Thursday, March 14th
More evidence continues to accumulate that a planet-wide catastrophe occurred some 13,000 years ago, supporting the controversial Younger Dryas Impact Hypothesis (which postulates that a fragmented comet slammed into the Earth around 12,800 years ago, causing massive effects ranging from rapid climate change to megafaunal extinctions and decreases in human populations.
In just the past year scientists have found evidence for a global conflagration at that time in which 10% of the planet was set on fire, as well as a massive 20 mile wide impact crater in Greenland that might be related.
The scientists first came across the evidenc while studying sediment layers at a well-known paleontological and archaeological site, Pilauco Bajo. They came across a “black mat” layer, 12,800 years in age, that coincided with the disappearance of South American Pleistocene megafauna fossils, an abrupt shift in regional vegetation and a disappearance of human artifacts.
According to University of California-Santa Barbara geology professor emeritus James Kennett, a member of the team, “the sequencing of these events looked like what had already been described in the YDB papers for North America and Western Europe”, and on further analyses they found microscopic spherules interpreted to have been formed by melting due to the extremely high temperatures associated with impact. The layer also contained peak concentrations of platinum and gold, and native iron particles rarely found in nature – a marker of extraterrestrial impacts.
Other evidence, which, Kennett noted, is consistent with previous and ongoing documentation of the region by Chilean scientists, pointed to a “very large environmental disruption at about 40 degrees south.” These included a large biomass burning event evidenced by, among other things, micro-charcoal and signs of burning in pollen samples collected at the impact layer. “It’s by far the biggest burn event in this region we see in the record that spans thousands of years,” Kennett said. Furthermore, he went on, the burning coincides with the timing of major YDB-related burning events in North America and western Europe. Interestingly, while this new discovery “greatly expands the extent of the YDB impact event” from previous discoveries in the northern hemisphere, it also provides a contrast in effects: north of the equator, conditions became colder and wetter at the onset of the Younger Dryas, but the opposite appears to have occurred in the southern hemisphere:
“The plant assemblages indicate that there was an abrupt and major shift in the vegetation from wet, cold conditions at Pilauco to warm, dry conditions,” Kennett said. According to him, the atmospheric zonal climatic belts shifted “like a seesaw,” with a synergistic mechanism, bringing warming to the Southern Hemisphere even as the Northern Hemisphere experienced cooling and expanding sea ice. The rapidity — within a few years — with which the climate shifted is best attributed to impact-related shifts in atmospheric systems, rather than to the slower oceanic processes, Kennett said. But overall the new discovery provides further support for a cosmic impact triggering the strange changes in conditions during the Younger Dryas, Kennett argued. “This is further evidence that the Younger Dryas climatic onset is an extreme global event, with major consequences on the animal life and the human life at the time”.
The full paper is available to read online: “Sedimentary record from Patagonia, southern Chile supports cosmic-impact triggering of biomass burning, climate change, and megafaunal extinctions at 12.8 ka” (PDF).
(thanks to @CosmicTusk)