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Made available in DSpace on 2022-04-28T19:47:15Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-12-01 Global Neoproterozoic glaciations are related to extreme environmental changes and the reprise of iron formation in the rock record. However, the lack of narrow age constraints on Cryogenian successions bearing iron-formation deposits prevents correlation and understanding of these deposits on a global scale. Our new multiproxy data reveal a long Cryogenian record for the Jacadigo Group (Urucum District, Brazil) spanning the Sturtian and Marinoan ice ages. Deposition of the basal sequence of the Urucum Formation was influenced by Sturtian continental glaciation and was followed by a transgressive interglacial record of >600 m of carbonates that terminates in a glacioeustatic unconformity. Overlying this, there are up to 500 m of shale and sandstone interpreted as coeval to global Marinoan glacial advance. Glacial outwash delta deposits at the top of the formation correlate with diamictite-filled pa-leovalleys and are covered by massive Fe and Mn deposits of the Santa Cruz Formation and local carbonate. This second transgression is related to Marinoan deglaciation. Detrital zircon provenance supports glaciostatic control on Cryogenian sedimentary yield at the margins of the Amazon craton. These findings reveal the sedimentary response to two marked events of glacioeustatic incision and transgression, culminating in massive banded iron deposition during the Marinoan cryochron. Faculdade de Tecnologia Universidade de Campinas Departamento de Geología Universidade Federal de Ouro Preto Instituto de Geociências Instituto de Astronomía Geofísica e Ciências Atmosféricas Universidade de São Paulo Departamento de Geologia Universidade Estadual Paulista Departamento de Geologia Universidade Estadual Paulista

Dunes form critical agents of bedload transport in all of the world’s big rivers, and constitute appreciable sources of bed roughness and flow resistance. Dunes also generate stratification that is the most common depositional feature of ancient riverine sediments. However, current models of dune dynamics and stratification are conditioned by bedform geometries observed in small rivers and laboratory experiments. For these dunes, the downstream lee-side is often assumed to be simple in shape and sloping at the angle of repose. Here we show, using a unique compilation of high-resolution bathymetry from a range of large rivers, that dunes are instead characterized predominantly by low-angle lee-side slopes (

Although large anabranching rivers are a very common element in the greatest modern drainage basins, the recognition of such systems in the rock record is hampered by insufficient sedimentological information from active rivers. That is particularly the case of bar-top depositional environments in large anabranching rivers, motivating the survey of six selected areas of seasonally emergent bars in the Solimoes and Japura rivers (western Brazilian Amazonia) using Ground Penetrating Radar, Sub Bottom Profiler and Multibeam Echosounder, as well as direct observation sediment sampling. GPR surveys and field observations indicate these bars are dominated by 0.5 to 4 m tall subaqueous dunes with the local presence of metric angle-of-repose bar-side surfaces. Downstream accretion components are characterized by radar facies indicating horizontal to low-angle downstream-dipping cosets of dm-scale to cm-scale cross-strata. Lateral accretion components are characterized by radar facies indicating m-scale high-angle cross-strata sets passing laterally to low-angle and inclined cosets composed of dm-scale cross-strata sets. Upstream accretion components are characterized by radar facies indicating upstream-inclined cosets of m- and dm-scale cross-strata sets with local mud drapes. Preservation of accretionary bar forms in these periodically exposed areas is supported by calculation of the coefficient of variation of peak discharge, which indicates low interannual peak discharge variability over the bar tops.

Made available in DSpace on 2019-10-04T12:35:30Z (GMT). No. of bitstreams: 0 Previous issue date: 2019-03-01 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) PROPE - UNESP The Itapucumi Group is recognized worldwide due to its well-preserved Ediacaran fossil assemblage. Despite its paleontological importance, this unit remains as the least studied South American Neoproterozoic sedimentary succession. Recorded at northern Paraguay, the Itapucumi Group is a similar to 400 m-thick siliciclastic and carbonate succession deposited on the Paleoproterozoic basement of the Rio Apa Craton. At west, this unit is deformed and metamorphosed, whereas the eastern domain constitutes an undeformed cratonic cover. The Itapucumi Group comprises, from base to top, siliciclastic rocks of the Vallemi Formation, succeeded by limestones and dolomites of the Camba Jhopo and Tagatiya Guazu formations, which are capped by marls and mudstones of the Cerro Curuzu Formation. The entire sedimentary succession consists of three depositional sequences deposited in a large rimmed carbonate platform open to the ocean westward: S.1, the lowermost predominantly terrigenous, and sequences S.2 and S.3, comprising carbonate and terrigenous facies associations. Carbon isotope data from limestones and dolostones show values of + 1.93 parts per thousand delta C-13 VPDB and Sr-87/Sr-86 ratios of 0.7084 and 0.7089, in agreement with a depositional age between 600 Ma and 550 Ma and coherent with the Cloudina biozone. These data support the paleogeographic correlation between the Itapucumi and Corumba groups at the margins of the Amazonian and Rio Apa Craton. The siliciclastic basal successions of both units, are interpreted as deposited in rift basins developed during the fragmentation of the Rodinia supercontinent (Cryogenian to Ediacaran). Later thermal subsidence led to the generation of a new accommodation space around 550 and 528 Ma, recording extensive carbonate platforms along the margins of Pampia, Amazonian and Rio Apa cratons. The deformation of the Itapucumi and Corumba basins started at around 528 Ma, and was controlled by the reactivation of listric and normal faults generated during the rift stage. The opposite tectonic vergence observed in the Vallemi and Paraguay fold-and-thrust belts can be ascribed to oppose master fault polarities in the precursor basins of this context, as well as to the rigid behavior of the Rio Apa Craton. The compressional phase ended around 484 Ma, and corresponding to the last stresses related to the Brasiliano Cycle and the closure of SW Gondwana. Univ Estadual Paulista, Dept Geol Aplicada, Inst Geociencias & Ciencias Exatas, Ave 24A,1515, BR-13506900 Rio Claro, Brazil Univ Estadual Campinas UNICAMP, Fac Tecnol, Rua Paschoal Marmo 1888, BR-13484332 Jd Nova Itdlia, Limeira, Brazil Univ Sao Paulo, Inst Energia & Ambiente, Ave Prof Luciano Gualberto 1289, BR-05508010 Sao Paulo, Brazil Univ Sao Paulo, Inst Geociencias, Rua Lago 562, BR-05508010 Sao Paulo, Brazil Univ Fed Sao Paulo, Dept Ecol & Biol Evolut, Rua Prof Artur Riedel 275, BR-09972270 Diadema, Brazil Univ Estadual Paulista, Inst Biociencias, Dept Zool, BR-18618000 Botucatu, SP, Brazil Univ Brasilia, Inst Geociencias, ICC Ala Cent, BR-70910900 Brasilia, DF, Brazil Fac Ciencias, Dept Geol, Calle Igua 4225, Montevideo 11400, Uruguay UNLP, CONICET, Ctr Invest Geol, Calle 1,644, RA-1900 La Plata, Buenos Aires, Argentina Univ Fed Pernambuco, NEG LABISE, Ave Acad Helio Ramos, BR-50670000 Recife, PE, Brazil Univ Estadual Paulista, Dept Geol Aplicada, Inst Geociencias & Ciencias Exatas, Ave 24A,1515, BR-13506900 Rio Claro, Brazil Univ Estadual Paulista, Inst Biociencias, Dept Zool, BR-18618000 Botucatu, SP, Brazil FAPESP: 2004/012330 FAPESP: 2010/19584-4 FAPESP: 2010/02677-0 FAPESP: 2015/24608-3 CNPq: 490234/2005-4 CNPq: 444070/2014-1

Made available in DSpace on 2021-06-25T10:57:53Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-01-01 Although virtual outcrops or digital outcrop model applications in geological studies are becoming increasingly common, virtually no attention has been given to acquisition of palaeocurrent data from cross-strata. Palaeocurrent indicators are abundant in the sedimentary record, mainly as cross-strata, and present compelling implications for basin analysis, plate tectonics and palaeoenvironmental reconstructions, as well as for sediment transport systems. Palaeocurrents from cross-strata also comprise a quantifiable parameter in sedimentary successions that can be used in quantitative modelling of depositional architecture with implications for reservoir characterization through outcrop analogue studies. A common obstacle in obtaining large cross-strata orientation datasets is the limited access to steep and high outcrop faces, as well as financial and time restrictions on field work. To overcome these issues, the simplest workflow for drone-based acquisition, photogrammetric processing and analysis of virtual outcrops aiming at the attainment of palaeocurrent data from cross-strata is appraised here. The results show that orientations of cross-beds measured on virtual outcrops, with and without ground control points, and using two different levels of resolution downsampling, are comparable to field measurements using analogue and electronic devices. Time and financial resources can thus be saved by using the straightforward method presented here to supplement palaeocurrent mapping across wide areas and distinct stratigraphic intervals. Geology Lab School of Technology University of Campinas, Rua Paschoal Marmo, 1888, Jardim Nova Itália Institute of Geosciences University of São Paulo, Rua do Lago, 562, Cidade Universitária Institute of Marine Science São Paulo Federal University, Rua Carvalho de Mendonça, 144, Encruzilhada Departamento de Geologia (DGEOL) / Programa de Pós-graduação em Geociências e Análise de Bacias Universidade Federal de Sergipe, Marechal Rondon Ave., Geology Bldg., Multi-user Complex, Rosa Elze Departamento de Geologia Aplicada Instituto de Geociências e Ciências Exatas Universidade Estadual Paulista/UNESP, Avenida 24-A, Bela Vista, 178 Departamento de Geologia Aplicada Instituto de Geociências e Ciências Exatas Universidade Estadual Paulista/UNESP, Avenida 24-A, Bela Vista, 178

International audience; Vase-shaped microfossils (VSMs) attributed to testate amoebae occur globally in diverse assemblages in Tonian rocks. These microfossils have thus been considered a potential biostratigraphic tool, especially for the interval between 789 and 729 Ma. Here we report a diverse and well-preserved in situ VSM assemblage, including several taxa previously considered as Tonian, within glacially influenced deposits for which sedimentological data support a Cryogenian age. However, the more robust recent multi-proxy correlation proposed by Freitas et al. (2021) indicates a Marinoan age for the studied succession. Detrital zircon data provide a maximum depositional weighted mean age of 749 ± 3 Ma for the VSM-bearing, organic-rich, fine-grained deposits within the Marinoan sequence in the Urucum Formation. Nine taxa are described from the fine-grained deposits in the upper Urucum Formation, Jacadigo Group, Brazil: Cycliocyrillium simplex, Bonniea dacruchares, Bonniea pytinaia, Bombycion micron, Limeta lageniformis, Palaeoarcella athanata, Trigonocyrillium horodyskii, Pakupaku kabin and cf. Taruma rata. The discovery of well-preserved in situ VSMs attributable to specific Tonian taxa within a Cryogenian succession challenges previous thinking that these organisms disappeared from marine ecosystems at the end of the Tonian.

O Neoproterozoico foi um periodo de grandes transformacoes ambientais no planeta, seu estudo fornece importantes informacoes a respeito da evolucao da crosta terrestre, da evolucao da vida e dos eventos climaticos extremos ocorridos na Terra. Neste trabalho e abordado o registro geologico de eventos climaticos extremos que precedem o surgimento da vida pluricelular na Terra por meio do estudo geocronologico e de proveniencia de graos de zircao detritico no contexto da Faixa Paraguai. Enfase foi dada na obtencao de novos dados para a Formacao Urucum (Grupo Jacadigo) e sua comparacao com unidades correlacionaveis da Faixa Paraguai. A distribuicao de idades encontrada para a Formacao Urucum demonstra ser semelhante ao ja publicado para outras unidades da Faixa Paraguai, sugerindo uma mesma conjuntura tectonica de aporte sedimentar. A grande diferenca na distribuicao de idades da Formacao Guaicurus sugere uma reorganizacao regional das areas fontes. Por fim, o zircao mais jovem encontrado nesse trabalho, com idade igual a 690 ± 18 Ma permitiu restringir o intervalo possivel de idade para a Formacao Urucum e o Grupo Jacadigo.

Made available in DSpace on 2019-10-06T17:06:46Z (GMT). No. of bitstreams: 0 Previous issue date: 2019-06-01 Petrobras Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) The Aptian is the age of the evaporitic transitional megasequence in the Brazilian marginal basins as well as in the interior rift basins of the northeast region. The Marizal Formation is interpreted as a fluvial system developed in the inherited rift axis of the Tucano Basin. In its middle portion, after a quick transgressive event, a mud-dominated interval took place, which is enclosed in the Amargosa Bed. This transgressive marker bed is rich in fish fossils with Tethyan affinity attesting to an estuarine environment in the southern portions of the basin. The same transgressive event occurs in the Barbalha Formation of the Araripe Basin, where a mud-dominated lacustrine system is interpreted in the Batateira Bed. While lakes developed in the Araripe Basin and a transitional marine environment is attested to the southern portions of the Tucano Basin, there is no information of how these systems were interconnected. Here we discuss sedimentologic, stratigraphic and geochemical data of the Amargosa Bed in the North Tucano Basin, correlating it with time equivalent marker beds of other locations in the Northeast Brazil. Our data show that deposition of the mixed carbonate-mud interval of the North Tucano Basin was developed in a saline lake with local evidences of seismic-induced soft-sediment deformation structures. Although climate seasonality controlled high-frequency base-level changes, our findings reveal that local fault reactivation was responsible for the space generation, triggering the lake formation in the basin depocenter. This situation is uncommon for thermal subsiding basins that lack mechanical influence and have several implications for the evolution of intracontinental rift basins of the Brazilian Cretaceous. Also, lakes from Araripe, Jatobá and North Tucano basins were probably connected by the continental paleodrainage existent in the Aptian, carrying sediments to the estuaries developed in the Central and South Tucano basins and, thus, to the developing South Atlantic Ocean. Instituto de Geociências e Ciências Exatas Universidade Estadual Paulista - Unesp, Avenida 24A, 1515 Faculdade de Tecnologia Universidade Estadual de Campinas, R. Paschoal Marmo, 1888, Jd. Nova Itália Laboratório de Geologia Sedimentar e Ambiental (LAGESE) Departamento de Geologia Universidade Federal de Pernambuco Instituto de Geociências e Ciências Exatas Universidade Estadual Paulista - Unesp, Avenida 24A, 1515 Petrobras: 2014/00519-9 FAPESP: 2016/19736-5

O objetivo do presente trabalho é construir modelos 3D de exposições rochosas de depósitos fluviais a partir de fotografias obtidas com a ajuda de drones e contribuir com o desenvolvimento de rotina relacionada à aplicação de modelos 3D ao estudo de sucessões fluviais. Para tanto, foram abordados depósitos previamente interpretados como barras fluviais de idade Aptiana na Bacia do Tucano, mais precisamente depósitos do topo do Membro Banzaê expostos na Fazenda Retiro, próximo à área urbana de Banzaê - BA. Foram processados, com a utilização do software Photoscan da Agisoft, dados relativos a duas campanhas de campo, realizadas em 2017 com drones do tipo asa-fixa e multirotor. Produtos resultantes dos levantamentos com o equipamento asa-fixa auxiliaram no planejamento dos levantamentos com o equipamento multirotor. A partir dos levantamentos com o multirotor foram obtidos afloramentos virtuais que possibilitaram a extração de parâmetros sedimentológicos quantificáveis, como orientações de superfícies e parâmetros dimensionais, comparáveis a dados obtidos diretamente em campo com trena e bússola.

O objetivo do presente trabalho é a caracterização de depósitos fluviais da Formação Marizal que representam o preenchimento de um canal abandonado. Para tanto, foram construídos modelos 3D das exposições a partir de fotografias obtidas com a ajuda de drones. Os depósitos estudados ocorrem no topo do Membro Banzaê, da Formação Marizal e situam-se no Povoado de Campo do Brito, a norte da sede urbana do município de Banzaê-BA, num dos acessos à localidade conhecida como Fazenda Retiro. Desenvolveu-se um fluxo de trabalho para a extração de dados sedimentológicos e interpretação detalhada dos modelos 3D resultantes do processamento com o software Photoscan da Agisoft de fotografias tiradas com drone do tipo multirotor. A partir dos levantamentos, foram obtidos afloramentos virtuais que possibilitaram a extração de parâmetros sedimentológicos quantificáveis, como orientações de superfícies e parâmetros dimensionais, comparáveis a dados obtidos diretamente em campo por técnicas convencionais.

Vase-shaped microfossils (VSMs) occur in dolostone clasts within conglomerates, breccias, and diamictites of the Neoproterozoic Urucum Formation, Jacadigo Group, southwest Brazil. Although their taphonomic history is distinct from those of other VSM assemblages, morphometric comparison of Urucum fossils with five others described previously from North America and Europe show that two of the Urucum species—the long-neckedLimeta lageniformisMorais, Fairchild, and Lahr in Morais et al., 2017 and the funnel-neckedPalaeoamphora urucumenseMorais et al., 2017—occur in the Kwagunt and Callison Lake assemblages, as doesPakupaku kabinRiedman, Porter, and Calver, 2017 recently described from the Togari Group, Tasmania.Obelix rootsii(Cohen, Irvine, and Strauss, 2017) new combination, previously known only from the Callison Lake Formation, is documented here from the Kwagunt Formation. In addition,Trigonocyrillium horodyskii(Bloeser, 1985) andBonniea dacrucharesPorter, Meisterfeld, and Knoll, 2003, first described from the Kwagunt assemblage, have now been found in the Urucum Formation. In light of this survey, 16 of the 18 validly described VSM species are now known to occur in the Kwagunt Formation and 13 in the Callison Lake Formation, with 12 of them shared by both formations. The fact that the Urucum VSM assemblage exhibits six of seven species in common with the Kwagunt Formation—L. lageniformis, P. urucumense, Cycliocyrillium simplexPorter, Meisterfeld, and Knoll, 2003,C. torquataPorter, Meisterfeld, and Knoll, 2003,B. dacrucharesPorter, Meisterfeld, and Knoll, 2003, andT. horodyskii(Bloeser, 1985)—and all but the last of these in common with the Callison Lake Formation supports correlation of these three assemblages and indicates that the source of the fossiliferous clasts within the Urucum Formation may well have been a now-vanished late Tonian carbonate platform.UUID:http://zoobank.org/ac0becd6-29ff-4491-80fa-0291730fba65

The emergence of soft-bodied metazoans and the radiation of the earliest skeletal organisms substantially changed the ecological dynamics of Ediacaran environments, leading to the genesis of biogenic hard-part deposits for the first time in Earth’s history. The impact of bioclast origin on sedimentary processes is analyzed herein, focusing on the sedimentology and taphonomy of shell concentrations dominated by the Ediacaran index fossil Cloudina from the Itapucumi Group, Paraguay. Skeletal concentrations include both dense accumulations of parautochthonous, disarticulated specimens (“Type 1 deposits”) and in situ specimens preserved as loosely packed assemblages (“Type 2 deposits”). At that time, Cloudina was the critical source of durable biomineralized hard parts in an environment nearly free of other bioclasts. The simple fabric and geometry of these accumulations are typical of Cambrian-style shell beds. Despite their Precambrian age, these deposits indicate that the establishment of the Phanerozoic style of marine substrates and preservation in early shell beds was determined more by the acquisition of hard parts than by environmental changes.

The massive Fe and Mn deposits of the Urucum district (Banda Alta Formation) and the iron formations from Fazenda Sao Manoel (Puga Formation) in Mato Grosso do Sul, Brazil, are associated with glacigenic deposits and represent the youngest and largest sedimentary Fe and associated Mn formation (IF;MnF) deposits of Cryogenian age in the world. The Urucum district IFs studied are predominantly composed of pure classical plane-parallel and stratified hematite–chert–iron - and intercalated manganese (cryptomelane) micro- and mesobands, whereas the IFs at Fazenda Sao Manoel are closely associated with diamictites and shales. Although the precise depositional age is unknown, maximum age constraints for the Puga IFs are defined by the youngest detrital zircon with an U-Pb age of 706 ± 9 Ma ( Babinski et al., 2013 ), a result which we here confirm by a U-Pb age of the youngest zircon of 695 ± 17 Ma from within shaly beds in the Urucum district IF succession. Redox-sensitive trace element signatures and tendency to hump-shaped Rare Earth Element + Yttrium (REY) patterns with negative Ce- but without Eu anomalies support the presence of an oxic surface water layer, fertilized by low temperature hydrothermal fluids injected from submarine thermal springs and/or, alternatively, by significant fresh water input directly derived from glacial meltdown. Strongly positively fractionated, authigenic chromium isotope signatures (average δ 53 Cr = 1.10 ± 0.4‰; n = 16; 2σ) prevailing throughout the entire stratigraphic section indicate that riverine supply of continentally-derived Cr, remained more or less constant throughout the glacier meltdown and IF depositional period. Cycling across a redoxcline and predominant deposition of the IF in anoxic deeper seawater of the Jacadigo basin is supported by the peculiar presence of subchondritic Y/Ho ratios, by decreased negative Ce anomalies and by shifts of LREE patterns towards higher values in the Urucum district IFs that are independent of detrital contamination. The strongly positively fractionated Cr isotope signatures measured in these iron formations are compatible with those from other iron formations and black shales deposited during the late Neoproterozoic and Precambrian-Cambrian transition worldwide and are in support of prevailing high atmospheric O 2 levels following the late Neoproterozoic glaciations that accompanied the evolution of macroscopic multicellular organisms.

The intriguing Ediacaran fossil Namacalathus is described from limestones of the Tagatiya Guazú Formation, Itapucumi Group, Paraguay. This is the fifth occurrence of the genus in the Ediacaran geological record. The Paraguayan Namacalathus specimens are preserved as partially complete spheroidal cups with an opening at the top and thin walled stems. The remains of this soft-calcified globe-shaped organism occur as sparse disarticulated parautochthonous fragments within bioclastic deposits dominated by Cloudina shells with subordinate Corumbella fragments. The co-occurrence of these three skeletal metazoan species in the same environmental context attests that the diversity of the Paraguayan accumulations is ecologically comparable to the typical skeletal assemblage of the Nama Group. The discovery of new samples of Namacalathus in the Itapucumi Group also indicates that this genus presented a broader paleobiogeographic distribution than previously thought and, in the same way as Cloudina, it represents a low latitude, shallow water metazoan of the Ediacaran Gondwana., Centro de Investigaciones Geológicas

Made available in DSpace on 2018-11-26T15:45:58Z (GMT). No. of bitstreams: 0 Previous issue date: 2017-12-01 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Petrobras This study, based on detailed sedimentologic and stratigraphic analysis of the Aptian succession preserved in the Reconcavo-Tucano-Jatoba Rift System (RTJ), present new elements for biostratigraphic correlation and paleogeographic reconstruction in the mid-Cretaceous South Atlantic realm, supporting novel interpretations on the tectonic and sedimentary evolution related to the W-Gondwana breakup. The Aptian sedimentary succession in the RTJ has been referred to as Marizal Formation, and interpreted as post-rift deposits. Detailed sedimentologic and stratigraphic studies of these deposits enabled the recognition and individualization of two distinctive sedimentary units that can be traced in the entire RTJ. These units are here described and named Banzae and Cicero Dantas members of the Marizal Formation. Their contact is locally marked by the fossiliferous successions of the here proposed Amargosa Bed, lying at the top of the Banzae Member. Both members of the Marizal Formation record large river systems captured by the Tucano Basin with the local development of eolian dune fields and fault bounded alluvial fans. The Amargosa Bed represents a regional-scale base level change preserved between the Aptian fluvial successions along the RTJ. Hence, the studied sedimentary record presents important implications for the timing and direction of marine ingressions affecting NE-Brazil interior basins during the Aptian. A remarkable contrast in preserved fluvial architecture between the Banzae Member, characterized by connected channel bodies, and the Cicero Dantas Member, characterized by isolated channel bodies within overbank fines, is here reported. The main interpreted control for the observed contrast in fluvial stratigraphy is sedimentary yield variation. The interval is also subject to the interpretation of a regional shift in the mechanism responsible for the subsidence of the basins formed during the Cretaceous break-up of the Central South Atlantic. This view is challenged by our results which reveal that basin forming extension continued throughout the Aptian. As a conclusion, the detailed stratigraphy of the Marizal Formation forward alternative geodynamic interpretations for the Aptian successions in northeastern Brazil, bringing new elements to the mid-Cretaceous biogeographical, paleogeographical and tectonic reconstructions of western Gondwana. (C) 2017 Elsevier Ltd. All rights reserved. Univ Estadual Campinas, Fac Tecnol, Rua Paschoal Marmo 1888, BR-13484332 Limeira, SP, Brazil Univ Sao Paulo, Inst Geociencias, Rua Lago 562,Cidade Univ, BR-05508900 Sao Paulo, SP, Brazil Univ Fed Sergipe, Dept Geol, Av Marechal Rondom S-N, BR-49100000 Sao Cristovao, SE, Brazil CPRM Serv Geol Brasil, Rua Costa 55, BR-01304010 Sao Paulo, SP, Brazil Univ Estadual Paulista, Inst Geociencias & Ciencias Exatas, Ave 24 A,1515, BR-13506900 Rio Claro, SP, Brazil Univ Estadual Paulista, Inst Geociencias & Ciencias Exatas, Ave 24 A,1515, BR-13506900 Rio Claro, SP, Brazil FAPESP: 2009/53363-8 FAPESP: 2013/01825-3 FAPESP: 2014/16739-8 FAPESP: 2016/03091-5 FAPESP: 2016/19736-5 FAPESP: 2010/51559-0 CAPES: PROEX-558/2011 CNPq: 301775/2012-5 Petrobras: 2014/00519-9

The interpretation of large river deposits from the rock record is hampered by the scarcity of direct observations of active large river systems. That is particularly true for deep-channel environments, where tens of meters deep flows dominate. These conditions are extremely different from what is found in smaller systems, from which current facies models were derived. MBES and shallow seismic surveys in a selected area of the Upper Amazonas River in Northern Brazil revealed the presence of large compound barchanoid dunes along the channel thalweg. The dunes are characterized by V-shaped, concave-downstream crest lines and convex-up longitudinal profiles, hundreds of meters wide, up to 300 m in wavelength and several meters high. Based on the morphology of compound dunes, expected preserved sedimentary structures are broad, large-scale, low-angle, concave up and downstream cross-strata, passing laterally and downstream to inclined cosets. Examples of such structures from large river deposits in the rock record are described in the Silurian Serra Grande Group and the Cretaceous Sao Sebastiao and Marizal formations in Northeastern Brazil, as well as in Triassic Hawkesburry Sandstone in Southeastern Australia and the Plio–Pleistocene Ica Formation in the western Amazon. All these sedimentary structures are found near channel base surfaces and are somewhat coarser than the overlying fluvial deposits, favoring the interpretation of thalweg depositional settings. The recognition of large barchanoid dunes as bedforms restricted to river thalwegs and probably to large river systems brings the possibility of establishing new criteria for the interpretation of fluvial system scale in the rock record. Sedimentary structures compatible with the morphological characteristics of these bedforms seem to be relatively common in large river deposits, given their initial recognition in five different fluvial successions in Brazil and Australia, potentially enabling substantial improvements in facies models for large rivers.

Modern alluvial plains, in contrast to their pre-Silurian counterparts, are characterized by the presence of meandering rivers in low-downstream-gradient areas, constituting efficient transport systems that maintain high bottom shear stresses in deep channels, which are made possible by bank stabilization, most commonly provided by vegetation in Earth’s recent history. Here we show, through numerical modeling and field-based description of large-scale exposures in Mesoproterozoic successions, that prevegetation rivers in low-downstream-gradient areas were markedly different from both younger meandering rivers and the common prevegetation sheet-braided rivers, showing deeper braided channels and greater floodplain preservation than the latter. These systems were less frequent and had lower transport efficiency than modern meandering rivers, implying differences in global-scale Earth-surface dynamics, from the weathering of silicate minerals in floodplains to the grain size distribution in all clastic depositional systems.

The interpretation of fluvial styles from the rock record is based for a significant part on the identification of different types of fluvial bars, characterized by the geometric relationship between structures indicative of palaeocurrent and surfaces interpreted as indicative of bar form and bar accretion direction. These surfaces of bar accretion are the boundaries of flood-related bar increment elements, which are typically less abundant in outcrops than what would be desirable, particularly in large river deposits in which each flood mobilizes large volumes of sediment, causing flood-increment boundary surfaces to be widely spaced. Cross-strata set boundaries, on the other hand, are abundant and indirectly reflect the process of unit bar accretion, inclined due to the combined effect of the unit bar surface inclination and the individual bedform climbing angle, in turn controlled by changes in flow structure caused by local bar-scale morphology. This work presents a new method to deduce the geometry of unit bar surfaces from measured pairs of cross-strata and cross-strata set boundaries. The method can be used in the absence of abundant flood-increment bounding surfaces; the study of real cases shows that, for both downstream and laterally accreting bars, the reconstructed planes are very similar to measured bar increment surfaces.

Made available in DSpace on 2018-11-27T20:01:12Z (GMT). No. of bitstreams: 0 Previous issue date: 2016-12-01 Petrobras Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Center for Geosciences Applied to Petroleum Geology - UNESPetro, IGCE/Unesp/Rio Claro Training of Human Resources in Petroleum Geology Program - UNESP The evolution of the Cretaceous basins of the Brazilian northeastern hinterland was associated with the Gondwana rifting and opening of the South Atlantic Ocean. The first marine ingression in northeastern Brazil occurred in the late Aptian and was recorded as the Santana Group of the Araripe Basin, which is currently an isolated basin, located hundreds of kilometers away from the Brazilian marginal basins. Bellow the first upper Aptian marine deposits, an important section of fossiliferous limestone (Lagerstatte) was deposited and preserved in the Crato Formation transitioning upward into evaporites of the Ipubi Formation. The direction of the marine ingression is controversial, with several possibilities being suggested, mainly due to the absence of other areas of upper Aptian marine sections within the hinterland. Serra do Tona is a sedimentary mesa with scarped edges where the upper part of the Marizal Formation crops out, displaying laminated limestones, litho-and chrono-correlated with those of the Crato Formation, is preserved. Therefore, this mixed upper Aptian section, at the North Tucano Basin (Serra do Tona), is a unique occurrence of utmost importance to the definition of sedimentary events and paleogeographical reconstruction of northeastern Brazil during the late Aptian. A detailed stratigraphic analysis allowed the definition and characterization of two upper Aptian depositional sequences bounded by regional disconformities. Both sequences are dominantly transgressive and carbonatesiliciclastic in composition. The lower sequence comprises the basal portion of the Marizal Formation and consists of a succession of fluvial sandstones, ending on a laterally continuous thin interval (

Ao sul da cidade de Corumbá, MS, ocorrem imponentes elevações topográficas constituídas por depósitos sedimentares neoproterozóicos do Grupo Jacadigo. Nessas montanhas, cujo conjunto é referido como Maciço do Urucum, assentam-se discordantemente sobre o embasamento rochas siliciclásticas da Formação Urucum com espessuras máximas da ordem de 200 a 300m. A seção continua com depósitos mistos de componentes siliciclásticos e GIFs (granular iron formations), por aproximadamente 100m, e com mais 300m de predomínio de BIFs (banded iron formations). Na periferia do Maciço do Urucum ocorrem rochas carbonáticas do Grupo Corumbá, principalmente das formações Bocaina e Tamengo. Foi esse o conjunto de rochas abordado no presente trabalho por estudos sedimentológicos e estratigráficos em escala de detalhe. A análise integrada de fácies e paleocorrentes permitiu interpretar os mecanismos tectônicos geradores de espaço de acomodação, a orientação da bacia sedimentar, a estruturação de seu preenchimento, implicações geotectônicas regionais e para modelos de deposição de formações ferríferas. Para o preenchimento da bacia, definida na presente dissertação como Bacia Jacadigo, foram interpretados 6 sistemas deposicionais: (I) sistemas de leques aluviais; (II) sistema lacustre; (III) sistema fluvial entrelaçado; (IV) sistema de corpo dágua principal; (V) sistema de fluxos gravitacionais subaquáticos; e (VI) sistema de plataforma carbonática. Esses sistemas foram classificados em 3 tratos tectônicos, sendo os 3 primeiros sistemas deposicionais, essencialmente siliciclásticos e continentais, referentes ao trato de iniciação do rift; os sistemas de corpo dágua principal e de fluxos gravitacionais associados correspondentes ao clímax do rift; e a plataforma carbonática referente ao pós-rift. Esse último caracterizado pela transição entre as formações Urucum e Bocaina, de modo que a classificação em tratos tectônicos reflete os significados geodinâmicos dos grupos Jacadigo e Corumbá. A distribuição espacial dos sistemas deposicionais e dos padrões de paleocorrentes levou à interpretação de uma orientação WNW-ESE para a zona de falhas mestras da Bacia Jacadigo. Essa interpretação implica na correlação do Grupo Jacadigo com a Faixa Chiquitos-Tucavaca e não com a Faixa Paraguai como proposto anteriormente. A distribuição das unidades neoproterozóicas no contexto geotectônico das faixas Chiquitos-Tucavaca e Paraguai levou a corroboração de um posicionamento adjacente da Bacia Jacadigo a uma junção tríplice supostamente soerguida por plumas mantélicas. Toda a sucessão do Grupo Jacadigo mais a sucessão do Morro do Puga, usualmente interpretadas como produtos de processos sedimentares sob influência glacial, foram interpretadas como resposta da sedimentação à tectônica na Bacia Jacadigo, sem necessariamente associação com processos glaciais. Foram distinguidos elementos estruturais da tectônica deformadora daqueles relativos à tectônica formadora do Grupo Jacadigo e sugerida uma conformação braquianticlinal das rochas aflorantes na área urbana de Corumbá, no Maciço do Urucum e nas áreas adjacentes. At the south of Corumbá, Mato Grosso do Sul state, there are huge topographic elevations made of Jacadigo Groups neoproterozoic sedimentary deposits. Those mountains are known as Maciço do Urucum. The basal unit named Urucum Formation is composed by siliciclastic rocks with maximum thickness of 200 to 300m. The sucession continues with mixed GIF (granular iron formation) and siliciclastic deposits for approximately 100m, and more 300m of almost only BIFs (banded iron formations). In the surroundings of Maciço do Urucum there are carbonatic rocks from the Corumbá Group, mainly from Bocaina and Tamengo formations. This research presents detailed information about sedimentology and stratigraphy of the Maciço do Urucum area and surrounding rocks. The integrated facies and paleocurrents analysis produced the following interpretations: tectonic mechanisms responsible for accommodation spaces, sedimentary basin orientation, filling styles, regional geotectonic implication and iron formation depositional models. About the filling style, six depositional systems of the here named Jacadigo Basin were interpreted: (I) alluvial fan system; (II) lacustrine system; (III) fluvial braided system; (IV) main water body system; (V) subaquatic gravitational flow system; and (VI) carbonate platform system. Those systems were classified in three tectonic system tracts. The first three depositional systems are made of continental siliciclastics and refer to the rift initiation; the main water body and associated gravitational flow systems corresponds to the rift climax; and the carbonate platform to the post rift. The post rift is characterized by the transition between Urucum and Bocaina formations. This transition reflects the geodynamic significance of Jacadigo and Corumbá groups. The spatial distribution of the depositional systems and associated paleocurrent patterns indicated a WNW-ESE orientation to the master fault zone of Jacadigo Basin. This interpretation implies the correlation of Jacadigo Group and Chiquitos-Tucavaca Belt instead of Paraguai Belt, as proposed before. The neoproterozoic units distribution at the geotectonic context of Chiquitos-Tucavaca and Paraguai belts corroborated the adjacent position of Jacadigo Basin to a triple junction supposedly a plume generated uplift. Rocks of Jacadigo Group and Morro do Puga, usually interpreted as glacial deposits, are interpreted here as sedimentation response to tectonics with no necessary relation to glacial processes. Deformation and formation tectonic structural elements were distinguished and a braquianticlinal structure is suggested for the units in the Corumbá and Maciço do Urucum area.

Sistemas deposicionais fluviais são de grande relevância para o avanço dos métodos de interpretação de sucessões siliciclásticas, por permitirem observações diretas de processos e produtos em sistemas ativos. A recente retomada de estudos sobre as relações processo-produto na escala de formas de leito e da geomorfologia fluvial, aliada ao avanço nos estudos de paleohidráulica e a uma crescente insatisfação com os modelos de fácies vigentes, traz a necessidade de reavaliação dos métodos e interpretações tradicionalmente aplicados a sucessões clásticas no registro geológico, e abre a possibilidade de avanços significativos decorrentes da aplicação de novos conceitos a sucessões fluviais bem expostas. Visando contribuir para a consolidação desses avanços e para sua incorporação aos métodos de estudo e interpretação de sucessões antigas, o presente trabalho tem como foco os depósitos aluviais aptianos da Formação Marizal na Bacia do Tucano, que por suas excepcionais exposições, continuidade lateral e contexto tectônico apresentam-se como objeto adequado para a meta pretendida. Desta forma, foram aplicados métodos tradicionais de análise de elementos arquiteturais, análises de fácies e análise de paleocorrentes, com abordagem e interpretações baseadas em avanços recentes, integradas a estudos de paleohidráulica e considerações quantitativas. É abordada também a implicação dos resultados obtidos em reconstruções paleogeográficas, paleotectônicas e paleobiogeográficas do contexto regional em que se insere a Bacia do Tucano no Aptiano. Os resultados foram organizados na forma de quatro artigos científicos. Revisão dos trabalhos prévios acerca da Formação Marizal são detalhadas no primeiro artigo, confrontados a novos dados que resultaram na apresentação de um novo panorama sedimentológico, estratigráfico e tectônico da unidade com base em levantamentos de campo concentrados nas áreas em que ocorrem suas melhores exposições, as sub-bacias do Tucano Norte e Central. Foram definidas duas sub-unidades, distintas do ponto de vista litoestratigráfico e de sua arquitetura ou densidade e conexão dos depósitos de canais fluviais. A unidade inferior, denominada Membro Banzaê, é caracterizada por depósitos de canais amalgamados enquanto a unidade superior, denominada Membro Cícero Dantas, é caracterizada por depósitos de canais isolados em meio a depósitos de planície de inundação. Os padrões de paleocorrentes observados em ambas as unidades corroboram, grosso modo, o predomínio de um sistema fluvial axial fluindo para sul ao longo da Bacia do Tucano. Contudo, padrões transversais, possivelmente associados a sistemas fluviais tributários, também foram observados. Um segundo artigo traz contribuição às reconstruções paleogeográficas e consequentemente à biogeografia aptiana no nordeste do recém individualizado continente da América do Sul. Nesse artigo são discutidas as implicações do registro sedimentar aptiano da Bacia do Tucano para a interpretação das principais redes de drenagem e das ingressões marinhas ligadas ao Oceano Tétis na região durante o Eocretáceo. O reconhecimento de uma camada fossilífera, representante de uma ingressão marinha (Camada Amargosa) apresenta importantes implicações paleobiogeográficas para o contexto regional em que se insere o RTJ, por ocorrer em posição estratigráfica específica, e até então incógnita, e conter a conhecida paleoictiofauna da Formação Marizal. Dessa forma, no presente trabalho foi dado contexto estratigráfico e consequentemente paleogeográfico para uma das ingressões marinhas do Cretáceo Médio registradas no nordeste do Brasil. Os resultados apresentados são complementados com mais duas contribuições, de caráter metodológico, baseadas na análise arquitetural dos depósitos fluviais da Formação Marizal. Assim, em um terceiro artigo é descrito um novo método para o tratamento de dados obtidos a partir de depósitos fluviais que deve resultar em interpretações mais precisas e melhor visualização das direções de acréscimo de barras fluviais. Outra vantagem do método proposto é a utilização de pares de atitudes de estratos frontais e limites de série de estratificações cruzadas planares, ou seja estruturas abundantes e de fácil mensuração, na reconstrução de superfícies de barras a partir do registro fluvial. A contribuição que compõe o último artigo traz discussão acerca da possibilidade de reconhecimento e individualização de elementos da geomorfologia fluvial, como barras unitárias, barras compostas e canais abandonados no registro fluvial antigo. Ênfase é dada à distinção entre os depósitos lateralmente adjacentes de preenchimento de canal abandonado e de barra, devido à dificuldade que vem sendo enfrentada na distinção entre esses elementos por meio de suas características sedimentares em depósitos de sistemas deposicionais ativos. Assim, no Membro Banzaê, foi possível, através de abordagem quantitativa sobre o porte de elementos arquiteturais e séries e considerações paleohidráulicas, reconhecer e individualizar depósitos prontamente correlacionáveis à dinâmica geomorfológica fluvial, como barras unitárias, preenchimentos de canal abandonado e sucessões de cinturões de canais limitadas por eventos de avulsão. Desta forma, o estudo da Formação Marizal nas sub-bacias do Tucano Norte Central revela o grande potencial de estudos detalhados de arquitetura deposicional aliados a estudos paleohidráulicos e contextualização regional tectônica e paleogeográfica de depósitos fluviais na obtenção de informações relevantes mesmo a partir de sucessões aparentemente homogêneas. Fluvial depositional systems are of great relevance to the advance of the methods of interpretation of clastic successions, as they enable direct observation of processes and products in active systems. Recent studies on the process-product relations at the bedform and fluvial geomorphology scales, coupled with advances in paleohydraulics and with a growing dissatisfaction with current facies models, brings the necessity of revaluation of the methods and interpretations traditionally applied to clastic successions in the rock record and opens the possibility of significant advances through the application of new concepts to well exposed fluvial successions. Aiming at a contribution to these new advances and their integration to the methods and interpretations of ancient successions, the present work focuses on Aptian alluvial deposits from the Marizal Formation in the Tucano Basin, which for their exceptional expositions, lateral continuity and tectonic context, are an ideal object for to reach the proposed goals. In this way, traditional methods of facies, architectural element and palaeocurrent analysis were applied, with approach and interpretations based on recent advances and integrated to paleohydraulic constraints and quantitative considerations. Implications of the results to paleogeographical, paleotectonic and paleobiogeographical reconstructions, in the context of the Tucano Basin, are also discussed. The results are organized in four scientific papers. Previous works on the Marizal Formation are reviewed in a first work, confronted to new data that lead to a new sedimentological, stratigraphical and tectonic model, based on field data obtained from the area were the best expositions are concentrated, in the central and north Tucano sub -basin. Two sub-units were defined, differentiated for their lithology and architecture, expressed in different connectivity of fluvial channel bodies. The lower unit, named Banzaê Member, is characterized by amalgamated channel deposits, while the upper unit, named Cícero Dantas Member, contains isolated channel bodies surrounded by flood plain deposits. Palaeocurrent patterns from both units corroborate the model of a main axial fluvial system flowing towards the south along the Tucano Basin. Nevertheless, transverse system where also recognized, probably related to tributary fluvial systems. A second work brings contributions to the paleogeographic reconstructions and consequently to the Aptian biogeography of the northeastern region of the then recently formed South American continent. The implication of the Aptian sedimentary record of the Tucano Basin for the interpretation of the main drainage networks are discussed, as well as for the marine incursions related to the Tethys Ocean. The recognition of a fossiliferous bed, recording a marine incursion in the basin (Amargosa Layer) have major paleogeographical implications for the regional context of the RTJ, since it occurs at a specific stratigraphic position, recognized for the first time, and contains the well know fish fossils of the Marizal Formation. In this way, the present work defines the stratigraphical and consequently context, for one of the marine ingression of the Middle Cretaceous recorded in northeastern Brazil. The presented results are complemented with two other contributions, with methodological scope, based on the architectural analysis of the fluvial deposits of the Marizal Formation. In this way, a third article contains the description of a new method for the processing of data obtained from fluvial deposits, which results in more precise reconstructions and visualization of accretion elements in bar forms. Another advantage of the proposed method is that it is based on measurement of foresets and cross-bed bounding surfaces, which are abundant and easily measurable structures, for the reconstruction of bar surfaces from the fluvial rock record. The contribution presented in the last article brings the discussion on the possibility of recognition and individualization of fluvial geomorphological elements, such as unit bars, compound bars and abandoned channel fills, from the rock record. Emphasis is placed on the distinction between laterally equivalent deposits of channel fill and bars, given the recently recognized difficulty in distinguishing these elements, based on sedimentological data, in active depositional systems. In this way, the study of a selected are of the Banzaê Member enabled, through a quantitative approach considering the scale of architectural elements and cross-sets as well as paleohydraulic constraints, the recognition and individualization of deposits attributed to the fluvial geomorphological dynamics, such as unit bars, abandoned channel fills and channel belt successions bounded by avulsion surfaces. Therefore, the study of the Marizal Formation in the central and north Tucano Basin reveals the great potential of detailed studies of depositional architecture, coupled with paleohydraulic studies and interpretation of regional tectonic and paleogeographic context of fluvial deposits, for the acquisition of relevant information even in apparently homogeneous successions.

The Jacadigo Group contains one of the largest sedimentary iron and associated manganese deposits of the Neoproterozoic. Despite its great relevance, no detailed sedimentological study concerning the unit has been carried out to date. Here we present detailed sedimentological data and interpretation on depositional systems, system tracts, external controls on basin evolution, basin configuration and regional tectonic setting of the Jacadigo Basin. Six depositional systems were recognized: (I) an alluvial fan system; (II) a siliciclastic lacustrine system; (III) a fan-delta system; (IV) a bedload-dominated river system; (V) an iron formation-dominated lacustrine or marine gulf system; and (VI) a rimmed carbonate platform system. The interpreted depositional systems are related to three tectonic system tracts. The first four depositional systems are mainly made of continental siliciclastics and refer to the rift initiation to early rift climax stage; the lake/gulf system corresponds to the mid to late rift climax stage and the carbonate platform represents the immediate to late post rift stage (Bocaina Formation deposits of the Ediacaran fossil-bearing Corumba Group). The spatial distribution of the depositional systems and associated paleocurrent patterns indicate a WNW-ESE orientation of the master fault zone related to the formation of the Jacadigo Basin. Thus, the iron formations of the Jacadigo Group were deposited in a starved waterbody related to maximum fault displacement and accommodation rates in a restricted continental rift basin. The Fe–Si–Mn source was probably related to hydrothermal plume activity that reached the basin through the fault system during maximum fault displacement phases. Our results also suggest a restricted tectono-sedimentary setting for the type section of the Puga Formation. The Jacadigo Group and the Puga Formation, usually interpreted as glacial deposits, are readdressed here as basin margin gravitational deposits with no necessary relation to glacial processes.

A fotogrametria digital vem se tornando uma importante ferramenta para a aquisição remota de dados. O uso de modelos digitais de afloramento (MDAs) para análise de fraturas tem crescido no ambito das geociencias. Structure-from-Motion Multi-view Stereo (SfM-MVS) é uma técnica recente, que permite a criação de MDAs de maneira mais simples e barata. Para direcionar um estudo aprofundado da aplicação de SfM-MVS na investigação de meios fraturados, a tese buscou responder quais parâmetros relacionados a estes sistemas podem ser obtidos através dos MDAs gerados por SfM-MVS, e quais fatores tem influencia sobre a precisao dos dados. Foram gerados modelos de diferentes afloramentos (rochas ígneas, sedimentares e metamórficas), utilizando conjuntos de imagens em diferentes escalas, capturados por diferentes câmeras e plataformas. Os modelos foram analisados em três abordagens: para obtenção de propriedades de fraturas; análise qualitativa dos fatores que influenciam na sua qualidade e dos dados derivados; e investigação dos níveis de qualidade de reconstrução oferecidos pelo programa Agisoft Metashape. Como resultado, foi produzida uma lista de boas práticas de levantamento de campo, para a construção de um MDA. Concluiuse que o RPA é a plataforma mais flexível para diferentes topografias, pois permite o planejamento prévio do levantamento ou pilotagem manual, enquanto oferece bom custo benefício. Na análise de fraturas, são facilmente implementados algoritmos que calculam orientação, espaçamento e persistência. Estes três parâmetros são dependentes da capacidade de identificação das fraturas no modelo 3D. Essa capacidade é influenciada pela resolução espacial e a presença de deformações no modelo. No caso da rugosidade, a dificuldade de quantificação está na conversão eficiente do Joint Roughness Coefficient (JRC) para o espaço tridimensional. Na investigação das opções oferecidas pelo Metashape, os dados analisados sugerem os pares precisao-qualidade high-high e highest-high como os de melhor custo-benefício, sendo o primeiromais seguro para aplicação em condições de campo. Os resultados obtidos apontam para a existência de um tripé, composto por três elementos altamente correlacionados: o escopo, o tempo e o custo. A alteração de um deles sem que haja impacto nos demais irá sacrificar a qualidade final do modelo, e consequentemente da análise. Outro resultado importante foi o desenvolvimento do aplicativo multiplataforma SurvAid, uma ferramenta de planejamento do levantamento de imagens; e do programa livre CAPI, dedicado à análise estrutural de MDAs. Como conclusão, SfM-MVS mostrou-se uma técnica poderosa para a geração de MDAs, que podem ser usados na análise de fraturas. Ainda assim, deve ser vista como uma ferramenta complementar ao trabalho de campo. Digital photogrammetry is becoming an important tool for remote data acquisition. The use of digital outcrop models (DOMs) for fracture analysis has grown in the field of geosciences. Structure-from-Motion- Multi-view Stereo (SfM-MVS) is a recent technique that allows the creation of DOMs in a simple and inexpensive way. To direct an in-depth study of the application of SfM-MVS in the investigation of fractured media, the thesis sought to answer which parameters related to these systems can be obtained through the 3D models generated by SfM-MVS, and which factors have an influence on the data accuracy. Models of different outcrops (igneous, sedimentary and metamorphic rocks) were generated using sets of images at different scales, captured by different cameras and platforms. The models were analyzed using three approaches: to measure fracture properties; qualitative analysis of the factors that influence its quality and the derived data; and investigation of the quality levels offered by Agisoft Metashape. As a result, a list of best practices for fieldwork for the construction of an DOM was produced. It was concluded that the RPA is the most flexible platform available for different topographies, as it allows flight planning or manual piloting, while offering a good cost-benefit. In fracture analysis, algorithms that calculate orientation, spacing and persistence are easily implemented. These three parameters depend on the ability to identify fractures in the generated 3D model. This, in turn, is influenced by the spatial resolution and the presence of deformations in the model. For roughness, the difficulty of quantification lies in the efficient conversion of the Joint Roughness Coefficient (JRC) to three-dimensional space. In investigating the options offered by the Metashape program, the analyzed data suggest the accuracy-quality pairs high-high and highest-high as the best costbenefit ones, the first being the safest for application in field conditions. The results obtained point to the existence of a tripod, composed of three highly correlated elements: scope, time and cost. Changing one of them without impacting the others will sacrifice the final quality of the model, and consequently of the analysis. Another important result was the development of the multiplatform application SurvAid, an image survey planning tool; and the open software CAPI, dedicated to the structural analysis of DOMs. In conclusion, SfM-MVS proved to be a powerful technique for generating MDAs, which can be used in fracture analysis. Still, it should be seen as a complementary tool to field work.

Esta pesquisa investigou microfósseis neoproterozoicos em forma de vaso (\"vase-shaped microfossils - VSMs\") da Formação Urucum (Grupo Jacadigo) e Formação Bocaina (Grupo Corumbá), ambas inseridas na Faixa Paraguai Sul, Brasil. Estes microfósseis foram comparados a outras ocorrências neoproterozoicas no mundo. O objetivo foi contribuir com o conhecimento de aspectos paleobiológicos, evolutivos e bioestratigráficos relacionados ao aparecimento de eucariontes unicelulares tecados em ecossistemas anteriores ao surgimento dos metazoários. Os VSMs podem ser atribuídos a quitinozoários, tintinídeos e foraminíferos, porém, características diagnósticas importantes apontam o grupo Amoebozoa como afinidade biológica mais próxima. A variedade morfológica e composicional observada em VSMs neoproterozoicos, inclusive nos exemplares brasileiros, documenta a mais antiga diversificação da vida unicelular eucariótica, presumivelmente heterotrófica, preservada no registro geológico. As diferentes fácies sedimentares contendo VSMs fornecem informações valiosas sobre fatores ambientais que podem ter sido importantes na diversificação bem como no seu possível desaparecimento entre o Neoproterozoico e o Mesozoico. Além disso, a ampla distribuição e variedade desses microfósseis sugerem uma possível aplicação bioestratigráfica. Microscopia petrográfica (MP) e Eletrônica de Varredura (MEV), Espectrometria de Energia Dispersiva de Raios X (EDS), Microscopia Confocal (MC), Espectroscopia Raman (ER), Catodoluminescência (CL) além de técnicas geoquímicas e geocronológicas foram aplicadas para caracterizar a composição e morfologia dos microfósseis, bem como para a rocha encaixante, visando inferir a natureza e paleoecologia dos organismos responsáveis pelas produção das tecas e o ambiente em que viveram, se diversificaram e desapareceram. This research investigated vase-shaped microfossils (VSMs) from the Urucum Formation (Jacadigo Group) and Bocaina Formation (Corumbá Group), both inserted in the Southern Paraguay Fold Belt, Brazil. These microfossils were compared to other neoproterozoic occurrences in the world. The aim was to contribute to the knowledge of paleobiological, evolutionary and biostratigraphic aspects related to the appearance of unicellular eukaryotes in the ecosystems that preceed the appearance of metazoans. VSMs can be attributed to quitinozoan, tintinids and foraminifera, but important diagnostic features point to the Amoebozoa group as the closest biological affinity. The morphological and compositional variety observed in neoproterozoic VSMs, including Brazilian specimens, documents the earliest diversification of eukaryotic unicellular life, presumably heterotrophic, preserved in the geological record. The different sedimentary facies containing VSMs provide valuable information about environmental factors that may have been important in the diversification as well as their possible disappearance between the Neoproterozoic to the Mesozoic. In addition, the wide distribution and variety of these microfossils suggest a possible biostratigraphic application. Petrography, Scanning electron microscopy, Confocal microscopy, Energy-dispersive X-ray spectroscopy, Raman spectroscopy, Cathodoluminescense, besides geochemical and geochronological techniques, were applied to characterize the composition and morphology of the microfossils, as well as for the host rock, in order to infer the nature and paleoecology of the organisms responsible for the production of the test and the environment in which they lived, diversified and probably disappeared

Uma das principais questões da geologia sedimentar fluvial é a identificação do porte dos depósitos fluviais no registro geológico. O seguinte trabalho desenvolveu um método para determinação de um indicador de escala do sistema fluvial independente das medidas de espessura de séries, com base na relação empírica entre o porte do sistema fluvial e o comprimento de onda da sinuosidade de seu canal principal. A Formação Marizal é interpretada como depósitos fluviais de rio entrelaçado do Aptiano, no município de Banzaê (Bahia-Brasil) as excelentes exposições e a continuidade lateral do Membro Banzaê permitiram a análise da distribuição espacial dos dados de paleocorrentes. Análise de 592 pares de estratificação cruzada e limite de séries permitiram reconhecer o predomínio de acréscimo frontal em barras arenosas, corroborando a interpretação de depósitos de rios entrelaçados. Para uma área de 250 Km², em 40 localidades tomaram-se 1264 medidas de estratificações cruzadas, permitindo a elaboração de mapas de paleocorrentes de três níveis estratigráficos de 10 a 15 m de espessura. Para cada estação pontual de medidas, foi possível estabelecer um erro em graus, com 95% de confiança, determinado pela análise de uma grande amostra (938 medidas em uma única estação) tomada como representativa da distribuição típica. Essa abordagem permitiu reconhecer a variação nos sentidos de paleocorrentes em uma malha de afloramentos e reconstituir a padrões de sinuosidade do sistema, dando como resultado 9 km de comprimento de onda da sinuosidade preservada no registro sedimentar. Novas medidas de espessura de séries de estratificação cruzada (n=2051) corroboram trabalhos anteriores, indicando média entre 21 e 23 cm para o Membro Banzaê, o que sugere canais com profundidade na escala de rios entrelaçados modernos de grande porte. A análise de rios entrelaçados ativos com vazão conhecida mostra que o comprimento de onda da sinuosidade está diretamente relacionado à vazão média anual. A comparação do comprimento de onda dos rios ativos com o obtido no registro geológico para a unidade estudada permite concluir que o rio responsável pela deposição do Membro Banzaê da Fm. Marizal foi de grande porte, equiparável a rios de bacia de drenagem regional, como o Irrawaddy (Mianmar) e o Brahmaputra (Índia-Bangladesh). One of the main questions in fluvial sedimentary geology is the recognition of the scale of past fluvial systems in the rock record. This work proposes a method for the assessment of fluvial system scale independent of cross-strata set thickness measurements, based on the empirical relation between the size of the fluvial system and the wavelength of the sinuosity in its main channel. The Marizal Formation is interpreted as deposits of an Aptian braided river. The excellent exposures of the Banzaê Member, in Banzaê municipality (Bahia State - Northeastern Brazil) and their lateral continuity, enabled an analysis of the spatial distribution of paleocurrent data. The analysis of 592 pairs of cross-strata set surfaces and cross-strata set bounding surfaces reveal the prevalence of downstream accretion in sandy bars, thus corroborating previous interpretations of a braided river. For an area of 250 Km², in 40 outcrops 1264 cross-strata set surfaces were measured, leading to paleocurrent maps for three 10 to 15 m thick stratigraphic levels. An error in degrees, with 95% of confidence, was attributed for each individual station, calculated based on the analysis of a large sample (938 measurements in one individual station) taken as representative of the typical distribution. This aproach enabled the recognition of the variability in local paleocurrent directions, leading to the reconstruction of the sinuosity patterns of the system, pointing to a 9 km wavelength for the preserved sinuosity. New cross-strata set thickness measurements (n=2051) corroborate previous works, with and mean thickness between 21 e 23 cm for the Banzaê Member, suggesting channel depths in the same scale of modern day large scale braided rivers. The analysis of active braided rivers with known discharge reveals that the sinuosity wavelength is directly correlated to the mean annual dischage. Comparison of modern day rivers sinuosity wavelengths with the results obtained for the studied unit in the rock record indicates that the river responsible for the deposition of the Banzaê Member of the Marizal Formation was one of large dimensions, comparable to rivers of regional-scale drainage basins such as the Irrawaddy (Mianmar) and the Brahmaputra (India-Bangladesh).