Monday, October 17, 2005

Global Warming and Fossils

I'm still working on a post on Homo floresiensis. In the meantime...
"Prehistoric global warming episodes from massive atmospheric pollution involving carbon dioxide and methane could have created and preserved "mass kills" of wildlife..."

According to recent research previous episodes of global warming may have played a role in fossil preservation. The research, conducted by Oregon geologist Gregory Retallack, involved comparing thousands of well preserved assemblages of fish, crustaceans, insects, starfish among others. According to the article, during the past 500 million years there are 41 instances of exceptional preservation:

Such exceptional assemblages were thought to have been preserved in environments that were unusually low in oxygen, highly saline, very cold, or extremely dry. What was not suspected until the new compilation was the global distribution of other exceptional fossil deposits of the same ages. Independent estimates of atmospheric pollution crises come from studies of carbon anomalies, microscopic pores of fossil leaves and climatic indicators from fossil soils. Methane outbursts from volcanically intruded coals and submarine gas hydrates are prime suspects for these lethal atmospheric pollution events.

"Lowered levels of oxygen can kill fish and other creatures in marginally aerated environments, and also preserve their carcasses from dismemberment and decay," said Retallack. "Data from carbon anomalies and microscopic leaf pores indicate that some of these killer greenhouses ramped up, within only a few thousand years, to intolerable levels of more than 10 times the modern level of atmospheric carbon dioxide. What stopped them from continuing on to a sterile greenhouse atmosphere like that of Venus? It was the widespread death and burial of animals and their carbon which created fossil bonanzas, the likes of which may have saved us from the heat sterilization experienced by our sister planet."