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Geology and Geochemistry of the Upper Miocene Phosphate Deposit Near New Cuyama, Santa Barbara County, California

U.S. GEOLOGICAL SURVEY BULLETIN 1635

Geology and Geochemistry of the Upper Miocene Phosphate Deposit Near New Cuyama, Santa Barbara County, California

By ALBERT E". ROBERTS AND THOMAS L. VERCOUTERE

U.S. GEOLOGICAL SURVEY BULLETIN 1635 DEPARTMENT OF THE INTERIOR DONALD PAUL MODEL, Secretary

U.S. GEOLOGICAL SURVEY Dallas L. Peck, Director

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1986

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

Roberts, Albert Eugene, 1921- Ceology and geochemistry of the Upper Miocene phosphate deposit near New Cuyama, Santa Barbara County, California.

(U.S. Geological Survey Bulletin 1635) Bibliography: p. 23-27. Supt. of Doc. No.: I 19.3:1635sa 1. Phosphate rock California New Cuyama. 2. Geology, stratigraphic Miocene. 3. Geology California New Cuyama. 4. Geochemistry California New Cuyama. I. Vercoutere, Thomas L. II. Title. III. Series.

QE75.B9 no. 1635 557.3 s [553.6'4] 85-600182 [QE471.15.P48] CONTENTS Glossary IV Abstract 1 Introduction 1 Location and areal extent 2 Scope of investigation 2 Acknowledgments 2 Methods of study 3 Definition of terms 3 Geologic setting 3 Stratigraphic summary 5 Structural summary 6 Santa Margarita Formation 9 General features 9 Fauna and age 10 Lithologic composition 10 Lower phosphatic mudstone member 10 Lower sandstone member 11 Upper phosphatic mudstone member 11 Upper sandstone member 11 Mineralogy and petrography of phosphatic components 11 Carbonate fluorapatite 11 Diagenetic alterations 12 Opal-CT 13 Carbonates 13 Mica and smectite groups 14 Chemical composition 15 : Major constituents 15 Minor constituents 15 Barium 16 Cadmium 16 Cerium 16 Manganese 17 Strontium 17 Thorium 17 Uranium 17 Zinc 19 Zirconium 19 Geochemical ratios 19 Phosphatic setting 19 Depositional environment 20 Phosphogenesis 20 Model for the Santa Margarita Formation 21 Phosphate resources of the upper phosphatic mudstone member of the Santa Margarita Formation 22 References cited 23 Stratigraphic sections and tables 7-12 30

PLATES In pocket i 1. Geologic map of Cuyama Valley phosphate area, Santa Barbara County, California 2. Structure sections of Cuyama Valley phosphate area, Santa Barbara County, California 3. Isopach of the upper phosphatic mudstone member of the Santa Margarita Formation, Cuyama> Val.ley phosphate area, Santa Barbara County, California 4. Columnar section and histogram of the major oxides of the trench 100 reference section, upper phosphatic mudstone member of the Santa Margarita Formation, Cuyama Valley phosphate area, Santa Barbara County, California 5. Correlation of trench data from the upper phosphatic mudstone member of the Santa Margarita Formation, Cuyama Valley phosphate area, Santa Barbara County, California 6. Photographs showing primary and secondary features of the phosphatic components in the upper phosphatic mudstone member of the Santa Margarita Formation, Cuyama Valley phosphate area, Santa Barbara County, California

Contents 111 FIGURES

1. Map showing location of the phosphate study area in Cuyama Valley, Santa Barbara County, California 2 2. Generalized stratigraphic column of the phosphate area in Cuyama Valley, Santa Barbara County, California 4 3. Map showing relation of-Salinian block to faults in California 7 4. Graph showing diagenetic variation of opal-CT d(101) spacing related to depth of burial 14 5. Columnar section of the upper phosphatic mudstone member of the Santa Margarita Formation showing ore zones used in tonnage estimates 22

TABLES

1. X-ray characteristics, d(101) spacing and 28, of opal-CT from the upper phosphatic mudstone member of the Santa Margarita Formation, at trench 100 in Cuyama Valley phosphate area, Santa Barbara County, California 14 2. Rapid rock analyses of the upper phosphatic mudstone member of the Santa Margarita Formation, at trench 296 in Cuyama Valley phosphate area, Santa Barbara County, California 15 3. Average chemical composition of phosphorite pellets from trench 299, stratigraphic unit 81, upper phosphatic mudstone member of the Santa Margarita Formation, Cuyama Valley phosphate area, Santa Barbara County, California 15 4. Semiquantitative spectrographic analyses of major and minor elements of phosphorite pellets from trench 299, stratigraphic unit 81, of the upper phosphatic mudstone member of the Santa Margarita Formation, Cuyama Valley phosphate area, Santa Barbara County, California 16 5. Uranium and thorium analyses of the upper phosphatic mudstone member of the Santa Margarita Formation, at trench 100 in Cuyama Valley phosphate area, Santa Barbara County, California 18 6. Inferred phosphate resources in the upper phosphatic mudstone member of the Santa Margarita Formation, Cuyama Valley phosphate area, Santa Barbara County, California 23 7. Semiquantitative spectrographic analyses of the upper phosphatic mudstone member of the Santa Margarita Formation, at trench 100 in Cuyama Valley phosphate area, Santa Barbara County, California 76 8. Semiquantitative spectrographic analyses of the upper phosphatic mudstone member of the Santa Margarita Formation, at trench 294 in Cuyama Valley phosphate area, Santa Barbara County, California 82 9. Semiquantitative spectrographic analyses of the upper phosphatic mudstone member of the Santa Margarita Formation, at trench 295 in Cuyama Valley phosphate area, Santa Barbara County, California 83 10. Semiquantitative spectrographic analyses of the upper phosphatic mudstone member of the Santa Margarita Formation, at trench 296 in Cuyama Valley phosphate area, Santa Barbara County, California 84 11. Semiquantitative spectrographic analyses of the upper phosphatic mudstone member of the Santa Margarita Formation, at trench 297 in Cuyama Valley phosphate area, Santa Barbara County, California 88 12. Semiquantitative spectrographic analyses of the upper phosphatic mudstone member of the Santa Margarita Formation, at trenches 299 and 300 in Cuyama Valley phosphate area, Santa Barbara County, California 89

GLOSSARY

Apatite. A group of minerals composed of varying amounts of calcium phosphate, fluorine, chlorine, hydroxyl, or carbonate as well as several minor elements. When not specified, the term refers to carbonate fluorapatite. Bentonite. Generally considered to be a claystone composed essentially of smectite (montmorillonite) clay minerals. It is formed by post-depositional alteration of volcanic ash. Claystone. An indurated rock containing more than two-thirds clay-size grains. Grainstone. A mud-free carbonate rock. Massive. A textural term for a compact, internally structureless (usually bioturbated) rock that may be fine- to coarse-grained. Muddy rock. Rocks with greater than 20 percent clay-size particles but insufficient to be classified as a mudstone or claystone. Mudstone. Rocks with subequal amounts of clay-size particles, silt, and very fine sand-size grains. Nodule. A constructional particle generally irregular in shape with contrasting composition from enclosing matrix and larger than 2 mm. This size corresponds to the sand-gravel boundary. Oolith. A constructional particle 0.0625 to 2 mm in diameten having internal concentric structure.

IV Contents Opal-CT. A form of silica derived from biogenic silica in which X-ray diffraction patterns indicate a poorly ordered or interlayered arrangement of cristobalite and tridymite lattices. Pellet. A constructional particle 0.0625 to 2 mm in diameter having no regular internal structure. Phosphorite. Rocks that contain more than 50 percent phosphatic framework. Porcellanite. A hard, dense, diagenetic alteration product of siliceous biogenic sediment caused by pressure owing to depth of burial. It is intermediate between diatomaceous mudstone and impure chert and less indurated, dense, and vitreous than chert. Sandstone. An indurated rock containing more than two-thirds sand-size grains. Sandy. Rocks with greater than 20 percent sand-size particles but insufficient to be classified a sandstone. Shale. A structural term for a fissile mudstone. Siltstone. An indurated rock containing more than two-thirds silt-size grains. Silty. Rocks with greater than 20 percent silt but insufficient to be classified a siltstone. Wackestone. A mud-supported carbonate sedimentary rock containing more than 10 percent grains.

Clastic rock terminology (Folk, 1957) Phosphatic framework point counts (%) Rock Components Very abundant >60 Claystone >% clay-size fraction Abundant 40-60 Mudstone Subequal amounts of clay-size particles, silt, Plentiful 20-40 and very fine sand-size grains Common 10-20 Siltstone >Va silt-size fraction Rare 1-10 Sandstone >% sand-size fraction Very rare

Rock beds, thickness (Maher, 1959) Composition of phosphate rocks Rock Phosphatic framework <%) English Metric Phosphorite >50 Beds Very phosphatic 40-50 Thick 2-1- ft 0.6+ m Phosphatic 20-40 Medium 6 in.-2 ft 150 mm-0.6 m Moderately phosphatic 10-20 Thin 2-6 in 50-150 mm Slightly phosphatic 1-10 Very thin !/2-2 in 12-50 mm

Laminae Thick '/i6-'/2 in. 1.5-12 mm Grain sizes (Powers, 1953) Thin <'/i6 in. <1.5 mm Panicle Size (mm) Granule 2.00 -4.00 Very coarse grain 1.00 -2.00 Coarse grain 0.50 -1.00 Sorting Medium grain 0.25 -0.50 Well-sorted grains 90 percent concentrated in 1 or 2 size classes Fine grain 0.125 -0.25 Medium-sorted grains 90 percent distributed in 3 or 4 size classes Very fine grain 0.0625-0.125 Poorly sorted grains 90 percent scattered in 5 or more size classes

Conversions

English/ Metric Metric/ English 1 in. 2.54 cm 1 cm 0.394 in. 1 ft 30.48 cm 1 m 39.37 in. I mi 1.609 km 1 m 3.28 ft 1 km 0.62 mi 1 short ton 0.907 metric ton 1 metric ton 1.102 short ton

Contents

Geology and Geochemistry of the Upper Miocene Phosphate Deposit Near New Cuyama, Santa Barbara County, California

Albert E. Roberts and Thomas L. Vercoutere

Abstract mudstone and select pelletal phosphorite beds are pre­ sented. The element concentrations of barium, cadmium, The Cuyama Valley phosphate deposit is situated cerium, strontium, thorium, uranium, zinc, and zirconium along the southern edge of the Cuyama Valley in the are compared and contrasted with the element con­ foothills of the Sierra Madre Mountains, a part of the Cal­ centrations of worldwide occurrences of phosphorites and ifornia Coast Ranges. The marine phosphate-bearing rocks shales. Emphasis is on mode of incorporation of trace ele­ in this area are part of the Santa Margarita Formation of ments into the sediments. provincial late Miocene age. The formation, which ranges A total of 138.58 million short tons (125.98 million met­ from 1025 ft (315 m) to 1,500 ft (640 m) in thickness in the ric tons) of greater than 8.0 percent P2O5 phosphate rock study area, is subdivided into two sandstone members and and 404.33 million short tons(367.57 million metric tons) of two phosphatic mudstone members. greater than 5.0 percent P2O5 phosphatic rock are calcu­ The Santa Margarita Formation has been folded into lated for the upper phosphatic mudstone member of the northwest-trending anticlines and synclines by compres­ Santa Margarita Formation in the Cuyama Valley phosphate sion from the southwest. Throughout much of the area, area. formational attitudes are nearly vertical or overturned. The area is cut by northwest-trending faults that are parallel to the axes of the folds and by faults that cut obliquely across INTRODUCTION the folds and offset the phosphatic members to the north­ east. California, a leading agricultural state, needs an ever- The phosphatic facies consists generally of brown to increasing amount of phosphorus, an essential element for gray, laminated to medium-thick beds of massive to graded plant growth, to improve crop yields. Current requirements pelletic and nodular phosphorite, phosphatic mudstone, for phosphorus are met from imports or byproducts of other mudstone, siltstone, and some fine-grained sandstone. industries, such as phosphoric acid from Searles Lake brines. Physical characteristics of the components of the phos­ Phosphate-bearing rocks are known' throughout much phatic facies suggest multiple stages of phosphatization. of California (Gower and Madsen, 1964; Dickert, 1966, 1971; The pellets range from very fine to medium-sand size, and Roberts, 1981); however, significant economic deposits have the nodules range from very coarse sand (2 mm) to medium-pebble size. Both, are generally structureless not been developed. The geologic provenance of California aggregates of submicrocrystalline carbonate fluorapatite suggests that the Miocene marine sedimentary rocks occur­ containing terrigenous clay, silt, sand grains, and diatoms ring in the Coast Ranges between San Francisco and Los or shell fragments. Angeles have the greatest potential for phosphatic deposits. Faunal assemblages and sedimentary structures in the Of these sedimentary rocks, the upper Miocene marine for­ phosphatic facies are evidence that the phosphatic facies mations in the southern part of the Coast Ranges contain formed as an outer offshore mud shelf deposit. Phosphate sufficient concentrations of phosphatic rock to warrant fur­ probably was precipitated below the sediment water inter­ ther study. face on the inner offshore shelf during prolonged calm- As part of the U.S. Geological Survey's program to water conditions. Occasional changes in sea level, accom­ evaluate the phosphate resources of the United States, a panied by changes in direction and energy of sea floor detailed stratigraphic and geochemical program was con­ currents, winnowed away some of the finer grained mate­ rial. This reworking process transformed slightly phos­ ducted during 1978 and 1979 on the strata of the upper phatic mudstones into phosphatic siltstones or phos­ phosphatic mudstone member of the Santa Margarita Forma­ phorites. tion in the Cuyama Valley, Santa Barbara County, Calif. The Major rock forming oxides, trace elements, and ura­ study area of the phosphate deposits is shown in figure I. Well nium and thorium analyses of the upper phosphatic data from the South Cuyama oil field and adjacent dry holes

Introduction 1 in the study area (pi. 1) were used to supply critical strat- bearing rock is of the greatest economic potential. This igraphic information not readily available in faulted or entailed mainly the description, measurement, and sampling weathered exposures. The report includes stratigraphic of stratigraphic sections. Fossil assemblages were collected descriptions of the upper phosphatic mudstone member of to establish stratigraphic control. Laboratory investigations the Santa Margarita Formation and locations of the samples. were made to identify the chemical and mineralogical com­ A tabulation of chemical and X-ray analyses for selected position of the phosphatic rocks, and to relate the physical, samples is included (Stratigraphic Sections and Tables 7-12). chemical, and biological environments to the formation and A compilation of the study area's phosphate resources is localization of the pelletal and nodular types of phosphatic included (table 6). rock in the marine sedimentary sequence. Such information is essential not only for understanding the origin and evaluat­ ing the resource potential of the phosphate deposit but also Location and Area! Extent for providing critical data for future regional exploration. The Cuyama Valley phosphate deposit is 5 mi (8 km) The stratigraphy and structure have been summarized south of the town of New Cuyama along the south edge of the to help the reader relate the upper Miocene phosphatic rocks Cuyama Valley in the foothills of the Sierra Madre Mountains in the Salinas-Cuyama basin near New Cuyama, Calif, to in Santa Barbara County, Calif, (fig. 1). The deposit covers an other phosphatic deposits. A detailed analysis of the tectonic area of about 15 sq mi (40 km2); the area is about 1.5 mi (2.5 development and related sedimentation of the entire strat­ km) wide and 10 mi (16 km) long and is oriented in a igraphic sequence near New Cuyama has not been done northwesterly direction. because it is beyond the scope of this report. For additional information the reader is referred to English (1916); Eaton (1939); Eaton and others (1941); Hill and Dibblee (1953); Scope of Investigation Hill and others (1958); Schwade and others (1958); Repen- The U.S. Geological Survey investigation of the phos­ ning and Vedder (1961); Cross (1962); Christensen (1965); phate deposit in the southern Cuyama Valley was concerned Addicott (1968); Clifton (1968, 1981); Vedder (1968, 1973, mainly with the areal distribution, lithofacies relationships, 1975); Vedder and Brown (1968); Fritsche (1969,1972); Page time-stratigraphic relations, and chemical and mineralogical (1970, 1981); Huffman (1972); Ross (1972, 1974, 1978); composition of the upper phosphatic mudstone member in Dibblee (1973a, b; 1976); Durham (1974); Johnson and Nor- the Santa Margarita Formation. The principal objective of the mark (1974); Vedder and Repenning (1975); Graham (1976, field investigations was to define areas in which phosphate- 1978); Howell and others (1977); Bartow (1978); Howell and Vedder (1978); and Lagoe (1984).

Acknowledgments Many scientists cooperated and provided assistance in this investigation of the Cuyama Valley phosphate area. The authors are particularly grateful to H. Edward Clifton, Howard D. Gower, Robert A. Gulbrandsen, Peter Oberlin­ dacher, Robert L. Phillips, and John G. Vedder for their suggestions on stratigraphic correlations and (or) resource evaluations. Also, during the course of this study John G. Vedder provided additional unpublished data which aided in better understanding the relationships of the stratigraphic facies. Howard D. Gower generously provided sample mate­ rial and measured sections from trenches in the study area and contributed to the correlation of phosphatic zones (pi. 5). The manuscript benefitted from the careful reviews of Robert A. Gulbrandsen, Peter Oberlindacher, and John G. Vedder. Pre­ liminary illustrations were reviewed and final copy was pre­ pared by Frances R. Mills. Field assistance and SEM 0 10 20 30 40 KILOMETERS

______I______photography were provided by Lawrence E. Mack. Field investigations were facilitated through the outstanding coop­ Figure 1. Location of phosphate study area (lined) in eration of Nicolas V. Bower and John H. Finney, operators of Cuyama Valley, Santa Barbara County, Calif. the Cuyama Phosphate Corporation.

Introduction Methods of Study Definition of Terms Stratigraphic sections were measured by Brunton com­ The phosphate mineral in the marine apatite deposit pass and tape traverses, described and sampled in trenches near New Cuyama is carbonate fluorapatite. Throughout the cut at intervals of 1,000-5,000 ft (305-1,525 m) or more deposit the mineral exhibits only a small range of composi­ normal to the strike of outcrop of the upper phosphatic tional variation; therefore, the term "apatite" is often used in mudstone member (pi. 1). Representative samples were col­ place of the full mineral name. The compositional rock terms lected usually from the middle of each lithologic unit, and used for phosphate-bearing rocks are classified on the quan­ channel samples were taken from every unit thicker than 2 ft tity of apatite pellets, nodules, grains, and other phosphate (0.6 m). Descriptions of these units include megascopic and material the phosphatic framework and apatite matrix microscopic determinations of physical properties and com­ that they contain. These terms are defined in the glossary. position supported by X-ray diffractometry and a scanning The definition of porcellanite is based on the works of electron microscope (SEM) equipped with an energy disper­ Bramlette (1946), Murata and Nakata (1974), and Murata and sive analysis of X-rays (EDAX) system (see "Stratigraphic Larson (1975). Much of the porcellanite in the study area Sections"). Color designations were based on the Rock-Color consists of opal-CT; 70 percent of the beds in the upper Chart of the National Research Council (Goddard and others, phosphatic mudstone member reference section (trench 100) 1948). contain opal-CT. The definition of opal-CT is based on that of To achieve optimum statistical reliability, 300 points on Jones and Segnit (1971). each thin section were counted for quartz, feldspars, apatite, The definitions of the clastic rocks are included in the clay minerals (matrix), carbonate minerals, iron oxides, and glossary. The terminology for claystone, mudstone, siltstone, accessory minerals. The totals were normalized to 100 per­ and sandstone is based on that of Folk (1957), and the cent and are included in the Stratigraphic sections. Owing to definitions of wackestone and grainstone are based on that of the inherent nature of mudrocks and for the purpose of this Dunham (1962, p. 118). study, the cement, unless easily discernible, was counted and Textural modifiers, such as muddy, sandy, and silty, included with the matrix. indicate the type and amount of admixture not indicated by Each thin section was assigned to one of seven rock the rock name. The definitions of muddy and silty are from types on the basis of mineral composition, grain size, and Krynine (1948, p. 141); these definitions are included in the texture; these types are: sandstone, siltstone, mudstone, clay- glossary. stone, phosphorite, wackestone, and grainstone, all of which The terminology used to describe the thickness of bed­ are described in "Stratigraphic Sections." ding of the rocks is modified from Maher (1959). The stand­ Water-smear mounts on glass slides were made from ards used for beds and laminae are included in the glossary. each whole-rock sample for X-ray analysis. To allow com­ Grain shape and angularity are in accord with the parisons to be made between each sample, 15 milligrams of roundness scale of Powers (1953). The scale for the grain powdered whole rock samples were used. Clay separates of sizes is in the glossary. The terms used to describe the sorting 12 previously determined smectite-rich samples from trench of grains are also in the glossary. Distributions of grains sizes 100 were prepared for semiquantitative clay mineral analysis were determined by conventional sieve and pipette analyses using methods described by Carroll (1970). Clay samples or microscopically with an eyepiece micrometer. were glycolated and analyzed by X-ray diffraction between The standard used in describing the relative abundance 63° 20 and 60° 20 at a chart speed of !/4 inch per second and a of fossils, and of some minerals, mineral groups, or other 20 scan speed of !/4 degree per minute to determine the (060) material, from very abundant to very rare, is in the glossary. d spacing and thereby determine whether the clays were The range of unit hardness was very arbitrarily A13 + -, Mg2 + -, or Fe2 + -rich clays. X-ray diffractograms assigned; essentially it was determined on the amount of were produced by using copper radiation generated at 45 kv matrix alteration and the type of cementation. The following and 14 ma, 400 counts per second, and a scanning rate of 1 terms were used: indurated, moderately indurated, weakly degree per minute. Uniform response of the Philips Norelco 1 indurated, and friable. X-ray diffractometer was maintained by periodic zero setting of the scalar rate meter. Peak positions in degrees 20 were GEOLOGIC SETTING corrected using the difference between the true quartz peak positions and observed quartz peak positions. The determina­ Marine phosphatic rocks are distributed throughout the tion of d spacings was made with CuK alpha 1 wave length. world and range in age from Precambrian to Quaternary. Marine phosphatic rocks in California are presently known in 1 Any use of trade names is for descriptive purposes only and does not imply sedimentary sequences that range in age from Ordovician to endorsement by the U.S. Geological Survey. Quaternary (Roberts, 1981); the best developed and most

Geologic Setting CALIFORNIA BENTHIC AGE FORAM- UNITS INIFERAL STAGES Quater nary Alluvium, fanglomerate, and terrace deposits Plio­ Morales(?) Formation cene Caliente(?) Formation ~~~~~~~Upper Vandstone n\eniber~ 10- co 5.2 Upper phosphatic mudstone member Mohnian Lower sandstone member I Lower phosphatic mudstone member _0) T3O Upper sandstone member Luisian Whiterock Bluff Shale Member 15- I Vludstone member and lower Relizian 2 co CQcJ sandstone member, 0 C/3 undivided 20- Saltos Shale Member CO Saucesian HI Painted Rock Sandstone Member LLJ Vaqueros Formation CO 24 25- Soda Lake Shale Member Quail Canyon Sandstone Member rrLLJ gocene O 30- LL Zemorrian LLJ m 35- CO HI LU 38- Refugian

CO dd Narizian O 45 Eocene

50- Ulatisian

CO HI Penutian-

Bulitian- Paleocene Unnamed strata 60- Ynezian

CO HI

65- Unnamed strata Creta ceous

Granitic and gneissic rocks 70 Denotes that age shown for unit is provincial

Figure 2. Generalized stratigraphic column of the Cuyama Valley phosphate area and surrounding region, Santa Barbara County, Calif. (Modified from Vedder, 1968, 1973; Vedder and Repenning, 1975.)

Geologic Setting widespread phosphatic rocks are in formations of Miocene The Paleocene and Eocene series is unconformably age. The principal phosphate deposits occur in the following overlain by the non-marine Simmler Formation and marine units: the Santos Shale Member of the Temblor Formation Vaqueros Formation in the Cuyama Valley area. In the subsur­ (Oligocene and lower Miocene) in the Temblor Range, the face at the South Cuyama oil field, the Vaqueros Formation Sandholdt Member of the Monterey Formation (middle ranges from 320 to 830 ft (100 to 250 m) in thickness and has Miocene) in the Santa Lucia and La Panza Ranges, and the been subdivided into the Quail Canyon Sandstone, Soda phosphatic members of the Santa Margarita Formation Lake Shale, and Painted Rock Sandstone Members (Hill and (upper Miocene) in the Sierra Madre and San Rafael Moun­ others, 1958; Dibblee, 1973b) (fig. 2). The Vaqueros Forma­ tains. tion south of the study area in the Sierra Madre Mountains, which is predominantly sandstone, has not been divided into members. The thickness of the Sierra Madre Mountains Stratigraphic Summary sequence ranges from 250 to 700 ft (75 to 215 m). These rocks The distribution of many complexly interrelated rock probably correlate with the Painted Rock Sandstone Member units in the southern California Coast Ranges represents an as described and mapped by Fritsche (1969). intricate geologic history. In or adjacent to the study area pre- The Quail Canyon Sandstone Member beneath the Late Cretaceous granitic and gneissic rocks form the base­ Cuyama Valley consists of thick-bedded, fine- to medium- ment complex. These rocks, lying between the San Andreas grained, well-sorted, greenish-gray to light-gray, calcareous and the Sur-Nacimiento faults (Vedder and Brown, 1968; sandstone. Beds are often lenticular and locally cross-strat­ Page, 1970; 1981;Dibblee, 1973b; 1976), were designated the ified. Thin interbeds of dark-gray or dark-brown siltstone are Salinia [Salinian] block by Reed (1933). Hill and others present locally. The thickness of this member in the South (1958, p. 2976) assumed that the granitic rocks were the Cuyama oil field is 60 ft (18 m) (Zulberti, 1954, pi. 3). The basement complex beneath the Cuyama Valley. Isotope stud­ Quail Canyon Sandstone Member contains sparse mollusks, ies [Rb/Sr and U/Pb] by Ross (1978, p. 519) indicate an age of including Pecten magnolia; the mollusks are suggestive of a 100-110 m.y. for the basement complex (fig. 2). provincial early Miocene age (Vedder and Repenning, 1975). The basement rocks in the southern part of the Salinian Vedder (oral commun., 1982) presently regards these fossils block are generally overlain by unnamed marine sedimentary as late Zemorrian (late Oligocene) on the basis of interna­ rocks, such as the 5,000+ ft (1,525+ m) thick sequence tional correlation data. exposed in the northwestern La Panza Range that contains The Soda Lake Shale Member is an indurated, dark- fossils diagnostic of Late Cretaceous age (Vedder and Brown, brown to black mudstone or siltstone with a few thin cal­ 1968). The Upper Cretaceous strata have a variety of marine careous-cemented sandstone beds. Cores from wells drilled and nonmarine lithofacies. In the La Panza Range exposures in the South Cuyama oil field contained sporadic phosphatic include massive conglomerate, sandstone, and mudstone pellets in this member. The Soda Lake in the South Cuyama deposited as shallow marine shelf deposits and in turbidite oil field ranges from 80 to 250 ft (25 to 75 m) in thickness sequences as a part of submarine fans (Howell and others, (Zulberti, 1954, pi. 3). The upper part of this member con­ 1977, p. 24). These deposits become thicker and finer grained tains a meager assemblage of lower bathyal early Saucesian to the southwest. This entire section of Cretaceous rocks is foraminiferal fauna (Hill and others, 1958, p. 2986; R. L. regionally truncated northeastward by younger strata. In the Pierce in Dibblee, 1973b, p. 18). Quatal Canyon at the east end of Cuyama Valley, Oligocene Conformably overlying the Soda Lake Shale Member and Miocene nonmarine sedimentary rocks of the Caliente in the Cuyama Valley area is the Painted Rock Sandstone Formation overlie the granitic basement. Member. In this area it is composed predominantly of sand­ South of the Cuyama Valley about 25,000 ft (7,625 m) stone that is thin to thick bedded, fine to coarse grained, and of sandstone and mudstone assigned to the Paleocene and locally clayey or silty. The rocks are composed of poorly to Eocene overlie the Upper Cretaceous series (Vedder, 1973, p. fairly sorted, subangular grains (mostly quartz and feldspar). 42). This sequence of unnamed marine slope and basin sedi­ They are calcareous, friable to indurated, and include occa­ ments is approximately half sandstone and the other half is sional siltstone interbeds. The Painted Rock ranges from 200 about equal amounts of conglomerate, siltstone, and to 520 ft (60 to 160 m) in thickness in the South Cuyama oil mudstone (Fritsche, 1969, p. 18). The sandstone is generally field (Zulberti, 1954, pi. 3) and is 700 ft (215 m) thick in the medium- to coarse-grained, light-olive-gray, impure arkose. Sierra Madre foothills (Fritsche, 1969, p. 38). North of the The siltstone and mudstone are olive-gray to dark-gray Cuyama Valley, the Painted Rock, which contains early graywacke. The conglomerate varies from greenish- to Miocene marine mollusks and Saucesian foraminifers (Ved­ brownish-gray and consists of subangular to rounded clasts of der and Repenning, 1975), is as much as 5,500 ft (1,678 m) igneous and metamorphic rocks. In the La Panza Range, thick (Vedder, 1973). Paleocene strata apparently conformably overlie Upper Cre­ Oil and gas production at the South Cuyama oil field is taceous rocks (Howell and others, 1977, p. 23); in the Sierra primarily from the Painted Rock Sandstone Member, locally Madre Mountains the contact is buried. designated the Dibblee oil zone (Eckis, 1952; Zulberti,

Geologic Setting 1954). Lesser production at this field is from the Quail Can­ Mountains and in the subsurface of Cuyama Valley is the yon Sandstone Member known locally as the Colgrove oil Santa Margarita Formation (fig. 2). This formation, which is zone (Eckis, 1952; Zulberti, 1954; Hill and others, 1958, p. 1,025 to 1,500 ft (315 to 460 m) thick, is subdivided into two 2984). sandstone members and two phosphatic mudstone members Sedimentary rocks conformably overlying the (Hill and others, 1958, p. 2996; Vedder and Repenning, Vaqueros Formation in the Cuyama Valley area had a very 1975). The sandstone units, which are lithologically similar complex depositional history of transgression and regression. to the sandstone in the Branch Canyon Sandstone, indicate a The change in sedimentation from coarse- to fine-grained continuing clastic source. The phosphatic mudstones suggest clastic deposits was gradual in some areas but abrupt in intervening tectonic stability accompanied with a decrease in others. Sandstone lenses and tongues that are lithologically coarse-grained clastic sediments. According to Vedder and similar to the Painted Rock are present in the lower part of the Repenning (1975), the sandstone members contain late Saltos Shale Member of the Monterey Shale. Also, the Saltos Miocene mollusks and echinoids and the phosphatic in this area has two distinct intertonguing sequences, one is mudstones contain provincial late Miocene foraminifers and brownish-gray, laminated to indistinctly bedded, indurated diatoms (see section on "Fauna and Age"). siltstone and mudstone sequence and the other is a massive, North of the Cuyama Valley, in the southern part of the gray, friable to indurated, sandy claystone sequence. Accord­ Caliente Range, is 4,200 ft (1,280 m) of varicolored non- ing to the subsurface data, the brownish-gray siltstone and marine conglomerate, sandstone, claystone, and basalt flows mudstone is the dominant lithology. Interpreted well data of the Caliente Formation (Hill and others, 1958, p. 2993). from the South Cuyama oil field indicates that the Saltos These nonmarine units extend southward interfingering with Shale Member has a thickness of 400 ft (120 m). In the study marine units of the Branch Canyon and Santa Margarita area the Saltos contains Relizian foraminifers (Vedder and Formations. In the study area a 400 ft (125 m) thick non- Repenning, 1975). marine sequence of pinkish-gray sandstone and reddish- Conformably overlying the Saltos Shale Member in the brown mudstone unconformably overlies the Santa Margarita study area is the lower sandstone member of the Branch Formation. This unit was questionably correlated with the Canyon Sandstone or the Whiterock Bluff Shale Member of upper part of the Caliente Formation by Vedder and Repen­ the Monterey Shale (fig. 2). Recurring marine sand deposi­ ning (1975). tion formed interfingering coarse-grained clastic materials In the Cuyama Valley and Sierra Madre foothills, the (Branch Canyon Sandstone) with very fine grained clastic upper Miocene formations are unconformably overlain by materials (Whiterock Bluff Shale Member). continental deposits of gravel, sand, and silt of the Morales(?) In the Cuyama Valley the Whiterock Bluff Shale Mem­ Formation (Hill and others, 1958, p. 2997). These sedimen­ ber is composed of 300 to 700 ft (90 to 215 m) of platy tary deposits, which are poorly consolidated, contain abun­ siliceous shale, cherty shale, and diatomaceous shale. The dant clasts from underlying formations and were probably Whiterock Bluff grades into the underlying Saltos and con­ deposited as alluvial fans and a floodplain. In the study area tains foraminifers diagnostic of late Relizian and Luisian this sequence is approximately 1,500 ft (460 m) thick. The Stages (Hill and others, 1958, p. 2991). Morales(?) Formation, which unconformably overlies folded A thick marine sandstone sequence exposed in Branch upper Miocene strata and is unconformably overlain by lower Canyon adjacent to the South Cuyama oil field was named the Pleistocene strata (Hill and others, 1958, p. 2998), is proba­ Branch Canyon "Formation" by Hill and others (1958, p. bly Pliocene in age. 2991). The formation intertongues southwest ward with In the study area the Morales(?) Formation is unconfor­ deeper water marine units of the Monterey Shale and Santa mably overlain by semiconsolidated gravel, sand, and silt Margarita Formation (fig. 2) and northeastward into the non- derived from older rocks in the Sierra Madre Mountains and marine Caliente Formation. These depositional relations, deposited in the foothills and Cuyama Valley as fanglomerate supplemented by invertebrate fauna and sedimentary struc­ deposits (Hill and others, 1958, p. 2998) and terraces. These tures, suggest a nearshore coastal environment (Clifton, deposits vary in color from olive gray to reddish brown and 1968, p. 185). In the area of the type section, the sequence is range in thickness from 0 to 900 ft (0 to 275 m). The age of the 3,800 ft (1,160 m) thick (Vedder, 1973, p. 48) and consists of fanglomerate deposits and terraces is post-Morales and pre- four unnamed mappable members (Vedder and Repenning, alluvium, probably Pleistocene. 1975). They are fine- to coarse-grained, locally con­ glomeratic, generally light-gray to pale-yellowish-gray, Structural Summary thick-bedded to massive, calcareous sandstone units with a few interbeds of siltstone and mudstone. Mollusks and echi- The structural history of the Salinian block (fig. 3) is noids from these units are provincial middle to late Miocene complicated. The complexity is due essentially to the bound­ in age (Vedder and Repenning, 1975). ary fault systems of the block, relief features on the basement- Conformably overlying the Monterey Shale and the complex surface, intensive folding of post-basement strata, Branch Canyon Sandstone in the foothills of the Sierra Madre extensive regional erosion, and late Tertiary cover (Graham,

Geologic Setting 100 MILES

v?t^ \iifc* Cordell 5^X Bank S.' '. ':; Farallon ^** Islands \

SANTA BARBARA COUNTY

Figure 3. Relation of Salinian block (shaded) to faults in California (modified after Ross, 1978).

Geologic Setting 1976). Interaction with adjoining crustal blocks caused recur­ four groups of sedimentary rocks: Upper Cretaceous, Pal- ring uplift or subsidence of the Salinian block and produced eocene and Eocene, Miocene, and post-Miocene. These extensive compression, faulting, and folding concurrently groups are discussed briefly in "Stratigraphic Summary" but with erosion and sedimentation. are mentioned here to emphasize the unconformities separat­ The Salinian block is a crustal unit of dominantly ing these groups, the uncoriformable angularity of pre- granitic rocks. Along its fault boundaries, three slices that Miocene groups, and the abrupt lithofacies changes, par­ contain abundant gneissic rocks have been identified by Ross ticularly within the Miocene groups (fig. 2). These lithofacies (1972, p. 34). The basement complex of the Salinian block is changes suggest periods of intermittent deformation along devoid of the Franciscan Complex and ultramafic rocks that the reactivated boundary fault systems. Clifton (1968, p. 183; form the basement in adjoining blocks. The northeast bound­ 1981) attributed cyclic deposition of middle and probably ary is delimited by the San Andreas fault zone. upper Miocene nearshore marine and beach environments Atwater (1970) described the San Andreas as a trans­ along the northern margin of the Salinas-Cuyama basin to form system forming a crustal plate boundary. Episodic repeated movement on the San Andreas fault. movement along this Neogene boundary resulted in a com­ Upper Cretaceous strata apparently were derived plex structural evolution of basin development and deforma­ largely from uplifted granitic segments forming the basement tion on the Salinian block. Movement associated with the of the Salinian block. Overlying the Upper Cretaceous strata Salinian block migrating relatively northwestward influenced is a thick sequence of Paleocene and Eocene rocks derived the sedimentary processes by changing sediment source areas from granitic basement and recycled Upper Cretaceous rocks. and rates of sedimentation. Hill and Dibblee (1953, p. 448) Unconformably overlying the Upper Cretaceous, Eocene, or postulated a cumulative right-lateral slip of several hundred granitic rocks is a thick sequence of Oligocene nonmarine miles along this system. Authors (Dickinson and Grantz, strata, Miocene marine and nonmarine strata, and volcanic 1968) presented a variety of evidence in support of Hill and flows deposited in a trough or basin. At the end of the Dibblee's estimate. Wentworth (1968) examined Upper Cre­ Miocene, uplift in the Caliente Range and the Sierra Madre taceous and lower Tertiary rocks along parts of the fault and Mountains renewed erosion and spread debris from the two inferred a right slip of at least 270 mi (435 km) since Late ranges into the Cuyama Valley forming the thick Pliocene(?) Cretaceous. Addicott (1968), after examining the middle Ter- alluvial deposits. Further tectonic activity during the rtiary rocks along the fault, suggested a right slip of 200 mi Pleistocene folded and faulted the area. Continuing erosion /(320 km) since the Oligocene, 170 mi (275 km) since the covered the valley and adjacent foothills with Quaternary early Miocene, 130 mi (210 km) since the middle Miocene, deposits. and 80 mi (130 km) since the late Miocene. Middle Tertiary downwarping between the boundary The southwest boundary of the Salinian block is con­ fault systems developed a long narrow depression in the trolled by the complex and poorly defined Sur-Nacimiento southern part of the Salinian block. Regional pal- fault system that also had a dominant influence on the area's eogeographic studies by Addicott (1968) indicate the general sedimentation. Although this northwest-trending fault system limits of this tectonic 'feature. It has been referred to as the parallels the San Andreas, it had a much different history. The Cuyama trough by English (1916, p. 207); as the Caliente long and complicated record of recurrent activity of differing trough by Eaton (1939, p. 258) and by Eaton and others (1941, types of movement was investigated by Vedder and Brown p. 198); as the Salinas-Cuyama basin by Schwade and others (1968), Page (1970, 1981), Champion and others (1980), (1958, p. 78); as the Carrizo-Cuyama basin by Cross (1962, p. Howell and others (1980), and Vedder and others (1980). 27) and Gribi (1963, p. 16); the Salinas basin by Graham Stratigraphic evidence along the Nacimiento fault demon­ (1978, p. 2216); and the Salinas basin and Caliente basin by strates large dip-slip and inconclusive strike-slip movements Blake and others (1978, p. 349). Addicott's (1968, p. 153, in the interval from post-Late Cretaceous to Miocene time. 156) middle and late Miocene paleogeographic maps support Late Cretaceous suturing of the Salinian block and its western the designation of Salinas-Cuyama basin by Schwade and neighbor followed by large-scale post-Campanian to early others (1958) for that time period, and their terminology is Eocene northward translation has been proposed by Cham­ used herein. pion and others (1980), Howell and others (1980), and Vedder Detailed quadrangle mapping in the Cuyama Valley and others (1980). and bordering Sierra Madre Mountains and Caliente Range Recurring strike-slip and dip-slip displacements on the by Vedder and Repenning (1975) indicates that the Cuyama boundary systems and consequent vertical movements on Valley is the surface expression of a large northwest-trending shear faults provided continuing changes in topographic asymmetric synclinal trough. This trough, a structural feature relief on the Salinian block. The distribution of sedimentary within the Salinas-Cuyama basin, is deepened between the formations in contact with the Salinian granitic rocks shows Whiterock and Morales fault systems on the north and the progressive burial on an irregular basement surface. South Cuyama and Ozena fault systems on the south. The preserved rock sequence for the Cuyama Valley Between these fault systems are older buried faults, such as segment of the southern part of the Salinian block consists of the Russell fault along which Vedder (1973, p. 47) inferred as

8 Geologic Setting much as 14 mi (22.5 km) of strike-slip offset of Miocene and diately east of the Salisbury Potrero quadrangle) (Vedder, older rocks. 1968; Fritsche, 1969, p. 155). The lower sandstone member is The phosphate-bearing Santa Margarita Formation has generally 450 ft (135 m) thick. The upper phosphatic been folded into northwest-trending anticlines and synclines mudstone member is 160 ft (50 m) thick in the northwestern by compression from the southwest (pi. 3). Throughout much part of the study area (trench 297, in "Stratigraphic Sec­ of the area, formational attitudes are nearly vertical or over­ tions"), 275 ft (85 m) thick near the center of the study area turned (pi. 2). The area is cut by northwest-trending faults that (trench 100, in "Stratigraphic Sections"), and 195 ft (60 m) parallel the axes of the folds and by faults that cut obliquely thick at the southeastern part of the study area (trench 296, in across the limbs of the folds (Vedder and Repenning, 1975; "Stratigraphic Sections"). The upper sandstone member pi. 1). ranges from 200 to 350 ft (60 to 105 m) in thickness owing to truncation by the overlying unit. Northeastward from the study area all members of the Santa Margarita interfinger with the upper part of the nonmarine Caliente Formation SANTA MARGARITA FORMATION (Vedder and Repenning, 1975). Eastward and southward the General Features Santa Margarita is truncated by younger rocks (Vedder, 1968; Fritsche, 1969). Northwestward the Santa Margarita con­ Massive sandstone and interbedded mudstone exposed tinues intermittently as a mappable unit in exposures approx­ near the town of Santa Margarita in San Luis Obispo County imately parallel to the axis of the Salinas-Cuyama basin were first described by Antisell (1856, p. 44). These strata, in (Dibblee, 1973a). the San Luis Obispo quadrangle, were later mapped by Fair­ The Santa Margarita Formation conformably overlies banks (1904), who formally named them the Santa Margarita the Monterey Shale and Branch Canyon Sandstone in the Formation. In a study of the stratigraphy and fossils of the central part of the Cuyama Valley (fig. 2). In the northern part Santa Margarita Formation, Richards (1933) specified the of the valley at the Russell Ranch oil field, the Santa Mar­ location of the type section and presented summaries of garita rests conformably upon the Whiterock Bluff Shale previous stratigraphic and paleontologic work. Many subse­ Member of the Monterey Shale. The Whiterock Bluff grades quent studies of the Santa Margarita and its stratigraphic laterally into the Branch Canyon Sandstone southeastward to equivalent have been made throughout the southern Coast the Cuyama Valley phosphate area and northeastward to the Ranges. For a comprehensive review of these studies and for Caliente Range. Both members of the Monterey Shale grade an inclusive regional examination of the Santa Margarita into the Branch Canyon Sandstone eastward from the Formation, the reader is referred to the detailed sedimen- Cuyama Valley phosphate area. Farther eastward, in the tologic study of Phillips (1981). For an account of the pro- vicinity of the Cuyama Badlands, the Branch Canyon grades gradational sequences in Miocene shoreline deposits in the into the nonmarine Caliente Formation. southeastern Caliente Range, the reader is referred to Clifton At the Cuyama Valley phosphate area the marine (1981). His discussion of the transgressive-regressive epi­ sequence of the Santa Margarita Formation grades into the sodes based on observations of the well-exposed sedimentary upper part of the nonmarine Caliente Formation northeast­ rocks of the Caliente Range is also pertinent to the middle and ward to the Caliente Range and eastward to the Cuyama upper Miocene sequences in Cuyama Valley. Badlands. Northwestward from the Cuyama Valley phosphate The Santa Margarita Formation in the Cuyama Valley area, the Santa Margarita maintains a similar lithology and was first geologically mapped and described by English marine fauna suggesting a northwest-southeast strandline (1916). In this early study, he recognized some of the rapid direction during deposition. The Santa Margarita Formation lateral facies changes. English (1916, p. 195) attributed the is unconformably overlain by a westernmost nonmarine varying lithology of the sedimentary sequence to erosion of tongue at the top of the Caliente(?) Formation (Vedder and the mainland and offshore islands because of differential Repenning, 1975) in the Cuyama Valley phosphate area. movements of subsidence and uplift that formed related areas Elsewhere in the Cuyama Valley, the Santa Margarita is of deposition. He (1916) included the Branch Canyon "For­ unconformably overlain by nonmarine beds of the Morales(?) mation" in his definition of the Santa Margarita Formation Formation. whereas Hill and others (1958) included the Santa Margarita In the Cuyama Valley area, the Santa Margarita Forma­ in the upper part of their Branch Canyon "Formation". tion consists of four members that represent two distinct The Santa Margarita Formation ranges from 1,025 to paleoenvironments defined by different sedimentary and pal­ 1,500 ft (315 to 460 m) in thickness and averages 1,350 ft eontologic characteristics. The sandstone members contain (410 m) thick in the study area. The lower phosphatic intertidal to shallow-water assemblages of mollusks, pel- mudstone member is approximately 150 ft (45 m) thick at the ecypods, echinoids, and diatoms indicative of a marine shelf- South Cuyama oil field; however, the member gradually thins sand environment. The phosphatic mudstone members repre­ eastward and pinches out in the vicinity of Goode Canyon in sent periods of greater tectonic stability with a consequent the northwest corner of the Fox Mountain quadrangle (imme­ decrease in sediment volume than the sandstone members.

Santa Margarita Formation Faunal assemblages of mollusks and diatoms in the phos- Unidentified pectinid phatic mudstone members suggest a marine offshore Balanus sp. environment of a slightly deeper water shelf-mud environ­ Astrodapsis whitneyi Remond ment than the sandstone members. Astrodapsis sp. Undifferentiated Santa Margarita Formation of Fritsche Unidentified bryozoan Fauna and Age Yoldia cooperii supramontereyensis Arnold Megafossils are common to rare in members of the Anadara sp. Santa Margarita Formation in the study area. Faunas were Modiolus sp. collected from this area and described by English (1916, p. Crassostrea titan (Conrad) 204), Eaton and others (1941, p. 242), Fritsche (1969, p. 169), Crassostrea sp. and Vedder and Repenning (1975). Fossil collections in sup­ Chlamys cf. C. proavus (Arnold) port of geologic mapping in the study area by Fritsche (1969) Lyropecten estrellanus (Conrad) and Vedder and Repenning (1975) provided the stratigraphic Lucinisca cf. L. nuttalli (Conrad) framework for this report. Faunas collected and identified by Chione temblorensis (Anderson) Fritsche (1969), and Vedder and Repenning (1975) from dementia pertenuis (Gabb) representative localities of members of the Santa Margarita Spisula catilliformis Conrad Formation are listed below: Cryptomya ovalis Conrad(?) Panopea generosa Gould Lower phosphatic mudstone member (Member A of Fritsche; Panopea tenuis Wiedey clay stone and shale member of Vedder and Repen­ Unidentified pectinid ning) Unidentified tellinid Crassostrea ashleyi (Hertlein) Astrodapsis sp. ' dementia pertenuis (Gabb) The above faunal collections from the Santa Margarita Aequipecten cf. A. discus (Conrad) Formation in the study area are generally indicative of provin­ Unidentified tellinid cial late Miocene age. This faunal assemblage is charac­ Nondiagnostic shallow-water foraminifers teristic of a shallow-water marine environment in a warm Lower sandstone member (Member B of Fritsche; sandstone temperate to subtropical climate. and conglomerate member of Vedder and Repenning) Forreria carisaensis (Anderson) Crassostrea eucorrugata (Hertlein) Lithologic Composition Crassostrea titan (Conrad) Crassostrea sp. Lower Phosphatic Mudstone Member Lyropecten estrellanus (Conrad) Unidentified pectinid The lower phosphatic mudstone member of the Santa Astrodapsis sp. Margarita Formation is poorly exposed in the study area. Isurus sp. Subsurface information at the South Cuyama oil field indi­ Desmostylus cf. D Hesperus Marsh cates a thickness of 150 feet (45 m). Field mapping of Vedder Upper phosphatic mudstone member (Member C of Fritsche; (1968) and Fritsche (1969) shows that the lower phosphatic claystone and clayey siltstone member of Vedder and mudstone member thins eastward and pinches out in the Fox Repenning) Mountain quadrangle. In the limited exposures the member is Crassostrea titan (Conrad) predominantly a phosphatic, siliceous mudstone with less Lucinisca cf. L. nuttalli (Conrad) than 30 percent interbedded siltstone, sandstone, and con­ Chione temblorensis (Anderson) glomerate. Outcrops are olive gray to greenish gray on fresh dementia pertenuis (Gabb) surfaces and yellowish gray on weathered surfaces. Individual Yoldia cooperii supramontereyensis Arnold lithologic units are laminated to thin bedded or indistinctly Unidentified tellinid bedded. Most of the siltstone and sandstone beds contain Nondiagnostic shallow-water foraminifers angular to subangular grains which are medium sorted. The Coscinodiscus sandstone units are often cross laminated. They are fine to Upper sandstone member (Member D of Fritsche; sandstone medium grained with lenses of coarse-grained sandstone and member of Vedder and Repenning) pebble conglomerate. The member contains only thin pelletal Turritella carrisaensis Anderson and Martin and nodular phosphorite zones with local concentrations at or Turritella sp. near the base; therefore, it is not considered a potential Crassostrea sp. phosphate resource.

10 Santa Margarita Formation Lower Sandstone Member with less than 10 percent interbedded mudstone and con­ glomerate. Outcrops are light gray and greenish gray on fresh The lower sandstone member of the Santa Margarita surfaces and light yellowish gray on weathered surfaces. Formation forms many of the foothills in the study area and is Individual beds are thick bedded and massive with lenses of generally exposed in canyons. The member is predominantly greenish-gray mudstone, clayey sandstone, and con­ sandstone with less than 20 percent interbedded mudstone glomerate. The sandstone units are poorly to medium sorted and conglomerate. Outcrops are light gray on fresh surfaces and contain subangular, very fine to coarse-size grains of and very pale orange to yellowish orange on weathered sur­ quartz, orthoclase, plagioclase, and igneous and meta­ faces. Individual beds are medium bedded to massive with morphic rock fragments. Turritella carrisaensis is the most lenses of mudstone or conglomerate. The sandstone units are abundant megafossil in the fossil beds. The cement is gener­ medium sorted and contain subangular, fine- to medium- ally siliceous and only locally calcareous. Some sandstone grained quartz, orthoclase, plagioclase, and igneous and met- beds are cross stratified. The member also contains a few thin amorphic rock fragments. The conglomerate beds, which are bentonite and bentonitic siltstone beds. In the lower part of poorly sorted, consist mainly of subrounded pebbles of pre­ the member phosphatic pellets are present in the fine-grained dominantly granitic and metamorphic rocks, and a few peb­ units (see "Stratigraphic Sections," trench 294). bles of sandstone, volcanic rocks, and shell fragments. The cement in the sandstone is generally siliceous; the beds with Mineralogy and Petrography calcareous cement contain common to abundant megafossils. Fossil beds are dominated by Crassostrea titan and of Phosphatic Components Lyropecten estrellanm. The member contains local con­ Carbonate Fluorapatite centrations of phosphate pellets and phosphatic casts of mol- lusks near its base. Phosphatic components in the upper phosphatic mudstone member of the Santa Margarita Formation are pellets that range from 0.10 to 0.35 mm in diameter (median Upper Phosphatic Mudstone member diameter is 0.20 mm), nodules that range from 2.0 to 30.0 The upper phosphatic mudstone member of the Santa mm in diameter, and phosphatized diatoms and pelecypod Margarita Formation is poorly exposed in the study area; casts. The pellets and nodules generally are structureless however, eight stratigraphic sections were obtained for study aggregates of submicrocrystalline carbonate fluorapatite, ter­ by trenching (see "Stratigraphic Sections" and pi. 5). In the rigenous clay-, silt-, and sand-size particles, and diatoms or reference section for this member (trench 100) the strat­ shell fragments. The pelecypod casts are phosphate- igraphic sequence consists of 50 percent mudstone, 25 per­ cemented sand grains that rarely contain foraminifers and cent siltstone, 10 percent claystone, 10 percent fine-grained sponge spicules. Although most mudstone and sandstone sandstone, and 5 percent phosphorite and bentonite. Most units are poorly sorted, zones containing the pellets are beds are phosphatic and siliceous. The average specific grav­ strikingly well sorted. ity of the phosphorite beds is 2.26. The lithologic units Phosphatic pellets, when examined in thin section, generally are laminated to thick-bedded, poorly to medium- display a variety of shapes, boundaries, internal structures, sorted sedimentary rocks consisting of fine sand size to less and sizes. Pellets commonly have been compressed and than silt size, angular to subrounded grains. Most beds are deformed against one another by compaction. The shapes of light gray to olive gray or yellowish gray and weather to these pellets vary from flattened ovals or elipsoids to. very shades of grayish orange or moderate brown. The framework irregular or broken pieces. Ellipsoidal pellets, the most com­ of the sedimentary rocks commonly consists of quartz and mon shape, generally are preferentially oriented with the long feldspar grains and lesser amounts of phosphatic pellets; the axis (typically two times as long as the short axis) parallel to matrix consists of carbonate fluorapatite and minerals of clay, the bedding plane. Ellipsoidal and spherical pellets usually carbonate, and iron oxide. Most of the units are massive, have grain inclusions, sharp boundaries, and a recognizable probably bioturbated, and contain fragments of diatoms, fish internal structure. Pellets that are irregular in shape com­ bones and scales, sponge spicules, echinoid spines, and monly have diffuse boundaries and no recognizable internal mollusk shells. The relation of the major chemical constitu­ structure. Pellets with an irregular shape and an indistinct ents and the lithologic composition for the upper phosphatic boundary that seem to grade into the surrounding matrix are mudstone member is illustrated on plate 4. designated incipient pellets (Gulbrandsen, 1960, p. c!20). Most of the phosphatic pellets have noncentered inclu­ sions of detrital silt to fine sand-size grains of quartz and Upper Sandstone Member minor amounts of feldspar. The detritaj grains commonly The upper sandstone member of the Santa Margarita protrude the boundary of this pellet type. There are a few Formation forms the foothills along the southern boundary of compound pellets made up of two or more pellets that are in the Cuyama Valley. The member is predominantly sandstone contact and that have been encased by silica, carbonate, or

Santa Margarita Formation 11 apatite. A significant number of pellets have inclusions of Investigations by Martens and Harriss (1970) have diatomaceous debris or shell fragments. The cores of many of demonstrated that the presence of Mg2+ ions, above a crit­ these pellets are the diatom Coscinodiscus; it is one of the ical value, inhibits the direct precipitation of crystalline car­ more resistant diatoms to dissolution during the formation of bonate fluorapatite. This critical value is always exceeded in phosphatic pellets (J. A. Barron, oral commun., 1979). Pel­ the open ocean because of the relatively high concentration of lets containing a complete frustule of this diatom are gener­ magnesium in sea water. A magnesium sink must form if the ally larger than other types of pellets (C, pi. 6). Ca/Mg ratio necessary for an uninhibited direct precipitation The pellets and nodules are dark brown to dark gray on of crystalline carbonate fluorapatite is to be reached. Inves­ fresh surfaces and yellowish gray to light gray on weathered tigations by several researchers have shown that the Mg2 + surfaces. The original color is essentially due to the presence concentration increases slightly in the top 50 cm then of carbonaceous material and iron oxides, and the secondary decreases with depth in the upper few meters of sediments color is due to the leaching of the carbonaceous material and (Bischoff and Sayles, 1972; Booth, 1974) while other alteration of the iron oxides. researchers have noted a general decrease in concentration Phosphatic ooliths occur with the phosphatic pellets, with depth in the upper few meters of sediment (Brooks and and externally they have a similar shape and size; however, others, 1968; Bischoff and Ku, 1970). The decrease suggests internally they are strikingly dissimilar. Microscopically, that the Mg2 + ions are being progressively removed with ooliths show distinct concentric zonation by changes in color depth by early diagenetic processes. Several possible and refractive indices. This concentric structure is due mostly diagenetic sinks may exist. Using chemical and miner- to alternating bands of apatite of different crystallinity. alogical data, Drever (1974) postulated that the most impor­ Because ooliths represent a minor fraction of the pellet popu­ tant mechanism for the removal of magnesium from pore lation, they are not separated in the point count percentages. water is the exchange of magnesium with iron in sheet sili­ Nodules generally are subrounded, are ellipsoidal to cates. The conditions considered most favorable for this reac­ irregular in shape, and are composed of apatite-cemented tion are in anaerobic environments where the Fe2+ in the clay. Most nodules are granule (2.0+ mm) size; however, a sheets reacts with H2S to form pyrite and Mg2 + replaces the few range in size from 1.0 to 2.0 cm. In all the units of the vacated sites (Drever, 1971). Alternatively, in a reducing upper phosphatic mudstone member that contained nodules, environment, Mg2+ may be replacing Fe2+ in iron oxide the finer grained clastic units (mudstone, claystone, and silt- sheaths that are not structurally bound to clays (Sholkovitz, stone) contained 67 percent of the nodule occurrences; 1972). Of less importance in the removal of magnesium may coarser grained clastic units (sandstones) contained 21 per­ be the formation of Mg-bearing carbonates, simple ion cent; and phosphorite units contained 4 percent. exchange, glauconite formation, and in situ formation of Many of the phosphatic pellets have undergone sepiolite and chlorite (Bischoff and Ku, 1970; Bischoff and diagenetic alteration ranging from slight boundary changes to Sayles, 1972). Another significant magnesium sink forms complete mineral replacement. Some pellets have calcareous when volcanic ash alters to bentonite. As the alteration pro­ rims; a few have siliceous rims. In some units, continued ceeds, magnesium is removed from the pore fluids and incor­ alteration is marked by replacement to clay and iron oxide porated in montmorillonite (Ross and Hendricks, 1945). The minerals. The progression of alteration of the pellets may have formation of montmorillonite from ash may be significant for contributed to the growth of interstitial apatite in the sur­ another reason as well as the removal of Mg2 + . Such altera­ rounding matrix. In general, the cementing matrix between tions occur in a relatively alkaline system (Slaughter and pellets or nodules is commonly phosphatic and less often Barley, 1965) a system where as the alkalinity increases the siliceous, mainly anhedral submicron opal-CT. Opal-CT lep- solubility of phosphate decreases (Gulbrandsen, 1969). ispheres rarely occur in voids on pellet surfaces. Another sink for Mg2+ ions is the formation of embryonic opal-CT lepispheres around magnesium hydroxide nuclei (Kastner and others, 1977). Since opal-CT is present in 70 percent of the beds in the upper phosphatic mudstone mem­ Diagenetic Alterations ber, a significant amount of magnesium may have been Investigation of the diagenetic alterations of the upper removed, albeit long after burial, from the pore solution by phosphatic mudstone member of the Santa Margarita Forma­ this mechanism. tion in trench 100 was conducted in an attempt to identify Petrographic and X-ray diffraction investigations did physiochemical changes that may have occurred within the not conclusively establish a quantitatively sufficient amount sediments and pore fluids; in particular, the changes that may of early diagenetic minerals to provide sinks for magnesium affect the Ca/Mg ratio by providing sinks for magnesium and as to affect the Ca/Mg ratio such that crystalline carbonate thus allowing the direct unimpeded precipitation of carbonate fluorapatite could precipitate directly from solution. fluorapatite. Data indicate the presence of several diagenetic However, post depositional changes in physiochemical con­ minerals, including opal-CT, dolomite, calcite, gypsum, ditions may have resulted in late diagenetic alteration or mica group, and the smectite group minerals. dissolution of the early diagenetic mineral sinks for magne-

12 Santa Margarita Formation sium releasing Mg2+ back into solution. Perhaps the magne­ rate of transformation from opal-A to opal-CT is increased sium needed for opal-CT lepishere nucleation was provided when nuclei containing magnesium and hydroxyl are pres­ by this mechanism. ent. Nuclei with Mg:OH = 1:2 attract silanol groups and act Modern marine carbonate fluorapatite has been identi­ as sites for opal-CT nucleation and subsequent growth of fied near the sediment water interface on the inner shelf of opal-CT lepispheres. A significant amount of magnesium Southwest Africa (Baturin, 1969; Baturin and others, 1972; may be removed from the pore solution by this process, even Price and Calvert, 1978) and Peru (Burnett, 1974; Manheim at a temperature of 50°C (Mariam Kastner, oral commun., and others, 1975; Burnett and others, 1980). The area of 1980). Because magnesium acts as an inhibitor in the pre­ formation is on the shelf and slope where an oxygen mini­ cipitation of carbonate fluorapatite (Martens and Harriss, mum zone impinges on the bottom, at depths of 330 to 1,640 1970), the initiation of opal-CT lepisphere formation with ft (100 to 500 m) (Manheim and others, 1975, p. 245). magnesium hydroxide nuclei may be an important factor in Although phosphate is enriched in this zone, there is no late phosphogenesis. Murata and Larson (1975), using X-ray unequivocal evidence for the direct precipitation of carbonate diffraction and SEM techniques on samples from a continu­ fluorapatite from sea water. Instead, recent experimental ous sequence at Chico-Martinez Creek in the Temblor Range, work (Gulbrandsen and others, 1984) demonstrates that an Calif, confirmed Bramlette's (1946) observations and initial amorphous solid phase of calcium phosphate is formed provided a subdivision of these siliceous rocks into three (the magnesium concentration has no inhibiting affect on the depth-controlled zones characterized by different poly- formation of amorphous calcium phosphate (Martens and morphs of silica. The three zones, in descending Stratigraphic Harriss, 1970)) and develops into a crystalline magnesium order, are: biogenic opal (opal-A of Jones and Segnit, 1971), phosphate, then it recrystallizes to carbonate fluorapatite with diagenetic cristobalite (opal-CT of Jones and Segnit, 1971), time. The recrystallization rate may be increased as magne­ and diagenetic quartz. Opal-CT undergoes a progressive sium is removed from the system, but the rate is not strictly decrease in the d(101) spacing because of gradual solid-state dependent on the absolute raising of the Ca/Mg ratio to the adjustments in the internal crystal structure. X-ray diffraction critical value. A decrease in free Mg2+ cations in the system analysis of opal-CT d( 101) spacing from a continuous section favors the crystalline phase in the kinetic reaction between through the upper phosphatic mudstone member of the Santa amorphous calcium phosphate and crystalline carbonate flu­ Margarita Formation in trench 100 (see table 1) show a range orapatite. Such an amorphous solid phase of calcium phos­ in the d( 101) spacing from 4.123 to 4.085 angstroms. Figure 4 phate in a modern phosphogenic environment off Southwest confirms the depth-related trend; solid state adjustments have Africa has been interpreted by Baturin (197la) on the basis of led to a smaller more ordered d( 101) spacing at the base of the X-ray line broadening. Crystallization is accompanied by an upper phosphatic mudstone member. The average geother- increase in P2O5 , CaO, CO2, and F and a decrease in Mg, mal gradient at the sample locality in Cuyama Valley is organic C, and other elements (Baturin, 197la). The changes approximately 35°/km (American Association of Petroleum in X-ray patterns and composition are supported by the Geologists, 1973), the same gradient found by Murata and experimental results of Gulbrandsen and others (1984). Inher­ Larson (1975) in the nearby Temblor Range. If the thermal ent in this mode of formation is the inclusion of impurities conductivity of the upper phosphatic mudstone member is (R. A. Gulbrandsen, written commun., 1980), including similar to the conductivity of the Monterey Shale in the organic matter, mineral fragments, and amorphous solids (pi. Temblor Range, a depth of burial to which the opal-CT 6, C, D, E, G, H, I, M) in the phosphatic pellets. equilibrated can be derived. The d(101) spacings between 4.123 and 4.085 angstroms in the upper phosphatic mudstone member, when compared to the findings of Murata Opal-CT and Larson (1975), suggest a depth of burial between 2,460 ft Opal-CT is present in 70 percent of the beds in the (750 m) and 3,280 ft (1,000 m). upper phosphatic mudstone member of the Santa Margarita Formation, trench 100, (see "Stratigraphic Sections") and is Carbonates a major component in 26 percent of the beds. Its origin and occurrence provide valuable information on' the late Dolomite is present in 17 percent of the beds in the diagenetic processes that have effected the phosphate-bearing upper phosphatic mudstone member of the Santa Margarita rocks of the Santa Margarita Formation. Bramlette (1946) Formation in trench 100 ("Stratigraphic Sections"). Individ­ introduced the concept of diagenetic alteration of siliceous ual beds (and laminae) containing dolomite consist of clay- oozes to form cristobalite and chert. The alteration occurs stone, mudstone, siltstone, sandstone, porcellanite, and through the solution and redeposition of siliceous biogenic wackestone. They contain between 0.32 percent and 3.1 sediment, predominantly diatom frustules. The transforma­ percent magnesium; most beds contain greater than 2.0 per­ tion was believed to be essentially dependent on the depth of cent. burial, temperature, and time; however, it has been experi­ The occurrence of dolomite observed in thin section mentally demonstrated (Kastner and others, 1977) that the is often patchy; polygonal crystals are typically less than

Santa Margarita Formation 13 Tablet. X-ray characteristics d(101) spacing and 20, of opal- 0.05 mm. In concentrated patches, the crystal mosaics have a CT from the upper phosphatic mudstone member of the wide range of plane intercrystalline boundaries; this type of Santa Margarita Formation at trench 100 in Cuyama Valley fabric has been defined as planomural (Bathurst, 1971, p. phosphate area, Santa Barbara County, Calif. 506). Baker and Kastner (1980) state that dolomite, common [Analyses by T. L. Vercoutere] in organic-rich marine sediments, is formed by a transforma­ tion of calcite to dolomite after transformation-inhibiting Sample No. d_(101) °29 Sample No. >2e SO42 ~ and dissolved silica are removed. Sulfates are Upper sandstone member Upper phosphatic mudstone member- Continued removed through their use as oxidants by anaerobic bacteria -LUU -L during biochemical degradation of organic matter (Demaison 100-35 Upper phosphatic mudstone member 100-36 -- -- and Moore, 1980). The removal of silica is facilitated by the 100-37 100-2 100-38 4 .114 21 .60 formation of opal-CT lepispheres. The presence of dolomite 100-3 4. 114 21. 60 100-39 in the opal-CT-rich upper phosphatic mudstone member indi­ 100-4 __ __ 100-5 4. 110 21. 62 100-40 4 .104 21 .65 cates that a sufficient concentration of Mg2+ remained in 100-6 4. 108 21. 63 100-41 100-42 4 .123 21 .55 solution after early diagenetic alterations concentrations in 100-7 100-43 4 .123 21 .55 100-8 4. 110 21. 62 100-44 _- -- excess of that needed to convert all the calcite to dolomite 100-9 ______100-45 4 .099^ 21 .68 (Baker and Kastner, 1980) and presumably high enough to 100-10 ' -- -- 100-11 100-46 inhibit the precipitation of carbonate fluorapatite. 100-47 4 .095 21 .70 100-12 100-48 4 .099 21 .68 Diagenetic calcite is present in very small quantities in 100-13 100-49 4 .104 21 .65 many samples and may be part of an earlier episode of 100-14 4. 114 21. 60 100-50 4 .099 21 .68 100-15 4. 114 21. 60 100-51 -- -- diagenesis prior to the deposition of the Santa Margarita

100-16 18 100-52 -- -- 100-53 4 .104 21 .65 Formation. Calcite, as observed in thin section, occurs as 100-17 4. 116 21. 59 -- -- 100-18 100-54 altered corners of clastic grains in the framework and in the 100-19 100-55 4 .104 21 .65 nuclei of pellets. 100-20 100-56 -- -- 100-21 100-57 4 .092 21 .72 / 100-22 4. 116 21. 59 100-58 4 .104 21 .65 100-59 4 .114 21 .60 Mica and Smectite Groups 100-23 100-24 4. 123 21. 55 100-60 -- -- 100-25 4. 110 21. 62 100-61 4 .095 21 .70 The mica group and smectite group minerals are present 100-26 4. 116 21. 59 100-62 -- -- in varying proportions in many samples in trench 100. Illite 100-27 4. 114 21. 60 100-63 .085 21 .75 and muscovite, the two mica group minerals identified in 100-28 4. 116 21. 59 100-64 4 100-29 100-65 4 .095 21 .70 samples from trench 100 are present in many mudstone and 100-30 4. 104 21. 65 100-66 -- -- 100-31 100-67 -- - - siltstone laminae (see "Stratigraphic Sections"). Illite is by 100-32 4. 095 21. 70 far the dominant of the two species present; muscovite, which Lower member 100-33 sandstone has been identified optically, is present only as an accessory 100-34 -- -- 100-35 100-68 mineral in several samples. The only member of the smectite group identified was montmorillonite. Montmorillonite is present with or without illite in many of the mudstone and siltstone laminae (see "Stratigraphic Sections"). In the bentonite beds, 4.18 montmorillonite is the only clay present, and it most likely

4.16 formed as an alteration product of volcanic glass. Clay sepa­ rates of 12 previously determined smectite-rich samples from 4.14 O trench 100 were analyzed to determine whether the clays were Z 4.12 A13+ -, Mg2+ -, or Fe2+ -rich clays. Preliminary results indicate that the smectite group minerals of selected samples Z O 4.08 from trench 100 are dominated by dioctahedral aluminum- rich montmorillonite. Therefore, smectite authigenesis does not appear to provide a quantitatively great enough magne­ 4.04 X> sium sink to effectively remove free magnesium from the 4.02 system as a whole but may be significant in removing Mg2 +

4.00 during the alteration of volcanic glass in the bentonite beds. 10 20 30 40 50 60 Another possible sink for magnesium involving smectites DISTANCE ABOVE BASE, IN METERS occurs when charge deficiencies in either the octahedral or tetrahedral layer of smectites are neutralized by an iso- Figure 4. Diagenetic variation of opal-CT c/(101) spacing related to depth of burial. Samples from trench 100, in morphous substitution of available cations. Values for the upper phosphatic mudstone member of the Santa Mar­ amount of Mg2 + occurring in isomorphous substitution in garita Formation. smectites has not been determined.

14 Santa Margarita Formation Chemical Composition high due to its high weight percent in carbonate fluorapatite, Samples of the upper phosphatic mudstone member of approximately 55 percent CaO (Manheim and Gulbrandsen, the Santa Margarita Formation consist primarily of quartz, 1979), and the presence of calcite and dolomite in much of the feldspars, carbonate fluorapatite, opal-CT, clay minerals, member. Phosphorus is low because phosphorite beds make carbonate minerals, accessory minerals (including biotite, up only a small part of the upper phosphatic mudstone chert, chlorite, glauconite, hematite, magnetite, muscovite, member; however, the P2O5 content of the pellets is high. A sphene, and zircon), and fossil shell and bone fragments (see phosphorite bed containing 80 percent pellets was selected "Stratigraphic sections"). The results of rapid rock, semi- for chemical analysis of the pellets (see table 12, trench 299, quantitative spectrographic, and delayed-neutron activation Stratigraphic Unit No. 81, Sample No. CB-la, Ib, Ic). The analyses of these samples are tabulated in tables 2-12. pelletal fraction weighed 21.5 g and separated into a 15.3-g heavy fraction (specific gravity greater than 2.73), a 3.2-g middle fraction (specific gravity of 2.68 to 2.73), and a 3.0-g Major Constituents light fraction (specific gravity less than 2.68). The chemical The major elements (calculated as oxides from rapid analyses of each fraction and the weighted averages are listed rock analysis) in the upper phosphatic mudstone member of in table 3 and the semiquantitative spectrographic analyses of the Santa Margarita Formation, in order of decreasing abun­ each fraction are listed in table 4. dance, are silicon, aluminum, calcium, phosphorus, iron, sodium, magnesium, and potassium (see table 2). The high silica content is due primarily to the high concentration of Minor Constituents opal-CT (alteration product from diatom frustules) and The minor elements in the upper phosphatic mudstone detrital quartz grains. Aluminum, contained primarily in the member of the Santa Margarita Formation are listed at the clay minerals, is in high concentrations because of the high end of the report (see tables 5, 7-12). The analysts identified ratio of aluminum-rich clay minerals to detrital minerals in the following minor elements in concentrations above the the upper phosphatic mudstone member. Calcium content is lower limit of detection: barium, beryllium, boron, cad­ mium, cerium, chromium, cobalt, copper, europium, gadolinium, gallium, lanthanum, lead, manganese, molyb­ Table 2. Rapid rock analyses for upper phosphatic mudstone member of the Santa Margarita Formation, at denum, neodymium, nickel, scandium, strontium, thorium, trench 296 in Cuyama Valley phosphate area, Santa Barbara uranium, vanadium, ytterbium, yttrium, zinc, and zir­ County, Calif. conium.

[Elements calculated in weight percent. Analyses were made by L. Artis, S. D. Bolts, J. W. Budinsky, and P. L. D. Elmore]

Strat. unit - 103 100 99 94 93 88 87 86 Field No CA-1 CA-Z CA-3 CA-5 CA-6 CA-7 CA-8 GA-9 Table 3. Average chemical composition of phosphorite pel­ Sample No 164744 164745 164746 164747 164748 164749 164750 164751 lets from trench 299, Stratigraphic unit 81, of the upper phosphatic mudstone member of the Santa Margarita For­ Al,5, 11.8 12.8 8.9 8.1 10.8 6.7 12.1 9.1 mation, Cuyama Valley phosphate area, Santa Barbara Fe'jO, 2.95 5.42 2.25 2.07 3.65 1.10 .73 1.99 County, Calif.

(Rapid rock analyses in weight percent; analyst, C. 0. Ingamells)

IUO+ ---- 2.9 4.2 3.2 3.8 3.3 1.8 3.8 Z.6 - i ~« < «- ~- ..... Specific gravity >2.73 2.68 to 2.73 '2.68 average P2°5 4 ' 5 1>5 8 - 5 14 ' 8 2<0 K1 K2 7 ' 7

Total 99 100 99 98 99 100 99 97

Strat. unit - 85 83 82 78 77 72 71 70 Field No CA-10 CA-11 CA-U CA-13 CA-14 G\-15 CA-16 CA-17 Sample No 164752 164753 164754 164755 164756 164757 164758 164759

SiO, 64.3 34.8 62.4 62.0 65.8 50.5 65.5 57.9 Al,0, --- 10.0 5.9 10.8 10.1 11. I 8.1 7.1 8.6

CaO - 5.2 25.9 4.5 8.5 3.6 16.3 6.7 11.2 . . Na,0 ----- 1.8 1.5 1.5 2.0 1.8 2.0 1.4 2.4 , ,,, - ,_ ., " |C,(5 - 1.7 1.3 1.8 1.9 1.9 1.9 1.1 1.7 F 3 ' 25 3 ' 48 3 ' j6 3 ' j3 HO- - 4.6 2.2 5.1 3.2 4.5 2.4 3.1 2.6 C0 , 3.61 3.78 3.89 3.67

_.. , n , n ,. ,. ,, ,. ,, ,, Total 99. 41 100.30 99.81 99.59 T»0-» ------.50 .ZO .54 .31 .44 .21 .35 . Zo P2 0^ .... 2.1 9., 1.1 5.9 2.7 10.3 1.5 7.2 Less 0=F 1 ' 37 1 ^ l ' 50

Total 99 9S 100 100 100 99 99 98 , 'From semiquand tative specr rngraphlr analysis hv rhrls HpropmiloR.

Santa Margarita Formation 15 Table 4. Semiquantitative spectrographic analyses of major Barium and minor chemical elements of phosphorite pellets from Barium concentrations in the study area range from 120 trench 299, stratigraphic unit 81, of the upper phosphatic mudstone member of the Santa Margarita Formation, to 1,200 ppm and for 83 samples (see tables 7-12), the Cuyama Valley phosphate area, Santa Barbara County, Calif. average concentration is 440 ppm. This value is in the 350 to 500 ppm range for the average phosphorite that was reported

[Semiquantitative spectrographic analys ight percent; analyst, Chris by Altschuler (1980, p. 23). Forty one of the 83 samples lleropoulos. n.d., not detected) analyzed for barium contain greater than or equal to 500 ppm Lab. No 64M-1346 64M-1347 64M-1348 Lab. No 64M-1346 64M-1347 64M-1348 Sample No - CB-la CB-lb CB-lc Sample No CB-la CB-lb CB-lc barium, the upper limit of Altschuler's (1980) average phos­ Si 3.0 3.0 3.0 Pb _ n.d. n.d n.d. Al - - 1.5 1.5 1.5 Pd _ n.d. n . d n . d . phorite. The lithologies of these 41 samples are sandstone, Fe .7 .7 .7 Pt -- n.d. n . d n.d. .7 .5 Re - n.d. n.d siltstone, mudstone, phosphorite, clay stone, and porcellanite; Ca __ >10.0 >10.0 >10.0 n.d. n.d. n . d n.d. Na .7 .7 .7 Sc .003 .0 33 .003 the highest concentrations of barium are found in sandstone. K n.d. n.d. n.d. Sn _ n.d. n . d n.d. Ti .1 .15 .07 Sr .175 .2 50 .200 The concentration of barium by planktonic organisms (Mar­ P ______>10.0 >10.0 >10.0 Mn _____ .007 .015 .01 n.d. n.d. tin and Knauer, 1973) and subsequent deposition within the n.d. n.d. Ag .00007 .00007 .00007 Th n.d. n . d n.d. oxygen-minimum zone may have been one source of barium A S ______n.d. n.d. 11 _ n.d. n.d n.d. Au ----- n.d. U n.d. n . d n.d. for the sediments and pore fluids. However, a relatively low V .007 Ba ------.03 .03 .04 .007 .007 n.d. n.d. n.d. correlation coefficient of 0.66 between Ba and P2O5 suggests Be ' .0003 .0003 .0003 Y _ -___ .02 .03 ' .02 Bi ------n.d. Yb .001 .0015 .001 that other sources of barium were important in concentrating Cd <.004 <.004 <.004 Z n ______.020 .020 .015 Ce <.015 <.015 <.015 Zr - .020 .030 .020 barium in the sediments. Substitution and adsorption may Co -_-- n d n d Looked for only when La or Co found : Cr - - .015 .015 .015 Pr ______0 0 0 have fixed the barium in several minerals within the sedi­ CU ______.005 .005 .005 Nd 0 0 0 Ga .0005 .0005 .0005 gm ______0 0 0 ments. Evidently some of the barium was incorporated into Ce n.d. n.d. Eu ______- 0 0 0 H f _. n.d. n d . n.d. the carbonate fluorapatite pellets (table 4). Looked for only when Y is found above Hg n.d. n.d. n.d. In ------.005 perce it : n.d. n.d. n.d. Cd 0 La .015 .015 .015 Tb _ - 0 Cadmium Li ------0 0 n.d. n.d. n.d. 0 Mo ______.003 .003 .003 Ho 0 0 0 Cadmium concentrations in the study area range from Nb n.d. n.d. n.d. Er 0 0 0 Ni .003 .002 .002 Tm __ 0 0 0 42 to 180 ppm (see tables 7-12), and for 38 samples with cadmium content above the level of detection; the average concentration is 71 ppm. This value is nearly four times larger than the 18 ppm cadmium for the average phosphorite that was reported by Altschuler (1980, p. 24). Majmundar (1975) found as much as 625 ppm cadmium in the phosphatic Many of the minor elements present in the upper phos­ rocks in the Monterey Formation north of the La Panza phatic mudstone member were concentrated from the water Range. Cadmium concentration mimics phosphate con­ column by organic and inorganic processes. The role of centration in the ocean water column as indicated by the organisms in concentrating trace elements may have been 0.998 correlation coefficient between the two (Bruland and active or passive. Trace elements such as barium, cadmium, others, 1978). Such a high correlation suggests that cad­ copper, nickel, radium, and strontium were concentrated mium, like phosphorus, is biologically fixed and concen­ along with nutrients while the organisms were alive. Other trated by phytoplankton. The correlation coefficient between trace elements were adsorbed or complexed to the hard and cadmium and P2O5 for the 38 samples, which is 0.87, soft body parts, forming metal-organic colloids, while the suggests that most of the cadmium is associated with carbon­ dead organisms settled through the water column. Clay parti­ ate fluorapatite; however, cadmium concentration in pellet cles, a primary constituent of the upper phosphatic mudstone separates below the detection level (table 4) indicates that member, may have been the sequestering agent for reactive cadmium is not a structural component of the carbonate minor elements and may represent another significant source fluorapatite. Perhaps the cadmium was introduced along with of minor elements concentrated in the sediments. The trace organic matter, and as diagenesis proceeded, it was released metal affinity for charged detrital particles may also be and adsorbed on clay minerals. The lithologies of the 38 beds responsible for the limited correlation between trace elements from which analyzed samples contain greater than 40 ppm and phosphate within individual beds of the upper phosphatic cadmium are phosphorite, mudstone, fine-grained sandstone, mudstone member. By whatever mechanism of concentration siltstone and claystone; all but nine beds contain greater than in the sediments and pore fluids, some of the minor elements 5 percent P2O5 . were then adsorbed on surfaces or substituted for other ions during precipitation and growth of the carbonate fluorapatite. Cerium Strontium, thorium, uranium, and the rare earths are proba­ Cerium concentrations in the study area range from 43 bly associated with the authigenic apatite of the phosphorite. to 220 ppm, and for 83 samples (see tables 7-12), the average The minor elements of significant concentration are: barium, concentration is 115 ppm. The lithologies of the analyzed cadmium, cerium, strontium, zinc, and zirconium. samples containing greater than 120 ppm cerium are phos-

16 Santa Margarita Formation phorite, siltstone, mudstone, fine-grained silty sandstone, derived from an active biological input rather than from claystone, and bentonite. The three highest concentrations passive particle sequestering and was substituted for calcium (220 ppm, 200 ppm, and 190 ppm) were found in phos­ in the carbonate fluorapatite structure. phorites and are somewhat higher than the normal abundance of cerium in marine apatite of 104 ppm as noted by Altschuler Thorium (1980, p. 22). Two bentonite beds (trench 100, stratigraphic Thorium concentration for samples from trench 100 are units 17 and 18) contained 170 ppm of cerium; these two given in table 5. Thorium content ranges from less than 2.8 to concentrations are among the 12 highest cerium con­ 32.8 ppm. The highest concentrations in trench 100 are in centrations found in the study area. The high cerium content three bentonite beds (stratigraphic unit 17 with 32.8 ppm Th; in these two beds may be the result of high cerium content in unit 18 with 29.5 ppm Th; and unit 65 with 19.3 ppm Th). The the volcanic glass from which the bentonite altered or particle major mineral constituent of these thorium-rich beds is sequestering of cerium from pore fluid or sea water. montmorillonite. Claystone beds with a substantial compo­ nent of montmorillonite also are relatively high in thorium. Manganese Thorium (ionic radius of 1.02 A) may act chemically similar Manganese concentrations in the study area range from to uranium and replace calcium in the fluorapatite structure 45 to 1,200 ppm, and for 83 samples (see tables 7-12), the (Manheim and Gulbrandsen, 1979); however, with a correla­ average concentration is 280 ppm. This value is below the tion coefficient of 0.56 for thorium and phosphate and the 1,230 ppm manganese content for the average phosphorite high thorium concentrations in montmorillonite-rich beds, it that was reported by Altschuler (1980, p. 24), however, a appears that most thorium was adsorbed on the surface of clay variation of three orders of magnitude in manganese content minerals. was observed by Altschuler (1980). These variations, accord­ ing to Landing and Bruland (1980), indicate the significance Uranium of local inputs and perhaps fluxes in redox conditions in the Marine phosphorites from all geologic ages contain sediment, and it is the redox conditions which ultimately uranium, typically in the range from 50 to 300 ppm (Cathcart, control the availability of manganese for substitution or 1978). Uranium is associated with the mineral carbonate adsorption in carbonate fluorapatite and other minerals. The fluorapatite and is believed to be replacing calcium (Ca2 + data in tables 3 and 4 indicate that apparently some substitu­ ionic radius of 0.99 A compared to U4+ ionic radius of 0.97 tion or adsorption of manganese has occurred in carbonate A) in the lattice or by substitution of one mole of (U02)2 + fluorapatite. The lithologies of the beds containing greater for two moles of Ca2+ on crystal surfaces (Altschuler and than 300 ppm of manganese are mudstone, sandstone, phos­ others, 1958). According to Thompson (1953), the uranium phorite, siltstone, claystone, and porcellanite. The five high­ content in marine phosphate rock, although not dependent est concentrations of manganese occur in mudstone and very entirely on P2O5 content, develops the best positive correla­ fine grained sandstone. tion with phosphate in rocks with a higher average uranium content. Altschuler and others (1958) later stated that ura­ Strontium nium concentration in marine apatite is related to the amount Strontium concentrations in the study area range from of reworking in the marine environment; the least amount of 150 to 3,000 ppm, and for 83 samples (see tables 7-12) the uranium is found in primary pellets and the most amount is average concentration is 790 ppm. This value is near the low found in phosphatic pebbles and nodules reworked several end of the 750 to 980 ppm range for the average phosphorite times. Statistical analysis of trace element content of phos­ that was reported by Altschuler (1980, p. 23). Of the 83 whole phorite worldwide (Altschuler, 1980) indicates that the aver­ rock samples analyzed, only 26 had strontium concentrations age marine phosphorite contains 120 ppm uranium; the greater than 1,000 ppm. The diverse lithologies associated average phosphorite is enriched by a factor of 30 over the with this level of concentration are claystone, mudstone, average shale (3.7 ppm uranium). The P2O5 content of the siltstone, sandstone, and phosphorite. Most of these beds average marine phosphorite containing 120 ppm uranium is contain greater than 20 percent phosphatic framework; those about 20 percent, thus, the phosphorite consists of more than that contain less than 20 percent phosphatic framework con­ 50 percent apatite and probably represents a moderate to tain clay- or silt-size particles as a primary constituent. Pellet highly reworked deposit. separates taken from a phosphorite bed (table 4) contain 0.2 The uranium content based on delayed-neutron activa­ weight percent of strontium; this amount is more than tion analysis for whole rock samples from trench 100 are Altschuler's (1980) average phosphorite by a factor of 2. A given in table 5. Uranium content ranges from 2.03 ppm in a correlation coefficient of 0.86 exists between Sr and P2O5 for porcellanite to 50.9 ppm in a pelletal phosphorite; the mean the 83 samples. The relatively large weight percent of stron­ uranium content is 12.7 ppm (standard deviation of 9.99 tium, high correlation coefficient between Sr and P2O5 , and ppm), an order of magnitude less than Altschuler's (1980) relatively high concentrations of strontium in plankton (Mar­ average marine phosphorite. The average P2O5 content for the tin and Knauer, 1973) suggest that strontium was primarily upper phosphatic mudstone member of the Santa Margarita

Santa Margarita Formation 17 Formation determined from trench 100 is 3.5 percent, also an and the relatively low P2O5 concentration for the upper order of magnitude less than the average marine phosphorite. phosphatic mudstone member as a whole. Applying Altschuler's (1980) average marine phos­ Several sample populations with progressively increas­ phorite for comparison to his (Altschuler and others, 1958) ing uranium concentrations were isolated and correlated with premise that uranium concentration is related to the amount P2O5 concentrations to test Thompson's (1953) hypothesis of reworking in the marine environment, the upper phos­ relating best positive correlation between uranium and P2O5 phatic mudstone member has been subjected to only minimal with higher average uranium content. The'same formula was amounts of reworking. Sedimentary structures in the upper used to derive the correlation coefficient. The correlation phosphatic mudstone member support this hypothesis. These coefficient of P2O5 and uranium, based on a population of 67 include laminations in many of the beds, sharp contacts samples in trench 100, had a value of 0.95; this value indi­ between beds of different composition, and low apatite con­ cates that 95 percent of the variation in uranium con­ centrations in most beds. The highest uranium concentrations centration can be explained by variation in P2O5 are in pelletal phosphorite beds that are massive and well concentration. A correlation coefficient of 0.96 was obtained sorted; these characteristics suggest that the beds have been when samples containing greater than 10.0 ppm uranium winnowed and reworked. A minimum of reworking, sug­ were used; a coefficient of 0.97 was obtained for samples gested by the uranium concentrations and sedimentary struc­ with greater than 15.0 ppm uranium and greater than 20.0 tures, may account for both the low uranium concentration ppm uranium. Thus, the correlation of uranium with P2O5

Table 5. Uranium and thorium analyses of the upper phosphatic mudstone member of the Santa Margarita Formation, at trench 100 in Cuyama Valley phosphate area, Santa Barbara County, Calif. [CV = Coeff. of Variation = one standard deviation, based on counting statistics expressed as percent of concentration. tf concentration = 0.0, CV >3Q percent or Th/U <1.0, then a 3-sigma detection limit is quoted preceded by '. Element deter­ minations based on delayed-neutron activation analyses by H. T. Millard, Jr., C. McFee, and C. Bliss]

Field No. Lab No. Weight Th CV U CV Th/U Field No. Lab No. Weight Th CV. U CV Th/U (g) (ppm) (ppm) (g) (ppm) (ppm) 100-1 M-136032 7.5600 <3.1 _ 3.99 2 _ 100-36 M-136099 6.8300 <11.0 40.4 1 100-2 M-136033 5.1600 17.9 10 7.95 2 2.25 100-37 M-136100 4.2800 <8.6 18.7 2, 100-3 M- 13 6034 5.3700 <5.4 10.0 2 100-38 M-136101 3.8300 10.0 19 5.97 3 1.67 100-4 M-136035 4.7700 19.3 8 4.89 3 3.94 100-39 M-136102 5.2900 <8.6 23.4 2 100-5 M-136036 3.2400 7.9 28 7.65 3 1.04 100-40 M-136103 3.9000 14.0 16 8.87 3 1.53

100-6 M-136037 3.9800 6.9 24 4.69 3 1.47 100-41 M-136104 5.5600 <6.5 __ 13.9 2 __ 100-7 M-136038 5.4200 <7.2 -- 17.0 2 -- 100-42 M-136105 4.4100 5.4 24 2.92 4 1.89 100-8 M-136039 3.9300 6.6 . 9.72 2 100-43 M-136106 4.6800 12.0 16 7.76 2 1.49 100-9 M- 13 6040 6.5100 16.3 12 13.4 2 1.21 100-44 M-136107 6.0300 < 13.0 50.9 1 100-10 M-136041 5.0600 15.7 12 8.50 2 1.85 100-45 M-136108 3.9400 7.7 23 5.27 3 1.47

100-11 M-136042 4.1600 15.2 '12 5.89 3 2.59 100-46 M-136109 6.5600 13.9 14 12.7 2 1.10 100-U M-136043 5.9800 <6.8 -- 16.8 2 -- 100-47 M-136110 4.4500 8.2 -- 17.9 2 -- 100-13 M- 13 6044 6.1600 < 8.7 27.4 1 100-48 M-136111 5.3500 11.7 13 4.92 3 2.37 100-14 M-136045 3.9100 16.0 15 12.9 2 1.28 100-49 M-136112 4.5200 12.0 16 7.16 3 1.62 100-15 M-136046 4.3400 16.0 16 13.9 2 1.13 100-50 M-136113 4.9900 9.6 27.4 2

100-16 M-136047 6.4500 < 9.9 __ 35.6 1 _ 100-51 M-136114 4.7500 29.5 7 7.13 2 4.14 100-17 M- 13 6048 4.3500 17.0 12 8.06 2 2.10 100-52 M-136115 5.1600 32.8 6 7.15 2 4.59 100-18 M-136049 6.8500 < 7.7 24.7 1 100-53 M-136116 5.5800 4.5 5.85 2 100-19 M-136050 5.1300 8.9 18 6.20 3 1.43 100-54 M-136117 7.0700 4.6 -- 8.68 2 -- 100-20 M-136051 5.0800 < 8.7 -- 23.7 2 100-55 M-136118 5.6100 11.0' 16 8.84 2 1.27

100-21 M- 13 60 52 5.7200 <10.0 _ 35.8 1 __ 100-56 M-136119 5.. 43 00 16.2 9 4.72 3 3.44 100-22 M-136053 4.3800 <6.9 -- 13.7 2 100-57 M-136120 5.4600 11.0 17 9.02 2 1.22 100-23 M- 136054 5.6300 <8.3 24.8 1 100-58 M-136121 4.4500 7.3 23 5.87 3 1.24 100-24 M-136055 5.5900 <2.8 2.03 4 100-59 M-136122 5.2500 12.2 14 7.26 2 1.68 100-25 M-136056 4.1800 10.5 15 4.15 3 2.52 100-60 M-136123 7.9800 4.7 10.5 2 --

100-26 M-136057 4.6000 <7.5 __ 16.6 2 100-61 M-136124 5.2300 8.3 16 3.92 3 ^2.10 100-27 M-136058 4.7800 <6.1 11.2 2 -- 100-62 M-136125 7.2900 5.9 15.3 1 100-28 M-136059 4.0400 13.0 16 8.95 2 1.47 100-63 M-136126 6.1100 6.0 20 3.11 3 1.92 100-29 M-136060 5.8400 <7.1 18.9 2 100-64 M-136127 4.8900 19.0 8 4.04 3 4.70 100-30 M-136061 3.5800 <4.8 -- 3.99 4 100-65 M-136128 6.3000 8.9 15 5.26 2 1.69

100-31 M-136062 5.0900 <7.8 __ 19.5 2 __ 100-66 M-136129 6.0000 18.5 10 10.5 2 1.76 100-32 M-136063 3.7500 9.2 21 6.51 3 1.41 100-67 M-136130 7.0700 8.30 13 3.63 3 2.28 100-33 M-136064 4.9600 <10.0 32.8 1 -- 100-34 M-136065 4.7500 18.4 12 11.1 2 1.66 100-35 M-136098 5.0500 15.5 14 11.0 2 1.41

18 Santa Margarita Formation does show an increase in positive correlation with higher member contained the most, that is, 620 ppm in stratigraphic average uranium content as suggested by Thompson (1953). unit 18, 540 ppm in stratigraphic unit 17, and 330 ppm in What is intriguing is the large discrepancy between the stratigraphic unit 13. Zirconium concentrations as high as results of Thompson's work (1953; 1954) on phosphatic rocks these in the bentonite beds require peralkaline volcanic ash as with uranium concentrations similar to those in the study area a source (Ferrara and Treuil, 1975); the zirconium is and the results from the study area. At uranium con­ attributed to the accessory mineral zircon derived from that centrations less than 100 ppm, comparable to uranium con­ ash. The Timber Mountain caldera complex, in south west centrations in the study area, Thompson (1953; 1954) found Nevada, was a major peralkaline volcanic center during the almost no meaningful correlation between phosphate and late Miocene and may have been the source area for the ash uranium. However, in the study area, where concentrations derived bentonite beds. are no greater than 50.9 ppm, very high correlations between uranium and phosphate concentrations were found. Geochemical Ratios Zinc The thorium-uranium ratio for individual beds is also Zinc concentrations in the study area range from 16 to given in table 5. The mean of the reported ratios is 2.00 and 220 ppm, and for 81 samples (see tables 7-12), the average the standard deviation is 0.97; these values are approximately concentration is 83 ppm. This value bears a closer midway between the values for shale (3.2) and average resemblance to the zinc content of average shale (95 ppm) marine phosphorite (0.055-0.07) reported by Altschuler than to the zinc content of average phosphorite (195 ppm) as (1980). reported by Altschuler (1980, p. 24). The average zinc content The mean zinc-cadmium ratio was determined for for beds lithologically classified as phosphorite is 160 ppm, whole-rock samples with cadmium concentrations above the also below Altschuler's (1980) average. Nonetheless, there is minimum level of detection. The mean zinc-cadmium ratio is good correlation between zinc and phosphate concentration 1.85, an order of magnitude less than the ratio for the average in the 81 analyzed samples; the correlation coefficient for Zn marine phosphorite (10.0) and two orders of magnitude less and P2O5 is 0.91. Zinc concentrations in the water column than the ratio for shale (300.0) as reported by Altschuler exhibit strong correlation with the nutrient silica (correlation (1980, p. 26). coefficient of 0.996) suggesting that zinc is concentrated by The average yttrium-lanthanum ratio for carbonate flu­ active biologic processes in surface waters and transported to orapatite in the upper phosphatic mudstone member is based the bottom as biogenic particles (Bruland, 1980). The high on three pellet separates from trench 299 (table 4). The ratio is correlation coefficient between zinc and phosphate in the 81 1.6, very similar to the 1.8 ratio of Y:La from concentrated samples from the upper phosphatic mudstone member of the apatite for the average phosphorite (Altschuler, 1980, p. 26). Santa Margarita Formation suggests that zinc may be incor­ The average cerium-lanthanum ratio in carbonate flu­ porated in the carbonate fluorapatite. The results of the semi- orapatite is not derived because the cerium content in pellet quantitative analysis of pellet separates (table 4) confirm the separates is below the level of detection (see table 4). The supposition that the concentration of zinc may be attributed to cerium-lanthanum ratio, determined from whole-rock sam­ substitution of zinc for calcium or surface adsorption in ples from trench 100 (see table 7), is 2.16. This value is the carbonate fluorapatite. Supporting evidence is provided by same within analytical error as the 2.1 cerium-lanthanum the highest zinc concentrations being found in phosphorite ratio for the average shale reported by Altschuler (1980). beds. The lithologies of other beds containing greater than 100 ppm zinc are: mudstone, sandstone, siltstone, and clay- stone, all of which contain greater than 5.0 percent P2O5 , 80 PHOSPHATIC SETTING percent of which contain greater than 7.0 percent P2O5 . Phosphogenesis is a controversial concept because the evidence from the variety of rock types and environments Zirconium which contain phosphate is inconclusive. Many hypotheses Zirconium concentrations in the study area range from have been developed to explain geographic or laboratory 12 to 620 ppm, and for 83 samples (see tables 7-12), the observations. Some of the hypotheses that are pertinent to the average concentration is 71 ppm. In the reference section of Cuyama Valley phosphate deposit are included in trench 100, the lithologic units in the lower part of the upper Gulbrandsen (1969), Baturin (1971b), Manheim and others phosphatic mudstone member of the Santa Margarita Forma­ (1975), Manheim and Gulbrandsen (1979), Price and Calvert tion had much higher concentrations of zirconium than the (1978), Riggs (1979), Burnett and others (1980), and Sheldon units in the upper part, particularly stratigraphic units 18 (1981). Changes in the physicochemical conditions during down to basal unit 1. Porcellanite in the upper part of the and after deposition of phosphatic material affect the stability member contained the least amount, that is, 12 ppm in and solubility of the material, and therefore the occurrence of stratigraphic unit 45, 44 ppm in stratigraphic unit 39; and phosphate-bearing rocks. These conditions may include bentonite and bentonitic siltstone in the lower part of the changes in: sea level, oceanic circulation patterns, depth of

Phosphatic Setting 19 impingement of the oxygen-minimum zone on the shelf and phatic members consist of mudstone, claystone, and siltstone slope, rates of surface biological productivity, rates of sedi­ with less than 20 percent sandstone (see "Stratigraphic Sec­ mentation, concentration of various elements and ions, and tions", trench 100). Phosphatic pellets and nodules in the pH, Eh, and alkalinity of the pore fluids. Detailed mudstone are common and phosphate in the matrix is com­ petrographic, SEM and EDAX, X-ray diffraction, and chem­ mon. Many of the beds at the base are graded with nodules, ical investigations allow the authors to model the phos- fish and mammal bones, and shell fragments. Often the base phogenic-diagenetic processes that led to the development of is a sharp irregular contact with the underlying unit. Most the Cuyama Valley phosphate deposits. beds are massive, occasionally vaguely bedded, suggesting bioturbation. Burrows filled with pellets or sand grains also suggest bioturbation. The megafaunal population is consider­ Depositional Environment ably less in the phosphatic mudstone members than in the Depositional structures and faunal assemblages of the sandstone members; this suggests reducing or low oxygen sandstone and mudstone members of the Santa Margarita conditions at the mudstone depositional site. Diatoms are Formation provide criteria for paleoenvironmental interpreta­ common in the mudstone members, and dissolution of the tion. The better preserved and more distinctive structures and more soluble species during diagenesis has added an increas­ faunas in the resistant sandstone members contribute to our ing amount of siliceous cement. understanding of the less resistant and often bioturbated but Phosphogenesis sparsely fossiliferous mudstone members. Because observa­ tions for depositional analysis of the upper phosphatic Petrographic and SEM investigations of the upper mudstone member are essentially limited to exposures in phosphatic mudstone member of the Santa Margarita Forma­ trenches, a detailed environmental assignment is impossible. tion suggest multiple, intermittent stages of the development However, using the sedimentary and faunal data for the or formation of apatite pellets. Phosphatic framework compo­ closely related sandstone members in support of the trench nents include: phosphatized diatoms (pi. 6, A, B, C), pellets information, a reasonable interpretation of the depositional with noncentered clastic inclusions, structureless pellets, environment of the upper phosphatic mudstone member was pellets with diatom frustule inclusions (pi. 6, D, F), phos­ made. phatized mollusk(?) and other shell fragments, fish bones (pi. Asymmetric ripple depositional structures, as well as 6, £), pellets with centered clastic inclusions (pi. 6, G), the faunas in the sandstone members, suggest that the sand­ phosphatic ooliths (pi. 6, //), compound pellets (pi. 6, /, K), stone members were deposited at shallow depths, 0-200 ft phosphatic intraclasts (pi. 6, L, MT), and apatite matrix. Per­ (0-60 m), adjacent to a marine shoreline in an area designated haps the first in a series of stages was the development of the inner offshore facies by Clifton and others (1971, p. 659). some of the apatite pellets. A subsequent stage may have been This environment extends to the depth limit of sand deposi­ the accretionary phosphatic growth or alteration of some tion or to where mud deposition starts. Many variables con­ preexisting material to iron oxides; this change indicates a trol this depth limit, thus precluding a firm bathymetric range changed environment. Either complete replacement of a pel­ for correlation. However, using the Continental Borderland of let by ferruginous material or the formation of a concentric southern California as a recent model for the late Miocene ferruginous band (pi. 6, J) around the pellet resulted. The depositional environment of the Cuyama Valley study area, limited occurrence of this type of pellet indicates that it was a the sand-mud boundary ranges from about 60 ft (18 m) to 200 temporally restricted phenomenon, perhaps occurring in the ft (60 m) as interpreted from Welday and Williams (1975). shallow subsurface when fluctuating redox conditions pre­ The sandstone members consist of fine- to medium-grained vailed. Petrographic evidence in the form of multiple colored sandstone beds with less than 20 percent interbedded bands of apatite (pi. 6, /) suggests that these two stages may mudstone and lenses of pebble conglomerate. Most of the have been repeated by environmental fluctuations. The sandstone units are unstratified as a result of bioturbation, development of apatite pellets occurred contemporaneously thus most beds are structureless. Internal structure for the few with the phosphatic replacement of calcareous shell frag­ nonbioturbated sandstone beds is gently inclined cross-strat­ ments and diatom frustules (pi. 6, C). The replacement of ification. shell fragments resulted in the obliteration of all internal Depositional arrangement of bedding, grain-size dis­ microstructure, thereby rendering identification of the shells tribution, lithology, and paleoecology of the phosphatic impossible. In some rocks, during a late stage of growth, mudstone members suggests that the mudstone members apatite accreted on individual pellets and formed concentric were deposited seaward on the offshore shelf in deeper water phosphatic bands (pi. 6, F, G) or incased groups of pellets and adjacent to the sandstone members. The interbedding of thereby formed compound pellets (pi. 6,1, K). The late stage sandstone and mudstone units throughout the offshore Santa may be distinguished from earlier stages by textural rela­ Margarita sequence may be attributed to transgressive- tionships such as different crystal size, lower transparency, regressive cyclic deposition relative to tectonic activity along differing amounts of inclusions, and a darker brown color. the northern margin of the basin (Clifton, 1981). The phos­ The inclusions and darker color may be due to contamination

20 Phosphatic Setting of the phosphate by organic matter (R. A. Gulbrandsen, oral pellets were subject to transport over a great distance because commun., 1980). the grains would likely be torn from the pellets (Cook, 1967). The phosphatic components of the Santa Margarita The protruding grain-surface texture in pellet-supported lami­ Formation may have originated in a variety of ways including: nae would probably be preserved if the pellets were concen­ precipitation below the sediment water interface, formation at trated by winnowing rather than by transport. Other support the sediment water interface, replacement of fecal pellets, and for this premise is the general lack of clastic material with replacement of calcareous material. Formation of the apatite presumably similar hydraulic equivalents in pellet-supported may have taken place below the sediment water interface laminae and lenses. No evidence in the internal structure of within interstitial pore spaces where pore fluids were super­ these pellets was found to indicate an authigenic origin for saturated with respect to amorphous calcium phosphate these clastic grains. (Baturin, 1978). These conditions have been observed in the pore fluids of shallow water fine-grained and diatomaceous Model for the Santa Margarita Formation sediments that are high in dissolved phosphorus (Baturin, 1972; Brooks and others, 1968). Under such conditions phos­ The exact processes that led to the formation of the phate precipitation may nucleate on diatom frustules (pi. 6, upper phosphatic mudstone member of the Santa Margarita A, B), carbonate detritus, fish bones (pi. 6, £), and clastic Formation in the study area are obscure. The model presented grains (pi. 6, G, H, I, K) (Baturin, 1978). Structureless here is a modification of the five step model of Baturin (1978, pellets with indistinct boundaries that seem to grade into the p. 181). It consists of biogenic-diagenetic processes of phos­ mudstone matrix suggest in situ formation of pellets. Baturin phate formation in fine-grained sediments, and subsequent (1978) stated that phosphate gels precipitated from pore water reworking of the sediments to concentrate the apatite pellets. may differ from the surrounding sediment only in the P2O5 The model does not attempt to explain all the sedimen- content; a self-purging of nonphosphatic components can tological features present in the phosphatic mudstone mem­ increase the P->O5 content during subsequent diagenesis thus bers of the Santa Margarita Formation, nor is the process of forming phosphatic grains and pellets. Fecal pellets from phosphogenesis as simple as presented in the model the burrowing organisms was suggested as a possible origin for available data is merely incorporated and assimilated in a some pellets (Baturin, 1978). The formation of phosphatic workable model. ooliths (pi. 6, H), if they originated by a similar process as The paleogeographic reconstruction (Addicott, 1968; carbonate ooliths, require movement and formed at the sedi­ Lagoe, 1984), the fossil evidence (Fritsche, 1969; Vedder and ment-water interface in a zone of agitation. Repenning, 1975), and the sedimentological features Several sedimentary features present in the upper phos­ (Clifton, 1981) suggest that the Cuyama Valley site of deposi­ phatic mudstone member of the Santa Margarita Formation tion of the Santa Margarita Formation was a subtropical shelf suggest that reworking and subsequent concentration of environment along a western continental margin. Upwelling phosphatic sediments were an integral part of phos- currents typically associated with these geographic locations phogenesis. These processes may, in part, account for the low provided the necessary supply of phosphorus and other variance in the size of the pellets (pi. 6, AO- Subrounded nutrients to support a high rate of biological productivity in phosphatic intraclasts and nodules with a matrix different the water column above the shelf. Upon the death and decom­ from the rock matrix indicate physical reworking and trans­ position of the diatoms and other phytoplankton, the phos­ port from a previous site of deposition. Ooliths, if formed in phorus is returned to the seawater or deposited in the organic- an agitated environment, were transported from a high energy matter detritus (Ketchum and Redfield, 1949); this process nearshore environment to a low energy offshore mud facies provided a means of transporting phosphorus to the sediment. (upper phosphatic mudstone member). Phosphatic frame­ High surface productivity combined with expansion of the work material, primarily pellets, is often concentrated in oxygen-minimum zone onto the shelf during the Neogene burrows, laminae, and lenses in a generally pellet-poor or polytaxic episode (Fischer and Arthur, 1977) led to an oxy­ pellet-free rock. In pellet-supported laminae of phosphatic gen-deficient bottom environment. A state of suboxia in the siltstone, mudstone, and sandstone, as well as phosphorite, water column may have existed because of an insufficient pellet size variability is low (pi. 6, AO with diameters ranging supply of free oxygen to meet the biochemical oxygen from 0.15 to 0.25 mm. Pellets of uniform size should have demand (Demaison and Moore, 1980). The suboxic condi­ similar hydraulic equivalents and respond comparably under tions enhanced the accumulation of decomposed organic- similar hydraulic conditions. Current and tidal velocities, as and phosphorus-rich diatomaceous sediment. Highly mobile well as storm wave orbital motion and wave action during organic phosphorus (Baturin, 1978) accumulated in the inter­ lower stands in sea level, may have been strong enough to stitial fluids until the fluids became supersaturated with winnow the lighter and smaller size material away and subse­ respect to a calcium phosphate solid phase, possibly an quently concentrate the pellets with a minimum of transport. amorphous phase. Precipitation of the calcium phosphate Clastic grains commonly protrude from the edges of phos­ began at acceptable nucleation sites and continued until the phatic pellets; such a texture could not form or remain if the pore fluids were no longer supersaturated.

Phosphatic Setting 21 Alternation of sandstone members with mudstone members of the Santa Margarita Formation in the Cuyama Trench 100 Valley indicates a cyclic pattern of minor regressions and transgressions during the Mohnian Stage of the Miocene. Vail and others (1977) identified very similar fluctuations in sea level on a global scale during the late Miocene. Hydro- logically quiet conditions necessary for the accumulation of fine-grained biogenic sediments (Baturin, 1978) existed dur­ ing the transgressive episodes of the Mohnian Stage. Both 2.2 5.8 argillaceous members of the Santa Margarita Formation are 9.4 6.5 Y//////A phosphatic. The upper member is thicker than the lower member, 275 ft (85 m) thick and 150 ft (45 m) thick, respec­ /W tively; this difference in thickness suggests a longer trans­ ' 9.2 //////// gressive episode in the upper member than in the lower 7.4 \ member if deposition occurred at equal rates, and a longer \ 9-2 I period for the accumulation of calcium phosphate (later con­ 3^ verted to apatite) in the sediments of the upper member than 6.2 40 in the lower member. Phosphatic components were then 1.4 8.9 concentrated in some beds by the process of winnowing and 18.9 reworking of the sediments in response to wave and current action. Laterally persistent beds of well-segregated relatively coarse material, in this case mainly pellets in a mudstone matrix, are characteristic of sediments that have been win­ nowed and reworked by waves (Clifton, 1973). At some time after the precipitation of amorphous 3.9 calcium phosphate, diagenetic removal of the crystalline 6.0 phase inhibiting Mg2+ was sufficient to begin the kinetic reaction between amorphous calcium phosphate and crys­ talline carbonate fluorapatite in the direction of the crystalline phase. Alternatively, sufficient time elapsed such that the inhibiting effects of Mg2+ no longer influenced the kinetic reaction and the phase change proceeded in the presence of magnesium ions. The end result was the formation of the carbonate fluorapatite now found at the Cuyama Valley phos­ phate site.

PHOSPHATE RESOURCES OF THE UPPER

PHOSPHATIC MUDSTONE MEMBER OF THE 31.5 SANTA MARGARITA FORMATION 5.9 Phosphate resources at the Cuyama Valley site were calculated for phosphatic rock containing a weighted average greater than 8.0 percent P2O5 and greater than 5.0 percent P2O5 (Fedewa and Hovland, 1981). The minimum thickness of phosphatic beds used in determining phosphate resource zones was 1 ft (0.3 m) (fig. 5, table 6) and the beds had less EXPLANATION than 600 ft (183 m) of overburden (pi. 3). A total of 138.58 Grade categories million short tons (125.98 million metric tons) greater than XNXN Includes beds with a weighted average 8.0 percent P2O5 phosphate rock and 404.33 million short ^^ greater than 8 percent P 2 05 '///A Includes beds with a weighted average tons (367.57 million metric tons) of greater than 5.0 percent '/'A greater than 5 percent P205

31,5 Thickness, in feet 5.9 , in percent

Figure 5. The ore zones used in tonnage estimates of the 19 Bed number phosphate in the upper phosphatic mudstone member of the Santa Margarita Formation.

22 Phosphate Resources P2OS phosphatic rock were calculated for the upper phos­ REFER phatic mudstone member of the Santa Margarita Formation in the Cuyama Valley phosphate area (table 6). AddicotlAddicott, W. O., 1968, Mid-Tertiary zoogeographic and pa- leoj;leogeographic discontinuities across the San Andreas fault, CalCalifornia, in Dickinson, W. R., and Grantz, A. A., eds., ProProceedings of conference on geologic problems of San AncAndreas fault system: Stanford University Publications, Geo­ logilogical Sciences, v. 11, p. 144-165. AltschulAltschuler, Z. S., 1980, The geochemistry of trace elements in Table 6. Inferred phosphate resources in marmarine phosphorites - Part 1. Characteristic abundances and the upper phosphatic mudstone member ennenrichment, in Bentor, Y. K., ed., Marine phosphorites-geo­ of the Santa Margarita Formation, chechemistry, occurrence, genesis: Society of Economic Paleon­ Cuyama Valley phosphate area, Santa Bar­ tolotologists and Mineralogists Special Publication, no. 29, 249 p. bara County, Calif. AltschulAltschuler, Z. S., Clarke, R. S., Jr., and Young, E. J., 1958, GeeGeochemistry of uranium in apatite and phosphorite: U.S. [Resources calculated for phosphate GeeGeological Survey Professional Paper 314-D, p. D45-D90. rock between ground surface and the AmericaAmerican Association of Petroleum Geologists, 1973, Geothermal 600-ft (183-m) isopach contour of overburden (pi. 3). Cumulative thick­ SurSurvey of North America Geothermal Gradient of Southern ness of ore zones determined by CalCalifornia: American Association Petroleum Geologists, Port­ weighted average of ?205 analyses cal­ folifolio Map Area 22, scale 1:1,000,000. culated by W. T. Fedewa and R. D. Hovland] Antisell, T., 1856, Geological report [Parke's surveys in California and near thirty-second parallel]: U.S. Pacific Railroad Explo­ Phosphate rock Block 5 percent 8 percent ratirations (U.S. 33d Congress, 2d session, S. Ex. Document 78, No. Short Metric Short Metric H. Ex. Document 91), v. 7, pt. 2, 204 p. (million tons) (million tons) Atwater, T., 1970, Implications of plate tectonics for the Cenozoic 1 21.56 19.69 7.38 6.71 tecttectonics of western North America: Geological Society of 2 8.10 7.36 2.77 2.52 AmAmerica Bulletin, v. 81, no. 12, p. 3513-3536. 3 10.87 9.88 3.73 3.39 4 2.22 2.02 .76 .69 Baker, FP. A., and Kastner, M., 1980, The origin of dolomite in 5 3.62 3.29 1.24 1.13 mamarine sediments [abs.]: Geological Society of America 6 8.10 7.36 2.77 2.52 AbAbstracts with Programs, 1980 Annual Meeting, v. 12, no. 7, p. 7 4.87 4.43 1.67 1.52 381381. 8 2.17 1.97 .74 .67 9 1.32 1.20 .45 .41 Bartow, J. A., 1978, Oligocene continental sedimentation in the 10 4.91 4.46 1.68 1.53 CalCaliente Range area, California: Journal of Sedimentary 11 2.68 2.44 .91 .83 PetPetrology, v. 48, no. 1, p. 75-98. 12 14.08 12.80 4.83 4.39 BathurstBathurst, R. G. C., 1971, Carbonate sediments and their diagenesis 13 23.54 21.40 8.07 7.34 (2n(2nd ed.), in Developments in Sedimentology, Volume 12: 14 9.48 8.62 3.25 2.95 15 16.17 14.70 5.56 5.05 ArrAmsterdam, Elsevier, 658 p. Baturin, G. N., 1969, Authigenic phosphate concretions in Recent 16 5.43 4.94 1.86 1.69 17 83.71 76.10 28.71 26.10 sedsediments of the southwest African shelf: Oceanography, v. 18 2.71 2.46 .92 .84 185189, no. 6, p. 227-230. 19 3.10 2.82 1.07 .97 197la, Stages of phosphorite formation on the ocean floor: 20 4.87 4.43 1.67 1.52 NaNature, Physical Science, v. 232, no. 29, p. 61-62. 21 22.99 20.90 7.87 7.15 1971b, Formation of phosphate sediments and water dynam­ 22 17.71 16.10 6.08 5.53 23 3.06 2.78 1.05 .95 icsics: Oceanology, v. 11, no. 3, p. 372-376. 24 7.44 6.76 2.55 2.32 1972, Phosphorus in interstitial waters of sediments of the 25 17.71 16.10 6.08 5.53 SoiSoutheastern Atlantic: Oceanology, v. 12, no. 6, p. 849-855 26 8.22 7.47 2.82 2.56 [En[English language edition of Okeanologiya]. 27 18.15 16.50 6.20 5.64 28 9.94 9.04 3.41 3.10 1978, Phosphorites: P. P. Shirshow Institute of Oceanology, 29 9.48 8.62 3.25 2.95 AcAcademy of Sciences of the U.S.S.R., Nauka Press, Moscow, 30 13.53 12.30 4.63 4.21 23^232 pp. [English translation]. 31 10.63 9.66 3.64 3.31 Baturin, G. N., Merkulova, K. I., and Chalov, P. I., 1972, Radi- 32 8.22 7.47 2.82 2.56 omometric evidence for Recent formation of phosphatic nodules in 33 3.75 3.41 1.29 1.17- 34 5.83 5.30 2.00 1.82 mamarine shelf sediments: Marine Geology, v. 13, no. 3, p. 35 2.19 1.99 .75 .68 M3M37-M41. 36 3.75 3.41 1.29 1.17 BischofBischoff, J. L., and Ku, T., 1970, Pore fluids of recent marine 37 2.82 2.56 .97 .88 secsediments: I., Oxidizing sediments of 20° N., continental rise 38 2.71 2.46 .92 .84 to Mid-Atlantic Ridge: Journal of Sedimentary Petrology, v. 39 2.71 2.46 .92 .84 40, no. 3, p. 960-972. Total 404.33 367.57 138.58 125.98 BischofBischoff, J. L.,andSayles, F. L., 1972, Pore fluid and mineralogical

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STRATIGRAPHIC SECTIONS AND TABLES 7-12 STRATIGRAPHIC SECTIONS Upper Miocene: Santa Margarita Formation: Upper phosphatic mudstone member: The upper Miocene rocks in the area of Cuyama Valley phosphate Unit No. deposit consist of resistant sandstone members and nonresistant phosphatic hi In M Cm mudstone members; the latter generally are not exposed. The upper phos­ 67. Claystone, siliceous, light-olive- phate mudstone member was exposed by trenching for detailed examination gray (5Y6/1), massive, angular and sampling. The sites for trenching were selected at those places where to subrounded grains, poorly geologic mapping indicated less structural complications and on steep slopes sorted. Framework, 15 percent where depth of weathering was at a minimum. Locations of the trenches are quartz, 4 percent feldspar, and shown on the geologic map (pi. 1) and on the structure contour map (pi. 3). 7 percent phosphatic pellets; Trenching was done by Nicols Industrial Minerals Corporation in 1963 matrix, 59 percent clay miner­ and by Cuyama Phosphate Corporation in 1965. The trenches of the Nicols als, 11 percent opal, and 4 Industrial Minerals Corporation are numbered 294, 295, 296, 297, 298, percent iron oxide. Quartz, 299, 300, and 301, and those of the Cuyama Phosphate Corporation are albite, orthoclase, opal-CT, numbered 50,75, 100,200, 300,400,500,600, and 700. Nicols trench 299 montmorillonite, and a trace of is the same as Cuyama Phosphate trench 75; trench 300 is the same for both; apatite(?) were detected by X- and Nicols trench 296 is the same as Cuyama Phosphate trench 600. Since ray diffraction analysis. Spe­ the cutting of these trenches, the phosphate rocks have eroded and slumped; cific gravity, 1.99. Sample therefore, they are now of little analytical value. Trench 100, which was recut 100-2 from middle of unit. 1 4 by Cuyama Phosphate Corporation in 1978, provided the detailed informa­ 66. Mudstone, silty, dolomitic, light- tion for this report and is designated herein a reference section. A geologic gray (N7) to light-olive-gray column showing location of lithologic samples and analytical data for the (5Y6/1) with moderate-brown reference section in trench 100 is shown on plate 4. (5YR4/4) iron oxide and black (Nl) pyrolusite coatings, mas­ sive to faintly laminated, indurated, angular to sub- Stratigraphic section of the upper phosphatic rounded grains, medium- mudstone member, Santa Margarita Formation of sorted, slightly bioturbated; Cuyama Valley phosphate area, Santa Barbara pelecypod casts and molds common, and diatoms and' County, Calif. sponge spicules rare in upper 10 ft (3.05m). Sample 100-3c contains 17 percent quartz, 6 Trench 100 (Reference Section) percent feldspar, 2 percent The section was measured and sampled by A. E. Roberts and L. E. Mack in phosphatic pellets and nodules, the Cuyama Phosphate Corporation trench 100 in 1978. Many contacts are 4 percent clay minerals, 62 gradational, therefore, the divisions between these Stratigraphic units were percent dolomite, 6 percent arbitrarily chosen depending on pellet content. The samples were described opal, and 3 percent iron oxide. petrographically by T. L. Vercoutere and A. E. Roberts. Pellet-bearing rocks Quartz, albite, orthoclase, dol­ were examined for mineral structure by L. E. Mack with the Cambridge omite, and a trace of opal-CT Stereoscan 180 Scanning Electron Microscope (SEM) equipped with an and montmorillonite were Energy Dispersive Analysis of X-rays (EDAX) system. Point count, specific detected by X-ray diffraction gravity, and X-ray diffraction analyses were made by T. L. Vercoutere. analysis. Sample 100-3a col­ Analytical data are presented in the lists of chemical and X-ray analyses. lected 0.6 m (2 ft) from top of LOCATION: NE'/4SW'/4 sec. 7, T. 9 N., R. 26 W. (S.B.B. & M.) in the New unit, specific gravity, 2.09; Cuyama, California Quadrangle. sample 100-3b collected 1.8 m ATTITUDE OF BEDDING: The average bedding strike is N. 60° W., and (6 ft) from top, specific gravity, the bedding dip varies from 50° SW. at unit 53, to 80° SW. at unit 37, to 1.90; sample 100-3c collected 69° SW. at unit 12, all overturned. 3 m (10 ft) from top, specific gravity, 2.22; sample 100-3d Upper Miocene: collected 4.2 m (14 ft) from Santa Margarita Formation: top, specific gravity, 2.06. 16 1 4 90 Upper sandstone member: 65. Bentonite, slightly silty, olive- Unit No. Thickness gray (5Y3/2) with light-brown Ft In M Cm (5YR5/6) iron-oxide stain, 68. Sandstone, light-yellowish-gray waxy luster, flaky texture, plas­ (5Y9/1), thick, very fine to tic when wet, nonphosphatic. coarse-grained, poorly sorted, Montmorillonite, quartz, albite, subangular to rounded grains, orthoclase, and illite were friable. Framework, 50 percent detected by X-ray diffraction quartz, 15 percent feldspar, and analysis. Sample 100-4 from less than 1 percent phosphatic middle of unit. 0 1 0 1 pellets; matrix, 30 percent clay 64. Claystone, siliceous, light-dusky- minerals, 4 percent carbonate. yellow (5Y7/4) when fresh, Specific gravity 2.36. Sample weathers yellowish-gray 100-1 from base of unit. Not Measured (5Y8/1), indurated, laminated;

30 Stratigraphic Sections Upper Miocene Continued Upper Miocene Continued Santa Margarita Formation Continued Santa Margarita Formation Continued Upper phosphatic mudstone member Continued Upper phosphatic mudstone member Continued Unit No, Thickness Ft In M Cm Ft In M Cm angular to subangular grains, (5Y6/1) with very dark yellow­ poorly sorted; floating grains as ish orange (10YR5/6) iron- large as medium size, rare; fish oxide stains and black (Nl) scales, rare. Framework, 5 per­ pyrolusite coatings, massive, cent quartz, 1 percent feldspar; indurated; small grains angular matrix 84 percent clay miner­ to subangular, larger grains als, 7 percent opal, and 3 subangular to rounded, poorly percent iron oxide. Opal-CT, sorted; floating grains medium quartz, albite, orthoclase, and to coarse, abundant. Contains montmori.llonite were detected phosphatic pellets, diatoms by X-ray diffraction analysis. common, foraminifers, pelec­ Specific gravity, 1.64. Sample ypod molds, and fish scales. 100-5 from middle of unit. 1 8 0 51 Framework, 33 percent quartz, 63. Mudstone, siliceous, very light 4 percent feldspar, 1 percent gray (N8) with dark-yellowish- carbonate fragments, 2 percent orange (IOYR6/6) iron-oxide chert, 23 percent phosphatic stains and black (Nl) pyrolusite pellets, 1 percent chlorite, and coatings, massive, indurated; 1 percent heavy minerals; grains angular to subangular, matrix, 7 percent clay miner­ poorly sorted; floating grains as als, 10 percent carbonate, 6 large as medium size, rare; percent apatite, and 12 percent pelecypod molds common, fish iron oxide. Quartz, albite, scales rare. Framework, 7 per­ orthoclase, apatite, and dol­ cent quartz, 3 percent feldspar, omite were detected by X-ray 1 percent heavy minerals; diffraction analysis. Specific matrix, 21 percent clay miner­ gravity, 2.19. Sample 100-8 als, 62 percent opal, and 6 from middle of unit. 11 4 3 45 percent iron oxide. Opal-CT, 60. Siltstone, sandy (fine- to coarse­ quartz, albite, orthoclase, illite, grained), very phosphatic, yel­ and montmorillonite were lowish-gray (5Y7/2) with detected by X-ray diffraction moderate-brown (5YR4/4) analysis. Specific gravity, 1.67. iron-oxide stain, friable to Sample 100-6 from middle of moderately indurated, grains unit. 0 8 0 20 subangular to rounded, poorly 62. Sandstone, very fine grained, sorted. Fish bones common. clayey, moderately phosphatic, Framework, 13 percent quartz, grayish-orange (10YR7/4), 8 percent feldspar, 40 percent thick, massive, indurated; small phosphatic pellets, and 3 per­ grains angular to subrounded, cent heavy minerals; matrix, 19 larger grains subangular to percent clay minerals, 3 per­ rounded, poorly sorted. Phos­ cent carbonate, 6 percent phatic pellets and nodules in apatite, and 8 percent iron lower 18 cm (7 in.), pelecypod oxide. Specific gravity, 2.35. molds to 4 cm size abundant, Sample 100-9 from middle of shell fragments rare, and fish unit. Correlation unit PI. 0205 bones rare. Framework, 32 per­ 59. Siltstone, phosphatic, very light cent quartz, 4 percent feldspar, brownish gray (5YR7/1) to 1 percent carbonate fragments, light-gray (N7), massive, indu­ 16 percent phosphatic pellets rated, poorly sorted, floating and nodules, 3 percent grains fine- to coarse-size and accessory minerals; matrix, 35 angular to subrounded com­ percent clay minerals, 1 per­ mon, phosphatized fish scales cent carbonate, and 8 percent common, fish bones and iron oxide. Quartz, albite, diatom molds rare. Framework, orthoclase, apatite, and illite 28 percent quartz, 3 percent were detected by X-ray diffrac­ feldspar, 20 percent phosphatic tion analysis. Specific gravity, pellets, and 1 percent accessory 2.31. Irregular basal contact. minerals; matrix, 28 percent Sample 100-7 from base of clay minerals, 1 percent unit. 2 1 0 64 carbonate, 11 percent opal and 61. Siltstone, siliceous, sandy, light- 8 percent iron oxide. Quartz, gray (N7) to light-olive-gray albite, orthoclase, apatite, and a

Stratigraphic Sections 31 Upper Miocene Continued Upper Miocene Continued Santa Margarita Formation Continued Santa Margarita Formation Continued Upper phosphatic mudstone member Continued Upper phosphatic mudstone member Continued Unit No. Thickness Unit No. Thickness Ft In M Cm ft In M Cm trace of opal-CT and analysis. Specific gravity, 2.27. montmorillonite(?) were Sample 100-12 from middle of detected by X-ray diffraction unit. Plate 6A from unit. Oil 0 28 analysis. Basal 30 cm (12 in.) 56. Clay stone, moderately phos­ is sandy siltstone, light-olive- phatic, dark-yellowish-gray gray (5Y6/1), with 40 percent (5Y8/1) with light-brown phosphatic pellets; marine (5YR5/6) stains, faintly lami­ mammal bone fragments at nated, grains subangular to base. Irregular sharp contact subrounded, floating grains to with underlying unit. Specific medium size, rare, poorly gravity, 1.90. Sample 100-10 sorted. Pelecypod molds as collected from 1.2 m (4 ft) much as 5 cm (2 in.) in diame­ from top. 8 0 2 44 ter rare; fish scales and pellet- 58. Mudstone, moderately phos­ filled burrows rare. Framework, phatic, dark-yellowish-gray 5 percent quartz, 2 percent (5Y7/1) with moderate-olive- feldspar, 16 percent phosphatic brown (5Y4/4) stains along pellets, and 2 percent joints, indurated, grains sub- glauconite; matrix, 57 percent angular to rounded, poorly clay minerals, 9 percent - sorted, floating grains as large carbonate, and 9 percent iron as coarse size rare; faint bed­ oxide. Quartz, apatite, albite, ding defined by laminae of orthoclase, gypsum, calcite, phosphatic diatoms and fish and a trace of illite were scales. Framework, 8 percent detected by X-ray diffraction quartz, 1 percent feldspar, 10 analysis. Specific gravity, 2.24. percent phosphatic pellets, and Sample 100-13 from middle of 3 percent heavy minerals; unit. 0 9 0 23 matrix, 41 percent clay miner­ 55. Phosphorite, silty, slightly cal­ als, 1 percent carbonate, 30 careous, light-gray (N7) but percent opal, and 6 percent mostly stained very dark yel­ iron oxide. Quartz, albite, lowish-orange (10YR5/6), orthoclase, opal-CT, massive, grains subangular to montmorillonite, and illite were subrounded, indurated, well detected by X-ray diffraction sorted but with some floating analysis. Specific gravity, 1.87. grains to coarse size; fish Sample 100-11 from middle of bones and scales common; unit. 2 2 0 66 mudstone intraclasts to 2 cm 57. Siltstone, phosphatic, sandy (very rare. Framework, 11 percent fine grained), mottled yellow­ quartz, 6 percent feldspar, 56 ish-gray (5Y7/2) to dark- percent phosphatic pellets, and orangish-brown (10YR4/6), 1 percent zeolite minera!(?); poorly sorted, floating grains matrix, 11 percent clay miner­ fine- to medium-size-common, als, 11 percent carbonate, and 4 grains subangular to sub- percent iron oxide. Specific rounded; swirled bedding, gravity 2.47. Sample 100-14 slightly burrowed; disc-shaped from middle of unit. Correla­ phosphatized diatoms abundant tion unit P2. 040 10 (cores of some pellets are the 54. Mudstone, moderately phos­ diatom genus Coscinodiscus); phatic, siliceous, light-gray fish bones and scales, intra- (N7) to light-greenish-gray clasts of siliceous mudstone (5GY7/1) with moderate-olive- rare. Framework, 20 percent brown (5Y4/4) stains along quartz, 4 percent feldspar, 37 joints, massive, indurated, percent phosphatic pellets, and floating grains to fine size, rare, 3 percent heavy minerals; grains subangular to sub- matrix, 18 percent clay miner­ rounded, medium-sorte^l, als, 5 percent apatite, 10 pelecypod molds to 5 cm (2 percent opal, and 3 percent in.), fish scales, diatom molds iron oxide. Quartz, apatite, common, and burrows rare. albite, orthoclase, and a trace Framework, 11 percent quartz, of calcite(?) and opal-CT were and 11 percent phosphatic pel­ detected by X-ray diffraction lets; matrix, 36 percent clay

32 Stratigraphic Sections Upper Miocene Continued Upper Miocene Continued Santa Margarita Formation Continued Santa Margarita Formation Continued Upper phosphatic mudstone member Continued Upper phosphatic mudstone member Continued Unit No. Thickness Unit No. Thickness Fl In M Cm Fl In M Cm minerals, 36 percent opal, and fish vertebrae and gastropod 6 percent iron oxide. Specific casts rare, mudstone intraclasts gravity, 1.87. Sample 100-15 to 8 cm (3 in.); silty at base, from middle of unit. Correla­ grains vary from subangular to tion unit SI. 3 0 0 91 rounded, phosphatic pellets 53. Mudstone, very phosphatic, yel­ and nodules at base decrease in lowish-gray (5 Y8/1) but size and number upward. typically stained very dark yel­ Framework, 23 percent quartz, lowish orange (10YR6/6), 8 percent feldspar, 3 percent massive, friable to moderately carbonate fragments, 33 per­ indurated, medium-sorted, cent phosphatic pellets and grains subangular to sub- nodules, and 3 percent zeolite rounded, floating grains to minerals(?); matrix, 6 percent coarse size rare, slightly bur­ clay minerals, 12 percent car­ rowed, fish bones rare, bonate, and 12 percent iron siliceous mudstone intraclasts oxide. Quartz, albite, rare. Framework, 10 percent orthoclase, apatite, dolomite, quartz, 1 percent feldspar, 45 and calcite, were detected by percent phosphatic pellets, and X-ray diffraction analysis. Spe­ 4 percent zeolite minerals(?); cific gravity, 2.24. Sample matrix, 18 percent clay miner­ 100-18 from middle of unit. 0 5 0 13 als, 3 percent carbonate, and 50. Claystone, yellowish-gray (5Y5/1) 19 percent iron oxide. Apatite, to light-olive-gray (5Y6/1) with quartz, albite, orthoclase, and a light-olive-brown (5Y5/6) trace of calcite were detected stains, massive to faintly lami­ by X-ray diffraction analysis. nated, indurated, angular to Specific gravity, 2.05. Sample subangular grains, medium- 100-16 from middle of unit. 0 7 0 18 sorted, floating grains to coarse 52. Mudstone, very phosphatic, size and claystone nodules sandy, dark-yellowish-gray rare; pelecypod molds abun­ (5Y7/1) with moderate-brown dant, fish scales and diatoms (5YR4/4)andblack(Nl) rare. Contains a few very light stajns, massive to faintly lami­ gray (N8) zones of leached nated, indurated, grains phosphatic pellets and molds subangular to rounded, of pellets. Framework, 7 per­ medium-sorted, floating grains cent quartz, 1 percent to coarse size very rare, and phosphatic pellets, and 1 per­ small phosphatic claystone cent heavy minerals; matrix, nodules rare; fish scales com­ 55 percent clay minerals, 5 mon, pelecypod molds rare. percent carbonate, 23 percent Framework, 21 percent quartz, opal, and 8 percent iron oxide. 5 percent feldspar, 1 percent Quartz, albite, orthoclase, opal- carbonate fragments, and 41 CT, and dolomite were percent phosphatic pellets and detected by X-ray diffraction nodules; matrix, 23 percent analysis. Specific gravity, 1.94. clay minerals, 1 percent Sample 100-19 from middle of carbonate, 6 percent opal, ands unit. 12 7 3 84 3 percent iron oxide. Quartz, 49. Sandstone, siliceous, dark- albite, orthoclase, apatite, opal- grayish-orange (10YR6/4), CT, montmorillonite, and a phosphatic, silty, graded bed­ trace of illite were detected by ding, moderately indurated, X-ray diffraction analysis. Spe­ fine- to coarse-grained, angular cific gravity, 2.01. Sample to subrounded grains, medium- 100-17 from middle of unit. 6 6 1 98 sorted, floating grains to coarse 51. Sandstone, grayish-orange size abundant, and nodules (10YR7/4) with dark-yellow­ rare, phosphatic pellets content ish-orange (10YR6/6) stains, decreases upward; fish bones phosphatic, dolomitic, graded and scales common, pelecypod bedding, indurated to weakly molds abundant. Framework, indurated, grains range from 27 percent quartz, 3 percent very fine to coarse size; poorly feldspar, 30 percent phosphatic sorted, fish scales common, pellets, and 2 percent zeolite

Stratigraphic Sections 33 Upper Miocene Continued Upper Miocene Continued Santa Margarita Formation Continued Santa Margarita Formation Continued Upper phosphatic mudstone member Continued Upper phosphatic mudstone member Continued Unit No. Thickness Ft In M Cm Ft In M Cm minerals(?); matrix, 24 percent shell and bone fragments, fish clay minerals, 10 percent opal, scales, and megafossil casts and 4 percent iron oxide. rare. Framework, 14 percent Quartz, albite, orthoclase, apa­ quartz, 5 percent feldspar, 16 tite, opal-CT, and a trace of percent dolomite, and 60 per­ illite and montmorillonite were cent phosphatic pellets and detected by X-ray diffraction nodules; matrix, 12 percent analysis. Specific gravity, 2.19. clay minerals, 7 percent dol­ Sample 100-20 from middle of omite, and 6 percent iron unit. Correlation unit S2. 110 33 oxide. Quartz, apatite, albite, 48. Phosphorite, sandy (very fine to orthoclase, and dolomite were fine-grained), and calcareous, detected by X-ray diffraction grayish-orange (10YR7/4), analysis. Specific gravity, 2.14. massive, weakly indurated, Sample 100-23 from middle of subangular to rounded grains, unit. 1 7 0 48 poorly sorted, floating grains as 45. Porcellanite, dolomitic, very light large as granule size common; gray (N8) to very pale orange phosphatic and siliceous fish­ (10YR4/4) with black (Nl) bone and shell fragments abun­ stains, massive, very indurated, dant, pelecypod casts rare; highly fractured. Specific grav­ burrows at basal contact com­ ity, 2.28. Sample 100-24 from mon; sharp irregular erosional middle of unit. 0 10 0 25 contact with underlying 44. Mudstone, siliceous, very light mudstone. Framework, 15 per­ brownish gray (5YR7/1) with cent quartz, 5 percent feldspar, light-olive-brown (5Y5/6) 52 percent phosphatic pellets stains, massive, very indurated, (cores of some pellets are the subangular to subrounded diatom genus Coscinodiscus) grains, poorly sorted; contains and nodules, and 2 percent very light gray (N8) phosphatic zeolite minerals(?); matrix, 16 pellets rare, molds of pellets percent clay minerals, and 10 common, phosphatic claystone percent iron oxide. Apatite, grains rare, fish scales com­ quartz, albite, and orthoclase mon, fish bones rare, diatom were detected by X-ray diffrac­ molds and megafossils rare. tion analysis. Specific gravity, Unit appears altered to iron 2.16. Sample 100-21 from mid­ oxide and clay-size minerals. dle of unit. 0 6 0 15 Quartz, albite, orthoclase, opal- 47. Mudstone, siliceous, slightly to , CT, and montmorillonite were moderately phosphatic, yellow­ detected by X-ray diffraction ish-gray (5Y8/1) with light- analysis. Specific gravity, 1.68. brown (5YR5/6) stains, faintly Sample 100-25 from middle of laminated, indurated, poorly ' unit. 6 2 1 sorted, floating grains as large 43. Mudstone, phosphatic, siliceous, as coarse size rare; phosphatic yellowish-gray (5Y7/1) with claystone nodules common; some black (Nl) pyrolusite(?) fish scales very abundant, fish coatings, faintly laminated, bones rare, burrows rare. indurated, angular to sub- Quartz, albite, orthoclase, opal- rounded grains, medium- CT, apatite, and a trace of sorted, floating grains as large montmorillonite were detected as coarse size rare. Slightly to by X-ray diffraction analysis. very phosphatic with pellet .Specific gravity, 1.77. Sample concentrations exceeding 50 100-22 from middle of unit. 1 2 0 36 percent in upper 8 in. (20 cm); 46. Phosphorite, dolomitic, sandy phosphatic claystone nodules (fine-grained), light-gray (N7) rare, pellet- filled burrows to grayish-orange (10YR7/4), common. Framework, 26 per­ massive to faintly bedded, cent quartz, 7 percent feldspar, moderately indurated, angular 20 percent phosphatie pellets, to rounded grains, very poorly and 3 percent zeolite miner­ sorted, floating grains as large als^); matrix, 31 percent clay as coarse size common; phos­ minerals, 1 percent carbonate, phatic framework consists of 8 percent opal, and 4 percent pellets, claystone nodules, iron oxide. Quartz, albite,

34 Stratigraphic Sections Upper Miocene Continued Upper Miocene Continued Santa Margarita Formation Continued Santa Margarita Formation Continued Upper phosphatic mudstone member Continued Upper phosphatic mudstone member Continued Unit No. Thickness Unit No. Thickness Ft In M Cm Ft In M Cm orthoclase, opal-CT, apatite, carbonate fragments, and 38 and illite were detected by X- percent phosphatic pellets and ray diffraction analysis. Spe­ nodules; matrix, 1 percent clay cific gravity, 2.04. Sample minerals, 36 percent carbonate, 100-26 from middle of unit. 3 8 1 12 and 2 percent iron oxide. 42. Phosphorite, very light gray (N8) Quartz, albite, orthoclase, cal- to dark-yellowish-gray (5Y7/1) cite, and apatite were detected with light-olive-brown (5Y5/6) by X-ray diffraction analysis. and moderate-brown (5YR4/4) Specific gravity, 2.40. Sample stains, massive to faintly bed­ 100-29 from middle of unit. 3 1 0 94 ded, indurated; local 39. Porcellanite, silty, yellowish-gray concentrations of pellets, phos­ (5Y8/1) to light-gray (N7) with phatic claystone nodules rare, dark-grayish-orange (10YR6/4) and fish scales common. and black (Nl) coatings, lami­ Framework, 11 percent quartz, nations faint and even, 6 percent feldspar, and 53 per­ indurated, angular to sub- cent phosphatic pellets; matrix, angular grains, poorly sorted, 26 percent clay minerals, and 4 floating grains to fine size very percent iron oxide. Quartz, rare. Contains fish scales and albite, orthoclase, and opal-CT megafossils common; phos­ were detected by X-ray diffrac­ phatic pellets and phosphatic tion analysis. Specific gravity, claystone nodules rare. Opal- 1.92. Sample 100-27 from CT, quartz, albite, orthoclase, middle of unit. 2 0 0 61 and illite were detected by X- 41. Mudstone, siliceous, light-gray ray diffraction analysis. Spe­ (N7) to yellowish-gray (5Y8/1) cific gravity, 1.67. Sample with light-olive-brown (5Y5/6) 100-30 from middle of unit. 2 7 0 79 stains, faintly laminated, indu- 38. Siltstone, phosphatic, sandy, mot­ N rated, angular to subangular tled yellowish-gray (5Y8/1) to grains, poorly sorted, floating very pale brown (5YR6/2) with grains to coarse size common. light-brown (5YR5/6) stains, Slightly phosphatic with scat­ massive, indurated, angular to tered phosphatic claystone subrounded grains, poorly nodules and lenses of molds of sorted, floating grains to coarse pellets, fish scales, and mega- size common, coarse grains fossils common. Contains 15 and nodules of phosphatic percent quartz, 4 percent phos­ claystone rare. Contains fish phatic pellets and nodules, 1 bones and scales common, percent accessory minerals, phosphatic pellet-filled burrows and 80 percent altered matrix common, one crab(?) skeletal of clay, opal, and iron-oxide fragment. Framework, 21 per­ minerals. Opal-CT, quartz, cent quartz, 6 percent feldspar, albite, orthoclase, 2 percent carbonate fragments, montmorillonite, and illite were 1 percent chert, 21 percent^ detected by X-ray diffraction phosphatic pellets and nodules, analysis. Specific gravity, 1.80. and 1 percent glauconite; Sample 100-28 from middle of matrix, 16 percent clay miner­ unit. 3 3 0 99 als, 1 percent carbonate, 26 40. Sandstone, phosphatic, cal­ percent opal, and 31 percent careous, silty, yellowish-gray iron oxide. Locally contains as (5Y7/2) and light-gray (N7) to much as 40 percent pellets. yellowish-gray (5Y8/1) Quartz, albite, apatite, mudstone lenses, massive, orthoclase, and opal-CT were indurated; swirled mudstone detected by X-ray diffraction laminations, rare, predomi­ analysis. Specific gravity, 2.01. nantly very fine, angular to Sample 100-31 from middle of subangular grains, medium- unit. 1 9 0 53 sorted, floating grains to coarse 37. Mudstone, siliceous, slightly silty, size abundant; fish bones and light- to very light gray (N7- scales, phosphatic nodules, N8) with many moderate- and pellet-filled burrows rare. brown (5YR4/4) and black Framework, 15 percent quartz, (Nl) stains, massive, indurated, 3 percent feldspar, 5 percent angular to rounded grains,

Stratigraphic Sections 35 Upper Miocene Continued Upper Miocene Continued Santa Margarita Formation Continued Santa Margarita Formation Continued Upper phosphatic mudstone member Continued Upper phosphatic mudstone member Continued Unit No. Thickness Unit No. Thickness Ft In M Cm Ft In M Cm medium-sorted, floating grains 100-34 from middle of unit. 2 6 0 76 to coarse size rare. Contains 34. Mudstone, phosphatic, yellowish- molds of pellets locally con­ gray (5Y8/1) with light-brown centrated in lenses rare, phos­ (5YR5/6) stains, faintly lami­ phatic claystone nodules rare, nated, indurated, subangular to diatom molds abundant, fish subrounded grains, poorly scales and megafossils com­ sorted, floating grains to coarse mon, and one crab(?) skeletal size common, phosphatic fragment. Opal-CT, quartz, claystone nodules very rare. albite, orthoclase, and Contains fish bones and scales montmorillonite were detected rare. Framework, 15 percent by X-ray diffraction analysis. quartz, 3 percent feldspar, 33 Specific gravity, 1.64. Sample percent phosphatic pellets, and 100-32 from middle of unit. 1 percent chlorite(?); matrix, 5 Correlation unit S3. 2 11 0 89 percent clay minerals, 1 per­ 36. Siltstone, phosphatic, sandy (fine­ cent carbonate, 35 percent grained), very pale yellowish opal, and 7 percent iron oxide. brown (10YR7/2) with light- Quartz, albite, apatite, brown (5YR6/4) stains, faintly orthoclase, opal-CT, and laminated, indurated, angular montmorillonite were detected to subrounded grains, poorly by X-ray diffraction analysis. sorted, floating grains to fine Specific gravity, 1.80. Sample size common, phosphatic 100-35 from middle of unit. 1 3 0 38 claystone nodules rare. Con­ 33. Phosphorite, dark-grayish-orange tains pelecypod molds as much (10YR6/4), massive to faintly as 5 cm in diameter rare. bedded, moderately indurated Framework, 17 percent quartz, to friable, angular to sub- 1 percent feldspar, and 27 per­ rounded grains, poorly sorted, cent phosphatic pellets (cores floating grains to coarse size of some pellets are the diatom abundant, phosphatic pellets genus Coscinodiscus); matrix, are well sorted (in the 0.1-0.2 30 percent clay minerals, 20 mm range). Contains fish percent opal, and 5 percent bones rare. Framework, 15 per­ iron oxide. Quartz, apatite, cent quartz, 4 percent feldspar, albite, opal-CT, and orthoclase 1 percent carbonate fragments, were detected by X-ray diffrac­ and 57 percent phosphatic pel­ tion analysis. Specific gravity, lets and nodules; matrix, 19 1.76. Sample 100-33 from percent clay minerals, 2 per­ middle of unit. 1 5 0 43 cent carbonate, 1 percent 35. Mudstone, moderately phos­ apatite, and 1 percent iron phatic, silty, dark-yellowish- oxide. Apatite, quartz, albite, gray (5Y7/1) to light-gray (N7) orthoclase, and a trace of cal- with dusky-yellow (5Y6/4), cite and montmorillonite were light-brown (5YR5/6) and detected by X-ray diffraction black (Nl) stains, massive, analysis. Specific gravity, 2.49. indurated, angular to sub- Sample 100-36 from middle of rounded grains, poorly sorted, unit. 1 8 0 51 floating grains to coarse size 32. Mudstone, phosphatic, pinkish- common, grayish-pink (5R8/2) gray (5YR8/1) to light-gray phosphatic claystone nodules (N7) with grayish-orange rare. Contains fish bones and (10YR7/4) stains, massive to scales rare. Framework, 17 per­ faintly bedded, indurated, cent quartz, 5 percent feldspar, slightly burrowed, subangular 1 percent carbonate fragments, to subrounded grains, poorly and 17 percent phosphatic pel­ sorted, floating grains to coarse lets; matrix, 21 percent clay size abundant, phosphatic pel­ minerals, 2 percent carbonate, lets are well sorted (in the 0.1- 30 percent opal, and 7 percent 0.2 mm range), pellets rarely iron oxide. Quartz, albite, apa­ concentrated in lenses, locally tite, orthoclase, opal-CT, and pellets are light-gray (N8) and montmorillonite were detected appear leached. Contains fish by X-ray diffraction analysis. scales rare. Framework, 20 per­ Specific gravity, 1.91. Sample cent quartz, 6 percent feldspar,

36 Stratigraphic Sections Upper Miocene Continued Upper Miocene Continued Santa Margarita Formation Continued Santa Margarita Formation Continued Upper phosphatic mudstone member Continued Upper phosphatic mudstone member Continued Unit No. Thickness Unit No. Ft In M Cm Ft In M Cm and 27 percent phosphatic pel­ phosphatic, very light gray lets; matrix, 30 percent clay (N8) with light-brown minerals and 17 percent opal. (5YR5/6) stains, massive, Basal 1 ft (0.3 m) contains as indurated, angular to sub- much as 40 percent pellets. rounded grains, medium- Quartz, albite, orthoclase, opal- sorted, floating grains to fine CT, and apatite were detected size very rare. Contains both by X-ray diffraction analysis. phosphatic pellets and molds Specific gravity, 1.79. Sample of pellets; fish scales rare. 100-37 from middle of unit. 11 11 3 63 Framework, 12 percent quartz, 31. Mudstone, siliceous, slightly 1 percent feldspar, and 3 per­ phosphatic, very light gray cent phosphatic pellets; matrix, (N8) with light-olive-brown 18 percent clay minerals, 2 (5Y5/6) stains, massive to percent carbonate, 56 percent faintly bedded, indurated, opal, and 8 percent iron oxide. angular to subangular grains, Quartz, albite, orthoclase, opal- medium-sorted, floating grains CT, and a trace of apatite, illite, to medium size rare, phos­ and montmorillonite were phatic claystone grains very detected by X-ray diffraction rare. Contains fish scales and analysis. Specific gravity, 1.89. diatom and pelecypod molds Sample 100-40 from middle of rare. Framework, 22 percent unit. 2 10 0 86 quartz, 6 percent feldspar, and 28. Siltstone, moderately phosphatic, 4 percent phosphatic pellets; sandy (very fine to fine­ matrix, 17 percent clay miner­ grained), very light gray (N8) als, 1 percent carbonate, 45 with light-olive-brown (5Y5/6) percent opal, and 5 percent and light-brown (5YR5/6) iron oxide. Phosphorite bed 1- stains, faintly laminated, indu­ ft (0.3 m) thick contains 70 rated, angular to subangular . percent pellets 2 ft (0.6 m) grains, poorly sorted, floating from top of unit. Opal-CT, grains to coarse size common; quartz, albite, orthoclase, light-grayish-pink (5YR8/1) montmorillonite, and illite were phosphatic claystone pellets detected by X-ray diffraction and nodules rare. Contains fish analysis. Specific gravity, 1.72. bones rare. Framework, 26 per­ Sample 100-38 from middle of cent quartz, 7 percent feldspar, unit. Correlation unit S4 at 15 percent phosphatic pellets base of unit. 7 4 2 24 and nodules, and 1 percent 30. Mudstone, moderately phos­ glauconite; matrix, 38 percent phatic, yellowish-gray (5Y8/1) clay minerals, 5 percent apa­ with light-brown (5YR5/6) tite, 6 percent iron oxide, and 2 stains, nonbedded to faintly percent carbonate. Quartz, bedded, moderately indurated, albite, orthoclase, apatite, and subangular to rounded grains, opal-CT were detected by X- poorly sorted, floating grains to ray diffraction analysis. Spe­ coarse size abundant. Contains cific gravity, 1.96. Sample 100- sponge spicules, fish scales 41 from middle of unit. Plate and bones, and burrows rare. 6B from unit. 1 11 0 58 Framework, 30 percent quartz, 27. Siltstone, moderately phosphatic, 10 percent feldspar, 2 percent sandy (very fine to fine­ carbonate fragments, and 12 ' grained), very light to light- percent phosphatic pellets; gray (N8-N7) with light-olive- matrix, 38 percent clay miner­ brown (5Y5/6) stains, massive, als, 6 percent apatite, and 2 indurated, angular to sub- percent iron oxide. Locally angular grains, poorly sorted, contains 20-70 percent pellets. floating grains to medium size Quartz, albite, apatite, abundant, grayish-pink (5R8/2) orthoclase, and a trace of opal- phosphatic claystone nodules CT were detected by X-ray common, scattered molds of diffraction analysis. Specific pellets, fish bones and scales, gravity, 2.20. Sample 100-39 and mammal(?) bones rare. from middle of unit. 1 3 0 38 Framework, 34 percent quartz, 29. Mudstone, siliceous, slightly 5 percent feldspar, 12 percent Stratigraphic Sections 37 Upper Miocene Continued Upper Miocene Continued Santa Margarita Formation Continued Santa Margarita Formation Continued Upper phosphatic mudstone member Continued Upper phosphatic mudstone member Continued Unit No. Unit No. Thickness Ft In M Cm Ft In M Cm phosphatic pellets and nodules, lowish-gray (5Y8/1) with very 3 percent accessory minerals, dark yellowish orange and 3 percent heavy minerals; (10YR5/6) stains, massive to matrix, 27 percent clay miner­ faintly laminated, indurated, als, 12 percent opal, and 4 angular to subangular grains, percent iron oxide. Opal-CT, medium-sorted, floating grains quartz, albite, apatite, and to fine size rare. Contains fish orthoclase were detected by X- scales common, pelecypod ray diffraction analysis. Spe­ molds rare. Framework, 6 per­ cific gravity, 2.20. Sample cent quartz, 1 percent feldspar, 100-42 from middle of unit. 1 9 0 53 and 2 percent phosphatic pel­ 26. Mudstone, moderately phos­ lets; matrix, 64 percent phatic, dolomitic, yellowish- dolomite, 2 percent apatite, 20 gray (5Y8/1) with moderate- percent opal, and 5 percent brown (5YR4/4) stains, mas­ iron oxide. Dolomite, quartz, sive, moderately indurated, albite, opal-CT, orthoclase, and slightly burrowed, subangular montmorillonite were detected to subrounded grains, poorly by X-ray diffraction analysis. sorted, floating grains to coarse Specific gravity, 1.77. Sample size rare, locally phosphatic 100-45 from middle of unit. 4 10 1 47 pellets concentrated in lenses 23. Sandstone, moderately phos­ and burrows, phosphatic clay- phatic, fine-grained, silty, stone nodules rare, fish scales yellowish-gray (5Y7/2), mas­ common, fish bones and pe- sive, weakly indurated, angular lecypod molds rare. to subrounded grains, medium- Framework, 8 percent quartz, 2 sorted, floating grains to coarse percent feldspar, 10 percent size rare. Contains pelecypod phosphatic pellets, and 1 per­ molds rare. Framework, 37 per­ cent heavy minerals; matrix, 17 cent quartz, 12 percent percent clay minerals, 29 per­ feldspar, and 19 percent phos­ cent dolomite, 28 percent opal, phatic pellets; matrix, 16 and 5 percent iron oxide. percent clay minerals, 7 per­ Quartz, albite, apatite, cent carbonate, and 11 percent orthoclase, opal-CT, dolomite, iron oxide. Quartz, albite, and a trace of montmorillonite orthoclase, apatite, and illite were detected by X-ray diffrac­ were detected by X-ray diffrac­ tion analysis. Specific gravity, tion analysis. Specific gravity 1.92. Sample 100-43 from not determined. Sample 100-46 middle of unit. 3 9 1 14 from middle of unit. 0 43 25. Phosphorite, calcareous, silty, 22. Mudstone, moderately phos­ dark-grayish-orange phatic, siliceous, silty, light- (10YR6/4), lenses to faintly gray (N7) to yellowish-gray laminated, moderately indu­ (5Y8/1) with moderate-brown rated to weakly indurated, (5YR4/6) stains, faintly lami­ subangular to subrounded nated, moderately indurated, grains, medium-sorted, floating angular to rounded grains, grains to medium-size rare; poorly sorted, floating grains to phosphatic nodules that aver­ medium size rare. Contains age 0.2 mm in diameter; fish small (1.0-2.0 cm) intraclasts bones and pelecypod molds of siliceous mudstone; fish rare. Framework, 8 percent scales and bones rare, one quartz, 7 percent feldspar, and mammal(?) bone fragment. 59 percent phosphatic pellets Framework, 15 percent quartz, and nodules; matrix, 11 percent 2 percent feldspar, and 15 per­ clay minerals, 11 percent car­ cent phosphatic pellets; matrix, bonate, and 4 percent iron 26 percent clay minerals, 2 oxide. Apatite, quartz, calcite, percent carbonate, 1 percent albite, and a trace of illite were apatite, 30 percent opal, and 9 detected by X-ray diffraction percent iron oxide. Quartz, analysis. Specific gravity, 2.51. albite, orthoclase, apatite, and Sample 100-44 from middle of opal-CT were detected by X- unit. Correlation unit P4. 0 11 0 28 ray diffraction analysis. Spe­ 24. Mudstone, dolomitic, silty, yel- cific gravity, 2.25. Sample 38 Stratigraphic Sections Upper Miocene Continued Upper Miocene Continued' Santa Margarita Formation Continued Santa Margarita Formation Continued Upper phosphatic mudstone member Continued Upper phosphatic mudstone member Continued Unit No. Thickness Thickness Ft In M Cm Ft In M Cm 100-47 from middle of unit. 2 6 0 76 cent quartz, 2 percent feldspar, 21. Mudstone, siliceous, ferruginous, 1 percent carbonate fragments, light-olive gray (5Y6/1) to and 50 percent phosphatic pel­ light-gray (N7) with light- lets and nodules; matrix, 26 olive-brown (5Y5/6) stains, percent clay minerals, 5 per­ massive to faintly laminated, cent opal, and 3 percent iron indurated, angular to sub- oxide. Quartz, apatite, albite, rounded grains, poorly sorted, opal-CT, orthoclase, and a floating grains to coarse size trace of illite were detected by rare. Contains fish scales rare. X-ray diffraction analysis. Spe­ Framework, 16 percent quartz, cific gravity, 2.15. Sample 3 percent feldspar, and 1 per­ 100-50 from middle of unit. 1 2 0 36 cent carbonate fragments; 18. Bentonite, muddy, grayish-yellow matrix, 29 percent clay miner­ (5Y8/4) to yellowish-gray als, and 51 percent iron oxide. (5Y7/2), massive, moderately Iron oxides include less than indurated. Montmorillonite, 10 percent pellets that probably gypsum, quartz, albite, and were phosphatic originally. orthoclase were detected by X- Lower 4 ft (1.22 m) contains ray diffraction analysis. Spe­ ' phosphorite lenses with as cific gravity not determined. much as 60 percent pellets. A Sample 100-51 from middle of 1-ft (0.3-m) bentonite bed is 1 unit. 1 10 0 56 ft (0.3 m) from base of unit. 17. Bentonite, silty, light-olive-gray Quartz, albite, orthoclase, illite, (5Y5/2) to dusky-yellow and montmorillonite were (5Y6/4), massive, friable, plas­ detected by X-ray diffraction tic when wet. Montmorillonite, analysis. Specific gravity, 1.79. gypsum, and a trace of quartz, Sample 100-48 from middle of albite, and anhydrite(?) were unit. 8 11 2 72 detected by X-ray diffraction 20. Mudstone, slightly phosphatic, analysis. Specific gravity not siliceous, silty, dark-pinkish- determined. Sample 100-52 gray (5YR7/1) with moderate- from middle of unit. Oil 0 28 brown (5YR4/4) stains, mas­ 16. Siltstone, slightly phosphatic, sive to faintly laminated, sandy (very fine to fine­ indurated, angular to sub- grained), yellowish-gray rounded grains, poorly sorted, (5Y8/1) with moderate-brown floating grains to medium size (5YR4/4)andblack(Nl) very rare; locally concentrated stains, massive to faintly lami­ phosphatic pellets some are nated, indurated, slightly partly leached. Contains fish burrowed, subangular to scales, rare. Framework, 9 per­ rounded grains, medium- cent quartz, and 5 percent sorted, floating grains to fine phosphatic pellets; matrix, 19 size very rare; phosphatic percent clay minerals, 60 per­ claystone nodules very rare; cent opal, and 7 percent iron fish scales and pelecypod oxide. Basal 1 ft (0.3 m) con­ molds rare. Framework, 29 per­ tains as much as 40 percent cent quartz, 9 percent feldspar, pellets. Quartz, albite, opal-CT, 1 percent chert, 6 percent phos­ orthoclase, and a trace of apa­ phatic pellets, and 1 percent tite were detected by X-ray heavy minerals; matrix, 31 per­ diffraction analysis. Specific cent clay minerals, 10 percent gravity, 1.87. Sample 100-49 dolomite, 10 percent opal, and from middle of unit. 12 7 3 84 3 percent iron oxide. Quartz, 19. Phosphorite, sandy (very fine dolomite, opal-CT, albite, grained), light-brownish-gray orthoclase, and apatite were (5YR6/1) to light-olive-gray detected by X-ray diffraction (5YR6/1) with light-brown analysis. Specific gravity, 2.40. (5YR5/6) stains, faint muddy Sample 100- 53 from middle of laminations, indurated, angular unit. 5 2 1 27 to subrounded grains, medium- 15. Sandstone, moderately phos­ sorted, floating grains to coarse phatic, very fine grained, very size very rare. Contains fish light gray (N8) to yellowish- scales rare. Framework, 13 per- gray (5Y8/1) with grayish- Stratigraphic Sections 39 Upper Miocene Continued Upper Miocene Continued Santa Margarita Formation Continued Santa Margarita Formation Continued Upper phosphatic mudstone member Continued Upper phosphatic mudstone member Continued Unit No. Thickness Unit No. Thickness Ft In M Cm Ft In M Cm orange (10YR7/4) stains, mas­ 12. Siltstone, moderately phosphatic, sive, moderately indurated to light- to very light gray (N7- weakly indurated, subangular N8) with light-olive-brown to subrounded grains, well (5Y5/6) stains, massive, indu­ sorted, floating grains to rated, angular to subrounded medium-size very rare; pe- grains, medium-sorted, floating lecypod molds abundant. grains to medium size very Framework, 35 percent quartz, rare; phosphatic claystone nod­ 11 percent feldspar, 4 percent ules very rare; disc-shaped chert, 15 percent phosphatic phosphatized diatoms (cores of pellets, and 2 percent heavy some pellets are the diatom minerals; matrix, 26 percent genus Coscinodiscus) abun­ clay minerals, 6 percent dant; fish scales rare. Quartz, carbonate, and 1 percent iron opal-CT, albite, orthoclase, and oxide. Quartz, calcite, albite, apatite were detected by X-ray orthoclase, apatite, and illite diffraction analysis. Specific were detected by X-ray diffrac­ gravity, 1.87. Sample 100-57 tion analysis. Specific gravity, from middle of unit. Plate 6C 2.44. Sample 100-54 from from unit. 4 8 1 42 middle of unit. 6 1 1 85 11. Mudstone, slightly to non- 14. Siltstone, phosphatic, sandy (very phosphatic, yellowish-gray fine to fine-grained), light- (5Y8/1) with moderate-brown olive-gray (5Y6/1) to yellow­ (5YR4/4) stains, massive, ish-gray (5Y8/1) with weakly indurated, angular to moderate-brown (5YR4/4) subrounded grains, poorly stains, massive, indurated, sorted. Unit poorly exposed angular to subrounded grains, no sample. 21 7 6 58 poorly sorted, floating grains to 10. Mudstone, silly and sandy (very medium size very rare; phos­ fine grained), yellowish-gray phatic claystone nodules very (5Y8/1) to pinkish-gray rare; fish scales rare. Fra­ (5YR8/1) with light-brown mework, 27 percent quartz, 9 (5YR5/6) stains, massive to percent feldspar, and 25 per­ faintly laminated, indurated, cent phosphatic pellets; matrix, very angular to subangular 27 percent clay minerals, 4 grains, medium-sorted; scat­ percent apatite, 4 percent opal, tered phosphatic pellets rare; and 4 percent iron oxide. Local fish scales rare. Framework, 5 pellet concentrations for unit percent quartz and 1 percent range from 15 to 60 percent. feldspar; matrix, 13 percent Quartz, albite, orthoclase, apa­ clay minerals, 75 percent opal, tite, and opal-CT were detected and 6 percent iron oxide. Opal- by X-ray diffraction analysis. CT, quartz, albite, orthoclase, Specific gravity, 2.22. Sample and a trace of illite were 100-55 from middle of unit. 5 1 1 55 detected by X-ray diffraction 13. Siltstone, bentonitic, siliceous, analysis. Specific gravity, 2.04. light-gray (N7), massive, Sample 100-58 from middle of weakly indurated, very angular unit. 11 4 3 45 to angular grains, medium- 9. Siltstone, moderately phosphatic, sorted, floating grains to fine sandy (very fine to fine­ size very rare. Contains grained), light-gray (N7) to yel­ mudstone intraclasts to 3 cm. lowish-gray (5Y7/2) with dark- Framework, 31 percent quartz, yellowish-orange (10YR6/6) 8 percent feldspar, and 1 per­ stains, massive to faintly bed­ cent chlorite; matrix, 25 ded, moderately indurated, percent clay minerals, 3 per­ swirled mudstone laminations cent apatite, 25 percent opal, rare, slightly burrowed, angular and 7 percent iron oxide. to rounded grains, poorly Quartz, montmorillonite, sorted, floating grains to coarse albite, and orthoclase were size common; phosphatic pel­ detected by X-ray diffraction lets decrease in number from analysis. Specific gravity, 2.07. base upward, pellets concen­ Sample 100-56 from middle of trated in burrows, phosphatic unit. 2 4 0 71 claystone nodules rare; fish

40 Stratigraphic Sections Upper Miocene Continued Upper Miocene Continued Santa Margarita Formation Continued Santa Margarita Formation Continued Upper phosphatic mudstone member Continued Upper phosphatic mudstone member Continued Unit No. Thickness Unit No. Thickness Ft In M Cm Ft In M Cm bones rare, scales and pelec- percent carbonate, 4 percent ypod molds rare. Framework, apatite, 10 percent opal, and 6 23 percent quartz, 11 percent percent iron oxide. Quartz, feldspar, 2 percent carbonate opal-CT, albite, and orthoclase fragments, and 17 percent were detected by X-ray diffrac­ phosphatic pellets; matrix, 27 tion analysis. Specific gravity, percent clay minerals, 8 per­ 1.78. Sample 100-61 from mid­ cent apatite(?), 8 percent opal, dle of unit. 15 0 4 57 and 4 percent iron oxide. 6. Sandstone, phosphatic, very fine Quartz, albite, orthoclase, opal- to fine-grained, silty, cal­ CT, and apatite were detected careous, grayish-orange by X-ray diffraction analysis. (10YR7/4), massive, weakly Specific gravity, 2.50. Sample indurated to indurated, sub- 100-59 from middle of unit. 3 3 0 99 angular to subrounded grains, 8. Sandstone, slightly phosphatic, poorly sorted, floating grains to very fine grained, very cal­ coarse size; small nodules careous, grayish-orange plentiful. Fish bones and pelec- (10YR7/4), massive, weakly ypod molds as much as 5 cm in indurated to indurated, angular diameter rare. Unit similar to to subrounded grains, poorly unit 8. Framework, 21 percent sorted, floating grains to gran­ quartz, 5 percent feldspar, and ule size, and scattered small 27 percent phosphatic pellets phosphatic claystone nodules and nodules; matrix, 3 percent and chert pebbles common. clay minerals, 38 percent car­ Fish bones and megafossils bonate, and 6 percent iron including many phosphatized oxide. Quartz, albite, dolomite, casts of pelecypods and gas­ orthoclase, calcite, and apatite tropods common. Very were detected by X-ray diffrac­ irregular base, very distinctive tion analysis. Specific gravity, unit. Framework, 17 percent 2.47. Sample 100-62 from quartz, 4 percent feldspar, 1 middle of unit. 1 7 0 48 percent carbonate fragments, 9 5. Sandstone, slightly phosphatic, percent phosphatic pellets, and very fine to fine-grained, silty, 2 percent heavy minerals; pale-grayish-orange (10YR8/4) matrix, 5 percent iron oxide, with moderate-brown (5YR4/4) and 62 percent carbonate and black (Nl) stains, massive, cement. Quartz, calcite, albite, indurated, very angular to sub- apatite, orthoclase, and dolo­ angular grains, medium-sorted, mite were detected by X-ray floating grains to coarse size diffraction analysis. Specific rare. Pelecypod molds and gravity, 2.46. Sample 100-60 casts as much as 6 cm in from middle of unit. 1 11 0 58 diameter rare, broken fish 7. Siltstone, slightly phosphatic, bones and scales rare, burrows clayey, sandy (very fine to very rare. Framework, 30 per­ medium-grained), bentonitic, cent quartz, 12 percent yellowish-gray (5Y8/1) to dark- feldspar, and 4 percent phos­ yellowish-gray (5Y7/1) with phatic pellets and nodules; very dark yellowish orange matrix, 28 percent clay miner­ (10YR5/6) stains, massive, als, 4 percent dolomite, 15 indurated, angular to sub- percent apatite(?), and 7 per­ rounded grains, poorly sorted, cent iron oxide. Quartz, floating grains to coarse size dolomite, albite, and orthoclase common. Most pellets average were detected by X-ray diffrac­ 0.1 mm, but some are greater tion analysis. Specific gravity, than 1.0 mm in diameter. Fish 2.24. Sample 100-63 from vertebrae (very rare), ribs, and middle of unit. 7 10 2 39 scales rare; concentrated in 4. Claystone, siliceous, silty, ben­ burrows. Framework, 35 per­ tonitic in part, yellowish-gray cent quartz, 6 percent feldspar, (5Y8/1) with light-brown 1 percent carbonate fragments, (5YR5/6) stains, massive, 7 percent phosphatic pellets, indurated, angular to sub- and 1 percent pyrite(?); matrix, rounded grains, poorly sorted. 29 percent clay minerals, 1 Sponge spicules common and

Stratigraphic Sections 41 Upper Miocene Continued Upper Miocene Continued Santa Margarita Formation Continued Santa Margarita Formation Continued Upper phosphatic mudstone member Continued Lower sandstone member Continued Thickness Thickness Ft In M Cm Ft In M Cm fish scales rare. Framework, 10 slightly calcareous, grains percent quartz, 1 percent fel­ medium- to well-sorted; float­ dspar, and 2 percent heavy ing grains as large as coarse minerals; matrix, 73 percent size, rare. Nonphosphatic clay minerals, 7 percent opal, except for rare fish bones and and 7 percent iron oxide. scales. Pelecypods shells rare. Montmorillonite, opal-CT, Medium- to coarse-grained quartz, albite, and orthoclase sandstone makes up most of were detected by X-ray diffrac­ the unit. Slightly to very cal­ tion analysis. Specific gravity careous, nonphosphatic, very not determined. Sample 100-64 pale orange (10YR8/2) to yel­ from middle of unit. 3 0 0 91 lowish-orange (10YR7/6); 3. Siltstone, clayey, sandy (very fine massive, moderately indurated to fine-grained), siliceous, very to friable; very fine grained light to light-gray (N8-N7) sand to pebbles, poorly sorted. with light-olive-brown (5Y6/6) Pectens and other mollusks and very dark yellowish orange very abundant; pelecypod (10YR5/6) stains, massive, shells and shell fragments moderately indurated, angular including oysters, Ostrea titan. to subangular grains, medium- Abundant quartz, albite, and sorted, floating grains to coarse orthoclase were detected by X- size very rare. Contains phos­ ray diffraction analysis. Spe­ phatic pellets very rare, fish cific gravity not determined. bones and scales rare, slightly Sample 100-67 from top of burrowed. Framework, 35 per­ unit. Not Measured cent quartz, 11 percent feldspar, 1 percent carbonate fragments, and 2 percent phos­ Trench 294 phatic pellets; matrix, 1 percent chlorite, 34 percent (Measured by H. D. Gower, 1964; E and F numbered samples described clay minerals, 4 percent petrographically by T. L. Vercoutere). carbonate, and 4 percent iron LOCATION: NW'/4SE'/4 sec. 6, T. 9 N., R. 26 W. (S.B.B.&M) in the New oxide. Abundant quartz, albite, Cuyama, California Quadrangle. orthoclase, and some opal-CT ATTITUDE OF BEDDING: Approximately N 50° W. Stratigraphic units were detected by X-ray diffrac­ 164-152 are in a road cut northwest of trench 294. A pipeline trench, south tion analysis. Specific gravity, of trench 294, contains units 107 to 164. 2.26. Sample 100-65 from middle of unit. 6721 Upper Miocene: 2. Clay stone, silty, bentonitic in part, Santa Margarita Formation: dusky-yellow (5Y6/4) with Upper sandstone member: some very light brown Unit No. Thickness (5YR7/4) stains, massive, n M , weakly indurated, angular to 164. Sandstone, fine-grained, silty, subrounded grains, medium- micaceous, grayish-orange, sorted, floating grains to fine weathers white, massive, fria­ ble, poorly sorted. Contains size rare. Montmorillonite, quartz, albite, and orthoclase large biotite(?) flakes. Grada- were detected by X-ray diffrac­ tional(?) base. Thickness tion analysis. Specific gravity approximate 15 0 4 57 not determined. Sample 100-66 163. Siltstone, sandy, slightly shaly. from middle of unit. 3 9 1 14 Most of unit fractures into small, angular fragments, fria­ Total thickness of upper phos­ ble. Two-inch (5-cm) calcite phatic mudstone member 272 2 8 93 vein at base. Thickness approx­ imate 7 2 2 18 Upper Miocene: 162. Sandstone, very fine grained, Santa Margarita Formation: light-gray to very pale orange. Lower sandstone member: Clams, very dark brown, phos­ phatic, very small, very 1. Sandstone, very fine to fine­ abundant. Unit appears highly grained, and medium- to burrowed; large burrow holes coarse-grained. Fine-grained penetrate underlying siltstone. sandstone: noncalcareous to Irregular base. 3 0 0 91

42 Stratigraphic Sections Upper Miocene Continued Upper Miocene Continued Santa Margarita Formation Continued Santa Margarita Formation Continued Upper sandstone member Continued Upper phosphatic mudstone member Continued Unit No. Thickness Unit No. Thickness Ft In M Cm In M Cm 161. Siltstone 1 2 0 36 (5-cm) zone of indurated, si­ 160. Bentonite and highly bentonitic liceous siltstone near base 0 10 0 25 siltstone 0 8 0 20 140. Sandstone, very fine grained, si­ 159. Siltstone 0 6 0 15 liceous, indurated; some small- 158. Sandstone, very fine grained, scale, irreg'ular, broken beds; light-gray to very pale orange. irregular base 1 0 0 30 Phosphatic pellets rare, dark- 139. Siltstone, very thin bedded; brown, coarse to very coarse, weakly indurated 1 1 0 33 local. Thickness approximate 138. Limestone, fossiliferous, indu­ 157. Siltstone, sandy, olive-gray to rated 1 0 0 30 olive-brown 137. Siltstone, calcareous, fos­ 156. Sandstone, very fine grained, siliferous, very thin bedded; light-gray; irregular thickness most beds 2 in. (5 cm) or less 2 0 061 155. Siltstone, olive-gray, massive; 136. Siltstone, olive- to light-gray, weathers into small angular moderately indurated; contains fragments 3 0 0 91 several bentonite beds, upper 154. Sandstone, very fine grained, and part may be slightly bentonitic; sandy siltstone; some crossbed- weathering patterns suggest ding 1 0 0 30 possibly very thinly bedded 6 0 1 83 153. Sandstone, very fine grained, thin 135. Sandstone, very fine grained, bedded [2-in. (5-cm) beds] 10 0 3 5 slightly phosphatic, light-gray 2 6 0 76 152. Sandstone, very fine grained, 134. Sandstone, very fine grained, massive. Appears clam-bored brown to brownish-gray; about in many places; lower 1 ft 5 percent phosphatic pellets 0 7 0 18 contains large internal molds of 133. Sandstone, very fine grained, clams. Phosphatic pellets, pale-orange-brown; some coarse-grained, 5 percent very crossbedding visible, may be dark brown, in lower part. Top foreset beds, dipping north­ half not closely examined 20 0 6 10 ward; phosphatic pellets, dark- 151. Bentonite and bentonitic siltstone 0 7 0 18 brown, fine-grained, locally 150. Siltstone, olive gray; about 5 per­ concentrated, pellets average cent coarse phosphatic pellets 20 percent in unit; clam bur­ in lower 2 ft (61 cm) 12 0 3 66 rows at base; very irregular 149. Sandstone very fine grained, silty; base 1 0 0 30 7 percent phosphatic pellets 1 6 0 46 132. Sandstone, very fine grained, and 148. Siltstone, olive gray; about 5 per­ sandy siltstone; some phos­ cent coarse very dark brown phatic pellets; lower part may phosphatic pellets 8 0 2 44 show foreset beds, dipping 147. Sandstone, very fine grained; 5 north 3617 percent phosphatic pellets in 131. Siltstone, siliceous, indurated 0 5 0 13 upper half, less at base; abun­ 130. Siltstone, siliceous, moderately dant fossils at base 4 0 1 22 indurated 0 5 0 13 Total measured thickness of upper 129. Siltstone, siliceous, indurated; sandstone member: 97 0 29 56 some light-gray phosphatic pel­ lets 1 10 0 56 Upper Miocene: 128. Siltstone, moderately indurated 1 0 0 30 Santa Margarita Formation Continued 127. Limestone, leached in places 0 6 015 Upper phosphatic mudstone member: 126. Siltstone, somewhat siliceous 3514 Unit No. Thickness 125. Sandstone, very fine grained, and Ft In M Cm sandy siltstone, orange-brown; 146. Siltstone and sandy siltstone; possibly crossbedded, in part; minor phosphate 3 0 0 91 15 percent phosphatic pellets; 145. Covered interval, weakly indu­ large clams at base; very irreg­ rated; probably mudstone 10 0 3 5 ular base 0 11 0 28 144. Sandstone, .very fine grained, 124. Siltstone 1 6 0 46 poorly sorted, indurated; some 123. Mudstone, light-gray, moderately reddish-brown phosphatic nod­ phosphatic, very sandy, partly ules at top as large as 1 in. (3 grain-supported. Sand, fine cm) 18 grained; grains subangular to 143. Siltstone, weakly indurated 28 subrounded, randomly ori­ 142. Siltstone, siliceous, indurated 28 ented, altered grain boundaries 141. Siltstone, weakly indurated; 2-in. common; incipient calcitization

Stratigraphic Sections 43 Upper Miocene Continued Upper Miocene Continued Santa Margarita Formation Continued Santa Margarita Formation Continued Upper phosphatic mudstone member Continued Upper phosphatic mudstone member Continued Thickness Thickness Ft In M Cm Fl In M Cm of grains rare; floating grains to nodules with grain inclusions very coarse size rare. Frame­ as large as 0.85 mm, and 12 work, 29 percent quartz, 13 percent fish-bone and shell percent feldspar, and 10 per­ fragments. Pellets, regular to cent phosphate; matrix, 46 slightly irregular spheroids, percent clay minerals and 2 range from 0.05 mm to 0.30 percent iron oxide; accessory mm in diameter, average diam­ minerals include hematite, eter 0.11 mm; predominantly magnetite, chlorite, muscovite, sharp boundaries, slightly and zircon. Phosphatic frame­ deformed peripherally at con­ work consists of 38 percent tacts with other grains and pellets with noncentered grain pellets; most stained with iron inclusions and 38 percent pel­ oxide, especially if nucleus is a lets with centered grain diatom. Contains fish bones inclusions of quartz, diatom and shell fragments as large as fragments, feldspar, very rare 1 mm; diatoms. Sample zircon, 17 percent structureless Fl208-38 1 0 0 30 pellets, 5 percent compound 119. Siltstone; bentonite bed 5 in. (13 pellets, and 2 percent shell and cm) above base 0 0 91 pebble fragments. Pellets are 118. Mudstone, phosphatic, pelletal, regular to slightly irregular sandy, silty, orangish-brown. spheroids between 0.10 mm Grains, subangular to sub- and 0.30 mm in diameter (aver­ rounded; randomly oriented, age 0.19 mm), with moderately poorly sorted; floating grains as sharp to slightly fuzzy bound­ large as coarse size. Frame­ aries and peripherally work, 14 percent quartz, 8 deformed when in contact with percent feldspar, 36 percent other pellets. Hematite staining phosphate; matrix, 25 percent tends to be in and around clay minerals, 7 percent apatite pellets. Hematite con­ cement, and 9 percent iron centrations form hematite-rich oxide; accessory minerals, 1 bands. Some crossbedding in percent, include chlorite, zir­ upper part of unit; abundant con, glauconite, and magnetite. burrows at and below base. Phosphatic framework, 17 per­ Very irregular base. Sample cent pellets with noncentered Fl208-39 from unit 1 2 0 36 inclusions and 28 percent pel­ 122. Siltstone; locally abundant phos­ lets with centered inclusions of phatic pellets 7 0 2 13 quartz, feldspar, diatom frag­ 121. Sandstone, silty, and sandy silt- ments, and hematite, 36 stone, light gray; about 5-10 percent structureless pellets, 6 percent light-gray phosphatic percent compound pellets, 6 pellets 2 0 0 61 percent nodules with and with­ 120. Mudstone, very sandy, moder­ out grain inclusions, 3 percent ately phosphatic, partly grain fish bones, and 6 percent shell supported, orangish-brown. fragments as large as 1 mm. Sand, fine-grained, subrounded Pellets, regular to irregular to subangular, medium-sorted, spheroids, range from 0.08 randomly oriented. Framework, mm and 0.70 mm in diameter 26 percent quartz, 13 percent (average 0.15 mm); sharp rims, feldspar, 17 percent phosphate; partially replaced with calcite matrix, 34 percent clay miner­ rare; most stained by hematite. als (matrix), 4 percent apatite Hematite staining and replace­ (cement), and 4 percent iron ment in pellets largely confined oxide; accessory minerals to the interior of pellets; degree include chlorite, hematite, of staining varies from barely magnetite, and calcite. Phos­ visible to completely opaque. phatic framework, 6 percent Sample F1208-37 from unit. pellets with noncentered inclu­ Figure 6D from unit 0 4 0 10 sions, and 53 percent pellets 117. Bentonite 0 .6 0 1.5 with centered inclusions of 116. Siltstone 4 0 1 22 quartz, feldspar, and diatom 115. Sandstone, very fine grained, fragments, 24 percent struc­ silty, slightly phosphatic 0205 tureless pellets, 6 percent 114. Siltstone 0 8 0 20 44 Stratigraphic Sections Upper Miocene Continued Upper Miocene Continued Santa Margarita Formation Continued Santa Margarita Formation Continued Upper phosphatic mudstone member Continued Upper phosphatic mudstone member Continued Unit No. Thickness Thickness In M Cm Ft In M Cm 113. Siltstone, very phosphatic, pel- 96. Siltstone, siliceous; contains letal, muddy, brown, poorly diatoms 0 8 0 20 sorted, partially framework 95. Siltstone, bentonitic, and ben- supported. Grains, subangular tonite 0308 to subrounded, randomly ori­ 94. Siltstone, siliceous 1 1 0 33 ented, boundaries commonly 93. Siltstone, bentonitic 0 .6 0 1.5 altered. Framework, 16 percent 92. Siltstone, siliceous, slightly ben­ quartz, 9 percent feldspar, 2 tonitic 0, 7 0 18 percent chert fragments, and 91. Bentonite trace 40 percent phosphatic; matrix, 90. Siltstone, siliceous; contains fo- 28 percent clay minerals, 5 raminiferal molds 1 1 0 33 percent iron oxide; accessory 89. Siltstone and bentonitic siltstone; minerals include hematite, some phosphatic pellets 0 4 0 10 magnetite, chlorite, muscovite, Sandstone, very fine grained, and and zircon. Phosphatic frame­ siltstone; indurated; about 15 work, 29 percent pellets with percent phosphatic pellets. noncentered inclusions and 22 Megafossils at base; sharp percent pellets with centered base. Correlation unit P2. Sam­ inclusions of quartz, diatom ple P2-294 from unit 2 2 0 66 fragments, feldspar, and 87. Siltstone, bentonitic 2 2 0 66 hematite, 27 percent struc­ 86. Siltstone, siliceous, moderately tureless pellets, 15 percent phosphatic; indurated; 1 ft (30 compound pellets, 3 percent cm) above base is 10-inch (25- nodules with inclusions, 4 per­ cm) bed of sandy siltstone with cent shell fragments. Pellets, 10 percent phosphatic pellets. spheroids range from 0.04 mm Correlation unit SI near middle 4 10 1 47 and 0.70 mm in diameter, aver­ 85. Bentonite and bentonitic siltstone 0 4 0 10 age diameter 0.16 mm; very 84. Siltstone, sandy, and very fine sharp to slightly fuzzy bound­ grained silty sandstone; indu­ aries, periphery commonly rated; about 1 percent deformed slightly at contacts phosphatic pellets 2 2 0 66 with grains or other pellets, 83 Siltstone, bentonitic to siliceous, and diatom fragments com­ possibly calcareous; weakly monly replaced partially by indurated; concretionary zone hematite. X-ray diffraction at top as much as 5 in. (13 cm) analysis indicates quartz, opal- thick, with porous, pale-orange CT and a minor component of concretions as much as 5 ft illite. Correlation unit PI. Sam­ (1.52 m) long; contains abun­ ples F1208-36 and PI-294 from dant foraminiferal molds. Thin unit 2 0 0 61 bentonite beds at base and 3.6 112. Siltstone, sandy; 15 percent phos­ ft (1.10m) above 5 0 1 52 phatic pellets 5 0 13 82 Siltstone, very sandy, pale-green­ 111. Bentonite 2 0 5 ish-gray; moderately indurated; 110. Siltstone 10 1 17 about 1 percent phosphatic pel­ 109. Siltstone; covered 0 0 91 lets, mostly coarse grained, 108. Sandstone, very fine grained 0 3 brown to pinkish 1 7 0 48 107. Siltstone, covered 1 68 81 Siltstone, pale-olive-gray; weakly 106. Limestone, cream-colored, indu­ indurated; brown in lower part. rated; highly fossiliferous 6 0-15 Rare phosphatic pellets; abun­ 105. Sandstone, very fine grained, dant fish scales 1 8 0 51 silty; poorly exposed 6 0 15 80 Wackestone, sandy, slightly phos­ 104. Siltstone, sandy, olive- to light- phatic, framework supported. gray 6 0 46 Grains, subangular to sub- 103. Sandstone, very fine grained, rounded, well-sorted, long axes silty; moderately indurated; subparallel; commonly incip- highly fossiliferous 5 0 13 iently calcitized. Framework, 102. Siltstone, bentonitic, olive-gray 6 0 15 32 percent quartz, 14 percent 101. Siltstone, sandy, olive-gray; small feldspar, 6 percent phosphatic; 'megafossils abundant 11 0 58 matrix 2 percent clay minerals, 100. Bentonite 6 0 15 42 percent carbonate minerals, 99. Siltstone, bentonitic 205 and 4 percent iron oxide, 98. Siltstone, siliceous 8 0 51 accessory minerals, 1 percent, 97. Bentonite and bentonitic siltstone I 0 3 include hematite and zircon. Stratigraphic Sections 45 Upper Miocene Continued Upper Miocene Continued Santa Margarita Formation Continued Santa Margarita Formation Continued Upper phosphatic mudstone member Continued Upper phosphatic mudstone member Continued Unit No. Thickness Unit No. Ft In M Cm Fl In M Cm Phosphatic framework, 17 per­ fragments and apatite veinlets cent pellets with noncentered oriented parallel to laminae. inclusions, and 17 percent pel­ Sample F1208-30 from unit 1 4 0 41 lets with centered inclusions of 78. Mudstone, moderately phos­ quartz, feldspar, hematite, and phatic, silty, sandy; siliceous diatom fragments, 50 percent matrix with hematite veinlets structureless pellets, and 16 and iron-oxide stain. Grains, percent fossil fragments. Pel­ very fine, subangular to sub- lets, regular to slightly rounded, poorly sorted, irregular spheroids, range from randomly oriented; commonly 0.09 mm to 0.55 mm in diam­ incipiently calcitized and feld­ eter, average diameter 0.18 spar commonly altered to mm; almost all boundaries sericite; rare floating grains as sharp, rarely fuzzy; large as coarse size. Frame­ rarely rimmed with hematite work, 18 percent quartz, 12 or calcite; protruding grains percent feldspar, and 17 per­ very rare. Graded bedding; cent phosphate; matrix, 47 some coarse sand in lower part percent clay minerals and 4 of unit. Upper 10 in. (25 cm) percent iron oxide; accessory of unit weakly indurated; rest minerals 1 percent, include of unit moderately indurated, glauconite, chlorite, hematite, semifriable. Contains shell and magnetite, zircon, and biotite. fish bone fragments less than 1 Phosphatic framework, 35 per­ mm long, some partially cent pellets with noncentered replaced by phosphate. Clam inclusions and 24 percent pel­ molds very abundant in lower lets with centered inclusions of part. Base, very irregular, with quartz, feldspar, diatom frag­ sand-filled burrows as much as ments, very rare fish bones, 3 in. (8 cm) deep and 2 in. (5 zircon, hematite, and chert, 39 cm) in diameter. Sample percent structureless pellets, F1208-31 from lower third of and 2 percent fish-bone and unit 3 10 1 17 shell fragments. Pellets, regular 79. Wackestone, silty, moderately to slightly irregular spheroids; phosphatic; very thinly lami­ range from 0.08 mm and 0.55 nated. Grains, subangular to mm in diameter; average diam­ subrounded, well-sorted. eter 0.20 mm; boundaries Framework, 18 percent quartz, sharp to fuzzy; rims commonly 10 percent feldspar, 10 percent siliceous and rarely hematitic; phosphate; matrix, 20 percent protruding and intruding grains clay minerals and 39 percent rare; nuclei rarely incipiently dolomite; accessory minerals, calcitized; hematite staining 2 percent, include glauconite, common. Sandy in lower part; chlorite, hematite, magnetite, lower 1 ft (30 cm) is very fine and muscovite. Phosphatic grained silty sandstone; indu­ framework, 38 percent pellets rated; few clam casts. Faint, with noncentered inclusions irregular small-scale lamina­ and 30 percent pellets with tions and possible cross- centered inclusions of quartz, bedding; may be broken by feldspar, zircon, chlorite, and burrows; poorly exposed at diatom fragments, 20 percent base. Sample F1208-32 from structureless pellets, 5 percent unit 2 0 0 61 fish bones, 5 percent shell 77. Siltstone, mostly very siliceous, fragments, and 2 percent incip­ some slightly siliceous. ient pellets. Pellets, regular to Weathered surface looks very slightly irregular spheroids, thin bedded. About 3 percent approximately 0.15 mm in phosphatic pellets locally. Fish diameter; boundaries very scales abundant fuzzy, rims commonly iron- 76. Sandstone, silty, and siltstone, enriched; nucleus commonly slightly sandy. Lower part, replaced by secondary calcite light-brown and fine-grained and rarely replaced by sandstone, upper part, pinkish hematite. Shell fragments as and very fine grained siltstone. much as 2 mm long; shell Sandstone grades up to silt- 46 Stratigraphic Sections Upper Miocene Continued Upper Miocene Continued Santa Margarita Formation Continued Santa Margarita Formation Continued Upper phosphatic mudstone member Continuednuec Upper phosphatic mudstone member Continued Unit No. Thickness Unit No. Ft In M Cm Ft In M Cm stone. Phosphatic pellets about 63. Phosphorite, dark-brown, sandy, 15 percent. Lower part contains siliceous matrix, grain sup­ megafossil casts and appears ported. Upper 4 inches (10 cm) burrowed. Base very irregular 2 6 0 76 of unit, 45 percent phosphatic 75. Siltstone, olive-gray 0 5 0 13 pellets, medium-grained, dark- 74. Dolomite, pale-red. Discon­ brown, some gray; remainder tinuous lens. 30 percent of unit, 70 percent pellets, insoluble residue 0 5 0 13 medium-grained, dark-brown. 73. Siltstone, mostly siliceous, light- Sand grains, subangular to gray. Breaks into sharp, small, subrounded, medium-grained, angular fragments. Microfossil medium-sorted, randomly ori­ impressions, small, abundant; ented; rarely incipiently some with weathered white calcitized. Framework, 31 per­ material. Basal 4 in. (10 cm), cent quartz, 18 percent sandy siltstone, weakly indu­ feldspar, and 7 percent phos­ rated. Correlation unit S2 5 1 1 55 phatic; matrix, 27 percent clay 72. Siltstone, sandy, siliceous, minerals, 1 percent micrite, 1 slightly phosphatic, moderately percent apatite, and 3 percent indurated. Quartz, coarse­ iron oxide; accessory minerals, grained, rare. Foraminiferal(?) 1 percent, include muscovite, impressions locally abundant 3 6 1 7 chlorite, magnetite, hematite, 71. Sandstone, very fine grained, and zircon. Small patches of silty, siliceous, indurated. Con­ apatite and micrite in matrix. tains some quartz, coarse­ X-ray diffraction analysis indi­ grained. Contains about 15 per­ cates matrix composed of opal- cent phosphatic pellets, light- CT and apatite. Phosphatic brown, locally concentrated framework, 40 percent pellets into lenses 1 1 0 33 with noncentered inclusions of 70. Bentonite and bentonitic siltstone. quartz, feldspar, and diatom Phosphatic pellets, white, fine­ fragments, 50 percent struc­ grained, 30 percent 0 5 0 13 tureless pellets, 5 percent 69. Siltstone and sandy siltstone, sili­ nodule fragments, and 5 per­ ceous, upper part indurated. cent shell fragments. Pellets, Phosphatic pellets, very fine to spheroids, regular to slightly fine-grained, about 25-30 per­ irregular; range from 0.08 mm cent in unit; in upper third of to 0.45 mm in diameter; aver­ unit, pellets brown and pitted, - age diameter 0.20 mm; rims, in rest of unit, pellets white to sharp to very sharp; protruding light-gray 2 8 0 81 grains rare; faint grain imprints 68. Bentonite and bentonitic siltstone. from compaction rare; nuclei Upper half, phosphatic pellets, rarely incipiently calcitized. white, very fine grained, 10 Few nodules, rounded; range percent; lower half, phosphatic from 0.3 mm to 1.6 mm, with pellets, light-brown to gray, and without inclusions. A few fine-grained, 25 percent. Pel­ siltstone clasts as long as 1.5 lets concentrated locally in i in. (3.8 cm) in base. Base, very lenses 1 1 0 33 irregular, burrowed. Burrows, 67. Siltstone, bentonitic. Phosphatic cross section oval-shaped, as pellets 15 percent 0 5 0 13 much as 2 in. (5 cm) in diame­ 66. Sandstone, calcareous, pale-red. ter; mostly parallel to base. Phosphatic pellets, light to Lens, 4 in. (10 cm) deep, cuts dark, fine-grained, 25 percent. into underlying unit, probably Many calcite veins cut unit 1 0 0 30 channel scour. Correlation unit 65. Siltstone, bentonitic, light-brown. P3. Samples F1208-33 and Phosphatic pellets, fine­ P3-294 from unit ' 0 36 grained, 15 percent 0 4 0 10 62. Claystone, slightly phosphatic, 64. Siltstone, siliceous; phosphatic slightly silty, faintly laminated; pellets, about 15 percent, hematitic patches and partings. microfossils in cores of many Grains, subangular to sub- pellets. Upper part, pale-red to rounded, poorly sorted; floating gray, very fine to fine-grained; grains, medium-size, rare; basal 4 inches (10 cm), light- grains very rarely incipiently brown, coarse-grained 2 8 0 81 calcitized. Framework, 8 per- Stratigraphic Sections 47 Upper Miocene Continued Upper Miocene Continued Santa Margarita Formation Continued Santa Margarita Formation Continued Upper phosphatic mudstone member Continued Upper phosphatic mudstone member Continued Unit No. Thickness Thickness Ft In M Cm Ft In M Cm cent quartz, 3 percent feldspar, chlorite, magnetite, zircon, and 2 percent structureless phos­ muscovite. Phosphatic frame­ phatic pellets; matrix, 84 work consists of 24 percent percent siliceous clay minerals, pellets with noncentered inclu­ 3 percent iron oxide, and very sions and 25 percent pellets rare chlorite. Pellets, spher­ with centered inclusions of oids, regular to irregular; range quartz and diatom fragments from 0.05 mm to 0.25 mm in (rare), 45 percent structureless diameter; boundaries, fuzzy to pellets, 4 percent compound very fuzzy; very many stained pellets, and 2 percent shell with hematite. Sample fragments (less than 1 mm). F1208:34 from unit 6 0 1 83 Pellets are regular to slightly 61. Siltstone, siliceous; indurated. irregular spheroids between Phosphatic pellets, gray, fine­ 0.08 mm and 0.35 mm in grained, about 15-20 percent; diameter, (average 0.15 mm) some are pitted 111 0 58 with fuzzy boundaries, pro­ 60. Sandstone, very fine grained, truding grains (rare), and silty, siliceous. Phosphatic pel­ hematite replacement (com­ lets, gray to light-grayish- mon). Sample F1208-43 from brown, fine-grained, about 10 unit 0205 percent 3 0 0 91 53. Mudstone, sandy, siliceous, mod­ 59. Siltstone, siliceous; some phos­ erately phosphatic. Sand phatic pellets 14 0 41 grains, subangular to sub- 58. Siltstone, highly sheared 0 4 010 rounded, fine, poorly sorted, 57. Mudstone and Siltstone, siliceous. randomly oriented; floating Phosphatic pellets, 5-10 per­ grains, as large as coarse-size cent in upper half and about 15 very rare; framework grains percent in lower half. Quartz, commonly altered to sericite very coarse grained, rare. Some and rarely to calcite. Frame­ microfossil molds 6 4 1 93 work, 19 percent quartz, 6 56. Siltstone and sandstone; sand, percent feldspar, 1 percent very fine grained, siliceous. chalcedony, 10 percent phos­ Phosphatic pellets, as much as phate; matrix, 61 percent clay 30 percent. Sheared zone. minerals, and 3 percent iron Thickness approximate 6 0 1 83 oxide. Phosphatic framework, 55. Claystone, siliceous; laminae, 50 percent pellets with noncen­ wavy; a few silty partings with tered inclusions and 30 percent grains, subangular to rounded, pellets with centered inclusions poorly sorted, preferentially of quartz, feldspar, and very oriented subparallel to laminae. rare chalcedony and diatom Framework, 3 percent quartz fragments, 18 percent struc­ and 2 percent feldspar; matrix, tureless pellets, and 2 percent 90 percent clay minerals and 5 shell and diatom fragments. percent iron oxide. Phosphatic Pellets, spheroids, regular to pellets, spheroidal, approx­ slightly irregular; range from imately 0.30 mm in diameter; 0.07 mm to 0.30 mm in diam­ boundaries of varying sharp­ eter; average diameter 0.13 ness; rare. Much hematite mm; boundaries, fuzzy to very staining. Sample Fl208-44 fuzzy; rims rarely of hematite; from unit 1 11 0 58 nuclei commonly incipiently 54. Claystone, slightly phosphatic, calcitized, protruding grains poorly sorted, subangular to rare. Correlation unit S3. Sam­ round, randomly oriented ple F1208-42 from unit 0 43 coarse silt-size grains; faintly 52. Mudstone, sandy, slightly phos­ laminated siliceous clays with phatic; faintly laminated grain- disseminated chlorite and rich and mud-pellet-rich zones; hematite. Contains 7 percent locally grain supported. quartz, 3 percent feldspar, 4 Grains, subangular to sub- percent phosphatic framework, rounded, very fine, poorly 84 percent clay minerals sorted. Framework, 31 percent (matrix), and 2 percent iron quartz, 2 percent feldspar, 5 oxides (matrix and staining); percent phosphate; matrix, 35 accessory minerals include percent clay minerals, 2 per-

48 Stratigraphic Sections Upper Miocene Continued Upper Miocene Continued Santa Margarita Formation Continued Santa Margarita Formation Continued Upper phosphatic mudstone member Continued Upper phosphatic mudstone member Continued Unit No. Thickness Unit No. Thickness Ft In M Cm Ft In M Cm cent carbonate replacement massive, indurated. Sheared. minerals, 7 percent iron oxide; Appears similar to stratigraphic accessory minerals include units 44 and 43 6 6 1 98 chlorite, magnetite, zircon, and 45. Siltstone and sandstone, siliceous; muscovite. Many banded con­ fractured 1 8 0 51 centrations of iron oxides 44. Sandstone, silty, siliceous; light- separate mud-pellet zones from gray; massive; sand, very fine grain zones. Phosphatic frame­ grained. Contains about 5 per­ work, 75 percent pellets with cent phosphatic pellets. Similar noncentered inclusions of in appearance and outcrop pat­ quartz, feldspar, and very rare tern to underlying unit 4 8 1 42 diatom fragments, 20 percent 43. Siltstone, sandy, siliceous, and structureless pellets, and 5 per­ porcelanite; massive 4 8 1 42 cent shell fragments. Pellets, 42. Bentonite and bentonitic siltstone. spheroids, regular to slightly Lower half mostly siliceous irregular; range from 0.08 mm siltstone. Fractured 0 8 0 20 to 0.60 mm in diameter; 41. Siltstone, siliceous. Phosphatic average diameter 0.20 mm; pellets, light-gray, 15 percent. boundaries, predominantly Lower third of unit sandy with sharp; commonly slightly 30 percent pellets 1 5 0 43 deformed peripherally; rims 40. Siltstone, siliceous; may include rarely siliceous. Nuclei, com­ bentonite; fractured. Phos­ monly ringed with hematite phatic pellets, 15 percent 1 8 0 51 stain; rarely incipiently cal- 39. Siltstone, siliceous. May contain citized. Sample Fl 208-41 from bentonite. Fractured I 5 0 43 unit 1 7 0 48 38. Sandstone, moderately phos­ 51. Siltstone, siliceous. Upper half, phatic, muddy, light-brown; moderately phosphatic 4 4 1 32 grain-supported. Grains, fine, 50. Siltstone, siliceous; fractured; 5 subangular to subrounded, percent phosphatic pellets 1 0 0 30 well-sorted, randomly oriented. 49. Mudstone, sandy, siliceous, Framework, 36 percent quartz, slightly phosphatic; faintly 19 percent feldspar, 2 percent laminated. Grains, angular to lithic fragments, and 11 per­ subangular, poorly sorted. cent phosphate; matrix, 28 Framwork, 35 percent quartz, 7 percent clay minerals, 4 per­ percent feldspar, and 9 percent cent iron oxide disseminated phosphate; matrix, 34 percent throughout matrix; accessory clay minerals, 10 percent car­ minerals include chlorite, bonate minerals, and 3 percent hematite, muscovite, magnetite, iron oxide; accessory minerals, and zircon. Phosphatic frame­ 2 percent, include glauconite, work, 39 percent pellets with chlorite, magnetite, zircon, and noncentered inclusions and 10 hematite. Phosphatic frame­ percent pellets with centered work, 44 percent structureless inclusions of quartz, diatom pellets, 32 percent pellets with fragments, feldspar, and noncentered inclusions and 10 hematite, 43 percent struc­ percent pellets with centered tureless pellets, 5 percent inclusions of quartz and fel­ nodule and shell fragments, dspar, 10 percent nodule and 3 percent compound pel­ fragments with grain inclusions lets. Pellets, spheroids, regular and 3 percent shell fragments to slightly irregular; range from less than I mm. Pellets, spher­ 0.12 mm to 0.45 mm in diame­ oidal, range from 0.10 mm to ter, average diameter 0.22 mm; 0.30 mm in diameter; bound­ boundaries, sharp; protruding aries fuzzy; rims rarely grains rare; commonly slightly calcareous; many rims of sec­ deformed peripherally at con­ ondary phosphate; nuclei rarely tacts with other pellets or incipiently calcitized. Sample grains; nuclei rarely incipiently Fl 2 10-4 from unit 1 8 0 51 calcitized. Unit looks very bur­ 48. Siltstone, siliceous 04010 rowed. Clam molds very 47. Bentonite 0205 abundant at base. Base very 46. Siltstone, sandy, siliceous; some irregular. Sample Fl208-40 coarse-grained quartz; most from unit 1 10 0 56 Stratigraphic Sections 49 Upper Miocene Continued Santa Margarita Formation Continued Upper Miocene Continued Upper phosphatic mudstone member Continued Santa Margarita Formation Continued Upper phosphatic mudstone member Continued Ft In M Cm Unit No. tickness 20. Sandstone, very fine grained, M Cm light-grayish-brown to pale- 37. Siltstone, somewhat bentonitic(?); orangish-gray. Irregular zone, olive-gray. Phosphatic pellets highly fossiliferous, about 2 ft light-gray, very fine grained, (51 cm) above base 3 10 1 17 about 5 to 10 percent. Correla­ 19. Siltstone, siliceous; weathers tion unit S4 3617 platy. Phosphatic pellets, light- 36. Bentonite(?) trace gray to pinkish-gray, about 5 35. Siltstone, siliceous, olive-gray 0 10 0 25 percent. Local calcareous con­ 34. Bentonite(?) trace cretions as large as 1.4 ft by 3 33. Siltstone, siliceous; phosphatic ft (43 cm by 91 cm) at base 11 50 pellets, brown, rare 0 10 0 25 18. Siltstone, siliceous 6 76 32. Sandstone, feldspathic, very fine 17. Siltstone, siliceous; 15 percent grained. Gradationally coars­ phosphatic pellets 1 4 0 41 ens to base of fine-grained 16. Siltstone siliceous; 5 percent sandstone. Phosphatic pellets, phosphatic pellets 1 6 0 46 brown, fine- to medium- 15. Sandstone, silty; sandy siltstone grained, about 5 percent; basal at top 74 2 in. (5 cm) contains 25 per­ 14. Bentonite; sheared 20 cent pellets. Basal, 1 ft (30 13. Siltstone, siliceous, indurated in cm), tan; contains many inter­ upper 1.6 ft (49cm) 1 70 nal molds of clams; very 12. Sandstone, very fine grained; 5 irregular base, sand-filled bur­ percent phosphatic pellets. rows penetrate underlying unit 210 0 86 Upper part, light-gray, very fine 31. Siltstone, olive-gray 1 10 0 56 grained; lower part, dark-brown 2 11 0 89 30. Siltstone, olive-gray; contains 11. Sandstone, orange-stained, 5 per­ about 20 percent phosphatic cent phosphatic pellets. Fossils pellets. Upper 2 in. (5 cm) of very abundant 0 10 0 25 unit, brownish-gray; contains 10. Sandstone, very fine grained, phosphatic pellets, brown, fine- light-tan; phosphatic pellets, to medium-grained, about 50 dark-brown, 5 percent. Fossils percent; grades upward into abundant at base 1 37 overlying unit. Correlation unit 9. Siltstone, siliceous; some phos­ P4 0 8 0 20 phatic pellets 29. Sandstone, calcareous, very light 8. Sandstone, calcareous. Unit thick­ gray; indurated. Fossils, very ness, variable; thins in places abundant 2 4 0 71 to 1 in. (3 cm). Fossils com­ 28. Bentonite(?) 0205 mon 18 27. Sandstone, very fine grained, 7. Siltstone, bentonitic, olive-gray 61 olive brown; phosphatic pel­ 6. Siltstone, siliceous, dark-gray; lets, dark-brown, few. Fossils indurated. About 15 percent at base 1 0 0 30 phosphatic pellets 0 41 26. Sandstone, gray, very abundant 5. Sandstone, somewhat calcareous; fossils 0 11 0 28 indurated. Phosphatic pellets, 25. Sandstone, fine-grained, brown; dark-brown, about 10 percent. phosphatic pellets, about 3 per­ Fossiliferous 1 1 0 33 cent. Fossils abundant 2 0 061 4. Siltstone; light-gray; appears 24. Sandstone, very fine to fine­ slightly diatomaceous 0 74 grained, brown. Fossils abun­ 3. Shale, olive-gray. Thickness esti­ dant 3617 mated for this unit and two 23. Siltstone, siliceous. Fossils locally underlying units 11 0 3 35 abundant. Sandstone, very fine grained, 6 in. (15 cm) zone 10 Total thickness of the upper phos- ______ft (3.05 m) above base; con­ phatic mudstone member 302 1 92 0 tains megafossils 16 6 5 3 Upper Miocene: 22. Sandstone, fine-grained. Phos­ Santa Margarita Formation: phatic pellets, dark-brown, 10 Lower sandstone member: * percent. Megafossils common 0 10 0 25 2. Sandstone and siltstone 11 0 3 35 21. Sandstone, fine-grained, brown; 1. Siltstone, light-gray, indurated 1 2 0 36 locally very well sorted. Phos­ phatic pellets, 5 percent. Total measured thickness of the ______Fossils very abundant 0^11 0 28 lower sandstone member 12 2 371 50 Stratigraphic Sections Trench 295 Upper Miocene Continued S.anta Margarita Formation Continued (Measured by H. D. Cower, 1964) Upper phosphatic mudstone member Continued LOCATION: SWMNWM sec. 8, T. 9 N., R. 26 W. (S.B.B. & M.) in the New Cuyama, California quadrangle Thickness Ft In M Cm ATTITUDE OF BEDDING: Approximately N. 50° W. 66° NE. small to very large; white, very TREND OF TRENCH: Approximately N. 45° E. small in upper 4 in. (10 cm); about 15 to 25 percent. Small Upper Miocene: fish-bone fragments abundant 1 2 0 36 Santa Margarita Formation: 80. Siltstone, and sandstone, very fine Upper phosphatic mudstone member: grained. Phosphatic pellets Unit No. Thickness about 5 percent. Contains fish Fl in M cm fragments ' 0 10 0 25 88. Siltstone and claystone, siliceous, 79. Sandstone, very fine grained, and light-gray to medium-gray, siltstone, bentonitic; highly greenish stains, locally, moder­ sheared. About 2 percent phos­ ately indurated; breaks into phatic pellets 0 7 0 18 irregular 2 to 4 in. (5 to 10 cm) 78. Sandstone, very fine grained; fragments. Phosphatic pellets, moderately indurated. Phos­ rare, very small, white to tan. phatic pellets, about 35 Small fish bones and scales percent. Quartz, coarse­ locally abundant 2 + 0 61 + grained, rare 0 6 015 87. Siltstone and claystone, siliceous, 77. Siltstone, siliceous. About 2 per­ moderately indurated but less cent phosphatic pellets. Fish so than overlying unit, breaks scales rare 1 0 0 30 into irregular '/i to 1 inch (0.6 76. Siltstone, siliceous. Phosphatic to 2.5 cm) fragments. Phos­ pellets rare except in lower 2 phatic pellets, locally in. (5 cm) of light-gray sili­ concentrated, make up less ceous shale which contains than 1 percent of unit. Fish about 15 percent 1 7 0 48 scales, scattered 1 7 0 48 75. Siltstone, probably bentonitic, 86. Claystone and siltstone, ben- medium-gray; sheared 0 7 018 tonitic; weakly indurated 0 5 013 74. Siltstone, siliceous; moderately 85. Siltstone, somewhat siliceous, indurated. Phosphatic pellets, moderately indurated. Phos­ rare 060 15 phatic pellets, brown, about 1 73. Siltstone, possibly bentonitic; percent. Unit, not completely medium-gray; weakly indu­ exposed, fractured; friable silt rated. Phosphatic pellets, about may be recent filling of cracks 1 1 0 33 3 percent 0 5 0 13 84. Sandstone, very fine grained, or 72. Sandstone, very fine grained, or siltstone, light-yellowish- siltstone; moderately indurated. brown; friable. Phosphatic pel­ Phosphatic pellets, range from lets, dark-brown, about 3-5 5 to 60 percent; average 25 percent; most abundant at top percent. Basal 6 in. (15 cm) of of unit Oil 0 28 unit is phosphatic siliceous 83. Sandstone, very fine grained, or mudstone, which was not siltstone. Upper third of unit, sampled. Very irregular contact moderately indurated. Phos­ between sandstone and phatic pellets, brown to tan, . mudstone. Correlation unit PI surfaces look waxy; content is upper 1 ft (30 cm). Sample ranges from 3-80 percent; aver­ PI-295 from upper 1 ft 1 6 0 46 ages 15 percent; most abundant 71. Siltstone, bentonitic; weakly in lower third of unit 1 '8 0 51 indurated 0205 82. Siltstone, somewhat siliceous, 70. Siltstone, siliceous. Phosphatic light-gray except for upper 7 pellets less than 1 percent. in. (18 cm) which is medium- Upper 1 in. (3 cm) of unit gray. Unit fractures into !/4 to 3/4 locally contains abundant pel­ in. (0.6 to 1.9 cm) fragments. lets 1 8 0 51 Friable zone of very fine 69. Siltstone, tuffaceous, weakly grained sandstone or siltstone, indurated. Poorly exposed 0 6 015 6 in. (15 cm), that is 7 in. (18 68. Siltstone, siliceous; about 5 per­ cm) below top may not be in cent phosphatic pellets 1 2 0 36 place. No pellets; some fish 67. Siltstone, bentonitic, and ben- scales 4 10 1 47 tonite; highly sheared. Slightly 81. Sandstone, very fine grained, or phosphatic 1 5 0 43 siltstone; moderately indurated. 66. Siltstone, or sandstone, very fine Phosphatic pellets, brown, very grained, calcareous; indurated; Stratigraphic Sections 51 Upper Miocene Continued Upper Miocene Continued Santa Margarita Formation Continued Santa Margarita Formation Continued Upper phosphatic mudstone member Continued Upper phosphatic mudstone member Continued Unit No. Thickness Unit No. Thickness Ft In M Cm Ft In M Cm broken. Phosphatic pellets rare. percent phosphatic pellets. Megafossils common 0 5 013 Irregular base 1 7 0 48 65. Siltstone, bentonitic, and ben- 47. Siltstone, light-olive, upper part tonite; slightly sheared 2 5 0 74 bentonitic. Bentonite, top 3 in. 64. Sandstone, very fine grained, or (8 cm). Microfossils, spherical, siltstone, siliceous; indurated. abundant 1 0 0 30 Phosphatic pellets, about 1 per­ 46. Siltstone, indurated. Phosphatic cent. Megafossil fragments pellets, about 10 percent. abundant 1 7 0 48 Microfossils, spherical, abun­ 63. Bentonite and bentonitic siltstone; dant 2 10 0 86 weakly indurated 111 0 58 45. Siltstone; locally indurated. 62. Siltstone, porcelaneous, to silty Abundant spherical micro- bentonite. Slightly phosphatic. fossils; rare fish scales 2 10 0 86 One megafossil fragment 0 7 018 44. Bentonite; some bentonitic silt- 61. Siltstone, siliceous, stone at base 1 4 041 diatomaceous, slightly phos­ 43. Siltstone, locally bentonitic. phatic. Upper 8 in. (20 cm) Microfossils, spherical, abun­ weakly indurated and probably dant 2 1 0 64 bentonitic 3514 42. Siltstone, locally bentonitic. 60. Sandstone, very fine grained, or Phosphatic pellets, rare, local, siltstone, may be tuffaceous; especially in upper 1 in. (3 upper half, light-greenish-gray; cm). Microfossils, spherical, lower half, weathered orange; abundant; fish scales, common 2 7 0 79 moderately indurated. Phos­ 41. Sandstone, very fine grained, yel­ phatic pellets, average about 30 lowish-brown; mostly friable. percent. Correlation unit P2. Phosphatic pellets, about 15 Sample/P2-295 from unit 0 10 0 25 percent in upper 2.3 ft (70 59. Siltstone, siliceous, very pale cm); about 5 percent in lower olive gray. Phosphatic pellets 0.5 ft (15 cm) 2 10 0 86 less than 1 percent. Some 40. Siltstone and porcelanite; slightly phosphatic fish scales. Correla­ phosphatic locally; thinly bed­ tion unit SI 3 8 1 12 ded. Top of unit, calcareous; 58. Sandstone, very fine grained; fria­ lower 1 ft (30 cm), indurated. ble at top. Middle third of unit Correlation unit S2 30091 contains megafossils and about 39. Siltstone; indurated. About 20 20 percent phosphate pellets; percent phosphatic pellets 1 6 0 46 other two-thirds about 5 per­ 38. Siltstone, somewhat porcelaneous 4 2 1 27 cent 1 1 0 33 37. Sandstone, very fine grained, yel­ 57. Porcellanite, indurated 0 5 0 13 lowish-gray, mostly friable. 56. Siltstone, calcareous; weakly Phosphatic pellets, very small, indurated 0103 about 10 percent 1 2 0 36 55. Siltstone, calcareous; moderately 36. Siltstone; indurated locally. Phos­ indurated, but weakly indu­ phatic pellets, very small, rated in upper 2 in. (5 cm) 080 20 * about 20 percent. Top of unit, 54. Porcellanite, silty and calcareous friable and bentonitic; in lower in places; indurated 0 4 010 7 in. (18 cm), slightly ben­ 53. Siltstone; slightly phosphatic; tonitic 2 4 0 71 appears tuffaceous; lower 6 in. 35. Sandstone, very fine grained; fria­ (15 cm) moderately indurated, ble. Some quartz, coarse­ contains a few megafossils 2 5 0 74 grained. Phosphatic pellets, 52. Claystone, bentonitic; light-olive- about 10 percent. Megafossils gray 0 4 0 10 rare 0205 51. Siltstone, light-gray; few poorly 34. Siltstone, some bentonite. Phos­ preserved megafossil casts 2 2 0 66 phatic pellets, irregularly 50. Siltstone; mostly indurated. Few distributed, about 20 percent 0 8 0 20 quartz grains, very coarse. Sili­ 33. Siltstone, siliceous. Phosphatic ceous^) microfossils, white, pellets, light-gray, about 20 spherical, very abundant, partly percent 1 10 0 56 leached out. Fish scales plen­ 32. Phosphorite, yellowish-brown; tiful. Thin bentonite bed at top 3 4 1 2 mostly friable to semifriable; 49. Bentonite 0 .4 0 .9 pelletal. Phosphatic pellets, 48. Sandstone, very fine grained, or averages 80 percent. Upper 2 siltstone; indurated. About 20 in. (5 cm) of unit, indurated; 52 Stratigraphic Sections Upper Miocene Continued Upper Miocene Continued Santa Margarita Formation Continued Santa Margarita Formation Continued Upper phosphatic mudstone member Continued Upper phosphatic mudstone member Continued Unit No. Thickness Unit No. Thickness Ft In M Cm Ft In M Cm contains about 30 percent average 30 percent in unit; phosphatic pellets. Correlation 10-50 percent in upper 7 in. unit P3 1 0 0 30 (18cm) 1 7 0 48 31. Sandstone, very fine grained; fria­ 9. Siltstone, bentonitic; olive-gray 3 0 091 ble to indurated. Phosphatic 8. Sandstone, very fine grained, pellets, about 20 percent 1 0 0 30 yellow; friable. Phosphatic pel­ 30. Bentonite trace lets, about 30 percent. 29. Siltstone and some sandstone, Burrows, very abundant; fish very fine grained; indurated. bones, abundant; small gas­ Phosphatic pellets, 30 percent tropods in base. Top sheared; in 7 in. (18cm) zone 3 ft (91 base sharp; thickness unrelia­ cm) below top of unit; 15 ble. Correlation unit P4. percent in underlying 2.4 ft (73 Sample P4-295 from unit 1 8 0 51 cm), and average of 5 percent 7. Porcellanite, silty, calcareous. in remainder of unit 9 7 2 92 Poorly preserved megafossils, 28. Phosphorite, about 70 percent abundant 1 2 0 36 pellets; indurated 1 2 0 36 6. Sandstone, very fine grained, 27. Siltstone, siliceous; indurated. light-brown, friable; probably Phosphatic pellets, less than 5 bentonitic 'at top. Poorly percent average in unit; most exposed 0 10 0 25 abundant in upper 6 in. (15 5. Siltstone, siliceous. Very abun­ cm). .Contains megafossils and dant megafossils 18051 possibly Foraminifera 2 1 0 64 4. Siltstone, siliceous 11 0 3 35 26. Siltstone, bentonitic(?); moder­ 3. Sandstone, very fine grained; ately indurated 0103 about 15 percent pellets 1 0 0 30 25. Siltstone; siliceous, indurated. 2. Siltstone, siliceous, slightly phos­ Phosphatic pellets, 5 percent. phatic 4 5 1 35 Correlation unit S3 1 6 0 46 1. Bentonite 0 11 0 28 24. Siltstone; indurated. Phosphatic Total measured thickness of upper pellets, 15-60 percent, mostly phosphatic mudstone member: 147 9 45 2 in upper part; unit about 30 Section to south is highly sheared due to proximity to Ozena fault percent indurated 1 5 0 43 23. Siltstone, siliceous; about 5 per­ cent phosphatic pellets 3 11 1 19 Trench 296 22. Sandstone, very fine grained, yellow; about 30 percent phos­ (Measured by H. D. Gower, 1964; F and E numbered samples described phatic pellets 0 7 0 18 petrographically by T. L. Vercoutere) 21. Bentonite 0205 20. Porcellanite, sheared 0 11 0 28 LOCATION: SEl^SW1/* sec. 8, T. 9 N., R. 26 W. (S.S.B.&M.) in the 19. Bentonite; porcellanite inclusions; Salisbury Potrero, California quadrangle sheared 0 4 0 10 ATTITUDE OF BEDDING: N. 38° W. 36° S. (good) 18. Porcellanite, indurated 0 10 0 25 TREND OF TRENCH: Approximately N. 80° E. 17. Siltstone, weakly indurated 0205 16. Siltstone, siliceous. Phosphatic Upper Miocene: pellets, 5 percent in upper half, Santa Margarita Formation: about 30 percent in lower half 2 6 0 76 Upper sandstone member: 15. Siltstone or very fine grained Unit No. Thickness sandstone; about 5-10 percent Ft in M i phosphatic pellets 2 7 0 79 120. Sandstone, white, friable; irreg­ 14. Porcellanite, indurated; ben- ular contact. Not measured tonitic, 1 in. (2 cm) and 2 ft (61 cm) above base 2 10 0 86 13. Siltstone, siliceous; about 5 per­ Upper Miocene: cent phosphatic pellets 0 7 0 20 Santa Margarita Formation: 12. Phosphorite, about 50 percent Upper phosphatic mudstone member: pellets; siliceous; siltstone matrix 0 10 0 25 119. Siltstone, brown- to olive-gray, 11. Siltstone, siliceous; about 3 per­ highly fractured; breaks into cent phosphatic pellets; small fragments; brown stains bentonite in top 2 in. (5 cm). on surface 1 6 0 46 Correlation unit S4. 2 8 0 81 118. Siltstone, brown- to olive-gray; 10. Phosphorite, 70 percent pellets, brown stains on surface; breaks sandy, light-brown. Pellets, into small fragments 1110 58 Stratigraphic Sections 53 Upper Miocene Continued Upper Miocene Continued Santa Margarita Formation Continued Santa Margarita Formation Continued Upper phosphatic mudstone member Continued Upper phosphatic mudstone member Continued Thickness Unit No. Thickness Ft In M Cm In M Cm 117. Siltstone, greenish-gray; dark- lower half, megafossils, resis­ bluish-gray stained surfaces; tant 2 0 0 61 somewhat more massive and 109. Siltstone, some parts look ben- breaks into larger pieces than tonitic, pale-olive-gray; stratigraphic unit 118. Phos­ moderately indurated. Fossils phatic pellets, small, brown, rare 0205 about 2 percent; small nodules 2 8 081 108. Siltstone, slightly calcareous, 116. Siltstone, light-gray; brown- light-gray; white-stained sur­ stained surfaces; even textured; face; indurated. Interbedded breaks into small fragments. with siltstone, bentonitic, Upper 10 in. (25 cm) benton- olive-gray, and bentonite. itic. Unit appears similar to Lower 2 ft (51 cm) of unit, stratigraphic unit 118 3 0 0 91 brown-stained, highly frac­ 115. Siltstone, greenish-gray. Few tured. Much of unit broken megafossil casts in lower part. because of swelling of ben­ Possible bentonite laminae 11 tonite 4 0 1 22 in. (28 cm) below top. Basal 5 107. Siltstone; light-gray; brown- in. (13 cm) very fine grained stained surfaces. Quartz grains, silty sandstone, contains 5 per­ coarse, abundant locally. Upper cent pellets. Similar to siltstone grades down to silty stratigraphic unit 117, except sandstone, very fine grained. only has !/2 percent phosphatic Phosphatic pellets, about 6 per­ pellets 2 7 0 79 cent. Fish bones, abundant 114. Siltstone, tan to light-gray; mas­ locally. Base more indurated sive. Highly fractured with fine than rest of unit 4 4 1 32 gypsum grains on fracture sur­ 106. Siltstone, siliceous, light-gray; faces; some fractures filled massive, indurated. Mega­ with sand, very fine grained. fossils and fish scales common. Contains some phosphatic pel­ Breaks into large blocks except lets and quartz, coarse-grained. in upper 8 in. (20 cm), which May contain some bentonite 0 8 0 20 is more shaly, light-olive-gray 3 1 0 94 113. Siltstone, greenish-gray; moderate 105. Siltstone, siliceous, light-gray, to very calcareous, especially massive, indurated. Phosphatic in 5 in. (15 cm) zone 1 ft (30 pellets, about 1 percent. Mam­ cm) above base; some sand­ mal bones, fish scales rare 1 6 0 46 stone, very fine grained, and 104. Siltstone, partly bentonitic; lami­ siltstone, sandy. Nodules, very nated 0 4 0 10 abundant. Phosphatic pellets, 103. Siltstone, sandy, light-gray to tan; dark-brown, about 4 percent. massive, moderately indurated. Quartz, coarse-grained, about 1 Phosphatic pellets, about 15 percent. Megafossils common. percent, pale-pinkish-gray at Similar to stratigraphic unit top, dark-brown at base. Sandy 117 381 12 siltstone grades down to very 112. Bentonite 0 4 0 10 fine grained sandstone or silt- 111. Siltstone, partly siliceous, slightly stone at base. Sample CA-1 phosphatic; highly fractured. from this and two underlying Few small fossils, Yoldia units 1 8 0 51 cooperii supramontereyensis 102. Sandstone, very fine grained; may Arnold and others. Six in. (15 be slightly bentonitic; very cm) below top 8 in. (20 cm) friable. Phosphatic pellets, indurated zone, light-gray with dark-brown, about 30 percent 0103 brown- stained surfaces. Lower 101. Sandstone, very fine grained, or 1.1 ft (33 cm), silty sandstone, siltstone. Phosphatic pellets, fine-grained siliceous with 5 light and dark brown, 20 per­ percent phosphatic pellets and cent. Base, very irregular; large nodules 3617 burrows present 0 8 0 20 110. Siltstone, siliceous, light-gray 100. Siltstone, light-gray, brown- brown-stained surfaces, indu­ stained. Upper part, ben- rated. Few phosphatic pellets. tonitic(?), laminated; lower Upper half, small fossils abun­ part, massive. Sample CA-2 dant; middle 5 in. (13 cm) is from unit 2 4 071 more shaly than rest of unit; 99. Sandstone. Phosphatic pellets, 25 54 Stratigraphic Sections Upper Miocene Continued Upper Miocene Continued Santa Margarita Formation Continued Santa Margarita Formation Continued Upper phosphatic mudstone member Continued Upper phosphatic mudstone member Continued Unit No. Thickness Unit No. Thickness In M Cm Ft In M Cm percent in 7 in. (18 cm) zone 4 gastropods abundant in lower in. (10 cm) below top; 45 part of unit. Sample CA-11 percent in lower 11 inches (28 from unit 1 1 0 33 cm). Sandy siltstone at top. 82. Siltstone, siliceous, somewhat Sample CA-3 from unit 1 10 0 56 calcareous, white; indurated. 98. Siltstone, light-gray with brown Sandy bed, calcareous, 2 in. (5 stains 4 0 41 cm) thick, weakly indurated, 1 97. Siltstone, bentonitic 4 0 10 in. (3 cm) below top. Sample 96. Siltstone; about 2 percent phos­ CA-12 from this unit and three phatic pellets II 0 28 underlying units 4 0 1 22 95. Siltstone; about 5 percent phos­ 81. Siltstone, siliceous, bentonitic; phatic pellets 205 moderately indurated in lower 94. Phosphorite, sandy; about 70 per­ half of unit 4 22 cent phosphatic pellets. 80. Bentonite 0 5 Correlation unit PI. Sample 79. Siltstone, siliceous, light-gray, CA-5 from unit 0 10 0 25 brown-stained; indurated. 93. Siltstone, bentonitic, and ben- Microfossils, white, abundant 2 5 0 74 tonite. Sample CA-6 from this 78. Sandstone, phosphatic, pelletal, and four underlying units 0308 muddy, light-gray. Grains, fine, 92. Siltstone; weathers brown. Few subangular to subrounded, phosphatic pellets. Bedding medium-sorted, randomly ori­ attitude: N. 38° W. 36° S. 3 0 0 91 ented; floating grains, medium 91. Siltstone, olive-gray, bentonitic at to coarse, rare. Framework sup­ top 1 8 0 51 ported. Framework, 33 percent 90. Sandstone, white, very fine quartz including polycrystalline grained. Contains black grains, quartz, rare, 9 percent feldspar, 15 percent, may be phosphatic 2 percent lithic fragments, 21 pellets. Upper half of unit, percent phosphatic; matrix, 33 silty, slightly calcareous, and percent clay minerals. Phos­ fossiliferous; lower half, sand­ phatic framework, 43 percent stone, orangish-brown, fine­ pellets with noncentered inclu­ grained, friable; contains abun­ sions and 28 percent pellets dant pebbles as long as 1/2 in. with centered inclusions of (1.3 cm). Base very irregular 0 6 0 15 quartz, feldspar, magnetite, zir­ 89. Siltstone, partly bentonitic; con, and diatom fragments, 18 weakly indurated. Some phos­ percent structureless pellets, 12 phatic pellets 1 2 0 36 percent shell and fish-bone 88. Sandstone, somewhat calcareous; fragments, 6 percent com­ indurated. Phosphatic pellets at pound pellets, 2 percent top. Small megafossils abun­ intraclasts, granule-size, sub- dant. Sample CA-7 from unit 1 1 0 33 rounded. Pellets, spheroids, 87. Siltstone, siliceous; contains regular to slightly irregular; phosphatic pellets, white, few. range from 0.09 mm to 0.35 Upper 2 ft (61 cm) of unit, mm in diameter; average diam­ bentonitic, broken; bentonite eter 0.17 mm; boundaries bed below it, 2 in. (5 cm). sharp; rims, rarely calcareous Sample CA-8 from unit 4 6 1 37 or secondary phosphate; few 86. Sandstone, very fine grained. nuclei incipiently calcitized. Phosphatic pellets, about 30 Some framework silicates percent. Some megafossils, incipiently altered to sericite or phosphatized. Top, possibly calcite. Samples CA-13, bentonitic; base, irregular, F1208-19, and El205-30 from sharp. Correlation unit P2. unit 1 10 0 56 Sample CA-9 from unit 1 0 0 30 77. Siltstone, slightly bentonitic, 85. Siltstone, siliceous; bentonitic(?) moderately indurated. Sample laminae. Sample CA-10 from CA-14 from this unit and four this and underlying unit 04010 underlying units 0 6 015 84. Siltstone, siliceous, slightly ben­ 76. Mudstone, phosphatic, pelletal, tonitic. Correlation unit SI 1 5 0 43 silty. Grains, subrounded, 83. Sandstone, very calcareous, poorly sorted; floating grains, poorly sorted. Phosphatic pel­ medium, rare. Framework, 13 lets, about 35 percent. Small percent quartz, 7 percent feld- Stratigraphic Sections 55 Upper Miocene Continued Upper Miocene Continued Santa Margarita Formation Continued Santa Margarita Formation Continued Upper phosphatic mudstone member Continued Upper phosphatic mudstone member Continued Thickness Unit No. Thickness Ft In M Cm Ft In M Cm spar, and 28 percent phosphate; hematite, 35 percent struc- matrix, 50 percent clay miner­ tureless pellets, 5 percent fossil als, and 2 percent iron oxide; fragments, and 4 percent primarily montmorillonite and medium- to granule-size, sub- disseminated illite and rounded intraclasts. Pellets, hematite; accessory minerals spheroids, regular to slightly include zircon, hematite, mus- irregular; range from 0.08 mm covite, magnetite, and chlorite. to 0.45 mm in diameter; aver­ Phosphatic framework, 50 per­ age 0.18 mm, boundaries, cent pellets with noncentered sharp; protruding grains, rare; inclusions and 7 percent pellets rims, siliceous, very rare; com­ with centered inclusions of pressed deformation, rare, and quartz and lesser amounts of nuclei commonly incipiently feldspar, diatom fragments, calcitized. Framework grains in magnetite, and rarely mus- early stages of altering to covite, 40 percent structureless sericite, common, and calcite, pellets and 3 percent shell frag­ rare. Samples CA-17, ments. Pellets, spheroids; range F1208-20, and E1205-31 from from 0.08 to- 0.40 mm in unit 1 2 0 36 diameter; average diameter 69. Porcellanite, indurated, brown- 0.20 mm; boundaries, moder­ stained. Sample CA-18 from ately sharp to fuzzy. unit 3617 Compound pellets, common, 68. Phosphorite and phosphatic especially in pellet-supported mudstone. Upper half of unit, areas where they may be 35 percent phosphatic pellets; slightly deformed and incased lower half, 55 percent. Sample by secondary phosphate. Ben- CA-19 from this and underly­ tonitic siltstone, 4 in. (10 cm) ing five units 1 2 0 36 zone, weakly indurated, 1.5 ft 67. Siltstone, bentonitic 0103 (46 cm) above base. Sample 66. Mudstone, brownish-gray to gray. F1208-18 from unit 40 Phosphatic pellets, 15 per- 75. Bentonite 5 cent(?) 1 10 0 56 74. Siltstone and porcelaneous silt- 65. Siltstone, slightly bentonitic, stone, some phosphatic pellets; olive-gray. Phosphatic pellets, slightly bentonitic at top 30 percent 0 6 0 15 73. Siltstone, porcelaneous 64. Siltstone, porcelaneous, cal­ 72. Phosphorite, 75 percent pellets, careous, light-gray. Phosphatic sandy, very fine grained; 35 pellets, 5 percent 0 6 0 15 percent pellets in upper 4 in. 63. Bentonite and bentonitic siltstone 0 .5 0 13 (10 cm). Sample CA-15 from 62. Siltstone, phosphatic, siliceous. unit 1 8 0 51 Phosphatic pellets, 30 percent. 71. Siltstone, siliceous, calcareous, Sample CA-20 from this and partly white stained; indurated. underlying unit 0 7 0 18 Some phosphatic pellets. Cor­ 61. Phosphorite, sandy, gray. Phos­ relation unit S2. Sample CA-16 phatic pellets, 60 percent. from unit 2 0 0 61 Correlation unit P3 1 5 0 43 70. Sandstone, very phosphatic, 60. Mudstone, siliceous. Phosphatic muddy. Grains, fine, sub- pellets; about 35 percent. For- angular to subrounded, poorly aminiferal molds. Sample sorted, randomly oriented; CA-21 from this and two floating grains, as large as underlying units 1 2 0 36 granule size. Framework, 17 59. Mudstone, siliceous. Phosphatic percent quartz, 10 percent feld­ pellets, 25 percent A 0 10 0 25 spar, 1 percent lithic 58. Sandstone, light-gray, very fine fragments, and 38 percent grained; semifriable to friable. phosphate; matrix, 33 percent Phosphatic pellets, average 30 clay minerals. Phosphatic percent 1 10 0 56 framework, 42 percent pellets 57. Mudstone, slightly phosphatic, with noncentered inclusions purplish-brown. Contains and 16 percent pellets with diatoms. Sample CA-22 from centered inclusions of quartz, unit 3 0 0 91 lithic fragments, feldspar, 56. Siltstone, siliceous, light-gray. diatom fragments, zircon, and Phosphatic pellets, 40 percent. 56 Stratigraphic Sections Upper Miocene Continued Upper Miocene Continued Santa Margarita Formation Continued Santa Margarita Formation Continued Upper phosphatic mudstone member Continued Upper phosphatic mudstone member Continued Unit No. Thickness Unit No. Thickness Fl In M Cm In M Cm Sample CA-23 from this and phosphate; matrix, 61 percent underlying unit Oil 0 28 clay minerals, and 16 percent 55. Sandstone, very phosphatic, silty, iron oxide (concentrated in muddy, light-gray. Grains, sub- patches as large as 6 mm angular to subrounded, poorly across); accessory minerals, 1 sorted, randomly oriented; percent, include hematite, mus- floating grains, as large as covite, chlorite, magnetite, and coarse-size, rare. Framework, glauconite. Phosphatic pellets, 21 percent quartz, 9 percent irregular ellipsoidal shape; feldspar, 1 percent lithic frag­ range from 0.12 to 0.6 mm in ments, 36 percent phosphate; diameter; boundaries fuzzy; matrix, 33 percent clay miner­ ^grains protrude. Grains and als. Phosphatic framework, 27 pellet nuclei incipiently cal- percent pellets with noncen- citized. Correlation unit S3. tered inclusions and 21 percent Sample F1208-23 from unit 1 6 0 46 pellets with centered inclusions 51. Mudstone, phosphatic, pelletal, of quartz, feldspar, hematite, sandy, silty. Grains, angular to and diatom fragments, 42 per­ subrounded, poorly sorted, ran­ cent structureless pellets, 5 domly oriented; floating percent compound pellets, 3 grains, as large as coarse size, percent granules without grain rare. Unit faintly laminated by inclusions, and 2 percent shell pellet-rich (pellet supported) fragments. Pellets, spheroidal and pellet-poor zones. Veins to ellipsoidal; average diameter rarely filled with hematite. 0.17 mm; boundaries, mostly Framework, 14 percent quartz, sharp; rims rarely calcareous; 9 percent feldspar, 27 percent secondary rims commonly phosphate; matrix, 47 percent phosphatic; grains rarely pro­ clay minerals; accessory miner­ trude; peripheries slightly als, 3 percent. Phosphatic deformed rarely; nuclei and framework, 45 percent pellets grains rarely incipiently cal- with noncentered inclusions citized. Sample F1208-21 from and 11 percent pellets with unit 1 0 0 30 centered inclusions of quartz, 54. Claystone, phosphatic, siliceous; feldspar, and diatom frag­ laminations, faint, wavy. ments, 23 percent structureless Grains, sand-size, subangular pellets, 6 percent compound to subrounded, medium-sorted; pellets, 4 percent pebble frag­ long axis subparallel to lami­ ments with grain inclusions, nae. Floating grains, as large and 11 percent shell fragments. as coarse-size, very rare. Pellets, spheroids, regular to Framework, 6 percent quartz, irregular; range from 0.08 mm and 2 percent feldspar; matrix, to 0.50 mm in diameter; 92 percent clay minerals. Phos­ boundaries, sharp to fuzzy; phatic framework, noncentered rims, siliceous and secondarily pellets and structureless pellets phosphatic, rare; commonly very rare. X-ray diffraction flattened compressionally; pro­ analysis indicates matrix has truding grains common; nuclei, abundant opal-CT and small incipiently calcitized and amounts of montmorillonite hematitized. X-ray diffraction and illite. Microfossils abun­ analysis indicates major com­ dant; some with original ponent of matrix opal-CT and skeletal material. Sample minor components Fl 208-22 from unit. Sample montmorillonite and illite. CA-24 from this and underly­ Sample Fl208-24 from unit 0 II 0 28 ing unit 2 5 0 74 50. Claystone, siliceous, silty; poorly 53. Siltstone, bentonitic(?); moder­ sorted. Similar to unit 52. ately indurated 0205 Sample CA-25 from unit 3 1 0 94 52. Claystone, silty, siliceous; lamina­ 49. Sandstone, very fine grained, tions, crude, wavey. Grains, white; friable to semifriable. ' silt- and sand-size, angular to Phosphatic pellets, 30 percent. subangular, poorly sorted. Sample CA-26 from unit 1 5 0 43 Framework, 14 percent quartz, 48. Porcellanite. Sample CA-27 from 7 percent feldspar, 1 percent unit 3 0 0 91 Stratigraphic Sections 57 Upper Miocene Continued I Upper Miocene Continued Santa Margarita Formation Continued Santa Margarita Formation Continued Upper phosphatic mudstone member Continued Upper phosphatic mudstone member Continued Thickness Unit No. Thickness Ft In M Cm Ft In M Cm 47. Sandstone, very fine grained, or grained. Phosphatic pellets, 15 siltstone, light-gray, greenish percent 6 0 1 83 color in lowest part. Phosphatic 23. Porcellanite and porcelaneous pellets, 25 percent. Sample siltstone 6 4 1 93 CA-28 from unit 2 8 0 81 22. Bentonite, grades downward to 46. Porcellanite, indurated. Sample sandstone, tan, bentonitic(?), CA-29 from unit 2 10 0 86 slightly phosphatic 0 6 0 15 45. Mudstone siliceous. Phosphatic 21. Sandstone, slightly phosphatic, pellets, about 40 percent. Sam­ fine-grained; indurated 0 5 0 13 ple CA-30 from this and seven 20. Sandstone, calcareous, slightly underlying units 0 6 0 15 phosphatic, conglomeratic. 44. Sandstone, siliceous. Phosphatic' Fossiliferous pellets, 40 percent 0 6 0 15 19. Siltstone 43. Bentonite 0103 18. Bentonite 42. Porcellanite and silty porcellanite, 17. Siltstone and sandstone, sili­ slightly phosphatic; may be ceous, very fine grained. faulted. Correlation unit S4 2 1 0 64 Thickness approximate 57 1 70 41. Phosphorite, brown, friable, 70 16. Siltstone, siliceous 1 8 0 51 percent pellets. Fossil frag­ 15. Bentonite trace ments at base. Base irregular 0 10 0 25 14. Siltstone. Some phosphatic pel­ 40. Siltstone, olive-brown. Phosphatic lets 1 1 0 33 pellets, dark-brown, 5 percent 13. Bentonite trace in upper half and 10 percent in 12. Siltstone and sandstone, very fine lower half grained. Slightly phosphatic 2 0 0 61 39. Sandstone, very phosphatic, feld- 11. Bentonite trace spathic, very fine grained; 10. Sandstone, very phosphatic, very friable to semifriable. Phos­ fine grained. Phosphatic pel­ phatic pellets, dark-brown, 45 lets, 50 percent. Very uncertain percent. Top, gradational; base, thickness 2 8 0 81 sharp. Correlation unit P4. 9. Limestone, white 0 7 0 18 Sample CA-31 from unit 1 10 0 56 8. Siltstone; phosphatic pellets, 10 38. Porcellanite, calcareous or dolo- percent 0 4 0 10 mitic. Possibly faulted 1 2 0 36 7. Sandstone, fine- to very fine 37. Bentonite 0103 grained. Phosphatic pellets, 40 36. Sandstone, very fine grained. percent 0 10 0 25 Phosphatic pellets, about 10 6. Porcellanite 1 11 0 58 percent 1 4 0 41 5. Siltstone, porcelaneous 1 1 0 33. 35. Siltstone and sandstone, feld- 4. Sandstone, very fine grained. spathic, very fine grained. Phosphatic pellets, 10 percent 1 7 0 48 Megafossils common 3719 3. Bentonite trace 34. Porcellanite 0 11 0 28 2. Siltstone; slightly phosphatic 2 8 0 81 32. Bentonite trace 1. Bentonite(?) trace 31. Porcellanite, indurated. Some Total measured thickness of upper megafossils, round 4 2 1 27 phosphatic mudstone member 192 8 58 72 30. Siltstone and sandstone, feld- spathic, very fine grained. Trench 297 Phosphatic pellets, about 10 percent 0 6 0 15 (Measured by H. D. Gower, 1964; E and F numbered samples described 29. Sandstone, phosphatic, feld- petrographically by T. L. Vercoutere). spathic, very fine grained. Phosphatic pellets, 40 percent 0 7 0 18 LOCATION: NW/4NW/4 sec. 35, T. 10 N., R. 27 W. (S.S.B. & M.) in the ' 28. Mudstone and siltstone, por- New Cuyama, California quadrangle celaneous; about 10 percent ATTITUDE OF BEDDING: Approximately N. 85° W. 65° S. phosphatic pellets 2 8 0 81 TREND OF TRENCH: Approximately north-south. Due to complex struc­ 27. Bentonite. Sample CA-35 from ture, thickness and attitude of Stratigraphic units 126-131 is approximate. unit 1 4 0 41 26. Siltstone, indurated. No phos­ Upper Miocene: phatic pellets 3 0 0 91 Santa Margarita Formation: 25. Siltstone, grades downward to Upper phosphatic mudstone member: very fine grained sandstone. Unit No. Thickness Phosphatic pellets, 10 percent 1 1 0 33 Ft in M cm 24. Sandstone, light-gray, very fine 131. Siltstone, grades downward into very fine grained sandstone or 58 Stratigraphic Sections Upper Miocene Continued Upper Miocene Continued Santa Margarita Formation Continued Santa Margarita Formation Continued Upper phosphatic mudstone member Continued Upper phosphatic mudstone member Continued Unit No. Thickness Unit No. Thickness Ft In M Cm Ft In M Cm siltstone, light-gray. Phosphatic 112. Bentonite and gypsum trace pellets, about 2 percent. Lower 111. Sandstone, silty, light-gray, very part, fossiliferous. Attitude, N. fine grained. Phosphatic pel­ 55° E. 40° SE., good 3412 lets, about 20-25 percent 2 4 0 71 130. Bentonite and bentonitic siltstone; 110. Siltstone, siliceous, and por- dark-greenish-gray to light- cellanite 0 7 0 18 olive-gray 0 8 0 20 109. Porcellanite; phosphatic pellets, 129. Siltstone and very fine grained less than 10 percent 2 6 0 76 sandstone, light-gray. Phos­ 108. Gypsum and bentonite 0 .2 0 .6 phatic pellets, about 3 percent. 107. Porcellanite, indurated. Phos­ Thickness uncertain 0 7 0 18 phatic pellets, rare * 0 8 0 20 128. Sandstone, very fine grained, or 106. Siltstone, sandy, siliceous. Quartz siltstone, light-gray. Unit con­ grains, coarse, common. Phos­ tains about 15 percent phatic pellets, about 25 phosphatic pellets and small percent, most abundant at base. nodules as large as 1/4 in. (0.6 Megafossils common Oil 0 28 cm). Megafossils. Unit looks 105. Siltstone, siliceous light-gray. like a till megascopically Fish scales very abundant. because of poor sorting of Base of unit, up dip, appears phosphatic pellets and nodules 1 0 0 30 phosphatic; may be faulted 1 0 0 30 127. Bentonite, bentonitic siltstone, 104. Bentonite 0 ' 1 0 3 and very fine grained sand­ 103. Siltstone, siliceous. Fish scales, stone; poorly sorted. Unit very abundant 1 8 051 contains several percent of 102. Sandstone, very fine grained, and coarse quartz grains, phos­ sandy siltstone. Phosphatic pel­ phatic pellets, and nodules. lets, 50 percent 1 4 0 41 Possible fault zone at top. 101. Bentonite and gypsum 0 .2 0 .6 Thickness approximate 0 11 0 28 100. Sandstone, very fine to fine­ 126. Sandstone, very fine grained, and grained, and siltstone, sandy, siltstone. Unit contains about light-gray at top, brown at base. 10 percent phosphatic pellets Phosphatic pellets, 50 percent 1 4 0 41 and small nodules. Pectens, 99. Siltstone, siliceous 1 1 0 33 original shells, abundant. Lower 5 in. (13 cm) of unit, silty. Attitude: N. 8° E. 30° SE. STRATIGRAPHIC UNITS 99 THROUGH 103 ARE REPEATED BY at top (poor); N. 15°W. 29° FOLDING NE. at base (poor) 2 4 0 71 125. Siltstone, light-gray. Fish scales, 98. Sandstone, fine-grained, and silt- common. Attitude: N. 55° E. stone, phosphatic, light-gray. 40° SE. (good) 0 5+ 0 134 Phosphatic pellets, 40 percent. 124. Bentonite 0 .4 0 .9 Correlation unit PI. Sample 123. Siltstone, light-gray 0 7 0 18 PI-297 from unit 0 10+ 0 25 122. Bentonite trace 97. Siltstone, siliceous; moderately 121. Siltstone, light-gray to light-tan 1 5 0 43 indurated; highly fractured. 120. Bentonite 0102 Two, thin bentonite beds 2.3 ft 119. Siltstone, slightly phosphatic, (70 cm) below top and 1 ft (30 light-gray. Megafossils scat­ cm) above base. Porcellanite, tered. Base, coarser grained 2 0 0 61 indurated, 5 in. (13 cm) bed 118. Bentonite and gypsum 0 .2 0 .6 containing abundant forami- 117. Siltstone to very fine grained niferal molds 2 ft (51 cm) sandstone, light-gray. Phos­ above base; 1 ft (30 cm) bed at phatic pellets, about 15 base. Thickness approximate 5111 80 percent, more abundant at base 2 0 0 61 96. Bentonite 0 .5 0 1.2 116. Gypsum and bentonite 0 .2 0 .6 95. Siltstone, porcelaneous. Base, 115. Sandstone, silty, light-gray, very phosphatic, 20 percent pellets fine grained. Phosphatic pel­ in lower 2 in. (5 cm) 0 6 0 15 lets, about 15 percent, most 94. Sandstone, phosphatic, brown, abundant at base 1 11 0 58 poorly sorted; 35 percent pel­ 114. Bentonite trace lets; phosphatized fossils, 113. Sandstone, light-gray, very fine small 0 4 0 10 grained. Phosphatic pellets, 20 93. Siltstone, siliceous. Mollusk frag­ percent; some nodules 1 5 0 43 ments, abundant, small 0 4 0 10

Stratigraphic Sections 59 Upper Miocene Continued Upper Miocene Continued Santa Margarita Formation Continued Santa Margarita Formation Continued Upper phosphatic mudstone member Continued Upper phosphatic mudstone member Continued Thickness Unit No. Thickness Ft In M Cm In M Cm 92. Porcellanite 1 4 0 41 86. Sandstone, calcareous, siliceous, 91. Bentonite 0 .6 0 1.5 white; indurated. Some phos­ 90. Porcellanite 2 6 0 76 phatic pellets. Coquina at top 0 4 010 89. Phosphorite, sandy, brown; friable 85. Siltstone, sandy, siliceous, light- to moderately indurated. Phos­ gray to brown. Phosphatic pel­ phatic pellets, 70 percent. lets, about 15 percent. Forami­ Megafossils, rare, at top. Cor­ niferal casts abundant at top. relation unit P2. Sample Unit grades into overlying unit 0 8 0 20 P2-297 from unit 1 0 0 30 84. Siltstone, siliceous 2 4 0 71 88. Siltstone, siliceous, sandy. Phos­ 83. Bentonite 0103 phatic pellets, 10 percent, in 82. Siltstone, siliceous 0 4 010 lower half. Correlation unit S1 1 2 0 36 81. Bentonite 0103 87. Grainstone and calcareous 80. Siltstone, siliceous, or por- mudstone, light-gray; very cellanite; somewhat sharp contact. Grainstone, very slickensided 0 5 0 13 phosphatic, very poorly sorted. 79. Bentonite 0205 Contains 14 percent quartz and 78. Siltstone, siliceous 0 4 010 feldspar grains, subangular to 77. Bentonite trace rounded, ranging from 0.07 to 76. Siltstone, siliceous. Sandy and 0.80 mm; 6 percent shell frag­ phosphatic at base 2 8 0 81 ments, calcareous, as long as 4 75. Mudstone, siliceous, moderately mm; 6 percent shell fragments, phosphatic. Phosphatic pellets, phosphatic, as long as 2 mm, 15 percent 1 0 0 30 partially replaced by silica 74. Mudstone, silty to sandy, moder­ (common); 5 percent pellets, ately phosphatic. Grains, very spheroidal, ranging from 0.25 fine, subangular to subrounded, mm to 0.60 mm in diameter, poorly sorted, randomly ori­ with centered (rare) and non- ented; floating grains, as large centered (common) inclusions as medium-size, rare; com­ of quartz, feldspar, diatom monly altered to sericite and fragments, and foraminifers; 10 rarely altered to calcite. Frame­ percent pellets, spheroidal, work, 17 percent quartz, 9 structureless, partially replaced percent feldspar, 1 percent by silica (rare), rarely rimmed chert, 19 percent phosphate; sharply with iron-oxide; 16 per­ matrix, 52 percent clay miner­ cent intraclasts with inclusions als; accessory minerals, 2 of pellets, carbonate shell frag­ percent include muscovite, ments, iron oxide, mineral magnetite, hematite, chlorite, grains, foraminiferal tests, and and zircon. Phosphatic frame­ diatom fragments; and 25 per­ work, 16 percent pellets with cent nodules without noncentered inclusions and 26 inclusions; shape, variable, percent pellets with centered mostly elongated, ranging from inclusions of quartz, feldspar, 0.03 to 3 mm in diameter; and diatom fragments; 47 per­ matrix of 25 percent carbonate cent structureless pellets; 11 minerals and 1 percent iron percent fish bones and shell oxide. Mudstone, calcareous, fragments, less than 1 mm slightly phosphatic; contains across. Pellets, spheroidal, approximately 5 percent sub- approximately 0.18 mm in angular silt to very fine sand diameter; boundaries, sharp to size fragments, 10 percent fuzzy; rims commonly sili­ foraminiferal tests infilled with ceous; protruding grains very sparry calcite, (some partially rare; very little peripheral silicified), 3 percent phosphatic deformation; nuclei rarely pellets, spheroidal, struc­ incipiently calcitized. Sample tureless, average 0.10 mm, 1 F1208-42 from unit 1 11 0 58 percent phosphatized shell 73. Mudstone, sandy, moderately fragments, less than 1 mm phosphatic; thickly laminated. long; matrix of 3 percent iron Grains, fine, subangular to sub- oxide and 78 percent micrite rounded, poorly sorted, (partly cement). Base sharp, randomly oriented. Framework, very irregular. Sample 19 percent quartz, 7 percent F1208-50 from unit 1 8 0 51 feldspar, and 18 percent phos- 60 Stratigraphic Sections Upper Miocene Continued Upper Miocene Continued Santa Margarita Formation Continued Santa Margarita Formation Continued Upper phosphatic mudstone member Continued Upper phosphatic mudstone member Continued Unit No. Thickness Unit No. Thickness In M Cm In M Cm phate; matrix, 50 percent clay fragments; boundaries fuzzy. minerals and 4 percent iron Few foraminiferal tests present. oxide; accessory minerals, 2 Correlation unit S2. Sample percent; include glauconite, E1204-1 from unit 2 7 0 79 muscovite, chlorite, magnetite, 61. Sandstone, silty, siliceous; very and zircon. Phosphatic frame­ fine grained, poorly sorted. work, 28 percent pellets with Phosphatic pellets, 15 percent 1 6 0 46 noncentered inclusions and 22 60. Siltstone, siliceous, very percent pellets with centered diatomaceous. Density fairly inclusions of quartz, feldspar, low. Fossil casts, abundant muscovite, magnetite, zircon, weathered 2 0 0 61 shell fragments (very rare), and 59. Phosphorite, light-gray to brown. diatom fragments, 49 percent Phosphatic pellets, 50 percent structureless pellets, and 1 per­ in upper half of unit; 70 per­ cent shell fragments, 0.5 mm cent in lower half 1 2 0 36 long. Pellets, spheroids, reg­ 58. Siltstone, bentonitic, and shale, ular to slightly irregular; range siliceous. Bentonite in lower 2 from 0.08 to 0.45 mm in in. (5 cm) of base 0 7 0 18 diameter; average diameter 57. Siltstone, siliceous. Unit sheared. 0.20 mm; boundaries, sharp, Phosphatic pellets, 20 percent. rarely fuzzy; rims, iron oxide, May contain bentonite 111 0 58 rare; periphery commonly 56. Phosphorite, tan, friable. Phos­ deformed slightly; nuclei rarely phatic pellets, 70 percent. incipiently calcitized. Sample Megafossils, poorly preserved, F1208-51 from upper half of rare. Correlation unit P3. Sam­ unit 1 0 94 ple P3-297 from unit 1 5 10 43 72. Siltstone, bentonitic(?) in places, 55. Siltstone, siliceous. Phosphatic olive-gray; weakly indurated 1 2 0 36 pellets, 5 percent 2 7 0 79 71. Sandstone, very fine grained, 54. Mudstone, siliceous. Phosphatic poorly sorted. Phosphatic pel­ pellets, 20 percent 1 1 0 33 lets, 10 percent. Megafossils, 53. Siltstone, siliceous, slightly phos­ abundant. Lower half, cal­ phatic 1 7 0 48 careous 0 6 15 52. Mudstone. Phosphatic pellets, 20 70. Siltstone, slightly bentonitic 0 6 15 percent. Thickness uncertain 1 0 0 30 69. Bentonite 0 .6 1.5 51. Porcellanite, diatomaceous, 68. Siltstone, slightly bentonitic 2 2 66 slightly phosphatic. Density, 67. Bentonite 0 .6 1.5 low. Thickness uncertain 1 4 041 66. Siltstone, siliceous 0 6 15 50. Phosphorite, very sandy, muddy, 65. Bentonite, and bentonitic siltstone 0 .5 1.5 light-tan; friable to semifriable. 64. Siltstone, sandy, light-gray. Phos­ Phosphatic pellets, 70 percent. phatic pellets, 10 percent 0 6 0 15 Quartz grains, coarse, abun­ 63. Sandstone, brown to tan to gray, dant ' 0 7 0 18 very fine to fine grained. Phos­ 49. Porcellanite 2 2 0 66 phatic pellets, 45 percent. 48. Mudstone, phosphatic, sandy, Large mammal(?) bones abun­ pelletal. Grains, fine, sub- dant. Base, sharp, irregular 2 0 0 61 angular to subrounded, poorly 62. Mudstone, calcareous, very sorted, randomly oriented; slightly phosphatic. Grains, floating grains as large as gran­ subangular silt, and fine to very ule size. Partly grain supported. fine sand, poorly sorted. Phosphatic pebble fragments as Framework, 4 percent quartz, 2 large as 2.5 mm. Framework percent feldspar, 1 percent grains commonly altered to phosphatic pellets, 10 percent sericite or rarely calcite. recrystallized shell fragments Framework, 18 percent quartz, including diatom frustules; 8 percent feldspar, and 31 per­ matrix, 82 percent carbonate; cent phosphatic; matrix, 40 accessory minerals, 1 percent, percent clay minerals and 2 include hematite, glauconite, percent carbonate minerals, and magnetite. Pellets, spher­ accessory minerals, 1 percent, oids, regular to irregular; range include chlorite, magnetite, zir­ from 0.09 mm to 0.21 mm in con, hematite, and muscovite. diameter; structureless or with Iron oxide commonly concen­ inclusions of quartz or diatom trated in approximately 1 mm Stratigraphic Sections 61 Upper Miocene Continued Upper Miocene Continued Santa Margarita Formation Continued Santa Margarita Formation Continued Upper phosphatic mudstone member Continued Upper phosphatic mudstone member Continued Unit No. Thickness Ft In M Cm Ft In M Cm patches. Phosphatic framework, relation unit S3 1 3 0 38 30 percent pellets with noncen- 44. Mudstone, sandy, slightly phos­ tered inclusions and 16 percent phatic. Grains, fine, subangular pellets with centered inclusions to subrounded, poorly sorted; of quartz, feldspar, zircon, and long axis oriented subparallel diatom fragments; 25 percent to crudely laminated sandy structureless pellets, 3 percent mudstone layers and mudstone compound pellets, 10 percent layers. Framework, 16 percent nodules with grain inclusions quartz, 8 percent feldspar, and (including grapestone), 3 per­ 9 percent phosphate; matrix, cent nodules without grain 56 percent clay minerals, 1 inclusions, and 13 percent shell percent carbonate minerals, and fish-bone fragments less and 9 percent iron oxide, than 1 mm long. Pellets, spher­ accessory minerals, 1 percent, oids, regular to irregular; range include chlorite, magnetite, zir­ from 0.08 mm to 0.40 mm in con, and muscovite. Phosphatic \ diameter; average diameter framework, 22 percent pellets 0.20 mm; boundaries, very with noncentered inclusions sharp; protruding grains rare; and 20 percent pellets with commonly slightly deformed centered inclusions of quartz, peripherally at contacts with feldspar, chlorite and diatom other pellets or grains; nuclei fragments, 47 percent struc­ incipiently calcitized. Sample tureless pellets, 8 percent shell F1208-48 from unit. Plate 6 N fragments less than 1 mm long, from unit 1 1 0 33 and 5 percent compound pel­ 47. Claystone, slightly phosphatic, lets. Pellets, spheroidal; silty; laminated, crudely len­ average diameter 0.17 mm; ticular, patches of disseminated boundaries sharp to fuzzy; hematite parallel to laminae. many rimmed with secondary Grains, angular to subrounded, phosphate and rarely rimmed poorly sorted, subparallel long with silica; nuclei rarely sec­ axes; floating grains, as large ondarily calcitized. Commonly as medium-size rare. Grains stained with hematite. Sample rarely partially calcitized; Fl208-46 from unit 0 8 0 20 quartz grains rarely opalized. 43. Mudstone, phosphatic, sandy; si­ Framework, 11 percent quartz, liceous matrix; fractured. 11 percent feldspar, 5 percent Grains fine to very fine phosphate; matrix, 68 percent / grained, angular to sub- clay minerals, 3 percent iron rounded, medium-sorted; oxide, 2 percent apatite; floating grains, as large as accessory minerals include coarse size, rare; grains com­ glauconite, zircon, muscovite, monly incipiently calcitized, and chlorite. Phosphatic frame­ especially in fractures. Frame­ work, 66 percent structureless work, 15 percent quartz, 11 pellets, 24 percent pellets with percent feldspar, and 35 per­ noncentered inclusions of cent phosphate; matrix, 32 quartz and diatom fragments, 5 percent clay minerals, and 2 percent nodules, and 5 percent percent carbonate minerals; shell fragments. Pellets, spher­ accessory minerals, 1 percent, oidal to pear-shaped; range include chlorite, zircon, mag­ from 0.06 to 0.25 mm in netite, and hematite. diameter; average 0.13 mm; Phosphatic framework, 25 per­ boundaries fuzzy to sharp, and cent pellets with noncentered protruding grains rare. Sample inclusions and 22 percent pel­ Fl208-47 from unit 0 8 0 20 lets with centered inclusions of 46. Bentonite 0205 quartz, feldspar, and diatom Fault zone; small, little dis­ fragments, 40 percent struc­ placement; N. 45° W. 78° SW. tureless pellets, 4 percent Questionable correlation of compound pellets, 6 percent bentonite bed (stratigraphic nodules without inclusions, unit 46) across fault. and 3 percent shell fragments 45. Porcellanite, and porcelaneous less than 1 mm long. Pellets, siltstone; contains fossils. Cor- spheroids, regular to slightly 62 Stratigraphic Sections Upper Miocene Continued Upper Miocene Continued Santa Margarita Formation Continued Santa Margarita Formation Continued Upper phosphatic mudstone member Continued Upper phosphatic mudstone member Continued Unit No. ' Thickness Unit No. Thickness Ft In M Cm Ft In M Cm irregular, range from 0.12 mm unit. Sample El203-18 from to 0.28 mm in diameter; unit. Phosphatic oolith (pi. 6 boundaries, sharp; commonly //) and phosphatic mudstone rimmed with secondary phos­ intraclasts (pi. 6 L) from unit 1 0 0 30 phate; commonly slightly 34. Porcellanite, phosphatic 1 0 0 30 deformed peripherally at con­ 33. Bentonite 0 .6 0 1.5 tacts with other pellets. Oolitic 32. Porcellanite, diatomaceous; very structure, very rare. Sample light weight. Some flattish El203-22A from unit 0 11 0 28 clams and fish scales. Indistinct 42. Siltstone, porcelaneous 2 2 0 66 phosphatic pellets forming(?) 41. Sandstone, very fine grained. in upper part. Correlation unit Phosphatic pellets, 20 percent. S4 2 1 0 64 Some burrows(?) 4 0 41 31. Sandstone, very fine to fine­ 40. Siltstone, porcelaneous 205 grained; friable to semifriable. 39. Sandstone, very fine grained, and Phosphatic pellets, 20 percent 111 0 58 siltstone 0 5 0 13 30. Porcellanite. Fragments of phos­ 38. Porcellanite, and porcelaneous phatic sandstone, spherical, siltstone; locally phosphatic irregularly rounded, as much as 37. Phosphorite, with irregular, 3 in. (8 cm) long 0 5 0 13 slightly phosphatic, mudstone 29. Bentonite(?) 0 .1 0 .3 laminations. Phosphatic pel­ 28. Porcellanite 0 10 0 25 lets, 60 percent. Upper 6 in. 27. Sandstone and siltstone. Phos­ (15 cm) of unit, phosphatic phatic pellets, 25 percent. porcellanite, 30 percent phos­ Base, sharp, irregular. Correla­ phatic pellets. Basal 2 in. (5 tion unit P4. Sample P4-297 cm) of unit, sandy, friable 1 1 0 33 from unit 0 11 0 28 36. Porcellanite, phosphatic, 30 per­ 26. Porcellanite, slightly calcareous, cent phosphatic pellets 0 6 0 15 white, indurated. Fossil molds, 35. Phosphorite, sandy, fine- to very very abundant 0 10 0 25 fine grained. Small pebbles, 25. Bentonite trace common. Phosphatic pellets, 24. Mudstone, phosphatic, pelletal; medium-sorted. Grains, siliceous matrix. Grains, angular to subrounded; floating angular to subangular, poorly grains, as large as coarse size, sorted, randomly oriented. common. Framework, quartz Framework, 8 percent quartz, 4 (common), feldspar (common), percent feldspar, 25 percent phosphate (abundant); matrix, phosphate; matrix, 59 percent siliceous clay minerals (com­ clay minerals, and 4 percent mon), carbonate (rare); iron oxide. Phosphatic frame­ accessory minerals include work, 38 percent pellets with chlorite, zircon, magnetite, and noncentered grain inclusions muscovite. Phosphatic frame­ and 4 percent pellets with cen­ work, pellets with centered and tered grain inclusions of noncentered inclusions of quartz, feldspar, zircon, chert, quartz, feldspar, diatom frag­ and diatom debris, 28 percent ments, and very rarely zircon, structureless pellets, 4 percent structureless pellets, ooliths, compound pellets, 8 percent compound pellets, and shell nodules with grain inclusions, fragments. Pellets, spheroids, 4 percent structureless nodules, regular to slightly irregular, and 16 percent shell fragments range from 0.12 mm to 0.30 as long as 4 mm. Pellets, mm in diameter; boundaries, spheroids, regular to irregular, sharp (abundant); rims, sili­ range from 0.10 mm to 0.35 ceous (rare); protruding and mm in diameter; boundaries, intruding grains (common); sharp; protruding grains com­ slightly deformed peripherally mon; compressional flattening (common). Upper and middle common; nuclei rarely incip- part of unit, small-scale iently calcitized. Many pellets crossbedding and burrows; concentrated in burrows with much of basal unit, reddish- an iron-oxide matrix. Few brown, friable. Mammal(?) megafossils in unit. Phos­ bones common at base. Some phorite pebble, pelletal, 1/4 in. distinct burrows in underlying (6 mm) rare. Sample El203-16 Stratigraphic Sections 63 Upper Miocene Continued Upper Miocene Continued Santa Margarita Formation Continued Santa Margarita Formation Continued Upper phosphatic mudstone member Continued Upper phosphatic mudstone member Continued Unit No. Thickness

In M Cm h'l In M Cm from unit 0 11 0 28 boundaries, sharp to fuzzy; 23. Sandstone, very fine grained, and protruding grains rare; rarely siltstone, slightly phosphatic. rimmed with secondary phos­ Contains megafossils 1 5 0 43 phate; nuclei rarely incipiently 22. Siltstone, siliceous 2 10 0 86 calcitized; interior region rarely 21. Bentonite 0 .6 0 1.5 stained with iron oxide. Sam­ 20. Siltstone, siliceous 1 6 0 46 ple El 203-10 from unit 1 2 0 36 19. Siltstone, siliceous. Phosphatic 7. Sandstone, very fine grained. pellets, 3 percent 2 5 0 74 Upper half of unit brown, fria­ 18. Sandstone, very fine to fine­ ble; base, white to light-gray. grained, friable. Flame struc­ Phosphatic pellets, about 40 tures indicate sand moved from percent in upper 6 in. (15 cm); north to south. Phosphatic pel­ slightly phosphatic in lower lets, 10 percent phosphatic in part 46 upper 2 ft (61 cm); 15 percent 6. Bentonite 66 in lower 1 ft (30 cm). Chert 5. Porcellanite, white to light-green­ nodules near base. Base, irreg­ ish-gray. Phosphatic pellets, 5 ular. Thickness uncertain for percent, mostly very fine this unit and nine underlying grained 1 8 0 51 units; may be some faulting 3 0 0 91 4. Siltstone, sandy, brown. Phos­ 17. Siltstone, and minor porcelaneous phatic pellets, 5 percent 3 2 0 97 siltstone. Some phosphatic pel­ 3. Sandstone, brown, fine-grained, lets, fine-grained, pitted 6 4 1 93 friable to semifriable, sheared. 16. Bentonite, and bentonitic silt- Phosphatic pellets, 10 percent 5 6 1 68 stone. Fault zone 0 8 0 20 2. Sandstone, light-gray, fine­ 15. Siltstone, siliceous, slightly phos­ grained, friable. Phosphatic phatic at base 1 7 0 48 pellets, about 10 percent 2 7 0 79 14. Siltstone, sandy. Phosphatic pel­ 1. Sandstone, fine-grained, light- lets, 2 percent 1 0 0 30 gray. Not measured 13. Bentonite 0 4 0 10 Total measured thickness of the 12. Porcellanite. Phosphatic pellets, 5 u pper phosphatic mudstone percent Oil 0 28 member: 158 5 48 21 11. Sandstone, very fine grained. Phosphatic pellets, 25 percent. Trench 299 Lower part, broken and sheared, possibly faulted Oil 0 28 (Measured by H. D. Cower, 1964) 10. Sandstone, fine-grained. Phos­ phatic pellets, less than or LOCATION: NE'ANE'X. sec. 12, T. 9 N., R. 27 W. (S.B.B. & M.); equal to 10 percent 12 0 36 1,486,800 ft W. and 507,400 ft N., California plane coordinate system; in 9. Sandstone, very fine grained. the New Cuyama, California, quadrangle. Phosphatic pellets, 5 percent 1 2 0 36 ATTITUDE OF BEDDING: approximately N. 40° W., near vertical to 8. Claystone, slightly phosphatic; slightly overturned faintly laminated. Grains, Trench 299 is a double trench. Trenches trend approximately N. 50° E. and sand-size, angular to sub- are offset approximately 75 ft (23 m) along strike. Upper 107 stratigraphic angular, poorly sorted. units were measured in the eastern trench; lower 32 stratigraphic units Framework, 12 percent quartz, were measured in the western trench. 4 percent feldspar, 7 percent phosphate; matrix, 76 percent Eastern Trench clay minerals; accessory miner­ als, 1 percent, include chlorite, Upper Miocene: magnetite, zircon, and mus- Santa Margarita Formation: covite. Phosphatic framework, Upper phosphatic mudstone member: 30 percent pellets with noncen- Unit No. Thickness tered inclusions and 30 percent Fi in M c pellets with centered inclusions 139. Siltstone. Not measured of quartz, feldspar, hematite, 138.. Bentonite 0 1 0 and diatom fragments, 39 per­ 137. Porcellanite and siltstone, cal­ cent structureless pellets, and 1 careous, thin-bedded, percent shell fragments less indurated. White-stained than 1 mm long. Pellets, spher­ weathered surface 22 oids, regular to slightly 136. Sandstone, reddish-brown, very irregular; range from 0.10 mm fine grained. Phosphatic pel­ to 0.30 mm in diameter; lets, 10 percent 0 1 0

64 Stratigraphic Sections Upper Miocene Continued Upper Miocene Continued Santa Margarita Formation Continued Santa Margarita Formation Continued Upper phosphatic mudstone member Continued Upper phosphatic mudstone member Continued Unit No. Thickness Unit No. Thickness Ft In M Cm In M Cm 135. Porcellanite and siltstone, cal­ Phosphatic pellets, about 20 careous, thin-bedded, percent. Thickness uncertain 1 4 0 41 indurated. White-stained 108. Bentonite, bentonitic siltstone, weathered surface 4 5 I 35 porcellanite, and siliceous silt- 134. Siltstone, bentonitic, and ben- stone. Broken zone 6721 tonite 3617 107. Mudstone, porcelaneous; indu­ 133. Siltstone and mudstone. Phos­ rated. Phosphatic pellets, 5 phatic pellets, 10 percent 1 6 0 46 percent 0 7 0 18 132. Sandstone, orange-brown, very 106. Mudstone, porcelaneous; indu­ fine grained; friable. Phos­ rated. Phosphatic pellets, phatic pellets, 10 percent 04 0 10 average 40 percent 1 4 041 131. Bentonite, siltstone, and siliceous 105. Bentonite 0 .5 0 1.2 siltstone; very friable 0 8 0 20 104. Porcellanite; indurated. Phos­ 130. Siltstone, siliceous, locally phos­ phatic pellets, probably phatic; moderately indurated. average 5 percent 2 0 061 Fracture, blocky 5 8 1 33 103. Siltstone, olive-gray; weakly 129. Mudstone, siliceous. Phosphatic indurated 0 4 0 41 pellets, 30 percent Oil 0 28 102. Porcellanite and porcelaneous 128. Bentonite 0205 mudstone, indurated 1 0 0 30 127. Siltstone, siliceous 010 0 25 101. Siltstone, siliceous, or tuff; 126. Bentonite trace weakly indurated in upper 1 in. 125. Siltstone, siliceous 0 11 0 28 (3 cm). Phosphatic at base 0 7 0 18 124. Phosphorite; phosphatic pellets, 100. Bentonite, bentonitic siltstone, 70 percent 0 8 0 20 and siltstone 1 8 051 123. Bentonite, phosphatic 0 6 015 99. Siltstone, siliceous. Some phos­ 122. Phosphorite; phosphatic pellets, phatic pellets, some may be 75 percent 0 8 0 20 bentonitic 2 0 0 61 121. Siltstone and siliceous siltstone 2 2 0 66 98. Bentonite 0 .6 0 1.5 120. Phosphorite. Phosphatic pellets, 97. Claystone; bentonitic(?). Phos­ 80 percent in unit except upper phatic pellets, 30 percent 0 4 0 10 4 in. (10 cm) where it is 40 96. Sandstone; tan to yellowish- percent. Correlation unit PI 1 1 0 33 brown, friable. Phosphatic pel­ 119. Siltstone, and siliceous siltstone. lets, 40 percent 2 0 0 61 Phosphatic pellets, about 5 per­ 95. Porcellanite, chalky; indurated to cent 2 0 6 61 very friable; weathers white. 118. Siltstone, bentonitic, and sil­ Probable bentonite bed, thin at iceous siltstone; weakly base. Thickness uncertain. This indurated 2 4 0 71 unit and five underlying units 117. Porcellanite, indurated 0 4 0 10 make up correlation unit S2 1 0 0 30 116. Bentonite, siltstone, and 94. Porcellanite; indurated 0103 weathered calcareous siltstone; 93. Bentonite 0103 weakly indurated. Some phos­ 92. Porcellanite; indurated 0 4 0 10 phatic pellets. Megafossils, 91. Bentonite 0 .6 0 1.5 rare 140 41 90. Porcellanite; indurated 0 5 0 13 115. Porcellanite, indurated 0 6 0 15 89. Mudstone, sandy at base. Phos­ 114. Siltstone, possibly bentonitic, phatic pellets, 40 percent 1 5 0 43 partly bentonite and weathered 88. Bentonite 0 .2 0 .6 calcareous siltstone; weakly 87. Porcellanite 1 4 0 41 indurated 3617 86. Porcellanite. Phosphatic pellets, 113. Porcellanite. Phosphatic pellets, 10 percent 04010 40 percent in lower 4 in. (10 85. Phosphorite, muddy, moderately cm) 070 18 indurated. Phosphatic pellets, 112. Phosphorite, sandy, brown, very 60 percent 1 0 0 30 fine grained; friable to semi- 84. Mudstone, porcelaneous. Phos­ friable. Phosphatic pellets, 70 phatic pellets, 10 percent 0 8 0 20 percent. Correlation unit P2 0 10 0 25 83. Bentonite and bentonitic siltstone, 111. Porcellanite, possibly calcareous, phosphatic; highly fractured. indurated. Correlation unit S1 0 7 0 18 Phosphatic pellets 20 percent 110. Porcellanite, broken, with thin, in upper half; 40 percent in irregular lenses of sandstone lower half 1 8 0 51 and phosphatic sandstone 1 0 0 30 82. Porcellanite; phosphatic pellets, 109. Sandstone, pale-yellowish-gray; 10 percent ' 0 10 0 25 very fine grained; very friable. 81. Phosphorite; phosphatic pellets,

Stratigraphic Sections 65 Upper Miocene Continued Upper Miocene Continued Santa Margarita Formation Continued Santa Margarita Formation Continued Upper phosphatic mudstone member Continued Upper phosphatic mudstone member Continued Unit No. Thickness Unit No. Thickness Ft In M Cm Ft In M Cm 80 percent. Base, sharp but 49. Porcellanite; slightly phosphatic 1 0 51 very irregular; amplitude of 48. Bentonite 0 0 1.5 grooves is 3 in. (8 cm). Sample 47. Porcellanite 2 0 79 CB-1 from unit. Correlation 46. Bentonite trace unit P3 1 4 0 41 45. Siltstone, siliceous. Phosphatic 80. Porcellanite; phosphatic pellets, nodules and pellets, about 5 10 percent v 0 10 0 25 percent 0 51 79. Bentonite 0 .6 0 1.5 44. Bentonite and siliceous siltstone; 78. Mudstone, siliceous; phosphatic broken zone 0 1 0 3 pellets, 5 percent 1 6 0 46 43. Porcellanite, indurated. Trace of 77. Bentonite(?) trace bentonite 10 in. (25 cm) above 76. Mudstone, siliceous; phosphatic base 0 43 pellets, 10 percent 0 5 0 13 42. Mudstone, siliceous. Phosphatic 75. Phosphorite, muddy, phosphatic pellets, 20 percent in upper 7 pellets, 70 percent 0 7 0 18 in. (18 cm); 40 percent in lower 74. Porcellanite 0205 unit 1 0 46 73. Bentonite 0 .2 0 .6 41. Bentonite 0 0 3 72. Mudstone, siliceous; phosphatic 40. Siltstone, siliceous. Phosphatic pellets, 5 percent 3 1 0 94 pellets, 5 percent 0 0 18 71. Bentonite 0 .6 0 1.5 39. Bentonite trace 70. Porcellanite, indurated 1 1 0 33 38. Siltstone, siliceous; indurated. 69. Mudstone, siliceous; phosphatic Phosphatic pellets, 5 percent 0 8 0 20 pellets, 20 percent 0 6 0 15 37. Phosphorite, sandy, yellowish- 68. Bentonite and very phosphatic brown; friable to semifriable. mudstone. Phosphatic pellets, Phosphatic pellets, 80 percent 1 0 0 30 average about 50 percent 1 0 0 30 36. Siltstone; some phosphate; olive- 67. Porcellanite. Phosphatic pellets, gray. This unit and underlying 30 percent in lower 4 in. (10 unit make up correlation unit cm) of unit; 5 percent in S4 0 10 remainder 1 1 0 33 35. Sandstone, phosphatic, brownish- 66. Phosphorite; phosphatic pellets, gray, very fine grained. average 65 percent 1 2 0 36 Weathered. Poorly exposed 0 11 0 28 65. Bentonite 0103 34. Siltstone, bentonitic, light-yellow­ 64. Porcellanite, indurated 1 1 0 33 ish-gray. Weathers white and 63. Bentonite; contains porcellanite chalky 1 2 fragments. Unit top and base 33. Sandstone; grades upward to silt- sharp 1 10 0 56 stone, yellowish-gray to 62. Porcellanite. This unit and two yellowish-brown; weathered underlying units make up cor­ white at top. Friable in lower 7 relation unit S3 0 4 0 10 in. (18 cm) to moderately indu­ 61. Bentonite 0 .6 0 1.5 rated upward. Phosphatic pel­ 60. Porcellanite 0 9 0 23 lets, about 25 percent 1 7 0 48 59. Bentonite 0103 Total measured thickness of upper 58. Porcellanite; phosphatic pellets, 5 phosphatic mudstone member percent 0 6 0 15 57. Phosphorite, muddy, por- in Eastern Trench: 110 7 33 69 celaneous. Phosphatic pellets, 80 percent pellets. Unit top, Section continues in Western Trench. Good correlation between trenches gradational 0 6 0 15 56. Porcellanite; indurated. Phos­ Western Trench phatic pellets, 20 percent 0 7 0 18 55. Bentonite 0 .6 0 1.5 Upper Miocene: 54. Porcellanite, indurated 1 1 0 33 .Santa Margarita Formation: 53. Bentonite; contains broken frag­ Upper phosphatic mudstone member: ments of porcellanite and bentonite 1 0 0 30 32. Sandstone, very fine grained, and 52. Porcellanite, indurated 1 0 0 30 sandy siltstone, light-gray. 51. Bentonite 0 .6 0 1.5 Phosphatic pellets, 30 percent. 50. Mudstone. Phosphatic pellets, Upper 1 ft (30 cm) of unit, very about 40 percent. Unit base, fine siltstone or claystone; con­ very sharp, irregular; contains tains phosphatic pellets, 5 load casts 0 11 0 28 percent. Correlation unit P4 3 1 0 94

66 Stratigraphic Sections Upper Miocene Continued Upper Miocene Continued Santa Margarita Formation Continued Santa Margarita Formation Continued Upper phosphatic mudstone member Continued Upper phosphatic mudstone member Continued Unit No. Thickness Unit No. Thickness In M Cm Ft In M Cm 31. Siltstone, siliceous; some green­ Total measured thickness of the ish-yellow stains. Some upper phosphatic mudstone megafossils 5 6 1 68 member in Western Trench: 64 0 19 49 30. Siltstone, somewhat bentonitic, Total thickness of the upper phos­ olive-gray 2 8 0 81 phatic mudstone member 29. Siltstone, sandy; slightly phos­ (Eastern and Western trenches): 174 7 53 18 phatic 2 0 0 61 28. Sandstone, very fine grained, and Upper Miocene: Siltstone, locally yellowish; Santa Margarita Formation: friable in lower part of unit. Lower sandstone member: Phosphatic pellets, 10 percent. Megafossils, abundant 2 0 0 61 Sandstone, very fine grained, and 27. Siltstone, siliceous, light-gray 4 6 1 37 siltstone, feldspathic, light- 26. Porcellanite, indurated . 2 0 0 61 gray. Thickness approximate 1 2 77 25. Phosphorite, muddy, silty, phos­ Sandstone, light-brown, very fine phatic pellets, 75 percent 0 6 0 15 grained. Phosphatic pellets, 10 24. Siltstone, siliceous 0 10 0 25 percent. Small fossils and some 23. Bentonite, and some bentonitic phosphatized shells, abundant. siltstone 1 6 0 46 Strata, broken up 0 11 0 28 22. Porcellanite, indurated 2 1 0 64 Sandstone, light-gray, very fine 21. Sandstojie, very fine grained, or grained, feldspathic. Unit siltstone. Phosphatic pellets, 5 coated white 2 2 49 percent 2 0 0 61 Sandstone,, very fine grained; 20. Sandstone, very fine grained, and weathered. Weathering yields siltstone, light-gray, friable to abundant hard sandstone frag­ moderately indurated 5 0 1 52 ments 2+ 0 61 + 19. Sandstone, very fine grained, yel­ Total measured thickness of lower lowish-orange-brown, very sandstone member: 20 2 6 15 friable 8 0 20 18. Siltstone, tuffaceous(?), light-gray 6 0 76 17. Bentonite and bentonitic siltstone 6 0 46 TRENCH 300 16. Porcellanite, siliceous, indurated. (Measured by H. D. Gower, 1964; E and F numbered samples described Massive at top 0 0 91 petrographically by T. L. Vercoutere) 15. Siltstone, siliceous 8 0 20 14. Siltstone; phosphatic pellets, 10 LOCATION: SWHSEVi sec. 7, T. 9 N., R. 26 W. (S.S.B. & M.) in the percent 7 0 18 Salisbury Potrero, California quadrangle 13. Siltstone; partly slightly phos­ ATTITUDE OF BEDDING: N. 54° W. 79° N. (good) in middle of trench phatic; light-gray 4 0 71 TREND OF TRENCH: Approximately N. 50° E. 12. Sandstone, very fine grained, fria­ Upper Miocene: ble. Phosphatic pellets, 50 Santa Margarita Formation: percent in lower part 5 1 4 Upper sandstone member: 11. Sandstone, very fine grained, Unit No. Thickness silty, light-gray. Phosphatic pel­ Ft hi M Cm lets, about 1 percent. Texture 78. Sandstone, yellowish-gray sugary 1 0 0 30 (5Y7/2) to light-olive-gray 10. Siltstone, tuffaceous(?), light- (5Y6/1), very fine grained, gray, massive, indurated; tex­ friable. Phosphatic pellets, ture sugary. Finer grained at dark-yellowish-brown base 6 6 1 98 (10YR4/2), fine- to coarse­ 9. Siltstone, siliceous, with some grained, 1 to 3 percent 5 4 1 63 bentonitic siltstone 5 6 1 68 77. Sandstone, yellowish-gray, fine­ 8. Siltstone, siliceous 0 4 0 10 grained; friable. Phosphatic 7. Bentonite 0 4 0 10 pellets, dark-yellowish-brown 6. Siltstone and very fine grained (10YR4/2), about 1 percent 4 4 1 32 sandstone 0 10 0 25 76. Sandstone, white, fine- to 5. Sandstone, reddish-brown to medium-grained; friable. Prob­ yellow, very friable. Phosphatic ably high feldspar content; pellets and nodules, about 10 weathered to koalinite 11 6 3 51 percent. Mollusks, locally Total measured thickness of the abundant 1 2 0 36 upper sandstone member 21 2 6 46

Stratigraphic Sections 67 Upper Miocene: Upper Miocene Continued Santa Margarita Formation: Santa Margarita Formation Continued Upper phosphatic mudstone member: Upper phosphatic mudstone member Continued Thickness Unit No. Thickness In M Cm Ft In M Cm 75. Siltstone, probably bentonitic, unit; phosphatic pellets with pale-olive (10Y6/2), highly some phosphatic disks (proba­ sheared. Some phosphatic pel­ bly diatoms or Foraminifera), lets, grayish-orange (10YR 20 percent in lower one-third 1 2 0 36 7/4), fine-grained 5 0 1 52 64. Mudstone, phosphatic, pelletal, 74. Siltstone, yellowish-gray (5Y7/2). silty; siliceous matrix. Grains, Phosphatic pellets, fine- to subangular to subrounded, medium-grained, 5 percent. poorly sorted, randomly ori­ Base of unit, dark-reddish- ented grains. Framework, 12 brown; paler upwards. Echi- percent quartz, 3 percent feld­ noid spines, as large as 1/4 in. spar, and 37 percent phosphate; (6 mm), abundant near base 1 4 041 matrix, 47 percent clay miner­ 73. Siltstone, probably bentonitic, als; accessory minerals, 1 slightly phosphatic, light-olive- percent, include zircon, mus- gray (5Y6/1); sheared 3 2 0 97 covite, chlorite, and magnetite. 72. Siltstone, yellowish-gray (5Y7/2). Phosphatic framework, 14 per­ Phosphatic pellets, dark-red­ cent pellets with noncentered dish-brown (10R3/4), fine- to inclusions and 43 percent pel­ medium-grained, about 3 per­ lets with centered inclusions of cent. Nodules, less than !/4 in. quartz feldspar and diatom (6 mm) long, abundant. Unit in frustules, 22 percent struc­ fault contact with underlying tureless pellets, 8 percent fish­ unit ' 1 8 0 51 bone fragments, 5 percent shell Section missing 17 0 5 19 fragments, 5 percent com­ 71. Siltstone, slightly siliceous, pound pellets, and 3 percent grayish-yellow (5Y8/4); phosphatic nodules. Pellets, patches of white caliche coat­ spheroids, regular to slightly ings. Quartz grains, very irregular; range from 0.06 to coarse, about 1 percent. Phos­ 0.35 mm in diameter; average phatic pellets, fine- to medium- diameter 0.12 mm; boundaries, grained, 1 percent. Few nod­ sharp to fuzzy; hematite rims ules. Small pebbles scattered in common. Pellet-supported this and underlying two units 2 2 0 66 areas, deformed pellets com­ 70. Siltstone, yellowish gray (5Y7/2); mon, and hematite staining highly sheared. Phosphatic pel­ abundant; pellet-free areas, lets, dark-reddish-brown, fine- staining absent. Siltstone, ben­ to medium-grained, 3 percent. tonitic, phosphatic, 3 in. (8 Nodules as large as 1/4 in. (6 1 cm) bed in center of unit. mm) common 2 2 0 66 Sample F1208-15 from unit. 69. Siltstone, slightly siliceous, yel­ Phosphatic pellet with centered lowish-gray to grayish-yellow; inclusions (pi. 6 C), fish ver­ indurated; sheared. Phosphatic tebrae (pi. 6 £), compound pellets, red-brown, very hard, phosphatic pellet (pi. 6 /), and rare, some caliche coated 3 2 0 97 structureless phosphatic pellet 68. Siltstone, yellowish-gray to (pi. 6F) 1 6 0 46 dusky-yellow (5Y6/4), sandy, 63. Siltstone, slightly siliceous, olive- phosphatic. Pellets, light- brown; sheared. Phosphatic brown at top; reddish-brown at pellets, about 2 percent. Silt- base 0 7 0 18 stone, bentonitic, 2 in. zone 5 67. Siltstone, siliceous; sheared. in. (13 cm) above base 111 0 58 Phosphatic pellets, light to 62. Phosphorite. Grains, silt-sized, dark, 3 percent 30091 subrounded, medium-sorted, 66. Sandstone, very fine grained, or randomly oriented; floating siltstone; sheared. Phosphatic grains, as large as medium pellets, dark-red-brown, fine- size, rare. Framework, 5 per­ to medium-grained; 50 percent cent quartz, 4 percent feldspar, in lower 7 in. (18 cm) of unit, 69 percent phosphate; matrix, 15 percent in remainder 2 0 0 61 12 percent siliceous clay miner­ 65. Siltstone, slightly siliceous, yel­ als, and 11 percent iron oxide. lowish-gray to dusky-yellow; Phosphatic framework, 26 per­ may be bentonitic at top of cent pellets with noncentered unit. Phosphatic pellets, 2 per­ pellets and 19 percent pellets cent in upper two-thirds of with centered inclusions of 68 Stratigraphic Sections Upper Miocene Continued Upper Miocene Continued Santa Margarita Formation Continued Santa Margarita Formation Continued Upper phosphatic mudstone member Continued Upper phosphatic mudstone member Continued Unit No. Thickness Unit No. Thickness In M Cm Ft In M Cm quartz, feldspar, and diatom- ately hard to semifriable. and shell-fragments, 46 per­ Nodules and phosphatic pel­ cent structureless pellets, and 9 lets, brown, fine- to coarse­ percent fossil fragments. Pel­ grained, 40 percent. Upper 2 lets, spheroids, regular to in. (5 cm) of unit, silty; phos­ slightly irregular; range from phatic pellets, 30 percent. 0.08 to 0.85 mm in diameter; Correlation unit P2 . 0 1 1 0 38 bimodal distribution, average 54. Siltstone, siliceous, slightly cal­ 0.15 mm and 0.50 mm in careous; indurated; sheared. diameter; boundaries, sharp; Phosphatic pellets, light- protruding grains rare; com- brown; 2 percent in upper half, pressional flattening slight 10 percent in lower half. Unit along contacts. Stain, iron coated with caliche. Correla­ oxide; hematite, substantial tion unit SI 0 41 amount in most areas, much 53. Sandstone, tan; friable; cut by concentrated along pellet rims. calcite veinlets. Phosphatic pel­ X-ray diffraction analysis indi­ lets, very pale orange to pale- cates presence of opal-CT. yellowish-brown, fine- to Base of unit, very irregular; coarse-grained, many disk- amplitude of 3 in. (8 cm); shaped and ellipsoidal, 40 per­ some burrows. Correlation unit cent. Basal contact, sharp 1 1 0 33 PI. Samples F1208-16 and 52. Limestone, indurated; speckled PI-300 from unit 1 0 0 30 with silt-size quartz. Unit 61. Siltstone, siliceous, olive-gray. coated with caliche 0 8 0 20 Phosphatic pellets, light- 51. Siltstone, olive-gray, bentonitic in grayish-orange to dark-brown, part; sheared 2 4 0 66 very fine- to coarse-grained, 3 50. Bentonite 01 03 percent. Bentonitic bed, thin, 5 49. Siltstone, olive-gray; some ben- in. (13 cm) above base I 10 0 56 tonite and hard porcellanite. 60. Siltstone, light-olive-gray; breaks Phosphatic pellets, distinctly into very fine fragments. Phos­ pinkish, very fine grained 1 I 0 33 phatic pellets, very abundant 48. Porcellanite, indurated, and sili­ locally at top. Bentonitic silt- ceous claystone; slightly stone in middle of unit 2 1 0 64 bentonitic 0 4 0 10 59. Siltstone, sandy, siliceous, 47. Siltstone, and bentonitic siltstone, slightly calcareous, white- olive-gray; moderately indu­ stained; hard. Phosphatic pel­ rated. Phosphatic pellets, lets, average 4 percent pinkish, very fine grained Oil 0 28 concentrated around abundant 46. Mudstone, phosphatic, pelletal, fish fragments. Basal 1 in. (3 silty; laminations, faintly wavy. cm) of unit, partly friable sand­ Grains, subangular to sub- stone with abundant phosphatic rounded, poorly sorted, nodules and 20 percent phos­ oriented subparallel to laminae; phatic pellets 0 5 013 floating grains to medium size. 58. Siltstone, bentonitic; very ben- Framework, 8 percent quartz, 4 tonitic in upper third of unit. percent feldspar, 24 percent Phosphatic pellets, 5 percent in phosphate; matrix, 62 percent lower two-thirds of unit. clay minerals, and 2 percent Sheared 1 0 0 30 iron oxide. Phosphatic frame­ 57. Siltstone, slightly calcareous, work, 53 percent pellets with some phosphate; white-stained; noncentered inclusions of indurated. Contains mega- quartz, feldspar, hematite, fossils 0 6 0 15 chlorite, and diatom fragments, 56. Siltstone. Phosphatic pellets, 32 percent structureless pellets, grayish-orange, fine- to coarse­ and 15 percent compound pel­ grained, about 1 percent. For- lets. Pellets, spheroids, regular aminiferal and megafossil to slightly irregular; range from molds locally abundant in 0. 13 mm to 0.75 mm in diame­ upper 1 ft (30 cm). Siltstone, ter; average diameter 0.30 mm; very bentonitic, 4 in. (10 cm) boundaries, sharp to fuzzy; bed 1 ft (30 cm) below top of rims of hematite rare and sec­ unit 3719 ondary phosphate common; 55. Sandstone, reddish-brown; moder- peripheral deformation slight; Stratigraphic Sections 69 Upper Miocene Continued Upper Miocene Continued Santa Margarita Formation Continued Santa Margarita Formation Continued Upper phosphatic mudstone member Continued Upper phosphatic mudstone member Continued Unit No. Thickness Unit No. Thickness Ft In M Cm Ft In M Cm concentrated in pellet-sup­ grains, rare; slight compres- ported lenses. Sample sional flattening; nuclei rarely Fl208-29 from unit 3719 incipiently calcitized; locally 45. Siltstone and bentonitic siltstone, pellet supported; oolitic struc­ olive-gray 0 4 0 10 tured pellets, very rare. Pebble 44. Siltstone, siliceous, sandy, light- fragments contain grains of gray when fresh; massive, silt-size material and pellets, indurated. Phosphatic pellets, very rare. Sample El205-14 10 percent Oil 0 28 from unit 41 43. Siltstone, and bentonitic siltstone, 34. Siltstone, siliceous 36 olive-gray. Phosphatic pellets, 33. Siltstone, bentonitic, and silt- scattered. Bentonite, 2 in. bed stone, olive-gray; moderately 1.1 ft (33 cm) below top of unit 2 6 0 76 indurated 10 42. Siltstone, siliceous, olive-gray; 32. Siltstone, siliceous 15 indurated; caliche-coated 0 5 0 13 31. Porcellanite: Phosphatic pellets, 41. Bentonite 0 .6 0 1.5 15 percent 0 4 0 10 40. Siltstone, olive-gray 0 4 0 10 30. Mudstone, very phosphatic, pel­ 39. Sandstone, fine-grained. Phos­ letal. Grains, angular to phatic pellets, 35 percent. subrounded, poorly sorted, ori­ Gradational basal contact 0 10 0 25 ented subparallel to thickly 38. Sandstone, fine-grained. Phos­ laminated alternating pellet- phatic pellets, light-gray to rich and grain-mud-rich sedi­ light-brown, fine- to medium- ments; floating grains, very grained, 45 percent. Quartz, coarse, rare. Framework, 10 coarse-grained, especially in percent quartz, 5 percent feld­ lower part of unit. Base, sharp 1 8 051 spar, 46 percent phosphate; 37. Siltstone, siliceous, may be matrix, 36 percent clay miner­ slightly calcareous; white- als, and 2 percent iron oxide; stained; indurated 0 7 0 18 accessory minerals, 1 percent, 36. Siltstone, siliceous, may be include zircon, chlorite, mag­ slightly calcareous; white- netite, and hematite. stained; indurated. Correlation Phosphatic framework, 33 per­ unit S2 1 10 0 56 cent pellets with noncentered 35. Mudstone, phosphatic, pelletal, inclusions and 28 percent pel­ sandy, fine-grained; lamina­ lets with centered inclusions of tions faint with grain-rich and quartz, feldspar, diatom frag­ grain-poor layers, stained with ments, and very rare zircon, 28 iron oxide. Grains, angular to percent structureless pellets, 8 subrounded, poorly sorted, ran­ percent compound pellets, 1 domly oriented; floating grains percent nodules without inclu­ as large as coarse size, rare. sions, and 2 percent shell Framework, 18 percent quartz, fragments as large as 1 mm. 6 percent feldspar, 28 percent Pellets, spheroidal, regular to phosphate; matrix, 45 percent slightly irregular; approx­ clay minerals, 2 percent iron imately 0.15 mm in diameter; oxide; accessory minerals, 1 boundaries, sharp, very abun­ percent, include chlorite, mag­ dant; rims commonly second­ netite, and zircon. Phosphatic ary phosphate; intruding grains framework, 39 percent pellets rare; in pellet-supported zones, with noncentered inclusions very much slight compres- and 11 percent pellets with sional flattening; nuclei, centered inclusions of quartz, incipiently calcitized; some feldspar, chert, and diatom poorly developed oolitic struc­ fragments, 30 percent struc­ ture, rare. Sample El205-15 tureless pellets, 5 percent from unit 1 1 0 33 compound pellets, 5 percent 29. Siltstone, sandy. Phosphatic pel­ pebble fragments, 10 percent lets, 15 percent. Quartz grains, shell fragments as large as 4 coarse 0 10 0 25 mm. Pellets, spheroidal; range 28. Siltstone, partly bentonitic. Phos­ from 0.09 mm to 0.30 mm in phatic pellets, very fine diameter; boundaries, sharp; grained, 20 percent. Bentonite, rims rarely calcareous or sec­ 1 in. (3 cm) bed 2 in. (5 cm) ondary phosphate; protruding below top of unit 0 41

70 Stratigraphic Sections Upper Miocene Continued Upper Miocene Continued Santa Margarita Formation Continued Santa Margarita Formation Continued Upper phosphatic mudstone member Continued Upper phosphatic mudstone member Continued Unit No. Unit No. Thickness Fl In M Cm Ft In M Cm 27. Siltstone, siliceous. Phosphatic eter 0.18 mm; boundaries, pellets, average 15 percent 0 5 0 13 sharp to slightly fuzzy; rims 26. Phosphorite, tan to brown. Phos­ commonly secondary phos­ phatic pellets, 75 percent. phate and commonly Base, very irregular, burrowed. calcareous; slight compres- Correlation unit P3 0 41 sional flattening common; 25. Siltstone, siliceous; massive; compound pellets rare. Frame­ indurated. Phosphatic pellets, work grains and pellet nuclei 20 percent. Concretion, pale- rarely incipiently calcitized. orange, small, one, at top of Shell fragment, phosphatized, unit 2 0 0 61 as large as 2 mm, rare. Base, 24. Siltstone, siliceous; massive; sharp, irregular. Sample indurated. Phosphatic pellets, F1208-13 from unit 1 0 0 30 about 50 percent in unit; 30 18. Siltstone, porcelaneous. Phos­ percent in upper 5 in. (13 cm). phatic pellets, 5 percent 0 7 0 18 Quartz grains, very coarse, 17. Claystone, siliceous, slightly locally abundant 1 2 0 36 phosphatic; laminations wavy. 23. Siltstone, moderately indurated. Clay matrix contains anas­ Phosphatic pellets, about 30 tomosing veins of iron oxide percent 0 5 0 13 and illite. Grains, subangular 22. Sandstone, very fine grained, or to subrounded, medium-sorted, siltstone; massive, indurated. randomly oriented; floating Phosphatic pellets, light-gray, grains, as large as very coarse 25 percent. Quartz grains, very size. Framework, 5 percent coarse, locally abundant, Base, quartz, 1 percent feldspar, 3 very irregular 1 6 0 46 percent phosphate; matrix, 89 21. Siltstone, siliceous, slightly phos­ percent clay minerals; phatic, indurated. Mudstone, accessory minerals, 1 percent, friable, 4 in. (10 cm) bed 6 in. include hematite, zircon, (15 cm) below top; contains sphene(?), magnetite, chlo- phosphatic pellets, 10 percent 1 0 64 rite(?). Phosphatic framework, 20. Mudstone, siliceous, phosphatic. 33 percent pellets with inclu­ Upper 7 in. (18 cm) of unit, sions of quartz and diatom indurated; contains phosphatic fragments, 64 percent struc­ pellets, more distinct than tureless pellets, and 3 percent those lower, 20 percent; indis­ phosphatized shell fragments. tinct, 40 percent in lower 1 ft Pellets, spheroids, regular to (30cm) 1 7 0 48 slightly irregular; range from 19. Mudstone, very phosphatic, pel- 0.10 mm to 0.30 mm in diame­ letal, silty; siliceous matrix. ter; boundaries predominantly Grains, angular to subrounded, fuzzy; rims illite(?)-coated, poorly sorted, randomly ori­ very rare. Sample F1208-8 ented; floating grains, as large from unit 2 0 36 as coarse size, rare. Frame­ 16. Bentonite and bentonitic siltstone 4 0 10 work, 11 percent quartz, 8 15. Claystone, silty, siliceous, slightly percent feldspar, 41 percent phosphatic; laminated, faint, phosphate, matrix, 38 percent wavey. Grains, subangular to clay minerals; accessory miner­ subrounded, poorly sorted, ran­ als, 2 percent, include zircon, domly oriented; floating grains hematite, magnetite, chlorite, as large as coarse size. Frame­ and muscovite. Phosphatic work, 13 percent quartz, 6 framework, 34 percent pellets percent feldspar, 3 percent with noncentered inclusions phosphate; matrix, 77 percent and 24 percent pellets with clay minerals; accessory miner­ centered inclusions of quartz, als, 1 percent, include zircon, feldspar, hematite, zircon, and biotite, hematite, chlorite, mus­ diatom fragments, and 37 per­ covite, magnetite, glauconite, cent structureless pellets, and 5 and sphene. Phosphatic frame­ percent nodules and fossil frag­ work, pellets with inclusions of ments. Pellets, spheriods, quartz, feldspar (rare), diatom regular to slightly irregular; fragments, and phosphatized range from 0.08 mm to 0.35 shell fragments as much as 2 mm in diameter; average diam- mm long, and structureless pel-

Stratigraphic Sections 71 Upper Miocene Continued Upper Miocene Continued Santa Margarita Formation Continued Santa Margarita Formation Continued Upper phosphatic mudstone member Continued Upper phosphatic mudstone member Continued Unit No. Thickness Unit No. Ft In M Cm Ft In M Cm lets. Pellets, spheroids; average phatic, slightly silty, siliceous. diameter 0.10 mm; boundaries, Hematite-rich muds faintly sharpness variable, mostly banded, approximately 1 mm fuzzy; minor secondary cal- wide, not laterally continuous citization of grains. X-ray as individual lamina but fairly diffraction analysis indicates continous as a zone. Grains, major clay mineral, angular to rounded, poorly montmorillonite; minor miner­ sorted; oriented subparallel to als, illite, and opal-CT. crude wavey laminae; floating Correlation unit S3. Sample grains, as large as coarse size, F1208-9 from unit 1 0 0 30 very rare. Framework, 7 per­ 14. Mudstone, phosphatic, silry, sili­ cent quartz, 3 percent feldspar, ceous; laminae, alternating 10 percent phosphate; matrix, pellet rich and pellet poor. 79 percent clay minerals; Pellet-rich laminae, pellet sup­ accessory minerals, 1 percent, ported; pellet-poor laminae, include muscovite, hematite, wavey fine laminae of alternat­ zircon, and magnetite. Phos­ ing illite-rich mud and phatic framework, 30 percent montmorillonite-iron oxide- pellets with noncentered grain rich mud. Grains, angular to inclusions and 20 percent pel­ subrounded, poorly sorted, ran­ lets with centered inclusions, domly oriented. Framework, 14 50 percent structureless pellets, percent quartz, 6 percent feld­ and 1 percent shell fragments spar, 35 percent phosphate; and diatom fragments, very matrix, 42 percent clay miner­ rare. Grain inclusions, quartz als, 2 percent iron oxide; predominates, lesser amounts accessory minerals, 1 percent. of feldspar, hematite (rare), and Phosphatic framework, 26 per­ diatom fragments (rare). Pel­ cent pellets with noncentered lets, spheroids; range from inclusions and 11 percent pel­ 0.06 mm to 50 mm in diame­ lets with centered inclusions of ter; average diameter 0.14 mm; quartz, feldspar, and diatom boundaries, range from sharp fragments (some nearly to fuzzy. Pellets with secondary whole), 43 percent struc­ phosphate rims, between 0.01 tureless pellets, 16 percent mm and 0.03 mm thick, com­ compound pellets, 3 percent mon, especially in hematite- shell fragments, and 1 percent rich laminae. Incipient pellets nodules (including pellet (rare) have smaller diameter grapestone). Pellets, spheroids; than other pellets. Incipient range from 0.6 mm to 0.50 secondary calcification of mm in diameter; average diam­ framework grains rare. Sample eter 0.18 mm; boundary F1208-11 near top; F1208-12 sharpness variable, pellets that near base 2 1 0 64 have been secondarily phos- 11. Sandstone, light-brown, very fine phatized commonly have grained. Phosphatic pellets, 25 slightly fuzzy boundaries. percent 1 4 0 41 Diagenetic alterations; frame­ 10. Porcellanite; massive; indurated. work grains commonly Phosphatic pellets, 5 percent. incipiently calcitized and pellet Base, faulted. Attitude of fault, nuclei rarely. Phosphatic pellets N. 60° E. 72° N. (good) 2 0 0 61 and nodules stained with Section missing 15 0 4 58 hematite. Sample F1208-10 9. Phosphorite; phosphatic siltstone near base. Compressed com­ in upper half of unit. Phos­ pound pellets (pi. 6 K), pellet phatic pellets, 30 percent in with ferruginous bands (fig. upper half and 60 percent in 10), and grapestone intraclast lower half. Large bone, mam- (pi. 6 M) from unit 0 10 0 25 mal(?), at base similar to bones 13. Siltstone, siliceous. Phosphatic in trench 297, stratigraphic pellets, 10 percent. Ben- unit 35 1 1 0 33 tonitic(?) zone, 4 in. (10 cm), 8. Siltstone, siliceous, indurated. weakly indurated, at base 0100 25 Phosphatic pellets, 5 percent 1 2 0 36 12. Claystone, moderately phos- 7. Wackestone, phosphatic,

72 Stratigraphic Sections Upper Miocene Continued Upper Miocene: Santa Margarita Formation Continued Santa Margarita Formation: Upper phosphatic mudstone member Continued Upper phosphatic mudstone member: Thickness Thickness In M Cm n M i medium-sorted, matrix sup­ 77. Sandstone, arkosic, kaolinitic(?), ported, carbonate cement. white, fine- to medium- Grains, subangular, randomly grained; semifriable. Quartz oriented. Framework, 6 percent grains, few 5+ 1 52 + quartz, 3 percent feldspar, 32 76. Covered interval. Probably silt- percent phosphate; matrix, 55 stone. Thickness approximate 3 0 091 percent carbonate, and 2 per­ 75. Siltstone, siliceous, grayish- cent iron oxide. Some frame­ brown (5YR3/2) to pale-yel­ work grains secondary cal- lowish brown (10YR6/2), citization. Phosphatic frame­ indurated. Locally, especially work, 60 percent pellets with in middle of unit, made up inclusions of quartz, feldspar, mostly of phosphatic pellets 0 6 0 15 hematite, zircon and diatom 74. Siltstone, siliceous to bentonitic; fragments and iron oxide greenish-gray; indurated to (rare); remainder are struc­ friable, thin-bedded. Phos­ tureless pellets. Pellets, phatic pellets, smooth surfaces, spheroids, regular to slightly irregular outlines, atypically irregular; range from 0.10 mm washed, scattered. Several clam to 0.30 mm in diameter; nuclei casts near top of unit 1 8 051 commonly partially calcitized. 73. Phosphorite, weathers brownish- Pellets with very sharp bound­ gray. Phosphatic pellets, light- aries commonly have gray; slightly polished, calcareous rims. Nodules, especially in lower part of unit; phosphatic, less than 1 mm 15 percent at top and 60 per­ long, rare. Large burrows at cent pellets at base; apparent base and in underlying ben- nodular aggregates at base. tonite and siltstone. Sample Base sheared 0 10 0 25 FI208-14 from unit 30 72. Siltstone, siliceous, platy, green­ Bentonite 5 ish-gray; indurated; sheared. Siltstone, olive-gray. Phosphatic Phosphatic pellets, 5 to 10 pellets, 5 percent. Correlation percent. Surfaces, caliche unit S4 33 encrusted, white 0 60 15 Bentonite 3 71. Claystone, medium-brown; phos­ Siltstone, and very fine grained phatic pellets, locally siliceous sandstone; 2 percent abundant. Grades into underly­ phosphatic pellets in lowest 6 ing unit 0 4 0 10 in. (15 cm) 2 0 0 61 70. Phosphorite, nodular, dark-brown. Sandstone, very fine grained and Nodules, as much as I in. (3 fine-grained. Phosphatic pel­ cm) long; many nodules are lets, 10 percent in very fine aggregated pellets, pellets scat­ grained sandstone and 15 per­ tered 0103 cent pellets in fine-grained 69. Claystone, slightly siliceous, sandstone in basal 7 in. (18 greenish-gray to light-gray. cm). Thickness, uncertain for Phosphatic(?) nodules, white, this unit and underlying unit 1 6 0 46 lenticular (1/4 in. x 3 in.) (0.6 Sandstone, fine-grained; sheared. cm x 7.6 cm), rare. Middle Phosphatic pellets, 20 percent unit, two zones, possibly ben- in upper 10 in. (25 cm) of unit tonite. Top unit, very fissile Oil 0 28 and 60 percent in lower part. 68. Siltstone, siliceous, light-gray, Correlation unit P4. Sample indurated 0103 300-P4 from unit 1 2 0 36 67. Bentonite 0 .6 0 1.5 Total measured thickness of upper 66. Siltstone, siliceous, yellowish- phosphatic mudstone member 130 11 39 90 gray (5 Y8/1); beds, '/2in. to 4 in. (1.3 cm to 10 cm), indu­ rated; interbeds, claystone, TRENCH 400 weakly indurated, relief is 4 or 5 in. (10 to 13 cm) between (Measured by H. D. Cower, 1971) claystone and siltstone. Appar­ LOCATION: SE'/4SE'/4 sec. 7, T. 9 N., R. 26 W. (S.S.B. & M.) in the ently no phosphate. Some fish- Salisbury Potrero, California quadrangle. . scale imprints on surfaces 3719 ATTITUDE OF BEDDING: Approximately N. 80° W. 65° S. overturned 65. Siltstone, platy, yellowish-gray. TREND OF TRENCH: Approximately N. 15° E. Some phosphatic nodules,

Stratigraphic Sections 73 Upper Miocene Continued Upper Miocene Continued Santa Margarita Formation Continued Santa Margarita Formation Continued Upper phosphatic mudstone member Continued Upper phosphatic mudstone member Continued Unit No. Thickness Thickness In M Cm Ft In M Cm white, small. Bentonitic(?) zones in upper half 2 0 0 61 claystone two thin beds in 42. Siltstone, pale-orange, friable, lower 6 in. (15cm) 1 11 0 58 foraminifers, light-colored, 64. Phosphorite and moderately phos­ abundant 0 .6 0 1.5 phatic siltstone, yellowish-gray 41. Claystone 0 4 0 10 to light-brown. Phosphatic pel­ 40. Bentonite, siliceous; indurated 0 6 015 lets, 10 percent at top and 80 39. Siltstone, siliceous, phosphatic in percent or more in lower part upper half. Foraminifers in of unit; phosphatic pebbles or lower half 0205 nodules as large as 1/2 in. (1.3 38. Claystone, siliceous, bentonitic, cm) largely make up basal and bentonite; grades down­ third of unit. Base, faulted; ward to tuff in lower 11 in. (28 partly burrowed by clams 0 10 0 25 cm). Basal 2 in. (5 cm), clayey, Section missing 24 6 7 47 friable 2. 4 0 71 63. Siltstone, siliceous; indurated 0 8 0 20 37. Phosphorite, siliceous, indurated. 62. Claystone and siltstone, ben- Upper unit, very phosphatic; tonitic, friable. Siltstone beds, middle unit, almost entirely siliceous, thin, indurated, few 1 5 0 43 phosphatic pellets, basal unit, 61. Siltstone, siliceous; indurated 0 4 0 10 moderately phosphatic 0 7 018 60. Tuff(?), light-orange to light-gray; 36. Bentonite(?) trace sugary texture 0205 35. Phosphorite, pelletal, siliceous; 59. Claystone, siliceous; very thin indurated. Unit top and base, bedded; moderately indurated 2 6 0 76 slightly phosphatic mudstone 0 7 018 58. Siltstone, siliceous, indurated. 34. Claystone, bentonitic(?), light- Abundant foraminifers 1 5 0 43 gray; slightly siliceous. 57. Bentonite, siliceous, indurated 0103 Mudstone at top. Partings in 56. Bentonite(?) and clayey mudstone 0 .5 0 1,2 most of unit 0 10 0 25 55. Phosphorite, silica cement, 33. Siltstone, siliceous; indurated Oil 0 28 brownish-gray; indurated. Base 32. Phosphorite, pelletal; indurated 0 4 0 10 irregular 0103 31. Claystone, bentonitic 0 5 0 13 54. Claystone, siliceous; weathers 30. Tuff, light-bluish-gray. Thickness light-gray; moderately indu­ uncertain, may be as much as 3 rated, harder in lower part of ft (91 cm) thick 1 2 0 36 unit. Upper part of unit, some 29. Phosphorite, siliceous; indurated. thin clayey mudstone and silty Some nodules or broken phos­ bentonite(?) beds 2 7 0 79 phatic nodules. Foraminiferal 53. Claystone, bentonitic 0205 siltstone at top of unit; sili­ 52. Siltstone, siliceous; indurated; ceous siltstone with leached- brown-weathering. Some out foraminifers in lower third. foraminiferal molds 0 4 0 10 Thickness uncertain. Correla­ 51. Claystone; slightly bentonitic(?); tion unit P2 1 0 0 30 weakly indurated 0103 28. Siltstone, siliceous; sheared. 50. Phosphorite, light-gray. Phos­ Claystone chert intraclasts. phatic pellets, polished, as Correlation unit SI 1 11 0 58 much as 80 percent. Base 27. Sandstone, very fine grained, and irregular. Correlation unit PI 0 7 0 18 sandy siltstone. Some phos­ 49. Siltstone, siliceous; indurated. phatic pellets. Possible Phosphatic pellets, locally phosphatic mudstone intra­ abundant 0 8 0 20 clasts, locally at base 0103 48. Bentonite and bentonitic clay- 26. Siltstone, siliceous, slightly phos­ stone 0103 phatic; thin-bedded; sheared. 47. Siltstone, phosphatic, siliceous; Foraminiferal molds, locally grades downward to pebbly abundant 1 4 0 41 phosphorite in lower half of 25. Phosphorite, pelletal. Nodules, unit. Contains phosphatic nod­ abundant in zone 4 in. (10 cm) ules and pellets 0 5 0 13 below top, and abundant in 46. Bentonite and bentonitic clay- base. Base irregular Oil 0 28 stone 0205 Sheared zone (fault). Assuming 45. Siltstone, siliceous, indurated 0 5 013 section repeated, overlying unit 44. Claystone, bentonitic, brown 0205 correlated across fault. 43. Claystone, siliceous (almost Unknown thickness cherty), dark-yellowish-orange; 24. Claystone, and siliceous siltstone. indurated. Some bentonitic Sheared to highly sheared in

74 Stratigraphic Sections Upper Miocene Continued Upper Miocene: Santa Margarita Formation Continued Santa Margarita Formation: Upper phosphatic mudstone member Continued Lower sandstone member: Unit No. Thickness In M Cm 6. Sandstone, arkosic, white, coarse­ lower part; probably not much grained. Middle unit, indu­ displacement^) 3 10 1 17 rated. Phosphatic pellets; few, 23. Phosphorite, pelletal. Nodules scattered 7 6 2 29 abundant in lower two-thirds of 5. Sandstone, very fine grained. unit. Base, irregular, with clam Poorly exposed 4 6 1 37 burrows 0 4 0 10 4. Siltstone, siliceous; indurated, in 22. Claystone, bentonitic, in lower part. Poorly exposed 10 0 3 5 two-thirds of unit, and 3. Sandstone, coarse-grained, mudstone, siliceous, indurated, quartz-rich; indurated 6 + 0 1 83 + in upper one-third; thin-bed­ 2. Sandstone; contains echinoderms 50 0 15 24 ded. Phosphorite, 1 in. (3 cm) 1. Sandstone; contains oysters 65 0 19 81 bed 6 in. (15 cm) above base 1 8 0 51 Total measured thickness of the 21. Phosphorite. Nodules abundant in lower sandstone member: 143+ 0 43 5 + lower part of unit 0 4 0 10 20. Siltstone, siliceous; interbedded with bentonitic claystone; thin- bedded. Fbraminifers, locally abundant 3 0 0 91 19. Phosphorite, silica-cemented, especially in upper part 0 4 010 18. Siltstone, siliceous; indurated 0 10 0 25 17. Claystone; upper part is locally siliceous and moderately indu­ rated; basal part is semifriable 1 4 041 16. Phosphorite, silica cemented, indurated 0 10 0 25 15. Siltstone, siliceous; indurated; foraminiferal molds 0205 14. Claystone, bentonitic 0205 13. Siltstone, siliceous; indurated 0103 12. Phosphorite, silica-cemented at top 0308 11. Siltstone, clayey; interbedded with some harder siliceous silt- stone. Correlation unit S2 7 10 2 39 10. Claystone, possibly some indu­ rated phosphorite beds; very highly sheared. Lower unit, bentonitic. Thickness approxi­ mate 7 0 2 13 9. Tuff and tuffaceous siltstone 3412 8. Phosphorite, pelletal, siliceous, and porcellanite; indurated. Correlation unit P3 0 7 0 18 Fault zone: N. 45° W., left lateral; section missing 58 6 17 84 7. Siltstone, siliceous, and clay- stone, slightly phosphatic 7 0 213 Total measured thickness of the upper phosphatic mudstone member: 171 2 51 53

Stratigraphic Sections 75 Table 7. Semiquantitative spectrographic analyses of the upper phosphatic mudstone member of the Santa Margarita Formation, at trench 100 in Cuyama Valley phosphate area, Santa Barbara County, Calif.

with symbol <. Si, Al, Fc, Mg, Ca, Na, K, Ti, P, Mn, and their oxides given in w

trographic analyses by M. J. Cremer, C. Heropoulos, and L . Mei]

Strat. unit - 68 67 66 65 64 63 Strat. unit - 68 67 66 65 64 63 Field No 100-1 100-2 100-3 100-4 100-5 100-6 Field No 100-1 100-2 100-3 100-4 100-5 100-6 Sample No - M-136032 M-136033 M-136034 M-136035 M-136036 M-136037 Sample No - M-136032 M-136033 M-1'36034 M-136035 M-136036 M-136037

Major elements reca Iculated as oxides.- (percent) Minor elements (ppm) continued

SiO, >73 45 41 36 54 >73 <22 <22 <22 <22 <22 <22 A1 2°3 6.2 8.1 4.9 7.9 5.3 4.4 <3.2 <3.2 <3.2 <3.2 <3.2 <3.2 .52 4.4 1.9 2.9 2.6 1.9 <4.6 <4.6 <4.6' <4.6 <4.6 <4.6 .14 2.2 4.3 2.5 1.3 .90 <320 <320 <320 <320 <320 <320 CaO ----- 2.0 2.1 5.9 .98 2.1 1.7 4.8 70 43 82 71 37

Na,O ----- 2.6 1.3 1.8 .67 1.2 1.2 3.1 2.4 1.6 2.5 2.1 1.5 5.2 11 13 3.9 13 14 .11 .53 .20 .47 .37 .23 .44 1.1 1.5 .63 1.8 1.2 .39 .94 '1.4 .14 .44 .34 30 52 22 21 M$ ----- .0075 .043 .041 .030 .022 .016 15 82 120 68 40 48

Major elements (percent) Strat. unit - 62 61 60 59 58 57 100-7 >34 21 19 17 25 >34 Field No 100-8 100-9 100-10 100-11 100-12 - M-136038 M-136039 M-136040 M-136041 M-136042 Al 3.3 4.3 2.6 4.2 2.8 2.3 Sample No M-136043 Fe .36 3.1 1.3 2.0 1.8 1.3 Major elements recalculated as Mg .086 1.3 2.6 1.5 .77 .54 oxides (percent) Ca 1.4 1.5 4.2 .70 1.5 1.2 SiO, ----- 51 51 47 49 49 34 6.4 1.9 .95 1.3 .50 .85 .85 5.3 6.8 7.0 6.8 4.5 Fe^Oj - 2.1 2.0 2.0 2.1 2.0 2.0 2.6 2.0 1.3 2.1 1.7 1.2 Mg6 ----- .066 .32 .12 .28 .22 .14 .78 1.2 .53 .81 1.4 .60 .17 .41 .59 .068 .19 .15 CaO 8.0 1.8 6.3 2.9 1.5 11 .0058 .033 .032 .023 .017 .012 Na,O 2.2 1.2 2.2 2.2 1.3 1.8 2.2 1.2 1.9 2.2 2.2 1.3 .25 Minor elements (ppm) .30 .25 .37 .40 .17 Plos - 4.8 .69 5.3 2.0 .69 8.9 MnO .037 Ag <0.10 <0.10 <0.10 <0.10 <0.10 <0.10 .026 .068 .028 .025 .052 As <150 <150 <150 <150 <150 <150 Major elements (per cent) B 4.6 33 26 37 22 14 1200 410 350 310 300 230 24 24 22 23 23 16 <3.4 2.8 3.6 3.7 3.6 2.4 1.4 <1.0 1.2 1.5 1.4 1.4 1.5 1.4 1.4 .47 .72 .32 .49 .82 .36 <32 <32 <32 <32 <32 <32 5.7 1.3 4.5 2.1 1.1 7.6 43 88 93 67 80 48 2.3 1.4 1.7 1.4 1.3 1.6 .89 1.6 1.6 .95 1.3 1.8 1.5 1.6 1.8 1.8 1.1 6.3 13 13 21 35 15 .15 .18 .15 .22 .24 .10 1.6 23 11 31 28 19 2.1 .30 2.3 .85 .30 3.9 Dy - <22 <22 <22 <22 <22 <22 .029 .020 .053 .022 .019 .040 .- in < 1.5 < 1.5 <1.5 <1.5 <1.5 <1.5 Minor elements (ppm)

5.3 11 6.5 13 7.0 3.6 "8 0.11 0.10 0.10 0.10 0.10 0.10 <150 <150 <150 <150 <150 <150

14 23 18 20 36 22 <6.8 <6.8 <6.8 <6.8 <6.8 <6.8 570 350 460 480 450 360

<6.8 <6.8 <6.8 <6.8 <6.8 <6.8 1.5 1.1 2.3 1.4 1.3 2.1

21 48 32 35 40 24 <32 <32 <32 <32 <32 <32 <68 <68 <68 <68 <68 <68 100 110 120 98 180 110 <22 <22 < 22 < 22 <22 <22 1.6 2.0 1.5 1.3 1.4 1.3

58 330 320 230 170 120 36 16 25 19 19 33 <2.2 <2.2 <2.2 <2.2 <2.2 <2.2 19 24 9.5 17 28 14 <2.2 <2.2 <2.2 <2.2 <2.2 <2.2 Dy - <22 <22 <22 <22 <22 <22 <46 74 <46 59 73 <46 1.5 6.0 10 7.9 14 10

Os <22 <22 <22 <22 <22 <22 5.5 6.0 5.8 8.3 9.7 5.4 6.9 <6.8 <6.8 <6.8 <6.8 <6.8

<68 <68 <68 <68 <68 <68 <6.8 <6.8 <6.8 <6.8 <6.8 <6.8 <6.8 <6.8 <6.8 <6.8 <6.8 <6.8

< 10 < 10 <6.8 <6.8 <6.8 <6.8 <6.8 <6.8 <2.2 <2.2 <2.2 <2.2 <2.2 <2.2 <3.2 <3.2 <3.2 <3.2 <3.2 <3.2 55 60 54 48 92 55 <46 <46 <46 <46 <46 <46 <68 <68 <68 <68 <68 <68 1.0 8.9 5.4 11 7.8 4.9 <22 <22 <22 <22 <22 <22

<22 <22 <22 <22 <22 <22 290 200 530 220 190 400 < 1.5 7.1 2.2 11 2.2 2.2 8.1 370 650 380 150 180 170 <2.2 <2.2 <2.2 <2.2 <2.2 <2.2 <460 <460 <460 <460 <460 <460 <46 71 <46 <46 77 63 TV < -U < 32 <32 <32 Nj 16 11 4R 5.R 1.R 7h

76 Table 7 Table 7. Semiquantitative spectrographic analyses of the upper phosphatic mudstone member of the Santa Margarita Formation, at trench 100 in Cuyama Valley phosphate area, Santa Barbara County, Calif. Continued

Strat. unit 62 61 60 59 58 57 Strat. unit 56 55 54 53 52 51 Field No 100-7 100-8 100-9 100-10 100-11 100-12 Field No 100-13 100-14 100-15 100-16 100-17 100-18 Sample No M-136038 M-136039 M-136040 M- 13 6041 M-13604Z M-136043 Sample No - M-136044 M-136045 M-136046 M-136047 M-136048 M-136049

Minor elements (ppm) continued Minor elements (ppm) continued

<22 <2Z ' <22 <22 <2Z <2Z <6.8 <6.8 <6.8 <6.8 <6.8 <6.8 <15 <15 <6.8 <6.8 <6.8 <6.8 <6.8 <6.8 <15 <15 <15 <15 77 54 55 85 48 55 <68 <68 <68 <68 <68 <68 <68 <68 <68 <68 <68 <68 <22 <22 <6.8 <6.8 <6.8 <6.8 <6.8 <6.8 <22 <22 <22 <2Z =10 170 160 700 300 140 <2.Z

<22

<22 <22 <22 <22 <22 <22 38 49 20 8.2 39 <1.5 <1.5 <1.5 <1.5 <1.5 <1.5 3.8 5.0 2.4 1.1 3.9 1500 600 550 2100 500 630 67 23 110 32 16 170 <460 <460 <460 <460 <460 <460 140 78 450 170 100 160 <32 <32 <32 <32 <32 <32

<22 <22 <22

Major elements recalculated as oxides (percent) <10 <10 <10 <10 <10 <10 65 36 33 68 Z6 41 SiO, - 26 43 39 18 54 39 5.2 3.2 Z.8 4.3 2.8 3.1 3.2 Ai2a, 3.6 5.7 5.1 3.2 7.0 170 43 30 180 57 75 1.7 3.2 1.4 2.4 2.0 2.1 90 140 110 230 87 120 .88 .96 1.1 .88 1.6 .65 CaO 15 4.9 5.0 21 3.1 6.0 Strat. unit 50 49 48 47 46 45 Field No -- 100-19 100-20 100-21 100-22 100-23 100-24 Na,O 1.0 1.3 1.3 1.5 1.3 1.8 Samp 1 e No M-136050 M-136051 M-136052 M-136053 M- 136054 M-136055 1.0 1.8 2.1 .76 1.9 1.5 TfO-, - .17 .28 .28 .13 .40 .11 Major elements reca Iculated as oxides (pe rcent) PO] - 12.0 3.7 3.4 12.0 1.4 4.8 .018 MHO .025 .022 .021 .090 .039 SiO, 45 39 28 41 32 36 AlA - 5.3 4.7 3.2 4.7 3.2 .72 Major elements (perccrit) 2.1 1.9 2.0 2.3 1.3 .57 $* ::::: 3.5 1.1 .50 1.3 2.3 5.1 12 20 18 8.6 25 18 CaO 4.1 9.2 13 4.2 13 6.6 1.9 3.0 2.7 1.7 3.7 1.7 1.2 1.7 1.4 1.5 2.2 .97 Na,O 1.1 1.6 1.1 1.2 1.5 .19 Mg .53 .58 .65 .53 .98 .39 K^6 - 1.8 1.7 .99 1.9 1.1 .37 11 3.5 3.6 15 2.2 4.3 Tfo^ ...... 33 .25 .14 .27 .12 .028 P2o] - .69 6.9 14.0 2.5 9.2 .66 .77 .93 .93 1.1 .95 1.3 Mto - .026 .028 .049 .027 '.026 .041 .85 1.5 1.7 .63 1.6 1.2 .10 .17 .17 .079 .24 .064 Major elements (per cent) >4.6 1.6 1.5 >4.6 .63 2.1 .019 .017 .016 .070 .030 .014 21 18 13 19 15 17 2.8 2.5 1.7 2.5 1.7 .38 Minor e 1 emen t s ( ppm) 1.5 1.3 1.4 1.6 .93 .40 Mg - 2.1 .66 .30 .79 1.4 3.1 Ag ...-. 0.16 0.10 0.10 0.10 0.10 0.10 2.9 6.6 9.3 3.0 9.5 4.7 <150 <150 <150 <150 <150 <150 .79 1.2 .81 .88 1.1 .14 25 22 24 24 37 15 1.5 1.4 .82 1.6 .89 .31 420 400 350 440 420 450 .20 .15 .083 .16 .071 .017 .30 3.0 <4.6 1.1 4.0 .29 3.0 1.8 1.6 2.9 1.5 1.1 .020 .022 .038 .021 .020 .032

50 32 32 42 32 32 Minor elements (ppm) 140 99 110 170 95 110 1.6 1.0 1.0 1.6 2.0 1.0 Ag ----- <0.10 <0.10 <0.10 <0.1Z <0.14 <0.10 <150 < 150 < 150 < 150 < 150 < 150 48 29 31 62 35 12 <10 < 10 < 10 < 10 <10 < 10 18 24 23 15 24 10 21 23 23 Z4 ZO 4.6 Dy <22

2.6 <1.0 1.8 3.Z 1.8 2.0 < 1.0 < 15 < 15 < 15 < 15 < 15 < 15 3.6 6.1 5.3 2.9 8.4 3.7 <32 <3Z 99 <32 46 <32 78 160 200 110 120 93 M.5 =1.5 1.3 1.5 2.0 2.6 1.3 < 1.0

Table 7 77 Table 7. Semiquantitative spectrographic analyses of the upper phosphatic mudstone member of the Santa Margarita Formation, at trench 100 in Cuyama Valley phosphate area, Santa Barbara County, Calif. Continued

Strat. unit 50 49 48 47 46 45 Strat. unit 44 43 4Z 41 40 39 Field No 100-19 100-20 100-21 100-22 100-23 100-24 Field No 100-Z5 100-Z6 100-Z7 100-28 100-29 100-30 Sample No M-136050 M-136051 M-136052 M-136053 M-1360S4 M-136055 Sample No M-136056 M-136057 M-136058 M-136059 M-136060 M-136061 Minor el aresnts (ppm) continued Minor elements (ppm) continued

5.1 4.5 8.0 4.3 1.5 85 59 56 69 45 <15 <15 <15 <15 <15 21 16 23 11 15 <1.5 <1.5 <1.5 <1.5 <1.5 Dy <22

ZOO 220 380 210 200 3ZO <6.8 <6.8 <6.8 <6.8 <6.8

Na,O 1.2 l.Z Z.O 1.2 1.6 .40 Major elements recalculated as oxides (pe rcent) Kjft - 2.1 1.6 2.5 2.3 1.8 1.1 TfOj .--. .32 .17 .28 .33 .18 .15 SiO, - 51 47 34 49 43 Zl POj - .66 4.1 1.3 .55 6.2 .60 Al^ - 4.9 4.5 3.4 8.7 5.9 3.4 vfio .032 .066 .017 .16 .039 .017 Z.3 1.1 3.3 Z.4 l.Z WP 1.1 .46 1.7 1.4 .46 Major elements (percent) 1.3 11 7.3 4.9 ZO Na2O 1.6 .53 1.1 1.5 1.3 l.Z 1.8 1.9 .93 1.0 Z.I '.96 Fe ----- 1.7 1.1 (l Z 1.6 QQ % :::: .11 .27 .14 .30 .25 .13 Mg - .36 52 .74 CO .55 .55 8.9 4.1 3.7 8.0 & :::: .021 .028 .049 .034 .036 .025

87 Major elements (percent)

ZZ 16 23 ZO 10 2.4 1.8 4.6 3.1 1.8 .030 .013 .025 .051 .013 .12 1.6 .80 2.3 1.7 .82 .66 .28 1.0 .83 .28 Minor elements (ppm) .96 7.5 5.2 3.5 14

Ag - .39 .80 1.1 .98 .89 1.6 .77 1.6 1.7 .80 .16 .081 .18 .15 .075 .Z4 3.9 1.8 1.6 3.5 .022 .038 .OZ6 .028 .019

1 ft Minor elements (ppm)

Ag - 0.10 0.10 0.14 O.Z3 0.34 <150 <150 <150 <150 < 150 rv. ____ 1 A s. > \ » h R 1 .1 1 .7 MO <10 <10 <10 <10 16 13 40 31 20 .17(1 ?nn inn inn i?n 4£n

78 Table 7 Table 7. Semiquantitative spectrographic analyses of the upper phosphatic mudstone member of the Santa Margarita Formation, at trench 100 in Cuyama Valley phosphate area, Santa Barbara County, Calif. Continued

Strat. unit 38 37 36 35 34 33 Strat. unit 32 31 30 29 28 Z7 Field No 100-31 100-32 100-33 100-34 100-35 100-36 Field No 100-37 100-38 100-39 100-40 100-41 100-4Z Samp 1 c No M-136062 M- 136063 M-136064 M-136065 M-136098 M-136099 Sample No M-136100 M-136101 M-13610Z M-136103 M-136104 M-136105

Minor el one nts (ppm) continued Minor e 1 emen t s ( ppm)

1.5 2.4 Z.I 2.0 3.1 Ag ...... 0.13 0.10 0.18 0.19 0.13 MS <15 <15 <15 <15 <150 <150 <150 '150 <150 57 <32 66 46 <32 100 <10 <10 <10 <10 <10 81 110 93 110 170 16 18 22 16 7.Z 1.7 2.2 6.1 Z.6 2.6 1.1 350 620 410 670 180

120 75 95 93 86 150 1.5 2.1 1.9 2.1 1.0 18 17 12 21 19 10 <15 <15 <15 <15 <15 Oy <22 <22 <22

7.6 6.5 3.7 13 11 4.1 91 130 99 120 49 <15 <15 <15 <15 <15 <15 17 14 17 17 1Z <1.5 <1.5 <1.5 <1.5 <1.5 <1.5 DV <22 .8 <6.8 <6.8 <1.5 Z.5 <1.5 <1.5 < l.-5

<6.8 <6.8 <6.8 <6.8 <6.8 <6.8 6.8 1Z 11 12 3.6 <15 <15 <15 <15 <15 <15 <15 <15 <1S <15 <15 49 28 61 47 40 90 <1.5 <1.5 <1.5 <1.5 *1..5 <68 <68 <68 <68 <68 <68 <15 <15 <15 <15 <15 <22 <22 <22 <22 <22 <22 <6.8 <6.8 <6.8 <6.8 <6.8

160 220 380 260 280 190 _,/ Q <6.8 <6.8 <6.8 <6.8 <6.8 13 2.4 11 2.3 20 22 <15 <15 <15 <15 <15 5.3 4.2 <2.2 3.6 8.2 <2.2 Z4 63 38 49 17 <46 64 48 <46 69 90 <68 <68 <68 <68 <68 38 14 7.2 57 42 34 <22

<22 <22 <22 <22 46 <22 100 410 140 180 48 <6.8 <6.8 <6.8 <6.8 9.7 <6.8 2.2 10 5.6 4.1 Z.Z <1.5 <1.5 <1.5 <1.5 <1.5 <1.5 4.0 3.7 6.1 6.5 Z.8 <68 <68 <68 <68 <68 <68 <46 <46 <46 <46 <46 <6.8 "<6.8 <6.8 <6.8 <6.8 <6.8 15 23 21 12 5.1

<10 <10 <10 <10 <10 <10 22 ZZ 22 22 ZZ <2.2 <2.2 <2.2 <2.2 <2.2 <2.2 6.8 14 6.8 12 6.8 <3.2 <3.2 <3.2 <3.2 <3.2 <3.2 <1.5 <1.5 <1.5 <1.S <1.5 <46 <46 <46 <46 <46 150 - <68 <68 <68 <68 <68 <68 8.0 7.6 10 9.9 8.3 11 <6.8 <6.8 <6.8 <6.8 <6.8

<22 <22 <22 <2Z <22 <22 <10 <10 <10 <10 <10 1.9 1.5 2.1 3.7 4.1 1.5 <2.2 <2.2 <2.2 <2.Z <2.2 690 210 1400 830 520 1700 <3.2 <3.Z 0.2 <3.Z <3.2 <460 <460 <460 <460 <460 <460 <46 150 <46 <46 <46 32 32 32 32 32 32 7.3 9.1 8.1 7.6 3.3

<22 <22 <22 <22 <22 <22 ZZ ZZ 22 ZZ ZZ <3.2 <3.2 <3.2 <3.2 <3.2 <3.2 1.8 3.3 2.5 4.4 1.5 <4.6 <4.6 <4.6 <4.6 <4.6 <4.6 Z80 960 1300 740 170 <320 <320 <320 <320 <320 <320 <460 <460 <460 <460 <460 52 61 39 65 57 41 <3Z <3Z <32 <3Z <32

<10 <10 <10 <10 <10 <10 <22 <22 73 Field No 100-43 100-44 100-45 100-46 100-47 100-48 AlA - 6.8 4.0 7.6 5.7 8.1 2.3 Sample No M-136106 M-136107 M-136108 M-136109 M-136110 M-136111 2.4 2.3 1.9 2.0 2.1 .80 1.0 5.0 1.0 1.2 .88 .35 5P ~: Major elements recalculated as oxides (percent) CaO 6.7 1.3 11 3.1 5.3 1.7 SiO, - 73 15 39 54 47 SI Na,O 1.3 .49 2.3 1.3 2.3 .32 A.g, . Z.I 5.S 7.6 6.1 8.3 K^ - 1.9 1.6 2.3 2.8 2.8 .89 2.4 1.0 2.4 1.6 2.4 Z.6 TtO, - .25 .20 .28 .28 .27 .12 1.1 .48 4.6 .56 1.3 1.1 P2°5 - - 5.0 .94 5.7 1.6 3.0 .64 3P :::: 20 5.3 7.3 8.5 Z.O NftO .029 .013 .053 .018 .023 .0062 Na,0 1.8 .70 .61 2.4 1.3 1.4 Major elements (per cent) K?0 -- 2.3 .70 1.9 3.3 1.6 2.4 TfOj - .30 .83 .27 .20 .27 .32 24 22 23 24 32 34 PA - Z.O 16.0 .87 3.7 7.3 .71 3.6 2.1 4.0 3.0 4.3 1.2 M50 .019 .062 .023 .019 .040 .057 1.7 1.6 1.3 1.4 1.5 .56 .63 .30 .60 .73 .53 .21 Major elements (percent) 4.8 .96 7.5 2.Z 3.8 1.2 7.2 18 .99 .36 1.7 .99 1.7 .24 25 ZZ 24 1.1 Z.9 4.0 3.2 4.4 1.6 1.3 2.3 1.9 2.3 .74 .71 1.7 1.1 1.7 1.8 .15 .12 .17 .17 .16 .074 Mg - to .Z9 2.8 .34 .76 .65 2.2 .41 2.5 .71 1.3 .28 r. __ .... 7 A A 1

Table 7 79 Table 7. Semiquantitative spectrographic analyses of the upper phosphatic mudstone member of the Santa Margarita Formation, at trench 100 in Cuyama Valley phosphate area, Santa Barbara County, Calif. Continued

Strat. unit 26 25 24 23 22 21 Strat. uni t 20 19 18 17 16 15 Field No 100-43 100-44 100-45 100-46 100-47 100-48 Field No 100-49 100-50 100-51 100-52 100-53 100-54 Sample No M-136106 M-136107 M-136108 M-136109 M-136110 M- 1361 11 Sample No M-13611Z M-136113 M-136114 M-136115 M-136116 M-136117 Majoi element -continued s (percent)- Major el ements (pe rcent)

.SZ .45 1.8 .98 1.0 16 20 16 23 18 .58 1.6 2.7 1.3 2.0 1.6 4.6 3.3 2.8 2.7 .05 .16 .12 .16 .19 .83 1.7 1.4 1.1 .62 6.7 . .38 1.6 3.2 .31 Mg .25 1.4 1.3 2.2 .25 .048 .018 .015 .031 .044 7.6 1.5 2.8 4.5 8.4

Minor elements (ppm) .92 .36 .16 1.0 1.0 1.0 .'77 .34 1.3 1.3 Ag - 0.14 0.13 0.17 0.10 .09 .17 .12 .09 .08 0.12 = .07 M50 <150 <150 <150 <150 3.7 .12 .59 1.4 <10 <10 <10 <10 <10 .034 .005 .004 .017 .082 24 32 17 27 22 520 320 720 430 530 Minor e 1 emen t s ( ppm) Ag 3.6 1.5 2.2 2.5 1.8 0.10 0.13 0.10 0.12 0.10 <15 <15 <15 <15 <15 < 150 < 150 < 150 < 150 < 150 180 <32 <32 68 <32 < 10 < 10 < 10 < 10 < 10 220 93 130 110 71 16 25 Z3 13 9.1 1.4 2.7 1.3 2.6 4.7 330 260 150 320 630

110 80 110 110 67 2.9 2.9 Z.Z 1.8 1.9 9.4 18 7.7 13 11 < 15 < 15 < 15 < 15 < 15 64 <32 <32 <32 65 Dy <22 <22 <22 <22 <22 <10 <10 <10 <10 <10 110 170 170 93 86 3.6 1.5 3.2 1.5 1.5 3.2 1.0 1.0 1.3 1.3

2.6 9.2 11 9.6 13 100 18 19 52 41 <15 <15 <15 <15 <15 11 7.9 7.4 9.3 3.0 Dy <22 <22 <22 <2Z <1.5 <1.5 <1.5 <1.5 <1.5

7.1 <6.8 <6.8 <6.8 <6.8 6.3 18 15 8.8 7.9 <15 <15 <15 <15 <15 < 15 < 15 < 15 < 15 < 15 120 36 62 54 36 < 1.5 < 1.5 < 1.5 < 1.5 < 1.5 <68 <68 <68 <68 <68 < 15 100 100 < 15 < 15 <22 <22 <22 <22 <22 <6.8 <6.8 <6.8 <6.8 < 6.8 <6.8 <6.8 <6.8 <6.8 <6.8 480 180 150 310 440 5.1 10 2.2 9.9 2.5 La -v- 49 74 78 Z8 3.7 3.6 9.9 36 2.2 6.6 <68 <68 <68 <68 <68 <46 56 <46 <46 50 <2Z <22 <22

<22 <22 <22 <22 <22 < 10 < 10 < 10 < 10 1.5 3.9 3.3 2.5 2.6 <2.2 <2.2 <2.2 <2.2 <2.2 3000 350 830 940 620 <3.2 <3.2 <3.2 <3.2 <3.Z <460 <460 <460 <460 <460 150 <46 <46 <46 <46 <32 <32 <32 <32 <32 6.9 7.7 6.2 5.2 6.1

<22 <22 <22 <22 <22 <2Z <22 <2Z < 22 < 22 <3.2 <3.2 <3.2 <3.2 <3.2 2.1 7.4 6.3 < 1.5 < 1.5 <4.6 <4.6 <4.6 <4.6 <4.6 1000 230 200 490 790 320 320 320 320 320 <460 <460 <460 <460 <460 41 68 32 60 55 <32 <32 <32 <3Z <32

< 10 < 10 <10 <10 < 10 < 22 < 22 < ZZ

< 10 < 10 < 10 < 10 < 10 Strat. unit 20 19 18 17 16 15 45 31 Zl 16 Z6 Field No 100-49 100-50 100-5Z 100-51 100-53 100-54 3.1 4.Z Z.7 Z.Z Z.I Sample No M-13611Z M-136113 M-136114 M-136115 M-136116 M-136117 140 43 51 54 91 130 620 540 150 160 Major elements recalculated as oxides (pe rcent)

SiO, ----- 73 34 43 34 49 39 Strat. uni t 14 13 12 11 10 9 A1 2°3 " 8.7 6.2 5.3 Field No 100-55 100-56 100-57 100-58 100-59 100-60 7.4 3.0 5.1 M-136118 2.9 1.2 2.4 2.0 1.6 .89 Sample No M-136119 M-136120 M-1361Z1 M-136122 M-1361Z3 5P .98 .41 Z.3 2.2 3.7 .41 CaO Z.I 11 2.1 3.9 6.3 12 Major elements recalculated as oxides (pe rcent) >73 >73 >73 >73 Na,O 1.6 1.2 .49 .22 1.4 1.4 SiO, >73 39 v 0 2.5 1.2 .93 .41 1.6 1.6 13 12 9.5 10 13 5.5 TtOj - .38 .15 .28 .20 .It .13 Z.I 2.6 3.2 Z.6 4.0 1.3 1.4 8.5 .28 .16 1.4 3.2 MgO .91 1.8 .93 .86 1.4 2.3 3$ ::::: .022 .044 .007 .006 .022 .11 CaO 5.5 2.2 4.3 2.4 5.0 31

80 Table 7 Table 7. Semiquantitative spectrographic analyses of the upper phosphatic mudstone member of the Santa Margarita Formation, at trench 100 in Cuyama Valley phosphate area, Santa Barbara County, Calif. Continued

Strat. unit 7 6 5 4 3 Z 1 Strat. unit 14 13 12 11 10 9 100-63 100-64 100-65 100-66 100-67 Field No 100-55 100-56 100-57 100-58 100-59 100-60 Field No 100-61 100-6Z Simple No - M-1361Z4 M-1361Z5 M-1361Z6 M-1361Z7 M-136128 M-1361Z9 M-136130 Simple No M-136118 M-136119 M-136120 M-136121 M-136122 M-136123 nt) Major elements recalculated as oxidesi (percent) continued SiO, >73 51 >73 >73 >73 51 >73 AlA ----- 9.3 6.6 8.1 11 10 10 13 Na,O i.b 1.6 2.2 1.5 2.2 2.3 2.6 1.9 1.6 3.3 Z.I Z.6 1.4 3.1 2.2 2.7 2.5. 3.4 1.9 £$::::: .95 3.0 5.0 Z.3 .85 2.8 1.5 .37 .38 .45 .45 .62 .17 CaO 1.7 14 5.5 1.8 Z.I 2.0 9.0 'J$% Z.I .32 2.8 1.3 2.8 6.0 ----- .021 .021 .025 .019 .058 .12 Na-O ----- 1.9 1.8 Z.3 1.5 Z.3 1.1 Z.6 K,6 -- Z.5 1.8 Z.I Z.I Z.5 1.6 3.1 tfOj - .37 .ZZ .Z8 .40 .37 .40 .37 Major elements (percent) P^ ...... 66 8.9 .78 .25 .48 .30 .66 NfiO - .019 .10 .048 .OZ1 .052 .013 .040 >34 >34 >34 >34 >18 6.2 5.0 5.3 6.8 2.9 Major elanjnts (perceiit) 1.8 2.2 1.8 2.8 .93 Mg - 1.1 .56 .52 .85 1.4 1.6 3.1 1.7 3.6 22 Ms ----- 1.2 1.6 1.1 1.6 1.7 1.8 2.2 2.1 2.8 1.6 .27 .27 .37 .10 .23 Z.6 .14 1.2 .56 1.2 2.6 .016 .019 .015 .045 .093 .031 Minor elements (ppm) Minor elemcnts (ppn) Ag -- 0.12 0.17 0.18 0.10 0.10 <150 <150 <150 <150 <150 <10 <10 <10 <10 <10 29 24 18 27 8.1 500 560 540 610 710

2.5 2.5 1.8 2.2 1.6 <15 <15 <15 <15 <15 <32 <32 <32 46 99 100 110 86 160 190 1.9 2.2 1.9 6.4 1.8

48 90 57 92 31 10 12 14 18 4.7 Dy -- < 22 < 22 < 22 < 22 < 22 < 10 < 10 < 10 < 10 < 10 1.5 2.4 1.8 2.2 1.5

Ga 16 17 14 11 16 8.5 < 15 < 15 < 15 < 15 < 15 < 1.5 < 1.5 < 1.5 < 1.5 < 1.5 < 15 < 15 < 15 < 15 < 15 <6.8 <6.8 <6.8 <6.8 <6.8 <6.8 <6.8 <6.8 < 6.8 <6.8 <6.8 <6.8

<6.8 <6.8 <6.8 <6.8 <6.8 < 15 < 15 < 15 < 15 < 15 44 46 46 73 80 <68 <68 <68 < 68 < 68 <22 <22 < 22 <22 <22

160 190 150 450 930 <2.2 <2.2 4.0 5.8 5.0 15 6.0 6.4 13 2.2 <46 <46 <46 74 <46 14 15 11 37 42

<22 <22 <22 <22 <22 13 11 9.2 15 1Z <10 <10 < 1.5 < 1.5 < 1.5 < 1.5 < 1.5 Ru ------«- AQ <68 <68 <68 < 68 < 68 <3.Z <3.Z <3.Z <3.Z <3.Z <3.Z <3.Z <6.8 <6.8 <6.8 <6.8 <6.8 Sc ...... 7.1 6.2 4.9 9.Z 6.9 9.3 5.0

< 10 < 10 < 10 < 10 < 10

<10 <10 <10 <10 < 10 20 36 30 54 52 3.1 3.8 3.1 5.4 4.2 41 45 26 75 130 inn nn iitn 170 77fl 7nn

Table 7 81 Table 8. Semiquantitative spectrographic analyses of the upper phosphatic mudstone member of the Santa Margarita Formation, at trench 294 in Cuyama Valley phosphate area, Santa Barbara County, Calif.

[Lower limit of detection of element concentration given with symbol <. Si, Al, Fe, Mg, Ca, Na, K, Ti, P, Mn, and their oxides given in weight percent; all others in parts per million. All element determinations based on Semiquantitative spectro­ graphic analyses by M. J. Cremer, C. Heropoulos, and L. Mei]

Strat. unit - 113 88 63 30 Strat. unit - 113 88 63 30 Field No - PI-294 P2-294 P3-294 P4-294 Field No PI-294 P2-294 P3-294 P4-294 Sample No W193356 W193357 W193358 W193359 Sample No W193356 W193357 W193358 W193359

Major elements recalculated as oxides (percent) Minor elements (ppm) continued

Si02 54 64 30 28 Ga 10 9.4 4.6 5 .5 A120 3 9.1 11 4. 0 7.8 Gd <6.8 9.5 12 <6 .8 Fe20 3 1.6 1.2 90 .89 Ge <4.6 <4.6 <4.6 <4 .6 MgO .63 .35 . 37 .50 Hf <100 <100 <100 <100 CaO -- - 8.8 4.8 10 11 Ho <6.8 <6.8 <6.8 <6 .8 Na2 0 1.3 2.0 1. 0 1.4 In <6.8 <6.8 <6.8 <6 .8 K20 1.3 1.9 1. 1 1.1 Ir <15 <15 <15 <15 Ti02 .23 .18 090 .12 La 48 69 61 45 P2o5 ______5.7 2.5 11 6.0 Li <68 <68 <68 <68 MnO .019 .017 025 .053 Lu <22 <22 <22 <22 Mn 150 410 Major elements (percent) 130 190 Mo 9.4 25 32 5 .9 Nb 10 <3.2 4.5 <3 .2 Si 25 30 14 13 Nd 59 <46 <46 M _ _ __ _ 4.8 5.6 2. 1 4.1 Ni 12 17 Fe 1.1 .83 63 .62 5-4 16 Mg ______.38 .21 . 22 .30 Os _

82 Table 8 Table 9. Semiquantitative spectrographic analyses of the upper phosphatic mudstone member of the Santa Margarita Formation, at trench 295 in Cuyama Valley phosphate area, Santa Barbara County, Calif.

[Lower limit of detection of element concentration given with symbol <. Si, Al, Fe, Mg, Ca, Na, K, Ti, P, Mn, and their oxides given in weight percent; all others in parts per million. All element determi-nations based on Semiquantitative spectrographic analyses by M. J. Cremer, C. Heropoulos, and L. Mei]

Strat. unit 72 60 32 8 Strat. unit 72 60 32 8 Field No --- PI-295 P2-295 P3-295 P4-295 Field No - PI-295 -2-295 P3-295 P4-295 Sample No ~ W193360 W193361 W193362 W193363 Sample No. ~ W193360 W103361 W193362 W193363

Major elements recalculated as oxides (percent) Minor elements (ppm) continued

SiO, 32 47 39 21 Gd - 8.8 11 6.8 6.8 Al-0, 5.7 7.9 9.3 3.6 Ge - <4.6 <4.6 <4.6 <4.6 Fe2°3 - 1.7 2.1 1.2 .82 Hf - <100 < 100 < 100 < 100 MgO .70 .51 .46 .50 Ho - <6.8 <6.8 <6.8 <6.8 CaO 12 10 14 20 In - <6.8 <6.8 <6.8 <6.8 Na 0 .89 1.3 1.2 .85 Ir - < 15 < 15 < 15 < 15 V ft ______.76 1.2 1.0 .88 La - 65 84 69 39 TtQ - .16 .13 .11 .092 Li <68 <68 <68 <68 P2°5 9.6 7.1 13 7.8 Lu - <22 <22 <22 <22 MnO .023 .058 .035 .035 Mn 180 450 Major elements (percent) Mo 8.2 16 9.1 4.6 MK _-____- 5.9 5.6 4.4 3.2 Si 15 22 18 10 Nd <46 <46 <46 <46 Al 3.0 4.2 4.9 1.9 Ni - 8.6 22 40 26 Fe 1.2 1.5 .81 .57 Mg .42 .31 .28 .30 Os 32 <10 <10 <10 Ca 8.5 7.2 9.8 14 Pb 11 12 < 10 < 10 Pd <1.5 < 1.5 < 1.5 < 1.5 Na .66 .95 .91 .63 Pr <68 <68 <68 <68 K .63 .99 .86 .73 Pt <6.8 <6.8 <6.8 <6.8 Ti .097 .076 .063 .05S P 4.2 3.1 5.7 3.4 Re <10 <10 <10 < 10 Mn .018 .045 .027 .027 PJi <1.0 <1.0 < 1.0 < 1.0 f\ <3.2 <3.2 <3.2 Minor elements (ppm) Sb <100 <100 <100 <100 9.4 7.7 9 ? 6.4 Ag .21 .10 .35 .13 As <150 <150 <150 <150 Sm <46 <46 <46 <46 Au < 10 < 10 < 10 < 10 Sn <6.8 <6.8 <6.8 <6.8 B ~ 37 27 31 15 Sr 900 780 1000 590 Ba 300 380 420 310 Ta ~ <320 <320 <320 <320 Tb <32 <32 <32 <32 Be 5.2 3.1 3.4 1.4 Bi <22 <22 <22 <22 Th <22 <22 <22 <22 Cd 42 50 96 140 TI <10 <10 <10 <10 Ce 130 160 130 70 Tm <4.6 <4.6 <4.6 <4.6 Co 6.1 4.6 2.5 2.1 u <320 <320 <320 <320 V ~ 43 39 40 23 Cr -- 66 60 79 39 Cu _. 18 14 16 9.0 W <10 <10 <10 <10 Dy -- <32 <32 <32 <32 y 47 77 67 37 -- < 10 < 10 <10 <10 Yb 4.1 6.7 4.8 2.2 Eu - <1.5 2.5 2.1 1.5 Zn 86 110 120 110 Ga 5.7 7.0 5.2 3.3 Zr 240 300 140 69

Table 9 83 Table 10. Semiquantitative spectrographic analyses of the upper phosphatic mudstone member of the Santa Margarita Formation, at trench 296 in Cuyama Valley phosphate area, Santa Barbara County, Calif.

[Element concentration less than the llower limit of detection is reported as n.d. (not detected). Si, Al, Fe, /Ig, Ca, Na, K, Ti , P, Mn given in weight percent; all others in parts pe:r million. All element determinations based on Semiquantitatiive spectrographic analyses by M. J. Cremer, C. Heropoulos, and L. Mei]

Strat. unit - 103 100 99 94 93 88 Strat. unit - 87 86 85 83 82 78 Field No CA-1 CA-2 CA-3 CA-5 CA-6 CA-7 Field No CA-8 CA-9 CA-10 CA-11 CA-12 CA-13 Sample No 64M-U19 64M-1220 64M-1221 64M-1222 64M-1223 64M-1224 Sample No 64M-1225 64M-1226 64M-1227 64M-1228 64M-1229 64M-1230

Major elements (percent) Major elements (percent)

>10 >10 >10 >10 >10 >10 Si >10 MO MO " 10 7.0 7.0 5.0 5.0 7.0 5.0 Al 5 5 5 7 5 2.0 3.0 1.5 2.0 2.0 1.0 Fe 1.5 2 1 2 1.5 MB .7 1.0 .7 .7 1.0 3.0 .7 1 1 1.5 .7 5.0 1.0 10.0 10.0 5.0 10.0 Ca 10 5 >10 3 7

2.0 1.5 1.5 1.5 1.5 1.5 Na 1.5 1.5 1.5 1.5 1.5 2.0 2.0 1.5 1.5 2.0 1.5 K 1.5 1.5 1.5 2 1.5 .3 .5 .3 .3 .5 .2 Ti .3 .5 .2 .5 .3 1.5 ' n.d. 3.0 7.0 0.7 n.d. P 3 1 3 n.d. 1.5 .015 .01 .05 .05 .03 .02 Mn - .03 .03 .02 .05 .02 .01

Minor elements (ppm) Minor elements (ppm) Ag , n.d. n.d. n.d. n.d* Ag ...... n.d. n. d* n.d. n.d. n.d. n.d. As n.d. n.d. n.d. n.d. n.d* n.d. n.d. n.d. n.d. n.d. n.d. Au n.d. n.d. n.d. n.d. n.d. n.d* n.d. n.d. n.d. n.d* n.d. B 20 30 15 30 15 20 30 20 15 15 15 Ba 500 50 50 50 70 700 500 500 500 500 300 Be 1.5 1 1 1 1.5 1.5 1.5 2 2 1 n.d. 3i n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. Cd n.d. n.d. n.d. n.d. n.d. n.d. n.d. Ce n.d. n.d. .n.d. n.d. n.d. Co n.d. 3 n.d. 3 2 3 5 n.d. 5 3 7 Cr 150 150 150 150 200 100 100 100 150 100 100 10 20 5 20 10 10 20 .7 .7 10 7 Cu ------Looked for Y is found above 50 ppm Dy ------Looked for only when Y is found above 50 ppm Dy only when 50 ppm Er Looked for only when Y is found above 50 ppm Er only when Y is found above n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. Eu n.d. n.d. n.d. 10 10 7 15 10 10 15 7 7 10 7 Ga Gd ------Looked for only when Y is found above 50 ppm Gd Looked for only when Y is found above 50 ppm n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. Ge n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d.. n.d. n.d. Hf n.d. Ho ------Looked for only when Y is found above 50 ppm Ho Looked for only when Y is found above 50 ppm n.d. n.d. n.d* n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. Looked for Pd or Pt found Ir ------Looked for only when Pt or Pd are found Ir only when La 70 30 50 30 50 30 30 50 70 30 n d . Li n.d. n.d. n.d. n.d. n.d* n.d. n.d. n.d. n.d. n.d. Lu only when Y is found above 50 ppm Lu Looked for only when Y is found above 50 ppm 150 100 500 500 300 200 Mn 300 200 500 200 100 5 10 . 3 15 5 n.d. Mo 5 n.d. 3 7 5 n.d. 5 n.d. n.d. n.d. n.d. Mb 5 n.d. n.d. 5 n.d. " <*- Nd n.d. n.d. n.d. n.d. 20 20 50 20 30 15 Ni 20 50 15 20 15 -. Looked for Os Looked for only when Pd or Pt Os only when Pd or Pt found 7 7 7 7 7 n.d. Pb 7 n.d. n.d. 7 n.d. Pd n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. Pr n.d. n.d. n.d. n.d. n.d. Pt Pt n.d. n.d. n.d. n.d: n.d.

Re n.d. n.d. n.d. n.d. Rh only when Pd or Pt found Looked for only when Pd or Pt ------Looked for Ru Looked for only when Pd or Pt found Ru only when Pd or Pt found n.d. n.d. n.d. n.d. n.d. n.d. Sb ,n . d . n.d. n.d. n.d. n.d. 7 10 10 10 7 n.d. Sc 7 5 $ 7 7

n.d* n.d. n.d. n.d. Sm n.d. n.d . n.d. n.d. n.d. n.d. n.d. n* d. n.d. n.d. Sn n.d. n.d. n.d. n.d. 700 200 700 1000 500 500 Sr 1000 300 1000 300 700 n.d* n.d. n.d. n.d. n.d. . Ta n.d. n.d. n.d. n.d. n.d. n.d. Looked for Tb ------Looked for only when Y is fouiid above 50 PP11 Tb only when Y is found above 50 ppm

n.d. n. d Th n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. 1 n.d. n.d* n.d. n.d. n.d. n.d. TI n.d. n.d. n.d* n.d. Tn Looked for only when Y is foui id above 50 ppm 1m only when Y is found above 50 ppm n. d . n.d. n.d. n.d. n.d. n.d. U n.d. n.d. n.d. v Looked for only when Y is fouiid above 50 ppm V 50 70 50 70 50

n.d. n.d* n.d. n.d. n.d. n.d. W n.d. n.d. n.d. n.d* n.d. 30 20 30 50 20 15 Y 50 20 30 15 50 5 3 1.5 3 1.5 1.5 Yb 5 2 3 1.5 3 n.d. n.d. n.d. n.d. n.d. Zn n.d. n.d. n.d. n.d. inn iin inn 200 150 100

84 Table 10 Table 10. Semiquantitative spectrographic analyses of the upper phosphatic mudstone member of the Santa Margarita Formation, at trench 296 in Cuyama Valley phosphate area, Santa Barbara County, Calif. Continued

Strat. unit - 77 7Z 71 70 69 68 Strat. unit - 62 60 57 56 54 50 Field No CA-14 CA-15 CA-16 CA-17 CA-18 CA-19 Field No CA-ZO CA-Z1 CA-ZZ CA-Z3 CA-Z4 CA-Z5 Sample No 64M-1Z31 64M-1Z3Z 64M-1Z33 64M-1Z34 64M-1Z35 64M-1Z36 Sample No 64M-1Z37 64M-1Z38 64M-1Z39 64M-1Z40 64M-1Z41 64M-1Z4Z

Major elements (pe rcent) Major elements (percent) >10 Si >10 >10 >10 >10 >10 Si >10 >10 >10 > 10 Al 7 5.0 7 7 7 Al 5 7 5 7 7 Fe 1.5 1.5 1 Z 1.5 Fe 1.5 Z 1.5 Z Z .7 Mg .5 1.5 .5 .7 1 Mg .7 .7 .7 .7 Ca >10 5 7 7 7 Ca 737 Z 5

Na 1.5 1.5 Z 1.5 1.5 Na 1.5 1.5 1.5 1.5 1.5 K 1.5 1.5 1.5 1.5 1.5 K 1.5 1.5 1.5 1.5 1.5 Ti .Z .3 .3 .5 .3 Ti .Z .3 .3 .3 .3 P 3 5 Z n.d. 1.5 P 1 1 3 7 1 Mn .03 .015 .01 .01 .015 Mn 5 .01 .01 .015 .01 .01

Minor elements (ppm) Minor elements (ppm)

Ag n.d. n.d. n.d. n.d. n.d* Ag As n.d. n.d. As n.d. n.d n.d. n.d. n.d. ------n.d. Au ...... n .d. n.d. n.d* n.d. n.d. n.d. Au n * d. n.d . n.d. n.d. n.d. B 15 ZO ZO 30 ZO B 15 ZO 15 15 15 Ba 700 300 700 300 500 Ba 700 500 500 500 500

Be Be 1 1 1.5 1 1 1.5 1 1.5 1 1 n.d. Bi n.d. Bi n.d. n.d n.d. n.d. Cd n.d. n.d. n.d n.d. Cd n.d. n.d. n.d. n.d* n.d. Ce Ce n.d. n.d n.d. 3 Co n.d. n.d. Z Z Z Z Co Z Z n.d. Z Z Ci 150 ZOO ZOO 150 ZOO Cr 150 150 ZOO 150 150 Cu 10 50 10 ZO 15 Cu 05 15 10 ZO 10 Dy - - Looked for only when Y is found above 50 ppm Dy for only when Y is foi md above 50 ppm --- - Looked Er .- Looked for only when Y is found above 50 ppm Er for only when Y is foi ind above 50 ppm n.d. Eu n.d. n.d. n.d n.d. n.d. n.d. Eu n.d. n.d. n.d. n.d. n.d. Ga 7 10 10 7 10 Ga 7 7 7 10 7 ----- Looked Gd - - Looked for only when Y is found above 50 ppm Gd for only when Y is totmd above 50 ppm Ge Ge n.d. n.d. n.d. Hf n.d. n.d. Hf n,d, n.d. n.d. n.d. ---- Looked Ho . Looked for only when Y is found above 50 ppm Ho for only when Y is fouind above 50 ppm In n.d. n.d. In n .d. n.d. n.d. n.d. n.d. n.d. Ir -- Looked for only when Pd or Pt found Ir ------Looked for only when Pd or Pt found La 30 30 30 30 30 La 70 0 10 n.d. 30 Li Li n.d. n.d. Lu Looked for only when Y is found above 50 ppm Lu ------Looked for only when Y is found above 50 ppm 100 Mn Mn 100 100 150 100 300 150 100 100 150 5 7 Mo Mo 7 7 5 5 n.d. 10 10 50 n.d. n.d. n.d. n.d. n.d* Nb 5 Mb n.d. n.d. 5 5 5 Nd ------n.d. n.d. n.d. n.d. n.d. n.d. Nd n.d. n.d. n.d. ZO Ni 15 15 ZO 15 15 Ni 30 30 ZO 15 30 Os for only when Pd or Pt found Os --- Looked for only when Pd or Pt found Pb 7 n.d. 7 n.d. n.d. n* d . Pb 7 n.d. 7 7 n.d. Pd n.d. n.d. n.d. n.d. n.d. Pd ------n.d. n.d. n.d . n.d. n.d. n. d . Pr Pr n.d. n.d. n.d. n.d. n.d. Pt n.d. n.d. n.d. n.d. n.d. Pt n.d. n.d. n.d. n.d. Re n.d. n.d. n.d. n.d. n.d. n.d. Re Rh Looked for only when Pd or Pt found Rh - Looked for only when Pd or Pt found Ru --_. Looked for only when Pd or Pt found Ru --- Looked for only when Pd or Pt found Sb n.d. n.d. n.d. n.d. n.d. Sb n.d. n.d. n.d. n.d. n.d. Sc 5 7 7 5 7 Sc 7 7 n.d. 10 7 7 Sm n.d. n.d. n.d. n.d. n.d. n.d. Sm n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. Sn Sn 700 ' - 1000 500 500 ZOO 300 Sr 3000 Sr 1000 ZOO 1000 150 700 Ta n .d. n.d. n.d. n.d. n.d. n.d. Ta Tb ----- Looked for only when Y is found above 50 ppm Tb Looked for only when Y is found above 50 ppm n.d . Th n.d. n.d. n.d. n.d. n.d. Th n.d. n.d. n.d. n.d. TI n.d. n.d. n.d. n.d. n.d. TI n.d. n.d. n.d. n.d. n.d. Tm ------Looked ]for only when Y is found above 50 ppm Tm ... - Looked for only when Y is found above 50 ppm n.d. U n.d. n.d. n.d. n.d. n.d. U n.d. n.d. n.d. n.d. 50 70 V 50 70 50 70 50 V 70 70 50 n.d. n.d. W n.d. n.d. n,d. n.d. n.d. w n.d. n.d. n.d. Y 70 10 50 10 Y ZO ZO 30 10 15 ZO 1.5 1.5 Yb 5131 Z Yb Z Z Z n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. 7, .--__._ i en Zr 150 150 100 100 150 100

Table 10 85 Table 10. Semiquantitative spectrographic analyses of the upper phosphatic mudstone member of the Santa Margarita Formation, at trench 296 in Cuyama Valley phosphate area, Santa Barbara County, Calif. Continued

Strat. unit - 49 48 47 46 45 39 27 Field No CA-26 CA-27 CA-28 CA-29 CA-30 CA-31 CA-35 Sample No 64M-1243 64M-1244 64M-1245 64M-1246 64M-1247 64M-1248 64M-1249

Major elements (percent)

Si >10 >10 >10 >10 >10 >10 >10 77757 7 7 T7 _ 1 2 1.0 1.0 2 1.0 2 Mg .5 .7 .7 .5 1 .7 1.5 Ca 72517 >10 3

2 1 1.5 1 1.5 2 .5 2 1.5 1.5 1.5 1.5 1.5.15' n.d. Ti .2 .3 .3 .15 .3 .3 2 51 n.d. Z 3 n.d. Mn .01 .007 .015 .005 .02 .05 .005

Minor elements (ppm)

Ag __ __ n.d. n.d. n.d. n.d. n.d. n.d. n.d. As n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. B __ 15 20 15 15 20 15 15 Ba 1000 500 700 200 500 700 150

1.5 1 1.5 n.d. 1.5 1 1.5 Bi n.d. n.d. n.d. n.d. n.d. n.d. n.d. C°A n.d. n.d. Ce n.d. n.d. n.d. n.d. n.d. n.d. n.d. Co n.d. 2 2 n.d. 2 n.d. n.d.

150 150 200 100 150 100 30 5 10 7 15 15 2 5 Dy Looked for only when Y is found above 50 ppm Er Looked for only when Y is found above 50 ppm Eu n.d. n.d. n.d. n.d. n.d. n.d. n.d.

10 10 10 7 10 7 15 CtA _ __ Looked for only when Y is found above 50 ppm Ge n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. Looked for only when Y is found above 50 ppm In n.d. n.d. n.d. n.d. n.d. n.d. n.d. Ir Looked for only when Pd or Pt found La 30 30 30 30 30 50 30 Li n.d. n.d. n.d. n.d. n.d. n.d. n.d. Lu Looked for only when Y is found above 50 ppm

Mn 100 70 150 50 200 500 50 Mo 753 n.d. 7 n.d. ' 5 Nb n.d. 5 5 n.d. n.d. n.d. 150 n.d. n.d. n.d. n.d. n.d. n.d. n.d. Ni 10 10 15 10 50 15 15

Os Looked for only when Pd or Pt found Pb 777 n.d. n.d. 7 7 Pd n.d. n.d. n.d. n.d. n.d. n.d. n.d. Pr - n.d. n.d. n.d. n.d. n.d. n.d. n.d. Pt n.d. n.d. n.d. n.d. n.d. n.d. n.d.

Re n.d. n.d. n.d. n.d. n.d. n.d. n.d. Rh Looked for only when Pd or Pt found Ru Looked for only when Pd or Pt found Sb n.d. n.d. n.d. n.d. n.d. n.d. n.d. Sc 555 n.d. 7 5 5

Sen n.d. n.d. n.d. n.d. n.d. n.d. n.d. Sn n.d. n.d. n.d. n.d. n.d. .n.d. 5 700 200 500 150 500 1000 150 Ta n.d. n.d. n.d. n.d. n.d. n.d. n.d. Looked for only when Y is found above 50 ppm

Th n.d. n.d. n.d. n.d. n.d. n.d. n.d. Tl n.d. n.d. n.d. n.d. n.d. n.d. n.d. Looked for only when Y is found above 50 ppm U n.d. n.d. n.d. n.d. n.d. n.d. n.d. 30 70 50 30 50 30 15

W n.d. n.d. n.d. n.d. n.d. n.d. n.d. Y 30 15 20 n.d. 20 50 10 Yb 3 1.5 2 n.d. 2 3 1 Zn n.d. n.d. n.d. n.d. n.d. n.d. n.d. "7, ____ -- ->nn i<;n ?nn <;n inn i<»n 5nn 86 Table 10 Table 10. Semiquantitative spectrographic analyses of the upper phosphatic mudstone member of the Santa Margarita Formation, at trench 296 in Cuyama Valley phosphate area, Santa Barbara County, Calif. Continued

[Lower limit of detection of element concentration given with symbol <. Si, Al, Fe, Mg, Ca, Na, K, Ti, P, Mn, and their oxides given in weight percent; all others in parts per million. All element determinations based on Semiquantitative spectrcgraphic analyses by M. J. Cremer, C. Heropoulos, and L. Mei]

Strat. unit - 94 86 61 Strat. unit - 94 86 61 Field No PI-296 P2-296 P3-296 Field No PI-296 P2-296 P3-296 Sample No W193364 W193365 W193366 Sample No W193364 W193365 W193366

Major elements recalculated as oxides Minor elements (ppm) continued

Ga 5.5 9.2 3 .7 Si0 2 32 60 26 Gd 6.8 6.8 6 .8 A1 20 3 - 8. 1 11 8. 3 Ge <4.6 <4.6 <4 .6 Fe2 0 3 - 2. 3 2 .0 94 Hf <100 <100 <100 MgO 68 .78 1. 3 Ho <6.8 <6.8 <6 .8 CaO 17 11 21 In <6.8 <6.8 <6 .8 Na2 0 89 1 .4 86 Ir <15 <15 <15 K20 83 1 .5 . 83 La 81 84 61 Ti02 16 .20 088 Li <68 <68 <68 P20 5 - 12 6 .2 10 Lu <22 <22 <22 MnO 026 .030 045 Mn 200 230 350 Mo 12 <2 Major elements (percent) 5.0 .2 Nb <3.2 . 4.7 <3 .2 Nd <46 <46 Si 15 28 12 Ni 12 16 13 Al 4. 3 5 .7 4. 4 Fe 1. 6 1 .4 66 Os <10 <10 <10 Mg 41 .47 77 Pb <10 <10 <10 Ca 12 8 .0 15 Pd <1.5 <1.5 <1 .5 Pr <68 <68 <68 Na 66 1 .0 64 Pt <6.8 <6.8 <6 .8 69 1 .2 69 Ti 095 .12 053 Re - <10 <10 <10 P 5. 4 2 .7 4. 5 Rh .0 Mn 020 .023 035 Ru <3.2 <3.2 <3 .2 <100 <100 <100 Minor elements (ppm) Sc 9.5 8.3 7 .6 Sm Ag 0. <46 <46 27 0 .23 0. 10 Sn <6.8 <6 As <150 <150 <150 <6.8 .8 Sr 1000 700 980 33 Ta <320 <320 <320 31 30 Tb <32 <32 <32 Ba 290 440 400 Th <22 Be 4. <22 <22 9 3 .6 2. 1 TI Bi <22 <22 <22 Tm Cd 61 <4.6 <4 .6 54 61 U <320 <320 <320 Ce 170 160 110 V 40 39 28 Co 2. 6 3. 1 2. 4 W Cr 76 54 70 57 Cu 14 72 52 14 8. 6 Yb 5.2 Dy < 32 <32 <32 6.3 3 .3 Er __ _ Zn 98 98 120 Zr 270 180 170 Eu 1. 7 2. 5 2. 9

Table 10 87 Table 11. Semiquantitative spectrographic analyses of the upper phosphatic mudstone member of the Santa Margarita Formation, at trench 297 in Cuyama Valley phosphate area, Santa Barbara County, Calif.

[Lower limit of detection of element concentration given with symbol <. Si, Al, Fe, Mg, Ca, Na, K, Ti, P, Mn, and their oxides given in weight percent; all others in parts per million. All element determinations based on Semiquantitative spec­ trographic analyses by M. J. Cretner, C. Heropoulos, and L. Hei]

Strat. unit - 98 89 56 27 Strat. unit - 98 89 56 27 Field No P2-297 P2-297 P3-297 P4-297 Field No P2-297 P2-297 P2-297 P2-297 Sample No W193367 W193368 W193369 W193370 Sample No W193367 W193368 W193369 W193370

Major elements recalculated as oxides (percent) Minor elements (ppm) continued

Sio2 32 36 26 43 Ga 6.2 6.3 2.5 6.1 A12 0 3 7.6 7.0 3.6 8.9 Gd 6.8 6.8 6.8 6.8 Fe 20 3 1.7 1.3 .84 1.7 Ge <4.6 <4.6 <4.6 <4.6 MgO .70 .70 .60 1.0 Hf <100 <100 <100 <100 Ho CaO 15 13 17 13 <6.8 <6.8 <6.8 <6.8 Na20 .92 1.3 .80 1.2 In <6.8 <6.S <6.8 <6.3 K2 0 .78 1.1 .60 1.0 Ir <15 <15 <15 <15 Ti02 14 .13 .098 .20 La 87 90 80 47 P2 05 12 11 23 8.7 Li <68 <68 <68 <68 MnO .032 .026 .037 .019 Lu <22 <22 <22 <22 Mn 250 200 290 150 Major elements (percent) Mo 39 20 16 110 Nb <3.2 <3.2 <3.2 Si 15 4.8 17 12 20 Nd 56 61 <46 <46 Al 4.0 3.7 1.9 4.7 Ni 17 17 11 19 Fe 1.2 .89 .59 1.2 Mg T- .42 .42 .36 .62 Os <10 <10 <10 <10 Ca 11 9.5 12 8.9 Pb <10 <10 <10 <10 Pd <1.5 <1.5 <1.5 <1.5 Na .68 .93 .59 .86 Pr <68 <68 <68 .65 <68 .95 .50 .86 Pt <6.8 <6.8 <6.8 <6.8 Ti .083 .078 .059 .12 p 5.3 4.6 <10 3 0 Re <10 <10 <10 <10 Mn .025 .020 .029 .015 Rh <1.0 <1.0 <1.0 <1.C Ru <3.2 <3.2 <3.2 <3.2 Sb <100 Minor elements (ppm) <100 <100 <100 Sc 11 7.7 10 9.7 Ag .23 .22 .35 .26 Sm <46 <46 <46 <46 As <150 <150 <150 <150 Sn <6.8 <6.8 <6.8 <6.8 Au <10 <10 <10 <10 Sr 1100 oo 840 1300 960 35 32 30 Ta < 3 20 <320 <320 <320 Ba 440 530 390 350 Tb < 32 <32 <32 <32 Be 3.6 2.7 4.9 2.5 Th <22 <22 <22 <22 Bi <22 <22 <22 <22 TI <10 <10 <10 <10 Cd 67 52 66 80 Tm <4.6 <4.6 <4.6 <4.6 Ce 170 190 170 93 U <32Q <320 <320 <320 Co 3.1 3.1 3.5 3.1 V 44 36 45 45 p*- L.r ~ 84 75 84 92 w .- <10 <10 <10 <10 Cu 13 18 13 15 Y . 71 69 74 40 Dy <32 <32 <32 <32 Yb - 5.4 4.8 4.9 3.3 Er <10 <10 <10 <10 Zn - 150 160 140 89 Eu <1.5 <1.5 2.1 2.0 Zr - 190 98 390 190

88 Table 11 Table 12. Semiquantitative spectrographic analyses of the upper phosphatic mudstone member of the Santa Margarita Formation, at trenches 299 and 300 in Cuyama Valley phosphate area, Santa Barbara County, Calif.

[Element concentration less than the lower limit of detection is reported as n.d. (not detected). Si, Al, Fe, Mg, Ca, Na, K, Ti, P, Mn, and their oxides given in weight percent; all others in parts per million. All element determinations based on Semiquantitative spectrographic analyses by M. J. Cremer, C. Heropoulos, and L. Mei]

TRENCH 299 TRENCH 300 TRENCH 299 TRENCH 300

Strat. unit - 81 81 81 62 Strat. unit - 81 81 81 62 Field No CB-la CB-lb CB-lc PI-300 Field No - CB-la CB-lb CB-lc PI-300 Sample No 64M-1346 64M-1347 64M-1348 W193371 Sample No - 64M-1346 64M-1347 64M-1348 W193371

Major elements recalculated as oxides (percent) Minor elements (ppm) continued

Sio2 _ 6.50 7.00 6. 06 >24 Ga - 5 5 5 4.1 A1 20 3 1.9 1.97 1. 87 4,.4 Gd - n.d. n.a. n.d. <6.8 Fe 20 3 .89 .36 37 2..0 Ge - n.d. n.d. n.d. <4.6 MgO .52 .50 51 ,75 Hf - n.d. n.d. n.d. <100 CaO 46.5 46.5 46. 8 >20 Ho - n.d. n.d. n.d. <6.8 Na20 .92 1.01 1. 00 1,.3 In - n.d. n.d. n.d. <6.8 K 20 .31 .32 33 .59 Ir Looked for only when Pt or Pd found <15 Ti02 .09 .12 06 .11 La -- 150 150 150 83 P2o5 30.57 30.18 30. 57 12 Li - n.a. n.d. n.d. <68 MnO Not reported .006 Lu Looked for only when Y is above 50 ppm <22 Mn - 70 150 100 510 Major elements (percent) Mo - 30 30 30 8.7 Nb - Si n.d. n.d n.d <3. 2 3.0 3.0 3. 0 >11 Md . <46 Al n.d. n.d. n.d. 1.5 1.5 1. 5 2.,3 Ni - 30 20 20 24 Fe .7 .7 7 1,,4 Mg .7 .7 . 5 ,45 for only when Pd or Pt found <10 Ca >10 >10 >10 >14 Pb - n.d. n.d. n.d. <10 Pd - n.d. <1.5 Na n.d. n.d. .7 .7 7 ,94 Pr - n.d. n.d. n.d. <68 n.d. n.d. d. Pt - n.a. n.d. n.d. <6.8 Ti .1 .15 07 ,068 , ~ p ^ i n 5. Re - n.d. n.d. < 10 Mn .007 .015 01 ,051 Rh Looked for only when Pd or Pt found <1. 0 <3.2 Minor elements (ppm) Sb - n.d. n.d. n.d. <100 C r __ __ _ . 30 30 30 9.6 Ag 0.7 0.7 0. 7 0.,14 Sm n.d. n.d. <46 As n.d. n.d. n.d. n. d. <150 Sn - n.d. <6.8 AU n.d . n.d. n.d. n.d. n . d. Sr -- 5000 5000 5000 1200 20 20 15 Ta - n.d . n.d. n.d. <320 Ba 200 300 300 230 Tb - n.d. n.d. n.d. <32 Be 3 3 3 4. 3 Th - n.d. n.d. <22 Bi n.d . n.d. n.d. n. d. <22 TI - n.d. <10 Cd 500 n.d. n.d. 300 300 85 Tm - n.d . n.d. n.d. <4.6 Ce n.d. n.d. n. d. 160 U - <320 Co n.d . n.d. n.d. n.d. n.d. n. d. 3. 6 V - 70 70 70 41 Cr 300 300 300 76 W - n.d. <10 Cu n.d . n.d. 30 30 30 17 Y -- 200 300 200 59 Dy n.d. 30 n. d. <32 Yb - Er 10 15 10 5.2 n.d. n.d. n . d. <10 Zn n.d. n.d. n.d. 140 Eu n.d. n.d. n. d. 2. " Zr - 100 150 70 170

Table 12 89 687-049/48007