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Study Questions Younger Dryas Event Comet Theories

May 14, 2014
Image Credit: Thinkstock

April Flowers for redOrbit.com – Your Universe Online

Approximately 128,000 years ago, near the end of the last Ice Age, there was a brief episode of glacial conditions called the Younger Dryas event. The Younger Dryas, named for a flower that flourished during this time, lasted about 1,000 years. There has been quite a bit of controversy in the scientific community regarding what might have initiated the event—with a wide range of theories, including one that has the event caused by a comet impacting the Earth. Proponents of this theory point to sediments containing deposits they believe could only result from such an impact.

A new study from Southern Methodist University (SMU) and published in Proceedings of the National Academy of Sciences disproves the comet impact theory.

David Meltzer, SMU professor of archeology and a leading expert on the Clovis culture, led the research team. Their findings, based on samples from 29 sites in North America and on three other continents, indicate that nearly all sediment layers purported to be from the Ice Age are actually either much younger or much older.

Although the scientific community agrees that the Younger Dryas period occurred, causing widespread cooling for a relatively short time, they do not agree on what caused it. Theories range from changes in ocean circulation patterns caused by glacial meltwater entering the ocean to the cosmic-impact theory.

Geological indicators that are extraterrestrial in origin are said to be the basis of the cosmic-impact theory. Meltzer said that the cosmic-impact theory is false, however, after a careful review of the dating of sediment samples from 29 sites reported to have such indicators. Of the 29, only three were found to have sediments that date to the window of time for the Ice Age.

“The supposed impact markers are undated or significantly older or younger than 12,800 years ago,” report the authors. “Either there were many more impacts than supposed, including one as recently as five centuries ago, or, far more likely, these are not extraterrestrial impact markers.”

At the 29 sites in North America and elsewhere, there is supposedly a Younger Dryas boundary layer that contains deposits of magnetic grains with iridium, magnetic microspherules, charcoal, soot, carbon spherules, glass-like carbon containing nanodiamonds, and fullerenes with extraterrestrial helium. These grains are supposedly extraterrestrial in origin, from a comet or other cosmic event impacting the Earth that dates to a 300-year span centered on 128,000 years ago.

To test the cosmic-impact theory and determine if these markers dated to the onset of the Younger Dryas, the team examined the existing stratigraphic and chronological data sets reported in the published scientific literature and accepted as proof by cosmic-impact proponents. The 29 sites were sorted initially by the availability of radiometric or numeric ages, then by the type of age control, if available, and whether the age control is secure.

Three of the sites lacked absolute age control:

  • Chobot, Alberta—the three Clovis points found lack stratigraphic context, and the majority of other diagnostic artifacts are younger than Clovis by thousands of years.
  • Morley, Alberta—without evidence, ridges are assumed to be chronologically correlated with Ice Age hills 1,600 miles away.
  • Paw Paw Cove, Maryland— according to the principal archaeologist, horizontal integrity of the Clovis artifacts found is compromised.

According to the Smithsonian, the Clovis culture is the oldest North American culture that we have much knowledge of, with sites ranging from Washington State to Venezuela. More than 10,000 Clovis points — made from jasper, chert, obsidian and other fine, brittle stones — have been found since their initial discovery in Clovis, New Mexico, in 1932. The oldest securely dated examples were unearthed in Texas, tracing back 13,500 years.

Radiometric or other potential numeric ages were found at the remaining 26 sites, but only three of these date to the Younger Dryas boundary layer.

The ages of eight of the sites were unrelated to the Younger Dryas boundary layer. An example would be at the Gainey, Michigan site where extensive stratigraphic mixing of artifacts found at the site makes it impossible to know their position to the supposed Younger Dryas boundary layer. What direct dating was obtained pointed to sometime after the 16th century CE.

Sediment in the skull of an extinct horse found at Wally’s Beach, Alberta was dated to an age of 10,980 using radiocarbon dating. These sediments purportedly point to extraterrestrial impact markers. In actuality, the date is from an extinct musk ox instead of a horse, and the fossil that yielded the supposed impact markers was not dated. The scientists could not find evidence suggesting that the Wally’s Beach fossils are all of the same age or even date to the Younger Dryas event onset.

The team demonstrates that the chronological results at nearly a dozen other sites are neither reliable nor valid as a result of significant statistical flaws in the analysis, the omission of ages from the models, and the disregard of statistical uncertainty that accompanies all radiometric dates.

In more cases than not, according to the findings, inferences about the ages of supposed Younger Dryas boundary layers are unsupported by replication.


Source: April Flowers for redOrbit.com – Your Universe Online



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