Oxygen and carbon isotopes in Jordanian phosphorites and associated fossils

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Journal of Asian Earth Sciences 29 (2007) 803–812

Oxygen and carbon isotopes in Jordanian phosphoritesand associated fossils

Rushdi M. Sadaqah a,*, Abdulkader M. Abed a, Kurt A. Grimm b, Peir K. Pufahl c

a Department of Applied and Environmental Geology, University of Jordan, P.O. Box 962033, 11196 Amman, Jordanb Department of Earth and Ocean Sciences, University of British Columbia, Canada

c Department of Geology, Acadia University, Wolfville, Nova Scotia, Canada

Received 23 February 2005; received in revised form 4 November 2005; accepted 5 May 2006

Abstract

Stable isotopes have proven to be efficient tools for paleoenvironmental analysis and interpretation of paleotemperature. Oxygen andcarbon isotopes were analyzed in carbonate flourapatite (francolite), oyster shells, tests of foraminifera and ostracods from the Phospho-rite Unit throughout Jordan.

Isotopic analysis showed d18O to be enriched in authigenic francolite in Upper Cretaceous in NW Jordan, indicating lower temper-atures, a deeper depositional environment and lower salinity than Central Jordan. In Central Jordan, the local basin of Hafira showsenrichment of d18O indicating a deeper depositional environment than shallower highs in Mutarammil and Wadi El-Hasa. The d13Cshows that the depositional environment was oxic to suboxic and may have reached the suboxic to anoxic interface in the deeper envi-ronment in NW Jordan.

d18O values in tests of foraminifera and ostracods are similar to d18O values of authigenic phosphate, which is enriched in NW Jordan,indicating lower temperature, lower salinity and a deeper environment than Central Jordan. In Central Jordan, d13C shows more deple-tion in the Sultani section due to land derived organic carbon (food web supply) carried by terrestrial water draining to the sea.

The d18O in oyster shells show an upward enrichment in the Wadi El-Hasa section, which indicate an increase of intense upwelling,enrichment of nutrients, development of productivity and growth of oyster buildups. Meanwhile, Hafira shows enrichment of d18O andlower temperature, in agreement with foraminifera and ostracods. The two samples of oysters from SE Jordan, although affected by dia-genesis, show heavier oxygen to the north, indicating a deeper water environment and lower salinity in the same basin.� 2006 Elsevier Ltd. All rights reserved.

Keywords: Jordan; Upper Cretaceous; Stable isotopes; Phosphorites; Oysters

1. Introduction

The stable isotopes of oxygen and carbon are useful inthe study of phosphorites, especially during environmentalanalysis and interpretations of paleotemperature. Oxygenand carbon are major constituents of francolite (McCle-llan, 1980; Nathan, 1984), and their stable isotopes are used

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doi:10.1016/j.jseaes.2006.05.005

* Corresponding author. Tel.: +962 6 5157653; fax: +962 6 4611070.E-mail addresses: [email protected] (R.M. Sadaqah), aabed@

ju.edu.jo (A.M. Abed), [email protected] (K.A. Grimm), [email protected] (P.K. Pufahl).

to make inferences regarding the paleoenvironment of for-mation, (i.e, precipitation took place under oxic, suboxic oranoxic conditions), in addition to their value in estimatingapproximate paleotemperature.

Oxygen isotopes in phosphates were originally used as athermometer by Urey et al. (1951) and Kolodny et al.(1983). Luz and Kolodny (1985) carried out experimentsto grow fish and rats and proved that in enzyme–catalystreactions, the exchange of d18O between water and PO4 isextremely rapid, requiring just minutes for total exchange.Meanwhile isotopic exchange of oxygen between aqueousinorganic solution and PO4 ions is slow as to be negligible

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even over geologic time at low temperature. Thus biogenicapatites have the properties required for an ideal geochem-ical recorder. Biogenic apatites respond sensitively duringtheir formation to the aqueous environment and preservetheir record after death.

Shemesh et al. (1983) found that the conditions forphosphate ovulite formation are similar to those of fishbones. They concluded that whole rock phosphorites areas good as fish bones for paleothermometry because: (1)the isotopic composition of oxygen in francolite is in equi-librium with water (Longinelli and Nuti, 1973; Kolodnyet al., 1983), (2) sedimentary apatite may preserve a recordof the environmental temperature and isotopic composi-tion of seawater from the early Proterozoic to present(Longinelli and Nuti, 1968; Shemesh et al., 1983).

The fractionation of oxygen isotopes between water andbiogenic phosphate is controlled by d18O of the seawaterand temperature. Therefore Longinelli and Nuti (1973)gave an equation for the temperature of formation, whichwas adjusted by Friedman and O‘Neil (1977) as follows:

t�C ¼ 111:4� 4:3ðdp � dw þ 0:5ÞKolodny et al. (1983) modified the equation as follows:

t�C ¼ 113:3� 4:38ðdp � dwÞWhere: t is the average growth or formation temperature

dp is the d18O value of phosphate on the SMOW scaledw is the d18O value of water on the SMOW scale

On the other hand, the isotopic composition of CaCO3

precipitated from aqueous solution is controlled by severalfactors, including the isotopic equilibrium temperature,pH, d13C value of CO2 gas in equilibrium with carbonateand bicarbonate ions in solution (Deines et al., 1974).

Series Stage Formation-Member

El-Hiyari (1985), Powell (1989

Early Paleocene

Paleogene Muwaqqar Chalk-Marl

Qatrana Phospho

Maastrichtian Bahiyah Coquin

Upper

Al-HisaPhosphorite

Sultani Phosphor

Cretaceous Campanian

Mutarammil CoquSantonianAmmansilicified limestone

Dhiban ChalkTafilaConiacian Ghudran

Mujib ChalkTuronian Wadi Sir

Shuaib

Cenomanian Hummar

Fuhais

Naur

Lower Kurnub (Hathira) SCretaceous

Fig. 1. The stratigraphical position

This isotope study aims to determine the redox condi-tions during the formation of phosphate and the paleotem-perature of the depositional environment. Isotopic analysisof d18O and d13C were carried out on carbonates in thefrancolite structure, oyster shells, foraminifera and ostrac-ods for the first time in Jordan.

2. Geological setting

The Phosphorite Formation (PF) in Jordan forms partof the main Tethyian giant phosphorite belt extending fromthe Caribbean in the west, through North Africa and theMiddle East in the east (Notholt, 1980; Notholt et al.,1989; Sheldon, 1987; Glenn et al., 1994; Lucas and Pre-vot-Lucas, 1995). The PF occurs in the Upper Creta-ceous–Maastrichtian rocks (Quennell, 1951; Burdon,1959; Karam, 1967; Bender, 1974; Hamam, 1977; Abedand Ashour, 1987; Cappetta, 1987; Cappetta et al., 1996)(Fig. 1). It outcrops along a belt east of the highlands thatboarder the Dead Sea-Jordan Valley and extends from NWof the country (Irbid area) through Central Jordan (El-Hasa and El-Abiad) towards the SE (Eshidiya) (Fig. 2).

The thickness of the PF formation in SE and NW Jor-dan is 10–15 m. It is around 60 m in the center of the coun-try due to the presence of oyster buildups in the middle ofthe formation. The thickness of these oyster buildups mayexceed 40 m (Abed and Sadaqah, 1998).

In NW Jordan, the PF is composed of friable phosphateparticles of different sizes, vertebrate bones and teeth. It ishighly fossiliferous and lacks detrital quartz. Intercalationsof chert, phosphatic chert, limestone and laminated marlare present. Compared to Central and SE Jordan, the PFis richer in foraminifera and lacks bioherm oyster buildups,which is a distinct difference.

Unit - Member Group - Formation

) Bender(1974) Burdon (1959 ), Masri (963)

Chalk-Marl Muwaqqar B3

rite

a Phosphorite Belqa B2b

ite Group Amman

Silicified

ina Limestone B2a

Massive Ghudra 1

Limestone Wadi Sir A7

Echinoidal Ajlun Shueib A5-A6

Limestone Group Hummar A4

Nodular Fuhais A3

Limestone Naur A1-A2

andstone Group

of the Jordanian phosphorites.

Fig. 2. Location map of the studied areas.

R.M. Sadaqah et al. / Journal of Asian Earth Sciences 29 (2007) 803–812 805

In Central Jordan, the PF is composed of marl, phos-phatic marl, chalk, chert, limestone and individual phos-phate beds. The components are the same as in NWJordan and differs in that it contains oyster coquina grain-stone, boundstone and buildups. Oyster buildups andcoquinas are 10–40 m thick in the middle of the section.The marl is similar to that in the NW. It is laminatedand includes lamina of autheginic phosphate. The later isusually reworked to produce the granular phosphorite.Although foraminifera is present, they are less abundantthan in NW Jordan.

In SE Jordan, the PF is slightly different from NWand Central Jordan in that it is proximal to the Nubiansandstone-facies shorlines. Therefore, quartz sandprevails at the base of the formation and grain sizedecrease upwards. Phosphate particles and rock associa-tions are similar to other locations. Oyster buildupsand coquinas are present in the northern part ofEshidiya, while stratigraphicaly equivalent marl is presentto the south towards the shorlines. Foraminifera is rarein the PF and the overlying formation, which mayindicate superhaline restricted basins during theMaastrichtian (Sadaqah, 2000).

3. Experimental techniques

3.1. Francolite

The selected francolite samples were chosen from NWand Central Jordan as in-situ, pristine phosphates (notreworked) embedded in the marl (Fig. 2). Similar samplesare lacking in SE Jordan. Fifteen samples from four sec-tions at four localities in NW Jordan, and 14 samples fromthree sections in three different localities in Central Jordan,were analyzed for carbon and oxygen isotopes in carbonateflour apatite (CFA).

The procedure for analyses was that of Silverman et al.(1952). Samples were prepared for analysis by dissolvingfree calcite with triammonium citrate for 50 h at 30 �C.To assure complete dissolution of calcite, each samplewas investigated by XRD, and in all cases, all CO2 extract-ed from the residue came from CO3

2� in the structure offrancolite.

The extraction of CO2 for isotopic analysis followed theprocedure of Kolodny and Kaplan (1970), where the sam-ple was reacted with phosphoric acid using the method ofMcCrea (1950).

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Some of the analysis were run twice and others threetimes. For all but one sample, the variation was less thanor equal to 0.2&. The average is reported in Table 1.

The analytical work was performed at the Laboratoryfor Stable Isotopes Studies at the University of Western

Table 1Isotopic compositions of oxygen and carbon in structural CO2�

3 offrancolite, & compared with other localities

Sample d13CPDB d18

OSMOWd18

OPDB

NW Jordan Tubna T1 �7.50 23.85 �6.86T3d �6.55 25.93 �4.84T9 �7.31 26.60 �4.19T21 �9.37 24.30 �6.43T23 �11.18 24.69 �6.04T33 �8.65 24.33 �6.39

Ziqlab Z3 �3.02 25.58 �5.18Jdeitta J7 �8.38 24.52 �6.20

J21 �3.49 26.90 �3.90Kufr Asad K1 �6.18 24.89 �5.85

K3 �2.42 27.02 �3.78K9 �7.79 22.41 �8.26K11 �5.45 23.49 �7.20K15 �4.72 24.74 �5.99K21 �4.29 23.78 �6.92

Central Jordan Wadi Hasa W30 �5.46 23.38 �7.31W43 �2.36 23.48 �7.22W46 �8.42 24.34 �6.37W49 �6.19 20.87 �9.74

Sultani S9 �5.82 21.85 �8.80S15 �8.00 22.00 �8.65S17 �6.74 23.86 �6.86S22 �7.19 23.19 �7.50S23 �7.26 23.34 �7.35

Hafira F13 �3.63 25.26 �5.49F15 �2.20 26.10 �4.67F16 �6.89 28.00 �2.83F18 �3.21 27.53 �3.28F20 �5.66 24.17 �6.54

Standard Calcite 0.97 25.75 �5.021.01 25.78 �4.990.85 26.22 �4.550.86 26.08 �4.69

Laboratory Gas Standard �43.81 10.18�43.80 10.19�43.78 10.20�43.79 10.21

Florida-Pliocenea NBL�1 �5.30 28.20N. Carolina-Miocenea ASP�66 �3.70 30.80Chatham risea KP�65 �0.30 31.40Montery Form.Baja-Cala ASP�49 �6.90 25.40Rusaifaa ASP�8 �9.90 21.80Rusaifaa ASP�9 �8.90 22.70Arad-Negeva ASP�6 �8.30 22.50Oron-Negeva ASP�84 �10.50 26.50Phosphoria Form. Idahoa ASP�3 �3.50 16.80Akashat-Iraq U.Cretacb 1 �7.20 �6.10Akashat-Iraq U.Cretacb 2 �7.00 �5.40Akashat-Iraq U.Cretacb 3 �8.50 �6.00Akashat-Iraq U.Cretacb 4 �8.30 �5.10Akashat-Iraq U.Cretacb 7 �9.60 �3.90Akashat-Iraq U.Cretacb 8 �9.00 �4.20

a Shemesh et al. (1988).b Al-Bassam (1980).

Ontario-Canada using the Micromass Prism II Mass Spec-trometer. The precision was 0.2& for d13C and 0.3& ford18O.

3.2. Oysters

Fifteen fresh samples from oyster buildups, which arecomposed of Ambigostrea vellie(Aqrabawi, 1993), werechosen for this study. Thirteen samples from three sec-tions in Central Jordan and two samples from Eshidiyawere chosen (Fig. 2). The samples were crushed to �80mesh then heated for about 20 min at 420 �C in a streamof purified flowing helium to get rid of organic com-pounds, then the residue of the samples were treatedwith 100% phosphoric acid in evacuated tubes (McCrea,1950). The evolved carbon dioxide was collected for 24 h,purified, and then analyzed. It was compared to a carbondioxide standard in the mass spectrometer with a doublecollector following the procedure of McKinny et al.(1950).

3.3. Foraminifera and ostracods

Stable isotopes of 18O and 13C were also measured inostracods and benthonic foraminifera from NW and Cen-tral Jordan. The samples from NW Jordan include oneostracod and two foraminifera that came from the KufurAsad section (K21 sample). Six samples were collectedfrom Ziqlab (Z3 sample), which consist of one ostracodand five benthonic forams. From Central Jordan, oneostracod sample was collected from Wadi El-Hasa (W43),while three samples were collected from the Sultani section.Sample S15 contains ostracods and benthonic foraminiferaand sample S22 contains ostracods (Table 3). Planktonswere scarce in the chosen samples (which were mainly forpristine phosphate), thus providing small samples for isoto-pic analysis. The most abundant foraminifera are buli-minds. Ostracods were not subjected to taxonomy.Theanalytical procedure was similar to the one applied tooysters.

4. Results

Table 1 presents the isotopic data of francolite as PDBpermil for 13C and PDB and SMOW for 18O, in additionto some literature results for comparisons. Figs. 3–5 illus-trate the relation between d18O and d13C relative to PDBin NW, central and all of Jordan, respectively.

For oysters, results of the analysis are expressed in dnotation relative to PDB for both carbon and oxygen inparts per thousand (permil &). Some of the sampleswere analyzed in duplicate and the mean is documented.The results are listed in Table 2 and illustrated inFig. 7.

For foraminifera and ostracods, the results of d18O andd13C are shown in d notation standard of PDB in Table 3and illustrated in Fig. 8.

Fig. 3. d13C& versus d18O& isotopic compositions of francolitecarbonate from NW Jordan.

Fig. 4. d13C& versus d18O& isotopic compositions of francolitecarbonate from Central Jordan.

Fig. 5. d13C& versus d18O& isotopic compositions of francolite carbon-ate from NW and Central Jordan , compared with other phosphoritedeposits. Results from the literature are after Compton et al. (1993),McArthur (1985), McArthur et al. (1987) and Shemesh et al. (1988).

Table 2Isotopic compositions of oxygen and carbon in oyster shells

Locality Sample d13CPDB& d18OPDB&

Central Jordan Hafira F11 �3.71 �2.89F12 �2.84 �2.54

Sultani S10 �6.43 �7.96S11 �6.51 �7.86S12 �5.75 �7.05

Wadi Hasa W5 �3.59 �2.39W32 �2.14 �4.58W33 �3.29 �11.26W34 �3.04 �9.83W35 �2.64 �9.07W36 �3.35 �6.76W37 �2.63 �6.08W41 �2.01 �6.46

SE Jordan Mine 1 MI11 �7.64 �8.96NW Mine 1 SH-RC2 �3.76 �4.59

Table 3Isotopic compositions of oxygen and carbon in forams and ostracods, &

Sample d13CPDB d18OPDB

NW Jordan Ziqlab Z-3/1 Pyramidulina �2.37 �4.30Z-3/2 Lenticulina �2.90 �5.67Z-3/3 Marginulina �2.47 �4.52Z-3/4 Stilostomella �1.94 �3.46Z-3/5 Anomalinoides �2.64 �4.10

Kufr Asad K-21/1 Pyramidulina �2.50 �4.39K-21/2 Lenticulina �2.83 �4.24

Central Jor. Sultani S-15/ Neobulimina �2.03 �5.92NW Jordan Ziqlab Z-3 Ostracods �3.79 �4.90

Kufr Asad K-21 Ostracods �3.68 �5.02Central Jor. Sultani S-15 Ostracods �8.32 �10.39

S-22 Ostracods �6.08 �9.64W. El-Hasa W-43 Ostracods �2.78 �8.43

R.M. Sadaqah et al. / Journal of Asian Earth Sciences 29 (2007) 803–812 807

5. Discussion and interpretation

5.1. Francolite

Differences in the d18O values of carbonates are inaccord with the temperature dependent oxygen

fractionation between calcium carbonate and ocean water.The d13C and d18O values of carbonates are important asenvironmental indicators (Keith et al., 1964), but the alter-ation of carbonate after deposition makes such interpreta-tion uncertain (Choquette, 1968). Shemesh et al. (1988)found that d18OCO3

, like d18Op, decreases with increasingage. Therefore d18OCO3

, like d18Op, is used forpaleothermometry.

Glenn et al. (1988) and Shemesh et al. (1983, 1987)argued that the large analytical uncertainties in d18O castdoubt on the general usefulness of using d18O in carbonateflour apatite CO3 for geological or paleotemperature inter-pretations. That is due to the poorly understood oxygenexchange reactions and relative fractionation effects onthe d18OP and d18OCO3

values. Meanwhile, the literatureis confusing because more than one scale is used for con-verting delta values to temperature due to differences inthe history of oceanic isotopes (Shackelton, 1984). Liet al. (1997), suggested that temperature correlation ofd18O fractionation appears to be reliable at relatively hightemperature >10 �C. Therefore, to avoid the effects of dia-genesis, the temperature was not deduced using any of theequations in the literature, but rather the relative changewas used for interpretation of paleoenvironment.

Fig. 6. Isotopic compositions of carbon in porewater bicarbonate ionsafter McArthur et al. (1986) and Compton et al. (1993). The sulfatereduction zone occurs within centimeters of the sediment-seawaterinterface.

808 R.M. Sadaqah et al. / Journal of Asian Earth Sciences 29 (2007) 803–812

5.1.1. Oxygen

The d18OCO3of Jordanian phosphorites falls between a

maximum of �2.83& in Central Jordan and �3.78& inNW Jordan, while a minimum of �9.74& is recorded inCentral Jordan and �8.28& PDB in NW Jordan (Table1).This lies within the range of many phosphorate localitiesworldwide (Shemesh et al., 1988).

In NW Jordan, there is little variation between the sec-tions (Fig. 3), but Tubna seems to have heavier O (average�5.79& PDB) than Kufur Asad (average �6.33& PDB),indicating warmer and shallower ocean water in KufurAsad relative to Tubna.

The phosphorites of Central Jordan can be subdividedinto two groups: the Hafira group and Sultani–Wadi ElHasa group (Fig. 3). Hafira samples are more enriched in18O compared to Sultani–Wadi El Hasa samples. Thisresult may indicate a warmer and shallower ocean waterin Sultani–Wadi El Hasa compared to the Hafira, the laterbeing a deeper and colder environment. This is in goodagreement with inferences made on the basis of macroand microfacies (Sadaqah, 2000). Consequently, the Hafirabasin and its main fault might have been active since theLate Cretaceous (Bender, 1974).

Moreover, Sultani and Wadi El Hasa have the samemicrofacies, macrofacies and geomorphology of the higherblock faulted areas, which affected the stratigraphy andstructural pattern (Sadaqah, 1983).

There is no clear difference between NW and CentralJordan. However, Central Jordan appears to have lighterO (�6.62& PDB for Central Jordan and �5,87& PDBfor NW Jordan) (Fig. 5) and higher temperature for a dis-tance of 250–300 km trending N–S.

5.1.2. Carbon

d13C values of Jordanian phosphorites range between+0.2 and �10.5& PDB. These values are within the rangeof recent and ancient phosphorites, suggesting good preser-vation over geologic time (Shemesh et al., 1988).

d13CCO3in phosphorites may be divided worldwide into

two groups on the basis of their d13CCO3values (McArthur,

1985; McArthur et al., 1987; Compton et al., 1993). (1) Agroup which has d13CCO3

values around 0& probablyinherited from the carbonate. This group formed byreplacement of carbonate on or near the sea floor (diage-netic) and includes the Chatham Rise, Australian shelf,and offshore Peru. (2) A second group has strongly nega-tive d13CCO3

values and includes most ancient phosphoritesand some recent samples from offshore Namibia (Shemeshet al., 1988). This group formed in oxic, suboxic and anoxicseafloor sediments having d13CCO3

values of 0 to �10&

PDB.Carbon isotopes are used to define Phosphorite Forma-

tion in the different oxic, suboxic and anoxic (sulfate reduc-ing) environments in sea floor sediments (Nathan andNielsen, 1980; McArthur, 1985; McArthur et al., 1986,1987; Compton et al., 1993). The sea floor sediments aredivided into oxic, suboxic and anoxic horizons with

variable depths (McArthur et al., 1986; Compton et al.,1993). The sulfate reduction zone was placed by Martenset al. (1978) at shallow burial depths of 1–100 cm in organ-ic sediments. The negative carbon isotopic composition ofCO3 in the francolite structure indicates that it formedwithin the oxic to suboxic zone (Fig. 6).

The assumed d13C of 0& for dissolved inorganic carbonin marine water (McArthur et al., 1986) is lowered by dis-solved organic carbon during oxic and suboxic diagenesisdue to CO2 diffusing upwards from degradation of organicmatter by bacteria. Carbon becomes enriched in 12C in theoxic and suboxic zones and d13C reaches �6& PDB. In thezone of sulfate reduction (anoxic), d13C drops down to�11& and become diffused at oxic/suboxic and subuox-ic/anoxic interfaces.

Jordanian phosphates however, belong to the authigen-itic, not diagenitic group. The carbon isotopic composi-tions of the Jordanian phosphorites are comparable tothose documented by McArthur et al. (1986), Shemeshet al. (1988) and Compton et al. (1993) in previous studiesof Rusaifa and El-Hasa. They also compare Jordanianphosphorites to onshore and offshore Morocco phospho-rites (McArthur et al., 1986), onshore phosphorite of CapeProvince in South Africa (Birch, 1979; Dingle et al., 1979),Akashat – Iraq (Al-Bassam, 1980), Babcock – Florida(Compton et al., 1993) and to those of Negev (Kolodnyand Kaplan, 1970; McArthur, 1980) as shown in Fig. 5.

R.M. Sadaqah et al. / Journal of Asian Earth Sciences 29 (2007) 803–812 809

In NW Jordan, d13C values fall within the range�2.42& to �11.18& and imply deposition within the oxicto suboxic zones and may reach the suboxic/anoxic inter-face. On the other hand, the phosphorites of Central Jor-dan d13C fall between �2.20& and �8.42&, indicatingtheir formation in the oxic and suboxic zones, which is inagreement with Ce negative anomalies and REE interpreta-tion (Sadaqah et al., 2005).

In conclusion, Jordanian phosphorites are: (1) authigen-ic in origin; (2) precipitated in oxic to suboxic zones; (3) notweathered as McArthur et al. (1986) and Shemesh et al.(1988) suggested, but have similar concentrations to Negevphosphorites (Kolodny and Kaplan, 1970; McArthur,1980; Shemesh et al., 1983); and (4) the temperatures wereslightly different in different basins and therefore may havebeen slightly higher in the south where Jordanian phospho-rites are slightly enriched in light O and C. This agrees withKolodny and Raab (1988) and Kolodny and Garrison(1994) that water temperature during the Cenomanian-Turonian in the Levant was 32–33 �C for shallow tropicalseas situated 8–15 �C north of the equator. This also agreeswith Jenkyns et al. (1994) for temperature of 27–28 �C inthe Cretaceous Sea in England during the same period(Barrera and Johnson, 1999).

5.2. Oxygen and carbon isotopes in oysters

Mollusks and forams build their shells of calcite and/oraragonite in isotopic equilibrium with surrounding water,and this is used to determine the paleotemperature wherethey lived (Wedepohl, 1969). Differences in d18O of fossilsare temperature dependent. The differences in d13C areenvironmentally controlled rather than species controlled(Keith et al., 1964). Variations in the d13C in shells areinfluenced by the proportion of land plants in the food sup-ply, or contributed by humus decay, to dissolved bicarbon-ate in the water(Keith et al., 1964).

5.2.1. Oxygen

The differences in d18O values are in accordance with theknown temperature-dependent oxygen fractionationbetween calcium carbonate and ocean water. This fraction-ation was controlled by upwelling of colder water from theE-NE (Reiss, 1988; Kolodny and Garrison, 1994) to theshallow marine epicontinental shelf and by the water depthfor oysters (Keith et al., 1964).

Heavier oxygen is enriched in the deeper Hafira sectionwhere oysters were not abundant enough to cause build-ups, while the lightest oxygen comes from the Wadi El-Hasa section where very thick (30–40 m), massive buildupsoccur.

The Wadi El-Hasa section is most interesting for oxygenisotope interpretation of oysters. The samples listed inTable 1 are labeled from bottom (W5) to top (W41). Sam-ple W5, although possibly affected by silicification, has thehighest d18O of �2.39& which indicates high 18O enrich-ment and consequently lower temperature within the depo-

sitional environment. It is located directly above theGhudran Formation, which is composed of pelagic chalk.This indicates deposition under lower temperature condi-tions. Sample W32 has a d18O value of �4.58&. This sam-ple was collected from highly fragmented coquina that mayhave a calcitic matrix and was recrystallized, and thereforeit is enriched in heavier oxygen. Samples W33, W34, W35,W36, W37 and W41, which are in ascending order in thesection, have d18O values increasing upwards from�11.36& to �6.08&, i.e, increasing enrichment of 18Oupwards in the section. This result represents a specialstage of lowstand or regression, with the highest tempera-ture at the base and lowest at the top. That is becauseupwelling became more active and productivity increasedsimultaneously with temperature decrease due to the influxof cold water and 18O enrichment.

The Sultani section has d18O values intermediatebetween Hafira and Wadi El-Hasa, ranging between�7.05& and �7.96&. The water depth may have beenintermediate between deeper Qaa’ El-Hafira and shallowerWadi El-Hasa as indicated by the overlying strata of coqu-inas and oyster buildups.

Two samples from Eshidiya, RC2 and MI 11, have d18Ovalues of �4.59& and �8.96& and may have been affectedby late diagenetic recrystallization and cementation andthus may not be representative.

Keith et al. (1964) and Keith and Weber (1964) came tothe same conclusion regarding the oxygen isotopic compo-sitions of mollusk shells from the Pacific and Atlanticoceans, extending from the equator to the Arctic.

5.2.2. Carbon

The d13C values of investigated oysters fall between�2.01& and �7.64&. The Wadi El-Hasa and Qaa’ El-Hafira sections (group W and F) are restricted to the nar-row range between �2.01& and �3.71& (Table 2, Fig. 7).This narrow range of 1.7& coincides with the ranges ofmarine carbonates (Keith and Weber, 1964; Keith et al.,1964). This could be attributed to less fresh water influenceand changing food supply. The analysis of different laminaand even different parts of the same lamina might haveinfluenced the results due to seasonal effects on food sup-ply. Slight variations up to 1& in the same shell may arisedepending on the time of the year and age of the shell formarine pelecypods (Keith et al., 1964).

Sample SH-RC2 from Eshidiya belongs to the abovementioned range. Sample MI11, which is located in mine1 and proximal to the extreme shorelines of the Tethys inthe south, has d13C value of �7.64& which is the lightestcarbon of all oysters. Although the sample may be affectedby diagenesis, it is expected to have lighter carbon due tothe effect of a fresh water stream flowing from the south.

The Sultani samples have d13C values ranging from�5.75& to �6.51& (Table 2, Fig. 7), indicating enrich-ment in lighter carbon. This is interpreted like MI11 ofEshidiya as mentioned earlier but with no evidence to sup-port the possibility of having fresh water streams draining

Fig. 7. d13C& versus d18O& isotopic compositions of oysters from central and SE Jordan. For comparison, diagenitic cement after Hugh (1993) isincluded.

810 R.M. Sadaqah et al. / Journal of Asian Earth Sciences 29 (2007) 803–812

into the shallow marine environment. The deficiency of 13Cin fresh water is due mainly to variable land plants andhumus contributions to the fresh water. Consequently,the deficiency of 13C in fresh water and land plants, whichultimately become incorporated in the food chain of aquat-ic animals, is reflected in their hard and soft tissues (Keithet al., 1964; Keith and Weber, 1964). Moreover, Keith andWeber (1964) went further and considered the land plantcontribution to marine carbonate as a function of proxim-ity to shorelines and deltas.

5.3. Oxygen and carbon isotopes in foraminifera and

ostracods

5.3.1. Oxygen

The d18O values of ostracods and benthos from NWJordan fall within the range of �3.36& and �5.67&. Thisenrichment of 18O indicates lower temperatures comparedto Central Jordan based on ostracods, formainifera, andoysters (Fig. 8). This agrees well with the increased depthof the depositional environments and decrease in tempera-tures towards the NW. The d18O of benthonic animals inthe Mishash Formation of Negev ranges between

Fig. 8. d13C& verses d18O& isotopic compositions of foraminifera andostracods from central and NW Jordan.

�0.37& and �1.42& (Almogi-Labin et al., 1993), whichimplies enrichment of 18O and lower temperatures for theNegev in terms of phosphorite depositional environments.

In Central Jordan, sample W43, which is an ostracodfrom the Wadi El-Hasa section, has a d18O value withinthe range of d18O for oysters in the same section. In the Sul-tani section, the d18O and d13C values of ostracods and for-ams are different in that the ostracods are more depleted inboth 13C and 18O. d13C and d18O values range between�6.08& to �8.32& and �9.64& to �10.39&, respective-ly. This correlates well with the oyster results and supportsthe interpretation that the depositional environment wasshallow, warmer and food was partly from land plants sup-plied by the rivers. The benthic foraminifera sample Neob-

ulimina farafransis from S15 has a d18O value �5.92&,which is more enriched in d18O compared to ostracodsand oysters, and thus indicates lower temperature and adeeper environment of deposition (Almogi-Labin et al.,1993).

5.3.2. Carbon

In NW Jordan, the d13C values of forams and ostracodsrange between �1.94& and �3.79&. Sample W43, anostracod from the Wadi El-Hasa section, and a benthicforaminifera from sample S15 in the Sultani section, fallwithin the same range. Ostracods from Sultani, samplesS15 and S22, are more depleted in 13C with d13C valuesof �8.32& and �6.08&, respectively. This agrees well withthe oyster values, indicating that there must have been awater and food supply from land that flowed into the shal-low-water environment. However, the Neobulimina assem-blage (S15 foraminifera, Table 3), according to Almogi-Labin et al. (1993), indicate somewhat higher 18O levelsthat could have resulted from flooding in terrestrialstreams.

6. Conclusions

The following conclusions can be drawn from the O andC isotopes.

R.M. Sadaqah et al. / Journal of Asian Earth Sciences 29 (2007) 803–812 811

1 The d18O of pristine phosphate, Central Jordan, indi-cates higher temperatures of formation compared toNW Jordan. Hafira has heavier O than Sultani andWadi El-Hasa, indicating lower temperatures and deeperdepositional environments.

2 The d13C of pristine phosphate in the Jordanian phos-phorites indicates authigenic precipitation in oxic to sub-oxic zones and may reach the suboxic to anoxic interfacein NW Jordanian phosphorites.

3 Oxygen isotopes in oyster carbonates show enrichmentof heavier oxygen in Hafira, indicating lower tempera-tures and deeper environments for phosphate d18O.Enrichment of heavier O upward in the sequence inWadi El-Hasa indicates intense upwelling during theMaastrichtian.

4 Carbon isotopes in the oysters show that local areas ofSultani might have included land plants possibly sup-plied by streams in a shallow water environment thatresulted in lower 13C concentrations.

5 d18O enrichment in foraminifera and ostracods in NWJordan indicate lower temperatures and greater depthsof formation relative to Central Jordan.

6 The ostracods in Sultani are more depleted in 13C, whichagrees with inferences made from the oyster data thatthe food supply was enriched in land plants.

Acknowledgements

The authors thank Profs. Ghaleb Jarrar, Ghazi Saffariniand Hani Khoury for revising the manuscript. We thankProf. S. Nasir, for his critical comments which greatly im-proved this work. Greatful thanks are also due to the Uni-versity of Western Ontario for the isotope analysis. Thisstudy was supported partly by a grant from the HigherCouncil for Science and Technology-Industrial ResearchFunds.

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Further reading

Craig, H., 1961. Standard for reporting concentration of deuterium andoxygen-18 in natural water. Science 133, 1833–1834.