back to top
27.8 C
New York
Tuesday, July 2, 2024
Home Blog Page 65

New study of fossil plants shows the emergence of the Pacific Northwest’s temperate forests

A fossil of a conifer called Cunninghamia.
A fossil of a conifer called Cunninghamia. Credit: Dr. David Greenwood

The iconic evergreen forests of the Pacific Northwest haven’t always been here.

In a recent study published in the journal Palaeogeography, Palaeoclimatology, and Palaeoecology, scientists describe the emergence of these ecosystems about 51-53 million-years-ago—a time with the highest-known global temperatures in the past 66-million-years—when the Pacific Northwest was a subtropical climate similar to today’s southern Florida.

So how did temperate forests emerge during a hot, humid climate? The answer lies within the fossil record and is made possible by another icon of the Pacific northwest—volcanic mountain chains.

Alexander Lowe, graduate of Brandon University in Manitoba, Canada, and current graduate student at the University of Washington and Burke Museum, and co-authors analyzed 3,700 fossils from a unique paleontological site called the McAbee Fossil Beds in southern British Columbia, Canada. The site is an ancient lakebed formed by the surrounding active volcanoes. The ash from multiple eruptions and other sediment washing into the lake preserved an abundance of beautiful plant and insect fossils, and also micro-fossils like pollen and spores.

The team sampled fossils from two different geologic layers, representing two different snapshots in time that are estimated to be only 10,000 – 100,000 years apart. This geologic rarity allowed for the authors to look at forest dynamics operating over thousands to tens of thousands of years of time. More often, paleontologists are drawing comparisons across millions of years of time and different locations.

Lowe and co-authors found the ancient forests consisted of several plants iconic to today’s Pacific Northwest region: cedars, firs, and other conifers, maples, birch and even ferns. A blooming of diversity of many species of both flowering plants and conifers were found in these layers. The most prevalent conifer found was Metasequoia occidentalis, the dawn redwood that is now native to eastern China. Of the flowering plants, Ulmus okanganensis (a species of elm), Fagus langevinii (a species of beech) and Alnus parvifolia (a species of alder) were the most abundant broadleaf species at the site.

“It is interesting that the plants we see dominating these ancient forests represent a mix of plants we find today in the Pacific Northwest, southeastern U.S., and eastern China. This mixture of plants resulted in a high diversity, probably comparable to that seen in modern tropics, despite these forests having existed then at higher elevations, and the fact there was cold hardy plants around, firs for example,” Lowe said. “It is also interesting that despite volcanic eruptions that were frequent and dynamic through time, the forest didn’t change much between the two layers we analyzed, so these forests were apparently quite resilient to volcanic eruptions.”

The team reconstructed the ancient temperature and precipitation using the shape and size of fossil leaves, and found it to be similar to modern day Seattle, despite then existing at higher elevations. Apparently, some of the iconic temperate plants of the Pacific Northwest thrived in this cooler high elevation pocket, when the rest of the region was a subtropical Florida-like climate. Volcanic activity that was frequent (but not devastating enough to wipe out all plants with each eruption) provided fertile soil. Also, lower elevations in the foothills of the mountains created zones where the temperate, cooler plants could mingle with the warm-loving plants, providing an environment for both groups of plants to coexist in a highly diverse mix of plant species.

In addition to better understanding the ecosystem of these early temperate forests, this study provides clues to what may happen with today’s concerns about climate change. By understanding how Pacific Northwest plants lived in subtropical condition of the past, we can better understand what may happen as temperatures rise in the region today.

“As we see in upland sites like McAbee, and increasingly today, cooler climate plant and animal species are pushed to higher elevations as the climate warms. But what happens when there is no higher to go? We lose those species,” Dr. David Greenwood said, Lowe’s previous advisor and coauthor on the McAbee study.

In the upcoming years as part of his Ph.D. research, Lowe is going to look at the fossil record during another, more recent warm period (17–15 million years ago) to see how plants and regional climates responded. Along with other Burke paleontologists, he plans to analyze fossils from Washington, Oregon, and Idaho.

This study provides ecological context in which to understand the diversification and evolution of plant families that now dominate temperate latitudes in the Northern Hemisphere, and what could potentially happen to this important ecosystem in the face of warming climates today.

Reference:
Alexander J. Lowe et al. Plant community ecology and climate on an upland volcanic landscape during the Early Eocene Climatic Optimum: McAbee Fossil Beds, British Columbia, Canada, Palaeogeography, Palaeoclimatology, Palaeoecology (2018). DOI: 10.1016/j.palaeo.2018.09.010

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

Indonesia’s devastating 2018 earthquake was a rare supershear, UCLA study finds

The devastating 7.5 magnitude earthquake that struck the Indonesian island of Sulawesi last September was a rare “supershear” earthquake, according to a study led by UCLA researchers.

Only a dozen supershear quakes have been identified in the past two decades, according to Lingsen Meng, UCLA’s Leon and Joanne V.C. Knopoff Professor of Physics and Geophysics and one of the report’s senior authors. The new study was published Feb. 4 in the journal Nature Geoscience.

Meng and a team of scientists from UCLA, France’s Geoazur Laboratory, the Jet Propulsion Laboratory at Caltech, and the Seismological Laboratory at Caltech analyzed the speed, timing and extent of the Palu earthquake. Using high-resolution observations of the seismic waves caused by the temblor, along with satellite radar and optical images, they found that the earthquake propagated unusually fast, which identified it as a supershear.

Supershear earthquakes are characterized by the rupture in Earth’s crust moving very fast along a fault, causing the up-and-down or side-to-side waves that shake the ground — called seismic shear waves — to intensify. Shear waves are created in standard earthquakes, too, but in supershear quakes, the rupture moving faster than the shear waves produces more energy in a shorter time, which is what makes supershears even more destructive.

“That intense shaking was responsible for the widespread landslides and liquefactions [the softening of soil caused by the shaking, which often causes buildings to sink into the mud] that followed the Palu earthquake,” Meng said.

In fact, he said, the vibrations produced by the shaking of supershear earthquakes is analogous to the sound vibrations of the sonic boom produced by supersonic jets.

UCLA graduate student Han Bao, the report’s first author, gathered publicly available ground-motion recordings from a sensor network in Australia — about 2,500 miles away from where the earthquake was centered — and used a UCLA-developed source imaging technique that tracks the growth of large earthquakes to determine its rupture speed. The technique is similar to how a smartphone user’s location can be determined by triangulating the times that phone signals arrive at cellphone antenna towers.

“Our technique uses a similar idea,” Meng said. “We measured the delays between different seismic sensors that record the seismic motions at set locations.”

The researchers could then use that to determine the location of the rupture at different times during the earthquake.

They determined that the minute-long quake moved away from the epicenter at 4.1 kilometers per second (or about 2.6 miles per second), faster than the surrounding shear-wave speed of 3.6 kilometers per second (2.3 miles per second). By comparison, non-shear earthquakes move at about 60 percent of that speed — around 2.2 kilometers per second (1.3 miles per second), Meng said.

Previous supershear earthquakes — like the magnitude 7.8 Kunlun earthquake in Tibet in 2001 and the magnitude 7.9 Denali earthquake in Alaska in 2002 — have occurred on faults that were remarkably straight, meaning that there were few obstacles to the quakes’ paths. But the researchers found on satellite images of the Palu quake that the fault line had two large bends. The temblor was so strong that the rupture was able to maintain a steady speed around these bends.

That could be an important lesson for seismologists and other scientists who assess earthquake hazards.

“If supershear earthquakes occur on nonplanar faults, as the Palu earthquake did, we have to consider the possibility of stronger shaking along California’s San Andreas fault, which has many bends, kinks and branches,” Meng said.

Supershear earthquakes typically start at sub-shear speed and then speed up as they continue. But Meng said the Palu earthquake progressed at supershear speed almost from its inception, which would imply that there was high stress in the rocks surrounding the fault — and therefore stronger shaking and more land movement in a compressed amount of time than would in standard earthquakes.

“Geometrically irregular rock fragments along the fault plane usually act as barriers preventing earthquakes,” Meng said. “However, if the pressure accumulates for a long time — for decades or even hundreds of years — an earthquake will eventually overcome the barriers and will go supershear right away.”

Among the paper’s other authors are Tian Feng, a UCLA graduate student, and Hui Huang, a UCLA postdoctoral scholar. The UCLA researchers were supported by the National Science Foundation and the Leon and Joanne V.C. Knopoff Foundation. The other authors are Cunren Liang of the Seismological Laboratory at Caltech; Eric Fielding and Christopher Milliner of JPL at Caltech and Jean-Paul Ampuero of Geoazur.

Reference:
Han Bao, Jean-Paul Ampuero, Lingsen Meng, Eric J. Fielding, Cunren Liang, Christopher W. D. Milliner, Tian Feng, Hui Huang. Early and persistent supershear rupture of the 2018 magnitude 7.5 Palu earthquake. Nature Geoscience, 2019; DOI: 10.1038/s41561-018-0297-z

Note: The above post is reprinted from materials provided by University of California – Los Angeles.

Discovery of the oldest evidence of mobility on Earth

Previously, the oldest traces of this kind found dated to approximately 600 million years ago: the Ediacaran period, also characterized by a peak in dioxygen and a proliferation in biodiversity. Scale bar: 1 cm. Credit: A. El Albani / IC2MP / CNRS - Université de Poitiers
Previously, the oldest traces of this kind found dated to approximately 600 million years ago: the Ediacaran period, also characterized by a peak in dioxygen and a proliferation in biodiversity. Scale bar: 1 cm. Credit: A. El Albani / IC2MP / CNRS – Université de Poitiers

An international and multi-disciplinary team coordinated by Abderrazak El Albani at the Institut de chimie des milieux et matériaux de Poitiers (CNRS/Université de Poitiers) has uncovered the oldest fossilised traces of motility. Whereas previous remnants were dated to 570 million years ago, this new evidence is 2.1 billion years old. They were discovered in a fossil deposit in Gabon, where the oldest multicellular organisms have already been found (1). These results appear in the 11 February 2019 edition of PNAS.

A few years ago, geologist Abderrazak El Albani and his team at the Institut de chimie des milieux et matériaux de Poitiers (CNRS/Université de Poitiers) discovered the oldest existing fossils of multicellular organisms in a deposit in Gabon. Located in the Franceville Basin, the deposit allowed scientists to re-date the appearance of multicellular life on Earth to 2.1 billion years — approximately 1.5 billion years earlier than previously thought (600 million). At the time, researchers showed that this rich biodiversity co-occurred with a peak in dioxygenation of the atmosphere (2), and developed in a calm and shallow marine environment.

In this same geological deposit, the team has now uncovered the existence of fossilised traces of motility. This shows that certain multicellular organisms in this primitive marine ecosystem were sophisticated enough to move through its mud, rich in organic matter.

The traces were analysed and reconstructed in 3D using X-ray computed micro-tomography, a non-destructive imaging technique. The more or less sinuous structures are tubular, of a generally consistent diameter of a few millimetres, and run through fine layers of sedimentary rock. Geometrical and chemical analysis reveals that they are biological in origin and appeared at the same time the sediment was deposited.

The traces are located next to fossilised microbial biofilms (3), which formed carpets between the superficial sedimentary layers. It is plausible that the organisms behind this phenomenon moved in search of nutritive elements and the dioxygen, both produced by cyanobacteria.

What did these living elements look like? Though difficult to know for certain, they may have been similar to colonial amoebae, which cluster together when resources become scarce, forming a type of slug, which moves in search of a more favourable environment.

Until now, the oldest traces of recognised movement were dated to 570 million years ago; an estimate that appeared to be confirmed by the molecular clock (4). Evidence of motility found in rock that is 2.1 billion years old raises new questions regarding the history of life: was this biological innovation the prelude to more perfected forms of movement, or an experiment cut short by the drastic drop in atmospheric oxygen rates which occurred approximately 2.083 billion years ago?

Notes:

(1) Nature, 2010 and PLOS ONE, 2014.

(2) PNAS, 2013.

(3) Geobiology, 2018.

(4) The principle is to explore variations between two species observed in similar regions of their DNA in order to estimate the time lapse since the era in which their nearest common ancestor lived.

Reference:
Abderrazak El Albani, M. Gabriela Mangano, Luis A. Buatois, Stefan Bengtson, Armelle Riboulleau, Andrey Bekker, Kurt Konhauser, Timothy Lyons, Claire Rollion-Bard, Olabode Bankole, Stellina Gwenaelle Lekele Baghekema, Alain Meunier, Alain Trentesaux, Arnaud Mazurier, Jeremie Aubineau, Claude Laforest, Claude Fontaine, Philippe Recourt, Ernest Chi Fru, Roberto Macchiarelli, Jean Yves Reynaud, François Gauthier-Lafaye, Donald E. Canfield. Organism motility in an oxygenated shallow-marine environment 2.1 billion years ago. Proceedings of the National Academy of Sciences, 2019; 201815721 DOI: 10.1073/pnas.1815721116

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

Giant ‘megalodon’ shark extinct earlier than previously thought

Megalodon extinction graphical abstract.
Megalodon extinction graphical abstract. Credit: Robert Boessenecker

Megalodon — a giant predatory shark that has inspired numerous documentaries, books and blockbuster movies — likely went extinct at least one million years earlier than previously thought, according to new research published Feb. 13 in PeerJ — the Journal of Life and Environmental Sciences.

Earlier research, which used a worldwide sample of fossils, suggested that the 50-foot-long, giant shark Otodus megalodon went extinct 2.6 million years ago. Another recent study attempted to link this extinction (and that of other marine species) with a supernova known to have occurred at about this time.

However, a team of researchers led by vertebrate paleontologist Robert Boessenecker with the College of Charleston, Charleston, South Carolina, noted that in many places there were problems with the data regarding individual fossils in the study estimating the extinction date.

In the new study, the researchers reported every fossil occurrence of O. megalodon from the densely sampled rock record of California and Baja California (Mexico) in order to estimate the extinction.

Besides Boessenecker, the research team included Dana Ehret, of New Jersey State Museum; Douglas Long, of the California Academy of Sciences; Morgan Churchill, of the University of Wisconsin Oshkosh; Evan Martin, of the San Diego Natural History Museum; and Sarah Boessenecker, of the University of Leicester, United Kingdom.

They found that genuine fossil occurrences were present until the end of the early Pliocene epoch, 3.6 million years ago. All later fossils either had poor data provenance and likely came from other fossil sites or showed evidence of being eroded from older deposits. Until 3.6 million years ago, O. megalodon had a continuous fossil record on the West Coast.

“We used the same worldwide dataset as earlier researchers but thoroughly vetted every fossil occurrence, and found that most of the dates had several problems-fossils with dates too young or imprecise, fossils that have been misidentified, or old dates that have since been refined by improvements in geology; and we now know the specimens are much younger,” Boessenecker said.

“After making extensive adjustments to this worldwide sample and statistically re-analyzing the data, we found that the extinction of O. megalodon must have happened at least one million years earlier than previously determined.”

This is a substantial adjustment as it means that O. megalodon likely went extinct long before a suite of strange seals, walruses, sea cows, porpoises, dolphins and whales all disappeared sometime about 1-2.5 million years ago.

“The extinction of O. megalodon was previously thought to be related to this marine mass extinction-but in reality, we now know the two are not immediately related,” Boessenecker said.

It also is further unclear if this proposed mass extinction is actually an extinction, as marine mammal fossils between 1 and 2 million years old are extraordinarily rare-giving a two-million- year-long period of “wiggle room.”

“Rather, it is possible that there was a period of faunal turnover (many species becoming extinct and many new species appearing) rather than a true immediate and catastrophic extinction caused by an astronomical cataclysm like a supernova,” Boessenecker said.

The researchers speculate that competition with the newly evolved modern great white shark (Carcharodon carcharias) is a more likely reason for megalodon’s extinction.

Great whites first show up with serrated teeth about 6 million years ago and only in the Pacific; by 4 million years ago, they are finally found worldwide.

“We propose that this short overlap (3.6-4 million years ago) was sufficient time for great white sharks to spread worldwide and outcompete O. megalodon throughout its range, driving it to extinction-rather than radiation from outer space,” Boessenecker said.

Reference:
Robert W. Boessenecker, Dana J. Ehret, Douglas J. Long, Morgan Churchill, Evan Martin, Sarah J. Boessenecker. The Early Pliocene extinction of the mega-toothed shark Otodus megalodon: a view from the eastern North Pacific. PeerJ, 2019; 7: e6088 DOI: 10.7717/peerj.6088

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

Neanderthal footprints found in Gibraltar

The place where the footprint was found
The place where the footprint was found. Credit: Universdad de Sevilla

The international journal Quaternary Science Reviews has just published a paper which has involved the participation of Gibraltarian scientists from The Gibraltar National Museum alongside colleagues from Spain, Portugal and Japan. The results which have been published come from an area of the Catalan Bay Sand Dune.

This work started ten years ago, when the first dates using the OSL method were obtained. It is then that the first traces of footprints left by vertebrates were found. In subsequent years the successive natural collapse of sand has revealed further material and has permitted a detailed study including new dates.

The sand sheets in the rampant dunes above Catalan Bay are a relic of the last glaciation, when sea level was up to 120 metres below present levels and a great field of dunes extended eastwards from the base of the Rock. The identified footprints correspond to species which are known, from fossil material, to have inhabited Gibraltar. The identified footprints correspond to Red Deer, Ibex, Aurochs, Leopard and Straight-tusked Elephant. In addition the scientists have found the footprint of a young human (106-126 cm in height), possibly Neanderthal, which dates to around 29 thousand years ago. It would coincide with late Neanderthal dates from Gorham’s Cave.

If confirmed to be Neanderthal, these dunes would become only the second site in the world with footprints attributed to these humans, the other being Vartop Cave in Romania. These findings add further international importance to the Gibraltar Pleistocene heritage, declared of World Heritage Value in 2016.

The research was supported by HM Government of Gibraltar under the Gibraltar Caves Project and the annual excavations in the Gibraltar Caves, with additional support to the external scientists from the Spanish EU project MICINN-FEDER: CGL2010-15810/BTE.

Minister for Heritage John Cortes MP commented, “This is extraordinary research and gives us an incredible insight into the wildlife community of Gibraltar’s past. We should all take a moment to imagine the scene when these animals walked across our landscape. It helps us understand the importance of looking after our heritage. I congratulate the research team on uncovering this fascinating, hidden evidence of our Rock’s past.”

Reference:
Fernando Muñiz, Luis M. Cáceres, Joaquín Rodríguez-Vidal, Carlos Neto de Carvalho, João Belo, Clive Finlayson, Geraldine Finlayson, Stewart Finlayson, Tatiana Izquierdo, Manuel Abad, Francisco J. Jiménez-Espejo, Saiko Sugisaki, Paula Gómez, Francisco Ruiz. Following the last Neanderthals: Mammal tracks in Late Pleistocene coastal dunes of Gibraltar (S Iberian Peninsula). Quaternary Science Reviews, 2019; DOI: 10.1016/j.quascirev.2019.01.013

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

Life thrived on Earth 3.5 billion years ago

Electron microscopy image of microbial cells which respire sulfate.
Electron microscopy image of microbial cells which respire sulfate. Credit: Guy Perkins and Mark Ellisman, National Center for Microscopy and Imaging Research

3.5 billion years ago Earth hosted life, but was it barely surviving, or thriving? A new study carried out by a multi institutional team with leadership including the Earth-Life Science Institute (ELSI) of Tokyo Institute of Technology (Tokyo Tech) provides new answers to this question. Microbial metabolism is recorded in billions of years of sulfur isotope ratios that agree with this study’s predictions, suggesting life throve in the ancient oceans. Using this data, scientists can more deeply link the geochemical record with cellular states and ecology.

Scientists want to know how long life has existed on Earth. If it has been around for almost as long as the planet, this suggests it is easy for life to originate and life should be common in the Universe. If it takes a long time to originate, this suggests there were very special conditions that had to occur. Dinosaurs, whose bones are presented in museums around the world, were preceded by billions of years by microbes. While microbes have left some physical evidence of their presence in the ancient geological record, they do not fossilize well, thus scientists use other methods for understanding whether life was present in the geological record.

Presently, the oldest evidence of microbial life on Earth comes to us in the form of stable isotopes. The chemical elements charted on the periodic are defined by the number of protons in their nuclei, for example, hydrogen atoms have one proton, helium atoms have two, carbon atoms contain six. In addition to protons, most atomic nuclei also contain neutrons, which are about as heavy as protons, but which don’t bear an electric charge. Atoms which contain the same number of protons, but variable numbers of neutrons are known as isotopes. While many isotopes are radioactive and thus decay into other elements, some do not undergo such reactions; these are known as “stable” isotopes. For example, the stable isotopes of carbon include carbon 12 (written as 12C for short, with 6 protons and 6 neutrons) and carbon 13 (13C, with 6 protons and 7 neutrons).

All living things, including humans, “eat and excrete.” That is to say, they take in food and expel waste. Microbes often eat simple compounds made available by the environment. For example, some are able to take in carbon dioxide (CO2) as a carbon source to build their own cells. Naturally occurring CO2 has a fairly constant ratio of 12C to 13C. However, 12CO2 is about 2 % lighter than 13CO2, so 12CO2 molecules diffuse and react slightly faster, and thus the microbes themselves become “isotopically light,” containing more 12C than 13C, and when they die and leave their remains in the fossil record, their stable isotopic signature remains, and is measurable. The isotopic composition, or “signature,” of such processes can be very specific to the microbes that produce them.

Besides carbon there are other chemical elements essential for living things. For example, sulfur, with 16 protons, has three naturally abundant stable isotopes, 32S (with 16 neutrons), 33S (with 17 neutrons) and 34S (with 18 neutrons). Sulfur isotope patterns left behind by microbes thus record the history of biological metabolism based on sulfur-containing compounds back to around 3.5 billion years ago. Hundreds of previous studies have examined wide variations in ancient and contemporary sulfur isotope ratios resulting from sulfate (a naturally occurring sulfur compound bonded to four oxygen atoms) metabolism. Many microbes are able to use sulfate as a fuel, and in the process excrete sulfide, another sulfur compound. The sulfide “waste” of ancient microbial metabolism is then stored in the geological record, and its isotope ratios can be measured by analyzing minerals such as the FeS2 mineral pyrite.

This new study reveals a primary biological control step in microbial sulfur metabolism, and clarifies which cellular states lead to which types of sulfur isotope fractionation. This allows scientists to link metabolism to isotopes: by knowing how metabolism changes stable isotope ratios, scientists can predict the isotopic signature organisms should leave behind. This study provides some of the first information regarding how robustly ancient life was metabolizing. Microbial sulfate metabolism is recorded in over a three billion years of sulfur isotope ratios that are in line with this study’s predictions, which suggest life was in fact thriving in the ancient oceans. This work opens up a new field of research, which ELSI Associate Professor Shawn McGlynn calls “evolutionary and isotopic enzymology.” Using this type of data, scientists can now proceed to other elements, such as carbon and nitrogen, and more completely link the geochemical record with cellular states and ecology via an understanding of enzyme evolution and Earth history.

Reference:
Min Sub Sim, Hideaki Ogata, Wolfgang Lubitz, Jess F. Adkins, Alex L. Sessions, Victoria J. Orphan, Shawn E. McGlynn. Role of APS reductase in biogeochemical sulfur isotope fractionation. Nature Communications, 2019; 10 (1) DOI: 10.1038/s41467-018-07878-4

Note: The above post is reprinted from materials provided by Tokyo Institute of Technology.

Fate of the subducted oceanic crust revealed by laboratory experiments

subducted oceanic crust inferred from this study.
A schematic image of subducted oceanic crust inferred from this study. Basalt and harzburgite layers of the oceanic crust accumulate beneath and above the 660 km discontinuity, respectively. Credit: Ehime University

Professor Tetsuo Irifune of the Geodynamics Research Center (GRC) of Ehime University heads a research group investigating the Earth’s interior by means of experiments at extreme pressures and temperatures, simulating those expected in the deepest regions of our planet.

Using a combination of ultrasonic techniques and a large volume press apparatus, GRC researchers were successful in measuring the sound velocities of CaSiO3 perovskite (CaPv), an important mineral of the mantle at depths below 560 km. This result allowed them to directly interpret seismic observations by a comparison with their velocity profiles obtained in the laboratory, and derived some composition models for the regions across the 660 km depth discontinuity that marks the boundary between the upper and lower mantle.

The scientific article that presents their results was published on January 10 in the journal Nature.

CaPv constitutes 7-10 vol% of the pyrolitic mantle and up to 30 vol% of subducted basaltic rocks below ~560 km depth and therefore is an important constituent mineral in both the mantle transition region (MTR; 410-660 km in depth) and lower mantle (660-2900 km in depth). CaPv also plays an important role in immobilizing heavy elements such as rare earth elements or actinides in the mantle due to its large calcium site, which can easily accommodate such large elements. But despite such importance, no measurements of sound velocities have been made CaPv at high temperatures, because this phase is unstable at ambient conditions and hence there was no adequate sample for such measurements.

“Because CaPv is only stable at pressure and temperature conditions of the mantle, we designed an experiment that allows us to synthesize this phase with the adequate shape and dimension under high pressure, then subsequently send an acoustic wave directly into the pressurized sample. Using this new approach, we can study high-pressure minerals, which are not stable at atmospheric conditions, such as CaPv.” says Steeve Gréaux, the researcher leading this project.

Professor Irifune and his team already demonstrated in 2008, that pyrolite, a hypothetical rock composition derived as a mixture of basalt and peridotite agree well with geophysical observations at depths down to 560 km, which was also reported in Nature. However, at that time, they could not draw further conclusions at depths lower than 560 km because there was no available data on CaPv. Their 2019 results became the last piece of a puzzle and allowed them to complete their hypotheses for the seismic structure of the mantle in between the depths of 560 km and 800 km.

“We did find that the cubic form of CaPv, which is most likely to be present in the mantle, has lower velocities than what was formerly predicted by theoretical studies. This result refutes previous models that proposed formation of CaPv in pyrolite could explain the steep velocity gradient above a depth of 660 km. On the other hand, it is in good agreement with a former study proposing the presence of basalts beneath a depth of 660 km on the basis of density measurements.” says Tetsuo Irifune.

These new results indeed show that the presence of subducted oceanic crust can explain the magnitude of the reduction of shear velocity below a depth of 660 km, as observed beneath North America. Incidentally, the model they proposed is very consistent with the recent discovery, in 2018, of CaPv in a natural diamond, which provides evidence for the presence of oceanic crust material in the uppermost lower mantle. It is also compatible with global-scale geodynamics calculations that predicted basalt enrichment beneath 660 km would stabilize the subducted slab in this region.

The authors conclude “CaPv, which was once called “invisible” in the lower mantle as this phase was predicted to have velocities similar to those of the most abundant mineral (MgSiO3 perovskite or bridgmanite) in fact holds velocities substantially lower than those of bridgmanite at depths of 660-800 km, which should greatly contribute to tracing the existence and recycling of the former oceanic crust in the Earth’s lower mantle..”

Reference:
Steeve Gréaux, Tetsuo Irifune, Yuji Higo, Yoshinori Tange, Takeshi Arimoto, Zhaodong Liu, Akihiro Yamada. Sound velocity of CaSiO3 perovskite suggests the presence of basaltic crust in the Earth’s lower mantle. Nature, 2019; 565 (7738): 218 DOI: 10.1038/s41586-018-0816-5

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

New oviraptorosaur species discovered in Mongolia

Gobiraptor reconstruction.
Gobiraptor reconstruction. Credit: Do Yoon Kim (2019)

A new oviraptorosaur species from the Late Cretaceous was discovered in Mongolia, according to a study published in February 6, 2019 in the open-access journal PLOS ONE by Yuong-Nam Lee from Seoul National University, South Korea, and colleagues.

Oviraptorosaurs were a diverse group of feathered, bird-like dinosaurs from the Cretaceous of Asia and North America. Despite the abundance of nearly complete oviraptorosaur skeletons discovered in southern China and Mongolia, the diet and feeding strategies of these toothless dinosaurs are still unclear. In this study, Lee and colleagues described an incomplete skeleton of an oviraptorosaur found in the Nemegt Formation of the Gobi desert of Mongolia.

The new species, named Gobiraptor minutus, can be distinguished from other oviraptorosaurs in having unusual thickened jaws. This unique morphology suggests that Gobiraptor used a crushing feeding strategy, supporting previous hypotheses that oviraptorosaurs probably fed on hard food items such as eggs, seeds or hard-shell mollusks. Histological analyses of the femur revealed that the specimen likely belonged to a very young individual.

The finding of a new oviraptorosaur species in the Nemegt Formation, which consists mostly of river and lake deposits, confirms that these dinosaurs were extremely well adapted to wet environments. The authors propose that different dietary strategies may explain the wide taxonomic diversity and evolutionary success of this group in the region.

The authors add: “A new oviraptorid dinosaur Gobiraptor minutus gen. et sp. nov. from the Upper Cretaceous Nemegt Formation is described here based on a single holotype specimen that includes incomplete cranial and postcranial elements. The unique morphology of the mandible and the accordingly inferred specialized diet of Gobiraptor also indicate that different dietary strategies may be one of important factors linked with the remarkably high diversity of oviraptorids in the Nemegt Basin.”

Reference:
Sungjin Lee, Yuong-Nam Lee, Anusuya Chinsamy, Junchang Lü, Rinchen Barsbold, Khishigjav Tsogtbaatar. A new baby oviraptorid dinosaur (Dinosauria: Theropoda) from the Upper Cretaceous Nemegt Formation of Mongolia. PLOS ONE, 2019; 14 (2): e0210867 DOI: 10.1371/journal.pone.0210867

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

Earliest known seed-eating perching bird discovered in Fossil Lake, Wyoming

Eofringillirostrum boudreauxi
The 52-million-year-old fossil of Eofringillirostrum boudreauxi, the earliest known perching bird with a beak for eating seeds. Credit: Copyright Lance Grande, Field Museum

Most of the birds you’ve ever seen — sparrows, finches, robins, crows — have one crucial thing in common: they’re all what scientists refer to as perching birds, or “passerines.” The passerines make up about 6,500 of the 10,000 bird species alive today. But while they’re everywhere now, they were once rare, and scientists are still learning about their origins. In a new paper in Current Biology, researchers have announced the discovery of one of the earliest known passerine birds, from 52 million years ago.

“This is one of the earliest known perching birds. It’s fascinating because passerines today make up most of all bird species, but they were extremely rare back then. This particular piece is just exquisite,” says Field Museum Neguanee Distinguished Service Curator Lance Grande, an author of the paper. “It is a complete skeleton with the feathers still attached, which is extremely rare in the fossil record of birds.”

The paper describes two new fossil bird species — one from Germany that lived 47 million years ago, and another that lived in what’s now Wyoming 52 million years ago, a period known as the Early Eocene. The Wyoming bird, Eofringillirostrum boudreauxi, is the earliest example of a bird with a finch-like beak, similar to today’s sparrows and finches. This legacy is reflected in its name; Eofringilllirostrum means “dawn finch beak.” (Meanwhile, boudreauxi is a nod to Terry and Gail Boudreaux, longtime supporters of science at the Field Museum.)”

The fossil birds’ finch-like, thick beaks hint at their diet. “These bills are particularly well-suited for consuming small, hard seeds,” says Daniel Ksepka, the paper’s lead author, curator at the Bruce Museum in Connecticut. Anyone with a birdfeeder knows that lots of birds are nuts for seeds, but seed-eating is a fairly recent biological phenomenon. “The earliest birds probably ate insects and fish, some may have been eating small lizards,” says Grande. “Until this discovery, we did not know much about the ecology of early passerines. E. boudreauxi gives us an important look at this.”

“We were able to show that a comparable diversity of bill types already developed in the Eocene in very early ancestors of passerines,” says co-author Gerald Mayr of the Senckenberg Research Institute in Frankfurt. “The great distance between the two fossil sites implies that these birds were widespread during the Eocene, while the scarcity of known fossils suggests a rather low number of individuals,” adds Ksepka.

While passerine birds were rare 52 million years ago, E. boudreauxi had the good luck to live and die near Fossil Lake, a site famous for perfect fossilization conditions.

“Fossil Lake is a really graphic picture of an entire community locked in stone — it has everything from fishes and crocs to insects, pollen, reptiles, birds, and early mammals,” says Grande. “We have spent so much time excavating this locality, that we have a record of even the very rare things.”

Grande notes that Fossil Lake provides a unique look at the ancient world — one of the most detailed pictures of life on Earth after the extinction of the dinosaurs (minus the birds) 65 million years ago. “Knowing what happened in the past gives us a better understanding of the present and may help us figure out where we are going for the future.”

With that in mind, Grande plans to continue his exploration of the locale. “I’ve been going to Fossil Lake every year for the last 35 years, and finding this bird is one of the reasons I keep going back. It’s so rich,” says Grande. “We keep finding things that no one’s ever seen before.”

Reference:
Daniel T. Ksepka, Lance Grande, Gerald Mayr. Oldest Finch-Beaked Birds Reveal Parallel Ecological Radiations in the Earliest Evolution of Passerines. Current Biology, 2019 DOI: 10.1016/j.cub.2018.12.040

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

Unusual microbes hold clues to early life

Scientists use the deep-diving robot Jason to collect water samples from oceanic crust at a subseafloor observatory off the coast of Washington. A recent study found that a group of unusual microbes living below the seafloor provides clues to the evolution of life on Earth, and potentially other planets. Credit: Woods Hole Oceanographic Institution, courtesy of University of California, Santa Cruz, US National Science Foundation, ROV Jason dive J2-711, 2013, AT26-03 cruise chief scientist Andrew Fisher
Scientists use the deep-diving robot Jason to collect water samples from oceanic crust at a subseafloor observatory off the coast of Washington. A recent study found that a group of unusual microbes living below the seafloor provides clues to the evolution of life on Earth, and potentially other planets. Credit: Woods Hole Oceanographic Institution, courtesy of University of California, Santa Cruz, US National Science Foundation, ROV Jason dive J2-711, 2013, AT26-03 cruise chief scientist Andrew Fisher

A new study has revealed how a group of deep-sea microbes provides clues to the evolution of life on Earth, according to a recent paper in The ISME Journal. Researchers used cutting-edge molecular methods to study these microbes, which thrive in the hot, oxygen-free fluids that flow through Earth’s crust.

Called Hydrothermarchaeota, this group of microbes lives in such an extreme environment that they have never been cultivated in a laboratory for study. A research team from Bigelow Laboratory for Ocean Sciences, the University of Hawai’i at Manoa, and the Department of Energy Joint Genome Institute bypassed the problem of cultivation with genetic sequencing methods called genomics, a suite of novel techniques used to sequence large groups of genetic information. They found that Hydrothermarchaeota may obtain energy by processing carbon monoxide and sulfate, which is an overlooked metabolic strategy. The microbes use energy from this process to grow as a form of chemosynthesis.

“The majority of life on Earth is microbial, and most microbes have never been cultivated,” said Beth Orcutt, a senior research scientist at Bigelow Laboratory and one of the study’s senior authors. “These findings emphasize why single cell genomics are such important tools for discovering how a huge proportion of life functions.”

Analyzing Hydrothermarchaeota genomes revealed that these microbes belong to the group of single-celled life known as archaea and evolved early in the history of life on Earth — as did their unusual metabolic processes. These observations suggest that the subsurface ocean crust is an important habitat for understanding how life evolved on Earth, and potentially other planets.

The researchers also found genetic evidence that Hydrothermarchaeota have the ability to move on their own. Motility offers a valuable survival strategy for the extreme environment they call home, which has a limited supply of nutrients essential to life.

“Studying these unique microbes can give us insights into both the history of Earth and the potential strategies of life on other planets,” said Stephanie Carr, first author on the paper and a former postdoctoral researcher with Orcutt who is now an assistant professor at Hartwick College. “Their survival strategies make them incredibly versatile, and they play an important, overlooked role in the subsurface environments where they live.”

In 2011, Orcutt and other project scientists sailed to the flank of the Juan de Fuca Ridge, a mid-ocean ridge off the coast of Washington where two ocean plates are separating and generating new oceanic crust. They used Woods Hole Oceanographic Institution’s deep-diving robot Jason to travel 2.6 km to the seafloor and collect samples of the fluid that flows through the deep crust.

These crustal fluids contained microbes that had never before been studied. Working in partnership with the Department of Energy Joint Genome Institute, the researchers sorted and analyzed the microbes in the Single Cell Genomics Center at Bigelow Laboratory. This cutting-edge research facility is directed by Ramunas Stepanauskas, a senior research scientist and study author. The project team also analyzed the microbes using metagenomics, a technique that extracts genomic information directly from environmental samples. These analyses yielded insights into the genetic blueprints of Hydrothermarchaeota, their relationship to other archaea, and the strategies they have evolved to survive in the subseafloor.

The researchers will build upon this discovery when they return to the Juan de Fuca Ridge in May 2019 to continue investigating the extreme microbes thriving below the seafloor. Orcutt will lead a cruise using ROV Jason with this team of researchers to further explore the subseafloor environment, leveraging funding from the National Science Foundation and NASA.

“The microbes living ‘buried alive’ below the seafloor are really intriguing to us, since they can survive on low amounts of energy,” Orcutt said. “We hope that our experiments on these weird microbes can show how they do this, so we can imagine how life might exist on other planets.”

Reference:
Stephanie A. Carr, Sean P. Jungbluth, Emiley A. Eloe-Fadrosh, Ramunas Stepanauskas, Tanja Woyke, Michael S. Rappé, Beth N. Orcutt. Carboxydotrophy potential of uncultivated Hydrothermarchaeota from the subseafloor crustal biosphere. The ISME Journal, 2019; DOI: 10.1038/s41396-019-0352-9

Note: The above post is reprinted from materials provided by Bigelow Laboratory for Ocean Sciences.

Researchers help define Southern Ocean’s geological features

pillow basalts from undersea volcanic eruptions,
Pillow basalts from undersea volcanic eruptions. Credit: National Science Foundation

New data collected by University of Wyoming researchers and others point to a newly defined mantle domain in a remote part of the Southern Ocean.

UW Department of Geology and Geophysics Professor Ken Sims and recent Ph.D. graduate Sean Scott are co-authors of an article, “An isotopically distinct Zealandia-Antarctic mantle domain in the Southern Ocean,” published by the scientific journal Nature Geoscience in January.

“The Australian-Antarctic Ridge is the remotest mid-ocean ridge in the world’s oceans and one of the last explored ridge segments, and, lo and behold, our isotope measurements of the samples we collected provided us with quite a surprise — an entirely new domain in the Earth’s mantle,” Sims says.

The two were part of a group investigating the Australian-Antarctic Ridge (AAR) that included researchers from the United States, South Korea and France. Known as the last gap in the mapping and sampling of seafloor spreading centers, AAR is a 1,200-mile expanse in the most remote parts of the ocean ridge system. Specifically, the team was looking to resolve questions surrounding the boundaries of Earth’s mantle domains as seen in ocean basalt formations created during mantle melting.

Those basalt formations are pushed up from the Earth’s mantle beneath the Indian and Pacific oceans through the ridges and have distinct isotopic compositions. That has created a long-accepted boundary at the Australian-Antarctic Discordance along the Southeast Indian Ridge. This boundary has been widely used to place constraints on large-scale patterns of the mantle flow and composition in the Earth’s upper mantle. However, sampling between the Indian and Pacific ridges was lacking, because of difficulty in obtaining samples.

Now, Sims, Scott and company present data from the region that show the ridge has isotopic compositions distinct from both the Pacific and Indian mantle domains. The data define a separate Zealandia-Antarctic domain that appears to have formed in response to the deep mantle upwelling and ensuing volcanism that led to the breakup of ancient supercontinent Gondwana around 90 million years ago. The Zealandia-Antarctic domain currently persists at the margins of the Antarctic continent.

The group surmises that the relatively shallow depths of the AAR may be the result of this deep mantle upwelling, and large offset transformations to the east may be its boundary with the Pacific domain.

Reference:
Sung-Hyun Park, Charles H. Langmuir, Kenneth W. W. Sims, Janne Blichert-Toft, Seung-Sep Kim, Sean R. Scott, Jian Lin, Hakkyum Choi, Yun-Seok Yang, Peter J. Michael. An isotopically distinct Zealandia–Antarctic mantle domain in the Southern Ocean. Nature Geoscience, 2019; DOI: 10.1038/s41561-018-0292-4

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

T. rex possessed a unique flexible skull

T. rex had an unusually flexible skull. Credit: Senckenberg
T. rex had an unusually flexible skull. Credit: Senckenberg

Senckenberg scientist Ingmar Werneburg, together with an international team, re-examined the skull structure of Tyrannosaurus rex. Using an “anatomical network analysis,” the researchers showed that the carnivorous dinosaur had an extremely flexible skull structure. Different bone modules led to a highly flexible muzzle that aided in tearing apart prey animals. The study was published today in the journal Scientific Reports.

Tyrannosaurus rex – the “King of the Tyrant Lizards” – owes its name in part to its impressive teeth and skull. The latter was subject to closer scrutiny by an international team of scientists from Germany, Switzerland, Great Britain, Spain, and the USA. “We compared the skull of T. rex with the skull construction of modern terrestrial vertebrates and used an anatomical network analysis to examine which skull bones are connected to each other,” explains the study’s lead author, PD Dr. Ingmar Werneburg of the Senckenberg Centre for Human Evolution and Palaeoenvironment at the University of Tübingen.

The analysis revealed that, among all groups of animals analyzed in the study, the large carnivore possessed the highest number of “skull modules” – skull bones that form units with adjacent bones. This resulted in a particularly high mobility of the skull. “We were most surprised to discover the presence of separate upper and lower muzzle modules, which probably could move independent of each other,” adds the scientist from Tübingen.

The researchers hypothesize that the feeding habits of Tyrannosaurus rex may have led to the complexity of its skull. The division into a lower and an upper muzzle module may have provided a certain amount of flexibility to the tooth-bearing part of the muzzle that aided in the forceful tearing of prey animals. “This trait, combined with teeth anchored within tooth pockets and two large temporal fenestrae (openings) as attachment points for the strong jaw muscles, made T. rex the ‘ideal carnivore,’ adds Werneburg in summary.

Reference:
Ingmar Werneburg et al. Unique skull network complexity of Tyrannosaurus rex among land vertebrates, Scientific Reports (2019). DOI: 10.1038/s41598-018-37976-8

Note: The above post is reprinted from materials provided by Senckenberg Research Institute and Natural History Museum.

First discovered fossil feather did not belong to iconic bird Archaeopteryx

The isolated Archaeopteryx feather is the first fossil feather ever discovered. Top image, the feather as it looks today under white light. Middle image, the original drawing from 1862 by Hermann von Meyer. Bottom image, Laser-Stimulated Fluorescence (LSF) showing the halo of the missing quill. Scale bar is 1cm. Credit: Copyright The University of Hong Kong
The isolated Archaeopteryx feather is the first fossil feather ever discovered. Top image, the feather as it looks today under white light. Middle image, the original drawing from 1862 by Hermann von Meyer. Bottom image, Laser-Stimulated Fluorescence (LSF) showing the halo of the missing quill. Scale bar is 1cm. Credit: Copyright The University of Hong Kong

A 150-year-old fossil feather mystery has been solved by an international research team including Dr Michael Pittman from the Department of Earth Sciences, The University of Hong Kong. Dr Pittman and his colleagues applied a novel imaging technique, Laser-Stimulated Fluorescence (LSF), revealing the missing quill of the first fossil feather ever discovered, dethroning an icon in the process.

This fossil feather was found in the Solnhofen area of southern Germany in 1861. The isolated feather was used to name the iconic fossil bird Archaeopteryx and was closely identified with its skeletons. Unlike the feather impressions preserved in some Archaeopteryx fossils, the isolated feather is preserved as a dark film. The detailed 1862 description of the feather mentions a rather long quill visible on the fossil, but this is unseen today. Even recent x-ray fluorescence and UV imaging studies did not end the debate of the “missing quill.” The original existence of this quill has therefore been debated and it was unclear if the single feather represented a primary, secondary, or primary covert feather.

The results of this study are described in the journal Scientific Reports, and underscore the potential and scientific importance of Laser-Stimulated Fluorescence, which is being developed by Thomas G Kaye of the Foundation for Scientific Advancement, USA and Dr Pittman. “My imaging work with Tom Kaye demonstrates that important discoveries remain to be made even in the most iconic and well-studied fossils,” says Dr Pittman.

With the help of the LSF images, the team finally solved the 150-year-old missing quill mystery. The now completely visible feather allowed detailed comparisons with the feather impressions of Archaeopteryx and with living birds. Before this LSF work, the feather was thought to represent a primary covert from Archaeopteryx, but this study shows that it differs from coverts of modern birds by lacking a distinct s-shaped centerline. The team also ruled out that the feather represented a primary, secondary, or tail feather of Archaeopteryx. Instead, the new data indicates that the isolated feather came from an unknown feathered dinosaur and that its attribution to Archaeopteryx was wrong. “It is amazing that this new technique allows us to resolve the 150-year-old mystery of the missing quill,” says Daniela Schwarz, co-author in the study and curator for the fossil reptiles and bird collection of the Museum für Naturkunde, Berlin. This discovery also demonstrates that the diversity of feathered dinosaurs was likely higher around the ancient Solnhofen Archipelago than previously thought. “The success of the LSF technique here is sure to lead to more discoveries and applications in other fields. But, you’ll have to wait and see what we find next!” added Tom Kaye, the study’s lead author.

Reference:
Thomas G. Kaye, Michael Pittman, Gerald Mayr, Daniela Schwarz, Xing Xu. Detection of lost calamus challenges identity of isolated Archaeopteryx feather. Scientific Reports, 2019; 9 (1) DOI: 10.1038/s41598-018-37343-7

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

These strange fossils are closely related to sea urchins

Stunningly well-preserved fossilized soft tissues of a stylophoran have recently been discovered
Stunningly well-preserved fossilized soft tissues of a stylophoran have recently been discovered. Shown here is the reconstruction of an individual of the stylophoran genus Thoralicystis. Stylophorans measured 0.5 to 4 cm and had flat, massive bodies or tests with paddle-like extensions, analogous to snowshoes, which allowed them to stay over soft seafloors. Credit: Rich Mooi / California Academy of Science

Just a few centimeters long, these animals thrived in the ocean roughly half a billion years ago. Because of their odd morphology, scientists have long struggled to find their branch on the tree of life.

Was their long appendage similar to a tail? That would make them ancestors of the vertebrates. However, their skeletons are made up of many calcite plates, suggestive of the bodies of echinoderms like sea urchins and starfish, even though they lack the characteristic symmetry of these animals.

A team led by Bertrand Lefebvre, a CNRS researcher at the Laboratoire de Géologie de Lyon, could finally settle this 150-year-old debate, using exceptionally preserved fossils from the Bou Izargane excavation in Morocco. Very unusually, the soft tissues of the fossilized creatures were preserved as pyrite, a ferrous mineral. By mapping the distribution of iron within the fossils, the researchers were able to clarify the fine structure of the appendage, which turns out to be comparable to that of a starfish arm. So these organisms had neither a head nor a tail, but rather a feeding arm.

Reference:
Bertrand Lefebvre et al. Exceptionally preserved soft parts in fossils from the Lower Ordovician of Morocco clarify stylophoran affinities within basal deuterostomes, Geobios (2018). DOI: 10.1016/j.geobios.2018.11.001

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

Earthquake with magnitude 7.5 in Indonesia—an unusual and steady speed

On the area map on the left, the colored background is the ground displacement induced by the Palu earthquake and the thin black line is the fault, both derived from satellite radar images. The black dot is the city of Palu. The circles are spots that radiated waves during the earthquake; their color indicates time (blue at the beginning, red at the end). The right figure shows the timing and position of these earthquake radiators. Their alignment indicates a steady earthquake speed of about 4.1 km/s Credit: © Han Bao et al., Nature Geoscience
On the area map on the left, the colored background is the ground displacement induced by the Palu earthquake and the thin black line is the fault, both derived from satellite radar images. The black dot is the city of Palu. The circles are spots that radiated waves during the earthquake; their color indicates time (blue at the beginning, red at the end). The right figure shows the timing and position of these earthquake radiators. Their alignment indicates a steady earthquake speed of about 4.1 km/s Credit: © Han Bao et al., Nature Geoscience

An international team of researchers from the French National Research Institute for Sustainable Development (IRD-France), Université Côte d”Azur, University of California Los Angeles and California Institute of Technology has determined the propagation speed of the 7.5 magnitude earthquake which occurred in Indonesia in September 2018: 4.1 km/s along 150 km. The results, which also shed light on the earthquake rupture path, are published on February 4th in Nature Geoscience.

Earthquakes happen when rocks on either side of a tectonic fault shift suddenly in opposite directions. Two main seismic waves that carry out shaking of a breaking fault are S-waves, which shear rocks and propagate at about 3.5 km/s, and P-waves, which compress rocks and propagate faster, at about 5 km/s.

Geophysical observations show that the speed at which an earthquake ruptures along the fault is either slower than S-waves or almost as fast as P-waves. The latter, so-called supershear earthquakes, occur very rarely and can produce very strong shaking. Only a few have been observed, and they happen on faults that are remarkably straight, geological “superhighways” that present little obstacle to speeding earthquakes.

“Forbidden” speed range

In this study, the international team coordinated by Jean-Paul Ampuero, seismologist at IRD and Université Côte d”Azur, analysed the 7.5 magnitude earthquake that rocked the Sulawesi island in Indonesia on September 28th, devastating Palu’s region.

The impact of the event—more than 2,000 deaths—was aggravated by a devastating sequence of secondary effects, involving soil liquefaction, landslides and a tsunami.

Thanks to a high-resolution analysis of seismological data, researchers identified the propagation speed of the earthquake: 4.1 km/s, an unusual speed, between the speed of S- and P-waves. “This is the first time we observed this speed so steadily,” underlines Jean-Paul Ampuero. “This earthquake ran in the ‘forbidden’ speed range, and can be considered as a supershear event, even if it’s not as fast as previous ones.”

By analyzing optical and radar images recorded by satellites especially re-tasked to observe the earthquake aftermath, the researchers determined the path of the fault rupture. They found that the fault was not straight, but had at least two major bends, and left more than five meters of ground offset across the city of Palu. ” This path has major obstacles, which should have reduced the earthquake’s speed, but it stayed at 4.1 km/s along 150 km,” says Jean-Paul Ampuero.

Toward a better anticipation of future earthquakes

The findings challenge current views of earthquakes in ways that could help researchers and public authorities prepare better for future events. “In classical earthquake models, faults live in idealized intact rocks “, says Ampuero, ” but real faults are wrapped in a layer of rocks that have been fractured and softened by previous earthquakes. Steady rupture at speeds that are unexpected on intact rocks can actually happen on damaged rocks, simply because they have slower seismic wave speeds.”

The Palu earthquake may offer the first clear test of such recent models if followed up by studies of the structure of the fault and its zone of damaged rocks. Because the impact of an earthquake depends strongly on its speed, such studies on other faults around the world could anticipate earthquake effects better.

Future work may also determine if the speed of the Palu earthquake enhanced its cascading effects, by promoting coastal and submarine landslides that in turn contributed to the tsunami.

Reference:
Early and persistent supershear rupture of the 2018 magnitude 7.5 Palu earthquake, Nature Geoscience (2019). DOI: 10.1038/s41561-018-0297-z

Note: The above post is reprinted from materials provided by Institut de recherche pour le développement.

Researchers unearth an ice age in the African desert

The drumlins were formed by fast-moving ice floes instead of slow melting ice. Credit: WVU
The drumlins were formed by fast-moving ice floes instead of slow melting ice. Credit: WVU

A field trip to Namibia to study volcanic rocks led to an unexpected discovery by West Virginia University geologists Graham Andrews and Sarah Brown.

While exploring the desert country in southern Africa, they stumbled upon a peculiar land formation—flat desert scattered with hundreds of long, steep hills. They quickly realized the bumpy landscape was shaped by drumlins, a type of hill often found in places once covered in glaciers, an abnormal characteristic for desert landscapes.

“We quickly realized what we were looking at because we both grew up in areas of the world that had been under glaciers, me in Northern Ireland and Sarah in northern Illinois,” said Andrews, an assistant professor of geology. “It’s not like anything we see in West Virginia where we’re used to flat areas and then gorges and steep-sided valleys down into hollows.”

After returning home from the trip, Andrews began researching the origins of the Namibian drumlins, only to learn they had never been studied.

“The last rocks we were shown on the trip are from a time period when southern Africa was covered by ice,” Andrews said. “People obviously knew that part of the world had been covered in ice at one time, but no one had ever mentioned anything about how the drumlins formed or that they were even there at all.”

Andrews teamed up with WVU geology senior Andy McGrady to use morphometrics, or measurements of shapes, to determine if the drumlins showed any patterns that would reflect regular behaviors as the ice carved them.

While normal glaciers have sequential patterns of growing and melting, they do not move much, Andrews explained. However, they determined that the drumlins featured large grooves, which showed that the ice had to be moving at a fast pace to carve the grooves.

These grooves demonstrated the first evidence of an ice stream in southern Africa in the late Paleozoic Age, which occurred about 300 million years ago.

“The ice carved big, long grooves in the rock as it moved,” Andrews said. “It wasn’t just that there was ice there, but there was an ice stream. It was an area where the ice was really moving fast.”

McGrady used freely available information from Google Earth and Google Maps to measure their length, width and height.

“This work is very important because not much has been published on these glacial features in Namibia,” said McGrady, a senior geology student from Hamlin. “It’s interesting to think that this was pioneer work in a sense, that this is one of the first papers to cover the characteristics of these features and gives some insight into how they were formed.”

Their findings also confirm that southern Africa was located over the South Pole during this period.

“These features provide yet another tie between southern Africa and south America to show they were once joined,” Andrews said.

The study, “First description of subglacial megalineations from the late Paleozoic ice age in southern Africa” is published in the Public Library of Science’s PLOS ONE journal.

“This is a great example of a fundamental discovery and new insights into the climatic history of our world that remain to be discovered,” said Tim Carr, chair of the Department of Geology and Geography.

Reference:
Graham D. Andrews et al, First description of subglacial megalineations from the late Paleozoic ice age in southern Africa, PLOS ONE (2019). DOI: 10.1371/journal.pone.0210673

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

MERMAIDs reveal secrets from below the ocean floor

Floating seismometers dubbed MERMAIDs -- Mobile Earthquake Recording in Marine Areas by Independent Divers -- reveal that Galapagos volcanoes are fed by a mantle plume reaching 1,900 km deep. By letting their nine MERMAIDs float freely for two years, an international team of researchers created an artificial network of oceanic seismometers that could fill in one of the blank areas on the global geologic map, where otherwise no seismic information is available. Drifting a mile below the surface, MERMAIDs cover a large area. The red circles show where a MERMAID picked up a seismic signal. Credit: Courtesy of the researchers
Floating seismometers dubbed MERMAIDs — Mobile Earthquake Recording in Marine Areas by Independent Divers — reveal that Galapagos volcanoes are fed by a mantle plume reaching 1,900 km deep. By letting their nine MERMAIDs float freely for two years, an international team of researchers created an artificial network of oceanic seismometers that could fill in one of the blank areas on the global geologic map, where otherwise no seismic information is available. Drifting a mile below the surface, MERMAIDs cover a large area. The red circles show where a MERMAID picked up a seismic signal. Credit: Courtesy of the researchers

Seismologists use waves generated by earthquakes to scan the interior of our planet, much like doctors image their patients using medical tomography. Earth imaging has helped us track down the deep origins of volcanic islands such as Hawaii, and identify the source zones of deep earthquakes.

“Imagine a radiologist forced to work with a CAT scanner that is missing two-thirds of its necessary sensors,” said Frederik Simons, a professor of geosciences at Princeton. “Two-thirds is the fraction of the Earth that is covered by oceans and therefore lacking seismic recording stations. Such is the situation faced by seismologists attempting to sharpen their images of the inside of our planet.”

Some 15 years ago, when he was a postdoctoral researcher, Simons partnered with Guust Nolet, now the George J. Magee Professor of Geoscience and Geological Engineering, Emeritus, and they resolved to remediate this situation by building an undersea robot equipped with a hydrophone — an underwater microphone that can pick up the sounds of distant earthquakes whose waves deliver acoustic energy into the oceans through the ocean floor.

This week, Nolet, Simons and an international team of researchers published the first scientific results from the revolutionary seismic floats, dubbed MERMAIDs — Mobile Earthquake Recording in Marine Areas by Independent Divers.

The researchers, from institutions in the United States, France, Ecuador and China, found that the volcanoes on Galápagos are fed by a source 1,200 miles (1,900 km) deep, via a narrow conduit that is bringing hot rock to the surface. Such “mantle plumes” were first proposed in 1971 by one of the fathers of plate tectonics, Princeton geophysicist W. Jason Morgan, but they have resisted attempts at detailed seismic imaging because they are found in the oceans, rarely near any seismic stations.

MERMAIDs drift passively, normally at a depth of 1,500 meters — about a mile below the sea surface — moving 2-3 miles per day. When one detects a possible incoming earthquake, it rises to the surface, usually within 95 minutes, to determine its position with GPS and transmit the seismic data.

By letting their nine robots float freely for two years, the scientists created an artificial network of oceanic seismometers that could fill in one of the blank areas on the global geologic map, where otherwise no seismic information is available.

The unexpectedly high temperature that their model shows in the Galápagos mantle plume “hints at the important role that plumes play in the mechanism that allows the Earth to keep itself warm,” said Nolet.

“Since the 19th century, when Lord Kelvin predicted that Earth should cool to be a dead planet within a hundred million years, geophysicists have struggled with the mystery that the Earth has kept a fairly constant temperature over more than 4.5 billion years,” Nolet explained. “It could have done so only if some of the original heat from its accretion, and that created since by radioactive minerals, could stay locked inside the lower mantle. But most models of the Earth predict that the mantle should be convecting vigorously and releasing this heat much more quickly. These results of the Galápagos experiment point to an alternative explanation: the lower mantle may well resist convection, and instead only bring heat to the surface in the form of mantle plumes such as the ones creating Galápagos and Hawaii.”

To further answer questions on the heat budget of the Earth and the role that mantle plumes play in it, Simons and Nolet have teamed up with seismologists from the Southern University of Science and Technology (SUSTech) in Shenzhen, China, and from the Japan Agency for Marine-Earth Science and Technology (JAMSTEC). Together, and with vessels provided by the French research fleet, they are in the process of launching some 50 MERMAIDs in the South Pacific to study the mantle plume region under the island of Tahiti.

“Stay tuned! There are many more discoveries to come,” said professor Yongshun (John) Chen, a 1989 Princeton graduate alumnus who is head of the Department of Ocean Science and Engineering at SUSTech, which is leading the next phase of what they and their international team have called EarthScope-Oceans.

Reference:
Guust Nolet, Yann Hello, Suzan van der Lee, Sébastien Bonnieux, Mario C. Ruiz, Nelson A. Pazmino, Anne Deschamps, Marc M. Regnier, Yvonne Font, Yongshun J. Chen, Frederik J. Simons. Imaging the Galápagos mantle plume with an unconventional application of floating seismometers. Scientific Reports, 2019; 9 (1) DOI: 10.1038/s41598-018-36835-w

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

The 210-million-year-old Smok was crushing bones like a hyena

Coprolites, or fossil droppings, of the dinosaur-like archosaur Smok wawelski contain lots of chewed-up bone fragments. This led researchers at Uppsala University to conclude that this top predator was exploiting bones for salt and marrow, a behavior often linked to mammals but seldom to archosaurs. Credit: Martin Qvarnström
Coprolites, or fossil droppings, of the dinosaur-like archosaur Smok wawelski contain lots of chewed-up bone fragments. This led researchers at Uppsala University to conclude that this top predator was exploiting bones for salt and marrow, a behavior often linked to mammals but seldom to archosaurs. Credit: Martin Qvarnström

Coprolites, or fossil droppings, of the dinosaur-like archosaur Smok wawelski contain lots of chewed-up bone fragments. This led researchers at Uppsala University to conclude that this top predator was exploiting bones for salt and marrow, a behavior often linked to mammals but seldom to archosaurs.

Most predatory dinosaurs used their blade-like teeth to feed on the flesh of their prey, but they are commonly not thought to be much of bone crushers. The major exception is seen in the large tyrannosaurids, such as Tyrannosaurus rex, that roamed North America toward the end of the age of dinosaurs. The tyrannosaurids are thought to have been osteophagous (voluntarily exploiting bone) based on findings of bone-rich coprolites, bite-marked bones, and their robust teeth being commonly worn.

In a study published in Scientific Reports, researchers from Uppsala University were able to link ten large coprolites to Smok wawelski, a top predator of a Late Triassic (210 million year old) assemblage unearthed in Poland. This bipedal, 5-6 meters long animal lived some 140 million years before the tyrannosaurids of North America and had a T. rex-like appearance, although it is not fully clear whether it was a true dinosaur or a dinosaur-like precursor.

Three of the coprolites were scanned using synchrotron microtomography. This method has just recently been applied to coprolites and works somewhat like a CT scanner in a hospital, with the difference that the energy in the x-ray beams is much stronger. This makes it possible to visualize internal structures in fossils in three dimensions.

The coprolites were shown to contain up to 50 percent of bones from prey animals such as large amphibians and juvenile dicynodonts. Several crushed serrated teeth, probably belonging to the coprolite producer itself, were also found in the coprolites. This means that the teeth were repeatedly crushed against the hard food items (and involuntarily ingested) and replaced by new ones.

Further evidence for a bone-crushing behaviour can also be found in the fossils from the same bone beds in Poland. These include worn teeth and bone-rich fossil regurgitates from Smok wawelski, as well as numerous crushed or bite-marked bones.

Several of the anatomical characters related to osteophagy, such as a massive head and robust body, seem to be shared by S. wawelski and the tyrannosaurids, despite them being distantly related and living 140 million years apart. These large predators therefore seem to provide evidence of similar feeding adaptations being independently acquired at the beginning and end of the age of dinosaurs.

Reference:
Martin Qvarnström, Per E. Ahlberg, Grzegorz Niedźwiedzki. Tyrannosaurid-like osteophagy by a Triassic archosaur. Scientific Reports, 2019; 9 (1) DOI: 10.1038/s41598-018-37540-4

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

Ancient asteroid impacts played a role in creation of Earth’s future continents

A model for the compositional evolution of the early Earth's crust due to fractional crystallization of impact melt sheets followed by detachment and sinking of their dense primitive portions towards the crust-mantle boundary. Credit: Rais Latypov
A model for the compositional evolution of the early Earth’s crust due to fractional crystallization of impact melt sheets followed by detachment and sinking of their dense primitive portions towards the crust-mantle boundary. Credit: Rais Latypov

The heavy bombardment of terrestrial planets by asteroids from space has contributed to the formation of the early evolved crust on Earth that later gave rise to continents — home to human civilisation.

More than 3.8 billion years ago, in a time period called the Hadean eon, our planet Earth was constantly bombarded by asteroids, which caused the large-scale melting of its surface rocks. Most of these surface rocks were basalts, and the asteroid impacts produced large pools of superheated impact melt of such composition. These basaltic pools were tens of kilometres thick, and thousands of kilometres in diameter.

“If you want to get an idea of what the surface of Earth looked like at that time, you can just look at the surface of the Moon which is covered by a vast amount of large impact craters,” says Professor Rais Latypov from the School of Geosciences of the University of the Witwatersrand in South Africa.

The subsequent fate of these ancient, giant melt sheet remains, however, highly debatable. It has been argued that, on cooling, they may have crystallized back into magmatic bodies of the same, broadly basaltic composition. In this scenario, asteroid impacts are supposed to play no role in the formation of the Earth’s early evolved crust.

An alternative model suggests that these sheets may undergo large-scale chemical change to produce layered magmatic intrusions, such as the Bushveld Complex in South Africa. In this scenario, asteroid impacts may have played an important role in producing various igneous rocks in the early Earth’s crust and therefore they may have contributed to its chemical evolution.

There is no direct way to rigorously test these two competing scenarios because the ancient Hadean impact melts have been later obliterated by plate tectonics. However, by studying the younger impact melt sheet of the Sudbury Igneous Complex (SIC) in Canada, Latypov and his research team have inferred that ancient asteroid impacts were capable of producing various rock types from the earlier Earth’s basaltic crust. Most importantly, these impacts may have made the crust compositionally more evolved, i.e. silica-rich in composition. Their research has been published in a paper in Nature Communications.

The SIC is the largest, best exposed and accessible asteroid impact melt sheet on Earth, which has resulted from a large asteroid impact 1.85 billion years ago. This impact produced a superheated melt sheet of up to 5 km thick. The SIC now shows a remarkable magmatic stratigraphy, with various layers of igneous rocks.

“Our field and geochemical observations — especially the discovery of large discrete bodies of melanorites throughout the entire stratigraphy of the SIC — allowed us to reassess current models for the formation of the SIC and firmly conclude that its conspicuous magmatic stratigraphy is the result of large-scale fractional crystallization,” says Latypov.

“An important implication is that more ancient and primitive Hadean impact melt sheets on the early Earth and other terrestrial planets would also have undergone near-surface, large-volume differentiation to produce compositionally stratified bodies. The detachment of dense primitive layers from these bodies and their sinking into the mantle would leave behind substantial volumes of evolved rocks (buoyant crustal blocks) in the Hadean crust. This would make the crust compositionally layered and increasingly more evolved from its base towards the Earth’s surface.”

“These impacts made the crust compositionally more evolved — in other words, silica-rich in composition,” says Latypov. “Traditionally, researchers believe that such silica-rich evolved rocks — which are essentially building buoyant blocks of our continents — can only be generated deep in the Earth, but we now argue that such blocks can be produced at new-surface conditions within impact melt pools.”

Reference:
Rais Latypov, Sofya Chistyakova, Richard Grieve, Hannu Huhma. Evidence for igneous differentiation in Sudbury Igneous Complex and impact-driven evolution of terrestrial planet proto-crusts. Nature Communications, 2019; 10 (1) DOI: 10.1038/s41467-019-08467-9

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

Earth’s largest extinction event likely took plants first

This is a view of Coalcliff in New South Wales, Australia, where researchers discovered evidence that Earth's largest extinction may have extinguished plant life nearly 400,000 years before marine animal species disappeared. Credit: Christopher Fielding
This is a view of Coalcliff in New South Wales, Australia, where researchers discovered evidence that Earth’s largest extinction may have extinguished plant life nearly 400,000 years before marine animal species disappeared. Credit: Christopher Fielding

Little life could endure the Earth-spanning cataclysm known as the Great Dying, but plants may have suffered its wrath long before many animal counterparts, says new research led by the University of Nebraska-Lincoln.

About 252 million years ago, with the planet’s continental crust mashed into the supercontinent called Pangaea, volcanoes in modern-day Siberia began erupting. Spewing carbon and methane into the atmosphere for roughly 2 million years, the eruption helped extinguish about 96 percent of oceanic life and 70 percent of land-based vertebrates — the largest extinction event in Earth’s history.

Yet the new study suggests that a byproduct of the eruption — nickel — may have driven some Australian plant life to extinction nearly 400,000 years before most marine species perished.

“That’s big news,” said lead author Christopher Fielding, professor of Earth and atmospheric sciences. “People have hinted at that, but nobody’s previously pinned it down. Now we have a timeline.”

The researchers reached the conclusion by studying fossilized pollen, the chemical composition and age of rock, and the layering of sediment on the southeastern cliffsides of Australia. There they discovered surprisingly high concentrations of nickel in the Sydney Basin’s mud-rock — surprising because there are no local sources of the element.

Tracy Frank, professor and chair of Earth and atmospheric sciences, said the finding points to the eruption of lava through nickel deposits in Siberia. That volcanism could have converted the nickel into an aerosol that drifted thousands of miles southward before descending on, and poisoning, much of the plant life there. Similar spikes in nickel have been recorded in other parts of the world, she said.

“So it was a combination of circumstances,” Fielding said. “And that’s a recurring theme through all five of the major mass extinctions in Earth’s history.”

If true, the phenomenon may have triggered a series of others: herbivores dying from the lack of plants, carnivores dying from a lack of herbivores, and toxic sediment eventually flushing into seas already reeling from rising carbon dioxide, acidification and temperatures.

‘It Lets Us See What’s Possible’

One of three married couples on the research team, Fielding and Frank also found evidence for another surprise. Much of the previous research into the Great Dying — often conducted at sites now near the equator — has unearthed abrupt coloration changes in sediment deposited during that span.

Shifts from grey to red sediment generally indicate that the volcanism’s ejection of ash and greenhouse gases altered the world’s climate in major ways, the researchers said. Yet that grey-red gradient is much more gradual at the Sydney Basin, Fielding said, suggesting that its distance from the eruption initially helped buffer it against the intense rises in temperature and aridity found elsewhere.

Though the time scale and magnitude of the Great Dying exceeded the planet’s current ecological crises, Frank said the emerging similarities — especially the spikes in greenhouse gases and continuous disappearance of species — make it a lesson worth studying.

“Looking back at these events in Earth’s history is useful because it lets us see what’s possible,” she said. “How has the Earth’s system been perturbed in the past? What happened where? How fast were the changes? It gives us a foundation to work from — a context for what’s happening now.”

The researchers detailed their findings in the journal Nature Communications. Fielding and Frank authored the study with Allen Tevyaw, graduate student in geosciences at Nebraska; Stephen McLoughlin, Vivi Vajda and Chris Mays from the Swedish Museum of Natural History; Arne Winguth and Cornelia Winguth from the University of Texas at Arlington; Robert Nicoll of Geoscience Australia; Malcolm Bocking of Bocking Associates; and James Crowley of Boise State University.

The National Science Foundation and the Swedish Research Council funded the team’s work.

Reference:
Christopher R. Fielding, Tracy D. Frank, Stephen McLoughlin, Vivi Vajda, Chris Mays, Allen P. Tevyaw, Arne Winguth, Cornelia Winguth, Robert S. Nicoll, Malcolm Bocking, James L. Crowley. Age and pattern of the southern high-latitude continental end-Permian extinction constrained by multiproxy analysis. Nature Communications, 2019; 10 (1) DOI: 10.1038/s41467-018-07934-z

Note: The above post is reprinted from materials provided by University of Nebraska-Lincoln. Original written by Scott Schrage.

1...646566...330Page 65 of 330

Related Articles

All
Facebook Instagram Linkedin TikTok Twitter Youtube
© © 2011-2024. All Rights Reserved.