First Brazilian Tektite Field Traces 6.3-Million-Year Cosmic Impact
Brazilian researchers have identified the country’s first tektite field, Geraisites, a collection of glassy fragments spread across Minas Gerais and adjacent states that indicate a substantial ancient impact. Dating with 40Ar/39Ar places the event at about 6.3 million years ago, during the Miocene, with isotopic signatures pointing to a very old continental crust source in the São Francisco craton. The field now spans over 900 km, and while no crater is yet known, the data imply a powerful impact with dispersed molten material; researchers plan aerogeophysical surveys and modeling to estimate the event’s energy, velocity, and crater geometry. This discovery expands South America’s sparse tektite record and suggests tektites may be more common than previously thought.
