Impact cratering: The South American record—Part 2

Crósta, Álvaro Penteado; Reimold, W. U.; Vasconcelos, Marcus Arthur Marçal de; Hauser, Natalia; Oliveira, Grace Juliana Gonçalves de; Maziviero, Mariana V.; Góes, Ana Maria

doi:10.1016/j.chemer.2018.09.002

Cited by 12 publications

(15 citation statements)

References 89 publications

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“…Similar observations were made by us in sandstone samples from a number of other impact structures, including Vargeão, Vista Alegre, Serra da Cangalha, Santa Marta, and Riachão (all in Brazil; for a recent review, refer to Crósta et al. ), as well as in a few samples from the Libyan BP and Oasis structures (for these latter cases: unpublished results by W. U. Reimold). These characteristics are likely the reason why—generally—PDFs have not been observed (reported from) so frequently in poorly consolidated or groundmass‐rich sedimentary rock.…”

Section: The Search For Shock Deformationsupporting

confidence: 78%

Shock deformation confirms the impact origin for the Cerro do Jarau, Rio Grande do Sul, Brazil, structure

Reimold

Crósta

Hasch

et al. 2018

Meteorit & Planetary Scien

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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 formations. The structure was first spotted on aerial photographs in the 1960s. Ever since, its origin has been debated, sometimes in terms of an endogenous (igneous) origin, sometimes as the result of an exogenous (meteorite impact) event. In recent years, a number of studies have been conducted in order to investigate its nature and origin. Although the results have indicated a possible impact origin, no conclusive evidence could be produced. The interpretation of an impact origin was mostly based on the morphological characteristics of the structure; geophysical data; as well as the occurrence of different breccia types; extensive deformation/silicification of the rocks within the structure, in particular the sandstones; and also on the widespread occurrence of low‐pressure deformation features, including some planar fractures (PFs). A detailed optical microscopic analysis of samples collected during a number of field campaigns since 2007 resulted in the disclosure of a large number of quartz grains from sandstone and monomict arenite breccia from the central part of the structure with PFs and feather features (FFs), as well as a number of quartz grains exhibiting planar deformation features (PDFs). While most of these latter grains only carry a single set of PDFs, we have observed several with two sets, and one grain with three sets of PDFs. Consequently, we here propose Cerro do Jarau as the seventh confirmed impact structure in Brazil. Cerro do Jarau, together with Vargeão Dome (Santa Catalina state) and Vista Alegre (Paraná State), is one of very few impact structures on Earth formed in basaltic rocks.

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Section: The Search For Shock Deformationsupporting

confidence: 78%

Shock deformation confirms the impact origin for the Cerro do Jarau, Rio Grande do Sul, Brazil, structure

Reimold

Crósta

Hasch

et al. 2018

Meteorit & Planetary Scien

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“…Two other impact structures were formed in the same stratigraphic unit in southern Brazil: Vargeão (Crósta et al. , , ) and Cerro do Jarau (Crósta et al. , ; Reimold et al.…”

Section: Introductionmentioning

confidence: 99%

“…Vista Alegre was described by Crósta et al. (, , ) as a complex impact structure, although a central elevation or peak, as commonly seen in complex structures, is not evident. This interpretation was based on the anomalous presence of sandstones in the innermost 3 km wide portion of the structure.…”

Section: Introductionmentioning

confidence: 99%

“…This suggests that the Piramboia/Botucatu formations were uplifted from their regular stratigraphic position underneath a layer of Serra Geral basaltic rocks; the thickness of width has been estimated at 700–900 m for this part of the Paraná Basin (Crósta et al. , , ).…”

Section: Introductionmentioning

confidence: 99%

“…() with the discovery of abundant aggregates of shatter cones and microscopic shock features (see also Crósta et al. ). The structure was formed in Cretaceous basalts of the Serra Geral Formation, within the Phanerozoic Paraná Basin.…”

Section: Introductionmentioning

confidence: 99%

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Insights about the formation of a complex impact structure formed in basalt from numerical modeling: The Vista Alegre structure, southern Brazil

Vasconcelos

Rocha

Crósta

et al. 2019

Meteorit & Planetary Scien

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We present the outcomes of simulations of the formation of the Vista Alegre impact structure, Paraná Basin, Brazil. The target comprised a thick sequence of volcanic rocks of predominantly basaltic composition of the Serra Geral Formation that had been deposited on top of sedimentary rocks (sandstones) of the Pirambóia/Botucatu formations. The cratering process was modeled using the iSALE shock physics code. Our best‐fit model suggests that (1) the crater was originally ~10 km in size; (2) it was formed in ~115 s by a stony projectile of 1000 m in diameter, for an assumed impact velocity of 12 km s−1; (3) target rocks underwent a peak pressure of ~20 GPa, in agreement with previous petrographic investigations of shock deformation. Furthermore, the model points out that the sedimentary strata below the layer of volcanic rocks were raised by ~650 meters at the central part of the crater, which resulted in the current partial exposure of the sandstones at the surface. The outcomes of our modeling suggest that parameters like cohesion and strength of the target rocks, after shock compression, determined the final morphology of the crater, especially the absence of a topographically prominent central peak. Finally, the results of the numerical modeling are roughly in agreement with gravity data over the structure, in particular with respect to the presence of the uplifted sedimentary strata, which are responsible for a low gravity signature at the center of the structure.

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Classification of terrestrial impact craters based on morphometric parameters using remote sensing data: a case study of Jeokjung-Chogye impact crater, South Korea

Emmanuel,

Yu,

Wang

et al. 2024

Geosci J

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Impact cratering: The South American record—Part 2

Cited by 12 publications

References 89 publications

Shock deformation confirms the impact origin for the Cerro do Jarau, Rio Grande do Sul, Brazil, structure

Shock deformation confirms the impact origin for the Cerro do Jarau, Rio Grande do Sul, Brazil, structure

Insights about the formation of a complex impact structure formed in basalt from numerical modeling: The Vista Alegre structure, southern Brazil

Classification of terrestrial impact craters based on morphometric parameters using remote sensing data: a case study of Jeokjung-Chogye impact crater, South Korea

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