The evidence for an impact event includes charred carbon-rich layers of soil that have been found at some 50 Clovis sites across the continent. The layers contain unusual materials (nanodiamonds, metallic microspherules, carbon spherules, magnetic spherules, iridium, platinum, charcoal, soot and fullerenes enriched in helium-3), which are interpreted to be potential evidence of an impact event, at the very bottom of black mats of organic material that marks the beginning of the Younger Dryas,[9][10] and it is claimed these cannot be explained by volcanic, anthropogenic, or other natural processes.[3]

Recent research has been reported that at Lake Cuitzeo, in the central Mexican state of Guanajuato, evidence supporting a modified version of the Younger Dryas impact hypothesis—involving a much smaller, non-cometary impactor—was found in lake bed cores dating to 12,900 BP. The reported evidence included nanodiamonds (including the hexagonal form called lonsdaleite), carbon spherules, and magnetic spherules. Multiple hypotheses were examined to account for these observations, though none were believed to be terrestrial. Lonsdaleite occurs naturally in asteroids and cosmic dust and as a result of extraterrestrial impacts on Earth. The analysis of the study has not been confirmed or repeated by other researchers.[11] Lonsdaleite has also been made artificially in laboratories.[12][13]

A 100-fold spike in the concentration of platinum has also been found in Greenland ice cores, dated to 12,890 BP with 5-year accuracy. This is interpreted as evidence against the Younger Dryas impact hypothesis by the study’s authors, but cited as evidence for the hypothesis by its proponents.