The Macae Formation, Campos Basin, Brazil

Revista Brasi leira de Geociencias 18(3):261. 272. setembro de 1988

TH E MACAE FORMATION, CAM POS BASIN, BRAZIL: ITS EVOLUTION IN THE CONTEXT OF THE INITIAL HISTORY OF THE SOUTH ATLANTIC

ADALI RICARDO SPADINI', }'ERNANDO ROBERTO ESTEVES", DI MAS D1AS.BRITO·, RICARDO LATGE MILWARD AZEVEDO', and RENE RODRIGUES'

ABSTRACT The Macal! Fonnation (Albian. Lower Turonian, Campos Basin) is very significan t for understanding the early history of the South Atlantic north of the Walvis Ridge/Sao Paulo Plateau system. Deposition of the unit imm ediately succeeded the Aptian evaporitic event. and preceeded the oceanic phase that began in post- Ear ly Turonian times. This is probably the best known Middle Cretaceo us carbonate record in the South Atlantic. It consists of the Lower Macae (Early to Middle Albian), fonned dominantly by limestones deposited mostly in shallow neriti c environment, and the Upper Maca6 (Late Albian-Early Turonian) with calcil utites overlain by marls and shales, deposited duri ng progressive sea level rise. A tidal flat system was devel oped in the southern portion of the basin during depos ition of the lowermost Maca6 Formation, with supratidal, intertidal, and lagoonal environments. Burrowed carbonate mudstones were deposited in shallow shef environments , and oo ids and peloids in a high energy offs hore shoal system. Hypersalinity prevai1led during that time, as suggested by the low biotic diversity and the carbon isotop e values. Very negative oxygen isotope values indicate that surface water temperatures were high. Oncolite limestones and subordinate calcilutites prevail in the middle and upper parts of the Low er Macae, chiefly deposited in shallow neriti c environment. Hypersalinity and high water temperature persisted, as indicated by paleoecological and isotopi c studies. The Maca6 sea was then a juvenile ecosystem, unstab le and poor in nutrients, with maximum depth values arou nd 50 m, Th e Upper Maca6 carbonate mudstone s. Late Albian in age. are rich in calcispberulids, Its abundant pelagic biota probably reflects desalinization and increase in nutrients of surface waters related to the South Atlantic expansion and consequent increase in water volume and circulation. Th e benthic foraminifera are suggestive ofdeep neriti c environments (100 ·200 m). "At the end of the latest Albia n, a rhythmic deposition or calcilutites and marl s was probably caused by climatic variations (dry/warm to warm/wet climate cycles). From the Cenomanian to the Turonian, already under a wannlwet climate. were deposited the fine- grained siliciclastics, mos tly in upper bathyal environment; episodic anoxi c conditio ns are represented by lamin ated black shales, freq uently rich in radio laria, and with a relatively high organic carbon content".

RESUMO A FOR/o1Al;AO MACA~ , BACIA DE CAMPOS. BRASIL: SUA EVOLUl;AO NO CONT EXTO DA HISTORIA INICIAL DO ATLANTICO SUL.AFormacao Macae (Albiano-Ecruronia no, Bacia de Campos) 6 muito significativa para 0 entendimento da hist6ria inicial do Atlant ico Sui ao norte do sistema Walvis Ridge-Plate de Sao Paulo. Sua deposicao sucedeu imediatamente ao evento eveporltico ai?tiano e precedeu a rase oceanica, que comecou em tempos pcs-eoturonianos. Ela l!. prov avelmente, 0 re grstrc cerbonanco mesocretscico mars bern conhecid o em todo 0 Atl1ntico SuI. E composta pelo Macal! In ferior (Eo- a Mesoalbiano), constitufdo dominantemente de calcarios, depositados sobretudoem meicnerftico . rasa , e pelo Maca6 Superior (Neoalbiano-Boturoniano), com calcilutitos sobrepostos por mar~ e fclhe Ihos, acumul ados em resposta a eventos transgressivos. Durante a deposicao da parte mats inferior da Per malj3.o Macae , urn sistema de planicies de marl! se desenvolveu a sui da bacia, com ambientes de supramare, Intermare e lagunas. Calcilutitos bioturbados precncheram frens ealmas de ambiente nerftico rasa enquanto ocides e pel6ides se acumularam em sistemas de bancos de alta energia desenv olvidos em freas distais. A baixa diversldade bi6 tica e os valores de isotopes de carbono sugerem que, naquele tempo, 0 eorpo mari nho era hipe:rsalino. Valores mui to negatives de isotopes de oxi~en io indicam

I NTRODUCTION The Albian carbonate sequences of hydrocarbons from structural-stratigraphic traps in six oil the eastern Brazilian margin contain the first typical records fields. of the South Atlantic Ocean. Among all these carbonate The main purpose of this work is to characterize the sequences, the Macae Formation of the Campos Basin is the depositional history of the Macae Fonnation in order to one that pre sents of greatest number of data, recovered from contribute to the global understanding of the initial con more than 300 wells, which provide valuable infonnation for text of the South Atlantic. The investigation was based the understanding of the South Atlantic evolution. The on sedimentological, biostratigraphic, paleoecological, and Macae Formation is economically important, as it produces geochemical data . The results summarizes the effort of many

... Centro de Pesquisas e Desenvol vimento da Petrob rds (Ccnpes), Cidade Unlverslrdria, llh a do Fundao, quadra 07, CEP 21910, Rio de Janeiro, RJ. Brasil •• Departamento de Exploracdc da Pctrobn'is (Depex), Av , Chile, 65, 132 andar, CEP 2003 1, Rio de Janeiro , RJ. Brasil 262 Revista Brasdeira de Geocunctas, Volume 18, J988

people in Petrob ras since the beginning of exploration in the Campos Basin. Previous detailed facies analysis of the Macae carbonates have been documented by several auth ors, following the pioneer discovery of Garoupa Field in 1974, the first oil field in the Campos Basin. Tessari & Tibana (1975) defin ed the general facies framework, establishing a generic depositional evolution . Carozzi et al. (1977) defined a diagenetic. depositional model for the Macae Formation. Falkenhcin (1981) concentrated on the general tecto-sedimentary setting, the identification of microfacies and environmental interpretation. Beltrami (1982), using wells and seismic data, established a region al distribution of the carbonate high energy facies along NE-SW structural trend . The siliciclastic section was studied by Guardado et al. (1983). . Esteves et al. (1987) proposed a general sedimentary evolution model for the Lower Macae, Guardado & Spadini (1987) established a depositional model relating previous rift struc tures and salt tectonics with the facies distribution. Detailed reservoir studies were performed by several authors (Franke 1981, Baumgarten et al. 1982, Spadini & Paumer 1983, Baumgarten et al. 1984, Paumer 1984, Scuta 1984, Franz 1987). Strong efforts in the biostra tigraphic research have been made in the Campos Basin since the first oil discover y in the Macae carbonate reservoirs (Gomide 1976, Uesugui 1976, Figure I - Location map ofthe Campos Basin Dias -Brito 1982, Gomide 1982, Dias-Brito 1985a, Moura & Praca 1985, Azevedo et al. 1987a, Shimabukuro et al. 1985, Richter 1985, 1987, Shimabukuro 1988, Moura 1988, by Schaller (1973). It comprises alluvial-lacustrine sediments Antunes 1988). Gomide (1982), based on calcareous of the rift phase, the evaporites of the transitional phase, and nanoplankton, defined an Albian/Cenomanian age for the carbonates and siliciclastics of the pre -oceanic and oceanic entire Macae sequence, reco gnizing only one biozone phases (Fig. 2). The Macae Forma tion, Albian to Early {Nannoconus truitti}. Uesugui (op. cit.). based on Turonian in age, characte rizes the deposition during the palynomorphs, established a sequence of thr ee informal pre-oceanic phase (Fig. 3), overlying the evapo rites of the biounits: the a/fa interval defined as probably Early Albian in Lagoa Feia Forma tion. The relationship between the age; the beta inter val defined as Middle Albian in age; and the biochronostratigraphic and lithostratigraphic units of the ganvna interval as Late Albian/Cenomanian in age. Macae Formatio n is showed in the figure 4. Dies-Brito (1985a), studying calcispherulids of the The Macae Forma tion is informally divided into Lowe r fine- grained limestones, 'defined two informal biozones: the and Upper Macae (Fig. 5). The former, Lower/M iddle Albian, Pithonel/a sphaerica and the Pithonella sphaericalPithone//a was deposited mostly in shallow neritic environme nt. The ovalislBonetocardiella conoidea zones. Dias-Brito compa red lowermost section of the Lower Macae is characterized by the distribution of the calcispherulids in the Campos Basin and dolomites, overlying in sharp contact the Lagoa Feia nodu lar those of the Leg 40, site 363, located in the Angola Basin anhydrite. The Upper Macae, Late Albian to Early Turonian (Bolli 1978), and considered the alfa zone as Early to Middle in age, is composed of calcilutites and marls, deposited as a Albian in age, and the beta zone as Late Albian . In a recent result of a tran sgression ove r the former shallow platform. paper where the biostratigraph y of the basin is summarized, The Macae Forma tion is wedge-shaped, pinching out Azevedo et al. (op . cit.}; using planktonic foraminifera, westward against the fault that limits the Lower Cretaceo us calcareous nannofossils and palyno morphs, considered the basin (Fig. 6).During all the Macae time, siliciclastic facies ganvna interval as Late Cenomanian to Early Turonian in age. occur on the coas tal portion s of the basin. A series of paleoecological interpretations of the Macae Two principal struct ural elements arc present in the carbonates has been made in this decade. The first Campos Basin: the high-angle normal faults of the rift phase, paleoecolo gical work was performed by Dias-Brito ( 1982), and the adias trophic struc tures , mostly normal listric faults, stud ying microfossils in thin -secti on. FoUowing this work, that affected the post-sal t sediments. The rif t phase is new contributions were given by several authors (Koutsoukos represented by horsts and grabe ns involving both basement 1984, Dias-Brito & Azevedo 1986, Azevedo et al. 1987b, and pre-salt sediments. The adiastrophic structures was Dias-Brito 1987, Koutsoukos 1987, Viviers & Azevedo, fonned due to basin tilting and differential compactation 1988).Environmental interpretations based on carbon and (Figueiredo et al. 1983). Salt movement resu lted in the oxygen isotope studies was made by Takaki & Rodri gues formation of pillows which controlled the distribution of (1984). Albian shallow water carbonate facies and the thickness of the lowermost section of the Lower Macae. With the STRATIGRAPHIC AND STRUCTURAL FRAME continuing evolution of the salt structure, syndepositional . WORK The Campos Basin (Fig. 1) is a typical continental listri c faults were generated, developin g struc tures of rollover margin basin of the Atlantic type . The basin has a minor type (Figueiredo et al. op. cit.), that caused abrupt lateral emergent area, and extends offshore to water deph ts grea ter facies changes at the top of the Lowe r Macae. 2 than 3,000 m, covering an area of 100,000 km • The Campos Basin was originated during the breaking of the Go ndwana THE LOWER MACAE SEDIMENTATION A ND supercontinent. The initial rifting occurre d during the Rio da PALEOECOLOGY The Lower Macae seque nce is Serra Stage, a Brazilian local unit of the Lower Cre taceous composed of two distinct sections: the basal one, just above (Asmus 1975, Asmus & Porto 1980). . the evaporites, is charac terized by strong dolomitization; the The stra tigraphy of the Ca mpos Basin was first established upper one, corresponding approximately to the middle and Revista Brasileirade Geocdncias, Volume 18, 1988 263

CHRONO LITHOSTRATIGRAPHY SEQUENCES STRATIGRAPHY H IT PLI ENE MIOCENE UJ o OLIGOCENE Z z EOCENE - .. w PALEOCENE a: u - MAASTRICHTIAN ex 0 CAMPANIAN SANTONIAN ::Ii CNIA IAN

PRE-OCEANIC

IGNEOUS BASEMENT + +++ + +1 P& Figure 2 - Stratigraphy of the Campos Basin (after Petrobrc'islDepexlSecamplSebipe) and related depositional sequences (modified from Dias-Brito & Azevedo /986)

upper portions of the sequence, is characterized by the feature, usually showing calcite drusy cement. The foss il predominance of algal grains (oncolites). Each section can be content is very poor. mostly ostracods and rare miliolids. Thin related to a particular depositional model. beds of oolite grainstones probably records deposition by storms. Periods of siliciclastic influx are represented by The basal section Tbe change of environmental ripple-laminated, fine-grained arkosic sandstones. 'conditions from the previous evaporitic setting led to the The lagoonal environment that occurs associated with the installation of the Maca6 carbonate system. A series of tidal flat belt is represented by bioturbated peUetoidal environments occur within a carbonate ramp (Fig. 1). mudstones, with a poor biotic content, including miliolids, A tidal flat system developed in the southern portion of the agglutinated foraminifera ; pelecypods and ostracods (plate 2a basin. This system includes the supratidal, intertidal. and and 2b). The occurrence of restricted lagoonal facies suggests lagoonal environments as defined by Shinn (1983), exhibiting .the presence of a barrier seaward of the subtidal lagoonal typical facies assemblages andvertical sequences (Fig. 8). The sediments, probably barrier islands, associated with tidal intertidal/supratidal belt is characterized by laminated deltas, composed by oolite grainstones, analogous to the mudstones, probably of algal origin (Plate Ib). Teepee modem Trucial Coast, Persian Gulf (Loreau & Purser 1973). structures and mudcracks are indicative of subaerial exposure Open shallow shelf environment is represented by (Plate Ia). Brecciacion associated with collapse is.a common bioturbated pelletoidal mudstones with echinoderms , small

Plate / - Tidal flat Macae fa cies. deposited just above the Lagoa Feia evaporites: 3. teepee structures, characterizing subaerial exposure; b. algal lamination in carbonate mudstones. Brecciacion and collapse developed locally 264 RevistaBrasi1eira de Geociencias, Volume 18. 1988

foraminifera and agglutinated foraminifera (Plate 2c). occurred at the onshore portions along the entire basin Graded dolograins tones (Plate 2d) occur intebedded with interfingering with shallow water carbonates. the mudstones. The shoal system is composed by a series of facies form ed Table 1 - Characteristics of the carbonate sedimentation, by oncolites, peloids, and ooids, with rare bioclasts . The based on core analysis. Section just above the Lagoa Feia variety of depositional texture and composition reflects evaporites more directly the difference in the water agitation than water dephr. Usually, the facies are arranged in a series of shallowing-upward cycles, beginning with peloidal Depositional Lagoonal E nvironment Tidal n at Sha llow neritic packstones and ending with oolite grainstones. The oolite grainstones are usually coarse-grained, some Pelletoidal times cross bedded (Plate 3a), indicating deposition in a mobile Facies Mudstones Pelleto idal mudstones mudstones dolograinstones sand shoal. Small ooids and composite grains are accessories. Where only ooids are present the facies is structureless. A Algal facies composed by ooids and peloids conunonly occurs Structures laminations Biotu rba tion Mud cracks Biotu rbation associated with the oolite grainstones, usually showing Teepees parallel laminae. Commonly the growth laminae of the ooids were destroyed by micritization (Spadini & Faria 1986). Miliolids Enchinodenns Fossils are rare in the oolitic facies, including echinoderm Biota Ostracods Ag"l utin ated Rotalids fragme nts and pelecypods. Submarine hardgrounds, with a Miliolids c ram. Ostraco ds pelecy pods Pelecypods few centimeters in thickness, oceur only locally. The oolitic facies corresponds to the highest depositional energy of the shoal system. . The deeper areas of the basin were the site of deposition of The oncolites display several sizes and shapes. They form carbonate mudstones, with a poor biotic content, mostly three principal depositional facies, reflecting different water planktonic foraminifera, calcispheru lids and echinoderm agitation. Peloids are the most common oncolite nuclei. Among fragments. These mudstones are interbedded with marls and the bioclastic nuclei, pelecypods and enchinoderms are the .shales. most common constituents. Structureless oncolite grainstone In the southern offs hore portion of the basin, related to facies (Plate 3b) are formed by regular concentric oncolite structural highs, were deposited facies composed by ooids and grains, usually 2- 3 mm in diameter. Peloids, composite peloids, in a high energy shoal system. These facies were grains, and ooids are also present. Bioclasts are rare (1-2 %), almost completely dolomitized, diffic ulting the recognition of including agglutinate foraminifera, textulariids, miliodis, the depositional texture. mollusks and echinoderms. Peloidalloncolite grainstones are In the northern portion of the basin, the marine carbonates normally associated with the oncolite grainstones; this facies grade westward to siliciclastic facies, mostly fan-delta is massive, sometimes burrowed, locally with parallel or sandstones and conglomera tes and shelf sandstones inclined laminae. The oncolite packstones are composed by (Guardado et at. 1983). Interbedded carbonate banks are oncolites 2-5 mm in diameter (Plate 3c), many of them composed by ooids, pelecypods, and rare red algae. Mixed displaying irregular gro wth bands. Oncolites up to I em occur facies were formed in response to storm and tidal processes locally. This fades is massive to burrowed and show s a (Fig. 9). variable percentage of peloids and microoncolites. Bioclasts The general depositional model of the Lower Macae are rare, including textularids, gastropods, pelecypods, correlates with a carbonate, ramp, mostly in shallow neritic echinoderms , miliolids, and hyaline foraminifera. environment (Fig. 7). The peloidal grainstones are commonly burrowed, with a The scarcity of biotic content is indicative that restrictive low percentage of ooids and oncolites, Bioclasts (up to 5%) conditions prevailed durin g the deposition of this sequence, include mostly echinoderm fragments, some textularids, and probably related to physical and chemical properties. This is milioids, and very rare planktonic foraminife ra. Peloidal true even for the environments out of the embayments and packstones have a higher percentage of bioclasts, principally lagoons. The light color, of shallow neritic carbonates, echinoderms (echinoids) and pelecypods. Other bioclasts, associated with common bioturbation indicates that including textularids, agglutinate foramini fera, and miliolids, hypersalinity was the restrictive factor of the environment. are less important. Gastropods and planktonic foraminifera The carbo n isotope values between 3,0 and 4,0°/00 PDB appear locally. Aggregate grains, oncolites, and ooids are standard (Fig. 10) are higher than that of a normal marine accessories in the packstones. , water and are also indicative of hypersalinity. The presence of The low energy shelf enviro nment is characterized by the evaporites just below the sequence also led to this inter deposition of fine-grained limestones. These facies are pretation. High water surface temperature is suggested by the mottled to wispy-laminated, with up to 5% of bioclasts (Plate oxygen isotope values around 5,0° /00 PDB stan dard and by the 3d). The bioclasts include mostly foraminifera and small predominance of oolitic and peloidal grains, which nowadays echinoderm fragments (possible related to pelagic species?). are observed only in tropical settings (Leonard et at. 1981). Micromollusks and ostracods are rare. The rare planktonic foraminifera are basically represented by hedbergellids and . The upper section The lithofacies of this part of the favusellids, while the scarse small benthic foraminifera Lower Macae were deposited on a car bonate ramp, in three comprises Lenticulina ~pp. , nodosarids, Trocholina spp.; depositional environments (Fig. 11): a. high energy shoal textularids and miliolids are very rare .Calcispherulidae are system, eveloped in the southern positive areas and in the also rare, locally reaching up to 5%, represented mostly by the NE shallow banks trend; b. shelf enviromnent used here as specie Pithonella sphaerica; Pithonella ovalis is scattered, and defmed by Wilson (1975) as an area on top of a ramp or rare . In the inner portions of the shelf the matrix of the platform, including a shallow portion adjacent to the shallow fine-grained limestones is peloidal (calcisiltite). In the outer bank (few tens of meters) and the deeper offshore areas, shelf homogeneous matrix is common, but the biota is similar implying in tens of meters, even a hundred meters deep." ; c. to that one of the inner portion. basinal environment corresponding to the deep-water areas, The basinal environment is also characterized by synonymous with "outermost ramp" (Budd & Loucks 1981). fme-grained limestones, but with a greater ammount of Each one of the enviromnent is characterized by distinct planktonic forams and calcispherulid s. Shales and marls occur facies assemblages and vertical sequences. Siliciclastic rocks interbedded with the limestones. Revista Brasi1eira de Geocu ncias, Volume 18, 1988 265

~ rORliAT ION "-liliA-RAT m ~T IMlUla' SO NIC LOC UC/fS ~ ~ ~ ~ ~ • CAMPOS SlWIS <> ...::: S ~ ~ ~ ... <: I g~ <> ~ I ~ • 'l. • • ,• ~ ~ <:• ~ IW:LS 1IT11 lI.D KlAJlA1S ~ ~ <> ... ~ ... ~ ~ ~ ., IlUOSTONE - NUL RHTTNICS :~~~::~~ "(II'l'fl_SU: ,...'"-'....,..,:. ..:..':. Off'IIUIfIC .... UQUUCf ~~ .",!: , •.,.. TOU'I'('IATlIYAl ~I ...~... ::...: ... W"" III1DSTon 'IITlI CACISMRULIOS ...... (lI'1I.OIIl1fll' -·...... ,...... 'U'I'O"U ..:....:;;.....r ~ PElO IDAL MIIDSTONE Off'lIfllme: Pllf -OCfUllC Off'II(III'1C ~ ~ PELOIDAL PAClSTONE kitff! c""eollAn C""IOllnE I SfOU(IICf EII'IIIIOllllfll ' ·." ~ il'1-lfi ONCOLITE PA C~ ST O NE / ~ t*S PHASE - -- 'w CR AI NSTOllE - I, 0 ;; OOLITE m illSTONE 5H'llOW SH_llOW · IIE.ITIC Utl ll C • ~

o 5

•• -<>- .\500,-?-i-----T---+------i------.--• ---.--• -----,•,--.-.-----;--,

TERTIRRY

~ PP E R RETRCEOUS _ ...

C R E T RC ~ D US

Figure 6 - Stratigraphic-structural dip section (datum at - 1,500 m). Both shallow (Lower Macae) and deep water (Upper Macae) carbonates grade westward to siliciclastic facies. The entire unit pinchs out against the f ault that limits the Lower Cretaceous sequence

NO SCALE

Figure 7 - Depositional modelfor the lowermost portion ofthe Lower Macae. Legend: see fig ure JI Revlsta BrasiJeira tie Geocuncios, Volume 18, 1988 267

Plate 2 - Carbonate facies photomicrographs of the basal section, Lower Macae: a. lagoonal fa cies. Micritic/pelletoidal mudstone with miliolids (center) and ' pelecypod fragme nts. Scattered quam grains; b. pelletoidal lagoonal sediment, with pelecypod fragments; c. shelf facies. Mudstone with rare echinoderms (center) and small Foraminifera; d. cloudy center-clear rim anhedral to euhedral dolomite crystals. Scale bar equal to 0.5 mm

Plate 3 - Facies ofthe uppermost section ofthe Lower Macae: a. crossbedded oolite grainstone; b. structureless oncolite grainstone; c. photomicrograph of large oncolite grains. Scale bar equal I mm; d. phatamicrograph of shelf mudstones. Echinodennfragments (E) and small foraminifera (arrow) are the most common fossils. Scale bar equal 0.2 mm 268 Revista Bm sileira de Geocii ncias. Volu me 18, 1988

SEni DESCRIPTION T BIOTA T ENVIRONMENT DESCRIPTION BIOTA ENVIRONMENT DEPTH,., CORE DEPT,., H CORE SEri I 4,12 ' sec Mll lOLiDS ECHlHQOEIlt,lS LAGOOl-lAL OSTRACODS IIH ERTIOAI. fL AT lllJRIlO'N£ D PELlETOIOAL MUDSTONE I\GG. UT ~ D F(lRAI,IS 5UR!!OWED LAMINATED MLCSTONE , PELECYPOOS I:ti . i .0': CClU.APSE 8IlECClA "'~T_ "'VI~ \ ·. ." -- . . , 2 . . .. ARl«lSIC SlJj DSTONE OSTRACODS INTEIlT1OAl. see · . " 1Xf:D OOLITE 'SANDSTONE PELECrPOOS t ...... , · . ~ - •• • All 'NT III • 4) 2!1 - '" '" .. . <-. - ,.....". w_'_ .n'....'OI'e.""'I . ....lOl llS ".., OSTRIlC:OCl' TIDAL f'\. /IT %ARI

PELECYPODS ~ OOUTE PIlCItSTONE ' !IlJIlIl()W£D MUDSTONE , """""'- --- GREEN AlGAE [V APORITI; ~ """""'" ~ I- ' ~" ' R'

Figure 8 - Vertical core sequence of supratidal to subtidal Figure 9 - Vertical sequence of mixed carbonate-siliciclastic fa cies, deposited just above the Lagoa Fcia evaporites facies in Ihe lowermost portion ofthe Lower Macae

Im l Echinoder m fragments, pelecypods, and amonoids are rare. GAMMA, - 8 ELECT RIC RAY T"- m The intermediate inter val is for med by rhy thmic carbonate

f ~: N mudstones and marls with basinwide distribution (Fig. 15). '!a' ... characterizing a chro nostratigrap hic mar ker (Spadini et af. 1987). The faunal content of this interval is similar to that of ~ : the basal section, but with aditional significative ammo unt of radiolarians. On the oth er hand , the carbonate matrix is here ~ -=:= ~~ formed by a large anunount of coccoliths (calcite platelets of => golden brown algae), characterizing a true chalk as defined by Scholle (1977) . The basal and intermediate interval facies were deposited in response to the progressive and acce ntuated sea level rise duri ng the Late Albian, in acco rdance with the global eustatic curve (Haq et 01. 1987). These limestones represe nts a typical pelagic sedimentation, as they are formed by coccoliths, which nowadays are responsible for generating significant ammounts of pelagic sediment (Mullins 1986). The paleoecological data, based on thc association of benthic 'w foraminifera, indicate that the . deposition occurred in ~ middle/d eep neritic environment (Azevedo et al. op. cit), with bathyal depths recognized in the northern portion of the basin "a: (Fig. 16). The higher biotic diversity and frequence, w ,. - R comparing with that of Lower Macae sequence , is att ributed - - ~ - :1 -- to the desalinization of the oceanic water, a process related to " the expansion of tbe South Atlantic (Dies -Brito 1982, 1985a, 1985b, 1987). The car bon isotope values are gradually less positive in this section (Fig. 16). pointing out to a better oceanic circulatio n. with the valucs approa ching to those of normal marin e limestones. The climate during the Late Albian was predominantl y warm and dry. similar to that of the Lower Macae, when the circulation paUern in the basin ~~~-~..--,-~---" ac"IPDBI presented a negative water balance (Dias -Brito 1982). The - 2 - I 0"'1"'2 +3 +4 +5 calcilutite/ marls rythms that characterizes the intermediate ,,,,,,,,, ,' 80,sIPOB) interval represent alternating warm/dry and wannfwet -1 -2 - 3 · 4 -5 · 6 -7 climatic cycles, preceding the drastic climatic change occurred Figure 10 - Carbon and oxygen isotopic data ofwhole rocks post-albian times causing the term ination of the cretaceous samples. The data are given as per-mil (leviation f rom PDB carbonate deposition in the Campos Basin. The connectio n between the North and South Atlantic that started in the standard Early to Middle Albian was in an advanced stage (Dies-Brito 1987). The occurrence of some spec ies of radiolarians Pithonella ovalts, Bonetocardiella conoidea and other spheres described by Kotzian & Eilert (1987) sugges ts that the Macae not fonnall y described until now (Dies-Brito 1982/ 5a). Sea was already connected even with the Nor th Pacific and Planktonic foraminifera are mostly represented by Ce ntral Pacific oceans. Hedbergella and Ticinella species. The benthic foraminifera The uppermost section of the Uppe r Macae, Late association is relatively impo rtan t when compared with that Cenomanian to Early Turonian. is characterized by marls, of the Lower Macae, and are formed by Gyro idinoides aff, with subordinate shales and sandstones turbidites. The marls praestans, Globorotalites michelinianus, Osangularia are usually bioturbated (Planolites and rare Zoophycus). The utaturensis, Dorothia levis, D . OXyCOIlO, Clavulina gabonica, faunal content of this section is totally different fro m those of Lagena apiculata, Lenticulina spp., Gavelinella spp. Bolivina, the albian carbonates (Azevedo et al. 1987). The frequence Haplaphragmoides. among others (Azevedo et af. 1987a). and diversity of the biotic content along this interval is highly Revtsta BrasiJeira de Geocu ncias, Volume 18. 1988 269

GRAINSTONES/PACKSTONES

MUDSTONES

DOLOMITES

CONGLOMERATES/ SANDSTONES NO SCALE

LAGOAFEIA EVAPORITES

[2i¢..J LAGOA FEIA SILICICLASTICS 1+++/1 BASEMENT

u·

o. "'''''. 41'

Figure JJ - Paleobathymetric map at the end of the Lower Macae time (from Azevedo et 00. / 987) n ' .•,- ':.~;.;: ~BASIN CARBONATE FACIES Among foraminifera. textuJarids dominant ; o variated. the are ""m they include Haplaphragmoides, Ammodiscus. Trochammina, Glomospira, Ammobaculites, Clavulina gabon ica and Figure 12 - Facies mllp at the end of the l.ower Manu! (from Doroth ia oxycona. The benthic calcareous foraminifera are Esteves et aI. 1987) represented by Lenticulina, Govetinetla, Gyroidinok' f aff. 2 70 Revista Brasueira de Geocirncias, Volume 18. 1988

Plate 4 - Late Albian carbonate mudstones: a. photomicrograph of calcispherulids-rich mudstones. Note the presence ofBonetocardiella conoidea specie (ar row) and rare radiolaria (R). Scale bar equal '0.15 nun; b . MEV photograph showing the matrix fa nned by coccoliths (C C). Euhedral crystals resulted from plates overgrowth

Otpth G AMMA SONe 1m) RAY

2~ 5 0 II-W w ::l; - 2.500

~50 'W 4 ~ ~ 8':> ([ 2.600 W 3 0 ...J 2.650

2}00 k<>,j SILICICLASTIC FACIES 1·. ,/1 DEEP WATER CARBONATE o ; "0.

Figure / 4 - Carbon and oxygen isotopic data of whole rocks Figure /5 - Facies map of 'he true Albian (Upper Macae). core samples. Uppermost section of the Lower Macae ami From Spadini ct aI. / 987 Upper Macae. The data are given as per-mil deviation fr om conditions (Azevedo et al. 1987); oth er times these anoxic PDB slandard strata have no fauna, but in other cases they are rich in planktonic foraminifer a andlor radiolarians. praestans, Lagena apiculata, Pleurostomella, Gyroidlna, T urbidites were channelized in the down thrown blocks of Globorotalites michelinianus, bolivlnids, and nodosarids. T he the growth fault s (Guardado et al. 1986). paleozooplankton is fonned by foraminifera and radiolarians. T he former comprise the genera Hedbergella, Heterohelix. CO NCLUS IO NS The Macae Formation nowadays is Globigerinelloids. and Whiteinella. Radiolarians are important probably the best kno wn mid -cretaceous sedimentary record elements in this interval. sometimes forming true siliceous of the South Atlantic. The Macae de position records ooze . As in the Late Albian . the radiolarian test s are significative oceanographic evenIs. impo rtanl for the global frequently calcitized. undersla nding of the South Atlantic Ocean evolution in its T his unit was deposited dominantly in a upper bathyal initial phases. setting (Fig. 17). the basin presenting a positive water balance. The shallow carbonate neritic sequence. Ea rly to Middle where evaporation was less than precipitation and ru noff. A t Albian in age (Lo wer Macae unit). represents a deposition in this time. already under a warm/wet climate. episodic anoxic an epicontinental sea similar to the presenl Persian Gulf. bUI events are registered as indicated by the deposition of eve nly in a more restricted regional setting. The sedimentation laminated black shales. These shales sometimes show a developed in an hypersaline environment. under high water monofauna o f the foraminifera Neo buiimina albertensis?, lemperatures. The climate was at that time warm and dry . The taxon similar 10 thai one nowadays adapled to anox ic base of this unit is formed mostly by peloidal/oolitic Revista Brasileira de Geocis ncias, Volume 18, 1988 271

I .. ' / .< '" ... / • ~ /

,,' .r c Figure 16 - Paleobathymetric map at the end of the Late Albian (from Azevedo et al. / 987) packstones/grainstones, intensively dolomitized , wherea s the middle and upper portions is formed mostly by oncolite-bearing limestones and mudstones. The biota content is characterized by the absence of typical bioelements known to be common in normal marine environments elsewhere at . that time. A close relationship is established between subsidence/sea level rise and the carbona te production, contributing to mantain the shallow neritic conditions during Figure 17 - Paleobathymetric map at the end of the Late the entire Lower Macae time. Cenomanian/Lower Turonian (from Aze vedo et al, 1987) The Upper Macae, comprising a carbo nate sequence (Late sedimentation in the Campos Basin. Albian) and a predo minantly marly section (Late Cenomanian The Late Cenomanian to Early T uronian deposits were to Early Turonian), records a progressive sea level rise. In the accumulated in 200-300 m water depth. Opposing the Late Albian, associated with the sea level change, the marine preceding phases, when the system presented a negative water ecosystem became less saline due to a expressive increase in balance, the basin was submitted to a positive water balance. the water interchange with the North and South Atlantic The climate was then warm and wet. Despite the advanced oceans. The fine-grained limestones, with abundant stage of the conti nental drifting, no fully normal marine ammou nts of calcispherulids, accumulated mostly in a deep conditions was reached at the time, as evidenced by the neritic environment, under warm/dry climatic conditions. At presence of black shales layers, accumulated in episodic the end of the Late Albian mustone -marl rhythms were anoxic events. Oceanic conditions are only recorded in the deposited as a response to wann/dry to warm/wet climatic sediments overlying the Macae deposits. cycles. These climatic altemances preceded the drastic Acknowledgements The authors wish to thank. to climatic change that occurred in the Cenomanian which Petrobras for permission to publish this paper. They are also caused the termination of the Cretaceous carbonate grateful to all colleagues that contributed fOT this work. REFERENCES ANT UNES, R.L. ; SONOKI, N.T.;CARMINATfI,M. 1988. The BAUMGARTEN. C.S . et aI. 1982. Projeto Garoupa. Rio de Janeiro, Bncbove Paleocanyon (Campos- Brasil): its Oligoce ne-Miocene Petrobras. (Int. report) history based on calcareous nannoplankton stratigraphy and BAUMGARTEN, C.S. et aI. 1984 . ProjetoBonito. Rio de Janeiro, seismostratigraphy. Rev. Bras . Gene .• 18(3):291 ~ 298 Petro bras. (Int. repo rt) ASMUS, H.E. 1975. Controle estrutural da deposicao rnesoz6ica nas BELTRAMI, C.V. 1982. Mapa paleogeogrdjico de progresso da bacias da margem continenta l brasileira. Rev . Bras . Geoc., Formacao Macae Inferior. Rio de Janeiro, Petrobras. (Int. report) 5(3):160- 165. BOL LI, H.M. 1978. Cretaceous and Paleogene calcisphaerulidae from ASMU S, H.E. & PORTO, R. 1980: A diferenca dos estagios iniciais da DSDP Leg 40, southeastern Atlantic, In: BOL LI , H .M . & RYAN , evolucjo da margem contine ntal brasileira: posslveis causas e W.E .F., Initial reports of the Deep Sea DriUing Project. implicaCJOes. In: CONGR . BRAS . GEOL.• 31, Baln. Carnborld, Washington, U.S. Gov . Print. Office. 40:8 19-83 7. 1980. A1Ulis... Baln. Camboriu, SBG. v. I, p. 225-239. BUDD, D.A. & LOUCKS , R.G. 1981. Smackover and Lo wer Buckner AZEVEDO, R.L.M.; GO MtDE , J.; VIV tE RS, M.C.; HASHIM OTO, Forma tions, South Texas: depositional systems on a Jurassic A.T. 1987a. Bioestratigrafia do Cretdceo marinho da Bacia de Carbonate Ramp. Bureau of Economic Geo logy. The University Campos, Brasil. Rev. Bras . Geoc.• 17(2):147-153. ofTexas at Austin. 120p . (Rep. Invest. 112) AZEV EDO , R.L.M .; GOMtDE, I.; VIVtERS, M.C. 1987b . CAROZZI,A.V .; FALKENHEIN, U.F.H .; LUCCHESI, C. F., Geo -historla da Bacia de Campos, Brasil: do Albiano ao MERCIa , R.; ANSALONI, B. 1977 . Microfacies and Maastrichtiano . Rev . Bras . Geoc., 17(2):139 -146. depos utonal-diagenetic evolution of Macae Carbonates 272 Revista BrasiJeira de Geocuncias, Volume 18, 1988

(AlbiLln-Cenomanian) . Rio de Janeiro, Petrob ras. (Int. report) MOURA, J.A. & ·PRA<;A, U.M . 1985. Ostracodes das seq uencias DIAS-BRITO. D. 1982 . Evolu~iio paleoecoJ6gica da Bacia de Campos nao -marinhas e tran sicionais mesoz6icas (andares Jiqui a e durante a deposicao des calcilutitos, margas e fol helhos da Alagoas ), Bacia de Campos. In: BRAS IL. MME. DN PM, Col. Pormacdo Macae! (A lbiano e Ceno maniano) . Bol. Tic. Petrobras. Trab, Paleont.• Brasffia. p. 40 1-40 8. (Geo l. 27 , Paleont. Est ral. 2) 25(2):84-97. MOURA, J.A . 1987. Biocronoestra tigrafia da sequencia nao -marinha DIAS·BRITO, D. 1985a. Calcisphaerulidae do Albiano da Bacia de do Cre taceo In feri or da Bacia de Campos. Brasil: Ostracodes . In: Campos, Rio de Janeiro. Brasil:' investigacoes taxo ne micas, CON GR. BRAS . PALEO NT ., 10, Rio de Janeiro. 1987. Ana is... biocronoestrat igrafl cas e paleoa mb ientais. In: BRAS IL , MM E, Rio de Janeiro, SBP. v. 2. p. 7 17-731. DNPM. Col. Trab. Paleont., Brasfha. p. 295 -305 . (Goo !. Paleont, MULLINS, H.T . 1986. Ca rbo nate depositional envi ro nme nts modem e Estral. 2) and ancient. Colorado School ofMines Quaterly J ., 81(2): 1-63. D IA S ~BRITO . D. 1985b. Ca lisphaeru lidae e microf6sscis assoc lados da PAUM ER , M.L. 1984 . Microf acies. evolucdo diagenetica e 0 mew Formacao Ponra do Mel -Ba cia Poti guar, Brasil: Co nsideracoes poroso dos reservatorias Macae no Cam po de Bicudo, Bacia de paleoecol6g icas e biocronoestrati graficas. In: BRA SIL, MM E, Cam pos. Brasi/. Ouro Preto , Univ. Fed . Ouro Preto . (M. Sc. DNPM . Col. Trab, Pateont ., Brasflia . p. 307 - 3 14. (Geol . 27, dissert . Thesis) Paleont. Estra l. 2) . RICHTER. AJ. 1985. Aplicacfio de nanof6ssei s calcdrios no DlAS-BR ITO, D. 191n . A Bacia de Campos no Mesocrctaceo : uma mapcam ento da disccrdancia pre-eoce nica na Bacia de Campos. con trib uicao A paleoccan ogra fia do Atli\ntico SuI Pri miti vo . Rev. In: BRAS IL, MME. DNPM. Col. Trab. Paleont., Brasll ia. p. Bras. Geoc., 17(2): 162-167. 471 -4 80 . (Goo!. 27 Paleont. Estral. 2) DlA S -BRITO, D. & AZEVEDO, R.L.M. 1986. As scquenctas RICHTER , A J . 1987. Suba flo ramcnto das discorddncias turoniana e deposicionais marinhas da Bacia de Campos sob a 6ptica campaniana no sui da Bacia de Campos. Rev. Bras , Geoc., paleoecol6gica . In:CONGR . BRA S . GEOL., 34, Goid nia , 1986. 17(2);173-1 76 . Anais... Goi ania, SBG . v. I , p. 38 -49 . SC HA LLER, II . 1973. Estratigrafia da Bacia de Campos. In: CONGR. EST EVES . F.R.; SPADINI. A.R.; MAKOTO.S . 1987. A BRAS . GEOL.• 27, Aracaju, 1973.Anais... Aracaju , SBG. v. 3, p. sedimentacao albo -turoniana (Formacao M aca~ ) da Bacia de 247- 258. Campos. In: SIMP . GEOL. REG IONAL RJ-ES, I, Rio de SCHOLLE, P.A. 1977. Chalk diagenesis and its relation to petrol eum Janeiro , 1987. Anais ... Rio de Janeiro, SBG. p. 27-42. exploratio n: oi l from chalks. a modem mi racle? AAPGBull.• FALKENH EI N, U.F.H. 1981 . Carbonate microfacies and depositional 61(7);982- 1009. evolution of the Macat Fonnation [Albian -Cenoma nian], Campos SCUTA , M.S . 1984 . Microfacies, diagenese e facies-reservasoeio do Basin. Brazil. Urba na, Univ . of Illi nois. (Ph. D. dissert. Th esis) Campo de Bonito, Bacia de Campos. Ouro Preto . Univ. Fed . Ouro FIGUEIREDO. A.M.F.: PEREI RA. MJ.: MOIIRIAK. W.U.: Prete. (M. Sc. dissert. Thes is) GAGLIANO NE. P.C .; TRI NDADE, L.A . 1983. Fatores que SIIIMABUKURO. S.: RICHT ER. A.J.; GO MIDE . J. 1985. controlam a ocorrencia de hidrocarbonetos na Bacia de Campos . Nanof6sse is catcarios: bioestrati grafi a do Mioceno ao Pteistoceno Rio de Janeiro. Petrobrds. (Int. report) na plata forma co ntinental brasileira. In: BRASIL, MM E. DNPM . FRANKE, M.R. 1981. Natural po rosity, diagenetic evolutio n and Col. Trab . Pateonr., Brasffia. p . 491 -501. (Geol. 27, Paleont. experimental porosity development of Maca; carbonates Estrat.2) Albian-Cenomanian, Campos Basin, Offshore Brazil. Urbana , SHIMA BUKURO, S. 1987. Caracrertzaceo pa1oobiol6gica do "Marco Univ. of Illinois. (Ph. D. disscrt. T hesis) Azu l": urn importan te marco estratigrafico oligocenlco na Bacia FRANZ, E.P. 1987. Analise da geologia de reservatdno dos carbonatos de Cam pos , Brasi l. In: CONGR. BRAS . PA LEO NT. , 10. Rio de da Formacao Macae do Campo de Enchova-Bacia de Campos, Janeiro . 1987 . Anais... Rio de Janeiro , SBP. v. 2. p. 1043-1053. Brasil. Ouro Preto, Univ . Fed . Ouro Prete . (M.Sc. disscrt. Thesis) SIIINN, E.A . 1983. Ti dal fla t enviro nme nt. ln: SC HOLLB , P.A. et at. GOMIDE . J. 1976. Estudo bioestratigrdfico da Bacia de Campos ed. Carbonate depositional environment. Tulsa, p- 171 - 2 10. plataforma continental brasiJeira. Rio de Janeiro, Petrobrds. (ln t. (AAPG Memoir 33) report) SPADlNI, A.R. 1982. Calcdrios de granu lacao fina da Formacao GOMIDE, J. 1982. Bioestrati grafia do nanoplancton calcarlo da Bacia Macae, Bacia de Cam pos. In: CON GR. BRAS . PETR6LEO, 2, de Cam pos.Bol. Tec.Petrobras, 25(3):129-137. Rio de janeiro, 1982. A'Mis ... Rio de Janeiro, IBP. (T rab. n!1 18). G UARDADO, L.R . et al. 1983. Estudo da serao de Agua Rasa da SPAD INI, A.R. & PAUMER, M.L. 1983. Os reservatorios Macaeno Fonnaoi o Macae na area N·NO da Bacia de Campos . Rio de Campo de pampa: 0 meio poroso e a diagenese. Rio de Jan eiro. Janeiro, Petrobras. (Int. re port) Petrcbrds. (Int. report) GUARDADO. L.R.: PERES . W.E.; CRUZ . C.E.S. 1986. Deposi tional SPA DlNI,A.R. & FA RIA, R.T. 1986. 06litos: sua oco rre ncia na' model and seismic expressio n o f turbidi tes in Ca mpos Basin, seq uencia carbonatica albiana da Bacia de Campos e seu interesse offshore Brazil. AAPG BuD., 70(5):597. co mo roch a-rese rvatdri o . In: CONGR. BRAS . GEOL ., 34. GU ARDADO, L.R. & SPA DIN I, A.R . 1987. Evolucao deposici onal e Goi anla, 1986. Anais... Go iania, SBG. v, 4, p. 1689·1700. distribui~ ao das focies de Macae Inferior (Eo mesoalbiano, Bacia SPADINI. A.R.; ESTEVES. F.R.; AZ EVEDO. R.L.M. 1987. 0 de Campos). B. Geoc. Petrobrds, 1(2):237- 239. ritrn ito do A lbiano Supe rior da Formacao Macae, Bacia de HAQ, B.U .; HARDENBOL, J.; VAIL, P.R. 1987. Chro no logy of Ca mpos: urn ma rco estra tigrafico com significado paleoa mbiental Fluctuating sea level since the Triassic. Science. 23 5: 1156-11 66 . e cro noestra tigrefico. In:CO NG R. BRAS . PAL EO NT .• 10, Rio HULT EB BRG , S. U. 1985. PithoneHa organica - a new calcareo us de Janeiro, 1987.Aoois... Rio de Janei ro, SBP. v , 2, p. 1027-1041. dinoflagellate with an inn er organic wall . Grana, 24: 115-1 20 , T AKAK I, T . & RODRIGU ES, R . 1984 . Isotopos estavei s do carbono e KE UPP, H. 1987 . Die kalkigen Dinofl agell atenzysten des Mittelalb bis oxigeni o dos calcarios co mo indicadores paleoambicntais , Bacia Unterc enoman von EscallesiBo ulonnais (N-Frank rcich), Facies, de Cam pos, Santos e Espfrito Santo. In:CON G R. BRAS . 16:37-88. GEOL., 33 , Rio de Janeiro, 1984. Anais ... Rio de Ja neiro,S HG. v. KOTZ IAN, S.C.B . & EILERT, V.B . 1987. Radio larios do Cre taceo 3. p. 4750-4 762 . "Medic" na Bacia de Campos, Brasil. In: CO NGR , BRA S. TESSARl, E. & TIBANA , P. 1975. tmerpretacao preliminar da PALEONT., W, Rio de Janeiro, 1987 . Anais ... Rio de Jan eiro. evolu{'{io sedimentokigica da Formacao Maca e. Rio de Ja neiro, SBP . v. 2. p. 783- 796 . Petrcbrds (Int. report) KOUTSOUKOS , E. A.M. 1984. Bvolucao paleoeco logica do Albiano UES UG UI, N. 1976. Intervalos bioestratigraficos do Bacia de Campos ac Maastrichtiano na !rea noroeste da Baci a de Ca m pos, Brasil , do Albiano ao Santoniano. Rio de Janeiro, Petrobras. (In t. report) com base em foraminfferos . In: CON GR. BRAS. GEOL., 33. Rio VIVIERS, M.C. & AZEVED O, R.L.M. 1988. The so utheastern area of de Janeiro. 1984 . Anais... Rio de Janeiro, S BG . v, 3, p. 685 -698. the Brazilian Co ntinental Mar gin : the evolution during the Middle KOUTSOUKOS , E.A .M. 1987. A area noroeste da Bacia de Campos, and Late Cre taceous as indicated by paleoecological data. Rt!V. Brasi l, do Mesocretaceo ao Neocretdceo: evolucao paleoam biental Bras. Geoc. 18(3):(00 prelo) e paleogeografica pelo estudo de Ioramfniferos. Rev. Bras. Geoc., WI LS ON, J.L. 1975. Carbonate facies in geologic history. 17(2):16 8-172- Springer- Verlag, 47 1 p. LEONARD. J.E .;CAME KUN. B.;PILKEY. 0 .11 .; FRIEDM AN. G. M. 198 1. Evaluatio n or .cotc-warer carbonates as a possible paleoc lima te indicator. Sed . Geol.. 28:1- 28. LOR EAU , J.P. & PURSER, B.H . 1973. Distri bution and ul trastructu re MANUSCRITO 518 o f Holocene ooids in the Persian Gulf . In: PU RSER,B.H. ed. The Recebldo em 08 de janeiro de 1988 Persian Gulf. New Yo rk, Spri nger-Verlag, p. 279-328. Revisao a ceita em 04 de malo de 1988