Topic ID #16824 - posted 3/6/2012 4:23 PM

New evidence from Central Mexico supporting the Younger Dryas extraterrestrial impact hypothesis.



Charlie Hatchett

Israde-Alcántara, I., J. L. Bischoff, G. Domínguez-Vázquez,
H.-C. Li, P. S. DeCarli, T. E. Bunch, J. H. Wittke, J. C.
Weaver, R. B. Firestone, A. West, J. P. Kennett, C. Mercer,
S. Xie, E. K. Richman, C. R. Kinzie, and W. S. Wolbach,
2012, New evidence from Central Mexico supporting the Y
ounger Dryas extraterrestrial impact hypothesis. Proceedings
of the National Academy of Sciences. Published online
before print March 5, 2012, doi: 10.1073/pnas.1110614109

Abstract

We report the discovery in Lake Cuitzeo in central Mexico of a black, carbon-rich, lacustrine layer, containing nanodiamonds, microspherules, and other unusual materials that date to the early Younger Dryas and are interpreted to result from an extraterrestrial impact. These proxies were found in a 27-m-long core as part of an interdisciplinary effort to extract a paleoclimate record back through the previous interglacial. Our attention focused early on an anomalous, 10-cm-thick, carbon-rich layer at a depth of 2.8 m that dates to 12.9 ka and coincides with a suite of anomalous coeval environmental and biotic changes independently recognized in other regional lake sequences. Collectively, these changes have produced the most distinctive boundary layer in the late Quaternary record. This layer contains a diverse, abundant assemblage of impact-related markers, including nanodiamonds, carbon spherules, and magnetic spherules with rapid melting/quenching textures, all reaching synchronous peaks immediately beneath a layer containing the largest peak of charcoal in the core. Analyses by multiple methods demonstrate the presence of three allotropes of nanodiamond: n-diamond, i-carbon, and hexagonal nanodiamond (lonsdaleite), in order of estimated relative abundance. This nanodiamond-rich layer is consistent with the Younger Dryas boundary layer found at numerous sites across North America, Greenland, and Western Europe. We have examined multiple hypotheses to account for these observations and find the evidence cannot be explained by any known terrestrial mechanism. It is, however, consistent with the Younger Dryas boundary impact hypothesis postulating a major extraterrestrial impact involving multiple airburst(s) and and/or ground impact(s) at 12.9 ka.

Press release:

Study Jointly Led by UCSB Researcher Supports Theory of
Extraterrestrial Impact. University of California at Santa
Barbara, Santa Barbara, California.

http://www.ia.ucsb.edu/pa/display.aspx?pkey=2662






Post ID#19424 - replied 3/7/2012 4:28 AM



Charlie Hatchett

Post ID#19430 - replied 3/8/2012 8:38 AM



marehart

You mean the layer or the guy with the sombrero?

I am having a hard time seeing how this could accomplish all that's being claimed for it.

Post ID#19435 - replied 3/11/2012 5:19 AM



Charlie Hatchett

LOL @ "the guy with the sombrero"!


Summary

Synchronous peaks in multiple YDB markers dating to 12.9 ka
were previously found at numerous sites across North and South
America and in Western Europe. At Lake Cuitzeo, magnetic impact
spherules, CSps, and NDs form abundance peaks within a
10 cm layer of sediment that dates to the early part of the YD,
beginning at 12.9 ka. These peaks coincide with anomalous environmental,
geochemical, and biotic changes evident at Lake Cuitzeo
and in other regional records, consistent with the occurrence of
an unusual event. Analyses of YDB acid-resistant extracts using
STEM, EDS, HRTEM, SAD, FFT, EELS, and EFTEM indicate
that Lake Cuitzeo nanoparticles are dominantly crystalline carbon
and display d-spacings that match various ND allotropes, including
lonsdaleite. These results are consistent with reports of abundant
NDs in the YDB in North America and Western Europe.
Although the origin of these YDB markers remains speculative,
any viable hypothesis must account for coeval abundance
peaks in NDs, magnetic impact spherules, CSps, and charcoal
in Lake Cuitzeo, along with apparently synchronous peaks at
other sites, spanning a wide area of Earth’s surface. Multiple
hypotheses have been proposed to explain these YDB peaks
in markers, and all but one can be rejected. For example, the magnetic
impact spherules and NDs cannot result from the influx of
cosmic material or from any known regular terrestrial mechanism,
including wildfires, volcanism, anthropogenesis, or alternatively,
misidentification of proxies. Currently, only one known
event, a cosmic impact, can explain the diverse, widely distributed
assemblage of proxies. In the entire geologic record, there are
only two known continent-wide layers with abundance peaks in
NDs, impact spherules, CSps, and aciniform soot, and those
are the KPg impact boundary at 65 Ma and the YDB boundary
at 12.9 ka.

Israde-Alcántara, I., J. L. Bischoff, G. Domínguez-Vázquez,
H.-C. Li, P. S. DeCarli, T. E. Bunch, J. H. Wittke, J. C.
Weaver, R. B. Firestone, A. West, J. P. Kennett, C. Mercer,
S. Xie, E. K. Richman, C. R. Kinzie, and W. S. Wolbach,
2012, New evidence from Central Mexico supporting the Y
ounger Dryas extraterrestrial impact hypothesis. Proceedings
of the National Academy of Sciences. Published online
before print March 5, 2012, doi: 10.1073/pnas.1110614109

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