Uranium in the 

Monterey Formation of 

California

U.S. GEOLOGICAL SURVEY BULLETIN 1581-A

Chapter A

Uranium in the 

Monterey Formation of 

California

By DAVID L. DURHAM

U.S. GEOLOGICAL SURVEY BULLETIN 1581

STUDIES OF URANIUM CONTENT AND GEOCHEMISTRY OF THE 

MONTEREY FORMATION, CALIFORNIA
DEPARTMENT OF THE INTERIOR 

DONALD PAUL MODEL, Secretary

U.S. GEOLOGICAL SURVEY 

Dallas L. Peck, Director

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON: 1987

For sale by the

Books and Open-File Reports Section

U.S. Geological Survey

Federal Center

Box 25425

Denver, CO 80225

Library of Congress Cataloging in Publication Data

Durham, David L., 1925- 

Uranium in the Monterey formation of California.

(Studies of uranium content and geochemistry of Monterey formation, 

California) (U.S. Geological Survey water-supply paper ; 1581-A)

Bibliography: p.

Supt. of Docs, no.: I 19.3:1581^A

1. Uranium ores California Pacific Coast. 2. Diagenesis CaliforniaPacific Coast. 3. Geology, Stratigraphic Miocene. 4. GeologyCalifornia Pacific Coast. 5. Geochemistry California Pacific Coast. 

I. Title. II. Series. III. Series: Geological Survey bulletin ; 1581-A. 

QE75.B9 no. 1581-A 557.3 s 85-600319 

[QE390.2.U7] [553.4'.932'09794
CONTENTS

Abstract Al 

Introduction Al

Purpose and scope of investigation Al 

Fieldwork and acknowledgments Al 

Monterey Formation A3 

Character A3

Environment of deposition A3 

Diagenesis A4

Uranium in Monterey Formation AS 

Form of uranium AS 

Analytical data AS 

Interpretation of analytical data A17 

Uranium in the marine environment A22 

Sea water A22 

Uranium content A22 

Extraction of uranium A22 

Role of organic carbon A22 

Role of phosphorus A24 

Role of silica A24 

Diatomaceous sediments A25 

Summary A25 

Conclusions A26 

References cited A26

FIGURES

1. Index map of localities A2

2-7. Histograms showing uranium contents of samples from the Monterey 

Formation:

2. Outcrop samples A9

3. Outcrop samples from the Temblor Range A10

4. Outcrop samples from outside the Temblor Range All

5. Samples of porcelanite, porcelaneous mudstone, and cherty 

porcelanite A12

6. Samples of diatomite and diatomaceous mudstone A13

7. Samples of calcareous mudstone A14

8. Graph showing thorium-uranium ratios for samples from the Monterey 

Formation A14

9. Typical X-ray diffractograms of porcelanite showing various height-towidth ratios (h/w) of (101) cristobalite peak A19

10. Graph showing relation of uranium content to stage of diagenesis of 

porcelanite samples A21

11. Graph showing relation of uranium content to organic carbon content of 

core samples from Monterey Formation and related rocks near Santa 

Maria A21

Contents III
TABLES

1. Uranium and thorium content of outcrop samples from Monterey 

Formation A6

2. Summary of uranium analyses of outcrop samples of Monterey 

Formation A8

3. Thorium analyses of outcrop samples from Monterey Formation A15

4. Analyses by emission spectroscopy for 19 elements in samples of Monterey 

Formation that have a wide range of uranium content A15

5. Uranium and thorium content of core samples from the Monterey 

Formation near the Temblor Range A16

6. Uranium, thorium, and organic carbon content of core samples from the 

Monterey Formation and related rocks from near Santa Maria A16

7. Uranium and thorium content of diatomite in cores taken on California 

Continental Borderland A17

8. Uranium and thorium content of lower Miocene diatom ooze from Bering 

Sea A17

9. Uranium and thorium content of siliceous sediments from the equatorial 

Pacific A18

10. Uranium and thorium content of siliceous rocks from South America and 

Mexico A18

11. Height-to-width ratio of the (101) cristobalite peak obtained by X-ray 

diffractometry of samples of porcelaneous rock A20

IV Contents
Studies of Uranium Content and Geochemistry of the 

Monterey Formation, California

Uranium in the Monterey Formation of California

By David L. Durham

Abstract

The Monterey Formation is chiefly marine diatomaceous, porcelaneous, and cherty rocks of Miocene age, which 

occurs in coastal California. These marine rocks originated 

as richly diatomaceous sediments that accumulated near the 

coast in a region of upwelling and high organic productivity, 

where decomposition of organic matter resulted in anoxic 

conditions on the sea-floor. Diagenesis that accompanied 

burial of the diatomaceous sediments converted the biogenous 

opal of diatoms to cristobalite (opal-CT) and quartz, producing the diatomite, porcelanite, and chert of the Monterey 

Formation.

The uranium content of analyzed samples from the 

Monterey Formation ranges from less than 2 to more than 1,850 

parts per million (ppm). The uranium content of 50 samples 

collected to represent various kinds of rock in the Monterey, 

but without regard to their radioactivity in the field, ranges from 

1.73 to 83.4 ppm, averages 11.1 ppm, and has a median value 

of 6.77 ppm. These values are considered representative of the 

formation.

It is remarkable that even at places in the Temblor Range 

where the Monterey contains more uranium than it does 

elsewhere, the only identified uranium minerals are of secondary origin, and they occur in quantities too small to account 

for the uranium present in the rock. Indeed, most of the 

uranium in the Monterey is associated with organic material, 

either by adsorption on the material or by incorporation in 

organic complexes.

Modern diatomaceous mud, which has accumulated 

under conditions like those of Monterey deposition, contains 

more uranium than most sediments. Sea water is an adequate 

and renewable source for the uranium in the mud, and the 

anoxic conditions associated with the mud deposition are conducive to the preservation of uranium-rich sediments, if not 

to their formation.

The Monterey Formation is a potential large-volume, lowgrade uranium source. It also is a potential source of secondary uranium for sandstone-type deposits in other formations.

INTRODUCTION

Purpose and Scope of the Investigation

In the mid-1950's low-grade uranium deposits were 

discovered by prospectors in the Temblor Range (fig. 1) 

of California (Bowes, 1955, p. 3; Troxel and Morton, 

1962, p. 335; Troxel and others, 1957, p. 678; Walker 

and others, 1956, p. 33-34). Interest in the deposits waned 

after only a limited amount of exploration and development work had been done, but interest revived briefly 

in the mid-1960's and again in the mid-1970's when the 

price of uranium made low-grade deposits more attractive. The Temblor Range uranium deposits occur in 

siliceous rocks that are commonly assigned to the 

Monterey Formation and are identical to rocks unequivocally assigned to the Monterey elsewhere. Certain 

questions concerning uranium in the Monterey Formation come immediately to mind: In what form does the 

uranium occur? Where did the uranium come from, and 

when? Are some kinds of rock in the Monterey richer 

in uranium than are other kinds? Is uranium enrichment 

of the formation limited to the Temblor Range, or is it 

more widespread? The purpose of this report is to address these questions by summarizing the character of the 

Monterey Formation, by reviewing data concerning the 

origin and diagenetic history of the Monterey, and by 

reporting and interpreting the results of analyses of 

samples from the formation. The geochemistry of 

uranium in the sea is considered, along with modern 

analogs of the sediments that formed the Monterey.

Fieldwork and Acknowledgments

Fieldwork was carried out in the Temblor Range 

in March, April, and October 1977, and elsewhere in 

October 1978 and April 1980.

Uranium in Monterey Formation A1
39°

123 C 122 C

\

38°

San Francisco

M 

/ v

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37

J

\

k

36°

7'/2 MINUTE QUADRANGLES

1 Sycamore Flat

2 Paraiso Springs

3 Jumpero Serra Peak

4 Reliz Canyon

5 Thompson Canyon

6 Bear Canyon

7 Cosio Knob

8 Espmosa Canyon

9 Williams Hill

10 Names Valley

11 Wunpost

12 Valleton

13 Stockdale Mountain

14 Bryson

15 Tierra Redonda Mountain

16 Bradley

17 Adelaida

18 Paso Robles

19 York Mountain

20 Templeton

21 Shale Point

22 Wilson Corner

23 Reward

24 Fellows

25 Mancopa

26 Casmalia

27 Lompoc

28 Los Alamos

29 Lompoc Hills

Santa Monica Mountains

,,,,,,

Los Angeles

X

1

3

\

S

>

2

4

6

V

5

7

9

14

JS

8

10

15

V

^

11

16

17

19

12

18

20

13

I*

 4

Lompoc 7

<*< fc"**,'<««

Figure 1. Index map of localities.

Delayed neutron determinations of uranium and 

thorium were made in the U.S. Geological Survey 

Analytical Laboratories by H. T. Millard, Jr., R. Bies, 

C. Bliss, M. F. Coughlin, S. Danahey, A. J. Eartel, 

C. M. Ellis, B. A. Keaten, R. J. Knight, S. W. Lasater, 

F. Lumen, C. McFee, R. L. Nelms, C. A. Ramsey, C. 

L. Shields, M. W. Sold, J. Storey, and R. B. Vaughn;

Harriet Neiman made eU determinations by beta-gamma 

sealer; M. Retsloff determined elements by emission spectroscopy. Mark Stanton made organic carbon determinations by combustion after acid leaching. Courteney 

Williamson made X-ray diffractograms of porcelanite 

samples and determined the height-to-width ratios of the 

(101) cristobalite peaks on them. G. G. Start made

A2 Studies, Uranium Content and Geochemistry, California
X-ray determinations of uranium minerals. J. A. Barren 

studies fossil diatoms and W. O. Addicott identified fossil 

mollusks from the Temblor Range. C. M. Isaacs and 

L. A. Beyer provided core samples. J. R. Hein contributed samples of diatomite from Mexico and South 

America and core samples of diatomite and diatomaceous 

sediments from the sea bottom. J. S. Rapp of the California Division of Mines and Geology provided information 

on uranium claims in the Temblor Range.

MONTEREY FORMATION

The Monterey Formation contains a variety of 

rocks, but as so aptly pointed out by Bramlette (1946, 

p. 2), "its siliceous character makes it one of the most 

distinctive and easily recognized of the formations in the 

thick Tertiary System of California." Biogenous opal of 

diatoms generally is acknowledged as the principal source 

of the silica in the formation. The Monterey and correlative units that have local names occurs in California from just north of San Francisco southward to the 

Los Angeles area. Some of the best known occurrences 

are at Newport Bay, in the Palos Verdes Hills, in the 

Santa Monica Mountains, near Santa Barbara, by 

Lompoc, near Santa Maria, in the Salinas Valley area, 

and in the Temblor Range (fig. 1). The thickness of the 

Monterey is as great as 8,000-10,000 feet in the southern 

Salinas Valley area (Durham, 1974, p. 32). The formation is marine and of Miocene age. It contains foraminifers representing Kleinpell's (1938) Saucesian, Relizian, 

Luisian, Mohnian, and Delmontian Stages in ascending 

order.

The rocks themselves hold many clues to the origin 

and history of the Monterey Formation, and presumably 

also to the origin of the uranium in the unit. The character 

of the rocks, their environment of deposition, and their 

diagenetic history all are important to an understanding 

of the uranium content of the Monterey.

Character

The Monterey Formation is made up mainly of 

diatomaceous, porcelaneous, and cherty rocks. Where 

diatomite and diatomaceous mudstone occur they are in 

the upper part of the formation as near Lompoc, in the 

Temblor Range, and in parts of the Salinas Valley. 

Porcelanite and porcelaneous mudstone generally constitute the bulk of the upper part of the Monterey; and 

cherty rocks, siliceous mudstone, and calcareous 

mudstone are more characteristic of the lower part of the 

unit. Even the calcareous mudstone has a high silica content. Dolomite beds and concretions occur throughout 

the formation, and locally the Monterey contains beds 

of vitric tuff and beds of pelletal phosphorite. Rocks of

the Monterey commonly are thin bedded or laminated, 

but at some places they are thick bedded or massive.

The most common rocks of the formation have a 

high silica content. For example, ten samples of diatomite 

and porcelaneous rocks analyzed by emission spectroscopy had 31-39 percent silicon (table 4). Analyses of 

siliceous Monterey rocks given by Bramlette (1946, p. 13) 

showed about 70-90 percent SiO2 . X-ray analysis reveals 

that the silica is mainly in the form of opal, cristobalite, 

and quartz. The rocks also contain an appreciable amount 

of organic carbon (table 6).

The lithologic character of the Monterey Formation places certain restraints on the origin of the unit. Any 

reconstruction of the conditions under which the 

Monterey formed must account for, among other things, 

the silica and organic-carbon content of the rock, the 

general lack of all but the finest clastic material, the common lamination of the rock, and the occurrence of 

phosphorite beds.

Environment of Deposition

The abundance of remains of marine organisms in 

the Monterey Formation demonstrates the marine origin 

of the unit. Investigations of fossil foraminifers (Arnal 

and Vedder, 1976; Bandy and Arnal, 1969; Bandy and 

Kolpack, 1963; Ingle, 1963b, 1967, 1972, 1973; Patet, 

1972; Smith, 1968), diatoms (Barren, 1973, 1975), fish 

(David, 1940a, 1943; Pierce, 1956), radiolarians (Casey 

and Price, 1973; Ingle, 1967), and silicoflagellates 

(Cornell, 1969; Mandra, 1959) allow the following generalizations concerning the environment of deposition of 

the Monterey:

(1) The sediments accumulated in basins generally near 

shore.

(2) Water depths and effective sill depths of the basins 

of deposition varied, but commonly were bathyal.

(3) The region was one of upwelling and high organic 

productivity.

(4) Bottom water was anoxic much of the time.

(5) The contribution of terrigenous clastic material was 

minor in areas of typical Monterey sedimentation.

(6) Water temperatures fluctuated, perhaps reflecting 

changes in current patterns, but probably were comparable generally to water temperatures off California today.

The conditions under which sediments of the 

Monterey Formation accumulated commonly are likened 

to conditions presently found on the California Continental Borderland and in parts of the Gulf of California 

(Ingle, 1963a, b, p. 1771; Bandy and Kolpack, 1963, 

p. 154). Brongersma-Sanders (1948, p. 5, 1951, p. 406) 

compared the sediments that formed the Monterey to 

those found today in Walvis Bay off southwest Africa,

Uranium in Monterey Formation A3
and noted (1957, p. 970) that the catastrophic mass killing of fish recorded in a bed of diatomite near Lompoc 

is the exact equivalent of a layer of fish deposited in Walvis 

Bay during an enormous mass extinction of fish in 1924. 

Bramlette (1946, p. 37-38) concluded that diatomaceous 

deposits of the Monterey appear to be due to a combination of high productivity of diatoms and relatively little 

deposition of clastic material. Brongersma-Sanders (1957, 

p. 970) considered that the open-sea conditions indicated 

by fossil fish in the Monterey, together with the presence 

of diatom ooze, demonstrates deposition in a region of 

upwelling and hypertorphic conditions. Lipps and Kalisky 

(1973) studied calcareous nannoplankton in Oligocene and 

Miocene rocks and concluded that (1) when the Monterey 

was deposited, the California coast was under the influence of a current that flowed south with a velocity nearly that of the modern California Current, and (2) 

upwelling probably was as important in the region during the Miocene as it is today.

In modern seas, areas of richly diatomaceous sediments occur where divergence of surface-water masses 

causes upwelling of deep waters rich in nutrients, especially silica (Brongersma-Sanders, 1948, p. 82; Calvert, 

1974, p. 278; Lisitsyn, 1967, p. 998; Ramsay, 1973, p. 199). 

Upwelling conditions may persist in an area for long 

periods of time. For example, Siesser (1980, p. 285) determined that the upwelling system off southwest Africa 

began about 10 million years ago, and Busch and Keller 

(1981, p. 707) noted that upwelling has continued off the 

coast of Peru since at least the late Miocene.

Conditions under which modern marine diatomaceous sediments accumulate permits the following generalizations, which can be compared to conditions already 

outlined for deposition of the Monterey Formation:

(1) Sustained upwelling of nutrient-rich waters to the surface and consequent prolific production in the 

euphotic zone is required (Brongersma-Sanders, 1948, 

p. 82; Calvert, 1974, p. 278; Lisitsyn, 1967, p. 998, 

Ramsay, 1973, p. 199).

(2) Turbulent water and strong bottom currents must be 

absent to allow settling of very fine grained material 

(Baturin, 1971b, p. 374; Lisitsyn, 1967, p. 1125).

(3) Sedimentation of diatoms is favored by production 

of robust forms (Brongersma-Sanders, 1948, p. 83; 

Lisitsyn, 1967, p. 999), and by incorporation of the 

diatoms in fecal pellets (Lisitsyn, 1972, p. 154; 

Schrader, 1971, p. 57; Smayda, 1971, p. 117).

(4) Little or no terrigenous clastic detritus or other material dilutes present-day diatomaceous deposits 

(Brongersma-Sanders, 1948, p. 82-83; Lisitsyn, 1967, 

p. 1121).

(5) Rapid sedimentation favors preservation of organic 

carbon (Muller and Suess, 1979, p. 1356), and 

decomposition of organic material in the sediments 

by sulfate-reducing bacteria produces H2S 

(Brongersma-Sanders, 1948, p. 89, 1966, p. 41; Berner, 

1978, p. 493; Boon and others, 1978, p. 638; Redfield 

and others, 1963, p. 42).

The anoxic conditions commonly associated with 

diatomaceous sediments are a consequence of, not a prerequisite for the accumulation of the sediments. However, 

because of the importance of a reducing environment in 

the geochemistry of uranium, the accumulation of 

diatomaceous sediments under anoxic conditions seems 

to be an important factor affecting uranium content of 

the sediments.

Diagenesis

Studies of the diagenesis of the Monterey Formation and similar rocks (Calvert, 1966; Hein and others, 

1978; lijima and Tada, 1981; Isaacs, 1979; Kastner and 

others, 1977; Murata and others, 1977; Murata and 

Larson, 1975; Murata and Nakata, 1974; Siever and Stein, 

1976) lead to the following generalizations concerning the 

formation:

(1) The Monterey began as richly diatomaceous 

sediments composed mainly of biogenous opal (opalA) extracted by diatoms from normal sea water to 

form their frustules.

(2) Early diagenesis of the sediments involved dissolution of the biogenous opal followed by precipitation 

of either inorganic opal or highly disordered cryptocrystalline cristobalite (opal-CT).

(3) Diagenesis continued with progressive ordering of 

cristobalite by a solid-state transformation.

(4) In the final stage of diagenesis, well-ordered 

cristobalite was converted to microcrystalline quartz, 

probably by a solution-precipitation process involving only limited migration of silica.

(5) The conversion of opal to cristobalite and quartz is 

a function mainly of temperature; the conversion also 

is affected by the purity of the diatomaceous sediments and the chemical nature of interstitial water.

(6) The cristobalite found in outcrops of Monterey rocks 

may be partly of secondary origin that is, added 

during or after uplift of the rocks.

A4 Studies, Uranium Content and Geochemistry, California
URANIUM IN THE MONTEREY FORMATION 

Form of Uranium

Autunite, meta-autunite, and uranophane were 

identified by X-ray diffractometry in samples of 

Monterey Formation from the Temblor Range. Carnotite 

is the only other uranium mineral reported from the area 

(Finch, 1967, p. 8). The identified uranium minerals are 

all secondary and are found on fracture and bedding surfaces. The concentration of uranium in fractured rock 

and fault zones is mentioned in descriptions of uranium 

deposits of the Temblor Range (Walker and others, 1956, 

p. 33; Troxel and others, 1957, p. 687). Finch (1967, p. 8) 

classified the Temblor Range deposits as epigenetic that 

is, deposits formed by precipitation from solutions that 

moved through the host rock and Osterwald (1965, 

p. 125) noted structural control of uranium mineralization at a claim in the Temblor Range. Obviously, then, 

the association of secondary uranium minerals with zones 

of broken rock is related to the ease with which 

uraniferous ground water can permeate such zones. But 

some samples contain much more uranium than can be 

accounted for by any secondary uranium minerals present. One sample (764005), for example, contained more 

than 1850 parts per million (ppm) uranium in rock almost 

devoid of identifiable uranium minerals. No uranium 

minerals were seen nor were any found by X-ray analysis 

in Monterey rocks outside the Temblor Range. Clearly, 

secondary uranium minerals do not account for all or 

even for very much of the uranium present in the 

Monterey Formation.

Langmuir (1978, p. 562) noted that autunite and 

uranophane most often occur near uraniferous alkalic igneous rocks, which tend to be low in vanadium and 

relatively high in silica or phosphate, or both. The term 

"alkalic igneous rocks" might be replaced in this statement by the term "rocks of the Monterey Formation." 

The notion that autunite precipitates from ground water 

where phosphate is present and vanadium rare and that 

uranophane forms in silica-rich systems deficient in 

vanadium and phosphate can apply as well to Monterey 

terrains as to igneous terrains. The abundance of secondary uranium minerals in the Temblor Range compared 

to any other areas of Monterey outcrops perhaps can be 

attributed to the effect of the aridity of the Temblor 

Range on the vadose-water regime there.

Five samples (764005, 764010, 771020, 772027, 

802037) from the Monterey Formation, which did not 

have any identifiable minerals, nevertheless did contain 

from 50 to 1850 ppm uranium. Radioluxographs of these

samples show a diffuse background radioactivity. The 

only concentrations of radioactivity were related to cracks 

and to iron oxide discoloration in the rock. The scanning 

electron microscope failed to show any identifiable 

uranium minerals even in the sample (764005) that contained more than 1850 ppm uranium (J. R. Hein, personal commun., 1981).

Analytical Data

Delayed neutron analysis of 111 outcrop samples 

from the Monterey Formation were made for uranium 

and thorium (table 1). Table 2 summarizes the data, and 

figures 2-7 show it graphically. All results given in the 

tables are in the form reported from the laboratory.

The uranium content of the 111 samples analyzed 

(fig. 2) ranged from about 1.7 to 1854 ppm1 , averaged 

54.12 ppm, and had a median value of 10.4 ppm, but 

these numbers have little meaning beyond showing that 

the Monterey Formation seems to have a higher uranium 

content than do most rocks certainly more than the 

average of 3-4 ppm uranium for all shale (Swanson, 1961, 

p. 70). The results of analyses of particular categories of 

samples were more revealing. Samples from the Temblor 

Range (fig. 3) had a higher average and median value than 

did other Monterey Formation samples, but this mainly 

was because of the high uranium content of samples from 

uranium prospects. Uranium values for samples from the 

Temblor Range, but not from prospects, were much 

closer to those for samples collected outside the range. 

Perhaps more significant are the results of analyses of 

50 samples collected to represent different kinds of rock 

within the Monterey Formation and without bias with 

regard to their radioactivity as measured in the field with 

a scintillation counter (fig. 4B). The uranium content of 

these 50 samples ranged from 1.73 to 83.4 ppm, had an 

average value of 11.1 ppm, and had a median value of 

6.77 ppm; these values probably can be considered 

representative of a large part of the Monterey throughout 

California, and they too show that the Monterey as a 

whole has a higher uranium content than do most 

formations.

Consideration of the uranium content of various 

kinds of rock in the Monterey Formation also is useful. 

The uranium content of 64 samples of porcelanite, the 

most common rock in the Monterey, ranged from 2.40 

to 767 ppm, had an average value of 48.41, and had a 

median value of 10.8 ppm (fig. 5), but these figures are

'Another analysis of one sample, 764005, showed 2380 ppm 

uranium. The reason for the discrepancy is unknown.

Uranium in Monterey Formation A5
Table 1. Uranium and thorium content of outcrop samples from Monterey Formation

[Counties: K, Kern; M, Monterey; SB, Santa Barbara; SLO, San Luis Obispo. Abbreviations for rocks: ch, chert; di, diatomite; do, dolomite; 

me, calcareous mudstone; md, diatomaceous mudstone; mp, porcelaneous mudstone; ms, siliceous mudstone; pc, cherty porcelanite; ph, phosphorite; 

po, porcelanite; ss, sandstone; tu, tuff. , leaders indicate no data]

Field 

No.

'764001A

'764001B

'764002

764003

'764005

'764006

'764007

'764008

'764009

'764010

771001

771008

771010

'771016

771020

'771021

771040

771051

'771064

'771065

771080

771083

'771120

771139

772009

'772015

'772027

'772031

'772035

772054A

772063

772083

'772111

772113

'772115

772122

772139

772140

772149

773009

773010

784001

784002

784003

784004

784005

784006

784007

784008

784009

784010

784011

Lab. No.

D 187770

D 187771

D187772

D187773

D 187774

D187775

D187776

D187777

D187778

D 187779

Ml 3 1628

M 13 1629

M131630

M131631

M131632

M131633

M131634

M131635

M131636

M131637

M131638

M131639

M 13 1640

M131641

M131642

M131643

M131644

M131645

M131646

M131647

M131648

M131649

M131650

M131651

M131652

M131653

M131654

M131655

M131656

D 192877

D192878

Ml 37998

Ml 37999

Ml 38000

Ml 38001

Ml 38002

Ml 38003

Ml 38004

Ml 38005

Ml 38006

Ml 38007

Ml 38008

Lat. N

35<05'55"

3S°05'55"

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Long. W

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119°34'50"

119°35'00"

119°3T05" 119°37'10"

119°36'40"

119°35'15"

119°37'00"

119°34'50"

119°33'10"

119°3ri5"

119°3r30"

119°33'55"

119°32'30"

119°32'25"

119°32'15"

121°13'40"

121 0H'55"

120°27'45"

120°27'45"

120°24'05"

120°23'55"

120°17'00"

120°26'20"

120°3r30" 120°22'20"

120°22'20"

121W30"

121W40"

Quadrangle 

(7'/2 min)

Maricopa

Maricopa

Maricopa

Maricopa

Fellows

Fellows

Fellows

Fellows

Reward

Shale Point

Fellows

Fellows

Fellows

Fellows

Fellows

Fellows

Fellows

Fellows

Fellows

Fellows

Fellows

Fellows

Fellows

Fellows

Fellows

Fellows

Fellows

Fellows

Fellows

Fellows

Fellows

Fellows

Fellows

Fellows

Fellows

Fellows

Fellows

Fellows

Fellows

Thompson Canyon

Thompson Canyon

Lompoc Hills

Lompoc Hills

Lompoc Hills

Lompoc Hills

Los Alamos

Lompoc

Casmalia

Wilson Corner

Wilson Corner

Williams Hill

Williams Hill

County

K

K

K

K

K

SLO

SLO

K

K

K

K

K

K

K

K

K

K

SLO

SLO

K

SLO

K

K

SLO

SLO

SLO

SLO

SLO

SLO

SLO

K

K

K

K

K

SLO

K

K

K

M

M

SB

SB

SB

SB

SB

SB

SB

SLO

SLO

M

M

Rock

po

po

po

po

di

di

di

po

po

po

di

di

mp

di

di

mp

mp

po

po

po

po

po

di

md

po

po

po

po

po

po

di

di

po

di

di

po

po

di

di

po

mp

di

ch

po

di

mp

di

di

po

ph

mp

mp

Scintillometer 

reading 

in field 

(c.p.s.)

630

580

800-900

200

6000

300-350

1800

2500

1800

600

160-180

110-130

160-180

250

120-130

1100-1200

140-160

300-600

800-900

2700

120-130

250

190

180-220

200-230

250-300

600-660

1300

1000-1200

130-150

90-100

120-130

230-250

100-120

200-210

110-120

180-210

180-220

220

90-110

70-90

200-220

70-80

110-120

120-130

80-90

160-180

160-180

420-470

220-250

U 

(ppm)

165.67

51.51

205.48

4.37

1854.73

31.83

290.21

259.78

149.00

83.13

10.4

4.44

20.2

44.2

12.2

86.6

3.10

20.1

71.5

344.

9.34

55.3

33.6

27.4

14.3

21.1

767.

109.

131.

21.9

5.46

2.58

74.3

44.2

18.6

4.40

7.99

77.9

22.2

3.28

5.81

8.40

3.21

18.5

2.26

11.5

7.65

3.58

10.7

39.8

55.4

18.9

Th 

(ppm)

6.02

_

10.

5.5

 

10.

15.

_

10.9

_ _

 

<7.6

<2.8

<7.3

8.2

<5.2

<6.5

6.8

<5.3

<8.8

<12.

<6.8

eU 

(ppm)

100

40

120

20

1220

30

240

200

150

60

20

10

30

50

10

120

10

30

120

250

20

50

30

40

30

40

390

110

130

20

10

10

50

20

20

10

10

50

30

10

<10

Th/U

1.38

0.96

1.77

 

 

___

1.07

___

1.05

4.22

 

 

<0.90

<0.87

<0.39

3.63

<0.45

<0.85

1.90

<0.50

<0.72

<0.22

<0.36

1 Sample from uranium prospect. 

A6 Studies, Uranium Content and Geochemistry, California
Table 1. Uranium and thorium content of outcrop samples from Monterey Formation Continued

Field

No.

784012

784013

784014

784015

784016

784017

784018

784019

784020

802001

802002

802003

802004

802005

802006

802007

802008

802009

802010

802011

802012

802013

802014

802015

802016

802017

802018

802019

802020

802021

802022

802023

802024

802025

802026

802027

802028

802029

802030

802031

802032

802033

802034

802035

802036

802037

802038

802039

802040

802041

802042

802043

802044

802045

802046

802047

802048

802049

802050

Lab. No.

Ml 38009

M138010

M138011

M138012

M138013

M138014

M138015

M138016

M138017

M 144058

M144059

M 144060

M144061

M 144062

M144063

M 144064

M144065

M 144066

M 144067

Ml 44068

M 144069

M 144070

M 144071

M144072

M 144073

M 144074

M 144075

M 144076

Ml 44077

Ml 44078

M 144079

M 144080

M 144081

Ml 44082

M 144083

M 144084

M 144085

M 144086

Ml 44087

M 144088

M 144089

M144090

M 144091

M144092

M144093

M 144094

M 144095

M 144096

M 144097

M144098

M 144099

M144100

M144101

M144102

M144103

M144104

M144105

M144106

M144107

Lat. N

35°50'55"

36 TO '20" 35°57'50"

36^8 '20"

36^8 '30"

36°13'35"

36°13'40"

36°13'40"

36°16'00"

36°14'10"

36°14'00"

36°14'30"

36°15'20"

36°16'45"

36°15'30"

36°15'30"

36°16'50"

36°12'10"

36°13'50"

36 ^5 '40"

36°04'40"

36TO'40"

36 TO.' 30"

36TO'30"

36 °04'45"

36 °Q4'35"

36°Q4'4Q"

36°04'40"

35°53'50"

35°54'50"

35°52'00"

35°51'05"

35°46'40"

35°47'40"

35°47'35"

35°54'00"

36<W40"

36W10"

35°58'30"

35°59'10"

35°59'15"

35°45'45"

35°56'45"

35°55'50"

35°59'40"

35°39'30"

35°38'05"

35°36'20"

35°37'35"

35°33'40"

35°28'50"

35°28'45"

35°28'45"

35°28'45"

35°28'35"

35°54'30"

35°14'15"

35°41'20"

35°53'10"

Long. W

121 ^2 '05"

121°15'00"

120°38'35"

121°13'00"

121°12'30"

121°16'40"

121°16'40"

121°16'40"

121°26'05"

121°28'15"

121°27'30"

121°26'00"

121°25'50"

121°27'00"

121°25'20"

121°25'20"

121°19'20"

121°16'30"

121°16'50" m^'so"

121°10'50"

121°H'00"

121°13'20"

121°13'20"

121°15'10"

121°16'40"

121°16'35"

121°16'35"

121^06'00"

121 ^5 '10"

121 TO '40"

121 TO '05"

120°53'20"

120°53'00"

120°51'50"

120°57'30"

121 TO '20"

I2l°04'00"

121TO'00"

121*01' 10*

120°57'40"

120°53'00"

120°39'45"

120°40'40"

120°38'45"

120°46'30"

120°51'20"

120°50'20"

120°44'00"

120°39'00"

120°24'45"

120°24'50"

120°24'50"

120°24'50"

120°24'40"

120°32'50"

120°46'40"

120°46'50"

121TO'55"

Quadrangle 

(7'/2 min)

Bryson

Bear Canyon

Valleton

Thompson Canyon

Thompson Canyon

Reliz Canyon

Reliz Canyon

Reliz Canyon

Sycamore Flat

Juniper o Serra Pk.

Junipero Serra Pk.

Junipero Serra Pk.

Sycamore Flat

Sycamore Flat

Sycamore Flat

Sycamore Flat

Paraiso Springs

Reliz Canyon

Reliz Canyon

Cosio Knob

Cosio Knob

Cosio Knob

Cosio Knob

Cosio Knob

Bear Canyon

Bear Canyon

Bear Canyon

Bear Canyon

Williams Hill

Williams Hill

Bryson

Bryson

Tierra Redonda Mtn.

Tierra Redonda Mtn.

Bradley

Hames Valley

Espinosa Canyon

Espinosa Canyon

Williams Hill

Williams Hill

Hames Valley

Tierra Redonda Mtn.

Valleton

Valleton

Valleton

Adelaida

Adelaida

York Mountain

Paso Robles

Templeton

Wilson Corner

Wilson Corner

Wilson Corner

Wilson Corner

Wilson Corner

Stockdale Mountain

Adelaida

Adelaida

Williams Hill

County

M

M

M

M

M

M

M

M

M

M

M

M

M

M

M

M

M

M

M

M

M

M

M

M

M

M

M

M

M

M

M

M

SLO

M

M

M

M

M

M

M

M

SLO

M

M

M

SLO

SLO

SLO

SLO

SLO

SLO

SLO

SLO

SLO

SLO

M

SLO

SLO

M

Rock

di

po

po

me

po

po

po

do

po

me

me

me

po

me

ph

po

mp

po

po

po

po

po

po

po

po

ss

ss

eh

po

po

po

me

me

po

eh

po

po

pc

po

mp

mp

me

mp

di

po

me

me

me

po

po

tu

eh

ms

ms

me

mp

me

po

do

Scintillometer 

reading 

in field 

(c.p.s.)

140

200-220

130-150

140-150

200-220

110-130

180-190

120-130

250-270

200-220

120-140

130-150

170-190

180-200

210-240

130-140

160-180

130-140

110-120

90-100

90-110

90-100

100-120

140-150

100-120

100-110

200-210

110-120

110-120

100-110

120-140

130-150

100-120

140-160

90-110

90-100

90-100

80

100-110

160-170

130-140

90-100

140-160

60-65

150-170

250-270

120-130

150-160

60-70

120-125

210-240

95-110

190-210

140-145

100-110

120-130

65-70

95-105

60-65

U 

(ppm)

14.0

21.8

8.71

10.5

14.3

4.13

9.65

2.28

22.4

12.3

6.01

7.00

8.95

13.5

83.4

5.34

5.81

8.06

8.56

6.30

6.65

7.07

2.48

10.2

5.04

6.42

45.0

1.73

9.93

12.2

11.3

19.9

10.5

6.02

6.17

6.89

5.88

2.40

6.80

10.9

2.84

6.28

15.3

2.66

12.7

52.6

6.74

16.3

4.72

22.4

9.45

2.31

9.88

5.29

4.52

3.24

2.80

5.39

6.44

Th 

(ppm)

<6.7

<6.5

<5.1

<4.4

<5.3

4.4

<4.6

<1.7

<5.9

16.9

<6.3

<6.5

12.

23.

<25.

8.7

12.

17.

<9.2

9.4

<8.8

<9.4

7.0

18.

<7.2

<4.9

<16.

<3.1

<10.

<11.

<8.7

<17.

<9.6

<6.6

7.9

<6.7

<9.1

<4.9

<6.4

16.

12.3

<8.2

<12.

7.4

13.

<19.

<8.2

<12.

<7.2

<14.

29.2

<3.4

33.0

<9.1

<4.8

12.4

<3.2

<5.4

<7.3

eU 

(ppm)

 -

30

20

10

40

30

70

10

20

20

20

10

20

10

10

60

10

10

60

10

40

30

40

10

40

10

10

10

30

10

10

20

10

10

10

30

20

60

10

30

10

10

50

10

30

20

10

10

30

10

10

Th/U

<0.48

<0.30

<0.59

<0.42

<0.37

1.07

<0.48

<0.75

<0.26

1.37

<1.05

<0.93

1.34

1.70

<0.30

1.63

2.07

2.11

<1.07

1.49

<1.32

<1.33

2.82

1.77

<1.43

<0.76

<0.36

<1.79

<1.01

<0.90

<0.77

<0.85

<0.91

<1.10

1.28

<0.97

<1.55

<2.04

<0.94

1.47

4.33

<1.31

<0.78

2.78

1.02

<0.36

<1.22

<0.74

<1.53

<0.63

3.09

<1.47

3.34

<1.72

<1.06

3.83

<1.14

<1.00

<1.13

Uranium in Monterey Formation A7
Table 2. Summary of uranium analyses of outcrop samples of Monterey Formation

Outcrop samples (fig. 2)

Samples

A. All samples 

B. Samples not from uranium prospects

Number of 

samples

111 

91

Uranium content (ppm)

Range

1.73-1854.73 

1.73- 73.4

Average

54.12 

13.35

Median

10.4 

8.40

A. All samples 

Samples from Temblor Range (fig. 3) B. Samples from uranium prospects

C. Samples not from uranium prospects

Samples from outside Temblor 

Range (fig. 4).

A. All samples

B. Samples collected without respect to 

radioactivity

Samples of porcelanite, porcelaneous A. All samples

mudstone, and cherty porcelanite B. Samples not from uranium prospects

(fig. 5). C. Samples from outside Temblor Range

Samples of diatomite and 

diatomaceous mudstone (fig. 6).

Calcareous mudstone (fig. 7)

A. All samples

B. Samples not from uranium prospects

C. Samples from outside Temblor Range

39

20

19

72

50

64

49

40

21

15

6

13

2.58-1854.73 132.31 33.6

18.6 -1854.73 239.61 97.8

2.58- 77.9 19.36 12.2

1.73- 83.4 10.6 7.36

1.73- 83.4 11.1 6.77

2.40- 767. 

2.40- 55.4 

2.40- 55.4

2.26-1854.73 

2.26- 77.9 

2.26- 14.0

2.80- 52.6

48.41 10.8

11.42 8.56

10.46 8.31

119.92

16.36

6.43

13.0

14.0

8.40

5.62

10.5

biased by inclusion of samples from uranium prospects 

in the Temblor Range. If samples from prospects are 

omitted, however, the range of uranium content of the 

remaining samples was 2.40-55.4 ppm, the average was 

11.42 ppm, and the median was 8.56 ppm. Samples of 

Monterey porcelanite from outside the Temblor Range 

had uranium content of 2.40-55.4 ppm, averaged 

10.46 ppm, and had a median of 8.31 ppm values not 

appreciably different from those obtained for Monterey 

porcelanite samples including those from the Temblor 

Range, but outside uranium prospects. This suggests that, 

except for the prospects, the uranium content of 

porcelanite in the Temblor Range is about the same as 

that elsewhere.

The uranium content of 21 samples of diatomite 

from the Monterey Formation (fig. 6) ranged from about 

2 to 1854 ppm, had an average value of 119.92 ppm, and

had a median value of 14.0 ppm. Again, these values are 

biased by inclusion of diatomite samples from uranium 

prospects. Only six samples of diatomite from outside the 

Temblor Range were analyzed too few from which to 

draw any well-founded conclusions but the uranium 

content of these six ranged from 2.26 to 14.0 ppm, had 

an average value of 6.43 ppm, and had a median value 

of 5.26 ppm, values which are somewhat greater than for 

many kinds of rock.

The uranium content of 13 samples of calcareous 

mudstone from the Monterey Formation in the southern 

Salinas Valley area (fig. 7) ranged from 2.80 to 52.6 ppm, 

had an average value of 13.0 ppm, and had a median 

value of 10.5 ppm. The uranium content of four samples 

of similar rock from Newport Bay (not included in table 

1 or fig. 7) ranged from 5.33 to 11.6 ppm and had an 

average value of 8.01 ppm. These values for Monterey

Text continues on page A14.

A8 Studies, Uranium Content and Geochemistry, California
NUMBER OF SAMPLES

_. N) 00 A O O O O O

O
50

40

> 

O

§30

0 20

cc

10

0

50

40

LLJ 

0_ 

5 

<

W

30

O

cc.

£20

10

OO O O O O O O

«- CM in O O O o O

T- CM m O O

^ CM

URANIUM (ppm)

B

URANIUM (ppm)

_ _ _ o o

o o o o o

^ CM in o O

«- CM

URANIUM (ppm)

Figure 3. Histograms showing uranium content of outcrop samples from Temblor Range; values are listed in table 

2. A, All samples. 8, Samples from uranium prospects. C, Samples not from uranium prospects.

A10 Studies, Uranium Content and Geochemistry, California
NUMBER OF SAMPLES PERCENT FREQUENCY

o o

41.8

50.0
40

30

20

10

B

 ~ CM mooooooo 

«- cs m o o o Q

"-cNmOOOOO O 

«- CM in O O O

CM m o o o o o

 CM m o o

«- CM in

URANIUM (ppm) URANIUM (ppm) URANIUM (ppm)

Figure 5. Histograms showing uranium content of porcelanite, porcelaneous mudstone, and cherty porcelanite; 

values are listed in table 2. A, All samples. B, Samples not from uranium prospects. C, Samples from outside the 

Temblor Range.

A12 Studies, Uranium Content and Geochemistry, California
B

50

40

LLJ

_l 

CL

30

O

DC 

LU 

CO

10

 -csinoooooo

O O

URANIUM(ppm) URANIUM (ppm) URANIUM (ppm)

Figure 6. Histograms showing uranium content of samples of diatomite and diatomaceous mudstone; values are 

listed in table 2. A, All samples. 8, Samples not from uranium prospects. C, Samples from outside the Temblor Range.

Uranium in Monterey Formation A13
50

40

o

z

UJ 30 

O

LLJ 

CC

a 20

cc

LLJ

a.

10

0

50

40

30

O 

cc

LLJ

co 20

10

 -CMlflOOOOOOOO 

«- CM in O OOOO

«- CM in o o 

URANIUM (ppm)

Figure 7. Histograms showing uranium content of samples of calcareous 

mudstone; values are listed in table 2.

calcareous mudstone are close to those for Monterey 

porcelanite from outside uranium prospects.

Only a few analyses of other kinds of rock from 

the Monterey Formation were made, all samples from 

outside the Temblor Range. The uranium content of four 

samples of chert ranged from 1.73 to 6.17 ppm, had an 

average value of 3.36 ppm, and had a median value of 

2.76 ppm. Two samples of dolomite contained 2.28 and

6.44 ppm uranium, two samples of bedded pellet 

phosphorite contained 39.8 and 83.4 ppm uranium, and 

a sample of vitric tuff contained 9.45 ppm uranium. Chert 

seems generally to have the lowest uranium content of 

the major kinds of rock in the Monterey. Dolomite beds 

and concretions also appear to have a uranium content 

lower than for most rocks in the formation. The high 

values for phosphorite are to be expected, considering the 

normal affinity of uranium for phosphorus. The uranium 

content of the tuff is in the normal range for siliceous 

volcanic rocks.

Dependable values for thorium content were obtained for only 26 outcrop samples from the Monterey 

Formation (table 3). If samples of tuff and siliceous 

mudstone are omitted, the thorium content of the remaining samples more typical of the Monterey ranged from 

4.4 to 18 ppm, had an average value of 11.24 ppm, and 

had a median value of 10.45 ppm. The thorium-uranium 

ratio ranges from 0.96 to 4.33 but more than half of the 

values are less than 2, and nearly all are less than 3 (fig. 

g)_ratio values that are less than for most rocks. Nearly all samples with uranium content greater than 3.5 ppm 

have thorium-uranium ratios between 1 and 2. There appears to be no other relation between either uranium or 

thorium values and the thorium-uranium ratio.

Ten outcrop samples from the Monterey Formation were analyzed by emission spectroscopy for 19 

elements other than uranium and thorium (table 4). The 

samples had a wide range of uranium content, but they 

all showed no obvious relation between uranium and any 

of the other elements listed.

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 

URANIUM (ppm)

Figure 8. Graph showing thorium-uranium ratios for samples 

from Monterey Formation. Abbreviations for rocks: C, chert; 

D, diatomite; MC, calcareous mudstone; MP, porcelaneous 

mudstone; P, porcelanite.

A14 Studies, Uranium Content and Geochemistry, California
Table 3. Thorium analyses of outcrop samples from Monterey Formation

[Abbreviations for rocks: ch, chert; di, diatomite; me, calcareous mudstone; mp, porcelaneous mudstone;

ms, siliceous mudstone; po, porcelanite; tu, tuff]

Field No.

764003

771001

771040

771080

772009

772083

784004

784007

784017

802001

802004

802005

802007

802008

802009

802011

802014

802015

802026

802031

802032

802035

802036

802042

802044

802047

Lab. No.

D 187773

M 13 1628

M131634

M131638

M131642

M131649

M138001

Ml 38004

M138014

M 144058

M144061

M 144062

M 144064

M 144065

M144066

M 144068

M 144071

M 144072

M 144083

M 144088

M 144089

M 144092

M 144093

M 144099

M144101

M144104

Rock

po

di

mp

po

po

di

di

di

po

me

po

me

po

mp

po

po

po

po

ch

mp

mp

di

po

tu

ms

mp

Th

(ppm)

6.02

10.

5.5

10.

15.

10.9

8.2

6.8

4.4

16.9

12.

23.

8.7

12.

17.

9.4

7.0

18.

7.9

16.

12.3

7.4

13.

29.2

33.0

12.4

U 

(ppm)

4.37

10.4

3.10

9.34

14.3

2.58

2.26

3.58

4.13

12.3

8.95

13.5

5.34

5.81

8.06

6.30

2.48

10.2

6.17

10.9

2.84

2.66

12.7

9.45

9.88

3.24

Th/U

1.38

0.96

1.77

1.07

1.05

4.22

3.63

1.90

1.07

1.37

1.34

1.70

1.63

2.07

2.11

1.49

2.82

1.77

1.28

1.47

4.33

2.78

1.02

3.09

3.34

3.83

Table 4. Analyses by emission spectroscopy for 19 elements in samples of Monterey Formation that have a wide range of uranium

content

[Abbreviations for rocks: di, diatomite; mp; porcelaneous mudstone; po, porcelanite]

Field

No.

772083

772063

784005

784020

771016

764010

Lab.

No.

M131649

M131648

Ml 38002

M138017

M131631

D187779

774001 A DI 87770

771065

772027

764005

M131637

M131644

D 187774

Rock

di

di

mp

po

di

po

po

po

po

di

U 

(ppm)

2.58

5.46

11.5

22.4

44.2

83.13

165.67

344.

767.

1854.73

B Ba Be Co Cr Cu Ga Mo Ni Sr V Y Zr

(ppm)

150

100

100

20

220

90

110

57

90

120

380

80

410

490

400

320

650

230

360

450

2.2

1.3

1.9

2.1

2.2

2.0

2.1

1.3

2.0

2.1

5.8 88

1.4 22

6.1 140

3.7 110

4.6 120

3.8 110

3.6 58

1.2 54

7.2 100

7.7 150

18 11

25 <10

27 13

43 15

46 11

42 12

50 11

25 <10

35 15

31 16

10 30

10 9.4

19 35

31 15

13 46

3668

12040

3427

39 26

<10 38

150 100

33 30

110 120

150 130

240 180

190 97

270 130

180 62

200 120

140 130

22 110

<10 <20

25 170

22 87

42 89

12 75

12 160

11 <20

16 82

24 180

Al K Mg Na P Si

(percent)

5.1 1.3 0.72 1.8 0.04 35

1.1 0.24 0.21 0.59<.02 <40

6.1 1.6 0.51 1.2 <.45 31

5.3 1.8 0.42 1.1 0.07 39

5.3 1.2 0.85 1.2 <.45 34

5.1 1.2 0.55 0.66 0.04 37

4.6 1.6 0.48 1.2 0.13 37

2.4 0.54 0.32 0.60 0.03 <40

5.6 1.3 0.59 0.90 0.06 34

6.4 1.4 0.67 1.3 <.45 33

Uranium in Monterey Formation A15
Table 5. Uranium and thorium content of core samples from the Monterey Formation near 

the Temblor Range

[Samples from wells of the Standard Oil Company of California located just east of Temblor Range in 

sec. 26, T. 12 N., R. 24 W.; Samples provided by L. A. Beyer and C. M. Isaacs. Abbreviations for rocks; 

md, diatomaceous mudstone; ms, siliceous mudstone; po, porcelanite; si, siltstone. , leaders indicate 

not present]

Well

Anza Pacific Corp. 59

Ethel D-101

Lab. No.

D 192869

D 192870

D192871

D192872

D192873

D192874

D192875

D192876

Depth 

(feet)

1265

1430

1489

1535

2077

1112

1165

1464

Rock

md

po

ms

po

po

ms

ms

si

U 

(ppm)

18.87

9.36

10.52

11.08

8.20

8.74

6.58

8.17

Th 

(ppm)

 

 

21.00

10.09

18.26

eU 

(ppm)

20

20

30

10

10

10

20

20

Th/U

 

 

2.00

1.53

2.24

Table 6. Uranium, thorium, and organic carbon content of core samples from the Monterey Formation and related rocks from

near Santa Maria

[Samples from wells of Union Oil Company; samples and stratigraphic data provided by C. M. Isaacs]

Well

Bradley 1

(sec. 26, T. 10 N.,

R. 34 W.)

Dome 18

(sec. 24, T. 9 N.,

R. 34 W.)

Newlove 51

(sec. 25, T. 9 N.,

R. 34 W.)

Lab. No.

D236001

D236000

D235997

D235999

D235998

D235980

D235981

D235982

D235983

D235984

D235985

D235986

D235987

D235988

D235989

D235990

D235991

D235992

D235993

D235994

D235995

D235996

Depth

(feet)

4156-4165

4840-4849

9868-9875

10,889-10,904

11,005-11,014

1395-1416

1783-1798

1937-1955

1980-2002

1980-2002

2018-2033

2119-2137

2154-2165

2240-2267

2262-2276

2435-2443

2625-2641

2660-2677

2677-2696

3451-3460

3475-3491

3491-3509

U 

(ppm)

8.43

13.4

4.53

2.93

17.1

2.79

4.32

11.6

14.5

12.2

8.08

13.1

13.1

20.6

15.8

32.2

16.5

14.0

3.02

3.78

4.13

4.07

Th

(ppm)

<4.7

<6.2

9.19

<2.6

<6.3

5.6

10.3

<6.6

<6.6

<6.6

<4.8

13.8

14.5

<7.9

<6.8

<10

<6.7

<6.2

5.8

11.7

6.9

8.79

Th/U Organic carbon Remarks 

(percent)

<0.56

<0.46

2.03

<0.89

<0.37

2.01

2.38

<0.57

<0.46

<0.54

<0.59

1.05

1.11

<0.38

<0.43

<0.31

<0.41

<0.44

1.81

3.10

1.67

2.16

3.44

14.4

0.74

1.39

2.13

0.86

0.91

3.45

4.15

3.85

4.53

9.26

7.47

7.24

6.40

12.7

9.48

7.85

4.05

2.22

2.11

1.87

Monterey Formation

Monterey Formation

Sisquoc Formation (dolomite)

Monterey Formation

Monterey Formation

Sisquoc Formation (clay rich)

Sisquoc Formation (clay rich)

Monterey Formation (cherty zone)

Monterey Formation (cherty zone)

Monterey Formation (cherty zone)

Monterey Formation (cherty zone)

Monterey Formation (cherty zone)

Monterey Formation (bentonitic)

Monterey Formation (bentonitic)

Monterey Formation (bentonitic)

Monterey Formation (bentonitic)

Monterey Formation (bentonitic)

Monterey Formation (bentonitic)

Monterey Formation (bentonitic)

Point Sal Formation

Point Sal Formation

Point Sal Formation

A16 Studies, Uranium Content and Geochemistry, California
Eight samples of Monterey Formation from cores 

from near the Temblor Range, and 22 samples of 

Monterey and related formations from cores from near 

Santa Maria were analyzed for uranium and thorium 

(tables 5,6). The results show that the Monterey, in these 

two areas at least, has as much or more uranium in the 

subsurface than it generally does at the surface. Also, the 

thorium-uranium ratios of the core samples generally are 

lower than ratios common in outcrop samples.

The 22 core samples from near Santa Maria also 

were analyzed for organic carbon (table 6). The organic 

carbon content of 16 samples from the Monterey Formation ranged from 1.39 to 14.4 percent, averaged 6.36 

percent, and had a median value near 6 percent.

The uranium content of seven samples of diatomite 

from cores of rocks correlative with the Monterey Formation taken on the California Continental Borderland 

ranged from about 7 to 41 ppm (table 7), values considerably higher than for most outcrop samples of the 

Monterey. On the other hand, the uranium content of 

lower Miocene diatom ooze from the Bering Sea (table

8), and of siliceous sediments from the equatorial Pacific 

(table 9) generally are less than 3 ppm, considerably less 

than for most rocks of the Monterey. However, 19 

samples of siliceous rocks from South America and Mexico were analyzed and found to have about the same 

uranium content as do similar rocks in the Monterey 

(table 10).

Interpretation of Analytical Data

If the samples from uranium prospects in the 

Temblor Range are omitted, samples of Monterey Formation analyzed show no systematic regional variation 

in uranium content. This seems to show that conditions 

that caused the accumulation of uranium prevailed 

wherever diatomaceous sediments of the Monterey 

formed; variations in uranium content depended on 

factors other than location. This suggestion is supported 

by the similarity of the uranium content of diatomite and 

porcelanite from Mexico and Peru to that of similar rocks

Table 7. Uranium and thorium content of diatomite in cores taken on California Continental Borderland 

[Samples provided by J. R. Hein. , leaders indicate no data]

Field No.

L2-78-SC-29

L2-78-SC-123

L2-78-SC-134

L2-78-SC-158

L2-78-SC-179

L2-78-SC-184

L2-78-SC-322

Lab. No.

D226938

D226939

D226940

D226941

D226942

D226943

D226944

Lat. N

33°51'42"

32°21'48"

32°19'24"

32°30'12"

32°32'54"

32°31'24"

33°50'12"

Long. W

119°28'12"

118°24'42"

118°52'24"

119°19'06"

119°37'12"

119°41'12"

119°53'

U 

(ppm)

19.8

41.6

17.5

9.36

7.17

20.0

24.2

Th eU 

(ppm) (ppm)

<19 _

<28 30

<16 <10

<10 20

<11 20

<16 10

<15 60

Th/U

<0.96

<0.67

<0.91

<1.07

<1.53

<0.80

<0.62

Table 8. Uranium and thorium content of lower Miocene diatom ooze from Bering Sea 

[Samples provided by J. R. Hein. , leaders indicate no data]

Field No.

19-184-7-1-110-112

19-184-10-2-118-120

19-184-17-2-86-88

19-185-6-3-95-97

19-188-2-1-120-124

19-188-8-6-145-147

19-188-15-2-134-136

19-190-1-1-48-50

19-190-13-1-105-108

19-192-4-3-130-132

19-192-14-3-40-42

19-192-20-1-100-104

Lab. No.

D226945

D226946

D226947

D226948

D226949

D226950

D226951

D226952

D226953

D226954

D226955

D226556

Lat.

53°42

53°42

53°42

53°25

54°25

54°25

54°25

55°33

55°33

53^00

53^00

53^00

N

'38"

'38"

'38"

'44"

'44"

'44"

'44"

'33"

'33"

'34"

'34"

'34"

Long.

170 °55'

170°55'

170 °55'

169 °14'

169 °14'

169 °14'

169 °14'

171°38'

171°38'

164 °42'

164 °42'

164 °42'

W

23"

23"

23"

35"

35"

35"

35"

25"

25"

49"

49"

49"

U 

(ppm)

2.31

2.48

2.01

1.43

2.56

1.5

<0.59

1.47

2.17

1.65

2.51

3.14

Th eU 

(ppm) (ppm)

<5.5

6.6

7.8

<5.5

<9.1

<7.5

<5.0

<5.6

<6.4

7.4

<6.4

<5.9

10

<10

10

10

10

20

<10

20

<10

40

10

20

Th/U

<2.38

2.66

3.88

<3.85

<3.55

<5.00

<8.47

<3.81

<2.95

4.48

<2.55

<1.88

Silt

Silt

Silt

Silt,

 _

Silt

Silt

Silt,

Silt

Silt

Remarks

and clay bearing.

bearing, clay rich.

bearing, clay rich.

clay, and spicule bearing.

and clay bearing.

and clay bearing.

clay, and carbonate bearing.

and clay rich.

bearing, clay rich.

Uranium in Monterey Formation A17
Table 9. Uranium and thorium content of siliceous sediments from the equatorial Pacific 

[Samples provided by J. R. Hein. , leaders indicate no data]

Field No. Lab. No. Lat. N Long. 6 W , U . (ppm) . T . (ppm)

, eU . 

(ppm)

Th/U Remarks

46-1-9-12CM-A D226977 9°20'42" 150°50'42" 2.32 11.

46-1-9-12CM-B 

52-42-4-7CM-A 

52-42-4-7CM-B 

48-19-22-26A

48-19-22-26B

D226978 9°20'42" 150°50'42" 1.8 22.

D226979 11°15'30" 1399Q3'18" 2.13 12.

D226980 11°15'30" 1399Q3'18" <2.5 <24

D226981 8°16'30" 151W30" 1.67 11.3

60

60

D226982 8°16'30" 1519Q7'30" <4.0 <40

4.74 Glass-bearing, clayey siliceous

ooze, 5160 m depth. 

12.2 Same, >44/x size fraction. 

5.63 Siliceous mud, 4871 m depth.

 Same >44/x size fraction. 

6.7 Glass-bearing, siliceous, fossilrich mud, 5045 m depth.

 Same >44/x size fraction.

of the Monterey. In other words, rocks similar to those 

in the Monterey have a similar range of uranium content, regardless of where they formed.

The uranium content of diatomite, porcelanite, and 

calcareous mudstone samples from the Monterey 

Formation except samples from uranium prospects 

were all in the same general range of values, but the 

uranium content of the few chert samples analyzed was 

lower. This difference suggests that uranium was lost during the later stages of diagenesis of Monterey rocks. To 

determine whether this apparent loss of uranium is 

gradual or abrupt, the uranium content of 29 samples of 

porcelanite was compared with the degree of diagenesis 

of the rock (table 11). The degree of diagenesis can be

approximated from the ordering of cristobalite as expressed by the height-to-width ratio of the (101) cristobalite peak obtained by X-ray diffractometry of 

whole-rock samples (fig. 9). For samples that contain less 

than 15 ppm uranium that is, samples that probably 

have not been enriched appreciably beyond their original 

uranium content the uranium content generally 

decreases with an increase in the degree of diagenesis (fig. 

10). This relationship suggests that uranium may be lost 

during diagenesis of porcelanite, and presumably this 

uranium would be available in mobile form for enrichment of other rocks.

Water-depth changes during Miocene time are not 

reflected in any trend of the uranium content of rocks

Table 10. Uranium and thorium content of siliceous rocks from South America and Mexico

[Sample collected by J. R. Hein. Abbreviations for rocks: ch, chert; di, diatomite; pc, cherty porcelanite; po, porcelanite]

Field No.

979-13-1A 

979-13-2C

979-15-1

979-18-1A

979- 18- IB

979-18-2B

979-18-2C

979-18-3

979-18-4B

979-18-4C

979-18-4D

979-18-4E

H6-1C

H6-1D

H6-2A

H6-2B

H6-2E

1179-1-1A

1179-1-1B

Lab. No.

D226957 

D226958

D226959

D226960

D226961

D226962

D226963

D226964

D226965

D226966

D226967

D226968

D226969

D226970

D226971

D226972

D226973

D226974

D226975

Lat.

2°35' 

2°35'

2°35'

14°35'

14°35'

14°30'

14°30'

14°35'

13°45'

13°45'

13°45'

13°45'

31905'

31905'

31905'

319Q5'

31905'

24°20'

24°20'

S 

S

S

S

S

S

S

S

S

S

S

S

N

N

N

N

N

N

N

Long. W

80°45' 

80°45'

80°45'

75°45'

75°45'

75°45'

75°45'

75°

76°25'

76°25'

76°25'

76°25'

115905'

115905'

1159Q5'

115905'

115905'

1119Q2'

111902'

Rock

ch 

ch

ch

di

di

di

di

di

di

di

di

di

di

di

di

di

di

pc

po

U 

(ppm)

<0.23 

0.80

1.41

6.04

5.42

4.69

4.13

5.78

49.8

19.2

14.0

2.67

5.64

5.31

6.21

6.50

7.63

2.23

3.19

Th eU 

(ppm) (ppm)

<2.2 

<2.6

<3.1

17.7

14.4

16.9

11.

<8.6

<30.

<14.

<15.

9.9

<9.3

8.4

<10.

<9.1

<12.

<4.2

<4.7

10 

10

10

20

60

30

10

20

40

<10

40

30

10

20

20

30

40

20

10

Th/U

<3.25

<2.20

2.93

2.65

3.60

2.66

<1.49

<0.60

<0.73

<1.07

3.71

<1.65

1.58

<1.61

<1.40

<1.57

<1.88

<1.47

Remarks

Miocene(?), Equador. 

Miocene(?), Equador.

Miocene(?), Equador.

Miocene(?), Peru.

Miocene(?), Peru.

Miocene(?), Peru.

Miocene(?), Peru.

Miocene(?), Peru.

Miocene(?), Peru.

Miocene(?), Peru.

Miocene(?), Peru.

Miocene(?), Peru.

Miocene-Pliocene ,

Miocene-Pliocene ,

Miocene-Pliocene,

Miocene-Pliocene ,

Miocene-Pliocene,

Baja Calif.

Baja Calif.

Baja Calif.

Baja Calif.

Baja Calif.

Miocene, Baja Calif.

Miocene, Baja Calif.

A18 Studies, Uranium Content and Geochemistry, California
w/2 w/2

26 24 22 20 18 

DEGREES 20

16 26 24 22 20 18 

DEGREES 26

16

26 24 22 20 18 

DEGREES 26

16 26 24 22 20 

DEGREES 26

18 16

Figure 9. Typical X-ray diffractograms of porcelanite showing various height-to-width ratios 

(h/w) of (101) cristobalite peak. Such ratios help to determine the degree of diagenesis 

of the rock.

Uranium in Monterey Formation A19
Table 11 . Height-to-width ratio of the (101) cristobalite peak 

obtained by X-ray diffractometry of samples of porcelaneous 

rock

Sample No.

764003

771080

772009

772122

772139

784005

784008

784014

784017

784018

802004

802007

802009

802010

802011

802012

802013

802014

802015

802016

802020

802021

802022

802025

802029

802030

802036

802040

802049

height/width

4.10

2.24

0.87

3.7

2.17

1.37

2.79

3.26

3.14

3.14

2.78

2.62

2.20

1.37

3.91

3.08

3.22

2.84

1.89

3.55

2.17

2.00

3.22

2.17

3.87

3.48

2.57

4.28

3.14

U (ppm)

4.37

9.34

14.3

4.40

7.99

11.5

10.7

8.71

4.13

9.65

8.95

5.34

8.06

8.56

6.30

6.65

7.07

2.48

10.2

5.04

9.93

12.2

11.3

6.02

2.40

6.80

12.7

4.72

5.39

of the Monterey Formation, which suggests that water 

depth was less important than other factors in the accumulation of uranium in the sediments that formed the 

Monterey. However, details concerning the conditions of 

deposition of most of the samples are too few to allow 

any firm conclusions regarding the relation of depositional environment to uranium content. On the other 

hand, it does seem likely that persistence of the anoxic 

conditions commonly associated with the deposition of 

diatomaceous sediments should be an important 

consideration.

Comparison of the uranium and thorium contents 

of samples from the Monterey Formation provides some 

insight into the source of the uranium found in the formation. A thorium-uranium ratio of 3 or 4 is characteristic of most rocks in the Earth's crust and of sediments

composed of debris from these rocks. On the other hand, 

sea water and water in streams that feed the sea have a 

very low ratio of dissolved thorium to uranium (Adams 

and Weaver, 1958, p. 429). This low ratio reflects the 

much greater solubility of uranium compared to thorium, 

and consequently the greater amount of uranium that 

goes into solution during weathering of terrestrial rocks. 

Adams and Weaver (1958, p. 415) concluded that a low 

(<2) thorium-uranium ratio in sediments or sedimentary 

rocks indicates that most of the uranium in the sediment 

or rock was extracted from water rather than contributed 

by detrital matter derived from rocks. Therefore, the 

generally low 2 or less thorium-uranium ratio in rocks 

of the Monterey Formation (tables 1, 3, 5, and 6) suggests 

that most of the uranium was derived from sea water. 

Such a conclusion is reasonable when it is realized

A20 Studies, Uranium Content and Geochemistry, California
15

1.10 

a

123 4 5 

HEIGHT/WIDTH, (101) CRISTOBALITE PEAK

Figure 10. Graph showing relation of uranium content to 

stage of diagenesis of porcelanite samples. (The degree of diagenesis is represented by the ordering of diagenetic cristobalite as expressed by the height-to-width ratio of the (101) 

cristobalite peak obtained by X-ray diffractometry; table 11.)

that nearly all the substance of pure diatomaceous rocks 

was derived from sea water. It also is compatible with 

the observation that some of the highest thorium-uranium 

values found in the Monterey occur in rocks such as 

mudstone that have a substantial proportion of 

terrigenous debris. Moreover, the commonly lower 

thorium/uranium values found in core samples, as compared to surface samples, can be interpreted as evidence 

that some uranium has been leached from the surface 

rocks during weathering.

Samples of diatom ooze from the Bering Sea (table 

8) and of siliceous sediments from the equatorial Pacific 

(table 9) have higher thorium-uranium ratios than are 

common in rocks of the Monterey Formation. However, 

these oceanic sediments formed under conditions quite 

different from conditions under which Monterey sediments accumulated. In fact, these oceanic sediments have 

a low uranium content, and their high thorium-uranium 

ratios indicate that what little uranium they have came 

from terrestrial particulate material rather than from sea 

water. By contrast, the thorium-uranium ratios of most 

samples of Montereylike rocks from South America and 

Mexico (table 10) are similar to the ratios for rocks from 

the Monterey Formation, which may suggest a similar, 

sea-water origin for the uranium in all Montereylike 

rocks.

The samples of pellet phosphorite from the 

Monterey Formation that were analyzed for uranium 

(samples 784009 and 802006) have, as expected, a higher 

uranium content than do most Monterey rocks. This comparatively high uranium content is easily attributed to the 

well-known affinity of uranium for phosphate minerals. 

However, the lack of any correlation between uranium 

and phosphorus in other kinds of Monterey rock that 

were analyzed for both elements (table 4) shows that little

or none of the uranium in these other rocks is involved 

with phosphate minerals.

The general increase in uranium content with increase in organic-carbon content of core samples of 

Monterey Formation (fig. 11) suggests that at least an appreciable part of the uranium in the samples is associated 

in some way with organic material. This is consistent with 

the work of Burton and Sullivan (1951, p. 884), who 

found an excellent correlation between carbon and 

uranium contents of Miocene shale from the Lawndale 

oil field near Los Angeles. Conversely, Ross (1952, p. 791) 

found that the radioactivity of Miocene shale from the 

Playa del Rey oil field, also near Los Angeles, is localized in inorganic nodules and layers, particularly in 

phosphatic material, rather than in organic layers and 

veinlets.

Although rocks of the Monterey Formation and 

equivalent beds generally are considered to be the principal source of oil in the reservoir rocks of California oil 

fields, California crude oil is not especially high in 

uranium. The uranium content of 11 samples of crude 

oil from Tertiary rocks of California given by Bell (1960, 

table 2) ranged from 0.1 to 37.7 parts per billion (ppb), 

averaged 5.04 ppb, and had a median value of 1.6 ppb. 

This compares to the range for crude oil generally from 

less than 1 ppb to a few tens ppb (Bell, 1960, p. 51). 

However, asphalt-bearing rocks of California contain 

more uranium than do most such rocks, and the asphalt 

likely originated in the Monterey Formation (Hail and 

others, 1956, p. 524; Bell, 1960; p. 54). Bell (1960, table 

3) listed the uranium contents of 51 samples of rock 

asphalt from California Tertiary rocks; the uranium

15

EXPLANATION 

° Sisquoc Formation 

. Monterey Formation 

x Point Sal Formation

10 15 20 25 

URANIUM (ppm)

30 35

Figure 11. Graph showing relation of uranium content to 

organic-carbon content of core samples from Monterey Formation and related rocks near Santa Maria.

Uranium in Monterey Formation A21
content ranged from 0.17 to 70.3 ppm,, averaged 5.22 

ppm, and had a median value of 1.6 ppm. These figures 

show that uranium is not concentrated more in rock 

asphalt than it is in the Monterey.

Although a connection between the uranium and 

organic-carbon contents of rocks from the Monterey Formation appears probable, it is difficult to consider 

petroleum to be responsible for the uranium in the formation, for the uranium content of both crude oil and 

asphalt are less than the uranium content of most 

Monterey rocks. To account for the uranium in the 

Monterey it seems best to review aspects of uranium in 

the marine environment. A considerable amount of information on uranium in sea water and in marine sediments is available.

URANIUM IN THE MARINE ENVIRONMENT 

Sea Water 

Uranium Content

Starik and Kolyadin (1957, p. 247) indicated that 

uranium occurs in sea water (1) in the colloidal state, (2) 

adsorbed on colloidal particles, and (3) as dispersed ions, 

including complexes with organic components of the 

water. Calculations concerning uranium supplied to and 

removed from the sea suggest that a steady state with 

respect to uranium is possible in the world ocean (Bloch, 

1980, p. 376). The calculations involve both particulate 

and dissolved uranium, but it seems likely that the dissolved uranium content of sea water does not vary 

greatly.

Goldberg (1963, p. 5) gave the uranium content of 

sea water as 3 ppb. Ku, Knauss, and Mathieu (1977) 

reviewed previous determinations and presented the 

results of their own analyses of 63 water samples from 

the Atlantic, Pacific, Arctic, and Antarctic Oceans. The 

uranium content of their samples ranged from 2.9 to 

3.6 ppb; they (1977, p. 1010) attributed the range to variation in the salinity of the water. They (1977, p. 1012) also 

determined the average uranium concentration of water 

in the open ocean (corrected to 35 parts per thousand 

salinity) to be 3.3 ±0.2 ppb. Hodge, Koide, and Goldberg 

(1979, p. 207) showed that some of the uranium in sea 

water is in particulate form, but Ku, Knauss, and Mathieu 

(1977, p. 1011) considered that nearly all is in the dissolved state. Sea water, then, seems to be an adequate 

and constant source of uranium, in the same way that 

sea water is the source of silica for diatomaceous 

sediments.

Extraction of Uranium

Evidence from the isotopic composition of uranium 

in modern marine sediments has been used to demonstrate 

that uranium presently is being extracted from sea water, 

but there seems to be no really clear evidence concerning 

the mechanism of extraction (Burton, 1965, p. 438). 

Uranium isotopes in sea water are in disequilibrium 

because 234U goes into solution more readily than does 

238U. The 234U/238U activity ratio in river water generally is greater than 1, and in residual solids it generally is 

about 1, or less. Thus, uranium from a terrigenous source 

in modern marine sediments may be identified by its 

234U/238U activity ratio of less than 1 (Hodge and others, 

1979, p. 207). For example, deep-sea clay has uranium 

concentrations and 234U/238U activity ratios similar to 

those of stream sediments, which shows that the clay is 

predominantly detrital. On the other hand, uranium concentrations in anoxic mud are much higher than in terrigenous debris, and the 234U/238U activity ratios for 

anoxic mud approach the sea-water value of 1.15, which 

indicates a sea-water origin for most of the uranium in 

the mud (Veeh, 1967, p. 147). Veeh, Calvert, and Price 

(1974, p. 193) used this evidence to determine that 

uranium is passing from sea water into diatomaceous 

sediments off California, Mexico, Central and South 

America, and southwest Africa. Application of the 

234U/238U activity ratio to finding the source of uranium 

is, of course, restricted to comparatively recent sediments.

Role of Organic Carbon

Although the means by which uranium is extracted 

from sea water and concentrated in marine sediments is 

uncertain, most investigators find a positive correlation 

between the uranium and organic-carbon contents of 

marine sediments (Baturin, 1968a, p. 345, 1973, p. 1034; 

Kuznetsov and others, 1968, p. 307; Mo and others, 

1971). Conversely, Veeh, Calvert, and Price (1974, p. 193) 

failed to find such a correlation for diatomaceous 

sediments off southwest Africa, either because no correlation exists or because it is masked by other factors 

that control distribution of uranium. Weber and Sackett 

(1981, p. 1328) also failed to find any correlation between 

uranium and organic carbon in sediments of the anoxic 

Orca Basin in the northwestern Gulf of Mexico.

Generally, the lowest uranium-organic carbon 

ratios occur in sandy and silty sediments deposited at 

relatively high rate, and the highest ratios occur in finegrained sediments enriched in both organic matter and 

uranium (Baturin, 1974, p. 190). Most deep-water oceanic 

sediments lack significant uranium enrichment because

A22 Studies, Uranium Content and Geochemistry, California
they contain little organic matter and are flushed by oxygenated water (Baturin and others, 1972, p. 281). 

Langmuir (1977, p. 27) suggested that clays, which are 

abundant in deep-water oceanic sediments, are relatively 

unimportant as concentrators of uranium. Balistrieri, 

Brewer, and Murray (1981, p. 119) suggested that the adsorption properties of particles sinking through the marine 

water column are controlled by organic coatings on the 

particles rather than by the properties of the particles 

themselves.

The general correlation of uranium and organic carbon in marine sediments could mean either that organic 

material incorporates uranium directly or that it produces 

a reducing environment favorable for chemical extraction 

of uranium from sea water. Baturin and Lisitsyn (1973, 

p. 878) reported experimental evidence that showed that 

uranium may be captured by organic matter under both 

anaerobic and aerobic conditions. Organic material that 

incorporates uranium directly might be in suspension, at 

the sediment surface, or within the sediments, but the 

water-sediment interface is considered the most likely 

place (Baturin, 1968a, p. 345, 347).

Baturin (1973, p. 1034) reported that uranium is not 

concentrated by living tissues, and thus extraction of 

uranium from sea water by organic material probably 

takes place not from the water column as a whole, but 

only at the bottom. But Degans, Khoo, and Michaelis 

(1977, p. 568) reported that in Black Sea sediments, 

uranium seems to be bound to planktonic rather than to 

land-derived organic debris. They tentatively concluded 

that certain organic compounds act as a substrate in the 

formation of hexavalent uranium complexes and concentrate uranium in the living cell as much as 10,000 times 

the uranium concentration in sea water. Thus, although 

reducing conditions may be needed for preservation of 

uranium-enriched debris, they may not be needed for fixation of uranium. Holland (1979, p. 1679) concluded that 

concentration of metals in organic-rich sediments apparently results more from chemical precipitation and 

from reactions with dead organic remains than from their 

incorporation in living organisms. Apparently, marine 

organisms can absorb uranium from sea water, and the 

concentration factor may be considerable (Zverev and 

others, 1976, p. 91), but the importance of organisms in 

extraction of uranium and the means by which they do 

it is uncertain.

Kuznetsov, Simonyak, Lisitsyn, and Frenklikh (1968, 

p. 307) concluded that there is little probability of biogenic 

extraction of uranium by suspended organic matter 

because they found little correlation between uranium and 

organic carbon in material collected from the water 

column in the Indian Ocean; they did find a direct

correlation between uranium and organic carbon in seafloor sediments, and they allowed that dissolved organic 

matter might interact with dissolved uranium, perhaps by 

ion exchange or chelation, and thereby transfer uranium 

to the bottom. Although the enhancement of uranium in 

sediments in anoxic regimes is well established, good 

evidence is lacking that reduction of uranium in the 

overlying water column contributes to the process (Burton, 1975, p. 102). More likely, uranium is removed from 

the sea water by reduction and sorption on organic matter on the sea floor (Baturin, 1969, p. 831; Baturin and 

others, 1976, p. 90; Kuznetsov and others, 1968, p. 310). 

Langmuir (1978, p. 565) considered that uranium after adsorption may be reduced to the U+4 of uraninite or coffinite by mobile reductants, such as hydrogen sulfide or 

methane, or by the sorbent itself. He (1977, p. 27) found 

good evidence that uranyl sorption is an important 

preconcentrating step leading to the formation of both 

uranyl and uranous minerals.

Baturn, Kochenov, and Kovaleva (1966, p. 174) explained a depletion of uranium in bottom water of the 

Black Sea by loss of uranium to the sediments, and 

Baturin (1968a, p. 345) concluded that the principal factor in the extraction of uranium by sediments is the 

geochemical activity of organic material the presence of 

hydrogen sulfide being only a marginal factor. Baturin 

(1974, p. 192) later generalized that the process by which 

uranium is concentrated in organic material in sediments 

is the same in basins with normal aeration as in basins 

with a hydrogen-sulfide environment. He then attributed 

the only slightly higher uranium-organic carbon ratio of 

anoxic sediments of the Black Sea, as compared to the 

ratio in sediments of normally aerated marine basins, to 

the extremely sluggish circulation of bottom water in the 

Black Sea. In other words, the enrichment of uranium in 

sediments depends, even under the best of other conditions on a continued supply of water undepleted in 

uranium. Baturin, Lebedev, and Mayev (1976, p. 89) considered that the accumulation of uranium in organic-rich 

sediments is independent of the hydrogen sulfide content 

of the water the hydrogen sulfide only affects the completeness with which uranium is extracted from the bottom layer of water.

The presence of hydrogen sulfide in diatomaceous 

and other highly organic sediments is common and indicates an anoxic regime. Samples of diatomaceous ooze 

taken from water depths greater than 60 m on the southwest African shelf had a pronounced odor of hydrogen 

sulfide, lacked an oxidized zone at the ocean floor surface, and had no sign of a benthonic fauna; these conditions indicate that below 60 m depth hydrogen sulfide 

there passes from the sediment into and remains in the

Uranium in Monterey Formation A23
bottom water, unlike at shallower depths where wave 

action aerates bottom water (Baturin and others, 1972, 

p. 282). But even in the highly anoxic Black Sea water 

Eh values are too high to allow precipitation of uranium 

by reduction of hexavalent to tetravalent uranium; 

however, interstitial waters in the upper layer of sediment 

may have Eh values low enough to allow such precipitation (Pokidin and others, 1972, p. 570). Ku, Knaus, and 

Mathieu (1977, p. 1013) found that the uranium content 

of pore water generally is close to, or slightly enriched 

over that of sea water, although Baturin (197la, p. 224) 

noted that during early diagenesis of sediments uranium 

passes into interstitial water, where its concentration may 

be tens or hundreds of times higher than in sea water. 

Regardless of conditions respecting pore water, the principal carriers of uranium in the sediment seems to be the 

components with maximum sorptive capacity organic 

matter and phosphates (Kochenov and others, 1977, p. 

86). Uranium is mobile during diagenesis of sediments, 

and apparently part of the uranium is in solution in the 

form of organometallic complexes (Baturin and 

Kochenov, 1973).

Bonatti, Fisher, Joensuu, and Rydell (1971) described a core of deep-sea hemipelagic sediment from off 

South America that had an upper oxidized zone above 

reduced sediments, and the upper oxidized zone is enriched in uranium, chromium, vanadium, and sulphur. 

They explained distribution of uranium in the core by the 

postdepositional mobility of uranium, mainly by diffusion in the interstitial solutions. They found no abrupt 

change in uranium concentration across the Eh interface 

in the core, but they noted a steady increase of uranium 

with depth in the reduced part of the core (1971, p. 196). 

They interpreted this increase as indicative of a slow, 

gradual reduction and fixation of uranium upon burial 

in the reduced zone.

In summary, organic material is instrumental in the 

formation of the anoxic environment necessary for the 

preservation of, if not for the extraction of uranium from 

sea water, and organic material is able to receive uranium 

by adsorption.

Role of Phosphorus

The conditions of up welling, high organic productivity, and accumulation of organic material that favor 

formation of uranium-enriched sediments also favor formation of phosphorite. The affinity of uranium for phosphate minerals is generally conceded, although Gavshin, 

Bobrov, and Zorkina (1974, p. 743) claimed that the correlation holds only for phosphates formed under certain 

circumstances and is not general. The uranium in 

phosphorite is believed to be in carbonate fluorapatite, 

where tetravalent uranium probably substitutes for Ca+2 

in the apatite crystal lattice, and hexavalent uranium is

chemically adsorbed on the mineral by surface reactions 

of uranyl ions (Cullen, 1978, p. M67). Organisms extract 

phosphorus from the surface waters and carry it to the 

sea floor when they die and sink to the bottom, but if 

extraction of phosphorus by organisms is not accompanied by extraction of uranium, then the common correlation of phosphorus and uranium in marine sediments 

must be the result of interaction of the two elements after 

death of the organisms (Kuznetsov and others, 1968, 

p. 310). Thus, the concentration of uranium in sea-bed 

phosphorites seems mainly syngenetic with respect to 

phosphorus (Baturin and Kochenov, 1974, p. 99). The 

uranium content of biogenic phosphate material incorporated in diatom ooze is sometimes appreciably higher 

than the uranium content of the enclosing sediments; 

nevertheless, the uranium in the phosphate accounts for 

no more than 5-10 percent of the total uranium in bulk 

samples of the ooze; most of the uranium is in some way 

related to organic matter (Baturin and others, 1972, 

p. 283).

Veeh, Calvert, and Price (1974, p. 196) found that 

bulk analyses of diatomaceous sediments from off southwest Africa showed no clear correlation between uranium 

and phosphate. They concluded from this that if the fixation of uranium in sediments is controlled by the 

presence of phosphorus, then the uranium content must 

be controlled primarily by a particular phosphate 

mineral presumably apatite that contains variable 

amounts of uranium. Another possibility is that the lack 

of correlation of uranium and phosphorus in marine 

sediments is due to an absence of biogenic phosphorus 

in the sediments (Baturin and Yemel'yanov, 1973, p. 

678).

Thus, although phosphorus is one possible agent 

for the extraction of uranium from sea water, it is by no 

means the only agent and probably is not the most important one.

Role of Silica

The possibility that part of the uranium found in 

the Monterey Formation is adsorbed onto, or otherwise 

involved with the opal of diatom frustules cannot be 

dismissed. Lewin (1961, p. 194) found that under particular conditions metal ions combine with the silica of diatom walls. Starik and Kolyadin (1957, p. 255) concluded 

that, under proper conditions, uranium in sea water exists as a hydrolyte that can be adsorbed on silica-bearing 

colloidal particles and is deposited on the sea bottom with 

these particles. Hurd (1973, p. 2275) pointed out that 

because of a strong negative charge on the surface of 

biogenic amorphous silica, the UO2 +2 ion can be strongly adsorbed on the diatom walls. Little information concerning the possible role of opal in extraction of uranium 

from sea water is available, but uranium enrichment of

A24 Studies, Uranium Content and Geochemistry, California
opal and cristobalite does occur although under circumstances different from those affecting the Monterey 

Formation. Zielinski (1980) described uraniferous secondary opal and chalcedony in Wyoming that formed from 

uraniferous, silica-saturated ground water. He proposed 

that both silica and uranium were released during dissolution of rhyolite glass and uranium was incorporated in 

silica gel, possibly by adsorption of uranyl-silica-hydroxyl 

complexes; dehydration of the gel then trapped the 

uranium. Glagolev (1964, p. 109) reported that cristobalite 

containing 1640 ppm uranium was evenly distributed in 

a hypogene alteration product from previously deposited 

uraniferous opal.

Diatomaceous Sediments

A considerable amount of data on the uranium content of marine sediments is available. The average uranium 

content of 742 samples listed by Baturin (1973, p. 1033) 

was 3.7 ppm, and if landlocked basins are excluded, the 

average for 516 samples was 3.0 ppm. The uranium content of upper Quaternary marine sediments and of the surface layer of oceanic sediments ranged from 0.1 to 10 ppm 

(Baturin, 1973, p. 1034). Kuznetsov, Simonyak, Lisitsyn, 

and Frenklikh (1968, p. 308) listed the uranium content 

of 57 samples of the surface layer of ocean sediments and 

found a range of 0.1-2.76 ppm, an average of 0.86 ppm, 

and a median value of 0.80 ppm. For comparison, the 

average uranium content of all shale has been estimated 

to be 3-4 ppm (Holland and Kulp, 1954, p. 203; Adams 

and others, 1959, table 7; Swanson, 1960, p. 4), about the 

same as for the outer few kilometers of the Earth's continental crust (Adams and others, 1959, p. 311). Baturin 

(1968b, p. 206) noted that the concentrations of metals 

that migrate only in suspension are relatively high in 

sediments of littoral zones, but the concentrations of 

metals that migrate in dissolved form, as does uranium, 

are relatively high in pelagic sediments. Boulad and 

Michard (1976, p. 82) studied cores from the southeast 

Atlantic Ocean that had oxidized sediments above reduced 

sediments, and they found the uranium content of the 

reduced sediments and their pore water to be greater than 

that of the oxidized sediments and their pore water. In 

landlocked seas uranium generally is concentrated in 

sediments in the centers of basins, but in the open ocean 

the sediments with the highest uranium content are on 

shelves and continental slopes (Baturin and Yemel'yanov, 

1973, p. 674). In the open-shelf seas, uranium tends to 

be concentrated in the fine-grained sediments of deep 

basins (Baturin, 1973, p. 1033). Spalding, Exner, and 

McKee (1973) found in cores from an anoxic basin that 

the dissolved uranium and dissolved organic-carbon concentrations of pore water showed an increase with depth 

in the core, although the concentrations of both in the 

sediments remained nearly constant.

Some, but not all, diatomaceous sediments have 

higher uranium content than the average for marine 

sediments. Veeh, Calvert, and Price (1974, p. 194, 200) 

reported that organic-rich diatomaceous sediments on the 

continental margin of southwest Africa contain about an 

order of magnitude more uranium than do ordinary terrigenous marine sediments from 10.2 to 54.6 ppm 

uranium in cores, with higher concentrations at depth 

than at the sea-floor surface. Von Backstrom (1974, 

p. 618) found that siliceous sediments in the same area 

contained 5-93 ppm uranium and averaged 21 ppm. 

Baturin (197la, p. 224) reported uranium concentrations 

in the interstitial water of diatomaceous ooze there of 

1.3-650 ppb, and he noted that the ooze itself is 

characterized by uranium enrichment. Baturin considered 

the uranium in the interstitial water as mobile and capable 

of redistribution both vertically and horizontally, but he 

pointed out (197la, p. 225) that diffusion of uranium into 

bottom water from diatomaceous ooze of the shelf and 

continental slope does not occur as it does from oxidized pelagic sediments. In shallow water where wave action aerates bottom water, uranium accumulates in the 

sediments to a lesser degree than it does under anoxic conditions (Baturin and others, 1972, p. 282-283).

The form of the uranium in marine sediments is in 

doubt. Veeh, Calvert, and Price (1974, p. 200) suggested 

that hexavalent uranium of sea water enters sediments 

by way of pore water and then is reduced to tetravalent 

uranium and incoroporated into carbonate fluorapatite 

growing diagenetically in the sediment. During a study 

of fission tracks of cores they found (1974, p. 193, 196) 

that uranium occurs off southwest Africa in diatomaceous mud as two principal modes: (1) finely and uniformly 

dispersed, and (2) in clusters, some of which could be 

traced to organic detritus or to small grains of 

phosphorite.

Summary

Several aspects of the occurrence of uranium in the 

marine environment are pertinent to an understanding 

of uranium in the Monterey Formation:

(1) Sea water is and has long been an adequate source 

for most of the uranium found in marine sediments 

that are enriched in uranium.

(2) Much of the uranium in sediments is connected in 

some way with organic material.

(3) The association of uranium and organic material 

begins, not with living organisms, and probably not 

during the sinking of dead organisms, but after the 

organic material is on the bottom, and perhaps partly 

after the organic material is buried.

(4) The principal process by which uranium is extracted 

from sea water most likely involves adsorption rather 

than chemical precipitation.

Uranium in Monterey Formation A25
(5) Anoxic conditions are conducive to the preservation 

of, if not to the formation of uranium-rich deposits.

(6) Some, but not all, richly diatomaceous sediments 

have uranium content higher than the average for all 

sediments.

(7) The uranium content of diatomaceous sediments can 

be greater below the surface than at the surface, and 

the uranium content of pore water can be considerably higher than that of sea water.

(8) Phosphatic material extracts uranium from sea water 

and adds to the total uranium content of diatomaceous sediments, but it is not the principal agent for 

uranium enrichment of most of the sediments.

CONCLUSIONS

The uranium in the Monterey Formation was derived chiefly from sea water at or near the time the 

Monterey sediments were deposited. Anoxic conditions 

associated with the accumulation of rich organic sediments certainly were conducive to the preservation of 

uranium-rich deposits, and perhaps to their formation. 

Except for certain secondary uranium minerals obviously related to vadose waters moving through rocks of the 

Monterey, the form of the uranium in the formation is 

uncertain. Most likely, the uranium is associated with 

organic matter, either by adsorption on organic material 

or by incorporation in organic complexes. Some uranium 

might be adsorbed on the biogenous opal of diatom 

frustules. During diagenesis of porcelanite, uranium probably is made available in a mobile form for enrichment 

of other rocks; chert, the end product of the diagenesis, 

has little uranium. The Monterey Formation, and similar 

rocks elsewhere, generally have more uranium than do 

most other kinds of rock. Within the Monterey, the cherty 

and dolomitic rocks, and the rocks having a high proportion of terrigenous clastic material generally have the 

lowest uranium content.

The uranium in the Monterey Formation apparently 

will have little commercial interest unless extraction of 

uranium from large volumes of low-grade material 

becomes economically feasible. However, a Monterey terrain could be a source of uranium for sandstone-type 

uranium deposits in other units. For example, uranium 

reported in the Sespe Formation near Ojai, California, 

could well have migrated from the Monterey.

REFERENCES CITED

Adams, J. A. S., Osmond, J. K., and Rogers, J. J. W., 1959, The 

geochemistry of thorium and uranium, Chapter 6 in Physics 

and Chemistry of the Earth, Volume 3: London, New York, 

Paris, Los Angeles, Pergamon Press, p. 298-348.

Adams, J. A. S., and Weaver, C. E., 1958, Thorium-to-uranium 

ratios as indicators of sedimentary processes Example 

of concept of geochemical facies: American Association 

of Petroleum Geologists Bulletin, v. 42, no. 2, p. 387-430.

Arnal, R. E., and Vedder, J. G., 1976, Late Miocene 

paleobathymetry of California Continental Borderland 

north of 32° [abs.]: American Association of Petroleum 

Geologists Bulletin, v. 60, no. 12, p. 2174.

Balistrieri, L., Brewer, P. G., and Murray, J. W., 1981, 

Scavenging residence times of trace metals and surface 

chemistry of sinking particles in the deep ocean: Deep-Sea 

Research, v. 28A, p. 101-121.

Bandy, O. L., and Arnal, R. E., 1969, Middle Tertiary 

basin development, San Joaquin Valley, California: 

Geological Society of America Bulletin, v. 80, no. 5, 

p. 783-819.

Bandy, O. L., and Kolpack, R. L., 1963, Foraminiferal and 

sedimentological trends in the Tertiary section of Tecolote 

Tunnel, California: Micr©paleontology, v. 9, no. 2, 

p. 117-170.

Barron, J. A., 1973, Late Miocene-early Pliocene paleotemperatures for California from marine diatom evidence: 

Palaeogeography, Palaeoclimatology, Palaeoecology, 

v. 14, no. 4, p. 277-291.

___1975, Late Miocene-early Pliocene marine diatoms from 

southern California: Palaeontographica, Abt. B, v. 151, 

p. 97-170.

Baturin, G. N. 1968a, Geochemistry of uranium in the Baltic: 

Geochemistry International, v. 5, no. 2, p. 344-348.

___1968b, Proportion of the forms of uranium migration 

in water from certain USSR rivers: Doklady Akademii 

Nauk SSSR, v. 178, p. 206-209.

___1969, Uranium in the surface layer of sediments of the 

northwestern Indian Ocean: Oceanology, v. 9, no. 6, 

p. 828-833.

___1971a, Uranium in oceanic ooze solutions of the southeastern Atlantic: Doklady Akademii Nauk SSSR 1971, v. 

198, p. 224-226.

___1971b, Formation of phosphate sediments and water 

dynamics: Oceanology, v. 11, no. 3, p. 372-376.

___1973, Uranium in the modern marine sedimentary cycle: 

Geochemistry International, v. 10, no. 5, p. 1031-1041.

___1974, Average ratios of uranium and organic matter in

Holocene sea and ocean sediments: Doklady Akademii

Nauk SSSR 1974, v. 207, p. 190-192. 

Baturin, G. N., and Kochenov, A. V., 1973, Uranium in the

interstitial waters of marine and oceanic sediments [abs.]:

Geochemistry International, v. 10, no. 5, p. 1169. 

___1974, Uranium content of oceanic phosphorites:

Lithology and Mineral Resources, v. 9, no. 1, p. 99-103. 

Baturin, G. N., Kochenov, A. V., and Kovaleva, S. A., 1966,

Some features of uranium distribution in Black Sea water:

Doklady Akademii Nauk SSSR, v. 166, p. 172-174. 

Baturin, G. N., Kochenov, A. V., and Senin, Y. M., 1972,

Uranium concentration in Recent ocean sediments in zones

of rising currents: Geochemistry International, v. 8, no.

2, p. 281-286. 

Baturin, G. N., Lebedev, L. L, and Mayev, Y. G., 1976,

Uranium in Caspian Sea sediments: Oceanology, v. 15, no.

1, p. 87-91.

A26 Studies, Uranium Content and Geochemistry, California
Baturin, G. N., and Lisitsyn, A. P., 1973, Uranium in the Bering Sea sediments: Oceanology, v. 13, no. 6, p. 876-881.

Baturin, G. N., and Yemel'yanov, Y. M., 1973, Uranium 

distribution in Mediterranean sedments: Oceanology, v. 13, 

no. 5, p. 674-679.

Bell, K. G., 1960, Uranium and other trace elements in 

petroleums and rock asphalts: U.S. Geological Survey Professional Paper 356-B, p. 45-65.

Berner, R. A., 1978, Sulfate reduction and the rate of deposition of marine sediments: Earth and Planetary Science 

Letters, v. 37, no. 3, p. 492-498.

Bloch, Salman, 1980, Some factors controlling the concentration of uranium in the world ocean: Geochimica et Cosmochimica Acta, v. 44, no. 2, p. 373-378.

Bonatti, Enrico, Fisher, D. E., Joensuu, Oiva, and Rydell, 

H. S., 1971, Postdepositional mobility of some transition 

elements, phosphorus, uranium, and thorium in deep sea 

sediments: Geochimica et Cosmochimica Acta, v. 35, no. 

2, p. 189-201.

Boon, J. J., De Leeuw, J. W., and Burlingame, A. L., 1978, 

Organic geochemistry of Walvis Bay diatomaceous oozeIH. Structural analysis of the monoenoic and polycyclic fatty 

acids: Geochimica et Cosmochimica Acta, v. 42, no. 6, p. 

631-644.

Boulad, A. P., and Michard, Gil, 1976, Etude de 1'uranium, 

du thorium et de leurs isotopes dan quelques carottes du 

Bassin Anagolais (Atlantique Sud-Est): Earth and Planetary Science Letters, v. 32, no. 1, p. 77-83.

Bowes, W. A., 1955, Uranium in the Kern County area [abs.]: 

Pacific Petroleum Geologist, v. 9, no. 5, p. 2-3.

Bramlette, M. N., 1946, The Monterey Formation of California and the origin of its siliceous rocks: U.S. Geological 

Survey Professional Paper 212, 57 p.

Brongersma-Sanders, Margaretha, 1948, The importance of 

upwelling water to vertebrate paleontology and oil geology: 

Verhandelingen der Koniklijke Nederlandsche Akademie 

van Wetenschappen, Afdeeling Naturrkunde (Tweede Sectie), v. 45, no. 4, p. 1-112.

___1951, On conditions favouring the preservation 

of chlorophyll in marine sediments, in World Petroleum 

Congress, Third, The Hague, 1951, Proceedings, Section I, Geology, Geophysics: Leiden, E. J. Brill, 

p. 401-413.

___1957, Mass mortality in the sea, Chapter 29 in Treatise 

on marine ecology and Paleocology, Volume 1, Ecology: 

Geological Society of America Memoir 67, p. 941-1010. 

.1966, The fertility of the sea and its bearing on the origin

of oil: The Advancement of Science, v. 23, no. 107, 

p. 41-46.

Burton, J. D., 1965, Radioactive nuclides in sea water, marine 

sediments, and marine organisms, Chapter 22 in Chemical 

Oceanography, Volume 1: London and New York, Academic Press, p. 425-475.

___1975, Radioactive nuclides in the marine environment, 

Chapter 18 in Chemical Oceanography, Volume 3, [2d ed.]: 

London, New York, San Francisco, Academic Press, 

p. 91-191.

Burton, V. L., and Sullivan, G. R., 1951, Carbon content and 

radioactivity of marine rocks: American Geophysical Union 

Transactions, v. 32, no. 6, p. 881-884.

Busch, W. H., and Keller, G. H., 1981, The physical properties of Peru-Chile continental margin sediments The influence of coastal upwelling on sediment properties: 

Journal of Sedimentary Petrology, v. 51, no. 3, p. 705-719.

Calvert, S. E., 1966, Accumulation of diatomaceous silica in 

the sediments of the Gulf of California: Geological Society of America Bulletin, v. 77, no. 6, p. 569-596.

___1974, Deposition and diagenesis of silica in marine 

sediments, in Pelagic sediments, on land and under the sea: 

International Association of Sedimentologists Special 

Publication 1, p. 273-299.

Casey, R. E., and Price, A. B., 1973, A tentative radiolarian 

zonation and paleo-oceanographic interpretation from 

Newport Bay, California, in Miocene sedimentary environments and biofacies, southeastern Los Angeles basin: Society of Economic Paleontologists and Mineralogists, Annual 

Meeting 1973, Trip 1, p. 67-70.

Cornell, W. C., 1969, Silicoflagellates as paleoenvironment indicators in the Modelo Formation (Miocene): Geological 

Society of America Abstracts with Programs, 1969, pt. 2, 

p. 6-7.

Cullen, D. J., 1978, The uranium content of submarine 

phosphorite and glauconite deposits on Chatham Rise, east 

of New Zealand: Marine Geology, v. 28, no. 3-4, 

p. M67-M78.

David, L. R., 1940a, Miocene fishes in well cores from Torranee in southern California: American Association of 

Petroleum Geologists Bulletin, v. 24, no. 12, p. 2182-2184.

____1940b, Upper Miocene fish from northern rim of the 

Santa Monica Mountains, California [abs.]: Geological 

Society of America Bulletin, v. 51, no. 12, pt. 2, 

p. 1982-1983.

___1943, Miocene fishes of southern California: Geological

Society of America Special Paper 43, 193 p.

Degens, E. T., Khoo, Francis, and Michaelis, Walter, 1977, 

Uranium anomaly in Black Sea sediments: Nature, v. 269, 

no. 5629, p. 566-569.

Durham, D. L., 1974, Geology of the southern Salinas Valley 

area, California: U.S. Geological Survey Professional 

Paper 819, 111 p.

Finch, W. L, 1967, Geology of epigenetic uranium deposits in 

sandstone in the United States: U.S. Geological Survey Professional Paper 538, 121 p.

Gavshin, V. M., Bobrov, V. A., and Zorkina, L. S., 1974, quantitative relations between uranium and phosphorus in 

phosphorites and phosphatic sedimentary rocks: Lithology 

and Mineral Resources, v. 9, no. 6, p. 740-746.

Glagolev, N. A., 1964, Uraniferous cristobalite and tridymite 

from limestone: Doklady Akademii Nauk SSSR, v. 143, 

p. 108-109.

Goldberg, E. D., 1963, The oceans as a chemical system, in The 

Sea, Volume 2: New York, Interscience Publishers, p. 3-25.

Hail, W. J., Jr., Myers, A. T., and Horr, C. A., 1956, Uranium 

in asphalt-bearing rocks of the western United States: U.S. 

Geological Survey Professional Paper 300, p. 521-526.

Hein, J. R., Scholl, D. W., Barren, J. A., Jones, M. G., and 

Miller, Jacquelyn, 1978, Diagenesis of late Cenozoic 

diatomaceous deposits and formation of the bottom 

simulating reflector in the southern Bering Sea: Sedimentology, v. 25, no. 2, p. 155-181.

Uranium in Monterey Formation A27
Hodge, V. F., Koide, M., and Goldberg, E. D., 1979, Particulate uranium, plutonium, and polonium in the biogeochemistries of the coastal zone: Nature, v. 277, no. 5693, 

p. 206-209.

Holland, H. D., 1979, Metals in black shales A reassessment: 

Economic Geology, v. 74, no. 7, p. 1676-1680.

Holland, H. D., and Kulp, J. L., 1954, The transport and 

deposition of uranium, ionium and radium in rivers, oceans, 

and ocean sediments: Geochimica et Cosmochimica Acta, 

v. 5, no. 5, p. 197-213.

Hurd, D. C., 1973, Interactions of biogenic opal, sediment and 

seawater in the central equatorial Pacific: Geochimica et 

Cosmochimica Acta, v. 37, p. 2257-2282.

lijima, Azuma, and Tada, Ryuji, 1981, Silica diagenesis of 

Neocene diatomaceous and volcaniclastic sediments in 

northern Japan: Sedimentology, v. 28, no. 2, p. 185-200.

Ingle, J. C., Jr., 1963a, Paleoecologic, sedimentary, and structural history of the late Tertiary Capistrano embayment, 

California [abs.]: American Association of Petroleum 

Geologists Bulletin, v. 47, no. 2, p. 361.

___1963b, Miocene-Pliocene paleoecology of San Fernando basin, California [abs.]: American Association of 

Petroleum Geologists Bulletin, v. 47, no. 9, p. 1771-1772.

___1967, Foraminiferal biofacies variation and the MiocenePliocene boundary in southern California: Bulletins of 

American Paleontology, v. 52, no. 236, p. 217-394.

___1972, Biostratigraphy and paleoecology of early Miocene 

through early Pleistocene benthonic and planktonic 

Foraminifera, San Joaquin Hills-Newport Bay, Orange 

County, California, in The Pacific Coast Miocene 

Biostratigraphic Symposium, Proceedings: Society of Economic Paleontologists and Mineralogists, Pacific Section, 

p. 255-283.

___1973, Biostratigraphy and paleoecology of early Miocene

through early Pleistocene benthonic and planktonic 

Foraminifera, San Joaquin Hills-Newport Bay-Dana Point 

area, Orange County, California, in Miocene sedimentary 

environments and biofacies, southeastern Los Angeles 

basin: Society of Economic Paleontologists and 

Mineralogists, Annual Meeting, 1973, Trip 1, p. 18-38.

Issacs, C. M., 1979, Lateral diagenesis in Monterey Shale, Santa 

Barbara coast, California [abs.]: American Association of 

Petroleum Geologists Bulletin, v. 63, no. 3, p. 473.

Kastner, M., Keene, J. B., and Gieskes, J. M., 1977, Diagenesis 

of siliceous oozes I. Chemical controls on the rate of opalA to opal-CT transformation An exerimental study: 

Geochimica et Cosmochimica Acta, v. 41, p. 1041-1059.

Kleinpell, R. M., 1938, Miocene stratigraphy of California 

Tulsa, Oklahoma, American Association of Petroleum 

Geologists, 450 p.

Kochenov, A. V., Korolev, K. G., Dubinchuk, V. T., and 

Medvedcv, Y. L., 1977, Experimental data on the conditions of precipitation of uranium from aqueous solutions: 

Geochemistry International, v. 14, no. 4, p. 82-87.

Ku, Teh-Lung, Knauss, K. G., and Mathieu, G. G., 1977, 

Uranium in open ocean Concentration and isotopic compositions: Deep-Sea Research, v. 24, no. 11, p. 1005-1017.

Kuznetsov, Y. A., Simonyak, Z. N., Lisitsyn, A. P., and 

Frenklikh, M. S., 1968, Uranium and radium in the surface layer of oceanic sediments: Geochemistry International, 

v. 5, no. 2, p. 306-313.

Langmuir, Donald, 1977, Uranium solution-mineral equilibria 

at low temperatures with applications to sedimentary ore 

deposits: U.S. Department of Energy Report G JO-1659-3, 

39 p.

___1978, Uranium solution-mineral equilibria at low temperatures with applications to sedimentary ore deposits: 

Geochimica et Cosmochimica Acta, v. 42, no. 6, 

p. 547-569.

Lewin, J. C., 1961, The dissolution of silica from diatom walls: 

Geochimica et Cosmochimica Acta, v. 21, nos. 3-4, 

p. 182-198.

Lipps, J. H., and Kalisky, Maurice, 1973, Calcareous nannoplankton biostratigraphy and paleoecology in OligoMiocene of California [abs.]: American Association of 

Petroleum Geologists Bulletin, v. 57, no. 2, p. 436.

Lisitsyn, A. P., 1967, Basic relationships in distribution of 

modern siliceous sediments and their connection with 

climatic zonation: International Geology Review, v. 9, no. 

5, p. 631-652; no. 6, p. 842-865; no. 7, p. 980-1004; no. 

8, p. 1114-1130.

___1972, Sedimentation in the World Ocean: Society of 

Economic Paleontologists and Mineralogists Special 

Publication no. 17, 218 p.

Mandra, Y. T., 1959, Use of fossil silicoflagellates in paleogeography [abs.]: Geological Society of America Bulletin, 

v. 70, no. 12, pt. 2, p. 1734.

Mo, T., Suttle, A. D., and Sackett, W. M., 1971, Uranium concentration in marine sediments [abs.]: Eos (American 

Geophysical Union Transactions), v. 52, no. 4, p. 361.

Muller, P. J., and Suess, E., 1979, Productivity, sedimentation rate, and sedimentary organic matter in the oceans 

I. Organic carbon preservation: Deep-Sea Research, v. 26, 

no. 12A, p. 1347-1362.

A28 Studies, Uranium Content and Geochemistry, California
Murata, K. J., Friedman, Irving, and Gleason, J. D., 1977, Oxygen isotope relations between diagenetic silica minerals in 

Monterey Shale, Temblor Range, California: American 

Journal of Science, v. 277, no. 3, p. 259-272.

Murata, K. J., and Larson, R. R., 1975, Diagenesis of Miocene 

siliceous shales, Temblor Range, California: U.S. Geological Survey Journal of Research, v. 3, no. 5, p. 553-556.

Murata, K. J., and Nakata, J. K., 1974, Cristobalitic stage in 

the diagenesis of diatomaceous shale: Science, v. 184, no. 

4136, p. 567-568.

Osterwald, F. W., 1965, Structural control of uranium-bearing 

vein deposits and districts in the conterminous United States: 

U.S. Geological Survey Professional Paper 455-G, p. 

121-146.

Patet, Alix, 1972, A subsurface study of the foraminiferal fauna 

of the Vaqueros, the Rincon, and the lower Monterey 

Formations from the Elwood oil field in Santa Barbara 

County, California, in The Pacific Coast Miocene Biostratigraphic Symposium, Proceedings: Society of Economic 

Paleontologists and Mineralogists, Pacific Section, 

p. 150-157.

Pierce, R. L., 1956, Upper Miocene Foraminifera and fish from 

the Los Angeles area, California: Journal of Paleontology, 

v. 30, no. 6, p. 1288-1314.

Pokidin, V. K., Kuznetsov, Y. V., Prozorovich, E. A., and 

Asadullayeva, F. A., 1972, Radioactivity of the Caspian Sea 

sediments and their deposition rates: Geochemistry International v. 9, no. 4, p. 567-575.

Ramsay, A. T. S., 1973, A history of organic siliceous sediments 

in oceans, in Organisms and continents through time: The 

Paleontological Association, Special Papers in Paleontology, no. 12, p. 199-234.

Redfield, A. C., Ketchum, B. H., and Richards, F. A., 1963, 

The influence of organisms on the composition of sea-water, 

in The Sea, Volume 2: New York, Interscience Publishers, 

p. 26-77.

Ross, V. F., 1952, Autoradiographic study of marine shales: 

Economic Geology, v. 47, no. 8, p. 783-793.

Schrader, Hans-Joachim, 1971, Fecal pellets Role in sedimentation of pelagic diatoms: Science, v. 174, no. 4004, 

p. 55-57.

Siesser, W. G., 1980, Late Miocene origin of the Benguela 

upwelling system off northern Namibia: Science, v. 208, p. 

283-285.

Siever, Raymond, and Stein, C. L., 1976, Models for the transformation of biogenic silica to chert [abs.]: Eos (American 

Geophysical Union Transactions), v. 57, no. 4, p. 256.

Smayda, T. J., 1971, Normal and accelerated sinking of phytoplankton in the sea: Marine Geology, v. 11, no. 2, 

p. 105-122.

Smith, P. B., 1968, Paleoenvironment of phosphate-bearing 

Monterey Shale in Salinas Valley, California: American 

Association of Petroleum Geologists Bulletin, v. 52, no. 9, 

p. 1785-1791.

Spalding, R. F., Exner, M. E., and McKee, T. R., 1973, 

Uranium geochemistry at the sediment-water interface of 

an anoxic basin [abs.]: Eos (American Geophysical Union 

Transactions), v. 54, no. 4, p. 341.

Starik, I. E. and Kolyadin, L. B., 1957, The occurrence of 

uranium in ocean water: Geochemistry No. 3, p. 245-256.

Swanson, V. E., 1960, Oil yield and uranium content of black 

shales: U.S. Geological Survey Professional Paper 356-A, 

p. 1-44.

___1961, Geology and geochemistry of uranium in marine 

black shales A review: U.S. Geological Survey Professional Paper 356-C, p. 67-112.

Troxel, B. W., and Morton, P. K., 1962, Mines and mineral 

resources of Kern County, California: California Division 

of Mines and Geology, County Report 1, 370 p.

Troxel, B. W., Stinson, M. C., and Chesterman, C. W., 1957, 

Uranium, in Mineral commodities of California: California Division of Mines Bulletin 176, p. 669-687.

Veeh, H. H., 1967, Deposition of uranium from the ocean: 

Earth and Planetary Science Letters, v. 3, p. 145-150.

Veeh, H. H. Calvert, S. E., and Price, N. B., 1974, Accumulation of uranium in sediments and phosphorites on the south 

west African shelf: Marine Chemistry, v. 2, no. 3, 

p. 189-202.

Von Backstrom, J. W., 1974, Other uranium deposits, in Formation of uranium ore deposits; Symposium on formation 

of uranium ore deposits, Athens, Greece, 6-10 May, 1974: 

Vienna, International Atomic Energy Agency, p. 605-624.

Walker, G. W., Levering, T. G., and Stephens, H. G., 1956, 

Radioactive deposits in California: California Division of 

Mines Special Report 49, 38 p.

Weber, F. F., Jr., and Sackett, W. M., 1981, Uranium geochemistry of Orca Basin: Geochimica et Cosmochimica 

Acta, v. 45, no. 8, p. 1321-1329.

Zielinski, R. A., 1980, Uranium in secondary silica A possible exploration guide: Economic Geology, v. 75, no. 4, 

p. 592-602.

Zverev, V. L., Spiridonov, A. L, and Shvets V. M., 1976, On 

the balance of uranium in the ocean: Geochemistry International, v. 13, no. 3, p. 88-93.

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