Cartografia Temática
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Resumo: Identifica e mapeia as localizações preferenciais de ocorrências das fácies sedimentares na Bacia de Curitiba em subsuperfície, mediante tratamento geoestatístico de dados litológicos de superfície e sub-superfície, contribuindo... more
Resumo: Identifica e mapeia as localizações preferenciais de ocorrências das fácies sedimentares na Bacia de Curitiba em subsuperfície, mediante tratamento geoestatístico de dados litológicos de superfície e sub-superfície, contribuindo para a melhor compreensão do comportamento espacial das litofácies que compõem a Formação Guabirotuba. O tratamento cartográfico temático, aqui apresentado, possibilitou o aprofundamento dos conhecimentos acerca da espacialidade tridimensional da faciologia sedimentar da Bacia de Curitiba e, dessa forma, também incrementou informações que contribuíram para a elucidação de sua evolução tectono-sedimentar, morfoestrutural e faciológica. Estruturalmente, o arcabouço da Bacia se configura numa depressão tectônica do tipo pull apart (com nítido controle retilinizado em sua borda noroeste), onde correm três principais depocentros, alinhados segundo a direção NNE-SSW, a mesma orientação do RCSB. Esses depocentros não são sincrônicos, mas ocorrem evolutivamente de SSW para NNE (com a tafrogenia), gerados por esforços transcorrentes NE-SW (não contínuos, mas espasmódicos) que perduraram do Oligoceno (idade muito provável para a gênese do Bacia de Curitiba) até o final do Plioceno ou Pleistoceno. Após esses momentos iniciais de tafrogenia e durante a vigência dos esforços transcorrentes NE-SW, a região sofre o início (ou aumento significativo) de esforços distensivos NW-SE; os quais produziram desnivelamento e basculamento na área a oriente da borda ativa do RCSB, formando um hemi-graben com declividade de leste para oeste. Com isto, deposita-se a fácies fluvial meandrante, a partir do Leste num segundo trend de sedimentação (ou segunda área-fonte), independente daquele instalado dentro da depressão pull apart. Os estágios finais de estruturação do arcabouço tectônico ocorreu, provavelmente, no Plio-Pleistoceno, e estão representados por falhamentos transversais ao RCSB (direção aproximada N-S) resultantes de esforços transtensionais e/ou transpressionais. Ao longo destes falhamentos, em rift, ocorrem as últimas deposições. Os sedimentos pertencentes à Bacia de Curitiba apresentam se, granulométrica e mineralogicamente, muito heterogêneos, apresentando litofácies rudáceas de orto a paraconglomeráticas, polimíticas, ostentando matrizes extremamente heterogêneas (desde granular e areia muito grossa até silto-argilosa). Os lamitos, muito imaturos e muito pobremente selecionados, apresentam desde areia média até argila; e com grande dispersão granulométrica tanto para as frações muito grossas como para as muito finas. De maneira geral, os sedimentos apresentam-se em corpos individualizados, ora maturos (para algumas areias retrabalhadas por drenagens), ora totalmente imaturos, geralmente sub-arcosianos a arcosianos (predominantes). Interpreta-se que os sedimentos sofreram curto transporte entre a área-fonte e a bacia deposicional (compatível com o modelo genético tectônico-sedimentar revelado pelo produto cartográfico ora apresentado) num ambiente climático árido a semiárido reinante na maioria da história deposicional, senão em sua totalidade. Quanto à faciologia dos depósitos, ocorrem cinco fácies sedimentares: leques aluviais proximais, leques aluviais medianos, leques aluviais distais, fluvial entrelaçado (braided) e fluvial meandrante. As três primeiras ocorrem, grosso modo, depositadas sequencialmente da borda para o depocentro da bacia pull apart, em sucessões interdigitadas e coalescentes. A fácies fluvial entrelaçado é produto de retrabalhamentos locais dos leques aluviais por drenagens intermitentes e perenes (representada por corpos arenosos mais bem selecionados). A fácies fluvial meandrante ocorre dispersa em toda a superfície aplainada de um bloco estrutural basculado em disposição de hemi-graben (a partir da área à leste, desde os contrafortes da Serra do Mar, rumo ao centro deposicional da bacia pull apart); apresentando-se tipicamente mais maturos, melhor selecionados e com estruturas sedimentares condizentes com ambiente fluvial meandrante. A presente pesquisa conclui pela indivisibilidade estratigráfica dos sedimentos presentes na Bacia de Curitiba, mantendo a tradicional e consagrada denominação de Formação Guabirotuba para os mesmos, uma vez que não foram encontrados elementos e evidências estratigráficas ou sedimentológicas que justifiquem qualquer desmembramento, como aqueles propostos em trabalhos anteriores.
Faciological mapping of the Sedimentary Basin of Curitiba (PR) : contribution of thematic cartography to morphostructural evolution
Abstract: Identifies and maps the preferred locations for occurrences of sedimentary facies in the Curitiba Basin on the subsurface, through geostatistical treatment of surface and sub-surface lithological data, contributing to a better understanding of the spatial behavior of the lithofacies that make up the Guabirotuba Formation. The thematic cartographic treatment, presented here, made it possible to deepen the knowledge about the three-dimensional spatiality of the sedimentary faciology of the Curitiba Basin and, thus, also increased information that contributed to the elucidation of its tectonic-sedimentary, morpho structural and physiological evolution. Structurally, the Basin framework is configured in a tectonic depression of the pull apart type (with clear retilinized control on its northwestern edge), where three main depocenters run, aligned according to the NNE-SSW direction, the same orientation as the RCSB. These depocenters are not synchronous, but they evolve from SSW to NNE (with the taphrogeny), generated by NE-SW (not continuous, but spasmodic) efforts that lasted from the Oligocene (very probable age for the genesis of the Curitiba Basin) until the end of the Pliocene or Pleistocene. After these initial moments of taphrogeny and during the ongoing NE-SW efforts, the region suffers the beginning (or significant increase) of NW-SE distensive efforts; which produced unevenness and tilting in the area east of the active edge of the RCSB, forming a hemi-graben with a slope from east to west. With this, the meandering river facies are deposited, from the East in a second sedimentation trend (or second source area), independent of that installed inside the pull apart depression. The final stages of structuring the tectonic framework probably occurred in the Plio-Pleistocene, and are represented by failures transversal to the RCSB (approximate direction N-S) resulting from tension and / or transpression efforts. Along these faults, in rift, the last depositions occur. The sediments belonging to the Curitiba Basin are granulometrically and mineralogically very heterogeneous, with rudimentary lithofacies from ortho to paraconglomerate, polymythic, showing extremely heterogeneous matrices (from granular and very coarse sand to silty-clay). The layers, very immature and very poorly selected, present from medium sand to clay; and with great granulometric dispersion for both very thick and very fine fractions. In general, the sediments are presented in individualized bodies, sometimes mature (for some sands reworked by drainages), now totally immature, generally sub-arcosian to arcosian (predominant). It is interpreted that the sediments suffered a short transport between the source area and the depositional basin (compatible with the tectonic-sedimentary genetic model revealed by the cartographic product presented here) in an arid to semiarid climatic environment that prevailed in most of the depositional history, if not in its wholeness. As for the faciology of the deposits, five sedimentary facies occur: proximal alluvial fans, medium alluvial fans, distal alluvial fans, braided and meandering fluvial. The first three occur, roughly speaking, deposited sequentially from the edge to the depocenter of the pull apart basin, in interdigitated and coalescent sequences. The interwoven river facies are the product of local reworking of alluvial fans by intermittent and perennial drains (represented by better-selected sandy bodies). The meandering river facies occur dispersed throughout the planed surface of a structural block tilted in a hemi-graben arrangement (from the area to the east, from the foothills of Serra do Mar, towards the depositional center of the pull apart basin); typically being more mature, better selected and with sedimentary structures consistent with meandering river environment. The present research concludes by the stratigraphic indivisibility of the sediments present in the Curitiba Basin, maintaining the traditional and consecrated denomination of Guabirotuba Formation for them, since no stratigraphic or sedimentological elements and evidence were found to justify any dismemberment, such as those proposed in works previous ones.
Faciological mapping of the Sedimentary Basin of Curitiba (PR) : contribution of thematic cartography to morphostructural evolution
Abstract: Identifies and maps the preferred locations for occurrences of sedimentary facies in the Curitiba Basin on the subsurface, through geostatistical treatment of surface and sub-surface lithological data, contributing to a better understanding of the spatial behavior of the lithofacies that make up the Guabirotuba Formation. The thematic cartographic treatment, presented here, made it possible to deepen the knowledge about the three-dimensional spatiality of the sedimentary faciology of the Curitiba Basin and, thus, also increased information that contributed to the elucidation of its tectonic-sedimentary, morpho structural and physiological evolution. Structurally, the Basin framework is configured in a tectonic depression of the pull apart type (with clear retilinized control on its northwestern edge), where three main depocenters run, aligned according to the NNE-SSW direction, the same orientation as the RCSB. These depocenters are not synchronous, but they evolve from SSW to NNE (with the taphrogeny), generated by NE-SW (not continuous, but spasmodic) efforts that lasted from the Oligocene (very probable age for the genesis of the Curitiba Basin) until the end of the Pliocene or Pleistocene. After these initial moments of taphrogeny and during the ongoing NE-SW efforts, the region suffers the beginning (or significant increase) of NW-SE distensive efforts; which produced unevenness and tilting in the area east of the active edge of the RCSB, forming a hemi-graben with a slope from east to west. With this, the meandering river facies are deposited, from the East in a second sedimentation trend (or second source area), independent of that installed inside the pull apart depression. The final stages of structuring the tectonic framework probably occurred in the Plio-Pleistocene, and are represented by failures transversal to the RCSB (approximate direction N-S) resulting from tension and / or transpression efforts. Along these faults, in rift, the last depositions occur. The sediments belonging to the Curitiba Basin are granulometrically and mineralogically very heterogeneous, with rudimentary lithofacies from ortho to paraconglomerate, polymythic, showing extremely heterogeneous matrices (from granular and very coarse sand to silty-clay). The layers, very immature and very poorly selected, present from medium sand to clay; and with great granulometric dispersion for both very thick and very fine fractions. In general, the sediments are presented in individualized bodies, sometimes mature (for some sands reworked by drainages), now totally immature, generally sub-arcosian to arcosian (predominant). It is interpreted that the sediments suffered a short transport between the source area and the depositional basin (compatible with the tectonic-sedimentary genetic model revealed by the cartographic product presented here) in an arid to semiarid climatic environment that prevailed in most of the depositional history, if not in its wholeness. As for the faciology of the deposits, five sedimentary facies occur: proximal alluvial fans, medium alluvial fans, distal alluvial fans, braided and meandering fluvial. The first three occur, roughly speaking, deposited sequentially from the edge to the depocenter of the pull apart basin, in interdigitated and coalescent sequences. The interwoven river facies are the product of local reworking of alluvial fans by intermittent and perennial drains (represented by better-selected sandy bodies). The meandering river facies occur dispersed throughout the planed surface of a structural block tilted in a hemi-graben arrangement (from the area to the east, from the foothills of Serra do Mar, towards the depositional center of the pull apart basin); typically being more mature, better selected and with sedimentary structures consistent with meandering river environment. The present research concludes by the stratigraphic indivisibility of the sediments present in the Curitiba Basin, maintaining the traditional and consecrated denomination of Guabirotuba Formation for them, since no stratigraphic or sedimentological elements and evidence were found to justify any dismemberment, such as those proposed in works previous ones.