the berriasian/valanginian boundary in the mediterranean ...hera.ugr.es/doi/15004302.pdf ·...

Cretaceous Research (2000) 21, 1–21doi:10.1006/cres.2000.0198, available online at http://www.idealibrary.com on

The Berriasian/Valanginian boundary in theMediterranean region: new data from theCaravaca and Cehegın sections, SE Spain

*R. Aguado, †M. Company and †J. M. Tavera

*Departamento de Geologıa, Universidad de Jaen, Escuela Universitaria Politecnica de Linares, 23700 Linares,Spain†Departamento de Estratigrafıa y Paleontologıa, Universidad de Granada, 18002 Granada, Spain

Revised manuscript accepted 18 October 1999

Biostratigraphic data provided by the sections of the Caravaca–Cehegın region, SE Spain, have contributed decisively to thelively debate that has taken place in recent years concerning the Berriasian/Valanginian boundary. This work presentsthe results from new integrated stratigraphic analyses of these sections, based on the distribution of ammonites, calpionellidsand calcareous nannofossils, and their calibration with the magnetic polarity scale. It is confirmed that the conflictinginterpretations in the literature on the distribution of some ammonites and calcareous nannofossil species are mainly due todifferences in taxonomic assignment. The event succession observed allows precise characterization of the Berriasian/Valanginian boundary, defined by the first occurrence of Calpionellites darderi. Some of the sections studied fulfil theprerequisites to be considered as potential boundary stratotypes. � 2000 Academic Press

K W: Berriasian/Valanginian boundary; biostratigraphic events; ammonites; calpionellids; calcareous nannofossils;magnetostratigraphy; stratotype; Betic Cordillera; SE Spain.

1. Introduction

Over the past 25 years, intense debate has takenplace concerning the definition of the Berriasian/Valanginian boundary in the Mediterranean region.Many of the arguments used in that discussion werebacked up by detailed biostratigraphic studies per-formed by different authors in several sections of theSubbetic Domain in the Caravaca–Cehegın region,Murcia, SE Spain (Figure 1).

Allemann et al. (1975) were the first to providesignificant data on the stratigraphic distribution ofammonites, calpionellids and nannofossils from theBerriasian/lowermost Valanginian of this region. Theirresults differed significantly from those published ear-lier by Le Hegarat & Remane (1968) and Le Hegarat(1973) for the same stratigraphic interval in SEFrance (Figure 2).

Some years later, two of us (Company & Tavera,1982) recognized a biostratigraphic succession in thesame sections of the Cehegın area, which was verysimilar to that described by Busnardo & Thieuloy(1979) in the Vocontian Basin, with three ammoniteassemblages which corresponded, respectively, to theBerriasella calisto Subzone and the Thurmanniceras

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otopeta and Thurmanniceras pertransiens Zones. Inthat work, the Berriasian/Valanginian boundary wasdefined by the appearance of Th. otopeta.

However, Hoedemaeker (1982) had shortly beforereached quite different conclusions in studying theRıo Argos sequence (Caravaca). This author placedthe Berriasian/Valanginian boundary at a lower strati-graphic level, coinciding with the base of the Tirnovellaalpillensis Subzone where, according to his interpret-ation, ammonites traditionally considered as charac-teristic of the Valanginian (i.e., the genera Neocomites,Olcostephanus, Sarasinella and Thurmanniceras)appeared together with typical Berriasian taxa. Inaddition, he placed the first appearance of Th. otopetasomewhat above that of Th. pertransiens, leading himto consider that the Th. otopeta Zone lacked faunaldistinctiveness and was, therefore, no more than ajunior synonym for the lower part of the Th. pertran-siens Subzone (sensu Le Hegarat & Remane, 1968), atwhich time the two species would have coexisted.

Both interpretations have been defended repeatedlyby their respective authors (Company, 1982, 1987;Hoedemaeker, 1983, 1984, 1987, 1991, 1995;Tavera, 1985; Tavera et al., 1986; Company &

� 2000 Academic Press

2 R. Aguado et al.

Tavera, 1992), without really providing any newarguments over the years.

To clarify these discrepancies in the data on sec-tions situated in such geographically close areas, wehave carried out new bed-by-bed sampling of thesesections and made a comparative analysis of thevertical distribution of the ammonites, calpionellidsand calcareous nannofossils. The results have enabledus to identify precisely the relative stratigraphic pos-ition of the bioevents that occurred in the latestBerriasian and the earliest Valanginian, leading us toreconsider the definition of the boundary betweenthese two stages. A preview of these results waspresented by Aguado et al. (1995).

2. Sections studied

The sections studied are located along the Rıo Argos,southwest of Caravaca, and in the area between thenorthern slope of the Sierra de Quıpar and the

Barranco de Canada Luenga, south of Cehegın(Figure 1).

From a geological viewpoint, both outcrops belongto the Subbetic Zone, which corresponds to thepelagic realm of the southern palaeomargin of theIberian Plate. Despite this and the fact that the presentdistance between the two areas does not exceed10 km, their lithologic sequences are notably different.Thus, in the northwestern area (Rıo Argos), theBerriasian is represented by basinal facies (marl-limestone rhythmites) of the Miravetes Formation. Bycontrast, pelagic swell facies (nodular limestones andother related lithologies) of the Tollo Formationoccurs in the area of Sierra de Quıpar-CanadaLuenga. From the top of the Berriasian, the basinfacies (Miravetes Formation) extends throughout theregion (Rey, 1995).

In the Rıo Argos area, we have studied the sectionY.Mv (Figure 3), situated near Cortijo de Miravetes,3 km southwest of Caravaca. This section has

Figure 1. Location of the sections. 1, Rıo Argos (section Y.Mv); 2, Canada Luenga (sections M.CL, Y.CL2, M.Qp2 andGE82); 3, Sierra de Quıpar (sections Y.Q3, and T.CE).

The Berriasian/Valanginian boundary in the Mediterranean region 3

been the subject of many biostratigraphic studies,such as those by Geel (1966), Allemann et al. (1975),Grun & Allemann (1975), Hoedemaeker (1982),Hoedemaeker & Leereveld (1995) and Leereveld(1997). For the present study, we have analysed onlythe upper part of the section, corresponding to theuppermost Berriasian–lowermost Valanginian interval(beds 230–276a). To facilitate comparison of theresults, we have maintained the original numberingof Hoedemaeker (1982), which was still clearlyvisible at outcrop when our field work was carriedout. The lithological succession is composed of arhythmic alternation of marly limestone beds (5–70 cm thick) and marly interbeds (varying betweena few cm and several m thick). The macrofaunais composed almost exclusively of ammonites, witha minor proportion of belemnites and benthicinvertebrates.

The other sections analysed are located, as statedabove, in the area of Sierra de Quıpar-CanadaLuenga. There are also numerous works that providedata on the biostratigraphy of the Berriasian/Valanginian boundary of this area (Kuhry, 1972;Allemann et al., 1975; Company & Tavera, 1982,

1992; Tavera, 1985; Company, 1987; Aguado,1993b). We have data from six sections (see Figure 1and Company, 1987, for details of their situation).Two of these (M.CL and Y.CL2), situated in theBarranco de Canada Luenga, some 3 km SSW ofCehegın, have been taken as reference sections andare represented, respectively, in Figures 4 and 5. Bothpresent very similar lithological sections. At the bot-tom, red nodular marly limestones crop out, under-lying an interval, 80–150 cm thick, of grey nodularlimestones with abundant crinoid fragments and arich macrofauna composed primarily of ammonites,echinoids and pygopids. These levels represent the topof the Tollo Formation, from which there is a changeupwards to the marl-limestone rhythmites of theMiravetes Formation. A magnetostratigraphic analysisof these two sections was reported by Ogg et al.(1988).

The thick monotonous lithological sequence of theRıo Argos section constitutes a complete and continu-ous record of the stratigraphic interval analysed. Incontrast, the sequences of Sierra de Quıpar-CanadaLuenga are relatively much less thick and show, intheir lower part (top of the Tollo Formation),

Figure 2. Correlation between several ammonite zonations proposed for the uppermost Berriasian and lowermostValanginian in SE France and SE Spain; dashed lines indicate that boundaries were not precisely defined.

4 R. Aguado et al.

evidence of a low net sedimentation rate, withfrequent interruptions in the deposit (includingomission surfaces and corrosion of the upper side ofthe fossils). Nevertheless, the fossil succession in these

sections is complete and can be well-correlated withthat of the Miravetes section. Thus, the presence ofstratigraphically significant gaps or condensations canbe ruled out.

Figure 3. Distribution of the most significant ammonite, calpionellid and calcareous nannofossil species in the Miravetessection (Y.Mv) (38�05�35�N, 1�53�32�W).


Figure 4. Distribution of the most significant ammonite, calpionellid and calcareous nannofossil species in section M.CL(Canada Luenga) (38�03�59�N, 1�48�39�W).

6 R. Aguado et al.

Figure 5. Distribution of the most significant ammonite, calpionellid and calcareous nannofossil species in section Y.CL2

(Canada Luenga) (38�04�05�N, 1�48�45�W).


3. Ammonite biostratigraphy

For the present study, we collected more than 2000ammonites bed-by-bed in the sections studied. Mostof the specimens come from limestone beds, althoughmany limonitized forms were found in the marlyinterbeds of the Miravetes section. The preservationof the specimens in the sections of Sierra de Quıpar-Canada Luenga is good, in some cases excellent.That of the specimens from the Miravetes sectionis mediocre but adequate for identifying for biostrati-graphical purposes.

The assemblages are composed exclusively ofMediterranean taxa (Bochianitidae, Haploceratidae,Lytoceratidae, Neocomitidae, Olcostephanidae, Phyl-loceratidae and Protetragonitidae). As indicated byWiedmann (in Allemann et al., 1975), the lytocerat-tids and phylloceratids, which are quite scarce in theswell facies of the Sierra de Quıpar-Canada Luengaarea, are much more frequent in the Miravetessection.

The faunal succession is practically identicalthroughout the sections studied. In all of them wehave recognized the three biostratigraphic unitsusually differentiated for this interval (Hoedemaeker& Bulot, 1990; Hoedemaeker & Company, 1993),i.e., from bottom to top: the T. alpillensis Subzone, theTh. otopeta (Sub)Zone and the Th. pertransiens Zone.Figures 3–5 represent the distribution of the strati-graphically most significant ammonite species in thereference sections.

3.1. Tirnovella alpillensis Subzone

Hoedemaeker (1982) created this biostratigraphicunit to refer to the interval from bed 230 to bed 261 ofthe Miravetes section in which, according to hisobservations, species of Berriasian age coexisted withothers belonging to the genera Neocomites, Sarasinella,Olcostephanus and Thurmanniceras, traditionally con-sidered as characteristic of the Valanginian. In fact,Hoedemaeker (1982) defined the base of this subzoneby the appearance of these ‘Valanginian’ forms andnot by the first occurrence of the index species, T.alpillensis, which would be at a somewhat lower level.

At first, Hoedemaeker (1982, 1983) correlated hisT. alpillensis Subzone with the B. calisto Subzone of LeHegarat & Remane (1968) in SE France. Subse-quently, however, he introduced a major modificationby considering that the Subzone of B. calisto shouldin reality correspond exclusively to the intervalfrom beds 223 to bed 230 of the Miravetes section(Hoedemaeker, 1984). According to this correlation,the T. alpillensis Subzone, characterized by a particular

assemblage of ‘Berriasian’ and ‘Valanginian’ species,would constitute a new, distinct biostratigraphic unit.The fact that this assemblage had not been recognizedin SE France could be explained, according toHoedemaeker (1984, 1995), by the presence of ahiatus in many of the French sections, among thesethe stratotype of Berrias. In other apparently completesections, such as those of Angles or La Faurie-Pusteau, Hoedemaeker (1984) interpreted this inter-val to have been assigned indiscriminately, by Frenchauthors, to the B. calisto Subzone.

The present study in no way confirms these inter-pretations. In fact, neither in the interval assigned byHoedemaeker to the T. alpillensis Subzone in theMiravetes section itself, nor in the equivalent levels ofthe Sierra de Quıpar-Canada Luenga sections, havewe found any specimen attributable to taxa character-istic of the Valanginian. Similar results have beenreported in other detailed studies recently carried outin various sections of SE France (Bulot et al., 1993;Blanc et al., 1994; Bulot & Thieuloy, 1995; Bulot,1995, 1996). As we have long maintained (Company,1982, 1987; Tavera, 1985), this discrepancy with thedata presented by Hoedemaeker (1982) cannot beexplained other than by a notable divergence in thetaxonomic identifications of the ammonites present inthe levels corresponding to the T. alpillensis Subzone.Thus, for example, the specimens figured byHoedemaeker (1982, pl. 5) as Neocomites premolicus,Thurmanniceras aff. thurmanni and Tirnovella gratiano-politensis are interpreted by us as more or less typicalforms of Tirnovella alpillensis and Fauriella boissieri.Comparable situations arise with many of the speci-mens in Hoedemaeker’s collection from these levels,which we have had the opportunity to examine, thanksto the kindness of our Dutch colleague. A similarconclusion was reached by Bulot (1995) from thestudy of the photographs of the same specimens.

According to our interpretation, the ammonite as-semblage from the T. alpillensis Subzone is composedof Berriasella calisto (d’Orbigny) (Figure 6g, h),Erdenella Paquieri (Simionescu), Fauriella boissieri(Pictet) (Figure 6a), Kilianella gr. chamalocensisMazenot (Figure 6b, d), Leptoceras studeri (Ooster),Protancyloceras spp., Tirnovella alpillensis (Mazenot)(Figure 6e, f), Spiticeras gr. multiforme Djanelidze(Figure 6i) and other species of Spiticeratinae, attribu-table provisionally (Company & Tavera, in prep.) tothe genera Groebericeras, Kilianiceras and Negreliceras,together with other forms of lesser biostratigraphicinterest. None of these species can be consideredcharacteristic of the Valanginian.

8 R. Aguado et al.

Furthermore, this assemblage is, as also pointed outby Bulot (1995), basically the same as that recognizedby Le Hegarat & Remane (1968) and Le Hegarat(1973) in the B. calisto Subzone of SE France; thus,contrary to the opinion of Hoedemaeker (1984),

we conclude that the T. alpillensis Subzone doesnot constitute a biostratigraphic unit distinct from theB. calisto Subzone. This conclusion, however, posesa methodological problem. On the one hand, theB. calisto Subzone is difficult to use, given the

Figure 6. a, Fauriella boissieri (Pictet), Y.CL2.5.134, T. alpillensis Subzone. b, Kilianella gr. chamalocensis Mazenot, M.CL.6,Th. otopeta Subzone. c, Kilianella lucensis Sayn, Y.Mv.266.4, Th. otopeta Subzone. d, Kilianella gr. chamalocensis Mazenot,Y.Mv.245.1, T. alpillensis Subzone. e, f, Tirnovella alpillensis (Mazenot); e, M.CL.4.10, T. alpillensis Subzone;f, Y.Mv.265.8, Th. otopeta Subzone. g, h, Berriasella calisto (d’Orbigny); g, M.CL.4.1, T. alpillensis Subzone; h,Y.Mv.244.9, T. alpillensis Subzone. i, Olcostephanus drumensis Kilian, M.CL.5.19, Th. otopeta Subzone.


imprecision of its original definition (Le Hegarat &Remane, 1968; LeHegarat, 1973). On the other, theT. alpillensis Subzone, which has already been admit-ted as valid in the standard zonations proposed for theMediterranean region (Hoedemaeker & Bulot, 1990;Hoedemaeker & Company, 1993), was created byHoedemaeker (1982) for an assemblage which, in ourinterpretation, does not exist. Bulot et al. (1993)offered a solution to this problem on redefining the T.alpillensis Subzone, drawing its lower boundary at theappearance of the index species. It is in this sense thatwe use this biostratigraphic unit here.

3.2. Thurmanniceras otopeta Subzone

According to the most recent interpretations(Company, 1987; Hoedemaeker & Bulot, 1990;Hoedemaeker & Company, 1993; Bulot et al., 1993;Blanc et al., 1994; Bulot, 1995), the base of thisbiostratigraphic unit is defined by the appearance ofthe index species, Th. otopeta Thieuloy (Figure 7c, d).Our data, which on this point practically coincide withthose of Hoedemaeker (1982), indicate that this‘event’ takes place in bed 263 of the Miravetes section.

The assemblage characteristic of this unit is com-posed mostly of species already present in the T.alpillensis Subzone. In addition to these, and togetherwith Th. otopeta, Tirnovella romani (Mazenot) andTirnovella sp. 1 (Figure 7g) appear, and, slightlyhigher, Kilianella lucensis Sayn (Figure 6c). At theselevels the first typical specimens of Olcostephanusdrumensis Kilian were also recorded, although itshould be mentioned that the transition between S. gr.multiforme and this species is very gradual.

The Th. otopeta Zone was created to cover thestratigraphic interval between ‘‘la faune franche aBerriasella calisto et les premieres apparitions deThurmanniceras pertransiens veritables’’ (Busnardo &Thieuloy, 1979, p. 60). This interval corresponds tothe ‘Horizon superieur a Kilianella aff. pexiptycha etThurmannites aff. pertransiens’ (=Beaucels Horizon) ofthe Berriasian of Mazenot (1939), characterized by itstypical Berriasian fauna, to which some taxa ofValanginian affinities are added. This horizon hadbeen transferred to the Valanginian by Busnardo & LeHegarat (1965) and kept there by Busnardo &Thieuloy (1979) and by most authors subsequently.Nevertheless, in 1992, during the 2nd Workshop ofthe Lower Cretaceous Cephalopod Team, some of theparticipants (i.e., Luc Bulot and ourselves) raised thepossibility of returning to the classical interpretationby including this unit in the Berriasian, given thedistinctiveness of its faunal assemblage, being com-posed mainly of Berriasian species (Hoedemaeker &

Company, 1993). This proposal, subsequently devel-oped by Bulot and colleagues (Bulot et al., 1993;Blanc et al., 1994; Bulot, 1995; Bulot & Thieuloy,1995) using data from the sections of SE France,has been followed here (see below in the discussionconcerning the Berriasian/Valanginian boundary).

The transfer of the Th. otopeta beds to the Berriasianjustifies the inclusion proposed by Bulot (1995) of aTh. otopeta Subzone in the uppermost part of the F.boissieri Zone, above the T. alpillensis Subzone.Although the assemblage of the Th. otopeta bedscoincides largely with that of the T. alpillensis Sub-zone, the first occurrence of Th. otopeta constitutes adatum level sufficiently significant to define a differentand potentially recognizable biostratigraphic unitthroughout most of the Mediterranean realm. In fact,besides SE France and the Betic Cordillera, Th.otopeta is present, although generally erroneouslyidentified, in assemblages from the northern Calcare-ous Alps (Immel, 1987, pl. 4, fig. 5), the westernCarpathians (Wierzbowski & Remane, 1992, pl. 3, fig.10), the Bakony Mountains (Fulop, 1964, pl. 14, fig.2), the Balkans (Nikolov, 1960, pl. 18, fig. 3) andCrimea (Baraboschkin, 1995).

Bulot (1995) defined, in the upper part of thisunit, a biohorizon characterized by the presence ofKilianella thieuloyi Bulot (=Th. otopeta ‘morphotype acotes epaisses’ in Thieuloy, 1979). We have notidentified any specimen that is strictly attributable tothis species in our material. It has not been possible,therefore, to characterize this biohorizon, recognizedup to now only in some sections of the southern areaof the Vocontian Basin.

3.3. Thurmanniceras pertransiens Zone

Created by Le Hegarat & Remane (1968), this bio-stratigraphic unit has been subjected to highly diver-gent interpretations. Here, we use it in the sense ofCompany (1987), according to which its lowerboundary is defined by the appearance of the indexspecies, Th. pertransiens (Sayn) (Figure 7e, f).

The first in situ record of true Th. pertransiens in theMiravetes section comes from the bed 269 (althoughsome limonitized specimens have been found scat-tered at the top of the marly interbed overlying the bed268). We consider, therefore, that the specimens fromlower levels attributed to this species by Wiedmann(in Allemann et al., 1975) and Hoedemaeker (1982)in reality correspond to Tirnovella sp. 1 and extrememorphotypes of Th. otopeta, which can show super-ficial similarities with Th. pertransiens (see also Bulot,1995; Bulot & Thieuloy, 1995).

10 R. Aguado et al.

The appearance of Th. pertransiens coincides witha major renewal in the ammonite fauna. Most ofthe species present in lower levels disappear. OnlyOlcostephanus drumensis, Kilianella lucensis and the lastrepresentatives of the genera Kilianiceras and Protancy-loceras, together with other species of broad strati-graphic distribution, pass into the Th. pertransiens Zone.

In addition, apart from the index species, new taxaappear near the base of the zone. These includeKilianella roubaudiana (D’Orbigny), Neocomites premoli-cus Sayn (Figure 7h), Sarasinella eucyrta (Sayn) andThurmanniceras gratianopolitense (Kilian) (Figure 7a, b),and confer to this faunal assemblage an aspect that isquite different from that of previous assemblages.

Figure 7. a, b, Thurmanniceras gratianopolitense (Sayn); a, M.CL.14.1, Th. pertransiens Zone; b, Y.Mv.269.47, Th.pertransiens Zone. c, d, Thurmanniceras otopeta Thieuloy; c, Y.Mv.266.10, Th. otopeta Subzone; d, M.CL.6.9, Th. otopetaSubzone. e, f, Thurmanniceras pertransiens (Sayn); e, Y.Mv.272.32, Th. pertransiens Zone; f, M.CL2.12.4, Th. pertransiensZone. g, Tirnovella sp.1, M.CL.6.7, Th. otopeta Subzone. h, Neocomites premolicus Sayn, Y.CL2.R, Th. pertransiensZone.


We have just cited, among the species appearing atthis level, Th. gratianopolitense. Following a traditionalcriterion, and lacking a more thorough revision ofthese forms, we include in this species the smallspecimens characteristic of the Mediterranean pelagicrealm for which Bulot (1995) created the species‘Fauriella’ kiliani. In fact, in the neritic facies ofthe Lower Valanginian of the western High Atlas(Morocco) it is common to find, in association withN. premolicus and Th. pertransiens, forms very close tothe type of Th. gratianopolitense, the juvenile stages ofwhich are comparable to the small specimens in theMediterranean Basin areas (Ettachfini, Company &Tavera, in preparation).

4. Calpionellid biostratigraphy

At present, there is an almost general consensus onthe stratigraphic distribution of the most significantcalpionellid species throughout the upper Berriasian/lowermost Valanginian interval. In fact, the standardzones defined by Allemann et al. (1971) continue tobe commonly applied, with only minor discrepanciespersisting in relation to their subdivision (Pop, 1994;Blanc, 1995; Blau & Grun, 1997; Grun & Blau 1997).

For the present work, we analysed two samplesfrom each limestone bed of the sections M.CL andY.CL2. From the section Y.Mv, we studied only theupper part, from bed 261 upwards. It should bepointed out that the samples from the Canada Luengasections contain abundant calpionellids in an excellentstate of preservation, but in those from the Miravetessection specimens are much scarcer and oftendeformed and/or recrystallized, frequently preventingreliable identification.

In the sections studied, we recognized the Calpionel-lopsis and Calpionellites Standard Zones. Throughoutthe stratigraphic interval occupied by these two zones,six significant bioevents are commonly recognized(Allemann & Remane, 1979; Remane et al., 1986;Pop, 1994). These are, successively, the first occur-rences of Calpionellopsis simplex (Colom), Calpionel-lopsis oblonga (Cadish), Lorenziella hungarica Knauer& Nagy, Precalpionellites murgeanui Pop, Calpionellitesdarderi (Colom) and Calpionellites major (Colom).

The first occurrence of Cs. simplex marks the lowerboundary of the Calpionellopsis Zone. According toAllemann & Remane (1979), this bioevent coincideswith the base of the F. boissieri ammonite Zone, wellbelow the interval analysed here. In the samplesstudied, Cs. simplex is infrequent, its last representa-tives being located in the Th. otopeta Subzone.

The first occurrence of Cs. oblonga has served todefine the base of the Cs. oblonga Subzone (Remane

et al., 1986). The evolutionary transition from Cs.simplex to Cs. oblonga is a gradual ‘event’ that takesplace around the boundary between the B. (M.)paramimouna and B. picteti ammonite Subzones, alsobelow the interval considered here. In our sections,Cs. oblonga constitutes, together with Tintinopsellacarpathica (Murgeanu & Filipescu), one of the mostabundant elements of the calpionellid assemblagespresent in the T. alpillensis and Th. otopeta Subzones.It continues to be well-represented at the base ofthe Th. pertransiens Zone, whereupon its frequencydeclines progressively until it disappears.

The first occurrence of L. hungarica was used byAllemann & Remane (1979) to define the base of theSubzone D3 in their zonal scheme for the VocontianBasin. This species has been found in most of thesamples studied here, although invariably as a veryminor component in the assemblages. Its scarcity andidentification difficulties have led some authors(Remane et al., 1986; Pop, 1986a, b) to reject this‘event’ as a valid biostratigraphic criterion.

As in SE France (Allemann & Remane, 1979), thefirst occurrence of P. murgeanui is located in theCanada Luenga sections in the upper part of the Th.otopeta Subzone. Even though this is a minor speciesin the calpionellid assemblages, its presence has beendetected in numerous areas of the Tethys, leading Pop(1986b, 1989) to create a P. murgeanui Subzone in theupper part of the Calpionellopsis Zone. According toBulot (1996), this subzone can be correlated with thebiohorizon of K. thieuloyi.

The first occurrence of Ct. darderi marks the base ofthe Calpionellites Zone. As pointed out previously(Company & Tavera, 1982), in the sections of theSierra de Quıpar-Canada Luenga area, this eventcoincides with the base of the Th. pertransiens Zone,in consonance with the observations of Allemann &Remane (1979) and Blanc et al. (1994) in SE France.In the Miravetes section, very likely owing to problemsof preservation, Allemann et al. (1975) did not findthis species, while Hoedemaeker & Leereveld (1995)reported its first occurrence at a much higher strati-graphic level. We have found some highly doubtfulspecimens in bed 269.

Several metres above the base of the Th. pertransiensZone in the Canada Luenga sections the first speci-mens attributable to Ct. caravacaensis Allemannappear. It is a well documented fact in various parts ofthe Tethys (Allemann & Trejo, 1975; Allemann &Remane, 1979; Pop, 1986b, c; Vasıcek et al., 1983)that the first appearance of Calpionellites with cylindri-cal loricae (Ct. caravacaensis and Ct. major) is strati-graphically higher than that of the forms withparabolic loricae (Ct. darderi and other closely related

12 R. Aguado et al.

species). This bioevent was used by Pop (1989, 1994)to define a Ct. major Subzone in the upper part of theCalpionellites Zone.

5. Nannofossil biostratigraphy

5.1. Material and methods

We have analysed the stratigraphic distribution of thecalcareous nannofossil species in both the Miravetessection (Y.Mv) and three sections in the Canada Luengaarea (M.CL, Y.CL2 and M.Qp2). All were sampledbed-by-bed, enabling a direct and detailed correlationwith the ammonite successions to be established.

A total of 114 samples have been studied. Smearslides were prepared from raw material, without anytype of treatment, in order to preserve as faithfully aspossible the original composition of the nannofossilassemblages. The study was carried out using a lightmicroscope at 1250� magnification, examining aminimum of 200 fields of view per sample. Nanno-fossils are in general abundant, constituting about 30–80% of the whole rock. Preservation seems to be closelyrelated to the lithology of the sample, varying from poorto moderate with overgrowth in marly limestones, andmoderate to good with only slight overgrowth and/oretching in the samples from the most marly intervals.The assemblages from thin marly beds intercalatedbetween the most limy intervals are quite poorly pre-served, but good enough so as not to have a detrimentaleffect on the results of the biostratigraphic study.

The diversity of the assemblages was generally high,with a total of 62 species recognized (see Appendix).In all cases, there is a clear predominance of cosmo-politan taxa (Biscutum spp., Cyclagelosphaera spp.,Diazomatolithus lehmanii, Lithraphidites carniolensis,Watznaueria spp., and Zeugrhabdotus spp.) togetherwith those more closely linked to the Tethyan realm(Calcicalathina praeoblongata sp. nov., Conusphaeramexicana, Diadorhombus rectus, Miravetesina favula,Nannoconus steinmannii, N. kamptneri, N. globulus, N.wintereri, Percivalia fenestrata, P. nebulosa, Rhagodiscusasper, Rucinolithus wisei, Tubodiscus spp. and Umbriagranulosa ssp. granulosa, among others). Nevertheless,we also detected the presence, although sporadic, ofsome taxa with boreal affinities, such as Kokia borealis,Sollasites horticus and Speetonia colligata (Perch-Nielsen, 1979, 1985, 1988; Mutterlose, 1987, 1992a,b; van Niel, 1994).

5.2. Nannofossil events around the Berriasian/Valanginian boundary

The entire stratigraphic interval analysed correspondsto the Retecapsa angustiforata Zone (Thierstein, 1971,

1973; Sissingh, 1977; Perch-Nielsen, 1979, 1985;Bralower et al., 1989). The lower boundary of thiszone is defined by the first occurrence of the indexspecies (Figure 8.34–36). This ‘event’ takes place inthe lower or middle part of the Berriasian (Braloweret al., 1989; Aguado, 1993a, b; Gardin & Manivit,1993; Hoedemaeker & Leereveld, 1995), well belowthe stratigraphic levels analysed here.

The upper boundary of the R. angustiforata Zonecoincides with the first occurrence of Calcicalanthinaoblongata (Figure 9.2–5). According to the resultsobtained by Aguado (1993a, b) from the samesections of Canada Luenga area, this ‘event’ is locatedin the upper part of the Th. pertransiens Zone, abovethe stratigraphic interval analysed here. A similarposition for this ‘event’ has been observed in SEFrance (Manivit, 1979; Bulot, 1996). However,Bergen (1994) placed the appearance of C. oblongatatowards the top of the Th. otopeta Zone in the Anglessection and references to this species are alsofrequent at much lower levels. Thus, for example,Hoedemaeker & Leereveld (1995) mentioned its pres-ence in the lower part of the T. alpillensis Subzone inthe Miravetes section. Approximately in that level, wehave detected the first record of forms similar to C.oblongata but with more primitive morphological char-acters which enable their differentiation at the specieslevel. The presence of these forms, which we identifyas C. praeoblongata sp. nov. (see Appendix and Figure8.29–33), has already been reported in other recentstudies (Calcicalathina sp. A, in Bergen, 1994; C. aff.oblongata, in Bulot, 1996). We believe that the speci-mens assigned by various authors to C. oblongata, butcoming from levels below the upper part of the Th.pertransiens (where true C. oblongata first appear),should be assigned to this new species.

Bralower et al. (1989) used the first occurrence ofPercivalia fenestrata (Figure 8.11–15) to divide the R.angustiforata Zone into two subzones, a lower Assipetrainfracretacea Subzone and an upper P. fenestrata Sub-zone. Nevertheless, the distinction of these two sub-zones is hindered in practice by a gradual andprogressive morphological transition between the typi-cal forms of Percivalia nebulosa (new combination forRhagodiscus nebulosus, see Appendix and Figure 8.1–5)and the morphotypes clearly assignable to Percivaliafenestrata s.s. This morphological transition was men-tioned by Bralower et al. (1989) and is illustrated byour specimens (Figure 8.6–10). Percivalia fenestratas.s. does not appear in our sections until the upperpart of the T. alpillensis Subzone, within the magneticpolarity zone M15r. We believe that the references tothis species at lower stratigraphic levels (Braloweret al., 1989; Ogg et al., 1991; Gardin & Manivit, 1993)

Figure 8. 1–5, Percivalia nebulosa comb. nov.; 1, proximal view, 45� to crossed nicols, sample Y.Mv.245; 2, same specimenas in 1, 0� to crossed nicols; 3, proximal view, 45� to crossed nicols, sample Y.Mv.234D; 4, proximal view, 30� to crossednicols, sample Y.Mv.236; 5, proximal view, 45� to crossed nicols, sample Y.CL2.4. 6–10, specimens intermediatebetween Percivalia nebulosa comb. nov. and Percivalia fenestrata; 6, distal side, 0� to crossed nicols, sample Y.Mv.236; 7,same specimen as in 6, 45� to crossed nicols; 8, distal view, 0� to crossed nicols, sample Y.CL2.6; 9, same specimen asin 8, 45� to crossed nicols; 10, proximal view, sample Y.CL2.6. 11–15, Percivalia fenestrata; 11, distal view, 0� to crossednicols, sample Y.CL2.25.2; 12, distal view, 0� to crossed nicols, sample M.CL.3; 13, proximal view, 0� to crossednicols, sample Y.CL2.25.1; 14, distal view, 0� to crossed nicols, sample Y.CL2.25.1; 15, distal view, 0� to crossed nicols,sample X. HA-6A (uppermost Barremian, specimen included for comparison). 16, Cyclagelosphaera margerelii, sampleY.CL2.25.1. 17, 18, Haqius ellipticus; 17, sample Y.CL2.6; 18, sample Y.CL2.26.1. 19, 20, Biscutum sp. 1; sampleY.CL2.7. 21, 22, Diazomatolithus lehmanii; 21, sample Y.CL2.12; 22, sample Y.CL2.14. 23, 24, Eiffellithus primus; 23,sample Y.CL2.21; 24, sample Y.CL2.11. 25–28 Rucinolithus wisei; 25, sample Y.CL2.7a; 26, sample M.CL.3; 27, sampleY.CL2.7; 28, sample Y.CL2.8. 29–33, Calcicalathina praeoblongata sp. nov.; 29, sample Y.CL2.7; 30, sample M.CL.3;31, sample Y.CL2.25.1; 32, sample Y.CL2.26.2; 33, sample Y.Mv.258. 34–36, Retecapsa angustiforata; 34, sampleY.CL2.8; 35, sample Y.CL2.11; 36, sample Y.CL2.11. 37, Assipetra infracretacea, sample Y.CL2.5. 38, Discorhabdusignotus, sample Y.Mv.236. 39, Staurolithites crux, sample Y.CL2.25.2. 40, 41, Conusphaera mexicana ssp. mexicana; 40,sample Y. CL2.6; 41, sample Y.CL2.26.3. 42, Retecapsa octofenestrata, sample Y.CL2.25.2. All cross-polarized lightmicrographs c. �3500.

14 R. Aguado et al.

Figure 9. 1, specimen approaching Calcicalathina oblongata, sample Y.CL2.26.3. 2–5, Calcicalathina oblongata, 2, sampleM.BG.9; 3, sample M.BG.12; 4, 5, lateral views, sample M.BG.9. 6–9, Tubodiscus jurapelagicus; 6, sample Y.CL2.26.3;7, sample Y.CL2.6; 8, sample Y.Mv.245; 9, sample Y.Mv.251. 10, 11, Tubodiscus verenae; 10, sample Y.CL2.17, highfocus; 11, same specimen as in 10, low focus. 12, 13, Speetonia colligata; 12, 0� to crossed nicols, sample Y.CL2.4; 13,same specimen as in 12, 45� to crossed nicols. 14–17, Cruciellipsis cuvillieri; 14, 15, sample Y.CL2.25.1; 16, sampleM.BG.9; 17, sample Y.CL2.5. 18, Zeugrhabdotus embergeri, sample Y.CL2.7a. 19, Micrantholithus obtusus, sampleY.CL2.6. 20, Micrantholithus hoschulzii, sample Y.CL2.6. 21, 22, Cyclagelosphaera deflandrei; 21, sample Y.CL2.7a; 22,sample Y.CL2.7a. 23, Zeugrhabdotus embergeri, sample Y.CL2.5. 24–27, Tubodiscus verenae; 24, sample Y.CL2.26.2,medium focus; 25, same specimen as in 24, high focus; 26, same specimen as in 24, low focus; 27, sample Y.Mv.245.28, Micrantholithus obtusus, sample Y.CL2.6. All cross-polarized light micrographs c. �3500.


may in fact correspond to specimens of an intermedi-ate morphology, which we include under P. nebulosa.The last consistent record of P. nebulosa is found inthe upper part of the T. alpillensis Subzone; their last,very sporadic, occurrences are in the Th. otopetaSubzone.

Another characteristic event of the interval analysedis the appearance of the genus Tubodiscus. In thesections investigated here, the representatives of thisgenus are scarce and do not present a continuousrecord. The first records of Tubodiscus jurapelagicus(Figure 9.6–9) are located in the lower part of the T.alpillensis Subzone, within the polarity zone M16n.The first forms assignable to Tubodiscus verenae(Figure 9.10, 11, 24–27) have been found in oursections coinciding approximately with the firstappearance of P. fenestrata (within the polarity zoneM15r), also slightly below that indicated by Braloweret al. (1989).

The last record of Umbria granulosa ssp. granulosa iswithin the T. alpillensis Subzone slightly above the firstrecords of T. jurapelagicus and C. praeoblongata andbelow the appearance of P. fenestrata and T. verenae(polarity zone M15r).

Rucinolithus wisei (Figure 8.25–28) is present in oursections from the base of the T. alpillensis Subzone. Itsfirst occurrence should occur at lower stratigraphiclevels.

Finally, Diadorhombus rectus is a scarce species, andwith a discontinuous record in our sections. There isno agreement among authors as to the level of its firstoccurrence. Thus, Bralower et al. (1989) placed itbelow the first occurrence of R. angustiforata, withinthe polarity zone M17r; Gardin & Manivit (1993)placed it at levels fluctuating between the middleBerriasian, slightly below the appearance of R. angus-tiforata, and the top of the Berriasian, above that of P.fenestrata. Finally, Bergen (1994) also placed it abovethat of P. fenestrata. In our sections, D. rectus is presentfrom the base of the T. alpillensis Subzone. The reasonfor these differences could be that D. rectus is generallysmall and scarce, and has delicate structures whichcan be easily obliterated by etching or overgrowth.

6. Magnetostratigraphy

As mentioned above, the magnetostratigraphy of theCanada Luenga sections was studied by Ogg et al.(1988). Both sections (M.CL and Y.CL2, which cor-respond, respectively, to VCY and VCZ in Ogg et al.,1988) display identical magnetic polarity sequenceswhich can be correlated with the interval between theupper part of the polarity zone M16n and the lowerpart of the polarity zone M14r. It should be pointed

out that, hitherto, these sections are the only ones inthe world in which it has been possible to establish adirect correlation between the magnetic polarity scaleand the ammonite zonation for this stratigraphicinterval (Ogg et al., 1991; Gradstein et al., 1994). TheMiravetes section, on the contrary, has proved in-adequate for magnetostratigraphic analysis because ofstrong magnetic overprinting (Hoedemaeker et al.,1997).

The data presented here, and in particular the newfindings that modify the location of certain bioeventsin the sequence, require a review of the correlationproposed by Ogg et al. (1988) between the magneto-stratigraphic scale and the ammonite and calpionellidzonations. According to these new data, the lowerboundary of the Th. otopeta Subzone practicallycoincides with the base of polarity zone M15n, thefirst occurrence of P. murgeanui is very near theboundary between M15n and M14r, and the base ofthe Th. pertransiens Zone (which coincides with thebase of the Calpionellites Zone) is situated in thelowermost part of the polarity zone M14r. Withrespect to the calcareous nannofossil bioevents, asindicated above, the first occurrences of T. jurapelagi-cus and C. praeoblongata are in the uppermost part ofM16n, whereas U. granulosa ssp. granulosa disappearsa little higher up, at the base of M15r. The firstoccurrence of P. fenestrata is in the upper part ofM15r, and the first occurrence of true C. oblongata isin the upper part of M14r, although it has not beenrecorded in the interval studied.

7. Conclusions: the Berriasian/Valanginianboundary

The comparative analysis of the vertical distribution ofammonites, calpionellids and calcareous nannofossilsin the sections studied reveals that the succession ofbiostratigraphic events is identical in all of the sections(Figure 10). This implies that the stratigraphicinterval assigned by Hoedemaeker (1982) to the T.alpillensis Subzone (which corresponds to levels 230–261 in the Miravetes section) is also integrally repre-sented in the Sierra de Quıpar-Canada Luengasections, and therefore invalidates Hoedemaeker’ssupposition (1984, 1995; see also Hoedemaeker &Leereveld, 1995) that the sediments corresponding tothis subzone are lacking in most of the sections knownfrom SE France and the Betic Cordillera, and thatrecords of these sediments exist only in the deepestareas of the basins. This would explain, according toHoedemaeker, why the ammonite assemblage fromthe T. alpillensis Subzone has been recognized hithertoonly in the Miravetes section. In reality, as we have

16 R. Aguado et al.

maintained repeatedly in the past, the composition ofthe assemblage from the T. alpillensis Subzone ispractically the same as that from the B. calisto Zone,and the differences pointed out by Hoedemaekerare exclusively owing to different taxonomic inter-pretations.

Largely as a result of these problems in the appliedammonite taxonomy, most of the members of theValanginian Working Group attending the SecondInternational Symposium on Cretaceous StageBoundaries (held in Brussels during 1995) voted infavour of situating the Berriasian/Valanginian bound-ary at the base of the Calpionellites Zone, defined bythe first occurrence of Calpionellites darderi (see Bulot,1996). We firmly support this alternative, given thatthis event furthermore fulfils a number of conditionsfor making it an excellent boundary level.

Firstly, Ct. darderi is a species that has a very widegeographic distribution, covering a very large part ofthe Tethys realm from Mexico to Anatolia, and beingrecorded in different types of pelagic and hemipelagicfacies, both in sections on land and in offshore bore-holes. It is easily recognizable in well-preservedsamples, but if the preservation is not so good, it maybe confused with P. murgeanui or with other Calpion-ellites species having parabolic loricae (Ct. coronata orCt. uncinata). However, as indicated by Remane(1985), the resulting stratigraphic error is not grave,because P. murgeanui first appears at the top of theCalpionellopsis Zone and the other Calpionellites speciesmentioned have stratigraphic ranges similar to that ofCt. darderi.

As discussed above, the first occurrence of Ct.darderi practically coincides with the base of the Th.pertransiens Zone (Figure 10). This has been con-firmed both in our sections and that in SE France.Thurmanniceras pertransiens is also known throughoutthe Mediterranean, from the western Atlas to Crimea(other records outside the Mediterranean area areprobably erroneous), being especially frequent inpelagic sediments. In platform areas, it is rather rareand replaced quantitatively by others such as N.premolicus, S. eucyrta and Th. gratianopolitense(Ettachfini et al., 1998), the first occurrence of whichalso approximately coincides with the base of theCalpionellites Zone. On the other hand, the presenceof Platylenticeras in the lower part of the Th. per-transiens Zone in SE France has led some authors(Hoedemaeker, 1987; Bulot, 1995) to correlate thebase of the Platylenticeras-Schichten, which marks thebeginning of the sub-boreal Valanginian, with the baseof the Th. pertransiens Zone.

Major events coinciding with this same stratigraphiclevel have also been detected in other groups of

organisms. Thus, Leereveld (1997) recorded the firstoccurrence of several species of dinoflagellates in beds268–271 of the Miravetes section (Th. pertransiensappears in bed 269), enabling him to define the baseof a Spiniferites spp. Zone at that level. Lakova et al.(1997) reported that a renewal in the calcareousdinocyst assemblages also coincides with the base ofthe Calpionellites Zone. Among the calcareous nanno-fossils, the most significant ‘event’ is the first occur-rence of Calcicalathina oblongata in the middle/upperpart of the Th. pertransiens Zone.

Evidently, this collection of bioevents accompany-ing the first occurrence of Ct. darderi, together with itslocation on the magnetostratigraphic scale (in thelower part of the magnetozone M14r), confer anextraordinary correlation potential for the boundarylevel chosen, far greater than those for the otherboundaries proposed previously (i.e., the base of theT. alpillensis Subzone and the base of the Th. otopetaSubzone). We believe that this is sufficient to acceptthis boundary level and to leave aside the question ofthe first appearance of ammonites with ‘Valanginianaffinities’, which traditionally has focused the discus-sion on the Berriasian/Valanginian boundary (seeBulot, 1995).

Finally, a historical reason also emerges. For theauthors who developed the concept of the Valanginianin the pelagic facies of SE France between the end ofthe 19th century and the beginning of the 20th(Kilian, Lory, Paquier, Sayn, etc.), this stage clearlybegan with the marls and marly limestones containingpyritized ammonites. This viewpoint predominateduntil much later; hence, Mazenot (1939) included his‘Horizon superieur a Kilianella aff. pexiptycha andThurmannites aff. pertransiens’ in the Berriasian. Thishorizon (‘‘bien repere stratigraphiquement et immedi-atement sous-jacent aux marnes valanginiennes a am-monites pyriteuses’’, according to Mazenot, 1939,p. 266), is equivalent to the present Th. otopeta Sub-zone, as discussed above. It was transferred to theValanginian at the Lyon Colloquium (Busnardo & LeHegarat, 1965) without really solid arguments havingbeen provided. The proposal to draw the Berriasian/Valanginian boundary at the base of the CalpionellitesZone thus represents a return to the classical conceptof this boundary.

In accord with the guidelines of the InternationalCommission on Stratigraphy, the definition of achronostratigraphic boundary should be based ona stratotype section which contains the most completepossible record of the events relevant for the recog-nition and correlation of this boundary. With regardto the Berriasian/Valanginian boundary, the Canada


Luenga sections clearly more than satisfy the require-ments (e.g., exposure quality, stratigraphic conti-nuity, fossil abundance and diversity, amenabilityto magnetostratigraphy and chemostratigraphy; seeCowie, 1990), to be considered, together withthe Montbrun-les-Bains section (Drome, SE France)proposed by Blanc et al. (1994), as potential boundarystratotypes.

Acknowledgements

This study has been co-financed by Project PB97-0826 (DGESIC, Spanish Ministry of Education andScience) and Research Group 4064 (Junta deAndalucıa). We acknowledge Ph. J. Hoedemaeker andJ. Mutterlose for critically reviewing the manuscript.

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Appendix

Taxonomy of the calcareous nannofossil species considered in thisstudy (R. Aguado)

Assipetra infracretacea (Thierstein, 1973) Roth, 1973 (Figure 9d)Axopodorhabdus cylindratus (Noel, 1965) Wind & Wise in Wise &Wind, 1977Biscutum ellipticum (Gorka, 1957) Grun in Grun & Allemann, 1975Biscutum sp. 1 (Figure 8s, t). We apply this species to forms that aresimilar to B. ellipticum but much larger, and with a markedly widerand open central area. They are rare, and have been found only inthe P. fenestrata Subzone of the Y.CL2 section.

Calcicalathina praeoblongata sp. nov.Figure 8.29–33

1993 Calcicalathina sp. A: Bergen, 1994, pl. 1, fig. 11a, b.

Holotype. Calcicalathina sp. A, in Bergen (1994, pl. 1, fig. 11).Type level and locality. Uppermost Berriasian, bed 245, Anglessection, SE France.Paratypes. Figure 8.29–33.Etymology. After prae-, before and oblongata, elongated. The namealludes to the fact that the first appearance of this species is earlierthan that of C. oblongata.

20 R. Aguado et al.

Description. Medium sized to relatively large murolith (maximumdiameter between 7–10 �m) showing an elevated, highly birefrin-gent central area covered by coarse granules. The rim is relativelywide (about 1/4 of the central area width) and is constructed ofdextrally imbricated elements when viewed from the distal side.

Remarks. This species can be distinguished from Calcicalathinaoblongata by having a smaller average size and a wider rim. Themaximum size/rim width ratio is about 19.6 for C. oblongata andnear to 7.6 for C. praeoblongata. It differs from R. asper in having anelevated, highly birefringent, central area with no central process.

Occurrence. Bergen (1994) reported the lowest occurrence of thisspecies in the lowermost Berriasian of SE France. In the presentstudy, it has been recorded from Upper Berriasian (T. alpillensisSubzone) to Lower Valanginian (Th. pertransiens Zone) sediments.The forms of late Berriasian to earliest Valanginian age reported asC. oblongata in Hoedemaeker & Leereveld (1995) probably corre-spond to this species. According to Bergen (1994), the highestoccurrence of this species is latest Aptian in age.

Calcicalathina oblongata (Worsley, 1971) Thierstein, 1971 (Figure9.2–5)Conusphaera mexicana Trejo, 1969 ssp. mexicana (Figure 8.40, 41)Cretarhabdus conicus Bramlette & Martini, 1964Cruciellipsis cuvillieri (Manivit, 1966) Thierstein, 1971 (Figure 9.14–17)Cyclagelosphaera deflandrei (Manivit, 1966) Roth, 1973 (Figure9.21, 22)Cyclagelosphaera margerelii Noel, 1965 (Figure 8.16)Cyclagelosphaera rotaclypeata Bukry, 1969Diadorhombus rectus Worsley, 1971Diazomatolithus lehmanii Noel, 1965 (Figure 8.21, 22)Diloma primitiva (Worsley, 1971) Wind & Cepek, 1979. Only veryrare specimens attributable to this species were found within thelower part of the Th. pertransiens Zone in the Y.Mv section.Discorhabdus ignotus (Gorka, 1957) Perch-Nielsen, 1968 (Figure8.38)Eiffellithus primus Applegate & Bergen, 1988 (Figure 8.23, 24). Todate, no stratigraphic connection has been detected between theNeocomian representatives often assigned to the genus EiffellithusReinhardt, 1965 (E. primus, E. striatus and E. windii) and the speciesfrom the middle and/or upper Cretaceous, such as E. eximius, E.monechiae and E. turriseiffelii. Applegate & Bergen (1988) justifiedthe assignment of E. primus, E. striatus and E. windii to this genus onthe basis of the presence of an axial cross and a shield composed oftwo cycles, a narrow outer one with dextrally imbricated elementsand an inner one formed by juxtaposed plates. If account is taken ofthe fact that the genus Eiffellithus was originally described with E.turriseiffelii as type species, and if a purely morphological taxonomyis to be avoided, there is no sense in assigning the Neocomian formsto this genus. An alternative genus for these could be TegumentumThierstein, 1972, which differs from Eiffellithus by the presence ofan outer cycle of slightly or non-imbricated elements and an innercycle of tabular and highly imbricated elements. However, accord-ing to Applegate & Bergen (1988), the structure that these formshave does not correspond well either to the characteristics of thegenus Tegumentum. More recently, Varol & Girgis (1994) groupedthe Neocomian forms under a new genus, Rothia, considering theirstructure to be different from that of genus Tegumentum. The studymethod used in the present work (light microscopy) and the state ofpreservation of the material, together with the scarcity of E. primus,has hampered detailed examination of the rim-structure of thisspecies. For this reason, pending detailed studies on this issue, wemaintain this species provisionally within the genus Eiffellithus, towhich it was originally assigned.Ellipsagelosphaera britannica (Stradner, 1963) Perch-Nielsen, 1968Ellipsagelosphaera fossacincta Black, 1971Ellipsagelosphaera ovata (Bukry, 1969) Black, 1973Haqius circumradiatus (Stover, 1966) Roth, 1978Haqius ellipticus (Grun in Grun & Allemann, 1975) Bown, 1992(Figure 8.17, 18)

Kokia borealis Perch-Nielsen, 1988. Very scarce specimens of thisspecies, considered to be of boreal affinity, have been found in somesamples from the base of the P. fenestrata Subzone.Lithraphidites carniolensis Deflandre, 1963Manivitella pemmatoidea (Deflandre ex Manivit, 1961) Thierstein,1971Micrantholithus hoschulzii (Reinhardt, 1966) Thierstein, 1971(Figure 9.20)Micrantholithus obtusus Stradner, 1963 (Figure 9.19, 28)Microstaurus chiastius (Worsley, 1971) Grun in Grun & Allemann,1975Microstaurus quadratus Black, 1971Miravetesina favula Grun in Grun & Allemann, 1975Nannoconus bermudezii Bronnimann, 1955Nannoconus cornuta Deres & Acheriteguy, 1980Nannoconus globulus Bronnimann, 1955Nannoconus kamptneri Bronnimann, 1955 ssp. kamptneriNannoconus kamptneri Bronnimann, 1955 ssp. minor Bralower inBralower et al., 1989Nannoconus steinmannii Kamptner, 1931 ssp. minor Deres &Acheriteguy, 1980Nannoconus steinmannii Kamptner, 1931 ssp. steinmanniiNannoconus wintereri Bralower & Thierstein in Bralower et al., 1989.Some specimens of this species were found only near the base of theT. alpillensis Subzone in the Y.Mv section.Percivalia fenestrata (Worsley, 1971) Wise, 1983 (Figure 8.11–15)Percivalia nebulosa (Bralower in Bralower et al., 1989) comb. nov.(Figure 8.1–5). The genus Rhagodiscus Reinhardt, 1967 is charac-terized by the presence of a rim of inclined elements and a centralarea that is completely covered by granular elements and commonlyhas a hollow central process. This species was originally assigned byBralower (in Bralower et al., 1989) to the genus Rhagodiscus basedon the structure and, in particular, on the partially granular natureof the central area. The same author concluded that the species‘Rhagodiscus nebulosus’ was a precursor of Percivalia fenestrata andinsisted on the presence of intermediate morphologies between bothspecies. During the course of our study, abundant specimens withintermediate characteristics were found (Figure 8.6–10). Whenexamined by light microscopy under crossed nicols, the represen-tatives of the genus Rhagodiscus display a highly birefringent rim anda weakly birefringent central area with the presence of granules,over which a hollow stem is often situated. ‘R. nebulosus’ does nothave a hollow central process but nevertheless has a central areawith a highly birefringent outer margin and counter-clockwise-curved extinction lines in proximal view. This same structureappears to be even more developed in P. fenestrata. In proximalview, the central area of the genus Percivalia Bukry, 1969, ischaracterized by the presence of various concentric tiers composedof elements oriented parallel to the elliptical margin. These tiers alsoreveal an adcentral inclination, creating a concave morphology. It isprecisely this type of structure in tiers that gives rise to the centralarea with a highly birefringent rim present in P. fenestrata. Based onthe optical similarity under crossed nicols, we conclude that theouter margin of ‘R. nebulosus’ should show, in proximal view, astructure with concentric tiers similar to that of P. fenestrata. Thislatter feature is not evident from the only illustration that we havefound in the literature, a scanning electron micrograph of theproximal side of ‘R. nebulosus’ (see Bralower et al., 1989, pl. 1, fig.21). The specimen figured in that illustration, however, shows signsof overgrowth, and thus the narrow fringe with the tiered structuresituated on the rim of the central area could very well be masked.Accepting, then, the presence of tiers on the rim of ‘R. nebulosus’ aswell as the absence of a hollow stem, and taking into account itsstructural resemblance to P. fenestrata and the existence of inter-mediate morphotypes between the two, we assign this species to thegenus Percivalia rather than to Rhagodiscus. Finally, in an attempt toseparate with more clarity the forms attributable to P. nebulosa fromthose ascribable to P. fenestrata, and given the existence of numer-ous intermediate morphologies, we have used the following criteria:(1) the widths of the birefringent rim of the central area (named x)and the non-birefringent central zone (named y) were measured;


(2) those forms in which y is greater than x were assigned to P.nebulosa; (3) the forms in which x is greater than y were assigned toP. fenestrata.Retecapsa angustiforata Black, 1971 (Figure 8.34–36).Retecapsa octofenestrata (Bralower in Bralower et al., 1989) Aguado,1993a (Figure 8.42)Retecapsa surirella (Deflandre in Deflandre & Fert, 1954) Grun inGrun & Allemann, 1975Rhagodiscus asper (Stradner, 1963) Reinhardt, 1967Rhagodiscus splendens (Deflandre, 1953) Verbeek, 1977Rotelapillus laffittei (Noel, 1957) Noel, 1973Rucinolithus pinnatus Bergen, 1994. Very scarce specimens of R.pinnatus were found in the lowermost part of the Th. pertransiensZone (samples 270, 273, 274, 276B) of the Y.Mv section.Rucinolithus wisei Thierstein, 1971 (Figure 8.25–28)Sollasites horticus (Stradner et al., 1966) Cepek & Hay, 1969Speetonia colligata Black, 1971 (Figure 9.12, 13)

Staurolithites crux (Deflandre in Deflandre & Fert, 1954) Caratini,1963 (Figure 8.39)Staurolithites mutterlosei Crux, 1989Stradnerlithus silvaradius (Filewicz et al. in Wise & Wind, 1977)Rahman & Roth, 1991Tubodiscus jurapelagicus (Worsley, 1971) Roth, 1973 (Figure 9.6–9).Tubodiscus verenae Thierstein, 1973 (Figure 9.10, 11, 24–27).Umbria granulosa Bralower & Thierstein, 1989 ssp. granulosaWatznaueria barnesae (Black in Black & Barnes, 1959) Perch-Nielsen, 1968Watznaueria biporta Bukry, 1969Watznaueria manivitae Bukry, 1973Zeugrhabdotus embergeri (Noel, 1959) Perch-Nielsen, 1984 (Figure9.18, 23)Zeugrhabdotus erectus (Deflandre in Deflandre & Fert, 1954)Reinhardt, 1965Zeugrhabdotus noeliae Rood et al., 1971