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How predatory plankton created modern ecosystems after ‘Snowball Earth’

Grand Canyon
Grand Canyon (stock image). Max Planck researchers found 635 million year-old molecules in rock samples from the Grand Canyon, most likely from predatory plankton. The microorganisms probably prepared the soil for today’s ecosystems after the earth thawed again after a phase of complete glaciation. Credit: Bon / Fotolia

Around 635 to 720 million years ago, during Earth’s most severe glacial period, Earth was twice almost completely covered by ice, according to current hypotheses. The question of how life survived these ‘Snowball Earth’ glaciations, lasting up to about 50 million years, has puzzled scientists for many decades. An international team, led by Dutch and German researchers of the Max Planck Society, now found the first detailed glimpse of life after the ‘Snowball’ in the form of newly discovered ancient molecules, buried in old rocks.

“All higher animal life forms, including us humans, produce cholesterol. Algae and bacteria produce their own characteristic fat molecules,” says first author Lennart van Maldegem from Max Planck Institute (MPI) for Biogeochemistry, who recently moved to the Australian National University in Canberra, Australia. “Such fat molecules can survive in rocks for millions of years, as the oldest (chemical) remnants of organisms, and tell us now what type of life thrived in the former oceans long ago.”

But the fossil fats the researchers recently discovered in Brazilian rocks, deposited just after the last Snowball glaciation, were not what they suspected. “Absolutely not,” says team-leader Christian Hallmann from MPI for Biogeochemistry. “We were completely puzzled, because these molecules looked quite different from what we’ve ever seen before!”

Using sophisticated separation techniques, the team managed to purify minuscule amounts of the mysterious molecule and identify its structure by nuclear magnetic resonance in the NMR department of Christian Griesinger at Max Planck Institute for Biophysical Chemistry. “This is highly remarkable itself,” according to Klaus Wolkenstein from MPI for Biophysical Chemistry and the Geoscience Centre of the University of Göttingen. “Never has a structure been elucidated with such a small amount of such an old molecule.” The structure was chemically identified as 25,28-bisnorgammacerane — abbreviated as BNG, as van Maldegem suggests.

Fossil fats most likely from heterotropic plankton

Yet the origin of the compound remained enigmatic. “We of course looked if we could find it elsewhere,” says van Maldegem, who then studied hundreds of ancient rock samples, with rather surprising success. “In particular the Grand Canyon rocks really were an eye-opener,” says Hallmann. Although nowadays mostly sweltering hot, these rocks had also been buried under kilometres of glacial ice around 700 million years ago. Detailed additional analyses of molecules in Grand Canyon rocks — including presumed BNG-precursors, the distribution of steroids and stable carbon isotopic patterns — led the authors to conclude that the new BNG molecule most likely derives from heterotrophic plankton, marine microbes that rely on consuming other organisms for gaining energy. “Unlike for example green algae that engage in photosynthesis and thus belong to autotrophic organisms, these heterotrophic microorganisms were true predators that gained energy by hunting and devouring other algae and bacteria,” according to van Maldegem.

Predatory species create room for algae and other plankton

While predation is common amongst plankton in modern oceans, the discovery that it was so prominent 635 million years ago, exactly after the Snowball Earth glaciation, is a big deal for the science community. “Parallel to the occurrence of the enigmatic BNG molecule we observe the transition from a world whose oceans contained virtually only bacteria, to a more modern Earth system containing many more algae. We think that massive predation helped to ‘clear’ out the bacteria-dominated oceans and make space for algae,” says van Maldegem. The resulting more complex feeding networks provided the dietary requirements for larger, more intricate lifeforms to evolve — including the lineages that all animals, and eventually we humans, derive from. The massive onset of predation probably played a crucial role in the transformation of our planet and its ecosystems to its present state.

Reference:
Lennart M. van Maldegem, Pierre Sansjofre, Johan W. H. Weijers, Klaus Wolkenstein, Paul K. Strother, Lars Wörmer, Jens Hefter, Benjamin J. Nettersheim, Yosuke Hoshino, Stefan Schouten, Jaap S. Sinninghe Damsté, Nilamoni Nath, Christian Griesinger, Nikolay B. Kuznetsov, Marcel Elie, Marcus Elvert, Erik Tegelaar, Gerd Gleixner, Christian Hallmann. Bisnorgammacerane traces predatory pressure and the persistent rise of algal ecosystems after Snowball Earth. Nature Communications, 2019; 10 (1) DOI: 10.1038/s41467-019-08306-x

Note: The above post is reprinted from materials provided by Max-Planck-Gesellschaft.

Earth’s continental nurseries discovered beneath mountains

The central Andes Mountains and surrounding landscape, as seen in this true-color image from NASA’s Terra spacecraft, formed over the past 170 million years as the Nazca Plate lying under the Pacific Ocean has forced its way under the South American Plate. Credit: NASA
The central Andes Mountains and surrounding landscape, as seen in this true-color image from NASA’s Terra spacecraft, formed over the past 170 million years as the Nazca Plate lying under the Pacific Ocean has forced its way under the South American Plate. Credit: NASA

In his free time last summer, Rice University geoscientist Ming Tang made a habit of comparing the niobium content in various rocks in a global minerals database. What he found was worth skipping a few nights out with friends.

In a paper published this month by Nature Communications, Tang, Rice petrologist Cin-Ty Lee and colleagues offered an answer to one of Earth science’s fundamental questions: Where do continents form?

“If our conclusions are correct, every piece of land that we are now sitting on got its start someplace like the Andes or Tibet, with very mountainous surfaces,” said Tang, lead author of the study and a postdoctoral research associate in Rice’s Department of Earth, Environmental and Planetary Sciences (EEPS). “Today, most places are flat because that is the stable stage of the continental crust. But what we found was that when the crust formed, it had to start out with mountain-building processes.”

The connection between niobium, one of Earth’s rarest elements, and continent formation is a story that plays out over billions of years at scales as small as molecules and as large as mountain ranges. The leading players are niobium and tantalum, rare metals so alike that geologists often think of them as twins.

“They have very similar chemical properties and behave almost identically in most geological processes,” Tang said. “If you measure tantalum and niobium, you find that their ratio is nearly constant in Earth’s mantle. That means that when you find more niobium in a rock, you will find more tantalum, and when you find less niobium, you will find less tantalum.”

The mantle is Earth’s thickest layer, spanning about 1,800 miles between the planet’s core and its thin outer crust. Earth scientists believe that little, if anything, moves between the mantle and core, but the mantle and everything above it — seafloor, oceans, continents and atmosphere — are connected, and many of the atoms on Earth’s surface today, including the atoms in humans and other living things, have cycled through the mantle one or more times in Earth’s 4.6 billion years.

The rocks in continents are an exception. Geologists have found some that are up to 4 billion years old, which means they were formed near the surface and stayed on the surface, without being recycled into the mantle. That’s due in part to the nature of continental crust, which is far less dense than the basaltic rocks beneath Earth’s oceans. Lee, professor and EEPS department chair, said it’s no coincidence that Earth is the only rocky planet known to have both continents and life.

“Every day we live on continents, and we take most of our resources from continents,” Lee said. “We have oxygen in the air to breath and just the right temperature to support complex life. These things are so common that we take them for granted, but Earth didn’t start off with these conditions. They developed later in Earth’s history. And the emergence of continents is one of the things that shaped our planet and made it more livable.”

Scientists still lack details about how continents got their start and how they grew to cover 30 percent of Earth’s surface, but one big clue relates to niobium and tantalum, the geochemical twins.

“On average, the rocks in continental crust have about 20 percent less niobium than they should compared to the rock we see everywhere else,” Tang said. “We believe this missing niobium is tied to the mystery of continents. By solving or finding the missing the niobium, we can get important information about how continents form.”

Geologists have known about the imbalance for decades. And it certainly suggests that the geochemical processes that produce continental crust also remove niobium. But where was the missing niobium?

That nagging question prompted Tang to spend his free time perusing records in the Max Planck Institute’s GEOROC database, a comprehensive global collection of published analyses of volcanic rocks.

Based on those searches and months of follow-up tests, Tang, Lee and colleagues offer the first physical evidence that “arclogites” (pronounced ARC-loh-jyts) are responsible for the missing niobium. Arclogites are cumulates, the leftover dross that accumulates near the base of continental arcs. On rare occasions, chunks of these cumulates erupt onto the surface from volcanos.

The Rice group first sent arclogite samples that Lee had collected in Arizona to their collaborator, Kang Chen, a research fellow based at the China University of Geosciences in Wuhan. Chen spent a month getting precise readings of the relative amounts of niobium and tantalum in the samples. The rocks were created when the High Sierras were an active continental arc, like the Andes today.

Chen’s tests confirmed high niobium-tantalum ratios, but to better understand the mechanism by which this signature was developed, Tang and Lee used high precision laser ablation and “inductively coupled plasma mass spectrometry” in Lee’s laboratory at Rice to reveal the mineral rutile was responsible.

“Rutile is the mineral that hosts the niobium,” he said. “It’s a naturally occurring form of titanium oxide, and it is what actually ‘sees’ the difference between niobium and tantalum and captures one more than the other.”

But that happens only under specific conditions. For example, Tang said that at temperatures above 1,000 degrees Celsius, rutile traps normal ratios of tantalum and niobium. It only begins to prefer niobium when temperatures drop below 1,000 degrees Celsius. Tang said the only known place with that set of conditions is deep beneath continental arcs, like the Andes today or the High Sierras about 80 million years ago.

“The reason you need high pressure is that titanium oxide is relatively rare,” he said. “You need very high pressure to force it to crystalize and fall out of the magma.”

In an earlier arclogite study published in Science Advances last May, Tang and Lee discovered a subtle chemical signature that can explain why continental crust is iron-depleted. Lee said that finding and the discovery about rutile and niobium illustrate the central importance of continental arcs in Earth history.

“Continental arcs are like a magic system that links everything together, from climate and oxygen concentrations in the atmosphere to ore deposits,” Lee said. “They’re a sink for carbon dioxide after they die. They can drive greenhouse or icehouse, and they are the building blocks of continents.”

Reference:
Ming Tang, Cin-Ty A. Lee, Kang Chen, Monica Erdman, Gelu Costin, Hehe Jiang. Nb/Ta systematics in arc magma differentiation and the role of arclogites in continent formation. Nature Communications, 2019; 10 (1) DOI: 10.1038/s41467-018-08198-3

Note: The above post is reprinted from materials provided by Rice University. Original written by Jade Boyd.

Iguana-sized dinosaur cousin discovered in Antarctica

A slab containing fossils of Antarctanax. Credit: Copyright Brandon Peecook, Field Museum
A slab containing fossils of Antarctanax. Credit: Copyright Brandon Peecook, Field Museum

Antarctica wasn’t always a frozen wasteland — 250 million years ago, it was covered in forests and rivers, and the temperature rarely dipped below freezing. It was also home to diverse wildlife, including early relatives of the dinosaurs. Scientists have just discovered the newest member of that family — an iguana-sized reptile whose name means “Antarctic king.”

“This new animal was an archosaur, an early relative of crocodiles and dinosaurs,” says Brandon Peecook, a Field Museum researcher and lead author of a paper in the Journal of Vertebrate Paleontology describing the new species. “On its own, it just looks a little like a lizard, but evolutionarily, it’s one of the first members of that big group. It tells us how dinosaurs and their closest relatives evolved and spread.”

The fossil skeleton is incomplete, but paleontologists still have a good feel for the animal, named Antarctanax shackletoni (the former means “Antarctic king,” the latter is a nod to polar explorer Ernest Shackleton). Based on its similarities to other fossil animals, Peecook and his coauthors (Roger Smith of the University of Witwatersrand and the Iziko South African Museum and Christian Sidor of the Burke Museum and University of Washington) surmise that Antarctanax was a carnivore that hunted bugs, early mammal relatives, and amphibians.

The most interesting thing about Antarctanax, though, is where it lived, and when. “The more we find out about prehistoric Antarctica, the weirder it is,” says Peecook, who is also affiliated with the Burke Museum. “We thought that Antarctic animals would be similar to the ones that were living in southern Africa, since those landmasses were joined back then. But we’re finding that Antarctica’s wildlife is surprisingly unique.”

About two million years before Antarctanax lived — the blink of an eye in geologic time — Earth underwent its biggest-ever mass extinction. Climate change, caused by volcanic eruptions, killed 90% of all animal life. The years immediately after that extinction event were an evolutionary free-for-all — with the slate wiped clean by the mass extinction, new groups of animals vied to fill the gaps. The archosaurs, including dinosaurs, were one of the groups that experienced enormous growth. “Before the mass extinction, archosaurs were only found around the Equator, but after it, they were everywhere,” says Peecook. “And Antarctica had a combination of these brand-new animals and stragglers of animals that were already extinct in most places — what paleontologists call ‘dead clades walking.’ You’ve got tomorrow’s animals and yesterday’s animals, cohabiting in a cool place.”

The fact that scientists have found Antarctanax helps bolster the idea that Antarctica was a place of rapid evolution and diversification after the mass extinction. “The more different kinds of animals we find, the more we learn about the pattern of archosaurs taking over after the mass extinction,” notes Peecook.

“Antarctica is one of those places on Earth, like the bottom of the sea, where we’re still in the very early stages of exploration,” says Peecook. “Antarctanax is our little part of discovering the history of Antarctica.”

Reference:
Brandon R. Peecook, Roger M. H. Smith, Christian A. Sidor. A novel archosauromorph from Antarctica and an updated review of a high-latitude vertebrate assemblage in the wake of the end-Permian mass extinction. Journal of Vertebrate Paleontology, 2019; 1 DOI: 10.1080/02724634.2018.1536664

Note: The above post is reprinted from materials provided by Field Museum.

Long-necked dinosaurs rotated their forefeet to the side

These are well preserved footprints of the find site in Morocco, with clearly visible claw impressions. Credit: The Society of Vertebrate Paleontology
These are well preserved footprints of the find site in Morocco, with clearly visible claw impressions. Credit: The Society of Vertebrate Paleontology

Long-necked dinosaurs (sauropods) could orient their forefeet both forward and sideways. The orientation of their feet depended on the speed and centre of mass of the animals. An international team of researchers investigated numerous dinosaur footprints in Morocco at the foot of the Atlas Mountains using state-of-the-art methods. By comparing them with other sauropods tracks, the scientists determined how the long-necked animals moved forward. The results have now been published in the Journal of Vertebrate Paleontology.

“Long-necked dinosaurs” (sauropods) were among the most successful herbivores of the Mesozoic Era — the age of the dinosaurs. Characteristic for this group were a barrel-shaped body on columnar legs as well as an extremely long neck, which ended in a relatively small head. Long-necked dinosaurs existed from about 210 to 66 million years ago — they thus had been able to assert themselves on earth for a very long period. Also their gigantism, with which they far surpassed other dinosaurs, points at their success.

Sauropods included the largest land animals in Earth history, some over 30 metres long and up to 70 tonnes in weight. “However, it is still unclear how exactly these giants moved,” says Jens Lallensack, paleontologist at the Institute of Geosciences and Meteorology at the University of Bonn in Germany. The limb joints were partly cartilaginous and therefore not fossilised, allowing only limited conclusions about the range of movement.

Detective work with 3D computer analyses

The missing pieces of the puzzle, however, can be reconstructed with the help of fossil footprints of the giants. An international team of researchers from Japan, Morocco and Germany, led by the University of Bonn, has now investigated an unique track site in Morocco at the foot of the Atlas Mountains. The site consists of a surface of 54 x 6 metres which was vertically positioned during mountain formation and shows hundreds of individual footprints, some of which overlap. A part of these footprints could be assigned to a total of nine trackways (sequences of individual footprints). “Working out individual tracks from this jumbled mess of footprints was detective work and only possible through the analysis of high-resolution 3D models on the computer,” says Dr. Oliver Wings of the Zentralmagazin Naturwissenschaftlicher Sammlungen der Martin-Luther-Universität Halle-Wittenberg in Germany.

The researchers were amazed by the results: the trackways are extremely narrow — the right and left footprints are almost in line. Also, the forefoot impressions are not directed forwards, as is typical for sauropod tracks, but point to the side, and sometimes even obliquely backwards. Even more: The animals were able to switch between both orientations as needed. “People are able to turn their palms downwards by crossing the ulna and radius,” says Dr. Michael Buchwitz of the Museum für Naturkunde Magdeburg. However, this complicated movement is limited to mammals and chameleons in today’s terrestrial vertebrates. It was not possible in other animals, including dinosaurs. Sauropods must therefore have found another way of turning the forefoot forwards.

How can the rotation of the forefoot be explained?

How can the rotation of the forefoot in the sauropod tracks be explained? The key probably lies in the mighty cartilage layers, which allowed great flexibility in the joints, especially in the shoulder. But why were the hands rotated outwards at all? “Outwardly facing hands with opposing palms were the original condition in the bipedal ancestors of the sauropods,” explains Shinobu Ishigaki of the Okayama University of Science, Japan. The question should therefore be why most sauropods turned their forefeet forwards — an anatomically difficult movement to implement.

A statistical analysis of sauropod tracks from all over the world could provide important clues: Apparently the animals tended to have outwardly directed forefeet when the foreleg was not used for active locomotion but only for carrying body weight. Thus the forefeet were often rotated further outwards when the animal moved slowly and the centre of mass of the body was far back. Only if the hands were also used for the forward drive, a forefoot directed to the front was advantageous. The analysis furthermore showed that the outer rotation of the forefeet was limited to smaller individuals, whereas in larger animals they were mostly directed forward. The large animals apparently could no longer rotate their forefeet sideways. “This loss of mobility was probably a direct result of their gigantism,” says Lallensack.

Reference:
Jens N. Lallensack, Shinobu Ishigaki, Abdelouahed Lagnaoui, Michael Buchwitz, Oliver Wings. Forelimb Orientation and Locomotion of Sauropod Dinosaurs: Insights from the ?Middle Jurassic Tafaytour Tracksites (Argana Basin, Morocco). Journal of Vertebrate Paleontology, 2019; 1 DOI: 10.1080/02724634.2018.1512501

Note: The above post is reprinted from materials provided by University of Bonn.

Fault lines are no barrier to safe storage of CO2 below ground

Carbon dioxide emissions can be securely stored in underground rocks, with minimal possibility of the gas escaping from fault lines back into the atmosphere, research by the University of Edinburgh has shown. Credit: Johannes Miocic
Carbon dioxide emissions can be securely stored in underground rocks, with minimal possibility of the gas escaping from fault lines back into the atmosphere, research by the University of Edinburgh has shown. Credit: Johannes Miocic

Carbon dioxide emissions can be captured and securely stored in underground rocks, even if geological faults are present, research has confirmed.

There is minimal possibility of the gas escaping from fault lines back into the atmosphere, the study has shown.

The findings are further evidence that an emerging technology known as Carbon Capture and Storage (CCS), in which CO2 gas emissions from industry are collected and transported for underground storage, is reliable.

Such an approach can reduce emissions of CO2 and help to limit the impact of climate change. If widely adopted, CCS could help meet targets set by the 2015 UN Paris Agreement, which seeks to limit climate warming to below 2C compared with pre-industrial levels.

The latest findings, from tests on a naturally occurring CO2 reservoir, may address public concerns over the proposed long-term storage of carbon dioxide in depleted gas and oil fields.

Scientists from the Universities of Edinburgh, Freiburg, Glasgow and Heidelberg studied a natural CO2 repository in Arizona, US, where gas migrates through geological faults to the surface.

Researchers used chemical analysis to calculate the amount of gas that had escaped the underground store over almost half a million years.

They found that a very small amount of carbon dioxide escaped the site each year, well within the safe levels needed for effective storage.

The study, published in Scientific Reports, was supported by the European Union and Natural Environment Research Council.

Dr Stuart Gilfillan, of the University of Edinburgh’s School of GeoSciences, who jointly led the study, said: “This shows that even sites with geological faults are robust, effective stores for CO2. This find significantly increases the number of sites around the world that may be suited to storage of this harmful greenhouse gas.”

Dr Johannes Miocic, of the University of Freiburg, who jointly led the study, said: “The safety of carbon dioxide storage is crucial for successful widespread implementation of much-needed carbon capture and storage technology. Our research shows that even imperfect sites can be secure stores for hundreds of thousands of years.”

Reference:
Johannes M. Miocic, Stuart M. V. Gilfillan, Norbert Frank, Andrea Schroeder-Ritzrau, Neil M. Burnside, R. Stuart Haszeldine. 420,000 year assessment of fault leakage rates shows geological carbon storage is secure. Scientific Reports, 2019; 9 (1) DOI: 10.1038/s41598-018-36974-0

Note: The above post is reprinted from materials provided by University of Edinburgh.

Scientists reconstruct ancient lost plates under Andes mountains

University of Houston researchers John Suppe, left, Jonny Wu and Yi-Wei Chen have reconstructed the ancient plates under the Andes Mountains. Credit: University of Houston
University of Houston researchers John Suppe, left, Jonny Wu and Yi-Wei Chen have reconstructed the ancient plates under the Andes Mountains. Credit: University of Houston

The Andes Mountains are the longest continuous mountain range in the world, stretching about 7,000 kilometers, or 4,300 miles, along the western coast of South America.

The Andean margin, where two tectonic plates meet, has long been considered the textbook example of a steady, continuous subduction event, where one plate slipped under another, eventually forming the mountain range seen today.

In a paper published in the journal Nature, geologists from the University of Houston demonstrate the reconstruction of the subduction of the Nazca Ocean plate, the remnants of which are currently found down to 1,500 kilometers, or about 900 miles, below the Earth’s surface.

Their results show that the formation of the Andean mountain range was more complicated than previous models suggested.

“The Andes Mountain formation has long been a paradigm of plate tectonics,” said Jonny Wu, assistant professor of geology at UH and a co-author of the paper.

When tectonic plates move under the Earth’s crust and enter the mantle, they do not disappear. Rather, they sink toward the core, like leaves sinking to the bottom of a lake. As these plates sink, they retain some of their shape, offering glimpses of what the Earth’s surface looked like millions of years ago.

These plate remnants can be imaged, similar to the way CT scans allow doctors to see inside of a patient, using data gleaned from earthquake waves.

“We have attempted to go back in time with more accuracy than anyone has ever done before. This has resulted in more detail than previously thought possible,” Wu said. “We’ve managed to go back to the age of the dinosaurs.”

Nazca Plate Subduction

The paper describes the deepest and oldest plate remnants reconstructed to date, with plates dating back to the Cretaceous Period.

“We found indications that when the slab reached the transition zone, it created signals on the surface,” said Yi-Wei Chen, a PhD geology student in the UH College of Natural Sciences and Mathematics and first author on the paper. A transition zone is a discontinuous layer in the Earth’s mantle, one which, when a sinking plate hits it, slows the plate’s movement, causing a build-up above it.

In addition to Wu and Chen, John Suppe, Distinguished Professor of Earth and Atmospheric Sciences at UH, is a co-author on the paper.

The researchers also found evidence for the idea that, instead of a steady, continuous subduction, at times the Nazca plate was torn away from the Andean margin, which led to volcanic activity. To confirm this, they modeled volcanic activity along the Andean margin.

“We were able to test this model by looking at the pattern of over 14,000 volcanic records along the Andes,” Wu said.

The work was conducted as part of the UH Center for Tectonics and Tomography, which is directed by Suppe.

“The Center for Tectonics and Tomography brings together experts from different fields in order to relate tomography, which is the imaging of the Earth’s interior from seismology, to the study of tectonics,” Wu said. “For example, the same techniques we use to explore for these lost plates are adapted from petroleum exploration techniques.”

Reference:
Yi-Wei Chen, Jonny Wu & John Suppe. Southward propagation of Nazca subduction along the Andes. Nature, 2019 DOI: 10.1038/s41586-018-0860-1

Note: The above post is reprinted from materials provided by University of Houston.

A reptile platypus from the early Triassic

Complete fossil and line drawing of Eretmorhipis carrolldongi.
Complete fossil and line drawing of Eretmorhipis carrolldongi. Related to the dolphin-like ichthyosaurs, Eretmorhipis evolved in a world devastated by the mass extinction event at the end of the Permian era. Credit: L. Cheng et al, Scientific Reports, Creative Commons 4.0

No animal alive today looks quite like a duckbilled platypus, but about 250 million years ago something very similar swam the shallow seas in what is now China, finding prey by touch with a cartilaginous bill. The newly discovered marine reptile Eretmorhipis carrolldongi from the lower Triassic period is described in the journal Scientific Reports Jan. 24.

Apart from its platypus-like bill, Eretmorhipis was about 70 centimeters long with a long rigid body, small head and tiny eyes, and four flippers for swimming and steering. Bony plates ran down the animal’s back.

Eretmorhipis was previously known only from partial fossils without a head, said Professor Ryosuke Motani, a paleontologist at the University of California, Davis Department of Earth and Planetary Sciences and coauthor on the paper.

“This is a very strange animal,” Motani said. “When I started thinking about the biology I was really puzzled.”

The two new fossils show the animal’s skull had bones that would have supported a bill of cartilage. Like the modern platypus, there is a large hole in the bones in the middle of the bill. In the platypus, the bill is filled with receptors that allow it to hunt by touch in muddy streams.

In the early Triassic, the area was covered by a shallow sea, about a meter deep, over a carbonate platform extending for hundreds of miles. Eretmorhipis fossils were found at what were deeper holes, or lagoons, in the platform. There are no fossils to show what Eretmorhipis ate, but it likely fed on shrimp, worms and other small invertebrates, Motani said.

Its long, bony body means that Eretmorhipis was probably a poor swimmer, Motani said.

“It wouldn’t survive in the modern world, but it didn’t have any rivals at the time,” he said.

Related to the dolphin-like ichthyosaurs, Eretmorhipis evolved in a world devastated by the mass extinction event at the end of the Permian era. The fossil provides more evidence of rapid evolution occurring during the early Triassic, Motani said.

Co-authors on the study are Long Cheng and Chun-bo Yan, Wuhan Centre of China Geological Survey, Wuhan; Da-yong Jiang, Peking University; Andrea Tintori, Università degli Studi di Milano, Italy; and Olivier Rieppel, The Field Museum, Chicago. The work was supported by grants from the China Geological Survey, the National Natural Science Foundation of China and the Ministry of Science and Technology.

Reference:
Long Cheng, Ryosuke Motani, Da-yong Jiang, Chun-bo Yan, Andrea Tintori, Olivier Rieppel. Early Triassic marine reptile representing the oldest record of unusually small eyes in reptiles indicating non-visual prey detection. Scientific Reports, 2019; 9 (1) DOI: 10.1038/s41598-018-37754-6

Note: The above post is reprinted from materials provided by University of California – Davis. Original written by Andy Fell.

Ancient carpet shark discovered with ‘spaceship-shaped’ teeth

One of the tiny fossilized teeth recovered from Galagadon, so named for the shape of its teeth, which resemble the spaceships in the video game Galaga. Credit: Copyright Terry Gates
One of the tiny fossilized teeth recovered from Galagadon, so named for the shape of its teeth, which resemble the spaceships in the video game Galaga. Credit: Copyright Terry Gates

The world of the dinosaurs just got a bit more bizarre with a newly discovered species of freshwater shark whose tiny teeth resemble the alien ships from the popular 1980s video game Galaga.

Unlike its gargantuan cousin the megalodon, Galagadon nordquistae was a small shark (approximately 12 to 18 inches long), related to modern-day carpet sharks such as the “whiskered” wobbegong. Galagadon once swam in the Cretaceous rivers of what is now South Dakota, and its remains were uncovered beside “Sue,” the world’s most famous T. rex fossil.

“The more we discover about the Cretaceous period just before the non-bird dinosaurs went extinct, the more fantastic that world becomes,” says Terry Gates, lecturer at North Carolina State University and research affiliate with the North Carolina Museum of Natural Sciences. Gates is lead author of a paper describing the new species along with colleagues Eric Gorscak and Peter J. Makovicky of the Field Museum of Natural History.

“It may seem odd today, but about 67 million years ago, what is now South Dakota was covered in forests, swamps and winding rivers,” Gates says. “Galagadon was not swooping in to prey on T. rex, Triceratops, or any other dinosaurs that happened into its streams. This shark had teeth that were good for catching small fish or crushing snails and crawdads.”

The tiny teeth — each one measuring less than a millimeter across — were discovered in the sediment left behind when paleontologists at the Field Museum uncovered the bones of “Sue,” currently the most complete T. rex specimen ever described. Gates sifted through the almost two tons of dirt with the help of volunteer Karen Nordquist, whom the species name, nordquistae, honors. Together, the pair recovered over two dozen teeth belonging to the new shark species.

“It amazes me that we can find microscopic shark teeth sitting right beside the bones of the largest predators of all time,” Gates says. “These teeth are the size of a sand grain. Without a microscope you’d just throw them away.”

Despite its diminutive size, Gates sees the discovery of Galagadon as an important addition to the fossil record. “Every species in an ecosystem plays a supporting role, keeping the whole network together,” he says. “There is no way for us to understand what changed in the ecosystem during the mass extinction at the end of the Cretaceous without knowing all the wonderful species that existed before.”

Gates credits the idea for Galagadon’s name to middle school teacher Nate Bourne, who worked alongside Gates in paleontologist Lindsay Zanno’s lab at the N.C. Museum of Natural Sciences.

Reference:
Terry A. Gates, Eric Gorscak, Peter J. Makovicky. New sharks and other chondrichthyans from the latest Maastrichtian (Late Cretaceous) of North America. Journal of Paleontology, 2019; 1 DOI: 10.1017/jpa.2018.92

Note: The above post is reprinted from materials provided by North Carolina State University.

Crocodiles have complex past

Representative Image

A new study throws into question the notion that today’s crocodiles and alligators have a simple evolutionary past.

Previous research has pointed to crocodiles and alligators starting with a land-based ancestor some 200 million years ago and then moving to fresh water, becoming the semi-aquatic ambush predators they are today.

But a new analysis, published online today in the journal Scientific Reports, offers a different story. Modern crocodiles and alligators came from a variety of surroundings beginning in the early Jurassic Period, and various species occupied a host of ecosystems over time, including land, estuarine, freshwater and marine.

As University of Iowa researcher and study co-author Christopher Brochu says, “Crocodiles are not living fossils. Transitions between land, sea, and freshwater were more frequent than we thought, and the transitions were not always land-to-freshwater or freshwater-to-marine.”

Brochu and colleagues from Stony Brook University pieced together crocodile and alligator ancestry by analyzing a large family tree showing the evolutionary history of living and extinct crocodylomorphs (modern crocodiles and alligators and their extinct relatives). The team was then able to predict the ancestral habitat for several divergence points on the evolutionary tree.

This suggests a complex evolutionary history not only of habitat, but of form. Those living at sea had paddles instead of limbs, and those on land often had hoof-like claws and long legs. These did not all evolve from ancestors that looked like modern crocodiles, as has long been assumed.

Reference:
Eric W. Wilberg, Alan H. Turner, Christopher A. Brochu. Evolutionary structure and timing of major habitat shifts in Crocodylomorpha. Scientific Reports, 2019; 9 (1) DOI: 10.1038/s41598-018-36795-1

Note: The above post is reprinted from materials provided by University of Iowa.

Fossilized slime of 100-million-year-old hagfish shakes up vertebrate family tree

Tethymyxine tapirostrum, is a 100-million-year-old, 12-inch long fish embedded in a slab of Cretaceous period limestone from Lebanon, believed to be the first detailed fossil of a hagfish.
Tethymyxine tapirostrum, is a 100-million-year-old, 12-inch long fish embedded in a slab of Cretaceous period limestone from Lebanon, believed to be the first detailed fossil of a hagfish. Credit: Tetsuto Miyashita, University of Chicago

Paleontologists at the University of Chicago have discovered the first detailed fossil of a hagfish, the slimy, eel-like carrion feeders of the ocean. The 100-million-year-old fossil helps answer questions about when these ancient, jawless fish branched off the evolutionary tree from the lineage that gave rise to modern-day jawed vertebrates, including bony fish and humans.

The fossil, named Tethymyxine tapirostrum,is a 12-inch long fish embedded in a slab of Cretaceous period limestone from Lebanon. It fills a 100-million-year gap in the fossil record and shows that hagfish are more closely related to the blood-sucking lamprey than to other fishes. This means that both hagfish and lampreys evolved their eel-like body shape and strange feeding systems after they branched off from the rest of the vertebrate line of ancestry about 500 million years ago.

“This is a major reorganization of the family tree of all fish and their descendants. This allows us to put an evolutionary date on unique traits that set hagfish apart from all other animals,” said Tetsuto Miyashita, PhD, a Chicago Fellow in the Department of Organismal Biology and Anatomy at UChicago who led the research. The findings are published this week in the Proceedings of the National Academy of Sciences.

The slimy dead giveaway

Modern-day hagfish are known for their bizarre, nightmarish appearance and unique defense mechanism. They don’t have eyes, or jaws or teeth to bite with, but instead use a spiky tongue-like apparatus to rasp flesh off dead fish and whales at the bottom of the ocean. When harassed, they can instantly turn the water around them into a cloud of slime, clogging the gills of would-be predators.

This ability to produce slime is what gave away the Tethymyxine fossil. Miyashita used an imaging technology called synchrotron scanning at Stanford University to identify chemical traces of soft tissue that were left behind in the limestone when the hagfish fossilized. These soft tissues are rarely preserved, which is why there are so few examples of ancient hagfish relatives to study.

The scanning picked up a signal for keratin, the same material that makes up fingernails in humans. Keratin, as it turns out, is a crucial part of what makes the hagfish slime defense so effective. Hagfish have a series of glands along their bodies that produce tiny packets of tightly-coiled keratin fibers, lubricated by mucus-y goo. When these packets hit seawater, the fibers explode and trap the water within, turning everything into shark-choking slop. The fibers are so strong that when dried out they resemble silk threads; they’re even being studied as possible biosynthetic fibers to make clothes and other materials.

Miyashita and his colleagues found more than a hundred concentrations of keratin along the body of the fossil, meaning that the ancient hagfish probably evolved its slime defense when the seas included fearsome predators such as plesiosaurs and ichthyosaurs that we no longer see today.

“We now have a fossil that can push back the origin of the hagfish-like body plan by hundreds of millions of years,” Miyashita said. “Now, the next question is how this changes our view of the relationships between all these early fish lineages.”

Shaking up the vertebrate family tree

Features of the new fossil help place hagfish and their relatives on the vertebrate family tree. In the past, scientists have disagreed about where they belonged, depending on how they tackled the question. Those who rely on fossil evidence alone tend to conclude that hagfish are so primitive that they are not even vertebrates. This implies that all fishes and their vertebrate descendants had a common ancestor that — more or less — looked like a hagfish.

But those who work with genetic data argue that hagfish and lampreys are more closely related to each other. This suggests that modern hagfish and lampreys are the odd ones out in the family tree of vertebrates. In that case, the primitive appearance of hagfish and lampreys is deceptive, and the common ancestor of all vertebrates was probably something more conventionally fish-like.

Miyashita’s work reconciles these two approaches, using physical evidence of the animal’s anatomy from the fossil to come to the same conclusion as the geneticists: that the hagfish and lampreys should be grouped separately from the rest of fishes.

“In a sense, this resets the agenda of how we understand these animals,” said Michael Coates, PhD, professor of organismal biology and anatomy at UChicago and a co-author of the new study. “Now we have this important corroboration that they are a group apart. Although they’re still part of vertebrate biodiversity, we now have to look at hagfish and lampreys more carefully, and recognize their apparent primitiveness as a specialized condition.

Paleontologists have increasingly used sophisticated imaging techniques in the past few years, but Miyashita’s research is one of a handful so far to use synchrotron scanning to identify chemical elements in a fossil. While it was crucial to detect anatomical structures in the hagfish fossil, he believes it can also be a useful tool to help scientists detect paint or glue used to embellish a fossil or even outright forge a specimen. Any attempt to spice up a fossil specimen leaves chemical fingerprints that light up like holiday decorations in a synchrotron scan.

“I’m impressed with what Tetsuto has marshaled here,” Coates said. “He’s maxed out all the different techniques and approaches that can be applied to this fossil to extract information from it, to understand it and to check it thoroughly.”

The study, “A Hagfish from the Cretaceous Tethys Sea and a Reconciliation of the Morphological-Molecular Conflict in Early Vertebrate Phylogeny,” was supported by the National Science Foundation and the National Science and Engineering Research Council (Canada). Additional authors include Robert Farrar and Peter Larson from the Black Hills Institute of Geological Research; Phillip Manning and Roy Wogelius from the University of Manchester; Nicholas Edwards and Uwe Bergmann from the SLAC National Accelerator Laboratory; Jennifer Anné from the Children’s Museum of Indianapolis; and Richard Palmer and Philip Currie from the University of Alberta.

Note: The above post is reprinted from materials provided by University of Chicago Medical Center. Original written by Matt Wood.

Large volcanic eruption in Scotland may have contributed to prehistoric global warming

This is a false color electron-microscope image of a resorbed apatite crystal (green) in pitchstone glass (blue). The composition of the pitchstone glass and the characteristic mineral textures are identical in the studied pitchstone sites of the Sgùrr of Eigg and Òigh-sgeir, although over 30km apart, indicating a common origin, and thus a large and geographically widespread volcanic eruption. Credit: Valentin Troll
This is a false color electron-microscope image of a resorbed apatite crystal (green) in pitchstone glass (blue). The composition of the pitchstone glass and the characteristic mineral textures are identical in the studied pitchstone sites of the Sgùrr of Eigg and Òigh-sgeir, although over 30km apart, indicating a common origin, and thus a large and geographically widespread volcanic eruption. Credit: Valentin Troll

Around 56 million years ago, global temperatures spiked. Researchers at Uppsala University and in the UK now show that a major explosive eruption from the Red Hills on the Isle of Skye may have been a contributing factor to the massive climate disturbance. Their findings have been published in the journal Scientific Reports.

Large explosive volcanic eruptions can have lasting effects on climate and have been held responsible for severe climate effects in Earth’s history. One such event occurred around 56 million years ago when global temperatures increased by 5-8 °C. This event has been named the Paleocene-Eocene Thermal Maximum (PETM). The warm period was associated with volcanic activity in the North Atlantic region, especially in Greenland, the British Isles and the present day North Sea region. However, until now, no large-scale explosive eruptions had been confirmed in current-day Scotland.

A team of researchers at Uppsala University, Sweden, the Universities of Durham and St Andrews in the UK, and the Scottish Environmental Research Centre in Glasgow, now seem to have found a missing piece of the puzzle. By studying volcanic rocks called pitchstones from islands more than 30 kilometres apart in the Inner Hebrides off the west coast of Scotland, the researchers have found plausible evidence of a major eruption from what is today the Isle of Skye.

The researchers used several different methods to compare the pitchstones recovered from the two sites (Sgùrr of Eigg and Òigh-sgeir) including isotope geochemistry. Samples from the two pitchstone outcrops display identical textures and compositions in all analyses, confirming that the two outcrops represent deposits of a single, massive and explosive volcanic eruption. The researcher’s geochemical data identify the Red Hills on Skye, around 40 kilometres to the North, as the most likely vent area for this large eruption. Using this vent location, a reconstruction estimates the eruption to have been similar in magnitude to the infamous Krakatoa eruption of 1883, one of the deadliest and most destructive volcanic events in recorded history.

Earth scientists have long thought that the Scottish sector of the North Atlantic Volcanic province did not see any large explosive eruptions at the time of the PETM. This notion is now contradicted by the findings of the current study and the researchers conclude that large explosive volcanic events in the Scottish sector of the North Atlantic Volcanic Province were likely a major contributing factor to the climate disturbance of the PETM.

Around 56 million years ago, global temperatures spiked. Researchers at Uppsala University and in the UK now show that a major explosive eruption from the Red Hills on the Isle of Skye may have been a contributing factor to the massive climate disturbance. Their findings have been published in the journal Scientific Reports.

Large explosive volcanic eruptions can have lasting effects on climate and have been held responsible for severe climate effects in Earth’s history. One such event occurred around 56 million years ago when global temperatures increased by 5-8 °C. This event has been named the Paleocene-Eocene Thermal Maximum (PETM). The warm period was associated with volcanic activity in the North Atlantic region, especially in Greenland, the British Isles and the present day North Sea region. However, until now, no large-scale explosive eruptions had been confirmed in current-day Scotland.

A team of researchers at Uppsala University, Sweden, the Universities of Durham and St Andrews in the UK, and the Scottish Environmental Research Centre in Glasgow, now seem to have found a missing piece of the puzzle. By studying volcanic rocks called pitchstones from islands more than 30 kilometres apart in the Inner Hebrides off the west coast of Scotland, the researchers have found plausible evidence of a major eruption from what is today the Isle of Skye.

The researchers used several different methods to compare the pitchstones recovered from the two sites (Sgùrr of Eigg and Òigh-sgeir) including isotope geochemistry. Samples from the two pitchstone outcrops display identical textures and compositions in all analyses, confirming that the two outcrops represent deposits of a single, massive and explosive volcanic eruption. The researcher’s geochemical data identify the Red Hills on Skye, around 40 kilometres to the North, as the most likely vent area for this large eruption. Using this vent location, a reconstruction estimates the eruption to have been similar in magnitude to the infamous Krakatoa eruption of 1883, one of the deadliest and most destructive volcanic events in recorded history.

Earth scientists have long thought that the Scottish sector of the North Atlantic Volcanic province did not see any large explosive eruptions at the time of the PETM. This notion is now contradicted by the findings of the current study and the researchers conclude that large explosive volcanic events in the Scottish sector of the North Atlantic Volcanic Province were likely a major contributing factor to the climate disturbance of the PETM.

Reference:
Valentin R. Troll, C. Henry Emeleus, Graeme R. Nicoll, Tobias Mattsson, Robert M. Ellam, Colin H. Donaldson, Chris Harris. A large explosive silicic eruption in the British Palaeogene Igneous Province. Scientific Reports, 2019; 9 (1) DOI: 10.1038/s41598-018-35855-w

Note: The above post is reprinted from materials provided by Uppsala University.

International Chronostratigraphic Chart “Version 2018/08”

International Chronostratigraphic Chart “Version 2018/08”
International Chronostratigraphic Chart “Version 2018/08”

Click here (PDF or JPG) to download the latest version (v2018/08) of the International Chronostratigraphic Chart.

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New study quantifies deep reaction behind ‘superdeep’ diamonds

Diamond
The Cullinan Diamond, the largest gem-quality diamond found, was discovered in South Africa in 1905. Superdeep diamonds have been uncovered at the same mine. Credit: Public Domain

Whether they are found in an engagement ring or an antique necklace, diamonds usually generate quick reactions from their recipients. Now, new research shows deep inside the Earth, fast reactions between subducted tectonic plates and the mantle at specific depths may be responsible for generating the most valuable diamonds.

The diamonds mined most often around the world are formed in the Earth’s mantle at depths of around 150-250 kilometers (93-155 miles). They are created by extreme pressure and temperature of at least 1050 degrees Celsius (1922 degrees Fahrenheit). Only a small amount of these diamonds make it to mineable regions since most are destroyed in the process of reaching the Earth’s crust via deep source volcanic eruptions.

But a tiny portion of mined diamonds, called sub-lithospheric or superdeep diamonds, are formed at much deeper depths than others, mostly in two rich zones at depths of 250-450 kilometers (155-279 miles) and 600-800 kilometers (372-497 miles). These diamonds stand out from others due to their compositions, which occasionally include materials from the deep Earth like majorite garnet, ferropericlase and bridgmanite.

“Although only composing 1 percent of the total mined diamonds, it seems lots of large and high-purity diamonds are superdeep diamonds, so they have good value as gems,” said Feng Zhu the lead author of the new study in Geophysical Research Letters, a journal of the American Geophysical Union, who was a post-doctoral geology researcher at the University of Michigan when he performed the research.

No previous theory has completely explained the reason why very few diamonds have been found near the surface from the area at depths of 450-600 kilometers (372-497 miles) – the region between the zones where most superdeep diamonds are formed.

The new study seeks to explain this phenomenon. Zhu, now a post-doctoral researcher at the University of Hawai’i, and his colleagues believe the two superdeep areas where diamonds are formed are rich in the gems due to high production rates. The new study explains what drives the diamond-producing reaction in some areas and what slows it down in other areas.

Diamond formation

According to the authors, diamonds can form anywhere in the mantle, which extends from about 35 to 2,890 kilometers (21-1,800 miles) below the Earth’s surface. However, humans rarely see most of the diamonds formed. Very few diamonds survive the volcanic trip to the Earth’s crust where we can sample them.

That means the chances of finding diamonds from deep regions in the mantle, which produce relatively few of the gems, is extremely small. Only 1 percent of mined diamonds come from superdeep regions.

“In our hypothesis, the production of diamonds at any depth in the mantle is possible, it’s just the production rate is different, so they have a different chance to be sampled in the crust,” Zhu said.

Creating diamonds

In order to mimic the extreme pressures experienced deep inside planets, the study’s authors used diamond anvil cells and a 1,000-ton multi-anvil apparatus at the University of Michigan. Both these devices allow researchers to compress sub-millimeter-sized material in extreme pressures. They compressed magnesium carbonate powder with iron foil in extreme heats and managed to create minuscule diamond grains visible through scanning electron microscopes.

They found that when conditions are right, diamond grains can form as quickly as every couple of minutes, and never took longer than a few hours to form, although the growth of gem diamonds may take much longer time in an actual melting fluid environment.

In the shallower region rich in superdeep diamond formation, 250-450 kilometers (155-279 miles) down, a subducting tectonic plate pushes under the Earth’s mantle. This supplies plenty of carbonate, which creates “factories on a conveyor belt” for diamonds when combined with the iron from the mantle, the authors said.

High temperatures promote reactions which form diamonds, but pressure does the opposite. At depths roughly 475 kilometers (295 miles) below the surface, the pressure increases, and the reactions slow down drastically, the authors said. That’s why few diamonds are found near the Earth surface coming from between 450-600 kilometers (372-497 miles).

“When your pressure reaches the diamond stable region, it will form. But when you increase pressure it will form at lower rates. You have a trade off there,” Zhu said.

One exception to this rule is in the deeper region of 600-800 kilometers (372-497 miles) beneath the surface. In this region, accumulation of carbonate due to the stagnation of tectonic slabs pushing downwards makes up for the overdose in pressure. So while the reactions slow down, higher temperatures and an abundance of carbonate makes for a diamond-rich region.

Zhu said the new study adds to scientists’ understanding of the Earth’s mantle, about which relatively little is known for sure.

“Superdeep diamond inclusions bring us the only mineral samples from the Earth’s deep mantle,” he said. “Seeing is believing, and these inclusions provide a solid ground for the studies on the inaccessible mantle.”

Reference:
Feng Zhu et al. Kinetic control on the depth distribution of superdeep diamonds, Geophysical Research Letters (2018). DOI: 10.1029/2018GL080740

Note: The above post is reprinted from materials provided by American Geophysical Union.This story is republished courtesy of AGU Blogs (http://blogs.agu.org), a community of Earth and space science blogs, hosted by the American Geophysical Union

Scientists find increase in asteroid impacts on ancient Earth by studying the Moon

Image depicts the change in impact rate modeled in this paper. Some of the craters used in the study on both the moon and Earth are highlighted in the background. Credit: Data from NASA GSFC / LRO / Arizona State University; Artwork by Rebecca Ghent
Image depicts the change in impact rate modeled in this paper. Some of the craters used in the study on both the moon and Earth are highlighted in the background. Credit: Data from NASA GSFC / LRO / Arizona State University; Artwork by Rebecca Ghent

An international team of scientists is challenging our understanding of a part of Earth’s history by looking at the Moon, the most complete and accessible chronicle of the asteroid collisions that carved our solar system.

In a study published today in Science, the team shows the number of asteroid impacts on the Moon and Earth increased by two to three times starting around 290 million years ago.

“Our research provides evidence for a dramatic change in the rate of asteroid impacts on both Earth and the Moon that occurred around the end of the Paleozoic era,” said lead author Sara Mazrouei, who recently earned her PhD in the Department of Earth Sciences in the Faculty of Arts & Science at the University of Toronto (U of T). “The implication is that since that time we have been in a period of relatively high rate of asteroid impacts that is 2.6 times higher than it was prior to 290 million years ago.”

It had been previously assumed that most of Earth’s older craters produced by asteroid impacts have been erased by erosion and other geologic processes. But the new research shows otherwise.

“The relative rarity of large craters on Earth older than 290 million years and younger than 650 million years is not because we lost the craters, but because the impact rate during that time was lower than it is now,” said Rebecca Ghent, an associate professor in U of T’s Department of Earth Sciences and one of the paper’s co-authors. “We expect this to be of interest to anyone interested in the impact history of both Earth and the Moon, and the role that it might have played in the history of life on Earth.”

Scientists have for decades tried to understand the rate that asteroids hit Earth by using radiometric dating of the rocks around them to determine their ages. But because it was believed erosion caused some craters to disappear, it was difficult to find an accurate impact rate and determine whether it had changed over time.

A way to sidestep this problem is to examine the Moon, which is hit by asteroids in the same proportions over time as Earth. But there was no way to determine the ages of lunar craters until NASA’s Lunar Reconnaissance Orbiter (LRO) started circling the Moon a decade ago and studying its surface.

“The LRO’s instruments have allowed scientists to peer back in time at the forces that shaped the Moon,” said Noah Petro, an LRO project scientist based at NASA Goddard Space Flight Center.

Using LRO data, the team was able to assemble a list of ages of all lunar craters younger than about a billion years. They did this by using data from LRO’s Diviner instrument, a radiometer that measures the heat radiating from the Moon’s surface, to monitor the rate of degradation of young craters.

During the lunar night, rocks radiate much more heat than fine-grained soil called regolith. This allows scientists to distinguish rocks from fine particles in thermal images. Ghent had previously used this information to calculate the rate at which large rocks around the Moon’s young craters — ejected onto the surface during asteroid impact — break down into soil as a result of a constant rain of tiny meteorites over tens of millions of years. By applying this idea, the team was able to calculate ages for previously un-dated lunar craters.

When compared to a similar timeline of Earth’s craters, they found the two bodies had recorded the same history of asteroid bombardment.

“It became clear that the reason why Earth has fewer older craters on its most stable regions is because the impact rate was lower up until about 290 million years ago,” said William Bottke, an asteroid expert at the Southwest Research Institute in Boulder, Colorado and another of the paper’s coauthors. “The answer to Earth’s impact rate was staring everyone right in the face.”

The reason for the jump in the impact rate is unknown, though the researchers speculate it might be related to large collisions taking place more than 300 million years ago in the main asteroid belt between the orbits of Mars and Jupiter. Such events can create debris that can reach the inner solar system.

Ghent and her colleagues found strong supporting evidence for their findings through a collaboration with Thomas Gernon, an Earth scientist based at the University of Southampton in England who works on a terrestrial feature called kimberlite pipes. These underground pipes are long-extinct volcanoes that stretch, in a carrot shape, a couple of kilometers below the surface, and are found on some of the least eroded regions of Earth in the same places preserved impact craters are found.

“The Canadian shield hosts some of the best-preserved and best-studied of this terrain — and also some of the best-studied large impact craters,” said Mazrouei.

Gernon showed that kimberlite pipes formed since about 650 million years ago had not experienced much erosion, indicating that the large impact craters younger than this on stable terrains must also be intact.

“This is how we know those craters represent a near-complete record,” Ghent said.

While the researchers weren’t the first to propose that the rate of asteroid strikes to Earth has fluctuated over the past billion years, they are the first to show it statistically and to quantify the rate.

“The findings may also have implications for the history of life on Earth, which is punctuated by extinction events and rapid evolution of new species,” said Ghent. “Though the forces driving these events are complicated and may include other geologic causes, such as large volcanic eruptions, combined with biological factors, asteroid impacts have surely played a role in this ongoing saga.

“The question is whether the predicted change in asteroid impacts can be directly linked to events that occurred long ago on Earth.”

The findings are described in the study “Earth and Moon impact flux increased at the end of the Paleozoic,” published in Science. Support for the research was provided by the National Science and Engineering Research Council of Canada, NASA’s Solar System Exploration Research Virtual Institute, and the Natural Environment Research Council of the United Kingdom.

Reference:
Sara Mazrouei, Rebecca R. Ghent, William F. Bottke, Alex H. Parker, Thomas M. Gernon. Earth and Moon impact flux increased at the end of the Paleozoic. Science, 2019 DOI: 10.1126/science.aar4058

Note: The above post is reprinted from materials provided by University of Toronto.

Geological fingerprinting of volcanic ash

The Santiaguito volcano: The Santiaguito dome complex in Guatemala regularly spews out plumes of gas and volcanic ash.
The Santiaguito volcano: The Santiaguito dome complex in Guatemala regularly spews out plumes of gas and volcanic ash.

Volcanic ash consists of tiny particles containing minerals and glass. LMU researchers have now used a new analytical technique based on quantitative chemical analysis under a scanning electron microscope to link their surface composition to activity during volcanic eruptions.

The Santiaguito volcanic complex in Guatemala first emerged in 1922, and has grown steadily since then. Over this period, one of the magma domes has discharged lava almost continuously, and often explosively releases clouds of gas and ash. Santiaguito is the source of some of the volcanic ash samples that Dr. Adrian Hornby of the Department of Earth and Environmental Sciences at LMU is analyzing as part of his EU-funded project AVAST (Advanced Volcanic ASh characTerisation). In a long-standing collaboration with researchers at the University of Liverpool, he has now applied a novel imaging procedure to examine ash samples collected on the flanks of Santiaguito. The results appear in the online journal Scientific Reports.

Volcanic ash consists of particles with diameter of less than 2 mm, and is typically made up of fragments of crystalline material and glass that are derived from magma. In the new study, Hornby employed a technology known as QEMSCAN (Quantitative Evaluation of Minerals by Scanning Electron Microscopy) Particle Mineralogical Analysis to investigate ash that had been vented in an explosive plume and ash from a pyroclastic flow caused by the sudden collapse of part of the rim of the active crater at the Santiaguito complex. “How magma fragments depends on the type of volcanic activity involved in its production, and this also changes the mineralogy that is found at the surfaces of the ash particles,” Hornby explains.

The surfaces of both Guatemalan ash samples exhibited various combinations of feldspar and glass, but the particles generated by the dome collapse had more glass and less feldspar on their surfaces than within the particles. This variation most probably reflects differences in fragmentation conditions between the two samples. “Our findings make a significant contribution to a better understanding of the origin and composition of volcanic ash – which is necessary to enable the risks associated with eruptions to be assessed.” In 2010, following the eruption of the Eyjafjallajökull volcano in Iceland, commercial air traffic in Europe was severely affected as the ash released by the event could damage aircraft jet engines.

Reference:
A. J. Hornby et al. Phase partitioning during fragmentation revealed by QEMSCAN Particle Mineralogical Analysis of volcanic ash, Scientific Reports (2019). DOI: 10.1038/s41598-018-36857-4

Note: The above post is reprinted from materials provided by Ludwig Maximilian University of Munich.

Waiting for the complete rupture

Where plates collide: The main frontal thrust (red line) extends over the entire length of the Himalayas. Credit: NASA Earth Observatory
Where plates collide: The main frontal thrust (red line) extends over the entire length of the Himalayas. Credit: NASA Earth Observatory

In April 2015, Nepal — and especially the region around the capital city, Kathmandu — was struck by a powerful tremor. An earthquake with a magnitude of 7.8 destroyed entire villages, traffic routes and cultural monuments, with a death toll of some 9,000.

However, the country may still face the threat of much stronger earthquakes with a magnitude of 8 or more. This is the conclusion reached by a group of earth scientists from ETH Zurich based on a new model of the collision zone between the Indian and Eurasian Plates in the vicinity of the Himalayas.

Using this model, the team of ETH researchers working with doctoral student Luca Dal Zilio, from the group led by Professor Taras Gerya at the Institute of Geophysics, has now performed the first high-resolution simulations of earthquake cycles in a cross-section of the rupture zone.

“In the 2015 quake, there was only a partial rupture of the major Himalayan fault separating the two continental plates. The frontal, near-surface section of the rupture zone, where the Indian Plate subducts beneath the Eurasian Plate, did not slip and remains under stress,” explains Dal Zilio, lead author of the study, which was recently published in the journal Nature Communications.

Normally, a major earthquake releases almost all the stress that has built up in the vicinity of the focus as a result of displacement of the plates. “Our model shows that, although the Gorkha earthquake reduced the stress level in part of the rupture zone, tension actually increased in the frontal section close to the foot of the Himalayas. The apparent paradox is that ‘medium-sized’ earthquakes such as Gorkha can create the conditions for an even larger earthquake,” says Dal Zilio.

Tremors of the magnitude of the Gorkha earthquake release stress only in the deeper subsections of the fault system over lengths of 100 kilometres. In turn, new and even greater stress builds up in the near-surface sections of the rupture zone.

According to the simulations performed by Dal Zilio and his colleagues, two or three further Gorkha quakes would be needed to build up sufficient stress for an earthquake with a magnitude of 8.1 or more. In a quake of this kind, the rupture zone breaks over the entire depth range, extending up to the Earth’s surface and laterally — along the Himalayan arc — for hundreds of kilometres. This ultimately leads to a complete stress release in this segment of the fault system, which extends to some 2,000 kilometres in total.

Historical data shows that mega events of this kind have also occurred in the past. For example, the Assam earthquake in 1950 had a magnitude of 8.6, with the rupture zone breaking over a length of several hundred kilometres and across the entire depth range. In 1505, a giant earthquake struck with sufficient power to produce an approximately 800-kilometre rupture on the major Himalayan fault. “The new model reveals that powerful earthquakes in the Himalayas have not just one form but at least two, and that their cycles partially overlap,” says Edi Kissling, Professor of Seismology and Geodynamics. Super earthquakes might occur with a periodicity of 400 to 600 years, whereas “medium-sized” quakes such as Gorkha have a recurrence time of up to a few hundred years. As the cycles overlap, the researchers expect powerful and dangerous earthquakes to occur at irregular intervals.

However, they cannot predict when another extremely large quake will next take place. “No one can predict earthquakes, not even with the new model. However, we can improve our understanding of the seismic hazard in a specific area and take appropriate precautions,” says Kissling.

The two-dimensional and high-resolution model also includes some research findings that were published after the Gorkha earthquake. To generate the simulations, the researchers used the Euler mainframe computer at ETH Zurich. “A three-dimensional model would be more accurate and would also allow us to make statements about the western and eastern fringes of the Himalayas. However, modelling the entire 2,000 kilometres of the rupture zone would require enormous computational power,” says Dal Zilio.

Reference:
Luca Dal Zilio, Ylona van Dinther, Taras Gerya, Jean-Philippe Avouac. Bimodal seismicity in the Himalaya controlled by fault friction and geometry. Nature Communications, 2019; 10 (1) DOI: 10.1038/s41467-018-07874-8

Note: The above post is reprinted from materials provided by ETH Zurich. Original written by Peter Rüegg.

Drilling deep for clues on earthquakes

Civil and Environmental Engineering Assistant Professor Hiroki Sone stands on the drilling vessel Chikyu’s heliport. Credit: Hiroki Sone

Lingering motion sickness is one of the occupational hazards of working at sea off the coast of Japan for three weeks. Hiroki Sone can attest to that, having spent part of the fall 2018 semester on the deepest scientific oceanic drilling project ever.

“Maybe I shouldn’t nod too much,” says the assistant professor of civil and environmental engineering at the University of Wisconsin-Madison, a day after returning stateside. “I’m feeling dizzy.”

Sone and Ph.D. student Zirou Jin are part of the international team of scientists working on the Nankai Trough Seismogenic Zone Experiment. In the final phase of the 11-year experiment, researchers are drilling below the Nankai Trough, the meeting point of the Eurasian and Philippine Sea tectonic plates and the source of repeated earthquakes. If successful, it would be the first time scientists have reached a depth at which earthquakes spawn in a subduction zone, where one plate (in this case, the Philippine Sea) pushes under another.

The drilling, which reached a record depth in early December 2018 and will continue until March 2019, will yield rock samples and allow the team to install sensors, potentially unearthing new clues about the processes that drive earthquakes.

“We want to understand what kind of forces are accumulating in this plate boundary, because that’s the driving force for ground motion during earthquakes,” says Sone. “To be directly in there and see the material really improves our understanding of what is actually happening.”

Sone grew up in a Japanese society that’s understandably wary of earthquakes, given the long history of seismic activity in the country. He remembers elementary school visits from a truck with a shaking room that enabled students to practice safety maneuvers.

He was a graduate student at Kyoto University working on a thesis about a deadly earthquake in Taiwan when he heard about plans for the first NanTroSEIZE Integrated Ocean Drilling Program expedition, which launched in 2007. Six years later, he joined his first expedition on the Nankai Trough.

This time, he’s leading the group’s physical properties team. When cuttings—the rock debris generated during drilling—come to the surface, Sone’s team examines their densities to calculate changes in porosity, the percentage of empty space in the rock that’s filled by water. Porosity typically decreases with depth, but the researchers look for exceptions to that trend that will indicate higher-than-expected fluid pressure. Scientists have long postulated that fluid pressure along tectonic plate interfaces is abnormally high, which could encourage a plate to slip like a puck on an air hockey table. But no one has measured that fluid pressure at this depth, Sone says.

“This is a good opportunity to test those hypotheses and validate theories or maybe disprove some of them,” he says.

Sone will helicopter back onto the drilling vessel Chikyu, whose name means earth in Japanese, again in January 2019, while Jin will work a pair of two-week shifts in February and March. Work days are long aboard the Chikyu, with 12-hour shifts and limited internet access.

But the promise of rock core samples—much larger and more useful than cuttings—at the end is a powerful motivator. Jin is studying cores from a previous expedition for her Ph.D. work on the viscoplastic properties—how materials flow and deform over time—in Nankai Trough’s accretionary prism, the collection of rocks and sediment formed during plate subduction.

“We try to see how the stress accumulates,” she says.

By taking cores from the plate interface and slowly deforming them in the lab, Sone says, scientists can better understand the forces building up during the 100 to 400 years between the earthquakes that generate tsunamis in the Nankai Trough.

“It’s important to understand how the earth ruptures during these large earthquakes that happen in a matter of minutes, and scientists have focused on that for many decades,” he says. “But what happens in between the 100 years? How does the force accumulate to get ready for the next earthquake? That is an equally, if not more, important questions to ask that we have not addressed in the community. We’d like to make a breakthrough there to better forecast seismic hazards around the world.”

Note: The above post is reprinted from materials provided by University of Wisconsin-Madison.

New computer modeling approach could improve understanding of megathrust earthquakes

Years before the devastating Tohoku earthquake struck the coast of Japan in 2011, the Earth’s crust near the site of the quake was starting to stir. Researchers at The University of Texas at Austin are using computer models to investigate if tiny tremors detected near this site could be connected to the disaster itself.

The research could help enhance scientists’ understanding of forces driving megathrust earthquakes — the world’s most powerful type of earthquake — and improve earthquake hazard assessment. The study was published on Dec.15, 2018, in Earth and Planetary Science Letters.

Lead author Thorsten Becker, a professor at the UT Jackson School of Geosciences and researcher at the University of Texas Institute for Geophysics, said that this was the first comprehensive study showing changes in barely perceptible tremor activity before the Tohoku megathrust earthquake.

“The part of the crust that is close to the place that eventually ruptured changes stress state a couple of years before the event,” said Becker. “By demonstrating this, our work complements studies of crustal deformation and our understanding of the forces driving earthquakes.”

The Institute for Geophysics is a research unit of the Jackson School of Geosciences.

While the location of the tremors raises questions about their potential linkage to the quake, Becker said that it’s unknown at the moment if the two events relate. However, the seismic signature of the tremors is helping refine a computer model that could help untangle the connection. This new modeling technique allows scientists to create a four-dimensional image of the Earth’s crust and interactions between tectonic plates, showing how forces pushing at the fault change over time.

Once the seismic data was inputted, the model matched observations of how the plate deformed in the years before and after the earthquake. This allowed the scientists to make inferences about the kind of forces taking place at the plate boundary, the point where one plate dives into the Earth’s hot, viscous mantle. In this semi-molten layer, solid rocks ooze and behave in unexpected ways, so understanding the dynamics of the layer could help identify the connection between pressure along a fault before and after a major earthquake.

The new research is significant because the model was originally developed using a different dataset: geodetic information about the shape of the Earth’s surface. By gaining similar results using different data sets — seismic waves and changes in the planet’s shape — scientists can be much more confident about the accuracy of earthquake models.

Becker believes that with the right research and support, advanced computer models can be used to study the physics of earthquakes and perhaps contribute to improved forecasts.

Currently, scientists can at best offer hazard maps showing known earthquake zones and a vague probability of an earthquake in the coming decades. Knowing more about when and where such a quake might strike, even within a few years, would represent a significant improvement on current earthquake forecasting and perhaps allow authorities and industry adequate time to prepare for such an event.

To this end, the authors hope their study will contribute to global efforts to improve earthquake hazard assessment, such as the Modeling Collaboratory for Subduction RCN, a new UT-led research collaboration network funded by the National Science Foundation (NSF).

The study was supported by the NSF and the Japanese Ministry of Education, Culture, Sports, Science and Technology.

Reference:
Thorsten W. Becker, Akinori Hashima, Andrew M. Freed, Hiroshi Sato. Stress change before and after the 2011 M9 Tohoku-oki earthquake. Earth and Planetary Science Letters, 2018; 504: 174 DOI: 10.1016/j.epsl.2018.09.035

Note: The above post is reprinted from materials provided by University of Texas at Austin.

Robot recreates the walk of a 290-million-year-old creature

This image from video provided by John Nyakatura in January 2019 shows computer-generated and robotic simulations of an Orobates Pabsti dinosaur’s footprints while walking. Nyakatura has spent years studying the four-legged plant-eater, which lived before the dinosaurs, and fascinates scientists “because of its position on the tree of life.”. Researchers believe the creature is a “stem amniote”—a likely ancestor of several groups of land-dwelling animals that later differentiated into modern mammals, birds and reptiles. Credit: John Nyakatura/Humboldt University via AP

How did the earliest land animals move? Scientists have used a nearly 300-million-year old fossil skeleton and preserved ancient footprints to create a moving robot model of prehistoric life.

Evolutionary biologist John Nyakatura at Humboldt University in Berlin has spent years studying a 290-million-year-old fossil dug up in central Germany’s Bromacker quarry in 2000. The four-legged plant-eater lived before the dinosaurs and fascinates scientists “because of its position on the tree of life,” said Nyakatura. Researchers believe the creature is a “stem amniote”—an early land-dwelling animal that later evolved into modern mammals, birds and reptiles.

Scientists believe the first amphibious animals emerged on land 350 million years ago and the first amniotes emerged around 310 million years ago.

The fossil, called Orabates pabsti, is a “beautifully preserved and articulated skeleton,” said Nyakatura. What’s more, scientists have previously identified fossilized footprints left by the 3-foot-long (90 cm) creature.

Nyakatura teamed up with robotics expert Kamilo Melo at the Swiss Federal Institute of Technology in Lausanne to develop a model of how the creature moved. Their results were published Wednesday in the journal Nature.

The researchers built a life-size replica of the prehistoric beast—”we carefully modeled each and every bone,” said Nyakatura—and then tested the motion in various ways that would lead its gait to match the ancient tracks, ruling out combinations that were not anatomically possible.

They repeated the exercise with a slightly-scaled up robot version , which they called OroBOT. The robot is made of motors connected by 3D-printed plastic and steel parts. The model “helps us to test real-world dynamics, to account for gravity and friction,” said Melo. The team also compared their models to living animals, including salamanders and iguanas.

Technology such as robotics, computer modeling and CT scans are transforming paleontology, “giving us ever more compelling reconstructions of the past,” said Andrew Farke, curator at the Raymond M. Alf Museum of Paleontology in Claremont, California, who was not involved in the study.

Based on the robot model, the scientists said they think the creature had more advanced locomotion than previously thought for such an early land animal. (Think more scampering than slithering.)

“It walked with a fairly upright posture,” said Melo. “It didn’t drag its belly or tail.”

University of Maryland paleontologist Thomas R. Holtz, who was not involved in the study, said the research suggests “an upright stance goes further back than we originally thought.”

Stuart Sumida, a paleontologist at California State University in San Bernardino and part of the initial team that excavated Orobates fossils, called it “an exciting study.” Sumida, who was not involved in the robot project, said the work provided “a much more confident window in to what happened long ago. It isn’t a time machine, but Nyakatura and colleagues have given us a tantalizing peek.”

Reference:
John A. Nyakatura et al. Reverse-engineering the locomotion of a stem amniote, Nature (2019). DOI: 10.1038/s41586-018-0851-2

Note: The above post is reprinted from materials provided by The Associated Press.

Fossil deposit is much richer than expected

CHW 189 from the private collection of Herman Winkelhorst (Netherlands). The neck of the animal is excellently preserved, but the rest is not. One possible explanation may be that this is the result of uneven colonization of the carcass by microorganisms and algae, which created a protective layer especially around the neck
CHW 189 from the private collection of Herman Winkelhorst (Netherlands). The neck of the animal is excellently preserved, but the rest is not. One possible explanation may be that this is the result of uneven colonization of the carcass by microorganisms and algae, which created a protective layer especially around the neck. Credit: © Photo: Jelle Heijne/Uni Bonn

It has long been known that a quarry near the Dutch town of Winterswijk is an Eldorado for fossil lovers. But even connoisseurs will be surprised just how outstanding the site actually is. A student at the University of Bonn, himself a Dutchman and passionate fossil collector, has now analyzed pieces from museums and private collections for his master’s thesis. He found an amazing amount of almost completely preserved skeletons, all between 242 and 247 million years old. The good condition is presumably due to particularly favorable development conditions. These make Winterswijk, which belongs to the so-called Germanic Basin, a cornucopia for paleontology. The study is published in the Paläontologische Zeitschrift.

Jelle Heijne examined exactly 327 remains of marine reptiles for his master’s thesis — collected partly from public museums, but primarily from about 20 private collections. He was particularly impressed by the high quality of the finds: “Among them were more than 20 contiguous skeletons,” he emphasizes. “Only very few complete skeleton finds are known from the other sites of the Germanic Basin, which stretches from England to Poland.”

In his study, the 25-year-old investigated the question of why the bones, which are over 240 million years old, have been preserved so well here. The reason is probably a combination of fortunate circumstances: At that time the Germanic Basin was a sea, which was extremely shallow in today’s Winterswijk. This is illustrated by the fossil footprints of terrestrial animals that were found not far from the reptile bones. The region probably resembled today’s Wadden Sea of the North Sea coast, but with a bottom that was not sandy but covered in lime silt.

The shallow depth ensured that cadavers quickly hit the ground, where they were then covered by sediment. If dead animals float in the water for a long time and are tossed back and forth by waves and currents, the probability increases that body parts, such as tail, limbs or head, are lost.

Another important factor was a process called “Stick’n’Peel” by paleontologists: The animal is colonized by microorganisms and algae that hold the skeleton together like a skin. “It was probably these two factors in particular that favored the occurrence of well-preserved finds,” explains Heijne.

In fact, there is some evidence for the Stick’n’Peel hypothesis. For example, some skeletons lack individual larger bones, while the small bones are complete — even though the latter are usually most likely to be carried away by the water. “Such unusual patterns typically occur when a skeleton is unevenly colonized and thus protected,” Heijne explains.

It has long been known that Winterswijk stands out among the sites of the Germanic Basin. Nevertheless, the large number of high-quality finds is likely to surprise even connoisseurs, especially since most of the finds are not accessible to the public. “I have been a member of an association of private collectors in the Netherlands for years,” Heijne explains. This was the ideal contact exchange for his study: “The collectors I approached were all proud to be able to contribute to the research on Winterswijk.”

Reference:
Jelle Heijne, Nicole Klein, P. Martin Sander. The uniquely diverse taphonomy of the marine reptile skeletons (Sauropterygia) from the Lower Muschelkalk (Anisian) of Winterswijk, The Netherlands. PalZ, 2019; DOI: 10.1007/s12542-018-0438-0

Note: The above post is reprinted from materials provided by University of Bonn.

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