* Astronomy

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Triassic-Jurassic extinction event

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RE: The 'Great Dying'

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Emeishan Traps

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Guadalupian Mass Extinction

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RE: The 'Great Dying'

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The largest mass extinction in the history of the earth could have been triggered off by giant salt lakes, whose emissions of halogenated gases changed the atmospheric composition so dramatically that vegetation was irretrievably damaged. At least that is what an international team of scientists have reported in the most recent edition of the "Proceedings of the Russian Academy of Sciences". At the Permian/Triassic boundary, 250 million years ago about 90 percent of the animal and plant species ashore became extinct. Previously it was thought that volcanic eruptions, the impacts of asteroids, or methane hydrate were instigating causes. The new theory is based on a comparison with today's biochemical and atmospheric chemical processes.

"Our calculations show that airborne pollutants from giant salt lakes like the Zechstein Sea must have had catastrophic effects at that time" - coauthor Dr. Ludwig Weibflog from the Helmholtz-Center for Environmental Research (UFZ).

Forecasts predict an increase in the surface areas of deserts and salt lakes due to climate change. That is why the researchers expect that the effects of these halogenated gases will equally increase.

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Permian Extinction Not a Global Event
Understanding the cause of the extinction that wiped out some 95% of the living species at the end of the Palaeozoic Era has been one of the greatest problems in the earth and life sciences. All explanations so far proposed have been based on global causes. This Special Paper from the Geological Society of America presents a new approach, one that focuses on the supercontinent of Pangea and the life-rich, enclosed oceanic realm, the Paleo-Tethys.

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Title: The terrestrial Permian-Triassic boundary event bed is a nonevent
Authors: Robert A. Gastaldo, Johann Neveling, C. Kittinger Clark and Sophia S. Newbury

A unique isochronous interval in the Karoo Basin, South Africa, previously has been interpreted to postdate vertebrate extinction at the Permian-Triassic boundary in the Bethulie area, Lootsberg Pass, and elsewhere. It is demonstrated that the laminated beds, or laminites, in the Bethulie region are stratigraphically indistinct. The heterolithic interval exposed on the Heldenmoed farm is ~8 m below the Bethel farm section, <1 km away. At Lootsberg Pass, the laminated interval is below the Permian-Triassic boundary as defined by vertebrate biostratigraphy, rather than overlying it. Hence, this interval, critical to models of end-Permian mass extinction, is neither isochronous across the basin nor unique. Rather, the lithofacies represents avulsion channel-fill deposits within aggradational landscapes. South African models for the response of terrestrial ecosystems to the perturbation in the marine realm require critical reevaluation.

Source

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Some scientists are saying that it wasnt a meteorite that killed the dinosaurs 250 million years ago, but tiny bacteria at the bottom of the ocean.
The popular theory about the mass extinction of 90% of all life on Earth back at the end of the Permian Era is that a huge meteorite slammed into the planet, causing a vast shockwave, huge tsunamis, and a firestorm that raged through the atmosphere for a vast distance.

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Ed ~ During the Permian, amphibians and reptiles were the abundant land animal.

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Title: Siberian gas venting and the end-Permian environmental crisis
Authors: Henrik Svensen, Sverre Planke, Alexander G. Polozov, Norbert Schmidbauer, Fernando Corfu, Yuri Y. Podladchikov, Bjørn Jamtveit

The end of the Permian period is marked by global warming and the biggest known mass extinction on Earth. The crisis is commonly attributed to the formation of the Siberian Traps Large Igneous Province although the causal mechanisms remain disputed. We show that heating of Tunguska Basin sediments by the ascending magma played a key role in triggering the crisis. Our conclusions are based on extensive fieldwork in Siberia in 2004 and 2006.Heating of organic-rich shale and petroleum bearing evaporites around sill intrusions led to greenhouse gas and halocarbon generation in sufficient volumes to cause global warming and atmospheric ozone depletion. Basin scale gas production potential estimates show that metamorphism of organic matter and petroleum could have generated N100,000 Gt CO2. The gases were released to the end-Permian atmosphere partly through spectacular pipe structures with kilometre-sized craters. Dating of a sill intrusion by the U-Pb method shows that the gas release occurred at 252.0±0.4 million years ago, overlapping in time with the end-Permian global warming and mass extinction. Heating experiments to 275 °C on petroleum-bearing rock salt from Siberia suggests that methyl chloride and methyl bromide were significant components of the erupted gases. The results indicate that global warming and ozone depletion were the two main drivers for the end-Permian environmental crisis. We demonstrate that the composition of the heated sedimentary rocks below the flood basalts is the most important factor in controlling whether a Large Igneous Provinces causes an environmental crisis or not. We propose that a similar mechanism could have been responsible for the Triassic-Jurassic (~200 Ma) global warming and mass extinction, based on the presence of thick sill intrusions in the evaporite deposits of the Amazon Basin in Brazil.

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