Middle Jurassic (Bajocian) Eastern Oregon

34 MIDDLE JURASSIC (BAJOCIAN) AMMONITES FROM EASTERN OREGON
genus Sonninia (Papillice1·as), as suggested by Westermann
(1969, p. 24). Another ammonite, Sonninites
hansoni McLearn ( 1926, p. 95, pl. 23, figs. 2, 3) could
be interpreted as a much worn specimen of S. (E.)
modesta Buckman, as suggested by its vertical umbilical
wall, abrupt umbilical edge, and the fine ribbing on its
inner whorls. Overall, this ammonite faunule from
Hudson Bay Mountain resembles the faunule in the
upper part of the Weberg Member and is probably
of the same age.
Another ammonite faunule, represented by Sonninia,
has been collected in the Rocky Mountains near Lake
Minnewanka in southwestern Alberta. It consists of a
few poorly preserved ammonites that have been identified
as Sonninia spp. undet. (Frebold, 1957, p. 48, 49,
pl. 19, figs. 2a, b, pl. 20) and Sonninia gracilis (Whiteaves)
(Frebold, 1957, p. 48, pl. 19, figs. 1a, b) and have
been correlated with the S onninia sowerbyi zone by
Frebold (1957, p. 13; 1964, table 1 opposite p. 24).
The same ammonites have been assigned to Witchellia,
Sonninia (Euhoploceras) and questionably to S.
(Alaskoceras) by Westermann (1969, p. 26, 94, 99, 107).
No faunal evidence has been found in western Canada
for the presence of beds equivalent to the European
Otoites sau.zei zone or the Parabigotites crassicostatus
ammonite faunule of southern Alaska and eastern
Oregon. Furthermore, the possibility that the sauzei
zone is represented in the Manning Park area, British
Columbia, by an association of Zemistepltan'us richardsoni
(Whiteaves) and Graphoceras crickmayi Frebold,
as suggested by Frebold (in Frebold and others,
1969, p. 18, 22, 25, 26, 32, 33, 35, pl. 2) seems most unlikely,
considering the range of Zernistephanus in Alaska
(Imlay, 1964a, p. B15, B16, B51 and B52), and the
range of Graphoceras in Europe (Arkell, 1956, p. 33).
A1nmonites representing the European Stephanoceras
hu1nphriesianum zone are widespread in British Columbia
and Alberta. (See references to McLearn, Warren,
and Frebold in Imlay, 1964a, p. B19.) This correlation
is based on the association of Teloceras, Stemmatoceras,
Stephanoceras, N ormannites and Ohond·roceras which
are common in that zone in Europe. It is based also on
the absence of such taxa as Witchellia, Papilliceras,
Otoites, E1nileia and Labryinthoceras which are characteristic
of the underlying Otoites sauze'i zone in Europe
and of the Parabigotites crassicostatus faunule in
southern Alaska and eastern Oregon.
WESTERN INTERIOR OF THE UNITED STATES
Marine Jurassic beds equivalent to the European
Stephanoceras humphriesianum zone have been identified
in the western interior of the United States only
in northwestern Montana. The evidence consists of an
association of Ohondroceras and Stemmatoceras near
the base of the Jurassic (I1nlay, 1967, p. 34, 59, 90-94,
pl. 6, figs. 1-3, 7, 8, pl. 7, figs. 1-13, pl. 8, pl. 9, pl. 12,
figs. 1-4) . The resemblance of the single specimen of
Olwndroceras present to 0. allani (McLearn) indicates
correlation with the highest known Bajocian beds in
Canada, with the topmost part of the Basey Member
of the Snowshoe Formation in the Suplee area, Oreg.,
and with equivalent beds near Seneca, Oreg.
Basal upper Bajocian beds, apparently equivalent
to the European Stre1wceras sub furcatum zone, occur
near the base of the Twin Creek Limestone in southeastern
Idaho, western Wyoming, and northern Utah
(Imlay, 1967, p. 28, 61). The age evidence consists of an
association of Stephanoceras, Stemmatoceras, Megaspltaeroceras
and Spiroceras (Imlay, 1967, p. 88-91, 96,
97). Derivation of this faunule from a transgression of
the Pacific Ocean is shown by the presence of identical
to similar ammonites in eastern Oregon, in the highest
Bajocian rocks exposed near Seneca and on Juniper
Mountain south of Brogan.
NORTHERN CALIFORNIA
From the Mormon Sandstone near 'Taylorsville (fig.
1) in the Sierra Nevada have been obtained a few ammonites
that constitute excellent evidence for correlation
with the European zone of Otoites sauzei and with
the Warm Springs Member of the Snowshoe Formation
in eastern Oregon. These correlations are based mainly
on the occurrence of the subgenus Sonninia (Papilliceras)
at several levels and particularly the species S.
( P.) stantoni Crickmay in the lower part of the formation.
The a.mmonites and their faunal units as described
by Crickmay ( 1933, p. 898, 899, 908-913) are listed from
top to bottom as follows :
PapilUcera.s juramontanum Crickmay (unit 8)
Holcophylloceras falciterum Crickmay (unit 7)
Papilliceras blackwelderi Crickmay (unit 7)
Otoites reesidei Crickmay (unit 7)
Ohondroceras russelli Grickmay (unit 7)
Papilliceras stantoni Crickmay (unit 5)
Stiphromorphites schucherti Crickmay (unit 4)
The above listed species of Papilliceras are identical,
or probably identical, with species in the Warm Springs
Member of the Snowshoe Formation in eastern Oregon.
Smvninia ( Papllliceras) juramontanum ( Crickmay)
(1933, p. 911, pl. 311) is probably represented at Lupher's
locality 206. S. (P.) blackwelderi Crickmay
(1933, p. 911, pl. 30, figs. 1-4) is probably identical with
S. (P.) cf. S. (P.) arenata (Quenstedt) from the upper
part of the member at USGS Mesozoic loc. 29241. S.