Geological Society, London, Memoirs

Chapter 48 Neoproterozoic successions of the São Francisco Craton, Brazil: the Bambuí, Una, Vazante and Vaza Barris/Miaba groups and their glaciogenic deposits

Aroldo Misi, Alan J. Kaufman, Karem Azmy, et al.

Geological Society, London, Memoirs 2011; v. 36; p. 509-522 doi: 10.1144/M36.48

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Neoproterozoic successions of the Sa˜o Francisco Craton, Brazil: the Bambuı´, Una, Vazante and Vaza Barris/Miaba groups and their glaciogenic deposits

AROLDO MISI1*, ALAN J. KAUFMAN2, KAREM AZMY3, MARCEL AUGUSTE DARDENNE4, ALCIDES NO´ BREGA SIAL5 & TOLENTINO FLA´ VIO DE OLIVEIRA6 1Metallogenesis Group, Department of Geology and Research Center on Geophysics and Geology (CPGG), Federal University of Bahia, Instituto de Geocieˆncias, Campus da Federac¸a˜o 40170-290, Salvador, Bahia, Brazil 2Departments of Geology and ESSIC, University of Maryland, College Park, Maryland, USA 3Department of Geology, Memorial University of Newfoundland, St. John’s, Canada 4Institute of Geosciences, University of Brasilia, Brasilia (DF), Brazil 5NEG-LABISE, Department of Geology, Federal University of Pernambuco, Recife (PE), 50670-000, Brazil 6Votorantim Metais, P.O. Box 03, 38780-000, Vazante, MG, Brazil *Corresponding author (e-mail: [email protected])

Abstract: The Neoproterozoic successions of the Saõ Francisco Craton are primarily represented by the Bambuı´ and Una groups, deposited in cratonic epicontinental basins, and by the Vazante and Vaza Barris/Miaba groups, which accumulated on passive margins on the edges of the craton. The epicontinental basins comprise three megasequences: glaciogenic, carbonate platform (marine) and dominantly continental siliciclastics. Possible correlative sequences are observed in the passive margin deposits. At least two major transgressive–regressive sea-level cycles occurred during the evolution of the carbonate megasequence, which lies above glaciomarine diamictites of probable early Cryogenian (i.e. Sturtian) age. C, O, Sr and S isotope trends from analyses of well-preserved samples, together with lithostratigraphic observations, provide reasonable correlations for most of the Neoproterozoic successions of the Saõ Francisco Craton. The 87Sr/86Sr record of these successions, ranging from 0.70769 to 0.70780, supports the proposed correlation with the Bambuı´, Una and Vaza/Barris successions, and with the basal units of the Vazante Group. In addition, C-isotope positive excursions ranging from þ8.7 to þ14‰ and negative excursions from –5.7 to –7‰ VPDB in the Bambuı´, Una and Vaza-Barris successions provide key markers for correlations. The precise ages of the sedimentation in these successions remains a matter of debate, but organic shales of two units of the Vazante Group have been dated by Re–Os techniques in two different laboratories, both yielding Mesoproterozoic ages. The Neoproterozoic and Mesoproterozoic successions preserve significant glaciogenic deposits.

The global occurrences of low-latitude Neoproterozoic glacial With these caveats in mind, aspects of the litho- and sediments and the texturally and isotopically anomalous post- sequence-stratigraphy, chemostratigraphy and radiometric ages glacial carbonates deposited during potential ‘Snowball Earth’ of the most representative glaciogenic and carbonate-rich succes- events (Hoffman et al. 1998a; Hyde et al. 2000; Hoffman & sions of the Saõ Francisco Craton, and their possible global corre- Schrag 2002) provide stratigraphic markers that have been used lation, are discussed in this chapter. for inter-continental correlations. However, the timing and duration of the Neoproterozoic ice ages are in most cases poorly Structural and geotectonic framework constrained, due to the lack of absolute ages from appropriate lithologies. This is the case for the carbonate-dominated Most of the glaciogenic successions of the Saõ Francisco Craton Vazante, Bambuı´ and Una groups (cf. Azmy et al. 2001, 2006; were likely deposited during extensional events related to the frag- Misi et al. 2007) on the Saõ Francisco Craton in east central mentation of the Rodinia supercontinent starting around 950 Ma Brazil (Fig. 48.1), although new chronometric techniques are and extending until c. 600 Ma (Condie 2002). These extensional revealing surprising results (cf. Babinski et al. 2007). events were episodic during the closure of the Pan-African-Brasi- In the absence of radiometric or biostratigraphic tie-lines in liano rift (Porada 1989; Brito-Neves et al. 1999; Condie 2002; these Neoproterozoic successions, time-series trends in stable Cordani et al. 2003). A relationship between Neoproterozoic gla- isotope signatures have been used as long-distance correlation ciation and extensional tectonics has been previously postulated tools for the cap carbonates and other carbonate lithofacies (e.g. Young 1995). throughout the marine sequences (e.g. Knoll et al. 1986; Derry These sedimentary successions deposited on the Saõ Francisco et al. 1989; Fairchild et al. 1990; Kaufman et al. 1991; Kaufman Craton were distributed in the following geotectonic settings & Knoll 1995; Jacobson & Kaufman 1999; Brasier & Shields (Misi et al. 2007) (Fig. 48.1): 2000; Azmy et al. 2001; Cozzi et al. 2004, Halverson et al. 2005; Azmy et al. 2006). However, a priori assumptions of the † mixed carbonate and siliciclastic strata deposited on tectoni- ages of some of the Neoproterozoic glacial deposits (i.e. Sturtian cally stable cratons, including the Bambuı´ and Una groups in v. Marinoan) in the absence of direct radiometric constraints the Saõ Francisco Basin and in the Ireceˆ, Campinas, Una- (Hoffman & Schrag 2002), and the likelihood of depositional Utinga and Ituaçu´ sub-basins, respectively; (and diagenetic) variations in C- and Sr-isotope compositions † intensely deformed mixed carbonate and siliciclastic strata in complicate the use of chemical stratigraphy for basin-to-basin passive-margin basins surrounding the stable cratons, including comparisons. In addition, correlations need to take into account part of the Vazante group (Brası´lia Fold Belt) and the Vaza the possibility of structural complications due to the tectonic Barris/Miaba group (Sergipano Fold Belt), among others sur- setting during and after sedimentation. rounding the cratonic area.

From:Arnaud, E., Halverson,G.P.&Shields-Zhou, G. (eds) The Geological Record of Neoproterozoic Glaciations. Geological Society, London, Memoirs, 36, 509–522. 0435-4052/11/$15.00 # The Geological Society of London 2011. DOI: 10.1144/M36.48 510 A. MISI ET AL.

Fig. 48.1. The Sa˜o Francisco Craton in NE Brazil with the Neoproterozoic cover (Sa˜o Francisco Supergroup) and the folded belts surrounding the cratonic area.

Some authors (Chang et al. 1988; Thomaz Filho et al. 1998; into three megasequences (glaciogenic, carbonate platform and Dardenne 2001; Pimentel et al. 2001) have postulated that the Neo- dominantly continental siliciclastic units) separated by erosional proterozoic sediments on the Saõ Francisco Craton accumulated in unconformities (Misi 2001; Misi et al. 2007). Each megasequence foreland basins during compressive events related to the Brasi- may have other smaller sequence boundaries that, when associated liano–Pan African orogeny. On the other hand, D’el Rey Silva with high-resolution chemostratigraphic data, may provide key (1999) demonstrated that sedimentation of the Vaza Baris/Miaba event markers for stratigraphic correlations. These megasequences domains in the Sergipano Belt (NE Brazil) occurred on a passive are briefly described below (Fig. 48.2). continental margin. The similarity of cyclic sedimentation in the marginal and epicontinental marine basins suggests that sediments Glaciogenic megasequence originally spanned the craton. Extensional tectonism associated with the glacial deposits ‘is indicated by the presence of large poly- Siliciclastic rocks at the base of the successions are dominated ... lithic clasts of both basement and cover in the diamictites point- by conglomerate, metagreywacke, diamictite, pelite and quartzite. ing to uplift-erosion of footwall and possibly hanging wall blocks These deposits are interpreted as having a continental glacial to a twice in the evolution of the basin’ (Dardenne 1978 , 1979, 1981; glacial–marine origin. Striated pavements and dropstones as D’el Rey Silva 1999, p. 463). Alkmim (1996) and Misi (1999) well as faceted and striated clasts in most of the lithofacies have demonstrated the existence of widespread aligned structures with been described (So¨fner 1973; Karfunkel & Hoppe 1988; Montes 8 8 orientation 10 N–20 W intersecting both the older Proterozoic 1977; Guimara˜es 1996; Uhlein et al. 2004). These lithofacies basement and the Neoproterozoic sedimentary cover (Fig. 48.1). unconformably overlie the Palaeoproterozoic/Archaean basement complex and the Mesoproterozoic Espinhaço Supergroup. They Stratigraphy constitute the Jequitaı´ Fm. in the Bambuı´ Group (states of Minas Gerais, Bahia and Goia´s), and the Bebedouro Fm. in the Una The Neoproterozoic successions of the Saõ Francisco Craton are Group (state of Bahia). In the passive margin basins, glacial dia- part of the Saõ Francisco Supergroup. They may be subdivided mictite is present in the Panelinha Fm. (Rio Pardo Group) and NEOPROTEROZOIC SUCCESSIONS OF THE SA˜ O FRANCISCO CRATON 511

Fig. 48.2. Megasequences of the Neoproterozoic successions of the Saõ Francisco Supergroup (modified from Misi et al. 2007). the Macau´bas Group, both of the Araçuaı´ Fold Belt, the Palestina (northern Bahia) and by part of the Vazante Group (western Fm. in the Vaza Barris/Miaba Group of the Sergipano Fold Belt, Minas Gerais), include possibly equivalent strata, although the tec- and the Santo Antonio do Bonito Fm. in the Vazante Group of tonic setting differs in each of these regions. The stratigraphic the Brasilia Fold Belt (Fig. 48.2). thicknesses in these marginal basins are greater than in the intra- In addition, Brody et al. (2004), Olcott et al. (2005) and Azmy cratonic basins, and parts were intensely deformed during the et al. (2006) document the presence of abundant dropstones in the Brasiliano–Pan African orogeny. black shale of the Serra do Poço Verde and Lapa formations higher At least two transgressive–regressive cycles are clearly rep- up in the Vazante Group. The Serra do Poço Verde shale is sand- resented in the carbonate platform sediments deposited in the intra- wiched between carbonate breccia, which may also be glacial in cratonic basins (Dardenne 1978b, 1979, 2000; Misi 1978; Misi origin (Olcott et al. 2005), and contains glendonite, a carbonate et al. 2007). The first cycle ends with an extensive sub-aerial mineral after ikaite that only forms in sediments at frigid tempera- exposure surface associated with tepee structures, replaced nodular tures. Based on recent geochronological data (Re–Os in black anhydrite, dissolution breccias, and laminated and columnar stro- shales, Azmy et al. 2008; Geboy et al. 2009), this possible glacio- matolites (Fig. 48.2). genic event is considered by some authors as Mesoproterozoic in age, as will be discussed later.

Table 48.1. Correlations between the Bambuı´ formations and the Una Carbonate platform megasequence (marine) Group units The carbonate platform facies are composed of limestone, dolo- Group stone, marl, shale and siltstone. Internal to the Saõ Francisco Lithotypes BAMBUÍ UNA , craton, the Bambuı´ Group (Dardenne 1978b, 1979, 2000) is subdi- (Formations)*, † (Units) ( Form.)‡ § vided into the following formations: Sete Lagoas (dolarenite with teepee structures at the top, laminated limestones and red argillac- Arkose, siltstone Três Marias – eous dolostone at the base), Serra de Santa Helena (marl and intercalated limestone), Lagoa do Jacare´ (black, organic-rich oolitic Siltstone, pelite and intercalated limestone Serra da Saudade – limestone) and Serra da Saudade (siltstone, pelites and intercalated limestone). In the Ireceˆ and Una-Utinga basins of the Una Group, Black organic -rich calcarenite and calcilutite Lagoa do Jacaré Unit A1 with oolitic and pisolitic limestones with the dominant carbonate succession has been subdivided into five interbedded pelite and marl informal units that correlate with those of the Bambuı´ Group (Misi & Souto 1975; Misi 1978; Misi & Veizer 1998): Unit C Grey marl, pelite and siltstone with black Serra de Santa Unit A (base of Sete Lagoas Fm.), Unit B (mid section of Sete Lagoas limestones Helena Fm.), Unit B1 (top of Sete Lagoas Fm.), Unit A (Serra de Sta. Clear grey dolarenite w/stromatolites and Sete Lagoas 3 Unit B1 tepee structures (Upper) Helena Fm.) and Unit A1 (Lagoa do Jacare´ Fm.) See Table 48.1 Laminated limestone and shale (Middle) Sete Lagoas 2 Unit B for a brief description of these facies. Salitre Formation The passive margin successions bordering the craton, which are Red argillaceous dolostone (Lower) Sete Lagoas 1 Unit C represented by the Vaza Barris/Miaba Group (NE of the Saõ Francisco Craton, in Bahia and Sergipe states), the Rio Pardo Diamictite, arkose, pelitic rocks Jequitaí Bebedouro Group (Bahia), the Rio Preto and Riacho do Pontal groups *Dardenne (1978), †Misi (1978), ‡Misi & Souto (1975) and §Branner (1911). 512 A. MISI ET AL.

Dominant continental siliciclastic megasequence (molasses) Vazante Group

Continental siliciclastic rocks composed of arkose, siltstone, phyl- The Vazante Group (Dardenne 2000, 2001) consists mainly of stro- lite and conglomerate constitute the Treˆs Marias Fm. of the matolitic carbonate muds and rhythmites deposited on a shallow Bambuı´ Group. The origin of these deposits is related to post- marine platform (Dardenne 2001) that extended more than tectonic molassic sedimentation along the borders of the cratonic 300 km north–south along the western margin of the craton. The area (Brito Neves & Cordani 1991). Whereas Brito Neves & succession now lies in the external zone of the Brası´lia Fold Belt Cordani (1991) claimed that the contact between the Treˆs Marias (Fig. 48.3) in the Saõ Francisco Basin (SFB). The stratigraphy of Fm. and the Bambuı´ Group is an erosional unconformity, others the marginal marine sediments of the Vazante Group (Fig. 48.4) have postulated a gradational contact between the Treˆs Marias has been studied in detail and refined by several authors (e.g. Dard- Fm. and the Serra da Saudade Fm. (Dardenne 1978b, 1979, enne 1978, 1979, 2000, 2001; Madalosso 1979; Karfunkel & Hoppe 2000; Martins-Neto, pers. comm; cf. Misi 2001). 1988; Fairchild et al. 1996; Azmy et al. 2001; Misi 2001; Misi et al. 2007). The Vazante sequence, from bottom to top, includes the Santo Antonio do Bonito, Rocinha, Lagamar, Serra do Garrote, Characteristics and distribution of the glaciogenic Serra do Poço Verde, Serra do Calcario and Serra da Lapa- Velosinho formations (Fig. 48.4). In the eastern part of the basin, deposits and associated strata carbonate, diamictite and shale of the Vazante Group are generally well preserved and little metamorphosed. To the west near the Bra- The Neoproterozoic glaciogenic deposits of the Saõ Francico Craton silia Fold Belt, however, the sediments are highly deformed and are widespread and found in the basal sections of the epicontinental have experienced amphibolite to granulite facies metamorphism basins of the Bambuı´ Group (Saõ Francisco Basin; see also Uhlein (Dardenne 1978a;Fucket al. 1994). Earlier studies indicated that et al. 2011) and the Una Group (Ireceˆ, Una-Utinga and Campinas the Vazante Group sediments accumulated in a passive margin sub-basins; see also Guimara˜es et al. 2011) and in the basal and setting (e.g. Dardenne 1979; Campos Neto 1984a, b;Fucket al. middle parts of the passive margin basin of the Vaza Barris/ 1994), which is consistent with the lack of volcanic input to the Miaba Group (Sergipano Fold Belt). The glaciogenic deposits of sequence. The northern and southern segments were separated by the Vazante Group (Brasilia Fold Belt) occur in the basal and a regional WSW–ESE lineament situated on the same latitude of upper parts of the sequence, but their ages are still a matter of the Federal District (DF, Fig. 48.1). They show distinct geotectonic debate, as will be discussed in subsequent sections. Figure 48.1 characteristics: intensely deformed in the southern segments with shows the distribution of these basins in the studied area. tectonic transport of great magnitude (from west to east), while in the northern segment the sedimentary units are less deformed and the stratigraphic organization remains well preserved, probably Bambuı´ and Una Groups due to the location of this segment at an upper crustal level of the granite-gneiss basement, ‘which acted as a rigid block in front The Bambuı´ Group in the Saõ Francisco Basin and the Una Group of the compressive trend of the Brasiliano Cycle’ (Dardenne in the Ireceˆ, Una-Utinga and Campinas sub-basins (Fig. 48.1) were 2000, p. 234). deposited in epicontinental, shallow-marine environments. Recent geochronological studies suggest that at least part of Remarkable lithostratigraphic and chemostratigraphic similarities what is referred to as the Vazante Group may predate the Bambuı´ support detailed correlation between these isolated sub-basins, Group (Geboy 2006; Rodrigues 2007; Azmy et al. 2008; Rodri- despite their present discontinuity. gues et al. 2008). Deposition in this likely once contiguous basin began with The Vazante Group rests on a glaciogenic unit (D), which con- dominantly glacial and glaciomarine sedimentation in the Jequitaı´ stitutes the uppermost part of the Santo Antonio do Bonito Fm. Fm. (Bambuı´ Group) and the Bebedouro Fm. (Una Group), as (Fig. 48.4). This diamictite contains faceted and striated cobbles represented by glacial diamictites, which contain faceted and and is overlain by the Cubataõ Fm., a thick stromatolitic dolostone. striated clasts, as well as dropstones in finely laminated pelites. New observations of dropstones in organic-rich shale sand- In some regions, this diamictite contains basement clasts in a wiched between previously recognized dolomite breccia in the fine-grained Fe-rich mudstone, and in the Sete Lagoas region, Serra do Poço Verde Fm. suggest the presence of a second glacial it is overlain by a carbonate lithofacies containing centimetre- horizon (D II) near the top of the succession (Olcott et al. 2005; scale sea-floor precipitates. Discontinuous aeolian sandstone with Azmy et al. 2006). The carbonate diamictites were found in variable thickness occurs above the Bebedouro Fm. diamictite exploration drill holes in a known geographic extension of over (Guimara˜es 1996). These units were deposited unconformably 150 km in an approximate north–south direction, between the over the Palaeoproterozoic and Archaean basement, as well as cities of Unai and Lagamar. In most of the area they are associated the Mesoproterozoic sedimentary rocks of the Espinhaço Super- with black shales and debris flows with fist-sized dropstones. The group (Fig. 48.1). preserved thickness of this unit ranges from 20 m to .100 m, and The carbonate platform marine sedimentation that follows was dolostone clasts vary from from millimetres to several metres deposited unconformably on the glaciogenic and glaciomarine in diameter. lithotypes. The lithostratigraphic units from the top to bottom This unit can be broken down into two distinct levels: one in the include formations with similar characteristics in the Bambuı´ upper Morro do Calca´rio Formation, frequently in unconformable and Una groups, as noted by Dardenne (1978b, 1979, 2000) and contact with the Lapa Fm., and a lower one in the Lower Poço Misi et al. (2007) (Table 48.1). Verde Fm. (DNPM hole 1-PSB01 from 275.50 to 304.50 m). The thickness of the glaciogenic megasequence ranges from 0 to Thin section observations revealed the presence of the unusual 150 m, while the thickness of the carbonate-rich interval is variable, cold-water carbonate ‘glendonite’ in some of the shale samples probably controlled by a basement fault system active during sedi- (Olcott et al. 2005), which may support the syn-glacial interpret- mentation (Dardenne 1978, 1979, 2000; Misi et al. 2007). Seismic ation of this unit. A sharp drop in d13C values is recorded in surveys from the central part of the Saõ Francisco Basin indicate bedded dolomite above the shale horizon in one core (Azmy that the carbonate platform is up to 1000 m thick (Teixeira et al. et al. 2001), and possible cap-carbonate lithofacies (red dolo- 1993). In contrast, it reaches only 600 m in thickness in the Sete stones) have been recognized in field exposures near Vazante Lagoas area (Pedrosa Soares et al. 1994), 400 m in the Serra do mine. A regional unconformity separating the Morro do Calca´rio Ramalho and Januaria-Itacarambi areas (Dardenne 1978b,1979, Fm. from the overlying Lapa Fm. occurs at the top of the upper 2000; Misi 1979), and 600 m in the Ireceˆ Basin (Misi 1979). diamictite (D II) (Misi et al. 2005). NEOPROTEROZOIC SUCCESSIONS OF THE SA˜ O FRANCISCO CRATON 513

Fig. 48.3. Simpliﬁed regional geological map of the Brasilia Belt showing the distribution of the Vazante Group, based on Marini et al. (1984), Dardenne (2000), Pimentel et al. (2001) and Valeriano et al. (2004).

Coupled with a negative d13C excursion in overlying carbonate represented by a lower siliciclastic megasequence (Jueteˆ, Itabaiana and marl, Brody et al. (2004) and Azmy et al. (2006) interpret basal and Ribeiro´polis formations) and an upper carbonate megase- Lapa sediments as a post-glacial cap-carbonate lithofacies. Alter- quence (Acaua˜ and Jacoca formations). According to D’el natively, the Morro do Calca´rio interval of carbonate breccia has Rey Silva (1999), ‘the lateral correlation between the formations been interpreted as debris-flow deposit along the western flank of each megasequence in Cycle 1 is constrained by their same of a stromatolitic platform, and thus may be intra-formational in stratigraphic position, by the strong similarity of the rock types, origin and not directly related to glaciation (Dardenne 1979, and by the fact that the Simaõ Dias Group forms a blanket of sili- 2000, 2006, 2007). ciclastics that is continuous across the craton-fold belt boundary’ (Fig. 48.6). Cycle 2 is similarly composed of a lower siliciclastic interval, including the Simaõ Dias Group and the Palestina Fm. Vaza Barris/Miaba Group and an upper carbonate interval, represented by the Olhos d’A´ gua Fm. The Sergipano belt was divided by D’el Rey Silva (1999) into three Carbonates of the Jacoca Fm., at the basal section of the Vaza tectonic domains: the cratonic Estaˆncia domain, the external Vaza Barris/Miaba Group, are in sharp contact with the Ribeiropolis Barris domain and the intermediate Macurure´ domain. These diamictite below. This unit is 0–300 m thick and locally reaches domains form a continuous wedge of craton, platform and basinal thicknesses of c. 500 m. It consists of diamictite with dropstones, deposits developed along a continental margin (Fig. 48.5). The metagreywacke and quartz-sericite phyllite overlying quartzites intermediate Macurure´ domain (max. thickness, 13 km) is com- of the Itabaiana Fm. D’el Rey Silva (1995, 1999) has reported posed of carbonate and siliciclastic sedimentary rocks with associ- volcanics within this formation. A typical section of the Jacoca ated metavolcanics. The Vaza Barris domain (1–4 km thick) Fm. starts with a thick layer of laminated grey to pink dolostone includes marine platform siliciclastic and carbonate sediments containing pyrite and chalcopyrite, followed up-section by a 3– with minor volcanic horizons, comprising the Miaba, Simaõ 15-m-thick layer of laminated dolostone, and dark grey to black Dias and Vaza Barris groups. The Estancia domain (1–3 km phyllites, followed by c. 10-m-thick massive dolostone (Sial thick) is composed of continental to shallow marine sediments. et al. 2009). This unit is overlain by a 40-m-thick heterolithic D’el Rey Silva (1999) described two sedimentary cycles in these sequence of grey limestones and dark to black phyllites and domains, each including two megasequences: Cycle 1 is finally by grey dolostones. 514 A. MISI ET AL.

(Bambuı´ Group) formations on the Sa˜o Francisco craton

n (Tables 48.1 & 48.2). Member Approx. Chemostratigraphy Group (m)

Formatio Thickness High-resolution chemostratigraphic studies have been conducted Serra da Lapa Velosinho 650 in the Ireceˆ Sub-basin (Fig. 48.1), Una Group (Torquato & Misi organic-rich shales 1977; Misi & Veizer 1998), in the Sa˜o Francisco Basin, Serra do Lapa DII Ramalho area (Powis 2006; Misi et al. 2007), in the Brasilia Fold Belt, Vazante Group (Azmy et al. 2001, 2006) and in the Ser- gipano Fold Belt (Sial et al. 2000, 2003, 2005, 2006a, b). Kawa-

do Upper Pamplona shita (1998) analysed Sr, C and O isotopes in the carbonate 300 sections at a lower stratigraphic resolution. The following review

Calcário

Morro is mostly based on the recent synthesis by Misi et al. (2007).

Ireceˆ Basin Middle Pamplona 400 One of the earliest isotopic studies of a post-glacial cap carbonate was performed in the Ireceˆ Basin (Una Group) by Torquato & Misi Lower Pamplona 200 (1977), although at the time the unit was considered lacustrine in origin. These authors analysed 85 carbonate samples for C and Upper Morro do Pinheiro 500 O isotopes through two complete sections of the Una Group. The results reveal a d13C trend from consistently negative values in Lower Morro do Pinheiro 500 the red argillaceous dolostone (Unit C, c. –6‰) immediately Serra do Poço Verde above diamictite of the Bebedouro Fm. to values c. 0‰ up-section (Units B and B1) and continuing to highly positive values (þ8‰, Unit A1). The negative values in the dolostone overlying the Bebe- douro Fm. diamictite are similar to post-glacial trends worldwide >1000 and may support the glacial interpretation for these deposits.

do Garrote This trend has been reproduced by Misi & Veizer (1998), who analysed well-preserved micro-samples that were ﬁrst characterized

VAZANTE by petrographic and geochemical techniques. In addition, these 87 86 Serra authors determined Sr/ Sr ratios on the best-preserved carbonates. The least radiogenic 87Sr/86Sr value of 0.70780 from Unit B Sumidouro is consistent with a sedimentation age between 750 and 600 Ma 250 (cf. Jacobsen & Kaufman 1999) (Fig. 48.7).

Lagamar Arrependido Saõ Francisco Basin 1000 The carbonates of the Bambuı´ Group in the Saõ Francisco Basin Rocinha have been the subject of many chemostratigraphic studies (e.g. arkosic sandstone Iyer et al. 1995; Kiang 1997; Kawashita 1998; Santos et al. D 2000, 2004; Kaufman et al. 2001). The most detailed chemostrati- 250 graphic study developed in the Bambuı´ Group thus far comes from high-resolution profiles from the Serra do Ramalho area, western

do Bonito Bahia (Powis 2006; Misi et al. 2007). Chemostratigraphic

St. Antonio studies have also been conducted by Iyer et al. (1995), Kaufman Fig. 48.4. Stratigraphic units of the Vazante Group. et al. (2001) and Vieira et al. (2007) in the Sete Lagoas area of the Saõ Francisco Basin. As in the Ireceˆ Basin, the d13C composition of carbonate rocks in the Serra do Ramalho and in the Sete The Olhos d’A´ gua Fm. (200–1300 m) is composed of inter- Lagoas area increase up-section from c. –4‰ at the base of the bedded limestones that become organic-rich towards the top. Sete Lagoas Fm. overlying glacial diamictite of the Jequitaı´ Fm. The upper section consists of c. 50 m of limestone–pelite inter- (assumed to be correlative to the Bebedouro Fm.) and rising stea- calations that are overlain by laminated limestones (40 m thick) dily up to c. þ14‰ near the top of the succession in Lagoa do culminating with a 30-m-thick layer of organic-rich limestone. Jacare´ Fm. The best-preserved samples (Mn/Sr 0.02) show a The lower section of laminated limestones is in sharp contact narrow range of 87Sr/86Sr values between 0.7074 and 0.7075 with the diamictites of the Palestina Fm., which is composed of (Fig. 48.7). metagreywackes with clasts up to 30 cm in diameter. The clasts are of gneiss, granite, quartz, quartzite, phyllite and metacarbonate supported in a quartz–sericite matrix. Lenses of Fe-cemented Brasilia Fold Belt (Vazante Group) quartzite unconformably overlie the siliciclastic sediments of the Simaõ Dias Group (Fig. 48.6). Petrographic investigations showed that some of the Vazante The Palestina Fm. is interpreted as a glaciogenic deposit. At a carbonates were affected by dolomitization, but examination of lower stratigraphic level, the equivalent Jueteˆ and Ribeiro´polis for- thin sections shows that these rocks have very fine-grained and mations (D’el Rey Silva 1999) are also interpreted as glaciogenic fabric-retentive dolomicrites (Azmy et al. 2001, 2006). Three gen- and may correlate with the Bebedouro (Una Group) and Jequitaı´ erations of secondary dolomitic cements have been observed, NEOPROTEROZOIC SUCCESSIONS OF THE SA˜ O FRANCISCO CRATON 515

Fig. 48.5. Simplified geological map of the Sergipano Belt, modified from D’el Rey Silva (1999). Basement domes: 1, Itabaiana; 2, Simaõ Dias; 3, Jirau do Ponciano. Main thrust and strike–slip fault: MF, Macurure´ fault; BMJF, Belo Monte-Jeremoabo fault; SMAF, Saõ Miguel do Aleixo fault; IF, Itaporanga˜ fault. including fibrous, equant and late fracture-filling phases (cf. Azmy Sergipano Fold Belt (Vaza Barris Group) et al. 2001). No significant increase in crystal size was observed associated with dolomitization, suggesting that the original sedi- Chemostratigraphic studies have been performed on some carbon- ment did not suffer from extensive and/or repeated meteoric ate units of the Vaza Barris Group by Kawashita (1998) and by Sial alteration. et al. (2000, 2003, 2005, 2006a, b). The first author determined The trace element compositions of the Vazante carbonates, least-altered 87Sr/86Sr ratios of 0.7078 in black limestones of the particularly those of the fabric retentive micrites, suggest signifi- Olhos d’A´ gua Fm. In addition Sial et al. (2000) report d13C low cant geochemical preservation (Azmy et al. 2001, 2006). The values of –4.7‰ immediately above diamictite of the Palestina C-isotope profiles reveal a negative shift up to 8‰ in dolomite Fm. These numbers increase up-section to values as high as beds above the dropstone-laden shale of the Serra do Poço þ10‰ in the upper Olhos d’A´ gua Fm. Sial et al. (2006a) also Verde Fm. (Fig. 48.8) and near the base of the Lapa Fm. report negative excursions as low as –5% in the lower carbonates (cf. Azmy et al. 2006; Misi et al. 2007). The least radiogenic of the Acaua˜ Fm. (equivalent to the Jacoca Fm.; Fig. 48.9) immedi- Sr-isotope values associated with the negative d13C shifts are ately above the diamictites of the Ribeiro´polis Fm., suggesting that 0.7061 in the Serra do Poço Verde Fm. and 0.7068 in the Lapa at least two important glaciogenic events are represented in the Fm. (Fig. 48.8). Vaza Barris Group. The results support a possible correlation of

Fig. 48.6. Summary stratigraphy of the Itabaiana dome area, based on D’el Rey Silva (1999). Megasequences: LSM, lower siliciclastic; LCM, lower carbonate (megasequences of Cycle I); USM, upper siliciclastic; UCM, upper carbonate (megasequences of Cycle II). Formations: JU, Jueteˆ A, Acaua˜; I, Itabaiana; R, Ribeiro´polis; JC, Jacoca; LP, Laegarto- Palmares; Ja, Jacare´; FP, Frei Paulo; P, Palestina; OA, Olthos d’A´ gua Formation. 516 A. MISI ET AL.

Table 48.2. Correlations between intracratonic and passive-margin basins Geochronological constraints

Brasiliano Fold Belt Intracratonic Basins Sergipano Fold Belt Passive-margin Basin Passive-margin Basin Despite the absence of reliable absolute geochronological age estimates in the platform carbonate successions of the Sa˜o Fran- Vazante group Bambuí group Una group Vaza barrís/miaba gr. (Formations) (Formations) (Units) (Form.) (Formations) cisco craton, there is a general agreement in considering a middle Cryogenian age for the Bambuı´ and Una groups. The Três Marias – – Serra da Lapa least radiogenic Sr isotope values of 0.7074–0.7077 and S (from

Units Morro do Calcário terrain) Serra sa Saudade – – stratform barite), with a mean value of c. þ30 per mil CDT in Serra do Poço Verde Lagoa do Jacaré A1 the Una Group, indicate that sedimentation likely occurred Olhos d’Água Serra de Santa Helena A between c. 780 Ma and 600 Ma (Misi & Veizer 1998; Misi et al. Serra da Garrote Sete Lagoas 3 B1 Palestina 1999). More recently, Babinski & Kaufman (2003) and Babinski

(overthrusted Mesoproterozoic Lagamar Simão Dias Group Sete Lagoas 2 B et al. (2007) determined new Pb/Pb carbonate ages from well-

itre Formation Rocinha Jacoca Sete Lagoas 1 C Sal preserved post-glacial sea-ﬂoor cements in the Sete Lagoas

Santo Antônio do Bonito Jequitaí Bebedouro Ribeirópolis Fm. of the Bambuı´ Group, suggest a depositional age of 740 + 22 Ma (MSDW ¼ 0.66). Notably, almost the same age (730 Ma, U–Pb in zircon) has been recorded by Brito-Neves (pers comm.) in acidic tuffs intercalated in the Ribeiro´polis the Vaza Barris Group with the carbonate platform successions of diamictites of the Vaza Barris/Miaba Group, in the Sergipano the Bambuı´ and Una Groups, as sustained by some authors (e.g. Belt. According to D’el Rey Silva (1999), sedimentation in the Ser- Misi 1979; Teixeira & Figueiredo 1991; Trompette 1994; D’el gipano Belt lasted from c. 1.0 Ga (U–Pb zircon in metavolcanics, Rey Silva 1999). The diamictites of the Ribeiro´polis Fm. may be Brito Neves et al. 1993) to possibly 0.65 Ga. equivalents of the Bebedouro and the Jequitaı´ formations (respect- On the other hand, the global stratigraphic correlation of the ively, from the Una and Bambuı´ groups), but no equivalent glacial Vazante Group in the Sa˜o Francisco Basin has been a challenging deposits correlating with the Palestina Fm. have been clearly issue. The resetting of the radiogenic clock by the major demonstrated from these epicontinental successions (Fig. 48.9 & Brası´lian–Pan African orogeny (c. 550–600 Ma) (Trindade Table 48.2). et al. 2004) and the scarcity of volcanic ash layers makes absolute

Fig. 48.7. Proposed lithostratigraphic and chemostratigraphic correlation between the Bambuı´ and Una Groups, respectively in the Sa˜o Francisco Basin (Serra do Ramalho area) and in the Ireceˆ Basin (Misi & Veizer 1998; Powis 2006; Misi et al. 2007). NEOPROTEROZOIC SUCCESSIONS OF THE SA˜ O FRANCISCO CRATON 517

the basal portion of the Lagamar Fm. with a maximum age of 1.95 Ga. consistent with the c. 1.35 Ga Re–Os ages obtained by Geboy (2006) from organic shales of the same unit.

Mineralization

Mineral deposits associated with Late Precambrian glacial and carbonate sediments of the Saõ Francisco craton include the following: † Fe–Mn deposits near Porteirinha (Minas Gerais state), which are intimately associated with glacial sedimentation of the Macau´bas Group in the Araçuaı´ belt, and likely related to exha- lative processes (Dardenne & Schobbenhaus 2001). † Phosphorite deposits interbedded with carbonates in the lower Vazante Group at Coromandel, Rocinha and Lagamar (Dard- enne et al. 1986, 1997; Da Rocha-Arau´jo et al. 1992; Sanches et al. 2007), at the base of the Sete Lagoas Fm. in the Bambuı´ Group at Campos Belos (Dardenne et al. 1986), in the lower half of the Serra da Saudade Fm. in the Bambuı´ Group at Cedro do Abaete´ (Dardenne et al. 1986; Lima et al. 2005), and in stromatolitic beds of the Salitre Fm. in the Ireceˆ basin (Misi & Kyle 1994). † Fluorite, barite and Pb–Zn deposits associated with the upper part of the first carbonate megacycle of the Bambuı´ Group near Janua´ria-Itacarambi, Montalvaˆnia and Serra do Ramalho (Dardenne 1979; Misi 1979; Dardenne & Freitas-Silva 1999). † Pb–Zn sulphide deposits associated with brecciated dolomite in the middle Vazante Group at Morro Agudo mine (Hitzman et al. 1995; Misi et al. 1998, 1999; Dardenne & Freitas-Silva 1999; Bettencourt et al. 2001; Monteiro 2002). † Zn silicate deposits associated with major fault structures at the Vazante mine, Minas Gerais (Dardenne & Freitas-Silva 1999; Bettencourt et al. 2001; Monteiro 2002; Misi et al. 2005). Fig. 48.8. Chemostratigraphy of the Vazante Group. geochronological age control of this succession problematic. The Discussion abundance of Conophyton metula Kirichenko in the Lagamar Fm. (Fig. 48.4) suggests an age estimate between 1350 Ma and Broadly speaking, the Neoproterozoic Era experienced at least three 950 Ma for the sedimentation of this part of the Vazante Group widespread ice ages, commonly referred to as the Gaskiers, Mar- (Cloud & Dardenne 1973). Nevertheless, Misi et al. (1997) and inoan and Sturtian events, which are radiometrically constrained Sanches et al. (2007) analysed carbonate fluorapatite and fine- to be c. 585 Ma (Newfoundland: Bowring et al. 2003; Halverson grained organic-rich limestone (micrite) from the lower Rocinha et al. 2005), c. 630 Ma (South China: Condon et al. 2005; Zhang Formation for their Sr-isotope composition. 87Sr/86Sr values et al. 2005) and c. 750 Ma (Namibia: Hoffman et al. 1996), respect- range from 0.70760 to 0.70790, similar to those reported for the ively. Some researchers suggest that these singular glacial events Bambuı´, Una and Vaza Barris/Miaba Groups. All seven samples may have been diachronous, spanning over tens of millions of had high total Sr (.1300 ppm) and low Mn–Sr (0.1–0.01), indi- years, or alternatively split into several discrete ice ages (e.g. cating a high degree of preservation of the original seawater signal. Kaufman et al. 1997; Kendall et al. 2006). In most cases, the Sm–Nd studies of provenance (Pimentel et al. 2001) on fine- glacial diamictites are overlain by texturally and isotopically enig- grained sediments of the Bambuı´, Vazante and Paranoa´ groups matic cap carbonates with strong negative C-isotope anomalies have furnished TDM model age intervals of 1.9–1.4 Ga, 2.3– (e.g. Kaufman et al. 1997; Hoffman et al. 1998b), which have 1.7 Ga and 2.3–1.9 Ga for the respective groups. According to also been recorded in syn- and immediately pre-glacial carbonates these authors, the provenance results suggest that the Vazante (e.g. Kaufman et al. 1997; Kennedy et al. 2001; Halverson et al. Group constitutes a transitional sequence between the Paranoa´ 2002). In contrast, S-isotope compositions in the cap carbonates pre- and Bambuı´ groups. serve remarkably positive d34S anomalies (e.g. Hurtgen et al. 2002). Recent Re–Os investigations of organic-rich shales of the upper In all the studied Neoproterozoic successions from the Saõ Fran- Vazante Group (Geboy 2006; Azmy et al. 2008) suggest a signifi- cisco craton, at least one horizon of glacial diamictite (generally cantly older, Mesoproterozoic age for the Morro do Calca´rio and recognized on the basis of faceted and striated clasts of hetero- Serra do Garrote units, with ages of c. 1 Ga and older. However, geneous composition in a fine-grained matrix) has been recog- U–Pb determinations on detrital zircons (Dardenne et al. 2003, nized. Most often, these glacial horizons occur at the base of the 2005; Dardenne 2007a; Rodrigues 2008; Rodrigues et al. 2008) succession. These ice age deposits are overlain by cap carbonates, indicated maximum depositional ages for the Santo Antonio do although in some cases a thin siliciclastic wedge, perhaps record- Bonito Fm. (diamictites at the basal section of the Vazante ing glacial outwash facies during meltback (Bailey & Peters 1998), Group, Fig. 48.4) of 988 + 15 Ma. Rodrigues et al. (2008) and separates the diamictite from carbonate lithofacies. Chemostrati- Rodrigues (2008) also report a significant Neoproterozoic zircon graphic studies (including C, S and Sr isotopes) and Pb/Pb population from the Rocinha Fm. in which the youngest grains dating of carbonates from these glaciogenic successions provide have been dated c. 925 Ma. Nonetheless, in the same study the tools for possible correlations with Neoproterozoic counterparts authors identified provenance patterns for the conglomerates at around the world. 518 A. MISI ET AL.

Fig. 48.9. Chemostratigraphy of the Vaza Barris/Miaba Groups (modiﬁed from Sial et al. 2000).

Perhaps of greatest interest are the correlation of Bambuı´, diamictite with the Otavi Group is missing and we regard it Una, Vazante and Vaza Barris/Miaba group deposits on the Saõ is possible that these glacial deposits instead correlate with Francisco Craton with Neoproterozoic equivalents on the Congo possibly younger glacial deposits of the Witvlei Group on the Craton in Namibia. If we accept that throughout much of the Kalahari Craton in southern Namibia (Kaufman et al. 1997; Mesoproterozoic and Neoproterozoic eras these cratons were Saylor et al. 1998). joined, the broadly equivalent sedimentary successions should On the western margin of the Sao Francisco Craton in Brazil, reveal striking similarities. However, whereas the well-studied the basal glacial deposit of the Vazante Group (Santo Antonio Otavi Group, in Namibia, hosts at least two cap carbonates atop do Bonito Fm.) has long been considered as an equivalent to the glacial sediments (Kaufman et al. 1991; Hoffmann & Prave basal diamictite of the Bambuı´ Group beneath the Sete Lagoas 1996; Hoffman et al. 1998b), only one ice age deposit is currently Fm. Overlying strata in both successions are variably mineralized recognized in the Bambuı´ and equivalent Una groups. Diamictites (phosphate and Pb–Zn) and contain thick carbonate intervals. from these units containing basement clasts in a fine-grained However, C-isotope compositions of the carbonates differ signifi- Fe-rich mudstone and overlained by a cap-carbonate lithofacies cantly. The d13C profile for Vazante carbonates is generally near with centimetre-scale sea-floor precipitates, are strikingly similar zero, and shows only minor excursions to negative values that to those of the younger Maieberg Fm. cap carbonate in Namibia. are interpreted to reflect cap-carbonate lithofacies (Azmy et al. The Sete Lagoas precipitates are preserved in limestone with nega- 2001, 2006). In contrast, the strongly negative d13C values of the tive d13C values and high Sr abundances. Sr-isotope compositions Sete Lagoas cap carbonate are followed by remarkably positive of these lithologies are consistently around 0.7073, which is an values (upwards to þ16‰) in overlying strata (Misi et al. 2007). exact match with the precipitate interval in the Maieberg Fm., sup- Thus the equivalence of these successions is suspect, although porting this intracontinental correlation. Notably, Pb/Pb dating of Sr-isotope compositions of lower Vazante phosphorites are quite the Sete Lagoas precipitates yielded an age of 740 + 22 Ma similar to those in well-preserved limestones of the Bambuı´ and (11-point isochron; MSWD ¼ 0.66; Babinski et al. 2007). Accep- Una groups (Misi & Veizer 1998). Further complicating the inter- tance of this date and the correlation with the precipitates in the basinal correlation is the presence of a second Vazante Group dia- Maieberg Fm. associates both of these post-glacial deposits with mictite (D II) in the Serra do Poço Verde Fm. (Fig. 48.2: Olcott the Sturtian ice age. This assignment is at odds with the view of et al. 2005; Azmy et al. 2006), and the possibility that the over- the Maieberg Fm. as the archetypical Marinoan cap carbonate lying Lapa Fm. was deposited during oceanic transgression after (Hoffman & Schrag 2002), and the c. 630 Ma age assigned to a third possible glacial event (Brody et al. 2004; Azmy et al. 2006). the underlying Ghaub diamictite by the correlation of this unit It has been suggested previously that the shale and marly car- with an ash-bearing diamictite in the deformed Swakop Group of bonate of the Lapa Fm. may be equivalent to the Rasthof Fm. in central Namibia (Hoffmann et al. 2004). Independent chemostrati- northern Namibia (the older of the two Otavi Group cap carbon- graphic evidence for the equivalence of the dated Swakop Group ates). This assignment, however, was based on comparable NEOPROTEROZOIC SUCCESSIONS OF THE SA˜ O FRANCISCO CRATON 519 negative d13C excursions in both units, and on a single Sr-isotope Babinski,M.&Kaufman, A. J. 2003. First direct dating of a Neoproter- value (c. 0.7068) from a dolomite cement in the basal Lapa For- ozoic post-glaciogenic cap carbonate. IV South American Symposium mation (Azmy et al. 2001, 2006) that matches with the lowest on Isotope Geology, Short Papers 1, 321–323. values recorded in Sr-rich Rasthof limestones. However, the Babinski,M.,Vieira,L.C.&Trindade, R. I. F. 2007. Direct dating of Sr-isotope equivalence of these units is problematic and, further- the Sete Lagoas cap carbonate (Bambuı´ Group, Brazil) and impli- more, new Re–Os age constraints for shale of the Lapa and cations for the Neoproteozoic glacial events. Terra Nova, 19, 401–406. older organic-rich lithologies in the Vazante Group suggest that Bailey Peters this succession may be far older than previously considered. ,C.M.& , S. E. 1998. Glacially influenced sedimentation in Re–Os age determinations on Lapa Fm. shale suggest an age of the late Neoproterozoic Mechum River Formation, Blue Ridge pro- vince, Virginia. Geology, 26, 623–626. close to one billion years (Azmy et al. 2008), and similar measure- Bettencourt, J. S., Monteiro, L. V. S., Bello, R. M. S., Oliveira,T. ments of organic-rich shale in the underlying Serra do Poço Verde F. & Juliani, C. 2001. Metalogeˆnese do Zinco e chumbo na and Serra do Garrote formations yield ages of c. 1.1 and 1.3 Ga regiaõ de Vazante-Paracatu, Minas Gerais. In: Pinto,C.P.& (Geboy 2006; Geboy et al. 2006, 2009). A Mesoproterozoic Martins-Neto, M. A. (eds) Bacia do Saõ Francisco: Geologia e age for this succession is consistent with the relative invariance recursos minerais. SBG-Nućleo de Minas Gerais, Belo Horizonte, of C-isotope trends in the Vazante Group, which are comparable 161–198. with the Paranoa´ Group stratigraphically beneath Bambuı´ Bowring, S., Myrow, P., Landing, E., Ramezani,J.&Grotzinger,J. sediments in central and eastern Brazil (Santos et al. 2000). 2003. Geochronological constraints on terminal Proterozoic events This older age is similarly suggested from Nd-isotope studies of and the rise of metazoans. Geophysical Research Abstracts (EGS, detrital grains in the Vazante Group (Pimentel et al. 2001) and Nice), 5, 219. the appearance of Conophyton metula Kirichenko stromatolites Brasier ,M.D.&Shields, G. 2000. Neoproterozoic chemostratigraphy (Cloud & Dardenne 1973), which are also known from the and correlation of the Port Askaig glaciation, Dalradian Supergroup Paranoa´ Group. of Scotland. Journal of the Geological Society of London, 157, The Re–Os ages provided by two different laboratories would 909–914. push the known record of Late Precambrian glaciation into the Brito Neves,B.B.,Van Schmus, W. R., Babinski,M.&Sabin, T. 1993. Mesoproterozoic Era, some 500 million years earlier than pre- O evento de magmatismo de 1,0 Ga nas faixas mo´ veis ao norte do viously considered. Further tests of the Re–Os ages, as well as Craa´ton Saõ Francisco. Sociedade Brasileira de Geologia, Simpo´sio o Cra´ton do Saõ Francisco 2, Salvador, Anais, 243–245. time-series elemental, isotopic and biomarker studies (cf. Olcott Brito-Neves Campos-Neto Fuck et al. 2005) of the Vazante Group, which are currently in progress, ,B.B., ,M.C.& , R. A. 1999. should shed light on the depositional environment of the glacio- From Rodinia to Western Gondwana: an approach to the Brasiliano– Episodes 22 genic Vazante Group and provide better resolution of these contro- Pan African Cycle and orogenic collage. , , 155–166. Brody, K. B., Kaufman, A. J., Eigenbrode, J .L. & Cody, G. D. 2004. versial age estimates. Biomarker geochemistry of a post-glacial Neoproterozoic succession in Brazil (Abstract), Geological Society of America, Abstracts with During the last ten years CNPq has provided funds for research on the Neoproter- Programs, 36, 477. ozoic basins of the Saõ Francisco Craton. Currently, A. M. receives support from Campos-Neto, M. C. 1984a. Litoestratigrafia, relaço˜es estratigra´ficas e project no. 486416/2006-2. A. J. K. acknowledges the NSF and NASA for evoluçaõ paleogeogra´fica dos grupos Canastra e Paranoa´ (regiaõ funding for work in the Proterozoic successions of Brazil, as well as the Deutsche Vazante-Lagamar, MG). Revista Brasileira de Geocieˆncias, 14, Forschungsgemeinschaft and Westfa¨lische Wilhelms-Universita¨tMu¨nster for 81–91. sabbatical funding in 2007–2008. A. N. S acknowledges support from the CNPq Campos Neto, M. C. 1984b. Geometria e fases de dobramentos brasilia- (grants PROSUL/CNPq 490136/2006-0 and 475657/2006-3) and PRONEX nos superpostos no oeste de Minas Gerais. Revista Brasileira de Geo- APQ-047-1.07/06 that have defrayed costs with fieldwork in Sergipe and cieˆncia, 14, 60–68. Bahia. We are grateful to the directors of Votorantim Metais for supporting Chang,H.K.,Miranda,F.P.&Alkmim, F. F. 1988. Consideraço˜es fieldwork at the Vazante area. This represents a contribution of the IUGS- and sobre a evoluçaõ tectoˆnica da Bacia do Saõ Francisco. In: 35th Con- UNESCO-funded IGCP (International Geoscience Programme) Project #512. gresso Brasileiro de Geologia (Bele´m), Anais, 5, 2076–2090. Cloud,P.E.&Dardenne, M. A. 1973. Proterozoic age of the Bambuı´ Group in Brazil. Geological Society of America Bulletin, 84, References 1673–1676. Condie, K. C. 2002. The supercontinent cycle: are there two patterns of Alkmim, F. F., Brito Neves,B.B.&Alves, J. A. C. 1993. Arcabouço cyclicity? Journal of African Earth Sciences, 35, 179–183. Tectoˆnico do Cra´ton do Saõ Francisco: uma revisaõ. In: Dominguez, Cordani,U.G.,Brito-Neves,B.B.&D’Agrella-Filho, M. S. 2003. J. M. L. & Misi, A. (eds) O Craton do Saõ Francisco SBG, SGM, From Rodinia to Gondwana: a review of the available evidence CNPq, 45–62. from South Ame´rica. Gondwana Research, 6, 275–283. Alkmim, F. F., Chemale, F., Jr. & Endo, I. 1996. A deformaçaõ das Condon,D.,Zhu,M.,Bowring, S., Wang,W.,Yang,A.&Jin, Y. 2005. coberturas proterozoícas do Craton do Saõ Francisco e o seu signifi- U–Pb ages from the Neoproterozoic Doushantuo Formation, China. cado tectoˆnico. Revista da Escola de Minas de Ouro Preto, 49, Science, 308, 95–97. 22–38. Cozzi,A.,Allen,P.&Grotzinger, J. 2004. Understanding carbonate Amaral,G.&Kawashita, K. 1967. Determinaço˜es da idade do Grupo ramp dynamics using d13C profiles: examples from the Neoprotero- Bambuı´ pelo me´todo Rb–Sr. 21st Congresso Brasileiro de Geologia. zoic Buah Formation of Oman. Terra Nova, 16, 62–67. Curitiba, Anais, 214–217. DA ROCHA ARAUJO, P. R., FLICOTEAUX, R., PARRON,C.&TROMPETTE,R. Azmy,K.,Veizer, J., Misi, A., Oliveira, T. F., Sanches,A.L.&Dard- 1992. Phosphorites of Rocinha mine, Patos de Minas (Minas Gerais enne, M. A. 2001. Dolomitization and isotope stratigraphy of the Brasil): genesis and evolution of a Middle Proterozoic Deposit tecto- Vazante Formation, Saõ Francisco Basin, Brazil. Precambrian nized by the Brasiliano Orogeny. Economic Geology, 87, 332–351. Research, 112, 303–329. Dardenne, M. A. 1978a. Zonaçaõ tectoˆnica na borda ocidental do Cra´ton Azmy,K.,Kaufman, A. J., Misi,A.&Oliveira, T. F. 2006. Isotope Saõ Francisco. 30th Congresso Brasileiro de Geologia, Recife, SBG, stratigraphy of the Lapa Formation, Saõ Francisco Basin, Brazil: 1, 299–308. implications for Late Neoproterozoic glacial events in South Dardenne, M. A. 1978b.Sıńtese sobre a estratigrafia do Grupo Bambuı´ America. Precambrian Research, 149, 231–248. no Brasil Central. 30th Congresso Brasileiro de Geologia,SBG,2, Azmy,K.,Kendall, B., Creaser,R.A.,Heaman,L.&de Oliveira, 597–610. T. F. 2008. Global correlation of the Vazante Group Saõ Francisco Dardenne, M. A. 1979. Les mine´ralisations de plomb, zinc, fluor du Pro- Basin, Brazil: Re–Os and U–Pb radiometric age constraints. Pre- te´rozoı¨que Supe´rieur dans le Bre´sil Central. The`se de Doctorat cambrian Research, 164, 160172. d’E´ tat, Universite´ de Paris VI. Coromandel. Dissertaçaõ de Mestrado. 520 A. MISI ET AL.

Dardenne, M. A. 1981. Os grupos Paranoa´ e Bambuı´ na Faixa Dobrada Guimara˜es, J. T. 1996. A Formaçaõ Bebedouro no Estado da Bahia; Brası´lia. An. Simp. Cra´ton Saõ Francisco e suas Faixas Marginais, faciologia, estratigrafia e ambientes de sedimentaçaõ. Dissertaçaõ Salvador, SBG, 140–157. (Mestrado em Geologia), Instituto de Geocieˆncias, Universidade Dardenne, M. A. 2000. The Brası´lia Fold Belt. In: Cordani,U.G., Federal da Bahia (UFBA), Brasil. Milani, E. J., Thomaz-Filho,A.&Campos, D. A. (eds) Tectonic Guimara˜es, J. T., Misi, A., Pedreira,A.J.&Dominguez, J. M. L. 2011. Evolution of South America. International Geological Congress, 31, The Bebedouro Formation, Una Group, Bahia (Brazil). In: Arnaud, Rio de Janeiro, 231–263. E., Halverson,G.P.&Shields-Zhou, G. (eds) The Geological Dardenne, M. A. 2001. Lithostratigraphic sedimentary sequence of the Record of Neoproterozoic Glaciations. Geological Society, London, Vazante Group. In: Misi,A.&Teixeira, J. B. G. (eds) Proterozoic Memoirs, 36, 503–508. Base Metal Deposits of Africa and South America. Proceedings of Halverson, G. P., Hoffman, P. F., Schrag,D.P.&Kaufman,A.J. the 1st Field Workshop IGCP 450, CNPq/UNESCO/IUGS, Belo 2002. A major perturbation of the carbon cycle before the Ghaub Horizonte and Paracatu (MG), Brazil, 48–50. glaciation (Neoproterozoic) in Namibia: prelude to snowball Earth. Dardenne, M. A. 2006. A glaciaçaõ neoproterozoíca do Grupo Vazante Geophysics, Geochemistry, Geosystems, 3, doi: 10.1029/2001G na Faixa Brası´lia: discussaõ e alternativas. Congresso Brasileiro de C000244. Geologia, 43, SBG, Aracaju, Resumos. Halverson, G. P., Hoffman,P.F.&Schrag, D. P. 2005. Toward a Dardenne, M. A. 2007a. The pseudo-diamictites of the Vazante Group. Neoproterozoic composite carbon isotope record. Geological Symposium IGCP 478, Stellenbosch, Abstracts. Society of America Bulletin, 117, 1181–1207. Dardenne, M. A. 2007b. Lithostratigraphy of the Vazante and Bambuı´ Hitzmann,M.W.,Thorman,C.H.,Romagna, G., Oliveira, T. F., groups in the Saõ Francisco Craton and the Brası´lia Fold Belt. Dardenne,M.A.&Drew, L. J. 1995. The Morro Agudo Zn–Pb IGCP 478, Stellenbosch, Abstracts. deposit, Minas Gerais, Brazil: a proterozoic Irish-type carbonate- Dardenne,M.A.&Freitas-Silva, F. H. 1999. Modelos gene´ticos dos hosted SEDEX – replacement deposit. Annual Meeting, New depo´sitos Pb-Zn nos grupos Bambuı´ e Vazante. Workshop: Depo´sitos Orleans, GSA, Abstract, 408. Minerais Brasileiros de Metais-Base. Salvador, CAPES-PADCT- Hoffman,P.F.&Schrag, D. P. 2002. The snowball Earth hypothesis: ADIMB, 86–93. testing the limits of global change. Terra Nova, 14, 129–155. Dardenne,M.A.&Schobbenhaus, C. 2001. Metalogeˆnese do Brasil. Hoffman , P. F., Hawkins, D. P., Isachsen,C.E.&Bowring, S. A. 1996. Editora UnB, Brası´lia, 392. Precise U–Pb zircon ages for early Damaran magmatism in the Dardenne,M.A.,Trompette, R., Magalha˜es,L.F.&Soares,L.A. Summas Mountains and Welwitschia inlier, northern Damara belt, 1986. Proterozoic and Cambrian phosphorites-regional review: Namibia. Geological Survey of Namibia Communications, 11, Brazil. In: Cook,P.J.&Shergold, J. H. (eds) Phosphate Deposit 47–52. of the World. Proterozoic and Cambrian Phosphorites. Cambridge Hoffman, P. F., Kaufman, A. J., Halverson,G.P.&Schrag,D.P. University Press, 116–131. 1998a. A Neoproterozoic snowball Earth. Science, 281, 1342–1346. Dardenne,M.A.,Freitas-Silva, F. H., Nogueira,G.M.S.&Souza, Hoffman, P. F., Kaufman,A.J.&Halverson, G. P. 1998b. Comings J. F. C. 1997. Depo´sitos de fosfato de Rocinha e Lagamar, Minas and goings of global glaciation on a Neoproterozoic tropical platform Gerais. In: Schobbenhaus, C., Queiroz,E.T.&Coelho, in Namibia. GSA Today, 8,1–9. C. E. S. (eds) Principais Depo´sitos Minerais do Brasil. DNPM/ Hoffmann, K.-H. & Prave, A. R. 1996. A preliminary note on a revised CPRM, IVC, 113–122. subdivision and regional correlation of the Otavi Group based on gla- Dardenne,M.A.,Pimentel,M.M.&Alvarenga,C.J.S.2003. ciogenic diamictites and associated cap dolostones. Communications Provenance of conglomerates of the Bambuı´, Jequitaı´, Vazante and of the Geological Survey of Namibia, 11, 77–82. Ibia´ groups, implications for the evolution of the Brası´lia Belt. Hoffmann, K.-H., Condon, D. J., Bowring,S.A.&Crowley,J.L. In: Sociedade Brasileira de Geologia, Simpo´sıó Nacional de Estudos 2004. A U–Pb zircon date from the Neoproterozoic Ghaub For- Tectoˆnicos, 9, International Symposium on Tectonics, 3,Armaçaõde mation, Namibia: Constraints on Marinoan glaciation. Geology, 32, Bu´zios, 2003. Boletim de Resumos, 47–50. 817–820. D’el-Rey Silva, L. J. H. 1995. Tectonic evolution of the Sergipano Belt, Hurtgen, M. T., Arthur, M. A., Suits,N.S.&Kaufman, A. J. 2002. northeastern Brazil. Revista Brasileira de Geocieˆncias, 25, 315–332. The sulfur isotopic composition of Neoproterozoic seawater sulfate: D’el Rey Silva, L. J. H. 1999. Basin infilling in the southern-central implications for a snowball earth? Earth Planet. Sci. Lett. 203, part of the Sergipano Belt (NE Brazil) and implications for the 413–430. evolution of Pan-African/Brasiliano cratons and Neoproterozoic Hyde, W. T., Crowley, T. J., Baum,S.K.&Peltier, W. R. 2000. sedimentary cover. Journal of South American Earth Sciences, 12, Neoproterozoic ‘snowball Earth’ simulations with a coupled 453–470. climate/icesheet model. Nature, 405, 425–429. Derry,L.A.,Keto, L. S., Jacobsen, S. B., Knoll,A.H.&Swett,K. Iyer , S. S., Babinski,M.,Krouse,H.R.&Chemale, F., Jr. 1995. Highly 1989. Sr isotopic variations of upper Proterozoic carbonates from 13C enriched carbonate and organic matter in the Neoproterozoic East Greenland and Svalbard. Geochimica Cosmochimica Acta, 53, sediments of the Bambuı´ Group, Brazil. Precambrian Research, 73, 2331–2339. 271–282. Fairchild, I. J., Marshall,J.D.&Bertrand-Safati, J. 1990. Strati- Jacobsen,S.B.&Kaufman, A. J. 1999. The Sr, C and O graphic shifts in carbon isotopes from Proterozoic stromatolitic isotope evolution of Neoproterozoic seawater. Chemical Geology, carbonates (Mauritania): influence of primary mineralogy and dia- 161, 37–57. genesis. American Journal of Science, 290A, 46–79. Karfunkel,J.&Hoppe, A. 1988. Late Proterozoic glaciation in Fairchild, T. R., Schopf,J.W.et al. 1996. Recent discoveries of Central-Eastern Brazil: synthesis and model. Paleogeography, Paleo- Proterozoic microfossils in south-central Brazil. Precambrian climatology, Paleoecology, 65, 1–21. Research, 80, 125–152. Kaufman,A.J.&Knoll, A. H. 1995. Neoproterozic variations in the C- Fuck,R.A.,Pimentel,M.M.&Silva, J. H. D. 1994. Compartimentaçaõ isotopic composition of seawater: stratigraphic and biogeochemical tectoˆnica na porçaõ oriental da Provıńcia Tocantins. Anais 388 implications. Precambrian Research, 73, 27–49. Congresso Brasileiro de Geologia, Camboriu´, SBG, 1, 215–216. Kaufman, A. J., Hayes,J.M.,Knoll,A.H.&Germs, G. J. B. 1991. Geboy, N. J. 2006. Rhenium–osmium age determinations of glaciogenic Isotopic compositions of carbonates and organic carbon from upper shales from the Mesoproterozoic Vazante Formation, Brazil.MS Proterozoic successions in Namibia: stratigraphic variation and the thesis, University of Maryland, 99. effect of diagenesis and metamorphism. Precambrian Research, 49, Geboy, N. J., Kaufman,A.J.&Walker, R. J. 2006. A stable isotope and 301–327. Re–Os study of organic-rich mudstones across a Proterozoic glacial Kaufman, A. J., Knoll,A.H.&Narbonne, G. M. 1997. Isotopes, ice cycle in Brazil. Geological Society of America Annual Meeting ages, and terminal Proterozoic earth history. Proceedings of the (Philadelphia), Abstracts, 38, 125. National Academy of Science USA, 94, 6600–6605. Geboy, N. J., Kaufman,A.J.et al. 2009. Evidence of Mesoproterozoic Kaufman, A. J., Varni,M.A.,Misi,A.&Brito-Neves, B. B. 2001. Ice Ages in Brazil. Internal report, unpublished. Anomalous d34S signatures in trace sulfate from a potential cap NEOPROTEROZOIC SUCCESSIONS OF THE SA˜ O FRANCISCO CRATON 521

carbonate in the Neoproterozoic Bambuı´ Group, Brazil. In: Misi,A. Francisco Craton, Brazil: a review and a possible metallogenic evol- & Teixeira, J. B. G. (organizers) Proterozoic Sediment-Hosted ution model. Ore Geology Reviews, 3, 263–304. Base Metal Deposits of Western Gondwana. I Field Workshop, Misi, A., Kaufman,A.J.et al. 2007. Chemostratigraphic correlation of Beolo Horizonte and Paracatu (Minas Gerais), Brazil, 62–65. Neoproterozoic successions in South America. Chemical Geology, Kawashita, K. 1998. Rochas carbona´ticas neoproterozoícas da Ame´rica 237, 161–185. do Sul: idades e infereˆncias quimioestratigra´ficas. Full professor Montes, A. S. L. 1997. O contexto estratigra´fico e sedimentolo´gico da thesis, University of Saõ Paulo, Brazil, 126. Formaçaõ Bebedouro na Bahia. Um possı´vel portador de diamantes. Kiang, C. H. 1997. Iso´topos esta´veis (C, H, O) e 87Sr/86Sr: implicaço˜es na MSc thesis, University of Brası´lia, Brazil. estratigrafia e na paleo-circulaçaõ de fluidos na Bacia do Saõ Fran- Monteiro, L. V. S. 2002. Modelamento metalogene´tico dos depo´sitos cisco. Full Professor Thesis, UNESP, Saõ Paulo, Brazil. de Vazante, Fagundes e Ambro´sia associados ao Grupo Vazante, Knoll,A.H.,Hayes,J.M.,Kaufman, A. J., Swett,K.&Lambert,L. Minas Gerais. Tese Doutorado, Universidade de Saõ Paulo- B. 1986. Secular variation in carbon isotope ratios from upper USP, 317. Proterozoic successions of Svalbard and East Greenland. Nature, Olcott,A.N.,Sessions, A. L., Corsetti, F. A., Kaufman,A.J.&de 321, 832–838. Oliviera, T. F. 2005. Direct evidence for significant primary Kendall, B., Creaser,R.A.&Selby, D. 2006. Re–Os geochronology production during widespread Neoproterozoic glaciation. Science, of post-glacial black shales in Australia: constraints on the timing of 310, 471–474. ‘Sturtian’ glaciation. Geology, 34, 729–732. Pedrosa-Soares, A. C., Dardenne,M.A.,Hasui,Y.,Castro,F.D.C., Kennedy, M. J., Christie-Blick,N.&Sohl, L. E. 2001. Are Proterozoic Carvalho,M.V.A.&Reis, A. C. 1994. Mapa Golo´gico do Estdo de cap carbonates and isotopic excursions a record of gas hydrate Minas gerais e Nota Explicativa. Secretaria de Recursos Minerais, destabilization following Earth’s coldest intervals? Geology, 29, Hı´dricos e Energe´ticos, Companhia Mineradora de Minas Gerais 443–446. (COMIG), mapas e texto, 97. Lima,O.N.B.,Uhlein,A.&Britto, W. 2005. Geologia dos depo´sitos Pimentel,M.M.,Dardenne,M.A.,Viana,M.G.,Costa,S.M.,Gioia, fosfa´ticos do Grupo Bambuı´ na Serra da Saudade, Cedro do Abaete´, L., Junges,S.&Seer, H. J. 2001. Nd isotopes and the provenance Minas Gerais. In: Short Papers-III Simpo´sio sobre o Craton do Saõ of sediments from the Neoproterozoic Brası´lia Belt, Central Brazil: Francisco, Salvador, SBG, 320–323. geodynamic implications. Journal of South American Earth Sciences, Madalosso, A. 1979. Stratigraphy and sedimentation of the Bambuı´ 14, 571–585. Group in Paracatu region, minas Gerais, Brazil. MA thesis, Univer- Porada, H. 1989. Pan-African rifting and orogenesis in southern to sity of Missouri, USA, 127. equatorial Africa and Eastern Brazil. Precambrian Research, 44, Marini, O. J., Fuck,R.A.,Danni, J. C., Dardenne,M.A.,Loguercio, 103–136. S. O. C. & Ramalho, R. 1984. As faixas de dobramentos Brası´lia, Powis, K. 2006. Stable isotope geochemistry of the Neoproterozoic Uruaçu e Paraguai-Araguaia e o Maciço Mediano de Goia´s. In: Bambuı´ Group at Serra do Ramalho, Bahia, Brazil. PhD thesis, Schobbenhaus, C., Campos,D.A.,Derze,G.R.&Asmus,H.E. Ottawa-Carleton Geoscience Center, University of Ottawa, Canada, (eds) Geologia do Brasil. Texto Explicativo do Mapa Geolo´gico do 197. Brasil e da A´ rea Oceaˆnica Adjacente Incluindo Depo´sitos Minerais. Rodrigues, J. B. 2007. Estudos de provenieˆncia de sedimentos da regiaõ Ministe´rio da Minas e Energias/Departamento Nacional da Centro-Oeste da Faixa Brası´lia-uma abordagem geocronolo´gica. Produçaõ Mineral, Brası´lia, 251–303. Exame de Qualificaçaõ Doutorado, Universidade de Brası´lia-UnB, Misi, A. 1978. Ciclos de sedimentaçaõ e mineralizaço˜es de Pb–Zn nas Brası´lia, 50. sequeˆncias Bambui (Supergrupo Saõ Francisco), Estado de Bahia. Rodrigues, J. B. 2008. Provenieˆncia de sedimentos dos grupos Canastra, XXX Congresso Brasileiro de Geologia. Sociedade Brasileira de Geo- lbia´, Vazante e Bambuı´, Um estudo de zirco˜es detrı´ticos e ldades logia, Anais, 4, 2548–2561. Modelo Sm–Nd. Dr. Thesis, University of Brasilia, Brasilia DF. Misi, A. 1979. O Grupo Bambuı´ no Estado da Bahia. In: Inda, H. V. (ed.) Rodrigues, J. B., Pimentel,M.M.,Buhn, B., Dardenne,M.A.& Geologia e Recursos Minerais do Estato da Bahia. Textos Ba´sicos, Alvarenga, C. J. S. 2008. Provenance of the Vazante Group– SME/CPM, Salvador, 1, 120–154. Preliminary data. VI South American Symposium on Isotope Misi, A. 1999. Um modelo de evoluçaõ metalogene´tica para os depo´sitos Geology, Bariloche, Argentina. Extented Abstracts, CD-ROM. de zinco e chumbo hospedados em sedimentos proterozoícos de Sanches, A. L., Misi,A.,Kaufman,A.J.&Azmy, K. 2007. As sucesso˜es cobertura do Craton do Saõ Francisco. Full Professror Thesis, carbona´ticas neoproterozoícas do Craton do Saõ Francisco e os Federal University of Bahia (Brazil). depo´sitos de fosfato: correlaço˜es e fosfogeˆnese, Revista Brasileira Misi, A. 2001. Estratigrafia isoto´pica das sequeˆncias do Supergrupo Saõ de Geocieˆncias, 37, 1034–1046. Francisco, coberturas neoproterozoícas do Cra´ton do Saõ Francisco. Santos, R. V., de Alvarenga, C. J. S., Dardenne, M. A., Sial,A.N.& Idade e correlaço˜es. In: Pinto,C.P.&Martins-Neto,M.A. Ferreira, V. F. 2000. Carbon and oxygen isotopes across (eds) Bacia do Saõ Francisco, Geologia e Recursos Naturais, SBG/ Meso-Neoproterozoic limestones from Central Brazil: Bambuı´ and MG, Belo Horizonte, 67–92. Paranoa´ groups. Precambrian Research, 104, 107–122. Misi,A.&Kyle, J. R. 1994. Upper Proterozoic carbonate Santos,R.V.,Alvarenga,C.J.S.et al. 2004. Carbon isotopes of stratigraphy, diagenesis, and stromatolitic phosphorite formation, Mesoproterozoic-Neoproterozoic sequences from Southern Saõ Ireceˆ Basin, Bahia, Brazil. Journal of Sedimentary Research, 64, Francisco Craton and Araçuaı´ Belt, Brazil: palaeogeographic impli- 299–310. cations. Journal of South American Earth Sciences, 18, 27–39. Misi,A.&Souto, P. G. 1975. Controle estratigra´fico das mineralizaço˜es Saylor, B. Z., Kaufman, A. J., Grotzinger,J.P.&Urban, F. 1998. A de Pb–Zn–F–Ba do Grupo Bambui, parte leste da Chapada de Ireceˆ composite reference section for terminal Proterozoic strata of (Bahia). Revista Brasileria de Geoscieˆncias, 5, 30–45. southern Namibia. Journal of Sedimentary Research, 68, 1223–1235. Misi,A.&Veizer, J. 1998. Neoproterozoic carbonate sequences of the Sial,A.N.,Ferreira, V. P., Almeida, A. R., Romano,A.W.,Parente, Una Group, Ireceˆ Basin, Brasil: chemostratigraphy, age and corre- C., Da Costa,M.L.&Santos, V. H. 2000. Carbon isotope lations. Precambrian Research, 89, 87–100. fluctuations in Precambrian carbonate sequences of several Misi,A.,Veizer, J., Kawashita,K.&Dardenne, M. A. 1997. The age localities in Brazil. Anais Academia Brasileira de Cieˆncias, 72, of the Neoproterozoic carbonate platform sedimentation based on 540–557. 87Sr/86Sr determinations, Bambuı´ and Una Groups, Brazil. I South Sial,A.N.,Ferreira, V. P., Moura,C.V.A.&Santos, V. H. 2003. American Symposium on Isotope Geology, Campos do Jordaõ, Saõ C-, O- and Sr-isotope stratigraphy of the Sturtian Jacoca and Olho Paulo, Brazil. Extented Abstracts, 199–200. D’Agua Formations, state of Sergipe, Northeastern Brazil. Short Misi,A.,Iyer,S.S.S.et al. 1999. Geological and isotopic constraints papers. IV South American Symposium on Isotope Geology. Salvador, on the metallogenic evolution of the Proterozoic sediment-hosted Bahia, 394–397. Pb–Zn (Ag) deposits of Brazil. Gondwana Research, 2, 47–65. Sial, A. N., Ferreira,V.P.et al. 2005. Two Neoproterozoic cap carbon- Misi,A.,Iyer,S.S.S.et al. 2005. Sediment-hosted lead–zinc deposits of ates in the states of Sergipe and Bahia, Northeastern Brazil: C- and the Neoproterozoic Bambui Group and correlative sequences, Saõ Sr-isotopes and mercury as paleoclimatic tracer. X Congresso 522 A. MISI ET AL.

Brasileiro de Geoquı´mica e II Simpo´sio de Geoquı´mica de Paı´ses do Trindade, R. I. F., D’Agrella-Filho,M.,Babinski,M.&Brito Neves, Mercosul, Porto de Galinhas. Short paper CD-ROM. B. B. 2004. Paleomagnetism and geochronology of the Bebedouro Sial, A. N., Ferreira,V.P.et al. 2006a. Chemostratigraphy cap carbonate: evidence for continental-scale Cambrian remagnetiza- of two Neoproterozoic cap carbonates from the Sergipano tion in the Saõ Francisco craton, Brazil. Precambrian Research, 128, belt (northeastern Brazil). Short Papers, V South American 83–103. Symposium on Isotope Geology (V SSAGI). Punta del Este, Trompette, R. 1994. Geology of Western Gondwana (2000–500 Ma). Uruguay, 314–317. A.A. Balkema, Rotterdam, 350. Sial,A.N.,Ferreira,V.P.et al. 2006b. C- and Sr-isotopes and mercury Uhlein,A.,Alvarenga, C. J. S., Trompette,R.,Dupont, H. S. J. B., as paleoclimatic tracer in two Neoproterozoic cap carbonates in Egydio-Silva,M.,Cukrov,N.&Lima, O. N. B. 2004. Glaciaçaõ northeastern Brazil. Snowball Earth Conference. Ascona, Suiça, neoproterozoíca sobre o Craton do Saõ Francisco e faixas dobradas 100–101. adjacentes. In: Mantesso-Neto,V.,Bartorelli, A., Carneiro, Sial, A. N., Dardenne,M.A.et al. 2009. The Saõ Francisco Paleocon- D. R. C. & Brito Neves, B. B. (eds) Geologia do Continente tinent. In: Neoproterozoic-Cambrian Tectonics, Global Change and Sul-Americano: Evoluçaõ da obra de Fernando Fla´vio de Almeida. Evolution: A Focus on Southwestern Gondwana. Developments in Beca Ed., Saõ Paulo, 539–553. Precambrian Geology, 16, 31–69. Uhlein,A.,de Alvarenga, C. J. S., Dardenne,M.A.&Trompette,R. So¨fner, B. 1973. Observaço˜es sobre a estratigrafia do Pre´-Cambriano R. 2011. The glaciogenic Jequitaı´ Formation, southeastern Brazil. da Chapada Diamantina Sudeste e da a´rea contı´gua. In: SBG, 27th In: Arnaud, E., Halverson,G.P.&Shields-Zhou, G. (eds) The Congresso Brasileiro de Geologia. Aracaju´, Anais, 1, 23–33. Geological Record of Neoproterozoic Glaciations. Geological Souza, J. C. F. 1997. Litoestratigrafia e sedimentologia da Formaçaõ Society, London, Memoirs, 36, 541–546. Vazante na regiaõ de Coromandel. MSc thesis, Universidade de Valeriano,C.M.,Dardenne,M.A.,Fonseca, M. A., Simo˜es,L.S.A. Brası´lia. & Seer, H. J. 2004. A Evoluçaõ Tectoˆnica da Faixa Brası´lia. In: Teixeira, L. B., Martins,M.&Braun, O. P. G. 1993. Evoluçaõ geo- Mantesso-Neto,V.,Bartorelli,A.,Carneiro,D.R.C.& lo´gica da Bacia Saõ Francisco com base em sı´smica de reflexaõe Brito Neves, B. B. (eds) Geologia do Continente Sul-Americano: me´todos potenciais. II Simpo´sio sobre o Craton do Saõ Francisco. Evoluçaõ da obra de Fernando Fla´vio de Almeida. Beca Edta, Saõ SBG, Nućleo Bahia, Anais, 179–181. Paulo, 575–593. Teixeira,W.&Figueiredo, M. C. H. 1991. An outline of Early Proter- Viera, L. C., Almeida, R. P., Trindade, R. I. F., Nogueira,A.C.R.& ozoic crustal evolution in the Saõ Francisco Craton, Brazil: a review. Janikian, L. 2007. A Formaçaõ Sete Lagoas em sua a´rea tipo: faćies, Precambrian Research, 53, 1–22. estratigrafia e sistemas deposicionais. Revista Brasileira de Geo- Thomaz-Filho,A.,Kawashita,K.&Cordani, U. G. 1998. A scieˆncias, 37, 1020–1033. origem do Grupo Bambuı´ no contexto da evoluçaõ geotectoˆnica e Young, G. M. 1995. Are Neoproterozoic glacial deposits preserved on the de idades radiome´tricas. Anais Academia Brasileira de Cieˆncias, margins of Laurentia related to the fragmentation of two superconti- 70, 527–548. nents? Geology, 23, 153–156. Torquato,J.R.F.&Misi, A. 1977. Medidas isoto´picas de carbono Zhang, S., Jiang,G.,Zhang, J., Song, B., Kennedy,M.J.&Christie- e oxigeˆnio em carbonatos do Grupo Bambui na regiaõ centro- Blick, N. 2005. U–Pb sensitive high-resolution ion microprobe ages norte do Estado da Bahia. Revista Brasileira de Geocieˆncias, 7, from the Doushantuo Formation in south China: constraints on late 14–24. Neoproterozoic glaciations: Geology, 33, 473–476.