Ammonites from the 'a Zones in - Northwestern California and Southwestern Oregon
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Ammonites from the
'a Zones in
Northwestern California
and Southwestern Oregon
GEOLOGICAL SURVEY PROFESSIONAL PAPER 647-BAmmonites from the
'a Zones in
Northwestern California
and Southwestern Oregon
By RALPH W. IMLAY and DAVID L. JONES
JURASSIC (TITHONIAN) AND CRETACEOUS BUCHIA ZONES IN
NORTHWESTERN CALIFORNIA AND SOUTHWESTERN OREGON
GEOLOGICAL SURVEY PROFESSIONAL PAPER 647-B
Some Late Jurassic and Early Cretaceous
ammonites date the Buchia zones and furnish
correlations with the Boreal and Tethyan Realms
UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1970UNITED STATES DEPARTMENT OF THE INTERIOR
WALTER J. HICKEL, Secretary
GEOLOGICAL SURVEY
William T. Pecora, Director
For sale by the Superintendent of Documents, U.S. Government Printing Omce
Washington, D.C. 20402 - Price $1.25 (paper cover)CONTENTS
Page Page
Abstract.__________________________________________ Bl Ages and correlations of the ammonite faunules Continued
Introduction. _ _____________________________________ 2 Cretaceous ammonites Continued
Biologic analysis.___________________________________ 2 Valanginian ammonites from the Buchia pacifica
Stratigraphic relationships of ammonites to Buchias__ 5 B14
Ages and correlations of the ammonite faunules________ 11 Valanginian ammonites from the Buchia keyser-
Jurassic ammonites-____________________________ 11 lingi zone. _______________________________ 16
Tithonian ammonites from the Buchia piochii Valanginian ammonites from the Buchia crassi-
zone____________________________________ 11 collis solida zone. ___________-___-______--- 17
Tithonian ammonites from the Buchia aff. B. Comparisons of ammonites with other ammonite faunules-- 17
okensis zone______________________________ 12 Geographic distribution______-__________--_____----_ 19
Cretaceous ammonites-_________________________ 12 Systematic descriptions________ _____________________ 2?
Berriasian ammonites from the Buchia uncitoides References ___________-______--------------__------ 53
zone____________________________________ 12 Index _____-______-___-_-------_-----_-_----------- £7
ILLUSTRATIONS
[Plates follow index]
PLATE 1. Phylloceras, Phyllocerasf, Bochianitesf, and Bochianites.
2. Lytoceras and Phylloceras.
3. Kossmatia, Proniceras, Spiticeras, and S. (Kilianicerast).
4. Spiticeras.
5. Groebericerast.
6. Groebericeras? and Protacanthodiscus.
7. Tollia and Polyptychites.
8. Tollia, Polyptychites, and Olcostephanus.
9. Olcostephanus and Pclyptychites.
10. Blanfordiceras and Substeueroceras.
11. Parodontoceras.
12. Aulacosphinctesf, Sarasinella, and Parodontoceras.
13. Thurmanniccras and Paskentites.
14. Neocomites, Neocosmocerasl, Neocosmoceras, and Kilianella.
15. Groebericeras"!.
Page
FIGURE 1. Stratigraphic relationships of ammonites with species of Buchia____________________---__-------------- B6
2. Correlation of latest Jurassic (Tithonian) and earliest Cretaceous (Berriasian and Valanginian) faunas in
California and Oregon.____________________________________________------------___-_----------_ 8
3. Index map of ammonite localities in the Buchia beds of southwestern Oregon_ __________________________ 19
4. Index map of ammonite localities in the Buchia beds of northwestern California-____________-_____---_-__ 19
5-8. Detailed index map of ammonite localities
5. In west-central part of the Colyear Springs quadrangle, California____ ---------------------------- 19
6. In the Paskenta area, California -------------------------------------------------------------
7. Near Newville, Calif_ ---------------------------------------------------------------------
8. In the Elk Creek area, California___ --------------------------------------------------------
inIV CONTENTS
TABLES
Page
TABLE 1. Some ammonite genera in Tithonian, Berriasian, and Valanginian beds in northern California and so^th-
western Oregon showing biological relationships of the genera, relative numbers available for study, and
stages represented-___________________________________________________________________________ B3
2. Geographic distribution of ammonites in the uppermost Jurassic (Tithonian) and Lower Cretaceous Buchia
beds of northwestern California and southwestern Oregon_____________-_____________-__________ .___ 20JURASSIC (TITHONIAN) AND CRETACEOUS BUCHIA ZONES IN NORTHWESTERN CALIFORNIA
AND SOUTHWESTERN OREGON
AMMONITES FROM THE BUCHIA ZONES IN NORTHWESTERN CALIFORNIA
AND SOUTHWESTERN OREGON
By EALPH W. IMLAT and DAVID L. JONES
ABSTRACT subgenus Negreliceras in California ranges through the low^r
Ammonites from the UMcTwa-bearing strata of northwestern two-thirds of the Buchia uncitoides zone and dates that pprt
California and southwestern Oregon represent the Tithonian as not younger than Berriasian.
stage at the top of the Jurassic and the Berriasian and Valan- Ammonites of middle and late Valanginian age are well
ginian stages at the base of the Cretaceous. These ammonites represented in California and Oregon. That beds of early Valpn-
are associated with various species of the pelecypod Buchia, ginian age are present has not been proved faunally. In Cr.li-
which from oldest to youngest include B. piochii (Gabb) and fornia, however, some specimens of Thurmanniceras in the
B. aff. B. oJcensis (Pavlow) of Tithonian age, B. uncitoides lower part of the Buchia pacifica zone could be dated as early
(Pavlow) of Berriasian age, B. padflea Jeletzky of early to Valanginian on the basis of stratigraphic position. The middle
middle Valanginian age, B. Jieyserlingi (Lahusen) of middle to part of the B. paciflca zone has furnished species of Thurman-
early late Valanginian age, and Buchia crassicollis solida (La- niceras and Kilianella that, by comparisons elsewhere, sug-
husen) of late Valangdnian age. The ages cited are based pri- gest a middle Valanginian age. The upper part of the B. pacifva
marily on the ammonites present but partly on the similarities zone contains a species of Tollia that is similar to a species
of the Buchia succession ito that in British 'Columbia and in the from the middle Valanginian of East Greenland. The preserve
Arctic region. As the succession of the species of Buchia is of Tollia itself is good evidence of an age not younger than
similar to that in western Canada, the strata characterized by middle Valanginian.
the species are herein considered assemblage zones in con- The overlying zone of Buchia keyserlingi in the Paskenta
formity with the usage in Canada. and Elk Creek quadrangles, California, contains such typi?al
Ammonites of Tithonian age have been found mostly along Valanginian ammonites as Sarasinella, Polyptychites, and Thur-
the west side of the Sacramento Valley, Calif. They include manniceras. The last two ammonites in the upper part of the
Kossmatia from the lower to middle parts of the B. piochii zone are associated with Crioceratites and Neocraspedites,
zone, Parodontoceras and Spiticeras from the upper part of the which in Eurasia are not known in beds older than late Valan-
B. piochii zone, and Substeueroceras, Parodontoceras, Proni- ginian. The upper part of the zone, therefore, is dated as late
ceras, Spiticeras, and Blanfordiccras from the B. aff. B. okensis Valanginian, but the lower part could be middle Valanginian,
zone. Of these ammonites, Kossmatia, by comparisons with the The highest Buchia zone, characterized by B. crassicollis
sequence in Mexico and Argentina, is evidence for a middle solida (Lahusen), has furnished diagnostic ammonites only in
Tithonian age, but it occurs also in New Zealand in beds of Oregon. These consist of Homolsomites and Olcostephanus that
late Kimmeridgian age and probably also in beds of middle by comparisons with species in Eurasia could be either latest
Kimmeridgian age. Parodontoceras is good evidence of a mid- Valanginian or earliest Hauterivian. A Valanginian age is
dle to late Tithonian age on the basis of its range in Mexico favored by the association of these ammonites with Buchia tfnd
and Argentina. The various ammonites listed from the B. aff. by their stratigraphic position directly below beds containing
B. okensis zone are excellent evidence for a late Tithonian age early Hauterivian ammonites.
equivalent to the highest Jurassic beds in Mexico and Argen- The affinities of most of the ammonites of latest Jurassic f nd
tina. An age not older than middle Tithonian for the lowest earliest Cretaceous ages from California and Oregon are south-
part of the Jurassic sequence along the west side of the Sacra- ern or Mediterranean. Only Tollia and Homolsomites are dis-
mento Valley is indicated by the absence of species of Buchia, tinctly Boreal. In addition, the genera Polyptychites and Neo-
such as B. mosquensis (Von Buch) and B. rugosa (Fischer), craspedites range from the Mediterranean to the Arctic but are
most common in central and northern Eurasia and are probably
which occur in beds of middle Kimmeridgian to middle Titho-
not of Mediterranean origin.
nian age from the State of Washington northward into Alaska
Ammonites are rather uncommon in the Uttcftia-bearing se-
and as high as the Dorsoplanites panderi zone (lower middle quence of northwestern California and southwestern Oregon
Volgian) on the Russian platform. except at the very top of the beds characterized by Buchia
Ammonites of Berriasian age from California and Oregon paciflca Jeletzky. Those beds also have furnished a fair variety
belong mostly to the subgenera Spiticeras (Negreliceras) and of pelecypods and gastropods. Elsewhere throughout the se-
8. (Spiticeras) but include also the genus Neocosmoceras. The quence the only common fossil is Buchia itself.
BlB2 JURASSIC AND CRETACEOUS BUCHIA ZONES IN CALIFORNIA AND OREGON
The ammonites on which this study is based total 454 speci- distribution by families, subfamilies, genera, and sub-
mens, of which 57 are assigned a Tithonian age, 103 a Berria- genera is shown in table 1. This table shows that the
sian age, and 294 a Valanginian age. One new genus, Paslien-
tites Imlay and Jones, of middle Valanginian age is described
Olcostephanidae include 70 percent and the Perriasel-
herein. New species include Phyllocerasl contrarium Imlay and lidae 17 percent of the specimens examined. Among
Jones, Proniccras maiipincnsc Imlay and Jones, Spiticeras the genera studied, Spiticeras includes abou4:. 24 per-
(Negreliceras) stonycnsc Imlay and Jones, Grocbericcrast cent, TolTia 44 percent, Thurmanniceras 6 percent, and
baileyi Imlay and Jones, and Neocosmoccras cuchrense Imlay Neocomites 7 percent of the 454 specimens. Among
and Jones.
INTRODUCTION these specimens the Tithonian is definitely represented
by 55 and questionably by two, the Berriasian by 101
The primary aim of this study is to determine the and questionably by two, and the Valanginian by 294.
ages of the Buchia-be&r'mg strata in northwestern Cali- These figures include all ammonites of Tithonian and
fornia and southwestern Oregon by means of the am- Berriasian ages but only part of the ammonites of
monites present. It has been necessary, therefore, to Valanginian age that have been found in northern
study those ammonites thoroughly, to compare them California and southwestern Oregon. Only those Val-
with similar ammonites elsewhere in the world, and to anginian ammonites are described herein that have not
determine their stratigraphic positions relative to the been described previously (Imlay, 1960), or that have
species of Buchia with which they are associated. This some bearing on correlations and age determinations,
has involved a simultaneous study of the characteris- or that are better preserved than any found previously.
tics and ranges of the species of Buchia in California On the generic and subgeneric level moft of the
and Oregon and comparisons of those species with the ammonites listed agree in most features with various
various species of Buchia from western British Colum- taxa denned in the "Treatise on Invertebrate Paleon-
bia described by Jeletzky (1965). That has led in turn tology'' (Arkell and others, 1957). Some ammonites
to recognition of a number of mappable Buchia zones that are assigned questionably to Kilianiceras, Aula-
of which some are identical with zones in British cospliinctes, and Neocosmoceras are represented by im-
Columbia. mature fragmentary specimens that do not show
This study includes all ammonites of latest Jurassic enough diagnostic features to place them def nitely in
(Tithonian) and earliest Cretaceous (Berriasian) ages their proper genus or subgenus. Other ammonites that
from northwestern California and southwestern Ore- are assigned questionably to Phylloceras, Bochianites,
gon that are available in the California Academy of and Groebericeras bear features that are not known in
Sciences, in the Museum of Paleontology at the Univer- those genera but that may not be of more than specific
sity of California in Berkeley, and in the laboratories value. Thus PJiyUoceras^ contrarium Imlay and Jones,
of the U. S. Geological Survey. It includes, also, some n. sp. has rursiradiate ribs on the upper parts of the
Early Cretaceous (Valanginian) ammonites for which flanks and venter, whereas in typical species of Phyl-
new information is available. It does not contain de- loceras the ribbing either crosses the venter trans-
scriptions of many other Valanginian ammonite spe- versely or arches gently forward. The generic assign-
cies that are described by Imlay (1960), although most ment of Bocliianites\ glennensis Anderson is ques-
of those species are mentioned and listed herein. It does tioned because its venter bears transverse rib^1 instead
of chevron-shaped ribs. The generic assignment of
contain descriptions and evaluations of most of the
Gi'oebericeras ? bayleyi Imlay and Jones, n. sp. is ques-
Tithonian-Valanginian ammonites described by An-
tioned because of the presence of umbilical tubercles.
derson (1938, 1945).
The family Perisphinctidae is represented only by
The authors are grateful for assistance and loan of three small immature specimens of Kossmatia. These
specimens to Leo G. Hertlein and G. Dallas Hanna of show such characteristic generic features rs fairly
the California Academy of Sciences at San Francisco, regular rib branching on the middle third of tl °- flanks,
to Wyatt Durham and Joseph H. Peck, Jr., of the chevronlike arrangement of ribs on the venter, presence
University of California at Berkeley, and to Horace of constrictions, and absence of tubercles.
G. Richards of the Philadelphia Academy of Natural The family Olcostephanidae is represented mostly by
Sciences. the genera Tollial and Spiticeras. It also includes a
BIOLOGIC ANALYSIS few specimens belonging to Proniceras, Groebericeras^ ,
The ammonites of latest Jurassic (Tithonian) and Olcostephaiius, and Polyptychites.
earliest Cretaceous (Berriasian and Valanginian) ages In the subfamily Spiticeratinae the identification of
that are described herein total 454 specimens. Their Proniceras is based on the presence of perisphinctoidAMMONITES FROM THE BUCHIA ZONES B3
TABLE 1. Some ammonite genera in Tithonian, Berriasian, and Valanginian beds in northern California and southwestern Oregon
showing biological relationships of the genera, relative numbers available for study, and stages represented
Family Subfamily Genus and subgenus Number of Stages
specimens
Phylloceratidae__- ___ _ Phylloceratinae Phylloceras _________ ______ 8 T, V
Phyllocerast . ______ __ _ _ ______ 5 T
Lytoceratidae _ Lytoceratinae. Lytoceras _ _____ _ ___..-____ 12 T, V
Bochianitidae Bochianitinae Bochianites*? _ __ ______ ______ 1 T?
Bochianites- _______ ______ 15 V
Perisphinctidae. __ __ _ Ataxioceratinae Kossmatia. __ _ ____ ___. _ - _ O T
Olcostephanidae _ Spiticeratinae. _ _ Proniceras,. _ _ ____ _ ___.______ 6 T
Spiticeras... . ____ _ ____.______ 10 T, B
S. (Kilianicerasl) _ ___ __ _ _.______ 3 B,V
S. (Negreliceras).. _ __ __ _ _ _____ 90 B
Groebericerasl __ _____ ___ ______ 1 T
Tolliinae _ _ _ _ ______ Tollia--...---...----.-. ____________ 200 V
Olcostephaninae. _ _ _ _ Olcostephanus ----- __ _ ___ _.. __ _ 1 V
Polyp tychitinae _ Polyptychites _ ______ 2 V
Berriasellidae_ _ _ _ _ _ Berriasellinae _ _ Blanfordiceras.- _ _ _____ ______ 3 B
Substeueroceras . _ ___ _____ 6 T
Protacanthodiscus.. . _____ _____ 1 T?
Parodontoceras- _ ____ ___ ,.____ 9 T
Himalavitinae___ __ Aulacosphinctes?--- __ _ _ 4 T
Neocomitinae_ __ _ Paskentites n. gen _ __ _____ ______ 8 V
Thurmanniceras _ _ ___ ___ ______ 27 V
Neocomites.. ___ ___ _ _____ _ _____ 32 V
Kilianella .. _____ _____ _...____ 3 V
Sarasinella...... _._ _______ _____ 2 V
Neocosmoceras.. .. ... _____ 1 B?
Neocosmocerasl _ ___ __ ___ _____ 1 B?
ribbing on the flanks, a chevronlike rib pattern on the typical of those genera and are similar to specimens1
venter, and pronounced forwardly inclined constric- previously described (Imlay, 1960, p. 203, 204).
tions and on the absence of tubercles and swellings. The subfamily Tolliinae is represented in the col-
The subgenus Spiticeras differs from Proniceras by the lections studied by the genus Tollia. This genus has s.
presence of acute umbilical tubercles, by rib branching compressed and fairly involute shell. The venter may
from these tubercles as well as higher on the flanks, be narrowly rounded or acute on the inner whorls but
and by the ribs on the venter arching forward only is moderately rounded on the outer whorls. The ribs
gently. In addition, one specimen bears lateral tubercles on the inner whorls are sharp, fine, bifurcate near the-
on its inner whorls, and other specimens bear radial middle, and project slightly forward on the venter.
swellings that are prolonged ventrally from the umbili- During growth the primary ribs become blunt, promi-
cal tubercles. The subgenus Negreliceras differs from nent, and concave forward, and the secondary ribs arise-
the subgenus Spiticeras by being compressed from early commonly by twos and threes but in some species by
growth stages, by having umbilical tubercles only, by fours and fives. On the largest septate whorls many
the presence of many weak secondary ribs, and by a secondary ribs arise freely on the flanks and a smooth
tendency for the body chamber to become smooth, par- area may develop between the primary and secondary
ticularly on the lower parts of the flanks. The subgenus ribs. All ribbing tends to fade on the largest septate
Kilianicems, doubtfully represented, differs from whorl preceding the adult body chamber. The adult
Spiticeras by having much coarser ribbing and two body whorl is smooth or nearly smooth. Constrictions
rows of tubercles that persist onto the larger whorls. are common on the internal molds of the septate whorls
The genus >Groebericeras resembles the subgenus and on the body whorl. The suture line is characterized
Negreliceras in having a compressed form and in de- by its first lateral lobe being shorter than its ventral
veloping a nearly smooth body whorl but differs by lobe.
being smoother from an earlier growth stage and by Within the Tolliinae the genus Tollia bears some
lacking tubercles except possibly on the smallest resemblance to Homolsomites (Crickmay, 1930, p. 63;
whorls. Imlay, 1956, p. 1143-1146; 1960, p. 201; Jeletzky, 1965,
The subfamilies Olcostephaninae and Polyptychi- p. 39; Shulgina, 1965, p. 81-88). It differs by having p,
tinae are represented respectively by fragmentary spe- wider and shallower umbilicus, a rounder whorl sec-
cimens of Olcostephanus and Polyptychites that are tion, longer primary ribs, fewer secondary ribs perB4 JURASSIC AND CRETACEOUS BVCHIA ZONES IN CALIFORNIA AND OREGON primary rib, less distinct junctions of secondary ribs The genus Siibsteueroceras is characterized by a with the primary ribs, rib branching at only one level, moderate to narrow umbilicus, a vertical umbilical less forward projection of secondary ribs oil the ven- wall, a broadly rounded to flat venter on the adult, a ter, loss of ribbing on the venter of the adult body lack of constrictions and tubercles, and by fine, gen- whorl, and a shorter first lateral lobe relative to the erally high flexuous ribs that branch at various heights ventral lobe. on the flanks, arch forward on the venter, and tend Tottia differs from Wellsia Imlay (1957, p. 275; to disappear or weaken on the adult body whorl. The 1960, p. 205-207; Shulgina, 1965, p. 84) in most of the ribs may be di-, tri-, or bidichotomous, or unbranched, same features that it differs from Homolsomites. In but are not virgatomous. A ventral groove is present addition it differs by having much stronger primary on the internal mold but is not present on the adult ribs that branch near instead of above the middle of wherever shell material is preserved. Siibsteueroceras the flanks and that persist on the flanks to a later differs from Kossmatia by lacking constrctions and growth stage. by having a broader and flatter venter, finer ribs, irreg- The family Berriasellidae is fairly well represented ular rib branching at various heights instead of on the by the subfamilies Berriasellinae, Neocomitinae, and middle third of the flanks, less strongly projected ribs doubtfully by the Himalayitinae. The genera listed on the middle third of the flanks, less strongly pro- under these families in table 1 are all represented by jected ribs on the venter, and a tendency of the ribs to typical specimens except Aulacosphinctes and Blan- fade out on the adult. Its rib pattern shows more fordiceras. The presence of Aulacosphinctes is ques- resemblance to that of Siibthurmannia, but it differs tioned because the specimen is too immature for certain from that genus by lacking constrictions and umbilical generic identification. The specimens assigned to Blan- tubercles and by its ribs not forking at th°, umbilical fordiceras are smaller and more compressed than most edge. species of that genus but closely resemble B. wallicJii The assignment of one small specimen from Califor- (Blanford) (Uhlig, 1910, pi. 29) and B. acuticosta nia to Protacanthodiscus is based on the presence of Uhlig (1910, p. 201-203, pi. 37, figs. 2a-c) from India biplicate Berriasellid-like ribbing on the flanks, lateral and related species from Pakistan (Spath, 1939, p. 45, and ventral tubercles, weak umbilical swellings, and a pi. 6, figs. 10, 13, 14) and Madagascar (Besairie, 1936, flat, nearly smooth venter. p. 136, pi. 11, figs. 17, 18). They also resemble "Hop- The genus Parodotitoceras is characterized by a mod- lites" australis Burckhardt (1903, p. 64, pi. 11, figs. erate to narrow umbilicus; by coarse geniiy flexuous 9-12) from Argentina, which Arkell and others (1957, ribs that incline forward on the flanks, bifurcate on p. L352) place in Blanfordiceras and Spath (1925, p. the middle third of the flanks, and cross the venter 145) assigns to his genus Pseudoblanfordia. nearly transversely; by the presence of constrictions; The genus Blanfordiceras typically has an elliptical and by the absence of a ventral groove on adult whorls. to subcircular whorl section that becomes stouter dur- It closely resembles Bernasella but differs by being ing growth. Its ribs are slightly sigmoidal, are highest more involute, by having much looser and more vari- near the middle of the flanks, project forward on the able ribbing, and in particular by lacking a ventral shoulders, and terminate in tubercles that border a groove on the adult body chamber wherevor the shell smooth midventral area. In most species the primary is preserved. Its inner whorls differ from the inner ribs bifurcate near the middle of the flanks; however, whorls of Siibsteueroceras by having constrictions, a in some species the primary ribs on the outer whorls more marked ventral groove, and less projected second- become loosely connected with the secondary ribs, and ary ribs. Its outer whorls differ from those of S'ub- other secondary ribs arise freely on the upper parts of steueroceras by having much stronger and higher ribs, the flanks. Adorally on the adult body chamber the by fairly regular bifurcation near or above the middle ventral groove weakens or disappears and the primary of the flanks instead of bi- or trifurcation at various ribs become widely spaced. In addition, tubercles or heights, and by the presence in some species of many large knots may develop at furcation points near the single ribs. middle of the flanks on the inflated species. Blanfordi- The subfamily Neocomitinae is represented by many ceras differs from Berriasella by its ribs being more specimens of Thurmanniceras and Neoccmites^ rare sigmoidal on the flanks, more projected on the venter, specimens of Kilianella, Sarasinella and Feocosmoce- highest near the middle of the flanks instead of near ras, and probably also by the new genus Paskentites. the umbilical edge, and much more widely spaced on Of these, Thurmanniceras is characterized by having the body chamber. a compressed moderately to fairly evolute shell, con-
AMMONITES FROM THE BUG HIA ZONES
strictions, lateral and ventral tubercles, and gently to lateral are conical to radially elongate and the ventral
strongly flexuous ribs that arise singly at the umbilical are spirally elongate. Its aperture bears prominent
edge, bifurcate near the middle of the flanks, and cross lateral lappets. Its outer whorl shows some resemblance
the venter transversely with slight or no reduction in to that of Protacanthodiscus but differs by the presence
strength. Many simple ribs may be present. Its inner of lateral lappets and of spirally arranged tubercles
whorls have a flattened venter, and its outer whorls a Its inner whorls differ from those of Protacanthodiscus
gently rounded venter. It differs from Neocomites by by the presence of coarse, simple, widely spaced tri-
having an oblique instead of a vertical umbilical wall, tuberculate ribs instead of closely to moderately spaced
a gently rounded instead of a truncated venter on adult biplicate ribs that bear only lateral and ventral
whorls, and by its ribs on adults arising singly at the tubercles.
umbilical edge and forking mostly near the middle The new genus Paskentites is characterized by r,
of the flanks. It differs, also, by lacking umbilical compressed shell, evolute coiling, coronate inner whorls
tubercles and a smooth midventral area except at a resembling Stephanoceras, perisphinctoid outer whorls^
very small size. and strong projection of ribs on the venter.
The genus Neocomites is characterized by having an
STRATIGRAPHIC RELATIONSHIPS OF AMMONITES
involute compressed shell, flattened flanks, a smooth TO BUCHIAS
flat venter that has rather sharp edges, a vertical
umbilical wall, umbilical and ventral tubercles only, The stratigraphic positions and ranges of the ammo-
and rather fine, fairly closely spaced flexuous ribs that nites described or mentioned herein relative to the
incline gently forward on the flanks and cross the ven- species of Buchia with which they are associated are
ter transversely. These ribs may arise singly or in shown diagrammatically in figure 1, which summarizes
pairs from small umbilical tubercles, commonly bifur- the stratigraphic data presented in detail under the
cate again near the middle of the flanks, terminate locality descriptions. A stratigraphic arrangement of
ventrally on the septate whorls in small obliquely the most characteristic ammonites relative to the spe-
arranged tubercles that border a smooth midventral cies of Buchia is shown in figure 2. These figures do
area, and on the adult body whorl may cross the venter not include certain species of Valanginian age from
transversely. California and Oregon whose associations with par-
The genus Kilianella is characterized by having a ticular species of Buchia are uncertain or unknown.
small evolute shell; an elliptical to suboctagonal whorl The ammonites of Tithonian age have been found
section; deep constrictions; a few weak umbilical, lat- mostly in the Paskenta-Elk Creek area in northwestern
eral, and ventral tubercles; a smooth venter; and strong California, west of Corning and Orland. In that area
gently flexuous ribs of which many remain simple. The the ammonite Kossmatia occurs from 4,000 to 5,000
ribs commonly bifurcate on the middle of the flanks feet above the base of the beds containing Buchia
and rarely at the umbilical edge. The ventral termina- piochii (Gabb) and also near the middle of those beds.
tions of the ribs are commonly broad and fairly strong. Considerably higher, but at least 2,000 feet below the
Adult specimens of KiUaneUa resemble immature spe- base of the beds containing Buchia aff. B. okensis
cimens of Thurmanniceras but may be distinguished by (Pavlow), occur a few ammonites belonging to Paro-
their ribs being more flexuous and generally much dontoceras, Groeberi-cerasl, Aulacosphinctesl , and
thicker ventrally and by bearing a few umbilical Phylloceras. Associated with B. aff. B. okensis (Pav-
tubercles. low) in the upper 500-1,000 feet of the Jurassic ar^
The genus Sarasinella resembles Neocomites in shape, the ammonites Phylloceras, Lytoceras, Proniceras, Spi-
involution, and ornamentation but differs by having ticeras, Blanfordiceras, Siibsteueroceras, Parodontoce-
lateral tubercles on its inner whorls, by its umbilical ras, and questionably Aiilacosphinctes.
The only ammonite of probable Jurassic age found
tubercles becoming increasingly stronger on its outer
in southwestern Oregon is an immature specimen of
whorl, and by its ribs on the outermost whorls com-
Proniceras (Mesozoic loc. 2074) that is associated with
monly arising in pairs from umbilical tubercles. Neocosmoceras i many specimens of Buchia uncitoides
The genus Neocosmoceras has a wide umbilicus, a (Pavlow), and a few specimens of B. piochii (Gabb).
polygonal whorl section, and a venter that changes The specimens of B. piochii and Proniceras have a
from concave to gently convex during growth. Its ribs slightly different matrix than the other fossils, which
are straight and widely spaced on the flanks and are suggests that they were obtained from different bedf.
interrupted on the venter. It bears three rows of strong N'eocosmoceras could also be late Tithonian in ag?.
to fairly strong tubercles of which the umbilical and judging by its stratigraphic distribution in Pakistan
365-J28 O 70 2B6 JURASSIC AND CRETACEOUS BUCHIA ZONES IN CALIFORNIA AND OREGON
= I
c -; _NvucrasperiitvK yiynntt UK Imlay
Blanfunlicei'as mlifornicMni Imlay and Jones, n. sp A
sp. undet ----- ~-Y
A
cf. S ktlhttui Imlay A
Prota/'atithfidifrun taffi (Anderson) ............?
Pamrfontorrrui stnrrxi (Stantonl
cf. P storrsi (Stanton)
refill ( Anderson )
........?
Aidneospliuictex't ditiblnetisin Anderson
? jenvinsi Anderson - -Y
? sp. juv
Paskentitfn paskentiit'tixis Imlay and Jones, n. sp
cf. P itagkviitiiensis Imlay and Jones, n. sp .............Y
Thurmnnnicvnis stippi ( Anderson 1
cf T. stippi ( Anderson)
jenkitisi (Anderson)
DE2
cf. T.jenkinsi (Anderson) . ... ...... -Y
ralifornirum (Stanton)
Neormmtex cf. AT. wichmunni Leanza .......... ...Y
cf . N. neueoniiensla (d'Orbigny) .. .. ..Y
cf. N. nencot/iieiisis var premultea (Sayn) A
sp . ......... Y
KilianeUa enisxiplicata (Stanton)
Sarasinflln cf.S xnhspinusa Uhlig
atigidatn (Stanton)
cf S iihligi Spath
sp
Neucnumnrerns eurfirenut' Imlay and Jones, n. sp A
? cross?' (Anderson)
FIGURE 1. Stratigraphic relationships of ammonites with species of BucMa. A questionk mark(?) indicates that association with
a particular species of Buehia is uncertain. Black bars show known stratigraphic ranges of the ammonite species! within
the Buchia zones. An X indicates that the exact stratigraphic position or range within the BucMa zone is unknown.
WB8 JURASSIC AND CRETACEOUS BUCHIA ZONES IN CALIFORNIA AND OREGON
European Characteristic fossils Characteristic fossils
series and in western
stages rthwestern California British Columbia
(after Jeletzky, 1965)
southwestern Oregon
Valanginian
Tallin mutabili Tollia Htutabilis
Tollia spp.
Biicftia aff.
B. okensis
Not
identified
Buchia
elder-
Buchia cf.B
ettsis blaiiforditinti
!H 8
FIGUEE 2. Correlation of latest Jurassic (Tithonian) and earliest Cretaceous (Berriasian and Valanginian) faunas in Cali-
fornia and Oregon.AMMONITES FROM THE BVCHIA ZONES B9
Characteristic fossils Characteristic fossils, Southern Europe Russian platform European
in Argentina (After Barbier, Debelmas, (After Sachs and Shulgina, Series and
in Mexico
(After Windhausen, 1918; and Thieuloy, 1965, Enay, 1964; Sachs, 1965; Gera-
stages
(Imlay 1943, 1M44, 1952,
Gerth, 1925; Weaver, 1964; Barthel, 1962) simov and Mikhailov, 1967)
Erben,19571 1931; Leanza, 1945; Gio-
vine, 195IJ; Arkell, 19561
nlcustephanua curtui
Liswfiia ? (('( rui
(not zoned) Valanginian
Pu! apt a flutes michulskii
and P Ktyserhngi
Tollia tulli
in Ural Mts.
Alyenti>iiceras nodtiliferu>n
and
Neocosaiueerus vgreyiu m
Cruspedites subditui
Berriasella
del phi
Dorsoi-ilanites patnleri
Mitiapilites
Subpla n Hex pxe udoscytli i
and
Hybonotitfr
FIGUBE 2. Continued.BIO JURASSIC AND CRETACEOUS BVCHIA ZONES IN CALIFORNIA AND OREGON (Fatmi, 1966, table 3), but the genus is generally con- niceras cf. T. stippi (Anderson) is from the lower 150 sidered indicative of a Berriasian age (Arkell and feet. Paskentites and Kilianella, Lytoceras, and Thur- others, 1957, p. L358). manniceras are from the middle third. Kilianella occurs The previous record of the late Tithonian genus also about 200 feet below the top. The upper 100-200 Pronicems at several other localities (Mesozoic Iocs. contain an abundance of Tollia mutabilis (ftanton) 3348, 3349, 25183, 25184) in southwestern Oregon (Im- and Bochianites paskentaensis Anderson along with a lay and others, 1959, p. 2780) was based mainly on few specimens of Sarasinella. fragments that could belong to the related genus Spiti- In the Buchia keyserlingi zone near Paskenta, Calif., ceras of late Tithonian to Berriasian age. Furthermore, Thurmanniceras jenkinsi (Anderson) ranges through- the presence of Buchia uncitoides (Pavlow) at Meso- out, T. stippi (Anderson) ranges through the middle zoic Iocs. 3348, 25183, 25184 indicates a Berriasian and upper parts, Neocraspedites and Polyptychites rather than a Tithonian age. It appears that the Titho- occur near or a little above the middle, and Sarasinella nian is represented in southwestern Oregon only by occurs near the base. Other ammonites associated with beds containing Buchia piochii (Gabb) that crop out B. keyserlingi but of uncertain stratigraphic position from the Dillard area (Imlay and others, 1959, fig. 1 because of faulting include Lytoceras saturnale Ander- on p. 2771) south westward to the coast. No occurrence son, Cnoceratites sp., some specimens of Neocraspe- of Buchia aff. B. okensis (Pavlow) has yet been found dites and Polyptychites tnchotomus (Stanton). In in Oregon. addition, Olcostephanus, Neocomites, and one speci- Ammonites of Berriasian age have been found with men of Polyptychites were obtained from the lower Buchia uncitoides (Pavlow) in a few places in both part of the B. keyserlingi zone near the Soi^th Fork California and Oregon and have hitherto been inter- of Cottonwood Creek in the west-central part of the preted as of Tithonian age. This mistake in age was Colyear Springs quadrangle. based mainly on the fact that crushed and immature In Oregon some of the ammonites of Valanginian specimens of B. uncitoides are difficult to distinguish age are not associated with Buchia in the collections, from B. piochii (Gabb) and that ammonites are not or the specimens of Buchia present are crurhed and common. In both States the ammonite evidence for a unidentifiable, or the collections were made over a Berriasian age consists of Neocosmoceras and Spiti- considerable distance and may contain Buchias from ceras (Negreliceras), although both occur rarely in different beds than the ammonites (Mesozoic Iocs. beds of late Tithonian age. Other ammonites associated 4386, 2154). Nonetheless, the ammonites Spiticeras with Buchia uncitoides (Pavlow) include /Spiticeras (Kilianicerasi.) (Mesozoic loc. 24702) and Sffrasinella (Spiticeras), 8. (Kilianiceras'l), and Phylloceras. The hyatti (Stanton) (Mesozoic loc. 4386) are associated subgenera Negreliceras and Spiticeras range through- with larger crushed Buchias that probably 13long to out most of the lower two-thirds of the beds containing B. pacifica Jeletzky. Sarasinella hyatti is, also, asso- Buchia uncitoides (Pavlow) in the area between Elder ciated with B. keyserlingi at three localities (Meso- Creek and Grindstone Creek in northwestern Cali- zoic Iocs. 4384, 4386, 26405; see Imlay, 196C, p. 187, fornia. In Oregon the stratigraphic positions of these 188). genera have not been determined with respect to the The presence of Buchia keyserlingi in Oregon is not base or top of the beds containing B. uncitoides by itself evidence for correlating the beds in which it (Pavlow). occurs with the Buchia keyserlingi zone in northwest- Ammonites of Valanginian age are much more com- ern California because B. keyserlingi in California mon in California and Oregon than are ammonites of occurs also with B. pacifica Jeletzky and in western Berriasian age or of Tithonian age older than the British Columbia occurs as low as B. uncitoides (Pav- zone of Buchia aff. B. okensis (Pavlow). Most of the low) . Also, in Oregon the position of Sarasinella hyatti Valanginian ammonites from California are associated and Buchia keyserlingi at Mesozoic Iocs. 4384 and either with Buchia pacifica Jeletzky or with B. keyser- 4386 appears to be lower stratigraphically than the lingi (Lahusen). In Oregon the association of certain beds containing Tollia mutabilis (Stanton) and large Valanginian ammonites, such as Olcostephanus and crushed Buchias at Mesozoic loc. 2154 (Imlay, 1960, Homolsomites, with B. crassicollis solida (Lahusen) is p. 173, 174). Evidently the sequence of Buchias and well established. ammonites has not yet been as well established in In California the relative positions of the ammonites southwestern Oregon as in California. within the Buchia pacifica zone are known mainly for In Oregon the zone of Buchia crassicollis solida has the Paskenta area. Among these ammonites, Thurman- furnished the ammonites Olcostephanus pecki Imlay,
AMMONITES FROM THE BUCHIA ZONES Bll
O. popen-oi Imlay, and Homolsomites quatsinoensis species of Kossmatia described by Anderson (1945, pi.
(Whiteaves) from several hundred feet of beds ex- 2, figs. 1, 3). Unfortunately, the specimen from Cali-
posed on the South Umpqua River near Days Creek fornia illustrated by Anderson (1945, pi. 2, figs. 4a, b)
in Douglas County (Imlay, 1960, p. 184, 185). These as Durangites is now lost, and a positive generic iden-
were obtained directly beneath beds containing Hau- tification cannot be made from the illustrations.
terivian ammonites (Imlay and others, 1959, p. 2775 The presence of Kossmatia in California is of con-
2782-2784). siderable age value because the genus occurs in Mexico
in abundance near the middle of the Tithonian sequence
AGES AND CORRELATIONS OF THE below beds characterized by Siibsteueroceras and above
AMMONITE FAUNULES
beds characterized by Pseudolioceras, Subplanites, anc1
JURASSIC AMMONITES Aulacosphinctoides (Burckhardt, 1912, p. 220-222,
TITHONIAN AMMONITES FROM THE BTJCHIA PIOCHII ZONE 1930, table 11 opposite p. 112; Imlay, 1939, p. 22, 23;
The lower 5,000-6,000 feet of the Buchia piochii zone 1943, p. 538, 539). Likewise, in Argentina, it occurr
in the Paskenta quadrangle of northwestern California high in the Tithonian (Krantz, 1928, p. 49) associated
is definitely Late Jurassic age, younger than early with Aulacosphinctes and above beds containing Paro-
Kimmeridgian, as shown by the presence of the ammo- dontoceras and Corongoceras, which in turn overlie
nites Kossmatia and Durangites^ (Anderson, 1945, p. beds containing Pseudolissoceras zitteli Burckhardt.
981-983; Stanton, 1895, p. 82) from 7,000 to 7,500 feet By contrast, in southern Europe and northern Africa
below the top of the B. piochii zone. The age of these Kossmatia is reported to range through the entire
beds is probably younger than Kimmeridgian, how- Tithonian (Mazenot, 1939, p. 129, 130) and its total
ever, considering the ranges of Kossmatia and Duran- worldwide range is Kimmeridgian through upper
gites in Mexico (Imlay, 1939, p. 22, 23), the resem- Tithonian (Arkell and others, 1957, p. L323).
blance of Buchia piochii (Gabb) to species near the The Kimmeridgian age for Kossmatia given bj*
top of the Jurassic in the Boreal region (Pavlow, 1907, Arkell is based on his studies of ammonites from $.
p. 82, 83), and the absence of Buchia mosquensis (von thick and apparently comfortable sequence exposed or
Buch) and B. rugosa (Fischer). The absence of the the shore of Kawhia Harbour in New Zealand (Flem-
last two species in California seems particularly sig- ing, 1960, p. 264-268; Fleming and Kear, 1960, p. 17-
nificant because they are common elsewhere in North 45; Stevens, 1965, p. 22-32, 132-135). At this place
America in beds of middle Kimmeridgian to middle Kossmatia occurs above the ammonites Idoceras, Sub-
Tithonian ages (Imlay, 1955, p. 74, 75, 85; 1959, p. neumayria, and Epicephalites of early Kimmeridgiar
157) and are common in Russia in the Volgian zones age and mostly below the ammonite Aulacosphinctoides
of Siibplanites sokolovi to Dorsoplanites panderi inclu- of late Kimmeridgian to middle Tithonian age. It
occurs also within the lower part of the local range
sive (Gerasimov and Mikhailov, 1967, p. 9, 19, 20).
of Aulacosphinctoides. Its age, therefore, at Kawhk,
This range is equated by the Russian paleontologists
Harbour is definitely late Kimmeridgian and, on the
just quoted with the southern English zones of Siib- basis of stratigraphic position, is partly middle Kim-
planites spp. to Zaraiskites albani inclusive (Arkell, meridgian.
1956, p. 10), which confirms an earlier statement by The upper 4,000-5,000 feet of the Buchia piochii
Spath (1936, p. 166, 167). zone is definitely middle to late Tithonian in age as
The presence of Durangites, if verified, would be shown by the stratigraphic position between occur-
particularly useful for an age determination, as the rences of Kossmatia below and Siibsteueroceras above
genus is known elsewhere near the top of the Jurassic and by the presence of the ammonites Parodontoceras
in Mexico (Burckhardt, 1912, p. 143, 205; Imlay, and Spiticeras. Of these, Parodontoceras (Mesozoic loc.
1939, p. 22, 23, 46-49) and in Cuba (Imlay, 1942, p. 1084), found several thousand feet below the top of
1433, 1436, 1452, pi. 3, figs. 5-7). In Mexico it occurs the zone, is excellent evidence for an age not older
commonly in association with Kossmatia, Micracan- than late middle Tithonian, and Spiticeras (Mesozoic
thoceras, and Hildoglochiceras just below beds con- loc, 1085), found a few hundred feet below the top of
taining Siibsteueroceras. In California Durangites was the zone, is evidence of an age not older than late
recorded by Anderson (1945, p. 1001) from CAS loc. Tithonian. Also, the presence of an ammonite re-
29694, which is 600 feet north of Hull's gate in sec. 35, sembling Groebericeras (Mesozoic loc. M2024), found
T. 25 N., R. 7 W., Paskenta quadrangle, and, there- about 2,100 feet below the top of the zone, favors an
fore, at about the same stratigraphic position as two age not older than late Tithonian because that genusB12 JURASSIC AND CRETACEOUS BUCHIA ZONES IN CALIFORNIA AND OREGON
lias been found only in beds of Berriasian age in table 3 opposite p. 34) and Argentina (Lesnza, 1945,
Argentina (Leanza, 1945, p. 82). p. 91, 92).
Only part of the Buchia piochii zone of California, Additional evidence for a Late Jurassic age consists
as defined herein, is equivalent to beds in western Brit- of the close resemblance of the species of Substeueroce-
ish Columbia and Arctic Canada that supposedly are ras and Parodontoceras in California to species of those
characterized by B. piochii (Gabb) (Jeletzky, 1965, genera in Mexico or Argentina. Thus, Siibsteueroceras
fig. 2 opposite p. 2). Exact equivalence seems unlikely stantoni Anderson (1945, p. 982, pi. 11, figs. 3, 4, pi. 15,
because the specimens of Buchia piochii (Gabb) from fig. 3) is similar to 8. siibqimdratum Imlay (1939, p.
California, including the type specimen, show scarcely 49, pi. 15, figs. 8, 12-15) from Mexico. Another species
any resemblance to the varieties assigned to that spe- of Substeueroceras, erroneously assigned to Berriasella
cies by Jeletzky (1965, pi. 1, figs. 3-6, 9). Furthermore,storrsi (Stanton) by Anderson (1945, p. 980, pi. 7, fig.
the specimens of Buchia from the lower part of the 1) closely resembles S. kellumi Imlay (1939, p. 50, pi.
B. piochii zone in California, described by Anderson 14, figs. 1-4) from Mexico and S. koeneni (Steuer)
(1945, p. 965-967, 973) under the names B. sollasi (1897, p. 171, pi. 17, figs. 1-5) from Soutl America.
(Pavlow), B. sp. A, B. aff. B. mosquensis (von Buch), In addition, Parodontoceras reedi (Anderson) (1945,
and B, elderensis (Anderson), all show considerable p. 978, pl.6, fig. 10, pi. 7, fig. 3) resembles eome speci-
resemblance to Buchia cf. B. blanfordiana (Stoliczka) mens of Parodontoceras from Mexico described as Ber-
riasella cf. B. calistoides (Behrendsen) by Burckhardt
of Jeletzky (1965, pi. 2, figs. 3, 4, 6, pi. 3, figs. 4-8),
which in western British Columbia occurs at the top of (1906, pi. 19, fig. 9; 1912, pi. 39, fig. 7). It also shows
the Jurassic sequence beneath a disconformity. This considerable resemblance to the finer variants of Paro-
comparison indicates that the lower part of the B. dontoceras calistoides (Behrendsen) from Argentina
piochii zone in California is equivalent to the B. cf. (Steuer, 1897, pi. 17, figs. 13-16; Leanza, 1945, pi. 5,
B. blanfordiana zone of western British Columbia and figs. 5, 6) and could fall within the range of variation
that the upper part of the Buchia piochii zone in Cali- of that species.
fornia may be represented in western British Columbia The Buchia aff. B. okensis zone has not yet been
by the disconformity below the basal Cretaceous zone recognized in southwestern Oregon. Its absence may be
of Buchia okensis as suggested by Jeletzky (1965, p. due to either a disconformity or a lack of detailed col-
17, 18). These correlations, if valid, explain why spe- lecting. Likewise, in western British Columbia, the
cimens resembling the holotype of B. piochii (Gabb) zone has not been recognized and probably is repre-
have not been illustrated from Canada and why the- sented by the disconformity beneath the B. okensis
various varieties of B. piochii described by Jeletzky zone (Jeletzky, 1965, figs. 1 and 2 opposite p. 2, p.
have not been found in California. 17). The beds in California that contain Buchia aff.
TITHONIAN AMMONITES FROM THE BUCHIA
B. okensis (Pavlow) are not equivalent to the B. oken-
AFF. B. OKENSIS ZONE sis zone in western British Columbia (Jeleftzky, 1965,
The beds in California that contain Buchia aff. B p. 20-26, fig. 1 opposite p. 2) or in northern Alaska
okensis (Pavlow) are considered to be of latest Jurassic (Imlay, 1961, p. 5, 6) because they lack the extremely
(late Tithonian) age because they contain the ammo- coarse ribbed variant of B. okensis (Pavlow) that oc-
nites Sufosteueroceras, Parodontoceras, Blanfordiceras,- curs in the other areas (Jeletzky, 1965, pi. 4, figs. 1,
Proniceras, and Spiticeras (Spiticeras) and are stra- 19, 20, pi. 5, fig. 7, pi. 6, figs. 1, 2, 4-6, pi. 7, fig. 3;
tigraphically just beneath a sequence characterized by Imlay, 1961, pi. 7, figs. 5, 9, 12, 17-20).
the pelecypod Buchia. uncitoides (Pavlow) and the
ammonite Spiticeras (Negreliceras}. The presence of CRETACEOUS AMMONITES
of these ammonites is excellent evidence for a Late BERRIASIAN AMMONITES FROM THE BUCHIA UNCITOIDES ZONE
Jurassic age because Spiticeras and Blmifordiceras have
not been found in beds older than late Tithonian The Buchia uncitoides zone in California is consid-
(Djanelidze, 1922, p. 29, 36), Proniceras is character- ered to be mainly of Berriasian age as shown by its
istic of the upper Tithonian (Djanelidze, 1922, p. 48, stratigraphic position directly above beds containing
52), Parodontoceras in Mexico (Imlay, 1939, table 3 the latest Tithonian ammonites Substeuerocera-s, Paro-
opposite p. 24; 1942, p. 1433, 1434) and Argentina (Le- d&nfoceras, and Proniceras and by the presence of
anza, 1945, p. 91, 92) occurs only in beds of middle to Spiticeras (Negreliceras} and S. (/Spiticeras) through-
late Tithonian age, and Substeueroc&ras is characteris- out the lower two-thirds of the zone. Of these ammo-
tic of the topmost Jurassic beds in Mexico (Imlay, 1939, nites, the subgenus Negreliceras is characteristic of theAMMONITES FROM THE BUCHIA ZONES B13
Berriasian, is represented by only one species from the abundance of the ammonite Spiticeras (Negreliceras),
upper Tithonian, and is unknown from the Valanginian and by its stratigraphic position directly on beds of
(Djanelidze, 1922, p. 48, 49, 51). The subgenus probable latest Jurassic age. Presumably the lower part
/Spiticeras ranges from the top of the Tithonian through of the B. uncitoides zone in California is equivalent
the Berriasian but no higher (Djanelidze, 1922, p. 51). to the B. okensis zone of British Columbia. An alter-
On the basis of ammonites, therefore, most of ih&Biichia nate explanation would be that the BucJiia okensis zone
uncitoides zone in California cannot be younger than in British Columbia is actually of Late Jurassic age
Berriasian and is unlikely to be as old as Tithonian. The and equivalent to the beds in California that contain
upper third of the B. uncitoides zone, however, has not BucJiia aft'. B. okensis (Pavlow). This possibility, how-
furnished ammonites and could be younger than ever, seems unlikely because in British Columbia B.
Berriasian. okensis and B. uncitoides are associated throughout
The beds in Oregon that contain Buchia- uncitoides their range, whereas in California B. aff. B. okensis
are similarly dated as Berriasian because of the presence (Pavlow) is associated with B. terebratuloides (Lahu-
of /Spiticeras (Negrelicera-s}, 8. (Spiticeras), 8. (Kili- sen) but not with B. uncitoides (Pavlow). Also, th?,
anicemsl.), and Neocosm-oceras, a genus known mainly BucJiia okensis zone in British Columbia contains r,n
from the Berriasian (Mazenot, 1939, p. 179,182; Wright extremely coarse ribbed variant of B. okensis that do^s
in Arkell and others, 1957, p. L358). The stratigraphic not occur in the B. aff. B. okensis zone in California.
position of these ammonites within the BucJim unci- In summation, the Buchia uncitoides zone in Cali-
taides zone in Oregon is not known. fornia and Oregon contains ammonites of Berriasim
The BucJiia uncitoides zone is widespread in north- age. It is correlated with beds in British Columbia that
western California and in southwestern Oregon. In contain both B. okensis (Pavlow) and B. uncitoides
California it directly overlies the B. aft1. B. okensis (Pavlow) as well as ammonites of Berriasian age. In
zone. In Oregon, by contrast, the B. uncitoides zone both California and British Columbia the upper third
rests directly either on beds containing Buchia piochii of the B. uncitoides zone has not furnished ammonites
(Gabb) or on basement rocks. BucJiia uncitoides (Pav- and could be as young as Valanginian.
low) is the characteristic species in the type section Correlation of the BucJiia uncitoides zone in Cali-
of the Riddle Formation exposed on the South Umpqua fornia, Oregon, and British Columbia with the faunal
River near Days Creek. In that section the species zones in northern Eurasia presents difficulties as dis-
ranges upward about 1,000 feet from 20 feet above the cussed by Jeletzky (1965, p. 34, 35). Apparently in
basal conglomerate into the third conglomerate (Imlay northern Eurasia B. okensis (Pavlow) ranges fnna
and others, 1959, p. 2776). the base of the Cretaceous through the zone of Surites
The BucJiia uncitoides zone in California and Oregon spasskemis (Nikitin) (Sachs and others, 1963, p. 61-
may be correlated approximately with the Buchia un- 63, table 7) and is associated with B. uncitoides (Pav-
citoides zone in western British Columbia on the basis low) only at the top of its range (Suntes analogus
of having the same characteristic species of BucJiia and subzone). The species B. uncitoides (Pavlow) definitely
the same genera and subgenera of the ammonite Spiti- ranges upward through the zone of Tollia tolli (Sachs
ceras (Jeletzky, 1965, p. 27-35, fig. 1 opposite p. 2). and others, 1963, p. 65), which the Russian paleontolo-
That ammonite on the west coast of Vancouver Island gists consider of late Berriasian age, and Jeletzl'y
(Jeletzky, 1965, pi. 11, figs. 2, 3, 7, pi. 12, figs. 4, 5) (1965, p. 34) considered of early Valanginian age. Still
ranges from 21 to 128 feet above the base of the BucJiia higher in the lower or middle Valanginian zone of
uncitoides zone, which is about 270 feet thick, and PolyptycJiites micJialskii are recorded B. uncitoides
dates the lower part of the zone as not younger than (Pavlow and B. cf. B. uncitoides (Pavlow) (Sachs
Berriasian. Additional evidence for a Berriasian age and others, 1963, p. 67, 68, 70, table 7). These records
is furnished by a small fragment of an ammonite (Je- show that in northern Eurasia the species B. uncitoides,
letzky, 1965, pi. 11, figs. 4a-d) belonging probably to if correctly identified, ranges from about middle Ber-
ProtacantJwdiscus or Neocosmoceras that was collected riasian to middle Valanginian.
about 167 feet above the base of the zone. The upper This apparent discrepancy between the vertical range
103 feet of the zone has not furnished any ammonites of Buchia uncitoides in northern Eurasia as compared
and could be younger than Berriasian. with its range in western Canada has been noted by
The BucJiia uncitoides zone in California differs Jeletzky (1965, p. 34, 35), who suggested that in Eur-
markedly from that zone in British Columbia by a asia the Berriasian species of Buchia may have been
near absence of B. okensis (Pavlow), by a much greater reworked into beds of Valanginian age or that tie
365-128 O 70 3B14 JURASSIC AND CRETACEOUS BUCHIA ZONES IN CALIFORNIA AND OREGON
Berriasian and Valanginian species of Buchia may 172-174) and Tollia mutdbilis (Stanton) (Imlay, 1960,
have been concentrated within a single thin bed as a p. 174).
consequence of extremely slow deposition. It is possible, The Buchia paci-fica zone in California and Oregon
of course, that B. uncitoides in western North America may be correlated with the Buchia pacificc1. zone in
actually ranges into the Valanginian or that it has a western British Columbia on the basis of having the
slightly different range than in Eurasia. Accurate cor- same species of Buchia, of having the same strati-
relations and age determinations of the Buchia unci- graphic position relative to older species of Buchia,
toides zone in western North America must await the and of also containing Tollia mutdbilis (Str.nton) in
discovery of well-preserved ammonites in the upper the upper part of the zone. This species ir western
part of the zone. British Columbia was obtained only in tin Bridge
VALANGINIAN AMMONITES FROM THE BUCHIA PACIFICA
River area and was identified by Jeletzky (1964a, pi.
ZONE 6, figs. 1, 8, 9; 1965, p. 47, 53, pi. 18, figs. 1, 6, 7) as
The age of the Buchia pacifica zone in California on Dichotomites cf. D. giganteus (Imlay), a species which
the basis of ammonites is probably entirely early to was originally described from California as Neocraspe-
middle Valanginian. Its lower part, about 150 feet dites giganteus Imlay (1960, p. 204, pi. 32, figs. 1-6).
above its base, has furnished the ammonite Thurman- Examination of plaster casts of the ammorites from
niceras, whose presence suggests an age not older than the Bridge River area show that they differ markedly
Valanginian (Busnardo, LeHegerat and Magne, 1965, from N. giganteus Imlay found in California. They
p. 27, 32). Its middle part has furnished species of have an oblique instead of a vertical umbilical wall;
Thurtnanniceras and Kilianella that could be of early a gently rounded instead of an abrupt umbilical edge;
Valanginian age but suggest a middle Valanginian age sharp, narrow primary ribs instead of broad indistinct
because the species present resemble species of middle primary ribs; and less flattened flanks. Furthermore,
Valanginian age known elsewhere (Imlay, 1960, p. one specimen (Jeletzky, 1964a, pi. 6, fig. 9b) bears a
172). Its upper part is definitely Valanginian, as shown conspicuous constriction at a size much larger than in
by the presence of SarasineUa, and is not younger than any genus of the subfamily Polyptychitinae, which in-
middle Valanginian, as shown by the presence of Tollia. cludes both Dichotomies and N eocraspedites (Wright
That genus in Russia ranges from the upper part of in Arkell and others, 1957, p. L348). Evidently the
the zone of Surites spasskensis (middle Berriasian) ammonites from the Bridge River area do not belong
into the zone of Temnoptychites hoplitoides (early to the same genus or subfamily as N. giganteus Imlay.
Valanginian) (Sachs and others, 1963, p. 68, tables 7, In contrast the three ammonites from tr.e Bridge
8; Sachs and Shulgina, 1964, table opposite p. 10). A River area, British Columbia, illustrated as Dichoto-
mites cf. D. giganteus (Imlay) by Jeletzky (1965, pi.
middle Valanginian age for T. mutdbilis (Stanton) is
16, figs. 1, 6, 7), agree very well in umbilical shape,
supported, however, by the resemblance to T. paucico-
whorl shape, sharp primary ribbing, fine dense secon-
stata (Donovan) (1953, p. 110, pi. 23, figs, la, b),
dary ribbing, and presence of constrictions with Dichot-
which occurs in East Greenland in association with omites tehaniaensis Anderson (1938, p. 158, pi. 28, fig.
the middle Valanginian ammonites Polyptychites and 2, pi. 30, fig. 6), which Imlay (1960, p. 201, pi. 28, figs.
Euryptychites. A middle Valanginian age is supported, 18-22) considers to be a finely ribbed variant of T.
also, by the stratigraphic position of the B. pacifica mutdbilis (Stanton). Likewise, the specimens from
zone below beds that have furnished ammonites of northeast British Columbia illustrated as Dichotomizes
late Valanginian age. cf. D. giganteus (Imlay) by Jeletzky (1964b, pi. 12,
The Buchia pacifica zone in southwestern Oregon is figs. 11-13) are similar to T. mutdbilis tehaniaensis
represented by the typical Buchia species at many (Anderson). They have finer and denser secordary ribs
localities from Riddle westward to the Pacific coast, than those on the holotype illustrated by Anderson
but the stratigraphic position of the zone relative to (1938, pi. 28, fig. 2; Imlay, 1960, pi. 28, fig?. 18, 19)
the adjoining Buchia zones has not been studied. Fur- but are not much finer ribbed than one specimen illus-
thermore, some of the older collections, such as from trated by Imlay (I960, pi. 28, fig. 21).
Mesozoic loc. 2154 and 2155, were made over distances Considering the close resemblances of these speci-
of about a mile and probably include collections from mens from British Columbia to T. mutdbilis tehamaen-
more than one Buchia zone. The B. pacifica zone ap- sis (Anderson), it is rather strikng that the other
pears to be represented, however, by collections con- variants of T. mutdbilis have not been found in asso-
taining Sarasinella hyatti (Stanton) (Imlay, 1960, p. ciation as in California. This might be explained as aYou can also read
