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.

Did Nanodiamonds Rain from the Sky as Woolly Mammoths Fell in their Tracks Across North America 12,900 Years Ago?

“…At Bull Creek, YDB nanodiamonds were initially reported at a concentration of 102 p.p.b. [3]. Later, Bement et al [8] reported a three order-of-magnitude larger 190 p.p.m.…”

“…Controversial 'i-carbon' is also reported at the YDB of many sites [6,7]. While neither are diamond polytypes, impact proponents describe them as nanodiamonds [3][4][5][6][7][8]. In YDB sediments, 'n-diamonds' are usually reported at higher abundances than diamond [6,7].…”

“…Further, we determined that measurements of a nanodiamond abundance spike at the YDB reported by [7], and other impact proponents that used similar techniques, are critically flawed and are not credible [9]. Note, that the majority of the reported YDB nanodiamonds are not diamond, but rather are a controversial modified form of diamond termed 'n-diamond' [3][4][5][6][7][8]. Controversial 'i-carbon' is also reported at the YDB of many sites [6,7].…”

“…Left: Predicted electron diffraction of 2H diamond (with both general and special extinctions), graphene, and graphene/graphane mixture. Shown also are those from graphene and graphene/graphane aggregates in YDB carbon spherules as well as those identified as 2H diamond (line widths represent error in our measurement of diffraction patterns reported in [3]), all from Santa Rosa Island, CA. Right: Native Cu nanocrystals in YDB carbon spherules (i.e., sclerotia [9]) from Santa Rosa Island, CA (gray scale LUT of STEM-EDXS elemental maps: black = minimum, white = maximum).…”

“…While there are no known impact structures in North America that date to the onset of the YD stadial, physical evidence of one or more impact/bolide events is argued present in a stratigraphic horizon that is inferred to date to the Bølling-Ållerod/YD boundary (YDB) and span several continents (North America, South America, Greenland Ice Sheet, Europe, and the Middle East). While many of the proposed impact markers have been abandoned or rejected [1], reports of elevated concentrations of nanometer-sized diamonds, in particular the rare 2H polytype of diamond, lonsdaleite, in YDB sediments and Greenland ice, continue to be presented as the strongest evidence for an impact [2][3][4][5][6][7][8].Nanodiamonds are reported to occur in YDB sediments and in millimeter-scale carbon forms (variously termed, 'glass-like', 'spherules', and 'elongates') in those sediments. The carbon forms are proposed to be products of the impact [2,7] and/or the resulting continent-wide wildfires [2,4].…”