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TOPIC: The 'Great Dying'
Blobrana


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Notchpeakia milleri
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James Miller, a geology professor at Missouri State University, now has his name on a group of tiny things that are millions of years old.
Miller was recently honoured for his work in discovering and identifying fossils by his geology colleagues, Jon Adrain of the University of Iowa and Steve Westrop of the University of Oklahoma. They named a new fossil they discovered in Miller's honour.

"It's recognition of the work I've done. It's kind of the Pulitzer Prize for the work I've done."

The trilobite fossil named after Miller — Notchpeakia milleri — was discovered in the same area of the mountain ranges of western Utah where Miller and many of his students conducted years of research.
A trilobite is an extinct arthropod that resembles a tiny horseshoe crab.

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Blobrana


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RE: The 'Great Dying'
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Title: Middle-Late Permian mass extinction on land
Authors: Gregory J. Retallack, Christine A. Metzger, Tara Greaver, A. Hope Jahren, Roger M.H. Smith, Nathan D. Sheldon

The end-Permian mass extinction has been envisaged as the nadir of biodiversity decline due to increasing volcanic gas emissions over some 9 million years. We propose a different tempo and mechanism of extinction because we recognize two separate but geologically abrupt mass extinctions on land, one terminating the Middle Permian (Guadalupian) at 260.4 Ma and a later one ending the Permian Period at 251 Ma. Our evidence comes from new palaeobotanical, paleopedological, and carbon isotopic studies of Portal Mountain, Antarctica, and comparable studies in the Karoo Basin, South Africa. Extinctions have long been apparent among marine invertebrates at both the end of the Guadalupian and end of the Permian, which were also times of warm-wet greenhouse climatic transients, marked soil erosion, transition from high- to low-sinuosity and braided streams, soil stagnation in wetlands, and profound negative carbon isotope anomalies. Both mass extinctions may have resulted from catastrophic methane outbursts to the atmosphere from coal intruded by feeder dikes to flood basalts, such as the end-Guadalupian Emeishan Basalt and end-Permian Siberian Traps.

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Title: Carbon isotopic evidence for terminal-Permian methane outbursts and their role in extinctions of animals, plants, coral reefs, and peat swamps
Authors: Gregory J. Retallack, Evelyn S. Krull

perminian2

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Blobrana


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About 95 percent of the Earth's marine species and 70 percent of its land species were wiped out during a "mass extinction" about 250 million years ago, according to Australian and American researchers.
The phenomenon fundamentally changed which species survived in the world's oceans. And the experts at James Cook University in Townsville, Queensland and the Field Museum in Chicago warned that modern human-induced changes to the ecosystem could have a similar impact.
The experts told in the latest edition of the journal Science how they came across the culling of species while examining figures on the numbers of marine life forms in communities over the past 540 million years.

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www.fieldmuseum.org

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Blobrana


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251 million years ago
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A major catastrophe 251 million years ago left life teetering on the brink of oblivion. Now for the first time we have a clear picture of what caused it, says leading palaeontologist Michael Benton
251 million years ago, at the end of the Permian period, life on Earth was almost completely wiped out by an environmental catastrophe of a magnitude never seen before or since. All over the world complex ecosystems were destroyed. In the sea, coral reefs, fishes, shellfish, trilobites, plankton, and many other groups disappeared. On land, the sabre-toothed gorgonopsian reptiles and their rhinoceros-sized prey, the dinocephalians and pareiasaurs, were wiped out forever. Only 5 per cent of species survived the catastrophe, and for the next 500,000 years life itself teetered on the brink of oblivion. What terrible event could have wrought such havoc?
Two theories have been proposed - the impact of a huge meteorite or comet over 10 kilometres in diameter, or a massive and prolonged volcanic eruption. Up to now the evidence has been equivocal. But the data has been accumulating over the past 10 years, and the picture is now clear enough to say with some certainty what happened.

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Blobrana


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Permian-Triassic extinction
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What really caused the largest mass extinction in Earth's history?
USC earth scientists will reveal new clues at the annual meeting of the Geological Society of America in Philadelphia Oct. 22-25.
The Permian-Triassic extinction, as it is called, is not the one that wiped out the dinosaurs. Nor is there strong evidence for a meteorite strike, as in that famous event, though the possibility has not been ruled out.
The most likely explanation for the disappearance of up to 90 percent of species 250 million years ago, said David Bottjer, is that "the earth got sick." Bottjer, professor of earth sciences in the USC College of Letters, Arts and Sciences, leads a research group presenting several new pieces of the P-T extinction puzzle.
Matthew Clapham, a recent Ph.D. graduate of Bottjer's laboratory, has found that species diversity and environmental changes were "decoupled" long before the extinction. Conditions on the planet were deteriorating long before species began to die off, casting doubt on the meteorite strike theory.

"People in the past used to think this big mass extinction was like a car hitting a wall," he said. Instead, Clapham's interpretation of the geological record shows "millions of years of environmental stress."

Pedro Marenco, a doctoral student in Bottjer's lab, has been testing a leading theory for the P-T extinction: that a warming of the earth and a slowdown in ocean circulation made it harder to replace the oxygen sucked out of the water by marine organisms. According to the theory, microbes would have saturated the water with hydrogen sulphide, a highly toxic chemical.
For a mass extinction "you really needed a good killer, and it (hydrogen sulphide) is really nasty stuff," Bottjer said.
Marenco has measured large changes in the concentration of sulphur isotopes that support the hydrogen sulphide theory.
Bottjer is slated to chair a symposium on the P-T extinction and, in a related presentation, to propose the Moenkopi geological formation in the American Southwest as a promising candidate for studying the extinction through analysis of the different stresses on land and sea during that period.
Bottjer's symposium, as well as his and Marenco's presentations, take place Oct. 24. Clapham presents his results Oct. 22.

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Blobrana


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Bedout High
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A geophysical study of the Bedout High, just off the west coast of Australia, a proposed Permian impact site.
The paper by Muller, R. D., A. Goncharov, and A. Kritski, 2006, Geophysical evaluation of the enigmatic Bedout basement high, offshore North-western Australia. Earth and Planetary Science Letters. vol. 237. pp. 264–284.

They concluded:

"The available geophysical and geological data are compatible with an interpretation of the Bedout structure as a basement high formed by two consecutive Palaeozoic and Mesozoic episodes of rifting roughly orthogonal to each other, associated with basin formation east and west of the Bedout High, but fail nearly all unequivocal criteria for impact crater recognition."



Late Jurassic rifting along the Australian North WestShelf: margin geometry and spreading ridge configuration


Combined GTOPO-ETOPO morphology of northwestern Australia and the adjacent oceanic areas in 5 km
resolution. Depth in 1000 m contour intervals (thin grey lines). Numbers indicate DSDP/ODP well sites, white colours indicate that oceanic basement was reached. AAP, Argo Abyssal Plain; GAP, Gascoyne Abyssal Plain; CAP, Cuvier Abyssal Plain; RR, Roo Rise; JR, Joey Rise; RT, Rowley Terrace; CT, Carnarvon Terrace; ScP, Scott Plateau; ExP, Exmouth Plateau; WP, Wombat Plateau; PS, Platypus Spur; CRFz, Cape Range fracture zone; NWC, Northwest Cape; CI, Christmas Island.
Inset shows the location of the Wharton Basin area (WB) and the Arafura Sea (AfS) with respect to main map.

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Bedout basement rise, offshore northwestern Australia: evidence of an unshocked mafic volcanic hyaloclastite volcanic breccia

Author: Andrew Glikson, Research School of Earth Science, Australian National University, A.N.U., Canberra, Australia

Core samples from Bedout-1 (3035.8-3044.95 m.), Bedout basement rise, offshore northwestern Australia, were examined by optical microscopy, SEM, EDS and WDS spectrometry. At this stratigraphic depth level Becker et al. (2004) interpret cryptocrystalline alteration zones around and within plagioclase in terms of shock-induced transformation of feldspar into diaplectic maskelynite glass _u postulating a ~200 km-large impact structure and thereby an impact connection of the Permian-Triassic boundary mass extinction.
However, the breccia is dominated by fragments of microlitic basalt and ophitic-textured dolerite with well preserved igneous textures, showing no evidence of shock metamorphism. Euhedral pseudomorphs of chlorite and amphibole, probably after pyroxene, protrude into or are enveloped by euhedral albite-twinned calcic plagioclase (andesine to bytownite). Minor phases include euhedral ilmenite needles and subhedral magnetite grains. Plagioclase is altered by cryptocrystalline albite and microcrystalline albite-chlorite matrix along crystal boundaries, along twin lamella and within internal oscillatory crystal zones, consistent with burial metamorphosed hydrovolcanic basalts and spilites (e.g. Amstutz, 1974). The volcanic fragments are set within, and injected by, microcrystalline intergranular mesostasis of mixed mineral fragments and volcanic meta-glass. Becker et al. (2004) refer to the breccia in part as product of Mg-rich sediments (e.g. dolomites). However, apart from the pristine igneous textures of the breccia, the transition element levels (chlorite in dolerite fragment "C Ni 97-160 ppm; Co 75-152 ppm; Cu 69-204 ppm; mesostasis "C Ni 29-45 ppm; Co 18-52 ppm; Cu 26-110 ppm) are consistent with Fe-rich basalts but exceed common abundances in carbonates and marls (BVTP, 1981; Wedepohl, 1978).
No shock metamorphic features, such as planar deformation features, are observed in the feldspar or in any other phases. No criteria for discriminating maskelynite and volcanic meta-glass are indicated by Becker et al. (2004). As formation (10-35 GPa) necessarily precedes diaplectic transformation into maskelynite (35-45 GPa) (French, 1998), a presence of maskelynite is inconsistent with the absence of PDF in the plagioclase _u a phase prone to the development of shock effects (e.g. Mory, 2000).
Little evidence exists for the hydrothermal activity which typically follows impact events. However, thanks to a partial development of a rim syncline-like structure in Triassic sediments around the Bedout rise, further testing of the origin of this remarkable structure is warranted. Amstutz, G.C., 1974, Spilites and Spilitic Rocks, Springer-Verlag, Berlin; Becker, L. et al., 2004, Science Express, 13.5.04; BVSP - Basaltic Volcanism Study Project, 1981, Pergamon; French, B.M., 1998, Traces of Catastrophe, Lunar and Planetary Contributions 954; Mory et al., 2000, Earth and Planetary Science, 177, 119-128; Wedepohl, K.H., Handbook of Geochemistry, Springer-Verlag, 1978.

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Blobrana


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RE: The 'Great Dying'
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New research findings by experts at China University of Geosciences in Wuhan propose that the mass biotic extinction was accomplished in at least two stages.
The section plane of the Changxing coalmine in Zhejiang province is a representative site which records the Great Dying 250 million years ago. After studying the molecular fossil near the borderline between the Permian period and Triassic period at the coalmine, professor Xie Shucheng and academician Yin Hongfu together with British experts discovered at least two biotic crises.
Xie Shucheng believes studies of the coalmine can show the mass extinction that happened 250 million years ago had multiple phases with the primary cause pinpointed on the earth itself rather than from extraterrestrial impactor. The research findings have been published on the renowned science magazine Nature.

Source: People'sDaily

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Blobrana


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Date:
Permian-Triassic extinction
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A clue to the catastrophic chain of events that led to Earth's largest-ever extinction has come from a sample of rock from the Dolomite mountains in Italy.
The Permian extinction 251 million years ago wiped out more than 90 per cent of marine life and 70 per cent of terrestrial life. Huge volcanic eruptions in Siberia were thought to be the cause, but exactly how has remained a mystery.
Mark Sephton at Imperial College London and his colleagues discovered the remains of cellulose molecules, a building block of plants, in sedimentary rock from the Dolomites. Cellulose is eaten by soil microbes, so it doesn't usually survive long enough to become embedded in rock records.

"Something catastrophic must have swept the soil into the sea, out of the microbes' reach" - Mark Sephton.

Acid gases from the eruption rained down as sulphuric acid, which caused the bacterial population to plummet and helped fungi to flourish. The acid gases would also have depleted the ozone layer, letting in more UV radiation. As the terrestrial ecosystem changed, land plants began to die out, loosening the soil so it was washed into the oceans where it blocked out light and devastated marine life.
With modern human activity putting soil under stress, the Permian extinction should be seen as warning.

"Soil erosion caused the Permian extinction. We must be careful that we don't reach a dangerous tipping point"- Mark Sephton.

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Blobrana


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RE: The 'Great Dying'
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The world's largest mass extinction was probably caused by poisonous volcanic gas, according to research published today.

The research, published in the journal Geology, reveals vital clues about the mass extinction at the end of the Permian period, 250 million years ago, when mammal-like reptiles known as synapsids roamed the earth.



Many scientists had previously thought that an asteroid hitting the earth or a deep-sea methane release had caused the extinction, which obliterated more than two-thirds of reptile and amphibian families.

However, analysis of a unique set of molecules found in rocks taken from the Dolomites in Italy has enabled scientists to build up a picture of what actually happened. The molecules are the remains of polysaccharides, large sugar-based structures common in plants and soil, and they tell the story of the extinction.
The molecules date from the same time as a major volcanic eruption that caused the greatest ever outpouring of basalt lava over vast swathes of land in present day Siberia.

The researchers believe that the volcanic gases from the eruption, which would have depleted earth's protective ozone layer and acidified the land and sea, killed rooted vegetation. This meant that soil was no longer retained and it washed into the surrounding oceans.
The chemistry of the rocks reveals that although the sugar molecules were found in marine sediments, they derived from land, supporting the theory that massive soil erosion caused them to end up in the sea.



Soil materials in the oceans would have blocked out light and soaked up oxygen. Analysis of rock chemistry suggests that after the soil crisis on land, the marine ecosystem succumbed to the stresses of environmental change and oceanic life faltered, completing a global catastrophe.

"The cause of the end Permian extinction has been highly controversial. We show that the terrestrial ecosystem was the first to suffer. The continent-wide nature of the event implies that it was caused by something in the atmosphere. The unique chemical data indicates that something fast and catastrophic happened on land" - Dr Mark Sephton, Imperial College London's Department of Earth Sciences and Engineering and lead author of the research.

"Similar to the 'Dead Zone' nowadays spreading in the Gulf of Mexico, the soil crisis could have caused a worldwide expanse of uninhabitable low-oxygen conditions in shallow marine waters. So what began on land ended in the sea. It seems there was no place to hide at this time of great dying" - Prof Henk Visscher, Utrecht University, also part of the research team.

"Land degradation is a worsening global problem thanks to human activity and soil erosion has caused the loss of a third of arable land over the last forty years. 35% of the Earth's land is now soil-free. Identifying the nature of the end Permian soil crisis may help us understand what is in store for us in the years ahead" - Dr Mark Sephton.



Dr Sephton believes that lessons can be learned in the present day from the damage caused by the end Permian extinction.

The research was carried out by an international team of scientists from the United Kingdom, the Netherlands and the United States.

Source

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Blobrana


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Rapid population growth, global warming and environmental degradation have ushered in the sixth mass extinction in the Earth's geological history according to Shu Degan, a noted palaeontologist with the Northwest China University.
Though less grave than the mass extinctions caused by planet collision and global volcanic eruption, mankind is "directing" a mass extinction more serious than the ones triggered by natural climate changes.

About 170 palaeontologists from 21 countries expressed their worries about the reducing bio-diversity at the Fourth International Symposium on Cambrian System. The five-day symposium ended on Tuesday 23 August, in Nanjing, capital of east China's Jiangsu Province.
They believe the industrial revolution is thought to have initiated a species disappearing rate alarmingly similar to the five mass extinctions in the Earth's geological history

The five mass extinctions in geological history were related to drastic changes in nature. The largest extinction occurred about 250 million years ago, eliminating about 95 percent of life. The most well-known extinction, of dinosaurs, occurred approximately 65 million years ago.
About 15,000 species are disappearing, more rapidly than any time in history, according to the 2004 global species survey issued by the World Conservation Union (ICUN). Figures published in Nature, a leading scientific journal, indicate that about 1 million land organisms will disappear in half a century.

"We have limited knowledge about the life composition on the Earth, but habitats are disappearing rapidly and mankind is uprooting life at an unprecedented speed" - Chia-Wei Li, palaeontologist with the Taiwan-based Tsing Hua University.

Human activity is causing the present mass extinction to occur more rapidly than those that had been triggered by natural factor. The extinction rate averaged to one species extinct at an hour. The latest rare species suspected to have turned extinct included the Hawaiian thrush, a kind of bird, and picea montigena, a kind of plant.
Though human beings have realized the importance of protecting biological diversity, they still in general pursue their specific interests at the cost of other species, making the extinction of other life inevitable.

For example, people spray disinfectants when threatened by epidemics such as Dengue or bird flu, drastically accelerating the extinction of some species in a short period of time.
The rapidly growing population will inevitably have disastrous results, and though humankind may survive, other species will not, according to Palmer Allison, director of the Institute for Cambrian Studies in the United States.

The scientists agreed that the present mass extinction may break the biological links between organisms, inevitably affecting humankind, and that people should learn to protect the environment and coexist harmoniously with the other life.

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