Placemark is of Sithylemenkat Lake, AK which is of meteoric origin. Its age is < 100,000 years. It is in the general region where the Mammoth blaster would have hit.

In the 1930's a collection of oriented lakes and bogs known as the Carolina Bays were first noticed as something unique. Over the decades since then various hypotheses have emerged to explain their origin. One strong candidate was always a meteor or comet that burst at low altitude, much like the Tunguska event . That evidence was strengthened recently when Richard Firestone and others found evidence of a layer of carbon deposited at various locations around North America.

Looking for further evidence, Firestone and others thought of a novel approach. The exploding meteor or comet would have produced debris that certainly have impacted Ice Age animals including individuals from the mega-fauna that inhabited North America at the time. Animals like Bison and Woolly Mammoths have large external hard parts, horns and tusks, that should preserve evidence of being blasted by high velocity meteoric fragments.

So They began looking for mammoth tusks gathered by collectors ( thousands of tusks have been found and are regularly sold ). They found a small but significant number of tusks that had evidence of having been peppered and micro-cratered by fast moving debris that has a high iron content. There is one major problem. Though something definitely blasted the tusks, the age of the tusks is about 33,000 - 34,000 years, rather than the 13,000 year old evidence they would need to match the event that may have created the Carolina Bays. Contamination may account for some differences between the various samples of a few thousand years but not for 20,000 years. So they propose that what they have found is evidence of an earlier event. And they keep searching for tusks of an age that will match the creation of the Carolina Bays.


Analysis of seven mammoth tusks, purchased from a Canadian fossils vendor, show the ancient beasts were killed by a meteor that struck around 34,000 years ago.

Image and caption source: http://dsc.discovery.com


Further resources:

Abstract of their report to the AGU:

Quote:

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Micrometeorite Impacts in Beringian Mammoth Tusks and a Bison Skull
AGU Fall Meeting, 10-14 December 2007, San Francisco, CA
Paper U23A-0865
Richard B. Firestone, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, United States
Allen West, GeoScience Consulting, Dewey, AZ, 86327, United States
Zsolt Stefanka and Zsolt Revay, Institute of Isotopes, Budapest, Hungary
Jonathon T. Hagstrum, U.S. Geological Survey, 345 Middlefield Road MS 937, Menlo Park, CA 94025, United States
Abstract: We have discovered what appear to be micrometeorites imbedded in seven Alaskan Mammoth tusks and a Siberian bison skull. The micrometeorites apparently shattered on impact leaving 2-5 mm hemispherical debris patterns surrounded by carbonized rings. Multiple impacts are observed on only one side of the tusks and skull consistent with the micrometeorites having come from a single direction. The impact sites are strongly magnetic indicating significant iron content. We analyzed several imbedded micrometeorite fragments from both tusks and skull with Laser Ablation Inductively-Coupled Plasma Mass Spectrometry (LA-ICP-MS) and X-ray Fluorescence (XRF). These analyses confirmed the high iron content and a uniform composition highly enriched in nickel and depleted in titanium. The Fe/Ni and Fe/Ti ratios are comparable to urelite meteorites and are unlike any terrestrial sources. Prompt Gamma-ray Activation Analysis (PGAA) of a micrometeorite extracted from the bison skull indicated it contained ~0.4 mg of iron, in agreement with a micrometeorite ~1 mm in diameter. Several tusks have an average radiocarbon age of ~33 ka. This age coincides with sudden increases in global radiocarbon ~35 ka agoa and 10Be ~32 ka agob, the Mono Lake geomagnetic excursion ~34 ka agoc, and significant declines in Beringian bison, horse, brown bear, and mammoth populations and genetic diversity <36 ka agod. The bison skull shows evidence of new bone growth over the micrometeorite impact sites indicating the animal survived the bombardment and is dated at ~26 ka which is younger than the tusks. This age is consistent with exposure of the bison to an enriched source of radiocarbon following the impact. It appears likely that the impacts, cosmogenic isotope increases, magnetic excursion, and population declines are related events (Occam’s razor), although their precise nature remains to be determined.

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