New evidence suggests that a comet
collision might have been the trigger for the Younger Dryas, contributing to
North America’s megafauna extinction. UC Santa Barbara’s James Kennett,
professor emeritus in the Department of Earth Science, posits that such an
extraterrestrial event did occur killing off woolly mammoths, giant ground
sloths and saber-tooth tigers 12,900 years ago.
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Originally published in 2007,
Kennett’s controversial Younger Dryas Boundary (YDB) hypothesis suggests that a
comet collision precipitated the Younger Dryas period of global cooling, which,
in turn, contributed to the extinction of many animals and altered human
adaptations. The nanodiamond is one type of material that could result from an
extraterrestrial collision, and the presence of nanodiamonds along Bull Creek
in the Oklahoma Panhandle lends credence to the YDB hypothesis.
More recently, another group of
earth scientists, including UCSB’s Alexander Simms and alumna Hanna Alexander,
re-examined the distribution of nanodiamonds in Bull Creek’s sedimentological
record to see if they could reproduce the original study’s evidence supporting
the YDB hypothesis. Their findings appear in the Proceedings of the National
Academy of Science.
“We were able to replicate some of
their results and we did find nanodiamonds right at the Younger Dryas
Boundary,” said Simms, an associate professor in UCSB. “However, we also found
a second spike of nanodiamonds more recently in the sedimentary record, sometime
within the past 3,000 years.”
The researchers analyzed 49 sediment
samples representing different time periods and environmental and climactic
settings, and identified high levels of nanodiamonds immediately below and just
above YDB deposits and in late-Holocene near-surface deposits. The late
Holocene began at the end of the Pleistocene 11,700 years ago and continues to
the present. The researchers found the presence of nanodiamonds is not caused
by environmental setting, soil formation, cultural activities, other climate
changes or the amount of time in which the landscape is stable. The
discovery of high concentrations of nanodiamonds from two distinct time periods
suggests that whatever process produced the elevated concentrations of
nanodiamonds at the onset of the Younger Dryas sediments may have also been
active in recent millennia in Bull Creek.
”Nanodiamonds are found in high
abundances at the YDB, giving some support to that theory,” Simms said.
“However, we did find it at one other site, which may or may not be caused by a
smaller but similar event nearby.”
Read more at University
of California of Santa Barbara.
Woolly
Mammoth and comet
images via Shutterstock, merged and morphed by Robin Blackstone.