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Evidence Of Meteor Impact
Found Off Australian Coast
by Donald Savage
May 13, 2004
Most scientists agree a meteor impact, called Chicxulub, in Mexico's Yucatan Peninsula, accompanied the extinction of the dinosaurs 65 million years ago. But until now, the time of the Great Dying 250 million years ago, when 90 percent of marine and 80 percent of land life perished, lacked evidence and a location for a similar impact event. Becker and her team found extensive evidence of a 125-mile-wide crater, called Bedout, off the northwestern coast of Australia... During recent research in Antarctica, Becker and her team found meteoric fragments in a thin claystone "breccia" layer, pointing to an end-Permian event. The breccia contains the impact debris that resettled in a layer of sediment at end-Permian time. They also found "shocked quartz" in this area and in Australia... Quartz can be fractured by extreme volcanic activity, but only in one direction. Shocked quartz is fractured in several directions and is therefore believed to be a good tracer for the impact of a meteor... The Bedout impact crater is also associated in time with extreme volcanism and the break-up of Pangea. "We think that mass extinctions may be defined by catastrophes like impact and volcanism occurring synchronously in time," Becker said. "This is what happened 65 million years ago at Chicxulub but was largely dismissed by scientists as merely a coincidence. With the discovery of Bedout, I don't think we can call such catastrophes occurring together a coincidence anymore," she added.

Popular Science for March 2004 (p 56) had a Dawn Stover piece on the Permian-Triassic extinction. There's a table showing four possibilities and a summary of points for each, and also writes that "it's possible that more than theory is correct." A huge impact on water would send a shockwave throughout the oceans and seas, with the potential of releasing the methane in gas hydrates and the poisonous hydrogen sulfide gas that displaces oxygen in the depths. She ignores that likelier possibility and writes instead that an impact could trigger volcanic eruptions, "which in turn could have kicked off deadly acid rain showers." My guess is, Dawn Stover went to Penn State and studied volcanology for a while. ;')

The Suspect The Theory The Evidence The Proponents The Holes

Asteroid impact A space rock strikes in the tropics, spews debris into the air and triggers lethal climate change Scientists found 250 million year old rocks from Antarctica and China said to contain meteorite fragments Researchers at the University of Rochester, Harvard, and UC Santa Barbara Scientists have yet to find the ultimate smoking gun, a crater

Sudden methane explosion A massive cloud of methane gas abruptly bursts from the ocean, cataclysmic flooding and fires ensue Great Dying fossils show a sudden sharp rise in carbon-12 isotopes, best explained by a methane belch Chemical engineer Gregory Ryskin at Northwestern University The explosion requires an improbable 10,000 gigatons of methane

Slow methane leak Volcanoes of frozen deposits leak methane over thousands of years, depleting oxygen The burrowing reptile Lystrosaurus, adapted for low-oxygen conditions, thrived during this period Researchers at the University of Oregon, the South African Museum, and the University of Washington The leak could not deplete enought oxygen to cause global death, critics say

Hydrogen sulfide stink bomb Lethal levels of hydrogen sulfide, emitted by anaerobic bacteria, are expelled from the ocean into the air Proponents are searching for signs of sulfur bacteria in Japanese sediments dated to the extinction Scientists at Penn State, the University of Colorado, and the University of Tokyo There's no proof that the upper layers of ancient oceans were devoid of oxygen

Newest to oldest, as if in strata, in order to observe the evolution. ;')

Meteor May Have Started Dinosaur Era
by Kenneth Chang
May 17, 2002
In the layer of rock corresponding to the extinction, the scientists found elevated amounts of the rare element iridium. A precious metal belonging to the platinum group of elements, iridium is more abundant in meteorites than in rocks on Earth. A similar spike of iridium in 65 million-year-old rocks gave rise in the 1970's to the theory that a meteor caused the demise of the dinosaurs... The levels are only about one-tenth as high as those found at the later extinction. That could mean that the meteor was smaller or contained less iridium... In the same rock layer, Dr. Olsen and his colleagues found a high concentration of fern spores -- considered an indicator of a major disruption in the environment. Because spores carried by the wind can travel long distances, ferns are often the first plants to return to a devastated landscape. The scientists found more evidence of rapid extinction in a database of 10,000 muddy footprints turned to rock in former lake basins from Virginia to Nova Scotia... Because the sediment piles up quickly in lake basins, the researchers were able to assign a date to each footprint, based on the layer of rock where it was found. They determined that the mix of animals walking across what is now the East Coast of North America changed suddenly about 200 million years ago. The tracks of several major reptile groups continue almost up to the layer of rock marking the end of the Triassic geologic period 202 million years ago, then vanish in younger layers from the Jurassic period... Last year, researchers led by Dr. Ward reported that the types of carbon in rock changed abruptly at this time, indicating a sudden dying off of plants over less than 50,000 years. The footprint research reinforces the hypothesis that the extinction was sudden.
Asteroid 'destroyed life 250m years ago'
by Dr David Whitehouse
BBC News Online
Friday, 23 February, 2001, 10:56 GMT
Earth's biggest mass extinction 251 million years ago was triggered by a collision with a comet or asteroid, US scientists say. They have reached this conclusion by looking at atoms from a star trapped inside molecular cages of carbon. The impact occurred when all the Earth's land was joined together into a supercontinent called Pangea... Researchers have no idea where on the planet's surface the space object came down, but they have identified traces of it. In rock layers laid down at the time, there is a much higher concentration of complex carbon molecules called fullerenes that have different types, or isotopes, of helium and argon trapped inside them... The researchers believe these particular fullerenes are extraterrestrial because the gases trapped inside have an unusual ratio of isotopes that indicate they were made in the atmosphere of a star that exploded before our Sun was born... The telltale fullerenes were extracted from sites in Japan, China and Hungary, where the sedimentary layer at the boundary between the Permian and Triassic periods had been exposed... The research was made difficult because there are few 251-million-year-old rocks left on Earth. Most rocks of that age have been recycled through the planet's tectonic processes.
Physics News Update
by Phillip F. Schewe and Ben Stein
December 14, 1992
An asteroid impact may have caused the mass extinction that occurred at the boundary between the Permian and Triassic periods 250 million years ago, said Michael Rampino (212-998-8995) of NYU at the AGU meeting. He asserted that he has found evidence---in the form of gravity anomalies and certain rock deposits---for such an impact in the South Atlantic, in an area where, many scientists believe, South America, Africa, and other land masses fit together in the primordial supercontinent called Gondwanaland. Rampino claims that the gradual breakup of Gondwanaland into present-day continents may have been initiated by the catastrophic impact. Another scientist at the meeting, Verne Oberbeck of NASA/Ames (415-604-5496) also believes an impact may have sundered Gondwanaland and that, in general, impacts should be given more credit for shaping earlier Earth geology. In particular, he believes that the small rock sediments called tillites, usually thought to result from the grinding and plowing action of glaciers, may in part be debris from impacts. Consequently, Oberbeck suggested, there might have been fewer glacial periods than is usually believed. Rampino went so far as to say that all tillites are of impact origin. Unlike the theory that describes the KT (Cretaceous-Tertiary) catastrophe 65 million years ago (when the dinosaurs became extinct) in terms of an asteroid impact, the notion that the PT catastrophe was caused by an impact or that tillites result from impacts is anything but a majority opinion; indeed, many scientists at the meeting were skeptical about Rampino's and Oberbeck's ideas. Thomas Crowley of the Applied Research Corp. (409-846-1403), a paleo-climatologist, said that his reaction to the proposed impact origin of tillites was one of "considerable disbelief, bordering on incredulity." For one thing, he said, tillite deposits are too extensive over time and physical extent to have been caused by an impact.

http://www.space.com/php/multimedia/imagedisplay/img_display.php?pic=060601_crater_gravity_02.jpg∩=Gravity+fluctuations+beneath+East+Antarctica+measured+by+GRACE+satellite.+Denser+regions+appear+more+red;+the+location+of+the+Wilkes+Land+crater+is+circled+(above+center).+Credit%3A+Ohio+State+University+

Bedout High: c.250 MYA, ~200km diameter The Bedout structure 300km west of Broome, in the Canning Basin off the coast of Western Australia, has been sited as one of the possible impacts that contributed to one of the greatest extinction events known. At the end of the Permian Period, around 250 MYA, it has been estimated that more than 90% of marine species, and 70% of terrestrial species, may have become extinct. The extinction event seems to have been a sudden, global occurrance, lasting less than a million years (which in geological terms is very rapid).

http://home.alphalink.com.au/~dannj/craters.htm

So many craters, so many extinctions...

I 'discovered' another one recently, named in 2003 IIRC. Not yet on the map of Australian Impact Craters.

Google pic follows...

The Suspect	The Theory	The Evidence	The Proponents	The Holes
Asteroid impact	A space rock strikes in the tropics, spews debris into the air and triggers lethal climate change	Scientists found 250 million year old rocks from Antarctica and China said to contain meteorite fragments	Researchers at the University of Rochester, Harvard, and UC Santa Barbara	Scientists have yet to find the ultimate smoking gun, a crater
Sudden methane explosion	A massive cloud of methane gas abruptly bursts from the ocean, cataclysmic flooding and fires ensue	Great Dying fossils show a sudden sharp rise in carbon-12 isotopes, best explained by a methane belch	Chemical engineer Gregory Ryskin at Northwestern University	The explosion requires an improbable 10,000 gigatons of methane
Slow methane leak	Volcanoes of frozen deposits leak methane over thousands of years, depleting oxygen	The burrowing reptile Lystrosaurus, adapted for low-oxygen conditions, thrived during this period	Researchers at the University of Oregon, the South African Museum, and the University of Washington	The leak could not deplete enought oxygen to cause global death, critics say
Hydrogen sulfide stink bomb	Lethal levels of hydrogen sulfide, emitted by anaerobic bacteria, are expelled from the ocean into the air	Proponents are searching for signs of sulfur bacteria in Japanese sediments dated to the extinction	Scientists at Penn State, the University of Colorado, and the University of Tokyo	There's no proof that the upper layers of ancient oceans were devoid of oxygen