Vargeão Dome
Vargeão Dome is a meteorite crater in Santa Catarina State, Brazil, straddling the municipalities of Vargeão, Faxinal dos Guedes, and Passos Maia.[1]
The crater is an almost perfectly circular depression with steep walls, 12 km in diameter and up to 225 m deep relative to its rim. Its age is estimated to be less than 70 million years (Cretaceous or younger)[2]
The meteorite impacted on the basaltic rocks of the Serra Geral Formation (Jurassic/Cretaceous). The crater displays several concentric rings and radial faults, and an eroded central bulge. The latter consists of impact breccias and sandstones from the Botucatu/Pirambóia Formation (Cretaceous/Triassic), which have been displaced about 700 m above their mean depth in the surrounding area. At least four post-impact lava flows have been identified between the rim and core. The impact origin of the structure is attested by the presence of shatter cones and shocked quartz grains.
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[edit] Discovery and studies
In 1978, Brazilian geologists A. Paiva Filho, C.A.V. Andrade and L.F. Scheibe [3] identified an anomalous circular structure in radar images produced by the RADAMBRASIL survey, and called it the Vargeão Dome. In the early 1980s E. Barbour Jr. and W.A.G. Correa [4] studied the structure in detail, in the context of oil/gas surveys of the area, and proposed a volcanic/tectonic origin for the structure. In 1982, Á. P. Crósta and A. Paiva Filho identified it as an impact crater.[5] Shocked quartz was identified by M. V. Coutinho in 1987, and the occurrence of maskelynite glass was reported by J. Hachiro and others in 1993 [6]
[edit] Conservation status
The area around and inside the crater has been heavely farmed since the end of the 19th century; Vargeão's city hall is locate inside the crater, near the southern rim. Nevertheless, the crater is still well-preserved. The local population is well aware of the impact origin of the structure, to the point that the town's official nickname is Meteor City.
[edit] References
- ^ "Vargeão Dome". Earth Impact Database. University of New Brunswick. http://www.passc.net/EarthImpactDatabase/vargeao-dome.html. Retrieved 2009-08-20.
- ^ Crosta, A.P.; Kazzuo-Vieira,C.; Choudhuri,A.; Schrank,A. (2005). Winge,M.; Schobbenhaus,C.; Berbert-Born,M.; Queiroz,E.T.; Campos,D.A.. ed. "Vargeão Dome, State of Santa Catarina - A meteoritic impact record on volcanic rocks of the Paraná Basin". Sítios Geológicos e Paleontológicos do Brasil. http://www.unb.br/ig/sigep/sitio114/sitio114english.pdf. Retrieved Available on line 23 february 2005.
- ^ Paiva Filho, A.; Andrade, C.A.V. de; Scheibe,L.F (1978.). "Uma janela estratigráfica no oeste de Santa Catarina: o Domo de Vargeão". Anais do 30° Congresso Brasileiro de Geologia. 1. Sociedade Brasileira de Geologia. pp. 08–412.
- ^ Barbour Jr., E.; Corrêa,W.A.G (1981). Geologia da Estrutura de Vargeão, SC. PauliPetro, Consórcio CESP/IPT. pp. 33.
- ^ Paiva Fº, A.; Crósta,A.P.; Amaral,G. (1982). "Utilização de dados de sensoriamento remoto no estudo estratigráfico e estrutural da Formação Serra Geral (Sul do Brasil)". Anais do II Simpósio Brasileiro de Sensoriamento Remoto. 1. Instituto Nacional de Pesquisas Espaciais (Brazil). pp. 135–142.
- ^ Hachiro,J.; Coutinho,J.M.V.; Frascá,M.H.B.de O.; Menezes,C.M (1993). "O astroblema de Vargeão (SC): evidências petrográficas de um crateramento criptoexplosivo por petardo extraterrestre". Atas do Simpósio Brasileiro de Geologia. 3. Sociedade Brasileira de Geologia. pp. 276–283.
