Cerro do Jarau crater is a diameter circular feature in the

Paraná Basin The Paraná Basin (, ) is a large cratonic sedimentary basin situated in the central-eastern part of South America. About 75% of its areal distribution occurs in Brazil, from Mato Grosso to Rio Grande do Sul states. The remainder area is distribu ...

Rio Grande do Sul Rio Grande do Sul (, ; ; "Great River of the South") is a Federative units of Brazil, state in the South Region, Brazil, southern region of Brazil. It is the Federative units of Brazil#List, fifth-most populous state and the List of Brazilian s ...

in southern

Brazil Brazil, officially the Federative Republic of Brazil, is the largest country in South America. It is the world's List of countries and dependencies by area, fifth-largest country by area and the List of countries and dependencies by population ...

, close to the border with

Uruguay Uruguay, officially the Oriental Republic of Uruguay, is a country in South America. It shares borders with Argentina to its west and southwest and Brazil to its north and northeast, while bordering the Río de la Plata to the south and the A ...

. The

Russian Academy of Sciences The Russian Academy of Sciences (RAS; ''Rossíyskaya akadémiya naúk'') consists of the national academy of Russia; a network of scientific research institutes from across the Russian Federation; and additional scientific and social units such ...

lists the structure as a probable

impact crater An impact crater is a depression (geology), depression in the surface of a solid astronomical body formed by the hypervelocity impact event, impact of a smaller object. In contrast to volcanic craters, which result from explosion or internal c ...

.Mikheeva, 2017

Description

Cerro do Jarau is a prominent, approximately wide, circular landform rising more than above the plains of the

pampas The Pampas (; from Quechua 'plain'), also known as the Pampas Plain, are fertile South American low grasslands that cover more than and include the Argentine provinces of Buenos Aires, La Pampa, Santa Fe, Entre Ríos, and Córdoba; all o ...

in southern Brazil. The name (meaning Jarau hills) comes from the prominent crests of silicified

sandstone Sandstone is a Clastic rock#Sedimentary clastic rocks, clastic sedimentary rock composed mainly of grain size, sand-sized (0.0625 to 2 mm) silicate mineral, silicate grains, Cementation (geology), cemented together by another mineral. Sand ...

s, which form a semiring of elevated hills in the northern part of the structure. The origin of this structure has been debated for decades, and varied suggestions of its formation include either endogenous tectonic processes or large meteorite impact. However, no conclusive evidence to support either hypothesis has been presented to date. This structure was formed in

Mesozoic The Mesozoic Era is the Era (geology), era of Earth's Geologic time scale, geological history, lasting from about , comprising the Triassic, Jurassic and Cretaceous Period (geology), Periods. It is characterized by the dominance of archosaurian r ...

volcano-sedimentary rocks of the

and consists of the

Jurassic The Jurassic ( ) is a Geological period, geologic period and System (stratigraphy), stratigraphic system that spanned from the end of the Triassic Period million years ago (Mya) to the beginning of the Cretaceous Period, approximately 143.1 Mya. ...

Cretaceous The Cretaceous ( ) is a geological period that lasted from about 143.1 to 66 mya (unit), million years ago (Mya). It is the third and final period of the Mesozoic Era (geology), Era, as well as the longest. At around 77.1 million years, it is the ...

Guará Guará is a municipality situated in the northern part of the state of São Paulo in Brazil. The population is 21,308 (2020 est.) in an area of 362 km2. The elevation is 573 m. This place name comes from the Tupi language for two animals com ...

(sandstones),

Botucatu Botucatu is a city in the southeastern region of Brazil and is located from São Paulo, the capital of the state of São Paulo. It has an estimated population of 148,130 (as of 2020) in an area of . It lies on the top of a plateau ( high). Botuca ...

(sandstones), and

Serra Geral The Serra Geral (General Mountains) is a mountain range in southern Brazil, constituting the southern portion of the Serra do Mar system which runs along Brazil's southeastern coast. The Serra Geral runs parallel to the Atlantic coast in Santa ...

(

basalt Basalt (; ) is an aphanite, aphanitic (fine-grained) extrusive igneous rock formed from the rapid cooling of low-viscosity lava rich in magnesium and iron (mafic lava) exposed at or very near the planetary surface, surface of a terrestrial ...

s) formations. The Botucatu Formation sandstones are intensely silicified and deformed, and were subject to radial and annular faulting. Investigations at Cerro do Jarau identified the occurrence of parautochthonous monomict lithic

breccia Breccia ( , ; ) is a rock composed of large angular broken fragments of minerals or Rock (geology), rocks cementation (geology), cemented together by a fine-grained matrix (geology), matrix. The word has its origins in the Italian language ...

and polymict breccias resembling

suevite Suevite is a rock consisting partly of melted material, typically forming a breccia containing glass and crystal or lithic fragments, formed during an impact event. It forms part of a group of rock types and structures that are known as impact ...

and striated joint surfaces resembling crude

shatter cone Shatter cones are rare geological features that are only known to form in the bedrock beneath meteorite impact craters or underground nuclear explosions. They are evidence that the rock has been subjected to a shock with pressures in the ran ...

s in sandstones and basalts. In addition, the first mineral deformation studies show the presence of rare planar features in

quartz Quartz is a hard, crystalline mineral composed of silica (silicon dioxide). The Atom, atoms are linked in a continuous framework of SiO4 silicon–oxygen Tetrahedral molecular geometry, tetrahedra, with each oxygen being shared between two tet ...

clasts in polymict breccias. The identification of these features at Cerro do Jarau is suggestive of an impact origin for the structure. If confirmed by further investigation of possible shock features, Cerro do Jarau would become the sixth known impact structure in Brazil, as well as the fifth basalt-hosted impact structure on Earth.Crósta et al., 2010 The crater formed in the same basaltic unit as the nearby

Vista Alegre crater The Vista Alegre crater is a meteorite crater in Coronel Vivida, Paraná State, Brazil. On the surface it appears as a circular, relatively flat plain within otherwise hilly terrain. Description It is in diameter and the age is estimated to ...

and the

Vargeão Dome Vargeão Dome is a meteorite impact crater, crater in Santa Catarina (state), Santa Catarina State, Brazil, straddling the municipalities of Vargeão, Faxinal dos Guedes, and Passos Maia. The crater is an almost perfectly circular depression with ...

.Crósta & Vasconcelos, 2013, p.1 The age of impact has been given at 117 Ma (

Aptian The Aptian is an age (geology), age in the geologic timescale or a stage (stratigraphy), stage in the stratigraphic column. It is a subdivision of the Early Cretaceous, Early or Lower Cretaceous epoch (geology), Epoch or series (stratigraphy), S ...

),Exoss, 2017 or a broader range from 128.7 to 105 Ma.

References

Bibliography

* * * * {{Portal bar, Geology, Brazil Impact craters of Brazil Possible impact craters on Earth Cretaceous impact craters Cretaceous Brazil Landforms of Rio Grande do Sul Craters

Description

See also

References

Bibliography