Bulletins of American paleontology (Bull. Am. paleontol.) Vol 1968

JUL

1

6 1932

3_C|fel

BULLETINS
AMERICAN

PALEONTOLOGY

VOL. XIX

JlUie JO, IQJ2

Harris Co.
Ithaca,

U.

vS.

N. Y.

A


trice List

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2

JUL

1

6 1932

BULLETINS
OF

AMERICAN

PALEONTOLOGY

VOL. XIX

June JO,

1 93

Harris Co.
Ithaca, N. Y.

U. S.

A



BUI.I,ETINS

OF

AMERICAN PAI.EONTOI.OGY
Vol. 19

No. 68

Contributions to the Tertiary Paleontology of

Northern Peru

:

Part

5,

The Peruvian Miocene

By
A. A. Olsson

June

j^u,

rgj2

Harris Co.
Ithaca, N. Y.

U.S. A.



:

FOREWORD
This paper devoted principally to the Peruvian Miocene concludes the series of articles entitled Contributions to the Tertiary

Paleontology of Northern Peru, of which Parts

dealing with the older Tertiaries have already appeared
Bulletins.

I

am

i

to

4

in these

deeply indebted to Dr. O. B. Hopkins, Chief

Geologist of the International Petroleum Co., for the privilege
release of stratigraphic data on Peru
encouragement and interest in the work.
I wish also to acknowledge the assistance received from the present and former members of the Geological Staff in Peru, particularly to Mr. A. Iddings, present Manager in Peru and to
Messrs. O. B. Boggs, J. S. Stewart, J. L. Stauft, Willard Berry,
C. W. Boughton, E. Emendorfer, L. W. Wiedey and V. Culbert.
In working over the Peruvian collections I have had the advantage of the constant advice of Professor G. D. Harris and
the use of the unexcelled collections and library of Tertiary
Paleontology at Cornell. During my repeated visits to the Philadelphia Academy, Drs. H. A. Pilsbr}' and E. G. Vanatta have

of publishing and

the

as well as his constant

most generously extended

to

me

the facilities of the z\cadem}-

for the study of the (Collections in their care.
to

I

am

also grateful

Professor C. Dunbar of Yale University for the privilege of

studying the Nelson collection and the loan of valuable type
material.

In this paper, the following

new subgenera and

sections are

proposed

new subgenus of Liicina Bruguiere
new subgenus of Pscudoiiiilflia Fischer
Chionopsis new section of Chione Megerle von Muhfeld

Hexacorhula new section of Bothrocorhida Gabb
Teiiuicorbiila new subgenus of Corbiila Bruguiere
PyrucUa new subgenus of CanccUaria Lamarck
Pcrunasso new subgenus of Buccuianops d'Orbign}Fusiiinsfeira new subgenus of Solciiostcira Dall

Illesca

Zorrita

Gloversville, N. Y.

January

25, 1932.



Olsson: Peruvian Miocene

CONTENTS
Review of literature dealing
Miocene

I.

II

The Miocene

.

1.

with

the

Peruvian

of Northern Peru

The Zorritos District
The Zorritos Group
The Lower Zorritos formation
The Variegated beds
b.
The Upper Zorritos formation
e.
The Cardalitos formation
B.
The Tumbez formation
C.
The Sechura District
A.

a.

2.

III.

Correlation and age

IV.

Faunae Affinities

V.

Tertiary History of the West Coast of South America
1.
2.
3.

VL

Introduction
The Bolivar Geosyncline
Tertiary Mountains and Climate

Systematic

description

of

Miocene

Mollusks

of

Northern Peru

a

review of the literature dealing with the peruvian
Miocene and later deposits

i.

The

earliest papers dealing

strictly paleontological,

with the Peruvian Tertiaries are

devoted to the description of small

fossil

from Paita and Zorritos. The first of these is found
in D'Orbigny's monumental work dealing with his travels and
research in South America and includes the description of a fewfossil species from the Paita region.
D'Orbigny did not personally visit any part of the Peruvian coast north of Callao, the
fossils from Paita having been collected by Gaudichaud and other
collections

travelers.

ii6,

pi.

Rustcllaria gaudichaudi (=Ectiiiocliihts)

14, figs.

6-8) as previously indicated,

is

(op,

an upper

cit.

p.

l-'.ocene

form common

in the Saman sandstones while Pcctitiiciili(s pa\(=P. iitaeqitalis Shy.) (p. 129, pi. 15, figs. 11-13) is common in the Mancora tablazo. Moiioccras blainz'illi (p. 116. pi. 6.
teiisis

'D'Orbigny, 1842, Voyage clans I'Amerique

Paleontologie, 1-188 pp. 22 pis.

meridionale.,

vol.

3,

pt.

4,


6

Bulletin 68

C)

fig.

i8,

from

19)

Paita,

near

hill

described without locality but suspected as being

was rediscovered
Our
Amotape.

beds at Santa Lucia

in the tablazo

specimens

with

exactly

agree

D'Orbigny's figure so that there can be no doubt but that Paita
Monoceras (Acanthisa)
is the type locality for this species.
has been recorded by Darwin, Hupe, Steinmann and
Moricke from the Coquimbo beds of northern Chile and this
blainvilli

species

is

therefore important in the correlation of these rocks

According to Hupe, there are two distinct
forms in the Coquimbo beds, the first of which he regarded as
typical and a second noded form to which Moricke later gave the
The figures given by Philippi included
varietal name nodosa.
the noded form (var. nodosa Moricke) and a,copy of D'Orbigny's
with northern Peru.

Cardium acuticostata

figure of blainvilli.

19-22) from Quiriquina

of Brongniart.
its

is

(p.

said to occur at Paita

120,

12, figs.

pi.

on the authority

Since acuticostata was described from a

identification with a Paita shell

petitiana (p. 123,

pi.

corded from Paita.

13, figs. 9-1 1)

must be qviestioned.
from Coquimbo, is

D'Orbigny's figure of

this species

cast,

Venus
also re-

resembles

dementia and the Paita record may be based on a specimen
dementia peruviana Olsson from the Saman sandstones.
D'Orbigny compares petitiana with Venus donibeyi Lamarck

a

of

which

is

a Protothaca and the internal cast figured with petitiana

belongs to a thick-shelled species.
ny's figure

A

was not

Philippi

who

copied D'Orbig-

able to recognize this species with certainty.

few other species described by D'Orbigny from unknown
although associated with Mesozoic forms

calities,

be Tertiary species from Peru and Chile.

lo-

may prove

to

Astarte dubia as in-

dicated by Woodring^, is possibl)' a dementia but it does not
resemble any of the Peruvian species and moreover is described
as having a lunule which would remove it from that genus.
The
Brachyuroid described as Portunus peruvianus is possible an

Eocene

species.

In 1870, Gabb^' published the descriptions and later the
2Woodring
U.

3Gabb

S.

1926, American Tertiary mollusks
Geol. Survey Prof. Paper 147, p. 42.

1870, Description of

new

2nd

the

genus

Clementia.

species of South American Tertiary. Am.
1877, Description of a collection of fossils
Dr. Antonio Raimondi in Peru, Journ. Acad. Nat. Sci. Phila.,

Jr. Conch., vol. 5, p. 263;

made by

of

fig-

ser., vol. 8, p. 262, pi. 35.


Olsson: PEcnviAN Miocene

ures of a small collection of Paita

fossils

submitted

h\-

Dr.

Antonio Raimondi, supplemented by a few forms obtained b\
Professor Orton. Of the seventeen species enumerated, ten are
Only a part of Gabb's species have been
considered as new.
rediscovered and a search of the Academy's collection at Philadelphia failed to locate the types of Raimondi's collection.
is

It

probable that they were returned to Peru after the completion

of Gabb's studies.
fossils

It is

known

both from the Eocene or

that Gabb, like D'Orbigny, had

Saman

sandstones and the tab-

Cerithmm Iccvisciduni and Ampullina ortoni are
species throughout northern Peru. Raeta
Eocene
common Upper
gibbosa is probably Gould's Raeta undulata, a recent West Coast
species. Steinmann"* has figured R. gibbosa from an internal cast
The Raeta is said by
collected in the tablazo beds above Paita.
Gabb to occur with Volut'ilithes plicifera, which has not been
rediscovered, and Pholas chiloe.nsis Molina, a recent species.
Gabb noted the variation in lithological character of the different
specimens and suggested that they belonged to two or more diflazo deposits.

ferent eras.
tinct

One

set consisting of a

mixture of living and ex-

species of similar appearance he considered as

Pliocene

in age.

The

first

from Peru, was pub-

description of Miocene fossils

lished in 1870 by E. T. Nelson^ in a graduation thesis in the

Transactions of the Connecticut

Academy

of Science.

This

was made by Professor F. H. Bradley and Mr. E. P.
Larkin in 1867 at Zorritos. Grzybowski who visited Zorritos in
1898, and Drs. Singewald and van Hoist who .collected Spieker's

material, obtained only a few of Nelson species and until recently,
the exact locality and horizon of most of Nelson's forms remained unknown. In a visit to Zorritos in 1925, I was fortunate
in rediscovering most of Nelson's species in a small block of
down-faulted beds exposed near the mouth of Quebrada Tucillal
collection

just north of the Zorritos school-house.

Since this fossiliferous

zone has a very limited development, there can be no doubt but
that it is the type locality of Nelson's species. Fifty-five species of
mollusks are recorded by Nelson of which twent}-three are deiSteinmann 1929, Geologic von Peru, Heidelberg,
sNelson 1870, On the MoUuscan Fauna of the
Trans. Conn. Acad. Sci., vol. 2, p. 186.

p. 257, fig. 261.
later Tertiary of

Peru,


Bulletin 68

A

scribed as new.

few

species are identified with recent

West

Coast forms, while the remainder are referred to their genera
only. Onl}- a part of the

new

species

were figured so that

until

Spieker restudied and refigured the collection, Nelson's work has

been

difficult to

use and a few of his species have been redescribed

by other authors.
carefully

many

Nelson's descriptions are generally good and he

compared

his

Nelson's paper .carries
is

specimens with recent forms to which

cases they are closely related.
little

biologic and no geologic significance

hardly true, as Nelson clearly recognized the close

which most of

his species

thereby proving

its

late

in

Spieker's criticism that

affinities

had with the recent West Coast fauna
Tertiary age as indicated by the title

of the paper.

The paleontological papers of D'Orbigny, Gabb and Nelson
had proved the occurrence of Tertiary formations in the coast
region of northern Peru but aside from the brief description of
the Paita cliffs by Orton*', Spruce's^ notes on the Chira and
Piura valleys and the principally geographical writings of Raimondi, the geology of this region remained practically unknown
until the appearance of Grzybowski's^ account of a geological reconnaissance from Paita to Tumbez in 1899. The geological complexity of the Peruvian region was however too great and the
small collections of fossils from Paita and Talara not sufficiently
diagnostic to permit accurate age determinations and consequently Grzybowski in the limited time which he devoted to this
reconnaissance failed to obtain a correct idea of the rock succession and the general structure.

Grzybowski however proved

the extensive development of Tertiary beds in the Peruvian
toral

lit-

and correctly determined the lower Miocene age of the

Zorritos formation.

Grzybowski's description of the geology of the Paita region is
accompanied by a diagrammatic sketch of the coast and a detailed

section of the tablazo cliiTs east of the city.
the coast

is

To

the west of Paita,

formed of Paleozoic phyllites as previously noted by

'iOrton, 1871, The Andes and the Amazon, New York, pp. 115, 116.
^Spruce 1863, Notes of a Botanist on the Amazon and Andes, edited by
A. R. Wallace 1908, pp. 330-333.
sGrzybowski 1899, Die Tertiarablagerungen des nordlichen Peru und ihre
Beitr. Geol. Pal. Sudamerika, N. Jahrb. Min. etc.
Molluskenfauna.

BB. 12 pp. 610-644,

pis. 15-20.


Olsson

Peiiuviak Miocene

:

Orton but apparently Grzybowski did not devote much time to

this section as he failed to discover the fossiliferous Eocene
sandstones w^hich occur here, resting on slates and immediatehTo the east there are high cliffs
overlain by tablazo deposits.
formed of two series of rocks. In the upper part are sandstones and conglomerates (a and b) to which Grzybowski gave
These are the Mancora tablazo dethe name Paita formation.
Grzybowski referred the
posits of Bosworth and later writers.
Paita "stufe" to the Pliocene on the basis of its faunal mixture
of living and extinct species, in part on the resemblance of certain forms to species from the Coquimbo beds of northern Chile
and from Gabb's earlier determination of a Pliocene age for a
These beds overlie uncon formpart of Raimondi's collection.
ably a shale series (c) which Grzybowski considered the same
These shales
as the shales which he later observed at Talara.
lying beneath the tablazo beds Grzybowski referred to the Upper Miocene but they are now known to belong to the Chira
formation and of Lower Oligocene age. Five species of mollusks
are described as new from the Paita or tablazo beds.
Pecten
paytensis is a synonym of Pecten ventricosiis Sowerby, a recent
Pecten intercostatus (renamed P. incus by Hanna and
species.
Israelsky)

may

be a valid species but has not been rediscovered.

Pecten densicinctus
Ostrea lunar is

tus.

species.

and
two

is

is

probably ventricosus or a young purpuraO. prismatica Gray, a recent

is

Ostrea oculata

is

probably no longer

feet or

more

species described

living.

Specimens of

in length are locally

beds near Santa Lucia

from

West Coast

a lai"ge species of the georgiana type

hill,

this large oyster,

common

in

the tablazo

The seven
unknown to me.

Talara and elsewhere.

the underlying shales are

Since 'these shales belong to the Chira formation,

the}-

are of

lower Oligocene age. Columhella turrita (renamed C. paytensis
by Hanna and Israelsky) from its figure, seems to be Ectinochilus gaiidichaudi previously described by D'Orbigny from Paita.

The
in age

tablazo section at Talara Grzybowski considered similar

and formation

to that

observed at Paita.

the base of the cliffs or "stufe c"

mation and correlated with

tlie

The

shales at

where named the Talara
shales at

Paita.

for-

The Talara

Eocene age and the name Talara formation has
been restricted to tlie lower Upper Eocene shales and sandstones
shales are of


Bulletin 68

10

which he

directly above the

10

Upper Eocene unconformity

at the

Lase of the Discocyclina peruviana zone and below the orbitoidal
Verdun sandstones (Saman formation). Six species are record-

ed from the Talara shales, five of which are described as new.

I

have failed

The

any of these forms.

to recognize

discussion of the geology of the Zorritos region and the

more
Boca Pan, Zorritos and

description and illustration of the Miocene fauna are the

important parts of Grzybowski's paper.
Caleto

described, followed by an account of

Grau are separately

the geology of the

Tumbez

valley as

far

as

As

Mangur,co.

Grzybowski's studies on the Zorritos Miocene will be frequently referred to later in this paper, further review of his work is
not needed in this place.
Douville's^ important papers establishing the

Eocene age of

the rocks at Negritos with the description of several
,cies

new

spe-

need only be mentioned as they do not contain references to

any Miocene forms.
Spieker's^" paper

entitled,

"The Paleontology

formation of the North Peruvian Oil Fields"

of the Zorritos
is

the most ex-

tensive report on the Peruvian Miocene which has yet appeared.
It is

based principally on

made by

fossil collections

wald and van Hoist in the Zorritos region.
of the paper

is

Drs. Singe-

valuable feature

the re-study and re-figuring of most of the Nelson

collection preserved in the

The

A

Peabody Museum

at

Yale University.

discussion of the stratigraphy of the Zorritos region

based upon the

upon the

earlier

studies of

principally in the interpretation of Grzybowski's section at

Paso.

is

van Hoist and Singewald and
work of Grzybowski. A few mistakes are made
field

Spieker subdivided the Zorritos

parts to which he gave the

Mai

formation into three

names the Lower

Zorritos, the Varie-

gated beds and the Upper Zorritos and indicated their physical

and faunal characteristics. These are well-marked rock groups
and may be easily recognized over a large area in the Zorritos
sDouville 1920, L'Eocene au Perou, Compt. Rend. Acad. Sci. Paris, vol.
171, p. 1345; 1921, Nouveaux fossiles de I'Eocene du Perou, C. R. som.
Melanges paleontologiques,
193-195;
1921,
Soc. Geol. France, pp.
Journ. Conchyl. vol. 66, pp. 1-18, 2 pis., 4 figs.

lOSpieker 1922, The Paleontology of the Zorritos Formation of the North
Peruvian Oil Fields, The Johns Hopkins University, Studies in Geology. No. 3,


Olsson: Pekuvtan Miocene

11

district.

11

Unfortunately Spieker makes the mistake

in consider-

at Mai Paso which he
Zorritos group.
The upper part of

ing the section measured by Grzybowski

copies as belonging to the
this section, or

beds a to

c

belong to the

Tumbez formation

of

Upper Miocene age and not to the Upper Zorritos sandstones
Beds c to i which Grzybowski considas believed by Spieker.

ered as Heath is a faulted section with part of the beds missing.
These rocks were considered as Variegated by Spieker. They
actually belong to the upper and lower part of the Cardalitos
shales.

Spieker discusses one-hundred and one species or varieties of
moilusks of which sixty-one are described as new, or renamed.
All these forms are considered as belonging to the Zorritos for-

mation although most of Nelson's species are now known to be
much younger in age as well as the few species belonging to the
Cardalitos shales. This mixture of Lower Miocene species such
as the group of Area (Senilia) chiriquiensis Gabb with such

Upper Miocene forms as Dosinia grandis Nelson is responsible
for the Middle Miocene appearance of the fauna noted by
In the treatment of certain genera such as the
Woodring.
Turrit ella, Area and Raeta, Spieker has excessively multiplied
the number of new species and subspecies which cannot be separated in a larger collection.

In an effort to determine the age

of the Zorritos formation, most of the fossils are

European and other foreign species while
recent forms

is

Many

usually lost sight of.

particularly those
related to species

from the Nelson

now

and of no great

affinities

with

Zorritos species and

West Coast while

European types

significance.

compared with

collection are very closely

living along the

indicated relationship with

tlieir

is

their

extremely doubtful

is comMiocene of the Vienna
similar American species

Dosinia grandis Nelson

pared with D. orbieularis Agassiz of the
basin and

is

said to have no closely

but as pointed out by Nelson, D. grandis

is

very near D. ponder-

Gray ranging from Lower California to Paita and has even

been figured as fossil from the Coquimbo beds of Chile by
osa

Philippi.

Discussing Turrit ella alturana

Nelson) comparison

is

ticularly T. dickersoni

made with

several

Spieker

(T.

plana

Eocene species par-

Anderson from California but

as

may

be

seen from the growth-lines, the Peruvian form has no relation-


12

Bulletin 68

12

ship with these

Eocene species but

is

simply a fossil subspecies

of T. broderi piano d'Orbigny of the recent Panama fauna. With
few exceptions, the Zorritos fauna is not well-preserved and its

therefore more difficult than is the case with the beaupreserved Miocene mollusks of the Caribbean region. On
the whole therefore, Spieker's~ study is an earnest effort in describing and illustrating the Zorritos fauna and his conclusion

study

is

tifully

regarding the age of the Zorritos formation

is

essentially cor-

rect.

Bosworth's" comprehensive book on the Geology of northern
Peru, appeared about the same time as Spieker's work on the
Zorritos formation. It deals however more particularly with the
older Tertiary and Quarternar_\- deposits centering about Negritos while the geology of the Miocene beds of Zorritos is only

touched upon.

briefly

figured by

Woods

Woods

Nine Miocene species are mentioned and

of which two are considered as

Crassatellites

charanensis

is

a

large

new

species.

specimen

of

Grzybowski's Eucrassatella nelsoni.
Professor Berry^- has contributed several papers dealing with
The first
fossil plants from the Tertiaries of northern Peru.
contribution
leaves

made

plant-beds

and

is

river of

is

devoted to the description of a collection of

fossil

The locality of these
1875 by C. F. Winslow.
stated as being about twenty miles south of the town
in

to 300 feet inland from the shores
Professor Berry correctly identifies this locality

Tumbez and 200

of the Pacific.

with the lignitiferous shales mentioned by Grzybowski in his
Following Grzybowski, these plant beds
section at Mai Paso.
are regarded as belonging to the

Heath stage while

their asso-

ciation with oyster beds as previously noted, lead Spieker to refer

them

to the Variegated.

These plant-bearing shales associated

with a seam of coal belong near the base of the Cardalitos shales
or just above the upper Zorritos sandstones and this zone
traced inland for

more than

a mile to the banks of

may

be

Ouebrada

i^Bosworth 1922, Geology of the Tertiary and Quarternary period of
North-West Peru, with an account of the Paleontology by H. Woods,
T. W. Vaug-han, J. A. Cushman and others.
i2Berry 1919, Miocene fossil plants from Northern Peru, Proc. U.
Mus., vol. 55, pp. 279-294, pis. 14-17.

S.

Nat.


Olsson: Peruvian Miocene

13

On

Charan.

basis of stratigraphy

13

and other considerations, the

age of this florule appears to be lower Middle Miocene or ap-

proximately equivalent to the Lower Gatun of the Canal Zone.

One species Guatteria culebrensis Berry is known from Gatun
and Culebra beds of the Canal Zone while Tapira lanceolaia
Englehardt is recorded from Loja.
Persea macro phylloides
Mnglehardt, cjuestionably identified, is found in the Navidad
beds of Chile and in Colombia. The Loja flora first described
in 1895 by Engelhardt, has usually been considered at Lower
Miocene.

has been

A recent study of new collections from this locality
made by Berry who concludes that the Loja flora be-

longs to the late Miocene.

A

second paper by Professor Berry

^'^

records the occurrence of Miocene rocks in the Santa Elena
peninsula of western Ecuador and the extension of the Zorritos

There are no Miocene rocks
Chira region and the supposed Zorritos species from Casa
Saman are Upper Eocene species belonging to the Saman forformation into the Chira valley.

in the

mation.

Several

Saman

species such as

dementia peruviana and

certain of the Turritellas have an LIpper Tertiary aspect and are
easily

mistaken for Miocene species.

The

other papers of Pro-

fessor Berry and Willard Berry deal with the older beds and

need not be discussed

A

in this review.

small collection of fossils obtained by Messrs Gester, Burtt

and May during geological reconnaissance trips in northern Peru
and deposited in the California Academy of Science, were described in a paper by Hanna and Israelsky^^.
Fourteen species
are considered of which eleven are described as new. Turrit ella
conqivistadorana, Melanatria
vilithes burtti

(?)

gesteri

{^Hannatoma),

Cla-

(=^Mancoriis) and "Surcula" mayi are Oligocene

species.
Five Miocene species are considered as new, two of
which namely Crassate'llites pizarroi and Clavilithes ( ?) atahiialpai are synonymous with Eucrassatella nelsoni Grzybowski and
i^Berry 1923, Extension of Miocene Zorritos Formation in Peru and Ecuador,

Pan-American Geologist,

vol.

40,

pp.

15-18.

i-tHanna and Israelsky 1925, Contribution to the Tertiary Paleontology of
Peru, Pi'oc. Calif. Acad. Sci., 4th series, vol. 14, No. 2, pp. 37-75, pis.
7, 8.


:

14

Bulletin 68

14

Northia "Sfruthiolaria" guttifera Grzybowski. This paper also
contains a check hst of Peruvian Tertiary species described up
to 1925 and the names of nine species having been found preoccupied, are changed.

The

practice of renaming species pre-

occupied b}' older names, without knowledge of the species in
question is open to criticism as it frequently leads to an unneces-

names and much confusion to later workThus Turritella robusta Grzybowski is renamed supraconers.
cava although as pointed out by Woodring there are at least
Area retractata
three earlier names available for this species.
sary multiplication of

Israelsky (=^. modesta Grzybowski) may eventuprove to be the same as Area macdonaldi Dall from Costa
Rica but common in the Miocene rocks of northern Colombia,

Hanna and
ally

Venezuela and Trinidad.

Grzybowski)

is

probably

Columbella
Ectinochilus

paytensis

(

= C.

turrita

gaudichaudi d'Orbigny

but as previously noted most of Grzybowski's Paita and Talara
species have not been rediscovered and their status must await

study of the type specimens.

A

short paper on the Geology of the lUescas region and in-

cluding an areal geologic

map

of this part of the Sechura desert

was published by A. Werenfels^^
of this region
to

mixed

is

in 1927.

The

general geology

well described but unfortunately apparently due

fossil collections or

wrong

paleontological determina-

and correlation of the different formations are
poorly understood and consequently the stratigraphic section
given by Werenfels requires considerable revision. The following table shows the changes necessary

tions,

the age

i^Werenfels 1927, Geology of the Illescas Region, Northern Peru (South
America). Eclogae Geologicae Helvetiae vol. 20, No. 4. pp 473-486,
pi. 17.


Olsson

15

Werenfels, 1927

Peruvian Miocene

Iddings

Montera formation
as Upper Eocene
Yapate sandstone
Salina beds

:

and

15

Olsson

Correct age

Sechura formation
unconformity

Pliocene

of

Zodiac Pt. as

Diatomaceous

Lower and Middle

earth and shales

Middle Miocene

Eocene
Amarilla

ss.

Montera formation

Yapate sandstone
of Trie Trae Pt.

as Middle Eocene

Lower Miocene

(break in section

through faulting)

Bayovar beds

Bayovar formation

Lower Oligocene

Saman formation

Upper Upper

as lower Eocene

Not recognized

Eocene
Gharaos sandstone
Upper Eocene

Lower Upper

Talara formation
(Olsson 1930)

Eocene

The Charaos formation, (p. 483) named from Charaos Nonura Bay, are the oldest Tertiary rocks in this region and not
the youngest as beheved by Werenfels.
principally of small Orbitoids

which

in

They contain

many

a fauna

cases are so abun-

dant as to form a foramini feral limestone. At several places where

upon slates or other
mountain rocks, the}' simulate to a remarkable degree, tablazo
deposits and the Maxiplan of Werenfels (elevation 390 feet)
south of Bayovar, represent these Eocene limestones and not a
true tablazo level. Werenfels lists Asterodisciis along with HclicolepUia and small Lepidocyclincc which places these beds about
these flat-lying foramini feral limestones rest

equivalent to the Talara formation of the Negritos region.

Charaos formation

is

also

The

found along the northeast side of the

Cerros de Illescas but they are not equivalent

Montera formation capping Corona

to

\\'erenfels'

which is of Pliocene
age. Small remnants of the Charaos formation have been found
capping a few of the mountain peaks within the Cerros tie
Illescas at elevations of 1200 to 1300 feet.
hill


16

Bulletin 68

16

The Ba}ovar beds occur

only in the cHff sections extending

from Bayovar to Trie Trac Point. Werenfels regarded these
foraminiferal shales as the oldest Tertiary deposits occuring in
the Sechura region and referred them to the Lower Negritos
formation or the Lower Eocene. Although the ,contact is not
visible, the Bayovar beds apparently rest upon the Sanian sandstones which occur just northwest of Bayovar and are of

Lower

Oligocene age.
East of Trie Trac Point and along Quebrada Montera, there
are excellent exposures of Miocene sandstones to which IdcUngs

and Olsson referred

Montera formation. The Mio-

in 1928, as the

incontestable although Werenfels

lists

Venericardia planicosta, Ostrea Buski, Meretrix Bosworthi,

etc.,

cene age of these rocks

is

from the Amarillas sandstones which are evidently the same beds.
For a complete list of the fossils of the Montera formation, the
reader is referred to the later pages of this paper. The Eocene
forms listed by Werenfels could not have been collected in the
Amarillas sandstones or else they are incorrectly determined
Miocene species. The Yapate sandstones of Trie Trac Point and
the Amarillas sandstones belong to the
to

Lower Miocene and

not

the Middle Eocene as indicated by Werenfels.

Exposures of diatomaceous earth occur around the borders of
clifif front near Yapate and
elsewhere. These deposits are clearly younger than the lower
Miocene sandstones of Quebrada Montera and Trie Trac and
are provisionally referred to the Middle Miocene. In a separate
paper, Werenfels^^ described these occurrences of diatomaceous
earth as belonging to the Eocene although he pointed out that
commonest diatom was identical with Coscinodiscus oculus iridis
Ehrenberg of the Monterey Shales of California.
The Montera formation capping Corona Hill is a whitish,

arenaceous limestone, often conglomeritic and rests unconformably on the underlying Miocene or even overlaps to a slight extent upon the Illescas slates. It contains no Orbitoids so abundant
in the Charaos (which Werenfels correlated with the Montera
beds) but such species as large Macrocallista and Dosinia grandis

the large salt basin and along the

leWerenfels 1926,
Helvetiae vol.

Diatomeenerde
19, pp. 630-631.

im

Eocan

von

Peru.

Eclog.

geolog.


Olsson: Peruvian Miocene

17

Nelson show

its late

Mio,cene or Pliocene

17

believed to be

It is

a,^e.

a coastal facies of the Sechura formation and of Pliocene age.

Marsters'^^ papers which deal in part with the Zorritos dis-

are very general in scope and have no paleontological nor

trict

stratigraphic value.

Deustua and Ouiroga^^ have

also described

the geology of the Zorritos region, in their papers dealing with

the petroleum resources of Peru.

Steinmann^®

his Geologic

in

von Peru, gives a short description of the Zorritos formation
based principally on Spieker. Steinmann following Grzybowski
still

places the Talara formation in the upper Tertiaries.

tella

Turri-

infrocorinata Grzybowski from the Mio,cene of Bayovar

is

figured so that Steinmann recognized the Miocene character of
the rocks in this district.

The
view,

only other paper which need be considered in this re-

is

that of Iddings

and Olsson^" published

in

1928.

This

paper gives a general account of the geology and stratigraph}of the entire Tertiary region of northern Peru from the Sechura
desert north to

Tumbez.

It

proved the remarkable completeness

Lower Eocene to the Upper
For the Miocene rocks, two new formational terms
were introduced, namely the Cardalitos and Tumbez which had
of the Peruvian Tertiaries from the

Miocene.

not been recognized before.

quent

in the

Reference

to this

paper will be fre-

course of the following pages.

II.

The Miocene

of

Northern Peru

Marine deposits of Miocene age occur in northern Peru in two
The most important are those of the ZorritosTumbez region and represent the extension of a Miocene embayment south from the Guayas district of Ecuador. This
northern embayment did not extend beyond Piedra Redonda.
separate districts.

1921, Outline of the Geology and Development of the Petroleum fields of Peru, with notes on other occurrences in the Peruvian Republic.
Bull. Am. Ass. Petroleum Geologists, vol. 5, pp.

i^iyiarsters

585-604.

isQuiroga 1925, Sintesis de la Mineria Peruana, Ministerio de Fomento,
tome. 2, la parte, Yacimientos Petroliferos.

i^Steimann 1929, Geologie von Peru, Heidelberg,
20lddings and

p.

199.

Geology of Northwest Peru,

Olsson 1928,
Petroleum Geologists, vol.

12,

No.

1,

pp. 1-39.

Bull.

Am.

Ass.

18

Bulletin 68

18

The second

district is

found

in the

Sechura desert and

in its

turn marks the northern end of a Miocene sedimentary basin
which probably at that time extended southward off the Peruvian coast and connected with the Miocene beh of the Paracas

No Miocene rocks occur in the intervening region
Peninsular.
and consequently only indirect communication existed between
Several Caribbean
these two areas of Miocene sedimentation.
Miocene
and in a simSechura
the

in
are
found
mollusks
types of
(Perunassa)
Buccinanops
forms
such
as
Zorritos
ilar way certain
probably of
Nelson
are
solida
sorritensis Nelson and Chorus
southern origin.

Aside from

this

intermingling, the Peruvian

two separate faunal provinces, the
northern or that of Zorritos being warm-water and distinctly
Caribbean in character while the southern or that of the Sechura
and Paracas belongs to a cooler-water type' as shown by the extensive development of diatomaceous earth and its fauna is probabty in large part of South Pacific origin as the Peruvian fauna
Fuller knowlsouth of Negritos and Punta Parinas is to-day.

edge of the Sechura Miocene and that of southern Peru would
Miocene clearly belongs

to

undoubtedly reveal a greater faunal likeness with the Chilian
Miocene than now appears to be the case.

The Zorritos District
Nelson's strictly paleontological study of a collection of 'Zorri-

had indicated the presence of late Tertiary rocks at
it remained for Grzybowski to definitely establish
the extensive development of Miocene strata in that district.
Boswortli also collected a few Miocene species of mollusks at
Zorritos which were studied by Woods.
Bosworth referred all
the Miocene rocks of northern Peru to one group which he called
the Zorritos formation and on his map shows these rocks as extending as far south as Punta Sal, thus covering the outcrop of
the Punta Bravo grits which are now known to be Middle Oligocene in age. Spieker also regarded the Zorritos Miocene as representing a single formation which he however divided into three
members, the Upper and Lower Zorritos sandstones and the
Variegated beds. In 1928, Iddings and Olsson divided the Zor-

tos fossils

Zorritos but


:

Olsson: Pekuvian Miocene

19

ritos

19

beds into three formations as follows

Upper Miocene Tumbez formation
Middle Miocene Cardalitos formation
Lower Miocene Zorritos formation

As Spieker
ritos

found, the Variegated beds and the

Upper Zor-

sandstones are .closely related while greater faunal differ-

ence exist between these rocks and the

our

sults of

own

Lower

Zorritos.

The

re-

studies have indicated that on faunal as well as

stratigraphic grounds, the

Lower and Upper

should be considered as

separate

Lower and L'pper

Zorritos sandstones

Together,

formations.

Zorritos formations

make up

the

the

Zorritos

group.

The

Tumbez

sandstones and conglomerates form
and a sandy soil supporting a growth
of small trees (Palo Santos Bursera graveolens, Hualtaco Loxopterygvnm huasango) and bushes while inland where precipitation is greater almost impregnable thickets of Ufias de gato are
frequent.
Many of these Miocene hills rise to commanding
heights.
Hills formed of the Zorritos sandstones include Cueva
Zorritos and

a rugged, hilly topography

de Leona, Pan de Azucar and Salvajal while

From

bez beds.
litos

raphy of low, rolling

become

Garita, Tucillal

in

the soft, easily

formation, a dense

La

whole or in part of the Tumweathering shales of the Cardais formed, and a subdued topog-

and Cerro Bruno are composed
,c!a}- soil

In the dry seasons these shale areas

hills.

dried and parched to an extreme degree but after rain

are converted into

meadows

of

tall

grasses, leguminous plants

and vines.

From
Heath

Piedra Redonda, the Zorritos sandstones overlying the

shales strike northeast, crossing

Zapotal just south of Vacura.
sandstones form the

hills

south and east are the

of

hills

Quebrada Boca Pan

at

East of Boca Pan, the Zorritos

Pan de Azucar. Somewhat further
of Animas and Salvajal separated

from the Pan de Azucar ridge by faulting so that the intervening
From Animas, the Zorritos

area belongs to the Heath shales.

sandstones extend east to the
ping the older beds so that

Bravo

grits

until at

first

Tumbez
the

river, gradually overlap-

Heath

shales, then the

Punta

disappear beneath the blanket of Miocene sediments

Rica Playa, the Zorritos sandstones

rest

directly

upon


:

Bulletin 68

20

granite and Eocene formations.

20

At Zapotal, the Lower Zorritos
with the Heath

sandstones are conformable and transitional
shales but in the

Tumbez

is

river are not

known.

As

district, the

unmistakable.

the Zorritos

transgressive character of

Conditions east of the

Tumbez

further south at Lobitos and Negritos, the rocks of the

Zorritos region, particularly along the coast, have been intensely faulted.

These are normal or gravity

faults

and they have

developed a complicated series of irregularly-shaped fault blocks
of greater or less

At Tumbez and

size.

in the region inland

from

Zorritos, the strata usually dip to the northwest so that in general

older beds are encountered on approaching the foot of the

tape mountains.

Amo-

Faults trend in various directions but the most

persistent and probably the youngest

are

trending roughly parallel to the coast.

downfaulted either on the north or south

large

These

strike

faults

faults

may

be

side.

The Zorritos Group

The name, the Zorritos formation or Zorritos stufe was given
bv Grzybowski^^ to the fossiliferous yellow sandstones which lie
above the Heath shales in the Zorritos district, the t3rpe section
being the exposures near Zorritos village and Boca Pan.
Zorritos,

Grzybowski

listed the

From

following species

Area Larldnii Nelson = A. chiriqmensis toroensis Spieker
"
septifera Grzybowski
/'
(Noetia) modeata Grzy. = A. retractata Hanna and Israelskv
Ffiammohia Darwini Phil.
Venericnrdia clovidenfi Grzy.
Turritella rotundata Grzy.= T. infracarinata Grzy.
Infracarinata Grzy.
Inca Grzy.
gothica Grzy. = T. Ufastigata Nelson
inconspicua Grzy.
rohusta Grzy. = T. abnipta Spieker
GabMana Grzy. = T. flicincta Grzy.
Splarium sexlineaPmm Nelson. = ArcMtectoniea
Stnithiolaria guttifera Grzy. = NortJiia

Venericardia clavidens is an Eocene species from Rica Playa
and was no doubt listed from Zorritos by mistake. Psainmobia
Darwini is a Tageloid and its identification with a Chilian species
2]

Grzybowski 1899,

op.

cit.,

p. 652.


Olsson: Peruvian Miocene

21

21

must be questioned while Area Larkinii Nelson
species but A.

this

gabbiana appears to be a synonym of
a CardaHtos species.

With exception

of Gzybowski's species are

is

probably not

toroensis Spieker.

chiriqitiensis

filicincta

which

Turrit ella
usuall\-

is

of these changes, the rest

common forms

in the

Upper Zorritos

formation as here understood.

At

Boca Pan, the Zorritos group may be divided
shown into three parts. The Lower and Upper

Zorritos and

as Spieker has

Zorritos formations are principally massive to well-bedded, soft

or hard, yellow or orange-colored sandstones and pebble conglomerates.

They

is

a middle

These deposits are particu-

Spieker called the Variegated beds.
larly well

Between these premember which

are locally fossiliferous.

dominately yellowish sandstones there

developed between Punta Picos and the village of Boca

Pan and along the west shore of Caleta Grau near Ouebrada
The name of Variegated beds aptly describes their
makeup and appearance. They consist of red, green, yellow to
Tijeretas.

chocolate-colored

interbedded

shales

with

stones, white grits, cobble conglomerates

rather pure cannel coal
frequent.

As

may

and

rust-colored
lignites.

sand-

Seams of

be present while fossil layers are

a rule the marine

moHusks are worn.

Brackish

water forms such as Potaiiiides, oysters and varieties of Area

ehiriquiensis are rather characteristic.

The Variegated beds

are

always more badly broken than the Lower and L'pper Zorritos
sandstones.

This intense deformation does not appear

a great structural significance but

is

to

have

probabl}- due in large de-

When wet
and treacherous and during the irregular rainy seasons they suffer greatl}' from slides
and slumping.
The Zorritos rocks are here considered as a
group since they are generall}' closely associated in the field.
gree to intra formational creep and surface slumping.
the Variegated beds

a.

The Lozver

become very

Zorritos

soft

foriiiatioii.

ference exist between the

Considerable faunal dif-

Lower and Upper

Zorritos and on

stratigraphic as well as faunal grounds, they should be consid-

ered as separate formations.
the

closing stage of the

were generally

laid

down

The Lower

Zorritos formation

is

Heath transgression and these rocks
in a shallowing sea which reached its

greatest restriction during the deposition of the Variegated beds.