title: Nanodiamonds in the Younger Dryas boundary sediment layer.
abstract: We report abundant nanodiamonds in sediments dating to 12.9 +/- 0.1 thousand calendar years before the present at multiple locations across North America. Selected area electron diffraction patterns reveal two diamond allotropes in this boundary layer but not above or below that interval. Cubic diamonds form under high temperature-pressure regimes, and n-diamonds also require extraordinary conditions, well outside the range of Earth's typical surficial processes but common to cosmic impacts. N-diamond concentrations range from approximately 10 to 3700 parts per billion by weight, comparable to amounts found in known impact layers. These diamonds provide strong evidence for Earth's collision with a rare swarm of carbonaceous chondrites or comets at the onset of the Younger Dryas cool interval, producing multiple airbursts and possible surface impacts, with severe repercussions for plants, animals, and humans in North America.
authors.affiliation: Department of Anthropology, University of Oregon, Eugene, OR 97403, USA. dkennett@uoregon.edu
authors.forename: D J
authors.initials: DJ
authors.lastname: Kennett
authors.forename: J P
authors.initials: JP
authors.lastname: Kennett
authors.forename: A
authors.initials: A
authors.lastname: West
authors.forename: C
authors.initials: C
authors.lastname: Mercer
authors.forename: S S Que
authors.initials: SS
authors.lastname: Hee
authors.forename: L
authors.initials: L
authors.lastname: Bement
authors.forename: T E
authors.initials: TE
authors.lastname: Bunch
authors.forename: M
authors.initials: M
authors.lastname: Sellers
authors.forename: W S
authors.initials: WS
authors.lastname: Wolbach
mesh_terms: D000818:Animals; D018130:Diamond; D053476:Extinction, Biological; D019015:Geologic Sediments; D019110:Meteoroids; D017348:Microscopy, Electron, Scanning Transmission; D049329:Nanostructures; D009656:North America; D013995:Time
chemical_list: D018130:Diamond