An artist’s impression of what an elaphrosaur may have looked like. Credit: Ruairidh Duncan
A chance discovery by a volunteer dinosaur digger has unearthed an unusual toothless dinosaur, known as an elaphrosaur, that roamed Australia 110 million years ago.
In early 2015, Dinosaur Dreaming volunteer Jessica Parker found a strange and delicate bone during the annual dig at the Cretaceous-aged fossil site known as Eric the Red West, near Cape Otway in Victoria.
The five centimetre long bone was identified at the Melbourne Museum as a vertebra. It was thought to be from a flying reptile called a pterosaur, albeit one quite different from the Ferrodraco lentoni, discovered in Queensland.
When Swinburne palaeontologists Dr. Stephen Poropat and Ph.D. candidate Adele Pentland attempted to work out what type of pterosaur it was, they hit a snag.
“Pterosaur neck vertebrae are very distinctive,” says Ms Pentland. “In all known pterosaurs, the body of the vertebra has a socket at the head end, and a ball or condyle at the body end. This vertebra had sockets at both ends, so it could not have been from a pterosaur.”
After extensive research Dr. Poropat and Ms Pentland reached a startling conclusion.
“We soon realised that the neck bone we were studying was from a theropod: a meat-eating dinosaur, related to Tyrannosaurus rex, Velociraptor, and modern birds,” says Dr. Poropat. “The only catch—this ‘meat-eating dinosaur’ probably didn’t eat meat!”
The new Victorian fossil is an excellent match for vertebrae from a strange group of theropods called elaphrosaurs or ‘light-footed lizards.”
And it’s a dinosaur out of time. Most of its known relatives—like Elaphrosaurus from Tanzania, and Limusaurus from China—lived near the end of the Jurassic Period, around 160–145 million years ago.
By contrast, the new Victorian elaphrosaur dates to almost 40 million years later, from the Early Cretaceous Period and is one of only two Cretaceous elaphrosaurs ever found. At around two metres long, it was also rather small for an elaphrosaur.
“Elaphrosaurs had long necks, stumpy arms with small hands, and relatively lightly built bodies,” Dr. Poropat says.
“As dinosaurs go, they were rather bizarre. The few known skulls of elaphrosaurs show that the youngsters had teeth, but that the adults lost their teeth and replaced them with a horny beak. We don’t know if this is true for the Victorian elaphrosaur yet—but we might find out if we ever discover a skull.”
The dinosaur graveyard at the Eric the Red West site awaits further exploration. Proposed digs this year have been postponed twice because of the bushfire season and the COVID-19 pandemic.
Palaeontologists hope to be able to return safely to Cape Otway to unearth more fossils soon.
The paper describing the new Victorian elaphrosaur is published in Gondwana Research.
Reference:
Stephen F. Poropat et al. First elaphrosaurine theropod dinosaur (Ceratosauria: Noasauridae) from Australia—A cervical vertebra from the Early Cretaceous of Victoria, Gondwana Research (2020). DOI: 10.1016/j.gr.2020.03.009
Robert Reisz examined fossils from the embryos of Lufengosaurus, an early sauropodomorph species that predates more recognizable sauropods. Credit: David Mazierski
In the age of giant reptiles, sauropods were the biggest of all. Long-tailed, long-necked species like Diplodocus and Apatosaurus were the largest dinosaurs. From tip to tail, some sauropods were up to 40 metres long.
These giant herbivores ranged across the globe and thrived throughout the age of dinosaurs, nearly 150 million years.
“Sauropods are the one group that was successful from the beginning of the age of dinosaurs until the very end,” says Robert Reisz, a paleontologist and professor of biology at U of T Mississauga.
Despite their enormous size, sauropods had relatively small heads and mouths. They fed by ripping plant material from trees and bushes, and would have needed to eat almost constantly.
But sauropods did not have the extensive chewing capabilities of the large headed duckbill dinosaurs which are well known for their massive dental batteries. Instead, sauropods like titanosaurs and diplodocids evolved a different strategy for dealing with harsh, hard to process plant materials, using simplified, small, pencil shaped, rapidly growing new teeth that were worn down and replaced very quickly.
In research published in Nature Communications, Reisz examined fossils from the embryos of Lufengosaurus, an early sauropodomorph species that predates more recognizable sauropods like titanosaurs and diplodocids, which came later. Found in China’s Yunnan province, the fossils provided a record of Lufengosaurus at different stages of development, and showed distinct phases of tooth development.
In one of these phases, Lufengosaurus embryos had pencil-like teeth that resemble those found in some adult diplodocid and titanosaur sauropods. The finding suggests that the similar tooth structures that emerged in later sauropod species evolved through the retention of features present in the early stages of development of their distant predecessors.
“This evolutionary phenomenon, called paedomorphosis, is more frequently associated with small animals, but in this case, we seem to see it in big animals too,” Reisz says.
While Reisz’ sauropod research relied on rare embryo fossils, his examination of an even more ancient reptile relied upon a relative abundance of specimens.
Captorhinus aguti is a reptile that lived in the Permian Period (289 million years ago), well before the age of dinosaurs. In research published in Current Biology, Reisz studied 95 Captorhinus fossils to identify whether these four-legged reptiles displayed traits associated with brain lateralization—the asymmetrical brain function that can be observed in humans, birds, mammals and reptiles.
“The best-known lateralization is human right-handedness, and we know that right-handed people also prefer to eat on the right side,” says Reisz.
This project came about because Diane Scott, research assistant to Reisz, noticed that in one nearly perfect skull of this reptile one side of the dentition was more worn than the other side. Reisz’s team used the large number of lower jaws of this reptile, all from a single site, in order to understand it’s population-level chewing preferences.
“When you only have one specimen, it doesn’t really tell you a story,” says Reisz. “Maybe there was something wrong with that individual—a muscle anomaly that caused it to happen. But here, we have a population-level examination, all from a single pocket.”
The right jaws of Captorhinus showed more wear than the left, suggesting that even 289 million years ago, reptiles were displaying traits associated with brain asymmetry.
“It’s circumstantial evidence, but we think this indicates a subdivision of the brain, and suggests that functional brain asymmetry is a deeply nested phenomenon in vertebrate evolution, and this is the first time that we’ve seen it in fossils.”
Reference:
Robert R. Reisz et al. Early Jurassic dinosaur fetal dental development and its significance for the evolution of sauropod dentition, Nature Communications (2020). DOI: 10.1038/s41467-020-16045-7
Robert R. Reisz et al. Lateralized Feeding Behavior in a Paleozoic Reptile, Current Biology (2020). DOI: 10.1016/j.cub.2020.04.026
In this artist’s depiction of wildlife from Alberta, Canada, 77 million years ago, the tyrannosaur Daspletosaurus hunts a young horned Spinops, while an adult Spinops tries to interfere and a Coronosaurus watches from a distance. Credit: Julius Csotonyi.
Long legs may make good runners, but they’re great for walking, too. Scientists have generally assumed that long-limbed dinosaurs evolved their leggy proportions for speed to catch prey and avoid predators.
But a new study by the University of Maryland’s Thomas Holtz and his colleagues suggests that long legs evolved among the biggest dinosaurs to help them conserve energy and go the distance as they ambled along searching for prey. The study was published in the journal PLOS ONE on May 13, 2020.
“The assumption tends to be that animals with adaptations for running, such as long legs, are adapted for a higher maximum speed, but this paper shows that there’s more to running than top speed,” said Thomas Holtz, principal lecturer in the UMD Department of Geology. “When you’re a bigger animal, those adaptations may also be for endurance and efficiency. It may be about being a marathoner rather than a sprinter.”
Holtz and his colleagues analyzed a variety of metrics like limb proportions, size ratio, body mass and gaits to estimate the top speeds of more than 70 species from a group of dinosaurs called theropods. Theropods ranged in size from less than a half-pound to more than nine tons. They included Tyrannosaurus rex and the many other two-legged predators that dominated the age of dinosaurs for 180 million years. Bipedalism and running speed have often been cited as major contributors to their success.
The study revealed a more nuanced story. According to the new analysis, longer legs were associated with higher top speeds in small and medium-sized dinosaurs, but that didn’t hold true for dinosaurs weighing over 2,200 pounds. Scientists have known that larger body size can limit speed, and the study showed that large dinosaur species with longer legs were no faster than their stubby-limbed brethren. But they moved more efficiently.
By calculating how much energy each dinosaur expended while moving at walking speeds, the researchers found that among the largest dinosaurs, those with longer legs needed less energy to cruise around.
“That’s actually a very beneficial savings, because predators tend to spend a great deal of their time foraging, searching for prey,” Holtz said. “If you are burning less fuel during the foraging part of the day, that’s an energy savings that dinosaurs with shorter leg forms didn’t get.”
These results highlight the often-overlooked impact of body proportions on running ability and the limiting effect of large body size on running speed. Clearly, there are different kinds of runners. This work should broaden the discussion about what it means to be adapted for running.
The research paper, “The fast and the frugal: Divergent locomotory strategies drive limb lengthening in theropod dinosaurs,” T. Alexander Dececchi, Aleksandra M. Mloszewska, Thomas R. Holtz Jr., Michael B. Habib, Hans C.E. Larsson, was published in the journal PLOS ONE on May 13, 2020.
Reference:
Dececchi TA, Mloszewska AM, Holtz TR Jr, Habib MB, Larsson HCE (2020) The fast and the frugal: Divergent locomotory strategies drive limb lengthening in theropod dinosaurs. PLoS ONE 15(5): e0223698. doi.org/10.1371/journal.pone.0223698
The only remnants of Pūhāhonu that are above sea level (Gardner Pinnacles). Credit: NOAA
In a recently published study, researchers from the University of Hawai’i at Mānoa School of Ocean and Earth Science and Technology revealed the largest and hottest shield volcano on Earth. A team of volcanologists and ocean explorers used several lines of evidence to determine Pūhāhonu, a volcano within the Papahānaumokuākea Marine National Monument now holds this distinction.
Geoscientists and the public have long thought Mauna Loa, a culturally-significant and active shield volcano on the Big Island of Hawai’i, was the largest volcano in the world. However, after surveying the ocean floor along the mostly submarine Hawaiian leeward volcano chain, chemically analyzing rocks in the UH Mānoa rock collection, and modeling the results of these studies, the research team came to a new conclusion. Pūhāhonu, meaning ‘turtle rising for breath’ in Hawaiian, is nearly twice as big as Mauna Loa.
“It has been proposed that hotspots that produce volcano chains like Hawai’i undergo progressive cooling over 1-2 million years and then die,” said Michael Garcia, lead author of the study and retired professor of Earth Sciences at SOEST. “However, we have learned from this study that hotspots can undergo pulses of melt production. A small pulse created the Midway cluster of now extinct volcanoes and another, much bigger one created Pūhāhonu. This will rewrite the textbooks on how mantle plumes work.”
In 1974, Pūhāhonu (then called Gardner Pinnacles) was suspected as the largest Hawaiian volcano based on very limited survey data. Subsequent studies of the Hawaiian Islands concluded that Mauna Loa was the largest volcano but they included the base of the volcano that is below sea level that was not considered in the 1974 study. The new comprehensive surveying and modeling, using methods similar to those used for Mauna Loa show that Pūhāhonu is the largest.
This study highlights Hawaiian volcanoes, not only now but for millions of years, have been erupting some of the hottest magma on Earth. This work also draws attention to an infrequently visited part of the state of Hawai’i that has ecological, historical and cultural importance.
“We are sharing with the science community and the public that we should be calling this volcano by the name the Hawaiians have given to it, rather than the western name for the two rocky small islands that are the only above sea level remnants of this once majestic volcano,” said Garcia.
Reference:
Michael O. Garcia et al, Pūhāhonu: Earth’s biggest and hottest shield volcano, Earth and Planetary Science Letters (2020). DOI: 10.1016/j.epsl.2020.116296
Three earthquakes in the Monterey Bay Area, occurring in 1838, 1890 and 1906, happened without a doubt on the San Andreas Fault, according to a new paper by a Portland State University researcher.
The paper, “New Insights into Paleoseismic Age Models on the Northern San Andreas Fault: Charcoal In-built ages and Updated Earthquake Correlations,” was recently published in the Bulletin of the Seismological Society of America.
Assistant Professor of Geology at PSU Ashley Streig said the new research confirms what her team first discovered in 2014: three earthquakes occurred within a 68-year period in the Bay Area on the San Andreas Fault.
“This is the first time there’s been geologic evidence of a surface rupture from the historic 1838 and 1890 earthquakes that we knew about from newspapers and other historical documents,” Streig said. “It basically meant that the 1800s were a century of doom.”
Building on the 2014 study, Streig said they were able to excavate a redwood slab from a tree felled by early Europeans, from one meter below the surface in the Bay Area. The tree was toppled before the three earthquakes in question occurred. That slab was used to determine the precise date logging first occurred in the area, and pinpointed the historic dates of the earthquakes. Further, they were able use the slab to develop a new model for determining recurrence intervals and more exact dating.
Streig used the dating technique wiggle matching for several measured carbon 14 samples from the tree slab and compared them with fluctuations in atmospheric carbon 14 concentrations over time to fingerprint the exact death of the tree and confirm the timing of the earthquakes. Because the researchers had an exact age from the slab, they were able to test how well the most commonly used material, charcoal, works in earthquake age models.
Charcoal is commonly used for dating and to constrain the ages of prehistoric earthquakes and develop an earthquake recurrence interval, but Streig said the charcoal can be hundreds of years older than the stratigraphic layer containing it, yielding an offset between what has been dated and the actual age of the earthquake. The new technique accounts for inbuilt charcoal ages — which account for the difference in time between the wood’s formation and the fire that generated said charcoal — and can better estimate the age of the event being studied.
“We were able to evaluate the inbuilt age of the charcoal incorporated in the deposits and find that charcoal ages are approximately 322 years older than the actual age of the deposit — so previous earthquake age models in this area using detrital charcoal would be offset roughly by this amount,” she said.
New earthquake age modeling using a method to correct for this charcoal inbuilt age, and age results from the tree stump are what give Streig absolute certainly that the 1838 and 1890 earthquakes in question occurred on the San Andreas Fault and during those years.
“We put the nail in the coffin,” she added.
Reference:
Ashley R. Streig; Ray J. Weldon, II; Glenn Biasi; Timothy E. Dawson; Daniel G. Gavin; Tom P. Guilderson. New Insights into Paleoseismic Age Models on the Northern San Andreas Fault: Charcoal Inbuilt Ages and Updated Earthquake Correlations. Bulletin of the Seismological Society of America, 2020 DOI: 10.1785/0120190307
A new study of Earth’s inner core used seismic data from repeating earthquakes, called doublets, to find that refracted waves, blue, rather than reflected waves, purple, change over time — providing the best evidence yet that Earth’s inner core is rotating. Credit: Michael Vincent
Exhaustive seismic data from repeating earthquakes and new data-processing methods have yielded the best evidence yet that the Earth’s inner core is rotating — revealing a better understanding of the hotly debated processes that control the planet’s magnetic field.
The new study by researchers from the University of Illinois at Urbana-Champaign is published in the journal Earth and Planetary Science Letters.
Geologists do not fully understand how the Earth’s magnetic field generator works, but suspect it is closely linked to dynamic processes near the inner core-outer core boundary area, the researchers said. Shifts in the location of the magnetic poles, changes in field strength and anomalous seismic data have prompted researchers to take a closer look.
“In 1996, a small but systematic change of seismic waves passing through the inner core was first detected by our group, which we interpreted as evidence for differential rotation of the inner core relative to the Earth’s surface,” said geology professor and study co-author Xiaodong Song, who is now at Peking University. “However, some studies believe that what we interpret as movement is instead the result of seismic waves reflecting off an alternately enlarging and shrinking inner core boundary, like growing mountains and cutting canyons.”
The researchers present seismic data from a range of geographic locations and repeating earthquakes, called doublets, that occur in the same spot over time. “Having data from the same location but different times allows us to differentiate between seismic signals that change due to localized variation in relief from those that change due to movement and rotation,” said Yi Yang, a graduate student and lead author of the study.
The team found that some of the earthquake-generated seismic waves penetrate through the iron body below the inner core boundary and change over time, which would not happen if the inner core were stationary, the researchers said. “Importantly, we are seeing that these refracted waves change before the reflected waves bounce off the inner core boundary, implying that the changes are coming from inside the inner core,” Song said.
The basis of the debate lies in the fact the prior studies looked at a relatively small pool of somewhat ambiguous data generated from a method that is highly dependent on accurate clock time, the researchers said.
“What makes our analysis different is our precise method for determining exactly when the changes in seismic signals occur and arrive at the various seismic stations across the globe,” Yang said. “We use a seismic wave that did not reach inner core as a reference wave in our calculations, which eliminates a lot of the ambiguity.”
This precise arrival time analysis, an extensive collection of the best quality data and careful statistical analysis performed by Yang, are what give this study its power, Song said. “This work confirms that the temporal changes come mostly, if not all, from the body of the inner core, and the idea that inner core surface changes are the sole source of the signal changes can now be ruled out,” he said.
Reference:
Yi Yang, Xiaodong Song. Origin of temporal changes of inner-core seismic waves. Earth and Planetary Science Letters, 2020; 541: 116267 DOI: 10.1016/j.epsl.2020.116267
Scientists from The University of Western Australian and University of Cambridge have made a chance discovery in UK museum collections, finding hollow ball-like structures in 80-million-year-old fossils from species believed to be related to starfish and sea urchins.
The scientists found the unusual structures known as buckyballs made up of a series of hexagons and pentagons in two species—the Uintacrinus socialis and Marsupites testudinarius. They believe the structures might have acted as a buoyancy chamber to allow the crinoid organisms to float in seawater, but also protect them.
UWA Adjunct Research Fellow Aaron Hunter from UWA’s School of Earth Sciences said crinoids were in a very dangerous place millions of years ago when the oceans were shallower and they shared them with predators such as crabs and fish.
“Survival was critical and the ball-like structures, able to withstand very heavy loads, formed around them to protect them from the harms of the ocean and aid buoyancy,” Dr. Hunter said.
“These animals could then spread around the world and have been found in chalk rocks from Texas, US to Kalbarri in Western Australia. They could form a snow shoe to sit on the bottom of the shallow oceans or float and relocate to safer places.”
Dr. Hunter said in comparing the two species, Marsupites testudinarius had fewer but relatively large plates, creating a stable structure.
“Uintacrinus socialis on the other hand has far more complex plates that form a dome,” he said.
“The structures are also found in the carbon molecule Buckminsterfullerene but this is the first time we have found such a structure in fossils and it still remains a mystery why these successful structures did not evolve again.”
“Later, architect Buckminster Fuller would rediscover and popularise these structures and apply them to creating iconic buildings such as the Eden project in Cornwall in UK. However most would recognise the structure in the humble soccer ball we know and love.”
This two-billion-year-old shungite records evidence for balmy, oxygen-rich conditions on the early Earth. Credit: K. Paiste.
Earth may have been far more oxygen-rich early in its history than previously thought, setting the stage for the evolution of complex life, according to new research by scientists at the University of Alberta and the University of Tartu in Estonia. The study provides evidence for elevated oxygen levels 2 billion years ago and flies in the face of previously accepted models.
The international team of researchers, led by UAlberta scientists, studied a Russian drill core containing shungite — a unique carbon-rich sedimentary rock deposited 2 billion years ago. The material provides several clues about oxygen concentrations on Earth’s surface at that time, including strikingly high levels of molybdenum, uranium, and rhenium, as well as elevated uranium isotope ratios.
“These trace metals are only thought to be common in Earth’s oceans and sediments when oxygen is abundant,” explained Kaarel Mänd, a PhD candidate in the University of Alberta’s Department of Earth and Atmospheric Sciences and lead author of the study. “These trace metal concentrations are unrivaled in early Earth’s history, suggesting elevated levels of oxygen at the time when the shungite was deposited.”
What’s puzzling, Mänd explained, is that many widely accepted models of Earth’s carbon and oxygen cycles predict that shungite should have been deposited at a time of rapid decrease in oxygen levels.
“What we found contradicts the prevailing view,” says Mänd, who is completing his PhD under the supervision of Professor Kurt Konhauser. “This will force the Earth science community to rethink what drove the carbon and oxygen cycles on the early Earth.”
The new findings also provide insight into the evolution of complex life. Earth’s “middle age” represents the backdrop for the appearance of eukaryotes. Eukaryotes are the precursors to all complex life, and require high oxygen levels in their environment to thrive. This study strengthens the idea that suitable conditions for the evolution of complex life on early Earth began much earlier than previously thought.
Future research will examine the delay between the initial rise of oxygen and the appearance and spread of eukaryotes, remaining an area of active research, one that University of Alberta and University of Tartu researchers are well positioned to help answer.
Reference:
Kaarel Mänd, Stefan V. Lalonde, Leslie J. Robbins, Marie Thoby, Kärt Paiste, Timmu Kreitsmann, Päärn Paiste, Christopher T. Reinhard, Alexandr E. Romashkin, Noah J. Planavsky, Kalle Kirsimäe, Aivo Lepland, Kurt O. Konhauser. Palaeoproterozoic oxygenated oceans following the Lomagundi–Jatuli Event. Nature Geoscience, 2020; 13 (4): 302 DOI: 10.1038/s41561-020-0558-5
Francis Macdonald walks along a road near Manitou Springs, Colorado, where an exposed outcrop shows a feature known as the “Great Unconformity.” Photo Credit: Rebecca Flowers
The geologic record is exactly that: a record. The strata of rock tell scientists about past environments, much like pages in an encyclopedia. Except this reference book has more pages missing than it has remaining. So geologists are tasked not only with understanding what is there, but also with figuring out what’s not, and where it went.
One omission in particular has puzzled scientists for well over a century. First noticed by John Wesley Powell in 1869 in the layers of the Grand Canyon, the Great Unconformity, as it’s known, accounts for more than one billion years of missing rock in certain places.
Scientists have developed several hypotheses to explain how, and when, this staggering amount of material may have been eroded. Now, UC Santa Barbara geologist Francis Macdonald and his colleagues at the University of Colorado, Boulder and at Colorado College believe they may have ruled out one of the more popular of these. Their study appears in the Proceedings of the National Academy of Sciences.
“There are unconformities all through the rock record,” explained Macdonald, a professor in the Department of Earth Science. “Unconformities are just gaps in time within the rock record. This one’s called the Great Unconformity because it was thought to be a particularly large gap, maybe a global gap.”
A leading thought is that glaciers scoured away kilometers of rock around 720 to 635 million years ago, during a time known as Snowball Earth, when the planet was completely covered by ice. This hypothesis even has the benefit of helping to explain the rapid emergence of complex organisms shortly thereafter, in the Cambrian explosion, since all this eroded material could have seeded the oceans with tremendous amounts of nutrients.
Macdonald was skeptical of this reasoning. Although analogues of the Great Unconformity appear throughout the world — with similar amounts of rock missing from similar stretches of time — they don’t line up perfectly. This casts doubt as to whether they were truly eroded by a global event like Snowball Earth.
Part of the challenge of investigating the Great Unconformity is that it happened so long ago, and the Earth is a messy system. “These rocks have been buried and eroded multiple times through their history,” Macdonald said.
Fortunately, the team was able to test this hypothesis using a technique called thermochronology. A few kilometers below the Earth’s surface, the temperature begins to rise as you get closer to the planet’s hot mantle. This creates a temperature gradient of roughly 50 degrees Celsius for every kilometer of depth. And this temperature regime can become imprinted in certain minerals.
As certain radioactive elements in rocks break down, Helium-4 is produced. In fact helium is constantly being generated, but the fraction retained in different minerals is a function of temperature. As a result, scientists can use the ratio of helium to thorium and uranium in certain minerals as a paleo-thermometer. This phenomenon enabled Macdonald and his coauthors to track how rock moved in the crust as it was buried and eroded through the ages.
“These unconformities are forming again and again through tectonic processes,” Macdonald said. “What’s really new is we can now access this much older history.”
The team took samples from granite just below the boundary of the Great Unconformity at Pikes Peak in Colorado. They extracted grains of a particularly resilient mineral, zircon, from the stone and analyzed the radio nucleotides of helium contained inside. The technique revealed that several kilometers of rock had been eroded from above this granite between 1,000 and 720 million years ago.
Importantly, this stretch of time definitively came before the Snowball Earth episodes. In fact, it lines up much better with the periods in which the supercontinent Rodinia was forming and breaking apart. This offers a clue to the processes that may have stricken these years from the geologic record.
“The basic hypothesis is that this large-scale erosion was driven by the formation and separation of supercontinents,” Macdonald said.
The Earth’s cycle of supercontinent formation and separation uplifts and erodes incredible extents of rock over long periods of time. And because supercontinent processes, by definition, involve a lot of land, their effects can appear fairly synchronous across the geologic record.
However, these processes don’t happen simultaneously, as they would in a global event like Snowball Earth. “It’s a messy process,” Macdonald said. “There are differences, and now we have the ability to perhaps resolve those differences and pull that record out.”
While Macdonald’s results are consistent with a tectonic origin for these great unconformities, they don’t end the debate. Geologists will need to complement this work with similar studies in other regions of the world in order to better constrain these events.
The mystery of the Great Unconformity is inherently tied to two of geology’s other great enigmas: the rise and fall of Snowball Earth and the sudden emergence of complex life in the Ediacaran and Cambrian. Progress in any one could help researchers finally crack the lot.
“The Cambrian explosion was Darwin’s dilemma,” Macdonald remarked. “This is a 200-year old question. If we can solve that, we would definitely be rock stars.”
Reference:
Rebecca M. Flowers, Francis A. Macdonald, Christine S. Siddoway, Rachel Havranek. Diachronous development of Great Unconformities before Neoproterozoic Snowball Earth. Proceedings of the National Academy of Sciences, 2020; 201913131 DOI: 10.1073/pnas.1913131117
Why a big volcanic blow-up at the popular travel destimation Santorini 3200 years ago, but just a few hundred kilometers away, no drama at the volcanoes on Aegina , Methana and Poros islands? Thin sections of the lavas from these four volcanoes yield some of the reasons why. Some minerals only form at greater depths – and the hornblende in the lava from Aegina island indicates that the magma chambers there are deeper than the those underneath the Santorini caldera. But plate tectonics add another, hidden reason also, found research from the University of Johannesburg. Credit: Prof Marlina A. Elburg, University of Johannesburg
At an idyllic island in the Mediterranean Sea, ocean covers up the site of a vast volcanic explosion from 3200 years ago. A few hundred kilometers north-west, three other islands still have their volcanic histories from a few million years ago mostly intact. No explosions there. So why the differences between the Santorini caldera and the Aegina, Methana and Poros lava domes? Researchers used volcanic “fingerprints’ and plate tectonics research to find out why.
The end of a civilisation
A big volcano blew up about 3200 years ago, right next to where Santorini island is in Greece today. During that eruption, liquid molten rock under the ground (magma) built up immense pressure, and then erupted into a lava explosion. The impact was so intense that the volcano collapsed into a huge basin called a caldera.
What had been an island-volcano, was then overrun by ocean, an event considered partially responsible for the demise of the Minoan civilisation.
Santorini Island became a popular travel destination with big ocean-going ships sailing over the caldera. The village of Phira perches on the cliff-edge of the remains of the volcano.
As idyllic as it looks, the Santorini volcano underneath the ocean still constitutes the biggest volcanic hazard for Europe, together with the Vesuvius volcano in Italy.
Toothpaste rather than fireworks
A few hundred kilometers north-west of Santorini, in Greece’s Saronic Gulf, much closer to Athens, a completely different kind of “volcano” looks much less dramatic.
The small islands of Aegina, Methana and Poros sport rounded hills with roads winding uphill in hairpin bends. These hills have volcanic ancestry too—but they are nothing like Santorini.
Here, liquid lava didn’t explode in a big eruption.
“There is no evidence that that large dramatic events ever took place at these islands,” says Prof Marlina A. Elburg, a Geology researcher at the University of Johannesburg.
“Thick blocky lava oozed out of magma chambers under the ground at these islands between 5.3 to 2.6 million years ago, during the Pliocene. The lava was so thick, it was more like toothpaste or putty than liquid. It formed lava domes rather than lava volcanoes.
“After a few million years’ worth of weathering, they’re well camouflaged hills, but they are still considered volcanically active,” she says.
How is it possible that volcanoes so close in geological time and space can behave to differently? The researchers used several techniques to find out.
Finding volcanic ‘fingerprints’
Elburg and co-author Ingrid Smet, a Ph.D. candidate at the time, analysed samples of the lavas in new whole rock analyses, in research published in Lithos.
The study followed on their previous research on the lavas at Methana, also published in Lithos.
They looked for the ratios of very specific elements in the samples, called isotope signatures. Isotope signatures work similar to ‘fingerprints’ for lavas—they help researchers figure out what the lavas were made of, where, and when they were formed.
“Mostly the isotope signatures matched what one would expect from where the islands are located in the Aegean volcanic arc,” says Elburg.
But there were surprises too.
Subterranean recycling machine
Underneath all these volcanoes at Aegina, Methana, Poros and Santorini, something else is going on in deep inside the crust of planet Earth. Running roughly east to west underneath the Mediterranean Sea is the Aegean volcanic arc. This arc is where the African tectonic plate ‘dives under’ the Aegean microplate.
The ‘diving under’ process is called subduction by geologists. It means that one part of the cool outer crust of Earth starts moving underneath another part of the crust, getting ‘recycled’ inside the hot liquid rock of the Earth’s mantle.
The islands of Aegina, Methana, Poros and Santorini are not just islands with volcanoes. All of them are an integral part of Earth’s ‘recycling machine’ that keeps renewing the crust underneath the planet’s oceans.
This raises the question: Why do these islands have such different ‘lava histories’, even though all of them are on the edge of the Aegean plate?
Some of the answers have to do with what goes into the lava “mixes” for the volcanoes.
Variable lava mix recipes
The African plate ‘dives under’ the Aegean plate in an oceanic trench in the Mediterranean Sea. This happens very slowly at a few centimeters per year. Which means the pristine cold basalt of the down-going African plate’s crust has been soaking in ocean water for millions of years before it enters the much warmer magma underneath the over-riding Aegean plate.
“The crust of the down-going plate now consists of altered rocks, containing minerals with water in them. These minerals become unstable during subduction because of the increasing pressure and temperature, and release their water,” says Elburg.
“This water lowers the melting point of the mantle, similar to what happens when adding salt to ice. That is why the mantle under the over-riding starts to melt. It is this molten material, or magma, that flows/oozes out of volcanoes/lava domes as lava.”
Another possible ingredient of the differing lavas is sediments in the oceanic trench at the subduction zone. At the Aegean Arc the down-going plate is covered by a very thick pile of ocean sediments. Some of the sediment is former continental crust.
A lot of this sediment is ‘scraped off’ when the plate subducts and forms an accretionary (or build-up) wedge. However, some of it is also going down into the mantle and getting mixed with the melting mantle wedge, she says.
Same plate, different lavas
Since Aegina, Methana, Poros and Santorini volcanoes are all part of the same subduction zone, the different volcanic activity raises several big questions. One of these is:
Why the thick blocky lava at the western volcanic centres Aegina, Methana and Poros 2.5 to 2 million years ago, but liquid lava at Santorini 3,200 years ago?
The answers to this creates other questions about the recycling behaviour of the planet we live on.
But subduction zones are tricky to study. It’s not possible to go to one of those and come back with some sample materials. Scientists still need more understanding of what role the overriding plate plays; how much interaction there is between ascending magmas and the crust they ascend through; and whether subduction-related magmas obtain their geochemical signature from the sediment that is recycled back into the earth, says Elburg.
“The answers to these questions can help us understand to what extent the melting processes that started at more than 100 kilometers deep in the mantle, continue when the magma is closer to the surface of the earth,” she says.
“This process of ‘crustal contamination’ is yet another ‘Earth recycling machine’, which may also influence the potential for ore deposits—like in the Andes, where major copper deposits are found, and where this ‘intracrustal recycling’ is thought to play an important role”.
Deeper vs shallower
One way of studying lavas is to put thin slices (called thin sections) under a microscope and identify the minerals. Because minerals need different conditions to form, their presence can say a lot about where and how magmas were mixed.
In this study the minerals indicated that Santorini lavas were more liquid because they formed at inside shallower magma chambers, while the western volcanic centre lavas were thicker and more blocky because they formed in deeper magma chambers.
“The thin sections of the Santorini lavas display pyroxenes and significant plagioclase. This indicates that the magma from which the crystals formed was located at shallow depths in the earth,” says Elburg.
And there is an invisible reason the magma was at shallower depths at Santorini.
“The tectonic plate above Santorini’s magma chambers is being pulled apart. In geology terms, it is under localised extension. And because the plate is being stretched out and Santorini is in the middle of it, Santorini happens to be at the thinnest part of the plate.
“With a magma chamber at a shallower depth, the roof will cave in when the chamber starts emptying itself during an eruption. This makes the eruption even worse and creates a caldera, as at Santorini,” she adds.
No explosions
In contrast, when they looked at the thin sections of the thick blocky lavas from Aegina and Methana, they found hornblende. The mineral was absent in the Santorini lavas.
Hornblende can only form if the magma is deep enough in the Earth. This indicates that the magma chambers on Aegina and Methana should be located deeper than on Santorini.
“With the magma chambers at greater depths for the western Aegina- Methana-Poros volcanoes, that makes for changes in the lava. There the magma chambers underneath the lava domes did not cave in. Additionally, the crystallization of the amphibole mineral group that includes hornblende, makes magma more viscous, or sticky. So it is more difficult for the magma to come to the surface in the first place.
Over-riding plate vs sediment
To figure out whether the over-riding plate or the ocean sediments were the bigger factor in creating thick blocky lavas, the researchers analysed specific ‘lava fingerprints’. These radiogenic isotope ratios gave them the best indication on which materials were mixed into the underground magmas for those lavas.
“We compared Santorini with Aegina-Poros-Methana lavas in terms of their geochemistry on 87Sr/86Sr, 143Nd/144Nd and 208Pb/204Pb. They were distinctly different. Then by combining the radiogenic isotope signature of the lavas with trace element ratios, we managed to pinpoint the down-going sediment as the biggest influence creating thick blocky lavas, not the overriding plate.
No one lava size
“We found that Aegina and Methana-Poros have their own individual volcanic histories, even though they’re part of the Aegean arc.
“This means that a simple one-size-fits-all explanation, based on crustal contamination history, for the difference in eruptive style compared to Santorini does not work.
“Modern subduction zones are not all alike. Even in one volcanic arc, more than one eruptive style points to differences in subduction processes,” concludes Elburg.
Reference:
Marlina A. Elburg et al, Geochemistry of lavas from Aegina and Poros (Aegean Arc, Greece): Distinguishing upper crustal contamination and source contamination in the Saronic Gulf area, Lithos (2020). DOI: 10.1016/j.lithos.2020.105416
Mud volcanoes are geological structures formed by the eruption of semi-liquid and gas-enriched mud breccia on the Earth’s surface or on the sea floor. The migration processes of geofluids around mud volcanoes could provide useful information about the mineralogical and geochemical characteristics of hydrocarbon-bleaching process and hydrocarbon migration pathways.
However, it remains unclear how organic-inorganic interactions take place in mud volcanic systems, particularly the alteration of surface processes induced by reducing geofluids in mud volcanic systems and the spatial variations in geochemical conditions along the main flowing route of erupting fluids.
Recently, scientists from the Northwest Institute of Eco-Environment and Resources of the Chinese Academy of Sciences performed a detailed field investigation and laboratory study to determine the mineral and chemical compositions as well as iron speciation of near surface rocks in the Baiyanggou mud volcano area.
They systematically collected a total of 11 rock samples along the main flow of geofluids running on the slope of the Baiyanggou mud volcanic system and analyzed for their mineralogical and chemical compositions as well as for iron species using X-ray diffraction, X-ray fluorescence spectrometry and Mossbauer spectroscopy, respectively.
Besides, they also used iron speciation in response to redox conditions for the first time as a tracer of geofluid processes in order to better understand the migration processes of geofluids.
The analytical results clearly indicated spatial variations for most geochemical parameters caused by redox fluctuation processes around the Baiyanggou mud volcanic system.
All these processes may provide useful information for a better understanding of hydrocarbon-rock interactions in the mud volcanic systems.
Moreover, the study results also indicated that the Iron speciation of the solid rocks in the seepage areas could be considered as a potential indicator for the migration of reducing geofluids including hydrocarbons located underground.
This study has been published in Applied Geochemistry in an article entitled “Mineralogical and geochemical characteristics of hydrocarbon-bleached rocks in Baiyanggou mud volcanoes, Xinjiang, NW China.”
Reference:
Wang Xu et al. Mineralogical and geochemical characteristics of hydrocarbon-bleached rocks in Baiyanggou mud volcanoes, Xinjiang, NW China, Applied Geochemistry (2020). DOI: 10.1016/j.apgeochem.2020.104572
A close-up image showing the damaged head and body of the Dorsetichthys bechei with the arms of the Clarkeiteuthis montefiorei clamped around it Credit: Malcolm Hart, Proceedings of the Geologists’ Association
Scientists have discovered the world’s oldest known example of a squid-like creature attacking its prey, in a fossil dating back almost 200 million years.
The fossil was found on the Jurassic coast of southern England in the 19th century and is currently housed within the collections of the British Geological Survey in Nottingham.
In a new analysis, researchers say it appears to show a creature—which they have identified as Clarkeiteuthis montefiorei—with a herring-like fish (Dorsetichthys bechei) in its jaws.
They say the position of the arms, alongside the body of the fish, suggests this is not a fortuitous quirk of fossilization but that it is recording an actual palaeobiological event.
They also believe it dates from the Sinemurian period (between 190 and 199 million years ago), which would predate any previously recorded similar sample by more than 10 million years.
The research was led by the University of Plymouth, in conjunction with the University of Kansas and Dorset-based company, The Forge Fossils.
It has been accepted for publication in Proceedings of the Geologists’ Association and will also be presented as part of Sharing Geoscience Online, a virtual alternative to the traditional General Assembly held annually by the European Geosciences Union (EGU).
Professor Malcolm Hart, Emeritus Professor in Plymouth and the study’s lead author, said: “Since the 19th century, the Blue Lias and Charmouth Mudstone formations of the Dorset coast have provided large numbers of important body fossils that inform our knowledge of coleoid palaeontology. In many of these mudstones, specimens of palaeobiological significance have been found, especially those with the arms and hooks with which the living animals caught their prey.
“This, however, is a most unusual if not extraordinary fossil as predation events are only very occasionally found in the geological record. It points to a particularly violent attack which ultimately appears to have caused the death, and subsequent preservation, of both animals.”
In their analysis, the researchers say the fossilised remains indicate a brutal incident in which the head bones of the fish were apparently crushed by its attacker.
They also suggest two potential hypotheses for how the two animals ultimately came to be preserved together for eternity.
Firstly, they suggest that the fish was too large for its attacker or became stuck in its jaws so that the pair—already dead—settled to the seafloor where they were preserved.
Alternatively, the Clarkeiteuthis took its prey to the seafloor in a display of ‘distraction sinking’ to avoid the possibility of being attacked by another predator. However, in doing so it entered waters low in oxygen and suffocated.
Turns out, you really can’t believe everything you see in the movies. Credit: University of Wisconsin Oshkosh
A new University of Wisconsin Oshkosh analysis of raptor teeth published in the peer-reviewed journal Palaeogeography, Palaeoclimatology, Palaeoecology shows that Velociraptors and their kin likely did not hunt in big, coordinated packs like dogs.
The raptors (Deinonychus antirrhopus) with their sickle-shaped talons were made famous in the 1993 blockbuster movie Jurassic Park, which portrayed them as highly intelligent, apex predators that worked in groups to hunt large prey.
“Raptorial dinosaurs often are shown as hunting in packs similar to wolves,” said Joseph Frederickson, a vertebrate paleontologist and director of the Weis Earth Science Museum on the UWO Fox Cities campus. “The evidence for this behavior, however, is not altogether convincing. Since we can’t watch these dinosaurs hunt in person, we must use indirect methods to determine their behavior in life.”
Frederickson led the study in partnership with two colleagues at the University of Oklahoma and Sam Noble Museum, Michael Engel and Richard Cifell.
Though widely accepted, evidence for the pack-hunting dinosaur proposed by the late famed Yale University paleontologist John Ostrom is relatively weak, Frederickson said.
“The problem with this idea is that living dinosaurs (birds) and their relatives (crocodilians) do not usually hunt in groups and rarely ever hunt prey larger than themselves,” he explained.
“Further, behavior like pack hunting does not fossilize so we can’t directly test whether the animals actually worked together to hunt prey.”
Recently, scientists have proposed a different model for behavior in raptors that is thought to be more like Komodo dragons or crocodiles, in which individuals may attack the same animal but cooperation is limited.
“We proposed in this study that there is a correlation between pack hunting and the diet of animals as they grow,” Frederickson said.
In Komodo dragons, babies are at risk of being eaten by adults, so they take refuge in trees, where they find a wealth of food unavailable to their larger ground-dwelling parents. Animals that hunt in packs do not generally show this dietary diversity.
“If we can look at the diet of young raptors versus old raptors, we can come up with a hypothesis for whether they hunted in groups,” Frederickson said.
To do this, the scientists considered the chemistry of teeth from the raptor Deinonychus, which lived in North America during the Cretaceous Period about 115 to 108 million years ago.
“Stable isotopes of carbon and oxygen were used to get an idea of diet and water sources for these animals. We also looked at a crocodilian and an herbivorous dinosaur from the same geologic formation,” he said.
The scientists found that the Cretaceous crocodilians, like modern species, show a difference in diet between the smallest and largest teeth, indicating a distinct transition in diet as they grew.
“This is what we would expect for an animal where the parents do not provide food for their young,” Frederickson said. “We also see the same pattern in the raptors, where the smallest teeth and the large teeth do not have the same average carbon isotope values, indicating they were eating different foods. This means the young were not being fed by the adults, which is why we believe Jurassic Park was wrong about raptor behavior.”
Frederickson added that the method used in this study to analyze carbon in teeth could be applied to see whether other extinct creatures may have hunted in packs.
Reference:
J.A. Frederickson et al, Ontogenetic dietary shifts in Deinonychus antirrhopus (Theropoda; Dromaeosauridae): Insights into the ecology and social behavior of raptorial dinosaurs through stable isotope analysis, Palaeogeography, Palaeoclimatology, Palaeoecology (2020). DOI: 10.1016/j.palaeo.2020.109780
Published in PLOS ONE today, a study by an international team from the Perot Museum of Nature and Science in Dallas and Hokkaido University in Japan further explores the proliferation of the most commonly occurring duck-billed dinosaur of the ancient Arctic as the genus Edmontosaurus. The findings reinforce that the hadrosaurs – dubbed “caribou of the Cretaceous” – had a geographical distribution of approximately 60 degrees of latitude, spanning the North American West from Alaska to Colorado. Credit: Masato Hattori
A new study by an international team from the Perot Museum of Nature and Science in Dallas and Hokkaido University and Okayama University of Science in Japan further explores the proliferation of the most commonly occurring duck-billed dinosaur of the ancient Arctic as the genus Edmontosaurus. The findings also reinforce that the hadrosaurs—known as the “caribou of the Cretaceous”—had a huge geographical distribution of approximately 60 degrees of latitude, spanning the North American West from Alaska to Colorado.
The scientific paper describing the find—titled “Re-examination of the cranial osteology of the Arctic Alaskan hadrosaurine with implications for its taxonomic status”—has been posted in PLOS ONE, an international, peer-reviewed, open-access online publication featuring reports on primary research from all scientific disciplines. The authors of the report are Ryuji Takasaki of Okayama University of Science in Japan; Anthony R. Fiorillo, Ph.D. and Ronald S. Tykoski, Ph.D. of the Perot Museum of Nature and Science in Dallas, Texas; and Yoshitsugu Kobayashi, Ph.D. of Hokkaido University Museum in Japan.
“Recent studies have identified new species of hadrosaurs in Alaska, but our research shows that these Arctic hadrosaurs actually belong to the genus Edmontosaurus, an abundant and previously recognized genus of duck-billed dinosaur known from Alberta south to Colorado,” said Takasaki.
The report states that anatomical comparisons and phylogenetic analyses clearly demonstrate that attribution of the Alaskan hadrosaurines to a unique genus Ugrunaaluk is inappropriate, and they are now considered as a junior synonym of Edmontosaurus, a hadrosaurines genus previously known from lower latitude North America roughly in between northern Colorado (N40?) to southern Alberta (N53?).
The fossils used for this study were found primarily in the Liscomb Bonebed, Prince Creek Formation of the North Slope of Alaska, the location of the first dinosaur fossils discovered in the Arctic.
The team’s research also show that the plant-eating hadrosaurs were taking over parts of North America during the Cretaceous, suggesting that Edmontosaurus was likely an ecological generalist.
“In other words, Edmontosaurus was a highly successful dinosaur that could adapt to a wide variety of environmental conditions,” said Fiorillo. “It’s not unrealistic to compare them to generalized animals today—such as mountain sheep, wolves and cougars in terms of their range and numbers—that also roam greater geographic distributions.”
Members of this team also found ties to Kamuysaurus japonicus, a new genus species they discovered near Hokkaido, Japan, and named in 2019.
“Combined with the newly named Kamuysaurus of Japan, Alaska Edmontosaurus shows that this group of hadrosaurs, the Edmontosaurini, were widely distributed in the northern circum-Pacific region, meaning that they were incredibly successful dinosaurs,” said Kobayashi. “It’s fascinating to think they likely used the ancestral Bering Land Bridge between Asia and North America for migration in a manner similar to mammoths, woolly rhinoceroses and early humans.”
Edmontosaurus belong to a clade Edmontosaurini as Kamuysaurus, a recently described hadrosaurine dinosaur from Japan, suggesting that Edmontosaurini widely distributed along the northern circum-Pacific region. North America and Asia were connected by Beringia during the Late Cretaceous, and some dinosaurs are believed to have traveled to the North American continent this way. Edmontosaurini is one of the dinosaur groups that may have ventured the North America-to-Asia pathway and adapted to the Arctic environment. Those creatures that stayed in North America evolved to Edmontosaurus, and those that stayed in Asia and moved on to Japan are believed to have evolved to Kamuysaurus.
“This study is a wonderful example of why paleontologists need to be more aware of how individual growth and life stage of fossils matter when we try to interpret the anatomical features preserved in them. If you don’t, you run the risk of erroneously erecting a new ‘genus’ or species based on juvenile traits that will change or vanish as the individual creature grows up—and winds up being an adult of an already-known ‘genus’ or species!,” said Tykoski. “Our study shows that was probably the case with these juvenile duck-billed dinosaurs from the ancient Arctic of Alaska.”
Fossilized teeth from the ancient lizard Priosphenodon show that it had durable tooth enamel—a feature much more common in mammals, according to U of A paleontologists. Credit: Aaron LeBlanc
A new study by University of Alberta paleontologists shows that one type of ancient reptiles evolved a special type of tooth enamel, similar to that of mammals, with high resistance to wear and tear.
The reptile—known as Priosphenodon—was a herbivore from the Late Cretaceous period that was about one metre long. Part of a group of reptiles called sphenodontians, they had the unique trait of adding new teeth to the back ends of their jaws instead of replacing them where they fell out.
“Priosphenodon has the strangest teeth I have personally ever seen,” said Aaron LeBlanc, a post-doctoral fellow in biological sciences and lead author on the study. “Some aspects of their dental anatomy are reminiscent of what happened in the evolution of early mammal teeth.”
The specimens were found in Argentina’s Río Negro province as part of ongoing collaborative fieldwork and research between U of A paleontologist Michael Caldwell and Argentinian paleontologist and fieldwork leader Sebastián Apesteguía.
To look closely at the teeth of Priosphenodon, the researchers cut open pieces of jaw and examined tissue-level detail preserved inside the teeth, and used non-invasive CT scans to examine more complete jaw specimens.
“Priosphenodon enamel is not only thicker than that of most other reptiles, the enamel crystals are ‘woven’ into long threads that run through the whole width of the enamel. These threads are called enamel prisms, and they are almost exclusively found in mammals,” said LeBlanc, who is working under Caldwell’s supervision.
“Our results suggest that strong selective pressures can force reptiles to come up with some very innovative solutions to the problems associated with tooth wear and abrasive diets—some of which mirror what happened in our earliest mammal ancestors.”
The scientists also noted there is one kind of lizard alive today that has prismatic enamel like Priosphenodon—the spiny-tailed lizard of Australia. Like Priosphenodon, it mostly eats plants and has lost the ability to replace its worn teeth. However, the two reptiles are not closely related.
Hans Larsson from McGill University also collaborated on the study, which was funded by the Agencia Nacional de Promoción Científica y Tecnológica in Argentina, National Geographic and the Natural Sciences and Engineering Research Council of Canada.
The study, “Unique Tooth Morphology and Prismatic Enamel in Late Cretaceous Sphenodontians from Argentina” was published in Current Biology.
Reference:
Aaron R.H. LeBlanc et al. Unique Tooth Morphology and Prismatic Enamel in Late Cretaceous Sphenodontians from Argentina, Current Biology (2020). DOI: 10.1016/j.cub.2020.02.071
Photomicrograph in crossed polars of precious-metal bearing peridotite. Note the optical zoning (light/dark bands) in the plagioclase (grey coloured mineral) in the central part of the image. The occurrence of this zoning was the focus of the study in question. The width of the image frame is 4 mm. Credit: Nat. Geosci. (2020).
Research carried out by scientists at Keele University, the University of Manchester and University College Dublin has shed new light on how precious metals are concentrated in igneous rocks.
The solidified remains of sub-volcanic magmatic intrusions host the greatest concentrations of platinum-group metals in the Earth’s crust, such as platinum, palladium and rhodium. Scientists refer to these bodies as layered mafic intrusions. Traditional models suggest that these layered intrusions form in large volume magma chambers, but this new research has found that it’s more likely small amounts of magma is repeatedly injected into a crystal mush.
The research, published in Nature Geoscience, demonstrates the case for re-evaluation of the long-held belief about how layered mafic intrusions are formed.
The research involved carrying out a detailed study on an approximately 60 million year old extinct volcano on the island of Rum in northwest Scotland. Mineral crystals in the Rum intrusion were analysed using a novel microsampling approach, to identify isotopic variations of the element strontium.
The measured strontium isotope variations provide evidence that crystallization of the minerals in and around precious-metal rich layers occurred within 10s to 100s of years. The data also show that layered intrusions such as on Rum form by repeated self-intrusion of magma during solidification rather than by protracted cooling from the bottom up and the top down.
This new insight has important implications for the understanding of precious-metal mineralization in mafic igneous systems more generally.
Keele University’s Dr. Ralf Gertisser, Reader in Mineralogy and Petrology in Keele’s School of Geography, Geology and the Environment, said: “The study significantly influences our understanding of how layered intrusions and the precious metal deposits within them form.”
Dr. Luke Hepworth, former Ph.D. student in the School of Geography, Geology and the Environment at Keele University, added: “There is scope for the model proposed here to be extrapolated to precious-metal-bearing rocks in larger, economically significant layered mafic intrusions such as the Bushveld Complex in South Africa and the Stillwater Complex in the U.S..”
Dr. Brian O’Driscoll, Senior Lecturer in Petrology at The University of Manchester, said: “These new data highlight that the crystallization of layered intrusions and their associated platinum-group metal mineralization may be a dynamic and rapid process. It will be exciting to see whether these ideas can be extended to other economically-important deposits in the future.”
Reference:
Luke N. Hepworth et al. Rapid crystallization of precious-metal-mineralized layers in mafic magmatic systems, Nature Geoscience (2020). DOI: 10.1038/s41561-020-0568-3
Life-like reconstruction of Adalatherium hui from the LateCretaceous of Madagascar. Credit: Denver Museum of Nature & Science/Andrey Atuchin.
In evolutionary terms, islands are the stuff of weirdness. It is on islands where animals evolve in isolation, often for millions of years, with different food sources, competitors, predators, and parasites…indeed, different everything compared to mainland species. As a result, they develop into different shapes and sizes and evolve into new species that, given enough time, spawn yet more new species.
Such is the case with the discovery of a new, bizarre 66-million-old mammal in Madagascar by a team of international researchers led by Dr. David Krause, senior curator of vertebrate paleontology at the Denver Museum of Nature & Science and professor emeritus at Stony Brook University, where part of the research was done. The discovery of this opossum-sized mammal that lived among dinosaurs and massive crocodiles on the fourth largest island on Earth was announced today in the journal Nature. Dr. James B. Rossie of Stony Brook University is one of the study’s co-authors. The late Yaoming Hu of Stony Brook University was also a co-author.
The finding of the new mammal, called Adalatherium, which is translated from the Malagasy and Greek languages and means “crazy beast,” is based on a nearly complete skeleton that is astoundingly well preserved. The skeleton is the most complete for any Mesozoic mammal yet discovered in the southern hemisphere.
Krause said that, “knowing what we know about the skeletal anatomy of all living and extinct mammals, it is difficult to imagine that a mammal like Adalatherium could have evolved; it bends and even breaks a lot of rules.”
In fact, although a life-like reconstruction might lead one to think that Adalatherium was a run-of-the-mill badger, its “normality” is literally only skin deep. Below the surface, its skeleton is nothing short of “outlandish.” It has primitive features in its snout region (like a septomaxilla bone) that hadn’t been seen for a hundred million years in the lineage leading to modern mammals.
“Its nasal cavity exhibits an amazing mosaic of features, some of which are very standard for a mammal, but some that I’ve never seen in anything before,” Rossie declared.
Adalatherium had more holes (foramina) on its face than any known mammal, holes that served as passageways for nerves and blood vessels supplying a very sensitive snout that was covered with whiskers. And there is one very large hole on the top of its snout for which there is just no parallel in any known mammal, living or extinct.
The teeth of Adalatherium are vastly different in construction than any known mammal. Its backbone had more vertebrae than any Mesozoic mammal and one of its leg bones was strangely curved.
About the size of a Virginia opossum, Adalatherium was also unusual in that it was very large for its day; most mammals that lived alongside dinosaurs were much smaller, mouse-sized on average.
Adalatherium belongs to an extinct group of mammals called gondwanatherians because they are only known from the ancient southern supercontinent of Gondwana. Gondwanatherian fossils were first found in Argentina in the 1980s but have since also been found in Africa, India, the Antarctic Peninsula, and Madagascar. Gondwanatherians were first thought to be related to modern-day sloths, anteaters, and armadillos but “now are known to have been part of a grand evolutionary experiment, doing their own thing, an experiment that failed and was snuffed out in the Eocene, about 45 million years ago,” Krause explained.
Prior to the discovery of the nearly complete skeleton of Adalatherium, gondwanatherians were only known from isolated teeth and jaw fragments, with the exception of a cranium from Madagascar described by Krause and his team in 2014.
The completeness and excellent preservation of the skeleton of Adalatherium potentially opens up new windows into what gondwanatherians looked like and how they lived, but the bizarre features still have the scientific team guessing.
As Krause’s primary collaborator Simone Hoffmann of the New York Institute of Technology put it, “Adalatherium is the oddest of oddballs. Trying to figure out how it moved is nearly impossible because, for instance, its front end is telling us a different story than its back end.” The research team is still uncovering clues but thinks that, although Adalatherium might have been a powerful digging animal, it was also capable of running and potentially even had other forms of locomotion.
The plate tectonic history of Gondwana provides independent evidence for why Adalatherium is so bizarre. Adalatherium was found in rocks dated to near the end of the Cretaceous, at 66 million years ago. Madagascar, with the Indian subcontinent attached to the east, separated from Africa over a hundred million years before and finally became isolated as an island in the Indian Ocean when the Indian subcontinent detached at approximately 88 million years ago and drifted northward. That left the lineage that ultimately resulted in Adalatherium to evolve, isolated from mainland populations, for over 20 million years — “ample time to develop its many ludicrous features,” said Krause.
The fossil record of early mammals from the northern hemisphere is roughly an order of magnitude better than from the south.
“Adalatherium is just one piece, but an important piece, in a very large puzzle on early mammalian evolution in the southern hemisphere,” Krause noted. “Unfortunately, most of the pieces are still missing.”
More than anything, this discovery underscores to the researchers how much more remains to be learned by making new discoveries of early mammals in Madagascar and other parts of the former Gondwana.
In addition to Krause, Hoffmann, and Rossie, other researchers involved in the new discovery — which was funded by the National Science Foundation and National Geographic Society — were: the late Yaoming Hu of Stony Brook University; John R. Wible of Carnegie Museum of Natural History; Guillermo W. Rougier of University of Louisville; E. Christopher Kirk of University of Texas at Austin; Joseph R. Groenke of Stony Brook University and Ohio University; Raymond R. Rogers of Macalester College; Julia A. Schultz of Institut für Geowissenschaften der Universität Bonn, Alistair R. Evans of Monash University and Museums Victoria; Wighart von Koenigswald of Institut für Geowissenschaften der Universität Bonn; and Lydia J. Rahantarisoa of Université d’Antananarivo.
The new Adalatherium mammal is just the latest of a series of bizarre back-boned animals discovered by Krause and his research team on Madagascar over the past 25 years. Earlier discoveries have included a giant, armored, predatory frog (Beelzebufo), a pug-nosed, vegetarian crocodile (Simosuchus), and a small, buck-toothed dinosaur (Masiakasaurus).
The island itself is filled with animals (and plants) found nowhere else on the planet, including hissing cockroaches, giraffe weevils, tomato frogs, Satanic leaf-tailed geckos, panther chameleons, and streaked tenrecs to name a few. And, of course, there is the signature group of mammals — lemurs — made famous in the animated “Madagascar” movies. Only a few thousand years ago, the Madagascar fauna also included 1400-pound elephant birds, gorilla-sized lemurs, and pygmy hippopotamuses.
Reference:
David W. Krause, Simone Hoffmann, Yaoming Hu, John R. Wible, Guillermo W. Rougier, E. Christopher Kirk, Joseph R. Groenke, Raymond R. Rogers, James B. Rossie, Julia A. Schultz, Alistair R. Evans, Wighart von Koenigswald, Lydia J. Rahantarisoa. Skeleton of a Cretaceous mammal from Madagascar reflects long-term insularity. Nature, 2020; DOI: 10.1038/s41586-020-2234-8
This 310-carat fine-quality Peridot from Zebirget, Egypt, is the largest known. Peridot is the gem name for a yellow-green mineral that occurs in volcanic rock. The mineral’s species name is Torsterite. Most of the world’s supply in mined in Arizona, hand-hammered out of basalt. A transparent gem, Peridot has a distinctive oily luster. The color ranges from pale golden-green to brownish green. From the Gem and Mineral collection of the Smithsonian’s National Museum of Natural History. ..Credit: Dane A. Penland (Smithsonian Institution)
Peridot Stone the world’s largest cut ever found is 311.78 carats (62.35 grams)! It was found on Zagbargad Island, Egypt, and is now located in the Smithsonian Museums, USA. Also, in the Diamond Treasury – Moscow, Russia, an exquisite 192.75 carat Peridot gemstone is kept. In addition, a Peridot gem of 146 carat is housed at the Geological Museum in London, England.
With the endowment the Smithsonian has added to the original collection no less than 13,000 specimens, bringing the total to nearly 30,000. The Smithsonian labelled the original mineral specimens with R1 to R6000 catalog numbers. The remaining 10,000 specimens represented specimens of gemstones and meteorites, rather than raw minerals.
The world’s largest known peridot lies within this enormous collection. The Smithsonian catalogs it as NMHN G3398-00 (MIN), weighing in at 311.8 carats and cut in a mixed cushion shape.
The peridot originated from Zabargad Island (St. John’s Island), in Egypt, according to the record of the Smithsonian. They describe it as a primary gem with a slightly yellow dark green colouration. The Smithsonian lists his previous catalog number as R00008.
Can it be that the original 6,000 mineral specimens belonging to Washington A. Roebling belonged to this beautiful peridote?
Definitely, more work is needed to address the issue. So, I sent an email for this specimen to the new archivist. I’ll be returning and updating this article when I hear back.
Zabargad Island
Zabargad Island in Foul Bay, Egypt is the largest of a group of islands. It covers an area of 1.74 square miles (4.50 square kilometres). It is not a quaternary volcanic island but instead an upthrusted portion of upper mantle material is thought to be. The closest island is called Rocky Island. The island is slightly north of the Cancer Tropic and is 235 meters (771 feet) tallest.
The island is considered peculiar geologically because it is an uplifted mantle, a part of the lithosphere of the sub-Red Sea. The island’s rocks are mostly the lower metamorphic crustal rocks. After African and Asian continental plates converged to cause uplifting of rocks in the lower crust, the island was present above sea level. The island comprises three peridotite masses, which are rich in peridot gemstone (olivine). The island is believed to be the first source of peridot discovered, in ancient times called topazios, hence the Greek name for the island, Topazios. Spinel-lherzolite layers of anhydrous Al-diopside pyroxenites and hydrous Cr-diopside pyroxenites are also to be found on the island.
The island is part of the Elba National Park meaning the island is conserved. However, the island was closed to the public for one year due to damage to corals and the disturbance of birds who breed on the island.
When was Peridot first discovered?
Peridot is a Gemstone of antiquity. Peridot’s existence dates back over 3,500 years, when the Egyptians found the gemstone. Peridot was strongly desired and worshiped during those days. The gemstone has been said to have magical powers, and has also been used to heal and defend. The ancient Egyptians claimed the Peridot stone was capable of warding off evil and defending against nightmares.
Where is Peridot found?
Most Peridots occur in lava rocks, but the gemstone has been found in meteorites as well – in its basic form! The most common and precious Peridots are present in Burma and Pakistani. Most trading Peridots, however, come from the USA, China, Vietnam and South Africa.
Peridot is a gem-quality olivine and a (Mg, Fe)2SiO4 type silicate mineral. The formulation approaches Mg2SiO4 because it is a magnesium-rich olivine (forsterite). The green colors of the gem depend on the structure of the iron contents. It occurs both in volcanic basalt and in pallastic meteorites in silica-deficient rocks. It is one of the two gems that have been observed to form in the rock of the upper mantle rather than in the earth’s crust. It’s gem-quality is unusual on the earth’s surface due to its environmental sensitivity when transporting deep into the mantle.
Peridot is a silicate of magnesium oxide; pure forsterite is colorless, but oxide substitute the green colors of some of the magnesium. Too much iron contributes to an attractive brown colored stone. It is the precious color without heavy yellow or brown distinctions, when it’s bright white. This altered barrel cut peridot is the most fine 46,16-carat stone in the National Gem Collection and Pakistan’s greatest peridot.
It is one of the few gemstones in one color only: an olive-green. But the size and color of the Green ranges from yellow to olive to brownish-gray in the crystal structure, depending upon the iron level of the structure. It may be medium-dark, pure white, in extreme situations, without a secondary yellow or brown mask.
Where is Peridot found?
The Olivine, a peridot type, is common to mafic and ultramatic rocks, frequently found in lava and in peridotite mantle xenoliths which carry Lava to the surface but only in a fraction of these environments does gem quality peridot occur.
Peridots in meteorites can also be detected.
It can be differentiated by composition and scale. A volcanically formed peridote typically has higher lithium, nickel and zinc concentrations than those present in meteorites.
Olivine is an abundant mineral, but peridot of gem quality is very unusual on the Earth’s surface due to its chemical instability. Olivine is typically classified as small grains and is not painted in a extremely heavy state. The variety that is used mostly to cut peridot diamonds, large forsterite crystals, is uncommon, which means olivines are considered valuable.
In the ancient world, mining of peridot, called topazios then, on St. John’s Island ” Zabargad Island “in the Red Sea began about 300 B.C.
The principal source of peridot olivine today is the San Carlos Apache Indian Reservation in Arizona. It is also mined at another location in Arizona, and in Arkansas, Hawaii, Nevada, and New Mexico at Kilbourne Hole, in the US; and in Australia, Brazil, China, Egypt, Kenya, Mexico, Myanmar (Burma), Norway, Pakistan, Saudi Arabia, South Africa, Sri Lanka, and Tanzania.
It’s crystals have been collected from some pallasite meteorites. These gems are given the name Moldavite to differentiate their origin. The most commonly studied pallasitic peridot belongs to the Indonesian Jeppara meteorite, but others exist such as the Brenham, Esquel, Fukang, and Imilac meteorites.
How much is a 1 carat peridot worth?
Peridot is around $50–80/ct in size. For the fine gems in the range of 1-2 ct, for the range of big fine gems up to $400-450 ct.
Is Peridot a natural stone?
A lot of Peridot gems come from ignorant environments. These gems form within the earth’s mantle to bring volcanic activity to the surface.
Are peridot stones valuable?
The price of peridot per carat is very varied. You will find beautiful peridot rings with silver setting for as little as $25, for example, and there are Peridot stones that can go a carat for around $900! The peridot value is determined by factors like colour, size, and quality.
An artistic cross-section through forming crust approximately 3-4 billion years ago. The presence or absence of plate tectonics during this time is a topic of vigorous scientific debate. A study led by Harvard geologists has found evidence that the crust moved quickly over Earth’s surface in the deep past, a hallmark of modern plate tectonics. This suggests that plate motion could have been a meaningful process in early Earth history. Credit: Alec Brenner, Harvard University
An enduring question in geology is when Earth’s tectonic plates began pushing and pulling in a process that helped the planet evolve and shaped its continents into the ones that exist today. Some researchers theorize it happened around four billion years ago, while others think it was closer to one billion.
A research team led by Harvard researchers looked for clues in ancient rocks (older than 3 billion years) from Australia and South Africa, and found that these plates were moving at least 3.2 billion years ago on the early Earth. In a portion of the Pilbra Craton in Western Australia, one of the oldest pieces of the Earth’s crust, scientists found a latitudinal drift of about 2.5 centimeters a year, and dated the motion to 3.2 billion years ago.
The researchers believe this shift is the earliest proof that modern-like plate motion happened between two to four billion years ago. It adds to growing research that tectonic movement occurred on the early Earth. The findings are published in Science Advances.
“Basically, this is one piece of geological evidence to extend the record of plate tectonics on Earth farther back in Earth history,” said Alec Brenner, one of the paper’s lead authors and a member Harvard’s Paleomagnetics Lab. “Based on the evidence we found, it looks like plate tectonics is a much more likely process to have occurred on the early Earth and that argues for an Earth that looks a lot more similar to today’s than a lot of people think.”
Plate tectonics is key to the evolution of life and the development of the planet. Today, the Earth’s outer shell consists of about 15 rigid blocks of crust. On them sit the planet’s continents and oceans. The movement of these plates shaped the location of the continents. It helped form new ones and it created unique landforms like mountain ranges. It also exposed new rocks to the atmosphere, which led to chemical reactions that stabilized Earth’s surface temperature over billions of years. A stable climate is crucial to the evolution of life.
When the first shifts occurred has long been an issue of considerable debate in geology. Any information that sheds light on it is valuable. The study, published on Earth Day, helps fill in some of the gaps. It also loosely suggests the earliest forms of life developed in a more moderate environment.
“We’re trying to understand the geophysical principles that drive the Earth,” said Roger Fu, one of the paper’s lead authors and an assistant professor of earth and planetary sciences in the Faculty of Arts and Science. “Plate tectonics cycles elements that are necessary for life into the Earth and out of it.”
“Currently, Earth is the only known planetary body that has robustly established plate tectonics of any kind,” said Brenner, a third-year graduate student in the Graduate School of Arts and Sciences. “It really behooves us as we search for planets in other solar systems to understand the whole set of processes that led to plate tectonics on Earth and what driving forces transpired to initiate it. That hopefully would give us a sense of how easy it is for plate tectonics to happen on other worlds, especially given all the linkages between plate tectonics, the evolution of life and the stabilization of climate.”
For the study, members of the project traveled to Pilbara Craton in Western Australia. A craton is a primordial, thick, and very stable piece of crust. They are usually found in the middle of tectonic plates and are the ancient hearts of the Earth’s continents.
This makes them the natural place to go to study the early Earth. The Pilbara Craton stretches about 300 miles across, covering approximately the same area as the state of Pennsylvania. Rocks there formed as early as 3.5 billion years ago.
In 2017, Fu and Brenner took samples from a portion called the Honeyeater Basalt. They drilled into the rocks there and collected core samples about an inch wide.
They brought the samples back to Fu’s lab in Cambridge, where they placed the samples into magnetometers and demagnetizing equipment. These instruments told them the rock’s magnetic history. The oldest, most stable bit of that history is hopefully when the rock formed. In this case, it was 3.2 billion years ago.
The team then used their data and data from other researchers, who’ve demagnetized rocks in nearby areas, to date when the rocks shifted from one point to another. They found a drift of 2.5 centimeters a year.
Fu and Brenner’s work differs from most studies because the scientists focused on measuring the position of the rocks over time while other work tends to focus on chemical structures in the rocks that suggest tectonic movement.
Researchers used the novel Quantum Diamond Microscope to confirm their findings from 3.2 billion years ago. The microscope images the magnetic fields and particles of a sample. It was developed in collaboration between researchers at Harvard and MIT.
In the paper, the researchers point out they weren’t able to rule out a phenomenon called “true polar wander.” It can also cause the Earth’s surface to shift. Their results lean more towards plate tectonic motion because of the time interval of this geological movement.
Fu and Brenner plan to keep analyzing data from the Pilbara Craton and other samples from around the world in future experiments. A love of the outdoors drives both of them, and so does an academic need to understand the Earth’s planetary history.
“This is part of our heritage,” Brenner said.
Reference:
Alec R. Brenner, Roger R. Fu, David A.D. Evans, Aleksey V. Smirnov, Raisa Trubko, Ian R. Rose. Paleomagnetic evidence for modern-like plate motion velocities at 3.2 Ga. Science Advances, 2020; 6 (17): eaaz8670 DOI: 10.1126/sciadv.aaz8670
