Wits University (University of the Witwatersrand, Johannesburg, South Africa) PhD student, Willem Kruger’s study on the state of magma within plutonic magmatic systems in the Earth’s crust has been published in the journal Nature Communications.
Working alongside his PhD supervisor, Professor Rais Latypov, from the Wits School of Geosciences, Kruger’s paper shows that basaltic magma chambers may develop as large bodies of crystal-free melts in the Earth’s crust. This study challenges a recently-emerged paradigm that magma chambers are huge masses of crystal-rich mush — in other words, crystals with just a very small amount of melt.
Attempts to understand the processes that operate in magma chambers in our planet’s crust is incredibly challenging as they are hidden from direct observations. Geologists must follow an indirect approach to study these features, such as examining their ancient fossilised remains that are exposed on Earth’s surface after millions of years of erosion.
To examine the state of magma within a chamber is very demanding, as it requires the study of the very contact between the crystallising margins of magma bodies (also called solidification fronts) and their liquid interiors.
Difficulties in understanding the behaviour of solidification fronts can fortunately be overcome by studying a particularly fascinating rock type, called massive magnetitite, from the Bushveld Complex in South Africa.
“Magnetitite contains chromium that is an extremely sensitive indicator of magma chamber processes and can be used to study solidification fronts in extreme detail,” says Kruger.
“By mapping the distribution of chromium in magnetitite in the field we can observe the two-dimensional propagation patterns of solidification fronts on a scale never done before.”
Kruger and Latypov found that all evolved liquid is effectively removed from the solidification front of magnetitite as it propagates towards the chamber interior. “This is because of extremely effective compositional convection that occurs during the crystallisation of magnetite. The process results in the solidification front to propagate as almost a completely solid surface.” says Latypov.
This research shows that such powerful compositional convection may inhibit the formation of crystal-rich mushes in basaltic magma chambers.
There are many reasons to believe that this process is not unique to magnetitite layers of the Bushveld Complex but will likely operate in other rock types as well, for instance, in the Bushveld’s economically important chromitite layers.
“Our results thus argue for the existence of large, liquid-dominated magma chambers hidden within the Earth’s crust,” says Kruger.
Reference:
Willem Kruger, Rais Latypov. Fossilized solidifications fronts in the Bushveld Complex argues for liquid-dominated magmatic systems. Nature Communications, 2020; 11 (1) DOI: 10.1038/s41467-020-16723-6
Three water-filled maars in the Eifel, Germany (Gemündener Maar, Weinfelder Maar, Schalkenmehrener Maar). Created by volcanic activity, maars are also found in other parts of Europe and on other continents, but Eifel-Maars are the classic example worldwide. Credit: Martin Schildgen / Wikimedia Commons
Scientists have discovered new evidence for active volcanism next door to some of the most densely populated areas of Europe. The study ‘crowd-sourced’ GPS monitoring data from antennae across western Europe to track subtle movements in the Earth’s surface, thought to be caused by a rising subsurface mantle plume. The work is published in Geophysical Journal International.
The Eifel region lies roughly between the cities of Aachen, Trier, and Koblenz, in west-central Germany. It is home to many ancient volcanic features, including the circular lakes known as ‘maars’.
These are the remnants of violent volcanic eruptions, such as the one which created Laacher See, the largest lake in the area. The explosion that created this is thought to have occurred around 13,000 years ago, with a similar explosive power to the cataclysmic Mount Pinatubo eruption in 1991.
In the new study, the team — based at the University of Nevada, Reno and the University of California, Los Angeles in the United States — used data from thousands of commercial and state-owned GPS antennae all over western Europe, to map out how the ground is moving vertically and horizontally as the Earth’s crust is pushed, stretched and sheared.
The research revealed that the region’s land surface is moving upward and outward over a large area centred on the Eifel, and including Luxembourg, eastern Belgium and the southernmost province of the Netherlands, Limburg.
“The Eifel area is the only region in the study where the ground motion appeared significantly greater than expected,” adds Prof. Kreemer. “The results indicate that a rising plume could explain the observed patterns and rate of ground movement.”
The new results complement those of a previous study in Geophysical Journal International that found seismic evidence of magma moving underneath the Laacher See. Both studies point towards the Eifel being an active volcanic system.
The implication of this study is that there may not only be an increased volcanic risk, but also a long-term seismic risk in this part of Europe. The researchers urge caution however: “This does not mean that an explosion or earthquake is imminent, or even possible again in this area. We and other scientists plan to continue monitoring the area using a variety of geophysical and geochemical techniques, in order to better understand and quantify any potential risks.”
Diamonds, those precious, sparkling jewels, are known as the hardest materials on Earth. They are a high-pressure form of carbon and found deep in the ground.
While diamonds are commonly thought of as hard and stable, carbon from about 100 miles beneath the African plate is being brought to shallower levels where diamond will become unstable. Molten rock (magma) brings the excess carbon towards the surface, and earthquakes open cracks that allow the carbon to be released into the air as carbon dioxide.
PhD student Sarah Jaye Oliva and Professor of Earth and Environmental Sciences and Marshall-Heape Chair in Geology Cynthia Ebinger are among a group of international researchers who co-authored a paper “Displaced cratonic mantle concentrates deep carbon during continental rifting,” which was published in the journal Nature on June 3.
“Somewhat amusedly,” Ebinger said, “the paper is evidence that Diamonds Aren’t Forever.”
The pair report on their findings about the African continent splitting in two and the massive amounts of CO2 (carbon dioxide) being released into the atmosphere.
Ebinger said of her student, “Sarah Jaye contributed to the gas measurements, and she analyzed the deep structure and state-of-stress data that enabled us to deduce the process leading to the excess CO2 in some rift zones.”
Oliva participated in a month-long campaign in 2018 to sample gases released diffusely through the soil and at springs that dot the East African Rift System in Tanzania.
Through the sampling, Oliva and other researchers found that CO2 fluxes [flows] and the number of earthquakes are highest where the rift intersects the edge of the ancient, thick cratonic plate that is more than 60 km (about 37 miles) thicker than the adjoining area.
Oliva said this made sense because the steep edge of the bottom of the plate is “where we expect magmas (molten rock material within the Earth that will cool to form igneous rock) to form and where faulting and fracture networks should be most intense.”
“The resulting faults and fissures, we think, act as conduits through the crust that concentrate fluxes of CO2 sourced from beneath,” said Oliva.
Modeling by the researchers also suggests that the mantle underneath the study region may be enriched in carbon due to the local erosion of the cratonic lithosphere that may even contain diamonds. (A craton is an old and stable part of the continental lithosphere, which consists of the Earth’s two topmost layers, the crust and the uppermost mantle.)
“The eroded material could melt as it moves towards thinner lithosphere, and this would be another factor in increasing the CO2 flux through the rift valley margin,” said Oliva.
She added, “Participating in this project was extremely rewarding for me. We, as seismologists, geodynamicists, structural geologists and geochemists all came together to understand how rifts help mobilize CO2 that is sequestered in the deep Earth. This newly liberated CO2 ultimately influences Earth’s climate over geologic time, temporarily contributing to global warming.”
Reference:
James D. Muirhead, Tobias P. Fischer, Sarah J. Oliva, Amani Laizer, Jolante van Wijk, Claire A. Currie, Hyunwoo Lee, Emily J. Judd, Emmanuel Kazimoto, Yuji Sano, Naoto Takahata, Christel Tiberi, Stephen F. Foley, Josef Dufek, Miriam C. Reiss, Cynthia J. Ebinger. Displaced cratonic mantle concentrates deep carbon during continental rifting. Nature, 2020; 582 (7810): 67 DOI: 10.1038/s41586-020-2328-3
Yellowstone National Park is an American national park located in Wyoming, Montana, and Idaho.
Throughout Earth’s long history, volcanic super-eruptions have been some of the most extreme events ever to affect our planet’s rugged surface. Surprisingly, even though these explosions eject enormous volumes of material — at least 1,000 times more than the 1980 eruption of Mount St. Helens — and have the potential to alter the planet’s climate, relatively few have been documented in the geologic record.
Now, in a study published in Geology, researchers have announced the discovery of two newly identified super-eruptions associated with the Yellowstone hotspot track, including what they believe was the volcanic province’s largest and most cataclysmic event. The results indicate the hotspot, which today fuels the famous geysers, mudpots, and fumaroles in Yellowstone National Park, may be waning in intensity.
The team used a combination of techniques, including bulk chemistry, magnetic data, and radio-isotopic dates, to correlate volcanic deposits scattered across tens of thousands of square kilometers. “We discovered that deposits previously believed to belong to multiple, smaller eruptions were in fact colossal sheets of volcanic material from two previously unknown super-eruptions at about 9.0 and 8.7 million years ago,” says Thomas Knott, a volcanologist at the University of Leicester and the paper’s lead author.
“The younger of the two, the Grey’s Landing super-eruption, is now the largest recorded event of the entire Snake-River-Yellowstone volcanic province,” says Knott. Based on the most recent collations of super-eruption sizes, he adds, “It is one of the top five eruptions of all time.”
The team, which also includes researchers from the British Geological Survey and the University of California, Santa Cruz, estimates the Grey’s Landing super-eruption was 30% larger than the previous record-holder (the well-known Huckleberry Ridge Tuff) and had devastating local and global effects. “The Grey’s Landing eruption enamelled an area the size of New Jersey in searing-hot volcanic glass that instantly sterilized the land surface,” says Knott. Anything located within this region, he says, would have been buried and most likely vaporized during the eruption. “Particulates would have choked the stratosphere,” adds Knott, “raining fine ash over the entire United States and gradually encompassing the globe.”
Both of the newly discovered super-eruptions occurred during the Miocene, the interval of geologic time spanning 23-5.3 million years ago. “These two new eruptions bring the total number of recorded Miocene super-eruptions at the Yellowstone-Snake River volcanic province to six,” says Knott. This means that the recurrence rate of Yellowstone hotspot super-eruptions during the Miocene was, on average, once every 500,000 years.
By comparison, Knott says, two super-eruptions have — so far — taken place in what is now Yellowstone National Park during the past three million years. “It therefore seems that the Yellowstone hotspot has experienced a three-fold decrease in its capacity to produce super-eruption events,” says Knott. “This is a very significant decline.”
These findings, says Knott, have little bearing on assessing the risk of another super-eruption occurring today in Yellowstone. “We have demonstrated that the recurrence rate of Yellowstone super-eruptions appears to be once every 1.5 million years,” he says. “The last super-eruption there was 630,000 years ago, suggesting we may have up to 900,000 years before another eruption of this scale occurs.” But this estimate, Knott hastens to add, is far from exact, and he emphasizes that continuous monitoring in the region, which is being conducted by the U.S. Geological Survey, “is a must” and that warnings of any uptick in activity would be issued well in advance.
This study, which builds on decades of contributions by many other researchers, grew out of a larger project investigating the productivity of major continental volcanic provinces. Those with super-eruptions are the result of colossal degrees of crustal melting over prolonged periods of time, says Knott, and therefore have a profound impact on the structure and composition of Earth’s crust in the regions where they occur.
Because studying these provinces is vital to understanding their role in shaping our planet’s crustal processes, Knott hopes this research foreshadows even more revelations. “We hope the methods and findings we present in our paper will enable the discovery of more new super-eruption records around the globe,” he says.
Reference:
Robert S. Coe, Simon Tapster, David R. Finn, Marc K. Reichow, Michael J. Branney, Thomas R. Knott. Discovery of two new super-eruptions from the Yellowstone hotspot track (USA): Is the Yellowstone hotspot waning? Geology, 2020; DOI: 10.1130/G47384.1
A blue, boron-bearing diamond with dark inclusions of a mineral called ferropericlase, which were examined as part of this study. This gem weighs 0.03 carats. Credit: Photo by Evan Smith/GIA.
A new study by University of Alberta geologists is proposing a new model for explaining the eruption of diamond-bearing kimberlites in Northern Alberta.
The research demonstrates that 90 to 70 million years ago, the movement of an ancient slab of oceanic rocks buried hundreds of kilometres beneath Earth’s surface caused the eruption of diamond-bearing kimberlite in Northern Alberta.
“We are able to provide a new theory about why we have diamond-bearing kimberlites in Northern Alberta, which has been a source of debate for decades,” explained Yunfeng Chen, who conducted this research as part of his graduate studies with Jeffrey Gu, professor in the Department of Physics. “Our work is based on geological, paleomagnetic, and seismic data from our collaborators both at the University of Alberta and around the world.”
The model enables scientists to match the seismic structures with the time and location of kimberlite eruptions in the area, explaining how these diamonds came to Earth’s surface in the Late Cretaceous period — and providing key insight for those on the hunt for other deposits in the region.
“The kimberlites in Northern Alberta were discovered in relatively young parts of Earth’s crust — an unconventional setting for diamond-bearing kimberlites,” added Chen. “This distant location relative to other major kimberlite groups in North America plus the large variability of compositions further highlight the complex nature of the origins of kimberlite.”
The multidisciplinary study combines the work of geophysical imaging, geochronological dating, and plate motion calculation.
“What we have observed in Northern Alberta is similar to Hawaii,” said Gu. “In both scenarios, a relatively stationary mantle heat source essentially burned through the migrating plates above it, leaving ‘scars’ on the Earth’s surface. Diamonds were carried to the surface through this ‘upwelling’ process.”
A key difference is that the generation of the mantle upwelling in Northern Alberta took place no deeper than 700 kilometres below surface, whereas the ongoing Hawaii ‘plume’ appears to have occurred much deeper, at approximately 2,900 kilometres under Earth’s surface.
Reference:
Shu-Huei Hung, Erdinc Saygin, Lei Wu, Larry M. Heaman, Yu Jeffrey Gu, Yunfeng Chen. Reconciling seismic structures and Late Cretaceous kimberlitemagmatism in northern Alberta, Canada. Geology, 2020; DOI: 10.1130/G47163.1
Proposed model for deep-carbon transport along a cratonic boundary in the EARS study region.
University of New Mexico (UNM) Professor of Earth and Planetary Sciences, Dr. Tobias Fischer and Syracuse University research fellow (now University of Auckland Lecturer), Dr. James Muirhead led an international team of interdisciplinary researchers to investigate the role of carbon in the break-up of continents.
This work, much of which has been funded by grants from the National Science Foundation, is a culmination of research efforts that started with former students from UNM and other US, French, Tanzanian and Kenyan universities.
It was first recognized by former UNM student, now assistant professor at Seoul National University, Dr. Hyunwoo Lee, that the East African Rift and continental rifts in general are significant sources of carbon degassed from the Earth’s mantle to the atmosphere. While later work by other groups showed that CO2 emissions from the East African Rift are variable along its 3,000 km extent, the question remained “where does all this carbon come from and how is it so efficiently released?”
Subsequent work by Fischer and collaborator Professor Stephen Foley from Macquarie University, Australia, proposed a model in which the degassing CO2 is ultimately sourced from carbon that has accumulated over billions of years at the base of the thick old cratonic lithosphere located in the center and edge of the East African Rift.
“The model suggests that this accumulated carbon originates from subducting oceanic plates and deep mantle plumes,” said Fischer. “These processes could deliver sufficient carbon to the bottom of very thick and billion year old continental lithosphere to explain the high CO2 fluxes observed in the actively deforming part of the rift.”
However, the model proposed by Fischer and Foley could not explain how this deep CO2 managed to leak out from the actively extending part of the rift, which is exactly where the current work connects the dots.
Muirhead and Fischer together with Master’s student Amani Laizer from University of Dar Es Salaam in Tanzania and geophysics Ph.D. student Sarah Jaye Oliva from Tulane University returned to Tanzania in 2018 and collected data and samples in locations where active rifting,
i.e. where the plates move apart, intersect the old thick craton that lies above a mantle plume. Gas samples were collected from hot springs in this region that have never been sampled before.
The analyses of these samples within the context of already existing data from the earlier work showed a striking difference in chemical composition of the gases that are released from the active rift and the craton. Craton gases are entirely crustal with no sign of any mantle gases, including CO2. Nitrogen and crustal helium dominate these craton gases. Rift gases on the other hand are stuffed with mantle CO2 and have a strong mantle helium isotope signature. Measured mantle CO2 fluxes are close to zero on the craton but surge in the adjacent actively extending rift.
“Right at the boundary between the craton and the deforming rift sits the world’s only currently erupting carbonatite volcano, Oldoinyo Lengai,” said Fischer. “This volcano erupts lavas that are so liquid they move like motor oil. The reason for this is that they are devoid of the silica that makes up most igneous rocks but contain about 30 percent carbon, a staggeringly high amount that gives the rock its name carbonatite. Looking back in geologic time, it turns out that there are many carbonatite volcanoes right at the edge of the Tanzania craton, but they are just not currently active.”
This distribution of carbonatites led the team to propose a mechanism that causes the lateral migration of the deep cratonic lithosphere where all that stored solid carbon is located, into the mantle at the edges of the craton.
This conceptual model also fits into quantitative physical models developed by Dr. Jolante van Wjik, professor at New Mexico Tech and Dr. Claire Currie, professor at University of Alberta, which shows that unusually thick and low density mantle rocks beneath a craton will be swept laterally by mantle flow, moving toward the thinner plate beneath the continental rift.
This material transfer may enhance melt production. Therefore, the research team concluded, lateral migration of deep cratonic lithosphere soaked with ancient accumulated carbon is ultimately responsible for carbonatite volcanism and the on-going continental break-up in this region of East Africa.
Reference:
Muirhead, J.D., Fischer, T.P., Oliva, S.J. et al. Displaced cratonic mantle concentrates deep carbon during continental rifting. Nature, 2020 DOI: 10.1038/s41586-020-2328-3
More than 110 million years ago, a lumbering 1,300-kilogram, armour-plated dinosaur ate its last meal, died, and was washed out to sea in what is now northern Alberta. This ancient beast then sank onto its thorny back, churning up mud in the seabed that entombed it — until its fossilized body was discovered in a mine near Fort McMurray in 2011.
Since then, researchers at the Royal Tyrrell Museum of Palaeontology in Drumheller, Alta., Brandon University, and the University of Saskatchewan (USask) have been working to unlock the extremely well-preserved nodosaur’s many secrets — including what this large armoured dinosaur (a type of ankylosaur) actually ate for its last meal.
“The finding of the actual preserved stomach contents from a dinosaur is extraordinarily rare, and this stomach recovered from the mummified nodosaur by the museum team is by far the best-preserved dinosaur stomach ever found to date,” said USask geologist Jim Basinger, a member of the team that analyzed the dinosaur’s stomach contents, a distinct mass about the size of a soccer ball.
“When people see this stunning fossil and are told that we know what its last meal was because its stomach was so well preserved inside the skeleton, it will almost bring the beast back to life for them, providing a glimpse of how the animal actually carried out its daily activities, where it lived, and what its preferred food was.”
There has been lots of speculation about what dinosaurs ate, but very little known. In a just-published article in Royal Society Open Science, the team led by Royal Tyrrell Museum palaeontologist Caleb Brown and Brandon University biologist David Greenwood provides detailed and definitive evidence of the diet of large, plant-eating dinosaurs — something that has not been known conclusively for any herbivorous dinosaur until now.
“This new study changes what we know about the diet of large herbivorous dinosaurs,” said Brown. “Our findings are also remarkable for what they can tell us about the animal’s interaction with its environment, details we don’t usually get just from the dinosaur skeleton.”
Previous studies had shown evidence of seeds and twigs in the gut but these studies offered no information as to the kinds of plants that had been eaten. While tooth and jaw shape, plant availability and digestibility have fuelled considerable speculation, the specific plants herbivorous dinosaurs consumed has been largely a mystery.
So what was the last meal of Borealopelta markmitchelli (which means “northern shield” and recognizes Mark Mitchell, the museum technician who spent more than five years carefully exposing the skin and bones of the dinosaur from the fossilized marine rock)?
“The last meal of our dinosaur was mostly fern leaves — 88 per cent chewed leaf material and seven per cent stems and twigs,” said Greenwood, who is also a USask adjunct professor.
“When we examined thin sections of the stomach contents under a microscope, we were shocked to see beautifully preserved and concentrated plant material. In marine rocks we almost never see such superb preservation of leaves, including the microscopic, spore-producing sporangia of ferns.”
Team members Basinger, Greenwood and Brandon University graduate student Jessica Kalyniuk compared the stomach contents with food plants known to be available from the study of fossil leaves from the same period in the region. They found that the dinosaur was a picky eater, choosing to eat particular ferns (leptosporangiate, the largest group of ferns today) over others, and not eating many cycad and conifer leaves common to the Early Cretaceous landscape.
Specifically, the team identified 48 palynomorphs (microfossils like pollen and spores) including moss or liverwort, 26 clubmosses and ferns, 13 gymnosperms (mostly conifers), and two angiosperms (flowering plants).
“Also, there is considerable charcoal in the stomach from burnt plant fragments, indicating that the animal was browsing in a recently burned area and was taking advantage of a recent fire and the flush of ferns that frequently emerges on a burned landscape,” said Greenwood.
“This adaptation to a fire ecology is new information. Like large herbivores alive today such as moose and deer, and elephants in Africa, these nodosaurs by their feeding would have shaped the vegetation on the landscape, possibly maintaining more open areas by their grazing.”
The team also found gastroliths, or gizzard stones, generally swallowed by animals such as herbivorous dinosaurs and today’s birds such as geese to aid digestion.
“We also know that based on how well-preserved both the plant fragments and animal itself are, the animal’s death and burial must have followed shortly after the last meal,” said Brown. “Plants give us a much better idea of season than animals, and they indicate that the last meal and the animal’s death and burial all happened in the late spring to mid-summer.”
“Taken together, these findings enable us to make inferences about the ecology of the animal, including how selective it was in choosing which plants to eat and how it may have exploited forest fire regrowth. It will also assist in understanding of dinosaur digestion and physiology.”
Borealopelta markmitchelli, discovered during mining operations at the Suncor Millennium open pit mine north of Fort McMurray, has been on display at the Royal Tyrrell Museum since 2017. The main chunk of the stomach mass is on display with the skeleton.
Other members of the team include museum scientists Donald Henderson and Dennis Braman, and Brandon University research associate and USask alumna Cathy Greenwood.
Research continues on Borealopelta markmitchelli — the best fossil of a nodosaur ever found — to learn more about its environment and behaviour while it was alive. Student Kalyniuk is currently expanding her work on fossil plants of this age to better understand the composition of the forests in which it lived. Many of the fossils she will examine are in Basinger’ collections at USask.
The research was funded by Canada Foundation for Innovation, Research Manitoba, Natural Sciences and Engineering Research Council of Canada, National Geographic Society, Royal Tyrrell Museum Cooperating Society, and Suncor Canada, as well as in-kind support from Olympus Canada.
Reference:
Caleb M. Brown, David R. Greenwood, Jessica E. Kalyniuk, Dennis R. Braman, Donald M. Henderson, Cathy L. Greenwood, James F. Basinger. Dietary palaeoecology of an Early Cretaceous armoured dinosaur (Ornithischia; Nodosauridae) based on floral analysis of stomach contents. Royal Society Open Science, 2020; 7 (6): 200305 DOI: 10.1098/rsos.200305
What the ankylosaur Bissektipelta archibaldi might look like. Credit: the authors of the paper.
Palaeontologists from St Petersburg University have been the first to study in detail the structure of the brain and blood vessels in the skull of the ankylosaur Bissektipelta archibaldi, an herbivorous dinosaur somewhat similar in appearance to a modern armadillo. Scientists produced the first three-dimensional computer reconstruction of a dinosaur endocast made in Russia,a digital cast of its braincase. It made it possible to determine that ankylosaurs, and Bissektipelta in particular, were capable of cooling their brains, had an extremely developed sense of smell, and heard low-frequency sounds. However, their brains were one and a half times smaller than that of modern animals of the same size.
Ankylosaurs appeared on Earth in the middle of the Jurassic—about 160 million years ago—and existed until the end of the dinosaur era, which ended 65 million years ago. These herbivorous animals were somewhat reminiscent of modern turtles or armadillos, were covered with thick armour, and sometimes even had a bony club on the tail. The researchers became interested in the uniquely preserved remains of ankylosaurs from Uzbekistan. Although these fossils have been known for 20 years, only now have the scientists had an opportunity to study the specimens from the inside using cutting-edge methods.
During the study, the palaeontologists examined three fragments of fossil skulls of the ankylosaur Bissektipelta archibaldi. They were found during a series of international expeditions URBAC (Uzbek / Russian / British / American / Canadian Joint Paleontological Expeditions) in the late 1990s and early 2000s at the Dzharakuduk locality in the Central Kyzylkum Desert, Uzbekistan. The scientists emphasise that it is unique, in that numerous remains of representatives of ~90-million-year-old fauna can be found there. These include dinosaurs, pterosaurs, crocodiles, birds, mammals and other vertebrates.
“This is really one of the richest locations in the world. The fauna of Dzharakuduk now has more than 100 species of ancient vertebrates,” said Pavel Skutschas, associate professor at St Petersburg University and an expert in Mesozoic vertebrates. “Of course, such a diversity of life would not have been found without large-scale field studies. A series of nine URBAC expeditions, undertaken from 1997 to 2006, pooled together the efforts of palaeontologists from many countries in the search for the bones of ancient animals.”
The material that was collected at that time comprises dozens of fragments of skulls and skeletons, and hundreds of thousands of isolated bones. Scientists still use them in their research and say that will provide studies for many years to come. At present, the three fragments of fossil ankylosaur braincases from Uzbekistan are stored at the Zoological Institute of the Russian Academy of Sciences. However, they have been temporarily transferred for research to the Department of Vertebrate Zoology at St Petersburg University.
Ankylosaurs lived on our planet for 100 million years
“Thanks to the development of computed tomography (CT) over the past 15 to 20 years, palaeontologists are able to learn more and more about the dinosaur brain and its structure,” said Ivan Kuzmin, the lead author of the article and a doctoral student at St Petersburg University.
“We decided to re-describe Bissektipelta archibaldi, and we managed to clarify its place on the phylogenetic tree of ankylosaurs. A 3-D reconstruction of the endocast of its brain cavity was made using CT. It is important to understand that the digital ‘cast’ of the braincase is not the brain itself. It is necessary to study it carefully to understand how big the actual brain was, where its parts were, how the vessels and nerves were housed.”
After meticulous work that lasted for three years, the scientists determined that a considerable part of the brain of Bissektipelta archibaldi was occupied by olfactory bulbs—about 60% of the size of the cerebral hemispheres. Bissektipelta likely had an extremely developed sense of smell, which probably helped it to look for food, the opposite sex, and to feel the approach of predators in time. It was of vital importance to know about any danger in advance because ankylosaurs had such heavy armor and a clumsy figure. The olfaction of ankylosaurs can even be compared with the olfaction of the famous predator Tyrannosaurus rex. Its olfactory bulbs were even larger, as they occupied about 65-70% of the size of the large hemispheres.
“Another interesting skill of the ankylosaur that we learned about is the ability to cool its brains in the literal sense,” said Ivan Kuzmin. “The network of veins and arteries in its braincase turned out to be very complicated: They did not go in a single direction, but constantly communicated with each other, like a system of railway tracks. The blood could have flowed in different directions and been redistributed, while maintaining the optimal brain temperature of the animal. For example, if the top of an ankylosaur’s head became warm, the vessels quickly diverted the warm blood and created a screening effect—as if a dinosaur put a sun hat on. Moreover, the endocranial vasculature of ankylosaurs turned out to be somewhat more like the vessels of present-day lizards than that of the closer extant relatives of dinosaurs—crocodiles or birds.”
Another important conclusion concerns the hearing of Bissektipelta archibaldi. The palaeontologists managed to examine the inner ear of the ancient animal. Its anatomy suggests the frequency of sounds that the ankylosaur could hear. The range turned out to have been from about 300 to 3,000 hertz—present-day crocodiles hear in the same range. These are quite low frequencies that correspond to the relatively large size of ankylosaurs. The larger the present-day animals are, the more low-frequency sounds they make and hear. The palaeontologists suggested that, during evolution, ankylosaurs increased in size, so later forms perceived sounds of even lower frequencies.
“Present-day animal species are characterized by a certain brain-body size relationship,” explained Ivan Kuzmin. “If you look at dinosaurs, then ankylosaurs and their closest relatives (stegosaurs) were almost outsiders. The mass of their brain turned out to be at least half less than what we would expect, based on a comparison with present-day animals. It was about 26.5 grams for a three-meter Bissektipelta. Its brain size can be compared with two walnuts. Nevertheless, ankylosaurs existed on the planet for 100 million years. They were quite successful in terms of evolution. However, judging by the size of their olfactory bulbs, they sniffed a little faster than they thought.”
At the next stage of their research, the scientists would like to study the fossil braincases of other species of ankylosaurs in order to test the hypotheses expressed in the paper. Additionally, the palaeontologists continue to use computed tomography and are currently working with digital endocranial casts of hadrosaurs—duck-billed dinosaurs whose remains were found at the same locality in Uzbekistan.
The research is published in Biological Communications.
The fossilized jaw of an Overoraptor chimentoi, a new species of dinosaur discovered in Argentine Patagonia
Fossilized remains of a new species of dinosaur that lived 90 million years ago have been discovered in Patagonia, Argentine paleontologists announced on Thursday.
The winged dinosaur had legs similar to the velociraptor and experts believe it may hold the key to revealing information about the evolution of birds.
The fossil remains, which measure less than a meter and a half in length, were discovered at a dig in the province of Rio Negro in Argentine Patagonia, around 1,100 kilometers (685 miles) from Buenos Aires, the scientific dissemination agency from the La Matanza university said.
It is a new species of carnivorous Paraves theropod that has been named Overoraptor chimentoi, explained Matias Motta, a researcher from the Argentine natural sciences museum.
It is related to another species found more than 10,000 kilometers away in Madagascar.
The first remains were discovered in 2013, with more fossils found in a second dig in 2018.
“This animal had a very sharp claw on its index toe, which certainly was used to attack prey, and it had a long and graceful leg, which indicates it was a running animal,” said Motta, the main author of the study published in The Science of Nature magazine.
“It was certainly fast, agile and, like all its relatives, it would have been carnivorous.”
Researchers were surprised to find that while its legs were similar to the “raptor” family of dinosaurs, its upper limbs were very long and robust, similar to modern birds.
The second dig uncovered many bones, including an almost complete foot, tail vertebrae and parts of a wing, said paleontologist Federico Brisson Egli.
Previous discoveries in Patagonia of dinosaurs with bird-like features belonged to the Unenlagia genus of dromaeosaurid theropods, which were agile and walked on their hind legs.
“Contrary to what we originally assumed, the Overoraptor is not part of the Unenlagia family, but from another group including a Madagascan species called Rahonavis,” said paleontologist Fernando Novas.
Note: The above post is reprinted from materials provided by AFP.
Image of pregnant ichthyosaur with octuplets. Credit: Copyright Nobumichi Tamura
Autumn was closing in fast on northern Nevada when Martin Sander took one last look around the excavation site in the Augusta Mountains 150 miles (241 kilometers) east of Reno.
The longtime paleontologist from Germany had been working summers in Nevada for 20 years by that point and believed in the maxim that, “we find the spectacular things on the second to last day or last day.”
It was Oct. 3, 2011, and Sander and his team were nearing the end of a two-week expedition in an area that’s a hotspot for ichthyosaur fossils.
Just getting to the site requires hours of driving on dirt from Winnemucca or Lovelock and hours more hiking from base camp.
When the team packs up and leaves for the season they know it might be months, or even years, before they return.
Sander’s decision to take another trip around the site proved fateful.
“The trick is you have to know what you are looking for,” said Sander, who described that final stroll as “wandering around in the field.”
At an outcropping around 6,000 feet (1,829 meters) in elevation he spotted what appeared to be fossilized remains of an ichthyosaur spine. Further, there was evidence the large, prehistoric, swimming reptile had been pregnant when it died.
“I found it and realized pretty quickly what I was looking at,” Sander said.
The next day, with cold and snow closing in, the team packed up the exposed fossils for further research. They returned in 2014 and excavated the rest.
Last month, they published a paper on the findings.
The ichthyosaur was the second-oldest pregnant specimen ever found and it was of a species that had never before been identified.
Even more remarkable, it was just one of two major ichthyosaur findings at the location in the Augusta Mountains.
“It is an incredible place and there is new stuff coming out all the time,” Sander said. “Everything we touch, new stuff is coming out of it.”
The other finding hasn’t yet been published in an academic journal, but it involves an ichthyosaur fossil Sander refers to as “the giant skull.”
While the paper detailing the specifics of the giant skull fossil aren’t yet published, Sander says the findings are, well, big.
“It is the first big thing that lived on this earth,” he said of the beast, which had a skull so big researchers had to borrow a beer truck to haul it away.
Although “the giant skull” may prove the more significant of the two recent discoveries, Sander says there’s plenty to celebrate about the pregnant ichthyosaur dubbed “Martina,” by the scientists.
For starters, at 246 million-years-old Martina is the second-oldest specimen of a pregnant ichthyosaur. The oldest is a 249-million-year-old specimen from China.
Martina is also a species of ichthyosaur, Cymbospondylus duelferi, that hasn’t been found anywhere else, according to Sander’s research.
Researchers know because literature reviews that were part of the scientific reporting showed Martina had characteristics not found in any other ichthyosaur fossils.
At about 12 feet (3.6 meters) long she was smaller than other ichthyosaurs, some of which are as large as 60 feet (18 meters) . Despite her smaller body, Martina’s teeth were larger than expected for an ichthyosaur of similar size.
The teeth, about an inch in length, would have helped her tear up prey such as squid or fish that were in the sea that covered what is now Nevada.
“She was a pretty fierce lady,” Sander said, comparing her to a much larger sample found in another Nevada range. “She is half the size but her teeth are nearly as big as the bigger one from the Humboldt Range.”
Martina and “the giant skull” also add to the diversity of Nevada’s ichthyosaur legacy. The specimens, both from the early triassic period, show how quickly life evolved following the Permian-Triassic extinction event.
The extinction event, which is thought to have wiped out as many as 96% of species, happened 252 million years ago.
That ichthyosaurs of immense size and diversity are found dating back to a few million years later suggests the animals evolved relatively quickly.
“The cool thing about it is … they just diversified crazily fast,” Sander said. “In Nevada you see this incredible explosion of ichthyosaurs.”
One of the reptiles’ adaptations, as Martina demonstrates, is they would have evolved from laying eggs to giving live birth, which would have been an advantage in their move to the sea, Sander said.
He compared it to the advantage a whale or dolphin has over a sea turtle, the latter of which is exposed, along with offspring, to danger by having to leave the water to lay eggs on shore.
“Most of the reptiles that returned to the sea, they all evolved this ability from egg laying to giving birth to live young,” he said.
While both Martina and the giant skull are exciting to researchers like Sander, they’ve also captured the imagination of people like craft brewer Tom Young, who has emerged as a major paleontology booster in Nevada.
Young, a former geologist, is the founder of Great Basin Brewing in Reno, which produces Ichthyosaur, or Icky, IPA. It was his beer truck researchers used to haul the giant skull from the Augusta Mountains to the Los Angeles Museum of Natural History.
And it’s Young whose made it his mission to popularize paleontology in Nevada.
“It is so important we preserve this and study these things to show where we are today and how we got here,” Young said. “You marvel as a human and realize the importance of our being here now, but at the same time you are looking at us as part of this much larger, huge universe.”
Young’s enthusiasm carries over to financial support. He’s contributed thousands of dollars, and plenty of beer, to research efforts. He’s also hosted brewery fundraisers that attract hundreds of people who want to hear directly from the scientists.
“I’m ecstatic when people give a crap about science,” Young said.
All three said they’d like to see the state develop a repository with the tools and talent to meet requirements for keeping ichthyosaur fossils recovered from public land.
Nevada’s Berlin-Ichthyosaur State Park retains fossils that are on display as they were found. But many significant finds are trucked to Berkeley or Los Angeles where there are repositories that meet federal standards.
“It should give Nevada some great pride we have some the coolest and biggest and meanest things to evolve on Earth here in our backyard,” Young said.
In recent years some of the most significant ichthyosaur findings have been outside Nevada, including an amphibious ichthyosaur from China that filled an evolutionary gap and a fossil in the United Kingdom from an ichthyosaur thought to be among the largest animals to ever live on the planet.
The paper on Martina and upcoming revelations about the giant skull will likely bring Nevada back into the spotlight.
Paula Noble, a professor of paleontology at University of Nevada, Reno, said that’s good news if it inspires more interest in science, especially among young people.
“Paleo is a great hook,” said Noble. “It is not just this stodgy thing we do in a lab.”
Note: The above post is reprinted from materials provided by The Associated Press.
El Niño events and high-latitude Eurasian warming are usually observed after large tropical eruptions. However, simulations of climate impacts by volcanos show large biases when compared with observations, calling for substantial improvements in climate models. The graph depicts the change in zonally averaged surface temperature in observations (the shaded part) and simulations (the line) after large tropical volcanic eruptions. The equation denotes the chemical reaction in the stratosphere. Credit: Advances in Atmospheric Sciences
Climatologists have found that if an ongoing Philippine volcanic eruption becomes more violent, the gases released are likely to produce an El Niño event during the 2020-21 winter, a more intense polar vortex and warming across Eurasia.
When Taal volcano near Manila started erupting on January 12, ash spewed 14 kilometers into the air, coating villages in a blanket of dust and affecting nearly 460,000 people, many of whom lost access to electricity and fresh water. Despite the significant impact, the eruption so far has been tame compared to some of the biggest eruptions in history, and the Philippine Institute of Volcanology and Seismology (PHIVOLCS) has since downgraded its alert.
But these same volcanologists now warn that the Taal volcano may merely be in a lull and that the risk of a more dangerous eruption still exists.
“The Taal eruption has been terrible for local communities,” said Fei Liu, a researcher with China’s Sun Yat-sen University, “but it has also become a deep global concern, with potentially hazardous consequences for the Earth’s climate.”
Fine ash and sulfur dioxide from eruptions block incoming solar radiation, thus reducing heat at Earth’s surface that in turn produces atmospheric warming. As a result, for a year after especially violent eruptions, temperatures can be cooler than normal across much of the planet. But in addition to the cooling, there can also be a warming in the first post-eruption winter in the northern hemisphere as surface temperatures rebounds.
However, there are still some gaps between the climate impacts of volcanoes projected by computer simulations and what observations demonstrate. So Liu’s team are using the Taal eruption as a real-time assessment tool of the impact of volcanic eruptions on the climate in order to improve models.
The team’s research, joined by scientists from Nanjing University of Information Science and Technology, University of Hawaii, Zhejiang University, Institute of Atmospheric Physics at Chinese Academy of Sciences, Nanjing Normal University, and University of Gothenburg, is reported as a “News &Views” article in Advances in Atmospheric Sciences.
The researchers took data on the scale of volcanic eruptions worldwide over the past 1,100 years taken from Greenland and Antarctica ice cores and inputted this into global climate models. This then allowed them to project the impact of the Taal eruption.
They reckon there is a high likelihood (83% probability) of an El Niño-like warming event during the 2020/21 winter if the magnitude of the Taal eruption reaches a mid-range “volcanic explosive index”. Such an eruption would also produce an enhanced polar vortex— a large area of low pressure and cold air surrounding the Earth’s North and South poles, which in turn would drive warming across the Eurasian continent.
The researchers’ next step will be to use the eruption to better assess impacts from stratospheric aerosol geo-engineering (also known as solar radiation management), a theoretical method of reducing global warming by injecting sulfate aerosols into the stratosphere via balloons that would work as a sort of ‘deliberate’ volcanic eruption.
Reference:
Fei Liu et al, Could the Recent Taal Volcano Eruption Trigger an El Niño and Lead to Eurasian Warming?, Advances in Atmospheric Sciences (2020). DOI: 10.1007/s00376-020-2041-z
The deep origin of craters and mounds was discovered using cutting edge 3D seismic technology which can penetrate deep into the ocean floor, and help scientists visualize the structures in the hard bedrock underneath. Illustration: M. Waage
A paper published in Science in 2017 described hundreds of massive, kilometer -wide, craters on the ocean floor in the Barents Sea. Today more than 600 gas flares are identified in and around these craters, releasing the greenhouse gas steadily into the water column. Another study, published the same year in PNAS, mapped several methane mounds, some 500m wide, in the Barents Sea. The mounds were considered to be signs of soon-to-happen methane expulsions that have created the said craters.
The most recent study in Scientific Reports looks into the depths far beneath these craters in the ocean floor and reveals the geological structures that have made the area prone to crater formation and subsequent methane expulsions.
“It turns out that this area has a very old fault system — essentially cracks in bedrock that likely formed 250 million years ago. Craters and mounds appear along different fault structures in this system. These structures control the size, placement, and shape of the craters. The methane that is leaking through the seafloor originates from these deep structures and is coming up through these cracks.” according to Malin Waage, a postdoc at CAGE, Centre for Arctic Gas Hydrate, Environment and Climate, and the first author of the study.
Cutting edge 3D seismic technology
The deep origin of craters and mounds was discovered using cutting edge 3D seismic technology which can penetrate deep into the ocean floor, and help scientists visualize the structures in the hard bedrock underneath.
“Our previous studies in the area hypothesized that climate warming and the retreat of the ice sheet some 20,000 years ago, caused the gas hydrates beneath the ice to melt leading to abrupt methane release and creating craters.”
Gas hydrates are a solid form of methane, among others, that is stable in cold temperatures and under pressure, which an enormous ice sheet provides. As the ocean warmed up, and the pressure of the ice sheet lifted, the methane ice in the seafloor melted and thus the craters were formed.
“This study, however, ads several layers to that picture, as we now see that there has been a structural weakness beneath these giant craters, for much longer than the last 20,000 years. Deep below the seafloor, the expansion of gas and release of water build up a muddy slurry which eventually erupted through the fractures and caused seafloor collapses and craters in the hard bedrock. Think of it as a building: A roof of a building can cave in if the ground structure is weak. We believe that this is what happened in the crater area after the last glaciation.” says Waage.
The Barents Sea is poorly understood
The exploration of petroleum resources in the Barents Sea is a hot topic in Norway and beyond as the area is a part of a vulnerable Arctic ecosystem. But the area’s geological system is poorly understood.
“Our 3D survey covered approximately 20 percent of the entire crater area. We believe that it is important to understand if similar fault systems exist in the larger context of the Barents Sea because they potentially could pose a threat to marine operations.”
Some of the questions that scientists, society and the industry does not know the answer to are: Will these weak structures lead to unpredictable and explosive methane release? Can such release and related geohazards be triggered by drilling? And can the gas reach the atmosphere in case of abrupt blow-outs, adding to the greenhouse gas budget?
“There is still very much that we don’t know about this system. But we are currently collecting and analyzing new data in the Barents Sea, dominated by similar crater structures. This can help us map in bigger detail the fault systems and associated weakness. ” says Waage.
Reference:
Malin Waage, Pavel Serov, Karin Andreassen, Kate A. Waghorn, Stefan Bünz. Geological controls of giant crater development on the Arctic seafloor. Scientific Reports, 2020; 10 (1) DOI: 10.1038/s41598-020-65018-9
UT Austin scientists found that the fossil millipede Kampecaris obanensis was 425 million years old. Credit: British Geological Survey
A 425-million-year-old millipede fossil from the Scottish island of Kerrera is the world’s oldest “bug”—older than any known fossil of an insect, arachnid or other related creepy-crawly, according to researchers at The University of Texas at Austin.
The findings offer new evidence about the origin and evolution of bugs and plants, suggesting that they evolved much more rapidly than some scientists believe, going from lake-hugging communities to complex forest ecosystems in just 40 million years.
“It’s a big jump from these tiny guys to very complex forest communities, and in the scheme of things, it didn’t take that long,” said Michael Brookfield, a research associate at UT Austin’s Jackson School of Geosciences and adjunct professor at the University of Massachusetts Boston. “It seems to be a rapid radiation of evolution from these mountain valleys, down to the lowlands, and then worldwide after that.”
The research was recently published in the journal Historical Biology. Brookfield led the study with co-authors including Elizabeth Catlos, a professor in the Jackson School’s Department of Geological Sciences, and Stephanie Suarez, a doctoral student at the University of Houston who made improvements to the fossil dating technique used in the study when she was an undergraduate at the Jackson School.
The team found that the ancient millipede fossil is 425 million years old, or about 75 million years younger than the age other scientists have estimated the oldest millipede to be using a technique known as molecular clock dating, which is based on DNA’s mutation rate. Other research using fossil dating found that the oldest fossil of a land-dwelling, stemmed plant (also from Scotland) is 425 million years old and 75 million years younger than molecular clock estimates.
Although it’s certainly possible there are older fossils of both bugs and plants, Brookfield said that the fact they haven’t been found—even in deposits known for preserving delicate fossils from this era—could indicate that the ancient millipede and plant fossils that have already been discovered are the oldest specimens.
If that’s the case, it also means both bugs and plants evolved much more rapidly than the timeline indicated by the molecular clock. Bountiful bug deposits have been dated to just 20 million years later than the fossils. And by 40 million years later, there’s evidence of thriving forest communities filled with spiders, insects and tall trees.
“Who is right, us or them?” Catlos said. “We’re setting up testable hypotheses—and this is where we are at in the research right now.”
Given their potential evolutionary significance, Brookfield said that he was surprised that this study was the first to address the age of the ancient millipedes.
Suarez said a reason could be the difficulty of extracting zircons—a microscopic mineral needed to precisely date the fossils—from the ashy rock sediment in which the fossil was preserved. As an undergraduate researcher at the Jackson School, Suarez developed a technique for separating the zircon grain from this type of sediment. It’s a process that takes practice to master. The zircons are easily flushed away when trying to loosen their grip on the sediment. And once they are successfully released from the surrounding rock, retrieving the zircons involves an eagle-eyed hunt with a pin glued to the tip of a pencil.
“That kind of work trained me for the work that I do here in Houston,” Suarez said. “It’s delicate work.”
As an undergraduate, Suarez used the technique to find that a different millipede specimen, thought to be the oldest bug specimen at the time, was about 14 million years younger than estimated—a discovery that stripped it of the title of oldest bug. Using the same technique, this study passes the distinction along to a new specimen.
Reference:
M. E. Brookfield et al. Myriapod divergence times differ between molecular clock and fossil evidence: U/Pb zircon ages of the earliest fossil millipede-bearing sediments and their significance, Historical Biology (2020). DOI: 10.1080/08912963.2020.1761351
This artist’s impression shows a view of the surface of the planet Proxima b orbiting the red dwarf star Proxima Centauri, the closest star to the Solar System. The double star Alpha Centauri AB also appears in the image to the upper-right of Proxima itself. Proxima b is a little more massive than the Earth and orbits in the habitable zone around Proxima Centauri, where the temperature is suitable for liquid water to exist on its surface. (Illustration by ESO/M. Kornmesser)
Yale geophysicists reported that Earth’s ever-shifting, underground network of tectonic plates was firmly in place more than 4 billion years ago — at least a billion years earlier than scientists generally thought.
Tectonic plates are large slabs of rock embedded in the Earth’s crust and upper mantle, the next layer down. The interactions of these plates shape all modern land masses and influence the major features of planetary geology — from earthquakes and volcanoes to the emergence of continents.
“Understanding when plate tectonics started on Earth has long been a fundamentally difficult problem,” said Jun Korenaga, a professor of earth and planetary sciences in Yale’s Faculty of Arts and Sciences and senior author of the new study, published in Science Advances. “As we go back deeper in time, we have fewer geological records.”
One promising proxy for determining if tectonic plates were operational is the growth of continents, Korenaga said. This is because the only way to build up a continent-sized chunk of land is for surrounding surface rock to keep sinking deeply over a long period — a process called subduction that is possible only through plate tectonics.
In the new study, Korenaga and Yale graduate student Meng Guo found evidence of continental growth starting as early as 4.4 billion years ago. They devised a geochemical simulation of the early Earth based on the element argon — an inert gas that land masses emit into the atmosphere. Argon is too heavy to escape Earth’s gravity, so it remains in the atmosphere like a geochemical ledger.
“Because of the peculiar characteristics of argon, we can deduce what has happened to the solid Earth by studying this atmospheric argon,” Korenaga said. “This makes it an excellent bookkeeper of ancient events.”
Most of the argon in Earth’s atmosphere is 40Ar — a product of the radioactive decay of 40K (potassium), which is found in the crust and mantle of continents. The researchers said their model looked at the atmospheric argon that has gradually accumulated over the history of the planet to determine the age of continental growth.
Part of the challenge in creating their simulation, the researchers said, was incorporating the effects of a geological process called “crustal recycling.” This refers to the cycle by which continental crust builds up, then is eroded into sediments, and eventually carried back underground by tectonic plate movements — until the cycle renews itself.
The simulation thus had to account for argon gas emissions that were not part of continental growth.
“The making of continental crust is not a one-way process,” Korenaga said.
Reference:
Meng Guo, Jun Korenaga. Argon constraints on the early growth of felsic continental crust. Science Advances, 2020; 6 (21): eaaz6234 DOI: 10.1126/sciadv.aaz6234
Note: The above post is reprinted from materials provided by Yale University. Original written by Jim Shelton.
URI graduate student Reilly Hayes (left) and undergraduate Amanda Bednarick examine an outcrop for fossils at Petrified Forest National Park as part of their research. Credit: Amanda Bednarick
A team of University of Rhode Island scientists and statisticians conducted a sophisticated quantitative analysis of a mass extinction that occurred 215 million years ago and found that the cause of the extinction was not an asteroid or climate change, as had previously been believed. Instead, the scientists concluded that the extinction did not occur suddenly or simultaneously, suggesting that the disappearance of a wide variety of species was not linked to any single catastrophic event.
Their research, based on paleontological field work carried out in sediments 227 to 205 million years old in Petrified Forest National Park, Arizona, was published in April in the journal Geology.
According to David Fastovsky, the URI professor of geosciences whose graduate student, Reilly Hayes, led the study, the global extinction of ancient Late Triassic vertebrates—the disappearance of which scientists call the Adamanian/Revueltian turnover—had never previously been reconstructed satisfactorily. Some researchers believed the extinction was triggered by the Manicouagan Impact, an asteroid impact that occurred in Quebec 215.5 million years ago, leaving a distinctive 750-square-mile lake. Others speculated that the extinction was linked to a hotter and drier climate that occurred at about the same time.
“Previous hypotheses seemed very nebulous, because nobody had ever approached this problem—or any ancient mass extinction problem—in the quantitative way that we did,” Fastovsky said. “In the end, we concluded that neither the asteroid impact nor the climate change had anything to do with the extinction, and that the extinction was certainly not as it had been described—abrupt and synchronous. In fact, it was diachronous and drawn-out.”
The Adamanian/Revueltian turnover was the perfect candidate for applying the quantitative methods employed by the research team, Fastovsky said. Because the fossil-rich layers at Petrified Forest National Park preserve a diversity of vertebrates from the period, including crocodile-like phytosaurs, armored aetosaurs, early dinosaurs, large crocodile-like amphibians, and other land-dwelling vertebrates, Hayes relocated the sites where known fossils were discovered and precisely determined their age by their position in the rock sequence. He was assisted by URI geosciences majors Amanda Bednarick and Catherine Tiley.
Hayes and URI Statistics Professor Gavino Puggioni then applied several Bayesian statistical algorithms to create “a probabilistic estimate” of when the animals most likely went extinct. This method allowed for an unusually precise assessment of the likelihood that the Adamanian vertebrates in the ancient ecosystem went extinct dramatically and synchronously, as would be expected with an asteroid impact.
Previous research concluded that the asteroid impact occurred 215.5 million years ago and the climate change some 3 to 5 million years later. The URI researchers demonstrated that the extinctions happened over an extended period between 222 million years ago and 212 million years ago. Some species of armored archosaurs Typothorax and Paratypothorax, for instance, went extinct about 6 million years before the impact and 10 million years before the climate change, while those of Acaenasuchus, Trilophosaurus and Calyptosuchus went extinct 2 to 3 million years before the impact. Desmatosuchus and Smilosuchus species, on the other hand, went extinct 2 to 3 million years after the impact and during the very early stages of the climate change.
“It was a long-lasting suite of extinctions that didn’t really occur at the same time as the impact or the climate change or anything else,” Fastovsky said. “No known instantaneous event occurred at the same time as the extinctions and thus might have caused them.”
The URI professor believes it will be difficult to apply these quantitative methods to calculate other mass extinctions because equally rich fossil data and precise radiometric dates for them aren’t available at other sites and for other time periods.
“This was like a test case, a perfect system for applying these techniques because you had to have enough fossils and sufficiently numerous and precise dates for them,” he said. “Other extinctions could potentially be studied in a similar way, but logistically it’s a tall mountain to climb. It’s possible there could be other ways to get at it, but it’s very time consuming and difficult.”
Credit: Pohang University of Science & Technology (POSTECH)
Climate change is occurring all over the globe as 1°C increase in Earth’s surface temperature has led to the sea level rise, abrupt melting of the Arctic sea ice, and the increase in extreme weather events such as heat waves, droughts, and floods. To accurately predict the anthropogenic climate changes under the increase in greenhouse gases, it is important to understand the effects of natural factors such as solar and volcanic activities. A recent study has shown how global precipitation decreases when volcanoes erupt in the tropics.
Professor Seung-Ki Min and Dr. Seungmok Paik of Division of Environmental Science and Engineering at POSTECH and researchers from the French National Centre for Scientific Research, Swiss Federal Institute of Technology in Zurich, and University of Edinburgh have released new findings that the El Niño induced by volcanic eruptions plays a key role in the decrease in global precipitation. So far, studies have shown that volcanic activity reduces precipitation across the globe, but its specific mechanism had been unclear. These research results were recently published in Science Advances, a sister journal of Science.
During the two to three years following Mount Pinatubo’s eruption in 1991, the average global temperature fell by about 0.2 degrees. This is because the massive dust including sulfur dioxide emitted by the eruption reflected the light from the sun and blocked its heat from reaching the Earth’s surface. Volcanic activities, along with this cooling effect, reduce the global terrestrial precipitation but its amplitude greatly varies depending on climate model simulations. For the first time, the joint research team confirmed that the main factor for the drop in precipitation after volcanic eruptions is the difference in El Niño’s response.
El Niño is a natural climate variability that occurs every three to eight years, with weakened trade winds in the equatorial Pacific Ocean and warmer sea surface temperatures in the equatorial eastern Pacific, causing extreme weather conditions across the globe including drought and heavy rains. Under El Niño’s influence, precipitation reduction occurs especially in the global monsoon regions, including Southeast Asia, India, South Africa, Australia and northern South America.
The team compared several climate model simulations and found that El Niño appeared in the year following a volcanic eruption in most models, with a significant drop in precipitation around the global monsoon region. In particular, the strength of El Niño was different for each simulation, and the stronger the El Niño, the more pronounced the reduction in precipitation occurred. The research team also found that the stronger the volcanic forcing and the greater the warm water volume in the western Pacific Ocean, a stronger El Niño developed, which in turn intensified the reduction in precipitation.
These findings are expected to be used to identify the side effects of geoengineering techniques and to predict the climate of the later years. In particular, it suggests that if geoengineering techniques are used to reduce global warming by spraying sulfur dioxide — the main component of volcanic ash — in the lower stratosphere to imitate artificial volcanoes, they could produce unexpected side effect of changing the precipitation patterns across the globe.
Professor Seung-Ki Min stated, “If geoengineering techniques are applied to mimic volcanoes and block sunlight, drought and water shortages may increase significantly in the monsoon regions — home to two-thirds of the world’s population.”
This research was supported by the Mid-career Researcher Program of the National Research Foundation of Korea.
Reference:
Seungmok Paik, Seung-Ki Min, Carley E. Iles, Erich M. Fischer, Andrew P. Schurer. Volcanic-induced global monsoon drying modulated by diverse El Niño responses. Science Advances, 2020; 6 (21): eaba1212 DOI: 10.1126/sciadv.aba1212
The attached image shows Wightia declivirostris flying over an oxbow lake in the valley of the ancient Wessex River that flowed from Devon to the Isle of Wight. Credit: Megan Jacobs
The first ever specimen of a pterodactyl, more commonly found in China and Brazil, has been found in the United Kingdom.
A fossil hunter recently discovered a peculiar shaped fragment of fossil bone while out walking his dog in Sandown Bay on the Isle of Wight.
Not sure what it was, he passed it to University of Portsmouth Palaeontology student Megan Jacobs, who thought it might be the jaw bone from a pterodactyl. Further research proved she was right.
However, this was no ordinary pterodactyl jaw. This one lacked teeth and was remarkably similar to a bizarre group of pterosaurs called ‘tapejarids’. They are better known from China and Brazil and have never previously been found in the UK.
Just last year a team from the University of Portsmouth discovered as similar specimen in North Africa (Morocco) which they named Afrotapejara.
The new specimen from the Isle of Wight has been named Wightia declivirostris.
Megan Jacobs said: “Although only a fragment of jaw, it has all the characteristic of a tapejarid jaw, including numerous tiny little holes that held minute sensory organs for detecting their food, and a downturned, finely pointed beak.
“Complete examples from Brazil and China show that they had large head crests, with the crest sometime being twice as big as the skull. The crests were probably used in sexual display and may have been brightly colored.”
The researchers determined that the Isle of Wight example seemed more closely related to the Chinese tapejarids rather than the Brazilian examples.
Co-author of the study Professor David Martill, a paleontologist from the University of Portsmouth, said: “This new species adds to the diversity of dinosaurs and other prehistoric reptiles found on the Island, which is now one of the most important places for Cretaceous dinosaurs in the world.”
The finder has kindly donated the specimen to Dinosaur Isle Museum at Sandown, where it is hoped it will go on display in the future.
Reference:
David M. Martill et al, First tapejarid pterosaur from the Wessex Formation (Wealden Group: Lower Cretaceous, Barremian) of the United Kingdom, Cretaceous Research (2020). DOI: 10.1016/j.cretres.2020.104487
A schematic diagram of the Earth’s deep oxygen factory shows the oxygenation and deoxygenation processes of hydrous mantle materials in the lower mantle across the ~1000 km depth beneath Earth’s surface. Under the conditions of Earth’s middle mantle, scientists discovered an oxygen-excess phase, (Mg,Fe)2O3+δ (0 < δ < 1) that can be formed with under-saturated water at >1000 kilometers depths. Those oxygen-excess materials may have long-termly oxidized the shallow mantle and the crust, which is essential to allow free oxygen to build up in Earth’s atmosphere. Credit: Science China Press
Subduction of hydrous materials imposes great influence on the structure, dynamics, and evolution of our planet. However, it is largely unclear how subducting slabs chemically interact with the middle mantle. Recently, an oxygen-excess phas (Mg,Fe)2O3+δ was discovered under conditions similar to the Earth’s middle mantle (~1000-2000 km) by a team of scientists from the Center of High Pressure Science and Technology Advanced Research (HPSTAR) and Stanford University.
This oxygen-excess phase is fully recoverable to ambient conditions for ex-situ investigation using transmission electron microscopy. It contains ferric iron as in hematite (Fe2O3) which is the most oxidized form of iron on the Earth’s surface, but this new phase holds more oxygen than hematite through interactions between oxygen atoms. The peculiar nature of oxygen in this new phase may revise our view on the mantle redox chemistry.
“We employed laboratory techniques to simulate the conditions deep inside the Earth and found an oxygen-excess phase emerged when hydrous mineral assemblages (e.g., ferropericlase mixed with brucite) were exposed to laser heating at pressures greater than 40 million times the atmospheric pressure on the Earth’s surface” said Dr. Jin Liu from HPTAR. “The formation of this new phase provides strong evidence that water acts as a strong oxidant at high pressure.”
“This phase could coexist with the pyrite-type phase hydrogen-bearing FeO2 at deep mantle conditions, whereas the two phases are distinct in crystal chemistry,” added Dr. Qingyang Hu from HPSTAR. “Unlike the formation of the pyrite-type phase which usually forms in deep lower mantle and requires a large quantity of water, this oxygen-excess phase can be formed with a moderate amount of water at mid-mantle conditions. The flexible formation conditions make it potentially a more widespread phase at depths greater than 1000 km in Earth’s mantle, occupying almost 2/3 of the mantle.” Furthermore, this oxygen-excess phase can co-exist with the major mantle minerals, bridgmanite and ferropericlase, under Earth’s lower-mantle conditions.
“The widespread presence of the oxygen-excess phase makes it and other oxygen-enriched oxides an important subject for the full range of future geochemistry and mineral physics studies,” suggested Dr. Ho-kwang Mao, director of HPSTAR. “Remarkably, this new phase is quenchable. As a matter of fact, most compounds synthesized under the lower mantle conditions and quenchable back to ambient conditions have been discovered and named as minerals such as bridgmanite (Mg,Fe)SiO3 and seifertite SiO2. Hence, this presents an opportunity to search for this oxygen excess phase in nature as diamond inclusions or meteorite shock products.”
The crystal structure of this oxygen excess phase may represent a structure prototype which will accommodate other Earth-abundant components (e.g. Al, Ca, Ti, and Ni). At the same time, the channel space in this oxygen-excess phase could offer a great flexibility not only for excess oxygen, but also for other volatiles (e.g. N, S, F, and Cl). Considering its structural versatility, the new phase could be an important volatile carrier in the deep mantle over geological time. More importantly, together with excess Fe3+ from the primordial lower mantle, those oxygen-excess materials may have in the long term oxidized the shallow mantle and the crust, which is fundamental to the evolution and habitability of complex life on the Earth’s surface.
These results suggest that the oxygen-excess phase may facilitate oxygen-excess reservoirs out of hydrated slab remnants at depths greater than 1000 km. Oceanic crusts in the mid-mantle thus might deeply regulate the rise of oxygen in Earth’s atmosphere and global habitability, like shallowly-recycled fluids. Such intriguing chemistry of deep oxygen sheds light on chemical and dynamic models of mantle slab remnants as well as the interaction and coevolution of Earth’s interior and surface.
Reference:
Jin Liu et al, Evidence for oxygenation of Fe-Mg oxides at mid-mantle conditions and the rise of deep oxygen, National Science Review (2020). DOI: 10.1093/nsr/nwaa096
Note: The above post is reprinted from materials provided by Science China Press.
Normal and malformed spores from East Greenland. Credit: John Marshall
Researchers at the University of Southampton have shown that an extinction event 360 million years ago, that killed much of the Earth’s plant and freshwater aquatic life, was caused by a brief breakdown of the ozone layer that shields the Earth from damaging ultraviolet (UV) radiation. This is a newly discovered extinction mechanism with profound implications for our warming world today.
There have been a number of mass extinction in the geological past. Only one was caused by an asteroid hitting the Earth, which was 66 million years ago when the dinosaurs became extinct. Three of the others, including the end Permian Great Dying, 252 million years ago, were caused by huge continental scale volcanic eruptions that destabilised the Earth’s atmospheres and oceans.
Now, scientists have found evidence showing it was high levels of UV radiation which collapsed forest ecosystems and killed off many species of fish and tetrapods (our four limbed ancestors) at the end of the Devonian geological period, 359 million years ago. This damaging burst of UV radiation occurred as part of one of the Earth’s climate cycles, rather than being caused by a huge volcanic eruption.
The ozone collapse occurred as the climate rapidly warmed following an intense ice age and the researchers suggest that the Earth today could reach comparable temperatures, possibly triggering a similar event. Their findings are published in the journal Science Advances.
The team collected rock samples during expeditions to mountainous polar-regions in East Greenland, which once formed a huge ancient lake bed in the arid interior of the Old Red Sandstone Continent, made up of Europe and North America. This lake was situated in the Earth’s southern hemisphere and would have been similar in nature to modern day Lake Chad on the edge of the Sahara Desert.
Other rocks were collected from the Andean Mountains above Lake Titicaca in Bolivia. These South American samples were from the southern continent of Gondwana, which was closer to the Devonian South Pole. They held clues as to what was happening at the edge of the melting Devonian ice sheet, allowing a comparison between the extinction event close to the pole and close to the equator.
Back in the lab, the rocks were dissolved in hydrofluoric acid, releasing microscopic plant spores (like pollen, but from fern like plants that didn’t have seeds or flowers) which had lain preserved for hundreds of millions of years. On microscopic examination, the scientists found many of the spores had bizarrely formed spines on their surface — a response to UV radiation damaging their DNA. Also, many spores had dark pigmented walls, thought to be a kind of protective ‘tan’, due to increased and damaging UV levels.
The scientists concluded that, during a time of rapid global warming, the ozone layer collapsed for a short period, exposing life on Earth to harmful levels of UV radiation and triggering a mass extinction event on land and in shallow water at the Devonian-Carboniferous boundary.
Following melting of the ice sheets, the climate was very warm, with the increased heat above continents pushing more naturally generated ozone destroying chemicals into the upper atmosphere. This let in high levels of UV-B radiation for several thousand years.
Lead researcher Professor John Marshall, of the University of Southampton’s School of Ocean and Earth Science, who is a National Geographic Explorer, comments: “Our ozone shield vanished for a short time in this ancient period, coinciding with a brief and quick warming of the Earth. Our ozone layer is naturally in a state of flux — constantly being created and lost — and we have shown this happened in the past too, without a catalyst such as a continental scale volcanic eruption.”
During the extinction, plants selectively survived, but were enormously disrupted as the forest ecosystem collapsed. The dominant group of armoured fish became extinct. Those that survived — sharks and bony fish — remain to this day the dominant fish in our ecosystems.
These extinctions came at a key time for the evolution of our own ancestors, the tetrapods. These early tetrapods are fish that evolved to have limbs rather than fins, but still mostly lived in water. Their limbs possessed many fingers and toes. The extinction reset the direction of their evolution with the post-extinction survivors being terrestrial and with the number of fingers and toes reduced to five.
Professor Marshall says his team’s findings have startling implications for life on Earth today: “Current estimates suggest we will reach similar global temperatures to those of 360 million years ago, with the possibility that a similar collapse of the ozone layer could occur again, exposing surface and shallow sea life to deadly radiation. This would move us from the current state of climate change, to a climate emergency.”
The remote locations visited in East Greenland are very difficult to access, with travel involving light aircraft capable of landing directly on the tundra. Transport within the vast field area was by inflatable boats equipped with outboard motors, all of which had to fit in the small aircraft.
All field logistics was organised by CASP, an independent charitable trust based in Cambridge specialising in remote geological fieldwork. Mike Curtis, Managing Director of CASP says: “We have a history of assisting research geologists such as John Marshall and colleagues to access remote field areas and we are particularly pleased that their research has proved to have such potentially profound implications.”
Reference:
John E. A. Marshall, Jon Lakin, Ian Troth, Sarah M. Wallace-Johnson. UV-B radiation was the Devonian-Carboniferous boundary terrestrial extinction kill mechanism. Science Advances, 2020; 6 (22): eaba0768 DOI: 10.1126/sciadv.aba0768
Subduction zones occur where one tectonic plate dives under another. New computer modeling by Magali Billen, professor of earth and planetary sciences at UC Davis, shows why earthquakes on these sinking plates cluster at certain depths and could give insight into processes deep in the Earth. (U.S. Geological Survey)
A new understanding of our planet’s deepest earthquakes could help unravel one of the most mysterious geophysical processes on Earth.
Deep earthquakes — those at least 300 kilometers below the surface — don’t typically cause damage, but they are often widely felt. These earthquakes can provide vital clues to understanding plate tectonics and the structure of the Earth’s interior. Due to the extremely high temperature and pressures where deep earthquakes occur, they likely stem from different physical and chemical processes than earthquakes near the surface. But it’s hard to gather information about deep earthquakes, so scientists don’t have a solid explanation for what causes them.
“We can’t directly see what’s happening where deep earthquakes occur,” said Magali Billen, professor of geophysics in the UC Davis Department of Earth and Planetary Sciences.
What’s driving deep earthquakes?
Billen builds numerical simulations of subduction zones, where one plate sinks below another, to better understand the forces controlling plate tectonics. Her recent work helps explain the distribution of deep earthquakes, showing that they most often strike in regions of “high strain” where a sinking tectonic plate bends and folds.
“These models provide compelling evidence that strain rate is an important factor in controlling where deep earthquakes occur,” she said.
The new understanding that deformation is a major factor in deep earthquakes should help scientists resolve which mechanisms trigger deep earthquakes and can provide new constraints on subduction zone structure and dynamics, Billen said.
“Once we understand deep earthquake physics better, we will be able to extract even more information about the dynamics of subduction, the key driver of plate tectonics,” she said.
Her findings were published May 27 in the journal Science Advances.
New way to study deep earthquakes
Deep earthquakes occur in subduction zones — where one of the tectonic plates floating on the surface of the Earth dives under another and is “subducted” into the mantle. Within the sinking slabs of crust, earthquakes cluster at some depths and are sparse in others. For example, many slabs exhibit large gaps in seismic activity below 410 kilometers in depth.
The gaps in seismicity line up with regions of the slab that are deforming more slowly in the numerical models, Billen said.
“Deformation is not the same everywhere in the plate,” Billen said. “That’s really what’s new here.”
Billen’s research was not originally intended to investigate deep earthquakes. Rather, she was trying to understand the slow back-and forth motion of deep ocean trenches, where plates bend downward in subduction zones.
“I decided out of curiosity to plot the deformation in the plate, and when I looked at the plot, the first thing that popped in my mind was ‘wow, this looks like the distribution of deep earthquakes,'” she said. “It was a total surprise.”
Mimicking the deep Earth
Billen’s model incorporates the latest data about phenomena such as the density of minerals, different layers in the sinking plate, and experimental observations of how rocks behave at high temperatures and pressures.
“This is the first model that really brings together the physical equations that describe the sinking of the plates and key physical properties of the rocks,” Billen said.
The results cannot distinguish between possible causes for deep earthquakes. However, they do provide new ways to explore what causes them, Billen said.
“Taking into account the added constraint of strain-rate should help to resolve which mechanisms are active in the subducting lithosphere, with the possibility that multiple mechanisms may be required,” she said.
The project was supported by a fellowship from the Alexander von Humboldt Foundation and an award from the National Science Foundation. The Computational Infrastructure for Geodynamics supports the CitcomS software used for the numerical simulations.
Reference:
Magali I. Billen. Deep slab seismicity limited by rate of deformation in the transition zone. Science Advances, 2020; 6 (22): eaaz7692 DOI: 10.1126/sciadv.aaz7692
