Foraminiferal Stages Research Articles

Benthic foraminiferal biotic events related to the Paleocene–Eocene Thermal Maximum along the California margin

Abstract The faunal expression of the Paleocene-Eocene Thermal Maximum (PETM) is well documented in deep-sea sediments. However, few studies have examined continental margin sections, especially active margins. The Moreno and Lodo formations, Central California, were deposited along the eastern margin of a north-south trending forearc basin on the convergent margin of California during the Cretaceous through Late Cenozoic. The Tumey Gulch section which includes the Moreno and Lodo formations, is 80 m thick, contains the Paleocene-Eocene boundary and Carbon Isotope Excursion (CIE), and was deposited at abyssal to lower bathyal depths along an active continental margin. Benthic foraminiferal assemblages from this section record faunal changes related to the PETM and a younger hyperthermal, ETM3 which include a disruption of the gradual shallowing of water depths and fluctuation of the CCD. Associated with the onset of the hyperthermals in this section is a red clay-siltstone layer (low calcium carbonate content) and an increase in smoothly finished dissolution resistant agglutinated benthic foraminiferal species which corresponds with a rapid shoaling of the CCD. The subsequent overcompensation is identified by a rapid change to shallower benthic biofacies faunas, increased sediment rate, current activity, and terrestrial organic matter which is associated with increased weathering. Further analysis of the foraminiferal faunas identified the benthic foraminiferal extinction event (BEE), deep water agglutinated faunal acmes, and fluctuations in the calcareous foraminiferal assemblages which indicate changes in the paleoenvironmental conditions (e.g., dissolved oxygen, sedimentation rates and current activity, and the influx of organic carbon) during the PETM and ETM3. The Ynezian, Bulitian, and Penutian California benthic foraminiferal stages are recognized in the Tumey Gulch section as well as the benthic foraminiferal extinction event (BEE) which occurs at the onset of the PETM and is distinguished by the last appearance of Paleocene species and the first appearance of many Eocene species. Agglutinated foraminiferal species dominate the late Paleocene through early Eocene part of the section indicating deposition occurred at abyssal depths and/or below the CCD and that the environment was oligotrophic with moderate to low organic flux. The Glomospira acme zone is recognized at the base of the CIE and just above the top of red clay-siltstone layer and suggests increased terrestrial organic matter and elevated sedimentation rates. The abundance of calcareous species, specifically Bulimina alazanensis, followed by the appearance of opportunistic taxa (Tappanina and Quadrimorphina) in the PETM interval indicates deposition within the lower bathyal biofacies and/or a drop in the depth of the CCD. Eocene species characteristic of the Survivor faunal group (Anomalinoides, Bulimina, Cibicidoides, and Pleurostomella) appear above this event. Foraminiferal assemblages dominated by agglutinated foraminifera appear in sediments overlying the PETM interval and indicate deposition occurred at abyssal depths and below the CCD. Calcareous foraminiferal assemblages appear higher in the section as water depths decrease. The presence of a second red clay-siltstone layer associated with a second isotope excursion and faunal changes in the upper part of the section indicate the presence of another hyperthermal, ETM3.

Neogene molluscan stages of the West Coast of North America

Neogene marine sediments of the West Coast of North America were deposited in a series of widely spaced basins that extended geographically from the western and northern Gulf of Alaska (60°N) to southern California (33°N). Rich molluscan faunas occur extensively throughout these deposits and form the basis for biostratigraphic schemes that are useful for correlating within and between individual basins. Early biostratigraphic work was concerned with faunas from particular horizons and with the stratigraphic range of diverse taxa, such as Pecten and Turritella, without reference to other fossil groups. Succeeding work increasingly dealt with the relationships of molluscan zones to benthic and, later, planktonic foraminiferal stages. In recent years the age limits of Neogene molluscan stages have become better documented by reference to planktonic microfossils from dated DSDP cores and onshore faunas. Neogene molluscan faunas from California, the Pacific Northwest states (Oregon and Washington), and southern Alaska have been treated separately due to differences in faunal composition and geographic isolation. As a result, a different biostratigraphic sequence has been described for each region. Pacific Northwest stages have been formally named and defined, and their names are also used informally for Alaskan faunas. California Neogene stages were proposed early in this century, are in need of redescription, and their usage is informal. Precise correlations between the three regional sequences have not yet been achieved, due to the low number of co-occurring species and the general lack of planktonic microfossils in these largely shallow-water faunas. The objectives of ongoing research include: fuller documentation of the faunas of California and Pacific Northwest stages; formal description of California stages; improved correlation between regional stage sequences; refinement of age estimates for stage boundaries; and, establishment of Neogene stages for Alaskan faunas.

Geochronology Bearing on Age of Monterey Formation, California: ABSTRACT

The name Monterey Formation or Monterey Shale has been applied to lithologically similar pelitic marine rocks of Miocene age exposed in the coastal regions of California. These rocks, characterized by unusually high proportions of silica, have been variously termed diatomite, porcelanite, porcelaeous shale and mudstone, chert, and cherty shale. The type area for the Monterey Formation was designated near Monterey, California. Although the Monterey Formation in general contains numerous ash, tuff, and bentonite beds, only a few of these volcanic units have been dated. It has been necessary to make use of both the isotopically dated horizons and Kleinpell's Miocene benthonic foraminiferal stages to construct a time-stratigraphic framework for the Monterey Formation at different locations. Ages for the various stage and zone boundaries, based on published and unpublished data, are as follows: Repettian-Stratotype B. oblique (Delmontian), ca. 5 m.y.B.P.; Stratotype B. oblique-Mohnian, ca. 7 m.y.B.P.; Mohnian-Luisian, ca. 12 m.y.B.P.; Luisian-Relizian, 14.0 to 14.9 m.y.B.P.; Relizian-Saucesian, 15.7 m.y.B.P. At the type area, an ash from the Canyon del Rey Diatomite Member, the uppermost member of the Monterey Formation, was dated at 11.3 ± 0.9 m.y. (F-T on zircon). Coupled with a Luisian age for the oldest strata, the type Monterey Formation spans, at most, the time interval from 15 to 10 m.y.B.P. In contrast, the Monterey Shale in the Palos Verde Hills encompasses the time interval from 15 to 5 m.y.B.P. based on isotopic data from the Altamira Shale, Valmonte Diatomite, and Malaga Mudstone Members, which contain foraminiferal assemblages characteristic of the Relizian, Luisian, and Mohnian Stages, and the B. oblique zone (Delmontian). At other localities where biostratigraphic and isotopic data are available, the rocks termed Monterey are not exact time equivalents of the type foramation, an observation made earlier by both Kleinpell and Bramlette. End_of_Article - Last_Page 966------------

Planktonic Calibration of Provincial Miocene Stages of California: ABSTRACT

Age assignments and correlations of Miocene marine strata in California are usually made with reference to a sequence of benthic foraminiferal stages. During the past decade refined calcareous and siliceous planktonic microfossil biochronologies have been developed that provide a means for calibrating the California provincial stages to international standards while also testing the chronostratigraphic reliability of correlations derived by equating stage diagnostic benthic foraminifer assemblages in different areas. Diatoms are particularly useful for dating the upper, silica-rich part of the Monterey Formation whereas calcareous nannofossils are useful for dating the lower part of the Monterey Formation and older Miocene units. Data from type sections show that the base of the Saucesian Stage is near the Oligocene-Miocene boundary of international usage, the base of the Relizian Stage falls at the base or in the lower part of the early Miocene Helicosphaera ampliaperta Zone (nannofossil), and the Luisian Stage essentially coincides with the middle Miocene Sphenolithus heteromorphus Zone (nannofossil) and the Denticulopsis lauta Zone to Subzone a of the Denticulopsis hustedtii--D. lauta Zone (diatom). The top of the type Mohnian Stage is within the latest Miocene to early Pliocene Nitzschia reinholdii Zone (diatom), whereas the type section of the Delmontian Stage is within Subzones b and c of the middle Miocene Denticulopsis hustedtii-D. lauta Zone. The type Delmontian is therefore equivalent to the lower Mo nian of most California sections. Compilation of data from throughout California indicates some overlap in time of benthic foraminifer assemblages diagnostic of the Zemorrian and Saucesian Stages and of the Relizian and Luisian Stages. The transition from Luisian to Mohnian benthic foraminifer assemblages, however, consistently occurs near the top of the Sphenolithus heteromorphus Zone and within Subzone a of the Denticulopsis hustedtii-D. lauta Zone. End_of_Article - Last_Page 974------------

Biostratigraphy of Monterey Formation, Palos Verde Hills, Southern California: ABSTRACT

Three members comprise the Monterey Formation in the Palos Verdes Hills: the Altamira Shale, The Valmonte Diatomite, and the Malaga Mudstone. Following the diatom zonation of Barron (in press), the middle to upper Altamira Shale ranges from Subzone b of the Denticulopsis lauta Zone through Subzone b of the Denticulopsis hustedtii-D. lauta Zone (14.5 to 12 m.y.B.P.), the Valmonte Diatomite ranges from Subzone b of the D. hustedtii-D. lauta Zone into the lower Thalassiosira antiqua Zone (13 to 8 m.y.B.P.), and the Malaga Mudstone ranges from the lower T. antiqua Zone into the lower Thalassiosira oestrupii Zone (8 to 4 m.y.B.P.), transgressing the Miocene-Pliocene boundary (5 m.y.B.P.). The overlap of up to one million years along the Altamira-Valmonte contact is not surpris ng since this contact is characterized by a diagenetic change of Opal-A to Opal-CT at most sites. The age distribution of outcrops reflects northwest-southeast-trending anticlinorium structure of the Palos Verdes Hills, but local sections are discontinuous and deformed due to slumping, folding, and faulting during Pliocene uplift of the hills. This is best seen at Malaga Cove where folds, faults, and slumps are visible along the sea cliffs, and a short hiatus marks the Valmonte-Malaga contact. The siliceous biostratigraphy of the Palos Verdes Hills correlates to that of the Monterey Formation at Newport Bay. However, the correlation of the siliceous zonation to the benthic foraminiferal stages (assigned by Woodring et al, and Warren) differs for the two areas. End_of_Article - Last_Page 982------------

Biostratigraphic Relation of Neogene Benthic Foraminifera from Southern California Outer Continental Borderland to Monterey Formation: ABSTRACT

In recent years there has been considerable discussion concerning the biostratigraphic correlations between planktonic zonations and the classical Neogene California benthic foraminiferal stages. One of the primary objectives of IPOD Leg 63 was to explore these correlations and to determine the possibility of temporal variation of the benthic stages between the outer continental borderland and land sections. Site 468 was drilled on the Patton Escarpment, which lies under the present southeastern margin of the California current system. The sediments yielded well-preserved calcareous and siliceous planktonic assemblages that ranged in age from Holocene to middle Miocene. Samples also contain abundant benthic foraminiferal assemblages that consist of species characteristic of both oceanic and continental margin environments. The benthic foraminiferal assemblages range from the Venturian stage of the Pleistocene to the Luisian-Relizian stages of the middle Miocene. Because of the dependence of benthic species on bottom environmental parameters, the dominant occurrence of lower bathyal to abyssal faunas present problems for direct correlations to local California stages. The majority of key species needed for recognition of the late and middle Miocene benthic stages, as defined in land sections, are indicative of upper to middle bathyal environments and are excluded from the deeper habitats because of environmental restrictions. The occurrence of the lower bathyal pseudo-Saucesian assemblage as a major faunal constituent in the late and middle Miocene samples furthers adds to the complexity of correlations etween the planktonic zonations and benthic foraminiferal stages. End_of_Article - Last_Page 902------------

Age and correlation of California Paleogene benthic foraminiferal stages : Poore, R. Z., 1980. Prof. Pap. U.S. geol. Surv., 1162-C: 8 pp

Age and correlation of California Paleogene benthic foraminiferal stages : Poore, R. Z., 1980. Prof. Pap. U.S. geol. Surv., 1162-C: 8 pp

Comment and Reply on ‘Comparison of Miocene provincial foraminiferal stages to coccolith zones in the California Continental Borderland’

Comment and Reply on ‘Comparison of Miocene provincial foraminiferal stages to coccolith zones in the California Continental Borderland’

Comment and Reply on ‘Comparison of Miocene provincial foraminiferal stages to coccolith zones in the California Continental Borderland’

Comment and Reply on ‘Comparison of Miocene provincial foraminiferal stages to coccolith zones in the California Continental Borderland’

Comparison of Miocene provincial foraminiferal stages to coccolith zones in the California Continental Borderland

Research Article| April 01, 1979 Comparison of Miocene provincial foraminiferal stages to coccolith zones in the California Continental Borderland James K. Crouch; James K. Crouch 1U.S. Geological Survey, Scripps Institution of Oceanography, La Jolla, California 92093 Search for other works by this author on: GSW Google Scholar David Bukry David Bukry 1U.S. Geological Survey, Scripps Institution of Oceanography, La Jolla, California 92093 Search for other works by this author on: GSW Google Scholar Author and Article Information James K. Crouch 1U.S. Geological Survey, Scripps Institution of Oceanography, La Jolla, California 92093 David Bukry 1U.S. Geological Survey, Scripps Institution of Oceanography, La Jolla, California 92093 Publisher: Geological Society of America First Online: 02 Jun 2017 Online ISSN: 1943-2682 Print ISSN: 0091-7613 Geological Society of America Geology (1979) 7 (4): 211–215. https://doi.org/10.1130/0091-7613(1979)7<211:COMPFS>2.0.CO;2 Article history First Online: 02 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation James K. Crouch, David Bukry; Comparison of Miocene provincial foraminiferal stages to coccolith zones in the California Continental Borderland. Geology 1979;; 7 (4): 211–215. doi: https://doi.org/10.1130/0091-7613(1979)7<211:COMPFS>2.0.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract Biostratigraphic ages determined by planktic coccoliths and benthic foraminifera for the same core samples from the California Continental Borderland suggest that a significant overlap exists among provincial Miocene stages of California and that some of the benthic foraminifera commonly used to recognize these stages are time-transgressive. For example, samples assigned to the middle Miocene Discoaster exilis Zone of coccoliths (∼ 14 ± 1 m.y.) are also assigned to the Relizian, Luisian, and lower Mohnian Stages on the basis of benthic foraminifera. Significantly, most past and current geologic interpretations of Cenozoic marine sequences in California rely heavily on provincial benthic foraminiferal stages and zones. Thus, the apparent overlapping of provincial stages has serious implications for geologic studies of the California Cenozoic and should be further investigated in sections onshore. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Age and Depositional Environments of Tertiary Rocks of Nootka Island, British Columbia (92-E): Mollusks Versus Foraminifers

Conflicting interpretations of age and depositional environment of the Tertiary rocks of Nootka Island and adjacent areas of Vancouver Island resulting from studies of their molluskan and foraminiferal faunas appear to be caused by:1. A conflict of opinion concerning the correlation of regional molluskan, foraminiferal, and mammalian stages now applied to the Tertiary rocks of Western North America with units of the international biochronological standard based on the European faunas and type sections.2. Underestimation of the regional (i.e. within individual regions of the Western North American Tertiary province) biochronological value of Tertiary mollusks and other invertebrate macrofossils by many foraminiferal specialists.3. Neglect of mollusks as paleoecological indices by some foraminiferal specialists.4. Misinterpretation of paleoecological value of fossil foraminifers by some foraminiferal specialists. The application of general considerations 1 to 4 to the Tertiary rocks of Nootka Island and adjacent areas of Vancouver Island indicates that:1. A micropaleontological interpretation of the whole of Divisions A and B as bathyal deposits formed at depths of about 2000 ft (610 m) is unwarranted. The molluskan fauna present in the greater part of these units indicates they are predominantly littoral to outer neritic (0 to 800 ft (0 to 244 m)) deposits. Only the middle part of Division B could have been a bathyal (i.e. more than 800 ft (244 m) deep) deposit.A turbiditic redeposition of coarse clastics of Division A into the bathyal depth is ruled out by the state of preservation of its macrofossils, lithology of rocks, and the abundance of regular rows of early diagenetic concretions which maintain their stratigraphic position over considerable distances. The shales of Division B are not redeposited turbidites for the same reasons. If the abundance of allegedly bathyal foraminifers throughout the thickness of these two units will be confirmed by proper documentation and by further research it would be necessary to interpret their association with neritic macro-invertebrates as having been caused by the influence of strong upwelling currents which lowered the temperature of inshore waters and so made them habitable for these foraminifers.2. The recently proposed late Eocene dating of the upper part of Division A and the lower and middle parts of Division B cannot be justified either by the molluskan or by the foraminiferal fauna. The previously proposed early to mid-Oligocene age of these units remains valid regardless of whether one places them into the late Refugian foraminiferal stage or in the Lincoln molluskan stage.3. Even if it is valid, the unsupported claim of the presence of Bulimina schencki fauna does not indicate the correlation of these beds with the late Narizian, as this fauna is closely allied to and is probably contemporary with the early Refugian faunas of southern California. However, these beds may be of a latest Eocene age if the presence of Bulimina schencki fauna will be confirmed.4. The upper part of Division B contains an apparently Lower Blakeley macrofauna suggestive of late Oligocene age in terms of the generally accepted molluskan chronology. The early to mid-Zemorrian (=mid-Oligocene) dating of its foraminifer fauna reflects the divergent micropaleontological tradition which favors the placement of the Oligocene/Miocene boundary at the top of the Zemorrian stage.5. The suggested late Miocene to early Pliocene age of a shallow water foraminifer fauna of Division C of Nootka Island is contradicted by its stratigraphic position underneath the reliably dated Division D (see below). Only the upper part of Division C appears to be a neritic to ?littoral deposit. Its lower part is more likely an outermost neritic to uppermost bathyal deposit.6. The rich and diagnostic upper Blakeley (=lower Miocene) molluskan fauna of Division D is indubitably correlative with that of the type Sooke Formation of Southeastern Vancouver Island and with that of the "Sooke" Formation of the Seattle area. The early Miocene age of these three units is confirmed by the presence of a primitive whale tentatively referred to the order of Archaeoceti and the desmostylan genus Cornwallius in the type Sooke Formation. These data discredit the recently proposed early to early middle Pliocene dating of foraminifers of the Division D and the type Sooke Formation.7. No post-lower Miocene rocks are known to outcrop anywhere on the western coast of Vancouver Island contrary to the recent claims of some micropaleontologists. Also, there is no evidence of an unconformity separating the lower Miocene Division D from the underlying Oligocene to ?lowest Miocene Divisions A, B, and C. All four units appear to form part of a single invasion of a shelf-like (predominantly outer neritic to uppermost bathyal) Oligocene – early Miocene sea onto the southwestern part of Nootka Island. This sea, which may have been deeper and represented by a different facies elsewhere (i.e. Hesquiat Peninsula, Pachena–Sooke area), apparently withdrew completely and permanently from the west coast of Vancouver Island in the latest early Miocene.

Historical Review of Early Pacific Coast Micropaleontology: ABSTRACT

From its beginnings in the wake of World War I, Pacific Coast industrial micropaleontology had at its disposal the superjacent stratigraphic column blocked out by predecessors chiefly on the basis of marine megafossils. Only a few stratigraphically isolated foraminiferal faunules had been recorded in print, as by Chapman and by Bagg. With the growing interest in micropaleontology, several such local microfaunules soon were being analyzed and taxonomically described, notably by the Hanna brothers, Wissler, Church, Hughes, Hobson, Barbat and von Estorff, Galliher, Goudkoff, the Stewarts, Parker, and Siegfus. Age equivalents of the classic Tertiary time-rock subdivisions of Series-Epoch magnitude had been recognized here by Conrad, Arnold, and others. Finer time-rock subdivi ions, however, still were spoken of in terms of faunas, usually as found in mapped and formally named formations. Soon, in spite of earlier traditions to the contrary, in the minds of geologists and palentologists alike, formational terminology was being transferred into time terminology, and unhappily so, as subsequently clarified by Schenck and Muller. Other finer subdivisons, based more intrinsically upon fossils, had previously been given zonal terms. Some were simply beds. J. C. Merriam's two valuable middle Tertiary Turritella zones proved, however, to be teilzones; eventually they were shown by Loel and Corey to overlap in time-stratigraphic range. Helpful echinoid bioseries proved limited in their correlative usefulness because of the lateral as well as vertical evolutionary sensitivity to selective environmental change. In turn, a fauna or an index fossil found at one or a few s ratigraphic zones within a formation, were apt automatically to be taken as indicative of the age of the entire formation. In short, correlations more refined in magnitude than an epoch were in essence local and particular synchroneities defying general classification, rather than biochronological deductions derived through references to some typifying standard stemming from multiple induced generalizations. Resultant confusion in semantics was reflected in the use of formational names for stages, as reflected in the West Coast Paleogene, and the analogous use of terms such as San Lorenzo, Vaqueros, Temblor, Santa Margarita, Pancho Rico, Repetto, and Pico. For refined correlations of the sort required for the recognition of structural and stratigraphic traps in oil exploration, such sy bols were woefully inadequate. With Elliot's perfection of the core-barrel for use in rotary drilling, the significance of micropaleontology for refined correlations in oil geology was immensely enhanced. The chief vehicle involved was detailed biostratigraphy, carried on in private industrial micropaleontology after the manner of 19th century paleontologist August Quenstedt. The first published record of such a local detailed biostratigraphic continuum was that of Herschel Driver in 1928, using informal taxonomy for natural phyletic realities. In the same year, consistency along strike, of Pliocene biostratigraphic units such as Driver's, was emphasized by the late O. C. (Jimmy) Wheeler, and soon also Neogene by Rankin, Lohman, and others. Yet biostratigraphy, left in a purely empirical state, has its chronologic hazards even over and above the factor of error that is inherent in any scientific deduction at its syllogistic best. Criticisms based on demonstrable lateral change in fauna were particularly telling; yet many geologists, by then wary, were nevertheless still thinking biochronologically in terms of William Smith's principle, which is not relevant below System-Period levels in paleontologic time-refinement. In 1933 Natland published his demonstrated parallels between five living, bathymetrically controlled, foraminiferal community-types (ecological formations) and comparable groupings in a nearby Pliocene sequence; and though his work did not extend to either whole true communities or faunules, and biostratig aphic chronology was not attempted until later, the significance of foraminiferal chorology and facies in biostratigraphic chronology was clearly documented. Meanwhile the late Ralph Reed--active field geologist, oil company executive, and voracious reader in the field of earth history generally--had suggested that seemingly Albert Oppel, Quenstedt's student, had managed to circumvent the stumbling blocks of both ecologic and lithologic facies by culling them out of biostratigraphic data for purposes of refined biostratigraphic chronology. The suggestion was appreciated by his associates, and the germ of the consequences already appears formally in a 1931 paper by Cushman and Laiming. Subsequently 15 benthonic foraminiferal stages and more than twice as many zones, in the sense of Oppelian zonation, have been recognized within the Pacific Coast provinces of the Tertiary. End_of_Article - Last_Page 435------------

Age and Correlation of the Ulatisian and Narizian Stages, California: Reply

Phillips questions the scientific value of data presented in Steineck and Gibson (1971) with regard to the intercontinental correlation and time-transgressive nature of California Paleogene benthonic foraminiferal stages. The intent of our note was to present a working hypothesis based on preliminary data which would be testable by future biostratigraphic investigation. It must be emphasized that the conclusions drawn by Steineck and Gibson were based on the analysis of more than 50 samples, along with a summary of pertinent literature, and are consistent with the available evidence. The Refugian Stage is of late Eocene age, the Narizian Stage is late middle Eocene, and the Ulatisian Stage is of early middle Eocene age when viewed in the context of planktonic microfossil correlations. Similarly, in the light of planktonic correlations, the Narizian Bulimina corrugata Zone of the Santa Barbara Embayment is equivalent in part to the Amphimorphina californica Zone of the San Diego Basin. Time-transgression of the California Paleogene benthonic foraminiferal stages is a reality. Furthermore, the views expressed in Steineck and Gibson (1971) are supported in the studies of Bukry and Kennedy (1969), Schmidt (1970 Schmidt (1971), and Brabb and others (1971).

Age and Correlation of the Eocene Ulatisian and Narizian Stages, California: Discussion

The review of the Narizian and Ulatisian benthonic foraminiferal Stages of California by Steineck and Gibson (1971) contains undocumented assumptions concerning the correlation of the Stages. Published data are misquoted or misinterpreted. Conclusions are drawn which do not follow from the data presented. The planktonic faunules reported by Steineck and Gibson are compatible with the foraminiferal Stages of Mallory (1959); no time transgression of either benthonic or planktonic foraminiferal zonations is indicated from the data they present. The Narizian plus the lower Refugian Stages are equivalent to upper Eocene in California usage. The very precise assignments of Steineck and Gibson such as “late early Eocene to early middle Eocene” for the Ulatisian Stage are without basis in either fact or principle.

Age and Correlation of the Eocene Ulatisian and Narizian Stages, California

Paleogene strata crop out along the western boundary of the San Joaquin Basin, in the Santa Barbara Embayment, and in the San Diego Basin, California. Eocene strata are represented by the Ulatisian and Narizian benthic foraminiferal stages (middle and late Eocene, respectively) of Mallory (1959). These provincial stages are used currently for both age assignment and interbasin correlation. Planktonic foraminifers in the Rose Canyon Shale, Poway Conglomerate, and the Matilija, Cozy Dell, Lodo, and Sacate Formations suggest that these formations, as a whole, range in age from late early Eocene to late middle Eocene. Previous authors assigned various elements of the aforementioned formations either to the Ulatisian or Narizian stages. Planktonic foraminiferid species suggest that the Ulatisian stage ranges in age from late early Eocene to early middle Eocene, and the Narizian stage ranges in age from early middle Eocene to late middle Eocene. The time-transgressive nature of ecologically controlled benthic foraminifers is apparent. Furthermore, stages based on benthic foraminifers are not valid means of correlation between tectonically discrete basins of deposition. The occurrence of Subbotina patagonica (Todd) in both the Rose Canyon Shale and Cozy Dell Formation suggests time-equivalence of the two units (early middle Eocene in age).

Geology and Exploration for Oil in the Huasna District, San Luis Obispo County: ABSTRACT

The Huasna district, an area of approximately 100 square miles, lies at the southern end of the Santa Lucia Range in the California Coast Range province about 12 miles northeast of the town of Santa Maria. Geologically it consists of a synclinal basin filled with Miocene sediments and interbedded volcanics. The basin is roughly limited on the east and west by two nearly parallel faults. On or near these boundaries Miocene strata are found in fault or depositional contact with Franciscan rocks on the west and Cretaceous sediments on the east. Anticlines have formed on the flanks of the major syncline. Middle and upper Miocene (Monterey) shales and sands crop out along the eastern flank of the syncline. Basinward they are overlain by 2,000 feet of Santa Margarita sands and shales. Wells drilled within the deeper portion of the basin penetrate 4,000-6,500 feet of brown cherty and siliceous shales and dark brown calcareous shales representing all the foraminiferal stages from upper Mohnian to Relizian. Shows of tarry oil occur throughout this interval both in outcrop and in wells, probably accounting for many of the shows of oil recorded by early tests in the district. At and throughout the basal portion of this predominantly shale section volcanic interbeds of tuff, agglomerate and ashy sands of middle and lower Miocene (Saucesian ?) age are encountered. Incomplete records on earlier wells and lack of deep stratigraphic penetration in more than one well near the center of the basin lead to some conjecture as to the nature and distribution of lower Miocene sediments. Thirty-five wells have been drilled in the Huasna district since 1898. Two or three wells have produced a small amount of oil. The Barneberg No. 2, drilled on the Tar Springs anticline, has produced 11,400 barrels of 16 degrees A.P.I. oil, which appears to have come from near the Santa Margarita-Monterey gradational contact and from within the underlying locally fractured shales. Recent wells drilled nearby failed to develop production. The possibilities of stratigraphic traps at depth within the basin and of better structural position on some of the asymmetric anticlines are indicated as being the objectives of future exploration in the district. End_of_Article - Last_Page 2630------------