The lower part of the "Myrtle formation" containing Aucella piochi
Gabb may be accepted as coming within the limits of the Knoxville series,
provisionally at least. The proper division of the "Myrtle formation"
into Lower Cretaceous and upper Jurassic portions constitutes an important
task for future exploration and mapping, and this will doubtless
be facilitated by the careful work of both Diller and Stanton.
In the discussion of the "Myrtle formation" in tbe Port Orford quadrangle
by Diller, it is readily seen tbat the strata containing Aucella
crassicollis and associated forms rest in some places upon beds containing
AuceUa piochi and in other places directly upon metamorphic rocks
(schists, serpentine, and gabbros), with neither Dothan nor Knoxville
beds intervening, as is often the case with the Paskenta group in California.
Another part of the "Myrtle formation" may represent the Horsetown
group, in part, as may be seen from the lists of species given by Stanton
(1895, p. 22, 23) from near Riddle, Of some 16 species listed by him,
half of them are known to occur in this group; some of them also occur in
the lower part of the Chico series in California.
On the map of the Riddle quadrangle (Diller and Kay, 1924), in most
places where the "Knoxville" beds are shown in contact with older rocks,
the latter belong to the basement complex, and no other rocks intervene.