Accession Number:

ADA557930

Title:

Evidence from Central Mexico Supporting the Younger Dryas Extraterrestrial Impact Hypothesis

Descriptive Note:

Journal article

Corporate Author:

OREGON UNIV EUGENE

Personal Author(s):

• Israde-Alcantara, Isabel
• Bischoff, James L.
• Dominguez-Vazquez, Gabriela
• Li, Hong-Chun
• DeCarli, Paul C.
• Bunch, Ted E.
• Wittke, James H.
• Weaver, James C.
• Firestone, Richard B.
• West, Allen

Report Date:

2012-03-05

Pagination or Media Count:

11.0

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 meltingquenching 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 airbursts andor ground impacts at 12.9 ka.

Descriptors:

• *BOUNDARY LAYER
• *GEOLOGIC FORMATION
• CARBON COMPOUNDS
• GEOLOGIC AGE DETERMINATION
• METEORITES
• MEXICO
• REPRINTS

Subject Categories:

• Geology, Geochemistry and Mineralogy

Distribution Statement:

APPROVED FOR PUBLIC RELEASE