Very fascinating.
On 3/30/19, Roger Loran Bailey <dmarc-noreply@xxxxxxxxxxxxx> wrote:
This isn't the kind of article I usually post here, but I found this
extremely interesting, so I thought I would share it.
https://news.berkeley.edu/2019/03/29/66-million-year-old-deathbed-linked-to-dinosaur-killing-meteor/
66 million-year-old deathbed linked to dinosaur-killing meteor
By Robert Sanders, Media relations| March 29, 2019
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graphic of dinosaur caught in tsunami
A meteor impact 66 million years ago generated a tsunami-like wave in an
inland sea that killed and buried fish, mammals, insects and a dinosaur,
the first victims of Earth’s last mass extinction event. The death scene
from within an hour of the impact has been excavated at an unprecedented
fossil site in North Dakota. (Graphics and photos courtesy of Robert
DePalma)
The beginning of the end started with violent shaking that raised giant
waves in the waters of an inland sea in what is now North Dakota.
Then, tiny glass beads began to fall like birdshot from the heavens. The
rain of glass was so heavy it may have set fire to much of the
vegetation on land. In the water, fish struggled to breathe as the beads
clogged their gills.
The heaving sea turned into a 30-foot wall of water when it reached the
mouth of a river, tossing hundreds, if not thousands, of fresh-water
fish — sturgeon and paddlefish — onto a sand bar and temporarily
reversing the flow of the river. Stranded by the receding water, the
fish were pelted by glass beads up to 5 millimeters in diameter, some
burying themselves inches deep in the mud. The torrent of rocks, like
fine sand, and small glass beads continued for another 10 to 20 minutes
before a second large wave inundated the shore and covered the fish with
gravel, sand and fine sediment, sealing them from the world for 66
million years.
This unique, fossilized graveyard — fish stacked one atop another and
mixed in with burned tree trunks, conifer branches, dead mammals,
mosasaur bones, insects, the partial carcass of a Triceratops, marine
microorganisms called dinoflagellates and snail-like marine cephalopods
called ammonites — was unearthed by paleontologist Robert DePalma over
the past six years in the Hell Creek Formation, not far from Bowman,
North Dakota. The evidence confirms a suspicion that nagged at DePalma
in his first digging season during the summer of 2013 — that this was a
killing field laid down soon after the asteroid impact that eventually
led to the extinction of all ground-dwelling dinosaurs. The impact at
the end of the Cretaceous Period, the so-called K-T boundary,
exterminated 75 percent of life on Earth.
“This is the first mass death assemblage of large organisms anyone has
found associated with the K-T boundary,” said DePalma, curator of
paleontology at the Palm Beach Museum of Natural History in Florida and
a doctoral student at the University of Kansas. “At no other K-T
boundary section on Earth can you find such a collection consisting of a
large number of species representing different ages of organisms and
different stages of life, all of which died at the same time, on the
same day.”
fossilized fish
Fossilized fish piled one atop another, suggesting that they were flung
ashore and died stranded together on a sand bar after the seiche withdrew.
In a paper to be published next week in the journal Proceedings of the
National Academy of Sciences, he and his American and European
colleagues, including two University of California, Berkeley,
geologists, describe the site, dubbed Tanis, and the evidence connecting
it with the asteroid or comet strike off Mexico’s Yucatan Peninsula 66
million years ago. That impact created a huge crater, called Chicxulub,
in the ocean floor and sent vaporized rock and cubic miles of asteroid
dust into the atmosphere. The cloud eventually enveloped Earth, setting
the stage for Earth’s last mass extinction.
“It’s like a museum of the end of the Cretaceous in a layer a
meter-and-a-half thick,” said Mark Richards, a UC Berkeley professor
emeritus of earth and planetary science who is now provost and professor
of earth and space sciences at the University of Washington.
Richards and Walter Alvarez, a UC Berkeley Professor of the Graduate
School who 40 years ago first hypothesized that a comet or asteroid
impact caused the mass extinction, were called in by DePalma and Dutch
scientist Jan Smit to consult on the rain of glass beads and the
tsunami-like waves that buried and preserved the fish. The beads, called
tektites, formed in the atmosphere from rock melted by the impact.
Tsunami vs. seiche
Richards and Alvarez determined that the fish could not have been
stranded and then buried by a typical tsunami, a single wave that would
have reached this previously unknown arm of the Western Interior Seaway
no less than 10 to 12 hours after the impact 3,000 kilometers away, if
it didn’t peter out before then. Their reasoning: The tektites would
have rained down within 45 minutes to an hour of the impact, unable to
create mudholes if the seabed had not already been exposed.
photo of Alvarez and DePalma
Walter Alvarez and Robert DePalma at the Tanis outcrop in North Dakota.
Instead, they argue, seismic waves likely arrived within 10 minutes of
the impact from what would have been the equivalent of a magnitude 10 or
11 earthquake, creating a seiche (pronounced saysh), a standing wave, in
the inland sea that is similar to water sloshing in a bathtub during an
earthquake. Though large earthquakes often generate seiches in enclosed
bodies of water, they’re seldom noticed, Richards said. The 2011 Tohoku
quake in Japan, a magnitude 9.0, created six-foot-high seiches 30
minutes later in a Norwegian fjord 8,000 kilometers away.
“The seismic waves start arising within nine to 10 minutes of the
impact, so they had a chance to get the water sloshing before all the
spherules (small spheres) had fallen out of the sky,” Richards said.
“These spherules coming in cratered the surface, making funnels — you
can see the deformed layers in what used to be soft mud — and then
rubble covered the spherules. No one has seen these funnels before.”
The tektites would have come in on a ballistic trajectory from space,
reaching terminal velocities of between 100 and 200 miles per hour,
according to Alvarez, who estimated their travel time decades ago.
“You can imagine standing there being pelted by these glass spherules.
They could have killed you,” Richards said. Many believe that the rain
of debris was so intense that the energy ignited wildfires over the
entire American continent, if not around the world.
tektites
Tektites, 1 millimeter spheres of glass, recovered from the Tanis fossil
bed.
“Tsunamis from the Chicxulub impact are certainly well-documented, but
no one knew how far something like that would go into an inland sea,”
DePalma said. “When Mark came aboard, he discovered a remarkable
artifact — that the incoming seismic waves from the impact site would
have arrived at just about the same time as the atmospheric travel time
of the ejecta. That was our big breakthrough.”
At least two huge seiches inundated the land, perhaps 20 minutes apart,
leaving six feet of deposits covering the fossils. Overlaying this is a
layer of clay rich in iridium, a metal rare on Earth, but common in
asteroids and comets. This layer is known as the K-T, or K-Pg boundary,
marking the end of the Cretaceous Period and the beginning of the
Tertiary Period, or Paleogene.
Iridium
In 1979, Alvarez and his father, Nobelist Luis Alvarez of UC Berkeley,
were the first to recognize the significance of iridium that is found in
66 million-year-old rock layers around the world. They proposed that a
comet or asteroid impact was responsible for both the iridium at the K-T
boundary and the mass extinction.
Smit, Richards and Alvarez
Jan Smit, Mark Richards and Walter Alvarez at the North Dakota site of
dinosaur-killing meteor’s first victims.
The impact would have melted the bedrock under the seafloor and
pulverized the asteroid, sending dust and melted rock into the
stratosphere, where winds would have carried them around the planet and
blotted out the sun for months, if not years. Debris wold have rained
down from the sky: not only tektites, but also rock debris from the
continental crust, including shocked quartz, whose crystal structure was
deformed by the impact.
The iridium-rich dust from the pulverized meteor would have been the
last to fall out of the atmosphere after the impact, capping off the
Cretaceous.
“When we proposed the impact hypothesis to explain the great extinction,
it was based just on finding an anomalous concentration of iridium — the
fingerprint of an asteroid or comet,” said Alvarez. “Since then, the
evidence has gradually built up. But it never crossed my mind that we
would find a deathbed like this.”
Key confirmation of the meteor hypothesis was the discovery of a buried
impact crater, Chicxulub, in the Caribbean and off the coast of the
Yucatan in Mexico, that was dated to exactly the age of the extinction.
Shocked quartz and glass spherules were also found in K-Pg layers
worldwide. The new discovery at Tanis is the first time the debris
produced in the impact was found along with animals killed in the
immediate aftermath of the impact.
<span data-mce-type="bookmark" style="display: inline-block; width: 0px;
overflow: hidden; line-height: 0;" class="mce_SELRES_start"></span>
Robert DePalma excavating at the Tanis fossil site in North Dakota.
“And now we have this magnificent and completely unexpected site that
Robert DePalma is excavating in North Dakota, which is so rich in
detailed information about what happened as a result of the impact,”
Alvarez said. “For me, it is very exciting and gratifying!”
Tektites
Jan Smit, a retired professor of sedimentary geology from Vrije
Universiteit in Amsterdam in The Netherlands who is considered the world
expert on tektites from the impact, joined DePalma to analyze and date
the tektites from the Tanis site. Many were found in near perfect
condition embedded in amber, which at the time was pliable pine pitch.
fossil logs and fish
Fish carcasses and two logs tossed together by the seiche created by
seismic waves from the meteor impact.
“I went to the site in 2015 and, in front of my eyes, he (DePalma)
uncovered a charred log or tree trunk about four meters long which was
covered in amber, which acted as sort of an aerogel and caught the
tektites when they were coming down,” Smit said. “It was a major
discovery, because the resin, the amber, covered the tektites
completely, and they are the most unaltered tektites I have seen so far,
not 1 percent of alteration. We dated them, and they came out to be
exactly from the K-T boundary.”
The tektites in the fishes’ gills are also a first.
“Paddlefish swim through the water with their mouths open, gaping, and
in this net, they catch tiny particles, food particles, in their gill
rakers, and then they swallow, like a whale shark or a baleen whale,”
Smit said. “They also caught tektites. That by itself is an amazing
fact. That means that the first direct victims of the impact are these
accumulations of fishes.”
Smit also noted that the buried body of a Triceratops and a duck-billed
hadrosaur proves beyond a doubt that dinosaurs were still alive at the
time of the impact.
“We have an amazing array of discoveries which will prove in the future
to be even more valuable,” Smit said. “We have fantastic deposits that
need to be studied from all different viewpoints. And I think we can
unravel the sequence of incoming ejecta from the Chicxulub impact in
great detail, which we would never have been able to do with all the
other deposits around the Gulf of Mexico.”
fossilized tail of fish
A perfectly preserved fish tail from Tanis deposit.
“So far, we have gone 40 years before something like this turned up that
may very well be unique,” Smit said. “So, we have to be very careful
with that place, how we dig it up and learn from it. This is a great
gift at the end of my career. Walter sees it as the same.”
Co-authors with DePalma, Smit, Richards and Alvarez are David Burnham of
the University of Kansas, Klaudia Kuiper of Vrije Universiteit, Phillip
Manning of Manchester University in the United Kingdom, Anton Oleinik of
Florida Atlantic University, Peter Larson of the Black Hills Institute
of Geological Research in South Dakota, Florentin Maurrasse of Florida
International University, Johan Vellekoop of Katholieke Universiteit
Leuven in Belgium and Loren Gurche of the Palm Beach Museum of Natural
History.
RELATED INFORMATION
•Prelude to extinction: a seismically induced onshore surge deposit at
the KPg boundary, North Dakota (PNAS)
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@bobthesciguy
These animals died within an hour of a meteor impact one hellish day 66
million years ago https://t.co/0emYX8UTjy v… https://t.co/cwh3zTpavK
about 1 day ago
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