2024-08-012024-08-012024-06-07GÓMEZ CEPEDA, Howard Snaider. Paleoambiente e proveniência da formação aprazível-cambriano, da Bacia Jaibaras, Estado do Ceará, Brasil. Orientador: José Bandeira Cavalcante da Silva Júnior. 2024. xii, 64 f. Dissertação (Mestrado em Geologia) - Programa de Pós-graduação em Geologia e Geoquímica, Instituto de Geociências, Universidade Federal do Pará, Belém, 2024. Disponível em:https://repositorio.ufpa.br/jspui/handle/2011/16385 . Acesso em:.https://repositorio.ufpa.br/jspui/handle/2011/16385The Ediacaran-Cambrian transition that generally involves as main record carbonate and siliciclastic rocks with the presence of ichnofossils, limit made difficult when exclusively siliciclastic successions occur with low or no frequency of fossils, and with discontinuous exposures laterally due to erosion events such as the Aprazível Formation. Positioned in the middle-late Cambrian, with an age of maximum deposition between 504 - 494 Ma (c. 499 ± 5 Ma). Previous studies focusing on depositional interpretations of the formations present in the Jaibaras Basin have considered the Aprazível Formation without having a defined agreement or consensus on which mechanisms were responsible for the deposition of the conglomerates and sandstones of this Formation. Also, petrographic and provenance studies with the objective of characterizing texture and mineralogical composition were done without advancing in the study of diagenesis. This work presents a reinterpretation of the depositional systems of the Aprazível Formation based on sedimentological and stratigraphic analyses of outcrops of the Jaibaras-Aprazível-Sobral region, northwestern Ceará State, northeastern Brazil. The detailed faciologic description of this siliciclastic succession aimed to propose a depositional and evolutionary model for this Formation. Three facies’ associations (FA) representative of deposits generated in alluvial systems were defined. Sheet-flow (Intermediate Alluvial) deposits (AF1) consist of layers of up to 5m of conglomerate and subordinate sandstone, generally massive, tabular, with subrounded volcanic clasts with irregular contour, fusiform, flattened to form a flame, stretched and with pointed terminations occurring both in the conglomerate layers and isolated in the sandstone layers. Braid Plain (Distal Alluvial) deposits (AF2), consisting of fine to coarse-grained sandstone, with predominant planar-parallel stratification and cross-stratification, the sandstone is often interbedded with conglomeratic levels (lags), and sometimes shows deformational structures, also shows volcanic clasts as in AF1. Ephemeral Lake deposits (AF3), predominantly sandstone intercalated with pelite, sandstone with a plane-parallel to massive lamination, supercritical and subcritical climbingripple cross lamination, laminated pelite with clayey drapes, occurrence of overburden. The interpretation given in previous studies that the Aprazível Formation has its area of occurrence restricted and delimited to the region between the Sobral-Pedro II and Café Ipueiras shear zones was modified according to which these deposits currently conform to the intermediate-distal part of an alluvial fan; system, without presenting the section of a proximal fan. This indicates that these fans were not only restricted to the Jaibaras Graben; but were more extensive than the present basin, indicating that the deposition basin of the Aprazível Formation was larger than is preserved in the Graben. In addition, the paleocurrent data and the dip direction of the Aprazível Formation to the SE along the Jaibaras Graben; indicate that the source of these rocks is in the NW. There is no variation in dip over time in both direction and angle; the paleocurrent is unidirectional, not axial, which is not typical of pull-apart type basins. The Aprazível Formation was affected by different diagenetic processes highlighting calcite, chlorite, and titanite authigenic cementation; alteration, dissolution, and replacement processes such as calcitization, sericitization, albitization, chloritization, and epidotization, some of them being hydrothermal processes.Acesso AbertoAttribution-NonCommercial-NoDerivs 3.0 Brazilhttp://creativecommons.org/licenses/by-nc-nd/3.0/br/Geologia estratigráfica cambrianoFácilesPetrogênese: DiagêneseBacia de JaibarasVulcânicaDissertaçãoCNPQ::CIENCIAS EXATAS E DA TERRA::GEOCIENCIASANÁLISE DE BACIAS SEDIMENTARESGEOLOGIA