Study Jointly Led by UCSB Researcher Finds New Evidence Supporting Theory of Extraterrestrial Impact

[OKIsItJustMe]

http://www.ia.ucsb.edu/pa/display.aspx?pkey=2748

[font face=Serif][font size=5]Study Jointly Led by UCSB Researcher Finds New Evidence Supporting Theory of Extraterrestrial Impact[/font]

June 11, 2012

[font size=3](Santa Barbara, Calif.) –– An 18-member international team of researchers that includes James Kennett, professor of earth science at UC Santa Barbara, has discovered melt-glass material in a thin layer of sedimentary rock in Pennsylvania, South Carolina, and Syria. According to the researchers, the material –– which dates back nearly 13,000 years –– was formed at temperatures of 1,700 to 2,200 degrees Celsius (3,100 to 3,600 degrees Fahrenheit), and is the result of a cosmic body impacting Earth.

These new data are the latest to strongly support the controversial Younger Dryas Boundary (YDB) hypothesis, which proposes that a cosmic impact occurred 12,900 years ago at the onset of an unusual cold climatic period called the Younger Dryas. This episode occurred at or close to the time of major extinction of the North American megafauna, including mammoths and giant ground sloths; and the disappearance of the prehistoric and widely distributed Clovis culture. The researchers' findings appear today in the Proceedings of the National Academy of Sciences.

"These scientists have identified three contemporaneous levels more than 12,000 years ago, on two continents yielding siliceous scoria-like objects (SLO's)," said H. Richard Lane, program director of National Science Foundation's Division of Earth Sciences, which funded the research. "SLO's are indicative of high-energy cosmic airbursts/impacts, bolstering the contention that these events induced the beginning of the Younger Dryas. That time was a major departure in biotic, human and climate history."

Morphological and geochemical evidence of the melt-glass confirms that the material is not cosmic, volcanic, or of human-made origin. "The very high temperature melt-glass appears identical to that produced in known cosmic impact events such as Meteor Crater in Arizona, and the Australasian tektite field," said Kennett.

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http://dx.doi.org/10.1073/pnas.1110614109

[Ghost Dog]

1. --> Laurentide Ice Sheet Retreat

Since the appearance of Clovis big game hunters on the North American continent has been redated to include a mere 300-500 years length, researchers have been trying to trace the reasons for its disappearance. One possible reason is the death of all of the big game Clovis was hunting--called the Pleistocene megafauna extinctions. The megafauna that disappeared between 15,000 and 10,000 years ago include mastodons, horses, camels, sloths, dire wolves, tapir, and short-faced bear. Because these megafauna disappeared at roughly the same time as the Clovis people (or at least their lifestyle), it has long been debated whether the Clovis people were the cause of the disappearance through overkill or merely the stressed-out survivors of a difficult climate change.

Climatically, the end of Clovis coincides with the onset of the Younger Dryas period (abbreviated YD), which was substantially colder, dryer and windier, compared to the late Pleistocene and the Early Holocene on either side of the YD. The end of the Pleistocene was a warming trend as the glaciers retreated; and the YD was an abrupt and nasty surprise, a 1000-year-long return to tundra conditions. The YD was one of our ancestors' occasional struggles with abrupt climate change, which in this case was very bad, especially considering the lack of central heating.

One of the geological markers of the Younger Dryas climatic episode is an organic-rich layer of soil called "sapropelic silt", "peaty muds", "paleo-aquolls" and most commonly, "black mat"...

... A formal paper, published in the Proceedings of the National Academy of Sciences in September of that year, described a thin sedimentary deposit immediately beneath the black mat, which contained high concentrations of magnetic grains with iridium, magnetic microspherules, glass-like carbon containing nanodiamonds, and fullerenes with extra-terrestrial helium. Firestone et al. argue that the stuff underneath the black mat represents the detritus of an explosive low-density object--a comet--which destablized the Laurentide Ice Sheet. Widespread fires ensued, followed by an accelerated melting of the ice sheet and then a cooling period (the YD), brought on perhaps perhaps by persistent cloudiness. This combination, they claim, led to the megafaunal extinctions and the end of the Clovis big game adaptation...

/... http://archaeology.about.com/b/2008/04/28/clovis-black-mats-and-extra-terrestrials.htm


The Younger Dryas Cold Event (ca. 12.9–11.6 ka) has long been viewed as the canonical abrupt climate event (Fig. 1). The North Atlantic region cooled during this interval with a weakening of Northern Hemisphere monsoon strength. The reduction in northward heat transport warmed the Southern Hemisphere due to a process commonly referred to as the bipolar-seesaw (e.g., Clark et al., 2002). Although it is generally accepted that the cold event resulted from a slowing Atlantic meridional overturning circulation (AMOC), the forcing of this AMOC reduction remains intensely debated.

The most common means of slowing AMOC involves the reduction of oceanic surface water density via an increase in freshwater discharge to the North Atlantic. The originally hypothesized source of freshwater was the eastward routing of Glacial Lake Agassiz from the Mississippi River to the St. Lawrence River, as the Laurentide Ice Sheet retreated northward out of the Great Lakes (Johnson and McClure, 1976; Rooth, 1982; Broecker, 2006). A clear Younger Dryas freshwater signal in the St. Lawrence Estuary (Keigwin and Jones, 1995; deVernal et al., 1996) only becomes apparent after accounting for other competing effects on commonly used freshwater proxies, in agreement with three other independent runoff proxies (Carlson et al., 2007). Lake Agassiz's eastern outlet history also presents an issue, as the most recent study suggested that the outlet remained closed until well after the start of the Younger Dryas, with the lake having no outlet for much of the Younger Dryas (Lowell et al., 2009). In contrast, a simple consideration of Lake Agassiz's water budget requires an outlet for the lake during the Younger Dryas (Carlson et al., 2009). This ongoing debate over the ultimate cause of the Younger Dryas has led to a search for other potential forcing mechanisms, such as an abrupt discharge of meltwater to the Arctic Ocean (Tarasov and Peltier, 2005) and a bolide impact (Firestone et al., 2007).

/... http://geology.gsapubs.org/content/38/4/383.full