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Nanodiamonds in the Younger Dryas Boundary Sediment Layer
TEM image of nanodiamonds
Achievement/Results
University of Oregon doctoral student Joshua Razink’s (UO Chemistry, Prof. James E. Hutchison, research advisor) National Science Foundation Integrative Graduate Education and Research Traineeship (IGERT) allowed him to conduct research in collaboration with a broad-based team of scientists who hypothesize that a mass extinction event that occurred in North America about 13,000 years ago was caused by climate change induced by a cosmic impact, rather than human predation. This research is important, as it is one of the few examples of humans surviving large-scale climatic change.
Razink’s work characterizing nanodiamonds in the Younger Dryas Boundary (YDB) Sediment Layer enhanced the discovery by the group that the nanodiamonds found in six locations in the United States exist only in sediment associated with the YDB layers, but not in the sediment layers above or below. “These discoveries provide strong evidence for a cosmic impact event at approximately 12,900 years ago that would have had enormous environmental consequences for plants, animals and humans across North America,” reported team leader Dr. Douglas J. Kennett, a University of Oregon archaeologist.
The YDB layer is a distinctive organic-rich black sedimentary layer. Fossils of the most common large genera are not found above this layer. Like the Cretaceous-Tertiary boundary, which is associated with the mass extinction of the dinosaurs, the YDB is rich in soot and nanodiamonds. Traditional cosmic impact markers, including an impact crater, are absent from the YDB. Thus, some believe over-hunting by humans caused the extinction event. However, these traditional markers also appear to be absent from the Tunguska airburst over Siberia in 1908, a widely accepted cosmic impact event.
Nanodiamonds as Cosmic Impact Markers
Three diamond polymorphs (cubic, hexagonal, and n-diamond) cannot be formed by mantle driven processes. They are found in meteorites and at impact craters, however. Hexagonal diamonds in particular are widely accepted cosmic impact markers. Hexagonal diamonds have been formed experimentally only at high temperatures (1000º to 1700º C) and pressures (greater than 15 Gpa). N-diamonds can be produced experimentally via TNT explosions.
Razink’s research used electron diffraction, dark field (DF) and high-resolution imaging to distinguish and selectively image the different diamond polymorphs. These investigations show a spike in the number of nanodiamonds at the proposed cosmic event ~13,000 years ago much like was seen when the Cretaceous-Tertiary boundary (dinosaur extinction) was studied.
This NSF-supported collaboration, led by UO’s Kennett, included James P. Kennett of the University of California, Santa Barbara; Allen West of GeoScience Consulting in Dewey, Arizona; James E. Hutchison, University of Oregon; and Sujing Xie, of the Center for Advanced Materials Characterization in Oregon (CAMCOR).
Address Goals
This research into nanodiamonds in the Younger Dryas Boundary (YDB) Sediment Layer provides evidence to support the hypothesis that a cosmic impact in North American about 12,900 years ago precipitated climate change which drove multiple species into extinction. The collaboration’s research findings are inconsistent with the alternative theory that overhunting by Clovis people led to the rapid extinction of large mammals at the end of the ice age.
The work for this research brought together scientists from nine institutions and 3 private research companies.
