Shocked quartz found at U.S. sites bolsters case for cosmic event at onset of Younger Dryas

New geological analyses of sediment from sites in California, Arizona and New Mexico have identified shocked quartz grains dated to about 12,800 years ago, researchers reported, a finding they say strengthens the case that a cosmic airburst or impact contributed to rapid ecological change at the start of the Younger Dryas.

The study, published in PLOS ONE, describes mineral grains whose crystal lattices show irreversible deformation and thermal alteration consistent with exposure to extremely high pressures and temperatures. Those features, the authors say, are characteristic of materials formed during large impacts or intense atmospheric explosions and were recovered from sediment layers that coincide with a continental "black mat" horizon associated with abrupt environmental change, megafaunal die-offs and the disappearance of distinctive Clovis stone tools.

Researchers collected samples from Blackwater Draw in New Mexico, Murray Springs in Arizona and Arlington Canyon on Santa Rosa Island, California. Blackwater Draw is the classic Clovis-type locality where the culture’s artifacts were first identified; Murray Springs preserves terminal Clovis artifacts and remains of extinct megafauna beneath a black mat; Arlington Canyon contains Clovis-era human remains and the extinction record of island pygmy mammoths. At each site, the shocked and partially melted quartz grains were extracted from layers precisely dated to the onset of the Younger Dryas, roughly 10,800 B.C.

The team used 10 independent laboratory methods to characterize fractures and glass-filled cracks in quartz and ran computer simulations to estimate the pressures and temperatures required to produce the observed features. They report that the southwestern U.S. grains resemble quartz from documented impact and airburst contexts, including Meteor Crater, nuclear airburst sites and previously reported Younger Dryas–age occurrences in Syria, the eastern United States, the Netherlands and Venezuela.

Many of the grains show evidence of temperatures above the melting point of quartz, with portions rendered amorphous and others showing recrystallization. The authors classify these materials as "thermally and mechanically shocked quartz," arguing that the combination of mechanical shock and high heat is most plausibly explained by an extraterrestrial airburst or impact event rather than ordinary geologic processes.

The deposition of shocked quartz at these well-documented archaeological localities coincides with a period when more than 70% of North American megafauna — including mammoths, camels, horses and saber-toothed cats — vanished and when archaeologists observe an abrupt end to the Clovis technocomplex. The study notes that many Clovis-age sites are capped by the same black mat at approximately the same age and that some locations record a multi-century hiatus in human occupation after that horizon. "The presence of airburst/impact-related materials at these key locations strengthens the temporal and spatial link between the proposed cosmic event and major ecological and cultural changes," the authors wrote.

The Younger Dryas — a sudden return to near-glacial conditions in the Northern Hemisphere that began about 12,800 years ago and lasted roughly 1,200 years — has been the subject of longstanding scientific debate. Some researchers have proposed that an extraterrestrial object or objects triggered the cooling and associated environmental disruptions; other scientists have pointed to alternative explanations such as changes in ocean circulation, meltwater routing and internal climate variability. The impact hypothesis has been contentious in part because different teams have reported divergent datasets and interpretations.

The new study provides additional mineralogical evidence that proponents say links an abrupt, high-energy event to the onset of the Younger Dryas and to contemporaneous archaeological and paleontological signals across North America. The authors emphasize that the sites they sampled are among the best-documented for studying the intersection of late-Pleistocene extinctions and human cultural change.

The publication stops short of asserting a single, continent-wide mechanism for all observed changes but argues that the spatial and temporal coincidence of shocked minerals, black-mat horizons and rapid biotic turnover warrants further investigation. The researchers call for additional sampling, multidisciplinary analyses and broader geographic testing to clarify the scale and consequences of the proposed airburst or impact and to place the new mineralogical data in the full context of late-Pleistocene climate and human history.