Geochemistry of the Mural Formation (Aptian-Albian) of the Bisbee Group,
publicité
Cretaceous Research 31 (2010) 400e414 Contents lists available at ScienceDirect Cretaceous Research journal homepage: www.elsevier.com/locate/CretRes 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 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 b a r t i c l e i n f o a b s t r a c t Article history: Received 8 May 2008 Accepted in revised form 14 May 2010 Available online 20 May 2010 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 concentrations 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 Al2O3 and SREE contents, high LaN/YbN 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 þ Y 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 terrigenous 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. Ó 2010 Elsevier Ltd. All rights reserved. Keywords: Geochemistry Rare Earth Element Provenance AptianeAlbian Limestone Mural Formation Northern Sonora México 1. Introduction Rare Earth Element (REE) concentrations, REE patterns, and the Eu and Ce anomalies in marine sediments provide useful information on marine depositional environments. Many workers have undertaken detailed studies on the REE to understand the pathways 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., * Corresponding author. E-mail address: [email protected] (J. Madhavaraju). 0195-6671/$ e see front matter Ó 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.cretres.2010.05.006 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). J. Madhavaraju et al. / 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 calcareous 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. 110 00 113 00 San Luis R. C. SONORA Sonoita ARIZONA Naco Agua Prieta Nogales Caborca Cananea 31 00 Sierra San Jose Santa Ana Cerro Pimas HERMOSILLO 0 20 29 00 60 120 Km Guaymas Obregon Navojoa Mexico Fig. 1. Location map of the studied sections of the Mural Formation. 27 00 401 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 Formations 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 ravinement 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 e CP) and the eastern part (Sierra San José e SSJ) 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 bioclastic 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 ammonites. 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 finegrained 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 402 J. Madhavaraju et al. / Cretaceous Research 31 (2010) 400e414 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) 400e414 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 limestones 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 e twenty 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 SiO2, Al2O3 and K2O are better than 1%, MnO is better than 2% and that of Fe2O3, CaO and MgO are better than 4%. Na2O, P2O5 and TiO2 are better than 6%, Trace elements (Cr, Sc, Sr and Zr) were measured using a Jobin Yvon 138 Ultrace Inductively Coupled Plasma Atomic Emission Spectrometer (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 published 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 þ Y pattern, Bau, 1996). Rare Earth Elements were normalized to the Post Archaean Australian Shale (PAAS) values of Taylor and McLennan (1985) for preparing REEnormalized diagrams. The Ce/Ce* (Ce anomaly) is calculated using the value of Ce (Cesample/CePAAS) 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 procedures (Biscaye, 1965; Muller, 1967; Grim, 1968; Hardy & Tucker, 1988) for whole rock mineralogy. The powder samples were scanned from 2e70 (2q) per minute. X-ray diffraction was used in a computer controlled Shimadzu Diffractometer system model 403 Table 1 Comparison of data of major oxides, trace and rare-earth elements for USGS reference sample MAG-1 (marine sediment) with the literature USGS certificate of analysis (Govindaraju 1994; see also USGS website). Oxide/Elements This Study* SiO2 Al2O3 Fe2O3 CaO MgO K2O Na2O MnO TiO2 P2O5 LOI Co Cr Sc Y Sr Zr Pb Th La Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Tm Yb Lu 50.72 16.48 7.11 1.42 3.11 3.59 3.60 0.10 0.70 0.17 14.09 20.2 77.1 e 24.91 133.7 125.6 28.44 11.96 41.46 87.32 10.06 38.10 7.61 1.66 5.89 1.28 5.92 1.16 3.09 0.56 2.70 0.53 Govindaraju 1994 Mean 50.4 16.4 6.8 1.37 3.0 3.55 3.83 0.098 0.75 0.16 e 20 97 17 28 150 130 24 12 43 88 e 38 7.5 1.6 5.8 0.960 5.2 1.0 3.0 0.43 2.6 0.4 0.96 0.30 0.60 0.10 0.10 0.17 0.11 0.009 0.07 0.021 e 1.6 8 1 3 15 13 3 1 4 9 e 5 0.6 0.14 0.7 0.090 0.3 0.1 e 0.43 0.3 0.04 Limits of detection** e 5 20 5 5 5 50 5 15 15 e 0.0287 e e 0.0075 e e 0.0598 0.0473 0.0044 0.0030 0.0031 0.0034 0.0034 0.0031 0.0036 0.0024 0.0024 0.0027 0.0024 0.0023 0.0029 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 measurements; For major elements in mg/L and for trace elements in ng/L. e not determined or not reported. 6000 with Cu ka radiation to estimate semi-quantitatively the minerals present. The dominant minerals identified in these limestone 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 variations are observed in SiO2 and Al2O3 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 Fe2O3 (Table 2). Those major and trace elements which are enriched in silicate minerals (eg. SiO2 and Al2O3) 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 404 J. Madhavaraju et al. / Cretaceous Research 31 (2010) 400e414 Table 2 Major oxides (wt%), trace and rare earth elements (ppm) concentrations for limestones of the Mural Formationa. Member/Sample no Clastic % Carbonate % SiO2 Al2O3 Fe2O3 CaO Cerro Pimas section Mesa Quemada CP47 CP45 Cerro La Espina CP43 CP41 CP38 CP36 CP33 Los Coyotes CP28 CP26 CP24 CP22 CP18 CP15 Tuape Shale CP12 CP10 CP9 CP6 Cerro La Ceja CP4 CP3 CP1 10.8 5.1 89.2 94.9 29.5 4.8 11.0 5.2 7.7 70.5 95.2 89.0 94.8 92.3 23.7 3.0 7.8 3.3 5.6 2.8 5.5 3.9 1.9 6.1 6.6 97.2 94.5 96.1 98.1 93.9 93.4 19.6 14.9 17.0 20.8 3.9 5.8 29.3 Sierra San José section Mesa Quemada SSJ27 11.3 Cerro La Espina SSJ25 6.7 SSJ23 7.9 SSJ21 5.9 SSJ18 1.2 SSJ16 5.9 Cerro La Puerta SSJ11 7.3 SSJ10 6.1 SSJ9 7.8 Los Coyotes SSJ7 8.4 SSJ6 38.1 Tuape Shale SSJ5 17.0 SSJ4 17.9 Cerro La Ceja SSJ3 42.3 SSJ2 39.2 Member/Sample no Cerro Pimas section Mesa Quemada CP47 CP45 Cerro La Espina CP43 CP41 CP38 CP36 CP33 Los Coyotes CP28 CP26 CP24 CP22 CP18 CP15 Tuape Shale CP12 CP10 C P9 CP6 Cerro La Ceja CP4 Th Na2O MnO TiO2 P2O5 LOI Total Co Cr Sc Zr 0.03 0.13 0.16 0.09 0.08 0.05 0.03 0.04 0.05 0.02 39.0 41.3 99.82 99.74 4.2 2.9 2.99 0.27 1.10 0.58 0.46 1.46 0.34 1.27 0.56 0.66 38.7 53.3 48.7 53.0 51.2 0.67 0.35 1.26 0.68 0.73 0.82 0.05 0.07 0.08 0.01 n.d. n.d. n.d. n.d. n.d. 0.15 0.06 0.12 0.09 0.08 0.12 0.02 0.05 0.02 0.03 0.03 0.02 0.02 0.02 0.02 31.4 100.00 42.0 99.41 39.1 99.49 41.4 99.73 40.8 99.59 4.3 2.8 6.9 4.6 3.2 9.1 1.0 4.9 3.5 4.6 1.8 3.9 2.9 1.5 3.4 5.4 0.14 0.65 0.48 0.10 0.48 0.47 0.28 0.65 0.65 0.25 1.81 0.78 54.1 52.0 53.2 54.9 51.9 51.5 0.35 0.41 0.26 0.09 0.51 0.18 0.01 0.14 0.10 0.01 0.08 0.12 n.d. n.d. n.d. n.d. n.d. n.d. 0.06 0.08 0.06 0.07 0.25 0.25 0.01 0.04 0.03 0.01 0.02 0.02 n.d. 0.02 0.02 0.01 0.02 0.01 42.7 41.3 41.9 42.4 41.1 40.5 99.45 2.9 99.19 3.7 99.60 4.3 99.34 3.0 99.57 10.1 99.23 4.5 80.4 85.1 83.0 79.2 14.2 9.9 13.1 16.9 2.75 1.73 1.33 2.04 1.66 1.33 1.37 1.36 44.2 46.8 46.1 43.5 0.69 1.20 0.32 0.45 0.44 0.20 0.14 0.45 n.d. 0.02 0.26 0.03 0.15 0.12 0.16 0.08 0.12 0.08 0.07 0.10 0.05 0.04 0.05 0.02 35.5 37.7 36.6 34.6 99.76 99.12 99.50 99.53 4.6 3.6 3.0 3.2 96.1 94.2 70.7 2.0 0.49 3.1 0.77 23.3 2.84 0.26 0.41 1.59 53.3 0.38 53.3 0.23 38.0 0.52 0.10 n.d. 0.17 0.02 0.29 0.66 0.01 0.07 0.69 0.03 0.04 0.12 0.02 0.04 0.06 42.5 41.4 31.1 99.09 99.55 99.17 2.2 5.3 3.4 7.7 0.61 6.8 0.87 9.1 1.78 2.5 1.6 6.6 1.9 9.5 24.8 510 391 298 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 93.3 92.1 94.1 98.8 94.1 4.3 6.5 4.2 0.3 4.6 0.51 0.46 0.44 0.08 0.21 0.60 0.12 0.10 0.06 0.16 51.7 50.7 52.6 54.6 52.5 n.d. 0.07 0.04 n.d. n.d. n.d. n.d. n.d. n.d. n.d. 0.07 0.02 0.01 0.01 0.01 0.02 0.02 0.01 0.01 0.02 0.01 0.01 0.01 0.01 0.01 41.3 40.7 41.7 43.4 41.4 99.39 99.53 99.84 99.15 99.76 2.8 2.2 2.1 2.1 1.98 4.0 3.6 2.8 2.7 3.0 4.3 3.8 1.5 10.1 1.2 6.2 0.8 1.8 1.5 5.0 313 390 439 407 434 92.7 93.7 93.2 4.7 0.90 3.9 0.84 4.8 0.78 0.50 0.44 0.37 51.7 0.96 52.6 0.90 52.3 0.78 0.06 n.d. 0.08 n.d. 0.10 n.d. 0.07 0.02 0.02 0.03 0.03 0.03 0.01 0.02 0.01 40.6 40.3 40.2 99.53 99.13 99.39 2.2 2.1 1.8 6.3 0.60 5.9 0.60 7.4 0.60 3.3 4.4 3.6 827 849 673 91.6 61.9 5.7 0.54 31.5 3.00 0.96 1.20 51.2 0.84 36.2 0.73 0.03 0.01 0.24 0.86 0.08 0.09 0.02 0.23 0.06 0.06 39.7 25.6 99.11 99.71 1.6 2.3 8.6 0.61 5.7 6.5 1183 11.9 1.59 18.0 70.3 753 83.0 82.1 12.5 1.78 13.5 1.92 0.86 0.92 46.1 0.72 49.7 0.78 0.20 0.34 0.21 0.37 0.08 0.09 0.10 0.11 0.04 0.04 36.5 31.6 99.22 99.24 2.2 1.9 15.2 1.42 8.0 52.2 19.3 2.00 13.8 43.8 699 520 57.7 60.8 31.7 6.26 29.6 6.00 0.94 1.48 37.3 0.80 32.8 1.03 0.59 2.03 1.21 0.07 0.29 0.07 0.21 0.30 0.08 0.08 19.9 100.10 27.3 99.94 2.7 2.8 10.5 2.42 11.3 57.4 21.4 4.20 12.1 50.6 528 481 La Ce Pr Nd 1.0 1.0 425 631 2.21 6.1 24.1 0.41 5.2 0.6 1.40 10.7 9.4 1.20 14.1 2.6 0.60 9.5 2.8 554 405 544 529 746 1.4 11.0 6.0 3.5 7.7 6.3 0.20 1.7 0.60 4.1 0.60 4.4 0.20 10.3 0.60 6.0 0.60 6.5 540 428 440 218 368 471 10.8 13.6 9.0 15.3 1.79 7.1 14.4 866 1.39 18.2 42.1 1116 0.81 8.4 5.9 503 2.19 13.2 24.1 705 0.40 0.20 0.20 0.20 0.20 5.1 4.7 Sr 49.9 0.20 53.0 0.31 0.88 0.93 0.73 0.68 0.85 11.3 1.00 10.4 1.00 Y 0.80 0.41 Pb 9.1 0.50 3.5 0.86 MgO K2O Sm Eu Gd Tb Dy Ho Er Tm Yb Lu 1.0 4.4 4.2 1.0 2.6 4.4 6.0 6.2 5.4 SREE 0.25 0.39 8 29 5.57 5.91 5.63 10.27 0.98 1.52 4.68 7.46 0.86 1.15 0.23 0.23 1.07 1.24 0.13 0.15 0.74 0.83 0.14 0.16 0.39 0.45 0.04 0.05 0.28 0.35 0.04 0.04 20.78 29.81 1.55 0.23 1.01 0.81 0.64 254 47 22 58 43 6.16 3.25 7.75 8.62 6.78 12.44 6.21 17.38 19.69 13.62 1.38 0.69 1.85 2.07 1.49 7.28 3.73 10.06 11.45 8.07 1.31 0.70 1.67 1.98 1.39 0.39 0.18 0.43 0.43 0.36 1.62 1.00 2.38 2.91 2.07 0.21 0.14 0.32 0.40 0.28 1.03 0.75 1.62 2.06 1.40 0.22 0.16 0.33 0.42 0.28 0.62 0.45 0.91 1.16 0.76 0.09 0.06 0.12 0.16 0.10 0.59 0.39 0.77 1.02 0.61 0.09 0.06 0.11 0.15 0.09 33.43 17.77 45.70 52.52 37.27 e 0.33 0.39 0.09 0.57 0.50 93 49 135 18 25 46 1.07 3.66 3.19 2.23 4.74 5.31 1.70 6.45 5.65 2.69 9.17 9.18 0.19 0.73 0.66 0.38 1.04 1.04 1.03 3.87 3.52 1.92 5.51 5.60 0.20 0.68 0.67 0.44 1.10 1.12 0.06 0.20 0.18 0.14 0.37 0.36 0.30 0.89 0.90 0.57 1.34 1.40 0.04 0.12 0.13 0.08 0.18 0.19 0.22 0.56 0.66 0.44 0.92 0.93 0.05 0.12 0.14 0.10 0.18 0.19 0.14 0.32 0.39 0.27 0.55 0.50 0.02 0.04 0.05 0.04 0.07 0.06 0.12 0.26 0.34 0.21 0.43 0.39 0.02 0.04 0.05 0.03 0.06 0.06 5.22 17.94 16.53 9.54 25.66 26.33 1.27 1.68 1.44 2.34 40 117 79 14 9.18 11.98 20.88 7.72 18.68 27.18 50.49 14.32 2.04 3.26 4.53 2.01 10.97 17.25 26.72 10.33 1.78 2.42 2.87 1.94 0.69 0.78 1.03 0.47 2.12 2.94 3.69 2.43 0.26 0.35 0.40 0.35 1.19 1.42 1.52 1.98 0.23 0.26 0.28 0.41 0.65 0.70 0.82 1.21 0.08 0.08 0.09 0.16 0.53 0.54 0.56 1.09 0.08 0.08 0.08 0.17 48.48 69.24 113.96 44.59 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) 400e414 405 Table 2 (continued ) Th La Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Tm Yb Lu CP3 CP1 1.13 1.34 67 41 6.49 13.51 11.50 28.94 1.59 3.05 8.04 16.52 1.32 2.17 0.36 0.49 1.57 2.77 0.20 0.33 1.07 1.45 0.21 0.28 0.58 0.85 0.07 0.12 0.48 0.77 0.07 0.12 33.55 71.37 0.72 25 6.69 13.64 1.39 7.54 1.21 0.75 1.48 0.18 0.83 0.17 0.48 0.06 0.40 0.06 34.88 0.35 0.12 0.08 0.01 0.07 13 7 17 9 26 3.77 1.06 0.91 0.53 0.92 7.77 1.87 1.59 0.73 1.26 0.81 0.21 0.19 0.09 0.16 4.44 1.10 0.98 0.45 0.82 0.70 0.18 0.16 0.09 0.14 0.19 0.05 0.04 0.028 0.04 6.50 0.24 0.23 0.14 0.21 0.12 0.03 0.03 0.014 0.03 0.56 0.17 0.17 0.08 0.15 0.12 0.04 0.037 0.017 0.03 0.31 0.115 0.11 0.05 0.10 0.04 0.018 0.017 0.007 0.01 0.36 0.11 0.114 0.043 0.09 0.04 0.017 0.018 0.006 0.012 25.73 5.21 4.60 2.28 3.97 0.44 0.31 0.36 14 34 9 2.95 2.37 2.51 4.64 3.55 3.71 0.55 0.46 0.48 2.83 2.34 2.44 0.46 0.41 0.42 0.13 0.11 0.12 0.61 0.55 0.63 0.08 0.08 0.08 0.41 0.40 0.43 0.09 0.09 0.09 0.26 0.24 0.27 0.04 0.03 0.04 0.22 0.21 0.22 0.03 0.03 0.03 13.30 10.87 11.47 0.77 3.11 11 15 9.36 19.48 21.51 43.03 2.56 4.57 13.45 24.40 1.78 3.38 0.37 0.68 2.10 4.45 0.25 0.62 1.06 3.10 0.19 0.65 0.54 1.91 0.07 0.27 0.42 1.77 0.07 0.27 53.73 108.58 1.19 1.97 21 34 6.66 12.19 13.26 19.72 1.68 2.58 8.62 13.31 1.27 2.06 0.39 0.44 1.50 2.65 0.20 0.36 0.94 1.81 0.19 0.39 0.56 1.14 0.08 0.15 0.50 0.98 0.08 0.15 35.93 57.93 2.80 3.23 15 6 10.55 12.68 21.80 27.70 2.41 3.35 12.68 17.51 1.93 2.80 0.52 0.81 2.37 3.18 0.34 0.44 1.77 2.18 0.38 0.44 1.11 1.29 0.16 0.18 1.06 1.19 0.16 0.18 57.24 73.93 Sierra San José section Mesa Quemada SSJ27 Cerro La Espina SSJ25 SSJ23 SSJ21 SSJ18 SSJ16 Cerro La Puerta SSJ11 SSJ10 SSJ9 Los Coyotes SSJ7 SSJ6 Tuape Shale SSJ5 SSJ4 Cerro La CejaSSJ3 SSJ2 a Pb SREE Member/Sample no Before data presentation, an attempt was made to round the data to the number of significant digits as suggested by Verma (2005). more enriched in silicate minerals than the CLP and CLE members. In contrast, the CLP and CLE members are more enriched in carbonate minerals than the CLC, TS, LC and MQ members. The observed variations in the major oxides concentrations within the same member from different localities may be due to the amount of clastic materials included in them. The bivariate plots of major oxides including certain trace elements vs the percentage of clastic materials present in the carbonate rocks provide useful information regarding the source of these materials (Parekh et al., 1977; Cullers, 2002). In addition, statistical approach will also useful to understand the statistically valid or invalid correlation (Verma et al., 2006). A Plot of the S(SiO2 þ Al2O3 þ Fe2O3 þ MgO þ Na2O þ K2O þ TiO2) vs the percentage of clastic materials show excellent linear correlation and also the linear plot extending from the origin (Fig. 3a). This suggests as expected that these oxides are mainly incorporated into the clastic materials rather than the calcite. In contrast, CaO and LOI have a perfect negative correlation with the percentage of clastic materials, suggesting that they are incorporated into the carbonate phase (Fig. 3b and c). These results are consistent with the other published studies (Parekh et al., 1977; Cullers, 2002). Trace elements concentrations and their ratios are given in Tables 2 and 3. The high field strength elements (HFSE), namely Zr, Y and Th, are resistant to weathering and alteration processes when compared with other trace elements (Taylor and McLennan, 1985). The limestones from the LC and MQ members contain a low concentration of Zr when compared with other members at the Cerro Pimas section (Table 2). The CLC, TS and LC members have higher concentrations of Zr than the CLP, CLE and MQ members at Sierra San José section (Table 2). Maximum concentrations of Y are found in the CLC, TS, LC and CLE members whereas low concentrations are found in the MQ Member at Cerro Pimas section (Table 2). In the Sierra San José section, the higher concentrations of Y are observed in the CLC, TS, LC and MQ members than the CLP and CLE members. Overall, the limestones of the Mural Formation contain high Sr content (Table 2). Plots of La, Ce, Sc and Th vs S(SiO2 þ Al2O3 þ Fe2O3 þ MgO þ Na2O þ K2O þ TiO2) yield significant positive correlation with the linear plots emanating slightly above the intersects of the X and Y axes (Fig. 4aed). This suggests that these elements are mainly housed in the clastic materials. Likewise, Sm, Eu, Tb, Yb, and Lu show a positive correlation with S(SiO2 þ Al2O3 þ Fe2O3 þ MgO þ Na2O þ K2O þ TiO2) which suggest that these elements are mainly associated with terrigenous particles (statistically significant at a strict significance level of 0.001; linear correlation coefficient r ¼ 0.64; 0.63; 0.71; 0.78; 0.79; respectively, n ¼ 35). These results are consistent with the other published studies (Parekh et al., 1977; Cullers, 2002). The enrichment and depletion of REE in the sediment are controlled by the major processes such as the terrigenous input from the continental area, authigenic removal of REE from the water column and early diagenesis (Sholkovitz, 1988). Seawater contributes lesser amount of REE to the sediments where as the sediments contain high REE concentration show non-seawater-like pattern (Nothdurft et al., 2004). The PAAS normalized Seawater REE patterns (Fig. 5) are characterized by (1) uniform light REE depletion, (2) a negative Ce anomaly, and (3) a slight positive La anomaly (e.g., De Baar et al., 1991; Bau and Dulski, 1996) and higher Y/Ho ratios (e.g., Bau, 1996). The limestones from the CP and SSJ sections show non-seawater-like REE þ Y patterns (CLC: NdN/YbN ¼ 1.52 0.42, n ¼ 5; TS: 1.95 1.17, n ¼ 6; LC: 1.18 0.65, n ¼ 8; CLP: 0.97 0.08, n ¼ 3, CLE: 0.92 0.15, n ¼ 10; MQ: 1.57 0.19, n ¼ 3; Fig. 6aef). Most of the samples contain positive La and negative Ce anomalies although some samples show slightly positive La and negative Ce anomalies to no anomalies. Most of the limestones from the CP and SSJ sections contain chondritic Y/Ho ratios (CLC: 30.1 2.7, n ¼ 5; TS: 34.2 5.0, n ¼ 5; LC: 32.1 2.4, n ¼ 7; CLE: 35.4 6.1, n ¼ 10; MQ: 32.5 3.3, n ¼ 3; respectively, Y/Ho Chondritic ratio: w28), but the limestones of the CLP member from the SSJ section contain slightly higher Y/Ho ratios (CLP: 41.8 6.4, n ¼ 3). Two samples contain high Y/Ho ratios (CP10: 70.15 and CP22: 102.5) which have been statistically proved as outliers using the method proposed by Verma and Quiroz-Ruiz (2006a,b). So, we have not included those samples with discordant outliers while calculating the mean and standard deviation to improve the authenticity of the data set (Verma et al., 2008). 406 J. Madhavaraju et al. / Cretaceous Research 31 (2010) 400e414 a b c Fig. 3. a, plot of the S(SiO2 þ Al2O3 þ Fe2O3 þ MgO þ Na2O þ K2O þ TiO2) vs clastic percentage in the limestones of the Mural Formation provides a linear plot with a correlation coefficient of 0.99. b, plot of the clastic (%) vs CaO content gives significant negative correlation with a correlation coefficient of 0.98. c, clastic (%) vs LOI plot exhibits a linear plot with a correlation coefficient of 0.98. 5. Discussion 5.1. Ce Anomaly Ce/Ce* ratios in limestones of the Cerro Pimas section ranges from 0.56 to 1.20, with a mean value of 0.91 (n ¼ 20); in limestones of the Sierra San José section this ratio ranges from 0.73 to 1.05 with a mean value of 0.90 (n ¼ 15). Noticeable variations are observed among different members of the Mural Formation. Many limestones of the Mural Formation exhibit less negative Ce anomalies than the deep-sea Indian Ocean carbonates (Nath et al., 1992), Arabian sea sediments (Nath et al., 1997), Cretaceous carbonates from Southern Alps (Bellanca et al., 1997), Maastrichtian carbonates of Southern India (Madhavaraju and Ramasamy, 1999), Indian Ocean waters (Bertram and Elderfield, 1993) and Pacific Ocean waters (Zhang and Nozaki, 1996). The depletion of Ce relative to the adjacent REE is one of the characteristic features of modern seawater. In seawater Ce/Ce* values range from <0.1 to 0.4 (Elderfield and Greaves, 1982; Piepgras and Jacobsen, 1992), but it is 1 in average shale (Murray et al., 1991a). The deficiency of Ce in seawater result from the oxidation of Ceþ3 to the less soluble Ceþ4 and subsequently its removal from the seawater through scavenging by suspended particles which settle through the water column (Sholkovitz et al., 1994). The Ce/Ce* values are not correlated very well with Al, Th and Zr (r ¼ 0.40; 0.35; 0.33; respectively), but Ce values are positively correlated with Al, Th and Zr (statistically significant at a strict significance level of 0.001; linear correlation coefficient r ¼ 0.55; 0.53; 0.58; respectively). Such moderate correlation of Ce and Ce/ Ce* with Al, Th and Zr suggests that other factors in addition to detrital input might have controlled the Ce distribution in the studied limestones. Seawater and marine carbonates exhibit a Ce deficient nature due to the scavenging of Ceþ4 by FeeMn oxides in the deep sea environments (Elderfield, 1988). The deep sea regions having a low sedimentation rate with a well developed oxic water column with a more active scavenging processes which initiate the coprecipitation of Ce(OH) on to FeeMn coatings on sedimentary particles. In the studied limestones the Ce/Ce* values, however, are not correlated with a scavenging-type particle reactive element (Ce/Ce* vs Pb: r ¼ 0.24), which indicates that the observed variations in Ce anomalies are probably unrelated to a scavenging process. Furthermore, the limestones of the Mural Formation were deposited in shallow marine environments (Lawton et al., 2004; González-León et al., 2008) where scavenging processes are limited when compared with deep sea regions. Many limestone samples from the Mural Formation contain positive Ce anomalies. The positive Ce anomalies mainly occur due to the paleoredox conditions (German and Elderfield, 1990), lithology and diagenesis (Nath et al., 1992; Madhavaraju and Ramasamy, 1999; Armstrong-Altrin et al., 2003; Madhavaraju and Lee, 2009) and Fe-organiceREE rich colloids from the riverine input (Sholkovitz, 1992). The variations in the bottom water oxygenation level in the carbonate rocks have been estimated using Ce/Ce* ratios (Wang et al., 1986; Piper, 1991). In the present study, Ce anomalies are inversely correlated with CaO contents (r ¼ 0.48) suggesting that the Ce/Ce* values, however, not related to bottom water oxygenation. The inclusion of REE-rich river-borne colloids in the coastal fringing reef resulted in the lack of a negative Ce anomaly (Nothdurft et al., 2004). The fluvial deltaic-influenced facies are present in the Cerro la Puerta and Cerro la Espina members at Cerro Pimas locations (González-León et al., 2008). The absence of a large Ce anomaly requires inclusion of material with a positive Ce anomaly relative to PAAS, and Fe-colloids from riverine input have such positive Ce anomaly (Sholkovitz, 1992). A comparison of Ce/Ce* values with the concentrations of Fe indicates that there is a moderate correlation ((statistically significant at a strict significance level of 0.001; linear correlation coefficient r ¼ 0.57) between them in these limestones. Hence, the observed variations in Ce content and Ce anomalies in the limestones of the Mural Formation may be due to the mixing of different portions of sediment components (dominantly biogenic and authigenic phases) which inherited the seawater-like Ce anomaly and of detrital materials (mainly alumino-silicates) with crust-like Ce anomaly. In addition, incorporation of Fe-colloids from riverine input might be partially responsible for the variations in Ce anomalies. J. Madhavaraju et al. / Cretaceous Research 31 (2010) 400e414 407 Table 3 Elemental ratios for limestones of the Mural Formation. Member/Sample no Cerro Pimas section Mesa Quemada CP47 CP45 Cerro La Espina CP43 CP41 CP38 CP36 CP33 Los Coyotes CP28 CP26 CP24 CP22 CP18 CP15 Tuape Shale CP12 CP10 C P9 CP6 Cerro La Ceja CP4 CP3 CP1 Sierra San José section Mesa Quemada SSJ27 Cerro La Espina SSJ25 SSJ23 SSJ21 SSJ18 SSJ16 Cerro La Puerta SSJ11 SSJ10 SSJ9 Los Coyotes SSJ7 SSJ6 Tuape Shale SSJ5 SSJ4 Cerro La Ceja SSJ3 SSJ2 La/Co Th/Sc Th/Co Th/Cr Cr/Th Ce/Ce* Eu/Eu* LaN/YbN NdN/YbN 5.57 5.91 1.33 2.05 0.25 0.39 0.06 0.14 0.02 0.04 45.00 26.69 0.56 0.79 1.13 0.91 1.47 1.25 1.39 1.77 36.07 29.56 2.79 7.93 5.54 7.18 11.3 1.44 1.17 1.12 1.89 2.13 0.70 0.56 0.72 0.68 1.07 0.36 0.08 0.15 0.18 0.20 0.17 0.23 0.21 0.23 0.14 5.89 4.43 4.84 4.32 7.14 0.99 0.95 1.05 1.07 0.99 1.26 1.01 1.02 0.84 1.00 0.77 0.62 0.74 0.62 0.82 1.10 0.80 1.09 0.93 1.10 27.68 32.75 32.33 33.45 33.96 5.35 6.10 5.32 11.15 7.90 8.85 0.37 0.99 0.73 0.74 0.47 1.17 e 0.55 0.65 0.45 0.95 0.83 e 0.09 0.09 0.03 0.06 0.11 e 0.03 0.07 0.03 0.07 0.08 e 33.27 15.26 38.78 13.44 12.54 0.84 0.91 0.89 0.67 0.95 0.89 1.17 1.21 1.09 1.33 1.44 1.35 0.44 1.04 0.69 0.78 0.82 1.01 0.70 1.24 0.86 0.77 1.07 1.20 33.60 34.00 31.57 102.50 33.28 34.05 5.13 8.62 25.78 3.53 2.02 3.32 7.01 2.40 0.71 1.21 1.78 1.07 0.28 0.47 0.48 0.73 0.12 0.12 0.16 0.15 8.47 8.10 6.23 6.54 1.00 1.00 1.20 0.84 1.67 1.38 1.49 1.02 1.28 1.64 2.75 0.52 1.72 2.66 3.96 0.79 31.04 70.15 29.89 32.12 7.59 7.46 7.59 2.10 1.22 4.01 2.48 1.30 0.75 0.68 0.21 0.40 0.20 0.17 0.15 5.09 6.01 6.81 0.78 0.82 1.04 0.98 1.17 0.94 1.81 0.99 1.30 2.22 1.39 1.78 28.00 31.48 34.00 4.81 2.12 0.52 0.23 0.36 2.76 1.00 2.64 1.23 1.56 31.88 9.43 5.30 4.55 2.65 4.60 1.35 0.49 0.43 0.25 0.46 0.88 0.60 0.40 0.05 0.35 0.13 0.06 0.04 e 0.04 0.09 0.03 0.03 e 0.02 11.37 29.58 34.88 e 42.71 1.03 0.88 0.87 0.75 0.73 0.42 1.12 0.98 1.22 1.09 0.77 0.72 0.62 1.00 0.75 1.02 0.83 0.73 0.87 0.75 35.42 40.00 32.70 48.24 45.94 4.92 3.95 4.18 1.34 1.11 1.38 0.73 0.52 0.60 0.20 0.15 0.20 0.07 0.05 0.05 14.39 19.10 20.58 0.83 0.79 0.77 1.15 1.10 1.10 0.99 0.85 0.84 1.06 0.93 0.91 36.22 51.65 39.14 15.34 12.25 5.78 8.66 1.26 1.96 0.48 1.38 0.09 0.26 11.16 3.83 1.01 1.05 0.90 0.83 1.64 0.81 2.66 1.15 30.11 27.71 4.69 6.10 3.03 6.45 0.84 0.99 0.54 1.04 0.08 0.10 12.75 9.80 0.92 0.82 1.33 0.89 0.98 0.92 1.44 1.13 42.32 35.46 4.36 3.02 3.89 4.59 1.16 0.77 1.03 1.17 0.27 0.15 3.74 6.63 1.00 1.00 1.14 1.28 0.73 0.79 0.99 1.23 29.66 27.34 La/Sc 5.2. Behaviour of Europium The limestones from Cerro Pimas and Sierra San Jose sections show large variations in Eu anomalies (Eu/Eu*: 0.84 to 1.67; 0.42 to 2.64; respectively). Most of the limestone samples contain positive Eu anomalies, whereas few samples contain negative Eu anomalies. Positive Eu anomalies are mainly found either in sediments affected by hydrothermal solutions (Michard et al., 1983; German et al., 1993; Siby et al., 2008); intense diagenesis (Murray et al., 1991b; MacRae et al., 1992) or variations in plagioclase content (Nath et al., 1992). Positive Eu anomalies are not common in seawater, which resulted due to hydrothermal discharges along mid-ocean ridges (Klinkhammer et al., 1983, 1994). Positive Eu anomalies have been well documented for hydrothermal vent fluids and sediment particulates in active ridge system (Michard et al., 1983; German et al., 1990, 1999; Douville et al., 1999). Hydrothermal solutions mainly originate in the deep marine environments but such an origin is unlikely for the limestones of the Mural Formation which were deposited in shallow marine environments (Lawton et al., 2004; González-León et al., 2008). Y/Ho Positive Eu anomalies have been reported from Amazon fan muds in which Eu2þ is precipitated from pore waters during diagenesis (MacRae et al., 1992). Unlike Ce which can undergo oxidation state changes in ambient seawater conditions, redox transformations from Eu3þ to Eu2þ require low oxidation-reduction potentials (pH 2e4) and high temperatures (>200 C) (Sverjensky, 1984; Bau, 1991). These conditions are generally absent in shallow marine environments. Petrographic and geochemical studies, suggest that the studied limestones were not subjected to intense diagenesis. The positive correlation between Eu and the immobile elements such as Y, Th and Zr (statistically significant at a strict significance level of 0.001; linear correlation coefficient r ¼ 0.69; 0.74; 0.53; respectively) supports the nondiagenetic influence on this element. The inclusion of small amount of feldspars may lead to positive Eu anomalies in the bulk sediments (Murray et al., 1991b). In the present study, Eu contents show significant positive correlation with Al2O3 which suggest the detrital origin of this element. Hence, the observed variations in Eu anomalies in the limestones of the Mural Formation may be due to the presence of feldspar content rather than hydrothermal events and diagenesis. 408 J. Madhavaraju et al. / Cretaceous Research 31 (2010) 400e414 Seawater/PAAS x 10-6 10 1 NPSW Coral Sea South Fiji basin Bay of Bengal Andaman Sea 0.1 0.01 La Ce Pr Nd Sm Eu Gd Tb Dy Y Ho Er Tm Yb Lu Elements Fig. 5. PAAS normalized REE patterns of modern seawaters (NPSW: North Pacific shallow water, Sagami trough (Alibio and Nozaki, 1999), Coral Sea: Coral sea (South Pacific shallow seawater, Zhang and Nozaki, 1996), South Fiji Basin: South Fiji Basin e Station SA12 (Zhang and Nozaki, 1996), Bay of Bengal: Bay of Bengal shallow water (Nozaki and Alibio, 2003) and Andaman Sea: Andaman Sea shallow water (Nozaki and Alibio, 2003). This interpretation is further supported by the enrichment of Sr in these limestone samples. 5.3. Source of REE Fig. 4. a, S(SiO2 þ Al2O3 þ Fe2O3 þ MgO þ Na2O þ K2O þ TiO2) vs Sc show significant positive correlation with correlation coefficient of 0.85. b, plot of the S(SiO2 þ Al2O3 þ Fe2O3 þ MgO þ Na2O þ K2O þ TiO2) vs Th content provides positive correlation with coefficient of 0.72. c, S(SiO2 þ Al2O3 þ Fe2O3 þ MgO þ Na2O þ K2O þ TiO2) vs La plot exhibits positive correlation (correlation coefficient of 0.70). d, plot of the S(SiO2 þ Al2O3 þ Fe2O3 þ MgO þ Na2O þ K2O þ TiO2) vs Ce content gives positive correlation with a correlation coefficient of 0.67. REE data have been used extensively to assess the pathways of biogenic and terrigenous fluxes from the source to the marine sediments (Piper, 1974; Murray and Leinen, 1993; Sholkovitz et al., 1994; Wray, 1995; Cullers, 1995). The concentration of REEs in seawater is mainly controlled by factors relating to input sources and scavenging processes related to depth, salinity, and oxygen levels (Elderfield, 1988; Piepgras and Jacobsen, 1992; Bertram and Elderfield, 1993; Greaves et al., 1999). The limestones of the Mural Formation exhibit distinctly nonseawater-like patterns (Fig. 6aef) which resulted from the presence of a variety of contaminants. The major source of contaminants are likely: 1) terrigenous fine-grained sediments having high REE content with non-seawater-like pattern (Elderfield et al., 1990), 2) Fe and Mn oxides (Bau et al., 1996) and 3) phosphates having a high affinity for REEs in diagenetic fluids (Byrne et al., 1996). The concentration of Al2O3 is closely related to clay content. So, Al2O3 concentration is considered as a proxy for shale contamination (Nothdurft et al., 2004). Most of the limestones from the Mural Formation show high values for Al2O3 (0.44 to 6.26%; except five samples which show low concentration) when compared to the average values of siliciclastic-contaminated carbonate rocks (0.42%; Veizer, 1983). The Al2O3 concentration shows positive correlation P with the REE content (statistically significant at a strict significance level of 0.001; linear correlation coefficient r ¼ 0.59, n ¼ 35) which suggest a moderate contamination. Trace elements such as Th and Sc have been used as indicators of shale contamination because of their higher concentrations in the PAAS than in marine carbonates (Webb and Kamber, 2000). The Th and Sc concentrations correlate well with Al2O3 contents (statistically significant at a strict significance level of 0.001; linear correlation coefficient r ¼ 0.81, r ¼ 0.90; respectively) which suggest the presence of shale contamination in the limestones of the Mural Formation. Many modern carbonates (particularly foraminifera) were contaminated by ferromanganese crusts (Palmer, 1985), which show a high affinity for the REEs, and the crusts incorporate them disproportionately (Bau et al., 1996). The limestones of the present P study show a positive correlation between the REE and Fe contents (statistically significant at a strict significance level of 1 0.1 CP1 SSJ2 CP3 SSJ3 CP4 d 1 Sample/PAAS a Sample/PAAS J. Madhavaraju et al. / Cretaceous Research 31 (2010) 400e414 0.1 409 SSJ9 La Ce Pr Nd Sm Eu Gd Tb Dy Y Ho La Er Tm Yb Lu Ce Pr Nd Sm Eu Gd Tb Dy CP9 SSJ4 CP10 SSJ5 1 e 10 Sample/PAAS Sample/PAAS 10 CP6 CP12 1 La CP33 SSJ16 Ce Pr Nd Sm Eu Gd Tb Dy Y Ho CP36 SSJ18 CP38 SSJ21 CP41 SSJ23 CP43 SSJ25 0.01 La Er Tm Yb Lu Ce Pr f CP15 CP18 CP22 CP24 CP26 CP28 SSJ6 SSJ7 0.01 La Ce Pr Nd Sm Eu Gd Tb Dy Nd Sm Eu Gd Tb Dy Y Ho Er Tm Yb Lu Elements Sample/PAAS Sample/PAAS Er Tm Yb Lu 0.1 Elements 0.1 Ho 0.001 0.1 1 Y Elements Elements c SSJ11 0.01 0.01 b SSJ10 Y Ho Er Tm Yb Lu Elements 1 CP45 CP47 SSJ27 0.1 0.01 La Ce Pr Nd Sm Eu Gd Tb Dy Y Ho Er Tm Yb Lu Elements Fig. 6. a, REE patterns of limestones of the CLC Member. b, PAAS normalised REE patterns of the TS Member. c, REE patterns of the LC Member. d, REE patterns of limestones of the CLP Member. e, REE patterns of limestones of the CLE Member. f, PAAS normalized REE patterns of limestones of the MQ Member. 0.001; linear correlation coefficient r ¼ 0.70). The average Fe2O3 concentrations (0.27%, n ¼ 35) of the present study is within the range of average carbonate (0.38%, Veizer, 1983) which suggest that the diagenetic Fe2O3 does not play a significant role in controlling the REE patterns in these limestones. Phosphates mainly incorporate REE disproportionally and they are altered easily by diagenesis (Reynard et al., 1999). The limestones of the present study show a positive correlation between P REE and P2O5 (statistically significant at a strict significance level of 0.001; linear correlation coefficient r ¼ 0.74). A poor correlation has been observed between P and NdN/YbN ratios (statistically significant at a strict significance level of 0.01; linear correlation coefficient r ¼ 0.42) in the limestones of the Mural Formation. Hence it is unlikely that the presence of minor quantity of P2O5 could affect the REE patterns of limestones of the Mural Formation. Thus, our data suggest that contamination by phosphate minerals or ferromanganese coatings is not likely. Yttrium is not removed from the seawater effectively when compared with its geological twin Ho, due to differing surface complex stabilities, thereby leading to a significant superchondritic marine Y/Ho ratio (Hogdahl et al., 1968; Zhang et al., 1994; Bau et al., 1995; Bau, 1996; Nozaki et al., 1997). The chemical sediments free from contamination generally display Y/Ho ratios between 44 and 74. But contaminations due to terrestrial detritus and volcanic ash have fairly constant chondritic Y/Ho values of w28. The limestones of the Mural Formation contain large variations in Y/Ho ratio (27.34 to 102.50). Like the Y/Ho ratio, Th and Sc also show significant variations among different members of the Mural Formation. Such variations in these limestones may be due to contamination by terrestrial detritus (Webb and Kamber, 2000). In the present study, most of the limestones of the Mural Formation show high values of Th, Sc and Zr and chondritic Y/Ho ratios, which suggests that these limestones appear to have been contaminated by terrigenous materials. The different members of the Mural Formation show slight variations in LaN/YbN ratios (Table 4). The LaN/YbN ratios of the CLC, TS and MQ members are more or less similar to the values proposed by Condie (1991; about 1.0) and Sholkovitz (1990; about 1.3) for terrigenous materials whereas the LC, CLP and CLE members show lower LaN/YbN ratios. The observed variations in the LaN/YbN ratios in the limestones of the Mural Formation suggest that the REE signals were mainly influenced by the incorporation of terrigenous materials into them. The LaN/YbN ratios of the Mural Formation are more or less similar to the Arabian Sea carbonate sediments (Nath et al., 1997) and Indian Ocean carbonate sediments (Nath et al., 1992) and lower than the shallow marine Albian and Maastrichtian limestones (Madhavaraju and Lee, 2009; Madhavaraju and Ramasamy, 1999; Table 4) of the Cauvery Basin and Kudankulam Formation (Armstrong-Altrin et al., 2003) of South India (Table 4). The limestones from the Mural Formation show non-seawaterlike patterns. The representative samples of the present study were compared with the limestones having non-seawater-like patterns (Fig. 7; Late Devonian coastal fringing reef, Nothdurft et al., 2004; Albian limestone, Madhavaraju and Lee, 2009; Maastrichtian limestone, Madhavaraju and Ramasamy, 1999; Miocene limestone, Armstrong-Altrin et al., 2003) which suggests that the inclusions of terrigenous materials in the carbonates as contaminants will mask 410 J. Madhavaraju et al. / Cretaceous Research 31 (2010) 400e414 Sample/PAAS 0.56 1.03 e 36.6 e 0.84 0.1 0.8 0.2 78 40 29 12 1.15 0.1 0.1 Y Ho Er Tm Yb Lu 0.91 0.13 1.0 0.45 35 28 49 6 1.16 0.34 0.97 0.13 1.91 0.22 39 25 48 6 1.2 0.08 0.76 0.2 1.8 0.5 73 20 42 8 0.58 0.1 Fig. 7. Representative samples of the Mural Formation with non-seawater-like signatures are compared with limestones exhibit LREE enriched REE þ Y pattern (DCFR: Late Devonian coastal fringing reef (Nothdurft et al., 2004), AL: Albian limestone (Madhavaraju and Lee, 2009), MAL: Maastrichtian limestone (Madhavaraju and Ramasamy, 1999) and ML: Miocene limestone (Kudankulam Formation, ArmstrongAltrin et al., 2003). 0.78 0.22 1.32 0.13 28 7 51 2 1.6 0.9 l k i j h f g e c d Present study, n ¼ 5. Present study, n ¼ 6. Present study, n ¼ 8. Present study, n ¼ 3. Present study, n ¼ 10. Present study, n ¼ 3. Present study, n ¼ 35. Madhavaraju and Lee, 2009, n ¼ 8. Madhavaraju and Ramasamy, 1999, n ¼ 8. Armstrong-Altrin et al., 2003, n ¼ 9. Nath et al., 1997, n ¼ 9. Nath et al., 1992, n ¼ 4. a b MQ CP10 SSJ6 ML Elements 0.93 0.12 0.74 0.12 23 19 51 5 1.0 0.24 CLE CP9 SSJ3 MAL 1 La Ce Pr Nd Sm Eu Gd Tb Dy 0.80 0.03 0.89 0.08 12 1 52 0.5 1.12 0.03 CLP CP4 SSJ2 DCFR 0.01 0.90 0.12 0.90 0.35 33 34 51 6 1.17 0.22 LC TS 0.96 0.14 1.35 0.80 62 28 46 2 1.3 0.29 0.93 0.12 1.12 0.40 51 23 43 10 1.1 0.14 Ce/Ce* LaN/YbN SREE CaO Eu/Eu* CLC CP1 CP33 AL 0.9 0.1 2.7 1.4 80 40 49 3 0.78 0.3 Indian Ocean carbonate sedimentsl Arabian Sea carbonate sedimentsk Kudankulam Formationj Maastrichtian limestonei Albian limestoneh Mural Formationg (average) f e d c b a Mural Formationaef Table 4 Average geochemical values of the Mural Formation compared to shallow and deep marine sediments. 10 the seawater signature due to their high concentration of the REE. The high content of Al2O3 and SREE, the elevated concentrations of Th and Sc, chondritic Y/Ho ratios, high LaN/YbN ratios and nonseawater-like REE patterns indicate that the terrigenous contaminations in the limestones of the Mural Formation are responsible for such variations in REE signals. The preservation of seawater REEþY pattern in limestone will only occur if detrital materials, marine or diagenetic authigenic phosphates (eg. Rasmussen et al., 1998) and ferromanganese encrustations (eg. Reitner, 1993) are nearly absent from the limestones. The inclusions of terrigenous materials in the carbonates as contaminants will mask the seawater signature due to their high concentration of REE in them. So, the depositional environment of limestone is more important to understand the REE geochemistry. In the present study, the limestone samples from LC Member (at CP section) and CLP and CLE members (at SSJ section) were deposited in an open shelf environment with little terrigneous contamination whereas the limestones from CLE (at CP section) and LC (at SSJ section) members contain high concentrations of terrigenous materials, respectively due to fluvial deltaic influence and deltafront depositional environments (González-León et al., 2008). Thus, the limestones deposited under both coastal and open shelf environments exhibit non-seawater-like REE þ Y patterns. The present study reveals that the limestones deposited in open shelf environments are also contaminated by some terrigenous particles. Hence, care may be taken to study the REE geochemistry of ancient limestone. The limestones devoid of terrigenous particles are suitable for understanding the REE patterns of ancient shallow seawater and also they serve as a valuable seawater proxy. The presence of a small quantity of terrigenous materials in the limestones will also reveal source rock information. The concentrations of certain immobile elements like La and Th are higher in silicic than in basic igneous rocks (Cullers, 1995). The felsic and mafic rocks show significant variations in La/Sc, La/Co, Th/ Sc, Th/Co and Th/Cr ratios which are most useful in understanding the provenance composition (Wronkiewicz and Condie, 1990; Cox et al., 1995; Cullers, 1995). The extent to which these elemental ratios that are useful in unraveling the provenance of terrigenous materials present in the carbonate rock is clearly addressed by Cullers (2002). In the present study, La/Sc, La/Co, Th/Co, Th/Cr, Cr/ Th, and Th/Sc are similar over a range of the S(SiO2 þ Al2O3 þ Fe2O3 þ MgO þ Na2O þ K2O þ TiO2) (Fig. 8). Our results are generally consistent with other studies (Cullers, 2002). J. Madhavaraju et al. / Cretaceous Research 31 (2010) 400e414 411 Fig. 8. Bivariate plots for the limestones of the Mural Formation. a, S(SiO2 þ Al2O3 þ Fe2O3 þ MgO þ Na2O þ K2O þ TiO2) vs La/Sc. b, S(SiO2 þ Al2O3 þ Fe2O3 þ MgO þ Na2O þ K2O þ TiO2) vs La/Co. c, S(SiO2 þ Al2O3 þ Fe2O3 þ MgO þ Na2O þ K2O þ TiO2) vs Th/Sc. d, S(SiO2 þ Al2O3 þ Fe2O3 þ MgO þ Na2O þ K2O þ TiO2) vs Th/Co. e, S(SiO2 þ Al2O3 þ Fe2O3 þ MgO þ Na2O þ K2O þ TiO2) vs Th/Cr. f, S(SiO2 þ Al2O3 þ Fe2O3 þ MgO þ Na2O þ K2O þ TiO2) vs Eu/Eu*. Table 5 Range of elemental ratios of the Mural Formation compared to felsic rocks, mafic rocks, Upper Continental Crust (UCC) and Post-Archaean Australian Shale (PAAS). Range of Mural Formationa Eu/Eu* La/Sc La/Co Th/Sc Th/Co Th/Cr Cr/Th a b c 0.42e2.64 2.65e25.78 0.25e8.66 0.05e2.48 0.03e1.38 0.02e0.36 2.76e45.0 Range of sedimentsb Felsic rocks Mafic rocks 0.40e0.94 2.50e16.3 1.80e13.8 0.84e20.5 0.67e19.4 0.13e2.7 4.00e15.0 0.71e0.95 0.43e0.86 0.14e0.38 0.05e0.22 0.04e1.40 0.018e0.046 25e500 Upper Continental Crustc Post-Archaean Australian average shalec 0.63 2.21 1.76 0.79 0.63 0.13 7.76 0.66 2.40 1.65 0.90 0.63 0.13 7.53 Present study, n ¼ 35. Cullers (1994, 2000); Cullers and Podkovyrov (2000); Cullers et al. (1988). Taylor and McLennan (1985). The La/Sc, La/Co, Th/Co, Th/Cr, Cr/Th, and Th/Sc ratios of the limestones of the Mural Formation have been compared with felsic and mafic rocks (fine fraction) as well as to upper continental crust (UCC) and PAAS values (Table 5) which suggest that these ratios are within the range of intermediate to felsic rocks. 6. Conclusions The high content of Al2O3, SREE, Th and Sc, low Y/Ho ratios, high LaN/YbN ratios and non-seawater-like REE patterns in the limestones of the Mural Formation indicate that the terrigenous contaminations is responsible for the variations in REE signals. The limestones of the Mural Formation were compared with the limestones having non-seawater-like patterns that indicate the inclusion of terrigenous materials in the carbonates, as contaminants will mask the seawater signature due to their high concentration of the REE in them. The limestone samples from CLP member show negative Ce anomalies (Ce/Ce*: 0.77 to 0.83, ave. 0.80 0.03, n ¼ 3) whereas CLC, TS, LC, CLE and MQ members show both negative and positive Ce anomalies (Ce/Ce*: 0.78 to 1.04, ave. 0.93 0.12, n ¼ 5; 412 J. Madhavaraju et al. / Cretaceous Research 31 (2010) 400e414 0.82 to 1.20, ave. 0.96 0.14, n ¼ 6; 0.67 to 1.05, ave. 0.90 0.12, n ¼ 8; 0.73 to 1.07, ave. 0.93 0.12, n ¼ 10; 0.56 to 1.00, ave. 0.78 0.22, n ¼ 3; respectively). The observed variations in Ce anomalies resulted from the inclusion of terrigenous materials as well as Fe-rich colloids from rivers. The limestones of the Mural Formation contain both negative and positive Eu anomalies relative to the PAAS. The CLP member shows least variations in Eu anomalies (Eu/Eu*: 1.10 to 1.15, ave. 1.12 0.03, n ¼ 3) whereas CLC, TS, LC, CLE and MQ members exhibit large variations in Eu anomalies (Eu/Eu*: 0.94 to 1.28, ave. 1.10 0.14, n ¼ 5; 0.89 to 1.67, ave. 1.30 0.29, n ¼ 6; 0.83 to 1.44, ave. 1.17 0.22, n ¼ 8; 0.42 to 1.26, ave. 1.0 0.24, n ¼ 10; 0.91 to 2.64, ave. 1.6 0.9, n ¼ 3; respectively). The observed positive Eu anomalies in the limestones are likely controlled by the feldspar content. The elemental ratios (La/Sc, La/Co, Th/Co, Th/Cr, Cr/Th, and Th/Sc) which are characteristics of provenance of terrigenous materials show the minimal variations with the changing percentage of the S(SiO2 þ Al2O3 þ Fe2O3 þ MgO þ Na2O þ K2O þ TiO2). The La/Sc, La/ Co, Th/Co, Th/Cr, Cr/Th, and Th/Sc ratios of the limestones of the Mural Formation have been compared with felsic and mafic rocks, upper continental crust (UCC) and PAAS values which indicate that the terrigenous materials included in the limestones of the Mural Formations were mainly derived from the intermediate to felsic rocks. Acknowledgements The first author would like to thank Dr. Thierry Calmus, ERNO, Instituto de Geología, Universidad Nacional Autónoma de Mexico for his support and encouragement during this work. We would like to thank Prof. S.P. Verma and Prof. R.L. Cullers for their critical reviews and constructive comments. We would like to thank Dr. Hannes Löser for his help during the field work. We acknowledge the support rendered by Universidad Nacional Autónoma de Mexico through PAPIIT Project No.IN121506-3. The field study of this work is partly supported by PAPIIT Project No. IN107803-3. We thank Mr. Pablo Peñaflor for powdering of limestone samples for geochemical studies. We also thank Dr. Teresa Pi I Puig, Instituto de Geología, Universidad Nacional Autónoma de México, México for her help in XRD analysis. This research was partly supported by Korea Science and Engineering Foundation (KOSEF) grants (R012000-000-00056-0 to YIL). References Alibio, D.S., Nozaki, Y., 1999. Rare earth elements in seawater: particle association, shale-normalisation, and Ce oxidation. Geochimica et Cosmochimica Acta 63, 363e372. Armstrong-Altrin, J.S., Verma, S.P., Madhavaraju, J., Lee, Y.I., Ramasamy, S., 2003. Geochemistry of Upper Miocene Kudankulam Limestones, Southern India. International Geological Review 45, 16e26. Barnett, V., Lewis, T., 1994. Outliers in Statistical Data, third ed. John Wiley & Sons, Chichester, UK, 584 pp. Bau, M., 1991. Rare earth element mobility during hydrothermal and metamorphic fluid-rock interaction and the significance of the oxidation state of europium. Chemical Geology 93, 219e230. Bau, M., 1996. Controls on fractionation of isovalent trace elements in magmatic and aqueous systems: evidence from Y/Ho, Zr/Hf and lanthanide tetrad effect. Contribution to Mineralogy and Petrology 123, 323e333. Bau, M., Dulski, P., 1996. Distribution of yttrium and rare earth elements in the Penge and Kuruman iron formation, Transvaal Supergroup, South Africa. Precambrian Research 79, 37e55. Bau, M., Dulski, P., Moller, P., 1995. Yttrium and holmium in South Pacific seawater: vertical distribution and possible fractionation behaviour. Chemie der Erde 55, 1e15. Bau, M., Koschinsky, A., Dulski, P., Hein, J.R., 1996. Comparison of the partitioning behaviours of yttrium, rare earth elements, and titanium between hydrogenetic marine ferromanganese crusts and seawater. Geochimica et Cosmochimica Acta 60, 1709e1725. Bellanca, A., Masetti, D., Neri, R., 1997. Rare earth elements in limestone/marlstone couplets from the Albian-Cenomanian Cismon section (Venetian region, northern Italy): assessing REE sensitivity to environmental changes. Chemical Geology 141, 141e152. Bertram, C.J., Elderfield, H., 1993. The geochemical balance of the rare earth elements and neodymium isotopes in the oceans. Geochimica et Cosmochimica Acta 57, 1957e1986. Bilodeau, W.L., Lindberg, F.A., 1983. Early Cretaceous tectonics and sedimentation in southern Arizona, southwestern New Mexico, and northern Sonora, Mexico. In: Reynolds, M.W., Dolly, E.D. (Eds.), Mesozoic Paleogeography of West-Central United States. Society of Economic Paleontologists and Mineralogists, Rocky Mountain Section, Rocky Mountain Paleogeography Symposium 2, pp. 173e188. Bilodeau, W.L., Kluth, C.F., Vedder, L.K., 1987. Regional stratigraphic, sedimentologic, and tectonic relationships of the Glance Conglomerate in southeastern Arizona. In: Dickinson, W.R., Klute, M.F. (Eds.), Mesozoic Rocks of Southern Arizona Adjacent Areas. Arizona Geological Society Digest, vol. 18, pp. 229e256. Biscaye, P.E., 1965. Mineralogy and sedimentation of recent deep sea clay in the Atlantic Ocean and adjacent seas and oceans. Bulletin Geological Society of America 76, 803e832. Byrne, R.H., Liu, X., Schijf, J., 1996. The influence of phosphate coprecipitation on rare earth element distributions in natural waters. Geochimica et Cosmochimica Acta 60, 3341e3346. Cantu-Chapa, A., 1976. Nuevas localidades del Kimeridgiano y Titoniano in Chihuahua (Norte de Mexico). Revista del Instituto Mexicano del Petroleo 7, 38e45. Condie, K.C., 1991. Another look at rare earth elements in shales. Geochimica et Cosmochimica Acta 55, 2527e2531. Cox, R., Lowe, D.R., Cullers, R.L., 1995. The influence of sediment recycling and basement composition on evolution of mudrock chemistry in the southwestern United States. Geochimica et Cosmochimica Acta 59, 2919e2940. Cullers, R.L., 1994. The controls on the major and trace element variation of shales, siltstones and sandstones of Pennsylvanian e Permian age from uplifted continental blocks in Colorado to platform sediment in Kansas, USA. Geochimica et Cosmochimica Acta 58, 4955e4972. Cullers, R.L., 1995. The controls on the major and trace element evolution of shales, siltstones and sandstones of Ordovician to Tertiary age in the Wet Mountain region, Colorado, U.S.A. Chemical Geology 123, 107e131. Cullers, R.L., 2000. The geochemistry of shales, siltstones and sandstones of PennsylvanianePermian age, Colorado, U.S.A.: implications for provenance and metamorphic studies. Lithos 51, 305e327. Cullers, R.L., 2002. Implications of elemental concentrations for provenance, redox conditions, and metamorphic studies of shales and limestones near Pueblo, CO, USA. Chemical Geology 191, 305e327. Cullers, R.L., Basu, A., Suttner, L., 1988. Geochemical signature of provenance in sand-size material in soils and stream sediments near the Tobacco Root batholith, Montana, USA. Chemical Geology 70, 335e348. Cullers, R.L., Podkovyrov, V.N., 2000. Geochemistry of the Mesoproterozoic Lakhanda shales in southeastern Yakutia, Russia: implications for mineralogical and provenance control, and recycling. Precambrian Research 104, 77e93. De Baar, H.J.W., Schijf, J., Byrne, R.H., 1991. Solution chemistry of the rare earth elements in seawater. European Journal of Solid State Inorganic Chemistry 28, 357e373. Dickinson, W.R., Klute, M.A., Swift, P.A., 1986. The Bisbee Basin and its bearing on late Mesozoic paleogeographic and paleotectonic relations between the Cordilleran and Carribean regions. In: Abbott, P.L. (Ed.), Cretaceous Stratigraphy, vol. 46. Pacific Section (SEPM) Book, Western North America, pp. 51e62. Dickinson, W.R., Klute, M.A., Swift, P.A., 1989. Cretaceous strata of southern Arizona. In: Jenney, J.P., Reynols, S.J. (Eds.), Geologic Evolution of Arizona. Arizona Geological Society Digest, vol. 17, pp. 447e462. Douville, E., Bienvenu, P., Charlou, J.L., Donval, J.P., Fouquet, Y., Appriou, P., Gamo, T., 1999. Yttrium and rare earth elements in fluids from various deep-sea hydrothermal systems. Geochimica et Cosmochimica Acta 63, 627e643. Elderfield, H., 1988. The oceanic chemistry of the rare earth elements. Philosophical Transactions of the Royal Society of London A325, 105e126. Elderfield, H., Greaves, M.J., 1982. The rare earth elements in seawater. Nature 296, 214e219. Elderfield, H., Upstill-Goddard, R., Sholkovitz, E.R., 1990. The rare earth elements in rivers, estuaries and coastal seas and their significance to the composition of ocean waters. Geochimica et Cosmochimica Acta 54, 971e991. German, C.R., Elderfield, H., 1990. Application of Ce anomaly as a paleoredox indicator: the ground rules. Paleoceanography 5, 823e833. German, C.R., Hergt, J., Palmer, M.R., Edmond, J.M., 1999. Geochemistry of a hydrothermal sediment core from the OBS ventfield, 218 N East Pacific rise. Chemical Geology 155, 65e75. German, C.R., Holliday, B.P., Elderfield, H., 1993. A geochemical study of metalliferous sediment from the TAG hydrothermal mound, 26 080 N, mid-Atlantic ridge. Journal of Geophysical Research 98, 9683e9692. German, C.R., Klinkhammer, G.P., Edmond, J.M., Mitra, A., Elderfield, H., 1990. Hydrothermal scavenging of rare earth elements in the ocean. Nature 345, 516e518. Giles, H.L., Hurley, P.W., Webster, H.W.M., 1995. Simple approach to the analysis of oxides, silicates, and carbonates using X-ray fluorescence spectrometry. X-ray Spectrometry 24, 205e218. González-León, C.M., Scott, R.W., Loser, H., Lawton, T.F., Robert, E., Valencia, V.A., 2008. Upper Aptian-Lower Albian Mural Formation: stratigraphy, biostratigraphy and depositional cycles on the Sonoran shelf, northern Mexico. Cretaceous Research 29, 249e266. J. Madhavaraju et al. / Cretaceous Research 31 (2010) 400e414 Govindaraju, K., 1994. 1994 compilation of working values and descriptions for 383 Geostandards. Geostandards Newsletter 18, 1e158. Greaves, M.J., Elderfield, H., Sholkovitz, E.R., 1999. Aeolian sources of rare earth elements to the Western Pacific Ocean. Marine Chemistry 68, 31e38. Grim, R.E., 1968. Clay Mineralogy. McGraw-Hill, New York, 600 pp. Hardy, R., Tucker, M., 1988. X-ray powder diffraction of sediments. In: Tucker, M. (Ed.), Techniques in Sedimentology. Blackwell Scientific Publications, Oxford, pp. 191e228. Hogdahl, O.T., Bowen, B.T., Melson, S., 1968. Neutron activation analysis of lanthanide elements in seawater. Advanced Chemical Series 73, 308e325. Holser, W.T., 1997. Evaluation of the application of rare earth elements to paleoceanography. Palaeogeography Palaeoclimatology Palaeoecology 132, 309e323. Jacques-Ayala, C., 1995. Paleogeography and provenance of the Lower Cretaceous Bisbee Group in the Caborca-Santa Ana area, northwestern Sonora. Special Paper. In: Jacques-Ayala, C., González-León, C.M., Roldan-Quintana, J. (Eds.), Studies on the Mesozoic of Sonora and adjacent areas, vol. 301. Geological Society of America, pp. 79e98. Jarvis, K.E., 1988. Inductively coupled plasma mass spectrometry: a new technique for the rapid or ultra-trace level determination of the rare earth elements in geological materials. Geological Society of America Bulletin 87, 725e737. Kamber, B.S., Webb, G.E., 2001. The geochemistry of late Archaean microbial carbonate: implications for ocean chemistry and continental erosion history. Geochimica et Cosmochimica Acta 65, 2509e2525. Klinkhammer, G.P., Elderfield, H., Edmond, J.M., Mitra, A., 1994. Geochemical implications of rare earth element patterns in hydrothermal fluids from midocean ridges. Geochimica et Cosmochimica Acta 58, 5105e5113. Klinkhammer, G., Elderfield, H., Hudson, A., 1983. Rare earth elements in seawater near hydrothermal vents. Nature 305, 185e188. Klute, M.A., 1991. Sedimentology, Sandstone Petrofacies, and Tectonic Setting of the Late Mesozoic Bisbee Basin, Southeastern Arizona. Unpublished Ph.D Dissertation, University of Arizona, 268 pp. Lawton, T.F., González-León, C.M., Lucas, S.G., Scott, R.W., 2004. Stratigraphy and sedimentology of the upper Aptian-upper Albian Mural Limestone (Bisbee Group) in northern Sonora, Mexico. Cretaceous Research 25, 43e60. Liu, Y.G., Miah, M.R.U., Schmitt, R.A., 1988. Cerium: a chemical tracer for paleooceanic redox conditions. Geochimica et Cosmochimica Acta 52, 1361e1371. Mack, G.H., Kolins, W.B., Galemore, J.A., 1986. Lower Cretaceous stratigraphy, depositional environments, and sediment dispersal in southwestern New Mexico. American Journal of Science 286, 309e331. MacRae, N.D., Nesbitt, H.W., Kronberg, B.I., 1992. Development of a positive Eu anomaly during diagenesis. Earth and Planetary Science Letters 109, 585e591. Madhavaraju, J., Lee, Y.I., 2009. Geochemistry of the Dalmiapuram Formation of the Uttatur Group (Early Cretaceous), Cauvery Basin, southeastern India: implications on provenance and paleo-redox conditions. Revista Mexicana de Ciencias Geológicas 26, 380e394. Madhavaraju, J., Ramasamy, S., 1999. Rare earth elements in limestones of Kallankurichchi Formation of Ariyalur Group, Tiruchirapalli Cretaceous, Tamil Nadu. Journal of the Geological Society of India 54, 291e301. Michard, A., Albarede, F., Michard, G., Minister, J.F., Charlow, J.L., 1983. Rare earth elements and uranium in high temperature solutions from East-Pacific rise hydrothermal vent field (13 N). Nature 303, 795e797. Muller, G., 1967. Methods in Sedimentary Petrology. Hefner Publishing Company, New York, 281 pp. Murray, R.W., Ten Brink, M.R.B., Gerlach, D.C., Russ III, G.P., Jones, D.L., 1991a. Rare earth, major and trace elements in chert from the Franciscan complex and Monterey Group, California: assessing REE sources to fine grained marine sediments. Geochimica et Cosmochimica Acta 55, 1875e1895. Murray, R.W., Ten Brink, M.R.B., Brumsack, H.J., Gerlach, D.C., Russ III, G.P., 1991b. Rare earth elements in Japan Sea sediments and diagenetic behaviour of Ce/Ce*: results from ODP Leg 127. Geochimica et Cosmochimica Acta 55, 2453e2466. Murray, R.W., Buchholdts ten Brink, M.R., Gerlach, D.C., Russ III, G.R., Jones, D.L., 1992. Interoceanic variation in the rare earth, major and trace element depositional chemistry of chert: perspective gained from DSDP and ODP record. Geochimica et Cosmochimica Acta 56, 1897e1913. Murray, R.W., Leinen, M., 1993. Chemical transport to the seafloor of the equatorial Pacific Ocean across a latitudinal transect at 135 W: tracking sedimentary major, trace and rare earth element fluxes at the Equator and the Intertropical Convergence Zone. Geochimica et Cosmochimica Acta 57, 4141e4163. Nath, B.N., Bau, M., Ramlingeswara Rao, B., Rao, Ch.M., 1997. Trace and rare earth elemental variation in Arabian Sea sediments through a transect across the oxygen minimum zone. Geochimica et Cosmochimica Acta 61, 2375e2388. Nath, B.N., Roelandts, I., Sudhakar, M., Plueger, W.L., 1992. Rare earth element patterns of the Central Indian Basin sediments related to their lithology. Geophysical Research Letters 19, 1197e1200. Norrish, K., Hutton, J.T., 1969. An accurate X-ray spectrographic method for analysis of a wide range of geological samples. Geochimica et Cosmochimica Acta 33, 431e453. Nothdurft, L.D., Webb, G.E., Kamber, B.S., 2004. Rare earth element geochemistry of Late Devonian reefal carbonates, Canning Basin, Western Australia: confirmation of seawater REE proxy in ancient limestones. Geochimica et Cosmochimica Acta 68, 263e283. 413 Nozaki, Y., Alibio, D.S., 2003. Importance of vertical geochemical processes in controlling the oceanic profiles of dissolved rare earth elements in northeastern Indian Ocean. Earth and Planetary Science Letters 205, 155e172. Nozaki, Y., Zhang, J., Amakawa, H., 1997. The fractionation between Y and Ho in the marine environment. Earth and Planetary Science Letters 148, 329e340. Palmer, M.R., 1985. Rare earth elements in foraminifera tests. Earth and Planetary Science Letters 73, 285e298. Parekh, P.P., Moller, P., Dulski, P., 1977. Distribution of trace elements between carbonate and non-carbonate phases of limestone. Earth and Planetary Science Letters 73, 285e298. Piepgras, D.J., Jacobsen, S.B., 1992. The behaviour of rare earth elements in seawater: precise determination of variations in the North Pacific water column. Geochimica et Cosmochimica Acta 56, 1851e1862. Piper, D.Z., 1974. Rare earth elements in the sedimentary cycle, a summary. Chemical Geology 14, 285e304. Piper, D.Z., 1991. Geochemistry of a Tertiary sedimentary phosphate deposit, Baja California Sur, Mexico. Chemical Geology 92, 283e316. Ransome, F.L., 1904. The geology and ore deposits of the Bisbee quadrangle Arizona. U.S. Geological Survey Professional Paper 21, 167. Rasmussen, B., Buick, R., Taylor, W.R., 1998. Removal of oceanic REE by authigenic precipitation of phosphate minerals. Earth and Planetary Science Letters 164, 135e149. Reitner, J., 1993. Modern cryptic microbialite/metazoan facies from Lizard Island (Great Barrier Reef, Australia): formation and concepts. Facies 29, 3e40. Reynard, B., Lecuyer, C., Grandjean, P., 1999. Crystal-chemical controls on rare earth element concentrations in fossil biogenic apatite and implications for paleoenvironmental reconstructions. Chemical Geology 155, 233e242. Santoyo, E., Verma, S.P., 2003. Determination of lanthanides in synthetic standards by reversed-phase high performance liquid chromatography with the aid of a weighted least-squares regression model: estimation of method sensitivities and detection limits. Journal of Chromatography A 997, 171e182. Scott, R.W., 1987. Stratigraphy and correlation of the Cretaceous Mural Limestone, Arizona and Sonora. In: Dickinson, W.R., Klute, M.F. (Eds.), Mesozoic rocks of Southern Arizona adjacent areas. Arizona Geological Society Digest, vol. 18, pp. 327e334. Sholkovitz, E.R., 1988. Rare earth elements in the sediments of the North Atlantic Ocean, Amazon delta, and East China Sea: reinterpretation of terrigenous input patterns to the oceans. American Journal of Science 288, 236e281. Sholkovitz, E.R., 1990. Rare earth elements in marine sediments and geochemical standards. Chemical Geology 88, 333e347. Sholkovitz, E.R., 1992. Chemical evolution of rare earth elements: fractionation between colloidal and solution phases of filtered river water. Earth and Planetary Science Letters 114, 77e84. Sholkovitz, E.R., Landing, W.M., Lewis, B.L., 1994. Ocean particle chemistry: the fractionation of rare earth elements between suspended particles and seawater. Geochimica et Cosmochimica Acta 58, 1567e1579. Siby, Kurian, Nath, B.N., Ramaswamy, V., Naman, D., Gnaneshwar Rao, Kamesh Raju, K.A., Selvaraj, K., Chen, C.T.A., 2008. Possible, detrital, diagenetic and hydrothermal sources for Holocene sediments of the Andaman backarc basin. Marine Geology 247, 178e193. Sverjensky, D.A., 1984. Europium redox equilibria in aqueous solution. Earth and Planetary Science Letters 67, 70e78. Taylor, S.R., McLennan, S.M., 1985. The Continental Crust: its Composition and Evolution. Blackwell, Oxford, 349 pp. Toyoda, K., Nakamura, Y., Masuda, A., 1990. Rare earth elements of Pacific pelagic sediments. Geochimica et Cosmochimica Acta 54, 1093e1103. Veizer, J., 1983. Trace elements and isotopes in sedimentary carbonates. In: Reeder, R.J. (Ed.), Carbonates: Mineralogy and Chemistry, vol. 11. Mineralogical Society of America, pp. 265e299. Verma, S.P., 2005. Estadística Básica para el Manejo de Datos Experimentales: Aplicación en la Geoquímica (Geoguimiometría). Universidad Nacional Autónoma de México, Mexico, D.F, 186 pp. Verma, S.P., Díaz-González, L., Sánchez-Upton, P., Santoyo, E., 2006. OYNYL: a new Computer Program for Ordinaly. York, and New York least-squares linear regressions. WSEAS Transactions on Environment and Development 2, 997e1002. Verma, S.P., Quiroz-Ruiz, A., 2006a. Critical values for six Dixon tests for outliers in normal samples up to sizes 100, and applications in science and engineering. Revista Mexicana de Ciencias Geológicas 23, 133e161. Verma, S.P., Quiroz-Ruiz, A., 2006b. Critical values for 22 discordancy test variants for outliers in normal samples up to sizes 100, and applications in science and engineering. Revista Mexicana de Ciencias Geológicas 23, 302e319. Verma, S.P., Quiroz-Ruiz, A., 2008. Critical values for 33 discordancy test variants for outliers in normal samples of very large sizes from 1000 to 30,000 and evaluation of different regression models for the interpolation and extrapolation of critical values. Revista Mexicana de Ciencias Geológicas 25, 369e381. Verma, S.P., Quiroz-Ruiz, A., Díaz-González, L., 2008. Critical values for 33 discordancy test variants for outliers in normal samples up to sizes 1000, and applications in quality control in Earth Sciences. Revista Mexicana de Ciencias Geológicas 25, 82e96. Verma, S.P., Santoyo, E., 2005. Is odd-even effect reflected in detection limits? Accreditation and Quality Assurance 10, 144e148. Verma, S.P., Santoyo, E., Velasco-Tapia, F., 2002. Statistical evaluation of analytical methods for the determination of rare-earth elements in geological materials and implications for detection limits. International Geology Review 44, 287e335. 414 J. Madhavaraju et al. / Cretaceous Research 31 (2010) 400e414 Wang, Y.L., Liu, Y.G., Schmitt, R.A., 1986. Rare earth element geochemistry of South Atlantic deep sea sediments: Ce anomaly change at w54 My. Geochimica et Cosmochimica Acta 50, 1337e1355. Webb, G.E., Kamber, B.S., 2000. Rare earth elements in Holocene reefal microbialites: a new shallow seawater proxy. Geochimica et Cosmochimica Acta 64, 1557e1565. Wray, D.S., 1995. Origin of clay-rich beds in Turonian shales from Lower Saxony, Germany e a rare-earth element study. Chemical Geology 119, 161e173. Wronkiewicz, D.J., Condie, K.C., 1990. Geochemistry and mineralogy of sediments from the Ventersdorp and Transvaal Supergroups, South Africa: cratonic evolution during the early Proterozoic. Geochimica et Cosmochimica Acta 54, 343e354. Zhang, J., Nozaki, Y., 1996. Rare earth elements and yttrium in seawater: ICP-MS determinations in the East Caroline, Coral Sea, and South Fiji basins of the western South Pacific Ocean. Geochimica et Cosmochimica Acta 60, 4631e4644. Zhang, Y.S., Amakawa, H., Nozaki, Y., 1994. The comparative behaviours of yttrium and lanthanides in the seawater of the North Pacific. Geophysical Research Letters 21, 2677e2680.
