Skip to comments.Evidence for deposition of 10 million tonnes of impact spherules across four continents 12,800 y ago
Posted on 05/23/2013 6:02:12 PM PDT by Renfield
We present detailed geochemical and morphological analyses of nearly 700 spherules from 18 sites in support of a major cosmic impact at the onset of the Younger Dryas episode (12.8 ka). The impact distributed ∼10 million tonnes of melted spherules over 50 million square kilometers on four continents. Origins of the spherules by volcanism, anthropogenesis, authigenesis, lightning, and meteoritic ablation are rejected on geochemical and morphological grounds. The spherules closely resemble known impact materials derived from surficial sediments melted at temperatures >2,200 °C. The spherules correlate with abundances of associated melt-glass, nanodiamonds, carbon spherules, aciniform carbon, charcoal, and iridium.
Airbursts/impacts by a fragmented comet or asteroid have been proposed at the Younger Dryas onset (12.80 ± 0.15 ka) based on identification of an assemblage of impact-related proxies, including microspherules, nanodiamonds, and iridium. Distributed across four continents at the Younger Dryas boundary (YDB), spherule peaks have been independently confirmed in eight studies, but unconfirmed in two others, resulting in continued dispute about their occurrence, distribution, and origin. To further address this dispute and better identify YDB spherules, we present results from one of the largest spherule investigations ever undertaken regarding spherule geochemistry, morphologies, origins, and processes of formation. We investigated 18 sites across North America, Europe, and the Middle East, performing nearly 700 analyses on spherules using energy dispersive X-ray spectroscopy for geochemical analyses and scanning electron microscopy for surface microstructural characterization. Twelve locations rank among the worlds premier end-Pleistocene archaeological sites, where the YDB marks a hiatus in human occupation or major changes in site use. Our results are consistent with melting of sediments to temperatures >2,200 °C by the thermal radiation and air shocks produced by passage of an extraterrestrial object through the atmosphere; they are inconsistent with volcanic, cosmic, anthropogenic, lightning, or authigenic sources. We also produced spherules from wood in the laboratory at >1,730 °C, indicating that impact-related incineration of biomass may have contributed to spherule production. At 12.8 ka, an estimated 10 million tonnes of spherules were distributed across ∼50 million square kilometers, similar to well-known impact strewnfields and consistent with a major cosmic impact event.
There was an impact on one of the great lakes at that time. Came from a northerly direction and is the subject of a book, The Cycle of Cosmic Catastrophes.
Awesome book. Learned about it through the SunkenCiv ping list. This paper supports the date that book had proposed for the impact.
Given whar has passed for "science" of late, I'd be interested in who did those two studies, how they were funded and what agenda driven groups they may/may not be associated with.
There seems to be good evidence, consistent evidence, that this event is what formed the Carolina Bays.
And was the event that killed off many of the megafauna, like the mastodons.
2200 degrees C????? Wow,
That is a good question. There must have been a major die-off associated with such a large event.
On Alaska's north slope, there are elliptical ponds that are very similar to Carolina Bays. These are Holocene (post-Younger-Dryas) in age, and in fact, are continuing to form and enlarge even now. That area was covered with ice during the Younger Dryas period. These ponds form as a result of emergent groundater freezing and expanding during the winter, which pushes soil away from the center of the body. I suspect Carolina Bays formed similarly.
I reluctantly agree....you're probably correct on the Carolina Bays.
Some of the other theories are far sexier/exciting though.
Interesting images, I never saw them before.
You may be right.
What makes me wonder about the Bays is if it was caused by impact, where are the rocks?
Without space debris, it’s an interesting theory and not much more.
Regarding that “Carolina Bay orientation” graphic: I worked in every South Carolina county blacked out in that illustration.
The Cycle of Cosmic Catastrophes:
Flood, Fire, and Famine
in the History of Civilization
by Richard Firestone,
Allen West, and
If I recall that impact was the last act in a rather complex chain of events. Remarkable concept.
Chunks of ice?