High-resolution integrated stratigraphy of the OAE1a and ...Methods of the quantitative...

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Cretaceous Research 56 (2015) 119e140

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Cretaceous Research

journal homepage: www.elsevier .com/locate/CretRes

High-resolution integrated stratigraphy of the OAE1aand enclosing strata from core drillings in the Bedoulian stratotype(Roquefort-La B�edoule, SE France)

Michel Moullade a, b, *, Guy Tronchetti b, Bruno Granier c, d, Andr�e Bornemann e, f,Wolfgang Kuhnt g, Janne Lorenzen g

a Centre de Recherches Micropal�eontologiques, Museum d’Histoire naturelle, 60 Bd Risso, F-06300 Nice, Franceb Centre de S�edimentologie-Pal�eontologie, Laboratoire de G�eologie des Syst�emes et des R�eservoirs Carbonat�es, Universit�e Aix-Marseille, 3 Pl. Victor Hugo,F-13331 Marseille Cedex 03, Francec Department of Ecology and Evolutionary Biology, The University of Kansas, 1200 Sunnyside Avenue, Lawrence, KS 66045, USAd D�ept. S.T.U., Fac. Sci. Tech., U.B.O., 6 av. Le Gorgeu, CS 93837, F-29238 Brest, Francee Institut für Geophysik und Geologie, Universit€at Leipzig, Talstr. 35, D-04103 Leipzig, Germanyf Bundesanstalt für Geowissenschaften und Rohstoffe, Stilleweg 2, D-30655 Hannover, Germanyg Institut für Geowissenschaften, Christian-Albrechts-Universit€at zu Kiel, Olshausenstr. 40, D-24118 Kiel, Germany

a r t i c l e i n f o

Article history:Received 23 October 2014Accepted in revised form 18 March 2015Available online

Keywords:OAE1aAptianBedoulianGargasianGSSPMicrobiostratigraphyIsotopic stratigraphy

* Corresponding author. Centre de Recherches Micd'Histoire naturelle, 60 Bd Risso, F-06300 Nice, Franc

E-mail address: [email protected] (M. Mo

http://dx.doi.org/10.1016/j.cretres.2015.03.0040195-6671/© 2015 Elsevier Ltd. All rights reserved.

a b s t r a c t

In 2009 two wells were drilled with 100% core recovery at Roquefort-La B�edoule (Bouches-du-Rhone, SEFrance), the historical Bedoulian stratotype. Here we present holostratigraphic results based on a detailedstudy of the cored sediments. Our work confirms that the La B�edoule area offers one of the best recordsfor the period spanning the late Bedoulian, the anoxic event OAE1a and the Bedoulian/Gargasian (lower-upper Aptian substages) transition. New data provide a refined succession of micropaleontogical eventsalready well correlated with ammonites from previous fieldwork and, thus, improve the cross-calibrationof bioevents with high-resolution isotope stratigraphy. Methods of the quantitative micropalaeontologyapplied on benthic foraminifera such as tritaxias help testing their probable orbitally triggered cyclicity,which might be used to precise estimates of duration of events such as OAE1a, the Dufrenoya furcataammonite Zone, the Globigerinelloides ferreolensis planktonic foraminiferal zone and the C7 isotopicstage.

The lithologic, biotic and possibly isotopic changes seen at the level of and around bed 170 (top of“Niveau Blanc” sensu auctorum) are strong arguments to use this key-level as the boundary between thetwo Aptian substages (or stages in an alternative classification) and to support the proposal of La B�edouleas a potential locality for the GSSP of the Gargasian Substage (or of historical Aptian sensu stricto, in thealternative classification).

© 2015 Elsevier Ltd. All rights reserved.

1. Introduction

With a duration of about 12 myr (Scott, 2014), the Aptian is oneof the three Cretaceous “superstages”, together with the Albian(15 myr) and the Campanian (11 myr), whereas most of the otherCretaceous stages are 6 myr in average length. This longevity mayexplain earlier somewhat confusing two- or three-fold divisions ofthe Aptian including two to three substages based on distinct

ropal�eontologiques, Museume. Tel.: þ33 (0)4 97 13 46 81.ullade).

stratotypes. Table 1 summarizes two recent proposals (Rebouletet al., 2011, 2014; Moullade et al., 2011) for the subdivision of thelatest Barremian to earliest Albian chronostratigraphic interval.Awaiting an official position of the International Commission ofStratigraphy (ICS), and in view not to confuse the reader, in thisworkwewill provisionally keep the terms Bedoulian and Gargasianfor naming the Lower and Upper Aptian, respectively. However, ourposition (Moullade et al., 2011) is to subdivide the interval betweenthe Barremian and the Albian into two distinct stages: 1) theBedoulian, upgraded from its rank of substage, and 2) the Aptiansensu initio, i.e., sensu d'Orbigny (1840), covering the Gargasian(a junior synonym of the original Aptian).

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Table 1Two recent proposals (Reboulet et al., 2011, 2014; Moullade et al., 2011) for the subdivision of the uppermost Barremian to lowermost Albian chronostratigraphic intervalcompared to Lyon 1963 Colloquium (Anonymous, 1965).

Substages Zones SubzonesCLANSAYESIAN Hypacanthoplites jacobi

Diadochoceras nodosocostatumParahoplites melchioris

Epicheloniceras buxtorfiEpicheloniceras gracile Epicheloniceras debileDufrenoyia dufrenoyiDufrenoyia furcata

Deshayesites grandis

Roboloceras hambrovi

Deshayesites luppovi

BEDOULIAN

APTI

AN

Lower Cretaceous Colloquium (Lyon, 1963)

GARGASIAN APTIAN

ALBIAN (pro parte )

ammonite zonation

(sensu stricto = Gargasian)

Deshayesites forbesi

Deshayesites oglanlensis

Deshayesites deshayesi

Dufrenoyia furcata

Moullade et al., 2011

StagesSubstages

Epicheloniceras martini

Acanthohoplites nolani

Reboulet et al., 2011

UPPER APTIAN

LOWER APTIAN BEDOULIAN

M. Moullade et al. / Cretaceous Research 56 (2015) 119e140120

Until recently the stratigraphy of the Bedoulian stratotypic areain south-Provence was based on a more or less continuous com-posite set of sections located in the territories of Cassis andRoquefort-La B�edoule (Bouches-du-Rhone, SE France) (Figs. 1e2).During the 19th Century and the first half of the 20th these lo-calities were especially well-known for their rich ammonitefaunas. Fabre-Taxy et al. (1965) published the first study of theBedoulian historical stratotype that integrated ammonite andmicrofossil biostratigraphy. This trend has been continued during

Fig. 1. Geographic location of the studied sections

the last decade (Moullade et al., 1998a,b, 2005; Ropolo et al., 1998,2006, 2008) and has been combined with chemostratigraphy(Renard & Raf�elis, 1998; Renard et al., 2005; Kuhnt et al., 1998,2011).

However, several upper Bedoulian levels (including beds ofanoxic event OAE1a), as well as its transition to the Gargasian,remained poorly accessible for field observation.

This prompted two of us (WK & MM) to undertake a project tocontinuously core in the stratotypic area of Roquefort-La B�edoule,

and drill holes in the Cassis-La B�edoule area.

Fig. 2. Lower Bedoulian to lower Gargasian composite succession at Cassis-La B�edoule (adapted from Moullade et al., 1998a, 2004; Ropolo et al., 2006, 2008).

M. Moullade et al. / Cretaceous Research 56 (2015) 119e140 121

which was carried out in 2009. Three holes (LB1, LB2, and LB3;Fig. 1) were drilled (Fl€ogel et al., 2010), with the main goal to obtaina continuous succession covering the upper Bedoulian (LB1eLB2)and the BedoulianeGargasian transition (LB3).

First biostratigraphic results based on occurrences of the mainforaminiferal markers from hole LB1 were published in a recentpaper (Lorenzen et al., 2013). The aim of the present work is toexpand this preliminary study by providing a higher-resolution


stratigraphic framework of the upper two-thirds of hole LB1 andthe entire hole LB3. This report is based on a larger set of additionaldata including benthic and planktonic foraminifera, isotopegeochemistry and to some extent ostracods and calcareous nan-nofossils. Integration with ammonite zones was performed bycorrelating the drilling results with lithological and faunal datacollected in the nearby outcrops (Moullade et al., 1998a; Ropoloet al., 2006, 2008; Kuhnt et al., 2011).

We used foraminifera, bulk-rock carbon isotope measurementsand natural gamma ray logging as main tools to establish a high-resolution stratigraphic framework for the LB1 and LB3 boreholes.This study represents a stratigraphically significant advancecompared to previously published results (Moullade et al., 1998a,b,and subsequent studies), which were based on a composite suc-cession of discrete outcrops implying possible observational gaps. Acontinuous succession and optimal core recovery gave us the op-portunity (i) of high-resolution sampling and (ii) to fill these gaps.

This study is also intended to show how such a synthesis ofcomplementary field and core-hole data in the Bedoulian stratotypicarea should strengthen theposition of Cassis-La B�edoule as anAptianreference section and a potential candidate for a GSSP of theboundary between two stratigraphic entities, understood either assub-stagesoras stages,whicheverclassificationwill be ratifiedby ICS.

2. Geographical setting

The geographic position of the boreholes is shown in Fig.1. HolesLB1 and LB2 are located within a dozenmetres of each other, 600mSW of the settlement of Les Fourniers. Both holes covered 67 m ofthe same sedimentary succession of mostly Bedoulian age. For thisstudy only LB1 has been sampled. Results from LB2 have not beentaken into consideration in this paper because its stratigraphic in-terval duplicates that of LB1. LB3 is located 1.25 km ENE of LB1/LB2,just to the south of the residential development of Les Tocchis. Herea 55m-thick succession including the uppermost Bedoulian and thelower part of the Gargasian was recovered. LB1 and LB3 overlap byfifteen metres on either side of the Bedoulian/Gargasian boundary.

3. Lithological nomenclature

Moullade et al. (1998a, 2004) described in detail the lithos-tratigraphy of the Bedoulian and Lower Gargasian beds from theCassis-La B�edoule stratotype area on the basis of a composite set ofdiscrete sections. Based on the respective lithologic composition,the authors divided the La B�edoule Formation into three Members:1) the Calcareous Member, subdivided in three Units (1, 2, 3),including the uppermost Barremian and the lower Bedoulian; 2)the Marly Calcareous Member, made of alternating marls andlimestones, divided in two Units (4, 5) and dated late Bedoulian;and 3) the Marly Member (Unit 6), dated early Gargasian. TheBedoulian/Gargasian boundary is defined at the top of key bed 170(lowest occurrence of the ammonite Dufrenoyia furcata and theplanktonic foraminifer Praehedbergella luterbacheri). Lithostrati-graphic features, as well as some key beds or levels and ammonitezonal markers are summarized in Fig. 2. These data will be used forinterpreting the drilled succession.

4. Material and methods

4.1. Microfossils (foraminifera and ostracods)

Hundred and five samples (48 from LB1 and 57 from LB3) weretaken at spacings of one metre for LB1 and half a metre for LB3 andstudied for foraminifera. Both the sediment sample and its washedresidue were dried and weighed. Samples were treated by

Rewoquat W 3690 (cationic tenside; see details in Moullade et al.,2005) before sieving through a 45 micron screen. The washedresidue of each sample was divided into two equal aliquots using amicrosplitter. (1) The first half was used for biostratigraphic ana-lyses, with identification and counting of all specimens from everybenthic and planktonic species. These data were used for con-structing the distribution tables of LB1 and LB3 (Figs. 3e4), forwhich we applied the same frequency-classes as those defined forthe Cassis-La B�edoule area byMoullade et al. (2005). (2) The secondhalf was dry-sieved through a 140 micron screen and a micro-splitter was used to get samples sizes of about 200 benthic fora-minifera among which every individual species or groups of closelyrelated species were counted. This technique allowed us to acquirevarious quantitative parameters in a comparable way (per gram ofdried sample) for all samples, such as the total number of benthics,number of agglutinated or calcareous forms, of tritaxias, lentic-ulinas, gavelinellas, falsogaudryinellas, etc.

The state of microfossil preservation from the core samples isvariable, ranging from poor to moderate in the Bedoulian andmoderate to good in the Gargasian. Ostracods are slightly betterpreserved than foraminifera. Specimens collected from the coresappeared less well-preserved than those from outcrop samples,possibly more resistant to corrosion by the Rewoquat.

4.2. Calcareous nannofossils

Two simple smear slides from each sample were preparedfollowing the standard procedure of Bown and Young (1998). Fromeach slide more than ~200 fields of view have been scanned forspecies of stratigraphic importance by using a polarizing light mi-croscope (Zeiss Axio-Imager) with a magnification of 1250�. Inorder to integrate the results into existing stratigraphic frameworksspecies reported by Sissingh and Prins (1977), Roth (1978), Perch-Nielsen (1985), Bown et al. (1998) and Bergen (1998) were usedto apply the NC zonation according to Roth (1978).

4.3. Natural gamma ray logging

The wire-line logging was performed with an Antares Aladdinlogging system, equipped with a GR5 sensor probe. The probe waslowered into the drill hole after the drilling was completed. Thewalls of the hole were not covered with a metal casing. Measure-ments (5 cm spacing) are reported as API (American PetroleumInstitute) radioactivity units.

4.4. Stable isotopes

For stable isotope measurements, core LB1 and LB3 weresampled at 20 cm interval. Stable isotopes were measured with aFinnigan MAT 251 mass spectrometer connected to a Carbo-Kiel(automated CO2 preparation) device at the Leibniz-Laboratory forRadiometric Dating and Isotope Research in Kiel, Germany. Theresults were calibrated by using the NBS 19 standard and are re-ported on the PeeDee Belemnite (PDB) scale. The mass spectrom-eter has an analytical uncertainty of <±0.04‰ for d13C and<±0.07‰ d18O for carbonate samples.

4.5. Carbon isotope stratigraphy

Based on data from the Cismon (Italy) and Roter Sattel(Switzerland) sections, Menegatti et al. (1998) developed anomenclature for segments of the Aptian carbon isotope curve(Fig. 5). According to major changes in the carbon isotope record,segments were defined and labelled from C1 to C8. We used thesedefinitions to correlate our carbon isotope curves. In the LB1

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Fig. 3. Distribution of Foraminifera and selected Ostracoda in hole LB1 at La B�edoule plotted against ammonite (Reboulet et al., 2011), calcareous nannofossil (Roth, 1978), isotope stages (Menegatti et al., 1998; this study), and the mainmarker levels (Moullade et al., 1998a; Ropolo et al., 2006, 2008; this study).

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Fig. 4. Distribution of Foraminifera and selected Ostracoda in hole LB3 at La B�edoule plotted against ammonite (Reboulet et al., 2011), calcareous nannofossil (Roth, 1978), isotope stages (Menegatti et al., 1998; this study), and the mainmarker levels (Moullade et al., 1998a; Ropolo et al., 2006, 2008; this study).

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4,5

Fig. 5. Comparison of bulk carbon isotope curves from La B�edoule area (Kuhnt et al., 2011; Lorenzen et al., 2013) with those of Rotter Sattel, Switzerland (Menegatti et al., 1998), Cismon, Italy (Li et al., 2008) and Cuchia (Spain, Najarroet al., 2011) [Scale bars ¼ 5 m].

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section, the anoxic event OAE 1a was identified on the basis of thestructure of the d13C excursion. Its beginning is defined by anegative shift at a depth of 36 m, which represents the boundarybetween segments C2 and C3, and the ends with a plateau aftersegment C6, at a depth of 17.50 m. The upper part of segment C7and the lower part of segment C8 were identified in LB3, the C7/C8boundary being identified on the basis of the beginning of anegative shift at a depth of 30 m.

5. Results

5.1. Lithostratigraphic key-levels

Previous studies of outcrops at the Cassis-La B�edoule railroadsection as well as the La B�edoule area (Fabre-Taxy et al., 1965;Moullade et al., 1998a, 2005) revealed several striking lithologicfeatures within the upper Bedoulian and lower Gargasian sequence(Fig. 2).

Even though based on lithologic, gamma ray logging, micropa-leontologic and isotopic data, it has not been easy to identify theoutcropping key-levels in the drilled sections. In contact with theatmosphere, small differences in chemical composition of the rocksare artificially accentuated by surface diagenesis, erosion and dif-ferential weathering. Yet gamma-ray logging as well as visual andcolorimetric observation of the cores have shown that changes insediment composition are actually much more gradual, makingbeds boundaries less distinct and, thus, less discernible than in thefield. In the case of these Bedoulian and Gargasian rocks, the clay/carbonate ratios vary only in a fairly narrow range; so well-markedalternations of indurated “calcareous” beds and softer “marly”levels seen in the field (as in theMarlyMember) were often difficultto correlate with the more diffuse features observed in the drilledsequence of LB3. Another source of uncertainty arose from the factthat the labelled stratotypic bedding nomenclature (Moullade et al.,1998a) comes from the Cassis section, where the succession isslightly thicker than at La B�edoule. Such an even slight condensa-tion from west to east leads to thickness variations, different or-ganization or even disappearance of some beds. However, bycombining various approaches, we were able to identify in thecores three more conspicuous lithostratigraphic elements knownfrom the field (Fig. 2):

� ‘Camping marls’. This 9.5 m-thick predominantly marlysequence was described (Moullade et al., 1998a; Kuhnt et al.,2011) from a section in the La B�edoule area, so called the“Camping section” (Figs. 1 and 6), located 300 m north of theLB1/LB2 drilling site. This conspicuous feature is well high-lighted by gamma-ray logging and consists of LB1-15 to -20cores, which include the top part of the isotopic stage C4 and thewhole C5eC6 stages, i.e., about the upper half of OAE1a.

� Key bed ‘170’ (Fig. 7). As labelled in the lithostratigraphicnomenclature of the stratotype in Moullade et al. (1998a), thisbenchmark is easily identifiable in the field in both Cassis and LaB�edoule sections. This is the uppermost ~1 m-thick bed of a~15 m-thick predominantly calcareous sequence attributed tothe ammonite Deshayesites grandis Subzone (Ropolo et al., 1998,2008). This sequence actually consists of an alternation of thinmarlstones and thicker limestones. Bed 170 has been identifiedin both holes; in LB1 it forms the upper two-thirds of core 4(Fig. 7b), and in LB3 it includes the lower half of core 29 plus thetop of core 30 (Fig. 7c).

� The 'triplet'. In the section called 'Les Camerlots-Les Tocchis',logged in 1963byone of us (MM)andpublished inMoullade et al.(1998a) (Fig. 1), the “triplet” consists of three more conspicuous0.4 to 0.5 m-thick marly calcareous beds within an otherwise

lower Gargasianmonotonous rhythmic succession of thinner 0.1to 0.25 m-thick beds (Fig. 8b). In the sixties this triplet formed asort of cuesta, i.e., a characteristic well individualized structurallandform that could be easily followed in the landscape in thearea between Les Fourniers and Les Tocchis, just north of thelocation chosen for drilling LB3. This area was not urbanized in1963 and offered a continuous record of the Bedoulian/Gargasiantransition, whereas today it is completely covered by residentialdevelopments.

This triplet can still be seen at Cassis, as three more prominentsuccessive beds cropping out in the first metres of the stope face ofLa Marcouline quarry (Figs. 1 and 8a).

Carbonate content and gamma-ray data of hole LB3 (Fig. 9) showa sequence of three better shaped successive peaks from �22to �24.60 m, which probably correspond to the triplet seen in thefield. But the lithological succession in LB3 cores between �20and �25 m (Fig. 8c) is not very diagnostic on this point. The threecalcareous beds observed at this level (in cores 15 to 17) do notclearly differ in thickness from calcareous beds of the enclosingintervals. However, correlations based on the microfaunal distri-bution help to remove the uncertainty because, in Les Tocchis, LaMarcouline and LB3, this triplet is located in the Globigerinelloidesferreolensis ferreolensis zone, just above the extinction of Schackoinagr. cabri.

5.2. Foraminifera

The tables (Figs. 3e4) built from the semi-quantitative distri-bution of each foraminiferal species show not only the overallcomposition of themicrofauna, but also bring out themainmarkersand the most significant bioevents, which allowed strengtheningand refinement of the current zonation.

5.2.1. Foraminiferal content and main markers (Figs. 3e4 & 10)We identified 55 species or groups of polymorphically undif-

ferentiated species (i.e., nodosarias, vaginulinas, etc.) among thebenthic and planktonic foraminiferal content of LB1 and LB3boreholes. Among these, 5 benthic and 5 planktonic taxa can beused as stratigraphic markers.

� Benthic agglutinated foraminifera: composed of rather long-ranging forms, this group does not include any significantstratigraphic marker in itself for the study interval. However,these forms commonly represent an important proportion ofthe benthic foraminiferal microfauna. The most common taxaare Tritaxia pyramidata Reuss, Falsogaudryinella moesiana(Neagu) and F. tealbyensis (Bartenstein). The semi-quantitativefirst approach by only using frequency classes shows somecyclicity in the distribution of T. pyramidata.We also note a trendof reversed frequencies of abundance between F. tealbyensis andF. moesiana. This confirms the results of Moullade and Tronchetti(2010), based on outcrop sample

� Benthic hyaline calcareous foraminifera: these are dominated bysmooth lenticulinas of the gibba-nuda group and gavelinellas ofthe flandrini group, which also show a certain cyclicity in theirdistribution, more or less synchronous with that of tritaxias. Inaddition five species, even if generally rare, are of stratigraphicimportance:- Lenticulina cf. heiermanni Bettenstaedt e even though a littletoo sporadic e and Globorotalites gr. bartensteini-intercedensBettenstaedt become extinct at or very near the Bedoulian/Gargasian boundary.

Fig. 6. The upper Bedoulian “Camping Marls” (beds 151 to 157). AeB: Camping of La B�edoule section, A) from Moullade et al. (1998a), B) from Kuhnt et al. (2011); C): hole LB1(adapted from Lorenzen et al., 2013).


- Lenticulina cf. nodosa (Reuss) and Astacolus crepidularis tri-carinella (Reuss) both become extinct 4.5 m above thisboundary.

- Oolina apiculata Reuss has its first appearance 5 m above thesame boundary.

� Planktonic foraminifera: among a fairly constant and homoge-neous stock over the duration of the studied period, whichconsists largely of small praehedbergellas and small few-chambered Globigerinelloides (Blowiella) emerge five taxawhose more accurately identified LO (lowest occurrence)allowed us to refine the zonation defined for the Aptian (Bed-oulian and Gargasian) stratotypes in our previous works(Moullade et al., 1998b, 2005, 2008):

- Schackoina (Leupoldina) gr. cabri Sigal; in hole LB1, the LOof thisgroup coincides with the boundary between isotopic stages C3and C4 sensuMenegatti et al. (1998). This confirms the result ofKuhnt et al. (2011) from the Camping outcrop section at LaB�edoule. In addition to the main bioevent based on its firstappearance, the evolution in the distribution of this group alsoallowed us to define three other bioevents: 1) the base (¼ up-permost Bedoulian) and 2) the top (¼level of simultaneousdisappearance of L. cf. nodosa/A. crepidularis tricarinella) of itsacme; and 3) its disappearance at the base of the G. ferreolensisferreolensis zone.

- Praehedbergella luterbacheri (Longoria); in both LB1 andLB3 holes, the LO of this 7-chambered low trochospiral

Fig. 7. BedoulianeGargasian transition including key bed 170 at: A) Cassis-La B�edoule Comte Quarry section; B) La B�edoule Les Tocchis section (both adapted from Moullade et al.,1998a); C) hole LB1 and d) hole LB3 (this work).


species is seen right at the top of key bed 170 (accordingto the bed numbering for the stratotype in Moullade et al.,1998a), i.e., exactly at the Bedoulian/Gargasian boundary.This species is relatively rare and very small (usually<100 mm) at its appearance, which falls within the ammoniteDufrenoyia furcata Zone. Then P. luterbacheri becomesmore common and increases in size during the Chelonicerasmartini Zone. Data from the two wells update previousstudies on foraminifera of the Aptian stratotypes (Moulladeet al., 2005, 2008). These studies suggested a slightlylater appearance of this taxon, at the level of the eventdefined by the simultaneous last occurrence of the benthicspecies Lenticulina cf. nodosa and Astacolus crepidularis tri-carinella. This slight discrepancy might be explained by thescarcity and small size of P. luterbacheri at the beginning of itsrange.

- Globigerinelloides ferreolensis heptacameratus Moullade, Tron-chetti & Bellier; this study confirms that this planispiral sub-species with seven chambers in the last whorl of theG. ferreolensis group evolutionarily derived from the trocho-spiral species P. luterbacheri, as already seen in the Apt stra-totype area (Moullade et al., 2008). In LB3, it occurs for the firsttime 2.5 m above the Lenticulina cf. nodosa/Astacolus crep-idularis tricarinella HO.

- Globigerinelloides ferreolensis ferreolensis (Moullade); this 8-chambered planispiral subspecies of the G. ferreolensis groupevolved from the subspecies heptacameratus at the extinctionlevel of Schackoina (Leupoldina) gr. cabri.

- Globigerinelloides barri (Bolli, Loeblich & Tappan); the firstoccurrence of this 9-chambered planispiral species is seen 5mabove that of G. ferreolensis ferreolensis. G. barri is rare in thefirst twelve metres of its range and becomes increasinglycommonwithin the uppermost fivemetres of LB3 hole, amongpopulations which are still dominated by 8-chambered Glo-bigerinelloides ferreolensis.

The flat area in which LB3 was implanted, dated by the occur-rence of G. barri, is located at the foot of disused quarries, the topof which provided few specimens of the following marker, the10-chambered planispiral species Globigerinelloides algerianus(Cushman & ten Dam).

5.2.2. BioeventsThe studied strata include four major events which involve the

almost simultaneous first occurrence and/or last occurrence ofseveral taxa:

(1) Level of first occurrence of Schackoina (Leupoldina) gr. cabri

Fig. 8. The lower Gargasian characteristic “triplet”. A) Cassis La Marcouline Quarry section (from Kuhnt & Moullade, 2007); B) La B�edoule Les Tocchis section (from Moullade et al.,1998a); and C) Hole LB3 (this work).


The first but very rare specimens of this planktonic group arefound in sample LB1-22-109 cm, at the boundary between the C3and C4 isotopic stages. In this sample, also the first indisputablespecimen of Lenticulina cf. nodosa is found; however, two metresbelow, a somewhat dubious specimen of this benthic form isalready present in sample LB1-24-14 cm. L. cf. nodosa has actually

been reported as appearing slightly earlier than S. gr. cabri inupper Bedoulian outcrops, such as Croagnes (Moullade et al.,2012) or Cassis-La B�edoule (Moullade et al., 1998b). Theseapparent slight discrepancies might result from the smaller size ofcore samples, thereby reducing the probability of finding rarespecies.

Fig. 9. Hole LB3: bulk carbon isotope, bulk oxygen isotope, carbonate content and natural gamma ray curves (measurements performed at the Institute of Geosciences of the University of Kiel, Germany). The possible Aparein shift isstarred.

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Fig. 10. Distribution of main benthic and planktonic foraminiferal markers and planktonic foraminiferal zones. For the ammonite and calcareous nannofossil zones see caption ofFigs. 3 and 4.


(2) Microfaunal turnover at the Bedoulian/Gargasian boundary.

This important bioevent is marked by the simultaneous extinc-tion of Globorotalites gr. bartensteini-intercedens and Lenticulina cf.heiermanni, occurring with the simultaneous first appearance ofPraehedbergella luterbacheri and P. gr. aptiensis-solidus. It should alsobe noted that the base of the acme of Schackoina (Leupoldina) gr.cabri is only 3 m below this quadruple datum. Incidentally, at this

level Spirillinaminima Schacko and Patellina subcretacea Cushman&Alexander temporarily disappear, their absence then spanning theentire lower Gargasian Dufrenoyia furcata Zone.Wewill return laterto a discussion on the palaeoecological significance of these twocalcareous benthic foraminifera.

(3) Microfaunal turnover at the Dufrenoyia furcata/Chelonicerasmartini zonal boundary.


This event is located at the uppermost part of the Prae-hedbergella luterbacheri foraminiferal zone. It corresponds to thesimultaneous extinction of Lenticulina cf. nodosa and Astacoluscrepidularis tricarinella, together with the end of the acme ofSchackoina (Leupoldina) gr. cabri. In addition, the ostracod markerProtocythere bedoulensis Moullade becomes extinct at this sameforaminiferal level. These contemporaneous events are almostdirectly followed by the first occurrence of Oolina apiculata andRamulina sp. gr. aculeata Wright.

(4) A last bioevent, which involves only two taxa, is located atthe boundary between the Globigerinelloides ferreolensisheptacameratus and G. ferreolensis ferreolensis foraminiferalzones. It is characterized by the first occurence ofG. ferreolensis ferreolensis, 0.50 m below the disppearance ofSchackoina (Leupoldina) gr. cabri. We will see later that theostracod marker Parataxodonta inornata (Kaye) first occursjust below this double foraminiferal datum.

5.2.3. Zonation (Fig. 10)On the basis of the markers distribution, the interval covered by

LB1 and LB3 boreholes is divided into 6 foraminiferal biozones:

� Globigerinelloides (Blowiella) blowi zone; the first 14 m of thestudied succession can be attributed to the upper part of thiszone. In SE France its lower limit corresponds to the lower/upperBedoulian boundary (Moullade et al., 1998c). The top of thiszone is placed at �32 m, between samples LB1-23-65 cm andLB1-22-109 cm.

� Schackoina (Leupoldina) cabri zone; this zone equals the upperhalf of the upper Bedoulian, including isotopic stages C4, C5, C6and the lower two-thirds of C7. The rather homogeneous dis-tribution of both planktonic and benthic foraminifera duringthis interval does not permit a further subdivision of this 30 mthick zone.

� Praehedbergella luterbacheri zone; this first zonal subdivision ofthe Gargasian covers 6 m of sediment in LB3, from sample LB3-29-58 cm to LB3-25-65, 5 cm; its lower 3 m-thick part overlapswith the top of LB1. The extension of this zone corresponds tothe lower half of the Dufrenoyia furcata ammonite Zone, i.e.,approximately to the Dufrenoyia furcata Subzone in Rebouletet al. (2011, 2014).

� Globigerinelloides ferreolensis heptacameratus zone; initiallycreated as a horizon (Moullade et al., 2008), this level, definedby the first appearance of the subspecies index, is here upgradedto zone. In LB3 this zone spans 8 m, from samples LB3-25-24 cmto LB3-19-80 cm.

� Globigerinelloides ferreolensis ferreolensis zone; this zone spansnearly 8 m, from samples LB3-18-77, 5 cm to LB3-14-83 cm.

� Globigerinelloides barri zone; the LB3 hole intersected slightlyover 18m of sediment attributed to this zone, from samples LB3-7-150 cm-to LB3 1-10 cm.

5.2.4. Palaeoecological remarksThe composition of the foraminiferal microfauna (benthic

especially) across the BedoulianeGargasian transition in holes LB1and LB3 provides a number of indices that confirm the generaltrend of a gradual increase of paleo-water depth and pelagic biotathrough time. This confirms the hypotheses of Moullade et al.(1998b) and Moullade and Tronchetti (2010).

Of particular interest is the final disappearance in sample-LB125e52 cm, within the C3 isotopic stage, of taxa such as Con-orboides spp. and small trocholinas of the infragranulata group

(Fig. 3). These small neritic forms, which are present only in thelower part of LB1, are the ultimate survivors of a microfaunal innerplatform assemblage, known as more abundant and more diverse(taxonomically and by the size of specimens, which may includelarger orbitolinids) in the upper Barremian and lowermost Bed-oulian of Cassis-La B�edoule (Moullade et al., 1998b). Theseshallow-water forms are also commonly found in strata thatdirectly overlie the uppermost bed of the Urgonian facies,of Bedoulian age, in the Apt basin (Moullade et al., 2012). In thelower part of LB1, Conorboides and Trocholina gr. infragranulata(Noth) are associated with abundant Patellina subcretacea, anothermember of the neritic assemblage mentioned above. P. subcretaceais thought to be bathymetrically more tolerant than the twoothers, as it occurs over a longer period of time, even thoughin lesser abundance, higher up in the section. As pointed out above,P. subcretacea and Spirillina minima temporarily disappear withinthe lower Gargasian Dufrenoyia furcata ammonite Zone. Thisleads us to consider this latter interval as that of the maximumpaleodepth in the South Provençal Basin, because these shallowerwater indicators reappear higher in the Cheloniceras martini Zone(Fig. 4).

An additional evidence points in the same direction. Comparedto the upper Bedoulian, in the lowermost Gargasian strata thenumber of planktonic species as well as that of individuals of eachspecies reach their maximum values.

5.2.5. Quantitative data (benthic foraminifera)From outcrop samples of the Bedoulian and Gargasian strato-

typic areas, Moullade and Tronchetti (2010) published abundancecurves based on counts of the main species or groups of benthicforaminifera. Despite locally insufficient sample spacing, this studyrevealed some cyclicity in the stratigraphic distribution of thestudied taxa.

As for LB1 and LB3 samples, the simple first approach of usingfrequency classes established during the biostratigraphic study(Figs. 3e4) reveals also a certain periodicity in the distribution ofthe best represented species or species groups. Moreover, there aretwo much more poorly microfossiliferous intervals inserted withinthe microfossil-rich succession:

- A 3 m-thick first sequence, from samples LB1-26-108 cm to LB1-27-158 cm, is virtually devoid of foraminiferal and ostracodmicrofauna. This practically barren interval corresponds to theend of the isotopic stage C2, follows a more diversified micro-fossiliferous interval and occurs just before the onset of OAE1a,during which the microfaunal density returns to normal values.

- A second similar interval begins at the level of sample LB1-13-65 cm, just at the boundary between isotopic stages C6 and C7,i.e., just above the top of OAE1a. This mostly barren intervalspans 8 m of sediment, which corresponds to the basal portionof C7.

To obtain more accurate statistical data on this periodicity, weconducted normalized counts on a known fraction of the secondhalf of the residue of each weighed sample (see Section 4.1.). Thisprotocol was used to calculate the number of specimens of eachtaxon per gram of sample (Appendices 1e2). The�140 mmmesh forscreening this fraction has emerged as the best compromise forminimizing biases of representation on a size basis. In the end, itappeared that both methods (raw frequency classes and normal-ized counts) produced broadly comparable results, but the latterallowed better comparisons between samples.

Tritaxia pyramidata, the group of lenticulinas (L. gr. gibba-nuda,L. cf. nodosa, L. cf. heiermanni), the gavelinellas (G. gr. flandrini) andfalsogaudryinellas (F.moesiana andmore incidentally F. tealbyensis)

Fig. 11. Abundance curves (number of specimens per gram of dried sediment >140 mm) of tritaxias (in blue) and gavelinellas (in green) for the overlapping part of holes LB1 andLB3.


are the most abundant taxa of these benthic foraminiferal assem-blages. Among these forms, T. pyramidata showed the most pro-nounced cyclicity, commonly with sharp “on-off” fluctuations(Figs. 11e12). Abundance variations of lenticulinas are much lesscontrasted but mostly in phase with those of tritaxias. The fre-quency fluctuations of gavelinellas, locally strongly contrasted, arealso quite consistent with those of tritaxias but may show occa-sionally a slight offset (Fig. 11).

These quantitative foraminiferal data provided an additionalcorrelation tool for the overlapping portion of the two holes(Figs. 11e12). For example the position of key bed 170 (see x 4.1),which was presumably identified on the basis of gamma-ray log-ging and lithology logs, then confirmed by biostratigraphy, is alsostrongly supported by the occurrence of a sharp abundance peak oftritaxias. Bed 170, which marks the Bedoulian/Gargasian boundary,is also distinguished over the whole Bedoulian underlyingsequence by providing the same record value (80 benthic forami-niferal specimens per gram of dried sediment) in both holes, i.e.,nearly twice that of the most productive Bedoulian levels.

5.3. Ostracods

This group is mainly represented in both Bedoulian and Gar-gasian strata by smooth long-ranging forms, among which thegenus Cytherella, and especially C. ovata (Roemer) and second-arily C. parallela (Reuss), is the most common. The ornamentedforms occur rather sporadically. Of these, three species confirmtheir value as biostratigraphic markers:- Protocythere bedoulensis; the first occurrence of this species isrecorded in the upper Bedoulian, within isotopic stage C4, andits disappearance occurs at the level of the simultaneousbenthic foraminiferal HO (Lenticulina cf. nodosa/Astacoluscrepidularis tricarinella) (see 4.1.2.) (Figs. 3e4). This triplemixed datum, which involves the last occurrence of twobenthic foraminifera and that of an ostracod, was alreadyrecognized in previous work on stratotypes (Moullade et al.,

2005). It is confirmed here and calibrated in a more reliablecontext than from outcrop material.

Within the first three metres of its range, i.e., the upper part ofthe isotopic stage C4 and the base of C5, P. bedoulensis isaccompanied by Hechticythere derooi (Oertli), which does notoccur higher up in LB1 cores. The somewhat erratic distributionof H. derooi in outcrops of the Aptian stratotypic area preventedus to retain this taxon as a marker.- Cytherelloidea bedouliana (Babinot); in LB1 and LB3, this rarespecies only occurs in the very uppermost metres of theBedoulian (Figs. 3e4). This confirms previous observationsmade at Cassis-La B�edoule (Fabre-Taxy et al., 1965) and LaTuili�ere (near Apt) (Babinot et al., 2007).

- Parataxodonta inornata; in LB3 this easily recognizable speciesis rare and shows a rather sporadic distribution. It has itslowest occurrence in the upper part of the Globigerinelloidesferreolensis heptacameratus foraminiferal zone, 1.5 m belowthat of G. ferreolensis ferreolensis (Fig. 4). However, in otherplaces P. inornata has also been documented slightly lower, i.e.,from the uppermost part of the Praehedbergella luterbacherizone (Moullade et al., 2005: Cassis-La Marcouline; Moulladeet al., 2009a, b: Gargas), but not below.

5.4. Calcareous nannofossils

Preservation of calcareous nannofossils is considered to bemoderate to poor; specimens are often highly fragmented andshow signs of overgrowth in carbonate-rich intervals indicating aslight early diagenetic overprint. The abundance of identifiablecalcareous nannofossils is generally low. Most smear slides arealmost barren or only few identifiable specimens have beenobserved. This state of preservation and the low abundance ofcalcareous nannofossils result in a very low diversity. Thus, theassemblages do not allow for ecological interpretations andhamper the development of a detailed, robust nannofossil-based

Fig. 12. Abundance curves (total number of specimens per 100 g of sample) of tritaxias in holes LB1 and LB3.


biostratigraphic scheme. Therefore, we did not provide a detailedrecord of the nannofossil species from this study; we simplyfocused on the identification of biostratigraphic markers.

Calcareous nannofossil assemblages are dominated by ratherdissolution-resistant forms, e.g., Watznaueria barnesiae (Black),various Rhagodiscus and Cretarhabdus species. In addition, typicalcommon components of mid-Cretaceous nannofossil assemblagesof the Tethyan region like Biscutum constans (G�orka) and nanno-conids were frequently found. However, most of these taxa are notof biostratigraphic importance for the studied interval.

Biostratigraphically, all samples studied from LB1 suggest anNC6 age as indicated by the sporadic occurrence of Hayesitesirregularis (Thierstein). From sample LB1-20, 13e15 cm (depth incore 28 m) upwards marker species indicating NC6B occurconsistently; these include Rhagodiscus angustus (Stradner), Eiffel-lithus hancockii Burnett and Cretarhabdus loriei (Gartner). NC7marker species like Eprolithus floralis (Stradner) or Braarudosphaeraafricana Stradner have not been observed in samples from LB1.

The basal part of LB3 belongs unequivocally into NC6B, whereasthe LO of E. floralis (base of NC7) has been identified in sample LB3-


32, 14e17 cm (depth 46.50 m). Because E. floralis is generally rareand usually poorly preserved, never more than two specimens havebeen identified per sample. The base of NC7B as approximated bythe HO of Micrantholithus hoschulzii (Reinhardt) by Bergen (1998)was observed in sample LB3-30, 64e68 cm (depth 43.99 m);however, this taxon is very rare in all studied samples questioningits application as a marker species. An abundance increase ofNannoconus truitti in section 26 and abovemay indicate thewidely-distributed “Nannoconus truitti (Br€onnimann) acme” which startswithin NC7B (Bown et al., 1998; Herrle & Mutterlose, 2003).

The nannofossil results strongly contrast with the findingsbased on planktonic foraminifera and gamma-ray wiggle matchingbetween boreholes as well as regional correlation with outcrops.Specifically, the NC6/7 boundary has not been observed in LB1,where it is expected to be due other stratigraphic techniques. In LB3the LO of E. floralis is slightly lower, specifically when compared tobiostratigraphic results from outcrops close to the drill sites(Bergen, 1998).

As a consequence of the scarcity and the suboptimal preserva-tion, calcareous nannofossil zonal boundaries drawn in Figs. 3e4, 9and 13, are not strictly derived from this study. To define theseboundaries we usually considered the results previously obtainedfrom field studies (Bergen, 1998) to be more reliable. These datahave been previously integrated into a stratigraphic frameworkwhich also included data from foraminifera, ostracods, ammonitesand carbon isotopes. Further, we refrain from a detailed discussionof the nannofossil results.

Fig. 13. Hole LB1: bulk carbon isotope, carbonate content and natural gamma ray cu

5.5. Carbon isotope stratigraphy

The first bulk-rock carbonate d13C and d18O curves from Bed-oulian field samples of Cassis were published by Kuhnt et al. (1998)and Moullade et al. (1998d). Even though sparse due to discon-tinuous outcrops, sampling of the middle part of the sectionpermitted for the first time delineation of the main d13C shift andidentification of OAE1a signature in the South-Provençal Basin.However, this insufficient sampling density hampered the reliableidentification of detailed isotopic stages as defined by Menegattiet al. (1998). Kuhnt and Moullade (2007) then extended the Bed-oulian curve into the lower part of the Gargasian in La Marcoulinequarry section, also at Cassis (Fig. 1).

In order to better document the middle part of the Bedoulian,Kuhnt et al. (2011) published a high resolution record based on amuch denser sampling (5 cm increments) carried out in the LaB�edoule Camping section (Fig. 1). Their curve defined the isotopicstages C4 to C6 in great detail, allowing subdivision of stage C4 intofour sub-stages (C4a, b, c, d) for the first time. Another importantresult of this work was to isotopically calibrate the Schackoina cabrilowest occurrence with the C3/C4 boundary.

Isotopic d13C and d18O measurements have also been performed(in 20 cm increments) on LB1 (Fig. 13) and LB3 (Fig. 9) cores. LB1records isotopic stages C2 to C7 in great detail (Lorenzen et al.,2013), providing a d13C reference curve for the Bedoulian basedon a continuous and dense sampling. Curves from La B�edoule areaare compared with those of Rotter Sattel, Switzerland (Menegatti

rves (modified from Lorenzen et al., 2013). The possible Aparein shift is starred.


et al., 1998), Cismon, Italy (revision by Li et al., 2008 of data fromMenegatti et al., 1998; Erba et al., 1999) and Cuchia (Spain, Najarroet al., 2011) (Fig. 5).

LB3 records almost all of stage C7 (themissing part being only itsextreme base, not reached by the drilling) and a large part of stageC8. The well identifiable boundary between C7 and C8 is locatedat �30 m, 4 m below the first occurrence of the planktonic fora-miniferal subspecies Globigerinelloides ferreolensis ferreolensis. Bycorrelation between the distribution of foraminifera in LB3 (thiswork) and in La Marcouline section (Moullade et al., 2005), thelatter also calibrated by ammonites (Ropolo et al., 2008), it ispossible for the first time to locate the C7/C8 boundary within theCheloniceras martini ammonite Zone, more specifically at the levelof the Epicheloniceras gracile Subzone.

We have also tried to look for the possible isotopic signature ofthe “Aparein” Aptian organic-rich level in the Bedoulian stratotypicarea. This level was first known from the Cantabrian region of Spain(García-Mond�ejar et al., 2009) and thought to be a subevent ofOAE1 or of local occurrence (Mill�an et al., 2009) on the basis of athin negative d13C shift. Since then, this event has been assumed tooccur within stage C7 in several other sections of various regions ofSpain, such as the Betic Cordillera (Nú~nez-Useche et al., 2014).

In fact the d13C curve obtained at Cassis by Kuhnt et al. (1998)shows a clear negative shift of 1.28‰ at its upper end, exactly atthe level of bed 174. This bed is located ~2.5 m above the top of thekey bed 170, in the first few metres of the ammonite Dufrenoyiafurcata Zone. This stratigraphic assignment is consistent with theSpanish context, which also involves the D. furcata Zone (Nú~nez-Useche et al., 2014).

However, the isotopic d13C signature within the first fewmetresof LB1 hole (Fig.13) is much less clear than in the Cassis section. Justabove bed 170, the LB1 curve shows a pattern of several narrowsuccessive oscillations, the most ample of which (at �2 m) is anegative shift of only 0.8‰ at the level of bed 173, 1.8 m above thetop of bed 170.

The same zigzag pattern is seen in LB3 (Fig. 9), but with amaximum negative shift of only 0.58‰, at �41 m, i.e., also 1.8 mabove bed 170.

Therefore, if present in the stratotype area, which seems likely atthe Cassis field section, the “Aparein-like” isotopic shift appears tobe much less conspicuous at La B�edoule, where the succession isslightly more condensed than at Cassis. Based on the distribution offoraminifera, this isotopic feature can be correlated with theextinction of the benthic foraminifera Lenticulina cf. heiermanni.Although very tenuous in the Bedoulian stratotype, this isotopicevent might permit subdivision of the long stage C7 into approxi-mately two equal parts, as already suggested by Nú~nez-Usecheet al. (2014).

6. Discussion

6.1. Bioevents

Once more we would like to draw the reader's attention tocertain errors and approximations, resulting in apparent dia-chronisms that deal with several of the main Aptian planktonicforaminiferal datums.- Globigerinelloides ferreolensis first appearance. This bioevent isoften mistakenly used in the literature as a marker of theboundary between the two subdivisions of the Aptian, i.e., theBedoulian/Gargasian boundary. All our previous work showsthat the first appearance of this species is located higher thanthis limit. The misplacement often results from erroneousattributions to G. ferreolensis of its ancestor, the 7-chamberedlow trochospiral species Praehedbergella luterbacheri. An

evolutionary transition occurs between the two taxa in thelowermost Gargasian. More weakly trochospiral specimensbecome increasingly sub-symmetric going up in the succes-sion; some intermediate specimens gradually make the tran-sition towards more conspicuously planispiral forms (Banner& Desai, 1988). These latter only have to be placed withinthe G. ferreolensis group (see also Moullade et al., 2005, Pl. 4,figs. 7e9). Errors of diagnosis of these weakly asymmetricaltransients may be aggravated because of poor preservationand/or insufficiently cleaned specimens. Therefore there isroom left for a Praehedbergella luterbacheri zone between theboundary and the actual G. ferreolensis FAD, as shown in thepresent work.

- Schackoina (Leupoldina) gr. cabri first appearance. It begins tobe more widely recognized that the first occurrence of themorphotypes (pustulans, cabri s. s.) of this planktonic forami-niferal group, which are easily identifiable by their elongatebulb-shaped chambers, is contemporaneous with the OAE1a.Our results (Kuhnt et al., 2011; Lorenzen et al., 2013; thisstudy) show that this bioevent occurs more precisely at theC3/C4 isotopic boundary. However, the scarcity and the smallsize of these forms in the lower part of their rangemay explainmany discrepancies in the calibration of this bioevent as seenin the literature.

- Larger Globigerinelloides lineage. The accurate delimitation ofthe successive zones based on the distribution of larger multi-chambered species of Globigerinelloides (ferreolensis heptaca-meratus, ferreolensis ferreolensis, barri, algerianus) implies thatall specialists speak the same taxonomic language. The orig-inal criterion of species differentiation within this planispir-ally coiled planktonic foraminiferal lineage is e and shouldalways be e based only on the number of chambers in the lastwhorl (see review in Moullade et al., 2005, 2008).

6.2. Microfaunal cyclicity

- Patterns of the abundance curves of tritaxiasIn their preliminary study of the distribution of Aptian strato-typic benthic foraminiferal microfauna, Moullade andTronchetti (2010) hypothesized a cyclic forcing of orbital typeto explain the synchronous fluctuations in abundance of theseorganisms. Their hypothesis was in line with other studiesinvolving, among others, the Cenomanian (Leary et al., 1989;Paul, 1992) or the Upper Albian (Coccioni & Galeotti, 1993;Tyszka, 2009). However, in order to validate their interpreta-tion, the authors stressed the need to resume such work on thebasis of a denser sampling of the Aptian stratotypic succession.With about 100% core recovery, holes LB1 and LB3 thereforeconstituted a material of choice for performing this kind ofinvestigation. It seemed to be an interesting possibility, aftercalibration, to use these micropaleontological quantitative dataas a kind of “biological” geochronometer.For this purpose, counts of specimens of Tritaxia pyramidataappeared to be the best tool. This long-ranging benthic agglu-tinated species is fairly large (mean size of ±250 mm), easy toidentify with its tricarinate perimeter, and emerged as the mostresponsive taxon by its abundance variations.On the basis of the variations of abundance curves of tritaxias, amarked contrast appears between the upper Bedoulian and thelower Gargasian patterns (Fig. 12):� Bedoulian

Two successive intervals can be defined, according to thepattern of their constitutive cycles (Fig. 12):


- From �45 m to �14 m in LB1, the fluctuations of distribution oftritaxias are clear, regular and mostly on/off. The main peaksallow a subdivision of this first interval into four regular first-order cycles with a wavelength of about 7 m. This long periodof stability corresponds to a set of strata including the entireOAE1a and the lowermost portion of the ammonite Deshaysitesgrandis Subzone.

- Conversely the overlying sequence (from �14 m to �4 m inLB1, �51 m to�43 m in LB3) shows a more uneven distribution,somewhat arhythmic, with tighter and more pronounced sec-ondary oscillations. It is unclear whether this interval, whichcorresponds to the upper part of the D. grandis Subzone andends with bed 170, consists of one or two cycles. In the case of atwo-fold subdivision, the pattern of a lower 6 m thick cycle (5a)recalls that of the underlying cycles 1 to 4, whereas an upper 4mthick cycle (5b) differs by more prominent and progressivelyincreasing second order peaks of tritaxias.� Gargasian

- Above bed 170, from �43 m to �37 m in hole LB3, the sequenceconsists of a well-defined 6 m-thick unique cycle (n� 6), whichshows a pattern reminiscent of that of the Bedoulian cycles 1e4.This cycle 6 spans the lower part of the Dufrenoyia furcata Zone.Only the 3 m-thick lower portion of cycle 6 is present at the topof hole LB1.

- The pattern of the remaining part of LB3 (from �37 m to the topof the hole) significantly differs from those of the underlyingstrata and its subdivision into first and second order cycles isless clear. In a first approach, this interval can be tentativelydivided into two parts:- from �37 m to �27 m, occurs a 10 m-thick cycle (n� 7) well-bounded by two marked peaks of abundance (�350 speci-mens) of tritaxias; this cycle is in turn clearly divided into fiveregular ± 2 m thick subcycles.

- the last interval, from�27 m to the top of hole LB3, shows lessregular oscillations (in wavelength and values) than thoseseen in cycle 7. Thus the subdivision of this thicker interval ishard to establish logically (how many main cycles?) and ismade still more complicated by the fact that the sequence isinterrupted by the top of the hole.

- Attempt of interpretationTo be able to interpret the variations shown by the abundancecurves of tritaxias in terms of orbital forcing we have to use timeestimates published in the literature. Considering the strongdissimilarity between the Bedoulian and the Gargasian patterns,these estimates have to be specific.� Bedoulian 1 to 4 cycles (including OAE1a)It is possible to calibrate most of the upper Bedoulian maincycles by using recently published estimates of the duration ofOAE1a, which are of 1.1 myr by Malinverno et al. (2010), 1.5 myrby Ogg and Hinnov (2012) and 1.36 myr by Scott (2014). In holeLB1, OAE1a is 20 m-thick, i.e., 55e75 kyr per metre of sediment,depending on the duration retained for the anoxic event. On thisbasis, the ~7 m thick tritaxias cycles observed in the intervalenclosing the anoxic event will range from 385 to 525 kyr, i.e.,within the range of long 405 kyr eccentricity cycles.Assuming that the sediment accumulation rate remained con-stant during cycles 1 to 4 and that the ~7m-thick tritaxias cyclesare actually orbitally triggered, we can calculate a duration of405x20/7 ¼ 1.157 myr for OAE1a, close to that proposed byMalinverno et al. (2010). The uniform 1 m routine sampling inLB1 has not been dense enough at this level for a clear recordingof smaller scale cycles, corresponding to the other orbital pa-rameters (precession, obliquity or even short eccentricitymode).

� Uppermost Bedoulian n� 5 cycleThe question arises to knowwhether this section comprises oneor two long eccentricity cycles. The latter hypothesis implies aminimum (80 kyr/m) of sediment accumulation rate at the levelof 5b.� GargasianThe Gargasian patterns are much less easy to decipher than the

Bedoulian ones. Based on a spectral analysis of Gargasian sedi-
mentary rhythms in La Marcouline section at Cassis, located 2 kmsouthwest of drill site LB3, Kuhnt and Moullade (2007) showedsignificant frequency peaks with a wavelength of about 1 m thatthey attributed to the precession (circa 20 kyr), and much longercycles with wavelength of 20 m, related to the long 405 kyr ec-centricity cycles. It should seem relevant to transpose these resultsto the Gargasian of La B�edoule, assuming a comparable sedimentaccumulation rates in these two very close locations. Thus, applyingthe Kuhnt and Moullade (2007) calculations, a Gargasian sedimentaccumulation rate of 20 kyr/m in Cassis and La B�edoule appears tobe about 3.5 times higher than during the late Bedoulian OAE1a(55e75 kyr/m, see above), or even 4 times higher than in the latestBedoulian, in the hypothesis of a two-fold subdivison of cycle 5.
On the basis of the position of the ‘Triplet’ key-level in La Mar-couline quarry (Kuhnt & Moullade, 2007, figs. 2 & 8) and in LB3(Fig. 12), we can attribute the 20 m thick interval beginning 2 mbelow the Triplet in LB3 (say hypothetically cycle n� 8) to a 405 kyrlong eccentricity cycle. Below the Triplet there is the better delin-eated but only 10 m thick cycle 7. Assuming that it also correspondsto a long 405 kyr long eccentricity cycle would imply a lower sedi-ment accumulation rate of 40 kyr/mat this level (insteadof 20kyr/min cycle 8), and that the second order oscillations seen within thiscycle 7 might correspond to the obliquity. The ~6.5 m thick cycle 6,the pattern of which is very similar to that of the 405 kyr well-calibratedBedoulian cycles 1 to4, is likely tohave the sameduration.

These calculations lead to a model of low sediment accumula-tion rate during the late Bedoulian, towards a maximum of sedi-mentary condensation at the level of the uppermost Bedouliancycle 5b, followed by progressively increasing rates during the earlyGargasian.

A recent paper of Ghirardi et al. (2014) may provide additionalways to verify our attempts of interpretating the Gargasian curve.Based on an orbital calibration of the Serre Chaitieu section in theVocontian basin, these authors proposed a duration for lowerGargasian biozones (Globigerinelloides ferreolensis: 1.22 myr,Dufrenoyia furcata: 0.6 myr) and the isotopic stage C7 (2.03 myr). Ifwe apply these values to the thicknesses measured for these unitsin holes LB3/LB1, we obtain a sediment accumulation rate of36.3 kyr/m for the section based on D. furcata duration; this israther consistent with our calculation derived from the hypothesisof cycles 6 and 7 being long eccentricity cycles.

Kuhnt and Moullade (2007) showed also that the G. ferreolensiszone at Cassis spans 33 precessional cycles and its duration is thusestimated to be approximately 0.76 myr (1.22 myr at Serre Chaitieuaccording to Ghirardi et al., 2014, instead). It is important to notethat all these authors used a broad concept of the G. ferreolensiszone which includes the G. ferreolensis heptacameratus,G. ferreolensis ferreolensis and G. barri zones as defined in the pre-sent article, i.e., 36 m of sediment in LaMarcouline section at Cassis.In hole LB3, the G. ferreolensis group first occurs at a depth of�36mand spans at least the remaining part of the hole. However, theequivalent of the past G. ferreolensis zone (used by Kuhnt &Moullade, 2007; Ghirardi et al., 2014) cannot be precisely identi-fied in LB3, since the zonal upper boundary (lowest occurrence ofG. algerianus) was not reached by the drilling but should have beenvery close. Considering our calculated durations of cycles 7 and 8


(0.8 myr together), added to an estimate of ~0.12 myr for the lowerpart of cycle 9 (assuming that the complete cycle is a long eccen-tricity cycle as n� 8), the duration of the G. ferreolensis ‘long’ zone inLa B�edoule should be of at least 0.92 myr. This value is intermediatebetween those proposed by Kuhnt and Moullade (2007), i.e., 0.76and Ghirardi et al. (2014), i.e., 1.22.

Using the same method of calculation for the isotopic stage C7(lower limit at�18m in LB1, upper limit at�30m in LB3, i.e., a totalthickness of ~27 m):

C7 ¼ [4/7 cycle 4 þ 1 cycle 5a þ 1 cycle 5b þ 1 cycle 6 þ 2/3 cycle7] � 0.4 myr ¼ 4.238 cycles � 0.4 myr ¼ 1.695 myr

led to a 1.7 myr maximum of duration, with a two-fold subdivisionof cycle 5, i.e., less than the 2.03 myr proposed by Ghirardi et al.(2014).

In conclusion, using raw abundance curves of tritaxias can helpidentify405kyr longeccentricitycycles in the type-Bedoulian,whichleads to assume a duration of 1.157 myr for OAE1a. However, moresophisticatedways of analysis (for instance spectral) are needed for apossible use of this tool towards a better detailed cyclostratigraphy,particularly in the Gargasian. Our approach led also to suspect amarked contrast in sediment accumulation rates from the upperBedoulian to the lower Gargasian at Cassis-La B�edoule, with amaximum of condensation in the topmost Bedoulian.

6.3. Geological importance of the Bedoulian stratotype

Over the last decades the development of concepts in definingstratigraphic boundaries led to an underestimation of the role ofhistorical stratotypes in favour of a concept of benchmarks (GSSP)focused on defining each stage by its base. This perspective haspromoted a search for new reference sections, that supposedlyovercome the deficiencies and inconsistencies arising fromincomplete stratotypic type sections.

As for the Aptian, two drill cores in the northern Tethys havebeen recently highlighted as references sections. At Cismon (NEItaly, where “Apticore”was drilled; Erba et al., 1999), Li et al. (2008)wrote “The 100% core recovery and existing high-resolution datarender APTICORE the highest quality reference section for OAE1a”.More recently the Poggio le Guaine core (near Piobbico, Umbria-Marche Basin, N. Apennines, Italy), “can be considered as a refer-ence section for the Aptian-Albian interval at low latitudes” accordingto Coccioni et al. (2012).

However, it should be noted that OAE1a, a well-recorded eventby drilling at La B�edoule, is there represented by 20 m of sediment,but is only 5.2 m thick at Cismon and 1.95 m at Poggio le Guaine.Therefore, the Bedoulian stratotype offers more favourable condi-tions for high-resolution studies than the Italian localities; thecondensation of these sections may even result in the loss of signalbecause of gaps in the record.

The Vocontian Basin, likewise, cannot constitute a reference areafor the interval that spans OAE1a and the Bedoulian/Gargasientransition. From the works of Herrle and Mutterlose (2003), Herrleet al. (2004, 2010), and Heimhofer et al. (2006) it appears effectivelythat the Vocontian mid-Aptian succession is very condensed oreven incomplete. The black shales (¼“niveau Goguel”) (¼OAE1a),which overlie disconformably the Barremo-Bedoulian limestonesand span isotopic stages C4 (pro parte) to C6, are only 3 m thick inthe section of Serre-Chaïtieu, which was considered as a referenceby the authors. In contrast the OAE1a interval is 20m thick at Cassis-La B�edoule, where a more detailed isotopic curve was documented.

Aptian sections in several areas of Spain (Cantabric, Subbetic,Prebetic, eastern Iberian chain) have been studied in detail theselast years using ammonite biostratigraphy and carbon isotope

stratigraphy (García-Mond�ejar et al., 2009; Mill�an et al., 2009;Najarro et al., 2011; Moreno-Bedmar et al., 2012; Gaona-Narvaezet al., 2012; Quijano et al., 2012; Aguado et al., 2014a,b). Some ofthese sections might be considered as references if a certainnumber of problems are solved, such as rare micropaleontologicaldata, strong differences of ammonite identification between spe-cialists (Moreno-Bedmar et al., 2014), and poorly or too discontin-uously fossiliferous sections unfavourable for high resolutionstratigraphic studies.

Following the pioneering review of Mutterlose and B€ockel(1998) and study of Bischoff and Mutterlose (1998), within thelast decade a bundle of holostratigraphic work (Lehmann et al.,2012; Heldt et al., 2012; Weib, 2012; Bottini & Mutterlose, 2012)has been published for the Aptian of the Boreal Realm (mainly N.Germany, Saxony Basin). These studies confirm that the dark“Fischschiefer” shales correspond to most of OAE1a. However,correlations with the Tethyan domain still remain imperfect,because in the Boreal Realm the biostratigraphic elements that areavailable in SE France for accurate dating (ammonites, planktonicforaminifera, even calcareous nannofossils) are rare and not alwaysas significant because communications between the two areaswere only progressively established during the Aptian.

Thus, the regional geological context is in favour of SE FranceAptian stratotypes as references. There, drill hole data such as thoseprovided by Lorenzen et al. (2013) and in this paper add to previ-ously published field work in Cassis-La B�edoule and Apt areas,which constitutes a considerable amount of information on theBedoulian and Gargasian high-resolution holostratigraphy. Thecorpus of available data allows, better than anywhere else, a high-resolution calibration of global events registered during this period.

7. Conclusion

Results obtained by our high-resolution stratigraphic study ofthe two drill holes at La B�edoule supplement previous field workcarried out over the last two decades. Here we present for the firsttime a detailed and continuous upper Bedoulian to lower Gargasianlithostratigraphic record put in parallel with an updated micro-faunal zonation. The latter is based on a succession of foraminiferalevents, calibrated with ammonites that are recognized in bothstratotypic areas of Apt and Cassis-La B�edoule. Some species ofornamented ostracods can also be used as additional markers.

This biostratigraphic framework can also be put in conjunctionwith a detailed isotopic chemostratigraphy, which shows that theLa B�edoule cores offer one of the best worldwide records of theOAE1a global event and provide a reference curve for the succes-sion of isotopic stages C2 to C8. It is also possible that the Cassis-LaB�edoule area recorded, though less obviously, the very shortnegative isotopic shift of the ‘Aparein level’ so far only detectedclearly in the Aptian of Spain. By correlating data from drill coresand stratotypic field sections, it is now possible to precisely locatethis brief event in the Cassis-La B�edoule area at the base of theDufrenoyia furcata (ammonites) and Praehedbergella luterbacheri(planktonic foraminifera) zones. This shift allows subdivision of thelong isotopic stage C7 in two subequal parts, which potentiallyrepresent an additional chemostratigraphic proxy for the definitionof the Bedoulian/Gargasian boundary.

In the stratotype, this boundary is fixed at the top of bed 170 andcorresponds to the quasi-simultaneous occurrence of the followingevents:

- Chemostratigraphy ¼ ~‘Aparein’ level,- Calcareous nannofossils ¼ ~ NC6/NC7 zonal boundary,- Planktonic foraminifera ¼ first appearance of 7-chamberedtrochospiral forms (Praehedbergella luterbacheri),


- Benthic foraminifera ¼ extinction of Lenticulina cf. heiermanni,- Ammonites ¼ extinction of the genus Deshayesites and firstappearance of the genus Dufrenoyia.

The database available, enriched by our results from LB1/LB3drill cores, encourages us to initiate a proposal that the Cassis-LaB�edoule area is a potential candidate for a GSSP of the base of theGargasian substage or, in the alternative current classification, toreiterate our proposal (Moullade et al., 2011) of this locality for aGSSP of the Aptian [sensu d'Orbigny, 1840] stage.

Acknowledgements

This work was supported by the German Research Foundation(SFB 754 sub-project A7). We thank the St€olben drilling companyfor their results and all their efforts, the Mayor, Vice-Mayor andstaff at the Mairie of Roquefort-La B�edoule for support and advice,Mrs. Fiani and family and Mr. and Mrs. Segura for grantingpermission to drill on their land. We are also greatly indebted toDrs. S. Fl€ogel (Geomar, Kiel) and C. Hagedorn (Geopartner,Luxembourg) for their assistance during the drilling operations.Professor RobertW. Scott (University of Tulsa, Oklahoma) is warmlythanked for his scientific advices and for having improved thelanguage level of this article. Last but not least, the originalmanuscript benefited from the reviews of three anonymous ref-erees, as well as the editorial comments of Eduardo Koutsoukos.

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Appendix A. Supplementary data

Supplementary data related to this article can be found at http://dx.doi.org/10.1016/j.cretres.2015.03.004.








































































































































































































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