Publication Date:
2009-01-03
Description:
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.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Kennett, D J -- Kennett, J P -- West, A -- Mercer, C -- Hee, S S Que -- Bement, L -- Bunch, T E -- Sellers, M -- Wolbach, W S -- New York, N.Y. -- Science. 2009 Jan 2;323(5910):94. doi: 10.1126/science.1162819.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Anthropology, University of Oregon, Eugene, OR 97403, USA. dkennett@uoregon.edu〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/19119227" target="_blank"〉PubMed〈/a〉
Keywords:
Animals
;
*Diamond
;
Extinction, Biological
;
*Geologic Sediments
;
*Meteoroids
;
Microscopy, Electron, Scanning Transmission
;
Nanostructures
;
North America
;
Time
Print ISSN:
0036-8075
Electronic ISSN:
1095-9203
Topics:
Biology
,
Chemistry and Pharmacology
,
Computer Science
,
Medicine
,
Natural Sciences in General
,
Physics
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