. Boletim IG, Instituto de Geociências, USP, V. 4 : 1 -- 20-1973

STRATlGRAPHY OF THE IGUAPE-CANANÉIA LAGOONAL REGION SEDIMENTARY DEPOSITS, STATE, °I PART I: FIELO OBSERVATlONS ANO GRAIN SIZE

BV

Kenitiro Suguio and Setembrino Petri

Departamento de Paleontologia e Eszratigrafia

RESUMO SUMMARY

No presente trabalho discutimos a história The possible geological history of the quater­ geológica dos eventos quaternários na planície nary events in the coastal plain of the Southern litorânea do Sul do Estado de São Paulo, na São Paulo State, in the area known as 19uape­ área conhecida como região lagunar Iguape-Cana­ C3!lanéia lagoonal region, is here presented. néia, tomando por base observações de campo e Field observations and sedimentological ana­ estudos de granulometria dos sedimentos, tanto Iysis made by the A., geophysical data and exami­ de amostras coletadas pelos A., bem como das nation of the samples from two stratigraphical obtidas de dois poços profundos perfurados pelo wells drilled by I.G.G. and the informations Instituto Geográfico e Geológico do Estado de from shallow research holes made by Geobrás São Paulo (I.G.G.) e de perfurações rasas executa­ SI A, Engineering and Foundations, made possi­ das pela Geobrás SI A, Engenharia e Fundações. ble the accomplishment of th~s work . . Os resultados de análises granulométricas per­ Grain size characteris1ics of the seodiments from mitiram confirmar nos ambientes atuais e reco­ the present environments were also compared .nhecer nos ambientes pretérit~ de sedimentação, with the grain size characteristics of the sediments os seus mecanismos de posicionais. fcom the ancient enviconments, allowing the As ãreias regressivas, tipo "blanket sands" ou . recognition of the depositional mechanisms of "sheet sands" (KRU.MBEIN e SLOSS. 1963, the ancient sediments. p. 550), já reconhecidas por autores prévios c~mo The regressive deposits, "blanket sands" or depósitos praias, embora sem uma caracterização "sheet sands" type (KRUMBEIN and SLOSS, muito clara, são aqui definidas de modo porme­ 1963, p. 550), already recognized as old beach norizado. Tais areias têm importância preponde­ rante na geologia regional da planície litorânea, sands by previous authors, never was clearly não só porque ocupam grandes extensões super­ characterized. Here they are descrihed, in detail. ficiais desta planície, mas também porque, como due to their great importance in the coastal plain consequência da sua persistência, constituem-se regional geology, not only because of their great em importante fonte fornecedora de detritos persistence, but also, as a consequence, because para os subambientes atuais. Para essa unidade they were the most important source of detrital litológica propõe-se a denominação Formação materials to the present sub-environments. To Cananéia. this Iithological unity is proposed the denomina­ As sequências transgressivas e regressivas, soto­ tion Cananéia Formation. postas à Formação Cananéia, somente puderam The recognition of the transgressive and re­ ser reconhecidas e estudadas graças às sondagens gressive sequences was possible only through the do l.G.G. studies of the I.G .G. stratigraphical wells.

-1- INTRODl'CTION . channel know/l· as Valo Grande was open to navigation in 1832. The waters of the Ribeira · The lagounal region known as 19uape-Cananéia then had a shortcut to the ocean, lncreásing is a strlp uI" land situated between the mouth · therefore their energy fo'r erosion of the banks of the Ribeira de 19uape River and the Ararapira and filling up of certain 'parts of the channel. outlet, just at the horder of the States of As a result the Valo Grande is menacing the São Paulo Ulld Paraná. Four great islands stretch town since then , mainly during floods. Only one along a hundred kilometers from northeast to . year after the channel was finished, this threat southwest, being called Iguape, Comprida, Cana­ was reported in written documents. néia and Cardoso (See figure 1). The lower Ribeira, incJuding great part of the The old Ribeira River and the Valo Grande are Old Ribeira (after the Valo Grande) winds in a two water passageways between the 19uape lsland broad valley with many oxbow lakes, subjected and the continent. The Iguape or Pequeno "sea" is a sound between Iguape and Comprida Islands to floods by the lides resulting in marshes and at the northeast tip and Comprida lsland and swamps. According to Geobrás report (1965, the continent southwestward. The Cubatão or v. I, p. 132) the meanders are stabilized within de Dentro "sea" is another sound between the last sixty years and the river, near and up Cananéia Island and the continent. The Cananéia Tres Barras, is very wider now as can be seen or the Fora "sea" is a sound between the Cana­ looking at the dry meanders showed in aerial néia and Comprida Islands. The inadequately ' photos. The fixation of the meanders and the called "bay of Trapandé" is a body of water increase in the w1dth could be caused by the between the Cananéia and Cardoso Islands. tides which acquired greater importance after Iguape Island is an artificial one. It was bom the excavation of Valo Grande. after tlle constniction of the Valo Grande Chan­ The 19uape Island has a sinuous outline. nel, built through division of part of the Ribeira Severa! mountains are scattered on 'the coastal de Iguape River, south from the Iguape Island. plain. The main ones are Morro da Paixão, the The Old Ribeira (Ribeira Velho) channel however nearest from the town, Morro dos Engenhos, the keeps on draining part of the Ribeira water highest (500 m above sea leveI), Morro do Pinhei­ nurth from the 19uape lsland. This river was an ro, Morro do Icapara, etc. Precambrian gneisses, important one to the earlier explorers as a natu­ schists and micaschists are the rocks of these ral way to get to the inland. In its way to the mountains. sea it runs eastward coming as near as 4 km The Comprida Island is long and narrow (70 from the Iguape town, then it bends northward km long while the maximum width is 5 km). tracing a bow figure before entering the ocean; A hill of alka!ine rocks (42 m high). Morrete, 20 km from the town ofIguape. The old Ribeira near the southwestern tip, looking to Cananéia harbor less than 3 km from the town of Iguape; "se a ", is the only elevation of the island. Except is located at a small Iake connected to the main for this hill , the greatest elevations in the whole . course of the Ribeira. The towers of the church island is only seven meters above sea leveI. The of 19uape could be seen from the boats so near southwestern half of the margin of the Compri­ they carne but th'ey had to keep on travelling da Island at the Pequeno "sea" side, is rather for still many hours, navigating more than 53 km, craggy, two to four meters high, up to Pedra facingthe swells of the ocean before reaching Balisa or do Tombo (The Pedra Balisa is a rocky the Iguape harbor. It was easier to ernload the knob within the Pequeno "sea", made up of bóats at the Ribeira harbor so the cargoes could alkaline rocks). The northeastern half is made up reach the town on the backs of "burros" of shoals and marshes. Several bands of dunes are (donkeys). The idea of an artificial channel developed in Compriçla Island, some 7 meters allowing the boats to reach directly the 19uape high, mainly at the ocean side. harbor had then .many defenders. The land between The Morro do São João, made up of alkaline the Ribeira harbor and the lown of 19uape is rocks (according to FREITAS, 1947) and 120 flat which, would facilitate the excavation of m high (KUTNER, 1962, p. 43), located at the the channel. After several years of work, the Cananéia Island, opposite to Comprida Island

- 2 - Morrete, is the only conspicuous elevations of At the meeting points, erosion prevails causing the {'ananéia Island. A submerged rocky knoh the formation ofbays (Subaúma and lririaia-Açu). known as "Lage do Argolão" seems to be a The winds are variable according to the hour !iaison between Morro do São João and Morrete. of the day and the season of the year. The Three nordmarkite samples from Morro do São prevailing winds however co'me from the south João were dated by K - A method resulting R2 perpendicular or athwart the shore (Geobrás million years as an average age (AMARAL et report, 1965, fig o I-IV-d-O1 and l-IV.d·02). ai., 1967). According to K UTNER (1962, p.54) the The mountainous Cardoso Island, south of region is not truly lagoonal since theTe is no Comprida Island , is constituted mainly of Precam­ gradation between marine and fluvial environ­ brian rocks. ments. The marine influence is more pronounced The salinities of the waters of this lagoonal in front of the outlets to the ocean and the region are highly variable, related to tides and fluvial influence is more strikingly noted in fresh water run-off. The whole Pequeno "sea", in front of the mouthes of the rivers. general, has a low salinity reaching a minimum This pape r was possible thanks to financiai . between the mouth of Valo Grande and the ou­ support f Tom the "Serviço do tlet of Icapara (See figure 1). The influence of ( *) of the " Departamento de Águas e Energia the Ribeira is less sensible between Pedra Balisa Elétrica" of the State oI' São Paulo through a and Cananéia. The lowermost salinity observed covenant with the University of São Paulo. We in this section was 200 /00. are deeply acknowledged to the "Instituto Geo­ The advancing tide in the Pequeno "sea" is gráfico e Geológico" of the State of São Paulo toward the northeast at the southwest extremety for the data from two drillings and for the per- . tip and toward southwest at the northeast extre­ mission to study their cores. We acknowledge also mity. The two currentes meet around Pedra Bali- the "Instituto Oceanográfico" of the University 5a and the mouth of the Subaúma River. The of São Paulo for the facilities granted during our mechanism of tide propagation was outlined field works from its oceanographical base at by MINIUSSI (1959). The advancing tide rea­ Cananéia. We want also to' express gratitude to ching Trapandé Bay is subdivided into two the following persons whose solicitudes, in a way currents, Ollt' of them running through Itapitan­ or another made our researches possible: Eng. gui and Cubatão "seas" and the other one run­ Schaia Akkerman and Prof. Fernando A. A. ning Úuough Cananéia "sea" toward the northe­ Mourão from S. V. R.; Eng. Jesuíno Felicíssimo ast tip of Cananéia Island; both currents meet Júnior and Geologists Sérgio Mezzalira and Carlos in the Cubatão "sea" near the mouth of the Torres from I.G.G.; Dra. Martha Vannucci, Dr. lririaia-Açu River. In a second phase of advancing . Vitor Sadowsky and Dra. Miryam B. Kutner from tide both currents meet at the northeastem tip the "Instituto Oceanográfico". And at last but , of the Cananéia lsland and keep on running not the least we want to thank Dr . Paulo M. B. toward the northeast to meet the southwestward Landim' for his help during the application of current around Subaúma, as mentioned before. SAHU's method.

(*). This Service (S .V.R.I was recently extinct and a new institution named "Superintendência de Desenvolvi· mento do Litoral Paulista (SUDELPA)" was organized to take its roles.

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. REGIONAL GEOLOGY FREIT AS (I947) studied the petrography GENERALlTIES of the alkaline rocks from Cananéia. SILVEIRA There are numerous geological papers publi­ (1952) published a regiorÍiu geomorphological shed on this region but they are either strictly study. BIGARELLA (I946) dealed with pro­ local or specific 50 many questions still persist blems of late cenozoic sedimentation. KUTNER about the local geology. principaUy related to (1962) studied some aspects of the Recent sedi­ the coastal plain and environs. mentation around the Cananéia lsland.

-4- The rainy c1imãte (average greater than 2.000 The principal kinds of recent sedimentary mm/year) is responsible for a heavy forest whi.;h · deposits in the coastal plain are: a1lied to a steep topography and lack of roads prevent the development of a systematic geolo­ 8eaches giClll survey mainly in the mountainous area. It was only in 1964 through a Brasconsult report The southern beaches of the State of São Pau­ lo are almost continuous interrupted only by and in 1965 through a voluminous report from a few foothills of some rocky bodies. The beach ' . Geobrás S/ A, both companies on contract with of the Comprida lsland, for ÍDstance, is almost Serviço do Vale do Ribeira, that more substantial 70 km long. Other long southern beaches, outside informations on a regional basis were possible the present area are: Praia Grande, 44 km long; which will be valuable for a regional planification Peruíbe, 25 km long; Una, 20 km long, etc. directed to the development of the region. The The sands of these beaches are fine-grained, first of the above mentioned reports brings a homogeneous and therefore make smooth slopes geological map plotted mainly through photo­ toward the ocean o Onty at occasional sites the interpretation. According to this map the base­ waves are violent and so the sands become coarser, ment around the 19uape-Cananéia lagoonal com­ for instance, at the southeastern tip of the plex are metamorphic ones belonging to the Comprida Island ( Beach). Precambrian Açungui Group: phyllites and micas­ chists, migmat ites and gneisses intruded by grani­ tes, adamellites and granodiorites. The a1kaline 8each ridges intrusions cut this complex. The Ribeira de Igua­ The Comprida lsland was born through lateral pe, the main river of the region, goes through accretions of old beach ridges so the ages of other kinds of rocks of the Açungui Group them become younger as one goes toward the (quartzites, amphibolites, diabases, Iimestones and present beach. The oldest ones could be 2.000 caIcoschists) before reaching the lagoonal region. to . 3.000 years old according to Geobrás report The Geobrás report dealed with a more lirnited (1965, V. I , p. 185). The different phases of the area which coincides with the one we studied. growth of the Comprida Island can be observed The first integrated out look of the lagoonal on aerial photos, by the scars of the old beach region carne from this reporto Severa I events ridges. Such. scars are described in the Geobrás which propitiated the present conditions were report and were also studied by PETRI and discussed, based on geomorJ'hological observa­ SUGUIO (1971a). tions. We believe our pape r is complementary of The aerial photos show that the beach ridges this and other reports, bringing informations curve near the mouth of the Ribeira, in the about a11 the sedimentary sequence and about Iguape Island. We can assume from this observa­ the geological events responsible for this sequen­ tion that the 19uape was originally an island ce . We hope our researches bringing new observa­ within the old Quaternary sea (photo 4353 from tions on events older than previous studied ones, "Levantamentos Aerofotogramétricos Cruzeiro will be of value for a better understanding of the do Sul S/A" - 1962). dynamics of the geological agents responsible The photos 5561 and 4804 (of the same set) for the present 19uape-Cananéia lagoonal complex. show the bending of the beach ridges around one of the inland extremities of the Juréia THE COASTAL PLAIN Mountains (between the mouth of the Ribeira and Peruíbe, toward the northeast). The old The coastal plain is narrow in the northern beach ridges are preserved in this area because the­ littoral of the State of São Paulo but in the re is no important rivers which could erode southern littoral it has a greater geographical them. The behavior of the Una de Aldeia River importance, acquiring in certain places a width as (which goes to the Ribeira River, above the great as 80 km (Brasconsult, .1964). lt is broken Papagaios Island) is very peculiar. Its headwaters however by some high ranges such as the Bananal are located about 20 km NE from the Juréia and ltatins. which approach the sea. headlands. 8elow this place, the Una Beach

-5- hegins and between this beach and Und de Aldeia at its narrower width, about 500 meters, the River, a monotonous beach ridges plain is deve- dunes occupy alI the width from the ocean to the . loped which ould be the easiest way for the Una Pequeno "sea" . de Aldeia River to meet the oceano This river, however, goes southwestward, parallel to the Regressive sands shore, and only gradually it bends toward the south flowing into the Ribeira River. It goes A blanket or sheet sand (KRUMBEIN and from the ,coastal plain into a crystaline basement SLOSS, 1963, p, 550) make up most of the area when it would be easier to winds on the coastal plain from the studied are a northward coastal plain. Furthermore the airphotos show an up to Peruíbe area and southward qown to the erosion of the old beach ridges by the Ribeira de State of Paraná. According to these authors, Iguape River near its mouth which could be this kind of deposition was possible on an area . taken as an evidence of the idea that the Ribeira undergoing very slow subsidence and fed by River once had its course ()n the now Valo Gran­ detritus enollgh to cause regression of the sea, de and later eroded the beach ridges in its new so the material would be located at a levei sli­ way to the sea. The airphotos suggest that the ghtly below base leveI. The strandline deposits are Una de Aldeia River Was once developed as a spread as a near by continuous succession of coastal river parallel to the shore, a very common parallel beaches. type of river io Brazilian coastal plains. The total area of the regressive blanket sand This ancestral river later · would have been preserved in the 19uape-Cananéia lagoonal region, captured by a tributary of the Ribeira de Iguape considering also the ocurrences beyond the River limits of the studied area, would be approxima tely 900 km2 as shown by SILVElRA's map (1952, p. 125). The average thickness of t1:lls Comprida Island Dunes ; j ..J • blanket sand as shown by the logs of the,wells l'he constant winds at the ocean side of the drilled by Geoorás anel I.G.G. was estimated as Comprida Island have reworked the beach sands 30 'meters, Applying the concept óf persisten~e and transported them inland resulting in four factorP,defined by McGUGAN (l9q5, p. 126) to aligned dune ridges, some up '10 7 m high, our blanket sand we carne , to' 90 x 106 (P = • ..; .: !

-6- basin, forming isolated elevations in the middle of described at other localities including cross-beds, . extensive coastal plain lowland, being selected . irregular beds, slumping structures, etc. Ali these places for banan plantations (See foto 4). Acoor­ . sedimentary ·structures are more clearly seen ding to BIGARELLA et al. (I 965 , umpublished when the heavy mineraIs concentrate along certain work), in the inland parts of the littoral plain, layers. in the continent, the altitudes of the "piçarras", We shall describe bellow the observed struc­ cliffs increase to values as great as 9,90 m. We tures of the "piçarra" in the 19uape-Cananéia propose to call this unity· of regressive sands, region . Cananéia Formation. We think the extensive sands which make up , Horizontal, paral/el stratification - This strati­ fication is the most common type observed in part of the coastal plains and alóng beaches of th'e outcrops. The structure is not clear on the southern l~ttoral of the State of São Paulo, fresh surfaces due to the extreme sorting of the at least from Itanhaem down to the south are the grains; it is better seen on weathered surfaces or results of reworking of these regressive sands, on rain or wave washed surfaces. The stratifica­ inasmuch as they have same textural characteris­ tion is incipient or well developed; in the fust tics . According to FULF ARO (I 971, verbal case the thicknesses of the layers are centimetric information) these characteristics were observed and in the second case there may be .rytlunic also in the samples from beaches of Bertioga laminations, contributing for the clearness of (northern part of Santos city). The sands of du­ the structures the concentrations of heavy mine­ nes and of the bottons of the bodies of water of raIs along the laminae. This stratification is very the Iguape-Cananéia lagoonal region are reworked similar to the one observed in the sands of the regressive sands as welJ. Furthermore, in the present beaches resulting from the reworking middle of dunes at the sides of the Cubatão - of the " piçarras" presenting also heavy minerals Pedro Taques road far to the northeast (near concentrations. It must be stressed that the Santos), there are banks made up of sands very horizontal parallel stratifications have a great similar to the Cananéia "piçarras". lateral persistence with only scattered little dis­ We selected an outcrop located 2.5 km from continuities or sunk parts shaped as V, 3 to 5 mm . ~ananéia, at the left side of the road Cananéia wide along the magnetite laminae. The shape to ferry-boat pier, as standard one for · and the size of these discontinuities are very these sands (see figure. 2) From top to bot­ regular bespeaking against an organogene structu­ tom we observed the foUowing sequence: re as could be made by a burrowing animal. (a) A very white leached portion (b) A brownish­ We didn't find any evidence of organic activity in black portion, with abundant humic acids and _other outcrops of the "piçarra". , a limonitic levei forming a crust 1 to 2 cm thick at the base (c) Horizontal to sub-horizontal Cross-beds - ,We found only small seale cross parallel well stratified beds. (d) Beds with an beds The thicknesses of the whole sets didn't go almost rythmic lamination very clearly stratified. beyond few meters andthe individualsets, few (e) An argillaceous bed, 2 to 3 cm thick. (f) Thick centimeters, and they never were more than 1 beds with an incipient stratification. meter longo The predominant type is the trough cross-beds, the tabular one was seldom observed_ Ali these layers with diffe rent structures have It seems that the trougl1 type resulted from cut a ' typical "piçarra" texture of fine and well and filJing because this type passes in the same sortcd sands, except the argillaceous bed. horizon to horizontal parallel stratification. Some­ lhe first two ,portions resulted from weathe- , times, we have a vertical sequence of cross­ ring agents and leaching from rain waters associa­ beddings (Figures 3 and 4). Incipient structures ted with the humic acids from plants. The are sometimes observed which could be ripple limonite is also a consequence of these ph,0flo­ drift cross laminations (See figure 4). There mena , probably originated from the action of seems to be a direct connection between cross­ the humic acids on magnetite. This outcrop doesn't beddings and the front of growth of old beach show other types of structures observed and ridp:es.

- 7 - Irregular stratifications and slumping structu­ for severaJ meters and reappearing at the sam~ res - There occur irregular stratifications between levei and with the same thickness. These inlerrup­ beds 01' horizontal parallel stratifications few cen­ tions rnight he explained hy an erosive phase timeters thick. These structures also hecome immediatcly after the mud deposit ion and the c\earer when there are layers rich in dark color abrupt interruption a1most perpendicular to the heavy minerais. lhis structure, when better bedd ing plane might bc connected with cracks developcu.looks like ripple drift cross lamination. developed hefúre lhe separat"ion of the hed. Slumping structures were seldom seem; the Limonitic structures - Every sedimentary causes for their scarcity may he the smoRibeira de Iguape river and its tributaries. They . . several points without thinning out; interrupted are developed also in the northeastern half of

I ·P I ':;ARR:''' FEATURES IN THE CANA NElA ISLANO(S.P.l

NEAR FERRY BOAr PIER TO CANANEIA TOWN ~______N o

FIGURE 2

r:-:-'""I L..---.J

1 - L [AC~[D ·PICARRA" IWHITEI 2 • ""IÇARRA' WITH HUMIC ACID AND IASAl LI"ONITE LAYER _ '.-"IÇAIIIIIIIA­ IIlr ... IW'IIIIEN'T srRAf l FICATION PARTIAlLY "\.IMOHITIIEO " . ... - " PiÇARRA" WELL STRATI'IED AND -LI .. O-

"lI1Irll(D" , -" PIÇAAIltA" YEAY W(LL S"RATI'IED • - ClAY lAYER C 2 TO , CM THICKJ. 1 . -"IÇARRA- WlrH ·. ": I PI(N'! STRATI FICATIO .. _

· -8 - ......

~.'~;. ;:~. ·~I~·. ·~~~~: ;~i ~ ·~t~.r i: ~'· ~.·;' ti~·•• s. ~ ~:~'~.:•••~ ~-~/~••. ~. -~.• ~· ~~·:~,~·: ~~·:F~·· ~~· ~~·;::~~:-:i:::: : ~~;: <'j:~ :(.~: :1~:::::~':: D: ~:: TO ~ ~:. ~'::,.

IEOOINI IIII!I~IIII~l!lIlIlIlIlIillI!I!li!!llIl!iI~Z~O~NTAL TO SUl-HORIZONTALIEOOIN, 1 INCI'IENT 'LAT 'ARALLEL ~~~~~~~==~~~~~±+~77~~~~==~l-~S~T~RATIFICATION

~i,-:: ; · L++3S::Y\X\ ··· ·· · · · __····· · INCIPIENT STRATIFICATION :--=: . ..:. ...: ~ . : ~.' . >- :.!. '~~ ~~~ . :.:.'. . -- FIGURE 3 - Crossbedding and paraIlel bedding "Piçarra" of 19uape Island - !capara outlet (scale = knife)

. the Comprida Island at the Pequeno "sea" si de The sands on the channel of the river near its and around Cananéia Island. The mode of a gra­ mouth can be explained by the geological nature nulometricalJy analysed mangrove sample fell of the coastaI plain made up of the regressive withi.n the 0.25 - O. I 25 mm interval as in the sands. The other rivers draining directly toward "piçarras," but with a greater contribution of the lagoons are small, with a 10w decJivity and the coarser and finer materiaIs. do not contribute significant1y to the lagoonal Fluvial Deposits sedimentation, most of them influenced by the The materiaIs brought from the highlands to tides. the Cananéia-Iguape lagoonal region by the rivers Deposits 01' the bottom 01' the lagoonal region do not seem to represent an important fraction. According to Geobrás (1965, v_ I, p. 221), the The sediments here are the resuIt of interaction Ribeira de Iguape River, the most important one of marine and fluvial environments. The bottom in the region, immediately do~n Eldorado Paulis­ sediments were analysed by Geobrás geologists ta works like a vast decantation pool in holding and by us. Their textures are cJearly related to practicaIly alI the material coming from the that of the "piçarra" even though disguised by higher basin. finer argillaceous material.

V IE R Y I" C I ~I E" T H o R I Z O" TA L F L A T STRATI FICAT 10N

CROSS IIEDDI"G

~~~~~~~~~~~~~~~t?~~~~ ~IR~REGULAR BEDDI"G ASSOCIATIED ~ __ WITH RI~~LE DRIFT CItOSS LAMINAIE

CROSS IIEDD! NII

FIGURE 4 - Cross bedding in the "Piçarra" of the comprida Island between Ubatuba-Pedrinhas.

-9- THE GEOPHYSICAL STUDIES According to ELLERT, the lowermost poinl of the basement in Comprida lsland at the ocean Some ideas on the crystaline basement covered side, is located 5.7 km from 'KOLLERT'S .by the sediments were possible thanks to. KOL­ point 3 and not in this point as interpreted by LERT's resistivity surveys and ELLERT's gravi­ this author. The lowermost point we called point metric studies. These surveys were restricted to 13. the northeastern half of the Comprida Island The point 13 would represent the hinge oftwo and the corresponding part of the continent tilted blocks, the SW block dipping NE and the bordering the Pequeno "se a" . NE block dipping SW. It is possible that a fault KOLLERT did two profiles, one along the occurs through this hinge and this fault would beach of the Comprida lsland (at the oceanic cross the Pequeno "sea" fault and would conti­ side) and the other on the continent, along the nue. through the valleys of Cordeiro River, road 19uape-Subaúma (See figure I). · flowing toward Pequeno "sea" and Pariquera­ Along the beach the basement would descend Mirim River, flowing toward Ribeira de 19uape gradually southwestward down to 2 km SW from River. These two valleys are remarkably aligned the place of l.G.G. well n.o 2 (KOLLERT's in spite -of the flowing at opposite directions. point n.03) and then would ascend gradually but Southwestward from this tectonic line Cordeiro always keeping alower leveI in relation to the continent proftle. The basement must keep on - Pariquera-Mirim, the Pequeno "sea" fault would disappear. ascending southwestward, because near the sou­ thwestern tip of the Comprida Island, alkaline Another possibility would be an erosion valley, rocks crop out (Morrete, as referred above) . . without faulting, 'crossing the Pequeno "sea" KOLLERT supposed that a fault occurred betwe­ fault In this case the! Cordeiro - Pariquera-Mirim en Comprida Island and the continent explaining tine would not be tectonic. in this way the difference of the leveis of the The uplift of the continent block and the basement. However, this difference could be sinking of the Comprida lsland block would pro­ explained as well simply by regional dip of the pitiate the development ofcoarse sedimentation, rather thick at the valley depression as found at basement toward the oceano The altitude of the l.G.G. well n.o 2. The conglomeratic sediments basement at l.G.G. well n.o . I is minus 45 would pass laterally to fmer deposits. meters and the supposed altitude of the basement The crystaline basement slope between the at the Comprida Beach (KOLLERT's point n.o place of I.G.G. well n.o 2 and Pedra Balisa, where 5) is minus 85 meters. The difference of leveI of the basement outcrops is of about 29 ( 17 m in a 40 meter in a distance of 4 kilometers will give distance of 500 m), whereas the slope between l. a slope value of 1/100 (or 34'). ao G.G. well n.o 1 and KOLLERT's point n.o 5 is ELLERT (verbal information) later did some ao 34'. The displacement of the basement there- gravimetric pro files, perpendic\flar to the Compri­ · fore was greater at the Pedra Balisa region. It da Island from the ocean to Pequeno "sea" in is evident that the basement dips northeastward order to test the fault hypothesis. According to from Pedra Balisa to I.G.G. well n.o I, whereas in , this author the Comprida lsland basement forros ,Comprida lsland it dips southwestward. The a "footstep", lower in altitude in relation to the , positions of the two tilted blocks are therefore basement of the continent, that is, there is no reverse. continuous slope from the basement of the conti­ nent to the basement of the Comprida Island. It is possible therefore that a fault occurs striking THE STRATIGRAPHIC DRILLlNGS IN THE NE and partially coinciding ' with the Pequeno AREA "sea". The Pedra Balisa, in the middle of the Pequeno "sea", made up of alkaline rocks could The drillings of the Instituto Geográfico e Geo­ be either an elevation of the basement by diffe­ lógico rential erosion before faulting or, which we think more probable, that the fault line is located The Instituto Geográfico e Geológico drilled between Pedra Balisa and Comprida Island. · two wells in 1964, in the region, based on KOL-

-10- LERT's study. The purpose of the two wells to de Estradas de Rodagem" ofthe' S'iate of São were to study the late cenozoic sedimentary se­ Paulo, drilled in th. are a for differeri't ·~rposes. quences. Several wells wére drilled in the' Cuba,tio "se a" , The first one was drilled in the contine!1t" , near Aroeira, to ', know 'l the 'conditions of the beside the road Iguape-Subaúma, ab,out 10 km terrail'l for a bridge; According to the described from Iguape (approximately latitude 240 46' and profiles, beds ar clay nch in organic matter rest longitude 470 38). The second one was drilled on 5 m sUty sand. Below the silty sand the:weathe­ in Comprida Island, about 29 km from itssouth­ red rock appears, which pus' into fresh granite. western tip at the ocean side (approximately latitude 240 52' and longitude 470 42'). The GRAIN SIZE ANALYSlS two wells are separated by a distance of 14.5 km (See ftgUre 1). Introduction We were able to recognize 4 sequences based KUfNER (1962) studied the grain sizes of on the lithological characteristics, which sequen­ 95 samples from the bottom sediments of Cana­ ces that were later conftrmed by the microorga­ n6ia "sea", Cubatão "sea" and Itapitangui "sea", nisms studies, of the sediments cut by those two , around Canan6ia Island, with the purpose of wells: In the well n.o 2, sandy and conglomeratic recognizing and evaluating the different agents I beds with subordinate sandy clay layers are the and factors responsible for the present sedimen­ oldest beds, supposedly resting on the crystaline tation in the region. According to this author basement (Sequence I). Above these beds the the sediments general1y are homogeneoul with sediments are fine, constituted mainly by silty TRASK's sorting coefficient between 1.0 and clays (Sequencell). Following these beds, the 4.0, the values lower than 2.5 beina more com­ sediments beC9me silt-sandy (Sequence IlI). The mon so they would be very well sorted. uppermost beds up these two wells are predo­ The Geobrás SI A, as mentioned before, drilled minantly fine, well sorted sands so loose they shallow wells as part of the program of an were the' only sediments not allo'wed to be cored extensivesurvey for S.V.R. Only sequence IV, (Sequence IV). The sediments of the last sequen­ constituted by regressive "blanket sands" was ce co~er most of the present coastal plain:'some­ cut by these wells. And, also 16 samples 'ofthe times weakly cemented' by ferruginous matter, ' surface sands were collected. From the samples forming the "piçarras" previously referred. collected during these surveys, 87 were submitted to mechanical analysis in the "Instituto de Pesqui­ The Geobrás drillings sas Tecnológicas" of the UniveI1ity of São Paulo. A great majority of these samples are fme, aImost This Company drilled 79 percussion wells, pure sands. 72 of tbem along Valo Grande (24 in each rnargin The extreme uniformity in grain sizes of the and 24 in the channel, and 7 scattered in the sediments from the lagoonal region ia well evi· Comprida lsland and Pequeno "sea"). denced by the 182 samples analysed in those two The drillings didn't go beyond 34.45 m deep works .. AlI these sediments are provenient from and 50 only the sequence IV was cut. However, "piçarras" (sequence IV) or reworked f. 'piçarras" significant data were acquired which together (sequence V); in this case there rnay be some with data from other sources made possible a grain size alterations in order to restore the reasonable picture of the characteristics and equilibrium with the new dynamic conditions of environment of deposition of this important a different environment. In other words: The sequence of sediments. sands deposited in equilibrium with the dynamic Beside the studied samples from the described conditions of a regressive sea making up the wells, additional samples from 16 localities in blankét sands would possibly have to modify Comprida Island, Pequeno "sea", Icapara outlet, their grain sizes even in a small degree, in order mouth of the Ribeira, Ribeira and Valo Grande to get in equilibrium with the conditions of were collected by the Geobrás. new envirortrnents of sedimentation (redeposition): Other institutions, for instance, "Departamen- beaches, dunes or lagoonal bottoms. If so, the .' -11- simple comparisons of the average or mean dia­ were drawn on arithmetic probábility pape r meters, of TRASK 's coefficient (So) or of homo· with "phi" scale. These curves were grouped geneity index, calculated by Ku1'NER (idem) into 7 classes, according to their geological and Geobrás (idem) are not enough for one to provenances: become aware of these minimum discrepancies a) Surface samples of great significance for the recognition of such Group 1 - "Piçarras" environmen ts. Group 2 - Dunes from Comprida Island With this possibility in mind we analysed Group 3 - Bottom sands from Cananéia and . 37 "piçarra" and its resedimentation products, Pequeno "se as" collected by uso The data of 32 samples from Group ·4 _. Beaches from Comprida Island the two wells drilled by I.G.G., analysed by the geologist CARLOS TORRES, kindly granted b) Subsurface samples by him, were also included in this study. These Group 5 - "Piçarras" drillings data were essential in the textural cha· Group 6 - Sequences II and III racterization of the sequences I, II and m, Group'7 - &,-al sands and conglomeratic saIl'is that do not crop in the studied area. (Sequence I). The cumulative curves for the "piçarra" Sampling were remarkably uniform principally those from We collected 51 samples from the Iguape· the surface samples.Furthermore, the beach and Canan~ia lagoonal region. Most of them come dune sands, originàted from reworking of the from '''piçarra'' banks; other samples come from "piçarras" have cumulative curves without any the bottom of Cananéia and Pequeno "seas" , appreciable differences from those of the "piçar• recent beaches and dunes and river channels. ras", even when some statistical parameters were compared as, for instance, the mean diame­ The samples underwent mechanical analysis, hea· ters or TRASK's sorting coefficients. The bottom vy minerals couting and Foraminifera and Algae sands, though predominant1y constitute d by re­ I inventories. In this paper are presented only the working "piçarras" have, notwithstanding subs­ results of the mechaniCal analysis. Details about tantial participation of argillaceous materiaIs the provenance of these samples are presented because of the lagoonal environment. The sam­ in the part 11 of this Project. pIes from the groups 6 and 7 carne from environ­ ments of sedimentation completely different Method of ana1ysis from other groups, 50 their cumulative curves The grain size of 37 samples chosen at random are perfect1y distinguished from the curves of were analysed. They were initially split, down the remaining ones (See figures 5a to 5i). to 50 to 60 grams. These fractions were sieved SAHU's graphic method (1964) - The size for particles larger than 0.062 mm and analysed frequency distributions of a sediment is more oÍ' by pippete in the case of smaller particles. less a reflection of the energy of the agent of The samples from the bottoms of the lagoons transport as we11 as they provide some indications were analysed not taking into account possible of the kinetic energy conditions within the operational errors during sieving, decantation, ~epositional environments. Several statisticaJ pa­ etc., that is, without controlling by comparison of rameters' were devised to express these relations the total weight before and after the analysis. We (FOLK and WARD, 1957; PASSEGA, 1957; proceeded thls way because according to KUT· FRIEDMAN, 1961, 1967; SAHU, 1964, etc.). NER (1962, p. 45), when this material is dried We were lucky with the application of the up the partic1es stick together into slumps of silt . SAHU's JIlethod. In this method the mean "phi" an el day practica11y impossible to desintegrate. deviation of a11 samples of a group (at least two samples) in the ordinate against the ratio using Results and in terpretations the stantlard deviation of kurtosis, mean size and variance of the group of ~amples in the abcissa Cumulative curves - The cumulative curves : are utilized on a log-log plot. Tile 'parameters

-12- used in this graphic method are those developed kable fact is that the points representing the by FOLK and WARD (1957). lhe SAHU's groups 2 and 4 located in the graphic very far graphic as applied to the Late Cenozoic sediments from the groups I and 5. As we have stated above of the studied region is shown in figure 6. the samples from these groups were not clearly Every one of the seven natural groups listed distinguished by other methods but they are above was plotted as a point in the graphic. lhe clearly separated by SAHU's metho(C Even 50 distributions of the points in the graphic allowed the points 2 and 4 were not plotted exactly the folJowing interpretations: into the areas corrrsponding to their true envi­ Point group 1 - Surface "piçarra": Deposition ronments, their locations show an unnústakable in a low energy shallow sea. liaison with the environments of the samples. Point group 2 - Dune samples from Comprida Another fact that ean be considered is about · Island: Deposition in a high energy aeolian en­ the location of the point group 3, which indicated vironment. fluvial environment. About this conclusion it is Paint group 3 - Bottom sands from Cananéia very interesting to mention that KlJfNER (idem, and Pequeno "seas": Deposition in a low energy p. 50) had recognized a hydrodynamic mechanism fluvial environment. in the channels around the Cananéia Island Point group 4 - 8each sands from Comprida with a characteristic of "two directions ~/ux Island: Deposition in a rather great energy beach type . river. " environment (energy between those of the groups We consider, therefore,' as confirmed the I and 2). hypothesis of reworking of the "piçarras" adjus- ' Paint group 5 - Subsurface "piçarras": Depoo ting themselves to the new energetic conditions sition in a low energy shallow sea. lhe position of the different environments of deposition. of the point representing these samples in the graphic, relatively far from the one representing CONCLUSIONS the group 1, might be explained by the prove­ J nance of these samples, from horizons straO­ Field observations and grain size analysis graphically lower than the samples of the group lo made by the authors, in connexion with the Point group 6 - Samples from sequences 11 previous works data, permit to reach some and I1I: Deposition in turbidity conditions, high conclusions: energy and viscosity. a) lhere are an extensive sedirnentary deposit, Paint group 7 - Conglomerates and conglo­ blanket sand type, constituted by homogeneous meratic sands from the base (!equence I): Depo­ and very well 50rted fine sand, in the 19uape­ sition in turhidity conditions with energy and Cananéia lagoonal region. viscosity higher than those from group ó. b) Not only because their great persistence, lhe points plotted in the SAHU's graphic, but also , as a consequence, these sedimentary relative to sequence V (recent bea<;hes, dunes deposits are the most important source of detrital and bottom sands), represent sedimentary envio, materiais to the present sub-environments. ronments c1early coincident with the environ­ c) In spite the great similarity, it is possible ments of the samples coUected. As for the older to recognize the little modifications to which sediments their environments were deduced by the "piçarras" sediments are subnútted in their other methods and even here the SAHU's graphic texture. during resedirnentation processes in mo­ confirmed those interpretations. The poinrs 1 dern environments hy application of the SAHU's ilnd 5 indicated deposition in a low energy method t 1964). sh~l\ow sea . beein~ concordant with previous d) It is possible to recognize also some well inteipretations, based on other characteristics defmed sedirnentary sequences below the Cana­ such as the shape of the rock body (Persistence néia Formation, revealed by the I.G.G. drillings. faclnr), stratigraphic position in relation to the Other characteristics and the final considera­ geologicaJ events, etc. Similarly the points 6 tions about the Neocenozoic sedimentary sequen­ anll 7 were also located in the graphic in positions ces in the 19uape-Cananéia lagoonal -region will tha! agree with previous interpretations. A rem-ar- he rresented in the second part bf this paper.

- }3- I"~t _ )''')5 (J , - t+ L+ 1.+ 1+ 1+ 1+ o 1- ,. .+ L+ • + ,+ .+ t+ ,+ 1 + o ,+ s+ .+ ; ~ o I s· e Q' I " o J:: .• lO

~ . 2

lO lO .. •

Õ õ •~ • lO • .. Z o .- '" o .. •Z I .. '"O ... g """ lO • .. O• lO '"o o ,- - - _._ _.•.. c .. ..O '"o '" o c :Ir n .. '"Z •O .. o n .. o.. ~ ~ ~ ! o•

.. ..o ..O .. ..

FIGURE 5.b .:.. Cumulative curves of groups 2-4 samples FIGURE 5.a - Cumulative curves of group 1 samples o •

CI) • -acu E

  • .... ;::l r-• (,) .. cu ..+ ,~ -;-

  • + ~ • ::> 0.01 _OI o.z O, t I 10 10 JO 40 50 lO 1'0 .o .0 t5 " ..., , _M ' C.!I • ...... ti: .IIINT 'IIIOUIIICT ftII

    o

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  • 0 0' O~ 0 .2 0.5 1 10 20 30 40 50 60 70 80 90 98 99 99.5 99.8 999 9999 c.) I,HIGHT FR,EQUENCY No! -~

    -15- o

    +

    +

    +

    + • "G. .. + ..n r- '" ..+

    +

    ..+ ..... 0 .01 O~O .I 0.2 0.5 I 5 10 20 30 40 50 6 (\ 70 80 9 95 98 99 99.599.8 999 99 9 ~

    WEIGHT FREOUENCr 1%1

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    + lO

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    + • "G... .. n ,.~ '" ..+ ..+ .. ..+ 001 OD50.1 0 .2 0 .5 I 2 lO 20 30 40 50 80 70 ao ' 90 95 91 99 99.5 99819.9 99.99

    WEIOHT FREQUENCY 1%1

    ':" 16- '0.0-.------__ ------______'0 .. " P LOT OF ff X SKfõ. S(er') 7.C 'Mz 6.~

    5 .C SHOWING THE DIFFERENCES BETWEEN THE DEPOSITlONAL 4 .C ENVIRON MENTS UGUAPE-CANANÉIAl

    3.0 ® GROUP 7 PlOT ACCOROINa TO SAKU (1964/. .7 SAII~Lf'

    2.0 TURBIDITES GROUP , I 12 'AII~L" ~(f2' ® liôROUP 3 \l .... II~Lf.

    0.9 0.11

    C.7 • fõAOUP 5 ® GROUP I O.E ~ .... II'LE. UI IAII~L'S ?5--4_ SURFACE SAIIPlE S :4 SHALLOW '"OU' 1 ' "IÇAIIIIAS' '.OU' t , DU.'S Of Til' COII.1I10 ..... L .... D '"OU'3 'OTTOM ...... LI. 'C ...... :, ...... 0 o. ! ~~~ DECREASIMIi M A R l N E ~'.: ~ "UA'E "'IAS" I (il GROUP 4 1110c­ ENER6Y -----v' '"OU' 4 , 'fACH'S OF TIII COM.IIIDA .SLAIIO ~ GROUP 2 3 .... II~L[. u=' IOI.J G2 3 5"'II~LfS O"" SUBSURFACE SANPlES '.OU' 5, 'PlÇAItItAS' .IIOU. 6, "OU'IIC" 11 AliO '" SKIô .S{ (f'} _ '.OU' 7, .A.... L C•• &Lo.," .. nc .... 01. S"Z aU'U'D-P[TIUOI" Ci.', lI '1~0 ______' 0.02,- ______.:::::~::_:;;~;:::;::;_:~------::;-----:;:----::~;::-;:::~:::;::::------0.03 0..04 0..0' 0..06 o.oe 0.1 0.2 O.~ 0.4 0., 0.& 01 0.1 o.a I. Q ____ -;~-----:::---:::--;:~;:-;I:2.0 3.0 4.0 ~o 1.0 7.0· :;:::.::::_------_:;::_----~::__:: 1.0 s.ofO.Q to.O 30.0 40.0 FIGURE 6 PROTO 1 DUNES NEAR TRE BEACR - Locality: Southeastern extremity of the Comprida Island.

    PROTO 2

    MAGNETITE AND ILLMENITE CON­ CENTRATION IN TRE BEACR - Loca­ lity: "Praia de Fora" beach of the Com­ prida Island.

    "FOOTSTEP" FORMED BY CANANÉIA FORMATION - Locality: Town ofCana­ néia, facéd to Cananéia "sea".

    -18- PROTO 4

    "TESTIMONY" OF CANANÉIA FOR­ MATION - Locality: Iguapé-Biguá road (The houses and the forest are situated on the erosion "testimony" and the banana plantation in the lower parts of the area).

    PROTO 5

    STRATIFICATION OF PRESENT BEACR SAND - Locality: Iguape Island, near the Icapara outlet

    PROTO 6

    BEDDING AND ARGILLACEOUS LAY­ ER OF TRE CANANÉIA FORMATION - Locality: Cananéia Island, where the figure 2 scheme was made)

    -19- BIBLlOGRAPHY Geobrás SI A report in 2 voI. for the "Ser­ viço do Vale do Ribeira" of the "Departa­ AMARAL, G. et aI. (1967) - "Potassium-argon mento de Águas e Energia Elétrica" of the ages of alkaline rocks from Southern Brasil" State of São Paulo. - Geochim. et Cosmochim. Acta, vol. 31, KRUMBEIN , W.C. and SLOSS, L.L. (1963) - p. 117-142. "Stratigraphv and Sedimentation" - Fre­ BARBOUR, A.P. (1966) - "Nota sobre a lateri­ eman and Co. ,.San .Francisco and London. zação e sua consequência no relevo do Território do Amapá" - BoI. Soco Bras. KUTNER, A.S. (1962) - "Granulometria dos . Geol., vol. 15, n.o 2, p. 5-31, São Paulo. sedimentos de fundo da região de Cananéia, BIGARELLA, J J . (I946) - "Contribuição ao São Paulo" - BoI. Soco Bras . GeoI. voI. estudo da planície litorânea do Estado do 11 , n.o 2, p. 41-45, São Paulo. Paraná" - Arquivos .de Biologia e Tecnolo­ McGUGAN, A. (1965) - "Occurrence and persis­ gia do I.B.P.T., Sep., vol. I, Art. 7, Curi­ tence of thin 'she/f deposits of uniform tiba, Paraná. lithology" - GeoI. Soco Amer. BulI. voI. BRASCONSULT SI A (1964) - "Plano de desen­ 76, p. 125-130. volvimento do Vale do Ribeira e Litoral MINIUSSI, l.C. (1959) - "Propagação da onda Sul - Comentário sobre a Formação Geo­ de maré em torno da Ilha de Cananéia" - lógica Regional" - Separata do trabalho Contribuições Avulsas do Instituto Oceano­ original, 3.a parte, título 1.0, capítulo 2.0, gráfico da Univ. de São Paulo, Oceanografia São Paulo. Física n.o 2, São Paulo. FOLK. R.L. and WARD, W.C. (1957) - "Braz os river bar, A study in the significance of PASSEGA, R. (1957) - 'Texture as characteristic grain size parameters" - Journal os Sed. of clastic deposition" - Amer. Assoe. Petrol., vol. 28, p. 3-26. Petrol. Geol. BulI., voI. 41, p. 1952-1984. FREITAS, R.O. de(l947) .- "Eruptivas alcalinas PETRJ, S. and. SUGUIO, K. ( 1971 a) - "Exemplo do trabalho do mar no litoral sul do Brasir' de Cananéia, Estado de São Paulo;Bol. - Not. Geomorf., vol. 11, n.o 21, p. 61-66, Fac. FiI. Ciên. Letras da Univ. de São Campínas, São Paulo. Paulo, n.091, Geol. n.o 4, 34 p., São Paulo. FRIEDMAN, G.M. (1961) - "Distinction betwe­ SAHU, B.K. (1964) - "Depositional mechanisms en dune, beach and river sands from their fram the size analysis of c/astic sediments" textural characteristics" - Journal of Sed. - Journal ofSed. PetroI., voI. 34, p. 73-83. PetroI., voI. 31, p. 514-529. SILVElRA,J.D.(1952) - "Baixadas litorâneas quentes e úmidas" - BoI. Fac. Filo. Ciên. FRIEDMAN, G.M. (1967) - "Dynamic processes Letras da Univ. de São Paulo, n.o 152,224 and statistical parameters compared from p., São Paulo. size frequency distributions of beach and SUGUIO, K. and BAREOUR, A.P. (1969) - river sands" - Journal of Sed. Petrol, voI., "Morfologia e gênese das estruturas limoní­ 37, p. 327-354. ticas dos sedimentos da Bacia de São Paulo" GEOBRÁS SI A (1965) - "Complexo Valo Gran­ - Anais da Acad. Bras. de Ciênc., voL de - Mar Pequeno e Ribeira de Ig~ape" - 41, n.o 2, p. 161-180, Rio de Janeiro.

    -20-