Detective mission to characterise and trace the history of a new African meteorite

November 27, 2018

Close-up of the meteorite fragment showing the fusion crust. Credit: Wits University

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Wits researchers go on a mission to describe, classify and trace the 4.5 billion-year-old history of a meteorite that landed in Madagascar.

Researchers from Wits and colleagues from the University of Antananarivo in Madagascar are on a “detective mission” to describe, classify and trace the history of a meteorite that landed in and around the small town of Benenitra in southwestern Madagascar shortly before the lunar eclipse on 27 July 2018.

News of the event in this remote area was brought to the attention of a Wits Geosciences graduate, Tim Marais, who was travelling in the area a few days after the meteorite fall. He collected some preliminary eyewitness accounts that reported a bright meteor fireball, a loud explosion and a rain of rock fragments that fell in and around Benenitra that, fortuitously, appear to have missed all people and buildings, and he was able to acquire several small fragments that residents had managed to locate. He delivered these to Professors Roger Gibson and Lewis Ashwal in the School of Geosciences at Wits and asked them to verify their extra-terrestrial origin. The signs of a dark fusion crust and small spheres in the rock matrix that were visible on broken surfaces appeared promising and the School’s Senior Technician, Caiphas Majola, was immediately commissioned to prepare a thin section of one of the fragments for microscopic analysis.

Tracing the history

Assessment of the thin section confirmed that it was, indeed, a meteorite and, more specifically, a relatively common type called a chondrite, referring to the small spherical chondrules that it contains. This established that the meteorite dates from the formation of our Solar System about 4.56 billion years ago.

At the same time, a news report appeared in the local Triatra Gazettenewspaper on 4 August regarding the eyewitness reports and showing a large specimen with a similar black fusion crust. To corroborate the event scientifically, the team approached Dr. Andry Ramanantsoa of the Laboratory of Seismology and Infrasound at the Institute and Observatory of Geophysics at the University of Antananarivo to investigate if there was any evidence that a significant explosion occurred in the atmosphere above Madagascar sometime in the evening of 27 July. Ramanantsoa was able to confirm, using infrasound data from the international Comprehensive Nuclear Test Ban Treaty Infrasound Station IS33 outside Antananarivo, that there had, indeed, been an “upper atmosphere energy release event” at 5.16 p.m. GMT (7.16 p.m. local time). Furthermore, he was able to identify that it occurred in a direction south-southwest of Antananarivo – the exact bearing of Benenitra.

The next step was to see if the blast wave from the atmospheric detonation was sufficiently large to have caused a ground vibration that could be detected by geophysical seismometers. For this the team turned to Dr. Andriamiranto (Ranto) Raveloson, a Postdoctoral Fellow and Technical Manager of the Africa Array Seismic Network that is co-ordinated from Wits. He was able to confirm a very faint seismic tremor at 5.17 p.m. GMT on the same night. The final confirmation that the fragment was related to a fall on 27 July was obtained from Dr. Matthias Laubenstein from the Laboratori Nazionali del Gran Sasso at the Istituto Nazionale di Fisica Nucleare in Italy, who measured the meteorite for rare cosmogenic nuclides that are created when an asteroid in Space is bombarded by high-energy cosmic rays. His measurements showed high levels of cosmogenic nuclides, consistent with the meteorite having entered Earth’s protective atmosphere only within the past few months.

Based on these findings, the team has submitted a request to the international Meteoritical Society to officially name and register Africa’s newest meteorite – Benenitra—on its database.

Classifying Africa’s newest meteorite

Ashwal and Gibson have refined the meteorite classification as an L6 chondrite. The name refers to the fact that it contains a low amount of iron (the “L”), and that it contains recognizable chondrules. Chondrules are the original building blocks of rocky bodies – such as asteroids and the Inner Planets – in Space. As these bodies grew larger, heat built up inside them – partly through gravitational collapse and partly because of radioactive elements – which caused the metals and chondrules to recrystallise and maybe even melt. Where temperatures were sufficiently high to melt the body, the denser metals were then able to settle towards the core of the body, with the less dense silicate melts rising towards the surface. Eventually the body would have cooled down sufficiently to solidify. The Benenitra meteorite appears to have got quite hot (the number “6” refers to the high amount of recrystallisation that occurred within the chondrules owing to this heating process) but only melted partially, allowing some of the chondrules to survive.

Poor Man’s Space Probe

The meteorite also has a thin shock-melt vein that is most likely related to a collision with another asteroid that shattered the original body and sent the fragment spinning off on its eventual collision course with Earth.

“Meteorites are commonly called The Poor Man’s Space Probe, because they deliver rocks from Outer Space to our door for free, where we can study the birth and history of other parts of our Solar System” says Gibson. The Benenitra meteorite fragment is being subjected to a range of other tests to establish properties such as its density and magnetism, and the team plans to write the results up soon in a scientific paper.

“The Benenitra meteorite is a new Space rock, but it is also a witnessed fall, which makes it part of special group of meteorites. It is part of our collective heritage as a species, planet and Solar System. It fell in a remote area that will henceforth be recognised internationally for the event on the evening of 27 July. Our project provides an opportunity to further strengthen scientific collaboration in the SADC region. Ultimately, one of our goals is to inform the people of Benenitra about the significance of what they witnessed and thus build greater awareness of science,” says Gibson.

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

Gigantic mammal ‘cousin’ discovered

November 27, 2018

During the Triassic period (252-201 million years ago) mammal-like reptiles called therapsids co-existed with ancestors to dinosaurs, crocodiles, mammals, pterosaurs, turtles, frogs, and lizards. One group of therapsids are the dicynodonts. Researchers at Uppsala University in Sweden, together with colleagues in Poland, have discovered fossils from a new genus of gigantic dicynodont. The new species Lisowicia bojani is described in the journal Science.

The earth is about 4.5 billion years old and has gone through many geological periods and dramatic change. During the Triassic period, about 252-201 million years ago, all land on Earth came together and formed the massive continent called Pangea. During this time, the first dinosaurs came into being as well as ancestors to crocodiles, mammals, pterosaurs, turtles, frogs, and lizards. Recently, scientists have become interested in another type of animal, therapsids. Therapsids were “mammal-like” reptiles and are ancestors to the mammals, including humans, found today. One group of therapsids is called dicynodonts. All species of dicynodonts were herbivores (plant eaters) and their sizes ranged from small burrowers to large browsers. Most of them were also toothless. They survived the Permian mass extinction and became the dominant terrestrial herbivores in the Middle and Late Triassic. They were thought to have died out before the dinosaurs became the dominant form of tetrapod on land.

For the first time, researchers in the research programme Evolution and Development at Uppsala University in collaboration with researchers at the Polish Academy of Sciences (Warsaw), have discovered fossils from a new species of dicynodont in the Polish village of Lisowice. The species was named Lisowicia bojani after the village and a German comparative anatomist named Ludwig Heinrich Bojanus who worked in Vilnius and is known for making several important anatomical discoveries. The findings show that the Lisowicia was about the size of a modern-day elephant, about 4.5 metres long, 2.6 metres high and weighed approximately 9 tons, which is 40 percent larger than any previously identified dicynodont. Analysis of the limb bones showed that they had a fast growth, much like a mammal or a dinosaur. It lived during the Late Triassic, about 210-205 million years ago, about 10 million years later than previous findings of dicynodonts.

“The discovery of Lisowicia changes our ideas about the latest history of dicynodonts, mammal Triassic relatives. It also raises far more questions about what really make them and dinosaurs so large,” says Dr Tomasz Sulej, Polish Academy of Sciences.

“Dicynodonts were amazingly successful animals in the Middle and Late Triassic. Lisowicia is the youngest dicynodont and the largest non-dinosaurian terrestrial tetrapod from the Triassic. It’s natural to want to know how dicynodonts became so large. Lisowicia is hugely exciting because it blows holes in many of our classic ideas of Triassic ‘mammal-like reptiles’,” says Dr Grzegorz Niedzwiedzki, Uppsala University.

The first findings of fossils from Lisowice in Poland were made in 2005 by Robert Borz?cki and Piotr Menducki. Since then, more than 1,000 bones and bone fragments have been collected from the area, including fossils from Lisowicia. The area is thought to have been a river deposit during the Late Triassic period.

The discovery of Lisowicia provides the first evidence that mammal-like elephant sized dicynodonts were present at the same time as the more well-known long-necked sauropodomorph dinosaurs, contrary to previous belief. Sauropodomorphs include species like the Diplodocus or Brachiosaurus. It fills a gap in the fossil record of dicynodonts and it shows that some anatomical features of limbs thought to characterize large mammals or dinosaurs evolved also in the non-mammalian synapsid. Finally, these findings from Poland are the first substantial finds of dicynodonts from the Late Triassic in Europe.

“The discovery of such an important new species is a once in a lifetime discovery,” says Dr Tomasz Sulej.

Reference:
Tomasz Sulej, Grzegorz Niedźwiedzki. An elephant-sized Late Triassic synapsid with erect limbs. Science, 2018; eaal4853 DOI: 10.1126/science.aal4853

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

Evolution: South Africa’s hominin record is a fair-weather friend

November 27, 2018

Field photograph of massive flowstone layers from one of the South African hominin caves, with red cave sediments underneath. Credit: Robyn Pickering

New research from an international team of scientists led by University of Cape Town isotope geochemist Dr Robyn Pickering is the first to provide a timeline for fossils from the caves within the Cradle of Humankind. It also sheds light on the climate conditions of our earliest ancestors in the area.

Published online in the journal Nature on 21 November 2018, the work corrects assumptions that the region’s fossil-rich caves could never be related to each other. In fact, the research suggests fossils from Cradle caves date to just six specific time periods.

“Unlike previous dating work, which often focused on one cave, sometimes even just one chamber of the cave, we are providing direct ages for eight caves and a model to explain the age of all the fossils from the entire region,” says Dr Robyn Pickering.

“Now we can link together the findings from separate caves and create a better picture of evolutionary history in southern Africa.”

The Cradle of Humankind is a World Heritage Site made up of complex fossil-bearing caves. It’s the world’s richest early hominin site and home to nearly 40% of all known human ancestor fossils, including the famous Australopithecus africanus skull nicknamed Mrs Ples.

Using uranium-lead dating, researchers analysed 28 flowstone layers that were found sandwiched between fossil-rich sediment in eight caves across the Cradle. The results revealed that the fossils in these caves date to six narrow time-windows between 3.2 and 1.3 million years ago.

“The flowstones are the key,” says Pickering. “We know they can only grow in caves during wet times, when there is more rain outside the cave. By dating the flowstones, we are picking out these times of increased rainfall. We therefore know that during the times in between, when the caves were open, the climate was drier and more like what we currently experience.”

This means the early hominins living in the Cradle experienced big changes in local climate, from wetter to drier conditions, at least six times between 3 and 1 million years ago. However, only the drier times are preserved in the caves, skewing the record of early human evolution.

Up until now, the lack of dating methods for Cradle fossils made it difficult for scientists to understand the relationship between East and South Africa hominin species. Moreover, the South African record has often been considered undateable compared to East Africa where volcanic ash layers allow for high resolution dating.

Professor Andy Herries, a co-author in the study at La Trobe University in Australia, notes that “while the South African record was the first to show Africa as the origin point for humans, the complexity of the caves and difficultly dating them has meant that the South African record has remained difficult to interpret.”

“In this study we show that the flowstones in the caves can act almost like the volcanic layers of East Africa, forming in different caves at the same time, allowing us to directly relate their sequences and fossils into a regional sequence,” he says.

Dr Pickering began dating the Cradle caves back in 2005 as part of her PhD research. This new publication is the result of 13 years of work and brings together a team of 10 scientists from South Africa, Australia and the US. The results return the Cradle to the forefront and open new opportunities for scientists to answer complex questions about human history in the region.

“Robyn and her team have made a major contribution to our understanding of human evolution,” says leading palaeoanthropologist Professor Bernard Wood, of the Center for the Advanced Study of Human Paleobiology at the George Washington University in the USA, who is not an author on the study.

“This is the most important advance to be made since the fossils themselves were discovered. Dates of fossils matter a lot. The value of the southern African evidence has been increased many-fold by this exemplary study of its temporal and depositional context.”

Reference:
Robyn Pickering, Andy I. R. Herries, Jon D. Woodhead, John C. Hellstrom, Helen E. Green, Bence Paul, Terrence Ritzman, David S. Strait, Benjamin J. Schoville, Phillip J. Hancox. U–Pb-dated flowstones restrict South African early hominin record to dry climate phases. Nature, 2018; DOI: 10.1038/s41586-018-0711-0

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

Human ancestors not to blame for ancient mammal extinctions in Africa

November 27, 2018

A fossil tooth of a hippo (Hippopotamus amphibius) (left) and a fossil tooth of a white rhinoceros (Ceratotherium simum) (right) , two of the few surviving megaherbivores, from the Late Pleistocene of western Kenya (left). Credit: J. Tyler Faith

New research disputes a long-held view that our earliest tool-bearing ancestors contributed to the demise of large mammals in Africa over the last several million years. Instead, the researchers argue that long-term environmental change drove the extinctions, mainly in the form of grassland expansion likely caused by falling atmospheric carbon dioxide (CO2) levels.

Tyler Faith, curator of archaeology at the Natural History Museum of Utah and assistant professor in the Department of Anthropology at the University of Utah, led the study. The research team also includes John Rowan from the University of Massachusetts Amherst, Andrew Du from the University of Chicago, and Paul Koch from the University of California, Santa Cruz.

The study is published today in the journal Science.

“Despite decades of literature asserting that early hominins impacted ancient African faunas, there have been few attempts to actually test this scenario or to explore alternatives,” Faith says. “We think our study is a major step towards understanding the depth of anthropogenic impacts on large mammal communities, and provides a convincing counter-argument to these long-held views about our early ancestors.”

To test for ancient hominin impacts, the researchers compiled a seven-million-year record of herbivore extinctions in eastern Africa, focusing on the very largest species, the so-called ‘megaherbivores’ (species over 2,000 lbs.) Though only five megaherbivores exist in Africa today, there was a much greater diversity in the past. For example, three-million-year-old ‘Lucy’ (Australopithecus afarensis) shared her woodland landscape with three giraffes, two rhinos, a hippo, and four elephant-like species at Hadar, Ethiopia.

When and why these species disappeared has long been a mystery for archaeologists and paleontologists, despite the evolution of tool-using and meat-eating hominins getting most of the blame.

“Our analyses show that there is a steady, long-term decline of megaherbivore diversity beginning around 4.6 million years ago. This extinction process kicks in over a million years before the very earliest evidence for human ancestors making tools or butchering animal carcasses and well before the appearance of any hominin species realistically capable of hunting them, like Homo erectus,” says Faith.

Taking a Closer Look

Faith and his team quantified long-term changes in eastern African megaherbivores using a dataset of more than 100 fossil assemblages spanning the last seven million years. The team also examined independent records of climatic and environmental trends and their effects, specifically global atmospheric CO2, stable carbon isotope records of vegetation structure, and stable carbon isotopes of eastern African fossil herbivore teeth, among others.

Their analysis reveals that over the last seven million years substantial megaherbivore extinctions occurred: 28 lineages became extinct, leading to the present-day communities lacking in large animals. These results highlight the great diversity of ancient megaherbivore communities, with many having far more megaherbivore species than exist today across Africa as a whole.

Further analysis showed that the onset of the megaherbivore decline began roughly 4.6 million years ago, and that the rate of diversity decline did not change following the appearance of Homo erectus, a human ancestor often blamed for the extinctions. Rather, Faith’s team argues that climate is more likely culprit.

“The key factor in the Plio-Pleistocene megaherbivore decline seems to be the expansion of grasslands, which is likely related to a global drop in atmospheric CO2 over the last five million years,” says John Rowan, a postdoctoral scientist from University of Massachusetts Amherst. “Low CO2 levels favor tropical grasses over trees, and as a consequence savannas became less woody and more open through time. We know that many of the extinct megaherbivores fed on woody vegetation, so they seem to disappear alongside their food source.”

The loss of massive herbivores may also account for other extinctions that have also been attributed to ancient hominins. Some scientist suggest that competition with increasingly carnivorous species of Homo led to the demise of numerous carnivores over the last few million years. Faith and his team suggest an alternative.

“We know there are also major extinctions among African carnivores at this time and that some of them, like saber-tooth cats, may have specialized on very large prey, perhaps juvenile elephants” says Paul Koch. “It could be that some of these carnivores disappeared with their megaherbivore prey.”

“Looking at all of the potential drivers of the megaherbivore decline, our analyses suggest that changing climate and environment played the key role in Africa’s past extinctions,” said Faith. “It follows that in the search for ancient hominin impacts on ancient African ecosystems, we must focus our attention on the one species known to be capable of causing them — us, Homo sapiens, over the last 300,000 years.”

Reference:
J. Tyler Faith, John Rowan, Andrew Du, Paul L. Koch. Plio-Pleistocene decline of African megaherbivores: No evidence for ancient hominin impacts. Science, 2018; 362 (6417): 938 DOI: 10.1126/science.aau2728

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

Earth’s cobalt deposits formed much later than previously believed

November 22, 2018

UAlberta geologists have used a new technique to measure the age of cobalt-copper ore in Central Africa—showing the deposits are 150 million years younger than previously thought. The findings could lead to the discovery of more sources of cobalt around the world. Photo credit: Getty Images.

Cobalt deposits in one of Earth’s largest cobalt-mining regions are 150 million years younger than previously thought, according to a new study by University of Alberta geologists.

Working with former post-doctoral fellow Nicolas Saintilan, U of A geochemist Robert Creaser, Canada Research Chair in Isotope Geochemistry, used a new, rhenium-osmium dating system to examine the rich cobalt deposits in the Democratic Republic of Congo.

Their results show that cobalt and copper mineralization occurred during a period of mountain building and deformation between 610 and 470 million years ago, suggesting that the deposits formed 100 to 150 million years more recently than originally thought.

The study also provides critical insight into exploration for cobalt, an important component in rechargeable lithium-ion batteries used in everything from smartphones to hybrid cars.

“Using this new knowledge of the timing of events that formed cobalt deposits, we can target regions for exploring known cobalt deposits and discovering new ones,” said Creaser.

Cobalt enables rechargeable batteries to stock energy without overheating. It is a strategic metal for the technological revolution, critical in efforts to face and remediate climate change.

Because of its use in lithium-ion batteries, cobalt is a hot commodity on the international market—creating steep competition. Most large cobalt deposits are located in developing or poverty-stricken regions in Central Africa. Exploration can be mired in human rights, geopolitical and sustainability issues, Creaser explained.

“The conundrum is that the western world needs cobalt, and the conditions in some places we currently get it from can be exploitative.

“The biggest value of this research is opening the possibility of finding more prospective areas worldwide for sources of cobalt. This background information helps exploration geologists develop ideas of where and where not to look,” said Creaser.

The research was supported by David Selby at Durham University in the United Kingdom. Key samples were provided by Stijn Dewaele at the Royal Museum for Central Africa in Belgium.

The paper, “Sulphide Re-Os Geochronology Links Orogenesis, Salt and Cu-Co Ores in the Central African Copperbelt,” was published in Scientific Reports.

Reference:
N. J. Saintilan et al. Sulphide Re-Os geochronology links orogenesis, salt and Cu-Co ores in the Central African Copperbelt, Scientific Reports (2018). DOI: 10.1038/s41598-018-33399-7

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

Oil extraction likely triggered mid-century earthquakes in L.A.

November 22, 2018

Angelenos play below derricks at Huntington Beach pier, c. 1930-40. In the early decades of the twentieth century, LA residents accepted ground subsidence and small earthquakes as the cost of producing oil. But discontent began to rumble in the late 1930s. Rapid exploitation of Wilmington, one of the largest oil fields in California, and the Huntington Beach field caused Long Beach harbor to sink, buckling railway lines and forcing the city to build higher piers. Credit: Orange County Archives

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World War II-era oil pumping under Los Angeles likely triggered a rash of mid-sized earthquakes in the 1930s and 1940s, potentially leading seismologists to overestimate the earthquake potential in the region, according to new research published in AGU’s Journal of Geophysical Research: Solid Earth.

Six independent earthquakes and two aftershocks of magnitude 4.4 to 5.1 shook L.A. between 1935 and 1944, a rate of about one every two years. The area also experienced a higher rate of low-intensity earthquakes during that time frame. After 1945, the rate dropped to one moderate earthquake every seven years.

The new study re-examined historical information about the earthquakes from archived newspaper reports of earthquake damage, postcard questionnaires collected by the Coast and Geodetic Survey, and other sources pulled from old files and the dusty corners of cyberspace.

The authors used this information to refine the earthquake locations identified by early earth-motion sensors. The first seismometers in the United States began monitoring earthquake activity in the L.A. region in 1932. It is known that these early instruments could err in locating earthquake epicenters by tens of miles because of the limitations of their clocks, and because the low-sensitivity instruments were so few, according to the study’s authors. Extrapolation of earthquake location from seismometer recordings relies on accurate time measurements.

Damage reports, which often specified street addresses or intersections, pinpointed confined regions of maximum damage at a distance from the locations indicated by these early seismometers and close to many active oil fields, according to the new research. The new study modeled stress on local faults based on archived data, finding areas of high stress matched the relocated epicenters.

“All these little earthquakes happened in the 1930s. It looked like the L.A. region was very active seismically, and of course it is quite active, but if you throw away those earthquakes induced by oil you come up with a lower rate of seismicity,” said Roger Bilham, a geologist at the University of Colorado Boulder and an author of the new study.

Unlike recent earthquakes associated with hydraulic fracturing in Oklahoma, the mid-century events were not caused by deep fluid injection but were likely caused by taking oil out of the ground, according to the new study.

The wide adoption in the late 1950s of water-flooding wells to recover more oil from waning reserves likely resolved the problem by balancing the volume of oil extracted with water injected, a technique now used around the world. Oil production does not cause earthquakes in L.A. today.

Most earthquakes in California are naturally caused and the L.A. region is seismically active. The new study’s authors said human industry in the L.A. basin in early twentieth century likely pushed some faults that were already under stress over the edge.

“If you do anything to the Earth, it always offers you an answer.” Bilham said. “These earthquakes that we modeled probably would have happened in the next few hundred years anyway. If an earthquake’s about to go, it doesn’t take much to make it happen sooner.”

L.A. oil boom

More than 9 billion barrels of oil have come out of the ground in the L.A. region since pioneering oil barons first tapped the Los Angeles City oil field in 1892.

Three of the earthquakes investigated in the new study occurred in the Wilmington and Torrence fields, where operators ramped up production rapidly in the late 1930 and early 1940s to support demand from the war. Oil companies sank more wells and drilled deeper, reaching the depth of active faults. The new study noted a pattern of earthquakes occurring within a few months of well expansion below 3 kilometers (1.9 miles).

The new study argues the cluster of earthquakes in the 1930s and 1940s could not be explained as aftershocks of the 1933 magnitude-6.3 Long Beach earthquake, as has been proposed by some seismologists, but were more likely instigated by pressure changes from pumping oil.

The oil companies themselves knew pumping was causing earthquakes, according to Bilham, because frequent small quakes within the oilfields damaged the wells, sometimes shutting down production for months. The expense of compensating for small earthquakes partially motivated the adoption of secondary oil recovery through water-flooding, he said.

“It turns out it would be almost impossible for the things they were doing in the 1930s not to produce earthquakes,” Bilham said. “In California, they were sucking out the oil so fast they were setting up these giant stresses near the oil fields, forces enough to break rock. And we know that they did break the rock because they produced earthquakes in the oil fields that severed the pipes.”

Seismological cold cases

Pumping increased the risk of sudden movement in nearby faults because removing fluid from the ground dropped the pressure under the wells, pulling on the surrounding rock.

Land sagged over sites of active pumping, sometimes leaving a visible dimple on the landscape. Based on records of the volume of oil pumped from the fields and the amount of subsidence, the authors of the new study calculated stresses induced in the rock. Damage reports from the time matched the areas of high stress.

“We know exactly how much Long Beach subsided, and we also know how much oil had been extracted and at what depth. So we were able to do a calculation to see whether the two things matched, and the calculation showed that it did,” Bilham said. “Armed with that, we asked ourselves what kinds of stresses occur at oil field depths, or near where these earthquakes were occurring. The stress turns out to be huge.”

David Simpson, president emeritus of the Incorporated Research Institutions for Seismology and a seismologist uninvolved in the new study, said scientists are constrained by the data available when looking at old cases, and there is always some possibility that these earthquakes were natural events, but he found the approach persuasive. Bringing relatively well-documented historic cases into discussion, he said, is important to advance policy, as well as the scientific and technical understanding of earthquakes.

“Going back and looking at old data with modern techniques—it’s a way of dusting off old cold cases in seismology, being the detective and trying to put the pieces together,” Simpson said. “It’s important to go back and look at these older cases and they’ve done, I think, a very careful job of reevaluating the data and looking for the possible connections.”

Reference:
Susan E. Hough et al. Revisiting Earthquakes in the Los Angeles, California, Basin During the Early Instrumental Period: Evidence for an Association with Oil Production, Journal of Geophysical Research: Solid Earth (2018). DOI: 10.1029/2017JB014616

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.

Fight over dinosaur fossils comes down to what’s a mineral

November 21, 2018

In this Nov. 14, 2013 file photo, one of two “dueling dinosaur” fossils is displayed in New York. Ownership of two fossilized dinosaur skeletons found on a Montana ranch in 2006 are the subject of a legal battle over whether they are part of a property’s surface rights or mineral rights. The 9th U.S. Circuit Court of Appeals issued a split decision saying fossils are minerals under mineral rights laws. Credit: AP Photo/Seth Wenig

About 66 million years after two dinosaurs died apparently locked in battle on the plains of modern-day Montana, an unusual fight over who owns the entangled fossils has become a multimillion-dollar issue that hinges on the legal definition of “mineral.”

The 9th U.S. Circuit Court of Appeals ruled last week that the “Dueling Dinosaurs” located on private land are minerals both scientifically and under mineral rights laws. The fossils belong both to the owners of the property where they were found and two brothers who kept two-thirds of the mineral rights to the land once owned by their father, a three-judge panel said in a split decision.

Eric Edward Nord, an attorney for the property owners, said the case is complex in dealing with who owns what’s on top of land vs. the minerals that make it up and addresses a unique question of mineral rights law related to dinosaur fossils that no court in the country has taken up before.

His clients own part of a ranch in the Hell Creek Formation of eastern Montana that’s rich with prehistoric fossils, including the Dueling Dinosaurs whose value had been appraised at $7 million to $9 million.

Lige and Mary Ann Murray bought it from George Severson, who also transferred part of his interest in the ranch to his sons, Jerry and Robert Severson. In 2005, the brothers sold their surface rights to the Murrays, but retained the mineral rights, court documents said.

At the time, neither side suspected valuable dinosaur fossils were buried on the ranch, court records said. A few months later, amateur paleontologist Clayton Phipps discovered the carnivore and herbivore apparently locked in battle. Imprints of the dinosaurs’ skin were also in the sediment.

A dispute arose in 2008 when the Seversons learned about the fossils—a 22-foot-long (7-meter-long) theropod and a 28-foot-long (9-meter-long) ceratopsian.

The Murrays sought a court order saying they owned the Dueling Dinosaurs, while the Seversons asked a judge to find that fossils are part of the property’s mineral estate and that they were entitled to partial ownership.

It had wider implications because the ranch is in an area that has numerous prehistoric creatures preserved in layers of clay and sandstone. Paleontologists have unearthed thousands of specimens now housed in museums and used for research.

But fossils discovered on private land can be privately owned, frustrating paleontologists who say valuable scientific information is being lost.

During the court case, the Dueling Dinosaurs were put up for auction in New York in November 2013. Bidding topped out at $5.5 million, less than the reserve price of $6 million.

A nearly complete Tyrannosaurus rex found on the property was sold to a Dutch museum for several million dollars in 2014, with the proceeds being held in escrow pending the outcome of the court case.

Other fossils found on the ranch also have been sold, including a triceratops skull that brought in more than $200,000, court records said.

The 9th Circuit decision on Nov. 6 overturned a federal judge’s 2016 opinion that fossils were not included in the ordinary definition of “mineral” because not all fossils with the same mineral composition are considered valuable.

“The composition of minerals found in the fossils does not make them valuable or worthless,” U.S. District Judge Susan Watters of Billings wrote. “Instead, the value turns on characteristics other than mineral composition, such as the completeness of the specimen, the species of dinosaur and how well it is preserved.”

The Seversons had appealed, arguing previous court cases determined that naturally occurring materials that have some special value meet the definition of minerals.

Attorneys for the Murrays asked the 9th Circuit this week for an extension of a Nov. 21 deadline to petition the judges to reconsider or for a hearing before an 11-judge panel.

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

Tiny raptor tracks lead to big discovery

November 21, 2018

Dinosaur reconstructions by Dr Anthony Romilio. Credit: University of Queensland

Tracks made by dinosaurs the size of sparrows have been discovered in South Korea by an international team of palaeontologists.

University of Queensland researcher Dr. Anthony Romilio was part of the team which described the tracks, which were originally found by Professor Kyung Soo Kim from Chinju National University of Education, South Korea.

“These 110-million-year-old footprints and trackways were made by carnivorous dinosaurs commonly known as raptors,” Dr. Romilio said.

“These new tracks are just one centimetre in length, which means the dinosaur that made them was an animal you could have easily held in your hand.

“They are the world’s smallest dinosaur tracks.”

To estimate the size of the dinosaur that made the tracks, the team measured the footprint length and multiplied the value by 4.5 to get an approximate hip height.

“The diminutive sizes of these new tracks are extraordinary; the tracks were made by tiny dinosaurs about the size of sparrows,” Dr. Romilio said.

“Raptors placed only two of their toes on the ground, while the third toe was retracted like a cat’s claw.”

The research team are unsure if the tracks were made by a small adult species, or baby dinosaurs.

“Very small dinosaur species like the Chinese Microraptor were crow-sized, but these had feet too large to match the South Korean footprints,” Dr. Romilio said.

“If the tracks were made by dinosaur chicks, we are unclear as to the specific dinosaur that made them, since dinosaurs such as Velociraptor and Utahraptor had larger feet then the ones discovered in these new tracks.”

Professor Kim said the Cretaceous lake deposits at the discovery site created perfect conditions that allowed for the preservation of tiny footprints rarely found elsewhere.

“In addition to tiny dinosaur tracks, we have footprints made by birds, pterosaurs, lizards, turtles, mammals, and even frogs,” he said.

“We have named these small tracks Dromaeosauriformipes rarus, which means rare footprints made by a member of the raptor family known as dromaeosaurs,” Professor Kim said.

The research is published in Scientific Reports and included scientists from South Korea, the United States, China, Spain and Australia.

Reference:
Kyung Soo Kim et al. Smallest known raptor tracks suggest microraptorine activity in lakeshore setting, Scientific Reports (2018). DOI: 10.1038/s41598-018-35289-4

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

Volcanoes and glaciers combine as powerful methane producers

November 21, 2018

Dr Peter Wynn, Lancaster University, taking a sample in Iceland. Credit: Dr Hugh Tuffen

Large amounts of the potent greenhouse gas methane are being released from an Icelandic glacier, scientists have discovered.

A study of Sólheimajökull glacier, which flows from the active, ice-covered volcano Katla, shows that up to 41 tonnes of methane is being released through meltwaters every day during the summer months. This is roughly equivalent to the methane produced by more than 136,000 belching cows.

The Lancaster university-led research, which is featured in Scientific Reports, is the first published field study to show methane release from glaciers on this scale.

“This is a huge amount of methane lost from the glacial meltwater stream into the atmosphere,” said Dr Peter Wynn, a glacial biogeochemist from the Lancaster Environment Centre and corresponding author of the study. “It greatly exceeds average methane loss from non-glacial rivers to the atmosphere reported in the scientific literature. It rivals some of the world’s most methane-producing wetlands; and represents more than twenty times the known methane emissions of all Europe’s other volcanoes put together.”

Dr Wynn added: “Methane has a global warming potential 28 times that of carbon dioxide (CO2). It is therefore important that we know about different sources of methane being released to the atmosphere and how they might change in the future.

“There has been a lot of speculation about whether or not glaciers can release methane. The beds of glaciers contain the perfect cocktail of conditions for methane production — microbes, low oxygen, organic matter and water — along with an impermeable cap of ice on the surface trapping the methane beneath.

“However, nobody has thoroughly investigated this in the field before and this is the strongest evidence yet that glaciers are releasing methane.”

The study comes out of PhD research carried out by Dr Rebecca Burns when she was a graduate researcher at Lancaster University through the Centre for Global Eco-innovation, part-funded by the European Regional Development Fund.

Dr Burns took water samples from the edge of the melt water lake in front of the Sólheimajökull glacier and measured the methane concentrations, comparing them with methane levels in nearby sediments and other rivers, to make sure that the methane wasn’t being released from the surrounding landscape.

“The highest concentrations were found at the point where the river emerges from underneath the glacier and enters the lake. This demonstrates the methane must be sourced from beneath the glacier,” Dr Wynn explains.

Using a mass spectrometer, which identifies the unique ‘fingerprint’ of the methane, the researchers discovered the methane is coming from microbiological activity at the bed of the glacier. But there is still a connection with the volcano.

“We believe that while the volcano is not producing the methane, it is providing the conditions that allow the microbes to thrive and release methane into the surrounding meltwaters,” Said Dr Wynn.

Normally when methane comes into contact with oxygen it combines to form CO2, so the methane effectively disappears. On a glacier, meltwaters rich in dissolved oxygen access the bed of the ice mass and convert any methane present into carbon dioxide.

“Understanding the seasonal evolution of Sólheimajökull’s subglacial drainage system and how it interacts with the Katla geothermal area formed part of this work,” said Professor Fiona Tweed, an expert in glacier hydrology at Staffordshire University and co-author of the study.

At Sólheimajökull when the meltwater reaches the glacier bed, it comes into contact with gases produced by the Katla volcano. These gases lower the oxygen content of the water, meaning some of the methane produced by the microbes can be dissolved into the water and transported out of the glacier without being converted to CO2.

Dr Hugh Tuffen, a volcanologist at Lancaster University and co-author on the study, said: “The heat from Katla volcano may greatly accelerate the generation of microbial methane, so in fact you could see Katla as a giant microbial incubator.

“Scientists have also recently discovered that Katla emits vast amounts of CO2 — it’s in the top five globally in terms of CO2 emissions from volcanoes — so Katla is certainly a very interesting, very gassy volcano.”

“Both Iceland and Antarctica have many ice-covered, active volcanoes and geothermal systems,” said Dr Burns. “The recent International Panel on Climate Change (IPCC) report highlights that current trajectories indicate global warming is likely to reach 1.5oC between 2030 and 2052, with greatest perceived climate sensitivity at higher latitudes. If methane produced under these ice caps has a means of escaping as the ice thins, there is the chance we may see short term increases in the release of methane from ice masses into the future.”

Andri Stefánsson, Professor of Hydrothermal Geochemistry at the University of Iceland, who was not involved in the study said: “These findings provide important and new information on the origin and fluxes of methane at the Earth’s surface and the significance of this greenhouse gas to the atmosphere from such systems.

However, the researchers caution that it is still unclear how these effects will play out. They believe that although there could be a short-term spike of methane released while the glacier melts and thins, in the long-term the process could be self-limiting as, along with other reasons, without the ice the conditions for methane production are removed.

Reference:
R. Burns, P. M. Wynn, P. Barker, N. McNamara, S. Oakley, N. Ostle, A. W. Stott, H. Tuffen, Zheng Zhou, F. S. Tweed, A. Chesler, M. Stuart. Direct isotopic evidence of biogenic methane production and efflux from beneath a temperate glacier. Scientific Reports, 2018; 8 (1) DOI: 10.1038/s41598-018-35253-2

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

Climate, life and the movement of continents: New connections

November 18, 2018

Planktonic foraminifera, such as these collected in the Gulf of Mexico, form the base of many marine and aquatic food chains. Upon death, their skeletons settle on the seafloor to form sedimentary rock such as limestone and chalk. Pressed together in sufficient quantities, such sedimentary rock could have a lubricating effect on the movement of continental plates. Credit: Randolph Femmer, USGS

A new study by The University of Texas at Austin has demonstrated a possible link between life on Earth and the movement of continents. The findings show that sediment, which is often comprised from pieces of dead organisms, could play a key role in determining the speed of continental drift. In addition to challenging existing ideas about how plates interact, the findings are important because they describe potential feedback mechanisms between tectonic movement, climate and life on Earth.

The study, published Nov. 15 in Earth and Planetary Science Letters, describes how sediment moving under or subducting beneath tectonic plates could regulate the movement of the plates and may even play a role in the rapid rise of mountain ranges and growth of continental crust.

The research was led by Thorsten Becker, a professor at the UT Jackson School of Geosciences and research scientist at its Institute for Geophysics (UTIG), and Whitney Behr, a research fellow at the Jackson School and professor at ETH Zurich in Switzerland.

Sediment is created when wind, water and ice erode existing rock or when the shells and skeletons of microscopic organisms like plankton accumulate on the seafloor. Sediment entering subduction zones has long been known to influence geological activity such as the frequency of earthquakes, but until now it was thought to have little influence on continental movement. That’s because the speed of subduction was believed to be dependent on the strength of the subducting plate as it bends and slides into the viscous mantle, the semi molten layer of rock beneath the Earth’s crust. Continental movement is driven by one plate sinking under another so, in this scenario, the strength of the portion of the plate being pulled into the Earth’s mantle (and the energy required to bend it) would be the primary control for the speed of the plate movement, with sediment having little effect.

However, prior research involving UTIG scientists had shown the subducting plates may be weaker and more sensitive to other influences than previously thought. This led researchers to look for other mechanisms that might impact plate velocity. They estimated how different types of rock might affect the plate interface ¬- the boundary where subducting plates meet. Subsequent modelling showed that rock made of sediment can create a lubricating effect between plates, accelerating subduction and increasing plate velocity.

This mechanism could set in motion a complex feedback loop. As plate velocity increases, there would be less time for sediment to accumulate, so the amount of subducting sediment would be reduced. This leads to slower subduction, which may allow for mountains to grow at plate boundaries as the force of the two plates running into each other causes uplift. In turn, erosion of those mountains by wind, water and other forces can produce more sediments which feed back into the subduction zone and restart the cycle by increasing the speed of subduction.

“The feedback mechanisms serve to regulate subduction speeds such that they don’t ‘runaway’ with extremely fast velocities,” said Behr.

Behr and Becker’s new model also offers a compelling explanation for variations found in plate speed, such as India’s dramatic northward acceleration some 70 million years ago. The authors propose that as India moved through equatorial seas teeming with life, an abundance of sedimentary rock formed by organic matter settling on the seafloor created a lubricating effect in the subducting plate. India’s march north accelerated from a stately 5 centimeters per year (about 2 inches) to an eye-watering 16 centimeters per year (about 6 inches). As the continent accelerated the amount of sediment being subducted decreased and India slowed before finally colliding with Asia.

Behr and Becker suggest these feedback mechanisms would have been very different in the early Earth before the formation of continents and the emergence of life. Although their model does not examine the origins of these feedback mechanisms, it does raise compelling questions about the interaction between continental movement and life on Earth.

“What is becoming clear is that the geological history of the incoming plate matters,” said Becker, who also holds the Shell Distinguished Chair in Geophysics at UT. “We will have to study in more detail how those possible feedback processes may work.”

Reference:
Whitney M. Behr, Thorsten W. Becker. Sediment control on subduction plate speeds. Earth and Planetary Science Letters, 2018; 502: 166 DOI: 10.1016/j.epsl.2018.08.057

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

Huge Crater Discovered in Greenland

November 17, 2018

Map of the bedrock topography beneath the ice sheet and the ice-free land surrounding the Hiawatha impact crater. The structure is 31 km wide, with a prominent rim surrounding the structure. In the central part of the impact structure, an area with elevated terrain is seen, which is typical for larger impact craters. Calculations shows that in order to generate an impact crater of this size, the earth was struck by a meteorite more than 1 km wide. Credit: The Natural History Museum of Denmark

Table of Contents

An international team lead by researchers from the Centre for GeoGenetics at the Natural History Museum of Denmark, University of Copenhagen have discovered a 31-km wide meteorite impact crater buried beneath the ice-sheet in the northern Greenland. This is the first time that a crater of any size has been found under one of Earth’s continental ice sheets. The researchers worked for last three years to verify their discovery, initially made in the 2015. The research is described in a new study just published in the internationally recognized journal Science Advances.

The crater measures more than 31 km in diameter, corresponding to an area bigger than Paris, and placing it among the 25 largest impact craters on Earth. The crater formed when a kilometre-wide iron meteorite smashed into northern Greenland, but has since been hidden under nearly a kilometre of ice.

“The crater is exceptionally well-preserved, and that is surprising, because glacier ice is an incredibly efficient erosive agent that would have quickly removed traces of the impact. But that means the crater must be rather young from a geological perspective. So far, it has not been possible to date the crater directly, but its condition strongly suggests that it formed after ice began to cover Greenland, so younger than 3 million years old and possibly as recently as 12,000 years ago — toward the end of the last ice age” says Professor Kurt H. Kjær from the Center for GeoGenetics at the Natural History Museum of Denmark.

Giant circular depression

The crater was first discovered in July 2015 as the researchers inspected a new map of the topography beneath Greenland’s ice-sheet. They noticed an enormous, but previously undetected circular depression under Hiawatha Glacier, sitting at the very edge of the ice sheet in northern Greenland.

“We immediately knew this was something special but at the same time it became clear that it would be difficult to confirm the origin of the depression,” says Professor Kjær.

In the courtyard at the Geological Museum in Copenhagen just outside the windows of the Center for GeoGenetics sits a 20-tonne iron meteorite found in North Greenland not far from the Hiawatha Glacier.

“It was therefore not such a leap to infer that the depression could be a previously undescribed meterorite crater, but initially we lacked the evidence,” reflects Associate Professor Nicolaj K. Larsen from Aarhus University.

The crucial evidence

Their suspicion that the giant depression was a meteorite crater was reinforced when the team sent a German research plane from the Alfred Wegener Institute to fly over the Hiawatha Glacier and map the crater and the overlying ice with a new powerful ice radar. Joseph MacGregor, a glaciologist at NASA, who participated in the study and is an expert in ice radar measurements adds:

“Previous radar measurements of Hiawatha Glacier were part of a long-term NASA effort to map Greenland’s changing ice cover. What we really needed to test our hypothesis was a dense and focused radar survey there. Our colleagues at the Alfred Wegener Institute and University of Kansas did exactly that with a next-generation radar system that exceeded all expectations and imaged the depression in stunning detail. A distinctly circular rim, central uplift, disturbed and undisturbed ice layering, and basal debris. It’s all there.”

In the summers of 2016 and 2017, the research team returned to the site to map tectonic structures in the rock near the foot of the glacier and collect samples of sediments washed out from the depression through a meltwater channel.

“Some of the quartz sand washed from the crater had planar deformation features indicative of a violent impact, and this is conclusive evidence that the depression beneath the Hiawatha Glacier is a meteorite crater, ” says Professor Larsen.

The consequences of the impact on the Earth’s climate and life

Earlier studies have shown that large impacts can profoundly affect Earth’s climate, with major consequences for life on Earth at the time. It is therefore very resonable to ask when and how and this meteorite impact at the Hiawatha Glacier affected the planet.

“The next step in the investigation will be to confidently date the impact. This will be a challenge, because it will probably require recovering material that melted during the impact from the bottom of the structure, but this is crucial if we are to understand how the Hiawatha impact affected life on Earth,” concludes Professor Kjær.

Reference:
Kurt H. Kjær, Nicolaj K. Larsen, Tobias Binder, Anders A. Bjørk, Olaf Eisen, Mark A. Fahnestock, Svend Funder, Adam A. Garde, Henning Haack, Veit Helm, Michael Houmark-Nielsen, Kristian K. Kjeldsen, Shfaqat A. Khan, Horst Machguth, Iain McDonald, Mathieu Morlighem, Jérémie Mouginot, John D. Paden, Tod E. Waight, Christian Weikusat, Eske Willerslev, Joseph A. MacGregor. A large impact crater beneath Hiawatha Glacier in northwest Greenland. Science Advances, 2018; 4 (11): eaar8173 DOI: 10.1126/sciadv.aar8173

Note: The above post is reprinted from materials provided by Faculty of Science – University of Copenhagen.

Seismic study reveals huge amount of water dragged into Earth’s interior

November 17, 2018

Slow-motion collisions of tectonic plates under the ocean drag about three times more water down into the deep Earth than previously estimated, according to a first-of-its-kind seismic study that spans the Mariana Trench.

The observations from the deepest ocean trench in the world have important implications for the global water cycle, according to researchers in Arts & Sciences at Washington University in St. Louis.

“People knew that subduction zones could bring down water, but they didn’t know how much water,” said Chen Cai, who recently completed his doctoral studies at Washington University. Cai is the first author of the study published in the Nov. 15 issue of the journal Nature.

“This research shows that subduction zones move far more water into Earth’s deep interior — many miles below the surface — than previously thought,” said Candace Major, a program director in the National Science Foundation’s Division of Ocean Sciences, which funded the study. “The results highlight the important role of subduction zones in Earth’s water cycle.”

“Previous estimates vary widely in the amount of water that is subducted deeper than 60 miles,” said Doug Wiens, the Robert S. Brookings Distinguished Professor in Earth and Planetary Sciences in Arts & Sciences and Cai’s research advisor for the study. “The main source of uncertainty in these calculations was the initial water content of the subducting uppermost mantle.”

To conduct this study, researchers listened to more than one year’s worth of Earth’s rumblings — from ambient noise to actual earthquakes — using a network of 19 passive, ocean-bottom seismographs deployed across the Mariana Trench, along with seven island-based seismographs. The trench is where the western Pacific Ocean plate slides beneath the Mariana plate and sinks deep into the Earth’s mantle as the plates slowly converge.

The new seismic observations paint a more nuanced picture of the Pacific plate bending into the trench — resolving its three-dimensional structure and tracking the relative speeds of types of rock that have different capabilities for holding water.

Rock can grab and hold onto water in a variety of ways.

Ocean water atop the plate runs down into the Earth’s crust and upper mantle along the fault lines that lace the area where plates collide and bend. Then it gets trapped. Under certain temperature and pressure conditions, chemical reactions force the water into a non-liquid form as hydrous minerals — wet rocks — locking the water into the rock in the geologic plate. All the while, the plate continues to crawl ever deeper into the Earth’s mantle, bringing the water along with it.

Previous studies at subduction zones like the Mariana Trench have noted that the subducting plate could hold water. But they could not determine how much water it held and how deep it went.

“Previous conventions were based on active source studies, which can only show the top 3-4 miles into the incoming plate,” Cai said.

He was referring to a type of seismic study that uses sound waves created with the blast of an air gun from aboard an ocean research vessel to create an image of the subsurface rock structure.

“They could not be very precise about how thick it is, or how hydrated it is,” Cai said. “Our study tried to constrain that. If water can penetrate deeper into the plate, it can stay there and be brought down to deeper depths.”

The seismic images that Cai and Wiens obtained show that the area of hydrated rock at the Mariana Trench extends almost 20 miles beneath the seafloor — much deeper than previously thought.

The amount of water that can be held in this block of hydrated rock is considerable.

For the Mariana Trench region alone, four times more water subducts than previously calculated. These features can be extrapolated to predict the conditions under other ocean trenches worldwide.

“If other old, cold subducting slabs contain similarly thick layers of hydrous mantle, then estimates of the global water flux into the mantle at depths greater than 60 miles must be increased by a factor of about three,” Wiens said.

And for water in the Earth, what goes down must come up. Sea levels have remained relatively stable over geologic time, varying by less than 1,000 ft. This means that all of the water that is going down into the Earth at subduction zones must be coming back up somehow, and not continuously piling up inside the Earth.

Scientists believe that most of the water that goes down at the trench comes back from the Earth into the atmosphere as water vapor when volcanoes erupt hundreds of miles away. But with the revised estimates of water from the new study, the amount of water going into the earth seems to greatly exceed the amount of water coming out.

“The estimates of water coming back out through the volcanic arc are probably very uncertain,” said Wiens, who hopes that this study will encourage other researchers to reconsider their models for how water moves back out of the Earth. “This study will probably cause some re-evaluation.”

Moving beyond the Mariana Trench, Wiens along with a team of other scientists has recently deployed a similar seismic network offshore in Alaska to consider how water is moved down into the Earth there.

“Does the amount of water vary substantially from one subduction zone to another, based on the kind of faulting that you have when the plate bends?” Wiens asked. “There’s been suggestions of that in Alaska and in Central America. But nobody has looked at the deeper structure yet like we were able to do in the Mariana Trench.”

Reference:
Chen Cai, Douglas A. Wiens, Weisen Shen, Melody Eimer. Water input into the Mariana subduction zone estimated from ocean-bottom seismic data. Nature, 2018; 563 (7731): 389 DOI: 10.1038/s41586-018-0655-4

Note: The above post is reprinted from materials provided by Washington University in St. Louis. Original written by Talia Ogliore.

Scientists Help Provide First-Ever Views of Elusive Energy Explosion

November 17, 2018

Artist depiction of the MMS spacecraft that provided the first view of magnetic reconnection. Credit: NASA/GSFC

Researchers at the University of New Hampshire have captured a difficult-to-view singular event involving “magnetic reconnection” — the process by which sparse particles and energy around Earth collide producing a quick but mighty explosion — in the Earth’s magnetotail, the magnetic environment that trails behind the planet.

Magnetic reconnection has remained a bit of a mystery to scientists. They know it exists and have documented the effects that the energy explosions can have — sparking auroras and possibly wreaking havoc on power grids in the case of extremely large events — but they haven’t completely understood the details. In a study published in the journal Science, the scientists outline the first views of the critical details of how this energy conversion process works in the Earth’s magnetotail.

“This was a remarkable event,” said Roy Torbert of the Space Science Center at UNH and deputy principal investigator for NASA’s Magnetospheric Multiscale mission, or MMS. “We have long known that it occurs in two types of regimes: asymmetric and symmetric but this is the first time we have seen a symmetric process.”

Magnetic reconnection occurs around Earth every day due to magnetic field lines twisting and reconnecting. It happens in different ways in different places, with different effects. Particles in highly ionized gases, called plasmas, can be converted and cause a single powerful explosion, just a fraction of a second long, that can lead to strong streams of electrons flying away at supersonic speeds. The view, which was detected as part of the scientists’ work on the MMS mission, had enough resolution to reveal its differences from other reconnection regimes around the planet like the asymmetric process found in the magnetopause around Earth which is closer to the sun.

“This is important because the more we know and understand about these reconnections,” said Torbert, “the more we can prepare for extreme events that are possible from reconnections around the Earth or anywhere in the universe.”

Magnetic reconnection also happens on the sun and across the universe — in all cases forcefully shooting out particles and driving much of the change we see in dynamic space environments — so learning about it around Earth also helps us understand reconnection in other places in the universe which cannot be reached by spacecraft. The more we understand about different types of magnetic reconnection, the more we can piece together what such explosions might look like elsewhere.

For the first reported asymmetrical event on October 16, 2015, and now this symmetrical event on July 11, 2017, NASA’s MMS mission made history by flying through magnetic reconnection events near the Earth. The four MMS spacecrafts launched from a single rocket were only inside the events for a few seconds, but the instruments which UNH researchers helped to develop were able to gather data at an unprecedented speed of one hundred times faster than ever before. As a result, for the first time, scientists could track the way the magnetic fields changed, new electric fields presented, as well as the speeds and direction of the various charged particles.

Reference:
R. B. Torbert, J. L. Burch, T. D. Phan, M. Hesse, M. R. Argall, J. Shuster, R. E. Ergun, L. Alm, R. Nakamura, K. J. Genestreti, D. J. Gershman, W. R. Paterson, D. L. Turner, I. Cohen, B. L. Giles, C. J. Pollock, S. Wang, L.-J. Chen, J. E. Stawarz, J. P. Eastwood, K. J. Hwang, C. Farrugia, I. Dors, H. Vaith, C. Mouikis, A. Ardakani, B. H. Mauk, S. A. Fuselier, C. T. Russell, R. J. Strangeway, T. E. Moore, J. F. Drake, M. A. Shay, Yuri V. Khotyaintsev, P.-A. Lindqvist, W. Baumjohann, F. D. Wilder, N. Ahmadi, J. C. Dorelli, L. A. Avanov, M. Oka, D. N. Baker, J. F. Fennell, J. B. Blake, A. N. Jaynes, O. Le Contel, S. M. Petrinec, B. Lavraud, Y. Saito. Electron-scale dynamics of the diffusion region during symmetric magnetic reconnection in space. Science, 2018; eaat2998 DOI: 10.1126/science.aat2998

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

Earth’s magnetic field measured using artificial stars at 90 kilometers altitude

November 17, 2018

The experiment on La Palma: The laser beam (yellow) generates an artificial guide star in the mesosphere. This light is collected in the receiver telescope (front left). The laser source and the receiver telescope are eight meters away from each other. Credit: Copyright Felipe Pedreros Bustos

The mesosphere, at heights between 85 and 100 kilometers above the Earth’s surface, contains a layer of atomic sodium. Astronomers use laser beams to create artificial stars, or laser guide stars (LGS), in this layer for improving the quality of astronomical observations. In 2011, researchers proposed that artificial guide stars could also be used to measure the Earth’s magnetic field in the mesosphere. An international group of scientists has recently managed to do this with a high degree of precision. The technique may also help to identify magnetic structures in the solid Earth’s lithosphere, to monitor space weather, and to measure electrical currents in the part of the atmosphere called ionosphere.

Astronomers have been using lasers to generate artificial stars for the past 20 years. A laser beam is directed from the ground into the atmosphere. In the sodium layer, it strikes sodium atoms, which absorb the energy of the laser and then start to glow. “The atoms emit light in all directions. Such artificial stars are barely visible to the naked eye but can be observed with telescopes,” explained Felipe Pedreros Bustos of Johannes Gutenberg University Mainz (JGU). In connection with the work on his doctoral thesis, the Chilean-born physicist has spent four years working on the project, which besides JGU involves the European Southern Observatory (ESO), the University of California, Berkeley and Rochester Scientific in the USA, the Italian National Institute for Astrophysics (INAF-OAR), and the University of British Columbia in Vancouver, Canada.

The artificial guide stars help astronomers to correct the distortions of light that travels through the atmosphere. The light from the artificial guide star is collected on the ground by telescopes, and the information is used to adjust in real time state-of-the-art deformable mirrors, compensating the distortions and allowing astronomical objects to be imaged sharply, down to the optical resolution, the so-called diffraction limit, of the telescope.

The precession of sodium atoms reveals the strength of the magnetic field

The participants in the collaborative project are using laser guide stars to measure the Earth’s magnetic field. An ESO LGS unit dedicated to Research and Development is housed in the Roque de los Muchachos Observatory on La Palma, the westernmost Canary Island. The availability and use of the LGS unit has allowed to perform the reported joint experiments, which also aim at increasing the brightness of laser guide stars. From the observatory, a laser beam is directed at the sodium layer which excites and spin-polarizes the atoms making most of their atomic spin point in the same direction. Due to the effect of the surrounding magnetic field, the polarized atomic spins rotate around the direction of the magnetic field similar to the motion of a gyroscope that is tilted from the vertical, a phenomenon known as Larmor precession. “A guide star becomes brighter when the modulation frequency of our laser coincides with the precession frequency of sodium,” explained Pedreros Bustos. “As the Larmor frequency is proportional to the strength of the magnetic field, we can use this method to measure the Earth’s magnetic field in the sodium layer.” The detection scheme is similar to a stroboscope.

Hence, the group has succeeded in using a well-studied, fundamental laboratory technique to observe the natural world. It fills a gap in our knowledge of the Earth’s magnetic field by allowing us to make ground-based observations of the mesosphere, which was previously difficult to access. Up to now, the magnetic field could only be directly measured on the ground, from airplanes, from balloons in the stratosphere, or from satellites.

In May 2018, a US-American research group had published similar findings. However, these latest measurements are much more precise, and scientists hope to improve them still further by using higher-energy lasers. “We can also use the technique to estimate atomic processes in the atmosphere, for example, how often sodium collides with other atoms such as oxygen or nitrogen. This is something that hasn’t been done before,” said Pedreros Bustos.

This artificial guide star measuring technique will be particularly useful in geophysics. It will make it possible to determine changes to the magnetic field of the Earth’s ionosphere caused by solar winds. In addition, observation of oceanic currents and large-scale magnetic structures in the upper mantle would be feasible by means of continuous surveillance of the Earth’s magnetic field at altitudes of 85 to 100 kilometers.

Reference:
Felipe Pedreros Bustos, Domenico Bonaccini Calia, Dmitry Budker, Mauro Centrone, Joschua Hellemeier, Paul Hickson, Ronald Holzlöhner, Simon Rochester. Remote sensing of geomagnetic fields and atomic collisions in the mesosphere. Nature Communications, 2018; 9 (1) DOI: 10.1038/s41467-018-06396-7

Note: The above post is reprinted from materials provided by Johannes Gutenberg Universitaet Mainz.

Climate change likely caused migration, demise of ancient Indus Valley civilization

November 17, 2018

The Indus civilization was the largest—but least known—of the first great urban cultures that also included Egypt and Mesopotamia. Named for one of their largest cities, the Harappans relied on river floods to fuel their agricultural surpluses. Today, numerous remains of the Harappan settlements are located in a vast desert region far from any flowing river. Credit: Liviu Giosan, Woods Hole Oceanographic Institution; Stefan Constantinescu, University of Bucharest; James P.M. Syvitski, University of Colorado

More than 4,000 years ago, the Harappa culture thrived in the Indus River Valley of what is now modern Pakistan and northwestern India, where they built sophisticated cities, invented sewage systems that predated ancient Rome’s, and engaged in long-distance trade with settlements in Mesopotamia. Yet by 1800 BCE, this advanced culture had abandoned their cities, moving instead to smaller villages in the Himalayan foothills. A new study from the Woods Hole Oceanographic Institution (WHOI) found evidence that climate change likely drove the Harappans to resettle far away from the floodplains of the Indus.

Beginning in roughly 2500 BCE, a shift in temperatures and weather patterns over the Indus valley caused summer monsoon rains to gradually dry up, making agriculture difficult or impossible near Harappan cities, says Liviu Giosan, a geologist at WHOI and lead author on the paper that published Nov. 13, 2018, in the journal Climate of the Past.

“Although fickle summer monsoons made agriculture difficult along the Indus, up in the foothills, moisture and rain would come more regularly,” Giosan says. “As winter storms from the Mediterranean hit the Himalayas, they created rain on the Pakistan side, and fed little streams there. Compared to the floods from monsoons that the Harappans were used to seeing in the Indus, it would have been relatively little water, but at least it would have been reliable.”

Evidence for this shift in seasonal rainfall — and the Harapans’ switch from relying on Indus floods to rains near the Himalaya in order to water crops — is difficult to find in soil samples. That’s why Giosan and his team focused on sediments from the ocean floor off Pakistan’s coast. After taking core samples at several sites in the Arabian Sea, he and his group examined the shells of single-celled plankton called foraminifera (or “forams”) that they found in the sediments, helping them understand which ones thrived in the summer, and which in winter.

Once he and the team identified the season based on the forams’ fossil remains, they were able to then focus on deeper clues to the region’s climate: paleo-DNA, fragments of ancient genetic material preserved in the sediments.

“The seafloor near the mouth of the Indus is a very low-oxygen environment, so whatever grows and dies in the water is very well preserved in the sediment,” says Giosan. “You can basically get fragments of DNA of nearly anything that’s lived there.”

During winter monsoons, he notes, strong winds bring nutrients from the deeper ocean to the surface, feeding a surge in plant and animal life. Likewise, weaker winds other times of year provide fewer nutrients, causing slightly less productivity in the waters offshore.

“The value of this approach is that it gives you a picture of the past biodiversity that you’d miss by relying on skeletal remains or a fossil record. And because we can sequence billions of DNA molecules in parallel, it gives a very high-resolution picture of how the ecosystem changed over time,” adds William Orsi, paleontologist and geobiologist at Ludwig Maximilian University of Munich, who collaborated with Giosan on the work.

Sure enough, based on evidence from the DNA, the pair found that winter monsoons seemed to become stronger — and summer monsoons weaker — towards the later years of the Harappan civilization, corresponding with the move from cities to villages.

“We don’t know whether Harappan caravans moved toward the foothills in a matter of months or this massive migration took place over centuries. What we do know is that when it concluded, their urban way of life ended,” Giosan says.

The rains in the foothills seem to have been enough to hold the rural Harapans over for the next millennium, but even those would eventually dry up, likely contributing to their ultimate demise.

“We can’t say that they disappeared entirely due to climate — at the same time, the Indo-Aryan culture was arriving in the region with Iron Age tools and horses and carts. But it’s very likely that the winter monsoon played a role,” Giosan says.

The big surprise of the research, Giosan notes, is how far-flung the roots of that climate change may have been. At the time, a “new ice age” was settling in, forcing colder air down from the Arctic into the Atlantic and northern Europe. That in turn pushed storms down into the Mediterranean, leading to an upswing in winter monsoons over the Indus valley.

“It’s remarkable, and there’s a powerful lesson for today,” he notes. “If you look at Syria and Africa, the migration out of those areas has some roots in climate change. This is just the beginning — sea level rise due to climate change can lead to huge migrations from low lying regions like Bangladesh, or from hurricane-prone regions in the southern U.S. Back then, the Harappans could cope with change by moving, but today, you’ll run into all sorts of borders. Political and social convulsions can then follow.”

Also collaborating on the study was Ann G. Dunlea, Samuel E. Munoz, Jeffrey. P. Donnelly, and Valier Galy of WHOI; William D. Orsi of Ludwig-Maximilians-Universität MuÌ?nchen; Marco Coolen and Cornelia Wuchter of Curtin University in Australia; Kaustubh Thirumalai of Brown University; Peter D. Clift of Louisiana State University; and Dorian Q. Fuller of University College, London.

The work was supported by the National Science Foundation’s Division of Ocean Sciences and internal WHOI funds.

Reference:
Liviu Giosan, William D. Orsi, Marco Coolen, Cornelia Wuchter, Ann G. Dunlea, Kaustubh Thirumalai, Samuel E. Munoz, Peter D. Clift, Jeffrey P. Donnelly, Valier Galy, Dorian Q. Fuller. Neoglacial climate anomalies and the Harappan metamorphosis. Climate of the Past, 2018; 14 (11): 1669 DOI: 10.5194/cp-14-1669-2018

Note: The above post is reprinted from materials provided by Woods Hole Oceanographic Institution.

Deep-time evolution of animal life on islands

November 17, 2018

A reconstruction of the Eocene of Turkey, where the small marsupial was found. Besides the marsupials, the fauna includes embrithopods (the rhino-like animals of the background, more related to elephants and sea cows), pleuraspidotheriids (primitive ungulates with a deer/dog look), a group of primates called omomyids, bats, tortoises and crocodiles. Credit: Oscar Sanisidro | University of Kansas

Islands have been vital laboratories for advancing evolutionary theory since the pioneering work of Charles Darwin and Alfred Russel Wallace in the 19th century.

Now, a new paper appearing in PLOS ONE from an international team of investigators describes two new fossil relatives of marsupials that shed light on how a unique island ecosystem evolved some 43 million years ago during the Eocene.

“Evolution in many ways is easier to study in an island context than on a large continent like North America because it’s a simpler ecosystem,” said coauthor K. Christopher Beard, Distinguished Foundation Professor of Ecology and Evolutionary Biology at the University of Kansas and senior curator with KU’s Biodiversity Institute and Natural History Museum. “Evolutionary biologists have been focusing on islands ever since Darwin and Wallace independently formulated their ideas about evolution based on their observations of plants and animals living on the Galapagos and the Malay archipelago, which is modern Indonesia.”

However, Beard said a poor fossil record for animals living on islands through “deep time,” or across a multimillion-year time frame, has hampered our understanding of exactly how island ecosystems are assembled. The new paper describes two new fossil species, identified from their teeth, that inhabited the Pontide region of modern-day north-central Turkey.

During the Eocene the Pontide region was an island in a larger version of the modern Mediterranean Sea called Tethys. At that time, Africa and Eurasia were not connected as they are today in the Middle East, but Africa was drifting northward due to plate tectonics and would eventually collide with Eurasia millions of years later. The Pontide region was sandwiched between these converging continents. This geological setting makes the Pontide region similar to the island of Sulawesi in the Indonesian archipelago, which is similarly sandwiched between the converging continents of Asia and Australia.

“No other ecosystem on the face of the planet from any time period matches what we’re finding in the Eocene of Turkey — it’s a completely unique mammalian ecosystem much like Madagascar is today,” he said. “But how did this island biota develop over time? You need fossils and time depth to see that. We’re able here to study in great detail how this ancient island evolved — where the different animals came from, how they got there and when they got there. Once they got there, some of these mammals, including one of the new marsupial lineages we’ve discovered, were able to diversify on the island. Most of the Eocene mammals on the Pontide island seem to have gotten there by swimming or rafting across parts of the Tethys Sea, instead of getting stranded on the island when it got separated from adjacent parts of Eurasia.”

Beard’s collaborators in the research were Grégoire Métais of the Museum national d’Histoire naturelle in Paris, John R. Kappelman of the University of Texas, Alexis Licht of the University of Washington, Faruk Ocakog?lu of Eskis?ehir Osmangazi University in Turkey, and KU’s Pauline M.C. Coster and Michael H. Taylor.

In the Pontide marsupial fossils — which have no living descendants — the team found evidence that distinctive forms of life that develop on islands are ill-fated in general, given enough time.

“One thing we know for sure is that the incredibly interesting and unique Eocene biota that occurred on this island in what is now Turkey at some point was totally eradicated,” Beard said. “It was eradicated when the island was reconnected to mainland Eurasia and more cosmopolitan animals were able to access it for the first time, driving the weird island biota to extinction. The message for conservation biology today is that island ecosystems are inherently ephemeral on the grand scale of macroevolutionary time. Today, conservation biologists are concerned about many endangered taxa on islands. The ugly truth that paleontology provides is that, given enough time, most island faunas are doomed to extinction. They’re cul-de-sacs of evolution — even though they’re wonderful places to study processes of evolution.”

Beard said the two newly described fossil marsupials — Galatiadelphys minor and Orhaniyeia nauta — lived near the top of the food chain on the Pontide of the Eocene, because mammalian carnivores were unable to reach the small island.

“One of weirdest things about the island fauna from the Pontides is that there are no true mammalian carnivores,” he stated. “There was nothing related to cats, dogs, bears or weasels — no modern mammalian predators. They couldn’t get to the Pontide terrain because it was a little island. So, these marsupials ecologically are taking their place at the top of the food chain.”

According to the KU researcher, the newly discovered fossils demonstrate geological context has a huge influence on how ecosystems are assembled on any given island.

“Current ideas about island evolution are based on some fairly simplistic, yet fairly effective, models,” Beard stated. “These models propose that organisms colonize islands based on two main factors — how big is the island and how far away is it from nearby continental landmasses? A bigger island makes a bigger target and hosts a greater diversity of habitats, making it easier for organisms to colonize the island and once they get there they have a better chance of surviving and maybe even diversifying.”

Based on his team’s findings from the Pontide region, Beard said that geological context was at least as important as an island’s size or distance from colonizing animals’ source territory.

“All men may have been created equal, but all islands were not. The geological context of the island — here it’s in a region of active tectonic convergence — we think is swamping these other factors, size and distance to mainland,” he said. “The oddest thing about the Pontide mammal fauna is that it contains a unique mixture of animals coming from Europe, Africa and Asia. Even our two new marsupials show different evolutionary roots in the north and the south. This makes sense because the Pontide island was being sandwiched between Eurasia and Africa, and animals were arriving there from multiple directions. We can make an interesting analogy with the modern island of Sulawesi in Indonesia, which like the Pontide terrain has a mixed fauna. It mainly hosts animals like tarsiers, pigs and shrews that are clearly related to Asian species, but you also have on Sulawesi species that are obviously related to mammals from New Guinea. If you look at plate tectonics today, Sulawesi is getting sandwiched between Australia and Asia in much the same way the Pontide was being sandwiched between Africa and Asia in the Eocene.”

Beard recently returned from Turkey where he and his team conducted more fieldwork. This research was funded by multiple sources including a major grant from the US National Science Foundation.

Reference:
Grégoire Métais, Pauline M. Coster, John R. Kappelman, Alexis Licht, Faruk Ocakoğlu, Michael H. Taylor, K. Christopher Beard. Eocene metatherians from Anatolia illuminate the assembly of an island fauna during Deep Time. PLOS ONE, 2018; 13 (11): e0206181 DOI: 10.1371/journal.pone.0206181

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

Ancient flower fossil points to core eudicot boom 99 million years ago

November 14, 2018

Lijinganthus revoluta embedded in a Myanmar amber. Credit: NIGPAS

About 140 years ago, Charles Darwin seemed to be bothered by evidence suggesting the sudden occurrence of numerous angiosperms in the mid-Cretaceous. Since Darwin’s theory of evolution implies that all organisms should increase gradually, the sudden appearance of angiosperms would have represented a headache in his theory.

Therefore, the sudden occurrence of numerous angiosperms (if seen by Darwin as “the origin of angiosperms”) would rightfully have been mysterious and abominable to him.

Over more than a century of study, however, people have found many angiosperms dating to earlier periods, suggesting the origin of angiosperms was much earlier than the mid-Cretaceous. So what was the phenomenon that bothered Darwin so much?

A group led by Prof. Wang Xin from the Nanjing Institute of Geology and Palaeontology (NIGPAS) of the Chinese Academy of Sciences may have an answer. In the Nov. 13, 2018 online issue of Scientific Reports, the scientists describe a flower, Lijinganthus revoluta, embedded in Burmese amber dating to 99 million years ago (Ma). The fossil is exquisite and complete, including all parts of a perfect pentamerous flower, namely, the calyx, corolla, stamens and gynoecium, and belongs to the pentapetalae of core eudicots.

Together with contemporaneous flowers and fruits, Lijinganthus indicates that core eudicots flourished on earth about 100 Ma. Although this group can be dated back to the Barremian (about 125 Ma) by their characteristic tricolpate pollen grains, eudicots did not dominate vegetation until about 20 million years later (mid-Cretaceous).

Accompanying this core eudicot boom, gnetales and bennettitales underwent rapid decline. Apparently, what bothered Darwin was not the assumed “origin of angiosperms,” but a core eudicot. According to current knowledge of the fossil record, angiosperms originated much earlier.

Reference:
Zhong-Jian Liu et al. The Core Eudicot Boom Registered in Myanmar Amber, Scientific Reports (2018). DOI: 10.1038/s41598-018-35100-4

Note: The above post is reprinted from materials provided by Chinese Academy of Sciences.

Rare fossil bird deepens mystery of avian extinctions

November 14, 2018

Reconstruction of a living Mirarce eatoni perched on the horns of the ceratopsian dinosaur Utahceratops gettyi, an animal that lived in Utah during the late Cretaceous 75 million years ago. Credit: Brian Engh illustration

During the late Cretaceous period, more than 65 million years ago, birds belonging to hundreds of different species flitted around the dinosaurs and through the forests as abundantly as they flit about our woods and fields today.

But after the cataclysm that wiped out most of the dinosaurs, only one group of birds remained: the ancestors of the birds we see today. Why did only one family survive the mass extinction?

A newly described fossil from one of those extinct bird groups, cousins of today’s birds, deepens that mystery.

The 75-million-year-old fossil, from a bird about the size of a turkey vulture, is the most complete skeleton discovered in North America of what are called enantiornithines (pronounced en-an-tea-or’-neth-eens), or opposite birds. Discovered in the Grand Staircase-Escalante area of Utah in 1992 by University of California, Berkeley, paleontologist Howard Hutchison, the fossil lay relatively untouched in University of California Museum of Paleontology at Berkeley until doctoral student Jessie Atterholt learned about it in 2009 and asked to study it.

Atterholt and Hutchison collaborated with Jingmai O’Conner, the leading expert on enantiornithines, to perform a detailed analysis of the fossil. Based on their study, enantiornithines in the late Cretaceous were the aerodynamic equals of the ancestors of today’s birds, able to fly strongly and agilely.

“We know that birds in the early Cretaceous, about 115 to 130 million years ago, were capable of flight but probably not as well adapted for it as modern birds,” said Atterholt, who is now an assistant professor and human anatomy instructor at the Western University of Health Sciences in Pomona, California. “What this new fossil shows is that enantiornithines, though totally separate from modern birds, evolved some of the same adaptations for highly refined, advanced flight styles.”

The fossil’s breast bone or sternum, where flight muscles attach, is more deeply keeled than other enantiornithines, implying a larger muscle and stronger flight more similar to modern birds. The wishbone is more V-shaped, like the wishbone of modern birds and unlike the U-shaped wishbone of earlier avians and their dinosaur ancestors. The wishbone or furcula is flexible and stores energy released during the wing stroke.

If enantiornithines in the late Cretaceous were just as advanced as modern birds, however, why did they die out with the dinosaurs while the ancestors of modern birds did not?

“This particular bird is about 75 million years old, about 10 million years before the die-off,” Atterholt said. “One of the really interesting and mysterious things about enantiornithines is that we find them throughout the Cretaceous, for roughly 100 million years of existence, and they were very successful. We find their fossils on every continent, all over the world, and their fossils are very, very common, in a lot of areas more common than the group that led to modern birds. And yet modern birds survived the extinction while enantiornithines go extinct.”

One recently proposed hypothesis argues that the enantiornithines were primarily forest dwellers, so that when forests went up in smoke after the asteroid strike that signaled the end of the Cretaceous — and the end of non-avian dinosaurs — the enantiornithines disappeared as well. Many enantiornithines have strong recurved claws ideal for perching and perhaps climbing, she said.

“I think it is a really interesting hypothesis and the best explanation I have heard so far,” Atterholt said. “But we need to do really rigorous studies of enantiornithines’ ecology, because right now that part of the puzzle is a little hand-wavey.”

Atterholt, Hutchison and O’Connor, who is at the Institute of Vertebrate Paleontology and Paleoanthropology in Beijing, China, published an analysis of the fossil today in the open-access journal PeerJ.

Theropod dinosaurs evolved into birds

All birds evolved from feathered theropods — the two-legged dinosaurs like T. rex — beginning about 150 million years ago, and developed into many lineages in the Cretaceous, between 146 and 65 million years ago.

Hutchison said that he came across the fossil eroding out of the ground in the rugged badlands of the Kaiparowits formation in the Grand Staircase-Escalante National Monument in Garfield County, Utah, just inside the boundary of the recently reduced monument. Having found bird fossils before, he recognized it as a late Cretaceous enantiornithine, and a rare one at that. Most birds from the Americas are from the late Cretaceous (100-66 million years ago) and known only from a single foot bone, often the metatarsus. This fossil was almost complete, missing only its head.

“In 1992, I was looking primarily for turtles,” Hutchison said. “But I pick up everything because I am interested in the total fauna. The other animals they occur with tells me more about the habitat.”

According to Hutchison, the area where the fossil was found dates from between 77 and 75 million years ago and was probably a major delta, like the Mississippi River delta, tropical and forested with lots of dinosaurs but also crocodiles, alligators, turtles and fish.

Unlike most bird fossils found outside America, in particular those from China, the fossil was not smashed flat. The classic early Cretaceous bird, Archaeopteryx, was flattened in sandstone, which preserved a beautiful panoply of feathers and the skeletal layout. Chinese enantiornithines, mostly from the early Cretaceous, are equally beautiful and smashed flatter than a pancake.

“On one hand, it’s great — you get the full skeleton most of the time, you get soft tissue preservation, including feathers. But it also means everything is crushed and deformed,” she said. “Not that our fossils have zero deformation, but overall most of the bones have really beautiful three-dimensional preservation, and just really, really great detail. We see places where muscles and tendons were attaching, all kinds of interesting stuff to anatomists.”

Once Hutchison prepared the fossils and placed them in the UC Museum of Paleontology collection, they drew the attention of a few budding and established paleontologists, but no one completed an analysis.

“The stuff is legendary. People in the vertebrate paleontology community have known about this thing forever and ever, and it just happened that everyone who was supposedly working on it got too busy and it fell by the wayside and just never happened,” Atterholt said. “I was honored and incredibly excited when Howard said that I could take on the project. I was over the moon.”

Her analysis showed that by the late Cretaceous, enantiornithines had evolved advanced adaptations for flying independent of today’s birds. In fact, they looked quite similar to modern birds: they were fully feathered and flew by flapping their wings like modern birds. The fossilized bird probably had teeth in the front of its beak and claws on its wings as well as feet. Some enantiornithines had prominent tail feathers that may have differed between male and female and been used for sexual display.

“It is quite likely that, if you saw one in real life and just glanced at it, you wouldn’t be able to distinguish it from a modern bird,” Atterholt said.

This fossil bird is also among the largest North American birds from the Cretaceous; most were the size of chickadees or crows.

“What is most exciting, however, are large patches on the forearm bones. These rough patches are quill knobs, and in modern birds they anchor the wing feathers to the skeleton to help strengthen them for active flight. This is the first discovery of quill knobs in any enantiornithine bird, which tells us that it was a very strong flier.”

Atterholt and her colleagues named the species Mirarce eatoni (meer-ark’-ee ee-tow’-nee). Mirarce combines the Latin word for wonderful, which pays homage to “the incredible, detailed, three-dimensional preservation of the fossil,” she said, with the mythical Greek character Arce, the winged messenger of the Titans. The species name honors Jeffrey Eaton, a paleontologist who for decades has worked on fossils from the Kaiparowits Formation. Eaton first enticed Hutchison to the area in search of turtles, and they were the first to report fossils from the area some 30 years ago.

Thousands of such fossils from the rocks of the Kaiparowits Formation, many of them dinosaurs, contributed to the establishment of the Grand Staircase-Escalante National Monument in 1996.

“This area contains one of the best Cretaceous fossil records in the entire world, underscoring the critical importance of protecting and preserving these parts of our natural heritage,” Atterholt said. “Reducing the size of the protected area puts some of our nation’s most valuable natural and scientific resources at risk.”

Hutchison’s field work was supported by the Annie M. Alexander endowment to the UCMP.

Reference:
Jessie Atterholt, J. Howard Hutchison, Jingmai K. O’Connor. The most complete enantiornithine from North America and a phylogenetic analysis of the Avisauridae. PeerJ, 2018; 6: e5910 DOI: 10.7717/peerj.5910

Note: The above post is reprinted from materials provided by University of California – Berkeley. Original written by Robert Sanders.

Most complete study on Europe’s greatest Hadrosaur site published

November 14, 2018

Pararhabdodon isonensis. Credit: Oscar Sanisidro / ICP

Table of Contents

The Basturs Poble site is what is known in English as a bone bed, a geological stratum containing a great amount of fossils. The stratum dates back some 70 million years. It is the only one to have been found in Europe exclusively containing hadrosaur remains. The excavations conducted during the past ten years have yielded approximately one thousand fossils. The remains are disjointed and possibly belong to only one species: the Pararhabdodon isonensis. “We think the individuals died due to unfavourable environmental conditions, perhaps an extreme dry spell. After their death, the remains got washed away by water and then began to fossilise, but we know that the place where they died was not far away from the site,” explains Víctor Fondevilla, researcher at the Institut Català de Paleontologia Miquel Crusafont (ICP) and the Universitat Autònoma de Barcelona (UAB) and first author of the paper.

The research recently published in PLOS ONE analysed the 270 fossil remains at the site which were prepared to be studied, including skulls, jaws, teeth, vertebrae and limb bones. Researchers however did not have enough with describing and measuring each specimen, they also analysed the interior of the fossils to extract information on the age of each individual. “We can cut open the fossils and analyse their inner structure. It gives us a lot of information on the vital cycle of each of the animals,” says ICREA research lecturer at ICP Meike Köhler. Similar to the rings of trees, in sections of elongated bones we find lines of arrested growth (LAGs) which are indicators corresponding to the alternation between favourable and unfavourable periods. In this way we can calculate at what age they died.

Using this system, palaeontologists detected that at the site were a large number of young individuals and, to a lesser extent, sub-adults and adults. But no recently hatched dinosaur fossils were found. “We estimated that the youngest individuals died at two years of age and that the adults were 14 to 15,” Fondevilla explains. The fact that researchers found so many young samples makes them think that the accumulation of bones at Basturs Poble represents a natural population of herbivores, where young individuals are more abundant. “It may also be that the abundance of young remains is due to these individuals being more vulnerable to crises and therefore dying in larger quantities than adults would,” the main researcher of the study comments.

Also participating in the study were researchers from the Museum of Conca Dellà and the Friulian Museum of Natural History in Udine, Italy.

Hadrosaurs, A Well-Known Group in Catalonia

Hadrosaurs, also known as “duck-billed” dinosaurs, are a group of ornithischian herbivorous dinosaurs which lived in the Late Cretaceous period. This is probably the most well-known group of dinosaurs. Among the subfamilies there are the lambeosaurines, which can be found in Catalonia’s sites. They characteristically had a robust medium to large-sized body (weighing one kilogramme when hatching and reaching up to 3000 kilogrammes as adults), with smaller front limbs and larger hind limbs. This last trait made it possible for them to walk on two or four feet indifferently.

The skull is long and duck-billed shaped, and the jaw holds rows of stacked teeth. Their most distinctive characteristic was their cranial crest, formed by several more or less developed cranial bones. What the crest was used for remains unclear, but scientists believe it could have acted as a resonating chamber with which to amplify sounds and facilitate recognising members of the same species. Other hypotheses point to the possibility of only males having crests which aimed to attract the females.

The Pararhabdodon isonensis species is only known to have existed in the Pallars Jussà region. [nbsp]The species was described in 1985 after the discovery of remains found at Sant Romà d’Abella and its specific name — isonensis — refers to the town of Isona located near the site. These dinosaurs measured from 6 to 7 metres in length and it is estimated that the adults weighed some three tonnes.

The Pyrenees, Home to the Last Dinosaurs in Europe

Catalonia is very rich in fossiliferous sediment. Of the most relevant are the pre-Pyrennean basins, which conserve remains of different life forms from the Late Cretaceous Period (between 70 and 66 million years ago). In geological terms, that is very shortly before the great extinction which marked the end of many life forms, including non-avian dinosaurs. Located at the Pyrennean sites, therefore, are the last dinosaurs to have lived in Europe, a few hundreds of years before they disappeared from the world entirely.

The Basturs Poble site was located by scientific communicator Marc Boada in August 2001. Upon discovering fossils on the surface, he contacted palaeontologists from the Museum of Conca Dellà. Few months later a palaeontology dig was conducted which confirmed the exceptional nature of this site. After a first research dig, twelve more campaigns have been conducted as part of research projects led by Àngel Galobart, Head of the Mesozoic Fauna Research Group at ICP, and Rodrigo Gaete from the Museum of Conca Dellà.

The fossils found at Basturs Poble are conserved at the Museum of Conca Dellà. The museum’s dinosaur exhibition hall contains a sample of the most outstanding bones found at the site and a life-size recreation of a Pararhabdodon isonensis dinosaur.

Reference:
Víctor Fondevilla, Fabio Marco Dalla Vecchia, Rodrigo Gaete, Àngel Galobart, Blanca Moncunill-Solé, Meike Köhler. Ontogeny and taxonomy of the hadrosaur (Dinosauria, Ornithopoda) remains from Basturs Poble bonebed (late early Maastrichtian, Tremp Syncline, Spain). PLOS ONE, 2018; 13 (10): e0206287 DOI: 10.1371/journal.pone.0206287

Note: The above post is reprinted from materials provided by Universitat Autonoma de Barcelona.

A toast to the proteins in dinosaur bones

November 14, 2018

Dinosaur blood vessel with adjacent bone matrix that still contains bone cells. These structures have a perfect morphological preservation over hundreds of millions of years, but are chemically transformed through oxidative crosslinking. The extract comes from a sauropod dinosaur. Credit: Jasmina Wiemann/Yale University

Burnt toast and dinosaur bones have a common trait, according to a new, Yale-led study. They both contain chemicals that, under the right conditions, transform original proteins into something new. It’s a process that may help researchers understand how soft-tissue cells inside dinosaur bones can survive for hundreds of millions of years.

A research team from Yale, the American Museum of Natural History, the University of Brussels, and the University of Bonn announced the discovery Nov. 9 in the journal Nature Communications.

Fossil soft tissue in dinosaur bones has been a controversial topic among researchers for quite some time. Hard tissues, such as bones, eggs, teeth, and enamel scales, are able to survive fossilization extremely well. Soft tissues, such as blood vessels, cells, and nerves — which are stored inside the hard tissue — are more delicate and thought to decay rapidly after death. These soft tissues are composed mainly of proteins, which are believed to completely degrade within about four million years.

Yet dinosaur bones are much older, roughly 100 million years old, and they occasionally preserve organic structures similar to cells and blood vessels. Various attempts to resolve this paradox have failed to provide a conclusive answer.

“We took on the challenge of understanding protein fossilization,” said Yale paleontologist Jasmina Wiemann, the study’s lead author. “We tested 35 samples of fossil bones, eggshells, and teeth to learn whether they preserve proteinaceous soft tissues, find out their chemical composition, and determine under what conditions they were able to survive for millions of years.”

The researchers discovered that soft tissues are preserved in samples from oxidative environments such as sandstones and shallow, marine limestones. The soft tissues were transformed into Advanced Glycoxidation and Lipoxidation end products (AGEs and ALEs), which are resistant to decay and degradation. They’re also structurally comparable to chemical compounds that stain the dark crust on toast.

AGEs and ALEs are characterized by a brownish color that stains fossil bones and teeth that contain them. The compounds are hydrophobic, which means they are resistant to the normal effects of water, and have properties that make it difficult for bacteria to consume them.

Wiemann and her colleagues made their discovery by decalcifying fossils and imaging the released soft tissue structures. They applied Raman microspectroscopy — a non-destructive method for analyzing both the inorganic and organic contents of a sample — to the extracted fossil soft tissues. During this process, laser energy directed at the tissue causes molecular vibrations that carry spectral fingerprints for the chemicals that are present.

Co-author Derek Briggs, Yale’s G. Evelyn Hutchinson Professor of Geology and Geophysics and a curator at the Yale Peabody Museum of Natural History, said the study points to localities where soft tissue may be found in fossil bones, including sandstones deposited from rivers, dune sands, and shallow marine limestones.

“Our results show how chemical alteration explains the fossilization of these soft tissues and identifies the types of environment where this process occurs,” Briggs said. “The payoff is a way of targeting settings in the field where this preservation is likely to occur, expanding an important source of evidence of the biology and ecology of ancient vertebrates.”

Additional co-authors of the study are Matteo Fabbri from Yale, Martin Sander and Tzu-Ruei Yang from the University of Bonn, Koen Stein from the University of Brussels, and Mark Norell from the American Museum of Natural History.

Reference:
Jasmina Wiemann, Matteo Fabbri, Tzu-Ruei Yang, Koen Stein, P. Martin Sander, Mark A. Norell, Derek E. G. Briggs. Fossilization transforms vertebrate hard tissue proteins into N-heterocyclic polymers. Nature Communications, 2018; 9 (1) DOI: 10.1038/s41467-018-07013-3

Note: The above post is reprinted from materials provided by Yale University. Original written by Jim Shelton.

Detective mission to characterise and trace the history of a new African meteorite

Tracing the history

Classifying Africa’s newest meteorite

Poor Man’s Space Probe

Gigantic mammal ‘cousin’ discovered

Evolution: South Africa’s hominin record is a fair-weather friend

Human ancestors not to blame for ancient mammal extinctions in Africa

Taking a Closer Look

Earth’s cobalt deposits formed much later than previously believed

Oil extraction likely triggered mid-century earthquakes in L.A.

L.A. oil boom

Seismological cold cases

Fight over dinosaur fossils comes down to what’s a mineral

Tiny raptor tracks lead to big discovery

Volcanoes and glaciers combine as powerful methane producers

Climate, life and the movement of continents: New connections

Huge Crater Discovered in Greenland

Giant circular depression

The crucial evidence

The consequences of the impact on the Earth’s climate and life

Seismic study reveals huge amount of water dragged into Earth’s interior

Scientists Help Provide First-Ever Views of Elusive Energy Explosion

Earth’s magnetic field measured using artificial stars at 90 kilometers altitude

The precession of sodium atoms reveals the strength of the magnetic field

Climate change likely caused migration, demise of ancient Indus Valley civilization

Deep-time evolution of animal life on islands

Ancient flower fossil points to core eudicot boom 99 million years ago

Rare fossil bird deepens mystery of avian extinctions

Theropod dinosaurs evolved into birds

Most complete study on Europe’s greatest Hadrosaur site published

Hadrosaurs, A Well-Known Group in Catalonia

The Pyrenees, Home to the Last Dinosaurs in Europe

A toast to the proteins in dinosaur bones

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