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Updated: Jun 21, 2026
09:13
Characterization of Ultra-fine Grained and Nanocrystalline Materials Using Transmission Kikuchi Diffraction
Published on: April 1, 2017
Shock-synthesized hexagonal diamonds in Younger Dryas boundary sediments
Douglas J Kennett1, James P Kennett, Allen West
1Department of Anthropology and Museum of Natural and Cultural History, University of Oregon, Eugene, OR 97403, USA. dkennett@uoregon.edu
Summary
Scientists found nanodiamonds, evidence of a cosmic impact, in sediments from the Younger Dryas (YD) period. This impact may have caused megafaunal extinctions and widespread biomass burning across North America.
Area of Science:
- Geology and Paleontology
- Planetary Science
- Archaeology
Background:
- The late Pleistocene megafaunal extinctions in North America are a subject of ongoing debate.
- A controversial hypothesis suggests a cosmic impact at the Allerød-Younger Dryas boundary (YDB) triggered these extinctions.
- Previous evidence for this impact hypothesis was limited by the absence of definitive impact markers like shocked minerals or craters.
Purpose of the Study:
- To investigate the presence of impact markers in YDB sediments.
- To provide further evidence supporting or refuting the cosmic impact hypothesis for megafaunal extinctions.
- To correlate potential impact events with ecological disruptions and extinctions.
Main Methods:
- Analysis of sediments from Arlington Canyon, Santa Rosa Island, California, dated to approximately 12,950 cal BP.
- Identification and characterization of shock-synthesized nanodiamonds, including lonsdaleite and other polymorphs.
- Analysis of associated proxies for biomass burning (charcoal, carbon spherules, soot) and sedimentological changes.
Main Results:
- Discovery of shock-synthesized hexagonal nanodiamonds (lonsdaleite) and other nanodiamonds in YDB sediments.
- Lonsdaleite, found only in meteorites and impact craters on Earth, strongly indicates a cosmic impact event.
- Co-occurrence of these nanodiamonds with widespread biomass burning proxies and evidence of ecological disruption, including the extinction of pygmy mammoths.
Conclusions:
- The presence of lonsdaleite and other nanodiamonds provides strong evidence for a cosmic impact event over North America at the YDB.
- This impact event is linked to significant biomass burning, abrupt ecological disruption, and megafaunal extinctions.
- The findings align with the Cretaceous-Tertiary impact event in their association of nanodiamonds, soot, and mass extinctions.
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