2025-08-12 カリフォルニア大学サンタバーバラ校（UCSB）
＜関連情報＞
- https://news.ucsb.edu/2025/021989/destructive-cosmic-airbursts-likely-more-common-previously-believed
- https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0328347
- https://www.scienceopen.com/hosted-document?doi=10.14293/ACI.2025.0004
バフィン湾の複数のコアから記録された、彗星塵、マイクロスフィア、および白金異常を含む12,800年前の層 A 12,800-year-old layer with cometary dust, microspherules, and platinum anomaly recorded in multiple cores from Baffin Bay
Christopher R. Moore ,Vladimir A. Tselmovich,Malcolm A. LeCompte,Allen West,Stephen J. Culver,David J. Mallinson,Mohammed Baalousha,James P. Kennett,William M. Napier,Michael Bizimis,Victor Adedeji,Seth R. Sutton,Gunther Kletetschka, [ … ],James A. Malley
PLOS One Published: August 6, 2025
DOI:https://doi.org/10.1371/journal.pone.0328347
Abstract
The Younger Dryas Impact Hypothesis (YDIH) posits that ~12,800 years ago Earth encountered the debris stream of a disintegrating comet, triggering hemisphere-wide airbursts, atmospheric dust loading, and the deposition of a distinctive suite of extraterrestrial (ET) impact proxies at the Younger Dryas Boundary (YDB). Until now, evidence supporting this hypothesis has come only from terrestrial sediment and ice-core records. Here we report the first discovery of similar impact-related proxies in ocean sediments from four marine cores in Baffin Bay that span the YDB layer at water depths of 0.5–2.4 km, minimizing the potential for modern contamination. Using scanning electron microscopy with energy-dispersive spectroscopy (SEM-EDS) and laser ablation ICP-MS, we detect synchronous abundance peaks of metallic debris geochemically consistent with cometary dust, co-occurring with iron- and silica-rich microspherules (4–163 μm) that are predominantly of terrestrial origin with minor (<2 wt%) ET contributions. These microspherules were likely formed by low-altitude touchdown airbursts and surface impacts of comet fragments and were widely dispersed. In addition, single-particle ICP-TOF-MS analysis reveals nanoparticles (<1 μm) enriched in platinum, iridium, nickel, and cobalt. Similar platinum-group element anomalies at the YDB have been documented at dozens of sites worldwide, strongly suggesting an ET source. Collectively, these findings provide robust support for the YDIH. The impact event likely triggered massive meltwater flooding, iceberg calving, and a temporary shutdown of thermohaline circulation, contributing to abrupt Younger Dryas cooling. Our identification of a YDB impact layer in deep marine sediments underscores the potential of oceanic records to broaden our understanding of this catastrophic event and its climatological impacts.
ルイジアナ州で記録された12,800年前の浅い空中爆発凹地と、衝撃を受けた石英と溶融物質の大量堆積物の証拠 Evidence of a 12,800-year-old Shallow Airburst Depression in Louisiana with Large Deposits of Shocked Quartz and Melted Materials
Robert Fitzenreiter, Kord Ernstson, Gunther Kletetschka, Malcolm A. LeCompte, Christopher R. Moore, James P. Kennett, Michael Bizimis, Florian Hofmann, Marian Takac, A. Victor Adedeji, Timothy Witwer, Julie E. Chouinard, Jesus Paulo Perez, Marc D. Young, Teresa M. Eaton, Matthew J. Valente, David B. Lanning Jr., Yoav Rapoport, Kailey Ellison, Argyro Reyes, Ravi Holladay, Michelle Madrigal, Julian Albanil, Charlie Sanchez, Allen West
Airbursts and Cratering Impacts Published:04 June 2025
DOI:10.14293/ACI.2025.0004
Abstract
We report evidence of a likely low-altitude cosmic airburst near Perkins, Louisiana, associated with semi-consolidated deposits containing abundant shocked quartz grains, a classical impact indicator, along with spherules, meltglass, and microbreccia. Analytical techniques employed on these materials include optical microscopy, the universal stage, electron microscopy (SEM, TEM, and STEM), cathodoluminescence, laser ablation (LA-ICP-MS), neutron activation (INAA), and radiometric dating. These analyses reveal that the deposits exhibit morphological and compositional similarities to known impact-related proxies. Radiocarbon dating and 40Ar/39Ar analyses constrain the likely age of deposition to between 30,000 and 10,000 calibrated years BP, with a concentration of dates clustering around 12,800 years BP (12,835-12,735 cal BP), coinciding with the age range of the Younger Dryas Boundary (YDB). Spherule and meltglass abundances, along with evidence of high-temperature mineral transformations, are consistent with the effects of a high-energy airburst or impact. Hydrocode modeling suggests that a touch-down airburst could plausibly account for the observed shallow depression, material dispersal patterns, and geochemical signatures. Our study suggests that a 300-m-long lake/depression at the Perkins site represents North America’s first identified YDB-age airburst crater.
