oppenheim (1936) devonian

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B U L L E T I N O F T H E A M E R I C A N A S S O C I A T I O N O F P E T R O L E U M G E O L O G I S T SV OL . 20, NO. 9 (SEPTEMBER, 1936). PP . 1208 1236. 6 FIGS.

G E O L O G Y O F D E V O N I A N A R E A S O F P A R A N AB A S I N I N B R A Z I L , U R U G U A Y , A N DP A R A G U A Y 1

V I C T O R O P P E N H E I M 2Rio de Janeiro, Brazi l

A B S T R A C TThis paper, representing the results of a detailed survey of the Devonian area inthe state of Parana, Brazil, gives some new data and field observations, valuable for abet ter understanding of the character of the Devonian sediments in the Parana Basin.Correlation is ma de w ith othe r De von ian a reas on the widely sep arated edges of thegreat basin, in the states of Matto Grosso and Goyaz, Brazi l , and the neighboring republics of Uruguay and Paraguay, as well as with the area of the valley of the Amazon(Fig. i ) . The comparat ive table shows the main characterist ics and thickness of the

rocks in the areas mentioned, as compared with some of those known in other parts ofSou th America, South Africa, and N ort h A merica.

INTR ODUC TIONThis paper is part of a report presented to the Mineral ProductionSurvey, Ministry of Agriculture of Brazil, and gives a resume of the

writer 's field work for this Government department during the latterpart of 1934 and the beginning of 1935.The Devonian area of the state of Parana has already been slightly

studied by 0. A. Derby, J. M. Clarke, and E. Oliveira in reports datedprevious to 1915. However, the writer believes that some new observations of detailed field work, as well as correlations with other newDevonian areas not known or mentioned by the preceding authors,amply justify this contribution. The writer hopes that the correlationof most of the known data on the basin of Parana and on some otherparts of South American may help establish a basis of thought andcertain deductions concerning geology and the possibilities for petroleum in the area studied.

The writer expresses his thanks to Domingos Fleury da Rocha, director general, and Avelino Ignacio de Oliveira, director of the Mineral Production Survey, for authorization to publish this paper. Heis indebted particularly to Djalma Guimaraes, director at the timethe study and survey of the region were performed, who also greatlyhelped in the presen t stu dy of several imp orta nt problems related to

1 Published with the permission of the director of the Federal Mineral ProductionSurvey of Brazil. Manuscript received, June 20, 1936.2 Consult ing geologist , Mineral Produ ction Survey, Avenida P asteur, 404,

1 2 0 8


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DEVONIAN AREAS OF PARANA BASIN 1209

FIG. 1.Distribution of Devonian areas in South America (modified after Garth). Occurrencesin Parana Basin are numbered: 1. State of Parana; 2. State of Matto Grosso; 3. State of Goyas; 4.Paraguay; 5. Uruguay.


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I 2 I O VICTOR OPPENHEIMthe area in question and to the area south of Brazil. Thanks are dueto Alvaro de Paiva Abreu, Affonso C. Alvim, and Birger Juell, all ofthe Mineral Production Survey, for efficient assistance in the fieldsurvey and mapping. For help in presentation of this paper, the writeris grateful to Joseph F. Brown.

As correlated reading, the bibliography accompanying this papershould be carefully considered.D E V O N I A N A R E A O F P A R A N A

The phyllites, quartzites, granites, and gneisses of the Basementcomplex, considerably folded, appear very much eroded and pene-planed beneath the unconformable Devonian sediments of the Paranaseries. Evidently a long period of erosion and exposure preceded thedepositing of this series. The absence of any fossil traces in the subjacent metamorphic rocks prevents an exact determination of thedurat ion of the great hiatus that preceded Devonian deposit ion. Theearliest satisfactory paleontological evidence is found in the excellentcollections of fossils in the upper part of the eo-Devonian shales.

The Devonian area in Parana appears in the form of a narrow,curved band between Serr inha, Parana ( lat i tude, approximately253S ' S.), and Faxina, Sao Paulo (latitude, approximately 23so' S.)(Fig. 2). This strip makes the western border of the basement rocksand extends in the form of a semicircle west of Curityba and Castro,a total distance, north and south, of more than 300 kilometers. Itsgreatest width, about 40 kilometers, east and west, is approximatelyon the parallel of latitude, 244o' S., where it also has maximum stra-tigraphic development. In its northeast and southeast extremities theband gradually narrows, sinking northwest and southwest, respectively, beneath the overlapping Permian glacial deposits. The westernmargin of the band, although showing various faults, as in PedraBranca, likewise dips under the same glacial sediments.

Only the eastern limit appears in the form of an abrupt erosionalescarpment or sandstone cuesta throughout almost its entire extension. North of the valley of the River Yapo the escarpment is knownas the Serra das Furn as, but farthe r south it takes various local name s,in the following north-south order: Serra de Sao Joaquim, west ofCastro; Serra de Itayacoca, east of Ponta Grossa; Serra de Sant'Annaand Serr inha at i ts southernmost extremity .

The total area occupied by the Devonian rocks in the state ofParana is approximately 5,640 square kilometers. In this area theParana series may be divided into two very distinct lithologicalgroups: (1) the lower beds, Furnas sandstones, having a superficial


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DEVONIAN AREAS OF PARANA BASIN I 2 I I

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Lower Deyontert

CmmmSes * Legend%Arehifo ek Furnas'furnas sandstone ' Base or sfrjtjIifcflwSto 4tfaiteGrDS$a\'fionta Qrossa shale \fHrma0o Bsnte SrvssaJ A-*** A Tfrm i PonM < * r e s S 3 r o r m 3 f !< " 'tfY/baoy SBMc&rtJ/W - inlerralafej in fianfa OfossaDiscorobnco(Meoirfoi-mity

*g/tersre fyrmatioo (largely glacial\hiqesl fer/nation mapped :Lower PermkYtntrmoef d bosalfe aistrfachs nss cammham tntasfJBasaflic intrusions observed on traversesl/tri/sao t& > stftnito-patfiro observada nos cominhamrntosSyenite -porphyry intrusions on traverses

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J Irarerjes atony roads

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fe.-fl & '*' * J T *'W.

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M I N F . P A L P R O D U C T I O NO F B R A Z I LG E O L O G I C A L W

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S U R V E Y

M A PO FTIPAGY REGION, PARANA

UNDER THE DIRECTION OF V. OPPENHE IMTOfOGPAPHr Br ALI/ARO P. ABREU ANDAFFONSC C ALVIM.TOMOGR APHIC CONTOUR INTERVAL2S METERS5 . F . P . M .PLGNm BEOLOSICG

REGIAO DETIBABY (PARANA)Organizada par Victor Oppenitoim

Topographic/ de Afvaro PAbreu e Affonto C. AM"

vicinity of Tibagy, Parana, Brazil.


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DEVONIAN AREAS OF PARANA BASIN 1 2 1 5

MISJ5

oI

0


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I 2 l 6 VICTOR OPPENHEIMmust have accompanied the trap effusions at the end of Triassic orJurassic time.4

The regional westward dip, common to the Upper Devonian bedsof the system, with the nearly horizontal position of the cross-beddedFurnas sandstones, discordant with the basement rocks, suggest thatthe alteration of the original position of the strata was of uniformcharacter and apparently associated with epeirogenic movements.From the conformation of the escarpments of the Furnas and of theescarpment faults, like Pedra Branca and the Serrinha, it may be deduced that these movements were upward east of the basin and downward w est of the ba sin.

The tectonics of the basin can be explained by a process of epeirogenic upthrust of the blocks of the basement and subsequent sinkingof the coastal mass. Isostatic movements of this character still occurand were observed on the present coast of Sao Paulo, Parana, andSanta Catharina by the writer and also by I. C. White (1908). Undoubtedly also, Triassic diastrophism considerably affected the basin,contributing to the formation of the various escarpments, faults, andfractures, as will be seen presently.

G E O L O G YFURNAS SANDST ONE

As state d before, the basal element of the Pa ran a series, the Fu rnassandstone, lies in discordance on the phyllites and mica-schists of theAsunguy series, which in the various contacts observed have dips of7o-8o. Contacts along the Serra das Furnas, on the roads, and alongthe Serra de Sao Joaquim and the Serra de Itayacoca show that theFurnas sandstone was deposited transgressively upon a surface deeplyeroded and peneplaned.

Known and descr ibed by var ious authors, the Furnas sandstoneappears in outcrops of great extent, as very uniform coarse sandstones, generally white or slightly yellowish, very hard, and resistantto erosion. Th ey are composed of grains of qu ar tz, as large as 1 millimeter in diameter, slightly rounded though some are angular, andwith abundant kaolinic cement. Very common are pebbles of whitequartz, fiat and round, 10-20 millimeters in diameter, sporadicallyscattered through the mass of sandstone, but most common in thelower part of the beds. At the base the pebbles form conglomerates,locally in extensive layers. The maximum thickness of the Furnassandstones, as lately observed, is 50-300 meters. In addition to these

4 Victor Oppenheim, "Rochas Gondwanicas e Geotogia do Petroleo do Brasi lMeridional , " Sen. Fom. Prod. Min., Ministerio AgricuUura, Bol. 5, Rio de Janeiro(i934)-


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DEVONIAN AREAS OF PARANA BASIN 1217typical occurrences, the beds appear in some outcrops as fine, friable,sandstones with intercalations of small pebbles of the same material.

FIG. 5.Escarpment of Furnas sandstones on road to Castro (Parana).

An interesting facies of Furnas was observed in various localities,as in the Jaguariaiva zone, in Tibagy, and in the Serra de S. Luiz dePuruna. Here, within the characteristic beds of sandstone, are intercalations of very micaceous, fine layers of thin shales resembling


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I 2 l 8 VICTOR OPPENHEIMphyllites, white or yellowish, and rather friable. Such interpositions,10-15 centimeters thick, were observed only in the localities cited,though presumably they must exist in many other outcrops.

The analyses of the Furnas sandstone show many traces of magnetite, which explains the red coloration so common in the areas ofdecomposed F urn as san dston e. With the exception of the tubes ofArenicolas, worms observed by Derby in the upper beds in ArroyoGrande, near Ponta Grossa, no other fossils of any kind are knownwithin the formation. In all typical outcrops the Furnas sandstone iscross-bedded.

Origin of Furnas sandstone.The lithologic character of theFurnas sandstone rather excludes the idea of eolian origin as might besupposed at first sight. The cross-bedded stratification, the conglome ratic com position and interpositions of beds of micaceous shales,and the dominantly lightin many places whitecolor of the sediments, considered in relation to the composition of the basementrocks, lead to the assumption that these sediments originated asestuarine deposits. The shaly interpositions in the sediments correspond with deposition in quiet water, while the conglomerates, particularly at the base of the beds, suggest deposition in swift curren ts .

These essential characteristics, combined with the complete absence of limestone, as well as the lithological aspects of the Furnas,may dispose of the supposition that the sandstone had marine origin,and suggest that it may have been deposited in coastal lanes or estuaries, as the writer is rather inclined to believe.

From the genetic point of view, the Furnas sandstone (like itshom otaxial eq uivale nts in other Lower Devonian areas of SouthAmerica, particularly the Carmen sandstone in Uruguay) is alsolithologically and stratigraphically identical with the Devonian sandstone of Cape Meredith in the Falkland Islands and with the TableMountain sandstone of Cape Colony, South Africa, which provesthey were derived from the disintegration of a common basement material. The area of origin of these sediments, so widely scattered, cannot be located except by supposing some land of high relief, whichmust have existed in the present basin of the Atlantic Ocean.

As previously pointed out,5 the existence of such a terrestrial areais supported by the evidences of glaciation and the westward movement of glaciers in the eo-Gondwana era of the western hemisphere;howe ver, there is nothin g more positive and concrete to sup 'hesetentat ive ideas.

6 Victor Oppenheim, op. tit.


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DEVONIAN AREAS OF PARANA BASINPONT A GROSSA FORMAT ION

Und er this term th e writer includes the fossiliferous sedim entaryrocks that Derby and E. Oliveira classified as the "Ponta Grossashale" and the "Tibagy sandstone." Unti l the present the Tibagysandstone has been considered as an upper horizon, independent ofthe P ont a Grossa shale; in part , such division should be justified by acertain faunal difference in the associated species of fossils. However,the field observations convince the writer that these sandy beds inter-placed in the Ponta Grossa shale proper represent merely local faciesof the latter. Consequently, the stratigraphic division could not bewell justified, and the combined beds should carry one name only. Thewriter prefers to conserve the existing nomenclature except for introducing the term, "Ponta Grossa formation," thus giving the notion ofan inseparable conjunction of the two facies of the same sediments,as they appear at Ponta Grossa and Tibagy.Besides this stratigraphic observation, proved by detailed surveysin Tibagy , as is shown hereafter, little can be added to the descriptionsof the Ponta Grossa shale and the Tibagy sandstone given by 0. A.Derby and E. Oliveira.

These very fossiliferous sediments surround the area of Furnassandston e in a strip , appro xim ately 10 kilometers in maxim um wid thand 200 kilometers in length, between the confluence of the riversBarra Mansa and Jaguariaiva on the north, and the station of Lagosouth of Ponta Grossa, passing at the most westerly outcrop betweenthe town of Tibagy and the escarpment of Pedra Branca.The thickness of the formation in the Tibagy zone, between theFurnas sandstone at the base and the Permian sediments at the top,is about 150 meters. In a boring at S. Jose de Paranapanema, 92meters of Devonian shale and sandstone were penetrated by the drillwithout reaching the base. No Tibagy sandstones were encounteredin this boring, either at the top or between the shale beds. In Tibagythese sandstones do not occupy the upper part of the Ponta Grossaformation, as might be supposed from published descriptions; butthey occur rather in its lower part.

The structure of the Ponta Grossa formation is characterized by aregional dip of io-i2 W. In addition to numerous intrusive bodies,which created local structures in Jaguariaiva and Tibagy, various contact faults and other planes of dislocation were observed. However,there was no evidence of any pronounced individual structures withinthe area of the shales or any vestige of folding or "over-thrusting"due to tangential forces anywhere in the area, although there aredomes and structural elevations, the result of intrusive bodies or their


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1 2 2 0 VICTOR OPPENHEIMramifications, which, as already mentioned, deeply affected the area.Ponta Grossa shale.Across wide areas the Ponta Grossa shaleappears with essentially identical characteristics, nearly everywhere

FIG. 6.Ponta Grossa shales near Jaguariaiva (Parana).consisting of clayey and clayey-sandy shales, micaceous, of mediumhardness, and, in most places, gray in color. In certain outcrops theupper layers are black, carbonaceous, and, in some places, possibly


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DEVON IAN AREAS OF PARANA BASIN 1221bituminous. At the surface the shales generally are red or yellow fromlater i t izat ion.

In addit ion to abundant pyri te , the beds commonly contain concretions and nodules of limestone, as well as thin intercalated lensesof sandstone of the same color as the shale. The Ponta Grossa shale isvery fossiliferous in ma ny o utc rop s. Th e localities, in which w ere foundmany collections of eo-Devonian marine fossils, are in the neighborhood of the cities of Ponta Grossa, Jaguariaiva, and Tibagy, fromwdiich J. M. Clarke classified about 41 genera and 19 species.

The fossiliferous beds found (in 1935) in the well at S. Jose deParanapanema, at 471-563 meters, did not furnish any new species,except Chonetes falclandicus Moris and Sharpe, whose holotype of theFalkland Islands was not previously known in Parana. This specieswas first identified by Aristomenes Duarte among the fossils from theboring.

All the abundant Devonian fauna of Parana was exhaustivelystudied and described by J. M. Clarke.6 Also, there are vegetable fossils in the Ponta Grossa shale discovered by the writer in an excavation at Bocaina, near Ponta Grossa.

New p lant fossils, previously un observed or not noted in the literature on Devonian rocks of Parana, have been described by the writerwith photographs and sketches in a communication to the BrazilianAcademy of Sciences.7 These fossils, although very incomplete, maybe found in other localities of the zone. They are of singular interestin being the first eo-Devonian flora found in southern Brazil and ultimately they may complete a flora possibly identical with that of theFalkland Islands, found and described by Halle and Anderson.

Tibagy sandstone.These sandstones are generally of fine texture,micaceous, feldspathic, yellowish gray, and com pact b ut friable. Untilthe present, they have been observed at only two places in the Tibagyzoneon the left bank of the River Tibagy, close to the town ofTib agy , and 6.5 kilometers w est of Tib agy , along the road to the Serrado Borja, in the stream of Sao Domingos.

In the first occurrence they form the bank of the river, extendingalong the left (west) bank for a distance of 100-150 meters and disappearing in the Ponta Grossa shales at the north. On the south theircontact with the Furnas sandstone is a fault.

Measured from the surface of the water, the thickness of thesesandstones is 16.5 meters to which can be added a minimum of 1.56 J . M. Clarke , "Fosse is devonianos do Parana ," Monographia do Servlco Geologice Mineralogico do Brasil (Rio de Janeiro) , Vol. I (1913).7 Victor Oppenheim, "Fosse is do Devoniano do Parana ," Annaes Acad. BrasileiraSci., Vol. 7, No. 4 (December, 1935).


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1 2 2 2 VICTOR OPPENHEIMme ters below the wa ter in the bed of the river. The pa rt above thewater gave the following column. Thicknessin MetersCompact sandstone, yellowish gray, micaceous, very hard 2.5Fine sandstone, clayey and shaley, micaceous, yellowish, soft 9.0Micaceous sandstone, fine, compact, light yellowish, fossiliferous 5.0

Above the last sandstones extends a bed of red and friable laterite,25-30 meters thick. A little farther nor th, on the road to the rivercrossing, as well as far toward the west, are outcrops of typical PontaGrossa shale. The same shale is found in the water wells of the cityof Tibagy. It occurs also on the right bank of the river and a littlefarther east it is in contact with the Furnas sandstone.

The Tibagy sandstones, in the locality described, are clearly horizontal and evidently represent lenticular interpositions within thePonta Grossa shale and at its base.The Furnas sandstone which crops out south of the Tibagy sandstones forms the banks of the river and appears in typical form, withqu artz p ebbles and cross-bedding. In th e wa ter course of Sao Domingosthe Tibagy sandstones crop out in the valley of this river, near thesource, about 500 meters east of the Serra de Sao Borja road. The

locality, a little below the source of the stream, is particularly fossiliferous; beds with abundant fossils crop out in this place along bothbanks of the stream. These beds are of yellow or gray micaceoussandstone, the texture of which varies from fine to medium. The sediments are very pyritic and ferruginous and contain several large fossilmolds in a ferruginous cement. The fossils are found in fine beds, veryfossiliferous, and alternating with fine layers of non-fossiliferous sandstones.

The thickness of the Tibagy sandstones in this locality is about 20meters. The sandstones in Sao Domingos are at a horizon higher thanthat of the outcrops on the River Tibagy and appear also in the formof a lenticular intercalation. They are surrounded and evidently overlain by the Ponta Grossa shale.The Ponta Grossa shale extends vertically for approximately 75

meters above the horizon of the sandstones of Tibagy, reaching 2kilometers north of the sandstone outcrop, and at 825 meters elevation they come in conta ct w ith the glacial sedime nts of the e scarpm entof "Pedra Branca." These sediments are evidently Permian in ageand not Furnas sandstone, as was supposed by Oliveira.8

Thus we see that the Tibagy sandstones are only local intercala-8 E. P. de Oliveira, "Geologia e recursos Mineraes do Estado do Parana," ServiceGeol. e. Min. do Brasil, Monographia VI (1927), p. 30.


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DEVON IAN AREAS OF PARANA BASINt i ons i n t he Pon t a Grossa sha l e and do no t occupy t he t op o f t hef o r m a t i o n ; o n t h e c o n t r a r y , a s s h o w n b y t h e e x a c t m e a s u r e m e n t o ft h e t w o a n d o n l y k n o w n o u t c r o p s d e s c r i b e d , t h e i r r e a l p o s i t i o n i s a tt h e l o w e s t p a r t o f t h e f o r m a t i o n . H o w e v e r , t h i s o c c u r r e n c e i s v e r yl o c a l , n o t h a v i n g b e e n o b s e r v e d i n o t h e r z o n e s o f t h e D e v o n i a n b a s i n .

I N T R U S I V E SB o r d e r i n g t h e r o c k s o f t h e B a s e m e n t c o m p l e x o n t h e e a s t a n d

s u r r o u n d e d b y G o n d w a n a s e d i m e n t s , t h e D e v o n i a n s t r i p o f P a r a n aw a s g r e a t l y s u b j e c t e d t o t h e s a m e a c t i o n of th e i n t r u s i v e s s o c h a r a c t e r i s t i c o f t h e G o n d w a n a s y s t e m . T h e s e a r e t h e v a r i o u s f o r m s o f b a s a l ta n d d i a b a s e i n t r u s i v e s o f t h e T r i a s s i c .

H o w e v e r , c o n s i d e r i n g t h a t i n t r u s i o n s o f b a s a l t a r e l i k e w i s e a b u n d a n t i n t h e b a s e m e n t r o c k s , f r o m t h e A r c h e o z o i c t o t h e l e s s m e t a m o r p h o s e d S i l u r i a n , a n d c o n s e q u e n t l y a r e a s s o c i a t e d w i t h v a r i o u s c y c l e so f d i a s t r o p h i s m , L a u r e n t i a n , H u r o n i a n , a n d C a l e d o n i a n , i t m a y b ea s s u m e d t h a t b a s i c i n j e c t i o n s a s s o c i a t e d w i t h t h a t l a s t c y c l e , c o n t i n u e di n t o t h e D e v o n i a n itself. However , e f f ec t s o f t ec ton i c fo ld ing were no to b s e r v e d i n t h e a r e a .

S o m e p h a s e of d i a s t r o p h i s m f in d s i t e x p r e s s i o n i n t h e D e v o n i a nr o c k s t h r o u g h t h e i n t e r e s t i n g o c c u r r e n c e o f a d i k e o f p o r p h y r y - s y e n i t e ,w h i c h t h e w r i t e r o b s e r v e d a t F o r t a l e z a , 1 8 k i l o m e t e r s e a s t of T i b a g ya n d i n t h e m i d d l e o f t h e l o n g c o n t a c t b e t w e e n t h e F u r n a s s a n d s t o n ea n d t h e P o n t a G r o s s a f o r m a t i o n . T h e o u t c r o p o f t h i s r o c k f o r m s ac o n s p i c u o u s l o c a l e l e v a t i o n a n d o n i t s w e s t b o r d e r i t i s a c c o m p a n i e db y a b a s a l t i c d i k e t h a t a p p a r e n t l y is y o u n g e r t h a n t h e p o r p h y r y -syen i t e . T he compos i t i on o f t he d i abase does no t d i f f e r f rom tha t o ft h e b a s i c m a g m a s c h a r a c t e r i s t i c o f s o u t h e r n B r a z i l .

A s t h e r e i s n o d i r e c t r e l a t i o n b e t w e e n t h e p o r p h y r y - s y e n i t e d e s c r i b e d a n d t h e g r a n i t e - p o r p h y r y o f t h e C a s t r o r e g i o n o r t h e g r a n i t eof J o a q u i m M u r t i n h o o n t h e e a s t , w h i c h f o r m s a g r e a t b a t h o l i t h b e l o w t h e F u r n a s s a n d s t o n e w i t h o u t , h o w e v e r , a l t e r i n g t h e l a t t e r , i t i sd i f f i cu l t t o show a d i r ec t r e l a t i on be tween t hese rocks . We can , neve r t h e l e s s , a s s u m e t h a t b o t h t h e g r a n i t i c i n t r u s i o n s a n d t h e s y e n i t e s p e r t a i n t o t h e s a m e C a l e d o n i a n c y c l e o r t o t h e d i a s t r o p h i s m i m m e d i a t e l ys u b s e q u e n t t o t h i s c y c l e .

T h e w r i t e r h e r e r e p r o d u c e s D j a l m a G u i m a r a e s ' d e s c r i p t i o n s o f t h eg r a n i t e s m e n t i o n e d .

Granitic porphyry, vicinity of Castro, state of Parana.This is a dark redrock with flesh-colored stains. These stains correspond to decomposed pheno-crysts of alkaline feldspar. Microscopically they are shown to be composed ofphenocrysts of quartz and alkal ine feldspar , decomposed ferromagnesianmineral , and a ground mass of micrographic texture, composed of quartz and


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1 2 2 4 VICTOR OPPENHEIMfeldspar. The feldspar is completely altered and impregnated with red oxideof iron. The rock is veined with quartz and from its profound alteration appears to have been subjected to hydrothermal action.Joaquim Murtinho granite.This granite is of medium red granulation,of the same magma as the porphyry of Castro, and is composed of perthiticmicrocline, quartz, and some albite in isolated crystals, small and corroded.It contains violet-colored fluorite in undeveloped crystals. The red color isdue to an impregnation of iron oxide, the ferromagnesian mineral being completely decomposed.

The syenite of Fortaleza is particularly notable, considering thatin this region it is generally only to the Silurian rocks that acid intrusions are attributed, and the characteristic Devonian plutonism beingma rked by basic intrusives, as is proved by the num erous intrusions ofbasalt observed in the Devonian rocks of the Amazon and MattoGrosso and likewise of Bolivia, North Argentina, and the FalklandIslands.

Comparing the occurrences of the outcrops of basic intrusion inthe Devonian area proper, it is observed that the Furnas sandstoneseems to be much less affected tha n the Po nta Grossa formation, due,possibly, to the greater lithological consistency of the Furnas sediments. One may note, however, that the Devonian strip seems to berelatively less affected by the intrusives and their apophyses than theneighboring regions of Gondwana rocks. One need not here describein detail the numerous outcrops of basalt in the area. The principaldikes are visible at the surface on any roads of the region.

ARE A BE T WE E N CAST RO AXD T IBAGVTh e profound reen tra nt between the escarpm ent of the Serra dasFurnas and that of the Serra de Sao Joaquim, as observed on roads 15kilometers west of Pirahy and 20 kilometers southwest of Castro, is

due essentially to the intense erosion of its valley by the River Yapo,which cuts the escarpment by a deep canyon extending from east towest across all the area of Furnas sandstone and discharges into theRiver Tibagy, 1.5 kilometers north of the town of the same name.

The elevated "monadnocks" of the basement rocks, observed infront of the Serra de Furnas, west of Pirahy, indicate that the originalcontact of sandstones with the basement did not extend eastwardmuch beyond the present limit.

The great difference in level between the plateau of the Furnas andthe area of th e bas em ent , is due as mu ch to profound erosion as to thedislocations. Thus, the strongly inclined phyllites and mica-schistsof the Assunguy series, which constitute the Basement complex alongthe greatest extent of the contact, are more easily decomposed and


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DEVONIAN AREAS OF PARANA BASINdestroyed by the erosion than the horizontal, sandy, and highly resista nt F urn as sand stone , creating, in this fashion, m any of the escarpments along the cuesta of the Serra.

On the road from Castro to Ponta Grossa, the topography of thecontact between the Assunguy series and the Furnas sandstone is,however, a gradual and almost imperceptible slope, as seen at Kilome ter 213, betw een the stations of Tronco and C aram beh y. TheFurnas sandstone extends from there southward to the left bank ofthe River Pitanguy, where it is in contact with the Ponta Grossaformation.

However, on the Serra de Itayacoca, 25 kilometers west of PontaGrossa, there are very pronounced faults along the contact betweenthe Furnas sandstone and the metamorphic rocks. Likewise, on theescarpm ent of the Serrinha in Sao Luiz de Pur un a, 10 kilometers westof Cam po Larg o, on the roa d from Cu rity ba, there are vestiges of faultsand characteristic phases of disintegration and progressive erosion ofthe borders of the escarpment. In long distances the elevation of thesebord ers of the esca rpm ent varies from 1,050 to 1,200 me ters above sea-level, and shows the widespread uniformity of deposition of theFurnas sandstone upon a rather even basement floor.

It is necessary to note that in the contact between the Furnassandstone and the Basement complex, at Kilometer 137 (3 kilometersfrom Joaquim Murtinho), batholiths of granite are observed. The restof the contact of the basement with the Furnas sandstone is composedmainly of metamorphic rocks of the Assunguy series.The area between the escarpment of the Serra de Furnas and thetown of Tibagy, 45 kilometers by road west of the town, is an elevatedplain with the graminaceous vegetation that characterizes the "Campos Geraes" of Parana. The plain has an elevation of 950-1,200 metersand is crossed by profou nd can yon s of v arious rivers and their trib utaries. Thus, the canyon of the River Yapo, 20 kilometers east of itsmouth, is 170 meters deep, cutting through the sandstones of theFurnas formation.

The thickness of the Furnas sandstone in this area is 50-250meters, far greater than the thickness heretofore described.Ap proxim ately 15 kilome ters east of Tiba gy, th e plate au of theCampos Geraes begins to descend gradually to the valley of the RiverTibagy, where the Furnas sandstone of the plateau disappears beneath the Ponta Grossa formation.

TIBAGYThis area, studied in detail, is part of the valley of the River

Tibagy, having as its western limit the escarpment of Pedra Branca,


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1 2 2 6 VICTOR OPPENHEIMwhich includes the abrupt elevations known locally as: Serro Mineiro,Serro Sao Lourenco, Serra da Borja, Serra Puxa Nervo, Serra doFrancez, and Serra da Pedra Branca, the last named being the mostconspicuous and the most southerly hill along the top of the escarpment. The eastern limit is formed by the right bank of the RiverTibagy and the plateau of the Furnas, already described.All this area, between the River Tibagy and the escarpment ofPedra Branca, is drained by the River Santa Rosa and its principalaffluentsthe Sant'Anna and the Sao Domingos. It is a plain underlain by the shales and sandstones of the Ponta Grossa formation,which here appears in its most complete development between thesubjacent Furnas sandstone in Prainha, in the River Tibagy, and theescarpment of Pedra Branca which is composed of sandstones andsuperposed Permian conglomerates.

The Furnas sandstone in Prainha, on the edge of the River Tibagyand in front of the town of the same name, is interstratified withlenticular, horizontal beds of phyllites, 20-30 centimeters thick; otherintercalations in the sandstone are beds of conglomerate with pebblesof white or gray quartz, rounded or flattened. This outcrop of theFurnas in Tibagy is the most westerly occurrence and, stratigraphi-cally, it is the lowest Devonian known in the Parana Basin.

Farther north the Furnas sandstone is in contact with the Tibagysandstones previously described, and, with the exception of the outcrop of the same sandstones of Sao Domingos, all the area as far as theescarpment of Pedra Branca is composed of Ponta Grossa shalecrossed by numerous basalt dikes.

Up to the contact with the sandstones of Pedra Branca, the greatest elevations of this zone do not exceed 860 meters, and only at thefoot of the cuesta does the land commence to rise sharply, formingbluffs which overlook the zone from elevations of 1,000-1,100 meters .

The shales of the area have predominant westward dip, though invarious outcrops there are local northwest and southwest dips, due tolocal faults and many intrusive bodies. Faults of vertical displacement apparently form the escarpment of Pedra Branca.

The Serra do Mineiro and Sao Lourenco, which constitute thenorthern extremities of the escarpment, are composed of coarse sandstones, friable, yellow or cream-gray in color, and irregular in texturefine to coarse. Th ey are cross-bedded an d lie discordantly above theDevonian shale. In Sao Lourenco and in Pedra Branca they formconspicuous cuestas.

In the Serra do Borja contact, on the road to Agua Clara, therecrops out a 5-meter bed of conglomerate with boulders of phyllites,


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DEVONIAN AREAS OF PARANA BASIN 1227quartz, and granite. This bed forms a transgressive contact overthe subjacent shale and is overlain by about 15 meters of the yellowish, coarse sandstone that characterizes all the escarpment. The samesuccession is observed also on the road to Puxa Nervo.

These beds, approximately 150-250 meters thick, with here andthere an exposure of glacial boulders, form the higher crests of theescarpment with elevations of r ,000-1,100 meters.

Th e lithologic chara cter of the sands tones, conglomeratic beds, andboulders, indicates that these formations belong to the Itarare series,deposited by Permian glaciers. In some outcrops the sandstones arevery similar to those of the Furnas, with which they can be confusedby an observer not familiar with the region. Thus, the writer observederosional remnants of these rocks in Fortaleza, on the road to Ven-tania, where they occur capping the Furnas sandstones at an elevation of about 1,100 meters. This occurrence is local and proves thatthe sediments of Pedra Branca once extended much farther east.

The escarpment terminates in a narrow, southern extension calledSerra da Pedra Branca from which the name of the whole escarpmentis derived.

Having originated apparently by a series of faults, the escarpmentwas intensely eroded by the River Tibagy and its affluents, forming atthe present time various profound reentrants and ramifications toward the west, near the Serra do Francez, Puxa Nervo, and at otherplaces. One of these fau lts, c learly visible, can be observed 2 kilometers from the River Santa Rosa, near the road to Queimados. Itmay be traced 150 meters north and south, the east side having beendownthrown vert ical ly .

At some contacts of the Devonian shales with the sandstones ofthe escarpment, as in the Corrego de Sant'Anna, the shales are muchdisturbed and tilted, indicating clearly the action of the faults, despitethe fact that erosion has leveled their original scarps. Various faultsare exposed on the east flank of the Serra do Francez. On the innerescarpm ent of this hill the faults trend east and w est and have a sm all,but very clear, vertical displacement.

The Permian beds of the escarpment dip 6-8 W., passing undera high plain which has an aspect characteristic of the Gondwanaareas. In numerous water courses of this region, there are outcrops ofgrayish or yellowish sandstones with sporadic glacial boulders ofsandstone or quartzite and many outcrops of intrusive bodies.

In the Agua Clara zone, ab out 25 kilometers west of Tibag y, a conspicuous elevation known as Morumby extends plainly north andsouth, the uplift having a crest and flanks that are symmetrical and


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1228 VICTOR OPPENHEIMquite abrupt, and reaches an elevation of 1,300 meters (aneroid). Itgives the impression of being a well formed anticline. The elevation,however, is a southerly continuation of a series of laccoliths whichextend northwest and southeast across the region for more than100 kilometers, passing northwest of Queimados and west of Mon-jolinho as the Serra de Ferreirinha. Farther south the uplift takes thename of Serra do Facao, which with successive ranges dominates theregion.

The position and character of this laccolith uplift, as well as itsextension parallel with the escarpment of the Serra da Boa Esperanca,m ay indica te a zone of regional fractures in the G ondw ana, suggestinga possible relation to the origin of the basaltic trap effusions of theSerra Geral farther west, which must have originated from a succession of effusions through great fractures in the Basement complex,possibly of a type related to the described laccoliths.

The common north and south trend of the regional uplifts, bothof the Serra do Facao and the Ferreirinha on the one side, and of thefaults of the Serra das Furnas, Serra da Pedra Branca and Serrinha,on the other, may indicate old lines of regional weaknessesin thecase of the Serra do Facao, it indicates fractures filled by basalt for along distance parallel with the Serra Geral.

C O R R E L A T I O N O P D E V O N I A N A R E A O F P A R A N A , W I T H A R E A SO F A M A Z O N , M A T T O G R O S S O , G O Y A Z , U R U G U A Y ,

A N D P A R A G U A YThe great synclinal depression of the River Parana shows, in itsfour extremities, isolated outcrops of eo-Devonian rocks with Lepto-coelia flalelites.Having described the eastern area in the state of Parana, the writernow will sketch the known Devonian north, west, and south of the

basin. The areas of Goyaz, Paraguay, and Uruguay were discoveredrecently and as yet have not furnished the data necessary for a complete , comparat ive strat igraphical study. However , comparison andanalysis of the essential stratigra phica l and lithological cha racteristicsso far as known may help elucidate such important questions as thegenesis of the Parana Basin, as well as the character of the Devoniansedimentation in this large part of the continent.

LOWER AMAZON VALLEYFossiliferous Devonian rocks are known at longitude, approxi

mately 5i-59 W. (Greenwich) and lat i tude 5- io S. , where theyoccupy two narrow strips along the lower Amazon River. Th e northern


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DEVONIAN AREAS OF PARANA BASIN 1 2 2 9strip is continuous, trending plainly east and west, but the southernstr ip is in terrup ted by outcrops of other rocks, presum ably Devonian,in the valley of the Xingu River, in the headwaters of the UruaraRiver, and in the valley of the Tapajoz River. Devonian fossils wereencountered, however, only at Erere, northwest of Monte Alegre, andin the rivers Ma ecuru and C urua , north ern affluents of the A mazon.In all the other areas considered Devonian, fossils were not encountered and their classification as Devonian is based on lithologic andstratigraphic characteristics. The fauna of Erere, Maecurii, and Curua,all in the stat e of Amazo nas, was carefully s tudied by H ar tt, R ath bu n,Derby, Clarke, and Katzer .

Diverging from the other Devonian areas in the southern part ofthe continent, the Devonian of the Amazon reveals a faunal rangefrom early Devonian of clearly northern type to mid-Devonian.

The beds of the Maecurii, according to the previously mentionedauthors, especially Clarke, are of eo-Devonian age and are related tothe sandstones of Curua, which represent only one of the faunal faciesof Maecuru, that can be associated with the Helderberg and Oriskanyformations of New York.

According to Clarke, the sandstones of Erere are evidently of themid-Devonian age and can well be correlated with the Onondaga-Hamilton of New York. Classified by one as well acquainted with thesouthern Devonian fauna as Clarke, this sub-division hardly leavesany do ubt. H owever, F . Katz er, in his work on the geology of the Amazon expresses the opinion that there are no paleontological or strati-graphical differences between the beds of Maecuru and those of Erereand th at the two are of the same eo-Devon ian age. Clarke, in his work,"Fosseis devonianos do Parana," points out , with just ice, that thereis not sufficient proof for such deduction. Studies later than that date(1913), which would alter this conception, have not been made yetand, at present, Clarke's division and correlation of the strata generally are accepted.

DuToit, furthermore, shows that the beds of Erere are related notonly to the mid -Dev onian of the United State s, bu t hav e a faunalaffinity also with the beds of Sica-Sica, Bolivia, through forms likeTropidolephus carinatus and Homalonotus dekaye.Katzer, who considers the beds of Erere more fully developed than

those of the Maecuru, estimates that the regional dip of the upperbeds is discordant with that of the beds of the Maecuru, which dipsouthwest .In this area it is possible that the local dips of the sedimentary

rocks could have been produced by the many intrusive dikes. The


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1 2 3 0 VICTOR OPPENHEIMstratigraphic position and the faunal characteristics of the AmazonDevonian suggest a mid-Devonian marine transgression, which transplanted northern Devonian forms to the southern regions. They suggest also that faunal development continued after the transgression,when the southern regions had been isolated from the northern Devonian species, but the transgression extended rather in the direction ofBolivia and w as not general.

MATTO GROSSODevonian rocks are known in Matto Grosso, northeast of Cuyaba,

in a strip included between Sant'Anna da Chapada and Lagoinhas inthe direction of Diamantino. The area now known extends about250 kilometers northwest and southeast and its greatest width, southeast of Cuyaba, is 100 kilometers.This occurrence was first studied by 0. A. Derby, L. von Ammon,

and H. Smith and is known as the Series da Chapada and as the MattoGrosso series. It lies on metamorphic rocks and is composed of a basalconglomerate overlain by red sandstone, coarse near the base, thetotal thickness being about 500 meters, according to the observationsof Derby, Leme, and others. The red sandstones are covered byfossiliferous shale with sandy intercalationsapproximately 50meters thickwhich correspond stratigraphically with the PontaGrossa formation in Parana.

The fauna of the shale, studied by Clarke, shows an affinity withthat of Parana and, in a lesser degree, with that of eastern Bolivia.On the other hand, the presence of Phacops brasilensis, among thespecies of trilobites found, suggests faunal affinity with the northernDevonian and especially with that of the Amazon, which is explainedby the geographical position of the basin of the Chapada of MattoGrosso, midway between the Devonian of Amazonas and that ofParana. To this may be at tr ibuted the intercalat ions of northernDevonian species in a typically southern fauna and also the intermediate character of the sediments.

The basal sandstones of the series may be compared with the Furnas sandstone of Parana, but the degree of similarity is much lessthan that between the known equivalents of the Furnas that lie onthe east and south sides of the Pa ran a Basin.

GOYAZA small area with Devonian fossils (Dalmanites) was discovered

20 kilometers north of the city of Rio Bonito in the state of Goyasand m entioned by Baker .9 This locality, however, has not been studied9 C. L. Baker, Jour. Geol., Vol. 31 (1923), pp . 66-6g .


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DEVON IAN AREAS OF PARANA BASIN 1 2 3 1thoroughly and no further details are known. An exploratory trip tothat region, taken by A. Ericksen at the end of 1935, confirmed therather wide extent of the Devonian sediments.

URUGUAYThe area of the Devonian in Uruguay is a narrow strip south of thevalley of the River Negro, between Arrow Cordobas (east of the De

partment of Durazno, limited by Cerro Largo) and Carmen farthersouth. Characteristic Devonian fossils were discovered by E. TerraArrocena, in 1926, in a well at Rincon de Alonso.

In 1934, in a voyage of study to Uruguay, the writer recognized asDevonian the white, coarse sandstone of Carmen, which he considersabsolutely identical with the Furnas sandstone of Parana, alreadydescribed. More than 40 different species of Devonian fossils wererecently recognized in shale from a series of drillings in that area.The Devonian basin of Uruguay, as in Parana, Brazil, is surrounded by an area of metamorphic basement rocks, which borderthe sediments farther sou th. N orth of the area, drillings, as in J agua ryand Passo Boracho, proved that the Devonian area does not extendnorthward below the Gondwana beds, which lie here directly abovethe basement.

The fact, according to Terra Arrocena, that the Devonian does notlikewise occur in the boring at Rincon del Bonete, west of the strip,where, presumably Devonian beds might exist, is very significant andindicates that these sediments in Uruguay had an element of isolateddiscontinuous deposition.

The fossiliferous shales, like those of the subjacent Carmen sandstone, have a surprising similarity to the corresponding beds in thestate of Parana, Brazil, from which they can not be distinguished. Ina personal letter, of February, 1935, Terra Arrocena stated thatabove the Carm en sand stone he recently found shale with Orbiculoideaand Leptocoelia, which definitely proved the Devonian age of theCarmen sandstone.

In the drillings, the shale reaches a thickness of 150 meters, whichcorresponds with that of the Ponta Grossa formation. The Carmensandstone, in a well in this locality, is 100 meters thick between thetop of the sandstone and the metamorphic basement. Because oferosion, the original thickness of the sandstone possibly may havebeen greater, unless the outcrop lies at an edge of deposition.

The fauna of the shales not only permits their paleogeographiccorrelation with the eo-Devonian of Parana, Brazil, and other southern are as, bu t also, since it include s species of the mid -De von ian


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1 2 3 2 VICTOR 0PPENHE1M(Hamilton), it permits correlation with the Sica-Sica beds of Boliviaand the Erere beds of the Amazon Valley. Thus, in certain faunalaspects, the Devonian shales of Uruguay differ from the PontaGrossa formation in Parana and show a marine transgression of thelater mid-Devonian, which is known in Paragu ay b ut not in Para na.

However, the positive lithological resemblance of the sediments ofUruguay and those of Parana prove the identity of conditions of deposition in the two areas , althoug h greatly s eparated from each oth er.On the other han d, the faunal characteristics, som ewh at differentbetween th e D evonian of P arag uay and M at to Grosso and theDevonian of Uruguay and Parana, and the lithological divergenciesbetween the two former and the two later areas, show that they arenot a continuation of the same sedimentary horizon, but rather arearea s of more or less isolated d eposition , which could h ave been separated by a few uplifts.

PARAGUAYThe Devonian area in Paraguay was first known through a smallcollection of typical Devonian fossils, including, Leptoco elia flabelitesConrad , Calmonia subseciva Clarke, and Tentaculites crotalinus

Salter. These were described by Beder and Windhausen in 1918, whocollected them about 60 or 80 kilometers northeast of Assuncion, northof the River Piribebuy, in the Cerro Aparipi and near Arroyos yEsteros.

The northern limit of this patch of Devonian is not well known,but i ts area appears to be small . Far ther south, the Devonian areanarrows and disappears under extensive beds of sandstone and basaltof the Triassic Sao Bento series, which occupies southern Paraguay,where it l ies directly on the b asem ent roc ks; no interven ing Devon ianrocks have been observed up to the present time.

In the localities described by Beder and Windhausen, the Devonian series is formed by clay-shales, white, grayish or yellowish, withlayers of secondary limonitic rock and micaceous sandstone. Thethickness of the shale group is estimated at 20 meters. Superimposedon it appear beds of medium-grained sandstone, micaceous, and redin color. All the beds of the series are horizontal and probably exceed70 meters in thickness. Beder subdivides them into the Aparipi shalesand clays at the base, and the Arroyos y Esteros sandstone at the top.

The presence of Tropidoleptus carinatus Conrad, a characteristicfossil of the beds of Huamampampa of Bolivia, which the sandstonesof Arroyos y Esteros resemble in lithologic character, indicates themid-D evon ian age of the sedim ents. Hen ce, the horizon is higher th an ,


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DEVONIAN AREAS OF PARANA BASINand distinct from, the eo-Devo nian of Para na, about 700 kilometersfarther east.One can see, therefore, the relation of the Devonian of Paraguay,with its evident incursions of northern species such as Phacops brasil-ensis from Matto Grosso, to the Devonian of the Amazon, and to bedsof the same age in Bolivia, as shown by DuToit.All these sediments are not only paleonto'.ogically somewhat distinct, but also petrographically rather different from the Devoniansediments of Parana and all those east of the basin. It is surprising,however, to note the lithologic similarity, even to the smallest detail,of the Devonian sediments of Parana to those of Uruguay, theFalkland Islands, and South Africa, according to all published descriptions; although just on the other side of the Parana Basin, acrossthe relatively sho rt d istanc e of 700 kilomete rs, these lithologic analo gies almost disappear, leaving in their place, as in Paraguay, merelythe paleogeographical relations common to all the Devonian of thishemisphere.

GE NE T IC CONSIDE RAT IONSThe characteristics of the Devonian sediments of Parana, as wellas the correlation of the Devonian outcrops that surround the ParanaBasin and which were not all known at the time of Clarke's study, suggest a paleogeographical distribution somewhat different from thatinferred by some authors who believe that the beds extend beneath

the Gondwana rocks of the Parana Basin. As a matter of fact, aspreviously mentioned, there are certain faunal and lithologic differences between the D evonian outcrop s east and those west of the basin.The Parana Devonian, in spite of being geographically nearer toParaguay than to Uruguay, is, nevertheless, in lithologic characteridentical with the latter and very different from the former. Thesame lithological identity holds with the Devonian of the FalklandIslands, much farther south.On the oth er han d, sm all bu t very significant faunal differencessuggest that the sea which deposited the fossiliferous sediments of the

Ponta Grossa formation in Parana and Uruguay did not extend westward across the whole basin of the Parana. This epicontinental seawas shallow, since all the marine sediments of this part of SouthAmerica are rather thin and were deposited perhaps in great lagoonsof salt water, periodically connected with each other, but usuallyseparated by terrestrial elevations. Apparently, such elevated land didexist in the presen t area of the Par an a B asin, separating the Devo niansea of Matto Grosso and Paraguay from that of Parana. However,


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TABLE ICORRELATION OF DEVONIAN IN BRAZIL AND OTHER AREAS OF SOUTH AMERIC

M

LowerDevonian;

//otthfimeelca.

1 tda w>o id-p T>r-i aas3

aMH

Uo1W)u0)- a!HQJrH n t a G t " o s s aS o t m a U o n( s c a l e s o jVon ta- Grtfo^Sfta n d s a n o s t o n e $ ~ f i b a g y ) , v e yS o S S l U j W o U St f i l c H n e s s( S o m e t e r s

f u c n a s s a n o -s t o n e s ^ w W i t ea n< S c o a r s e( w i t V i o o t r5 j - o s s \ \ s )

f r t i c k n e s s S o m t f c t s

T o t a l t h i c k n e s s4 - oo m e t e r s

Stateofffatta CiTossa

f o s s i U ^ f e r o o ss h a l e s W i thS a n o y I n te r c a l a t i o n s

" r t i i c . U n e . s sS o m e t e sC o a r s e , c e oS a n d s t o n e sw i t h b a s a lC o r i Q ^ o M i e t -oXe.-S

" T h i c V M n e S s5 b o ( w 5 ? ) m e f c f i

Total


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DEVONIAN AREAS OF PARANA BASIN 1 2 3 5the indirect connection that permitted inter-migration of the characteristic species common to all the Devonian areas of America,might have been through Uruguay, thus surrounding the supposedland uplift in the present depression of Parana. This hypothesis confirms the formation of the basin of Parana in the epoch of intensediastrophism and Triassic effusions, which followed the epeirogenicsinking of the Basement complex which created the great graben ofthe Parana Basin . This tentat ive reconstruction, a l though hypothetical, nevertheless, explains the paleontological and lithological differences between the two Devonian areas relatively close to each other,east and west of the present basin.

An important factor in favor of the thesis of deposition of theParana Devonian in probably discontinuous lakes is found also in theresults of the various borings made north and west of the Devonian inUruguay. In most of the test wells basement rocks were encounteredimmediately below the Gondwana cap, thus confirming the interrupted deposition of the Devonian.

Concluding this at tempt to reconstruct the eo-Devonian paleo-geography of the Parana Basin, we must infer that there are manyelements indicating that the present basin of Parana probably was anelevated land at that time, possibly a continuation of present somewhat similar low uplifts in Minas Geraes and Goyas, and that thesesank during the Triassic diastrophism. Considering the preceding correlation of the new Devonian areas, one is not quite justified in supposing that the basin persisted as a synclinal depression from eo-Paleozoic to the present time. Proof of this idea would be aided bydrilling deep test wells west of the area of Devonian exposed inPa ran a .

As to the thickness of the De vonian sedim ents below the Gond wanarocks, the corre lation table g iven here show s th a t in none of theknown areas of this southern continent, do the Devonian sedimentsreach a thickness of 1,000 meters.

In the basin of the Parana, we can presume that the thicknessesare hardly greater than 500 meters, including both the fossiliferousshales at the top of the Devonian and the much thicker barren sandstones at the base. However, test borings west of the Rio Parana certainly would help solve many problems and be of great interest.

B I B L I O G R A P H YANDERSON, J. G. , "The Geology of the Falkland Islands," Wissenschraftl. ErgebnisseSchwed. Siidpolar-Expedition, 1901-1903 (Stockh olm), Vol. 3, No. 2 (1916).BEDER AND WINDHAUSEN, "Sobre la presencia del Dev6nico en la parte media de laRepubl ica de l Par agu ay," Bol. Acad. Nac. Ciencias de Cordoba, Vol. 23 (1918).BONAREIXI, G., "Terc era con tribuc i6n al conocim iento geologico de las regiones petrolif-


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