Pancho Rico Formation 

Salinas Valley, California 

G E 0 L 0 G I CAL SURVEY P R 0 FE S S I 0 N A L PAPER 524-A 

Pancho Rico Formation 

Salinas Valley, California 

By DAVID L. DURHAM and WARREN 0. ADDICOTT 

SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY 

GEOLOGICAL SURVEY PROFESSIONAL PAPER 524-A 

A study of stratigraphy and paleontology of 

Pliocene marine strata in southern Salinas 

Vallry, California 

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1965 

SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY 

PANCHO RICO FORMATION, SALINAS VALLEY, CALIFORNIA 

By DAVID L. DuRHAM and WARREN 0. AnniCOTT 

ABSTRACT 

The Pancho Rico Formation of Pliocene age comprises sandy 

marine strata and interbedded finer grainr.d rocks. It generally 

overlies the marine Monterey Shale of Miocene age and underlies the nonmarine Paso Robles Formation of Pliocene and 

fleistocene( ?) age in southern Monterey County, Calif. Lo-

~ally it lies on the basement complex or on the Santa Margalita Formation of upper Miocene age. It crops otrt from north 

of King City southeastward for more than 50 miles to beyond 

the Nacimiento River and Vineyard Canyon. The Pancho Rico 

contains sandstone, mudstone, porcelaneous mudstone, porcelanite, diatomaceous mudstone, and conglomerate. Where the 

Pancho Rico overlies the Monterey Shale, its lower contact is at 

the base of the stratigraphically lowest sandstone unit above the 

typically finer grained Monterey. ·where the Pancho Rico overlies the Santa Margarita Formation, its lower contact is at the 

top of the stratigraphically highest bed that contains Ostrea 

titan, a giant oyster characteristic of the Santa Margarita. 

The upper contact of the Pancho Rico is at the top of the stratigraphically highest lithologic unit that contains marine fossils. 

Both the upper and lower contacts are conformable and gradational. At some localities the unit probably intertongues with 

the Paso Robles Formation, and at others, with the Monterey 

Shale. The thickness of the Pancho Rico ranges from less than 

20 feet to more than1,000 feet. 

The molluscan fauna of the Pancho Rico Formation consists 

principally of species not previously reported from the Salinas 

Valley area. Among the 141 larger invertebrate taxa recorded 

in this paper are many species indicative of Pliocene age, as 

that epoch is recognized in the Pacific Coast megafossil 

chronology. Faunal correlation is made with the type Jacalitos 

)!'ormation-exposed near Coalinga-a biostratigraphic unit 

that has been traditionally regarded as the standard for the 

lower Pliocene of the Pacific Coast. 

The molluscan fauna of the Pancho Rico implies a shallowwater marine environment considerably warmer than exists 

today at comparable latitudes and similar to that off the west 

coast of Baja California, Mexico. The wide distribution of 

several warm-water indicators in the early Pliocene of the 

Salinas Valley area and the absence of these indicators from 

contemporaneous strata to the north and northwest suggest 

that a Pliocene seaway connected the Salinas Valley area to the 

Santa Maria basin to the south. Local moderate-depth assemblages in exposures of the Pancho Rico Formation in the 

northwestern part of the area are of a northern, cool-water type 

and may indicate interchange with Pliocene faunas to the north 

through a northwest-trending marine trough. 

INTRODUCTION 

Sandy marine strata succeed mudstone, porcelanite, 

and chert beds of the Monterey Shale at most places in 

the Salinas Valley, southern Monterey County, Calif. 

These sandy strata, together with interspersed finer 

grained rocks, constitute the Paneho Rico Formation 

(Durham and Addicott, 1964). The following diseussion of the lithologic eharacter, stratigraphic relations, 

and thickness of the Pancho Rico Formation is by Durham, and is based on geologic 1napping and related 

studies (Durham, 1963, 1964, 1965). Paleontologic. determinations, correlation of strata, and discussion of 

mollusean paleoecology and paleogeography are by Addicott. 'The Pancho Rico was referred to as an unnamed formation of Pliocene age in three previous reports (Durham, 1963, 1964,1965). 

ACKNOWLEDGMENTS 

E. J. Moore studied eolleetions of fossil mollusks from 

18 localities (see list of fossil loes., M902-M1067) in 

1960 and 1961. These collections were rexamined and 

additional fossils were colleeted during preparation of 

this paper. Most of the echinoid identifications were 

made by J. Wyatt Durham. C. L. Rice made the initial 

collections frmn localities between San Lucas and Pancho Rico Creek in 1960. J. G. Vedder and C. A. Hepenning eolleeted the fossils from locality M982, northwest of Bradle,y, in 1960. A. Myra l{een provided access to the Stanford University collections and lent 

some specimens figured herein. J. H. Peck, Jr., arranged a loan of specimens from the Pliocene 

collections in the University of California Museum 

of Paleontology. 

Al 
A2 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY 

DEFINITION OF THE PANCHO RICO FORMATION 

Reed (1925, p. 606) "grouped together as the Poncho 

Rico 1 formation" 1narine "diatomite * * * clastic 

shale, yellowish sandstone, and conglomerate beds" on 

the east side of the Salinas Valley. He presumably 

intended that the marine strata exposed along Pancho 

Rico Creek should be considered typical of the formation, although he later (Reed, 1933, p. 231) admitted 

that the unit had "never yet been adequately defined." 

To help overcome this need, we defined the Pancho Rico 

Formation as comprising the sandy marine strata and 

interbedded finer grained rocks that generally overlie 

the marine Monterey Shale and underlie the nonmarine 

Paso Robles Formation in the Salinas Vall~y area, 

southern Monterey County (Durham and Addicott, 

1964). Locally the Pancho Rico overlies units other 

than the Monterey, as northeast of IGng City, where 

it lies nonconformably on the basement complex, and 

about 35 n1iles farther southeast near Vineyard Canyon, 

where it apparently lies conformably on the Santa Margarita Formation. Where the Pancho Rico overlies the 

Monterey, the contact is conformable and is at the base 

of the stratigraphically lowest sandstone unit above the 

typically finer grained Monterey. Sandstone beds occurring locally in the Monterey Shale in the subsurface 

near the Salinas River (Gribi, 1963, p. 19) are distinguished from lithologically similar beds in the Pancho 

Rico by their lo,ver stratigraphic position and their 

proximity to the sloping surface of the basement complex. The contact of the Pancho Rico with the overlying nonmarine Paso Robles Formation is conformable 

and is placed at the top of the stratigraphically highest 

lithologic unit containing marine fossils. The Pancho 

Rico Formation, as so defined, includes beds in the lower 

part that are lithologically identical with those in the 

Monterey Shale, and beds in the upper part that are 

lithologically similar to those in the Paso Robles Formation. In this sense, both upper and lower contacts of the 

Pancho Rico are gradational and probably intertonguing. 

Strata exposed along Pancho Rico Creek are considered typical of the Pancho Rico Formation for the 

purpose of definition, but designation of a particular 

sequence of beds as typical of the unit must be qualified 

1 Authors' note: Maps available to Reed-for example, the 1915 edition of the Priest Valley 30-minute quadrangle-have the "Poncho 

Rico" Creek joining the Salinas River at San Ardo. Later maps, including the 1927 reprint of the Pril'st Valley 30-minute quadrangle, have the 

differently spelled name "Pancho Rico" for the same stream. Gudde 

(1949, p. 269) listed the name "Poncho Rico," but stated that it "probably commemorates Francisco ('Pancho') Rico, grantee of San Lorenzo 

grant, November 16, 1842." The U.S. Board on Geographic Names 

(1961, p. 13) favored the spelling "Pancho Rico" for th~> stream, and 

this is obviously the proper form for the name of the formation. However, in this discussion of the work of others, the spelling employed by 

each investigator is used where reference is made to his work. 

by recognition o:f lateral variation in lithologic character, thickness, and stratigraphic relations. 

Many geologists have assigned part or all of the 

Pancho Rico Formation, as here defined, to the Santa 

Margarita Formation (fig. 2). However, use of the 

name Santa Margarita in the Salinas Valley is considered appropriate only at the type area, near the town 

of Santa Margarita, and in adjacent areas where beds 

occur that are similar to typical Santa Margarita in 

both lithologic character and stratigraphic position 

(Durham and Addicott, 1964). At the type area, the 

Santa Margarita overlies the Monterey Shale and is 

light-colored massive coarse-grained arkosic sandstone 

that locally contains numerous large fossil oysters. The 

concept that the Santa Margarita is progressively 

younger northward from the type area is commonly 

accepted, mainly on the basis of including in the Santa 

Margarita at least some beds that here are considered 

part of the Pancho Rico. The concept of a northward 

time transgression by the Santa Margarita is rejected 

in favor of the idea that in the southern part of the 

Salinas Valley the Santa Margarita overlies the Monterey but that farther north it intertongues with the 

uppermost part of that formation (Durham and Addicott, 1964). Accordingly, the Santa Margarita in 

southern Monterey County is considered to be a lenticular sandstone unit at or near the top of the Monterey, 

whereas the Pancho Rico Formation overlies both. 

AREAL DISTRIBUTION 

The Pancho Rico Formation crops out on the east 

side of the Salinas Valley from north of King City 

southeastward for about 50 miles to beyond Vineyard 

Canyon. It crops out at places along the west side of 

the valley from north of the Arroyo Seco southeastward 

for about 50 miles to beyond the Nacimiento River. It 

also crops out farther west, in the San Antonio River 

Valley, north and northwest of Jolon and south of 

Lockwood (fig. 1). 

PREVIOUS NOMENCLATURE 

Names previously applied to strata of late Miocene 

and Pliocene age in the Salinas Valley and the nomenclature used in this paper are shown in figure 2. Intertonguing relations are omitted from the diagram, and 

correlation of unit boundaries from column to column 

may be inexact. Figure 2 illustrates the divergence 

of opinion among previous investigators as to classification of strata here assigned to the Pancho Rico 

Formation. However, as indicated in the following 

discussion, all previous investigators have recognized 

the generally sandy nature of the sequence of strata that 

succeeds the Monterey Shale. 
PANCHO RICO FORMATION, SALINAS VALLEY, CALIFORNIA 

R 3 E R 4 E R 5 E R 6 E R 7 E R 8 E 121° R 9 E R 10 E R 11 E R 12 E R. 13 E R. 14 E 

~ ~'-----~~----J~--------~------'~·-------t--------r-----~ 

(\ 1', 

Point Conception 

"' 

Area of 

report 

Coalinga 

Santa Maria 

Ventura 

Angeles 

sin 

EXPLANATION 

I J ""-, 

L__ -"""" >:.San Benito ~ 

I )7 

~ U\ 

~~\--t--+--t--------,l--Paso-+--Rob_Ies•lf-zc '1 < 

Areas that contain outcrops of Pancho Rico Formation 

~ 

~~ ® Location of columnar sections 

X M902 Fossil locality (numbers preceded by M are USGS 

locality numbers; others Univ. California numbers) 

1LOJ_~L-~~~-~I~II~~-----------------\L0 ______________ ~2~ MILES \ 121° 

FIGURE 1.-Fossil and columnar-section localities and Pancho Rico Formation outcrop areas. 

A3 

T 16 S 

T 17 S 

T 18 S. 

T. 19 S 

T. 21 S. 

T 22 S 

T. 23 S 

T. 24 S. 

T. 26 S. 

T. 27 S 

T. 28 S 
ELDRIDGE HAMLIN 

(1901) (1904) 

MYLAR NORTHEAST QUARRY, SIDE NORTHEAST SALINAS OF KING VALLEY CITY 

Paso Robles Paso Robles 

Formation Formation 

San Pablo Santa 

Formation Margarita 

Formation 

Monterey 

Shale 

"Talus" 

(Overlies Monterey 

"granite") Shale 

PACK AND REED CLARK BRAMLETTE AND DAVIESS KILKENNY HUGHES ENGLISH ENGLISH (1918) TALIAFERRO (1943a) AND OTHERS THIS PAPER 

(1915) (1925) (1940) (1944) (1952) (1963) 

HAMES SARGENT EAST SIDE VALLEY TO PINE VALLEY SALINAS EAST OF HAMES VALLEY CANYON TO WEST SIDE EAST SIDE SAN ARDO OIL SAN ARDO SALINAS WEST OF TO VINEYARD VALLEY KING CITY AREA VINEYARD SALINAS SALINAS FIELD OIL FIELD SALINAS VALLEY 

VALLEY SAN ARDO CANYON CANYON VALLEY VALLEY 

Tulare Paso Robles Paso Robles Paso Robles Paso Robles Paso Robles Paso Robles Paso Robles Paso Paso Robles Paso Robles 

Formation Formation Formation Formation Formation Formation Formation Formation Robles Formation Formation 

Formation (in part) 

Santa Etchegoin Etchegoi n Poncho Poncho Etchego1n Etchegoin Pancho Pancho Pancho Rico Pancho Rico Formation 

Margarita and and Rico RICO Formation Formation Rico Rico Formation 

Formation Jacalitos Jacalitos Formation Formation "Manne Formation Sands 

Formations Formations Pliocene" 

Q. 

:J 

0 

0 

Santa /] Margarita 

Format1on Santa Santa Santa 

/'/ 

Margarita Margarita Margarita 

Formation Formation Sandstone 

Kmg City 

Formation 1 

v 

"' D"'om•r (Overlies Salinas Upper (j) Santa :J 

0 mudstone "granitic Shale c shale Monterey (Overlies E Margarita ~~ Pancho 0 member of "basal 0 Shale "'"' Rico rocks") :;:; member Formation E.<: Monterey j complex") "' (Mclure ~U) Mudstone Shale i5 Shale) 

i5 

"' '--------

~ "' Santa 

~ Margarita 

"' Lower Santa Santa Santa Upper Santa Formation c sandstone Marganta Salinas Margarita Monterey Margarita sand Margarita 

"' (f) member Formation Shale Shale Sandstone member Sands Sandstone 

c 

0 

:;:; 

] Lombardi Lombardi 

Siltstone Silt 

"' Monterey Shale ·~ c (in part) 0 

~ Lombardi :;:; Lombardi 

~ Sand E Sand 

"' c ~ 

"' :>, (f) Aurignac (j) Aurignac 

Siltstone (j) Silt c 

~ 

Aurignac Aurignac 

Sand Sand 

- -'--- -

FIGURE 2.-Stratigraphic nomenclature of strata of late Miocene and Pliocene age in the southern Salinas Valley area. 

I 

I 

-

> 

~ 

~ 0 

~ M 

~ 

Q 

0 

!Z 

f-3 

~ 

ti3 

q 

1-3 

H 

0 

z 

[[l 

~ 

0 

M 

~ ~ 

~ 

0 

M 

0 

t"l 

0 

~ 
PANCHO RICO FORMATION, SALINAS VALLEY, CALIFORNIA A5 

EAST SIDE OF SALINAS VALLEY 

Marine strata exposed east of King City have a complex nomenclatural history but are assigned to the 

Pancho Rico Formation in this report. Eldridge 

( 1901, p. 408-409) listed, in ascending order, the following three units (here all assigned to the Pancho Rico) 

above the basement complex near Mylar Quarry, northeast of King City : 

1. A basal unit of bituminous sandstone and coarser 

debris that he considered to be talus material associated with an old topographic high on the 

surface of the basement complex. 

2. An intermediate unit 400-500 feet thick that he assigned to the "softer, chalky variety" of "Monterey 

Shales." 

3. An upper unit about 150 feet thick that he regarded 

as "shales of the San Pablo" Formation. 

Hamlin ( 1904, p. 17) also considered "soft chalky shale" 

that overlies bituminous beds at Mylar Quarry as 

"probably a portion of the Monterey Shale." He 

(Hamlin, 1904, p. 15) considered the succeeding beds 

to be in the Santa Margarita Formation, which he represented as "sandstone at the base, grading upward into 

soft chalk -like shale and cia y shale." Waring ( 1914, 

p. 422) also assigned fossiliferous beds east of King 

City to the Santa Margarita. Pack and English (1915, 

p. 133) designated the entire sequence of marine strata 

er:posed east of IGng City as Santa Margarita. They 

noted that beds near Lonoak-equivalent to those called 

Monterey Shale by Eldridge-are "largely of diatomaceous and elay shale," including "relatively little 

interstratified sand," and form a unit that is locally 

sandy, grades laterally into sandstone, and contains 

fossils which indicate that it should be grouped with 

the overlying more sandy beds. 

Nomland (1917a, p. 207) recorded fossils that he considered "indicative of middle Etchegoin" in "lightcolored shale and volcanic ash" near Lonoak. Clark 

(1935, p. 1050) once believed that all the marine strata 

east of IGng City belonged to the Santa Margarita Formation. Later he (Clark, 1940; 1943, p. 190) gave the 

name IGng City Formation to sandy marine beds that 

overlie the basement complex and assigned the succeeding marine beds to the Poncho Rico Formation. Bramlette and Daviess (1944) speculated that conglomeratic 

sandstone overlying the basement complex east of l{ing 

City is Clark's IGng City Formation, but they coneluded that more likely his "formation" simply represents a faunal division of the Pancho Rico. They also 

indicated tha:t along the north side of San Lorenzo 

Creek, diatomaceous mudstone beds of the Pancho Rico 

Formation grade eastward into porcelaneous mudstone. 

Kilkenny ( 1948, p. 2260) considered the bituminous 

sandstone beds at Mylar Quarry to be in the Santa 

Margarita Formation. Turner (1963, p. 37), however, 

reported that sandstone beds overlying the basement 

complex along San Lorenzo Creek, and superadjacent 

shale, siltstone, and sandstone beds, belong to the Pancho 

Rico Formation. 

The Pancho Rico Formation farther south on the 

east side of the Salinas Valley has an equally confused 

history of nomenclature. Strata discussed here are 

assigned to the Pancho Rico unless otherwise noted. 

Waring ( 1914, p. 422, 423) designated sandy marine 

strata exposed near Vineyard Canyon Indian V allev 

' oJ' and Big Sandy Creek as J acalitos and Etchegoin Formations, names originally applied to units in the 

Coalinga district of the San Joaquin Valley. Pack and 

English (1915, pl. 5) mapped rocks exposed along Pancho Rico Creek as "diatomaceous and clay shale, sandy 

shale, sandstone, and shale-pebble beds, regarded as 

equivalent to Santa Margarita Formation." N omland 

( 19'17 a, p. 215) noted that beds of ''lower Etchegoin" 

age crop out in Vineyard Canyon and Indian Valley. 

English (1918, p. 230-232) pointed out that sandy 

beds in this area "corresponding to the J acalitos and 

Etchegoin Forn1ations" range considerably in thickness 

lithologic character, and faunal content. He also men~ tioned that these beds conformably overlie a unit (here 

considered a diatmnaceous 1nudstone member of the 

Monterey Shale) that he called a shale member of the 

Santa Margarita Formation, and are in turn overlain 

conformably by the Paso Robles Formation. Reed 

( 1925, p. 591, 606) casually introduced the name 

"Poncho Rico Formation" for beds in the eastern part 

of the Salinas Valley area, obviously including strata 

exposed along Pancho Rico Creek. Taliaferro ( 1943a, 

fig. 189) mapped as Etchegoin Formation sandy 1narine 

beds that crop out between Sargent and Vineyard Canyons. Bramlette and Daviess (1944) listed the following three lithologic units each about 200 feet thick, exposed along Pancho Rico Creek : (a) A lower unit of 

sandstone, exposed in the headwaters of the creek, (b) 

an intermediate unit of "somewhat siliceous" mudstone, 

and (c) an upper unit of "generally rusty-orange" sandstone. They pointed out that the sandstone and mudstone are commonly interbedded, and that the proportion of sandstone to mudstone varies laterally. They 

considered the "light-colored diatomaceous mudstone· 

and interbedded sandstone" exposed between Pancho 

Rico and San Lorenzo Creeks to the north to be typical 

of the Pancho Rico Formation. Baldwin ( 1950, p. 

1988) assigned ''diatomaceous and silty mudstones" in 

the San Ardo oil-field area to the Pancho Rico Formation (probably equivalent to beds assigned to the diatomaceous mudstone member of the Monterey Shale). 
A6 SHORTER CONTRIBUTIONS' TO GENERAL GEOLOGY 

These were described as occurring above a local unconformity and underlying "ochre-brown, dirty and pebbly 

fossiliferrous sands which are locally called Etchegoin." 

He also said that "Etchegoin sands * * * finger out in 

diatomaceous Pancho Rico shale." 

WEST SIDE OF SALINAS VALLEY 

Most of the sandy strata exposed between l{ing City 

and the Arroyo Seco were regarded as the Santa Margarita Formation by previous investigators, but those 

discussed below are assigned to the Pancho Rico Formation unless otherwise noted. Hamlin ( 1904, p. 18) assigned bituminous sandstone beds exposed northwest 

of King City, near the mouth of Thompson Canyon, to 

the basal part of the Santa Margarita. Reed ( 1925, p. 

593) assigned these sandy strata to the Santa Margarita, 

together with sandy beds that overlie the Monterey 

Shale in the Arroyo Seco and in Reliz Canyon. Clark 

(1929, p. 25; 1930, p. 767) recognized that beds equivalent to the "J acalitos horizon" occur in the Arroyo Seco 

area. l{leinpell (1930, p. 30) stated that "a series of 

gritty, white, fine, calcareous sandstones" overlying the 

Monterey Shale in Reliz Canyon are "generally classifled as Santa Margarita because of the apparently similar field relations to the south at the 'type Santa Margarita.'" He later (Kleinpell, 1938, p. 7) described the 

contact of the Monterey with the overlying sandstone 

unit in Reliz Canyon as "typicaly gradational." Nickell 

(1931) relegated beds that overlie the Monterey Shale 

near the Arroyo Seco to the Santa Margarita Sandstone. 

Clark (1930, p. 781-782), in a discussion of the area 

west and northwest of l{ing City, claimed that "unconformably on the Salinas [Monterey] shales are several 

hundred feet of sandstones and shales referable to the 

Santa Margarita horizon (upper Miocene) and unconformably on the latter beds is * * * the continental 

Paso Robles formation. * * * between the Paso Robles 

and the Santa Margarita formations are several hundred feet of sandstones containing a lower Pliocene 

fauna. * * * these marine Pliocene deposits are cut 

out as the result of the overlapping of the Paso Robles." 

Taliaferro (1943b, p. 140) described as "gradational 

and conformable" the contact between the Monterey 

Shale and overlying sandy beds in Reliz Canyon that 

he designated Santa Margarita Formation. Schombel 

(1943, p. 467) listed a sequence of five stratigraphic 

units (the second, third, and fourth are here assigned to 

the Pancho Rico) in the Soledad 15-minute quadrangle, 

including the area along the Arroyo Seco: (a) Monterey 

Shale, (b) Santa Margarita, Miocene sandstone, (c) 

Poncho Rico, Pliocene~ sandstone, (d) J acalitos, Pliocene sandstone and shale, and (e) Paso Robles, Pliocene-Pleistocene continental beds. Bramlette and 

Daviess (1944) believed that the sandy beds overlying 

the Monterey near the Arroyo Seco belong to the Santa 

Margarita Sandstone, but they recognized that the beds 

are probably of early Pliocene age. They also stated 

that bituminous san~stone beds northwest of King City 

form a "transitional zone from the Monterey siliceous 

rocks to the overlying Santa Margarita sandstone." 

Kilkenny (1948, p. 2260) referred these beds to the 

Santa Margarita. 

Many investigators have studied the Pancho Rico 

Formation exp()sed west of the Salinas River between 

San Ardo and the San Antonio River, chiefly because 

the unit in that area contains bituminous sandstone 

beds. Strata discussed below are assigned to the 

Pancho Rico, unless otherwise noted. Eldridge ( 1901, 

p. 410) placed sandy marine beds exposed west of San 

Ardoin the "middle Neocene [San Pablo] Series." He 

described the stratigraphic sequence as shale at the base, 

"overlain by 125 feet of sandstone varyingly impregnated with bitumen, * * * followed by about 400 feet 

of shale, which is in turn overlain by a succession of 

shale and [bituminous] sandstone, a half dozen beds 

each." HamJin (1904, p. 16) placed the bituminous 

beds exposed west of San Ardo in the Monterey Shale 

but pointed out that they differ from the more typical 

Mont~rey: "some beds a,re soft and chalk-like, others 

contain an unusual percentage of fine sand and mica 

flakes, interstratified with beds of quartzose sandstone." 

In addition, he indicated that "the upper 770 feet of 

this formation consists of alternating beds of chalk-like 

shale and sandstone." Waring (1914, p. 434) also assigned the bituminous sandstone beds west of San Ardo 

to the Santa Margarita Formation. English (1918, p. 

229) stated that the basal beds in the unit west of San 

Ardo that he considered Santa Margarita Formation 

are "shaly and are overlain by the typical sandstone, 

followed by more shale and interbedded sandstone." 

Kew (1920, p. 104) considered echinoid-bearing beds 

at the mouth of Swain Valley to be part of the Santa 

Margarita Formation. Reed ( 1925, p. 593, 594) assigned sandstone beds exposed in the ba·1k of the Salinas 

River, 6~ miles south of San Ardo, to the Santa Margarita Formation. Taliaferro (1943b, p. 140) stated 

that the contact between the Salinas (Monterey) Shale 

and the overlying Santa Margarita Formation in the 

area north of Bradley and west of the Salinas River 

is "gradational and conformable." Bramlette and 

Daviess ( 1944) regarded bituminous sandstone beds 

southwest of San Ardo as part of a "transitional zone 

from the Monterey siliceous rocks to the overlying 

Santa Margarita sandstone." Mandra (1963, p. 104) 

favored the name Pancho Rico for sandy beds exposed 

southwest of Hames Valley. 
PANCHO RICO FORMATION, SALINAS VALLEY, CALIFORNIA A7 

Bituminous sandstone beds that crop out near the San 

Antonio River, about 6 miles southwest of Bradley, are 

probably part of the Paso Robles Formation. Eldridge (1901, p. 411) considered them "perhaps of a 

:formation younger than the Monterey Series." Fairbanks ( 1900, p. 144) referred them to the base of the 

San Pablo Formation. Hamlin (1904, p. 19) described 

them as the basal beds of the Santa Margarita Formation, and Waring ( 1914, p. 435) also placed them in the 

Santa Margarita Formation. English (1918, p. 240) 

called them Paso Robles Formation. Taliaferro 

( 1943a, p. 460) assigned them to "the base of the Etchegoin where it rests unconformably on organic Salinas 

[Monterey] Shale." Bramlette and Daviess (1944) 

terrried these beds "basal Pliocene strata" and described 

them as lying unconformably on the Monterey Shale. 

Kilkenny (1948, p. 2260) placed them "at the base of 

the Poncho Rico." 

The Pancho Rico Formation farther west in the San 

Antonio River valley has received scant attention. 

Reed ( 1925, p. 593) assigned the sandy beds overlying 

the Monterey Shale to the Santa Margarita Formation. 

These beds are now assigned to the Pancho Rico. 

LITHOLOGIC CHARACTER 

The Pancho Rico Formation contains fine- to coarsegrained sandstone, mudstone, porcelaneous mudstone, 

porcelanite, diatomaceous mudstone, and conglomerate. 

The abundan~ of sandstone in the Pancho Rico distinguishes it f~om the Monterey Shale, which contains 

lenticular sandstone beds only. Diatomaceous mudstone is more qommon in the Pancho Rico on the east 

side of the S~linas Valley than on the west side. 

Porcelaneous rocks are common on the west side but are 

scarce on the ea~t side. Larger invertebrate fossils with 

shell material rreserved are most abundant in beds of 

medium- and qoarse-grained sandstone, but molds and 

casts of fossilsl occur in both coarse- and fine-grained 

rocks. Figure i 3 shows the generalized lithologic character of the Pa~cho Rico at six representative localities. 

SANDSTONE 

The sandstode most characteristic of the Pancho Rico 

Formation is fi~e or very fine grained, massive, arkosic, 

noncalcareous, 1and yellowish gray or very pale orange 

(fig. 4). It copsists of angular grains in a matrix of 

silt and clay, a~d in places it contains a few scattered 

medium or coatse sand grains. Fine-grained and very 

fine grained sapdstone on the east side of the Salinas 

Valley is gene~ally friable, but ordinarily mi. the west 

side it is well !indurated. 

Medium- andj coarse-grained sandstone is interbedded 

with finer grained rocks in the upper part of the Pancho 

Rico Formation (fig. 5). It forms massive beds as 

much as 10 feet thick and is generally arkosic, poorly 

sorted, yellowish gray, dusky yellow, or yellowish 

brown, and ranges from friable to well indurated. 

Some of it is calcareous; most of it has a matrix of very 

fine grained sand, silt, and clay. Fossil mollusks and 

echinoids are abundant in some beds (fig. 6) . 

Sandstone at the base of the Pancho Rico Formation 

east of l{ing City in Sweetwater Canyon (fig. 3, col. C), 

where the unit lies on the basement complex, is medium 

grained, massive, arkosic, noncaleareous, friable, and 

yellowish gray. The grains are angular to subrounded 

and range from 0.15 to 1 mm in 1ength, although most 

are about 0.3 mm long. 

MUDSTONE 

Mudstone in the Pancho Rico Formation on the east 

side of the Salinas Valley, and locally in the lower part 

of the Formation on the west side of the valley, is typically massive, noncalcareous, and white or yellowish 

gray, and consists of a few scattered very fine sand 

grains and mica flakes in a matrix of silt and clay (fig. 

7). Diatom frustules are abundant in the rock, and 

molds of pelecypods and fish scales are loeally common. 

Mudstone in the Pancho Rico on the west side of the 

valley ordinarily resembles that in the underlying Monterey Shale. It is generally massive, noncalcareous, 

yellowish gray or very pale orange, and well indurated. 

It is commonly porcelaneous, and in some places it 

grades into porcelanite. 

CONGLOMERATE 

Distinctive conglomerate that occurs in the upper 

part of the Pancho Rico Formation contains pebbles, 

granules, molds of small mollusks, iish teeth and bones, 

echinoid spines, and other organic debris scattered in 

a matrix of mudstone or very fine grained sandstone. 

The larger pebbles are generally porcelanite or porcelaneous mudstone, presumably derived from the Monterey Shale; some smaller clasts are quartz or basement 

rock. The beds are 1-2 feet thick and are pale orange 

or dark yellowish orange, in marked contrast to the 

lighter colored enclosing rock. The pebbles, granules, 

and organic. remains are commonly coated or discolored by grayish-brown phosphatic material. 

Pebble and cobble conglomerate beds, generally similar to those in the overlying Paso Robles Formation, 

occur in the upper part of the Paneho Rieo Formation 

on the east side of the Salinas Valley, especially south 

of Pine Valley. These beds eontain fossil manne 

mollusks and echinoids in some places. 
A 

RELIZ CANYON 

FAULT 

[

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Paso Robles 

Formation 

Pancho 

Rico 

Formation 

Approximate latitude of King City 

B 

BRANSTETTER 

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MISSION CREEK 

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Approximate latitude of San Ardo 

Paso Robles 

Formation 

Pancho Rico 

Formation 

Monterey 

Shale 

E 

NORTHEAST OF 

SWAIN VALLEY 

F 

WALKER CANYON 

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EXPLANATION 

Mudstone 

Diatomaceous mudstone 

Porcelanite and porcelaneous mudstone 

Sandstone, fine and very fine grained 

Sandstone, medium- and coarse-grained 

Conglomerate and conglomeratic sandstone 

Lithologic symbols omitted for rocks 

that are concealed 

FIGURE 3.-Representative columnar sections of the Pancho Rioo Formation. 

> 00 

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PANCHO RICO FORMATION, SALINAS VALLEY, CALIFORNIA A9 

F~GURE. 5.- Medium- and coarse-grained sandstone, locally 

pebbly, and interbedded mudstone at fossil locality M1935, 

east of San Ardo oil field in Walker Canyon. The ledgeforming bed at the top of the outcrop contains abundant 

fossil echinoids. 

STRATIGRAPHIC RELATIONS 

East of King City the Pancho Rico Formation lies 

nonconformably on the basement complex. Southeastward, toward Pancho Rico Creek, the base is concealed. In Sargent Canyon, and from there southeastward to Indian Valley, the Pancho Rico overlies a diatomaceous mudstone unit that is correlated, on the 

basis of lithologic character and stratigraphic position, 

with the diatomaceous mudstone member of the Mon-

'780-8S4 0-65-2 

l!'IGURE 7.-Massive diatomaceous mudstone at fossil locality 

M977, on south bank of Pancho Ric'J Creek. Dark band 

just above pick is sandy fossiliferous layer that grades into 

the adjacent mudstone. The beds are nearly flat. 

terey Shale, which is exposed west of the Salinas River 

around Hames Valley (fig. 3, col. E, F). The lower 

contact of the Pancho Rico from Sargent Canyon to 

Indian Valley is at the base of the stratigraphically 

lowest sandstone unit above the diatomaceous mudstone member of the Monterey. The contact is gradational, for some diatomaceous mudstone beds occur 

above the sandstone beds that mark the base of, the 

Pancho Rico ; and it is intertonguing, for the base is 
AIO SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY 

not at the same stratigraphic horizon throughout the 

area. In both Indian Valley and nearby valleys, and 

for a short distance southeast of that vicinity, the 

diatomaceous mudstone member either pinches out or 

grades laterally into porcelaneous rocks, and the Pancho Rico lies conformably on porcelaneous rocks assigned' to the Monterey Shale. The lower contact of 

the Pancho Rico in this area is at the base of the 

stratigraphically lowest sandstone beds above the finer 

grained rocks typical of the Monterey. Farther 

southeastward, in Vineyard Canyon, the Pancho Rico 

lies on the Santa Margarita Formation, apparently 

conformably. In this area the lower part of the 

Pancho Rico is massive friable noncalcareous finegrained grayish-yellow or yellowish-gray sandstone 

that contains scattered coarser grains and locally 

abundant fossil mollusks. Some beds of porcelaneous 

rock occur stratigraphically above the basal sandstone. 

The underlying Santa Margarita Formation in Vineyard Canyon is sandstone that is massive, friable, noncalcareous, well sorted, fine grained, and grayish 

orange, and locally contains numerous large fossil 

oysters. The contact is at the top of the stratigraphically-highei?t giant oyster-bearing bed. 

On the west side of the Salinas Valley, the Pancho 

Rico Formation lies confonnably on the Monterey 

Shale. The contact is gradational-rocks like those in 

the Monterey also occur in the Pancho Rico-and it is 

probably not at the same stratigraphic horizon 

throughout the area owing to lateral change in the 

lithologic character of the sandstone beds that define 

the base of the Pancho Rico. West of King City and 

in the San Antonio River Valley, the lower contact of 

the Pancho Rico Formation is at the base of the stratigraphically lowest unit of fine-grained sandstone 

above the Monterey Shale (fig. 3, col. A, D). Northeast of Hames Valley (fig. 3, col. E) the lower contact 

of the Pancho Rico is at the base of the stratigraphically lowest sandstone beds above the diatomaceous 

mudstone member o£ the Monterey, but mudstone identical with that in the Monterey locally occurs above 

the basal sandstone beds in the Pancho Rico. Near 

the Nacimiento River the lower contact of the Pancho 

Rico is at the base of the stratigraphically lowest marine 

sandstone beds above porcelaneous, cherty, or diatomaceous rocks of the Monterey. 

The Pancho Rico underlies the nonmarine Paso 

Robles Formation with apparent conformity. The upper contact of the Pancho Rico is placed at the top of 

the stratigraphically highest marine fossil-bearing beds. 

East and west of King City, the contact coincides with 

the base of the stratigraphically lowest prominent conglomerate bed (fig. 3, col. B, C), which generally consists of pebbles of porcelaneous rock and chert in a 

matrix of sand and opaline cement. This conglomerate 

and the overlying strata are unfossiliferous. Farther 

south, conglomerate occurs in the Pancho Rico as well 

as in the Paso Robles. The upper contact of the Pancho 

Rico may not be at the same stratigraphic horizon 

throughout the area because of possible intertonguing 

of marine and nonmarine beds. 

THICKNESS 

The Pancho Rico Formation is about 275 feet thick in 

Sweetwater Canyon, where it lies on the basement complex (fig. 3, col. C), and is more than 500 feet thick 10 

miles farther southeast, near Pine Valley, where the base 

is concealed. It is 450-550 feet thick 10 miles southeast 

of Pine Valley, near Sargent Canyon, where both the 

base and the top are exposed (fig. 3, col. F), and it is 

about 650 feet thick near Indian Valley. Structure sections between Sargent Canyon and Indian Valley suggest that thickening of the Pancho Rico between the two 

areas is due to intertonguing of the unit with the underlying diatomaceous mudstone member of the Monterey 

Shale. The Pancho Rico is about 850 feet thick west of 

Reliz Canyon and may be more than 1,000 feet thick 

between Reliz Canyon and the Salinas River. It is 

about 850 feet thick at the mouth of Thompson Canyon. 

The Pancho Rico is nearly 900 feet thick north o£ Jolon 

(fig. 3, col. D), but it is only about 200 feet thick near 

the San Antonio River south of Lockwood and is even 

thinner nearby. The unit is 100-200 feet thick northeast of Hames Valley (fig. 3, col. E) but is only about 

20 feet thick at places along the Nacimiento River. 

Variation in the thickness of the Pancho Rico Formation is partly due to intertonguing caused by lack of 

coevality of deposition and is probably partly related 

to unlike sedimentation rates. 

FAUNAL COMPOSITION 

The fauna of the Pancho Rico Formation consists of 

141 larger marine invertebrate taxa (table 1), principally mollusks, but includes locally abundant echinoids, barnacles, and brachiopods. As it is now known, 

the Pancho Rico fauna is larger than any other invertebrate fauna from Pliocene formations in central California, but it is smaller than faunas of this age from the 

Santa Maria basin, Ventura basin, Los Angeles basin 

and, presumably, the San Diego area, all in southern 

California. Although the number of taxa might be 

increased by additional collecting, the taxa enumerated 

in truble 1 are considered representative of at least the 

more common faunal elements. 

In earlier reports, the only invertebrate class in the 

Pancho Rico Formation that received more than passing 
PANCHO RICO FORMAT'ION, SALINAS VALLEY, CALIFORNIA All 

attention was the Echinoidea (Kew, 1920; Grant and 

Hertlein, 1938 ; Hall, 1962) . The large representation 

of Pliocene mollusks in the Pancho Rico was not apparent from the few species listed by Arnold ( 1906, p. 

64, 67), vVoodring and Bramlette (1950, p. 102, 106), 

Hertlein (in Mandra, 1963, p. 104), and Tagga,rt and 

Kraetsch (1963). Most mollusks listed in table 1 are 

named species that have not been previously reported 

from the Salinas Valley area. About 10 percent of the 

mollusks are undescribed. 

Taxa other than muricids, ostreids, pectinids, barnacles, brachiopods, and echinoids were, in large part, 

identified from casts 1nade from external molds of the 

original shells. The generally poor preservation of 

shell material is probably the reason that this fauna 

has not been extensively studied. Approximately onefourth of the larger invertebrates now known from the 

Pancho Rico Formation are figured in plates 1-5. 

Among the figured specimens are a majority of the taxa 

regarded as diagnostic of Pliocene age as well as other 

characteristic but longer ranging species. 

Clypeasteroid echinoids are represented by abundant 

Astrodapsislocally and by Dendraster at several localities between Sweetwater Canyon and Walker Canyon. 

Brachiopods of the genus Terebratalia are very abundant in an area near the mouth of Reliz Canyon. Barnacles of the genus Balan'Lts are widespread and 

abundant. Specimens of B. gregari'U8 attain a length 

of at least 198 mm (Pilsbry, 1916, p. 127). In some 

areas they form biostromal units composed almost exclusively of articulated barnacle plates (fig. 6). Opercular valves of B. gregari'U8, abundant at many localities, are illustrated on plates 1 and 2. 

The invertebrate fauna of the Pancho Rico Formation 

is largest in the area between J(ing City and Bradley, 

east of the Salinas River. Characteristic shallow-water 

taxa in collections from that area include Astrodapsis 

spp., F orreria belcheri (Hinds), 0 alicantharus kettlemanensis (Arnold), Orucibulum (Dispotaea) n. sp., 

Ostrea atwood-! Gabb, Lyropecten termin'U8 (Arnold), 

Protothaca tenerrirrw (Carpenter), Florimetis biangulata (Carpenter), and B alanu,s gregari'LU3 (Conrad) . 

A moderate-depth 2 assemblage consisting of several 

species not found elsewhere in the Pancho Rico Formation occurs in the upper San Antonio River valley and 

in Reliz Canyon. Among these distinctive species are 

Terebratalia arnoldi Hertlein and Grant, Turcica caffea 

brevis Stewart, Orepidula n. sp., an apparently undescribed species of Ohlamys, and Jf acoma br·ota Dall. 

2 Moderate depth is here regarded as greater than about 10-15 fathoms and less than 100 fathoms. It includes part of the inner sublittoral 

zone (low tide to 50 fathoms), and all of the outher sublittoral zone 

(50-100 fathoms) as defined by Hedgpeth (1957, p. 18). 

Foraminifera from a few localities in the Pancho 

Rico Formation have been reported by Cushman and 

Grant (1927, p. 75), Hughes (1963, p. 95), and Gribi 

(in Taggart and J{raetsch, 1963) . Taxa listed by these 

investigators include Elphidium hughesi Cushman and 

Grant, E. hannai Cushman and Grant, B1tliminella 

eleganti.'58irna ( d' Orbigny), Eponides cf. E. per"111vian'U8 

(d' Orbigny), and E. ewigua (Brady). A small assemblage collected during this investigation and identified 

by Patsy J. Smith (this report, p. A17) contains a few 

additional species. 

AGE AND CORRELATION 

Identifiable fossils have not been recovered from porcelaneous and diatomaceous rocks of the Monterey Shale 

that underlie basal sandstone beds of the Pancho Rico 

Formation. Ho,vever, megafossils indicative of a late 

Miocene age occur in arenaceous strata mapped as Santa 

Margarita Sandstone by Taliaferro ( 1943a, p. 457) between Portuguese and Ranchito Canyons, northeast of 

San Miguel. In Vineyard Canyon the Santa Margarita 

Formation underlies fossiliferous Pancho Rico Formation (1napped as Etchegoin Formation by Taliaferro, 

1943a). Collections from a giant-oyster biostrome at 

the top of the Santa Margarita in Vineyard Canyon 

(USGS loc. M1968 [12 ft. stratigraphically below 

M1969]) include the following taxa which suggest a 

Miocene age: 

Mytilus sp. 

Ostrea titan Conrad 

Ostrea cf. 0. vesperti.na Conrad 

Lyropecten cf. L. estrellanus (Conrad) 

Chione c:f. 0. temblorensis (Anderson) 

Oryptomya? sp. (internal molds,) 

Balanus gregarius (Conrad) 

Two other species that are reported from near Vineyard 

Canyon, Forreria perelegans (Nomland) (Nomland, 

1917b, p. 312) and Aeq1dpecten disc'U8 (Conrad) (Taggart and l{raetsch, 1963), are known only from strata 

of Miocene age. 

A foraminiferal assemblage from the middle fork of 

Vineyard Canyon, nearly 2 miles northwest of locality 

M:l968, identified as upper Delmontian (by Standard 

Oil Co., in Taggart and l{raetsch, 1963, loc. 2259) , 

includes the following species: 

N onion montereyanum Cushman and Galliher 

Elphidium httghesi Cushman and Grant 

Eponides exigua (Brady) 

N onionella rniocenica Cushman 

Nonionella cushntan'i (Cushman) 

Nonionella cf. N. belddgensis (Barbat and Johnson) 

This locality seems to be stratigraphically lower in Taliaferro's Santa Margarita Sandstone ( 1943a, p. 457) 

than is megafossil locality M1968. 
TABLE 1.-Larger invertebrates from the Pancho Rico Formation 

[Identifications by W. 0. Addicott unless otherwise noted. X, present as identified;?, doubtful identification; cf., similar form, specimen(s) incomplete or too poorly preserved for definite identification; aff., com- parable but apparently different form; sp., species not determinable; ?sp., genus questionably identified) 

West of Salinas River East of Salinas River 

~~~lil~l~l~l~l~l~l~l~l~ ~\i\~\i\!\;[i\~1~1~\l\i\i\~I~I~I~ISI!i!l~l~l~l~l! ECHINOIDS: 1 

ABtrodapsis arnoldi Pack (pl. 1, fig. 9). ______________________________________________________________________________ cf. ____ X ________________ X 2 sp. s ________________________ ---- _______ _ crassus Kew ____________________________________________________________________________________________________________________ X 4 ____________________________________ ---- ---- ____ ----

ie~~;{Tid~~~£;~~~~~~============= ==== ==== ==== ==== ==== ==== ==== ~ 5 ==== ==== ==== ==== ==== ==== ==== ==== ==== cf.-- ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== :~z~~~!~~s~e!i~~~~~===:::::::::::: :::: :::: :::: :::: :::: :::: :::: : __ :::: :::: :::: :::: :::: :::: :::: :_a_ :::: ci.-- :::: :::: :::: :::: :::: :::: :::: :::: :::: :::: x-- :::: :::: :::: Ci.-- :::: :::: :::: :::: 

sp. [A. whitneyi-A. jacalitosensis 

Denar~~~~PJP=========================== ==== ==== ==== ==== ==== ==== :::: ==== ==== ==== :::: :::: :::: ====X-- ==== ==== ~ ==== :::: ==== X-- ==== ==== ==== ==== :::: ==== ~ ==== :::: ====1====1====1====1====1==== 

BRACHIOPODS: 

Discinisca cumingi Broderip _____________ 

1

'sp. 

Terebratalia arnoldi Hertlein and Grant (pl. 2, figs. 3, 4) _______________________ X ----~- ---~----~----~- ---~----~----~-- --~----~----~----~----~----~----~----~----l----l----1----l-- --1----1----1----1----1----1----1----1----1----1----1----1----1----1----1 X 

X ----•----1----1----1----J----J----•----•----•----1----1----I ----1----I----I ----1 ---• I----I----1 ----I----I----I----1----1----I ----1----I----1----I ----1----1----1----I----I----

GASTROPODS: 

Diodora n. sp.? aff. D. inaequalis (SowCalliostoma c:u~:S~o<J:~? coalingense afgc~>climmanTnan=:::::: Arnold (pl. 5, ~~~~ :::: :::: :::: :::: :::: :::: :::: :::: :::: :::: :::: :::: :::: :::: :::: :::: :::: :::: :::: :::: :::: : __ :::: : __ :::: x-2- :::: :::: :::: :::: :::: :::: :::: :::=~::::~:::: figs. 6, 7) __ •. ------------------------- ____________________________ sp. cf. ________________________________ X ____________________________ X sp. ____ ---- ____ ---- X ____ X ---- ---- ---- etchegoinense Nomland ______________________________________________________________________________________ X ____ cf. ________________________ X ____________ X ____ ---- ---- ---- ----

cf. C. ligatum (Gould) __________________________________________________________________________________________________________________________________ X ________________ ---- ____ ----

Margarites cf. M. condoni Dall _______________________________________________________ X ____________ ---- ____ ---- ---- ____ ---- ________ ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ----

Tur~~~ ~: ?~~~J!e~ 1%~~l~~wari:===== x·- X-- ==== ==== ==== ==== ==== .:::: ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== ~~~~ ==== ==== ==== :_

7

Epitonium (Nitidiscala) cf. E. eelense · _ ==== ==== ==== : __ ==== ==== ==== ==== ==== ==== ==== ==== 

~F~lYE~~~::rg~;:l~~f~i~:~~~~5= cooperi forma nova N omland (pl. 4, :::: :::: :::: :::: :::: :::: ~== :::: ~~~ ~== :::: ~== :::: :::: :::: :::: :::: ~-- :::: :::: :::: ~== ~== :::: ~== ::::,~=2= :::: :::: :::: ~== :::I:::[J::::[J~== fig. 3)----------------------------- ---- ---- ---- ____ ---- ____ --------X 

gonostoma hemphilli Applin, ----1----I----1----•----1----1----1----I ----1----1----1----1----1----1----1----1----1 ----I----I ----1----1----1----I---- J ----I----I ----1---- in Merriam (pl. 5, figs. 18, 19) ___________________ ---- ____________ ----X ----X ----X ---- ---- ---- ---- ---- ---- ---- ---- ---- --------X ---- ---- ---- ---- ---- ------------~----~----~----~X 

~~~~cl~-~~~!~i~~~!· ~~~ir]~~- !~~= x·- :::: :::: :::: :::: :::: :::: :::: :::: :::: :::: :::: :::: =::: :::: :::: =::: :::: x-- :::: :::: :::: :::: : __ f 7 :::: ~ 2 : __ : __ ~ :::: : __ :::: :::: :::: ::::1:::: Bittium cf. B. attenuatum muUijilosum Bartsch ______________________________________________________ sp. ____________________________________________ sp. ________ ---· ________________ sp. ____ ----X ---- ---- ____ ---- ____ , ____ , ___ _ Bittium casmaliense Bartsch (pl. 5, fig. · 10) ___________________________________________ cr. ________________ X ---" ________ ? ____ cf. ____ ---- ____________________________________ ----X ____ X sp. ---- ---- ____ ---- ---- ---- ~---

casmaliense Bartsch. Strongly 

~~~ffi~:tfl!~?J.=t=_=~= ~;; ~~;; ~~;; =~;: =~=~ ~;; ~:: ~:: ~~; ~~;; ~;; ~:: ~;;~ ~=~= ~~~~ ~~=; ~~;~ ~~;; ~:: ;;;; ~:; ;;;: ~:: ~:~ ~;; ~;;; ~:.~ ;;~; ~-== ~:; ~:~ ~;; ~;; ~== ;~~~ ;;:; ;~;~ 

~~: s~: &.:~:r~~;~a~~~)====== ~== ~== ==== ==== ==== ==== ==== ==== ~~~ ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== ~= = ==== ~~ ==== ~== ~== ==== ~~~~ ==== ==== ==== ==== ==== 

~~~$~~1!:~~~;:;::~;; Ceratostoma foliatum ( Gmelin) (pl. 2, ~~~; ==~~ ;;~~ ~; ;:~; ;;;~ ~~=; ~~~; ~~;: ;~~~ ~:;; ~~: ;;;: ;;:; ;:~: ~;~; ;~;; ;;;; ~;; ~:; ~== ;::; §p: ~:: ~:': ~== ~:·: ~;·; ~:-- ~;; ;~=~ ~== =~;~ ;~;; ~;~~ ;~~t:; figs. 6, 8) __ --------------------------- ? ________________________________________________ ---- ---- ---- ____ X nuttaUi (Conrad)? __ ---------------- ____________________________________________________ ---- ____________ X 

Forreria belcheri (Hinds) (pl. 4, figs. 5, 

8; pl. 5, fig. 22) _- --------------------- ---- ---- ---- ____ ---- ____ ---- ---- ---- ____ sp. ---- ---- ---- ---- X & ---- ? ---- ---- ?sp. ---- X ---- X sp. X 2 ---- X 

Jaton fi:.fi3r (Shaskyus) _c~!~~~~~-~~~~~~~-~~~·-- festivus (Hinds) ___________ ~- ---- ---- cf. ____________________________________________________________________________________________________ 

---- ____ ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- X ---- ---- X ---- ---- ---- X ---- ---- ---- ---- -·-- X X a ___________________________________ ----~----~----~----~----~----~----~----~----_ 

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SCAPHOPOD: 

Dentalium? sp __ ------------------------1----1----1----1----1----1----1----1 X 

PELECYPODS: 

Nuc'IJ:lana taphria (Dall)- --------------- ---- ________ ---- ---- ---- ---- ---- ---- X ---- ---- ----~----~----~----~----~----~----~----~----~----~----~----~----~----~----~----~---10 1----~----~--~-~- ---~ =---~ ====1 ====c== 

X~tt.~~~fi~~if~~~~!~~~i!~~~~~~~~~~~~~~~ ~-- ~-- ~~~~ ~~~~ ~~~~ ~~~~ :;.-- ~~~~ ~~~~ ~~~~ ~~~~ ~~~~ ~~~~ ~~~~ ~~~~ ~~~~ ~~~~ ~~~~ ~~~~ ~~~~ ~-- ~~~~ ~-- ~~~~ :;.-- ~~~~ ~-- ~-3- :_J~~~ ~~~~ ~~~~ :~~- s~~- ____ cr. ·---- <Anadara) trilineata forma canalis 

(Conrad) (pl. 5, fig. 1) _ ----------- ____________________________ X ________________ cf. 

(Larkinia) camuloensis (Osmont) 

;,;,~~~~f;~::G::;~~ '~l; ~;~; ;;l; ~-n ~~) ~::: cf.~~ l;l; ;;;; ;ll; ;;;·~~;; ;ll; ;l;; :::~ l·-;ll;~l~~~: ;;;; ::::~~:~ l;;; ;-;-1,~;: ;:;; ;:;; :-~: ;~.- ~;: ;l;~ l;l-;;;; ;~;,;;;: ~~: ~~-):.; Ostrea atwoodi Gabb (pl. 3, figs. 3, 7) ____ X ________________________ X ________________ X sp. X X X ____ X ________ X X X X 7 ____ X X X ____ ·sp. X X 1o ---- X ---- ----

Chl~~~~~~ff~·~.~~~~~~:~;~~~uroda=== n. ~ ~~~- ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== ~~~- ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== sp.? ___ -------------------------- ____________ X 11 ________________________________________ X ____________________________________________________________________ ---- ---- ---- ---- ---- Hinnites giganteus (Gray) _______________________________________________________________ X ________________________________________ X ____________ X 3 ________________________________ ----

Lyropecten cerrosensis (Gabb) (pl. 3, 

figes~le;;anu8-(c"Olliad5-<"PCi,-fii.-55=== terminus (Arnold) (pl. 1, figs. 1, 10; ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== cC x-- ====a.-- x-- ==== ====a.-- ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== ====l====c==~==== pl. 2, figs. 1, 10) _______________________________ ?sp. cf. ?sp. ____ sp. cf. X sp. ________ X ____ X 

Patinopecten lohri Hertlein 13 (pl. 1, fig. 4; pl. 3, fig. 1; pl. 4, fig. 1) _________________________________________________________ X ____ X 

Lima cf. L. hemphilli Hertlein and : __ ~ : __ ~ ~~~~~ ~~~~~ ~~~~~~~~~~~~~~~: __ I ~~~~I :_7

_1 ~~~~I : __ I ~--1: __ 1 ::~~1: ___ 1 ~~~~I : __ I ~~~~I ~--I X 

i~~Et:=~~~~~=(=&~~~i~:::::::::::::: Cyclocardia californica (Dall) (pl. 5, figs. :::: :::: :::: =::: ==== :=:: ::=: ::=: ==== ==== ==== ==== ~== :::: ==== ~== ==== ~-- ==== ==== ==== ==== ==== :::: :::= ==== :::= ==== ==== ==== ==== :::: ==== ==== ::=:~::=:~::=: 

i~¥~~~~~~~~); ~;: ~::· ;;;l ;;;; ::~: ~~- ~·;; ~~: ~~; l;;; ~~~ ;;;; ;:;; cf.~~ ;;l; ;;;ll~;- ~~- ~:: ;;;: ~-~ ~;~ :~:- ;;;; ~;: )-l= ~~ ._:~ ~~= ::~: ;:;; ~:l-:;~ l;;~ ;;;: ~:::~-~ Trachycardium quadragenarium (Con- ? rad) _ --------------------------------- ____________________________ ? sp. ? ________________________________ ---.- X ________________ ?sp. ____________ X ____________ cf. ---- ----

See footnotes at end of table. 

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TABLE 1.-Laruer invertebrates from the Pancho Rico Format,ion-Oontinued 

West of Salinas River East of Salinas River 

I I I ' I I ~~~~ ~~~~~~~~~~~g[~[~[s[s[s[~l~[~[~[~[~[~[~l~l~l~ ~ ~ 00 8 ~ 8 ~ ~ ~ ~ ~ g 

~~~1~1Sl1Sl ;l ~~IS] ~1$11~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ 

------------------------- PELECYPODS-Continued 

l~~~1:~~u~~Y~~.-<J Dosinia cf. D. ponderosa ~~1iir~=(={;i~ir5== Gray (pl. 1, ==== ==== ==== ==== ==== ==== ~== ==== ~~~~ ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== ~~~~ ~~~= ~~~~ ==== ~~~ ==== ~==[]===I===[]====~==== 

~~~~t~~~~=i~~~~~:_:::~~ ~~~~ ~:~~ ~==~ :~~~ ~=~~ ~:: ~~~: ~~~: ~;; ~~=~ ~:: ~~~~ ~~~~ ::~~ ~~~: ~=~~ ~~~: ~:: ~~~~ :~~~ :~:: =~=~ ~::: ~~~~ ~~~~ :::~ ~~=~ ~~~~ ~~=~ :~:~ ~=~I~IJ~~I~IJ~~~ aff. C. gnidia (Broderip and Sowerby) _______________________________ ---- ---- ---- ---- ---- ---- X 

Protothaca cf. P. lacinata hannibali Howe ________________________________ sp. ________________________ ----X ________ sp. ____________________ ---- ____________ X ____ ---- ____ ----X ____ X ?sp. ~--- ____ ? X ---- ---- ---- cf. P. staminea (Conrad) ____________________________________ X ____________________________________________________________________________________________________________ ---- _______ _ 

tenerri1na (Carpenter) ___ ----------- ________ X X u ________ X ____ X ________________________________________________ X ________ X 7 ____ X ____ ? ________________ X ---- ---- ---- Cumingia californica Conrad?----------- ________________________________________________________________________________________________ X ____________________________________ ---- _______ _ Spisula mercedensis Packard ____________________________________ sp. ____ sp. ________ sp. sp. ____________________________________________________ X ________ cf. ________________ ---- ---- ----

hemphilli (Dall)? _ ------------------ ---- ---- ____________________ ---- ____________________ ---- ---- ---- ---- ____ ---- ________________ ---- ---- ---- ________ X ____ ---- ---- X ---- ---- X ---- Tresus nuttalli (Conrad) ________________________________________________ ?sp. ____________________________________________________ ?sp. ____________ X sp.3 ____ ? ________________ ---- ?sp. ---- Tellina cf. T. aragonia DalL ____________________________________________________________________ ---- ________ ---- ____________________ ---- ____ ---- ________ X ____________________ ---- ---- ---- idae DalL ______________________________________________________________________________________________ cf. ________________ X ________________________________________________ cf. 

cf. T. lutea Wood ___________________________________________________ ? ____________________________________________________________________________ X ________________________ ----.----

M~1~~~~~:~~:~ nasuta (Conrad) ____________________________ !~~=;?~~!~~~ ~~~= ::~: ~ X ~~~ ==~: ____________ ~:: ~::: :: 

X ? X ~~ ~~~~ :~:~ cf 

=~=~ =~=~ ? X ;::: =~== ____________________________________________________ =~~ ~ ~~~~ =~~= : ~:~ :~:~ ~~=: =~== :: ~~ ~~:: ~~=~ ~~:~ ~:,: ~~-:: ---- ~~~~ X 2 ~~~~ ____ ~~~= X X ~ -? ? ~~ ~~ :::: ~;_:: X ==~~ ____ ~~~~ ---- :~~~ ? =~~~ secta (Conrad) ______________________________________________________________________________________________________________________________________ X X X ____________ ---- ____ , ___ _ 

Macoma? aff. M. arctata (Conrad) ___________________ X X ________________________________ ---- ________________________________________ ----~---- ____________________________ --------X 

Florimetis biangulata (Carpenter) (pl. 4, 

sa~giu~~ofar-ia-Ci.-s.-1iuttailTcoi1iad.~==== ==== ==== ==== ==== ==== ==== ~-- ==== ~-- ~-- ~-- ~-- ==== ==== ==== ==== ==== ==== ==== ==== ==== ~-- ~-- ==== ~- ~--- ~-- ~- ~ ~-- ~-- ~-- ==== ~-- ==== ~--, ___ _ n. sp.? ______________________________ ---- ________________________ ---- ____________ ---- ____ ---- ---- ____ ---- ---- ________________ X 

===] x-7-lsil:-1 ?---1 ==== lsil:-1 x--lci.--1 ==== 1 ==== 1 ==== 1 ====lei.-- lei.-- Solen perrini Clark __ ------------------- ________________________ cf. ________________ ? ____________________________ X ________ X 

Siliqua cf. S. media (Sower by) of Wood- ring [and Bramlette], 1950 ____________ ---- ---- ________________ ----X ____________________ ---- ---- ________ ---- ________ ---- ____ ---- ____ ---- ---- ________________________ X ---- ---- ____ , ___ _ Cryptomya californica Conrad ___________ ---- ____ ?sp. ____________ X ________________ X ____ ---- ________ ---- ---- X X ____ ---- ________ ---- X X 2 ________________________ ---- ---- cf. 

~;,~~~l~~~~}g~?=;~~~~~~~~~ =~~~ :~:~ ~;~~ ~:: :::~ :::~ ~=~= ~~== ~~~~ ~::: ~~~~ :~:: ~==~ =~~~ ~~== ~~=~ ~~~~ ~:: ~~~~ ~:: :==~ ~~~~ ~~=~ ~==~ ~~=~ ~== ~-,- ~~~~ ~~~~ ~:: ~~~~ ~==~ ~~:: ==~~ ~=~~ :]!:=: 

BARNACLES: 

Balanus wegarius (Conrad) (pl. 1, figs. 2

, ~: ~P~ -~-l~_ :_ ~~-s~-~·-~~==============1 ~---1 ~---1 ====I==== I ====I ====I ====1 ~--~~~·--1 ====I ====I==== I ====I ====i ====i ~ 14l ====I ~--1 ====I ====I==== I ====1~:~-~ ~--1 ====I==== ~~---1 ~--1 ~--1 ====I~--~~:~-~~:~-~ ====1 ====I==== I==== sp. (small) ______________________________________________ ------------ ________ -------- ----1---- ---- ----1---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- X ---- ---- ---- ---- ---- ---- ---- ----

1 Echinoid identifications from USGS collections, excepting loc. M1966. by J. Wyatt Durham. 2 Occurrence in collection numbered M1966 from same locality. 3 Occurrence in collection from UCMP loc. A3424. about 1 mile ESE. 4 Occurrence at loc. M976 almost 2 miles NNE of M975. s Occurrence at loc. Ml674 about 500 feet S. of M982 and somewhat higher stratigraphically. Astrodapsis 

salinasensis and Astrodapsis cf. A. fernandoensh have also been identified from loc. M1674 by J. Wyatt 

Durham. 

6 Occurrence in University of California Museum of Paleontology (UCMP) collection from USGS loc. 

M1341 which is about Y2 mile SE of M913. 7 Occurrence in collection numbered M1939 from same locality. s Present in Stanford University collection from loc. CIOOl, "3 miles E. of San Lucas, Calif." R. B. 

Moran, collector. 

o Occurrence in collection from UCMP loc. 3572, which is equivalent to M1966. 10 Field identification. n Occurrence at loc. M1064 about Y2 mile WSW of M1066. 12 Occurrence in collection from UCMP loc. A911, 500 feet N. of WU cor. sec. 14 T. 21 S., R. 9 E., 

MDB&M, with Lyropecten terminus Arnold. 13 Also recorded with Lyropecten terminus Arnold from "2 miles S. of San Lucas" (Arnold, 1906, p. 64 as Pecten oweni Arnold) and from "17'2 miles SW of Lonoak post office" (Nomland, 1917a, p. 215, also asP. 

oweni). l4 Occurrence in collection from loc. M2279 from same gully. Species represented by large, concentrically sculptured scuta and terga which lack radial sculpture. 

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PANCHO RICO FORMATION, SALINAS VALLEY, CALIFORNIA A15 

Larger invertebrate fossils from the Pancho Rico 

Formation that are diagnostic or strongly suggestive 

of Pliocene age, as that epoch is used in the standard 

Pacific Coast provincial megafossil chronology (Weaver 

and others, 1944; Durham. J. Wyatt, 1954) are: 

Gastropods : 

Oalliostoma coalingense (Arnold) 

Oalliostoma etchcgoinense (Nomland) 

Turritella cooperi forma nova N omland 8 

Turritella u·onostoma hemphilli Applin, in Merriam 

Turritella vanvlecki Arnold 

Bittium casmaliense Bartsch 

Thais etchegoinensis (Arnold) ribbed form 

Thais collomi Carson 

Oalicanthar·us cf. 0. humerosus ( Gabb) 

Oalicantharus kettlemanensis (Arnold) 

Nassarius coalingensis (Arnold) 

N assarius grammatus ( Dall) 

Clavus coalingensis (Arnold) 8 

Pelecypods : 

Area cf. A. santamariensis Reinhart 

Anadara camuloensis (Osmont) 

M ytilus coalingensis Arnold 

Ostrea atwoodi Gabb 

Lyropecten terminus (Arnold) 2 

Lyropecten cerrosensis ( Gabb) 

Patinopecten lohri (Hertlein) 

Oyclocardia californica (Dall) 

Macoma af]inis Nomland 

Spisula mercedensis Packard 

Mya arena1'ia Linne 

Echinoids: 

Astrodapsis arnoldi Kew 3 

Astrodapsis fernandoensis Pack 8 

Brachiopod : 

Terebratalia arnoldi Hertlein and Grant 

An arcid pelecypod, identified as Area cf. A. santamariensis, is abundant at USGS locality M1969 in Vineyard Canyon. This species was previously recorded 

only from the type locality in the Pliocene Careaga 

Sandstone of the Santa Maria basin and from Pliocene 

strata in the northern Whittier Hills, on the east side of 

the Los Angeles basin, Calif.4 Anadara C(J;muloensi.s 

was reported from a locality about 2:1f2 miles south of 

San Ardo by Reinhart ( 1943, p. 65). Pat-ino pecten 

lohri, a common species at USGS locali.ty M2280, is also 

represented in collections at the University of California 

and at Stanford University. It was reported from 

strata included in the Pancho Rico Formation by Woodring and Bramlette (1950, p. 102), and as "Pecten oweni 

Arnold" both by Arnold ( 1906, p. 64) from "2 miles 

south of San Lucas," and by Nomland (1917a, p. 215) 

from Lon oak, northeast of IGng City. lJf ya arenaria, 

although reintroduced in historic tin1e on the Pacific 

3 Considered diagnostic of an early Pliocene age. 

4 Stark, H. E., 1949, Geology and paleontology of the northern Whittier Hills, California: Claremont, Calif., Claremont Graduate School 

unpub. M.A. thesis. 

780-884 0-65--3 

Coast, became locally extinct by the end of the Pliocene 

in California. It is in a collection from USGS locality 

M1934, near the top of the Pancho Rico Formation, and 

has been tentatively identified from USGS locality 

M980 at the type area on Pancho Rico Creek. 

Brachiopods identified as Terebratalia arnoldi on the 

basis of a very weak medial sulcus on the pedicle valve 

and a corresponding low fold on the brachial valve are 

abundant at localities M902 and M981 in Reliz Canyon. 

A deformed specimen from UCMP locality 3953 (M902 

of this report) that Hertlein and Grant (1944, p. 142) 

stated "appears related to Terebratalia transversa 

caurina Gould," a species characterized by an opposite 

arrangement of mesial flexures, probably is this species. 

Terebratalia arnoldi, here reported from the Salinas 

Valley area for the first time, is known only from Pliocene strata (Hertlein and Grant, 1944, p. 120); yet it 

appears to be closely related to the living T. occidentalis 

Dall and has been treated as a synonym of that species 

by some paleontologists (Woodring and Bramlette, 

1950, p. 86) . 

Lyropecten ter1ninus, 5 perhaps the most characteristic mollusk in the Pancho Rico Formation, is generally 

recognized as an early Pliocene "J acalitos Stage" species in central California, although it is reported from 

a single locality (UCMP 2096) in the "lowest invertebrate fossiliferous zone" north of Coalinga, a unit that 

was included in the Etchegoin Formation by N omland 

(1917a, p. 228 and table facing p. 230). However, 

Arnold and Anderson's (1910, p. 125-133) more comprehensive list of fossils from the Etchegoin does not 

include L. termbmts. Neither is this species reported 

from the Etchegoin Formation at Kettleman Hills nor 

in the 1\::reyenhagen Hills-J acalitos Creek area, south of 

Coalinga. 

At least 10 species or subspecies of Astrodapsis have 

been reported from the Pancho Rico Formation (Kew, 

1920; Richards, 1935; Mandra, 1963). Although the 

majority are considered Pliocene guides, some species 

that also occur in the Miocene have been identified: A. 

twnidus, A. 'Whitneyi, and A. 'margaritanus. Another 

5 On the basis of collections from the Salinas Valley area, Lyropecten 

tm-minus (pl. 1, figs. 1, 10; pl. 2, figs. 1, 10) is here differentiated from 

I .. Psfrf:llanus (pl. 1, fig. 5), its precursor, by its fewer and broader 

primary ribs (about 14 or 15 as contrasted with 17 or more on L. 

etdn:llanus) ; broader interspaces that are incompletely filled with an 

interrib; and generally flatter, less inflated valves. Because L. terminus can be satisfact.or-ily- discriminated -from L. estrellanus and because it has a stratigraphic range that is almost entirely exclusive of 

that of L. est1·ellanus, it is here treated as a separate species as a matter 

of stratigraphic utility. The occurrence of L. estrellanus with Pliocene 

mollusks at locality M2050 and at a few other localities near the base 

of the Pancho Rico Formation is evidence of a local range that extends 

upward into the lowest part of the Pliocene, as that term is customarily 

used in the provincial molluscan chronology. A comprehensive discm:l"ion of the genus Lyropecten and its Miocene and Pliocene species, 

including L. estrellanus and L. terminus, was made by Woodring (1938, 

p. 33-35). 
A16 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY 

species, A. salinMensis (A. antiselli, of authors), has 

been treated as a Miocene or Pliocene taxon, although 

it occurs at the type locality and elsewhere with Pliocene mollusks including Patinopeeten lohri, Lyropeeten 

term,inu8, and Ostrea atrwoodi. Mollusks of undoubted 

Pliocene age also occur at the type locality of A. spatio8U8, in Powell Canyon (UCMP loc. 3572). The varying 

identifications of echinoids are difficult to reconcile with 

stratigraphic ocurrence and tend to cast some doubt 

on the utility of these echinoids for biostratigraphic 

correlation, at the species level, without supporting 

molluscan evidence. Hall (1962) proposed a reduction 

of the large number of available echinoid names into 

species groups, which could be used for biostratigraphic 

correlation. To his recognition of two species of Astrodapsis from the Pancho Rico Formation, A. arnold,i and 

A. spatiosus, however, should be added at least one 

species referable to hi8 A. rwhitneyi-A. jaealitosensis 

lineage (represented by Astrodapsis aff. A. euyamanus 

(this report), A. margaritanus (Kew, 1920), A. 

rwhitneyi (Mandra, 1963), and Astrodapsis sp. (this 

report) ) . Another seemingly di8tinct species, here reported for the first time from the Pancho Rico Formation, i8 A. fernandoensis, from USGS localities M982 

and M903. Hall's (1962) assignment of a Miocene age 

to the Pancho Rico Formation can be disregarded on 

the basis of the large representation of Pliocene mollusks. The echinoids listed in table 1 were identified 

by J. Wyatt Durham (oral commun., January 1964), 

who, contrary to the view of Hall, believed that the 

early echinoid names of Kew (1920) should be retained, 

at least in large part. 

A tripartite chronostratigraphic division of the Pliocene strata in California based upon larger invertebrates 

from the J acalitos, Etchegoin, and San Joaquin Formations in the Coalinga district has been used at least 

since Woodring and others (1940, p. 104, correlation 

chart opposite p. 106) informally designated these units 

as lower, middle, and upper Pliocene, respectively. 

Clark ( 1929, p. 24-28, correlation chart) seemingly had 

the concept of chronostratigraphic units of approximate stage magnitude in mind when he employed a 

threefold division of the Pliocene of California, although he used the inappropriate term "horizon" for 

these units. He recognized that know ledge was insufficient, at that-time, to permit satisfactory definition 

of his J acalitos and Etchegoin "horizons" and "upper 

Pliocene." Later, Gale (in Grant and Gale, 1931, p. 21, 

61) advocated a threefold division of Pliocene strata in 

coastal southern California. Although Gale did not 

specifically denote standard sections and faunas, he used 

the names "J acalitos zone," "San Diego zone," and 

"Santa Barbara zone" (p. 69-70) for the lower, middle, 

and upper Pliocene, respectively. The "Santa Barba,ra 

zone" was considered early Pleistocene, in part. Recognition of these series subdivisions in other California 

basins on strictly biostratigraphic data is difficult and 

is commonly subjective or predicated entirely on stratigraphic position. 6 

Faunal data for the J acalitos Formation date back 

to Nomland's (1917a) early work, which by modern 

standards must be considered generalized. More refined stratigraphic studies by Woodring and others 

(1940) at Kettleman Hills are the basis for recognition 

of the Etch ego in and San Joaquin "Stages." Aside 

from the difficulty of equating older paleontologic data 

classified by faunal assemblages with modern determinations that are documented stratigraphically, there is 

the problem of correlating the base of the incompletely 

exposed section of the Etchegoin Formation at Kettleman Hills with the type section of the J acalitos Formation in the Kreyenhagen Hills area to the west. 

The J acalitos fa una listed by N omland ( 1917 a, p. 211-

213) in his summary treatment of the Pliocene stratigraphy of the Coalinga district is the best standard 

available for lower. Pliocene biostratigraphic correlation. Nomland's list includes his Chione els1nerensis 

zone and Turritella nova zone, both of which were originally included in the informal definition of the J acalitos as a "stage" by Clark (1943, p. 190). However, 

Gale (in Grant and Gale, 1931, p. 52) equated the Chione 

el8merensis zone with the J acalitos and considered the 

overlying Turritella nova zone to be middle Pliocene 

in age. Woodring, Stewart, and Richards (1940, p. 

104) observed that the presence of Ficus ( Trophosyeon) 

in the Turritella nova zone is suggestive of the J acalitos. 

From N omland's list, Turritella coo peri forma nova, 

Clavus coalingensi<s, and Lyropeeten terminus, which 

occur in the Pancho Rico, are considered to be early 

Pliocene species. Additional evidence of the early Pliocene age of the Pancho Rico is the joint occurrence of 

the echinoid genera Astrodapsis and Dendraster, late 

Miocene~early Pliocene and Pliocene-Recent taxa, respectively. Two species of Astrodapsis-A. arnoldi 

and A. fernandoensis-in the Pancho Rico are generally 

regarded as early Pliocene forms. 

A number of species that occur in both the J acalitos 

and Etchegoin Formations do not range above the lower 

part of the Etchegoin exposed at Kettleman Hills. 

These would seemingly be useful in a twofold division 

of the central California Pliocene strata, and such a 

partition might be more realistic than division into 

lower, middle, and upper Pliocene. Species that would 

6 Problems with this chronology have led some geologists to imply 

that a twofold division of the Pliocene would be more realistic, at least 

in eertain areas of southern California (Vedder, 1960, p. B327 ; Winterer 

and Durham, 1962, p. 322). 
PANCHO RICO FORMATION, SALINAS VALLEY, CALIFORNIA A17 

be early Pliocene guides are 0 alicantharus kettlemanensis, Ostrea at1voodi, and Pat·inopecten lohri. All 

these species are present in the Pancho Rico Fonnation, 

and the first two are sufficiently abundant and widespread to be considered characteristic. 

As previously mentioned, the fauna of the Pancho 

Rico Formation compares most closely with that of the 

J acaJitos Formation in the Coalinga district. Of the 

95 species of larger invertebrates listed by N omland 

(1917a, p. 211-213), more than half are represented by 

very closely related or identical taxa in the Pancho Rico 

Formation. The similarity of the Pancho Rico and 

J acalitos faunas led earlier investigators (N omland, 

1917b, p. 305; Clark, 1943, p. 190; Woodring and Bramlette, 1950, p. 102) to correlate these formations and 

to classify the Salinas Valley strata as lower Pliocene. 

However, evaluation of this long-standing interpretation has been difficult in the absence of faunal documentation. The evidence for an early Pliocene age, in the 

traditional provincial usage, is occurrence of five species 

regarded as early Pliocene guides, faunal similarity 

with the .standard lower Pliocene section in the San 

Joaquin Valley, and the joint occurrence of the echinojd 

genera Astrodapsis and Dendraster. 

Strata included by Wilson (1943) in the Etchegoin 

Group in the San Benito quadrangle, about 20-25 miles 

due north of King City and on the northeast side of 

the San Andreas fault, are correlative with the Pancho 

Rico Formation. The presence of Lyropecten termin1ts 

and the joint occurrence of species of Astrodapsis and 

Dendraster in the basal 400 feet of the marine part of 

the group are evidence of a J acalitos age. Because the 

fauna of these beds was not segregated stratigraphically 

from those of the overlying strata, which contain assemblages comparable to those in the younger part of 

! the Coalinga Pliocene sequence (Wilson, 1943, p. 245), 

detailed comparison and correlation with the Pancho 

Rico Formation are not made. 

The megafossils in the upper part of the Sisquoc 

Formation of the Santa Maria basin and in the Pancho 

Rico Formation are similar. More than half of 42 taxa 

listed from the basin facies of the Sisquoc Formation by 

Woodring and Bramlette ( 1950, table opposite p. 34) 

, are represented by identical or closely related forms in 

the Pancho Rico Formation. At least 20 of the 25 larger 

invertebrates from the marginal facies of the Sisquoc, 

the Tinaquaic Sandstone ~fember, are represented in 

the Pancho Rico Formation. In the absence of distinc-

. tive early Pliocene guides, the upper parts of both facies 

of the Sisquoc were considered middle Pliocene by 

Woodring and Bramlette. Because the Pancho Rico 

Formation does contain early Pliocene invertebrate fossils, it may be older, at least in part, than the Sisquoc, 

in spite of considerable similarity in the faunas of the 

Pancho Rico and the upper part of the Sisquoc. 

Woodring and Bi·amlette (1950, p. 100-101) observed 

that the Foraminifera from the upper part of the 

basin facies of the Sisquoc "have more of a late Miocene 

than a Pliocene aspect," whereas the lower and middle 

parts of the basin facies contain "a few megafossils that 

have Pliocene affinities." This condition is similar to 

that in the Pancho Rico Formation, where Foraminifera suggestive of Dehnontian age and megafossils that 

are clearly of Pliocene age occur together. 

Units similar in age to the Pancho Rico Formation 

are present in the Ventura and Los Angeles basins of 

southen1 California. The lower Pliocene strata in 

those areas accumulated predominantly at bathyal 

depths, and for that reason the larger invertebrates and 

Foraminifera have little similarity to the shallow-water 

assemblages from the Pancho Rico. A notable exception is the Pliocene fauna of the Towsley Formation of 

late Miocene a.nd early Pliocene age in the eastern Ventura basin (Winterer and Durham, 1962, p. 296-306); 

this fauna contains shallow-water 1nollusks and echinoids that suggest correlation with the Pancho Rico 

Formation. 7 

Problems of interbasinal correlation of Pliocene strata based on larger invertebrates were discussed in considerable detail by Woodring, Stewart, and Richards 

( 1940) and by Woodring and Bramlette ( 1950) . Little can be added to their conclusions other than documentation of the early Pliocene age of the Pancho Rico 

Formation and reiteration of the difficulty in recognition and correlation of a threefold division of the 

Pliocene on biostratigraphic evidence alone. 

Foraminifera from the Pancho Rico Formation have 

been interpreted as indicating either a Miocene or a 

Pliocene age. Kleinpell (1938, fig. 14) assigned a 

:foraminiferal faunule from the Pancho Rico Formation 

in Long Valley to his upper Delmontian Stage, which 

he equated with echinoid zones listed as Astrodaps.Zs 

salinasensis and A. spatiostts. Foraminifera identified 

by Patsy J. Smith (written commun. 1963) as Elphid·iurn hug hesi (abundant), A m1nonia beccarii (common), 

Buliminella elegantiss·ima (abundant), Boli~vina cf. B. 

girardensis (rare), B oli1'ina cf. B malagensis (rare) , 

and Bolivina obliqua (rare), from USGS locality 

Mf7 46, between Walker and Powell Canyons, are regarded as indicative of "an upper Mohnian or 'Delmontian' age." On the other hand, Hughes ( 19·63, p. 95) 

regarded Foraminifera from the Pancho Rico in the 

7 Many shallow-water assemblages in the Towsley Formation were 

displaced into much deeper water, as is indicated by their occurrence 

with bathyal mollusks at several localities (Winterer and Durham, 

1962, p. 306-307). 
A18 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY 

San Ardo oil-field area as Pliocene, and younger than 

Delmontian. Taggart and Kraetsch ( 1963) listed E. 

A. Gribi, Jr., as the source of a Pliocene determination 

of a foraminiferal assemblage from Long Valley that 

is about the same as that listed by Hughes from the 

San Ardo oil-field area. 

MOLLUSCAN PALEOECOLOGY AND PALEOGEOGRAPHY 

The molluscan fauna of the Pancho Rico Formation 

consists of taxa whose living representatives or modern 

analogs are usually found in the shallow nearshore areas 

of the northeastern Pacific Ocean. Many of the stillliving species are known to range into water deeper 

than 10-15 fathoms, but exclusively moderate-depth 

taxa are found only in collections from USGS localities 

M902 and M981 in Reliz Canyon. These localities are 

near the northwestern end of the outcrop area of the 

Pancho Rico and have an upusual faunal composition 

with respect to assemblages frmn the type area on Pancho Rico Creek and elsewhere on the east side of Salinas 

Valley. Water depths of 30 fathoms or more are suggested by the presence of Tu,rcica sp. and abundant 

Terebratalia arnoldi Hertlein and Grant. Turcica has 

a bathymetric range of from 10 to 35 fathoms off the 

Pacific Coast (Coan in Keen, 1963, p. 104); Terebratalia arnoldi is represented in the northeastern Pacific by 

a modern analog, T. occidentalis (Dall), which ranges 

from 30 to 75 fathoms (Woodring and Bramlette, 1950, 

p. 95). Many other taxa in these collections have 

shallow to moderate depth ranges, but some, such as 

Orepidula n. sp., Ostrea atwoodi, and Balanus gregarius ~ suggest relatively shallow depths in the sublittoral zone. It is possible that these taxa may have 

been displaced downslope from their original habitat. 

The genus Patinopecten may indicate moderate depths, 

according to the bathymetric range of from 20 to 

more than 100 fathoms listed by Grau (1959, p. 148) 

for the modern P. caurinu.s. However, extinct Pliocene 

species of Patinopecten may possibly have ranged into 

somewhat shallower water, as is indicated by their frequent occurence in assemblages of shallow-water aspect. 

The shallow-water aspect of the coarser grained 

strata in the Pancho Rico Formation, suggested by the 

larger invertebrates, is confirmed by foraminifera from 

a few localities in the interbedded finer grained rocks. 

Foraminiferal assemblages f.vom the Pancho Rico are 

characterized by Elphid,iU'm and B~tlirlninella elegantissima,, taxa generally considered to be reliable indicators 

of shallow-water, nearshore shelf environments (Bandy 

and Arnal, 1960, p. 1927; Bandy, 1964, p. 141). 

The occurrence in the Pancho Rico Formation of 

several taxa now known only from lower latitudes suggests that the local early Pliocene marine climate was 

generally warmer than modern marine climates at comparable latitudes off the central California coast. In 

terms of the modern distribution of living species and 

modern analogs, the fauna of the Pancho Rico Formation is suggestive of the modern Californian molluscan 

province, as recognized by Valentine (1961), which extends from Point Conception (lat 34.5° N.) to Cedros 

Island (lat 28° N.). Taxa with southern affinities that 

are sufficiently abundant to be termed "common" are 

Oruoibulum ( Dispotaea), Turritella (three species referable to the T. broderipiana stock: T. gonostoma hemphilli, T. vanvlecki, and Turritella n. sp.), Anadara, 

Lyropecten, and a Chione allied to 0. gnidia. Taxa 

perhaps more suggestive of the Panamic molluscan 

province than of Valentine's (1961) adjoining Ca1ifornian molluscan province include Diodora n. sp ~, the 

three turritellas of the T. broderipiana stock, Orassispira n. sp., Dosinia, Area, and an undescribed species 

of Glans comparable to the modern G. radiata (Sowerby). However, modern analogs of these taxa range 

northward into a zone of overlap between the Panamic 

and Californian molluscan provinces (lat 22° N.-28° 

N.), an area that is usually regarded as subtropical. 

The only exclusively Panamic or tropical taxon known 

from the Pancho Rico Formation is 11/iltha sp. from 

locality l\{903, near San Lucas, and from locality 

M204 7, west of San Miguel near the southernmost exposures of the forn1ation. The living representative of 

this genus in the northeastern Pacific Ocean JJfiltha 

mantusi ( Dall) , was found as far north as the south end 

of Baja California and has been dredged from a more 

northern locality in the Gulf of California near Guayamas (D. R. Shasky, oral commun., June 1964). With 

the possible exception of some of the turritellas, these 

warm-water taxa occur near the base of the Pancho 

Rico Formation in assemblages of shallow-water aspect. 

Both faunal similarity with the Pliocene of the Santa 

Maria basin and the presence of a small element of 

warm-water mollusks in the widespread shallow-water 

facies of the Pancho Rico Formation imply interchange 

of 1narine life between the southern Salinas V r.Iley area 

and the Santa Maria basin, to the southeast, during 

early Pliocene ti1ne. A westward shoaling and possible 

depositional limit of the Pancho Rico Formation, at 

least in the southwestern part of the outcrop area, is suggested by the relatively thin sequence of coarse-grained 

clastic rocks containing abundant mollusks indicative of 

shallow water. Scattered exposures of this facies occur 

from near Lockwood (USGS loc. M1455) southward 

to the Nacimiento River area (USGS loc. M2050), the 

southern1nost known exposure of the formation. Farther south nonmarine strata of the Paso Robles Formation overlap marine beds of early to late Miocene age 
PANCHO RICO FORMATION, SALINAS VALLEY, CALIFORNIA A19 

and rest on granitic basement (Jennings, 1958). Although subsurface relations of the Pancho Rico Formation to the overlying Paso Robles Formation in this area 

are not adequately known, it is possible that the nonmarine strata may conceal evidence of a marine depositional basin that may have extended much farther southeast. If the Pliocene marine basin of the Salinas Valley 

area was once connected to the western oceanic area 

through the Santa Maria basin, as is suggested by 

faunal evidence, the seaway must have crossed the present crest of the Santa Lucia Range and possibly passed 

through the Huasna basin southeast of San Luis Obispo. 

Strata of probable early Pliocene age are exposed in 

the Huasna syncline near Saucelito and Phoenix Creeks 

(Jennings, 1958), about 40 miles southeast of the southernmost known occurrence of the Pancho Rico Formation. A small collection of mollusks from UCLA locality 4159 in the Phoenix-Saucelito area, identified by Hall 

(1962, p. 61), includes the following: Astrodapsis 

spatiosus Kew, A. rwhitneyi Remond, Mytilus ooalin.gensis Arnold, Ostrea atrwoodi Gabb, and Pecten (Lyropeoten) estrellanus Conrad, n. subsp. ( ? ) This collection 

is from a unit that Hall (1962) included in the Santa 

Margarita Formation and considered to be Miocene. 

He compared it on echinoid evidence with the Pancho 

Rico Formation, a unit which he also considered to be 

}fiocene but on the basis of a foraminiferal assemblage. 

Certainly the mollusks, if not the echinoids, are suggestive of Pliocene age as that term is used in this report. 

The alternate possibility that there was no marine 

connection to the south and that the warn1-water taxa 

are 1nerely Miocene relicts, or are directly evolved from 

Miocene species, cannot be entirely discounted. This 

idea seems less probable, however, because some of the 

taxa with southern affinities, such as Oruoibuium (Dispotaea), Glans n. sp., and~Orassispira n. sp., made their 

initial appearance in the Pliocene strata of this central 

California area. 

Faunal similarity to presumably contemporaneous 

molluscan assemblages from the lower part of the 

Purisima Formation in the southern Santa Cruz Mountains, some 60-70 n1iles to the northwest, is less apparent. 

Comparable depth assemblages from the Purisima 

(Arnold, 1908; Martin, 1916; Cummings and others, 

1962), although containing fewer species than those of 

the Pancho Rico Formation, seem to represent markedly 

cooler water conditions. Thickening of the Pancho 

Rico to a maximum measured thickness greater than 

1,000 feet in the northwestern part of the outcrop area, 

local deepening of the depositional basin suggested by 

the benthonic mollusks from that area, and the diminution of grain size of strata might be taken as evidence 

of a seaway or marine trough leading northwestward 

toward the present position of Monterey Bay. Such a 

marine connection would provide a direct path of migration for some of the cool water, northern forms that are 

locally abundant and characteristic of the northwestern 

exposur~s of the Pancho Rico Formation. Some of the 

taxa with northern affinities in the Pancho Rico are 

Ohlmnys n. sp. aff. C. nipponen,sis, Mya arenaria, M. 

truncata, Tellilna cf. T.ltutea, lJ,f aomna brota, and Siliqua 

cf. S. med-ia. For the most part these species are represented by isolated individuals and are not characteriRtic of the formation. 

A more circuitous route by which northern species 

could have migrated into the Salinas Valley area during 

deposition of the Pancho Rico Formation was through 

the San Benito trough, a linear Pliocene depositional 

basin immediately east of the San Andreas fault and 

extending south ward from near Hollister to the Coalinga area. The northernmost known occurrence of early 

Pliocene species characteristic of the so-called J acalitos 

Stage are near San Benito (vVilson, 1943, p. 245), but 

the biostratigraphy of Pliocene strata northwest of that 

area is not well known. The presence of Dosinla with 

Pliocene species in the Purisima Formation of the Sargent oil field in the north end of the San Benito trough 

(Martin, 1916, p. 245) is suggestive of an early Pliocene 

age at that latitude, and of the existence of a seaway 

bordering the east side of the San Andreas fault in the 

Hollister-San Benito area. 

COLLECTION -LOCALITY DESCRIPTIONS 

U.S. Geological Survey (USGS) Oenozoic Localities 

M902. East side of Reliz Canyon, 650 ft S., 1,875 ft W. of NE 

cor. sec. 35, T. 19 S., R. 6 E., Reliz Canyon quadrangle. 

Collector: D. L. Durham, 1960. 

M903. Sandstone bluff on west side of State Highway 198, 425 

ft S., 425 ft W. of NE cor. sec. 5, T. 21 S., R. 9 E., San 

Lucas quadrangle. Collectors: D. L. Durham, 1959; 

W. 0. Addicott and D. L. Durham, 1964. 

M913. North side of Wildhorse Canyon, 2,650 ft N., 1,075 ft E. 

of SW cor. sec. 8, T. 20 S., R. 9 E., San Lucas quadrangle. Collector : D. L. Durham, 1960. 

M918. Ridge northwest of Pine Canyon, 2,000 ft N., 1,475 ft W. 

of SID cor. sec. 23, T. 20 S., R. 7 E., Thompson Canyon 

quadrangle. Collector: D. L. Durham, 1959. 

M952. North of Sweetwater Canyon, 800ft N., 2,250 ft E. of SW 

cor. sec. 32, T. 19 S., R. 9 E., San Lucas quadrangle. 

Collector: D. L. Durham, 1959. 

M975. About 1 mile north of San Ardo, 300 ft S., 1,000 ft E. of 

NW cor. sec. 9, T. 22 S., R. 10 E., San Ardo 15-minute 

quadrangle. Collector : C. L. Rice, 1960. 

M976. North of Pancho Rico Creek, 2,600 ft S., 600ft W. of NE 

cor. sec. 3, T. 22 S., R. 10 E., San Ardo 15-minute quadrangle. Collector: C. L. Rice, 1960. 

M977. Base of bluff on south side of Pancho Rico Creek, 1,000 

ft N., 3,100 ft W. of SE cor. sec. 11, T. 22 S., R. 10 E., 

San Ardo 15-minute quadrangle. Collector : D. L. 

Durham, 1960. Same as USGS locality M1939. 
A20 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY 

M979. South side of Pancho Rico Creek, 700ft S., 1,200 ft W. of 

NE cor. sec. 15, T. 22 S., R. 10 E., San Ardo 15-minute 

quadrangle. Collector: D. L. Durham, 1960. 

lVl980. Base of bluff on south side of Pancho Rico Creek, 1,600 

ft N., 1,400 ft "\V. of SE cor. sec. 11, T. 22 S., R. 10 E., 

San Ardo 15-minute quadrangle. Collector: D. L. 

Durham, 1960. Same· as USGS locality M1929. 

M981. East side of Reliz Canyon, 650 ft N., 1,950 ft W. of SE 

cor. sec. 26, T. 19 S., R. 6 E., Reliz Canyon quadrangle. 

Collector: D. L. Durham, 1960. 

lVl982. Roadcut on west side of U.S. Highway 101, 150 ft N., 

2,525 ft W. of SEcor. sec. 25, T. 23 S., R. 10 E., Wunpost 

quadrangle. Collectors: J. G. Vedder and C. A. 

Repenning, 1960. 

M996. Ridge between :\!looney Canyon and Pine Valley, 900 ft 

S., 150ft E. of NW cor. sec. 15, T. 21 S., R. 10 E., San 

Ardo 15-minute quadrangle. Collector : C. L. Rice, 1960. 

M1060. West of Jolon Road, 2,325 ft west along section line from 

NE cor. sec. 2, T. 22 S., R. 7 E., Cosio Knob quadrangle. 

Collector: D. L. Durham, 1960. 

M1064. Ridg~ east of Mission Creek, 19,550 ft N., 2,100 ft E. of 

SW cor. Co~io Knob quadrangle, on Hunter Liggett 

Military Reservation. Collector: D. L. Durham, 1961. 

M1066. Between Mission Creek and Sulphur Spring Canyon, in 

unsurveyed land, 20,350 ft N., 4,575 ft E. of SW cor. 

of Cosio Knob quadrangle, on Hunter Liggett Military 

Reservation. Collector: D. L. Durham, 1961. 

M1067. On ridge between Mission Creek and Sulphur Spring 

Canyon, in unsurveyed land, 9,275 ft N., 2,475 ft E. of 

SW cor. of Cosio Knob quadrangle, on Hunter Liggett 

Military Reservation. Collector: D. L. Durham, 1961. 

M1341. North side of Wildhorse Canyon, in NW1A,SEIA sec. 8, 

T. 20 S., R. 9 E., San Lucas quadrangle. Collectors : 

J. A. Wolfe and V. A. Zullo, 1961. 

M1455. Roadcut on west side of San Antonio River road, 2,975 

ft N., 650 ft E. of SW cor. sec. 36, T. 23 S., R. 8 E., 

Williams Hill quadrangle. Collector: D. L. Durham, 

1962. 

M1674. In bed of Swain Creek on west side of U.S. Highway 

101, 475 ft S., 2,525 ft E. of NW cor. sec. 36, T. 23 S., 

R. 10 E., Wunpost quadrangle. Collector : D. L. Durham, 1962. 

M1676. On first ridge west of Salinas River, 1,050 ft N., 2,500 ft 

W. of SE cor. sec. 29, T. 22 S., R. 10 E., Hames Valley 

quadrangle. Collectors : D. L. Durham and D. C. 

Wiese, 1962. 

M1929. Same as locality M980. Collectors : ,V. 0. Addicott 

and D. L. Durham, 1963. 

M1930. On west side of Indian Valley, 2,175 ft S., 2,100 ft W. 

of NE cor. sec. 9, T. 23 S., R. 12 E., Valleton quadrangle. Collector : D. L. Durham, 1963. 

M1933. 225 ft S., 950 ft W. of NE cor. sec. 15, T. 23 S., R. 12 E., 

Valleton quadrangle. Collector: D. L. Durham, 1963. 

M1934. Railroad cut east of Salinas River, just north of Sarah 

Canyon, 550 ft N., 175 ft W. of SE cor. sec. 25, T. 23 

S~ R. 10 E., Wunpost quadrangle. Collectors: W. 0. 

Addicott and D. L. Durham, 1963. 

M1935. North side of Walker Canyon, 900ft N., 850ft W. of SE 

cor. sec. 28, T. 22 S., R. 11 E., Wunpost quadrangle. 

Collectors: ·w. 0. Addicott and D. L. Durham, 1963. 

M1939. Same as locality M977. Collectors: W. 0. Addicott and 

D. L. Durham, 1963. 

M1966. North side of Powell Canyon, 50ft N., 1,550 ft E. of SW 

cor. sec. 36, T. 22 S., R. 11 E., Valleton quadrangle. 

Collectors: W. 0. Addicott and D. L. Durham, 1964. 

M1967. Top of ridge between Powell Canyon and Canada Montuosa, 500 ft N., 1,550 ft E. of S'V cor. sec. 36, T. 22 

S., R. 11 E., Valleton quadrangle. Collectors: W. 0. 

Addicott and D. L. Durham, 1964. 

M1969. Near top of ridge southeast of Vineyard Canyon road, 

about 12 ft stratigraphically above USGS locality 

M1968 (Santa Margarita Formation), 2,625 ft N., 1,850 

ft E. of SW cor. sec. 34, T. 23 S., R. 13 E., Stockdale 

Mountain quadrangle. Collectors: W. 0. Addicott 

and D. L. Durham, 1964. 

M1970. Railroad cut at mouth of first small gully south of USGS 

locality l\11934 ; approximately 20 ft stratigraphically 

below M1934, 425 ft N., 175 ft W. 00: SE cor. sec. 25, 

T. 23 S., R. 10 E., 'Vunpost quadrangle. Collectors,: 

W. 0. Addicott and D. L. Durham, 1964. 

M2047. 550 ft N., 225 ft W. of SE cor. sec. 19, T. 25 S., R. 11 E., 

Adelaida quadrangle. Collectors: W. 0. Addicott, D. 

L. Durham, and R. J. McLaughlin, 1964. 

M2050. 2,225 ft N., 1,250 ft W. of SEcor. sec. 29, T. 25 S., R. 11 

E., Adelaida quadrangle. Collector~: W. 0. Addi·cott, 

D. L. Durham, and R. J. McLaughlin, 1964. 

M2278. Cut on grade between San Lorenzo Creek and summit of 

State Highway 198, 11,300 ft E., 1,200 ft N. of SW co·r. 

sec. 14, T. 20 S., R. 10 E., San Ardo 15-minute quadrangle. Alt. 1,325 ft. Collector: W. 0. Addicott, 

1964. 

M2279. Float collection near head of small gully on north side 

of Wildhorse Canyon, 2,500 ft N., 300ft W. of SEcor. 

sec. 8, T. 20 S., R. 9 E., King City 15-minute quadrangle. Collector: W. 0. Addicott, 1964. 

M228f' In southwestern trending canyon near center of SW:JA, 

sec. 29, T. 18 S., R. 9 E., Greenfield quadrangle. Alt. 

about 1,350 ft. Collector : W. 0. Addicott, 1964. 

M2282. North side of Lynch Canyon, 300ft N., 1,600 ft E. of SW 

cor. sec. 8, T. 22 S., R. 11 E., San Ardo 15-minute 

quadrangle. Collector: W. 0. Addicott, 1964. 

M2283. East side of road from Lynch Canyon to abandoned well 

location, 2,300 ft S., 2,200 ft E. of NW cor. sec. 8, T. 22 

S., R. 11 E., San Ardo 15-minute quadrangle. Collector: W. 0. Addicott, 1964. 

:.\If746. Between 'Valker and Powell Canyons, 3,250 ft N., 750 

ft E. of S'V cor. sec. 25, T. 22 S., R. 11 E., Valleton 

quadrangle. Collector : D. L. Durham, 1963. 

University of California Museum of Paleontology 

( TJCMP) localities 

A906. North wall of "' uuuurse Canyon, 1,000 ft S. of E cor. sec. 

8, T. 20 S., R. 9 E., King City quadrangle. 100 ft 

below base of barren Paso Robles gravels. Collector: 

J. Kirby, 1931. 

A911. In steep hill slope 150 ft north of State Highway, 500 ft 

N. of Wl4 cor. sec. 14, T. 21 ·S., R. 9 E., Priest Valley 

quadrangle. Collector: J. Kirby, 1931. 

A914. Southeast side of Indian Valley, 1 mile north of Eagle 

School, in NE1h,NE~ sec. 21, T. 23 S., R. 12 E., San 

Miguel quadrangle. 100-150 ft below base of Paso 

Robles }formation. Collector: J. Kirby, 1931. 

A3161. In canyon on east side of Bitterwater-King City road, 

in NEIA SW% sec. 29, T. 18 S., R. 9 E., Mertz quadrangle. Collector: N. R. Park, 1939. 
PANCHO RICO FORMATION, SALINAS VALLEY, CALIFORNIA A21 

A3241. East of Peachtree Valley in center of sec. 1, T. 21 S., 

R. 11 E., Priest Valley quadrangle. Collectors: N. L. 

Taliaferro and class, 1937. 

A3296. Center of south line of SW~NW* sec. 26, T. 24 S., R. 

10 E. 

A3424. Middle of sec. 10, T. 22 S., 12 E., Priest Valley 30-minute 

quadrangle. 

A3425. On ridge at head of Sargent Canyon, NW~ cor. sec. 9, T. 

22 S., R. 12 E., Priest Valley 30-minute quadrangle. 

A3572. Same as USGS Cenozoic locality M1966. 

A3895. East side of Hog Canyon, 17 miles northeast of San 

Miguel, center of sec. 18, T. 24 S., R 14 E. 

A4945. Same as USGS Cenozoic locality Ml341. 

A4946. In cut of farm road about 100 yds south of Highway 

198 in center of E% sec. 33, T. 20 S., R. 9 E., Priest 

Valley 30-minute quadrangle. Collector: Paleo 137 

class, 1949. 

B4926. About 190ft above base of undifferentiated marine Pliocene and Paso Robles Formation in SE~SE~ projected sec. 8, T. 22 S., R. 7 E., King City quadrangle. 

Collector: R. Weidman, 1953-1956. 

Stanford University (SU) locality 

ClOOl. Three miles east of San Lucas, Monterey County, Calif. 

Collector : R. B. Moran. 

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from the Santa Cruz Mountains, California: U.S. Natl. 

Museum Proc., v. 34, no. 1617, p. 345-390. 

Arnold, Ralph, and Anderson, Robert, 1910, Geology and oil 

resources of the Coalinga district, California: U.S. Geol. 

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Baldwin, T. A., 1950, San Ardo-a stratigraphic analysis of a 

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Bandy, 0. L., 1964, Foraminiferal trends associated with deepwater sands, San Pedro and Santa Monica basins, California: Jour. Paleontology, v. 38, p. 138-148. 

Bandy, 0. L., and Arnal, R. E., 1960, Concepts of foraminiferal 

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Pliocene and Pleistocene Mollusca of California : San Diego 

Soc. Nat. History Mem., v. 1, 1036 p. 

Grant, U. S., 4th, and Hertlein, L. G., 1938, The west American 

Cenozoic Echinoidea: California Univ. Pubs. Math. Phys. 

Sci., v. 2, 225 p. 

Gran, Gilbert, 1959, Pectinidae of the eastern Pacific (Alan 

Hancock Pacific Expeditions, v. 23) : Los Angeles, Calif., 

Univ. Southern California, 308 p. 

Gribi, E. A., Jr., 1963, The Salinas basin oil province, in Guidebook to the geology o.f Salinas Valley and the San Andreas 

fault: Am. Assoc. Petroleum Geologists Soc. Econ. Paleontologists and Mineralogists, Pacific Sec., Ann. Spring Field 

Trip 1963, p. 16--27. 

Gudde, E. G., 1949, California place names: Berkeley and Los 

Angeles, California Univ. Press, 431 p. 

Hall, C. A., 1962, Evolution of the echinoid genus Astrodapsis: 

California Univ. Pub. Geol. Sci. Bull., v. 40, no. 2, p. 47-180. 

Hamlin, Homer, 1904, Water resources of Salinas Valley, California: U.S. Geol. Survey Water-Supply Paper 89, 91 p. 

Hedgpeth, J. W., 1957, Classification of marine environments, 

Chap. 6 of Ladd, H. S., ed., Paleoecology : Geol. Soc. America 

Mem. 67, v. 1, p. 17-28. 

Hertlein, L. G., and Grant, U. S., 4th, 1944, the Cenozoic Brachiopoda of western North America: California Univ. Pubs. 

Math. Phys. Sci., v. 3, 236 p. 

Hughes, A. W., 1963, The two sides of Salinas, a biostratigraphic 

outline of Salinas Valley sediments, in Guidebook to the 

geology of Salinas Valley and the San Andreas fault: Am. 

Assoc. Petroleum Geologists-Soc. Econ. Paleontologists and 

Mineralogists, Pacific Sec., Ann. Spring Field Trip 1963, 

p. 94-97. 

Jennings, C. W., 1958, Geologic map of California, Olaf P. 

Jenkins edition, San Luis Obispo sheet: California Div. 

Mines. 
A22 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY 

Keen, A. Myra, 1963, Marine molluscan genera of western North 

America: Stanford, Calif., Stanford Univ. Press, 126 p. 

Kew, w·. S. ·w., 1920, Cretaceous and Cenozoic Echinoidea of the 

Pacific Coast of North America: California Univ. Dept. 

Geology Bull., v .. 12, no. 2, p. 23-236. 

Kilkenny, .J. E., 1948, Geology and exploration for oil in Salinas 

Valley, California: Am. Assoc. Petroleum Geologists Bull., 

v. 32, no. 12, p. 2254-2268. 

Kilkenney, .J. E., chm., and others, 1952, Cenozoic cohefation 

section, Salinas Valley from San Antonio River northerly to 

San Andreas fault through San Ardo oil field, California : 

Am. Assoc. Petroleum Geologists, Pacific Sec. 

Kleinpell, R. 1\:L, 1930, Zonal distribution of the Miocene Foraminifera in Reliz Canyon, California : Micropaleontology 

Bull., v. 2, no. 2, p. 27-32. 

--- 1938, Miocene stratigraphy of California : Tulsa, Okla., 

Am. Assoc. Petroleum Geologists, 450 p. 

Mandra, Y. T., 1963 Buttle diatomite, a new member of the 

Monterey Formation, Salinas Valley, Califonria, in Guidebook to the geology of the Salinas Valley and the San 

Andreas fault: Am. Assoc. Petroleum Geologists-Soc. Econ. 

Paleontologists and Mineralogists, Pacific Sec., Ann. Spring 

Field Trip 1963, p. 104-105. 

Martin, Bruce, 1916, The Pliocene of middle and northern California: California Univ. Dept. Geology Bull., v. 9, no. 15, p. 

215--259. 

Nickell, F. A., 1931, Geology of the Soledad quadrangle [central 

California] [abs.]: Geol. Soc. America Bull., v. 42, no. 1, p. 

313-314. 

Nomland, J. 0., 1917a, The Etchegoin Pliocene of Middle California: California Univ. Dept. Geology Bull., v. 10, no. 14, 

p. 191-254. 

--- 1917b, Fauna of the Santa Margarita beds in the North 

Coalinga region of California: California Univ. Dept. Geology Bull., v. 10, no. 18, p. 293-326. 

Pilsbry, H. A., 1916, The sessile barnacles ( Girripedia) contained in the collections of the U.S. National Museum, including a monograph of the American species: U.S. Natl. 

Mus. Bull. 93,366 p., 76 pls. 

Pack, R. W., and English, ,V, A., 1915, Geology and oil prospect:,; 

in Waltham, Priest Bitterwater, and Peachtree Valleys, 

California: U.S. Geol. Survey Bull. 581, p. 119-160. 

Reed, R. D., 1925, The post-Monterey disturbance in the Salinas 

Valley, California: Jour. Geology, v. 33, no. 6, p. 588-607. 

--- 1933, Geology of Califon1ia : Tulsa, Okla., Am. Assoc. 

Petroleum Geologists, 355 p. 

Reinhart, P. ,V,, 1943, Mesozoic and Cenowic Arcidae from the 

Pacific slope of North America : Geol. Soc. America Spec. 

Papers 47, 117 p. 

Richards, G. L., .Jr., 1935, Revision of some California species of 

A8trodapsis: San Diego Soc. Nat. History Trans., v. 8, no. 

9, p. 59-66. 

Schombel, L. F., 1943, Soledad quadrangle [California] : California Div. Mines Bull. 118, p. 467-470. 

Taggart, Larry, and Kraetsch, R. B., compilers, 1963, Fossil register of Salinas Valley area, in Guidebook to the geology 

of Salinas Valley and the San Andreas fault: Am. Assoc. 

Petroleum Geologists-Soc. Econ. Paleontologists and Mineralogists, Pacific Sec., Ann. Spring Field Trip 1963, p. 54. 

Talia.ferro, N. L., 1943a, Bradley-San Miguel district [California] : California Div. Mines Bull. 118, p. 456-462. 

---1943b, Geologic history and structure of the central Coast 

Ranges of California: California Div. Mines Bull. 118, p. 

119-163. 

Turner, F. E., 1963, The Mee Ranch area, Peachtree Valley, 

Monterey County, California, in Guidebook to the geology 

of Salinas Valley and the San Andreas fault: Am. Assoc. 

Petroleum Geologists-Soc. Econ. Paleontologists and Mineralogists, Pacific Sec., Ann. Spring Field Trip 1963, p. 

35--37. 

U.S. Board on Geographic Names, 1961, Decisions on names in 

the United States, decisions rendered from May-August 

1961: Washington, U.S. Dept. Interior, Decision list 6102, 

81 p. 

Valentine, J. W., 1961, Paleoecologic molluscan geography of the 

Californian Pleistocene: California Univ. Pub. Geol. Sci. 

Bull., v. 34, no. 7, p. 309-442. 

Vedder, J. G. 1960, Previously unreported Pliocene Mollusca 

from the southeastern Los Angeles basin [California], 

in Geological Research 1960: U.S. Geol. Survey Prof. Paper 

400-B, p. B326-B328. 

Waring, C. A., 1914, Geology and possibilities of oil in portions 

of Monterey, San Luis Obispo, and San Benito Counties, 

[Chap.] 10 of McLaughlin, R. P., Petroleum industry of 

California : California Mining Bur. Bull. 69, p. 418-438. 

Weaver, C. E., chm., and others, 1944, Correlation of the marine 

Cenozoic fonnations· of western North America [Chart no. 

11] : Geol. Soc. America Bull., v. 55, no. 5, p. 569-598. 

Wilson, I. F., 1943, Geology of the San Benito quadrangle, California : California Jour. Mines and Geology, v. 39, no. 2, p. 

183-270. 

Winterer, E. L., and Durham, D. L., 1962, Geology of southeastern Ventura basin, Los Angeles County, California: 

U.S. Geol. Survey Prof. Paper 334-H, p. 275--366. 

Woodring, W. P., 1938, Lower Pliocene mollusks and echinoids 

from the Los Angeles basin, California, and their inferred 

environment: U.S. Geol. Survey Prof. Paper 190, 67 p., 9 pls. 

Woodring, W. P., and Bramlette, M. N., 1950, Geology and 

Paleontology of the Santa Maria district, California: U.S. 

Geol. Survey Prof. Paper 222, 185 p. 

Woodring, W. P., Stewart, Ralph, and Richards, R. W., 1940, 

Geology of the Kettleman Hills oil field, California ; stratigraphy, paleontology, and structure: U.S. Geol. Survey 

Prof. Paper 195, 170 p. 
PLATES 1-5 
PLATE 1 

FIGURES 1, 10. Lyropecten terminus (Arnold). 

USGS Cenozoic loc. M1935, Walker Canyon. 

1. Left valve. Length 90 mm, height 82 mm. USNM 649083. 

10. Right valve. Length 116 mm, height 101 mm. USNM 649084. 

2, 3, 6, 8. Balanus gregarius (Conrad). 

USGS Cenozoic loc. M903, %mile northeast of San Lucas. 

2, 8. Scutum. l-ength 26 mm, width 16.5 mm. USNM 649171. 

3, 6. Scutum. Length 29.5 mm, width 22 mm. USNM 649172. 

4. Patinopecten lohri (Hertlein). 

Left valve. Length 61 mm, height 68 mm. SUPTC 9753. Long Valley, Monterey County. 

5. Lyropecten estrellanus (Conrad). 

Right valve. Length 69 mm, height 60 mm. USNM 649085. USGS Cenozoic lac. M2050, 6 miles southwest 

of San Miguel. 

7. Dosinia cf. D. ponderosa (Gray). 

Length 70 mm. USNM 649086. USGS Cenozoic lac. M2047, 7 miles southwest of San Miguel. 

9. Astrodapsis arnoldi Pack. 

Length 70 mm, width 66 mm, height 14 mm. USNM 649087. USGS Cenozoic loc. M1929, lower part of Pancho 

Rico Creek. 
GEOLOGICAL SURVEY PROFESSIONAL PAPER 524-A PLATE 1 

2 

MOLLUSKS, BARNACLE, AND ECHINOID OF THE PANCHO RICO FORMATION 
PLATE 2 

FIGURES 1, 10. Lyropecten terminus (Arnold). 

1. Right valve. Length 105 mm, height 96 mm. USN.M 649088. USGS Cenozoic loc. M1676, about 2}f 

miles south of San Ardo. 

10. Left valve. Length 124 mm, height 115 mm. USNM 649089. USGS Cenozoic loc. M1939, lower part of 

Pancho Rico Creek. 

2. Anadara (Anadara) trilineata (Conrad). 

Length 25.4 mm. USNM 649090, a rubber cast. USGS Cenozoic loc. M996, Pine Valley. 

3, 5. Terebratalia arnoldi Hertlein and Grant. 

USNM 649091. USGS Cenozoic loc. M902, Reliz Canyon. 

3. Brachial valve. Length 30.5 mm. 

4. Pedicle valve. Length 33 mm, height (ventral margin crushed) 22 mm. 

4, 9. Balanus sp. 

Tergum. Length 16.2 mm, width 8 mm. USNM 649173. USGS Cenozoic loc. M1933, Indian Valley. 

6, 8. Ceratostoma foliatum (Gmelin). 

Height 53 mm, width 34 mm. SUPTC 9754. Sec. 27, T. 20 S., R. 9 E., Long Valley. 

7. Macoma affinis Nomland. 

Length 32.3 mm, height 23 mm. USNM 649092, a rubber cast. USGS Cenozoic loc. M979, lower part of Pancho 

Rico Creek. 
GEOLOGICAL SURVEY 

6 

MOLLUSKS, BARNACLE, AND BRACHIOPOD OF THE PANCHO RICO FORMATION 
PLATE 3 

FIGURE 1. Patinopecten lohri (Hertlein). 

Left valve. Length 107 mm, height 97 mm. UCMP 36467. UCMP loc. A3161, between Bitterwater Road and 

Becker Valley. 

2. M ya arenaria Linne. 

Length (nearly complete) 63 mm, height 44.5 mm. USNM 649093. USGS Cenozoic loc. M1934, Railroad cut 

north of Sarah Canyon. 

3, 7. Ostrea atwoodi Gabb. 

Length 54 mm, height 59 mm. USNM 649094, USGS Cenozoic loc. M1939, lower part of Pancho Rico Creek. 

4. Crepidula nummaria Gould. 

Height 30 mm, width 19 mm. USNM 649095, a rubber cast. USGS Cenozoic loc. M1929, lower part of Pancho 

Rico Creek. 

5. Kelletia cf. K. kelleti (Forbes). 

Height 40.5 mm, width 22.5 mm. USNM 649096, a rubber cast. USGS Cenozoic loc. M1934, railroad cut north 

of Sarah Canyon. 

6. Thais etchegoinensis Arnold. 

Ribbed form. Height 59 mm, width 39.5 rom. SUPTC 9755. SU loc. C1001, 3 miles east of San Lucas. 

8. Lyropecten cerrosensis (Gabb). 

Right valve. Length 123 mm, height 112 mm. UCMP 36469. UCMP loc. A911, about 3 miles southeast of 

San Lucas. 
GEOLOGICAL SURVEY PROFESSIONAL PAPER 524-A PLATE 3 

2 

5 

3 

MOLLUSKS OF THE PANCHO RICO FORMATION 
FIGURE 

PLATE 4 

1. Patinopecten lohri (Hertlein). 

Right valve. Length 113 mm, height 102 mm. UCMP 36468. UCMP loc. A3161, between Bitterwater Road 

and Becker Valley. 

2. Florimetis biangulata (Carpenter). 

Length 77 mm, height 62.5 mm, width 34.4 mm. USNM 649097. USGS Cenozoic loc. M1929, lower part of 

Pancho Rico Creek. 

3. Turritella cooperi forma nova N omland. 

Height 18.5 mm, width 12.4 mm. USNM 649098. USGS Cenozoic loc. M1676, about 2}'2 miles south of San Ardo. 

4. Cancellaria tritonidea Gabb. 

Height 63.5 mm, width 48 mm. UCMP 36470. UCMP loc. B4926, about ~ miles northeast of San Antonio 

Mission. 

5, 8. Forreria belcheri (Hinds). 

Height 101 mm, width 96 mm.. UCMP 15177. UCMP loc. A4945, north side of Wildhorse Canyon. 

6, 7. Thais collomi Carson. 

Juvenile specimen. Height 27.9 mm, width 17.5 mm. UCMP 36471. UCMP loc. A4946, Long Valley. 
GEOLOGICAL SURVEY PROFESSIONAL PAPER 524-A PLATE 4 

MOLLUSKS OF THE PANCHO RICO FORMATION 
FIGURE 

PLATE 5 

1. Anadara (Anadara) trilineata forma canalis (Conrad). 

Length 23 mm, height 20 mm. USNM 649099, a rubber cast. USGS Cenozoic loc. M982. Reliz Canyon. 

2, 4. Calicaniharus kettlemanensis (Arnold). 

USGS Cenozoic loc. M1929, lower part of Pancho Rico Czeek. 

2. Height 39.5 mm, width 3'9 mm. USNM 649100, a rubber cast. 

4. Weakly noded form. Height 43 mm, width 32.5 mm. USNM 649101, a rubber cast. 

3. Calicantharus cf. C. fortis angulata (Arnold). 

Fragment of body whorl and spire. Width 17 mm. USNM 649102, a rubber cast. USGS Cenozoic loc. M980, 

lower part of Pancho Rico Creek. 

5. Diodora n. sp.? aff. D. inaequalis (Sowerby). 

6, 7. 

Incomplete rubber cast. Height 17 mm. USNM 649103. USGS Cenozoic loc. M977, lower part of Pancho 

Rico Creek. 

Calliostoma coalingense Arnold. 

6. Height 12.4 mm, width 13.5 mm. USNM 649104, a rubber cast. USGS Cenozoic loc. M1930, Indian Valley. 

7. Height 13.5 mm, width 15 mm. USNM 649105, a rubber cast. USGS Cenozoic loc. M979, lower part of 

Pancho Rico Creek. 

8. Calicantharus cf. C. fortis (Carpenter) . 

Body whorl slightly crushed. Height 36.5 mm, width 23 mm. USNM 649106, a rubber cast. USGS Cenozoic 

loc. M1939, lower part of Pancho Rico Creek. 

9. Turritella cooperi Carpenter. 

10, 15. 

11, 14. 

12. 

Body whorl slightly crushed . Height 37.5 mm, with 9.8 mm. USMN 649107, a rubbet cast. USGS Cenozoic 

loc. Ml929, lower part of Pancho Rico Creek. 

Bittium casmaliense (Bartsch). 

10. Incomplete rubber cast. Width of last complete whorl 7.5 mm. USNM 649108. USGS Cenozoic loc. 

M1929, lower part of Pancho Rico Creek. 

15. Strongly sculptured form. Height 19.3 mm, width 8.5 mm. USNM 649109, a rubber cast. USGS Cenozoic loc. M1967, Powell Canyon. 

Turritella vanvlecki Arnold. 

11. Incomplete rubber cast. Width of last complete whorl 15.5 mm. USNM 649110. USGS Cenozoic loc. 

M 1935, Walker Canyon. 

14. Height 26.8 mm, width 11.5 mm. USNM 649111. USGS Cenozoic loc. M1934, railroad cut north of Sarah 

Canyon. 

Nassarius aff. N. californianus (Conrad). 

Height 8.8 mm, width 5.4 mm. USNM 649112, a rubber cast. 

south of San Ardo. 

USGS Cenozoic loc. M1676, about 2~f miles 

13. Forreria cf. F. coalingensis (Arnold). 

Height 27 mm, width 18.2 mm. UCMP 36472. UCMP loc. A906, north side of Wildhorse Canyon. 

16, 17. Cyclocardia californica (Dall). 

16. Immatuze specimen. Length 9.6 mm, width 9.2 mm. USNM 649113, a rubber cast. USGS Cenozoic loc. 

M982, highway cut 3 miles northwest of Bradley. 

17. Length 22.7 mm, USNM 649114, a rubber cast, USGS Cenozoic Joe. M1935, Walker Canyon. 

18, 19. Turrilella gonostoma hemphilli Applin in Merziam. 

USGS Cenozoic loc. M982, highway cut 3 miles northwest of Bradley. 

18. Height 33 mm, width 11.5 mm. USNM 649115, a rubber cast. 

19. Height 38.5 mm, width 15.4 mm. USNM 649116, a rubber cast. 

20. Nassarius salinasensis Addicott. 

Height 17.8 mm, width 8.9 mm. USNM 648598, a rubber cast. USGS Cenozoic loc. M977, lower part of 

Pancho Rico Creek. 

21. N assarius ( Caesia) coalingensis (Arnold) . 

Height 23.4 mm, width 12.3 mm. USNM 649117, a rubber cast. USGS Cenozoic loc. M979, lower part of 

Pancho Rico Creek. 

22. Forreria belcheri (Hinds). 

Height about 74 mm, width about 64 mm. UCMP 15178. UCMP loc. A4945, Wildhorse Canyon. 
GEOLOGICAL SURVEY 

1 

5 

10 

9 

15 

18 

2 

6 

11 12 

PROFESSIONAL PAPER 524-A PLATE 5 

3 

-.,"~ ... , \" . - ~ . 

' . ' 

' (' 1-l ... --- •.. - :· 

'PI -~- ' 

7 

13 

17 

8 

14 

MOLLUSKS OF THE PANCHO RICO FORMATION