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New evidence shows Younger Dryas not caused by comet

New evidence unearthed by researchers from the University of Oklahoma, Oklahoma State University, the University of California at Santa Barbara, and the University of Arkansas published in the Jan. 20, 2014, edition of the journal Proceedings of the National Academy of Sciences argues against the initiation of the Younger Dryas climate event by an extraterrestrial source.

Three temperature proxies showing the Younger Dryas event.
William M. Connolley This file is licensed under the Creative Commons Attribution-Share Alike 3.0 Unported license.

Previously, researchers had proposed that the Younger Dryas event was initiated by a comet explosion or the explosion of several comets based on the evidence of nanodiamonds that would have been produced from the action of the explosive heat on sand in various regions across the Earth.

The scientists inspected the occurrence of nanodiamonds in the laminated strata of the Beaver River basin in Oklahoma. There is no comet impact crater known to have been found in the vicinity of the Beaver River.

Nanodiamonds were found in the region that corresponded to the time frame of the Younger Dryas about 10,900 years ago but the cubic form of the nanodiamonds argues against formation from the heat of a comet impact.

Nanodiamonds were found in layers of strata as late as the late Holocene and in sediments less than 3,000 years old. The shape and cubic form of these nanodiamonds argue for a source from graphene that was not part of an extraterrestrial event.

The change in climate, flora, and fauna on Earth that occurred during the Younger Dryas event is considered to have been caused comet impacts by the new research but later impacts or other events were the source of nanodiamonds found as long as 7,000 years after the initiation of the Younger Dryas.