More studies are showing support for the Younger Dryas Impact Hypothesis, which increasingly looks like it had an impact on a global basis. In my view, this is the most plausible explanation.
The Younger Dryas Impact Hypothesis, controversial from the time it was presented in 2007, proposes that an asteroid or comet hit the Earth about 12,800 years ago causing a period of extreme cooling that contributed to extinctions of more than 35 species of megafauna including giant sloths, sabre-tooth cats, mastodons and mammoths. It also coincides with a serious decline in early human populations such as the Clovis culture and is believed to have caused massive wildfires that could have blocked sunlight, causing an "impact winter" near the end of the Pleistocene Epoch. . . .
While the brief return to ice-age conditions during the Younger Dryas period has been well-documented, the reasons for it and the decline of human populations and animals have remained unclear. The impact hypothesis was proposed as a possible trigger for these abrupt climate changes that lasted about 1,400 years.
There is also evidence supporting Greenland as a primary impact location:
[A] team of researchers found unusually high concentrations of platinum and iridium in outwash sediments from a recently discovered crater in Greenland that could have been the impact point. Although the crater hasn't been precisely dated yet, Moore says the possibility is good that it could be the "smoking gun" that scientists have been looking for to confirm a cosmic event. Additionally, data from South America and elsewhere suggests the event may have actually included multiple impacts and airbursts over the entire globe.The journal reference for the article quoted above is:
Christopher R. Moore, et al., "Sediment Cores from White Pond, South Carolina, contain a Platinum Anomaly, Pyrogenic Carbon Peak, and Coprophilous Spore Decline at 12.8 ka." 9(1) Scientific Reports (2019).. DOI: 10.1038/s41598-019-51552-8
But, multiple other similar anomalies in other locations are also noted:
Moore also was lead author on a previous paper documenting sites in North America where platinum spikes have been found and a co-author on several other papers that document elevated levels of platinum in archaeological sites, including Pilauco, Chile -- the first discovery of evidence in the Southern Hemisphere.
"First, we thought it was a North American event, and then there was evidence in Europe and elsewhere that it was a Northern Hemisphere event. And now with the research in Chile and South Africa, it looks like it was probably a global event," he says.
Several prior posts at this blog have examined this hypothesis in more depth:
* Younger Dryas, North American Extinctions And End Of Clovis Culture Tied To ET Impact (March 10, 2017).
* Oldest Temple In World May Have Been Built In Reaction To A Comet Impact (April 21, 2017).
* Hiding In Plain Sight (May 3, 2017).
* Clovis Was A Culture That Lasted Only 300 Years (June 25, 2018).
* The Younger Dryas Impact Hypothesis (July 6, 2018).