Fossil of the enlarged claws on the forelimbs of Therizinosaurus cheloniformes Credit: Dr Stephan Lautenschlager
How claw form and function changed during the evolution from dinosaurs to birds is explored by a new University of Bristol study into the claws of a group of theropod dinosaurs known as therizinosaurs.
Theropod dinosaurs, a group which includes such famous species as Tyrannosaurus rex and Velociraptor, are often regarded as carnivorous and predatory animals, using their sharp teeth and claws to capture and dispatch prey. However, a detailed look at the claws on their forelimbs revealed that the form and shape of theropod claws are highly variable and might also have been used for other tasks.
Therizinosaurs were very large animals, up to 7m tall Credit: Dr Stephan Lautenschlager
Inspired by this broad spectrum of claw morphologies, Dr Stephan Lautenschlager from Bristol’s School of Earth Sciences studied the differences in claw shape and how these are related to different functions.
His research focussed on the therizinosaurs, an unusual group of theropods which lived between 145 and 66 million years ago. Therizinosaurs were very large animals, up to 7m tall, with claws more than 50cm long on their forelimbs, elongated necks and a coat of primitive, down-like feathers along their bodies. But in spite of their bizarre appearance, therizinosaurs were peaceful herbivores.
Dr Lautenschlager said: “Theropod dinosaurs were all bipedal, which means their forelimbs were no longer involved in walking as in other dinosaurs. This allowed them to develop a whole new suite of claw shapes adapted to different functions.”
In order to fully understand how these different claws on the forelimbs were used, detailed computer models were created to simulate a variety of possible functions for different species and claw morphologies.
Illustration showing different claw shapes in therizinosaur dinosaurs and the adaptation to specific functions Credit: Dr Stephan Lautenschlager
The dinosaur claws were also compared to the claws of mammals, still alive today, whose function (that is, how and for what the claws are used) is already known.
In the course of evolution, several theropod groups, including therizinosaurs, changed from being carnivores to become plant-eaters. This new study reveals that, during this transition, theropod dinosaurs developed a large variety of claw shapes adapted to specific functions, such as digging, grasping or piercing.
Dr Lautenschlager said: “It’s fascinating to see that, with the shift from a carnivorous to a plant-based diet, we find a large variety of claw shapes adapted to different functions. This suggests that dietary adaptations were an important driver during the evolution of theropod dinosaurs and their transition to modern birds.”
Note : The above story is based on materials provided by University of Bristol.
Chemical Formula: Pb14(As,Sb)6S23 Locality: Binnental, Valais, Switzerland. Name Origin: Named after H. Jordan from Saarbrucken.
Jordanite is a sulfosalt mineral with chemical formula Pb14(As,Sb)6S23 in the monoclinic crystal system, named after the German scientist Dr H. Jordan (1808–1887) who discovered it in 1864.
Lead-grey in colour (frequently displaying an iridescent tarnish), its streak is black and its lustre is metallic. Jordanite has a hardness of 3 on Mohs scale, has a density of approximately 6.4, and a conchoidal fracture.
The type locality is the Lengenbach Quarry in the Binn Valley, Wallis, Switzerland.
Physical Properties
Cleavage: {010} Distinct Color: Lead gray. Density: 5.5 – 6.4, Average = 5.95 Diaphaneity: Opaque Fracture: Brittle – Conchoidal – Very brittle fracture producing small, conchoidal fragments. Hardness: 3 – Calcite Luster: Metallic Streak: black
The image shows two Qianzhousaurus individuals hunting. The one in the foreground is chasing a small feathered dinosaur called Nankangia and the one in the background is eating a lizard. Fossils of these three species are known from the ca. 72-66 million-year-old site in Ganzhou, China, where Qianzhousaurus was found. Credit: Chuang Zhao
Scientists have discovered a new species of long-snouted tyrannosaur, nicknamed Pinocchio rex, which stalked Earth more than 66 million years ago.
Researchers say the animal, which belonged to the same dinosaur family as Tyrannosaurus rex, was a fearsome carnivore that lived in Asia during the late Cretaceous period.
The newly found ancient predator looked very different from most other tyrannosaurs. It had an elongated skull and long, narrow teeth compared with the deeper, more powerful jaws and thick teeth of a conventional T. rex.
Palaeontologists were uncertain of the existence of long-snouted tyrannosaurs until the remains of the dinosaur — named Qianzhousaurus sinensis — were unearthed in southern China.
Until now, only two fossilised tyrannosaurs with elongated heads had been found, both of which were juveniles. It was unclear whether these were a new class of dinosaur or if they were at an early growth stage, and might have gone on to develop deeper, more robust skulls.
The new specimen, described by scientists from the Chinese Academy of Geological Sciences and the University of Edinburgh, is of an animal nearing adulthood. It was found largely intact and remarkably well preserved, thereby confirming the existence of tyrannosaur species with long snouts.
Experts say Qianzhousaurus sinensis lived alongside deep-snouted tyrannosaurs but would not have been in direct competition with them, as they were larger and probably hunted different prey.
Following the find, researchers have created a new branch of the tyrannosaur family for specimens with very long snouts, and they expect more dinosaurs to be added to the group as excavations in Asia continue to identify new species.
Qianzhousaurus sinensis lived until around 66 million years ago when all of the dinosaurs became extinct, likely as the result of a deadly asteroid impact.
Findings from the study, funded by the Natural Science Foundation of China and the National Science Foundation, are published in the journal Nature Communications.
Dr Steve Brusatte, of the University of Edinburgh’s School of GeoSciences, and one of the authors of the study, said: “This is a different breed of tyrannosaur. It has the familiar toothy grin of T. rex, but its snout was much longer and it had a row of horns on its nose. It might have looked a little comical, but it would have been as deadly as any other tyrannosaur, and maybe even a little faster and stealthier.”
Professor Junchang Lü, of the Institute of Geology, Chinese Academy of Geological Sciences, said: “The new discovery is very important. Along with Alioramus from Mongolia, it shows that the long-snouted tyrannosaurids were widely distributed in Asia. Although we are only starting to learn about them, the long-snouted tyrannosaurs were apparently one of the main groups of predatory dinosaurs in Asia.”
Note : The above story is based on materials provided by University of Edinburgh.
This is a map showing the structure and contour of the Bow City crater. Color variation shows meters above sea level. Credit: Alberta Geographic Survey/University of Alberta
The discovery of an ancient ring-like structure in southern Alberta suggests the area was struck by a meteorite large enough to leave an eight-kilometre-wide crater, producing an explosion strong enough to destroy present-day Calgary, say researchers from the Alberta Geological Survey and University of Alberta.
The first hints about the impact site near the southern Alberta hamlet of Bow City were discovered by a geologist with the Alberta Geological Survey and studied by a U of A team led by Doug Schmitt, Canada Research Chair in Rock Physics.
Time and glaciers have buried and eroded much of the evidence, making it impossible at this point to say with full certainty the ring-like structure was caused by a meteorite impact, but that’s what seismic and geological evidence strongly suggests, said Schmitt, a professor in the Faculty of Science and co-author of a new paper about the discovery.
“We know that the impact occurred within the last 70 million years, and in that time about 1.5 km of sediment has been eroded. That makes it really hard to pin down and actually date the impact.”
Erosion has worn away all but the “roots” of the crater, leaving a semicircular depression eight kilometres across with a central peak. Schmitt says that when it formed, the crater likely reached a depth of 1.6 to 2.4 km — the kind of impact his graduate student Wei Xie calculated would have had devastating consequences for life in the area.
“An impact of this magnitude would kill everything for quite a distance,” he said. “If it happened today, Calgary (200 km to the northwest) would be completely fried and in Edmonton (500 km northwest), every window would have been blown out. Something of that size, throwing that much debris in the air, potentially would have global consequences; there could have been ramifications for decades.”
The impact site was first discovered in 2009 by geologist Paul Glombick, who at the time was working on a geological map of the area for the Alberta Geological Survey. Glombick relied on existing geophysical log data from the oil and gas industry when he discovered a bowl-shaped structure.
The Alberta Geological Survey contacted the U of A and Schmitt to explore further, peeking into Earth by analyzing seismic data donated by industry. Schmitt’s student, Todd Brown, later confirmed a crater-like structure.
Note : The above story is based on materials provided by University of Alberta.
Chemical Formula: NaBa2Ce2FeTi2[Si4O12]2O2(OH,F)·H2O Locality: Benitoite Gem mine, head waters of the San Benito River, Joaquin Ridge, Diablo Range, 1 mile south of Santa Rita Peak, San Benito Co. California. Name Origin: Named after its locality.
Joaquinite, which was discovered in 1909, is a pretty rare mineral. It is most renown for its association with other exotic minerals such as the sapphire blue benitoite, the red-black neptunite and the snow white natrolite. If it were not for these minerals which are found in San Benito County, California; joaquinite might not be so well known. It forms typically small, sparkling, brown to yellow, well formed crystals usually scattered on massive green serpentine.
Joaquinite is a product of some very unusual hydrothermal solutions. These solutions contained the elements titanium, niobium, lithium, barium, niobium, manganese, fluorine, cerium and several others. Anyone of them by themselves is not that unusual, but together in one solution and in such high concentrations is quite unusual. How they came to be combined like this is not yet well understood, but their product of unusual silicate minerals is much appreciated.
Physical Properties
Cleavage: Good Color: Brown, Honey yellow, Orange. Density: 3.62 – 3.98, Average = 3.8 Diaphaneity: Transparent to Translucent Fracture: Brittle – Generally displayed by glasses and most non-metallic minerals. Hardness: 5-5.5 – Apatite-Knife Blade Luminescence: Non-fluorescent. Luster: Vitreous (Glassy)
A rock the size of a small city hurtles towards Earth, smashing a crater bigger than the span between Washington, D.C. and New York City. The heat and shockwave raises the temperature of the atmosphere above boiling as huge seismic waves ripple through the Earth’s crust.
New research indicates that such an impact may have happened to our planet, although (thankfully) it was long before civilization arose. About 3.26 billion years ago, an object between 23 and 26 miles wide (37 and 58 kilometers) crashed into the Earth somewhere and left geological evidence behind in South Africa. Surprisingly, the impact may have made the Earth a friendlier place for life because it corresponds with this planet’s establishment of plate tectonics.
Finding the crater, though, is likely an impossible task. There are few rocks of this age on the entire Earth, the notable exception being the nearly 4-billion-old Canadian Shield that stretches across much of eastern Canada. Little remains of that era of history, making it necessary for researchers to do detective work to learn more about the impactor.
“It’s like the aftermath of a tornado where the insurance company won’t pay because your car was sucked off of your driveway and you can’t find the car, so they can’t pay it,” said Norm Sleep, a geophysicist at Stanford University who led the research. “You don’t know if it was stolen or damaged or wrecked or whatever because you can’t find it. We have the same difficulty.”
Sleep and departmental co-author Donald Lowe published their research in the journal Geochemistry, Geophysics and Geosystems in April. The paper is called “Physics of crustal fracturing and chert dike formation triggered by asteroid impact, ∼3.26 Ga, Barberton greenstone belt, South Africa.”
Starting up plate tectonics?
The only life in that era was microbial, although Lowe pointed out they would have struggled with their new circumstances. “To say the least, it would have adversely affected life near the surface,” he said.
While whole microbe communities could have been wiped out, on the species level many would have survived. Life was all over the Earth and not just in the area of the impact, and microbes are better able to withstand sudden temperature changes than more advanced lifeforms.
Perhaps microbes would have suffered after the impact, but in its wake, the impactor could have helped change our planet into one that better supports complex life. Lowe pointed out that plate tectonics seems to have appeared around 3 billion to 3.2 billion years ago, around the same time the impactor smashed into the Earth.
Huge as it was, the impactor was probably too small to have affected plate tectonics all over the Earth, said Lowe and Sleep. In the local area, however, it could have caused great upheaval. Moreover, the impactor crashed into the Earth during an era known as the Late Heavy Bombardment, when rocks and comets smashed into our planet and all the other ones. The Moon still bears scars from that time. The Earth’s have eroded away, but the effects may still linger.
The Barberton Greenstone Belt in South Africa. Credit: Jesse Allen/Landsat/USGS
If enough big objects hit the Earth frequently enough, it could have broken up the primitive plate structure on our planet into the plate tectonics we have today, they said. This has important implications for life, as other researchers have said that plate tectonics might be necessary for complex life to exist.
In 2009, Tilman Spohn, director of the German Space Research Centre Institute of Planetary Research, argued that plate tectonics replenishes the nutrition necessary for life. Rubbing plates together, pushing plates below each other, or raising them up would have mixed the chemistry of the Earth, providing fresh material to counteract what had been eaten up by bacteria on the Earth’s surface.
Finding the evidence
Lowe found the possible “ground truth” of an impactor in the Barberton Greenstone Belt, where he has spent summers for decades. Barberton is named for the nearby eponymous town in South Africa, which is located about 250 miles (400 kilometers) east of Johannesburg and a little north of the Swaziland border.
Barberton was a popular location for gold seekers in the 1880s, but more recently it has been harvested for its biological and geological features. Rocks in the region are around 3.5 billion years old, and host fossils of microscopic life that likely exceed 3 billion years.
“It’s one of the few areas on the surface of the Earth that preserves sedimentary layers this old,” Lowe said.
The sedimentary layers are important because sediments show biological activity that took place at the Earth’s surface where microbes exist, especially those performing photosynthesis.
About 30 years ago, scientists discovered layers of small particles with “strange properties,” Lowe said. These were formed by the condensation of liquid rock droplets. Further analysis showed they were rich in iridium. Iridium is a rare element on the Earth’s surface today and was one of the indicators scientists used to identify the K-T Boundary, the layer of material left after an impactor probably killed off the dinosaurs about 66 million years ago.
More recently, Lowe’s group identified eight layers in the particles that impactors likely created. The paper focuses on one of those layers. In the field, Lowe’s group collected spherical particles the size of a grain of sand that were abundant throughout the layer. Further examination in the lab revealed they were rich in iridium and platinum, both common meteorite elements.
Extraterrestrial remnants
Another clue came from the isotopes (types) of chromium. The surface rocks on Earth have a uniform ratio of chromium isotopes, but Lowe and a colleague in San Diego found that the isotopes in this layer had a different ratio. The unusual proportions, along with the iridium, the platinum and the widespread distribution of the layer, all suggested this was produced by an impact.
The crash happened somewhere far away, though.
A large impactor slams into the Earth in this artist’s impression. Credit: NASA/Don Davis
“In the area around a crater, the rocks of this age would have been destroyed,” Lowe said. “We’ve never found evidence that we were at or close to an actual crater.”
Perhaps further examination of the greenstone will turn up more information on this impactor, but similar sites will be hard to come by. There are few regions like the Barberton around today, so that scientists will have trouble finding other impactors that could have affected plate tectonics.
Even if the impactor did break up a primitive solid crust into plate tectonics, it’s unclear how necessary plate tectonics is for life, Sleep said.
“Part of the handicap is we only have one planet in the Solar System where we have plate tectonics, where it is occurring now, and any evidence for it on Venus and Mars is at best very tenuous. We think it’s likely to occur on other objects, but we don’t really know,” Sleep said.
Life on Earth is also adapted to plate tectonics, he pointed out, and as we have not found life elsewhere it is hard to say if tectonics are necessary for life to exist. Even when looking outside of the Solar System, it will be a challenge to detect plate tectonics on extrasolar planets because they are so far away.
Note : The above story is based on materials provided byAstrobio net
Bathymetry of a 70-kilometer long section of the rift zone in the Red Sea. In the lower right is the same section in the previous resolution. Credit: Graphics: N. Augustin, GEOMAR
The Red Sea has turned out to be an ideal study object for marine geologists. There they can observe the formation of an ocean in its early phase. However, the Red Sea seemed to go through a different birthing process than the other oceans. Now, scientists at the GEOMAR Helmholtz Centre for Ocean Research Kiel and the King Abdulaziz University in Jeddah have been able to show that salt glaciers have distorted the previous models. The study was just published in the international journal Earth and Planetary Science Letters.
Pacific, Atlantic and Indian Ocean, with the land masses of the Americas, Europe, Asia, Africa and Australia in between — that’s how we know our Earth. From a geologist’s point of view, however, this is only a snapshot. Over the course of Earth’s history, many different continents have formed and split again. In between oceans were created, new seafloor was formed and disappeared again: Plate tectonics is the generic term for these processes.
The Red Sea, where currently the Arabian Peninsula separates from Africa, is one of the few places on earth where the splitting of a continent and the emergence of the ocean can be observed. During a three-year joint project, the Jeddah Transect Project (JTP), researchers at the GEOMAR Helmholtz Centre for Ocean Research Kiel and the King Abdulaziz University (KAU) in Jeddah, Saudi Arabia, have taken a close look at this crack in Earth’s crust by means of seabed mapping, sampling and magnetic modeling. “The findings have shed new light on the early stages of oceanic basins, and they specifically change the school of thought on the Red Sea,” says Dr. Nico Augustin from GEOMAR, lead author of the study.
It is, and was, undisputed that a continent is stretched and thinned out by volcanic activity before it ruptures and a new ocean basin is formed. The rifting occurs where the greatest stretching takes place. However, the detailed processes during the break-up are debated in research. On the one hand, one needs to better understand the dynamics of our home planet. “On the other hand, most marine oil and gas resources are located near such former fracture zones. This research can therefore also have economic and political implications,” says Professor Colin Devey (GEOMAR), co-author of the study.
Until now, conventional knowledge said that a continent is breaking apart more or less simultaneously along an entire line, and the ocean basin is formed all at once. The Red Sea, however, did not fit into this picture. Here, a model was favored with several smaller fracture zones, lined up one after the other, that would unite gradually, which in turn would lead to a relatively slow emergence of the ocean during a long transition phase. “Our studies show that the Red Sea is not an exception but that it takes its place in line with the other ocean basins,” says Augustin. The previous picture we had of the ocean floor in the Red Sea was simply corrupted by salt glaciers. “The volcanic rocks we recovered are similar to those from other normal mid-ocean ridges,” says co-author Froukje van der Zwan, working on her PhD as part of the JTP.
During the early formation stages of the Red Sea, the area was covered by a very shallow sea that dried up repeatedly. This created thick salt deposits that later on broke apart with the continental crust. Over geologic time periods, salt shows tar-like behavior and begins to flow. “Our new high-resolution seabed maps and magnetic modeling show that the kilometer-thick salt deposits, after the break-up of the Arabian Plate from Africa, flowed like glaciers toward the newly created trench and thus over the oceanic crust due to gravity,” says Augustin. Since these submarine salt glaciers do not cover the rifting zone uniformly over the entire length, the impression of several small fracture zones was created.
The consequences of this discovery are profound: For one, there really seems to be only one single mechanism worldwide for the dispersal of a continent. And secondly, is not yet known how much ocean crust is covered by salt. This questions the previous dating of the opening of the Red Sea. In addition, the volcanically active trench rift zone of the Red Sea, surrounded by salt glaciers, is host of a giant sink filled with a very hot and very salty solution. “Since the sediment in the salt solution is rich in metals, this so-called Atlantis II Deep is also of economic interest,” says co-author Devey. It is quite conceivable that over the course of Earth’s history similar deposits associated with volcanism and salt deposits were created during the opening phase of other oceans. “Thus, our studies help to clarify older research questions. But they also provide starting points for new investigations in all of the oceans,” says Augustin.
Note : The above story is based on materials provided by Helmholtz Centre for Ocean Research Kiel (GEOMAR).
This image shows the Zhadang glacier south of lake Nam Tso on the nortern ridge of the Nyainqentanglha mountain range (Tibet, China). Credit: Tino Pieczonka (TU Dresden)
An international team led by glaciologists from the University of Colorado Boulder and Trent University in Ontario, Canada has completed the first mapping of virtually all of the world’s glaciers—including their locations and sizes—allowing for calculations of their volumes and ongoing contributions to global sea rise as the world warms.
The team mapped and catalogued some 198,000 glaciers around the world as part of the massive Randolph Glacier Inventory, or RGI, to better understand rising seas over the coming decades as anthropogenic greenhouse gases heat the planet. Led by CU-Boulder Professor Tad Pfeffer and Trent University Professor Graham Cogley, the team included 74 scientists from 18 countries, most working on an unpaid, volunteer basis.
The project was undertaken in large part to provide the best information possible for the recently released Fifth Assessment of the Intergovernmental Panel on Climate Change, or IPCC. While the Greenland and Antarctic ice sheets are both losing mass, it is the smaller glaciers that are contributing the most to rising seas now and that will continue to do so into the next century, said Pfeffer, a lead author on the new IPCC sea rise chapter and fellow at CU-Boulder’s Institute of Arctic and Alpine Research.
“I don’t think anyone could make meaningful progress on projecting glacier changes if the Randolph inventory was not available,” said Pfeffer, the first author on the RGI paper published online today in the Journal of Glaciology. Pfeffer said while funding for mountain glacier research has almost completely dried up in the United States in recent years with the exception of grants from NASA, there has been continuing funding by a number of European groups.
Since the world’s glaciers are expected to shrink drastically in the next century as the temperatures rise, the new RGI—named after one of the group’s meeting places in New Hampshire—is critical, said Pfeffer. In the RGI each individual glacier is represented by an accurate, computerized outline, making forecasts of glacier-climate interactions more precise.
“This means that people can now do research that they simply could not do before,” said Cogley, the corresponding author on the new Journal of Glaciology paper. “It’s now possible to conduct much more robust modeling for what might happen to these glaciers in the future.”
As part of the RGI effort, the team mapped intricate glacier complexes in places like Alaska, Patagonia, central Asia and the Himalayas, as well as the peripheral glaciers surrounding the two great ice sheets in Greenland and Antarctica, said Pfeffer. “In order to model these glaciers, we have to know their individual characteristics, not simply an average or aggregate picture. That was one of the most difficult parts of the project.”
The team used satellite images and maps to outline the area and location of each glacier. The researchers can combine that information with a digital elevation model, then use a technique known as “power law scaling” to determine volumes of various collections of glaciers.
In addition to impacting global sea rise, the melting of the world’s glaciers over the next 100 years will severely affect regional water resources for uses like irrigation and hydropower, said Pfeffer. The melting also has implications for natural hazards like “glacier outburst” floods that may occur as the glaciers shrink, he said.
The total extent of glaciers in the RGI is roughly 280,000 square miles or 727,000 square kilometers—an area slightly larger than Texas or about the size of Germany, Denmark and Poland combined. The team estimated that the corresponding total volume of sea rise collectively held by the glaciers is 14 to 18 inches, or 350 to 470 millimeters.
The new estimates are less than some previous estimates, and in total they are less than 1 percent of the amount of water stored in the Greenland and Antarctic ice sheets, which collectively contain slightly more than 200 feet, or 63 meters, of sea rise.
“A lot of people think that the contribution of glaciers to sea rise is insignificant when compared with the big ice sheets,” said Pfeffer, also a professor in CU-Boulder’s civil, environmental and architectural engineering department. “But in the first several decades of the present century it is going to be this glacier reservoir that will be the primary contributor to sea rise. The real concern for city planners and coastal engineers will be in the coming decades, because 2100 is pretty far off to have to make meaningful decisions.”
Part of the RGI was based on the Global Land Ice Measurements from Space Initiative, or GLIMS, which involved more than 60 institutions from around the world and which contributed the baseline dataset for the RGI. Another important research data tool for the RGI was the European-funded program “Ice2Sea,” which brings together scientific and operational expertise from 24 leading institutions across Europe and beyond.
The GLIMS glacier database and website are maintained by CU-Boulder’s National Snow and Ice Data Center, or NSIDC. The GLIMS research team at NSIDC includes principal investigator Richard Armstrong, technical lead Bruce Raup and remote-sensing specialist Siri Jodha Singh Khalsa.
NSIDC is part of the Cooperative Institute for Research in Environmental Sciences, or CIRES, a joint venture between CU-Boulder and the National Oceanic and Atmospheric Administration.
Note : The above story is based on materials provided by University of Colorado at Boulder
Chemical Formula: Al6(BO3)5(F,OH)3 Locality: Soktujberg, Adun-Tchilon and Baikal, Russia. Name Origin: Named after the Russian mineralogist, P. V. Jeremejev (1820-1899).
Jeremejevite is a rare aluminium borate mineral with variable fluoride and hydroxide ions. Its chemical formula is Al6(BO3)5(F,OH)3.
It was first described in 1883 for an occurrence on Mt. Soktui, Nerschinsk district, Adun-Chilon Mountains, Siberia. It was named after Russian mineralogist Pavel Vladimirovich Eremeev (Jeremejev, German) (1830–1899).
It occurs as a late hydrothermal phase in granitic pegmatites in association with albite, tourmaline, quartz and rarely gypsum. It has also been reported from the Pamir Mountains of Tajikistan, Namibia and the Eifel district, Germany.
Physical Properties
Cleavage: None Color: Colorless, White, Yellowish white, Bluish white. Density: 3.28 – 3.31, Average = 3.29 Diaphaneity: Transparent Fracture: Conchoidal – Fractures developed in brittle materials characterized by smoothly curving surfaces, (e.g. quartz). Hardness: 7 – Quartz Luminescence: Non-fluorescent. Luster: Vitreous (Glassy) Streak: white
The Holocene is a geological epoch which began at the end of the Pleistocene (at 11,700 calendar years BP) and continues to the present. The Holocene is part of the Quaternary period. Its name comes from the Greek words ὅλος (holos, whole or entire) and καινός (kainos, new), meaning “entirely recent”. It has been identified with the current warm period, known as MIS 1 and based on that past evidence, can be considered an interglacial in the current ice age.
The Holocene also encompasses within it the growth and impacts of the human species world-wide, including all its written history and overall significant transition toward urban living in the present. Human impacts of the modern era on the Earth and its ecosystems may be considered of global significance for future evolution of living species, including approximately synchronous lithospheric evidence, or more recently atmospheric evidence of human impacts. Given these, a new term Anthropocene, is specifically proposed and used informally only for the very latest part of modern history and of significant human impact since the epoch of the Neolithic Revolution (around 12,000 years BP).
Overview
It is accepted by the International Commission on Stratigraphy that the Holocene started approximately 11,700 years BP (before present). The period follows the last glacial period (regionally known as the Wisconsinan Glacial Period, the Baltic-Scandinavian Ice Age, or the Weichsel glacial). The Holocene can be subdivided into five time intervals, or chronozones, based on climatic fluctuations:
Preboreal (10 ka – 9 ka),
Boreal (9 ka – 8 ka),
Atlantic (8 ka – 5 ka),
Subboreal (5 ka – 2.5 ka) and
Subatlantic (2.5 ka – present).
Note: “ka” means “thousand years” (non-calibrated C14 dates)
The Blytt-Sernander classification of climatic periods defined, initially, by plant remains in peat mosses, is now being explored currently by geologists working in different regions studying sea levels, peat bogs and ice core samples by a variety of methods, with a view toward further verifying and refining the Blytt-Sernander sequence. They find a general correspondence across Eurasia and North America, though the method was once thought to be of no interest. The scheme was defined for Northern Europe, but the climate changes were claimed to occur more widely. The periods of the scheme include a few of the final pre-Holocene oscillations of the last glacial period and then classify climates of more recent prehistory.
Paleontologists have defined no faunal stages for the Holocene. If subdivision is necessary, periods of human technological development, such as the Mesolithic, Neolithic, and Bronze Age, are usually used. However, the time periods referenced by these terms vary with the emergence of those technologies in different parts of the world.
Climatically, the Holocene may be divided evenly into the Hypsithermal and Neoglacial periods; the boundary coincides with the start of the Bronze Age in European civilization. According to some scholars, a third division, the Anthropocene, began in the 18th century.
Continental motions due to plate tectonics are less than a kilometre over a span of only 10,000 years. However, ice melt caused world sea levels to rise about 35 m (115 ft) in the early part of the Holocene. In addition, many areas above about 40 degrees north latitude had been depressed by the weight of the Pleistocene glaciers and rose as much as 180 m (590 ft) due to post-glacial rebound over the late Pleistocene and Holocene, and are still rising today.
The sea level rise and temporary land depression allowed temporary marine incursions into areas that are now far from the sea. Holocene marine fossils are known from Vermont, Quebec, Ontario, Maine, New Hampshire, and Michigan. Other than higher-latitude temporary marine incursions associated with glacial depression, Holocene fossils are found primarily in lakebed, floodplain, and cave deposits. Holocene marine deposits along low-latitude coastlines are rare because the rise in sea levels during the period exceeds any likely tectonic uplift of non-glacial origin.
Post-glacial rebound in the Scandinavia region resulted in the formation of the Baltic Sea. The region continues to rise, still causing weak earthquakes across Northern Europe. The equivalent event in North America was the rebound of Hudson Bay, as it shrank from its larger, immediate post-glacial Tyrrell Sea phase, to near its present boundaries.
Climate
Temperature variations during the Holocene
Climate has been fairly stable over the Holocene. Ice core records show that before the Holocene there was global warming after the end of the last ice age and cooling periods, but climate changes became more regional at the start of the Younger Dryas. During the transition from last glacial to holocene, the Huelmo/Mascardi Cold Reversal in the Southern Hemisphere began before the Younger Dryas, and the maximum warmth flowed south to north from 11,000 to 7,000 years ago. It appears that this was influenced by the residual glacial ice remaining in the Northern Hemisphere until the later date.
The hypsithermal was a period of warming in which the global climate became warmer. However, the warming was probably not uniform across the world. This period of warmth ended about 5,500 years ago with the descent into the Neoglacial. At that time, the climate was not unlike today’s, but there was a slightly warmer period from the 10th–14th centuries known as the Medieval Warm Period. This was followed by the Little Ice Age, from the 13th or 14th century to the mid 19th century, which was a period of significant cooling, though not everywhere as severe as previous times during neoglaciation.
The Holocene warming is an interglacial period and there is no reason to believe that it represents a permanent end to the current ice age. However, the current global warming may result in the Earth becoming warmer than the Eemian Stage, which peaked at roughly 125,000 years ago and was warmer than the Holocene. This prediction is sometimes referred to as a super-interglacial.
Compared to glacial conditions, habitable zones have expanded northwards, reaching their northernmost point during the hypsithermal. Greater moisture in the polar regions has caused the disappearance of steppe-tundra.
Animal and plant life have not evolved much during the relatively short Holocene, but there have been major shifts in the distributions of plants and animals. A number of large animals including mammoths and mastodons, saber-toothed cats like Smilodon and Homotherium, and giant sloths disappeared in the late Pleistocene and early Holocene—especially in North America, where animals that survived elsewhere (including horses and camels) became extinct. This extinction of American megafauna has been explained as caused by the arrival of the ancestors of Amerindians; though most scientists assert that climatic change also contributed. In addition, a discredited bolide impact over North America which was hypothesized to have triggered the Younger Dryas.
Throughout the world, ecosystems in cooler climates that were previously regional have been isolated in higher altitude ecological “islands”.
The 8.2 ka event, an abrupt cold spell recorded as a negative excursion in the δ18O record lasting 400 years, is the most prominent climatic event occurring in the Holocene epoch, and may have marked a resurgence of ice cover. It is thought that this event was caused by the final drainage of Lake Agassiz, which had been confined by the glaciers, disrupting the thermohaline circulation of the Atlantic.
Human developments
The beginning of the Holocene corresponds with the beginning of the Mesolithic age in most of Europe; but in regions such as the Middle East and Anatolia with a very early neolithisation, Epipaleolithic is preferred in place of Mesolithic. Cultures in this period include: Hamburgian, Federmesser, and the Natufian culture, during which the oldest inhabited places still existing on Earth were first settled, such as Jericho in the Middle East, as well as evolving archeological evidence of proto-religion at locations such as Göbekli Tepe, as long ago as the 9th millennium BC.
Both are followed by the aceramic Neolithic (Pre-Pottery Neolithic A and Pre-Pottery Neolithic B) and the pottery Neolithic. The Late Holocene brought advancements such as the bow and arrow and saw new methods of warfare in North America. Spear throwers and their large points were replaced by the bow and arrow with its small narrow points beginning in Oregon and Washington. Villages built on defensive bluffs indicate increased warfare, leading to food gathering in communal groups rather than individual hunting for protection.
Impact events
Many meteorite events which occurred in the Holocene have so far been found in Europe, in bodies of water such as the Indian Ocean and in Russia, near the remote region of Siberia. Siberia is also the site of a modern impact event in 1908 known as the Tunguska Event. It has been speculated that an impact such as that represented today by the Burckle Crater could have dramatically affected human culture in its early history by the creation of megatsunamis, perhaps inspiring deluge or inundation myths such as that of Noah’s Flood.
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The Pleistocene is the geological epoch which lasted from about 2,588,000 to 11,700 years ago, spanning the world’s recent period of repeated glaciations.
Charles Lyell introduced this term in 1839 to describe strata in Sicily that had at least 70% of their molluscan fauna still living today. This distinguished it from the older Pliocene Epoch, which Lyell had originally thought to be the youngest fossil rock layer. He constructed the name “Pleistocene” (“Most New” or “Newest”) from the Greek πλεῖστος, pleīstos, “most”, and καινός, kainós (latinized as cænus), “new”; this contrasting with the immediately preceding Pleiocene (“More New” or “Newer”, from πλείων, pleíōn, “more”, and kainós; usual spelling: Pliocene), and the immediately subsequent Holocene (“wholly new” or “entirely new”, from ὅλος, hólos, “whole”, and kainós) epoch, which extends to the present time.
The Pleistocene is the first epoch of the Quaternary Period or sixth epoch of the Cenozoic Era. The end of the Pleistocene corresponds with the end of the last glacial period. It also corresponds with the end of the Paleolithic age used in archaeology. In the ICS timescale, the Pleistocene is divided into four stages or ages, the Gelasian, Calabrian, Ionian and Tarantian. All of these stages were defined in southern Europe. In addition to this international subdivision, various regional subdivisions are often used.
Before a change finally confirmed in 2009 by the International Union of Geological Sciences, the time boundary between the Pleistocene and the preceding Pliocene was regarded as being at 1.806 million years before the present, as opposed to the currently accepted 2.588 million years BP: publications from the preceding years may use either definition of the period.
Dating
The Pleistocene has been dated from 2.588 million (±5,000) to 11,700 years before present (BP), with the end date expressed in radiocarbon years as 10,000 carbon-14 years BP. It covers most of the latest period of repeated glaciation, up to and including the Younger Dryas cold spell. The end of the Younger Dryas has been dated to about 9640 BC (11,654 calendar years BP). It was not until after the development of radiocarbon dating, however, that Pleistocene archaeological excavations shifted to stratified caves and rock-shelters as opposed to open-air river-terrace sites.
In 2009 the International Union of Geological Sciences (IUGS) confirmed a change in time period for the Pleistocene, changing the start date from 1.806 to 2.588 million years BP, and accepted the base of the Gelasian as the base of the Pleistocene, namely the base of the Monte San Nicola GSSP.The IUGS has yet to approve a type section, Global Boundary Stratotype Section and Point (GSSP), for the upper Pleistocene/Holocene boundary (i.e. the upper boundary). The proposed section is the North Greenland Ice Core Project ice core 75° 06′ N 42° 18′ W. The lower boundary of the Pleistocene Series is formally defined magnetostratigraphically as the base of the Matuyama (C2r) chronozone, isotopic stage 103. Above this point there are notable extinctions of the calcareous nanofossils: Discoaster pentaradiatus and Discoaster surculus.
The Pleistocene covers the recent period of repeated glaciations. The name Plio-Pleistocene has in the past been used to mean the last ice age. The revised definition of the Quaternary, by pushing back the start date of the Pleistocene to 2.58 Ma, results in the inclusion of all the recent repeated glaciations within the Pleistocene.
Paleogeography and climate
The modern continents were essentially at their present positions during the Pleistocene, the plates upon which they sit probably having moved no more than 100 km relative to each other since the beginning of the period.
According to Mark Lynas (through collected data), the Pleistocene’s overall climate could be characterized as a continuous El Niño with trade winds in the south Pacific weakening or heading east, warm air rising near Peru, warm water spreading from the west Pacific and the Indian Ocean to the east Pacific, and other El Niño markers.
Glacial features
Pleistocene climate was marked by repeated glacial cycles in which continental glaciers pushed to the 40th parallel in some places. It is estimated that, at maximum glacial extent, 30% of the Earth’s surface was covered by ice. In addition, a zone of permafrost stretched southward from the edge of the glacial sheet, a few hundred kilometres in North America, and several hundred in Eurasia. The mean annual temperature at the edge of the ice was −6 °C (21 °F); at the edge of the permafrost, 0 °C (32 °F).
The maximum extent of glacial ice in the north polar area during the Pleistocene period.
Each glacial advance tied up huge volumes of water in continental ice sheets 1,500 to 3,000 metres (4,900–9,800 ft) thick, resulting in temporary sea-level drops of 100 metres (300 ft) or more over the entire surface of the Earth. During interglacial times, such as at present, drowned coastlines were common, mitigated by isostatic or other emergent motion of some regions.
The effects of glaciation were global. Antarctica was ice-bound throughout the Pleistocene as well as the preceding Pliocene. The Andes were covered in the south by the Patagonian ice cap. There were glaciers in New Zealand and Tasmania. The current decaying glaciers of Mount Kenya, Mount Kilimanjaro, and the Ruwenzori Range in east and central Africa were larger. Glaciers existed in the mountains of Ethiopia and to the west in the Atlas mountains.
In the northern hemisphere, many glaciers fused into one. The Cordilleran ice sheet covered the North American northwest; the east was covered by the Laurentide. The Fenno-Scandian ice sheet rested on northern Europe, including Great Britain; the Alpine ice sheet on the Alps. Scattered domes stretched across Siberia and the Arctic shelf. The northern seas were ice-covered.
South of the ice sheets large lakes accumulated because outlets were blocked and the cooler air slowed evaporation. When the Laurentide ice sheet retreated, north central North America was totally covered by Lake Agassiz. Over a hundred basins, now dry or nearly so, were overflowing in the North American west. Lake Bonneville, for example, stood where Great Salt Lake now does. In Eurasia, large lakes developed as a result of the runoff from the glaciers. Rivers were larger, had a more copious flow, and were braided. African lakes were fuller, apparently from decreased evaporation. Deserts on the other hand were drier and more extensive. Rainfall was lower because of the decrease in oceanic and other evaporation.
Major events
Over 11 major glacial events have been identified, as well as many minor glacial events. A major glacial event is a general glacial excursion, termed a “glacial.” Glacials are separated by “interglacials”. During a glacial, the glacier experiences minor advances and retreats. The minor excursion is a “stadial”; times between stadials are “interstadials”.
These events are defined differently in different regions of the glacial range, which have their own glacial history depending on latitude, terrain and climate. There is a general correspondence between glacials in different regions. Investigators often interchange the names if the glacial geology of a region is in the process of being defined. However, it is generally incorrect to apply the name of a glacial in one region to another.
For most of the 20th century only a few regions had been studied and the names were relatively few. Today the geologists of different nations are taking more of an interest in Pleistocene glaciology. As a consequence, the number of names is expanding rapidly and will continue to expand. Many of the advances and stadials remain unnamed. Also, the terrestrial evidence for some of them has been erased or obscured by larger ones, but evidence remains from the study of cyclical climate changes.
The glacials in the following tables show historical usages, are a simplification of a much more complex cycle of variation in climate and terrain, and are generally no longer used. These names have been abandoned in favor of numeric data because many of the correlations were found to be either inexact or incorrect and more than four major glacials have been recognized since the historical terminology was established.
Corresponding to the terms glacial and interglacial, the terms pluvial and interpluvial are in use (Latin: pluvia, rain). A pluvial is a warmer period of increased rainfall; an interpluvial, of decreased rainfall. Formerly a pluvial was thought to correspond to a glacial in regions not iced, and in some cases it does. Rainfall is cyclical also. Pluvials and interpluvials are widespread.
There is no systematic correspondence of pluvials to glacials, however. Moreover, regional pluvials do not correspond to each other globally. For example, some have used the term “Riss pluvial” in Egyptian contexts. Any coincidence is an accident of regional factors. Only a few of the names for pluvials in restricted regions have been strategraphically defined.
Palaeocycles
The sum of transient factors acting at the Earth’s surface is cyclical: climate, ocean currents and other movements, wind currents, temperature, etc. The waveform response comes from the underlying cyclical motions of the planet, which eventually drag all the transients into harmony with them. The repeated glaciations of the Pleistocene were caused by the same factors.
Milankovitch cycles
Glaciation in the Pleistocene was a series of glacials and interglacials, stadials and interstadials, mirroring periodic changes in climate. The main factor at work in climate cycling is now believed to be Milankovitch cycles. These are periodic variations in regional and planetary solar radiation reaching the Earth caused by several repeating changes in the Earth’s motion.
Milankovitch cycles cannot be the sole factor responsible for the variations in climate since they explain neither the long term cooling trend over the Plio-Pleistocene, nor the millennial variations in the Greenland Ice Cores. Milankovitch pacing seems to best explain glaciation events with periodicity of 100,000, 40,000, and 20,000 years. Such a pattern seems to fit the information on climate change found in oxygen isotope cores. The timing of our present interglacial interval (known as the Holocene, Postglacial, or the Present Interglacial) to that of the previous interglacial, beginning about 130,000 years ago (The Eemian Interglacial), suggests that the next glacial would likely begin in about 3,000 years.
Oxygen isotope ratio cycles
In oxygen isotope ratio analysis, variations in the ratio of O18 to O16 (two isotopes of oxygen) by mass (measured by a mass spectrometer) present in the calcite of oceanic core samples is used as a diagnostic of ancient ocean temperature change and therefore of climate change. Cold oceans are richer in O18, which is included in the tests of the microorganisms (foraminifera) contributing the calcite.
A more recent version of the sampling process makes use of modern glacial ice cores. Although less rich in O18 than sea water, the snow that fell on the glacier year by year nevertheless contained O18 and O16 in a ratio that depended on the mean annual temperature.
Temperature and climate change are cyclical when plotted on a graph of temperature versus time. Temperature coordinates are given in the form of a deviation from today’s annual mean temperature, taken as zero. This sort of graph is based on another of isotope ratio versus time. Ratios are converted to a percentage difference from the ratio found in standard mean ocean water (SMOW).
The graph in either form appears as a waveform with overtones. One half of a period is a Marine isotopic stage (MIS). It indicates a glacial (below zero) or an interglacial (above zero). Overtones are stadials or interstadials.
According to this evidence, Earth experienced 102 MIS stages beginning at about 2.588 Ma BP in the Early Pleistocene Gelasian. Early Pleistocene stages were shallow and frequent. The latest were the most intense and most widely spaced.
By convention, stages are numbered from the Holocene, which is MIS1. Glacials receive an even number; interglacials, odd. The first major glacial was MIS2-4 at about 85–11 ka BP. The largest glacials were 2, 6, 12, and 16; the warmest interglacials, 1, 5, 9 and 11. For matching of MIS numbers to named stages, see under the articles for those names.
Fauna
Both marine and continental faunas were essentially modern and many animals, specifically, mammals were much larger than their modern relatives .
The severe climatic changes during the ice age had major impacts on the fauna and flora. With each advance of the ice, large areas of the continents became totally depopulated, and plants and animals retreating southward in front of the advancing glacier faced tremendous stress. The most severe stress resulted from drastic climatic changes, reduced living space, and curtailed food supply. A major extinction event of large mammals (megafauna), which included mammoths, mastodons, saber-toothed cats, glyptodons, ground sloths, Irish elk, cave bears, and short-faced bears, began late in the Pleistocene and continued into the Holocene. Neanderthals also became extinct during this period. At the end of the last ice age, cold-blooded animals, smaller mammals like wood mice, migratory birds, and swifter animals like whitetail deer had replaced the megafauna and migrated north.
The extinctions were especially severe in North America where native horses and camels were eliminated.
Asian land mammal ages (ALMA) include Zhoukoudianian, Nihewanian, and Yushean.
European land mammal ages (ELMA) include Gelasian (2.5—1.8 Ma).
North American land mammal ages (NALMA) include Blancan (4.75–1.8), Irvingtonian (1.8–0.24) and Rancholabrean (0.24–0.01) in millions of years. The Blancan extends significantly back into the Pliocene.
South American land mammal ages (SALMA) include Uquian (2.5–1.5), Ensenadan (1.5–0.3) and Lujanian (0.3–0.01) in millions of years. The Uquian extends significantly back into the Pliocene.
Humans
Scientific evidence indicates that humans evolved into their present form during the Pleistocene.In the beginning of the Pleistocene Paranthropus species are still present, as well as early human ancestors, but during the lower Palaeolithic they disappeared, and the only hominid species found in fossilic records is Homo erectus for much of the Pleistocene. The Middle and late Palaeolithic saw the appearance of new types of humans, as well as the development of more elaborate tools than found in previous eras. According to mitochondrial timing techniques, modern humans migrated from Africa after the Riss glaciation in the middle Palaeolithic during the Eemian Stage, spreading all over the ice-free world during the late Pleistocene. A 2005 study posits that humans in this migration interbred with archaic human forms already outside of Africa by the late Pleistocene, incorporating archaic human genetic material into the modern human gene pool.
Deposits
Pleistocene non-marine sediments are found primarily in fluvial deposits, lakebeds, slope and loess deposits as well as in the large amounts of material moved about by glaciers. Less common are cave deposits, travertines and volcanic deposits (lavas, ashes). Pleistocene marine deposits are found primarily in shallow marine basins mostly (but with important exceptions) in areas within a few tens of kilometers of the modern shoreline. In a few geologically active areas such as the Southern California coast, Pleistocene marine deposits may be found at elevations of several hundred meters.
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The Quaternary Period /kwəˈtɜrnəri/ is the most recent of the three periods of the Cenozoic Era in the geologic time scale of the ICS.It follows the Neogene Period and spans from 2.588 ± 0.005 million years ago to the present. Traditionally it was preceded by Tertiary which is no longer recognized as a formal geological unit but is still in colloquial use.
This relatively short geological period is characterized by a series of glaciations and by the appearance and expansion of anatomically modern humans.
Also of note, all objects that are suitable for carbon dating are enclosed in this period.
The Quaternary includes two geologic epochs: the Pleistocene and Holocene.
A proposed but as yet informal third epoch, the Anthropocene, has also gained credence as the time in which humans began to profoundly affect and change the global environment, although its start date is still disputed.
Research history
The term Quaternary (“fourth”) was proposed by Giovanni Arduino in 1759 for alluvial deposits in the Po River valley in northern Italy. It was introduced by Jules Desnoyers in 1829 for sediments of France’s Seine Basin that seemed clearly to be younger than Tertiary Period rocks.
The Quaternary Period follows the Neogene Period and extends to the present. The Quaternary covers the time span of glaciations classified as the Pleistocene, and includes the present interglacial period, the Holocene.
This places the start of the Quaternary at the onset of Northern Hemisphere glaciation approximately 2.6 million years ago. Prior to 2009, the Pleistocene was defined to be from 1.805 million years ago to the present, so the current definition of the Pleistocene includes a portion of what was, prior to 2009, defined as the Pliocene.
Quaternary stratigraphers usually worked with regional subdivisions. From the 1970s, the International Commission on Stratigraphy (ICS) tried to make a single geologic time scale based on GSSP’s, which could be used internationally. The Quaternary subdivisions were defined based on biostratigraphy instead of paleoclimate.
This led to the problem that the proposed base of the Pleistocene was at 1.805 Mya, long after the start of the major glaciations of the northern hemisphere. The ICS then proposed to abolish use of the name Quaternary altogether, which appeared unacceptable to the International Union for Quaternary Research (INQUA).
In 2009, it was decided to make the Quaternary the youngest period of the Cenozoic Era with its base at 2.588 Mya and including the Gelasian stage, which was formerly considered part of the Neogene Period and Pliocene Epoch.
Geology
The 2.6 million years of the Quaternary represents the time during which recognizable humans existed. Over this short time period, there has been relatively little change in the distribution of the continents due to plate tectonics.
The Quaternary geological record is preserved in greater detail than that for earlier periods.
The major geographical changes during this time period included the emergence of the Strait of Bosphorus and Skagerrak during glacial epochs, which respectively turned the Black Sea and Baltic Sea into fresh water, followed by their flooding (and return to salt water) by rising sea level; the periodic filling of the English Channel, forming a land bridge between Britain and the European mainland; the periodic closing of the Bering Strait, forming the land bridge between Asia and North America; and the periodic flash flooding of Scablands of the American Northwest by glacial water.
The current extent of Hudson Bay, the Great Lakes and other major lakes of North America are a consequence of the Canadian Shield’s readjustment since the last ice age; different shorelines have existed over the course of Quaternary time.
Climate
The climate was one of periodic glaciations with continental glaciers moving as far from the poles as 40 degrees latitude. There was a major extinction of large mammals in Northern areas at the end of the Pleistocene Epoch. Many forms such as saber-toothed cats, mammoths, mastodons, glyptodonts, etc., became extinct worldwide. Others, including horses, camels and American cheetahs became extinct in North America.
Quaternary glaciation
Glaciation took place repeatedly during the Quaternary Ice Age – a term coined by Schimper in 1839 that began with the start of the Quaternary about 2.58 Mya and continues to the present-day.
Last glacial period
Artist’s impression of Earth during the Last Glacial Maximum
In 1821, a Swiss engineer, Ignaz Venetz, presented an article in which he suggested the presence of traces of the passage of a glacier at a considerable distance from the Alps. This idea was initially disputed by another Swiss scientist, Louis Agassiz, but when he undertook to disprove it, he ended up affirming his colleague’s hypothesis. A year later, Agassiz raised the hypothesis of a great glacial period that would have had long-reaching general effects. This idea gained him international fame and led to the establishment of the Glacial Theory.
In time, thanks to the refinement of geology, it has been demonstrated that there were several periods of glacial advance and retreat and that past temperatures on Earth were very different from today. In particular, the Milankovitch cycles of Milutin Milankovitch are based on the premise that variations in incoming solar radiation are a fundamental factor controlling Earth’s climate.
During this time, substantial glaciers advanced and retreated over much of North America and Europe, parts of South America and Asia, and all of Antarctica. The Great Lakes formed and giant mammals thrived in parts of North America and Eurasia not covered in ice. These mammals became extinct when the glacial period Age ended about 11,700 years ago. Modern humans evolved about 190,000 years ago (source: Leakey). During the Quaternary period, mammals, flowering plants, and insects dominated the land.
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Using friction experiments University of Liverpool scientists have shown that frictional melting plays a role in determining how a volcano will erupt. Credit: Dr. Jackie Kendrick
A new discovery in the study of how lava dome volcanoes erupt may help in the development of methods to predict how a volcanic eruption will behave, say scientists at the University of Liverpool.
Volcanologists at the University have discovered that a process called frictional melting plays a role in determining how a volcano will erupt, by dictating how fast magma can ascend to the surface, and how much resistance it faces en-route.
The process occurs in lava dome volcanoes when magma and rocks melt as they rub against each other due to intense heat. This creates a stop start movement in the magma as it makes its way towards Earth’s surface. The magma sticks to the rock and stops moving until enough pressure builds up, prompting it to shift forward again (a process called stick-slip).
Volcanologist, Dr Jackie Kendrick, who lead the research said: “Seismologists have long known that frictional melting takes place when large tectonic earthquakes occur. It is also thought that the stick-slip process that frictional melting generates is concurrent to ‘seismic drumbeats’ which are the regular, rhythmic small earthquakes which have been recently found to accompany large volcanic eruptions.
“Using friction experiments we have shown that the extent of frictional melting depends on the composition of the rock and magma, which determines how fast or slow the magma travels to the surface during the eruption.”
Analysis of lava collected from Mount St. Helens, USA and the Soufrière Hills volcano in Montserrat by volcanology researchers from the University’s School of Environmental Sciences revealed remnants of pseudotachylyte, a cooled frictional melt. Evidence showed that the process took place in the conduit, the channel which lava passes through on its way to erupt.
Dr Kendrick, from the University’s School of Environmental Sciences, added: “The closer we get to understanding the way magma behaves, the closer we will get to the ultimate goal: predicting volcanic activity when unrest begins. Whilst we can reasonably predict when a volcanic eruption is about to happen, this new knowledge will help us to predict how the eruption will behave.
“With a rapidly growing population inhabiting the flanks of active volcanoes, understanding the behaviour of lava domes becomes an increasing challenge for volcanologists.”
Note : The above story is based on materials provided by University of Liverpool.
Jarosite Bristol Silver Mine, Pioche, Lincoln County, Nevada, USA Miniature, 5.8 x 5.7 x 4.5 cm “Courtesy of Rob Lavinsky, The Arkenstone, www.iRocks.com”
Chemical Formula: KFe3+3(SO4)2(OH)6 Locality: Barranco Jaroso in southern Spain. Name Origin: Named after its locality.
Jarosite is a basic hydrous sulfate of potassium and iron with a chemical formula of KFe3+3(SO4)2(OH)6. This sulfate mineral is formed in ore deposits by the oxidation of iron sulfides. Jarosite is often produced as a byproduct during the purification and refining of zinc and is also commonly associated with acid mine drainage and acid sulfate soil environments.
History
Jarosite was first described in 1852 by August Breithaupt in the Barranco del Jaroso in the Sierra Almagrera (near Los Lobos, Cuevas del Almanzora, Almería, Spain). The name jarosite is also directly derived from Jara, the Spanish name of a yellow flower that belongs to the genus cistus and grows in this sierra. The mineral and the flower have the same color.
In 2004 jarosite was detected on Mars by a Mössbauer spectrometer on the MER-B rover, which has been interpreted as strong evidence that Mars once possessed large amounts of liquid water.
Mysterious spheres of clay, 1.5 to 5 inches in diameter, covered with jarosite have recently been discovered beneath the Temple of the Feathered Serpent an ancient six level stepped pyramid 30 miles from Mexico City.
The Pliocene is the period in the geologic timescale that extends from 5.332 million to 2.588 million years before present. It is the second and youngest epoch of the Neogene Period in the Cenozoic Era. The Pliocene follows the Miocene Epoch and is followed by the Pleistocene Epoch. Prior to the 2009 revision of the geologic time scale, which placed the 4 most recent major glaciations entirely within the Pleistocene, the Pliocene also included the Gelasian stage, which lasted from 2.588 to 1.806 million years ago, and is now included in the Pleistocene.
As with other older geologic periods, the geological strata that define the start and end are well identified but the exact dates of the start and end of the epoch are slightly uncertain. The boundaries defining the Pliocene are not set at an easily identified worldwide event but rather at regional boundaries between the warmer Miocene and the relatively cooler Pleistocene. The upper boundary was set at the start of the Pleistocene glaciations.
Etymology
The Pliocene was named by Sir Charles Lyell. The name comes from the Greek words πλεῖον (pleion, “more”) and καινός (kainos, “new”) and means roughly “continuation of the recent”, referring to the essentially modern marine mollusc faunas. H.W. Fowler called the term (along with other examples such as pleistocene and miocene) a “regrettable barbarism” and an indication that even “a good classical scholar” such as Lyell should have requested a philologist’s help when coining words.
Subdivisions
In the official timescale of the ICS, the Pliocene is subdivided into two stages. From youngest to oldest they are:
Piacenzian (3.600–2.588 Ma)
Zanclean (5.332–3.600 Ma)
The Piacenzian is sometimes referred to as the Late Pliocene, whereas the Zanclean is referred to as the Early Pliocene.In the system of
North American Land Mammal Ages (NALMA) include Hemphillian (9–4.75 Ma), and Blancan (4.75–1.806 Ma). The Blancan extends forward into the Pleistocene.
South American Land Mammal Ages (SALMA) include Montehermosan (6.8–4.0 Ma), Chapadmalalan (4.0–3.0 Ma) and Uquian (3.0–1.2 Ma).
In the Paratethys area (central Europe and parts of western Asia) the Pliocene contains the Dacian (roughly equal to the Zanclean) and Romanian (roughly equal to the Piacenzian and Gelasian together) stages. As usual in stratigraphy, there are many other regional and local subdivisions in use.In Britain the Pliocene is divided into the following stages (old to young): Gedgravian, Waltonian, Pre-Ludhamian, Ludhamian, Thurnian, Bramertonian or Antian, Pre-Pastonian or Baventian, Pastonian and Beestonian. In the Netherlands the Pliocene is divided into these stages (old to young): Brunssumian C, Reuverian A, Reuverian B, Reuverian C, Praetiglian, Tiglian A, Tiglian B, Tiglian C1-4b, Tiglian C4c, Tiglian C5, Tiglian C6 and Eburonian. The exact correlations between these local stages and the ICS stages is still a matter of detail.
Climate
Mid-Pliocene reconstructed annual sea surface temperature anomaly
The global average temperature in the mid-Pliocene (3.3–3 mya) was 2–3 °C higher than today,global sea level 25 m higher and the Northern hemisphere ice sheet was ephemeral before the onset of extensive glaciation over Greenland that occurred in the late Pliocene around 3 Ma. The formation of an Arctic ice cap is signaled by an abrupt shift in oxygen isotope ratios and ice-rafted cobbles in the North Atlantic and North Pacific ocean beds. Mid-latitude glaciation was probably underway before the end of the epoch. The global cooling that occurred during the Pliocene may have spurred on the disappearance of forests and the spread of grasslands and savannas.
Paleogeography
Continents continued to drift, moving from positions possibly as far as 250 km from their present locations to positions only 70 km from their current locations. South America became linked to North America through the Isthmus of Panama during the Pliocene, making possible the Great American Interchange and bringing a nearly complete end to South America’s distinctive large marsupial predator and native ungulate faunas. The formation of the Isthmus had major consequences on global temperatures, since warm equatorial ocean currents were cut off and an Atlantic cooling cycle began, with cold Arctic and Antarctic waters dropping temperatures in the now-isolated Atlantic Ocean.
Africa’s collision with Europe formed the Mediterranean Sea, cutting off the remnants of the Tethys Ocean. The border between the Miocene and the Pliocene is also the time of the Messinian salinity crisis.
Sea level changes exposed the land-bridge between Alaska and Asia.
Pliocene marine rocks are well exposed in the Mediterranean, India, and China. Elsewhere, they are exposed largely near shores.
Flora
The change to a cooler, dry, seasonal climate had considerable impacts on Pliocene vegetation, reducing tropical species worldwide. Deciduous forests proliferated, coniferous forests and tundra covered much of the north, and grasslands spread on all continents (except Antarctica). Tropical forests were limited to a tight band around the equator, and in addition to dry savannahs, deserts appeared in Asia and Africa.
Fauna
Both marine and continental faunas were essentially modern, although continental faunas were a bit more primitive than today. The first recognizable hominins, the australopithecines, appeared in the Pliocene.
The land mass collisions meant great migration and mixing of previously isolated species, such as in the Great American Interchange. Herbivores got bigger, as did specialized predators.
In North America, rodents, large mastodons and gomphotheres, and opossums continued successfully, while hoofed animals (ungulates) declined, with camel, deer and horse all seeing populations recede. Rhinos, three toed horses (Nannippus), oreodonts, protoceratids, and chalicotheres went extinct. Borophagine dogs and Agriotherium went extinct, but other carnivores including the weasel family diversified, and dogs and fast-running hunting bears did well. Ground sloths, huge glyptodonts, and armadillos came north with the formation of the Isthmus of Panama.
In Eurasia rodents did well, while primate distribution declined. Elephants, gomphotheres and stegodonts were successful in Asia, and hyraxes migrated north from Africa. Horse diversity declined, while tapirs and rhinos did fairly well. Cows and antelopes were successful, and some camel species crossed into Asia from North America. Hyenas and early saber-toothed cats appeared, joining other predators including dogs, bears and weasels.
Africa was dominated by hoofed animals, and primates continued their evolution, with australopithecines (some of the first hominids) appearing in the late Pliocene. Rodents were successful, and elephant populations increased. Cows and antelopes continued diversification and overtaking pigs in numbers of species. Early giraffes appeared, and camels migrated via Asia from North America. Horses and modern rhinos came onto the scene. Bears, dogs and weasels (originally from North America) joined cats, hyenas and civets as the African predators, forcing hyenas to adapt as specialized scavengers.
South America was invaded by North American species for the first time since the Cretaceous, with North American rodents and primates mixing with southern forms. Litopterns and the notoungulates, South American natives, were mostly wiped out, except for the macrauchenids and toxodonts, which managed to survive. Small weasel-like carnivorous mustelids, coatis and short faced bears migrated from the north. Grazing glyptodonts, browsing giant ground sloths and smaller caviomorph rodents, pampatheres, and armadillos did the opposite, migrating to the north and thriving there.
The marsupials remained the dominant Australian mammals, with herbivore forms including wombats and kangaroos, and the huge diprotodon. Carnivorous marsupials continued hunting in the Pliocene, including dasyurids, the dog-like thylacine and cat-like Thylacoleo. The first rodents arrived in Australia. The modern platypus, a monotreme, appeared.
The predatory South American phorusrhacids were rare in this time; among the last was Titanis, a large phorusrhacid that migrated to North America and rivaled mammals as top predator. Other birds probably evolved at this time, some modern, some now extinct.
Reptiles and amphibians
Alligators and crocodiles died out in Europe as the climate cooled. Venomous snake genera continued to increase as more rodents and birds evolved. Rattlesnakes first appeared in the Pliocene. The modern species Alligator mississippiensis, having evolved in the Miocene, continued into the Pliocene, except with a more northern range; specimens have been found in very late Miocene deposits of Tennessee. Giant tortoises still thrived in North America, with genera like Hesperotestudo. Madtsoid snakes were still present in Australia. The amphibian order Allocaudata went extinct.
Oceans
Oceans continued to be relatively warm during the Pliocene, though they continued cooling. The Arctic ice cap formed, drying the climate and increasing cool shallow currents in the North Atlantic. Deep cold currents flowed from the Antarctic.The formation of the Isthmus of Panama about 3.5 million years ago cut off the final remnant of what was once essentially a circum-equatorial current that had existed since the Cretaceous and the early Cenozoic. This may have contributed to further cooling of the oceans worldwide.
The Pliocene seas were alive with sea cows, seals and sea lions.
Supernovae
In 2002, Narciso Benítez et al. calculated that roughly 2 million years ago, around the end of the Pliocene epoch, a group of bright O and B stars called the Scorpius-Centaurus OB association passed within 130 light-years of Earth and that one or more supernova explosions gave rise to a feature known as the Local Bubble. Such a close explosion could have damaged the Earth’s ozone layer and caused the extinction of some ocean life (at its peak, a supernova of this size could have the same absolute magnitude as an entire galaxy of 200 billion stars).Note : The above story is based on materials provided by Wikipedia
The Miocene is the first geological epoch of the Neogene period and extends from about 23.03 to 5.332 million years ago (Ma). The Miocene was named by Sir Charles Lyell. Its name comes from the Greek words μείων (meiōn, “less”) and καινός (kainos, “new”) and means “less recent” because it has 18% fewer modern sea invertebrates than the Pliocene. The Miocene follows the Oligocene epoch and is followed by the Pliocene epoch.
The earth went from the Oligocene through the Miocene and into the Pliocene as it cooled into a series of ice ages. The Miocene boundaries are not marked by a single distinct global event but consist rather of regional boundaries between the warmer Oligocene and the cooler Pliocene.
The apes arose and diversified during the Miocene epoch, becoming widespread in the Old World. In fact, by the end of this epoch, the ancestors of humans had split away from the ancestors of the chimpanzees to follow their own evolutionary path. As in the Oligocene before it, grasslands continued to expand and forests to dwindle in extent. In the Miocene seas, kelp forests made their first appearance and soon became one of Earth’s most productive ecosystems. The plants and animals of the Miocene were fairly modern. Mammals and birds were well-established. Whales, seals, and kelp spread. The Miocene epoch is of particular interest to geologists and palaeoclimatologists as major phases of Himalayan uplift had occurred during the Miocene epoch affecting monsoonal patterns in Asia, which were interlinked with glaciations in the northern hemisphere.
Subdivisions
The Miocene faunal stages from youngest to oldest are typically named according to the International Commission on Stratigraphy:
Messinian (7.246–5.332 Ma)
Tortonian (11.608–7.246 Ma)
Serravallian (13.65–11.608 Ma)
Langhian (15.97–13.65 Ma)
Burdigalian (20.43–15.97 Ma)
Aquitanian (23.03–20.43 Ma)
These subdivisions within the Miocene are defined by the relative abundance of different species of calcareous nanofossils (calcite platelets shed by brown single-celled algae) and foraminifera (single-celled protists with diagnostic shells). Two subdivisions each form the Early, Middle and Late Miocene. Regionally, other systems are used. These ages often extend across the ICS epoch boundary into the Pliocene and Oligocene.
Paleogeography
Continents continued to drift toward their present positions. Of the modern geologic features, only the land bridge between South America and North America was absent, although South America was approaching the western subduction zone in the Pacific Ocean, causing both the rise of the Andes and a southward extension of the Meso-American peninsula.
Mountain building took place in western North America, Europe, and East Asia. Both continental and marine Miocene deposits are common worldwide with marine outcrops common near modern shorelines. Well studied continental exposures occur in the North American Great Plains and in Argentina.
India continued to collide with Asia, creating dramatic new mountain ranges. The Tethys Seaway continued to shrink and then disappeared as Africa collided with Eurasia in the Turkish–Arabian region between 19 and 12 Ma. The subsequent uplift of mountains in the western Mediterranean region and a global fall in sea levels combined to cause a temporary drying up of the Mediterranean Sea (known as the Messinian salinity crisis) near the end of the Miocene.
The global trend was towards increasing aridity caused primarily by global cooling reducing the ability of the atmosphere to absorb moisture. Uplift of East Africa in the late Miocene was partly responsible for the shrinking of tropical rain forests in that region, and Australia got drier as it entered a zone of low rainfall in the Late Miocene.
Climate
Climates remained moderately warm, although the slow global cooling that eventually led to the Pleistocene glaciations continued.
Although a long-term cooling trend was well underway, there is evidence of a warm period during the Miocene when the global climate rivalled that of the Oligocene. The Miocene warming began 21 million years ago and continued until 14 million years ago, when global temperatures took a sharp drop – the Middle Miocene Climate Transition (MMCT). By 8 million years ago, temperatures dropped sharply once again, and the Antarctic ice sheet was already approaching its present-day size and thickness. Greenland may have begun to have large glaciers as early as 7 to 8 million years ago,[citation needed] although the climate for the most part remained warm enough to support forests there well into the Pliocene.
Life
Life during the Miocene Epoch was mostly supported by the two newly formed biomes, kelp forests and grasslands. This allows for more grazers, such as horses, rhinoceroses,and hippos. Ninety five percent of modern plants existed by the end of this epoch.
Flora
The coevolution of gritty, fibrous, fire-tolerant grasses and long-legged gregarious ungulates with high-crowned teeth, led to a major expansion of grass-grazer ecosystems, with roaming herds of large, swift grazers pursued by predators across broad sweeps of open grasslands, displacing desert, woodland, and browsers. The higher organic content and water retention of the deeper and richer grassland soils, with long term burial of carbon in sediments, produced a carbon and water vapor sink. This, combined with higher surface albedo and lower evapotranspiration of grassland, contributed to a cooler, drier climate. C4 grasses, which are able to assimilate carbon dioxide and water more efficiently than C3 grasses, expanded to become ecologically significant near the end of the Miocene between 6 and 7 million years ago. The expansion of grasslands and radiations among terrestrial herbivores correlates to fluctuations in CO2.
Cycads between 11.5 and 5 m.y.a. began to rediversify after previous declines in variety due to climatic changes, and thus modern cycads are not a good model for a “living fossil”.
Fauna
Both marine and continental fauna were fairly modern, although marine mammals were less numerous. Only in isolated South America and Australia did widely divergent fauna exist.
In the Early Miocene, several Oligocene groups were still diverse, including nimravids, entelodonts, and three-toed horses. Like in the previous Oligocene epoch, oreodonts were still diverse, only to disappear in the earliest Pliocene. During the later Miocene mammals were more modern, with easily recognizable dogs, bears, raccoons, horses, beaver, deer, camels, and whales, along with now extinct groups like borophagine dogs, gomphotheres, three-toed horses, and semi-aquatic and hornless rhinos like Teleoceras and Aphelops. Islands began to form between South and North America in the Late Miocene, allowing ground sloths like Thinobadistes to island-hop to North America. The expansion of silica-rich C4 grasses led to worldwide extinctions of herbivorous species without high-crowned teeth.
Unequivocally recognizable dabbling ducks, plovers, typical owls, cockatoos and crows appear during the Miocene. By the epoch’s end, all or almost all modern bird families are believed to have been present; the few post-Miocene bird fossils which cannot be placed in the evolutionary tree with full confidence are simply too badly preserved, rather than too equivocal in character. Marine birds reached their highest diversity ever in the course of this epoch.
Approximately 100 species of apes lived during this time. They ranged over much of the Old World and varied widely in size, diet, and anatomy. Due to scanty fossil evidence it is unclear which ape or apes contributed to the modern hominid clade, but molecular evidence indicates this ape lived from between 15 to 12 million years ago.
In the oceans, brown algae, called kelp, proliferated, supporting new species of sea life, including otters, fish and various invertebrates.
Cetaceans attained their greatest diversity during the Miocene, with over 20 recognized genera in comparison to only six living genera. This diversification correlates with emergence of gigantic macro-predators such as megatoothed sharks and raptorial sperm whales. Prominent examples are C. megalodon and L. melvillei. Other notable large sharks were C. chubutensis, Isurus hastalis, and Hemipristis serra.
Crocodilians also showed signs of diversification during Miocene. The largest form among them was a gigantic caiman Purussaurus which inhabited South America. Another gigantic form was a false gharial Rhamphosuchus, which inhabited modern age India. A strange form Mourasuchus also thrived alongside Purussaurus. This species developed a specialized filter-feeding mechanism, and it likely preyed upon small fauna despite its gigantic size.
The pinnipeds, which appeared near the end of the Oligocene, became more aquatic. Prominent genus was Allodesmus. A ferocious walrus, Pelagiarctos may have preyed upon other species of pinnipeds including Allodesmus.
Furthermore, South American waters witnessed the arrival of Megapiranha paranensis, which were considerably larger than modern age piranhas.
Oceans
There is evidence from oxygen isotopes at Deep Sea Drilling Program sites that ice began to build up in Antarctica about 36 Ma during the Eocene. Further marked decreases in temperature during the Middle Miocene at 15 Ma probably reflect increased ice growth in Antarctica. It can therefore be assumed that East Antarctica had some glaciers during the early to mid Miocene (23–15 Ma). Oceans cooled partly due to the formation of the Antarctic Circumpolar Current, and about 15 million years ago the ice cap in the southern hemisphere started to grow to its present form. The Greenland ice cap developed later, in the Middle Pliocene time, about 3 million years ago.
The “Middle Miocene disruption” refers to a wave of extinctions of terrestrial and aquatic life forms that occurred following the Miocene Climatic Optimum (18 to 16 Ma), around 14.8 to 14.5 million years ago, during the Langhian stage of the mid-Miocene. A major and permanent cooling step occurred between 14.8 and 14.1 Ma, associated with increased production of cold Antarctic deep waters and a major growth of the East Antarctic ice sheet. A Middle Miocene δ18O increase, that is, a relative increase in the heavier isotope of oxygen, has been noted in the Pacific, the Southern Ocean and the South Atlantic.
Note : The above story is based on materials provided by Wikipedia
The Neogene is a geologic period and system in the International Commission on Stratigraphy (ICS) Geologic Timescale starting 23.03 ± 0.05 million years ago and ending 2.588 million years ago. The second period in the Cenozoic Era, it follows the Paleogene Period and is succeeded by the Quaternary Period. The Neogene is subdivided into two epochs, the earlier Miocene and the later Pliocene.
The Neogene covers about 20 million years. During this period, mammals and birds continued to evolve into roughly modern forms, while other groups of life remained relatively unchanged. Early hominids, the ancestors of humans, appeared in Africa. Some continental movement took place, the most significant event being the connection of North and South America at the Isthmus of Panama, late in the Pliocene. This cut off the warm ocean currents from the Pacific to the Atlantic ocean, leaving only the Gulf Stream to transfer heat to the Arctic Ocean. The global climate cooled considerably over the course of the Neogene, culminating in a series of continental glaciations in the Quaternary Period that follows.
Divisions
In ICS terminology, from upper (later, more recent) to lower (earlier):The Pliocene Epoch is subdivided into 2 ages:
Piacenzian Age, preceded by
Zanclean Age
The Miocene Epoch is subdivided into 6 ages:
Messinian Age, preceded by
Tortonian Age
Serravallian Age
Langhian Age
Burdigalian Age
Aquitanian Age
In different geophysical regions of the world, other regional names are also used for the same or overlapping ages and other timeline subdivisions.The terms Neogene System (formal) and upper Tertiary System (informal) describe the rocks deposited during the Neogene Period
Climate and geography
The continents in the Neogene were very close to their current positions. The isthmus of Panama formed, connecting North and South America. India continued to collide with Asia, forming the Himalayas. Sea levels fell, exposing land bridges between Africa and Eurasia and between Eurasia and North America.
The global climate became seasonal and continued its overall drying and cooling trend which began in the beginning of the Paleogene. The ice caps on both poles began to grow and thicken, and by the end of the period the first of a series of glaciations of the current Ice Age began.
Flora and fauna
Marine and continental flora and fauna were fairly modern at this time. Mammals and birds continued to be the dominant terrestrial vertebrates, and took many forms as they adapted to various habitats. The first hominids, the ancestors of humans, appeared in Africa and spread into Eurasia.
In response to the cooler, seasonal climate, tropical plant species gave way to deciduous ones and grasslands replaced many forests. Grasses therefore greatly diversified, and herbivorous mammals evolved alongside it, creating the many grazing animals of today such as horses, antelope, and bison.
Disagreements
The Neogene traditionally ended at the end of the Pliocene Epoch, just before the older definition of the beginning of the Quaternary Period; many time scales show this division.
However, there was a movement amongst geologists (particularly Neogene Marine Geologists) to also include ongoing geological time (Quaternary) in the Neogene, while others (particularly Quaternary Terrestrial Geologists) insist the Quaternary to be a separate period of distinctly different record. The somewhat confusing terminology and disagreement amongst geologists on where to draw what hierarchical boundaries, is due to the comparatively fine divisibility of time units as time approaches the present, and due to geological preservation that causes the youngest sedimentary geological record to be preserved over a much larger area and to reflect many more environments, than the older geological record. By dividing the Cenozoic Era into three (arguably two) periods (Paleogene, Neogene, Quaternary) instead of 7 epochs, the periods are more closely comparable to the duration of periods in the Mesozoic and Paleozoic eras.
The ICS once proposed that the Quaternary be considered a sub-era (sub-erathem) of the Neogene, with a beginning date of 2.588 Ma, namely the start of the Gelasian Stage. In the 2004 proposal of the International Commission on Stratigraphy (ICS), the Neogene would have consisted of the Miocene and Pliocene epochs. The International Union for Quaternary Research (INQUA) counterproposed that the Neogene and the Pliocene end at 2.588 Ma, that the Gelasian be transferred to the Pleistocene, and the Quaternary be recognized as the third period in the Cenozoic, citing key changes in Earth’s climate, oceans, and biota that occurred 2.588 Ma and its correspondence to the Gauss-Matuyama magnetostratigraphic boundary. In 2006 ICS and INQUA reached a compromise that made Quaternary a subera, subdividing Cenozoic into the old classical Tertiary and Quaternary, a compromise that was rejected by International Union of Geological Sciences because it split both Neogene and Pliocene in two.
Following formal discussions at the International Geological Congress, Oslo Norway, August 2008, the International Commission on Stratigraphy (ICS) decided in May 2009 to make the Quaternary the youngest period of the Cenozoic Era with its base at 2.588 Mya and including the Gelasian age, which was formerly considered part of the Neogene Period and Pliocene Epoch. Thus the Neogene Period ends bounding the succeeding Quaternary Period at 2.588 Mya.
Note : The above story is based on materials provided by Wikipedia
Chemical Formula: Pb4FeSb6S14 Locality: Cornwall, England, UK. Name Origin: Named after the Scottish Mineralogist, R. Jameson (1774-1854).
Jamesonite is a sulfosalt mineral, a lead, iron, antimony sulfide with formula Pb4FeSb6S14. With the addition of manganese it forms a series with benavidesite. It is a dark grey metallic mineral which forms acicular prismatic monoclinic crystals. It is soft with a Mohs hardness of 2.5 and has a specific gravity of 5.5 – 5.6. It is one of the few sulfide minerals to form fibrous or needle like crystals. It can also form large prismatic crystals similar to stibnite with which it can be associated. It is usually found in low to moderate temperature hydrothermal deposits.
It was named for Scottish mineralogist Robert Jameson (1774–1854). It was first identified in 1825 in Cornwall, England. It is also reported from South Dakota and Arkansas, USA; Zacatecas, Mexico; and Romania.
Physical Properties
Cleavage: {001} Perfect Color: Lead gray, Steel gray, Dark lead gray. Density: 5.5 – 5.63, Average = 5.56 Diaphaneity: Opaque Fracture: Brittle – Generally displayed by glasses and most non-metallic minerals. Hardness: 2.5 – Finger Nail Luminescence: Non-fluorescent. Luster: Metallic Magnetism: Nonmagnetic Streak: black. grayish
This artist’s concept of Jupiter’s moon Ganymede, the largest moon in the solar system, illustrates the ”club sandwich” model of its interior oceans. Credit: Reuters/NASA/JPL-Caltech/Handout
(Reuters) – As club sandwiches go, this undoubtedly is the biggest one in the solar system.
Scientists said on Friday that Jupiter’s moon Ganymede may possess ice and liquid oceans stacked up in several layers much like the popular multilayered sandwich. They added that this arrangement may raise the chances that this distant icy world harbors life.
NASA’s Galileo spacecraft flew by Ganymede in the 1990s and confirmed the presence of an interior ocean, also finding evidence for salty water perhaps from the salt known as magnesium sulfate.
Ganymede, which with its diameter of about 3,300 miles (5,300 km), is the largest moon in the solar system and is bigger than the planet Mercury.
A team of scientists performed computer modeling of Ganymede’s ocean, taking into account for the first time how salt increases the density of liquids under the type of extreme conditions present inside Ganymede. Their work followed experiments in the laboratory that simulated such salty seas.
While earlier research suggested a routine “sandwich” arrangement in which there is ice at the surface, then a layer of liquid water and another layer of ice on the bottom, this new study indicated there might be more layers than that.
Steve Vance, an astrobiologist at NASA’s Jet Propulsion Laboratory in California, said the arrangement might be like this: at the top, a layer of ice on the moon’s surface, with a layer of water below that, then a second layer of ice, another layer of water underneath that, then a third layer of ice, with a final layer of water at the bottom above the rocky seafloor.
“That would make it the largest club sandwich in the solar system,” Vance said in a telephone interview. “I suppose I’m also a fan of club sandwiches. My fiancée points out that I order them every time we go out to eat.”
Ganymede boasts a lot of water, perhaps 25 times the volume of Earth’s oceans. Its oceans are estimated to be about 500 miles (800 km) deep.
With enough salt, liquid water on Ganymede could become so dense that it sinks to the very bottom, the researchers said. That means water may be sloshing on top of rock, a situation that may foster conditions suitable for the development of microbial life.
Some scientists suspect that life first formed on Earth in bubbling thermal vents on the ocean floor.
“Our understanding of how life came about on Earth involves the interaction between water and rock. This (research) provides a stronger possibility for those kinds of interactions to take place on Ganymede,” added Vance, whose study was published in the journal Planetary and Space Science.
Ganymede is one of five moons in the solar system thought to have oceans hidden below icy surfaces. Two other moons, Europa and Callisto, orbit the big gas planet Jupiter. The moons Titan and Enceladus circle the ringed gas planet Saturn.
“We’re providing a more realistic view into ocean structure in Ganymede’s interior. We’re showing that the salinity has a tangible effect on the ocean,” Vance said.
Note : The above story is based on materials provided by Will Dunham; Editing by Lisa Shumaker For Reuters
For the past 5 million years, erosion rates in the Alps have been higher than before. A new study links the increase to processes within the Earth’s interior, thus refuting the hypothesis that the phenomenon is related to long-term climate change.
Tectonic forces originating deep within the interior of the Earth are responsible for the rise of the Alps. The process began some 35 million years ago, when northward convergence of the African Plate brought it into collision with the tectonic microplates arrayed along the southern margin of the European Plate. This collision between continental plates resulted in formation of the Alpine mountain range. But as its peaks were raised ever higher, the relentless powers of erosion were eating into their substance. The rocks were slowly fragmented and transported as sediments downslope into the Alpine foreland. “The rate of erosion began to accelerate about 5 million years ago, and in recent years researchers have linked this to global changes in climate,” says LMU geologist Professor Anke Friedrich, who has now studied the process in detail.
In cooperation with Professor Fritz Schlunegger of the University of Berne, Friedrich has used a new methodological approach to analyze the course of erosion in the Alps and its foreland basin in detail. “The method, which was developed in my Institute, enables us to combine datasets obtained using different techniques and analyze them as a whole,” Friedrich explains. This allowed us to systematically investigate a much larger region than was previously possible. The results confirmed that the rate of erosion did indeed increase sharply around 5 million years ago – but not everywhere.
Erosion accelerated only in the West
The rate of erosion increased primarily in the Western sector of the region studied. Moreover, the area affected extends beyond the boundaries of the Alpine mountains, and encompasses the whole of the foreland basin to the North – including the gravel plains around Munich gravel. Furthermore, sediment accumulation increases systematically along a front that runs from Salzburg via Munich to Zürich and Geneva. This finding contradicts the notion that the increase can be ascribed to climatic factors, since these would be expected to have their greatest effect in the uplands rather than in the low-lying basin to the North. Surprisingly, the study uncovered little evidence for increased erosion in the Eastern Alps.
The researchers believe that tectonic forces rather than climatic changes must be invoked to account for this pattern of erosion. The Southern margin of the Eurasian Plate is fragmented into several microplates, and the so-called Adriatic Plate, which forms a large part of the Eastern Alps is being thrust on top of the European Plate. About 5 million years ago, the direction of convergence of the Adriatic Plate changed, causing it to rotate away from the European Plate, and thus partially unburdening the latter.
“As a result of this unloading, the level of the continental crust in the Western Alps has been rising, making it more susceptible to erosion,” says Friedrich. Moreover, this rebound process more than compensates for the erosion rate. It thus explains why the highest peaks in the Alps are found in the West, even though erosion has removed a packet of sediments some 2500 meters thick from the vicinity of Mont Blanc and the Matterhorn.
Note : The above story is based on materials provided by Ludwig Maximilian University of Munich
