Sanidine spherules at the Cretaceous-Tertiary boundary indicate a large impact event

The hypothesis that a catastrophic impact of an extraterrestrial body caused the terminal Cretaceous mass extinctions of dinosaurs, planktonic foraminfera and other species is now accepted as respectable following the discovery of a worldwide iridium enrichment in the Cretaceous-Tertiary (K-T) boundary clay^1-5. In the basal lamina of the K-T boundary clay of Caravaca (Spain)⁷ numerous spherules were discovered composed of finely crystallized, almost pure K-feldspar in the structural state of high sanidine. It is concluded here that these spherules solidified from a melt and were probably derived from the impacting body. This poses problems as high K-values are not reported from bulk analyses of meteorites⁶. The K-feldspar phenocrysts reported in some iron meteorites²³ suggest the body may have been a metal-sulphide-silicate planetesimal. A cometary body is suggested as an alternative.