The new dinosaur species is estimated up to 10 meters long and 4-5 tons. Credit: Christophe Hendrickx; CC-BY
A new dinosaur species found in Portugal may be the largest land predator discovered in Europe, as well as one of the largest carnivorous dinosaurs from the Jurassic, according to a paper published in PLOS ONE on March 5, 2014 by co-authors Christophe Hendrickx and Octavio Mateus from Universidade Nova de Lisboa and Museu da Lourinhã.
Scientists discovered bones belonging to this dinosaur north of Lisbon. They were originally believed to be Torvosaurus tanneri, a dinosaur species from North America. Closer comparison of the shin bone, upper jawbone, teeth, and partial tail vertebrae suggest to the authors that it may warrant a new species name, Torvosaurus gurneyi.
T. gurneyi had blade-shaped teeth up to 10 cm long, which indicates it may have been at the top of the food chain in the Iberian Peninsula roughly 150 million years ago. The scientists estimate that the dinosaur could reach 10 meters long and weigh around 4 to 5 tons. The number of teeth, as well as size and shape of the mouth, may differentiate the European and the American Torvosaurus. The fossil of the upper jaw of T. tanneri has 11 or more teeth, while T. gurneyi has fewer than 11. Additionally, the mouth bones have a different shape and structure. The new dinosaur is the second species of Torvosaurus to be named.
“This is not the largest predatory dinosaur we know. Tyrannosaurus, Carcharodontosaurus, and Giganotosaurus from the Cretaceous were bigger animals,” said Christophe Hendrickx. “With a skull of 115 cm, Torvosaurus gurneyi was however one of the largest terrestrial carnivores at this epoch, and an active predator that hunted other large dinosaurs, as evidenced by blade shape teeth up to 10 cm.” Fossil evidences of closely related dinosaurs suggest that this large predator may have already been covered with proto-feathers. Recently described dinosaur embryos from Portugal are also ascribed to the new species of Torvosaurus.
Note : The above story is based on materials provided by PLOS.
Optical microscopy image in cross polarized light of a natural olivine polycrystal (Oman mylonite). Credit: S. Demouchy, Montpellier
Earth’s mantle is a solid layer that undergoes slow, continuous convective motion. But how do these rocks deform, thus making such motion possible, given that minerals such as olivine (the main constituent of the upper mantle) do not exhibit enough defects in their crystal lattice to explain the deformations observed in nature? A team led by the Unité Matériaux et Transformations (CNRS/Université Lille 1/Ecole Nationale Supérieure de Chimie de Lille) has provided an unexpected answer to this question.
It involves little known and hitherto neglected crystal defects, known as ‘disclinations’, which are located at the boundaries between the mineral grains that make up rocks. Focusing on olivine, the researchers have for the first time managed to observe such defects and model the behavior of grain boundaries when subjected to a mechanical stress.
The findings, which have just been published in Nature, go well beyond the scope of the geosciences: they provide a new, extremely powerful tool for the study of the dynamics of solids and for the materials sciences in general.
Earth continuously releases its heat via convective motion in Earth’s mantle, which underlies the crust. Understanding this convection is therefore fundamental to the study of plate tectonics. The mantle is made up of solid rocks. In order for convective motion to occur, it must be possible for the crystal lattice of these rocks to deform. Until now, this was a paradox that science was unable to fully resolve. While defects in the crystal lattice, called dislocations, provide a very good explanation of the plasticity of metals, they are insufficient to explain the deformations undergone by certain mantle rocks.
The researchers suspected that the solution was to be found at the boundaries between the mineral grains that make up rocks. However, they lacked the conceptual tools needed to describe and model the role played by these boundaries in the plasticity of rocks.
Researchers at the Unité Matériaux et Transformations (CNRS/Université Lille 1/Ecole Nationale Supérieure de Chimie de Lille) in collaboration with researchers at the Laboratoire Géosciences Montpellier (CNRS/Université Montpellier 2) and the Laboratoire d’Etude des Microstructures et de Mécanique des Matériaux (CNRS/Université de Lorraine/Arts et Métiers ParisTech/Ecole Nationale d’Ingénieurs de Metz) have now explained this role. They have shown that the crystal lattice of the grain boundaries exhibits highly specific defects known as ‘disclinations’, which had hitherto been neglected. The researchers succeeded in observing them for the first time in samples of olivine (which makes up as much as 60% of the upper mantle) by using an electron microscope and specific image processing. They even went further: based on a mathematical model, they showed that these disclinations provided an explanation for the plasticity of olivine. When mechanical stress is applied, the disclinations enable the grain boundaries to move, thus allowing olivine to deform in any direction. Flow in the mantle is thus no longer incompatible with its rigidity.
This research goes beyond explaining the plasticity of rocks in Earth’s mantle: it is a major step forward in materials science. Consideration of disclinations should provide scientists with a new tool to explain many phenomena related to the mechanics of solids. The scientists intend to continue their research into the structure of grain boundaries, not only in other minerals but also in other solids such as metals.
Note : The above story is based on materials provided by CNRS.
Earth’s magnetic field, or magnetosphere, stretches from the planet’s core out into space, where it meets the solar wind, a stream of charged particles emitted by the sun. For the most part, the magnetosphere acts as a shield to protect Earth from this high-energy solar activity.
But when this field comes into contact with the sun’s magnetic field — a process called “magnetic reconnection” — powerful electrical currents from the sun can stream into Earth’s atmosphere, whipping up geomagnetic storms and space weather phenomena that can affect high-altitude aircraft, as well as astronauts on the International Space Station.
Now scientists at MIT and NASA have identified a process in Earth’s magnetosphere that reinforces its shielding effect, keeping incoming solar energy at bay.
By combining observations from the ground and in space, the team observed a plume of low-energy plasma particles that essentially hitches a ride along magnetic field lines — streaming from Earth’s lower atmosphere up to the point, tens of thousands of kilometers above the surface, where the planet’s magnetic field connects with that of the sun. In this region, which the scientists call the “merging point,” the presence of cold, dense plasma slows magnetic reconnection, blunting the sun’s effects on Earth.
“The Earth’s magnetic field protects life on the surface from the full impact of these solar outbursts,” says John Foster, associate director of MIT’s Haystack Observatory. “Reconnection strips away some of our magnetic shield and lets energy leak in, giving us large, violent storms. These plasmas get pulled into space and slow down the reconnection process, so the impact of the sun on the Earth is less violent.”
Foster and his colleagues publish their results in this week’s issue of Science. The team includes Philip Erickson, principal research scientist at Haystack Observatory, as well as Brian Walsh and David Sibeck at NASA’s Goddard Space Flight Center.
Mapping Earth’s magnetic shield
For more than a decade, scientists at Haystack Observatory have studied plasma plume phenomena using a ground-based technique called GPS-TEC, in which scientists analyze radio signals transmitted from GPS satellites to more than 1,000 receivers on the ground. Large space-weather events, such as geomagnetic storms, can alter the incoming radio waves — a distortion that scientists can use to determine the concentration of plasma particles in the upper atmosphere. Using this data, they can produce two-dimensional global maps of atmospheric phenomena, such as plasma plumes.
These ground-based observations have helped shed light on key characteristics of these plumes, such as how often they occur, and what makes some plumes stronger than others. But as Foster notes, this two-dimensional mapping technique gives an estimate only of what space weather might look like in the low-altitude regions of the magnetosphere. To get a more precise, three-dimensional picture of the entire magnetosphere would require observations directly from space.
Toward this end, Foster approached Walsh with data showing a plasma plume emanating from Earth’s surface, and extending up into the lower layers of the magnetosphere, during a moderate solar storm in January 2013. Walsh checked the date against the orbital trajectories of three spacecraft that have been circling the Earth to study auroras in the atmosphere.
As it turns out, all three spacecraft crossed the point in the magnetosphere at which Foster had detected a plasma plume from the ground. The team analyzed data from each spacecraft, and found that the same cold, dense plasma plume stretched all the way up to where the solar storm made contact with Earth’s magnetic field.
A river of plasma
Foster says the observations from space validate measurements from the ground. What’s more, the combination of space- and ground-based data give a highly detailed picture of a natural defensive mechanism in Earth’s magnetosphere.
“This higher-density, cold plasma changes about every plasma physics process it comes in contact with,” Foster says. “It slows down reconnection, and it can contribute to the generation of waves that, in turn, accelerate particles in other parts of the magnetosphere. So it’s a recirculation process, and really fascinating.”
Foster likens this plume phenomenon to a “river of particles,” and says it is not unlike the Gulf Stream, a powerful ocean current that influences the temperature and other properties of surrounding waters. On an atmospheric scale, he says, plasma particles can behave in a similar way, redistributing throughout the atmosphere to form plumes that “flow through a huge circulation system, with a lot of different consequences.”
“What these types of studies are showing is just how dynamic this entire system is,” Foster adds.
Note : The above story is based on materials provided by Massachusetts Institute of Technology.
Euclase Alto do Giz pegmatite, Equador, Rio Grande do Norte, Brazil Miniature, 4.2 x 2.4 x 2.2 cm “Courtesy of Rob Lavinsky, The Arkenstone, www.iRocks.com”
Chemical Formula: BeAl(SiO4)(OH) Locality: Orenburg district in the southern Urals, Russia. Name Origin: From the Greek eu – “well” and klasis – “breaking.”Euclase is a beryllium aluminium hydroxide silicate mineral (BeAl(SiO4)(OH)). It crystallizes in the monoclinic crystal system and is typically massive to fibrous as well as in slender prismatic crystals. It is related to beryl (Be3Al2Si6O18) and other beryllium minerals. It is a product of the decomposition of beryl in pegmatites.Euclase crystals are noted for their blue color, ranging from very pale to dark blue. The mineral may also be colorless, white, or light green. Cleavage is perfect, parallel to the clinopinacoid, and this suggested to René Just Haüy the name euclase, from the Greek εὖ, easily, and κλάσις, fracture. The ready cleavage renders the crystals fragile with a tendency to chip, and thus detracts from its use for personal ornament. When cut it resembles certain kinds of beryl and topaz, from which it may be distinguished by its specific gravity (3.1). Its hardness (7.5) is similar to beryl (7.5 – 8), and a bit less than that of topaz (8).It was first reported in 1792 from the Orenburg district in the southern Urals, Russia, where it is found with topaz and chrysoberyl in the gold-bearing gravels of the Sanarka (nowadays probably, Sakmara River, Mednogorsk district, Orenburgskaya Oblast’). Its type locality is Ouro Prêto, Minas Gerais, Southeast Region, Brazil, where it occurs with topaz. It is found rarely in the mica-schist of the Rauris in the Austrian Alps.
Physical Properties
Cleavage: {010} Perfect Color: Blue, Colorless, White, Light blue, Light green. Density: 2.987 – 3.1, Average = 3.04 Diaphaneity: Transparent to translucent Fracture: Brittle – Generally displayed by glasses and most non-metallic minerals. Hardness: 7.5 – Garnet Luminescence: Non-fluorescent. Luster: Vitreous (Glassy) Streak: white
The magnetite database can help exploration geologists distinguish between barren and mineralised areas of land. Credit: David Clarke
Finding ways to target mineral deposits in remote and deeply covered areas, such as in WA’s often thick regolith cover, has been a major motivating factor in collaborative research between Australian and US scientists.
Exploring the use of magnetite as a pathfinder mineral, the study involved the CSIRO Minerals Down Under Flagship, University of WA’s Centre for Exploration Targeting and the US Geological Survey at Denver’s Central Mineral and Environmental Resources Science Centre.
Study co-author Patrick Nadoll, who is based at Kensington’s CSIRO Earth Science Resource Engineering, says a steadily growing magnetite chemistry database is showing distinctive compositional trends that can discriminate between hydrothermal (formed from water) and igneous (formed from lava or magma) magnetite.
“This helps exploration geologists find mineral deposits distal to the main mineralisation,” he says.
“The composition of igneous and hydrothermal magnetite is governed by several chemical and physical factors, such as temperature and fluid composition.
“Variations in the concentrations of key minor and trace elements represent a compositional signature that can fingerprint host rocks and mineral deposits.”
Main discriminator elements for magnetite are magnesium, aluminium, titanium, vanadium, chromium, manganese, cobalt, nickel, zinc, and gallium which are commonly present at detectable levels (10 to 1000 parts per million).
They display systematic variations across different types of mineral deposits and can also help to differentiate barren from mineralised areas.
“The use of statistical data exploration has been particularly helpful to find trends and patterns in large databases,” Dr Nadoll says.
“And the occurrence, abundance and composition of mineral inclusions in magnetite can also be a useful guide for exploration.
“For example, sulfide inclusions in magnetite are indicative for hydrothermal magnetite from sulfidic hydrothermal ore deposits such as skarn or porphyry deposits.”
Several differences between magnetite minor and trace element data for magnetite were found for different locations around the world—but Dr Nadoll says the variations are controlled by different formation conditions rather than representing a geographical signature.
“Overall, hydrothermal magnetite from a specific mineral deposit type and igneous magnetite from a specific host rock show a characteristic range of minor and trace element concentrations, which is their compositional signature,” he says.
“Magnetite from magnesian skarn deposits in the US will have similar compositional signatures to magnetite from the same deposit type in Indonesia.”
Following on from the research, Dr Nadoll says magnetite from glacigenic or stream sediments, or from regolith cover, can serve as an indicator for mineral exploration.
Note : The above story is based on materials provided by Science Network WA
This illustration shows the plumbing system beneath the Sierra Negra volcano. Credit: Cynthia Ebinger, University of Rochester
The Galápagos Islands are home to some of the most active volcanoes in the world, with more than 50 eruptions in the last 200 years. Yet until recently, scientists knew far more about the history of finches, tortoises, and iguanas than of the volcanoes on which these unusual fauna had evolved.
Now research out of the University of Rochester is providing a better picture of the subterranean plumbing system that feeds the Galápagos volcanoes, as well as a major difference with another Pacific Island chain — the Hawaiian Islands. The findings have been published in the Journal of Geophysical Research: Solid Earth.
“With a better understanding of what’s beneath the volcanoes, we’ll now be able to more accurately measure underground activity,” said Cynthia Ebinger, a professor of earth and environmental sciences. “That should help us better anticipate earthquakes and eruptions, and mitigate the hazards associated with them.”
Ebinger’s team, which included Mario Ruiz from the Instituto Geofisico Escuela Politecnica Nacional in Quito, Ecuador, buried 15 seismometers around Sierra Negra, the largest and most active volcano in the Galápagos. The equipment was used to measure the velocity and direction of different sound waves generated by earthquakes as they traveled under Sierra Negra. Since the behavior of the waves varies according to the temperature and types of material they’re passing through, the data collected allowed the researchers to construct a 3D image of the plumbing system beneath the volcano, using a technique similar to a CAT-scan.
Five kilometers down is the beginning of a large magma chamber lying partially within old oceanic crust that had been buried by more than 8 km of eruptive rock layers. And the oceanic crust has what appears to be a thick underplating of rock formed when magma that was working its way toward the surface became trapped under the crust and cooled — very much like the processes that occur under the Hawaiian Islands.
The researchers found that the Galápagos had something else in common with the Hawaiian Islands. Their data suggest the presence of a large chamber filled with crystal-mush magma — cooled magma that includes crystallized minerals.
The Galápagos Islands formed from a hotspot of magma located in an oceanic plate — called Nazca — about 600 miles of Ecuador, in a process very similar to how the Hawaiian Islands were created. Magma rising from the hotspot eventually hardened into an island. Then, as the Nazca plate inched its way westward, new islands formed in the same manner, resulting in the present-day Galápagos Archipelago.
While there are several similarities between the two island chains, Ebinger uncovered a major difference. The older volcanos in the Hawaiian Islands are dormant, because they’ve moved away from the hotspot that provided the source of magma. In the Galápagos, the volcanoes are connected to the same plumbing system. By studying satellite views of the volcanoes, Ebinger and colleagues noticed that, as the magma would sink in one, it would rise in a different volcano — indicating that that some of the youngest volcanoes had magma connections, even if those connections were temporary.
“Not only do we have a better understanding of the physical properties of Sierra Negra,” said Ebinger, “we have increased out knowledge of island volcano systems, in general.”
The Galápagos Islands are home to some of the most active volcanoes in the world, with more than 50 eruptions in the last 200 years. Yet until recently, scientists knew far more about the history of finches, tortoises, and iguanas than of the volcanoes on which these unusual fauna had evolved.
Now research out of the University of Rochester is providing a better picture of the subterranean plumbing system that feeds the Galápagos volcanoes, as well as a major difference with another Pacific Island chain — the Hawaiian Islands.
Note : The above story is based on materials provided by University of Rochester.
Anchiornis huxleyi Image: Michael DiGiorgio, Yale University
Paleontologists studying fossilized feathers have proposed that the shapes of certain microscopic structures inside the feathers can tell us the color of ancient birds. But new research from North Carolina State University demonstrates that it is not yet possible to tell if these structures — thought to be melanosomes — are what they seem, or if they are merely the remnants of ancient bacteria.
Melanosomes are small, pigment-filled sacs located inside the cells of feathers and other pigmented tissues of vertebrates. They contain melanin, which can give feathers colors ranging from brownish-red to gray to solid black. Melanosomes are either oblong or round in shape, and the identification of these small bodies in preserved feathers has led to speculation about the physiology, habitats, coloration and lifestyles of the extinct animals, including dinosaurs, that once possessed them.
But melanosomes are not the only round and oblong microscopic structures that might show up in fossilized feathers. In fact, the microbes that drove the decomposition of the animal prior to fossilization share the same size and shape as melanosomes, and they would also be present in feathers during decay.
Alison Moyer, a Ph.D. candidate in paleontology at NC State, wanted to find out whether these structures could be definitively identified as either melanosome or microbe. Using black and brown chicken feathers — chickens are one of the closest living relatives to both dinosaurs and ancient birds — Moyer grew bacteria over them to replicate what we see in the fossil record. She used three different types of microscopy to examine the patterns of biofilm growth, and then compared those structures to melanosomes inside of chicken feathers that she had sliced open. Finally, she compared both microbes and actual melanosomes to structures in a fossilized feather from Gansus yumenensis, an avian dinosaur that lived about 120 million years ago, and to published images of fossil “melanosomes” by others. Her findings led to more questions.
“These structures could be original to the bird, or they could be a biofilm which has grown over and degraded the feather — if the latter, they would also produce round or elongated structures that are not melanosomes,” Moyer says. “Melanosomes are embedded in keratin, which is a very tough protein, so they’re hard to see unless there’s been some degradation. But the bacteria are doing the degrading, and so that may be what we’re seeing, rather than the melanosome itself. It’s impossible to say with certainty what these structures are without more data, including fine scale chemical data.”
The research appears online in Scientific Reports. Possible next steps for Moyer include testing for the presence of keratin or bacteria within the fossils, by looking for their molecular signals.
“The technology that we have available to us as paleontologists now is amazing, and will make it much easier to test all of the hypotheses we develop about these fossils,” Moyer says. “In the meantime, perhaps we can establish some basic criteria for identifying these structures as melanosomes, such as whether they’re found within the feather’s interior, or externally.”
The research was funded in part by the National Science Foundation and the David and Lucille Packard foundation. The fossil feather was provided by the Gansu Geological Museum in Lanzhou, Gansu, China.
Note : The above story is based on materials provided by North Carolina State University.
Chemical Formula: Co3(AsO4)2 · 8H2O Locality: Grube Daniel, Schneeberg, Germany. Name Origin: Named from the Greek, erythros for “red.”
Erythrite or red cobalt is a secondary hydrated cobalt arsenate mineral with the formula (Co3(AsO4)2 · 8H2O). Erythrite and annabergite (Ni3(AsO4)2·8H2O) (nickel arsenate) form a complete series with the general formula (Co,Ni)3(AsO4)2·8H2O.
Erythrite crystallizes in the monoclinic system and forms prismatic crystals. The color is crimson to pink and occurs as a secondary coating known as cobalt bloom on cobalt arsenide minerals. Well-formed crystals are rare, with most of the mineral manifesting in crusts or small reniform aggregates.
Erythrite was first described in 1832 for an occurrence in Grube Daniel, Schneeberg, Saxony, and takes its name from the Greek έρυθρος (erythros), meaning red. Historically, erythrite itself has not been an economically important mineral, but the prospector may use it as a guide to associated cobalt and native silver.
Erythrite occurs as a secondary mineral in the oxide zone of Co–Ni–As bearing mineral deposits. It occurs in association with cobaltite, skutterudite, symplesite, roselite-beta, scorodite, pharmacosiderite, adamite, morenosite, retgersite, and malachite.
Notable localities are Cobalt, Ontario; Schneeberg, Saxony, Germany; Joachimsthal, Czech Republic; Cornwall, England; Bou Azzer, Morocco; the Blackbird mine, Lemhi County, Idaho; Sara Alicia mine, near Alamos, Sonora, Mexico; Mt. Cobalt, Queensland and the Dome Rock copper mine, Mingary, South Australia.
Physical Properties
Cleavage: {010} Perfect Color: Colorless, Violet red, Light pink, Purple red. Density: 3.06 – 3.18, Average = 3.12 Diaphaneity: Transparent to subtranslucent Fracture: Sectile – Curved shavings or scrapings produced by a knife blade, (e.g. graphite). Hardness: 1.5-2 – Talc-Gypsum Luminescence: Non-fluorescent. Luster: Pearly Streak: pinkish red
Asthenosphere and lithospheric plate Credit: Nicholas Schmerr/University of Maryland
The Earth’s outer layer is made up of a series of moving, interacting plates whose motion at the surface generates earthquakes, creates volcanoes and builds mountains. Geoscientists have long sought to understand the plates’ fundamental properties and the mechanisms that cause them to move and drift, and the questions have become the subjects of lively debate.
A study published online Feb. 27 by the journal Science is a significant step toward answering those questions.
Researchers led by Caroline Beghein, assistant professor of earth, planetary and space sciences in UCLA’s College of Letters and Science, used a technique called seismic tomography to study the structure of the Pacific Plate — one of eight to 12 major plates at the surface of the Earth. The technique enabled them to determine the plate’s thickness, and to image the interior of the plate and the underlying mantle (the layer between the Earth’s crust and outer core), which they were able to relate to the direction of flow of rocks in the mantle.
“Rocks deform and flow slowly inside the Earth’s mantle, which makes the plates move at the surface,” said Beghein, the paper’s lead author. “Our research enables us to image the interior of the plate and helps us figure out how it formed and evolved.” The findings might apply to other oceanic plates as well.
Even with the new findings, Beghein said, the fundamental properties of plates “are still somewhat enigmatic.”
Seismic tomography is similar to commonly used medical imaging techniques like computed tomography, or CT, scans. But instead of using X-rays, seismic tomography employs recordings of the seismic waves generated by earthquakes, allowing scientists to detect variations in the speed of seismic waves inside the Earth. Those variations can reveal different layers within the mantle, and can help scientists determine the temperature and chemistry of the mantle rocks by comparing observed variations in wave speed with predictions from other types of geophysical data.
Seismologists often use other types of seismic data to identify this layering: They detect seismic waves that bounce off the interface that separates two layers. In their study, Beghein and co-authors compared the layering they observed using seismic tomography with the layers revealed by these other types of data. Comparing results from the different methods is a continuing challenge for geoscientists, but it is an important part of helping them understand the Earth’s structure.
“We overcame this challenge by trying to push the observational science to the highest resolutions, allowing us to more readily compare observations across datasets,” said Nicholas Schmerr, the study’s co-author and an assistant research scientist in geology at the University of Maryland.
The researchers were the first to discover that the Pacific Plate is formed by a combination of mechanisms: The plate thickens as the rocks of the mantle cool, the chemical makeup of the rocks that form the plate changes with depth, and the mechanical behavior of the rocks change with depth and their proximity to where the plate is being formed at the mid-ocean ridge.
“By modeling the behavior of seismic waves in Earth’s mantle, we discovered a transition inside the plate from the top, where the rocks didn’t deform or flow very much, to the bottom of the plate, where they are more strongly deformed by tectonic forces,” Beghein said. “This transition corresponds to a boundary between the layers that we can image with seismology and that we attribute to changes in rock composition.”
Oceanic plates form at ocean ridges and disappear into the Earth’s mantle, a process known as subduction. Among geoscientists, there is still considerable debate about what drives this evolution. Beghein and her research team advanced our understanding of how oceanic plates form and evolve as they age by using and comparing two sets of seismic data; the study revealed the presence of a compositional boundary inside the plate that appears to be linked to the formation of the plate itself.
Other co-authors of the research are Kaiqing Yuan and Zheng Xing, graduate students in UCLA’s Department of Earth, Planetary and Space Sciences.
Note : The above story is based on materials provided by University of California – Los Angeles.
This is the fossil of the salamander Chunerpeton showing not only the preserved skeleton but also the skin and even external gills. Credit: Society of Vertebrate Paleontology
Over the last two decades, huge numbers of fossils have been collected from the western Liaoning Province and adjacent parts of northeastern China, including exceptionally preserved feathered dinosaurs, early birds, and mammals. Most of these specimens are from the Cretaceous Period, including the famous Jehol Biota.
However, in recent years many fossils have emerged from sites that are 30 million years earlier, from the Middle-Upper Jurassic Period, providing an exceptional window on life approximately 160 million years ago. A new paper published in latest issue of the Journal of Vertebrate Paleontology shows that several of these Jurassic sites are linked together by shared species and can be recognized as representing a single fossil fauna and flora, containing superbly preserved specimens of a diverse group of amphibian, mammal, and reptile species.
This fossil assemblage, newly named the Daohugou Biota after a village near one of the major localities in Inner Mongolia, China, dates from a time when many important vertebrate groups, including our own group, mammals, were undergoing evolutionary diversification. The Daohugou Biota makes an immense contribution to our understanding of vertebrate evolution during this period, with such notable creatures as the oldest known gliding mammal, another early mammal that may have swum with a beaver-like tail, the oldest dinosaurs preserved with feathers, and a pterosaur that represents an important transitional form between two major groups. As described by Dr. Corwin Sullivan, lead author of the study, “The Daohugou Biota gives us a look at a rarely glimpsed side of the Middle to Late Jurassic — not a parade of galumphing giants, but an assemblage of quirky little creatures like feathered dinosaurs, pterosaurs with ‘advanced’ heads on ‘primitive’ bodies, and the Mesozoic equivalent of a flying squirrel.”
Almost more impressive than the diversity of the biota is the preservation of many of the vertebrate specimens, including complete or nearly-complete skeletons associated with preserved soft tissues such as feathers, fur, skin or even, in some of the salamanders, external gills. Dr Yuan Wang, co-author of the study, explained, “The Daohugou amphibians are crucially important in the study of the phylogeny and early radiation of modern amphibian groups.”
Dr. Paul Barrett, dinosaur researcher at the Natural History Museum, London, who was not involved with the study, commented, “Daohugou is proving to be one of the key sites for understanding the evolution of feathered dinosaurs, early mammals, and flying reptiles, due largely to the fantastic levels of preservation. Many of the fossils are stunning and offer vast amounts of information. There are only a handful of similar sites elsewhere in the world and this article represents the first comprehensive attempt to draw all of the relevant information together into a single benchmark paper.” Because the Daohugou Biota and the much better studied Jehol Biota are similar in preservational mode and geographic location, but separated by tens of millions of years, they give palaeontologists an outstanding, even unique, opportunity to study changes in the fauna of this region over a significant span of geological time and an important period in vertebrate evolution. As Dr. Sullivan further remarked, “The Cretaceous feathered dinosaurs of northeastern China have been astonishing palaeontologists and the public for almost two decades now, and the Daohugou Biota preserves their Jurassic counterparts in the same region. As prequels go, it’s pretty exciting.”
Note : The above story is based on materials provided by Society of Vertebrate Paleontology.
Chemical Formula: {Ca2}{Al2Fe3+}(Si2O7)(SiO4)O(OH) Locality: Common world wide. Name Origin: From the Greek epidosis – “addition.”
Description
Well-developed crystals of epidote, {Ca2}{Al2Fe3+}(Si2O7)(SiO4)O(OH), crystallizing in the monoclinic system, are of frequent occurrence: they are commonly prismatic in habit, the direction of elongation being perpendicular to the single plane of symmetry. The faces are often deeply striated and crystals are often twinned. Many of the characters of the mineral vary with the amount of iron present for instance, the color, the optical constants, and the specific gravity. The color is green, grey, brown or nearly black, but usually a characteristic shade of yellowish-green or pistachio-green. It displays strong pleochroism, the pleochroic colors being usually green, yellow and brown. Clinozoisite is green, white or pale rose-red group species containing very little iron, thus having the same chemical composition as the orthorhombic mineral zoisite. The name is derived from the Greek word “epidosis” (επίδοσις) which means “addition” in allusion to one side of the ideal prism being longer than the other.
Epidote is an abundant rock-forming mineral, but one of secondary origin. It occurs in marble and schistose rocks of metamorphic origin. It is also a product of hydrothermal alteration of various minerals (feldspars, micas, pyroxenes, amphiboles, garnets, and others) composing igneous rocks. A rock composed of quartz and epidote is known as epidosite. Well-developed crystals are found at many localities: Knappenwand, near the Großvenediger in the Untersulzbachthal in Salzburg, as magnificent, dark green crystals of long prismatic habit in cavities in epidote schist, with asbestos, adularia, calcite, and apatite; the Ala valley and Traversella in Piedmont; Arendal in Norway; Le Bourg-d’Oisans in Dauphiné; Haddam in Connecticut; Prince of Wales Island in Alaska, here as large, dark green, tabular crystals with copper ores in metamorphosed limestone.
The perfectly transparent, dark green crystals from the Knappenwand and from Brazil have occasionally been cut as gemstones.
Physical Properties
Cleavage: {001} Perfect Color: Yellowish green, Brownish green, Black, Yellow, Gray. Density: 3.3 – 3.6, Average = 3.45 Diaphaneity: Transparent to translucent to opaque Fracture: Regular – Flat surfaces (not cleavage) fractured in a regular pattern. Hardness: 7 – Quartz Luminescence: Non-fluorescent. Luster: Vitreous (Glassy) Streak: grayish white
The Silurian is a geologic period and system that extends from the end of the Ordovician Period, about 443.4 ± 1.5 million years ago (mya), to the beginning of the Devonian Period, about 419.2 ± 3.2 mya (ICS, 2004). As with other geologic periods, the rock beds that define the period’s start and end are well identified, but the exact dates are uncertain by several million years. The base of the Silurian is set at a major extinction event when 60% of marine species were wiped out. See Ordovician-Silurian extinction events.
A significant evolutionary milestone during the Silurian was the diversification of jawed and bony fish. Life also began to appear on land in the form of small, moss-like, vascular plants which grew beside lakes, streams, and coastlines, and also in the form of small terrestrial arthropods. However, terrestrial life would not greatly diversify and affect the landscape until the Devonian.
History of study
The Silurian system was first identified by British geologist Sir Roderick Impey Murchison, who was examining fossil-bearing sedimentary rock strata in south Wales in the early 1830s. He named the sequences for a Celtic tribe of Wales, the Silures, inspired by his friend Adam Sedgwick, who had named the period of his study the Cambrian, the Latin name for Wales. This naming does not indicate any correlation between the occurrence of the Silurian rocks and the land inhabited by the Silures; cf. Geology of Wales, Tribes of Wales. In 1835 the two men presented a joint paper, under the title On the Silurian and Cambrian Systems, Exhibiting the Order in which the Older Sedimentary Strata Succeed each other in England and Wales, which was the germ of the modern geological time scale. As it was first identified, the “Silurian” series when traced farther afield quickly came to overlap Sedgwick’s “Cambrian” sequence, however, provoking furious disagreements that ended the friendship. Charles Lapworth resolved the conflict by defining a new Ordovician system including the contested beds. An early alternative name for the Silurian was “Gotlandian” after the strata of the Baltic island of Gotland.
The French geologist Joachim Barrande, building on Murchison’s work, used the term Silurian in a more comprehensive sense than was justified by subsequent knowledge. He divided the Silurian rocks of Bohemia into eight stages. His interpretation was questioned in 1854 by Edward Forbes, and the later stages of Barrande, F, G and H, have since been shown to be Devonian. Despite these modifications in the original groupings of the strata, it is recognized that Barrande established Bohemia as a classic ground for the study of the earliest fossils.
Subdivisions
Llandovery
The Llandovery Epoch lasted from 443.4 ± 1.5 to 433.4 ± 2.8 mya, and is subdivided into three stages: the Rhuddanian, lasting until 440.8 million years ago, the Aeronian, lasting to 438.5 million years ago, and the Telychian. The epoch is named for the town of Llandovery in Carmarthenshire, Wales.
Wenlock
The Wenlock, which lasted from 433.4 ± 1.5 to 427.4 ± 2.8 mya, is subdivided into the Sheinwoodian (to 430.5 million years ago) and Homerian ages. It is named after Wenlock Edge in Shropshire, England. During the Wenlock, the oldest known tracheophytes of the genus Cooksonia, appear. The complexity of slightly younger Gondwana plants like Baragwanathia indicates a much longer history for vascular plants, perhaps extending into the early Silurian or even Ordovician. See Evolutionary history of plants. The first terrestrial animals also appear in the Wenlock, represented by air-breathing millipedes from Scotland.
Ludlow
The Ludlow, lasting from 427.4 ± 1.5 to 423 ± 2.8 mya, comprises the Gorstian stage, lasting until 425.6 million years ago, and the Ludfordian stage. It is named for the town of Ludlow in Shropshire, England.
Přídolí
The Pridoli, lasting from 423 ± 1.5 to 419.2 ± 2.8 mya, is the final and shortest epoch of the Silurian. It is named after one locality at the Homolka a Přídolí nature reserve near the Prague suburb Slivenec in the Czech Republic. Přídolí is the old name of a cadastral field area.
Regional stages
In North America a different suite of regional stages is sometimes used:
With the supercontinent Gondwana covering the equator and much of the southern hemisphere, a large ocean occupied most of the northern half of the globe. The high sea levels of the Silurian and the relatively flat land (with few significant mountain belts) resulted in a number of island chains, and thus a rich diversity of environmental settings.
During the Silurian, Gondwana continued a slow southward drift to high southern latitudes, but there is evidence that the Silurian icecaps were less extensive than those of the late Ordovician glaciation. The southern continents remained united during this period. The melting of icecaps and glaciers contributed to a rise in sea level, recognizable from the fact that Silurian sediments overlie eroded Ordovician sediments, forming an unconformity. The continents of Avalonia, Baltica, and Laurentia drifted together near the equator, starting the formation of a second supercontinent known as Euramerica.
When the proto-Europe collided with North America, the collision folded coastal sediments that had been accumulating since the Cambrian off the east coast of North America and the west coast of Europe. This event is the Caledonian orogeny, a spate of mountain building that stretched from New York State through conjoined Europe and Greenland to Norway. At the end of the Silurian, sea levels dropped again, leaving telltale basins of evaporites in a basin extending from Michigan to West Virginia, and the new mountain ranges were rapidly eroded. The Teays River, flowing into the shallow mid-continental sea, eroded Ordovician strata, leaving traces in the Silurian strata of northern Ohio and Indiana.
The vast ocean of Panthalassa covered most of the northern hemisphere. Other minor oceans include two phases of the Tethys— the Proto-Tethys and Paleo-Tethys— the Rheic Ocean, a seaway of the Iapetus Ocean (now in between Avalonia and Laurentia), and the newly formed Ural Ocean.
Climate and sea level
The blue graph shows the apparent percentage (not the absolute number) of marine animal genera becoming extinct during any given time interval. It does not represent all marine species, just those that are readily fossilized.
The Silurian period enjoyed relatively stable and warm temperatures, in contrast with the extreme glaciations of the Ordovician before it, and the extreme heat of the ensuing Devonian. Sea levels rose from their Hirnantian low throughout the first half of the Silurian; they subsequently fell throughout the rest of the period, although smaller scale patterns are superimposed on this general trend; fifteen high-stands can be identified, and the highest Silurian sea level was probably around 140 m higher than the lowest level reached.
During this period, the Earth entered a long, warm greenhouse phase, and warm shallow seas covered much of the equatorial land masses. Early in the Silurian, glaciers retreated back into the South Pole until they almost disappeared in the middle of Silurian. The period witnessed a relative stabilization of the Earth’s general climate, ending the previous pattern of erratic climatic fluctuations. Layers of broken shells (called coquina) provide strong evidence of a climate dominated by violent storms generated then as now by warm sea surfaces. Later in the Silurian, the climate cooled slightly, but in the Silurian-Devonian boundary, the climate became warmer.
Perturbations
The climate and carbon cycle appears to be rather unsettled during the Silurian, which has a higher concentration of isotopic excursions than any other period. The Ireviken event, Mulde event and Lau event each represent isotopic excursions following a minor mass extinction and associated with rapid sea-level change, in addition to the larger extinction at the end of the Silurian. Each one leaves a similar signature in the geological record, both geochemically and biologically; pelagic (free-swimming) organisms were particularly hard hit, as were brachiopods, corals and trilobites, and extinctions rarely occur in a rapid series of fast bursts.
The Silurian was the first period to see macrofossils of extensive terrestrial biota, in the form of moss forests along lakes and streams. However, the land fauna did not have a major impact on the Earth until it diversified in the Devonian.
The first fossil records of vascular plants, that is, land plants with tissues that carry food, appeared in the second half of the Silurian period. The earliest known representatives of this group are Cooksonia (mostly from the northern hemisphere) and Baragwanathia (from Australia). Most of the sediments containing Cooksonia are marine in nature. Preferred habitats were likely along rivers and streams. Baragwanathia, appears to be almost as old dating to the Early Ludlow (420 million years) and has branching stems and needle-like leaves of 10-20 cm. The plant shows a high degree of development in relation to its age. As mentioned, fossils of this plant are only found in Australia.
The much-branched Psilophyton was a primitive Silurian land plant with xylem and phloem but no differentiation in root, stem or leaf. It reproduced by spores, had stomata on every surface, and probably photosynthesized in every tissue exposed to light. Rhyniophyta and primitive lycopods were other land plants that first appear during this period. Neither mosses nor the earliest vascular plants had deep roots. Silurian rocks often have a brownish tint, possibly a result of extensive erosion of the early soils.
The first bony fish, the Osteichthyes, appeared, represented by the Acanthodians covered with bony scales; fish reached considerable diversity and developed movable jaws, adapted from the supports of the front two or three gill arches. A diverse fauna of Eurypterids (sea scorpions)—some of them several meters in length—prowled the shallow Silurian seas of North America; many of their fossils have been found in New York state. Leeches also made their appearance during the Silurian Period. Brachiopods, bryozoa, molluscs, hederelloids, tentaculitoids, crinoids and trilobites were abundant and diverse.
Reef abundance was patchy; sometimes fossils are frequent but at other points are virtually absent from the rock record.
The earliest known terrestrial animals appear during the Mid Silurian, including the millipede Pneumodesmus. Some evidence also suggests the presence of predatory trigonotarbid arachnoids and myriapods in Late Silurian facies. Predatory invertebrates would indicate that simple food webs were in place that included non-predatory prey animals. Extrapolating back from Early Devonian biota, Andrew Jeram et al. in 1990 suggested a food web based on as yet undiscovered detritivores and grazers on micro-organisms.
Note : The above story is based on materials provided by Wikipedia
The Ob River , also Obi, is a major river in western Siberia, Russia and is the world’s fifth longest river. It is the westernmost of the three great Siberian rivers that flow into the Arctic Ocean (the other two being the Yenisei River and the Lena River). The Gulf of Ob is the world’s longest estuary.
Names
The Ob is known to the Khanty people as the As, Yag, Kolta and Yema; to the Nenets people as the Kolta or Kuay; and to the Siberian Tatars as the Umar or Omass. Possibly from Proto-Indo-Iranian *ap- ‘river, water’ (compare Tajik ob, ‘water’).
Geography
Map of the Ob River watershed
The Ob forms 16 miles (26 km) southwest of Biysk in Altai Krai at the confluence of the Biya and Katun rivers. Both these streams have their origin in the Altay Mountains, the Biya issuing from Lake Teletskoye, the Katun, 700 kilometres (430 mi) long, bursting out of a glacier on Mount Byelukha.
The river splits into more than one arm, especially after joining the large Irtysh tributary at about 69° E. (Originating in China, the Irtysh is actually longer than the Ob from source to the point of their confluence.) From the source of the Irtysh to the mouth of the Ob, the river flow is the longest in Russia at 5,410 kilometres (3,360 mi). Other noteworthy tributaries are: from the east, the Tom, Chulym, Ket, Tym and Vakh rivers; and, from the west and south, the Vasyugan, Irtysh (with the Ishim and Tobol rivers), and Sosva rivers.
The Ob zigzags west and north until it reaches 55° N, where it curves round to the northwest, and again north, wheeling finally eastwards into the Gulf of Ob, a 600-mile (970 km)-long bay of the Kara Sea, separating the Yamal Peninsula from the Gydan Peninsula.
The combined Ob-Irtysh system, the third-longest river system of Asia (after China’s Yangtze and Yellow rivers), is 5,410 kilometres (3,360 mi) long, and the area of its basin 2,990,000 square kilometres (1,150,000 sq mi). The river basin of the Ob consists mostly of steppe, taiga, swamps, tundra, and semi-desert topography. The floodplains of the Ob are characterized by many tributaries and lakes. The Ob is ice-bound at southern Barnaul from early in November to near the end of April, and at northern Salekhard, 100 miles (160 km) above its mouth, from the end of October to the beginning of June. The Ob River crosses several climatic zones. The upper Ob valley, in the south, grows grapes, melons and watermelons, whereas the lower reaches of the Ob are Arctic tundra. The most comfortable climate for the rest on the Ob – are Biysk, Barnaul, and Novosibirsk.
Note : The above story is based on materials provided by Wikipedia
Chemical Formula: Na2Be2Si6O15 · H2O Locality: Island of Aro, Langesundfiord, Norway. Name Origin: From the Greek epi, “near” and didymos, “twin”, for its dimorphous relationship with eudidymite
Physical Properties
Cleavage: {001} Perfect, {010} Perfect Color: Colorless, White, Gray, Yellow, Blue. Density: 2.55 Diaphaneity: Transparent to translucent Fracture: Brittle – Generally displayed by glasses and most non-metallic minerals. Hardness: 5.5 – Knife Blade Luster: Vitreous (Glassy) Streak: white
Blame the grasses (Image: Per Moller/Johanna Anjar)
IT WAS the superfoods wot dunnit. Woolly mammoths may have starved to death when changes in the climate deprived them of their best food: flowering herbs.
Perhaps unexpectedly given their size and the chilly climates they lived in, woolly mammoths are thought to have survived on a diet of steppe grasses. But that’s not the whole story. A study of frozen stomach contents and frozen DNA found in the dirt across the Arctic suggests that the ice-age megafauna primarily ate a richer class of plants called forbs.
At first glance the difference seems negligible. Forbs are flowering herbs, and modern examples include clover. But whereas grasses are tough to digest and relatively low in nutrients, forbs are high in protein.
By painstakingly looking at the plant DNA found in permafrost samples dug out of 200 locations across the Arctic, Eske Willerslev at the University of Copenhagen in Denmark and his colleagues were able to paint a picture of the landscape between 50,000 years ago and today. They found that at first, the far north was covered in a rich diversity of forbs. What’s more, the gut contents of some of the big animals that lived in the region, like mammoths and woolly rhinoceroses, showed that these nutritious wild flowers were an important part of their diet (Nature, DOI: 10.1038/nature12921).
“This is technically a great achievement,” says Adrian Lister of the Natural History Museum in London.
But the forbs didn’t last. “Around 20,000 years ago, at the height of the ice age, the environment became very, very cold and dry, and we see a major drop-off in the diversity of forbs,” says Willerslev. “They still dominate the ecosystem, but their diversity declines.”
The real killer came at the end of the ice age 12,000 years ago. Grasses and shrubs began to take the place of the forbs – a change in the landscape that coincided with the decline of the iconic ice-age megafauna. As forbs are stimulated by being trampled underfoot, the decline in forbs from 20,000 years ago probably brought about a feedback cycle in which having fewer animals caused plant diversity to fall, further reducing food supplies and animal populations.
“Our study really changes the general concept that before the last warming period you had a massive grass steppe that was fundamental to sustaining a huge diversity of mammals,” says Willerslev. “In fact it was a diverse steppe of forbs and these were probably crucial.”
The theory may also explain why reindeer were the only big ice-age animalsMovie Camera to survive. Today, reindeer munch on grasses and sedges in summer, and eke a living out of low-energy lichen in the winter. The forbs’ decline would have passed them by.
Note : The above story is based on materials provided by Catherine Brahic to newscientist
Mineral mining is on hold (Image: Nautilus Minerals)
Deep-sea mining is floundering. The leading company in the race to mine the ocean floor has fallen out with its host government, while other projects have been delayed until the environmental effects are better understood.
In 2011, Papua New Guinea gave Canadian firm Nautilus Minerals a licence to mine a field of hydrothermal vents in its waters, called Solwara 1, provided the country could buy a 30 per cent stake. The vents contain high-grade metal ores, including copper that is far more concentrated than most land-based deposits.
Scientists say the vents need more study first. “We don’t know enough about the ecology, the ecosystems and the resilience of these systems,” says Joanna Parr of CSIRO in Sydney, Australia.
Now Nautilus claims Papua New Guinea hasn’t paid up, so it is ending the agreement and suing for damages.
Race to the bottom
Nautilus was racing to be the first in the world to mine the sea floor. Now UK Seabed Resources, a subsidiary of Lockheed Martin, could take the lead. It has a licence to explore an area of the Pacific sea floor in international waters for minerals.But it has a lot of work to do to catch up with Nautilus. “There is no proposed mining operation similar to that proposed for Solwara at such an advanced stage,” says Parr.
Meanwhile some governments are delaying deep-sea mining for ecological reasons, says Parr, with moratoria off the coasts of Australia and Namibia.
“Governments are realising this isn’t just a flash in the pan,” she says. “It’s something that is building towards an industry.”
Note : The above story is based on materials provided by Michael Slezak to newscientist
Eosphorite on Rose Quartz with Zanazziite Taquaral, Minas Gerais, Brazil Small Cabinet, 5.9 x 4.7 x 3.3 cm “Courtesy of Rob Lavinsky, The Arkenstone, www.iRocks.com”
Chemical Formula: (Mn,Fe)Al(PO4)(OH)2 · H2O Locality: Branchville, Fairfield County, Connecticut, USA. Name Origin: Named from the Greek for “dawn-bearing,” in allusion to the pink color.Eosphorite is a pink manganese hydrous phosphate mineral with chemical formula: (Mn,Fe)Al(PO4)(OH)2 · H2O.
Eosphorite crystallizes in the monoclinic crystal system. It forms slender prismatic crystals which often form radiating or spherical clusters. The crystals often show pseudo–orthorhombic forms due to twinning.
Eosphorite forms a series with childrenite, the iron rich member, with divalent iron replacing most of the manganese in the crystal lattice. The two endmembers are isostructural but differ in their properties, such as crystal habit, coloration, and optical properties.
It was first described in 1878 for an occurrence in the Branchville Mica Mine in Branchville, Fairfield County, Connecticut, USA. Its name is derived from the Greek έωσφορος for “dawn-bearing,” because of its pink color. It occurs worldwide typically as a secondary mineral in phosphate rich granitic pegmatites in association with rhodochrosite, lithiophilite, triphylite, triploidite, dickinsonite, albite, cookeite, apatite, beryllonite, hydroxyl-herderite, and tourmaline. An attractive combination of eosphorite and rose quartz occurs at Taquaral, Minas Gerais, Brazil.
The Ordovician /ɔrdəˈvɪʃən/ is a geologic period and system, the second of six of the Paleozoic Era, and covers the time between 485.4 ± 1.9 to 443.4 ± 1.5 million years ago (ICS, 2004). It follows the Cambrian Period and is followed by the Silurian Period. The Ordovician, named after the Celtic tribe of the Ordovices, was defined by Charles Lapworth in 1879 to resolve a dispute between followers of Adam Sedgwick and Roderick Murchison, who were placing the same rock beds in northern Wales into the Cambrian and Silurian periods respectively.
Lapworth, recognizing that the fossil fauna in the disputed strata were different from those of either the Cambrian or the Silurian periods, realized that they should be placed in a period of their own. While recognition of the distinct Ordovician Period was slow in the United Kingdom, other areas of the world accepted it quickly. It received international sanction in 1960, when it was adopted as an official period of the Paleozoic Era by the International Geological Congress.Life continued to flourish during the Ordovician as it did in the Cambrian, although the end of the period was marked by a significant mass extinction. Invertebrates, namely mollusks and arthropods, dominated the oceans. Fish, the world’s first true vertebrates, continued to evolve, and those with jaws may have first appeared late in the period. Life had yet to diversify on land.
Extinction events
Ordovician-Silurian extinction event- occurred at the end of the period approximately 443 million years ago. 60% of marine genera went extinct. The cause of the extinction was predicted to be a gamma-ray burst.
Cambrian-Ordovician extinction event- occurred at the start of the period 485 million years ago.
Dating
The Ordovician Period started at a major extinction event called the Cambrian–Ordovician extinction events about 485.4 ± 1.9 Mya (million years ago), and lasted for about 44.6 million years. It ended with the Ordovician–Silurian extinction event, about 443.4 ± 1.5 Mya (ICS, 2004) that wiped out 60% of marine genera.
The dates given are recent radiometric dates and vary slightly from those used in other sources. This second period of the Paleozoic era created abundant fossils and in some regions, major petroleum and gas reservoirs.
The boundary chosen for the beginning both of the Ordovician Period and the Tremadocian stage is highly useful. Since it correlates well with the occurrence of widespread graptolite, conodont, and trilobite species, the base of the Tremadocian allows scientists not only to relate these species to each other, but to species that occur with them in other areas as well. This makes it easier to place many more species in time relative to the beginning of the Ordovician Period.
Subdivisions
A number of regional terms have been used to refer to subdivisions of the Ordovician Period. In 2008, the ICS erected a formal international system of subdivisions, illustrated to the right.
The Ordovician Period in Britain was traditionally broken into Early (Tremadocian and Arenig), Middle (Llanvirn [subdivided into Abereiddian and Llandeilian] and Llandeilo) and Late (Caradoc and Ashgill) epochs. The corresponding rocks of the Ordovician System are referred to as coming from the Lower, Middle, or Upper part of the column. The faunal stages (subdivisions of epochs) from youngest to oldest are:
Late Ordovician
Hirnantian/Gamach (Ashgill)
Rawtheyan/Richmond (Ashgill)
Cautleyan/Richmond (Ashgill)
Pusgillian/Maysville/Richmond (Ashgill)
Middle Ordovician
Trenton (Caradoc)
Onnian/Maysville/Eden (Caradoc)
Actonian/Eden (Caradoc)
Marshbrookian/Sherman (Caradoc)
Longvillian/Sherman (Caradoc)
Soudleyan/Kirkfield (Caradoc)
Harnagian/Rockland (Caradoc)
Costonian/Black River (Caradoc)
Chazy (Llandeilo)
Llandeilo (Llandeilo)
Whiterock (Llanvirn)
Llanvirn (Llanvirn)
Early Ordovician
Cassinian (Arenig)
Arenig/Jefferson/Castleman (Arenig)
Tremadoc/Deming/Gaconadian (Tremadoc)
British stages
The Tremadoc corresponds to the (modern) Tremadocian. The Floian corresponds to the lower Arenig; the Arenig continues until the early Darriwilian, subsuming the Dapingian. The Llanvirn occupies the rest of the Darriwilian, and terminates with it at the base of the Late Ordovician. The Sandbian represents the first half of the Caradoc; the Caradoc ends in the mid-Katian, and the Ashgill represents the last half of the Katian, plus the Hirnantian.
Paleogeography
Sea levels were high during the Ordovician; in fact during the Tremadocian, marine transgressions worldwide were the greatest for which evidence is preserved in the rocks.
During the Ordovician, the southern continents were collected into a single continent called Gondwana. Gondwana started the period in equatorial latitudes and, as the period progressed, drifted toward the South Pole. Early in the Ordovician, the continents Laurentia (present-day North America), Siberia, and Baltica (present-day northern Europe) were still independent continents (since the break-up of the supercontinent Pannotia earlier), but Baltica began to move towards Laurentia later in the period, causing the Iapetus Ocean to shrink between them. The small continent Avalonia separated from Gondwana and began to head north towards Baltica and Laurentia. The Rheic Ocean between Gondwana and Avalonia was formed as a result.
A major mountain-building episode was the Taconic orogeny that was well under way in Cambrian times. In the beginning of the Late Ordovician, from 460 to 450 Ma, volcanoes along the margin of the Iapetus Ocean spewed massive amounts of carbon dioxide into the atmosphere, turning the planet into a hothouse. These volcanic island arcs eventually collided with proto North America to form the Appalachian mountains. By the end of the Late Ordovician these volcanic emissions had stopped. Gondwana had by that time neared or approached the pole and was largely glaciated.
Ordovician meteor event
The Ordovician meteor event is a proposed shower of meteors that occurred during the Middle Ordovician period, roughly 470 million years ago. It is not associated with any major extinction event.
Geochemistry
The Ordovician was a time of calcite sea geochemistry in which low-magnesium calcite was the primary inorganic marine precipitate of calcium carbonate. Carbonate hardgrounds were thus very common, along with calcitic ooids, calcitic cements, and invertebrate faunas with dominantly calcitic skeletons.
Unlike Cambrian times, when calcite production was dominated by microbial and non-biological processes, animals (and macroalgae) became a dominant source of calcareous material in Ordovician deposits.
Climate and sea level
The Ordovician saw the highest sea levels of the Paleozoic, and the low relief of the continents led to many shelf deposits being formed under hundreds of metres of water. Sea level rose more or less continuously throughout the Early Ordovician, levelling off somewhat during the middle of the period. Locally, some regressions occurred, but sea level rise continued in the beginning of the Late Ordovician. A change was soon on the cards, however, and sea levels fell steadily in accord with the cooling temperatures for the ~30 million years leading up to the Hirnantian glaciation. Within this icy stage, sea level seems to have risen and dropped somewhat, but despite much study the details remain unresolved.
At the beginning of the period, around 485.4 ± 1.9 million years ago, the climate was very hot due to high levels of CO2, which gave a strong greenhouse effect. The marine waters are assumed to have been around 45°C (113°F), which restricted the diversification of complex multi-cellular organisms. But over time, the climate became cooler, and around 460 million years ago, the ocean temperatures became comparable to those of present day equatorial waters.
As with North America and Europe, Gondwana was largely covered with shallow seas during the Ordovician. Shallow clear waters over continental shelves encouraged the growth of organisms that deposit calcium carbonates in their shells and hard parts. The Panthalassic Ocean covered much of the northern hemisphere, and other minor oceans included Proto-Tethys, Paleo-Tethys, Khanty Ocean, which was closed off by the Late Ordovician, Iapetus Ocean, and the new Rheic Ocean.
As the Ordovician progressed, we see evidence of glaciers on the land we now know as Africa and South America. At the time these land masses were sitting at the South Pole, and covered by ice caps.
Life
For most of the Late Ordovician, life continued to flourish, but at and near the end of the period there were mass-extinction events that seriously affected planktonic forms like conodonts, graptolites, and some groups of trilobites (Agnostida and Ptychopariida, which completely died out, and the Asaphida, which were much reduced). Brachiopods, bryozoans and echinoderms were also heavily affected, and the endocerid cephalopods died out completely, except for possible rare Silurian forms. The Ordovician–Silurian Extinction Events may have been caused by an ice age that occurred at the end of the Ordovician period as the end of the Late Ordovician was one of the coldest times in the last 600 million years of earth history.
On the whole, the fauna that emerged in the Ordovician set the template for the remainder of the Palaeozoic. The fauna was dominated by tiered communities of suspension feeders, mainly with short food chains; this said, the ecological system reached a new grade of complexity far beyond that of the Cambrian fauna, which has persisted until the present day.
Though less famous than the Cambrian explosion, the Ordovician featured an adaptive radiation, the Ordovician radiation, that was no less remarkable; marine faunal genera increased fourfold, resulting in 12% of all known Phanerozoic marine fauna. Another change in the fauna was the strong increase in filter feeding organisms. The trilobite, inarticulate brachiopod, archaeocyathid, and eocrinoid faunas of the Cambrian were succeeded by those that dominated the rest of the Paleozoic, such as articulate brachiopods, cephalopods, and crinoids. Articulate brachiopods, in particular, largely replaced trilobites in shelf communities. Their success epitomizes the greatly increased diversity of carbonate shell-secreting organisms in the Ordovician compared to the Cambrian.
In North America and Europe, the Ordovician was a time of shallow continental seas rich in life. Trilobites and brachiopods in particular were rich and diverse. Although solitary corals date back to at least the Cambrian, reef-forming corals appeared in the early Ordovician, corresponding to an increase in the stability of carbonate and thus a new abundance of calcifying animals.
Molluscs, which appeared during the Cambrian or even the Ediacaran, became common and varied, especially bivalves, gastropods, and nautiloid cephalopods.
Now-extinct marine animals called graptolites thrived in the oceans. Some new cystoids and crinoids appeared.
It was long thought that the first true vertebrates (fish — Ostracoderms) appeared in the Ordovician, but recent discoveries in China reveal that they probably originated in the Early Cambrian. The very first gnathostome (jawed fish) appeared in the Late Ordovician epoch.
During the Middle Ordovician there was a large increase in the intensity and diversity of bioeroding organisms. This is known as the Ordovician Bioerosion Revolution. It is marked by a sudden abundance of hard substrate trace fossils such as Trypanites, Palaeosabella and Petroxestes.
Fossiliferous limestone slab from the Liberty Formation (Upper Ordovician) of Caesar Creek State Park near Waynesville, Ohio. Specimen found by College of Wooster student Willy Nelson.
In the Early Ordovician, trilobites were joined by many new types of organisms, including tabulate corals, strophomenid, rhynchonellid, and many new orthid brachiopods, bryozoans, planktonic graptolites and conodonts, and many types of molluscs and echinoderms, including the ophiuroids (“brittle stars”) and the first sea stars. Nevertheless the trilobites remained abundant, with all the Late Cambrian orders continuing, and being joined by the new group Phacopida. The first evidence of land plants also appeared; see Evolutionary history of life.
In the Middle Ordovician, the trilobite-dominated Early Ordovician communities were replaced by generally more mixed ecosystems, in which brachiopods, bryozoans, molluscs, cornulitids, tentaculitids and echinoderms all flourished, tabulate corals diversified and the first rugose corals appeared; trilobites were no longer predominant. The planktonic graptolites remained diverse, with the Diplograptina making their appearance. Bioerosion became an important process, particularly in the thick calcitic skeletons of corals, bryozoans and brachiopods, and on the extensive carbonate hardgrounds that appear in abundance at this time. One of the earliest known armoured agnathan (“ostracoderm”) vertebrate, Arandaspis, dates from the Middle Ordovician.
Trilobites in the Ordovician were very different from their predecessors in the Cambrian. Many trilobites developed bizarre spines and nodules to defend against predators such as primitive sharks and nautiloids while other trilobites such as Aeglina prisca evolved to become swimming forms. Some trilobites even developed shovel-like snouts for ploughing through muddy sea bottoms. Another unusual clade of trilobites known as the trinucleids developed a broad pitted margin around their head shields. Some trilobites such as Asaphus kowalewski evolved long eyestalks to assist in detecting predators whereas other trilobite eyes in contrast disappeared completely.
Flora
Green algae were common in the Late Cambrian (perhaps earlier) and in the Ordovician. Terrestrial plants probably evolved from green algae, first appearing as tiny non-vascular forms resembling liverworts. Fossil spores from land plants have been identified in uppermost Ordovician sediments. The green algae were similar to today’s sea moss.Colonization of land would have been limited to shorelines
Among the first land fungi may have been arbuscular mycorrhiza fungi (Glomerales), playing a crucial role in facilitating the colonization of land by plants through mycorrhizal symbiosis, which makes mineral nutrients available to plant cells; such fossilized fungal hyphae and spores from the Ordovician of Wisconsin have been found with an age of about 460 million years ago, a time when the land flora most likely only consisted of plants similar to non-vascular bryophytes.
End of the period
The Ordovician came to a close in a series of extinction events that, taken together, comprise the second largest of the five major extinction events in Earth’s history in terms of percentage of genera that went extinct. The only larger one was the Permian-Triassic extinction event.
The extinctions occurred approximately 447–444 million years ago and mark the boundary between the Ordovician and the following Silurian Period. At that time all complex multicellular organisms lived in the sea, and about 49% of genera of fauna disappeared forever; brachiopods and bryozoans were greatly reduced, along with many trilobite, conodont and graptolite families.
The most commonly accepted theory is that these events were triggered by the onset of most cold conditions in the late Katian, followed by an ice age, in the Hirnantian faunal stage, that ended the long, stable greenhouse conditions typical of the Ordovician.
The ice age was possibly not long-lasting, study of oxygen isotopes in fossil brachiopods showing that its duration could have been only 0.5 to 1.5 million years. Other researchers (Page et al.) estimate more temperate conditions did not return until the late Silurian.
The late Ordovician glaciation event was preceded by a fall in atmospheric carbon dioxide (from 7000 ppm to 4400 ppm), which selectively affected the shallow seas where most organisms lived. As the southern supercontinent Gondwana drifted over the South Pole, ice caps formed on it, which have been detected in Upper Ordovician rock strata of North Africa and then-adjacent northeastern South America, which were south-polar locations at the time.
Glaciation locks up water from the world-ocean, and the interglacials free it, causing sea levels repeatedly to drop and rise; the vast shallow intra-continental Ordovician seas withdrew, which eliminated many ecological niches, then returned carrying diminished founder populations lacking many whole families of organisms, then withdrew again with the next pulse of glaciation, eliminating biological diversity at each change.Species limited to a single epicontinental sea on a given landmass were severely affected. Tropical lifeforms were hit particularly hard in the first wave of extinction, while cool-water species were hit worst in the second pulse.
Surviving species were those that coped with the changed conditions and filled the ecological niches left by the extinctions.
At the end of the second event, melting glaciers caused the sea level to rise and stabilise once more. The rebound of life’s diversity with the permanent re-flooding of continental shelves at the onset of the Silurian saw increased biodiversity within the surviving Orders.
Melott et al. (2004) suggested a ten-second gamma ray burst could have destroyed the ozone layer and exposed terrestrial and marine surface-dwelling life to deadly radiation and initiated global cooling.
Note : The above story is based on materials provided by Wikipedia
The Yellow River or Huang He is the second-longest river in Asia, following the Yangtze River, and the sixth-longest in the world at the estimated length of 5,464 km (3,395 mi). Originating in the Bayan Har Mountains in Qinghai province of western China, it flows through nine provinces, and it empties into the Bohai Sea near the city of Dongying in Shandong province. The Yellow River basin has an east–west extent of about 1,900 kilometers (1,180 mi) and a north–south extent of about 1,100 km (680 mi). Its total basin area is about 742,443 square kilometers (286,659 sq mi).
The Yellow River is called “the cradle of Chinese civilization”, because its basin was the birthplace of ancient Chinese civilization, and it was the most prosperous region in early Chinese history. However, frequent devastating floods and course changes produced by the continual elevation of the river bed, sometimes above the level of its surrounding farm fields, has also earned it the unenviable names China’s Sorrow and Scourge of the Sons of Han.
Name
Early Chinese literature including the Yu Gong or Tribute of Yu dating to the Warring States period (475 – 221 BC) refers to the Yellow River as simply 河 (Old Chinese: *C.gˤaj), a character that has come to mean “river” in modern usage. The first appearance of the name 黃河 (Old Chinese: *N-kʷˤaŋ C.gˤaj; Middle Chinese: Hwang Ha) is in the Book of Han written during the Western Han dynasty (206 BC – AD 9). The adjective “yellow” describes the perennial color of the muddy water in the lower course of the river, which arises from soil (loess) being carried downstream.
One of its older Mongolian names was the “Black River”, because the river runs clear before it enters the Loess Plateau, but the current name of the river among Inner Mongolians is Ȟatan Gol (Хатан гол, “Queen River”). In Mongolia itself, it is simply called the Šar Mörön (Шар мөрөн, “Yellow River”).
In Qinghai, the river’s Tibetan name is “River of the Peacock” (Tibetan: རྨ་ཆུ།, Ma Chu; Chinese: s 玛曲, t 瑪曲, p Mǎ Qū).
The name Hwang Ho in English is the Postal Map romanization of the river’s Mandarin name.
Geography
According to the China Exploration and Research Society, the source of the Yellow River is at 34° 29′ 31.1″ N, 96° 20′ 24.6″ E in the Bayan Har Mountains near the eastern edge of the Yushu Tibetan Autonomous Prefecture. The source tributuaries drain into Gyaring Lake and Ngoring Lake on the western edge of Golog Prefecture high in the Bayan Har Mountains of Qinghai. In the Zoige Basin along the boundary with Gansu, the Yellow River loops northwest and then northeast before turning south, creating the “Ordos Loop”, and then flows generally eastward across the North China Plain to the Gulf of Bohai, draining a basin of 752,443 square kilometers (290,520 sq mi) which nourishes 140 million people with drinking water and irrigation.
The Yellow River passes through seven present-day provinces and two autonomous regions, namely (from west to east) Qinghai, Gansu, Ningxia, Inner Mongolia, Shaanxi, Shanxi, Henan, and Shandong. Major cities along the present course of the Yellow River include (from west to east) Lanzhou, Yinchuan, Wuhai, Baotou, Luoyang, Zhengzhou, Kaifeng, and Jinan. The current mouth of the Yellow River is located at Kenli County, Shandong.
The river is commonly divided into three stages. These are roughly the northeast of the Tibetan Plateau, the Ordos Loop and the North China Plain. However, different scholars have different opinions on how the three stages are divided.[citation needed] This article adopts the division used by the Yellow River Conservancy Commission.
Note : The above story is based on materials provided by Wikipedia
A hypothetical model of the circum-Atlantic region at present-day, if Africa had split into two parts along the West African Rift system. Here, the north-west part of present day Africa would have moved with the South American continent, forming a “Saharan Atlantic ocean”. Credit: Sascha Brune/Christian Heine
Break-up of the supercontinent Gondwana about 130 Million years ago could have lead to a completely different shape of the African and South American continent with an ocean south of today’s Sahara desert, as geoscientists from the University of Sydney and the GFZ German Research Centre for Geosciences have shown through the use of sophisticated plate tectonic and three-dimensional numerical modelling.
The study highlights the importance of rift orientation relative to extension direction as key factor deciding whether an ocean basin opens or an aborted rift basin forms in the continental interior.
For hundreds of millions of years, the southern continents of South America, Africa, Antarctica, Australia, and India were united in the supercontinent Gondwana. While the causes for Gondwana’s fragmentation are still debated, it is clear that the supercontinent first split along along the East African coast in a western and eastern part before separation of South America from Africa took place. Today’s continental margins along the South Atlantic ocean and the subsurface graben structure of the West African Rift system in the African continent, extending from Nigeria northwards to Libya, provide key insights on the processes that shaped present-day Africa and South America.
Christian Heine (University of Sydney) and Sascha Brune (GFZ) investigated why the South Atlantic part of this giant rift system evolved into an ocean basin, whereas its northern part along the West African Rift became stuck.
“Extension along the so-called South Atlantic and West African rift systems was about to split the African-South American part of Gondwana North-South into nearly equal halves, generating a South Atlantic and a Saharan Atlantic Ocean,” geoscientist Sascha Brune explains. “In a dramatic plate tectonic twist, however, a competing rift along the present-day Equatorial Atlantic margins, won over the West African rift, causing it to become extinct, avoiding the break-up of the African continent and the formation of a Saharan Atlantic ocean.”
The complex numerical models provide a strikingly simple explanation: the larger the angle between rift trend and extensional direction, the more force is required to maintain a rift system. The West African rift featured a nearly orthogonal orientation with respect to westward extension which required distinctly more force than its ultimately successful Equatorial Atlantic opponent.
Note : The above story is based on materials provided by Helmholtz Centre Potsdam – GFZ German Research Centre for Geosciences.
