Dartmouth Professor Mukul Sharma and his team reported the discovery of the first conclusive evidence linking an extraterrestrial impact event in Canada with the beginning of the Younger Dryas period in the Sept. 2, 2013, edition of the journal Proceedings of the National Academy of Sciences.
A meteor or comet impact about 12,900 years ago produced climate cooling and drying that resulted in the demise of the larger North American animals like saber-toothed cats, giant sloths, and mastodons. The same event marked the end of the Clovis hunter-gatherer culture in favor of the adoption of farming and animal husbandry. The effects of the impact event were felt across the globe and are considered to be responsible for the adoption of farming in parts of the Near East.
The researchers examined the chemical composition of spherules (droplets of solidified molten rock expelled by the impact of a comet or meteor) found in Younger Dryas boundary layers at sites in Pennsylvania and New Jersey. The mineral composition and geochemistry of these new finds are identical to spherules found in Quebec.
The newly discovered spherules do not originate from the Corossal crater in Quebec. This fact leads the researchers to conclude that a series of comet or meteor impacts caused the beginning of the Younger Dryas 12,900 years ago.