Geochemistry of the Mural Formation (Aptian-Albian) of the Bisbee Group,

Geochemistry of the Mural Formation (Aptian-Albian) of the Bisbee Group,
Northern Sonora, Mexico
J. Madhavaraju
a ,
*
, C.M. González-León
a
, Yong Il Lee
b
, J.S. Armstrong-Altrin
c
, L.M. Reyes-Campero
d
a
Estación Regional del Noroeste, Instituto de Geologia, Universidad Nacional Autónoma de México, Apartado Postal 1039, Hermosillo, Sonora 83000, México
b
School of Earth and Environmental Sciences, Seoul National University, Seoul 151-747, Republic of Korea
c
Instituto de Ciencias del Mar y Limnología, Geología Marina y Ambiental, Universidad Nacional Autónoma de México, Circuito Exterior s/n, 04510 México D.F., México
d
Servicio Geológico Mexicano, Gerencia de Hidrogeología y Geología Ambiental, Blvd. Felipe Ángeles Km. 93.50-4, Pachuca de Soto, Hidalgo 42080, México
article info
Article history:
Received 8 May 2008
Accepted in revised form 14 May 2010
Available online 20 May 2010
Keywords:
Geochemistry
Rare Earth Element
Provenance
AptianeAlbian Limestone
Mural Formation
Northern Sonora
México
abstract
The elemental content (major, trace and rare earth elements) of 35 AptianeAlbian limestone samples
from the Mural Formation has been determined to provide information on depositional conditions and
provenance. The limestones of the Mural Formation show large variations in terrigenous and carbonate
contents (1.2 to 42.3% and 57.7 to 98.8% respectively). Small variations are observed in CaO concentra-
tions in the Tuape Shale, Cerro La Puerta and Mesa Quemada members whereas large variations are
found in the Cerro La Ceja, Los Coyotes and Cerro La Espina members. The majority of the limestones
show high values of Th, Sc and Zr. Large variations in SREE content are observed among different
members of the Mural Formation. Most limestones from the Mural Formation record non-seawater-like
REEþY signatures. The limestones show large variations in Ce anomalies which may be due to mixing of
sediment components (biogenic and authigenic phases) and detrital materials including Fe-colloids from
fluvial input. Most of the limestones show positive Eu anomalies, but some samples show negative Eu
anomalies (Eu/Eu
*
: 0.42 to 2.62).
The large variations in terrigenous percentage, high Al
2
O
3
and SREE contents, high La
N
/Yb
N
ratios, low
Y/Ho ratios and non-seawater-like REE patterns suggest that the observed variations in SREE contents
are mainly controlled by the amount of detrital sediments in the limestones of the Mural Formation. The
limestones of the Mural Formation were deposited under both coastal and open shelf environments, and
they exhibit non-seawater-like REE þY patterns. The presence of terrigenous materials in these
carbonates as contaminants effectively masks the seawater signature due to their high concentration of
the REE. Thus, trying to decipher the palaeoceanographic conditions represented by ancient carbonate
rocks should be done cautiously since limestones deposited under open marine environments may also
be contaminated by some amount of terrigenous particles. The presence of small quantities of terrige-
nous materials in the limestones can also reveal source rock information. The La/Sc, La/Co, Th/Sc, Th/Cr,
Th/Co and Cr/Th ratios suggest that the terrigenous materials present in the limestones were mainly
derived from a nearby exposed basement of intermediate to felsic igneous rocks.
Ó2010 Elsevier Ltd. All rights reserved.
1. Introduction
Rare Earth Element (REE) concentrations, REE patterns, and the
Eu and Ce anomalies in marine sediments provide useful infor-
mation on marine depositional environments. Many workers have
undertaken detailed studies on the REE to understand the path-
ways of biogenic and terrigenous fluxes from the source to the
marine sediments (Piper, 1974; Murray and Leinen, 1993;
Sholkovitz et al., 1994). The REE concentrations in seawater are
mainly controlled by factors relating to different input sources (e.g.,
terrestrial input from continental weathering, hydrothermal input)
and scavenging processes related to depth, salinity and oxygen
levels (Elderfield, 1988; Piepgras and Jacobsen, 1992; Greaves et al.,
1999). Rare Earth Elements generally reflect uniform trivalent
behaviour except for Ce and Eu which exhibit multiple oxidation
states. Shale-normalized seawater REE patterns are characterized
by i) LREE depletion, ii) negative Ce anomalies and iii) a slight
positive La anomaly (e.g. de Baar et al., 1991; Bau and Dulski, 1996).
Y and Ho are chemically similar in charge and ionic radius, but Ho is
more readily removed from seawater than Y because of its surface
complexation behaviour (Nozaki et al., 1997), thus seawater
exhibits distinctly a high Y/Ho ratio than the terrigenous materials
(e.g. Bau, 1996).
*Corresponding author.
E-mail address: [email protected] (J. Madhavaraju).
Contents lists available at ScienceDirect
Cretaceous Research
journal homepage: www.elsevier.com/locate/CretRes
0195-6671/$ esee front matter Ó2010 Elsevier Ltd. All rights reserved.
doi:10.1016/j.cretres.2010.05.006
Cretaceous Research 31 (2010) 400e414

The distribution of REEs and Ce anomalies in marine sediments
may be influenced by depositional environments such as proximity
to source area (Murray et al., 1991a), widespread marine anoxia (Liu
et al., 1988; German and Elderfield, 1990; Murray et al., 1991b),
surface productivity variation (Toyoda et al., 1990), oceanic redox
conditions (Liu et al., 1988; German and Elderfield, 1990) and
lithology and diagenesis (Nath et al., 1992; Madhavaraju and
Ramasamy, 1999; Armstrong-Altrin et al., 2003; Madhavaraju and
Lee, 2009). Ce anomalies in marine sediments are considered by
some as reliable indicators for understanding the paleoredox
conditions (Liu et al., 1988), although several workers have raised
doubts about their effectiveness (German and Elderfield, 1990;
Murray et al., 1991b; Nath et al., 1992, 1997).
The REE signatures in ancient marine environment provide
information on secular changes in detrital influx and oxygenation
conditions in the water column (e.g. Holser, 1997; Kamber and
Webb, 2001). The seawater signatures are, however, completely
masked by the incorporation of terrigenous materials, which have
relatively high, non-seawater-like REE contents (Murray et al.,1992;
Webb and Kamber, 2000; Nothdurft et al., 2004; Madhavaraju and
Lee, 2009). The identification of the terrigenous particles present
in the marine carbonate rocks as contaminants is an important
aspect to understand the geochemistry of carbonate rocks.
The Lower Cretaceous, shallow marine siliciclastic and calcar-
eous strata of the Mural Formation are exposed in northern Sonora,
northwest Mexico in a 300 km long transect that extends from
Sierra El Chanate (westernmost part) to Cerro El Caloso Pitaycachi
(northeastern most outcrop). Along this transect, González-León
et al. (2008) reported the stratigraphy and biostratigraphy of
several sections, including the Cerro Pimas and Sierra San José
sections (Figs. 1 and 2) of which we discuss herein the major, trace
and REE geochemistry of their limestone beds. The aims of our
study are to determine the influence of terrigenous materials on the
REE characteristics of carbonate rocks, to document the variations
in Ce anomalies and to unravel the probable reason for significant
positive Eu anomalies in the limestones of the Mural Formation.
2. Geology and Stratigraphy
The Lower Cretaceous sedimentary succession assigned to the
Bisbee Group is well exposed in the north-central part of the state
of Sonora, Mexico. This succession has similar stratigraphic and
lithologic characteristics to the younger formations of the Bisbee
Group (Ransome, 1904) of southern Arizona and New Mexico in the
United States of America, and is correlative with strata exposed in
northern Mexico (Cantu-Chapa, 1976; Bilodeau and Lindberg, 1983;
Mack et al., 1986; Dickinson et al., 1989; Jacques-Ayala, 1995;
Lawton et al., 2004). In Arizona the Bisbee Group consists of the
Glance Conglomerate and the Morita, Mural and Cintura Forma-
tions that were deposited in a rift basin, termed the Bisbee Basin.
The older unit is the Glance Conglomerate composed of cobble- to
boulder-conglomerate with local interbeds of volcanic flows and
tuffs, which represent syntectonic rift deposits (Bilodeau et al.,
1987; Lawton et al., 2004).
The Morita and Cintura Formations are composed of reddish
brown siltstone and lenticular beds of arkose and feldspathic
arenite (Dickinson et al., 1986; Klute, 1991)that were deposited
under fluvial conditions. These two formations are difficult to
distinguish based only on their lithological characteristics. Hence,
the intervening marine Mural Formation is key to understanding
Lower Cretaceous stratigraphy and basin configuration in the area.
The fossiliferous clastic and carbonate strata of the Mural
Formation were deposited during a major marine transgression
during AptianeAlbian time (Scott, 1987) in the region of Sonora and
Arizona where it overlies the Morita Formation on a sharp ravine-
ment surface and grades upward into the Cintura Formation.
Lawton et al. (2004) defined six members in the Mural Formation in
north-central Sonora (Fig. 2), which from the base upwards are the
Cerro La Ceja, Tuape Shale, Los Coyotes, Cerro La Puerta, Cerro La
Espina and Mesa Quemada members. The lithostratigraphic studies
of different members of the Mural Formation show minor facies
changes from west to east. The facies characteristics and regional
correlation of different members of the Mural Formation indicate
that the depositional environments of this formation varied from
restricted shelf with deltaic and fluvial influence to open shelf with
coral rudist buildups, to offshore shelf. For the present study, we
have collected limestone samples from the western part (Cerro
Pimas eCP) and the eastern part (Sierra San José eSSJ) of the
Bisbee Basin in northern Sonora. Here the limestones of the Mural
Formation were deposited in a nearshore environment with deltaic
and fluvial influence to open marine environments (González-León
et al., 2008). Most of the limestone samples contain varied amounts
of terrigenous materials.
The Cerro La Ceja (CLC) Member consists of interbedded bio-
clastic limestone, siltstone and calcareous sandstone. The limestone
beds are grey, brown and dark yellowish brown, bioturbated and
locally sandy. Siltstone beds are grey, green and reddish brown with
calcareous nodules. The Tuape Shale (TS) Member is mainly
composed of grey to black mudstone and shale, shaly limestone and
subordinate amount of siltstone and fine grained sandstone.
Limestone occurs as thin beds which contain oysters and ammo-
nites. The Los Coyotes (LC) Member consists of thin beds of brown
mudstone, calcareous siltstone, shaly limestone, massive brown
siltstone, fine-grained sandstone and bioclastic limestone. This
member contains abundant fossils such as oysters, trigoniids,
gastropods, bivalves and echinoderms. The Cerro La Puerta (CLP)
Member is composed of mostly black shale and thin beds of fine-
grained sandstone and fossiliferous limestone. The limestone
exhibits distinct bedding-parallel burrows on the upper bed
surfaces, and it contains fossils including oysters and Orbitolina; the
black shale contains calcareous nodules. The Cerro La Espina (CLE)
Member consists mainly of massive limestone with thin beds of
SONORA ARIZONA
HERMOSILLO
Santa Ana
Caborca
Sonoita
San Luis
R. C.
Nogales
Cananea
Agua Prieta
Naco
Cerro
Pimas
Sierra
San Jose
Guaymas
Obregon
Navojoa
060 12020
Km
Mexico
113 00 110 00
31 00
29 00
27 00
Fig. 1. Location map of the studied sections of the Mural Formation.
J. Madhavaraju et al. / Cretaceous Research 31 (2010) 400e414 401

Fig. 2. Lithostratigraphic sections of the Mural Formation in Cerro Pimas and Sierra San José areas (modified after González-León et al., 2008).
J. Madhavaraju et al. / Cretaceous Research 31 (2010) 400e414402

siltstone, mudstone, fine grained sandstone and shaly limestone.
The limestone beds are lenticular and fossiliferous with Orbitolina,
gastropods, corals, rudists and other bivalves and the shaly lime-
stones contain abundant oysters. The Mesa Quemada (MQ)
Member includes green mudstone, light grey or red siltstone,
sandstone and bioclastic limestone. Sandstone beds are fine- to
very fine-grained with local parallel laminations. The bioclastic
limestone contains numerous oysters.
3. Material and methods
The stratigraphy of several sections of the Mural Formation
exposed in the northern part of Sonora has recently been studied by
Lawton et al. (2004) and González-León et al. (2008). Among them,
carbonate rocks are well exposed at the Cerro Pimas and Sierra San
José sections (Fig. 2). In our present study, thirty-five limestone
samples from these two sections were analyzed etwenty from the
Cerro Pimas section and fifteen from the Sierra San José section. We
consider these to be representative limestone samples from the
western and northeastern part of the Bisbee Basin in order to
establish the geochemical variations in the two sections that are
separated by about 150 km within the Bisbee Basin.
Care was taken to remove the weathered materials from the
surface of the limestone samples. The selected samples were
washed with distilled water several times, air dried and powdered
in an agate mortar. Then, fused glass beads were prepared for major
element analysis using a Phillip PW 1480 X-ray fluorescence
spectrometer with a rhodium X-ray source (see Norrish and Hutton,
1969; Giles et al., 1995). The accuracy of SiO
2
,Al
2
O
3
and K
2
Oare
better than 1%, MnO is better than 2% and that of Fe
2
O
3
, CaO and
MgO are better than 4%. Na
2
O, P
2
O
5
and TiO
2
are better than 6%,
Trace elements (Cr, Sc, Sr and Zr) were measured using a Jobin Yvon
138 Ultrace Inductively Coupled Plasma Atomic Emission Spec-
trometer (ICP-AES). Rare Earth Elements and certain other trace
elements (Co, Y, Th and Pb) were analyzed using a VG elemental PQ
II plus Inductively Coupled Plasma Mass Spectrometer (ICP-MS)
(see Jarvis, 1988). The sedimentary geochemical standard rock,
MAG-1, obtained from the USGS, was used for calibration. The
result from the analyses of MAG-1 are compared with the pub-
lished values compiled by Govindaraju (1994) which shows better
precision of our data and also compatible with the published values
(Table 1). The precision for trace elements like Co, Zr and Th are
better than 3% whereas Cr, Sr, Y and Pb are better than 10%. The
analytical accuracy of all REEs is better than 4% (except Tb, Dy, Ho,
Tm and Lu). The precision of Tb, Dy, Ho, Tm and Lu are more than
10%. The limits of detection for the analytical procedure are also
listed in Table 1. They mainly agree with the findings mentioned by
earlier workers (Verma et al., 2002; Santoyo and Verma, 2003;
Verma and Santoyo, 2005). Major, trace and Rare Earth elements
were analyzed at the Korea Basic Science Institute. Three analyses
were made for each sample and then averaged. Yttrium is inserted
between Dy and Ho in the REE pattern according to its identical
charge and similar radius (REE þY pattern, Bau, 1996). Rare Earth
Elements were normalized to the Post Archaean Australian Shale
(PAAS) values of Taylor and McLennan (1985) for preparing REE-
normalized diagrams. The Ce/Ce
*
(Ce anomaly) is calculated using
the value of Ce (Ce
sample
/Ce
PAAS
) and the predicted value of Ce
*
is
obtained from the interpolation from the PAAS-normalised values
of La and Pr. The Eu/Eu
*
(Eu anomaly) is also calculated in similar
way using the values of Sm, Eu and Gd.
Thirty-five samples were analyzed using standard XRD proce-
dures (Biscaye, 1965; Muller, 1967; Grim, 1968; Hardy & Tucker,
1988) for whole rock mineralogy. The powder samples were
scanned from 2e70
(2 q ) per minute. X-ray diffraction was used in
a computer controlled Shimadzu Diffractometer system model
6000 with Cu k
a radiation to estimate semi-quantitatively the
minerals present. The dominant minerals identified in these lime-
stone samples are quartz, feldspar and calcite. The clastic and
carbonate percentages are given in Table 2.
4. Results
The concentrations of major elements in the studied limestones
samples of the Mural Formation are given in Table 2. Large varia-
tions are observed in SiO
2
and Al
2
O
3
contents (Table 2) among
different members of the Mural Formation in both sections. In the
Cerro Pimas section, the CaO content in the CLC, TS, LC, CLE and MQ
varies significantly (Table 2). Small variations are observed in CaO
concentrations in the CLC, TS, CLP, CLE and MQ members whereas
large variations are found only in the LC Member of Sierra San José
section (Table 2). The limestones from both sections show low
contents of Fe
2
O
3
(Table 2). Those major and trace elements which
are enriched in silicate minerals (eg. SiO
2
and Al
2
O
3
) are higher in
the CLC, TS, CLE and MQ members than the LC member from the
Cerro Pimas sections. In contrast, major and trace elements that are
housed in the carbonate minerals (eg. CaO and Sr) are higher in the
LC member than the other members of the Cerro Pimas section. The
CLC, TS, LC and MQ members from the Sierra San José section are
Table 1
Comparison of data of major oxides, trace and rare-earth elements for USGS refer-
ence sample MAG-1 (marine sediment) with the literature USGS certificate of
analysis (Govindaraju 1994; see also USGS website).
Oxide/Elements This Study
*
Govindaraju 1994 Limits of detection
**
Mean 
SiO
2
50.72 50.4 0.96 e
Al
2
O
3
16.48 16.4 0.30 5
Fe
2
O
3
7.11 6.8 0.60 20
CaO 1.42 1.37 0.10 5
MgO 3.11 3.0 0.10 5
K
2
O 3.59 3.55 0.17 5
Na
2
O 3.60 3.83 0.11 50
MnO 0.10 0.098 0.009 5
TiO
2
0.70 0.75 0.07 15
P
2
O
5
0.17 0.16 0.021 15
LOI 14.09 eee
Co 20.2 20 1.6 0.0287
Cr 77.1 97 8 e
Sc e17 1 e
Y 24.91 28 3 0.0075
Sr 133.7 150 15 e
Zr 125.6 130 13 e
Pb 28.44 24 3 0.0598
Th 11.96 12 1 0.0473
La 41.46 43 4 0.0044
Ce 87.32 88 9 0.0030
Pr 10.06 ee0.0031
Nd 38.10 38 5 0.0034
Sm 7.61 7.5 0.6 0.0034
Eu 1.66 1.6 0.14 0.0031
Gd 5.89 5.8 0.7 0.0036
Tb 1.28 0.960 0.090 0.0024
Dy 5.92 5.2 0.3 0.0024
Ho 1.16 1.0 0.1 0.0027
Er 3.09 3.0 e0.0024
Tm 0.56 0.43 0.43 0.0023
Yb 2.70 2.6 0.3 0.0029
Lu 0.53 0.4 0.04 0.0018
*
Major oxides in wt% are analysed by XRF (average of 43 measurements); trace
elements in ppm by ICP-AES and ICP-MS (average of 6 measurements). The obtained
data were not tested statistically to find out the discordant outliers and it will be
undertaken in our future work (Barnett and Lewis, 1994; Verma, 2005; Verma and
Quiroz-Ruiz, 2006a, 2006b, 2008; Verma et al., 2008).
**
Limit of Detection: Three times the standard deviation of seven blank measure-
ments; For major elements in
m g/L and for trace elements in ng/L.
enot determined or not reported.
J. Madhavaraju et al. / Cretaceous Research 31 (2010) 400e414 403

Table 2
Major oxides (wt%), trace and rare earth elements (ppm) concentrations for limestones of the Mural Formation
a
.
Member/Sample no Clastic % Carbonate % SiO
2
Al
2
O
3
Fe
2
O
3
CaO MgO K
2
ONa
2
O MnO TiO
2
P
2
O
5
LOI Total Co Cr Sc Y Zr Sr
Cerro Pimas section
Mesa Quemada
CP47 10.8 89.2 9.1 0.50 0.80 49.9 0.20 0.03 0.13 0.08 0.03 0.05 39.0 99.82 4.2 11.3 1.00 5.1 1.0 425
CP45 5.1 94.9 3.5 0.86 0.41 53.0 0.31 0.16 0.09 0.05 0.04 0.02 41.3 99.74 2.9 10.4 1.00 4.7 1.0 631
Cerro La Espina
CP43 29.5 70.5 23.7 2.99 1.46 38.7 0.67 0.82 n.d. 0.15 0.12 0.03 31.4 100.00 4.3 9.1 2.21 6.1 24.1 554
CP41 4.8 95.2 3.0 0.27 0.34 53.3 0.35 0.05 n.d. 0.06 0.02 0.02 42.0 99.41 2.8 1.0 0.41 5.2 0.6 405
CP38 11.0 89.0 7.8 1.10 1.27 48.7 1.26 0.07 n.d. 0.12 0.05 0.02 39.1 99.49 6.9 4.9 1.40 10.7 9.4 544
CP36 5.2 94.8 3.3 0.58 0.56 53.0 0.68 0.08 n.d. 0.09 0.02 0.02 41.4 99.73 4.6 3.5 1.20 14.1 2.6 529
CP33 7.7 92.3 5.6 0.46 0.66 51.2 0.73 0.01 n.d. 0.08 0.03 0.02 40.8 99.59 3.2 4.6 0.60 9.5 2.8 746
Los Coyotes
CP28 2.8 97.2 1.8 0.14 0.28 54.1 0.35 0.01 n.d. 0.06 0.01 n.d. 42.7 99.45 2.9 1.4 0.20 1.7 1.0 540
CP26 5.5 94.5 3.9 0.65 0.65 52.0 0.41 0.14 n.d. 0.08 0.04 0.02 41.3 99.19 3.7 11.0 0.60 4.1 4.4 428
CP24 3.9 96.1 2.9 0.48 0.65 53.2 0.26 0.10 n.d. 0.06 0.03 0.02 41.9 99.60 4.3 6.0 0.60 4.4 4.2 440
CP22 1.9 98.1 1.5 0.10 0.25 54.9 0.09 0.01 n.d. 0.07 0.01 0.01 42.4 99.34 3.0 3.5 0.20 10.3 1.0 218
CP18 6.1 93.9 3.4 0.48 1.81 51.9 0.51 0.08 n.d. 0.25 0.02 0.02 41.1 99.57 10.1 7.7 0.60 6.0 2.6 368
CP15 6.6 93.4 5.4 0.47 0.78 51.5 0.18 0.12 n.d. 0.25 0.02 0.01 40.5 99.23 4.5 6.3 0.60 6.5 4.4 471
Tuape Shale
CP12 19.6 80.4 14.2 2.75 1.66 44.2 0.69 0.44 n.d. 0.15 0.12 0.05 35.5 99.76 4.6 10.8 1.79 7.1 14.4 866
CP10 14.9 85.1 9.9 1.73 1.33 46.8 1.20 0.20 0.02 0.12 0.08 0.04 37.7 99.12 3.6 13.6 1.39 18.2 42.1 1116
CP9 17.0 83.0 13.1 1.33 1.37 46.1 0.32 0.14 0.26 0.16 0.07 0.05 36.6 99.50 3.0 9.0 0.81 8.4 5.9 503
CP6 20.8 79.2 16.9 2.04 1.36 43.5 0.45 0.45 0.03 0.08 0.10 0.02 34.6 99.53 3.2 15.3 2.19 13.2 24.1 705
Cerro La Ceja
CP4 3.9 96.1 2.0 0.49 0.26 53.3 0.38 0.10 n.d. 0.01 0.03 0.02 42.5 99.09 2.2 7.7 0.61 2.5 1.6 510
CP3 5.8 94.2 3.1 0.77 0.41 53.3 0.23 0.17 0.02 0.07 0.04 0.04 41.4 99.55 5.3 6.8 0.87 6.6 1.9 391
CP1 29.3 70.7 23.3 2.84 1.59 38.0 0.52 0.29 0.66 0.69 0.12 0.06 31.1 99.17 3.4 9.1 1.78 9.5 24.8 298
Sierra San José section
Mesa Quemada
SSJ27 11.3 88.7 8.2 1.56 0.59 49.1 0.50 0.29 0.05 0.44 0.06 0.03 38.8 99.62 3.2 2.0 1.39 5.4 6.6 983
Cerro La Espina
SSJ25 6.7 93.3 4.3 0.51 0.60 51.7 0.88 n.d. n.d. 0.07 0.02 0.01 41.3 99.39 2.8 4.0 0.40 4.3 3.8 313
SSJ23 7.9 92.1 6.5 0.46 0.12 50.7 0.93 0.07 n.d. 0.02 0.02 0.01 40.7 99.53 2.2 3.6 0.20 1.5 10.1 390
SSJ21 5.9 94.1 4.2 0.44 0.10 52.6 0.73 0.04 n.d. 0.01 0.01 0.01 41.7 99.84 2.1 2.8 0.20 1.2 6.2 439
SSJ18 1.2 98.8 0.3 0.08 0.06 54.6 0.68 n.d. n.d. 0.01 0.01 0.01 43.4 99.15 2.1 2.7 0.20 0.8 1.8 407
SSJ16 5.9 94.1 4.6 0.21 0.16 52.5 0.85 n.d. n.d. 0.01 0.02 0.01 41.4 99.76 1.98 3.0 0.20 1.5 5.0 434
Cerro La Puerta
SSJ11 7.3 92.7 4.7 0.90 0.50 51.7 0.96 0.06 n.d. 0.07 0.03 0.01 40.6 99.53 2.2 6.3 0.60 3.3 6.0 827
SSJ10 6.1 93.7 3.9 0.84 0.44 52.6 0.90 0.08 n.d. 0.02 0.03 0.02 40.3 99.13 2.1 5.9 0.60 4.4 6.2 849
SSJ9 7.8 93.2 4.8 0.78 0.37 52.3 0.78 0.10 n.d. 0.02 0.03 0.01 40.2 99.39 1.8 7.4 0.60 3.6 5.4 673
Los Coyotes
SSJ7 8.4 91.6 5.7 0.54 0.96 51.2 0.84 0.03 0.01 0.08 0.02 0.06 39.7 99.11 1.6 8.6 0.61 5.7 6.5 1183
SSJ6 38.1 61.9 31.5 3.00 1.20 36.2 0.73 0.24 0.86 0.09 0.23 0.06 25.6 99.71 2.3 11.9 1.59 18.0 70.3 753
Tuape Shale
SSJ5 17.0 83.0 12.5 1.78 0.86 46.1 0.72 0.20 0.34 0.08 0.10 0.04 36.5 99.22 2.2 15.2 1.42 8.0 52.2 699
SSJ4 17.9 82.1 13.5 1.92 0.92 49.7 0.78 0.21 0.37 0.09 0.11 0.04 31.6 99.24 1.9 19.3 2.00 13.8 43.8 520
Cerro La Ceja
SSJ3 42.3 57.7 31.7 6.26 0.94 37.3 0.80 0.59 2.03 0.29 0.21 0.08 19.9 100.10 2.7 10.5 2.42 11.3 57.4 528
SSJ2 39.2 60.8 29.6 6.00 1.48 32.8 1.03 1.21 0.07 0.07 0.30 0.08 27.3 99.94 2.8 21.4 4.20 12.1 50.6 481
Member/Sample no Th Pb La Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Tm Yb Lu SREE
Cerro Pimas section
Mesa Quemada
CP47 0.25 8 5.57 5.63 0.98 4.68 0.86 0.23 1.07 0.13 0.74 0.14 0.39 0.04 0.28 0.04 20.78
CP45 0.39 29 5.91 10.27 1.52 7.46 1.15 0.23 1.24 0.15 0.83 0.16 0.45 0.05 0.35 0.04 29.81
Cerro La Espina
CP43 1.55 254 6.16 12.44 1.38 7.28 1.31 0.39 1.62 0.21 1.03 0.22 0.62 0.09 0.59 0.09 33.43
CP41 0.23 47 3.25 6.21 0.69 3.73 0.70 0.18 1.00 0.14 0.75 0.16 0.45 0.06 0.39 0.06 17.77
CP38 1.01 22 7.75 17.38 1.85 10.06 1.67 0.43 2.38 0.32 1.62 0.33 0.91 0.12 0.77 0.11 45.70
CP36 0.81 58 8.62 19.69 2.07 11.45 1.98 0.43 2.91 0.40 2.06 0.42 1.16 0.16 1.02 0.15 52.52
CP33 0.64 43 6.78 13.62 1.49 8.07 1.39 0.36 2.07 0.28 1.40 0.28 0.76 0.10 0.61 0.09 37.27
Los Coyotes
CP28 e93 1.07 1.70 0.19 1.03 0.20 0.06 0.30 0.04 0.22 0.05 0.14 0.02 0.12 0.02 5.22
CP26 0.33 49 3.66 6.45 0.73 3.87 0.68 0.20 0.89 0.12 0.56 0.12 0.32 0.04 0.26 0.04 17.94
CP24 0.39 135 3.19 5.65 0.66 3.52 0.67 0.18 0.90 0.13 0.66 0.14 0.39 0.05 0.34 0.05 16.53
CP22 0.09 18 2.23 2.69 0.38 1.92 0.44 0.14 0.57 0.08 0.44 0.10 0.27 0.04 0.21 0.03 9.54
CP18 0.57 25 4.74 9.17 1.04 5.51 1.10 0.37 1.34 0.18 0.92 0.18 0.55 0.07 0.43 0.06 25.66
CP15 0.50 46 5.31 9.18 1.04 5.60 1.12 0.36 1.40 0.19 0.93 0.19 0.50 0.06 0.39 0.06 26.33
Tuape Shale
CP12 1.27 40 9.18 18.68 2.04 10.97 1.78 0.69 2.12 0.26 1.19 0.23 0.65 0.08 0.53 0.08 48.48
CP10 1.68 117 11.98 27.18 3.26 17.25 2.42 0.78 2.94 0.35 1.42 0.26 0.70 0.08 0.54 0.08 69.24
C P9 1.44 79 20.88 50.49 4.53 26.72 2.87 1.03 3.69 0.40 1.52 0.28 0.82 0.09 0.56 0.08 113.96
CP6 2.34 14 7.72 14.32 2.01 10.33 1.94 0.47 2.43 0.35 1.98 0.41 1.21 0.16 1.09 0.17 44.59
Cerro La Ceja
CP4 1.51 19 4.63 7.40 1.03 5.05 0.75 0.17 0.89 0.12 0.45 0.09 0.24 0.04 0.19 0.03 21.08
J. Madhavaraju et al. / Cretaceous Research 31 (2010) 400e414404