A Greenland ice-core study by Michail Petaev, Shichun Huang, Stein Jacobsen, and Alan Zindler found almost no iridium but detected a pronounced platinum spike beginning exactly 12,900 years ago.
Notes on verification
Confirmed by original PNAS paper (Petaev et al. 2013) and corroborated by independent science journalism (Phys.org, EarthDate) and PubMed abstract. Exact dating and Pt/Ir findings consistently match across sources. Interpretation of cause (impact vs. volcanic) has since been debated, but the factual finding itself is well-supported. [cascade flags: aggregator_dropped_primary_exists | tier=silver indep_score=0.983 clusters=3 claim_tier=notable]
Sources
- Did a Comet Really Kill the Mammoths 12,900 Years Ago? (seed:history_and_archaeology)
- https://www.pnas.org/doi/10.1073/pnas.1303924110 (corroboration)
- https://pubmed.ncbi.nlm.nih.gov/23878232/ (corroboration)
- https://www.earthdate.org/episodes/platinum-record-for-the-ice-age (corroboration)