To test two competing hypotheses for the Younger Dryas trigger (extraterrestrial impact versus volcanism), we analyzed a high-resolution multiproxy record from Hall’s Cave, Texas, which preserves a continuous sedimentary archive from the Last Glacial Maximum through the Holocene. A Bayesian age–depth model based on 61 radiocarbon dates places the Younger Dryas Boundary (YDB) at 12,780 ± 170 cal BP, coincident with abrupt cooling, aridification, and sharply reduced sedimentation. At this boundary, biotic indicators record major ecological disruption, including a collapse of megafaunal dung-fungus spores and declining species richness. Geochemical profiles (magnetic susceptibility, δ 15 N, C/N, Hg/TOC) document hydroclimatic change and show no pronounced Hg/TOC enrichment at the YDB, indicating no evidence for a significant Hg-rich volcanic input at Hall’s Cave. In contrast, the YDB layer contains multiple high-temperature and shock proxies, including melted microspherules, carbon spherules, soot, nanodiamonds, and shocked quartz, identified using SEM-EDS and TEM analyses. Single-particle ICP-TOF-MS detects enrichments in Ni–Fe, Co–Fe, Fe–Si, Al–Ir, and Ti–Ir nanoparticle associations, including element combinations characteristic of meteoritic material and high-temperature condensation. These proxies define a two-step sequence consisting of a condensed boundary layer containing high-temperature and high-pressure (shock metamorphism) materials, followed by an early Younger Dryas interval characterized by increased dust input consistent with regional aridification. Collectively, the chronological, geochemical, mineralogical, and faunal evidence indicates a high-temperature and high-pressure event at ~12.8 ka and supports an extraterrestrial airburst or impact as the most consistent explanation for the Younger Dryas Boundary, in agreement with the Younger Dryas Impact Hypothesis (YDIH).
Moore et al. (2026) studied this question.