Evidence for an extraterrestrial impact 12,900 years ago that contributed to megafaunal extinctions and the Younger Dryas cooling

A carbon-rich black layer, dating to ∼12.9 ka, has been previously identified at ∼50 Clovis-age sites across North America and appears contemporaneous with the abrupt onset of Younger Dryas (YD) cooling. The in situ bones of extinct Pleistocene megafauna and Clovistool assemblages occur below this black layer but not within or above it. Causes for the extinctions, the YD cooling, and the termination of Clovisculture have long been controversial. In this paper, we provide evidence for an extraterrestrial (ET) impact event at ?12.9 ka, which, we hypothesize, caused abrupt environmental changes that contributed to YD cooling, major ecological reorganization, broad-scale extinctions, and rapid human behavioral shifts at the end of the Clovis Period. Clovis-age sites in North American are overlain by a thin, discrete layer with varying peak abundances of: (1) magnetic grains with iridium, (2) magnetic microspherules (3) charcoal, (4) soot, (5) carbon spherules, (6) glass-like carbon, and (7) fullerenes with ET helium, all of which are evidence for an ET impact and associated biomass burning at ∼12.9 ka.This layer also extends throughout at least fifteen Carolina Bays, which are unique, elliptical wetlands, oriented to the northwest across the Atlantic Coastal Plain. We propose that one or more large, low-density ET objects exploded over northern North America, partially destabilizing the Laurentide Ice Sheet and triggering YD cooling. The shock wave, thermal pulse, and event-related environmental effects (e.g., extensive biomass burning, food limitations) contributed to the end-Pleistocene megafaunal extinctions and adaptive shifts among PaleoAmericans in North America