Almeida et al_1981_Brazilian Structural Provinces

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Earth-Science Reviews, 17 (1981) 1--29 1 
Elsevier Scientific Publishing Company, Amsterdam -- Printed in The Netherlands 
Brazilian Structural Provinces: An Introduction 
F.F.M. DE ALMEIDA l, y. HASUI 2, B.B. DE BRITO NEVES 3 and R.A. FUCK 4 
1 Instituto Oeoci~ncias, Universidade de SEo Paulo, S~o Paulo, SP (Brazil) 
2 Instituto Pesquisa Tecnoldgica de S~o Paulo, S~o Paulo, SP (Brazil) 
3 Dept. Geologia, Universidade Federal de Pernambuco, Recife, PE (Brazil) 
4 Dept. Geoci$ncias, Universidade de BraszTia, Brasilia, DF (Brazil) 
ABSTRACT 
De Almeida, F.F.M., Hasui, Y., De Brito Neves, B.B. and Fuck, R.A., 1981. Brazilian 
structural provinces: an introduction. Earth-Sci. Rev., 17: 1--29. 
The territory of Brazil coincides almost entirely with the South American Platform, 
the crystalline core of the continent. Its basement is composed of ancient metamorphic 
and igneous rocks and it has not suffered any tectonic regeneration since the beginning 
of the Phanerozoic. Sedimentary rocks with almost horizontal bedding cover this crystal- 
line basement. This latter shows ages as old as Early Precambrian, although ages between 
500 and 1000 m.y. are conspicuously frequent. The cratonic areas became consolidated 
more than 1700 m.y. ago, whereas the fold belts formed essentially between 500 and 
1700 m.y. ago. The sedimentary cover accumulated from the Early Silurian in three large 
intracratonic basins, until the platform became completely stabilized. A Late Jurassic to 
Early Cretaceous reactivation, caused by the break-up of the ancient Gondwana conti- 
nent, created another basin sequence chiefly along the Atlantic continental margin. 
Based on the nature of the crystalline basement rocks and the sedimentary cover, ten 
structural provinces can be distinguished: 
(1) Rio Branco Province, in the north of the country, occupied by the Guyana Shield 
and still only poorly known, with an important fold belt developed during the so-called 
Transamazonian Cycle (2000 ± 200 m.y.) with high-grade metamorphic rocks and only 
slight influence of later events. 
(2) Tapaj6s Province, in central Brazil, corresponding to the Amazonas or Guapor6 
Craton, showing chiefly Precambrian crystalline rocks and behaving as an cratonic area 
during the Phanerozoie. 
(3) Sffo Francisco Province, located on the Atlantic Shield, with its basement covered 
by rocks of different ages, chiefly affected by the Brasiliano Cycle (between 1000 and 
500 m.y.) and constituting another cratonic area. 
(4) Tocantins Province, between the Amazonas and S~'o Francisco Cratons, with the 
oldest rocks in its centre (ages over 2600 m.y.), and at the eastern and western borders 
metamorphic sequences of various fold belts, and almost no Phanerozoic deposits. 
(5) Mantiqueira Province, located along the southern part of the Atlantic coast, 
affected chiefly by the Brasiliano folding cycle. 
(6) Borborema Province, in the northeast Brazilian fold belt, affected by the Brasiliano 
Cycle in a very complex way, and with important faulted zones. It was reactivated in 
Phanerozoic times, when also sedimentary covers accumulated. 
(7) Amazonas Province, represented by the Amazonas sedimentary basin (syneclise), 
and subdivided into four parts by three important arcs. 
0012-8252/81/0000---0000/$ 07.25 © Elsevier Scientific Publishing Company 
(8) Parnaiba Province, coinciding with the P iau f - Maranh~b syneclise, and filled with 
a rather thick sedimentary sequence. 
(9) Paran~ Province, the sedimentary basin of southern Brazil, in which the well- 
known Late Paleozoic glaciation features are found, and which possesses an extensive 
cover of basaltic rocks of Late Jurassic to Early Cretaceous age. 
(10) Coastal Province and Continental Margin, the youngest structural unit, developed 
during the separation of the continent and represented by rift-valleys and coastal basins 
filled with Mesozoic---Cenozoic deposits of various kinds. 
GENERALITIES 
The complete Brazilian territory forms part of the South American Plat- 
form whose youngest geosynclinal foldings were consolidated at the beginning 
of the Phanerozoic. This basement, composed of metamorphic and igneous 
rocks, almost entirely of Precambrian age, crops out widely in the country. 
It occupies an area of about 4.6 × 106 km 2, subdivided in three large shields 
which extend into neighbouring countries: that of the Guyanas in the north, 
the Central Brazilian Shield inland south of the Amazon river, and the Atlan- 
tic Shield situated along the Atlantic border (Fig. 1). 
The sedimentary cover of the South American Platform accumulated from 
the Early Silurian on, chiefly filling three large sedimentary basins of syne- 
clise character: Amazonas, Piauf--Maranh~o and Paran~. Smaller areas of 
variously aged covers, including Precambriar~, occur scattered over the above- 
mentioned shields. 
Considering the nature of the exposed basement and its cover, it becomes 
possible to recognize structural provinces (Fig. 2). These are large areas 
which show features of stratigraphic, tectonic, metamorphic and magmatic 
evolution, different from those presented by the bordering provinces. 
The limits of these provinces as indicated on Fig. 2 are of two types: geo- 
logically defined and arbitrarily limited. Those of the first type include limits 
established following structural components of major size such as faults or 
fault zones, metamorphic fronts, rapid transitions of fold belts into their 
forelands, or erosional borders of large sedimentary basins. The conventional 
limits include those that are geologically undefined, either by the particular 
conditions of their structure, or due to lack of adequate knowledge, or 
because of being covered; they also include transitional limits with a certain 
degree of gradual passage from marginal folding zones into deformed plat- 
form covers. As the limit of the continental margin, the isobath of 2000 m 
which is almost entirely included in Brazilian territory, was adopted. 
In the tectonic evolution of the platform basement, two older areas are 
distinguished (cratons) which in times more recent than 1800 m.y. have no 
longer been subjected to the geosynclinal evolution. The largest of these is 
the Amazonian Craton, naturally subdivided into two provinces by the Area: 
zonas sedimentary basin. The northern province, included in the Guyana 
Shield, is called Rio Branco Province, the southern one, forming part of the 
1 000 km 
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Fig. 1. The major geotecton ic regions of South America. Legend: 1 = Andean Chain; 2 = 
Patagonian Platform; 3 = South American Platform: a, Phanerozoic covers; b Precambrian 
basement. I = Guyana Shield; H = Central Brazil ian Shield; III= Atlantic Shield. 
Central Brazilian Shield, is the Tapa]ds Province. The SEo Francisco Province, 
in the Atlantic Shield, coincides with another cratonic area of ancient con- 
solidation. 
The other three provinces of the basement have as a common character- 
istic the persistence of geosynclinal evolution up to the end of the Pre- 
cambrian, with final phenomena such as tectonic activity, uplift of mountain 
chains, molasse accumulation, subsequent volcanic plutonism, pegmatite 
formation, etc., already developed during the Cambro-Ordovician. Accord- 
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Fig. 2. The structura l provinces of Brazil. Legend: 1 = Rio Branco; 2 = Tapaj6s; 3 = S~'o 
Francisco; 4 = Tocant ins ; 5 = Mant iqueira; 6 = Borborema; 7 = Amazon ian ; 8 = Parna~a; 
9 = Paran~; 10 = CoastalProvince and Cont inenta l Margin. Dashed lines represent conven- 
t ional l imits of provinces. 
ing to their geographic situation and position in relation to the ancient 
cratons, one can distinguish, within the Central Brazilian Shield, the Tocan- 
tins Province and within the Atlantic Shield the Borborema and Mantiqueira 
Provinces. 
The three large sedimentary basins represent areas of persistent subsidence 
during the Phanerozoic, with a consequent accumulation of thick sedimentary 
sequences and basaltic rocks. They constitute other provinces named after 
the sedimentary basins proper: Amazonas, Parnaiba and Parand. Finally, 
the small sedimentary coastal basins and their submerged extension on the 
continental margin characterize the youngest of the Brazilian geological pro- 
vinces: the Coastal and Continental Margin Province. 
As thus defined, the provinces may be grouped according to the successive 
TABLE I 
Brazilian structural provinces 
Guyana 
Shield 
Central 
Brazilian 
Shield 
Atlantic Shield Sedimentary covers 
Cratons 
(consolidated at 
more than 
1700 m.y.) 
Fold belts, 
formed between 
1700 and 
500 m.y. 
Basins 
(syneclises) of 
Paleozoic age 
Basins of 
Mesozoic- 
Cenozoic age 
Rio Branco TapajSs 
Tocantins 
S~'o Francisco 
Borborema 
Mantiqueira 
Amazonas 
Parnaiba 
Paran~ 
Coastal and 
Continental Margin 
stages during the structural evolution of the country (Table I); they are 
characterized in their order of decreasing age. 
Although having distinct characteristics and histories, these ten provinces 
present many interdependent relations in their structural evolution. The 
TapajSs and S~o Francisco provinces constituted the forelands of the geo- 
synclines in which the fold belts developed, these latter characterizing the 
three younger basement provinces. Together with their forelands, these 
folded zones show evolutionary conditions comparable to miogeosynclines 
with evident tectonic transport towards them. The sedimentary sequences 
developed in these geosynclines are chronologically equivalent to the 
deposits covering the nearby cratons, so that one stratigraphical set may 
belong to two contiguous provinces. 
The sedimentary basins which characterize the Paran~ and Parnaiba Pro- 
vinces are neatly superimposed on these basement structures, which were 
the last to stabilise and from which their configuration inherited many 
structural trends. Only the Amazonas basin appeared during the Early Silu- 
rian, in a crustal area of very ancient consolidation. 
RIO BRANCO PROVINCE 
The Rio Branco Province (Fig. 3) is situated in a region almost entirely 
covered by a dense tropical forest. It is abundantly drained by large rivers 
and its low relief generally does not exceed 600 m. In spite of this, in the 
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Fig. 3. Rio Branco (1) and Tapaj6s (2) provinces. Legend: 1 = Lower and Middle Pre- 
cambrian undifferentiated complexes; 2 = Trans-Amazonian areas; 3 = Precambrian 
cratonic granites; 4 = sedimentary (b) and volcano-sedimentary (a) covers of Upper Pre- 
cambrian age; 5 = sedimentary covers related to the adjacent Brasiliano fold belt; 6 = 
Phanerozoic sedimentary covers. Heavy lines represent province boundaries; light discon- 
t inuous lines represent folding trends• 
mountains which limit it to the north, there exist heights of over 2000 m, 
e.g., the Neblina Peak {2992 m), the highest mountain on the South Ameri- 
can continent outside the Andes. Geologically the province is constituted 
chiefly of metamorphic and igneous rocks of Precambrian age, locally over- 
lain by thin post-Paleozoic covers. 
The Guyana Complex is exposed in the major part of the province, con- 
stituting the basement upon which the younger geological units lie in angu- 
lar unconformity. In its still poorly known structure there mainly participate 
different types of gneisses in amphibolitic to granulitic facies, migmatites, 
amphibolites and numerous intrusive rocks with predominance of granites 
I 
and granodiorites. Intense granitization and migmatization phenomena 
took place in this complex, even before the development of the Transama- 
zonian Cycle. 
The structures of the Guyana Complex display trends generally oriented 
in the northwest quadrant, with sinuosities towards E--W. The granulitic 
complex of Manuku, south of Guyana, with a supposed age of more than 
2600 m.y. extends into the area of the province. Also in the eastern part of 
Amap~i, probably very old granulitic rocks are abundant. It is supposed that 
the major part of the Guyana Complex is constituted of rocks with pre- 
Transamazonian ages; these were remobilized and isotopically rejuvenated 
during this cycle, as indicated by the radiometric ages determined. 
A significant fold belt developed in the large geosyncline of the Trans- 
amazonian Cycle (2000 + 200 m.y.) in the region north of the Rio Branco 
Province. Its ramifications extend chiefly into the eastern region where they 
constitute isolated strips of metasedimentary rocks oriented to the north- 
west and lying with angular unconformity upon the Guyana Complex. These 
strips contain schists, itabirites, quartzites, amphibolites and serpentinites, 
metamorphosed in greenschist to amphibolite facies. They are included in 
the Vila Nova Group which has in its gondites the proto-ore of an important 
lateritic manganese deposit. Radiometric age determinations indicate about 
2000 m.y. for the metamorphism of this group, it thus being attributed to 
the Transamazonian Cycle. Isolated occurrences of metasediments appear in 
the extreme north (Cauani Group) and west (Tuntff Group) of the province, 
also tentatively attributed to the same cycle. 
As a late stage in the evolution of the Transamazonian Fold Belt there 
took place extensive volcanic--plutonic phenomena of acid to intermediate 
character. The non-metamorphosed and lightly deformed rocks of the belt 
comprise the so-called Burumfi and Iricoum~ formations, both exposed at 
the northern border of the province. These rocks extend into the neighbour- 
ing countries, where they appear folded and somewhat metamorphosed. The 
age of this volcanism is about 1850 m.y. It was followed by the deposition 
of continental molasses of the end of the cycle, represented by the Roraima 
Group and by a thermal basic magmatism which formed numerous gabbro 
and dolerite sills and dykes. The age of these eruptive rocks, about 1800 
m.y., marks the end of the Transamazonian Cycle in the Guyana Shield. 
The time interval between 1800 and 1000 m.y. is distinguished in the Rio 
Branco Province by a series of proto-activation processes of the ancient 
craton. These processes produced an intense and diversified faulting, vol- 
canism and plutonism, as well as accumulation of detritic sediments in 
smaller local basins. The magmatic activity affected almost the whole pro- 
vince but was particularly intense in its eastern region, east of the Branco 
river and near to the Amazon Basin. It took place chiefly between 1450 and 
1750 m.y., producing outflows of rhyolites, rhyodacites, dacites, andesites 
and the respective pyroclastics, as well as associated sediments. Numerous 
intrusions of granites, some of rapakivi type, of granodiorites, diorites, gab- 
bros, syenites and alkali-syenites have been associated with this volcanism. 
Between about 1300 and 1100 m.y. another phase of proto-activation 
occurred in the province, manifested chiefly by intensive faulting, devel- 
opment of wide mylonite and cataclasite belts, local metamorphism and 
intrusion of alkali-syenites. This phenomenon, also known in the neigh- 
bouring countries, is known in Brazil as the Jari-Balsino Episode. 
During the Paleozoic the Guyana Shield seems to have passed through 
a longphase of stabilization, remaining emerged and acting as a distributive 
province for the sediments which accumulated in the Amazonas Basin in the 
south and in the Andean region in the west. During this long erosional pro- 
cess the youngest Precambrian cover became destroyed, but near the margins 
of the ~Amazonas Basin some remnants have been preserved, represented by 
undeformed continental detrital beds, which make up the Prosperanqa and 
Sete Quedas Formations existing between the Mapuera and Negro rivers. 
With the tectonic--magmatic reactivation suffered by the South American 
Platform during the Mesozoic, some of the ancient faults in the Guyana 
Shield were reactivated. The Takutu graben in Guyana, is the most expres- 
sive manifestation of this phenomenon in the shield. It has been filled by 
basaltic and andesitic lavas (Apoterf Formation) of Jurassic age, associated 
with continental sediments (Takutu Formation). This graben and its deposits 
extend up to the upper Branco river basin in the centre-north of the province. 
Also related to the Mesozoic reactivation in the Rio Branco Province are 
intrusions of alkali-syenites (Catrimani) and of diabases, the latter forming 
an important group of NNW-oriented dykes situated near the coast of 
Amap~ (Cassipord diabase). 
Tertiary and Quaternary detrital cover extends over an appreciable area of 
the western region of the province, near the major rivers as well as along the 
coast. 
TAPAJOS PROVINCE 
The TapajSs Province (Fig. 3) covers an area of about 1,670,000 km ~, 
corresponding to that part of the Amazonian Craton known as the Guapord 
Craton. Only in a rather reduced part are its Precambrian rocks covered by 
remnants of Phanerozoic deposits. The province presents a low relief, with 
altitudes generally not over 600 m. It is covered with a dense tropical forest 
which makes geological investigation quite difficult. 
The Xingu Complex, comprising the major part of the exposed Precam- 
brian rocks, is chiefly constituted of gneisses and migmatites of amphibolitic 
to granulitic facies in which there locally occurs amphibolites, quartzites, 
schists and other metasediments and metavolcanics as well as numerous 
intrusive bodies of granites, granodiorites and other igneous rocks. The domi- 
nating structural trends are directed generally in the northwest quadrant, but 
in the extreme west of the province some NNE--NE trends are present. 
The ages of the Xingu Complex rocks have not been definitely established. 
It is supposed that a great part were formed more than 2500 m.y. ago, as is 
suggested by a few isolated radiometric determinations; however, diverse 
later tectonic--thermic episodes have imprinted younger ages upon the rocks. 
Above all during the Transamazonian Cycle, the remobilization and isotopic 
rejuvenation phenomena of this basement were important, with many 
granites being formed. It is probable that part of the gneisses and migmatites 
of the complex have originated from the sediments and volcanic rocks of the 
Transamazonian Cycle. 
A fold belt with certainty belonging to this cycle occurs in the eastern 
region of the province. The constituting Gr~o Par~ Group is composed of 
quartzites, phyUites, micaschists, jaspilites, itabirites and basic metavol- 
canics. An important occurrence of banded iron ore (Serra dos Caraj~s) 
is associated with this group. The late molasses of this cycle are represented 
by the Rio Freco Formation, with known granitic plutons about 1850 m.y. 
old, in the same area, representing episodes of the end of the cycle. 
Between 1700 and 1450 m.y. almost the entire area of the Tapaj6s 
Province was affected by significant faulting, volcanism and plutonism of 
acid to intermediate nature, and sedimentation processes. The phenomena 
constitute the Par~ Event, homologous with that occurring at the same time 
in the Rio Branco Province. The volcanic rocks, attributed to the Uatum~ 
Group, are widely distributed through the province and are rhyolites, rhyo- 
dacites, andesites and equivalent pyroclastics. Numerous intrusions of com- 
monly alkalic cratonic granites, granodiorites, diorites, gabbros, syenites 
and diabase dykes are other magmatic manifestations of this event. Con- 
tinental and marine sedimentary rocks, sometimes associated with the vol- 
canic rocks, crop out in many places. Those belonging to the Beneficiente 
Group stand out due to their extent, in the centre-north of the province. 
The intense faulting conditioned the distribution of effusive and intrusive 
rocks as well as of the sedimentary basins and the deformation of their 
deposits. A few of these covers have been lightly metamorphosed during 
this event. 
Another tectonic--thermic event of proto-activation, called the Madeira 
Event, took place at about 1300--1100 m.y., especially in the centra and 
west of the province. Ancient faults then also became reactivated, sediment 
cover folded and metamorphosed, accompanied by a new phase of intrusion 
of cratonic granites and isotopic rejuvenation of ancient basement rocks. 
The intrusion of the alkali-syenite of Canama dates from this period. These 
processes of the Madeira Event correspond to those of the Jari-Falsino Event 
of the Rio Branco Province. 
The final proto-activation process of the Tapaj6s Province is the Ron- 
10 
dSnia Event, affecting the western area at 1000 m.y. It was also marked by 
faulting, cratonic granite and granodiorite intrusion, some with ring struc- 
tures, and extrusion of rhyolites, andesites, trachytes and basalts. Associated 
with this event there occurred an important tin mineralization. 
Probably less than 1000 m.y. ago detrital continental sedimentary cover 
(Prainha, Secunduri and Riozinho do Afrfzio formations) developed in sub- 
horizontal positions. These covers are correlative with the Prosperanqa and 
Seta Quedas covers of the Rio Branco Province, and to the Modoquena, 
Araras, Alto Paraguai and other groups of the eastern border of the TapajSs 
Province, representing extensions over the foreland of deposits from adjacent 
geosynclines of the Tocantins Province. The Jacadigo Group at this border, 
known for its important deposits of sedimentary iron and manganese ores, 
was possibly also deposited at the end of the Precambrian. 
During the Phanerozoic the province behaved as a shield, providing detri- 
tus to the sedimentary basins of the Amazonas and the Devonian sediments 
of the Andean region. Only along its borders neo-Cretaceous (part of the 
Parecfs Group) and Cenozoic deposits accumulated, with the manifestation 
of the Jurassic volcanism of the Serra de Tapirapu~. 
SAO FRANCISCO PROVINCE 
The S~o Francisco Province (Fig. 4) is a tableland in the inner part of 
which elevations attain between 500 and 1000 m and it is drained by the S~o 
Francisco river and directly to the ocean in its eastern part. North of that 
river the relief is table-form with altitudes not greater than 900 m, but in the 
east the tableland has a mountainous aspect with local elevations of nearly 
1800 m in the extreme south. The province is covered chiefly by a savannah 
vegetation. Structurally it differs greatly from the bordering provinces due to 
its role as a cratonic foreland of the geosynclinal fold belts developed in it 
at the end of the Precambrian. Its limits with these provinces are for a great 
part conventional because they developed in tectonic transition zones. 
The basement of the S~:o Francisco Province is for the greater part over- 
lain by cover of various ages, but where it is exposed there occur granitic-- 
gneissic complexes, greatly migmatized and with metamorphic facies varying 
from high-grade amphibolite to granulite. They have been dissected by 
numerous intrusions, principally of granitoid, but also of mafic to ultramafic 
nature. These complexes have radiometric ages of2600 m.y., apparently 
corresponding to the remobflization epoch of the basement, with extensive 
granitization and migmatization features during the so-called Jequi~ Event. 
These phenomena acted partly upon rocks older than 3100 m.y., locally 
identified in the east of the province. The sinuous structural trends of this 
basement are oriented about N--S in the east of the province where granu- 
litic rocks of various types are most abundant. In the central area, where the 
ancient basement became uncovered by the structures of the Serra do Espin- 
haqo, granitic--migmatitic complexes dominate, with trends oriented to the 
NNW parallel to the structures of this range. 
11 
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Fig. 4. Sgo Francisco Province. Legend: 1 = Lower and Middle Precambrian undi f feren- 
t iated complexes; 2 = Jacob ina belt ; 3 = Pre-Brasil iano sedimentary and metased imentary 
covers; 4 = sed imentary covers related to ne ighbour ing Brasil iano fold belts; 5 = molasse 
deposits; 6 = Phanerozoic sed imentary covers. Heavy lines represent major faults; l ight 
d iscont inuous lines represent folding trends. 
Supracrustal structures of limited extent, affected by the rheomorphic 
remobilization of the basement, locally cover the gneissic--migmatitic com- 
plexes. They are constituted by various types of metasediments, meta- 
volcanics and metamorphosed mafic and ultramafic intrusives in schist to 
12 
low-grade amphibolite facies. They have been interpreted as greenstone belts, 
but their age of older than 2600 m.y. has only been proven up to now for 
the Rio das Velhas Group in the extreme south of the province, that con- 
tains the largest gold mine in the country. The age of the Roquira Forma- 
tion, in the centre of the province, is still doubtful, but it is probably very 
old; it contains an important occurrence of lead. 
The Transamazonian geotectonic cycle (2000 + 200 m.y.) acted upon 
restricted parts of the province, developing fold belts, remnants of which are 
represented by the Jacobina Group and its possible extension (Contendas) in 
the State of Bahia, and by the Minas Supergroup of the extreme south of the 
province in the State of Minas Gerais. These belts are constituted of very 
thick sequences of metasediments of clastic and chemical origin, with meta- 
basitic intercalations, intensively folded and metamorphosed in a chiefly 
greenschist facies. The Minas Supergroup is famous because of its important 
mines of banded iron ore of the so-called Quadril~tero Ferrffero. During the 
Transamazonian Cycle intrusions occurred in various places in the province, 
principally of granitic rocks. 
The Serra do Espinha~o, situated in the centre of the province, in the 
State of Bahia, constitutes a zone of NNW-oriented folds, tectonized and 
metamorphosed in greenschist facies at about 1200 -+ 100 m.y. ago. This 
zone developed between 1700 and 1100 m.y. ago in a region where the base- 
ment is cut through by ancient and extensive faults, upon which a sequence 
of about 4000 m of sediment accumulated. This sedimentation does not 
characterize a geosynclinal environment, but rather a tectonically very active 
paraplatform with homologues in the Tapaj6s Province. Outside of the 
Espinhaqo fold belt, as is also the case in the latter province, the beds 
become gradually thinner, with the metamorphism disappearing, changing to 
the character of a tabular platform cover (Chapada Diamantina Group) 
deformations of which are of induced nature due to local movement of the 
basement faults. 
The upper stage of the Precambrian cover on the craton represents the 
extension upon it of the deposits accumulated in the geosynclines developed 
at its borders during the Brasiliano Cycle. In this cover remnants are recog- 
nized of a continental glaciation which took place at the end of the Pre- 
cambrian (Macafibas Group); the ample extension of pelitic and carbonatic 
sedimentation correlates with the pre-inversion limestones of the above geo- 
synclines as well as the remnants of the final molasses of this cycle. This 
cover, in part lightly metamorphosed, has been deformed in various areas 
either by reflex action of the tecto-genesis of the marginal folded zones or 
by the reactivation of basement faults in the inner part of the province. The 
Brasiliano co~;er complex developed between 1000 m.y. and the beginning 
of the Phanerozoic whenthe molasses accumulated. They are associated with 
important deposits of lead, zinc, sedimentary phosphates and carbonates. 
The Phanerozoic cover has been preserved on the craton, in Mesozoic 
coastal rift-valleys formed during the opening of the ocean, attaining thick- 
13 
nesses of thousands of meters, as in the RecSncavo graben in the State of 
Bahia. In the inner part of the province there subsist remainders of extensive 
but thin continental sediment cover of Late Cretaceous to Tertiary age as 
well as the Quaternary sedimentation of the river floodplains. 
TOCANTINS PROVINCE 
The Tocantins Province (Fig. 5) is situated between the Amazonian and 
S~o Francisco cratons and limited to the north and south, respectively, by 
the sedimentary basins of Parnaiba and Paran~. The province appears as a 
region chiefly covered by savannah, with local forests. Its relief is low with 
isolated ranges standing out, but it becomes elevated to about 1200 m above 
sea level in the centre of the State of Goi~s, in the so-called Planalto Central. 
The great lowlands of the Pantanal in Mato Grosso, and of the Araguaia in 
Goi~s belong to this province. 
Three structurally distinct regions can be recognized in the Tocantins 
Province: a central region corresponding in its major part to the median 
massif of Goi~s; an eastern one coinciding approximately with the Uruaqu 
and Brasflia fold belts; and a western region with the Paraquay--Araguaia 
fold belts. 
The oldest rocks of the province, with ages older than 2600 m.y., consti- 
tute the major part of the central region. They are chiefly various types of 
gneisses, including granulitic rocks locally migmatized and penetrated by 
granitoid rocks of various ages. In structural and possibly also lithological 
terms, two realms can be distinguished in the central region, separated at 
about the 16°S parallel by a deflection of the structures, called the Pirineus 
Megaflexure, which affected the youngest folded rocks as well as those of 
the older basement. South of this flexure NW--NNW-oriented structural 
directions dominate, whereas to the north they are more NNE--NE aligned. 
In the eastern part of the southern segment there occurs a large zone of 
granulitic rocks. All rocks of the province present the effects of polymeta- 
morphism, episodic fracturing of different ages and isotopic rejuvenation. 
Intrusive basic and ultrabasic rocks are common, they are locally mineralized 
with copper and nickel sulphides, and some of them are completely talcified 
and serpentinized. Ultramafic--alkalic massifs of Cretaceous age, with epi- 
genetic mineralization of nickel are known from Ipor~, Montes Claros de 
Goi~s and other localities. 
In the northern segment of the central region very ancient gneisses 
dominate, of granodioritic aspect and with diffuse foliation and generally 
without banding. In some areas such rocks constitute the basement for vol- 
cano-sedimentary sequences, represented by green rocks (chlorite-schists, 
talc-actinolite-schists and amphibolites) associated with ferruginous quart- 
zites, itabirites and schists. These sequences appear mineralized in gold, 
copper, talc and amphibolic asbestos. In the eastern part of the region there 
occur the great mafic--ultramafic complexes of Goian~sia--Barro Alto, 
14 
o km 
56 
44 
Fig. 5. Tocantins Province. Legend: 1 = Older basementreworked during the Upper Pre- 
cambrian (Goi~s Massif in the central region and part of the Guaxup4 Massif at the south- 
eastern corner); 2 = Uruaqu fold belt; 3 -- Brasiliano fold belts (Brasflia belt bordering 
the S~o Francisco Province, Paraguay--Araguaia belt bordering the Tapaj6s province); 
4 -- sedimentary covers related to the adjacent Brasiliano belts; 5 = Phanerozoic sedi- 
mentary covers. 
Niquel~ndia and Cana Brava, associated with granulites, the last two com- 
plexes being surrounded by younger metasedimentary rocks. These com- 
plexes have ages older than 3000 m.y. and show mineralizations of Ni, 
Cu and Co; in Cana Brava the principal Brazilian chrysolitic asbestos mine is 
found. Granulites have also been recognized southeast of Porto Nacional and 
15 
more to the east a belt of greenstones has recently been identified. 
The Uruaqu fold belt in the east of the Tocantins Province is still a poorly 
defined unit, extending from Natividade (Goi~s) to the region of Arax~ 
(Minas Gerais) from where it continues eastward. In Go i~ and also in Minas 
Gerais, the basement of the Uruaqu fold belt is composed of granulites, 
gneisses, amphibolites and calco~silicated rocks which constitute the Gua- 
xup~ Massif. This massif has a triangular form and separates the southern 
part of the fold belt in two branches, oriented NW and NE, the latter limited 
by a important transcurrent fault. 
The Uruaqu fold belt is constituted of pelitic and psammitic metasedi- 
ments as well as metabasites. Its folds are of holomorphic character, verging 
to the S~o Francisco Craton. North of the Pirineus Megaflexure the domina- 
ting directions of these folds are oriented between NNE and the meridian, 
whereas in the south they have a general NW direction. Generally it is sup- 
posed that these rocks belong to the Uruaquano Cycle, the chief metamor- 
phism of which should have occurred about 1000 m.y. ago, although some 
recent authors consider the possibility of these rocks being older and 
belonging to the Transamazonian Cycle. Granitic rocks are rare in this fold 
belt, occurring in brachyanticlines the granitic nuclei of which may contain 
cassiterite. 
The Brasflia fold belt, whose length is over 1100 km, developed at the 
western and southern flank of the S~o Francisco Craton during the Brasi- 
liano Cycle. The sedimentation, of miogeosynclinai character, started with a 
fine detritic sedimentation, followed by psammites and pelites with inter- 
calated limestones and dolomites. The folds of holomorphic type verge 
towards the craton; they have been metamorphosed in greenschist facies, 
both phenomena decreasing in the same direction. The magmatic activity 
related to the evolution of this fold belt is restricted to andesitic volcanism 
in the north of the belt, and to the intrusion of a few granite plutons in the 
south. Thrust faults are frequent, indicating a movement towards the craton 
border. A molassoid sedimentation, developed at the end of the cycle, covers 
the fold belt as well as the craton proper. Carbonate rocks, sedimentary 
phosphates, lead and zinc constitute its mineral resources. 
The Paraguay--Araguaia fold belt developed at the border of the Ama- 
zonian Craton, similarly to the relationship between the Brasflia belt and the 
S~o Francisco Craton. It shows an S-type curved form extending over 3200 
km. Its extremes are covered by the sediments of the Parnaiba and Paran~ 
basins. A great part of the fold belt is covered by modern sediments of the 
Araguaia Plain in which the large Bananal island is found, in Goi~s State, and 
the Mato Grosso Pantanal. In its southern part two phases of geosynclinal 
evolution can be distinguished, in the first of which when later folded and 
metamorphosed, flysch-type sediments were deposited. During the second 
phase a conglomerate was deposited, indicating a marine transgression, fol- 
lowed by a glacial-marine deposition and, in angular unconformity, an 
upper carbonatic unit with stromatolitic structures, capped by pelites. The 
16 
metamorphism is in greenschist facies and an intense holomorphic folding 
parallel to the axis of the belt, verges towards the Amazonian Craton. A few 
post-tectonic granitic plutons of about 500 m.y. age occur in the middle 
part of the belt. The last stratigraphic unit, possibly older than the intrusions, 
corresponds to molassic deposits that are partly continental and chiefly accu- 
mulated in a foredeep which extends from the fold belt over the craton 
border. In the region of Corumb,'i, State of Mato Grosso, there occur arkoses 
followed by a sequence of alternating beds of ferruginous jaspilite, compact 
hematite, thick-bedded cryptomelane and intercalated clastic sediments. 
Enormous reserves of iron and manganese ore occur in this Jacadigo Group, 
the age of which is still uncertain. 
In the northern part of the belt the basal sequence is composed of gneisses, 
schists and quartzites, with conformable and unconformable amphibolites. 
Then follows a series of terrigenous sediments, represented by phyllites, sub- 
ordinated quartzites and some limestone intercalations, capped by a mag- 
matic--sedimentary sequence, represented by chlorite-schists, talc-actinolite- 
schists and metabasites. There occur numerous unconformable bodies of 
mafic and ultramafic rocks changed into serpentinites and magnesian schists. 
This magmatism is related to the Tocantins--Araguaia geosuture, developed 
at the eastern limit of the Amazonian Craton. The metamorphism of the 
belt decreases rapidly from east to west, passing from an amphibolite facies 
into a greenschist facies, reducing to anchymetamorphic transformations 
near the border of the craton. Granitic rocks appear locally, in brachyanti- 
clinal nuclei surrounded by banded gneisses. 
The Phanerozoic sedimentation in the Tocantins Province remains limited 
to the filling of the Agua Bonita graben in Goi~s, with supposed Devonian 
beds, and to relicts of Cretaceous and Cenozoic continental covers, among 
which stand out those of the Pantanal of Mato Grosso (with thicknesses of 
up to 500 m) and of the Araguaia plain. Late Cretaceous alkalic magmatism, 
as well as intrusions of Early Cretaceous diabase dykes, occurred in various 
parts of the south of the province. 
MANTIQUEIRA PROVINCE 
The Mantiqueira Province (Fig. 6) is situated along the Atlantic coast 
south of latitude 15°S, extending to the frontier with Uruguay. It occupies 
an area of about 450,000 km 2, and is bordered at one side by the coastal 
basins and the continental margin and at the other side by the S~o Francisco, 
Tocantins and Paran~ Provinces. The Mantiqueira Province presents an 
almost entirely mountainous region, with altitudes higher than 1500 m in 
the coastal mountain range; the culminating point is the Pico da Bandeira 
which with its 2890 m constitutes the highest peak of the eastern part of the 
continent. 
In the northern part of the province is situated the southeastern fold belt, 
developed during the Brasiliano Cycle, and constituted by three fold systems 
17 
5 
3 4 
1 2 
""'":'":""."! ":" "1 
4 
-~2s 
3 
500 km 
Fig. 6. Mant iqueira Province. Legend: 1 -- Older basement reworked dur ing the Upper 
Precambr ian (a -- Pelotas Massif, b = Joinvil le Massif, c = part of the Guaxup~ Massif); 
2 = Brasil iano fold belts (A = Tijucas belt, B = Apiai belt, C = S~'o Roque belt, D = Ara- 
quaf belt) ; 3 = metased imentary area related to the Ara~uaf belt (Rio Pardo Group) ; 4 = 
molasse deposits; 5 -- Phanerozoic sed imentary covers. Heavy l ines represent major faults. 
separated by two median massifs with a general NE orientation. 
The fold systems have been formed by geosynclinal sequences which in 
the better studied areas exhibit a lower psammitic--pelitic sequence, with 
carbonate lenses nearthe top and an upper, chiefly pelitic, sequence of 
flysch-type character. These rocks have been metamorphosed into a green- 
schist and amphibolite facies under low P/T. In large areas they underwent 
migmatization processes• The folding was intense, polyphase and of linear 
type, with poorly evidence vergence. The pre-tectonic magmatism of mafic 
18 
nature is poorly developed, contrary to the syntectonic magmatism of acid 
nature represented by numerous stocks and batholiths dated at about 650 
m.y. There also exist post-tectonic intrusions, less frequently forming stocks 
and batholiths, dated at about 540 m.y. 
In the median massifs the pre-Brasiliano basement is exposed as nuclei 
with granulites, charnockites, mafic and ultramafic rocks, and migmatites of 
the Middle and Early Precambrian. 
Numerous small basins developed at the final evolution stage of the folded 
region. They are located within the fold systems and its margins and filled 
with molassic sediments and acid to intermediate lavas with thicknesses of 
over 5000 m. The older molasses have been folded, whereas the younger 
ones have only been tilted by faulting. The cited volcanic rocks and the 
associated granitoid plutons hav# been dated at 450--500 m.y. 
Bundles of thrust faults, chiefly longitudinal, divide the southeastern fold 
belt in sections. The faults seem to be ancient and deep, having passed 
through a phase of intense reactivation at the end of the Precambrian and 
the beginning of the Paleozoic when they affected the metamorphites and 
granites formed during the Brasiliano Cycle. 
The area between latitudes 23 ° and 24°S is characterized by a structure 
of faulted blocks where the Brasiliano structures curving towards N60E are 
replaced by the pre-Brasiliano ones situated more to the north. The limits of 
this transition are still not defined, due to absence of detailed investigations. 
The principal mineral resources of the southeastern fold belt are the vein 
deposits of Pb--Zn associated with limestones, Au and Cu in the molassic 
basins of the south of Brazil, W and Sn in gneisses, feldspars and lithium- 
bearing minerals of the pegmatites, Mn and Ti associated with the older 
rocks. 
During the Paleozoic, the Ponta Grossa and Rio Grande arcs developed at 
the borders of the Paran~ Basin, exercising their influence strongly on the 
modelling of the basin and the delimitation of the province. 
With the Mesozoic--Cenozoic reactivation of the South American Plat- 
form, there occurred the intrusion of a number of diabase dykes and the 
formation of many alkalic plugs, some with associated carbonatites, within 
the Ponta Grossa and Rio Grande arcs. Reactivation of ancient faults as well 
as newly formed ones permitted the development of a relief and the appear- 
ance of some small taphrogenic basins filled with Cenozoic fluvial and 
lacustrine sediments. 
In the north of the Mantiqueira Province is othe Ara~ual fold belt, devel- 
oped during the Brasiliano Cycle at the borders of the S~o Francisco Craton. 
Near this belt, north of 19°S, the structures have a NNE orientation, but 
near !5°S they turn to ESE after a strong inflection, reaching the coastal 
plain at the northern limit of the province. 
In the part with NNE orientation, the belt is constituted by geosynclinal 
pelitic to psefitic sediments, with associated limestones, itabirites and mafic 
volcanic rocks, composing the Macaubas Group. Pebbly greywackes exist in 
19 
this sequence that seem to be glacial-marine sediments correlated to the 
deposits of glacial origin found on the S~o Francisco Craton (Jequitai 
Formation). The sediments present a metamorphism varying from green- 
schist to amphibolite facies, with increasing intensity going away from the 
craton. Radiometric age determinations point to 600 m.y. for the meta- 
morphism and about 517 m.y. for the final granites. Holomorphic folds and 
large thrust faults affected these rocks, verging towards the craton. 
The northern part of the fold belt is still poorly known and the limits 
between the Mantiqueira and S~o Francisco Provinces are still not precise, 
except in the coastal area where they coincide with the Planalto fault. 
The rocks of amphibolitic facies of the Araquaf belt pass into the gneisses 
and migmatites, with associated schists, quartzites, gondites, calco-silicate 
rocks, marbles, charnockites and acid to basic granites, of older ages. The 
limit has not been fixed due to sparse research in the area. 
In the remainder of the Mantiqueira Province some lithostratigraphic units 
have been described whose mutual relations are still not explained. In its 
southern part units are recognized with metasediments of amphibolitic to 
granulitic facies, with an age of about 2000 m.y. (Paraiba, Amparo, Itan- 
homi groups, Juiz de Fora Formation) and attributed to the Paraiba do Sul 
fold belt developed during the Transamazonian Cycle. In the central-south- 
ern part gneisses are found with associated mafic and ultramafic rocks, with 
ages older than 2600 m.y. (Barbacena and Mantiqueira Formations), upon 
which the Paraiba Group should lie unconformably. 
The Brasiliano Cycle affected these units intensively, producing deforma- 
tion, blastic modifications, and intense migmatization and granitization. 
Thus pegmatites were formed which in the centre-north of the zone contain 
a district producing various types of gemstones. 
BORBOREMA PROVINCE 
The Borborema Province (Fig. 7) covers an area of about 380,000 km 2, 
coinciding with the Nordeste fold belt, developed during the Brasiliano 
Cycle. It is limited by the S~o Francisco and Parnaiba provinces as well as 
the coastal basins and continental margin. In the major part of its area it has 
a semi-arid climate with the development of large pediments. The residual 
erosion relief only rarely exceeds altitudes of 1000 m. 
The region of Brasiliano folds presents a complex arrangement, in mosaic, 
including different systems of linear folds mutually separated by elevated 
parts of the basement, either related to faults or not. 
The folding systems of Sergipe and Medio-Coreau are situated at the 
extreme southeast and northwest of the province, respectively. They have 
a marginal disposition in relation to the S~o Francisco and SXo Lufz cratons. 
In these systems similar sets of metasediments are present in which a level 
of carbonate rocks, thousands of meters thick, is intercalated within terri- 
genous clastics of various types. These sequences generally extend to the 
20 
5 
3 4 
o • 
8:1: 
. . . . :..-:~ 
I 
42 3 
1 2 ~ 
40 
36 
L 200 krn, 
Fig. 7. Borborema Prov ince. Legend: 1 -- Older basement reworked dur ing the Upper 
P recambr ian (a -- Pernambuco- -A lagoas Massif , b = Teixeira Massif , c -- R io P i ranhas 
Massif , d = TrSia Massif , e = Santa Quit~ria Massif) ; 2 = Brasi l iano fo ld belts (A = Sergipan 
bel t , w i th o = outer zone and i = inner zone , B = R iacho do Ponta l belt , C ~ P iancS- -A l to 
Brfgida belt , D = Pa je f i - -Para~a belt , E = Ser id5 belt , F = Jaguar ibe bel t , G = Curu- - 
Indep~nd~nc ia belt , H = M~dio Coreafi be l t ) ; 3 -- sed imentary covers correlat ive o f the 
Brasi l iano belts ; 4 = molasse depos i ts ; 5 = Phanerozo ic sed imentary covers. Heavy l ines 
represent ma jor faults. 
borders of the neighbouring cratonic nuclei, with decreasing thickness and 
degree of deformation. The holomorphic folds are arranged following the 
craton borders in relation to which they verge• 
The fold systems farther away from the ancient cratons are constituted of 
21 
psammitic--pelitic metasediments of at least two cycles, those of the younger 
one prograding in relation to those of the older cycle and of the basement 
highs. 
An intense holomorphicfolding exhibits vergences towards the inner 
massifs which are partially covered by geosynclinal deposits with attenuated 
deformations. The metamorphism is of plurifacial character, with facies 
variations of greenschist to amphibolite, under low P/T. Migmatization is 
frequent, chiefly in the basal terrigenous sequences. 
The pre-folding magmatism was of basic nature and not very intense. The 
syntectonic magmatism was extremely active, constituted of stocks and 
batholiths of granitoid rocks dated at about 650 m.y. The late tectonic grani- 
tic magmatism, the only one occurring in the marginal zones, took place 
about 540 m.y. ago. 
Molassic deposits accumulated in backdeeps and foredeeps associated with 
the marginal systems, extending even over the cratons with decreasing thick- 
ness and degree of deformation. The materials seem to have been deposited 
between 510 and 470 m.y. 
The basement highs constitute median massifs and geanticlines, exposing 
gneissic--migmatitic complexes of Early to Middle Precambrian age, remo- 
bilized during the Brasiliano Cycle. 
A complex fault system of large size divides the province into sections, 
separating the fold systems or cutting through them. These faults seem to be 
very old, deep and reactivated on different occasions, with variable character. 
The transcurrent character noted on the maps, is only the most obvious, 
having occurred late during the Brasiliano Cycle. The general trend of the 
province's structures is arranged as a fan opening towards the northeast, 
diagonally to the coast. It suffered deviations and inflections due to the 
faulting movements; two of these faults, the lineaments of Pernambuco and 
Patos or Paraiba, both with a W--E direction, stand out in this assemblage 
due to their size. 
The principal mineral deposits of the province are Be, Ta and Li associated 
with the pegmatites, W and Mo in scarns, Fe, magnesite, marble and graphite. 
There exist remnants of the Paleozoic and Mesozoic cover associated with 
various small taphrogenic basins, originated by reactivation of ancient faults. 
These sediments are relicts of formerly more extensive cover, bound to the 
primitive extent of the Parnaiba and RecSncavo--Tucano--Jatob~ basins. 
Cretaceous diabase dykes and Tertiary alkalic--basaltic volcanic products 
occur locally. Remains of thin Tertiary and Quaternary sedimentary covers 
lie upon erosion surfaces, escalated from the coast inland. 
AMAZONAS PROVINCE 
The Amazonas Province coincides with the great sedimentary basin which 
developed upon the Amazonian Craton during the Paleozoic (Fig. 8). It is an 
extensive low-lying region of about 1,250,000 km 2 , the relief only becoming 
22 
::i::.::....:.! ii : . • :'-. . ~ +oo 
:i:.!. i: :' :iil l 
: . .%" : . . . : - i . . " . . . ' . . : . . : 
::il 
20_ I 
y. , - . : ..... : .. . - . . . 
I P 30- - -.}.- 
Fig. 8. Amazonian (7), Parnafba (8) and Paran~ (9) Provinces. Countour lines represent 
the depth of the basement in ki lometers. Arches: A = Iquitos, B = Purus, C = Gurup~, D = 
Tocantins, E = Ferrer--Urbano Santos, F = S~o Francisco, G = Goi~nia, H = Asuncion, I = 
Ponta Grossa, J = Rio Grande. Basins: P = Acre, Q = Upper Amazon, R = Middle Amazon, 
S = Parnafba, T = Paran~. 
higher than 200 m in the extreme west of the province, near Peru. It is 
drained by the Amazon river, running in its axis, and covered by a dense 
tropical forest. The important Cenozoic continental sedimentation covers 
the Paleozoic structures which only crop out in narrow strips along the basin 
borders. 
The evolution of the Amazonas Basin during the Paleozoic has been 
largely affected by the presence of three transverse arched ridges, Iquitos 
in the west, Purus in the centre and Gurup~ in the east. The tectonic action 
of these arcs strongly conditioned many of the erosion and sedimentation 
23 
processes which took place in the basin, as well as subdividing it in four sub- 
basins: Acre in the west, Upper and Middle Amazonas, and Maraj6 or Lower 
Amazonas, this latter already belonging to the coastal province. 
The Paleozoic marine transgression in the Amazonas Basin started during 
the Early Silurian if not during the latest Ordovician. The detritic sedimen- 
tation took place in environments varying between tidal flats and neritic 
bottoms. A regression and again a transgression followed during the Devo- 
nian when the sea remained in the basin between the Emsian and Frasnian. 
The thick sequence of detrital sediments then accumulated, represents 
environments ranging between littoral and infraneritic, to even bathyal. A 
long hiatus followed until the sea returned once more to occupy the basin 
during the Late Carboniferous and deposited detritic sediments, limestones 
and evaporites (in this order), with a total thickness of 3000 m in the Middle 
Amazonas area. The neritic sedimentation environment points to a progres- 
sive closure of the basin, culminating in the accumulation of up to 1200 m 
of evaporites, with intercalated limestones and shales. Probably the action of 
the Gurup~ horst provoked this closure. 
Continental beds identified in wells seem to indicate a Permian sedimenta- 
tion in the area of greatest thicknesses of sediment in the Middle Amazonas 
basin. A great quantity of diabase dykes and sills, some of them attaining 
hundreds of meters in thickness, occur intercalated in the Paleozoic beds. 
This magmatism, that took place in more than one phase, developed between 
the end of the Carboniferous and the Early Jurassic, based on isotopic 
datings. The outflows which must have existed, have been eroded before the 
Tertiary. 
In the Middle Amazonas basin continental layers of Late Cretaceous age 
are also known. The accumulated sediments upon the craton border, near 
the Andean region of Peru, extended to the extreme west of the province 
where they became folded and faulted. 
The Cenozoic sedimentation, chiefly from the Tertiary, is completely con- 
tinental, covering the major part of the province. It may attain a thickness 
of about 1500 m, in the Upper Amazonas area. The Quaternary deposits 
remain limited to the low floodplains of the big rivers. 
PARNAIBA PROVINCE 
The Parnaiba Province (Fig. 8) is situated in the north of Brazil, with an 
area of about 650,000 km 2. It coincides chiefly with the sedimentary basin 
• of Piaui--Maranh~o, but in its northern part Precambrian basement rocks are 
locally exposed. The major part of the province has a tabular relief with con- 
centric cuestas, their altitudes generally not being higher than 600 m. 
The subsidence of the basin started in the Early Silurian or possibly during 
the Late Ordovician, after a long period of erosion of the basement rocks 
of the South American Platform. The basal sedimentation, of littoral and 
neritic origin, is composed of medium- to coarse-grained sandstones with 
24 
conglomeratic intercalations capped by fine sandstones, siltstones and shales 
attaining a thickness of 700 m. Shales follow, with sandstone intercalations 
resulting from the marine transgression of the Early Devonian. During the 
Middle Devonian there occurred a short regression phase marked by deltaic 
sandstones, followed by a wide transgression which, during the Late Devo- 
nian (Famennian), was responsible for the accumulation of a thick sequence 
of dark, frequently bituminous shales. Then there took place a regression of 
the sea, and during the Early Carboniferous the extent of the basin was 
reduced. The initially marine sedimentation became continental, with fluvial 
sandstones, sfltstones, lacustrine shales and thin coal beds. The clastic sedi- 
mentation continued during the Late Carboniferous, but near its top it con- 
tains fossiliferous limestone beds of a periodic ingression of the sea. In the 
Early Permian therefollows a continental sedimentation of sandstones, sili- 
cified limestones, siltstones with beds of oolitic chert, and gypsum. 
After these episodes the region was uplifted and underwent a long period 
of erosion and non-deposition, interrupted during the Late Triassic by a limnic 
sedimentation of silt- and claystones, with a few sandstones. Then the first 
sign of basaltic magmatism appeared, becoming quite important during the 
Late Jurassic and Early Cretaceous, and responsible for large outflows which 
cover eolian sandstones, indicative of a dry climate during that period. 
Numerous sills and dykes were introduced within the layers of the basin. 
In the north of the basin there follows, after the basaltic magmatism, a 
large and shallow Cretaceous sedimentary basin which probably continued 
towards the east of the province. The sedimentation in this basin started 
with eolian sandstones, capped by fine clastics with banks of limestone and 
gypsum, proving that a marine ingression took place during the Aptian. The 
Cretaceous sedimentation ended in the Albian, with the deposition of sand- 
stones, siltstones and shales from lacustrine, fluvial, estuarine and deltaic 
environments. These layers possess marine equivalents in the Barreirinhas 
coastal basin. 
During the Cenozoic the province suffered erosion such that the sediments 
of this time now only occur near the coast. 
At the northern border of the Parnaiba Province, there arose during the 
Early Cretaceous the so~alled Ferrer--Urbano Santos arc, with orientation 
parallel to the coast. The rupture of the northern flank of the ridge by suc- 
cessive normal faults was the origin of the coastal basins of graben type of 
Bragan~a, S~o Luiz, and Barreirinhas. 
The appearance of the Ferrer--Urbano Santos arc brought to the surface 
Precambrian structures which crop out in isolated spots through the Meso- 
zoic-Cenozoic cover. They permit the recognition of two geological and 
geochronological realms separated by a zone of cataclastic rocks in which 
penetrate intrusions of maflc to intermediate character, of Cretaceous age. 
This strip coincides with the axis of the above arc. North of it, gneisses and 
migmatites with structural trends oriented to the NW and intercepted by 
granitic bodies, show radiometric ages of more than 1600 m.y., and their 
~2 
25 
Fig. 9. Middle Northern region of Brazil. Legend: 1 --- Trans-Amazonian basement and 
covers; 2 -- Brasiliano belts (A -- Gurupi belt, B = M~dio Coreafi belt); 3 = sedimentary 
covers correlative of the Brasiliano belts; 4 = molasse deposits; 5 = Phanerozoic sedimen- 
tary covers. Heavy lines represent major faults; discontinuous line indicate the southern 
limit of the S~o Lugs Craton. 
cover of slightly deformed arkosic psammites is dated at about 900 m.y. The 
eastern outcrops, situated east of S~o Luiz to the State of Cear~, present 
Brasiliano K/Ar ages. South of the above strip, gneisses, quartzites and phyl- 
lites with orientations between NNW and N--8 also show Brasiliano ages, as 
obtained by various methods. 
It is supposed that the older structures present in this region form part of 
a primitive cratonic nucleus (S~o Luiz) which originally continued into the 
Craton of West Africa, with reworking during the Brasiliano Cycle (Fig. 9). 
The structural region situated south of the cataclastic zone must represent an 
extension of the Brasiliano folding systems of the neighbouring provinces. 
Gold is the principal mineral product of this area with Precambrian rocks. 
PARANA PROVINCE 
The Paran~ Province (Fig. 8) corresponds to the Paran~ sedimentary basin, 
one of the large syneclises which became implanted upon the South American 
Platform from the Silurian on. It is limited by the Tocantinas and Mantiqu- 
eira Provinces and presents between 29 ° and 30°S a projection reaching the 
Atlantic Ocean. The relief of the province is constituted by high-lying table- 
land and concentric cuestas, drained by the Uruguay and Paran~ rivers. At its 
higher eastern border the altitudes rarely surpass 1200 m, but do attain 1808 
m on the Igreja hill on the basaltic highland in Santa Catarina. 
26 
The form and size of the Paran~ Basin varied much during geological time, 
due to slow tectonic oscillations as indicated by the paleogeographical recon- 
structions. At present it occupies an area of about 1,200,000 km 2 in Brazil, 
extending into Paraguay, Uruguay and Argentina. The present basin con- 
figuration reflects some tectonic features which acted at its border in the 
Paleozoic and Mesozoic, such as the Goi~nia flexure and the arcs of Central 
Paraguay, Ponta Grossa and Rio Grande. 
The evolution of the basin during the Devonian shows an extensive marine 
transgression coming from the west. During the Carboniferous the marine 
ingressions become episodic, passing in the Permian to continental sedimen- 
tation which continued from then on. The oldest fossfliferous sediments 
dated in the Paran~ Basin are of Silurian age and are recognized in Paraguay; 
there is no proof that they extend into Brazil. In the Devonian, the sea 
remained in the basin between the Koblenzian and Frasnian, with the deposi- 
tion of initially coarse detrital sediments followed by black shales, attaining 
a total thickness of 1000 m. 
During the Late Carboniferous the basin accumulated an up to 1500 m 
thick continental sedimentary sequence, for the greater part resulting from 
five advances of inland ice. During interglacial phases three marine ingressions 
left lithological records in the Carboniferous column, also including post- 
glacial sediments. 
The Permian is represented by sedimentary rocks which attain thicknesses 
of 1700 m, deposited without interruption with the post-glacial Carboni- 
ferous units, under conditions of restricted waters passing gradually to 
fluvial. The pack is dominantly pelitic, reflecting a slow subsidence of the 
basin. 
From the end of the Paleozoic on, erosion processes became dominant; 
only one record of Late Triassic sediments is known from the south of Brazil, 
represented by about 200 m thick fluvial, fossiliferous sedimentary rocks. 
During the Late Jurassic the reactivation process of the South American 
Platform supervened. There occurred an extensive continental sedimentation 
covering an area of over 1,300,000 km 2 with eolian, locally fluvial and 
fluvio-lacustrine deposits which may attain a 400 m thickness. These sedi- 
ments have been covered by basalt outflows which also occur intercalated. 
The outflows may attain a total thickness of 1,529 m in the centre-north of 
the province, whereas the calculated volume exceeds 650,000 km 3. Together 
with this magmatism a large quantity of dykes was formed, some with thick- 
nesses of 100 m and lengths of tens of kilometers that are present chiefly at 
the eastern border of the basin and in the Mantiqueira Province. Sills up to 
200 m thick also occur intercalated in the sedimentary rocks. 
Accompanying the basaltic volcanism and following it during the Late 
Cretaceous, an alkali magmatism took place at various sites along the basin 
borders, originating numerous types of ultramafic, mafic and intermediate 
rocks, many of them still present within the province. 
During the Late Cretaceous fluvial sediments were deposited initially in 
27 
restricted areas, afterwards extending over the entire southern half of the 
province. These sediments possess thicknesses of not more than 300 m. 
In the Tertiary the coastal area was uplifted and a thin fluvial sedimenta- 
tion started to invade the province related to a drainage that was not very 
much different from the present one. 
In the whole province the beds are generally slightly dipping towards the 
inland. Local deformations have been observed, associated with faults or 
igneous intrusions. 
Themineral wealth of the Paran~ Province is associated with sedimentary 
rocks (coal, pyrobitumen and limestone) and to magmatics, chiefly those of 
alkalic affiliation. 
COASTAL PROVINCE AND CONTINENTAL MARGIN 
The youngest structural province considered here, developed from the 
Late Jurassic on at the ocean border, having contacts with almost all other 
provinces. 
The coastal plain is the physiographic feature of the emerged part of this 
province; it is a surface a few meters above sea level, composed of alluvial, 
transitional, and coastal marine deposits, locally remobilized by wind action. 
The plain is characteristically narrow and very elongated, even discontinuous 
at some sites. Its major expressions remain restricted to the Amazon river 
mouth {400 km) and some other river systems which supply Holocene deltas 
such as those of the Parnaiba, Jaguaribe, Sffo Francisco, Doce, Paraiba do Sul 
and other rivers. Generally the plain continues landward in the form of low 
tablelands until a few tens of meters above sea level, comprising Cretaceous 
and Tertiary continental and marine sediments which reach the crystalline 
rocks at the limit of the province. 
The Brazilian continental margin, the submerged part of the province, 
shows variable physiographic and sedimentary connotations visualized in 
three distinct segments. 
Along the northern coast, from Amap~ to Maranhffo, the shelf is up to 
200 km wide, rather shallow and with a very regular surface. The gradient 
and the relief of the slope vary greatly; the Amazon cone is the most impor- 
tant feature. The surface deposits are chiefly sandy. Off the coast of the 
eastern part of northeastern Brazil that shows a very irregular shelf surface 
followed by an abrupt break to the slope, the surface deposits are mainly 
bioclastic, the terrigenous sediments remaining restricted to the neighbour- 
hood of the river mouths. Off the coast between Bahia and Rio Grande do 
Sui the shelf always presents variable widths and depths, is rich in important 
physiographical features, and has an abrupt slope. From Rio de Janeiro 
southward the fine terrigenous deposits become dominant, with absence of 
carbonate sediments. 
In their distinct phases, the differences in the structural patterns of the 
crystalline basement and in the tectonic style of the evolution o f the Brazi- 
28 
lian continental margin, permit a separation into three parts in relation to 
the coastal basins formed during the process of continental break-up. 
The southern part started its evolution first, during the Late Jurassic. It 
presents a tension tectonic style with faults more or less parallel to the 
basement structures. The stratigraphical column of the then formed basins is 
the most complete, concerning the lithological record of the successive stages 
of the continental separation process. The northern part from Rio Grande do 
Norte to the Amazon presents identical tectonic style, with faults almost 
diagonal to the basement structures and a neo-Cretaceous superimposed 
compression style. Its evolution and lithostratigraphic record dated from the 
Albian on, with important deflections from the initial stages. The inter- 
mediate part of Pernambuco and Paraiba contains the last basin to be formed 
(during the Late Cretaceous) with structures perpendicular to the Precam- 
brian basement directions, marking the border of the so-called 'transverse 
zone'. It presents in relative terms a smaller subsidence, although the ten- 
sional tectonic style has been confirmed. 
The principal mineral resources of these basins are petroleum, gas, eva- 
porites, carbonate rocks and sedimentary phosphate. 
CONCLUSIONS 
With its almost continental size, Brazil possesses very diverse geological 
and geotectonical features, formed during different epochs of the earth's 
history. The best synthesis of these features is given by a division of the terri- 
tory into ten structural provinces. 
The provinces are based on the fundamental characteristics of their base- 
ment rocks and younger covers, including lithology, structure and age. 
Finally, also spatial distribution and geographical setting have been con- 
sidered, so that every province represents a natural geological region. At the 
present state of knowledge about Brazilian geology, the limits between these 
provinces are chiefly arbitrary. 
Three provinces -- Rio Branco, Tapaj6s and S~o Francisco - - inc lude 
ancient cratonic nuclei, composed of gneissic--migmatitic complexes, granu- 
lites and also greenstones, whose youngest folded belts show a Middle Pre- 
cambrian age. The Late Proterozoic cover occurs frequently in these cratons, 
presenting immature clastic and volcanogenic lithologies as well as disconti- 
nuous folding. 
The other basement provinces -- Tocantins, Borborema and Mantiqueira -- 
are located adjacent to the three cratonic ones; their lithological and struc- 
tural features were chiefly imposed during the Brasiliano Cycle (1000--500 
m.y.), with evidence of a Proterozoic geosynclinal evolution. Thick molassic 
covers of Cambro-Ordovician age testify to the end of this evolution. 
Another three provinces refer to sedimentary covers, present in three 
broad syneclises -- Parnalba, Paran~ and Amazon -- extending over hundreds 
of thousand of square kilometers, whose evolutive processes are chiefly 
29 
Paleozoic (post-Ordovician), showing some five thick cratonic sedimentary 
sequences with isopachs of up to 5000 m in the depositional centre. 
The youngest province is the Atlantic coast and continental margin, more 
than 8000 km long. The sedimentary sequences have accumulated in coastal 
grabens and half-grabens, as clastics and carbonates of Cretaceous and Ceno- 
zoic age, and they form the evidence for the successive stages during the pro- 
cess of continental break-up (rift) and beginning of continental drift. 
[Received September 4, 1980]