Meteorite impact craters in south America a Brief Review.

ACEVEDO, R.D.; ROCCA, M.; RABASSA, J.; PONCE, J. F.

Londres

Encuentro; 74th Annual Meeting of the Meteoritical Society; 2011

The first enumeration of impact craters sites in South America is presented here. Proximately twenty proven, suspected and disproven structures have been identified by several sources in this continent until now. But everyone events proposed here aren’t really produced by impacts at all. About some of them reasonable doubts exist. Brazil leading the record containing almost half detected and following itin the list Argentina. In Bolivia, Peru, Chile, and Colombia only a few were observed. The rest of countries are awaiting for new discoveries. The following possible and confirmed meteorite impact structures have been reported for this continent, country by country: ARGENTINA. Campo del Cielo (S 27º 30', W 61º 42'). Impact crater strewn field. At list twenty craters with an age of about 4000 years over sandy-clay sediments of Quaternary-Recent age. The impactor was an iron-nickel Apollo-type asteroid (meteorite type IA) and plenty of meteorite specimens survived the impact. Bajada del Diablo (S 42º 45', W 67º 30'). A very remarkable site of a new very large meteorite impact craters field. Almost 200 structures were identified there. Age is estimated between 0.13 and 0.78 Ma. Other possible craters are Rio Cuarto (S 32 º 52', W 64º 14'), Islas Malvinas (S 51º 00', W 62º 00'), Salar del Hombre Muerto (S 25º 12', W 66 º 55'), Antofalla (S 26º 15', W 68º 00'), La Dulce (S 38 º 14', W 59º 12'), and General San Martin (S 38 º 00', W 63 º 18'). BOLIVIA. Iturralde (S 12º 35', W 67º 38'). On Quaternary alluvial deposits, 8 km in diameter. Llica (S 19º 49', W 68º 19') 2.8 x 2.5 km, without specific geological information. BRASIL. Araguainha Dome (S 16º 46', W 52º 59'). This is so far the largest well stated impact crater in South America. It is a 40-km diameter crater in Paleozoic sediments of the Parana´ Basin. Serra da Cangalha(S 8º 05', W 46º 51'). Total diameter of multiple rings has been estimated at 12 km; in Paleozoic sediments in the Parnaiba Basin. Vergeao (S 26º 50', W 52º 10'). It is a 12.4 kilometer-diameter circular depression located on Cretaceous basalts and Jurassic/Triassic sandstones of the Sao Bento Group of Parana´ Basin. Vista Alegre (S 25º 57', W 52º 41'). It is a 9.5 km-wide circular structure in the Parana State, and it is located on the Cretaceous basalts of the Serra Geral formation. Riachao (S 7º 42', W 46º 38'). 4.0 km diameter in sedimentary rocks of the Paranaiba Basin(sandstones from the Pedra de Fogo Formation). 200 Ma. Other possible craters are Gilbues (S 10º 10', W 45º 14'), Sao Miguel do Tapuio (S 5º 38', W 41º 24'), Cerro Jarau (S 30º 12', W 56_33'), Inajah (S 8º 40', W 51º 00'), Piratininga (S 22 º 28', W 49_09'), and Colonia (S 23º 52', W 46º 42').COLOMBIA. Rio Vichada (N 4º 30', W 69º 15'). Has a diameter of 50 km and it is the largest possible impact structure ever reported in the continental South America. Rocks exposed there include Precambrian meta-sedimentary and granitoid bodies with an extensive sedimentary Tertiary cover. CHILE. Monturaqui (S 23º 56', W 68 º 17') is emplaced in Jurassic granite rocks, overlain by a thin Tertiary-Quaternary ignimbrite sheet. The impacting asteroid was metallic: an iron-nickel object; 1 Ma. PERU. Carancas (S 16º 40', W 69º 02'). H4–5 type ordinary chondrite fall on September 15, 2007 digging a crater of 15 m.