The holotype of the species Retrophyllum oxyphyllum (comb. nov.), previously thought to be the oldest known bamboo. Credit: Peter Wilf
A fossilised leafy branch from the early Eocene in Patagonia described in 1941 is still often cited as the oldest bamboo fossil and the main fossil evidence for a Gondwanan origin of bamboos. However, a recent examination by Dr. Peter Wilf from Pennsylvania State University revealed the real nature of Chusquea oxyphylla. The recent findings, published in the paper in the open-access journal Phytokeys, show that it is actually a conifer.
The corrected identification is significant because the fossil in question was the only bamboo macrofossil still considered from the ancient southern supercontinent of Gondwana. The oldest microfossil evidence for bamboo in the Northern Hemisphere belongs to the Middle Eocene, while other South American fossils are not older than Pliocene.
Over the last decades, some authors have doubted whether the Patagonian fossil was really a bamboo or even a grass species at all. But despite its general significance, modern-day re-examinations of the original specimen were never published. Most scientists referring to it had a chance to study only a photograph found in the original publication from 1941 by the famous Argentine botanists Joaquín Frenguelli and Lorenzo Parodi.
In his recent study of the holotype specimen at Museo de La Plata, Argentina, Dr. Peter Wilf revealed that the fossil does not resemble members of the Chusquea genus or any other bamboo.
“There is no evidence of bamboo-type nodes, sheaths or ligules. Areas that may resemble any bamboo features consist only of the broken departure points of leaf bases diverging from the twig. The decurrent, extensively clasping leaves are quite unlike the characteristically pseudopetiolate leaves of bamboos, and the heterofacially twisted free-leaf bases do not occur in any bamboo or grass,” wrote Dr. Wilf.
Instead, Wilf linked the holotype to the recently described fossils of the conifer genus Retrophyllum from the same fossil site, the prolific Laguna del Hunco fossil lake-beds in Chubut Province, Argentina. It matches precisely the distichous fossil foliage form of Retrophyllum spiralifolium, which was described based on a large set of data — a suite of 82 specimens collected from both Laguna del Hunco and the early middle Eocene Río Pichileufú site in Río Negro Province.
Retrophyllum is a genus of six living species of rainforest conifers. Its habitat lies in both the Neotropics and the tropical West Pacific.
The gathered evidence firmly confirms that Chusquea oxyphylla has nothing in common with bamboos. Thus, it requires renaming. Preserving the priority of the older name, Wilf combined Chusquea oxyphylla and Retrophyllum spiralifolium into Retrophyllum oxyphyllum.
The exclusion of a living New World bamboo genus from the overall floral list for Eocene Patagonia weakens the New World biogeographic signal of the late-Gondwanan vegetation of South America, which already showed much stronger links to living floras of the tropical West Pacific.
The strongest New World signal remaining in Eocene Patagonia based on well-described macrofossils comes from fossil fruits of Physalis (a genus of flowering plants including tomatillos and ground cherries), which is an entirely American genus, concludes Dr. Wilf.
Reference:
Peter Wilf. Eocene “Chusquea” fossil from Patagonia is a conifer, not a bamboo. PhytoKeys, 2020; 139: 77 DOI: 10.3897/phytokeys.139.48717
Note: The above post is reprinted from materials provided by Pensoft Publishers. The original story is licensed under a Creative Commons License.
The Siberian Traps, the scene of ancient volcanic eruptions 252 million years ago that led to a massive extinction of life on Earth. CCNY researchers Ellen Gales and Benjamin Black obtained samples for their study there. Credit: B. Black and L.T. Elkins-Tanton.
An emerging scientific consensus is that gases—in particular carbon gases–released by volcanic eruptions millions of years ago contributed to some of Earth’s greatest mass extinctions. But new research at The City College of New York suggests that that’s not the entire story.
“The key finding of our research is that carbon from massive, ancient volcanic eruptions does not line up well with the geochemical clues that tell us about how some of Earth’s most profound mass extinctions occurred,” said Benjamin Black, assistant professor in CCNY’s Division of Science, whose expertise includes effects of volcanism on climate and mass extinctions.
The study by Black with his M.S. in geology student Ellen Gales, the lead author, is entitled “Carbonatites as a record of the carbon isotope composition of large igneous province outgassing.” It appears in the current issue of the journal Earth and Planetary Science Letters, and is a product of Gales’ thesis work.
The new data does not rule out volcanism as the culprit in driving past mass extinctions, the article points out. But it does conclude that there must have been something extra at work.
“Ellen’s work is new in that scientists have previously guessed what the geochemical fingerprint of CO2 from these giant eruptions might be, but our findings are some of the first direct measurements of this fingerprint,” said Black.
“Our finding challenges the idea that carbon from this kind of eruption might be special, and therefore capable of easily matching changes in the carbon cycle during mass extinctions. It also helps us understand how volcanic eruptions move carbon—a key ingredient for life and climate—around inside the Earth and between the solid Earth and the atmosphere,” said Gales.
In addition, the CCNY research also offers insights into Earth’s current climate. “Right now, people are releasing large quantities of CO2 into the atmosphere. In a way, we are heading into almost uncharted territory,” noted Black. “This scale of CO2 release has only happened a few times in Earth’s history, for example during rare, enormous volcanic eruptions like the ones we studied.”
Consequently, Black pointed out, even though volcanic eruptions on the scale of these enormous volcanic provinces are not expected any time soon, understanding the environmental changes triggered by prodigious volcanic CO2 release in the deep past is important for understanding how Earth’s climate could change in the coming centuries.
The researchers used samples collected from ancient volcanic eruptions including the 252-million-year-old Siberian Traps. They included data collected at Columbia University’s Lamont-Doherty Earth Observatory.
Reference:
Ellen Gales et al. Carbonatites as a record of the carbon isotope composition of large igneous province outgassing, Earth and Planetary Science Letters (2020). DOI: 10.1016/j.epsl.2020.116076
Allosaurus jimmadseni, a new species of dinosaur discovered in Utah, has a distinctive crest that runs from the eyes to the nose. Credit: Todd Marshall
A remarkable new species of meat-eating dinosaur has been unveiled at the Natural History Museum of Utah. Paleontologists unearthed the first specimen in early 1990s in Dinosaur National Monument in northeastern Utah. The huge carnivore inhabited the flood plains of western North America during the Late Jurassic Period, between 157-152 million years ago, making it the geologically oldest species of Allosaurus, predating the more well-known state fossil of Utah, Allosaurus fragilis. The newly named dinosaur Allosaurus jimmadseni, was announced today in the open-access scientific journal PeerJ.
The species belongs to the allosauroids, a group of small to large-bodied, two-legged carnivorous dinosaurs that lived during the Jurassic and Cretaceous periods. Allosaurus jimmadseni, possesses several unique features, among them a short narrow skull with low facial crests extending from the horns in front of the eyes forward to the nose and a relatively narrow back of the skull with a flat surface to the bottom of the skull under the eyes. The skull was weaker with less of an overlapping field of vision than its younger cousin Allosaurus fragilis. Allosaurus jimmadseni evolved at least 5 million years earlier than fragilis, and was the most common and the top predator in its ecosystem. It had relatively long legs and tail, and long arms with three sharp claws. The name Allosaurus translates as “different reptile,” and the second part, jimmadseni, honors Utah State Paleontologist James H. Madsen Jr.
Following an initial description by Othniel C. Marsh in 1877, Allosaurus quickly became the best known—indeed the quintessential—Jurassic theropod. The taxonomic composition of the genus has long been a debate over the past 130 years. Paleontologists argue that there are anywhere between one and 12 species of Allosaurus in the Morrison Formation of North America. This study recognizes only two species—A. fragilis and A. jimmadseni.
“Previously, paleontologists thought there was only one species of Allosaurus in Jurassic North America, but this study shows there were two species—the newly described Allosaurus jimmadseni evolved at least 5 million years earlier than its younger cousin, Allosaurus fragilis,” said co-lead author Mark Loewen, research associate at the Natural History Museum of Utah, and associate professor in the Department of Geology and Geophysics at the University of Utah led the study. “The skull of Allosaurus jimmadseni is more lightly built than its later relative Allosaurus fragilis, suggesting a different feeding behavior between the two.”
“Recognizing a new species of dinosaur in rocks that have been intensely investigated for over 150 years is an outstanding experience of discovery. Allosaurus jimmadseni is a great example of just how much more we have to learn about the world of dinosaurs. Many more exciting fossils await discovery in the Jurassic rocks of the American West,” said Daniel Chure, retired paleontologist at Dinosaur National Monument and co-lead author of the study.
George Engelmann of the University of Nebraska, Omaha initially discovered the initial skeleton of the new species within Dinosaur National Monument in 1990. In 1996, several years after the headless skeleton was collected, the radioactive skull belonging to the skeleton using a radiation detector by Ramal Jones of the University of Utah. Both skeleton and skull were excavated by teams from Dinosaur National Monument.
“Big Al,” another specimen belonging to the new species, was discovered in Wyoming on United States Bureau of Land Management (BLM) land in 1991 and is housed in the collections of the Museum of The Rockies in Bozeman, Montana. Previously thought to belong to Allosaurus fragilis, “Big Al” was featured in the BBC’s 2001 “Walking with Dinosaurs: Ballad of Big Al” video. Over the last 30 years, crews from various museums have collected and prepared materials of this new species. Other specimens include “Big Al Two” at the Saurier Museum Aathal in Switzerland and Allosaurus material from the Dry Mesa Quarry of Colorado at Brigham Young University.
“This exciting new study illustrates the importance of continued paleontological investigations on public lands in the West. Discovery of this new taxon of dinosaur will provide important information about the life and times of Jurassic dinosaurs and represents another unique component of America’s Heritage,” said Brent Breithaupt, BLM regional paleontologist.
Early Morrison Formation dinosaurs were replaced by some of the most iconic dinosaurs of the Late Jurassic
Allosaurus jimmadseni lived on the semi-arid Morrison Formation floodplains of the interior of western North America. The older rocks of the Morrison Formation preserve a fauna of dinosaurs distinct from the iconic younger Morrison Formation faunas that include Allosaurus fragilis, Diplodocus and Stegosaurus. Paleontologists have recently determined that specimens of this new species of dinosaur lived in several places throughout the western interior of North America (Utah, Colorado and Wyoming).
Study summary
Dinosaurs were the dominant members of terrestrial ecosystems during the Mesozoic. However, the pattern of evolution and turnover of ecosystems during the middle Mesozoic remains poorly understood. The authors report the discovery of the earliest member of the group of large-bodied allosauroids in the Morrison Formation ecosystem that was replaced by Allosaurus fragilis and illustrate changes acquired in the genus over time. The study includes an in-depth description of every bone of the skull and comparisons with the cranial materials of other carnivorous dinosaurs. Finally, the study recognizes just two species of Allosaurus in North America with Allosaurus fragilis replacing its earlier relative Allosaurus jimmadseni.
Fact sheet: Major points of the paper
A remarkable new species of meat-eating dinosaur, Allosaurus jimmadseni, is described based on two spectacularly complete skeletons. The first specimen was unearthed in Dinosaur National Monument, in northeastern Utah.
Allosaurus jimmadseni is distinguished by a number of unique features, including low crests running from above the eyes to the snout and a relatively narrow back of the skull with a flat surface to the bottom of the upper skull under the eyes. The skull was weaker with less of an overlapping field of vision than its younger cousin Allosaurus fragilis.
At 155 million years old, Allosaurus jimmadseni is the geologically-oldest species of Allosaurus predating the more well-known State Fossil of Utah Allosaurus fragilis.
Allosaurus jimmadseni was the most common and the top predator in its ecosystem. It had relatively long legs and tail, and long arms with three sharp claws.
Study design
Comparison of the bones with all other known allosauroid dinosaurs indicate that the species possessed unique features of the upper jaw and cheeks (maxilla and jugal) and a decorative crest stretching from just in front of the eyes to the nose.
Many of the comparisons were made with the thousands of bones of Allosaurus fragilis collected from the famous Cleveland-Lloyd Dinosaur Quarry administered by the Bureau of Land Management that are housed in the collections of the Natural History Museum of Utah.
On the basis of these features, the scientific team named it a new genus and species of dinosaur, Allosaurus jimmadseni (translating to “Jim Madsen’s different reptile”).
Allosaurus jimmadseni is particularly notable for its slender, narrow skull with short sharp nasal crests compared to its close relative and successor Allosaurus fragilis.
The study was funded in part by the University of Utah, the National Park Service and the National Science Foundation.
New dinosaur name: Allosaurus jimmadseni
The first part of the name, Allosaurus, (a·luh·SAW·ruhs) can be translated from Greek as the “other”, “strange” or “different” and “lizard” or “reptile” literally to “different reptile”. The second part of the name jimmadseni (gym-MAD-sehn-eye) honors the late Utah State Paleontologist James Madsen Jr. who excavated and studied tens of thousands of Allosaurus bones from the famous Cleveland-Lloyd Dinosaur Quarry in central Utah and contributed greatly to the knowledge of Allosaurus.
Size
Allosaurus jimmadseni was approximately 26 to 29 feet (8-9 meters) long.
Allosaurus jimmadseni weighed around 4000 lbs. (1.8 metric tonnes).
Relationships
Allosaurus jimmadseni belongs to a group of carnivorous dinosaurs called “allosauroids,” the same group as the famous Allosaurus fragilis.
Other dinosaurs found in rocks containing Allosaurus jimmadseni include the carnivorous theropods Torvosaurus and Ceratosaurus; the long-necked sauropods Haplocanthosaurus and Supersaurus; and the plate-backed stegosaur Hesperosaurus.
Allosaurus jimmadseni is closely related to the State Fossil of Utah, Allosaurus fragilis.
Anatomy
Allosaurus jimmadseni was a two-legged carnivore, with long forelimbs and sharp, recurved claws that were likely used for grasping prey.
Like other allosauroid dinosaurs, Allosaurus jimmadseni had a large head full of 80 sharp teeth. It was also the most common carnivore in its ecosystem.
Age and geography
Allosaurus jimmadseni lived during the Kimmeridgian stage of the Late Jurassic period, which spanned from approximately 157 million to 152 million years ago.
Allosaurus jimmadseni lived in a semi-arid inland basin filled with floodplains, braided stream systems, lakes, and seasonal mudflats along the western interior of North America.
Allosaurus jimmadseni represents the earliest species of Allosaurus in the world.
Discovery
Allosaurus jimmadseni can be found in a geologic unit known as the Salt Wash Member of the Morrison Formation and its equivalents exposed in Colorado, Wyoming, and Utah.
The first specimen of Allosaurus jimmadseni was discovered in the National Park Service administered by Dinosaur National Monument in Uintah County, near Vernal, Utah.
Allosaurus jimmadseni was first discovered by George Engelmann of the University of Nebraska, Omaha on July 15, 1990 during a contracted paleontological inventory of the Morrison Formation of Dinosaur National Monument.
Another specimen of Allosaurus jimmadseni known as “Big Al,” was found on land administered by the U.S. Department of the Interior’s Bureau of Land Management in Wyoming.
Further specimens of Allosaurus jimmadseni have been subsequently recognized in the collections of various museums.
Allosaurus jimmadseni specimens are permanently housed in the collections of Dinosaur National Monument, Utah; the Museum of the Rockies, Bozeman, Montana; the Saurier Museum of Aathal, Switzerland; the South Dakota School of Mines, Rapid City, South Dakota; Brigham Young University’s Museum of Paleontology, Provo, Utah; and the United States National Museum (Smithsonian) Washington D.C.
These discoveries are the result of a continuing collaboration between the Natural History Museum of Utah, the National Park Service, and the Bureau of Land Management.
Excavation
The first skeleton of Allosaurus jimmadseni was excavated during the summers of 1990 to 1994 by staff of the National Park Service’s Dinosaur National Monument. The skeleton block was so heavy it required the use of explosives to remove surrounding rock and a helicopter to fly out the 2700 kg block. The head of the skeleton was missing
The first bones of Allosaurus jimmadseni discovered included toes and some tail vertebrae. Later excavation revealed most of an articulated skeleton missing the head and part of the tail.
The radioactive skull of the first specimen of Allosaurus jimmadseni, which had previously eluded discovery, was found in 1996 by Ramal Jones of the University of Utah using a radiation detector.
Preparation
It required seven years to fully prepare all of the bones of Allosaurus jimmadseni.
Much of the preparation was done by then Dinosaur National Monument employees Scott
Madsen and Ann Elder, with some assistance from Dinosaur National Monument volunteers and students at Brigham Young University.
Other
The Natural History Museum of Utah houses the world’s largest collection of Allosaurus fossils, which are frequently studied by researchers from around the world.
More than 270 National Park Service (NPS) areas preserve fossils even though only 16 of those were established wholly or in part for their fossils. Fossils in NPS areas can be found in the rocks or sediments of a park, in museum collections, and in cultural contexts (building stones, artifacts, historical legends, and documents).
The United States Bureau of Land Management manages more land—247 million acres—than any other federal agency, and manages paleontological resources using scientific principles and expertise.
Reference:
Daniel J. Chure et al, Cranial anatomy of Allosaurus jimmadseni, a new species from the lower part of the Morrison Formation (Upper Jurassic) of Western North America, PeerJ (2020). DOI: 10.7717/peerj.7803
New international research led by the University of St Andrews presents a novel way to understand the structure and formation of our oldest continents.
The research, published in the journal Earth and Planetary Science Letters reveals how the team from St Andrews, Greenland, Australia, Denmark, and Canada, used magmatic rocks, sourced from deep within the Earth, to sample the interior of cratons as a means to understand how they were formed.
Cratons are the ancient, stable, heart of the Earth’s continents, and their formation was a prerequisite for the evolution of complex life. The North Atlantic Craton extends from Northern Scotland through Greenland to North America, and contains the oldest crust known on Earth—up to 3.8 billion years old. How these ancient cratons were built is a major scientific debate, informing on one of the most fundamental questions in Earth science: when did plate tectonics begin operating?
Plate tectonics—the cycle of rigid tectonic plates in constant horizontal motion across the surface of the planet—makes Earth unique within the rocky planets of the solar system. Plate tectonics started at some point after the Earth formed 4.6 billion years ago, but it is unclear exactly when. Some scientists believe craton formation occurred as a result of plate tectonics, whereby they were assembled via horizontal stacking of crust. Others believe cratons were formed through non-plate tectonic processes, growing via so-called “vertical tectonics.”
The ability to understand the architecture of cratons and therefore how and when they were formed is, however, problematic, due to the difficulty in sampling rocks from within the deep crust and mantle, which in West Greenland is up to 250 km thick.
To address this, the research team used deep-sourced magmatic rocks known as kimberlites to sample the deep parts of the North Atlantic Craton. Kimberlites, which are famous for bringing diamonds to the surface, originate from the upper mantle, more than 100 km below Earth’s surface. As they ascend through the craton, their magma collects pieces of crust along the way, pieces that are hidden at the surface. In this way, kimberlites can sample parts of the deep continent that are otherwise inaccessible.
The researchers sampled a kimberlite from the coast of West Greenland, near Maniitsoq, and extracted from it microscopic zircon grains, each less than the width of a human hair, originating from crust deep within the craton. The team analysed these grains using high-precision laser ablation mass spectrometry.
Analysis revealed the age and chemistry of the zircon grains, which suggested that beneath the 3.0 billion-years old crust which today forms the Maniitsoq region, lies much older 3.8 billion-year-old crust. This older crust is today only found at the surface 150 km south of the kimberlite locality. Therefore, for it to have been sampled by the kimberlite, parts of it must have been transported laterally beneath the crust that is now at the surface, sometime after 3.0 billion years ago.
Lead scientist Dr. Nick Gardiner of the School of Earth and Environmental Sciences, University of St Andrews, said: “The kimberlite sample offers up these ancient zircon grains which imply the North Atlantic Craton was assembled by horizontally stacking different-aged slices of continental crust, likely in the late Archaean Eon after 3.0 billion years ago. These findings imply some cratons were formed through plate tectonic processes.”
The paper, “North Atlantic Craton architecture revealed by kimberlite-hosted crustal zircons,” is published in Earth and Planetary Science Letters
Reference:
Nicholas J. Gardiner et al. North Atlantic Craton architecture revealed by kimberlite-hosted crustal zircons, Earth and Planetary Science Letters (2020). DOI: 10.1016/j.epsl.2020.116091
For nearly a week, a series of earthquakes have been shaking the area around Grindavik, not far from the steaming waters of the “Blue Lagoon,” a popular geothermal spa in southwestern Iceland on the Reykjanes Peninsula
Small earthquakes and a so-called “inflation” of the mountain, signalling a potential volcanic eruption, have been reported near Iceland’s famous “Blue Lagoon,” local authorities said Monday.
The Icelandic Met Office declared a state of uncertainty over the weekend, following days of several smaller earthquakes and a swelling of the mountain.
Alert levels for aviation were also raised from “green” to “yellow,” defined as when a volcano “is experiencing signs of elevated unrest above known background levels.”
For nearly a week, a series of earthquakes have been shaking the area around Grindavik, not far from the steaming waters of the “Blue Lagoon,” a popular geothermal spa in southwestern Iceland on the Reykjanes Peninsula.
The largest recorded quake had a magnitude of 3.7.
Swarms of earthquakes are not unusual in the area, but the fact that they were occurring alongside an “unusually fast” inflation of Mount Thorbjorn, a few kilometres (miles) from Grindavik, was “a cause for concern and closer monitoring,” according to the Icelandic Met Office.
A rise of about 3.0-4.0 millimetres a day has been detected, totalling 2.0 centimetres on Sunday, and is suspected to be from magma accumulation a few kilometres under ground.
Depending on the cause, a few scenarios are being considered.
If the rise is due to accumulation of magma in the volcano, it could either simply cease or continue to build up, potentially leading to an eruption.
But if the rise is due to tectonic activity, it could signal more powerful earthquakes in store.
The peninsula is located on the Mid-Atlantic Ridge, where the North American and Eurasian tectonic plates diverge.
“It’s too soon to try to distinguish which (scenario) is the most likely,” Pall Einarsson, professor of geophysics at the Faculty of Earth Sciences at the University of Iceland, told AFP.
Einarsson said that in the event of an eruption it would be “the most peaceful kind you can think of.”
“We always have to plan for the worst, so we are planning for an eruption, but the most likely scenario is that this event will just stop,” said Rognvaldur Olafsson, chief inspector at the Department of Civil Protection and Emergency Management.
New measuring instruments were due to be installed on Monday to monitor the activity more closely.
In 2010, eruptions at Eyjafjallajokull sent a huge cloud of smoke and ash over Europe, resulting in the cancellation of more than 100,000 flights, stranding some eight million passengers.
The last known eruption on the Reykjanes Peninsula was nearly 800 years ago.
However, according to Einarsson, eruptions in this region of Iceland are “effusive” with a narrow flow of lava and a small amount of ash, meaning they are not likely to cause harm to people.
Note: The above post is reprinted from materials provided by AFP.
Core samples from the fault zone of the Japan Trench were recovered by the JFAST project and analyzed for evidence of past large earthquakes.
In the aftermath of the devastating Tohoku-Oki earthquake that struck off the coast of Japan in March 2011, seismologists were stunned by the unprecedented 50 meters of shallow displacement along the fault, which ruptured all the way to the surface of the seafloor. This extreme slip at shallow depths exacerbated the massive tsunami that, together with the magnitude 9.1 earthquake, caused extensive damage and loss of life in Japan.
In a new study, published January 27 in Nature Communications, researchers used a novel technique to study the faults in the Japan Trench, the subduction zone where the Tohoku-Oki earthquake struck. Their findings reveal a long history of large earthquakes in this fault zone, where they found multiple faults with evidence of more than 10 meters of slip during large earthquakes.
“We found evidence of many large earthquakes that have ruptured to the seafloor and could have generated tsunamis like the one that struck in 2011,” said coauthor Pratigya Polissar, associate professor of ocean sciences at UC Santa Cruz.
Japanese researchers looking at onshore sediment deposits have found evidence of at least three similar tsunamis having occurred in this region at roughly 1,000-year intervals. The new study suggests there have been even more large earthquakes on this fault zone than those that left behind onshore evidence of big tsunamis, said coauthor Heather Savage, associate professor of Earth and planetary sciences at UC Santa Cruz.
Savage and Polissar have developed a technique for assessing the history of earthquake slip on a fault by analyzing organic molecules trapped in sedimentary rocks. Originally synthesized by marine algae and other organisms, these “biomarkers” are altered or destroyed by heat, including the frictional heating that occurs when a fault slips during an earthquake. Through extensive laboratory testing over the past decade, Savage and Polissar have developed methods for quantifying the thermal evolution of these biomarkers and using them to reconstruct the temperature history of a fault.
The Japan Trench Fast Drilling Project (JFAST) drilled into the fault zone in 2012, extracting cores and installing a temperature observatory. UCSC seismologist Emily Brodsky helped organize JFAST, which yielded the first direct measurement of the frictional heat produced by the fault slip during an earthquake (see earlier story). This heat dissipates after the earthquake, however, so the signal is small and transient.
“The biomarkers give us a way to detect permanent changes in the rock that preserve a record of heating on the fault,” Savage said.
For the new study, the researchers examined the JFAST cores, which extended through the fault zone into the subducting plate below. “It’s a complex fault zone, and there were a lot of faults throughout the core. We were able to say which faults had evidence of large earthquakes in the past,” Savage said.
One of their goals was to understand whether some rock types in the fault zone were more prone to large slip in an earthquake than other rocks. The cores passed through layers of mudstones and clays with different frictional strengths. But the biomarker analysis showed evidence of large seismic slip on faults in all the different rock types. The researchers concluded that differences in frictional properties do not necessarily determine the likelihood of large shallow slip or seismic hazard.
Savage and Polissar began working on the biomarker technique as postdoctoral researchers at UC Santa Cruz, publishing their first paper on it with Brodsky in 2011. They continued developing it as researchers at the Lamont-Doherty Earth Observatory of Columbia University, before returning to UC Santa Cruz as faculty members in 2019. Hannah Rabinowitz, the first author of the new paper, worked with them as a graduate student at Columbia and is now at the U.S. Department of Energy.
“We’ve tested this technique in different rocks with different ages and heating histories, and we can now say yes, there was an earthquake on this fault, and we can tell if there was a large one or many small ones,” Savage said. “We can now take this technique to other faults to learn more about their histories.”
In addition to Rabinowitz, Savage, and Polissar, the coauthors of the paper include Christie Rowe and James Kirkpatrick at McGill University. This work was funded by the National Science Foundation. The JFAST project was sponsored by the International Ocean Drilling Program (IODP).
Reference:
Hannah S. Rabinowitz, Heather M. Savage, Pratigya J. Polissar, Christie D. Rowe, James D. Kirkpatrick. Earthquake slip surfaces identified by biomarker thermal maturity within the 2011 Tohoku-Oki earthquake fault zone. Nature Communications, 2020; 11 (1) DOI: 10.1038/s41467-020-14447-1
A map of Vancouver Island showing the locations of seismic instruments considered by the research group. The grey shaded region delineates where slow earthquakes occur. Credit: University of Ottawa
A team of researchers at the University of Ottawa has made an important breakthrough that will help better understand the origin and behavior of slow earthquakes, a new type of earthquake discovered by scientists nearly 20 years ago.
These earthquakes produce movement so slow—a single event can last for days, even months—that they are virtually imperceptible. Less fearsome and devastating than regular earthquakes, they do not trigger seismic waves or tsunamis. They occur in regions where a tectonic plate slides underneath another one, called ”subduction zone faults”, adjacent but deeper to where regular earthquakes occur. They also behave very differently than their regular counterparts. But how? And more importantly: why?
Pascal Audet, Associate Professor in the Department of Earth and Environmental Sciences at uOttawa, along with his seismology research group (Jeremy Gosselin, Clément Estève, Morgan McLellan, Stephen G. Mosher and former uOttawa postdoctoral student Andrew J. Schaeffer), were able to find answers to these questions.
“Our work presents unprecedented evidence that these slow earthquakes are related to dynamic fluid processes at the boundary between tectonic plates,” said first author and uOttawa Ph.D. student, Jeremy Gosselin. “These slow earthquakes are quite complex, and many theoretical models of slow earthquakes require the pressure of these fluids to fluctuate during an earthquake cycle.”
Using a technique similar to ultrasound imagery and recordings of earthquakes, Audet and his team were able to map the structure of the Earth where these slow earthquakes occur. By analyzing the properties of the rocks where these earthquakes happened, they were able to reach their conclusions.
In fact, in 2009, Professor Audet had himself presented evidence that slow earthquakes occurred in regions with unusually high fluid pressures within the Earth.
“The rocks at those depths are saturated with fluids, although the quantities are minuscule,” explained Professor Pascal Audet. “At a depth of 40 km, the pressure exerted on the rocks is very high, which normally tends to drive the fluids out, like a sponge that someone squeezes. However, these fluids are imprisoned in the rocks and are virtually incompressible; the fluid pressure therefore rises to very high values, which essentially weakens the rocks and generates slow earthquakes.”
Several studies over the past years had suggested these events are related to dynamic changes in fluid pressure, but until now, no conclusive empirical evidence had been established. “We were keen to repeat Professor Audet’s previous work to look for time-varying changes in fluid pressures during slow earthquakes,” explained Jeremy Gosselin. “What we discovered confirmed our suspicions and we were able to establish the first direct evidence that fluid pressures do, in fact, fluctuate during slow earthquakes.”
Reference:
Jeremy M. Gosselin et al, Seismic evidence for megathrust fault-valve behavior during episodic tremor and slip, Science Advances (2020). DOI: 10.1126/sciadv.aay5174
The Yarrabubba Impact Structure. CREDIT: Google Earth
Curtin University scientists have discovered Earth’s oldest asteroid strike occurred at Yarrabubba, in outback Western Australia, and coincided with the end of a global deep freeze known as a Snowball Earth.
The research, published in the leading journal Nature Communications, used isotopic analysis of minerals to calculate the precise age of the Yarrabubba crater for the first time, putting it at 2.229 billion years old — making it 200 million years older than the next oldest impact.
Lead author Dr Timmons Erickson, from Curtin’s School of Earth and Planetary Sciences and NASA’s Johnson Space Center, together with a team including Professor Chris Kirkland, Associate Professor Nicholas Timms and Senior Research Fellow Dr Aaron Cavosie, all from Curtin’s School of Earth and Planetary Sciences, analysed the minerals zircon and monazite that were ‘shock recrystallized’ by the asteroid strike, at the base of the eroded crater to determine the exact age of Yarrabubba.
The team inferred that the impact may have occurred into an ice-covered landscape, vaporised a large volume of ice into the atmosphere, and produced a 70km diameter crater in the rocks beneath.
Professor Kirkland said the timing raised the possibility that the Earth’s oldest asteroid impact may have helped lift the planet out of a deep freeze.
“Yarrabubba, which sits between Sandstone and Meekatharra in central WA, had been recognised as an impact structure for many years, but its age wasn’t well determined,” Professor Kirkland said.
“Now we know the Yarrabubba crater was made right at the end of what’s commonly referred to as the early Snowball Earth — a time when the atmosphere and oceans were evolving and becoming more oxygenated and when rocks deposited on many continents recorded glacial conditions.”
Associate Professor Nicholas Timms noted the precise coincidence between the Yarrabubba impact and the disappearance of glacial deposits.
“The age of the Yarrabubba impact matches the demise of a series of ancient glaciations. After the impact, glacial deposits are absent in the rock record for 400 million years. This twist of fate suggests that the large meteorite impact may have influenced global climate,” Associate Professor Timms said.
“Numerical modelling further supports the connection between the effects of large impacts into ice and global climate change. Calculations indicated that an impact into an ice-covered continent could have sent half a trillion tons of water vapour — an important greenhouse gas — into the atmosphere. This finding raises the question whether this impact may have tipped the scales enough to end glacial conditions.”
Dr Aaron Cavosie said the Yarrabubba study may have potentially significant implications for future impact crater discoveries.
“Our findings highlight that acquiring precise ages of known craters is important — this one sat in plain sight for nearly two decades before its significance was realised. Yarrabubba is about half the age of the Earth and it raises the question of whether all older impact craters have been eroded or if they are still out there waiting to be discovered,” Dr Cavosie said.
Reference:
Timmons M. Erickson, Christopher L. Kirkland, Nicholas E. Timms, Aaron J. Cavosie, Thomas M. Davison. Precise radiometric age establishes Yarrabubba, Western Australia, as Earth’s oldest recognised meteorite impact structure. Nature Communications, 2020; 11 (1) DOI: 10.1038/s41467-019-13985-7
Note: The above post is reprinted from materials provided by Curtin University. Original written by Lucien Wilkinson.
Volcanic activity did not play a direct role in the mass extinction event that killed the dinosaurs, according to an international, Yale-led team of researchers. It was all about the asteroid.
In a break from a number of other recent studies, Yale assistant professor of geology & geophysics Pincelli Hull and her colleagues argue in a new research paper in Science that environmental impacts from massive volcanic eruptions in India in the region known as the Deccan Traps happened well before the Cretaceous-Paleogene extinction event 66 million years ago and therefore did not contribute to the mass extinction.
Most scientists acknowledge that the mass extinction event, also known as K-Pg, occurred after an asteroid slammed into Earth. Some researchers also have focused on the role of volcanoes in K-Pg due to indications that volcanic activity happened around the same time.
“Volcanoes can drive mass extinctions because they release lots of gases, like SO2 and CO2, that can alter the climate and acidify the world,” said Hull, lead author of the new study. “But recent work has focused on the timing of lava eruption rather than gas release.”
To pinpoint the timing of volcanic gas emission, Hull and her colleagues compared global temperature change and the carbon isotopes (an isotope is an atom with a higher or lower number of neutrons than normal) from marine fossils with models of the climatic effect of CO2 release. They concluded that most of the gas release happened well before the asteroid impact — and that the asteroid was the sole driver of extinction.
“Volcanic activity in the late Cretaceous caused a gradual global warming event of about two degrees, but not mass extinction,” said former Yale researcher Michael Henehan, who compiled the temperature records for the study. “A number of species moved toward the North and South poles but moved back well before the asteroid impact.”
Added Hull, “A lot of people have speculated that volcanoes mattered to K-Pg, and we’re saying, ‘No, they didn’t.'”
Recent work on the Deccan Traps, in India, has also pointed to massive eruptions in the immediate aftermath of the K-Pg mass extinction. These results have puzzled scientists because there is no warming event to match. The new study suggests an answer to this puzzle, as well.
“The K-Pg extinction was a mass extinction and this profoundly altered the global carbon cycle,” said Yale postdoctoral associate Donald Penman, the study’s modeler. “Our results show that these changes would allow the ocean to absorb an enormous amount of CO2 on long time scales — perhaps hiding the warming effects of volcanism in the aftermath of the event.”
The International Ocean Discovery Program, the National Science Foundation, and Yale University helped fund the research.
Reference:
Pincelli M. Hull, André Bornemann, Donald E. Penman, Michael J. Henehan, Richard D. Norris, Paul A. Wilson, Peter Blum, Laia Alegret, Sietske J. Batenburg, Paul R. Bown, Timothy J. Bralower, Cecile Cournede, Alexander Deutsch, Barbara Donner, Oliver Friedrich, Sofie Jehle, Hojung Kim, Dick Kroon, Peter C. Lippert, Dominik Loroch, Iris Moebius, Kazuyoshi Moriya, Daniel J. Peppe, Gregory E. Ravizza, Ursula Röhl, Jonathan D. Schueth, Julio Sepúlveda, Philip F. Sexton, Elizabeth C. Sibert, Kasia K. Śliwińska, Roger E. Summons, Ellen Thomas, Thomas Westerhold, Jessica H. Whiteside, Tatsuhiko Yamaguchi, James C. Zachos. On impact and volcanism across the Cretaceous-Paleogene boundary. Science, 2020 DOI: 10.1126/science.aay5055
Note: The above post is reprinted from materials provided by Yale University. Original written by Jim Shelton.
New insights into how microbial life was quickly re-established following the mass extinction of the dinosaurs have been detailed for the first time by Curtin University-led research.
The research, published in Geology, analyzed biomarkers, also known as molecular fossils, found in drill core rock samples from the center of the Chicxulub crater located in deep sea waters of the Gulf of Mexico.
The findings suggest that remains from land plants, fungi and coastal microbial mats, like modern stromatolites, were transported into the crater through wave activity during a giant tsunami in the immediate aftermath of the giant asteroid impact credited with causing the extinction of the dinosaurs, 66 million years ago.
Lead author Ph.D. candidate Bettina Schaefer, from the WA-Organic and Isotope Geochemistry Centre (WA-OIGC) in Curtin’s School of Earth and Planetary Sciences, said the research study provided the first molecular evidence of many forms of photosynthetic life present in the Chicxulub crater, demonstrating how resilient microorganisms were after experiencing abnormally hostile conditions following the asteroid’s impact.
“Our research shows that when the dust from the asteroid’s impact settled and sunlight returned to ideal levels, there was a rapid resurgence of land plants, dinoflagellates, cyanobacteria and all forms of anaerobic photosynthetic sulfur bacteria, including those from microbial mats in the crater area,” Ms Schaefer said.
John Curtin Distinguished Professor Kliti Grice, the founding director of WA-OIGC in Curtin’s School of Earth and Planetary Sciences, said the research findings further suggested the phytoplankton communities in the post-impact crater basin continued to produce and evolve at a “rapid” rate.
“The development and productivity of phytoplankton was accompanied by major transitions in nutrient and oxygen supplies that shaped the recovery of microbial life. There was so much going on in such a short time frame, it really was like a post-apocalyptic microbial mayhem was happening in the Chicxulub crater.”
Reference:
Bettina Schaefer et al. Microbial life in the nascent Chicxulub crater, Geology (2020). DOI: 10.1130/G46799.1
Fault zone with broken rock inside stippled lines and faulting directions of each rock segment outlined by half arrows. Photo credit: Henrik Drake. Illustration: Mikael Tillberg.
Constraining the history of earthquakes produced by bedrock fracturing is important for predicting seismic activity and plate tectonic evolution. In a new study published in the Nature journal Scientific Reports Jan 17, 2020, a team of researchers presents a new microscale technique to determine the age of crystals grown during repeated activation of natural rock fractures over a time range of billions of years.
The dramatic energy release of an earthquake forms as bedrock segments move in relative opposite directions to each other due to the collision or spreading of the tectonic plates that makes up the Earth’s crust. The movement occurs along fault planes where new mineral crystals grow simultaneously.
The bedrock of Scandinavia, up to two billion years old, displays an extensive network of fractures formed at different episodes stretching from the early history of the Scandinavian crust to modern times. In rock samples retrieved from deep boreholes in Sweden, new microscale radioisotopic dating of individual fault crystals reveals the dominant fracturing episodes affecting Scandinavia.
Mikael Tillberg, a doctoral student at the Linnaeus University, Sweden, and first author of the paper, explains, “The ages of our analysed crystals matches several distinct periods of extensive mountain range formation when plate boundaries were directly neighboring Scandinavia. These temporal constraints demonstrate that our newly developed approach is suitable to untangle complex fracturing histories.”
Thomas Zack, of Gothenburg University, Sweden, and a co-author of the study, describes how the dating method works. “Specific minerals contain radiogenic elements where certain isotopes decay over time. The abundances of these isotopes in tiny crystals formed on fracture surfaces are measured with high precision and detailed spatial resolution.”
“The link between crystal growth and the frictional movement of earthquakes is ensured by identifying striation lines formed on fracture surface crystals by the movement. This microscopic investigation precedes age analysis to enable a simple and robust procedure for dating of faulting,” Henrik Drake at Linnaeus University, also a co-author, adds.
Mikael Tillberg summarizes on the significance and possible future applications of this technique:
“Repeated earthquake episodes produce a chaotic array of broken rock and mineral growth even in a single crystal or on a particular fracture surface. Our methodology can resolve these sequences and connect the microscale mechanisms involved in fracturing to continent-wide plate tectonic forces. This allows reconstruction of geological models for diverse applications such as seismicity and infrastructure engineering.”
Reference:
Mikael Tillberg et al. In situ Rb-Sr dating of slickenfibres in deep crystalline basement faults, Scientific Reports (2020). DOI: 10.1038/s41598-019-57262-5
The fossil (left) was unearthed in Wisconsin in 1985. Scientists analyzed it and discovered the ancient animal’s respiratory and circulatory organs (center) were near-identical to those of a modern-day scorpion (right). Credit: Andrew Wendruff
Scientists studying fossils collected 35 years ago have identified them as the oldest-known scorpion species, a prehistoric animal from about 437 million years ago. The researchers found that the animal likely had the capacity to breathe in both ancient oceans and on land.
The discovery provides new information about how animals transitioned from living in the sea to living entirely on land: The scorpion’s respiratory and circulatory systems are almost identical to those of our modern-day scorpions — which spend their lives exclusively on land — and operate similarly to those of a horseshoe crab, which lives mostly in the water, but which is capable of forays onto land for short periods of time.
The researchers named the new scorpion Parioscorpio venator. The genus name means “progenitor scorpion,” and the species name means “hunter.” They outlined their findings in a study published today in the journal Scientific Reports.
“We’re looking at the oldest known scorpion — the oldest known member of the arachnid lineage, which has been one of the most successful land-going creatures in all of Earth history,” said Loren Babcock, an author of the study and a professor of earth sciences at The Ohio State University.
“And beyond that, what is of even greater significance is that we’ve identified a mechanism by which animals made that critical transition from a marine habitat to a terrestrial habitat. It provides a model for other kinds of animals that have made that transition including, potentially, vertebrate animals. It’s a groundbreaking discovery.”
The “hunter scorpion” fossils were unearthed in 1985 from a site in Wisconsin that was once a small pool at the base of an island cliff face. They had remained unstudied in a museum at the University of Wisconsin for more than 30 years when one of Babcock’s doctoral students, Andrew Wendruff — now an adjunct professor at Otterbein University in Westerville — decided to examine the fossils in detail.
Wendruff and Babcock knew almost immediately that the fossils were scorpions. But, initially, they were not sure how close these fossils were to the roots of arachnid evolutionary history. The earliest known scorpion to that point had been found in Scotland and dated to about 434 million years ago. Scorpions, paleontologists knew, were one of the first animals to live on land full-time.
The Wisconsin fossils, the researchers ultimately determined, are between 1 million and 3 million years older than the fossil from Scotland. They figured out how old this scorpion was from other fossils in the same formation. Those fossils came from creatures that scientists think lived between 436.5 and 437.5 million years ago, during the early part of the Silurian period, the third period in the Paleozoic era.
“People often think we use carbon dating to determine the age of fossils, but that doesn’t work for something this old,” Wendruff said. “But we date things with ash beds — and when we don’t have volcanic ash beds, we use these microfossils and correlate the years when those creatures were on Earth. It’s a little bit of comparative dating.”
The Wisconsin fossils — from a formation that contains fossils known as the Waukesha Biota — show features typical of a scorpion, but detailed analysis showed some characteristics that were not previously known in any scorpion, such as additional body segments and a short “tail” region, all of which shed light on the ancestry of this group.
Wendruff examined the fossils under a microscope, and took detailed, high-resolution photographs of the fossils from different angles. Bits of the animal’s internal organs, preserved in the rock, began to emerge. He identified the appendages, a chamber where the animal would have stored its venom, and — most importantly — the remains of its respiratory and circulatory systems.
This scorpion is about 2.5 centimeters long — about the same size as many scorpions in the world today. And, Babcock said, it shows a crucial evolutionary link between the way ancient ancestors of scorpions respired under water, and the way modern-day scorpions breathe on land. Internally, the respiratory-circulatory system has a structure just like that found in today’s scorpions.
“The inner workings of the respiratory-circulatory system in this animal are, shape-wise, identical to those of the arachnids and scorpions that breathe air exclusively,” Babcock said. “But it also is incredibly similar to what we recognize in marine arthropods like horseshoe crabs. So, it looks like this scorpion, this lineage, must have been pre-adapted to life on land, meaning they had the morphologic capability to make that transition, even before they first stepped onto land.”
Paleontologists have for years debated how animals moved from sea to land. Some fossils show walking traces in the sand that may be as old as 560 million years, but these traces may have been made in prehistoric surf — meaning it is difficult to know whether animals were living on land or darting out from their homes in the ancient ocean.
But with these prehistoric scorpions, Wendruff said, there was little doubt that they could survive on land because of the similarities to modern-day scorpions in the respiratory and circulatory systems.
Reference:
Andrew J. Wendruff, Loren E. Babcock, Christian S. Wirkner, Joanne Kluessendorf & Donald G. Mikulic. A Silurian ancestral scorpion with fossilised internal anatomy illustrating a pathway to arachnid terrestrialisation. Scientific Reports, 2020 DOI: 10.1038/s41598-019-56010-z
Note: The above post is reprinted from materials provided by Ohio State University. Original written by Laura Arenschield.
Satellite image of the Gibraltar Arc. Credit: NASA
A new study made by researchers at the Institute of Earth Sciences Jaume Almera of the Spanish National Research Council (ICTJA-CSIC) has been able to describe the effects of the lithospheric structure on the topography of the Strait of Gibraltar area. This new research shows the deep structure of the plate boundary between Africa and Eurasia across the Gibraltar Arc. It describes the distribution of density, temperature and composition of the lithosphere and sublithosphere (up to 400 km deep).
The study, published recently in Journal of Geophysical Research: Solid Earth, estimates that the topography of the Strait of Gibraltar in the orogenic domain of the Betics and the Rif subsides by 1500 meters and is linked to the subduction in the Gibraltar Arc region.
“We’ve been able to describe the lithospheric geometry and to identify sublithospheric anomalies of temperature and density and to link them with their topographic effects on the surface, in the area of the Gibraltar Strait and the Alborán Sea,” said Ivone Jiménez-Munt, a researcher at the ICTJA-CSIC and first author of the study.
“The thickening of the lithosphere beneath the Betics and Rif tectonic domain is linked with the subduction of the Iberian plate, visible in the seismic tomography. We estimate that the weight of this lithospheric slab sinking into the mantle may have pulled down the topography of the Strait of Gibraltar by about 1500 m,” said Jiménez- Munt.
“The latest part of this subsidence could be responsible for the reconnection of the Atlantic Ocean and the Mediterranean Sea, leading to the reflooding of the Mediterranean after the Messinian Salinity Crisis,” researchers stated in the article.
The new model proposed in this study constructs the lithospheric structure along a 945 km long geotransect, a profile that extends from the south of the South Iberian Massif to the Anti-Atlas, crossing the Betics-Rif orogen, the Strait of Gibraltar, and the Atlas Mountains. The study area is the result of the convergence between the African plate, moving towards the north, and the Iberian plate.
The work shows significant variations at the boundary between the lithosphere, the outermost Earth layer that includes the crust and part of the upper mantle, and the asthenosphere, a denser and more fluid layer of the mantle, over which the lithosphere moves. Under the Betics and Rif mountain ranges the boundary between lithosphere and asthenosphere reaches its maximum values, about 220 and 260 km deep, respectively.
The researchers developed this model using the new LitMod2D _2.0 modelling code which integrates petrological (chemical composition of the mantle), geophysical (gravimetry, geoid, heat flow, topography) and existing seismic data.
“While we were developing the model, we found difficulties in fitting all the observables. We detected anomalies in the geoid and gravimetric data,” said Ivone Jiménez- Munt. “The geoid is very sensitive to deep density anomalies,” she added. These mismatches could only be explained by the presence of the subducting slab of the Iberian plate under the Alboran Sea east of the studied profile.
“We think that this colder and heavier sinking plate may have some influence on the detected anomaly of the geoid,” said Jiménez-Munt. Researchers incorporated a body with the same geochemical composition as the Iberian plate and colder than the surrounding asthenosphere into the model. They were then able to fit the observables. “This sublithospheric anomaly incorporated into the model simulates the subducting plate. By estimating its density, we were able to simulate its effect on the surface,” explained Jiménez- Munt.
The studied area is complex. “This is the plate boundary between Africa and Eurasia, but in this area, the boundary is diffused and producing a large deformation area. In the past, this boundary had been jumping between the south of the Iberian Peninsula and the north, in the Pyrenees, and at present is distributed between the Betics and North Africa. Although it is a convergent boundary, there had been periods of extension, and the hypothesis that it is an arcuate subduction is becoming stronger; that is, a subduction characterized by “breaking off ” of the subducting slab from its upper part from east to west,” says Jiménez- Munt.
Montserrat Torné, Manel Fernández, Jaume Verges, Ajay Kumar, Alberto Carballo and Daniel García-Castellanos are the other ICTJA-CSIC researchers involved in this research.
Reference:
I. Jiménez‐Munt et al. Deep Seated Density Anomalies Across the Iberia‐Africa Plate Boundary and Its Topographic Response, Journal of Geophysical Research: Solid Earth (2019). DOI: 10.1029/2019JB018445
Charoite (K(Ca, Na)2Si4O10(OH, F)·H2O) is a rare mineral silicate, first described in 1978 and named for the River Chara. It was recorded only from Aldan Shield, Republic of Sakha, Siberia, Russia. It is located where a Murunskii Massif syenite has intruded into and altered calcareous deposits which create a metasomatite of potassium feldspar.
Charoite colors are indeed unmistakable, ranging from light lilac to lavender and from near-violet to medium-deep violet. Within a single specimen, most charoite gemstones show many violet to purple colors, and shape with very unique patterns, often swirling, streaking, or feather-like in nature. The spinning shapes are called a charoite signature characteristic and owed to its interlocking complex fibrous crystal structure.
Charoite was named after the Chary River of Yakutia, the location where it was first discovered, around 1940. Despite the fact that it was first made sometime during the 1940s, it is considered a relatively recent gemstone, as it was not launched until 1978 on a commercial level. To this day the only source of charoite gemstones has been the Murun complex in the Sakha Republic, Siberia.
Charoite forms from calcareous deposits transformed by heat, pressure and injection of special chemicals (alkali-rich intrusions of nephline syenite). This process is known as’ contact metamorphism’ and is thought to be a common phenomenon in geology. Given that the forming mechanism is quite simple, it has never been fully understood why charoite occurrences are uncommon and limited only to the small region from which they are mined.
Charoite mostly appears opaque in clarity but it may seem somewhat transparent in some cases Charoite’s mild to moderate chatoyancy, best seen in species with higher translucency, is one of the most desirable characteristics. The chatoyantness adds pearly luster to the silky. Light-colored inclusions, as well as fibrous and fine-grained parallel inclusions, are very common as they are responsible for the attractive chatoyancy phenomenon (the cat’s eye effect).
Topaz is a silicate aluminum and fluorine mineral with the Al2SiO4(F, OH)2 chemical formula. Topaz crystallizes in the orthorhombic system, and its crystals are mostly pyramidal and other faces terminated with prismatics. It is one of the hardest naturally occurring minerals (Mohs hardness of 8) and is the most difficult of any mineral silicate. This longevity paired with its normal flexibility and changing.
What Color Is Topaz?
Natural topaz is translucent and colourless, just like natural corundum. The wide range of topaz colors available are due either to natural trace impurities or crystal structural defects. Diversity in color is also caused by changes produced by the gemstone industry. Topaz is available in a variety of colors from yellow, orange, gray, purple, blue, black, violet and green.
Colorless topaz is fairly common and is rarely given a dazzling cut and sold as a diamond replacement. Indeed one of the world’s most famous topaz gemstones is a colorless topaz originally thought to be a diamond.
The most common colors of untreated topaz are pale yellow, brown and gray. Pastel shades of light-green, violet and pink are also found. The most popular topaz color is blue. Indeed, blue topaz is the perennial top selling jewelry stone in the USA.
The most valuable topaz colour known as imperial topaz, is an orange to pink colour. The exact color is not well known for imperial topaz, so a wide range of golden orange, peach and pink topaz are offered under this name. Several light-pink topaz gems are the result of treatment with heat.
What is the rarest color of topaz?
Imperial Topaz, also known as Precious Topaz is the rarest and most valuable of the Topaz family, coming in colors ranging from golden yellow to the extremely prized sherry pink color.
What causes color in topaz ?
Tpoaz which is aluminum flurosilicate is normally colorless in the absence of impurities. The main impurity contained in topaz is iron, but iron does not directly impart any color to topaz as chromium impurities do in rubies, which impart the red color. Within rubies the chromium atoms are directly excited by the absorption of visible light photons. As they return to their ground states, the chromium atoms that leap to an excited state emit light in the red region of the visible spectrum. In the case of topaz, the iron atoms create another unstable species in the crystal and this new species moves to an excited state by absorbing a visible photon of light that emits light from different regions of the spectrum, depending on their wavelength, as they return to the earth, giving rise to the variety of colors found in topaz, including the golden yellow or golden brown color
Naturally colored topaz like yellow, orange and brown topaz contain stable to light color centers. If a colorless topaz is irradiated by ultraviolet light, x-rays, gamma rays or high-energy electrons, we can get a color of yellow, orange or gray, but this color is typically unstable and will disappear in light after a few days. But blue topaz created by irradiation creates color centers that are stable like natural blue topaz color centers and therefore do not fade in light. Only heating will kill these color centers, when the topaz is colorless again.
Color varieties are often known simply by the name of the hue— blue topaz, green topaz, and so on — but there are a few special trade names, too. Imperial topaz is a medium to deep-red reddish orange. This is one of the most expensive shades of the stone. Sherry topaz-named after the sherry wine-is a brown to orange color or brownish. Stones are often called precious topaz in this color range to help differentiate them from the closely colored but less costly citrine and smoky quartz.
Representative Image: An example of a Pallasite meteorite (from the Esquel fall) on display in the Vale Inco Limited Gallery of Minerals at the Royal Ontario Museum. Credit: Captmondo/Wikimedia
Stars have life cycles. They’re born when bits of dust and gas floating through space find each other and collapse in on each other and heat up. They burn for millions to billions of years, and then they die. When they die, they pitch the particles that formed in their winds out into space, and those bits of stardust eventually form new stars, along with new planets and moons and meteorites. And in a meteorite that fell fifty years ago in Australia, scientists have now discovered stardust that formed 5 to 7 billion years ago — the oldest solid material ever found on Earth.
“This is one of the most exciting studies I’ve worked on,” says Philipp Heck, a curator at the Field Museum, associate professor at the University of Chicago, and lead author of a paper describing the findings in the Proceedings of the National Academy of Sciences. “These are the oldest solid materials ever found, and they tell us about how stars formed in our galaxy.”
The materials Heck and his colleagues examined are called presolar grains-minerals formed before the Sun was born. “They’re solid samples of stars, real stardust,” says Heck. These bits of stardust became trapped in meteorites where they remained unchanged for billions of years, making them time capsules of the time before the solar system..
But presolar grains are hard to come by. They’re rare, found only in about five percent of meteorites that have fallen to Earth, and they’re tiny-a hundred of the biggest ones would fit on the period at the end of this sentence. But the Field Museum has the largest portion of the Murchison meteorite, a treasure trove of presolar grains that fell in Australia in 1969 and that the people of Murchison, Victoria, made available to science. Presolar grains for this study were isolated from the Murchison meteorite for this study about 30 years ago at the University of Chicago.
“It starts with crushing fragments of the meteorite down into a powder ,” explains Jennika Greer, a graduate student at the Field Museum and the University of Chicago and co-author of the study. “Once all the pieces are segregated, it’s a kind of paste, and it has a pungent characteristic-it smells like rotten peanut butter.”
This “rotten-peanut-butter-meteorite paste” was then dissolved with acid, until only the presolar grains remained. “It’s like burning down the haystack to find the needle,” says Heck.
Once the presolar grains were isolated, the researchers figured out from what types of stars they came and how old they were. “We used exposure age data, which basically measures their exposure to cosmic rays, which are high-energy particles that fly through our galaxy and penetrate solid matter,” explains Heck. “Some of these cosmic rays interact with the matter and form new elements. And the longer they get exposed, the more those elements form.
“I compare this with putting out a bucket in a rainstorm. Assuming the rainfall is constant, the amount of water that accumulates in the bucket tells you how long it was exposed,” he adds. By measuring how many of these new cosmic-ray produced elements are present in a presolar grain, we can tell how long it was exposed to cosmic rays, which tells us how old it is.
The researchers learned that some of the presolar grains in their sample were the oldest ever discovered-based on how many cosmic rays they’d soaked up, most of the grains had to be 4.6 to 4.9 billion years old, and some grains were even older than 5.5 billion years. For context, our Sun is 4.6 billion years old, and Earth is 4.5 billion.
But the age of the presolar grains wasn’t the end of the discovery. Since presolar grains are formed when a star dies, they can tell us about the history of stars. And 7 billion years ago, there was apparently a bumper crop of new stars forming-a sort of astral baby boom.
“We have more young grains that we expected,” says Heck. “Our hypothesis is that the majority of those grains, which are 4.9 to 4.6 billion years old, formed in an episode of enhanced star formation. There was a time before the start of the Solar System when more stars formed than normal.”
This finding is ammo in a debate between scientists about whether or not new stars form at a steady rate, or if there are highs and lows in the number of new stars over time. “Some people think that the star formation rate of the galaxy is constant,” says Heck. “But thanks to these grains, we now have direct evidence for a period of enhanced star formation in our galaxy seven billion years ago with samples from meteorites. This is one of the key findings of our study.”
Heck notes that this isn’t the only unexpected thing his team found. As almost a side note to the main research questions, in examining the way that the minerals in the grains interacted with cosmic rays, the researchers also learned that presolar grains often float through space stuck together in large clusters, “like granola,” says Heck. “No one thought this was possible at that scale.”
Heck and his colleagues look forward to all of these discoveries furthering our knowledge of our galaxy. “With this study, we have directly determined the lifetimes of stardust. We hope this will be picked up and studied so that people can use this as input for models of the whole galactic life cycle,” he says.
Heck notes that there are lifetimes’ worth of questions left to answer about presolar grains and the early Solar System. “I wish we had more people working on it to learn more about our home galaxy, the Milky Way,” he says.
“Once learning about this, how do you want to study anything else?” says Greer. “It’s awesome, it’s the most interesting thing in the world.”
“I always wanted to do astronomy with geological samples I can hold in my hand,” says Heck. “It’s so exciting to look at the history of our galaxy. Stardust is the oldest material to reach Earth, and from it, we can learn about our parent stars, the origin of the carbon in our bodies, the origin of the oxygen we breathe. With stardust, we can trace that material back to the time before the Sun.”
“It’s the next best thing to being able to take a sample directly from a star,” says Greer.
This study was contributed to by researchers from the Field Museum, University of Chicago, Lawrence Livermore National Laboratory, Washington University, Harvard Medical School, ETH Zurich, and the Australian National University. Funding was provided by NASA, the TAWANI Foundation, the National Science Foundation, the Department of Energy, the Swiss National Science Foundation, the Brazilian National Council for Scientific and Technological Development and the Field Museum’s Science and Scholarship Funding Committee.
Reference:
Philipp R. Heck, Jennika Greer, Levke Kööp, Reto Trappitsch, Frank Gyngard, Henner Busemann, Colin Maden, Janaína N. Ávila, Andrew M. Davis, Rainer Wieler. Lifetimes of interstellar dust from cosmic ray exposure ages of presolar silicon carbide. Proceedings of the National Academy of Sciences, Jan. 13, 2020; DOI: 10.1073/pnas.1904573117
A fossilized cloudinomorph from the Montgomery Mountains near Pahrump, Nevada. This is representative of the fossil that was analyzed in the study.
A 550-million-year-old fossilized digestive tract found in the Nevada desert could be a key find in understanding the early history of animals on Earth.
Over a half-billion years ago, life on Earth was composed of simple ocean organisms unlike anything living in today’s oceans. Then, beginning about 540 million years ago, animal structures changed dramatically.
During this time, ancestors of many animal groups we know today appeared, such as primitive crustaceans and worms, yet for years scientists did not know how these two seemingly unrelated communities of animals were connected, until now. An analysis of tubular fossils by scientists led by Jim Schiffbauer at the University of Missouri provides evidence of a 550 million-year-old digestive tract — one of the oldest known examples of fossilized internal anatomical structures — and reveals what scientists believe is a possible answer to the question of how these animals are connected.
The study was published in Nature Communications, a journal of Nature.
“Not only are these structures the oldest guts yet discovered, but they also help to resolve the long-debated evolutionary positioning of this important fossil group,” said Schiffbauer, an associate professor of geological sciences in the MU College of Arts and Science and director of the X-ray Microanalysis Core facility. “These fossils fit within a very recognizable group of organisms — the cloudinids — that scientists use to identify the last 10 to 15 million years of the Ediacaran Period, or the period of time just before the Cambrian Explosion. We can now say that their anatomical structure appears much more worm-like than coral-like.”
The Cambrian Explosion is widely considered by scientists to be the point in history of life on Earth when the ancestors of many animal groups we know today emerged.
In the study, the scientists used MU’s X-ray Microanalysis Core facility to take a unique analytical approach for geological science — micro-CT imaging — that created a digital 3D image of the fossil. This technique allowed the scientists to view what was inside the fossil structure.
“With CT imaging, we can quickly assess key internal features and then analyze the entire fossil without potentially damaging it,” said co-author Tara Selly, a research assistant professor in the Department of Geological Sciences and assistant director of the X-ray Microanalysis Core facility.
The study, “Discovery of bilaterian-type through-guts in cloudinomorphs from the terminal Ediacaran Period,” was published in Nature Communications. Other authors include Sarah Jacquet from MU; Rachel Merz from Swarthmore College; Michael Strange from the University of Nevada, Las Vegas; Yaoping Cai from Northwest University in Xi’an, China; and Lyle Nelson and Emmy Smith from Johns Hopkins University.
Funding was provided by grants from the NSF Sedimentary Geology and Paleobiology Program (CAREER 1652351) and Instrumentation and Facilities Program (1636643). The content is solely the responsibility of the authors and does not necessarily represent the official views of the funding agencies.
Reference:
James D. Schiffbauer, Tara Selly, Sarah M. Jacquet, Rachel A. Merz, Lyle L. Nelson, Michael A. Strange, Yaoping Cai, Emily F. Smith. Discovery of bilaterian-type through-guts in cloudinomorphs from the terminal Ediacaran Period. Nature Communications, 2020; 11 (1) DOI: 10.1038/s41467-019-13882-z
The fire agate is a semi-precious natural gemstone which has only been discovered in certain areas of central, northern Mexico (New Mexico, Arizona and California) and in the southwestern United States (New Mexicans). These areas were subjected to massive volcanic activity during the Tertiary Period, around 24-36 million years ago.
Fire agate gemstone deposits were formed in these particular regions approximately 24-36 million years ago when the areas were subjected to massive volcanic activity during the Tertiary Period. Geological conditions within these different regions vary which produce differences in the type and style of fire agate found in each region. The agate formation, size, color and fire layer thickness all vary within these different geographic locations.
Ithave beautiful iridescent rainbow colors, similar to opal, with a Mohs scale hardness measurement of between 5 and 7 which reduces scratching when polished gemstones are put in jewellery. The vibrant iridescent rainbow colors found in fire agates, created by the Schiller effect as found in mother-of-pearl, are caused by the alternating layers of silica and iron oxide, which diffract and allow light to pass through and form a color interference within the stone’s microstructure layering causing the fire effect for which it is named.
Mohs scale hardness: 6 – 7 Color: Blue to yellow to red Formula mass: 60 g / mol Luster: Waxy, vitreous, dull, greasy, silky Crystal system: Trigonal, monoclinic
How fire agate is formed?
It is a type of chalcedony (SiO2) which contains multiple, extremely thin layers of the iron oxide minerals of Goethite (FeO(OH)) and Limonite (FeO(OH)·nH20) imbedded within, and commonly completely enclosed by, semi-transparent to translucent layers of cryptocrystalline chalcedony. When cut and polished down to the layers containing the iron oxides, the stone displays a metallic, shimmering iridescence known as the Schiller Effect, where light is reflected and refracted off the various layers containing the Goethite and Limonite iron oxides to give the exquisite play of colors—or “fire”—for which the gemstone is named. Colors displayed by the “fire” vary greatly, the most common being shades of orangish brown, but also all shades and tones of yellow, orange, red, and green, and more rarely, purples and blues.
Is fire agate rare?
It is by far more rare than diamonds, emeralds or rubies. Gem quality which has been found only in the past sixty years in parts of California, Arizona and Mexico, making it the rarest, most colorful gem in the world.
Where is fire agate found?
The fire agate is a semi-precious natural gemstone which has only been discovered in certain areas of central, northern Mexico (New Mexico, Arizona and California)
The following is a list of some different minerals Sites . Some of these sites are open for public rockhounding and other are private mining claims or are situated on a restricted public country where any form of mineral collection is forbidden.
Black Hills, Arizona – BLM Public Rockhounding Site
Oatman, Arizona – Cuesta Fire Agate Mine
Opal Hill, California – Opal Hill Fire Agate Mine
Round Mountain, Arizona – BLM Public Rockhounding Site
Saddle Mountain, Arizona – Outdoor Recreation and Fire Agate Rockhounding Site
Deer Creek, Arizona, Fire Agate Location
Slaughter Mountain, Arizona – San Carlos Apache Fire Agate Mine
100 million-year-old amber piece with lizard leg and mycomycete (arrow). Credit: Alexander Schmidt, University of Göttingen and Scientific Reports
Most people associate the idea of creatures trapped in amber with insects or spiders, which are preserved lifelike in fossil tree resin. An international research team of palaeontologists and biologists from the Universities of Göttingen and Helsinki, and the American Museum of Natural History in New York has now discovered the oldest slime mould identified to date. The fossil is about 100 million years old and is exquisitely preserved in amber from Myanmar. The results have been published in the journal Scientific Reports.
Slime moulds, also called myxomycetes, belong to a group known as “Amoebozoa.” These are microscopic organisms that live most of the time as single mobile cells hidden in the soil or in rotting wood, where they eat bacteria. However, they can join together to form complex, beautiful and delicate fruiting bodies, which serve to make and spread spores.
Since fossil slime moulds are extremely rare, studying their evolutionary history has been very difficult. So far, there have only been two confirmed reports of fossils of fruiting bodies and these are just 35 to 40 million years old. The discovery of fossil myxomycetes is very unlikely because their fruiting bodies are extremely short-lived. The researchers are therefore astounded by the chain of events that must have led to the preservation of this newly identified fossil.
“The fragile fruiting bodies were most likely torn from the tree bark by a lizard, which was also caught in the sticky tree resin, and finally embedded in it together with the reptile,” says Professor Jouko Rikkinen from the University of Helsinki. The lizard detached the fruiting bodies at a relatively early stage when the spores had not yet been released, which now reveals valuable information about the evolutionary history of these fascinating organisms.
The researchers were surprised by the discovery that the slime mould can easily be assigned to a genus still living today. “The fossil provides unique insights into the longevity of the ecological adaptations of myxomycetes,” explains palaeontologist Professor Alexander Schmidt from the University of Göttingen, lead author of the study.
“We interpret this as evidence of strong environmental selection. It seems that slime moulds that spread very small spores using the wind had an advantage,” says Rikkinen. The ability of slime moulds to develop long-lasting resting stages in their life cycle, which can last for years, probably also contributes to the remarkable similarity of the fossil to its closest present-day relatives.
Reference:
Jouko Rikkinen et al, Morphological stasis in the first myxomycete from the Mesozoic, and the likely role of cryptobiosis, Scientific Reports (2019). DOI: 10.1038/s41598-019-55622-9
The skull of the juvenile T. rex, “Jane”, was slender with knife-like teeth, having not yet grown big enough to crush bone. Credit to Scott A. Williams
Without a doubt, Tyrannosaurus rex is the most famous dinosaur in the world. The 40-foot-long predator with bone crushing teeth inside a five-foot long head are the stuff of legend. Now, a look within the bones of two mid-sized, immature T. rex allow scientists to learn about the tyrant king’s terrible teens as well.
In the early 2000s, the fossil skeletons of two comparatively small T. rex were collected from Carter County, Montana, by Burpee Museum of Natural History in Rockford, Illinois. Nicknamed “Jane” and “Petey,” the tyrannosaurs would have been slightly taller than a draft horse and twice as long.
The team led by Holly Woodward, Ph.D., from Oklahoma State University Center for Health Sciences studied Jane and Petey to better understand T. rex life history.
The study “Growing up Tyrannosaurus rex: histology refutes pygmy ‘Nanotyrannus’ and supports ontogenetic niche partitioning in juvenile Tyrannosaurus” appears in the peer-reviewed journal Science Advances.
Co-authors include Jack Horner, presidential fellow at Chapman University; Nathan Myhrvold, founder and CEO of Intellectual Ventures; Katie Tremaine, graduate student at Montana State University; Scott Williams, paleontology lab and field specialist at Museum of the Rockies; and Lindsay Zanno, division head of paleontology at the North Carolina Museum of Natural Sciences. Supplemental histological work was conducted at the Diane Gabriel Histology Labs at Museum of the Rockies/Montana State University.
“Historically, many museums would collect the biggest, most impressive fossils of a dinosaur species for display and ignore the others,” said Woodward. “The problem is that those smaller fossils may be from younger animals. So, for a long while we’ve had large gaps in our understanding of how dinosaurs grew up, and T. rex is no exception.”
The smaller size of Jane and Petey is what make them so incredibly important. Not only can scientists now study how the bones and proportions changed as T. rex matured, but they can also utilize paleohistology — the study of fossil bone microstructure — to learn about juvenile growth rates and ages. Woodward and her team removed thin slices from the leg bones of Jane and Petey and examined them at high magnification.
“To me, it’s always amazing to find that if you have something like a huge fossilized dinosaur bone, it’s fossilized on the microscopic level as well,” Woodward said. “And by comparing these fossilized microstructures to similar features found in modern bone, we know they provide clues to metabolism, growth rate, and age.”
The team determined that the small T. rex were growing as fast as modern-day warm-blooded animals such as mammals and birds. Woodward and her colleagues also found that by counting the annual rings within the bone, much like counting tree rings, Jane and Petey were teenaged T.rex when they died; 13 and 15 years old, respectively.
There had been speculation that the two small skeletons weren’t T. rex at all, but a smaller pygmy relative Nanotyrannus. Study of the bones using histology led the researchers to the conclusion that the skeletons were juvenile T. rex and not a new pygmy species.
Instead, Woodward points out, because it took T. rex up to twenty years to reach adult size, the tyrant king probably underwent drastic changes as it matured. Juveniles such as Jane and Petey were fast, fleet footed, and had knife-like teeth for cutting, whereas adults were lumbering bone crushers. Not only that, but Woodward’s team discovered that growing T. rex could do a neat trick: if its food source was scarce during a particular year, it just didn’t grow as much. And if food was plentiful, it grew a lot.
“The spacing between annual growth rings record how much an individual grows from one year to the next. The spacing between the rings within Jane, Petey, and even older individuals is inconsistent — some years the spacing is close together, and other years it’s spread apart,” said Woodward.
The research by Woodward and her team writes a new chapter in the early years of the world’s most famous dinosaur, providing evidence that it assumed the crown of tyrant king long before it reached adult size.
Reference:
Holly N. Woodward, Katie Tremaine, Scott A. Williams, Lindsay E. Zanno, John R. Horner, Nathan Myhrvold. Growing up Tyrannosaurus rex: Osteohistology refutes the pygmy “Nanotyrannus” and supports ontogenetic niche partitioning in juvenile Tyrannosaurus. Science Advances, 2020; 6 (1): eaax6250 DOI: 10.1126/sciadv.aax6250
