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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, Faculte 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®co 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 esta 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; Herve 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,
E. DõÂaz-MartõÂnez et al. / Journal of South American Earth Sciences 13 (2000) 511±525514
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
E. DõÂaz-MartõÂnez et al. / Journal of South American Earth Sciences 13 (2000) 511±525 515
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
E. DõÂaz-MartõÂnez et al. / Journal of South American Earth Sciences 13 (2000) 511±525516
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
E. DõÂaz-MartõÂnez et al. / Journal of South American Earth Sciences 13 (2000) 511±525 517
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
E. DõÂaz-MartõÂnez et al. / Journal of South American Earth Sciences 13 (2000) 511±525518
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
E. DõÂaz-MartõÂnez et al. / Journal of South American Earth Sciences 13 (2000) 511±525 519
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
E. DõÂaz-MartõÂnez et al. / Journal of South American Earth Sciences 13 (2000) 511±525520
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
E. DõÂaz-MartõÂnez et al. / Journal of South American Earth Sciences 13 (2000) 511±525 521
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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