Evidence for deposition of 10 million tonnes of impact spherules across four continents 12,800 y ago Authors
Significance 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 world’s 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
Very high-temperature impact melt products as evidence for cosmic airbursts and impacts 12,900 years ago Authors
It has been proposed that fragments of an asteroid or comet impacted Earth, deposited silica-and iron-rich microspherules and other proxies across several continents, and triggered the Younger Dryas cooling episode 12,900 years ago. Although many independent groups have confirmed the impact evidence, the hypothesis remains controversial because some groups have failed to do so. We examined sediment sequences from 18 dated Younger Dryas boundary (YDB) sites across three continents (North America, Europe, and Asia), spanning 12,000 km around nearly one-third of the planet. All sites display abundant microspherules in the YDB with none or few above and below. In addition, three sites (Abu Hureyra, Syria; Melrose, Pennsylvania; and Blackville, South Carolina) display vesicular, high-temperature, siliceous scoria-like objects, or SLOs, that match the spherules geochemically. We compared YDB objects with melt products from a known cosmic impact (Meteor Crater, Arizona) and from the 1945 Trinity nuclear airburst in Socorro, New Mexico, and found that all of these high-energy events produced material that is geochemically and morphologically comparable, including: (i) high-temperature, rapidly quenched microspherules and SLOs; (ii) corundum,mullite, and suessite (Fe 3 Si), a rare meteoritic mineral that forms under high temperatures; (iii) melted SiO 2 glass, or lechatelierite, with flow textures (or schlieren) that form at > 2,200 °C; and (iv) particles with features indicative of high-energy interparticle collisions. These results are inconsistent with anthropogenic, volcanic, authigenic, and cosmic materials, yet consistent with cosmic ejecta, supporting the hypothesis of extraterrestrial airbursts/impacts 12,900 years ago. The wide geographic distribution of SLOs is consistent with multiple impactors.
Intersection with the debris of a large (50–100 km) short-period comet during the Upper Palaeolithic provides a satisfactory explanation for the catastrophe of celestial origin which has been postulated to have occurred around 12 900 BP, and which presaged a return to ice age conditions of duration ∼1300 yr. The Taurid Complex appears to be the debris of this erstwhile comet; it includes at least 19 of the brightest near-Earth objects. Subkilometre bodies in meteor streams may present the greatest regional impact hazard on time-scales of human concern.
Originally posted by kimish
My question is, what type of impact does all of this have on human evolution (if you believe in that)?
Nonetheless, interesting read, thank you for posting. S&F from kimish
When Sah'-te came home he found that his beads were gone. "Who stole my beads?" he asked.
He then took his yah'-tse [the stick the people used to wear crossways in a twist of their back hair] and stood it up in the fire, and oo'-loop the flame climbed it and stood on the top. He then
took the yah'-tse with the flame at one end and said he would find out who stole his shell money. First he pointed it to the north, but nothing happened; then to the west, and nothing happened; then east; then up; then down, and still nothing happened. Then he pointed it south toward Tu'-le-yo'-me and the flame leaped from the stick and spread swiftly down the east side of Lower Lake, burning the grass and brush and making a great smoke.
In the evening Wek'-wek came out of the roundhouse at Tu'-le-yo'-me and saw the country to the north on fire. He went in and told his grandfather that something was burning on Clear Lake.
Ol'-le the Coyote-man answered, "That's nothing; the people up there are burning tules."
Ol'-le knew what Wek'-wek had done, and knew that Sah'-te had sent the fire, for Ol'-le was a magician and knew everything, but he did not tell Wek'-wek that he knew.
After a while Wek'-wek came out again and looked at the fire and saw that it was much nearer and was coming on swiftly. He was afraid, and went back and told his grandfather that the fire was too near and too hot and would soon reach them. After a little he went out again and came back and said, "Grandfather, the fire is coming fast; it is on this side of the lake and is awfully hot."
Ol'-le answered, "That's nothing; the people at Lower Lake are burning tules."
But now the roar and heat of the fire were terrible, even inside the roundhouse, and Wek'-wek thought they would soon burn. He was so badly frightened that he told his grandfather what he had done. He said, "Grandfather, I stole Sah'-te's hoo'-yah and put it in the creek, and now I'm afraid we shall burn."
Then Ol'-le took a sack and came out of the roundhouse and struck the sack against an oak tree, and fog came out. He struck the tree several times and each time more fog came out and spread around.
Then he went back in the house and got another sack and beat the tree, and more fog came, and then rain. He said to Wek'-wek,"It is going to rain for ten days and ten nights." And it did rain, and the rain covered the whole country till all the land and all the hills and all the mountains were under water--everything except the top of Oo-de'-pow-we (Mount Konokti, on the west side of Clear Lake) which was so high that its top stuck out a little.
This was' the beginning of a series of calamities which nearly destroyed the great tribe of Ah-wah-nee'-chees. First a great drouth prevailed, and the crops failed, and the streams of water dried up. The deer went wild and wandered away. Then a dark cloud of smoke arose in the East and obscured the sun, so that it gave no heat,
and many of the people perished from cold and hunger. Then the earth shook terribly and groaned with great pain, and enormous rocks fell from the walls around Ah-wah'-nee. The great dome called Tis-sa'-ack was burst asunder, and half of it fell into the Valley. A fire burst out of the earth in the East, and the ca'-lah (snow) on the sky mountains was changed to water, which flowed down and formed the Lake Ah-wei'-yah. 1 And all the streams were filled to overflowing, and still the waters rose, and there was a great flood, so that a large part of the Valley became a lake, and many persons were drowned
More New Mexico Craters
Much of the academic community assume that a typical catastrophic impact event consists of a single, large bolide. When asked what he thought of the possibility of a cluster impact event of smaller fragments, NASA’s David Morrison expressed doubt. He said he thought such an event would be “highly unlikely”. And since he’s the senior scientist at the NASA Ames Research Center, his views are representative of mainstream planetary science.
But ongoing inventories of the objects orbiting in the Taurid complex are bringing data to light that indicates that, in fact, the last extinction level impact event in the northern hemisphere was probably the work of a very large cluster of debris from a large disintegrating comet, not the kinetic impact of a single, solid bolide.
And in a 2009 paper by W.M. Napier, and titled Comets, Catastrophes, and Earth’s History we read ,
“The evidence that an exceptionally large (50-100 km) comet entered a short-period, Earth-crossing orbit during the upper Paleolithic, and underwent a series of disintegrations, now seems compelling. The idea is not new, but it has been strengthened by an accumulation of evidence from radar studies of the interplanetary environment, from the LDEF experiment, from numerical simulations of the Taurid complex meteoroids and ‘asteroids’, and from the latter’s highly significant orbital clustering around Comet Encke.
The disintegration of this massive Taurid Complex progenitor over some tens of thousands of years would yield meteoroid swarms which could easily lead to brief, catastrophic episodes of multiple bombardment by sub-kilometer bolides, and it is tempting to see the event at ~12,900 BP as an instance of this. Whether it actually happened is a matter for Earth scientists, but from the astronomical point of view a meteoroid swarm is a much more probable event than a 4 km comet collision.”
If Professor Napier is correct, we should expect to find the planetary scarring of a geologically recent super cluster impact event of smaller fragments somewhere in North America.
And in the world according to Google Earth, that planetary scarring does indeed exist. And a good case can be made that New Mexico, and West Texas, were a couple of the major impact zones. But in spite of posting pictures of these ‘enigmatic depressions’ for a couple of years now, none of the mainstream scientists I’ve written to seems to be interested in talking about them. And I haven’t been able to find evidence that anyone has done any real science at any of them either.
Originally posted by punkinworks10
reply to post by Byrd
The work that has come out in the last couple of years is extremely convincing, and the science is solid.
First I recommend reading Napiers papers on the Taurid Progenitor comet and it's break up into the taurid complex it provides a solid astronomical foundation for the kinds of evidence being found.
Then Bosloughs work on modeling an airburst shows what you expect from an airburst of a body in a certain spockets for ge. Even though he is a critic of this idea his work has helped to further the understanding of what happend.
The latest paper on the microspheruls found on 4 continents addresses the concerns raised by opponents of the theory, exhaustively details how these objects were formed and they can only be the product of an extra terrestrial event, not man made not volcanic, or natural fires.
From what I understand from my reading is that in the continental US, nothing larger than coyote, on average, survived the younger dryas boundary event.I'm not saying the only reason for the extinctions was this event , but in the northwestern hemisphere it sealed the deal, through immediate loss of habitat, and sustained loss via the lack of sunlight, as it was blocked by the clouds of smoke and dust . Herbivores were lost almost immediately, the large carnivores that preyed on them were next , they survived in small isolated pockest, for a while.
It was the small carnivores and omnivores that survived, which is just what you have.
Originally posted by Hanslune
reply to post by punkinworks10
The historic Elk range was the entire continental US plus a nice chunk of Canada.
Question on Bison (buffalo) I thought they are descendent from Bison Occidentalis which wasn't a small creature - do you have a link that explains this theory?
The Bison latifrons (Giant Bison or Longhorn Bison) species was replaced by the smaller Bison antiquus. Bison antiquus appeared in the North American Fossil record approximately 250,000 years ago. Bison antiquus in turn evolved into the Bison occidentalis, then into the yet smaller Bison bison — the modern American bison — some 5,000 to 10,000 years ago. Some researchers consider Bison occidentalis to be a sub-species of Bison antiquus
Obispo, CA 93407-0329, USA
Buchanan et al. (1) assert that the radiocarbon record from the United States and Canada does not support the extraterrestrial impact hypothesis, but their claims do not hold true for the California archaeological record. Fluted projectile points marking Paleoindian occupations have been reported from no fewer than 51 locations in California (2), and no fewer than 38 sites have produced radiocarbon evidence for occupation between 10,500 and 9,000 calibrated yrs BP (3). Only two sites have produced fluted points and early Holocene occupational residues together in stratified context. At the same time, none of the sites that have produced radiocarbon evidence for occupation between 10,500 and 9,000 calibrated yrs BP have yielded fluted points. There are no archaeological sites in California that have reliable radiocarbon dates between 12,900 and 12,200 calibrated yrs BP and precious few that date between 12,000 and 10,500 calibrated yrs BP. The earliest archaeological record from California is therefore marked by a strong cultural unconformity between the late Pleistocene and the early Holocene that is consistent with a significant disruptive event of the type described by Firestone et al. (4) and Kennett et al. (5). A more careful evaluation of the full cultural and archaeological record from the regions discussed by Buchanan et al. (1) would likely show similar patterns.
Cosmogenic nuclide enhancement via deposition from long-period comets as a test of the Younger Dryas impact hypothesis
Andrew C. Overholt, Adrian L. Melott
(Submitted on 24 Jul 2013)
We explore the idea that detectable excursions in 26Al may arise from direct deposition by any bolide, and excursions in 14C and 10Be abundances in the atmosphere may result from long-period comet impacts. This is very different from the usual processes of production by cosmic rays within Earths atmosphere. Long-period comets experience greatly increased cosmic ray flux beyond the protection of the suns magnetic field. We report the computed amount of 14C, 10Be, and 26Al present on long-period comets as a function of comet mass. We find that the amount of nuclide mass on large long-period comets entering the Earths atmosphere may be sufficient for creating anomalies in the records of 14C and 10Be from past impacts. In particular, the estimated mass of the proposed Younger Dryas comet is consistent with its having deposited sufficient isotopes to account for recorded 14C and 10Be increases at that time. The 26Al/10Be ratio is much larger in extraterrestrial objects than in the atmosphere, and so, we note that measuring this ratio in ice cores is a suitable definitive test for the Younger Dryas impact hypothesis, even if the hypothetical bolide is not a long-period comet and/or did not contribute to the 14C and 10Be increases.
One explanation of the abrupt cooling episode known as the Younger Dryas (YD) is a cosmic impact or airburst at the YD boundary (YDB) that triggered cooling and resulted in other calamities, including the disappearance of the Clovis culture and the extinction of many large mammal species. We tested the YDB impact hypothesis by analyzing ice samples from the Greenland Ice Sheet Project 2 (GISP2) ice core across the Bølling-Allerød/YD boundary for major and trace elements. We found a large Pt anomaly at the YDB, not accompanied by a prominent Ir anomaly, with the Pt/Ir ratios at the Pt peak exceeding those in known terrestrial and extraterrestrial materials. Whereas the highly fractionated Pt/Ir ratio rules out mantle or chondritic sources of the Pt anomaly, it does not allow positive identification of the source. Circumstantial evidence such as very high, superchondritic Pt/Al ratios associated with the Pt anomaly and its timing, different from other major events recorded on the GISP2 ice core such as well-understood sulfate spikes caused by volcanic activity and the ammonium and nitrate spike due to the biomass destruction, hints for an extraterrestrial source of Pt. Such a source could have been a highly differentiated object like an Ir-poor iron meteorite that is unlikely to result in an airburst or trigger wide wildfires proposed by the YDB impact hypothesis.
Previous work has ascribed a cosmic impact origin to black, high-temperature, carbon-encrusted beds (2–3 cm thick), associated with the Younger Dryas readvance of ice at 12.8 ka during the Late Glacial in the northern Andes of Venezuela. The evidence for this includes carbon spherules, aluminosilicate melt rocks, melted coatings of glass-like amorphous carbon, and Fe-Mn on sands and clasts derived from local felsic gneiss and granite. These sediments have been subjected to renewed investigation using high-resolution scanning electron microscopy and energy-dispersive spectrometry, and new data show that spherules at site MUM7B exhibit unique morphologies and compositions. Molar oxide weight percentages prove the spherules are not volcanic and show little overlap with cosmic materials. Spherule microstructures display quench melting and, thus, could not have formed from slow geological authigenic, diagenetic, or metamorphic processes. Instead, geochemical values for the Venezuelan samples plot within the limits of impact-related materials, including tektites, ejecta, and impact spherules from a number of craters and strewnfields (cf. Chicxulub Crater, Chesapeake Bay Crater, Tunguska, Australasian tektite field, Lake Bosumtwi Crater, Ries Crater, and others). These results are identical to previously reported spherules from the Younger Dryas boundary layer (YDB) on three continents, North America, Europe, and Asia, and the most likely origin is from a cosmic impact/airburst 12.8 ka, as previously proposed. The MUM7B site is one of the two southernmost sites (Venezuela and Peru) in South America, thus extending the evidence supporting the YDB impact event into a new hemisphere on a new continent
Recent Developments in the Analysis of the Black Mat Layer and Cosmic Impact at 12.8 ka
Bibs and Bios: William C. Mahaney, Leslie Keiser, David H. Krinsley, Allen West!, Randy Dirszowsky, Chris C.R. Allen, Pedro Costa
Article first published online: 6 DEC 2013
Geografiska Annaler: Series A, Physical Geography
Recent analyses of sediment samples from “black mat” sites in South America and Europe support previous interpretations of an ET impact event that reversed the Late Glacial demise of LGM ice during the Bølling Allerød warming, resulting in a resurgence of ice termed the Younger Dryas (YD) cooling episode. The breakup or impact of a cosmic vehicle at the YD boundary coincides with the onset of a 1-kyr long interval of glacial resurgence, one of the most studied events of the Late Pleistocene. New analytical databases reveal a corpus of data indicating that the cosmic impact was a real event, most possibly a cosmic airburst from Earth’s encounter with the Taurid Complex comet or unknown asteroid, an event that led to cosmic fragments exploding interhemispherically over widely dispersed areas, including the northern Andes of Venezuela and the Alps on the Italian/French frontier. While the databases in the two areas differ somewhat, the overall interpretation is that microtextural evidence in weathering rinds and in sands of associated paleosols and glaciofluvial deposits carry undeniable attributes of melted glassy carbon and Fe spherules, planar deformation features, shock-melted and contorted quartz, occasional transition and platinum metals, and brecciated and impacted minerals of diverse lithologies. In concert with other black mat localities in the Western USA, the Netherlands, coastal France, Syria, Central Asia, Peru, Argentina and Mexico, it appears that a widespread cosmic impact by an asteroid or comet is responsible for deposition of the black mat at the onset of the YD glacial event. Whether or not the impact caused a 1-kyr interval of glacial climate depends upon whether or not the Earth had multiple centuries-long episodic encounters with the Taurid Complex or asteroid remnants; impact-related changes in microclimates sustained climatic forcing sufficient to maintain positive mass balances in the reformed ice; and/or inertia in the Atlantic thermohaline circulation system persisted for 1 kyr.
The hypothesis that a cosmic impact could have generated the YD reversal is still hotly debated in the literature (Haynes 2008; Pinter and Ishman 2008; Ge et al. 2009; Kenntt et al., 2009). Recent critical reviews of the YD event by Van der Hammen and Van Geel (2008) and Broecker et al. (2010) argue, respectively, that charcoal in paleosols of the Allerød–YD transition were not caused by impact, and that the impact event, by itself, could not have caused a glacial advance lasting 1 kyr. The evidence reported here conclusively contradicts alternative hypotheses for the onset of the YD glacial advance, with the most conclusive evidence coming from aerodynamically modified Fe spherules and microspherules, melted and contorted quartz and other lithologies, and carbon mats welded to various minerals.[/ex
edit on 2-1-2014 by punkinworks10 because: (no reason given)