 Proponents have reported materials including nanodiamonds, metallic microspherules, carbon spherules, magnetic spherules, iridium, platinum, platinum/palladium ratios, charcoal, soot, and fullerenes enriched with helium-3 that they interpret as evidence for an impact event that marks the beginning of the Younger Dryas.Proponents of the hypothesis claim that these data cannot be adequately explained by volcanic, anthropogenic, or other natural processes.It is hypothesized that this impact event brought about the extinction of many species of North American Pleistocene megafauna.