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The Paleocene-Eocene Thermal Maximum (PETM) is a period about 55 million years ago where the climate warmed more than 5 degrees Celsius over a period of 20 thousand years as a result of a surge of 2,000 gigatons of carbon released into the atmosphere. The PETM is associated with an enormous deep-sea mass extinction and with diversification of life on sea and land. The cause of the PETM has been a mystery.
At the recent annual meeting of the Geological Society of America a group of researchers presented research suggesting a large comet impact stirred up the carbon that led to the PETM. The crux of their argument, which was just published in Science , is the discovery of dark, glassy spheres, known as microtektites, found in New Jersey core samples. Microtektites are created and dispersed during high-speed impacts. Additionally, just above the microtektite layer is a charcoal layer with signs of charred plants that would come from widespread wildfires ignited by the impact.
This discovery has been flying around the community for a while and has generated a lot of excitement. Ellen Thomas, a geologist at Wesleyan University believes they have found microtektites. and if they can date them to the start of the PETM, she will consider it real evidence of an impact. “If they have not dated them,” she says, “I think they may well be contamination.”
Others, like Gerald Dickens, an oceanographer at Rice University in Houston, are not at all convinced: “They have completely misinterpreted the data and missed the correct, and more cool, story.” He argues that the microtektites and charcoal were distributed throughout the sediment layer, but microbial activity at the top of the layer degraded the material making it disappear. Since the remaining material is only at the bottom of the sediment, this results in the appearance of a boundary that looks important, but really isn't.
The scientists are cautious about how a small impact might fit in that chain of climate events—not all extraterrestrial strikes are the same. The PETM strike may have been a world-changing event like the dinosaur killer just 10 million years earlier. Or, it could have been like the object that struck and excavated the Chesapeake Bay 35 million years ago: locally devastating, but globally survivable.
(Score: 2, Informative) by khallow on Sunday October 16 2016, @06:13AM
My wild assed guess is the area of maximal ignorance which probably still has limestone in it. That would be the continental shelf off of the Mid-Atlantic states. Perhaps where the Hudson River empties into the Atlantic (assuming that the impact was near where they found the tektites).