In the Greenland ice core studied by Petaev and colleagues, platinum concentration increased by more than a hundredfold over roughly 20 years before subsiding.
Notes on verification
Confirmed directly by the original PNAS paper (Petaev et al. 2013) and its follow-up reply, with figures matching closely (~100-fold rise over ~14 y, decline over ~7 y, totaling ~20 y). Independent contemporaneous reporting (Phys.org) and later peer-reviewed literature corroborate the magnitude and timescale. Some post-2020 studies debate the interpretation (impact vs. volcanic origin), but not the specific numerical claim being verified. [cascade flags: aggregator_dropped_primary_exists | tier=silver indep_score=1.0 clusters=2 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://pmc.ncbi.nlm.nih.gov/articles/PMC5343653/ (corroboration)
- https://www.pnas.org/doi/10.1073/pnas.1320772111 (corroboration)