THE SYSTEM OF CONTINENTAL RIFTS BORDERING THE SANTOS BASIN, BRAZIL
FEltNANDO F. ~1. DE AU\1EIOA Jnsfi tuto de (~e('(têr.ctas. Universidade de São Paulo São Paulo, Brazil
ABSTRACT It is suggested tnat lhe late rifting of lhe eleva.ted ccnt.inenta l reg-íon 15 due to a process Opposite vertical rnovernents exceeding eleven of gravltational slidlng towards the Basl n. fi kilometers have occurred since lhe Lower Cre- result af the proximity ot the two provtnccs ond taceous belwecn the Santos Baaín, localed on lhe the ímmense diffcrcnce in basement levei h(>- continental margin, and lhe neighboring con- tween lhem. tinental regíon. The geodynamic process wae accompanied, between the Crelaceous and Eoce- lNTltOOUCTIOl': ne, by íntense fissural basaltlc magmatism as well as central type alkaline volcanism. After The Santos Bastn is a mcso-cenoaoic. tcc- lhe volcanism ceased, when a great difference in tonto de preaalon futl of basalts and scdímcuts, leveI had been established between the tWQ tecto- located on the continental margin between the me provinces, a syslem or rifts, whose depres- States of Rio de Janeiro and Santa Catnrtna. sicns were part.l y occupied by sedimenlary basins, In front of the Basln, the Atlantic pla teau ot developed tn lhe region. This tectoruc syslem southeas tem Brazil enda In I1ttoral scarps, 800 evolved from an erosion surface of probable to 2200 rneters high, .ín a mountain chaln strctch- Eocenic age, deformed since the Oligocene. The ing 1200 kilometers, genericaJJy known as the rlfts (the most notable of which ts lhe one lhat Serra do Mar. contatns the mlddle valley of the Paraiba do The complex or tectonic vnlleva, block Sul Rivet- and lhe Taubaté Basin) are bordered mountains and smal1er xedímcntary baains or by hlgh mountains, whíoh were elevated during tectonlc origino whlch form the Serra. du ~far the process of subaídence ín the areas between Rltt SY8tem, representa one of the most nota hle them. topographlc and structurat uspecta or the Attnn- ln tte geographlc [ocatíon, the system of ttc margtn of the Arnertcas. The opposlte vertical rlfts wae Intiuenced by , the proxtmtty of the movements whlch took place in thls region aince Santos Bnsln and the presence of a grea t system the Late Jurasslc probably exceeded 11 krn or or anctent trsnscurrent rauits. The Jntter, reacti- dlf!erence in level between lhe híghest mountnlns vated In the Cembro-Ordovíctnn. cuts obHquely and the Santos Bàeih basement. These move- the precamhrlan metamorphlc structurea or the mente were accompariíed In par t by Intense region nnd WBS pa rtlally reactlvated slnce the Mesozoíc. Thls system seems to have also ln- megmattam "'h1ch produced trom ultrabasic and rtuencec the general ccntour of the coaet as tholeiltic rocks to pernlkaline granites. well as the northern border of lhe Santos Bastn. TIl•• eísmtc. actlvl~y or the reglon. af thougfr whtch is IImlted by 11 large tautt on the conti- eak, aeems to trtdlcate tbat the rift syetem i~ nental shelf. not entlrcly inactive. 16 F'ERNANDO }o.,. M. DE ALMEIDA THE SYSTEM DF CONTINENTAL RIFTS BDRDERING THE SANTOS BASIN, B.RAZfL 17
Thc st udy or $0 great a differential vertical mov~ment. nccompunied by auch mngmatfsm, bee~ partly migmatiz.ed and granttlzed. The and Rio de Janeiro. has its rectiJinear eourse perrnitted them to delineate 'the Bastn In parto wlthm a. plate prescnts a suoject or specíaí Inte- belt fi late dcvelopment took place durtng the determJned largely by a vast dextral transcurrcnt and to determine its great thickness of scdlments m rest, for whích an adequats explRnation has not Ca bro-Ordovlcian. At that time. the mnlaasea tnult of the late BraziUano systcrn (Almeida. (Ewlng et aI., 1969). Butler (1910) discuss e. the vet becn found in medem geodynnrnic modela. formed and the subsequent volcantsm occurred Hasul and Carneiro, 1976). The Trans-Amazon~c nature of the Baaln's sediments, basing hís con- together with the intrusion of numeroun post- etructures were markedly inflected ENE because clusíons on selsmlc reflectlon prorües. He poJnted Although lhe Scna do Mar Rift System haa klnematic g,ranite plutons. After the fOlding of thís as well as other late Braziliano faults. ln out lhe existence ot salt domes and unatyzed nol y~t bee n fully xtudied, and has been mapped ~henomena or the Ribeira beIt, an intense fault- addltlon to the coastune, the fault Itself, whlch the conditIons in which the sedimentation devel- onl:: m a Jimiled urea. lhe a.vailable knowledge mg process occurred, possibly as a resuít of the bordera tne northem part of the Santos Bastn, oped. Seismograph1c research by Petrobrás in pel.lllt~ a charHctcri7.flllon or íta major corupo- reactivation or deep, anelent lineamcnts. Thts adopt the ENE trend of the large cambrc- 1969 was pubUshed by Baccar (l970) , whlle nents. Mor-covcr. it pennits a tcntativc Jnter. fault system is 'composed of larg'e dextr-al, trans- orôcvícíen faults. In the States of Santa Ca- Leyden and hlo collaborators descrlbed In 1971 pretat íon (")1" rts evotutton, with rcspect to the current .fauIts, trending prlmarlly ENE. They tarina and Paranã, the coastal region 19 devel- the resulta obtained with new setsrníc, gravl- ~cvelopment o( thc Santos Baaín. The Baain thus obhquely cross and inflect the precambrian oped in the Jo1nvUe median masstr, Itaelf not rnetrlc and magnetometric proflles taken through- rtsetr has 'bcen inv(>f.!tigatcdvcry liltle as yet. structures which gcneraJly trend NE to ENE arrected In Its Interior by that fault systcm; out the BaBln. Mlrand& (1970) nollfied the Those arca.s least investigated, lhe States' or (Flg. 1). lnformatlon on the Late Brazlllano the coastline as well as the faulted flexure resulte of the setamtc rerractíon and ref1ectlon Pnt-aná nnel Santa Cn tnrtna wlll not be described bordering the Santos Baain trend NNE, accomp- by not-e. fnult system is sUII incomplete, some of its research undertaken Petrobrás whtc h led to major components having only recently been anled at thI8 potnt by tertlary inults or the the discovery or the large Santos fault. Shortly Identifted. N~vertheless, many of Jts major faults Serra do Mar, Identltled by Maack In 1947. atterw.rds,· Petrobrãs begnn the rtrst drilllngs TIni: ANf'II':NT iõ;TltlJCTfJRF;S and mínor assoclated faults are already weü In the Basln .. P08T-PALEOZOIC STRUCTURES :.ocumented ín field atudles by varlous Inves-, Despiu ali these Invcstigatlons the Santos . Wlth t rte excep ttnn or minor continental se- .lgators. Some of lhe faults present belta or Buln Is BUlionly barely known. d'mentary bll!'lins Hnd Httora! sedimentation th mtensc eutaclasUc deformatton, hundreds or From the beglnnlng of the Wealdlan reactí- ~\'hnlc const.m rcglon !Jonlcring lhe Santos ~aSi: vallon, the e!ellCl'lbedreglon became rrubjoct to 1'he Buln 18 open towards the ocenu where metera thtck. The author .maintains that some ot 1.':; compcsccí of prN':unbl'ian metamorphic rocks an Intenso tectonlem and magmatllm. Two 01 It bordara the São Paulo plateau. It.'l continental these ancient fautts suffered local vertical mo- penet~ated h.:, granilc~ whose ages go up to th~ the most notable reSUlta ot these phenomena are edge ta bordered by lhe Santos fauJt wnose ellp vements duríng- the Wealdian reactlvati~n (Al- Ordovictan he lnajol'ity or these rocks belong lhe upUit oi the Ponta Gro... arch anel the OR the nortb exceeds 3000 m. However. It be- meida, 1969), as did the documented case or to the Ribe~r. folucd bett (Almeidn ct al., 1973J. overtlow oi lho Paraná Baatn'. b•••••lta.· comes o. Jarge tnult flexure in the SW. F'ig. 1 the CantareJra tault zone, north of tha ctt . c:,olved dur-j ng- the Late Precarnbria (BraziIiano was ndapted irom Leyden et et. (1971), to lhe Qf São Paulo. y TIlo Ponta Gr_ arch I. 11 large upllftad CycleJ, 01' to its infrasttucture. area correspond1ng to the ocean, and has lhe structure wttOM lÍXIlIInclln•• NW, normal to the Magnetometrlc studies indicate that the Santos fault outllned. It shaws lhe Basin's .Thc oldcst I'ocks Hre exposed in one of the cORBlIlneoi lhe 8tata Di Parl\M. Although It. above-mentioned precarnbrian structures extend deepest zone On lhe continental slopc in fmnt meclHl~ nJ~tssifR or the belt, that of Joinvile orlgln seema to ·extend to Uppor Paleozolc, the to ~e ba~ement of a large part of the Santos ot the Stn.te af São Paulo's coaslllnc. The ha~ (HnsuI e-t n.", 1975). Despite policyclic rework- structure suttered Intanse uplltt, •• Umatad by Basm which evolved on the continental crust. sement h!l tound to be over 8000 m under sen mg. maRsif Bowen (l966) at 7.~ km. between lhe Late the sUl! rctnins R-Ar rlldlometric )evel. Bacéar (1970, Flg. 5) shows a depth of
Rí ver devetop s in H tectontc depreasion 220 krn Iabeled Campo's surface. He considered tt to be long. g'enerüll y trending gNg of lhe precnmbrian older lhan Japi which he called Cristas Médias ~----"" structures. Oeotogtcar. g-eomorphotogícal and CAverage Crests) surface. The aulhor in 1964 gecphyaical etudtes. nlthough still incomplete, dernonstrated that the two surfaces proposed by \ " ", " oS' " , \ 11ttest to the tectontc nature aí the depression, Martonne are actually only one which wae elev- . ,.. rccogrriaed by Maull (1930) as a graben. The ated tectanicaUy in the Serra da Mantiquelra " nverag'e width of lhe Puraiba do Sul Rift Valley region. \ Is ctoec to 25 km. T'he difference in level, A geomorphological analysis seems to indi- W I between thc eroston surrace which levels the cale that the Paratba do Sul graben eollapsed I- bordertng mountains of Serra da Mantiqueira ín the axis of a large arched uplift, possibly nnd Ser-ra du Bocai nn , and lhe base of the faulted In lhe flanks, where the Japi surface o scdiments trmt. pfll'tially.fill the depresston, ts waa 'elevated to almost 900 m (Almeida, 1964). Z HIOO m. T'b e Itoor of the grabcn ts irregular: This interpretation is based on field observations, o: fi. medtum elevntton. the Cnchoeira Paulista the examlnatlon of lopographical maps and on W O uplifled hloc k. r-ises up to 800 m above sea the analysis of lhe drainage system of the upper O:z lcvel. It is c rosseô by lhe Paralba do Sul River Rio Grande hydrographic basin. The basin's 0- in a deep v a.lley. weet of this elevatton, the major rtvers are dispersed radia1Jy in the m(/) Tn.uba.té Bu s in. partially full of sedtrnents. has highest zone of the SeITa da Mantiqueira. Flg. 1 - COfll!tnl Mt"\1rlnr~~ h(}r.ll"'rln~ thp Sllnt')!! B:l.'1.1n. 20 FERNANDO F. M. DE ALMEIDA NW a. mountafn existed on íts southern síde. though THE SÃO PAULO BASIN PARANÁ BAStN only the Serra da. Bocainn and its prolongation. tbe Serra de Quebra Cangalha rematn today. The tectonlc ortgln of the Slo Paulo Basln where the c1ty of the same name Ia Jocated, The upwarping the mountaíns nelghboring or waa conjectured by Washburne (1930) and lhe Par-afbn. do Sul rlft ehould have occurred Freltes (1951) and later conflrmed by the author more or Ices aímultaneous to the suoetõence of In 1955. e Basín'a northem border touches a lhe middle regton. However, when the large arge, late Brazlllano transourreet fault, tren- oligocene lake was formed, the marginal eleva- dlng E-W. Dur\ng the fonnaUon of the Basín, tions should have had Httle topographic premi- thls fault snffered a vertical movement. nence, as Rfch (1!l!'>3) observed. Thts explatna the maturity and the esscntiaUy pelitic character The São Paulo Basín 10 close to 70 km long accompanled lengthwise by the TI.tê River. of the Tremembé Formation, contrastíng wlth lt doesn't seems to be bordered by faults to the granule.r and mineraloglcally Immature the south, 90 !t may be consldei'ed a half-gTllben. nature or the upper formation (Suguio, 1968). At the northem edge, cIose to the f'ault zone Geophysical studies are sUll acai-ce on the that limita the Basin, the tnrckneee of the sedt- Parntba do Sul rift. In a recent work. Davlno ments of the São Paulo Formatlon ortglnally and Harnlyi (1973) present results of gravi- reached elose to 300 m. The Formation appeara metrtc and rnagnetometr-íc surveys or the graben, to be an interflngertng of psammltlc and pellUc the adjacent mountains and the uplifted block beds, the latter predominating In the upper part. of the CachoeJra Paulista. Thc Bougucr g'rnvl- The Basin contatns deposits of flood plains metrlc map indlcatcs lsoanornaly lines nlong the and fluvial channels, accumulated ln a tropical' geuern! dlrection of the rift, wlth decreaslng climate. The proceaa was not accompanled by regional anornaues towards the interior of the upwarping of lhe bordertng fault block on the basln nnd 'wtth negntivc anomnlies near the north. The latter !s called the Serra da Cants- NNW edge, wnere lhey reach -10 mgals. As relra, wnose altitude 113close to 1200 m, similar to the Jap! surrace, where not deformed. a reeult. fi reduced deficlcncy of mass compatible with the srrrall lh1ckness of sedtments retalned The sedlmentary São Paulo Ba81n 18 sur- in the 'I'nu baté Bnaiu ts observed. 'I'hls con- rounded by preeambrínn rock elevatlons (Cou- traste wlth lhe posttíve nnomaües of up to 30 tlnho, 1972; Sadowskl, 1974) wh1ch the Alto Tletê er0810n surface leveled to nearly 850 m. mgals which are observed on its elevated edges. The author maíntaíns that sueh a .urtace, of 1n additlon the magnetometric map (vertical presumable Neogene age was depressed ln the component) preaents ísoanomaly Unes trending fault zone, thus orlginating the Basln. 'fhe in lhe general dlrectlon of the valley, witll Basin's basement reveala acctdents which in part vatues decreaslng from lhe el~vated southern should be due to faults trending NE, (Kollert borde r of the valjey to the north, varying Irem nnd Davlno, 1963). -/-14 to _10 gumrnas. 'l'he age of the Sli.o Paulo Fonnatlon 18 dlttlcult to determine sinee It doeIII!.'tba"., fOllSiIs. Very IIttle is known still about the modern l!..=!=J o lts probable correlatlon with the upper !ayers = ueee- Senonlon rautts eaeocteted wf th the downthrow of the .oo,ion sol' of the Taubatê Damn mnkes the generaLattrlbu- Bouru Group grnben, lt eeems that It8 marginal scarps are tion of Plfõcene age acceptable. not n result of unique, large fa.ults, but rather PCOlt:lOzlZOiC (lf a aystem of smnll, normal faults, eeveral of THE GUANABARA RIF'T which have already been identitled ln the fleld I f lhe eonttnimtal borâer of the Bflnlol'J Bu!n, FtJ:. 2 - Po •• lble tectono.maamRtlc uolut 00 n:l rlU a.nd df:poatted a lreal thickn~'lll 0'( eV8)'lOrltc8 over lhe rPrang+pant and Pannuti, 1966; Sugulo, 1968; The topographícally depressed and elongated 1) Durlng lho ApUan, lhe eee noodeC! tbe onel to the northwetJl tht!le lav{l8 cover pateczotc p('dlments. Cordnni et aJ., 1974l. Transverse faults along region on which the Guannbara Bay resta W8S Lower CrelaeeouI bua1tl~ lavlUl. ln lh.o PAraM :a~~n, prol'TefllfIIlvé IlUbeidcnc(', nceumulated detrtc Mdimentl'l the rift cut the layers of the pllocene formation, Interpreted In 1944 by Ruellan to be a graben 2) Durlng lho Lower. genonfnn, the 8nnlo' BIl3I, fnated dunni; lho UPP(lr Oretaeeoua, ncxt to th(l Bantoe from the er'OlloD of lhe Serrll do Mar, Tha latter orte the elen.ted bor<1er of the 8QnloB Bn.8ln. or a tectonic depreesion siluated between f8ult as noted by Suguio (ep. (~It.).Mlnor ondulations fautt, The fI"t pbate af atkAl'ne 'VOlcanltmt oee'=e o:Oleanl.in procreHed to the Interior or lhe CQIIUnent. of the layers accompany those faults (Campos, blocks t!lted NNW. F'reltas (1951, 1956) labeled :1) Between the campanlan an4 PaleoceM. lhe depo.tted In the Parant Dallln. 1952. 1952a). It «1ft valley Campo Grande-Guanabara-Río Bo- At the end of tbe &enontan, lhe Bauna Q1'Ot1P.'WU.. aeUvtty ln tho regton, thé derormattou er tbe Japi nIto>, notlng Its extenslon to the bay of llha 4) Durlng the 011coeen~. atter lhe end of th~ 'O'oleanlc I ff~"" uparched. whHe lhe PArolba ~r:\b!"n erasl" eurft\Ce commeneed (")" In Flg. 24). The JQ.pl eT08 on :: lllke evolved tn thé interior or thp. ~rnh •.•n. C. Wushburne (1930) noted a regional jncli~ Grande. The reglon has not been tectonlcally t to o began U•• downthrow ." lhe ufal cone. At uw,moment. 8. :et d naUon of the Taubnté Bnsin's layers towards the studled In deta!! 8u1flclent1y to exclude the alter- In' wbleh .edlmmta of lhe Tremembó :Alnnatlon ac:~~:t o~ 'UH~gr: aben "ubllided markedly. pl\rll)' ('.olllp~n- Serra da Mantiqueira, which later observattons' natlve proposed by Ruellan: that It 10 an Inten- 5) DUrtng lhe PUoeene and the Qua.tematY. lhe bu Fonnntlon, The upw8rjllng or lhe nelghborlnJ.'( mnuntalllR confirmed, indicnting a structural assymelry, sely eroded. fault~angle depression. Mted by lhe pUoeene Ic<:umulet\!on of lhe 8&0 Paulo M.anUquellil o.nd the Serrn. da. Boeatns. ln 'ta prG· contlnued slmultaneoulty, repreeenled by !e dS:t"~a:(\ a.bandoned lhe allroHne tnlruRloo8 or lhe 1~IAnd af wes81ve retreat due to eroRlon,. the Se .! I hcd detrltnl sedlm('nt!; to lhe Santos Br\!!II1. A tI. ACRrl. bral'l. eMltc., (]978), 48. (Suplemento) sao SebnstlAo and 'Olher n(!lghb THE SYSTEM OF CONTINENTAL RIFTS BORDERING THE SANTOS BASIN. BRAZIL 23 GUlmar~es ~]947), observing the aJignment of the alknhne Il1lrusions afon thís . identified next to the edge of the Parafba do. sugge.'lted tha.t 't g depresstnn, Sul River delta. Goíâe, where the magmatism of this phase Is sedíments as a basement. During the Aptian. I Jl111y correspond to a fault I zune, whkh Images or the ERTS-l sal notable for its abundance of melnnoeratic auca- an epicontinental sea coming trom the south scern to ccrrobors.ts. ellite The Campos surface's probabJe Eoce (Maack, 1969) penetrated the original rtrt. In mar-ka the maximum a e Hm ne age Jine rocks. I the desert cUmate of the time, t.hts sea preclpt- f- Thc Guanabal';t Rift extends nt J t bara Rlft. The maestrl!hthm lt tor the Guana- The second aub-phase evolved during the cani.sm and th to Pateocene vot, tated the g-reat volume of evaporítes or lhe JOl1 I~etwcen the Barr-a de Sáo João :a:d 200 Campanian and Paleocene (or Lower Eocene, e small calcareous C b ' lower pnrt ot the Baatn'a sedimentary t1tting. Scpetlbn Ba.y. 1C the Ilh G the associated wlth the Rfft I t a ,uçu BBSIn, should the 53 m . y. daUng of the Cabo Frio rocks b . a rnnda Bay were to Iatter since it ' ex 5 ed prevtous to the The Serra do Mar did not extat at that time as be confirrned) . This phase seems· to be charac- e JOcluded i n lhe calculn tton, lhe Rift wouJd mations is' was not fiIJed by lava, Infor- i a hlgh rellef bordering the Bnairt. teristlc of the erea occupied by the tectonlc :each 280 km. TlJe wtdth of lhe Guanabara B th . Incomplete for an interpretatIon or 1.~ bet wecn 2!l t., 10 ay system of Serra do Mar. Its intruslve centera The ancestra.l Serra do Mar W8$ fnrmcd . th' . km. Il llal'l'Ows howeveJ' e evolution of this structure, Similar to th Paraiba do Sul G b e at-e located in the interior ai the rifts or on durlng the Upper Cretaceous probably before m . e RIO BOJlito merfdlnn A tOpographícaIJ ' have j ra en, the Rift alao aeema to depL esscd region, not flooded by lhe ;Y lhe bordering mountalns. Leucocrntic and me- the Senontan: only st ra ttg-rnphtc atudles of lhe neogeni~ t:~e~n morphologicaJ features to B pr'('Rcnts fi n~Jjr;>fof low büts ( d seu. I socratic rocks, such as nephellne syenites, foyat- Santos Basin wUl define the aetual date uccut-e- with orne pulsntion, possibly eeaocíated br-inn rocka Th . . orme or precam. tely. e Serm do 'Mar. einerged In a place not de . e HII{flhne Intrusions ot the Serra a prolonged eroston. .tes, tjotítes. pulaskltes, ttnguaítes, umptekites, .rv;endn~hH. of Rio Bonito and or the Morro phonoütes. nordmarkttes, ete., predomlnate abso- -tO<> tu h'Om the Santos fault, and aínce then de Sfio Jorro stfllld out in the rclief. MAGMATIS~r Iutely ín these centere. Even peralka1ine granltea haa retrated to ItJJ present poslUon as • result occur In Itatlaía (Ribeiro Filho, 1967). ;:;otLert!!!lon.fFlg. 2). d 1'he ~C(!llmulnt:ed scdiments are very Hmited The fissural basaltic magmsUsm of th an thfn 111 the mtes-lm- or the rift. In addT Because of the Iittle knowledge now avat- The Senoniah and the Paleocene were mo- raná Bastn (Serra Geral b e Pa- to Quater-na I'y fltlVi;t! ~edimeniatlon thi 1 IOn ticnlly tholeiitic thou h with asalts), Characte.ris_ lable. It 18 dlrflcult to clarlry the relattonantp merit,s ot great tectontc acttvf ty ín the Serra do linental layers OCCUrarouJld lhe Guan n con- variatlons (RU g important chernIcal thnt may nave exletild between lhe alkaUne Mar fegton, whlch was rtsing by that time. The pos~ibly related to til S. abat-a Bay, Late J egg, 197::i), occurred between tha nmg mauam and tectoníca In thia reglon. Tbere Sêrra .co Mar' suppltcd sedímente to the Paraná The I e ao Paulo Formation urassic and Lower C IH crenrty a geograpblc_assoclatlon. partlçularly Basln in the interior of the conttnent, whet'e ut C::thn .;,mn I. fHlJlt~an,;'e Jacustrine Basln oi et aI. J966) Th' retaceous (Amarat second eu' ~Oç . south of Nlterói, was filled by a hundred excee~ing 2· miJlil~nmagmatis~ affected an area wlth respect to the magmatlc 8ub:phas •. the end of the Senontan the Bauru Oroup began , meters 01: calcfl1'cous Lhí k . square kllometers ín S The Itattata, Paolia,Quatro and Morro ~ondo to aceumulate. The Santos Basín alao began America, particularJy in the central d outh (rom thcl'maJ aouroas 11" lC ness, onginating centers are 8ltuated wbere tbe Ja.pt· 8urtace to aecumulate Uttoral and mnrine aedimenta ot remnins t Ccu t.o 105·31 ..e•mz, :938), Marnmalian zones south ot the 14" an eaatern roee hlgheat In Slo Paulo. TIl.·enUre magmaUc Upper Cretaceous age, as confirmed by core log • õJ~ contamed j th extended up to lSOO k parn.llel. In BraziJ, tt reou,s cnvilies indiente an Upper P ~ e calca- lhen active Ponta G m from the consto The proco.. preceeded· til•. development of the rifts data. The aJkaU.ne volcanlsm that A.ccompanied The calcareous Hre pl'Obabl Lo a ,eocene age. by swal'ms af d' b rOSsa arch was penetrated now expolled on,~ cQnUnent. An IntoMa! ot thliJ tectonlc pulsaUon was more inten~e in t11C 01' L,lte Cret Y wel PaJeocene IR ase dykes whJch trended NW prolonged tecton1é caím ,eparat.ed lhe ma.gma- .reglan durlng the Lower Senonlan and bclwecn alk ,: n~eo1l8, {'Ol1tempol'lmeous with the paralleUng their axls Th ' ~he :t~lIe. volcanJsm in the ncighborhood, to which with . ese were associated t1"1n and tlle rlrt.ng, nece80llry for the IlIghly the CA.mpanlan and Paleocene. The Jutler took a8m seenl~ to he genetically tied. same some alkaline intrusion centers, having the developed elaboraUon ar the J apt .roolon surtaee place more ln the Interior. in the region where d age a~ the basalts (Fig. 1). The Serra and the almo.t tolal de.tructlon or th. etu.lvo lhe cenozoic ritts begnn to develop. A tcntaUve The Guana ba l'it Rift is bordered b . o Mar regIon was at that ti . products of that msgtnatl8in by eroslon. rclatlonshlp may be eslabUshed between lhe moun tains, especialJy t tI' y h1gh tenslon fractures, Jnto which a . me sub]ect to Serra do Mar i~ locnll ~ le north where the of d' n Immense number Compan1an-Paleocene tectonic-magmatic epísode. OJ'gãos. The ;ntter's \ . nown as lhe Serra dos r nd I~~~e dykes penetrated. These trended NE nnd the deposlUon of the sedlmentnry unit B 226:.l m which resul;s il~frhest. altitude ('eaches , wlthout having been associated .th {Butler, 1970). It i5 interesting to keep in with the d . n dlfference in contemporaneous, central_t . \VI levei The facUI tnteren<:ce dlscu88ed above mind that I.JC Pichon and Hayes 11971) a.ttribu- , epression af over 2000 ' . Eions. On the othcr hand ype alkahlle intru- arld' pa,'Uy includes lhe \Vem'in m. l.hl!) value aCCur rare Iam h ,however, there did lend to the tolrowlni InterpretnUon of the ted an important varJation in the ocean floor Sena dos O - g by eroslOn. The 1966). prop yre dykcs (Damasceno, tcctonle evoluUon ar the reglob, Belween lhe ~preadlng of the Atlantic to the ::;tlmc time rgam: W:I,., inlcrpf'cted b R 11 11944) to be . . y ue an Lnle Jurasslc and Lower Cretaceous, a pheno- tnterva!. Call1pOs f n block ongmally.leveled by the A.rter the Turonian a menon In the upper mantle, possibly of a therma.l WNW. SUr see, fAUltcd NNE nnd in~lined The Japi erosion surface represcnls the cnd t~ok plnce. The m8g~ati:w \magmatic Ph~se orlgln. resulted In the elevatlon of the modern of a long erosive processo probably rcaching tically a central t vas charactens_ Serra do Mar regton anel the Ponta Grossa arch, The elevated southel'n bnrder . lh ype, marltedly alkaline 'th back to lhe Eocene. It leveled the ~cnonian e r..bsencc of tholeiitic basalts. ' WI with lhe subsequent fracturlng provoked by lJar-ely J'eaches 1000 1l1. Jt is v of lhe Rlft alkaline intrusions. but. those of ItntiHia und the few available Potassium_Ar onTo jUd~e from erosion, transformed in th : ery worn by tenslon and nbundant lholeUtlc flB8ural volca- that two different sub g ages, lt seems Passa Quatro, formed between the Mncsll'ichtian (Serra da. Carioc~ N't ó' e LlttoraJ ma~sifs nlsm. The colneldence of thls proces! with the processo The oJdest phases occurred in this and Danian. remained as residual relie(s. '<. I er I massif, ete.). widcly admlUed South Atta.ntic opening slnce Faults Jike the Rio B ·t Lower Senonian, repre;::te:eveloped during the the Late Jurnsstc ar Early Cretaceous (Maxwell The down-faulting of the Parníba do Sul ]065), RI'e found' t1 '. ~nJa fault (Rosler, exposed on the Sã p by intrusive centera ct a1., 1970) leada one to cansider these pheno- Graben began during the Oligocene. togethcr telJite imnges III le mterlOr af the Rlft. Sn- o auJo coast (e é nearby islands (Sã S b' anan Ia) and meno. related to the taphrogenesis with whtch t.he with the sirnultaneous deformation of t.he Japl this fault f:'O,~~em to indicnte lhe extension af o e astJão MontA d .. . Buzio., Vitória). Thls sub- h ' o e Tngo, )\.,(. _ the Gunnab'l.ra Bay to th , sepRratlon or the contlncnts was lnltlated. At surface and its upwarping nt the edgc!'l of the on o de SJt.o João. 'rhe f' e to the reglon next to th f P ase V/as not Iimited lhe westcrn border of the original rlft, a system depression. The formatíon of the Gtmnabnra tinues to th '. ault probably con- ! . e c0ntll1cntnl ~helf on the S:- T ~he Santos Ba.sin, but :at~ult .flexures bordering I of (oulta and tlexures exlsled, or whlch lhe Rift as well as the movement of impl")f't:wt fault FllUlt which .Petrnbnh; .' . ao OJn6 mtensely in the . er lt WIlS manlfested I , Santos fn\llt would becomc a part. To .lhe east biocks In the Serra do Mar, In an nn'n.. tnday C •. lc('hllJCIaIlS (Asmus 19-0. fnulted on th reglOn similarly f1exured nnd alllpn!-! f·t 11., 1!)7'I' P , (..•• of the rlft bordar, the SR.lltos BaRin was down- cavered by the continental shelf, prohnhly tonk , , onte :md Asmus, 1976) raná Basin ine northeastern border of the Pa- the States or Minal'3 Gerais nnd fa\llted, havlng basalt.tc lavas of Lower Creta- place nt lhe same time. This tectonic n.divitv .411. Arlltl. õr(lJ;. (';(1",." ceou!>nge, pnssibly lntercalnted with continentn.l which. seems to hnve eoincided with :"tn IIl1lple (l!Jifil. 4,~. (SlIpl!'l11('nt.o) Ali. Acori. brr'8, Ci~"c., (1976). 411. ISuplt"'TI1l'ut,») 24 FERNANDO F. M. DE ALMEIDA THE SYSTEM OF CONTINENTAL RIFTS BORDERING THE SANTOS BABIN, BRAZlJJ 25 regresaíon of tne sea, already documenled in . 2 - TIle alkallne magmatlsm occurred dur- the Esplrito Smto Baeln (Asmus, 1972), IR POS- ring the ttrst part of that rnovement, Indícattng REFERENCES terIor to any k.rrown volcanlsm in the regIon. 'I'hls acttvíty should be reflected ln the Santos a genetic connotatlon between the two pheno- mena. However, the rJfting or the continental ALMEIDA F F. :M. de - 1965 - As camadea de pos J M - 19528. - Xtsto betumtuoeo. Cnns. Bastn, po8sib~ to bc reune in the layer of 'SãO P~ulo' e fi tectêníca da. Serra. da Cantare Ira CA~ae. 'Petr61e·o. Relatório 1951, pp. 221·233. Rio de block developed after the Eocene when the mag- seismic velocity 2.4 km/sec., (seeBaccar, 1970. Soe. Bras. Oeotoata. BoI. n. 4, v. 2. pp. 23-40. São .Jenetro. matlc activity ín .the area had ceased. Fig. 5), whhh directly covers the crystatlíne Paulo. CAMPOS, C. W. M., PONTE. F. C. and MI1JRA. K. basement of the continental shelf. Le Pichon ALMEIDA, F. r. M. de - 1964 - Fundamentos ge~~~. - 1974 - Geology of lhe Brazlllan conttnentat 3 - The system of rltts developed In fi margln. 111. Burk, C. A. and Drnke, C, L., ~~~t~~~: nlld Hnyes (!!)71) 3 tfrtbuted another occaston gtcoe do relevo paullata. Inst. Geog. Geol6g , region where an intense taultlng took place BoI. n. 41, PI>. 169·263. São Paul!). The Geology of Continental Marglns. PP. • . of rmportant va r-rnnon ín lhe procese or the durlng- the Cambro-Ordovlcian, together wíth the Sprtnger-Verlag, Berlln. Atlantic sprelding to lhe Middle Tertlary. ALl\lEIDA, F. F. M. de - 1969 - Structure anel reacUvatJon or major transcurrent faults appro- dvnnmtcs or the Brazlllan ccastet area. Intern. CORDANI, U. o., COIMBRA, A. M., BOTTURA. J. A. and RODRI(:,U'ES, E. L. M, - 1974 - Oeotoma A thlrd tcc tontc pufaatlon affected the xirnateJy paraJ1eJ1ng the northwestem border of úPper Mantle Svmpoeta, n. 22·B, v. II, ~P. 2'9·38. xrextcc d~ reglAo de Crueeíro e Cachoeira Paullstll e I:IU!\ Serra do Mar s yss t.em, probably during Pliocene. the Santos Basín and the nelghborlng coast. ímportâncte na. JnterpretaçAo dn. evolução tcctõníce lhe se me Urre in whlch the São P<\ulo Basin Some ot these rautts represent ancient deep ue do Vale do Parnlba. CEPEGE, Unlv, SãO, Paulo. ALMacEtjIDvaA.tton P'. aFr . tMhe. deSou-th 19A7me2 -rJca'rn'ectPolnoatt-ormamgmaanj r~o"'-Iogla, Ciência e Técnica, n, 6•. PP. 9-,10. SI\c.. orlginated and wa.s fllled witb sedlments. Sfmul- Uneaments of Precambrian age. asscctet.ed mtnerettzatton. XXIV tntern. Oect. õong., ,Paulo. Pré- taneousry, thcsubsidence or the Taubaté and Re- Sect. 3, pp, 339·346. Montreal. COUTINliO, '$. :M, V. _ 1972 _ Petrolcgte do sende Baslna )ecame accentuated. These basíns 4 - The layers of the Santo. Baaín do not reveal folds other than those due to halokinesls ALMEIDA F. F. M. de, AMARAL, G., CORDANI, CambrJano em 810 Paulo e erredoree. IlIst. ~.~~~ were atso flI'ed wtth clastíe continental sedí- U. G. 'nnd KAWASHITA, K. - 1973 - The Pre· etêncíee, Uni". Silo Paulo, BoI. n. s, pp. ments, This process was accompnnied by an ar local movernents next to the faults, maklng it cnmbrten evctutlcn of the South Amerlcan cratonlc 810 Paulo. accentuation)f the relief of the netghbonng improbable that compression stresses caused the margln aoutb of lhe Amuon Rlvcr. 'n Nalrn, E, M. como, C. de P, _ 19ti3 _ A bacll\ catcárta de IInd Slhell, F, G., Editor8: 'lhe Ocean Bnetna and ltaboraf e & tectênícà da costa eudeate do Brasil. mountains am l'ifts whlch at that time assumed elevation or the continental block with tts con- Mnrgln8, v. I, pp. <441-0148.Plenum Pub. Co .. Ncw Dlv, Geol. K1ner., Not. Pret. E!tudo.l!l, n. 75, p. eequent division ínto rlfts. theil' modern Ispect~. Presumably, it was at that York. . 12, Rio de Janeiro, time thnt the em an, conttnentsl unfosstliferous. The causes of the Jarge opposíte vertical ALMEIDA P". F. 14. de. liA SUl. Y. end CAJtN'Er'llO, DU~O •. m./O. _ 1966 _ E!tudo prcuuünar rlas snud-cln y depH'lits nccur-red, represented by the C D •R - 1976 - O lineamento de Âl~m PIl' roch~ bUlcae.e uttrabblcB.ll dll reglAo de Ubatuba. movements between the Santos Basín and the tntba. A~R4. Bralll. Ci~n,. Anais, v. 48 (tn p'r~•• ). J:ttado de SIô Paulo, Acad. Brss. Cíõnc .. Anais, Alexandra (farnná.) and Pariquera-Açú (São nelghboring continental area are dlfflcult to AMARAL, O.. COltDA.NI. U. O.• KAWASJU~A) ,Jt. ir"<~;~<~,"pp293.;804. Rio de Janeiro. Paulo) FOrnlltions, together with those that explaín, posslbly having been a consequence of end RI!lYNOLD8,J. K. - 1961 - P.to •• lum-'A...... ISl~ó: À...~na''HARALYI, N. L. I!l. _ 1973 _ Le- exist a round :he Guanabara Bay. The Pltocene movements ín the upper mantle. However, the dR.tl\ of baaalUo roclc.lJ rrom lIOutherD Brutl, tuaentoa ,éotfeleo. no vale do Peratbn. XXVII was a time cf genen:\lized epeirogenic elevation exiatlng difference in leveI between the elevated õecehem. COllmochem. Aetll. ,. 81. n, '.:, pp. \t ~et 'Btú, de ~Iogla, Anal1J ün pteea) . ArncaJa. of the entírr central anel eastern regfon of continental border and the floor of the Basin JI7-142. .. IIWtNG, J',;LJI!l'I)I!lN, ·R.• nd ElWING, M. _ 1969 _ ASMUS. H. E. - 1972 - Esplrlto Santo - A· patttn'l_ :' " !tetn.cUOIt, _,6ootlnl' wtth expendeble eonobuova. Brazil, whicll resulted in a.n intense erosive could have been a Cause of the late rlfting of or the eaeteee BruUlan maralnal b •• ln.~ ,..:.:r ~r. A.I8Óc. ~elr. Oeol., Buli., ", 63. pp, 174-181. process and çonsequent sedimentation in the the continental block. Peper nresenteâ at the 57th Amer. A•• oe. ~etroL~:~. M~âoV; n; A. _ 1969 _ Rlfts of the Bnlkal CORsta) regiOls, represented by the Barreiras Geal., Annunl Meetlng. Denver, U.S.A •. (Not. . ~ ~tatn. ,..ton. TectonophyslCl. v. 8, pp. 433-466. Group. The latter may be tentatively reJated IlIIes in 1970 suggested a proces. of gra- PubU.hed). ~GU'A.NI, A• .,,4 PANNUTI. E. L. _ 1966 _ to the more recent layers of the continental vltational sliding towards the continental margin BACCAR. M. A. - 1970 - Evldênctu gcon.léu no "tuao. htdro16clcoa na bacia de Taubaté entre 1n order to expIaln the origin of some of the ~helf with sdsrnic ví'locitics of 1.85 km/sec., Jl8c:.ote sedlmentar no PIate.au de 810 Paulo. XXIV . Jacarel .e' Qutrlrtm. lnst. Géoit. Geológico, BoI. Cong. BrAS. Geologia, Anah, pp. 201·210. Brullla., .. whosc deposifion !'StllJ proceeds. A low seismlc large. neighboring, continental grabens, Such ao ,'.u, .2, 1. pp. 810 Paulo, arlivity of Ue tectonlc system of the Serra do explnnatlon would best flt the example of the BEDERKE. E, - 1965 - Tha dentopment ot Eu1"Opean . S b o. origem da Serra do .Mar rift system rather than the others rlrt". 1" ThB World Rlft 8y.etem, Geol. SUM. Ca· l'JtIU'TAB., R., O. de - 1001 ; I o ~:o~raf1n. n. 20, Mar seems b indicnte thet lt ls not cntirely nadA, paper 66~14.PP. 213·219.Ottawa. bacia d. 810 Paulo. &1. au, inaC'tive. he cites, not only because of the great proxlmity pp. eo-u. &ao Paulo, BIGARELLA, J. J.• nd ANDRJ.D!J, G. O. - lIea, - 14 li sobre af the Santos Bastn, but also because af the Cont"lbullon ro lhe .tudy of the Drul1lm.·Qúa... J'RlÚTA8, J\. '0', 4e _ 19156 Con!l eraç e.s •• ORWI)I" O," THI~ JUFT SYSTF:~t great differcnce in level established in the region. ~ D teotônlca e reolorl8. do Vale do Parnlba. J::,ng. temary. lu \Vr1ght. H. E., Jr. and .Frey, ", a. Jil{ner. MeUlutTIa, v. XXIV, n. 143. pp. 276-283. The cambro·ordovlcian faulta could have tn some Editor": Internlltlon81 Studles of the Quat.4rnllry. Rio de Janeiro. Geol. Soe. Amerlea, Spee. Paper 84. PP. ~S3-41S1. The avalable knowJedge 00 the Santos way facllltated the process, whlch would also Basin and tte Sermo do Mar rlfl"i is evldently explain the tlJtlng of the faulted blocks towards BIGARELLA, J. J., :MOUSINHO. M. R. an d DA GUIMARAESlInu. ln., t. D,Tee-noJ.194I7nd-uel.OrlBleomi, n.da6s. ,r~ChJ,~. :.~~~~ insu(ficient fa-the prcsentatbnof a sOtisfactory the interior of the contInent. SILVA. J. X. -l9Ma-Proceaee.nd ent'lronment" Horizonte. o( the Br9Zlllo.n QU8lern8ry. Curltlba, Brun, Unh', genetic mOdl1 expIainlng the!r origin. Any IUBU!, Y., CARNEIRO, C. D. R. .nd COIMBRA. hypothesis, h)wever, should take the following ACKNOWLEDGF:ME~~S Prr..ss, p. 71. A, M, _ 19715 _ The Ribeira toldc I belt. Rev. BOWl!:N, R. L. - 1966 - The p:aran' B18111 rleo4 BTR8. Geoeien., v. 6, n. 4, (ln {lre8!). fl1cts lnto eOT.sideration: laV88 Bnd thelr struetural r~l.ttonl wlth the Ponta d The n.uthor thanks the Instituto de PeB~ GrossR arch Intern. Fleld lnat OUldebook, Brll,zll, ILLtES 1. H. _ 1970 _ Graben tectanlcs as rei ale 1 - TJ1C systcln of rifts developed late on guisas EspecIais, the ceasion of MSS images of rp, X/l - X/IS, W8l1hlngtoll. to ~rulJt..mantle Interaetlon. f1t, IllIes, J. G. nnd Ule rising ba-der of the continent, adjacent to Muner, 8L, Editora: Graben Problcmll. Interno the ERTS-l satcUite, the Professors Y. Hasul BUTLER. L. w. - 1970 - Sballo .•••• truclure ot the Upper M.e.nt1e Project, SclenUtlc Report n, 21, a basjn subsding since the .Aptinn time. The continental ma.rrln, .authern Br9.zl1 sne! Urul\JflY. pp .•• 27. Bch'Welzerbart'sche VerlagsbuchhA.ndlung. nppos,ite verlc;al rnovcmcnt reached a minlmum and G. R. Sadowski for provlding sugge.stlons Geo!. Soc. Amerlca, Bull. v. 81, PP. 1079·1096. 8tuttgart. or 11 km in L distnnce of 200km, for the improvement of the manuscrfpt and Marta Morria for her ald in 1t8 t1'anslatlon. CAMPOS, J. M. ~ 1963 - A jazIda plrobetumln084 KOLLl'!lRT R and DAVINO, A. _ 1963 _ Levanln. do "Ale do Perfllba. Blng. Mlner, Metalurgia.. V. mento ~ra~lmêtrlco na. cidade de Slo P!;lulo. Eng. XVI, n. 90, PP. H7-421. Rio de .rlUlelro. Ali. Aend. bn.'l. (Snplcmento) Ao ••• Aoc4. bnII. 0'4"0 .., (976), 48. (Suplemento) ~ 2G FERNANDO F·. ar. DE: ALME1DA t I l\llncr. MelaIUl·gia. v. XXXVIII. n, 224. p;l. 79-82. MEZZALIRA, S. aud COUTO, C. de P. - 19i1 - NO'.a Rio de jnnr+ro, ccncettuacêo geccrunolôglca de 'r'remem bé. Estado ! de Silo Paulo, Brnall. Bímp. Bras. de Pnteontotogfu. J081\ f LEINZ, V. - 1!l:18- O~ enleá rios de São Nítcrõt. Acad. Bros. Ctên.. Anais, L 4.:1(Su!)lcmento), PI). Eatndo do Rio. MineI'. Metnlurgla, v. n, n. 15. pp. 4.73-488. Rio de Janeiro. 153-15ã. Hlo de Janeiro. l\flNIOLI. B, - 191:l - Aspectos lttotõgtcos da rcgll\o LI!; PICHON, X. 1\ntl HAYES. D. E. - 1971 - "1\'(01'- ntcrênea Ptcavra-Barre velha. Santa Catnrtue. Iust, I t g;nnl oHset1!. rrncture eonee euõ the eartv openlng de Oeocíênctea. Untv. São Paulo .. (Thesls, not pu- of tlte South AUrmtlc. JOUI". Geophya. Rna., v. 76. bllshe I'. 1G8. pJ). l047-l057. pubüehed). I\Jr:CONNEr .•L. R. B. - Hl69 - Fundamental Inu lt RUELLAN. F. - 1944 - Evolução geomorfolõgtca de zoucs fn lhe Ouíann nud West Ah'iC8n Shlelds In bata da Guannbara e regtõee vizinhas. Rev. Bras. rr-lntlon to rn-oaumeü lixes or Atlanllc spreudíng . de Geografia, Ano VI. n. 4. PP. 4045-509. Rio de Gcol. Soe. Amert-a. Buli" V. 80, PP. 1775-1782. Jenelro. l\IrCONNELL, R. 13. - 1974.- Bvotutton or taphrogentc SADOWSKI, G. R. - 1974 - TectOnlca. da. Serra do üucnments In continental ptatrorme. Geol. Rund- Cubatâo, Slo Paulo. Inst. Geoc\ênclas, Untv. SAo scbeu, 13. 6:\. H. 2. S. :189-4.:10. Paulo. (Thesls, not pubtlehedj . .MELCHER, G. C .. GOMES. C. B. CORDANI. U. G.. SUGUIO, K. - 1968 - Contrtbutção à geologia da bacia RETTENCOURT. J .S"OAMASCENO. E. C.. GI- de Taubaté. Fac. Fllos. Ciên. Letras. Unlv. SAo RAROT. v. A. V. .nnd MELFI. A.. J. - 1973 - Paulo. (Thesls, not publíshed). Geologia e petrotogta das rochas metnmõrücaa e J::"Tnnltlcaa nasocíudns do vale do rio Ribeira. de WASHBURNE, C. W. - 1930 - Petroleum geology ht\IOPC, SAo Paulo e Pnrané. Rer. Bras. Geoclêu .. or the Btate o! SAo Paulo, Brazll. Com. Geog. v. :t. n. 2. pp. 97-12:J. Geol. São Paulo, BoI. n, 22, P. 282. .1", Aoad. lJ)·(l~. C/I111C., (976), 48, (Suplomento)