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Palaeogeographic and stratigraphic distribution of mid-late
Oxfordianforaminiferal assemblages in the Prebetic Zone
(Betic Cordillera, Southern Spain)
Distribution paléogéographique et stratigraphique des
associationsdes foraminifères de l’Oxfordien moyen-supérieur de la
Zone Prébétique
(Cordillère bétique, sud-est Espagne)
Federico Olóriz *, Matías Reolid, Francisco J.
Rodríguez-Tovar
Dept. Estratigrafía y Paleontología, Facultad de Ciencias,
Universidad de Granada, Campus Fuentenueva, 18071, Granada,
Spain
Received 29 August 2002; accepted 14 March 2003
Abstract
Middle-Upper Oxfordian assemblages of foraminifera in the
Prebetic Zone (Betic Cordillera, SE Spain) were analysed at the
genus levelto determine their composition, relative abundance,
diversity, and dominance, as well as the size of the specimens. A
relationship has beenestablished between lithofacies,
palaeogeography and composition of foraminiferal assemblages, the
former two also determining thestratigraphic record of these
microfossil assemblages. Two assemblages of foraminifera serve to
identify relatively distal and proximal areasin the Prebetic shelf.
The distal assemblage is characterized by higher diversity,
specimens of greater size, and more abundant planktic
andagglutinated forms. Benthic forms include Ophthalmidium,
Epistomina and colonies of encrusting foraminifera. The proximal
assemblageshows lower diversity, lower abundance of planktic forms,
Epistomina and encrusting nubeculariids, and a greater abundance of
spirillinidsand Reofax. On the whole, planktic foraminifera
decrease upwards in the studied succession, which, together with
decreasing nodularity,could be related to system tract conditions
previously proposed for Oxfordian deposits in the southern
palaeomargin of Iberia.
© 2003 Éditions scientifiques et médicales Elsevier SAS. All
rights reserved.
Résumé
L’étude des associations de foraminifères de la Zone Prébétique
(Cordillère Bétique, Sud-Est de l’Espagne) a consisté en l’analyse
de lacomposition, de l’abondance, de la dominance, de la diversité
et de la taille des foraminifères. Les résultats diffèrent selon
les lithofaciès, lapaléogéographie et la stratigraphie. Nous
présentons ici la répartition des foraminifères en deux assemblages
caractéristiques du secteur distalet du secteur proximal de la
plate-forme. Le premier est caractérisé par une diversité élevée,
une grande taille des individus et par la dominancedes
foraminifères planctoniques, des agglutinants, des Ophthalmidium,
des Epistomina et des foraminifères encroûtants.
L’assemblageproximal est surtout caractérisé par une proportion
moins grande des foraminifères planctoniques et des nubéculaires
encroûtants, parl’absence d’Epistomina et par une grande proportion
de spirillines et de Reofax. Ainsi, les associations varient en
fonction d’un gradientdistal-proximal. L’évolution stratigraphique
des assemblages indique une diminution progressive des
foraminifères planctoniques. Ceci peutêtre interprété, compte tenu
de l’aspect noduleux des lithofaciès, comme résultant de variations
du niveau marin relatif, comme cela avait déjàété proposé dans des
travaux antérieurs sur les sédiments de l’Oxfordien dans la
plate-forme du SE de l’Ibérie.
© 2003 Éditions scientifiques et médicales Elsevier SAS. All
rights reserved.
Keywords: Foraminiferal assemblages; Palaeoecology; Lithofacies;
Palaeogeography; Sequence stratigraphy; Mid-late Oxfordian;
Prebetic
Mots clés : Foraminifères ; Paléoécologie ; Lithofaciès ;
Paléogéographie ; Stratigraphie séquentielle ; Oxfordien
moyen-supérieur ; Prébétique
* Corresponding author.E-mail address: [email protected] (F.
Olóriz).
Geobios 36 (2003) 733–747
www.elsevier.com/locate/geobio
© 2003 Éditions scientifiques et médicales Elsevier SAS. All
rights reserved.doi:10.1016/j.geobios.2003.03.006
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1. Introduction
Oxfordian deposits register the first phase of
pelagic-hemipelagic sedimentation in the Prebetic Zone after
devel-opment of a broad generalized carbonate shelf
environmentduring the Early-Middle Jurassic. Study of the Oxfordian
isof great relevance in determining the structuring of the
sub-Iberian palaeomargin, the development of the
epicontinentalshelf and the evolution of its palaeoenvironmental
conditionsduring the Late Jurassic. However, few studies focused
onthese materials have been carried out, and most of these havebeen
of a regional scope. Only recently have updated reportsbeen
published on specific aspects of Oxfordian fossil assem-blages
concerning sponge bioherms (Acosta et al., 1988),ammonite
biostratigraphy (Olóriz et al., 1999) and macroin-vertebrate
taphonomy (Olóriz et al., 2002a, b).
Analysis of microfacies and foraminiferal assemblages iscrucial
to characterize palaeoenvironmental conditions in theepicontinental
shelf that developed during the Late Jurassic.Early papers on these
topics focused on the biozonation ofthe uppermost Jurassic-Lower
Cretaceous interval (García-Hernández, 1978, 1981; García-Hernández
and López-Garrido, 1979). Subsequently, García-Hernández et
al.(1981) began to study Oxfordian lithofacies and
microfacies,which have been characterized in detail in recent
papers(Olóriz et al., 2002a).
The present study comprises the first detailed analysis ofthe
composition of foraminiferal assemblages, registered in
aproximal-distal gradient along the epicontinental shelf
thatdeveloped on the southeastern margin of Iberia during
theMiddle-Late Oxfordian (Antecedens-Bifurcatus Chron-zones). The
integrated analysis of these assemblages (com-position, abundance
and diversity) and their relation withlithofacies identified will
facilitate their interpretation in thecontext of the environmental
evolution that occurred on thisshelf environment.
2. Geological setting
The studied outcrops are located in the Prebetic Zone(Fig. 1),
the outermost and most northerly part of the BeticCordillera (SE
Spain), which is divided into internal andexternal sectors
(Jerez-Mir, 1973). The Internal Prebetic isstructured in folds and
presents a thicker and more completeMesozoic cover, with a
predominance of marine deposits.The External Prebetic is structured
in tectonic sheets and itsMesozoic cover is thinner, records
numerous stratigraphicgaps, and shows a predominance of Jurassic
with respect toCretaceous deposits and an abundance of shallow
facies oflagunal-marine type with continental intercalations.
Fromthe palaeogeographic standpoint, the Prebetic Zone repre-sents
part of the epicontinental marine shelf system thatdeveloped on the
S-SE margin of Iberia during the Mesozoic,with the Algarve shelf
(S. Portugal) being the westernequivalent. The External and
Internal Prebetic correspond,respectively, to the relatively
proximal and distal palaeogeo-
graphic domains. Upper Jurassic outcrops in the Prebetic
areusually grouped into two sectors, central and eastern
ones(Olóriz et al., 1992), the former corresponding to Sierra
deCazorla and Sierra de Segura, and the latter corresponding tothe
outcrops further to the east. The western sector is onlyknown
through data from subsurface geology.
The present study is focused on the stratigraphic
intervalranging from the Antecedens Zone (Middle Oxfordian) to
theBifurcatus Zone (Upper Oxfordian). The studied successionis
bounded at the base by a discontinuity at the top of Lowerand
Middle Jurassic oolitic limestones and dolomites. Theupper boundary
is recognized by the record of Epipeltocerasand is usually related
to a slight increase in the clay content.Relatively distal areas of
the shelf (Internal Prebetic) arecharacterized by lithofacies with
abundant lumps and on-coids of nubeculariids, and show more
condensed sectionscomposed of deposits corresponding to the lumpy
lithofaciesgroup (Olóriz et al., 2002a). A high siliciclastic
content isfound in the more proximal areas (External Prebetic),
whichshow a predominance of marl-limestone rhythmites in thecentral
sector of the External Prebetic and of spongiolithiclimestones
eastwards.
3. Materials and methods
Four profiles were selected (Figs. 1 and 2), two belongingto the
External Prebetic (central sector: Riogazas-Chorro II;eastern
sector: Pozo Cañada) and two to the Internal Prebetic(Navalperal
and Río Segura). Detailed previous studies ofthese profiles have
been carried out by Olóriz et al. (1999,2002a).
Riogazas-Chorro II profile (RGCHSP): Located in thewestern part
of Sierra de Cazorla (province of Jaén). Thestudied Oxfordian
succession, approximately 8.4 m thick, isformed by 0.2 m of
limestone with ferruginous ooids, 0.6 mof spongiolithic limestone
and approximately 7.6 m of marl-limestone rhythmite, which at the
base presents a microbialbuildup with sponges.
Pozo Cañada profile (PC): Located in a small ravine tothe SE of
the village of Pozo Cañada (province of Albacete),and continuing
along the whole northern slope of Sierra delChortal. The Oxfordian
succession analysed, measuring ap-proximately 13.5 m thick, begins
with a level of limestonewith ferruginous ooids, 0.1 m thick, above
which are 13.4 mof spongiolithic limestone.
Navalperal profile (NV): Located in Sierra de Segura(province of
Jaén), on the W slope of the Calar de Navalperal.The stratigraphic
succession studied in the Oxfordian isabout 11 m thick, and mainly
composed of nodular-likelimestones. The bottom 2 m are dolomitized
and possess onlyfew, poorly preserved fossils. Above this level are
1.5 m oflumpy-oncolitic limestone, 2.7 m of condensed
lumpy-oncolitic limestone and, finally, 4.8 m of
lumpy-oncoliticlimestone.
Río Segura profile (RS): Located in Sierra de Segura(province of
Albacete), between the villages of Yeste and
734 F. Olóriz et al. / Geobios 36 (2003) 733–747
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Santiago de la Espada. The studied Oxfordian succession is11 m
thick. The bottom 2.8 m are formed by nodular-likelimestones
intercalated with well-stratified limestone beds.Following these
are 1.6 m of condensed lumpy-oncolitic andmore nodular limestone
with abundant ammonoids. Finally,there are 6.6 m of lumpy-oncolitic
limestone in minor se-quences of decreasing nodularity.
The foraminiferal assemblages were studied by analysing90 thin
sections obtained from 52 sampling stations. Westudied and compared
microfossil assemblages registered indeposits with high carbonate
content, such as the lithofaciesbelonging to the spongiolithic
limestone and lumpy lime-stone lithofacies groups. Thus, we
analysed the sessilebenthic foraminiferal assemblages together with
the rest ofthe assemblage of vagile foraminifera. The former are
espe-cially important in relation to sponges and biogenic
encrust-ments to interpret eco-sedimentary conditions, as noted
byGaillard (1983) and Olóriz et al. (2002a). The main
limitationencountered with this approach was the difficulty of
distin-guishing some genera of foraminifera in thin sections, as
was
the case of nodosarids (e.g. Nodosaria-Dentalina
andLenticulina-Astacolus) and nubeculariids (e.g.
Nubecularia-Nubeculinella). We studied more than 10 600
specimenscorresponding to 42 genera, including Tubiphytes and
Koski-nobullina; the systematic position of the latter two taxa
hasnot been definitively established, but in many cases they
havebeen interpreted as encrusting foraminifera (Werner,
1986;Leinfelder et al., 1993a; Schmid, 1995, 1996). Three
compo-sitional spectra were considered, and pie-diagrams were
con-structed to represent the foraminiferal assemblages (Figs. 2,3,
5 and 6):
• Spectrum A. This represents the whole assemblage andconsists
of three groups of foraminifera differentiatedaccording to their
lifestyle: a) planktic, b) vagile benthicand c) sessile
benthic.
• Spectrum B. This represents the internal composition ofthe
assemblage of vagile benthic foraminifera, and isformed by five
components: a) ophthalmidiids; b) spirill-inids; c) nodosarids; d)
agglutinated forms; and e) otherforaminifera, generally present as
secondary components.
Fig. 1. Location and geological sketch of the Prebetic Zone
(Betic Cordillera, SE Spain), with indication of the sections
studied (NV = Navalperal, PC = PozoCañada, RGCHSP = Riogazas-Chorro
II, RS = Río Segura).Fig. 1. Localisation géographique et cadre
géologique de la Zone Prébétique (Cordillère Bétique, Sud-Est de
l’Espagne), avec indication des coupes étudiées(NV = Navalperal, PC
= Pozo Cañada, RGCHSP = Riogazas-Chorro II, RS = Río Segura).
735F. Olóriz et al. / Geobios 36 (2003) 733–747
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Fig. 2. Lithological columns for sections studied in the
Internal (NV, RS) and the External Prebetic (central sector:
RGCHSP; eastern sector: PC) showinglithofacies distribution and
biostratigraphy. Composition of foraminiferal assemblages: A (total
assemblage), B (vagile benthics), C (sessile benthics). Changesin
the abundance of encrusting nubeculariids and diversity of
foraminifera in the succession studied.Fig. 2. Logs lithologiques
des coupes étudiées dans le Prébétique Interne (NV, RS) et Externe
(secteur central : RGCHSP ; secteur oriental : PC) montrant
larépartition des lithofaciès et la biostratigraphie. Composition
des associations de foraminifères : A (ensemble de la faune), B
(benthiques vagiles), C (bentiquessessiles). Changements dans
l’abondance des nubécularidés encroûtants et diversité des
foraminifères dans la succession étudiée.
736 F. Olóriz et al. / Geobios 36 (2003) 733–747
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• Spectrum C. This represents the internal composition ofthe
assemblage of sessile benthic foraminifera, and isformed by four
components: a) siliceous agglutinatedforaminifera; b) Bullopora; c)
Tubiphytes; and d) un-specified sessile foraminifera. Colonial
encrusting fora-minifera were not included, due to the difficulty
ofdistinguishing the number of individuals in a colony onthe basis
of thin sections (e.g. Nubecularia, Nubecu-linella and
Koskinobullina). A separate analysis wasperformed for nubeculariids
because of their great im-portance in both biogenic encrustments
and oncoids.
Other palaeoecological parameters studied that character-ize
foraminiferal assemblages were: a) abundance (number
of specimens recorded per unit of surface area in thin
sec-tion); b) diversity, both in number of genera and the
alphaindex (the a-diversity of Fisher et al., 1943); c) dominance,
atthe genus level; and d) specimen size. Following
palaeoeco-logical interpretations made of shell morphology
(Bernhard,1986; Corliss, 1991; Nagy, 1992; Tyszka, 1994; Nagy et
al.,1995), for the assemblages of benthic foraminifera recordedwe
established three groups, which are related to their micro-habitat
depth within the substrate:
• Epifaunal foraminifera: living on the sediment surfaceor in
the topmost centimetre (Corliss, 1991). This groupincludes all the
sessile foraminifera, as well as ophthal-midiids, miliolids, spiral
agglutinated foraminifera (Am-modiscoides, Glomospira and
Trochammina) and spiralcalcareous foraminifera (spirillinids,
Epistomina, Tro-cholina, etc), except Lenticulina.
• Shallow infaunal foraminifera: living in the sediment ata
depth of less than 2 cm (Corliss, 1991), and formed byelongated
agglutinated foraminifera, predominantlyuniserial ones and those
which may be streptospiral orplanispiral in their initial states
(Ammobaculites, Ammo-marginulina and Haplophragmium), as well as by
elon-gated calcareous foraminifera (nodosarids such as No-dosaria,
Dentalina and Planularia).
• Ubiquitous foraminifera: represented both by Lenticu-lina,
which tolerates a wide range of microhabitats, fromepifaunal to
deep infaunal (Tyszka, 1994), and by unis-erial (Reophax) and
biserial (undifferentiated textular-ids) agglutinated foraminifera,
the latter varying be-tween shallow and deep infaunal
microhabitat.
Finally, analysis of fragmentation was performed in orderto test
whether the foraminiferal assemblages registered cor-responded to a
greater or lesser degree to palaeobiocenosis,or whether distortions
had occurred due to post-mortemtransportation. According to Parson
and Brett (1991), thefragmentation threshold for each specimen is
variable, and soit is preferable to use a single species or genus
found in all theenvironments registered. In the present case, a
preliminaryanalysis enabled us to determine that fragmentation
wasrestricted almost exclusively to the genus Lenticulina. In
theremaining groups, no more than 5% of specimens were foundto be
fragmented. Thus, Lenticulina was chosen for thetaphonomic study,
being a ubiquitous organism that ispresent in all the profiles and
one that is interpreted as beingendobenthic and epibenthic (i.e.
ubiquitous as consideredabove).
4. Results
In general terms, and after excluding the
foraminiferalassemblage recorded in the ferruginous oolitic
limestonelithofacies due to its local record, the average
foraminiferalassemblage in the Prebetic domain corresponding to
theTransversarium? and Bifurcatus Zones is abundant and
di-versified, dominated by vagile benthic foraminifera
(58%),followed by planktic foraminifera (30%) and sessile
benthic
Fig. 3. Composition of foraminiferal assemblages according to
lithofacies.Pie-diagrams as in Figure 2.Fig. 3. Composition des
associations de foraminifères par rapport au litho-faciès.
Diagrammes circulaires comme dans la Figure 2.
737F. Olóriz et al. / Geobios 36 (2003) 733–747
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foraminifera (12%). The assemblage of vagile benthic
fora-minifera mainly consists of agglutinated forms (36%)
andspirillinids (28%). Nodosarids and porcelaneous foramin-ifera
are normally present as minor components. Plankticforaminifera are
represented exclusively by the genus Globu-ligerina. The assemblage
of sessile benthic foraminifera isdominated by nubeculariids.
Non-colonial sessile benthicforaminifera are dominated by siliceous
agglutinated fora-minifera (44%), followed by Tubiphytes (28%),
while Bul-lopora and other undetermined foraminifera comprise
therest of the assemblage. A detailed analysis of
foraminiferalassemblages in the four profiles selected (Fig. 2)
revealedimportant differences that might be related to the
lithofacies(Figs. 3 and 4), palaeogeography (Figs. 5 and 6) and
stratig-raphy.
4.1. Foraminiferal assemblages and lithofacies
Detailed analysis of the different groups of foraminiferareveals
the close relationship with lithofacies (Fig. 2), interms of
composition, abundance and diversity of the assem-blages
registered. According to lithofacies, the followingfeatures can be
distinguished (Fig. 3):
4.1.1. Ferruginous oolitic limestoneThis limestone level is 10
cm thick, with irregular mor-
phology and ferruginous surfaces that bound small rockybodies.
It is found exclusively in the External Prebetic(Fig. 2) and
possibly belongs to the Antecedens Zone(Acosta, 1989). Its fabric
varies from grain-supported tomatrix-supported, and shows a
packstone-wackestone tex-
Fig. 4. Relative content in significant genera of foraminifera
(>1%) in the assemblages registered, and their diversity
according to lithofacies.Fig. 4. Contenu relatif de genres
significatifs de foraminifères (>1%) dans les associations
enregistrées, avec leur diversité par rapport au lithofaciès.
738 F. Olóriz et al. / Geobios 36 (2003) 733–747
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ture containing abundant ferruginous ooids, peloids, quartzand
bioclasts, mainly fragments of crinoids and foraminifera.
This lithofacies is characterized by a great abundance
offoraminifera, especially planktic foraminifera (81%), in
con-trast to the scarcity of encrusting benthic foraminifera.Among
the vagile benthic foraminifera, there are similarquantities of
spirillinids, nodosarids, agglutinated and otherforaminifera, with
a lesser abundance of ophthalmidiids. Thenodosarids belong mainly
to the genus Lenticulina, showinga thick, large shell (average 270
µm) and frequent fragmen-
tation (72% of the specimens). There is a notably high
pro-portion of Epistomina and Trocholina, which are more abun-dant
than in other lithofacies, and the absence ofnubeculariids is
significant. This lithofacies contains a totalof 14 genera, of
which only 10 exceeded 1% of relativeabundance (Fig. 4), and there
was a strong predominance ofplanktic foraminifera. The a-diversity
value of Fisher et al.(1943) for the assemblage of benthic
foraminifera was 2.7.The benthos is dominated by epifauna, mainly
representedby planispiral calcareous foraminifera.
Fig. 5. Composition of foraminiferal assemblages in pie-diagrams
as in Figure 2. Palaeogeographic distribution and size changes in
selected genera and/orgroups of foraminifera, as well as
foraminiferal diversity, across a proximal (External Prebetic) –
distal (Internal Prebetic) transect in the Prebetic Zone. Legendas
in Figure 2.Fig. 5. Composition des associations de foraminifères
dans les diagrammes circulaires comme dans la Figure 2.
Distribution paléogéographique et changementsde taille dans des
genres et/ou groupes de foraminifères représentatifs, ainsi que la
diversité des foraminifères, à travers un transect allant d’un
domaine proximal(Prébétique Externe) à un domaine distal
(Prébétique Interne) dans la Zone Prébétique. Même légende que la
Figure 2.
739F. Olóriz et al. / Geobios 36 (2003) 733–747
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4.1.2. Condensed and bioclasts-rich lumpy-oncoliticlimestone
This lithologic term refers to limestones of nodular,
lumpyappearance, with indistinct, irregular stratification
surfacesand a large quantity of ammonoids. This lithofacies is
foundonly in the Internal Prebetic, in the lower part of the
BifurcatusZone (Olóriz et al., 2002a) (Fig. 2). The fabric is
intermediatebetween grain-supported and matrix-supported and its
com-ponents show random distribution. The texture is
packstone-wackestone with lumps and oncoids of nubeculariids.
Thislithology shows a high proportion of skeletal grains.
The abundance of foraminifera is high, the assemblagebeing
mainly composed of Globuligerina (45%), vagilebenthic foraminifera,
and to a lesser extent, sessile benthicforaminifera. The vagile
benthic foraminifera are mainlyagglutinated forms, followed by
ophthalmidiids and spirill-inids. The sessile foraminifera are
predominantly siliceousagglutinated and Bullopora. Nubeculariids
are very abundantand constitute a fundamental part of the oncoids.
The pres-ence of fragmented shells is limited exclusively to
specimensof thick-shelled Lenticulina (20%). A total of 23 genera
areidentified, of which 13 are present exceeding 1%, with a
clear
Fig. 6. Composition of foraminiferal assemblages according to
palaeogeography and the stratigraphic interval and horizons
recognized, from the AntecedensZone (Acosta, 1989) to the
Bifurcatus Zone in the Prebetic. Pie-diagrams as in Figure 2.Fig.
6. Composition des associations de foraminifères en fonction de la
paléogéographie, de l’intervalle stratigraphique et des horizons
reconnus, depuis la Zoneà Antecedens (Acosta, 1989) jusqu’à la Zone
à Bifurcatus dans le Prébétique. Diagrammes circulaires comme dans
la Figure 2.
740 F. Olóriz et al. / Geobios 36 (2003) 733–747
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predominance of Globuligerina (Figs. 3 and 4). Thea-diversity
value for the assemblage of benthic foraminiferais 4.6. The
microbenthos is mainly comprised of Ophthalm-idium, Spirillina,
Bullopora, Tubiphytes and Epistomina,which indicates a predominance
of epifaunal microhabitats.
4.1.3. Lumpy-oncolitic limestoneThis lithofacies, recorded
exclusively in the Transver-
sarium? and Bifurcatus Zones in the Internal Prebetic(Fig. 2),
is composed of limestones of nodular-like appear-ance. The fabric
is grain- and matrix-supported, with noparticular distribution of
components. The texture comprisespackstone and wackestone in which
the most common grainsare lumps, oncoids of nubeculariids, peloids
and bioclasts.
The abundance of foraminifera varies greatly, being high-est in
the lumpy-oncolitic limestone that precedes the con-densed
lithofacies. The foraminiferal assemblage is domi-nated by vagile
benthic foraminifera (58%), followed byplanktic foraminifera, and
finally, sessile benthic foramin-ifera (Fig. 3). The assemblage of
vagile benthic foraminiferais dominated by agglutinated forms
(Ammobaculites andReophax). The assemblage of sessile benthic
foraminifera ismainly comprised of Tubiphytes and siliceous
agglutinatedforms. Nubeculariids are very abundant. There is a low
pro-portion of fragmented specimens of Lenticulina (23%). Inthis
lithofacies, we registered a total of 28 genera, of which11
exceeded 1% of relative abundance, with a predominanceof
Globuligerina (Fig. 4). The a-diversity value for the as-semblage
of benthic foraminifera is 4.3. The main micro-habitat in the
microbenthos corresponds to vagile epifauna.Increased occurrence of
sessile epifauna as well as of shallowinfaunal foraminifera, mainly
Ammobaculites, has been reg-istered in the lumpy-oncolitic
limestone recorded in the up-per part of the Bifurcatus Zone.
4.1.4. Spongiolithic limestoneThis lithofacies is composed of
well-stratified limestones
characterized by a great abundance of sponges, which com-prise a
fundamental part of the rock. The lithofacies onlyappears in the
External Prebetic, in the Transversarium? andBifurcatus Zones (Fig.
2). The fabric varies from grain- tomatrix-supported, with a
packstone-wackestone textureshowing bioclasts (e.g. foraminifera,
sponge spicules, frag-ments of echinoderms), lumps, tuberoids and
oncoids ofnubeculariids.
There is a generally high abundance of foraminifera, thesebeing
mainly vagile benthic foraminifera (64%), followed byplanktic forms
and, finally, sessile benthic ones (Fig. 3). Theassemblage of
vagile benthic foraminifera is dominated byspirillinids (43%),
followed by agglutinated forms. The oph-thalmidiids and nodosarids
are the least abundant. The sessilebenthic assemblage is mainly
comprised of siliceous agglu-tinated forms. The proportions of
nubeculariids are high butvariable. Fragmented specimens of
Lenticulina (35%) aremainly the remains of large, thick-shelled
individuals. Thislithofacies presents the largest number of genera
identified
(29), of which 12 appear in a proportion exceeding 1% of
therelative abundance in this assemblage (Fig. 4). There is
loweroverall dominance in this lithofacies, the principal
compo-nents being Spirillina, Globuligerina and Reophax (Fig.
4).Despite the high number of genera identified, their ratio tothe
number of individuals recorded in the benthic foramin-iferal
assemblage provides an a-diversity value of 3.8. In
themicrobenthos, there was observed to be a predominance
ofepifaunal microhabitats and a large proportion of foramin-ifera
with a potentially deep infaunal microhabitat (Reophaxand
Lenticulina).
4.1.5. Marl-limestone rhythmiteThis lithofacies is constituted
of well-stratified limestones
and marls, with a predominance of limestone beds. It isrecorded
in the Transversarium? and Bifurcatus Zones of theRGCHSP profile
(External Prebetic) (Fig. 2). It presents agrain-supported fabric,
constituted of very small homometricgrains (
-
lesser extent, Redmondoides and Ammodiscoides. The Inter-nal
Prebetic is also characterized by the highest proportionsof
ophthalmidiids and the lowest proportions of
spirillinids.Nodosarids are mainly planispiral-shaped, while
uniserialforms are very scarce. With respect to the assemblage
ofsessile benthic foraminifera, there is predominance of sili-ceous
agglutinated foraminifera and of Tubiphytes, in addi-tion to
numerous colonies of nubeculariids. The proportionof fragmented
foraminifera is low, with only Lenticulinapresenting higher values
(22%). The Internal Prebetic has anaverage a-diversity value of
4.3.
4.2.2. External PrebeticThe assemblage is clearly dominated by
vagile benthic
foraminifera, except locally in ferruginous oolitic limestonesat
the base of the succession. There is a notable decrease inthe
proportions of planktic foraminifera and encrusting nube-culariids
in comparison with the Internal Prebetic, especiallyin the central
sector of the External Prebetic in relation to thewidespread record
of marl-limestone rhythmites. The domi-nant assemblage of vagile
benthic foraminifera in the Exter-nal Prebetic is mainly composed
of spirillinids. Agglutinatedforms present similar values in the
central and eastern sectorsof the External Prebetic, but they are
less numerous than inthe Internal Prebetic. In the External
Prebetic, Reophax ismore abundant than Ammobaculites, both of these
generashowing specimens smaller than in the Internal Prebetic.
Theaverage abundance of the ophthalmidiids is clearly lowerthan
that registered in the Internal Prebetic, while nodosaridsare
somewhat more abundant. With respect to sessile fora-minifera,
there is a clear differentiation between the easternand central
sectors, which is related to the change in lithofa-cies. Eastwards
in the External Prebetic, there is a predomi-nance of siliceous
agglutinated foraminifera, while in thecentral sector there are
abundant fragments of Tubiphytes inthe marl-limestone rhythmite.
Colonial sessile foraminiferaare mainly nubeculariids, and they are
much more abundantin the spongiolithic limestone and in microbial
buildup withsponges. There are no colonies of nubeculariids in the
marl-limestone rhythmite. Fragmentation of foraminifera isgreater
than in the Internal Prebetic, although limited almostexclusively
to large specimens of Lenticula. The averagea-diversity value in
the External Prebetic is 3.4, being higherin the eastern sector
than in the central one (a-diversity in thePC profile = 3.6, and in
the RGCHSP profile = 3.3). Thisreduction in a-diversity values in
the more proximal areascoincides with the decrease in the average
size of the mostabundant foraminifera in the assemblages
(Globuligerina,Reophax, Ammobaculites, Lenticulina and uniserial
nodosa-rids), with the exception of Spirillina, which is
slightlylarger.
4.3. Stratigraphic distribution
The stratigraphic variations in foraminiferal assemblagesin the
four profiles studied allow us to differentiate twostratigraphic
intervals (Fig. 2). These stratigraphic intervals
are preceded in the External Prebetic by a horizon comprisedof
ferruginous oolitic limestone, which corresponds to theAntecedens
Zone according to Acosta (1989). This horizoncontains the highest
proportions of planktic foraminifera.Sessile benthic foraminifera
are scarce in the central sector ofthe External Prebetic and absent
from the eastern sector (PC).Epistomina in the central sector and
Trocholina in the easternsector are abundant, as are the
geographically unrestrictedand mainly fragmented Lenticulina (72%).
The scarce sessilebenthic foraminifera mainly correspond to
Bullopora tuber-culata, while nubeculariids are virtually absent.
Globulige-rina presents the highest abundance in the ferruginous
ooliticlimestone showing the largest size registered for this
genus(170 µm). Moreover, the ferruginous oolitic limestone
con-tains the greatest abundance of foraminifera, with the
pre-dominance of Globuligerina, and provides highly
variablea-diversity values for benthic foraminifera (3.9 in
RGCHSPand 1.5 in PC).
Stratigraphic interval I: Corresponds to the Transver-sarium?
Zone and/or to the lower part of the Bifurcatus Zone.It is
characterized by a reduction in the abundance and size
ofGlobuligerina, mainly in the External Prebetic. In the Exter-nal
Prebetic the abundance of encrusting foraminifera in-creases in
relation with the occurrence of both the spongi-olithic limestone
(eastern sector) and the microbial buildupwith sponges (central
sector). The assemblage of vagilebenthic foraminifera in the
External Prebetic is dominated byspirillinids and agglutinated
forms (mainly Reophax), whilein the Internal Prebetic there is a
predominance of the latter(especially Ammobaculites) and/or
Ophthalmidium. Thesessile benthic foraminifera in all the Prebetic
mainly consistof siliceous agglutinated forms, and then Bullopora
tubercu-lata. The high proportion of fragmented Tubiphytes in
thecentral sector of the External Prebetic is related to the
devel-opment of marl-limestone rhythmites. Colonies of
nubecu-lariids are very abundant in this stratigraphic interval,
exceptin marl-limestone rhythmites. Fragmentation in Lenticulinais
high in the central sector of the External Prebetic (49%),but lower
than in the underlying ferruginous oolitic lime-stone. Moreover,
the proportion of specimens of fragmentedLenticulina in the
External Prebetic (43%) is greater than inthe Internal Prebetic
(22%). Nevertheless, contrary trends areobserved for stratigraphic
interval I in the two domains of thePrebetic: the proportion of
fragmented Lenticulina increasesupwards in the External Prebetic,
but a corresponding de-crease occurs in the Internal Prebetic. In
general, thea-diversity values are higher for the assemblage of
benthicforaminifera in the Internal Prebetic (4.3) than in the
ExternalPrebetic (3.5), where the lowest values are recorded in
thecentral sector, related to the known record in
marl-limestonerhythmites. Throughout stratigraphic interval I,
there is atrend for diversity to decrease in the External Prebetic,
and toincrease in the Internal Prebetic. The abundance of
foramin-ifera is greater at the lowermost part of this interval for
all theprofiles studied, although it is less accentuated in the
centralsector of the External Prebetic.
742 F. Olóriz et al. / Geobios 36 (2003) 733–747
-
Stratigraphic interval II: Corresponds to part of the
Bifur-catus Zone (Fig. 2). The most notable feature in this
intervalis the severe reduction in the abundance of Globuligerina.
Inthe central sector of the External Prebetic, the occurrence
ofthis genus diminishes to disappearance upwards in the Bifur-catus
Zone (RGCHSP), but its last occurrence is known closeto the
Transversarium/Bifurcatus boundary eastwards (PC).With respect to
stratigraphic interval I, the record of vagileforaminifera shows:
a) an increase in the relative abundanceof agglutinated forms
(Ammobaculites and Reophax) in theInternal Prebetic (NV and RS),
together with their increasedsize throughout the Prebetic; b) a
reduction in the relativeabundance of Ophthalmidium in the Internal
Prebetic; c) thedisappearance of Epistomina; d) a decrease in the
relativeabundance of uniserial nodosarids; and e) less
fragmentationof Lenticulina in the External Prebetic (36%) in
contrast toslightly higher values in the Internal Prebetic (23%).
In theassemblage of sessile benthic foraminifera, there is an
in-creased occurrence of Tubiphytes, at the expense of
siliceousagglutinated forms, in the Internal Prebetic. In
qualitativeterms, nubeculariids remain the most significant
encrustingforaminifera. The a-diversity values for the assemblage
ofbenthic foraminifera are variable in the different profiles,
andno clear trend was identified. The abundance of foraminiferais
lower than in stratigraphic interval I.
5. Discussion
5.1. Foraminiferal assemblages and palaeogeography
Overall, the clear predominance of vagile benthic fora-minifera
and the abundance of sessile benthic foraminifera inthe microfossil
assemblage registered in the Prebetic domainare characteristic of a
shelf environment. A detailed quanti-tative analysis enables two
type assemblages of foraminiferato be distinguished for the
Prebetic, which are closely relatedto palaeogeography (Fig. 5):
• Distal assemblage. Observed in outcrops from the Inter-nal
Prebetic, and characterized by the following:C Highest proportions
of Globuligerina and of encrust-
ing nubeculariids (Nubecularia-Nubeculinella).C The assemblage
of vagile benthic foraminifera is
dominated by uniserial-agglutinated forms, mainlyAmmobaculites
followed by Reophax, and containsfew specimens of spiral
agglutinated forms (Ammodis-coides, Glomospira and Trochammina).
Ophthalm-idium and Epistomina are present in highest
propor-tions.
C The sessile benthic foraminifera are
predominantlynubeculariids, a fundamental component of the on-coids
in the lumpy lithofacies group, while the remain-ing sessile
benthics are mainly constituted of siliceousagglutinated forms.
C Fragmentation is low, and mainly found in specimensof
thick-shelled Lenticulina. On average, 22% of thespecimens of
Lenticulina are fragmented.
C The largest average sizes of Globuligerina,
Lenticulina,uniserial nodosarids, Ammobaculites and Reophax.
C Highest diversity values for assemblages of
benthicforaminifera.
• Proximal assemblage. Registered in profiles from theExternal
Prebetic. Distinguished from the previouslycharacterized distal
assemblage by the following:C Lower proportions of Globuligerina
and of encrusting
nubeculariids.C Vagile benthic foraminifera are dominated by
spirill-
inids. Lower proportion of ophthalmidiids and agglu-tinated
forms, the latter being less diversified andmainly constituted of
Reophax. Spiral agglutinatedforms are almost non-existent. Among
nodosarids,there is a higher proportion of uniserial forms.
C Sessile benthic foraminifera show the predominanceof
nubeculariids, although their abundance is lowerthan in the distal
assemblage (see above). The relativeabundance of non-colonial
sessile benthic foramin-ifera varies according to lithology.
C Higher proportion of fragmented specimens, mainlythick forms
of Lenticulina (35% in the eastern sectorand 43% in the central
sector) and, to a lesser degree,of Tubiphytes in marl-limestone
rhythmites.
C Smaller average size of foraminifera, except in thecase of
Spirillina.
C Lower diversity values for benthic foraminifera.By
distinguishing these two type assemblages, it is pos-
sible to establish a basic pattern for the distribution of
fora-minifera in relation to the proximal-distal gradient (Fig.
5).In general terms, the foraminiferal assemblages confirm
theincrease in distance from shore towards the Internal
Prebetic,which is mainly reflected in the higher proportion of
plankticforaminifera seawards. In the Internal Prebetic,
particularlynoteworthy is the appearance of Epistomina, which is
tradi-tionally, considered a deep benthic foraminifer found on
theouter edge of the shelf (Bernier, 1984; Samson, 2001). Al-though
present in scarce numbers, the distribution of Epis-tomina is very
significant, and related to intervals whereGlobuligerina is more
abundant.
In this context of proximal-distal differentiation, param-eters
such as the variations in the sedimentation rate, silici-clastic
inflows and the availability of nutrients may deter-mine local
variations in foraminiferal assemblages. Thehigher proportion of
mainly colonial sessile benthic foramin-ifera such as
Nubecularia-Nubeculinella, found in distal ar-eas, may be explained
in terms of the lower sedimentationrate. Their reduction towards
more proximal areas is relatedto increased inflows of
siliciclastics, this situation beingmore marked in the central
sector of the External Prebetic,where marl-limestone rhythmites
predominate. In this sense,the fragmentation of foraminifera
constitutes a valuable toolfor interpreting possible transportation
of their shells. Theincidence of fragmentation is very low among
the differentgroups of foraminifera, generally less than 5% of the
speci-mens, being greater among the nodosarids, especially in
743F. Olóriz et al. / Geobios 36 (2003) 733–747
-
Lenticulina. Fragmented Lenticulina mostly correspond tothick,
sometimes ornamented forms. The proportion of Len-ticulina with
fragmentation is greater towards more proximalareas, becoming more
marked in the central sector, which isrelated to the presence of
marl-limestone rhythmites. Thisdistribution indicates that, on the
whole, Lenticulina remainsproceed from more proximal areas, which
at present do notcrop out, and so the specimens of Lenticulina
resistant totransportation would be observed as the only elements
thatare clearly allochtonous within the foraminiferal assem-blages
studied. The other groups of foraminifera identifiedpresent almost
no fragmentation and could be consideredautochthonous to
para-autochthonous.
The above-described distribution of foraminiferal assem-blages
for the Prebetic is coherent with the interpretationsmade of Middle
Oxfordian benthic foraminifera in a shelf-basin transect in SE
France (Bouhamdi, 2000; Bouhamdi etal., 2000, 2001). The latter
authors related the abundance ofSpirillina on the shelf to the
availability of trophic resources,fundamentally photosynthetic
primary production. This con-clusion is consistent with the greater
proportion of spirillin-ids observed in the lithofacies of
spongiolithic limestone inthe External Prebetic, and with the
higher content of nutrients(Leinfelder et al., 1993b related it to
the presence of spongesin a nutrient- and organic matter-rich
environment, but seeKrautter, 1998). The decreased occurrence of
Spirillina as acomponent of the vagile benthos towards more distal
areas iscompensated by an increase of ophthalmidiids and
aggluti-nated forms, both of which are interpreted as good
indicatorsof distance from the shore (Gaillard, 1983; Bouhamdi,
2000;Bouhamdi et al., 2001). Among the vagile agglutinated
fora-minifera, Reophax is more abundant towards proximal areas,and
Ammobaculites towards distal ones, both genera beingvery abundant
on the whole shelf. According to Tyszka(1994) Reophax would be a
potentially deeper infaunal fora-minifer. Thus, the distribution of
infaunal agglutinated formsobserved in the Prebetic would indicate
palaeogeographicdifferences in the ecological conditions of the
first few cen-timetres within the substrate, which presumably would
bemore unstable landwards. The External Prebetic,
especiallyeastwards, would provide higher productivity (i.e.
ampleavailability of nutrients) evidenced by the abundance of
spir-illinids (Bouhamdi et al., 2001) and sponges (Leinfelder
etal., 1993b). In this context, the presence of shallow
infaunalforms (e.g. Ammobaculites, Nodosaria, Dentalina), as wellas
potentially deep infaunal ones (Reophax), could be inter-preted as
being related to the good oxygenation of the seaf-loor (i.e.
mesothophic conditions following the model pro-posed by Jorissen et
al., 1995). The reduced numbers ofspirillinids and sponges towards
distal areas (Internal Preb-etic) could be indicative of a lower
availability of nutrients(more oligotrophic conditions), which
would mainly be con-sumed on the surface and in the first few
centimetres of thesediment. This would explain the reduction in
numbers of thepotentially deep infaunal genera (e.g. Reophax) with
respectto the shallow infaunal ones (Ammobaculites). Greater
stabil-
ity in seafloor conditions towards outermost areas is in
accor-dance with the data obtained.
5.2. Palaeoenvironmental evolution
Morpho-group distribution, abundance, diversity anddominance, as
well as the relative abundance of calcareouswith respect to
agglutinated forms in foraminiferal assem-blages have been applied
in interpretations based on se-quence stratigraphy (e.g. Cubaynes
et al., 1989, 1990; Bon-net et al., 1991, 1992; Haig and Lynch,
1993; Rey et al.,1994; Hylton and Hart, 2000; Nagy et al., 2001).
However,most of these interpretations were based exclusively
onvariations in the assemblages of benthic foraminifera withina
single lithology. The variety of lithofacies observed in
theprofiles studied in the Prebetic could reflect differences in
theenvironmental conditions that affected the meiofauna, whichwould
make it unwise to interpret relative variations of thesea level
solely on the basis of the microbenthos. For thisreason, a careful
analysis has been made of the relativeabundance of planktic versus
benthic foraminifera in theinterpretations of fluctuations in
relative sea level, taking intoaccount the independence of planktic
forms with respect tothe palaeoecological conditions at the
seafloor.
The initial horizon of ferruginous oolitic limestone, be-longing
to the Antecedens Zone (Acosta, 1989), is character-ized by the
great abundance of foraminifera, by the predomi-nance of planktic
forms and by the scarcity of benthicforaminifera, both vagile and
sessile. The foraminiferal as-semblage presents a mixture of
proximal (i.e. shallow) anddistal (but not necessarily deep)
elements, showing highestabundances for Globuligerina, Epistomina
and Trocholina(the latter being typical of high-energy, shallow
environ-ments). The environmental energy must have been
relativelyhigh, as shown by the abundance of nodosarids with
signifi-cant fragmentation, especially specimens of
thick-shelledLenticulina, which presents in the highest
fragmentation.The scarcity or absence of sessile benthic
foraminifera, on-coids and other biogenic encrustments could be
related to thefact of rapid deposition. The ferruginous oolitic
limestonehas been interpreted as the result of a transgressive
pulsethroughout the Prebetic that gave rise to the start of
LateJurassic hemipelagic deposition over the Early-Middle Ju-rassic
carbonate shelf (García-Hernández et al., 1980, 1989;Acosta, 1989).
Consequently, this could be interpreted asevidence for episodes of
rapid deposition that incorporatederoded materials, such as
ferruginous ooids and lateritic clayminerals (Acosta, 1989), as
well as abundant angular grainsof quartz, delivered from relatively
proximal areas. Both themicrofacies and the state of preservation
of skeletal remainsof macroinvertebrates are congruent with
deposits that oc-curred under storm conditions.
Stratigraphic interval I, corresponding to the Transver-sarium?
and/or the lower part of the Bifurcatus Zones, ischaracterized by a
lesser occurrence of Globuligerina withrespect to the locally
underlying ferruginous oolitic lime-stone, although Globuligerina
abundance remains high.
744 F. Olóriz et al. / Geobios 36 (2003) 733–747
-
Moreover, there is an increase in the record of colonial
sessilebenthic foraminifera (nubeculariids), possibly related to
alower sedimentation rate. The studied area in the centralsector
presents a lower increase in sessile benthic foramin-ifera, this
being related to the development of the microbialbuildup with
sponges. In the marl-limestone rhythmite,sessile benthic
foraminifera are normally scarce, and onlyfragments of Tubiphytes
appear. This fact was possiblyforced by the greater rate of
siliciclastic inflows together withthe small grain size (mainly
peloids), a combination whichimpeded colonization by nubeculariids
and other sessileforaminifera. High incidence of fragmentation in
Tubiphytesas well as in numerous specimens of Lenticulina,
althoughthe latter in a lesser proportion than in the ferruginous
ooliticlimestone, indicates a certain but minor degree of
transporta-tion, which is coherent with the absence of tractive
sedimen-tary structures. This is all concordant with the
topographicdifferences interpreted by Olóriz et al. (2002a) for the
Preb-etic shelf, the central sector of the External Prebetic being
atopographically more depressed zone than the eastern sector,which
explains its higher siliciclastic content and the occur-rence of
fragmented, presumably allochtonous remains offoraminifera. The
widespread development of microbial en-crustments on skeletal
remains promoted an increase in thenodular appearance of the
condensed and bioclasts-richlumpy-oncolitic limestone (Internal
Prebetic) and, to a lesserextent, in that of the spongiolithic
limestone (eastern sectorof the External Prebetic). These features
are interpreted asbeing related to decreased sedimentation rate
during a gener-alized increase in the distance from shore of the
studiedsections in the Prebetic Zone, within the general context
ofprogressing transgressive system tract conditions for thistime
period (Marques et al., 1991; Olóriz et al., 2002a, b).This
interpretation is compatible with the relation establishedbetween
both the growth of microbial buildups and spongebioherms in the
Jurassic and the record of episodes of sealevel rise at the third
order (Leinfelder et al., 1994).
Stratigraphic interval II, corresponding to the upper partof the
Bifurcatus Zone, is characterized by a decrease in theabundance of
foraminifera, with a notable diminution inGlobuligerina, Epistomina
and encrusting nubeculariids inall the sectors studied (Figs. 2 and
6). The assemblages ofvagile and sessile benthic foraminifera do
not present anyimportant variations with respect to stratigraphic
interval I.However, the Internal Prebetic sections studied evidence
anincrease in vagile benthic agglutinated foraminifera and
adecrease in sessile benthic siliceous agglutinated forms,
thislatter reduction being compensated by Tubiphytes. All
thelithofacies undergo a decrease in nodularity, which in
theInternal Prebetic is reflected in the facies change of
con-densed and bioclasts-rich lumpy-oncolitic limestones
tolumpy-oncolitic limestones. The results obtained indicate
adecrease in distance from shore in all the Prebetic domains,which
could be interpreted as being in accordance with therecord of
progressing highstand system tract conditions for
the Bifurcatus Zone in the Prebetic Zone (Marques et al.,1991;
Olóriz et al., 2002a, b).
6. Conclusions
Analysis of the foraminiferal assemblages
(composition,abundance, diversity and size of the specimens)
observed inOxfordian profiles (Antecedens to Bifurcatus Zones)
fromthe Prebetic Zone reveals their relation with lithofacies
andidentifies their palaeogeographic and stratigraphic
distribu-tion.
Two foraminiferal assemblages characterize relativelydistal and
proximal areas in the Prebetic Zone:
• Distal Assemblage: recognized in the profiles of theInternal
Prebetic. This area contains the greatest abun-dance of
Globuligerina, Epistomina and encrustingnubeculariids. The vagile
benthic foraminifera aredominated by uniserial-agglutinated forms,
mainly Am-mobaculites, and Ophthalmidium. Diversity of
benthicforaminifera is greatest and the largest average sizes
ofGlobuligerina, Lenticulina, uniserial nodosarids, Am-mobaculites
and Reophax are found.
• Proximal Assemblage: recognized in the profiles of theExternal
Prebetic. This area contains lower proportionsof Globuligerina,
Epistomina and encrusting nubecu-lariids. The vagile benthic
assemblage is dominated byspirillinids, followed by
uniserial-agglutinated forms,mainly Reophax. Diversity is less than
in the distalassemblage, as is the size of specimens, except in
thecase of Spirillina.
In the profiles studied, the variations observed in
theforaminiferal assemblages within the stratigraphic
intervalselected and their relationships with lithofacies have
beenanalysed and interpreted in the context of sequence
stratigra-phy. The oldest deposits (Antecedens Chron; Acosta,
1989),registered only in the most proximal areas (External
Preb-etic), correspond to the initial flooding on the shelf,
withrapid, high-energy deposits and a mixture of elements
pro-ceeding from proximal (e.g. Trocholina, fragmented nodosa-rids)
and distal areas (e.g. Globuligerina and Epistomina).All of this is
coherent with the context of a transgressivepulse. Subsequently,
two stratigraphic intervals were distin-guished. The first of these
(Transversarium? and/or the lowerpart of the Bifurcatus Zones) is
found throughout the domain,with high proportions of Globuligerina,
increased abundanceof colonial sessile benthic foraminifera, great
lithofaciesheterogeneity and an increase in nodularity in distal
areas(Internal Prebetic). All these factors are considered to
berelated to the development of transgressive system tract
con-ditions. The second interval (Bifurcatus Zone p.p.)
containslower proportions of Globuligerina and of encrusting
nube-culariids, while Epistomina is absent, and fewer
nodular-likedeposits are observed. These features are interpreted
as beingrelated to the development of highstand system tract
condi-tions.
745F. Olóriz et al. / Geobios 36 (2003) 733–747
-
Acknowledgements
M. Reolid is grateful to Drs. C. Gaillard and P. Hantzper-gue
for research facilities provided at Université ClaudeBernard
Lyon-1. The authors are indebted to J. Rey (Univer-sité
Paul-Sabatier, Toulouse) and M.A. Kaminski (UniversityCollege
London) who made valuable suggestions duringrevision. This research
was funded by projects PB97-0803(DGICYT) and BTE2002-3029 (CICYT),
and developedwithin the research program of the EMMI Group
(RNM-178,Junta de Andalucía).
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Palaeogeographic and stratigraphic distribution of mid-late
Oxfordian foraminiferal assemblages in the Prebetic Zone (Betic
Cordillera, Southern Spain)IntroductionGeological settingMaterials
and methodsResultsForaminiferal assemblages and
lithofaciesFerruginous oolitic limestoneCondensed and
bioclasts-rich lumpy-oncolitic limestone Lumpy-oncolitic
limestoneSpongiolithic limestoneMarl-limestone rhythmite
Palaeogeographic distributionInternal Prebetic External
Prebetic
Stratigraphic distribution
Discussion5.1. Foraminiferal assemblages and
palaeogeographyPalaeoenvironmental evolution
Conclusions
AcknowledgementsReferences