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) by hubie on Sunday October 16 2016, @08:55PM
Thanks for the comma support. I had it in there because I was joining two opposing ideas: a) the deep-sea extinction, and b) the sudden diversification of life in the sea and on land. Without the comma it sounds confusing that there was an extinction event in the sea, but that there was a diversification of life in the sea. I suppose I could have broken it up into two sentences, but as it was just background info setting up the story, I didn't want to put too much text at the expense of telling everyone what the real point of the story was.
That being said, I'm only just a simple country physicist and I have not had my writings subject to the rigorous criticism as my friends in the humanities have endured.