Cretaceous Research (2001) 22, 145–156doi:10.1006/cres.2000.0249, available online at http://www.idealibrary.com on

Biostratigraphy of the Aptian–MiddleCenomanian platform to basin domain in thePrebetic Zone of Alicante, SE Spain: calibrationbetween shallow water benthonic and pelagicscales

*J. M. Castro, †M. Company, *G. A. de Gea and *R. Aguado

*Departamento de Geologıa, Universidad de Jaen, 23071 Jaen, Spain†Departamento de Estratigrafıa y Paleontologıa, Universidad de Granada, 18071 Granada, Spain

Revised manuscript accepted 13 December 2000

The biostratigraphy of platform carbonates and adjacent basins outcropping in the Prebetic Zone of Alicante, south-easternSpain, is presented. With this aim, 42 sections from 13 major outcrops, of Aptian–Middle Cenomanian age, were analysed.Ten biostratigraphic units based upon benthonic foraminifers have been distinguished within this interval. Comparison withother previously published biozonations shows, in general, a good agreement, but several differences have arisen, interpretedmainly to be related to palaeogeography and palaeoecological factors. The presence of ammonites, planktonic foraminifersand calcareous nannofossils in the sections studied has enabled the calibration of the zonation proposed with thebiostratigraphic schemes based on these fossil groups. Also, a few data from rudists have been integrated.

� 2001 Academic Press

K W: Lower Cretaceous; biostratigraphy; benthonic foraminifers; orbitolinids; ammonites; Alicante; Spain.

1. Introduction

In the Lower Cretaceous of the Mediterranean area,broad, shallow, carbonate platforms are recorded,with development of ‘Urgonian facies’; the lateralequivalents of these platform successions are thickmarly units, sometimes of dark, fine-grained sedi-ments reflecting dysoxic/anoxic episodes, depositedon hemipelagic environments. The shallow carbonateplatforms were extensively colonised by benthonicfauna, especially foraminifers but also calcareousalgae, corals, sponges, and bivalves such as rudists. Onthe other hand, the hemipelagic domain providedhabitats for ammonites, planktonic foraminifers,which flourished mainly from the late Barremianonwards, and calcareous nannofossils.

Correlation between the sedimentary eventsrecorded both in pelagic and shallow platform settingsneeds to be demonstrated within an accurate biostrati-graphic framework. We have, therefore, carried out alithostratigraphic, biostratigraphic, sedimentologicaland sequence stratigraphic analysis of 42 sectionslocated in 13 selected Lower Cretaceous exposuresof the Prebetic Zone in Alicante (Figure 1). Our

0195–6671/01/020145+12 $35.00/0

objectives are, first, to provide the benthonic fora-miniferal biostratigraphy of the Upper Barremian–Middle Cenomanian interval in the Prebetic Platformof Alicante and, second, to attempt a correlation of thebenthonic and pelagic schemes based on the presenceof fossils typical of pelagic sediments in the sectionsstudied.

The study area was selected because of (1) goodoutcrop conditions of various, almost continuoussections of carbonate platform sediments, withabundant, diverse and well-preserved benthonicfossils, and (2) the presence of fossils typical of pelagicsediments (ammonites, planktonic foraminifers andcalcareous nannofossils), both within the marlyformations and beds intercalated between the plat-form limestones, and also within the limestones(planktonic foraminifers).

The first led to the execution of a chart of thestratigraphic distribution of benthonic foraminifers,enabling the recognition of ten biostratigraphic units.The second allowed us to calibrate directly thebenthonic data to the current ammonite, plank-tonic foraminifer, and calcareous nannofossil

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146 J. M. Castro et al.

biostratigraphic schemes, resulting in a rather precisecorrelation between Lower Cretaceous platforms andbasinal settings.

2. Geological setting, depositionalenvironments and stratigraphy

The Prebetic Zone of Alicante represents the moredistal part of the Prebetic Platform and its transitionto hemipelagic environments. Therefore, shallowplatform and hemipelagic sediments present verticaland lateral facies changes between them (Granier,1994; Castro & Ruiz-Ortiz, 1994, 1995; Ruiz-Ortiz &Castro, 1998; Castro, 1998; Aguado et al., 1999).

The Upper Barremian–Middle Cenomanian inter-val in the Prebetic of Alicante has been subdividedinto ten lithostratigraphic formations (Castro, 1998),seven of which are composed of shallow platformlimestones, and the other three of hemipelagic sedi-ments. Lateral and vertical changes between them canbe observed, as demonstrated in Figure 2. All of theformations show an overall facies change from theproximal northern sections towards the more distalsouthern outcrops.

2.1. Almadich Formation (sensu Castro, 1998)

This formation is composed of alternating hemi-pelagic marls and marlstones, with rare fine-grainedpeloidal packstones. Locally, a thick level of blackshales and dark marls occurs. This unit is richin pelagic fauna, with ammonites and planktonicforaminifers, and calcareous nannofossils (Aguadoet al., 1999). Its age, deduced from the three fossilgroups present, ranges from late Barremian to latestAptian in the more distal outcrops, and from lateearly Aptian to mid Aptian (Gargasian) in the moreproximal sections (Figure 2). The formation wasdeposited on the distal part of a carbonate ramp, attimes under anoxic/dysoxic conditions.

Figure 1. A, simplified geological map of the Iberian peninsula. B, geological map of SE Spain and location of the studyarea. C, location of the Lower Cretaceous outcrops; the main sections studied correspond to the following outcrops: Sa

de Mariola (4 sections), Benicadell (3), Planes (1), Seguilı (2), Sa Penon (1), Castell de la Solana (5), Carrascal deParcent (11), Javea (4), Cau (2), Llorenca (3), Puig Campana (2), Sa Helada (2), Cabezon de Oro (2).

2.2. Llopis Formation (sensu Castro, 1998)

The Llopis Formation is restricted to the morenorthern and proximal sector of the study area, as itchanges laterally towards the south into the AlmadichFormation (Figure 2). It is composed of calcarenites,coral boundstones and rudist floatstones, with rareintercalations of marls. It varies considerably in thick-ness (30–190 m) and facies laterally. The changes inthickness are irregular, and interpreted as reflecting

Biostratigraphy of the Aptian–Middle Cenomanian platform to basin domain, Alicante, Spain 147

local variations in the subsidence rate (Castro, 1998;Castro & Ruiz-Ortiz, 2000). Facies change fromdominant rudist floatstones in proximal areas tocalcarenites and marls in the distal sections.

The age of this formation has been accuratelydetermined as latest Barremian–early Aptian bymeans of the benthonic foraminifers and rudistspresent in the limestones, and the ammonites presentin the lowermost beds in the more distal outcrops.Ammonites from the underlying and overlying marlshave also helped to date the formation, which wasdeposited on a shallow carbonate platform in diversesedimentary environments ranging from lagoon tobarrier reef and open middle platform.

Figure 2. Chronostratigraphic and lithostratigraphic scheme for the Barremian–Cenomanian succession of the Prebetic ofAlicante (time scale from Gradstein et al., 1994). B. units: biostratigraphic units discussed herein.

2.3. Seguilı Formation (sensu Castro, 1998)

This formation is 80–380 m thick and composedmainly of grey limestones with rare, thin beds ofmarls. The lithofacies associations are highly diverse,

with rudist floatstones predominant, accompanied byrudstones, mudstones, grainstones and packstones.

The age of the formation, deduced from thebenthonic foraminifers, ranges from Gargasian toearliest Albian. Lateral and vertical relationshipsbetween the Seguilı, Almadich and Sacaras formations(Figure 2) provide very valuable biostratigraphicinformation, allowing calibration of the distribution ofthe benthonic foraminifers with that of the openmarine fauna of ammonites and planktonic fora-minifers, and with calcareous nannofossils present inthe Almadich Formation (Aguado et al., 1999).

The Seguilı Formation reflects deposition indiverse environments within a shallow carbonateplatform. Lagoonal facies are the best developed;other facies associations present correspond to shallowcalcarenitic or reef barrier, open platform, and at thebase of the formation, tidal influenced mixedcarbonate-terrigenous environments (Ruiz-Ortiz &Castro, 1998).

148 J. M. Castro et al.

2.4. Sacaras Formation (sensu Vilas et al., 1982)

This formation is composed of alternating ochre lime-stones and marls, with a variable content of quartz.The facies change gradually from proximal sections,where calcarenites, massive corals and marls contain-ing abundant planar orbitolinids are present, to distalparts, characterized by nodular limestones with redalgae and a higher proportion of marls and quartz, andeven alternations of dark grey marls and hummocky,cross-stratified calcarenites.

The formation is Albian in age. It has been datedmainly on the basis of benthonic foraminifers, but alsopartly on calcareous nannofossils recovered fromseveral intercalated hemipelagic levels. It wasdeposited on a broad open platform with a moderateflux of terrigenous sediments from the continent(Castro, 1998). The facies on this platform changegradually towards the south to deposits that reflectdeeper and more distal environments.

2.5. Jumilla Formation (sensu Martın-Chivelet, 1993)

This formation is composed largely of grey limestoneswith rudists. The most representative facies are float-stones, but rudstones, calcarenites, mudstones, coralboundstones, marlstones and, locally, black pebblesare also present. Its age is considered to be middle lateAlbian, as deduced from the composition of thebenthonic fauna, principally the orbitolinids, and alsothe rudists. The formation was deposited on a shallowcarbonate platform, in which a lagoon was flanked bya high-energy barrier of large carbonate sand bodiesand coral-rudist patches.

2.6. Caliza de Jaen Formation and DolomıticaFormation (sensu Garcıa-Hernandez et al., 1982)

These two formations are coeval (Figure 2), differ-entiated only by the presence or absence of dolomite.The Caliza de Jaen Formation has been subdividedinto two informal members: a lower unit composed ofsandy calcarenites and marls, with abundant largeorbitolinids, and an upper unit of peloidal limestoneswith calcispheres, orbitolinids and alveolinids. TheDolomıtica Formation is made up of dolomites,within which facies equivalent to those of the Calizade Jaen Formation can occasionally be recognized.

The age of both formations has been established aslatest Albian–middle Cenomanian, based mainlyupon the presence of benthonic and rare planktonicforaminifers. The formations were deposited on anopen platform, in which the sedimentary environ-mental conditions gradually changed from a mixed

carbonate terrigenous to a pure carbonate system,with an overall transgressive tendency.

2.7. Represa Formation (sensu Van Veen, 1969)

This formation represents the distal equivalent of theupper Albian part of the Sacaras, Jumilla and Calizade Jaen formations (Figure 2). It is composed ofseveral hundreds of metres of hemipelagic marlsand marlstones, and grades laterally to a 5-m-thickcondensed glauconite-rich level (Cabezon de Orosections). It contains echinoids, ammonites, plank-tonic foraminifers and calcareous nannofossils thatindicate a late Albian age. It was deposited on a distalhemipelagic ramp, with swells surrounded by rapidlysubsiding areas, controlled by local tectonics.

2.8. Quipar-Jorquera Formation (sensu Comas et al.,1982)

This formation represents the distal equivalent of theCaliza de Jaen Formation (Figure 2). It is composedof a 550-m-thick succession of hemipelagic marls andmarlstones, with nodular chert, locally affected byslumping (Granier, 1987). It ranges in age from latestAlbian to Maastrichtian, and was deposited on a distalramp, with resedimentation processes active duringthe early Cenomanian. We studied the part of theformation that has been dated as latest Albian–middleCenomanian on the basis of planktonic foraminifers(Granier, 1987).

3. Biostratigraphy

The biostratigraphic distribution of benthonic fauna isstrongly dependent on ecological conditions, resultingin significant differences between the biozonationsestablished in diverse regional settings. There aremany references on the biostratigraphy of benthonicforaminifers for the Lower Cretaceous of the PrebeticZone (Busnardo et al., 1968; Fourcade, 1970;Fourcade et al., 1972; Garcıa-Hernandez, 1978,1981; Azema et al., 1979; Granier, 1987; Masseet al., 1992; Martın-Chivelet, 1993, 1994; Castro &Ruiz-Ortiz, 1995; Castro, 1996, 1998). In addition,several studies have presented the results of bio-stratigraphic investigations on benthonic foraminifersfrom other Alpine domains (Moullade, 1974;Masse, 1976; Peybernes, 1976; Bartenstein, 1979;Arnaud-Vanneau, 1980; Neumann & Schroeder,1981; Pascal, 1984). Schroeder & Neumann (1985)published a synthesis of the biostratigraphic data ofthe mid-Cretaceous benthonic foraminifers of theMediterranean region.

Biostratigraphy of the Aptian–Middle Cenomanian platform to basin domain, Alicante, Spain 149

The almost continuous record of abundant, diver-sified, and well-preserved benthonic foraminifers fromthe Prebetic carbonate platforms has allowed theconstruction of a biostratigraphic scheme that addssignificant data to those previously published from thePrebetic domain (Garcıa-Hernandez, 1981; Masseet al., 1992; Martın-Chivelet, 1993). Ten biozones,based on the vertical distribution of shallow-waterbenthonic taxa, are proposed here. Because of theoccurrence of pelagic organisms either in interbeddedlayers or in heteropic hemipelagic units, the proposedbiozones have been directly calibrated to theestablished ammonite and calcareous nannofossilschemes, resulting in a substantial improvement of thebiostratigraphy and chronostratigraphy of the LowerCretaceous carbonate platform successions of thePrebetic domain, which possibly can apply to otherTethyan areas. The vertical distributions of selectedshallow-water benthonic foraminifers, planktonicforaminifers and ammonites are shown in Figure 3,plotted against the formations studied in the Alicantearea and the standard zones based on ammonites andcalcareous plankton (foraminifers and calcareousnannofossils). In Figure 4 the proposed biozones arecompared with those identified by previous authors.

Biostratigraphic unit 1. This unit occurs in the LlopisFormation (Figures 2, 3). It is an assemblage biozonethat is characterized by the presence of Choffatelladecipiens Schlumberger, Neotrocholina friburgensisGuillaume & Reichel (Figure 5A) and Palorbitolinalenticularis Blumenbach (Figure 5H). Other taxapresent are Debarina haounerensis Fourcade & Raoult,Derventina filipescui Neagu (Figure 5D), Dictyoconussp., several species of the genus Orbitolinopsis [O.cuvillieri Moullade (Figure 5F), O. gr. kiliani Silvestri,O. kiliani (Figure 5B), O. buccifer Arnaud-Vanneau& Thieuloy (Figure 5G), O. praesimplex Schroeder(Figure 5E) and O. pygmaea Arnaud-Vanneau], andParacoskinolina maynci (Chevalier) (Figure 3).

The vertical distribution of the taxa within unit 1allows us to differentiate two associations, theirboundary being defined by the first occurrence of O.buccifer, O. praesimplex and O. pygmaea (Figure 3).Nevertheless, this differentiation can be made onlylocally and, therefore, has not been used to definea formal biostratigraphic unit. It would be theequivalent of biozone 1 (with O. cuvillieri andRectodictyoconus? giganteus) of Masse et al. (1992).This seems to correlate with the O. gr. kiliani andO. praesimplex Zones of Garcıa-Hernandez (1981),which respectively correspond to the two associationsrecognized here (Figure 4).

Following the previous zonations, the age of unit 1is latest Barremian–early Aptian p.p. (earlyBedoulian). This age assignment is supported by dataon other fossil groups. In this unit, which is rich inrudists, Offneria cf. interrupta Paquier, Pachytraga sp.and Monopleuridae have been recognized (J. P.Masse and P. W. Skelton, pers. comm., 1998), thefirst two taxa being characteristic of the Lower Aptian(Masse et al., 1992; Masse, 1995). Moreover, in thebasal part of the Llopis Formation in the Castell de laSolana section, and above a bed containing Choffatelladecipiens, there is a marly level with ammonites:Barremites strettostoma (Uhlig), Kutatissites sp.,Procheloniceras cf. pachistephanum (Uhlig) and Pseudo-haploceras gr. matheroni (d’Orbigny) (Figure 3). Thisassociation indicates the uppermost Barremian (upperpart of the Sarasini Zone) or the basal Aptian (lowerpart of the Tuarkyricus Zone). Moreover, higherin the Llopis Formation, several specimens ofDeshayesites sp., of early Aptian age, were collected.Finally, in the more distal areas the lower part of theAlmadich Formation (which is the lateral equivalentof the Llopis Formation) contains, among otherammonites, Deshayesites cf. luppovi Bogdanova, D. cf.euglyphus Casey and D. forbesi Casey, forms whichcharacterise the Weissi Zone.

The data provided by planktonic foraminifersfrom the lower part of the Almadich Formation indistal areas agree with those provided by ammonites(Figure 3). Hence, the planktonic foraminiferalassemblages, which are mainly composed of repre-sentatives of the Praehedbergellidae (Aguado et al.,1999) such as Blefuscuiana (B. aptiana, B. daminiae,B. excelsa, B. infracretacea, B. laculata, Blefuscuiana sp.cf. B. praetrocoidea), Blowiella (B. blowi), Gorbachikella(G. kugleri) and Praehedbergella (P. sigali, P. tuschep-sensis), characterise the Upper Barremian–LowerAptian B. blowi Zone of Moullade (1974), or the P.kutnetsovae and B. blowi Zones of Moullade et al.(1998).

The calcareous nannofossils from the same levelscorrespond to the Hayesites irregularis nannofossilZone (Thierstein, 1971), and NC6 Zone of Moulladeet al. (1998), which are of early Aptian age.

Biostratigraphic unit 2. Unit 2 correlates with thebiozones of Praeorbitolina-Mesorbitolina, Iraqia simplex,and Dictyoconus pachymarginalis, based on the firstappearance of O. (Mesorbitolina) minuta of Masse et al.(1992) (Masse, pers. comm., 2000). It also correlateswith the ‘beds’ with Praeorbitolina and Mesorbitolinalotzei, the Iraqia simplex Biozone, and the ‘beds’ withMesorbitolina parva defined by Garcıa-Hernandez(1981) (Figure 4). It is almost devoid of shallow-water

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Biostratigraphy of the Aptian–Middle Cenomanian platform to basin domain, Alicante, Spain 151

benthonic forms because it is entirely within thehemipelagic Almadich Formation. Only a few speci-mens of Palorbitolina lenticularis are present in themore proximal sections of Benicadell (Figure 1).Champetier (1972) also recorded Orbitolina (Mesorbi-tolina) lotzei Schroeder and Orbitolina (Mesorbitolina)parva Douglass from the same section. Therefore, thecorrelation has been based on the presence of otherfossil groups and on its stratigraphic position betweenbiozones 1 and 3.

Unit 2 contains ammonites, planktonic foraminifersand calcareous nannofossils that indicate a late Early–early Late Aptian age. The ammonites are locallyabundant (Busnardo et al., 1968; Company et al.,1982; Castro, 1998; Aguado et al., 1999) and allowrecognition of the Deshayesi, Furcata and Sub-nodosocostatum zones (Hoedemaeker et al., 1993).The following common planktonic foraminifers(Aguado et al., 1999) led to the identification of thezones: B. blowi (Moullade et al., 1998), Schackoina

cabri (Bolli, 1959; Moullade et al., 1998), Globigerinel-loides ferreolensis (Moullade, 1966; Moullade et al.,1998), and G. algerianus (Moullade, 1966).

The calcareous nannofossil assemblages belong tothe Hayesites irregularis Zone and to the lower part ofthe Rhagodiscus angustus Zone (Applegate & Bergen,1988; Aguado et al., 1996, 1999; Figure 3), andcorrelate with biozones NC6A and the lower part ofNC6B of Moullade et al. (1998).

Biostratigraphic unit 3. This unit appears within thelower part of the Seguilı Formation in the northernsections (Figure 1) and disappears laterally towardsthe south and south-east where it is replaced by theAlmadich Formation (Figure 2). The base of thisinterval biozone is defined by the first occurrence ofOrbitolina (Mesorbitolina) texana Roemer (Figure 5I),referred to Orbitolina minuta in Masse et al. (1992).Other taxa present are Nautiloculina cretaceaPeybernes, Orbitolinopsis sp., Sabaudia auruncensisChiocchini & Di Napoli (Figure 5J) and, occasionallyin the lowermost beds, Derventina filipescui (Figure 3).

Unit 3 correlates with biozone 5 (Orbitolinopsisreticulata and O. aquitanica) of Masse et al. (1992) andwith the lower part of the Mesorbitolina texana Biozoneof Garcıa-Hernandez (1981) (Figure 4). Its age couldbe late Aptian p.p., following Garcıa-Hernandez(1981) or, more precisely, mid Aptian (Gargasian)after Masse et al. (1992).

In the study area, the correlation with theequivalent levels of the upper part of the AlmadichFormation in the more distal Cau and Sierra Heladasections (Figures 1, 2) enables a more accurate datingfor this unit. These levels have provided ammonitesthat are characteristic of the Melchioris Zone (Para-hoplites cf. melchioris Anthula and Colombiceras tobleriJacob) and the Nolani Zone (Acanthoplites nolaniSeunes and A. gr. aschiltaensis Anthula) (Granier,1987; Castro, 1998; Aguado et al., 1999). The plank-tonic foraminifers found in the same levels belong tothe G. algerianus, H. trocoidea and T. bejaouaensiszones. The calcareous nannofossils contained in theselevels belong to the R. angustus Zone, which correlateswith the upper part of the biozone NC6B of Moulladeet al. (1998). These data suggest that the age of unit 3is late Middle–early Late Aptian (late Gargasian–earlyClansayesian) (Figure 3).

Figure 4. Correlation between the biozonation proposedin this work and the previously published biozonesmentioned in the text. Garcıa-Hernandez (1981) bio-zonation: A, O. cuvillieri; B, O. praesimplex; C, M. lotzeiand I. simplex; D, M. texana; D1, P. cuvillieri; E, N.conulus; F, M. aperta. The distribution of selectedbenthonic taxa according to Schroeder & Neuman(1985) are also plotted.

Biostratigraphic unit 4. This unit is recorded within themiddle part of the Seguilı Formation, which repre-sents the maximum horizontal extent of this formation(Figure 2). It is an interval biozone defined fromthe first occurrence of Orbitolina (Mesorbitolina)subconcava Schroeder, referred to as O. (M.) texana in

152 J. M. Castro et al.

Biostratigraphy of the Aptian–Middle Cenomanian platform to basin domain, Alicante, Spain 153

Masse et al. (1992), and the first occurrence ofSimplorbitolina manasi Ciry & Rat (Figure 5L). Themost characteristic taxa of this unit are Pseudochoff-atella cuvillieri Deloffre (Figure 5M) and Simplorbi-tolina chauvei Fourcade (Figure 5K), which canappear at the same level or somewhat higher than O.(M.) texana in different sections. Other taxa encoun-tered in this biozone are Cuneolina gr. pavoniaD’Orbigny, Nautiloculina cretacea, Orbitolinopsis sp.,Pseudocyclammina hedbergi and Sabaudia auruncensis(Figure 5J) (Figure 3).

Unit 4 correlates with biozone 6 (with Pseudochoff-atella cuvillieri) of Masse et al. (1992), and with thePseudochoffatella cuvillieri bed within the Mesorbitolinatexana Biozone of Garcıa-Hernandez (1981) (Figure4). According to Garcıa-Hernandez (1981), this unitis Late Aptian p.p., whereas Masse et al. (1992)indicated the more precise age of latest MiddleAptian.

Our data suggest a slightly different age for unit 4in the sections studied. The unit overlies theAlmadich Formation in the more distal sections. Asdiscussed above, the uppermost part of the AlmadichFormation can be assigned to the upper MiddleAptian and lower Upper Aptian (Melchioris andNolani ammonite zones). P. cuvillieri was formerlyascribed to the upper Middle Aptian (upperGargasian) on the basis of a lateral correlation withthe Subnodosocostatum-Nutfieldiensis ammonitezones in the Pyrenees (Peybernes, 1976). On theother hand, Pascal (1984) indicated a wider verticaldistribution for P. cuvillieri, from the upper MiddleAptian to the basal Albian. Moreover, Granier(1987) ascribed the P. cuvillieri levels in SierraHelada, also considered here (Figures 1, 2), to theLower Albian, based on the presence of Favusellawashitensis Carsey (Figure 5P) in the calcareniticlevels below the P. cuvillieri beds. According toLongoria (1984), however, the first representativesof the genus Favusella are already present in theupper Aptian, so the occurrence of F. washitensiscannot be used for a precise age determination. Inaddition, there are no characteristic Albian forms inthis unit. Consequently, in the absence of ammo-nites, and taking into account the age assignment ofthe overlying biostratigraphic unit 5 (see below) we

consider that unit 4 belongs to the Clansayesian, andis latest Aptian in age.

Biostratigraphic unit 5. This unit occurs in the upper-most part of the Seguilı Formation, present only in thecentral parts of the study area and locally in the SierraHelada, and in the basal part of the Sacaras Formation(Figure 2). It is an assemblage biozone, characterisedby the co-occurrence of the last specimens of P.cuvillieri and S. chauvei with the earliest forms ofHensonina lenticularis Henson (Figure 5N) and Sim-plorbitolina manasi (Figure 5L). Other taxa present inthis unit are O. (M.) texana and Sabaudia auruncensis.

Unit 5 has not been observed in other parts of thePrebetic Zone (Garcıa-Hernandez, 1978, 1981;Masse et al., 1992; Castro, 1996). In the same area ofAlicante, Granier (1987) indicated the co-occurrenceof P. cuvillieri with H. lenticularis in the Puig Campanasections. In other cordilleras it occurs locally (Saint-Marc, 1977; Pascal, 1984. Following these references,and taking into account that P. cuvillieri and S. chauveiare considered to be Aptian forms, and S. manasi andH. lenticularis are regarded as Albian forms by mostauthors, we propose that this biostratigraphic unitbe placed at the Aptian/Albian transition (fromthe ammonite zones of Jacobi to Tardefurcata;Hoedemaeker et al. 1993).

The absence hitherto of unit 5 in other parts of thePrebetic Zone can be attributed to palaeogeography:during its deposition in the Prebetic of Alicante, asedimentary break could have occurred in more proxi-mal parts of the platform (Ruiz-Ortiz & Castro, 1998;Castro, 1998).

Figure 5. Photographs of the benthonic foraminiferal taxa encountered during the course of this study. A, Neotrocholinafriburgensis. B, Orbitolinopsis kiliani. C, Dictyoconus sp. D, Derventina filipescui. E, Orbitolinopsis praesimplex. F,Orbitolinopsis cuvillieri. G, Orbitolinopsis buccifer. H, Palorbitolina lenticularis. I, Orbitolina (Mesorbitolina) texana. J,Sabaudia auruncensis. K, Simplorbitolina chauvei. L, Simplorbitolina manasi. M, Pseudochoffatella cuvillieri (scale barrepresents 1.3 mm). N, Hensonina lenticularis. O, Simplorbitolina conulus. P, Favusella washitensis. Q, Neorbitolinopsisconulus. R, Orbitolina (Orbitolina) gr. sefini-durandelgai.

Biostratigraphic unit 6. This unit is recorded within thelower part of the Sacaras Formation. It is an intervalbiozone, the lower limit of which is defined by the lastoccurrence of P. cuvillieri and S. chauvei; the upperboundary coincides with the first occurrence ofSimplorbitolina conulus Schroeder (Figure 5O). Itis characterised by the presence of S. manasi(Figure 5L); other taxa present are Cuneolina gr.pavonia, H. lenticularis and O. (M.) texana. Unit 6coincides with biozone 7 (with S. manasi) of Masseet al. (1992), and with the S. manasi horizon of the M.texana Zone of Garcıa-Hernandez (1981) (Figure 4).

154 J. M. Castro et al.

According to these authors, its age is early Albian.Following Schroeder & Neumann (1985), and alsogiven its position above biostratigraphic unit 5,it would correlate with the upper part of theTardefurcata and the lower part of Mammillatumammonite zones.

Biostratigraphic unit 7. This unit is within the upperpart of the Sacaras Formation. The lower boundary ofthis interval biozone is defined by the first occurrenceof S. conulus, and the upper one by the first occurrenceof Neorbitolinopsis conulus (Douville) (Figure 5Q). Thelast occurrence of S. manasi is within this unit. Othertaxa present are H. lenticularis and O. (M.) texana(Figure 3).

Unit 7 correlates with biozone 8 and the base ofbiozone 9 of Masse et al. (1992), and with the S.conulus horizon of Garcıa-Hernandez (1981) (Figure4). Its age, according to most authors, is early Albianp.p.–middle Albian p.p. The calcareous nannofossilassemblages found in the upper part of this unitbelong to the Cribosphaerella ehrenbergii Subzone of thePrediscosphaera columnata Zone (Aguado, 1993),which corresponds to the middle and upper parts ofthe Middle Albian. The rare ammonites found inthe unit do not provide additional biostratigraphicprecision. We have only found one specimen ofDesmoceras sp., whereas Granier (1987) indicated theoccurrence in the Sierra Helada section of Oxytro-pidoceras sp., suggesting an age between late EarlyAlbian (Mammillatum Zone) and Middle Albian(Figure 3). This age attribution agrees with the corre-lation proposed by Schroeder & Neumann (1985)(Figure 4).

Biostratigraphic unit 8. This unit comprises theuppermost part of the Sacaras Formation, the entireJumilla Formation, and the base of the Caliza de JaenFormation (Figure 2). It is a taxon-range zone, char-acterized by the occurrence of N. conulus, the first andlast occurrences of which define its boundaries. Otherforaminifers common within this unit are Cuneolinapavonia parva D’Orbigny, H. lenticularis, Neoiraqiaconvexa Danilova, O. (M.) texana and S. conulus.Some rudists, such as Caprina choffati Douville, arealso present (L. Vilas and J. Martın-Chivelet, pers.comm., 1991).

Neorbitolinopsis conulus (Figure 5Q) is a species thathas been considered a reliable marker for the lowerpart of the Upper Albian in most of the publishedbiozonations (Schroeder & Neumann, 1985) (Figure4). Other authors have considered the first occurrenceof N. conulus to be within the uppermost part of theMiddle Albian (Masse et al., 1992). Following these

authors, we consider that unit 8 ranges from theuppermost Middle Albian to the lower part of theUpper Albian. It correlates with the N. conulus Zoneof Garcıa-Hernandez (1981). Masse et al. (1992)divided this unit into two biozones, taking the firstoccurrence of N. convexa as the boundary betweenthem (Figure 4). This subdivision could be appliedherein to only one section (Seguilı, Figure 1) becauseN. convexa is very rare.

The Jumilla Formation changes distally towards theRepresa Formation, but there are no exposures wherethe transition could be observed. Within the marlylevels of the latter formation, in the southernmostsections (Puig Campana and Cabezon de Oro;Figures 1, 2), there is a glauconitic condensed levelyielding abundant ammonites (Stoliczkaia disparD’Orbigny and Mortoniceras sp. among others). Theirage is between latest Middle Albian (Lautus Zone)and Late Albian (Inflatum and Dispar zones) (Lillo,1973; Granier, 1987; Castro, 1998), supporting theage proposed for unit 8.

Biostratigraphic unit 9. This unit is recorded within thelower part of the Caliza de Jaen Formation, except forthe basal bed. It is an interval biozone. The lowerboundary is defined by the last occurrence of N.conulus, which coincides with the first occurrence ofOrbitolina (Orbitolina) durandelgai Schroeder andOrbitolina (Orbitolina) sefini Henson (Figure 5R).Other taxa present in this biozone are H. lenticularisand Orbitolina (Mesorbitolina) aperta Erman.

Unit 9 correlates with the Mesorbitolina aperta bio-zone of Garcıa-Hernandez (1981), and with the O.(O.) durandelgai Biozone of Martın-Chivelet (1993)(Figure 4). There is a good agreement betweenthe authors in ascribing a latest Albian–earliestCenomanian age to this faunal assemblage in thePrebetic Zone (Figure 4). Following Garcıa et al.(1993), unit 9 correlates with the upper part of theDispar and, probably, the lower part of the Mantelliammonite zones.

Biostratigraphic unit 10. This unit occurs in the upperpart of the Caliza de Jaen Formation. Its basal bound-ary is defined by the first occurrence of Orbitolina(Conicorbitolina) conica D’Archiac. The last occur-rence of O. (M.) aperta, and the first occurrence ofPraealveolina simplex Reichel are within it (Figure 3).The upper boundary in the study area coincides witha major stratigraphic break, and cannot be character-ised biostratigraphically.

The correlation of unit 10 with other biozones fromthe Prebetic is not easy. It is based on the underlyingbiozone, and sequence stratigraphic correlation. It is

Biostratigraphy of the Aptian–Middle Cenomanian platform to basin domain, Alicante, Spain 155

probably equivalent to the interval biozone, withoutfossils, defined by Martın-Chivelet (1993) betweenthe O. (O.) durandelgai Biozone and the Ichtyosarcolitesrudist Biozone (Figure 4). The uppermost biozone ofGarcıa-Hernandez (1981) is the M. aperta Zone,which would correspond to the lower part of our unit10 (Figure 4).

Samples from the upper part of unit 10 yield theplanktonic foraminifer Rotalipora brotzeni Sigal, whichranges from the Lower to Middle Cenomanian. Wepropose, therefore, an Early Cenomanian p.p. (upperpart of the Mantelli ammonite Zone) to MiddleCenomanian p.p. (Rhotomagense Zone) age for thisbiostratigraphic unit.

4. Conclusions

The uppermost Barremian–Middle Cenomanianinterval is represented in the Prebetic Zone of Alicanteby eight formations of mainly shallow platformcarbonates, which were affected by some importanttransgressive episodes that led to the developmentof hemipelagic conditions. Shallow water benthonicforaminifers are common in the successions, andammonites, planktonic foraminifers and calcareousnannofossils are also present.

Our analysis of the vertical distribution of shallow-water benthonic foraminifers, including the orbitoli-nids, has allowed the definition of ten biostratigraphicunits, the correlation of which shows that, in general,the biozonation proposed is in good agreement withthose previously published for the same intervals andfacies. The main difference concerns the identificationof biozone 5 (close to the Aptian/Albian boundary);this is not recognized in other parts of the BeticRealm. Moreover, our data on the hemipelagic fauna(ammonites, planktonic foraminifers and calcareousnannofossils), has enabled us to correlate the biozonesproposed with the scales based on these groups and,thereby, to improve their age assignment. The overallcalibration provides an integrated biostratigraphicscheme that has potential for regional correlation.

Piedra and A. Carrillo at the Geology Department,University of Jaen. This study was co-financed byProjects PB97-0826, PB-960429 and PB-93-1150-C02-02 (DGICYT) and Research Groups 4064 andRNM200 (Junta de Andalucıa).

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