SALT LAKE CITY (Oct. 16, 2005) -- Prehistoric global warming episodesfrom massive atmospheric pollution involving carbon dioxide and methanecould have created and preserved "mass kills" of wildlife, according toa University of Oregon study presented at the Geological Society ofAmerica's annual meeting.
The work, done by Gregory Retallack, professor of geologic sciences atOregon, involved a worldwide compilation of thousands of exceptionallywell preserved fossil assemblages of fish, crustaceans, insects,starfish and other life forms. There are only about 41 episodes ofexceptional preservation from the last 500 million years, and eachepisode is widely distributed around the world.
Well known examples of such preservation of complete soft-bodied fishand other creatures include the Burgess Shale (dating to the MiddleCambrian Period of about 508 million years ago and found near Field,British Columbia) and the Solnhofen Plattenkalk (dating to the LateJurassic Period of about 150 million years ago and found in Bavaria,Germany). Such exceptional assemblages were thought to have beenpreserved in environments that were unusually low in oxygen, highlysaline, very cold, or extremely dry. What was not suspected until thenew compilation was the global distribution of other exceptional fossildeposits of the same ages. Independent estimates of atmosphericpollution crises come from studies of carbon anomalies, microscopicpores of fossil leaves and climatic indicators from fossil soils.Methane outbursts from volcanically intruded coals and submarine gashydrates are prime suspects for these lethal atmospheric pollutionevents.
"Lowered levels of oxygen can kill fish and other creatures inmarginally aerated environments, and also preserve their carcasses fromdismemberment and decay," said Retallack. "Data from carbon anomaliesand microscopic leaf pores indicate that some of these killergreenhouses ramped up, within only a few thousand years, to intolerablelevels of more than 10 times the modern level of atmospheric carbondioxide. What stopped them from continuing on to a sterile greenhouseatmosphere like that of Venus? It was the widespread death and burialof animals and their carbon which created fossil bonanzas, the likes ofwhich may have saved us from the heat sterilization experienced by oursister planet."
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