SHERIDEN CAVE, OHIO: There are [Younger Dryas Boundary] peaks in magnetic spherules, meltglass, nanodiamonds, Pt, and Ir. A charcoal-rich black mat dates to the [Younger Dryas] onset and contains peak abundances of charcoal, AC/soot, carbon spherules, and nanodiamonds that are closely associated with the last known Clovis artifacts in the cave. The black-mat layer is in direct contact with the wildfire-charred bones of two mega-mammals, the flat-headed peccary ( ) and the giant beaver ( ), that are the last known examples anywhere in the world of those extinct species.