Tectonic Cycles and Sedimentary Sequences in the Brazilian Intracratonic Basins

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 by widespread continental sedimentation nature, and the preserved thickness of suc- under platform conditions. The second cessive stratigraphic units at basin depocen- The geometry and petrology of sedimen- reactivation cycle was responsible for ac- ters. These criteria permit a semiquantita- tary rocks preserved in the three intra- cumulation of the Zeta sequence (Ceno- tive evaluation of oscillatory movements of cratonic basins of the Brazilian craton zoic), which was characterized by thin re- the Brazilian craton. Figures 3, 4, and 5 il- (Paraná, Parnaiba, and Amazon) indicate sidual deposits on an extensive Tertiary lustrate the nature of the stratigraphic rec- the history and character of vertical move- peneplain and by accumulations in Quater- ord, amount of subsidence, and rate of ments of the cratonic area. Cyclic succes- nary basins, the latter of minor importance subsidence for the three intracratonic ba- sions of erosional and depositional events except where adjacent to the uplifted east- sins. The age assignments for each strati- are synchronous on the Brazilian craton ern continental margin. graphic unit are according to biostrati- and are correlated with cratons of other graphic works of Lange (1967a, 1967b), continents. The principal evolutionary INTRODUCTION Daemon and Quadros (1970), and Daemon stages of the Brazilian craton are inter- and Contreiras (1971); absolute ages are preted as tectonic-sedimentary cycles, each In this paper the geological evolution of from Kulp (1961) and Harland and others represented by a stratigraphic record iden- the Brazilian craton is investigated in terms (1964). tified as a sequence, and each distinguished of the major sedimentary and erosional by its own special characteristics. events of Phanerozoic time. Vertical move- STAGES AND CYCLES OF Cambrian-Ordovician sedimentary rocks, ments, particularly those of cyclical charac- TECTONIC-SEDIMENTARY representing deposition in paraplatform ter, have been determined from amount of EVOLUTION OF BRAZILIAN basins during a transitional stage at the subsidence and rates of accumulation of INTRACRATONIC BASINS close of the Brazilian orogenic cycle, are as- sediments in the three intracratonic basins signed to the Alpha sequence. The Beta (Paraná, Parnaiba, and Amazon) of the The lithological associations and the un- (Ordovician and Silurian), Gamma (Devon- Brazilian craton (Fig. 1). conformities, mentioned above, in the three ian-early Carboniferous), and Delta (late The question of cyclical evolution of interior basins document the variation of Carboniferous-Late Permian sequences) cratonic areas of North America and the the depositional interface in relation to base and the Delta-A subsequence (Middle Russian platform have been considered by level through Phanerozoic time. Triassic-Jurassic), corresponding to Sloss (1963,1964,1972) and by Ronov and Episodes of subsidence in interior basins geotectonic cycles of the cratonic stabiliza- others (1969), respectively. Sloss (1963) are characterized by an initial phase of con- tion stage, indicate accumulation in large proposed that major stratigraphic succes- tinental sedimentation; the depositional in- subsiding basins. The succession of facies in sions separated by interregional uncon- terface is below base level, but the rate of each of these sequences documents cyclical formities were identified as stratigraphic se- sediment supply compensates for subsi- changes in the ratio of sediment supply to quences recognized as the preserved record dence. With continuing subsidence at an ac- subsidence. Marine transgression and basin of cratonic subsidence and accompanying celerated rate, the depositional interface subsidence increased progressively through sedimentation followed by an episode of passes below sea level to initiate marine the Devonian phase of the Gamma se- broad uplift and erosion. Wheeler (1958) sedimentation. The greater the ratio of quence and declined thereafter, in a pattern expressed a similar concept in his definition subsidence to sediment supply, the deeper similar to that of the North American cra- of depositional holosomes. Gomes (1968), the depositional interface becomes, and vice ton and the Russian platform. The fre- Almeida (1969), Ghignone (1972), and Ful- versa. Thus, regression, continental sed- quency of stratigraphic discordances in the faro and Landim (1976) studied deposi- imentation, deltaic progradation, or the ap- three lower sequences suggests a higher de- tional cycles in Brazilian intracratonic ba- pearance of areas of nondeposition or ero- gree of cratonic upwarping, progressively sins, subdividing the Phanerozoic succession define events characterized by subsi- diminishing to a stage of maximum stabili- sion into units designated as holostromes, dence rates that are less than the rate of sed- zation during Delta-A deposition, perhaps sequences, or stages (Fig. 2) with iment accumulation, or by tectonic uplift. related to conditions immediately prior to similarities and differences that are dis- Figure 3 represents the geomorphological rupture of the Gondwana plate. cussed below. position of the depositional interface under Breakup of the Gondwana plate, accom- To evaluate the variations of cratonic these conditions (it does not necessarily ex- panied by volcanism and remobilization of tectonism we have used the following data press only oscillatory tectonic motions). In cratonic areas, initiated the reactivation and criteria: volume and thickness of sedi- constructing the curves, consideration has stage during which two geotectonic cycles ment per time unit, area of preserved sedi- been given to the entire history of each ba- are recognized. The first, represented by the ment representing successive stratigraphic sin, including both aggradational and de- Epsilon sequence (Cretaceous), began with units, episodes of transgression and regres- gradational regimes. The nature of ob- local subsidence in isolated basins, followed sion, stratigraphic unconformities and their served stratigraphic discontinuities (from

Geological Society of America Bulletin, v. 89, p. 181-191, 9 figs., February 1978, Doc. no. 80203.

181

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NORTH AMERICA SOUTH AMERICA FULFARO SLOSS GOMES ALMEIDA GHIGNONE ndLANDIM SOARES et al. 1963 1968 1969 1972 1976 THIS PAPER 21 2T T Iff 5 2: Y 4 K ZUNI m E 12 J 3 I

P m n ni ABSAROKA : 2 u C —L GAMMft' I lb D n n S 10

i € I

W- -E AM PB PR

Figure 2. Subdivision of Brazilian Phanerozoic stratigraphie succession into sequences by several authors, compared to North American sequences of Sloss (1963).

Figure 1. Location of the three major Brazilian intracratonic basins and quantity of material accumulated and their basements. 1, Sedimentary cover from Precambrian to Holocene; 2, preserved in a chronostratigraphic unit is middle Paleozoic cratonic areas (structural trends); 3, late Precambrian the record of tectonic movement in the ba- cratonic areas: I, Amazon; II, Sao Francisco; 4, approximate boundaries of sin, whereas the kind of material supplied intracratonic basins; 5, approximate boundaries of cratonic areas in late Precambrian time. to the basin is determined by tectonic activity in the source area. diastem to angular unconformity) and of graphic sequences represent the sediments Examination of the data given in Figures the depositional environment (from conti- deposited in each cycle when basinal areas 3, 4, and 5 leads to the following conclu- nental to abyssal marine) are interpreted were below depositional base level. Figure 4 sions: (1) The preserved stratigraphie rec- from the sedimentary record in order to shows the amount of subsidence at the de- ord of the Brazilian craton can be divided identify the amount of vertical motion pocenter of each basin in each of the into six sequences — Alpha (Cambrian- characteristic of each basinal area during tectonic-sedimentary cycles. The curves Early Ordovician), Beta (Late Ordovi- each cycle. show cumulative maximum thicknesses as a cian-Silurian), Gamma (Early Devo- Episodes of broad cratonic uplift corre- function of geologic time for each cycle; the nian-Early Carboniferous), Delta (late spond to times of clastic supply to basin slopes of the curves are functions of subsi- Carboniferous-Late Permian or Early sedimentation and to times of erosion of dence rates. Subsidence ratios, shown in Triassic), Epsilon (Late Jurassic-Late Cre- previously accumulated deposits. The na- Figure 5, represent thicknesses per unit time taceous), and Zeta (Tertiry). Strata dated as ture of uplift at depositional sites is esti- for successive stratigraphic units at basin Middle Triassic to Late Jurassic are here mated by the angularity of the unconfor- depocenters. Subsidence of broad regions is provisionally identified as subsequence mity separating adjacent sequences. Local considered the fundamental control of the Delta-A (Piramboia, Botucatu, and Sam- and regional disconformities and angular cumulative sedimentation and preservation baiba Formations). (2) The six sequences unconformities were evaluated to suggest of sediments in cratonic areas. Sea-level correspond to tectonic cycles that were syn- rate of uplift. Successions characterized by changes are modifying factors in environ- chronous in the three basins but whose closely spaced diastems indicate that the mental conditions, but we cannot attribute dynamic evolution was different in each rate of subsidence was approximately equal to eustatic movement hundreds or thou- basin and different in each epoch of the to or less than the rate of uplife of adjacent sands of metres of continental or even same basin. (3) Two of the Brazilian se- source areas. continental-marine sediments. The vol- quences, Gamma and Delta, are represented The curves of Figure 3 permit visualiza- umetric capacity for accumulation in a by the most complete stratigraphie record tion of successive events of subsidence and basin is determined by subsidence; there- and show the best development of tectonic uplift in the three basins and thus delineate fore, the thickness of a chronostratigraphic cycles. (4) The Brazilian craton behaved dif- the tectonic-sedimentary cycles on the unit is a measure of minimum subsidence in ferently during Paleozoic time than during Brazilian craton. The successive strati- the time span of its accumulation. Thus, the Mesozoic and Cenozoic time.

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sion called the Trombetas Formation ac- SEQUENCES cumulated. The second tectonic- ALPHA I BETA GAMMA | DELTA EPSILON ZETA sedimentary cycle began with slow regional A- Amazon Basin subsidence, leading to the deposition of continental and lagoonal well-sorted A.U. sandstones and fine clastic rocks, succeeded LAU. by tidal-flat deposits related to an east-to- D. west Silurian transgression. The beds in- Dt. [} f] / * - clude the Autas Mirim Member (Caputo C.S. and others, 1972) or lower Trombetas CM. - V J \ l{ l\ / ^ L. Formation (Ludwig, 1964). These basal de- N. posits are overlain by fine quartzose A, sandstones of an epineritic environment I I I I I (Nhamundá Member), recording a transgression and culminating in infraneritic de- B-Parnaiba Basin posits of fine clastic rocks with beds of A.U. utcanlsm chert, hematite, and siderite (Pitanga LA.U. Member; Lange, 1967a; Ludwig, 1964). D. The top of the sequences in the Amazon

Dt K 1» • V A / Basin is represented by sandstones and C.S. siltstones of the Manacapuru Member. C.M. \/\j In the Paraná Basin, the Beta sequence is L. N: represented by the Caacupé Group, which A, crops out only at the southwestern border of the basin, near the Asuncion arch. The I I T I I strata represent a northeastward transgres- C-Parand Basin sion over an early-subsiding part of the

A.U. Paraná Basin. Equivalent strata have not

L.A.U. been penetrated by drilling in the basin in-

0. terior farther to the east. The Caacupé Dt. Group is composed of reddish sandstones A A C.S. \(\ ft < /I I wit' h shale intercalations that include several fossiliferous horizons. The dominant C.M. \J\ 1 \ l\/w- - - L. depositional environment was transitional N, A/ = vy ^ - from littoral to fluvial; transgressive episodes are indicated by sedimentary structures and sandstone textures (Bigarella and Comte, 1969) suggesting west-northwest current directions. These vector properties A.U.-Anqular unconformity L.A.U.-Low-angle unconformity D. - Disconformity are the reverse of those indicated by Per- C.S.-Continental sandy L. -Littoral A. - Abyssal mian strata. C.M.-Continental muddy N. -Neritic Dt.-Diostem 1 1 1 1 1 DM. Francisco The Beta sequence is not present in the 1 I 1 1 1 Parnaiba Basin, although some authors 00 500 400 300 200 100 m. y. 61 J K K T have assigned a Silurian age to the Serra C | o | s |DJDm|Du|CL| CU |PL|PM|PU| KW U| L | U| Grande Formation of the Parnaiba Basin, Figure 3. Geomorphological expression of oscillatory movements in the three major Brazilian correlating it with the Furnas Formation of basins. the Paraná Basin. Other workers (Ghig- none, 1972; Daemon and Quadros, 1970) Alpha Sequence (Melcher and others, 1973). The Alpha se- have assigned a Devonian age to the Serra quence represents the first Phanerozoic Grande Formation; these strata are con- The Alpha Sequence, including Cambrian tectonic-sedimentary cycle of cratonic formably overlain by Devonian marine to Ordovician strata, is little known in character on the Brazilian platform; it is sedimentary deposits and may be consid- Brazil. Almeida (1969) considered the correlative with the Sauk sequence of the ered to represent the initial phase of the strata to mark the transition from the North American craton and the earliest part third (Gamma) sedimentation cycle. Brazilian orogenic cycle to platform condi- of the Caledonian cycle of the Russian plat- The Beta sequence is Late Ordovician tions. Basal sandstones and siltstones are form. Chronologically, sequence 1 of and Silurian in age. The basal 300 m of this succeeded by carbonate rocks, suggesting Almeida (1969) and Ghignone (1972) cor- sequence in the Amazon Basin, the that stable conditions prevailed in Cam- responds to the Alpha sequence. Inasmuch Nhamunda and Autas-Mirim Members of brian and Ordovician time in the Amazon as the strata described by these authors the Trombetas Formation (Caputo and region. Equivalent deposits indicating comprise deposits of a precratonic tran- others, 1972) are Late Ordovician in age. cratonic sedimentation are not known in sitional stage, they are not included in our The overlying Pitanga Member, corre- the Paraná and Parnaiba Basins. During discussion, despite chronologic equivalence sponding to the median cycle phase of Ordovician time the period of transition is to the Alpha sequence. maximum subsidence (Lange, 1967a), is represented by immature clastic and vol- lower Lhandoverian (Early Silurian) in age. canic rocks (andesites and rhyolites) in in- Beta Sequence A similar time span is attributed to the termontane depressions at the same time as Caacupé Group in Paraguay (Harrington, the post-tectonic granitic intrusions (500 to The Beta sequence is well developed in 1956). 540 m.y. ago) of the Ribeira orogenic belt the Amazon Basin, where a 900-m succes- The Beta sequence correlates with the

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Tippecanoe sequence of the North Ameri- can craton (Sloss, 1963), representing the second tectonic cycle of the Brazilian cratonic area; together with the Alpha sequence, the Beta sequence corresponds to the Caledonian cycle of Ronov and others (1969). Almeida (1969) and Ghignone (1972) included the Beta and Gamma sequences 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 Gamma sequence (Maecuru Formation; Lange 1967a; Dae- mon and Contreiras, 1971). The separation of the Beta and Gamma sequences in the Parnaiba and Paraná Basins is complicated by the absence of paleontologic criteria in strata considered to form the Gamma sequence. In the central region of the Paraná Basin the Furnas Formation appears to interfinger with the Ponta Grossa Formation, whereas minor unconformities are present at the contact between the two units on the eastern 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 holostromes la and lb) has been noted by Gomes (1968). Some authors (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- Figure 4. Subsidence amounts, determined from thickness of sediments accumulated in depocenter tion of the Serra Grande and Maecuru of basin in each sequence. Formations is corroborated by Messner and Wooldridge (1964) and Lange (1967a). preceding the Devonian transgression. The The Gamma sequence developed in a dif- absence of coarse clastic deposits at the base ferent manner in the Parnaiba Basin. Here, Gamma Sequence of the sequence in the Amazon Basin as in the Paraná Basin, the geologic history suggests that the area did not undergo sig- is distinct from that of the Amazon Basin. The Gamma sequence represents the nificant uplift in the preceding erosional At the initiation of sedimentation of the third Phanerozoic tectonic-sedimentary cy- phase. The overlying Erere Formation third Phanerozoic tectonic-sedimentary cycle, which is the first to be well developed in shows microfloral changes (Daemon and cle, the Parnaiba basin received a large sup- all three Brazilian interior basins. Subsi- Contreiras, 1971), indicating a slight dim- ply of coarse material derived from its east- dence of the Brazilian craton during this inution of the depth of the basin; a similar ern margin; the resulting accumulation is cycle is more pronounced than in the pre- condition is reflected by reduction of the the Serra Grande Formation. This unit is ceding cycles. subsidence ratio (Fig. 2). This episode was characterized by thinning and by reduction in grain size from east to west (Messner and In the Amazon Basin, more than 1,300 m followed by acceleration of subsidence and Wooldridge, 1964). Observations on the of Gamma sediments have accumulated, transgression, leading to deposition of a east flank of the basin indicate generally mainly fine clastics. The base of the se- thick succession of fine clastic material northwest current directions, although quence is marked by fine- to medium- (lower part of the Curua Formation), which southwest components occur in the basal grained sandstones with shale and siltstone includes zones interpreted by Ludwig part of the unit (Bigarella and Salamuni, intercalations (Maecuru Formation, depos- (1964) as turbidites (Curiri Member of 1967). The Serra Grande Formation consti- ited in epineritic to littoral environments Lange, 1967a), indicating deepening of the tutes the first episode of sedimentation (Jatapu Member), transitional to infranerit- basin to abyssal depths. Regression began under platform conditions in the Parnaiba ic conditions (Lontra Member; Lange, at the end of Devonian time; early Carbon- Basin area. 1967a; Ludwig, 1964). The absence of iferous sedimentation was dominated by lit- continental sedimentation in this part of the toral environments (Faro Member) and the The depositional phase represented by sequence suggests a region of low relief, deposition of thin coal seams in a succes- the Serra Grande Formation, characterized only slightly above sea level, immediately sion dominated by sand. by immature sediments, wedge geometry,

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and great thickness, is difficult to recon- struct in paleogeographic and tectonic SEQUENCES terms. The upper part of the Serra Grande ALPHA BETA 1 GAMMA DELTA EPSILON 1 ZETA Formation, in the sense of Messner and o- Wooldridge (1964), represents a distal iiJ i ^ \ /i \ / t \ v i 10 - facies deposited in a littoral environment / " \ / \ / v (micaceous siltstones and bituminous 20 - ». 30 - ! / \/ shales). Progressive subsidence of the basin 40 - 1 1 1 / V and reduction of the source area led to 1 1 " marine transgression and the deposition of 50 - 1 1 a thick succession of fine clastics, the 60 - Pimenteiras Formation, in littoral to nerit- A-Amazon Basin ic environments (Andrade, 1972). In the middle of the Gamma cycle, the Parnaiba I I I I I Basin returned to a condition of mobility, 0 - • ' \ / \ / \ i • A / \ /\ VA I marked by the Cabecas Formation, a sandy 10 - 1 / S / \ / V / x 1 facies of infraneritic and deltaic environ- 20 - | f \ 1 V V \ / ments. Pebbly mudstones in the latter unit 1 / " \l 30 - 1 / " E are considered to be turbidites (Ludwig, \ 40 - 1 / 1964), following the interpretation applied E to the Curuá Formation in the Amazon Ba- 50 - sin. The easterly gradation of sandstones to 60 - shales, the restricted-circulation environ- B-Parnaiba Basin

ments in the Pimenteiras Formation (Agu- I I I I I iar, 1971), and the presence of pebbles of metamorphic rock in the conglomerates 0 - \ /1 i > ! \ suggest a reactivation of the source area, 10 - W \ a / ! particularly on its eastern flank and, more 20 \ l \ V \ I \ >- 30 N locally, at the northwestern margin. E Reorganization of the basin was followed \ 40 - : V E v 11 by a phase of stability and recurrence of 50 uniform subsidence, accompanied by the es- w• 60 tablishment of homogeneous conditions of C-Parana' Basin sedimentation represented by shales, siltstones, and mature sandstones of the Longá | 1 | | 1 Oil. FroncUco 6 00 500 400 300 200 100 Formation (Upper Devonian). The record m. y. of the Gamma sequence closes in the Par- 1 € I 0 I S KJ°MK|CLI Cu |P|>MM khkl KL T naiba Basin with regression marked by Figure 5. Variation of subsidence rate through the cycles. Note reduction of subsidence rate at quartzose sandstones, local intercalations middle of cycle. of shales and conglomerates, and an upper unit of variegated purple siltstones and pansion of the area of subsidence led to regressive phase, probably associated with shales bearing thin calcareous beds (Poti onlap over regions close to the relict uplifts an influx of coarse clastic material at the Formation, lower Carboniferous) represent- and to sedimentation under conditions of top of the unit. These clastics were re- ing marshy, deltaic, and beach environ- high energy release and unidirectional worked in littoral environments, forming ments (Andrade, 1972). channel flows (see Appendix 3 in Bigarella conglomerate lenses of discoidal quartzite Development of the Gamma sequence in and others, 1966). Poor sorting, small-scale and quartz pebbles intercalated with silt- the Parnaiba Basin is similar to that of the planar cross-bedding, pebbles at the base of stones and shales at the base of the Sao Paraná Basin, where the record is less com- sedimentation units, and general lack of Domingos Member. Dark-gray, in some plete, lacking part of the Upper Devonian mud suggest fluvial sedimentation in anas- places bituminous, shales of this member and all of the lower Carboniferous. The tomosing channels. In higher parts of the represent a resumption of subsidence dur- Furnas Formation, the earliest deposits of unit, the sandstones exhibit better sorting, ing Middle to Late Devonian time. The re- the cycle, suggests the tectonic conditions of low-angle cross-bedding, and worm- gressive deposits of this cycle in the Paraná an intracratonic basin. As in the case of the burrows, which indicate littoral environ- Basin are not recorded; presumably they Serra Grande Formation, thick conglom- ments. Although there is evidence of a dis- were removed during the succeeding ero- eratic sandstones of the Furnas Formation continuity between the Furnas Formation sional episode. probably represent erosion and topographic and the overlying Ponta Grossa Formation, The Gamma sequence is Devonian and reduction of uplifts developed in the Ribeira in the interior of the basin the two units ap- Mississippian in age, thus correlating with orogenic belt. As are the first platform sed- pear to be vertically and laterally intergra- the Kaskaskia sequence of Sloss (1963) and iments, the sandstones are texturally imma- dational (Lange, 1967b). with the lower Hercynian subcycle of the ture (high angularity of grains and poor The Ponta Grossa Formation appears to Russian platform. The sequence is equiva- sorting) and are marked by high feldspar represent the neritic facies of the Devonian lent to holostrome lb of Gomes (1968) and content. transgression; deepening of the basin dur- to the upper part of sequence II of Almeida The lower part of the Furnas Formation, ing the first half of the cycle (Early Devo- (1969) and Ghignone (1972), and with se- including almost all of the outcrops in the nian) is recorded in the mudstones, shales, quence I of Fulfaro and Landim (1976). State of Paraná, represents continental dep- and basal sandy intercalations of the osition of the initial subsidence phase, with Jaguariaiva Member (Lange and Petri, Delta Sequence highlands to the east and northeast, repre- 1967). Fine-grained sandstones intercalated senting uplift of the Ribeira belt during the with micaceous shale of the Tibagi Member The Delta sequence, corresponding to the preceding transition stage. Progressive ex- (Early and Middle Devonian) represent a last Paleozoic tectonic-sedimentary cycle, is

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well developed in each of the three Brazilian lations of siltstones, shales, carbonates, and bedded siltstones (Passinho Shale) were de- interior basins and presents characteristic chert, locally containing marine fossils (An- posited in epineritic and tidal-flat environ- facies associations. drade, 1972). Thicknesses as well as pro- ments (Medeiros, 1973). Following this In the Amazon Basin, the Delta sequence portions of fine to coarse clastics and of marine regression, fluvial and deltaic sedi- represents a dominantly chemical (nonter- chemical to clastic sediments are moder- ments of the base of the Rio Bonito Forma- rigenous) sedimentation cycle, reflecting ately variable, as observed, for example, in tion prograded over the marine beds, in stabilization of the region or a very low rate Petrobrás wells VG-1R-MA and CL-l-MA. some places with sharp contacts, as near of uplift in the surrounding areas. Sedimen- This complexly intercalated succession, the Teixeira Soares and Sao Joáo do Triunfo in tation began with a marine transgression upper member of the Piaui Formation Paraná State (Ramos, 1967; Medeiros, from the west (late Carboniferous; Carozzi (Lower to Middle Permian) reflects the 1973). Across the Ponta Grossa arch, as can and others, 1972) and deposition of a thin deepening and slight differentiation of the be observed in Petrobrás well 1-R-L-PR succession of sandstones with thin interca- basin. The Piaui Formation is overlain by near Reserva in northern Paraná State, the lations of shale and carbonate rock (Monte the Pedra de Fogo Formation, consisting of fine clastic section of the upper ltararé is not Alegre Formation). These sediments reflect intercalations of anhydrite, dolomite, and developed. In this area, erosion affected a littoral environment with only a small limestone. The carbonate rocks bear oolite earlier deposits. In the embayment to the contribution of continental sedimentation. and pisolites and appear to represent an in- north of the arch this phase is represented In the following phase, under continuing crease in water depths within the basin. by immature micaceous fluvial sandstones equilibrium between moderate subsidence Prevailing arid climates are responsible for at the base, as in Paraná State, exhibiting an and moderate sediment supply, tidal-flat anhydrite in thick beds and for intercala- abrupt contact with underlying rhythmites environments prevailed. Low rates of sup- tions of fine reddish clastics, including and fine littoral sandstones of the preceding ply of terrigenous material favored an ini- fluvial-lacustrine sandstones (Motuca For- phase. These beds, named the Tiete Forma- tial dominance of carbonate sedimentation, mation) representing the basin-filling phase. tion by Barbosa and Almeida (1953) and passing to an evaporite domain (Itaituba The Delta sequence in the Paraná Basin is Tiete facies by Soares (1972), represent the Formation), marking reactivation of the better documented because of an extensive progradation of continental sedimentation Purus arch. An episode of sand deposition outcrop belt on the eastern and southern and must be correlated with basal sand- (lower Nova Olinda Formation) followed; flanks of the basin. Maximum thicknesses stones of the Rio Bonito Formation. Thus, this influx of clastic material produced a reach 2,550 m in the southwestern part of both sides of the Ponta Grossa arch re- shallowing of the basin, while some areas, Sao Paulo State. The cycle was charac- sponded to similar states of basin evolution, such as the upper Amazon River, subsided terized by relatively high rates of subsidence marked by reorganization of intrabasin tec- more rapidly and received a greater load of and by glaciation during accumulation of tonics, upwarping, and increase in the rate sediment (Carozzi and others, 1972), indi- the lower half of the sequence, leading to of sediment supply coupled with reduction cating reorganization of basin framework. local periglacial sedimentation and an of the basinal subsidence rates, leading to The second half of the cycle is marked by a influx of clastic material in the basin in- regression and progradational deposition. reduction in the influx of terrigenous sedi- terior. The first stage of the cycle is partially During this phase, at the end of Middle ments, the imposition of a higher degree of represented by conglomeratic sandstones, Permian time, the northern part of the basin restriction related to renewed upwarp, and rhythmically bedded mudstones, and dia- was uplifted, creating conditions of non- progressive climatic aridity, leading to a mictites of fluvial and lacustrine origin, plus deposition and erosion and producing the dominance of evaporitic sedimentation. tillites. This succession, particularly the unconformity at the succeeding Tatui For- However, in the middle of this phase, there lower part of the ltararé Formation in Sao mation (Soares, 1972). Fluviodeltaic de- appear intercalations of carbonate rock as- Paulo and Paraná States, is reddish brown posits of the lower sandy interval of the Rio sociated with fine clastic rock derived from (Tommasi, 1973; Soares and Landim, Bonito Formation may be considered as a west of the Purus arch, suggesting a deepen- 1973). Lacustrine, fluvial, and glacial de- part of the ltararé Formation equivalent to ing of basinal waters. At the close of the posits constitute an average of one-third of the Tiete facies of Sao Paulo State, which cycle (Late Permian), evaporitic sedimenta- the ltararé Formation in outcrops at the also includes coal-bearing beds (Medeiros, tion was progressively replaced, from the eastern flank of the basin. The middle one- 1973). basin margins toward the interior, by fine third of the ltararé Formation is charac- In Middle Permian time, regional subsi- clastic deposits, commonly reddish, with terized by pale-gray color and includes dence resumed, developing a nearly sym- minor carbonate and anhydrite intercala- sandstones with thick intercalations of metrical sedimentary cycle. To the south of tions; these redbeds of the Andira Forma- siltstones and shales, reflecting deepening of the Ponta Grossa arch, marine transgres- tion are believed to represent lacustrine en- the basin and the initiation of marine trans- sion reworked the basal parts of the Rio vironments. gression from the southwest (Early Per- Bonito Formation to deposit a succession of The Delta sequence in the Amazon Basin mian). The Mafra beds, the middle unit of siltstone, sandstone, and limestone in lit- is approximately 2,500 m thick. The low the formation in the sense of Tommasi toral, epineritic, and tidal-flat environ- proportion of clastic rock, about one- (1973), includes marine strata. In Sao Paulo ments, represented by the middle and upper fourth, indicates lower rates of supply of State, fine sandstones associated with the parts of the Rio Bonito Formation detrital material from surrounding sources Monte Mor coal deposits represent a trans- (Medeiros, 1973). Northward from the while the basin grew uniformly at high to gression of littoral environments, which, at Ponta Grossa arch, this transgression de- moderate rates in the presence of shallow their maximum extent, are represented by posited very fine grained purple sandstones water and an arid climate. silty sediments, in some places rhythmically and slightly calcareous sandy siltstones of The Delta sequence in the Parnaiba Basin bedded and bearing syndeformational supratidal environments (Soares, 1972; is dominated by continental clastic rocks, structures, intercalated with well-sorted Soares and Landim, 1973) over the erosion with significant carbonates and anhydrites sandstones (Capivari beds). This unit in- surface cut on ltararé strata. In the southern in the middle. The base of the sequence is cludes intercalations of the thicker and part of the basin, the area of sedimentation marked by reddish fluvial sandstones and more extensive bodies of diamictite. progressively expanded as the rate of subsi- conglomerates of the lower member of the At the end of Early Permian time, uplift dence increased, such that succeeding de- Piaui Formation (upper Carboniferous). of the Ponta Grossa arch was accelerated, posits onlapped across earlier strata. With These beds are succeeded by a largely sandy reaching a climax in Middle Permian time. continued transgression, littoral and section, particularly prominent in the During this epoch, in the embayment south epineritic sediments of the Paleromo For- southern part of the basin, bearing interca- of the Ponta Grossa uplift, rhythmically mation were deposited on the crystalline

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basement of the basin margin, as in Rio tion) of fluvio-lacustrine environments. exhibited the highest degree of tectonic ac- Grande do Sul. To the north, under condi- These sediments may have been derived in tivity, matched by an equilibrium between tions of uniform and moderate subsidence, part from reworking of sediments of the the rate of supply of detrital sediment and were developed littoral environments: in- preceding phase. Red coloration of the the high rate of subsidence, thus maintain- tertidal, beach, and lagoon. Progressive upper part of the Estrada Nova Formation ing a relatively stable depositional interface deepening of the basin from south to north in Sao Paulo State (facies of Corumbatai at near—base level conditions. The rate of reduced the rate of supply of detrital sedi- type) are not to be confused with the red- accumulation of sediment, 25 km3/ m.y., ments and led to conditions of restricted beds of the Rio do Rasto Formation. It is was greater than that achieved in other ba- circulation, represented by siltstone, suggested that the red color below the pre- sins or in other cycles in the Paraná Basin. bituminous black shale, and dolomitic Triassic unconformity is not necessarily re- Accumulation rates were maximal at the limestone of the Irati Formation, and by lated to depositional conditions. Permian-Carboniferous boundary and dur- dark-gray mudstone of the Serra Alta Tectonic behavior and physiographic ex- ing Late Permian time (Figs. 6 , 7). Member. pression were developed quite differently The age of the base of the Delta sequence The second half of the Delta cycle was during this cycle in the Brazilian basins. The ranges from late Westphalian in the Ama- characterized by a southward increase in Amazon Basin was characterized by high zon Basin to Stephanian in the Parnaiba and the rate of subsidence, accompanied by an rates of subsidence, low rates of uplift, re- Paraná Basins (Daemon and Contreiras, increase in the rate of supply of detrital sed- stricted environments, and an arid climate, 1971; Daemon and Quadros, 1970). Ero- iments and uplift of the basin margins. En- in contrast to the Parnaiba Basin, with its sion of the top of the Delta sequence makes vironments dominated by tidal and suprati- low rates of subsidence and uplift, more it difficult to define the end of the cycle; dal flats are represented by the Estrada open circulation conditions, and semiarid however, the Estrada Nova Formation is of Nova Formation. At the end of Permian continental environments. At the same time Kazanian age (Late Permian), and it is time, the northern and southern flanks of in the Paraná Basin, glacial climates pre- probable that deposition of the Rio do the basin were uplifted and the central area vailed at the beginning of the cycle, passing Rasto Formation extended into Early of the basin continued to subside, receiving to humid climates in the middle, and to Triassic time. The Delta sequence correlates continental redbeds (Rio do Rasto Forma- semiaridity at the close. The Paraná Basin with part of the the Absaroka sequence of the North American craton and the upper subcycle of the Hercynian of the Russian platform. It also correlates with sequence II, A-Pornaibo Bosin 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 patterns of tectonic evolution changed markedly. Some areas, such as the North American craton 600 300 100 and Russian platform, resumed cyclical pat- 45 - terns, during Jurassic time, and other regions, such as the Brazilian craton and the 40 "HB-Paran o Basin Siberian platform, developed a completely different behavior pattern. In Brazil, sed- 35 imentation was restricted to continental environments and lacked uniformity and 30 periodicity. Triassic and Jurassic sedimentation in the 25 Paraná Basin indicates a high degree of tectonic stability of the entire region. The ^ 20 - io Pirambóia Formation (Middle Triassic to E Early Jurassic), for example, consists of fluvial sandstones marked by a high degree * 15 of textural and mineralogical maturity, and numerous diastems, suggesting a moderate 10 supply rate of sediment combined with low rates of subsidence. Unlike the "normal" 5 0». frond««« cycles of previous sequences, there are 5Ò0 4Ò0 300 200 100 0 numerous upward-fining subcycles, with a t € I 0 I 5 NDMIDUICLI CU IPLIPMIPUUL KkKI KL Kl I general increase in mean grain size toward the top of the sequence (Soares, 1975). Locally the basal strata of the Botucatu Sediment accumulation rate Formation (Jurassic) contain a typical Accumulation mean rate during the cycle heavy-mineral suite of the Pirambóia For- mation (Wu and Soares, 1974). Although the Botucatu Formation is texturally more Figure 6. Sediment accumulation rate and accumulation mean rate for Parnaiba and Parana Ba- mature and contains lower percentages of sins. feldspar than the Pirambóia, its heavy-

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the north flank of the basin (Codó Forma- tion), and ending with a fluvial redbed facies (ltapecuru Formation), which onlapped extensively across the cratonic interior. In the Paraná Basin, the Epsilon sequence is represented by eolian and fluvio- lacustrine deposits of the northern 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 Mar, 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 sandstones overlapped earlier units at the basin margins and, in the vicinity of alkalic volcanism, developed facies characterized by major contributions of volcanogenic sediments (Uberaba facies). These sandstones of the Epsilon sequence are arkosic, with a de- crease in mineralogical maturity both from older to younger units and from south to north. In the middle Amazon Basin, the Epsilon sequence is represented by 500 m of conti- mineral suite is similar to the underlying geometry. Volcanism began earlier in the nental deposits ranging from Early to Late unit. The heavy minerals include grains of Parnaiba Basin than in the region of the Cretaceous age and assigned to the Alter do higher angularity than those of the Piram- Paraná Basin, and the intravolcanic Chào Formation (Daemon and Contreiras, bóia, plus a significant percentage of Corda-Pastos Bons sedimentary deposits 1971). magnetite and ilmenite (Wu and Soares, correlate with the prevolcanic Botucatu of The Epsilon sequence reflects a new stage 1974), suggesting rapid accumulation and the Paraná region. in the evolution of the Brazilian craton, a contemporary volcanism. Triassic-Jurassic sedimentation is not re- stage of reactivation (Wealdenian reactiva- These data indicate a slow, progressive corded in the Amazon Basin, only volcanic tion of Almeida, 1969). The evolutionary rate of uplift of source areas during this activity. pattern does not reflect a cyclical epei- stage of sedimentation in early Mesozoic We provisionally consider the sandy rogenic model. It was controlled by time, a pattern markedly different from Mesozoic deposits underlain by volcanic breakup of the Gondwana continent and those of the Paleozoic epeirogenic cycles. In flows in the Paraná and Parnaiba Basins to the development of the South Atlantic rift the Paraná Basin, this phase culminated constitute subsequence Delta-A. The basalts (Estrella, 1972) and associated marginal with an episode of intense volcanic activity are additions to the lithological associations basins. and basinal subsidence. of normal sequences, but are not related to Sedimentation in this upper Mesozoic se- The Delta-A cycle closed with an episode the cyclical evolution of the cratonic areas. quence in the interior of the continent was of Late Jurassic and Early Cretaceous vol- The Delta-A subsequence, although not related to three pericratonic events or con- canism, represented by extensive flows that representative of a typical epeirogenic cycle, ditions: (1) broad crustal upwarp of the rift covered the area of Botucatu accumulation has correlatives in both the North American region, increasing the rate of supply of sed- and probably extended across the source craton and the Russian platform. iment to the slowly subsiding interior de- areas of Botucatu sediments. pression, (2) development of open fissures, Early conditions in the cycle in the Par- Epsilon Sequence accompanied by the outpouring of tholeiitic naiba Basin were similar to those of the lavas, and (3) increasing upwarp of interior Paraná Basin. Sandy fluviatile and eolian Deposition of the Epsilon sequence fol- arches (Canastra-Goiania and Tocantins), sedimentation, represented by the Sam- lowed closely after the episode of volcanic followed by extrusion of alkalic magma. baiba Formation, is overlain by basalts of activity at the close of Delta-A deposition. The Epsilon sequence reflects differential the Mosquito Formation of Jurassic or In the Parnaiba Basin, Epsilon sedimenta- movements, faulting, tilting of blocks, and Jurassic-Cretaceous age (Cunha and Car- tion began in Early Jurassic time with dep- basaltic to alkalic volcanism in the cratonic neiro, 1972). Above the basalts, local de- osition of the basal conglomerates of the interior. This sequence corresponds to the posits of polymictic conglomerates accumu- Pastos Bons and Corda Formations. Sed- Zuni sequence of the North American cra- lated, overlain by massive to cross-bedded imentation in the first half of the cycle was ton (Sloss, 1963), which also exhibits sandstones with intercalations of lacustrine interrupted by extrusion of the volcanic marked differences from Paleozoic cycles. shales of Jurassic age (Corda and Pastos flows of the Sardinha Formation in Early Bons Formations). Cretaceous time. Sedimentation in the sec- Zeta Sequence Early Cretaceous basaltic lava flows ond half of this cycle began with deposition (Aguiar, 1971) occur locally above the of the Grajaú sandstones under semiarid The Zeta sequence includes thin Tertiary Corda Formation. These strata, interbed- fluvial conditions, passing upward to gray deposits, covering the broad Sul Americana ded with volcanic rocks, exhibit a variable shale, locally containing marine fossils near peneplanation surface defined by King

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—Regression base level Figure 8. Correlation among sequences and oscillatory movements in North American, Brazilian, eastern European, and African cratons. In A, B, and C, correlations are based on preserved sedimentary deposits and in D, E, and F on base-level relative movements.

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(1956). These deposits are characterized by sedimentation in the areas of the Paraná We have identified five phases in the fluvial dark-red sediments with conglom- and Parnaiba Basins. The Gamma se- Paleozoic cycles, each phase being repre- erate and sandstones (containing dia- quence, Devonian to lower Carboniferous, sented in the stratigraphic record by a par- monds). Quaternary erosion (the Velhas represents the first well-defined cycle doc- ticular association of facies and each repre- and Paraguassu erosive cycles of King, 1956) umented in all three Brazilian basins. senting the sedimentary response of a given reduced the region covered by these sedi- Cratonic subsidence was more pronounced basin to a particular tectonic state. The five ments to local areas: the Cachoeirinha than in the preceding cycles. The Delta se- phases of epeirogenic cycles that we have Formation and its correlates in the Paraná quence, late Carboniferous to Late Per- identified can be characterized as follows Basin and the Nova Iorque beds in Mar- mian, is characterized by the closest ap- (Fig.9): (1) initiation of basin subsidence, anháo State. proach to a complete epeirogenic cycle, rapid expansion of the area of continental Major evidence of the cycle is in the (Sloss, 1964). The Delta-A subsequence, deposition, sandy sediments, sometimes in- Amazon Basin, where deposits, named the Middle Triassic to Jurassic, appears to be cluding pebbly fluvial and piedmont facies, Cruzeiro Formation, reach an average linked to the process of crustal upwarping overlain by fine clastics including coal pyri- thickness of 500 m, increasing to the west and volcanism that immediately preceded tic shales of lacustrine and marshy facies; (Daemon and Contreiras, 1971). Condi- the rupture of the Gondwana plate. The closely spaced diastems; (2) acceleration of tions of sedimentation were associated with Cretaceous Epsilon sequence is charac- basin subsidence, with the rate of sediment the upwarp of the Andes, which produced a terized by general cratonic subsidence, ini- supply lower than the rate of subsidence; wedge-shaped body of clastics derived from tially in isolated basins and later as a broad deepening of the basin accompanied by sources external to the craton. In northern, stable platform of continental sedimenta- transgression; initiation of marked differ- northeastern, and eastern marginal regions tion. The sequence reflects rifting of the entiation of the rate of subsidence of basinal of the craton, correlative fluvial, deltaic, South Atlantic. The Tertiary Zeta sequence and peripheral areas; littoral sandstones; and marine sediments reflect a broad subsi- is poorly developed, comprising residual euxinic shales; basinal carbonates and dence and transgression of the continent deposits associated with an extensive Ter- evaporites; establishment of well-defined during the Zeta cycle. tiary peneplain, and is preserved in small lithologic facies belts; (3) reorganization of The Zeta sequence reflects emergence of Quaternary relia basins of slight subsi- basin tectonic patterns; renewed uplift of the Brazilian subcontinent during Cenozoic dence. marginal areas; development of basin- time. The sequence correlates with the Tejas During Paleozoic time, the Brazilian ba- interior uplifts and local sub-basins accom- sequence of Sloss (1963) and corresponds sins evolved according to an epeirogenic panied by partial regressions, with local to sequence VI of Ghignone (1972). cycle, similar to that observed by Sloss progradation; overall reduction of subsi- (1964) in the North American craton. His dence rate; small deltas; intraformational CONCLUSIONS model for an epeirogenic sequence is conglomerates; local disconformities; (4) characterized by five lithologic associations cessation of intrabasin differential move- As demonstrated by the stratigraphic that represent five phases in the develop- ments; renewed acceleration of basin subsi- record in three Brazilian intracratonic ba- ment of each epeirogenic cycle. We have at- dence; maximal trangression accompanied sins — Paraná, Parnaiba, and Amazon — tempted here to establish a model that in- by achievement of maximum depth of the evolution of the interiors of cratonic cludes the observation of the tectonic be- water in the basin interior; fine clastic, car- continental plates was conditioned by dif- havior of Brazilian basins, based on the var- bonate, and evaporite deposits; and (5) ferentiation into regions of cumulative sub- iation of subsidence rates (Fig. 5), their cessation of basin subsidence; broad sidence and sedimentation (basins) and re- stratigraphic record (Fig. 9), and the ex- cratonic uplift; basin filling by fine to coarse gions of uplift and sediment supply pansion of areas of sedimentation (Fig. 7). clastic material, with upward transition (arches). Phanerozoic evolution of the -OL 0u- OL- Cu—Pu« El Brazilian basins was cyclical and divisible BASINS into craton-wide synchronous events of ALPHA BETA 'GAMMA DELTA erosion and sedimentation (Fig. 8). I ANDIRA FARO Each sequence constitutes the record of a MANACAPURU

tectonic cycle characterized by (1) regional 1 O PITANGA NOVA cratonic subsidence, (2) reduction of areas M OLINDA

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from reducing to oxidizing conditions; lit- 1972, Controle tectónico sinsedimentar dos Melcher, G. C., Gomes, C. B., Cordani, U. C., toral facies succeeded by reddish fluvio- carbonatos permo-carboniferos das For- Bettencourt, J. S., Damasceno, E. C., lacustrine facies concurrent with erosion of mates ltaituba e Nova Olinda da Bacia do Girardi, V.A.V., and Melfis, A. J., 1973, marginal deposits, succeeded by widespread Amazonas, Brasil: Brazilian Geol. Cong., Geologia e petrologia das rochas meta- 26th, Belém 1972, Proc., v. 3, p. 47-64. mórficas e graníticas associadas do vale do erosion. Cunha, F.M.B., and Carneiro, R. G., 1972, In- Rio Ribeira, SP e PR: Rev. Brasileira This systematization of events that mark terpretado fotogeológica do Centro-Oéste Geociéncias, v. 3, p. 97-123. development of an epeirogenic cycle is a da Bacia do Maranháo: Brazilian Geol. Messner, J. C., and Wooldridge, L.C.P., 1964, gross simplification of the observed pat- Cong., 26th, Belém 1972, Proc., v. 3, Maranháo Paleozoic basin and Cretaceous terns. p. 65-80. coastal basins, North Brazil: Am. Assoc. Pe- Phase 3 of the observed pattern is of par- Daemon, R. F. and Contreiras, C.J.A., 1971, troleum Geologists Bull., v. 48, p. 1475- ticular interest because it is also observed in Zoneamento palinológico da Bacia do 1512. almost all North American epeirogenic cy- Amazonas: Brazilian Geol. Cong., 25th, Ramos, A. N., 1967, Análise estratigráfica da 0 cles. Sào Paulo 1971, Proc., v. 3, p. 79-92. Formad Rio Bonito: Bol. Téc. Petrobrás, Daemon, R. F. and Quadros, L. P., 1970, Bioes- v. 10, no. 3/4, p. 357-407. tratigrafia do Neopaleozóico da Bacia do Roña, P. A., 1973, Relations between rates of ACKNOWLEDGMENTS Paraná: Brazilian Geol. Cong., 24th, sediment accumulation on continental Brasilia 1970, Proc., p. 359-412. shelves, sea-floor spreading and eustasy in- We are greatly indebted to L. L. Sloss, Dearney, R., 1966, Orogenic fold-belts and a ferred from the central North Atlantic: who kindly read the manuscript and pro- hypothesis of Earth evolution: Physics and Geol. Soc. America Bull., v. 84, p. 2851- vided helpful criticism. Parts of this study Chemistry of Earth, v. 7, p. 1-114. 2872. were financed by Funda?áo de Amparo á Estrella, G. O., 1972, O estágio "rift" nas bacias Ronov, A. B., Migdisov, A. A., and Barskaya, Pesquisa do Estado de Sao Paulo (FAPESP). marginais do leste brasileiro: Brazilian N. V., 1969, Tectonic cycles and regu- Geol. Cong., 26th, Belém 1972, Proc., v. 3, larities in the development of sedimentary p. 29-34. rocks and paleogeographic environments of REFERENCES CITED Fulfaro, V. 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