TOWARDS AN INTEGRATED BIOSTRATIGRAPHYOF THE UPPER APTIAN-MAASTRICHTIAN

OF THE SERGIPE BASIN, BRAZIL

Eduardo A. M. KOUTSOUKOS (*) & Peter BENGTSON (**)

(*) Petrobnis - CENPES - DIVEX/SEBIPE, Cidade Universitliria, Quadra 7, Iiha do Fundao, 21949-900 Rio deJaneiro, RJ, Brazil.(**) Geologisch-Palaontologisches Institut der Universitat Heidelberg, Im Neuenheimer Feld 234, W-6900 Hei­delberg, Germany.

Docum. Lab. Geol. Lyon, nO 125, 1993, p. 241-262, 8 fig.

241

ResumeVers une biostratigraphie integree de I'Aptien superieur-Maastrichtien du bassin de Sergipe, BresilLes echantillons d' age Aptien superieur aMaastrichtien, collectes sur le terrain ou en subsurface dans le bassin

de Sergipe du Nord-Est bresilien contiennent des associations abondantes et diversifiees de foraminif'eres, radiolaires etostracodes, representant des environnements allant de paralique (estran et lagon) abathyal inferieur. Les ammonites sontabondantes dans la serie carbonatee d'age aConiacien, et permettant une subdivision macrobiostratigraphique detailleefacilement applicable sur le terrain. On presente un premier essai d'integration des zonations de foraminif'eres etd'ammonites pour le Cretace de Sergipe, en utilisant la methode d'intercalibration. Les zones de foraminif'eres etd'ammonites sont principalement des zones d'Oppel, dont les lirnites sont marquees, pour les foraminif'eres, par leurapparition ou disparition locale, et pour les ammonites, par leur premiere occurrence locale. Des zones reposant sur desassociations de foraminif'eres benthiques, localement applicables, et plutOt contrOlees par le milieu, sont proposees pourI'Aptien sup6rieur. Pour I' intervalle Aptien-Albien,la zonation integree est encore tres provisoire. Un grande nombre decorrelations biostratigraphiques de premier ordre reste aetablir, en se basant sur l'echantillonnage integre de coupescontenant ala fois des microfaunes diagnostiques et des ammonites.MOTS-CLES : Aptien, Albien, Cenomien, Turonien, Coniacien, Santonien, Campanien, Maastrichtien, Cretace infe­rieur, Cretace superieur, biostratigraphie, methode d'intercalibration, methode d'integration totale, zone d'Oppel,paleoenvironnements, foraminiferes, ammonites, echinodermes, inocecames, bassinde Sergipe, Bresil, Ocean AtlantiqueSud.

ResumenHacia una bioestratigrafia integrada del Aptiano superior-Maastrkhtiano de la Cuenca de Sergipe, Brasll.Muestras de campo y de subsuelo, collectadas en capas del Aptiano superior al Maastrichtiano de la Cuenca de

Sergipe en el Nordeste de Brasil, contienen asociaciones ricas y diversificadas de foraminiferos, radiolarios y ostra.codos,que representan medios sedimentarios desde el ambiente panilico (llanura mareica y lagon) hasta el batial inferior. Losammonites son abundantes en la secuencia mayormente carbonatada de edad Aptiano a Coniaciano, y forman la base deuna zonaci6n macrobioestratignifica detallada facilmente utilisable en el campo. Se propone un primer intento deintegraci6n de las zonaciones de foraminfferos y ammonites para el Cretaceo de Sergipe, utilizando el metodo deintercalibraci6n. Las zonas tanto de foraminfferos como de ammonites son mayormente zonas de Oppel, cuyos lfmitesestan marcados, para los foraminfferos, por su primera 0 ultima ocurrencia local, y para los ammonites, por sus primerasapariciones locales. Zonas de asociaci6n de foraminiferos bent6nicos, localmente aplicables y rolls bien controladas porel medio, estan propuestas para el Aptiano superior. Para el intervalo Aptiano-Albiano,la zonaci6n integrada estli todavfamuy provisional. Un numero importante de correlaciones bioestratigraficas de primer orden quedan por ser establecidas,basandose sobre el muestro integrado de secciones que contengan a la vez microf6siles diagn6sticos y ammonites.PALABRAS CLAVE : Aptiano, Albiano, Cenomaniano, Turoniano, Coniaciano, Santoniano, Campaniano, Maastrich­tiano, Cretliceo inferior, Cretliceo superior, bioestratigraffa, metodo de intercalibraci6n, metodo de integraci6n total,zonas de Oppel, medios sedimentarios, foraminiferos, ammonites, equinoideos, inoceramideos, Cuenca de Sergipe,Brasil, Oceano Atlantico Sur.

Abstract

Towards an integrated biostratigraphy of the upper Aptian-Maastrichtian of the Sergipe Basin, Brazil.Upper Aptian to Maastrichtian surface and subsurface samples from the Sergipe Basin in north-eastern Brazil

yield abundant and diversified assemblages of foraminiferids, radiolarians and ostracods, representing environments thatrange from paralic (tidal flat and lagoon) to lower bathyal settings. Ammonites are abundant in the Aptian to Coniaciancarbonate-dominated sequence and form the basis for a detailed macrobiostratigraphical subdivision, which can easilybe applied in the field. A first attempt is made to integrate the foraminiferid and ammonite zonations for the SergipeCretaceous, using the intercalibration method. The foraminiferal and ammonite zones are chiefly Oppel zones, the boun­daries of which are marked for foraminiferids by local first andIor last appearances and for ammonites by local firstappearances. Locally applicable assemblage zones, which are more environmentally controlled, are proposed for benthicforaminiferids of the upper Aptian. For the Aptian-Albian interval the integrated biozonation is as yet highly provisio­nal. A considerable amount of first-order biostratigraphical correlation is yet to be done, based on integrated sampling ofsections that contain both diagnostic microfossils and ammonites.KEYWORDS: Aptian, Albian, Cenomanian, Turonian, Coniacian, Santonian, Campanian, Maastrichtian, LowerCretaceous, Upper Cretaceous, biostratigraphy, total-integration method, intercalibration method, Oppel zones, pa­laeoenvironrnents, Forarninifera, ammonites, echinoids, inocerarnids, Sergipe Basin, Brazil, South Atlantic Ocean.

242

INTRODUCTION

The fonnation of the Brazilian marginal basins is directly related to the rupture of the African-SouthAmerican plate. Separation of the two continents took place along a typical, divergent, Atlantic-typecontinental margin extending along nearly 8 000 km. The depositional basins on both sides of the presentSouth Atlantic thus have a common evolutionary history, which encompasses four main tectonosedimentaryphases (Ojeda & Fugita 1976; Ponte & Asmus 1976; Ojeda 1982; Asmus & Baisch 1983): pre-rift [lateJurassic(?) to earliest Cretaceousl, rift [earliest Cretaceous to early(?) Aptianl, transitional, proto-marine,evaporitic (Aptian), and a marine drift phase (late Aptian to Recent).The palaeogeographic setting of theSergipe Basin in north-eastem Brazil (fig. 1) during the mid- and late Cretaceous is a direct consequence ofthe strong tectonic activity that affected the area since the beginning of the rifting between South America andAfrica in the early Cretaceous. The basin consists ofa series of half-grabens with a regional dip averaging 10­

15° to the south-east, resulting from NE-SW trending nonnal faults.

post-Coniacian(piayabuyu Formation)

Cenomanian-Coniacian(Cotinguiba Formation)

Aptian-Cenomanian(Riachuelo Formation)

POTIGUAR

.::: JEQUITINHONHA

.::. CUMURUXATIBA........ MUCURI

o pre-Aptian

fault

o 500./ ....' ---:"k-m~,

N

r50,

km

.. .. .. .. .. .... .. .. .... .. .. .. .. .. .. .. .... .. .. .... .. .. ... .. .. .... .. .. ... .. .. .....

o,

SERGIPEBASIN

11 0

Fig. 1 - Geology of onshore portion of the Sergipe Basin (from Berthou & Bengtson 1988).A =Aracaju, E =Estiincia, I =Itaporanga, J =Japaratuba.

243

TheSergipe Basin contains oneofthe mostextensive middle Cretaceous marine carbonate successionsamong the northern South Atlantic basins. The sequence, although far from complete, spans the upper Aptianto middle Coniacian interval (fig. 2) and can be subdivided into two main depositional systems (cf.Koutsoukos et al., in press) :

(1) a mixed carbonate-siliciclastic platform system (latest Aptian to Albian : Riachuelo Formation,normally about 500 m thick, locally up to 1 700 m) ;

(2) a carbonate ramp system, chiefly developed as a massive succession of fine-grained deep-waterlimestones (Cenomanian to mid-Coniacian : Cotinguiba Formation, normally about 200 m thick, locallyexceeding 1 000 m).

The carbonate-dominated succession is overlain unconformably by a sequence of siliciclastic depo­sits; these form the Pia~abu~u Formation (upper Coniacian or Santonian to Miocene or Pliocene, up to andexceeding 2 000 m).

Form.

Ulhostratigraphy

Members

Calumbi (Cal)

Sapucari (Sap)

Aracaju (Aju)

SE

_ Tq_-_ - _ - _ Aguilhada (Ag)

Maruim (Mar)

Taquari (Tq)

Angico(An)

---------------------------=============~===-g-===~=

Facies relationships

-----------------------------------------------

--==~=~=~=~=~~=~=~=~~~~~~=~~~--------------------------------------------------------------------------------------=-=-=-:Cal:-=-=:-=-=-=-=-=-=-=-=-=-=-------------------------_._------------------------------------_._-------------------------

:'cl!i"n"

~:·.;til Conglomerates Ma StagesNW

E--~ Shales70 Maastricht.

1:::::::::1 Sandstones

~ Carbonate- mudstones

Campanianm Ooliticloncolitic 80

• grainstones orpackstones

~DolomiticSanlonian

limestones c........90 Turonian

I::: -:- ::::1 SiltstonesCenomanian

rV"V' Unconformity

100Albian

110

Fig. 2 - Schematic stratigraphy of the marine Cretaceous sequences of the Sergipe Basin.

The stratigraphy and the depositional and geological history of the marine Cretaceous ofSergipe havebeen described by Schaller (1970), Ojeda & Fugita (1976), Bandeira Jr. (1978), Feij6 (1980), Schaller et al.(1980), Bengtson (1983), Berthou & Bengtson (1988), Lana (1990), and Koutsoukos et al. (in press), amongothers. Biostratigraphical research has until now been focused on individual fossil groups, with onlypreliminary attempts at integrating the different schemes. A systematic survey initiated by P. and S. I.Bengtson in the 1970's (see Bengtson 1983) provides the basis for a detailed integrated biostratigraphycomprising all biostratigraphically important groups. In this paper we report on the results achieved to dateusing chiefly foraminiferids and ammonites. We also discuss the palaeoenvironmental conclusions drawnfrom the occurrences of the faunas, in particular the microfossils.

The paper is a contribution to IGCP Project 242 «Cretaceous of Latin America».

244

BIOSTRATIGRAPHY

BiostratigraphicaI integrationIntegrated biostratigraphy, in the true sense of the term, is a technique that is still in its infancy.

Although it is a well-known fact that all organisms are facies-bound to a varying degree, it is only during thelast decades that biostratigraphers seem to have realised that more precise and reliable results can be achievedifdiagnostic fossils from as many different groups as possible are applied simultaneously instead ofonly onegroup at a time. The term «integrated biostratigraphy» is in common use today ; however, much of what islabelled as integrated biostratigraphy consists ofcomparisonsofexisting biozonal schemes for different fossilgroups rather than truly integrated biostratigraphy based on detailed integrated sampling. Most of thebiostratigraphical work underlying such zonal comparisons dates back to the not-too-distant time when eachfossil group was sampled and studied in isolation. These single-group zonal schemes and biozonalcomparisons must be used with caution when attemptinl!; to establish an integrated biostratigraphy. An inte­grated biostratigraphy can be achieved and presented in tW0 nrincipal ways (fig. 3), by using: (1) the total­integration method, by which the entire biota is treated as one large fossil group, and by WhICh the diagnostictaxa, irrespective of systematic position, are singled out and used for the definition and characterization ofbiozones; (2) the intercalibration method, by which conventional single-group zonal schemes are used and/or erected but through precise stratigraphical control are fIrmly calibrated to each other (for an exemplarywork of this kind, see, for example, Rasplus et al. 1987). Integrated biostratigraphy based on the total­integration method can perhaps be seen as the only truly integrated biostratigraphy and, indeed, it is temptingto conceive as a final goal an all-embracing biostratigraphical zonation scheme, whereby zones can beidentified using members of virtually any fossil group. However, to establish an integrated biostratigraphy ofthis kind would mean that entirely new zonations had to be produced to replace existing single-group zonalschemes, a huge task that has no prospects of being completed within the foreseeable future. Another disad­vantage of the total-integration method is that zones will be based on varying properties (first appearances,last appearances, acmes, etc.) of probably several tens of taxa, which will contribute to making zonal

definitions unclear and of difficult use.The intercalibration method aims at calibrating existing and new single-group zonal schemes through

improved stratigraphical control. This method utilizes all available biostratigraphical information, old andnew, with its faults and virtues, and may therefore give less precise results than the total-integration method.However, biozones will be more clearly defined and easier to grasp and apply than those based on the total­integration method. Also, comparisons with other areas will be easier to make, as biogeographic restraints canbe avoided with the selection ofcommon diagnostic taxa, and because further improvements and refinementscan be made without upsetting the entire integrated biozonal scheme. In our work on an integrated Cretaceousbiostratigraphy of Sergipe we have opted for the intercalibration method.

Review of foraminiferal and ammonite biozonal integration.The current integrated foraminiferal-ammonite biostratigraphical scheme for the Aptian-Maastrich­

tian of the Sergipe Basin is shown in fig. 4. Several studies have focused on the palaeontology andbiostratigraphy of this basin (see Bengtson 1983 for a review; also Berthou & Bengtson 1988). The firstattempt atan ammonite zonation was by Beurlen (1961) for the upper Aptian and Albian, whereas Petri (1962)proposed a foraminiferal zonation for the entire Albian-Maastrichtian interval. Petri also attempted tocorrelate the microbiostratigraphical scheme with the macrofossil succession, which until then hadbeen basedchiefly on the work ofMaury (1937). Beurlen (1969,1970) complemented K. Beurlen's (1961) ammonitezonation with a Cenomanian-lower Coniacian subdivision; further additions to this zonation were byReyment& Tait(1972), Reyment etal. (1976), Bengtson (1979, 1983),andSmith & Bengtson (1991). Freitas(1984) discussed the stratigraphy and distribution of calcareous nannofossils in the basin. Lower Turonianinoceramid bivalves and Albian to Coniacian echinoids were subsequently described by Hessel (1988) and

Smith (1991), respectively.A microbiostratigraphical scheme was proposed by Koutsoukos (1989), based on foraminiferids; 23

planktonic and benthic foraminiferid zones were recognized for the upper Aptian-Maastrichtian strata. Workis currently in progress to fully integrate and refme the foraminiferid and ammonite biozonal schemes(Koutsoukos & Bengtson, in preparation), based on joint studies of further field sections. The timing of the

245

first marine connection between the central and South Atlantic oceans is indicated by ammonites andmicrofossils contained in the lowermost marine beds of the Riachuelo Formation (Bengtson & Koutsoukos1992). The sequence has yielded upper Aptian ammonites of the early douvilleiceratid lineage Cheloniceras­Eodouvilleiceras. The upper Aptian is subdivided with planktonic foraminiferids into two zones, the Globi­gerinelloides barri-Hedbergella (H.) gorbachikae and Globigerinelloides ex. gr. maridalensis-Hedbergel­la (H.) similis zones. The upper boundary of the latter zone is defined by the last appearance of diagnosticspecies like G. barri (Bolli,Loeblich & Tappan, 1957), G. exgr. maridalensis(Bolli, 1959),andH. (H.)similisLongoria, 1974, among others, at or near the Aptian-Albian boundary (Koutsoukos 1989, Bengtson &Koutsoukos 1992). The zone correlates with the lower part of the Globigerinelloidesferreolensis-Ticinellabejaouensis Zone of van Hinte(1976) ; see fig. 5.

TOTAL-INTEGRATION METHOD

Zone 4ammonites, foraminifers,dinoflagellates, pollen,

bivalves, echinoids,radiolarians, etc.

Zone 3ammonites, foraminifers,dinoflagellates, pollen,

bivalves, eChinoids,radiolarians, etc.

Zone 2ammonites, foraminifers,dinoflagellates, pollen,ostracods, bivalves,etc.

Zone 1ammonites, foraminifers,dinoflagellates, pollen,

bivalves, echinoids,radiolarians, etc.

INTERCALlBRATION METHOD

Fig. 3 - Hypothetical zonationsto illustrate the total-integra­tion and intercalibration me­thods.

AMMONITES FORAMINIFERS DINOFLAGELLATES BIVALVES

ZoneA4 ZoneF4 Zone 04

ammonites foraminifers dinoflagellates Zone 83

bivalves

ZoneA3 Zone F3 Zone 03

dinoflagellatesammonites foraminifers

Zone 02 Zone 82ZoneA2

ZoneF2 dinoflagellates bivalves

ammonitesforaminifers

Zone 01ZoneA1 ZoneF1 Zone 81dinoflagellates

ammonites foraminifers bivalves

246

FORAMINIFERAL ZONES

AGES "STANDARD AMMONITEZONES" ZONES PLANKTONIC BENTHIC

G. contusa-G. aegyptiaca O. clarki-P. kickapooensis

Maastrichtian G. gansseri-G. stuartiformis G. loetterlei-a. velascoensis

G. ex gr. fornicata- G. ex gr. beaumontiana-G.finneiana G. nonionoides

G. orientalis-G. ventricosa L. gouskovi-O. clavata

Campanian G. patelliformis-G. elevatal S. bramlettei-stuartiformis plexus R. ex gr. szajnochae

Dicarinella asymetrica N. texana-O. clarki

Santonian

D. concavata-M. sinuosa L. revoluta-G. spinea

ConiacianPeroniceras tridorsatum S. armatus-P lenti

Gavellinella sp. A-B. onilahyense- A. cretacea-D. primitiva Valvulineria sp. AForrester/a (H.) petrocor/ensis Forresteria

SUbprionocyclus Suprionocyclus-Valvulineria sp. B-

Dicarinella prim/t/va G. berthelini-plummerae-neptuni Reesidites reussi plexusTuronian

Mammites nodosoides M. nodoso/des-K. turon/ense H. aprica- G.levis-

W. amudar/ense- H. (W) baltica N. ex gr. obscuraWatinoceras spp. K.se/tzj

V. harttii- H (W) archaeocretacea- G. obesa-G. levisNeocardioceras juddii P. footeanum H. reussi

Meto/coceras E. septemseriatum H. (W) aprica- G. levis-Discammina sp. AG. bentonensis

gesfinianumP harpax-T. aft. sornayi

H.(W) baltica- Nodosaria ex. gr. obscura-Cenomanian Acanthoceras jukesbrowne/ A. jukesbr.-E. pen/ago H(W) brittonensis Gibicides sp. ATurrilites acutus-costatus A. spathi-Dunveganoc.

P. delrioensis- L. (?) cf. thalmanniformis-Mantelliceras

G.lozoi- R. appenninica S. cretaceamantelli

H. betaitraensis

R. brotzeni Gibides sp. A-P. complanata

MortonicerasH. (H.) gorbachikae- N. subcretacea-

Morton/cerasT. raynaudi T. ex gr. excavata

inflatum G. texomaensis- N. subcretacea-Elobiceras B. breggiens/s S. cf. crassicosta

B. breggiensis- G. berthefini-plummerae-Albian Euhopfites ?

T. ex gr. primula reussi plexus-G. cf.gradatalautus Oxytropidoceras

T. ex gr. primula-E. spinufifera-E. carpenteriT. bejaouaensis

T. bejaouaensisa. schloenbachi-

Douvilleiceras P.IS. ex gr. dividensmamillatum Douvilleiceras

----- ? -----.- G. cushmani- E. carpenteri-G. filiformisLeymeriella regularis ? T. bejaouaensis

G. ex gr. maridalensis- L. ex gr. sUbangulata-H (H.) similis L. ex gr. nodosa

Late Epicheloniceras- A. cf. copro/ithiformis-Aptian Diadochoceras- B. cf. hedbergi-

Eodouvilleiceras G. barri- H.lueckei

H (H.) gorbachikae L. ciryi-L. nodosaria-

M. ex gr. aequivoca

Fig. 4 - Integrated foramlnlferid-ammonite blostratlgraphy of the marine Cretaceous of the Serglpe Basin.(Foraminiferids after Koutsoukos 1989 ; Aptian ammonites from Bengtson & Koutsoukos 1992; Albian ammonitesmodified after Beurlen 1969. 1970; Cenomanian-Coniacian ammonites modified after Bengtson 1983. Smith & Bengtson1991 and S. I. Bengtson (Uppsala). personal communication 1992; age lengths not to scale).

247

Stages This study

Contusotruncana contusa­Globotruncana aegyptiaca

Zone

Gansserina gansseri­GJobotruncanda stuartiformis

Zone

Caron1985

A. mayaroensis

van Hint.1976

A. msyafOBns;S

G. contusa

MaastrIChtlanl- _

ContU50truncana ex gr. fornicata­Globotruncana linneiana

Zone

Globotruncana orientalis­Globotruncana ventricosa

Zone

CampanlanContusotruncana patelliformis­

Globotruncanita elevata/stuartiformis plexus

Zone

Dicarinella asymetricaZone

G. gansseri

G. aegyptiaca

G. havanensis

G, ca/carata

G. ventricosa

G. elevara

D. asymetrica

G.stuar1i

G. gansseri

G. scutilla

G, calcarata

G. 5ubspinosa

G. stuartiformis

G, elevata

G. concavata­G. elevata

Santonian

Coniacian

Turonian

Ciear/nella conCBvata­Marginorruncana sinuosa

Zone

Archaeoglobigerinacretacea­

Ciearinells primitivaZone

Dlc,Wile/la primitivilZone

Hedbecge"" (W) apcica-

beI1l1~;~;'5jS

Hedbergella (W) baltica­Hedb, (W) brittonensJs

Zone

D, conC8vata

D. prirnilivB

M sigali

H. helvetica

W archaeocretacea

R. cushmani

G. sigali­G. concavata

G. renzi­G, siga/i

"G. " helvetica

H.lehmani

R, cushmani

Cenomanian f----:--...,..,-----­Praecglobotruncana

delrioensis-Rotalipora appenninica

Zone

Rotalipora brotzeniZone

Hedbe1;~f~aef~)r~;~~~~7ikae--Zone

Globigerinelloidestexomaensis­

Biticine/la breggiensisZone

AlblanaiticinelJa breggiensis­Tlcmella ex gr. primula

Zone

Tic. ex gr, primulaTicineJ1a beJaouaensis Zone

R reicheli

R. brotzeni

R. appenninica

R. ticinensis

R. subticiensis

a, breggiensis

T primula

R. gandolfii-R. greenhornensis

R. ap'b~~~~a-

f---------P ticinensis­

P. buxtorfi

T (a.) breggiensis

T. praeticinensis

Ticinella bejaouaensis Zone

G~bigerinelloidescushmani­Tlcmelfa be]aousensis Zone

UpperAptlan

Globigerinelloides ex gr,maridale~~iiisHro~e:geJla (H)

Globigerinelloldes barri­HedbergelJai~jegorbachikae

T bejaouaensis

H. gorbachikae

G. algerians

T bejaouaensis

1---------G. ferffJOJensis­T. bejaouaensis

H.trocoidelt­G. ferreolensis

248

Fig. 5 - Correlation ofplankto­nlc foramlnlferal zonal sche­mes proposed for the Aptian­Maastrlchtlan (stage thicknes­ses not to scale).

Thepositionof the Aptian-Albian boundary in Sergipe is difficult to determine in terms of the so-calledstandard zonation. The upper Aptian Hypaeanthoplites jaeobi and the lower AlbianLeymeriella tardefureatazones of north-west Europe (Hancock 1991) are not recognizable in Sergipe, if at all present in the TethyanRealm. Indirect correlation, based on the Cheloniceras-Eodouvilleieeras lineage representatives, points to abroadly late Aptian age for the lowermost marine beds. The absence of the genusDouvilleieeras in these bedsis also significant. Because of the limited geographical distribution of the L. tardefureata Zone, Hancock(1991) suggested that the first appearance of species ofDouvilleieeras should be used instead to define thebase of the Albian. This would mean a shift to a slightly higher boundary, although with the advantage of itsbeing globally recognizable.

Above the upper Aptian fauna in Sergipe there occurs Douvilleieeras sp., which we interpret aslowermost Albian. This species is followed byDouvilleieeras ex gr. mammillatum (Schlotheim, 1813), whichcan be correlated with the upper lower Albian Douvilleieeras mammillatum Zone of north-west Europe. Thelower and middle Albian Douvilleieeras and Oxytropidoeeras ammonite zones of Sergipe are each subdivi­ded into two planktonic foraminiferal zones, the Globigerinelloides eushmani-Ticinella bejaouaensis andTicinella bejaouaensis zones, .and the T,icinella ex gr. primula-Ticinella bejaouaensis and Bitieinellabreggiensis-Tieinella ex gr. primula zones, respectively. These are based chiefly on abundances of Ticinellabejaouaensis Sigal, 1966, as well as on occurrences of species of Globigerinelloides and Hedbergella. Forcorrelation with other areas, see figs. 4 and 5.

The overlying upper Albian Elobieeras and Mortonieeras ammonite wnes are represented by theGlobigerinelloides texomaensis-BiticinellabreggiensisandHedbergella (H.) gorbaehikae-Ticinella raynau­di planktonic foraminiferal zones, respectively. Correlation with the north-westEuropean ammonite zonation(Hancock 1991) is hampered by increased ammonite provincialism in the late Albian, and only a broadassignment to the Mortonieeras (M.) inflatum Zone is possible. The Stoliezkaia dispar «standard» zone hasnot been identified in Sergipe and may be missing.

The lower Cenomanian, i. e. the base of the Cotinguiba Formation, is represented by two foraminiferalzones, Rotalipora brotzeni and Praeglobotruneana delrioensis-Rotalipora appenniniea zones, respectively,in part corresponding to the Graysonites lozoi-Hypoturrilites betaitraensis ammonite wne. This zone corre­lates with the broader Mantellieeras mantelli Zone of north-west Europe, although its exact vertiCal exten­sion in relation to this wne is as yet uncertain. The Albian-Cenomanian boundary is not exposed in Sergipe,but is recorded in well-sections at the boundary between the foraminiferid zones of Hedbergella (H.)gorbaehikae-Tieinella raynaudi and Rotalipora brotzeni. The middle-upper Cenomanian Hedbergella(Whiteinella) baltiea-Hedbergella (W.) brittonensis Zone appears to be subdivisible into three zones on thebasisofammonites. The lower two, theAeompsoeerasspathi-DunveganoeerasandAeanthoeerasjukesbrownei­Euealyeoeeras pentagonum zones, correspond broadly to the middle Cenomanian Turrilites eostatus-aeutusand Aeanthoeeras jukesbrowni subzones of north-west Europe (Hancock 1991), respectively. The upperCenomanian Hedbergella (Whiteinella) apriea-Globigerinelloides bentonensis foraminiferal zone containSthe globally distributed ammonite Euomphaloeeras septemseriatum (Cragin, 1893), which is diagnostic forthe Metoieoeeras geslinianum «standard» wne [M. geslinianum (d'Orbigny, 1850) is with doubt recorded inSergipe from the underlying Pseudoealyeoeeras harpax-Thomelites aff. sornayi Zone].

Above the apriea-bentonensis/septemseriatum zones correlation becomes difficult; in particular theposition of the Cenomanian-Turonian boundary is uncertain. Smith & Bengtson (1991, p. 9) tentativelycorrelated the Vaseoeeras harttii-Pseudaspidoeerasfooteanum ammonite zone with the Neoeardioeerasjuddii Zone of north-west Europe, i. e. uppermost Cenomanian. This is in agreement with the succession in,for example, Portugal, where P.footeanum (Stoliczka, 1864) occurs in the N. juddii Zone (Berthou 1984).Hancock (1991, p. 273-274) discussed the varying defmitions of the Cenomanian-Turonian boundary, andKennedy & Cobban (1991) proposed that the boundary should be drawn at the base of a Watinoeerasdevonense Zone, which is recognizable in Europe and in the U.S. Western Interior. W. devonense Wright &Kennedy, 1981, itself does not occur in Sergipe, but the faunal association of the Watinoeeras amudariense­Kamerunoeeras seitzi ammonite zone places this zone firmly in the lower Turonian, and at least partialcontemporaneity with the W. devonense Zone appears probable. The underlying «problematic» V. harttii-P.footeanum Zone contains pseudotissotiids known from other areas, where they have consistently beenreferred to the Turonian. Other elements of this zone, for example, Euomphaloeeras aff. septemseriatum,point rather to a Cenomanian age (cf. also the Cenomanian occurrence ofP.footeanum in Portugal (Berthou1984», which suggests a mixed assemblage. Occurrences in this zone of the inocerarnid bivalve Mytiloides

249

(cf. Kauffman & Bengtson 1985) are as yet to be evaluated. The coeval Hedbergella (Whiteinella)archaeocretacea-Heterohelix reussi foraminiferal zone lacks diagnostic elements for interregional correla­tion. The H. (W.) archaeocretacea-H. reussi and V. harttii-P.footeanum zones are thus here interpreted asstraddling the Cenomanian-Turonian boundary, using the defmition of Kennedy & Cobban (1991).

The lower-middle Turonian is represented by the planktonic foraminiferal zone of Hedbergella(Whiteinella) aprica-Hedbergella (Whiteinella) baltica and the two ammonite zones of Watinocerasamudariense-Kamerunoceras seitzi and Mammites nodosoides-Kamerunoceras turoniense. These zonescorrelate well with the Watinoceras spp. and Mammitesnodosoides zonesofnorth-west Europe, respectively.The middle Turonian Collignoniceras woollgari «standard» zone has not been recognized in Sergipe,probably in part owing to significant depositional breaks in the present onshore part of the basin (Bengtson1983). The upper Turonian is represented by the approximately coeval Dicarinella primitiva andSubprionocyclus-Reesidites zones, which correlatewell with the SubprionocyclusneptuniZoneofnorth-westEurope.

The lower-middle Coniacian interval is represented by the Archaeoglobigerina cretacea-Dicarinellaprimitiva foraminiferal zone and the Barroisiceras onilahyense-Forr;esteria and Solgerites armatus­Prionocycloceras lenti ammonite zones, respectively. Coniacian international zonation is in a state of flux,and the Sergipe sequences cannot as yet be firmly tied to the European or other schemes. It is possible thatthe lower Coniacian is partly missing in Sergipe, at least in the present onshore areas. TheSolgerites armatus­Prionocycloceras lenti Zone marks the endof the carbonate-dominated depositional cycle in Sergipe. In mostonshore areas there follows a significant hiatus, whereas locally offshore the sequence is more complete. Theforaminiferal zone of Dicarinella concavata-Marginotruncana sinuosa spans the Coniacian-Santonianboundary.

Only a few ammonites have as yet been found in the clastic deposits formed during the post-Coniaciancycle, the Pial;abul;u Formation (Bengtson et al., in prep.). The biostratigraphy is based on planktonic fora­miniferids, supported by benthic foraminiferal assemblages.

Zonal definitions and characterizationsIn the following, zones are defined and characterized in chronostratigraphical order, using the most

diagnostic taxa. Additional, stratigraphically less useful taxa, are not listed.Some zones are sharply defined, others are more vaguely characterized, many (especially for

ammonites) are based on recorded assemblages. For several fossil groups only isolated observations of taxaare available (e. g. echinoids, inoceramids, non-inoceramid bivalves, gastropods) ; these are currently beingintegrated into the scheme.

Because of caving and sample mixing that commonly occurs in oil-well cuttings, normally only thetop down-hole occurrences (the evolutionary extinction datum level or the local last appearance in thestratigraphical section due to major environmental changes) of microfossils and their peaks of abundanceshave biostratigraphical significance. However, with the careful examination of all the assemblages anddifferentiation of caved and/or reworked specimens (e. g., decrease in abundance and stray occurrences, dif­ferentiation in colour and preservation) it was also possible to record the first appearances ofseveral taxa (seefigs. 6-7), thereby allowing the establishment of a more refined microbiostratigraphical framework.

The benthic microfaunas are depth-related and biostratigraphically less useful than the planktonicones. However, facies-constant stratigraphical sequences, where no major environmental change has takenplace over a long time-interval, occur within the thick succession of the Pial;abul;u Formation (CalumbiMember) in the offshore south-eastern part of the basin (Mosqueiro Low). The study of these strata allowsthe selection of benthic zonal markers and the precise recognition of their first appearance and extinctionlevels, which provide potentially isochronous zonal boundaries for the post-Coniacian deposits within thebasin.

Unless otherwise indicated the foraminiferal and ammonite zones are Oppelzones (Hedberg 1976,p. 58), the boundaries ofwhich are marked for ammonites chiefly by first appearances and for foraminiferidsby first and/or last appearances. The zones are named after one or more characteristic taxa that occur in thezone, although not necessarily confined to the zone. More environmentally controlled, locally applicableassemblage zones (sensu Hedberg 1976, p. 50-52) are proposed for thebenthic foraminiferids of the upperAptian.

250

PLANKTONIC FORAMINIFERA

Ages Zones

e. contusa-G. aegyptiaca

First app.datums

Last app.datums

le. contusaG. aeflyptiacaP. vanans

-

------------------------~--------C. patelliformisG. gansseriG.osetta

G. gansseri-G. stuartiformis G. ventricosa

JG. cretacea S. stuartiformis

_ _ _ _ _ _ _ _ _ _ _ _ _ _ G..f:tr:r: i -~ _

C. fornica taC. ex gr. fornicata- G. bulloides

G. /inneiana G. /inneianaG. subspinosa

~--~--~---------------------------------

~.J

-CIII'2III

>- Q.

~ Ew III

U

C

Sl .!!!.. l:.J 0...

- CIII

Early If)

l:

LateIII'u

~.!!!c

l; 0w U

Late c- .!!!Middle

C0

>--- ...Early .=

~ c.J .!!!

l:I-- III

MiddleE0

I-- l:~ CIIl; Uw

Sl...J

C

- .!!!J:I.. :cc'5..,

:EI--

>-'l:·01W

Sl CIII

01 a.J

cc- -- - -

lG' Imneiana

G. onenta/is-G. ventncosa G. onentallsG. ventricosa

-------------- ~:~~;~~--~--------G. stuartiformisG. elevata plexus

H. reussi

,~-. barri - - -. ~'1 gr. .mfl.ridal.__..J.H..d.§I,!!i[s__

251

Fig. 6 - FAD and LAD of biostrati­graphically important planktonicForaminiferida (age lengths not to

scale).

BENTHIC FORAMINIFERA ------- ---------ValvulineriB

G-: berthe7inr: - - -.. sp. B~. bertheli~ plummeras-

Ages Zones First app. Last app. 10 plummerae-- reU$S; plexus

datums datums...J

I: _ !!u:.Si_pl!.X~ _ V!!./~"~8~a_s~ ~ _---------1--:-.!II G./evisI:

B. ex gr. colonensis .., e G.f8vis- N. ex 9r. obscuraN. aspsrs I.....!... ~ N. ex gr. obscura Gaboni!a cf. paNa

O. clarki- N. canadenss~

P. kickapooensis O. c/arki .. ------- --------- 11:01le'a- - - --P. k;ckapooensis w

~ I: C ex gr. triJamra P. rsussi G. obesa-G. levis Cassidella ex gr.

~P arena!a P. plummerse G.obess viscidus

------- ;- - - - - - -- G~ iOBiter/er - - - - ------ -------- ---------.g A. impexu5G.loetterl~ O. ve/ascoensis A. paterslla..

~. ~~.P,~~:;'~~tariai O. vslascoensis .. G.l8vis- A. imp8XUS Discammina sp .A101- ------- --------- ~.8X-g,:-b8aumont;anus...J Discammina sp. A A. patereJJa

Discammina sp .A -

~ C. ex Qr. G. nonionoides Gabonita levisbeaumontJana- P. ex gr. prolixa ------- -------- --------w G, nonionoides

I A...;. cl '!..aa.m!nt.!r~ _P. ex gr. fang I: NOdOSaria ex. gr. Cibicides sp.A.!IIP.§J~ay _ ____

I: obscura-£. supracretsces .!! ~

CiblcK1es sp, A N~e~ ~ o~s:..u,! _ _------- ---------G. corrects ~ L. tormarpensisG.lorneiana I:

G. sandidgei~ ~ L. (?)cf L. (?) cf. thalmannii·

~ r-- Ihalmanniformis- formisG. subconica $. crelacea-' L. gouskovi S. cretaceae

N. rugosa Spiroloculina sp .A------- -------- ---------L.6:a~~7a-

O. ex gr. halfe/di fl- A. ex gr. globigerin;- O. clavata

I /ormis V. amaraJi w Cibldes sp.A-I:

G. mOnlere/ensisP complanata Cibicides sp. A.!II O. navarroana S. cI.crass/costatsI: K. ex gr. conV8rsa P comp/anata

l!- L. gouskovi P. faylorensis ------ -------- ---------E P spinafa N. subcretacea

tl ------- --------- T( ---- --- N. subcretacea- R. tetrahedralis

E. velascoensis P. jarvisi T. ex gr. 8xcavataR. tetrahedra/is

T ex gr.excavata~ G. nacatochensis R . ex gr. szajnochae~ ..w G. subconica 10 ------ -------- ----------

G. loetterlei ...J N. subcrelacea- N. subcretaceaS. bramlene~ H. ex gr. subsphaerica S. et. crassicosla S. et. crassicostata

R. ex gr, szajnochae

~. tgl'~~~7~%inata------ -------- ---------

G. berthefini- 0. schloenbachiS. bramJettei lJIum.merae- G. berthelini-T!!aE.e!i. _____ --------- r-- rsussl p1exus- plummerae...------- G. cf.gradata

'!.u:,sij''!.x,:s _ _ _G. cf. gradata

ill"" ". o1l ------ ---------Glaphyrammina sp. A .., E. carpenteri

~N. texana-o, clarki N. texana :i E. spmuUfera-

C. ex gr. ~iscidusG. cf. mulfisepta

0. darkl I: E, carpenteri-' I: 0. clavara .!II E. spinu/nera

.!! ------- -------- ITG~ s~i;ea- - - - -r-- & ------ -------- ---------I: ~ E. chapmani

~ M. ozawai1- ~ O. schloenbachi- T. ex gr. excavata PIS ex gr. dividens

~f ex gr bulletaPIS. ex gr. divid&ns

>- O. sch/oenbachiiii G. spissocostara

~w R. ex gr. globulosa ------ -------- ---------A~ e~ ~. :z~n~c~a~ w 8. hedbe'~i

L revoIU'B- rr ~-'v~Ii~O~Si;(;j ;p-A E'J.arcrcw:Z-G. filiformls

G, spineaL. revoluta E. carpenteri

E. aracajuensis G./Hiformis

! G. ex gr. beccariiformis ------ ~ 6! ~. :!.iv~d~~ _ ---------I: G. correctasu';,:rr.:;a-

L. ex gr. nodosa.!II G. sandldgei L. ex gr. sUbangulataj Gavelinopsis(?) sp. B L. ex gr. nodosa B. nonioninoidesI: L. revoluta I: --A.cT-- --------.3 P ex gr. capitosa .. .!II A. cf. coprofithiformis

,- ------ loo- -------- j ~coprolithiformis- 8. hedbe'9i

~ GaveJlne7Ja-sp B - - 8 cl. hedber9i-H.lueckel H.luecksl

>- Gavel/inella sp. A- L formarpensls -"LCi';--- L. nodosaria1.i Valvulineria sp. A T. ex r SUbCOnlC8 L. ciryiw Valvu~ne"a sp B L. nodosaria-

__ ~. ~xJ,f-!eg,ui~OC!. M. ex gr. aequivocs------- ---------~--------

Fig. 7 - FAD and LAD ofbiostratigraphlcally important benthlc Foraminiferlda (age lengths not to scale).

Owing to the limited vertical extent of most outcrop sections (nonnally only a few metres) in relationto the considerable total thickness of the carbonate sequence (well over 500 m), no significant faunal shiftswere nonnally observed during macrofossil sampling of each locality. Bed-by-bed sampling was thereforenot considered practical; however, as a result of this broad collecting procedure some samples may representmixed assemblages.

Macrofossil sampling in Sergipe is hampered by lack ofcontinuous outcrop. Nonnally small quarriesand road cuttings expose only up to a few metres of section, and initial collecting procedures yielded only asmall number of specimens. The few existing larger quarries have in many cases yielded sizeable collections

252

of biostratigraphically significant macrofossils ; however, because the material was collected chiefly byquarry workers, the relative position in sequence of most of the specimens is unknown. Position in sequenceof isolated localities was inferred mainly on the basis of regional dip and altitude of the beds exposed. Thus,in contrast to microbiostratigraphical procedures, the true first appearances and the true vertical distributionof the diagnostic macrofossil taxa have not been observed.

For the definition of the base ofeach ammonite zone, the first appearance ofa well-known, abundant,wide-spread, and easily identifiable taxon was chosen. In addition to the defining taxon, a number of othertaxa characterize the zone and thus aid in its identification.

Reference sections and profiles for the biownes will be given in a forthcoming publication (Koutsou­kos & Bengtson, in preparation)..

Legend - The abbreviations given after the diagnostic taxa listed represent local biotic events andoccurrences, recorded at outcrop and in well-sections in the Sergipe Basin.

(FAD) =First Appearance Datum(FAWZ) = First Appearance Within Zone(LAD) =Last Appearance Datum(LAWZ) =Last Appearance Within Zone(TR) = Total Range(AC) = ACme (abundance peak)(OWZ) =Occurrence Within Zone(OWZPR) = Occurrence Within Zone, Probably Restricted to zone

PLANKTONIC FORAMINIFERIDA

The succession of planktonic foraminiferids is based in part on the works of Masters (1977),Robaszynski & Caron (1979), Robaszynski et al. (1984) and Caron (1985).

Globigerinelloides barri-Hedbergella (H.) gorbachikae Zone: Hedbergella (H.) trocoidea (Gandol­fi, 1942) (FAWZ), Hedbergella (H.) gorbachikae Longoria, 1974 (FAWZ), Globigerinelloides barri (Bolli,Loeblich & Tappan, 1957) (OWZ). Assigned age: late Aptian.

Globigerinelloides ex gr. maridalensis-Hedbergella (H.) similis Zone: Ticinella spp. (FAD), Globi­gerinelloids barri (Bolli, Loeblich & Tappan, 1957) (LAD), Globigerinelloidsferreolensis (Moullade, 1961)(LAD), Globigerinelloids ex gr. maridalensis (Bolli, 1959) (LAD), Hedbergella (H.) similis Longoria, 1974(LAD), Ticinella bejaouaensis Sigal, 1966 (FAD, AC; "1st abundance peak"). Assigned age: late Aptian.

Globigerinelloides cushmani-Ticinella bejaouaensis Zone: Globigerinelloids cushmani (Tappan,1943) (FAD), Ticinella bejaouaensis Sigal, 1966(AC; "2nd abundancepeak"). Assigned age :earliestAlbian.

Ticinella bejaouaensis Zone: Category: Acme-wne (sensu Hedberg, 1976, p. 59-60). Hedbergella(H.) subcretacea (Tappan, 1943) (FAD), Ticinella bejaouaensis Sigal, 1966 (AC ; "3rd abundance peak").Assigned age: early Albian.

Tiein'ella ex gr. primula-Tieinella bejaouaensis Zone: Hedbergella (H.) ex gr. simplex (Morrow,1934) (FAD), Globigerinelloides bentonensis (Morrow, 1934) (FAD), Ticinella ex gr.primulaLuterbacher,1963 (FAD), Globigerinelloides cushmani (Tappan, 1943) (LAD), Ticinella bejaouaensis Sigal, 1966(LAD). Assigned age: mid-Albian.

Bi/ieinella breggiensis-Tieinella ex gr. primula Zone: Biticinella breggiensis (Gandolfi, 1942)(FAD), Ticinella raynaudi Sigal, 1966 (FAD), Ticinella madecassiana Sigal, 1966 (TR?), large-sizedTicinellinae (AC ; «4th abundance peak»; in the upper limit). Assigned age: mid to late Albian.

Globigerinelloides texomaensis-Bitieinella breggiensis Zone: Globigerinelloides texomaensisMi­chael, 1972 (FAD), Praeglobotruncana delrioensis (plummer, 1931) (FAD), Heterohelix spp. (FAD),Biticinella breggiensis (Gandolfi, 1942) (LAD), Ticinella ex gr. primula Luterbacher, 1963 (LAD). Assignedage: late Albian.

Hedbergella (H.) gorbachikae-Ticinella raynaudi Zone: Guembelitria cenomana (Keller, 1935)(FAD), Globigerinelloides texomaensis Michael, 1972 (LAD), Hedbergella (H.) gorbachikae Longoria,1974 (LAD), Ticinella spp. (T. raynaudi Sigal, 1966, T. roberti (Gandolfi, 1942); (LAD). Assignedage : latestAlbian.

253

Rotaliporabrol%eni Zone: Rotaliporabrotzeni (Sigal. 1948) (FAD/LAD ;lR). Assigned age: earliestCenomanian.

Praeglobotruncana delrioensis-Rotalipora appenninica Zone :Hedbergella (Favusella) washiten­sis (Carsey. 1926) (LAD). Praeglobotruncana delrioensis (plummer. 1931) (LAD). Rotalipora appennini­ca (Reoz. 1936) (LAD). Assigned age: early to mid-Cenomanian.

Hedbergella (Whiteinelltl) baltica-Hedbergella (W.) brittonensis Zone: Hedbergella (Whiteinella)baltica Douglas & Rankin. 1969 (FAD). Hedbergella (Whiteinella) brittonensis Loeblich & Tappan. 1961(FAD). Assigned age: mid to late Cenomanian.

Hedbergelltl (W.)aprka-Globigerinelloides bentonensis Zone: Hedbergella (Whiteinella) aprica(Loeblich & Tappan. 1961) (FAD), Globigerinelloides bentonensis (Morrow. 1934) (LAD). Assigned age:late Cenomanian.

Hedbergella (W.) archaeocretacea-Heterohelix reussi Zone: Hedbergella (Whiteinella) archaeo­eretacea Pessagno. 1967 (FAD). Heterohelix reussi (Cushman. 1938) (FAWZ). Assigned age: latest Ceno­manian to earliest Turonian.

Hedbergelltl (W.) aprka-Hedbergella (W.) baUica Zon~ : Marginotruncana undulata (Lehmann.1963) (FAD). Hedbergella (Whiteinella) aprica (Loeblich & Tappan. 1961) (LAD). Hedbergella (Whitei­nella) baltica Douglas & Rankin,l969 (LAD), Heterohelix moremani (Cushman. 1938) (LAWZ). Assignedage: early to late Turonian.

Dicarinella primitiva Zone: Dicarinella primiliva (Dalbiez. 1955) (FAD). Guembelilria cenomana(Keller. 1935) (LAD). Assigned age: latest Turonian.

Archaeoglobigerina cretacea-Dicarinellaprimitiva Zone: Archaeoglobigerina spp. (A. blowi Pes­sagno. 1967,A. erelacea (d'Orbigny. 1840) ; (FAD). Dicarinella primiliva (Dalbiez. 1955) (LAD). Hedber­gella (H.) ex gr. simplex (Morrow. 1934) (LAD). Assigned age: early to mid-Coniacian.

Dicarinelltl concavata-Marginotruncana sinuosa Zone: Marginotruncana sinuosa Porthault. 1970(FAD). Dicarinella concavala (Brotzen. 1934) (FAD/LAD ; lR?). Hedbergella (H.) flandrini Porthault.1970 (LAD), Marginotruncana renzi (Gandolfi. 1942) (LAWZ; late Coniacian).Marginotruncana undulata(Lehmann. 1963) (LAWZ ; late Coniacian). Conlusolruncana ex gr.fornicata (plummer. 1931) (FAWZ;Santonian). Ventilabrella auslinana Cushman. 1938 (FAWZ; Santonian). Assigned age: late Coniacian toearly-late Santonian.

Dicarinella asymetrica Zone: Dicarinella asymelrica (Sigal. 1952) (FAD/LAD; lR?), Hedbergel­la (H.) ex gr. delrioensis (Carsey. 1926) (LAD). Assigned age: late Santonian.

Contusotruncana patellijormis-Globotruncanita elevata-stuartijormis plexus Zone :Contusotruncana patelliformis (Gandolfi, 1955) (FAD). Globotruncanita elevata (Brotzen. 1934) - G. stuar­tiformis (Dalbiez, 1955) plexus (FAD/LAD; lR?). G/obotruncanella havanensis (Voorwijk. 1937) (FAD).G/obotruncanita stuartiformis S.s. (FAD), Heterohe/ix reussi (Cushman) (LAWZ). Assigned age: earlyCampanian.

Globotruncana orientaUs-Globotruncana ventricosa Zone: Globotruncana linneiana (d'Orbigny.1839) (FAD). G. bu/loides Vogler, 1941 (FAD). G. orienta/is El Naggar. 1966 (FAD). G. ventricosa White.1928 (FAD). Globotruncanita subspinosa (pessagno. 1960) (FAD). P/anog/obu/ina varians (Rzehak. 1895)(FAD). Pseudotextu/aria e/egans (Rzehak, 1891) (FAD). Rugog/obigerina ex gr. rugosa (plummer. 1926)(FAD). G/obotruncanita stuarti (de Lapparent. 1918) (FAD). Assigned age: early-late Campanian.

Contusotruncana ex gr. jornicata-Globotruncana linneiana Zone: Pseudotextularia browniMasters. 1976 (FAD). Pseudoguembelina palpebra Bronnimann & Brown, 1953 (FAD), Contusotruncanaex gc. fornicata (plummer. 1931) (LAD), G/obotruncana bu/loides Vogler, 1941 (LAD). G. /inneiana(d'Orbigny. 1839) (LAD). Globotruncanita subspinosa (pessagno. 1960) (LAD). Gansserina gansseri(Bolli. 1951) (FAWZ). Globotruncana aegyptiaca Nakkady, 1950 (FAWZ), G/obotruncanella peta/oidea(Gandolfi. 1955) (FAWZ). Assigned age: early Maastrichtian.

Gansserinagansseri-Globotruncanita stuartiformisZone: Contusotruncanapatelliformis (Gandol­fi, 1955) (LAD). Globotruncanita pettersi (Gandolfi. 1955) (FAD), Guembe/itria eretacea Cushman. 1933(FAD). Gansserina gansseri (Bolli. 1951) (LAD). G/obotruncana rosetta (Carsey. 1926) (LAD). G.ventricosa White. 1928(LAD).G/obotruncanita stuartiformis (Dalbiez. 1955) S.s. (LAD). Assigned age: lateMaastrichtian.

Contusotruncana contusa-Globotruncana aegyptiaca Zone: Contusotruncana contusa (Cushman,1926) (LFAD/LLAD ; lR). Globotruncana aegyptiaca Nakkady. 1950 (LAD). P/anoglobu/ina varians

254

(Rzehak, 1895) (TR), and Globotruncana spp. (LAD), Rugoglobigerina spp. (LAD), Archaeoglobigerinaspp. (LAD), Globotruncanita spp. (LAD), Globigerinelloides spp. (LAD). Assigned age: latest Maastrieh­tian.

BENTHIC FORAMINIFERIDA

Ungulogavelinella ciryi-Lingulonodosaria nodosaria-Marginulina ex gr. aequivoca Zone: Cate­gory: Assemblage-zone. Lingulogavelinella ciryi Malapris-Bizouard, 1967 (OWZ), Lingulonodosaria no­dosaria (Reuss, 1863) (OWZ),Marginulina ex gr. aequivoca Reuss, 1863 (OWZ). Assigned age: late Aptian.

Ammobaculites cr. coprolithiformis-Buccicrenata hedbergi-Haplophragmium lueckei Zone:Category: Assemblage-zone. Ammobaculites cf. coprolithiformis (Sehwager, 1867) (OWZ), Buccicrenatahedbergi (Mayne, 1953) (OWZ), Haplophragmium lueckei (Cushman & Hedberg, 1941) (OWZ). Assignedage: late Aptian.

Lenticulina ex gr. sUbangulata~Lenticulina ex gr. nodosa Zone: Lenticulina ex gr. subangulata(Reuss, 1863) (FAD),Budashevaella nonioninoides (Reuss, 1863) (FAD), Lenticulina ex gr. nodosa (Reuss,1863) (LAD). Assigned age: late Aptian.

Epistomina carpenteri-Gaudryinopsisfl1iformisZone: Epistomina carpenteri (Reuss, 1863) (FAD),E.chapmanitenDam, 1948 (FAD),Gaudryinopsiscf.gradata(Berthelin, 1880) (FAD),Pseudogaudryinella/Spiroplectinata ex gr. dividens (Grabert, 1959) (FAD), Buccicrenata hedbergi (Maync, 1953) (LAD),Gaudryinopsis filiformis (Berthelin, 1880) (LAD). Assigned age: earliest Albian.

Osangulariaschloenbachi~Pseudogaudryinella/Spiroplectinata. ex gr.dividensZone: Osangulariaschloenbachi (Reuss, 1863) (FAD), Pseudogaudryinella/Spiroplectinata ex gr. dividens (Grabert, 1959)(LAD), Epistomina chapmani ten Dam, 1948 (LAD), Gavelinella barremiana Beuenstaedt, 1952 - G.flandrini Moullade, 1960 plexus (LAD), Budashevaella nonioninoides (Reuss, 1863) (LAD), Marssonellaozawai Cushman, 1936 (LAD), Tristix ex gr. excavata (Reuss, 1863) (FAWZ). Assigned age: early Albian.

Epistomina spinulifera-Epistomina carpenteri Zone: Epistomina spinulifera (Reuss, 1863) (FAD),Cassidella ex gr. viscidus (Khan, 1950) (FAD), Epistomina carpenteri (Reuss, 1863) (LAD), Globorotali­tes eL multisepta (Brotzen, 1936) (LAD). Assigned age: mid-Albian.

Gavelinella berthelini-plummerae-reussi plexus-Gaudryinopsis cf. gradata Zone : Osangulariaschloenbachi (Reuss, 1863) (LAD), Quasispiroplectammina ex gr. alexanderi (Lalieker, 1935) (LAD), Q. exgr. goodlandana (Lalicker, 1935) (LAD), Q. linki (petri, 1962) (LAD), Gaudryinopsis ef. gradata (Berthe­lin, 1880) (LAWZ), Gavelinella berthelini (Keller, 1935) - G. plummerae (Tappan, 1940) - G. reussi (Khan,1950) plexus (FAWZ), Textularia ex gr. subconica Franke, 1928 (FAWZ). Assigned age: mid to late Albian.

Neobulimina subcretacea-Saracenaria cf. crassicosta Zone: Neobulimina subcretacea Cushman,1936 (FAD), Saracenaria ef. crassicosta Eiehenberg, 1933 (FAD). Assigned age: late Albian.

Neobulimina subcretacea-Tristix. ex gr. excavata Zone: Ramulina tetrahedralis Ludbrook, 1966(FADILAD; TR?), Neobulimina subcretacea Cushman, 1936 (LAD), Tristix ex gr. excavata (Reuss, 1863)(LAD), Lenticulina ex gr. subangulata (Reuss, 1863) (LAD). Assigned age: latest Albian.

Cibicides sp. A-Planularia complanata Zone: Cibicides sp. A (FAD), Planularia complanata(Reuss, 1845) (FAD), Praebulimina ex gr. nannina (Tappan, 1940) (FAD), Saracenaria ef. crassicostaEichenberg, 1933 (LAWZ). Assigned age: earliest Cenomanian.

Lingulogavelinella(?) cr. thalmanniformis-Spiroloculina cretacea Zone: Lingulogavelinella(?) ef.thalmanniformis (plotnikova, 1962) (FAD), Lingulogavelinella tormarpensis (Brotzen, 1942) (FAD),Spiroloculina cretaceaReuss, 1854 (FADILAD ;TR?), Spiroloculina sp. A (FAD), Gavelinella sp. A (FAD).Assigned age: early Cenomanian.

Nodosaria ex gr. obscura-Cibicides sp. A Zone: Nodosaria ex gr. obscura Reuss, 1845 (FAD),Cibieides sp. A (LAD). Assigned age: mid to late Cenomanian.

Gabonita levis-Discammina sp. A Zone: Gabonita levis (de Klasz, Marie & Recat, 1961) (FAD),Ammobaculites impexus Eieher, 1965 (FADILAD; TR?), Ammomarginulina paterella Eieher, 1967 (FAD/LAD; TR?), Discammina sp. A (FADILAD ; TR?). Assigned age: late Cenomanian.

Gabonita obesa - Gabonita levis Zone: Gabonita obesa (de Klasz, Marie & Rerat, 1961) (FAD/LAD; TR?), Buliminella sp. A (FAD), Cassidella ex gr. viscidus (Khan, 1950) (LAD), Gabonita levis (deKlasz, Marie & Rerat, 1961) (AC). Assigned age: latest Cenomanian-earliest Turonian.

255

Gabonita levis-NodosariIJ ex gr.obsCllra Zone: Gabonita cf. parva (de Klasz, Marie & Meijer, 1960)(FAD), Gabonita levis(de Klasz, Marie&Rerat, 1961) (LAD), Nodosariaexgr. obscuraReuss, 1845 (LAD).Assigned age : early to late Turonian.

ValvlllineriIJ sp. A-GavelinelllJ berthelini-plllmmerae-rellssi plexus Zone: Valvulineria sp. A(FAD), Bolivina cf. incrassata Reuss, 1851 (FAD), Gavelinella berthelini (Keller, 1935) - G. plummerae(Tappan, 1940) - G. reussi (Khan, 1950) plexus (LAD). Assigned age: latest Turonian.

GavelinelllJ sp. A-ValvlllineriIJ sp. A Zone: Gavelinella sp. A (LAD), Valvulineria sp. A (LAD),Lingulogavelinel/a tormarpensis (Brotzen, 1942) (LAD), Turrispirillina ex gr. subconica Tappan, 1943(LAD). Assigned age: early to mid-Coniacian.

Lenticlllina revolllta-Globorotalites spinea Zone: Lenticulina revoluta (Israelsky, 1955) (FAD/LAWZ ; late Coniacian ; TR?), Gavelinopsis sp. A (FAD/LAWZ ; late Coniacian ; TR?),Globorotalitesspinea (Cushman, 1926) (FAD/LAD ; TR?), Eponides aracajuensis Petri, 1962 (FAD), Gavelinella ex gr.beccariiformis (White, 1928) (FAD), G. correcta (Carsey, 1926) (FAD), G. sandidgei (Brotzen, 1936)(FAD), Gaudryina laevigata Franke, 1914 (FAD), Pseudogaudryinel/a ex gc. capitosa (Cushman, 1933)(FAD), Gavelinella spissocostata (Cushman, 1938 (FAWZ ; Santonian), Reussel/a ex gr. szajnochae(Grzybowski, 1896) (FAWZ; Santonian), Dorothia ex gr. bul/eta (Carsey, 1926) (FAWZ; Santonian),Re­curvoides ex gr. globulosa (Grzybowski, 1896) (FAWZ; Santonian). Assigned age: late Coniacian to early­late Santonian.

Nllttallinella texana-Orthokarstenia clarki Zone: Nuttallinel/a texana (Cushman, 1938) (FAD),Orthokarstenia clarki (Cushman & Campbell, 1936) (FAD), O. clavata (Chenouard, de Klasz & Meijer,1960) (FAD), Bolivina ex gr. afra (Reyment, 1959) (FAD), Verneuilina cretacea Karrer, 1870 (FAD),Glaphyrammina sp. A (FAD/LAD ; TR?). Assigned age: late Santonian.

Siphogenerinoides bramlettei-Rellssella ex gr. s1lJjnochae Zone: Siphogenerinoides bramletteiCushman, 1929 (FAD), Ellipsoglandulina velascoensis Cushman, 1926 (FAD), Gavelinella nacatochensis(Cushman, 1938) (FAD), Globorotalites subconica (Morrow, 1934) (FAD), Gyroidinoides loetterlei (Tap­pan, 1940) (FAD), Osangularia navarroana (Cushman, 1938) (FAD), Planulina taylorensis (Carsey, 1926)(FAD), Hagenowella ex gr. subsphaerica (Reuss, 1846) (FAD), Recurvoides cf. subturbinata (Grzybowski,1898) (FAD), Trochamminoidesflagleri Cushman & Hedberg, 1941 (FAD), Reussella ex gr. szajnochae(Grzybowski, 1896) (LAD), Pullenia jarvisi Cushman, 1936 (LAD). Assigned age: early Campanian.

Lacosteina gouskovi-Orthokarstenia clavata Zone: Lacosteina gouskovi Marie, 1945 (FAD/LAD;TR?), Ammoglobigerina ex gr. globigeriniformis (parker & Jones, 1865) (FAD), Epistomina supracretaceaten Dam, 1948 (FAD/LAD; TR?), GavelinellamonterelensisMarie, 1941 (FAD),Karreriellaexgr. conversa(Grzybowski, 1901) (FAD), Neoflabelina rugosa (d'Orbigny, 1840) (FAD/LAD ; TR?), Praebuliminaspinata (Cushman & Campbell,1935) (FAD), Osangularianavarroana (Cushman, 1938) (LAWZ),Planulinataylorensis (Carsey, 1926) (LAWZ), Orthokarstenia clavata (Chenouard, de Klasz & Meijer, 1960) (LAD),Gavelinella correcta (Carsey, 1926) (LAD), G.lorneiana (d'Orbigny, 1840) (LAD), G. sandidgei (Brotzen,1936) (LAD), Globorotalites subconica (Morrow, 1934) (LAD), Orithostel/a ex gc. halfeldi (petri, 1962)(FAD), Valvulineria amaraliPetri, 1962 (LAD),B. ex gr. afra (AC; at the upper limit). Assigned age: earlyto late Campanian.

Cibicides ex gr. beaumontiana-Gyroidinoides nonionoides Zone: Ammobaculitescf.fragmentariaCushman, 1927 (FAD), Cibicidesex gr. beaumontiana (d'Orbigny, 1840) (LAD), Gyroidinoidesnonionoides(Bandy, 1951) (LAD), Neoflabelina reticulata (Reuss, 1851) (LAD), N. ex gr. pilulifera (Cushman &Campbell, 1935) (LAWZ), Praebulimina ex gr.fang de Klasz, Magne & Rerat, 1963 (LAD), P. ex gc. prolixa(Cushman & Parker, 1925) (LAD), P. spinata (Cushman & Campbell, 1935) (LAD). Assigned age: earlyMaastrichtian.

Gyroidinoides loetterki-OsanglllariIJ velascoensis Zone: Gyroidinoides loetterlei (Tappan, 1940)(LAD), Osangularia velascoensis (Cushman, 1925) (LAD), Nodogenerina stephensoni (Cushman, 1936)(LAD), Praebulimina ex gr. bantu de Klasz, Magne & Rerat, 1963 (LAD), Ammobaculites cf.fragmentariaCushman, 1927 (LAD), RzehakinaflSsistomata (Grzybowski, 1901) (LAD), Verneuilina cretosa Cushman,1933 (LAD). Assigned age: late Maastrichtian.

Orthokarstenia clarki-Praeblllimina kickapooensis Zone: Clavlllinoides ex gr. trilatera (Cushman,1926) (FAD), Gaudryinopsis glabrata (Cushman, 1933) (FAD),Pseudoclavulina arenata (Cushman, 1933)(FAD), Orthokarstenia clarki (Cushman & Campbell, 1936) (LAD), Buliminel/a ex gc. colonensis Cushman

256

& Hedberg, 1930 (LAD), Neobulimina aspera (Cushman & Parker, 1940) (LAD), N. canadensis Cushman& Wickenden, 1928 (LAD), Praebulimina kickapooensis (Cole, 1938) (LAD), P. reussi (Morrow, 1934)(LAD), Pseudouvigerina plummerae Cushman, 1927 (LAD). Assigned age: latest Maastrichtian.

AMMONITES

Epicheloniceras·Diadochoceras.EodouYilleicerasZone: Category: Assemblage wne.Epichelonice­ras sp. (OWZ), Diadochoceras sp. (OWZ), Eodouvilleiceras horridum (Riedel, 1937) (OWZ), Eodouvillei­ceras sp. (OWZ), <<Dufrenoyia» cf.justinae Hill, 1893 (OWZ). Assigned age: late Aptian.

Douvilleiceras Zone: Douvilleicerasex gr. mammillatum (Schlotheim, 1813) (FAD),Douvilleicerasinaequinodum (Quenstedt, 1849) (OWZPR). Assigned age: early Albian.

Oxytropidoceras Zone: Oxytropidoceras buarquianum (White, 1887) (FAD), Oxytropidoceras spp.(OWZ). Assigned age: mid Albian.

Elobiceras Zone: Elobiceras intermedium Spath, 1922 (FAD), Elobiceras sp. (OWZ). Assignedage: early late Albian.

Mortoniceras Zone: Mortonicerascf.lastroensis Maury, 1937 (FAD), Mortoniceras spp. (OWZPR),Neokentroceras cf. tectorium (White, 1887) (OWZPR). Assigned age: latest Albian.

Graysonites lozoi·Hypoturrilites betaitraensis Zone: Graysonites lozoi Young, 1958 (FAD),Sharpeicerasvohipalense Collignon, 1964 (OWZPR), Hypoturrilites betaitraensis Klinger & Kennedy,1978 (OWZPR), Stoliczkaia (Shumarinaia) africana Pervinquiere, 1907 (OWZPR), Forbesiceras brundret­ti(Young, 1958) (OWZPR). Assigned age: early Cenomanian.

Acompsoceras spathi·Dunveganoceras Zone: Acompsoceras spathi Basse, 1940 (FAD), Acompso­ceras aff. renevieri (Sharpe, 1857) (OWZPR), Dunveganoceras sp. (OWZPR), Euomphaloceras (E.) meri­dionale (Stoliczka, 1864) (OWZ), Turrilites scheuchzerianus Bosc, 1801 (OWZ). Assigned age: early midCenomanian.

Acanthoceras jukesbrownei·Eucalycoceraspentagonum Zone: Acanthocerasjukesbrownei (Spath,1926) (FAD), Eucalycoceraspentagonum (Jukes-Browne & Hill, 1896) (OWZ). Assigned age : late mid Ce­nomanian.

Pseudocalycoceras harpax·Thomelites aft sornayi Zone: Pseudocalycoceras harpax (Stoliczka,1864) (FAD), Thomelites aff. sornayi (Thomel, 1967) (OWZPR). Assigned age: early late Cenomanian.

Euomphaloceras septemseriatum Zone: Euomphaloceras septemseriatum (Cragin, 1893) (FAD),Pseudaspidoceras pseudonodosoides (Choffat, 1899) (OWZ), Vascoceras gamai Choffat, 1899 (OWZ),Thomasites gongilensis (Woods, 1911) (OWZ). Assigned age: latest Cenomanian.

Vascoceras harttii·Pseudaspidocerasfooteanum Zone: Pseudotissotia nigeriensis (Woods, 1911)(FAD), Pseudotissotia gabonensis Lombard, 1931 (OWZPR), Vascoceras hamii (Hyatt, 1870) (OWZPR),Pseudaspidoceras footeanum (Stoliczka, 1864) (OWZ), Wrightoceras sp. (OWZ). Assigned age: latestCenomanian-earliest Turonian.

Watinoceras amudariense·Kamerunoceras seitziZone: Watinoceras amudariense (Arkhangel'skij,1916) (FAD), Kamerunoceras seitzi (Riedel, 1932) (OWZ), Mitonia reesidei (Maury, 1937) (OWZPR).Assigned age: early Turonian.

. Mammites nodosoides·Kamerunoceras turoniense Zone: Mammites nodosoides (Schltiter, 1871)(FAD), Kamerunoceras turoniense (d'Orbigny, 1850) (OWZPR), Fagesia bomba Eck, 1909 (OWZPR),Romaniceras deverianum (d'Orbigny, 1841) (OWZ). Assigned age: early-mid Turonian.

Subprionocyclus·Reesidites Zone : Subprionocyclus sp. (FAD), Reesidites sp. (OWZPR),Paralenticeras leonhardianum (Karsten, 1858) (OWZ). Assigned age: late Turonian.

Bllrroisiceras (B.) onilahyense.Forresteria Zone: Barroisiceras (B.) onilahyense Basse, 1948(FAD), Forresteria sp: (OWZ). Assigned age: early Coniacian.

Solgerites armatus·Prionocycloceras lenti Zone : Solgerites armatus (Solger, 1904) (FAD),Prionocycloceras lenti (Gerhardt, 1897) (OWZ), Prionocycloceras guayabanum (Steinmann, 1897) (OWZ),Heterotissotia sp. (OWZ), Bostrychoceras indicum (Stoliczka, 1865) (OWZ), Peroniceras spp. (OWZ).Assigned age: mid Coniacian.

257

OTHER MACROFOSSILS

Among the various macrofossil groups, other than ammonites, only inoceramid bivalves seem to havethe biostratigraphical potential to allow the establishment of a detailed separate zonal scheme. Even so, aninoceramid zonation for Sergipe will probably only comprise the Turonian and Coniacian stages, since ino­ceramids are not abundant enough in other parts of the sequence. Based on studies ofa restricted geographicarea, Ressel (1988) recognized two distinct lower Turonian inoceramid associations: a lower Mytiloides my­tiloides and an upperMytiloides hercynicus association. To determine whether theseassociations are laterallypersistent and thus potential biozones requires further study. They appear to fall entirely within the ammonitezone ofMammites nodosoides-Kamerunoceras turoniense. Acharacteristic and easily recognizable taxon inthe lower inoceramid association is the new genus Rhyssomytiloides Ressel, 1988, which can then aid in theidentification of the nodosoides-turoniense Zone. Other inoceramid taxa described by Ressel (1988) do notseem to be confmed to one zone only.

Kauffman & Bengtson (1985) listed a number of provisionally determined inoceramid taxa ; thematerial is still under study and will eventually be integrated with the current biostratigraphical scheme.

Ofother macrofossil groups, only the echinoids have as yet received full systematic treatment (Smith1991). Although a separate biozonation for echinoids is not justified, selected species were found to beconfined to one or two ammonite zones and thus potentially biostratigraphically useful (Smith & Bengtson1991, fig. 3). For example, the occurrence of Micropedina olisiponensis (Forbes, 1850) in the lower upperCenomanian Pseudocalycoceras harpax-Thomelites aff. sornayi Zone is consistent with its occurrence inPortugal and North Africa [Berthou & Lauverjat 1978 ; Smith & Bengtson 1988, fig. 3 (although wronglygiven as middle Cenomanian on pp. 11,32)].

PALAEOENVIRONMENTAL EVOLUTIONOF THE SERGIPE BASIN

Several authors have discussed the palaeoenvironmenta! developmentof the Sergipe Basin during theCretaceous, for example, Berthou & Bengtson (1988), Koutsoukos (1989), and Koutsoukos et al. (1991a,1991b). We attempt here a synthesis of the time range that extends from the earliest marine incursion untilthe end of the Cretaceous. Interpretations are based on our integrated biostratigraphical work presented here,within the currently available sedimentological and teetono-sedimentary framework.

The passage from the transitional, evaporitic phase to a fully marine drift phase was characterized byprogressive crusta! extension and thinning. This allowed for the establishment ofa narrow epicontinental sea,coupled with the gradual development of oceanic conditions in the central South Atlantic. Open marineconditions were established in Sergipe by late Aptian times, with neritic-oceanic circulation patterns, andsurface-water exchange between the central and South Atlantic oceans (Bengtson & Koutsoukos 1992),possibly even at intermediate water-depths (epipelagic to mesopelagic) (Koutsoukos 1992). A mixedcarbonate-siliciclastic platform system (the Riachuelo Formation) developed from the late Aptian to lateAlbian, with paralic (lagoonal and tidal flats) to upper bathyal environments. Intermittent dysoxic-anoxicconditions occurred, with a «maximum» oxygen-depletion event in the late Aptian-earliest Albian (fig. 8). Arelative sea-level rise during the early Cenomanian caused the drowning of the shallow-water Riachueloplatform. Fine-grained deep-water limestones of a carbonate ramp system (Cenomanian to middle Conia­cian ; the Cotinguiba Formation), accumulated in neritic to upper bathyal environments, with moderatelydysoxic to truly anoxic bottom conditions and well oxygenated epipelagic water masses (Koutsoulcos et al.1991b). Two «maximum» oxygen depletion events (dysaerobic to anaerobic) are recorded in the succession(fig. 8) : in the early Cenomanian, and at the Cenomanian-Turonian boundary. More oxidized conditions(dysaerobic to aerobic) are apparent from the middle-upper Albian and lower-middle Turonian deposits,probably as a consequence ofless restricted oceanic exchange between the central and South Atlantic oceans,with the progressive establishment of open oceanic circulation patterns (Koutsoukos et al. 1991b).

In the late Coniacian-early Santonian a major oceanographic event ended the carbonate-dominateddepositional cycle in the Sergipe Basin. The final structural detachment of the South American and African

258

plates restrltM in the establishmentofadeep-ocean circulation regime. The basin was abruptly tilted seawardsalong a NE-SW-trending rotational axis, which caused uplift of the north-western margin of the basin andcreated a prominent submarine topography (Koutsoukos & Hart 1990, fig. 13). Simultaneously there was arapid change from a dominantly dry to a more humid and warm climate, probably caused by the developmentof a high-pressure atmospheric cell at low latitudes over the widening Atlantic watermasses (e.g., Parrish &Curtis 1982, Chang et al. 1988). This climatic turnover caused increased siliciclastic influx to the basin (dueto intensifi~ continental runoft), the material of which wasderived from the uplifted areas in the north-west.Thick successionsofshales and, suboidimltely, turbiditic sandstones weredeposited; these form the Calumbi.Member of the Pi~abu~u Formation.

Stages

Maastrichtian

Campanian

Santonian

Coniacian

Turonian

Cenomanian

Albian

Upper Aptian

Planktonicforaminiferal

zones

C. contusa-G. aegyptiaca

G. gansseri-G. stuartiformis

C. ex gr. fornicata-G. linneiana

.G. orientalis-G. ventricosa

G. patelliformis-G. elevatalstuartifonnis plexus

Dicarinella asymetrica

D concavata-M sinuosa

A. cretacea-D. primitiva

Dicarinella primitiva

H. aprica­H. (W) baltica

H. (W) archaeocretacea­H. reussi

H. (W) aprJca-G. bentonensis

H(W) baltica­H. (W) brittonensis

P delrioensis-R. appennil1ica

R. brotzeni

H. (H.) gorbachlkae­T raynaudi

G. texomaensis­B. breggiensis

B. breggiel1sis­.' T ex gr. primula

T ex gr. prJmula­T bejaouaensis

T beJaouaensis

G. cushmani­T bejaouaensis

G. ex gr. maridalensls-H (H.) slmilisG. barri-H. (H.] gorbachlkae

NW

Palaeobathymetricevolution

SE

, , ,

: :: :.: :.:.:.: :.;.: :.:.: :::::::.

I>,'cnlQl"0, cEI'&35 'I <5~ ,"550.1

Fig. 8 - Palaeobathymetric evolution of the Serglpe Basin. Shaded areas Indicate time ofmaximum dysoxlc-anoxicepisodes. The left-hand side of the diagram corresponds to the present-day, north-western onshore border of the basin(Riachuelo and ltaporanga highs), and the right-hand side to the south-eastern limit of the studied area (off-shore area ofwelll-SES-3 : Koutsoukos 1992, fig. 1) (from Koutspukos 1992, fig. 2(E) ; stage thicknesses not to scale). '

259

Apalaeobathymebic maximum appears to haveoccurred in the early Campanian (fig. 8) (Koutsoukos1989), when the bathymebically deepest environments are recorded in all the sites studied. Foraminiferalspeciesdiversity reachedapeak in theCampanian,probably in response to increased nicheavailability, whichpromoted evolutionary diversification.

Palaeoenvironmental conclusionsThe marine Cretaceouspalaeoenvironmental evolution ofthe basin can be subdivided into three major

phases: (1) a late Aptian to late Albian paralic to upper bathyal phase (mixed carbonate-siliciclastic platformsystem; Riachuelo Formation) ; (2) an early Cenomanian to mid-Coniacian neritic to upper bathyal phase(carbonate ramp system; Cotinguiba Formation) ;and (3) a late Coniacian or Santonian to late Maasbichtianmiddle-deep neritic to lower bathyal phase (siliciclastic system; Calumbi MemberofPia~b~u Formation).Foraminiferal species diversity reached a peak in the Campanian. This was associated with a palaeobathyme­bic maximum, probably in the early Campanian, from when the deepest environments are recordedat all thesites studied.

AcknowledgementsWe thank Petr61eo Brasileiro S.A. (petrobnis), Rio de Janeiro, for permission to publish the paper.

Paleontologiska institutionen, Uppsala University (Sweden), provided working facilities for P. B. duringresearch visits in 1991-1992. Marta C. Viviers (petrobnis) advised on the microfossil zonations, Suzana I.Bengtson (Uppsala) revised determinations of the lower Cenomanian ammonites, and Pierre-Yves Berthou(Paris) contributed stratigraphical data on echinoids. We thank P.Y. Berthou and FrancisRobaszynski (Mons)for reviewing the manuscript for publication. The final drafting of the illustrations was by Rolf Koch andRainer Ziihlke (Universitat Heidelberg), using Aldus FreeHand on a Macintosh Quadra 950. Part of theunderlying work was financed by grants to P. B. from the Swedish Natural Science Research Council (NFR).

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