Bacias Intracratônicas - Geologia do Brasil 2

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Tectonic cycles and sedimentary sequences in 
the Brazilian intracratonic basins 
PAULO CESAR SOARES ] Departamento de Geocièncias, Universidade Estadual Paulista, Rio Claro, Sào Paulo, 
PAULO MILTON BARBOSA LAND IM J Brazil 
VICENTE JOSE FULFARO Instituto de Geocièncias, Universidade de Sào Paulo, Sào Paulo, Brazil 
ABSTRACT 
The geometry and petrology of sedimen-
tary rocks preserved in the three intra-
cratonic basins of the Brazilian craton 
(Paraná, Parnaiba, and Amazon) indicate 
the history and character of vertical move-
ments of the cratonic area. Cyclic succes-
sions of erosional and depositional events 
are synchronous on the Brazilian craton 
and are correlated with cratons of other 
continents. The principal evolut ionary 
stages of the Brazilian craton are inter-
preted as tectonic-sedimentary cycles, each 
represented by a stratigraphic record iden-
tified as a sequence, and each distinguished 
by its own special characteristics. 
Cambrian-Ordovician sedimentary rocks, 
representing deposition in paraplatform 
basins during a transitional stage at the 
close of the Brazilian orogenic cycle, are as-
signed to the Alpha sequence. The Beta 
(Ordovician and Silurian), Gamma (Devon-
ian-ear ly Carboniferous), and Delta (late 
Carboni fe rous-Late Permian sequences) 
and the Delta-A subsequence (Middle 
T r i a s s i c - J u r a s s i c ) , c o r r e s p o n d i n g to 
geotectonic cycles of the cratonic stabiliza-
tion stage, indicate accumulation in large 
subsiding basins. The succession of facies in 
each of these sequences documents cyclical 
changes in the ratio of sediment supply to 
subsidence. Marine transgression and basin 
subsidence increased progressively through 
the Devonian phase of the Gamma se-
quence and declined thereafter, in a pattern 
similar to that of the North American cra-
ton and the Russian platform. The fre-
quency of stratigraphic discordances in the 
three lower sequences suggests a higher de-
gree of cratonic upwarping, progressively 
diminishing to a stage of maximum stabili-
zation during Delta-A deposition, perhaps 
related to conditions immediately prior to 
rupture of the Gondwana plate. 
Breakup of the Gondwana plate, accom-
panied by volcanism and remobilization of 
cratonic areas, initiated the reactivation 
stage during which two geotectonic cycles 
are recognized. The first, represented by the 
Epsilon sequence (Cretaceous), began with 
local subsidence in isolated basins, followed 
by widespread continental sedimentation 
under platform conditions. The second 
reactivation cycle was responsible for ac-
cumulation of the Zeta sequence (Ceno-
zoic), which was characterized by thin re-
sidual deposits on an extensive Tertiary 
peneplain and by accumulations in Quater-
nary basins, the latter of minor importance 
except where adjacent to the uplifted east-
ern continental margin. 
INTRODUCTION 
In this paper the geological evolution of 
the Brazilian craton is investigated in terms 
of the major sedimentary and erosional 
events of Phanerozoic time. Vertical move-
ments, particularly those of cyclical charac-
ter, have been determined from amount of 
subsidence and rates of accumulation of 
sediments in the three intracratonic basins 
(Paraná, Parnaiba, and Amazon) of the 
Brazilian craton (Fig. 1). 
The question of cyclical evolution of 
cratonic areas of North America and the 
Russian platform have been considered by 
Sloss (1963,1964,1972) and by Ronov and 
others (1969), respectively. Sloss (1963) 
proposed that major stratigraphic succes-
sions separated by interregional uncon-
formities were identified as stratigraphic se-
quences recognized as the preserved record 
of cratonic subsidence and accompanying 
sedimentation followed by an episode of 
broad uplift and erosion. Wheeler (1958) 
expressed a similar concept in his definition 
of depositional holosomes. Gomes (1968), 
Almeida (1969), Ghignone (1972), and Ful-
faro and Landim (1976) studied deposi-
tional cycles in Brazilian intracratonic ba-
sins, subdividing the Phanerozoic succes-
sion into units designated as holostromes, 
s e q u e n c e s , o r s t a g e s (Fig . 2) w i t h 
similarities and differences that are dis-
cussed below. 
To evaluate the variations of cratonic 
tectonism we have used the following data 
and criteria: volume and thickness of sedi-
ment per time unit, area of preserved sedi-
ment representing successive stratigraphic 
units, episodes of transgression and regres-
sion, stratigraphic unconformities and their 
nature, and the preserved thickness of suc-
cessive stratigraphic units at basin depocen-
ters. These criteria permit a semiquantita-
tive evaluation of oscillatory movements of 
the Brazilian craton. Figures 3, 4, and 5 il-
lustrate the nature of the stratigraphic rec-
ord, amount of subsidence, and rate of 
subsidence for the three intracratonic ba-
sins. The age assignments for each strati-
graphic unit are according to biostrati-
graphic works of Lange (1967a, 1967b), 
Daemon and Quadros (1970), and Daemon 
and Contreiras (1971); absolute ages are 
from Kulp (1961) and Harland and others 
(1964). 
STAGES AND CYCLES OF 
TECTONIC-SEDIMENTARY 
EVOLUTION OF BRAZILIAN 
INTRACRATONIC BASINS 
The lithological associations and the un-
conformities, mentioned above, in the three 
interior basins document the variation of 
the depositional interface in relation to base 
level through Phanerozoic time. 
Episodes of subsidence in interior basins 
are characterized by an initial phase of con-
tinental sedimentation; the depositional in-
terface is below base level, but the rate of 
sediment supply compensates for subsi-
dence. With continuing subsidence at an ac-
celerated rate, the depositional interface 
passes below sea level to initiate marine 
sedimentation. The greater the ratio of 
subsidence to sediment supply, the deeper 
the depositional interface becomes, and vice 
versa. Thus, regression, continental sed-
imentation, deltaic progradation, or the ap-
pearance of areas of nondeposition or ero-
sion define events characterized by subsi-
dence rates that are less than the rate of sed-
iment accumulation, or by tectonic uplift. 
Figure 3 represents the geomorphological 
position of the depositional interface under 
these conditions (it does not necessarily ex-
press only oscillatory tectonic motions). In 
constructing the curves, consideration has 
been given to the entire history of each ba-
sin, including both aggradational and de-
gradational regimes. The nature of ob-
served stratigraphic discontinuities (from 
Geological Society of America Bulletin, v. 89, p. 1 8 1 - 1 9 1 , 9 figs., February 1978, Doc. no. 80203. 
181 
182 SO ARES AND OTHERS 
Figure 1. L o c a t i o n o f the three m a j o r Braz i l ian intracratonic b a s i n s a n d 
their b a s e m e n t s . 1, S e d i m e n t a r y c o v e r f r o m Precambr ian to H o l o c e n e ; 2 , 
m i d d l e P a l e o z o i c craton ic areas (structural trends); 3 , late Precambr ian 
cra ton ic areas: I , A m a z o n ; I I , S a o Franc isco; 4 , a p p r o x i m a t e b o u n d a r i e s o f 
in tracraton ic bas ins ; 5 , a p p r o x i m a t e b o u n d a r i e s o f craton ic areas in late 
Precambr ian t ime . 
NORTH 
AMERICA SOUTH AMERICA 
SLOSS 
1963 
GOMES 
1968 
ALMEIDA 
1969 
GHIGNONE 
1972 
FULFARO 
ndLANDIM 
1976 
SOARES et a l . 
THIS PAPER 
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n 
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0 
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I 
W - - E AM PB PR 
Figure 2 . S u b d iv i s i on o f Braz i l ian P h a n e r o z o i c s trat igraphie s u c c e s s i o n 
into s e q u e n c e s by several au thors , c o m p a r e d to N o r t h A m e r i c a n s e q u e n c e s 
of S loss ( 1 9 6 3 ) . 
quant i ty of materia l accumula ted and 
preserved in a chronostratigraphic unit is 
the record of tectonic movement in the ba-
sin, whereas the kind of material supplied 
to the basin is determined by tectonic activ-
ity in the source area. 
Examinat ion of the data given in Figures 
3, 4, and 5 leads to the following conclu-
sions: (1) The preserved stratigraphie rec-
ord of the Brazilian craton can be divided 
into six sequences — Alpha ( C a m b r i a n -
Early Ordovician) , Beta (Late Ordovi-
c i a n - S i l u r i a n ) , G a m m a (Ear ly Devo-
n i a n - E a r l y Carboni ferous) , Delta (late 
C a r b o n i f e r o u s - L a t e Permian or Early 
Triassic), Epsilon (Late Ju rass ic -La te Cre-
taceous), and Zeta (Tertiry). Strata dated as 
Middle Triassic to Late Jurassic are here 
provis ional ly identified as subsequence 
Delta-A (Piramboia, Botucatu, and Sam-
baiba Formations). (2) The six sequences 
correspond to tectonic cycles that were syn-
chronous in the three basins but whose 
dynamic evolution was different in each 
basin and different in each epoch of the 
same basin. (3) Two of the Brazilian se-
quences, Gamma and Delta, are represented 
by the most complete stratigraphie record 
and show the best development of tectonic 
cycles. (4) The Brazilian craton behaved dif-
ferently during Paleozoic time than during 
Mesozoic and Cenozoic time. 
diastem to angular unconformity) and of 
the depositional environment (from conti-
nental to abyssal marine) are interpreted 
f rom the sedimentary record in order to 
identify the amoun t of vertical motion 
characteristic of each basinal area during 
each cycle. 
Episodes of broad cratonic uplift corre-
spond to times of clastic supply to basin 
sedimentation and to times of erosion of 
previously accumulated deposits. The na-
ture of uplift at depositional sites is esti-
mated by the angularity of the unconfor-
mity separating adjacent sequences. Local 
and regional disconformities and angular 
unconformities were evaluated to suggest 
rate of uplift. Successions characterized by 
closely spaced diastems indicate that the 
rate of subsidence was approximately equal 
to or less than the rate of uplife of adjacent 
source areas. 
The curves of Figure 3 permit visualiza-
tion of successive events of subsidence and 
uplift in the three basins and thus delineate 
the tec tonic-sedimentary cycles on the 
Brazilian cra ton. The successive strati-
graphic sequences represent the sediments 
deposited in each cycle when basinal areas 
were below depositional base level. Figure 4 
shows the amount of subsidence at the de-
pocenter of each basin in each of the 
tectonic-sedimentary cycles. The curves 
show cumulative maximum thicknesses as a 
function of geologic time for each cycle; the 
slopes of the curves are functions of subsi-
dence rates. Subsidence ratios, shown in 
Figure 5, represent thicknesses per unit time 
for successive stratigraphic units at basin 
depocenters. Subsidence of broad regions is 
considered the fundamental control of the 
cumulative sedimentation and preservation 
of sediments in cratonic areas. Sea-level 
changes are modifying factors in environ-
mental conditions, but we cannot attr ibute 
to eustatic movement hundreds or thou-
sands of metres of continental or even 
cont inenta l -mar ine sediments. T h e vol-
umetric capacity for accumulation in a 
basin is determined by subsidence; there-
fore, the thickness of a chronostrat igraphic 
unit is a measure of minimum subsidence in 
the time span of its accumulation. Thus, the 
BRAZILIAN INTRACRATONIC BASINS 183 
A.U. 
L A U . 
D. 
Dt. 
S E Q U E N C E S 
A.U. 
L A U . 
D. 
Dt. 
A L P H A I B E T A G A M M A | D E L T A E P S I L O N Z E T A 
A.U. 
L A U . 
D. 
Dt. 
A - Amazon Basin 
[ } f ] / * -
C.S. 
CM. - V J \ l { l \ / ^ 
L . 
N. 
A , 
I I I I I 
A.U. 
LA.U. 
D. 
Dt 
B - P a r n a i b a Basin 
utcanlsm 
K 1» • V A / 
C.S. 
C.M. \ / \ j 
L . 
N: 
A , 
I I T I I 
A.U. 
L.A.U. 
0 . 
Dt. 
C - P a r a n d Basin 
\(\ ft < / I I A A ' C.S. 
C.M. \J \ 1 \ l \ / w - - -
L . 
N, 
A/ 
= vy ^ -
A.U.-Anqular unconformity L .A .U. -Low-ang le unconformi ty D. - Disconformi ty 
C.S.-Continental sandy L. - L i t t o r a l A. - Abyssal 
C.M.-Continental muddy N. -Ner i t i c D t . - D i o s t e m 
1 1 1 1 1 DM. Francisco 
61 m. y. 
1 I 1 1 1 
00 5 0 0 4 0 0 3 0 0 2 0 0 1 0 0 
C | o | s | D J D m | D u | C L | C U | P L | P M | P U | K W J U | K L | K U | T 
Figure 3 . G e o m o r p h o l o g i c a l e x p r e s s i o n o f osc i l la tory m o v e m e n t s in the three m a j o r Brazi l ian 
bas ins . 
Alpha Sequence 
The Alpha Sequence, including Cambrian 
to Ordovician strata, is little known in 
Brazil. Almeida (1969) considered the 
strata to mark the transition from the 
Brazilian orogenic cycle to platform condi-
tions. Basal sandstones and siltstones are 
succeeded by carbonate rocks, suggesting 
that stable conditions prevailed in Cam-
brian and Ordovician time in the Amazon 
region. Equiva len t depos i t s ind ica t ing 
cratonic sedimentation are not known in 
the Paraná and Parnaiba Basins. During 
Ordovician time the period of transition is 
represented by immature clastic and vol-
canic rocks (andesites and rhyolites) in in-
termontane depressions at the same time as 
the post-tectonic granitic intrusions (500 to 
540 m.y. ago) of the Ribeira orogenic belt 
(Melcher and others, 1973). The Alpha se-
quence represents the first Phanerozoic 
t ec ton ic - sed imenta ry cycle of c ra ton ic 
character on the Brazilian platform; it is 
correlative with the Sauk sequence of the 
Nor th American craton and the earliest par t 
of the Caledonian cycle of the Russian plat-
fo rm. Chrono log ica l ly , sequence 1 of 
Almeida (1969) and Ghignone (1972) cor-
responds to the Alpha sequence. Inasmuch 
as the strata described by these authors 
comprise deposits of a precratonic tran-
sitional stage, they are not included in our 
discussion, despite chronologic equivalence 
to the Alpha sequence. 
Beta Sequence 
The Beta sequence is well developed in 
the Amazon Basin, where a 900-m succes-
sion called the Trombetas Formation ac-
c u m u l a t e d . T h e s e c o n d t e c t o n i c -
sedimentary cycle began with slow regional 
subsidence, leading to the deposition of 
c o n t i n e n t a l a n d l a g o o n a l we l l - so r t ed 
sandstones and fine clastic rocks, succeeded 
by tidal-flat deposits related to an east-to-
west Silurian transgression. The beds in-
clude the Autas Mirim Member (Caputo 
and others, 1972) or lower Trombetas 
Formation (Ludwig, 1964). These basal de-
pos i t s are over la in by fine qua r t zose 
sandstones of an epineritic environment 
(Nhamundá Member) , recording a trans-
gression and culminating in infraneritic de-
posits of fine clastic rocks with beds of 
cher t , hemat i t e , and s ider i te (Pi tanga 
Member ; Lange, 1967a; Ludwig, 1964). 
The top of the sequences in the Amazon 
Basin is represented by sandstones and 
siltstones of the Manacapuru Member . 
In the Paraná Basin, the Beta sequence is 
represented by the Caacupé Group, which 
crops out only at the southwestern border 
of the basin, near the Asuncion arch. The 
strata represent a northeastward transgres-
sion over an early-subsiding par t of the 
Paraná Basin. Equivalent strata have not 
been penetrated by drilling in the basin in-
terior farther to the east. The Caacupé 
Group is composed of reddish sandstones 
with shale intercalations that include sev-
eral fossiliferous horizons. The dominant 
depositional environment was transitional 
from littoral to fluvial; transgressive epi-
sodes are indicated by sedimentary struc-
tures and sandstone textures (Bigarella and 
Comte, 1969) suggesting west-northwest 
current directions. These vector properties 
are the reverse of those indicated by Per-
mian strata. 
The Beta sequence is not present in the 
Parnaiba Basin, al though some authors 
have assigned a Silurian age to the Serra 
Grande Formation of theParnaiba Basin, 
correlating it with the Furnas Formation of 
the Paraná Basin. Other workers (Ghig-
none, 1972; Daemon and Quadros, 1970) 
have assigned a Devonian age to the Serra 
Grande Formation; these strata are con-
formably overlain by Devonian marine 
sedimentary deposits and may be consid-
ered to represent the initial phase of the 
third (Gamma) sedimentation cycle. 
The Beta sequence is Late Ordovician 
and Silurian in age. The basal 300 m of this 
s e q u e n c e in t he A m a z o n B a s i n , t h e 
Nhamunda and Autas-Mirim Members of 
the Trombetas Format ion (Caputo and 
others, 1972) are Late Ordovician in age. 
The overlying Pitanga M e m b e r , corre-
sponding to the median cycle phase of 
maximum subsidence (Lange, 1967a), is 
lower Lhandoverian (Early Silurian) in age. 
A similar time span is attributed to the 
Caacupé Group in Paraguay (Harrington, 
1956). 
The Beta sequence correlates with the 
184 SO ARES AND OTHERS 
Figure 4 . Subsidence amounts , determined from thickness of sediments accumulated in depocenter 
of basin in each sequence. 
Tippecanoe sequence of the Nor th Ameri-
can craton (Sloss, 1963), representing the 
second tectonic cycle of the Brazilian 
cratonic area; together with the Alpha se-
quence, the Beta sequence corresponds to 
the Caledonian cycle of Ronov and others 
(1969). Almeida (1969) and Ghignone 
(1972) included the Beta and G a m m a se-
quences in their sequence II, wherever suit-
able paleontologic data were available. 
There is an important hiatus between the 
top of the Beta sequence (Early Silurian) 
and the base of the G a m m a sequence 
(Maecuru Formation; Lange 1967a; Dae-
mon and Contreiras, 1971). The separation 
of the Beta and G a m m a sequences in the 
Parnaiba and Paraná Basins is complicated 
by the absence of paleontologic criteria in 
strata considered to form the Gamma se-
quence. 
In the central region of the Paraná Basin 
the Furnas Format ion appears to interfinger 
with the Ponta Grossa Formation, whereas 
minor unconformities are present at the 
contact between the two units on the east-
ern flank of the basin. An interfingering re-
lationship is also suggested by strata of 
Furnas type at the northwestern flank of the 
basin (Glaser, 1969). An unconformity 
separating Silurian and Devonian strata in 
the Amazon Basin (differentiating holo-
stromes l a and lb ) has been noted by 
Gomes (1968). 
Some au tho r s (for example , Aguiar , 
1971) have correlated the Serra Grande 
Formation to the Trombetas Formation, 
but such equivalence is not supported by 
lithologic or paleontologic evidence. Rath-
er, the two units represent different geologic 
events characterized by different records 
(fine clastic rocks rich in marine fossils in 
the Amazon Basin versus coarse continental 
clastics of the Parnaiba Basin). The correla-
tion of the Serra Grande and Maecuru 
Formations is corroborated by Messner and 
Wooldridge (1964) and Lange (1967a). 
G a m m a Sequence 
The G a m m a sequence represents the 
third Phanerozoic tectonic-sedimentary cy-
cle, which is the first to be well developed in 
all three Brazilian interior basins. Subsi-
dence of the Brazilian craton during this 
cycle is more pronounced than in the pre-
ceding cycles. 
In the Amazon Basin, more than 1,300 m 
of G a m m a sediments have accumulated, 
mainly fine clastics. The base of the se-
quence is marked by fine- to medium-
grained sandstones with shale and siltstone 
intercalations (Maecuru Formation, depos-
ited in epineritic to littoral environments 
(Jatapu Member) , transitional to infranerit-
ic condi t ions (Lontra M e m b e r ; Lange, 
1967a; Ludwig, 1964). The absence of 
continental sedimentation in this par t of the 
sequence suggests a region of low relief, 
only slightly above sea level, immediately 
preceding the Devonian transgression. The 
absence of coarse clastic deposits at the base 
of the sequence in the Amazon Basin 
suggests that the area did not undergo sig-
nificant uplift in the preceding erosional 
phase . The overlying Erere Fo rma t ion 
shows microfloral changes (Daemon and 
Contreiras, 1971), indicating a slight dim-
inution of the depth of the basin; a similar 
condition is reflected by reduction of the 
subsidence ratio (Fig. 2). This episode was 
followed by acceleration of subsidence and 
transgression, leading to deposition of a 
thick succession of fine clastic material 
(lower part of the Curua Formation), which 
includes zones in te rpre ted by Ludwig 
(1964) as turbidites (Curiri Member of 
Lange, 1967a), indicating deepening of the 
basin to abyssal depths. Regression began 
at the end of Devonian time; early Carbon-
iferous sedimentation was dominated by lit-
toral environments (Faro Member) and the 
deposition of thin coal seams in a succes-
sion dominated by sand. 
The Gamma sequence developed in a dif-
ferent manner in the Parnaiba Basin. Here, 
as in the Paraná Basin, the geologic history 
is distinct f rom that of the Amazon Basin. 
At the initiation of sedimentation of the 
third Phanerozoic tectonic-sedimentary cy-
cle, the Parnaiba basin received a large sup-
ply of coarse material derived f rom its east-
ern margin; the resulting accumulation is 
the Serra Grande Formation. This unit is 
characterized by thinning and by reduction 
in grain size f rom east to west (Messner and 
Wooldridge, 1964). Observations on the 
east flank of the basin indicate generally 
nor thwes t cur ren t direct ions, a l though 
southwest components occur in the basal 
par t of the unit (Bigarella and Salamuni, 
1967). The Serra Grande Formation consti-
tutes the first episode of sedimentation 
under platform conditions in the Parnaiba 
Basin area. 
The depositional phase represented by 
the Serra Grande Formation, characterized 
by immature sediments, wedge geometry, 
BRAZILIAN INTRACRATONIC BASINS 185 
S E Q U E N C E S 
A L P H A B E T A 1 G A M M A D E L T A E P S I L O N 1 Z E T A 
o -
10 -
2 0 -
». 3 0 -
4 0 -
5 0 -
6 0 -
i i i i \ t \ i J ^ \ / \ / v 
/ " \ / \ / v 
! / \ / 
1 1 1 / V 
1 1 " 
1 1 
A-Amazon Basin 
I I I I I 
0 -
10 -
2 0 -
3 0 -
E 
\ 4 0 -
E 
5 0 -
6 0 -
• ' \ / \ / \ i 
• A / \ / \ V A I 1 / S / \ / V / x 1 
| f \ 1 V V \ / 
1 / " \l 
1 / " 
1 / 
B-Parnaiba Basin 
I I I I I 
0 -
10 -
2 0 
>- 3 0 
E 
\ 4 0 -
E 
5 0 
6 0 
\ / 1 i > ! \ 
W \ a / ! 
\ l \ V \ I \ 
: V N 
v 1 1 
w • 
C-Parana' Basin 
| 1 | | 1 Oil. FroncUco 
6 m. y. 0 0 5 0 0 4 0 0 3 0 0 2 0 0 1 0 0 
1 € I 0 I S K J ° M K | C L I Cu |P |>MM k h k l K L T 
Figure 5 . Variat ion of subsidence rate through the cycles. N o t e reduction of subsidence rate at 
middle of cycle. 
and great thickness, is difficult to recon-
struct in paleogeographic and tectonic 
terms. The upper part of the Serra Grande 
Formation, in the sense of Messner and 
Wooldridge (1964), represents a distal 
facies deposited in a littoral environment 
(micaceous si l ts tones and b i tuminous 
shales). Progressive subsidence of the basin 
and reduction of the source area led to 
marine transgression and the deposition of 
a thick succession of fine clastics, the 
Pimenteiras Formation, in littoral to nerit-
ic environments (Andrade, 1972). In the 
middle of the Gamma cycle, the Parnaiba 
Basin returned to a condition of mobility, 
marked by the Cabecas Formation, a sandy 
facies of infraneritic and deltaic environ-
ments. Pebbly mudstones in the latter unit 
are considered to be turbidites (Ludwig, 
1964), following the interpretation applied 
to the Curuá Formation in the Amazon Ba-
sin. The easterly gradation of sandstones to 
shales, the restricted-circulation environ-
ments in the Pimenteiras Formation (Agu-
iar, 1971), and the presence of pebbles of 
metamorphic rock in the conglomerates 
suggest a reactivation of the source area, 
particularly on its eastern flank and, more 
locally, at the northwestern margin. 
Reorganization of the basin was followed 
by a phase of stability and recurrence of 
uniform subsidence, accompaniedby the es-
tablishment of homogeneous conditions of 
sedimentation represented by shales, silt-
stones, and mature sandstones of the Longá 
Formation (Upper Devonian). The record 
of the Gamma sequence closes in the Par-
naiba Basin with regression marked by 
quartzose sandstones, local intercalations 
of shales and conglomerates, and an upper 
unit of variegated purple siltstones and 
shales bearing thin calcareous beds (Poti 
Formation, lower Carboniferous) represent-
ing marshy, deltaic, and beach environ-
ments (Andrade, 1972). 
Development of the Gamma sequence in 
the Parnaiba Basin is similar to that of the 
Paraná Basin, where the record is less com-
plete, lacking part of the Upper Devonian 
and all of the lower Carboniferous. The 
Furnas Formation, the earliest deposits of 
the cycle, suggests the tectonic conditions of 
an intracratonic basin. As in the case of the 
Serra Grande Formation, thick conglom-
eratic sandstones of the Furnas Formation 
probably represent erosion and topographic 
reduction of uplifts developed in the Ribeira 
orogenic belt. As are the first platform sed-
iments, the sandstones are texturally imma-
ture (high angularity of grains and poor 
sorting) and are marked by high feldspar 
content. 
The lower part of the Furnas Formation, 
including almost all of the outcrops in the 
State of Paraná, represents continental dep-
osition of the initial subsidence phase, with 
highlands to the east and northeast, repre-
senting uplift of the Ribeira belt during the 
preceding transition stage. Progressive ex-
pansion of the area of subsidence led to 
onlap over regions close to the relict uplifts 
and to sedimentation under conditions of 
high energy release and unidirectional 
channel flows (see Appendix 3 in Bigarella 
and others, 1966). Poor sorting, small-scale 
planar cross-bedding, pebbles at the base of 
sedimentation units, and general lack of 
mud suggest fluvial sedimentation in anas-
tomosing channels. In higher parts of the 
unit, the sandstones exhibit better sorting, 
low-angle c ross -bedding , and w o r m -
burrows, which indicate littoral environ-
ments. Although there is evidence of a dis-
continuity between the Furnas Formation 
and the overlying Ponta Grossa Formation, 
in the interior of the basin the two units ap-
pear to be vertically and laterally intergra-
dational (Lange, 1967b). 
The Ponta Grossa Formation appears to 
represent the neritic facies of the Devonian 
transgression; deepening of the basin dur-
ing the first half of the cycle (Early Devo-
nian) is recorded in the mudstones, shales, 
and basal sandy intercalat ions of the 
Jaguariaiva Member (Lange and Petri, 
1967). Fine-grained sandstones intercalated 
with micaceous shale of the Tibagi Member 
(Early and Middle Devonian) represent a 
regressive phase, probably associated with 
an influx of coarse clastic material at the 
top of the unit. These clastics were re-
worked in littoral environments, forming 
conglomerate lenses of discoidal quartzite 
and quartz pebbles intercalated with silt-
stones and shales at the base of the Sao 
Domingos Member. Dark-gray, in some 
places bituminous, shales of this member 
represent a resumption of subsidence dur-
ing Middle to Late Devonian time. The re-
gressive deposits of this cycle in the Paraná 
Basin are not recorded; presumably they 
were removed during the succeeding ero-
sional episode. 
The Gamma sequence is Devonian and 
Mississippian in age, thus correlating with 
the Kaskaskia sequence of Sloss (1963) and 
with the lower Hercynian subcycle of the 
Russian platform. The sequence is equiva-
lent to holostrome l b of Gomes (1968) and 
to the upper part of sequence II of Almeida 
(1969) and Ghignone (1972), and with se-
quence I of Fulfaro and Landim (1976). 
Delta Sequence 
The Delta sequence, corresponding to the 
last Paleozoic tectonic-sedimentary cycle, is 
186 SO ARES AND OTHERS 
well developed in each of the three Brazilian 
interior basins and presents characteristic 
facies associations. 
In the Amazon Basin, the Delta sequence 
represents a dominantly chemical (nonter-
rigenous) sedimentation cycle, reflecting 
stabilization of the region or a very low rate 
of uplift in the surrounding areas. Sedimen-
tation began with a marine transgression 
f rom the west (late Carboniferous; Carozzi 
and others, 1972) and deposition of a thin 
succession of sandstones with thin interca-
lations of shale and carbonate rock (Monte 
Alegre Formation). These sediments reflect 
a littoral environment with only a small 
contribution of continental sedimentation. 
In the following phase, under continuing 
equilibrium between moderate subsidence 
and moderate sediment supply, tidal-flat 
environments prevailed. Low rates of sup-
ply of terrigenous material favored an ini-
tial dominance of carbonate sedimentation, 
passing to an evaporite domain (Itaituba 
Formation), marking reactivation of the 
Purus arch. An episode of sand deposition 
(lower Nova Olinda Formation) followed; 
this influx of clastic material produced a 
shallowing of the basin, while some areas, 
such as the upper Amazon River, subsided 
more rapidly and received a greater load of 
sediment (Carozzi and others, 1972), indi-
cating reorganization of basin f ramework. 
The second half of the cycle is marked by a 
reduction in the influx of terrigenous sedi-
ments, the imposition of a higher degree of 
restriction related to renewed upwarp, and 
progressive climatic aridity, leading to a 
dominance of evaporit ic sedimentat ion. 
However, in the middle of this phase, there 
appear intercalations of carbonate rock as-
sociated with fine clastic rock derived f rom 
west of the Purus arch, suggesting a deepen-
ing of basinal waters. At the close of the 
cycle (Late Permian), evaporitic sedimenta-
tion was progressively replaced, f rom the 
basin margins toward the interior, by fine 
clastic deposits, commonly reddish, with 
minor carbonate and anhydrite intercala-
tions; these redbeds of the Andira Forma-
tion are believed to represent lacustrine en-
vironments. 
The Delta sequence in the Amazon Basin 
is approximately 2 ,500 m thick. The low 
propor t ion of clastic rock, abou t one-
fourth, indicates lower rates of supply of 
detrital material f rom surrounding sources 
while the basin grew uniformly at high to 
moderate rates in the presence of shallow 
water and an arid climate. 
The Delta sequence in the Parnaiba Basin 
is dominated by continental clastic rocks, 
with significant carbonates and anhydrites 
in the middle. The base of the sequence is 
marked by reddish fluvial sandstones and 
conglomerates of the lower member of the 
Piaui Format ion (upper Carboniferous) . 
These beds are succeeded by a largely sandy 
sect ion, par t icu lar ly p r o m i n e n t in the 
southern par t of the basin, bearing interca-
lations of siltstones, shales, carbonates, and 
chert, locally containing marine fossils (An-
drade, 1972). Thicknesses as well as pro-
port ions of fine to coarse clastics and of 
chemical to clastic sediments are moder-
ately variable, as observed, for example, in 
Petrobrás wells VG-1R-MA and CL- l -MA. 
This complexly intercalated succession, the 
upper member of the Piaui Format ion 
(Lower to Middle Permian) reflects the 
deepening and slight differentiation of the 
basin. The Piaui Formation is overlain by 
the Pedra de Fogo Formation, consisting of 
intercalations of anhydrite, dolomite, and 
limestone. The carbonate rocks bear oolite 
and pisolites and appear to represent an in-
crease in water depths within the basin. 
Prevailing arid climates are responsible for 
anhydrite in thick beds and for intercala-
tions of fine reddish clastics, including 
fluvial-lacustrine sandstones (Motuca For-
mation) representing the basin-filling phase. 
The Delta sequence in the Paraná Basin is 
better documented because of an extensive 
outcrop belt on the eastern and southern 
flanks of the basin. Max imum thicknesses 
reach 2 ,550 m in the southwestern par tof 
Sao Paulo State. The cycle was charac-
terized by relatively high rates of subsidence 
and by glaciation during accumulation of 
the lower half of the sequence, leading to 
local periglacial sed imenta t ion and an 
influx of clastic material in the basin in-
terior. The first stage of the cycle is partially 
represented by conglomeratic sandstones, 
rhythmically bedded mudstones, and dia-
mictites of fluvial and lacustrine origin, plus 
tillites. This succession, particularly the 
lower par t of the ltararé Formation in Sao 
Paulo and Paraná States, is reddish brown 
(Tommasi , 1973 ; Soares and Land im, 
1973). Lacustrine, fluvial, and glacial de-
posits constitute an average of one-third of 
the ltararé Formation in outcrops at the 
eastern flank of the basin. The middle one-
third of the ltararé Formation is charac-
terized by pale-gray color and includes 
sandstones with thick intercalat ions of 
siltstones and shales, reflecting deepening of 
the basin and the initiation of marine trans-
gression f rom the southwest (Early Per-
mian). The Maf ra beds, the middle unit of 
the format ion in the sense of Tommasi 
(1973), includes marine strata. In Sao Paulo 
State, fine sandstones associated with the 
Monte Mor coal deposits represent a trans-
gression of littoral environments, which, at 
their maximum extent, are represented by 
silty sediments, in some places rhythmically 
bedded and bear ing s y n d e f o r m a t i o n a l 
structures, intercalated with well-sorted 
sandstones (Capivari beds). This unit in-
cludes intercalations of the thicker and 
more extensive bodies of diamictite. 
At the end of Early Permian time, uplift 
of the Ponta Grossa arch was accelerated, 
reaching a climax in Middle Permian time. 
During this epoch, in the embayment south 
of the Ponta Grossa uplift, rhythmically 
bedded siltstones (Passinho Shale) were de-
posited in epineritic and tidal-flat environ-
ments (Medeiros, 1973). Following this 
marine regression, fluvial and deltaic sedi-
ments of the base of the Rio Bonito Forma-
tion prograded over the marine beds, in 
some places with sharp contacts, as near 
Teixeira Soares and Sao Joáo do Tr iunfo in 
Paraná State (Ramos, 1967; Medeiros , 
1973). Across the Ponta Grossa arch, as can 
be observed in Petrobrás well 1-R-L-PR 
near Reserva in northern Paraná State, the 
fine clastic section of the upper ltararé is not 
developed. In this area, erosion affected 
earlier deposits. In the embayment to the 
north of the arch this phase is represented 
by immature micaceous fluvial sandstones 
at the base, as in Paraná State, exhibiting an 
abrupt contact with underlying rhythmites 
and fine littoral sandstones of the preceding 
phase. These beds, named the Tiete Forma-
tion by Barbosa and Almeida (1953) and 
Tiete facies by Soares (1972), represent the 
progradat ion of continental sedimentation 
and must be correlated with basal sand-
stones of the Rio Bonito Formation. Thus, 
both sides of the Ponta Grossa arch re-
sponded to similar states of basin evolution, 
marked by reorganization of intrabasin tec-
tonics, upwarping, and increase in the rate 
of sediment supply coupled with reduction 
of the basinal subsidence rates, leading to 
regression and progradational deposition. 
During this phase, a t the end of Middle 
Permian time, the northern par t of the basin 
was uplifted, creating conditions of non-
deposition and erosion and producing the 
unconformity at the succeeding Tatui For-
mation (Soares, 1972). Fluviodeltaic de-
posits of the lower sandy interval of the Rio 
Bonito Formation may be considered as a 
part of the l tararé Formation equivalent to 
the Tiete facies of Sao Paulo State, which 
also includes coal-bearing beds (Medeiros, 
1973). 
In Middle Permian time, regional subsi-
dence resumed, developing a nearly sym-
metrical sedimentary cycle. To the south of 
the Ponta Grossa arch, marine transgres-
sion reworked the basal parts of the Rio 
Bonito Formation to deposit a succession of 
siltstone, sandstone, and limestone in lit-
toral , epineritic, and tidal-flat environ-
ments, represented by the middle and upper 
p a r t s of t h e R i o B o n i t o F o r m a t i o n 
(Medeiros, 1973). N o r t h w a r d f rom the 
Ponta Grossa arch, this transgression de-
posited very fine grained purple sandstones 
and slightly calcareous sandy siltstones of 
suprat idal environments (Soares, 1972; 
Soares and Landim, 1973) over the erosion 
surface cut on l tararé strata. In the southern 
par t of the basin, the area of sedimentation 
progressively expanded as the rate of subsi-
dence increased, such that succeeding de-
posits onlapped across earlier strata. With 
c o n t i n u e d t r a n s g r e s s i o n , l i t t o r a l a n d 
epineritic sediments of the Paleromo For-
mation were deposited on the crystalline 
BRAZILIAN INTRACRATONIC BASINS 187 
basement of the basin margin, as in Rio 
Grande do Sul. T o the north, under condi-
tions of uniform and moderate subsidence, 
were developed littoral environments: in-
tertidal, beach, and lagoon. Progressive 
deepening of the basin f rom south to north 
reduced the rate of supply of detrital sedi-
ments and led to conditions of restricted 
c i r c u l a t i o n , r e p r e s e n t e d by s i l t s t one , 
b i tuminous black shale, and dolomit ic 
limestone of the Irati Formation, and by 
dark-gray muds tone of the Serra Alta 
Member . 
The second half of the Delta cycle was 
characterized by a southward increase in 
the rate of subsidence, accompanied by an 
increase in the rate of supply of detrital sed-
iments and uplift of the basin margins. En-
vironments dominated by tidal and suprati-
dal flats are represented by the Estrada 
Nova Formation. At the end of Permian 
time, the northern and southern flanks of 
the basin were uplifted and the central area 
of the basin continued to subside, receiving 
continental redbeds (Rio do Rasto Forma-
tion) of fluvio-lacustrine environments . 
These sediments may have been derived in 
part f rom reworking of sediments of the 
preceding phase. Red coloration of the 
upper part of the Estrada Nova Formation 
in Sao Paulo State (facies of Corumbatai 
type) are not to be confused with the red-
beds of the Rio do Rasto Formation. It is 
suggested that the red color below the pre-
Triassic unconformity is not necessarily re-
lated to depositional conditions. 
Tectonic behavior and physiographic ex-
pression were developed quite differently 
during this cycle in the Brazilian basins. The 
Amazon Basin was characterized by high 
rates of subsidence, low rates of uplift, re-
stricted environments, and an arid climate, 
in contrast to the Parnaiba Basin, with its 
low rates of subsidence and uplift, more 
open circulation conditions, and semiarid 
continental environments. At the same time 
in the Paraná Basin, glacial climates pre-
vailed at the beginning of the cycle, passing 
to humid climates in the middle, and to 
semiaridity at the close. The Paraná Basin 
A-Pornaibo Bosin 
600 
4 5 -
3 0 0 100 
4 0 "H 
35 
30 
25 
^ 20 -
io 
E 
* 15 
10 
5 
B-Parano Basin 
0». frond««« 
5Ò0 4Ò0 3 0 0 2 0 0 100 0 
€ I 0 I 5 N D M I D U I C L I C U I P L I P M I P U U L K k K I K L K l t I 
Sediment accumulation rate 
Accumulation mean rate during the cycle 
Figure 6 . Sediment accumulat ion rate and accumulat ion mean rate for Parnaiba and Parana Ba-
sins. 
exhibited the highest degree of tectonic ac-
tivity, matched by an equilibrium between 
the rate of supply of detrital sediment and 
the high rate of subsidence, thus maintain-
ing a relatively stable depositional interface 
at near—base level conditions. The rate of 
accumulation of sediment, 25 km3/ m.y., 
was greater than that achieved in other ba-
sins or in other cycles in the Paraná Basin. 
Accumulation rates were maximal at the 
Permian-Carboniferous boundary and dur-
ing Late Permian time (Figs. 6 , 7). 
The age of the base of the Delta sequence 
ranges f rom late Westphalian in the Ama-
zon Basinto Stephanian in the Parnaiba and 
Paraná Basins (Daemon and Contreiras, 
1971; Daemon and Quadros , 1970). Ero-
sion of the top of the Delta sequence makes 
it difficult t o define the end of the cycle; 
however, the Estrada Nova Formation is of 
Kazanian age (Late Permian), and it is 
probable that deposition of the Rio do 
R a s t o F o r m a t i o n ex t ended in to Early 
Triassic time. The Delta sequence correlates 
with par t of the the Absaroka sequence of 
the Nor th American craton and the upper 
subcycle of the Hercynian of the Russian 
pla t form. It also correlates with sequence II, 
of Gomes (1968), sequence III of Almeida 
(1969) and Ghignone (1972), and sequence 
II of Fulfaro and Landim (1976), excepting 
the Botucatu and Pirambóia Formations. 
Delta-A Subsequence 
In Triassic time, with the general uplift of 
cratonic areas and of orogenic belts of the 
Hercynian cycle, Paleozoic pa t te rns of 
tectonic evolution changed markedly. Some 
areas, such as the Nor th American craton 
and Russian platform, resumed cyclical pat-
terns, during Jurassic time, and other re-
gions, such as the Brazilian craton and the 
Siberian platform, developed a completely 
different behavior pattern. In Brazil, sed-
imentation was restricted to continental 
environments and lacked uniformity and 
periodicity. 
Triassic and Jurassic sedimentation in the 
Paraná Basin indicates a high degree of 
tectonic stability of the entire region. The 
Pirambóia Formation (Middle Triassic to 
Early Jurassic), for example, consists of 
fluvial sandstones marked by a high degree 
of textural and mineralogical maturity, and 
numerous diastems, suggesting a moderate 
supply rate of sediment combined with low 
rates of subsidence. Unlike the " n o r m a l " 
cycles of previous sequences, there are 
numerous upward-fining subcycles, with a 
general increase in mean grain size toward 
the top of the sequence (Soares, 1975). 
Locally the basal strata of the Botucatu 
Format ion (Jurassic) conta in a typical 
heavy-mineral suite of the Pirambóia For-
mation (Wu and Soares, 1974). Although 
the Botucatu Formation is texturally more 
mature and contains lower percentages of 
feldspar than the Pirambóia, its heavy-
188 SO ARES AND OTHERS 
mineral suite is similar to the underlying 
unit. The heavy minerals include grains of 
higher angularity than those of the Piram-
bóia , p lus a s ignif icant pe rcen tage of 
magnetite and ilmenite (Wu and Soares, 
1974), suggesting rapid accumulation and 
contemporary volcanism. 
These data indicate a slow, progressive 
rate of uplift of source areas during this 
stage of sedimentation in early Mesozoic 
time, a pat tern markedly different f rom 
those of the Paleozoic epeirogenic cycles. In 
the Paraná Basin, this phase culminated 
with an episode of intense volcanic activity 
and basinal subsidence. 
The Delta-A cycle closed with an episode 
of Late Jurassic and Early Cretaceous vol-
canism, represented by extensive flows that 
covered the area of Botucatu accumulation 
and probably extended across the source 
areas of Botucatu sediments. 
Early conditions in the cycle in the Par-
naiba Basin were similar to those of the 
Paraná Basin. Sandy fluviatile and eolian 
sedimentation, represented by the Sam-
baiba Formation, is overlain by basalts of 
the Mosqui to Formation of Jurassic or 
Jurassic-Cretaceous age (Cunha and Car-
neiro, 1972). Above the basalts, local de-
posits of polymictic conglomerates accumu-
lated, overlain by massive to cross-bedded 
sandstones with intercalations of lacustrine 
shales of Jurassic age (Corda and Pastos 
Bons Formations). 
Early Cre taceous basalt ic lava flows 
(Aguiar, 1971) occur locally above the 
Corda Formation. These strata, interbed-
ded with volcanic rocks, exhibit a variable 
geometry. Volcanism began earlier in the 
Parnaiba Basin than in the region of the 
P a r a n á Bas in , a n d the i n t r a v o l c a n i c 
C o r d a - P a s t o s Bons sedimentary deposits 
correlate with the prevolcanic Botucatu of 
the Paraná region. 
Triassic-Jurassic sedimentation is no t re-
corded in the Amazon Basin, only volcanic 
activity. 
W e provisionally consider the sandy 
Mesozoic deposits underlain by volcanic 
flows in the Paraná and Parnaiba Basins to 
constitute subsequence Delta-A. The basalts 
are additions to the lithological associations 
of normal sequences, but are not related to 
the cyclical evolution of the cratonic areas. 
The Delta-A subsequence, al though not 
representative of a typical epeirogenic cycle, 
has correlatives in both the Nor th American 
craton and the Russian platform. 
Epsilon Sequence 
Deposition of the Epsilon sequence fol-
lowed closely after the episode of volcanic 
activity at the close of Delta-A deposition. 
In the Parnaiba Basin, Epsilon sedimenta-
tion began in Early Jurassic time with dep-
osition of the basal conglomerates of the 
Pastos Bons and Corda Formations. Sed-
imentation in the first half of the cycle was 
interrupted by extrusion of the volcanic 
flows of the Sardinha Formation in Early 
Cretaceous time. Sedimentation in the sec-
ond half of this cycle began with deposition 
of the Grajaú sandstones under semiarid 
fluvial conditions, passing upward to gray 
shale, locally containing marine fossils near 
the north flank of the basin (Codó Forma-
tion), and ending with a fluvial redbed 
facies (ltapecuru Formation), which on-
lapped extensively across the cratonic in-
terior. 
In the Paraná Basin, the Epsilon sequence 
is r e p r e s e n t e d by eo l i an a n d f luvio-
lacustrine deposits of the nor thern basinal 
area. Deposition began, probably in Early 
Cretaceous time, with eolian sedimentation 
(Caiuá Formation), succeeded by flood-
plain deposition concurrent with uplift of 
the Canastra-Goiania arch and Serra do 
M a r , accompanied by alkalic volcanism. 
Such conditions significantly modified the 
character of sedimentation, creating over-
loaded, braided rivers in a semiarid climate 
(Bauru Formation). Coarse-grained sand-
stones overlapped earlier units at the basin 
margins and, in the vicinity of alkalic vol-
canism, developed facies characterized by 
major contributions of volcanogenic sedi-
ments (Uberaba facies). These sandstones of 
the Epsilon sequence are arkosic, with a de-
crease in mineralogical maturi ty both f rom 
older to younger units and from south to 
north. 
In the middle Amazon Basin, the Epsilon 
sequence is represented by 500 m of conti-
nental deposits ranging f rom Early to Late 
Cretaceous age and assigned to the Alter do 
Chào Formation (Daemon and Contreiras, 
1971). 
The Epsilon sequence reflects a new stage 
in the evolution of the Brazilian craton, a 
stage of reactivation (Wealdenian reactiva-
tion of Almeida, 1969). The evolutionary 
pat tern does not reflect a cyclical epei-
rogen i c m o d e l . It was c o n t r o l l e d by 
breakup of the Gondwana continent and 
the development of the South Atlantic rift 
(Estrella, 1972) and associated marginal 
basins. 
Sedimentation in this upper Mesozoic se-
quence in the interior of the continent was 
related to three pericratonic events or con-
ditions: (1) broad crustal upwarp of the rift 
region, increasing the rate of supply of sed-
iment to the slowly subsiding interior de-
pression, (2) development of open fissures, 
accompanied by the outpouring of tholeiitic 
lavas, and (3) increasing upwarp of interior 
arches (Canastra-Goiania and Tocantins), 
followed by extrusion of alkalic magma. 
The Epsilon sequence reflects differential 
movements, faulting, tilting of blocks, and 
basaltic to alkalic volcanism in the cratonic 
interior. This sequence corresponds to the 
Zuni sequence of the Nor th American cra-
ton (Sloss, 1963), which also exhibits 
marked differences f rom Paleozoic cycles. 
Zeta Sequence 
The Zeta sequence includes thin Tertiary 
deposits, covering the broad Sul Americana 
peneplana t ion surface defined by King 
RUSSIAN PLATFORM WESTERN CANADA BRAZIL BRAZIL ".'AFRICANORTH AMERICA 
— R e g r e s s i o n b a s e level 
Figure 8 . C o r r e l a t i o n a m o n g s e q u e n c e s a n d osc i l la tory m o v e m e n t s in N o r t h A m e r i c a n , Braz i l ian , 
eastern E u r o p e a n , and A f r i c a n cratons . In A , B , a n d C , corre la t ions are b a s e d o n preserved s e d i m e n -
tary depos i t s a n d in D , E, a n d F o n base- level relative m o v e m e n t s . 
190 SO ARES AND OTHERS 
(1956). These deposits are characterized by 
fluvial dark-red sediments with conglom-
erate and sands tones (conta in ing dia-
monds). Quaternary erosion (the Velhas 
and Paraguassu erosive cycles of King, 1956) 
reduced the region covered by these sedi-
ments to local areas: the Cachoeir inha 
Formation and its correlates in the Paraná 
Basin and the Nova Iorque beds in Mar-
anháo State. 
Majo r evidence of the cycle is in the 
Amazon Basin, where deposits, named the 
Cruzei ro Fo rma t ion , reach an average 
thickness of 500 m, increasing to the west 
(Daemon and Contreiras, 1971). Condi-
tions of sedimentation were associated with 
the upwarp of the Andes, which produced a 
wedge-shaped body of clastics derived f rom 
sources external to the craton. In northern, 
northeastern, and eastern marginal regions 
of the craton, correlative fluvial, deltaic, 
and marine sediments reflect a broad subsi-
dence and transgression of the continent 
during the Zeta cycle. 
The Zeta sequence reflects emergence of 
the Brazilian subcontinent during Cenozoic 
time. The sequence correlates with the Tejas 
sequence of Sloss (1963) and corresponds 
to sequence VI of Ghignone (1972). 
C O N C L U S I O N S 
As demonst ra ted by the stratigraphic 
record in three Brazilian intracratonic ba-
sins — Paraná, Parnaiba, and Amazon — 
the evolution of the interiors of cratonic 
continental plates was conditioned by dif-
ferentiation into regions of cumulative sub-
sidence and sedimentation (basins) and re-
g i o n s of u p l i f t a n d s e d i m e n t s u p p l y 
(arches). Phanerozoic evolut ion of the 
Brazilian basins was cyclical and divisible 
into craton-wide synchronous events of 
erosion and sedimentation (Fig. 8). 
Each sequence constitutes the record of a 
tectonic cycle characterized by (1) regional 
cratonic subsidence, (2) reduction of areas 
undergoing erosion with a minimum supply 
of terrigenous clastic sediments, and (3) 
broad uplift and reduction of areas of 
s e d i m e n t a t i o n . T h e g e o l o g i c r e c o r d 
preserved in the basins can be divided into 
six major sequences: Alpha, Beta, Gamma, 
Delta, Epsilon, and Zeta, with one subse-
quence, Delta-A, corresponding to a cycle 
expressed differently and nonsystematically 
in each of the three basins. 
The Alpha sequence, comparising Cam-
brian to Ordovician deposits, is preserved 
only in some areas, such as the Amazon 
Basin. In other areas, the time of deposition 
of the Alpha sequence was marked by tran-
sition f rom geosynclinal to platform condi-
tions. The Beta sequence, consisting of 
sedimentary deposits of Ordovician and 
Silurian age, is confined to the Amazon Ba-
sin. It also marks the beginning of cratonic 
sedimentation in the areas of the Paraná 
and Parna iba Basins. The G a m m a se-
quence, Devonian to lower Carboniferous, 
represents the first well-defined cycle doc-
umented in all three Brazil ian basins. 
Cratonic subsidence was more pronounced 
than in the preceding cycles. The Delta se-
quence, late Carboniferous to Late Per-
mian, is characterized by the closest ap-
proach to a complete epeirogenic cycle, 
(Sloss, 1964). The Delta-A subsequence, 
Middle Triassic to Jurassic, appears to be 
linked to the process of crustal upwarping 
and volcanism that immediately preceded 
the rupture of the Gondwana plate. The 
Cretaceous Epsilon sequence is charac-
terized by general cratonic subsidence, ini-
tially in isolated basins and later as a broad 
stable pla t form of continental sedimenta-
tion. The sequence reflects rifting of the 
South Atlantic. The Tertiary Zeta sequence 
is poorly developed, comprising residual 
deposits associated with an extensive Ter-
tiary peneplain, and is preserved in small 
Quaternary r e l i a basins of slight subsi-
dence. 
During Paleozoic time, the Brazilian ba-
sins evolved according to an epeirogenic 
cycle, similar to that observed by Sloss 
(1964) in the Nor th American craton. His 
model for an epeirogenic sequence is 
characterized by five lithologic associations 
that represent five phases in the develop-
ment of each epeirogenic cycle. We have at-
tempted here to establish a model that in-
cludes the observation of the tectonic be-
havior of Brazilian basins, based on the var-
iation of subsidence rates (Fig. 5), their 
stratigraphic record (Fig. 9), and the ex-
pansion of areas of sedimentation (Fig. 7). 
W e have identified five phases in the 
Paleozoic cycles, each phase being repre-
sented in the stratigraphic record by a par-
ticular association of facies and each repre-
senting the sedimentary response of a given 
basin to a particular tectonic state. The five 
phases of epeirogenic cycles that we have 
identified can be characterized as follows 
(Fig.9): (1) initiation of basin subsidence, 
rapid expansion of the area of continental 
deposition, sandy sediments, sometimes in-
cluding pebbly fluvial and piedmont facies, 
overlain by fine clastics including coal pyri-
tic shales of lacustrine and marshy facies; 
closely spaced diastems; (2) acceleration of 
basin subsidence, with the rate of sediment 
supply lower than the rate of subsidence; 
deepening of the basin accompanied by 
transgression; initiation of marked differ-
entiation of the rate of subsidence of basinal 
and peripheral areas; littoral sandstones; 
euxinic shales; basinal carbonates and 
evaporites; establishment of well-defined 
lithologic facies belts; (3) reorganization of 
basin tectonic patterns; renewed uplift of 
marginal areas; development of basin-
interior uplifts and local sub-basins accom-
panied by partial regressions, with local 
progradat ion; overall reduction of subsi-
dence rate; small deltas; intraformational 
conglomerates; local disconformities; (4) 
cessation of intrabasin differential move-
ments; renewed acceleration of basin subsi-
dence; maximal trangression accompanied 
by achievement of max imum depth of 
water in the basin interior; fine clastic, car-
bonate, and evaporite deposits; and (5) 
cessa t ion of bas in subs idence ; b r o a d 
cratonic uplift; basin filling by fine to coarse 
clastic material, with upward transition 
Figure 9 . Stratigraphic 
record of Paleozoic cycles 
and respective phases. 
BASINS 
O 
M 
<X 
m 
ce 
2 
<t 
CE 
£ 
- O L 
ALPHA 
_5_ 
_ 4 _ 
3 
2 
1 
5 
4 
? 
A C A R I ' 
MANACAPURU 
1 PITANGA 
O 
CE NHAMUNDA 
0u-
BETA 
FORMATIONS 
MEMBERS 
O L -
'GAMMA 
I 
FARO 
ERERE 
ZD 
§ LONTRA 
Y JATAPU 
<x 
ANDIRA 
NOVA 
OLINDA 
I TAI TUBA 
fclONTE ALEGRA 
POTI 
LONGA 
CABEÇAS 
PIMENTEIRAS 
SERRA GRANDEl 
TIBAGI 
JAGUARIAIVA 
FURNAS 
Cu—Pu« El 
DELTA 
MOTUCA 
"PEDRA DE 
_ FOGO 
UPPER 
LOWER 
RIODO RASTRO 
^JRADANOVA 
PALERMO ta tu i 
RIO BONITO 
UPPER 
CC. 
G MIOOLE 
* * LOWER 
BRAZILIAN INTRACRATONIC BASINS 191 
f rom reducing to oxidizing conditions; lit-
toral facies succeeded by reddish fluvio-
lacustrine facies concurrent with erosion of 
marginal deposits, succeeded by widespread 
erosion. 
This systematization of events that mark 
development of an epeirogenic cycle is a 
gross simplification of the observed pat-
terns. 
Phase 3 of the observed pattern is of par-
ticular interest because it is also observed in 
almost all Nor th American epeirogenic cy-
cles. 
A C K N O W L E D G M E N T S 
We are greatly indebted to L. L. Sloss, 
who kindly read the manuscript and pro-
vided helpful criticism. Parts of this study 
were financed by Funda?áo de Amparo á 
Pesquisa do Estado de Sao Paulo (FAPESP). 
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