The Albian-Cenomanian Boundary in Northern California
The Albian-Cenomanian boundary in northern California
Michael A. Murphy University of California, Davis, California 95616 Peter U. Rodda California Academy of Sciences, San Francisco, California 94118
ABSTRACT curred during the Albian–Cenomanian for Ͼ30 yr (Popenoe et al., 1960), and the transition and reflect rapid uplift and ero- area is famous for its ammonites. There is no internationally agreed-upon sion of a sedimentary, volcanic, and plu- The purpose of this paper is to review the stratotype for the Albian-Cenomanian tonic terrane to the north and east and, question of the definition of the Albian-Ce- (Lower Cretaceous–Upper Cretaceous) perhaps, accompanied by rapid sea-level nomanian boundary and proposed bound- boundary. Type sections in France for the changes. ary stratotypes, to describe the equivalent Albian and Cenomanian Stages are inade- Collation of the ammonite biostratigra- interval in the Cottonwood district, Califor- quate for this purpose. The proposed phy herein with previously established fo- nia, to collate the ammonite, foraminiferal, boundary stratotype sections in North Af- raminiferal and radiolarian biostratigra- and radiolarian biostratigraphies, and to dis- rica and Texas that were discussed in phies for the Dry Creek sequence suggests cuss the implications and potential of the Copenhagen at the 1983 Third Interna- that it is a prime Pacific-rim reference sec- California sequence to contribute to the un- tional Symposium on the Cretaceous Sys- tion for faunas in the Albian-Cenomanian derstanding of this boundary on a global tem (Birkelund et al., 1984) are inade- boundary interval and that previous corre- scale. quately documented, facies restricted, or lation of the uppermost Chickabally Mem- both. The widespread occurrence of the am- ber with the Cenomanian is incorrect, as REVIEW OF THE ALBIAN- monites Stoliczkaia and Mortoniceras in the Albian and Cenomanian stages are cur- CENOMANIAN BOUNDARY upper Albian and of Mantelliceras in the Ce- rently understood.1 This affects correlation nomanian classically bracket the boundary and changes the dating of some units in Cal- A review of the Albian-Cenomanian and must be used until the boundary is for- ifornia in the Franciscan Complex from Ce- boundary literature on a global scale leads mally defined. Recent work in North Africa nomanian to Albian. us to conclude that there is no ideal section (Robaszynski et al., 1993) promises an for an ammonite-based, boundary strato- Albian-Cenomanian boundary definition INTRODUCTION type because few places retain a record of based on lineages within these taxa. the Albian-Cenomanian boundary interval The ammonite-based Albian-Cenomani- The Cottonwood district in northern Cal- in superposition that is complete (in the an boundary in northern California is be- ifornia exposes a thick sequence of fossilif- sense of Sadler, 1981). Nevertheless, the tween the last occurrence of the typically Al- erous marine sedimentary rocks ranging in widespread occurrences of Stoliczkaia and bian genera Mortoniceras and Stoliczkaia age from Early Cretaceous–Late Creta- Mortoniceras in the upper Albian and of and the entry of mantelliceratine juveniles ceous (?Hauterivian–Late Turonian) (Mur- Mantelliceras in the lower Cenomanian clas- (probably Graysonites) associated with Ma- phy et al., 1964; Murphy et al., 1969). These sically bracket the boundary and the selec- riella. Pseudouhligella japonicum, heretofore strata and fossils have been the object of tion of a criterion within this interval would regarded as a Cenomanian indicator in Ja- study for more than a century, and the area be appropriate. Such a criterion for defining pan, Alaska, and California, occurs in Cal- has long been recognized as having the most the exact boundary, however, has been elu- ifornia in upper Albian and lower Cenoman- continuous and richly fossiliferous sequence sive, and the GSSP (global stratotype sec- ian faunas. of Lower Cretaceous strata in western tion and point) has yet to be chosen for the The boundary sequence in California is North America (Murphy, 1956; Matsumoto, base of the Cenomanian.2 This lack of def- best exposed along Dry Creek in northern 1960; Dailey, 1973; Pessagno, 1977). This se- inition results partly from taxonomic rea- Tehama County, where an angular relation- quence has served as the standard of refer- sons, but also from variations in preserva- ship within the Budden Canyon Formation, ence for the Pacific Coast of North America tion and biofacies and from provincial resulting from channel cutting on deep-sea differences (Kennedy, 1984, p. 149; Young, fans, separates upper Albian ammonite- 1986); however, the primary reason has bearing rocks of the Chickabally Member been our inability to discover a section that 1 from Lower Cenomanian ammonite-bear- A recommendation for establishing the stra- shows the position of an evolutionary event totype of the Albian-Cenomanian boundary at the ing rocks of the Bald Hills Member. Al- Mont Risou section in the Vocontienne region of of widespread application within the tradi- though angular relationships and coarse- France was made to the Subcommission on Cre- tional boundary interval. grained strata of the lower Bald Hills taceous Stratigraphy by the Cenomanian Working The traditional approach has been to Member are present in the boundary inter- Group (Tro¨ger, 1995, p. 148). This recommenda- search for a criterion among the ammonites, val, no known ammonite zone is missing. tion has yet to be ratified by the SCSA, the In- ternational Commission on Stratigraphy, or the These relationships are interpreted to mean International Union of Geological Sciences, that relatively continuous sedimentation oc- which is necessary before it is formally accepted. 2See footnote 1.
GSA Bulletin; February 1996; v. 108; no. 2; p. 235–250; 7 figures; 2 tables.
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but the vagaries of distribution and preser- izations of faunas rather than on definitions The difficulty in finding a suitable strato- vation of ammonite taxa have frustrated the of their boundaries (Magniez-Jannin and type for the Albian-Cenomanian boundary selection of an ammonite-based boundary Rat, 1980; Juignet, 1980). The current ap- is that the beds in the Albian–Cenomanian that is widely applicable in the interval be- proach for setting chronostratigraphic transition yield more or less provincial or tween the last Mortoniceras/Stoliczkaia and boundaries (McLaren, 1977; Murphy, 1977, facies-restricted faunas that are difficult to the first Mantelliceras. Changes in the plank- p. 214; 1994, p. 267; Salvador, 1994) stresses correlate. Moreover, peculiarities of preser- tonic microfossils do not occur close enough the definition of lower boundaries based on vation in different areas inhibit proper iden- to the change in the ammonite faunas to recognition of biologic events in the stratal tification. In Sarthe and in Britain, the low- preserve the traditional meanings of the record and has made most type areas un- est fauna agreed to be Cenomanian is stages (Robaszynski and Ame´dro 1986). For suitable as boundary stratotypes, because characterized as the Neostlingoceras carci- this reason no one, except perhaps Salaj the classical stages generally are separated tanense Zone, and faunas are preserved as (1980), has suggested abandoning the clas- from adjacent strata by breaks of various du- phosphatic replacements of moderate-sized sically defined boundaries, such as they are, rations. The type Albian in the Aube district specimens. In North Africa, the lowest Ce- in favor of ones defined by planktonic mi- is a composite of seven partially overlapping nomanian is characterized as the Hypotur- crofossils. Benthonic taxa, other than Inoc- sections that expose part of what is now in- rilites schneegansi Zone, and ammonites are eramus (Kauffman, 1977), generally are re- cluded in the Albian, but none of them in- preserved as pyritic internal molds of juve- garded as too facies dependent to use for cludes either the lower or upper boundary of niles. Apparently contemporaneous beds in chronostratigraphic interpretations (but see the stage as currently understood (Ame´dro, Texas yield Graysonites, but beds with Ple- Kauffmann, 1975, for a strongly dissenting 1992, p. 190–191). sioturrilites brazoensis lie below Graysonites view). In any case, no one has constructed a In the case of the base of the Cenoman- and above characteristic Albian strata with comprehensive biostratigraphic subdivision ian, the type sequence near Le Mans Mortoniceras (Young, 1986), and the faunas of the Albian-Cenomanian boundary inter- (Sarthe) rests unconformably on Jurassic are preserved as internal molds of mature val based on benthonic megafossils. rocks or on glauconitic sands correlated with specimens. Recent work in the central Tu- The English paleontologists Hancock, the upper Albian (Juignet, 1980, his Figs. 2 nisian Atlas Mountains (Robaszynski et al., Kennedy, and Wright and their continental and 3). The area is obviously not appropri- 1993, 1994) has documented a more com- colleagues Ame´dro, Juignet, and Robaszyn- ate for a boundary stratotype, although pletesuccessionacrosstheAlbian-Cenoman- ski have made considerable progress unrav- some upper Albian strata are present in this ian boundary with the presence of the clas- eling the stratigraphy of the Albian–Ceno- sequence. The exposures are inadequate sical ammonite faunas above and below (see manian type regions in France and the (Robaszynski, 1984), the early Cenomanian discussion of North Africa below), and this taxonomy of the ammonites. Work in North transgressive deposits of the southwestern section presently holds the greatest promise Africa by Robaszynski, Ame´dro, and their Paris Basin are not of the right facies, and as a stratotype, as it is both complete and colleagues is directed towards proposing a the ammonite sequence is not complete characterized by a phosphatic preservation stratotype in the area south of El Kef, Tu- enough to correlate these rocks directly with of the ammonites that permits comparison nisia (Robaszynski et al., 1993, 1994). This those in nearby North Africa and other with other areas. proposal may eventually be recognized as more distant regions (Hancock, 1984). This the best possibility for an internationally conclusion has been reinforced by recent THE COPENHAGEN agreed-upon boundary for the Lower Cre- work in North Africa (Robaszynski et al., RECOMMENDATIONS taceous-Upper Cretaceous (Albian-Ceno- 1993, his Fig. 26), which demonstrates that manian) boundary (see discussion under two zones of mantelliceratine ammonites in Kennedy (1984) reviewed the history of North Africa below). However, the lack of North Africa are missing at the base of the the Albian-Cenomanian boundary at the studies of variation and ontogeny, lamented Cenomanian in western Europe. Because of Copenhagen symposium and recommended by Matsumoto and Inoma (1975, p. 267) for these deficiencies, no decision has been that the appearance of either Hypoturrilites Stoliczkaia, and not remedied by subsequent made on an appropriate place to select a Dubourdieu or Neostlingoceras Klinger and work (Scholz, 1979), still hampers proper boundary stratotype in spite of extensive re- Kennedy be selected to define the base of identification of a wide range of taxa. Bio- view, especially before and during the Third the Cenomanian, and that the boundary stratigraphic discussions in the literature, International Symposium on the Cretaceous stratotype be located in the sequence at with notable exceptions (e.g., Ame´dro, System in Copenhagen in 1983, but also Djebel Fguira Salah near Pont du Fahs, Tu- 1992; Destombes, 1979), are based on the since that meeting (Matsumoto and Inoma, nisia. This recommendation was modified at identification of zones rather than on pre- 1975; Juignet, 1977; Kennedy and Hancock, this international symposium (Birkelund et sentation of the ranges of identified speci- 1977; Sissingh, 1978; Mancini, 1979; Birke- al., 1984), and two potential stratotypes, one mens in measured stratigraphic sections. lund et al., 1984; Hancock, 1984, 1991; in North Africa and one in Texas, both This general lack of raw data inhibits a Kennedy, 1984; Young, 1986). The conclu- based on ammonites, were recommended comprehensive biostratigraphic synthesis sion of the Copenhagen Symposium that for further investigation. Although forami- through the boundary interval. more work should be done on the ammonite niferal-based boundaries were discussed, no succession before making a decision (Birke- recommendation for further investigation THE TYPE AREAS lund et al., 1984) still stands, although some was suggested for this group (Birkelund et writers have apparently adopted the appear- al., 1984, p. 11). Like most stages, the Albian of the Aube ance of mantelliceratine ammonites as the The taxa discussed at the Copenhagen and Cenomanian of the Sarthe regions in base of the Cenomanian (Hancock, 1991; meeting as candidates for defining the France were based originally on character- Robaszynski et al., 1993). boundary and the suggested event are listed
236 Geological Society of America Bulletin, February 1996
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The section at Pont du Fahs can no doubt be observed in a single traverse, but the re- ported fossiliferous localities from the num- bered stratigraphic units are up to 0.5 km from one another (Solignac, 1927, p. 170). A perusal of Castany (1951), who worked in the same region, shows that the situation was still the same in 1951. The difficulty at Pont du Fahs has been partially ameliorated by Stranik et al. (1974) and Bellier (1985), who recollected the ammonites in this sec- tion in connection with foraminiferal stud- ies. The latter reported Pervinquieria inflata (ϭ Mortoniceras inflatum) and Mortoniceras condolianum from the upper Albian, and the former reported Sciponoceras baculoides in Table 1. These taxa and the two possible and Bellier (1985) have used the section and Mantelliceras aff. M. couloni from the stratotypes are discussed below. near the village of Pont du Fahs in Tunisia, Cenomanian. Neither pair of taxa comes A review of coccolithophore zonations a potential stratotype for the Tethyan re- from a stratigraphic level that elsewhere is at (Sissingh, 1977) shows that the only substan- gion, as a standard of reference for corre- the upper or lower limit of the stage. Sub- tive changes in this group pertinent to this lations based on foraminifera. They sup- sequent work by Salaj (1980, p. 69) on this discussion are either well down in the tra- ported their correlations with ammonite section improved the ammonite succession ditional Albian (base of the Eiffellithus tur- data from the area as cited in Solignac by adding Mantelliceras martimpreyi (ϭ M. riseiffeli Partial-Range Zone), or well up in (1927), Castany (1951), Jauzein (1967), and saxbii) above the occurrence of S. baculoides the Cenomanian (base of the Microrhabdu- Stranik et al. (1974), as well as from their and Stoliczkaia dispar var. africana 10 m be- lus decoratus Partial-Range Zone) and, own work. low. Most writers now agree that M. saxbii therefore, not of interest to the Albian-Ce- Solignac’s (1927) monograph on the ge- occurs above Hypoturrilites (e.g., Robaszyn- nomanian boundary problem. ology of northern Tunisia includes a de- ski et al., 1993, their Fig. 5). In terms of the scription of the area around Pont du Fahs. described ammonite sequence the northern North Africa According to Solignac (p. 172) and earlier Tunisian section still does not qualify as a conclusions by Pervinquie`re (1903, p. 72), site for the GSSP. The section at Pont du Previous to the work of Robaszynski et al. the Vraconian (upper Albian) there con- Fahs appears to have great potential, but the (1993), several workers (Salaj, 1973, 1980, tains a fauna of mixed, but predominantly data have not yet been collected that show 1984; Salaj and Bellier, 1978; Hancock, Cenomanian aspect. The text and the dia- the position of a biological event in the in- 1984; Kennedy 1984, 1986; Bellier, 1985) grams in Solignac (1927, p. 151–181) clearly terval between definitely Cenomanian and discussed a potential boundary stratotype in indicate that collections listed are from in- definitely Albian strata. the Tethyan province that may be a more tervals of strata of similar lithology that are Hancock (1984, p. 126) claimed that an widely applicable standard of reference. The lumped together as a single horizon (‘‘ni- area 50 km southwest of El Kef, western Tu- area along the Algeria-Tunisian border in veau’’). These data cannot, therefore, be nisia, is probably the best section. Salaj the vicinity of Ouenza, Algeria, one of the used for precise biostratigraphy even if the (1980) and Wonders (1980) described the sites mentioned, was described in great de- taxonomic nomenclature is modernized. In foraminiferal biostratigraphy of this area tail by Dubourdieu (1956). He stated, (1956, addition, there are indications of overlap of but without mentioning any ammonites. For p. 273), ‘‘The lower Cenomanian is devoid species that today are regarded as typically foraminifera-based biostratigraphy, good of organic remains in the region where the Albian or typically Cenomanian. For exam- sections across the boundary interval appear Vraconian [ϭ uppermost Albian of Western ple, at Ragoubet Lalla Manna the lowest to be at Oued Mennsia, to the north of Pont Europe] has been dated. The limit of the unit (no. 1) contains the typically Cenoman- du Fahs, Tunisia (Bellier 1985, p. 41) and at two substages can only be placed, therefore, ian ‘‘Acanthoceras martimpreyi’’ Coquand El Burrueco, Spain (Wonders, 1980, p. 16). with the aid of lithologic correlations, cor- (ϭ Mantelliceras saxbii according to Ken- Robaszynski et al., (1993) provided inte- relations facilitated by the existence of an nedy and Hancock, 1971, p. 437), and the grated biostratigraphic and sequence strat- episode of marly limestone deposition very overlying unit has yielded Mortoniceras in- igraphic interpretations for a section in the consistently present at the base of the Ce- flatum, a typically upper Albian species Kalaat Senan region in central Tunisia south nomanian...’’ (our translation). He esti- (Solignac, 1927, p. 178). This overlap is also of El Kef that appears to be the most com- mated (1956, p. 274) that the margin of error found in the Pont du Fahs section where ‘‘A. plete yet described, and may be a suitable could not exceed 20–30 m, which is only martimpreyi’’ appears in unit 2 with M. in- candidate for a boundary stratotype. Con- about 2% of the Albian–Cenomanian se- flatum and Stoliczkaia dispar. The latter two sequently, they have proposed that the KZ quence in the area. The interpretation of species are also reported from the overlying section near Kef el Azreg ‘‘would be an ex- this sequence evidently depends on litho- bed 3 (Solignac, 1927, p. 170). These appar- cellent choice for an Albian-Cenomanian logic correlation of the ‘‘lower Cenomani- ent discrepancies need to be resolved (see boundary stratotype within the Tethyan re- an’’ and not on direct superposition. Salaj also reviews by Hancock, 1984, p. 125; 1991, gion’’ (Robaszynski et al., 1993, P. 401). (1973, 1980, 1984), Salaj and Bellier (1978), p. 272). They show a succession of ammonite zones
Geological Society of America Bulletin, February 1996 237
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that includes members of the traditional up- range of the genus Plesioturrilites in Texas these rocks is generally similar throughout, per Albian Stoliczkaia dispar Zone, includ- and northern Mexico is expressly given as although the internal stratigraphy is com- ing Stoliczkaia dispar and Mariella bergeri, uppermost Albian to lower Cenomanian but plex (Murphy et al., 1969; Bailey and Jones, followed by Mantelliceras and Hypoturrilites extending above the range of Graysonites 1973). Rapid lateral and vertical facies a short distance above. They conclude that (Young, 1986, his Fig. 1). (An apparent er- changes and lenticularity characterize the the sequence of ammonites found in the ror in this figure has the upper ranges of units, and megafossils are rare in most ex- lowest of four beds of phosphatic nodules mortoniceratine genera, including Drakeo- posures. In some places, particularly in the represent the evolutionary first occurrences ceras, ending below the uppermost Albian drainage basin of Cottonwood Creek at the of both Mantelliceras and Hypoturrilites. Drakeoceras drakei Zone.) Renz (1968, northern end of the outcrop belt, ammo- Hopefully, they will soon document the pa- p. 91) has, in fact, described a species of nites are common, well preserved, and occur leontologic succession there and present a Plesioturrilites from the type section of the with a variety of microfossils. Persistent col- more detailed discussion of the evolutionary Vraconian (ϭ upper Albian, Stoliczkaia dis- lecting over a period of years (in the case of sequence. This proposal has great merit and par Zone) in Switzerland. ammonites) or taking especially large sam- appears to be the best candidate so far pro- The Plesioturrilites brazoensis Zone has ples (in the case of microfossils) will yield posed for the Albian-Cenomanian boundary not been identified outside of Texas nor significant faunas. The section exposed GSSP. does it occur with more widely distributed along Dry Creek (Fig. 1) is of particular sig- taxa. Young and Powell (1978, p. 2) empha- nificance because of the excellent, easily ac- Texas sized the restriction of this fauna to local cessible exposures and the co-occurrence of shelf carbonate facies. It cannot at present ammonites, foraminifera, and radiolaria The second recommendation of the be used as a global standard of reference. (Jones et al., 1978; Marianos and Zingula, Copenhagen symposium was for further If, however, the base of the Graysonites 1966; Murphy et al., 1969; Dailey, 1973; Pes- study of the base of the Graysonites adkinsi adkinsi Zone is to be considered as the stan- sagno, 1976, 1977). Zone in Texas as a potential stratotype. dard for the base of the Cenomanian, there Our earlier work (Murphy et al., 1969; Graysonites is probably the most widespread is currently more potential for correlation to Murphy and Rodda, 1960) and the present of all the taxa present in the lowest interval other parts of the world. In Texas, Grayso- work suggest that the prolonged period of of the Cenomanian and may represent the nites appears to range down into the upper basin development along the Early Creta- same taxon as represented by the ‘‘Subman- part of the P. brazoensis Zone (Young, 1986, ceous coast of California was periodically telliceras’’ juveniles found in the marls at the his Fig. 1). Mancini’s (1979) treatment of punctuated by accelerated tectonic and vol- base of the Cenomanian of North Africa the same stratigraphic interval also provides canic activity, especially during the Barre- (Hancock, 1991, p. 271). However, Young only zonal range data and does not resolve mian, early Aptian, and late Albian–early (1986, p. 1217; see also Young and Powell, these problems. Cenomanian. During these times, the de- 1978; Young, 1979) has recommended that The main frustration with the Texas sec- velopment of local discontinuities and the base of the Plesioturrilites brazoensis tion is that no actual stratigraphic range deposition of coarse sands and conglom- Zone be regarded as the base of the Ceno- data concerning critical ammonites, such erate were interspersed with the more qui- manian in Texas. as the species of Graysonites or its sup- escent deposition of fine-grained, deep- The P. brazoensis Zone, marked by a posed progenitors, has been given. Until this water sequences. ‘‘...sudden flood of Plesioturrilites brazoen- appears, the Texas section cannot be During the late Albian–early Cenomani- sis ...’’(Young and Powell, 1978, p. 4), is evaluated. an, coarse sediment from the north and east above the highest mortoniceratine and be- was delivered to the fans and fan channels at low the Graysonites adkinsi Zone. The total THE ALBIAN-CENOMANIAN the base of the submarine slope. Erosion to stratigraphic range of P. brazoensis, given BOUNDARY IN NORTHERN the east cannibalized penecontemporane- only in terms of zones, spans all the Ceno- CALIFORNIA ous sediments and fossils of late Albian age, manian except the uppermost zone (Young as well as earlier Cretaceous deposits. Some and Powell, 1978, their Fig. 5). However, Rocks of the Great Valley Sequence of of these have been found reworked in con- Young (1979, p. 15) and Young and Powell Jurassic and Cretaceous ages crop out along glomerates and pebbly mudstones (Murphy (1978, p. 4) implied that P. brazoensis also the west side of the Sacramento Valley from and Rodda, 1960). Subsidence rates were so can occur below the P. brazoensis Zone, pre- Redding to Vacaville in the foothills of the high in the areas now exposed that signifi- sumably in the uppermost Albian. The total northern Coast Ranges. The lithology of cant biostratigraphic gaps did not develop.
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Figure 1. Location map, columnar section, and range chart, Dry Creek Section, Tehama County, California. The approximate position of the Dry Creek section in the Chickabally Mountain quadrangle is shown on the small scale map along highway 36. The columnar section is a synthesis of three partial sections numbered I to III. Numbers preceeded by ‘‘D’’ to the right of the columnar section are approximate positions of Dailey’s (1973) samples; M. and Z. 25 is approximate position of locality 25 of Marianos and Zingula (1966); NSF 934 is position of Pessagno’s (1977) highest locality in this section. Ammonite occurrences indicated by range bars and ticks; arrowhead indicates specimens were recovered from strata lower than those shown in the columnar section. Question marks indicate identifications based on fragmental material. S-478 indicates the position of a semipermanent marker placed in sandstone bed 1. Numbers 1–7 on columnar section indicate sandstone beds shown in the photograph, Figure 3. See legend for lithologic symbols.
238 Geological Society of America Bulletin, February 1996
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The age of the initial cutting and filling of the bed and along the banks of Dry Creek, the eastern hills of the Coast Ranges, those the channels does, however, vary discernibly which is followed closely by California State of the Dry Creek section are disturbed by along the present strike of the outcrop. On Highway 36 (Fig. 1). The creek exposes the many faults of unknown displacement that Huling Creek and the North Fork of Cot- Chickabally, Bald Hills, and Gas Point are difficult or impossible to map because of tonwood Creek, it is late Albian; on Roaring Members of the Budden Canyon Formation the great thickness of similar rocks and the River it is later than early Cenomanian (Murphy et al., 1964). The Albian-Cenoman- limited exposures away from the major (Matsumoto, 1959b, p. 66); on Dry Creek it ian boundary in California is best illustrated streams (Murphy et al., 1969). Also, some is within the Albian-Cenomanian boundary by the 200 m of strata that straddle the con- parts of the stream section are covered by interval (Fig. 2). The Dry Creek section is tact between the Chickabally and Bald Hills alluvium or only ephemerally exposed. For the most important section across the Members. This section has been referred to these reasons, we present the section in boundary because it contains both upper Al- previously by Anderson (1958), Peterson, three segments that are internally intact and bian and lower Cenomanian ammonites and (1963), Marianos and Zingula (1966), Pes- virtually completely exposed, either in the microfossils (at least in the Albian part), sagno (1976, 1977), Dailey (1973), and creek bed or in the adjacent bluffs (Figs. 1 whereas the other sections are not as con- Jones et al. (1978). Figure 1 illustrates the and 3). tinuously fossiliferous. part of the Dry Creek section pertinent to The three segments represent only the the Albian-Cenomanian boundary and inte- upper part of the upper Albian and the The Dry Creek Section grates the microfossil biostratigraphies of lower part of the lower Cenomanian, but Marianos and Zingula (1966), Dailey they contain Ͼ200 m of strata and several Jones et al. (1978) have estimated that (1973), and Pessagno (1977) with the angular discordances in the basal part of the more than 3500 m of Albian–Turonian present study. Bald Hills Member. The discordances are strata are exposed almost continuously in As is characteristic of the rocks exposed in interpreted as local, deep-sea fan channels
Figure 2. Generalized north-south transect along strike of strata bracketing the Albian/Cenomanian boundary, Shasta and Tehama Middle Fork of Cottonwood ؍ Roaring River, MF ؍ North Fork of Cottonwood Creek, RR ؍ Huling Creek, NF ؍ Counties, California. HC Dry Creek. Conglomerate units in the Bald Hills Member are shown in approximate positions with exaggerated thicknesses ؍ Creek, DC and stylized shapes. Only the uppermost occurrences of Ticinella primula and Beudanticeras haydeni are shown. All records of Graysonites are shown. No fossils have been recovered from the Middle Fork of Cottonwood Creek in this interval. Positions of Roaring River localities are reconstructed from Shell Oil Company field maps made by Mahlon Kirk for ammonites, and from maps and columnar sections in Dailey (1973) for foraminifers. It is not possible to show either a time or lithologic reference datum whose exact position is known in all of the sections. The Albian-Cenomanian boundary has no particular relationship to the lowest conglomerate in a section. The lower conglomerates are Albian age at Huling Creek/North Fork sections, lower Cenomanian on Roaring River, and in an interval of uncertainty between the two stages on Dry Creek. Angular relationships at the base of the lowest conglomerate of the Bald Hills Member were observed on Huling Creek and on the Middle Fork of Cottonwood Creek, and within the lower part of the Bald Hills Member on Dry Creek.
240 Geological Society of America Bulletin, February 1996
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Figure 3. View of the Dry Creek section II from California State Highway 36. The numbered, persistent sandstone beds that cross the outcrop correspond to the numbered beds in Figure 1. S 478 indicates the position of a numbered stake placed as a marker in bed number 1. Labeled conglomerates are lower beds of the Bald Hills Member.
that represent an insignificant amount of Section III again follows the north side of 5, 32 cm thick, laminated with parting line- time in the Dry Creek section. They are the stream bed from just below the basal ation internally and flute casts; no. 6, 51 cm probably contemporaneous with an uncon- conglomerate of the Bald Hills Member to a thick, laminated with parting lineation in- formity to the east under the Neogene and point several hundred meters east. Sections ternally; and no. 7, two closely spaced sand- Holocene cover of the Sacramento Valley, I and II expose all but 10 m of section near stone beds aggregating 56 cm thick, the which is inferred from evidence north of Dry the top of the Chickabally Member. lower bed massive with weak sole marks, Creek of (1) reworking at about this level on The ammonites found in section II are load casts, and a rippled top and the top bed the North Fork of Cottonwood Creek (Mur- scattered individuals that occur usually in laminated. All the sandstone beds are inter- phy and Rodda, 1960); (2) the persistence orange-weathering, purplish gray limestone preted as turbidites. throughout the Ono quadrangle of upper lenses and nodules in massive or faintly lam- Outcrops are poor near the top of Section Albian–Cenomanian polymictic conglomer- inated siltstone, similar to the occurrences II because of soil creep. This condition is ates containing clasts of volcanic and plu- of most fossils in the region. They are not partly remedied in the stream bed exposures tonic rocks, chert, nodular limestone, and abundant, but the wide expanse of the out- at the base of section III, but a small interval sandstone (Murphy et al., 1969); and (3) crop, especially in section II, has provided remains unexposed near the top of the thickness variation in the upper Chickabally an unusual opportunity to evaluate some el- Chickabally Member in both areas. Member between Huling Creek and the ements of the uppermost Albian fauna. The Sections I and II are mostly, if not en- North Fork of Cottonwood Creek (Fig. 2). sequence of occurrence of the ammonites in tirely, late Albian in age based on the co- Section I (Fig. 1, map) follows the north section II is determined by their relationship occurrence of Mortoniceras and Stoliczkaia side of the stream bed along the base of the to several persistent sandstone beds that tra- (Fig. 1) that are part of the richer upper high stream cut to the point where a persis- verse the cut. The sandstone beds are num- Albian fauna from the northern part of the tent sandstone bed (sandstone 1 in Fig. 3) bered in Figures 1 and 3. They show the Ono quadrangle, partially described by that can be traced across the face of the cut following characteristics: no. 1, 20 cm thick, Anderson (1958) and Murphy and Rodda intersects the stream bed. Sandstone 1 is the massive with flute casts; no. 2, 20 cm thick, (1959, 1960). The age-significant ammonites base of section II, which traverses the face of laminated without substratal marks; no. 3, that we have identified in the Dry Creek II the cut, extends up into the gully on the east 41 cm thick, laminated with parting linea- section are Mortoniceras (Durnovarites) cf. side of the cut, and ends just below the basal tion internally and flute casts; no. 4, 91 cm M. (D.) perinflatum, Stoliczkaia notha, Beu- conglomerate of the Bald Hills Member. thick, massive without substratal marks; no. danticeras haydeni, and Mesopuzosia colu-
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saense. The genera Mortoniceras and Beu- pebbly mudstones, and the polymictic con- worked fossils have been found in the con- danticeras have never been recorded glomerates. In addition, both the pebbly glomerates on Dry Creek, but on the North anywhere above the upper Albian, and mudstones and the nodular siltstones are cut Fork of Cottonwood Creek fossils of Barre- Stoliczkaia notha is also from upper Albian by the polymictic conglomerates. The earli- mian–late Albian age have been found in strata. The upper3mofsection II have not est channels were cut into the nodular silt- clasts in the lowest conglomerate of the Bald yielded specifically identifiable ammonites. stones and were filled by pebbly mudstone; Hills Member (Murphy and Rodda, 1960). Section III contains the lowest units of the later channels, which cut both units, were On the North Fork of Cottonwood Creek, Bald Hills Member and begins in the bed of filled by polymictic conglomerate (Figs. 4 the lowest coarse-grained interval of the Dry Creek just below where the basal con- and 5). The repetition of these rock types in Bald Hills Member is bracketed by upper glomeratic beds intersect the stream bed. the lower part of the Bald Hills Member Albian ammonites of the Stoliczkaia dispar The basal bed is a 3-m-thick, lenticular peb- suggests an episodic cause, perhaps related Zone. The analogous interval on Dry Creek bly mudstone. Above the basal bed is an in- to the volcanic and tectonic activity along is bracketed by Stoliczkaia dispar Zone am- tact framework, polymictic cobble conglom- the Nevadan orogenic belt to the east or to monites below and mantelliceratine ammo- erate containing lenses of pebbles and local the back-and-forth migration of the distrib- nites above (Fig. 2). areas of imbricated clasts. Clasts of nodular utary fan channels. limestone similar to those in the underlying The channels and the channel fills appear Ammonites in the Dry Creek Section Chickabally Member and porphyritic vol- to have developed in a deep-water setting on canic rocks are prominent constituents of the slope or at its base. The background Several ammonite species in the Dry the unit, but metamorphic, granitic, and sedimentation of pelagic siltstone, with Creek section are Tethyan species, but the chert clasts are also present. The rocks in the planktonic foraminifers, radiolarians, and presence of some of these in California has 1.5 m of section above the conglomerate nektonic ammonites, is interbedded with been masked in the past by a provincial no- were covered by alluvium during our work, channel-fill deposits through the lower part menclature. These include Stoliczkaia notha but are inferred to be mudstone and silt- of the Bald Hills Member. The pebbly mud- (Fig. 6A), Anagaudryceras buddha (Fig. 6I), stone because of their recessive weathering stones, sandstones, and polymictic conglom- species of Mariella (Figs. 6B, 6C, 6E, 6F, and profile. The triad of lithologies—siltstone, erates that fill the channels contain frag- 6H), Tetragonites rectangularis (Fig. 6D), pebbly mudstone, conglomerate—is more mented marine mollusks with thick shells, and Mortoniceras (Durnovarites) cf. M. (D). or less repeated up through the well-ex- such as rudist and arcoid bivalves, derived perinflatum (Fig. 5B). Others are wide- posed lower part of the Bald Hills Member from shallow-water environments. Sand- spread in the Pacific region but also may on Dry Creek (Figs. 4B and 5C) and also on stones and pebbly mudstones display fea- have a few questionable citations in the Te- the Middle Fork of Cottonwood Creek tures characteristic of turbidite and grain- thyan regions. They include Graysonites about 3.5 km north where it is thicker and flow deposits, such as flute casts (Fig. 4), flat wooldridgei (Fig. 4d), Pseudouhligella japoni- also well exposed (Fig. 4A). Two packages tops and irregular bases, ripple lamination cum (Figs. 4G–4I) and P. dawsoni (Mat- of lithic wackes interbedded with mostly in the upper few centimeters, and unori- sumoto, 1959a, his Pl. 14–16). Some are ap- massive siltstones, 8.3 m thick and 12.6 m ented clasts. parently indigenous species, found only in thick, respectively, lie above the conglomer- These features in combination suggest California, such as Beudanticeras haydeni atic units (Fig. 5C). The sandstones are len- that the basin continuously received sedi- (Murphy and Rodda, 1960, their Pl. 105, ticular in outcrop (Fig. 5C) and have flat ments from the bordering eastern and figs. 1 and 2) and Mesopuzosia colusaense tops and irregular and sole-marked bases northern highlands, but that the locus of (Murphy and Rodda, 1960, their Pl. 102; (Fig. 4C). Some of the beds are graded, but sedimentation shifted from place to place Rodda and Murphy, 1991, their Figs. 7–10). most are laminated or internally massive. and was interrupted locally at times of pe- This mixture of forms makes this section They are interpreted as turbidites that ac- riodic uplift along the Nevadan trend. Be- valuable for correlating the Pacific region cumulated in and around channels on a sub- cause the amount of sediment was so great sections with those of Europe and North marine fan at the base of the slope. and the subsidence so rapid, no particular Africa. The ranges and levels of occur- Several outcrops show angular relation- section lacks a significant interval, despite rence are plotted on Figure 1 and listed in ships between the nodular siltstones, the episodic erosion and deposition. No re- Table 2. Most collecting localities provide
ä
Figure 4. (A) Contact of the Upper Chickabally Member and the Bald Hills Member on the Middle Fork of Cottonwood Creek. Thin-bedded siltstones of the Upper Chickabally Member are truncated at the base of the Bald Hills Member by pebbly mudstone (wedge-shaped in this view) and both are truncated by polymictic conglomerate. These three lithologies are repeated several times in the lower part of the Bald Hills Member. (B) Same triad of rock types in the Bald Hills Member on Dry Creek, showing truncation of thinly laminated beds by pebbly mudstone followed by polymictic conglomerate. Hammer handle rests on pebbly mudstone, hammer head on conglomerate. (C) Flute casts on the base of a sandstone bed in the lower Bald Hills Member in the Dry Creek section III. (D) Graysonites wooldridgei Young; Dry Creek section III; 80 m above the base of the Bald Hills Member; California Academy of Sciences Geology catalog number (CASG) 65033.01 (؋0.95). (E and F) Graysonites wooldridgei?; juvenile specimen from Dry Creek section III; 31 m above the base of the Bald Hills Member; CASG 65032.01; (E) outer whorl (؋0.95); (F) inner whorl of same specimen (؋1.9). (G–I) Pseudouhligella japonicum (Yabe); Dry Creek section III; 31 m above the base of the Bald Hills Member; (G) CASG 65032.02 (؋0.95); (H–I) CASG 65032.03 .(؋0.95)
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Figure 5. (A) Beudanticeras haydeni (Gabb);DryCreeksectionII;5mabovesand- stone bed 5; California Academy of Sciences Geology catalog number (CASG) 65042.01 .؋0.95). (B) Mortoniceras (Durnovarites) cf) M. (D.) perinflatum (Spath); Dry Creek sec- tion II; 6.5 m above sandstone bed 4; CASG -؋0.95). (C) Third triad of silt) 65001.01 stone, pebbly mudstone, and conglomerate, Bald Hills Member, Dry Creek section III. Lower resistant bed extending diagonally across middle of photo is lenticular sand- stone and conglomerate above pebbly mud- stone. In upper part of the section, lenticu- lar laminated lithic wackes are interbedded with siltstone.
only single specimens; population samples are extremely rare. As a consequence our taxonomic philosophy is necessarily mor- photypic and virtually typologic. Only a few specimens of Stoliczkaia have been recovered from northern California; one of the specimens from the Dry Creek section (Dry Creek II), identified as Stolic- zkaia notha (Fig. 6A), is a crushed shell with coarse ribbing and a moderately large um- bilicus for the species. It most closely resem- bles the specimen from Hungary figured by Scholz (1979, p. 15, his Fig. 3) and identified as var. notha. The second (Fig. 6G) is a frag- ment of a relatively small, coarsely ribbed living chamber. If Scholz’s (1979) conclusion that all described Tethyan ‘‘species’’ belong to a single, highly variable species is ac- cepted, then our specimens could be iden- tified as S. dispar. Our reservations in ac- cepting Scholz’s conclusions are because he did not present his data concerning the vari- ation in the umbilical diameter in terms of fossil populations from particular horizons, but rather lumped all data together in his Figure 22. Although the work appears sound, it is not usable for precise biostratig- raphy or taxonomy because it cannot be in- dependently analyzed. J.-L. Latil, (1993, written commun.), who has studied Stolicz- kaia from southeastern France, preferred to identify this specimen as S. notha, which he restricted to his lower dispar Subzone of the dispar Zone. We agree with this identifica- tion. Most information in the literature in- dicates that S. dispar is confined to the upper Albian, although one report from North Af- rica suggested that it occurs with mantelli- ceratine ammonites at Pont du Fahs (Soli- gnac, 1927, p. 170). This would put its upper limit in the lower Cenomanian. However, both Ame´dro and Latil (1993, personal
244 Geological Society of America Bulletin, February 1996
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communications) regarded this report as an This means, firstly, that Pseudouhligella cality plots, even on the very small scale error, and Latil (1993, written commun.) japonicum ranges down into the upper Al- maps they used, are the best means of re- stated, ‘‘...the typical dispar is very rare bian in California. We have collected this construction of the sampled horizons. We everywhere and restricted to the middle part species 150 m and 200 m below the top of can be sure from these plots that all of their of the Dispar Zone.’’ It appears, therefore, the Upper Chickabally Member, well within samples from below the lowest conglomer- that the use of S. dispar and/or S. notha as the upper Albian part of the Dry Creek sec- ate bed (Dailey, 1973; locality D3502 is the Albian indicators is valid. tion. Jones et al. (1978, p. 7) also recorded highest of these) were taken below our sand- Beudanticeras is known only from the Al- P. japonicum from an estimated 75 m below stone bed 4 in section Dry Creek II (Figs. 1, bian (Kennedy and Hancock, 1978, p. 8, 9). the top of the Chickabally Member on Dry 3, and 7). As Figure 7 clearly shows, if Dai- Breistroffer (1947, p. 54) remarked that Beu- Creek, and they used this occurrence as the ley’s identifications are accepted (however, danticeras is one of the genera that com- base of the Cenomanian, although by our see discussion of nomenclature in Appen- pletely disappears before the upper Albian interpretation this horizon is within the up- dix), (1) the uppermost occurrences of Pla- dispar Zone in Europe. In the Dry Creek per Albian. This suggests that correlations nomalina buxtorfi, Hedbergella planispira, section, however, B. haydeni (Fig. 5A) oc- around the Pacific rim using P. japonicum as Ticinella primula, and T. roberti and (2) the curs 5 m above sandstone marker bed 5. a marker for the Cenomanian need to be lowest occurrences of Praeglobotruncana This occurrence is above the biostratigraph- reevaluated (Matsumoto, 1959b, p. 6; Jones, delrioensis, Rotalipora evoluta, and R. green- ic ranges of the upper Albian species Mor- 1967, p. 4; Jeletzky, 1977, p. 116). Secondly, hornensis all occur in the upper Albian in the toniceras cf. M. perinflatum and Stoliczkaia Beudanticeras haydeni ranges higher than S. Dry Creek section, because they lie below notha (Fig. 1) in the same section. We con- notha in the Dry Creek section. This may the last occurrence of Mortoniceras, Beudan- clude, therefore, that most, if not all, of the expand the range of Beudanticeras, in Cali- ticeras haydeni, and Stoliczkaia notha.Ofthe Dry Creek II section is late Albian in age. fornia at least, into the upper part of the ranges plotted diagrammatically in Figure 7, Anagaudryceras buddha, on the other Stoliczkaia dispar Zone. only those of T. primula and H. planispira hand, is reported to range from the Upper are considered representative of their true Foraminifera in the Dry Creek Section biostratigraphic ranges in northern Califor- Albian into the Turonian (Kennedy and nia, because these taxa are reported as Klinger, 1979, p. 152). A. buddha (Fig. 6I) Two studies deal with the foraminiferal abundant at most sample sites throughout occurs with mantelliceratine ammonites in faunas of the Dry Creek Section in the their observed taxon range zones in the Dry the Dry Creek III section and also occurs Albian-Cenomanian boundary interval (Ma- Creek section (Dailey, 1973, his Fig. 10). within the range of Mortoniceras in Dry rianos and Zingula, 1966; Dailey, 1973) with Since Dailey’s 1973 paper, a great deal of Creek section II. generally similar results. Sampling for both taxonomic work has been done on forami- There seems to be a consensus that man- studies covered the upper Chickabally niferal assemblages around the Albian-Ce- telliceratine ammonites characterize the Ce- Member, but Dailey (1973) did not sample nomanian boundary (Masters, 1977, Bellier, nomanian (Hancock, 1991; Mancini, 1979; in the Bald Hills Member. Unpublished 1985; Groupe T.E.F.P., 1979; Salaj, 1980; Young, 1986). If we accept that position un- notes of the Humble Oil and Refining Com- Wonders, 1980; Caron, 1985; Sliter, 1989). til the boundary question is settled by a sub- pany field party indicate that Marianos and Two papers, Pessagno (1977) and Masters commission of the International Commis- Zingula (1966) had samples from the Bald (1977), deal directly with the Dry Creek sec- sion on Stratigraphy of the International Hills interval, but they report no recovery tion, and several papers deal with the taxa Union of Geological Sciences, the lowest from these strata. that have been identified from it (see Ap- beds that we can definitely date as Ceno- The sampling programs indicate that Ro- pendix). It seems to us from a review of this manian occur 31 m above the base of section talipora and Praeglobotruncana appear in literature that no foraminifera would con- III (Fig. 1). At that level, a juvenile mantel- the upper 300 m (approximately) of the up- stitute a good criterion for defining the liceratine ammonite that we identify as per Chickabally Member, and Planomalina Albian-Cenomanian boundary within the Graysonites wooldridgei? (Figs. 4E and 4F) buxtorfi is also present in this interval. approximate interval accepted by most strat- occurs with abundant Pseudouhligella ja- Ticinella primula makes its last appearance igraphers, although several taxa may be used ponicum (Figs. 4G–4I). (The morphologic in the same interval (Dailey, 1973, his to help identify that boundary (Robaszynski similarity among juveniles of Stoliczkaia and Fig. 10). et al., 1993) after it has been defined. Mantelliceratinae makes small specimens Two problems prevent us from accurately impossible to identify accurately and em- locating the sample sites of Marianos and Radiolaria in the Dry Creek Section phasizes the need for ontogenetic studies Zingula (1966) and Dailey (1973), although through this interval.) A second horizon at they present their data both in measured Pessagno has described the radiolarian 80 m has also yielded mantelliceratine am- sections and on maps: (1) a fault near the faunas of the Dry Creek section in a series of monites that we identify as Graysonites wool- base of the Bald Hills Member is not men- papers (see Pessagno, 1977, for references). dridgei Young (1958) (Fig. 4D). They occur tioned in either paper; and (2) the lowest He dated his upper four samples NSF 934– with Mariella morphotypes (Figs. 6B, 6C, observed outcrop of a conglomerate bed, 937 as Cenomanian in age based on the fo- 6E, 6F, and 6H), Sciponoceras sp., and which is used as a marker datum for the mea- ram work of Marianos and Zingula (1966) Pseudouhligella japonicum. surements reported in both papers, is de- and Dailey (1973) and identifications of Based on these considerations, the base of pendent on seasonal and yearly changes in ammonites by David Jones of the U.S. the Cenomanian on Dry Creek lies in the the alluvial cover in the stream bed. Some Geological Survey. Faced with apparently interval between the highest Beudanticeras years it is one bed and other years a lower conflicting evidence from the ammonite and the lowest Graysonites. bed is exposed. For these reasons, their lo- identifications of Pseudouhligella japonicum,
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then believed to be a Cenomanian species, vides an important link to regions around source area to the east and northeast, or eu- below Mortoniceras (Matsumoto, 1959b, the Pacific rim. static lowering of sea level, or both. These p. 6; Jones, 1967, p. 4), he considered that Ammonite studies have not produced a large, rapid movements, however, produced the weight of the evidence favored an early criterion that would establish precise inter- no significant biostratigraphic gap in the Cenomanian age (Pessagno, 1977, p. 16–19). continental correlations, although this may Albian-Cenomanian boundary interval at It is now certain that P. japonicum occurs be possible in central Tunisia when the am- Dry Creek. well down in the upper Albian and that his monite succession there is documented (Ro- highest locality, NSF 934, is far below the baszynski et al., 1993). Several lineages are ACKNOWLEDGMENTS top of our Dry Creek II section (Fig. 1). For known to cross the boundary interval: Ma- these reasons, especially the last, the age as- riella, Pseudouhligella, Stoliczkaia-Mantelli- We are indebted to Clarence Schuchman, signments of his localities NSF 934–937 to ceratinae, and Sciponoceras. These should Philip A. Summers, and J. I. Valenzuela- the Cenomanian must be changed to late be added to the list of potential candidates Rı´os for assistance in the field and labora- Albian. This change has implications for the listed in Table 1. tory. Their continuing contribution to this correlations that he made between the The Pacific realm ammonite species, project has been invaluable. We thank Great Valley Sequence and the Franciscan Pseudouhligella japonicum, ranges from up- Lester Shoup Jr., Larry Lalaguna, Andrew Complex, especially near the Geysers in per Albian to Cenomanian. In the lower part Noble, Marie Hoff, and John Kite for pro- Sonoma County, California. The cherts ex- of its range it occurs with other typical Al- viding access to ranch properties. Rich Mooi posed along Big Sulphur Creek in Sonoma bian ammonite taxa, Mortoniceras, Stolicz- and Jean Demouthe helped prepare Table County and many of the species reported kaia, Pseudouhligella dawsoni; in the upper 2. The manuscript benefited from reviews by from them also must now be assigned a late part, with mantelliceratine ammonites and J. Mount, F. Ame´dro, J.-L. Latil, W. Sliter, Albian age. Mariella. The biostratigraphic range of Beu- S. Kidwell, and W. Cobban. F. Ame´dro and danticeras haydeni is in the Stoliczkaia dispar J.-L. Latil also gave us the benefit of their CONCLUSIONS Zone and slightly above in the Dry Creek II extensive knowledge of European and section. North African faunas and advised us both in The potential stratotypes for the base of Collation of ammonite and foraminiferal the field and museum in France and Cali- the Cenomanian Stage listed by the Third studies in the Dry Creek section and review fornia. This work was supported by National International Symposium on the Cretaceous of the foraminiferal literature show that all Science Foundation grant EAR-9117992 System held in Copenhagen in 1983 (Birke- of Marianos and Zingula’s (1966) and Dai- and by the University of California, River- lund et al., 1984; Table 2) still have not pro- ley’s (1973) localities in the Chickabally side, Intramural Research Fund and the In- duced the data to qualify them for the Member of the Budden Canyon Formation House Research Fund of the California GSSP, and the Albian-Cenomanian bound- are late Albian age. Academy of Sciences. ary remains undefined. Nevertheless, there Studies of radiolarians from the Dry appears to be consensus that faunas with Creek section lack detailed sampling APPENDIX Stoliczkaia, Beudanticeras, and Mortoniceras through the boundary interval, we are not A sampling of the published work on forami- are Albian, and mantelliceratine ammonites yet able to evaluate their potential. It is clear nifera has led us to conclude that disagreement are Cenomanian. These conclusions are that Pessagno’s localities NSF 934–937 are concerning taxonomy and stratigraphic ranges of supported by the KZ section in Tunisia in the upper Albian. This requires revision mid-Cretaceous taxa have not been resolved. Sig- (Robaszynski et al., 1993). A main unsolved of the dating of rocks in the Franciscan nificantforaminiferalspecies-ranktaxainthestrat- igraphic interval discussed in this paper include taxonomic problem is how to identify juve- Complex along Big Sulphur Creek to late Rotalipora brotzeni (Sigal), R. evoluta Sigal, R. niles in the transition from Stoliczkaia to Albian. Studies of other microfossil groups greenhornensis (Morrow), R. appenninica (Renz), Mantelliceratinae. are not available in the pertinent parts of the R. tehamaensis Marianos and Zingula, R. balar- The Dry Creek section in Tehama Dry Creek section. naensis Gandolfi, R. globotruncanoides Sigal, Prae- County, California contains a sequence of The Albian-Cenomanian boundary in globotruncana delrioensis (Plummer), Ticinella roberti (Gandolfi), and Planomalina buxtorfi ammonites, foraminifera, and radiolaria northern California is in a thick sequence of (Gandolfi). Below we summarize differing opin- that is as complete as any in the world, ex- pelagic siltstones and fine-grained sand- ions concerning the identity and stratigraphic cept perhaps the KZ section in Tunisia. stones interbedded with pebbly mudstones ranges of these taxa. In addition, Figure 7 illus- The Dry Creek section is an important and polymictic conglomerates that are in- trates the published disagreements in the taxon- omy and stratigraphic ranges of the Albian–Ce- confirmation of the sequence across the terpreted as having accumulated as part of a nomanian foraminifera in the Dry Creek section. Albian-Cenomanian boundary in other re- deep-sea fan. The coarse-grained deposits Rotalipora evoluta and R. brotzeni were consid- gions of the Tethyan province, and it pro- reflect accelerated tectonic activity in the ered distinct species by Salaj and Samuel (1966,
ä
Figure 6. (A) Stoliczkaia notha (Seeley); Dry Creek section II; 1.1 m above sandstone bed 4; California Academy of Sciences Geology catalog number (CASG) 65049.01. (B, C, E, F, and H) Mariella spp.; Dry Creek section III; 80 m above the base of the Bald Hills Member; (B) CASG 65033.02; (C) CASG 65033.03; (E) CASG 65033.04; (F) CASG 65033.05; (H) CASG 65033.06. (D) Tetragonites rectangularis (Wiedmann); Dry Creek section II; 5 m above sandstone bed 3; CASG 65023.01. (G) Stoliczkaia sp. (d’Orbigny); Dry Creek section II; 1.8 m above sandstone bed 1; CASG 65002.01. (I) Anagaudryceras buddha (Forbes); Dry Creek section II; 17.1 m above sandstone bed 1; CASG .All figures ؋0.95 .65035.01
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et al. (1993, p. 406, their Fig. 6) identified R. te- hamaensis and showed its range as lowest Cenomanian. A reviewer of this paper suggested that the specimens identified by Marianos and Zingula as R. appenninica are R. balernaensis. Rotalipora bal- ernaensis was synonymized with R. appenninica by Lehmann (1966, p. 160), Masters (1977, p. 501), Wonders (1978, p. 130), and Caron (1985, p. 67). However, Caron (in Robaszynski et al., 1993) ap- parently changed her mind and showed R. baler- naensis as a species with three morphs. Salaj and Samuel (1966, p. 178) and Sliter (1989, p. 5) con- sidered R. balernaensis a distinct species, but Salaj and Samuel gave its age as lower to middle Ce- nomanian, while Sliter indicated a range from lat- est Albian to earliest Cenomanian. Robaszynski et al. (1993, p. 406, their Fig. 6) showed ranges for the three morphs of R. balernaensis: upper Albi- an–lower Cenomanian, upper Albian–middle Ce- nomanian, and lower Cenomanian. Praeglobotruncana delrioensis was identified from the Dry Creek section by Marianos and Zin- gula (1966). Dailey (1973, p. 83) and Masters (1977, p. 487) agreed, but Pessagno (1977, p. 17) included P. delrioensis with P. stephani. Ticinella roberti Figure 7. Ranges of foraminifera in the Dry Creek section from Marianos and Zingula of Marianos and Zingula is mostly T. primula according to Dailey (1973, (1966, lined bars) and Dailey (1973, solid bars). Numbers 25 and 26 approximately rep- p. 86), but Masters (1977, p. 529) agreed with resent horizons of Marianos and Zingula; D numbers indicate relative positions of Dailey’s Marianos and Zingula (1966). samples; NSF numbers are from Pessagno (1977). Marianos and Zingula locality 25 (1966, Planomalina buxtorfi ranges from the upper Al- p. 334) and Dailey locality D 3499 (1973, p. 93) are both reported to be 125 ft (38 m) below bian into the lower Cenomanian, according to Loeblich and Tappan (1961, p. 269), Salaj and the lowest conglomerate in the Bald Hills Member. (a) Ticinella roberti, identified by Mari- Samuel (1966, their table 21), Postuma (1971, mostly T. primula, Dailey, 1973, p. 86); (b) p. 105–110), Sigal (1977, p. 105), and Bellier ؍) (anos and Zingula and Masters (1977 Praeglobotruncana stephani and P. delrioensis of Marianos and Zingula and of Masters (1978, p. 28; 1985 p. 48, 55). However, Robaszyn- ,P. stephani of Pessagno, 1977, p. 17); (c) Rotalipora tehamaensis Marianos and ski (1984), Caron (1985, p. 36), and Sliter (1989 ؍) (1977) P. buxtorfi Zingula ( R. greenhornenis of Douglas, 1970, p. 24; Masters, 1977, p. 510 ( R. evoluta of p. 5) indicated that is restricted to the .upper Albian ؍ ؍ Pessagno, 1977, p. 17); (d) Rotalipora appenninica of Marianos and Zingula and of Masters R. evoluta of Dailey, 1973, p. 84; Pessagno, 1977, p. 17). For further ؍) (p. 498 ,1977) discussion of taxonomic problems illustrated here see Appendix. REFERENCES CITED Ame´dro, F., 1992, L’Albien du Bassin Anglo-Parisien: Ammo- nites, zonation phyle´tique, se´quences: Bulletin Centres Re- cherches Exploration-Production Elf Aquitaine, v. 16, p. 187–233. p. 28), Bellier (1978, p. 28), and Caron (1985, her manian Mantelliceras martimpreyi (ammonite) Anderson, F. M., 1958, Upper Cretaceous of the Pacific Coast: Fig. 6). On the other hand, Loeblich and Tappan Zone. Sigal apparently assumed that this ammo- Geological Society of America Memoir 71, 378 p., 75 pl. (1961, p. 299), Pessagno (1967, p. 291), Postuma nite zone marked the base of the Cenomanian, Bailey, E. H., and Jones, D. L., 1973, Preliminary lithologic map Colyear Springs quadrangle, California: U.S. Geological (1971, p. 80), and Wonders (1978, p 133) synon- but it is actually above the lowest Cenomanian Survey Miscellaneous Field Studies Map MF-517. ymized R. brotzeni with R. greenhornensis and ei- (Kennedy and Hancock, 1971; Robaszynski, 1984; Bellier, J. P., 1978, Zones de foraminife`res planctonique du Ceno- manien tunisien: Ge´ologie Me´diterrane´enne, v. 5, no. 1, ther treated R. evoluta as a distinct species or syn- Robaszynski et al., 1993). Caron (1985, her Fig. 6) p. 27–29. onymized it with R. appenninica (Masters, 1977). shows the base of the R. brotzeni Zone coincident Bellier, J. P., 1985, Foraminife`res planctonique du Cre´tace´e de Marianos and Zingula (1966, their Fig. 3) identi- with the base of the Cenomanian, but elsewhere Tunisie septentrionale: Utilisation stratigraphique des formes trochospirales de l’Albien au Maastrichtien: Me´m- fied R. appenninica from the Dry Creek section. in her paper (her Fig. 3) correlates the base of the oires de la Socie´te´Ge´ologique de France, n.s., v. 146, Dailey (1973, p. 84) changed their identification same zone with the upper part of the Stoliczkaia p. 1–70, pl. 1–8. to R. evoluta. Masters (1977, p. 492), in a com- dispar Zone of the upper Albian. Porthault (1978, Birkelund, T., Hancock, J. M., Hart, M. B., Rawson, P. F., Rem- ane, J., Robaszynski, F., Schmid, F., and Surlyk, F., 1984, prehensive review of Cretaceous planktonic fo- p. 190) also recorded R. brotzeni from the top of Cretaceous stage boundaries—Proposals: Bulletin of the Ge- raminifera, agreed with the original identification the S. dispar ammonite Zone. ological Society of Denmark, v. 33, p. 3–20. Breistroffer, M., 1947, Suˆr les zones d’ammonites dans l’Albien de by Marianos and Zingula (1966). Robaszynski et Marianos and Zingula (1966, p. 339) described France et d’Angleterre: Grenoble, Travaux du Laboratoire al. (1993, p. 406, their Fig. 6) treated R. evoluta a new species, Rotalipora tehamaensis, from the Ge´ologique, v. 26, p. 17–104. and R. appenninica as valid species and recog- upper Albian (their locality 26). Douglas (1969, Caron, M., 1985, Cretaceous planktic foraminifera, in Bolli, H. M., Saunders, J. B., and Perch-Nielsen, K., eds., Plankton stra- nized four separate morphotypes of R. appen- p. 174; 1970, p. 24) synonymized R. tehamaensis tigraphy: Cambridge, Cambridge University Press, p. 17–86. ninica. Three of them range from the upper Al- with R. greenhornensis, and this conclusion was Castany, G., 1951, E´tude ge´ologique de l’Atlas Tunisien oriental: Tunis, Annales des Mines et de Ge´ologie, v. 8, p. 1–632. bian through part or all of the lower Cenomanian. supported by Dailey (1973, p. 85) and Masters Dailey, D. H., 1973, Early Cretaceous foraminifera from the Bud- Robaszynski et al. (1993, p. 406, their Fig. 6) (1977, p. 510). Virtually all authors have given the den Canyon Formation, northwestern Sacramento Valley, gave the range of R. greenhornensis in terms of two range of R. greenhornensis as mid-Cenomanian California: University of California Publications in the Ge- ological Sciences, v. 106, p. 1–111, 19 pl. morphs, which are lower Cenomanian and lower and higher. Pessagno (1977, p. 17), however, syn- Destombes, P., 1979, Les ammonites de l’Albien infe´rieur et Cenomanian–middle Cenomanian. They also onymized R. tehamaensis with R. evoluta, and he moyen dans les stratotypes de l’Albien: Gisements, pale´on- tologie, biozonation, in Rat, P., and nine others, eds., changed the identification of Robaszynski et al. considered this occurrence as lower Cenomanian. L’Albien de L’Aube: Paris, C.N.R.S. collection, Les strato- (1979) of R. brotzeni to R. globotruncanoides (Ro- Locality 26 of Marianos and Zingula, from types franc¸ais, 5, p. 51–193. baszynski et al., 1993, p. 401). whence R. tehamaensis is described, is within the Douglas, R. G., 1969, Upper Cretaceous planktonic foraminifera in northern California, Part 1—Systematics: Micropaleon- Sigal (1977, p. 105) correlated the base of the R. range of the ammonites Stoliczkaia and Mor- tology, v. 15, p. 151–209. brotzeni Zone with the base of the lower Ceno- toniceras and is, thus, Albian in age. Robaszynski Douglas, R. G., 1970, Planktonic foraminifera described from the
Geological Society of America Bulletin, February 1996 249
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