N ew Concepts on the D evelopm ent of East Brazilian M arginal Basins by H ung K . Chang, R enato 0 . K ow sm ann and A ntonio M .F. de Figueiredo

O ne obvious focus in recent years for B razilian geology has able im provem ents in the acquisition of data (especially been the m arginal basins of the eastern part of the country, seism ic) along the m arginal basins. T he other is the devel- w hich now produce 70 ％of Brazil's oil. Indeed this region is opm ent of conceptual m odels for the therm o-m echanical now regarded as a classic A tlantic-type m argin. The behaviour of sedim entary basins and the recognition o f authors review here recent seism ic data and basin m odels, global variations in M esozoic-C enozoic sea levels. w h ich e n ab le a rec o nstru ction o f th e J urassic-C re ta ce o us stratigraphy and its relationship to the evolution of the The general Jurassic to C retaceous stratigraphy of the A tlantic O cean. (E d.) eastern Brazil offshore basins (Fig. 2) can be represented by five m egasequences: continental, transitional evaporitic, In t ro d u c tio n shallow carbonate platform , m arine transgressive and m arine regressive (Ponte et aL , 1978). These m ega- The continental m arg in of Eastern B razil com prises six rift- sequences are linked to the continental breakup of the initiated basins (Sergipe-A lagoas, B ahia Sul, Espirito Santo, Pangea and to the evolution of the A tlantic O cean. C am pos, Santos and P elotas), w hich occupy the coastal plain, continental shelf and slope o f the w estern portion of T he C ontinental M egasequence the Sou th A tlantic O cean (F ig. 1). Since the late 1960s, Three synrift sequences com prise the continental m ega- w hen offshore exploration for hydrocarbons began, a la rge sequence, based on their characteristic facies associations am ount of geological and geophysical data has been obtained (Fig. 3) and structural styles, and follow ing a schem e used o n th e s e b a s in s. by Figueiredo (1981). The first sequence (Syn-R ift I) is T w o m ajor developm ents have helped to increase our know l- hardly affected by faulting, w hereas the other tw o (Syn-R ift edge of the origin and developm ent of these basins in recent II and 111) are subject to intense faulting. years (see Ponte and A sm us, 1978; O jeda, 1982, and A sm us Syn二丝望_. During the latest Jurassic (Dom Jogo or Volgian and Baisch, 1983, for general review s). O ne is the consider- Stage, see F igure 2, tw o areas becam e separate as a con- sequence of the initial process of G ondw analand breakup. ｝ ‘三经二 ＿ To the north of the E spirito Santo B asin, a huge depression 8 0 ' 三至至呈至呈全丝呈兰 16 0 * ；石． form ed, know n as the "A frican-Brazilian D epression" (Ponte et al., 197 1). This w as rapidly filled w ith a com plex package of arid alluvial fans and by coarse-g rained fluvial deposits 0 - w ith subordinate evaporites, representing local playa一ake environm ents. E olian deposits are also com m on in this sequence. To the south data are lacking, but the sequence here is thought to be com posed of the sam e sedim entary sequence present to the north or volcanics, or both, as in the low er C ongo R iver B asin of Zaire (R . Palagi, personal com m unicatio n).

S v n-rift 11: T h e inc eD tio n o f the m a in rift Dh ase . in th e - 2 0 ' h a riy L;re ta c eo us tii io aa b e rra- a ra tu o r iN e oc o m ia n stag e s), 2 0 、 、 S A N T O S generated a series of a rapidly subsiding half-grabens along the entire m argin. T o the no rth, a series of deep and strat- ified lakes form ed and filled w ith dark-coloured organic-rich shales and by turbidites associated w ith fluvial-deltaic cla stic s. Su bo rd ina te os trac od al ca lca ren ite s a re rela ted to episodic flooding. T o the south, how ever, volcanism w as very active (Fig. 3). AIS 匆久 T he volcanic-sedim entary sequence is best studied in the 洲尹 C a m pos Basin, w here it is com posed o f basalt fl ow s, vol- caniclastics and sedim entary rocks w ith ages ranging from 120 to 130 M a (M izusaki, 1986; Ponte and A sm us, 1978). B07 60- ＼ M izusaki recognizes areas w ith subaqueous, laeustrine and 明． subaereal volcanism , the latter characterized by explosive episodes. Fi gure 1 ： Location of the East Brazil marginal b as in s . S . M ar : S er r a do M a r co a s ta l ra n ge . Later, lakes becam e progressively shallow er and volcanic SE/A l: Sergipe众lagoas Basin . ESP . SANTO: Espirito events less m arked. Shallow lakes to the north w ere slow ly S a n t o B a s i n . filled by very extensive, cyclic fluvial-deltaic clastics con-

194 E PISO D ES, Vol. 11, N o. 3, Septem ber 1988 0 W S A N 下 O S E IW C A M 户 O S E lW S E R G IP E / A L A G O A S E － H O LO C E N E / P L E IS T O ‘ 跳参是笼厂呈多牙扭 ＾ P L IO C E N E 比 舀签5 ＜ 之z 二 于任 万三于三 毛夕 M IO C E N E 瑟砂毛 手 卜－ 比 O L IG O C E N E 田 1 E O C E N E P A L EO C E N E S 户笠瘩蓉昌 仁毛 艺 礼 n M A A S T R IC H T IA N 二 三子二三二气笼二习 卜痊 竺廷 从 o 氮 口奏窦t7孟备之二二 - sm 山 C A M P A N IA N 0 艺竺 互或竺梦 艺己 竺 芡多婆获 三 } q 哎 卜三口 任二 鬓 －L S A N T O N IA N 乏忿弓芍吞燕K 创 匕定后 二毛只目 于三I uJ ?-I是笔分叹 O 公 卜玄于舀＝＝ ＝洲 户万二三 匡 C O N IA C IA N 桩三笼 决三 刹 b }丈d 口城丈二 石乙饭乃甘口 0 T U R O N IA N 到 阵 n． C E N O M A N IA N ．恻翔日纽戴｛围 〔三二污 S 3 石 n A L B IA N ．O O 几 -f 国 石。巴弋 0 哎 A L A G O A S J 曰 J 1 、 护、护、子、J 、 子、目产、2 、护、韶、廿 、2 、子 、矛 鬓鬓爵翼德 山 J IQ U IN 止 0 } 墓幸 B U R A C IC A 矛 葺舀霭 =q_ 远理全霆 0－ 气， ． 一 1 夕 v v V v v V v v v v V v v v v v v v v v v V v v v V v v V v V 心 ．。 二 一， A R A T U / R IO D A S E R R A V v V v V v v V v v v v v v v V v V V v v v v v v V V V v v v 菩月生毛 二户吧少竺当冲任丛笼仪 夕 V/ V V V V V V V V V V V V D O M J O A O 盘 ‘二士J二三二三二二云二之匕二二 ？ 盗气 二少甲二 IVV：篮攀署举署

P 十 ＋ ＋ ＋ 画 ＋ 十 十 十 ＋ ＋ ＋ ＋ ＋ ＋ I ＋ 十 ＋ 十 ＋ 图B A S E M E N T ｝毛是冬｝S H A L E JJ_J -i｝H A L IT E P"- __ C A LC IL U T IT E 盈V O L C A N IC 匡口 S A N D S T O N E 既盈 A N H Y D R IT E 匝因 M A R L C O Q U IN A 嚎澎：1C O N G L O M E R A T E 卜气月 C A L C A R E N IT E ｝烤忿｝T U R B ID IT IC ,SA N D ST O N E

F ig ur e 2 : S t ra ti g rap h ic c h ar t o f th r ee r ep r es en 一 tative margin al basins of E a s t B r a z i l . A r r o w s m a r k T he Transitional E vaporitic M egasequence t r a n s i t i o n b e t w e e n 付a r i n e T ran sg re s si ve an d M a r in e This m egasequence, deposited during the A lagoas (A ptian) R eg re s si ve m e ga se qu en c e s . Stage, is com posed of sedim ents typical of the transition be tw ee n c on tin en t an d m a rin e e n viron m e nts. It w a s d e- trolled 勿 rapid base-level changes in response to clim atic posited over a w idespread post-rift unconform ity (Fig. 2) variations. T o the south, sedim entation w as characterized responsible for the general peneplanation of the rift topog- by fine-grained lacustrine rocks associated w ith voleani- rap hy. In places this fl at-lying surface w as coverid by a clastics. In this region alkaline and saline lakes dom inated, relatively thin, coarse elastic w edge derived from the as dem onstrated by the presence of thick oolitic talc- adjacent highlands, but it w as gradually inundated by salty stevensite rocks (R ehim et al., 1986). w ater com ing from the ocean to the south. C onglom erates S vn -rift III: T h is se a uen c e. d eD O Sited d u rina th e B u ra cic a- and poorly sorted sandstones w ere deposited and gradually overlain by fine-grained clasties and euxinic, saline, jiqu ia w a rre m ian) stag e s, is cn a ra cte rize a r)y tne pre se n ce of very extensive and laterally continuous beds of coquinas, org anic-rich shales. intercalated w ith coarse to fine-grained siliciclastic m ate- A narrow evaporitic seaw ay form ed along the entire East rial (F ig. 3). T he coquinas are form ed by calcarenites and Brazilian m argin north of Pelotas Basin and resulted in the calcirudites com posed of ostracods, pelecypods, and som e deposition of a com plete suite of evaporites (Figs. 2, 3). gastropods. T he original salt thickness is estim ated to be about 2000 in in the depocenters of this saline gulf. F or the C am pos B asin, B ertani and C arozzi (1984) inter- preted the coquina-clastic sequence in term s o f playa-lake This evaporitic section has been w ell studied by Szatm ari and pluvial-lake environm ents, associated w ith cyclic expan- and others (1979) in the Sergipe-A lagoas Basin. T w o distinct sions and contractions of the lakes. In the playa-lake envi- periods of evaporite sedim entation in a very shallow envi- ronm ent, coarse clastics (alluvial fans) graded into sand and ronm ent 一progressive and recessive 一w ere recognized, m ud flats. In the low lands, carbonate flats w ere developed associated w ith a gradual increase in salinity follow ed by an adjacent to saline lakes, w here m atrix-supported ostracodal initially abrupt and then gradual dilution of the brines. T he biocalcarenites w ere deposited, and in the centers of the sedim ents of these tw o cycles provide evidence of several lakes euxinic shales w ere form ed. T he pluvial-lake environ- other less dom inant cycles reflecting changes in salinity and d etrital c on tent. In su c cessiv e o rde r o f fo rm atio n the m ent w as active during flooding events, w hen grain-sup- dom inant com ponents are anhydrite, halite, carnalite and ported pelecypod biocalcarenites covered very large areas o f th e b asin. finally tachyhydrite. Silvinite and halite are the -m ajor com ponents o f the recessive suite. In the Sergipe-A lagoas B asin (Figueiredo, 1981) this se- In other basins the evapo rite sequence is poorly know n, but quence is represented by m ixed clastic-carbonate sedi- there is good evidence for the existence o f highly soluble m entation. Larg e pelecypod-carbonate banks deposited in sa lts. T h e con tro l a nd d istribu tio n o f th ese suites a re no t very shallow areas flank the principal point-sources (rivers) w ell understood, but the m assive salt deposits located in responsible for the deposition of fan-delta, fluvial-deltaic distal portions of the m argin are probably halite. and slope-basin terrigenous sedim ents. A t the end of this sequence the elastic sedim entation prograded across the The Shallow C arbonate Platform M egasequence e n tire ba sin an d b u ried the c arb on a te b an k s. D uring the A lbian Stage, the gradual opening of the incip- T he evolutiona:ry pattern of the continental m egasequence ient seaw ay resulted in the A lagoas evaporites being suc- resem bles that of the East A frican R ift as proposed by L e ceeded by an extensive high-energy carbonate platform F ournier and others (1985), despite the differences in the (Fig. 3) co m posed of shallow -w ater lim estones c o n s ing of duration of rifting. There is an excellent agreem ent four m ain com ponents: oncolites, pellets, oolites and bio- betw een the sequence subdivisions (Syn-R ift 1, 11, 111) and clasts. T he latter are the least im portant and reflect the stages 1, 3a, and 3b of these w orkers. restricted saline conditions still present in these waters.

E PISO D ES, Vol. 11, N o. 3, Septem ber 1988 1 9 5 A long the ancient A lbian coastline, fan-delta clastic w ith A lb ian m a rls a nd is characterized by the Presence of S a n d s t o n e bodies covering a s m u e h a s 2 0 0 system s w e r e also developed and interm ixed w ith the car- verw “些tinuous “叩ds勺 b o n a t e r o c k s . D olo m itize d llm eston es a r e r a t h e r a b u n d a n t K lll‘一 I n e e n a n n e llZ e U system 15 confined in dePressions Proouceo oy nalOKlnesls w ltnln tne U enom anian一uronian in t h e b a s a l part of the Platfo rm ，but rigid fram ew ork Stru etu re S su c h as re e fs a re a b sen t． In ba sinal a rea s ca 卜 shales and 15 charaeterized by raPid variations in both fa cies e ilu tites an d ea le isiltite s in te reala ted w ith m arls a nd sha le s a nd th ickn e ss． are the dom inant fa eies． The dePositional m odel develoPed The M arine R egressive M ega sequenee for this sequence 15 a tyPical carbonate ram P disturbed by This sequenee 15 com Posed of a set of synchronous dePos－ salt tectonics （Spadini et aL ，in Press） that controlled the itional system s （fa n delta，fl uvlal一deltaic，terrigenous shelf， shallow 一w ater carbonate facies distribution，and esPecially 。arbonate Platfo rm ，sloPe and basin）seism ically character－ the o nc olit少 oo lite sh oa ls． ized by an offlaP Pattern underneath the Present continental M arine Tran sgressive M egasequence shelf． In som e areas this Progradational Pattern 15 rePlaced In the late A lbian the hig h－energ y carbonate sequence w as by an ag radational build－uP of a high－energ y carbonate fo llow ed by a low 一ene馆y sequenee com Posed of oalcilutites， platform . T he passage from the transgressive to regressive m arls and shales． T hese w ere dePosited in a gradually sequence varies in age along the m argin (see F ig. 2). deepening environm ent （deep neritic to uPper bathyal） as In the southern area siliciclastic system s dom inate, w hereas indicated by the Paleoeeologieal studies of D ias－B rito （1982） in the northern area platform carbonates are w ell devel- and K ou tsoukos and D ias-B rito (1987). The calcilutites are oped. D eep-w ater system s also reflect this difference: the m assive and rhythm ically bedded w ith m a rls an d sha les C am pos Basin contains very large turbidite sand bodies, tow ards the top of the sequence. P lan k to nic fo ram in ife rs w hereas those in Sergipe-A lagoas are sand poor. and calcispberes are abundant, w ith m inor benthic fora- In the Ca m pos Basin, the m ajor occurrences of large uncon- m inifers, carbonacous fragm ents and m icas. A n im portant fined deep-w ater sand bodies are associated w ith relative C enom anian-Turonian anoxic event w as registered w hen the sea-level falls. D uring these periods the exposure of the R a diola ria ns b a s in depth reached 200-300 m . and plank- silicicla stic -rich c on tin en ta l she lf resulted in th e in tro d u c- d ive rsifie d to n ic fo ra m in ife ra a re a bun d an t and highly (A zevedo et al., 1987). tion of huge amounts of s)a n d into the deep basin. Turbiditic fans as large as 3uU kin‘ w ere oeposlteo ano seism ic oata T urb id ite sed im e nta tion is present along the entire m argin, suggest the presence of even larger fans under the present a n d is b e s t s tu d ie d in t he C am pos B a s in . T w o m od e ls o f c o n t in e n t a l slope. Salt m ovem ents in s o m e a r e a s h a v e deep-w ater turbiditic se d im e n ta t io n h a v e b e e n 记e ntifie d 一 strongly affected the geom etry and distribution of these blanket and channelized system s. T h e fo r m e r is a s so c ia te d deep-w ater sand bodies. 户耳界汉二获价一不刃一口一 ． D. JO A O

N R IO D A S E R R A -A R A T U 血 敬 ． B UR AC IC A -JIQ U I百

日R A Z IL A L A G O A S

A L B IA N

欲 少 S E /A L

B A H IA S U L

V / E S P S A N T O 口 圈 V O LC A N IC S 圈E VA P O R IT IC S YST E M S 盘 F L UV IA L - D E LT A IC 困C O Q U IN A 患S Y S T E M S ASYLSLTUEVMIASL/FLUVIAL SPLHATLFLOORWM C S0Y3STEMS

F i gur e 3 Paleogeographic reconstructions for the Syn-Rift sequences I (D om J050)，II (Rio da Serra- A r at u ) , III (BuracicaIJiquig)，and the Transitional Evaporitic (Alagoas ) and Shallow Carbon ate P l a t f o r m (Albian ) megasequences.

1 9 6 E PISO D ES, Vol. 11, N o. 3, Septem ber 1988 T ectonic Setting m obile belts and suture zones separating crustal blocks of different rheological behaviour determ ined the location of M any plate tectonic reconstructions o f the early S outh the border faults of the basins and o f the neighbouring highs A tlantic have been proposed since the fa m ous 1965 fit by that separate them . These provinces also exerted controls B ullard and his colleagues. Early m odels m atched coastline on the lim its of the com partm ents subject to differential shapes or adjacent isobaths and m oved the continental crustal stretching; they also determ ined the orientation of m asses of South A m erica and A frica along fracture zone th e stru ctures w ithin th e ba sins. flow lines, thus determ ining early poles of rotation. A m uch m ore sophisticated reconstruction, involving plate kine- S A N T O S ④ m atics: w as presented by R abinow itz and L aB recque (1979), 5 based on the identification of M -series m agnetic anom alies to the south of the W alvis-Sgo Paulo ridges. T he continents 15 w ere m oved apart as single rigid blocks according to the location and ages of the anom alies. The large gap covered 25 by evaporites to the north of the ridges w as assum ed to be form ed by oceanic crust (C ande and R abinow itz, 1978). 35 Th e realization by A ustin and U chupi (1982), based on seism ic reflection data, that m ost of the M anom alies 5 0 o c cu rre d o v er th inn e d c on tin en tal c ru st altere d th ese re- C A M P O S S E/A L constructions considerably. A ccording to them , sea-floor 。 spreading in the South A tlantic w as initiated m uch later 5 1 0 than previously believed, around anom aly M 4 tim e (H auter- 15 ivian 一125 M a ago). N orth of the W alvis-Sgo Paulo ridges 2 0 oceanic crust w as em placed near the A ptian-A lbian bound- 25 ary 113 M a ago, aft er evaporite deposition over stretched 性0 曰 c on tine n tal c ru st. 35 Th e strong contrast in both oceanic and thinned continental 5 0 10 0 5 0 10 0 km crust betw een segm ents north and south of the W alvis一go Pa ulo ridges is due to a large shear zone (C urie, 1984). A l- F ig ur e 4 : Cr us ta l s tr uc t ur e ba s ed o n t ec to n ic s ub - though the exact location and tim e of initiation of this pro- sidence and gravity modellin g. Upper mantle (V); posed shear zone is still under debate, it introduced the im - continental crust (crosses); R ift Stage Continental portant notion that the South A m erican plate m ay not have Megasequence (dotted); Post-Rift Stage megasequen - been so rigid a fter all. V ink (1982) proposed a propagating ces : Transitional Evaporitic (hachured), Shallow rift m echanism for the continental splitting of South A m er- Carbonate P latform and Marin e Transgressive (blank)， ica and A frica. H is m odel w as corroborated by S zatm ari Marine Regressive (dashed)。 and others (1985), in their study o f structural evidence in the rift sequence of the B razilian m arginal basins. The R ift Stage T he B razilian m arginal basins w ere first introduced into the G ravity and tectonic subsidence m odelling along the East plate tectonic context by E strella (1972) and A sm us and Porto (1972). L ater A sm us and Ponte (1973) and Ponte and Brazilian m a rgin suggests that individual basins w ere subject A sm us (1978) subdivided basin evolution into four tectonic to different am ounts of stretching. T hese differences w ere taken-up by transfer zones, w hich are expressed by sig nif- stages: pre-rift, rift valley, proto-oceanic, and continental icant apparent offsets in the trace of basin hing e zones. m argin. G enetic interp retation of the early stages of basin The latter separate unstretched from stretched continental developm ent (A sm us and Porto, 1980) w ere inspired by the crust and are recognized by accentuated deepening of base- m odels of Sleep (1971) and M ilanovsky (1972). T he East m ent and shallow ing of the M oho discontinuity. The trans- B razilian m argin w as grouped into tw o rifting styles, dom ic fer zones usually extend offshore as oceanic fracture zones, (Santos and C am pos basins) and interdom ic (Bahia S ul and and the m ost conspicuous of the form er occur in the south, Sergipe-A lagoas basins), according to the presence of vol- betw een the Pelotas, Santos and C am pos basins (Fig. 5). canism and the absence of pre-rift sedim ents. T hese styles T he Pelotas-Santos transfer zone is m arked by the F lorian- can be basically translated into active and passive rifting, respectively. 6polis H igh-Sgo Paulo R idge com plex, w hich acted as the southernm ost barrier to A lagoas (A ptian) evaporite deposi- T he pow er and conceptual elegance o f M cK enzie's (1978) tion. The transfer zone betw een C am pos and Santos basins m odel of lithospheric stretching proved to be very useful in is delineated by a very conspicuous east-w est trend of the explaining the developm ent of the East B razilian m arginal hinge zone adjacent to the R io de Janeiro Fracture Z one, basins, as in other passive m argins of the w orld. A pplica- w hich term inates against the C abo F rio H igh. tions o f the m odel in the Santos and Sergipe-A lagoas basins C ontinental stretching in the region of the P elotas Basin (C hang and K ow sm ann, 1984, 1986) and the C am pos B asin probably started in the M iddle to Late Jurassic. O nly the (M ohriak and D ew ey, 1987) confirm ed that uniform and top of the rift sequence com posed of seaw ard dipping basalt non-uniform stretching of the lithosphere together w ith flow s (F ontana, 1987) has been dated, w ith K -A r ages tw o-stage basin subsidence (m echanical rifting follow ed by approxim ating 120 M a. Stretching to the north of the therm al contraction) am plified by flexural loading of sedi- Florianbpolis H igh-Sgo Paulo R idge probably started som e- m ents account for the evolutionary pattern of these basins w hat later, during the D om Jo5o Stage (Syn-R ift 1). T he (F ig . 4). A lternative m odels involving sim ple-shear (W ernicke, 1985) inspired subsequent proposals for basin R econcavo-T ucano A ulacogen and the onshore portion of the Sergipe-A lagoas B asin contain the best developed section of developm ent along the N o rtheast Brazil m a rgin (U ssam i et R io da Serra-A ratu rift sequence (Syn-R ift II), probably al., 1986; C astro, 1987). A lthough there is a great volum e because of the rotation of regional continental blocks that of data on the East B razil basins, this is still insufficient in preceded the m ain event of rifting along the adjacent depth of penetration to confirm any of these m odels. m argin (L ana and M ilani, 1986). A n indisputable fact is that the com position and structural in the Santos and C a m pos basins, these basal rift sedim ents fabric o f the underlying Precam brian basem ent exerted a (Syn-R ift II) have not been recovered and m ay be dom inated strong control in basin em placem ent and evolution (C ordani by rift basalts. The top of these lavas defines basem ent, et al., 1984). C ratonic shield areas, adjacent poly cyclic w ith K -A r ages rang ing from 135 M a and clustering around

E PISO D E S, V ol. 11, N o. 3, Sep tem ber 1988 1 9 7 120 M a (Fodor et al., 1983; M izusaki, 1986). The m ain pulse P ost-R ift Stage of stretching and the full developm ent of the hinge line along the East B razil m argin occurred at the sam e general T he general post-rift tectonic subsidence can be approxi- tim e during the B uracica-JiquiA stages (Syn-R ift III). m ated, as in other passive m arzins. bv an exDonential decav curve cnaracteristic ot titnosp neric cow ing and contraction 5 0 0 4 0 0 (C hang and K ow sm ann, 1984, 1986). This subsidence pro- duced the seaw ard tilting of the continental m argin, w hich w as infilled by a thick w edge of m arine sedim ents. T his w edge w as intensively affected by listric faulting w ith a sole at the base of the A lagoas evaporite deposits (F ig. 6). 10 0 - The faults cross progressively younger strata seaw ard.

T he faulting and consequent form ation of rollover structures have been m ainly attributed to salt flow age triggered by the m a rgin tilt (Figuelredo et al., 1985). H ow ever, recent detailed studies in the Sergipe-A lagoas Basin (Lim a, 1987) dem onstrate on a la rge scale that basem ent, m ajor uncon- form ity and post-rift sedim ents are all gently w arp ed to form large, single rollover structures, thus suggesting that ._._.._...... 3 .. 5...k .Am.0...1 .. .FA.1+,.2. A.0U.2A. '.k.A 3.}r. mn.A ...A...... D w ooj-lMta-foF r r Z34 m assive brittle failure in the upper crust has occurred dur- C -1一RJ F Z -O r ing the post-rift phase until very recent tim es. ．． ．．．．． ．．．．．．．．．．．．．． ．．． T he orientation of listric faults bounding these crustal d e tac h m en t su rfac es follo w s a nc ien t P rote ro zo ic thrust faults, indicating that the latter w ere reactivated by the 1.SAP LOAa PTmAEU ALUO 1= :0N2o}- GMMM} post-rift tensile stresses. A sand m odel experim ent and ‘ ． ‘‘苗～ ．．．．．．．．．． ．．．．． ．．．．． independent rock m echanics calculations conducted by Lim a

3 0 0- F F Z 茜势 (1987) suggest that shallow crustal failure w ill occur at very low angles of tilting (1-3 degrees). The larg e extent of the 福杏 coastal flexural onlap, characteristic of the T ertiary section 6 0 0 k m B y of the E ast B razilian basins (F ig. 4), is m ainly a conse- quence of the increasing flexural rigidity of the cooling ‘Of沃下万票共弃弃烈 lithosphere. 35km工毕汀“”－－－一 ”””””’ T ectonic m ovem ents in the form of coastal range uplift (up F ig ur e 5 : S imp l if i ed t ec t on ic el em en t s of th e E as t to 2000 in) in Southeast B razil (Serra do M ar, F ig. 1) and 刀r a z i l i a刀 m a rg in , sh ow in g con t o ur s of eq ua l ex t en 一 generalized plateau uplift of the hinterland (less than sion factor 5 (see text for exp lanation )． S ec- 1500 in), dom inated the L ate C retaceous一e rtia叮 scenario t i o n s A -A ， a n d B - B I i l l u s t r a t e v a r i a t i o n s i n t h e of the East B razil m argin. In parallel, late Senonian and degree of crustal stretchin g-th inning . Sgo Paulo E ocene volcanic activity occurred along the southeastern P lateau (hachured ); FH (Florian6polis High)；CFH B razil m argin in the form of alkaline rocks on land and (Cabo Frio High ); SPR (Sgo Paulo Ridge ); FF Z (Flori- alkali-basalts offshore (Ponte and A sm us, 1978-, A sm us and an如olis Fracture Zone ); RJFZ (Rio de Janeiro Frac- Porto, 1980; A lm eida, 1983). Therm al anom alies induced by ture Zon e); MFZ (Maceio Fracture Zon e)。Fracture hot-spots and oceanic fracture zones have been called upon zones compiled by A smus (1984)。

O A A

竺摺吮淤 一；艺 A generalized unconform ity, produced during the 卜 ﹂ 盆盆 二 届祥 E , late Jiquig-early Alagoas stages, m arked the end 卜︵ 比一 卜· 燕 攀 of rifting. This unconform ity separates the tilted 多 仍 1 O and block-faulted rift sequence from the over- ︶ d O M A R IN E N 2 D lying post-rift sequence (Figs. 6 and 7). The un- O 工 R E G R E S S IV E conform ity is m ost conspicuous near the hinge O 万刃起肠 F z;2. t LJ 书 盆 ：泞 之 兰～． zo ne . w h e re fa c tors suc h a s th e rm al a nd fle xu ral S 愁 矍禧 早汪 器 bulges could have contributed to its em placem ent, 肋 尚 鬓TRANINSEGR an d w h e re lim ite d te c to nic su bsid en ce e nh an ce d 召乙 毖 (;U 3 P L A I the vulnerability of the rift sequence to base- E V A PO R IT IC level changes. The angular nature of the uncon- 集琴藻暴莽馨箕 毛5 峪 砂‘半少 m:.I} C O N T IN E N T A L 4 -0 - form ity, so prom inent at this proxim al site, gen- 袋 、、白ASA LT erally becom es m ore subtle seaw ards. 李醉兴易聆薪书举深羚一膝豁 5 0 10 k .

A 今F ia ur e 6 : S e ism ic s ec t ion fr om th e i (; a m p o s B a s i n s n o w i n a 亡n e r e cT i o n a i u n c o n - M A R IN E 夔参奢昌秀轰基 牌 男 巴 二巴巴巴巴巴巴二 ，． ．． ．．． ．． 口， 浪 拳愁李鬓架蓦只 I z o r m l 亡u s e p a r a t i n q 亡n e j

198 EPISO D E S, Vol. 11, N o. 3, Septem ber 1988 m to explain these late stage m agm atic events (A sm us nd－ definition of this extension factor) just offshore of the hinge R E M A C , 1978) and the uplift of the continent (A sm us a zone to 150% 0 ＝2.5) along the shelf edge and further to Ferrari鲤R EM A C , 1978; Smith, 1982). 230 ％ (0 二 3.3) at the continent/ocean boundary (F ig. 5). T hen contours, w hich are offset by the transfer zones Isostatic adjustm ent of the basin and its edge has been adjacent to interbasinal highs and oceanic fracture zones, invoked to explain the coastal uplift (A sm us and FI e r r ari, converge northw ards tow ard Sergipe-A lagoas Basin, 19 7 8; M a c ed o in R E M A C . 19 8 7). F lexu ral reb o un d du e to im plying that the area of significant extension dim inishes tn e u nio aa m g a sso c ia tea w itn c ru sta i ia iiure tu o n ca iv e s, e i fro m sou th to no rth. al., 1979) appears to be an attractive m echanism to produce uplift. H ow ever, these concepts have only been proposed on F oucher and others (1982) presented an elegant m odel in a qualitative basis. w hich the partial m elting of asthenospheric m antle is a function o f the degree of lithospheric extension or thinning. F irst m otion studies of earthquakes indicate that the E ast F or a lithosphere 125 kin thick, partial m elting at the top of B ra zilian continental block is presently in a state of com - the asthenosphere (13500C) w ill begin as it rises adia- pression (A ssum pggo et al., 1985). T his is com patible w ith a batically to approxim ately 60 km （、20 kbar). This im plies m id-ocean ridge push from the east and blocking of the that partial m elting should occur w hen the litbosphere is Sou th A m erican plate in a subduction setting from the thinned by m ore than 50％ (0 ＞ 2.0). Partial m elting in w est. It is plausible that this state of stress has been am ounts significant enough (10 ％）to form oceanic crust w ill operating since the initiation o f sea-floor speading in the occur only w hen the lithosphere is stretched by a beta South A tlantic. T his com pressive stress field m ust have fa ctor o f 3 to 4. com peted w ith the tensile stresses generated by the seaw ard tilting of the m argin because both occurred during the post-rift stage. T he interplay in tim e and space betw een T O P O F these stress fi elds cannot as yet be distinguished. S A L T C ontinent-O cean B oundary T he continent-ocean crustal boundary to the south o f the BA SE O F 愈 Sgo Paulo R idge is not as w ell established as on the con- S A LT 卜 N jugate, southw estern m argin of A frica, w here it lies along ︵ 国 1 7－ 芝 琴 目 ano m aly M 4 (A ustin and U chupi, 1982). H ow ever, seism ic 叨 卜 叮 refraction data (L eyden et al., 1971；K ow sm ann et al., 1977) ︶ 山 O 兰 indicate that it should lie under the continental slope at N Z O V 山 least 700 kin landw ard of its position north of the S勃 Paulo O 9－ 0 R idge (F ig. 5). 山 0 5 IQ－ To the north of the Sgo Paulo R idge, geophysical evidence indicates that this crustal boundary lies along the salt scarp Figure 8 : S eismic section off Campos Basin across (Fig. 8) that delineates the seaw ard edge of the A lagoas the salt structure m ark in g the offshore limit of evaporites (K ow sm arm et al., 1982). This scarp strikes A lagoas (Ap tian) evapor ite deposition in the Western roughly north-south and parallels the first identifiable S o u th A t la n tic . Th e s c arp i s be l ie ve d to li e a lon g oceanic m agnetic anom aly (M 34, 84 M a) in the region the contin entlocean crustal boundary , with oceanic (Fig. 5). Sea-floor spreading is believed to have started crust of Early Albian age lying to the right。 L oca- here during the earliest A lbian tim e, thus splitting the te d on F ig ur e 5 a s se ct io n D . evaporite basin into tw o conjugate portions (L eyden et al., 1976). A ssigning the end of the rifting event in the m a馆inal basins as latest Jiquih to earliest A lagoas and the onset o f T he degree of lithospheric thinning not only influences the sea7-floor spreading as earliest A lbian poses a problem am ount of partial m elt produced but should also control the because there m ay be as m uch as 5 M a betw een them . com position of m agm a generated (R ingw ood, 1975). P artial The region of stretched continental crust along the E ast m elts of less than 10％ should produce alkali-basalt; m elts B razilian m argin, bracketed by the hinge zone and the salt above this value should generate tholeiitic m agm as. T hese scarp, is roughly triangular in shape being w idest in the com positional predictions are born out in the C am pos and south W o Paulo Plateau) and narrow est in the north. T hus, Santos basins w here alkali-basalts predom inate (F odor and V etter, 1984; M izusaki, 1986). A m ore tholefitic suite is the integrated extension factors should be greater in the expected to occur in the distal portions o f these basins W o south than in the north, although m easured extension factors P aulo Plateau). w ithin individual basins do not necessarily conform w ith this pattern. T his configuration has considerable im plications in H o w ever, the degree of the lithospheric thinning does not the occurrence of rift stage volcanism as w ill be show n later. alone explain w hy rift volcanism w as so intense in the L ithospheric Thinning southeast B razil m argin and is virtually absent in the rift basins to the north of Espirito Santo, since beta values The m egasequences characteristic of the East B razilian greater than 2.0 are present in all basins. The key differ- m ar-gin follow a pattern that is predicted by various factors ence here is the area affected by sig nificant degree (0 >2.0) that in general control basin evolution along passive of stretching. T he larger the area involved, the larger the m argins. R egional differences observed w ithin these m ega- volum e of m agm a generated at the base of the lithosp here sequences are m odulated by local controls that can be (C hang and K ow sm ann, 1984), and large quantities of m olten integrated in a general context. m aterial w ill obviously be m ore successful in eventually O ne of the striking contrasts in the rift stage stratigraphy reaching the surface of the crust than w ill sm all quantities. here is the conspicuous presence of volcanics in the Syn-R ift T he area of significant stretching is m uch larger in the II Sequence in the basins south of E spirito Santo and their Santos and C am pos basins w here volcanism occurred, than it absence in the basins to the north o f it (F ig. 3). This distri- is, for exam ple, in Sergipe-A lagoas w here volcanics are bution can be explained by the pattern of lithosp heric absent (Fig. 5). extension of the East B razilian m argin to the north of the Florian6polis H igh-Sgo Paulo R idge, as deduced from tec- Lithospheric stretching during the rift stage did not occur tonic subsidence studies using the A iry co m pensation. These sm oothly, but rather in distinct pulses, w hich greatly show that the am ount of extension varies from approxi- influenced facies distribution. F or instance in the Sergipe- m ately 100％ 0 二 2.0, see M cK enzie, 1978, for precise A lagoas Basin w here rift stratigraphy is best recorded,

E PISO D E S, Vol. 11, N o. 3, Septem ber 1988 1 9 9 m inim um estim ates point to a three-fold increase in sedi- T he C enom anian C lim ate C hange m entation rate during the JiquiA Stage w hen com pared to T h e tran sition fro m calcilu tite s to sh ales an d m a rls in th e the earlier stages of the rifting. late A lbian and C enom anian is conspicuously reflected in The Evaporitic Basin and the C arbonate Platform w ell logs. A significant change fro m dry to hum id clim ate The great South A tlantic evapo ritic basin, so characteristic during the C enom anian has been docum ented by L im a (1983) and Vakra m eev (1984). It coincides w ith the establishm ent of the A lagoas Stage, w as conditioned by a w arm and dry clim ate, already prevalent during rift stage and induced by a o f anoxic conditions along the B razilian m argin (D ias-Brito, low continental pressure cell (P arrish and C urtis, 1982). It 1982; A rai, in press) and the South A tlantic (A rthur and Schlanger, 1979; H erbin et al., 1987). The clim atic change w as also a result of the continental con figuration that allow ed the influx of seaw ater into a silled elongated basin, w as probably due to the developm ent of a sub-tropical high from an established ocean to the south (Leyden et al.. 1976. pressure cell over the enlarged South A tlantic w aterm ass A rthur and Schlanger, 1979). The restriction w as form ed by (Parrish and C urtis, 1982). the Sgo Paulo-W alvis R idge pair and w as enhanced bv a natural step occurring betw een the stretched continental crust to th e n orth an d o c ea nic c ru st to the so ut h. The com position of the evaporites around the South A tlantic ranges from highly soluble m agnesian and potash chlorides to halite and anhydrite (Szatm ari et al., 1979; de R uiter, 1979). A shallow -w ater origin for the highly soluble salts is invoked by these authors. H ow ever, the origin of the m as- sive halite deposits so prom inent on the Sgo Paulo Plateau and conjugate equivalent is not so clear (Leyden, 1976). N evertheless, the carbonate platform m egasequence that follow ed spanning the entire continental m arg in w as esta blish e d u n der sha llow n e ritic c on d itio ns. T h us m ost o f th e o ffsho re h alite is be lie v ed to ha v e a c cu m ula te d un d er sh allow -w ater co nd itio ns. T he progressive w idening of the South A tlantic p roto-ocean during the A lbian developed geochem ical conditions that perm itted carbonate platform -form ing biota to proliferate B (F ig. 3). M icrofacies and paleontological studies in the B razilian m arginal basins have show n that carbonate plat- form sedim entation occurred under arid and shallow , neritic conditions (D ias-B rito, 1982, 1987; K outsoukos and D ias- B rito, 1987, A zevedo et al., 1987; Spadini et al., in press). The scarcity and low diversity of the biota, the light colour 3 日O ～3 of the c arbo na tes a nd th e bio tu rba tion w ere u sed b v D ia s- urito klu?3z, 1US-1) to conclude that hypersalinity w as the 0 L IC O CE N E m a in fa cto r in de te rm in ina th e c he m ic al e nv iro n m en t. T h e C C N O M AN 吞N nig n c on c en tration o t ‘，‘ w eita -- u 二 J-4 t o n the F D B standard, according to Spadini et al., in press) corroborates the hypersalinity. 仁～争 日伯书

The clim ate during the carbonate platform deposition w as 六 ，扣 w arm and dry (D ias-B rito, 1982). T his conclusion, based upon petrographic evidence, agrees w ith that advocated by L im a (1983) and Vakram eev (1984) w ho respectively studied the flora of B razil and of tropical A frica and South A m erica during the E arly C retaceous. T he A lbian D row ning Event T he shallow carbonate platform deposition along the m argin Figure 9: 刀etail of well log showin g abrupt p as- w as term inated rather abrup tly by a drow ning event that sage from shallow water limestones (Photo A , onco- occurred som etim e during m iddle to late A lbian. In the liths) to deeper water lim estones (Photo C , calci一 C am pos B asin the lithological record of this event consists sphere-rich calcilutite) and marls . Gamma-ray peak of a level rich in glauconite pellets and phosphorite w ithin a coincides with the hardground rich in glaucon ite calcilutite unit (F ig. 9). This m arker bed, w hich is easily identified by a ga m m a-ray peak, represents a hardground pellets (G ) and phosphorite (P 一photo B )． indicative of non-deposition and signals an increase in paleo- depth. T his sudden rise in sea level has been estim ated at T he com bined tectonic subsidence (Fig. 10) becam e m ore over 50 m for the entire continental m argin of Brazil, based evident after the end of the carbonate platform sedim ent- on benthic fora m inifers (K outsoukos and D ias-Brito, 1987). ation. B asin starvation in conjunction w ith enhanced con- tine n tal run o ff d ue to a m o re hu m id clim ate led to th e This drow ning event was m arked enough to dim inish car- deposition of transgressive shaly um t& bonate production to t h point w here platform a c c r e t io n w a s unable to accom pany the fi rst-order eustatic s e a 一e v e l Transgression to R egression ris e tha t c ulm ina ted in the L a te C re tac eo us. T h is e v e n t is The change from a transgressive to a regressive style of a lso w e ll d o c u m e n t e d in the sedim entary section o f t h e m arine deposition is one o f the m ost striking features of the M alv inas/F a lkla nd P lateau (Basov and K rasheninnikov, stratigraphy of the E ast B razilian m arginal basins. It is 1983). If this regional event proves to be of global signif- m arked by the change from a generally bathyal m arine onlap icance, it m ay be responsible for the w orldw ide dem ise of sequence to a shallow ing upw ard offlapping w edge, w hose carbonate platform s reported by Schlager (1981). landw ard edge consists of an ever-expanding coastal plain.

2 0 0 E PISO D ES, Vol. 11, N o. 3, Septem ber 1988 处is transition, how ever, is not synchronous in all b a s in s T he northw ard decrease in the age of the initiation of the 吸F i9 · 2). In the Santos B asin it occurred ve即 early, in t h e m arine regressive sequence can be explained by the location late T uronian (Pereira et al., 1986), but in the C am pos B asin of the coastal range, Serra do M ar. T his is closest to the it took place later, during the early Paleocene (D ias-B rito Santos Basin (F ig. 1) to w hich it supplied large volum es of and A zevedo, 1986). In the Sergipe-A lagoas B asin, this coarse elastic sedim ents (Santos Form ation). The m ore transition is placed very late in the Eo cene. distant C am p os Basin, on the other hand, received a rela- The ultim ate developm ent of the m arine regressive tively sm aller volum e of m ore fine-grained clastics. Serra sequence is easy to explain, in term s of tectonic subs:idence do M ar never contributed any sedim ent to the basins north and sea level. T he tim ing of initiation o f this sequence, of Espirito Santo. variable from basin to basin, involves another com ponent, nam ely the rate of local sedim ent supply. F or basins at S u m m ary least 135 M a old, such as the B razilian m arginal basins, The key factors in the developm ent of the stratigraphic therm al subsidence becam e alm ost negligible from the beginning of the T ertiary onw ards. m egasequences of the E ast B razil m arginal basins are sum - m arized in Figure 11. T he im portance attributed to a single T E C T O N IC I- .-- I ，，。一 ，．尸一 ，，一 ，．⋯ 、 I factor in any one stage is, of course, an over-sim plification, STAGE Ir"r ’｝ rua ’一Mir ’‘’NLNIVIAL) I and m any others w ere no doubt active. H o w ever, the vol- 习 · 咬 M A R I N E canic infill of the basins is indeed controlled by essentially 1一 卜 ST R A T IG R A P H IC 2 2 R IS E H IG HSTA N D SE A LE V E L FA L L one factor 一lithospheric extension. 0 因 T R A N G R ./ M EG ASEQUEN CE 0 2 R E G R E S S IV E 9｝鬓 R EG R A cknow ledgem ents 0 0 、 r 、 ︵ ． 、 E ． A n early version of this paper benefited from the conth- 名1 0 J． 厂TECTONIC ︶ ． bu tion o f L a e rc io G .F . A ran h a. T h e a u th ors w ish to tha n k 田 ， ︵ se E O 2 0 4o D im as D ias-Brito and M all Spadini for helpful discussions 曰 N ． ︶ 田 ． －J regarding carbonate platform sedim entation. T hanks are 0 ． ． S 的一3 0 门 2Oo due to Jorg e C . D ella Favera and G iuseppe B accocoli fo r ． V g L n r ． their constructive com m ents on the m anuscript. s 4 0 l 砰0 月 一 让COMPOSITESEA LEVEL 3 5 。︵m 11 5 10 0 80 60 4 0 2 0 引酬 N E O C 哗｝葺10}1 }28}I "N} 1U -0a<｝ EOC. JOLIG] MIOC 朴 酬 Figure 10 : Compo site subsidence curve and its D r. H .K . C hang is C hief of the relationship to the stratigraphic megasequen ces G eology Section of the P etrobrAs C ur v e wa s c on st r uc te d b y c om bi n in g f ir s t o r de r s e a- R esearch and D evelopm ent C enter l e v e l a n d t e c t o n i c s u b s i d e n c e c u r v e s . S e a - l e v e l (C idade U niversitaria, R io de Jan- curve based on Vail and others (1977, dotted) and eiro, 21910, Brazil). H e is cur- P itm an (1 9 78 ) 。 rently w orking on sim ulation m o d e ls o f b a s in e v o lu tio n . In contrast, the first order sea-level curves, as constructed by Vail and others (1977), Pitm an (1978), and H allam (1984) show a conspicuous overall global sea-level drop throughout the C enozoic, although the exact m agnitude of this drop is still under debate. T herefore, the resultant rate of change of the com posite subsidence curve (F ig. 10) is negligible. 赢 This im plies that alm ost any sedim ent infill in the basin w ill necessarily have to prograde into deeper w aters, in order to R .O . K o w s m a n n is a ls o b a s e d a t keep below base level. In this w ay, the m arine regressive the P e tro brAs R esea rc h a nd sequence is developed. R egression, how ever, can start even D evelop m ent C enter in R io de before the com posite subsidence curve is reduced to a neg- Janeiro, w here he w orks in m arine ligible rate. This w ill occur w henever the rate of sedim ent geology and basin studies. supply overcom es the rate of the com posite subsidence.

尸．一 － ．．叫 M E G A 一S E Q . L IT H O LO G Y DR IV ING M EC. K E Y FA C TO R S

S E D . 国 │ R E G R E S S IV E │ │T H E R M A L │ │ S U P P LY 2 ├───────┤ │ C O O L IN G │ │ 蒸 左│TRANSGRESSIVE ├────────┤ │ │ ＜ │ │ │一 I ～ ！一 卜二 │ │ S E A D r. A .M .F . de F igueiredo is at the 芝 │ │ │ ├────────┤I ～ I ～ ｝一 丫 │ │ │ │ Petrobras Exp loration D epartm ent L E V E L S H A LLO W o │1 o I o I宇 │ ││ │ (A v. C hile, 65, R io de Janeiro C03 PLATFORM │ 今丫 ├────────┤ 目 │挥斗 漂 要 │ │ │ │ │ │ 20031). H e is D ivision M anager for T R A N S IT IO N A L j j │ - j -I 」│ │ │ the southern B razil m argin and has J j J J │ │ │ C L IM AT E c oo rdin ated th e w o rk o f ba sin 今 0 0 0 o o o o │ o │ ││ analysis groups for m any parts of D EG R E E the coastal region. C O N T IN EN T A L │ │ E X 下 E N S I O N││ O F EX T EN S IO N v vv 六险二一 │ │ │ │

F i gu re 11 ： K ey fa c to r s ac t iv e in th e d ev e lop m en t of the stratigraphic m egasequences o f t h e E a s t P r a z 一 ili an m a r gin a l b as in s .

EPISO D ES, Vol. 11, N o. 3, Septem ber 1988 201 R e fe re nc es K outsouko s, E .A . and D ias-Brito, D ., 1987. Paleobatim etria da m a rg ern contine ntal do Alm eida, F.F.M . d e, 1983. R elag5es tect6nicas da s rochas alca linas m eso z61cas da regilo Bra sil durante o A lbiano. R evista Brasileira de G eoci6ncias, v. 17, p . 86-91. m eridional da plataform a sul-am ericana. R evista B rasileira de G eo ci6neias, v. 13, no. 3, K ow sm ann, R.O ., L eyden, R . and Franciscon i, 0 ., 1977. M arine seism ic investigations, P. Ip9-158. Southern B razil m argin. A m erican A ssoc iation of Pe troleum G eolog ists B ulletin, v. 6 1, p. 546-557. A rai, M ., in p ress. G eoc he rnical reconnaissanc e of M id-C retaceous anoxic event in the Santos B asin, B razil. R evista Bra sileira de G eoci6ncias. Ko wsm ann, R .O ., C osta, M .P .A ., Bo a flora, M .P., A lm elda, H .P . and G uim araes, P.P., 1982. A rthur, M .A . and Schlanger, S.O ., 1979. C retaceous ocea nic anoxic events as causal facto rs G eologia estru tural do Plato de Silo Paulo. A nais do Congresso B rasilelro d e G cologia, 32, in the develop m ent o f ree f-reservoired giant oil fields. A m e rica n A ssociation o f Petro leu m Salvador, v. 4, p. 1558-15 69. G eolog ists B ulletin, v. 63, no. 6, p. 870-885. L ana, M . and M ilani, E.J., 1986. A m ic ropla ca do nord este brasileiro 一u rn elem ento d ina- m ico no rifteam en to cret5cico in ferior. A nais do C ongresso B rasileiro de G eologia, 34, A sm us, H .E ., 1 984. G eologia da m a rgern contine ntal brasileira. In : Schobbenhaus, G . (coor,d.), G eologia do B rasil, T exto explicativo do M apa G eol6g ico do B rasil e da Area G o iania, v. 3, p. 1131-1144. oceAnica adjacente incluindo dep 6sitos m inerais escala 1:2,500,000. D N PM , p. 443-472. Le F ournier, J., C horo w icz, J. T ho uin, C ., B alzer, F., C he re t, P .Y ., et al., 1985. 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Classificaggo des bac ias sedim entares brasileiras seg undo G eologists B ulletin, v. 55, p. 2)6 1-2173. a tect6nica de places. A nais do C ong resso S ociedade B rasileira de G eologia, 26, Bel6m , v. 2了沐 67-90. L eyden, R ., A sm us, H .E ., Ze m bruscki, S.G . and B ryan, G ., 1976. S outh A tlantic diapiric A sm us, H .E . and Porto, R ., 1980. D iferencas no s estagios iniciais da e vo luggo tect6 nica da structures. A m erican A ssociation of P etroleum G eologists 日ulletin, v. 60, p. 196- 212. m argem continental brasileira : possiveis causas e im p licagi5es. A na is do C ong resso B ras- Lim a, C .C ., 1987. E struturacilo pos-rift da porq Ao sergipana da B acia S erg ip e-A lagoas: o ileiro d e Geologia 31, C am boriu, v. 1, p . 225-239. pap al do basculam ento a des descon tinuidades do em basam ento. T ese de m estrado, U niversidade F ed eral de O uro Preto, 37 8p. A ssum p g5o . M ., Suare z, G . and Ve loso, J.A ., 1985. Fa ult plane solutions of intraplate earthquake s in B razil: som e constraints on the regional stress field . Tectonop hysic s, v. 113, Lim a, M .R ., 1983. Paleoclim atic reconstructio n of the B razilian C retac eous based on no. 3-4, p. 283-293. palynological data. R ev ista Brasileira de G eoci}ncias, v. 13, p. 2 23-228. A ustin, J.A . and U chupi, E ., 1982. Contine ntal 一ocea nic crustal transition off Sou thw est M acedo, J.M ., 198 7. E vo luggo estrutural da Bacia de S an tos a breas continentais adja- A frica. A m erican A ssociation of Petroleum G eologists B ulletin, v. 66, no. 9, p. 1328-1347. cen tes. T ess de m estrado, U niversidarle F ederal de O uro Preto, 165p. A zevedo, R .L ., G om id e, J . and V iviers, M .C ., 1987. G eohist6 ria da B acia d e C am pos － M c K enzie, D .P ., 1978. So m e rem arks on the d evelop m ent of sedim entary basins. Earth and B rasil, do A lbiano ao M aestrichtiano. R evista B rasileira de G eoci6ncia s, v. 17, p. 139-146. Planeta ry Science Le tte rs, v. 40, no. 1, p. 2 5-32. Baso v, I.A . and K rasheninniko v, V.A ., 1983. B en thonic fo ram inife rs in M esozoic and C eno- M ilarovsk},, A .A ., 197 2. C o ntinental rift zones: their arrangem ent and dev elop m ent. zoic sed im ents of the Southw estern A tlantic as a n indicators of p aleoenvironm ent. In: T ectonophysics, v. 15, no. 1/2, p. 65-70. Initial Reports of the D eep sea D rilling P roject, } 71, pa rt 2. U .S. G overnm ent P rinting M izusaki, A .M .P .P -, 1986. R ochas ig nea s basicas do N eocom iano da Bacia d e C a m pos; O ffice, W ashingto n, D .C ., p . 739-7 87. caracte rfsticas e c om po rtam ento co m o reservat6rio de hidrocarbonetos. T ess de m estrado, Bertand, R .T . and Ca rozzi, A .V ., 1984. M ic rofacies, d ep ositional m odels and d iagenesis of U niversidade F ed eral do R io de Janeiro, 104p. Lagoa F eia Form ation (L ow er C retaceous), Ca m pos B asin, o ffshore B ra zil. Se rie C ik c ia, M ohria k, W .U . and D ew ey, J.F ., 19a 7. D eep seism ic reflectors in the C a m pos B asin, off- T6cnica e P etr6leo, Petr obr6s/C EN P ES/S IN TE P , } 14, 104p . sho re B razil. G eophysical Jou rnal of the R oyal A stronom ical Society, v. 89, no. 1, p. 133- Bullard, E.C .,Everett, J.E. and Sm ith, A .G ., 1965. T he fit of the continents around the 14 0. A tlantic. In: Sy m posiu m o n C ontinental D rift. Philosophical T ransactions of the R oyal O jeda, H .A ., 1982. Structural fram ew ork, stratigrap hy and evolution o f B razilia n m arginal Society o f London, v. 258A , no. 1088, p. 41-51. basins. A m e rican A ssociation of Petroleum G eolog ists B ulletin, v. 66, no. 6, p. 7 32-749. C ande, S.C . and R abinow itz, P.D ., 1978. M esozoic sea floo r spreading borde ring conjugate co ntinental m a rgins o f A ngola and B razil. T enth A n nual O cean T ec hn ology C onference, Parrish, J.T . and C urtis, R .L ., 1982. A tm osp he ric c irc ulat元on, up w elling and org anic-rich ro cks in the M esozoic and C enozoic eras. Palaeog eo graphy, Palaeoclim atology and Pa la e- , 2,p. 1869-1876. oecology, v. 40, no. 1-3, p . 31-66. C astro, A .C ., 198 7. T he N ortheastern B razil and G abon basins: a double rifting system Pem ira, M .J., B arbosa , C .M ., A gm , J., G om es, J.13., A ranha, L .G .F., S aito, PA., R am os, associated w ith m ultip le crustal detach m ent surfaces. T ectonics, v. 6, no. 6, p . 727- 738. M .A ., C arvalho, M .D ., Stam ato, M . and B ag ni, 0 ., 1986. Estratigra fia da B acia de Santo s: C hang , H .K . and Ko wsm ann, R .O ., 1984. Subsidencia t6rm ica e esp essura c rustal d a Bacia analise das sequencias, sistem as d ep osiciona is e revis5o litoestra tig rafica. A na is do Co n- de Santo s. A nais do C ongresso B rasileiro de G eologia, 33, R io de Janeiro, v. 4, p . 1602- gresso B ra sileiro de G eolo gia, 34, G oiania, v. 1, p . 65-7 9. 1 6 1 4 . 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2 0 2 EPISO D ES, V ol. 11, N o. 3, Septem ber 1988