Conetary impact as the cause of Paleolithic extinctions and the Younger-Dryas



It does seem as though the evidence for the so-called Younger-Dryas
impact is real and not just a figment of Richard Firestone's
imagination. W.M. Napier (astronomer) has now tied his work on
catastrophism to the findings of nanodiamonds, evidence of wild fires,
extinctions and the climate change of the Younger-Dryas. This is of
relevance to archaeologists as the impact explains a number of
archaeological boundaries, including the end of the Clovis.

See http://arxiv.org/abs/1003.0744

" Intersection with the debris of a large (50-100 km)
short-period comet during the Upper Palaeolithic provides a
satisfactory explanation for the catastrophe of celestial origin
which has been postulated to have occurred around 12900 BP,
and which presaged a return to ice age conditions of duration
~1300 years. The Taurid Complex appears to be the debris of
this erstwhile comet; it includes at least 19 of the brightest
near-Earth objects. Sub-kilometre bodies in meteor streams
may present the greatest regional impact hazard on timescales
of human concern.

Comments: 7 pages, 3 figures; accepted for Monthly Notices of
the Royal Astronomical Society (definitive version will be
available at www.blackwell-synergy.com) "



I have been informed via a personal communication that the paper
includes:

Begin quote
----------------------------------------
WAS A GIANT COMET RESPONSIBLE FOR A
NORTH AMERICAN CATASTROPHE IN 11,000 BC?

13,000 years ago the Earth was struck by thousands of Tunguska-sized
cometary fragments over the course of an hour, leading to a dramatic
cooling of the planet, according to astronomer Professor Bill Napier
of the Cardiff University Astrobiology Centre. He presents his new
model in the journal Monthly Notices of the Royal Astronomical
Society.

The cooling, by as much as 8 degrees C, interrupted the warming which
was occurring at the end of the last ice age and caused glaciers to
readvance. Evidence has been found that this catastrophic change was
associated with some extraordinary extraterrestrial event. The
boundary is marked by the occurrence of a "black mat" layer a few
centimeters thick found at many sites throughout the United States
containing high levels of soot indicative of continental-scale
wildfires, as well as microscopic hexagonal diamonds (nanodiamonds)
which are produced by shocks and are only found in meteorites or
impact craters. These findings led to the suggestion that the
catastrophic changes of that time were caused by the impact of an
asteroid or comet 4 km across on the Laurentide ice sheet, which at
that time covered what would become Canada and the northern part of
the United States.

The cooling lasted over a thousand years, and its onset coincides with
the rapid extinction of 35 genera of North American mammals, as well
as the disruption of the Palaeoindian culture. The chief objection to
the idea of a big impact is that the odds against the Earth being
struck by an asteroid this large only 13,000 years ago are a thousand
to one against. And the heat generated by the rising fireball would be
limited by the curvature of the horizon and could not explain the
continent-wide occurrence of wildfires.

Professor Napier has now come up with an astronomical model which
accounts for the major features of the catastrophe without involving
such an improbable event. According to his model, the Earth ran into a
dense trail of material from a large disintegrating comet. He points
out that there is compelling evidence that such a comet entered the
inner planetary system between 20,000 and 30,000 years ago and has
been fragmenting ever since, giving rise to a number of closely
related meteor streams and comoving asteroids known as the Taurid
Complex.

In the course of the giant comet's disintegration, the environment of
the interplanetary system would have been hazardous and the Earth
would probably have run through at least one dense swarm of cometary
material. The new model indicates that such an encounter would last
for about an hour during which thousands of impacts would take place
over continental dimensions, each releasing the energy of a
megaton-class nuclear bomb, generating the extensive wildfires which
took place at that time. The nanodiamonds at the extinction boundary
would then be explained as having come in with the comet swarm.

One recent meteorite is known which may have come from this giant
comet progenitor: the Tagish Lake meteorite, which fell over Yukon
Territory in January 2000. It has the highest abundance of
nanodiamonds of any meteorite so far analyzed.

Professor Napier sums up his model: "A large comet has been
disintegrating in the near-Earth environment for the past 20,000 to
30,000 years, and running into thousands of fragments from this comet
is a much more likely event than a single large collision. It gives a
convincing match to the major geophysical features at this boundary."
---------------------------------------------
End quote





Eric Stevens
.



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