Recognition of Middle Miocene 

Foraminifers in Highly Indurated Rocks of the 

Monterey Formation, 

Coastal Santa Maria Province, 

Central California

Geophysical section offshore Santa Maria basin

Geologic section onshore Santa Maria basin

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Chapter L

Recognition of Middle Miocene 

Foraminifers in Highly Indurated 

Rocks of the Monterey Formation, Coastal 

Santa Maria Province, Central California

By KENNETH L. FINGER

U.S. GEOLOGICAL SURVEY BULLETIN 1995

EVOLUTION OF SEDIMENTARY BASINS/ONSHORE OIL AND GAS INVESTIGATIONSSANTA MARIA PROVINCE

Edited by Margaret A. Keller
U.S. DEPARTMENT OF THE INTERIOR 

BRUCE BABBITT, Secretary

U.S. GEOLOGICAL SURVEY 

Gordon P. Eaton, Director

Any use of trade, product, or firm names

in this publication is for descriptive purposes only

and does not imply endorsement by the U.S. Government

Text and illustrations edited by James W. Hendley

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON: 1995

For sale by

U.S. Geological Survey, Map Distribution 

Box 25286, MS 306, Federal Center, 

Denver, CO 80225

Library of Congress Cataloging in Publication Data

Finger, Kenneth L.

Recognition of Middle Miocene foraminifers in highly indurated 

rocks of the Monterey Formation, coastal Santa Maria Province, 

central California / by Kenneth L. Finger.

p. cm.--(Evolutlon of sedimentary basins/onshore oil and 

gas investigations-Santa Maria Province; L) (U.S. Geological 

Survey Bulletin: 1995)

Includes bibliographical references (p. - ).

Supt. of Docs, no.; 119.3:1995-1

1. Foraminifera, Fossil-California-Santa Maria basin. 

2. Paleontology-Miocene. 3. Monterey Formation (Calif.) 

(.Title. II. Series. III. Series: Evolution of sedimentary 

basins/onshore oil and gas investigations-Santa Maria Province: 

ch. L.

QE75.B9 no. 1995-L 

[QE772] 

557.3 s--dc20

[563'.I2'09794] 95-22276

CIP
CONTENTS

Abstract LI 

Introduction LI

Acknowledgments L2 

Mussel Rock section L2

Geographic location L2

Previous work L3

Collections L5

Recovery and preservation L5

Faunal assemblages L6

Biostratigraphy L6

Depositional paleoenvironment L10

Synopsis L10 

Lions Head section L10

Geographic location L10

Previous work Lll

Collections L12

Recovery and preservation L12

Faunal assemblages L13

Biostratigraphy L13

Depositional paleoenvironment L16

Synopsis L16 

Rodeo Canyon section L17

Geographic location L17

Previous work L17

Collections L18

Recovery and preservation L18

Faunal assemblages L18

Biostratigraphy L18

Depositional paleoenvironment L20

Synopsis L21 

Discussion L21 

Summary L23 

References L23 

Appendixes

A. Mussel Rock section lithologic and processing log of samples L26

B. Lions Head section lithologic and processing log of samples L28

C. Rodeo Canyon section lithologic and processing log of samples L29

PLATES

[Plates follow references]

1-19. Foraminifers, Monterey Formation, Mussel Rock section

20-33. Foraminifers, Monterey Formation, Lions Head section

34-36. Foraminiferal pelletal phosphorite, Monterey Formation, Rodeo Canyon section

37-46. Foraminifers, Monterey Formation, Rodeo Canyon section

Contents III
FIGURES

1. Map of sampled stratigraphic sections in Santa Maria basin referred to in this 

study L2

2. Chronostratigraphic correlation chart for middle Early Miocene to Early Pliocene of 

California L3

3. Composite geologic column of Monterey Formation in Santa Maria basin L4

4. Sample locality map of Mussel Rock section L4

5. Stratigraphic column of Mussel Rock section denoting positions of collected samples 

(CRC-40398 and CRC-41356 collections) L5

6. Chemical analysis of outer test wall of Valvulineria robusta specimen from Mussel 

Rock section, sample CRC-40398-3 L6

7. Chemical analysis of test infilling of Valvulineria robusta specimen shown in 

figure 6 L7

8. Map of sample localities in the Monterey Formation, Lions Head section Lll

9. Stratigraphic column of Lions Head section denoting positions of collected samples 

(CRC-40471 collection) Lll

10. Chemical analysis of test wall ofPullenia miocenica specimen from Lions Head 

section, sample CRC-40471 -6 L12

11. Chemical analysis of infilling of Rectuvigerina branneri specimen from Lions Head 

section, sample CRC-40471 -6 L13

12. Chemical analysis of test wall of Lenticulina smileyi specimen from Lions Head 

section, sample CRC-40471-6 L14

13. Chemical analysis of test infilling of Lenticulina smileyi specimen shown in 

figure 12 L15

14. Chemical analysis of pyrite (FeS2) framboids infilling Lenticulina smileyi specimen 

shown in figure 12 L16

15. Sample locality map of Rodeo Canyon section L17

16. Stratigraphic column of Rodeo Canyon section denoting positions of collected 

samples (CRC-40661 collection) L18

17. Chemical analysis of outer surface of phosphatic pellet (with foraminifer nucleus) from 

Rodeo Canyon section, sample CRC-40661-1 L19

18. Chemical analysis of internal mold of Protoglobobulimina pseudoaffinis specimen 

encased within phosphatic pellet shown in figure 17 L20

TABLES

1. Foraminiferal checklist, Point Sal and Monterey Formations, Mussel Rock section L8

2. Foraminiferal checklist, Monterey Formation, Lions Head section L17

3. Foraminiferal assemblage in pelletal phosphorite sample, Monterey Formation, Rodeo 

Canyon section L21

4. Checklist of Monterey Formation Foraminifera species versus plate numbers L22

IV Contents
Recognition of Middle Miocene Foraminifers in 

Highly Indurated Rocks of the Monterey Formation, 

Coastal Santa Maria Province, Central California

By Kenneth L. Finger1

ABSTRACT

Investigations were undertaken to identify and interpret foraminiferal assemblages in six outcrop sections of 

the Monterey Formation in the onshore Santa Maria basin, 

Calif. Mussel Rock, Lions Head, Point Pedernales, Rodeo Canyon, S weeney Road, and Manville Quarry. The purpose of this study was to complement existing 

lithostratigraphic and siliceous microfossil data from these 

sections with traditional benthic foraminiferal stage correlations. Most of these rocks are devoid of foraminifers, 

owing to their relatively high diagenetic alteration in which 

the foraminiferal calcite was converted into dolomite. No 

foraminifers were recovered from Point Pedernales or within 

the Manville Quarry, and only one specimen was obtained 

from Sweeney Road. Most, but not all, of the coastal outcrops at Mussel Rock, Lions Head, and Rodeo Canyon are 

similarly devoid of foraminifers. The few foraminifer-bearing rocks at these localities are highly indurated, rendering 

it difficult to isolate specimens by conventional processing 

techniques. Most specimens freed from the rock matrix are 

poorly preserved and not easily identified. To compensate 

for these hindrances, foraminifers were studied in petrographic thin sections. The stage-diagnostic benthic foraminiferal assemblages recognized are those of (1) the RelizianLuisian for the lower calcareous-siliceous member of the 

Monterey Formation at Rodeo Canyon, (2) the RelizianLuisian for the lower part of the phosphatic member of the 

Monterey Formation at Lions Head, (3) the Luisian for the 

upper part of the phosphatic member at Lions Head, (4) the 

Luisian for the lower part of the phosphatic member at 

Mussel Rock, and (5) the Mohnian for the upper part of the 

phosphatic member at Mussel Rock.

The assemblages recovered from Mussel Rock and 

Lions Head contain foraminifers indicative of deposition in 

the lower middle-bathyal (1,500-2,000 m) zone. The 

Relizian-Luisian foraminiferal assemblage at Rodeo Canyon occurs in a pelletal phosphorite formed on a sedimentstarved bank at a water depth of about 1,500 m and later 

redeposited as a turbidite on the basin floor.

'Department of Geology, Irvine Valley College, 5500 Irvine 

Center Drive, Irvine, CA 92720.

Manuscript approved for publication May 3,1995.

Paleoenvironmental marker species indicate that the 

Relizian-Luisian, Luisian, and Mohnian foraminiferal assemblages in the calcareous mudstones of the phosphatic 

member of the Monterey Formation along the Santa Maria 

coast are bathymetrically mixed associations deposited at 

lower middle-bathyal (1,500-2,000 m) depths.

This document contains an extensive set of faunal illustrations that will provide paleontologists and petrographers working on the Monterey Formation with an ample 

visual reference for recognizing similar foraminiferal assemblages in correlative stratigraphic sections.

INTRODUCTION

The purpose of this study of foraminiferal assemblages 

in the Monterey Formation was to complement a 

lithostratigraphic study on selected outcrops in Santa Maria 

basin (fig. 1) and was intended to provide regional correlations that possibly could be extended into the adjacent offshore areas. This report incorporates a slightly updated version (Finger, 1992) of Barron's (1986a, b) biostratigraphic 

correlation chart for the Neogene of California (fig. 2) and 

utilizes the lithostratigraphic subdivisions of the Monterey 

Formation proposed by MacKinnon (1989a) for the Santa 

Maria basin (fig. 3). Initial biostratigraphic studies were 

restricted to siliceous microfossils (for example, Akers and 

others, 1987) because biogenically derived silica is abundant in many of the rocks in the sections investigated. During the course of these studies, it became apparent that siliceous microfossils are generally rare or absent in the 

calcareous mudstones of the lower part of the Monterey Formation, where foraminifers were more likely to be present. 

Thus, an investigation of the foraminiferal fauna was undertaken in order to complete the biostratigraphic analysis.

Six sections in western Santa Barbara County were 

selected for foraminiferal studies Mussel Rock, Lions 

Head, Point Pedernales, Rodeo Canyon, Sweeney Road, and 

Manville Quarry. In the coastal bluffs at Mussel Rock, Lions Head, and Rodeo Canyon, foraminifers are restricted to 

the Point Sal Formation (equivalent to the lowest part of the 

Monterey Formation in other regions; Woodring and 

Bramlette, 1950) and the lower calcareous-siliceous memRecognition of Middle Miocene Foraminifers in the Monterey Formation, Santa Maria Province, California L1
her and the phosphatic member of the lower part of the 

Monterey Formation. One other suite of 20 samples collected in the lower part of the Monterey Formation from 

Point Pedernales yielded no foraminifers. Samples from the 

overlying upper calcareous-siliceous member (22 samples) 

and clayey-siliceous member (7 samples) of the upper part 

of the Monterey Formation and the Sisquoc Formation (15 

samples) at Point Pedernales were similarly devoid of foraminifers. Rocks collected from the Sweeny Road section 

yielded only one specimen from the 50 samples collected in 

the upper part of the Monterey Formation (see Akers and 

others, 1987) and none from the 23 samples collected in the 

Sisquoc Formation. Although there is excellent recovery 

from the upper part of the Monterey Formation exposed 

along the access road to the Manville Quarry (Finger, 1992; 

also Govean and Garrison, 1981; Ingle, 1985), younger 

Monterey and Sisquoc Formation rocks within the quarry 

are devoid of foraminifers and rich in siliceous microfossils 

(Barron, 1975, 1976). When compared to the assemblages 

recovered from Mussel Rock, Lions Head, and Rodeo Canyon, those from the Manville Quarry access road are 

younger, better preserved, and characterized by higher abundances and species diversities. I have detailed their faunal 

succession in another publication (see Finger, 1992). These 

intrabasinal differences suggest that local variations in depo34° 26'

Figure 1. Map showing sampled stratigraphic sections in 

Santa Maria basin referred to in this study.

sitional and diagenetic processes have been important factors in determining the preservation of foraminifers in these 

rock units.

The present investigation focuses on the recognition 

of foraminifers in the coastal sections of Mussel Rock, Lions Head, and Rodeo Canyon. The foraminiferal fauna of 

the Mussel Rock section was selected for initial study because it yielded the most abundant and best preserved 

foraminifers of the three sections discussed here. Documentation of this fauna provided a valuable basis for studying 

the other sections. The foraminifers obtained from the Lions Head section are more difficult to isolate from the rocks 

and are in much poorer states of preservation. Foraminifers 

recovered from the Rodeo Canyon section were the most 

difficult to analyze because they were obscured within a 

single sample of pelletal. Faced with the challenge of identifying species thin sectioned in petrographic slides without 

the aid of associated "free" specimens, a reference guide 

for this mode identifying foraminifers from the Miocene of 

California had to be developed first. After formulating an 

efficient method of thin sectioning specimens (Finger and 

Armstrong, 1984), the identification guide was compiled 

(Finger, 1990), enabling recognition of the assemblages from 

Santa Maria basin.

ACKNOWLEDGMENTS

This study was undertaken at Chevron Oil Field Research Company, La Habra, Calif. I thank G.L. Armstrong, 

T.C. MacKinnon, RJ. Navarrette, J.S. Compton, W.H. Akers, 

and R.E. Marolt for their assistance, contributions, and cooperation throughout various phases of this study. I am also 

grateful to T.C. MacKinnon, S.R. Jacobson, andPJ. Hoffman 

for their internal reviews of the manuscript. Chevron Oil 

Field Research Company kindly granted permission to publish this report. Formal reviews by J.C. Ingle, Jr. (Stanford 

University), M.B. Lagoe (University of Texas, Austin), and 

C.M. Isaacs (U.S. Geological Survey, Menlo Park), as well 

as editorial suggestions by M.A. Keller, S.W. Starratt, and 

J.W. Hendley (U.S. Geological Survey, Menlo Park), were 

most beneficial in finalizing this manuscript for publication.

MUSSEL ROCK SECTION 

GEOGRAPHIC LOCATION

Mussel Rock is named for the irregularly shaped promontory of seaward-projecting outcrops located west of 

Guadalupe and Santa Maria on the coastal edge of the 

Casmalia Hills (fig. 4) and is situated near the midpoint of 

the stratigraphic section that extends between Rancho 

Guadalupe Dunes County Park to the north and Point Sal to

L2 Evolution of Sedimentary Basins/Onshore Oil and Gas Investigations Santa Maria Province
the south. The term "Mussel Rock" is used herein in reference to this section, not the actual promontory. Overlying 

the Point Sal ophiolite (Hopson and Frano, 1977), the Mussel Rock section includes the Great Valley sequence 

(McLean, 1991) and the Lospe, Point Sal, Monterey, and 

Sisquoc Formations (fig. 5).

PREVIOUS WORK

The Mussel Rock section has been referred to in several reports on the geology of the Santa Maria basin, including Woodring and Bramlette (1950), Pisciotto (1981), 

Pisciotto and Garrison (1981), and Grivetti (1982). In his

comprehensive dissertation on Miocene foraminiferal biostratigraphy of California, R.M. Kleinpell (1938, p. 119) referred to the presence of Relizian strata north of Point Sal 

but did not specifically mention its fauna. A year later, C.R. 

Canfield (1939), a paleontologist for Union Oil Company 

of California, presented a lithostratigraphic framework for 

the Santa Maria district in which he described the corresponding foraminiferal associations. Wissler and Dreyer 

(1943), also of Union Oil, named these biostratigraphic 

zones and related them to the benthic foraminiferal stages 

of Kleinpell (1938); however, Mussel Rock was not noted 

among the subject sections in either of these publications. 

Woodring and Bramlette (1950, p. 21-22) provided 

the only previous formal publication on foraminifers in the

Epoch Chron Magnetic 

Polarity [Anom

Diatom 

Zone

Calcareous

Nannofossil

Zone

Planktic 

Foram 

Zone

Benthic 

Foram 

Zone

PLIOCENE

- 5 -

- 6 -

- 7 -

- 9 -

-10-

-11 -

-12-

-13-

-14-

-15-

16-

-17-

-18-

10

11

12

13

14

15

16

17

4A

>5A

5B

5D

Thalassiosira 

oestrupii

Nitzschia 

reinholdii

Thalassiosira , 

antiqua c

Denticulopsis 

hustedtii

s js

I!

!»li

Actinocyclus 

ingens

CN10

CN9

CN8

CN7

CN6

CN5

CN4

CN3

CN2

CN1c

N19

N18

"Delmontian"

N17

L _ .

N16

N15

N14

N13

N12

N11

N10 Late

N9

Early

N8

Relizian

N7

N6

N5

Late 

Early

Saucesian

Figure 2. Chronostratigraphic correlation chart for middle Early Miocene to Early 

Pliocene of California (Finger, 1992, slightly modified from Barren, 1986a, b).

Recognition of Middle Miocene Foraminifers in the Monterey Formation, Santa Maria Province, California L3
-1200m 

(3937ft)

-1100

-1000

-900

** " ""****

« * ,-. a /TO « A X X

oonKHBHBrcf.c c jj

VVVVVVVVVVV 

VVVVVVVVVVV

vvvvvvvvvvv

VVVVVVVVVVV

vvvvvvvvvvv 

vvvvvvvvvvv

Diatomaceous Mudstone 

Mudstone

Carbonate Mudstone 

Phosphatic Mudstone 

Poroelanite

Mussel Rock section. Their foraminiferal checklist is composed of seven assemblages one from a Mussel Rock locality roughly equivalent to my sample CRC-40398-4 (note 

CRC indicates samples stored at Chevron Petroleum Technology Center (formerly Chevron Oil Field Research Company), La Habra, Calif.), three from Lions Head, and three 

from Casmalia Hills. In discussing the Point Sal Formation 

between Point Sal and Mussel Rock, Woodring and 

Bramlette (1950, p. 17) noted that "Much of the mudstone 

contains Foraminifera, generally poorly preserved." It is 

probably for this reason that they did not include a corresponding species list in their report.

Ingle (1985) and Rider (1985) included analyses of 

foraminifers and siliceous microfossils, respectively, from 

the Mussel Rock section in their papers. Ingle (1985) discussed the relationship between the depositional history of

(T Rancho Guadalupe Dunes County Park)

(Guadalupe -»)

Pacific Ocean

Figure 4. Sample locality map of Mussel Rock section. 

Sample numbers refer to CRC-3098 collection, except those 

preceded by asterisk, which denotes CRC-43156 collection. 

Some intermediate numbers not plotted for clarity. See figure 

1 for section location.

-4 Figure 3. Composite geologic column of Monterey 

Formation in Santa Maria basin (from MacKinnon, 1989a).

L4 Evolution of Sedimentary Basins/Onshore Oil and Gas Investigations Santa Maria Province
the Mussel Rock section and that of Santa Maria basin in 

the context of regional and global Neogene 

paleoceanography. Additional findings on the diatom biostratigraphy of this section was provided by White and others (1992).

of the Monterey Formation exposed by interim storms. 

Lithologic descriptions of all the samples and designation 

of those (primarily mudstones) selectively processed for 

foraminifers are given in appendix A.

COLLECTIONS

In May 1982, W.H. Akers and G.L. Armstrong collected 77 samples (CRC-40398 collection) at Mussel Rock, 

mostly from the Monterey and Sisquoc Formations, for siliceous microfossil studies (Armstrong, oral commun., 1982). 

Another seven samples (CRC-43156 collection) were obtained from the Mussel Rock section by myself, G.L. 

Armstrong, and R.E. Marolt in July 1984 (figs. 4 and 5). 

This supplementary collection was obtained from outcrops

RECOVERY AND PRESERVATION

Foraminifers are present in only 4 of 31 samples processed from the Monterey Formation at Mussel Rock, with 

recovery restricted to the phosphatic member. In contrast, 

five of the six processed samples from the Point Sal Formation yield foraminifers. This selective preservation and differential recovery is similar to that reported by Woodring 

and Bramlette (1950).

The foraminifers illustrated as scanning electron micrographs in plates 1 to 5 are among the better preserved

Monterey 

Formation

Point Sal

Formation

(1400 ft)

Lospe

Formation

(700 ft)

Great Valley Sequence

Point Sal 

Ophiolite

Ctayey-Slllceoiw Member

Upper CalcareowSlllceoiu Member 

^| Phosphallc Member 

FT*] Point Sal Ophiollle

Figure 5. Stratigraphic column of Mussel Rock section denoting positions 

of collected samples (CRC-40398 and CRC-43156 collections). Some 

intermediate numbers not plotted for clarity. Great Valley sequence (McLean, 

1991) and Point Sal ophiolite (Hopson and Frano, 1977) names not adopted 

by U.S. Geological Survey.

Recognition of Middle Miocene Foraminifers in the Monterey Formation, Santa Maria Province, California L5
specimens isolated from the Monterey Formation at Mussel 

Rock; their condition is atypical of the total assemblage 

most specimens are poorly preserved. Partial dissolution is 

probably responsible for the frosting of test surfaces and 

the thinning of test walls, which render the foraminifers 

susceptible to further destruction. Replacement by phosphate 

or silica is not evident (fig. 6); infillings of calcite (fig. 7) 

probably encouraged the preservation of these eroded tests, 

which might have otherwise disintegrated.

FAUNAL ASSEMBLAGES

Combining conventional free-specimen viewing with 

my thin-section study (pis. 6-19) improved the ability to 

identify and quantify taxa. The samples of the Monterey 

and Point Sal Formations from Mussel Rock yielded 75 

benthic and 8 planktic species of Foraminifera (table 1); 

this composite assemblage has more than five times the 

number of species recorded by Woodring and Bramlette

(1950) from the Mussel Rock section. The tally of foraminifers collected from the Point Sal Formation (table 1) is composed of 35 benthic and 6 planktic species, most of which 

are also found in the superjacent Monterey Formation. Both 

formations' assemblages actually contain more species, as 

poorly preserved specimens of apparently different indeterminate species are lumped by genera because it was impossible to consistently differentiate them. Also, the many indeterminate taxa observed in thin section have been excluded 

from these lists.

BIOSTRATIGRAPHY

Foraminiferal biostratigraphy in the Miocene of California has been based almost exclusively on the benthic 

fauna because associated diagnostic planktic foraminifers 

are rarely encountered. For nearly half a century, the main 

source of referral has been the extensive framework of 

benthic foraminiferal successions described by Kleinpell

4000--

3500--

3000

2500--

Au

2000--

O 

o

1500-

1000--

500--

0-

Au

0 4567 

KILO ELECTRONVOLTS

8 10

Figure 6. Chemical analysis of outer test wall of Valvulineria robusta specimen from Mussel Rock section, sample CRC-40398- 

3. Test is composed of calcite, indicated by Ca peaks. Other element peaks represent sediment contaminants (Si) and plug 

(Cu) and coating (Au) used for scanning electron microscopy.

L6 Evolution of Sedimentary Basins/Onshore Oil and Gas Investigations Santa Maria Province
(1938). It has been increasingly evident that Kleinpell's pioneering subdivision of the Miocene of California was based 

on much diachronous and geographically limited data, as 

expected from benthic foraminiferal distributions in a heterogeneous array of coastal basins. I interpret benthic foraminiferal zones as local biostratigraphic units and refrain 

from correlating the Mussel Rock section with Kleinpell's 

composite zonation. Regional application of Kleinpell's 

Miocene stages is less problematic because these larger biostratigraphic units reflect more widespread fauna! changes. 

Their time-transgressive nature, and the basis for recognizing them, however, is in need of careful scrutiny.

The inadequate taxonomic base about which Kleinpell 

(1938) constructed his biostratigraphic framework has led 

to much confusion about the Miocene of California. In his 

"revisit," Kleinpell (1980) criticizes the interim work of 

others for their species misidentifications, impossible associations, and lack of useful faunal illustrations. Among those 

taken to task are Woodring and Bramlette (1950) for having 

presented "conflicting" evidence in six of their seven assemblages checklisted from their lower member of the 

Monterey Formation in the western Santa Maria district. In 

response to the apparent need for clarification of his species concepts, Kleinpell (1980) supplemented his comments 

with 26 plates of California Miocene foraminifers. Nevertheless, his appended gallery remains incomplete and its use 

is hindered by many ambiguous or invalid species concepts. 

If analyzed on the basis of the species ranges determined by 

Kleinpell (1938,1980), the Mussel Rock assemblages documented in this report would fall into his category of "impossible associations" because of their "discordant" species. 

The discrepancies in size and content between my 

sample CRC-40398-4 (table 1) and Woodring and 

Bramlette's (1950, p. 21-22) sample 9 probably are attributable to sampling of different strata and subjective identifications. If both samples happened to be from precisely the 

same stratigraphic horizon (a most unlikely coincidence, 

particularly after nearly half a century of coastal erosion), 

the coeval assemblages would represent separate 

thanatotopes. For comparative purposes, Woodring and

2000- -

1600--

1200--

c/)

O 

O

B00--

400--

4567 

KILO ELECTRONVOLTS

8 10

Figure 7. Chemical analysis of test infilling of Valvulineria robusta specimen shown in figure 6. Infilling is composed of 

calcite, indicated by Ca peaks. Other element peaks represent sediment contaminants (Si) and plug (Cu) and coating (Au) 

used for scanning electron microscopy.

Recognition of Middle Miocene Foraminifers in the Monterey Formation, Santa Maria Province, California L7
FORAMINIFERA SPECIES

BENTHICS

Ambitropus evax

Anomalinoides salinasensis

Baggjna californica

Botivina advena

Bolivina advena ornate

Bolivina a/a/a

Bolivina blakei

Bolivina brevior

Bolivina californica

Bolivina churcH

Bolivina imbticala

Bolivina modeloensis

Bolivina parva

Bolivina pseudospissa

Bolivina spp. indet.

Buccella oregonensis

Bulimina subcalva

Buliminella elegantissima

Cibicides spp.

Cibicidoides mckannai

Concavella gyroidinalormis

Dentalina pseudoobtiqua

Bphidium granti

Fursenkoina sp.

Gavelinopsis sp.

Globocassidulina neomargareta

Guttulina sp.

Gyroidina healdi

Gyroidina rosatornis

Hansenisca rotundimargo

Hanzawala depaoloi

Haplophragmoides sp.

Holmanella baggi

Islandiella modeloensis

Kleinpella calilomiensis

Lagena apiopleura

Lenfcvlina dougjasi

Lentculina reedi

Lenfcvlina srrileyi

Marginulinopsis beali

Megastomella capitanensis

Nodogenerina advena

Nodogenerina irregularis

Nodogenerina sagrinensis

Nodosaria ewaldi

Nodosaria spp. ?

Oolina melo

Oolina sp.

ParaKssurina sp.

Paralrondicularia mioconica

Protoglobobulimina pseudotorta

Proxifrons vaughani

Pseudononion costilerum

Pseudononion indsum

Pseudononion sp.

PseudoparreUa subperuviana

Pullenia mioceruca

Rectuvigerina branneri

Rutherfordoides calilomiensis

Saracenaria schencki

Siphonodosaria montereyana

Sphaeroidina chilostomata

Suggrunda kleinpelli

Trifarina Huens

Uvigerinahannai

Uvigerinahootsi

LMgerina subperegrina

LMgerina spp.

Uvigerinella californica

Uvigerinella californica ornate

Valvulineria californica

Valvulineria miocenica

Valvulineria robusta

Valvulineria sp.

Genus and species indeterminate

PLANKTICS

Globigerina bulloides

Globigerina pseudodperoensis

Globigerina quinqueloba

Globigerina sp.

Globigerinella pseudobesa

Globigerinita uvula

Globorolalia praesdtula

Tenuitellinata angusSumbilicata

Point Sal Fm.

80

F

VR

F

VR

80

F

C

A

81

A

F

R

F

R

C

A

R

R

81

F

A

R

82

A

R

VR

A

VR

VR

VR

F

82

A

C

A

A

83

C

A

R

VR

R

VR

VR

A

C

VR

VR

63

A

R

F

F

84

A

F

A

F

A

F

F

R

R

F

R

F

VR

VR

F

F

R

R

R

VR

F

VR

A

R

F

R

A

84

A

C

F

C

Monterey Fm.

2

VR

R

F

F

F

R

F

R

VR

F

C

R

F

R

VR

F

VR

VR

F

VR

R

R

R

VR

R

R

2

A

F

F

VR

VR

VR

F

A

3

A

R

A

C

C

A

A

VR

C

VR

F

A

VR

F

F

F

R

VR

C

R

F

VR

VR

VR

F

C

A

C

F

3

C

F

VR

F

4

C

F

F

R

R

VR

F

R

VR

R

C

VR

VR

R

VR

R

C

R

F

F

VR

R

R

VR

VR

R

4

F

R

5

VR

VR

R

A

F

VR

R

F

A

F

C

R

VR

F

F

VR

R

VR

VR

A

5

 ^ Table 1 . Foraminifera species checklist for Point Sal and 

Monterey Formations (CRC-40398 collection), Mussel Rock 

section

[Abundance Key: A, abundant; C, common; F, few; R, rare; VR, very rare]

Bramlette's (1950) assemblage data are listed below with 

my table 1 synonymies bracketed (see table 1 for frequency 

abbreviations noted below in parentheses):

Bolivina californica Cushman (F)

Bolivina imbricata Cushman (C)

Bolivina parva Cushman & Galliher (C) [=?Bolivina 

spp. indet.]

Bolivina salinasensis Kleinpell (F) [=Wolivina spp. 

indet.]

Bulimina pseudoaffinis Kleinpell (R) 

\Protoglobobulimina pseudotorta (Cushman)]

Buliminella subfusiformis Cushman (C)

Cibicides cf. C. altamiraensis Kleinpell (C) 

[-ICibicides sp. or Cibicidoides mckannai (Galloway and Wissler)]

Cibicides relizensis Kleinpell (F) [not seen]

Entosolenia sp. (F) [=lFissurina sp.; not seen]

Globigerina bulloides d'Orbigny (A)

Lagena acuticosta Reuss of Kleinpell (C) [=L. 

apiopleura Loeblich and Tappan]

Lagena sp. (R) [not seen]

Pulvinulinella subperuviana Cushman (F) 

[=Pseudoparrella]

Siphogenerina branneri Cushman (F) [=Rectuvigerina 

branneri (Bagg)]

Uvigerinella californica Cushman (F)

Valvulineria californica van obesa Cushman (R) [var. 

not distinguished]

In reference to their list of assemblages from Mussel 

Rock, Lions Head, and Casmalia Hills, Woodring and 

Bramlette (1950, p. 21) deduced, "The large foraminiferal 

fauna of the lower member of the Monterey shale represents the upper part of Kleinpell's Relizian stage and all of 

his Luisian stage. Siphogenerina is a conspicuous genus of 

the fauna, 5. branneri being common in the lower part of 

the member and 5. collomi in the upper part." However, 

they did not provide zonal assignments for these assemblages, probably because they could not relate them more 

specifically to Kleinpell's (1938) biostratigraphy. On this 

point, Kleinpell (1980, p. 28, 33) insinuated the problem 

lies with Woodring and Bramlette's (1950) misidentification 

of species.

I am reluctant to rely on the Siphogenerina biostratigraphy proposed by Kleinpell (1938) and modified by 

Kleinpell and Tipton (in Kleinpell, 1980) because the designated species appear to be gradational ecophenotypes of 

what is most likely a single polyphenotypic species. Referral to type descriptions, type figures, and the many illustrations included in Kleinpell's (1980) "revisit" reveals an inL8 Evolution of Sedimentary Basins/Onshore Oil and Gas Investigations Santa Maria Province
comprehensible methodology. To illustrate the complications 

of employing the criteria of Kleinpell (1938) and Kleinpell 

and Tipton (1980), my recording of 5. hughesi Cushman in 

the phosphatic member of the Monterey Formation at Mussel Rock would indicate that the unit is of early Relizian 

age. Kleinpell (1980) may have defended his system by suggesting that my forms are reworked 5. hughesi or worn specimens of a younger costate species. My discussion below 

illustrates that, for other reasons, the foraminifers present 

in the phosphatic member at Mussel Rock cannot be assigned to lower Relizian strata.

Because California Miocene Siphogenerina have 

evaded taxonomically consistent usage, I have adopted the 

first of the California Miocene species named in the literature, Rectuvigerina branneri (Bagg), to designate a large 

portion of the plexus. The overall composition of single and 

composite assemblages should be analyzed, with less emphasis placed on the absolute first and last appearances of 

those species designated by Kleinpell (1938,1980) as markers. Because many of these marker species are difficult to 

differentiate and their biostratigraphic ranges extend beyond 

those documented by Kleinpell (1938,1980), careful attention should be paid to their acmes. In some cases, species 

acmes, derived from the semiquantitative ranges tabulated 

by Kleinpell (1938, table 18) and Finger (1992), might be 

more widespread and reliable for age dating than first and 

last occurrence datums. Relative abundances of species are 

often the only criterion useful in analyzing isolated samples 

or brief stratigraphic sections, where subjacent and 

superjacent data on the faunal succession are lacking.

I prefer to correlate California Miocene sections on 

as local a basis as possible. In general, this approach improves accuracy and provides a more sound interpretation. 

Prior to publication and general acceptance of Kleinpell's 

(1938) regional synthesis, localized biostratigraphies were 

commonplace. Unfortunately, these local basin frameworks 

were put aside by subsequent workers who incorrectly presumed that Kleinpell's was the definitive reference for the 

California Miocene. In fact, the original local biostratigraphic scheme formulated by Canfield (1939) and Wissler 

and Dreyer (1943) is still very useful in correlating sequences 

in the Santa Maria basin.

Canfield (1939) designated the lowest and thickest unit 

of the Monterey Formation as the Siltstone and Shell zone, 

adding in a footnote that the name Point Sal Formation would 

be proposed. He noted that its "local silty facies foraminiferal fauna" is characterized by Buliminella subfusiformis 

Cushman, Valvulineria ornata Cushman, and Uvigerinella 

obesa Cushman. My samples from the Point Sal Formation 

match Canfield's (1939) lithologic and paleontologic descriptions of the Siltstone and Shell zone fairly well. Wissler 

and Dreyer (1943) referred to their corresponding biostratigraphic unit as Foram zone 7, the Valvulineria ornataUvigerinella obesa zone, which they assigned to the Relizian 

stage. The predominance ofBolivina advena Cushman s.s.

in my samples is also typical of Relizian thanatofacies 

(Kleinpell, 1938, 1980).

Similar Relizian assemblages encountered elsewhere 

in the Santa Maria district are documented by Woodring 

and Bramlette (1950). In reference to a species of benthic 

foraminifer present in many of these assemblages, Woodring 

and others (1943, p. 1344) stated, "The variety of 

Siphogenerina hughesi, which shows numerous very fine 

costae, is associated elsewhere with the typical noncostate 

form of that species." Thus, they correlated the Point Sal 

Formation with Kleinpell's (1938) Siphogenerina hughesi 

Zone, or the lower part of the Relizian stage. This deduction was retained almost verbatim in the report by Woodring 

and Bramlette (1950, p. 17). The only other occurrence I 

know of where Siphogenerina populations predominantly 

consist of the finely costate form (= Rectuvigerina loeblichi 

Finger and Lipps) is in the "classic" Relizian section along 

Graves Creek, near Atascadero in the Salinas basin (Finger 

and others, 1990). Recovery of this species in the adjacent 

Santa Maria basin suggests that these occurrences may be 

coeval. Using a hand lens, I perused the Point Sal Formation north of Point Sal in search of strata bearing 

Rectuvigerina, but none were observed nor were any recovered later from the processed samples.

Mussel Rock sample localities CRC-40398-2, -3, and 

-4 in the phosphatic member of the Monterey Formation 

yielded a composite benthic foraminiferal assemblage, 

which includes the characteristic Luisian association of 

Anomalinoides salinasensis, Bolivina advena ornata, 

Marginulinopsis beali, Pullenia miocenica, Rectuvigerina 

branneri, and Valvulineria californica. Canfield (1939) 

noted that the association of Anomalinoides salinasensis and 

Siphogenerina characterizes his Dark Brown zone. Wissler 

and Dreyer (1943) subsequently referred to this biostratigraphic unit as Foram zone 5, the Siphogenerina collomiSiphogenerina nuciformis zone, and correlated it with the 

Luisian stage. The lithology of this zone is described by 

Canfield (1939) as consisting of "a moderately hard series 

of fractured fairly interbedded chocolate-brown and buff 

phosphatic semiplaty foraminiferal shale." The Dark Brown 

zone derives its name from its common staining by oil saturation.

Sample CRC-40398-2 from the basal exposure of the 

phosphatic member of the Monterey Formation yielded several specimens of Globorotaliapraescitula Blow, a planktic 

foraminifer with a relatively short biostratigraphic range. 

In the middle latitudes, this species ranges from the 

Catapsydrax dissimilis Zone to the Globorotalia 

peripheroronda-peripheroacuta overlap Zone (Kennett and 

Srinivasan, 1983), an interval approximately from 20 to 14 

Ma (Keller and Barren, 1981; Poore and others, 1981). 

Sample CRC-40398-2 also yielded Denticulinopsis lauta 

(Bailey) Simonsen and Coscinodiscus lewisianus Greville, 

diatoms which have a concurrent range of 16.0 to 14.6 Ma 

(R.J. Navarrette, oral commun., 1984), supporting the early

Recognition of Middle Miocene Foraminifers in the Monterey Formation, Santa Maria Province, California L9
middle Miocene age implied by the Luisian benthic foraminifers (see fig. 2). The superjacent foraminifer-bearing 

rocks did not yield any diagnostic planktic foraminifers or 

siliceous microfossils.

Sample locality CRC-40398-5, also in the phosphatic 

member, yielded an assemblage that includes Baggina 

californica, Concavella gyroidinaformis, andMegastomella 

capitanensis, the only three species noted by Canfield (1939) 

as diagnostic of his Buff and Brown zone. Wissler and 

Dreyer (1943) referred to their corresponding faunal unit as 

Foram zone 4, the Baggina californica zone (earliest 

Mohnian). The assignment of my sample to the lowermost 

Mohnian is supported by its stratigraphic position, the concurrence of the three species noted above, and the absence 

of the characteristic Luisian association (mentioned for the 

three subjacent samples) in this otherwise rich and diverse 

assemblage. Canfield (1939) described the lithology of his 

Buff and Brown zone as "a series of moderately hard 

interbedded chocolate-brown semiplaty foraminiferal and 

buff-colored phosphatic shales."

The Luisian and earliest Mohnian foraminiferal ages 

determined for the lower part of the Monterey Formation at 

Mussel Rock are congruous with the younger siliceous microfossil datums recognized in the overlying section. 

Cyrtocapsella tetrapera (Haeckel), a radiolarian with a last 

appearance datum of about 12.7 to 12.4 Ma (Nigrini and 

Lombari, 1984), occurs in sample CRC-40398-10 (W.H. 

Akers, oral commun., 1984), indicating that the lower part 

of the upper calcareous-siliceous member of the Monterey 

Formation at Mussel Rock is concurrent with the lower part 

of the Mohnian.

DEPOSITIONAL PALEOENVIRONMENT

On the basis of its Eocene to Holocene occurrences 

and associations, "Siphogenerina" is considered to be an 

indicator of warm climatic regions (Kleinpell, 1938). Its last 

appearance datum in California is accompanied by the disappearance of many other warm-temperate to subtropical 

taxa at the Luisian-Mohnian boundary and their replacement by cold-temperate to subpolar species. Isotopic studies on deep-sea benthic foraminifers (for example, Savin 

and others, 1981) provide evidence that a global cooling 

trend commenced in the middle Miocene.

Paleobathymetries for the Neogene of California are 

determined from the upper depth limits of benthic foraminifers listed by Ingle (1980, 1985). Several species in my 

Monterey Formation assemblages indicate basin-floor deposition at lower middle-bathyal depths (1,500-2,000 m) 

Anomalinoides salinasensis, Gyroidina rosaformis, 

Nodogenerina sagrinensis, and Pullenia miocenica. Although neritic indicators are present, the composite assemblage consists primarily of bathyal species. Mixed associations of this sort are typical in the Monterey Formation and 

indicate that most of the mudstones that constitute the 

Monterey Formation are turbidites (see Ingle, 1980, 1985). 

Although the rare specimens of Gyroidina rosaformis 

and Siphonodosaria advena in the Point Sal Formation suggest deposition at depths similar to that of the Monterey 

Formation, their associated mixed assemblages predominantly consist of transported shelf species. Thus, the 

paleoenvironment of deposition for both formations is lower 

middle bathyal, but their primary sources of sediment differ. In general, proximal turbidite sequences of sand and 

silt constitute the Point Sal Formation, whereas distal turbidites and hemipelagites constitute the very fine grained 

sediments of the Monterey Formation. Laminations in most 

Monterey Formation rocks, including three of the foraminiferal samples from Mussel Rock (CRC-40398-2, -3, -4), 

are indicative of low-oxygen bottom waters in the depositional basin.

SYNOPSIS

Foraminifers recovered from the Point Sal and 

Monterey Formations at Mussel Rock provide useful data 

on the age and depositional history of the Santa Maria basin. Studies of foraminiferal assemblages isolated from the 

rocks and thin sectioned in petrographic slides indicate that 

(1) proximal silt and sand turbidites in the Point Sal Formation were deposited at bathyal depths greater than 1,500 m 

during the Relizian (latest early and earliest middle Miocene) 

and (2) distal mud turbidites in the phosphatic member of 

the lower Monterey Formation were deposited at similar 

bathyal depths during the Luisian (early middle Miocene) 

and earliest Mohnian (late middle Miocene). These foraminiferal data complement younger siliceous microfossil 

datums determined from the superjacent strata of the 

Monterey and Sisquoc Formations.

LIONS HEAD SECTION

GEOGRAPHIC LOCATION

Lions Head is a prominent knoll located 8 km southeast of Point Sal along the coastline southwest of Santa Maria 

(figs. 1 and 8). The sampled section is located along the 

beach just south of this knoll (fig. 8) and is within the confines of the Vandenberg Air Force Base. The section is part 

of the northeast flank of a syncline (Woodring and Bramlette, 

1950) and consists of the phosphatic and upper calcareoussiliceous members of the Monterey Formation. Upsection 

(northwest along the coastline), the basal exposure of the 

phosphatic member is in fault contact with the Point Sal 

ophiolite of Hopson and Frano (1977; figs. 8 and 9).

L10 Evolution of Sedimentary Basins/Onshore Oil and Gas Investigations Santa Maria Province
PREVIOUS WORK

The Lions Head section has received mention in other 

reports on the geology and paleontology of the Santa Maria 

district, notably Woodring and Bramlette (1950), Pisciotto 

(1981), Pisciotto and Garrison (1981), Grivetti (1982), 

Compton and Siever (1984), Wornardt (1986), Dunham and 

Blake (1987), MacKinnon (1989b), White (1989), and 

Dunham and Cotton-Thornton (1990).

Although they had studied foraminiferal sequences 

elsewhere in the Santa Maria basin, neither Kleinpell (1938), 

Canfield (1939), Wissler and Dreyer (1943), nor Woodring 

and others (1943) mentioned Lions Head. However, 

Woodring and Bramlette (1950, p. 21-22 table) provided 

data on the foraminiferal assemblages in three samples (their 

10, lOa, lOb) from the lower section, which they identified 

as the lower member of the Monterey Formation.

Without presenting any detailed biostratigraphy, 

Dunham and Blake (1987) identified 13 foraminiferal species in "the lower Monterey section" at Lions Head (the 

section below the sand-covered section) and correlated them 

with the late Relizian and upper to middle-bathyal water 

depths. Although the Luisian is not mentioned in their description of the sequence, they noted that the middle 

Monterey Formation section (the section above the sandFigure 8. Map of sample localities in the Monterey Formation, 

Lions Head section. Sample numbers refer to CRC-40471 

collection. Some intermediate numbers not plotted for clarity. 

See figure 1 for section location.

covered section) is within the Denticulopsis hustedtii-D. 

lauta subzones (c) to (a), indicating an early Mohnian age. 

In a subsequent paper, Dunham and Cotton-Thornton (1990) 

presented limited biostratigraphic data for three Lions Head 

samples: (1) Their oldest age-diagnostic assemblage, which 

occurs 42 ft above the base of the section, is correlated with 

the Relizian on the basis of Siphogenerina branneri and 

Valvulineria robusta, (2) a foraminiferal assemblage recovered from approximately 35 ft below the top of the lower 

section is assigned to the Luisian on the basis of occurrences 

of Suggrunda kleinpelli, Hemicristellaria beali, and 

Anomalina salinasensis, and (3) a sparse population of 

Uvigerinella californica from another sample about 120 ft 

higher in the stratigraphic section is interpreted as possibly 

Luisian. Although all six of the aforementioned species range 

into the Saucesian of coastal California (Finger, 1992), M.L. 

Cotton (oral commun., 1993) confirmed that the ages assigned to these three assemblages are based on strict correlation with the foraminiferal sequences in the stratotypes 

(see Billman and Hopkins, 1980).

Wornardt (1986; also see Grivetti, 1982) recognized 

two diatom datums in the upper part of the Lions Head section utilizing the methodology later published by Lagle 

(1984) for recovering siliceous microfossils (diatoms, radiFeet

900-

600<

folded above

: ;.;"<: Upper :H->; 

/.Calcareous-V; 

 ;{'. Siliceous^//; 

.; ;' . Member :; ' :.-;

CRC-40471

:»

-16 

15 

14

Interval 

Covered

Monterey 

Formation 30°

Point Sal 

Ophiolite

Phosphatic 

Member

v r Fault

 ^

-12

-11

10

-9

-8

-7

-6 

5 

4 

3 

2 

1

Upper Calcareous-Siliceous Member 

Phosphatic Member 

Point Sal Ophlollte

Figure 9. Stratigraphic column of Lions Head 

section denoting positions of collected samples 

(CRC-40471 collection).

Recognition of Middle Miocene Foraminifers in the Monterey Formation, Santa Maria Province, California L11
olarians, and silicoflagellates) from dolostones. White (1989) 

also identified diatoms in this part of the Lions Head section. Although the laboratory at Chevron Oil Field Research 

Company attempted similar processing, none of my samples 

yielded any siliceous microfossils.

COLLECTIONS

In June 1983, G.L. Armstrong and I collected 18 

samples (CRC-40471 collection) from the 995-ft stratigraphic section of the Monterey Formation at Lions Head 

(figs. 8 and 9). Lithologic descriptions of the samples and 

designation of those selectively processed for foraminifers 

are given in appendix B. An apparent discrepancy between 

our stratigraphic measurements and those of Dunham and 

Blake (1987) has not been resolved.

RECOVERY AND PRESERVATION

Foraminifers are present in all of the thin sections prepared from the phosphatic member of the Monterey Formation at Lions Head. The abundance of foraminifers in these 

rocks is similar to that evident in the semiquantitative data 

presented by Woodring and Bramlette (1950).

The foraminifers illustrated in scanning electron micrographs (pi. 20) are typical of those isolated from the Lions Head section by conventional processing. As previously 

noted, the recovered specimens are very poorly preserved, 

and most could not be completely freed from the indurated 

mudstone matrix. Few species are recognizable in this condition. Chemical analyses (figs. 10-14) reveal that the specimens are composed primarily of calcite, although it is questionable whether any of the original shell material remains. 

The tests appear to be partially dissolved and (or) recrystal4000--

0 4567 

KILO ELECTRONVOLTS

8 10

Figure 10. Chemical analysis of test wall of Pullenia miocenica specimen from Lions Head section, sample CRC-40471-6. 

Ca peaks indicate that it is composed of calcite. Other element peaks indicate sediment contaminants (Si) and plug (Cu) and 

coating (Au) used for scanning electron microscopy.

L12 Evolution of Sedimentary Basins/Onshore Oil and Gas Investigations Santa Maria Province
lized, with infillings mostly of calcite. In some cases, the 

infillings include aggregates of pyrite framboids (fig. 14).

FAUNAL ASSEMBLAGES

Analysis of the Lions Head fauna is based almost exclusively on the examination of petrographic slides. Twentyfive species of Foraminifera are identified in the present 

study (table 2). In comparison, Woodring and Bramlette 

(1950, p. 21-22) listed 33 benthic and 1 planktic species 

isolated from three samples from this section. Their larger 

list and recognition of seven bolivinid species suggests that 

they examined better-preserved assemblages collected from 

less-indurated strata. Because Woodring and Bramlette list 

only fossiliferous sample localities, I do not know how many 

indurated and nonfossiliferous samples may have been excluded from their report.

BIOSTRATIGRAPHY

As noted in the previous discussion of the Mussel Rock 

section, it appears that Woodring and others (1943) and 

Woodring and Bramlette (1950) correlated the lower member of the Monterey Formation primarily, if not entirely, on 

Kleinpell's (1938) Siphogenerina biostratigraphy. They 

similarly interpreted the lower member of the Monterey 

Formation in the Santa Maria district as late Relizian through 

Luisian, with "5. branneri common in the lower part and 5. 

collomi in the upper part," but neither report offered refined 

ages for individual assemblages. In reference to Woodring 

and Bramlette's (1950) checklist, Kleinpell (1980, p. 33) 

noted, "From the lower member of the overlying Monterey 

(p. 21-22, 100, 137) come seven assemblages, again not 

stratigraphically allocated but, with only one exception (lOb, 

"not plotted"), showing conflicting evidence." The commas 

in this statement appear misplaced, for only the lOb assem4000--

3500--

3000--

2500 

c/)

2000--

O 

O

1500--

1000--

500--

4567 

KILO ELECTRONVOLTS

B 10

Figure 11. Chemical analysis of infilling of Rectuvigerina branneri specimen from Lions Head section, sample CRC-40471- 

6. Ca peaks indicate that it is composed of calcite. Other element peaks represent sediment contaminants (Si) and plug (Cu) 

and coating (Au) used for scanning electron microscopy.

Recognition of Middle Miocene Foraminifers in the Monterey Formation, Santa Maria Province, California L13
blage from Lions Head lists the most obvious conflict of 5. 

branneri and 5. collomi, and Kleinpell (1980, p. 28) refuted 

the identification of 5. collomi. Woodring and Bramlette's 

(1950) checklist included many other species associations 

that defy KleinpelFs scheme, but Kleinpell did not discuss 

those taxa nor did he assign specific ages to any of Woodring 

and Bramlette's (1950) assemblages.

Dominant species in the present study's Lions Head 

composite assemblage include Anomalinoides salinasensis, 

Nodogenerina sagrinensis, and Pullenia miocenica. 

Rectuvigerina branneri is less common but nonetheless most 

conspicuous. The overall fauna is similar to the benthic foraminiferal thanatofacies noted by Woodring and others 

(1943), Woodring and Bramlette (1950), Dunham and Blake 

(1987), and Dunham and Cotton-Thornton (1990) for the 

lower member of the Monterey Formation in this region. 

Regional biostratigraphic ranges (see Finger, 1990, 1992) 

indicate that all of the assemblages documented by these 

authors are characteristic of both the Relizian and Luisian 

stages; however, when species acmes are considered (see

Finger, 1992), the concurrence of Anomalinoides 

salinasensis and Pullenia miocenica in the upper part of the 

lower section at Lions Head (sample localities CRC-40471- 

6 through -12) suggest a Luisian age. The meager assemblages characteristic of the lower part of the section are less 

definitive. Woodring and Bramlette's (1950) recovery of 

Anomalinoides salinasensis and Pullenia miocenica from 

all three of their Lions Head samples, including their lowest sample, which they assigned to the lower part of the 

lower member of the Monterey Formation, may be evidence 

of a Luisian age for the entire foraminiferal sequence. As 

noted above, Dunham and Cotton-Thornton (1990) correlated the lower member of the Monterey Formation with 

the type Relizian, but their adoption of Kleinpell's (1938) 

method of interbasinal benthic zonation is dubious (see Finger, 1990). Subdividing the Lions Head sequence into substages or biozones would not appear to be possible, let alone 

meaningful.

On the basis of lithology and paleontology, the phosphatic member of the Monterey Formation at Lions Head

4000- -

3500--

4567 

KILO ELECTRONVOLTS

8 10

Figure 12. Chemical analysis of test wall of Lenticulina smileyi specimen from Lions Head section, sample CRC-40471-6. 

Ca peaks indicate that it is composed of calcite. Other element peaks represent sediment contaminants (Si) and plug (Cu) 

and coating (Au) used for scanning electron microscopy.

L14 Evolution of Sedimentary Basins/Onshore Oil and Gas Investigations Santa Maria Province
resembles Canfield's (1939) Dark Brown zone and Wissler 

and Dreyer's (1943) Foram zone 5, the Siphogenerina 

collomi-Siphogenerina nuciformis Zone, which I correlate 

with the early Luisian stage and the lower part of the phosphatic member at Mussel Rock. The upper part of the phosphatic member is not exposed at Lions Head; hence, I did 

not recover the early Mohnian thanatofacies recognized at 

Mussel Rock. The faunal similarity and close proximity of 

the Lions Head and correlative Mussel Rock sections suggests that these sediments may have been deposited as part 

of the same lower middle-bathyal facies that characterized 

the floor of the Santa Maria basin during the early middle 

Miocene.

Although Luisian foraminiferal assemblages have 

been recognized within the latest early to early middle Miocene interval of approximately 17 to 11 Ma on the basis of 

their associations with calcareous nannofossils (Crouch and 

Bukry, 1979; Arnal and others, 1980), correlation with the 

calcareous nannofossil and diatom zonations of its stratotype 

places the Luisian in the early middle Miocene, about 15.7

to 13.8 Ma. Unfortunately, time-significant planktic foraminifers are rarely encountered in the Miocene of California and the Lions Head section is no exception. By multiplying the thickness of strata by an estimated rate of 

deposition, Srivastava (1984) calculated that the lower 70 

m (210 ft) of the Lions Head section, which yielded "early 

to middle Miocene" palynomorph assemblages, should date 

at about 16 to 15 Ma. This age range straddles the RelizianLuisian boundary.

In Grivetti's (1982) regional study, C.W. Lagle extracted diatoms from two dolostone samples in the 274 to 

275-m (899 to 902 ft) interval of the Lions Head section, 

which W.W. Wornardt identified as the Denticulinopsis 

hustedtii-Denticulinopsis lauta Zone, with the higher sample 

assigned to subzones (b) and (c). This zonal assignment is 

supported by White's (1989) analysis of diatoms in the lower 

65 m of the upper Lions Head section. In the middle latitudes, subzones (b) and (c) range from 12.6 to 8.9 Ma, within 

the interval of planktic foraminiferal zones N12 to N15. 

Therefore, it can be concluded that at least part of the upper

z

D

O 

O

4000 

3500--

300B--

2500--

2000 

1500-

1000-

500--

0 4567 

KILO ELECTRONVOLTS

8 10

Figure 13. Chemical analysis of test infilling of Lenticulina smileyi specimen shown in figure 12. Ca peaks indicate that it is 

composed of calcite. The small Fe and S peaks indicate pyrite, probably beneath the calcite surface. Other element peaks 

represent sediment contaminants (Si) and plug (Cu) and coating (Au) used for scanning electron microscopy.

Recognition of Middle Miocene Foraminifers in the Monterey Formation, Santa Maria Province, California L15
calcareous-siliceous member of the Monterey Formation at 

Lions Head is late middle Miocene. Although foraminifers 

were not recovered from these rocks, the diatom horizons 

correlate with rocks of the lower Mohnian benthic foraminiferal stage. Thus, the Relizian-Luisian age determined for 

the lower Lions Head section makes stratigraphic sense and 

the Luisian/Mohnian boundary is buried.

DEPOSITIONS. PALEOENVIRONMENT

According to Ingle (1980, 1985), Anomalinoides 

salinasensis, Gyroidina rosaformis, Nodogenerina 

sagrinensis, and Pullenia miocenica are among the deepest-dwelling paleobathymetric marker species in the Lions 

Head fauna. As concluded for the correlative part of the 

Mussel Rock section, most of the phosphatic member of 

the Monterey Formation at Lions Head was deposited as 

mud turbidites and hemipelagites at lower middle-bathyal 

depths (1,500-2,000 m). The Luisian benthic foraminiferal

fauna suggests prevailing subtropical to warm-temperate 

waters. Laminated sediments common throughout much of 

the Lions Head section indicate that low-oxygen conditions 

prevailed in the depositional paleoenvironment during the 

middle and late Miocene.

SYNOPSIS

The phosphatic member of the Monterey Formation 

at Lions Head contains a relatively warm-water lower 

middle-bathyal Relizian (upper lower Miocene)? to Luisian 

(lower middle Miocene) foraminiferal thanatofacies. The 

composite assemblage is most similar to the Luisian 

thanatofacies recovered from the lower part of the phosphatic member at Mussel Rock with which it is correlated. 

The upper part of the phosphatic member is not exposed at 

Lions Head; therefore, early Mohnian foraminifers similar 

to those recognized at Mussel Rock were not recovered. The 

overlying upper calcareous-siliceous member of the

4000- -

3500--

3000--

2500--

0)

O 

o

2000+

1500

1000-

500-

0 4567 

KILO ELECTRONVOLTS

10

Figure 14. Chemical analysis of pyrite (FeS2) framboids infilling Lenticulina smileyi specimen shown in figure 12. Test is 

composed of calcite, indicated by Ca peaks. Other element peaks represent sediment contaminants (Si) and plug (Cu) and 

coating (Au) used for scanning electron microscopy.

L16 Evolution of Sedimentary Basins/Onshore Oil and Gas Investigations Santa Maria Province
Table 2. Foraminifera species checklist, Monterey Formation, 

Lions Head section (CRC-40471 collection)

[Solid boxes denote presence of species]

Monterey Formation at Lions Head is devoid of foraminifers, but diatom datums indicate that part of this member is 

concurrent with the early Mohnian (late middle Miocene).

PREVIOUS WORK

Since the discovery of the Point Arguello Oil Field in 

1981 (see Grain and others, 1985), the stratigraphy of the 

nearby Rodeo Canyon section has been viewed as having 

particular significance. Until recently, however, the Rodeo 

Canyon section had rarely been mentioned in the regional 

literature, perhaps because of its relative inaccessibility and 

its location on the fringe of the Santa Barbara-Ventura basin. Although Arnold and Anderson (1907, pi. 1) and Dibblee 

(1950, pi. 1) plot the Monterey Formation along this part of 

the California coastline on their regional maps, they do not 

specifically refer to this section in text. Prior to the U.S. 

Geological Survey Bulletin 1995 series, published studies 

involving the Rodeo Canyon section included studies on 

dolomites by Compton and Siever (1984), paleomagnetic 

stratigraphy by Hornafius (1985) and Hornafius and others

(1986), diatom biostratigraphy by Wornardt (1986), and 

phosphorites and phosphatic rocks by Garrison and others

(1987).

Using Lagle's (1984) technique for extracting diatoms 

from dolomites, Wornardt (1986) determined that two 

samples in the upper part of the Rodeo Canyon section were 

within the Denticulopsis lauta-Denticulopsis hustedtii Zone, 

subzones (b) to (d). These subzones range from 12.6 to 8.4 

Ma in age and correlate with the lower Mohnian to lowest 

upper Mohnian benthic foraminiferal stage.

RODEO CANYON SECTION 

GEOGRAPHIC LOCATION

This coastal locality is situated on Vandenberg Air 

Force Base property, 4 km southeast of Point Arguello and 

about 25 km southwest of Lompoc (fig. 1). The stratigraphic 

section investigated extends westward from the mouth of 

Canada del Rodeo, for which it is named (fig. 15). This section has been also referred to as "Boathouse Beach" because 

of the building situated at its western end.

Although previous studies included the Rodeo Canyon section within the Santa Maria province, it is probably 

within the western end of the Santa Barbara embayment. 

This is because (1) it is situated southeast of the Arguello 

High (see Fischer, 1976; Isaacs, 1981), (2) the Tranquillon 

Volcanics (Hornafius and others, 1982) consist here of altered water-lain tuff, whereas at Point Pedernales, just north 

of Point Arguello, they are composed of welded tuffs and 

rhyolite agglomerate, and (3) the mudstones of the upper 

Oligocene-lower Miocene Rincon Formation, which represent the initial deep-water subsidence of the Santa Barbara 

embayment, are exposed in Canada del Rodeo (Dibblee, 

1950).

' Boathouse Area

Vandenberg Air Force Base

15 '? "

Pacific Ocean

Meters 

500

1000 2000 

Feet

Figure 15. Sample locality map of Rodeo Canyon section. 

Sample numbers refer to CRC-40661 collection. Some 

intermediate numbers not plotted for clarity. See figure 1 for 

section location.

Recognition of Middle Miocene Foraminifers in the Monterey Formation, Santa Maria Province, California L17
COLLECTIONS

At least 1,038 ft (316 m) of the Monterey Formation 

disconformably overlies the Tranquillon Volcanics flanking the mouth of Canada del Rodeo (fig. 16). Complex structure and unexposed intervals render detailed measurement 

of the superjacent stratigraphic section impossible. Although 

the lower calcareous-siliceous and upper calcareous-siliceous members of the Monterey Formation are recognizable here, an intermediate interval lacks the diagnostic lithology (for example, predominantly phosphatic mudstones 

and dolostones) of the phosphatic member and instead has 

an atypical abundance of porcellanite and chert. Because it

folded above

CRC-40661

-16

Interval folded and 

possibly faulted; 

stratigraphic 

relationships 

uncertain.

Monterey 

Formation

Feet

900-

600-

300-

Tranquillon 

Volcanics

Upper Calcareous-Siliceous Member 

Lower Calcareous-Siliceous Member 

Tranquillon Volcanics

Figure 16. Stratigraphic column of Rodeo 

Canyon section denoting positions of collected 

samples (CRC-40661 collection). "Phosphatic 

member" interval is stratigraphically positioned 

where the phosphatic member should be, but it 

is more transitional than distinct from the 

adjacent members.

is lithologically transitional between the subjacent and 

superjacent members, this part of the section is instead referred to as the "phosphatic member" interval (fig. 16).

In August 1983, G.L. Armstrong and I collected 15 

samples (CRC-40661-1 to -15) from the Rodeo Canyon section and obtained an additional sample (CRC-40661-16) 

collected by T.C. MacKinnon for microfossil analyses (figs. 

15 and 16). Although only the basal sample (CRC-40661- 

1) revealed foraminifers at low magnification in the field 

and laboratory, another relatively soft sample (CRC-40661 - 

6) was also selected for processing using the conventional 

laboratory washing method designed to isolate foraminifers 

from clastic rocks. Lithologic descriptions of the samples 

and designation of those selectively processed for foraminifers are given in appendix C.

RECOVERY AND PRESERVATION

Foraminifers were recovered only from the pelletal 

phosphorite (sample CRC-40661-1) near the base of the 

Rodeo Canyon section. The unevenly distributed specimens 

are obscured by pelletal encasements of cellophane or by 

the phosphatic matrix (fig. 17; pis. 34-37) and the specimens themselves are composed of cellophane (fig. 18). 

Examination of petrographic slides makes it possible to view 

these hidden specimens (pis. 38-46).

FAUNAL ASSEMBLAGE

Nineteen species of Foraminifera are identified in the 

eight petrographic slides made from sample CRC-40661-1 

(table 3). /tecfwv/gen'wa branneri and Protoglobobulimina 

pseudotorta dominate the assemblage. Also common are 

Anomalinoides salinasensis, Pullenia miocenica, and 

Valvulineria robusta.

BIOSTRATIGRAPHY

The benthic foraminiferal assemblage recovered from 

the base of the Rodeo Canyon section is immediately recognizable as part of the warm-temperate to subtropical 

Relizian to Luisian fauna, particularly by the conspicuous 

presence of Rectuvigerina branneri. The concurrence of 

Anomalinoides salinasensis, Cancris baggi, Pullenia 

miocenica, and Valvulineria californica suggests that this 

assemblage is Relizian to Luisian in age (Kleinpell, 1938; 

Finger, 1992). The common occurrence in this association 

of Valvulineria robusta, which most frequently occurs in 

the Relizian (Kleinpell, 1938; Finger, 1992) and characterizes the Relizian stratotype (Billman and Hopkins, 1980), 

suggests that the assemblage is of late Relizian age rather 

than Luisian age. Although KleinpeH's (1938) restriction of

L18 Evolution of Sedimentary Basins/Onshore Oil and Gas Investigations Santa Maria Province
Cancris baggi to the late Relizian would seem to support 

this, I have recovered both Valvulineria robusta and Cancris 

baggi from rocks of Saucesian, Relizian, and Luisian age 

(Finger, 1992). Overall, the assemblage is very similar to 

those recovered from the phosphatic member of the 

Monterey Formation at Mussel Rock and Lions Head, assemblages which are interpreted herein as Luisian in age. 

Lack of a more complete foraminiferal sequence in the Rodeo Canyon section precludes refining the age determination for the pelletal phosphorite (sample CRC-40661-1), 

especially because the Relizian and Luisian stages often are 

difficult to differentiate. Under these circumstances, and for 

reasons discussed below, I am inclined to place the basal 

exposure of the Rodeo Canyon section within the late 

Relizian to early Luisian interval.

Although the sequence of porcelanites and dolostones 

in the lower part of the Rodeo Canyon section differs from 

the lithology of Canfield's (1939) Dark Brown zone, which 

is characterized by phosphatic shales, their respective 

biofacies are similar. Wissler and Dreyer (1943)

biostratigraphically referred to Canfield's (1939) unit as 

Foram zone 5, the Siphogenerina collomi-Siphogenerina 

nuciformis zone, and correlated it with the Luisian stage. 

Woodring and others (1943) and Woodring and Bramlette 

(1950) described similar sections in the Santa Maria basin 

as part of their lower member of the Monterey Formation, 

to which they apply an age of late Relizian and Luisian. 

None of these previous workers in the Santa Maria area, 

however, included the Rodeo Canyon section in their studies. Pisciotto (1981, fig. 3) correlates the Dark Brown zone 

with the upper part of his calcareous facies and the lower 

part of his phosphatic facies. I similarly relate the corresponding faunal zone to the transitional "phosphatic member" (fig. 16).

The Tranquillon Volcanics, which underlie the 

Monterey Formation at Rodeo Canyon, have an age of 

17±1.2 Ma near the Santa Ynez River (Turner, 1970), approximately 32 km to the east. On the basis of adjacent foraminiferal sequences in the Santa Barbara basin, Kleinpell 

and Weaver (1963, fig. 2) placed the Tranquillon Volcanics

4000--

3500 

3000- 

2500- 

CO

2000- 

O 

O

1500--

1000--

500--

12345 

KILO ELECTRONVOLTS

Figure 17. Chemical analysis of outer surface of phosphatic pellet (with foraminifer nucleus) from Rodeo Canyon section, 

sample CRC-40661-1. Ca and P peaks indicate that pellet is composed of cellophane. Other element peaks represent 

sediment contaminants (Si) and plug (Cu) and coating (Au) used for scanning electron microscopy.

Recognition of Middle Miocene Foraminifers in the Monterey Formation, Santa Maria Province, California L19
within the late Saucesian, whereas Carson (1965) interpreted 

it as the Saucesian-Relizian boundary. The latter correlation had been established previously by the Standard Oil 

Company of California, as noted by Dibblee (1950). More 

recently, DePaolo and Finger (1991) used high-resolution 

strontium isotope chronostratigraphy and biostratigraphy to 

determine that the age of the basal Monterey in the Salinas 

and Ventura basins is 17.85±0.10 Ma. In the Rodeo Canyon 

section, however, the contact between the Tranquillon 

Volcanics and Monterey Formation appears to be erosional, 

and the superjacent foraminiferal assemblage indicates that 

a substantial period of depositional time is missing here.

The late Relizian to early Luisian foraminiferal age 

for the basal part of the exposure at Rodeo Canyon is supported by three diatom datums recognized in overlying strata 

(RJ. Navarrette, oral commun., 1984). Sample locality CRC40661-8 in the basal part of the "phosphatic member" is 

within Denticulopsis lauta subzone (b), which has an age 

range of 15.0 to 13.7 Ma and correlates with the late Luisian. 

In the superjacent upper calcareous-siliceous member, 

sample localities CRC-40661-13 and -15 are within

2000--

Denticulopsis hustedtii-Denticulopsis lauta subzones (b) and 

(c), respectively. This interval has an age range of 13.5 to 

1 1.0 Ma and correlates for the most part with the early 

Mohnian or late middle Miocene.

DEPOSITIONAL PALEOENVIRONMENT

Although the number of observable specimens and 

recognizable species are limited by the preservational state 

of the foraminiferal assemblage recovered from Rodeo Canyon, the recognized taxa appear to be sufficient for an interpretation of the depositional paleoenvironment. 

Anomalinoides salinasensis, Gyroidina rosaformis, and 

Pullenia miocenica are listed by Ingle (1980, 1985) as species with upper-depth limits within the lower middle-bathyal 

zone (1,500-2,000 m), indicating that they were deposited 

within this depth interval.

The sedimentology of the pelletal phosphorite has significant implications in the depositional history of the lower 

Rodeo Canyon section. In the Miocene of California, pelletal

1600--

1200- 

CO

O 

o

800--

400--

0 2 3 

KILO ELECTRONVOLTS

Figure 18. Chemical analysis of internal mold of Protoglobobulimina pseudoaffinis specimen encased within phosphatic 

pellet shown in figure 17. Ca and P peaks indicate that mold is composed of cellophane. Other element peaks represent 

sediment contaminants (Si) and plug (Cu) and coating (Au) used for scanning electron microscopy.

L20 Evolution of Sedimentary Basins/Onshore Oil and Gas Investigations Santa Maria Province
Table 3. Foraminiferal assemblage in 

pelletal phosphorite sample (CRC-40661- 

1), Monterey Formation, Rodeo Canyon 

section

FORAMINIFERA SPECIES

Anomalinoides salinasensis 

Bolivina advena? 

Buliminella subfusiformis 

Cancris baggi 

Globigerina bulloides 

Globigerina pseudociperoensis 

Globigerina sp.? 

Gyroidina rosaformis 

Islandiella modeloensis 

Lenticulina smileyi 

Marginulinopsis beali 

Praeglobobulimina galliheri 

Protoglobobulimina pseudotorta 

Pseudoparrella subperuviana 

Pullenia miocenica 

Rectuvigerina branneri 

Siphonodosaria quadrulata 

Valvulineria californica 

Valvulineria robusta

phosphorite is often present in strata representing the initial 

downwarping of a basin. Although their internal contents 

are rarely observed, cellophane pellets bearing California 

Miocene foraminifers as their nuclei have previously been 

recorded off southern California (Dietz and others, 1942) 

and in the lowermost Graves Creek section near Atascadero, 

San Luis Obispo County, Calif. (Graham, 1980). I also have 

found them in the lower part of the Monterey Formation on 

San Clemente Island and in the lower Rincon Formation 

along Los Sauces Creek, Ventura County, Calif. (Finger, 

1983).

Although it has been postulated that pelletal phosphorite originates as fecal pellets of indiscriminate deposit feeders (Dietz and others, 1942), the mechanism of its deposition remains unclear (Bentor, 1980; Baturin, 1982). Ingle 

(1980) states that pelletal phosphorite accumulates at the 

upper (200-500 m) and lower (1,000-1,500 m) boundaries 

of the intersection between the oxygen-minimum zone and 

continental slope or basin sill. Pisciotto and Garrison (1981) 

and Garrison and others (1987, 1990) noted that veneers of 

pelletal phosphorite tend to form on sediment-starved isolated bank tops at the fringes of the oxygen-minimum zone 

and may be redeposited as basin-floor turbidites. Garrison 

and others (1987) classified the basal lithofacies of the 

Monterey Formation at Rodeo Canyon as a banktop 

glaucophosphorite.

The upper-depth limits (see Ingle, 1980,1985) of the 

encased foraminifers at Rodeo Canyon suggest that the pellets probably formed near the 1,500-m lower edge of the 

oxygen-minimum layer. The phosphorite is unsorted and 

overlain by laminated rocks, implying that it was displaced 

into the deeper basin by slumping off an adjacent bank. The 

laminated rocks that predominate above the phosphorite in 

the Rodeo Canyon section are evidence that low-oxygen (< 

0.1 mL/L) bottom conditions existed in the depositional 

basin (see Ingle, 1980, 1985). These conditions are attributed to the intersection of the oxygen-minimum layer with 

the basin sill (see Ingle, 1980, 1985; Blake, 1981; Pisciotto 

and Garrison, 1981). On the basis of field relationships and 

regional histories (see Ingle, 1980,1985), the initial subsidence of the basin, the development of low-oxygen bottom 

waters, and the slumping of bank sediments were almost 

concurrent events.

SYNOPSIS

At Rodeo Canyon, foraminifers are restricted to a lens 

of pelletal phosphorite in the basal part of the lower calcareous-siliceous member of the Monterey Formation. Thinsection study and lithostratigraphic correlation reveal that 

the foraminiferal assemblage is most diagnostic of the late 

Relizian (latest early and earliest middle Miocene) to early 

Luisian (early middle Miocene) interval. This conclusion 

suggests that the Rodeo Canyon assemblage is slightly older 

than the foraminiferal assemblages recovered from the phosphatic member at Mussel Rock and Lions Head. The lithologic and paleontologic evidence indicates that the phosphorite at Rodeo Canyon formed at a depth of approximately 

1,500 m on a bank that was intersected by the oxygen-minimum zone. Paleobathymetric marker species indicate subsequent redeposition in the lower middle-bathyal zone 

(1,500-2,000 m).

DISCUSSION

Two methods of sample processing were employed 

in this foraminiferal study. Samples were washed by conventional laboratory techniques through a 200-mesh (75 \im 

openings) screen to yield a sand residue from which isolated specimens were picked, sorted, and identified. Selected 

specimens are illustrated as scanning electron micrographs 

in plates 1 to 5, 20, and 34. Selected indurated mudstones 

that yielded foraminifers were also thin sectioned because 

most of the specimens could not be cleanly extracted nor 

were they well preserved. These samples were sectioned 

both parallel and perpendicular to bedding. From these, petrographic slides were prepared and then analyzed by comparing observed specimens with reference thin sections prepared by the technique of Finger and Armstrong (1984).

Recognition of Middle Miocene Foraminifers in the Monterey Formation, Santa Maria Province, California L21
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L22 Evolution of Sedimentary Basins/Onshore Oil and Gas Investigations Santa Maria Province
Identifying California Miocene foraminifers in thin 

section can be particularly difficult at the species level; admittedly, educated guesswork is often involved. Although 

the "Atlas of California Miocene Foraminifera" (Finger, 

1990) enhances one's ability to recognize these species in 

petrographic thin sections, actual application of the data in 

the atlas will always be confronted with the problems of 

differentiating morphologically similar species, as well as 

specimens that are partially dissolved, distorted, obscured, 

or fragmented. Minor misidentifications should not significantly affect interpretations if correlations are based primarily on associations of biostratigraphic marker species that 

are distinct and readily recognizable forms.

Scanning electron micrographs of the best preserved 

specimens isolated from the rocks and photomicrographs 

of most of the better preserved specimens recognized in the 

petrographic slides are shown on plates 1 to 43. This comprehensive set of illustrations enhances the reader's ability 

to comprehend the condition, composition, and interpretation of the Santa Maria fauna. The table 4 checklist is a 

convenient index to the 55 species figured on these plates.

SUMMARY

Foraminifers present in some of the highly indurated 

rocks from the Mussel Rock, Lions Head, and Rodeo Canyon sections can be identified in petrographic slides. Petrographic study reveals foraminiferal associations indicating 

(1) a Relizian-Luisian age for the lower calcareous-siliceous 

member of the Monterey Formation at Rodeo Canyon, (2) a 

Relizian-Luisian age for the lower part of the phosphatic 

member of the Monterey Formation at Lions Head, (3) a 

Luisian age for the upper part of the phosphatic member at 

Lions Head, (4) a Luisian age for the lower part of the phosphatic member at Mussel Rock, and (5) a Mohnian age for 

the upper part of the phosphatic member at Mussel Rock.

Paleobathymetric marker species indicate that the 

Luisian and Mohnian assemblages in the calcareous mudstones of the phosphatic member of the Monterey Formation are mixed associations deposited at lower middlebathyal (1,500-2,000 m) depths. The Relizian assemblage 

at Rodeo Canyon occurs in a pelletal phosphorite that initially formed on a sediment-starved bank at a water depth 

of about 1,500 m; it subsequently was redeposited at lower 

middle-bathyal depths.

The absence of foraminifers in most of the rocks 

sampled from the Mussel Rock, Lions Head, Point 

Pedernales, Rodeo Canyon, Sweeney Road, and Manville 

Quarry sections may be attributable to any or all of the following: (1) an elevated calcium-carbonate compensation 

depth, (2) early diagenetic dissolution and incorporation of 

test calcite into dolomite, and (or) (3) outcrop leaching. The 

lack of foraminifers in the lower Monterey Formation at

Point Pedernales is particularly perplexing because several 

assemblages were recovered from the coeval rocks at Mussel Rock, Lions Head, and Rodeo Canyon. Such local variations may reflect local differences in depositional 

paleoenvironments and (or) diagenesis.

REFERENCES

Akers, W.H., Marolt, R.E., and Navarrette, R.J., 1987, Late 

Miocene and early Pliocene siliceous microfossils from 

the upper Monterey and lower Sisquoc Formations, 

Sweeny Road, Santa Barbara County, California: Tulane 

Studies in Geology and Paleontology, v. 20, nos. 1-3, 

p. 1-112.

Arnal, R.E., Crouch, J.K., and Bukry, David, 1980, Comments and reply on "Comparison of Miocene Provincial Foraminiferal Stages to Coccolith Zones in the California Continental Borderland": Geology, v. 8, no. 1, p. 

2-5.

Arnold, Ralph, and Anderson, Robert, 1907, Geology and 

oil resources of the Santa Maria oil district, Santa Barbara County, California: U.S. Geological Survey Bulletin 322, 161 p.

Barron, J.A., 1975, Marine diatom biostratigraphy of the 

upper Miocene-lower Pliocene strata of southern California: Journal of Paleontology, v. 49, no. 4, p. 619- 

632.

 1976, Marine diatom and silicoflagellate biostratigraphy of the type Delmontian Stage and the type 

Bolivina obliqua Zone, California: U.S. Geological 

Survey Journal of Research, v. 4, no. 3, p. 339-351.

 1986a, Updated diatom biostratigraphy for the 

Monterey Formation of California, in Casey, R.E., and 

Barron, J.A., eds., Siliceous microfossil and microplankton of the Monterey Formation and modern 

analogs: Los Angeles, Pacific Section, Society of Economic Paleontologists and Mineralogists, p. 105-119. 

-1986b, Paleoceanographic and tectonic controls on

deposition of the Monterey Formation and related siliceous rocks in California: Palaeogeography, 

Palaeoclimatology, Palaeoecology, v. 53, p. 27-45.

Baturin, G.N., 1982, Phosphorites on the sea floor: Elsevier 

Scientific Publishing Company, Developments in Sedimentology 33, 343 p.

Bentor, Y.K., 1980, Phosphorites the unsolved problems, 

in Bentor, Y.K., ed., Marine phosphorites geochemistry, occurrence, and origin: Society of Economic Paleontologists and Mineralogists Special Publication, no. 

29, p. 3-18.

Billman, H.G., and Hopkins, A.A., Jr., 1980, The stratigraphic distribution of the Foraminifera at the type locality of the Luisian Stage, in Blake, G.H., ed., NeoRecognition of Middle Miocene Foraminifers in the Monterey Formation, Santa Maria Province, California L23
gene biostratigraphy of the northern La Panza Range, 

San Luis Obispo County, California: Los Angeles, Pacific Section, Society of Economic Paleontologists and 

Mineralogists, p. 1-9.

Blake, G.H., 1981, Biostratigraphic relationship of Neogene 

benthic Foraminifera from the Southern California 

Outer Continental Borderland to the Monterey Formation, in Garrison, R.E., and Douglas, R.G., eds., The 

Monterey Formation and related siliceous rocks of California: Los Angeles, Pacific Section, Society of Economic Paleontologists and Mineralogists, p. 1-14.

Canfield, C.R., 1939, Subsurface stratigraphy of Santa Maria 

Valley oil field and adjacent parts of Santa Maria Valley, California: American Association of Petroleum Geologists Bulletin, v. 23, no. 1, p. 45-81.

Carson, C.M., 1965, The Rincon Formation, in Carson, 

C.M., and Whaley, H.M., eds., Western Santa Ynez 

Mountains, Santa Barbara County, California: Coast 

Geological Society, Society of Economic Paleontologist and Mineralogists, Pacific Section, Guidebook, p. 

38-41, plus unnumbered pocket-figure.

Compton, J.S., and Siever, Raymond, 1984, Stratigraphy 

and dolostone occurrence in the Miocene Monterey Formation, Santa Maria Basin, California in Garrison, R.E., 

and others, eds., Dolomites of the Monterey Formation 

and other organic-rich units: Los Angeles, Pacific Section, Society of Economic Paleontologists and Mineralogists, p. 141-153.

Grain, W.E., Mero, W.E., and Patterson, Don, 1985, Geology of the Point Arguello discovery: American Association of Petroleum Geologists Bulletin, v. 69, no. 4, 

p. 537-545.

Crouch, J.K., and Bukry, David, 1979, Comparison of Miocene provincial foraminiferal stages to coccolith zones 

in the California Continental Borderland: Geology, v. 

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L24 Evolution of Sedimentary Basins/Onshore Oil and Gas Investigations Santa Maria Province
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Recognition of Middle Miocene Foraminifers in the Monterey Formation, Santa Maria Province, California L25
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Formation and modern analogs: Los Angeles, Pacific 

Section, Society of Economic Paleontologists and Mineralogists, Special Publication 45, p. 141-147.

APPENDIX A. MUSSEL ROCK SECTION 

LITHOLOGIC AND PROCESSING LOG OF 

SAMPLES

Lithologic descriptions of collected samples examined 

in the laboratory. Bedding thicknesses are defined as follows: laminated, <3 mm; thin bedded, 3 to 40 mm; massive, 

neither laminated nor bedded in hand sample and probably 

thick bedded (>40 mm) in field.

SAMPLES CRC-40398-1 TO -84

Note: Washed residues were prepared from the following samples, all of which were devoid of Foraminifera: 

1, 6, 7, 11, 14, 17, 22, 24, 29, 32, 36,40,44,48, 52, 56, 60, 

64, 68, 72, 76, 79.

POINT SAL FORMATION (SAMPLE 1)

(1) Top exposure: Massive greenish gray-brown slightly 

calcareous siltstone.

MONTEREY FORMATION 

(SAMPLES 2 THROUGH 62)

PHOSPHATIC MEMBER (SAMPLES 2 THROUGH 6)

(2) 0 ft: Light-brown thin-bedded calcareous mudstone. 

Washed residue and four thin sections prepared.

(3) 112 ft: Light-brown thin-bedded to laminated calcare^ 

ous mudstone. Washed residue and six thin sections 

prepared.

(4) 150 ft: Light-brown thin-bedded to laminated calcareous mudstone. Washed residue and four thin sections 

prepared.

(5) 195 ft: Light-brown thin-bedded to laminated calcareous mudstone. Washed residue and four thin sections 

prepared.

(6) 325 ft: Buff to dark-brown thin-bedded phosphatic siliceous mudstone and dark-brown dolomitic mudstone 

or dolostone.

L26 Evolution of Sedimentary Basins/Onshore Oil and Gas Investigations Santa Maria Province
UPPER CALCAREOUS-SILICEOUS MEMBER 

(SAMPLES 7 THROUGH 23)

(7) 390 ft: Buff to dark-brown thin-bedded phosphatic siliceous mudstone and light-brown thick-bedded 

porcellanite.

(8) 390 ft: Light-brown thin-bedded to weakly laminated 

dolomitic siliceous mudstone.

(9) 430 ft: Dark-brown massive to very faintly laminated 

dolostone or dolomitic porcellanite.

(10) 430 ft: Light-gray-brown poorly laminated to massive 

dolomitic siliceous mudstone or dolostone and darkbrown very faintly laminated siliceous mudstone.

(11) 480 ft: Medium-brown poorly thin-bedded siliceous 

mudstone and black laminated chert.

(12) 515 ft: Brown-gray massive medium dolostone.

(13) 530 ft: Medium-brown thin-bedded siliceous dolostone 

and medium-brown laminated siliceous mudstone.

(14) 590 ft: Buff- to dark-brown very thinly laminated phosphatic siliceous mudstone.

(15) 658 ft: Same as No. 14.

(16) 735 ft: Light-brown chert-laminated siliceous mudstone.

(17) 802 ft: Medium- to light-brown thinly laminated siliceous mudstone.

(18) 840 ft: Light-brown laminated dolomitic siliceous mudstone.

(19) 855 ft: White laminated and medium-brown laminated 

siliceous mudstone.

(20) 890 ft: Light-brown laminated siliceous mudstone.

(21) 924 ft: Light- to medium-brown laminated siliceous 

mudstone, light-brown dolomitic siliceous mudstone, 

and light-brown laminated chert.

(22) 950 ft: Light-brown laminated to thin-bedded siliceous 

mudstone and light-brown laminated siliceous mudstone.

(23) 975 ft: Same as No. 22 and dark-brown massive dolomitic porcellanite.

CLAYEY-SILICEOUS MEMBER (SAMPLES 24 THROUGH 62)

Owing to the structural discontinuity and complexity 

of the strata in the interval above sample 23, the following 

section was measured separately with its base at the cliff 

north of Mussel Rock (see fig. 5).

Note: Supplementary collection (CRC-43156) of 

seven samples from the siliceous member logged at end of 

appendix A.

(24) 85 ft: Same as No. 22.

(25) 95 ft: White and light-brown laminated siliceous mudstone.

(26) 135 ft: Light-brown faintly laminated dolomitic siliceous mudstone.

(27) 145 ft: Light-brown faintly laminated to massive siliceous mudstone, some of which tends toward 

porcellanite.

(28) 390 ft: Same as No. 27.

(29) 400 ft: Same as No. 27 but highly fractured.

(30) 410 ft: Same as No. 27 but with some porcellanite and 

asphalt in some fractures.

(31) 903 ft: Buff to light-brown laminated to thin-bedded 

siliceous mudstone.

(32) 930 ft: Same as No. 31.

(33) 980 ft: Light-gray laminated to thin-bedded porcellanite.

(34) 1020 ft: Light-brown laminated diatomaceous mudstone.

(35) 1030 ft: Medium-brown laminated to thin-bedded diatomaceous mudstone.

(36) 1045 ft: Same as No. 35 but slightly darker brown.

(37) 1185 ft: Same as No. 36.

(38) 1220 ft: Same as No. 36 but greenish gray to medium 

brown.

(39) 1228 ft: Same as No. 36.

(40) 1270 ft: Same as No. 36 and massive dark-gray to medium-brown diatomaceous mudstone.

(41) 1280 ft: Medium-greenish-brown massive to very 

faintly thin-bedded mudstone.

(42) 1290 ft: Medium-greenish-brown massive to very 

faintly thin-bedded mudstone.

(43) 1305 ft: Very faintly greenish-medium-brown laminated 

diatomaceous mudstone.

(44) 1350 ft: Same as No. 43.

(45) 1362 ft: Same as No. 43.

(46) 1375 ft: Medium-greenish-gray-brown laminated to 

thin-bedded diatomaceous mudstone.

(47) 1387 ft: Same as No. 43.

(48) 1400 ft: Medium-dark-greenish-brown laminated to 

thin-bedded diatomaceous mudstone.

(49) 1412 ft: Greenish-gray-brown laminated diatomaceous 

mudstone.

(50) 1470 ft: Light- to medium-brown laminated diatomaceous mudstone.

(51) 1480 ft: Same as No. 49.

(52) 1490 ft: Light- to medium-brown laminated to thinbedded diatomaceous mudstone.

(53) 1505 ft: Same as No. 52 but all laminated.

(54) 1525 ft: Same as No. 52 but all medium brown.

(55) 1545 ft: Same as No. 49.

(56) 1565 ft: Greenish-gray-brown faintly laminated to thinbedded diatomaceous mudstone.

(57) 1585 ft: Medium-brown laminated to thin-bedded diatomaceous mudstone.

(58) 1605 ft: Same as No. 57 but slightly more greenish.

(59) 1625 ft: Light- to medium-brown laminated diatomaceous mudstone.

(60) 1645 ft: Greenish-gray-brown laminated to thin-bedded diatomaceous mudstone.

(61) 1655 ft: Medium-greenish-gray faintly thin-bedded 

diatomaceous mudstone.

(62) 1663 ft: Light-brown laminated to thin-bedded diatomaceous mudstone.

Recognition of Middle Miocene Foraminifers in the Monterey Formation, Santa Maria Province, California L27
SISQUOC FORMATION 

(SAMPLES 63 THROUGH 78)

(63) 1671 ft: Two-foot-thick layer of glazed black 1/4- to 5- 

in-long phosphatic nodules embedded in grayish-brown 

diatomaceous mudstone; interior of nodules light-brown 

to buff with some orange staining.

(64) 1679 ft: Light-gray to buff massive diatomaceous mudstone or muddy diatomite.

(65) 1687 ft: Slightly green medium-gray massive diatomaceous mudstone.

(66) 1696 ft: Same as No. 65 but medium brown.

(67) 1705 ft: Light-brown massive diatomaceous siltstone.

(68) 1720 ft: Medium-greenish-gray massive diatomaceous 

mudstone.

(69) 1730 ft: Same as No. 68.

(70) 1740 ft: Same as No. 68.

(71) 1750 ft: Dark-greenish-gray massive diatomaceous siltstone.

(72) 1760 ft: Same as No. 71.

(73) 1770 ft: Same as No. 71 but light gray.

(74) 1785 ft: Buff massive diatomaceous(?) siltstone or silty 

mudstone.

(75) 1800 ft: Light-greenish-tan massive diatomaceous(?) 

silty mudstone.

(76) 1810 ft: Light-greenish-tan massive diatomaceous(?) 

silty mudstone.

(77) 1820 ft: Light-greenish-gray massive diatomaceous(?) 

siltstone.

(78) 1903 ft: Same as No. 77.

SUPPLEMENTARY COLLECTION 

(SAMPLES CR0-43156-1 THROUGH -7)

MONTEREY FORMATION

CLAYEY-SILICEOUS MEMBER

Washed residues were prepared from each of the seven 

samples.

(1) 0 ft: Medium-brown faintly thin-bedded slightly dolomitic and slightly phosphatic mudstone.

(2) 43 ft: Dark-brown thin-bedded to laminated to massive 

slightly dolomitic mudstone with laminae and thin 

lenses of light-buff phosphate and dark-brown to gray 

massive dolostone.

(3) 55 to 65 ft: Composite sample of medium- to dark-brown 

thin-bedded to massive mudstones and medium- to 

dark-brown massive dolostone.

(4) 76 ft: Medium-brown faintly laminated to thin-bedded 

mudstone.

(5) 127 ft: Same as No. 4.

(6) 185 ft: Highly fractured medium- to dark-brown very 

poorly thin-bedded to laminated mudstone.

(7) 261 ft: Medium gray-brown laminated mudstone.

APPENDIX B. LIONS HEAD SECTION 

LITHOLOGIC AND PROCESSING LOG OF 

SAMPLES

LOSPE FORMATION (SAMPLE 79)

(79) 10 ft above fault contact with Espada Formation: Medium-gray massive slightly calcareous mudstone.

Lithologic descriptions of collected samples examined 

in the laboratory. Bedding thicknesses are defined as follows: laminated, <3 mm; thin bedded, 3 to 40 mm; massive, 

neither laminated nor bedded in hand sample and probably 

thick bedded (>40 mm) in field.

POINT SAL FORMATION 

(SAMPLES 80 THROUGH 84)

Washed residues and two thin sections were prepared 

from each of these five samples.

(80) Basal exposure, 10 ft above fault contact with Lospe 

Formation: Medium-brown-gray faintly thin-bedded 

foraminiferal mudstone.

(81) 40 ft: Same as No. 80, with occasional white laminae 

and fish scales.

(82) Upsection from No. 81, footage not measured lightgray shale.

(83) Upsection from No. 82, footage not measured lightgray shale.

(84) Upsection from No. 83, footage not measured darkgreenish-gray shale.

SAMPLES CRC-40471-1 TO -18 

MONTEREY FORMATION

PHOSPHATIC MEMBER (SAMPLES 1 THROUGH 12)

(1) 22 ft: Alternately light- and medium-brown laminated 

to thin-bedded to massive slightly dolomitic phosphatic 

mudstone and buff faintly laminated calcareous silty 

dolostone; Foraminifera visible in both rock types at 

30x. Two thin sections of mudstone prepared.

(2) 65 ft : Alternately light- and dark-brown thin-bedded 

calcareous phosphatic mudstone with Foraminifera visible at 30x and light-brown massive limestone. Two 

thin sections of mudstone prepared.

L28 Evolution of Sedimentary Basins/Onshore Oil and Gas Investigations Santa Maria Province
(3) 110 ft: Alternately medium- and dark-brown thin-bedded to massive calcareous phosphatic mudstone and buff 

massive limestone; Foraminifera visible in both rocks 

at 30x. Two thin sections of mudstone prepared.

(4) 165 ft : Alternately gray and dark-brown laminated to 

thin-bedded slightly calcareous phosphatic mudstone 

and dark-brown faintly laminated slightly calcareous 

dolostone; Foraminifera visible in both rocks at 30x. 

Two thin sections of mudstone prepared.

(5) 210 ft: Alternately light- and medium-brown thin-bedded flaggy phosphatic mudstone with Foraminifera visible at 30x and medium-brown laminated to thin-bedded sandy limestone. Washed residue and two thin 

sections of mudstone prepared.

(6) 240 ft: Alternately light- and dark-brown laminated to 

thin-bedded calcareous phosphatic mudstone with Foraminifera visible at 30x. Washed residue and two thin 

sections prepared.

(7) 285 ft: Alternately light- and dark-brown thin-bedded 

to massive slightly calcareous phosphatic mudstone; 

Foraminifera not visible at 30x.

(8) 315 ft: Alternately light- and dark-brown laminated to 

thin-bedded siliceous phosphatic mudstone; Foraminifera not visible at 30x.

(9) 370 ft: Alternately light- and dark-brown laminated to 

thin-bedded calcareous phosphatic mudstone with Foraminifera visible at 30x. Two thin sections of mudstone 

prepared.

(10) 435 ft : Alternately light- and medium-brown faintly 

thin-bedded to massive calcareous phosphatic mudstone 

with Foraminifera visible at 30x. Washed residue and 

two thin sections prepared.

(11)515 ft: Medium-brown faintly thin-bedded to massive 

calcareous phosphatic mudstone with Foraminifera visible at 30x. Two thin sections prepared.

(12) 590 ft: Alternately light- and medium-brown laminated 

to thin-bedded calcareous phosphatic mudstone with 

Foraminifera visible at 30x. Two thin sections prepared.

UPPER CALCAREOUS-SILICEOUS MEMBER 

(SAMPLES 13 THROUGH 18)

(13) 750 ft: Dark-brown to black faintly laminated to massive siliceous mudstone and light-brown faintly laminated siliceous dolostone; Foraminifera not visible at 

30x.

(14) 830 ft: Light-brown faintly laminated siliceous mudstone and indistinctly laminated to thin-bedded black 

chert; Foraminifera not visible at 30x.

(15) 870 ft: Dark-brown massive but flaggy siliceous mudstone and medium-brown massive dolostone; Foraminifera not visible at 30x.

(16) 920 ft: Light-brown to black faintly laminated to massive siliceous mudstone and black chert with white laminae; Foraminifera not visible at 30x.

(17) 970 ft: Black massive but flaggy siliceous mudstone 

and medium-gray laminated dolostone; Foraminifera 

not visible at 30x.

(18) 995 ft: Light-brown laminated siliceous dolostone and 

black chert with contorted white laminae; Foraminifera 

not visible at 30x.

APPENDIX C. RODEO CANYON 

SECTION LITHOLOGIC AND 

PROCESSING LOG OF SAMPLES

Lithologic descriptions of collected samples examined 

in the laboratory. Bedding thicknesses are defined as follows: laminated, <3 mm; thin bedded, 3 to 40 mm; massive, 

neither laminated nor bedded in hand sample and probably 

thick bedded (>40 mm) in field.

SAMPLES CRC-40661-1 TO -16

MONTEREY FORMATION 

(SAMPLES 1 THROUGH 16)

LOWER CALCAREOUS-SILICEOUS MEMBER 

(SAMPLES 1 THROUGH 7)

(1) 0 ft (base of section): Buff massive pelletal phosphorite 

with Foraminifera and fish debris common. Washed 

residue and eight thin-sections prepared.

(2) 130 ft: Buff faintly laminated dolomitic porcellanite with 

fish debris.

(3) 230 ft: Buff laminated dolomitic porcellanite with some 

fish debris.

(4) 328 ft: Buff laminated very dolomitic porcellanite with 

some fish debris.

(5) 421 ft: Buff to gray faintly laminated porcellaneous 

dolostone.

(6) 484 ft: Buff to brown laminated slightly dolomitic siliceous mudstone and buff porcelaneous dolostone. 

Washed residue prepared from mudstone.

(7) 565 ft: Buff to brown laminated porcellanite.

"PHOSPHATIC MEMBER" INTERVAL 

(SAMPLES 8 THROUGH 12)

Note: Recognition of this unit and its boundaries are 

uncertain.

(8) 715 ft: Buff to brown massive porcelaneous dolostone.

(9) 756 ft: Buff sugary massive dolostone with irregular blebs 

of brown chert.

(10) 820 ft: Buff sugary massive dolostone.

(Note: The remaining section is structurally complex; 

thus, sample heights are estimated.)

Recognition of Middle Miocene Foraminifers in the Monterey Formation, Santa Maria Province, California L29
(11) -820 ft: Buff to brown laminated to thin-bedded 

dolostone.

(12) ~858 ft: Buff sugary dolostone poorly laminated with 

irregular blebs of brown dolomitic chert.

UPPER CALCAREOUS-SILICEOUS MEMBER 

(SAMPLES 13 THROUGH 16)

(13) ~910 ft: Buff poorly laminated porcelaneous dolostone 

with lenses of brown chert.

(14) ~980 ft: Buff sugary massive dolostone.

(15) -1038 ft: Buff faintly laminated porcelaneous 

dolostone.

(16) Above No. 15 (stratigraphic position uncertain): Buff 

sugary massive dolostone.

L30 Evolution of Sedimentary Basins/Onshore Oil and Gas Investigations Santa Maria Province
PLATES 1-46

[CRC numbers are samples stored at Chevron Petroleum Technology Company (formerly 

Chevron Oil Field Research Company), La Habra, Calif.]
PL ATE 1

Scanning electron micrographs of foraminifers, Monterey Formation, Mussel Rock section.

Figure 1. Lagena apiopleura Loeblich and Tappan, side view, x240, CRC-40398-2.

2. Lenticulina douglasi Finger, side view, x90, CRC-40398-5.

3. Saracenaria schencki Cushman and Hobson, oblique side view, x80, CRC40398-5.

4. Marginulinopsis beali (Cushman), oblique side view, x53, CRC-40398-3.

5. Pseudoparrella subperuviana (Cushman), spiral view, x253, CRC-40398-3.

6. Concavella gyroidinaformis (Cushman and Goudkoff), spiral view, x!76, CRC40398-5.

7. Valvulineria robusta (Kleinpell), umbilical view, x90, CRC-40398-2.

8. Siphonodosaria montereyana Finger and Lipps, side view, x33, CRC-40398-3.

9. Siphonodosaria advena (Cushman and Laiming), side view, x93, CRC-40398-3.

10. Ambitropus evax (Bandy), spiral view, xlOO, CRC-40398-3.
U.S. GEOLOGICAL SURVEY BULLETIN 1995-L PLATE 1

10

FORAMINIFERS, MONTEREY FORMATION, MUSSEL ROCK SECTION
	PL ATE 2

Scanning electron micrographs of foraminifers, Monterey Formation, Mussel Rock section.

Figure 1. Bolivina churchi Kleinpell and Tipton, side view, x80, CRC-40398-3.

2. Bolivina californica Cushman, side view, x!68, CRC-40398-3.

3. Bolivina brevior Cushman var., side view, x238, CRC-40398-2.

4. Bolivina advena ornata Cushman, side view, x!60, CRC-40398-3.

5. Bolivina imbricata Cushman, side view, x!30, CRC-40398-2.

6. Bolivina modeloensis Cushman and Kleinpell, side view, x!30, CRC-40398-2.

7. Rectuvigerina branneri (Cushman), side view, x35, CRC-40398-3.

8. Rectuvigerina hughesi (Cushman), side view, x60, CRC-40398-3.

9. Bulimina subcalva Cushman and K.C. Stewart, side view, x!30, CRC-40398-4.

10. Protoglobobulimina pseudotorta (Cushman), side view, x92, CRC-40398-3.

11. Praeglobobulimina galliheri (Kleinpell), side view, x63, CRC-40398-5.
U.S. GEOLOGICAL SURVEY BULLETIN 1995-L PLATE 2

8

11

FORAMINIFERS, MONTEREY FORMATION, MUSSEL ROCK SECTION
PL ATE 3

Scanning electron micrographs of foraminifers, Monterey Formation, Mussel Rock section.

Figure 1. Baggina californica Cushman, umbilical view, x80, CRC-40398-3.

2. Holmanella baggi (Kleinpell), side view, x!84, CRC-40398-2.

3. Buliminella subfusiformis Cushman, side view, x!47, CRC-40398-3.

4. Islandiella modeloensis (Rankin), side view, x!46, CRC-40398-3.

5. Elphidium granti Kleinpell, side view, x220, CRC-40398-2.

6. Siphonodosaria quadrulata (Cushman and Laiming), side view of segment,

	x!30, CRC-40398-5.

7,8. Pullenia miocenica Kleinpell, xl 10, CRC-40398-5: 7, side view; 8, edge view.

9. Suggrunda kleinpelli Bramlerte, side view, x!70, CRC-40398-5.
U.S. GEOLOGICAL SURVEY BULLETIN 1995-L PLATE 3

FORAMINIFERS, MONTEREY FORMATION, MUSSEL ROCK SECTION
PL ATE 4

Scanning electron micrographs of foraminifers, Monterey Formation, Mussel Rock section.

Figure 1. Cibicidoides mckannai Galloway and Wissler, spiral view, x!90, CRC-40398-2.

2. Hanzawaia depaoloi Finger and Lipps, umbilical view, x!40, CRC-40398-2.

3. Uvigeri,:a hannai Kleinpell, side view, x83, CRC-40398-5.

4. Globigerina pseudobesa (Salvatorini), umbilical view, xl 16, CRC-40398-3.

5. Tenuitellinata angustiumbilicata (Bolli), umbilical view, x327, CRC-40398-3.

6. Trifarina fluens (Cushman and McCulloch?), side view, x!30, CRC-40398-2.

7,8. Globorotalia praescitula Blow, x260, CRC-40398-2: 7, spiral view; 8,

	umbilical view. 

9. Kleinpella californiensis (Cushman), side view, x!50, CRC-40398-3.
U.S. GEOLOGICAL SURVEY BULLETIN 1995-L PLATE 4

FORAMINIFERS, MONTEREY FORMATION, MUSSEL ROCK SECTION
PLATES

Scanning electron micrographs of foraminifers, Monterey Formation, Mussel Rock section.

Figures 1,2. Buccella oregonensis (Cushman, Stewart, and Stewart), x240, CRC-40398-2: 

1, side view; 2, umbilical view.

3. Gyroidina rosaformis (Cushman and Kleinpell), spiral view, x263, CRC40398-3.

4. Valvulineria californica Cushman, umbilical view, x80, CRC-40398-3.

5. Holmanella baggi (Kleinpell), side view, x80, CRC-40398-3.

6. Anomalinoides salinasensis (Kleinpell), spiral view, x90, CRC-40398-3.
U.S. GEOLOGICAL SURVEY BULLETIN 1995-L PLATE 5
PL ATE 6

Photomicrographs of Anomalinoides salinasensis (Kleinpell) in petrographic thin sections, 

Monterey Formation, Mussel Rock section.

Figure 1. x!28, CRC-40398-3, slide no. 3-5, parallel to bedding.

2. x!28, CRC-40398-2, slide no. 3-2, parallel to bedding.

3. x!28, CRC-40398-4, slide no. 3-9, parallel to bedding.

4. x!28, CRC-40398-3, slide no. 3-7, parallel to bedding.

5. x!28, CRC-40398-3, slide no. 3-8, perpendicular to bedding.

6. x200, CRC-40398-4, slide no. 3-9, parallel to bedding.

7. x!28, CRC-40398-4, slide no. 3-9, parallel to bedding.

8. x!28, CRC-40398-4, slide no. 3-9, parallel to bedding.

9. x200, CRC-40398-3, slide no. 3-6, parallel to bedding.
U.S. GEOLOGICAL SURVEY BULLETIN 1995-L PLATE 6

#*** sa

 ?^

f& ^--vj

FORAMINIFERS, MONTEREY FORMATION, MUSSEL ROCK SECTION
PLATE?

Photomicrographs of Anomalinoides salinasensis (Kleinpell) in petrographic thin sections, 

Monterey Formation, Mussel Rock section.

Figure 1. x80, CRC-40398-4, slide no. 3-9, parallel to bedding.

2. x!28, CRC-40398-3, slide no. 3-7, parallel to bedding.

3. x!28, CRC-40398-3, slide no. 3-5, parallel to bedding.

4. x80, CRC-40398-3, slide no. 3-7, parallel to bedding.

5. x!28, CRC-40398-3, slide no. 3-7, parallel to bedding.

6. x80, CRC-40398-4, slide no. 3-9, parallel to bedding.

7. X200, CRC-40398-3, slide no. 3-7, parallel to bedding.

8. x!28, CRC-40398-4, slide no. 3-9, parallel to bedding.

9. X200, CRC-40398-3, slide no. 3-5, parallel to bedding.
U.S. GEOLOGICAL SURVEY BULLETIN 1995-L PLATE 7

FORAMINIFERS, MONTEREY FORMATION, MUSSEL ROCK SECTION
PLATES

Photomicrographs of Anomalinoides salinasensis (Kleinpell) in petrographic thin sections, 

Monterey Formation, Mussel Rock section.

Figure 1. x!28, CRC-40398-3, slide no. 3-7, parallel to bedding.

2. x200, CRC-40398-3(3V), perpendicular to bedding.

3. x!28, CRC-40398-3, slide no. 3-5, parallel to bedding.

4. x!28, CRC-40398-3, slide no. 3-5, parallel to bedding.

5. x!28, CRC-40398-3, slide no. 3-5, parallel to bedding.

6. x!28, CRC-40398-3, slide no. 3-7, parallel to bedding.

7. x200, CRC-40398-3(3V), perpendicular to bedding.

8. x!28, CRC-40398-3, slide no. 3-7, parallel to bedding.
U.S. GEOLOGICAL SURVEY BULLETIN 1995-L PLATE

8

FORAMINIFERS, MONTEREY FORMATION, MUSSEL ROCK SECTION
PL ATE 9

Photomicrographs of foraminifers in petrographic thin sections, Monterey Formation, Mussel 

Rock section.

Figure 1. Anomalinoides salinasensis (Kleinpell), x80, CRC-40398-4, slide no. 3-9, 

parallel to bedding.

2. Anomalinoides salinasensis (Kleinpell), x80, CRC-40398-4, slide no. 3-9, 

parallel to bedding.

3. Anomalinoides salinasensis (Kleinpell), x200, CRC-40398-3, slide no. 3-7, 

parallel to bedding.

4. Anomalinoides salinasensis (Kleinpell), x!28, CRC-40398-3, slide no. 3-6, 

parallel to bedding.

5. Anomalinoides salinasensis (Kleinpell), x200, CRC-40398-3(3H), parallel to 

bedding.

6. Anomalinoides salinasensis (Kleinpell), x!28, CRC-40398-3, slide no. 3-5, 

parallel to bedding.

7. Anomalinoides salinasensis (Kleinpell), x200, CRC-40398-3(3H), parallel to 

bedding.

8. Anomalinoides salinasensis (Kleinpell), x!28, CRC-40398-3, slide no. 3-8, 

perpendicular to bedding.

9. Uvigerina hannai Kleinpell, x200, CRC-40398-5, slide no. 3-16, perpendicular to 

bedding.
U.S. GEOLOGICAL SURVEY BULLETIN 1995-L PLATE 9

FORAMINIFERS, MONTEREY FORMATION, MUSSEL ROCK SECTION
PLATE 10

Photomicrographs of Rectuvigerina branneri (Bagg) in petrographic thin sections, Monterey 

Formation, Mussel Rock section.

Figure 1. x!28, CRC-40398-3(3V), perpendicular to bedding.

2. x80, CRC-40398-3(3V), perpendicular to bedding.

3. x80, CRC-40398-3(3V), perpendicular to bedding.

4. x80, CRC-40398-3(3H), parallel to bedding.

5. x80, CRC-40398-3(3H), parallel to bedding.

6. x50, CRC-40398-3(3H), parallel to bedding.

7. x80, CRC-40398-3, slide no. 3-7, parallel to bedding.

8. x80, CRC-40398-4, slide no. 3-9, parallel to bedding.

9. x80, CRC-40398-4, slide no. 3-9, parallel to bedding.

10. x!28, CRC-40398-3, slide no. 3-2, parallel to bedding.
U.S. GEOLOGICAL SURVEY BULLETIN 1995-L PLATE 10

10

FORAMINIFERS, MONTEREY FORMATION, MUSSEL ROCK SECTION
PLATE 11

Photomicrographs of Rectuvigerina branneri (Bagg) in petrographic thin sections, Monterey 

Formation, Mussel Rock section.

Figure 1. x80, CRC-40398-3, slide no. 3-8, perpendicular to bedding.

2. x200, CRC-40398-3(3V), perpendicular to bedding.

3. x80, CRC-40398-3, slide no. 3-5, parallel to bedding.

4. x80, CRC-40398-3, slide no. 3-5, parallel to bedding.

5. x80, CRC-40398-3(3H), parallel to bedding.

6. x!28, CRC-40398-3(3H), parallel to bedding.

7. x!28, CRC-40398-3, slide no. 3-8, perpendicular to bedding.

8. x80, CRC-40398-3, slide no. 3-5, parallel to bedding.

9. x80, CRC-40398-3, slide no. 3-5, parallel to bedding.
U.S. GEOLOGICAL SURVEY BULLETIN 1995-L PLATE 11

FORAMINIFERS, MONTEREY FORMATION, MUSSEL ROCK SECTION
PLATE 12

Photomicrographs of foraminifers in petrographic thin sections, Monterey Formation, Mussel 

Rock section.

Figures 1,2. Gyroidina rosaformis (Cushman and Kleinpell), x!28, CRC-40398-4, slide 

no. 3-9, parallel to bedding, and x320, CRC-40398-3, slide no. 3-7, parallel 

to bedding, respectively.

3. Rectuvigerina branneri (Bagg), x50, CRC-40398-3(3H), parallel to bedding.

4. Pseudoparrella subperuviana (Cushman): x320, CRC-40398-3, slide no. 3- 

5, parallel to bedding.

5. Rectuvigerina branneri (Bagg), x80, CRC-40398-3(3H), parallel to bedding. 

6,7. Baggina californica Cushman, x200, CRC-40398-4, slide no. 3-9, parallel to

bedding, and x!28, CRC-40398-4, slide no. 3-9, parallel to bedding,

respectively. 

8. Rectuvigerina branneri (Bagg), xSO.4, CRC-40398-3(3H), parallel to

bedding.
U.S. GEOLOGICAL SURVEY BULLETIN 1995-L PLATE 12

8

FORAMINIFERS, MONTEREY FORMATION, MUSSEL ROCK SECTION
PLATE 13

Photomicrographs of foraminifers in petrographic thin sections, Monterey Formation, Mussel 

Rock section.

Figure 1. Valvulineria californica Cushman, x80, CRC-40398-3(3V), perpendicular to

bedding. 

2. Anomalinoides salinasensis (Kleinpell), x!28, CRC-40398-4, slide no. 3-9,

parallel to bedding.

3-5. Valvulineria robusta (Kleinpell): 3, x!28, CRC-40398-4, slide no. 3-9, parallel 

to bedding; 4, x80, CRC-40398-4(3-10; 5, x200, CRC-40398-4, slide no. 3-9, 

parallel to bedding.

6-9. Bolivina advena ornata Cushman: 6, x!28, CRC-40398-5, slide no. 3-16, 

perpendicular to bedding; 7, x200, CRC-40398-3(3H), parallel to bedding; 8, 

x200, CRC-40398-4, slide no. 3-9, parallel to bedding; 9, x200, CRC-40398-4, 

slide no. 3-9, parallel to bedding.

10. Buliminella subfusiformis Cushman, X320, CRC-40398-4, slide no. 3-9, parallel 

to bedding.
U.S. GEOLOGICAL SURVEY BULLETIN 1995-L PLATE 13

7 F^BVB I^BUtfV'C) ^^Ha^f^lO

FORAMINIFERS, MONTEREY FORMATION, MUSSEL ROCK SECTION
PLATE 14

Photomicrographs of foraminifers in petrographic thin sections, Monterey Formation, Mussel 

Rock section.

Figures 1,2. Pullenia miocenica Kleinpell, x200, CRC-40398-5, slide no. 3-14, parallel to 

bedding, and x80, CRC-40398-4, slide no. 3-9, parallel to bedding, 

respectively.

3. Buliminella subfusiformis Cushman, x200, CRC-40398-5, slide no. 3-16,

perpendicular to bedding.

4-7. Pullenia miocenica Kleinpell: 4, x200, CRC-40398-4, slide no. 3-9, parallel 

to bedding; 5, x200, CRC-40398-3(3V), perpendicular to bedding; 6, x200, 

CRC-40398-4, slide no. 3-9, parallel to bedding; 7, x320, CRC-40398-4, 

slide no. 3-10, parallel to bedding.

8. Bolivina imbricata Cushman, x200, CRC-40398-3(3H), parallel to bedding.
U.S. GEOLOGICAL SURVEY BULLETIN 1995-L PLATE 14

8

FORAMINIFERS, MONTEREY FORMATION, MUSSEL ROCK SECTION
PLATE 15

Photomicrographs of foraminifers in petrographic thin sections, Monterey Formation, Mussel 

Rock section.

Figure 1. Islandiella modeloensis (Rankin), x!28, CRC-40398-4, slide no. 3-9, parallel to

bedding. 

2. Gyroidina rosaformis (Cushman and Kleinpell), x320, CRC-40398-4, slide no.

3-10, parallel to bedding. 

3,4. Islandiella modeloensis (Rankin), x!28, CRC-40398-5, slide no. 3-16,

perpendicular to bedding, and x200, CRC-40398-3(3V), perpendicular to bedding,

respectively. 

5,6. Siphonodosaria montereyana Finger and Lipps, x50, CRC-40398-4, slide no. 3-

10, parallel to bedding, and x50, CRC-40398-4, slide no. 3-10, parallel to

bedding, respectively.

7. Nodosaria ewaldi Reuss, late segment, x200, CRC-40398-3(3H), parallel to 

bedding.

8. Pseudoparrella subperuviana (Cushman), x200, CRC-40398-3(3H), parallel to 

bedding.

9. Islandiella modeloensis (Rankin), x80, CRC-40398-4, slide no. 3-9, parallel to 

bedding.

10. Islandiella modeloensis (Rankin), x!28, CRC-40398-5, slide no. 3-16, 

perpendicular to bedding.
U.S. GEOLOGICAL SURVEY BULLETIN 1995-L PLATE 15

10

ff& FU*^mr9

FORAMINIFERS, MONTEREY FORMATION, MUSSEL ROCK SECTION
PLATE 16

Photomicrographs of foraminifers in petrographic thin sections, Monterey Formation, Mussel 

Rock section.

Figure 1. Pseudoparrella subperuviana (Cushman), x!28, CRC-40398-3(3H), parallel to

bedding.

2,3. Gyroidina rosaformis (Cushman and Kleinpell), x200, CRC-40398-3(3V), 

perpendicular to bedding, and x!28, CRC-40398-3(3H), parallel to bedding, 

respectively.

4. Siphonodosaria advena (Cushman and Laiming), X128, CRC-40398-5, slide no. 

3-16, perpendicular to bedding.

5. Nodogenerina sagrinensis (Bagg), x!28, CRC-40398-3, slide no. 3-5, parallel to 

bedding.

6. Nodosaria ewaldi Reuss, x50, CRC-40398-4, slide no. 3-10, parallel to bedding.

7. Siphonodosaria montereyana Finger and Lipps, x32, CRC-40398-4, slide no. 3-

10, parallel to bedding.

8,9. Nodogenerina sagrinensis (Bagg), x200, CRC-40398-4, slide no. 3-10, parallel 

to bedding, and x!28, CRC-40398-3, slide no. 3-7, parallel to bedding, 

respectively.

10. Nodosaria ewaldi Reuss, x80, CRC-40398-3, slide no. 3-9, parallel to bedding.

11. Nodogenerina sagrinensis (Bagg), x50, CRC-40398-4, slide no. 3-9, parallel to

bedding. 

12,13. Siphonodosaria montereyana Finger and Lipps, x50, CRC-40398-3, slide no. 3-

9, parallel to bedding, and x32, CRC-40398-4, slide no. 3-10, parallel to

bedding, respectively. 

14,15. Nodogenerina sagrinensis (Bagg), x!28, CRC-40398-4, slide no. 3-9, parallel to

bedding, and x80, CRC-40398-4, slide no. 3-9, parallel to bedding, respectively.
U.S. GEOLOGICAL SURVEY BULLETIN 1995-L PLATE 16

15

FORAMINIFERS, MONTEREY FORMATION, MUSSEL ROCK SECTION
PLATE 17

Photomicrographs of foraminifers in petrographic thin sections, Monterey Formation, Mussel 

Rock section.

Figure 1-4. Protoglobobuliminapseudotorta (Cushman): 1, x!28, CRC-40398-3(3H), 

parallel to bedding; 2, x80, CRC-40398-3(3H), parallel to bedding; 3, x!28, 

CRC-40398-3(3H), parallel to bedding; 4, x!28, CRC-40398-3(3H), parallel 

to bedding.

5. Islandiella modeloensis (Rankin), X200, CRC-40398-5, slide no. 3-16, 

perpendicular to bedding.

6. Protoglobobulimina pseudotorta (Cushman), x!28, CRC-40398-3(3H), 

parallel to bedding.

7. Islandiella modeloensis (Rankin), x200, CRC-40398-4, slide no. 3-9, parallel 

to bedding.

8. Anomalinoides salinasensis (Kleinpell), x200, CRC-40398-4, slide no. 3-9, 

parallel to bedding.

9. Proxifrons vaughani (Cushman), x!28, CRC-40398-3(3H), parallel to 

bedding.
U.S. GEOLOGICAL SURVEY BULLETIN 1995-L PLATE 17

8

FORAMINIFERS, MONTEREY FORMATION, MUSSEL ROCK SECTION
PLATE 18

Photomicrographs of foraminifers in petrographic thin sections, Monterey Formation, Mussel 

Rock section.

Figures 1-3. Uvigerina hannai Kleinpell: 1, x200, CRC-40398-5, slide no. 3-14, parallel 

to bedding; 2, x200, CRC-40398-5, slide no. 3-14, parallel to bedding; 3, 

x200, CRC-40398-5, slide no. 3-14, parallel to bedding.

4,5. Siphonodosaria montereyana Finger and Lipps, x80, CRC-40398-3, slide 

no. 3-7, parallel to bedding, and x50, CRC-40398-4, slide no. 3-9, parallel to 

bedding, respectively.

6-8. Uvigerina hannai Kleinpell: 6, X200, CRC-40398-5, slide no. 3-14, parallel 

to bedding; 7, x!28, CRC-40398-5, slide no. 3-16, perpendicular to bedding; 

8, x200, CRC-40398-5, slide no. 3-14, parallel to bedding.
U.S. GEOLOGICAL SURVEY BULLETIN 1995-L PLATE 18

8

FORAMINIFERS, MONTEREY FORMATION, MUSSEL ROCK SECTION
PLATE 19

Photomicrographs of foraminifers in petrographic thin sections, Monterey Formation, Mussel 

Rock section.

Figures 1-5. Uvigerina hannai Kleinpell: 1, x200, CRC-40398-5, slide no. 3-14, parallel 

to bedding; 2, x200, CRC-40398-5, slide no. 3-14, parallel to bedding; 3, 

x200, CRC-40398-5, slide no. 3-14, parallel to bedding; 4, x200, CRC40398-5, slide no. 3-14, parallel to bedding; 5, x200, CRC-40398-5, slide 

no. 3-16, perpendicular to bedding.

6. Pseudoparrella subperuviana (Cushman), x200, CRC-40398-3, slide no. 3- 

7, parallel to bedding.

7. Trifarinafluens (Todd), x200, CRC-40398-5, slide no. 3-16, perpendicular

to bedding.

8,9. Uvigerina hannai Kleinpell, x!28, CRC-40398-5, slide no. 3-16, 

perpendicular to bedding, and x200, CRC-40398-5, slide no. 3-16, 

perpendicular to bedding, respectively.
U.S. GEOLOGICAL SURVEY BULLETIN 1995-L PLATE 19

FORAMINIFERS, MONTEREY FORMATION, MUSSEL ROCK SECTION
PL ATE 20

Scanning electron micrographs of foraminifers from phosphatic member (CRC-40471-6), 

Monterey Formation, Lions Head section.

Figure 1. Rectuvigerina branneri (Bagg), x90.

2. Valvulineria californica Cushman, x!30.

3. Rectuvigerina branneri (Bagg), xlOO.

4. Baggina californica Cushman, x!20.

5. Pullenia miocenica Kleinpell, x!60.

6. Lenticulina smiley i (Kleinpell), x!50.
U.S. GEOLOGICAL SURVEY BULLETIN 1995-L PLATE 20

FORAMINIFERS, MONTEREY FORMATION, LIONS HEAD SECTION
PLATE21

Photomicrographs of Rectuvigerina branneri (Bagg) in petrographic thin sections, Monterey 

Formation, Lions Head section.

Figure 1. x80, CRC-40471-2, slide no. 12, parallel to bedding.

2. x80, CRC-40471-9, slide no. 7, perpendicular to bedding.

3. x80, CRC-40471-9, slide no. 17, parallel to bedding.

4. x80, CRC-40471-12, slide no. 20, parallel to bedding.

5. x50, CRC-40471-12, slide no. 10, perpendicular to bedding.

6. x80, CRC-40471-9, slide no. 17, parallel to bedding.

7. x80, CRC-40471-12, slide no. 20, parallel to bedding.

8. x80, CRC-40471-10, slide no. 8, perpendicular to bedding.

9. x80, CRC-40471-6, slide no. 6, perpendicular to bedding.

10. x80, CRC-40471-9, slide no. 7, perpendicular to bedding.
U.S. GEOLOGICAL SURVEY BULLETIN 1995-L PLATE 21

FORAMINIFERS, MONTEREY FORMATION, LIONS HEAD SECTION
PL ATE 22

Photomicrographs of Rectuvigerina branneri (Bagg) in petrographic thin sections, Monterey 

Formation, Lions Head section.

Figure 1. x80, CRC-40471-4, slide no. 4, perpendicular to bedding.

2. x80, CRC-40471-2, slide no. 12, parallel to bedding.

3. x80, CRC-40471-9, slide no. 7, perpendicular to bedding.

4. x80, CRC-40471-2, slide no. 12, parallel to bedding.

5. x80, CRC-40471-2, slide no. 12, parallel to bedding.

6. x50, CRC-40471-9, slide no. 17, parallel to bedding.

7. x50, CRC-40471-9, slide no. 17, parallel to bedding.

8. x80, CRC-40471-9, slide no. 17, parallel to bedding.

9. x80, CRC-40471-9, slide no. 7, perpendicular to bedding.

10. x!28, CRC-40471-4, slide no. 4, perpendicular to bedding.

11. x80, CRC-40471-9, slide no. 7, perpendicular to bedding.

12. x80, CRC-40471-9, slide no. 7, perpendicular to bedding.

13. x200, CRC-40471-12, slide no. 10, perpendicular to bedding.
U.S. GEOLOGICAL SURVEY BULLETIN 1995-L PLATE 22

FORAMINIFERS, MONTEREY FORMATION, LIONS HEAD SECTION
PL ATE 23

Photomicrographs ofPullenia miocenica Kleinpell in petrographic thin sections, Monterey 

Formation, Lions Head section.

Figure 1. x200, CRC-40471-9, slide no. 17, parallel to bedding.

2. x!28, CRC-40471-12, slide no. 20, parallel to bedding.

3. x!28, CRC-40471-9, slide no. 17, parallel to bedding.

4. x80, CRC-40471-9, slide no. 17, parallel to bedding.

5. x200, CRC-40471-10, slide no. 18, parallel to bedding.

6. x200, CRC-40471-12, slide no. 10, perpendicular to bedding.

7. x200, CRC-40471-12, slide no. 10, perpendicular to bedding.

8. x200, CRC-40471-12, slide no. 20, parallel to bedding.

9. x200, CRC-40471-10, slide no. 18, parallel to bedding.

10. x!28, CRC-40471-9, slide no. 7, perpendicular to bedding.
U.S. GEOLOGICAL SURVEY BULLETIN 1995-L PLATE 23

10

FORAMINIFERS, MONTEREY FORMATION, LIONS HEAD SECTION
PLATE 24

Photomicrographs of foraminifers in petrographic thin sections, Monterey Formation, Lions Head 

section.

Figures 1-6. Pullenia miocenica Kleinpell: 1, x!28, CRC-40471-6, slide no. 6,

perpendicular to bedding; 2, x!28, CRC-40471-12H, parallel to bedding; 3, 

x!28, CRC-40471-12H, parallel to bedding; 4, x200, CRC-40471-12V, 

perpendicular to bedding; 5, x200, CRC-40471-10H, parallel to bedding; 6, 

x200, CRC-40471-12H, parallel to bedding.

7-9. Bolivina advena ornata Cushman: 7, x320, CRC-40471-12H, parallel to 

bedding; 8, x200, CRC-40471-12H, parallel to bedding; 9, x200, CRC40471-12H, parallel to bedding. 

10. Bolivina californica Cushman, x320, CRC-40471-12H, parallel to bedding.
U.S. GEOLOGICAL SURVEY BULLETIN 1995-L PLATE 24

10

FORAMINIFERS, MONTEREY FORMATION, LIONS HEAD SECTION
PLATE 25

Photomicrographs of Anomalinoides salinasensis (Kleinpell) in petrographic thin sections, 

Monterey Formation, Lions Head section.

Figure 1. x200, CRC-40471-11, slide no. 9, perpendicular to bedding.

2. x200, CRC-40471-11, slide no. 9, perpendicular to bedding.

3. x!28, CRC-40471-12, slide no. 20, parallel to bedding.

4. x!28, CRC-40471-10, slide no. 18, parallel to bedding.

5. x200, CRC-40471-12, slide no. 20, parallel to bedding.

6. x200, CRC-40471-11, slide no. 19, parallel to bedding.

7. x 128, CRC-40471-10, slide no. 8, perpendicular to bedding.

8. x320, CRC-40471-12, slide no. 20, parallel to bedding.
U.S. GEOLOGICAL SURVEY BULLETIN 1995-L PLATE 25

8

FORAMINIFERS, MONTEREY FORMATION, LIONS HEAD SECTION
PLATE 26

Photomicrographs of Anomalinoides salinasensis (Kleinpell) in petrographic thin sections, 

Monterey Formation, Lions Head section.

Figure 1. x320, CRC-40471-3, slide no. 13, parallel to bedding.

2. x80, CRC-40471-10, slide no. 18, parallel to bedding.

3. x80, CRC-40471-11, slide no. 19, parallel to bedding.

4. x200, CRC-40471-11, slide no. 9, perpendicular to bedding.

5. x200, CRC-40471-11, slide no. 19, parallel to bedding.

6. x200, CRC-40471-12, slide no. 20, parallel to bedding.

7. x!28, CRC-40471-10, slide no. 18, parallel to bedding.

8. x200, CRC-40471-12, slide no. 10, perpendicular to bedding.

9. x200, CRC-40471-12, slide no. 20, parallel to bedding.
U.S. GEOLOGICAL SURVEY BULLETIN 1995-L PLATE 26

8

7 ^^^ U&^^^^^> g

FORAMINIFERS, MONTEREY FORMATION, LIONS HEAD SECTION
PLATE 27

Photomicrographs of Anomalinoides salinasensis (Kleinpell) in petrographic thin sections, 

Monterey Formation, Lions Head section.

Figure 1. x320, CRC-40471-5, slide no. 15, parallel to bedding.

2. x80, CRC-40471-1 1, slide no. 19, parallel to bedding.

3. x320, CRC-40471-10, slide no. 18, parallel to bedding.

4. x200, CRC-40471-12, slide no. 20, parallel to bedding.

5. x200, CRC-40471-9, slide no. 7, perpendicular to bedding.

6. x200, CRC-40471-12, slide no. 20, parallel to bedding.

7. x320, CRC-40471-12, slide no. 20, parallel to bedding.

8. x200, CRC-40471-12, slide no. 20, parallel to bedding.

9. x200, CRC-40471-12, slide no. 20, parallel to bedding.
U.S. GEOLOGICAL SURVEY BULLETIN 1995-L PLATE 27

FORAMINIFERS, MONTEREY FORMATION, LIONS HEAD SECTION
PLATE 28

Photomicrographs of foraminifers in petrographic thin sections, Monterey Formation, Lions Head 

section.

Figures 1,2. Islandiella modeloensis (Rankin), x200, CRC-40471-9, slide no. 17, parallel 

to bedding, and x200, CRC-40471-9, slide no. 17, parallel to bedding, 

respectively.

3. Rectuvigerina branneri (Bagg), x 128, CRC-40471 -12, slide no. 10, 

perpendicular to bedding.

4. Islandiella modeloensis (Rankin), x200, CRC-40471-10, slide no. 18, 

parallel to bedding.

5. Gyroidina rosaformis (Cushman and Kleinpell), x320, CRC-40471-9, slide 

no. 17, parallel to bedding.

6. Islandiella modeloensis (Rankin), x320, CRC-40471-9, slide no. 17, parallel

to bedding.

7-9. Valvulineria californica Cushman: 7, x200, CRC-40471-9, slide no. 17, 

parallel to bedding; 8, x80, CRC-40471-10, slide no. 18, parallel to 

bedding; 9, x!28, CRC-40471-6, slide no. 6, perpendicular to bedding.
U.S. GEOLOGICAL SURVEY BULLETIN 1995-L PLATE 28

FORAMINIFERS, MONTEREY FORMATION, LIONS HEAD SECTION
PLATE 29

Photomicrographs of foraminifers in petrographic thin sections, Monterey Formation, Lions Head.

Figure 1. Baggina californica Cushman, x200, CRC-40471-10, slide no. 18, parallel to 

bedding.

2. Islandiella modeloensisl (Rankin), x!28, CRC-40471-6, slide no. 6, 

perpendicular to bedding.

3. Bolivina advena ornata Cushman, x320, CRC-40471-12, slide no. 20, parallel to

bedding. 

4,5. Baggina californica Cushman, x200, CRC-40471-12, slide no. 20, parallel to

bedding, and x200, CRC-40471-12, slide no. 20, parallel to bedding,

respectively. 

6. Bolivina blakei Finger and Lipps, x!28, CRC-40471-10, slide no. 18, parallel to

bedding. 

7,8. Baggina californica Cushman, x200, CRC-40471-12, slide no. 20, parallel to

bedding, and x200, CRC-40471-10, slide no. 18, parallel to bedding,

respectively. 

9. Bolivina californica Cushman, x200, CRC-40471-12, slide no. 20, parallel to

bedding.
U.S. GEOLOGICAL SURVEY BULLETIN 1995-L PLATE 29

7 K^^^^^F" 8

FORAMINIFERS, MONTEREY FORMATION, LIONS HEAD SECTION
PLATE 30

Photomicrographs of foraminifers in petrographic thin sections, Monterey Formation, Lions Head 

section.

Figure 1. Megastomella capitanensis (Cushman and Kleinpell), x320, CRC-40471-5, slide

no. 15, parallel to bedding.

2,3. Gyroidina rosaformis (Cushman and Kleinpell), x200, CRC-40471-9, slide no. 

17, parallel to bedding, and x320, CRC-40471-10, slide no. 18, parallel to 

bedding, respectively. 

4. Pseudoparrella subperuviana (Cushman), x!28, CRC-40471-5, slide no. 15,

parallel to bedding.

5-10. Gyroidina rosaformis (Cushman and Kleinpell): 5, x320, CRC 40471-12, slide 

no. 20, parallel to bedding; 6, x320, CRC-40471-12, slide no. 20, parallel to 

bedding; 7, x320, CRC-40471-10, slide no. 18, parallel to bedding; 8, x320, 

CRC-40471-12, slide no. 20, parallel to bedding; 9, x320, CRC-40471-11, slide 

no. 19, parallel to bedding; 10, x200, CRC-40471-12, slide no. 20, parallel to 

bedding.
U.S. GEOLOGICAL SURVEY BULLETIN 1995-L PLATE 30

10

FORAMINIFERS, MONTEREY FORMATION, LIONS HEAD SECTION
PLATE 31

Photomicrographs of foraminifers in petrographic thin sections, Monterey Formation, Lions Head 

section.

Figure 1. Nodogenerina sagrinensis (Bagg), x80, CRC-40471-6, slide no. 6, perpendicular

to bedding.

2,3. Tenuitellinata angustiumbilicata (Bolli), x320, CRC-40471-3, slide no. 13, 

parallel to bedding, and x320, CRC-40471-3, slide no. 13, parallel to bedding, 

respectively.

4. Globigerina bulloides d'Orbigny, x200, CRC-40471-3, slide no. 3, perpendicular 

to bedding.

5. Lenticulina miocenica (Chapman), x200, CRC-40471-6, slide no. 6, 

perpendicular to bedding.

6. Lenticulina smileyi (Kleinpell), x80, CRC-40471-10, slide no. 8, perpendicular to 

bedding.

7. Globigerina bulloides d'Orbigny, x200, CRC-40471-3, slide no. 13, parallel to

bedding. 

8-10. Lenticulina smileyi (Kleinpell): 8, x200, CRC-40471-6, slide no. 6,

perpendicular to bedding; 9, x50, CRC-40471-10, slide no. 18, parallel to 

bedding; 10, x!28, CRC-40471-6, slide no. 6, perpendicular to bedding.
U.S. GEOLOGICAL SURVEY BULLETIN 1995-L PLATE 31

8 E^HflBV 9

FORAMINIFERS, MONTEREY FORMATION, LIONS HEAD SECTION
PL ATE 32

Photomicrographs of foraminifers in petrographic thin sections, Monterey Formation, Lions Head.

Figures 1-10. Nodogenerina sagrinewis (Bagg): 1, x80, CRC-40471-10, slide no. 18, 

parallel to bedding; 2, x!28, CRC-40471-12, slide no. 20, parallel to 

bedding; 3, x!28, CRC-40471-11, slide no. 9, perpendicular to bedding; 4, 

x!28, CRC-40471-11, slide no. 19, parallel to bedding; 5, x80, CRC40471-12, slide no. 20, parallel to bedding; 6, x80, CRC-40471-10, slide 

no. 18, parallel to bedding; 7, x200, CRC-40471-12, slide no. 10, 

perpendicular to bedding; 8, x!28, CRC-40471-12, slide no. 20, parallel to 

bedding; 9, x200, CRC-40471-12, slide no. 20, parallel to bedding; 10, 

x!28, CRC-40471-10, slide no. 18, parallel to bedding.

11. Siphonodosaria montereyana Finger and Lipps, x32, CRC-40471-12, slide 

no. 20, parallel to bedding.

12. Nodosaria ewaldi Reuss, x!28, CRC-40471-11, slide no. 9, perpendicular

to bedding.

13,14. Typical examples of crushed foraminifers, x80, CRC-40471-12, slide no. 

10, perpendicular to bedding, and x50, CRC-40471-12, slide no. 10, 

perpendicular to bedding, respectively.
U.S. GEOLOGICAL SURVEY BULLETIN 1995-L PLATE 32

14

FORAMINIFERS, MONTEREY FORMATION, LIONS HEAD SECTION
PLATE 33

Photomicrographs of foraminifers in petrographic thin sections, Monterey Formation, Lions Head.

Figure 1. Bulimina cf. B. subacuminata Cushman and R.E. Stewart, x!28, CRC-40471-12,

slide no. 10, perpendicular to bedding. 

2. Siphonodosaria quadrulata (Cushman and Parker), x200, CRC-40471-10, slide

no. 18, parallel to bedding. 

3-6. Nodogenerina sagrinensis (Bagg): 3, x80, CRC-40471-10, slide no. 18, parallel

to bedding; 4, x200, CRC-40471-12, slide no. 20, parallel to bedding; 5, x200,

CRC-40471-12, slide no. 20, parallel to bedding; 6, x80, CRC-40471-11, slide

no. 19, parallel to bedding. 

7,8. Siphonodosaria quadrulata (Cushman and Parker), x80, CRC-40471-10, slide

no. 18, parallel to bedding, and x80, CRC-40471-10, slide no. 18, parallel to

bedding, respectively.

9. Bolivina californica Cushman, x200, CRC-40471-2, slide no. 12, parallel to 

bedding.

10. Nodogenerina sagrinensis (Bagg), x50, CRC-40471-10, slide no. 8, 

perpendicular to bedding.

11. Buliminella subfusiformis Cushman, x320, CRC-40471-12, slide no. 20, parallel 

to bedding.

12. Protoglobobuliminapseudotortal (Cushman), x200, CRC-40471-3, slide no. 13, 

parallel to bedding.

13. Holmanella baggi (Kleinpell), x200, CRC-40471-12, slide no. 20, parallel to 

bedding.
U.S. GEOLOGICAL SURVEY BULLETIN 1995-L PLATE 33

13

FORAMINIFERS, MONTEREY FORMATION, LIONS HEAD SECTION
PLATE 34

Photomicrographs (x25) of foraminiferal pelletal phosphorite in petrographic thin section CRC40661-1, slide no. 1-12, parallel to bedding, basal lower calcareous-siliceous member, Monterey 

Formation, Rodeo Canyon section.
U.S. GEOLOGICAL SURVEY BULLETIN 1995-L PLATE 34

FORAMINIFERAL PELLET AL PHOSPHORITE, MONTEREY FORMATION,

RODEO CANYON SECTION
PLATE 35

Photomicrographs (x25) of foraminiferal pelletal phosphorite in petrographic thin section CRC40661-1, slide no. 1-7, parallel to bedding, basal lower calcareous-siliceous member, Monterey 

Formation, Rodeo Canyon section.
U.S. GEOLOGICAL SURVEY BULLETIN 1995-L PLATE 35

FORAMINIFERAL PELLET AL PHOSPHORITE, MONTEREY FORMATION,

RODEO CANYON SECTION
PLATE 36

Photomicrographs (x25) of foraminiferal pelletal phosphorite in petrographic thin sections CRC40661-1, slide no. 1-9, parallel to bedding (top photomicrograph) and CRC-40661-1, slide no. 1- 

9, parallel to bedding (bottom photomicrograph), basal lower calcareous-siliceous member, 

Monterey Formation, Rodeo Canyon section.
U.S. GEOLOGICAL SURVEY BULLETIN 1995-L PLATE 36

FORAMINIFERAL PELLETAL PHOSPHORITE, MONTEREY FORMATION,

RODEO CANYON SECTION
PLATE 37

Scanning electron micrographs of internal molds of foraminifers from pelletal phosphorite (CRC40660-1), basal lower calcareous-siliceous member, Monterey Formation, Rodeo Canyon section.

Figure 1. Rectuvigerina branneri (Bagg), side view, x50.

2. Rectuvigerina branneri (Bagg), side view, x60.

3. Rectuvigerina branneri (Bagg), side view, x50.

4. Marginulinopsis beali (Cushman), side View, xlOO.

5. Protoglobobulimina pseudotorta (Cushman), side view, x80.

6. Valvulineria robusta (Kleinpell), side view, x70.

7. Valvulineria robusta (Kleinpell), side view, x90.

8. Valvulineria robusta (Kleinpell), side view, x70.

9. Protoglobobulimina pseudotorta (Cushman) and Valvulineria robusta (Kleinpell), 

	side views, x60.

10. Valvulineria robusta (Kleinpell), side view, x60.
U.S. GEOLOGICAL SURVEY BULLETIN 1995-L PLATE 37

10

FORAMINIFERS, MONTEREY FORMATION, RODEO CANYON SECTION
PLATE 38

Photomicrographs of Rectuvigerina branneri (Bagg) in petrographic thin sections, basal lower 

calcareous-siliceous member, Monterey Formation, Rodeo Canyon section.

Figure 1. x!28, CRC-40661-1, slide no. 1-7, parallel to bedding.

2. x80, CRC-40661-1, slide no. 1-6, parallel to bedding.

3. x80, CRC-40661-1, slide no. 1-6, parallel to bedding.

4. x!28, CRC-40661-1, slide no. 1-5, parallel to bedding.

5. x80, CRC-40661-1, slide no. 1-5, parallel to bedding.

6. x!28, CRC-40661-1, slide no. 1-7, parallel to bedding.

7. x80, CRC-40661-1, slide no. 1-7, parallel to bedding.

8. x80, CRC-40661-1, slide no. 1-7, parallel to bedding.
U.S. GEOLOGICAL SURVEY BULLETIN 1995-L PLATE 38

FORAMINIFERS, MONTEREY FORMATION, RODEO CANYON SECTION
PLATE 39

Photomicrographs of foraminifers in petrographic thin sections, basal lower calcareous-siliceous 

member, Monterey Formation, Rodeo Canyon section.

Figures 1-7. Rectuvigerina branneri (Bagg): 1, x50, CRC-40661-1, slide no. 1-6, parallel 

to bedding; 2, x50, CRC-40661-1, slide no. 1-6, parallel to bedding; 3, x50, 

CRC-40661-1, slide no. 1-6, parallel to bedding; 4, x50, CRC-40661-1, 

slide no. 1-6, parallel to bedding; 5, x50, CRC-40661-1, slide no. 1-6, 

parallel to bedding; 6, x50, CRC-40661-1, slide no. 1-6, parallel to bedding; 

7, x50, CRC-40661-1, slide no. 1-6, parallel to bedding.

8. Protoglobobulimina pseudotorta (Cushman), x80, CRC-40661-1, slide no. 

1-7, parallel to bedding.

9. Bolivina advenat Cushman, x320, CRC-40661-1, slide no. 1-6, parallel to 

bedding.
U.S. GEOLOGICAL SURVEY BULLETIN 1995-L PLATE 39

FORAMINIFERS, MONTEREY FORMATION, RODEO CANYON SECTION
PLATE 40

Photomicrographs of foraminifers in petrographic thin sections, basal lower calcareous-siliceous 

member, Monterey Formation, Rodeo Canyon section.

Figures 1-5. Pullenia miocenica Kleinpell: 1, x200, CRC-40661-1, slide no. 1-7, parallel 

to bedding; 2, x200, CRC-40661-1, slide no. 1-6, parallel to bedding; 3, 

x!28, CRC-40661-1, slide no. 1-7, parallel to bedding; 4, x200, CRC40661-1, slide no. 1-7, parallel to bedding; 5, x320, CRC-40661-1, slide no. 

1-6, parallel to bedding.

6. Siphonodosaria quadrulata (Cushman and Laiming), x50, CRC-40661-1, 

slide no. 1-6, parallel to bedding.

7. Globigerina bulloides d'Orbigny, x250, CRC-40661-1, slide no. 1-9, parallel 

to bedding.

8. Globigerinapseudociperoensis Blow, x250, CRC-40661-1, slide no. 1-9, 

parallel to bedding.

9. Globigerina sp.?, x250, CRC-40661-1, slide no. 1-9, parallel to bedding.
U.S. GEOLOGICAL SURVEY BULLETIN 1995-L PLATE 40

FORAMINIFERS, MONTEREY FORMATION, RODEO CANYON SECTION
PLATE 41

Photomicrographs of foraminifers in petrographic thin sections, basal lower calcareous-siliceous 

member, Monterey Formation, Rodeo Canyon section.

Figures 1,2. Pullenia miocenica Kleinpell, x200, CRC-40661-1, slide no. 1-9, parallel to 

bedding, and x250, CRC-40661-1, slide no. 1-12, parallel to bedding, 

respectively. 

3. Islandiella modeloensis (Rankin), x 128, CRC-40661 -1, slide no. 1-12,

parallel to bedding.

4,5. Pullenia miocenica Kleinpell, x320, CRC-40661 -1, slide no. 1 -12, parallel to 

bedding, and x250, CRC-40661-1, slide no. 1-12, parallel to bedding, 

respectively.

6. Islandiella modeloensis (Rankin), x!28, CRC-40661-1, slide no. 1-9, parallel 

to bedding.

7. Cancris baggi Cushman and Kleinpell, xlOO, CRC-40661-1, slide no. 1-12,

parallel to bedding.

8,9. Valvulineria robusta (Kleinpell), x 128, CRC-40661 -1, slide no. 1 -12, 

parallel to bedding, and xlOO, CRC-40661-1, slide no. 1-11, parallel to 

bedding, respectively.
U.S. GEOLOGICAL SURVEY BULLETIN 1995-L PLATE 41

FORAMINIFERS, MONTEREY FORMATION, RODEO CANYON SECTION
PL ATE 42

Photomicrographs of Valvulineria robusta (Kleinpell) in petrographic thin sections, basal lower 

calcareous-siliceous member, Monterey Formation, Rodeo Canyon section.

Figure 1. x80, CRC-40661-1, slide no. 1-6, parallel to bedding.

2. x80, CRC-40661-1, slide no. 1-5, parallel to bedding.

3. x 128, CRC-40661 -1, slide no. 1 -7, parallel to bedding.

4. x!28, CRC-40661-1, slide no. 1-6, parallel to bedding.

5. x80, CRC-40661-1, slide no. 1-6, parallel to bedding.

6. x!28, CRC-40661-1, slide no. 1-6, parallel to bedding.

7. x 128, CRC-40661 -1, slide no. 1 -6, parallel to bedding.

8. x 128, CRC-40661 -1, slide no. 1 -5, parallel to bedding.

9. x!28, CRC-40661-1, slide no. 1-6, parallel to bedding.
U.S. GEOLOGICAL SURVEY BULLETIN 1995-L PLATE 42

7 t^*±*'^,4mr s

FORAMINIFERS, MONTEREY FORMATION, RODEO CANYON SECTION
PL ATE 43

Photomicrographs of foraminifers in petrographic thin sections, basal lower calcareous-siliceous 

member, Monterey Formation, Rodeo Canyon section.

Figures 1-4. Anomalinoides salinasenis (Kleinpell): 1, x200, CRC-40661-1, slide no. 1- 

6, parallel to bedding; 2, x!28, CRC-40661-1, slide no. 1-5, parallel to 

bedding; 3, x!28, CRC-40661-1, slide no. 1-6, parallel to bedding; 4, x200, 

CRC-40661-1, slide no. 1-5, parallel to bedding.

5-8. Valvulineria robusta (Kleinpell): 5, x200, CRC-40661-1, slide no. 1-7, 

parallel to bedding; 6, x!28, CRC-40661-1, slide no. 1-7, parallel to 

bedding; 7, x!28, CRC-40661-1, slide no. 1-7, parallel to bedding; 8, x!28, 

CRC-40661-1, slide no. 1-7, parallel to bedding.
U.S. GEOLOGICAL SURVEY BULLETIN 1995-L PLATE 43

8

FORAMINIFERS, MONTEREY FORMATION, RODEO CANYON SECTION
PLATE 44

Photomicrographs of foraminifers in petrographic thin sections, basal lower calcareous-siliceous 

member, Monterey Formation, Rodeo Canyon section.

Figures 1-3. Anomalinoides salinasenis (Kleinpell): 1, x200, CRC-40661-1, slide no. 1- 

12, parallel to bedding; 2, x!28, CRC-40661-1, slide no. 1-9, parallel to 

bedding; 3, x!28, CRC-40661-1, slide no. 1-6, parallel to bedding. 

4. Rectuvigerina branneri (Bagg), x40, CRC-40661-1, slide no. 1-11, parallel

to bedding.

5,6. Lenticulina smileyi (Kleinpell) xlOO, CRC-40661-1, slide no. 1-8, parallel to 

bedding, and xlOO, CRC-40661-1, slide no. 1-11, parallel to bedding, 

respectively.

7. Gyroidina rosaformis (Cushman and Kleinpell), x200, CRC-40661-1, slide 

no. 1-12, parallel to bedding.

8. Rectuvigerina branneri (Bagg), x51, CRC-40661 -1, slide no. 1-11, parallel

to bedding.

9,10. Praeglobobulimina galliheri (Kleinpell), x!60, CRC-40661-1, slide no. 1- 

12, parallel to bedding, and x!60, CRC-40661-1, slide no. 1-12, parallel to 

bedding, respectively.

11. Protoglobobulimina pseudotorta (Cushman), x!28, CRC-40661-1, slide no. 

1-10, parallel to bedding.
U.S. GEOLOGICAL SURVEY BULLETIN 1995-L PLATE 44

FORAMINIFERS, MONTEREY FORMATION, RODEO CANYON SECTION
PL ATE 45

Photomicrographs of foraminifers in petrographic thin sections, basal lower calcareous-siliceous 

member, Monterey Formation, Rodeo Canyon section.

Figure 1. Valvulineria californica Cushman, x80, CRC-40661-1, slide no. 1-7, parallel to

bedding. 

2. Buliminella subfmiformis Cushman, x320, CRC-40661-1, slide no. 1-6, parallel

to bedding.

3,4. Protoglobobulimina pseudotorta (Cushman), x 128, CRC-40661 -1, slide no. 1 -7, 

parallel to bedding, and x!28, CRC-40661-1, slide no. 1-7, parallel to bedding, 

respectively. 

5. Islandiella modeloemis (Rankin), x80, CRC-40661-1, slide no. 1-7, parallel to

bedding.

6,7. Protoglobobulimina pseudotorta (Cushman), X128, CRC-40661-1, slide no. 1-6, 

parallel to bedding, and x!28, CRC-40661-1, slide no. 1-7, parallel to bedding, 

respectively.

8. Buliminella subfusiformis Cushman, x320, CRC-40661-1, slide no. 1-6, parallel 

to bedding.

9. Protoglobobulimina pseudotorta (Cushman), x200, CRC-40661-1, slide no. 1-7, 

parallel to bedding.
U.S. GEOLOGICAL SURVEY BULLETIN 1995-L PLATE 45

7 miv8 orTani^i 

FORAMINIFERS, MONTEREY FORMATION, RODEO CANYON SECTION
PLATE 46

Photomicrographs of foraminifers in petrographic thin sections, basal lower calcareous-siliceous 

member, Monterey Formation, Rodeo Canyon section.

Figure 1. Buliminella subfusiformis Cushman, x320, CRC-40661-1, slide no. 1-7, parallel

to bedding. 

2-6. Protoglobobulimina pseudotorta (Kleinpell): 2, x!28, CRC-40661-1, slide no.

1-7, parallel to bedding; 3, x!28, CRC-40661-1, slide no. 1-7, parallel to

bedding; 4, x!28, CRC-40661-1, slide no. 1-5, parallel to bedding; 5, x80,

CRC-40661-1, slide no. 1-7, parallel to bedding; 6, x!28, CRC-40661-1, slide

no. 1-5, parallel to bedding. 

7,8. Anomalinoides salinasemis (Kleinpell), x250, CRC-40661-1, slide no. 1-9,

parallel to bedding, and x200, CRC-40661-1, slide no. 1-9, parallel to bedding,

respectively.
U.S. GEOLOGICAL SURVEY BULLETIN 1995-L PLATE 46

8

FORAMINIFERS, MONTEREY FORMATION, RODEO CANYON SECTION

SELECTED SERIES OF U.S. GEOLOGICAL SURVEY PUBLICATIONS

Periodicals

Earthquakes & Volcanoes (issued bimonthly). 

Preliminary Determination of Epicenters (issued monthly).

Technical Books and Reports

Professional Papers are mainly comprehensive scientific reports 

of wide and lasting interest and importance to professional scientists 

and engineers. Included are reports on the results of resource studies 

and of topographic, hydrologic, and geologic investigations. They also 

include collections of related papers addressing different aspects of a 

single scientific topic.

Bulletins contain significant data and interpretations that are of lasting scientific interest but are generally more limited in scope or geographic coverage than Professional Papers. They include the results of 

resource studies and of geologic and topographic investigations, as well 

as collections of short papers related to a specific topic.

Water-Supply Papers are comprehensive reports that present significant interpretive results of hydrologic investigations of wide interest 

to professional geologists, hydrologists, and engineers. The series covers 

investigations in all phases of hydrology, including hydrogeology, availability of water, quality of water, and use of water.

Circulars present administrative information or important scientific information of wide popular interest in a format designed for distribution at no cost to the public. Information is usually of short-term 

interest.

Water-Resource Investigations Reports are papers of an 

interpretive nature made available to the public outside the formal 

USGS publications series. Copies are reproduced on request unlike 

formal USGS publications, and they are also available for public 

inspection at depositories indicated in USGS catalogs.

Open-File Reports include unpublished manuscript reports, maps, 

and other material that are made available for public consultation at 

depositories. They are a nonpermanent form of publication that may 

be cited in other publications as sources of information.

Maps

Geologic Quadrangle Maps are multicolor geologic maps on topographic bases in 7 Yz- or 15-minute quadrangle formats (scales mainly 

1:24,000 or 1:62,500) showing bedrock, surficial, or engineering geology. Maps generally include brief texts; some maps include structure 

and columnar sections only.

Geophysical Investigations Maps are on topographic or planimetric bases at various scales; they show results of surveys using 

geophysical techniques, such as gravity, magnetic, seismic, or radioactivity, which reflect subsurface structures that are of economic or geologic significance. Many maps include correlations with the geology.

Miscellaneous Investigations Series Maps are on planimetric or 

topographic bases of regular and irregular areas at various scales; they 

present a wide variety of format and subject matter. The series also 

includes 7 /4-minute quadrangle photogeologic maps on planimetric 

bases that show geology as interpreted from aerial photographs. Series 

also includes maps of Mars and the Moon.

Coal Investigations Maps are geologic maps on topographic or 

planimetric bases at various scales showing bedrock or surficial geology, stratigraphy, and structural relations in certain coal-resource 

areas.

Oil and Gas Investigations Charts show stratigraphic information for certain oil and gas fields and other areas having petroleum 

potential.

Miscellaneous Field Studies Maps are multicolor or black-andwhite maps on topographic or planimetric bases on quadrangle or irregular areas at various scales. Pre-1971 maps show bedrock geology 

in relation to specific mining or mineral-deposit problems; post-1971 

maps are primarily black-and-white maps on various subjects, such as 

environmental studies or wilderness mineral investigations.

Hydrologic Investigations Atlases are multicolor or black-andwhite maps on topographic or planimetric bases presenting a wide range 

of geohydrologic data of both regular and irregular areas; principal 

scale is 1:24,000, and regional studies are at 1:250,000 scale or smaller.

Catalogs

Permanent catalogs, as well as some others, giving comprehensive 

listings of U.S. Geological Survey publications are available under the 

conditions indicated below from the U.S. Geological Survey, Books 

and Open-File Reports Sales, Federal Center, Box 25286, Denver, CO 

80225. (See latest Price and Availability List.)

"Publications of the Geological Survey, 1879-1961" may be purchased by mail and over the counter in paperback book form and as a 

set of microfiche.

"Publications of the Geological Survey, 1962-1970" may be purchased by mail and over the counter in paperback book form and as a 

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"Publications of the Geological Survey, 1971-1981" may be purchased by mail and over the counter in paperback book form (two 

volumes, publications listing and index) and as a set of microfiche.

Supplements for 1982, 1983, 1984, 1985, 1986, and for subsequent years since the last permanent catalog may be purchased by mail 

and over the counter in paperback book form.

State catalogs, "List of U.S. Geological Survey Geologic and 

Water-Supply Reports and Maps For (State)," may be purchased by 

mail and over the counter in paperback booklet form only.

'Trice and Availability List of U.S. Geological Survey Publications," issued annually, is available free of charge in paperback booklet form only.

Selected copies of a monthly catalog "New Publications of the 

U.S. Geological Survey" are available free of charge by mail or may 

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wishing a free subscription to the monthly catalog "New Publications 

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Survey, 582 National Center, Reston, VA 22092.

Note. Prices of Government publications listed in older catalogs, 

announcements, and publications may be incorrect. Therefore, the prices 

charged may differ from the prices in catalogs, announcements, and 

publications.