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Geosphere
Late Triassic stratigraphy and facies from northeastern Mexico: Tectonic
setting and provenance
José Rafael Barboza-Gudiño, Aurora Zavala-Monsiváis, Gastón Venegas-Rodríguez and Luís Daniel
Barajas-Nigoche
Geosphere 2010;6;621-640
doi: 10.1130/GES00545.1
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Notes
© 2010 Geological Society of America
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Late Triassic stratigraphy and facies from northeastern Mexico:
Tectonic setting and provenance
José Rafael Barboza-Gudiño*
Aurora Zavala-Monsiváis*
Gastón Venegas-Rodríguez*
Luís Daniel Barajas-Nigoche*
Universidad Autónoma de San Luis Potosí, Instituto de Geología, Manuel Nava No. 5, Zona Universitaria, 78240,
San Luis Potosí, México
ABSTRACT
Triassic strata in northeastern Mexico distributed over an area of ~120,000 km2 have
received relatively little attention in paleogeographic and tectonic reconstructions of
western equatorial Pangea. Triassic marine
sequences of the Zacatecas Formation in
western San Luis Potosí and Zacatecas
constitute facies corresponding to different
sections of a submarine fan system previously described as the Potosí fan and were
deposited on the paleo-Pacific margin of
Pangea. New geochronologic data and field
observations permit revision of the stratigraphy from Late Triassic to Early Jurassic
fluvial deposits of the Huizachal Group that
crop out in Nuevo León and Tamaulipas and
indicate a link between the lower part of this
succession (Triassic strata) and the Potosí
fan. This work proposes and defines the
El Alamar formation, which represents the
only Triassic strata of the Huizachal Group
(lower part of the Late Triassic–Early Jurassic La Boca Formation), and is interpreted as
a continental succession that records a major
fluvial system draining equatorial Pangea
and flowing west into the Potosí fan. Petrographic and geochemical studies indicate
that both Triassic successions, the Zacatecas
Formation (marine) and El Alamar formation (continental) have continental block and
recycled orogenic provenances. U-Pb detrital
zircon geochronology by laser ablation–
multicollector–inductively coupled plasma–
mass spectrometry show three main zircon
age populations: (1) Grenvillian (1300–
*E-mails: Barboza-Gudiño: [email protected];
Zavala-Monsiváis: [email protected];
Venegas-Rodríguez: [email protected]
.mx; Barajas-Nigoche: [email protected].
900 Ma); (2) Pan-African (700–500 Ma);
and (3) dominant Permian–Triassic (280–
240 Ma). The presence of these zircons displays evidence of sources in Grenvillian
Oaxaquia block, Pan-African terrains such
as Yucatan and southeastern Texas, and a
prominent contribution from the Permian–
Triassic east Mexico magmatic arc. Notable
is the absence of detrital contributions from
the southwestern North American craton. The geochronological data thus argue
against proposed southeastward displacement of Triassic successions and their basement to their current position as proposed by
the Mojave-Sonora megashear hypothesis.
We propose that continental Triassic strata
were deposited in eastern Mexico before the
opening of the Gulf of Mexico basin, and are
thus autochthonous and transported detritus
toward the ancient Pacific margin into the
Potosí fan, which is also autochthonous.
INTRODUCTION
Triassic successions in northeastern Mexico have been known for more than 100 years
(Burckhardt and Scalia, 1905), but they are
still poorly understood. Outcrops of Triassic strata are isolated across the Mesa Central
province in the states of Zacatecas and San Luis
Potosí and in the core of anticlines or related
to basement uplifts of the Sierra Madre Oriental in Nuevo León and Tamaulipas, Mexico
(Fig. 1). The Triassic strata in the Mesa Central
province (marine) have been assigned to the
Zacatecas Formation (Carrillo-Bravo, 1968, in
Silva-Romo et al., 2000), La Ballena formation (Silva-Romo, 1994) and Taray Formation
(Córdoba-Méndez, 1964), and in the Sierra
Madre Oriental (continental), to the Huizachal
Formation (sensu Carrillo-Bravo, 1961) or
La Boca Formation (sensu Mixon et al., 1959).
A generalized stratigraphic framework for both
provinces is illustrated in Figure 2.
Shortening deformation during the Laramide
orogeny and mid-Cenozoic extensional tectonics widely affected these rocks, and they
are extensively covered by Late Jurassic to
Cretaceous limestones and Cenozoic volcanic
rocks and alluvial deposits, thereby rendering
facies interpretations, basin-wide correlations,
and paleogeographic reconstructions difficult.
Much discussion exists regarding their precise
age, correlation, environments of deposition,
sediment provenance, and tectonic setting. This
uncertainty limits our ability to test tectonic
models for the evolution of this region during
the early Mesozoic (Anderson and Schmidt,
1983; Salvador, 1987), which was an important
time of tectonic transition on the western margin of Pangea. Furthermore, Triassic and Early
Jurassic strata in northeastern Mexico contain a
record of a variety of sedimentary environments
in western equatorial Pangea that may improve
our understanding of paleoclimatic, paleobiologic, and paleoceanographic events during this
particular period of Earth history.
The age has been established in several
localities by means of their fossil fauna (Burckhardt and Scalia, 1905; Cantú-Chapa, 1969;
Gómez-Luna et al., 1998) or flora (Mixon et al.,
1959; Weber, 1997; Silva-Pineda and BuitrónSanchez, 1999), but in many other localities
age relations remain unknown due to a lack of
fossils. Uncertainties regarding the age, tectonic
setting, and transport history of these strata create opposing models for the early Mesozoic
paleogeography of western Pangea, resulting
in an association of presumably coeval strata
from highly contrasting tectonic settings, now
in close geographic proximity. Subaerial volcanic rocks and redbeds interpreted as deposits of a continental magmatic arc (Jones et al.,
1995; Bartolini et al., 2003; Barboza-Gudiño
Geosphere; October 2010; v. 6; no. 5; p. 621–640; doi: 10.1130/GES00545.1; 14 figures; 3 tables; 1 supplemental table file.
For permission to copy, contact [email protected]
© 2010 Geological Society of America
621
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Barboza-Gudiño et al.
101°
COAHUILA
useful in this region because they permit correlation of strata from different coeval sedimentary environments. In addition, they are useful in
deciphering contrasting possible source regions
for detritus in the Late Triassic strata.
TEXAS
NUEVO LEON
REYNOSA
MONTERREY
N
PARRAS
SIE
yra
Te
de
rra
Sie
RR SALTILLO
GALEANA
A
LINARES
M San Marcos
AD
TAMAULIPAS
RE
El Alamar
CONCEPCIÓN DEL ORO
Huizachal-Peregrina
EN
TR
torce
de Ca
Sierra
O
AC
MATEHUALA
CHARCAS
CIUDAD VICTORIA
Bustamante
TULA
AL
SAN LUIS POTOSÍ
Valle del Huizachal
N-America
a fr
it
ach
Cortéz
Late Triassic (marine)
Late Triassic (continental)
uila
Oaxaquia
north
south
e
adr
101°
h
Coa
M
S.
SAN LUIS POTOSÍ
ont
Ou
ZACATECAS
La Ballena
(Sierra de Salinas)
24°
Golf of Mexico
ES
Miquihuana
L
TA
M
Tapona 1
well
anticlinorium
Aramberri
IEN
ZACATECAS
OR
24°
100 km
Cuicateco
ya
Ma
Guerrero
composite terrane
Mixteca
Areas of Precambrian-Paleozoic
outcrops without Triassic deposits
Jurassic redbeds
and volcanic rocks
Figure 1. Pre-Late Jurassic localities in central to northeastern Mexico (modified after
Barboza-Gudiño et al., 1999). Shown are Late Triassic exposures of the marine and continental facies, post-Triassic redbeds, exposures of pre-Mesozoic crystalline rocks, in some
cases interpreted as areas of no deposition during the Triassic, and the main volcanic centers
of the Early Jurassic volcanic arc that crop out.
et al., 2008) are near roughly coeval volcanic
rocks and redbeds interpreted as a continental
rift in the Sierra Madre Oriental in Nuevo León
and Tamaulipas (Michalzik, 1991). Some (i.e.,
Jones et al., 1995) have sought to explain these
seemingly incompatible tectonic settings by
reference to the inferred allochthonous nature
of Mexico with respect to the North American
craton, suggesting that early Mesozoic strata in
north-central Mexico were displaced along the
hypothetical Mojave-Sonora megashear. Those
models were criticized by Molina-Garza and
Iriondo (2005), because early Mesozoic volcanic rocks in north-central Mexico appear to
overlie basement of a very different nature than
622
their inferred counterparts in northwest Sonora,
where they are inferred to have formed. The correlation of Mesozoic rift basins in northeastern
Mexico with presumably coeval strata in northeastern North America is also uncertain.
We report detrital zircon geochronology data
from key stratigraphic sections across northeastern Mexico. These data require a new model for
the tectonic evolution and paleogeography of this
region. The stratigraphic sections studied (Fig. 1)
are distributed over an area of ~120,000 km2,
where ties between outcrops within this region,
based only in lithologic character, are tenuous
(Barboza-Gudiño et al., 1999). Nevertheless,
detrital zircon provenance data are particularly
Geosphere, October 2010
POTOSÍ FAN: THE TRIASSIC MARINE
FACIES OF THE MESA CENTRAL
It is well established that Middle to Late
Triassic marine rocks are exposed across the
Mesa Central. Triassic outcrops of siliciclastic
sedimentary rocks in the vicinity of the city of
Zacatecas (Fig. 1) were first reported by Burckhardt and Scalia (1905), who described Triassic
fossils including several ammonites (Sirenites
Smithi n. sp., Trachyceras sp., Clionites sp.,
Juvavites sp.) as well as bivalves (23 species of
Palaeoneilo and unidentified Aviculids) from
a classic locality at Arroyo La Pimienta. This
fauna is considered of Carnian age (Burckhardt
and Scalia, 1905; Gutierrez-Amador, 1908;
Maldonado-Koerdell, 1948). Although never
formally defined, these rocks were first named
Triásico de Zacatecas (Gutierrez-Amador,
1908), and are currently known as the Zacatecas Formation (Carrillo-Bravo, 1968, in SilvaRomo et al., 2000; Martínez-Pérez, 1972;
Carrillo-Bravo, 1982). There are no known
exposures of the base of this unit or other preTriassic rocks in the Mesa Central region, their
total thickness anywhere is not known, and
nowhere can a continuous section of >300 or
400 m be measured, because intense folding
and numerous thrust and normal faults affect
the succession.
The most recent studies of the Triassic rocks
in western San Luis Potosí and Zacatecas are
sedimentologic, stratigraphic, and tectonic
studies interpreting such successions as part
of a submarine fan system at the paleo-Pacific
margin of North America (Centeno-García and
Silva-Romo, 1997; Silva-Romo et al., 2000;
Hoppe et al., 2002; Centeno-García, 2005),
named the Potosí fan by Centeno-García (2005).
Silva-Romo (1994) informally referred to a
sequence of marine siliciclastic turbiditic layers
and minor carbonate rocks in La Ballena, in the
central part of Sierra de Salinas, ~150 km east
of Zacatecas, as La Ballena formation (Figs. 1
and 3A). These strata contain a Late Triassic
fauna including Sirenites sp. (Chavez-Aguirre,
1968), Clionites sp., Paleoneilo sp., and Halovia sp. (Silva-Romo, 1994), Meginoceras sp.,
and Clionitites sp. (Gómez-Luna et al., 1998).
Gómez-Luna et al. (1998) pointed out that this
fauna is similar to those reported from Triassic
Pacific provinces in Nevada and British Columbia in the western Cordillera and, based on the
presence of Clionitites sp. and Meginoceras
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Late Triassic facies from northeastern Mexico
Callovian
SILVA-ROMO
et al. (2000)
CARRILLOBRAVO (1982)
Zuloaga
Formation
Zuloaga
Formation
Zuloaga
Formation
Nazas
Formation
Bathonian
Bajocian
Aalenian
Toarcian
RIO
BLANCO
MEMBER
Nazas
Formation
Pliensbachian
Sinemurian
Hettanguian
Carnian
Zacatecas
Formation
Zacatecas
Formation
Norian
El Alamar
Formation
Zacatecas
Formation
Rhaetian
Nazas
Formation
NAZAS
FM.
La Joya
Formation
La Joya
Formation
La Ballena
Formation
V. SED.
MEMBER
LA JOYA
FM.
Kimmeridgian
Oxfordian
this work
Huayacocotla
Formation
LA BOCA
ALOFORMATION
LOS SAN PEDROS ALOGROUP
LA BOCA
FORMAT.
LATE TRIASSIC
HUIZACHAL
FORMATION
HUIZACH. ALOF.
LA JOYA
FORMAT.
HUIZACHALGROUP
LA JOYA
FORMATION
ZULOAGA
FORMATION
FORMATION
ZULOAGA
FORMATION
LA BOCA
ZULOAGA
FORMATION
ZULOAGA GROUP
ZULOAGA
FORMATION
this work
HUIZACHALGROUP
RUEDA-G.
et al. (1993)
LA JOYA
FORMATION
CARRILLOBRAVO (1961)
ZULOAGA GROUP
MIXON et al.
(1959)
CLASTIC
MEMBER
ZULOAGA
FORMATION
HUIZACHAL
FORMATION
EARLY JURASSIC
LATE JURASSIC
IMLAY
(1943)
Mesa Central
Sierra Madre Oriental
Figure 2. Stratigraphic subdivisions proposed by different authors for the early Mesozoic successions exposed in the Sierra Madre Oriental
from Nuevo León and Tamaulipas and the Mesa Central province in San Luis Potosí and Zacatecas. References for different stratigraphic
nomenclature cited in text.
sp., assigned a Ladinian age for a lower fossiliferous horizon in the succession. For an upper
fossiliferous horizon, according to their fauna,
Gómez-Luna et al. (1998) considered an early
Carnian age. A measured section is located
1.7 km to the north of the town of La Ballena
(Fig. 4). Coordinates for the base of the section
are 22°28.150′N/101°42.499′W, and it consists
of interstratified sandstone, siltstone, and shale
with uncommon occurrences of conglomeratic
sandstone and quartzite. These rocks are dark
gray on fresh surfaces and brown to grayishyellow on weathered surfaces. The lithofacies
succession (Figs. 4, 5A, and 5B) is interpreted
as middle to lower fan facies associated with
well developed C and B facies, as well as
A facies (after Mutti and Ricci-Lucchi, 1972);
these lithofacies correspond to channel margins, suprafan lobes, and channel environments,
respectively.
At Sierra de Charcas in San Luis Potosí (Figs.
1 and 3B) the Triassic succession is called the
Zacatecas Formation (Martínez-Pérez, 1972)
or La Ballena formation (Centeno-García
and Silva-Romo, 1997). Cantú-Chapa (1969)
reported early Carnian Juvavites sp., CuevasPérez (1985) reported Carnian conodonts, and
Gallo-Padilla et al. (1993) reported the Carnian
ammonoids Anatomites aff. herbichi Mojsisovics and Aulacoceras sp. The best-preserved and
most extensive exposures of this area are located
a few kilometers west of the town of Charcas, in
an area also known as the San Rafael–La Trinidad anticlinorium. Several isolated minor outcrops are in the Presa de Santa Gertrudis area
and Sierra La Tapona, northwest of Charcas. In
the Sierra de Charcas, an ~200-m-thick section
was measured and described by Hoppe (2000).
The same locality was studied by us, and further described (Fig. 4) following the facies
designations of Mutti and Ricci-Lucchi (1972).
Coordinates for the base of the section are
23°04.300′N/101°11.700′W. This succession
consists of turbiditic sandstones, commonly
with partial Bouma sequences, conglomeratic
sandstones, and graywacke, alternating with
siltstone and shale, although generally such
pelitic layers are subordinate (Fig. 5C). The
Geosphere, October 2010
graywacke beds contain internally graded bedding, as well as slump deposits; load and groove
casts are the most common sole marks (Figs.
5D, 5E). The components of the sandstones are
monocrystalline quartz and minor polycrystalline quartz, feldspar, as well as shale intraclasts
and detrital mica in a matrix of detrital and diagenetic quartz, muscovite + illite, and chlorite
layers. The lithofacies identified in the Charcas
sections in order of their abundance in this area
are facies A (channel), followed by facies B and
C (representing channel margin environments),
and subordinate facies D, E, F, and G (suprafan
lobe, levee, and interchannel flats), corresponding to a midfan or suprafan zone.
The succession at Sierra de Catorce (Figs. 1
and 3C) consists of finely laminated shale and
intercalated thin siltstone and sandstone layers
(Fig. 5F). The main exposures in this area occur
along the General and Ojo de Agua Canyons,
in the northwestern part of the sierra. In addition, there are outcrops of comparable strata
in the southern Sierra de Catorce along the
El Astillero Canyon. At this locality the Triassic
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Barboza-Gudiño et al.
101°45′
N
Llanura
El Salado
A
Peñón Blanco
101°40′
22°32′
22°32′
Sierra de Catorce
C
Matehuala
B
Sierra de Charcas
Salinas de
Charcas
Hidalgo
Zacatecas
A
San Luis
Potosí
Sierra de Salinas
San Luis
Potosí
Aguascalientes
0
MÉXICO
50
Rioverde
100
Río
Co
ma
n
ja
Ciudad Valles
200 km
Golfo
de México
1
2
3
San Luis
Potosí
LA BALLENA
23°10′
B
C
uerta
La H
Cerro
Verde
101°45′
101°10′
100°05′
23°10′
Río
2 km
22°25′20″
22°25′20″
Palm
Las
oyo
Arr
23°45′
as
Cenozoic cover
Ca
ña
POBLAZON
LA TRINIDAD
Ar
roy
o
MORELOS
Ch
arc
as
Vie
jas
da
O
jo
de
Magmatic rocks
C. LA CALABAZA
Ag
ua
89
Late Jurassic-Cretaceous limestones
EL TEPOZAN
EL SALTO
SAN ANTONIO
DE LAS HUERTAS
23°05′
Lower to Middle Jurassic redbeds
CH06-1
RC06-31
EL PERDIDO
POTRERO
EL LLANO
EL LLANO
C. LA DESCUBRIDORA
LA BUFA
SAN RAFAEL
SANTA CRUZ
DE CARRETAS
Lower Jurassic volcanic rocks
LOS CATORCE
ELMAZO
Triassic fluvial and marine sequences
REAL DE CATORCE
C. EL QUEMADO
CH06-1 Sample
23°40′
REGO
CAÑON EL BOR
Detachment
101°15′
Normal fault
2 km
A
sSAN
tanza
. Ma
JUAN DE
MATANZAS
2 km
23°00′
Fold axis (antiform)
Figure 3. Geologic sketch maps of the main localities with outcrops of marine Triassic rocks in San Luis Potosí and eastern Zacatecas
state. (A) La Ballena area, northern Sierra de Salinas. (B) La Trinidad–San Rafael anticlinorium, west of Charcas. (C) Northwestern
Sierra de Catorce.
age of the succession is inferred from lithologic
similarities and stratigraphic position. There
are no reports of Triassic fossils in this locality,
and an older age has been suggested by a possible late Paleozoic fossil flora (Franco-Rubio,
1999) and late Paleozoic spores (Bacon, 1978).
624
Detrital zircon data and new geochronological
data obtained from pre–Late Jurassic rocks in
Sierra de Catorce, described herein, demonstrate that this inference is incorrect and are
consistent with a Late Triassic age of deposition. The facies associations in Real de Catorce
Geosphere, October 2010
are comparable with those of Charcas, with a
few differences attributable to an evident predominance in these outcrops of the interchannel
deposits (lithofaces D, E, and G), and subordinate suprafan, levee, and channel deposits. For
this study a partial section of the succession
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Late Triassic facies from northeastern Mexico
Sierra de Salinas
Sierra de Catorce
Early Jurassic volcanics
Early Jurassic volcanics
Early Jurassic
shallow marine
and fluvial
deposits
BDE
LITHOLOGY
Volcanogenic products
Limestone
cross-bedded orthoquartzite
Sierra de Charcas
Conglomerate
Early Jurassic
volcanics
DEG
Thin-bedded shale and siltstone
Medium to thick-bedded sandstone
EDGF
Thin-laminated sandstone and shale
A
BDE
Mudstone
BC
C
A
Environments
N
S
EGF
DE
Po st-Tr iassic
d ep o sit s
E
0
W
Shallow marine
Lithofacies of Mutti and
Ricci Lucchi (1972) for
submarine fan deposits.
A
A
Channel margin
BC
Channel
A
Suprafan lobe
BDE
Levee
EDGF
BDE
Inter-channel zone
DEG
EDGF
Structures
A
Lat e Tr iassic
su bm ar in e fan
BC
C
Fluvial
DE
DEG
Graded bedding
Cross-lamination
AB
Wavy or convolute bedding
BC
Flute casts
Groove casts
Load casts
Bed truncations or pinching out
m
CB
DE
20
Slumps
Fining upward
10
0.0
Channel, Scour and fill
N
W
E
0
S
Ichnofauna
Intraclasts (clay)
Fossiliferous beds
Unconformity
Figure 4. Lithologic sections of the Late Triassic marine sequence, measured in La Ballena, Sierra de Charcas, and Sierra de
Catorce (see text for coordinates).
Geosphere, October 2010
625
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Barboza-Gudiño et al.
A
B
C
D
E
F
Figure 5. Facies of Potosí fan. (A) Flute casts on base of fine-grained sandstone bed, La Ballena area. Hammer used for scale is 32 cm
long. (B) Strongly deformed interchannel mudstone (facies G?) in La Ballena, Sierra de Salinas. Pen used for scale is 14 cm long.
(C) Thick-bedded sandstone of facies B (facies designations after Mutti and Ricci-Lucchi, 1972) showing upward-thickening cycles,
typical for channels or lobes at the base of distributary channels (normal position), Charcas area, San Luis Potosí. Persons are about
1.7 m. (D) Crossing groove casts at the base of thick-bedded turbidites, Charcas area. (E) Sandstone blocks floating in a fine-grained
sandstone matrix. Inner fan slump deposits of facies F in the Charcas outcrops. Hammer used for scale is 32 cm long. (F) Upwardthinning fine-grained sandstone to siltstone cycles of facies D and E (top to the left) in the Sierra de Catorce area, San Luis Potosí.
Hammer used for scale is 32 cm long.
626
Geosphere, October 2010
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Late Triassic facies from northeastern Mexico
cropping out in the Sierra de Catorce was also
measured in detail (coordinates of the base:
23.42.099′N/100°54.750′W (Fig. 4).
A relatively poorly understood succession of
intensely deformed fine-grained siltstone, shale,
lithic sandstone, and minor conglomerate and
carbonate rocks exposed along the Arroyo del
Taray in the Sierra de Teyra (Fig. 1) of northern Zacatecas was named the Taray Formation
(Córdoba-Méndez, 1964). The age of the Taray
Formation has been interpreted as late Paleozoic
(Córdoba-Méndez, 1964), Late Triassic (SilvaRomo et al., 2000), and Jurassic (Anderson
et al., 2005). Because of similar lithology and
stratigraphic position, this unit or part of it can
be correlated with the Triassic rocks described
in the Mesa Central and considered part of the
Potosi fan.
Using information provided by PEMEX
(in Tristán-González et al., 1995) from the
Tapona-1 well, north of Charcas (Fig. 1), it is
thought that there is a structural increase in the
thickness of this rock body, because several
folds and imbrications affect these strata and the
more than 4640 m drilled (the total depth of
the well represents the Triassic turbidite sequence)
without reaching the base. We estimate, without a
palinspastic reconstruction, a possible area extent
of the Potosí fan system of >120,000 km2. Several paleoflow patterns observed from groove
casts, flute casts, and cross-lamination in the
different localities (Fig. 4) show west-southwest
paleocurrent patterns.
It is also important to point out that in several
places, such as the Sierra de Teyra in northern
Zacatecas, or possible localities in Guanajuato
and Querétaro, such Triassic successions occur
as structural complexes interlayered with ophiolitic rocks and older sedimentary and metamorphic olistoliths. These exotic rocks are
enclosed in Triassic sand and mudstone-siltstone
strongly deformed matrix, a mélange indicating
ancient subduction or accretionary complexes
(Centeno-García, 2005).
Unconformably overlying the Triassic strata
in all localities in the Mesa Central, there is a
volcanic and volcaniclastic succession including basaltic andesites, rhyolites, and redbeds
assigned to the Nazas Formation (PantojaAlor, 1972) as well as a poorly understood
Early Jurassic succession of flat marine sedimentary rocks interlayered in the Sierra de
Catorce with the basal part of the Nazas Formation (Barboza-Gudiño et al., 2004; VenegasRodriguez et al., 2009).
The Triassic succession is inferred to overlie
Grenvillian granulitic basement on the basis of
several xenoliths contained in Cenozoic volcanic rocks in western San Luis Potosí (Ruiz
et al., 1988; Schaaf et al., 1994). This crystal-
line basement is believed to end to the west,
where the submarine fan deposits (Potosí fan)
have been interpreted to overlie oceanic crust
in Zacatecas (Centeno-García and Silva-Romo,
1997; Centeno-García, 2005), changing to an
ophiolitic complex in Guerrero-Michoacán and
Baja California (Centeno-García, 2005). At the
different localities the Triassic successions were
defined as lithostratigraphic units or in some
cases as structural complexes. We propose to
retain the name Zacatecas Formation for all the
successions of the Potosí fan that can be distinguished as a lithostratigraphic unit (e.g., Zacatecas, La Ballena, Charcas, and Real de Catorce)
and to use the term “complex” associated with
a local name for highly deformed rock bodies
consisting of a heterogeneous mixture of two or
more rock types, in some cases without a primary stratification preserved (e.g., Taray complex, Arteaga complex).
EL ALAMAR FLUVIAL SYSTEM:
CONTINENTAL FACIES OF THE
SIERRA MADRE ORIENTAL
Late Triassic and Early Jurassic strata in the
Sierra Madre Oriental in northeastern Mexico are
referred to as the Huizachal Group (Mixon et al.,
1959), consisting of the Late Triassic to Early
Jurassic La Boca Formation and the unconformably overlying La Joya Formation of Middle to
Late Jurassic age. These strata have been studied since the 1920s and stratigraphic nomenclature has evolved (Fig. 2). Heim (1940) assigned
a pre–Late Jurassic age for redbeds exposed in
the Huizachal, Peregrina, and Novillo Canyons,
in the Huizachal-Peregrina uplift, and the areas
of Miquihuana and Aramberri in Tamaulipas and
Nuevo León (Fig. 1). A Huizachal Formation
consisting of continental hematitic sandstone,
conglomerate, mudstone, and minor volcanic
rocks was formally defined by Imlay et al. (1948)
at the type locality in the Huizachal Canyon
20 km southwest of Ciudad Victoria, Tamaulipas.
Mixon et al. (1959) reported, in the lower
unit of their Huizachal Group, defined as
La Boca Formation, a floral assemblage of Late
Triassic age containing Pterophylum fragile,
Pterophylum inaequalle Fontaine, Cephalotaxopsis carolinensis, and Podozamites, which
were revised by Weber (1997) to Laurozamites
yaqui, “Ctenophylum braunianum,” Elatocladus ex gr. Carolinensis, and questionable
fragments of Podosamites, respectively. Weber
(1997) suggested that the flora is indicative of
the Late Triassic and more precisely of the Carnian or Norian.
The continental redbeds assigned to the upper
part of the La Boca Formation were deposited
during a period of crustal extension that fol-
Geosphere, October 2010
lowed Early Jurassic magmatic arc activity
(Fastovsky et al., 2005; Barboza-Gudiño et al.,
2008). Rocks of the La Boca Formation also
interfinger with volcanogenic deposits at several localities, including Huizachal and La Boca
Canyons, and contain a fossil assemblage of
vertebrate fauna, which allows assignment to
an Early to Middle Jurassic age for redbeds that
crop out in the Huizachal Canyon (Clark et al.,
1994). Typically, the La Joya Formation unconformably overlies the La Boca Formation and
represents the basal strata of the marine Late
Jurassic through Cretaceous succession.
By the last revision of the early Mesozoic
stratigraphy from the region, Rueda-Gaxiola
et al. (1993, 1999) proposed the Los San Pedros
allogroup, which includes a basal volcanogenic
unit in the Rio Blanco allomember, which is
overlain by a volcano-sedimentary allomember,
conforming both the Rhaetian–Hettangtian
Huizachal alloformation. The overlying
Sinemurian–Pliensbachian redbed succession
was defined by Rueda-Gaxiola et al. (1993) as
the La Boca alloformation. However, the type
locality of the Rio Blanco allomember was
defined north of Aramberri Nuevo León. At
this locality, 65 km away from the type locality of the La Boca alloformation, the volcanic
rocks yielded a U-Pb zircon age of 193 ± 0.2 Ma
(Barboza-Gudiño et al., 2008) directly overlying Paleozoic schist (Meiburg et al., 1987), and
the Triassic succession was not deposited.
Late Triassic continental strata in Nuevo
León and Tamaulipas (Figs. 1 and 6) consist of
sandstone, conglomeratic sandstone, siltstone,
and mudstone. The facies associations correspond to proximal alluvial fan, braided stream,
and distal meandering stream deposits, showing
several west-southwest paleocurrent patterns
that are in accordance with channel and trunk
orientations (Fig. 7). Such Triassic successions
in Tamaulipas (Fig. 6A) unconformably overlie Paleozoic strata or Precambrian–Paleozoic
basement, and are overlain by the Jurassic
redbeds considered as the upper part of the
La Boca Formation. In Nuevo Leon their
base is not exposed and there is no evidence
of deposition of Early Jurassic redbeds in this
area. This suggests a complex paleogeographic
distribution of basement uplift areas or horsts
during early Mesozoic time. Uplifts were probably separated by elongate grabens occupied
by trunk streams of the fluvial systems, as proposed by Michalzik (1991). The best-exposed
and best-preserved of these depocenters is the
San Marcos–El Alamar area of southern Nuevo
León, near the town of Galeana (Fig. 6B). Triassic fluvial successions are well exposed along
federal highway 58 (San Roberto-Linares).
Other exposures are also located near Santa
627
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Barboza-Gudiño et al.
TO LINARES
24°°00′
GOLFO
DE
MÉXICO
B
C
99°°30′
TAMAULIPAS
TA
MA
UL
IPA
S
NUEVO
LEÓN
24°°00′
NUEVO
LEÓN
MÉXICO
A
LB06-1
AC
IZ
100°°00′
B
Rancho
Nuevo
Santa Ana
GR
RE
PE
L-
24°°52′
La Crucita
HA
101°°14′
24°52′
GALEANA
La Boca
Nogales
HU
A. San Marcos Area
B. El Alamar Canyon
C. Huizachal-Peregrina Anticlinorium
A
N
Rancho
Nuevo
IN
AA
IC
NT
El Carrizo
SAN MARCOS
UM
RI
NO
LI
CIUDAD
VICTORIA
101°°14′
SM06-1
100°00′
Francisco
5 km
SANTA CLARA
24°°37′
24°°37′
24°°36′
Río de
San José
24°°36′
C
400 km
Lower Jurassic volcanic rocks
SIER
0
99°°30′
ABL
RA P
ILLO
San Felipe
Triassic fluvial succession
Joya
Verde
50
Huizachal
(TS = El Alamar Formation Type Section)
Independencia
Precambrian and Paleozoic rocks
El Alamar
24°31′
5 km
99°°52′
100°°00′
Late Jurassic-Cretaceous limestones
Lower to Middle Jurassic redbeds
El Encinal
Pablillo
El Taray
2.5 km
Cenozoic
cover
I. Madero
24°31′
Puerto de
Arrazola
SM06-1 = Sample
23°°33′
23°°33′
Figure 6. Geologic sketch maps of the Late Triassic continental sequence that crops out in the Sierra Madre Oriental, northeastern
Mexico. (A) San Marcos area, south of Galeana, Nuevo León. (B) El Alamar Canyon, Nuevo León. (C) Huizachal-Peregrina anticlinorium,
Tamaulipas (for key, see Fig. 3).
Clara, 2 km west of state highway 2, and at
El Alamar Canyon in the Sierra de Pablillo
(Fig. 6C). Triassic fluvial strata in the Galeana
area are the oldest rocks exposed in this region
and there are no exposures of their bases or
of any older strata. We measured three partial sections of continental strata in San Marcos (coordinates of the bottom of measured
section: 24°40.750′N/100°06.000′W) and El
628
Alamar Canyon, Nuevo León (coordinates:
24°55.130′N/099°55.000′W), and in La Boca
Canyon, Tamaulipas (Fig. 7). The section
at San Marcos has a minimum thickness of
180 m, and the El Alamar Canyon section
is more than 350 m thick. The succession
exposed consists of thick-bedded, medium- to
coarse-grained arkosic sandstone, predominantly gray, light green, or brownish-red. Sev-
Geosphere, October 2010
eral of the sandstones contain basal gravelly
to pebbly conglomeratic lag horizons, changing upward into finely laminated sandstones
and siltstones, commonly overlain by mudstones. The most abundant sedimentary structures are trough cross-beds and channel scours
(Figs. 8A, 8B); tabular burrows are common
in fine-grained facies. These lithologies represent fining-upward cycles, tens of meters in
Downloaded from geosphere.gsapubs.org on September 30, 2010
Late Triassic facies from northeastern Mexico
El Alamar Canyon
Upper Jurassic
La Casita Fm.
Upper Jurassic
La Joya Fm.
La Boca Canyon
Volcanogenic
deposits
Early Jurassic
fluvial and
shallow marine
deposits
N
W
n = 66
E
0
Fl
S
Gm
Fl
Sp
?
San Marcos area
Gt
Volcanogenic products
Limestone and marl
Limestone and gypsum
Mudstone
Siltstone
St
Gm
LITHOLOGY
Sl
St
Sp
Medium- to thick-bedded sandstone
Structureless pebbly sandstone
Cross-bedded sandstone
Sp
Fl
Fm
St
St
Sp
Conglomerate
Gm
Environments
Sl
St
Mafic sills
P
Fl
Fm
St
Gm
Floodplain
Sand flats
Gt
Gm
Sh
Sp
Minor channel system
Gm
Major channel system
Fm
Structures
St
Gm
Sl
Gm
Gt
Gt
Sp
100 m
Trough cross-beds
Small trough cross-beds
St
Gt
Graded bedding
Sl
P
Trench
Plants and rootlets
Sl
Gm
Sp
50
Sp
Sl
Tubular burrows
Sh
Fining upward
Gm
Chanel, scour and fill
Permo-Triassic (?) magmatic rocks
0
Concretions
Intraclasts (clay)
Fossiliferous beds
Facies code after Miall (1977, 1978)
Unconformity
Figure 7. Lithologic sections of the Late Triassic continental sequence, measured in La Boca Canyon, El Alamar Canyon, and
San Marcos area (see text for exact location).
Geosphere, October 2010
629
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Barboza-Gudiño et al.
A
B
C
D
E
F
Figure 8. Facies of El Alamar River. (A) Trough cross-bedding, developed in coarse-grained sandstone (facies St
after Miall, 1977, 1978). (B) Channel-fill sandstones incising mudstones in a road outcrop at San Marcos area.
(C) Poorly sorted conglomerate of the Gm facies, composed mainly of quartz, chert, quartzite greenstone, and
black shale pebbles, cropping out in La Boca Canyon, Tamaulipas. (D) Facies P of silicified concretions in mudstones, El Alamar Canyon. (E) Petrified trunk (chert and carbonate) in a conglomeratic sandstone, El Alamar
Canyon, Nuevo León. (F) Rhizoliths (five circular sections around the hammer) in fine-grained sandstone to
siltstone facies of the flood-plain deposits in the San Marcos area, Nuevo León. Hammer for scale is 32 cm long.
All facies designations herein are after Miall (1977, 1978).
thickness, interpreted as basal channels overlain by sand flats and overbank deposits,
formed in low sinuosity streams and braided
channels. Michalzik (1991) interpreted this
cyclic deposition as Donjek-type fluvial sedimentation, and recognized different lithofacies
630
using the codes of Miall (1977): conglomerate
(Fig. 8C) facies (Gm, Gt), trough and planar
cross-beds as well as horizontal-bedded coarse
sandstone (St, Sp, Sh), horizontal bedded and
planar cross-bedded sandstone (Sh, Sl), laminated and massive siltstone facies (Fl, Fm),
Geosphere, October 2010
and mudstone to siltstone facies with carbonate concretions (Fig. 8D) (Fm, P). There is a
notable abundance of petrified wood (Fig. 8E)
in the form of centimeter-long fragments of
tree trunks as much as 10 m long identified
as Araucarioxylon sp. (R.A. Scott, personal
Downloaded from geosphere.gsapubs.org on September 30, 2010
Late Triassic facies from northeastern Mexico
commun., in Carrillo-Bravo, 1961). The petrified wood is commonly associated with
Gm and Gt conglomerates and St, Sp coarsegrained sandstone, which represent channel
and channel bar deposits, principally in the
sequences exposed in La Boca canyon, in
Tamaulipas, and El Alamar Canyon, in Nuevo
León (Fig. 7). The section at La Boca canyon is
~350 m in thickness. Its base is not exposed as
it is in fault contact with Permian(?) intrusive
rocks (base of the measured section at coordinates 23°54.500′N/099°20.280′W).
Several decimeter-sized cylindrical burrow
casts are associated with the siltstone and mudstone facies, which represent floodplain deposits. Such structures are common in the upper
part of the sequence exposed in Cerro La Nieve,
in the San Marcos area. The burrows are perpendicular to bedding, as cylindrical 20–30-cmlong casts 5–15 cm in diameter. The casts are
filled by gray, green, and yellow siltstone and
mudstone, similar to the surrounding rocks
(Figs. 7 and 8F). Michalzik (1991) interpreted
these trace fossils as lungfish burrows, similar
to those reported in Late Triassic strata of the
Colorado Plateau (Dubiel et al., 1987). There
has been discussion on the origin of such similar
structures described from the Colorado Plateau
(McAllister et al., 1988), that were later interpreted as crayfish burrows and finally as rhizoliths (Tanner and Lucas, 2006). Burrows are
common in mudstones, and in silicified pedogenic gray to light green calcretes.
STRATIGRAPHIC REVISION
The Late Triassic–Early Jurassic continental facies, included in the La Boca Formation of Nuevo Leon and Tamaulipas, requires
stratigraphic revision. New field and analytical
evidence demonstrate the existence of a Late
Triassic fluvial succession, separated from an
overlying Early Jurassic volcanic-sedimentary
redbed succession. Interlayered volcanic rocks
yielded a 189.0 ± 0.2 Ma age (U-Pb, zircon) in
the basal part of the Jurassic redbeds exposed
in the Huizachal Valley (Fastovsky et al., 2005)
and a 193 ± 0.2 Ma U-Pb zircon age (BarbozaGudiño et al., 2008) for an ignimbrite of the
Aramberri area; both ages are younger than the
Triassic redbeds that crop out in the western and
northern part of the Huizachal Peregrina anticlinorium and the El Alamar–San Marcos area
in Nuevo León. In consequence, the basal Rio
Blanco allomember of the Huizachal alloformation, as defined by Rueda-Gaxiola et al. (1993),
is evidently Early Jurassic in age.
Considering the confusion generated by the
inclusion of the studied Triassic succession
within a formally defined stratigraphic unit of
Late Triassic–Early Jurassic age (La Boca Formation sensu Mixon et al., 1959), we formally
propose a new stratigraphic unit, named the El
Alamar formation, for the Late Triassic succession. The purpose of this newly defined unit is
to differentiate the Late Triassic succession,
which is identifiable by lithologic character-
istics and stratigraphic position. The name El
Alamar formation is derived from El Alamar
Canyon in the Sierra de Pablillo, Nuevo León,
where the proposed unit stratotype is located.
The defined type section is located in the western wall of El Alamar Canyon, 1.5 km north of
El Alamar de Abajo Ranch (Fig. 6C). El Alamar Canyon is located in the source area of the
Rio Pablillo, which drains the internal part of
the Sierra Madre to the Gulf of Mexico coastal
plain in the region of Linares, Nuevo León.
This locality may be accessed via an 11 km
route through the sierra, departing from the
town of Pablillo at the Nuevo León highway 2,
with good accessibility for a field vehicle. The
base of the sequence is not exposed, but the
measured section from the top at the coordinates
24°33.083′N/099°55.500′W to bottom at the
coordinates 24°55.133′N/099°55.000′W, consists of more than 350 m of siliciclastic fluvial
deposits as described in Table 1 (see also Fig. 7).
In the Huizachal-Peregrina anticlinorium
in Tamaulipas incomplete sections of El Alamar formation unconformably overlie Paleozoic metamorphic, sedimentary, and magmatic
rocks; the formation is in turn unconformably
overlain by Jurassic redbeds and volcanogenic
rocks (upper La Boca Formation sensu Mixon
et al., 1959) and/or Late Jurassic redbeds of the
La Joya Formation (upper Huizachal Group
sensu Mixon et al., 1959).
The Triassic sequence of the El Alamar
formation was considered by Carrillo-Bravo
TABLE 1. SIMPLIFIED MEASURED SECTION OF THE EL ALAMAR FORMATION AT
TYPE SECTION IN EL ALAMAR CANYON, STATE OF NUEVO LEÓN
Lithology
Unconformity, breccia (La Joya Formation)
Siltstone to mudstone, red-brown, fine planar cross-lamination
Sandstone to siltstone, red, mica rich, fine laminated, medium-bedded, small trough cross-bedding
Pebbly sandstone, red, structureless, conglomeratic sandstone
Coarse-grained to medium-grained sandstone to laminated, gray to red-brown siltstone, structureless
Conglomerate to conglomeratic sandstone with abundant white quartz pebbles
Siltstone to mudstone, red-purple and gray-green with conglomeratic lenses
Conglomeratic sandstone
Fine- to medium-grained sandstone, green
Coarse-grained and conglomeratic sandstone, gray-pink, mica rich, petrified wood, red-brown siltstone layers
Medium- to coarse-grained sandstone and siltstone, black shale intraclasts
Poorly sorted conglomerate, medium- to coarse-grained sandstone, conglomeratic sandstone
Siltstone, gray-green to medium-grained structureless sandstone
Poorly sorted conglomerate, well-rounded pebbles, quartz, quartzite, gray-black chert, and greenstone
Medium-grained sandstone, siltstone to mudstone, green to red-purple, medium-bedded, structureless
Conglomeratic sandstone
Medium-grained sandstone, laminated
Fine-grained sandstone to siltstone, red-purple, including chert and oxide concretions
Medium- to coarse-grained sandstone and conglomeratic sandstone, petrified wood fragments
Fine-grained sandstone and fine laminated siltstone, gray-green
Medium-grained, structureless sandstone and interbedded poorly sorted conglomerates, petrified wood
Conglomeratic sandstone changing upward to fine-grained and fine-laminated gray mica-rich sandstone
Medium- to coarse-grained sandstone, cross-bedding
Fine-grained sandstone, purple-red, thick-bedded, planar cross-lamination
Thick-bedded red conglomeratic to medium-grained sandstone, large planar cross-bedding
Base not exposed
Total thickness
Note: See text and Figure 6C for location.
Geosphere, October 2010
Depth
(m)
top
24
43
23
20
5
45
3
23
15
14
10
8
5
20
1
8
5
10
12
6
2
8
10
30
bottom
350
631
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Barboza-Gudiño et al.
632
succession of continental redbeds (La Boca
Formation) was generated during arc activity in
northeastern Mexico. The La Boca Formation
was deposited in an extensional period during
and after the magmatic arc activity. The La Boca
Formation is in turn unconformably overlain by
the La Joya Formation (Mixon et al., 1959),
which represents the base of the marine Late
Jurassic transgressive sequence coeval with
opening of the Gulf of Mexico.
ANALYTICAL RESULTS
U-Pb geochronology of detrital zircons was
performed to determine the maximal deposition age as well as the provenance of four sandstone samples. The samples CH06–1 (Charcas,
San Luis Potosí), RC06–31 (Sierra de Catorce,
San Luis Potosí), SM06–1 (San Marcos,
Nuevo León), and LB06–1 (La Boca Canyon,
Tamaulipas) were analyzed by laser ablation–
multicollector–inductively coupled plasma
mass spectrometry (LA-MC-ICPMS) at the Arizona LaserChron Center, following the separa-
tion and analysis techniques described in detail
in Gehrels et al. (2006). The analysis involves
the ablation of zircon with a New Wave/Lambda
Physic DUV193 Excimer laser (operating at a
wavelength of 193 nm) using a spot diameter of
15–35 µm. LA-ICPMS analysis is particularly
well suited for detrital zircon studies because of
the rapid generation of large data sets; we analyzed ~100 zircon crystals from each sample.
For each analysis, the errors in determining
206
Pb/238U and 206Pb/204Pb result in a measurement error of ~1%–2% (at 2σ level) in the
206
Pb/238U age. The errors in measurement of
206
Pb/207Pb and 206Pb/204Pb also result in ~1%–
2% (at 2σ level) uncertainty in age for grains
that are older than 1.0 Ga, but are substantially
larger for younger grains due to low intensity of
the 207Pb signal. For most analyses, the crossover in precision of 206Pb/238U and 206Pb/207Pb
ages occurs at 0.8–1.0 Ga.
The resulting ages are plotted in concordia
diagrams (Fig. 9) and are also shown on ageprobability plots (Ludwig, 2003). These plots
show each age and its uncertainty (measurement
S
CA
AR
CH
2600
Pb/ 238U
CE
2200
E
RD
R
TO
CA
206
(1961) as the basal part of the Huizachal Formation following the first definition of Imlay
et al. (1948), and this corresponds to member B
of La Boca Formation as described by Mixon
(1963) and originally defined by Mixon et al.
(1959). Member A of Mixon (1963) also corresponds to his member C, and appears as a
basal unit as a result of stratigraphic repetition
caused by normal and strike-slip faults. Strata
of the Triassic El Alamar formation were probably included in the Jurassic redbed succession
of the La Boca alloformation as defined by
Rueda-Gaxiola et al. (1993).
The El Alamar formation was identified on
the basis of similar lithology and a comparable
fluvial facies and subfacies along the western
flank of the Huizachal-Peregrina anticlinorium.
El Alamar strata are not exposed in the Huizachal
Valley south of Ciudad Victoria. In the San Marcos area, south of Galeana, Nuevo León, it is
well exposed along the federal highway 58, km
76.5, but is absent in the Miquihuana-Aramberri
area in southern Nuevo León and Tamaulipas,
where Paleozoic schist and phyllites are well
exposed, underlying Jurassic redbeds or volcanic rocks and Cretaceous marine beds.
The main criterion that permits discrimination
of the El Alamar and La Boca fluvial successions
is the conspicuous absence of volcanic rocks or
volcanogenic layers in the Triassic succession
(El Alamar Formation), in contrast to a common
occurrence of volcanogenic strata in the overlaying deposits of the Jurassic succession (La Boca
Formation). In addition, a general gray-green
and occasionally yellow to dark brown color is
distinctive of the El Alamar formation. This is in
contrast to a consistent red-purple and red-brown
color of the overlying Jurassic strata. The presence of abundant petrified wood is also characteristic of the Triassic unit.
The biostratigraphic age of the El Alamar formation is determined on the basis of Carnian–
Norian floras first reported by Mixon et al.
(1959) and reinterpreted by Weber (1997). A
Late Triassic age of deposition is also in agreement with an Early Triassic (245 Ma) maximum
depositional age indicated by the zircon geochronology described in the following. The El
Alamar formation is thus the same age as the
Late Triassic Zacatecas Formation, which represents the marine counterpart of the El Alamar
fluvial system. We show here that they also have
very similar provenance characteristics.
Volcanic and volcaniclastic strata overlying
the Triassic successions throughout the Mesa
Central and at several localities in the Sierra
Madre Oriental have been interpreted as remnants of the Early Jurassic Nazas continental arc
(Jones et al., 1995; Barboza-Gudiño et al., 1998;
Bartolini, 1998; Bartolini et al., 2003). A coeval
OS
1800
N
SA
RC
MA
1400
LA
CA
BO
1000
600
200
207
Pb/ 235U
Figure 9. U/Pb concordia-diagrams for the analyzed samples (2σ error ellipses). Locations
of samples are shown in Figures 3 (Potosí fan: RC06–31, CH06–1) and 6 (El Alamar River:
LB06–1, SM06–1).
Geosphere, October 2010
Downloaded from geosphere.gsapubs.org on September 30, 2010
Late Triassic facies from northeastern Mexico
25
CHARCAS
254 Ma
R e la t iv e p r o b a b ilit y
20
15
10
527 Ma
423 Ma
5
687 Ma
1242 Ma
1025 Ma
0
9
254 Ma
REAL DE CATORCE
8
7
R e la t iv e p r o b a b ilit y
960 Ma
6
5
4
583 Ma
3
Figure 10. Probability density
distribution histogram plots of
detrital zircons; all the samples show a main pick by 245–
269 Ma, corresponding with the
Permian–Triassic magmatic arc,
There are present also as main
populations, Pan-African (600–
450 Ma) and Grenvillian (1250–
900 Ma) zircons.
1167 Ma
508 Ma
2
1524 Ma1788 Ma
1
0
12
SAN MARCOS
269 Ma
977 Ma
10
R e la t iv e p r o b a b ilit y
8
1200 Ma
6
4
598 Ma
1315 Ma
2
0
245 Ma
LA BOCA
60
50
R e la t iv e p r o b a b ilit y
error only) as a normal distribution, and add all
ages from a sample into a single curve (Fig. 10;
Supplemental Table File1).
Maximal depositional ages between 216 and
214 Ma (sample collected in La Boca Canyon)
and 230 and 225 Ma (sample collected in the
Sierra de Charcas) correspond to the Late Triassic. The absence of Early Jurassic zircons also
indicates deposition of the succession prior to
the presence of the Early Jurassic volcanic arc
in the region, so that a real depositional age for
the analyzed samples in the Late Triassic may
be inferred, as also known from biostratigraphic
data for the marine sequence (Cantú-Chapa,
1969; Cuevas-Pérez, 1985; Gómez-Luna, 1998;
Gallo-Padilla et al., 1993) and the Late Triassic
flora found in the fluvial sequence exposed in
Nuevo León and Tamaulipas (Carrillo-Bravo,
1961; Mixon et al., 1959; Mixon, 1963; Weber,
1997). The maximum age of deposition for the
turbiditic succession exposed in the Sierra de
Catorce, San Luis Potosí, is 230–225 Ma (three
zircon ages between 237 and 209 Ma) and confirms a post–Late Permian age for these strata,
consistent with an interpreted Late Triassic age
(Martínez-Perez, 1972; López-Infanzón, 1986;
Cuevas Perez, 1985; Barboza-Gudiño et al.,
1999), but incompatible with an interpreted
late Paleozoic age (e.g., Bacon, 1978; Bartolini,
1998; Franco-Rubio, 1999).
A fundamental goal of the detrital zircon
geochronology was also the comparison of the
results between the analyzed samples in order
to correlate their maximal age of deposition, as
well as to compare provenance similarities. As
shown in Figures 9 and 10, there are notable
contributions of a Permian–Triassic detrital
zircon age population (280–245 Ma) in all of
the samples, corresponding with the eastern
Mexico Permian–Triassic magmatic arc, which
yields K-Ar ages from 284 to 232 Ma (Torres
et al., 1999; Dickinson and Lawton, 2001).
Other Paleozoic ages (467–420 Ma) probably
correspond to Ordovician–Silurian magmatic
rocks described in peri-Gondwanan terranes of
Mexico, like the Acatlán Complex (Miller et al.,
2007) or detrital zircon age populations present
in the Granjeno Schist in northeastern Mexico
(Nance et al., 2007) or the El Fuerte Formation
in Sinaloa (Vega-Granillo et al., 2008). There
are other populations present that correspond
to the Pan-African (700–500 Ma) and Grenvillian (1300–900 Ma) events, as well as subordinate Paleoproterozoic–Archean zircon age
populations. In sample LB06–1, collected in
40
30
20
10
1
Supplemental Table File. Excel file of four tables.
If you are viewing the PDF of this paper or reading it offline, please visit http://dx.doi.org/10.1130/
GES00545.S1 or the full-text article on www.gsapubs
.org to view the supplemental table file.
0
0
400
800
1200
1600
2000
2400
2800
Ma
Geosphere, October 2010
633
Downloaded from geosphere.gsapubs.org on September 30, 2010
Barboza-Gudiño et al.
Qt
Qm
Real de Catorce
Charcas
La Ballena
La Boca
Cañón del Novillo
Cañón del Alamar
San Marcos
Peregrina
Craton
interior
Transitional
continental
Recycled
orogenic
Craton
interior
Quartzose
recycled
Transitional
continental
Mixed
Transitional
recycled
Basement
uplift
Dissected arc
Dissected arc
Basement
uplift
Transitional arc
Transitional arc
undissected arc
Lithic
recycled
undissected arc
Lt
F
F
L
Figure 11. Ternary diagram (after Dickinson 1985), based on monocrystalline quartz (Qm), total feldspar (F), and lithic grains (Lt), showing provenance of the Triassic rocks from several localities in northeastern Mexico. Qm—monocrystalline quartz; F—feldspar—potassium
feldspar (K)+plagioclase (Pl); L—lithic fragments; Lt—L+ polycrystalline quartz (Qp).
La Boca Canyon, >70% of the zircons yielded
ages in the range 300–200 Ma, corresponding
to the Permian–Triassic arc, with an age pick
near 245 Ma and subordinate Pan-African and
Grenvillian zircon populations. This is probably
a result of the proximity of several outcrops of
the Permian magmatic rocks observed in the
Huizachal-Peregrina anticlinorium, close to
the depocenters of the fluvial facies.
The Charcas locality, the most western sampled locality, is also characterized by a prominent Late Permian peak (centered at 254 Ma
and accounting for 35% of the grains analyzed),
small populations of a few grains each for the
Mesoproterozoic (1300–900 Ma), Pan-African
(700–500 Ma), early Paleozoic (Silurian), and
isolated grains of Archean and Paleoproterozoic
age. The Real de Catorce locality shares the
abundance of Late Permian grains (20 grains
making 20% of the analyzed grains), but also
contains distinct peaks of Pan-African (508 and
583 Ma), Grenville (960 and 1167 Ma), and few
Paleoproterozoic grains. The section of the El
Alamar formation at the San Marcos locality is
nearly identical to the Real de Catorce locality.
Perhaps as notable as the presence of
Permian, Pan-African, and Grenvillian zircons
is the absence of Yavapai (ca. 1.7 Ga), Mazatzal
(ca. 1.6 Ga), and Mesoproterozoic (1.45–1.40 Ga)
zircons that might have been derived from basement typical of the American southwest (Amato
et al., 2008), and are present in Triassic strata
of the Colorado Plateau (Dickinson et al., 2007)
and Sonora (e.g., Gehrels and Stewart, 1998;
Gonzalez-León et al., 2005, 2009).
634
In order to correlate the studied sequences,
sediment-petrographic and geochemical studies were performed to define provenances
and a possible link between the Late Triassic fluvial deposits of El Alamar River (El
Alamar formation) and the Potosí fan (Zacatecas Formation). Like the distinct zircon age
populations, the sandstone petrology suggests similar source areas. This is shown by
applying petrographic and geochemical techniques such as the provenance triangles (after
Dickinson, 1985) that show continental block
and recycled orogen provenances (Fig. 11;
Table 2) and geochemical methods as shown
TABLE 2. POINT COUNTING DATA OF 16 SANDSTONE SAMPLES FROM THE
EL ALAMAR FORMATION (NUEVO LEÓN AND TAMAULIPAS) AND 9 SAMPLES
FROM THE ZACATECAS FORMATION (SAN LUIS POTOSÍ–ZACATECAS)
Sample
Qp
Qm
K
P
Ls
Lv
Lm
Mx
Total
Qt
El Alamar Formation
989
CAL.01
38
549
179
44
49
0
16
114
587
257
CAL.04
18
150
35
20
22
4
8
0
168
998
CAL1.1.
14
552
278
56
7
0
19
72
566
281
CAL1.1.1.
9
205
26
15
8
3
12
3
214
92
CAL1.1.4.
0
75
5
0
0
0
0
12
75
993
CAL1.1.8.
21
489
175
4
26
0
10
268
510
92
CAL1.1.3.
10
35
10
15
5
4
8
5
45
931
CAL1.2.4.
15
417
352
87
15
0
17
28
432
892
CN-2.1.
37
569
10
0
39
0
51
186
606
432
CN-2.2
64
225
5
0
27
0
12
99
289
1083
LBP03
37
502
297
99
4
2
34
108
539
1182
PRGRI
101
665
0
0
54
0
103
259
766
949
SMP2.1
51
417
164
14
56
13
65
169
468
795
SMP2.3
32
363
178
30
34
4
7
147
395
1273
SMP2.4
80
677
124
24
94
10
82
182
757
1065
SMP2.6
78
413
211
22
74
4
76
187
491
Lt
65
34
26
23
0
36
17
32
90
39
40
157
134
45
186
154
Zacatecas Formation
1030
CHR3.03.
60
482
258
61
23
3
49
94
542
75
1099
CHR6.03.
59
559
271
87
29
20
34
40
618
83
968
CHR8.03
68
475
226
48
54
5
27
65
543
86
1029
CHR9.03
66
492
261
73
27
2
64
44
558
93
89
ENC-1
0
35
25
10
5
4
3
7
35
12
1019
LB01
40
472
369
57
21
0
6
54
512
27
735
RC23
30
461
80
0
35
0
6
123
491
41
581
RC25
32
490
20
0
11
0
15
13
522
26
687
RC27
177
277
20
0
29
0
26
158
454
55
Note: Qp—polycrystalline quartz; Qm—monocrystalline quartz; K—potassic feldspar; P—plagioclase;
Ls—sedimentary lithic fragments; Lv—volcanic lithic fragments; Lm—metamorphic lithic fragments; Mx—matrix;
Qt—total quartz; Lt—total lithic fragments,
Geosphere, October 2010
Downloaded from geosphere.gsapubs.org on September 30, 2010
Late Triassic facies from northeastern Mexico
Rock/Chondrite
1000
El Alamar C.
Novillo C.
La Boca C.
San Marcos
100
10
A
1000 1
Rock/Chondrite
in the chondrite-normalized rare earth element (REE) plot (Fig. 12A). All REE patterns
show a negative Eu anomaly. This is indicative of provenance from igneous rocks, which
are formed by intracrustal differentiation with
plagioclase fractionation in the upper continental crust. There is a notable similarity with
light REE enrichment and a flat heavy REE
sector in all the cases. The Th/Sc versus Zr/Sc
plots (Fig. 12B) shows a zircon addition as a
result of sediment recycling; this is typical for
trailing-edge turbidites in a passive margin
(McLennan et al., 1993). Chemical data of the
six analyzed samples are shown in Table 3.
The only available isotopic data for Triassic
sediments are whole-rock Sm-Nd analyses of
sandstones collected in La Ballena and Zacatecas, reported by Centeno-García and SilvaRomo (1997); the initial εNd ratios are –5.2 and
–5.5, respectively, and are indicative of an old
upper continental crust provenance, as well as
the Nd-model ages of 1.6–1.3 Ga, in agreement with a model with an old continental
block. Likely sources are thus the Precambrian
Oaxaquia block and Pan-African basement in
the east-northeast part of the region.
Real de Catorce
La Ballena
Charcas
100
10
1
La Ce Pr NdSm Eu Gd Tb Dy Ho Er Tm Yb Lu
DISCUSSION
10
acid
Sediment Recycling
(Zircon Addition)
source rock
1
Th / Sc
.1
B
Compositional
Variations
.01
basic
The age, correlation, and tectonic and
paleogeographic settings of Triassic strata in
north-central and northeastern Mexico have
been the subject of considerable debate (see
Bartolini et al., 2001, and references therein).
A key observation is that volcanic and volcaniclastic rocks of Early Jurassic age overlie Triassic marine strata in north-central Mexico
(Fig. 13), for example at Sierra de Charcas,
Sierra de Catorce (Real de Catorce), and Sierra
de Salinas (La Ballena). Comparable Early
Jurassic strata also containing volcanic detritus
and flows overlie the Triassic fluvial succession assigned here to the El Alamar formation
in Nuevo León and Tamaulipas. Thus the Triassic redbeds of the El Alamar formation in
the region can be distinguished from younger
La Boca redbeds by the absence of volcanic
components and its distinct Triassic flora. Fossil flora indicate a Late Triassic age for the El
Alamar formation, which is thus at least in part
correlative with Late Triassic marine strata in
Zacatecas and San Luis Potosí, for which a
Ladinian–Carnian age is indicated by ammonoide fauna. The fact that Early Jurassic volcanic rocks overlie Triassic rocks and the lack
of Middle or Late Triassic detrital zircons in
Triassic strata studied suggest that a continental volcanic arc was not established in northcentral and northeastern Mexico until Early
Jurassic time. Triassic strata show no evidence
Figure 12. (A) Chondritenormalized rare earth element
(REE) patterns of 17 analyzed
samples. All rocks show very
similar patterns with light REE
enrichment and a flat heavy
REE pattern, characteristic for
a passive margin setting and a
negative Eu anomaly, typical for
upper continental crust with
an old upper continental crust
provenance (McLennan et al.,
1993). (B) Th/Sc versus Zr/Sc
(after McLennan et al., 1993)
for fine-grained sandstones
to mudstones from continental
to marine Triassic rocks from
northeastern Mexico. All analyzed rocks show a high Zr/Sc
ratio, typical for turbidite sands
from passive margins or for
recycling sediment because of
zircon addition. C.—canyon.
Charcas
La Boca
La Ballena
Novillo Canyon
El Alamar Canyon
San Marcos
R. de Catorce
composition
mafic
felsic
.001
.1
1
10
100
1000
Zr / Sc
of contemporaneous magmatism. Furthermore,
our results suggest that a gap in arc magmatism existed between the Early Triassic and the
Early Jurassic in northern Mexico. Admittedly,
our data set is small and Triassic magmatism
is evident in Coahuila (Molina-Garza and
Iriondo, 2005); therefore our data suggest at
least a significant decrease in magmatic activity, if not a complete gap in magmatism.
A large distance separates Triassic strata in
north-central and northwestern Mexico from
Geosphere, October 2010
other exposed Triassic successions, such as
pelagic strata and associated ophiolites of the
San Hipólito Formation in Baja California
(Sedlock and Yukio, 1990), Triassic continental to transitional marine strata of the Barranca Group in central Sonora (Stewart and
Roldán-Quintana, 1991), and Triassic shallow
to deep marine strata of the Antimonio and
Río Asunción Formations in northwest Sonora
(González-León et al., 2005). Thus establishing any relationship (paleogeographic,
635
636
76.95
0.475
9.58
5.15
1.10
0.031
0.42
2.29
0.67
0.11
3.21
99.98
63.33
0.584
11.34
4.71
1.51
0.061
6.51
1.63
2.26
0.13
8.03
100
69.07
0.710
14.24
6.71
1.49
0.030
0.36
1.25
2.57
0.14
3.41
99.97
73.13
0.839
11.77
4.78
0.95
0.036
1.34
2.44
1.67
0.11
3.20
100
69.42
0.951
10.07
5.18
2.11
0.119
3.92
1.40
1.59
0.12
5.20
100
77.26
0.657
10.36
3.69
2.06
0.058
0.28
1.50
1.23
0.07
3.00
100
69.82
0.770
13.43
5.77
2.19
0.036
0.26
0.16
2.98
0.07
4.04
99.53
28.33
0.464
11.46
11.31
4.44
0.501
21.13
0.17
1.47
0.14
19.96
99.37
66.13
0.569
14.81
4.38
3.51
0.155
1.74
0.23
3.63
0.32
4.59
100
81.25
0.577
12.22
0.47
0.17
0.003
0.05
0.20
1.70
0.05
2.38
99.07
65.31
0.996
15.69
8.42
1.86
0.036
0.14
0.40
2.96
0.05
4.28
100
74.86
0.537
11.58
3.74
1.20
0.044
0.46
2.64
1.68
0.08
2.40
99.21
TABLE 3. MAJOR AND TRACE ELEMENT COMPOSITION OF TRIASSIC SEDIMENTS FROM NORTHEASTERN MEXICO
Real de Catorce
San Marcos
El Alamar
La Boca
El Novillo
RC 23
RC 17
SMP 2.3B SMP 2.6B CAL 1.1 CAL 1.1.1 CAL 1.1.4 CAL 1.17
LB 3
CN 2.1
CN 1.3
CHR 1-3
62.07
0.874
18.54
5.43
1.92
0.035
0.43
0.71
4.37
0.15
5.39
99.92
66.87
0.804
14.81
2.14
0.77
0.017
0.80
0.87
3.43
0.08
9.55
100
Charcas
CHR 2-3 CHR 5-3
64.45
0.902
17.65
3.83
1.42
0.018
0.33
0.46
4.33
0.09
6.31
99.78
CHR 7-3
Trace elements (ppm)
Rb
179
35
30
91
84
53
57
37
108
62
126
71
92
67
198
138
190
Ba
1,040
197
139
411
606
653
582
325
927
634
905
557
773
411
927
721
1,010
Th
12.4
9.10
5.73
6.89
9.68
7.90
5.21
6.21
9.82
7.19
13.9
10.4
7.66
6.98
15.4
11.2
14.3
U
3.15
1.83
1.53
1.80
2.04
1.57
1.25
1.61
2.12
1.83
2.73
2.89
1.15
2.00
3.01
3.44
3.27
Ta
0.90
0.59
0.49
0.65
0.67
0.59
0.61
0.53
0.78
0.48
0.93
1.05
0.56
0.50
1.02
0.80
1.01
Nb
10.8
7.6
6.7
9.1
9.4
9.3
9.5
7.7
10.6
7.1
11.4
11.8
9.0
7.9
13.1
11.6
13.1
Pb
19
11
–5
–5
–5
5
–5
–5
–5
8
6
8
6
5
13
6
12
Sr
70
50
47
150
24
40
62
48
18
99
23
69
96
62
38
48
34
Zr
156
362
206
151
343
380
297
396
188
85
237
278
274
178
198
212
237
Hf
3.9
9.3
6.4
4.5
8.2
9.5
7.7
9.8
5.7
2.8
6.6
7.5
7.3
4.9
5.3
5.7
6.4
Y
34.0
17.0
22.4
26.9
19.9
17.5
25.0
17.9
21.4
48.9
45.6
22.5
17.4
15.7
36.1
27.9
28.8
Sc
19
8
7
11
13
11
13
9
15
13
12
7
20
10
21
16
19
V
206
60
54
82
101
78
82
62
104
81
59
53
116
70
152
141
149
Cr
139
35
34
57
46
42
92
32
57
61
–20
31
77
36
83
64
81
Co
6
6
6
9
17
9
16
7
13
43
17
–1
16
7
10
6
6
Ni
35
–20
28
27
–20
–20
40
–20
26
77
–20
–20
31
–20
24
–20
–20
Cs
10.5
1.8
4.2
7.1
5.8
2.4
6.4
3.4
9.4
5.2
5.0
2.9
9.0
15.8
28.0
17.3
30.9
Zn
127
–30
–30
–30
52
32
54
56
90
202
110
–30
47
–30
58
–30
55
La
28.2
26.6
17.8
39.3
29.9
22.9
26.0
18.7
18.5
34.2
57.8
32.0
43.1
20.3
36.5
29.9
33.3
Ce
50.4
55.4
36.8
49.1
59.8
50.4
55.1
38.5
34.6
84.1
101
68.1
107
41.3
79.1
62.1
70.5
Pr
5.59
6.40
4.24
7.68
6.82
6.05
7.02
4.62
3.89
9.07
13.2
7.83
12.0
4.88
9.44
7.26
8.32
Nd
21.2
25.2
17.1
31.9
25.5
24.9
28.5
18.4
15.3
38.2
52.0
29.9
49.6
19.2
38.1
28.5
32.0
Sm
4.78
5.15
3.94
6.52
4.52
5.56
5.92
3.89
3.16
9.61
11.0
5.99
8.82
3.82
8.06
5.67
6.39
Eu
1.16
0.992
1.04
1.39
1.07
1.36
1.41
0.893
0.661
2.50
2.03
1.01
1.68
0.641
1.66
1.21
1.20
Tl
1.12
0.28
0.26
0.76
0.60
0.40
0.42
0.29
0.81
0.46
0.93
0.54
0.90
0.45
1.28
0.78
1.01
Gd
5.55
4.14
4.79
6.49
4.07
4.71
5.31
3.59
3.25
10.3
9.45
4.40
5.30
3.37
7.19
4.79
4.95
Tb
1.00
0.64
0.83
0.92
0.67
0.71
0.88
0.63
0.61
1.72
1.49
0.79
0.73
0.54
1.25
0.87
0.91
Dy
5.72
3.38
4.65
4.97
3.89
3.61
4.82
3.51
3.94
9.24
8.18
4.48
3.81
3.12
6.95
5.25
5.52
Ho
1.16
0.64
0.87
0.91
0.76
0.69
0.93
0.69
0.83
1.68
1.61
0.86
0.71
0.60
1.35
1.04
1.09
Er
3.72
2.11
2.66
2.86
2.51
2.18
3.03
2.17
2.87
5.08
5.39
2.84
2.30
1.99
4.29
3.38
3.58
Tm
0.579
0.316
0.377
0.415
0.377
0.315
0.450
0.314
0.459
0.703
0.848
0.442
0.347
0.302
0.645
0.521
0.565
Yb
3.42
2.04
2.18
2.53
2.47
2.05
2.89
1.90
2.96
4.19
5.08
2.60
2.26
1.81
3.77
3.04
3.30
Lu
0.544
0.324
0.334
0.392
0.391
0.329
0.426
0.297
0.458
0.627
0.829
0.406
0.362
0.298
0.585
0.489
0.541
Note: LOI—loss on ignition. Analyses performed by inductively coupled plasma–mass spectrometry at Activation Laboratories, Ltd. (Ancaster, Ontario, Canada). For sample locations, see Figures 3 and 6.
Locality
La Ballena
Sample
LBP 02
LBP 03
Major elements (wt%)
SiO2
61.69
79.88
0.790
0.627
Ti O2
17.61
9.21
Al2O3
5.62
3.37
Fe2O3
MgO
1.87
0.60
MnO
0.013
0.040
CaO
0.39
0.60
0.64
3.00
Na2O
3.72
0.79
K2O
0.13
0.10
P2O5
LOI
6.91
1.79
Total
99.37
100
Downloaded from geosphere.gsapubs.org on September 30, 2010
Barboza-Gudiño et al.
Geosphere, October 2010
Downloaded from geosphere.gsapubs.org on September 30, 2010
Late Triassic facies from northeastern Mexico
LA BALLENA
CHARCAS
REAL DE
CATORCE
MIQUIHUANA
ARAMBERRI
CAÑÓN DEL
NOVILLO
VALLE DEL
HUIZACHAL
CAÑÓN DE
LA BOCA
SAN MARCOS
La Casita Formation
Cretaceous Carbonates
La Caja Formation
La Joya Formation
Zuloaga Formation
NazasFormation
Red beds
Zuloaga Formation
Olvido Gyps
Minas Viejas Gyps La Joya Formation
La Boca Formation
CAÑÓN DEL
ALAMAR
Zuloaga Formation
Zuloaga Group
Volcanic rocks Huizachal
Marginal marine facies
(Huayacocotla Formation)
Group
Precambrian-Paleozoic metamorphic basement
El Alamar formation
Zacatecas Formation
Figure 13. Correlation of pre-Cretaceous units of the studied areas in central to northeastern Mexico. Late Triassic El Alamar formation
overlies Paleozoic magmatic, metamorphic, and sedimentary rocks in the northern part of the Huizachal-Peregrina anticlinorium and is
absent in the Aramberri-Miquihuana high. The base of the marine turbiditic sequence (Zacatecas Formation) of the Potosí Fan is unknown,
and probably overlies continental crust at the western margin of nuclear Mexico and far to the west on ancient oceanic crust.
tectonic, or other) between the Triassic successions in northeastern Mexico and other
Triassic sections along in the Pacific margin
is difficult. Nonetheless, all Triassic sections
across northern Mexico are consistent with the
proposal that Mexico faced an open oceanic
basin to the west in Triassic time (OrtegaGutiérrez et al., 1994).
Nearly half of the detrital zircons in each of
the four samples were likely derived from the
eastern Mexico Permian arc, which encompasses outcrops near Las Delicias in Coahuila,
subsurface plutonic rocks in Tamaulipas, the La
Mixtequita massif in Oaxaca, and the Chiapas
massif (Torres et al., 1999; Weber et al., 2003).
A large component was derived from bedrock
sources of Grenvillian age (1250–900 Ma) of
the Oaxaquian subcontinent (Ortega-Gutiérrez
et al., 1995) or possibly reworked from
Ouachita rock assemblages. A potential source
for Pan-African zircons exists in basement
rocks of the Yucatan Peninsula (then positioned
against the Texas and Louisiana coast (MolinaGarza et al., 1992), Coahuila (Lopez et al.,
2001), southeast Texas, and Florida (Dallmeyer
et al., 1987; Mueller et al., 1994), although they
may also have been recycled from Paleozoic
strata of the Ouachita orogen. Detrital zircons
in Triassic rocks in north-central and northeastern Mexico show some similarity with Triassic
rocks of the Dockum Group. The Trujillo Formation contains important populations of PanAfrican (700–380 Ma) and Grenvillian (1250–
900 Ma; Fox et al., 2005; Dickinson and
Gehrels, 2008) zircons.
Detrital zircons typical of the American
Southwest are absent from both marine and
continental Triassic rocks studied. In contrast,
zircons in the Barranca Group, in Sonora, show
a distinct peak of grains with ages near 1.42 Ga
(Gehrels and Stewart, 1998; González-León
et al., 2009), consistent with its close relationship with the western Cordillera.
Strata of the Zacatecas Formation and associated strata in Charcas and Real de Catorce
are interpreted as part of a large-scale submarine fan system, the Potosí fan (CentenoGarcía, 2005). Submarine fans are typically
associated with extensive fluvial systems that
drain a large continental basin. Thus, as a first
approximation we hypothesize the relationship between the El Alamar fluvial system
and the Potosí fan probably as the result of
the river valley draining an extensive portion
of western equatorial Pangea during Triassic
time, with flow to the paleo-Pacific margin
to the west (Fig. 14). Paleocurrent geochemical and detrital zircon data all support this
hypothesis, which is based on their zircon
provenance from Grenvillian and Pan-African
basement rocks as well as the Permian–
Triassic magmatic arc. In addition, the consistent directions of sediment transport based
in some types of measured directional structures (e.g., flute casts and groove casts) in
the marine facies, represented in Figure 4, or
cross-bedding, and channel and trunk orientation in the continental facies (Fig. 7), agree in
all the cases with paleocurrent patterns toward
the west and southwest.
Geosphere, October 2010
The Triassic strata of northeastern Mexico
have important implications for the existence of the Mojave-Sonora megashear, a
great buried left-lateral strike-slip fault that
is inferred to have displaced ~800 km most
of northern Mexico, including the Ouachita
suture and the Jurassic continental arc of
northern Sonora, southeastward in Jurassic
time (Anderson and Silver, 1979; Anderson
and Schmidt, 1983; Jones et al., 1995). The
Triassic marine strata in Zacatecas and San
Luis Potosí and Triassic continental strata
in Tamaulipas and Nuevo León are south
of the inferred trace of the Mojave-Sonora
megashear. Had this displacement existed,
these units should have been located 800 km
to the northwest of their present position in
Triassic time. Detrital zircon geochronology
for Triassic rocks does not support the model
of large left-lateral displacement. Besides the
absence of detrital zircons from Precambrian
provinces such as Yavapai and Mazatzal, and
Mesoproterozoic zircons (1.45–1.40 Ga), we
note that a suitable source for Pan-African zircons could not be easily found had these rocks
been in a position suggested by reconstruction of displacement by the Mojave-Sonora
megashear. Furthermore, Grenvillian zircon
sources in northwest Mexico are restricted to
ages of ca. 1.2–1.1 Ga (Barbeau et al., 2005;
Dickinson et al., 2007), whereas zircons in
the Zacatecas Formation and the El Alamar
formation are more typical of Oaxaquia Grenvillian ages (1250–900 Ma; Keppie et al.,
2001; Solari et al., 2003, 2004).
637
Downloaded from geosphere.gsapubs.org on September 30, 2010
be
lt
Barboza-Gudiño et al.
hit
a
North America
(Laurentia)
ac
Florid
Ou
a
tán
a
c
Yu
Alamar
River
Fa
n
Gr
a
ui
aq
sí
ax
O
Po
to
ca
i
r
e )
m
a
A
n
a
uthndw
o
S o
(G
an
jen
o-A
c
atl
án
Nascent Early Late Paleozoic
Mesozoic
subduction
subduction
Paleo-Pacific
Permo-Triassic
arc
be
lt
Permo-Triassic plutons
Pan-African blocks
Grenvillean basement
Figure 14. Paleogeographic reconstruction of Mexico for the time during deposition of the
Potosí fan (Late Triassic) indicating provenance from Grenvillian (Oaxaquia block), PanAfrican (Yucatan, actual southeasternmost United States, and Gondwana), and Permian–
Triassic (east Mexico magmatic arc) sources. Detrital zircon geochronology, paleo-flow patterns, petrography, and geochemical studies support such sources as well as sources from
the Ouachita collisional belt.
ACKNOWLEDGMENTS
We acknowledge support from projects CONACYT
2002-CO2-41239 (Consejo Nacional de Ciencia
y Tecnología), Programa de Apoyo al Desarrollo
Universitario (PROADU) 2003-01-24-001-53, and
Fondo de Apoyo a las Investigación FAI/UASLP
C06-FAI-11-33.70 (Universidad Autónoma de San
Luis Potosí). We thank Victor Valencia and Alexander
Pullen (LaserChron Laboratory, University of Arizona) for technical support and suggestions, Kelly
Hayes and Delfino Ruvalcaba for revision of the
English text, and Roberto Molina Garza for revision and suggestions. We appreciate the constructive
reviews of Timothy F. Lawton, Spencer G. Lucas, and
William R. Dickinson.
REFERENCES CITED
Amato, J.M., Boullion, A.O., Serna, A.M., Sanders, A.E.,
Farmer, G.L., Gehrels, G.E., and Wooden, J.L., 2008,
Evolution of the Mazatzal province and the timing of
the Mazatzal orogeny: Insights of U-Pb geochronology and geochemistry of igneous and metasedimentary
rocks in southern New Mexico: Geological Society of
America Bulletin, v. 120, p. 328–346, doi: 10.1130/
B26200.1.
638
Anderson, T.H., and Schmidt, V.A., 1983, A model of the
evolution of Middle America and the Gulf of Mexico–
Caribbean Sea region during Mesozoic time: Geological Society of America Bulletin, v. 94, p. 941–966, doi:
10.1130/0016-7606(1983)94<941:TEOMAA>2.0
.CO;2.
Anderson, T.H., and Silver, L.T., 1979, The role of the
Mojave-Sonora megashear in the tectonic evolution of
northern Sonora, in Anderson, T.H., and Roldán Quintana, J., eds., Geology of northern Sonora Guidebook,
Annual Meeting of the Geological Society of America:
Estación Noroeste, Instituto de Geología, Universidad
Nacional Autónoma de México and the University of
Pittsburgh, p. 59–68.
Anderson, T.H., Jones, N.W., and McKee, J.W., 2005, The
Taray Formation: Jurassic(?) mélange in northern
Mexico—Tectonic implications, in Anderson T.H.,
et al., eds., The Mojave-Sonora megashear hypothesis:
Development, assessment and alternatives: Geological
Society of America Special Paper 393, p. 233–258, doi:
10.1130/0-8137-2393-0.427.
Bacon, R.W., 1978, Geology of the northern Sierra de
Catorce, San Luis Potosí, México [M.S. thesis]:
Arlington, University of Texas, 124 p.
Barbeau, D.L., Jr., Ducea, M.N., Gehrels, G.E., Kidder, S.,
Wetmore, P.H., and Saleeby, J.B., 2005, U-Pb detritalzircon geochronology of northern Salinian basement
and cover rocks: Geological Society of America Bulletin, v. 117, p. 466–481, doi: 10.1130/B25496.1.
Geosphere, October 2010
Barboza-Gudiño, J.R., Tristan-Gónzalez, M., and TorresHernández, J.R., 1999, Tectonic setting of preOxfordian units from central and northeastern Mexico:
A review, in Bartolini, C., et al., eds., Mesozoic sedimentary and tectonic history of north-central Mexico:
Geological Society of America Special Paper 340,
p. 197–210, doi: 10.1130/0-8137-2340-X.197.
Barboza-Gudiño, J.R., Torres-Hernández, J.R., and TristánGonzález, M., 1998, The Late Triassic–Early Jurassic
active continental margin of western North America in
northeastern México: Geofísica Internacional, v. 37,
p. 283–292.
Barboza-Gudiño, J.R., Hoppe, M., Gómez-Anguiano, M.,
and Martínez-Macías, P.R., 2004, Aportaciones para la
interpretación estratigráfica y estructural de la porción
noroccidental de la Sierra de Catorce, San Luis Potosí,
México: Revista Mexicana de Ciencias Geológicas,
v. 21, p. 299–319.
Barboza-Gudiño, J.R., Orozco-Esquivel, M.T., GómezAnguiano, M., and Zavala-Monsiváis, A., 2008, The
Early Mesozoic volcanic arc of western North America in northeastern Mexico: Journal of South American Earth Sciences, v. 25, p. 49–63, doi: 10.1016/
j.jsames.2007.08.003.
Bartolini, C., 1998, Stratigraphy, geochemistry, geochronology and tectonic setting of the Mesozoic Nazas Formation, north-central Mexico [Ph.D. thesis]: El Paso,
University of Texas, 557 p.
Bartolini, C., Lang, H., Cantú-Chapa, A., and BarbozaGudiño, J.R., 2001, The Triassic Zacatecas Formation
in central Mexico: Paleotectonic, paleogeographic
and paleobiogeographic implications, in Bartolini, C.,
et al., eds., The western Gulf of Mexico Basin: Tectonics, sedimentary basins and petroleum systems: American Association of Petroleum Geologists Memoir 75,
p. 295–315.
Bartolini, C., Lang, H., and Spell, T., 2003, Geochronology,
geochemistry, and tectonic setting of the Mesozoic
Nazas arc in north-central Mexico, and its continuation to northern South America, in Bartolini, C., et al.,
eds., The Circum-Gulf of Mexico and the Caribbean:
Hydrocarbon habitats, basin formation and plate tectonics: American Association of Petroleum Geologists
Memoir 79, p. 427–461.
Burckhardt, C., and Scalia, S., 1905, La faune marine du
Trias Supérieur de Zacatecas: Instituto de Geología de
México Boletín 21, 44 p.
Cantú-Chapa, A., 1969, Una nueva localidad del Triásico
Superior marino en México: Instituto Mexicano del
Petróleo Revista, v. 1, p. 71–72.
Carrillo-Bravo, J., 1961, Geología del Anticlinorio HuizachalPeregrina al NW de Ciudad Victoria, Tamaulipas:
Asociación Mexicana de Geólogos Petroleros Boletin
(Instituto de Estudios de Poblacion y Desarrollo,
Dominican Republic), v. 13, p. 1–98.
Carrillo-Bravo, J., 1982, Exploración petrolera de la Cuenca
Mesozoica del Centro de México: Boletín de la Asociación Mexicana de Geólogos Petroleros, v. 34, p. 21–46.
Centeno-García, E., 2005, Review of upper Paleozoic and
Mesozoic stratigraphy and depositional environments
of central and west Mexico: Constraints on terrane
analysis and paleogeography, in Anderson, T.H.,
et al., eds., The Mojave-Sonora megashear hypothesis:
Development, assessment and alternatives: Geological
Society of America Special Paper 393, p. 233–258, doi:
10.1130/0-8137-2393-0.233.
Centeno-García, E., and Silva-Romo, G., 1997, Petrogenesis
and tectonic evolution of central Mexico during
Triassic–Jurassic time: Revista Mexicana de Ciencias
Geológicas, v. 14, no. 2, p. 244–260.
Chávez-Aguirre, R., 1968, Bósquejo Geológico de la Sierra
Peñón Blanco, Zacatecas [thesis]: Facultad de Ingeniería,
Universidad Nacional Autónoma de México, 67 p.
Clark, J.M., Montellano, M., Hopson, J.A., Hernández, R.R.,
and Fastovsky, D.E., 1994, An Early or Middle Jurassic tetrapod assemblage from the La Boca Formation,
northeastern Mexico, in Fraser, N.C., and Sues, H.-D.,
eds., In the shadow of the dinosaurs: Cambridge, Cambridge University Press, p. 294–302.
Córdoba-Méndez, D.A., 1964, Geology of Apizolaya quadrangle (east half), northern Zacatecas, Mexico [M.S.
thesis]: Austin, University of Texas, 111 p.
Downloaded from geosphere.gsapubs.org on September 30, 2010
Late Triassic facies from northeastern Mexico
Cuevas Pérez, E., 1985, Geologie des Alteren Mesozoikums
in Zacatecas und San Luis Potosí, Mexiko [Ph.D.
thesis]: Marburg, Germany, Philipps-Universität Marburg, 182 p.
Dallmeyer, R.D., Caen-Vachette, M., and Villeneuve, M.,
1987, Emplacement age of the post-tectonic granites
in southern Guinea (West Africa) and the peninsular
Florida subsurface: Implications for origins of southern Appalachians exotic terranes: Geological Society
of America Bulletin, v. 99, p. 87–93, doi: 10.1130/
0016-7606(1987)99<87:EAOPGI>2.0.CO;2.
Dickinson, W.R., 1985, Interpreting provenance relations
from detrital modes of sandstones, in Zuffa, G.G.,
ed., Provenance of arenites: Lancaster, Pennsylvania,
Reidel Publishing, p. 333–361.
Dickinson, W.R., and Gehrels, G.E., 2008, U-Pb ages of
detrital zircons in relation to paleogeography: Triassic
paleodrainage networks and sediment dispersal across
southwest Laurentia: Journal of Sedimentary Research,
v. 78, p. 745–764, doi: 10.2110/jsr.2008.088.
Dickinson, W.R., and Lawton, T.F., 2001, Carboniferous to
Cretaceous assembly and fragmentation of Mexico:
Geological Society of America Bulletin, v. 113, p.
1142–1160, doi: 10.1130/0016-7606(2001)113<1142
:CTCAAF>2.0.CO;2.
Dickinson, W.R., Gehrels, G.E., Fox, J.D., Stair, K.N.,
Anderson, C.E., Ojha, J., Brown, R.A., Norton, M.B.,
Riggs, N.R., and Lehman, T.M., 2007, Sediment dispersal in Triassic fluvial systems of southwest Laurentia: Insights from U-Pb ages of detrital zircons: Geological Society of America Abstracts with Programs,
v. 39, no. 6, p. 235.
Dubiel, R.F., Blodgett, R.H., and Bown, T.M., 1987, Lungfish burrows in the Upper Triassic Chinle and Dolores
Formations, Colorado Plateau: Journal of Sedimentary
Petrology, v. 57, p. 512–521.
Fastovsky, D.E., Hermes, O.D., Strater, N.H., Bowring,
S.A., Clark, J.M., Montellano, M., and Hernández,
R.R., 2005, Pre-Late Jurassic, fossil-bearing volcanic and sedimentary red beds of Huizachal Canyon,
Tamaulipas, Mexico, in Anderson T.H., et al., eds., The
Mojave-Sonora megashear hypothesis: Development,
assessment and alternatives: Geological Society of
America Special Paper 393, p. 233–258, doi: 10.1130/
0-8137-2393-0.401.
Fox, J.D., Stair, K.N., and Lehman, T.M., 2005, Detrital zircons in Upper Triassic strata of the Upper Chinle and
Dockum Groups, New Mexico and Texas (abs.): 101st
Annual Meeting of the Cordilleran Section, Geological
Society of America, Abstracts with Programs, v. 38,
no., 5, p. 10.
Franco-Rubio, M., 1999, Geology of the basement below
the decollement surface, Sierra de Catorce, San Luis
Potosí, México, in Bartolini, C., et al., eds., Mesozoic
sedimentary and tectonic history of north-central Mexico: Geological Society of America Special Paper 340,
p. 211–227, doi: 10.1130/0-8137-2340-X.211.
Gallo-Padilla, I., Gómez-Luna, M.E., Contreras, B., and
Cedillo, P.E., 1993, Hallazgos Paleontológicos del
Triásico marino en la región central de México: Revista
de la Sociedad Mexicana de Paleontología, v. 6, p. 1–9.
Gehrels, G.E., and Stewart, J.H., 1998, Detrital zircon
U-Pb geochronology of Cambrian to Triassic miogeoclinal strata of Sonora, Mexico: Journal of Geophysical Research, v. 103, p. 2471–2488, doi: 10.1029/
97JB03251.
Gehrels, G.E., Valencia, V.A., and Pullen, A., 2006,
Detrital zircon geochronology by laser ablation multicollector ICPMS at the Arizona LaserChron Center, in
Olszewski, T., ed., Geochronology: Emerging opportunities: Paleontology Society Short Course: Paleontological Society Papers, v. 12, p. 67–76.
Gómez-Luna, M.E., Cedillo-Pardo, E., Contreras, B.,
Gallo-Padilla, I., and Martínez-Cortés, C. A., 1998, El
Triásico marino de la Mesa Central de México: Implicaciones Paleogeográficas: II convención sobre la evolución geológica de México y de recursos asociados,
Simposia y Coloquio, extended abstracts, p. 67–71.
González-León, C.M., Stanley, G.D., Jr., Gehrels, G.E., and
Centeno-García, E., 2005, New data on the lithostratigraphy, detrital zircon and Nd isotope provenance, and
paleogeographic setting of the El Antimonio Group,
Sonora, Mexico, in Anderson T.H., et al., eds., The
Mojave-Sonora megashear hypothesis: Development,
assessment and alternatives: Geological Society of
America Special Paper 393, p. 259–282, doi: 10.1130/
0-8137-2393-0.259.
Gonzalez-León, C.M., Valencia, V.A., Lawton, T.F., Amato,
J.M., Gehrels, G.F., Leggett, W.J., Montijo-Contreras,
O., and Fernández, M.A., 2009, The lower Mesozoic record of detrital zircon U-Pb geochronology of
Sonora, Mexico and its paleogeographic implications:
Revista Mexicana de Ciencias Geológicas, v. 26,
p. 301–314.
Gutierrez-Amador, M., 1908, Las capas cárnicas de Zacatecas: Boletín de la Sociedad Geológica Mexicana, v. 4,
p. 29–35.
Heim, A., 1940, The front ranges of the Sierra Madre Oriental, Mexico, from Ciudad Victoria to Tamazunchale:
Eclogae Geologicae Helvetiae, v. 33, p. 313–352.
Hoppe, M., 2000, Geologische Kartierung (1:10 000) im
Gebiet Ojo de Agua, nordwestliche Sierra de Catorce
und sedimentpetrologische Untersuchungen an präober jurassischen Sedimenten (“Zacatecas Formation”). [M.S. thesis]: Clausthal-Zellerfeld, Germany,
Technische Universität Clausthal, 235 p.
Hoppe, M., Barboza-Gudiño, J.R., and Schulz, H.M., 2002,
Late Triassic submarine fan in northwestern San Luis
Potosí, México—Lithology, facies and diagenesis:
Neues Jahrbuch für Geologie und Paläontologie,
v. 2002, p. 705–724.
Imlay, R.W., Cepeda, E., Álvarez, M., Jr., and Diaz, T., 1948,
Stratigraphic relations of certain Jurassic formations in
eastern Mexico: American Association of Petroleum
Geologists Bulletin, v. 32, p. 1750–1761.
Jones, N.W., McKee, J.W., Anderson, T.H., and Silver, L.T.,
1995, Jurassic volcanic rocks in northeastern Mexico:
A possible remnant of a Cordilleran magmatic arc, in
Jacques-Ayala, C., et al., eds., Studies on the Mesozoic of Sonora and adjacent areas: Geological Society of America Special Paper 301, p. 179–190, doi:
10.1130/0-8137-2301-9.179.
Keppie, J.D., Dostal, J., Ortega-Gutierrez, F., and López, R.,
2001, A Grenvillian arc on the margin of Amazonia:
Evidence from the southern Oaxacan Complex, southern Mexico: Precambrian Research, v. 112, p. 165–
181, doi: 10.1016/S0301-9268(00)00150-9.
Lopez, R., Cameron, K.L., and Jones, N.W., 2001, Evidence
of Paleoproterozoic, Grenvillian and Pan African age
Gondwanan crust beneath northeastern Mexico: Precambrian Research, v. 107, p. 195–214, doi: 10.1016/
S0301-9268(00)00140-6.
López-Infanzón, M., 1986, Estudio petrogenético de las
rocas ígneas en las Formaciones Huizachal y Nazas:
Boletín de la Sociedad Geológica Mexicana, v. 47,
no. 2, p. 1–42.
Ludwig, K.R., 2003, Isoplot 3.00: A geochronological toolkit for Microsoft Excel: Berkeley Geochronology Center Special Publication 4, 70 p.
Maldonado-Koerdell, M., 1948, Nuevos datos geológicos y
paleontológicos sobre el Triásico de Zacatecas: Anales
de la Escuela Nacional de Ciencias Biológicas, v. 5,
p. 291–306.
Martínez-Pérez, J., 1972, Exploración geológica del área
El Estribo-San Francisco, San Luis Potosí: Boletín
de la Asociación Mexicana de Geólogos Petroleros,
v. 24, p. 327–402.
McAllister, J.A., Dubiel, R.F., Blodgett, R.H., and Bown,
T.M., 1988, Lungfish burrows in the Upper Triassic
Chinle and Dolores formations, Colorado Plateau;
comments on the recognition criteria of fossil lungfish
burrows: Discussion and Reply: Journal of Sedimentary Research, v. 58, p. 365–369.
McLennan, S.M., Hemming, S., McDaniel, D.K., and
Hanson, G.N., 1993, Geochemical approaches to
sedimentation, provenance, and tectonics, in Johnsson,
M.J., and Basu, A., eds., Processes controlling the
composition of clastic sediments: Geological Society of America Special Paper 284, p. 21–40, doi:
10.1130/0091-7613(2001)029<0627:TIOAPA>2.0
.CO;2.
Meiburg, P., Chapa-Guerrero, J.R., Grotehusmann, I.,
Kustusch, T., Lentzy, P., de León-Gómez, H., and
Mansilla-Terán, M.A., 1987, El basamento pre-Cretácico
Geosphere, October 2010
de Aramberri—estructura clave para comprender el
décollement de la cubierta jurásica/cretácica de la
Sierra Madre Oriental, México: Actas Facultad de
Ciencias de la Tierra, Universidad Autónoma de Nuevo
León, v. 2, p. 15–22.
Miall, A.D., 1977, A review of the braided-river depositional
environment: Earth-Science Reviews, v. 13, p. 1–62,
doi: 10.1016/0012-8252(77)90055-1.
Miall, A.D., 1978, Lithofacies types and vertical profile
models in braided river deposits: A summary, in Miall
A. D., ed., Fluvial sedimentology: Canadian Society of
Petroleum Geologists Memoir 5, p. 597–604.
Michalzik, D., 1991, Facies sequence of Triassic–Jurassic
red beds in the Sierra Madre Oriental (NE Mexico)
and its relation to the early opening of the Gulf of
Mexico: Sedimentary Geology, v. 71, p. 243–259, doi:
10.1016/0037-0738(91)90105-M.
Miller, B.V., Dostal, J., Keppie, J.D., Nance, R.D., OrtegaRivera, and Lee, J.K.W., 2007, Ordovician calcalkaline granitoids in the Acatlán Complex, southern Mexico: Geochemical and geochronologic data
and implications for the tectonics of the Gondwanan margin of the Rheic Ocean, in Linneman, U.,
et al., eds., The evolution of the Rheic Ocean: From
Avalonian-Cadomian active margin to Alleghenian–
Variscan collision: Geological Society of America Special Paper 423, p. 465–475, doi: 10.1130/
2007.2423(23).
Mixon, R.B., 1963, The Jurassic formations of the Ciudad
Victoria region, Tamaulipas, Mexico [PhD thesis]:
Baton Rouge, Louisiana State University, 98 p.
Mixon, R.B., Murray, G.E., and Diaz, T.G., 1959, Age and
correlation of Huizachal Group (Mesozoic), state of
Tamaulipas, Mexico: American Association of Petroleum Geologists Bulletin, v. 43, p. 757–771.
Molina-Garza, R.S., and Iriondo, A., 2005, La megacizalla
Mojave-Sonora: La hipótesis, la controversia y el
estado actual del conocimiento: Boletín de la Sociedad
Geológica Mexicana, v. 57, no. 1, p. 1–26.
Molina-Garza, R.S., Van der Voo, R., and Urrutia-Fucugauchi,
J., 1992, Paleomagnetism of the Chiapas massif,
southern Mexico: Evidence for rotation of the Maya
Block and implications for the opening of the Gulf
of Mexico: Geological Society of America Bulletin,
v. 104, p. 1156–1168, doi: 10.1130/0016-7606(1992)104
<1156:POTCMS>2.3.CO;2.
Mueller, P.A., Heatherinton, A.L., Wooden, J.L., Shuster,
R.D., Nutman, A.P., and Williams, I.S., 1994, Precambrian zircons from the Florida basement: A Gondwanan connection: Geology, v. 22, p. 119–122, doi:
10.1130/0091-7613(1994)022<0119:PZFTFB>2.3
.CO;2.
Mutti, E., and Ricci-Lucchi, F., 1972, Le torbiditi dell ’apennino settentrionale; introfuzione all ‘analisi di facies:
Memorie della Società Geologica Italiana, v. 11,
p. 161–199 (English translation, 1978, in International
Geology Review, v. 20, p. 125–166).
Nance, R.D., Fernández-Suárez, J., Keppie, J.D., Storey,
C., and Jeffries, T.E., 2007, Provenance of the Granjeno Schist, Ciudad Victoria, Mexico: Detrital zircon U-Pb age constraints and implications for the
Paleozoic paleogeography of the Rheic Ocean, in
Linneman, U., et al., eds., The evolution of the Rheic
Ocean: From Avalonian-Cadomian active margin to
Alleghenian-Variscan collision: Geological Society of
America Special Paper 423, p. 453–464, doi: 10.1130/
2007.2423(22).
Ortega-Gutiérrez, F., Sedlock, R.L., and Speed, R.C., 1994,
Phanerozoic tectonic evolution of Mexico, in Speed,
R.C., ed., Phanerozoic evolution of North American
continent-ocean transitions: Boulder, Colorado, Geological Society of America, Continent-Ocean Transect
Volume, p. 265–306.
Ortega-Gutiérrez, F., Ruiz, J., and Centeno-García, E., 1995,
Oaxaquia, a Proterozoic microcontinent accreted to
North America during the late Paleozoic: Geology, v. 23,
p. 1127–1130, doi: 10.1130/0091-7613(1995)023<1127
:OAPMAT>2.3.CO;2.
Pantoja-Alor, J., 1972, La Formación Nazas del Levantamiento de Villa Juárez, Estado de Durango: Memorias
de la Segunda Convención Nacional de la Sociedad
Geológica Mexicana, p. 25–31.
639
Downloaded from geosphere.gsapubs.org on September 30, 2010
Barboza-Gudiño et al.
Rueda-Gaxiola, J., Dueñas, M.A., Rodríguez, J.L., Minero,
M., and Uribe, G., 1993, Los Anticlinorios de
Huizachal-Peregrina y de Huayacocotla: Dos partes
de la fosa de Huayacocotla–El Alamar: Boletín de la
Asociación Mexicana de Geólogos Petroleros, v. 43,
p. 1–29.
Rueda-Gaxiola, J., López-Ocampo, E., Dueñas, M.A.,
Rodríguez, J.L., and Torres-Rivero, A., 1999, Palynostratigraphical method: Basis for defining stratigraphy and age of the Los San Pedros allogroup,
Huizachal-Peregrina anticlinorium, Mexico, in Bartolini, C., et al., eds., Mesozoic sedimentary and tectonic
history of north-central Mexico: Geological Society of America Special Paper 340, p. 229–269, doi:
10.1130/0-8137-2340-X.229.
Ruiz, J., Patchett, P.J., and Ortega-Gutierrez, F., 1988,
Proterozoic and Phanerozoic basement terranes of
Mexico from Nd isotopic studies: Geological Society of America Bulletin, v. 100, p. 274–281, doi:
10.1130/0016-7606(1988)100<0274:PAPBTO>2.3
.CO;2.
Salvador, A., 1987, Late Triassic–Jurassic paleogeography
and origin of the Gulf of Mexico Basin: American
Association of Petroleum Geologists Bulletin, v. 71,
p. 419–451.
Schaaf, P., Heinrich, W., and Besch, T., 1994, Composition in Sm-Nd isotopic data of the lower crust beneath
San Luis Potosí, central Mexico: Evidence from a
granulite-facies xenolith suite: Chemical Geology,
v. 118, p. 63–84, doi: 10.1016/0009-2541(94)90170-8.
Sedlock, R.L., and Yukio, I., 1990, Lithology and biostratigraphy of Franciscan-like chert and associated rocks
in west-central Baja California, Mexico: Geological
Society of America Bulletin, v. 102, p. 852–864, doi:
10.1130/0016-7606(1990)102<0852:LABOFL>2.3
.CO;2.
Silva-Pineda, A., and Buitrón-Sánchez, B.E., 1999, Mesozoic redbed floras in east-central Mexico and their
stratigraphic relationships with marine beds, in Bartolini, C., et al., eds., Mesozoic sedimentary and tectonic
640
history of north-central Mexico: Geological Society of America Special Paper 340, p. 151–160, doi:
10.1130/0-8137-2340-X.151.
Silva-Romo, G., 1994, Estudio de la estratigrafía y estructuras tectónicas de la Sierra de Salinas, estados de San
Luis Potosí y Zacatecas [M.S. thesis]: Facultad de
Ciencias, Universidad Nacional Autónoma de México,
144 p.
Silva-Romo, G., Arellano-Gil, J., Mendoza-Rosales, C.,
and Nieto-Obregón, J., 2000, A submarine fan in the
Mesa Central, Mexico: Journal of South American
Earth Sciences, v. 13, p. 429–442, doi: 10.1016/S08959811(00)00034-1.
Solari, L.A., Keppie, J.D., Ortega-Gutierrez, F., Cameron,
K.L., Lopez, R., and Hames, W.R., 2003, 990 and 1100
Ma Grenvillian tectonothermal events in the northern Oaxacan Complex, southern Mexico: Roots of
an orogen: Tectonophysiscs, v. 365, p. 257–282, doi:
10.1016/S0040-1951(03)00025-8.
Solari, L.A., Keppie, J.D., Ortega-Gutierrez, F., Cameron,
K.L., and Lopez, R., 2004, ~990 Ma peak granulitic metamorphism and amalgamation of Oaxaquia,
México: U-Pb zircon geochronological and common Pb isotopic data: Revista Mexicana de Ciencias
Geológicas, v. 21, no. 2, p. 212–225.
Stewart, H.H., and Roldán-Quintana, J., 1991, Upper Triassic Barranca Group; nonmarine and shallow-marine
rift-basin deposits of northwestern Mexico, in PerezSegura, E., and Jacques-Ayala, C., eds., Studies of
Sonoran geology: Geological Society of America Special Paper 254, p. 19–36.
Tanner, L.H., and Lucas, S.G., 2006, Calcretes of the Upper
Triassic Chinle Group, Four Corners region, southwestern U.S.A.: Climatic implications, in Alonso-Zarza,
A.M., and Tanner, L.H., eds., Paleoenvironmental
record and applications of calcretes and palustrine
carbonates: Geological Society of America Special
Paper 416, p. 53–74, doi: 10.1130/2006.2416(04).
Torres, R., Ruiz, J., Patchett, P.J., and Grajales, J.M., 1999,
Permo-Triassic continental arc in eastern México:
Geosphere, October 2010
Tectonic implications, for reconstructions of southern
North America, in Bartolini, C., et al., eds., Mesozoic
sedimentary and tectonic history of north-central Mexico: Geological Society of America Special Paper 340,
p. 191–196, doi: 10.1130/0-8137-2340-X.191.
Tristán-González, M., Torrez-Hernández, J.R., and MataSegura, J.L., 1995, Geología de la Hoja Presa de
Santa Gertrudis, S.L.P.: Instituto de Geología, Universidad Autónoma de San Luis Potosí, Folleto Técnico
no. 122, 50 p.
Vega-Granillo, R., Salgado-Souto, S., Herrera-Urbina,
S., Valencia, V., Ruiz, J., Mesa-Figueroa, D., and
Talavera-Mendoza, O., 2008, U-Pb detrital zircon data
of the Rio Fuerte Formation (NW Mexico): Its periGondwanan provenance and exotic nature in relation to
southwestern North America: Journal of South American Earth Sciences, v. 26, p. 343–354, doi: 10.1016/
j.jsames.2008.08.011.
Venegas-Rodriguez, G., Barboza-Gudiño, J.R., and LópezDoncel, R.A., 2009, Geocronología de circones detríticos en capas del Jurásico Inferior de las áreas de la
Sierra de Catorce y El Alamito en el estado de San Luis
Potosí: Revista Mexicana de Ciencias Geológicas,
v. 26, no. 2, p. 466–481.
Weber, B.L., Schaaf, P., Valencia, V.A., Iriondo, A., and
Ortega-Gutierrez, F., 2003, Provenance ages of late
Paleozoic sandstones (Santa Rosa Formation) from the
Maya block, SE Mexico: Implications on the tectonic
evolution of western Pangea: Revista Mexicana de
Ciencias Geológicas, v. 23, no. 3, p. 262–276.
Weber, R., 1997, How old is the Triassic flora of Sonora and
Tamaulipas and news on Leonardian floras in Puebla
and Hidalgo, México: Revista Mexicana de Ciencias
Geológicas, v. 14, no. 2, p. 225–243.
MANUSCRIPT RECEIVED 11 SEPTEMBER 2009
REVISED MANUSCRIPT RECEIVED 12 JANUARY 2010
MANUSCRIPT ACCEPTED 21 JANUARY 2010