66-million-year-old deathbed linked to dinosaur-killing meteor

66-million-year-old deathbed linked to dinosaur-killing meteor
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 (Triceratops), the first victims of a cataclysm that led to Earth's last mass extinction. The death scene from within an hour of the impact has been excavated at an unprecedented fossil site in North Dakota. Credit: 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 , 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."

In a paper to appear 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.

66-million-year-old deathbed linked to dinosaur-killing meteor
Tektites, 1 millimeter spheres of glass, recovered from the Tanis fossil bed. They were produced by the Chicxulub impact and fell within an hour of the impact. Credit: Robert DePalma

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.

"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 was responsible for both the iridium at the K-T boundary and the mass extinction.

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 would 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.

"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.

"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."

"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."


Explore further

What was the impact that killed the dinosaurs?

More information: "Prelude to Extinction: a seismically induced onshore surge deposit at the KPg boundary, North Dakota," by Robert DePalma et al. Proceedings of the National Academy of Sciences (2019). www.pnas.org/cgi/doi/10.1073/pnas.1817407116
Citation: 66-million-year-old deathbed linked to dinosaur-killing meteor (2019, March 29) retrieved 23 July 2019 from https://phys.org/news/2019-03-million-year-old-deathbed-linked-dinosaur-killing-meteor.html
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Mar 29, 2019
I hope they save a large percentage of this area for future archeologists. They will have access to imaging tech and other things that will make removing everything with our current techniques, criminal in their minds.

Luckily we will also have better computers available to figure out buried areas of similar attributes that we will not have ruined with our caveman removal and documentation systems.

Mar 29, 2019
I hope they save a large percentage of this area for future archeologists. They will have access to imaging tech and other things that will make removing everything with our current techniques, criminal in their minds.


F them.

Mar 29, 2019
Asteroids and the Nemesis theory of the extinction of Dinosaurs . . . and the life at the bottom of the sea, hence life may have started out not dependent on oxygen were two major discoveries that I grew up with in the 1980s. I grew up thinking these things were common place knowledge.

Mar 29, 2019
There are some things that are best left alone for future generations to explore and research. But the ancient artifacts such as bones and tektites are possibly too delicate to leave them be, as the environment in which they have lain for millions of years may suddenly or slowly change, and those artifacts could be lost or broken. Picture evidence is not enough, so that it is imperative for these researchers to classify and save as much as they can carry away to museums/laboratories.
The researchers are aware of what carelessness can do to a site such as where they have found all of these amazing artifacts. I am certain that they tread carefully with each step, never knowing what is underneath them.

Mar 29, 2019
What a stunning discovery.
There are some things that are best left alone for future generations to explore and research
What a stunningly stupid thing to say.
we will not have ruined with our caveman removal
Oh sorry, what a stunningly stupid thing to repeat.

Mar 29, 2019
Amazing. This is the site that shows how the dinosaurs died and mammals conquered the world. Finally, we don't have to listen to the cranks who don't "believe in it" and think the babble by the drunken stone age sheep herders about the super magic daddy in the sky is better than real geology and paleontology.

Mar 29, 2019
Amazing. This is the site that shows how the dinosaurs died and mammals conquered the world. Finally, we don't have to listen to the cranks who don't "believe in it" and think the babble by the drunken stone age sheep herders about the super magic daddy in the sky is better than real geology and paleontology.
Well I dunno. Martians probably had nukes by then. It could have been an attack.

Ask pussytard.

Mar 29, 2019
I recently finished re-reading (for the third or fourth time!) 'T. rex and the Crater of Doom', by Walter Alvarez (mentioned in the above article). Great book. Details how they considered various hypotheses for the iridium anomaly, before settling on the impact theory, as more and more evidence pointed that way. Culminating with the discovery of the crater. Highly recommended if you can get your hands on it. It is available in ebook format.

https://en.wikipe..._of_Doom

Mar 29, 2019
The KPg Killing Fields.

Key dating find: "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 now know 'to the day' when the non-avian dinosaurs ended.

What a stunning discovery.
There are some things that are best left alone for future generations to explore and research
What a stunningly stupid thing to say.
we will not have ruined with our caveman removal
Oh sorry, what a stunningly stupid thing to repeat.


OK, blocking trolls has its problems, I dunno why they attack science learning how to do science instead of hail the advances. Most likely because it advances. Oy.

Mar 29, 2019
Amazing. This is the site that shows how the dinosaurs died and mammals conquered the world. Finally, we don't have to listen to the cranks who don't "believe in it" and think the babble by the drunken stone age sheep herders about the super magic daddy in the sky is better than real geology and paleontology.
Well I dunno. Martians probably had nukes by then. It could have been an attack.

Ask pussytard.
says SpookyOtto

Ask yourself, pussytard. Otto knows all about his 900 foot tall glassy headed reclining Martians. Isn't that right, pussytard?

Mar 29, 2019
The KPg Killing Fields.

Key dating find: "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 now know 'to the day' when the non-avian dinosaurs ended.

What a stunning discovery.
There are some things that are best left alone for future generations to explore and research
What a stunningly stupid thing to say.
we will not have ruined with our caveman removal
Oh sorry, what a stunningly stupid thing to repeat.


OK, blocking trolls has its problems, I dunno why they attack science learning how to do science instead of hail the advances. Most likely because it advances. Oy.
says tbglarsson

It largely depends on what you consider as trolling. Down voting trolls whose opinions are GIGO, such as CS and DS and their sock puppies are known to despise any NEW science which they themselves failed to conceive of first.

Mar 29, 2019
.....any NEW science which they themselves failed to conceive of first.


You have never presented any new science. You don't understand science.

Mar 29, 2019
.....any NEW science which they themselves failed to conceive of first.


You have never presented any new science. You don't understand science.
says Castrovagina

I was roundly ridiculed by you, observicist, Da Schniebo and some others for expounding on my belief that "time" that is conflated with Space in Einstein's Spacetime - is nonexistent. I explained all the reasons as to WHY and how "time" doesn't exist, and I was down voted continuously by all the usual suspects. There were some who did agree with my hypothesis and understood how sensible it is to not include "time" in math equations along with Space since "time" is only a concept that is conceived by the human mind.
You did not agree, so from what I recall, you went on a name-calling spree in order to get your point across. I was not intimidated and my hypothesis still stands. Lies about me were told by Da Schniebo and his master, Captain Dumpy. I think you have read them also.

Mar 29, 2019

I was roundly ridiculed by you, observicist, Da Schniebo and some others for expounding on my belief that "time" that is conflated with Space in Einstein's Spacetime - is nonexistent. I explained all the reasons as to WHY and how "time" doesn't exist, and I was down voted continuously by all the usual suspects. There were some who did agree with my hypothesis and understood how sensible it is to not include "time" in math equations along with Space since "time" is only a concept that is conceived by the human mind.
You did not agree, so from what I recall, you went on a name-calling spree in order to get your point across. I was not intimidated and my hypothesis still stands. Lies about me were told by Da Schniebo and his master, Captain Dumpy. I think you have read them also.


You were talking crap. And still are. You are clueless. Science is not your thing.

Mar 29, 2019

I was roundly ridiculed by you, observicist, Da Schniebo and some others for expounding on my belief that "time" that is conflated with Space in Einstein's Spacetime - is nonexistent. I explained all the reasons as to WHY and how "time" doesn't exist, and I was down voted continuously by all the usual suspects. There were some who did agree with my hypothesis and understood how sensible it is to not include "time" in math equations along with Space since "time" is only a concept that is conceived by the human mind.
You did not agree, so from what I recall, you went on a name-calling spree in order to get your point across. I was not intimidated and my hypothesis still stands. Lies about me were told by Da Schniebo and his master, Captain Dumpy. I think you have read them also.


You were talking crap. And still are. You are clueless. Science is not your thing.
says Castrovagina

To YOU it was crap. But there are some scientists who agree with my hypothesis wrt time

Mar 30, 2019
To YOU it was crap. But there are some scientists who agree with my hypothesis wrt time


No there are not.

Mar 30, 2019
Special theory of relativity. "On the Electrodynamics of Moving Bodies," Einstein, 1905.

No repeatable experiment has ever shown it to be wrong.

This theory uses space and time dimensions, and specifies how they interconvert with one another. Its assumptions are few, usually limited to 2 or 3 depending on the derivation you prefer. Note that by "interconvert" I mean what one observer sees as space, another can see as time, and vice versa. Based on the fact of much confirming and no denying experimental fact, it appears to be a law of nature.

Mar 30, 2019
flashgordon
Asteroids and the Nemesis theory of the extinction of Dinosaurs . . . and the life at the bottom of the sea, hence life may have started out not dependent on oxygen were two major discoveries that I grew up with in the 1980s. I grew up thinking these things were common place knowledge.


The reason the Nemesis hypothesis went out of vogue was because as Prof. Luis Alvarez got older he started to look more and more ethnic. This was obviously not to the liking of the supremacist establishment and a concerted campaign was initiated, lead by the likes of Robert T. Bakkker, to discredit the whole idea. However, as the evidence has accumulated the truth of the matter has been revealed. It would be interesting see if the rest of the hypothesis can be confirmed, that is, whether or not an actual sister or companion star exists in orbit around our own Sun. This last piece of data would put the confirmed Nemesis Theory in the ranks of the Theory of Evolution or even Relativity.

Mar 30, 2019
Do you know, I watched the drama of the Chixulub extinction develop, and never once thought of the ethnicity of the players? I only paid attention to the evidence and the theories. I guess I'm naive.

Mar 30, 2019
@Da Schneib.
Note that by "interconvert" I mean what one observer sees as space, another can see as time, and vice versa.
A question, mate: What exactly do you mean by the phrase "see as time"?
and never once thought of the ethnicity of the players? I only paid attention to the evidence and the theories. I guess I'm naive.
A very laudable thing, mate. Kudos! It would have been great if you had extended that courtesy to cover all other 'personal attributes' of source/interlocutor; and had applied that courtesy in every case (especially with me) so that we could have avoided all the personal crap intruding from your end due to your oft-evident personal prejudice/animus in lieu of objective/impartial attention to the science/logics posted for your/others' benefit. Still, better-some-than-none; and better-late-than-never, hey mate? I look forward to even better things from you, DS. Keep up the self-improvement trajectory you now seem to be on. Much appreciated. :)

Mar 30, 2019
There are some things that are best left alone for future generations to explore and research. But the ancient artifacts such as bones and tektites are possibly too delicate to leave them be, as the environment in which they have lain for millions of years may suddenly or slowly change, and those artifacts could be lost or broken. Picture evidence is not enough, so that it is imperative for these researchers to classify and save as much as they can carry away to museums/laboratories.
The researchers are aware of what carelessness can do to a site such as where they have found all of these amazing artifacts. I am certain that they tread carefully with each step, never knowing what is underneath them.


They aren't "artifacts." Artifacts are items that were made or modified by human beings. Terminology matters. I'm thinking you don't have a very good notion of how fieldwork is performed, nor how physical context is preserved.

Mar 31, 2019
There's an excellent article about this in The New Yorker (print, for April 19) and website. It deals not only with the site and its issues, but the primary investigator. Speaking as a person trained in prehistory, who's been following this since the days of Alvarez father and son, it's a fine reporting job. It doesn't substitute for the academic paper, but it will take a non-professional into the issues very nicely.

https://www.newyo...urs-died

Those commenting here who demonstrate ignorance of paleontological fieldwork would do well to read it.

Mar 31, 2019
I venture that far more water was propelled into the atmosphere and it contributed significantly to the extinction.

Apr 29, 2019
flashgordon
Asteroids and the Nemesis theory of the extinction of Dinosaurs . . . and the life at the bottom of the sea, hence life may have started out not dependent on oxygen were two major discoveries that I grew up with in the 1980s. I grew up thinking these things were common place knowledge.


The reason the Nemesis hypothesis went out of vogue was because as Prof. Luis Alvarez got older he started to look more and more ethnic. ... This last piece of data would put the confirmed Nemesis Theory in the ranks of the Theory of Evolution or even Relativity.


There are problematic confusions between Alvarez's Chixculub impact theory of extinction and a fringe theory on the planetary system, which is inconsistent with the extinction record [c.d Alroy 2009]. The impact has nothing to do with relativity theory, nor with "went out of vogues" - it is current consensus - nor scientists ethnicity. Nature and its facts are not culturally "racist".

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