Physics doctoral student Ann Xian Hu operates the FEI Titan TEM in the Institute for Nanoscience and Engineering at the University of Arkansas
(Photo: Submitted)
FAYETTEVILLE, Ark. — A researcher at the University of
Arkansas helped confirm the existence of high levels of nanodiamonds in soil
samples collected in the Oklahoma Panhandle, supporting a hypothesis that an
extraterrestrial event about 11,000 years ago caused significant global cooling
that contributed to the extinction of many animals.
Mourad Benamara, director of the university’s Arkansas Nano
& Bio Materials Characterization Facility, analyzed the soils using
transmission electron microscopy, a technique that is capable of creating
images at significantly higher resolution than microscopes that use light.
“I provided the expertise in the structural and chemical
analysis of the soil samples collected by collaborators at the University of
Oklahoma at different locations of the Bull Creek area in western Oklahoma,”
Benamara said. “The U of A has a powerful Titan microscope that is fitted with electron
energy loss spectroscopy, and this complex instrumentation can provide ultimate
results in terms of image and energy resolution. I used the Titan to
identify traces in spectra allowing the identification of some forms of carbon.
That allowed the extraction of information about the presence of nanodiamonds.”
The Arkansas Nano & Bio Materials Characterization
Facility is located in the Institute for Science and Engineering at the
University of Arkansas.
The results of the University of Oklahoma-led study were
published Jan. 21 by the Proceedings of
the National Academy of Sciences, U.S.A, in a paper titled “Quantifying the
distribution of nanodiamonds in pre-Younger Dryas to recent age deposits along
Bull Creek, Oklahoma Panhandle, USA.”
Nanodiamonds are extremely tiny diamonds that are found in
meteorites and rocks associated with meteorite impact events. Leland Bement, a
scientist at the Oklahoma Archeological Survey, said nanodiamonds are one of
several markers that have been proposed to indicate that a comet hit or
exploded above the Earth about 11,000 years ago and triggered the cold event
known as the Younger Dryas.
The research team wanted to verify the presence of
nanodiamonds in sediments in Bull Creek at the start of the Younger Dryas and see
if deposits of other ages also contained concentrations of nanodiamonds, Bement
said.
“So we sought sediment deposits that could be dated to
episodes of other climate extremes such as the last glacial maximum 20,000
years ago and another reversal at 8,200 years ago,” Bement said. “The end
result of our study was that we confirmed the existence of a huge spike in
nanodiamonds at the beginning of the Younger Dryas, but we also found a similar
large spike in deposits less than 3,000 years old.”
The team also looked for different kinds of sediments in Bull
Creek, including windblown, stream-lain and erosional as well as sediments that
had undergone soil formation processes.
“We did not find nanodiamond spikes in any of those
sediments,” Bement said. “Therefore, some other event or process than those
listed above were responsible for the high spike in nanodiamonds. This means
that the hypothesis that nanodiamonds were created by a comet strike or airburst
cannot be ruled out based on our findings. In addition, a similar source should
be considered for the spike in nanodiamonds in deposits less than 3,000 years
old.”
Bement co-led the project with Andrew Madden, an associate
professor of geology at the University of Oklahoma. Collaborators in addition
to Benamara were Brian Carter and Scott Fine at Oklahoma State University;
Andrew Swindle, University of Oklahoma; and Alexander Simms and Hanna M.
Alexander at the University of California, Santa Barbara.