Shocked quartz at three U.S. sites bolsters case for late‑Ice Age cosmic airburst at onset of Younger Dryas

Researchers report discovery of shocked quartz in sediment layers at three well‑studied North American sites, evidence they say is consistent with a large atmospheric explosion or impact at the onset of the Younger Dryas cooling about 12,800 years ago. The study, published in PLOS ONE, ties microstructural damage and thermal alteration in quartz grains to pressures and temperatures associated with high‑energy events, and places those altered grains precisely in the horizon that marks abrupt environmental and cultural change.

The research team collected samples from Blackwater Draw in New Mexico, Murray Springs in Arizona and Arlington Canyon on Santa Rosa Island, California — locations long noted in archaeological literature for their association with Clovis‑period artifacts and the so‑called "black mat" that overlies terminal Clovis deposits. Using a suite of 10 laboratory techniques, the investigators identified shocked quartz grains with glass‑filled fractures, regions of recrystallized silica and amorphous zones that indicate exposure to extreme pressure and heat. Computer simulations of the pressures and velocities required to produce the observed features showed close correspondence with known impact and airburst events, the paper says.

At each site the shocked grains occur in sediment layers dated to the onset of the Younger Dryas, a rapid cooling event that began roughly 12,800 years ago and persisted for about 1,200 years. The horizon also coincides with the abrupt disappearance of Clovis‑style stone tools and large‑scale losses among North American megafauna, including mammoths, camels, horses and saber‑toothed cats. At Blackwater Draw and Murray Springs, the black mat overlies Clovis artifacts and mammoth remains; Murray Springs also preserves hundreds of footprints that appear to have been rapidly buried. Arlington Canyon contains Clovis‑era human remains beneath a similar mat and shows a multi‑century gap before later human reoccupation.

The quartz grains recovered by the team commonly display both mechanical shock features and signs of thermal alteration, with some zones exhibiting melting and recrystallization. The authors note that the melting point of quartz is around 3,123 degrees Fahrenheit and that the grains’ combination of thermally and mechanically induced changes matches signatures observed at known impact localities and at nuclear airburst sites. Comparative material cited in the study includes samples from Meteor Crater in Arizona and purported Younger Dryas layers reported from sites in Syria, the eastern United States, the Netherlands and Venezuela.

The study frames these mineralogical findings as strengthening a temporal and spatial link between a proposed cosmic event and the broad ecological and cultural changes at the start of the Younger Dryas. The authors emphasize that the sites chosen for study are among the best documented for terminal Clovis deposits and argue that the presence of airburst‑ or impact‑related materials at multiple, geographically separated locations supports a continental‑scale disturbance.

The idea that a comet or series of fragments might have triggered abrupt cooling and widespread ecological disruption at the Younger Dryas onset has been discussed and debated for decades. Proponents have argued that an atmospheric explosion or impact could have injected dust and aerosols into the atmosphere, disrupted ocean circulation and precipitated rapid climate change. Critics of the "Younger Dryas impact hypothesis" have pointed to patchy evidence and alternative explanations, including climatic shifts caused by changes in oceanic circulation or freshwater inputs to the North Atlantic. The PLOS ONE paper presents new mineralogical data that its authors say address prior gaps by providing direct evidence of extreme pressures and temperatures at multiple relevant sites.

Archaeological indicators support a notable cultural disruption around the Younger Dryas boundary. Clovis‑era tool types and butchery sites disappear abruptly in many stratigraphic sequences at roughly the same horizon where the shocked quartz was found, and some regions show a centuries‑long hiatus in human occupation before reestablishment of post‑Clovis communities. Megafaunal extinctions during this interval also occurred rapidly in the geological record, a temporal coincidence the authors highlight.

The researchers report that the shocked quartz grains were isolated and tested with a combination of optical microscopy, scanning electron microscopy, transmission electron microscopy, Raman spectroscopy and other methods to characterize microstructure, composition and thermal history. Simulations constrained the magnitudes of shock needed to produce the observed deformation and melting, and the team compared those constraints to known impact and airburst scenarios. While the paper does not attempt to reconstruct a single, detailed impact trajectory or identify a surviving crater in North America, the authors note morphological similarities between the grains and those from recognized high‑pressure contexts.

The publication adds to a body of literature that has sought geologic and chemical markers of high‑energy extraterrestrial events at the Younger Dryas boundary. The authors acknowledge that some geoscientists remain cautious and that interpretation of proxy records is complex, but state that the combination of mineralogical evidence, stratigraphic context and archaeological correlations merits further investigation. They call for expanded sampling, numerical modeling and interdisciplinary study to refine the timing, extent and mechanisms by which any cosmic event could have influenced climate, ecosystems and human societies at the end of the last Ice Age.

By situating the shocked quartz in well‑dated, archeologically significant layers, the paper aims to narrow the temporal link between a physical high‑energy event and simultaneous biological and cultural changes. Whether the new mineralogical evidence will shift the broader scientific consensus on the Younger Dryas remains to be seen; the study provides a detailed dataset that advocates say should inform ongoing debate and future field and laboratory work.