Animals killed by Chicxulub impact found in North Dakota?

[rogue06]

This will be an extraordinary discovery if it pans out, for it seems that scientists may have uncovered a site where the creatures living there were killed as a result of the asteroid impact in the Gulf of Mexico, off Chicxulub (Yucatán Peninsula), that caused the extinction of all nonavian dinosaurs approximately 66mya.

The site is in Tanis, in southwestern North Dakota, and is part of the famous Late Cretaceous Hell's Creek formation. That's roughly 3000km (18464mi.) from Chicxulub. It was discovered in 2008 and has generated a great deal of buzz, but now what has been discovered there and how it seems to provide moment-by-moment details caused by the impact event.

Among the discoveries is a preserved, articulated leg from a Thescelosaurus, a small, bipedal ornithischian dinosaur, that was "complete with scaly skin." This revealed that Thescelosaurus were "very scaly like lizards" which weren't feathered like their meat-eating contemporaries.

But what is likely the most important find are the articulated and cartilaginous salt and freshwater fish, including sturgeon and paddlefish, as well as marine reptiles, that were found together miles inland, and that had numerous microtektites (molten spherical debris particles ejected from the impact) embedded in their gills that they breathed in when the particles entered the river.

The researchers reported they also found a huge number of "near perfect" primary (that is, not reworked) microtektites, that are "almost indistinguishable" in chemical composition from previously reported Chicxulub tektites, found buried contemporaneous to the fossils in their own impact holes in the soft riverbed mud, and also preserved in amber on tree trunks.

Among some of the other discoveries were the remains of pterosaurs (flying reptiles) of previously unknown types, and a fossilized egg complete with an unborn baby inside (a first in North America). There was a turtle impaled by a tree branch, some skin from a Triceratops, broken bones from virtually every known group of dinosaurs previously found in the formation, 30 to 40cm (12' to 15.75") long primitive feathers likely from dinosaurs, small mammals inside of burrows, drowned ant nests with ants inside and chambers filled with debris from the asteroid.

A good deal of the animal remains and plant material are preserved in exquisite three-dimensional detail and even at times are upright, rather than pressed flat as usual, their remains thrown together by the massive wave movements.

Still, as critics note, it won't be until after researchers in a number of specific disciplines have thoroughly analyzed the discovery to make sure that these creatures hadn't died before the impact and were moved together by the disaster and only appear to have died simultaneously.

I'm a little hesitant when something like this starts getting big time attention in that things tend to get overhyped (Ardi for instance). Still, the fish with what appears to be debris from Chicxulub trapped in their gills is rather telling.

Source: Tanis: Fossil of dinosaur killed in asteroid strike found, scientists claim

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Scientists have presented a stunningly preserved leg of a dinosaur.

The limb, complete with skin, is just one of a series of remarkable finds emerging from the Tanis fossil site in the US State of North Dakota.

But it's not just their exquisite condition that's turning heads - it's what these ancient specimens are purported to represent.

The claim is the Tanis creatures were killed and entombed on the actual day a giant asteroid struck Earth.

The day 66 million years ago when the reign of the dinosaurs ended and the rise of mammals began.

Very few dinosaur remains have been found in the rocks that record even the final few thousand years before the impact. To have a specimen from the cataclysm itself would be extraordinary.

The BBC has spent three years filming at Tanis for a show to be broadcast on 15 April, narrated by Sir David Attenborough.

• 'Dinosaur asteroid' wrought springtime devastation
• Dinosaurs suffered catastrophic 'winter'
• Dinosaur asteroid's trajectory was 'perfect storm'

Sir David will review the discoveries, many that will be getting their first public viewing.

Along with that leg, there are fish that breathed in impact debris as it rained down from the sky.

We see a fossil turtle that was skewered by a wooden stake; the remains of small mammals and the burrows they made; skin from a horned triceratops; the embryo of a flying pterosaur inside its egg; and what appears to be a fragment from the asteroid impactor itself.

"We've got so many details with this site that tell us what happened moment by moment, it's almost like watching it play out in the movies. You look at the rock column, you look at the fossils there, and it brings you back to that day," says Robert DePalma, the University of Manchester, UK, graduate student who leads the Tanis dig.

It's now widely accepted that a roughly 12km-wide space rock hit our planet to cause the last mass extinction.

The impact site has been identified in the Gulf of Mexico, off the Yucatan Peninsula. That's some 3,000km away from Tanis, but such was the energy imparted in the event, its devastation was felt far and wide.

The North Dakota fossil site is a chaotic jumble.

The remains of animals and plants seem to have been rolled together into a sediment dump by waves of river water set in train by unimaginable earth tremors. Aquatic organisms are mixed in with the land-based creatures.

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The sturgeon and paddlefish in this fossil tangle are key. They have small particles stuck in their gills. These are the spherules of molten rock kicked out from the impact that then fell back across the planet. The fish would have breathed in the particles as they entered the river.

The spherules have been linked chemically and by radiometric dating to the Mexican impact location, and in two of the particles recovered from preserved tree resin there are also tiny inclusions that imply an extra-terrestrial origin.

"When we noticed there were inclusions within these little glass spherules, we chemically analysed them at the Diamond X-ray synchrotron near Oxford," explains Prof Phil Manning, who is Mr DePalma's PhD supervisor at Manchester.

"We were able to pull apart the chemistry and identify the composition of that material. All the evidence, all of the chemical data, from that study suggests strongly that we're looking at a piece of the impactor; of the asteroid that ended it for the dinosaurs."

The existence of Tanis, and the claims made for it, first emerged in the public sphere in the New Yorker Magazine in 2019. This caused a furore at the time.

Science usually demands the initial presentation of new discoveries is made in the pages of a scholarly journal. A few peer-reviewed papers have now been published, and the dig team promises many more as it works through the meticulous process of extracting, preparing and describing the fossils.

To make its TV programme, the BBC called in outside consultants to examine a number of the finds.

Prof Paul Barrett from London's Natural History Museum looked at the leg. He's an expert in ornithischian (mostly plant-eating) dinosaurs.

"It's a Thescelosaurus. It's from a group that we didn't have any previous record of what its skin looked like, and it shows very conclusively that these animals were very scaly like lizards. They weren't feathered like their meat-eating contemporaries.

"This looks like an animal whose leg has simply been ripped off really quickly. There's no evidence on the leg of disease, there are no obvious pathologies, there's no trace of the leg being scavenged, such as bite marks or bits of it that are missing," he tells me.

"So, the best idea that we have is that this is an animal that died more or less instantaneously."

The big question is whether this dinosaur did actually die on the day the asteroid struck, as a direct result of the ensuing cataclysm. The Tanis team thinks it very likely did, given the limb's position in the dig sediments.

If that is the case, it would be quite the discovery.

But Prof Steve Brusatte from University of Edinburgh says he's sceptical - for the time being.

He's acted as another of the BBC's outside consultants. He wants to see the arguments presented in more peer-reviewed articles, and for some palaeo-scientists with very specific specialisms to go into the site to give their independent assessment.

Prof Brusatte says it's possible, for example, that animals that had died before the impact were exhumed by the violence on the day and then re-interred in a way that made their deaths appear concurrent.

"Those fish with the spherules in their gills, they're an absolute calling card for the asteroid. But for some of the other claims - I'd say they have a lot circumstantial evidence that hasn't yet been presented to the jury," he says.

"For some of these discoveries, though, does it even matter if they died on the day or years before? The pterosaur egg with a pterosaur baby inside is super-rare; there's nothing else like it from North America. It doesn't all have to be about the asteroid."

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A pterosaur embryo inside an egg

There's no doubting the pterosaur egg is special.

With modern X-ray technology it's possible to determine the chemistry and properties of the egg shell. It was likely leathery rather than hard, which may indicate the pterosaur mother buried the egg in sand or sediment like a turtle.

It's also possible with X-ray tomography to extract virtually the bones of the pterosaur chick inside, to print them and reconstruct what the animal would have looked like. Mr DePalma has done this.

The baby pterosaur was probably a type of azhdarchid, a group of flying reptiles whose adult wings could reach more than 10m from tip to tip.

Mr DePalma gave a special lecture on the Tanis discoveries to an audience at the US space agency Nasa's Goddard Space Flight Center on Wednesday. He and Prof Manning will also present their latest data to the European Geosciences Union General Assembly in May.

Dinosaurs: The Final Day with Sir David Attenborough will be broadcast on BBC One on 15 April at 18:30 BST. A version has been made for the US science series Nova on the PBS network to be broadcast later in the year.


Source

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[*more pictures and a video in story above*]

Tanis_fossil_site,_fish_with_ejecta_clustered_in_the_gill_region.jpg
This fossil fish from Tanis shows microtektites (molten splattered glass droplets) that are a chemical match for ejecta
from the Chicxulub crater The microtektites are concentrated in large numbers in the gillsof approximately half of
the fish fossils, demonstrating that the fish were alive when the impact occurred

The most recent release, Supplementary Information for A SEISMICALLY INDUCED ONSHORE SURGE DEPOSIT AT THE KPG BOUNDARY, NORTH DAKOTA, a pdf of additional information on their preliminary paper A seismically induced onshore surge deposit at the KPg boundary, North Dakota published in 2019, from which here is the very long abstract:

SIGNIFICANCE

The Chicxulub impact played a crucial role in the Cretaceous–Paleogene extinction. However the earliest postimpact effects, critical to fully decode the profound influence on Earth’s biota, are poorly understood due to a lack of high-temporal-resolution contemporaneous deposits. The Tanis site, which preserves a rapidly deposited, ejecta-bearing bed in the Hell Creek Formation, helps to resolve that long-standing deficit. Emplaced immediately (minutes to hours) after impact, Tanis provides a postimpact “snapshot,” including ejecta accretion and faunal mass death, advancing our understanding of the immediate effects of the Chicxulub impact. Moreover, we demonstrate that the depositional event, calculated to have coincided with the arrival of seismic waves from Chicxulub, likely resulted from a seismically coupled local seiche.

ABSTRACT

The most immediate effects of the terminal-Cretaceous Chicxulub impact, essential to understanding the global-scale environmental and biotic collapses that mark the Cretaceous–Paleogene extinction, are poorly resolved despite extensive previous work. Here, we help to resolve this by describing a rapidly emplaced, high-energy onshore surge deposit from the terrestrial Hell Creek Formation in Montana. Associated ejecta and a cap of iridium-rich impactite reveal that its emplacement coincided with the Chicxulub event. Acipenseriform fish, densely packed in the deposit, contain ejecta spherules in their gills and were buried by an inland-directed surge that inundated a deeply incised river channel before accretion of the fine-grained impactite. Although this deposit displays all of the physical characteristics of a tsunami runup, the timing (<1 hour postimpact) is instead consistent with the arrival of strong seismic waves from the magnitude M_w ∼10 to 11 earthquake generated by the Chicxulub impact, identifying a seismically coupled seiche inundation as the likely cause. Our findings present high-resolution chronology of the immediate aftereffects of the Chicxulub impact event in the Western Interior, and report an impact-triggered onshore mix of marine and terrestrial sedimentation—potentially a significant advancement for eventually resolving both the complex dynamics of debris ejection and the full nature and extent of biotic disruptions that took place in the first moments postimpact.

The Chicxulub meteoric impact marks the end of the Cretaceous and the onset of profound planet-scale climatic changes that initiated a mass extinction in the earliest Cenozoic (1, 2). Intimately associated with the third-greatest global extinction, a variety of immediate and protracted results have been proposed for the Chicxulub impact, including atmospheric perturbations and long-term global climatic shifts (3), possible impact-induced volcanism (4), and eventual worldwide ecological collapse (1). More-instantaneous effects, much more poorly resolved, include seismic disturbances (5–7) and the triggering of seiches (harmonic waves that can develop in large bodies of water) and megatsunami (8–10). Some of the most visually apparent disturbances are the tsunami/seiches recorded in high-energy sediment packages up to 9 m thick in marine deposits throughout the Gulf Coastal Plain and Caribbean (8–10). It is problematic, however, to trace their geographic extent in the Western Interior Seaway (WIS) because the terminal-Cretaceous geologic record for that depositional system is not preserved. In addition, evidence of onshore inundation by Chicxulub tsunami is thus-far unknown.

Regrettably, in the geologic record, there is a lack of coeval records with high temporal resolution on the scale of minutes to hours. Consequently, and despite voluminous previous work on the Chicxulub impact, a full understanding of the effects and ecological impact during the first hours or days postimpact has not been resolved. Here, we report the Tanis site, which documents a turbulently deposited, rapidly emplaced sediment package directly overlain by the Cretaceous–Paleogene (KPg) boundary tonstein. The site, situated in the continental Hell Creek Formation in southwestern North Dakota (Fig. 1), displays inland-directed flow indicators and holds a mixture of Late Cretaceous marine and continental biota, implying that its emplacement is related to sudden onshore inundation surges. A suite of ejecta types, including ejecta spherules preserved within the deposit sediments (captured by the gills of fish entombed within the deposit and preserved as unaltered glassy spherules embedded in amber), indicate that deposition occurred shortly after a major bolide impact. Unaltered impact-melt glass exhibits a clear geochemical and geochronological link with the Chicxulub impact. A well-defined cap of iridium-bearing, fine-grained impactite tonstein directly overlying the deposit provides a well-constrained chronology—that is, after impact but before the finest ejecta settled—that can provide a detailed record of conditions shortly after the impact. The time frame indicated by the embedded ejecta and capping tonstein at Tanis overlaps with arrival times calculated for seismic waves generated by the Chicxulub impact, a peculiar coincidence that suggests the impact played a causative role in triggering the Tanis depositional event. Tanis is noteworthy in recording a brief period of time that directly followed (within tens of minutes to hours) the Chicxulub impact. Furthermore, the possibly impact-triggered depositional event is a phenomenon thus-far undocumented in continental facies. The Tanis site therefore provides another dimension to our understanding of how the Chicxulub impact could have affected life on Earth.

[rogue06]

A New York Times piece focused on the likelihood that bits of the Chicxulub asteroid were also found at the site. Since it's behind a paywall, I'll post the pertinent bit

Source: Shards of Asteroid That Killed the Dinosaurs May Have Been Found in Fossil Site

[...]



When the object hit Earth, carving a crater about 100 miles wide and nearly 20 miles deep, molten rock splashed into the air and cooled into spherules of glass, one of the distinct calling cards of meteor impacts. In the 2019 paper, Mr. DePalma and his colleagues described how spherules raining down from the sky clogged the gills of paddlefish and sturgeon, suffocating them.

Usually the outsides of impact spherules have been mineralogically transformed by millions of years of chemical reactions with water. But at Tanis, some of them landed in tree resin, which provided a protective enclosure of amber, keeping them almost as pristine as the day they formed.

In the latest findings, which have not yet been published in a peer-reviewed scientific journal, Mr. DePalma and his research colleagues focused on bits of unmelted rock within the glass.

“All these little dirty nuggets in there,” said Mr. DePalma, a graduate student at the University of Manchester in England and an adjunct professor at Florida Atlantic University. “Every single speck that takes away from this beautiful clear glass is a piece of debris.”

Finding amber-encased spherules, he said, was the equivalent of sending someone back in time to the day of the impact, “collecting a sample, bottling it up and preserving it for scientists right now.”

520502a5-4c76-45ff-a713-0707c64c798e.jpg
Fish fossils and Triceratops skin on display during the presentation
at the Goddard Space Flight Center on Wednesday.

Most of the rock bits contain high levels of strontium and calcium -- indications that they were part of the limestone crust where the meteor hit.

But the composition of fragments within two of the spherules were “wildly different,” Mr. DePalma said.

“They were not enriched with calcium and strontium as we would have expected,” he said.

Instead they contained higher levels of elements like iron, chromium and nickel. That mineralogy points to the presence of an asteroid, and in particular a type known as carbonaceous chondrites.

“To see a piece of the culprit is just a goose-bumpy experience,” Mr. DePalma said.

The finding supports a discovery reported in 1998 by Frank Kyte, a geochemist at the University of California, Los Angeles. Dr. Kyte said he had found a fragment of the meteor in a core sample drilled off Hawaii, more than 5,000 miles from Chicxulub. Dr. Kyte said that fragment, about a tenth of an inch across, came from the impact event, but other scientists were skeptical that any bits of the meteor could have survived.

“It actually falls in line with what Frank Kyte was telling us years ago,” Mr. DePalma said.


Source

© Copyright Original Source

[Bill the Cat]

Why did I think this was talking about one of the NSA?

[shunyadragon]

I have read of this concerning the articulated leg, but thank you for the comprehensive references.

[rogue06]

Why did I think this was talking about one of the NSA?

The earliest squirrel dates back to roughly 36 mya -- although rodent squirrel-like ancestors date back to nearly 40 mya. Chicxulub occurred 66 mya (give or take a couple weeks).

IOW, while Master Po is indeed venerable, he ain't that old.

And there is no "u", "l" or "b" in the squirrel alphabet