KOCSIS, L., DULAI, A., BITNER, M.A. VENNEMANN, T. & COOPER, M. (2012): Geochemical composition of...

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Geochemical compositions of Neogene phosphatic brachiopods: Implications forancient environmental and marine conditions

László Kocsis a,⁎, Alfréd Dulai b, Maria Aleksandra Bitner c, Torsten Vennemann a, Matthew Cooper d

a Institut de Minéralogie et Géochimie, Université de Lausanne, L'Anthropôle, CH-1015 Lausanne, Switzerlandb Department of Paleontology and Geology, Hungarian Natural History Museum, P.O. Box 137 H-1431, Budapest, Hungaryc Institute of Paleobiology, Polish Academy of Sciences, ul. Twarda 51/55, PL-00-818 Warszawa, Polandd School of Ocean and Earth Science, University of Southampton, National Oceanography Centre Southampton, European Way, SO14 3ZH, UK

a b s t r a c ta r t i c l e i n f o

Article history:Received 12 July 2011Received in revised form 24 January 2012Accepted 3 February 2012Available online 12 February 2012

Keywords:North SeaParatethysBrachiopodsPhosphateIsotopesPalaeo-environment

Isotopic and trace element compositions of Miocene and Pliocene phosphatic brachiopods (Lingulidaeand Discinidae) from southern North Sea, the Central Paratethys and the Atlantic coast of Europe were inves-tigated in order to trace past environmental conditions and marine connections between the northern borealand the southern subtropical–tropical marine basins. The North Sea genus Glottidia yielded low εNd and highδ18OPO4 values through the Mio-Pliocene indicating cold habitat temperature where the local seawater wasdominated by the Atlantic Ocean. In contrast, the Middle Miocene Lingulidae and Discinidae of the Paratethysinhabited warm subtropical seawater with the possible influence of the Indian Ocean via the Mediterranean,as supported by their average εNd value of −8.3. The combined geochemical data support a thermal andmarine separation of the Paratethys from the North Sea with no direct connection or major exchange ofwater from the Miocene onwards.The temperature in the Paratethys was very similar to that inferred from brachiopods from the MiddleMiocene of western France, but the seawater εNd value here is identical to that of contemporaneous AtlanticOcean. A Late Miocene lingulid brachiopod from southern Portugal has a high δ18OPO4, similar to the speci-mens investigated from the North Sea, reflecting either a deep water habitat or formation after the onsetof major global cooling that resulted in an increased δ18O value of seawater. The εNd value of −8.4 for thissite is compatible with an influence of Mediterranean outflow.

© 2012 Elsevier B.V. All rights reserved.

1. Introduction

Geochemical compositions of fossil biogenic apatite have beenwidely used to describe ancient marine environmental conditions.Oxygen isotope compositions of fish teeth are a reliable proxy forthe temperature of the ambient water (e.g., Longinelli & Nuti, 1973;Kolodny et al., 1983; Pucéat et al., 2010), while their strontium andneodymium isotope ratios may help place constraints on the palaeo-oceanography (e.g., Staudigel et al., 1985; Elderfield & Pagett, 1986;Ingram, 1995; Vennemann & Hegner, 1998; Thomas et al., 2003;Martin & Scher, 2004; Pucéat et al., 2005; Kocsis et al., 2009).

A number of studies have also dealt with the geochemical compo-sitions of both fossil and modern phosphatic brachiopods (Longinelli,1966; Longinelli & Nuti, 1968; Lécuyer et al., 1996b, 1998; Wenzelet al., 2000; Rodland et al., 2003; Bassett et al., 2007). The Sr- andNd-isotopic compositions of their shells may be used in a similarway as those of fossil fish remains to help interpret the palaeo-

oceanography. However, the use of their oxygen isotopic compositionas a palaeo-temperature proxy is not straightforward. While Lécuyeret al. (1996b) reported equilibrium fractionations between modernlingulid brachiopods and seawater, Rodland et al. (2003) showedvariations as high as 4‰ in individual shells and attributed these tovital effects. In addition, Wenzel et al. (2000) pointed out that fossilshells have a higher susceptibility to diagenetic alteration comparedto denser, enamel type biogenic apatite of fish teeth.

This study is focused on the geochemical composition of Mioceneand Pliocene phosphatic brachiopods from the southern North Sea,the Central Paratethys, and the Atlantic coast of Europe. Fossils fromthese different palaeo-geographical regions allow us to investigatewhether strontium and neodymium isotopic compositions of thebrachiopods can give any characteristic geochemical information forthese marine basins. These basins were linked by seaways at certaintimes during the Neogene (cf. Rögl, 1998), hence with the aid ofthese geochemical analyses connections could be further traced.Oxygen isotopic compositions of the brachiopods are also analyzedas a means of evaluating ancient living conditions and the impact ofpossible vital effects and/or diagenetic alteration are to be discussedin details.

Palaeogeography, Palaeoclimatology, Palaeoecology 326–328 (2012) 66–77

⁎ Corresponding author.E-mail address: [email protected] (L. Kocsis).

0031-0182/$ – see front matter © 2012 Elsevier B.V. All rights reserved.doi:10.1016/j.palaeo.2012.02.004

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1.1. Palaeo-geographical background

From the Early Oligocene the Tethyan seaway linking the Atlanticand the Indian Oceans began to close gradually due to the conver-gence of the European and African continental plates. In the souththe Mediterranean Sea was formed, while in the north a large epicon-tinental sea, the Paratethys developed. It extended from the RhôneBasin via the North-Alpine Foreland Basin (NAFB) to the CentralParatethys (Vienna, Styrian, and Pannonian Basins, Carpathian fore-deep) fromwhere it extended further east into the Eastern Paratethys(Fig. 1). This epicontinental sea had a connection with the North Seavia the Rhine Graben during the Oligocene, and several intermittentlinks existed with the Mediterranean and the Indian Ocean during theMiocene (Fig. 1; Rögl, 1998; Kowalewski et al., 2002; Meulenkamp &Sissingh, 2003; Popov et al., 2004).

The North Sea maintained a northerly connection with theAtlantic Ocean during the entire Mio-Pliocene, although sea-levelfluctuation and sometimes enhanced river input often influencedthe local settings (Rasser et al., 2008). The different sub-basins ofthe Paratethys had variable conditions alternating between marineto brackish and freshwater environments. These circumstances andthe existence of gateways toward the open sea depended on sea-levelvariation often relating to local tectonism. The youngest marinedeposits in the NAFB occurred in the Lower Miocene, while in theCentral Paratethys normal marine conditions ceased only after the lateMiddle Miocene. In the Eastern Paratethys these conditions prevailedtill the latest Miocene (Rögl, 1998; Popov et al., 2004). At the end ofthe Miocene some of the sub-basins eventually filled up by sediments,others turned to large brackish or freshwater basins.

The complex palaeo-geographical and marine relationshipsamong these basins have been investigated by neodymium isotopicratios in foraminifera (Jacobs et al., 1996; Mühlstrasser, 2002; Kocsiset al., 2008), ostracods (Janz & Vennemann, 2005), phosphorites(Stille et al., 1996), and shark teeth (Vennemann & Hegner, 1998;Kocsis et al., 2009). While these studies focused on the Mediterraneanand the Paratethys and their relative connections to the globaloceans, our research extends this to the North Sea and the Atlanticcoast of Europe with the aim of using the phosphatic brachiopods(Figs. 2–3) to trace possible links between these sub-basins.

1.2. Linguliform brachiopods

Linguliform brachiopods have a long geological history extendingto the Early Paleozoic and two families, Lingulidae and Discinidae, still

have modern representatives. They differ in ecology though: theLingulidae live in vertical burrows in compact and stable sedimentsunder the influence of moderate currents, while the Discinidae attachthemselves to hard surfaces (Emig, 1997). Their shells are generallyrare in the Miocene-Pliocene fossil records, often taken to indicatea low preservation potential (Emig, 1990), but locally they may beabundant and well-preserved.

Fossil Lingulidae shows apparent faunal provincialism: Glottidia iswidespread in the North Sea region (Chuang, 1964), while Lingula oc-curs in the Central Paratethys (Emig & Bitner, 2005). The Discinidae,however, can be found in the North Sea, the Atlantic coast of Franceand in the Central Paratethys as well, and clear provincialism hasnot been observed at the genus level, although a taxonomical reviewis still required. Because all of these brachiopods belong to the orderof Lingulida (Holmer & Popov, 2000) they are here referred to aslingulids.

The shells of lingulids are composed of prismatic layers ofcarbonate-fluorapatite (francolite) alternating with layers of chitin-ous organic matter (Iijima & Moriwaki, 1990; Williams et al., 1992,2000; Cusack et al., 1997, 1999). In modern Lingula, Glottidia andDiscinisca the basic mineral components are apatite granules up to10 nm in size, with a chitino-proteinaceous coating (Williams et al.,1992, 2000; Cusack et al., 1999). The shell succession is characterizedby a rhythmic set of laminae with two types of lamination—the bacu-late lamination in Glottidia and Discinisca and the virgose laminationin Lingula (Fig. 3, Williams et al., 1992, 2000).

The proportion of organic compounds can reach about 25–50%(Jope, 1965). Post-mortem the chitino-phosphate shells disintegratedue to rapid degradation of the organic matrix and within 2–3 weeksthe valves may completely disappear from the sediment (Emig, 1990).Once buried in the sediment, hydrolysis of the organic matrix isthe first diagenetic change noted, often coinciding with precipitationof secondary apatite or other minerals in the interstitial space, furtherstabilizing the original shell structure (e.g., Lucas & Prévôt, 1991;Kolodny et al., 1996). This process is often accompanied by trace ele-ment uptake from the ambient pore fluid (e.g., Lécuyer et al., 1998;Trueman & Tuross, 2002).

The post-mortem growth of apatite may change the bulk traceelement and isotopic compositions of the original biogenic apatite(e.g., Kolodny et al., 1996; Lécuyer et al., 1998; Tütken et al., 2008).Consequently care must be taken with the interpretation of the Sr-isotopic ratios as palaeo-seawater proxies (e.g., Martin & Scher,2004; Kocsis et al., 2007) or the δ18O values as palaeo-thermometer(Kolodny et al., 1983; Lécuyer et al., 1996a).

Fig. 1. Palaeo-geographicmap of the Early-MiddleMiocenemarine basins between Eurasia and Africa and the possible gateways between the Atlantic and the Indian Oceans (adaptedafter Popov et al., 2004). The gray areas are correspondent to land, whereas white to sea. Abbreviations: NAFB—North Alpine Foreland Basin; RG—Rhine Graben; RV—Rhône Valley.

67L. Kocsis et al. / Palaeogeography, Palaeoclimatology, Palaeoecology 326–328 (2012) 66–77


1.2.1. Oxygen isotope compositions of lingulid brachiopodsA general apatite chemical formula can be given such as Ca5(PO4,

CO3)3(CO3, F, OH) highlighting the most common oxygen bearing sitesin the mineral. Most of the reported oxygen isotope analysesof lingulid brachiopod focused on the PO4

3− ion, which is thought tobe particularly well-preserved over geologic timescales (Longinelli,1966; Lécuyer et al., 1996b; 1998; Wenzel et al., 2000). In these casesthe phosphate ion is separated and precipitated as BiPO4 or Ag3PO4

(e.g., O'Neil et al., 1994). Oxygen isotope composition of modern lingu-lids prepared and analyzed in thisway, correlatedwellwith the temper-ature and isotopic composition of seawater according to the followingequation: T (°C)=(112.2±15.3)–(4.20±0.71)×(d18OPO4–d18Osea)(Lécuyer et al., 1996b).

Other published lingulid oxygen isotope data were obtained withlaser-based in-situ measurements (Wenzel et al., 2000; Rodland etal., 2003). The advantage of the latter method is that it can analyzevery small samples (e.g. conodonts) or distinct growth zones withinsingle specimens. The disadvantage of the laser-based method isthat the values obtained may differ depending on the structure andcomposition of the apatite. Besides the phosphate group (PO4

3−),other molecules containing oxygen can occur within apatite (CO3

2−,OH−, H2O, residual organics). For dense material like enamel withvery low carbonate and organic matter content, the influence ofthese minor ions on measured δ18OPO4 values may be small and canperhaps be neglected. However, in the case of lingulid shells, whereapatite and organic rich layers alternate, the results for the δ18OPO4

values using the laser-based method must be interpreted with care.Applying the laser-based method, Rodland et al. (2003) reported

variations as high as 4‰ in δ18OPO4 values in individual modern shellsand even higher, about 5‰ variations, in one Triassic lingulid. Theseresults were interpreted as reflecting a strong vital effect and non-equilibrium precipitation of phosphate by lingulid brachiopods,a conclusion different from that of Lécuyer et al. (1996b) who demon-strated that modern lingulids secrete their phosphate shells in isoto-pic equilibrium with seawater. The detailed in-situ oxygen isotopeanalyses of Rodland et al. (2003) suggest a more complex metabolismin lingulids than that previously assumed. However, the analyticalmethod may not be without pitfalls and it remains to be confirmed

that the range in values are due to variation in the phosphate anddo not result from an interference or contribution of oxygen fromdifferent oxygen-bearing ions that are known to have different com-positions. In addition, any residual organic matter left within thelingulids may have adverse effects on the measurements made asthe presence of carbon may stabilize gasses other than the CO2 forexample CO. A combined influence of alternative oxygen-bearingspecies and/or interfering gasses may indeed be indicated by theoxygen isotope profiles of Rodland et al. (2003), especially wherethe large variations measured occur in a cyclic manner (cf. Rodlandet al., 2003: Fig. 7) reflecting, for example a cyclic carbonate content.

The silver-phosphate method, where the phosphate ion is sepa-rated, clearly overcomes these problems. Our strategy in this studyis to use the silver-phosphate method in order to reduce any compli-cations of other oxygen-bearing ions and other interfering moleculesdescribed above, and apparently analyzing bulk samples reflects wellthe average environmental conditions (Lécuyer et al., 1996b).

2. Material and analytical methods

The majority of the studied fossils come from the collection of theNetherlands Centre for Biodiversity (NCB), Naturalis, in Leiden, whileothers were directly collected from outcrops (Figs. 2–3). Glottidiaspecimens and one Discinisca from the southern North Sea region ofEarly and Middle-Late Miocene ages (Berchem and Breda Formations)were sampled from boreholes in the Netherlands. Pliocene fossilswere sampled from boreholes or outcrops in Belgium (Kattendijk andLillo Formations, Louwye et al., 2004; Louwye, 2005), the Netherlands(Delden Member, Breda Formation, Bosch & Wesselingh, 2006) andEngland (Coralline Crag, De Schepper et al., 2009). In the CentralParatethys Lingula and Disciniscawere collected in Poland and Hungaryfrom Badenian sediments (Emig & Bitner, 2005), a period equivalentto the Langhian–Early Serravallian (Fig. 2). In addition, two MiddleMiocene Discinisca were analyzed from western-central France(“faluns” deposits, Margerel, 2009), and one Late Miocene Lingulidaefrom southern Portugal (Cacela Formation, Santos et al., 2003). Formore details about the investigated localities see Table 1.

Fig. 2. Stratigraphic stages of the Mediterranean Tethys and Central Paratethys after Gradstein et al. (2004), Rögl (1998), and Harzhauser and Piller (2007), and the stratigraphicspread of the studied sample localities. Error bars indicate uncertainties in the stratigraphic position of the samples. In the last block the Sr-isotopic composition of the samplesare compared to those of the global open-ocean Sr-isotope evolution curve (McArthur et al., 2001), with the ages for the samples assigned based on their stratigraphic positions.For more details see Tables 1 and 2. Abbreviations: B—Belgium; FR—France; GB—Great Britain; HU—Hungary; NL—Netherland; P—Portugal; PL—Poland.

68 L. Kocsis et al. / Palaeogeography, Palaeoclimatology, Palaeoecology 326–328 (2012) 66–77


Between 1 and 5 brachiopod shells or shell fragments were se-lected for geochemical analyses from each of the studied localities.The valves were first washed in distilled water in an ultrasonicbath to remove adhering sediment and subsequently crushed andhomogenized in an agate mortar. Depending on the size of the shells,between 10 and 100 mg of powder was obtained. At this stage, somesub-samples were checked for the purity of the biogenic apatite byX-ray diffraction. The bulk samples were run on a Philips XPert Prodiffractometer with a copper tube, 2θ scanned from 2 to 76° at stepsof 0.02° and 1° a minute. The diffraction pattern was interpreted usingPhilips propriety software.

Samples destined for isotopic study were pre-treated in two stepsfollowing the methods of Koch et al. (1997): soaked in 2.5% NaOCl for24 h; followed by a wash in 1N acetic acid-Ca-acetate (pH=4.5, 6 h),finally rinsed in distilled water several times and split for the differentgeochemical analyses.

For the study of shell ultrastructure of Lingula, the shell was em-bedded in Araldite 2020 resin, cut and polished, then etched with5% HCl for a few seconds before coating with platinumfor observationunder a scanning electron microscope (using a Philips XL-20microscope).

2.1. Oxygen and carbon isotope compositions of structural carbonate(δ18OCO3, δ13C)

The sample powders were analyzed using a Gasbench II coupledto a Finnigan MAT Delta Plus XL mass spectrometer. The measuredisotopic ratios were normalized to an in-house Carrara marblecalcite standard that has been calibrated against NBS-19. Theanalytical precision for this method is better than ±0.1‰ for Oand C isotopes (e.g., Spötl & Vennemann, 2003). The δ18O and δ13Cvalues are expressed in δ-notation relative to VSMOW and VPDB,respectively.

2.2. Oxygen isotope composition of phosphate (δ18OPO4)

The analyses followed a preparation technique adapted afterO'Neil et al. (1994) and Dettman et al. (2001). The cleaned sampleswere dissolved in HF and the obtained solutions neutralized (25%NH4OH), followed by rapid precipitation of Ag3PO4. After drying at70 °C, the silver-phosphate was analyzed via reduction with graphitein a TC/EA (high-temperature conversion elemental analyzer)(Vennemann et al., 2002) coupled to a Finnigan MAT Delta Plus XL

Fig. 3. A) 1. Glottidia cf. dumortieri (Nyst), Antwerpen, NCB Naturalis, Leiden. 2. Lingula dregeri Andreae, Korytnica, Muzeum Ziemi, Warsaw, MZ VIII Bra-1204/2. 3. Discinisca fallens(Wood), Vliegveld, Haamstede, NCB Naturalis, Leiden, SEM. 4. Discinisca leopolitana (Friedberg), Huta Lubycka, NCB Naturalis, Leiden, SEM. 5. Discinisca polonica Radwańska &Radwański, Korytnica, NCB Naturalis, Leiden, SEM. 6–8: Transverse sections of Lingula dregeri Andreae, microstructure composed of spheroidal, and compact and virgose laminae,Budapest, Örs vezér Square, HNHM. Scale bars for 1–5: 1 mm, for 6: 50 μm, for 7: 10 μm and for 8: 5 μm. B) X-ray diffraction patterns of Glottidia show only apatite phases.



mass spectrometer. International NBS-120c phosphorite rock stan-dard was prepared and run together with the samples. Both standardsand samples were measured at least as triplicates. Oxygen isotopecompositions are expressed in the δ-notation relative to VSMOW.The replicates of TU-1 (21.11‰) and TU-2 (5.45‰) internal standardsaveraged±0.3‰ (1σ), while NBS-120c standard yielded 21.5±0.3‰.This NBS-120c value is comparable with those reported by Lécuyeret al. (1996b), when a fractionation equation for modern lingulidswas established.

2.3. Trace elements composition

Prior to the Sr and Nd separation and isotope ratio measurements,the dissolved bulk samples were analyzed for trace element concen-trations on a Thermo Fisher Scientific X-SERIES 2 ICP-MS (inductivelycoupled plasma mass spectrometer). The instrument was tunedfor sensitivity and stability using a 10 ppb multi-element tuning solu-tion (CTUNEA250). The measurements were made with standardsand blanks bracketing the samples and using In and Re as internalstandards.

2.4. Strontium and neodymium isotopes

The 87Sr/86Sr and 143Nd/144Nd ratios were analyzed on a VG-Micromass Sector 54 Thermal Ionization Mass Spectrometer (TIMS).A multi-dynamic peak jumping procedure was used with a 88Srbeam size of 2V and 144Nd beam size of 1V. This followed separationof the Sr using Sr-Spec columns and loading onto Ta filaments with a

Ta activator solution. The Nd separation was carried out using a 2columns procedure, a cation column to remove themajor elements, fol-lowed by a Ln-Spec column to separate Nd from Sm. The Nd sampleswere loaded onto the Ta sides of a Ta–Re–Ta triple filament assembly.The NIST 987 Sr standard yielded 87Sr/86Sr ratio of 0.710253±6 (2σ)and the JNdi standard a 143Nd/144Nd ratio of 0.512095±4 (2σ). Thedata presented here were corrected to the accepted isotopic ratiosof NIST 987 (0.710248) and JNdi (0.512115). 143Nd/144Nd ratios are

expressed as εNd ¼143Nd=144Ndð Þmeasured143Nd=144Ndð Þ0CHUR

−1� �

� 104, where 143Nd/144Nd

for present day CHUR is 0.512638 (Jacobsen & Wasserburg, 1980).Stable isotope analyses were done at University of Lausanne (IMG-

UNIL), Switzerland, while trace element compositions and radiogenicisotope ratios were analyzed at the University of Southampton, U.K.

3. Results

X-ray diffraction analyses of some large Glottidia specimens con-firmed that only apatite was in the shells, and the SEM imagingshow good preservation of microstructures in the brachiopods(Fig. 3). This data suggests that the studied shells did not completelyrecrystallize, nor contain secondary minerals other than perhaps ad-ditional apatite.

The ΣREE concentrations in the fossils vary between 100 and5300 ppm, which suggests some enrichment, likely during early dia-genesis (Lécuyer et al., 1998; Trueman & Tuross, 2002). Phosphaticbrachiopods from the Paratethys gave an average εNd of −8.3±0.8(n=7), while samples from the North Sea clearly have much

Table 1List of the studied brachiopods with all the related information about their provenance, their stratigraphic position and references about the age of the host sediments.

North Sea (NL, B, UK) Locality Lithostratigraphy Series Stage Reference Age range(Ma)

Glottidia sp. Antwerpen, B Sand, Kattendijk Fm. Pliocene Zanclean Louwye et al. (2004) 4.4–5Glottidia sp. Antwerpen, B Oorderen Sand Mbr.,

Lillo Fm.,Pliocene late Zanclean to early

PiacenzianLouwye et al. (2004) 2.7–4.4

Glottidia sp. Gedgrave, Suffolk, GB Coralline Crag—0.55–0.85m Pliocene Zanclean De Schepper et al. (2009) 3.8–4.4Glottidia sp. Gedgrave, Suffolk, GB Coralline Crag—1.7–1.9 m Pliocene Zanclean De Schepper et al. (2009) 3.8–4.4Glottidia sp. Delden drillhole, NL Delden Mbr., Breda

Fm.—6.5–7 mLate Miocene-Pliocene

late Messinian (?)to early Piacenzian

Pers. comm. Dr. Pouwer at NCBand Bosch and Wesselingh (2006)

2.7–6

Glottidia sp. Neede II drillhole, NL Delden Mbr., BredaFm.—34.5–35.5 m

Late Miocene-Pliocene



2.7–6

Glottidia sp. Neede II drillhole, NL Delden Mbr., BredaFm.—42.5–43.5 m

Late Miocene-Pliocene



2.7–6

Glottidia sp. Beugen, NL Breda Fm.—65–66 m Miocene Serravallian–Tortonian Pers. comm. Dr. Pouwer at NCB 7.2–13.7Glottidia sp. Beugen, NL Breda Fm.—75–76 m Miocene Serravallian–Tortonian Pers. comm. Dr. Pouwer at NCB 7.2–13.7Glottidia sp. Beugen, NL Breda Fm.—76–79 m Miocene Serravallian–Tortonian Pers. comm. Dr. Pouwer at NCB 7.2–13.7Discinisca fallens Vliegveld Haamstede,

NLEdegem Sand Mbr.,Berchem Fm.—144–147 m

Miocene early Burdigalian Louwye (2005) 19.5–20

Atlantic coast (FR, P)?Lingula sp. Cacela Velha, P Cacela Formation Miocene Upper Tortonian Santos et al. (2003) 7.5–8.2Discinisca sp. Mirebeau, FR “Faluns” deposits Miocene Langhian and base of

SerravallianMargerel (2009) 13.5–16

Discinisca sp. Mirebeau, FR “Faluns” deposits Miocene Langhian and base ofSerravallian

Margerel (2009) 13.5–16

Central Paratethys (PL, H)Discinisca leopolitana Huta Lubycka, PL Sand, Zelebsko Formation Miocene Upper Badenian (~Langhian) Popiel-Barczyk (1980) 13–14.5Lingula dregeri Lipa, PL Clay, Zelebsko Formation Miocene Upper Badenian (~Langhian) Bielecka (1967) 13–14.5Lingula dregeri Budapest, H Rákos Limestone

FormationMiocene Upper Badenian (~Langhian) Bitner et al. (2012) 13–14.5

Lingula dregeri Korytnica, PL Heterostegina sand,Pinczów Formation

Miocene Lower Badenian (~Langhian) Emig and Bitner (2005) 14.5–16

Discinisca polonica Korytnica, PL Clay, Lithophaga Zona,PinczówFormation

Miocene Lower Badenian (~Langhian) Radwańska and Radwański (1984) 14.5–16

Discinisca polonica Korytnica, PL Oyster Bed, PinczówFormation

Miocene Lower Badenian (~Langhian) Radwańska and Radwański (1984) 14.5–16

Discinisca leopolitana Rybnica, PL Sand, Machów Formation Miocene Lower Badenian (~Langhian) Radwańska and Radwański (1984) 14.5–16

Abbreviations: B—Belgium; FR—France; GB—Great Britain; HU—Hungary; NL—Netherland; P—Portugal; PL—Poland; Fm.—Formation; Mbr.—Member.



lower values of −11.9±0.6 (n=11). The εNd value of the French bra-chiopod is in the range of values typically measured for the North Sea,while the specimen from Portugal has a value similar to those of theParatethys (Fig. 4). The Sr isotope ratios in the fossils are between0.708672 and 0.709089 with a general pattern of increasing ratiowith decreasing biostratigraphic age of the sample locality (Fig. 2).

The oxygen isotope composition of the structural phosphate(δ18OPO4) in the studied brachiopods varies between 20.4 and24.7‰ (Figs. 5–6). The highest values were measured for the NorthSea specimens (24.0±0.5‰, n=11), while the low values were mea-sured for lingulids from the Central Paratethys (21.7±0.8‰, n=7).The sample from Portugal had a δ18OPO4 value similar to the NorthSea specimens, while the two analyses from France are similar tothe Central Paratethyan lingulids.

The oxygen isotope compositions of structural carbonate (δ18OCO3)have about 1.8 to 4.2‰ higher values relative to δ18OPO4, while theδ13C values have a range between−1.6 and−5.8‰. For the completedata set see Table 2.

4. Discussion

The early diagenetic modification of the geochemical compositionof brachiopod shells in terms of possible secondary apatite precipita-tion, re-crystallization and trace element uptake, may preclude adirect interpretation of in-vivo palaeo-environmental conditions.However, the combined geochemical data do place constraints onthe environmental conditions under which the lingulid shells wereformed as discussed below.

4.1. Strontium and neodymium isotope ratios and palaeo-oceanographicinferences

The high REE contents of the fossils and their small deviation fromthe global Sr-evolution curve (Fig. 2) suggest that the compositionsmay have been altered during early diagenesis. Though, local effectson the seawater Sr-budget in the sub-basins might have played im-portant role and could also result in deviation from the global Sr

Fig. 4. εNd values of lingulids illustrated on Early, Middle, Late Miocene, and Pliocene palaeo-maps modified after Popov et al. (2004). Each orange circle represents individualanalyses of phosphatic brachiopods from different layers or different localities. White circles on the Late Miocene map are the same data used on the Middle Miocene one, asthese sampling sites have larger uncertainties in their biostratigraphic age (cf. Fig. 2). The Early Miocene map shows additional data: red triangles are εNd values of shark teethfrom the North Alpine Foreland Basin and the Central Paratethys (Kocsis et al., 2009: >17 Ma; Vennemann & Hegner, 1998) and the red star represents phosphorite data fromMalta (Stille et al., 1996: 16–17 Ma). On the Late Miocene map additional εNd values illustrated by a red star is for the Mediterranean derived from foraminifers (Kocsis et al.,2008: 8.4–10.7 Ma). In the corner of the maps the εNd values of contemporaneous Atlantic and Indian Oceans are indicated. Note the similarities in εNd values between the Para-tethys and the Indian Ocean, and between the North Sea and the Atlantic Ocean.



curve, the high REE concentration clearly indicate trace element ex-change with pore fluid. It is known that the Sr-isotopic ratio of marinepore fluids can deviate from contemporary seawater, with whichfossils may still interact (Martin & Scher, 2004). Hence, biogenicapatite cannot be used for precise indirect dating using the Sr-isotope stratigraphy, but estimates of depositional ages are in manycases still possible (Martin & Scher, 2004). This latter possibilitymay apply to part of the samples of the Mio-Pliocene lingulids, astheir projected Sr-isotope ratios do intercept the Sr-evolution linewithin the estimated stratigraphic age brackets defined for the givensampling localities (Fig. 2).

Neodymium is present only in very low concentration (b1 ppb) inmodern biogenic apatite (e.g., Vennemann et al., 2001) but fossilsoften have concentrations that are much higher (Trueman & Tuross,2002). Any palaeo-oceanographic interpretation of Nd-isotopic ratiosmeasured in the fossils, therefore, is based on two assumptions.Firstly, the majority of the Nd was incorporated during early diagene-sis while the fossils still interactedwithmarine pore fluids. The secondis that this early enrichment in Nd will subsequently be preserved. Anuptake of Nd during early diagenesis, that is within less than 106 years,is generally proposed (Trueman & Tuross, 2002; Kohn, 2008). In con-trast, more recently Kocsis et al. (2010) and Herwartz et al. (2011),on the basis of Lu–Hf measurements, indicated that biogenic apatitedoes not necessarily behave as a closed system. The older the fossilsare, the higher the deviation might be relative to the values at thetime of formation. However, in the view of the relatively young agesof the investigated lingulids, the REE concentrations in the fossilsof this study may still be those obtained during early diagenesis(e.g., Martin & Scher, 2004; Kocsis et al., 2010).

As such, if the εNd values of the fossils of this study are interpretedas reflecting marine fluids, then the distinct values between the sam-ples from the Paratethys and the North Sea (t(11)=10.39; pb0.05)would indicate distinct marine basins. The low Nd-isotopic ratios inthe fossils from the North Sea localities are similar to those reported

for the Atlantic Ocean at the estimated time of their formation(Fig. 4; Burton et al., 1999; Frank, 2002). This is also the case for thesample from western France as it has value similar to those of theAtlantic, even though the Nd-isotope ratio has a higher standarddeviation that may possibly be related to the low Nd-content(Table 2). In contrast to the other samples, those from the sedimentsof the Central Paratethys domain have relatively high εNd values thatare identical to those measured previously for the Paratethys ofthis Early-Middle Miocene age (Fig. 4; Vennemann & Hegner, 1998;Kocsis et al., 2009), and are also similar to those estimated for thecontemporaneous Indian Ocean (O'Nions et al., 1998; Frank, 2002)and the Mediterranean Sea (Jacobs et al., 1996; Stille et al., 1996;Kocsis et al., 2008).

However, Nd has short residence time in seawater, much shorterthan oceanic mixing time (Frank, 2002), therefore the Nd-budget ofshallow marine basins can be easily controlled by local Nd-input.The influence of local input in the Paratethys and the Mediterraneanwere investigated by parallel analyses of Nd and Sr isotope ratiosof marine fossils and their embedding sediments with the successof distinguishing between common marine εNd values and certainstrong local influences for the given sub-basins (Kocsis et al., 2008,2009). The observed similar εNd values to the Indian Ocean presentsthe possibility to interpret the data as these regions were connectedby seaways, especially when these data supported by strong palaeon-tological evidences. Regarding the North Sea and the possible effectsof the hinterland geology on local seawater chemistry, Jeandel et al.(2007) reported data from rocks around the North Sea with εNdvalues vary between −11 and −14. If this range is taken representa-tive, then from different proportion of these source rocks the hereanalyzed εNd values of the lingulids could be constrained. However,if the scenario of Atlantic seawater incursion is rejected and onlyintensive local control on the basin is assumed then much largerdeviation from the Sr-evolution curve would be expected as well.

The combined Sr- and Nd-isotope compositions measured here aretherefore, interpreted as compatible with representing early diageneticbut still marine pore fluids at the time of fossilization. Further on thesemarinefluids are indicative of either North Sea/Atlantic compositions orof marine waters from the Central Paratethys/Mediterranean. Thiswould also imply that the North Sea basin was not connected to thatof the Paratethys from the Miocene onwards. However, a possibleshort-lived connection between the North Sea and the northern CentralParatethys (Carpathian foredeep) was suggested on the base of similarplankton fauna (pteropods) in the two basins during the MiddleMiocene (e.g., Gürs & Janssen, 2002). If this seaway really existed, theresolution of our data does not allow observing it or the short durationof this connection did not accompany with large amount of water ex-change between the basins which should have led to mixed εNd signal.

The εNd value of the sample from southern Portugal is similarto those reported from the Paratethys and the Mediterranean (Fig. 4).This could support the possible influence of the Mediterranean outflowon the Atlantic during the Late Miocene, which phenomenon wasalso recorded by other archives (c.f., Abouchami et al., 1999; Kocsiset al., 2008).

4.2. Oxygen isotope compositions of lingulid brachiopods

The range of δ18OPO4 values in the Mio-Pliocene lingulids are verysimilar to those reported from modern specimens (Lécuyer et al.,1996b; 1998) and notably higher compared to those from thePaleozoic (Longinelli, 1966; Lécuyer et al., 1998; Wenzel et al.,2000). Bulk δ18OPO4 analyses of modern lingulids by Lécuyer et al.(1996b) indicate good correlation with the temperature and isotopiccomposition of seawater, therefore, the oxygen isotope results ofthis study, if original values are preserved, can be investigated furtherand could relate to former ancient seawater conditions.

Fig. 5. Comparison of oxygen isotope compositions of phosphate and carbonate fromlingulid brachiopod shells. The Mio-Pliocene data (orange circles) are compared todata from the literature. Common error bars are in the up-left corner, if differentthey are marked at the given sample point. Note the large error derived from averagedlaser-based in-situ analyses for δ18OPO4 by Rodland et al. (2003). Straight line reflectsphosphate isotope compositions in equilibrium with carbonate after Iacumin et al.(1996). Dashed line reflects calculated distribution according to temperature equationsof Kolodny et al. (1983) and O'Neil et al. (1969). The black arrow indicates the possiblediagenetic pathway.



4.2.1. δ18OPO4: preservation vs. diagenesisIf δ18OPO4 values are to be used to calculate ambient water

temperatures the original values must be retained. For example, thelow δ18OPO4 values of Paleozoic lingulids have been interpreted asthe influence of late diagenesis in the presence of meteoric waters(Longinelli, 1966; Wenzel et al., 2000).

One method used to estimate the effects of diagenesis is to com-pare the offset between δ18OCO3 and δ18OPO4 (Δ18Oc-p) in the apatite.Empirical studies of modern vertebrate bones have shown a Δ18Oc-p

offset of about 8–9‰ (Bryant et al., 1996; Iacumin et al., 1996). A sim-ilar offset can be calculated for co-existing apatite and calcite in thetemperature range of 10–37 °C when their respective water-mineralfractionation equations are combined (O'Neil et al., 1969; Longinelli& Nuti, 1973; Kolodny et al., 1983). More recently, an experimentalstudy on inorganic precipitation of hydroxyl-apatite confirmedthese Δ18Oc-p values, but also noted a weak temperature dependenceof Δ18Oc-p of about 7.5 to 9.1‰ as the temperature decreases(37→10 °C) (Lécuyer et al., 2010). As a consequence, this could beapplied in a simplified way as the maximum range that might beexpected in unaltered biogenic apatite fossils.

However, in modern fish no such correlation between the δ18OCO3

and δ18OPO4 values is observed (e.g., Kolodny & Luz, 1991) indicatingthat carbonate in fish bone is not precipitated in oxygen equilibriumwith the phosphate, whichmight also be the case for lingulids. Indeed,this fractionation has also been interpreted in an inverse fashion, withfossil fish teeth showing Δ18Oc-p close to the reported equilibriumvalue of 8.5‰, indicating complete re-equilibration of the phosphateand carbonate with the pore fluids during diagenesis (Kolodny &Luz, 1991; Kolodny et al., 1996). It is also well documented thatcarbonate oxygen in the apatite is more susceptible to alterationunder inorganic, diagenetic conditions (e.g., Kohn & Cerling, 2002).However, the situation may be different under microbiologically me-diated conditions, where the phosphate oxygenmight also be affected(e.g., Blake et al., 1997; Zazzo et al., 2004). Diagenetic fluids, if ofmeteoric origin, would generally lower the δ18O values of marinefossils. But if the oxygen isotope composition of the diagenetic fluidsin which microbially mediated reactions occur is the same as thatin which the original bioapatite formed (e.g., seawater), then partialre-equilibration of phosphate with this water at similar temperatureswould not be detectable in the δ18OPO4 values (Blake et al., 1997).

Fig. 6. δ18OPO4 values of lingulids illustrated on Early, Middle, and Late Miocene, and Pliocene palaeo-maps modified after Popov et al. (2004). Each circle represents individualanalyses of phosphatic brachiopods from different layers or different localities. White circles on the Late Miocene map are the same data used on the Middle Miocene one, asthese sampling sites have larger uncertainties in their biostratigraphic age (cf. Fig. 2). Additional data on the Early Miocene map: red triangles are δ18OPO4 values of shark teethfrom the North Alpine Foreland Basin and Central Paratethys (Kocsis et al., 2009: >17 Ma; Vennemann & Hegner, 1998). Note the high δ18OPO4 values from the North Sea thatrepresent colder conditions (blue arrow) relative to other sites (red arrows).



For the samples in this study the Δ18Oc-p values range from 1.8 to4.2‰. If these data are plotted on a carbonate (δ18OCO3) vs. phosphate(δ18OPO4) diagram together with available data from the literaturethen some general trends can be observed (Fig. 5). Modern lingulidseither fit on the Δ18Oc-p=8.5‰ correlation line or those analyzedby laser-method are positioned slightly below or above it (cf. Fig. 5,Rodland et al., 2003). In contrast, most of the fossil lingulids plotabove the line, with some exceptions of Paleozoic samples that alsoplot onto the line (Fig. 5).

The relatively close dispersion of modern lingulids around theequilibrium line suggests that carbonate in lingulids might be precip-itated in oxygen equilibrium with the phosphate. But to prove thishypothesis a more detailed study is necessary. In contrast, the verylow δ18OPO4 and δ18OCO3 values in Paleozoic lingulids indicate thatboth isotopic compositions could have been altered and in somecases complete re-equilibration of the two phases was reached duringdiagenesis (Fig. 5). On the other hand, the Mio-Pliocene brachiopodsanalyzed in this study may indicate a preferential alteration of theδ18OCO3 values rather than those of the phosphate (Fig. 5).

The above information, together with the good structural preser-vation (Fig. 3) and the interpretations of the εNd values (Fig. 4)would support that the shells analyzed here were likely only influ-enced by marine pore fluids during early diagenesis, hence allowingthe δ18OPO4 values to still reflect the seawater conditions at the timeof the shell formations (Fig. 6).

4.3. North Sea versus Paratethys

The geographical distance and the statistically significant differ-ence between the average δ18OPO4 values (t(8)=−6.76; pb0.05) ofthe lingulids from the Central Paratethys and the North Sea sedi-ments, may be taken to indicate that either the two marine basinshad different average seawater temperatures or isotopic composi-tions. The sampling strategy, based on bulk samples, reduces thepossibility that the differences between the sample localities aredue to different vital effects in the diverse lingulids. Further evidencecomes from the Discinidae which were analyzed from both regionswith these brachiopods yielding similar δ18OPO4 values to the domi-nant genera of the North Sea and the Central Paratethys, Glottidia

and Lingula, respectively. As such it is likely that the difference in iso-topic compositions between the localities is related to different envi-ronmental conditions that existed during the formation of the apatite.

To determine the absolute ambient temperature of seawaterrequires knowledge of the δ18O of water (cf. equation in Section1.2.1). In general, the oxygen isotope composition of seawater isassumed to be about −1‰ for interglacial, Greenhouse climatic con-ditions and 0.5‰ for glacial periods. However, in smaller semi-closedbasins, evaporation or input of freshwater, may either in- or decreasethe typical open ocean δ18O values, making temperature calculationsdifficult to do with precision. Therefore, the relative variations amongthe examined populations are considered first.

As a first approximation assuming similar oxygen isotope compo-sition for seawater, the differences in δ18O values of the CentralParatethys and North Sea samples would imply temperature differ-ences of about 8–10 °C, with cooler conditions for the North Seamarine basin compared to that of the Paratethys during the MiddleMiocene.

As a second approach, if it is assumed that the brachiopods lived ata similar preferred temperature range for the two regions, althoughit is known that the temperature tolerance can be highly variableamong modern lingulid populations (Emig, 1997). Nevertheless, ifthe ambient temperature were the same in the two basins, the differ-ence in mean δ18O values of 2 to 2.5‰ between the two populationswould also imply a difference of about 2 to 2.5‰ for the ambientwater. This may imply either strong evaporation for the MioceneNorth Sea or an important freshwater input for the Paratethys.However, during the Early-Middle Badenian it is estimated thatevaporation was important for the Central Paratethys domain, priorto the establishment of strong freshwater input only after about13.5 Ma (Báldi, 2006). In the shallow marine basin of western France,a study of sympatric marine mammals and fish also indicated evapo-rative processes to have been important (Lécuyer et al., 1996a). As aconsequence, the North Sea should have experienced even strongerevaporation than the other Middle Miocene localities. However,given the geographical situation of the studied localities (Fig. 6),and in the view of available geological data, this interpretationis considered unlikely (e.g., Meulenkamp & Sissingh, 2003; Kováčet al., 2007; Rasser et al., 2008).

Table 2Geochemical composition of the investigated samples.

North Sea (NL, B, UK) Sr(ppm)

Nd(ppm)

ΣREE(ppm)

87Sr/86Sr +/− 143Nd/144Nd +/− εNd δ18OPO4

VSMOWStd. δ18O

VPDBδ18OCO3

VSMOWStd. Δ18O

CO3–PO4δ13CVPDB

Std.

Glottidia sp. 3377 77 410 0.709077 0.000011 0.512023 0.000008 −12.0 23.7 0.3 −4.4 26.4 0.1 2.7 −4.6 0.1Glottidia sp. 3066 27 149 0.709089 0.000011 0.512021 0.000012 −12.0 23.5 0.1 −4.2 26.6 0.1 3.1 −5.8 0.1Glottidia sp. 3216 48 258 0.709013 0.000011 0.512015 0.000024 −12.2 24.5 0.1 −3.3 27.5 0.1 3.0 −3.3 0.1Glottidia sp. 3062 49 261 0.709056 0.000011 0.511953 0.000027 −13.4 24.7 0.2 – – – – – –

Glottidia sp. 2821 532 2880 0.709013 0.000013 0.512019 0.000008 −12.1 24.6 0.1 −3.6 27.2 0.2 2.6 −5.2 0.1Glottidia sp. 2945 683 3615 0.709061 0.000011 0.512046 0.000020 −11.5 23.9 0.0 – – – – – –

Glottidia sp. 2739 1046 5361 0.708980 0.000013 0.512061 0.000008 −11.3 24.2 0.0 – – – – – –

Glottidia sp. 3392 151 782 0.708789 0.000013 0.512063 0.000008 −11.2 23.9 0.1 −3.5 27.3 0.1 3.4 −3.8 0.1Glottidia sp. 4088 132 653 0.708732 0.000010 0.512048 0.000008 −11.5 23.9 0.2 −4.0 26.8 0.1 2.8 −4.5 0.1Glottidia sp. 4545 265 1271 0.708766 0.000011 0.512037 0.000009 −11.7 23.4 0.2 – – – – – –

Discinisca fallens 3595 577 3299 0.708672 0.000013 0.511998 0.000022 −12.5 23.6 0.1 – – – – – –

Atlantic coast (FR, P)?Lingula sp. 2925 249 1346 0.708949 0.000011 0.512206 0.000017 −8.4 23.4 0.0 −3.8 27.0 0.1 3.6 −4.5 0.2Discinisca sp. 2652 16 98 0.708891 0.000013 0.512012 0.000172 −12.2 21.6 0.2 – – – – – –

Discinisca sp. 2775 16 105 0.708943 0.000011 – – – 21.5 0.1 – – – – – –

Central Paratethys (PL, H)Discinisca leopolitana 4057 561 2826 0.708906 0.000011 0.512220 0.000006 −8.2 21.9 0.1 – – – – – –

Lingula dregeri 3609 322 1428 0.708890 0.000011 0.512199 0.000006 −8.6 22.3 0.1 −6.6 24.1 0.1 1.8 −4.4 0.1Lingula dregeri – – – 0.708809 0.000009 0.512276 0.000059 −7.1 20.7 0.5 – 22.8 0.1 2.1 −2.9 0.1Lingula dregeri 4243 191 776 0.708796 0.000014 0.512199 0.000019 −8.6 20.4 0.4 – – – – – –

Discinisca polonica 4782 208 1037 0.708855 0.000014 0.512166 0.000007 −9.2 22.5 0.1 −4.1 26.7 0.1 4.2 −1.6 0.0Discinisca polonica 3893 197 971 0.708878 0.000011 0.512171 0.000007 −9.1 21.8 0.4 – – – – – –

Discinisca leopolitana 4559 264 1584 – 0.000027 0.512248 0.000006 −7.6 22.3 0.4 – – – – – –

Abbreviations: B—Belgium; FR—France; GB—Great Britain; HU—Hungary; NL—Netherland; P—Portugal; PL—Poland.



From the above discussion it is clear that the high δ18OPO4 valuesmeasured in the North Sea specimens are more likely to be relatedto lower seawater temperatures. To express the δ18OPO4 values inabsolute temperatures the fractionation equation of Lécuyer et al.(1996b) can be used in which the δ18O value of seawater assumedto be −0.5‰ for the Mio-Pliocene (e.g., Lear et al., 2000). Under theseconditions, the current results indicate a temperature variation inNorth Sea between 4±2 and 14±1 °C during the Mio-Pliocene, whilethat for the Central Paratethys it varied from 15±2 to 25±2 °C inthe Middle Miocene. These temperatures are comparable with thehabitat range of modern brachiopods (Emig, 1997), further supportinga preservation of the δ18O values.

The environmental condition for the brachiopods from the NorthSea seems to remain very stable through time in the view of thevery similar Miocene and Pliocene oxygen isotope values (assumingsimilar δ18O values for water). This can be explained by an adaptationto a constant habitat depth of this species with a possible cold waterinflow from the North Atlantic.

The oxygen isotopic compositions of the lingulids from westernFrance reflect warm temperature conditions similar to those of theCentral Paratethys during the Middle Miocene. Comparable tempera-ture ranges were reported from shark teeth in the Paratethys(Vennemann & Hegner, 1998; Kocsis et al., 2009). As all these locali-ties, together with those of the North Sea were at similar palaeo-latitude, it suggests that the North Sea was thermally separated andits seawater was possibly influenced by cold water inflow from thenorth (Fig. 6).

The high δ18OPO4 value of the Late Miocene lingulid from south-ern Portugal can also be related to a cold water habitat. Alterna-tively, the data can be linked to the global cooling trend reflectedby the gradually increasing oxygen isotope composition in benthicforaminifera after 14–15 Ma ago (Miller et al., 1987, 1991; Zachoset al., 2001), which was also recorded in the Mediterranean(Turco et al., 2001; Kocsis et al., 2008). This increase in δ18O valuesin seawater relates to the growing ice-sheet accumulated inAntarctica. Although shallow water deposits in the Paratethysand western France around 13.5–16 Ma ago show still warmmarine conditions (Fig. 6), but by the time of the deposition atthe Portugal site (7.8 Ma) shallow marine seawater could be alsoinfluenced by the global cooling and the related increased δ18Ovalue of seawater.

5. Conclusions

Geochemical compositions of Miocene and Pliocene phosphaticbrachiopods were examined from localities representing the NorthSea, the Central Paratethys, as well as sites from the Atlantic coastof Europe, in order to trace past environmental conditions andmarine connections between the northern boreal and the southernsubtropical–tropical marine basins.

The combined geochemical compositions of the brachiopod shells,supported by their good structural preservation, are interpreted asrepresenting the environmental conditions. Markedly different watermasses and temperature regimes from the North Sea samples andthose of the Paratethys region are indicated.

The εNd data of the lingulids support an inflow of Atlantic Oceanwater to the North Sea, while the Paratethyan lingulids have εNdvalues that are similar to those of the contemporaneous IndianOcean. The data set further suggests that there was no direct connec-tion or major exchange of water between the two marine basinsfrom the Miocene onwards. Thermally distinct water masses for theMiocene North Sea and the Central Paratethys are also indicated bydifferences in oxygen isotope compositions of the brachiopods. TheNorth Sea lingulid population has average δ18OPO4 values that are2–2.5‰ higher than those in the Paratethys, suggestive of colderand constant habitat temperatures for the Mio-Pliocene brachiopods.

In contrast, the Paratethyan brachiopods formed their shells underwarmer, subtropical conditions.

The δ18OPO4 values of brachiopods from the Middle Mioceneof western France are similar to that of analyzed from the CentralParatethys indicating comparable temperature regime, but the sea-water εNd value here is identical to that of contemporaneous AtlanticOcean. Contrary the Late Miocene brachiopod from southern Portugalyielded εNd value that is similar to the Mediterranean at the timereflecting the influence of Mediterranean outflow on the Atlantic.The high δ18OPO4 from this site shows either a deep water habitatfor the lingulid or formation of the shells after the onset of majorglobal cooling that resulted in an increased δ18O value of seawater.

Acknowledgments

The authors thank the Netherlands Centre for Biodiversity (NCB),Naturalis, in Leiden for providing fossils for this research and Dr.Frank Wesselingh and Ronald Pouwer at NCB for their assistancewith the sampling. L.K. received support from the Swiss NationalScience Foundation (SNF PBLA2-119669 and SNF PZ00P2_126407/1)and from a grant to Clive Trueman, NERC (NE/C00390X/1), whenthis research was conducted. A.D. was supported by the HungarianScientific Research Fund (OTKA K77451) and European Commission'sSynthesys project to Leiden (NL-TAF-3270). The authors appreciatethe detailed constructive reviews of D.L. Rodland and three otheranonymous reviewers on an earlier version of the manuscript.

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