The impact of a comet or asteroid 12,900 years ago on the Laurentide Ice Sheet triggered
a cataclysm that caused great devastation in North America and the onset of a global
winter.
A layer of dark soil called a black mat marks the transition between our modern world and
a land previously populated by large animals like mastodons, short-face bears and giant
armadillos.
This is an image of the Murray Springs Clovis site in Arizona.
The Murray Springs Clovis Site is 14 miles southwest from Tombstone, Arizona, which is
known for its Wild West history.
A paper published in 2007 by Richard Firestone and 25 co-authors presented evidence for an
extraterrestrial impact 12,900 years ago that contributed to the megafaunal extinctions
and the Younger Dryas cooling.
This paper became the foundation of what is now called the Younger Dryas Impact Hypothesis.
The abstract mentions a carbon-rich black layer, dating to 12,900 years ago, that has
been previously identified at 50 Clovis-age sites across North America and appears contemporaneous
with the abrupt onset of the Younger Dryas cooling.
The bones of extinct Pleistocene megafauna, along with Clovis tools, occur below this
black layer but not within or above it.
The paper includes an image of the Murray Springs Clovis site in Arizona, and points
out that the dark line along the arroyo wall is the black mat that dates to 12,900 years
ago.
The Younger Dryas Boundary or YDB markers, including magnetic grains and microspherules,
iridium, soot, and fullerenes with extraterrestrial helium, are present in the few centimeters
just below the black mat at the top of the underlying sediment.
This line represents the surface at the end of the Clovis period before the formation
of the black mat.
Clovis artifacts, a fire pit, and an almost fully articulated skeleton of an adult mammoth
were recovered at Murray Springs with the black mat draped over them.
Excavations by Vance Haynes and colleagues also revealed hundreds of mammoth footprints
in the sand infilled by black mat sediments.
These footprints and the mammoth skeleton appear to have been preserved by rapid burial
after the YDB event.
No Clovis points or extinct megafaunal remains have been recovered from or above the black
mat, indicating that the mammoths and Clovis hunting technology disappeared simultaneously.
Vance Haynes submitted an article for publication just one month after Firestone in 2007, but
the paper was published only in 2008.
The title is intended for experts in archeology.
We need to translate it into more understandable language.
The term Younger Dryas refers to a cooling period that started 12,900 years ago and lasted
for 1300 years.
The word Rancholabrean is derived from the Rancho La Brea fossil site, which is more
commonly known as La Brea Tar Pits in Los Angeles, California.
The Rancholabarean termination refers to the time when Pleistocene mammals such as mammoths
and saber toothed tigers became extinct at the onset of the Younger Dryas cooling event.
The paper describes 97 archaeological sites, two thirds of which have a black organic-rich
layer or black mat in the form of mollic paleosols, aquolls, diatomites, or algal mats with radiocarbon
ages suggesting that they are stratigraphic manifestations of the Younger Dryas cooling
episode.
A mollic paleosol is a dark layer of soil that was formed in a past geological period,
an aquoll is a layer of soil formed under wet conditions, diatomites are the fossilized
remains of diatoms, which are microalgae, and algal mats are microbial mats that form
on the surface of water or rocks.
This black mat covers the Clovis-age surface on which the last remnants of the terminal
Pleistocene megafauna are recorded.
Haynes says that the extinction of the megafauna appears to have been catastrophic, seemingly
too sudden and extensive for either human predation or climate change to have been the
primary cause.
Haynes acknowledges the recent evidence for an extraterrestrial impact, but he does not
find it compelling yet.
The paper by Haynes has a map of the United States showing 57 locations with black mats
of Younger Dryas age represented as filled circles.
The open circles are 27 localities with Pleistocene-Holocene transitional sediments but with no black mats.
Notice that most of the black mats are in the western part of the United States.
Vance Haynes attributes the black mats to relatively moist conditions as a result of
higher water tables, indicated by the presence of wet-meadow soils, algal mats and pond sediments.
Some black mats do not have enough charcoal to indicate extensive biomass burning.
We will come back to this map later.
In 2018, Broughton and Weitzel published a paper titled Population reconstructions for
humans and megafauna suggest mixed causes for North American Pleistocene extinctions.
These authors are trying to figure out the cause of the megafaunal extinctions.
The abstract says: Dozens of large mammals such as mammoth and mastodon disappeared in
North America at the end of the Pleistocene with climate change and overkill by human
hunters the most widely-argued causes.
However, the population dynamics of humans and megafauna preceding extinctions have received
little attention even though such information may be telling as we expect increasing human
populations to be correlated with megafaunal declines if hunting caused extinctions.
No such trends are expected if climate change was the primary cause.
We present tests of these hypotheses here by using summed calibrated radiocarbon date
distributions to reconstruct population levels of megafauna and humans.
The results suggest that the causes for extinctions varied across taxa and by region.
In three cases, extinctions appear linked to hunting, while in five others they are
consistent with the ecological effects of climate change and in a final case, both hunting
and climate change appear responsible.
Broughton and Weitzel only consider climate change and human predation as the causes of
the megafaunal extinctions.
They do not consider a catastrophic extraterrestrial impact.
The paper has a map of the contiguous United States and southern Canada that indicates
the frequency of dates by state or province for the directly dated megafauna sample and
the distribution of archeological radiocarbon dates from the Canadian Archaeological Radiocarbon
Database used in the study.
The absence of megafauna fossils in the southern United States is notable.
The states of Arkansas, Louisiana, Mississippi, Alabama, Georgia, South Carolina and North
Carolina don't seem to have megafauna fossil evidence at all.
Before examining the maps of the black mats and the megafauna fossils, let us review the
Glacier Ice Impact Hypothesis published in 2017, which proposes four mechanisms for the
formation of the Carolina Bays.
First, a meteorite impact on the Laurentide Ice Sheet ejected glacier ice boulders in
ballistic trajectories.
The secondary impacts by the ice boulders liquefied unconsolidated ground.
Oblique impacts of ice boulders on liquefied ground created inclined conical cavities,
and viscous relaxation reduced the depth of the conical cavities to produce shallow elliptical
bays.
Michael Davias determined that Saginaw Bay is the convergence point of the Carolina Bays
and the Nebraska Rainwater Basins.
These impact structures only occur within a radius of 1500 kilometers from Saginaw Bay,
which was the range of ballistic sedimentation of the ejecta curtain.
When we draw a circle with a radius of 1500 kilometers from Saginaw Bay, which is thought
to be the location from where the glacier ice boulders were ejected by an extraterrestrial
impact, we notice that the black mats are found mostly beyond the 1500 kilometer radius,
away from where the secondary glacier ice bombardment occurred.
This image combines the black mat map by Haynes and the megafauna fossil map by Broughton
and Weitzel.
The circle marks the 1500 kilometer radius from Saginaw Bay.
Let us take a look at the Carolina Bays in South Carolina.
A recent video calculated the energy of the impacts that created the Carolina Bays in
Marlboro County, South Carolina.
The detailed analysis of the overlapping impacts indicated that Marlboro County, South Carolina
received a glacier ice bombardment with energy of 7.95 megatons of TNT per square kilometer.
That is about 8 megatons per square kilometer.
With this tremendous glacier ice bombardment, all the megafauna like the mammoths, short-faced
bears, giant armadillos and all the forest plants would have been completely obliterated
and there would be no remains to be fossilized.
Another recent video calculated the energy of emplacement of the smaller Carolina Bays
that are found in New Jersey as 880 kilotons per square kilometer.
The density of the Carolina Bays enable us to deduce the distribution of the ejecta from
the extraterrestrial impact.
The bays in Marlboro County, South Carolina are large and overlapping.
They correspond to a kinetic energy of almost 8 megatons of TNT per square kilometer.
That is enough to grind up megafauna into a paste that leaves nothing to fossilize.
In New Jersey, the bays are small and correspond to a kinetic energy of 880 kilotons of TNT
per square kilometer.
That is enough to kill all the megafauna, but not enough to completely pulverize them,
so some bones remain to be fossilized.
The megafauna extinction map also tells us something about the ejecta curtain.
The lack of fossils in Arkansas, Louisiana, Mississippi, and Alabama indicates that the
impacts of the glacier ice were just as powerful in these states as in South Carolina, but
these states have no Carolina Bays because the ground is hard and could not be liquefied
to allow the formation of inclined conical cavities.
The impacts on hard ground shattered the ice projectiles and pulverized the megafauna,
but they did not leave the geological evidence that we find in the Atlantic Coastal Plain.
It is interesting to see that archeology and geology complement each other to provide a
more complete story of the Earth's recent past.
12,900 years ago, an extraterrestrial impact on the Laurentide Ice Sheet ejected pieces
of ice in ballistic trajectories.
The secondary impacts on unconsolidated ground created the Carolina Bays and the Nebraska
Rainwater Basins.
The impacts on hard ground created shards of ice and thick clouds of ice particles.
Nuclear explosions can provide an analogy of what happened when the ejecta curtain collapsed.
On July 6, 1962, an atomic blast in Nevada with energy of 104 kilotons of TNT exploded
upward and outward displacing more than eleven million tons of soil.
A circular area of the desert floor five miles or 8 kilometers across was obscured by fast-expanding
dust clouds moving out horizontally from the blast site like a pyroclastic surge.
This image shows the start of the expansion of the low-hanging dust cloud far beyond the
area covered by the ejecta.
Similar surface dynamics may have been responsible for the black mats.
within the circle of ballistic sedimentation, the vegetation was ground up and worked into
the soil, so there was no vegetation on the surface to create a black mat.
Beyond the ballistic sedimentation circle, the air pressure of the falling ice projectiles
blew a cloud of ice particles that covered grasses and trees like an avalanche.
The thick coating of ice smothered the vegetation and created the moist conditions that promoted
growth of algae to form the black mats.
Before concluding the topic of the black mat, I want to point out that the black mat is
at a very shallow depth from the modern surface.
In this picture, we can estimate that the black mat is about 2 feet or about 60 centimeters
below the surface.
One of the reasons why the Carolina Bays have been assumed to have originated by wind and
water processes is because the dates obtained for the bays by Optically Stimulated Luminescence
or OSL have a range spanning thousands of years that would make it impossible for all
the bays to have been created contemporaneously.
However, the samples for OSL have to be taken more than one meter below the land surface
to minimize cosmogenic dose errors, but this requirement may result in obtaining samples
that are far deeper than the surface of 12,900 years ago.
This will cause the OSL dates to correspond to very old terrain, and not to the time of
bay formation.
Thank you for joining me in the investigation of the Carolina Bays and the Younger Dryas
cataclysm.
My book about the Carolina Bays is available at Amazon.
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Bays and the mechanism of their formation.