Delimitação de blocos estruturais de diferentes escalas em seqüências mezosóicas do Estado do Rio Grande do Sul: implicações bioestratigraficas

Photolineaments and stream alignments, visible on radar and satellite images and on aerial photos of varied scales, define structural blocks in sedimentary rocks, characterized by a certain stratigraphic homogeneity, allowing the possibility of correlation on heavily vegetated areas. At the central portion of the Rio Grande do Sul State (Southern Brazil), six structural blocks were recognized (Santa Maria, São João do Polêsine, Faxinal do Soturno, Agudo, Paraíso do Sul and Candelária), based on fault displacements on the order of 100 m, which is more than the average thickness of some lithostratigraphic units. At the Santa Maria block, groundwater wells and field data allowed to recognize five structural subblocks (Cabeceira do Raimundo, Tancredo Neves, Cidade, Km 3, Camobi), with fault displacements averaging 30 m. The identified fault displacements, in lithofaciologically similar deposits, lead to a biostratigraphic discontinuity, from block to block, produced by the lateral juxtaposition of different biozones. The main alignments show distinct cenozones on each side, leading to difficulties on litho- and biostratigraphic correlations, at the regional scale. This study seeks to demonstrate that the advance on the comprehension of stratigraphic correlations at the central portion of the Rio Grande do Sul State must consider the structural compartmentalization of the region. Keywords: Triassic, Santa Maria Formation, Caturrita Formation, post-depositional tectonics.Fotolineamentos e alinhamentos de drenagem, visíveis em imagens de radar e satélite e em aerofotos de variadas escalas, permitem delimitar blocos estruturais em rochas sedimentares, caracterizados por certa homogeneidade estratigráfica, abrindo a possibilidade de correlações em áreas densamente vegetadas. Na região central do Estado do Rio Grande do Sul (sul do Brasil), seis blocos estruturais foram reconhecidos (Santa Maria, São João do Polêsine, Faxinal do Soturno, Agudo, Paraíso do Sul e Candelária), com base em rejeitos médios de cerca de 100 m, que chegam a ultrapassar a espessura média de algumas unidades litoestratigráficas. No bloco Santa Maria, a utilização de perfis geológicos em poços de captação de água subterrânea, aliada aos trabalhos de campo, permitiu reconhecer cinco sub-blocos estruturais (Cabeceira do Raimundo, Tancredo Neves, Cidade, Km 3, Camobi), com rejeito médio da ordem de 30 m. Os rejeitos identificados, em depósitos litofaciologicamente muito similares, levam ao desordenamento bioestratigráfico pela justaposição lateral de diferentes biozonas. Os principais lineamentos colocam lado a lado assembléias fossilíferas, pertencentes a distintas cenozonas, acarretando em dificuldades de correlação lito e bioestratigráfica, em escala regional. Este estudo procura demonstrar que o avanço na compreensão das correlações bioestratigráficas da porção central do Estado do Rio Grande do Sul deverá necessariamente considerar a compartimentação estrutural da região. Palavras-chave: Triássico, Formação Santa Maria, Formação Caturrita, tectônica pós-deposicional

Delimitação de blocos estruturais de diferentes escalas em seqüências mezosóicas do Estado do Rio Grande do Sul: implicações bioestratigraficas

Photolineaments and stream alignments, visible on radar and satellite images and on aerial photos of varied scales, define structural blocks in sedimentary rocks, characterized by a certain stratigraphic homogeneity, allowing the possibility of correlation on heavily vegetated areas. At the central portion of the Rio Grande do Sul State (Southern Brazil), six structural blocks were recognized (Santa Maria, São João do Polêsine, Faxinal do Soturno, Agudo, Paraíso do Sul and Candelária), based on fault displacements on the order of 100 m, which is more than the average thickness of some lithostratigraphic units. At the Santa Maria block, groundwater wells and field data allowed to recognize five structural subblocks (Cabeceira do Raimundo, Tancredo Neves, Cidade, Km 3, Camobi), with fault displacements averaging 30 m. The identified fault displacements, in lithofaciologically similar deposits, lead to a biostratigraphic discontinuity, from block to block, produced by the lateral juxtaposition of different biozones. The main alignments show distinct cenozones on each side, leading to difficulties on litho- and biostratigraphic correlations, at the regional scale. This study seeks to demonstrate that the advance on the comprehension of stratigraphic correlations at the central portion of the Rio Grande do Sul State must consider the structural compartmentalization of the region. Keywords: Triassic, Santa Maria Formation, Caturrita Formation, post-depositional tectonics.Fotolineamentos e alinhamentos de drenagem, visíveis em imagens de radar e satélite e em aerofotos de variadas escalas, permitem delimitar blocos estruturais em rochas sedimentares, caracterizados por certa homogeneidade estratigráfica, abrindo a possibilidade de correlações em áreas densamente vegetadas. Na região central do Estado do Rio Grande do Sul (sul do Brasil), seis blocos estruturais foram reconhecidos (Santa Maria, São João do Polêsine, Faxinal do Soturno, Agudo, Paraíso do Sul e Candelária), com base em rejeitos médios de cerca de 100 m, que chegam a ultrapassar a espessura média de algumas unidades litoestratigráficas. No bloco Santa Maria, a utilização de perfis geológicos em poços de captação de água subterrânea, aliada aos trabalhos de campo, permitiu reconhecer cinco sub-blocos estruturais (Cabeceira do Raimundo, Tancredo Neves, Cidade, Km 3, Camobi), com rejeito médio da ordem de 30 m. Os rejeitos identificados, em depósitos litofaciologicamente muito similares, levam ao desordenamento bioestratigráfico pela justaposição lateral de diferentes biozonas. Os principais lineamentos colocam lado a lado assembléias fossilíferas, pertencentes a distintas cenozonas, acarretando em dificuldades de correlação lito e bioestratigráfica, em escala regional. Este estudo procura demonstrar que o avanço na compreensão das correlações bioestratigráficas da porção central do Estado do Rio Grande do Sul deverá necessariamente considerar a compartimentação estrutural da região. Palavras-chave: Triássico, Formação Santa Maria, Formação Caturrita, tectônica pós-deposicional

Paleoalterações e Carbonatos em Depósitos Aluviais na Região de Santa Maria, Triássico Médio a Superior do Sul do Brasil

Five types of paleo-weathering and carbonate precipitation were recognized in fine-grained deposits of the Alemoa Member, Santa Maria Formation, Middle to Upper Triassic of southern Brazil. The fauna and flora found in these lithologies are important dating tools, but only in a generic way, misleading the time involved in periods of deposition and non deposition. The identified types of deposits are (i) reddish mudstones, with none or little paleo-weathering, (ii) mottled mudstones, with incipient pedogenesis, mainly mottling, destratification, animal and vegetal colonization, (iii) carbonate veins, with more evidences of exposure and root action, (iv) carbonate siltstones/sandstones, where restricted fluvial deposits are cemented by phreatic carbonate, and (v) carbonate nodules and lenses, in which small lenses of a very compact calcrete are at the top and in the center of carbonated siltstone/sandstone beds, distinguished by its crystalinity, hardness and brighter color. The recorded microfacies point to a cyclic variation of the mainly high phreatic level, forming cracks and pedotubules (pedogenesis) filled with carbonate and Fe and Mn oxides (phreatic). The identification of five distinct pedofacies and the stratigraphic correlation in the sedimentary package of the Alemoa Member (base, middle or topmost position) suggest a probable association of paleo-weathering processes and vertebrate preservation. Near channel facies, mainly at the base and top, present smaller exposure periods and higher variations on the phreatic level, and consequently, the best preserved vertebrate fossils. On the other hand, facies which are far from the channel, record more subaerial exposure and more significant phreatic variation, leading to more advanced (although still incipient) paleo-weathering and carbonate precipitation, and to a worst fossil preservation

Sobre a ocorrência de vertebrados fósseis triássicos na Região de Santana da Boa Vista (RS)

O trabalho não apresenta resumo

Divulgação de dados ambientais e socioeconômicos na internet usando um modelo baseado no uso de ferramentas livres

The article presents a model based on the use of free tools aiming at the publication of socioeconomic and environmental data and dissemination of information on the internet. The structure of this model makes it possible to present information as tables, graphs, pictures or web maps. The choice of a particular presentation format is determined according to the goals of the developer. As a result of this work the user will create a virtual geographic database for the generation of static information and interactive web maps. The main tools used are the Spring geographic information system, MySQL relational database, PHP script and Apache HTTP server.Key words: Web mapping, free tools, Spring Web, Geographic Information System.Um modelo baseado no uso de ferramentas livres é apresentado, visando à publicação de dados socioeconômicos e ambientais e divulgação de informações na internet. A estrutura deste modelo permite que as informações sejam apresentadas sob a forma de tabelas, gráficos, fotos ou mapas para a web. A escolha de um determinado formato de apresentação da informação é determinada de acordo com os objetivos do desenvolvedor. Como resultado do trabalho, o usuário criará um banco de dados geográficos virtual para gerar informações estáticas e mapas interativos para a web. As principais ferramentas utilizadas foram o sistema de informações geográficas Spring, banco de dados relacional MySQL, PHP script e o servidor Apache HTTP.Palavras-chave: mapeamento via Web, ferramentas livres, Spring Web, Sistema de Informação Geográfica

Lowstand Turbidites and Delta Systems of the Itararé Group in the Vidal Ramos region (SC), southern Brazil

Turbidites have captioned the attention of sedimentologists during the last decades due their importance as hydrocarbon reservoirs. However, their relationship to delta systems still deserves further studies. This paper presents examples from a late deglacial to early post-glacial deltaic and turbidite strata exposed in the surroundings of Vidal Ramos (Santa Catarina State, Brazil), southern portion of the Paraná Basin. There, the uppermost part of the Mafra Formation and the Rio do Sul Formation onlap the Proterozoic basement and comprises an up to 360 m thick package. It includes (base to top) black shales, mass transport deposits (MTD) and sandy turbidites (Mafra Formation) as well as thin bedded turbidites (tbt), including one interval of black shales and sandy turbidites, overlain by proximal delta front sandstones (Rio do Sul Formation). The analysis of the succession shows two more than 150 m thick coarsening-upwards deltaic successions composed of turbidite sand sheets at their base (prodelta), followed by partially collapsed thin bedded turbidites (delta slope wedge) and delta front sandstones. Both turbidite sand-sheets abruptly overlay black shale intervals related to maximum flooding surfaces and therefore record correlative conformities. A detailed stratigraphic section elaborated from the correlation of four logs (1/100) suggests that distal delta front sands includes both thin bedded turbidites and wave reworked sands whereas the proximal delta front was dominated by long-lived underflows (hyperpycnal flows). The succession suggests that the most expressive turbidite beds (base of the delta systems) have resulted from relative sea-level falls (early lowstand) whereas the thin-bedded turbidites were related to the development of the late lowstand wedge. Black shales represent the transgressive systems tract and HST were not deposited or preserved in the area. High sediment supply associated with lowstand tracts could explain the occasional (Vidal Ramos) to common occurrence of slope failures (slumps and diamictites) involving thin bedded turbidites and delta front sandstones. This situation is quite logical in terms of deglacial periods, and resulting high sediment supply, within a long-term icehouse context, with prevalence of lowstand to transgressive settings

Paleoalterações e Carbonatos em Depósitos Aluviais na Região de Santa Maria, Triássico Médio a Superior do Sul do Brasil

Five types of paleo-weathering and carbonate precipitation were recognized in fine-grained deposits of the Alemoa Member, Santa Maria Formation, Middle to Upper Triassic of southern Brazil. The fauna and flora found in these lithologies are important dating tools, but only in a generic way, misleading the time involved in periods of deposition and non deposition. The identified types of deposits are (i) reddish mudstones, with none or little paleo-weathering, (ii) mottled mudstones, with incipient pedogenesis, mainly mottling, destratification, animal and vegetal colonization, (iii) carbonate veins, with more evidences of exposure and root action, (iv) carbonate siltstones/sandstones, where restricted fluvial deposits are cemented by phreatic carbonate, and (v) carbonate nodules and lenses, in which small lenses of a very compact calcrete are at the top and in the center of carbonated siltstone/sandstone beds, distinguished by its crystalinity, hardness and brighter color. The recorded microfacies point to a cyclic variation of the mainly high phreatic level, forming cracks and pedotubules (pedogenesis) filled with carbonate and Fe and Mn oxides (phreatic). The identification of five distinct pedofacies and the stratigraphic correlation in the sedimentary package of the Alemoa Member (base, middle or topmost position) suggest a probable association of paleo-weathering processes and vertebrate preservation. Near channel facies, mainly at the base and top, present smaller exposure periods and higher variations on the phreatic level, and consequently, the best preserved vertebrate fossils. On the other hand, facies which are far from the channel, record more subaerial exposure and more significant phreatic variation, leading to more advanced (although still incipient) paleo-weathering and carbonate precipitation, and to a worst fossil preservation

Lowstand Turbidites and Delta Systems of the Itararé Group in the Vidal Ramos region (SC), southern Brazil

Turbidites have captioned the attention of sedimentologists during the last decades due their importance as hydrocarbon reservoirs. However, their relationship to delta systems still deserves further studies. This paper presents examples from a late deglacial to early post-glacial deltaic and turbidite strata exposed in the surroundings of Vidal Ramos (Santa Catarina State, Brazil), southern portion of the Paraná Basin. There, the uppermost part of the Mafra Formation and the Rio do Sul Formation onlap the Proterozoic basement and comprises an up to 360 m thick package. It includes (base to top) black shales, mass transport deposits (MTD) and sandy turbidites (Mafra Formation) as well as thin bedded turbidites (tbt), including one interval of black shales and sandy turbidites, overlain by proximal delta front sandstones (Rio do Sul Formation). The analysis of the succession shows two more than 150 m thick coarsening-upwards deltaic successions composed of turbidite sand sheets at their base (prodelta), followed by partially collapsed thin bedded turbidites (delta slope wedge) and delta front sandstones. Both turbidite sand-sheets abruptly overlay black shale intervals related to maximum flooding surfaces and therefore record correlative conformities. A detailed stratigraphic section elaborated from the correlation of four logs (1/100) suggests that distal delta front sands includes both thin bedded turbidites and wave reworked sands whereas the proximal delta front was dominated by long-lived underflows (hyperpycnal flows). The succession suggests that the most expressive turbidite beds (base of the delta systems) have resulted from relative sea-level falls (early lowstand) whereas the thin-bedded turbidites were related to the development of the late lowstand wedge. Black shales represent the transgressive systems tract and HST were not deposited or preserved in the area. High sediment supply associated with lowstand tracts could explain the occasional (Vidal Ramos) to common occurrence of slope failures (slumps and diamictites) involving thin bedded turbidites and delta front sandstones. This situation is quite logical in terms of deglacial periods, and resulting high sediment supply, within a long-term icehouse context, with prevalence of lowstand to transgressive settings

Facies and depositional architecture according to a jet efflux model of a late Paleozoic tidewater grounding-line system from the Itararé Group (Paraná Basin), southern Brazil

During the Late Paleozoic, the Gondwana supercontinent was affected by multiple glacial and deglacial episodes known as "The Late Paleozoic Ice Age" (LPIA). In Brazil, the evidence of this episode is recorded mainly by widespread glacial deposits preserved in the Paraná Basin that contain the most extensive record of glaciation (Itararé Group) in Gondwana. The Pennsylvanian to early Permian glaciogenic deposits of the Itararé Group (Paraná Basin) are widely known and cover an extensive area in southern Brazil. In the Doutor Pedrinho area (Santa Catarina state, southern Brazil), three glacial cycles of glacier advance and retreat were described. The focus of this article is to detail the base of the second glacial episodes or Sequence II. The entire sequence records a deglacial system tract that is represented by a proximal glacial grounding-line system covered by marine mudstones and shales associated with a rapid flooding of the proglacial area. This study deals with the ice proximal grounding-line systems herein interpreted according to lab model named plane-wall jet with jump. Detailed facies analysis allowed the identification of several facies ranging from boulder-rich conglomerates to fine-grained sandstones. No fine-grained deposits such as siltstone or shale were recorded. According to this model, the deposits are a product of a supercritical plane-wall outflow jet that changes to a subcritical jet downflow from a hydraulic jump. The hydraulic jump forms an important energy boundary that is indicated by an abrupt change in grain size and cut-and-fill structures that occur at the middle-fan. The sedimentary facies and facies associations show a downflow trend that can be subdivided into three distinct stages of flow development: (1) a zone of flow establishment (ZFE), (2) a zone of transition (ZFT), and (3) an established zone (ZEF). The proximal discharge is characterized by hyperconcentrated-to-concentrated flow due to the high energy and sediment-laden nature of the flows. At the transitional zone, a hydraulic jump produces a rapid shift of conglomeratic to sandy facies with associated scour features. Towards the distal zones, the jet detaches to originate a vertical turbulent jet characterized by more diluted flows. Discussion of fan facies and architecture within a framework of jet-efflux dynamics provides an improved understanding of grounding-line fans systems that produce coarse-grained strata commonly enclosed by fine-grained rocks. The results have clear implication in terms of prediction of facies tract and geometry of oil and gas reservoirs deposited under similar conditions. And also can be useful to identifying the position of a glacial terminus through time.Fil: Aquino, Carolina Danielski. Universidade do Vale do Rio Dos Sinos; BrasilFil: Buso, Victoria Valdez. Universidade do Vale do Rio Dos Sinos; BrasilFil: Faccini, Ubiratan Ferrucio. Universidade do Vale do Rio Dos Sinos; BrasilFil: Milana, Juan Pablo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan. Centro de Investigaciones de la Geosfera y Biosfera. Universidad Nacional de San Juan. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones de la Geosfera y Biosfera; ArgentinaFil: Paim, Paulo Sergio Gomes. Universidade do Vale do Rio Dos Sinos; Brasi

Stratigraphic distribution, taphonomy and paleoenvironments of Spinicaudata in the Triassic and Jurassic of the Paraná Basin

Due to the chitino-phosphatic nature of Spinicaudata conchostracan exoskeletons, their carapaces exhibit a low preservational potential compared to other bivalve groups. However, the recent studies point towards the increased tolerance of the carapace against the physical processes. Due to this peculiar characteristic, conchostracan carapace have been utilized as precise temporal markers in estimating stratigraphic and taphonomic parameters. The same characteristic also makes the spinicaudatans useful in evaluating the depositional processes and environments. The present work aims at providing a paleoenvironmental and stratigraphic analysis of conchostracans (Spinicaudata) from the Triassic-Jurassic of the Paraná Basin (Santa Maria and Caturrita formations) in terms of the sedimentary facies analysis, depositional system characterization, and analysis of the taphonomic signatures of the fossiliferous horizons within these formations. The results from the taphonomic study delineates the presence of 4 distinct fossil assemblages based on the causative mechanism and fundamental characteristics of the fossil concentrations: two taphonomic assemblages in the laminated mudstone beds deposited from the decanting fine-grained sediments in floodplains; the sandstone beds with plane parallel laminations and dune- and ripple-cross-stratifications deposited from the flooding-related overflow in the floodplains; and the association of laminated mudstone and massive sandstone beds deposited as the river mouth bars. The results show that the taphonomic signatures, e.g., closed valves, may indicate the various patterns of autochthony and allochthony. In the fine-grained floodplain assemblages, the high degree of preservation can be attributed to autochthony in the conchostracans, whereas the preservational condition of floodplain sandstone sheet and mouth bar assemblages point toward parautochthony and even allochthony. Therefore, the preservational quality of conchostracan exoskeletons is likely a function of parameters, e.g., the transport duration, the distance from life position, and the magnitude of events causing their final burial. Within the observed species, the recognition of Eustheria minuta in the stratigraphic level of the Passo das Tropas creek corroborates an age for these deposits between the late Middle Triassic and early Upper Triassic. The presence of a new form, likely related to the family Fushunograptidae in sediments from the Caturrita Formation, suggests a Jurassic age for these deposits.Fil: Jenisch, Alan Gregory. Universidade do Vale do Rio Dos Sinos; BrasilFil: Lehn, Ilana. Universidade do Vale do Rio Dos Sinos; BrasilFil: Gallego, Oscar Florencio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Centro de Ecología Aplicada del Litoral. Universidad Nacional del Nordeste. Centro de Ecología Aplicada del Litoral; ArgentinaFil: Monferran, Mateo Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Centro de Ecología Aplicada del Litoral. Universidad Nacional del Nordeste. Centro de Ecología Aplicada del Litoral; ArgentinaFil: Horodyski, Rodrigo Scalise. Universidade do Vale do Rio Dos Sinos; BrasilFil: Faccini, Ubiratan Ferrucio. Universidade do Vale do Rio Dos Sinos; Brasi