Impact Structures in Brazil

Abstract

Studies carried out in the last ten years resulted in the recognItIOn of several circular structures in the Brazilian territory which have, as common characteristics, the presence of similarities with well-known structures in other countries and planets attributed to impact with celestial bodies, and the absence of evidence for a terrestrial endogeneous origin. Those structures presently number six, ranging in diameter from three to 40kilo-meters. Two of them, Araguainha and Serra da Cangalha, were studied in some detail and presented enough evidence for their impact origin, including impact metamorphism features and morphologic/structural styles. The other four, Colonia, Sao Miguel do Tapuio, Vargeao and Riachao, are still poorly known, but the available data are very suggestive for their impact origin. Similar structures were identified by remote sensing studies, mainly in the Amazon region, but no field data are available yet. It is believed that the whole number of impact structures in Brazil is more than six, mainly due to the size of the territory (8.Smillion square kilometers).