The Angara River is a 1,779-kilometer-long (1,105 mi) river in Irkutsk Oblast and Krasnoyarsk Krai, south-east Siberia, Russia. It is the river that drains Lake Baikal, and is the headwater tributary of the Yenisei River.
Leaving Lake Baikal near the settlement of Listvyanka (at 51.867°N 104.818°E), the Angara flows north past the Irkutsk Oblast’s cities of Irkutsk, Angarsk, Bratsk, and Ust-Ilimsk. It then turns west, enters the Krasnoyarsk Krai, and falls into the Yenisei near Strelka (at 58.102°N 92.991°E, 40 km south-east of Lesosibirsk).
Below its junction with the Ilim River, the Angara has been known in the past as the Upper Tunguska (Russian: Верхняя Тунгуска, Verkhnyaya Tunguska). Confusingly, some maps (e.g., 1773 atlas by Kitchen) referred to this same section of the Angara as Nizhnyaya Tunguska, i.e. the Lower Tunguska – the name that is currently applied to another river.
Note : The above story is based on materials provided by Wikipedia
The female skull still had its teeth intact, which made the find even rarer. Credit: Photo by Lacey Nobles
In the dangerous waters of an ancient oxbow lake created by a flooded and unnamed meandering river, the female phytosaur died and sank to the bottom 205 million years ago. About 40 yards away the remains of a larger male also came to rest, and both disappeared in a tomb of soil and sediment.
Evidence for the cause of their deaths and the rest of their bodies have vanished with time, but their skulls remained. After careful research, a Texas Tech paleontologist says he and others have discovered a new species of the Triassic-age monster in the wilds of West Texas.
Their findings were published in the peer-reviewed journal Earth and Environmental Science Transactions of the Royal Society of Edinburgh.
Bill Mueller, assistant curator of Paleontology at the Museum of Texas Tech University, said the team named their find Machaeroprosopus lottorum after the Lott family who own the ranch on which the animal was discovered.
“We found them in an area we’d been excavating in,” Mueller said. “I think we’ve gotten four skulls out of
Cunningham, currently a field research assistant at the museum and a retired firefighter, remembered finding the unusual female skull on June 27, 2001. After removing it from the mudstone, he recalls looking it over carefully with others and wondering if his discovery would add a new animal to science.
“It was really well preserved with the teeth and everything,” Cunningham said. “Finding one with teeth is pretty rare. It was so odd, but when they come out of the ground, you have a long way to go to actually see what you have because they’re still covered in matrix. We were all kind of in awe of it. It had this long, skinny snout. It was quite a bit different. It took me years to get it prepped and ready. At the time, I was working full-time and I did that on my days off.” By looking an opening on the skull called the supratemporal fenestra, the snout and the shape of the bones at the back of the head, the team compared it to other phytosaurs and determined they’d discovered a separate species.
While West Texas is dry and dusty today, Mueller said the landscape looked more like a swampy, tropical rainforest during the Triassic period. Our planet’s landmasses had converged to form the supercontinent of Pangaea. In the forest undergrowth covered by tall conifers and choked with ferns, phytosaurs lurked beneath the water and waited for prey.
“A phytosaur resembles a crocodile,” Mueller said. “They had basically the same lifestyle as the modern
Bill Mueller stands in front of the case that houses the skull, bottom right, of the new phytosaur species.
crocodile by living in and around the water, eating fish, and whatever animals came to the margins of the rivers and lakes. But one of the big differences is the external nares, the nose, is back up next to its eyes instead of at the end of its snout.”
Mueller said scientists can tell the sexes of the animals by a distinctive feature on males. A bony crest stretched from the nostrils by the eyes to the tip of the animal’s beak — a feature lady phytosaurs probably found sexy.
Judging by the female’s skull size, which is more than three feet in length, Mueller guessed she would have measured 16 to 17 feet in length from nose to tail tip. The male would have measured about 17 to 18 feet. Their thin jaws suggested they hunted mainly fish as opposed to big prey.
Mueller said phytosaurs lived throughout the Triassic period from 230 to 203 million years ago, but died out during a mysterious mass extinction. Highly successful animals, they are commonly found because these animals liked to live in swampy areas and were more likely to become covered in sediment and fossilized.
that area already. Doug Cunningham found this specimen, and then we dug it up. When he found it, just the very back end of the skull was sticking out of the ground. The rest was buried. We excavated it and brought it into the museum to finish preparation.”
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Note : The above story is based on materials provided by Texas Tech University. The original article was written by John Davis.
Tourists flock to Italy to see Michelangelo’s David and other iconic hunks of Renaissance stone, but in a trip over spring break, a group of Columbia students got to visit rocks that have shaped the world in even more profound ways. In the limestone outcrops of Italy’s Apennine Mountains, geologist Walter Alvarez collected some of the earliest evidence that a massive fireball falling from space some 66 million years ago was responsible for killing off the dinosaurs. Geologists have trekked to the region since then to study that catastrophic event as well as others imprinted in these rocks.
In March, it was the Columbia students’ turn. Led by Steven Goldstein and Sidney Hemming, scientists at Columbia’s Lamont-Doherty Earth Observatory, and visiting scientist David Barbeau, the students touched evidence of undersea mudslides, the drying of the Mediterranean Sea, and several extinction crises, including the one that ended the Age of Dinosaurs.
From about 200 million years ago to 6 million years ago, the vast, shallow Tethys Sea covered much of the Apennines, in Italy’s Umbria-Marche region. As the tiny plants and animals that lived in the sea died, their shells and skeletons piled up, leaving a record of the environment in which they lived. Later, tectonic forces rearranged this landscape, forming the Apennines in several bouts of squeezing and stretching. The activity left limestones made up of tiny microfossils exposed on land, providing a page-by-page story of the past.
More than any other geologist, Alvarez and his late father, Luis, are responsible for putting these rocks on the map. Now a professor-emeritus at University of California, Berkeley, the younger Alvarez began his career at Lamont-Doherty Earth Observatory in the late 1960s at the height of the plate tectonic revolution. In the 1970s, Alvarez traveled to the Bottaccione Gorge in Gubbio to measure magnetic reversals recorded in the rock to understand how seafloor spreading had moved Earth’s continents. Earth’s magnetic field periodically flips, leaving invisible stripes on the seafloor where magma rising from the mantle is magnetized in a northerly or southerly direction. These stripes also showed up in the Apennines, and Alvarez hoped that by dating them using the microfossils in each layer, he could learn more about the movement of continents.
But he stumbled across another mystery. At about 66 million years ago, the one-celled Globotruncana foraminifera suddenly disappeared from the fossil record, replaced by a smaller, more opportunistic species. Separating the two species was a half-inch of mud with no life at all. Testing the clay, Alvarez discovered high levels of the rare element iridium-an element rare on Earth’s surface but common in space. In a 1980 paper in Science, Alvarez hypothesized that a large comet or asteroid had fallen to Earth, kicking up a dust layer that blocked out the sun, starving much of life on earth. The dinosaurs and more than half of Earth’s species died during this time, marking the end of the Cretaceous period and start of the Tertiary, or in geology jargon: the K/T, boundary. In the late 1970s, two geophysicists searching for oil off Mexico’s Yucatán Peninsula discovered a 110-mile wide crater but it was many years before the Chicxulub crater was conclusively linked to Alvarez’s theory.
Sandro Montanari met Alvarez on one of his field trips to Gubbio, and at Alvarez’s encouragement, flew to California to pursue a PhD in geology. Among other things, Montanari collected evidence for a mega-tsunami in the Gulf of Mexico triggered by a six-mile wide asteroid crashing into the Yucatán. Eventually, Montanari returned to Italy and with Alvarez, bought and restored a farming hamlet, Coldigioco, outside the town of Apiro. Since 1992, Coldigioco has served as a base camp for geologists working in the area. Barbeau spent a summer there as a student at Carleton College, so when his colleagues at Lamont were searching for a new place to take students on spring break, Barbeau suggested the Apennines.
In the weeks leading up to the trip, the students read scientific papers detailing the discoveries made in this region and took turns presenting the material in class. They covered Italy’s tectonics and the evidence for several mass extinctions recorded in the Apennines’ exposed marine sediments of the Apennines—the K/T extinctions 66 million years ago; the Paleocene-Eocene Thermal Maximum, about 55 million years ago, when a rapid warming of the planet killed off many species, leading to the rise of some modern mammals; and the Eocene-Oligocene extinctions, about 34 million years ago, marked by a rapid cooling and the emergence of ice on Antarctica.
They would also study the drying of the Mediterranean Sea in an event called the Messinian Salinity Crisis, about 6 million years ago, and how scientists, including Lamont’s William Ryan, pieced the story together from sediments collected at sea; and the formation of the Frasassi Caves, discovered by their guide, Montanari, as a teenager. One day after their plane landed in Milan, they were on the ground, seeing, tasting and touching the places they had read about.
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The above story is based on materials provided by Columbia University
This is a Dimetrodon skull with histological thin section tooth detail by Danielle Dufault. Credit: Danielle Dufault
The first top predators to walk on land were not afraid to bite off more than they could chew, a University of Toronto Mississauga study has found.
Graduate student and lead author Kirstin Brink along with Professor Robert Reisz from U of T Mississauga’s Department of Biology suggest that Dimetrodon, a carnivore that walked on land between 298 million and 272 million years ago, was the first terrestrial vertebrate to develop serrated ziphodont teeth.
According to the study published in Nature Communications, ziphodont teeth, with their serrated edges, produced a more-efficient bite and would have allowed Dimetrodon to eat prey much larger than itself.
While most meat-eating dinosaurs possessed ziphodont teeth, fossil evidence suggests serrated teeth first evolved in Dimetrodon some 40 million years earlier than theropod dinosaurs.
“Technologies such as scanning electron microscope (SEM) and histology allowed us to examine these teeth in detail to reveal previously unknown patterns in the evolutionary history of Dimetrodon,” Brink said.
The four-meter-long Dimetrodon was the top of the terrestrial food chain in the Early Permian Period and is considered to be the forerunner of mammals.
According to Brink and Reisz’s research, Dimetrodon had a diversity of previously unknown tooth structures and were also the first terrestrial vertebrate to develop cusps — teeth with raised points on the crown, which are dominant in mammals.
The study also suggests ziphodont teeth were confined to later species of Dimetrodon, indicating a gradual change in feeding habits.
“This research is an important step in reconstructing the structure of ancient complex communities,” Reisz said.
“Teeth tell us a lot more about the ecology of animals than just looking at the skeleton.”
“We already know from fossil evidence which animals existed at that time but now with this type of research we are starting to piece together how the members of these communities interacted.”
Brink and Reisz studied the changes in Dimetrodon teeth across 25 million years of evolution.
The analysis indicated the changes in tooth structure occurred in the absence of any significant evolution in skull morphology. This, Brink and Reisz suggest, indicates a change in feeding style and trophic interactions.
“The steak knife configuration of these teeth and the architecture of the skull suggest Dimetrodon was able to grab and rip and dismember large prey,” Reisz said.
“Teeth fossils have attracted a lot of attention in dinosaurs but much less is known about the animals that lived during this first chapter in terrestrial evolution.”
Note : The above story is based on materials provided by University of Toronto.
Scientists studying methane-producing microbes, like the ones found in deep-sea hydrothermal vents pictured here, discovered that a protein critical to photosynthesis likely developed on Earth long before oxygen became available. Credit: Image courtesy of Virginia Tech
An international team of researchers led by scientists at Virginia Tech and the University of California, Berkeley has discovered that a process that turns on photosynthesis in plants likely developed on Earth in ancient microbes 2.5 billion years ago, long before oxygen became available.
The research offers new perspective on evolutionary biology, microbiology, and the production of natural gas, and may shed light on climate change, agriculture, and human health.
“By looking at this one mechanism that was not previously studied, we will be able to develop new basic information that potentially has broad impact on contemporary issues ranging from climate change to obesity,” said Biswarup Mukhopadhyay, an associate professor of biochemistry at the Virginia Tech College of Agriculture and Life Sciences, and the senior author of the study. He is also a faculty member at the Virginia Bioinformatics Institute. Plant and microbial biology professor emeritus Bob B. Buchanan co-led the research and co-authored the paper.
The findings were described this week in an early online edition of the Proceedings of the National Academy of Sciences.
This research concerns methane-forming archaea, a group of microbes known as methanogens, which live in areas where oxygen is absent. Methane is the main component of natural gas and a potent greenhouse gas.
“This innovative work demonstrates the importance of a new global regulatory system in methanogens,” said William Whitman, a professor of microbiology at the University of Georgia who is familiar with the study, but not connected to it. “Understanding this system will provide the tools to use these economically important microorganisms better.”
Methanogens play a key role in carbon cycling. When plants die, some of their biomass is trapped in areas that are devoid of oxygen, such as the bottom of lakes.
Methanogens help convert the residual biological material to methane, which other organisms convert to carbon dioxide — a product that can be used by plants.
This natural process for producing methane forms the basis for treating municipal and industrial wastes, helps reduce pollution, and provides methane for fuel. The same process allows natural gas production from agricultural residues, a renewable resource.
Methanogens also play an important role in agriculture and human health. They live in the digestive systems of cattle and sheep where they facilitate the digestion of feed consumed in the diet.
Efforts to control methanogens in specific ways may improve feed utilization and enhance the production of meat and milk, researchers say.
Methanogens are additionally a factor in human nutrition. The organisms live in the large intestine, where they enhance the breakdown of food. Some have proposed that restricting this activity of methanogens could help alleviate obesity.
The team investigated an ancient type of methanogen, Methanocaldococcus jannaschii, which lives in deep-sea hydrothermal vents or volcanoes where environmental conditions mimic those that existed on the early Earth.
They found that the protein thioredoxin, which plays a major role in contemporary photosynthesis, could repair many of the organism’s proteins damaged by oxygen.
Since methanogens developed before oxygen appeared on earth, the evidence raises the possibility that thioredoxin-based metabolic regulation could have come into play for managing anaerobic life long before the advent of oxygen.
“It is rewarding to see that our decades of research on thioredoxin and photosynthesis are contributing to understanding the ancient process of methane formation,” Buchanan said. “It is an excellent illustration of how a process that proved successful early in evolution has been retained in the development of highly complex forms of life.”
Dwi Susanti, the lead author, recently received her doctoral degree in genetics, bioinformatics and computational biology from the Virginia Bioinformatics Institute, and is currently a postdoctoral scholar in the Department of Biochemistry at Virginia Tech.
Usha Loganathan, a graduate student in the Department of Biological Sciences in the College of Science at Virginia Tech, also participated in the study. William H. Vensel of the Western Regional Research Center in Albany, Calif., provided proteomics expertise as did Joshua Wong of University of California, Berkeley. Rebecca De Santis and Ruth Schmitz-Streit of University of Kiel in Germany, and Monica Balsera of the Institute of Natural Resources and Agrobiology of Salamanca in Spain also worked on the project
Grants from the National Science Foundation, the National Aeronautics and Space Administration, and the U.S. Department of Agriculture helped support the research.
Note : The above story is based on materials provided by Virginia Tech (Virginia Polytechnic Institute and State University).
Chemical Formula: CaMgSi2O6 Locality: Wide spread occurrence. Name Origin: From the Greek dis – “two kinds” and opsis – “opinion.”
Diopside is a monoclinic pyroxene mineral with composition MgCaSi2O6. It forms complete solid solution series with hedenbergite (FeCaSi2O6) and augite, and partial solid solutions with orthopyroxene and pigeonite. It forms variably colored, but typically dull green crystals in the monoclinic prismatic class. It has two distinct prismatic cleavages at 87 and 93° typical of the pyroxene series. It has a Mohs hardness of six, a Vickers hardness of 7.7 GPa at a load of 0.98 N, and a specific gravity of 3.25 to 3.55. It is transparent to translucent with indices of refraction of nα=1.663–1.699, nβ=1.671–1.705, and nγ=1.693–1.728. The optic angle is 58° to 63°.
Physical Properties of Diopside
Cleavage: {110} Good, {???} Indistinct Color: Blue, Brown, Colorless, Green, Gray. Density: 3.25 – 3.55, Average = 3.4 Diaphaneity: Transparent to translucent Fracture: Brittle – Conchoidal – Very brittle fracture producing small, conchoidal fragments. Hardness: 6 – Orthoclase Luminescence: Sometimes fluorescent.- red-purple Luster: Vitreous (Glassy) Streak: white green
Scientists at the University of Liverpool have shown that deep sea fault zones could transport much larger amounts of water from the Earth’s oceans to the upper mantle than previously thought.
Water is carried mantle by deep sea fault zones which penetrate the oceanic plate as it bends into the subduction zone. Subduction, where an oceanic tectonic plate is forced beneath another plate, causes large earthquakes such as the recent Tohoku earthquake, as well as many earthquakes that occur hundreds of kilometers below the Earth’s surface.
Seismic modelling
Seismologists at Liverpool have estimated that over the age of the Earth, the Japan subduction zone alone could transport the equivalent of up to three and a half times the water of all the Earth’s oceans to its mantle.
Using seismic modelling techniques the researchers analysed earthquakes which occurred more than 100 km below the Earth’s surface in the Wadati-Benioff zone, a plane of Earthquakes that occur in the oceanic plate as it sinks deep into the mantle.
Analysis of the seismic waves from these earthquakes shows that they occurred on 1 – 2 km wide fault zones with low seismic velocities. Seismic waves travel slower in these fault zones than in the rest of the subducting plate because the sea water that percolated through the faults reacted with the oceanic rocks to form serpentinite – a mineral that contains water.
Some of the water carried to the mantle by these hydrated fault zones is released as the tectonic plate heats up. This water causes the mantle material to melt, causing volcanoes above the subduction zone such as those that form the Pacific ‘ring of fire’. Some water is transported deeper into the mantle, and is stored in the deep Earth.
“It has been known for a long time that subducting plates carry oceanic water to the mantle,” said Tom Garth, a PhD student in the Earthquake Seismology research group led by Professor Andreas Rietbrock.
“This water causes melting in the mantle, which leads to arc releasing some of the water back into the atmosphere. Part of the subducted water however is carried deeper into the mantle and may be stored there.
Large amounts of water deep in the Earth
“We found that fault zones that form in the deep oceanic trench offshore Northern Japan persist to depths of up to 150 km. These hydrated fault zones can carry large amounts of water, suggesting that subduction zones carry much more water from the ocean down to the mantle than has previously been suggested.
“This supports the theory that there are large amounts of water stored deep in the Earth.”
Understanding how much water is delivered to the mantle contributes to knowledge of how the mantle convects, and how it melts, which helps to understand how plate tectonics began, and how the continental crust was formed.
Note : The above story is based on materials provided by University of Liverpool
New research, published in Earth and Planetary Research Letters, led by scientists from the University of Cambridge, used plankton – tiny bugs, whose shells litter the ocean floors. By drilling into the seabed scientists can extract shells from plankton which lived millions of years ago.
‘The shells we used are of a type of plankton called foraminifera. They’re only about one tenth of a millimetre big, or small rather, and have been around over 150 million years, so we get a really well-preserved record of them in marine sediments going back tens of millions of years,’ explains Oscar Branson, a PhD student at the University of Cambridge and lead author of the study. ‘Recently people have been analysing them for climate records, but now we realise they’re more complex.’
As plankton grow they build a bit more onto their shells every day by turning elements in the sea water into harder minerals and adding them on. The impurities in the shell depend on what was in the sea water as the plankton grew, so these million-year-old shells can give us an almost daily snapshot of the chemistry of the oceans as it was when they were still alive.
‘We realised plankton have these growth bands, like tree rings, which we thought might tell us something in more detail. It turns out these bands are produced almost daily so you may one day be able to get a 5 day weather report by looking at them,’ Branson says.
The team used a synchrotron in California to study the shells, which let them find out how much magnesium was in each growth band compared to other chemicals.
Synchrotrons use magnetic and electrical fields to accelerate particles round a huge ring. As these charged particles approach the speed of light they give off radiation known as synchrotron light.
Researchers divert this light away from the main ring and down a targeted beamline, where it can be used in a similar way to an X-ray to study the structure of matter at tiny scales.
‘The concentration of magnesium changes depending on temperature of sea water, so by finding out how much there was in the shell it should allow us to find out the temperature of seawater virtually each day for the last 150 million years,’ says Branson.
The magnesium is more likely to be built into shells in warmer waters because it replaces calcium in their atomic structure.
‘Our X-ray data show that the trace magnesium sits inside the crystalline mineral structure of the plankton shell,’ concludes Professor Simon Redfern of the University of Cambridge, who also worked on the project. ‘That’s important because it validates previous assumptions about using magnesium contents as a measure of past ocean temperature.’
Note : The above story is based on materials provided by PlanetEarth Online
Chemical Formula: Cu9S5 Locality: In the USA, at Butte, Silver Bow Co., Montana. Name Origin: From the Greek for “two kinds” or “sexes,” in reference to the presumed presence of both cuprous and cupric ions.
Digenite is a copper sulfide mineral with formula: Cu9S5. Digenite is a black to dark blue opaque mineral that crystallizes with a trigonal – hexagonal scalenohedral structure. In habit it is usually massive, but does often show pseudo-cubic forms. It has poor to indistinct cleavage and a brittle fracture. It has a Mohs hardness of 2.5 to 3 and a specific gravity of 5.6. It is found in copper sulfide deposits of both primary and supergene occurrences. It is typically associated with and often intergrown with chalcocite, covellite, djurleite, bornite, chalcopyrite and pyrite. The type locality is Sangerhausen, Thuringia, Germany, in copper slate deposits.
Occurrence
Digenite occurs in the transitional zone of supergene oxidation of primary sulfide ore deposits, at the interface between the upper and lower saprolite ore zones. It is rarely an important mineral for copper ores, as it is more usually replaced by chalcocite further up in the weathering profile, and is a minor weathering product of primary chalcopyrite. Natural digenite always contains a small amount of iron and is considered to be stable only in the Cu-Fe-S system.
In the Deflector and Deflector West Cu-Au lode deposits of the Gullewa Greenstone Belt, Western Australia, digenite is an important constituent of the transitional Cu-Au ore. However, it is difficult to treat metallurgically and remains a refractory ore type. In this locality digenite is found with covellite, chalcocite and bornite.
It was first described in 1844 from the type locality of Sangerhausen, Saxony-Anhalt, Germany. The name is from the Greek digenus meaning of two origins in reference to its close resemblance with chalcocite and covellite.
Physical Properties of Digenite
Cleavage: {???} Indistinct Color: Blue, Dark blue, Black. Density: 5.6 Diaphaneity: Opaque Fracture: Brittle – Conchoidal – Very brittle fracture producing small, conchoidal fragments. Hardness: 2.5-3 – Finger Nail-Calcite Luster: Sub Metallic Streak: grayish black
Yenisei (Russian: Енисе́й), also written as Yenisey, is the largest river system flowing to the Arctic Ocean. It is the central of the three great Siberian rivers that flow into the Arctic Ocean (the other two being the Ob River and the Lena River). Rising in Mongolia, it follows a northerly course to the Yenisei Gulf in the Kara Sea, draining a large part of central Siberia, the longest stream following the Yenisei-Angara-Selenga-Ider river system.
The upper reaches, subject to rapids and flooding, pass through sparsely populated areas. The middle section is controlled by a series of massive hydroelectric dams fuelling significant Russian primary industry. Partly built by gulag labor in Soviet times, industrial contamination remains a serious problem in an area hard to police. Moving on through sparsely populated taiga, the Yenisei swells with numerous tributaries and finally reaches the Kara Sea in desolate tundra where it is icebound for more than half the year.
The maximum depth of the Yenisei River is 80 feet (24 m) and the average depth is 45 feet (14 m). The depth of river outflow is 106 feet (32 m) and inflow is 101 feet (31 m).
The Yenisei basin, including Lake Baikal
Course
The river flows through Khakassia.
Lake Baikal
The 320 km (200 mi) partly navigable Upper Angara River feeds into the northern end of Lake Baikal from the Buryat Republic but the largest inflow is from the Selenga which forms a delta on the south-eastern side.
Lower Yenisei
The Great Kaz joins the Yenisei 300 kilometres (190 mi) downstream from Strelka. It is noteworthy for its connection to the Ob via the Ob-Yenisei canal and the Ket River.
Note : The above story is based on materials provided by Wikipedia
The work is expected to help discover new mineral deposits in WA, but the technique isn’t just limited to mining. Credit: Paul Reid
Mark Jessell has travelled half way around the world to help develop 3D software technology that will allow us to scratch beneath the earth’s surface and tell us more about such things as our mineral and water resources.
Professor Jessell is an internationally renowned structural geologist who recently moved to Perth to take up one of three prestigious WA Research Fellowships.
He is now based at the Centre for Exploration Targeting at the University of Western Australia.
He says good data is the key to unlocking the earth’s secrets.
“One of the problems is that we don’t have enough data,” he says.
“Even though we have lots of data, it’s not enough.
“We can a have a photograph of the surface, but what’s going on beneath the surface is much less sure.
“One of the problems we have is that the software at the moment isn’t really adapted to take in that uncertainty.”
As part of his research over the next few years, Prof Jessell will be looking at modifying and re-writing existing 3D software to tweak it to WA conditions.
“What we’re going to try to do is develop things that sit on top of existing packages that are specifically aimed at solving our problems,” he says.
Part of the work will focus on what is called geological inversion, which involves using geophysical data in 3D models and showing what is under the earth’s surface.
It is innovative technology – and the high-powered computing facilities such as those at the recently-opened Pawsey Centre was one of the things that attracted him to Perth.
“For the geophysical inversion side of our project, the access to that supercomputing facility is a big draw[card],” he says.
The work is expected to help discover new mineral deposits in WA, but the technique isn’t just limited to mining.
“The 3D geology of Western Australia is important to lots of other groups apart from the minerals industry,” he says.
“It’s also important to anybody who is worried about water in WA because the water we have comes from beneath the surface.
“And where it’s stored and where it goes and how it interacts with runoff from agriculture is all controlled by the 3D distribution of the geology.
“This is a big topic and its not something we’re going to be able to do alone.
“I’ve got colleagues at the CSIRO and the Geological Survey of WA and what we hope to do is have a critical mass of people working together on this problem.”
Note : The above story is based on materials provided by Science Network WA
Locality: Common world wide. Name Origin: From the Greek word “to scatter,” referring to the mineral’s easy disintegration in the blowpipe flame.
Diaspore also known as empholite, kayserite, or tanatarite, is an aluminium oxide hydroxide mineral, α-AlO(OH), crystallizing in the orthorhombic system and isomorphous with goethite. It occurs sometimes as flattened crystals, but usually as lamellar or scaly masses, the flattened surface being a direction of perfect cleavage on which the lustre is markedly pearly in character. It is colorless or greyish-white, yellowish, sometimes violet in color, and varies from translucent to transparent. It may be readily distinguished from other colorless transparent minerals with a perfect cleavage and pearly luster—like mica, talc, brucite, and gypsum— by its greater hardness of 6.5 – 7. The specific gravity is 3.4. When heated before the blowpipe it decrepitates violently, breaking up into white pearly scales.
The mineral occurs as an alteration product of corundum or emery and is found in granular limestone and other crystalline rocks. Well-developed crystals are found in the emery deposits of the Urals and at Chester, Massachusetts, and in kaolin at Schemnitz in Hungary. If obtainable in large quantity, it would be of economic importance as a source of aluminium.
Diaspore, along with gibbsite and boehmite, is a major component of the aluminium ore bauxite.
It was first described in 1801 for an occurrence in Mramorsk Zavod, Sverdlovskaya Oblast, Middle Urals, Russia. The name is from the Greek for διασπείρειυ, to scatter, in allusion to its decrepitation on heating.
Ottomanite, and zultanite are trade names for gem-quality diaspore (also known as Turkish diaspore) from the İlbir Mountains of southwest Turkey.
Physical Properties of Diaspore
Cleavage: {010} Perfect, {110} Good Color: White, Greenish gray, Grayish brown, Colorless, Yellow. Density: 3.3 – 3.5, Average = 3.4 Diaphaneity: Transparent to subtranslucent Fracture: Brittle – Conchoidal – Very brittle fracture producing small, conchoidal fragments. Hardness: 6.5-7 – Pyrite-Quartz Luminescence: Non-fluorescent. Luster: Vitreous – Pearly Streak: white
Photos :
This sample of diaspore is displayed in the Smithsonian Museum of Natural History. The sample is about 3 cm across and is from Mugla, Menderes Mountains, Anatolia, Turkey.DIASPORE on MARGARITEMugla Province, Aegean Region, Turkey Miniature, 3.8 x 2.6 x 2.3 cm “Courtesy of Rob Lavinsky, The Arkenstone, www.iRocks.com”
At roughly 50-60 feet long, the Yongjinglong individual discovered was a medium-sized Titanosaur. Anatomical evidence, however, points to it being a juvenile; adults may have been larger.Credit: University of Pennsylvania
A team led by University of Pennsylvania paleontologists has characterized a new dinosaur based on fossil remains found in northwestern China. The species, a plant-eating sauropod named Yongjinglong datangi, roamed during the Early Cretaceous period, more than 100 million years ago. This sauropod belonged to a group known as Titanosauria, members of which were among the largest living creatures to ever walk the earth.
At roughly 50-60 feet long, the Yongjinglong individual discovered was a medium-sized Titanosaur. Anatomical evidence, however, points to it being a juvenile; adults may have been larger.
The find, reported in the journal PLOS ONE, helps clarify relationships among several sauropod species that have been found in the last few decades in China and elsewhere. Its features suggest that Yongjinglong is among the most derived, or evolutionarily advanced, of the Titanosaurs yet discovered from Asia.
Doctoral student Liguo Li and professor Peter Dodson, who have affiliations in both the School of Veterinary Medicine’s Department of Animal Biology and the School of Arts and Sciences’ Department of Earth and Environmental Science, led the work. They partnered with Hailu You, a former student of Dodson’s, who now works at the Chinese Academy of Sciences’ Institute of Vertebrate Paleontology and Paleoanthropology, and Daqing Li of the Gansu Geological Museum in Lanzhou, China.
Until very recently, the United States was the epicenter for dinosaur diversity, but China surpassed the U.S. in 2007 in terms of species found. This latest discovery was made in the southeastern Lanzhou-Minhe Basin of China’s Gansu Province, about an hour’s drive from the province’s capital, Lanzhou. Two other Titanosaurs from the same period, Huanghetitan liujiaxiaensis and Daxiatitan binglingi, were discovered within the last decade in a valley one kilometer from the Yongjinglong fossils.
“As recently as 1997 only a handful of dinosaurs were known from Gansu,” Dodson said. “Now it’s one of the leading areas of China. This dinosaur is one more of the treasures of Gansu.”
During a trip to Gansu, Liguo Li was invited to study the remains, which had been in storage since being unearthed in 2008. They consisted of three teeth, eight vertebrae, the left shoulder blade, and the right radius and ulna.
The anatomical features of the bones bear some resemblance to another Titanosaur that had been discovered by paleontologists in China in 1929, named Euhelopus zdanskyi. But the team was able to identify a number of unique characteristics.
“The shoulder blade was very long, nearly 2 meters, with sides that were nearly parallel, unlike many other Titanosaurs whose scapulae bow outward,” Li said.
The scapula was so long, indeed, that it did not appear to fit in the animal’s body cavity if placed in a horizontal or vertical orientation, as is the case with other dinosaurs. Instead, Li and colleagues suggest the bone must have been oriented at an angle of 50 degrees from the horizontal.
In addition, an unfused portion of the shoulder blade indicated to the researchers that the animal under investigation was a juvenile or subadult.
“The scapula and coracoid aren’t fused here,” Li said. “It is open, leaving potential for growth.”
Thus, a full-grown adult might be larger than this 50-60 foot long individual. Future finds may help elucidate just how much larger, the researchers noted.
The ulna and radius were well preserved, enough so that the researchers could identify grooves and ridges they believe correspond with the locations of muscle attachments in the dinosaur’s leg.
The researchers were also able to draw evidence about the dinosaur’s relationship to other species from the vertebrae, one of which was from the neck and the other seven from the trunk. Notably, the vertebrae had large cavities in the interior that the team believes provided space for air sacs in the dinosaur’s body.
“These spaces are unusually large in this species,” Dodson said. “It’s believed that dinosaurs, like birds, had air sacs in their trunk, abdominal cavity and neck as a way of lightening the body.”
In addition, the longest tooth they found was nearly 15 centimeters long. Another shorter tooth contained unique characteristics, including two “buttresses,” or bony ridges, on the internal side, while Euhelopus had only one buttress on its teeth.
To gain a sense of where Yongjinglong sits on the family tree of sauropods, the researchers were able to compare its characteristics with specimens from elsewhere in China, as well as from Africa, South America and the U.S.
“We used standard paleontological techniques to compare it with phylogenies based on other specimens,” Dodson said. “It is definitely much more derived than Euhelopus and shows close similarities to derived species from South America.”
Not only does the discovery point to the fact that Titanosaurs encompass a diverse group of dinosaurs, but it also supports the growing consensus that sauropods were a dominant group in the Early Cretaceous — a view that U.S. specimens alone could not confirm.
“Based on U.S. fossils, it was once thought that sauropods dominated herbivorous dinosaur fauna during the Jurassic but became almost extinct during the Cretaceous,” Dodson said. “We now realize that, in other parts of the world, particularly in South America and Asia, sauropod dinosaurs continued to flourish in the Cretaceous, so the thought that they were minor components is no longer a tenable view.”
Note : The above story is based on materials provided by University of Pennsylvania. Note: Materials may be edited for content and length.
Ancient rocks in Quebec hold secrets to the early Earth
Provocative new research published this month in the journal Geology suggests that oceanic plate subduction was operating from the earliest times in Earth’s history, meaning conditions for the formation of life may have existed up to a billion years earlier than generally thought.
These findings came from a team of Australian researchers, who analysed similarities between modern-day subduction zones near Japan and early-Earth rock sequences from Quebec, Canada.
Subduction is a process whereby an oceanic plate descends beneath another plate (a characteristic of modern plate tectonics).
Lead author, Macquarie University’s Professor Simon Turner says, “Modern subduction settings, such as the Mariana arc, have all the right chemical ingredients to grow and sustain primitive life forms.
“From the similarities of our research into the earlier deposits from Canada, it follows that the conditions for the formation of life may have existed much earlier, with subduction starting far longer ago than we’d thought previously.”
The early Earth’s geological processes remain a fundamental question for the earth sciences and the rareness of rocks from this time period make exploration a significant challenge.
“We expect that this research will result in a lot of debate across the discipline, as there’s much that is yet to be discovered in the processes and earliest records of subduction. Our next steps are to investigate Zn isotopes which could show whether high pH fluids were present to stabilise amino acids, and we’ll continue to explore the secrets under the Earth’s crust”.
Note : The above story is based on materials provided by Macquarie University
Degassing lava erupts onto the seafloor at NW Rota-1 volcano, creating a billowing cloudy plume that is extremely acidic, and is full of carbon dioxide and sulfur. Credit: Woods Hole Oceanographic Institution
Oregon State University scientists have discovered how to pinpoint the time and place of underwater volcanic eruptions using satellite images.
Volcanic eruptions on the ocean floor can spew large amounts of pumice and fine particles, as well as hot water that brings nutrients to the surface, resulting in plumes of algae. The plumes are picked up as shades of green in satellite images.
“Some volcanic eruptions take place hundreds of feet below water and show no changes to the sea surface to the naked eye,” said Robert O’Malley, an OSU research assistant in botany and plant pathology in OSU’s College of Agricultural Sciences. “It’s amazing an orbiting satellite can detect color changes that indicate an eruption has taken place. Many times you can’t spot an eruption if you were floating over it in a boat.”
Underwater volcanic eruptions are rarely detected, so little is known about them, according to Mike Behrenfeld, an OSU expert in marine algae and and one of the researchers on the project.
“Satellite measurements of the planet are made every day,” Behrenfeld said, “so this new method provides another tool for spotting these dramatic events that affect life in the oceans.”
O’Malley and Behrenfeld developed a process for analyzing low-resolution images to show evidence of eruptions, which can extend over thousands of square miles, by matching five known eruptions with data from NASA satellites.
“We measured sunlight going into the ocean interacting with particles consistent with underwater volcanic eruptions,” said O’Malley. “From there, we found we could connect color data with documented eruptions. Now we have a better idea of what to look for in the data when we don’t know about the eruption first.”
Next, the researchers plan to test how well their method works as eruptions are happening. Further study will also focus on the depth at which eruptions can be detected.
The study was published in the journal Remote Sensing of the Environment.
Note : The above story is based on materials provided by Oregon State University
Chemical Formula: Na3[AlF6] Locality: Ivigtut and Arksukfiord, West Greenland. Name Origin: Named from the Greek, kryos “frost” and lithos “stone.”
Cryolite (Na3[AlF6]), sodium hexafluoroaluminate) is an uncommon mineral identified with the once large deposit at Ivigtût on the west coast of Greenland, depleted by 1987.
It was historically used as an ore of aluminium and later in the electrolytic processing of the aluminium-rich oxide ore bauxite (itself a combination of aluminium oxide minerals such as gibbsite, boehmite and diaspore). The difficulty of separating aluminium from oxygen in the oxide ores was overcome by the use of cryolite as a flux to dissolve the oxide mineral(s).
Pure cryolite itself melts at 1012 °C (1285 K), and it can dissolve the aluminium oxides sufficiently well to allow easy extraction of the aluminium by electrolysis. Substantial energy is still needed for both heating the materials and the electrolysis, but it is much more energy-efficient than melting the oxides themselves. As natural cryolite is too rare to be used for this purpose, synthetic sodium aluminium fluoride is produced from the common mineral fluorite.
Cryolite occurs as glassy, colorless, white-reddish to gray-black prismatic monoclinic crystals. It has a Mohs hardness of 2.5 to 3 and a specific gravity of about 2.95 to 3.0. It is translucent to transparent with a very low refractive index of about 1.34, which is very close to that of water; thus if immersed in water, cryolite becomes essentially invisible.
Cryolite has also been reported at Pikes Peak, Colorado; Mont Saint-Hilaire, Quebec; and at Miass, Russia. It is also known in small quantities in Brazil, the Czech Republic, Namibia, Norway, Ukraine, and several American states.
Cryolite was first described in 1799 from a deposit of it in Ivigtut and nearby Arsuk Fjord, Southwest Greenland. The name is derived from the Greek language words cryò = chill, and lithòs = stone. The Pennsylvania Salt Manufacturing Company used large amounts of cryolite to make caustic soda at its Natrona, Pennsylvania works during the 19th and 20th centuries.
Physical Properties of Cryolite
Cleavage: None Color: Brownish black, Colorless, Gray, White, Reddish brown. Density: 2.95 – 3, Average = 2.97 Diaphaneity: Transparent to translucent Fracture: Uneven – Flat surfaces (not cleavage) fractured in an uneven pattern. Hardness: 2.5-3 – Finger Nail-Calcite Luminescence: Fluorescent, Short UV=bluish white. Luster: Vitreous – Greasy Streak: white
A new study led by scientists at the University of Miami (UM) Rosenstiel School of Marine and Atmospheric Science uncovered a previously unknown magma chamber deep below the most active volcano in the world – Kilauea.Credit: Image courtesy of University of Miami Rosenstiel School of Marine & Atmospheric Science
A new study led by scientists at the University of Miami (UM) Rosenstiel School of Marine and Atmospheric Science uncovered a previously unknown magma chamber deep below the most active volcano in the world — Kilauea. This is the first geophysical observation that large magma chambers exist in the deeper parts of the volcano system.
Scientists analyzed the seismic waves that travel through the volcano to understand the internal structure of the volcanic system. Using the seismic data, the researchers developed a three-dimensional velocity model of a magma anomaly to determine the size, depth and composition of the lava chamber, which is several kilometers in diameter and located at a depth of 8-11 km (5 — 6.8 miles).
“It was known before that Kilauea had small, shallow magma chambers,” said Guoqing Lin, UM Rosenstiel School assistant professor of geology and geophysics and lead author of the study. “This study is the first geophysical observation that large magma chambers exist in the deep oceanic crust below.”
The study also showed that the deep chamber is composed of “magma mush,” a mixture of 10-percent magma and 90-percent rock. The crustal magma reservoir below Kilauea is similar to those widely observed beneath volcanoes located at mid-ocean ridges.
“Understanding these magma bodies are a high priority because of the hazard posed by the volcano,” said Falk Amelung, co-author and professor of geology and geophysics at the UM Rosenstiel School. “Kilauea volcano produces many small earthquakes and paying particular attention to new seismic activity near this body will help us to better understand where future lava eruptions will come from.”
Scientists are still unraveling the mysteries of the deep internal network of magma chambers and lava tubes of Kilauea, which has been in continuous eruption for more than 30 years and is currently the most active volcano in the world.
Note : The above story is based on materials provided by University of Miami Rosenstiel School of Marine & Atmospheric Science. Note: Materials may be edited for content and length.
The Neoproterozoic Era is the unit of geologic time from 1,000 to 541 million years ago.
The terminal Era of the formal Proterozoic Eon (or the informal “Precambrian”), it is further subdivided into the Tonian, Cryogenian, and Ediacaran Periods.
The most severe glaciation known in the geologic record occurred during the Cryogenian, when ice sheets reached the equator and formed a possible “Snowball Earth”.
The earliest fossils of multicellular life are found in the Ediacaran, including the earliest animals.
Geology
At the onset of the Neoproterozoic the supercontinent Rodinia, which had assembled during the late Mesoproterozoic, straddled the equator. During the Tonian, rifting commenced which broke Rodinia into a number of individual land masses.
Possibly as a consequence of the low-latitude position of most continents, several large-scale glacial events occurred during the Neoproterozoic Era including the Sturtian and Marinoan glaciations of the Cryogenian.
These glaciations are believed to have been so severe that there were ice sheets at the equator—a state known as the “Snowball Earth”.
Subdivisions
The Russians divide the Siberian Neoproterozoic into the Baikalian from 850 to 650 Ma (loosely equivalent to the Cryogenian), which overlies the Mayanian, from 1000 to 850 Ma, then the Aimchanian.
Paleobiology
The idea of the Neoproterozoic Era came on the scene relatively recently — after about 1960. Nineteenth century paleontologists set the start of multicelled life at the first appearance of hard-shelled animals called trilobites and archeocyathids.
This set the beginning of the Cambrian period. In the early 20th century, paleontologists started finding fossils of multicellular animals that predated the Cambrian boundary. A complex fauna was found in South West Africa in the 1920s but was misdated.
Another was found in South Australia in the 1940s but was not thoroughly examined until the late 1950s. Other possible early fossils were found in Russia, England, Canada, and elsewhere (see Ediacaran biota). Some were determined to be pseudofossils, but others were revealed to be members of rather complex biotas that are still poorly understood. At least 25 regions worldwide yielded metazoan fossils prior to the classical Cambrian boundary.
A few of the early animals appear possibly to be ancestors of modern animals. Most fall into ambiguous groups of frond-like organisms; discoids that might be holdfasts for stalked organisms (“medusoids”); mattress-like forms; small calcaerous tubes; and armored animals of unknown provenance.
These were most commonly known as Vendian biota until the formal naming of the Period, and are currently known as Ediacaran biota. Most were soft bodied. The relationships, if any, to modern forms are obscure. Some paleontologists relate many or most of these forms to modern animals. Others acknowledge a few possible or even likely relationships but feel that most of the Ediacaran forms are representatives of unknown animal types.
In addition to Ediacaran biota, later two other types of biota were discovered in China (the so-called Doushantuo formation and Hainan formation).
Terminal period
The nomenclature for the terminal period of the Neoproterozoic has been unstable. Russian geologists referred to the last period of the Neoproterozoic as the Vendian, while Chinese geologists referred to it as the Sinian, and most Australians and North Americans used the name Ediacaran.
However, in 2004, the International Union of Geological Sciences ratified the Ediacaran age to be a geological age of the Neoproterozoic, ranging from ~635 to 541.0 ± 1.0 million years ago. The Ediacaran boundaries are the only Precambrian boundaries defined by biologic Global Boundary Stratotype Section and Points, rather than the absolute Global Standard Stratigraphic Ages.
Note : The above story is based on materials provided by Wikipedia
The Mesoproterozoic Era is a geologic era that occurred from 1,600 to 1,000 million years ago. The Mesoproterozoic was the first period of Earth’s history of which a respectable geological record survives. Continents existed in the Paleoproterozoic, but we know little about them. The continental masses of the Mesoproterozoic are more or less the same ones that are with us today.
The major events of this era are the formation of the Rodinia supercontinent, the breakup of the Columbia supercontinent, and the evolution of sexual reproduction.
This era is marked by the further development of continental plates and plate tectonics. At the end of this era, the continental plates that had developed were more or less the same we have today. This is the first era of which a good geological record still exists today.
The first large-scale mountain building episode, the Grenville Orogeny, for which extensive evidence still survives, happened in this period.
This era was the high point of the Stromatolites before they declined in the Neoproterozoic.
The era saw the development of sexual reproduction, which greatly increased the complexity of life to come. It was the start of development of communal living among organisms, the multicellular organisms.
It was an Era of apparently critical, but still poorly understood, changes in the chemistry of the sea, the sediments of the earth, and the composition of the air. Oxygen levels had risen to perhaps 1% of today’s levels at the beginning of the era and continued rising throughout the Era.
Subdivisions
The subdivisions of the Mesoproterozoic are, obviously, arbitrary divisions based on time. They are not geostratigraphic or biostratigraphic units. The base of the Mesoproterozoic is defined chronometrically, in terms of years, rather than by the appearance or disappearance of some organism. This gives an illusory sense of certainty. Radiometric dating is a good tool, and gets better each decade.[citation needed] This creates some problems. As a practical matter, radiometric dates have an error margin of 1-2%. That sounds good, but it means that two sites, both measured to be at the exact base of the Ectasian, might differ in age by over 50 My. Since the Ectasian is only 200 My long, that’s a serious matter. And this accounts only for random error. Systematic errors can be caused by extraterrestrial events, by geochemical or biochemical sorting of isotopes, and human error. Thus far, biostratigraphy has usually proved considerably more exact. In addition, a thoughtful choice of biological marker can be used as a signal to expect a whole host of ecological changes. The difference between a Changhsingian and an Induan deposit isn’t just a matter of a few years. The world changed hugely at the end of the Permian.
By contrast, the transition from Calymmian to Ectasian has no meaning beyond calendar time. The usual reason given for the use of a chronometric system is that there is insufficient biological activity or geochemical change to find useful markers. That is a position which is now a little uncertain and is going to become increasingly tenuous over the next few years. For example, there are a number of good potential markers in the rise and decline of “Christmas tree” stromatolites, in the coming and going of banded iron formations, the appearance of stable carbon-13 isotope (13C) excursions, and so on. These have real meaning for the geologist and paleontologist.
For that matter, they are not completely without biological markers. There has been considerable progress in studying and identifying fossil bacteria and Eukarya. The cyanobacterium Archaeoellipsoides is one relatively common form, apparently known from several species. It is probably related to the extant Anabaena and indicates the presence of significant free oxygen. Oxygen levels also had significant effects on ocean chemistry; continental weathering rates increased and provided sulfates and nitrates as nutrients. It would be remarkable if this didn’t result in new populations of both bacterial and eukaryotic organisms. Since the presence of these cells would be tied directly to important geochemical events, they would make ideal organisms for biostratigraphy.
Note : The above story is based on materials provided by Wikipedia
The Paleoproterozoic is the first of the three sub-divisions (eras) of the Proterozoic occurring between 2,500 to 1,600 million years ago. This is when the continents first stabilized. This is also when cyanobacteria evolved, a type of bacteria which uses the biochemical process of photosynthesis to produce energy and oxygen.
Paleontological evidence on the Earth’s rotational history suggests that ~1.8 billion years ago, there were about 450 days in a year, implying 20 hour days.
Geography
Modern Plate tectonics began with the Paleoproterozoic. The Paleoproterozoic was the era of continental shield formation. By and large, the Earth’s Archean crust seems to have been both fragmented and somewhat unstable. Some paleogeographers assert that an episode of continent formation — in fact a supercontinent — was present at the end of the Archean. Kump & Barley (2007). However, if that was the case, then those continents were unstable and disappeared without a trace over the next few hundred My. The majority view is that modern style continents and familiar plate tectonics began not long before the Paleoproterozoic.
Continental shields formed from small cratons. It was during the Paleoproterozoic that small islands of crust were first stitched together to form the stable nuclei of the continents we know today. This may something of an overstatement, since relatively broad islands of Archean stability are found in the rocks northeastern Canada and Greenland (the Laurentian or Canadian Shield), Western Australia (Pilbarra Craton), and South Africa (Kapvaal Craton). These became the nuclei of the North American, Australian, and (in part) African continents, respectively. However, even in these cases, the continental craton in its present form was the product of suturing several smaller units. That suturing process largely occurred in the Paleoproterozoic. In other cases (e.g., India, South America, and North China), both crust and shield were largely products of the Paleoproterozoic.
Now that we have extruded this patently over-broad generalization, we had best defend the thesis with some concrete examples.
For example, the core of South America formed around Amazonia in the Paleoproterozoic. The geologically stable core of South America is the Amazonian craton, roughly coterminous with northern and central Brazil and the inland areas of Venezuela, both Guyanas, and Suriname. Most of western South America is composed of ephemeral orogenic mountain ranges which come and go on timescales of a few 100 My. Other bits and pieces have joined (Uruguay) or left (Central Texas?) Amazonia at various times in the geological past. However, the unchanging hub of all this activity was Amazonia. The only other significant cratons now associated with South America, the São Francisco and Rio de la Plata, are both immigrants from Africa. Iacumin et al. (2001).
The only large stretches of Archean basement remaining in Amazonia are located in the eastern section of Amazonia, mostly in the southeastern corner. Most of the rest of Amazonia was intruded and sutured together in the Paleoproterozoic. The only significant exception is the northwestern Rio Negro Province, which lies along the Brazilian-Columbian border. This province formed as an extension of Amazonia in the Mesoproterozoic. Tassinari & Macambira (1999); Sial et al. (1999). For the subsequent development of the region, Brito Neves et al. (1999).
Baltica, the core of Europe, formed from the merger of three cratons in the Paleoproterozoic. The formation of Baltica – the continent which was to become Europe — is one of the best-known examples. Baltica formed in the Paleoproterozoic from the fusion of three cratons: Fennoscandia (Scandinavia, the Baltics, Belarus, Eastern Poland, part of Scotland, and northern European Russia), Volgo-Uralia (the Volga Basin of Russia), and Sarmatia (the Trans-Caucasus region, the Ukraine, Moldavia and part of Romania). Gee & Stephenson (2006). The process of consolidation was complete by the end of the Paleoproterozoic. Virtually all further growth in the Proterozoic came by way of extensional tectonics and the incorporation of bits and pieces of other adjacent continents. Bingen et al. (2008).
India has a similar history. Similarly, India appears to be an amalgamation of four cratons. One of these is a small, late accretion to the southern tip (southern Tamil Nadu and Kerala). The rest consists of three Archean cratons which consolidated at the end of the Paleoproterozoic. Sankaran (1999).
The shift in continent-building style is correlated with a shift in large volcanic belts from marine to terrestrial settings. Recently Kump & Barley (2007), devised an ingenious test of the general concept. They collected a large database of reasonably characterized “large igneous provinces.” LIPs are broad areas of volcanic activity. They are usually manifestations of the chafing and irritation which occurs when two cratons come in contact. During the Archean, the vast majority (80% or more) of LIPs happened under water. At the beginning of the Proterozoic, the proportions abruptly reverse. About 80% of known Proterozoic LIPs were terrestrial. The most parsimonious explanation is that cratons were now consolidating, so that the boundaries between adjacent cratons most often lay in the interior of larger masses — continents.
The trigger may have been the accumulation of a critical amount of rigid continental crust. In fact, something more fundamental may have happened — a change in the tectonic behavior of cratons somewhat analogous to a change of state between two crystal forms. The break between Archean and Proterozoic LIP locations is quite sharp, and the ~80% level is fairly steady for the rest of Earth history. The Early Paleoproterozoic is also the earliest time that normal plate boundaries, boundaries between essentially rigid crust elements, are seen in the geological record. Stanley (1998). Stanley also notes that the total volume of continental crust first approached present value at the end of the Archean. It seems likely that the volume of continental crust, the formation of continental shields, and the development of “normal” plate tectonics are related, although the mechanics have not been worked out.
Paleoatmosphere
Before the significant increase in atmospheric oxygen almost all life that existed was anaerobic, that is, the metabolism of life depended on a form of cellular respiration that did not require oxygen.
Free oxygen in large amounts is toxic to most anaerobic bacteria. It is widely believed that the majority of existent anaerobic life on Earth died off. The only life that remained was either resistant to the oxidizing and poisonous effects of oxygen, or spent its life-cycle in an oxygen-free environment. This main event is called the oxygen catastrophe.
Lifeforms
The crown eukaryotes, from which all modern day eukaryotic lineages have arisen have been dated to the paleoproterozoic era. By ~1 Gy the latest common ancestors between the ciliate and flagellate lineages probably diverged. The Francevillian Group and Grypania fossils and the first eukaryotes also appeared during this time.
Geological events
During this era the earliest global-scale continent-continent collisional belts developed.
These continent and mountain building events are represented by the 2.1-2.0 Ga (Ga = billion year) Transamazonian and Eburnean Orogens in South America and West Africa; the ~2.0 Ga Limpopo Belt in southern Africa; the 1.9–1.8 Ga Trans-Hudson, Penokean, Taltson–Thelon, Wopmay, Ungava and Torngat orogens in North America, the 1.9–1.8 Ga Nagssugtoqidain Orogen in Greenland; the 1.9–1.8 Ga Kola–Karelia, Svecofennian, Volhyn-Central Russian, and Pachelma Orogens in Baltica (Eastern Europe); the 1.9–1.8 Ga Akitkan Orogen in Siberia; the ~1.95 Ga Khondalite Belt and ~1.85 Ga Trans-North China Orogen in North China.
These continental collisional belts are interpreted as having resulted from 2.0-1.8 Ga global-scale collisional events that led to the assembly of a Paleo-Mesoproterozoic supercontinent named “Columbia” or “Nuna”.
Note : The above story is based on materials provided by Wikipedia , Palaeos
