Diaz_Permico _chile.pdf

Permian marine sedimentation in northern Chile: new paleontologicalevidence from the Juan de Morales Formation, and regional

paleogeographic implications

E. DõÂaz-MartõÂneza,*, B. Mametb, P.E. Isaacsonc, G.W. Graderd

aInstituto de GeologõÂa EconoÂmica (CSIC-UCM), Facultad de Ciencias GeoloÂgicas, 28040 Madrid, SpainbDepartment des Sciences de la Terre, FaculteÂ des Sciences, University Libre de Bruxelles, CP 160/02, B-1050 Bruxelles, Belgium

cDepartment of Geology, University of Idaho, Moscow, ID 83844, USAdDepartment of Geological Engineering, University of Idaho, Moscow, ID 83844, USA

Received 31 October 1998; revised 30 November 1999; accepted 31 January 2000

Abstract

Permian marine sedimentary rocks that crop out in northern Chile are closely related to the development of a Late Paleozoic magmatic arc.

A study of Upper Paleozoic units east of Iquique (208S) identi®ed three members within the Juan de Morales Formation, each of which were

deposited in a different sedimentary environment. A coarse-grained terrigenous basal member represents alluvial sedimentation from a local

volcanic source. A mixed carbonate-terrigenous middle member represents coastal and proximal shallow marine sedimentation during a

relative sea-level rise related with a global transgression. Preliminary foraminifer biostratigraphy of this middle member identi®ed a late

Early Permian (late Artinskian±Kungurian) highly impoverished nodosarid±geinitzinid assemblage lacking fusulines and algae, which is

characteristic of temperate cold waters and/or disphotic zone. The upper ®ne-grained terrigenous member represents shallow marine

siliciclastic sedimentation under storm in¯uence. The Juan de Morales Formation consists of continental, coastal and shallow marine

sediments deposited at the active western margin of Gondwana at mid to low latitudes. A revised late Early Permian age and similar

paleogeography and sedimentary environments are also proposed for the HuentelauqueÂn Formation and related units of northern and central

Chile, Arizaro Formation of northwestern Argentina, and equivalent units of southernmost Peru. q 2000 Elsevier Science Ltd. All rights

reserved.

ResuÂmen

En el norte de Chile a¯oran rocas sedimentarias peÂrmicas de origen marino, en estrecha relacioÂn con el desarrollo de un arco magmaÂtico

del Paleozoico superior. El estudio de las unidades del Paleozoico superior al este de Iquique (208S) ha permitido identi®car tres miembros

dentro de la FormacioÂn Juan de Morales, cada uno de ellos depositado en un medio sedimentario diferente. El miembro basal terrõÂgeno de

grano grueso representa sedimentacioÂn aluvial procedente de un aÂrea fuente local cercana de tipo volcaÂnico. El miembro medio de tipo mixto

terrõÂgeno-carbonatado representa sedimentacioÂn costera y marina somera proximal durante una subida relativa del nivel del mar relacionada

con una transgresioÂn global. La bioestratigrafõÂa preliminar de foraminõÂferos de este miembro medio identi®coÂ una asociacioÂn de nodosaÂridos

y geinitzõÂnidos altamente empobrecida, de edad Eo-PeÂrmico tardõÂo (Artinskiano superior±Kunguriano) sin fusulinas ni algas, caracterõÂstica

de aguas frõÂas templadas y/o zona disfoÂtica. El miembro superior terrõÂgeno de grano ®no representa sedimentacioÂn siliciclaÂstica marina

somera bajo la in¯uencia de tormentas. La FormacioÂn Juan de Morales estaÂ compuesta por sedimentos continentales, costeros y marinos

someros, depositados en el margen activo del borde occidental de Gondwana, y en latitudes medias a bajas. Se propone asõÂ mismo una edad

revisada de PeÂrmico inferior tardõÂo, y paleogeografõÂa y ambientes sedimentarios similares para la FormacioÂn HuentelauqueÂn y otras unidades

relacionadas del norte y centro de Chile, FormacioÂn Arizaro del noroeste argentino, y unidades equivalentes del extremo sur del PeruÂ.

q 2000 Elsevier Science Ltd. All rights reserved.

Keywords: Permian; Foraminifer; Brachiopod; Biostratigraphy; Paleogeography; Chile; Gondwana; Andes

Journal of South American Earth Sciences 13 (2000) 511±525

0895-9811/00/$ - see front matter q 2000 Elsevier Science Ltd. All rights reserved.

PII: S0895-9811(00)00043-2

www.elsevier.nl/locate/jsames

* Corresponding author. Centro de Astrobiologica (INTA-CSIC), Carretera de Ajalvir Km 4, 28850 TorrejoÂn de Ardoz, Madrid, Spain. Tel.: 134

915201936; 915202089; Fax: 134-915201074.

E-mail address: [email protected] (E. DõÂaz-MartõÂnez).

1. Introduction

The Paleozoic evolution of Chile resulted from its

tectonic setting as part of what then was the southwestern

active margin of the supercontinent Gondwana. The succes-

sive deformation and orogenic phases affecting this margin

during the Phanerozoic have resulted in the progressive

fragmentation and obliteration of the previous geological

record. Hence, as we try to decipher this geological record,

the evidence present in its older units is obscured by later

events.

Outcrops of Late Paleozoic marine sedimentary succes-

sions occur in northern Chile. They represent part of the

sedimentary record of the continental proto-Paci®c

margin of Gondwana, which can be traced from the

Venezuelan Andes to the Southern Andes and the

Antarctic Peninsula (Zeil, 1979). The northernmost Late

Paleozoic outcrops in Chile are present along the eastern

¯ank of the Cerro Juan de Morales (20808 0), east of

Iquique (Fig. 1). These rocks have been known since

the geological mapping of the area by Galli (1968). In

his work, Galli identi®ed a Late Carboniferous age for

the Juan de Morales Formation, mostly determined in

correlation with similar facies and invertebrate megafauna

present in the Copacabana Formation of Bolivia. Outcrops

with similar facies and megafauna in adjacent regions are

now better known and have been described for northern

Chile (Chong and Cecioni, 1976; Ferraris and Di Biase,

1978; von Hillebrandt and Davidson, 1979; Zeil, 1979;

Davidson et al., 1981; HerveÂ et al., 1981; SepuÂlveda

and Naranjo, 1982; Niemeyer et al., 1985; Breitkreuz,

1986; Breitkreuz et al., 1988; Marinovic et al., 1995),

northern Argentina (AcenÄolaza et al., 1972; Benedetto,

1976; Donato and Vergari, 1985), Bolivia (Chamot,

1965; Sakagami, 1986; Isaacson et al., 1993; Dalenz

and Merino, 1994; and many others), as well as in central

Chile (Rivano and SepuÂlveda, 1983, 1985). The connec-

tion and precise age and correlation among all the series

of outcrops is still not fully understood at this time, owing

to the Mesozoic and Cenozoic cover and severe deforma-

tion and erosion of the Upper Paleozoic units. This paper

attempts to contribute with new litho- and biostratigraphic

data to the understanding of the Late Paleozoic paleogeo-

graphic evolution of northern Chile, and how it relates

with coeval deposits in adjacent regions at the former

active margin of Gondwana. This is achieved by

reassessing the stratigraphy, age, paleoenvironments of

deposition and paleogeography of the Juan de Morales

Formation within its regional context, including a

reappraisal of the age of the coeval Arizaro Formation

(northwestern Argentina) and HuentelauqueÂn Formation

(central Chile) under the light of recent biostratigraphic

data.

2. Regional geology

The hill called Cerro Juan de Morales (2389 m) is located

about 80 km east of Iquique, in northern Chile, at the eastern

margin of the intermontane lowlands of Pampa del

Tamarugal (1000±1500 m), which is part of the Valle

Longitudinal (Longitudinal Valley) or DepresioÂn Central

(Central Depression). Hence, Cerro Juan de Morales is

located towards the base of the western ¯ank of the Chilean

Precordillera and Andean Western Cordillera (Fig. 1).

Outcrops of Late Paleozoic age display a general N±S

distribution along the southeastern ¯ank of the hill (Fig.

2). These outcrops are limited by reverse faults subparallel

to bedding, which inhibit good correlation along strike

because of the partial gaps originated by these faults.

This Late Paleozoic sequence unconformably underlies

Cenozoic sedimentary, volcaniclastic, and volcanic

deposits, and consists of three units (Galli, 1968): Quipisca,

Juan de Morales, and Diablo Formations. The Quipisca

Formation consists of more than 800 m of dacitic and

rhyolitic tuffs and breccias, with an unknown thickness

due to the basal fault contact with younger units. It records

volcanic activity prior to the deposition of the Juan de

Morales Formation, which unconformably overlies it. The

age of the Quipisca Formation was considered as ªundiffer-

entiated Paleozoicº by Galli (1968), and although there are

no absolute age determinations available, it is here consid-

ered an equivalent of other Late Carboniferous±Permian

volcanic and volcaniclastic units located to the south, such

E. DõÂaz-MartõÂnez et al. / Journal of South American Earth Sciences 13 (2000) 511±525512

IQUIQUE

PozoAlmonte Tambillo

Mamiña

Pacific

Ocean

Duplijsa

2000m

3000m

1000m

Sagasca

Cerro Juan de Morales2389m

0 20km

To Airport

N70ºW20ºS

Fig. 1. Location of the study area (star), east of Iquique, in northern Chile.

as the Collahuasi Formation (Vergara and Thomas, 1984). If

this were the case, the Quipisca Formation would also be

part of the so-called ªPeine Groupº. This name was

proposed by Bahlburg and Breitkreuz (1991) for all north

Chilean Late Paleozoic volcanosedimentary successions,

although Breitkreuz (1995) also used it for a particular

formation east of the Salar de Atacama (see also Breitkreuz

and Zeil, 1994). The overlying Juan de Morales Formation

consists of an overall ®ning-upwards sequence of silici-

clastic and carbonate rocks, with a thickness exceeding

140 m. Its age has been considered Late Carboniferous

since the work of Galli (1968), except for the broad Permian

age determination of Barthel in Zeil (1964, 1979, p. 104).

In the present study, we establish a mid- Permian age (late

Artinskian±Kungurian) for the middle member of the Juan

de Morales Formation, based on foraminifer biostratigraphy

(see below). The Diablo Formation consists of conglomer-

ates, sandstones and shales with a thickness exceeding

250 m. A Permian-Triassic age was proposed by Galli

(1968), although a Cretaceous age may also be possible

(Bogdanic, 1990). The geology of the source area during

deposition of the Diablo Formation consisted of a volcanic

arc over crystalline basement, as identi®ed by clasts in

conglomerates (dacites, rhyolites and metamorphic rocks),

and sandstone composition (arkoses and graywackes).

Salinas (1986) also identi®ed a similar provenance for the

Machani Formation, in southernmost Peru. The Quipisca,

Juan de Morales and Diablo Formations constitute the

Upper Paleozoic package of the area, which is affected by

faults subparallel to strike, intruded by the Cretaceous

granitoids that constitute the Cerro Juan de Morales, and

covered by Cenozoic conglomerates, sandstones,

ignimbrites and tuffs (Fig. 2).

The Upper Paleozoic outcrops are reached from the north

via the road from Pozo Almonte to MaminÄa (Fig. 1), where

former gravel roads leading to the site have been washed

away in recent years, so that the access is done walking from

the Duplijsa curves towards the south, and down along the

upper reaches of the Quebrada Honda (Fig. 2). From the

south, the outcrops may be reached via the road from

Tambillo to MaminÄa, near Sagasca (Figs. 1 and 2), and

then walking down into the creeks, although steep relief

complicates access.

3. Stratigraphy and sedimentology

The good description provided by Galli (1968) for the

type section of the Juan de Morales Formation allowed us

to represent it in an idealized schematic column (Fig. 3).

The analysis of these data, in conjunction with the more

detailed stratigraphic column that we measured 1 km

NNW of the type section, allows us to differentiate three

distinct members. The basal member consists of grayish and

reddish conglomerates and coarse sandstones. Our study

only covered the upper part of this member (level 1 in

Fig. 3), so that the observations and interpretation must be

considered as very preliminary. Sedimentary structures in

the conglomerates are not conspicuous, but both normal and

reverse grading is present. No other internal structure such

as clast imbrication or cross-strati®cation could be

observed, so that the conglomerate facies are interpreted

as originated by mass-transport processes like debris

¯ows. Sandstones in the basal member are structureless,

cross-bedded and parallel-laminated, and are interpreted

as originating from tractive currents. The sedimentary envir-

onment identi®ed for this basal member may then be

proposed as alluvial fans with a local volcanic source area.

The middle member of the Juan de Morales Formation is

heterolithic, consisting of sandstone, shale, conglomerate,

E. DõÂaz-MartõÂnez et al. / Journal of South American Earth Sciences 13 (2000) 511±525 513

20º10’

20º09’

20º08’

32

31

69º20’

CerroJuán deMorales

K

K

K

TQ

Juánde

Morales

Fault

Imagua Fau lt

TQ

TQ

K

PTrP

CP

TQ

PTrP

CP

Unconformity

Fault

Creek

Fossiliferous bed

NB

A

QuebradaH

onda

Tambil

lo- Mam

iñaRoa

d

0

1

2km

Quebrada Mamiña

TQ Cenozoic cover

K Cretaceous igneous rocks

PTr Diablo Formation

P Juan de Morales Formation

CP Quipisca Formation A Type section

B Studied section

Fig. 2. Geologic map of the Late Paleozoic outcrops of Cerro Juan de

Morales (after Galli, 1968), with location of the type section of the Juan

de Morales Formation, and the section measured and sampled for this study,

both shown in Fig. 3. Geographic location in Fig. 1.

marl, and limestone. Apart from the effect of the strike-

parallel faults previously mentioned, which modify the

sequence observed at different locations along strike, impor-

tant lateral facies changes may also be observed which take

place in rather short distances within the length of the

outcrops (4 km). This is shown in Fig. 3 by comparing our

section (levels 2 through 11) with the equivalent part of the

type section, in aspects such as the absence of the 9 m-thick

middle conglomerate bed, and the presence of thin carbo-

nate beds throughout the middle member, not just as a single

9 m-thick carbonate bed as in the type section. The sand-

stones in the lower part of this member (levels 2 to 4) are

cross-bedded and laminated (horizontal and low-angle), and

include thin carbonate interbeds (dolostones with no fossil

remains). This part may be interpreted as coastal deposits

(delta or strand plain). No detailed facies study was under-

taken in order to identify the relative in¯uence of the differ-

ent processes present in this environment (¯uvial currents,


10m

0

20m

0

JM-11

JM-10aJM-10b

12

10

11

9

8

JM-8aJM-8b

JM-8c

7

6

5

4

JM-5

3

2

1

Marl, shale

Limestone

Sandstone

Conglomerate

Quipisca Fm.

Diablo Fm.

JUA

N D

EM

OR

ALE

SF

OR

MAT

ION

STUDIED SECTIONTYPE SECTION

Fig. 3. Type stratigraphic column for the Juan de Morales Formation as described by Galli (1968), and location within it of the interval measured and sampled

for this study, indicating the levels and location of samples mentioned in the text. For location of sections see Fig. 2.

waves, tides, etc.), although Galli (1968) does mention

paleocurrents coming from the east. The middle part of

the member (levels 5 to 8) displays a gradual decrease of

siliciclastic grain-size and sediment input, and an increase

of carbonate deposition. Laminated and bioturbated marls

and shales may be interpreted as lagoonal deposits, whereas

the limestones (mostly packstones and grainstones) may be

interpreted as bioclastic bars. The fossil fauna present in this

middle member is very rich, and consists of foraminifers,

bryozoans, brachiopods, gastropods, crinoids, pelecypods

and ostracodes. The most conspicuous are the large silici®ed

productid brachiopods (predominantly Waagenoconcha

humboldti), which are left over from the erosion of the

marl beds and cover the surface of the outcrop. This relative

abundance of brachiopods is the most probable origin of the

packstones and grainstones present in level 8 (Fig. 3), and

consisting almost exclusively of brachiopod spines (see

description of JM-8 below). Delicate branching bryozoans

appear from the ®rst carbonate beds (JM-5, Fig. 3). The

upper part (levels 9 to 11) consists of marls and shales

with thin carbonate interbeds, which may be interpreted as

more distal deposits (below wave action).

We interpret the sequence observed in this middle

member of the Juan de Morales Formation as the result of

a relative sea-level rise and progressive reduction of clastic

sediment input favoring enhanced carbonate deposition.

Beginning with the continental deposits of the lower

member, a gradual shift can be observed in the middle

member from coastal deposits towards deeper and more

distal environments, characteristic of an open, shallow

marine carbonate platform. The upper member begins

with a ®ning and thinning sequence of sandstone beds

with hummocky cross-strati®cation and wave ripples

(level 12) which continues upsection into ®ner-grained

gray shales and siltstones (not measured in our section).

The change from the middle to the upper member in the

Juan de Morales Formation results from the reduction of

carbonate deposition, and increase of clastic input under

storm and wave action.

The in¯uence of a common source area consisting of a

volcanic arc over metamorphic basement may be identi®ed

from the composition of sandstones and conglomerate clasts

in the Juan de Morales and Diablo Formations. The under-

lying pyroclastic rocks of the Quipisca Formation record the

magmatic activity of this arc, and are the probable source for

the volcanic clasts included in the two overlying units.

Therefore, all three of the Upper Paleozoic units at the

Cerro Juan de Morales were deposited in proximity to a

magmatic arc, and record its activity and later gradual

erosion. This common tectonic setting may be considered

as evidence to include them within a single tectonosedimen-

tary package deposited in a forearc or intra-arc setting. Late

Carboniferous and Permian intra-arc sedimentation has

been described to the south and southeast of the Cerro

Juan de Morales, in northern Chile (22±258S) (Bahlburg

and Breitkreuz, 1991; Breitkreuz et al., 1992; Breitkreuz

and Zeil, 1994). Even closer are the Late Carboniferous±

Permian tuffs and lavas of the Collahuasi Formation, and the

Permian Chara and Escorial plutons, located 60 km SE of

Cerro Juan de Morales (Vergara and Thomas, 1984).

According to these authors, and considering the present

position of the remnants of the arc, a forearc setting

would seem the most appropriate geodynamic interpretation

for the Juan de Morales Upper Paleozoic deposits (Figs. 4±

6). However, the precise original location of the Juan de

Morales Late Paleozoic sedimentary and volcaniclastic


Salar deNavidad

CerroPalestina

Cerro1584

CerroJuan deMorales

D

JM

Q

CC

Limestone

Sandstone

Shale, mudstone, marl

Volcanic and volcaniclastic rocks

Conglomerate

Diamictite (mudflow?)

?

?

CA

Triassic

Carbonif.

Permian

J

KLate

Carbonif.-Early

Permianshallowmarine

carbonatesand volcanic

deposits

?Devonian-Early Carb.

marineturbidites

LatePermian-Triassic

terrestrialand volcanic

deposits

Fore

arc

Tran

sitio

nal

Intr

a-ar

c

Fig. 4. Correlation of selected Upper Paleozoic sequences in northern Chile (not to scale; modi®ed after Bahlburg et al., 1987), indicating their approximate

age, type of sedimentary environments, and proposed tectonic setting of deposition. Codes: CA, Cerro del Arbol Fm.; CC, Cerros de Cuevitas Fm.; D, Diablo

Fm.; JM, Juan de Morales Fm.; J, Jurassic marine deposits; K, Cretaceous volcanic deposits; Q, Quipisca Fm.

package with respect to the magmatic arc is not yet known,

due to later wrenching, faulting, intrusion, deformation and

erosion of the record during the Mesozoic and Cenozoic.

Whereas the marine character of the middle member of the

Juan de Morales Formation would favor a forearc position,

the presence of intrusive bodies located to the southwest of

the Cerro Juan de Morales and dated as Carboniferous

(Skarmeta and Marinovic, 1981), suggests an intra-arc posi-

tion, if extended parallel to the main body of arc remnants

(Figs. 5 and 6).

4. Paleontology

Whereas the fossil fauna present in the Juan de Morales

Formation and other Upper Paleozoic units of northern

Chile clearly identi®es a shallow marine environment, its

precise age has been under discussion. Galli (1968) based

the Late Carboniferous age of the Juan de Morales Forma-

tion on the determination of his fossil samples carried out by

CorvalaÂn (1963, unpublished report), who identi®ed

brachiopods (Waagenoconcha sp., resembling W. delicatula

Campbell and W. humboldti d'Orbigny, Punctospirifer sp.,

resembling P. patulus Chronic and P. kentuckiensis

(Shumard), Chonetes sp. cf. C. granulifer Owen, Composita

subtilita Hall, Derbya sp., Lingula sp.), as well as other

invertebrates (Polypora megastoma de Kon., Straparolus

sp. cf. S. subrugosus Meek and Worthen, Palaeoneilo sp.).

Galli studied the area during the 1950s, and also published

his results in different Chilean journals. At the same time, in

1962, W. Zeil also sampled the Juan de Morales Formation,

and gave his samples to K.W. Barthel (in Zeil, 1964), who

identi®ed Batostomella crassa Lonsdale, Spiriferina sp. cf.

S. pulchra (Meek), Punctospirifer billingsi (Shumard),

Waagenoconcha montpelierensis (Girty) and ªCyathocri-

nitesº sp. Zeil (1964) considered this assemblage as

Permian and, based on the presence of W. montpelierensis,

proposed a middle Permian (Guadalupian) age in correla-

tion with the North American sequence, where the species

W. montpelierensis is restricted. The foraminifer taxa iden-

ti®ed for our work support the Permian age proposed by Zeil

(1964, 1979) for the Juan de Morales Formation, although

not as young as middle Permian (Guadalupian), but late

Early Permian instead (see below).

Other Upper Paleozoic units along the western Central

Andean region have also yielded fossil fauna pointing to an

Early Permian age of the marine carbonate deposits. The

Machani Formation (near Tacna, in southernmost Peru, 17±

188S) contains the bivalve Myalina pliopetina (Newell),

considered as Early Permian, together with other unidenti-

®ed bivalves, gastropods and crinoids (Salinas, 1986).

Breitkreuz (1986) mentioned algae and equinoid spines

from limestone beds in the Collahuasi Formation, identify-

ing Permian marine in¯uence in that area (21±228S). Lime-

stone beds at the Cerro 1584 (Cerro del Arbol Formation,

after Marinovic et al., 1995) (248S) contain brachiopods

(Spiriferinidae cf. Spiriferellina sp., and Hustedia sp. cf.

H. meridionalis) considered as Early Permian, as well as

bryozoans (Streblotrypa sp.), foraminifera, gastropods,

pelycopods, and ®sh remains (Breitkreuz, 1986). Hoover

and Ross (in Breitkreuz, 1986) and Bahlburg et al. (1987)

noted the absence of the typical warm-water foraminifera

(fusulinids) in this unit, as contrasted to taxa from the

Copacabana Formation in Peru and Bolivia, and in coeval

units in southern Chile. Our data on foraminifer biostrati-

graphy favor this interpretation of rather cold temperate

waters of the north Chilean faunas, at least for the late

Early Permian (see below). Marinovic et al. (1995) collected

an assemblage in the Cerro del Arbol Formation consisting

of bryozoans, corals (Lophophyllidium? sp.), brachiopods

(Kochiproductus or Dictyoclostus sp., Linoproductus cora


W E

C. de Cuevit as Fm.C. del Arbol Fm.

Chile Argentina

Arizaro Fm.Cerro Oscuro Fm.

?

0 50km

Juan de Morales Fm.Quipisca Fm.

Machani Fm.

23-24ºS

20-21ºS

16-18ºS

Chile Bolivia

Peru Bolivia

Copacabana Fm.Yaurichambi Fm.

Copacabana Fm.Yaurichambi Fm.

CollahuasiFormation

Iscay GroupMitu Group

“Peine Group”(Tuina, Cas, Peine,

La Tabla, Pular, etc.)

?

?

Proto-PacificOcean

CoastalCordillera Western Cordillera Puna

Modern morphology

Fig. 5. Tectonic setting of Late Carboniferous±Early Permian basins in the

Central Andes (16±268S), modi®ed after Bahlburg and Breitkreuz (1991)

and Breitkreuz and Zeil (1994), and indication of their stratigraphic record

at different latitudes (see also Fig. 6). The star indicates the relative location

of the Juan de Morales Formation during the Permian, and with respect to

the modern morphology.

(d'Orbigny), Kozlowskia sp., Hustedia aff. meridionalis

Chronic, Chleiothyridina sp., Dielasma sp., Neospirifer

sp. cf. N. cameratus, Phricodothyris? sp.), gastropods

(Babylonites sp.), bivalves (undetermined pectinids),

ammonoids, crinoids and serpulids. According to this

fauna, they assigned the Cerro del Arbol Formation an

Early Permian age. To the east, in northwestern Argentina

(238S), the Arizaro Formation contains foraminifera

(endothyrids), rugose corals, bryozoans, brachiopods,

gastropods, bivalves and crinoids, and was considered of

Late Carboniferous±Early Permian age in correlation with

the Copacabana Formation of Bolivia (AcenÄolaza et al.,

1972). A more detailed work on the foraminifera of the

Arizaro Formation led Benedetto (1976) to propose an

Early±Middle Permian age for this unit, discarding the

idea of a Late Carboniferous age for its base. Our results

agree with this latter work, although we also suggest a

revision of the taxa identi®ed in it (see below).

Further to the south, von Hillebrandt and Davidson

(1979) described a 300 m-thick mixed carbonate-

siliciclastic unit in the Sierra de Fraga (278S), containing

corals, bryozoans, brachiopods (productids), gastropods

(Bellerophon sp.) and crinoids (Pentacrinus?), and assigned

it a Late Carboniferous±Permian age. In the HuentelauqueÂn

area (31±328S), the carbonate beds in the La Cantera

Member of the HuentelauqueÂn Formation yielded sponge

spicules, bryozoans, brachiopods (productids), bivalves,

gastropods, crinoids, and plant remains (Rivano and

SepuÂlveda, 1983, 1985). Based on foraminifera (Tetrataxis

sp., Agathammina sp., Earlandinita sp., Eoschubertella?

sp., Monotaxinoides? sp.), these same authors proposed a

temperate to cold-water environment, and a Late Carboni-

ferous±Early Permian age for this member, although their

determinations require some revision, as evidenced by our

re-interpretation of their plates (see below).

5. Foraminifer biostratigraphy

A preliminary study of the small foraminifers present in

the carbonate rocks of the middle member was conducted in

order to assess the age of the Juan de Morales Formation.

This assessment has to be considered with caution due to

three main reasons that make the stratigraphic use of

Permian small foraminifers quite dif®cult. The ®rst reason

is that most of the reliable biostratigraphic data are indexed

on fusulines, and that no coherent independent zonation has

been proposed for the small forms. The second problem is

that the majority of published work is derived from the

Tethyan Realm, while information on North and South

America is scarce. The third drawback is that stages used

in different parts of the world are in a state of ¯ux. A recent

attempt to conciliate the Russian, North American and

Chinese schemes has been adopted by the Permian Subcom-

mission on Permian Stratigraphy, but there are still consid-

erable dif®culties to equate the different zonations (see


Fig. 6. Paleogeography of the Central Andes and adjacent areas between 14 and 268S during the Early Permian. Compiled and modi®ed after Dalmayrac et al.

(1980), Salinas (1986), Ellison (1990), Breitkreuz et al. (1992), LoÂpez-GamundõÂ et al. (1994), Sempere (1995), DõÂaz-MartõÂnez (1996) and LoÂpez-GamundõÂ and

Breitkreuz (1997). Note that there is no palinspastic restoration of Mesozoic and Cenozoic tectonic deformation. Abbreviations: Ar, Arizaro Fm.; Ca, Cangapi

Fm.; CA, Cerro del Arbol Fm.; Col, Collahuasi Fm.; Cop, Copacabana Fm.; JM, Juan de Morales Fm.; Ma, Machani Fm.; MI, Mitu and Iscay Groups; Pe,

ªPeine Groupº.

Permophiles (1996, 1997) for discussion). The present note

focuses exclusively on the Permian north Chilean outcrop of

the Cerro Juan de Morales, and is the ®rst attempt to use in

this part of the world small calcareous secreted foraminifers

for age determination, and the previously mentioned draw-

backs and uncertainties must be kept in mind.

Samples for the biostratigraphic study were taken from

three different levels (8, 10 and 11; Fig. 3), with three beds

sampled from level 8, two from level 10, and one from level

11. Five samples were taken from each bed at different

points along strike, in order to consider lateral changes

(e.g. a total of 15 samples from level 8). The observed

microfacies and fauna are described below:

JM-8 contains brachiopod spine grainstones/packstones.

Spines are often current oriented. Additional megafauna is

composed of punctate and inpunctate brachiopod valves,

scattered bryozoan fronds, gastropods, crinoids, pelecypods

and ostracodes. Some samples are extensively bioturbated.

JM-10 is composed of cherti®ed bryozoan/brachiopod

spines/valves grainstones/packstones. Echinoderms and

mollusks are present. Recrystallization and cherti®cation

of the matrix is widespread.

JM-11 yields brachiopod/bryozoan packstones with

patches of grainstones. Current action and reworking are

less obvious than in JM-8 and 10.

The algal micro¯ora is nearly absent, with some fragments

of micritized thalli. There are no identi®able chlorophytes,

rhodophytes or cyanophytes, which constitutes a marked

contrast with the Bolivian Permian of Lake Titicaca

(Mamet, 1995).

Foraminifers are present in the three studied levels, but

they are diagenetically altered. Recrystallization and cherti-

®cation are common, and obscure the original structure of

the test, thus inhibiting the possibility of appropriate ®gure

plates and more detailed or speci®c determinations. There

are, however, enough microfossils for generic identi®cation

(Table 1). As the facies and fossil content are quite

consistent, the three levels will be considered as biostrati-

graphic equivalents in the following discussion. The vast

majority of the microfauna belongs to the Nodosariaceae

and Geinitzinidae. There is a conspicuous absence of

Palaeotextulariidae (Cribrogenerina, Climacammina),

Tetrataxidae (Tetrataxis, Polytaxis), Bradynidae

(Bradyina), Biseriamminidae (Globivalvulina), and Pseudo-

vidalinidae (Asselodiscus, Pseudovidalina). Tetrataxidae

also seem to be present in the coeval HuentelauqueÂn Forma-

tion (see below). A fortiori, there are no representatives of

the fusulines in the Juan de Morales Formation (compare

with Baryshnikov et al., 1992, for complete Early Permian

assemblages). The microfauna is therefore impoverished. It

could indicate cold temperate temperature and/or base of the

disphotic zone, and an environment compatible with the

near-absence of calcareous micro¯ora. Coeval units within

the northern Chilean region (Cerro del Arbol Formation at

Cerro 1584) have also been noted to lack any typical warm-

water foraminifera (fusulinids), as opposed to the co-eval

Copacabana Formation in Peru and Bolivia, and other units

in southern Chile (Douglass and Nestell, 1976; Bahlburg et

al., 1987).

Syzrania, Protonodasaria and Nodosinelloides range

from the Late Carboniferous to the Permian (Pinard and

Mamet, 1998) and are of little use. More interesting is the

presence of Langella±Pachiphloia associated with Frondi-

cularia. This assemblage is similar to the impoverished

microfauna described by Stemmerik et al. (1996) from

late Artinskian±Kungurian carbonates of the Kim Fjelde

Formation (North Greenland). It also correlates well with

the Kapp Starostin Formation of the Spitzbergen described

by Sosipatrova (1967, 1969). In the Timan-Pechora Basin of

Arctic Russia, Konovalova (1997) reports a similar assem-

blage that she attributes to the Kungurian. Pronina (1990)

also reports somewhat similar assemblages from the

Kungurian±Kazanian of Transcaucasia. Finally, in China,

the Langella±Pachyphloia assemblage N2 is considered as

Longlinian (Artinskian) by Sheng and Jin (1994), and is

overlain by the Misselina claudiae Zone of the Chihsian

Stage (Early Yangsingian) (Fu, 1987). Table 2 provides a

correlation of the above mentioned Permian successions,

with the global Permian chronostratigraphic subdivisions

proposed by the IUGS Subcommission on Permian Strati-

graphy (Jin Yugan et al., 1997).

In the Bolivian Lake Titicaca region, the Artinskian

carbonates towards the top of the Copacabana Formation

of the Titicaca Group (Chamot, 1965; DõÂaz-MartõÂnez,

1991) have extensive foramineral fauna and algal ¯ora

(Sakagami, 1986; Sakagami and Mizuno, 1994). The

highest exposed beds of the Eoparafusulina Zone at

Yaurichambi (A. d'Orbigny's type locality NW of La Paz)

have primitive Pachyphloia associated with Geinitzina and

Nodosinelloides (Mamet, 1996). The more advanced

Langella±Frondicularia has not been identi®ed. It is

therefore reasonable to assume that the Juan de Morales

microfauna is of a slightly younger age, thus Late

Artinskian? to Kungurian. No foraminiferal representatives

of Late Permian age have been identi®ed in the Chilean or

Bolivian rocks.

Although a highly impoverished nodosarid±geinitzinid

assemblage lacking fusulines and algae, the Juan de Morales

microfauna is Late Early Permian (Late Artinskian? to


Table 1

Foraminifera found in carbonate samples of the middle member of the Juan

de Morales Formation. See location of samples in Figs. 2 and 3

JM-8 JM-10 JM-11

Frondicularia sp. X X X

Frontinodosaria sp. X X

Geinitzina sp. X X

Langella sp. X X X

Nodosinelloides sp. X X

Neohemigordius sp. X

Pachyploia sp. X X X

Syzrania sp. X

Kungurian) or slightly younger? (Late Visuralian). It has

temperate cold and/or disphotic zone characters. It is

impossible to reach more stratigraphic precision, as

foraminiferal equivalents are only known from distant basins

that belong to different realms. Direct South American

counterparts are only known from the HuentelauqueÂn

Formation of central Chile and Arizaro Formation of

northwest Argentina, as described below.

It is also interesting to note that in the Canadian Arctic, a

sudden drop of temperature is underlined by the passage of

the Chloroforam to Bryoderm assemblages (Beauchamp,

1994; Beauchamp and TheÂriault, 1994). A similar tempera-

ture drop is observed at the same time between fusulinid-

algal rich grainstones of the Copacabana Group of Bolivia

and the nodosarid impoverished fauna of the Chilean Juan

de Morales. As suggested by the Permian paleogeographic

and paleoclimatic maps proposed by Golonka et al. (1994),

these lower temperatures may be interpreted as a result of

the upwelling of cold bottom currents reaching the forearc

(similar to today's conditions along the coast of Peru and

Chile). The interior (backarc) basin of the Copacabana

Formation would not be affected by these currents due to

the barrier effect of the magmatic arc (Fig. 6).

Rivano and SepuÂlveda (1983) illustrate microfossils from

the HuentelauqueÂn Formation that they attribute to the Late

Carboniferous. The fossils are poorly preserved and their

identi®cations are only tentative. Most of the foraminiferal

walls are dissolved and partially or completely replaced by

cement. As the classi®cation of foraminifers is based

essentially on wall structure, their proposed identi®cations

of Earlandinita, Agathammina, Eoschubertella and

Monotaxinoides could be transferred to ªEndothyranellaº,

ªGlomospiraº, ªNeohemigordiusº, etc. None of these taxa

have precise biostratigraphic connotation. The only speci-

mens ®gured by Rivano and SepuÂlveda (1983) that have

retained part of their original wall structure are illustrated

in their Plate I, Fig. 1, and Plate 2, Fig. 5, which they

identi®ed as Tetrataxis sp. and a coral, respectively. The

®rst is an oblique axial section of a trochoid tetrataxidae,

with a wide umbilicus and secondary chamberlets. The

second is a horizontal section through the radial secondary

partitions. The characters clearly indicate the presence of

the genus Abadehella in their sample of the HuentelauqueÂn

Formation near the type locality of this unit, at 31840 0S.

The genus Abadehella was erected by Okimura et al.

(1975) for a Permian tetrataxidae. Its partitioning by

secondary chamberlets is very characteristic, and is

reminiscent of that observed among two other Paleozoic

foraminifers, the Frasnian Multiseptida (M. farewelli)

(Mamet and Plafker, 1982) and the ViseÂan Valvulinella

(V. youngi) (Brady, 1876). Since its ®rst description, Abade-

hella has been widely recognized and illustrated from

Greece, Turkey, Iran, Afghanistan, the Pamirs, India (Cash-

mir, Ladakh), Malaysia, Vietnam, Cambodia, Indonesia,

New Zealand, South China, and Japan (Ishii et al., 1975;

Aw et al., 1977; Lys et al., 1980; Okimura and Ishii, 1981;

Vachard, 1981; Vachard and Montenat, 1981; Okimura et

al., 1985; Kobayashi, 1986; Nguyen, 1986; Wang, 1986;

Kobayashi, 1988a,b; Lin et al., 1990; Vachard and FerrieÁre,

1991; Vachard and Clift, 1993; Kobayashi, 1996; Pronina,

1996). The genus is not restricted to the Tethys, as generally

accepted (Kobayashi, 1996), and there are reports from the

Siberian Far East and Circum-Paci®c ªexotic terranesº

(Pronina, 1989; Davydov et al., 1996; Stevens et al., 1997).

With regard to the age proposed for the HuentelauqueÂn

Formation by Rivano and SepuÂlveda (1983), and how it

relates to the Late Early Permian (Late Artinskian±

Kungurian) age here proposed for the Juan de Morales


Table 2

Correlation of Permian successions mentioned in the text, with the global Permian chronostratigraphic subdivisions proposed by the IUGS Subcommission on

Permian Stratigraphy (Jin Yugan et al., 1997)

Series Stages Southern Urals(traditional standard)

South China(reference sequences)

Lopingian

Guadalupian

Cisuralian

Asselian

Sakmarian

Artinskian

Kungurian

Roadian

Wordian

Capitanian

Wuchiapingian

Changhsingian251

253

264

272

280

285

292

Tatarian

Kazanian

Ufimian

Kungurian

Artinskian

Sakmarian

Asselian

LOW

ER

UP

PE

R

Chuanshanian

Yangsingian

LopingianChanghsingian

Wuchiapingian

Zisongian

Longlinian

Chihsian

Maokouan

Ma

Formation, the following comments are of consideration.

Johnson (1951) illustrated samples from the Middle Permian

of the Apache Mountains (Texas), including two sections of

ªAnthracoporellaº (Plate 7, Figs. 6 and 7) that are actually

basal sections of Abadehella. We have personally observed

this genus in Guadalupian forereef carbonates in the Apache

Mountains. It is associated with Codonofusiella, Dagmarita,

Geinitzina, Langella and Pachyploia, an assemblage resem-

bling that found in the Juan de Morales Formation. Vachard

and Miconnet (1990) mentioned the presence of Abadehella in

the Wordian of Mexico (collection of TeÂllez-GiroÂn and

Nestell). Three years later, Vachard (in Vachard et al., 1993)

illustrated the genus from Central Mexico. Integration of all

the published data indicate that Abadehella is of Middle to

Late Permian age (Kobayashi, 1996). The oldest known occur-

rence is in the Murgabian (Wordian) Neoschwagerina simplex

Zone of the Funabuseyama Formation (Japan). The youngest

occurrence is in the Changxingian Palaeofusulina sinensis

Zone of the Changxing Formation (southern China). The

presence of Abadehella in the HuentelauqueÂn Formation

therefore excludes a Late Carboniferous age, at least for

the carbonate bed sampled by Rivano and SepuÂlveda

(1983), so that its oldest possible age is also Late Early

Permian (Artinskian±Kungurian), and may thus be corre-

lated with the Juan de Morales Formation.

Finally, a few comments are due with respect to some

earlier works on Late Paleozoic small foraminifera in the

Andes. Douglass and Nestell (1976) studied Late Paleozoic

foraminifera from southernmost Chile (Guarello and

Tarlton Islands of the Madre de Dios Archipelago). Most

of the taxa they described were fusulinids, and actually very

few were small foraminifera. Benedetto (1976) studied

foraminifera from the Arizaro Formation in northwest

Argentina. Both studies were written in the early seventies,

when small foraminifera were poorly known and their

taxonomy was being developed. Our re-interpretation of

their plates suggests that revised determinations are needed.

For instance, the genus Parathikinella (Plate I, Fig. 4±6),

Earlandia (Plate I, Fig. 3), and Nodosinella (Plate II, Fig. 1±

3) mentioned by Benedetto (1976) seem to be misidenti®ed,

and would, respectively, be Syzranella (Moscovian to Mid

Permian), Syzrania (Mid Carboniferous to Mid Permian),

and Nodosinelloides (very abundant in Permian, although

already reported in Kasimovian). Furthermore, Moravam-

minidae indet. (Plate I, Fig. 7) is certainly Tezakina sp.,

which is exclusively Lower Permian (Cisuralian), and

Pachyphloia sp. (Plate II, Fig. 4) is doubtful (if it is a true

Pachyphloia, it would be post-Artinskian). Therefore, in

accordance with the revised determinations, and with the

absence of Abadehella in the assemblage, we propose an


Fig. 7. Specimens of conjoined valves of Waagenoconcha humboldti d'Orbigny from Juan de Morales Formation (level 7; Fig. 3), northern Chile. (1) side view

(X1); (2) view of brachial valve exterior, showing fold and posterior concentration of spines (X0.8); (3) view of pedicle valve exterior, showing sulcus and

concentration of spines (X0.8); (4) view of brachial valve exterior of second specimen (X0.8).

Artinskian or slightly younger age (Late Early Permian to

early Middle Permian) for the foraminiferal assemblage in

the Arizaro Formation. This revised age is very similar to

the Late Early Permian (Late Artinskian±Kungurian) age

we propose for the Juan de Morales Formation, and would

con®rm that both units may also be correlated.

6. Brachiopod biostratigraphy

The Late Carboniferous and Permian brachiopod faunas

of Peru, Bolivia, and Chile have not been thoroughly

reviewed for some time. In his summary of the Paleozoic

guide fossils for Bolivia, Branisa (1965) commented that

very little had been done on the faunas since the work of

Kozlowski (1914) and Newell et al. (1953). However, there

are various lists of Permian age brachiopods published since

the work of Branisa. Samtleben (1971) provided a detailed

study of productids and spiriferids from the Copacabana

Formation at three locations (Yaurichambi, Yaco and

Apillapampa) in Bolivia. More recently, Birhuet (1993)

proposed a brachiopod-based biostratigraphic scheme for

the Copacabana Formation, and Dalenz and Merino

(1994) attempted a zonation of this same unit based on the

entire invertebrate and conodont fauna found in it.

Romero et al. (1995) had included brachiopods in faunal

lists from Copacabana Formation localities in southern

Peru. Conspicuous in the faunas are Rhipidomella cora,

Lissochonetes assula, Kiangsiella pinquis, Dictyoclostus

boliviensis, Dictyoclostus inca, Linoproductus cora,

Juresania hispida, Derbya buchi, Streptorhynchus cyrano,

Neospirifer condor, Kozlowskia capaci, Reticulariina

atava, Reticulariina patula, Wellerella osagensis

peruviana, Wellerella minuta and Composita minuscula.

In Peru, the equivalent of the Copacabana Formation of

Bolivia is traditionally considered with the rank of group,

following the work of Newell et al. (1953), although it has

been proposed to modify the rank to formation (DõÂaz-

MartõÂnez, 1999). This unit was considered as Late Carboni-

ferous in age until the work of Newell et al. (1953), and was

considered as Early Permian afterwards. Biostratigraphic

zonation of the Copacabana Formation based on foramini-

fera and calcareous algae demonstrated that the lower part

of the unit is of Late Carboniferous age in most of the

northern Central Andes (Mamet, 1995, 1996). For our

interest, the large productid genera present in the upper

(Permian) part of the Copacabana Formation are important

in these lists, as the Waagenoconcha ªpavementº found at

the Cerro Juan de Morales outcrops is rather unique in the

Andes Permian. In Bolivia, the large productids include

Linoproductus cora, Kochiproductus peruvianus, and

Chaoiella sp. Branisa (1965) includes Waagenoconcha

humboldti and Dictyoclostus inca among intermediate-

sized productids.

There has been little work completed and published on

the megafossil paleontology of the Permian sedimentary

rocks in northern Chile. Some of the better outcrops are in

the Cerros de Cuevitas (near Salar de Navidad), Cerro 1584

(near Augusta Victoria), and at Aguas Blancas (Niemeyer et

al., 1985; Marinovic et al., 1995). P.E. Isaacson recovered

large numbers of Kozlowskia capaci in coquinas from the

Cerros de Cuevitas, along with other invertebrates, although

these ®ndings have not been published yet. At the Aguas

Blancas locality, V. Covacevich identi®ed the following

brachiopod taxa: Kochiproductus or Dictyoclostus sp.,

Linoproductus cora, Kozlowskia sp., Hustedia aff. H.

meridionalis, Cleiothyridina sp., Dielasma sp., and various

spiriferids.

With regard to the Juan de Morales locality, Galli (1968;

p. 17) listed the following brachiopods: Waagenoconcha

humboldti, Punctospirifer kentuckiensis, and Chonetes

granulifer. Contained in the northern Chilean fauna, and

apparently absent from Peru, is Waagenoconcha (Fig. 7).

An important concentration of large silici®ed productid

brachiopod specimens (predominantly Waagenoconcha

humboldti) was found in the measured section (levels 7

through 11; Fig. 3). This ªpavementº is left over from the

erosion and dissolution of the marls and carbonate beds, and

covers the surface of the outcrop. According to Cooper and

Grant (1975), Waagenoconcha is easily distinguishable

from other productids (namely Linoproductus and Kochi-

productus) on account of its large size, and arrangement

and shape of its spines. The most closely related genus,

Bathymyonia, has a very similar shape and size, although

its spines are much more elongate and occur at the same

density throughout shell length. Waagenoconcha's spines

are more densely packed at the shell's posterior third and

occur along growth lamellae in a more subdued fashion

towards shell anterior. Although, the Chilean specimens

are abraded, the differences in spine packing are evident

(Fig. 7). Species assignment favors W. humboldti, on

account of length±width ratios, size, and spine placements.

W. montpelierensis (see above) has been re-assigned to W.

magni®ca (Cooper and Grant, 1975; p. 1046). This species

is quite different from W. humboldti because of its smaller

size. W. humboldti is rarely found in West Texas in the

Permian (Wolcampian) part of the Gaptank Formation,

and it is more common higher in the section: Cathedral

Mountain and Word Formations. According to the Late

Artinskian±Kungurian age here identi®ed for the Juan de

Morales Formation based on the foraminifer biostrati-

graphy, a similarly younger age is also identi®ed for the

W. humboldti specimens in the northern Chilean outcrops.

7. Paleogeographic implications

The Quipisca Formation was considered by Galli (1968)

as ªundifferentiated Paleozoicº age. Given the revised

Permian age of the Juan de Morales Formation, as opposed

to its previous interpretation as Late Carboniferous, it is now

possible to correlate with con®dence the underlying


volcanic rocks of the Quipisca Formation with other Late

Carboniferous and Early Permian volcanic rocks of northern

Chile located to the south of the study area (Vergara and

Thomas, 1984; Breitkreuz et al., 1989, 1992;; Bahlburg and

Breitkreuz, 1991; Breitkreuz and Zeil, 1994). Furthermore,

volcanic and volcaniclastic units in southern Peru (Mitu and

Iscay Groups) have yielded middle Permian absolute ages

(Ellison, 1990). As stated above, the Quipisca Formation

records the activity of a magmatic arc, and the overlying

Juan de Morales and Diablo Formations record its erosion

and dismantling. Galli (1968) mentioned a progressive

upsection increase of the in¯uence of a crystalline source

area, indicated by clasts of metamorphic rocks and hydro-

thermal quartz, as well as muscovite abundance. This may

be interpreted as a result of the progressive erosion and

dismantling of the volcanic arc, rooted on continental

crust at the margin of Gondwana. Therefore, all three

units (Quipisca, Juan de Morales and Diablo Formations)

are here considered to be deposited in a forearc or intra-arc

setting, depending on the relative position with respect to

the magmatic arc (see above, and Figs. 5 and 6).

The revised younger age for the Juan de Morales Forma-

tion based on foraminifer biostratigraphy is signi®cant

because it supports the possibility of a younger age for

similar carbonate-bearing units in northern and central

Chile (Cerros de Cuevitas near Salar de Navidad, Cerro

del Arbol Formation at Cerro 1584 and Cerro Palestina,

Sierra de Fraga, etc.), and in northwestern Argentina

(Arizaro Formation at Salar de Arizaro) (see also Figs. 4±

6). The aforementioned identi®cation of Abadehella in the

HuentelauqueÂn Formation, and the revision of small fora-

minifera in the Arizaro Formation, further supports this

possibility. The interest of the results provided by small

foraminifer biostratigraphy in our study suggest that it is

an appropriate methodology to be applied in the biostrati-

graphy of Upper Paleozoic carbonate sedimentary

sequences of South America, and future studies in the area

should be pursued to corroborate the correlations and ages

proposed here.

According to the younger (Artinskian±Kungurian) age

here identi®ed for the Juan de Morales Formation and

related units deposited in a forearc setting along the western

margin of Gondwana, their deposition only coincided

during a small time interval (,3 Ma?) with the older

(Bashkirian±Artinskian) Copacabana Formation of Peru

and Bolivia, deposited in a retroarc position. This

diachroneity may have precluded the possibility of direct

connection between the two basins, one of them open to

the (proto-) Paci®c, and the other one connecting with the

Amazonas and Parnaiba basins in Brazil, and with North

America (West Texas) through Ecuador, Colombia and

Venezuela. Their different fossil faunal assemblages are

the result of: (1) the different age of the deposits; (2) the

different paleobiogeographic connections for faunal

exchange; and (3) the different paleogeographic position

with respect to oceanic currents, warmer for the epiconti-

nental sea (Copacabana Formation), and colder for the outer

margin of the continent (Juan de Morales Formation and

related units), probably exposed to upwelling of cold

currents coming from the south. If truly absent from Peru,

the presence of Waagenoconcha humboldti, earlier in the

upper Copacabana Formation in Bolivia, and later in the

northern Chilean Permian units, may be used as evidence

for connection between these two basins (backarc and fore-

arc, respectively) at about 188S (Fig. 6). Further research

should consider the possibility of using this conspicuous

taxon as an indicator of cold temperate waters reaching

these basins.

8. Conclusions

Foraminifer biostratigraphy of the middle member of the

Juan de Morales Formation in northern Chile favors a revised

Artinskian±Kungurian age, as opposed to the Late Carboni-

ferous age formerly assigned to this unit. A similar revised age

is also proposed for the HuentelauqueÂn Formation of central

Chile, and for other Upper Paleozoic marine carbonate units

along the Andes: Tacna (S Peru), Cerros de Cuevitas (Salar de

Navidad), Cerro Palestina, Cerro 1584, Cerro del Arbol, and

Sierra de Fraga (N Chile), Salar de Arizaro (NW Argentina),

etc. The deposits consist of alluvial, ¯uvial, deltaic, coastal,

and shallow marine carbonates and siliciclastics, with variable

input of volcanic material. Sedimentation took place at the

active margin of Gondwana, in a forearc and intra-arc tectonic

setting, under temperate to cold waters, and at mid to low

latitudes. The conspicuous presence of a large productoid

(Waagenoconcha humboldti) concentrated in beds, suggests

it could also be used as an indicator for cold temperate waters

from upwelling currents reaching the marginal basins in the

region during the Permian.

Acknowledgements

Funding for this project was granted by the Petroleum

Research Fund of the American Chemical Society. J.

Jacay of Univ. Nac. de San Marcos at Lima, and M.J. Martin

of SERNAGEOMIN library at Santiago kindly helped with

reference acquisition. J. Davidson helped with advice for

®eld logistics. Ch. Breitkreuz and an unknown reviewer

are acknowledged for their contribution to improve the

contents of this paper.

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