Ammonites from the 'a Zones in - Northwestern California and Southwestern Oregon

 
Ammonites from the
       'a Zones in
Northwestern California
and Southwestern Oregon
GEOLOGICAL   SURVEY   PROFESSIONAL   PAPER 647-B
Ammonites 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 : 1970
UNITED 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___ --------------------------------------------------------
                                                                                                                     in
IV                                                        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_____________-_____________-__________ .___           20
JURASSIC (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.
                                                                                                                            Bl
B2                 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 perisphinctoid
AMMONITES 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 per
B4                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   2
B6   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.

                                                                                                                                                 W
B8                       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 genus
B12                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 the
AMMONITES 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   3
B14               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 a
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