Claims

The Younger Dryas boundary proxy assemblage — microspherules, nanodiamonds, platinum-group-element enrichments, and high-temperature melt products — is diagnostic of extraterrestrial impact rather than of terrestrial processes.

Nanodiamond-rich layers, including reported hexagonal lonsdaleite, occur in Younger Dryas boundary sediments at multiple sites.

Magnetic microspherule abundance peaks occur in Younger Dryas boundary sediments at sites across four continents.

Glassy melt products requiring formation temperatures above roughly 1,500–2,200 °C occur in strata near the Younger Dryas onset at several sites.

Dark, organic-rich "black mat" horizons occur at many terminal- Pleistocene sites in North America, frequently overlying the last in-place megafaunal remains and Clovis artifacts.

A platinum anomaly spanning roughly 21 years, averaging ~30 parts per trillion with a single-sample peak of ~80 ppt, occurs in the GISP2 Greenland ice core near the Younger Dryas onset.

On the GICC05 ice-core timescale, the GISP2 platinum anomaly occurs several decades (about 45 years) after the onset of Younger Dryas cooling in the Greenland ice-core record.

Sediment layers dated near the Younger Dryas onset at multiple North American sites contain platinum enrichments substantially above local background.

Independent laboratories applying their own sampling and identification protocols have repeatedly failed to reproduce the claimed Younger Dryas boundary proxy peaks, and no standardized identification criteria exist for the key markers.

The reported proxy peaks at sites across four continents form a single isochronous layer dating to approximately 12,835–12,735 cal BP.

Earth's encounter with debris from a fragmenting giant short-period comet — the proposed Taurid Complex progenitor — provides a viable astronomical scenario for multiple dispersed airbursts without a large crater.

No impact crater securely dated to ~12.8 ka is known anywhere on Earth; the Hiawatha crater beneath the Greenland ice, once discussed as a candidate, has been directly dated to approximately 58 million years.

Charcoal, soot, and combustion-aerosol peaks at the Younger Dryas onset record an exceptional, continental-to-hemispheric biomass-burning episode.

Impact-related environmental catastrophe contributed substantially to the extinction of North American megafauna at the terminal Pleistocene.

The proposed impact caused a continent-wide human population collapse and the termination of the Clovis technocomplex.

Approximately 35 genera of North American megafauna went extinct in the late Pleistocene, with available last-appearance dates consistent with a concentrated terminal-Pleistocene extinction interval.

One or more cosmic impacts or airbursts around 12,800 years ago triggered the Younger Dryas cooling, contributed substantially to the North American megafaunal extinctions, and disrupted the Clovis technocomplex.

An impact or airburst event initiated the freshwater or atmospheric perturbation that triggered the Atlantic circulation disruption behind the Younger Dryas cooling.

The Younger Dryas cooling was proximately produced by a major weakening or reorganization of the Atlantic Meridional Overturning Circulation.

Synchronised Greenland and Antarctic ice-core sulphate records show a cluster of four major bipolar volcanic eruptions in the roughly 110 years immediately before the Younger Dryas onset, with a cumulative Northern Hemisphere radiative forcing exceeding that of the most volcanically active periods of the Common Era.

Both flagship 2025 YDIH papers — the Baffin Bay cometary-dust study and the shocked-quartz study — were retracted by PLOS ONE on 11 February 2026 for chronology, sampling, and identification defects, and the influential 2017 North American platinum paper was formally corrected in May 2026 to withdraw its extraterrestrial-source conclusion.