Abstract:Cerro do Jarau is a conspicuous, circular morpho‐structural feature in Rio Grande do Sul State (Brazil), with a central elevated core in the otherwise flat “Pampas” terrain typical for the border regions between Brazil and Uruguay. The structure has a diameter of approximately 13.5 km. It is centered at 30o12′S and 56o32′W and was formed on basaltic flows of the Cretaceous Serra Geral Formation, which is part of the Paraná‐Etendeka Large Igneous Province (LIP), and in sandstones of the Botucatu and Guará forma… Show more
“…Such a skewed distribution of shock levels has also been demonstrated for the Cerro do Jarau structure in the Paraná Basin, Brazil, by Reimold et al. (2019). That no higher shock levels were identified (so far) for the innermost sector of the structure could hint at a significant amount of erosion for Nova Colinas.…”
The Nova Colinas structure is an approximately 7 km wide, nearly circular feature centered at 07°09 0 33″S/46°06 0 30″W in Nova Colinas municipality in southwestern Maranhão State, Brazil. The area has been investigated for 40 yr and it has been suggested repeatedly that the structure could be of impact origin-without proof having been furnished. Magnetic anomaly maps depict the structure clearly with a strong, positive magnetic anomaly over the apparent rim zone. The central area is characterized by significant positive K and Th radiometric anomalies. Fieldwork showed that the structure has annular features along the outside and some prominent, structurally dissected hills in the interior. Thirty-three arenite samples were collected for petrographic analysis, mostly from within the structure. Microdeformation, in the form of cataclasis; concussion fractures related to compaction, and presence of planar fractures, feather features, and planar deformation features in quartz are reported. Three samples with a multitude of quartz grains with these microdeformations were analyzed by universal stage to determine the crystallographic orientations of planar fractures and planar deformation features. The results provide robust evidence that these microdeformation features represent shock metamorphism, with low (approximately 5-10 GPa) to moderate (10-16 and 10-20 GPa) shock levels. Thus, the Nova Colinas structure is now confirmed as a bona fide meteorite impact structure. The structure is moderately eroded, as shown by the absence of stronger shock deformation. The still limited available structural geological field evidence, paired with remote sensing and geophysical data, indicates that the innermost part of the structure may have a sizable remnant of a central uplift. The Nova Colinas impact age is only poorly constrained from stratigraphic inference to an upper limit of about 200-250 Ma.
“…Such a skewed distribution of shock levels has also been demonstrated for the Cerro do Jarau structure in the Paraná Basin, Brazil, by Reimold et al. (2019). That no higher shock levels were identified (so far) for the innermost sector of the structure could hint at a significant amount of erosion for Nova Colinas.…”
The Nova Colinas structure is an approximately 7 km wide, nearly circular feature centered at 07°09 0 33″S/46°06 0 30″W in Nova Colinas municipality in southwestern Maranhão State, Brazil. The area has been investigated for 40 yr and it has been suggested repeatedly that the structure could be of impact origin-without proof having been furnished. Magnetic anomaly maps depict the structure clearly with a strong, positive magnetic anomaly over the apparent rim zone. The central area is characterized by significant positive K and Th radiometric anomalies. Fieldwork showed that the structure has annular features along the outside and some prominent, structurally dissected hills in the interior. Thirty-three arenite samples were collected for petrographic analysis, mostly from within the structure. Microdeformation, in the form of cataclasis; concussion fractures related to compaction, and presence of planar fractures, feather features, and planar deformation features in quartz are reported. Three samples with a multitude of quartz grains with these microdeformations were analyzed by universal stage to determine the crystallographic orientations of planar fractures and planar deformation features. The results provide robust evidence that these microdeformation features represent shock metamorphism, with low (approximately 5-10 GPa) to moderate (10-16 and 10-20 GPa) shock levels. Thus, the Nova Colinas structure is now confirmed as a bona fide meteorite impact structure. The structure is moderately eroded, as shown by the absence of stronger shock deformation. The still limited available structural geological field evidence, paired with remote sensing and geophysical data, indicates that the innermost part of the structure may have a sizable remnant of a central uplift. The Nova Colinas impact age is only poorly constrained from stratigraphic inference to an upper limit of about 200-250 Ma.
“…3J) (Philipp et al, 2010;Crósta et al, 2010a). Microestruturas dos tipos PF e PDF em cristais de quartzo e em feldspato (Philipp et al, 2010;Crósta et al, 2010a) e, recentemente, a identi icação de microfraturas do tipo FF (Reimold et al, 2018) con irmam a passagem das ondas de choque em rochas impactadas (Fig. 3L).…”
Section: 3 Feições Metamór Icas Do Impactounclassified
Fotogra ia aeŕea do setor norte da Serra do Segredo, em Caçapava do Sul, RS, onde se destacam a Pedra do Segredo, em primeiro plano, e a Pedra da Abelha, logo à esquerda, geoformas esculpidas sobre conglomerados luviais da Bacia do Camaquã. Ao fundo, alguns cerros formados por rochas metamór icas e o imponente alto de Caçapava, sobre granitoides diversos, rochas que registram diferentes momentos do Ciclo Brasiliano no sul do Brasil. A paisagem faz parte do Geoparque Caçapava Aspirante Unesco e é parcialmente inserida no Parque Natural Municipal da Pedra do Segredo. Imagem obtida por Felipe Guadagnin. Legenda de André Weissheimer de Borba e Felipe Guadagnin.
“…Dra. Débora Correia Rios da Universidade Federal da Bahia (UFBA), com trabalhos científicos e projetos de extensão vinculados à disseminação da Meteorítica (Carvalho et al, 2018, o Centro de Rádio-Astronomia e Astrofísica Mackenzie (CRAAM) da Universidade Presbiteriana Mackenzie, idealizado pelo Prof. Pierre Kaufmann [1938Kaufmann [ -2017, um dos precursores do monitoramento por radioastronomia no país (Kaufmann et al, 1989, Valio et al, 2013 e o grupo liderado pelo Prof. Dr. Alvaro Penteado Crósta da Universidade Estadual de Campinas (Unicamp), especializado no sensoriamento remoto de estruturas de impacto, tanto na Terra (Reimold et al, 2018, Vasconcelos et al, 2019, como em outros corpos celestes (Crósta et al, 2021, Villaça et al, 2021.…”
Este trabalho de revisão bibliográfica descreve a origem, os desdobramentos históricos e o panorama geral da Meteorítica. A humanidade possui contato com meteoritos desde a Pré-História, quando o conhecimento era associado a tradições culturais. A partir da observação sistemática de quedas, e da coleta de amostras, foram iniciados os estudos que possibilitaram constatar sua origem espacial. Com o avanço e o refinamento das técnicas de caracterização tornou-se possível explorar progressivamente a composição e estrutura dos meteoritos, permitindo inferir os processos de formação cósmica. A Meteorítica no Brasil se iniciou no século XVIII. O país possui mais de 70 meteoritos registrados, com alguns exemplares proeminentes, como o meteorito Angra dos Reis. Apresenta-se uma síntese da obra de alguns autores nacionais, como contribuição para difundir o conhecimento geocientífico.
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